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Патент USA US2121256

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Juhe 21, 1938.
2,121,256
B. s. MINOR
SHEAVE BLOCK CONSTRUCTION
Filed Jan. 2'7, 1956
2 Sheets-Sheet l
’
gnwcnko'o
Ban‘ 5 Minor‘
June 21, 1938.
2,121,256
B. s. MINOR '
SHEAVE BLOCK CONSTRUCTION
Filed Jan. 27, 1936
38266 32 41 42
_ 2 Sheets-Sheet 2
40
26a 45’
‘95
94
65
9
87 86 65
Z] wow/Wye
' 60m‘ 5. Minor
Patented June 21, 1938 '
, 2,121,255
paired stares Parent ort‘ics
2,121,256
SHEAVE BLOCK CONSTRUCTION
Burt 5. Minor, San Pedro, (lalili, assignor to
Regan Forge & Engineering Company, a cor
poration of California
Application January 27, 1936,’.Serial No. 60,989
14 Claims. (01. 254-492)
This invention relates to hoisting equipment of drill pipe. Little or no attention has to be
‘ used in, connection with the drilling of wells
given to the swinging of the'traveling block.
and is an improvement of ,my invention N0.‘U. S.
1,570,271 entitled Sheave block issued January 19,
r
1926.
.
0
This type of equipment, especially under mod
ern drilling practice, must be capable of hoist
ing extremely heavy loads at a high rate of speed,
also the traveling block must be of suf?cient
10 weight so that when-it is rove with multiple
cable lines, it will maintain sufficient tension on
the line to withdraw it from the hoisting drum
when the traveling block is lowered without a
load attached and likewise properly spool the
cable line on the‘ drum when the traveling block
is raised with no load attached. ‘It is well’rec
‘ognized that when the cable line is smoothly and
tightly wound upon the hoisting drum, the life
of the cable line is greatly increased.
so
‘ V
-
The ever increasing depths to which wells ar
being drilled, require that the cable line be like
wise increased in diameter and be compounded
with a greater number of reevings, also, the
sheaves must be of the maximum practical di
0 ameter tovreduce bending stresses in "the cable
' lines.
Likewise the increased loads required to
be hoisted require bearings of a greater capacity
and of anti-friction type.
'
The rate of speed at which the blocks can be
N O operated also depends upon the time required
I by the derrick man for attaching and detach
ing the drill pipe and casing as it is being'with
drawn or run in the well hole, which in turn is
governed, to a degree, by theattention which
must be given to the lateral swinging, of the
traveling block to avoid colliding with the “?n
ger board” or the pipe stacked behind the same.
With the types ‘of blocks being used at pres
ent, if the number of sheaves be increased to
lo more nearly meet the present requirements the
traveling block becomes so wide across the face
‘ width of the sheaves that the space behind the
?nger board, and in whichv the drill pipe is
stacked is so reduced that at times, when, the
45 well hole is drilled to great depths, all of the'
_
[It therefore becomes a primary object of this '
invention to produce a sheave block design of
the class described which is so designed that the
face width of the block is materially reduced be U!
yond what has heretofore been obtained in blocks
with'a ‘corresponding number of sheaves thereby
improving working conditions in the derrick and
facilitating drilling operations.
,
There is also an advantage gained in having
the sheaves of the crown block grouped closely
together, as it‘ permits the cable lines leading
from the crown block sheaves to the traveling,
block sheaves to fair lead more ‘correctly in line
with the grooves of the sheaves, also the cable
15"
line leading from the crown block sheaves to
the hoisting drum will fair lead'to a more cen
tral position ‘on the drum thereby improving
spooling of the cable line on‘ the hoisting drum
and consequently increasing the life of the line. 20
In the sheave block construction shown in my
former patent referred to hereinabove, I pro
vide ‘a design in which the bearing surfaces for
the sheaves is substantially increased ‘without in
creasing the overall face width of the sheave 25'
assembly. This is accomplished by arranging
the sheaves in two vertically spaced groups and
in staggered relation with each other, the sheaves
being supported ‘between plates and each sheave
having gudgeon bearings in the two adjacent
plates.‘ In this type of construction the vertical
distance between the axes of ‘the two groups of
sheaves is less than the radius of the individual
sheaves‘ and the face width of the sheave as
sembly is substantially equal to the combined
cross sectional thicknesses or widths of the indi
vidual
In the
sheaves
deviceand
contemplated
plates.‘
by the present in
vention I propose to provide added bearing sur
faces for, the sheaves by-arrang'ing them in stag
gered relation with each other and supporting
them between spaced plates, but in addition to
this my invention contemplates a novel construc
tion and arrangement of the sheaves and plates,
drill pipe cannot be stacked in the same corner, I whereby the overall face width of the sheave as
‘requiring that part of the drill pipe be stacked sembly is substantially less than the combined
in other corners of the derrick.
cross sectional widths of the sheavesv and plates.
By reducing the width of traveling block, it ‘ In one preferred form of my invention I provide
will be seen that the above conditions will be a sheave assembly consisting of two vertically
greatly improved, the ?ngerboard can be moved spaced groups of sheaves in which the overall‘
more closely to ‘the center of the derrick, allow
face width of the sheave assembly is less than the
ing the stands of drill pipe to be positioned more combined cross sectional widths of the sheaves
‘ closely to the point of application, also allow
alone. In other, words, this invention contem
.55 ing more room in which to stand more stands plates a sheave assembly consisting of two ver
2
2,121,256
tically spaced banks of sheaves in which the
overall width of the entire sheave assembly is
approximately equal to the overall width of the
widest bank alone. My invention also contem
plates the use of equal diameter sheaves through
out the entire assembly and the arrangement of
such sheaves in a manner such that the lines
or cables leading from the sheaves in one group
will pass between the ?anges of adjacent sheaves
10 in the other group.
My invention also contemplates improved bear
ing means for supporting the sheaves in assem
blies of the general character referred to above.
The details in the construction of certain pre
15 ferred forms of my invention will be best un
derstood from the following description of the
accompanying drawings which are chosen for
illustrative purposes only and in which
Fig. 1 is a vertical section illustrating a pre
20 ferred embodiment of the invention;
Fig. 2 is a vertical section taken in a plane
represented by the line 2—-2 of Fig. 1;
Fig. 3 is a plan section taken in a plane repre—
sented by the line 3—3 of Fig. 1, showing the bot
25 tom sheave and bearing assembly in outside view
and illustrating the ‘manner in which the sheaves
of one group are spaced apart to permit the lines
or cables from the other group being rove there
between;
30.
,
Fig. 4 is an enlarged fragmentary sectional ele
vation taken in a plane represented by the line
4—4 of Fig. 2 and‘ illustrating one preferred form
of sheave bearing construction contemplated by
this invention;
35
Fig. 5 is a sectional elevation similar to Fig.
1 showing a modi?ed form of the invention;
Fig. 6 is a sectional elevation taken in a plane
represented by the line B—6 of Fig. 5, and
Fig. 7 is an enlarged sectional elevation which
40 may be considered as having been taken in a plane
represented by the lines 1-4 of Fig. 6 and illus
trates the details in the construction of another
form of sheave bearing mounting. .
45
More particularly describing the invention as
herein illustrated, reference numeral ll indicates
what I may term a frame which embodies two
longitudinal main side plates l2 and I2’ con
nected at their upper ends through the medium of
a top cross member or pin l3 provided with
spacers generally indicated by reference numeral
50 [4, and at their lower ends through the medium
of a bottom cross pin l 5 which is associated with
spacing collars generally indicated by reference
numeral I6.
-
It will be observed that I have chosen for the
55 purpose of illustrating the invention herein a
traveling block such as is used in oil well drilling
practice in which event the top spacing members
l4 constitute the lower loops in a strap assembly
I8 whereby the traveling block assembly may be
60 suspended from a system of lines or cables (not
shown) and the bottom spacing members l6 con
stitute portions of a bottom strap assembly H!
which is adapted to be connected through a yoke
attachment 20 to an elevator hook or other suit
In this connection, how
ever, it is to be understood that the invention'con
templated herein is not many way limited to
use in connection with a traveling block assem~
bly since by slight modi?cation in the frame con
65 able attaching means.
70
groups of sheaves indicated generally by reference
numerals 22 and 23 which are supported on axle
or bearing means indicated at 24 and 25. In
the form shown in Figs. 1 and 2 the bottom group
22 consists of three sheaves 22a, 22b and 22c 11
and the top group consists of two sheaves 23a
and 231). It will be understood of course that the
number of sheaves may be varied within rela
tively wide limits depending upon the maximum
loads which the unit is designed to handle but in 10
all events when following this form of the in
vention, the two groups of sheaves are arranged
so that their peripheries at the adjacent edges
are either adjacent to or slightly-spaced away
from each other and the sheaves in the two 15
groups are in horizontally staggered relation.
In order that the individual sheave members
may have the bearing surface required for the
great loads which they must carry, it is important
that the sheaves be supported from plate mem 20
bers mounted in and forming part of the frame.
Also, since I am employing sheaves of equal diam
eter throughout, it is important as pointed out
above, that the individual sheaves in one group
be arranged in horizontally staggered relation 25
with the individual sheaves of the other group
so that the lines or cables may pass from the
sheaves in one group between adjacent sheaves
in the other group and since this invention con
templates a sheave construction of minimum face 30
width, the present embodiment of my invention
is designed so that the ?anges of the sheaves in
one group overlap the ?anges of two adjacent
sheaves in the other group. Inother words, it
will be observed from Fig. 1 that the ?anges on 35
the sheave 23a, for example, both overlie or over~
lap the inside ?anges 0f sheaves 22a and 22b in
the lower group 22 and as will be observed from
Fig. 3 the space between the adjacent sheaves is
just suf?cient to permit a cable as indicated at 40
C being passed therebetween.
For the purpose of obtaining the various fea
tures enumerated above, with a sheave assembly
of minimum length, I provide supporting means
for the upper group of sheaves 23 which are
shown as comprising a plurality of sheave sup
porting plates 26a, 26b and 260, such plates being
suspended from the top cross support l3 and ex
tending downwardly adjacent the sheaves in
group 23, terminating at the intermediate portion 50
of the frame.
These plates 28, etc. are shown
as being triangular in shape ‘but may assume any
desired shape so long as their transverse diam
' eters are less than the diameter of the sheaves
to permit free action of the lines or cables.
The lower ends of these plates are provided
with openings 28 and 28' which receive inter
mediate cross supports or pins 29 and 29’, such
pins being mounted on the main face plates l2
and I2’ and constituting a part of the frame. 60
This group of top supporting plates 26a. etc., are
individually provided with medial openings 30
through which the bearing means 25 extend.
The details in the construction of the bearing
means will be described later in the speci?cation 65
but su?ice it to say at this time that it consists
of a main cross pin 3| having its ends secured
in the side plates I2 and i2’ and individual roller
bearing assemblies 32 which support the respec
tive sheaves.
70
struction the unit can be readily adapted for rigid
Associated with the bottom group of sheaves
support and use as a crown block in conjunction
22 are bottom supporting plates 33a and 33b
which are mounted on the pins 29 and 29' at their
upper ends and are secured in the cross pin l5
with a traveling block of the type shown herein.
In this form .of my invention the sheave as
.75 sembly itself consists of two vertically spaced
, at their lower ends.
These plates 33a and 33b 75
- 2,121,256
are also ‘shown as being of ‘substantially triangu
lar form with the apex of the triangle at the
lower end and are provided with medial openings
30’ through which the bearing assembly 24 ‘for
' the bottom group of sheaves extends.
It will be observed from Fig. 1 that the indi
vidual plates in each group are opposite the indi
vidual sheaves in. the other group, also that the
cross sectional width of these plates is less than
10 the cross sectional width of the sheaves sothat
, the flanges of the sheaves in the one group over
lap the flanges of the sheaves of the other group
and the overall face Width of the complete sheave
assembly is thereby substantially less than the
combined widths of the individual sheaves and
consequently is much less- than the combined
widths of the individual sheaves and plates.
Although various types of bearing mountings
may be employed for supporting the sheaves in
20 a construction of the type described above, I have
shown in Fig.4 a preferred form of bearing con
struction in which it will be observed that the
cross pin 3! is secured between the. two main face
plates l2 and i2’ through the medium of bushing
members 35 and 35' threaded on opposite ends of
the pin and locked in place by means of dowel
screws 36. Spacing rings 38 and 38' are shown
as being interposed between the main face plates
and the outer sheave supporting plates 26a and
28o. The roller bearing mountings 32 are shown
as comprising outer race members 40 mounted
in and locked with the sheaves in any suitable
manner. inner race members Ill which ‘are sweat
e-cl or otherwise rigidly secured on the pin 3i and
rollers 42 interposed therebetw-een and held in
place in any conventional manner such as by
means of retaining rings d3. For the purpose of
lubricating the bearings I show the pin 3! as
being provided with ducts Ml, the outer ends of
40 which are equipped with grease gun connections
indicated at 45.
l
i
v
'
-
It will be observed from Fig. 2 that the trans
verse width of the main plates l2 ‘and i2’ is
slightly greater than the diameters of the sheaves
'22 and 23 and forthe purpose of giving added
rigidity to the frame and also protecting the’
sheave assembly, I show the space between the
side edges of these main plates as being equipped
with cover plates 48: and 618’ which are secured
to the main plates in any suitable manner such
as by means of overlapping ears and set screws 49.
As was pointed out above in connection with
the description of Fig. 2, both the top and bottom
sheave supporting plates are mounted on the pins
55 29 ‘and Z9’ and with this construction in order
to obtain a unit of minimum length, in other
words, to bring the sheaves into close proximity
with each. other, it is an important feature that
the inner edge of each plate ‘be formed‘ in concave
60 relation with the oppositely disposed sheave mem
her which,
has been indicated above, ‘is in the.
same plane with the plate. in question. In other
words, the inner edges of the plates in groups 26a
associated with the usual suspending or rigid sup
porting means discussed in a general way above.
The chief distinction between this form of my
invention and that described in connection with
'Figs. 1 and 2 resides in the fact that the plate
members 62a, 62b, 62c, 62d, and 62e extend
throughout the full length of the frame having
their opposite ends supported by the pins iii and
BI’.
‘
>
‘The sheaves in this form of my invention are 10
arranged in two groups vertically spaced from
each other as indicated by reference numerals
M and E5. The individual sheaves in these two
groups are arranged‘ in horizontally staggered
relation with each other and are of substantially 15
equal diameter throughout, like the sheaves de
scribed in connection with Figs. land 2.
In order to obtain a decreased overall length
of the unit, the axle means 66 and 67! which sup
port the two sheaves groups are spaced‘ apart
from each other at a distince only slightly greater
than the radial distance from the axle to the
periphery of the sheave group. In this way the
two groups of sheaves‘ extend past each other in
vertical planes so that a portion of one group lies 25
between a corresponding portion ‘of the sheaves
in the other group. .
It will be observed from Fig., 5 thatthe indi
vidual sheaves are provided with flange members
which are of greater cross ‘sectional width than 30
the spokes or webs of the sheaves. and I take
advantage of this fact and the structural feature
just pointed out above, to provide a unit which
includes sheave. supporting plates between the
sheaves of the two vertically spaced groups and 35
which at the same time givesa sheave assembly
having an overall face width substantially equal
to the combined cross sectional ‘widths of the
sheave ?anges and substantially less than the
combined cross sectional width of the sheave 40
?anges and the plates. This feature of construc-
tion is obtained by forming the plates 552a etc._
with oppositely disposed dished portions which
extend in opposite horizontalv directions toward
the centers or spoked regions of the top and bot 45
tom sheaves between which each plate is situated.
. Take for example, the plate 620 which is situ
ated between the top sheave Mb and the bottom
sheave 852). It will be observed that this plate is’
provided with a dished portion ‘iii which extends 50
inwardly from the region adjacent the ‘flange of >
the sheave Mb toward the center of such sheave
and it is also provided with a second dished por
tion ‘H which extends in the opposite direction
being disposed inwardly from the flange of the 55
sheave 65b toward the center of the latter sheave;
In order that the ?anges of these two sheaves bib
and 55b may be brought into substantial contact
with each other, I provide the plates (Me, for
example) with openings iii and ‘l4’ (see Fig. 6) 60
which are situated in the region where the flanges
of the two sheaves cross.
In this way, I am
able to obtain a sheave assembly consisting of
etc. and 330. etc. are curved as indicated at 5!]
two vertically disposed and horizontally staggered
and 50'.
groups of sheaves provided with sheave support 65
ing plates between the individual sheaves of the
-
'
In the form of my invention shown in Figs. 5
and 6 I obtain a further decrease in overall length
of the unit with a slight sacri?ce innarrowness
of the sheave assembly. This sheave block con
struction embodies a frame structure which is
the same in its essential elements as the frame
construction described in connection with Figs. ‘1
and 2 in that it embodies main face plates 60 and
6B’ and top and bottom cross members or cross
pins ii! and 6|’ respectively, such frame being
two groups in which the thickness of the plates.
may be entirely eliminated in the overall face
width of the sheave assembly.
In this‘construction like that shown in Figs. 1 70
and 2, various types of bearing structures may
be used in supporting the sheave members and in
Fig. 7 I have shown one preferred form of such
construction in which reference numeral an indi
cates a retaining pin to which a pluralityof bear
75.
4
2,121,256
ing collars 8| and 82 are rigidly secured. These
bearing collars are provided with ?xed flanges
83 and 84 against which the hub portions 85 of
the sheaves are adapted to ?t and to be held in
' rigid engagement in any suitable manner such
as by means of washers 86 and rivets 81.
The
bearing members 8| and 82 are supported by
roller bearings 88 and 89. The roller bearings 88
are contained in a bearing cup 9!! which is welded
10' or otherwise secured in an opening 9| formed
in the main face plate 60' and the bearings 89 are
contained in journal boxes 93 which in turn have
their opposite ends mounted in openings 94
formed in adjacent plate members. These bear
ings may be lubricated through the use of suita
ble passages 96 formed in the shaft or spindle 8E!
and equipped with grease gun connections (not
shown).
It is to be understood that while I have herein
20 described and illustrated certain preferred em
bodiments of my invention and have illustrated
the same as being applied to a traveling block,
that the invention is not limited to the precise
structural details nor to the precise application
25 described above, but includes within its scope
whatever changes or modi?cations fairly come
within the spirit of the appended claims.
I claim as my invention:
1. A sheave block construction embodying: a
30 frame; vertically spaced sheave supporting means
in said frame; two groups of equal diameter
sheaves mounted on said sheave supporting
means; and plate means. interposed between the
successive sheaves in said groups and cooperating
35 with said frame to support said sheave support
ing means, the sheaves. in said upper group being
spaced in horizontally staggered relation with the
sheaves in said lower group, and the complete
sheave assembly comprised of the plates and
40% sheaves of both groups being arranged so that its
overall width is less than the combined thickness
of the individual plates and sheaves therein.
2. A sheave block construction embodying: a
frame; vertically spaced sheave supporting means
in said frame; and two groups of equal diameter
sheaves mounted on said sheave supporting
means, the sheaves in said upper group being
mounted in horizontally staggered relation with
50
from the sheaves in one group may be rove be
tween the sheaves of the other group and the
complete bank of sheaves being arranged so that
its overall width is less than the combined widths
of the individual sheaves therein.
5. In a sheave block construction, the combi
nation of: a frame; a cross support in the top
of said frame; a group of horizontally spaced
plate members suspended from said top cross
support and extending down to the intermediate 10
portion of said frame; a pair of intermediate
cross supports extending through spaced points
in the bottom of said top group of plate mem
bers; a group of bottom plate members mounted
on said intermediate cross support between the
successive top plate members; top sheave bearing
means extending through the medial portions of
said top plates; bottom sheave bearing means ex
tending through the medial portions of said bot
tom plates; and sheaves mounted on said top and
bottom bearing means between top and bottom
plates.
6. In a sheave block construction the combi
nation of: a frame; a cross support in the top of
said frame; a group of horizontally spaced plate
members suspended from said top cross support
and extending down to the intermediate portion
of said frame; a pair of intermediate cross sup
ports extending through spaced points in the
bottom of said top group of plate members; a °
group of bottom plate members mounted on said
intermediate cross support between the successive
top plate members; top sheave bearing means ex
tending through the medial portions of said top
plates; bottom sheave bearing means extending :'
through the medial portions of said bottom
plates; and sheaves mounted on said top and bot
tom means between the successive top and bot
tom plates, said sheaves and plates being so ar
ranged that the sheaves of one group and the 40
plates of the other group lie in the same vertical
planes.
'
'7. In a sheave block construction the combi
nation of: a frame; a cross support in the top
of said frame; a group of horizontally spaced
plate members suspended from said top cross
support and extending down to the intermediate
portion of said frame; a pair of intermediate cross
the sheaves in said lower group, and the com
supports extending through spaced points in the
plete sheave assembly being arranged so that its
overall width is less than the combined widths
bottom of said top group of plate members; a 50
group of bottom plate members mounted in said
intermediate cross support between the successive
of the individual sheaves therein.
,
3. A sheave block construction embodying: a
frame; vertically spaced sheave supporting means
in said frame; two groups of equal diameter
sheaves mounted on said sheave supporting
means; and plate means interposed between the
successive sheaves in said groups and cooper
ating with said frame to support said sheave sup
60 porting means, the sheaves in said upper group
being spaced in horizontally staggered relation
top plate members; top sheave bearing means
extending through the medial portions of said
top plates; bottom sheave bearing means extend
ing through the medial portions of said bottom
plates; and sheaves mounted on said top and bot
tom bearing means between the successive top
and bottom plates, said sheaves and plates being
so arranged that the sheaves in one group and 60
the plates in the other group lie in the same ver
with the sheaves in said lower group whereby
tical planes and the inner edges of the plates in
lines from the sheaves in one group may be rove
each group being formed in concave relation with
between the sheaves of the other group and the
65 complete sheave
assembly comprised of said
sheaves and plates being arranged so that its
overall width is less than the combined thickness
of the individual plates and sheaves therein.
4. A sheave block construction embodying: a
70 frame; vertically spaced sheave supporting means
in said frame; and two groups of equal diameter
sheaves mounted on said sheave supporting
means, the sheaves in said upper group being
mounted in horizontally staggered relation with
75 the sheaves in said lower group whereby lines
the peripheries of the corresponding sheaves in
the other group.
65
8. In a sheave block construction, the combina
tion of: a frame; a cross support in the top of
said frame; a group of horizontally spaced plate
members suspended from said top cross support
and extending down to the intermediate portion 70
of said frame; an intermediate plate support ex
tending through the bottom of said top group of
plate members; a group of bottom plate members
mounted on said intermediate support between
the successive top plates and extending down 75
2,121,256
wardly therefrom; top and bottom sheave bear
ing means extending through the medial portions
of said top and bottom groups of plates; and
sheaves mounted on said top and bottom bearing
means between the successive top and bottom
plates.
9. In a sheave block construction, the combi
nation of : a frame; a group of horizontally
spaced top plate members mounted in the upper
10 end of said frame; a group of horizontally spaced
bottom plate members mounted in said frame be
low and between the respective top plates; means
interlocking the adjacent end portions of the re
spective top and bottom plates; and sheaves
15 mounted between the respective plates of said top
and bottom groups.
10. In a sheave block construction, the com
bination of: a frame, a group of horizontally
spaced top plate members mounted in the upper
20 end of said frame; a group of horizontally spaced
bottom plate members mounted in said frame
below and between the respective top plates; and
sheaves mounted between the respective plates of
said top and bottom groups‘, the sheaves of one
25 group being positioned in the same plane and in
vertically spaced relation with the plates of the
other group and said plates being of less width
than said sheaves whereby the sheaves in one
group are caused to horizontally overlap the
30 sheaves in the other group.
‘
11. In a sheave block construction, the com
5
being dished in opposite directions toward the
centers of the top and bottom sheaves between
which it is situated.
12. In a sheave block construction the com
bination of : a frame; a plurality of horizontally
spaced plates mounted in said frame; and a plu
rality of equal diameter sheaves rotatably mount
ed between said plates in staggered relation there
by forming two vertically spaced groups, the
axis of each group being outside of and adjacent 10
the periphery of the other group, so that the pe
ripheries of the two groups overlap, each plate
member being dished in opposite directions to
ward the centers of the top and bottom sheaves
between which it is situated and said plates being 15
provided with openings in the regions where the
projected peripheries of the adjacent sheaves in
tersect.
-
a
13. In a sheave block construction, the com
bination of: a frame; a group of horizontally 20
spaced plates mounted in said frame; sheaves
mounted between the plates to form two vertically
spaced groups, the sheaves of one group being
horizontally staggered with relation to the
sheaves of the other group, said plates being hori 25
zontally offset in pairs adjacent the respective
sheaves in each group.
,
14. In a sheave block construction, the com
bination of: a frame; a group of horizontally
spaced plates mounted in said frame; sheaves
mounted between the plates to form two vertically
bination of: a frame; a plurality of horizontally
spaced plates mounted in said frame; and a plu
spaced groups, the sheaves of one group overlap
rality of equal diameter sheaves rotatably mount
tion to those of the other group, said plates being
horizontally offset in pairs adjacent the respec 35
tive sheaves in each group.
BURT S. MINOR.
ed between said plates in staggered relation there
by forming two vertically spaced groups, the axis
of each group being outside of and adjacent the
periphery of the other group, each plate member
ping and being horizontally staggered with rela
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