CA1108438A - Stress-relieved v-ribbed belt and method for making same - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
An endless V-ribbed power transmission belt and method of making same is provided herein. The belt is made primarily of an elastomeric material and has a tension section, a load-carrying section and a ribbed compression section ad-jacent to the load-carring section. The belt includes stress-relief means in the ribbed portion of the belt. Such stress-relief means comprises a plurality of folded fabric portions which extend into the ribs at spaced intervals along the end-less path of the belt. Each of the folded portions has associated portions of fabric in contact at an associated interface. The interface thus serves as stress-relief slits for for belt. The associated portions of fabric serving as fabric cushions on op-posite sides of an associated stress-relief slit. The belt thus has high flexibility, and large load-carrying capacity, yet is capable of operating over extended time periods in a stress-relieved and cool manner.

Description

This invention relates to endless Fo~r tran.~mlssion belts of the type known as-"V~rib~ed", "nLltiple rib" or nLlti-ribbed".
V~ribbed belts havLng tran~verse slits or cuts in the ribs there-of ha~e been proposed ~2reto~ore and ex~mples of such belts are shown in u.S. Pa~ent No. 2,728,239. Howev~r, belts of the type shown in this E~tent, when operated around so-called backside driv~ sheaves, are subjected t~ con-siderable stresses, generally resulting in cracks emanating from the top ~f the slits or cuts to the top of the helt.
Further, belt~ o~ the type shcwn in U.S. Patent 2,728,239, where notches are cut into the ribbed portion o the belt, while providing de-sired ~1~ ~ ility, d3 not always pr~vide optimum support ~or their associ ated load-carrying section.
A~cordin~ly, the ne~d exists of a simple and eoonomical V-ribbed endless power transmission belt havlng high ~lexibility and large load-carrying capaci~y, yet capable o~ operating over extended timer periods in a stress-relieved and oool m~nner~
It is therefore an object of one broad asp0ct of the present in-vention to provide an ~ ved V-ri ~ endle~s power transmission kelt.
AnDther object o another aspect o~ the pre~ent invention is to provide a m~thvd for making an improv~d V-rihbed endless power tran.qmlssion b~lt.
In accordance with a broad aspect of the present Lnventionl th~re . .. .. . , . _ , .. .. . .. . . _ . . _ _ . . . . . .. .. ..
is provided an e~les~ ~ er tran~ml~sion belt made primarily of an elas-tomeric material and oomp~isLng a tension ~ection, a load-carrying section and a ri~bed oompres~ion seation havLng stres~-r~lief means in the ri~bed portion of ~he co~pre3~ion~section. Mbre particularly, the belt of an aspect of this lnv~ntion has a rikbed ~ection defined by a ~lurality of xibs, the ribs being deflned by a plurality o~ alternatin~ projections and re-cesses. The ribbed sestion ha~ stress-ralief mean~ oomprisiny a plurality of folded f~bric poxtions ext2nding i~bo the ribs at spaced interval .
, L3~
the endless path of the belt. Each of the folded fabric portions has associated portions of fabric in contact at an associated interface which serve as stress-relief slits for the be~lts.
Additionally, the associated portions of Eabric serve as fabric cushions on opposite sides of -the associated stress-relief slit.
By one variant, thereof, the stress-relief means extends a distance of 0.3 and 0 95 times the thickness of the compression section.
By another variant, the compression section is a fiber~reinforced elastomeric layer.
By a variant~ the folded portions may be either equally or unequally spaced alon~ the endless path.
~ By another variant~ the compression section has an ; elastomeric bottom layer and at least one additional layer ar-ranged inwardly o* the bottom layer.
- By a variation thereof, the additional layer is a fiber-reinforced elastomeric layer By another aspect of this invention a method is pro-vided for making an endless power transmission belt made pri-marily of an elas-tomeric materiaI, the belt comprising a tension section, a load-carrying section adjacent the tension section and a ribbed compression section adjacent the load-carrying ; section defined by a plurality of ribs, -the ribbed section having stress-relief means comprising a plurality of folded fabric portions extending into the ribs at spaced intervals along the endless pa-th of the belt, each o~ the folded portions having associated portions of fabric in contact at an associated in-ter-face, the interface serving as stress-relief slits for the belt, and the associated portions of the fabric serving as fabric - 3 ~

' ''` ~

- .

3~
cushions on opposite sides of an associated stress-relief slit, the method comprises the steps of; (a~ fabricatin~ a vulcanized belt sleeve defining the tension section, the load-carrying section and the compression section; (b) providing -the compres-. :

`
~ .

~ 3 a -~ ~-J

' 3~
sion section with a plurality of folded portions each having associated portions of fabric material arranged closely ad-jacent each other, tc3 the folded portions to extend inwardly into the compression section$ and (d) cutting the sleeve to de-fine a plurality of longitudinal ribs in the compression section.
By one variant, step (g) of fabricating the sleeve comprises the steps of; (i) wrapping at least' one layer of -~ fabric around a cylindrical drum having a central longitudinal axis; ~:~ii) wrapping a first layer of elastomeric cushion material, a layer of load-carrying cord and a second layer of elastomeric cushion material consecutively around the fabric~
wrapped drum; (iii) wrapping a folded portion assembly com prising an elas-tomeric material having a plurali-ty of fabric-lined grooves on the outer surface thereof around the second elastomeric cushion layer; and (iv) vulcanizing the resulting sleeve, By another variant, the folded portion assembly is formed by the steps of; (i) lining a member having a plurality of alternating ridges and grooves with a fabric material to -: 20 define fabric-lined ridges and grooves; (ii) placing a plurality of elongated strips of elastomeric material in the fabric-lined grooves; and (iii) lay;ng a sheet of elastomeric materîal over the strips to define the assembly.
By one variation -thereof, the placing step (ii) com-prises placing a plurality of elongated strips of elastomeric material, which are free of reinforcing means, in the fabric-lined grooves.
By another variation, the laying step. (iii) comprises:
laying a sheet of elastomeric material, the sheet being free of _ 1~
. -' ' ' ~ ~ ' . ' .

3i~3 reinforcing means, over ~:he strips.
By a further variation, the laying step comprises laying a sheet of elastomeric material, the shee-t having re-inforcing means dispersed there-through 7 over the strips.
In the aceompanying drawings, Figure 1 is a perspective view illustrating one exemplary embodiment o* the endless power transmission belt of one aspect of this invention;

_ 4 a -.
: . ' ' ' Figure ~ is a fragmentary cross-sectional vi~w taken at the line

2-2 of Figure l;
Figure~ 3, 4 and 5 illustrate a series of method steps which may be employed to define the belt of Figure 1; and, Fig~re 6 ie a fragm~n~ary cro~ ectional view illustratLng another exemplary ~nbodiment of the kelt of another aspect of this invention.
Reference is ncw ~adc to Figures 1 and 2 o~ the drawing which illustrate an Qxe~plary embodLment of an endless power transmission belt of one aspect o~ this invention which is desi~nated generally by the reference n~eral 2. The belt 2 is capable of carrying substantial loads, has opti-mum flexihility, and is, in e~sen~e, a stress-xelieved multi-ribhed belt.
The belt 2 compri~e~ a ten~ion section which is designated gener-ally by the reference numeral 4, a load-carrying ~e,ction 6, and a compres-sion section 8, The tension section 4 of ~he belt 2 comprise~ a top fabric c3ver 5 which is impregnated wi~h a ~uitable elas ~ ic compound. Alte~natively, as shcwn in Figure 6, the ten~ion ~ection 4A can oomprise a suitable elas-tcmeric ccmpound 7A which i~ adjoined on one side ther~of by the cover 5 and by the load-carryLng ~ection ~A o~ it~ opposite side.
R~fe~ring again to Figures 1 and ~, the load-carrying ~ection 6 - oo~yrises a helically~wound load-carrying cord 10 which is suitably embedded in a known manner in an elaatomeric cuehion bas3 12. ~owever, it will ~e appreciated that the load-carrying section 6 can be ~ade of any ~uitable material a~d utilizlny an~ suitable technlque kncwn in the art.
The oompre~lDn ~ectio~ 8 comprises a ribbed section 14 defined by a plurality of longit ~ ly ~xtending ribs each designated by the same refer~nce numeral 16, and the rib~ 16 are de~ined by a plurality of alterna~-ing projections 17 and reces~e~ 18. The oompression ~ection 8 has means for --- S ---- : ~ . - - : :
~ . : . . .

8~3~3 stress-relief of the belt thereof around associat~d sheaves. l~e stress-. relief ~eans is designated g~nerally by tha reference nu~.eral 20 and com~
p~ises a folded pvrtion of fabric ~xtending m to the oompression section at spaced po~itions, which is this example of this aspect of the in~ention are equally spaced along the endla85 path of the compression section and hence along the enlless path of the belt. Alternatively, the stress-relief means can be staggered~
Each of th~ ~olded portion~ 20 ha~ associated portions 22 of fab-ric in contact at an associated interface 24 hereby the i~terfaces 24 deflned ~0 by associated portions 22 serve, in essence, as s~ress-relief slits ~or the belt 2~ FuIther, the assccia~ed portion~ 22 serve as fabric cu~hions on opposite sides of an associated s~xe~s-relief slit as defined by the as~ociated in~exface 24.
As the belt 2 travels around associated ~heaves or pulleys, the belt tends to compre~s the compres3ion sectlon 8 in the usual manner while stretching the ten~ion section 4 of ~he belt. The compression of the comr pression section 8 is easily accDmDdated by the cushio m ng action provided by the foldel portions 22 of the fabric which also define the interfaces 24 and serve a~ ~tress~-relief ~lits whereby the belt 2 is flexed in an easier manner with minimum Lnternal ~tres~e~, thus pro~iding nU~LUmUm hysteresis, thereb~ enabling the belt 2 ~o run in a cooler mannar.
m e load-carrying section 6 of the belt 2 i~ provided with opki mum support by the portions 22 in face-to-face contact at interfaces 24 and the ~lastomeric m~terial comprisLng ~he layer 14. Additionally, the belt 2 has high fl~xibili~y without rsquir mg the provision of teeth or cut notches in the co~pros~ion section. O~viously~ ~he ~rovision of teeth or notches in the compre~ion ~ection a~ a~hieved in previously proposed kelts, results in a reduced amDunt of support of the load-carrying section of such previously prcposed belt~.

- :

: The balt 2 can be made utilizing any suitable technique or method kncwn in ~he art; hcwever, the belt 2 is preferably m~de utilizing the method steps described her~inafter and as shown in Figures 3~ 4 an~ 5 of the draw mg wher~by a belt sl~ave is first defined and a pl~rality of belts 2 i~ cut from ~uch sleeva.
m e method of an aspect of this invention ccmprises the steps of lining a member 26, as shGwn in Figure 3, ~hich has a plurality of alter-nating ridges 28 and groove~ 30, such a~, for example, a metal forming m~m~
ber, with a fabric m~terial which i~ designa~ed by the ref~rence numexal ~2 to define fabric-lined rid~es and groove~. A plurality of elongated strips 34 of elasbomeric ma~erial are then placed in the fabric lined grGove~ and a ~heet ~6 (ihown having an exaggerated thickness) of elastcmeric material is pla~ed or laid over the ~trip~ to define an assembly which is d~signated generally by the refarence numeral 38.
The ~elt 91eeve~ designated generally by the reference numeral 40 is built up in inverted ~agbion on a aylindrical dn~n 42 as shown in Figure 4. m e drum 42 ha~ a right circular cylindrical outside ~urface 44 and is a oonventional drun used to build up, cure and cool a kelt sleeve 40. m e belt Rleeve 40 is buil~ ~ by wrappLng consecutively, one or m~re layer~ of fabric 46, a layex o elasbomeric cu3hion ~aterial 48, a layer of helically-w~ ~ load-carryl~g cord 50, and a layer o~ e~asto~eric cushion material 48.
The assembly 38 i~ re~oved or suitakly lifted awa~ from th~ m~er 26 and such assembly i9 wrapped around the out~ide cushion layer 48 with the fabric layer 32 to the outside, ~hereby oompleting the uncured sleeve. me uncured belt sleeve 40 is ~rappad or otherwise .unwardly compressively ancircled and thereaf~er cured in the ~ual known manner. The curing action causes the strip3 34 and 3heet 36 to flcw toge ~ a~ a unitary ~ass which when the individual belts 2 are out ~rom such sleeve define layer 14 of the com~res-sion section. The cured sle~e 40 is then oDol~d utilizing techniques ~hich 7 ~

.- . - - . . . : ~. .

: - : , '. : . .. ' ' :

are kncwn in the art.
me ribs 16 are ~hen defined in the cured sleeve 40 by die cutting or by grinding, as sh~wn in Figure 5. The drwm 42 is supportel ~y rotation on suitable support ~eans, not shawn, and a suitable cutting means sh~wn as a rotary wheel 52 having a grinding face o~ suitable cro~s-section is emr ployed to precisely define the ribs. m e grinding ~heel 52 is rotated while rota~in~ the slee~e 40. As the sleeve 40 is ground to define the ribs 16, the fabric 32 is remDve~, except in the folded portions 22. The belts 2 are -then cut from sleeve 40 in kncw~ m~nner.
Another exemplary embodiment of the belt of another aspec-t of this invention is shown in Figure 6. The belt illustrated in ~iyure 6 is simi-lar bo the belt 2; therefore, such belt is designated by the re~erence numr eral 2A and representative part~ of each belt similar to corresp~ndin~ parts of belt 2 are designated by the same reference numeral as in belt 2 followed by an assc~iated letter designaticn A and will not be described in detail.
Only those oamponent parts o~ belt 2A which are different from corresponding parts of belt 2 will be d~signated ~y ~ew reference numerals.
The difference bet~een the belt 2A of Figure 6 and the belt 2 are that the tension section 4A instead of having a single ~abric layer ~A has a layer 7A of ela~tomeric material k~ween the load-carryin~ section 6~ and the top fabric layer 5A; and that the compression section ~ has a platform l~yer 54 o~ elastomeLi¢ ~aterial between the load-carrying ~ection 6A and ths ribbed section 14A.
In this di3closuxe of aspects of this inv~ntion each of the belts is shcwn by cro59 hatching as beiny an ela~tomeric material in the form of rubber. Hcwever, it will be appreciated that each belt may be made of one or mDre sultable ~la~tom~ria material~ including natural and synthetic rub-ber and other synthetic plastic m~terials. Additionally one or ~Dre layers of such ~ can have reinforcin~ means, such as, for example, fibers - 7 a -,: ' ' . .:

,.
.

, ' thereby ~efining an elastomeric rubber matrix loaded with fibers. ~or example, the ribked section 14 o~ the belt 2 shc~ in Figure 1 can be a suitable ala~tcmeric xubber oompound having up to about 40 parts of ~ibers 56 dispersed therethrough. These fibers 56 can be any ~uitable material known in the art, and may be of any sultable diameter and length and arranged in any desired pattern relativs ~o the longitudinal axis of the belt as~soci ated therewith to ~ t the de~ired characteristics to ~uch belt. l~e plat~onm layer 54 of the kelt 2A ~hown in .Figure 6 also comprises the ~ibers 56A.
In this disclosure reference is made to the fabric layers 5 and 5A, and to fabric material 32 and fabric portions 22. Each o~ such layers, material and p~rtions m~y be ~D~2n fahric, n~n-woven fabric, or knit~ed fabric, as desired.
The folded porticns 20 can extend into the compression section 8 a dis~ance equal to about 0.3 to about O.9S ti~es the thicknes~ of the comr pre~sion ~ection 8 of the finish2d bYlt. ~y proper selection of the member 26 shown in Figure 3 and d~pth of cutting ox grinding the ribs 16 and re-ces es 18, a~ sh~wn in Figuro 5, the finished belt can have transversely connected asso~iated ~abric portion~ 22 - .

... ~ . . . .

Claims (13)

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

1. An endless power transmission belt made primarily of an elastomeric material and comprising a tension section, a load-carrying section adjacent said tension section and a ribbed compression section adjacent said load-carrying section defined by a plurality of ribs, said ribbed section having stress-relief means comprising a plurality of folded fabric portions extending into said ribs at spaced intervals along the endless path of said belt, each of said folded portions having associated portions of fabric in contact at an associated interface, said interface serving as stress-relief slits for said belt, and said associated portions of said fabric serving as fabric cushions on opposite sides of an associated stress-relief slit.

2. The belt of claim 1 wherein said stress-relief means extends a distance of 0.3 to 0.95 times the thickness of said compression section.

3. The belt of claim 1 wherein said compression section is a fiber-reinforced elastomeric layer.

4. The belt of claim 1 wherein said folded portions are equally spaced along said endless path.

5. The belt of claim 1 wherein said folded portions are unequally spaced along said endless path.

6. The belt of claim 1 wherein said compression section has an elastomeric bottom layer and at least one additional layer arranged inwardly of said bottom layer.

7. The belt of claim 6 wherein said additional layer is a fiber-reinforced elastomeric layer.

8. A method of making an endless power transmission belt made primarily of an elastomeric material, said belt com-prising a tension section, a load-carrying section adjacent said tension section and a ribbed compression section adjacent said load-carrying section defined by a plurality of ribs, said ribbed section having stress-relief means comprising a plurality of folded fabric portions extending into said ribs at spaced intervals along the endless path of said belt, each of said folded portions having associated portions of fabric in contact at an associated interface, said interface serving as stress-relief slits for said belt, and said associated portions of said fabric serving as fabric cushions on opposite sides of an as-sociated stress-relief slit, which method comprises the steps of: (a) fabricating a vulcanized belt sleeve defining said tension sections, said load-carrying section and said compres-sion section; (b) providing said compression section with a plurality of folded portions, each said folded portion having associated portions of fabric material arranged closely adjacent each other; (c) arranging said folded portions to extend inward-ly into said compression section; and (d) cutting said sleeve to define a plurality of longitudinal ribs in said compression section.

9. The method of claim 8 wherein said step (a) of fabricating said sleeve comprises the steps of: (i) wrapping at least one layer of fabric around a cylindrical drum having a central longitudinal axis; (ii) wrapping a first layer of elastomeric cushion material, a layer of load-carrying cord and a second layer of elastomeric cushion material consecutively around said fabric-wrapped drum; (iii) wrapping a folded-portion assembly comprising an elastomeric material having a plurality of fabric-lined grooves on the outer surface thereof around said second elastomeric cushion layer; and (iv) vulcanizing the resulting sleeve.

10. The method of claim 9 wherein said folded-portion assembly is formed by the steps of; (i) lining a member having a plurality of alternating ridges and grooves with a fabric material to define fabric-lined ridges and grooves; (ii) placing a plurality of elongated strips of elastomeric material in said fabric-lined grooves; and (iii) laying a sheet of elastomeric material over said strips to define said assembly

11. The method of claim 10 wherein said placing step (ii) comprises placing a plurality of elongated strips of elastomeric material which is free of reinforcing means in said fabric-lined grooves.

12. The method of claims 10 or 11 wherein said laying step (iii) comprises: laying a sheet of elastomeric material, said sheet being free of reinforcing means, over said strips.

13. The method of claims 10 or 11 wherein said laying step (iii) comprises: laying a sheet of elastomeric material, said sheet having reinforcing means dispersed therethrough, over said strips.