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Патент USA US2111421

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March 15, 1938.
F, @_ FAiLE
March 15, 1938.
Filed April 19, 1954
3 Sheeìs-Shee't 2
March 15, 1938.
Filed April 19, 1934
3 Sheets-Sheet 5
Patented Mar. 15, 1938
Fred G. Fails, Cleveland, Ohio, assigner to The
Leonard Electric Manufacturing Company,
Üleveland, Ghic, a corporation of Ohio
Application April i9, 1934, Serial No.
6 Claims.
The general object of this invention is to pro
vide an improved electric switch of the double
break multiple-contact type.
A further object is to provide a heavy duty
5 multiple Contact electric switch wherein arcing
during making and breaking of the circuits is
greatly reduced and dangerous arcing eliminated.
A further object is to provide an electric switch
the contacts of which must be closed by appli~
10 cation of positive manual pressure and rigidly
locked in closed position by the saine pressure
as against being maintained in closed position
by resilient or other non-positive means.
A specific object is to provide an improved
15 manually operable electric switch wherein the
operations of both opening and closing the cirn
>cuit or circuits are quickly accomplished manu
ally but independently of the intentional speed
of manual operation; in other words, a “fool
20 proof” switch of this type.
A further object is to provide a “quicknnake”
and “quick break” switch in which the separable
circuit making and breaking elements are for
cibly engaged and disengaged without depend
ing upon springs to effect either engagement or
disengagement or to maintain engagement.
Still another object is to provide an exceed
ingly compact industrial multiple contact double
break switch.
A further object is to provide an electric
switch wherein the separable contact elements
are positively engaged and disengaged by the
application of manual pressure and with a wiping
wedging action.
A further object is to provide a multiple con
tact switch and casing wherein the necessary
operating elements extend only from the race
of the casing, whereby a plurality of switches ci
the type described may be mounted directly ad
40 jacent each other and efec-tively yet independ
ently operated.
A further object is to provide an industrial
multiple contact switch and fuse supporting unit
wherein fuses of different capacity and size may
be easily and quickly installed by simple ad
justment of the parts of the unit.
Still another object is to provide a multiple
contact switch including spaced stationary con
tacts and bridging movable contacts cooperable
DI C2 therewith wherein the movable contacts are so
arranged and supported that full electrical con~
tact with the stationary contacts is assured not
withstanding variations in the contac ing surfaces
and other variations incident to manufacturing
-’ the parts on a quantity production basis.
(Cl, E60-6G)
A still further object is to provide a multiple
Contact switch wherein the electrically inde~
pendent conductor elements of the switch are
more eiïectively insulated from each other to
reduce cross or short circuiting and leakage.
Other objects and features will become appar
ent from the following description wherein ref
erence is made to the drawings. ille essential
novel characteristics are summarized in the
Referring to the drawings:
Fig, i is a plan view of the switch and casing,
the right hand portion ci the casing being
broken away to show the construction of certain
of the switch parts and fuse supports;
Fig. Z is a sectional view as indicated by the
line 2_2 on Fig. 1;
Fig. 3 is a side elevation of the mechanism
which will be hereinafter referred to as the
switch unit;
Fig. Il is a transverse sectional view of the
switch unit taken along the line fl-¿l oi” Fig. l;
Fig. 5 is a detail view showing seine el" the
parts illustrated in
3 but in a different rela
tive position; and
Figs. 6 and 7 are diagrammatic sectional views
showing Various relationships between the sta
tionaryand movable contact elements oi the
switch; and
Fig. S is a detail view showing a modined 30
arrangement of contacts.
Referring further 'to the drawings, the casing
l :nay comprise a boxlike casing element having a
bottorn^` panel il and perimetral walls 3 bent up
from the base and suitably joined at the corners, 35
the casing being completed by a hired cover
panel and a movable. cover panel f5, both panels
having perimetral side
end wall flanges 'i
adapted to telesoopingly engage the
3 oi the main
part. rlìhe panel is hinged 40
to the panel 5 as at
permitting the panel to
be swung outwardly and away from the walls 3
exposing the interior or the. casing.
Located within the casing and secured to the
base panel 2 is a block it of suitable insulation 45
material such as colo molded asbestos composi
tion, this bloclr being secured -to the panel 2 as by
four screws ii extending through openings in
the cover portions oi the block
and into
threaded bosses i2 in 'the bottom panel. The
block it constitutes a unitary rigid base for the
switch unit. As shown in Figs. l, 2 and e, the
block is rectangular in shape and carries at its
sides relatively heavy bracket elements i3, pref
erably sheet rnetal, these being substantially 55
identical in form.
The bracket elements I3 have
inwardly extending flanges i5 disposed between
the underside of the switch base Ill and the cas
ing panel 2, the bracket elements being secured
to the base block I0 by means of the flanges and
suitable screws (not shown) extending through
the iianges and into suitable threaded inserts
(not shown) in the base block.
The outer ends of the bracket elements I3
carry ears i5 bent parallel to the flanges I5, the
ears being apertured to receive suitable fasten
ing screws, one being shown at I'I, Figs. 1 and
for securing the fixed panel 5 of the casing
cover to the switch unit.
The separable contacts of the switch are ar
- ranged as follows:
Mounted on the base block I0 are a plurality
of stationary electrical contacts 20, (six being
present in the illustrated embodiment) these be
20 ing substantially identical in form and electrical
ly connected to electric service wires in a manner
to be hereinafter described. The contacts 20 are
ence of the stationary and movable contacts and
conductors of the different sets notwithstanding
a considerable accumulation of foreign matter
which may be more or less electrically conductive.
Likelihood of short or cross circuiting is further
rendered negligible by reason of the fact that the
overlapping surfaces of the insulation members
clean themselves during the operation of the
switch to open and closed position, that is during
inward and outward throw of the cross head. 10
The arrangement further permits the electrically
independent contacts and conductors to be placed
closer together, saving space, i. e. permitting
greater compactness of construction. Further
protection against the accumulation of foreign
matter is afforded by cross strips of insulating
material 35 and 38 (asbestos board e. g.), see
Figs. 1 and 2. These strips are secured to the
outer edge surfaces of the barrier strips 30 and
3i as by suitable screws 39 and hold the barrier 20
strips firmly in parallel relationship.
It will be noted in Figs. 2 and 4 that the mov
able contacts 22 are secured in respective rec
tangular recesses or troughs 40 on the inward
side of the insulating cross bar 23. It will also 25
arranged in pairs, see Fig. 2, and the contacts of
each pair are adapted to be bridged by respective
generally V-shaped movable contact elements
or blades 22, three being shown (see Fig. 4) car
be noted from Fig. 4 particularly, that the same
ried on a cross head 24 including an insulating
side of the insulating cross bar is recessed as at
cross bar 23 (asbestos composition e. g.) and a
metal bar 25 inset into a rectangular channel 2‘I
bar and, being rectangular in cross section and
4I for the reception of the barrier strips of in
sulation 30 and 3|. Thus when the insulating
cross bar 23 is forced inwardly toward the base 30
block I0, the different sets of contacts and con
ductors are further insulated from each other
about three times as deep as it is wide, the bar
prevents any bending of the cross head such as
would tend to make say one of the blades 22 seat
or unseat with respect to its contacts 20 ahead of
the other blades.
ping portions of the cross bar and the barrier
strips. Likewise, the outermost contacts and con 85
ductors are fully insulated from the metal parts
of the switch, particularly the brackets I3 and
the outer side of the insulating bar. The bar
25 will be hereinafter referred to as the pressure
The bar 25 is less wide than the channel 21
wherefore the insulating bar 23 may float slightly
with reference to the pressure bar which latter
1ras its ends slidably fitted to parallel slots 26 in
ie respective brackets I3, the slots guiding the
pressure bar for true right line movement in and
out to open and close the switch contact elements
2D and 22. The pressure bar is secured in the
channel 2l by cross pieces 28 (see Figs. 2 and 4)
which are, in turn, securely fastened to the in
sulating bar 23 as by means of screws and thread
ed inserts (not shown) in the insulation material.
e individual sets of movable and stationary
contacts and the conductor elements associated
with the fixed contacts are effectively separated
from each other by barrier strips 39 (hard as
bestos board e. g.) and the outermost contacts
and conductors, that is, those nearest the bracket
elements I3 are insulated from the latter by bar
against cross circuiting by leakage by overlap
switch operating parts carried thereon.
The movable contacts or blades 22 (as shown
in Figs. 6 and '7) each comprises a single V 40
shaped bar having outwardly extending ears 22’.
seated at the bottom of the respective rectan
gular troughs 40. Suitable screws 42, extending
inwardly through openings 43 in the insulating
bar 23, are threaded into the ears 22’ and hold 45
the contact members 22 in fixed position on the
insulating bar 23. The stationary contacts 20
re also V-shaped and each comprises spaced
contact arms 50, see Figs. 4, 6, and '7, connected
by a base loop 5I. The base loop is generally rec 60
tangular as shown and the bottommost portion
is apertured as at 52 to receive attaching screws
53 extending upwardly from the base block in
suitable openings therein as shown in Fig. 2.
Preferably the arms 50 are buttressed by gen
erally U-shaped spring members 55, the arms of
rier strips 3l, constructed similarly to the bar
rier strips 30. The contours of the barrier strips
3D and 3l are best illustrated in Fig. 2. The strips
60 have substantially straight inner edges and these
rest in grooves 33 in the base block I0, said edges
extending the entire length of the base block.
which extend in embracing relation to the con
tact arms 50. The bases of the spring members
are likewise apertured to receive the screws 53.
The screws threadingly engage openings 56 in 60
conductor bars 51 and 51’.
The barrier strips, incidentally, greatly strengthen
angularity between the arms of the V-shaped
movable contacts or blades 20 and the resilient
arms 50 of the ñxed contacts is dissimilar, the 65
angle between the arms 5i) being smaller. The
purpose of this is to provide a yielding wedging
and sliding Contact between the arm portions
the block against transverse cracking. Each of
the strips 33 and 3l is cut cut at 34 substantially
centrally thereof and rectangularly as shown in
Fig. 2 to embrace the insulating cross bar 23.
The latter has parallel grooves 35 on its oppo
site surfaces into which the marginal portions
of the barrier strips adjacent the rectangular
notches 34 extend.
The tongue and groove relationships just de
scribed between the insulating cross bar and the
rectangular notches 34 in the barrier strips 3i)
75 and 3| further insures the electrical independ
Referring to Fig. 6, it will be noted that the
of the contacts 20 and 22 as the same are brought
together. Fig. 6 illustrates in broken lines at
22x the condition when the contacts 20 are first
brought into engagement with the arms 59 and in
Fig. 7, the full Contact position with respect to
both cont-acts is shown.
As shown in Fig. 2, the conductor bars 5l (one
being shown) extend to suitable detachable con
rollers occupy the circumferentially extending
ductor wires 58 secured as by screws 59 to
portions 19h of the cam slots and are retained
threaded metallic inserts 59' in the base block.
The bars 51’ extend from the respective oon
tacts 20 and are electrically associated with suit
able iuse clips 60, see Figs. 1 and 2. The fuse
clips 60 are of conventional construction and
may be secured to» the base block I0 by suit
able screws Si engaging threaded inserts 6l’ in
the base block.
A fuse of conventional type adapted to be
supported by clips such as 60 is shown in Fig. 1
at F. Each of the fuses has one of its ends
in this position, see Fig. 3, by the shoulder 19e.
lThe path of the shoulder 19e intercepts a` poru
tion of the normal path of the roller while the
roller is traveling along such portion and con
supported by one of the clips 60, just described,
and the opposite end by one of a series of similar
fuse clips 62 (one being shown) connected with
conductor wires 63. The clips 62 and connec
tions are carried on a common insulating block
t5 secured to the base panel 2 of the switch cas
ing as by suitable screws 61. The block may
be positioned as illustrated in Fig. 1 or, if it
is desired that a shorter fuse (of less capacity)
be employed, then. the b-lock 65 may be moved
toward the base block l0 of the switch, the
screws 61 then entering other openings, one of
which is shown at 68, Fig. 1, in the casing panel
This adjustment may be done by means of
a screw driver without having to remove the
casing l from. the wall or to disturb the switch
The operating mechanism for the cross head 24
is best shown in Figs. 1, 3 and 5. Supported
on a suitable rock shaft 10 mounted in the
brackets i3 are a pair of pressure bar operating
cams 12 and 13. One of these operating cams,
namely 13, has an extension 14 passing out
wardly through a slot 5a in the fixed portion 5
of the casing cover and this extension 14 carries
an operating handle 15, mounted on a suitable
40 pin 16, by which the operating cams are turned
manually to move the cross head. The exten
sion 14 also has an arm 14a (Fig. 3) projecting
into closely overlying relation to the movable
cover panel 6 when the switch is closed whereby
opening of this cover panel about its hinges 8
automatically opens the switch contacts.
sequently the roller must be slightly stressed out
of its normal path by the shoulder to pass the
same, whereupon it lies in the portion 1Gb as
shown in Fig. 5 and must remain in this position 10
due to the fact that the circumference of the
roller is closer, at a point beyond the shoulder,
to the pivotal axis 10 than is the point of con
tact of the shoulder with the roller circum
ference. This accomplishes the desired result 15
of holding the blades and contacts 22 and 2S
rmly in full contact against accidental dis
lodgment and assists in the quick making and
breaking operations oi the switch by interpos
ing a “hazard” with respect to both operations. 20
Various parts of the switch are subject to sub
stantial stresses as the rollers ride from one
portion of the cam slots to the other but the
parts so subjected are sturdily built to withstand
the strains and the rollers and cams are hard 25
ened to withstand the wear.
The cross head 24 is normally biased into open
position by suitable springs 82 and levers 83,
the springs being connected to the respective
bracket elements i3 and to the levers 83, as 30
shown in Fig. 3. The levers are pivoted to suit~
able ñxed pins 34 on the brackets i3 and have
slots 85 emb-racing the pins 18 of the pressure bar.
As will be seen from Fig. 3, the springs 82 tend,
on contracting, to throw the pressure bar to 35
switch contact releasing position. These springs
and levers 82 and 83 accomplish “quick break~
ing” of the contacts at 2€? and 22 as soon as the
pressure bar operating cams are turned to move
the rollers 8G beyond the shoulders 19o. The 40
manual force necessarily required to release the
rollers adds to the quick breaking action or the
springs 82.
In order that the operator cannot hold back
the cross head against the quick breaking action, -45
just described, the operating handle 15 has a lost
Openings 14h and 14o' may also be provided
motion connection with the cam 13, as illustrated
in the cam extension 14 for the purpose of
permitting the cam to be locked (as with a
padlock) with the switch contacts in open or
closed position as desired.
Preferably the pressure bar operating cams
in Fig. 3.
have non-circular openings 11, one only being
shown, embracing complementary non-circular
To secure “quick making” of the contacts a
sliding bar 90 is provided generally parallel t
the slots 26 of the bracket element i3 shown
Fig. 4, the bar 9U being carried on the pin
between the cam 13 and lever 83. A strap
is shown for additionally securing the bar Sii
f end portions of the rock shaft 10 and the cam
may be held onto said non-circular shaft por
position, the strap being secured to the adjacent 55
tions by suitable cotter pins as shown. The
opposite ends of the pressure bar 25 have sub
latter permitting the strap to be swung aside
about the rivet to permit assembly of the bar
90 into position. Near the lower end of the bar
9U is an inwardly extending pin 9i of a diame 60
stantially cylindrical pins 18 preferably integral
therewith and extending through cam slots. 19
in the respective cams 12 and 13. The slots
are identical in contour and the contour is best
illustrated in Fig. 5. The pressure bar pins 18
carry suitable hardened rollers 80 which ride
on the cam surfaces of the slots 19 which will
now be described.
Each cam slot 19 has a portion 19a extending
generally radially from the axis of the rock
shaft and a circumferentially extending portion
19h, the latter portions forming retaining shoul
ders 19e for the respective rollers 8B. When the
switch contacts 2B are in the open position, illus
traied in Figs. 2 and 4, the rollers 80 occupy the
radial portions 19a of the cam slots and when
lthe contacts are closed, ‘see Figs. 3> and '7, the
bracket I3 as by a rivet 94’ and screw 94” the
ter substantially the same as the width of the
slot 26 but easily slidable therein.
The slot 25
has, near its lower end, a notch G2 which, in the
closing operation of the switch, receives the pin
9| as a “hazard” and impedes the closing opera 65
tion of the switch due to the fact that the end
of the bar 9D, which carries the pin 9|, is drawn
toward the notch by a suitable tension spring 93
and bar 90atrespectively.
its opposite ends to the bracket
The relationship of the switch contacts and
blades at a time when the pin âl engages the
notch 92 is shown in Fig. 6, (full line showings
of both parts). Referring to Fig. 5 and assurn«
ing that the cam 13 is being rotated in a counter 75
clockwise direction (closing the switch) it will
be seen that before the rollers B0 can enter the
circumferentially extending portions '19h of the
cam slots the pin 9| will have to be forced out
of the notch. This requires considerable force
and the speed and pressure of the operator’s
hand on the handle 'l5 must be increased sev
eral fold after the pin encounters the notch 92
and before the switch contacts can be fully
10 closed. The detaining forces are released upon
the pin slipping out of the notch but the excess
pressure on the operating handle continues mo
mentarily and is always sufficient to quickly
close the contacts and seat the rollers 80 into
provided with one or more reinforcing bars of
copper e. g. as at |05 and |06, the portion there
of between the two wedge-shaped elements of
a single contact bar being secured to the insu
lating cross bar 23 as by screws for example
(not shown) entering suitable openings in the
reinforcing bar or bars. The stationary con
tacts may be made as shown in Fig. 8, separate
arm strips being shown as secured in slots |01
in .a base element oi' copper e. g. |08.
The arrangement of V-shaped contact ele
ments may be reversed if desired; that is to say,
the wedge members may be carried on the base
block in some instances and the wedge receiving
15 the circumferential portions of the cam slots,
contact members carried on the cross head.
mechanically locking the contacts in closed po
sition (see Figs. 3 and 7).
In connection with Fig. 5 it should be noted
that the pin 9| is embraced by the notch 92 about
20 substantially one half of the pin circumference.
In addition, a line through the axis of the pin
9| and axis of the pin 10, by which the bar 9G
is carried, intersects the wall of the notch 92
beyond the pin in the direction of movement
toward contact making position. Thus when
moved toward contact making position, as` the
pin 9| becomes fully seated in the notch 92, it
becomes very diñicult to‘ unseat by pressure
I claim:
1. In an electric switch, an insulating base,
spaced contacts carried by the base, a. frame
carried by the base and surmounting the same,
exerted on the bar 90 in the same direction.
30 Upon movement in the opposite direction, how
ever, this line of force lies outwardly beyond the
wall of the notch so that the pin can wedge the
bar 90 to the right and release. It is for this
reason that the speed of movement, as above
35 mentioned, is important.
When operating at
suflicient speed the pin 9| will not become fully
seated in the notch as it passes the same and
consequently the resisting wall of the notch will
be operating well out on the sloping surface of
40 the pin 9| and the bar 90 will be moved onward
to the right. A speed sufficient to cause the pin
9| to partially jump the notch 92, however, is
also such as to assure that the contact making
position will be reached as the operator cannot
45 even intentionally arrest movement from so
lgreat a speed between the time the pin 9| jumps
the notch and the blades come into contact.
When the pin 9| has moved to a position in
which it has passed the notch 92 or is only par
tially seated therein so that it can be moved
onwardly and not restrained by the notch, the
roller 80 will have passed the peak 'l9c of the
cam and will promptly be locked in position for
maintaining the contact relation of the con
In heavier duty types of switches it is neces
sary to increase the gauge of the metal of the
contacts to an extent such that the design of
contacts illustrated in Figs. 4 and ’l is somewhat
impractical. In such cases, it is preferred to
make the generally V-shaped movable contact
members or blades in generally triangular shape,
as illustrated in Fig. 8 at |90, the edges of the
strip forming the blade being adjacent the arms
|0| of the fixed contacts rather than opposite
the fixed contacts as in the previously described
arrangement. This modification of contacts
preferably includes pressure affording spring ele
ments such as |02 for the movable contact.
said frame having parallel slots at opposite sides 20
of the base, a cross head mounted in said slots
and a bridging contact element carried on the
cross head adapted to cooperate with the spaced
contacts, operating means carried on said frame
for moving the cross head inwardly and out 25
wardly in the slots, and a hazard device carried
by said cross head and comprising a bar piv
otally mounted on the crosshead for swinging
movement transversely of one of the slots and
having a pin slidable in said one of the slots, 30
the latter slot having a notch adapted to re
ceive the pin during its inward movement in a
direction to close the switch, and resilient means
yieldably urging the bar transversely of said
one of said slots and opposing movement of the 35
pin out of the notch at a time when the elec
trical contacts are in approximately closed posi
2. In an electric switch, cooperable contactors,
a carrier supporting one of said contactors and
movable toward and away from the other con
tactor for effecting the contact relation, a frame
movably supporting said carrier, lineal guides
for guiding said contactors to and from con
tact relation, an operating cam pivotally mount» 45
ed on the frame, a pin on the carrier engage
able with the cam for operation of the carrier
thereby and guided lineally in said guides, and
the pivotal axis of the cam being spaced later
ally from the path of travel of the pin, said cam
including a pin actuating cam surface extend
ing generally radially from the pivot axis of the
cam and shaped so that the force of `the cam
is applied generally parallel to the lineal guides
during substantially the entire movement of the
carrier and a pin retaining surface extending
generally circumferentially of the pivot axis of
the cam, said circumferentially extending sur
face being engageable with the pin only in the
closed position of the contactors and having a 60
shoulder for locking the pin in seated position,
means yieldably urging said carrier away from
contact making position, hazard means cooper
able with the carrier when the carrier is moved
almost to contact making position by the cam
with a predetermined force >applied to the cam
and opposing further movement toward said po
sition, said hazard means being inoperative to
oppose -said movement consequent upon a pre
70 spring |92, as illustrated, comprises a generally
-determined greater force .applied to .and by said
U-shaped strip of spring metal secured between
cam for moving the carrier toward the contact
the arms |03 of the movable Contact, with the
base secured to the closed portion of the strip
forming the blade |00 `as by a rivet or screw
75 (not shown). The movable contact may also be
position, said hazard means being positioned to
operate just prior to the engagement of the pin
by the pin retaining surface of the cam.
3. In an electrical switch, a pair of cooperable
contactors, a carrier supporting one contactor
and being movable toward and away from the
other contactor for effecting the contact relation,
a frame, a guideway in the frame, a guide on the
carrier accommodated in the guideway for guid
ing the carrier in a generally linear path to and
from contact making position, a cam pivotally
mounted on the frame for rocking movement, the
pivotal axis being offset transversely of the path
10 of travel of the carrier from the guideway, said
5. In an electrical switch, a pair of cooperable
contactors, a carrier supporting one contactor
and being movable toward and away from the
other contactor for effecting the Contact relation,
a frame, a guideway in the frame, a guide on the
carrier accommodated in the guideway for guiding
the carrier in a generally linear path to and from
contact making position, a cam pivotally mount
ed on the frame for rocking movement, the piv
etal axis being offset transversely of the path of 10
cam having an operating surface coacting with
travel of the carrier from the guídeway, said cam
the guide for moving the carrier to Contact mak
î“ving an operating surface coasting with the
ne for moving the carrier to contact making
ing position, said surface extending transversely
of the path of travel of the guide in the guideway
and being conñgured to extend at substantially
right angles to the guideway at the instantaneous
guide engaging portion of the surface throughout
the major portion of the travel of the carrier,
whereby the force and movement delivered by the
surface is substantially directly parallel to and
along the guideway.
íl. In an electrical switch, a pair of cooperable
contactors, a carrier supporting one contactor and
being movable toward and away from the other
contactor for eiîecting the contact relation, a
frame, a guideway in the frame, a guide on the
carrier accommodated in the guideway for guid
ing the carrier in a generally linear path to and
from contact making position, a camA pivotally
mounted on the frame for rocking movement, the
pivotal axis being offset transversely of the path
of travel of the carrier from the guideway, and
positioned close to the level of the guide when
the carrier is in fully open position, said cam
having an operating surface coacting with the
guide for moving the carrier to contact making
position, said surface extending transversely of
the path of travel of the guide in the guideway
and being configured to extend at substantially
right angles to the guideway at the instantaneous
guide engaging portion of the surface throughout
the major portion of the travel of the carrier,
whereby the force and movement delivered by the
surface is substantially directly parallel to and
along the guìdeway.
osition, said surface extending transversely of
path of travel of the guide in the guideway 15
nd being configured to extend at an angle to
the guideway at the instantaneous guide engag
ing portion of the surface such that the greatest
component of force of the surface on the guide is
parallel to the guideway throughout substantially 20
the entire movement of the carrier.
6. In an electrical switch, a switch box, a pair
of cooperable contactors mounted therein, a car
rier supporting one contactor and being movable
toward and away from the other contactor for ef
fecting the contact relation, a frame for support
ing and guiding the movable contactor, a cam piv
otallv mounted on the frame for rocking move
ment and being cooperable with the movable con
tactor for moving the same to contact making po 30
sition, said switch box having a front wall ex
tending at right angles to the plane of the cam
and a door hinged to the switch box and forming
a continuation of the front Wall when closed, said
front wall having a slot, said cam having a por 35
tion extending through said slot to the outside
ci the box, said extending portion of the cam hav
ing a lug portion overlying said door when the
door is in closed position and being engaged by
said door upon opening thereof to move the cam 40
to contact breaking position, and an operating
handle connected to the outwardly extending por
tion of the cam.
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