GB2192148A - Apparatus for making annular polymeric articles - Google Patents

Abstract

An apparatus for making annular polymeric articles such as toothed belts comprises a base (27) on which there is mounted a core (25) having an outer shaped surface for receiving the components of a workpiece (19) thereon, and press elements (15) arranged around the core (25) and kinematically linked with a power drive (not shown) for moving them radially inwardly in the course of press-forming. The outer surfaces (18) of the press elements (15) are tapered, the press elements (15) being linked with the power drive through an intermediate element (16) having an inner tapered surface (17) for cooperating with the tapered surfaces (18) of the press elements (15). An annular projection (20) cooperates with an annular groove (22) to cause retraction of the press elements (15) on mould-opening movement of intermediate element (16). Another embodiment is shown in Figures 1 and 2 (not shown). <IMAGE>

Description

SPECIFICATION Apparatus for making annular polymeric articles This invention relates generally to the manufacture of rubber articles, and more particularly to apparatus for making annular polymeric articles.

The present invention is most suitable for use in the manufacture of flat endless toothed belts.

Other possible applications include fabrication of a range of annular articles from polymer materials.

The essence ofthe present invention resides in that in an apparatus for making annular polymeric articles comprising a base on which there is mounted a core having an outer shaped surface for placing a workpiece thereon, and press elements arranged around the core and kinematically linked with a power drive for moving them radially in the course of press-forming, according to the invention, an outer surface of the press elements at least at one side thereof is tapered, whereas the press elements are linked with the power drive through at least one intermediate element fashioned as a cup having an innertapered surface cooperating withthetapered surface of the press elements.

Preferably, the intermediate element has an annular projection with an outertapered surface par allelwiththetaperedsurfaceofthe intermediate element, whereas the press elements have at the end thereof facing the intermediate element an annular groove with a tapered surface cooperating with the tapered surface of the annular projection when the press elements are drawn apart, the press elements having a means for preventing their movement axially relative to the core.

The aforedescribed arrangement makes it possible to simplify disassembling ofthe apparatus subsequentto vulcanizing the article.

Desirably,the core has projecting tapered tailpieces, whereas the intermediate element and the base have tapered holes for receiving the tail pieces of the core.

The above arrangement affords accurate centering ofthe core relative to the forming surface ofthe press elements.

The apparatus for making annular polymeric articles embodying the present invention is relatively easy to manufacture and is capable of making fabric lined toothed belts of sufficiently high quality at low costs involved. The apparatus is highly efficient and has a long service life.

The invention will now be described in greater detail with reference to various specific embodiments thereof taken in conjunction with the accompanying drawings, in which: Figure 1 is a longitudinal sectional view of an apparatus for making annular polymeric articles ac cording to the invention; Figure 2 is a section taken along the line Il-Il in Figure 1; Figure 3 is a longitudinal sectional view of another modified form ofthe apparatus for making annular polymeric articles with an annular projection illustrating its position at the end of the forming process; Figure 4illustrates the apparatus represented in Figure 3 in an open position; Figure 5is a section taken along the lineV-V in Figure3; Figure 6is a section taken along the line VI-VI in Figure 3;; Figure 7is an enlarged view of the section Ain Figure3; and Figure Bshows the same as represented in Figure 7 in a drawn-apart position.

An apparatus for making annular polymeric articles comprises a core 1 having an outer shaped surface for assembling thereon a workpiece 2 which includes a lining cloth, a carrying cord, and a layer of polymer material. The workpiece 2 is represented schematically in Figures 1 and 2. The core 1 is formed by longitudinally extending sectors 3 and 4 (Figure 2) arranged around a central rod Sand held in place at the ends bytailpieces 6 (Figure 1) and 7 ofthe core 1 drawn together by a nut Son the rod 5. Press elements 9 having at the outer side two tapered surfaces 10facing each otherbytheirlarge bases are secured around the core. Attached to the ends of the core 1 are flanges 11 between which the press elements 9 are disposed.In order to move radially,the press elements 9 are connected to a power drive (not shown) of a press unit (not shown). This connection is effected through intermediate elements 12 provided at the opposite ends of the core 1. Each such intermediate element 12 is fashioned as a cup having an inner tapered surface 13 cooperating with respective tapered surface 10 of the press element 9.

For preliminarily centering the core 1 relative to the intermediate elements 12, the latter have holes 12a to receivetailpieces 1 4 of the rod 5.

The tail pieces 6 and 7 of the core 1 are tapered, whereas the intermediate elements 12 have holes 1into receive the tailpieces 14 of the rod 5.

In the embodiment herein described the lower intermediate element 12 also serves as a base for the core 1.

Referring now to Figure 3, there is shown an apparatus for making annular polymeric articles in which the radial displacement of press element 15 in the course offorming is effected by axially moving one intermediate element 16 having an inner (joining) tapered surface 17 (Figure 4) cooperating with an outer (joining) tapered surface 18 of the press elements 15. In order to open the apparatus aftervulcanizing an article 19, the intermediate element 16 is provided with an annular projection 20 having an outer (separating) tapered surface 21 parallel with the tapered surface 17.At the end side of the press elements 15facing the intermediate element 16 there is provided an annular groove 22 having a tapered (separating) surface 23 corresponding to the tapered (separating) surface 21 ofthe annular projection 20.

For simplifying the manufacture of the apparatus the surfaces 17 and 21 intheembodimentdescribedare provided in separate parts rigidly interconnected by means of a pin 24.

The press elements 15 are held against axial displacement relative to a core 25 by a lock means in the form of T-shaped grooves and prpjections 26 (Figure 6) provided in the press elements 15 and in a base 27 rigidly connected to a lower plate 28 (Figure 4). The intermediate element 16 is rigidly connected to an upper plate 29 of the press. In orderto secure the core 25, the base 27 and intermediate element 16 are provided with holes 30 having tapered portionsto receivetailpieces3l of conical shape. After drawing the press elements 15 away from the core 25 with the article 19, they are fixed in place relative to the base 27 by ball locks 32 and recesses 33 in the press elements 15. Ashell 34functions as a guideforthe intermediate element 16 attheinitial stage of its travel, this shell 34 being rigidly affixed to the base 27.

The apparatus for making annular polymeric articles with reference to Figures 1 and 2 operates in the following manner.

The workpiece 2 comprised of a lining cloth, cord and a polymer material is placed on the assembled core 1. Mounted onto the workpiece 2 between the flanges 11 of the core 1 are the press elements 9 embracing the workpiece 2. The core 1 with thework- piece 2 and press elements 9 is then secured in the intermediate element 1 2 so thatthetailpiece 14 of the rod 5 enters the cylindrical hole 12a ofthe intermediate element 12. The second intermediate element 12 is fitted onto the core 1 with theworkpiece 2 and press elements 9 so thatthe tailpiece 14 ofthe rod would enter the cylindrical hole 1 2a.The tapered tailpieces 6 and 7 of the core 1 are received by the tapered holes 12b ofthe intermediate elements 12to center the core 1 with the workpiece 2 relative to the intermediate elements 12. The thus assembled apparatus is placed in a chamber (not shown) of a vulcanizing press between its plates (not shown).

When the press plates are drawn together, the axial movement of the plates imparted to the intermediate element 12 istranslated to a radial movement ofthe press elements 9 thanks to cooperation of the tapered surfaces 13 of the intermediate elements 12 with the tapered surfaces 10 ofthe press elements 9.

Asa result of the radial movement of the press elements 9 drawn together around the workpiece 2 the desired article is formed. The angle of taper of the conical surfaces 10 of the press elements 9 and the innertapered surface 13 of the intermediate elements 12 is greater by 20to 3 than the steel-to-steel friction angle. It isforthis reason that the speed of radial movement of the press elements 9 during forming the article is less than the axial speed ofthe intermediate elements 12, or the speed at which the plates of the press are drawntogether.Therefore, the pressure exerted on the polymer material is relatively uniform through the entire body of the article being formed, the lining cloth being thus capable to conform to theshape ofthe cores. The polymer material tends to uniformly occupy the space between the cloth and the outer surface ofthe article. Thanks to thatthe reduced rate at which formation ofthe articletakes place, while keeping the rate of drawing the press plates together relatively high, the amount of polymer material forced into the longitudinal joints between the press elements is minimized to result in reduced polymer waste.

The radial movement of the press elements 9 or press-forming of the article is terminated at the point of drawing the press elements together, when their inner cylindrical forming surface assumes a regular cylindrical shape substantiallyconcentrical with the outer surface of the core 1. At this point the tail pieces 6 and 7 of the core 1 mate with the intermediate elements 12 about their smaller innertapered surface.

Subsequent to vulcanization, the apparatus is removed from the chamber of the vulcanizing press to be disassembled. At first, the intermediate elements 12 are removed, after which the press elements 9 are extracted, and the core 1 is disassembled, whereby a roll of vulcanized article is obtained, which isthereafter cut into pieces of desired width. Flash is removed from the outer surface of the finished article atthe points where the press elements 9 are joined. The outer surface of the article needs no finishing because the innerforming surface of the press elements is accurately machined. The end product is therefore of high quality and low cost. The service life of the rigid press elements of the apparatus is higherthanthatoftheflexibleshell used in the prior art apparatus.

The apparatus for making annular polymeric articles with reference to Figures 3,4 and 5 operates as follows.

The workpiece 19 is placed on the assembled core 25. To do that, the outer shaped surface ofthe core is lined with the lining cloth, whereas the carrying cord is wound on the cloth and a layer of polymer is placed onto the cord. Alternatively, it is possible to fabricate an article without the lining cloth and cord. The core 25 is then secured in the base 27 that it could entertogetherwith the workpiece 19 a space confined by the forming cylindrical surfaces of the separ- ated press elements 15, the tapered surface of the tailpiece 31 of the core 25 entering the hole30 ofthe base 27.When drawing together the lower and upper plates 28 and 29 of the press on which the base 27 and intermediate element 16 are secured, the intermediate element 16 is caused to enter the cylindrical shell 34 mounted on and secured to the base 27. The annular projection 20 is lowered together with the intermediate element 16. In the course offurther lowering of the intermediate element 16 its joining tapered surface 17 cooperates with the respective joining tapered surface 18 of the press element 15, whereby the latter are displaced radially toward the center of the apparatus to uniformly squeeze the workpiece 19. The intermediate element 16 is stopped in its lowest position at the point when it is brought in contactwith the end face plane of the press elements 15. The annular projection 20 is lowered in the annular groove 22 of the press elements 15 to assume a position with clearances as shown in Figure 7. At this point the core 25 is centered bythe tapered surfaces of the tailpieces 31 in the tapered portions of the holes 30 ofthe intermediate element 16 and base 27, whereas the longitudinal joints between the press elements 15 are closed forthethus formed article to occupy a closed space under pressure. Excess polymer material escapes through excess holes (not shown). In this position the article is vulcanized.

Afterterminating the vulcanization process the plates 28 and 29 ofthe press are drawn apart. The intermediate element 16 with the annular projection 20 is raised for the separating tapered surface 21 of the annular projection 20to cooperate with the re spective separating tapered surface 23 ofthe annular groove 22 of the press elements 15 drawing the press elements 15 in a radial direction away from the center of the apparatus. The projection 26 of the base 27 acts to hold by its shelves the press elements 15to preventtheirupward movement together with the intermediate element 16. In addition, the projection 26 executes radial orientation ofthe press elements 15 when they are drawn together and separated.

Afterthe intermediate element 16 has been raised to a height H (Figure 8) equaltothe maximum penetration of the annular projection 20 into the annular groove 22 of the press elements 15, the latter are fixed by the locks 32 and recesses 33 provided at the underside ofthe press elements 15. Locking ofthe press elements 15 ensures their correct position re lativetothejoining tapered surface 17 ofthe intermediate element 16, which prevents damage to the apparatus during a subsequent forming operation.

After the vulcanization and drawing the plates 28 and 29 ofthe press apart, the core 25 with the article 19 are extracted from the apparatus. The core 25 is then disassembled, and the finished article is removed therefrom. The cycle of making articles 19 in the apparatus is thereafter repeated.

The use in the present apparatus of wedge-type mechanisms for radially drawing together and separating the press elements arranged around the article being formed makes it possible to deform the article at a relatively slow rate to thereby ensure a sufficiently high quality at a relatively high production rate. Thanks to the accurately machined cylindrical forming surface of the press elements coaxial with the contoured surface of the core, no extra surface grinding ofthe smooth surface ofthe article is required, which ensures a relatively low production cost ofthe article. Replacement of a flexible forming shell used in the prior art apparatus by rigid press elements, in combination with the structural simplicity and operational reliability of the proposed apparatus, ensure its extended service life.

Pilot models ofthe apparatus are being tested.

Toothed belts of 1 to 4 mm modulus and 800 mm in length have been produced. The belts made by the proposed apparatus have a 3 to 5 times the service life of belts fabricated by prior art apparatus with a flexibleforming shell.

Claims (3)

1. An apparatus for making annular polymeric articles comprising a base on which there is mounted a core having an outer shaped surface for placing a workpiecethereon, and press elements arranged around the core and kinematically linked with a power drive for moving them radially in the course of press forming; an outer surface of the press elements at least at one side thereof being tapered, whereas the press elements are linked with the power drive through at least one intermediate el ementfashioned as a cup having an innertapered surface cooperating with the tapered surface of the press elements

2.An apparatus as claimed in claim 1, in which the intermediate element has an annular projection with an outer tapered surface parallel with the tapered surface of the intermediate element, whereas the press elements are provided at the side thereof facing the intermediate element with an annular groove having a tapered surface cooperating with the tapered surface of the annular projection when the press elements are drawn apart, the press elements having a means for preventing their move mentaxially relative to the core.

3. An apparatus for making annular polymeric articles, substantially as herein described with reference to the accompanying drawings.

3. An apparatus as claimed in claim 1, in which the core has a projecting tapered tailpiece, whereas the intermediate element and the base have tapered holes for receiving the tailpieces of the core.

4. An apparatus for making annular polymeric articles substantially as described heretofore with re ference to the accompanying drawings.

Amendments to the claims have been filed, and have the following effect: (a) Claims 1 to 4 above have been deleted or textually amended.

(b) New ortextually amended claims have been filed asfollows:

1. An apparatus for making annular polymeric articles comprising a base, a core mounted on the base and having a radially outer surface shaped to receive a workpiece, a plurality of press elements arranged around the core and radially movable during press forming to press against the workpiece, a cup-shaped intermediate element linking the press elements to a drive, the intermediate element having anouterannularwall having a tapered inner surface cooperating with a frusto-conical outersurfaceof said press elements, and an inner annular projection having an outer surface parallel with said tapered inner surface of the annularwall, the projection being arranged to cooperate with a correspondingly shaped groove in the press elements whereby axial movement of the intermediate element by the drive effects radial movement of the press elements, and means for preventing axial movement of the press elements with respect to the core.

2. An apparatus according to claim 1,wherein the core has a projecting tapered tailpiece and the intermediate element and the base each have a tapered recess for receiving the tailpiece.