CA1131937A

CA1131937A - Modular chain belt

Info

Publication number: CA1131937A
Application number: CA303,486A
Authority: CA
Inventors: James M. Lapeyre
Original assignee: Laitram LLC
Current assignee: Laitram LLC
Priority date: 1977-05-31
Filing date: 1978-05-16
Publication date: 1982-09-21
Also published as: FR2393201B1; NL187083C; DE2823842A1; NL7805879A; DE2823842C2; NL187083B; FR2393201A1; BE867620A; GB1603276A

Abstract

ABSTRACT OF THE DISCLOSURE
A chain belt formed of a plurality of pivotally connected preassembled parallel links. Each link includes a driving tooth protruding from one surface of the link midway between the pivo-tal axes of the link. The tooth is preferably formed so that its faces are a pair of intersecting, convex, cylindrical seg-ments of like radii of curvature, the cylindrical axes of the segments being located such that the curvature of the faces insures that there is no scrubbing action where the belt is driven by a sprocket, the teeth of which are shaped to provide an inversely curved mating surface with the link teeth.

Description

This invention relates to articu}ated or linked belts, and particularly with a novel belt comprising modules each comprising a plurality of preassembled link-liXe ele~ents.
It has long been known that en less belts, in the for~ of ~ I
loop, can be used particularly as a conveyor, for the trans-mission of power, and for the transmission of precise angular , ~ relationships, i.e. as a timing belt. The simplest form is a loop of flat, flexible material driven by frictional engagement, but such belts provide little, if ar.v, intrinsic resistance to distortion under carrying load and :end to slip. Hence, their virtue is primarily in their cost, but they find little applica-tion for precision power transmission, timing or conveyance. For lS the latter applications, the preferred belt is a chain drive.
Precision steel roller chains and inverted tooth or silent chains are considered primarily power trans~ission andJor power timing chains, particularly at average to high speed conditions.
The well known silent or "invertedH tooth driving chains ~ are generally characterized in that each driving link i9 usually provided with a pair of teeth extending outwardly from the link : . .
from approximately the pivotal axes of the latter, parallel to one another and perpendicularly to the pitch line. While in theory;these links have no sliding action in or out of the grooves 1 25 ~ of an associated sprooket wheel and are hence considered noiseless, ~ : . ' . ' ::

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i~3~937 in practice, the link teeth and sprocket teeth engage one another with a scuffing or rubbing contact, known as "scrubbing", with attendant wear on the teeth. Additionally, in a typical operation of a silent chain, the contact between the driving and driven faces of the chain teeth and sprocket teeth is substantially along a line or a narrow area of the tooth faces extending parallel to the rotational axis of the sprocket wheel. The dri~ing pressure, being thus concentrated over this very small area, typically requires that the teeth surfaces be specially hardened to reduce wear.
Prior art silent chains also claim to reduce the detrimental effect of chordal action, i.e. the vibratory motion of the chain as it engages the sprocket wheel. This vibratory motion is anifes~ as a periodic acceleration and deceleration of the chain, lS and a rise and fall of the links of the latter with respect to its lineiof engagement with the sprocket wheel. Such chordal action, of course, is not present in a fully flexible belt such as a rubber timing belt, for the laiter simply conforms at every point to the pitch circle of the sprocket wheel. However, for a chain formed of substantially rigid links which are pivotally joined to one another, flexible conformation to the pitch circle of the sprocket wheel is impossible. Roller chains and the like exhibit marked chordal a¢tion which limits high speed load arrying capabillty and makes transfer of the load from the chain o a stationary comb tangent to the sprocket wheel, particularly . .
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.. . ~ - :.. ,. : , perilous for fragile items being carried by the chain. In order to reduce the chordal action of some current silent chains, the designers have provided ingenious pin and rocker joints and involute chain teeth and sprocket teeth. When such teeth engage ; 5 one another, the contact poin~ of the pin and rocker joint shifts upward and causes the pitch of the chain to elongate, reducing chordal action. -In U.S. Patent 3,870,141 issued March 11, 1975, there is disclosed a chain link belt particularly useful as a conveyor, capable of carrying heavy loads and transmitting substantial power at fairly high speeds. The chain belt therein disclosed is particularly advantageous in that, being modular, it is very easily assembled and repaired.
The modular belt of U.S. Patent 3,870,141 is generally formed of a first plurality of link ends, each formed to circum-scribe a pivotal hole and a second plurality of link ends, each also formed to circumscribe a pivotal hole, the pivotal holes ` in each plurality of link ends being respectively aligned along la common axis. The axes of the pivot holes of each plurality of ~ ~ ¦link ends are parallel with one another. Each link end of the ~ ? ~ ~
first plurality is joined to a corresponding link end of the second plurality through at least one cross-rib which lies etween and substantially parallel to the axes of the two plura-lities of pivotal holes. The link ends are dimensioned and spaced apart by a distance sli~htly greater than their respective ::' rJC~22 CIP -3-~, -,~

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-` 1131937 widths. Thus, when the link ends of one module are nested or enga~ed with the link ends of another module bv a common pivot pin extending through the pivotal holes in the respective link ends, the engagement of adjacent link ends tends to minimize the transmission of twisting shear to the pivot rod. Consequently, very advantageously the modules, chain belt and pivot pins of U.S. Patent 3,870,141 can be formed of polymeric materials, thereby minimizing costs~ providing high strength with light . weight and avoiding lubrication problems. This chain belt can withstand severe extremes of processing tem~eratures, and highly corrosive environments such as are encountered frequently in laundries, food proces.sing and other manufacturing processes.
~ To drive the chain belt of U.S. Patent 3,870,141, there is : usually provided a sprocket wheel with extending teeth arranged :~: 15 ~ in staggered relation alon~ the axis of rotation so that the teeth can enaage a similarly .stagaered array of openings formed by adjacënt engaged modules. These sprocket teeth bear against : the portion of the link end wbich circumscribes the pivotal hole~
~The present invention is directed toward a novel chain link .10 ~ having a driving tooth protruding therefrom intermediate pivot axes ;: located at opposite~:ends of the link, the tooth having working surfaces of a unique configuration as hereinafter described. This - ; novel chain link can be assembled to form a module for a c~ain belt generally of the t~pe described in U.S. Patent 3,870,141 but ':
25: particularly adapted to provide very precise power transmission and/or timing requlrements. To this end, the present invention is also typically embodied in a modularly structured chain belt in which each module is .formed of a plurality of lin~.s each having a pair of link ends each formed to circumscrihe respective pivotal '~ .

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holes, a number of links heing arranged so that a first set of such holes in first plurality o~ such link ends are aligned along a common first linear axis, and a second set of such holes in a second plurality of such link ends are aligned along a second common linear axis, the first and second axes being parallel to one another. In t~e module formed of links of the present inven-tion, each of the link ends of the first plurality is joined with the corresponding ones of link ends of the second plurality throug an intermediate portion. In emhodiments where the links are integrally joined to one another, the intermediate portion ex-tend substantially parallel to the first and second axes. Appende to, and preferably formed integrally with each link is a single driving tooth which protrudes intermediate the first and second axes generally in a fixst direction perpendicular to a plane com~on to those axes. The tooth is preferably formed with its working surfaces as a like pair o plano-convex surfaces each being typically a substantially cylindrical segment of like radius of curvature, the respective cylindrical axis of each such seg-ment being between the first and second axes through the pivotal ~ holes. The term "working surface" is intended to refer to that surface of a tooth adapted to engage a driving element such as a ~- ~ ¦sprocket or an element to be driven, as the case may be.A particular object of the present invention is to provide a link of the type descrihed which, in conjunction with a sprocket wheel of appropriate configuration, exhihits substantially no scrubbing action. Another object of the present invention is to provide a link of the type described, a plurality of which when formed into a hinged, endless belt used in conjunction with an appropriate sprocket wheel, exhibits remarkably small chordal action.

~C-22 CIP -5-- ~3~;37 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.
Broadly speaking the present invention provides a module for constructing linked structures for use as hinged, endless belts, the module comprising, in combination: a first plurality of link ends of substantially identical width, each link end of the first plurality being formed to circum-scribe a pivotal hole, the holes of the first plurality being arranged coaxially along a first pivotal axis, the first plurality of link ends being spaced from one another by approximately the width; a second plurality of link ends of substantially identical width, each link end of the second plurality being formed to circumscribe a pivotal hole, the holes of the second plurality being arranged coaxially along a second pivotal axis parallel to the first axis, the second plurality of link ends being spaced from one another by approximately the width; an intermediate portion integrally formed with and joining the first and second plurality of link ends so as to preserve the parallel relation of the axes; a driving tooth formed integrally with and protruding from the intermediate portion substantially normal to the pitch line between the first and second axes intermediate the latter;
the tooth having a pair of working surfaces, each of the working surfaces having a shape in the range between and .~
::~ including that of a cylindrical segment and a chord of the - segment; the axis of each working surface being parallel with the pivotal axes of the link and positioned intermediate the pivotal axes or coincident with the pivotal axis furthest from that surface; the pair of working surfaces being part of a pair of sd/ ~ -6~

~ 7 intersecting loci; the shape of each of the working surfaces being such that the -tangent angle of each such surface is not more than 90, the tangent angle being defined between a tangent at a point on one working surface and a line joining that point to the opposite pivotal axis; and each of the plurality of link ends of the module being pivotally engageable to one of the plurality of link ends of adjacent modules.
Furthermore the present invention may be seen to provlde a linked belt assembly comprising: a plurality of links, each having at least a pair of opposite link ends each circum-scribing a pivotal hole centered about a respective one of a pair of parallel pivotal axes, and a rigid intermediate section :
joining the link ends; the link ends having no driving engage-ment with an associated sprocket wheel; each of selected ones of the links having at least one driving tooth protruding from the intermediate section substantially normal to the pitch line between the pivotal axes and intermediate the pivotal Y
axes; the tooth having a pair of working surfaces, each of the : ~ . working~surfaces having a shape in the range between and ~lncluding that of a cylindrical segment and a chord of the segment; the axis of each working surface being parallel with the pivotal axes of the link and positioned intermediate the ~; pivotal axes or coincident wlth the pivotal axis furthest from that surface; a pair of working surfaces belng part of a pair : of intersecting loci; the shape of each of the working surfaces being such that the tangent angle of each such surface is not more than 90, the tangent angle being defined between a tangent .~ at a point on one working surface and a line joining that point-to the opposite pivotal axis; each of the link ends of each link being pivotally connected to a link end of adjacent links by means extending through the holes; a toothed sprocket wheel having recesses between adjacent teeth thereof, each of the ; recesses including a pair of facing surfaces of shape corres-~ . q ~. .

~ sd ~ -6A-~131937 ,, ponding to the pair o working surfaces of the driving tooth;
and only the teeth of the connected links being in driving ~
engagement with the recesses of the sprocket wheel, the engaged linked belt and sprocket wheel exhibiting minimal scrubbing action and chordal action.
For a fuller understanding of the nature and objects of the present 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 typical link formed according to the principles of the present invention;
Fig. 2 is an enlarged view of a section taken along the line 2-2 of Fig. l;
Fig. 3 is a perspective view of a module formed of ~; links of Flg. l;
~- Fig. 3A is a top plan view of the module of Fig. 3;
Fig. 4 is a section taken along the line 4-4 of Fig.
3A;
Fig. S is a side view of a portion of a linked belt 20 ~ ; formed of the modules of Fig. 3, in engagement with a driving sprocket wheel, shown only in fragment;
Fig. 6 is a front elevation view of a modification ~ of the module of Fig. 3, particularly adapted for use with a ;-~ V-sheave sprocket drive7 t~
Fig. 7 is a front elevation of the mirror form of the module of Fig. 6;
Fig. 8 is a fragmentary showing of a V-sheave , . - ::.
~- sprocket drive only taken along the line 8-8 of Fig. 5;
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~`` 1131~37 Fig. 9 is an end view of yet another modification of a link formed according to the principles of the present invention;
Fig. 10, appearing on the same sheet as Fig. 1, is an end view of yet another modification of a link formed according to the principles of the present invention;
Fig. 11, appearing on the same sheet as Fig. 1, is an end view of an extreme form of a link formed according to the principles of the present invention;
Fig, 12, appearing on the same sheet as Fig. 1, is an end view of a double-toothed version of a link formed according to the principles of the present invention;
Fig. 13A is a diagram showing the relation of the teeth of links of the present invention to a sprocket wheel formed according to the present invention;
Eig. 13B is a simplified version of the diagram of Fig. 13 shcwing the displacement of a link tooth and sprccket wheel through an angle of 15 relative to the sprocket center line;
Fig. 13C is a diagram similar to Fig. 13A but in which the link ~' ~ tooth surfaces æ e not formed within the teachings of the present invention;
- ~ 20 Fig. 13D is a diagram similar to Fig. 13A but in which the centers of curvature of the tooth faces are coincident with the pivotal axes of the l mk7 Fig. 14 is a side view of a portion of a belt formed from the modules of Fig~ 3 arranged to serpentine through a pair of counter-rotating driv m g sprcckets;
Fig. 15, appearing on the same sheet as Fig. 1, is an end view of yet another modification of a link of the present invention.
~; Fig. 16 is a diagram according to the present invention useful ~' in analyzing the chordal action of the belt and sprccket wheel of the ~, .
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31937 1~
ll ' I Fig. 17 is a graph showing the chordal variations in velocity lusin~ a twelve tooth sprocket wheel in the pres~nt invention.
In Fig. 1 there is shown a typical link of the present inven-tion designated generally at reference numeral 21 formed as an ' elongated element having a pair of parallel side surfaces (only one~
of which is shown). A first link section or end 22 is formed to circumscribe a pivot hole 24 having a central pivotal axis A nor-mal to the axis of elongation of link 21, the opposite link section or end 26 being similarly formed to circumscribe another pivotal ', ` hole 28 having a central pivotal axis B parallel to axis A.
Appended to and preferably formed integrally with link 21 is included at least one driving tooth 32 which protrudes generally ~ in a direction perpendicular to the common plane through the 1~ ~ first and second pivotal axes A and B and intermediate, prefer- ¦

ably midway, between the latter. The side surfaces of tooth 32 are, in this embodiment, coextensive with and coplanar with the corresponding side surfaces (such as surface 23) of link 21. As shown particularly in Fig. 2, the faces of tooth 32 are formed preferably of a pair of plano-convex, e.g. cylindrical surfaces J~
20~ 34 and 35 which intersect one~another. Surfaces 34 and 35 are 9hown as substantially right-angled cylindrical segments having like radii of curvature, the cylindrical axes or axes of rotation Pl and P2 respectively of surfaces 34 and 35 being parallel to one another and disposed between and in a plane parallel t~ or 1 1 coplanar with first and second pivotal axes A and B. For example, as shown in Fig. 2, surface 34 has a radius of curvature Rl, the origin or center of curvature lyin~ at axis Pl, here show~ disposed ~' ~, ~ - .. " . - .
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` i 1~937 between and intersecting pitch line L through pivotal axes A and B
of holes 24 and 28. Similarly, surface 35 has a radius of curva-ture which is centered as axis P2 similarly intersecting line L
and lies between the centers of pivotal axes A and B of holes 24 and 28. It will be seen therefore that the intersection of sur-faces 34 and 35 lies along a line I (shown as a point) parallel to and equidistant from the first and second axes A and B, so that tooth 32 is preferably bilaterally symmetrical about line I.
The configuration of surfaces 34 and 35 of tooth 32 shown in 1~0 Fig. 2 are not only plano-convex, but the locations of the axes of curvature thereof are of great importance. Specifically, axis P2 is at some distance d from axis A and axis Pl is the same distance from axis B, i.e. they are equidistant from the nearest respective pivotal axis. Axes Pl and P2 are in a common plane parallel to or coplanar with the common plane of axes A and B. For any point X
on surface 34, there is a tangent T which, of course, is a perpen-dicular to Rl the radius of curvature of surface 34 to point ~.
;~ The location of axis PI must then he such that an angle ~ between ¦tangent T and line D, which extends from point X perpendicularly to the pivotal axis (here axis B) nearest to axis Pl, is not more than 90 when observed looking into the convex surface of the opposite face (here surface 35). Because as noted, the tooth is bilaterally s~mmetrical, this constraint a~plies also to the location of axis P2 with respect to axis A and any point on sur-face 35. If angle ~, hereinafter in this specification and claims referred to as the tangent angle, is 90 or less for each tooth surface, then as discussed hereinafter, the tooth will seat in a corresponding groove of a sprocket ~heel without scru~bing. Not only does the structure of tooth 32 provide a non-scruh action, but when used with appropriate sprocket wheels, typically a minimum of twelve or more grooves matched to Il ~ 1131~337 tooth 32, chordal action is reduced very suhstantially over prior roller chain structures formed of links 21, as will be described hereinafter.
Reference is now made to Figs. 3 and 3A inclusive wherein there is illustrated one embodiment of a chain link module.incor-porating tbe principles of the present invention. This module, generally designated at 20, is designed to be formed as an inte-gral unit typically, but not necessaril~ of poly~eric material by any of a numher of conventional molding processes. The polymer used is preferably a glass-reinforced polyproo~lene, but many other materials can be used as well. ~qodule 20 comprises a mul-tiplicitv of elongated, parallel, spaced-apart, links 21 which for the sake of convenience in illustration and exposition, are . shown to be five in number, although it is to be understood that the module can and frequently does, comprise a substantially ~:~: greater or lesser number of such links 21. All of links 21 have substantially the same length and width, and thus the length di-mension of module 20 is determined by the length of the individ-ual links while the width o$ module 20 is determined by the ~: 20 number of links, their width and the spacing there~etween. In : : : the embodiment shown in Figs. 3 and 3A, all of links 21 are ~: ~ preferably rigidly joined together and held in substantially parallel relation by an integrally ormed intermediate section 30, thus forming a rigid, open or slotted structure in which the parallel link ends alternate with slots 31. Alternati~ely, module :~ 20 can be formed of a plurality of links 21 and requisite spacers to provide slots 31, all held together mechanically as by adhesive or the like. The length of each slot is at least equal to twice the distance between the center of a hole such as 24 and the ~,,,, ` 1131937 distal extr~mity of associated link 22, there~y provi~ing suffi-cient space into which a corresponding link end of another like module can fit so that the respective holes in the fitted link ends are registered with coaxial pivot holes. Link ends 22 and 26 are held spaced apart by ad~acent surfaces by a distance just slightly greater (e.g. 0.~03 inches or less) than the width of the link ends so that the link ends of each module may fit snugly but movably between the link ends of an adjacent module with parallel facing surfaces in contact with one another.
Thus, as shown particularly in Fig. 3A, the module includes a first plurality of pivot holes 24 which are all aligned coaxially along first linear pivotal axis "A" and a second plurality of pivotal holes 28 which are similarly coaxially al1gned along second linear pivotal axis "B", the ~irst and second linear axes lS A and B being parallel to one another. The respective pluralities of aligned pivot holes are intended to receive pivot rods or pins which arle adapted to pivotally connect module 20 with like modules nd-to-end while laterally aligning the adjacent modules. In the ~ mbodiment shown wherein module 20 is formed of integrally molded - 20 together links 21 and intermediate section 30, the face width ofeach tooth 32 is selected so as to form an integral unit tooth which extends across the entire width of module 20, i.e. from one end element 21 to the other end element 21. This form of tooth 32 lends itself to ready molding in the formation of the modules and provides a large and stable driving surface, as will be described later herein. However, unit tooth 32 can be molded to be of some-what different width than the width of module 20 between end ele-ments 21 and can be formed, instead, simply as a plurality of in-dividual, arranged teeth 32 corresponding to the respective links.
The modules, subject to the above-described constraints on the geometry of the working surfaces of tooth 32, may take a number of slightly different configurations. Some examples of alternative configurations are shown , . .

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` i` 1131937 in Figs. 9, 10 and 15 wherein respectively the module of Fig. 9 includes a dished portion or concavity 36 in the portion thereof opposite tooth 32, concavity 36 being in the form of a trough having its long axis substantially parallel to linear axes A and B through holes 24 and 28. A linked belt formed of the modules of Fig. 9 would have a corrugated upper surface with the corru-- gations extending in a direction substantially perpendicular to the direction of belt travel, and for example, would provide either a high speed drainage surface for some articles to be conveyed thereon or a surface capable of engaging and carrying :~
various articles of appropriate size. It will be seen that `~ tooth 32 of the module of Fig. 9 is formed of a pair of surfaces ~ 34 and 35 in substantially the same manner as the tooth shown in `;; Figs. 1, 3 and 4. However, it will also be seen that the apex of tooth 32 in Fig. 9 however has been provided with a separate radius of curvature so as to blunt the apex somewhat.
Alternatively, as shown in Fig. 10, faaes 34 and 35 are cylindrical segments and the surface of the module opposite tooth 32 is maintained as a substantially flat surface (at least 20~ along the link-like elements 21). However, the apex of tooth 32 'r~ has been truncated~as at 37;so as to provide a relief spacc with regard to a prooket grOGve, or so that the teeth of the ~procXet ;~ can be shortened if desired.
In a modification of the module of Fig. 10 shown in Fig. 15, ;25 tooth 32 is faced with substantially flat surfaces 34A and 35A
which can be chords or part of chords of the cylindrical segments .
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~ ~ , 11 ; 1131937 l l constituting faces 34 and 35 o, the device of Fig. 10. Surfaces 34A and 35A need not be flat bu~ can assume a curvature lying between the cylindrical curvature o,' faces 34 and 35 of Fig. 10 and a plane forming a chord to ihat cylindrical curvature so long as the tangent angle is not more than 90 as noted.
A plurality of modules 20 are assembled in end-to-end (and if desired side-to-side) relation to form belt 36 (shown in fragment) when connected by pivot rods 38 as shown in Fig. 5.
~ oles 24 of one module and holes 28 of the next module are ioined by pivot rod 38 to create a pin-and-bushing type of joint. It will be appreciated that intermediate section 30 as reinforced by its connection with tooth 32 unctions to support elemenrs 21 against lateral forces tending to separate the links as well as on twisting or bending forces on the modules which would tend to shear pivot pins 38. To drive belt 36 formed by linking a pluralit~ of modules 20 together with pins 38, there is provided a simple sprocket wheel 40 shown oDly in fragment, sprocket wheel ¦having a plurality of radial teeth 42. Each groove defined by surfaces 44 and 45 lying between adjacent teeth 42 are shaped to ¦mate, at least in major part, with the corresponding surfaces 34 and 35 of teeth 32, i.e~ surfaces 44 and 45 are cylindrical egments which are the inverse of surfaces 34 and 35 respectively, n that the former surfaces are concave where the latter surfaces re convex. It will be appreciated that when a pair of modules ~25 20 are coupled to oné another by pivot pin 38 because the modules re staggered the width of the co~bined modules is greater than ', . . . .
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ll 1131937 the width of a single module by at least a width of one link-like element 21. The axial width of the driving teeth 42 on sprocket wheel 40 should therefore preferably have a width at least equal to or greater than the width of the coupled modules.
As noted earlier, the curves employed in shaping tooth 32 and the matching sprocket serve to insure that the tooth faces cannot rub or abrade the sprocket surface during entry to exit, i.e. obviates scrubbing action, thereby minimizing wear and permitting high speed operation.
~his can be demonstrated by a numerical analysis of the - relationship between the position of arc centers for tooth pro-file relative to link pivot points, and the scrubbing action of belt links on the driving sprocket. Assu~e for example that conveyor belt 36 approaches the driving sprocket wheel 40 and 15 ~ is supported upon carrying ways so that the centers of the pivot rods 38 connecting the individual conveyor belt links 20 approach wheel 40 on a horizontal line. When any pivot rod center reaches ; the vertical center line of the driving sprocket, it is fully supported by the sprocket. Referring particularly to Fig~ 16A

2~0 ~ ~ (in which only teeth-32 are shown as part of a link, and teeth 32 re in truncated form as in Fig~ 15) it can be seen that pivot od 38A i~ on the vertica} cen~er line CL 90 that tooth 32A is fully seated in an appropria~e groove on sprocket wheel 40, while tooth 32B is approaching wheel 40 and quite separate from the latter. As the c-nter of pivot rod 38A is carried around the :"' ~, `.:'.,.- . . , ` ~13~37 ¦sprocket wheel, it follows a circular path P. Therefore, the ¦center of any pivot rod approaches the drivin~ sprocket on a ¦straight horizontal line L to the s~rocket vertical center line ¦CL then follows a circular path P at the pitch radius R around S ¦the sprocket wheel.
¦ The vertical height of ~he center of pivot rod 38A above ¦the sprocket center is equal to the pitch radius R. Radius R
is determined by the conveyor belt pitch pt of 1.1811 inches ¦(30mm) and the number of teeth in the sprocket. For a 12-tooth ¦sprocket, pitch radius R is (1.1811/2)/sin 15 = 2.2817 inches.
¦This distance R is 1.93185 times the pitch. Conversely, the ¦pitch is .5176R for a 12-tooth sprocket. The radius to the pro-¦file of the conveyor belt link was chosen as 0.748 inches. The ¦distance from the sprocket center to the line pt between centers ¦38A and 38B in Fig. 13A is 2.2817 cos 15 = 2.2040 inches. With these factors known, it is possible to calculate the position of a pivot rod center for any sprocket position or any point along a straight line connecting the pivot rod centers of a conveyor belt link. The reason for wanting to locate the position of these points is that the centers of the arcs which define the profiles of the conveyor belt link which engage the sprocket lie along this line. For exemplary purposes, the centers for ~he arcs which define the belt tooth faces or profiles have been selected at a distance d which is one-quarter of a pitch in from ~25 the pivot rod centers or pivot points, so that the tangent angle as noted is less than 90.

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1~31937 ~ext, consider the position shown in Fig. 13B, where the pivot point 38A has advanced 15 with respect to Fig. 13A beyond ihe vertical center line. The belt link center line pt connect-ing the pivot points made an angle ~ with the horizontal line L.
The sine of the angle ~ is 1.93185(1 - cos a), where a is the angle the line G connecting pivot point 38A and the sprocket center makes with the vertical center line CL. For a = 15, ~ = arc sin 1.93185(1 - Cos 15) = 3.774. At a distance of one-quarter the pitch left of pivot point 38A, i.e. at point H, ~ 10 the vertical distance below horizontal line L is .75(1.1811) ; sin 3.774 = .0583 inches. Point H is the center of the radius to the tooth face or profile. The vertical distance to point J, the center of the radius to the sprocket tooth face, from horizontal line L is 2.2817 - 2.2040 or .0777 inches. This is 15 ~ .0194 inches below point H as as shown, tooth 32B will not rub on the sprocket.
~;~ Next, consider the position shown in Fig~ 13C, again with the ; ngle a equal to 15. This time, the centers Of curvature for the aces of tooth 32B are shown located one-quarter pitch outside Z0~ the pivot points so that the tangent angle is greater than 90.
pgain~ ~ is 3.774 sinae a is ~till 15. Point H is 1.25(1.1811) in 3.774 - .0972 inches below the horiæontal line. Point J
is 2.2040 inches above the sprocket center or .0777 inches below he horizontal line. Therefore, point J is .0195 inches above oint H. For this case, the link tooth face wCuld be theoretically , ~,,..
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ll 1131937 below the sprocket tooth face. Since Ihis cannot happen prac-tically, the link tooth face will rub on the sprocket tooth face it drops into its seat (while the sprocket rotates 30), and pivot point 38C will be lifted above horizontal line L.
As a fourth and final case, consider the position shown in Fig. 13D. Again, the angle ~ is chosen as 15, but this time the centers for the belt link tooth faces are selected in the unique positions of exactly at the pivot points, and the tangent angle equals 90. The distance o~ point H would be 1.000(1.1811) sin 3.774 = .0777 inches below the horizontal line. Point J
would be 2.2817 - 2.2040 or .0777 inches below the horizontal line. Therefore, point J and H would be coincidental, and the link tooth face and the sprocke~ tooth face would be coinci-dental. Theoretically r they would be in contact as the belt link dropped into its sprocket seat, but with no rubbing pressure between `the two.
As earlier noted, only the pivot points of the belt lie on ¦the pitch circle as they travel around the sprocket wheel, and lines connecting the pivot points fall below the pitch circle.
The links approaching the driving sprocket, therefore, have a ; variable velocity characteristic of the chordal efect. The belt made with links as hereinbeore described can be analyzed for chordal effect by determining the distance traveled by a ivot point as it approaches the driving sprocket for a small angle of sprocket rotation~ `
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~ -17-~:
, Il 113193'7 A twelve-tooth sprocket with a conveyor belt pitch of 1.1811 inches (30mm) will be assumed for this analysis as shown in Fig.
16 because, as well known, sprockels with more teeth will exhibit less chordal aciion proporiionalely. The pitch radius R is again assumed to be (1.1811/2)/sin 15 = 2.2817 inches, i.e. 1.93185 times ihe pitch. The angle ~ is ~he angle between an ex~ension of the horizontal line L upon which ~he pivoi points approach and a line pl connecting piVOI points 38A and 38B. The sine of Ihis angle is 1.93185 (1 - cos ~) where ~ is the angle line G through the sprockel center and pivot point 38B makes with the sprocket verlical center line CL. The horizontal distance from che vertical cenler line Ch to ~he pivot poin~ 38~ is Rsina. The horizontal distance between pivot points 38B and 38A is Qcos~. Therefore, pivol point 38A is shown at Qcos~ - Rsina to the left of the sprock ~t ; 15 vertical center line CL.
; To determine the velocity variation, the distance from pivot ~:
poinl 38A lo the sprocket vertical cenler line was calculated for every two degrees of sprocket rotation and a plot of the velocity varia~ion for about 30 of driving sprocket rotation is shown in ig. 17.
With ~his analysis in hand, ic is seen that the conveyor belt action and veloaicy variation are considerably different from that of a roller chain running on a sprocket with the same number of teeth. For example, a similarly dimensioned roller ~25 chain would rise and fall approaching a Iwelve-iooih sprocket, and the velocity variation from chordal action would be about 7.2 percent. The preseni invention exhibits an improvement of abou~ 700% over such a chain.

,- . .

1131937 ~ ~

In one particularly desir~ahle form of the present invention as shown in Figs. 6 and 7, module 20 is formed with at least one edge or end element 21 designated as edge guide 43 having a width which is smaller at or near tooth 32 (the bottom portion as shown) than at the top (as shown) so that the edge of end link or element 21 is tapered or beveled through an angle a as sho~m in Fig. 6.
A helt can then be formed of modules such as is shown in Fig. 6, by providing that each alternative module is simply a reversed form of the module of Fig. 6 so that edge guide 43 alternates ~10 from left to right along the belt. ~hen this belt is assembled by joining the alternately reversed modules with pivot pins 38, the cross section of the belt will have a ~7-shaped configuration, thus providing a link belt which also then possess attributes of V-belts. To drive such a link belt with a V-shaped configuration, ;~ sprocket wheel 40 of Fig. 5 can have the configration of a pitched ¦chain sheave~ such as is shown in Fig. 8 where the central hub or sprocket with teeth 42 is disposed between a pair of circular ¦flange~s shaped as shallow conical discs 44. The conical angle of discs 44 should be matched to the taper angle, u, of the module ~ ~ shown in Fig. 6 to gain the advantages of V-belts.
The links of the present invention, such as are shown in Fig. 1 can also be assembled to form a belt in which only evexy other (or third, fourth, etc.) pivotally coupled link (or module as the case may be) ~ears a tooth 32 particularly when the links or modules are very small. Further, one can assemble .
'':.
~ -19-, .... .

, ~ 113~37 ~

a belt in which teeth 32 do not necessarily all ~rotrude in the same direction radially either inwardly or outwardly with respect to the endless loop formed by the helt. For example, as shown in Fig. 14, the links or modules formed therefrom may be assembled so that teeth 32 protrude radially (with respect to the loop formed by the belt) in alternately opposite directions. When used with a pair of counter-rotating driving sprockets 4OA and 40B (similar to sprocket 40 of Fig. 5) the belt of Fig. 11 can be driven along a tortuous or serpentine path with substantially no slippage or power loss and therefore provides a very precise timing belt. Alternatively, one can employ a double-tooth link such as is shown in Fig. 12 which includes a second tooth 32A
extending on the opposite side of the module fram tooth 32 and formed of two cylindrical surfaces centered on axes denoted as P2 and Pl or even other pointæ.
As shown in Fiq. 11, when the pitch of a link (i.e. the dis-tance between axes A and B) is sufficiently large in relation to the thickness or height of the link, one can generate both sur-faces 34 and 35 about a single axis shown as point P3 lying ~20 ~ equidistant between axes A and B. It will be apparent that the closer to the midpoint between A and B one places the axes o revolution of surfaces 34 and 35, the shallower will become toot~
~, 32 (the extreme case being the clrcular segment shown as tooth 32 in Fig. 11), but the tooth separation (i.e. the spacing be-tween tooth and sprocket surfaces per angular degree of movement of~ the link about either pivotal axis A or B) is maximized.
,.~ . .
:; ~

: 11 i , .

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A module for constructing linked structures for use as hinged, endless belts, said module comprising, in combination:
a first plurality of link ends of substantially identical width, each link end of said first plurality being formed to circumscribe a pivotal hole, the holes of said first plurality being arranged coaxially along a first pivotal axis, said first plurality of link ends being spaced from one another by approximately said width;
a second plurality of link ends of substantially identical width, each link end of said second plurality being formed to circumscribe a pivotal hole, said holes of said second plurality being arranged coaxially along a second pivotal axis parallel to said first axis, said second plurality of link ends being spaced from one another by approximately said width;
an intermediate portion integrally formed with and joining said first and second plurality of link ends so as to preserve the parallel relation of said axes;
a driving tooth formed integrally with and protruding from said intermediate portion substantially normal to the pitch line between said first and second axes intermediate the latter;
said tooth having a pair of working surfaces, each of the working surfaces having a shape in the range between and including that of a cylindrical segment and a chord of said segment;
the axis of each working surface being parallel with the pivotal axes of the link and positioned intermediate the pivotal axes or coincident with the pivotal axis furthest from that surface;
the pair of working surfaces being part of a pair of intersecting loci;
the shape of each of the working surfaces being such that the tangent angle of each such surface is not more than 90°, the tangent angle being defined between a tangent at a point on one working surface and a line joining that point to the opposite pivotal axis; and each of said plurality of link ends of said module being pivotally engageable to one of the plurality of link ends of adjacent modules.

2. A module for constructing linked structures for use as hinged, endless belts, said module comprising, in combination:
a first plurality of link ends of substantially identical width, each link end of said first plurality being formed to circumscribe a pivotal hole, the holes of said first plurality being arranged coaxially along a first pivotal axis, said first plurality of link ends being spaced from one another by approximately said width;
a second plurality of link ends of substantially identical width, each link end of said second plurality being formed to circumscribe a pivotal hole, said holes of said second plurality being arranged coaxially along a second pivotal axis parallel to said first axis, said second plurality of link ends being spaced from one another by approximately said width;.
an intermediate portion integrally formed with and joining said first and second plurality of link ends so as to preserve the parallel relation of said axes;
a driving tooth formed integrally with and protruding from said intermediate portion substantially normal to the pitch line between said first and second axes intermediate the latter;
said tooth having a pair of working surfaces, each of the working surfaces having a shape in the range between and including that of a cylindrical segment and a chord of said segment;

the axis of each working surface being parallel with the pivotal axes of the link and positioned intermediate the pivotal axes or coincident with the pivotal axis furthest from that surface;
the pair of working surfaces being part of a pair of intersecting loci;
the shape of each of the working surfaces being such that the tangent angle of each such surface is not more than 90°, the tangent angle being defined between a tangent at a point on one working surface and a line joining that point to the opposite pivotal axis; and one side of said module being tapered such that in cross-section the module is smaller near the driving tooth, the taper having an angular configuration to mate with a corres-ponding V-shaped wheel;
each of said plurality of link ends of said module being pivotally engageable to one of the plurality of link ends of adjacent modules.

3. A module as defined in claim 2 wherein a plurality of said modules are pivotally connected at engaged link ends, the tapered side of each module being opposite to the tapered side of adjacent modules to provide an average cross-section of said belt having a V-shape configured to mate with a corresponding V-shaped wheel.

4. A linked belt assembly comprising:
a plurality of links, each having at least a pair of opposite link ends each circumscribing a pivotal hole centered about a respective one of a pair of parallel pivotal axes, and a rigid intermediate section joining said link ends;
said link ends having no driving engagement with an associated sprocket wheel;
each of selected ones of said links having at least one driving tooth protruding from said intermediate section substantially normal to the pitch line between said pivotal axes and intermediate said pivotal axes;
said tooth having a pair of working surfaces, each of the working surfaces having a shape in the range between and including that of a cylindrical segment and a chord of said segment;
the axis of each working surface being parallel with the pivotal axes of the link and positioned intermediate the pivotal axes or coincident with the pivotal axis furthest from that surface;
a pair of working surfaces being part of a pair of intersecting loci;
the shape of each of the working surfaces being such that the tangent angle of each such surface is not more than 90°, the tangent angle being defined between a tangent at a point on one working surface and a line joining that point to the opposite pivotal axis;
each of the link ends of each link being pivotally connected to a link end of adjacent links by means extending through said holes;
a toothed sprocket wheel having recesses between adjacent teeth thereof, each of said recesses including a pair of facing surfaces of shape corresponding to the pair of working surfaces of said driving tooth; and only the teeth of said connected links being in driving engagement with the recesses of said sprocket wheel, the engaged linked belt and sprocket wheel exhibiting minimal scrubbing action and chordal action,

5. A linked belt assembly as defined in claim 4 wherein said plurality of links each includes a rigid intermediate section having solid material along the axis of driving force.

6. A linked belt assembly as defined in claim 4 wherein said working surfaces are like surfaces with substantially identical radii of curvature.

7. A linked belt assembly as defined in claim 4 wherein said tooth is blunted, adjacent said line of intersection, by a surface formed as a cylindrical segment having its axis on said line of intersection.

8. A linked belt assembly as defined in claim 4 wherein said tooth is truncated adjacent said line of intersection.

9. A linked belt assembly as defined in claim 4 wherein said working surfaces are each formed having the curvature of a cylindrical segment.

10. A linked belt assembly as defined in claim 9 wherein the axes of said cylindrical segments lie substantially in the common plane of said pivotal axes.

11. A linked belt assembly as defined in claim 9 wherein the radii of curvature of said surfaces are centered at a common cylindrical axis.

12. A-linked belt assembly as defined in claim 4 wherein said link ends and tooth are of the same width.

13. A linked belt assembly as defined in claim 4 wherein said link ends are of the same width and said tooth is slightly less than twice as wide as the width of said link ends.

14. A linked belt assembly comprising:
a plurality of linked modules, each having a first plurality of link ends of substantially identical width, each link end circumscribing a pivotal hole, said holes of said first plurality being arranged coaxially along a first pivotal axis, a second plurality of link ends of said substantially identical width, each link end being formed to circumscribe a pivotal hole, said holes of said second plurality being arranged coaxially along a second pivotal axis parallel to said first axis, and an intermediate portion joining said first and second plurality of link ends so as to preserve the parallel relation of said axes;

said link ends having no driving engagement with an associated sprocket wheel;
each of selected ones of said modules having at least one driving tooth protruding from said intermediate portion substantially normal to the pitch line between said pivotal axes and intermediate the latter;
said tooth having a pair of working surfaces, each of the working surfaces having a shape in the range between and including that of a cylindrical segment and a chord of said segment;
the axis of each working surface being parallel with the pivotal axes of the link and positioned intermediate the pivotal axes or coincident with the pivotal axis furthest from that surface;
the pair of working surfaces being part of a pair of intersecting loci;
the shape of each of the working surfaces being such that the tangent angle of each such surface is not more than 90°, the tangent angle being defined between a tangent at a point on one working surface and a line joining that point to the opposite pivotal axis;
one of said pluralities of link ends of each said module being engaged between and substantially in contact with one of said pluralities of link ends in an adjacent module except for the individual link ends positioned at the extreme sides of said belt;:
means extending through said holes pivotally connecting said modules at engaged link ends;
a toothed sprocket wheel having recesses between adjacent teeth thereof, each of said recesses including a pair of facing surfaces of shape corresponding to the pair of working surfaces of said driving tooth; and only the teeth of said connected links being in driving engagement with the recesses of said sprocket wheel, the engaged linked belt and sprocket wheel exhibiting minimal scrubbing action and chordal action.

15. A linked belt assembly as defined in claim 14 wherein said working surfaces and facing surfaces are cylindrical segments of substantially like radius of curvature.

16. A linked belt assembly as defined in claim 14 wherein said links are each of integral construction.

17. A linked belt assembly as defined in claim 14 wherein said working surfaces are curved and said facing surfaces are curved and inverse to the curved working surfaces.

18. A linked belt assembly as defined in claim 14 wherein said working surfaces are each formed having the curvature of a cylindrical segment.

19. A linked belt assembly as defined in claim 18 wherein the axes of said cylindrical segments lies substantially in a plane common to said first and second axes.

20. A linked belt assembly as defined in claim 14 wherein said first and second pluralities are the same number.

21. A linked belt assembly as defined in claim 20 wherein each link end of said first plurality is joined to a corres-ponding link end of said second plurality by a section having a substantially straight edge and an opposite edge which is the cross-section of said tooth.

22. A linked belt assembly as defined in claim 20 wherein each link end of said first plurality is joined to a corres-ponding link end of said second plurality by a section having a curved edge and an opposite edge which is the cross-section of said tooth.

23. A linked belt assembly as defined in claim 14 including a second driving tooth formed integrally with and protruding from said module in a direction opposite to said one tooth.

24 . A linked belt assembly as defined in claim 23 wherein said second tooth has a pair of surfaces formed sub-stantially the same as said surfaces of said one tooth.

25. A linked belt assembly as defined in claim 14 wherein said cylindrical axes lie substantially intermediate said first and second axis and coplanar therewith.

26. A linked belt assembly as defined in claim 14 wherein all of said teeth protrude from said belt in the same direction relative to the plane of said belt.

27. A linked belt assembly as defined in claim 14 wherein a first number of said teeth protrude from said belt in one direction relative to the plane of said belt and a second number of said teeth protrude from said belt in an opposite direction.

28. A linked belt assembly as defined in claim 14 wherein the direction in which said teeth protrude from said belt alternates module by module.

29. A linked belt assembly as defined in claim 14 wherein at least one side of each said module is beveled and said modules are arranged with said one side of successive linked modules being on opposite edges of said belt so that the average cross-section of said belt is V-shaped.