U.S. patent number RE30,341 [Application Number 05/918,329] was granted by the patent office on 1980-07-22 for conveyor drive.
This patent grant is currently assigned to The Laitram Corporation. Invention is credited to James M. Lapeyre.
United States Patent |
RE30,341 |
Lapeyre |
July 22, 1980 |
Conveyor drive
Abstract
A sprocket drive assembly designed for a modular chain link
conveyor belt subject to relatively large variations in width due
to changing ambient conditions such as large cyclic temperature
changes. The assembly includes a drive shaft with a square cross
section and a plurality of sprockets mounted on the shaft for
rotation thereby. One sprocket is fixed against axial movement to
provide for proper belt tracking while the remaining sprockets, the
number depending upon the width of the belt and the load carried
thereby, are located on opposite sides of the fixed sprocket and
are free to move axially to accommodate for changes in belt
width.
Inventors: |
Lapeyre; James M. (New Orleans,
LA) |
Assignee: |
The Laitram Corporation (New
Orleans, LA)
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Family
ID: |
25440192 |
Appl.
No.: |
05/918,329 |
Filed: |
June 22, 1978 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
244773 |
Apr 17, 1972 |
03724285 |
Apr 3, 1973 |
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Current U.S.
Class: |
198/834; 474/161;
474/164 |
Current CPC
Class: |
B65G
23/06 (20130101); F16H 55/30 (20130101) |
Current International
Class: |
B65G
23/00 (20060101); B65G 23/06 (20060101); F16H
55/30 (20060101); F16H 55/02 (20060101); F16H
055/30 () |
Field of
Search: |
;74/243FC,243R,231R,245C,243C,247 ;198/834,817,851,853 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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15058 of |
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1899 |
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GB |
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16820 of |
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1905 |
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GB |
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Primary Examiner: Braun; Leslie
Attorney, Agent or Firm: Schiller & Pandiscio
Parent Case Text
.[.This application is a continuation-in-part of copending U.S.
Pat. application Ser. No. 187,746 filed Oct. 8, 1971, in turn a
continuation-in-part of U.S. Pat. application Ser. No. 63,523,
filed Aug. 13, 1970, now abandoned..].
Claims
What is claimed is:
1. A sprocket and drive shaft assembly for a chain link conveyor
belt subject to variations in width comprising, in combination:
a drive shaft with a substantially uniform, noncircular cross
section; and
a plurality of sprockets mounted in driven engagement on said shaft
for supporting and driving a conveyor belt; one of said sprockets
being releasably locked against axial motion to provide for proper
belt tracking, all other of said sprockets being free to move
axially.
2. A sprocket and drive shaft assembly as defined in claim 1
including at least three of said sprockets, wherein said one
sprocket locked against axial motion is centrally located with
respect to said other sprockets.
3. A sprocket and drive shaft assembly as defined in claim 1
wherein said shaft has a square cross section and said sprockets
are formed with square holes for sliding engagement around said
shaft.
4. A support and drive assembly for a conveyor belt composed of
link modules having intermediate sections and intermeshed end
sections pivotally connected to one another, said assembly
comprising, in combination:
a linear rotary shaft having a substantially uniform, noncircular
cross section throughout a major portion of its length;
a plurality of sprockets mounted on said shaft each including a
hub, a wheel portion and teeth extending radially therefrom for
supporting the end sections of the link modules of a conveyor belt
and projecting into openings in the belt into driving engagement
with the end sections;
said hubs being formed with an axial opening therethrough adapted
to fit in driving engagement around said shaft while providing
sufficient clearance between the surfaces of said holes and said
shaft to permit free axial motion of said sprockets on said shaft;
and
means engaged with said shaft for releasably restraining one of
said sprockets against axial movement to insure proper tracking of
said belt, all other sprockets mounted on said shaft being movable
axially to accommodate variations in the width of the belt.
5. A support and drive assembly as defined in claim 4 wherein said
shaft has a rectilinear cross section and said openings in said
sprockets conform to said shaft.
6. A support and drive assembly as defined in claim 4 wherein said
noncircular portion of said shaft is symmetrical with respect to
the axis of rotation of said shaft.
7. A support and drive assembly as defined in claim 6 wherein said
shaft has a substantially square cross section and said holes in
said hubs are square.
8. A support and drive assembly as defined in claim 7 wherein said
means for restraining said one sprocket against axial movement
include two sets of axially spaced slots in the corners of said
shaft and C rings engaged around said shaft and in said slots
adjacent opposite ends of said hub of said one sprocket.
9. A support and drive assembly as defined in claim 4 including at
least three of said sprockets mounted on said shaft including a
medial sprocket restrained against axial motion and the remaining
sprockets being substantially freely movable axially.
10. A support and drive assembly as defined in claim 9 wherein said
medial sprocket is mounted to engage a belt substantially midway
between the sides thereof.
11. A support and drive assembly as defined in claim 10 wherein
said shaft has a substantially square cross section symmetrical
with respect to the rotational axis of said shaft and said holes in
said supports have square cross sections symmetrically located with
respect to the peripheries of said sprockets.
12. A support and drive assembly as defined in claim 4 wherein each
of said teeth includes a shoulder portion relatively wide axially,
for engaging and supporting the end sections of a belt and a
relatively narrow end portion for projecting into openings in the
belt.
13. A support and drive assembly as defined in claim 12 wherein
said wheel portion of each of said sprockets includes surface
sections intermediate said teeth having noncircular surfaces
providing clearance for the intermediate sections of the belt link
modules.
14. A support and drive assembly as defined in claim 13 wherein
said intermediate surface sections are substantially planar.
15. A support and drive assembly as defined in claim 12 wherein
each of said sprockets includes an even number of said teeth and
said end portions of alternate teeth are offset axially.
16. A support and drive assembly as defined in claim 4 wherein said
shaft and said openings have substantially square cross sections
symmetrical with respect to the axis of rotation of thereof and
said sprockets are molded plastic units.
17. A support and drive assembly as defined in claim 16 wherein
said means for restraining said one sprocket against axial movement
include two sets of axially spaced slots in the corners of said
shaft and .[.Crings.]. .Iadd.C ring .Iaddend.engaged around said
shaft and in said slots adjacent opposite ends of said hub of said
one sprocket. .[.
18. A sprocket wheel of the type having a central hub, a rim
circumscribing said hub, and means joining said hub and rim to one
another, and comprising
a first plurality of sprocket teeth and a second like plurality of
sprocket teeth, both mounted on said rim and extending radially
outwardly therefrom;
the teeth of said first plurality being alternatingly disposed with
respect to the teeth of said second plurality around said rim;
the outwardly extending end portions of the teeth of said first
plurality being spaced axially with respect to said hub, from the
outwardly extending end portions of the teeth of said second
plurality..]. .[.19. A sprocket wheel as defined in claim 18
wherein said first and second pluralities are equal to one
another..]. .[.20. A sprocket wheel as defined in claim 18 wherein
said end portions of said first plurality of teeth lie
substantially in a common plane, and said end portions of said
second plurality of teeth are substantially coplanar in a plane
parallel
to and spaced from said common plane..]. .[.21. A sprocket wheel as
defined in claim 18 wherein each of said teeth includes a shoulder
portion relatively wide axially with respect to said hub, and
having a relatively narrow end portion..]. .[.22. A sprocket wheel
as defined in claim 21 wherein said shoulder portion of each of
said sprockets includes surface sections intermediate said teeth
and having non-circular surfaces..].
Description
This invention is concerned with conveyors, and particularly with
an improved conveyor including a novel sprocket drive assembly.
In .[.the aforementioned U.S. Pat. applications.]. .Iadd.U.S. Pat.
No. 3,870,141 .Iaddend.there is shown and described a chain link
conveyor belt formed of a multiplicity of pivotally interlocked and
generally rectangular modules each including end sections in the
form of spaced links with aligned holes for pivot rods which
pivotally join the modules, and a connecting section for supporting
objects carried by the conveyor belt. The end sections of pivotally
connected modules are intermeshed and arranged in overlapping
relation in the direction of belt travel. Both the width and length
of the belt can be varied by changing the number of modules. The
link modules are designed to be formed simply by molding polymeric
plastics and are especially suited for use under severe operating
conditions, especially intermittent and cyclic changes in ambient
conditions including temperature and processing or cleaning fluids.
Typical operating environments are those encountered, for example,
in food processing and packaging where the material being conveyed
is subjected to a variety of processing operations involving
different liquids and a wide range of temperatures.
Employing conveyor belting of this type under varying loads and
changing ambient conditions ranging, for example, from immersion in
boiling water or steam to temperatures near or below freezing,
presents a number of difficult problems with regard to the driving
and supporting structures for the belting. For example, such
structures should match the belt in capability to stand up under
the same severe operating environments, and should also accommodate
a variety of belt widths as well as compensate for rapid and/or
cyclic belt width variations due to expansion and shrinkage
resulting from ambient condition changes, particularly,
temperature, while also assuring proper tracking of the conveyor
belt. The conveyor belt described in said .[.applications.].
.Iadd.U.S. Pat. No. 3,870,141 .Iaddend.is particularly adapted for
ease of cleaning and operation without lubrication and these
advantages, particularly in food processing, are also desired of
the support and drive system.
Objects of the invention are to provide a novel and improved
sprocket drive assembly readily adaptable for different width chain
link conveyor belts of the type described; to provide such an
assembly capable of operating reliably with proper tracking of a
conveyor belt under a wide range of operating conditions and loads
and to provide such an assembly capable of accommodating cyclic and
substantial variations in belt width.
These and other objects of the invention are achieved in an
assembly including a drive shaft of non-circular cross-section, and
a plurality of sprockets preferably formed of a molded organic
polymer, mounted in driven relation on the shaft. All of the
sprockets but one, which is preferably centrally located, are
freely movable axially on the shaft to accommodate for changes in
belt width while the fixed sprocket, which is readily removable,
assures proper tracking of the belt.
Other objects of the invention, will, in part, be obvious and will,
in part, appear hereinafter.
The invention accordingly comprises the apparatus possessing the
construction, combination of elements and arrangement of parts,
which are exemplified in the following detailed disclosure, and the
scope of the application of which will be indicated in the
claims.
For a fuller understanding of the nature and objects of the
invention, reference should be had to the following detailed
description taken in connection with the accompanying drawings
wherein:
FIG. 1 is a perspective view of a drive shaft and sprocket assembly
embodying the invention;
FIG. 2 is a perspective view of a portion of a conveyor belt
typical of those employed in conjunction with the invention;
FIG. 3 is an elevation view, partially in section, showing the
drive shaft and sprocket assembly in engagement with the chain link
belt of FIG. 2, and
FIG. 4 a front elevation view in section showing an assembly of the
present invention involving a plurality of sprockets.
The drive shaft and sprocket assembly of the invention is
especially designed for use with a chain link conveyor belt of the
type described in the aforementioned .[.application.]. .Iadd.U.S.
Pat. 3,870,141 .Iaddend.and illustrated, for example in FIG. 2 of
the drawings. The conveyor belt is composed of a multiplicity of
similar link modules generally designated 10, pivotally connected
end-to-end in overlapping, "bricklayer" relation. Each module 10 is
designed to be formed as an integral unit, preferably of a
polymeric plastic material, by a conventional molding process and,
in the form shown, comprises a multiplicity of elongated, parallel,
spaced link-like elements each including end sections 12 joined by
an intermediate connecting section 14. The link-like elements are
joined as a unit by at least one and preferably a pair of spaced
cross-members 16 formed integrally with connecting sections 14 to
form a rigid, open grid or perforated structure. End sections 12
are wider and deeper than connecting sections 14 to form openings
between links and are formed with parallel planar facing surfaces
each spaced from adjacent surfaces by just slightly greater (e.g.
0.003 inch) than the thickness (width) of the end sections so that
the end sections of the link elements of each module fit snugly but
movably between the end sections of every other module with the
parallel facing surfaces in contact with one another. Each of end
sections 12 is formed so as to circumscribe a corresponding one of
aligned holes 18 for receiving pivot pins or rods 20 adapted to
pivotally connect the modules end-to-end while laterally aligning
adjacent modules.
The ends of the cross-members extend beyond the immediate sections
of the lateral link-like elements to planes spaced from the center
surfaces of the end section by half thickness thereof so that
cross-members of laterally adjacent modules will abut one another
when assembled as a conveyor belt. Cross-members 16 function to
maintain the link-like elements in parallel relation so that the
faces of end sections 12 are kept parallel and pivot holes 18 are
kept aligned, thereby placing rods 20 in multiple shear and
minimizing bending stresses across the rods. End sections 12 have
at least a particlly circular cross-section (when viewed in side
elevation) and a depth equal to the depth of cross-members 16 so
that both portions of the upper and lower edges or surfaces of the
end sections and cross-members are located in substantially
parallel planes, for self supporting a belt made of a number of
coupled modules as well as articles carried thereon.
A multiplicity of modules 10 are assembled in end-to-end and
side-by-side relation to form a conveyor by pivot rods 20.
Cross-members 16 function to absorb lateral forces on the link-like
elements tending to separate the links, as well as bending forces
on the modules tending to bend the pivot pins. Additionally, where
the end sections are formed with parallel planar facing surfaces
spaced so that the end sections of another like module fit or mate
snugly yet with a minimum of friction, the fit of the end sections
constitutes significantly to the ability of pivot-connected modules
to resist deformation due to bending forces across the axis of the
pivot pin. Thus, each pivot pin is subjected primarily to a large
number of small shear forces so that the strength requirements for
the pivot pins are small as compared with a conveyor composed of
individual chain links. The use of circumscribed holes 18, i.e.,
holes completely surrounded by the material of the end section, of
course permits the pins to positively lock respective modules
together while permitting independent rotation of end-to-end
connected modules about the pins. To add strength to a conveyor
made up of rows of modules located side-by-side, the modules of
each row are staggered with respect to the modules of adjacent rows
as shown in FIG. 2, in which different modules are designated 10a,
10b, 10c, 10d and 10e. In this way, the joints of adjacent modules
in each row fall at an intermediate position, typically midway
between the sides of adjacent modules in the next row, so that, in
effect, the cross-members overlap in bricklayer fashion to resist
bending stresses which might otherwise be transmitted to the pivot
pins. A conveyor of any desired width can be formed by employing
whole modules or portions thereof as shown in FIG. 2.
When such modules are assembled as in FIG. 2 to form a belt or
mesh, the openings such as 17 between adjacent end sections 12 of
one module are offset the width of an end section 12 with respect
to corresponding openings 17 of the other connected module. Thus,
to drive each successive module with a wheel or sprocket having
teeth intended to fit into openings 17, the sprocket teeth are
alternately offset axially from one another by the width of an end
section 12 of the modules. However, a sprocket wheel having a
series of successive in-line teeth can be used if the "offset" is
provided in the module itself. To achieve this, the end sections of
each link-like element are offset so that intermediate sections 14
of each link-like element lie along a straight line which meets
corresponding end sections 12 the latter being formed as described,
with aligned holes 18 for rods 20 at a slight angle.
A typical use of a conveyor including a belt and support and drive
assembly providing a severe test of its design is in the processing
of food products involving a corrosive liquid such as salt water.
Heretofore, conveyors for such purposes have been formed of
stainless steel to resist corrosion and permit cleaning including,
for example, the use of detergents and steam. Understandably, such
conveyors are difficult and expensive to fabricate and assemble;
are heavy thus necessitating substantial and expensive support and
driving structures and requiring large amounts of power to operate;
wear out rapidly because of the difficulty in providing for
lubrication; tend to break when bent or stressed; and are difficult
to repair. The conveyor module is intended to be formed of a
relatively light weight, organic polymeric plastic material such as
polyethylene, polypropylene, polycarbonate, or the like, which is
compatible with corrosive liquids and atmospheres and can be formed
by conventional molding processes.
Reference is now made to FIGS. 1 and 3 of the drawings wherein
there are illustrated, respectively, a shaft and sprocket drive
assembly in perspective, and in elevation and partial section in
combination with a conveyor belt of the type illustrated in FIG. 2.
All sprockets, each designated 30, (only one is shown), are
substantially identical. The sprocket takes the general form of a
wheel having a hub 32, a generally circular web or flange 34
extending radially from the hub and a peripheral rim 36 including a
multiplicity of radially extending teeth generally designated 38.
Sprocket 30 is designed to be formed of a polymeric plastic
material or metal, by conventional molding methods. Plastics such
as employed in the belt links, particularly materials such as
polycarbonates, are preferred because of their strength combined
with light weight, wear and impact resistance, compatibility with a
variety of atmospheres, resistance to damage resulting from changes
in ambient conditions such as temperature, humidity, etc., ease of
cleaning, and low cost should replacement be required.
The sprocket 30 is designed to be mounted in driven (torsional)
engagement on a support and drive shaft designated 40, preferably
having a uniform square cross section throughout the length of the
sprocket suspension portion of the shaft. Although other
noncircular cross sections such as hexagonal may be employed, the
square cross section is preferred because it provides maximum
strength coupled with maximized driving force-imparting surfaces
and corners, is symmetrical with respect to the rotational axis and
lends itself to fabrication simply and easily of a variety or
combination of materials.
A typical shaft illustrated in FIG. 1 includes a square
cross-sectioned sprocket drive and support section 42 and
cylindrical end sections on which the shaft is adapted to be
mounted for rotation. Metals such as aluminum and steel are
preferred for strength, the former having the advantage of
lightness and ease of fabrication. Combinations of materials may be
employed to advantage such as a cylindrical steel shaft, either
solid or hollow, preferred for both strength and cost, around which
is secured a sleeve having a square, external configuration, formed
of aluminum or other material selected because of its lightness,
ease of fabrication, e.g. adaptability to molding or extrusion,
and/or its resistance to damage by the environment in which it is
designed to operate. In most instances, aluminum drive shafts will
be anodized and/or coated with a protective polymer such as
polytetrafluoroethylene which is resistant to both harsh
environments and wear resulting from axial motion of the sprockets.
However, the latter, when formed of plastics, have a low
coefficient of friction thus resulting in ease of axial motion as
well as reducing or eliminating drive shaft wear. For particular
applications, it may be desirable to form the drive shaft sleeve
entirely of a relatively inert material such as stainless steel or
a polymeric plastic which is the same as or similar to that
comprising the belt links and/or sprockets.
Hub 32 of sprocket .[.38.]. .Iadd.30 .Iaddend.is relatively long
axially to provide for maximum driving engagement surface area for
contacting the shaft and has a symmetrical square external
configuration to minimize material cost without sacrificing
torsional strength. The flange or web portion 34 of the sprocket is
relatively thin (axially) and supports the rim section 36 which is
relatively wise in order to provide support for the adjacent end
sections 18 of at least two .[.pivotty.]. .Iadd.pivotally
.Iaddend.connected conveyor belt links. The belt is preferably
supported at end sections 18 so that there is clearance between the
sprocket rim and connecting sections 14 and cross-members 16 of the
belt to provide for fluid circulation through and around the belt
at the sprockets. For this purpose, the sprocket teeth, generally
designated 38, each include a shoulder portion 46 having a
cylindrical surface sufficiently wide (axially) to engage and
support at least two adjacent end sections 18 of connected belt
links. The external peripheral surface of the sprocket rim 36
between teeth is substantially planar in the form shown. Extending
radially from the shoulder portion of each tooth is a relatively
narrow (axially) end or drive portion adapted to project into an
opening 17 between connecting sections 14 and a cross-member 16
into driving engagement with an end section 12 of a belt link. End
portion 48 of teeth 38 are shown offset axially as required by the
modular belt link construction shown in FIG. 2. The sprocket
includes an even number of teeth (ten as shown) so that there are
an equal number of teeth offset in each direction.
As shown particularly in FIG. 4, each drive shaft and sprocket
assembly will include at least two and preferably three sprockets
with one of the sprockets 30a being fixed against axial motion in
order to insure proper tracking of the belt. The other sprocket or
sprockets 30b and 30c, the number being dependent upon belt width
and loading, are free to move axially on drive shaft 40 in order to
accommodate for variations in belt width resulting from various
factors, primarily large changes in temperature. The hub hole size
and shaft sizes are designed to permit this freedom of motion while
the square cross section is ideally suited to permit axial motion
and simultaneously prevent rotational motion of the shaft relative
to the sprocket.
Since all of the sprockets are substantially identical and
interchangable, at least for a particular belt design, the
retaining means for releasably maintaining one of the sprockets
against axial motion are mounted on the drive shaft. These means
are located preferably so as to axially fix the sprocket closest
the center of the belt when there are three or more sprockets
thereby minimizing the axial motion of the other sprockets. In the
form shown particularly in FIG. 1 the retaining means comprise
conventional C rings 50 engaged around the drive shaft in grooves
52 formed in the corners of the shaft. The rings and grooves 50 and
52 are spaced by a distance approximately equal to the axial length
of a sprocket hub 32, to prevent motion of the hub. C rings are
used and preferred because they can be removed easily for sprocket
replacement while the grooves 52 in which they are engaged have the
advantages that they do not interfere with axial sprocket motion
when changing sprockets nor do they significantly weaken the shaft.
This structure is also simple, inexpensive and easy to form and to
maintain and tends to remain clean and free of accumulation of
materials carried on the conveyor.
In keeping with many of the advantages of the design conveyor link
modules, the sprocket is also designed to be formed of a polymeric
plastic material by conventional molding methods. Similarly, the
design of the sprocket and the choice of the particular materials
employed are based on such factors as strength, durability,
resistance to ambient conditions, wear and impact resistance,
relatively low cost and freedom from maintainence problems
including lubrication. Changing sprockets and any other
maintainence are convenient and easy.
Since certain changes may be made in the above apparatus without
departing from the scope of the invention herein involved, it is
intended that all matter contained in the above description or
shown in the accompanying drawings shall be interpreted as
illustrative and not in a limiting sense.
* * * * *