US3317987A - Method and device for rolling thinwall bearings - Google Patents

Description

MyfQ, 1967 E. ROEMER 3,317,987

METHOD AND DEVICE FOR ROLLiNG THINWALL BEARINGS Fi led J n. 25, 1965' I s Sheets-Sheet 1 fR/Cf/ Rama-x? lnventor May 9, 1967 E. ROEMER 7 3,317,937

} METHOD AND DEVICE FOR ROLLINQTHINWALL BEARINGS F lled Jan. 125, 1965 s Sheets-Sheet 2 m V/ in E- V75 v j V Inventor A/CH Ram/9? KIGHVT May'9, 1967 E. ROEMER ,9

METHOD AND DEVICE FOR ROLLING THINWALL BEARINGS 'Filed Jan. 25, 196 5 5 Sheets-Sheet? l'nvehtof- Ema/J Ram 1,5

United States Patent 8 Claims. ci. 29 149.s)

This invention relates to a method and apparatus for rolling thinwall bearings out of strip material coated with antifriction metal.

Two fundamentally different methods are known for the serial manufacture of thinwall bearings from strip material coated with antifriction metal. :In the hitherto conventional pressing and bending method, in which the thinwall bearing receives its final form, the individual metal layers, including the steel back, undergo a nonuniform thickening. For this reason the running surface of the bearing must be subjected to a chip-removing process after the pressing operation. Moreover, the minimum layer thickness which can be achieved in a serial manufacture by a chip-removing process after the pressing operation, is around 0.1 mm., owing to the above-mentioned thickening. Nevertheless thinner antifriction metal layers would be desirable, since the fatigue impact strength of the bearing increase as the antifriction metal layer becomes thinner. Hitherto the art was restricted to applying by electroplating thin metal layers on the bearing after it had been completely processed mechanically. However, only few antifriction metal alloys are suitable for electroplating.

In order to eliminate the difiiculties and drawbacks which arise with the pressing or stamping of thinwall bearings, attempts have been made to bend bearings out of strip material coated with antifriction metal. It is known to use a system of three rolls for this purpose, of which one roll acts on the coated side of the strip and two rolls on the uncoated side thereof. One of the rolls acting on the uncoated side of the strip material is adjust-ed with the roll opposite it to the thickness of the strip material and the other disposed at a distance therefrom to be determined in each individual case, which in turn determines the bending radius of the thinwall bearing thus produced. After the bending, a half bearing is sawn oif, the end of the strip being clamped for this purpose. During the sawing there is the danger that chips will get into the roll gap and be pressed into the strip during the bending thereof. If the bearing half is cut off instead of being sawn ofi, the strip would have to be clamped still more firmly in order to avoid excessive deformation of the bearing. The clamping both for sawing and also for cutting, however, leaves imprints in the running surface of the hearing, so that this surface will require to be machined in any case. This known procedure also makes it impossible to cut sheet blanks to size before bending, and to bend them individually into the desired form for the bearing subsequently, since the loss. of material resulting therefrom would be inadmissibly high. Due to the fact that the desired form or curvature is produced only when all three rolls contact the band or strip simultaneously, the leading piece of the strip which serves for introducing the strip would have to be cut away as waste.

It is finally also known to bend U-profiles into flange bearings, a system of two rolls being used for this purpose. A holding claw grips the leading end of the U- profile and presses it against the lower roll. The upper roll is so adjusted that the height of the flanges is reduced, whereas the middle part, that is the barrel of the bearing is not reduced in thickness. The U-profiles are so long that one half-shell can be fashioned out of the blank. After the bending and cutting off of the ends, the thinwall bearing must be calibrated in a press and running surfaces processed by chip removal.

According to the invention, however, a method and apparatus are provided which eliminate entirely or to a great extent the processing of the running surface of the bearing. It is thus made possible to produce thinwall bearings from strip material which is coated only with an extremely thin layer of antifriction metal, for example, less than 0.1 mm. in thickness.

This is achieved, according to the invention, by forming the thinwall hearings in two working stages, namely a preliminary bending stage and a final rolling stage effecting a reduction in the thickness of the material. Whereas in the first working stage, namely the preliminary bending, no thickness reduction of the material is required, an appreciable reduction in thickness is effected in the final rolling. Experiments have shown that accurate parallelism of the generatrixes of the cylindrical bearing back can be achieved only by the two above-mentioned working stages, namely the preliminary bending and the final rolling. A calibration of the thinwall bearing after the final rolling is no longer necessary.

For the method according to the invention it is particularly advantageous to cut in advance individual sheet blanks to the proper size out of the strip material coated with antifriction metal and to hold these blanks at an angle of about 60 to 90 degrees, preferably about degrees, to the roller plane by means of a device which feeds them to a pair of rolls, thereby pre-bending them, and then to effect the final rolling between this pair of rolls.

Contrary to the known bending procedures, the radius of the thinwall bearing is, according to the invention, determined by the radius of the roll acting on the coated side of the strip material. It is therefore especially advantageous to hold the pre-bent workpieces with their front end resting firmly on the periphery of the roll acting on the coated side of the strip material during the final rolling operation. This can be effected by a holding claw which grips the leading end of the blank. It is, however, also possible to cut the blanks exactly to size except for an allowance for machining the parting surfaces, so that they correspond to the thinwall bearings to be produced, and to hold them laterally at their front end against the roll which is to act on their coated side during the final rolling. The length of the blanks can be calculated very simply from the predetermined reduction in the metal thickness. The thickness of the strip blanks should be reduced by at least 0.5%, preferably 1% during the final rolling.

By working the previously cut strip blanks according to the method of the invention, particularly the latter embodiment thereof, the special advantage is attained that the specific roll pressure is higher at the front and rear ends of the blanks than in those regions in which the roll gap is filled entirely by the blank. The blanks are therefore rolled somewhat thinner at their two ends than at their intermediate portion. This enables the parting line relief desired in thinwall bearings to be obtained without special afterprocessing. Moreover it is possible by suitably fashioning the strip from which the blanks are cut to produce a tapering wall thickness of the thinwall bearing, so that a so-called lemon or oval bore is produced when the bearing halves are in position.

Finally, the method according to the invention also offers the possibility of forming in the same procedure the holding cams frequently desired in thinwall bearings for preventing the bearing halves from twisting in their housing. According to the invention a holding cam can be produced during the final rolling of the blanks in that the blank is transported in such a manner that its rear end in the direction of travel passes over a knife projecting from the roll surface.

Particularly well suited for fashioning thinwall bearings from strip material coated with antifriction metal is a device in which, in front of a pair of rolls adjustable to the final wall thickness of the bearing, a feed shoe is arranged which extends up to the gap or nip of the pair of rolls, the surface of this shoe being fashioned as a guide surface for the rear side of the sheet material to be processed, and arranged to slope from the roll gap at an angle of about to 30 degrees, preferably 10 degrees, towards the rear and towards the roll acting on the coated side of the strip material. The diameter of this roll acting on the coated side of the strip material corresponds to the internal diameter of the bearings to be manufactured. This roller can also be equipped with the holding claws and with devices for producing holding cams on the thinwall bearings.

Further characteristics and advantages of the invention will become apparent from the following description of several embodiments illustrated by way of example in the accompanying drawings, in which FIGURE 1 depicts diagrammatically the fundamental method according to the invention;

FIGURE 2 illustrates the arrangement of a holding claw in one embodiment of the invention;

FIGURE 3 shows diagrammatically the arrangement of a pair of lateral holding claws in a second embodiment of the invention;

FIGURE 4 is a section taken on line IV-IV of FIG- URE 3;

FIGURE 5 is a diagrammatic partial view of support and a thinwall bearing with a holding cam, and

FIGURE 6 shows a device for producing the holding cam.

In the examples shown in the drawings, a blank 1 is first cut out of strip material coated with antifriction metal. The dimensions of this blank can be calculated in accordance with the size of the bearing to be produced, taking into consideration the reduction in the thickness of the material which occurs during the production of the bearing.

The blanks 1 thus cut to size are fed by means of a shoe 2 to the gap between a pair of rolls 3,4. The underside of the feed shoe 2 shown in FIGURE 1 is fashioned to guide the back of the blank 1, that is the side which is not coated, and slopes at an angle of alpha relative to the perpendicular or normal of the roll plane 6 from the rear of this plane towards the roll 3 which is to act on the coated side of the blank 1. As experiments have shown, the angle alpha may lie between 0 and 30 degrees. An angle alpha of about 10 degrees has proven to be particularly advantageous. Due to the feed shoe 2 a zone A is formed between the end of the shoe and the actual roll nip in which the blank 1 is to be prebent. This first working stage is followed immediately by a rolling zone B between the rolls 3 and 4. While in the example illustrated the prebending process in zone A takes place without reduction in the thickness of the blanks 1, a reduction in thickness of at least 0.5% is effected in the zone B. Experiments have shown that with a total thickness reduction of about 1%, the best parallelism of the generatrixes of the cylindrical bearing back is attained. The thinwall bearings formed by the method according to the invention require no machining of the running surfaces. Only the parting surfaces 7 require finishing, which may only necessitate a surface treatment without appreciable loss of material, due to the blanks 1 having been accurately cut to the previously calculated size.

As, in order to form the bearing, the blanks are to be fashioned to the circumference of the roll 3 which is to act on their coated side, it is advantageous to hold the front edges of the blanks 1 firmly against the circum- 4 ference of the roll 3 which is to act on the coated side of the blank.

According to FIGURE 2, this may be effected, for example with the aid of a holding claw 8 which is mounted in the roll 3 so that it is practically radially retractable and can engage the leading edge of the blank 1. However, in order to achieve high precision, it is necessary, when using such a holding claw 8, to arrange a corresponding recess 9 in the counter-roll. This, however, makes it necessary to drive the two rolls 3 and 4 synchronously. Due to the recess 9, the two rolls 3 and 4 can then run without interruption and remain at a uniform distance apart. However, a portion of the leading end of the blank 1 will not be subjected to the action of the rolls because of the recess 9 and must therefore be cut off. This loss of material is, however, insignificant in some cases as compared with the advantage attainable by this embodiment of the invention.

The embodiment according to FIGURE 2 is particularly suitable for the manufacture of bearings in small numbers. A particular advantage of this embodiment of the invention is that the holding claw 8 is independent of the width of the bearing to be manufactured and moreover very heavy forces can be exerted on the leading edge of the blanks 1 by this holding claw 8.

For thinwall bearings which are to be produced in very large numbers the embodiment illustrated in FIGURE 3 is particularly suitable. Here two lateral holding claws 10 are provided which are mounted each with a ringshaped holder 11 on a shaft 12 carrying the roll 3, one claw 10 being located on each side of the roll 3 which is to act on the coated side of the blank 1. Between these ring-shaped holders 11 and the machine frame 13 which carries the roll shaft 12, pressure devices 14 are arranged which are so constructed that they push the holding claws 14 towards each other in the axial direction of the roll 3 so that they enter the gap between the rolls. The holding claws 10 project into the roll gap and terminate in an oblique surface 15 which becomes wider towards the roll 3 and tapers into a cutting edge towards the roll 4. These claws 10 can therefore grip the blanks laterally and hold them firmly against the surface of the roll 3.

The rolling process is not obstructed by the holding claws 10. This arrangement and construction of the holding claws 10 possesses the further advantage that the whole of the blanks can be utilized for forming the thinwall-bearing, with the exception of a slight amount of machining, for example reaming, on the parting surfaces, in order to adjust the peripheral length accurately and obtain the required finish of the parting surfaces.

The use of blanks 1 whose length is only insignificantly greater than half the running periphery of the bearings, besides saving material and avoiding an additional working stage for the cutting and sawing, also offers a further advantage. In thinwall bearings a so-called parting line relief is generally provided. This consists in making the wall thickness in the immediate vicinity of the parting surfaces somewhat less than in the remaining portion of the bearing. This prevents the oil film from being scraped off when the bearing is in use as a result of a slight and usually unavoidable error in fitting. The inveniton makes use of the fact that as the blank runs into the gap between the rolls the specific pressure is greater than when the entire gap is filled with material. As a result the wall thickness of the bearing is less at the leading end than in the middle part of the bearing. The same phenomenon also occurs at the rear end of the blank and is likewise utilized by the invention. By using blanks which are only insignificantly longer than the periphery of the hearing, it is possible to roll the blanks to finished wall thickness, including the reduction in wall thickness at the parting surfaces. Moreover, it is also possible by appropriately shaping in transverse direction the strip from which the blanks are cut transversely, to produce a tapering wall thickness of the blanks for bearings with so-called lemon or oval bore, since the thickness profiling taken over from the shaping of the strip in the longitudinal direction of the blanks is maintained to a degree that can be calculated in advance during the final rolling in the procedure according to the invention.

Within the scope of the invention, it is also particularly advantageous to produce during the final rolling of the thinwall bearing the holding cams which are frequently required in such bearings. As FIGURE 5 shows, these holding cams 20 serve to secure the bearings 21 against twisting in their housing 22. For this purpose notches 23 are formed in the bearing housing 22 which receive the holding cams 20. The holding cam 20 there fore consists substantially of a portion of the blank which is pressed outwards from the strip material at one of the parting surfaces of the bearing. According to FIGURE 6, this holding cam is produced simultaneously in the final rolling of the bearing blank 21 by mounting a knife 24 in the roll 2 which acts on the coated side of the blank 1 from which the bearing 21 is made, which knife projects beyond the circumference of the roll 3 and cooperates with cutting side edges of a corresponding recess 25 in the counter-roll 4. The knife 24 is so arranged that it acts on the end of the blank 1 or bearing 21 formed therefrom. In the example illustrated, the knife 24 is in the form of a nose of triangular cross-section which projects beyond the circumference of the roll 3 with its cutting edge pointing away from the roll at more than a tangent.

All the features set forth in the above description, the claims and the drawings may be of significant importance to the invention by themselves or in any conceivable combination.

I claim:

1. The method of forming thinwall straight, arcuate bearing shells which are axially straight throughout the r entire axial length, from strip material coated with antifriction metal, said method including the steps of bending the strip material and subsequently finish-rolling the bent material with simultaneous reduction in the thickness thereof by at least .5 preferably 1.0%.

2. The method of claim 1, comprising the additional stages of first cutting the strip material into a measured length, passing the cut length with the aid of a feed member between rolls at an angle of from 60 to 90, preferably 80, with respect to the plane of said rolls, the reduction in thickness occurring between the rolls and the bending occurring in the vicinity of the feed member and immediately ahead of the gap between the rolls.

3. The method of claim 2, wherein the material is cut to a longitudinal dimension which is substantially equal to the finished size except for surface treatment of the parting end surfaces, and wherein there is the additional step of holding side portions of the cut length adjacent the forward edge thereof against the roll engaging the coated side of the cut length during the final rolling thereof.

4. Method of claim 3 and including the additional stage of forming a retainer cam in the trailing edge of the cut length as it passes between the rolls.

5. An apparatus for forming thinwall bearings from strip material coated on one side with antifriction metal, comprising in combination:

(a) a pair of cooperable sheet-metal attenuating pressure rolls arranged parallel to each other with an intervening gap for receiving a band of metal to bend and attenuate the same, said gap being smaller than the thickness of the metal band which is to be received by the rollers,

(b) a feed shoe extending to the gap between the rolls for engagement with the back surface of the strip material,

(c) said shoe making an angle of from 0 to 30, preferably 10, with respect to a normal of the plane of the rolls and in the direction of the roll intended for engagement with the coated side of the strip material,

((1) said roll having a diameter substantially corresponding to the internal diameter of the thinwall bearing to be produced.

6. Apparatus as in claim 5, wherein:

(a) two holding claws are provided at the sides of the roll intended for engagement with the coated side of the strip material to turn therewith, said claws adapted to engage the opposite side edges of the strip material,

(b) means are provided for moving said claws axially towards each other to clamp the strip material.

7. Apparatus as in claim 5, wherein a holding claw is provided on the roll intended for engagement with the coated side of the strip material.

8. Apparatus as in claim 7, wherein:

(a) said holding claw is radially retractible in the said roll,

(-b) the other roll having a recess to receive the holding claw during the rotation of the rolls.

References Cited by the Examiner UNITED STATES PATENTS 1,872,600 8/1932 Manning 29-1495 2,275,218 3/1942 Chambers 72-149 X 2,353,925 7/1944 Pattison 72 132 2,737,707 3/1956 Highet et al. 29-1495 2,756,803 7/ 1956 Faeber 72149 JOHN F. CAMPBELL, Primary Examiner.

THOMAS H. EAGER, Examiner.

Claims (1)

1. THE METHOD OF FORMING THINWALL STRAIGHT, ARCUATE BEARING SHELLS WHICH ARE AXIALLY STRAIGHT THROUGHOUT THEIR ENTIRE AXIAL LENGTH, FROM STRIP MATERIAL COATED WITH ANTIFRICTION METAL, SAID METHOD INCLUDING THE STEPS OF BENDING THE STRIP MATERIAL AND SUBSEQUENTLY FINISH-ROLLING THE BENT MATERIAL WITH SIMULTANEOUS REDUCTION IN THE THICKNESS THEREOF BY AT LEAST .5%, PREFERABLY 1.0%.

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