US3899912A

US3899912A - Method and device for cold-forming rolling elements

Info

Publication number: US3899912A
Application number: US375122A
Authority: US
Inventors: Michel Orain
Original assignee: Glaenzer Spicer SA
Current assignee: Glaenzer Spicer SA
Priority date: 1972-07-10
Filing date: 1973-06-29
Publication date: 1975-08-19
Anticipated expiration: 1992-08-19
Also published as: JPS4943866A; FR2191957B1; JPS5246180B2; GB1426340A; SE412016B; IT989739B; DE2334145A1; FR2191957A1

Abstract

A method for cold-forming rolling elements in the form of bodies of revolution with external rolling surfaces having straight or curved generatrices extending between portion of relatively large and relatively small diameter uses a generally cylindrical blank. The diameter of the blank is substantially equal to the greatest diameter of the element to be formed. The blank is forced into a die cup having an internal profile which is identical to the rolling surface profile, against a counter-force which increases as the blank is forced into the cup. The penetration of the blank into the cup is halted at a predetermined stage. The invention is applicable to forming bearing rollers.

Description

United States Patent Orain Aug. 19, 1975 METHOD AND DEVICE FOR 2,267,229 12/1941 Zimmerman 29 149.5 R

COLD FORMING ROLLING ELENIENTS 3,513,683 5/1970 Moore 72/359 75 Inventor: Michel Grain, FOREIGN PATENTS OR APPLICATIONS Conflans-Sainte-Honoflne, France 56,819 5/1891 Germany 72/354 [73] Assignee: lS)oc iete tFXnOnyme: Glaenzer Spicer, Primary Examiner Richard J. Herbst olssy rmce Attorney, Agent, or FirmBaldwin, Wight & Brown [22] Filed: June 29, 1973 Appl. No.: 375,122

Foreign Application Priority Data July 10, 1972 France 72.24973 References Cited UNITED STATES PATENTS 10/1920 Rydbeck 72/354 1/1934 Langhammer 29/149.5 R

[ 5 7 ABSTRACT is halted at a predetermined stage. The invention is applicable to forming bearing rollers.

6 Claims, 7 Drawing Figures PATENTED A1161 9 I915 sum 2 05 1 METHOD AND DEVICE FOR COLD-FORMING ROLLING ELEMENTS The present invention concerns the cold-forming of rolling elements such as rollers for homokinetic couplings or bearings having a tapering rolling surface which may be conical, part-spherical or toroidal for example.

In the conventional process steel rollers are formed by machining a blank on a lathe, quenching the machined blank and finishing the rolling surfaces, the end faces and the bore. These machining and finishing operations, which are essential for maintaining precision and constant dimensions, must be carried out in 'sequence on special machines, which result in high costs.

The object of the invention is a method with which rollers of constant high-precision dimensions can be very economically produced from blanks requiring only very simple preparatory machining, using a single machine requiring only a single working stroke.

In accordance with the invention there is provided a method for cold-forming a rolling element comprising a body of revolution with an external rolling surface having straight or curved generatrices extending between a portion of relatively large diameter and a portion of relatively small diameter, in which method a cylindrical blank, the diameter of which is substantially equal to the maximum diameter of the element, is compressed in a cup whose internal profile is identical to the external profile of the element by overcoming an increasing counter-pressure exerted on the blank, the forcing of the blank into the cup being halted at a predetermined stage.

The invention also includes apparatus for carrying out this method, the apparatus comprising a die formed with a cup having an internal wall the profile of which is identical to the external profile of the rolling surface of the element and which communicates via a conical extension of the wall with a plane bearing face of the die which is perpendicular to the axis of revolution of the cup, the die being formed with a passage extending the cup surface remote from the plane bearing face and having a diameter substantially equal to the smallest diameter of the element, a sliding ejector being disposed in the bore and engaging resilient means arranged to provide a force resisting movement of the ejector into the passage and which increases with the degree of penetration, the apparatus further comprising a plunger having a first bearing face adapted to engage the bearing face of the die and a circular second bearing face projecting from the first bearing face, having the same form as the greatest diameter face of the element, and being arranged to enter the conical extension of the cup wall, the die and plunger being mounted for relative displacement so that the second bearing face of the plunger enters the cup, while being maintained strictly coaxial with the cup, until the first bearing face of the plunger engages the bearing face of the die.

When the rolling element comprises an axial bore the blank is formed with a corresponding bore, preferably of slightly greater diameter than that of the finished element, and a mandrel provided with external bumishing elements and projecting into the die cup through the hollow ejector is mounted for coaxial movement within the ejector, the mandrel and bumishing elements having a diameter identical to that of the bore in the element.

Examples of applications of the invention are described in detail hereinafter with reference to the accompanying drawings in which:

FIG. 1 is a diametral section of a half-roller with a part-spherical external surface cold-formed in accordance with the invention;

FIG. 2 is an analogous view of the blank from which the half-roller of FIG. 1 is formed;

FIG. 3 is an axial vertical section of a machine for forming the half-roller of FIG. 1 from the blank of FIG. 2, shown in an initial operative position;

FIG. 4 is an analogous section of the machine in its final working position;

FIG. 5 is a side elevation of a roller with a conical external rolling surface, formed in accordance with the invention, showing text gauges for the roller in diametral section;

FIGS. 6 and 7 are views, analogous to FIGS. 3 and 4 respectively, of the machine for forming the roller of FIG. 5.

The half-roller 1 shown in FIG. 1 is intended for use in a universal transmission coupling, forming with an identical half-roller a roller which automatically takes up play. The part-spherical surface 2 of the roller, having a radius R, rolls on ways of part-circular section, as described in French Patent Application No. 7 043,789 filed by the applicants on Dec. 4, 1970 and its associated certificate of addition No. 7200.035 of Jan. 3, 1972.

The bore 3 of such a half-roller pivots on one axis of the transmission coupling while the plane face 4 bears against a special washer (not shown) disposed between the half-rollers l, as described in the above-mentioned patent application and its certificate of addition.

Proper operation of a coupling including this type of roller calls for the following criteria for the halfrollers:

a. the bore 3 must have a precise diameter and a very smooth surface;

b. the part-spherical zone 2 must have a good surface finish and be precisely centred on the bore 3, its radius of curvature R must have an exactly determined value and its centre must occupy a precise position in relation to the face 4;

c. the face 4 must be flat and exactly perpendicular to the bore 3 and must be precisely situated with respect to the centre of curvature of the partspherical zone 2.

These requirements can be satisfied by means of the method and cold-forming machine in accordance with the invention.

The machine (FIG. 3) includes a die 6 with an axial bore 7 whose diameter is substantially equal to the external diameter of face 5 of the half-roller 1 and which flares in its upper portion to form a cup 8 with a partspherical surface conforming exactly to the partspherical surface of the half-roller l. The cup 8 is extended as far as the upper face 9 of the die 6 by a flare 10 which is slightly conical, with a half-angle at the summit of the order of 5 for example.

A plunger 1 l co-operates with the die 6 and has a flat lower face 12 with a central circular projection 13 having a flat lower face 14 the diameter of which is substantially equal or very slightly less than the maximum diameter of the half-roller l. The plunger 11 has an axial bore 15 the diameter of which is slightly greater than that of the bore 3 in the half-roller 1.

The die 6 rests on the't'able -16 of a press which has an aperture 17 through which can passa tubular ejector 18 the outside diameter'of which is substantially equal to the diameter of the axial bore 7 of the die 6 while the inside diameter is slightly greater than that of the bore 3 in the half-roller l.

The ejector 18has a collar 19 (FIG. 4) at its lower end which bears on a helical spring 20 resting'on the base 21 of a cylindrical housing 22 mounted beneath the press table by means of bolt 23 by means of which the die 6 is locked on the table 16.

Vertically reciprocable inside the ejector 18 is a burnisher 24 comprising a cylindrical mandrel slightly tapered at its upper end 25 and having a series of annular projections 26 forming burnishing rings.

, The plunger 11 is mounted at the end of the press piston 27.

Themechanism and controls of the press and the burnisher 24 have not been shown. They will be well known to those skilled in the art and form no part of the present invention.

The machine operates as follows:

The blank used is shown in FIG. 2. It consists of a ring 28 of hard tempered steel, formed on an automatic lathe. The only high precision requirement in respect of the machining of this ring concerns the concentricity of its bore 29 in relation to its external cylindrical surface 30. Said concentricity must be as perfect as commercially possible, since otherwise the final product has a tendency to be irregular in shape and dimensions. The ring includes

chamfers

31, 32, 33 and 24 which can be machined or cold-formed. The chamfers are provided so that the finished article has no sharp edges.

The press piston 27 and the plunger 11 are displaced from the die 6 and the ejector 18 and burnisher 24 are initially in the positions shown in FIG. 3. The lubricated blank 28 is placed in the conical flare of the die cup 8. The lubrication may be done conventionally, as with graphitised grease for example. The blank rests on the upper end of the ejector l8, and the press actuated so that the plunger 16 exerts a forming thrust on the blank to force it into the part-spherical cup 8. In this first stage the blank is axially retained on its lower face by the ejector 18 which exerts on it a force F which increases as the ejector is pushed back. This force is provided by the spring 20, but any suitable elastic, mechanical, hydraulic or pneumatic system could be used instead of a spring. The walls of the bore 29 in the blank are pressed against the cylindrical surface of the burnisher 24.

The piston 27 descends until the lower face 12 of the plunger 11 abuts the upper face 9 of the die 6 (FIG. 4), this abutment ensuring precise final relative positions of the lower face 14 of the central projection 13 of the plunger and the part-spherical surface of the cup 8. The thrust F exerted by the ejector 18 is regulated so that the pressure on the part-spherical surface 8 developed by hydrostatic reaction is sufficient to provide correct forming and polishing of the partspherical surface 2 of the half-roller. It should be noted that the position of the lower face 5 of the roller can vary as a function of the blanks volume and without disadvantage since this face has no operative function.

When the external surface of the half-roller has been formed in this manner, the burnisher 24 is raised to the position 24a shown in dashed outline in FIG. 4 and then returned to its former position. In this way the bore 3 of the roller is precisely dimensioned and polished.

The press piston 27 is then raised to raise the plunger 11 and the ejector 18 moves upwardly under the action of the spring 20 to eject the finished product.

As has been mentioned, the invention is also applicable to forming rollers or other bodies of revolution, without these necessarily having a part-spherical outer surface. The invention is applicable, for example. to forming conical rollers such as are used in roller bear- In S.

FIG. 5 shows such a roller 35 having a conical surface of revolution 36 with its apex at 0 and a conical or substantially conical surface 37 with apex at 0'. The angle of intersection a of the generatrices of the two surfaces is about 90. The cone angle of the surface 35 is 13.

The precision requirements for such a roller are concerned with:

a. the cone angles of the conical surfaces;

b. the exact coincidence of the two cone axis;

c. the exactitude of the spacing h between

test calibration elements

38 and 39 in the form of rings, edges 40 and 41 of which respectively engage the

conical surfaces

36 and 37 of the roller 30.

The surface finish for each cone must be very good.

In use of the roller 30 the cone 36 carries the load on the bearing while the conical region 37 provides axial location of the rollers by contact a check or edge on one of the bearing rings. The generatrices of this region are short. The central region 42 has no function and need not be precisely formed. Likewise the lower face 43 of the roller need not be precisely located, formed or finished. It should be noted that the roller surface 37 need not be conical. It could instead be slightly spherical for example.

A machine for making such a roller in accordance with the invention is shown in FIG. 6. It includes a die 44 with an axial bore 45 which is upwardly flared to form a cup 46 with a conical surface whose cone angle is identical to that of the

roller surface

36, 13 in this example. The conical cup 46 leads into a passage 47 which opens onto the upper face of the die 44 and which forms a flat bearing face 48.

A plunger 49 co-operates with the die 44 and has cylindrical outer surface 50 whose diameter corresponds to that of the die bore 47. On a flat lower face 51 of the plunger 49 is a central and circular projection 52 whose diameter is substantially equal to the diameter of the largest base of the roller to be formed. The lower face 53 of the projection 52 is conical or substantially conical and has a profile identical to that of the roller surface 37.

The plunger 49 includes a conduit 54 which opens onto the summit of the cone formed by face 53 of the projection 52 and the upper portion of the outer wall 50 of the plunger. This conduit serves for removal of the lubricant with which the blank is coated at the beginning of the forming operation.

The die 44 rests on a press table 55 which has a central opening 56 through which passes an ejector 57 comprising a cylindrical mandrel having substantially the same diameter as the bore 45 of the die 44.

At its lower end the ejector has a threaded portion 58 onto which is screwed a plate 59 which bears on a spring 60 resting on the base 61 of a housing 62 fastened beneath the press table 55 by means of bolts 63 which also serve to lock the die 44 on the table 55.

On its upper face the plunger 49 has a threaded nipple 64 screwed into a threaded axial bore 65 in the press piston 66.

The roller shown in FIG. 5 is made with this machine in the following manner:

The cylindrical blank 67 (FIG. 6) in hard tempered steel has plane and substantially parallel end faces whose diameter is substantially equal to that of the largest base of the roller to be formed. The edges of theblank are chamfered at 68 and 69 so that after the forming operation the roller has no sharp edges.

It is most important that said blank has a perfectly constant diameter along its whole length, in order to obtain a final product having precise dimensions and a shape which corresponds exactly to what is desired. For this purpose, blanks 67 are obtained by cutting section of given length in a cylindrical metal bar which has been previously milled at the required diameter along its whole length.

The appropriately lubricated blank is placed in the conical cup 46 of the die 44 so as to rest on the end of the ejector 37 which is initially in the position shown in FIG. 6.

The press piston 66 is then lowered so that the projection 52 on the plunger 49 axially compressed the blank 67 in the conical die cup 46, overcoming the re sistance F of the spring 60 acting on the ejector 57 (FIG. 7). As it descends the plunger 49 is exactly centred in relation to the die 44 due to its penetration into the bore 47 in the latter, and, at the end of its strokes, the lower face 51 of the plunger 49 is stopped at a precise position by its abutment with the bearing face 48 of the die. This ensures a precise and constant dimension 11 between the

conical surfaces

36 and 37 of the roller, the precision of their cone angles and surface finish being ensured by the

surfaces

46 and 53 of the die 44 and a plunger 49 respectively. Exact coincidence of the cone angles is assured by the centring of the plunger 49 in the bore 47.

As hereinabove mentioned the precision of the dimensions of the final product depends from the constancy of the diameter of the initial blank. If this necessity is correctly taken into account, a remarkably precise product can be obtained, and this by mere milling of the initial bar from which the blanks are cut, whereas experience has shown that, in the previously known processes for cold forming of rollers of the considered type it was not possible to obtain precise shapes, and that an individual milling of each roller had to be performed, such a milling of relatively small, frustoconical parts being of course, as a whole, much larger, more complicated and more expensive than the milling of a simple cylindrical bar from which a considerable num ber of blanks may be cut.

Once the roller of FIG. 1 or FIG. 5 has been formed it is hardened by quenching and suitably polished, in a drum for example.

It will be appreciated that the invention is not limited to the two just-given examples, and that the invention is applicable to the cold-forming of various other forms of article.

We claim:

1. Apparatus for carrying out a method for coldforming a rolling element comprising a body of revolution with an external rolling surface having straight or curved generatrices extending between a portion of relatively large diameter, and a portion of relatively small diameter, in which method a cylindrical blank, the diameter of which is substantially equal to the maximum diameter of the element, is compressed in a cup whose internal profile is identical to the external profile of the element by overcoming an increasing counter-pressure exerted on the blank; the forcing of the blank into the cup being halted at a predetermined stage, said apparatus comprising a die formed with a cup having an internal wall the profile of which is identical to the external profile of said rolling surface of said element, a plane bearing face of said die perpendicular to the revolution axis of said cup, a conical extension of said wall in communication with said plane bearing face of the die, a passage in said die extending from said cup surface remote from said plane bearing face and having a diameter substantially equal to the smallest diameter of said element, a sliding ejector disposed in said bore, counter-pressure means arranged to provide a force resisting movement of said ejector into said passage and which increases with the degree of penetration, a plunger having a first bearing face adapted to engage said bearing face of the die and a circular second bearing face projecting from said first bearing face, said second bearing face having the same form as the greatest diameter face of said element and being of a size to enter said conical extension of said cup wall, said die and said plunger being mounted for relative displacement so that said second bearing face of said plunger enters said cup, while being maintained strictly coaxial with said cup, until said first bearing face of said plunger engages said bearing face of said die.

2. Apparatus according to claim 1 in which said ejector is hollow and including a mandrel external burnishing elements on said mandrel which project into the said cup through said hollow ejector which is mounted for coaxial movement within said ejector, said mandrel and said burnishing elements having a diameter identi' cal to that of said bore in said element.

3. Apparatus according to claim 1 in which the wall of said die cup is part-spherical or toroidal.

4. Apparatus according to claim 1 in which said die cup has the form of a cone of revolution.

5. Apparatus according to claim 1 including a press on a table of which said die is located and to a piston of which said plunger is connected.

6. Apparatus according to claim 1 wherein said counter-pressure means are resilient means.

Claims

1. Apparatus for carrying out a method for cold-forming a rolling element comprising a body of revolution with an external rolling surface having straight or curved generatrices extending between a portion of relatively large diameter, and a portion of relatively small diameter, in which method a cylindrical blank, the diameter of which is substantially equal to the maximum diameter of the element, is compressed in a cup whose internal profile is identical to the external profile of the element by overcoming an increasing counter-pressure exerted on the blank; the forcing of the blank into the cup being halted at a predetermined stage, said apparatus comprising a die formed with a cup having an internal wall the profile of which is identical to the external profile of said rolling surface of said element, a plane bearing face of said die perpendicular to the revolution axis of said cup, a conical extension of said wall in communication with said plane bearing face of the die, a passage in said die extending from said cup surface remote from said plane bearing face and having a diameter substantially equal to the smallest diameter of said element, a sliding ejector disposed in said bore, counter-pressure means arranged to provide a force resisting movement of said ejector into said passage and which increases with the degree of penetration, a plunger having a first bearing face adapted to engage said bearing face of the die and a circular second bearing face projecting from said first bearing face, said second bearing face having the same form as the greatest diameter face of said element and being of a size to enter said conical extension of said cup wall, said die and said plunger being mounted for relative displacement so that said second bearing face of said plunger enters said cup, while being maintained strictly coaxial with said cup, until said first bearing face of said plunger engages said bearing face of said die.

2. Apparatus according to claim 1 in which said ejector is hollow and including a mandrel external burnishing elemenTs on said mandrel which project into the said cup through said hollow ejector which is mounted for coaxial movement within said ejector, said mandrel and said burnishing elements having a diameter identical to that of said bore in said element.