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Патент USA US3025944

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March 20, 1962
K. w. BROLING
3,025,932
SLACK ADJUSTER
Filed Feb. 19, 1959
8 Sheets-Sheet 1
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Maréh 20, 1962
K. w. BROLING
3,025,932
SLACK ADJUSTER
Filed Feb. 19, 1959
8 Sheets-Sheet 2
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March 20, 1962
3,025,932
K. w. BROLING
SLACK ADJUSTER
Filed Feb; 19, 1959
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March 20, 1962
K, w, BROLING
3,025,932
SLACK ADJUSTER
Filed Feb. 19, 1959
8 Sheets-Sheet 4
March 20, 1962
3,025,932’
K. W. BROLING
SLACK ADJUSTER
Filed Feb. 19, 1959
8 Sheets-Sheet 5
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‘March 20, 1962
K. W. BROLING
3,025,932
SLACK ADJUSTER
Filed Feb. 19, 1959
8 Sheets-Sheet 6
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March 20, 1962
K. w. BROLING
3,025,932
SLACK ADJUSTER
Filed Feb. 19, 1959
8 Sheets-Sheet ‘7
March 20, 1962
K. w. BROLING
3,025,932
SLACK ADJUSTER
Fi‘led Feb. 19, 1959
8 Sheets-Sheet 8
United States Patent 0
3,025,932
Patented Mar. 20, 1.962:
2
1
3,025,932
SLACK ADJUSTER
Keith W. Broling, Homewood, Ill., assignor to Universai
Railway Devices Company, a corporation of Delaware
Filed Feb. 19, 1959, Ser. No. 794,363
5 Claims. (Cl. 188-200)
larly for association
braking system, and
tion of such a dead
has certain inherent
with the dead lever of a foundation
in the course of the normal opera
lever of a braking system, the lever
movements that are induced by the
fundamental characteristics of normal railway braking
systems, and a further and important object of the pres
ent system is to enable these normal movements of they
dead lever of a braking system to be utilized and co
This invention relates to slack adjusters for the brak
ordinated with the slack adjusting system to minimize
ing systems of railway cars, and it relates particularly to
the forces required for attaining the two-way slack ad—
such slack adjusters that have a two-way adjusting action
justing operation.
for either taking up or letting out slack in the braking
Other and further objects of the present invention will
system.
be apparent from the following description and claims,
Two-way slack adjusters have been known for many
and are illustrated in the accompanying drawings, which,
years but have failed to gain any degree of acceptance
because of operational and maintenance problems in 15 by way of illustration, show a preferred embodiment of
the present invention and the principles thereof, and
volved in the slack adjusters that have been proposed
and used.
what is now considered to be the best mode in which to
apply these principles. Other embodiments of the in
Thus, in the slack adjusters as heretofore proposed,
vention embodying the same or equivalent principles may
the apparatus has been dependent upon various types of
clutches that have been found to be unduly sensitive and 20 be used and structural changes may be made as desired
by those skilled in the art without departing from the
hard to maintain in use. Such clutching arrangements
invention.
have included friction clutches, and wedge-type clutches,
In the drawings:
and these clutching devices have been found to be un
FIG. 1 is a plan view of the frame of a railway car
reliable in use. In another form of two-way slack ad
illustrating
a two-way slack adjuster embodying the fea
juster that has been used reliance has been had on a 25
tures of the present invention and associated with the:
rotative adjusting nut movable along a fairly long lead
' braking system;
-
adjusting screw, and in such slack adjusters, the par
FIG. 1A is a fragmentary portion of the system shown
ticular lead employed upon the screw threaded member
in
FIG. 1 with the push rod and related parts in their
has in most instances been such that the adjusted posi
released relationship;
tion of the device might be disturbed in the course of 30
FIG. 2 is a side elevational view of the apparatus
the sudden impacts that are often encountered in cou
shown in FIG. 1;
pling and switching operations in a railway yard. An
FIG.
3
is
a
side
elevational
view
of
the
slack
adjuster’
other di?iculty that has been found in prior two-way
shown in FIG. 1;
slack adjusters has ‘been that the mechanism has been
FIG. 4 is a horizontal cross sectional view of the unit
of such a character as to require substantially full en 35
shown in FIG. 3;
closure so that where dirt did accumulate within the
-
FIGS. 4A and 4B are fragmentary vertical sectional
housing of such structure it could not be released there
views taken along the lines 4A—4A and 4B—-4B of
from in the courseof normal use. Hence the devices
FIG. 4.
were not self cleaning as is required with equipment used
FIG. 4C is a perspective view of the takeup pawl and
in the braking system of railway cars.
40 the associated control means;
In the view of the foregoing it is the primary object
FIG. 5 is a right hand end view of the unit shown in
of the present invention to provide a two-way slack ad
FIG. 4, the view being turned 90° in a counterclock
juster which overcomes the foregoing difficulties and ob
wise direction in order to conserve space, the view be-‘
jections so as to be reliable and effective in use. An
ing taken from the line 5—5 of FIG. 4;
object related to the foregoing is to provide such a two 45
FIG. 6 is a vertical sectional view taken through the
way slack adjuster that will withstand the rough usage
unitof
FIG. 4 the view being taken along the line 6-6
and which will maintain its adjusted position even though
of FIG. 4;
'
the equipment may be subjected to sudden impacts.
FIG. 7 is a bottom plan view of‘ the portion of the
Another important object of the present invention is
the view being taken from the line 7-7 of FIG. 3;
to provide a two-way slack adjuster that is extremely 50 unit,
FIG. 8 is a schematic timing diagram illustrating the
rugged in character and which does not require a full
push rod travel and the pull rod travel in a long stroke,’
enclosure of the operating parts, thus to render the slack
a normal stroke, and a short stroke thereof, and further
adjuster self cleaning to the extent that is required in
illustrating the movements of the rack of the unit in the
railway brake apparatus. A related object is to provide
related brake release ‘cycles;v
a two-way slack adjuster in which the slack adjusting 55
I FIGS. 9, 10 and 11 are. schematic views similar to
forces required in either take up or let out of the slack
FIG. 3 and showing the important operating parts of the
are minimized so as to avoid the necessity for utilizing
slack adjusting unit in a normal length operating stroke;
any substantial portion of the brake applying forces in
FIG.
9 representing the parts in their at rest positions;
the operation of the slack adjusters.
FIG. 10 representing the fully operated positions, and
As above pointed out, the slack adjuster of the pres
ent invention is of such a character as to withstand sud
den impacts such as those encountered in coupling and
switching operations without disturbing the adjustment
60 FIG. 11 representing the released or at rest positions at
q the end of the cycle;
FIGS. 12 to 14 are views similar to FIGS. 9 ‘to 11v
but pertaining to a long stroke of the push rod wherein a
of the device, and another important object of the pres
ent invention is to enable this to be accomplished by 65 take up operation is performed; FIG. 12 showing the at
rest position, FIG. 13 showing the fully applied position,
elements of the apparatus that are utilized in the adjust
and FIG. 14 showing the released position assumed after
ment of slack, and to enable the working forces of the
' a take up operation of the unit.
brake applying operation to be taken by other means
FIGS. 15 and 16, considered along with FIG. 14, show
included in the slack adjuster so as to thereby protect
the different positions of the parts in a normal operation
the adjusting elements of apparatus from the relatively
large forces that are involved in the brake application. 70 that follows a take up operation so that FIG. 15 illus~
The present two-way slack adjuster is adapted particu l - trates the position of the parts at the end of the brake
52,025,932
3
applying operationrthat followsva take up cycle, while
FIG. 16 illustrates the parts after the release of the
.
4
.
shaft 22 and the lug 35. The rocking assembly 34 has a
lever 36 projecting radially therefrom, and this lever, at
its end, has a spring rod 38 pivoted thereto, the other end
of the spring rod being slidable through a bracket 39
formed on the housing 3%}, and rtherewbeing a spring 40
acting between the bracket 39 and an enlarged ?ange 38F
formed on the rod 33. The spring rod 338 thus acts nor;
mally to urge the rocking assembly 34. in a clockwise
applying operation; FIG. 19 showing the parts when ‘the
direction to the position shown in FIG. 3, and this posi
unit has partially returned toward its _at rest position
and FIG. 20 showing the fully returned position of the 10 tion is determined by a nut 39F which engages the bracket
‘39. When the ‘brakes are applied and the pull rod 24 is
parts after the performance of the let-out operation; and
pulled to the right, as shown in FIGS. 1 and 3, the rock
as to the next normal cycle, FIG. 21 shows the parts when
the brakes are fully applied, while FIG. 22 shows the
ing assembly 34 is rocked in ‘counterclockwise direction,
FIG. 3, through a rocking stroke which in extent repre
parts at the end of the brake release operation.
15 sents the length of the stroke of the push rod 25. This
The Apparatus and Its Association With the Braking
stroke length therefore constitutes a mechanical indicai
brakes;
FIGS. 17 to 22 are diagrammatic views that illustrate
a short cycle of the apparatus as well as the next normal
cycle; FIG. 17 illustrating the normal at rest position;
FIG. 18 illustrating the end of a short stroke brake
System
For the purposes of disclosure the present invention is
tion as to whether slack adjustment is proper or Whether
slack needs to be taken up or let out, and means are
associated therewith the rocking assembly 34 for accom
illustrated herein as embodied in an automatic two-way
slack adjusting unit 20 and is shown as applied to the 20 plishing such automatic adjustment as required.
The rack R is somewhat T-shaped in cross section
adjustment of the anchoring pivot of the dead lever 21 of
as will be evident in FIG. 6 of the drawings, and at its
a conventional foundation braking system for railway
left end, as viewed in FIGS. 1 and 3, the rack R extends
cars. The slack adjusting unit 20 is mounted on the car
through an opening 42 formed in an end wall 43 of the
frame adjacent to the stationary pivot point of the dead
lever 21 of the braking system so that the dead lever 21 25 housing 3%. An angle bar 44 is mounted on the wall 43
to provide an elongated surface alongwhich the rack R
may be operatively connected to the unit 20, ‘as will be
may slide, and a similar angle 45 is mounted on the
described, and each time the car brakes are operated
end wall 43 at opening 42 to provide a similar relatively
through an application and release cycle the slack ad
long contact surface for engaging the upper teeth of the
justing unit 20 is operated through a cycle in which the
rack to guide the same. _
unit is responsive to push rod travel to maintain the same
At its right hand end, the rack R has an enlarged vhead
slack adjustment, to take up slack, or to let out slack,
H which forms a bifurcation through which the brake
as determined by such push rod travel.
For operating the unit 20 in accordance with push rod
travel, the unit 20 has a laterally extending rock shaft 22
lever pin 31 extends in connecting the dead lever 21
of the system to the rack R, it being noted that the dead
connected thereto, as will be explained, and a lever 23 35 lever 21 extends through an elongated slot 398 formed
in the side Wall of the housing 36. The enlarged head H
?xed to the shaft 22 has a pull rod 24 connected thereto
and extending lengthwise of the car to a point adjacent
and roughly parallel to the path of movement of the
push rod 25 of a brake cylinder 26. The push rod 25
has a bracket 25B thereon which connects the push rod
to one end of the live lever 21L, and the bracket 25B
is extended laterally from the push rod 25 and the pull
rod 24 extends through this bracket. The pull rod 24
also is utilized in guiding and supporting the right hand
end of the rack R. Thus, as shown in FIGS. 3 and 5,
a pair of angle bars 46 are ?xed on the inner sides of
the housing 30 to support the head H in the longitudinal
sliding movement of the rack R.
It is by longitudinal adjustment of the rack R that
the slack in the braking system is adjusted, the rack R
being shifted to the left in FIG. 3 to take up slack, and
has stop or abutment nuts 27 thereon that are so adjusted
that after the push rod 25 has been advanced for a pre 45 being shifted to the right in FIG. 3 to let out slack. This
determined distance, the bracket 255 will engage the nuts
27 andwill impart rocking movement to the rock shaft 22
in accordance with the length of the stroke of the push
rod 25. ‘This rocking movement thus varies in accord
ance with Whether or not the braking system has slack
therein within the normal or correct range, or embodies
too much or too little slack, and in accordance with the
extent of the rocking movement of the shaft 22, the auto
matic slack adjusting unit 20 is effective when required to
is accomplished by mechanism located in the housing
30 and actuated by the rocking assembly 34.
The rack R, as hereinabove pointed out, is generally
T-shaped in cross section and has a series of rack teeth
U cut into its upper surface, these teeth being ?at~topped
and relatively broad, but being at a predetermined spac
ing for purposes that will hereinafter appear. In the
lower face of the rack, a series of rack teeth L are formed
upwardly into the bottom surface, the teeth L having
either take up or let out slack in the system, as will be 55 the same spacing as the teeth U, but being more nearly
described.
pointed in character and having their opposite faces at
a somewhat greater slope.
The Structure of the Unit 20
The unit 20 comprises an elongated U-shaped housing
.
The T-shaped form or" the rack R provides ?anges F
that are located along the bottom edges of the rack
30 that is ?xed as by brackets 30B to an element of the 60 and these ?anges are utilized as mounting and support
ing means for other structural elements of the adjuster.
car frame, and within the housing 30' an anchoring or
traction means in the form of a relatively long slack ad
justing rack R is mounted for longitudinal movement.
Thus, a take-up carriage 50 has a generally U-shaped
At one side of the‘ housing 30 and near the left hand
is mounted which contains a rocking assembly 34 which
has a projecting lug 35 for connecting the end of the
rock shaft 22 to the assembly 34. The lug 35 is located
and may be reciprocated along the track R, as will be
described. The carriage 50 has a take-up pawl 52 pivoted
thereon between the opposite sides of the right hand end
portion of the carriage 50 and the pivotal support is
provided by transverse pin 53. The pawl 52 extends
at one side of a squared recess 34R formed in an axial
in the left hand direction from its pivot 53 as will be
formation, as will be evident in FIG. 6, and near its open
upper face has a pair of inwardly facing grooves 51
The end of the dead lever 21 is connected by a brake
lever pin 31 to the right hand end of the rack R as shown 65 that slidably embrace thev two ?anges P so that the car
riage 50 may be supported on and beneath the rack R
in FIGS. 1 and 4. t
,
end thereof as shown in FIG. 4, an exterior housing 32
relation in the assembly 34, and after the squared end
evidentin FIG. 3, and it has a forward end face that is
disposed at such an angle that when the pawl is pivoted
it is locked inv position. by a pin extended through the 75 clockwise into a tooth space, the end face will be parallel
of the shaft 22 is inserted into the socket or recess 34R,
3,025,932‘
5
gagement with the rack teeth L during the brake-01f pe
riods due to engagement of an upwardly projecting arm
68A of the pawl by the left hand end of the carriage 50.
When the carriage 50 is moved to the right, as will be
to the face of the tooth that is located just to the left
of such end face, and with this relationship the application
of endwise pressure engaging these faces will act to hold
the pawl 52 in its engaged relationship with respect to
the tooth L with which it has been engaged.
_ described, in the course of a brake application, the pawl
68 is allowed to engage one of the rack teeth L so that
The take-up pawl 52, however, tends to drop by gravity
out of its engaged relationship, but at certain times in
the cycle of operation of the mechanism, the pawl is
yieldingly urged toward an engaged relationship with
it is the pawl 63 which holds the rack R in position against
the brake applying forces.
52 and to the left as viewed in FIG. 7, and these arms
are connected by a follower pin 55? so that the pin 55F
may engage the lower surface of the pawl 52 to urge
the same yieldingly toward an engaging relation to the 20
disposed within the complemental opening within the
The carriages 50 and 66 are operated through re
respect to the rack. In the present instance, this is ac 10 ciprocating movements in opposite directions in the course
of a brake-applying and brake-releasing operation, and
complished by a pawl weight 55 that is pivoted on the
such movements are attained by effectually coupling the
pivot pin 53. The pawl weight 55 is extended to the
carriages 5t) and 69 to the rocking unit 34 which has its
right from the pivot pin 53 so as to normally tend to
inner or left hand end, as viewed in FIG. 6, projecting
rock in a clockwise direction about the pin 53, and
a pair of arms 55A extend to the left in spaced relation 15 through the adjacent wall of the housing 30. Thus, the
rocking unit 34 has a circular head 34H that is rotatably
from the pawl weight 55 on opposite sides of the pawl
respective rack. As above pointed out, however, this
yielding engaging force is applied to the pawl 52 in a
controlled manner according to the position of the lower
side wall of the housing 30, and means are provided on
the left hand end face of this head, FIG. 6, for actuating
the carriages 50 and 69.
In the present instance, these connections between the
head 34H and the carriages are somewhat in the nature
of geared connections. Thus, on the left hand face of the
head 34H, a projection is formed in which a plurality of'
carriage 50. This involves a cam action in which a lateral
extension of the pin 55P engages as a cam follower with 25 gear teeth 34T are arranged to mesh with complemental
gear teeth StlT formed as an upwardly facing rack on and
a stationary cam 57. The cam 57 is triangular in its gen
projected laterally from one side of the carriage 50. By
engagement of the teeth MT and StiT, the carriage 50
may be reciprocated throughout a limited range along the
side, and these faces 57L and 57R diverge upwardly, as
will be evident in FIG. 3. The cam 57 is located in a 30 rack R by rocking movement of the rocking assembly 34,
and there is a positive timed relationship of such recipro
?xed position on the inner side of the left hand wall
eral form and has a face 57L on its left hand side as
viewed in FIG. 3, and it has a face 57R on its right hand
cating movement and such rocking movement in both di
of the housing 30, as viewed in FIG. 6, so that the cam
rections of operation.
57 is effective to disable the pawl weight 55 during certain
portions of a reciprocating stroke of the carriage 50, as
will be described.
Above the rack R, and generally above the location
mounted, and this upper carriage is generally U-shaped
The head 34H also has means thereon for controlling
and limiting the movement of the upper carriage 60.
Thus, an abutment shoulder 34S facing in a clockwise
direction, as viewed in FIGURES 3 and 4A, and having
a surface formation quite like one side of the teeth 34T,
desired upward displacement by close spacing of the top
the carriage 56 with the holding pawl 68, the carriages
of the carriage 50, an upper or let-out carriage 66 is
is arranged to engage an abutment shoulder 60S onthe
in form so that the carriage 60 rides along the upper
surface of the rack R and has downwardly projecting 40 carriage 6t), and the arrangement is such that when the
rocking assembly 34 is rotated in a clockwise direction by
?anges 60F along the sides of the rack to locate the
the spring 40 to the limit established by engagement of
carriage 60 thereon. The carriage 60 is held against un
5t) and 60 will occupy the normal positions shown in
wall of the housing 30. The carriage 60 has a let-out
pawl 62 pivoted thereon by a transverse pivoted pin 63, 45 FIG. 3. In the actuation of the rocking member 34 in
the counterclockwise direction in the course of a brake
and the pawl 62 extends in a right hand direction from the
application, the lower carriage St) is moved to the right,
pivot 63 and has a forward or end face which may have
and the upper carriage 60 is allowed to move to the left
under the in?uence of its spring 65. Such left hand move
an engaging relationship by gravity. The carriage 60 is 50 ment of the carriage 6% is timed approximately with the
movement of the carriage 56, but is terminated by en
normally urged in a left hand direction by an expansive
gagement of the arm 69A with an arcuate surface 34A
coil spring 65 that acts between a ?xed abutment 66
formed on the head 34H. Thus, the carriage 60 comes
depending from the inner surface of the top wall of the
to rest, while continued rocking movement of the member
housing 30 and a projecting arm 60A that is formed at
the right hand end of the carriage 60 so as to project 55 34 in a counterclockwise direction will cause continued
right hand conditioning stroke of the carriage 50.
generally toward the rocking unit 34, and this arm 66A
In such movements, a cam 56C formed on the car
functions also in limiting the extent of left hand or condi
riage 50 is arranged to move under a laterally projecting
tioning movement of the carriage 60, as will be described.
arm 62A on the let-out pawl 62, and during the brake
Take-up pawl 52 and the let-out pawl 62 function in
holding the rack R in its set position during the periods 60 release operation this attains a controlling action in re
spect to the let-out pawl 62, as will be described.
when the brakes are released, and of course they func
When the carriages 5t} and 60 are moved in their op
tion in performing the take-up or let-out operations. A
posite or return directions toward their home positions,
holding pawl 68 is also provided which is ineffective dur
these home positions are determined by engagement of
ing the brake-off periods, but which is rendered effective
a flat surface engagement with the adjacent face of any
one of the upper teeth U. The pawl 62 is urged toward
and serves as the holding means for the rack R during 65 the rear or left hand vertical face of the cam 50C at 50H,
FIG. 3, with the opposed right hand face of one of the
downward ?anges 60F of the carriage 60.
brake application. The holding pawl 63 is mounted on
a pivot pin 69 that extends between the side walls of
the housing 30 beneath the rack R, and the pawl 68 com—
The Normal Shifting Movements of the Rack R
prises one arm of a three-armed unit, and the arm that
affords the pawl extends to the left from the pivot pin 70 Before considering the manner of operation of the con;
’ trol unit 20 in the various types of brake applying cycles,
69. The pawl 63 has an arm 68W extending to the right
and the arm 68W is wide and heavy so as to constitute a
it is important to consider the normal movements of the
weight which tends to rock the pawl 63 in a clockwise
rack R which take place particularly in the release por
direction so as to thereby engage the pawl 68 with the
tion of the braking cycle. This is important because the
rack teeth L. The pawl 68, however, is held out of en
75:
cooperation of the take up pawl 52, and the let out pawli
egozsese
8
6
62 and the holding pawl 63 with the teeth of the raclt'R
is dependent in part upon the longitudinal relation of the
rack and its teeth to'these pawls.
Thus, when a brake application is initiated, there is an
advancing movement of the push rod 25 which starts to
U-6 is located to the right of the pawl 62 at the time when
the pawl is released. Hence, in a short cycle, the pawl 62
may enter the space between the teeth U-5 and U-6 to
‘accomplish the let out operation as will be described in
further detail hereinafter. Thus the gradual relaxation
take up’ the slack in the braking system, and when this
or left hand movement of the rack R in the release of the
movement of the push rod has taken up the lost motion
between the bracket 25B and the adjusting nuts 27, the
brakes is‘ utilized under the present invention in enabling
the unit 24) to distinguish between a normal stroke of the
push rod and a short stroke of the push rod.
cycle of operation of the‘ slack adjusting unit 21} is ini-_
ti'ated. Up to this point in the braking- cycle, the rack R
has been urged in a right hand direction, FIG. 3, but has
been held against appreciable movement by the take up
pawl 52. However, in the ?rst portion of the right hand
01' conditioning movement of the take-up carriage 5d,
In Normal Push Rod Travel
In FIG. 8 the extent of movement of the push rod in a
selected cycle within the normal range is indicated in the
line 72 as being eight inches, and the relaxation in the
the holding pawl 68 is released for movement to its en
system causes the return movement of the rack R to move
gaged relationship with respect to the rack R, and since
the carriage St‘) is at this time moving toward the right
the tooth U-6 into position beneath the pawl 22 before
as viewed in FIG. 3, the holding pawl 68 will be engaged
by a particular one of the lower teeth L of the rack R,
that that thereafter in the braking cycle, the rack Q is 20
held against right hand displacement by the anchoring
action of the holding pawl 68. As soon as the holding
pawl 68 assumes control of the rack R, the locking en
gagement of the pawl 52 with the tooth with which it has
been engaged is released, and the pawl 52 is free to drop
down and out of engagement with respect to rack R, it
being noted that at certain other points in the stroke of
the pawl rides oil of the cam 50C.
In Short Push Rod Travel
Further comparison is afforded in lines 74 and '75 of
FIG. 8 where the push rod movement in a short stroke of
just under 7 inches is indicated in line ‘74, while relaxa
tion or left hand movement of the rack R, as indicated in
line 75, does not progress fast enough to locate the tooth
U-6 beneath the pawl 62 prior to release of this pawl.
As will behereinafter described in further detail, the
let out pawl 62, at certain times in the cycle of operation‘
the carriage 59', the pawl 52 will be urged toward en
gag‘ement with the rack by the pawl weight 55 under con
of the unit 20, is held in a raised position by the cam 50C
of the carriage 5i}, and in the release cycle, this pawl rides
trol of the cam 57.
30 oil of the cam 56C at the same point in the cycle of the
The rack R is‘ thus anchored‘in a ?xed position by hold
control unit 26‘ as this point is spaced from the normal
ing pawl 68 early in the brake application cycle, and as
at rest relation of the parts. This release point for the
the extension or actuation of the push rod 25 continues;
pawl 62 has been indicated at 76 in FIG. 8, and remains
the brake shoes are brought into braking engagement with
the same regardless of the length of the piston rod stroke.
the car‘ wheels and the push rod movement is terminated. 35 Thus, it may be pointed out generally that the manner of
According to common practice, the push rod stroke
engagement of the pawl 62 with the upper teeth U of the
should be kept within a limited range which for purposes
rack R is varied according to the endwise position of the
of explanation will be assumed to be between seven and
rack R at the same time when the let out pawl 62 rides off
nine inches, and any stroke greater than nine inches indi
cates that slack should be taken up in the system, while
a push rod stroke of less than seven inches indicates that
slack should be let out in the braking system. The need
for a take up operation arises because of wear in the
system and particularly due to progressive wear of the
several brake shoes. The need for let out operation
arises when one or more worn brake shoes are removed
and replaced by new and relatively thick brake shoes.
In a Long Push‘ Rod’ Stroke
In FIG. 8 of the drawings, 1 have illustrated graphically,
and in a somewhat diagrammatic manner, three lengths
of push rod strokes, and have indicated the portion of such
stroke which constitutes lost motion and what portion
constitutes the operating cycle of the control unit 29.
FIG. 8 further illustrates the operation of the rack R in
the release cycle of such push rod operations, and it might
be noted that FIG. 8, in this regard, should be read from
right to left. Thus, in FIG, 8, the line 70 indicates a con~
trol unit operation where the push rod travel is just under
nine inches, or in other words, just long enough to indi 60
cate that a take-up operation of the control unit should
take place.
_
In line 71 of FIG. 8, it is indicated that in the release
cycle. of the braking apparatus, the rack R starts a return
of the cam 50C.
In line 71 that pertains to a long stroke of the push rod,
and line 73 of FIG. 8 that pertains to the normal stroke
of the push rod, it will be evident that by the time the
pawl 62 is released the rack R has moved to the left (indi
cated along the vertical scale) in an amount su?icient to
locate the tooth U-6 under the pawl 62, but in contrast
to this, as shown in line 75 of FIG. 8, pertaining to a
short push rod stroke, it will be evident that by the time
the pawl 62 is released, the rack R has moved a somewhat
smaller distance to the left, so that when the let out pawl
62 is released by the cam 50C, the pawl 62 may enter the
tooth space between the teeth U—5 and U-6. This
mechanical distinction is provided between the normal
push [rod operation and the short push rod operation.
This causes the let out pawl 62 to drop into engagement
with the rack R during the return or right hand move
ment of the carriage 60 so as to cause a let out operation
of the unit 20, as will be explained hereinafter.
Normal at Rest Relationships of the Parts
In FIGS. 3, 4 and 7 the parts of the unit 20 are illus
trated in the normal positions which they occupy when
the brakes are released, while among the several views
that illustrate sequential operations of the unit, FIG; 9
shows the at rest positioning of the parts in a diagram
movement and shifts gradually to the left at a rate that is 65 matic fashion as the several pawls 52, 62 and 68 are
generally proportional to rate of the return stroke of the
related to particular teeth of the rack R. Thus, when the
push rod 25.
brakes are released, the lower end of the arm 36 of the
unit 20' is located and in its most left hand or home posi
tion of FIG. 9, and the lower carriage 50 is in engage
This return or left hand movement of the rack R
serves in the long cycle, and in the normal cycle, of opera
tion of the unit 20 to move the tooth U-6 into position
beneath the pawl 62 before this pawl is released by the
cam 50C, and in contrast to this, in a short cycle of opera
tion of the unit 28', the return or left hand movement of
the rack R does not progress to the same extent before the
pawl 62 is released,- so that in the short cycle, the tooth
ment with and has withdrawn the holding pawl 68. This
home position of the carriage 50 has been diagrammati
cally indicated by reference to an indicating or index line
150 that is so located as to be ‘aligned with the right hand
edge of the carriage 50 when the carriage is in home posi
tion. Thus, displacement of the carriage 50 with respect
3,025,932
'9
10
the release operation, ‘as will be described. In‘the right
‘to the index line 150 in FIGS. 9 to 22 is indicative of the
extent to which the carriage 50 has been moved from its
hand movement of the lower carriage 50 and the pawl 52,
home position.
the rack R also moves to the right, but as this happens
Similarly, the upper carriage 66 is at this time in its
the carriage 50 releases the holding pawl 68 in such
timed relation that the pawl 68 engages the tooth L-2 so
as to stop movement of the track R in the position in which
4; and in FIG. 9, the relationship is indicated by location
it is shown in FIG. 10.
of the center of the pivot pin 63 opposite a ?xed indicat
The movement of the carriage 60' continues until the
ing or index line 163. Hence, displacement of the car
‘upper carriage reaches the limit of its left hand move
riage 60 in subsequent diagrammatic views is shown by
the horizontal distance between the pivot 63 and the index 10 ment as shown in FIG. 10, and after the carriage 60 has
most right hand or home position shown in FIGS. 3 and
line 163.
stopped, the lower carriage 50 continues its right hand
When the upper and lower carriages 56‘ and 6%} are thus
movement in timed relation to the rocking movement of
disposed in their home positions, the pawls 62 and 52
' the arm 36. As the lower carriage 56 moves to the right
the follower 55F moves into contact with the cam 57 so
bear a predetermined relation to particular teeth U and
L of the rack R, and for illustrative purposes the teeth 15 that the pawl weight 55 is disabled for a portion of the
stroke and the pawl 52 drops downwardly. Then the
U and L, as shown in FEGS. 9 to 22, have been numeri
follower 55F passes the cam 57 and the pawl 52 is urged
cally identi?ed and differentiated. Thus, in the diagram
toward the rack R, vbut since the cycle illustrated in FIG.
matic views, the lower rack teeth have been numbered
10 is a normal cycle of substantially eight inch push rod
from left to right as teeth U-5 to U~9; and as a further
aid in visualizing the operation of the unit, upper tooth 20 travel, the pawl 52 engages the end edge of the tooth
L—8 and does not enter a tooth space. It may be noted
U-7 which is in a position for cooperation with the pawl
that since the pawl 52 has not entered a tooth space, it
62, lower tooth L-7 which is in position for cooperation
will be inactive in the return movement of the carriage
with lower pawl 52, and lower tooth L-2 which is in
51’), as will be described.
position for cooperation with the holding pawl 68, have
25
In the brake release operation, after a normal stroke
been shaded to some extent.
.
e
of the push rod, the parts of the unit 20' return from the
As shown in FIG. 9, the upper or let-out pawl 62 is
position shown in FIG. 10 to the position shown in FIG.
fully engaged with the tooth U~7, while the lower or take
11, and it should be observed that the position shown in
up pawl 52 is partially engaged with the space between
FIG. 11 corresponds with the position shown in FIG. 9.
teeth L-7 and L-8, and is being acted upon by the pawl
In other words, the rack R has been returned to its orig
weight 55 so that in the event of a right hand shift of the
inal position and there has been no take-up or let-out
rack R, the pawl 52 will fully engage the tooth L-7 and
operation of the unit.
will limit such shift of the rack R. Further, the holding
In the course of the release operation, it will be ob
pawl 68 which is at this time disengaged, is so related
served that the rack R moves to the left from its work
to the rack R that in the next brake application the pawl
66 will engage the tooth L-2, as will be apparent herein 35 ing position toward its returned position, as indicated
along the vertical scale by the sloping line 73A, and this
after.
movement is roughly proportioned to the push rod return
The rack R is shifted from the position thus described,
travel. in the selected example, this return movement
both in normal operations of the unit 20 and in those
progresses to such an extent that the tooth U-6 of the
cycles where take-up or let-out operations take place, and
to illustrate such changes in the rack positioning, co 40 rack R is located beneath the pawl 62 before the pawl
62 rides o? the cam 50C, it being recalled that this release
operating index marks 77 and 77R have been included in
of pawl 62 takes place at a predetermined point 76 in the
H68. 9 to 22 on the housing 30 and the rack R, respec
operation of the unit 20 regardless of the length of the
tively. These index marks are aligned in FIG. 9 where
the rack R is in a selected position of rest, and relative 45 push rod stroke.
During the time when the rack R is moving to the left
displacement of the marks 77 and 77R in other views
as aforesaid, the return movement of the lower carriage
serve to illustrate the various changed positions of the
50 is initiated and the follower SSP engages the cam 57
rack R.
so that the pawl weight 55 is rendered ineffective and the
Operation Within the Normal Range
pawl 52 drops out of engagement with respect to the
50
In H68. 9, l0 and 11 the operation of the unit 20 in
rack R. Similarly, the cam 50C remains in its position
a normal stroke has been illustrated; FIG. 9 showing the
beneath the pawl 62 so that the upper or let-out pawl 62
relation of the parts prior to the brake application; FIG.
is held in its raised or ineffective position until the point
10 showing the relationship at the end of a brake appli
76 in the cycle has been reached. While the pawl 62 is
cation where the push rod travel is about eight inches, 55 supported by the cam 50C, the relaxation movement of
and H6. 11 showing the parts after completion of the
the rack has progressed somewhat more than one-half one
brake release.
tooth space to the left, and has served to locate the top
During the initial portion of the push rod travel, the
of the tooth U—6 directly beneath the upper pawl 62.
lost motion between the bracket 25B and the abutment
Hence, as the return movement of the upper carriage 6t]
nuts 27 is taken up, and during this time the arm 36 of 60
continues, and the left hand return movement of the
the unit remains at rest. As the lost motion is thus being
lower
carriage 50 and its cam 50C continues, the upper
taken up, the take up of slack in the brake system is initi
pawl 62 is ?nally released at the point 76 indicated in
ated and will apply right hand forces to the rack R to
FIG. 8, and the upper pawl 62 drops into the tooth space
move the same until the pawl 52 fully enters the tooth
space and engages the tooth L-7, whereupon right hand 65 adjacent the upper tooth U-7 as shown in FIG. 11. This
is the same tooth space that the pawl 62 occupied prior
shifting movement of the rack R is temporarily stopped.
to the operation of the unit.
In the course of initial right hand movement of the rack
As to the lower pawl, the cam 57 has retained control
R the pawl 62 is of course raised so that it rests on top
of the pawl weight 55 until after the relaxation movement
of tooth U-6.
When the lost motion has been taken up, movement 70 of the rack R has moved the tooth L-7 beyond the pawl
52, and hence, as the carriage 50 continues its left hand
of the arm 36 of the unit 20 is started. As the movement
of the arm 36 progresses, the lower carriage 50 moves
return movement, the pawl 52 moves into the tooth space
between the teeth L-7 and L—8, this being the original
to the right and the upper carriage 60 moves to the left.
space that the pawl occupied prior to the operation of the
The cam 50C is moved into position under the pawl 62
so as to exert a controlling action on the pawl 62 during 75 unit 20.
3,025,932
11
12
Operation When the Push Rod Stroke Exceeds the
Normal Range
the tooth space between the teeth'L43 and L-4, and while‘
The operation of the unit 20 when the push rod ex
ceeds the normal ‘range is shown in FIGS. 12 to 14, and
in such an operation the unit 20 is effective to cause
fake-up operation in which the rack R is shifted one
tooth to the left to the position shown in FIG. 14.
The at rest position of the parts is shown in FIG. 12
and is exactly the same as in FIGS. 9 and 11 previously
placed su?iciently to the left to cause take-up operation
of the system.
In FIGS. 15 and 16, when taken in connection with
FIG. 14, the next braking cycle has been illustrated, and
all of the parts of the unit have not assumed full-y re
stored positions, the rack R has nevertheless been dis;
because there has been a take~up operation of the sys;
tem, this next operation of the unit 26 may be classi?ed
as a normal operation. Thus in the next braking appli-'
described. In the initial portion of the brake application,
cation, the parts of the unit 26 move from the positions
the movements of the parts of the unit 12 are exactly like
shown in FIG. 14 to the positions shown in FIG. 15.
The holding pawl 68 becomes effective on the tooth L-3
rather than on the tooth L-2 which it engaged prior to
the movements previously described that take place in a .
normal push rod stroke, and the important distinction re-'
sides in the added rocking movement of the arm 36 which
the take-up operation of the unit. Similarly, the upper
results in added conditioning travel of the lower carriage 15' pawl 62 assumes a position over the upper tooth U-6
51? toward the right. The upper carriage 69, however,
rather than over the upper tooth U—5.
has a limited conditioning travel so that its conditioning
travel in a long stroke of the push rod is the same as in
the normal push rod stroke.
7 The added travel of the lower carriage 5t} and its cam
In the brake release operation, the parts return to the
positions shown in FIG. 16 and go through a cycle of
240V movements exactly like the movements described with re
spect to the FIGS. 10 and 11, with exception, however,
that the various pawls cooperate with a different group
50C will be evident by a comparison of FIG. 13 with
FIG. 10, and it will be evident that as a result of this
of teeth of the rack R. Thus, at the end of the brake
added conditioning travel of the lower carriage 50 toward
the right, the lower pawl 52 rides olf of the end of the
tooth L-S. In this respect, FIGS; 10 and 13 should be
compared. When this occurs, the cam follower 55F has
moved to the right beyond the effective range of the sta
tionary cam 57 so that the lower‘ pawl 52 is being urged
upwardly, and as a result, the lower pawl 52 enters the
tooth space between the teeth L-8 and L-9, as shown in
FIG. 13. Thus, at the end of a brake application where
the push rod stroke exceeds the normal range, the parts
occupy the ‘relationships shown in FIG. 13.
In the brake release operation, the lower carriage 50
immediately starts its return movement to the left, and
release cycle, as shown in FIG. 16, the lower pawl 52 is
partially engaged with the tooth space between the teeth
L'~8 and L~§ as distinguished from the position of engage
ment shown inFIG. 12. Furthermore, the upper pawl
62 engages with the tooth space between the teeth U-’7
and U~8 rather than between the‘ teeth U-6 and U-7.
Thus, the parts of the unit 20 have been returned to rest
positions corresponding. to the positions of FIG. 12, but
with the rack R displaced one tooth to the left, or in other
words, one tooth in a take-up direction.
‘ Operation When Piston Travel Is Below Normal Range
In‘ FIGS. 17 to 20, the let-out operation of the unit
in a short piston rod stroke has been illustrated, and
since in such operation the parts do not in every instance
this tooth and will maintain such engagement so long as
assume the exact relationships at the end of the cycle that
there is an effective endwise force acting between the
they
had in the beginning of the'cycle, FIGS. 21 and 22
pawl 52 and the tooth L—8. The left hand force is of 40 have been employed to illustrate the normal cycle of op
course applied to the carriage 50 by the return spring 40
eration that follows a cycle where the push rod travel is
the face of the lower pawl 52 engages the tooth L—8, as
shown in FIG. 13, and is thus locked in engagement with
of the unit 20 so that so long as the braking system re-‘
mains under substantial tension, the pawl 52 cannot cause‘
left hand movement of the rack R. However, when the
tension on the rack R is reduced to an‘ amount that is less
than the force applied by the take-up pawl 52, the rack
R is moved to the left by the action‘ of the pawl 52.
This left hand movement of the rack R constitutes a
less than‘ normal.
45
,
I FIG. 17v shows the positions of the‘ parts of the unit
20 in‘ their at rest positions, and these positions are the
same as those shown in FIGS.’ 9 and 12 that have been
previously described. In‘ the brake application, the ini
tial movements of the parts are the same as herein‘b'efo‘re'
described in respect to the‘ normal cycle and the long
cycle, but in a short cycle, the lower carriage 50 has a
pointed out that the pawl weight 55 in the release cycle 50 shorter stroke‘ and comes to rest in the position shown in
goes through its normal movements as the follower 55P
FIG; 18. The upper carriage 60‘ and the upper pawl
moves under the cam 57, but as above pointed out, the‘
62, however, have substantially the same length of condi
take-up pawl 52 has been locked in its engaged relation
t‘ioning stroke in a short cycle of operation as in the
ship with the rack so that in such release cycle, the op
normal and long cycles. The differences in the stroke of
eration of the pawl weight 55 may be said to constitute
the lower carriage 50 is clearly evident by comparison of
an idle cycle thereof.
FIGS. 10 and_18,> the relationship of the carriage 50 to
In the brake release cycle that takes place, as above
the index mark 150 being substantially different.
described, after a long push rod stroke‘, it should be ob
> With respect to the upper pawl 62, it will be noted
served that while the lower pawl 52 has entered a dif
that in a shorter stroke as illustrated in FIG. 18, the
ferent tooth space and has effected a take-up operation
pawl 62 comes to rest over the top of the upper tooth
on the rack R, the upper pawl 62 drops into the same
U-S which is substantially the same as in the normal
tooth space that it occupied’ at the beginning- of the cycle
stroke of the unit, but the relationship of the upper pawl
of operation of the unit 20, and this will be evident by
62 to the cam 50C is‘ somewhat different because of the
comparison of FIGS. 12 and 14. Furthermore, the posi
shorter conditioning stroke that has been imparted to the
tion of the parts shown in FIG. 14 is somewhat different 65 lower carriage 50. Here again a comparison of FIGS.
than the position shown in FIG. 12, this being caused by
10 and 18 is helpful.
the fact that the pawl 52 remains in engagement with
The shorter stroke of the carriage 50 also results in a
the tooth L—8 while the upper pawl ‘62 engages the
somewhat different relationship of the lower pawl 52'
tooth U-7. This relationship serves to hold the rack R
to the rack R, it being noted that in the short stroke of
in position against inertia forces that may arise because
the unit, the pawl 52 remains partially in position be-'
of coupling and like operations. _ However, the fact that
tween the' lower teeth 11-7 and L-8.
the lower carriage 50 has not fully returned to its initial
In the brake release operation, however, a different
position allows the holding pawlv 68 to remain in an en
functioning of the parts takes place, and FIG. 19 of the
take-up operation in the braking system. It might be
gaged relationship. However, as the rack R has been.
drawings shows the position of the parts at substantially
moved to the left, the holding pawl 68 has moved into 75 the time of the release of the pawl 62 by the cam 50C.
13"
8,025,932
In particular it should be noted in FIG. 19 that the re-."
turn or left hand movement of the rack R, at the time
14
the lower tooth L-l, this being in contrast to its engage
ment with the lower tooth L—2 in the preceding cycle of
operation of the unit. This will be evident upon compari
when thepawl 62 is released, has not progressed to such
son of FIGS. 18 and 21. The pawls 52 and 62, as shown
a point that the tooth U-6 is beneath the pawl, but in
in FIG. 21, assume positions corresponding with the posi
contrast, has been relatively slower, so that the tooth
tions shown in the end of a normal brake operation as
space between the teeth U-S and U-6 is beneath the
illustrated in FIG. 10, but it will be noted that the lower
pawl 62. This timing is illustrated in FIG. 8 of the draw
pawl 52 in FIG. 21 is located opposite the lower tooth
ings where the return movement of the rack R is shown
L—7 as contrasted with its location opposite the tooth
by the line 75A. The different positioning of the rack
R in this instance results from the fact that the release 10 L~8 in FIG. 10. Similarly, the upper pawl 62 in FIG. 21
is located directly over the upper tooth U-4 rather than
has started at a different point in the cycle of the unit
over the upper tooth U-S, as shown in FIGS. 10 and 18.
20, so that prior to the point 76 in the cycle, the rack
Hence, when the brakes are applied in a cycle follow
R has not moved through the same proportion of its
ing a short or let out cycle of the unit 20, the rack R is
return stroke.
Thus, as will be evident in FIG. 19, which illustrates 15 placed under tension in a position that is displaced one
tooth to the right of the position that is occupied in the
the positions at this time in the cycle, the pawl 62 is
previous brake applying operation. As a result of this,
allowed to enter the tooth space between the teeth U-S
the push rod 25 goes through a normal stroke, and this
and U-6 and as shown in FIG. 19, the pawl 62 has only
is evident by the ?nal location of the arm 36 as shown in
partially entered the tooth space, but this entry is suf
FIG. 21. This position corresponds approximately with
iicient to stop the left hand or relaxation movement of
the position shown in FIG. 10 which of course shows a
the rack R. It will be evident by a comparison of the
normal cycle in the unit 20.
index marks 77 and 77R in FIGS. 18 and 19 that the
When the brakes are released, the parts of the unit 20
rack R has moved through a part of its normal relaxation
return from the positions shown in FIG. 21 to the posi
movement, but upon engagement of the pawl 62 with the
tooth U—6, such relaxation or left hand movement of the 25 tions shown in FIG. 22, and this relationship of the parts
as shown in FIG. 22, is precisely like the initial relation
rack R has been stopped. At this time in the cycle the
ship shown in FIG. 17 except that the rack R has been
lower carriage 50 has just engaged the arm 68A of the
displaced one tooth to the right from the position shown
holding pawl 68 'so that continued return movement of
in FIG. 17. The apparatus has thus been effective to ac
the carriage 50 will complete the withdrawal of the hold
ing pawl 68 to a point where the pawl cannot interfere 30 complish the desired let out function.
The short stroke operation of the unit 20 has been
with the further let out or right hand movement of the
described with relation to a stroke just slightly less than
rack R, as will now be described.
the lower limit of the normal working stroke, and such a
The arm 36 of the unit 20 will of course continue its
situation probably represents the most frequently en
return movement from the position shown in FIG. 19
to the position shown in FIG. 20, and as this takes place 35 countered situation where a let out operation is required.
There are, however, instances where a let out operation
the lower carriage 5t) completes its return movement, and
must be performed where the operating stroke of the unit
when the follower 55F rides off of the lower point of the
20 is considerably shorter than the stroke hereinbefore
cam 57, the pawl 52 will be opposite the lower end of
the tooth L—7.
Hence, as the return left movement of
the lower carriage 50 is completed the pawl 52 will par
tially enter the tooth space between the lower teeth L-6
and L-7, as shown in FIG. 20.
As the upper carriage 60 completes its return or right
hand movement, the pawl 62 will move from the posi
tion shown in FIG. 19 to the position shown in FIG. 20
to impart a slight right hand or let out movement to the 45
rack R so that the parts come to rest in the position shown ,
in FIG. 20.
The let out of the rack R has thus been
accomplished in part by limiting or stopping its relaxa
tion movement and in part by the return movement of
the pawl 62 after it has engaged the rack.
described.
Such a situation may arise where more than
one new brake shoe is substituted in the braking system of
the car, and in such an instance, an extremely short stroke
such as a stroke of about 4% inches may result in the
unit 20. In the unit 20, as herein illustrated, an auto
matic let out operation will be instituted in such a short
stroke, and in FIG. 8 of the drawings, the relaxation or
return movement of the rack R in such an extremely short
stroke has been indicated at 75B. In such operation, re
turn or relaxation movement of the rack R progresses
even more slowly than in the relaxation cycle indicated at
‘ 75A so that when the let out pawl 62 is released by the
cam 50C, the tooth space between the teeth U-S and
This let out movement that is thus accomplished in a
U-6 is located beneath the pawl 62 so that the pawl may
short cycle of operation of the unit 20 shifts the rack R
enter such space and produce a let out operation in the
slightly less than one tooth space to the right, and this.
same manner as was described hereinbefore.
results, in the assumed example, from the fact that the
Varying Operating and Installation Conditions
55
pawl 62 did not fully enter the tooth space between the
upper teeth U-S and U-6. The shifting movements of
In the foregoing description, the unit 20 has been as
the rack R, however, does amount to substantially a full .
tooth space so that an elfective let out operation has been ,
accomplished.
This will be evident by a comparison
of the position of the rack in FIGS. 17 and 20. The parts,
however, do not in such-an instance, assume a fully
normal relationship with respect to each other and ‘with
the rack, and for this reason FIGS. 21 and 22 have been
included as illustrating the next normal cycle of the unit
sumed to operate through its various types of cycles in
response to speci?c lengths of push rod travel, but it
must be recognized that in actual practice, the operation
of the unit varies to some extent according to whether or
not the car is standing or is moving at the time of a brake
application. Thus the points in the piston rod travel at
which the various types of operation of the unit are to
65 take place are established in practice with the understand
20.
ing that there may be slight but relatively unimportant
Thus, in such a succeeding normal cycle of the unit 20,
variations in actual performance due to varying conditions '
the parts move from the position shown in FIG. 20 to
that are encountered.
the position shown in FIG; 21.‘ In such movements the
The present unit is adapted for installation on cars
parts go through substantially the same movements as
hereinbefore described, particularly with respect to the 70 having AAR foundation braking systems, and the pro
vision of the lost motion connection between the pull rod
normal cycle illustrated in FIGS. 12 to 14.
24 and the push rod 25 enables the unit to be coordinated
However, this normal cycle causes the holding pawl 68 '
with the braking system in which it is being incorporated
to assume a different relation to the rack R, and this is the
vso'as to meet operating standards desired. Adjustment of
result of the let out operation thatjhas been described.
Thus, the holding pawl '68 moves‘ into engagement with 75 the nuts 27 on the pull rod serves to determine the length
3,025,932‘
15'
of push rod travel that is to establish the lower limit of»
the normal range, and such adjustment serves also to
tionships according to'the amount of relaxation movement
of the member that has taken place-when the let out pawl
establish the upper limit of the normal range of opera
is freed.--
tions, the length of such normal operating range is being
established by the tooth spacing in the rack R in combina~
2. vIn a railway foundation braking system having a
dead lever the anchoring fulcrum-of which is urged and
tion with the form and extent of the cam 57 and the cam
tends to move in‘ a'let out direction as the brakes are
50C. Speci?cally, it may be pointed out that in the unit
20, as herein disclosed, the tooth space that is employed is
% inch, the maximum stroke of the upper carriage 60 is
about 1/2 inch, while the maximum stroke of the lower
carriage is on the order of 11/2 inches. Moreover, the at
rest relation and the operating sequence of the holding
pawl 68 and the take up pawl 52 may be said to resemble
applied and which fulcrum is urged and tends to move
but take-up direction as the-brakes are released, the com
an escapement which acts to assure a limited displacement
,
I
bination of a two way automatic slack adjuster comprising
a stationarily mounted housing, an elongated rack mount
ed in said housing for’ longitudinal shifting movement and
connected at one end to said anchoring fulcrum to adjust;
ably govern the‘slack in the brake gear according to- the
longitudinal relation of the rack to the housing, a hold;
of the rack R as the brakes are applied so that the‘ 15 ing pawl on’ said housing to engage said rack to resist
movement of the rack in a let out direction when the brake
return of relaxation movement of the rack in the release
gear is placed under tension in a brake application, a rock
cycle may be utilized in providing a mechanical distinc
ing‘ assembly mounted ori said housing and connected with
the push rod of the brake gear for operation through
Conclusion
rocking strokes the length of‘ which is varied according
to the extent of push rod travel, yielding means operative
From the foregoing description it will be apparent that
ly connected with said rocking assembly to impart return
the present invention provides a two-way slack adjuster
movement thereto during return movement‘ of the push
which embodies reliable clutch structures in the nature of
rod,- a take-up carriage and a let out carriage mounted
a_ ratchet and pawl so that these clutch structures are in
e?ect self cleaning and are extremely rugged in use. It 25 for'niove'ment'along said rack, take up and let out pawls'
on the ‘respective take-up‘ and let-out carriages yieldingly
will also be apparent that the present invention provides a
tion between push rod strokes of different lengths.
two-way slack adjuster in which the normal‘ working forces
in the brake application arev taken by a holding device‘in‘
the form of a pawl which is rendered ineiiective while
urged toward engaged relationwith respect to‘the rack
and each having a ‘self locking engagement with the rack,
means operated by said rocking-‘assembly to normally
maintain said carriagesv in home‘ positions wherein said
the brakes are released, and in which the adjustable ele;‘ 30
take up and let out pawls both engage said rack to hold
ment of the unit is maintained in its adjusted relation
against undesired displacement due to impacts by the
the same against undesired longitudinal displacement, said
last mentioned means being operable during brake applica
means which are selectively effective for producing let out
or take up operation of the adjustable member.
tion to cause conditioning movements of said let out car
It will also be apparent that the present invention pro—‘
" ri'a'ge in a take up direction and said take up carriage in a
vides a two-way‘ slack adjuster wherein the slack adjusting
operations in both directions are performed during the
brake releasing portion of the braking cycle so that the
forces necessary to accomplish such adjusting operations
let out direction, means operated when said take up car
ri'age is in its‘v home position to disengage said holding
may be minimized.
Thus, while a preferred embodiment of the invention
has been illustrated herein, it is to be understood that
changes and variations may be made by those skilled in
the art without departing from the spirit and scope of the
pawl, control means including a stationary cam for dis‘
eh'g'aging'said‘ take up pawl, soon after the start of a condi
40 tionirig movement’ of the take-up carriage and effective to
maintain the pawl disengaged until the take up carriage
has moved beyond a normal stroke and then to permit en
gage'rhént of the take up pawl with theirack, said control
means being ineffective to disengage the take up pawl in
45 a‘ return stroke following such engagement, and a cam on
said take up carriage effective shortly after the start the
I claim:
1. A slack adjuster for use in a railway braking system
start ‘of the conditioning strokes of said carriages to engage
having an element constituting a tension member in the
the let out pawl to hold the same disengaged and to re-~
brake gear and urged in a let out direction as the brakes’
lease said let out pawl shortly before the completion of
are applied and through a relaxation movement in a take 50 the return movements of said carriages, said release of
said let out pawl acting when the rocking assemblyhas
up direction as the brakes are released, said adjuster com
appending claims.
prising a housing, a rigid toothed member movably
mounted in said housing and adapted for connection‘ with
moved through a normal stroke or a long stroke to engage
said let out pawl with the end of a ratchet tooth and acting
when the rocking assembly has moved through a short
such an element of a braking system, a holding pawl and
a take up pawl engageable with said member to hold the 55 stroke, to engage said let out pawl with‘ a tooth space.
3. In a railway braking system, a rigid toothed member
same against let out movement, a let out pawl engageable
constituting. a tension member in the brake gear and urged
with the member to hold the same against take up move
in a let out direction as the brakes are applied and through
ment, an operator mounted in said housing and adapted
for connection to the push rod of the braking system for
a relaxation movement in a take updirection as the brakes
movement through conditioning and return strokes the 60 are released, an operator connected to the push rod of the
braking system‘ for movement through conditioning and
length of which varies according to the extent of push rod
return strokes the length of which‘ varies according to the
movement, control means in said housing actuated by said
operator as the brakes are applied to engage the takeup
extent of push r'od movement, a frame, a holding pawl
and a take up pawl supported relative to the frame for
pawl and the holding pawl in succession and with an es
capement action with the toothed member to permit limit 65 engagement with the toothed member to control move
ed displacement of the member in a let out direction to a
ment thereof in a let out direction, said holding and take
working position in which it is stopped by the holding
up pawls being?v actuated and controlled by said operator
as the brakes are applied to engage the take-up pawl and
the holding pawl with different teeth of the toothed mem
pawl, said control means acting in a long stroke of the
operator to render said take up pawl effective on the
toothed member to impart take up movement thereto, and 70 ber in succession and with an escapement action to permit
limited displacement of the member in a let out direction
further control means on said housing actuated by said
to a working position in which it is stopped by the holding
operator to disengage the let out pawl as the brakes are
applied and effective at a predetermined point in the re
pawl, additional control means effective in a long stroke
of the operator to render said take-up pawl effective on
turn stroke of the operator to free said let out pawl for
the toothed member to impart take up movement thereto,
engagement with the toothed member in di?erent rela
3,025,932
17
18
and a let out pawl supported relative to the frame and
engageable with the toothed member to prevent movement
of the toothed member in a take-up direction, said let out
5. A slack adjuster for use in a railway braking system
having an element constituting a tension member in the
brake gear and urged in a let out direction as the brakes
panel being actuated and controlled by said operator to
maintain the let out pawl out of engagement with toothed
are applied and through a relaxation movement in a take
up direction as the brakes are released, said adjuster com~
member as the brakes are released to permit relaxation
movement of the toothed member and said operator being
prising a housing, a rigid toothed member movably mount
ed in said housing and adapted for connection with such
an element of a braking system, an operator mounted in
effective at a predetermined point in the return stroke of
said housing and adapted for connection to the push rod
the operator to free said let out pawl for engagement with
the toothed member in di?erent relationships according to 10 of the braking system for movement from a home position
through conditioning and return strokes the length of
the extent of the relaxation movement that has taken place
which varies according to the extent of push rod move
when said pawl is freed.
ment, a holding pawl connected to said housing for en
4. In a railway braking system having brake gear
gagement with the rack to hold the same against let out
operated by a push rod of a brake cylinder and including
movement, means governed by said operator to disengage
a force transmitting rigid toothed member that is op
said holding pawl at the end of a return stroke of the
positely shiftable in let out and take up directions for
operator and engage the holding pawl with the member
adjusting the slack in the brake gear and which is urged
at the beginning of a conditioning stroke of the operator,
in a let out direction as the brakes are applied and is
a take up pawl and a let out pawl, ?rst and second control
urged through a relaxation movement in a take up direc
tion as the brakm are released, the combination of a pair 20 means in said housing actuated by said operator to effect
engagement of both the take up pawl and the let out pawl
of pawls mounted for engagement with said toothed mem
with the tooth member when said operator is in its home
ber and operated by said push rod with an escapement
position and to disengage said let out pawl and said take
action to control and permit limited movement of said
up pawl after said holding pawl has been engaged, said
member in a let out direction from an initial relaxed posi<
tion to a working position, means by the push rod and 25 ?rst control means acting in a long stroke of the operator
to render said take up pawl effective on the toothed mem
operable upon one of said pawls in a brake release opera
her to impart take up movement thereto, and said second
tion in response to an unduly long push rod stroke to
control means operating at a predetermined point in the
render said one pawl e?ective to impart take up move
return stroke of the operator to free said let out pawl for
ment to said member to establish a new relaxed position
therefor, a third pawl mounted for engagement with the 30 engagement with the toothed member in ditterent relation
ships according to the amount of relaxation movement
toothed member and control means for said third pawl
operated by said push rod and rendered e?ective on said
third pawl during a brake release in response to an unduly
short push rod stroke engage the third pawl with the
toothed member to limit the relaxation movement of the
toothed member and impart let out movement thereto so
as to let out slack in the brake gear and establish another
relaxed position for such member, and said control means
being responsive in part to the relative rate of relaxation
movement of said member to render said third pawl effec
tive to stop said toothed member in its initial relaxed posi
tion when the push rod has operated through a normal
stroke.
of the member that has taken place when the let out pawl
is freed.
References Cited in the ?le of this patent
UNITED STATES PATENTS
593,553
1,074,558
1,801,854
1,947,405
1,991,262
Nicholson et al _________ __ Nov. 9,
O’Brien ______________ __ Sept. 30,
Farmer ______________ __ Apr. 21,
Camp ________________ __ Feb. 13,
Sauvage ______________ __ Feb. 12,
1897
1913
1931
1934
1935
2,886,145
Vaught et a1 ___________ __ May 12, 1959
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