GB2087270A

GB2087270A - Method of manufacturing pulleys

Info

Publication number: GB2087270A
Application number: GB8036768A
Authority: GB
Original assignee: Drive Manufacturing Inc
Current assignee: Drive Manufacturing Inc
Priority date: 1977-02-04
Filing date: 1980-11-17
Publication date: 1982-05-26
Also published as: FR2495508A1; CA1094356A; FR2495508B1; DE3042312A1; JPS5788929A; GB2087270B; JPH0261340B2; DE3042312C2

Abstract

This invention relates to a method of making pulleys and pulley blanks from sheet metal. The sheet metal is stamped into pulley blanks 15 having an upstanding cylindrical wall, the cylindrical wall 112 is then thickened by being partially collapsed axially, followed by radial compression e.g. by contacting with a roller 70. The roller can have a plurality of v-shaped grooves on its surface, to form a pulley for use with a poly v-belt. <IMAGE>

Description

SPECIFICATION Method of pulley manufacture and product This application relates to a method of thickening sheet metal in selected areas. In a more preferred embodiment, this application relates to a method of making pulleys from sheet metal.

The method of making pulleys from sheet metal has long been known. Such pulleys are often made by a metal spinning process, such as that shown in Wickwire et al, U.S. Patent 2,685,856, dated August 10, 1954, or Harrison et ai, U.S. Patent 1,828,464 dated October 1931. Both of these patents show making of pulleys with a single v-groove, which can be used to contain and provide power to a v-belt. It is possible also to make pulleys having two v-shaped grooves by a metal spinning process, as shown in U.S. Patent 2,892,431 of Killian et al, dated June 20, 1959.However, this involves more complicated machinery, and is also subject to difficulty because the formation of the v-grooves causes metal flow, leading to thinned portions of the pulley wall around the v-grooves which may lead to failure of the pulley in operation.

It has been proposed to form pulleys having more than two v-grooves by the use of metal dies, as has been disclosed in U.S. Patent 3,368,376 of Previte, dated February 13, 1968. However, this process would require complicated dies with expanding arcuate segments, and has not, as far as the applicant is aware, ever been used commercially.

The formation of v-grooves in the side of a pulley in any of the aforesaid processes can lead to thinning of the pulley wall, and therefore failure of the pulley. One reason for this is that a considerable amount of metal flow must necessarily occur in these processes, and it is difficult to guide this flow in such a way that all portions of the finished v-groove in the pulley are of adequate thickness.

Accordingly, it is necessary to start from a fairly heavy gauge metal, so that the final pulley will be of sufficient strength to resist the torsional stresses which would tend to drive it out-of-round in operation.

The existing spun pulleys have been usable with respect to single v-belts, which are belts having one flat side and one side shaped in an outwardly pointing vee configuration. However, for many years, other belts, known as poly v-belts, have been used in a number of operations, such as for the powering of specialized machinery. These belts have one flat side and a plurality (usually six) of vee portions extending outwardly on the opposite side, in a sawtooth pattern. The production of pulleys to engage such belts has been difficult, as the sawtooth like configuration of a poly v-belt requires a number of sharply pointed vee configurations on the pulley, in relatively close proximity to one another.

This uses up a great deal of metal. Accordingly, a relatively thick walled pulley can must be used if traditional metal spinning techniques, or a die stamping technique such as that of Previte is to be employed. The resulting pulleys would be heavy and expensive to make, and have not found favour in automobile manufacture, where low cost and weight reduction are desirable for commercial acceptance.

The lack of effective, low cost, light-weight pulleys has prevented the widespread adoption of poly v-belts by the automobile industry, despite other inherent advantages which have been recognized for such belts.

In most spinning or die-stamping methods, the pulley blank is formed initially by drawing a flat piece of metal into a shape having a base and an upstanding cylindrical walls. This blank is commonly known as a "can". The pulley grooves are rolled or die-stamped into the wall of the can. Accordingly, the initial flat piece of metal must be chosen to be of a sufficient thickness so that the can wall, after drawing, is of sufficient thickness to make v-grooves of adequate strength for the intended application.

However, the drawing process produces a wall which is either the same thickness as, or slightly thinner than, the base. Accordingly, in the present processes, the minimum thickness permissible for the starting piece of metal is determined by the minimum thickness tolerable in the walls of the can.

As the can base is subjected to iesser stresses than the wall during formation of the pulley, it need not be as thick or strong as the wall. It would therefore be advantageous in many cases, from a cost point of view, to provide a pulley can which has a wall which isthickerthan its base.

Accordingly, it is the object of the present invention to provide a method for thickening the approximately cylindrical wall portions of a pulley blank or "can" wihoutthickening the base portions of the can, so that the wall portion will be more robust and thicker than would otherwise be possible with the thickness of sheet metal used to form the pulley can.

It is another object of the invention to prepare pulleys having one or more, preferably at least 4, v-grooves in their sides, such v-grooves having relatively sharp bottoms to their vees. It is another object to form a generalized method of thickening the sheet metal of vertical walls of a drawn can, so as to strengthen the vertical upstanding walls. It is another object to provide light-weight, strong pulleys for the purpose of powering poly v-belts in automobiles.

According to the invention, we provide a method of thickening and/or indenting the wall of a sheet metal cylinder, to render it suitable for use as a pulley, comprising (a) providing a sheet metal formation having a circular base and a cylindrical wall upstanding from the circumference of the base, (b) partially collapsing said wall in an axial direction and (c) compressing the partially collapsed wall radially with sufficient force to deform and thicken said wall.

The compressing step may be carried out by contacting the partially collapsed wall externally, optionally while supporting it internally, with a former, said former and said cylinder being rotatable and one of them being caused to rotate. Preferably, the former comprises the edge of a roller, which edge may be a plane cylindrical edge or may carry one or more ridges. According to one embodiment of the invention, the partially collapsed wall is contacted sequentially with a roller having a plane cylindrical edge and a roller having a ridged cylindrical edge.

Where a roller having a plurality of edge ridges is utilised, the ridges are preferably parallel to each other and may be oriented either substantially normal to the axis of rotation of the roller or substantially parallel to the said axis, being spaced apart from each other around the periphery of the roller.

According to a further embodiment of the invention, the wall of the sheet metal cylinder is provided with flanges and these may be formed either prior to or during the collapsing step.

According to further embodiments of the invention, the method is adapted for thickening the wall of a sheet metal cylinder, the sheet metal having a predetermined minimum permissible thickness, whereby a thickened annular wall portion is formed integral with the circular base of the sheet metal formation, the thickened annular wall portion having a thickness greater than said predetermined minimum thickness, by partially collapsing an annular section of the sheet metal formation having an axial extent greater than the axial extent of said annular wall portion to an axial extent equal to that of said annular wall portion without materially changing the thickness thereof but not completely such that interior surface portions thereof are interengaged, and moving the partially collapsed section radially inwardly while restraining the same against axial expansion and radially inward movement beyond a predetermined radial position so that the interior peripheral surface area of said partially collapsed section is reduced without portions thereof interengaging.

The thickened annular wall portion may then be indented by having a poly v-belt receiving configuration rolled in the exterior periphery thereof while the interior periphery thereof is supported in a straight axially extending configuration. Prior to the moving step in the formation of the thickened annular wall portion, the sheet metal formation may have a pair of flanges formed on opposite sides of said annular section which extend radially and axially outwardly of said thickened wall portion after the formation of the latter, one of said flanges being formed by folding upon itself another annular section of said sheet metal formation adjacent said first mentioned annular section.

The invention will be described by way of example with reference to the accompanying drawings, in which: Figure 1 represents a sheet of sheet metal which is usable to form a pulley can.

Figure 2 is a cross-ectional view of one form of a pulley can formed from the metal of Figure 1.

Figure 2a and 2b show cross-sectional views of alternate forms of the base of the pulley can.

Figure 3 shows a cross-sectional view of the pulley can of Figure 2 mounted in a conventional metal spinning apparatus.

Figure 4a shows a partial cross-sectional view of the can of Figure 2 and Figure 4b shows a partial cross-sectional view of the same can, illustrating a flange-forming step which can optionally be performed prior to partial collapsing of the can.

Figure 5 shows a partial cross-sectional view of the can of Figure 2, showing one method of collapsing the can partially.

Figure 6a and 6b show a partial cross-sectional view of the can of Figure 2, illustrating successive steps of an alternative way of collapsing the can partially.

Figures 7a and 7b show successive steps in the forming of v-grooves in a partially collapsed can.

Figures 8a and 8b show successive steps in thickenening the walls of a partially collapsed can without forming v-grooves.

Figure 9 shows the formation of v-grooves in a can after the step of Figure 8.

In its simplest form in manufacturing a pulley suitable for poly v-belt use on automobiles, a pulley can is formed by deep drawing or spinning, in a conventional way, a sheet of flat metal. The particular sheet metal can be any of those conventionally used in spun pulley manufacture. The most common of these are sheet aluminium and hot rolled, commercial quality, low carbon sheet steel. The sheet of sheet metal, such as shown in Figure 1, has for example a thickness of 0.2 cm. Thicker sheet metal can of course be used, and the upper limit to thickness depends upon the ultimate use envisaged for the pulley to be made, and the pressures able to be exerted by the drawing and spinning equipment to be used.The use of thin sheet metal (i.e., between 0.178 cm and 0.279 cm in thickness) is preferred as the particular advantages of the present invention are much more pronounced when thin sheet metal is used, as then the invention provides pulleys from such thin sheet metal which have performance characteristics which could otherwise have only been obtained from pulleys made of a thicker grade of the particular sheet metal.

As stated above, a pulley blank (which is henceforth called a "can") is made according to conventional methods on a conventional deep drawing or rolling machine. Such a machine stamps a circular portion out of a sheet of sheet metal 1 (Figure 1) and draws it into a can having a base, and an upstanding cylindrical wall. The can may be of any desired dimension, depending upon the size of the equipment being used, and the size of the required final pulley. For example, for 15.24 cm pulleys (a size often used in auotmobiles) a circular piece nine inches in diameter is stamped out, and is drawn into a can with a 22.86 cm diameter base and a 5.08 cm high wall. Atypical can is shown as 15 in Figure 2.

The can of Figure 2 has a stepped base portion 10 and upstanding cylindrical wall 11. The base portion 10 is usually pierced in its center by a hole at 12 in conventional manner, to provide for registration on metal spinning equipment. Other holes may be pierced for registration purposes or for use as bolt holes when the pulley is completed. Additionally, the shape of the base 10 of the can need not be stepped as shown in Figure 2, but may instead be of flat or sloped configuration as shown in Figures 2a and 2b.

Instead of a single hole, several holes may be pierced in the base in any desired pattern, as shown at 13 in Figure 2b. If desired, the pulley blank may be fitted with a hub formed of a separate piece of metal, as for example shown in United States Patent 2,696,740 issued Dscejnber 1, 1954.

According to the method of the invention, the can is placed in a conventional general purpose, metal spinning machine. Such machines are available commercially, and will not be illustrated here. As is usual, the machine is provided with chucks to hold a workpiece for rotation and with tool holders to move selected tools toward and away from the axis of rotation of the workpiece. The machine is also capable of compressing a workpiece along its axis of rotation.

Figure 3 shows a can of the form of Figure 2 positioned in a metal spinning machine between bottom chuck 20, and top chuck 23. The axis of rotation of the can is shown by the line a-a through the chucks and the can. As is common in the pulley spinning art, the can is correctly oriented so that its axis of rotation is the centre axis of the cylindrical can wall. Such orientation can be achieved by means of a can holding groove 21 in the bottom chuck 20, and a central spindle 24 extending from chuck 23 and engaging hole 12, or by any other known means.

If desired, cylindrical internal support block 60 may be secured to the chuck 20 for rotation therewith. The block 60 has an indentation 61, to house spindle 24 when chucks 23 and 20 are moved together a predetermined distance.

It is preferred, for reasons to be described later, that the inner side of groove 21 be sloped, rather than vertical, as indicated at 25 in Figure 3. Top chuck 23 also has a sloping annular portion 26 facing the slope 25, also as shown in Figure 3.

If desired, a step of forming outer and inner flanges in the pulley wall can be carried out before thickening of the wall and forming the grooves in it.

Such a step is not absolutely necessary, as flanges can conveniently be formed during the course of subsequent steps of pulley formation, as will be described. However, it is sometimes convenient to form the flanges first, as this may permit better control of the partial collapse of the pulley wall, as described later.

The step of flange formation is shown in Figures 4a and 4b. Figure 4a shows a can positioned as shown in Figure 3, but with a roller 50 approaching it. The roller 50 is rotatable about an axis c-c parallel to a-a and is movable toward and away from axis a-a. The roller 50 has a generally cylindrical smooth outer face 51, and two sloped portions 52 and 53 each adjacent to the cylindrical face 51 shown in Figure 4a. Alternatively, the face of the roller can be slightly concave if desired. As is known in the art, such a roller can be mounted on springs, so that it can move axially up and down slightly in response to pressures on its periphery. In the example shown, the roller is unpowered.

The chucks 20 and 23 are rotated simultaneously, at the same speed and in the same direction, carrying with them the can 15 and block 60. As this rotation is occurring, the roller 50 is moved into contact with the wall 11 of the can 15. Simultaneously, chuck 23 is moved downwardly a predetermined distance, so that, as the face 51 contacts the can wall 11 and continues to move inwardly, the metal atthe join between base 10 and wall 11 (shown at 16) is folded over by the pressure of the roller 51 bearing against the can. The sloping portion 52 of the roller helps fold over the metal at 16 smoothly, to form a flange. Similarly, the sloping portion 53 helps form a flange smoothly at the end 17 of the can wall which is most remote from the base.The roller 50 is moved inwardly toward the axis a-a a predetermined amount, having regard to the amount of downward movement of the chuck 23, so that the areas 16 and 17 of the wall 11 are folded into the position shown in Figure 4b, without undue stretching. Preferably (but not necessarily) the internal block 60 extends outwardly just sufficiently so that its external face 62 provides a backing support for the wall 11, when the roller 50 is at the innermost limit of its travel toward the axis a-a. It is preferred, however, that the block 60 should be of such a height that there is a gap, indicated as 63 between the base 10 and the block 60 after this operation, so that the chuck 23 can be moved in subsequent steps of the pulley formation closer to the chuck 20, without the necessity of changing blocks 60.However, instead of leaving a space 63, it is also possible to dispense completely with the block 60 during the step shown in Figures 4a and 4b, or else, after completion of the step shown in Figures 4a and 4b, to remove the block 60 and replace it with a block having a smaller vertical height, before going onto further steps.

The steps shown in Figures 4a and 4b create two flanges 18 and 19, with a flat portion 117 between them. It will be noted that the flange 19 lies along the sloping portion 25 of the chuck 20 and is in fact formed between the sloping portion 53 of the roller 50 and the sloping portion 25 of the chuck 20. The slope of portion 25 should be pre-chosen so that it will provide a smooth back to assist in formation of flange 19.

As stated above, the step shown in Figures 4a and 4b is optional. It has the effect of accurately sizing two flanges 18 and 19, which flanges are found to be useful in pulleys for poly v-belts, as they help to retain the poly v-belt in position when the pulley is ultimately formed. In the subsequent description, it will be assumed that the step of flange formation as shown in Figures 4a and 4b has not been carried out, but it will be understood by one skilled in the art that the steps to be described can be carried out with a pulley blank having flanges 18 and 19 as obtained from the carrying out of the steps shown in Figures 4aand4b.

If the step of Figures 4a and 4b is not carried out, the first step to be performed on a pulley can in the process according to the invention is the partial collapsing of the wall 11 of the pulley can 15. Such partial collapsing can be carried out in several ways.

One way (which is not preferred) is by a step of bulging the can as shown in U.S.- Patent 2,929,345 of Zatyko, dated March 22, 1960. This step is not preferred as it requires special equipment, which must be specially mounted on the spinning machine for the purpose of the step, and subsequently removed so that other steps can be carried out. An alternative, and also not preferred manner, is simply to apply axial pressure to the chuck 23, causing the wall 11 to buckle, as shown at 112 in Figure 5. The buckling occurs in an irregular manner. The block 60 need not be present during the operation of partial collapse of the wall 11 to the approximate shape shown at 112, but it can be present if desired.As will be obvious to one skilled in the art, the irregular buckling could also be carried out after flanges 18 and 19 have been formed by the method shown in Figures 4a and 4b.

An alternative, and preferrd manner of partially collapsing the wall 11 is shown in Figures 6a and 6b.

Figures 6a and 6b show a pair of rollers 31 and 32, which rotate about an axis b-b. These rollers are separated from one another by a compresssion spring 33. Each of the rollers has a face with a sloping portion 34, a blunt extension 35, and a curved portion 36, which is located nearest the other roller. The two rollers are separated by the spring 33 a distance such that the projections 35 will engage wall 11, when the rollers 32 and 33 are moved together toward the wall, at fairly widely spaced points on wall 11.

In the partial collapse of the can wall according to the method of Figures 6a and 6b, the chucks 20 and 23 are powered to rotate the can 11, and the rollers 31 and 32 are moved into contact with the can 11. As the rollers contact the can 11, they will of course begin rotating as well, as the rotation of the can 11 will cause them to rotate. The projections 35 will of course be the first portions of rollers 31 and 32 to contact the can wall 11. As soon as the portions 35 have contacted the wall, the chuck 23 is moved toward the chuck 20, at the same time as the rollers 32 and 31 are moved together toward the axis a-a.

This will cause the can wall 11 to buckle, and, at the same time, the buckling will be controlled somewhat by the fact that the projections 35 will tend to stay in contact with the same portion of the can wall that they originally contacted, with the spring 23 compressing as the chuck 23 moves toward the chuck 20.

This will cause the can wall to lie along the contour of the curved roller face 36, as shown in Figure 6b.

The amount by which the rollers 31 and 32 should approach the axis a-a, and the design of the contours 36 and the amount of movement of the chuck 23 will be obvious to a man skilled in the art. It is generally preferred to have the rollers 31 and 32 end up in face to face contact with one another, so that no point or burr on the metal is formed by a gap between the two faces 36, such as indicated at 37. However, if a burr or point is formed, this is not detrimental, as it will be removed during the later processing steps.

After the rollers 31 and 32 are withdrawn further controlled collapse can be carried out by moving the chucks 20 and 23 closer to one another by a desired amount The form of partially collapsed wall formed by the method of Figures 6a and 6b is shown in Figure 6b at 113. It will be noted that the shape of the collapsed wall is somewhat more regular than is formed by the method of Figure 5. Hereinafter, further steps of the invention will be described with respect to a wall of form 112, but it is understood that this disclosure applies equally to a wall of form 113.

No matter which method is used to collapse the wall, it is preferred that the wall 11 be collapsed so that its final height (hl) (see Figure 5) is from 25% t 75% of its original height h (see Figure 2). If a flange has been formed by the step of Figure 4 prior to the collapse, the "collapsed" height h1 includes the height of the flanges 18 and 19. Conveniently, the height of block 60 is such that, after collapse has occured by the desired amount, the block is in contact with the base 10 of the can, as shown in Figures 5 and 7a.

Once the wall has been collapsed into the shape 112 or 113, the operator can, according to the invention, either perform on it the steps of Figures 7a - and 7b to obtain a final pulley suitable for use with a poly-v-groove belt, or else the steps of Figures 8a and 8b to obtain a pulley having a thickened upright wall and which is suitable for use with a flat belt. If the steps of Figures 8a and 8b are carried out, a subsequent step can (if desired) be carried out as is shown in Figure 9, to convert the pulley thus formed into one suitable for use with a poly v-belt.

Referring now to Figures 7a and 7b, one method of forming a pulley suitable for use with a poly v-belt from a collapsed can having a configuration 112 or 113, will now be described. Figure 7a shows a roller 40, which rotates about an axis d-d, parallel to the axis a-a. The face of roller 40 is provided with a number of sharp projections 41, spaced from one another by v-shaped indentations 42. The number and shape of projections 41 is the same as the number and shape of projections on the poly v-belt with which the pulley to be made is intended to be used. In the example shown in Figure 7a, there are six projections 41 separated by five indentations 42, in the same configuration as is used in a common type of v-belt. The top of the roller 40 has a sloped transition surface 43 between its face and its top.

Similarly, there is a sloped transition surface 44 between the face and the bottom of the roller. The chucks 20 and 23 are set into motion simultaneously and in the same direction, causing the partially collapsed can to rotate. The axis d-d is then moved toward the axis a-a. When the face of the roller 40 comes in contact with the can, the roller also begins to rotate. The surface 43, as it engages the can, squeezes a portion 114 of the metal of the can wall against the sloped surface 26 of upper chuck 23, forming a flange. Similarly, the sloped surface 44 squeezes a portion 115 of metal against the sloped surface 25 of bottom chuck 20, forming a bottom flange. These two flanges are identical with the flanges formed at 18 and 19 in the step described with respect to Figure 4. If the step of Figure 4 has been carried out, and the flanges are already formed, the sloped portions 43 and 44 merely nest against the pre-existing flanges, and do little if any deformation of metal.

The sharp projections 42 cut into the metal of the can wall 112, and deform it If the can wall were not partially collapsed, i.e., if it were in the same state as is shown in Figure 2 at 11, the sharp projections would cut deeply into the thin sheet metal of the wall. If the sheet metal were relatively thin, i.e., below about 0.279 cm and the depth of the indentations 42 from the projections 41 was approximately 0.317 cm insufficient metal would flow into the indentations 42 to fill such indentations before the sharp projections 41 cut entirely through the metal of wall 11, or else approached so nearly to cutting through the wall as to render the wall 11 extremely weak. However, according to the method of the invention, the collapsed portion 1 12 of the wall provides more metal than a straight cylindrical wall would do.This gives sufficient metal, even when sheet metal of initial thickness of 0.203 cm is used, to fill completely 0.317 cm indentations at 42, while still retaining a strong wall.

The roller 40 is moved towards axis a-a until the indentations 42 have all been filled with metal. The final form of the can wall is shown in Figure 7b. Itwill be noted that there is an appreciable thickness of metal indicated by the distance y between the points 41 and the inside 116 of the can wall which now rests firmly against the exterior wall 62 of the backing block 60: The indentations 42 are fully filled with metal of the wall, as shown by the dimension x.

Generally speaking, where the height h1 is from .25 to .75 of the height h1, a thickness of wall plus projections (dimensions y plus x in Figure 7b) of from about 1.5 to 2.5 of the thickness of the original sheet metal can be obtained from sheet metals in the thickness range of about 0.178 to 0.33 cm. The relative size of dimensions y and x will of course depend on the size, shape and number of projections 42, and upon how close to the wall 62 the roller 40 is allowed to approach. In order to obtain a strong pulley, for use in an automobile, the roller 40 is allowed to approach the wall 62 only closely enough so that the minimum wall thickness y will be 0.102 cm. A smaller minimum thickness would of course be permissible if the pulley were designed for uses requiring less strength.

During the operation of Figure 7, the backing block 60 is extremely important, as its wall 62 assists in distributing the metal of can wall 112 so that it fills all of the indentations 42.

After the roller 40 has come to the position of Figure 7b, it is removed, and the pulley can, which has now been fully formed into a pulley suitable for use with a poly v-belt, is removed. It will be noted that the pulley thus formed has two flanges, 18 and 19, which give it considerable dimensional stability, and has a series of grooves (the mirror image of projections 41 and identations 42 of the roller) for use with a poly v-belt.

An alternative arrangement, for use in making a pulley with a flat face, is shown in Figures 8a and 8b.

Turning first to Figure 8a, a roller 70, rotating around an axis e-e which is parallel to axis a-a is shown. This roller has a flat face 71 and two sloped portions 72 and 73. Portion 72 joins the flat face 71 to the top of the roller, whereas portion 73 joins the flat face to the bottom of the roller. The width of the face 71 is just slightly smaller than the width of the face 62 of backing block 60, and the slope of the sloped surface 72 and 73 are chosen having regard to the slopes of surface 26 and 25 with which they will co-act to form flanges.

The chucks 20 and 23 are caused to rotate simultaneously and in the same direction, carrying the can 20 with them. The axis e-e of the roller 70 is caused to move toward the axis a-a, with the roller oriented opposite the can as shown in Figure 8a. The flat face 71 contacts the collapsed portion 112 of the can wall, pushing it against wall 62 of backing block 60. Simultaneously, sloped surface 72 of roller 70 squeezes a portion of the metal of the can wall against surface 26 of chuck 23, to form a flange, and surface 73 squeezes a portion of the metal of the can wall against sloped surface 25, also forming a flange.

Because of the bulged or partially collapsed surface of the wall of the can, there is more metal than would be needed merely to make a flat wall of the same thickness as the metal of the base. Thus, when the roller 70 approaches the wall 62, the thick, smooth wall of metal 111 is formed, having smooth surfaces against faces 71 and 62. The advance of the roller 70 is stopped at a predetermined place having regard to the amount of collapse which has been carried out in forming the buckled or collapsing wall 112, such that the newly formed wall 111 will be of a desired thickness. Generally, the thickness obtained will be somewhat in excess of the sheet metal forming the base 10 (excluding any strengthening members or hubs) such as about from 1-1/4 to 2 times (preferably 1-1/3 to 1-1/2 times) the thickness of the base 10.

Obviously, if the roller 70 were advanced closer to the axis a-a, excess metal could squeeze out around the edges of the roller, leading to a thinner wall 111, but this would not be desirable, and does not form part of this invention. Having regard to the teachings herein, a person skilled in the art can easily determine the amount of collapse required to give a suitable thickness 111, as he may require.

If the flanges 18 and 19 have been preformed, as shown in Figures 4a and 4b, then the faces 72 and 73 will not in themselves form flanges, but will merely mate smoothly against the pre-existing flanges 18 and 19, preventing metal from escaping from the area between face 62 and face 71, where the new, thickerwall 111 is being formed.

After the condition shown in Figure 8b has been reached, the roller 70 is withdrawn, and the pulley can is removed from the chucks 20 and 23. A pulley can having a smooth, robust wall 111 has been formed, which is suitable as a pulley for a flat belt.

The pulley also has flanges 18 and 19, which serve to retain the belt in place.

It will be noted that the steps of Figures 7 and 8 each result intrinsically in a pulley having flanges 18 and 19. Generally, it is preferred to retain these flanges, and one of the advantages of the invention is that the flange reduces the possibility of slippage of v-belts from pulleys formed according to the invention. However, it is possible, if desired, to remove the flanges 18 and 19 by means of a roller which nips off the flanges (as is known in the spun pulley art for removing unwanted flanges or burrs) or by other conventional methods. Therefore, although the flanges form a very desirable part of the invention, it is understood that unflanged pulleys also can be made by a process according to the invention.

If desired, instead of removing the pulley as formed with wall 111 from the chucks 20 and 23, the pulley can instead be subjected to the application of roller 40, as shown in Figure 9 following the steps shown in Figures 8a and 8b. The roller 40 approaches in a manner similar to that described with respect to Figures 7a and 7b, but, on this occasion, it engages flat, thick wall 111, rather than the buckled wall 112. However, the result obtained is the same as was obtained by the steps described in Figures 7a and 7b, as can be seen by comparing Figure 9 to Figure 7b.

In the foregoing disclosure, the contacting of the various rollers with the surface of the can wall has been accomplished by rotating the two chucks 20 and 23 at the same speed and in the same direction, entraining the can 15 along with them. The roller or rollers which then contact the surface of the can wall (such as, for example roller 40 or roller 70) are freely rotatable, but are not powered. When they contact the can wall, they are caused to rotate by their contact with the rotating can, at the same speed as the rotating can. It is of course within the scope of the invention to have the chucks 20 and 23 freely rotatable, and instead to power the roller which approaches the can wall. Alternately (although this is not preferred) both the roller and the chucks 20 and 23 could be powered so that both the can and the roller are caused to rotate.The directions of rotation should preferably be such that, at the point of contact of the roller and the can, the two are moving in the same direction. However, they need not be moving at exactly the same speed, and, under some circumstances, it is even possible to obtain good results with the can and the roller moving in different directions, although this is not preferred.

Certain examples of the making of pulleys according to the disclosure given herein will now be given.

Example I A can of the form shown in Figure 2 is drawn by conventional means from sheet steel of thickness 0.203 cm to have a width of 16.76 cm and a height h of 5.08 cm. The can is collapsed according to the step shown in Figure 5 to a height h1 of 2.54 cm. The method steps with respect to Figures 7a and 7b are then preformed on the can using a roller 40 having six grooves spaced 0.356 cm from one another and having a depth of indentation 42 of 0.356 cm. The roller 40 is moved toward axis a-a until the distance between wall 62 and the projections 42 is 0.127 cm.

When the roller 40 is removed and the can is removed from the chucks, it is found to be well formed groove pulley having two flanges (18 and 19 in the drawings) of approximately 16.76 cm in diameter and a central v-belt receiving portion having an average diameter of 15.24 cm and having six grooves corresponding to projections 41. Each of these grooves is 0.356 cm in depth, and the total depth of metal measured from the bottom of a vee to the inside of the can (the distance yin Figure 7b) is 0.127 cm. The variation of depth between the six v-grooves is insignificant, being less than 0.005 cm.

The dimensions are substantially constant around the diameter of a pulley.

Example II A sheet of sheet metal 0.203 cm in thickness is preformed into a can of the same shape as that described in Example I. The can is collapsed according to the step shown in Figure 5 to a height h, of 2. 54 cm. The steps illustrated in Figures 8a and 8b are carried out on the can. The roller 70 is allowed to approach the wall 30 such that the distance between face 71 and face 62 is 0.305 cm. When the roller 70 is withdrawn, the can is removed from the chucks 20 and 22, it is found to have a v-belt receiving portion 15.24 cm in diameter and two flanges approximately 16.76 cm in diameter at each side of the v-belt receiving portion. The thickness of the wall of the v-belt receiving portion is 0.305 cm and the pulley is smoothly cylindrical in its v-belt receiving portion.

Example 111 A pulley formed according to the teachings of Example II is treated by a subsequent step as illustrated in Figure 9 and the associated disclosure.

The roller 40 is permitted to approach so that the projections 42 are a distance of 0.127 cm from the face 62. When the roller is withdrawn and the can is removed from the chucks 20 and 23, a poly v-belt pulley which is indistinguishable from the pulley formed in Example I is formed.

Each of the pulleys formed in Examples l, ll and III is found to be highly resistant to being forced out of round, and is judged to be suitable for automotive and indeed heavy truck applications.

It is understood that the invention is not limited to the exact roller structure shown, nor to the exact pulley shapes illustrated, because the particular shapes of the rollers can be varied to provide other structural embodiments without departing from the scope of the present invention.

Claims

1. A method of thickening and/or indenting the wall of a sheet metal cylinder, to render it suitable for use as a pulley, comprising (a) providing a sheet metal formation having a circular base and a cylindrical wall upstanding from the circumference of the base, (b) partially collapsing said wall in an axial direction and (c) compressing the partially collapsed wall radially with sufficient force to deform and thicken said wall.

2. A method according to claim 1 in which the compressing step is carried out by contacting the partially collapsed wall externally with a former, said former and said cylinder being rotatable and one of them being caused to rotate.

3. A method according to claim 2 in which the former comprises the edge of a roller.

4. A method according to claim 2 in which the partially collapsed wall is supported internally.

5. A method according to claim 3 in which the roller has a plane cylindrical edge.

6. A method according to claim 3 in which the roller has a cylindrical edge which carries one or more ridges.

7. A method according to claim 3 or claim 4 in which the partially collapsed wall is contacted sequentially with a roller having a plane cylindircal edge and a roller having a cylindrical edge which carries one or more ridges.

8. A method according to claim 6 or claim 7 in which a plurality of ridges are present, the ridges being parallel to each other and oriented substantially normal to the axis of rotation of the roller.

9. A method according to claim 6 or claim 7 in which a plurality of ridges are present, being aligned substantially parallel to the axis of rotation of the roller and being spaced apartfrom each other around the periphery of the roller.

10. A method according to any preceding claim wherein prior to or during the collapsing step the cylindrical wall is provided with flanges.

11. A method according to claim 1 wherein the wall of a sheet metal cylinder is thickened, the sheet metal having a predetermined minimum permissible thickness, comprising: forming integral with the circular base of the sheet metal formation a thickened annular wall portion which has a thickness greater than said predetermined minimum thickness, said thickened wall portion being formed by partially collapsing an annular section of the sheet metal formation having an axial extent greater than the axial extent of said annular wall portion to an axial extent equal to that of said annular wall portion without materiallly changing the thickness thereof but not completely such that interior surface portions thereof are interengaged, and moving the partialy collapsed section radially inwardly while restraining the same against axial expansion and radially inward movement beyond a predetermined radial postion so that the interior peripheral surface area of said partially collapsed section is reduced without portions thereof interengaging.

12. A method according to claim 10 wherein the thickened annular wall portion after being formed by the steps aforesaid is indented by having a poly v-belt receiving configuration rolled in the exterior periphery thereof while the interior periphery thereof is supported in a stright axially extending configuration.

13. A method according to claim 11 wherein prior to the moving step in the formation of said thickened annular wall portion, the sheet metal formation has a pair of flanges formed on opposite sides of said annular section which extend radially and axially outwardly of said thickened wall portion after the formation of the latter, one of said flanges being formed byfolding upon itself another annular section of said sheet metal formation adjacent said first mentioned annular section.

14. A method according to any preceding claim wherein the thickness of said thickened wall or wall portion is greater than the thickeness of the base or said predetermined minimum permissible thickness by a factor of from 1-1/4 to 2.

15. A method according to claim 14wherein said factor is 1-1/3 to 1-1/2.

16. A method of forming a pulley as hereinbefore described with reference to the accompanying drawings.

17. A method of forming a pulley as hereinbefore described with reference to the Examples.