GB2106443A

GB2106443A - Moulding power transmission belts

Info

Publication number: GB2106443A
Application number: GB08222801A
Authority: GB
Inventors: Junji Imamura
Original assignee: Mitsuboshi Belting Ltd
Current assignee: Mitsuboshi Belting Ltd
Priority date: 1981-08-07
Filing date: 1982-08-06
Publication date: 1983-04-13
Also published as: ATA302782A; AT398054B; GB2106443B; CA1182969A; JPH0141490B2; JPS5825948A

Abstract

In a method of forming a power transmission belt an uncured belt sleeve (41) is provided on an expansible portion (14) of a mandrel (12), and may be formed in situ thereon. The mandrel (12), with the belt sleeve (41) provided thereon, is disposed coaxially within a radially inwardly grooved mould (29). The uncured belt sleeve (41) is urged radially outwardly into the grooved surface (28) of the mould (29) by expansion of the mandrel (12), and curing of the belt sleeve (41) is effected by heating the mould (29). The cured belt structure is readily removed from the apparatus for further processing, such as for dividing the wide cured belt structure into individual belts. The grooves (28) may be trapezoidal rather than triangular in shape. <IMAGE>

Description

SPECIFICATION Method of, and apparatus for, forming power transmission belts This invention relates to the manufacture of power transmission belts and in particular to a method of, and apparatus for, forming such belts.

in one convenient method of forming power transmission belts, layers of belt material are wrapped about the outer layer of a cylindrical drum or mandrel. Illustratively, the layers successively wrapped about the mandrel include a rubber-coated fabric, an adhesive rubber sheet, spirally wound tensile cords, and a rubber sheet of preselected thickness. The wrapped structure defines a wide belt sleeve which is then suitably cured while retained on the outer surface of the mandrel. The outer surface of the cured sleeve is conveniently further treated as by grinding or cutting to define a plurality of ribs. The rubber material removed by the grinding or cutting operation in forming the ribs becomes scrap material and as a substantial amount of such rubber material is removed in forming such ribs, substantial unnecessary expense is incurred.

Another problem which arises in such a conventional method of forming transmission belts is the difficulty of grinding or cutting the ribs accurately as any deviation from a true circumferential forming operation provides irregularly configured rib structures, resulting in poor power transmission operation.

Another known method of forming power transmission belts is illustrated in our Japanese Utility Model Publication No. 30621/1970. As disclosed therein, a preformed, wide, tubular unvulcanized belt sleeve is inserted into a ring mould having V-grooves on the inner surface thereof. A flexible, cylindrical packing is disposed adjacent the inner surface of the belt sleeve and pressurized fluid, such as steam, is delivered to the centre of the packing.The opposite ends of the packing are sealed and the fluid pressure urges the belt sleeve against the V-grooves of the mould to form resulting V-ribs in the belt sleeve, thereby defining a poly-V power transmission belt This method has the disadvantage of requiring the forming of the belt sleeve in a prior manufacturing step, for instance by forming the belt sleeve on another mandrel and then transferring it to the final apparatus discussed above. If the circumferential length of the belt sleeve produced on the first mandrel is greater than necessary for accurate accommodation in the mould of the second apparatus, the tensile or strength cord layers tend to have waves therein extending laterally of the belt.Such waving of the tensile cords causes them to expand irregularly on the sides of the belt, which not only presents a poor appearance to the belt, but causes the belt to irregularly extend and vibrate during power transmission.

Where the belt formed on the first mandrel has a circumferential length iess than that providing an accurate fit with the mould of the second apparatus, inexact moulding of the V-shaped ribs in the sleeve results, again causing problems in the use of the resulting belt upon power transmission.

Moreover, it is difficult to support the preformed belt sleeve in the mould because of the flexibility thereof so that, upon conducting the curing operation, inaccurate conformity of the belt sleeve to the mould often results.

According to one aspect of the present invention, there is provided a method of forming a power transmission belt, comprising the steps of: providing a belt sleeve coaxially on a radially expansible cylindrical mandrel; disposing a mould spaced coaxially outwardly of the belt sleeve; expanding the mandrel to urge the belt sleeve radially outwardly against the mould; and curing the belt sleeve while maintaining it against the mould.

The present invention makes it possible to form a power transmission belt whilst eliminating or reducing the disadvantages and problems of the prior art methods and apparatuses, in a novel and simple manner.

Preferably, the belt sleeve is formed in situ by urging a plurality of desired layers of belt sleeve material about the expansible mandrel.

Preferably, the expansible mandrel comprises a rigid inner portion and a resilient outer portion seated, when not in use, on the rigid portion.

The present invention comprehends the provision of means for expanding the expansible portion in the form of pressuized fluid delivered to between the rigid inner portion of the mandrel and the resilient outer portion.

Another aspect of the present invention provides an apparatus suitable for use in forming a power transmission belt comprising: a radially expansible cylindrical mandrel; means for providing a belt sleeve coaxially on the mandrel; means for disposing a mould spaced coaxially outwardly of the mandrel and of any belt sleeve thereon; means for expanding the mandrel to urge any belt sleeve thereon radially outwardly against the mould; and means capable, in use, of curing a belt sleeve while maintaining it against the mould.

In an illustrated embodiment of the apparatus of the present invention (referred to in more detail hereinbelow), the resilient outer portion of the mandrel comprises a tubular element having its axially opposite ends clamped sealingly to the rigid portion.of the mandrel.

The curing of the belt sleeve may at least partially be effected by providing heat to the mould.

In one form, the mould comprises a split annular mould which may be circumferentially opened upon completion of the curing operation to permit facilitated release of the cured belt from the apparatus.

The present invention comprehends the subsequent cutting of the formed belt sleeve to define a plurality of multirib belts or,'alternatively, cutting the formed belt sleeve between each of the formed ribs to form a plurality of individual Vbelts, as desired.

The grooves of the mould may comprise a suitable cross-section groove as desired, including a triangular or trapezoidal grooves.

The rigid mandrel portion may be provided with a recess for receiving the resilient expansible mandrel portion.

To facilitate separation of the cured sleeve from the mandrel, means may be provided for applying a suction pressure to between the expansible portion of the mandrel and the rigid portion thereof so as to draw the expansible portion away from the cured sleeve and back into seated engagement with the rigid mandrel portion.

The method and apparatus of the present invention are extremely simple and economical while yet providing an improved, low cost power transmission belt manufacture.

BRIEF DESCRIPTION OF THE DRAWING Other features and advantages of the invention will be apparent from the following description taken in connection with the accompanying drawing wherein: FIGURE 1 is a diametric section of an apparatus forforming a power transmission belt, embodying the invention; FIGURE 2 is a diametric section similar to that of Figure 1 but illustrating the arrangement during the sleeve curing step; FIGURE 3 is a side elevation of a split annular mold for use in the apparatus; FIGURE 4 is a fragmentary perspective view of a power transmission belt formed in the apparatus; FIGURE 5 is a fragmentary section illustrating a modified form of mold groove for forming a trapezoidal rib in the cured sleeve; FIGURE 6 is a fragmentary perspective view illustrating a power transmission belt having trapezoidal section ribs as produced by the mold of Figure 5; and FIGURE 7 is a fragmentary perspective view of an individual V-belt having a trapezoidal cross section such as formed by dividing the belt structure of Figure 6 into individual V-belt sections.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the illustrative embodiment of the invention as disclosed in the drawing, apparatus generally designated 10 is provided for forming a power transmission belt, such as belt 11 illustrated in Figure 4..

More specifically, the belt forming apparatus 10 includes a mandrel generally designated 12 including a rigid cylindrical inner portion 13 and an expansible tubular outer portion 14.

The expansible mandrel portion is seated on the circumferential outer surface of the rigid inner portion in a recess 1 5 therein to define a cylindrical outer support surface 16.

As further illustrated in Figure 1, the mandrel inner portion 1 3 is further defined by enlarged annular grooves 1 7 and 18 at the axially opposite ends of recess 1 5 for receiving complementary enlarged axially opposite ends 1 9 and 20 of the mandrel portion 14. The end portions 19 and 20 are clamped in the grooves 17 and 18 by suitable clamp rings 21 and 22 secured to the rigid mandrel portion 13 by suitable threaded fasteners 23.

A belt sleeve generally designated 41 is formed in situ on the outer surface 16 of mandrel portion 1 4. The belt sleeve may be formed in the conventional manner by wrapping successively about the surface 16 a rubber-coated fabric 24, an adhesive rubber layer 25, a plurality of high strength tensile cords 26, which illustratively may be formed of polyester fibers, polyamide fibers, etc., and a compression rubber layer 27 of substantial thickness in which the desired ribs are formed. The different layers are best illustrated in Figure 4.

The belt sleeve 41 is in an uncured state at the beginning of the manufacturing operation, as illustrated in Figure 1. The sleeve is urged radially outwardly into engagement with a grooved inner surface 28 of a tubular mold 29 disposed coaxially of the mandrel and in outwardly spaced relationship to the belt sleeve 41, as shown in Figure 1. In the embodiment of Figure 1, the grooved surface 28 defines a plurality of triangular grooves. As further shown in Figure 1, the mold may be provided with a suitable passage 30 and fluid connectors 31 for passing heated fluid, such as steam, through the mold for use in curing the belt sleeve in the manufacture of the transmission belt.

The belt sleeve is expanded radially outwardly into the grooved surface 28 by suitable radial expansion of the expansible portion 14 of the mandrel. As shown in Figure 1, a pressurized fluid conduit 32 is connected to a fitting 33 opening through the rigid mandrel portion 13 to between the expansible portion 14 and the rigid portion 13.

Conduit 32 is connected to a source of pressurized fluid 34, such as a source of high pressure steam or high pressure air as desired. A suitable control valve 35 is provided for controlling the delivery of the high pressure fluid to conduit 32.

The valve selectively connects conduit 32 further to a vacuum pump 36.

Thus, expansion of the mandrel portion 14 is effected by the delivery of pressurized fluid through conduit 32 to the fitting 33 and retraction of the expansible portion 14 of the mandrel is effected by application of suction pressure thereto from the pump 36.

Upon completion of the forming of the belt sleeve 41 on the mandrel surface 16, pressurized fluid is introduced through fitting 33 from source 34 to expand the mandrel portion 14 radially outwardly and urge the rubber layer 27 of the belt sleeve into the grooved surface 28 of mold 29, as illustrated in Figure 2. As shown, the pressurized fluid is retained in the space 37 between the rigid mandrel portion 1 3 and expansible mandrel portion 14 by the sealed connection of the end portions 19 and 20 to the rigid mandrel portion 13.

Where the high pressure fluid comprises steam, thermal energy from the steam is transferred to the belt sleeve to assist in the curing thereof. The relatively soft uncured rubber layer 27 is readily urged into the grooved surface 28 so as to permit facilitated formation of the desired V-rib structure in the cured belt.

To maintain concentric relationship between the mold and the mandrel, and thereby assure accurate forming of the ribs in the cured belt, the mandrel and mold are coaxially accurately mounted to a supporting base 38.

Upon completion of the curing of the expanded belt sleeve, the expansible mandrel portion 14 is retracted as by application of vacuum pressure thereto from vacuum pump 36, thereby separating the mandrel portion 14 from the inner surface of the cured belt and permitting facilitated removal of the cured belt from the apparatus 10.

In one form, the mold 29 comprises a split annular mold, as illustrated in Figure 3, wherein diametrically opposite portions 39 and 40 of the mold are defined by interlocking tongue and groove means. Thus, facilitated removal of the cured belt may be effected by firstly opening the mold to disengage the formed ribs from the grooved surface 28.

The spacing between the outer surface of the belt sleeve 41 and the grooved surface 28 illustrated as W in Figure 1 is preselected to provide sufficient clearance for facilitated manufacture, while at the same time minimizing the amount of expansion necessary to effect the engagement of the belt sleeve rubber portion 27 with the grooved surface 28.

The invention comprehends, in the illustrated embodiment, the forming of the belt sleeve 41 on the mandrel remotely of the mold 29. Where this is effected remotely of the apparatus 10, the mandrel with the wound belt sleeve thereon is then brought to the apparatus 10 and the connection to conduit 32 is effected through the fitting 33 after the assembly is installed coaxially within the mold 29 on base 38. Thus, the steps of forming the uncured belt sleeves on the mandrel may be effected separately for facilitated seriatim production of a plurality of power transmission belts in this manner.

In illustrating the invention in Figures 1-4, the grooved surface 28 of the mold has been shown as triangular. Where it is desired to provide trapezoidal ribs in the molded power transmission belt, a modified mold 42 is provided, having trapezoidal grooves 43, as illustrated in Figure 5.

The manufacturing operation utilizing the mold 42 is identical to the operation discussed above relative to the use of mold 29. Thus, as seen in Figure 4, triangular ribs 44 are produced in the belt 11 by the triangularly grooved mold 29, whereas trapezoidal ribs 45 are produced in the belt 46 resulting from the use of mold 42.

Either of the belts 11 or 46 may be further divided circumferentially as as to produce individual V-belts, such as V-belt 47 illustrated in Figure 7 produced by separating the individual rib portions of belt 46.

Thus, the invention comprehends an improved method and apparatus for forming power transmission belts wherein the uncured belt sleeve is formed in situ on the mandrel and the mandrel is subsequently expanded to urge the relatively soft, uncured rubber portion thereof into a coaxial surrounding grooved mold, permitting the sleeve belt to be cured while retained in association with the mold so as to form a plurality of ribs without waste in a novel and simple economical manner.

The apparatus is arranged for facilitated assembly and disassembly so as to facilitate the mounting of the uncured belt sleeve in the apparatus and the removal of the cured belt therefrom.

As will be obvious to those skilled in the art, the specific construction of the belt sleeve may be varied as desired, and any suitable form of mold groove configuration may be utilized to provide any desired rib configuration.

As indicated above, the method and apparatus are extremely simple and economical while yet providing a highly improved, low cost power transmission belt manufacture.

The foregoing disclosure of specific embodiments is illustrative of the broad inventive concepts comprehended by the invention.

Claims

1. A method of forming a power transmission belt, comprising the steps of: providing a belt sleeve coaxially on a radially expansible cylindrical mandrel; disposing a mould spaced coaxially outwardly of the belt sleeve; expanding the mandrel to urge the belt sleeve radially outwardly against the mould; and curing the belt sleeve while maintaining it against the mould.

2. A method according to Claim 1, wherein the belt sleeve is wrapped about the expansible mandrel.

3. A method according to Claim 1 or 2, wherein the belt sleeve is formed in situ on the mandrel by urging a plurality of layers of belt-forming materials successively about the expansible mandrel.

4. A method according to Claim 1,2 or 3, wherein the expansible mandrel comprises a rigid inner portion and a resilient outer portion being seated on the inner portion during the provision of the belt sleeve on the outer portion.

5. A method according to any preceding claim, wherein the mould defines a plurality of inwardly opening annular grooves into which the belt sleeve is pressed by the expanded mandrel to form a corresponding plurality of annular ribs in the cured sleeve.

6. A method according to Claim 5, wherein the grooves in the mould have a triangular crosssection.

7. A method according to Claim 5, wherein the grooves in the mould have a trapezoidal crosssection.

8. A method according to any preceding claim, which includes the further step of cutting the cured sleeve circumferentially at axially spaced positions to divide the cured sleeve into a plurality of formed belts.

9. A method according to Claim 8 when appendant to Claim 5, 6 or 7, wherein the cured sleeve is cut circumferentially between each rib to form a plurality of individual V-belts.

1 0. A method according to any preceding claim, wherein the step of curing comprises applying heat to the belt sleeve through the mould.

11. A method according to any preceding claim, which also includes opening the mould upon completion of the curing step to release the cured belt.

12. A method according to any preceding claim, wherein steam is provided under pressure to the mandrel to effect the expansion thereof and to effect at least a portion of the curing action.

13. A method according to Claim 1, substantially as hereinbefore described with reference to the accompanying drawings.

14. A power transmission belt whenever formed by a method according to any preceding claim.

1 5. An apparatus suitable for use in forming a power transmission belt comprising: a radially expansible cylindrical mandrel; means for providing a belt sleeve coaxially on the mandrel; means for disposing a mould spaced coaxially outwardly of the mandrel and of any belt sleeve thereon; means for expanding the mandrel to urge any belt sleeve thereon radially outwardly against the mould; and means capable, in use, of curing a belt sleeve while maintaining it against the mould.

1 6. An apparatus as claimed in Claim 15, wherein the mandrel comprises a rigid inner portion and an extensible outer portion, and the means for expanding the mandrel comprises means for providing fluid under pressure between the mandrel inner and outer portions.

1 7. An apparatus as claimed in Claim 15, wherein the mandrel comprises a rigid inner portion defining a radially outwardly opening recess and an expansible outer portion capable of being received in the recess, and the means for expanding the mandrel comprises means for providing fluid under pressure between the mandrel inner and outer portions.

18. An apparatus as claimed in Claim 16 or 17, wherein the mandrel comprises a rigid inner portion, a generally tubular expansible outer portion, and clamp rings at axially opposite ends of the outer portion clamping the outer portion sealingly to the inner portion.

19. An apparatus as claimed in Claim 1 6, 17 or 18, which also includes means for providing suction pressure between the mandrel inner and outer portions upon completion of a curing operation.

20. An apparatus as claimed in any one of Claims 1 5 to 1 9, wherein the means for curing the belt sleeve comprises means for heating the mould.

21. An apparatus as claimed in any one of Claims 15 to 20, wherein the mould comprises a split annular mould.

22. An apparaus as claimed in any one of claims 1 5 to 21, wherein the mould is provided with a plurality of circumferentially coaxial grooves for forming ribs in the outer surface of the expanded cured belt sleeve.

23. An apparatus as claimed in Claim 15, substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.