US2077336A - Apparatus for forming circular bushings - Google Patents

Description

April 13, 1937. V J, C, LEMWNG V 2,077,336

` APPARATUS FOR FORMING CIRCULAR BUSHINGS Filed Jan. 7, 1935 3 Skleets-Sheet 2 NVENTOR' ..fa/517 Lemmz'gy MJWHQLWLW f :ZLLY

ATTORNEYS April 13, 1937.

J. c. LEMMING 2,077,336

Filed Jan. 7, 1935.

INVENTOR ..z/afin fl Lamra/1117 W His A-noRNEYs Patented Apr. 13, 1937 UNITED STATES APPAEATUS FOR. FORMING CIRCULAR BUSHINGS John C. Lemming, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application January 7, 1935, Serial No. 588

Claims.

This invention relates to an apparatus for' forming circular bearing bushings or similar forms from fiat metal stock.

An object of the'invention is to provide an im- 5 proved means for making bushings having uniformly exact finished dimensions and which will have uniformly smooth and efficient interior bearing surfaces.

This application is a continuation-in-part of my copending application Serial No. 577,246,

filed November 25, 1931.

In making bushings according to the disclosure of said prior application, the opposed ends of the U-form blank directly abut each other with a high pressure while said U-form blank is being buckled outwardly into circular form by the approaching semi-cylindrical dies. Such direct abutment of the ends of the U-form sometimes causes one or the other of the end surfaces of these ends to be scored or grooved at or below the inside surface of the formed bushing. Then when the formed bushing has its inside surface cut away slightly by the usual reaming or other suitable finishing operation, a small axially extending score or groove will be exposed on the inside or bearing surface of the finished bushing.

Any such axially extending groove in the bearing surface is objectionable since it has been found to often be the cause of Vibration of the shaft running in the bearing, or more rapid wear of the bearing. Such an axial groove in the finished bushings often occurs when the material used for the blank is quite soft, such as ordinary bearing bronze stock.

An improvement included in the disclosure of the present application is the longitudinal inwardly projecting web or key in one of the semicylindrical dies against which the opposed ends of the U-form abut during the buckling oper- 40 ation, thus preventing any objectionable scoring or grooving of the end surfaces of the ends of the U-shaped blank. This eliminates the above described a-Xial groove at the seam of the finished bearing in all cases whether or not the material 45 of the blank is quite soft.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred embodi- 50 ment of the present invention is clearly shown.

In the drawings:

Figs. 1 to 8 are substantially identical `with Figs. 1 to 8 of my said copending application Serial No. 577,246.

metal from which the bushing is to be formed.

Fig. 2 shows the fiat strip being sheared off and bent into U -form by a reciprocating die.

Fig. 3 shows the U-form in position between two exterior half-dies and an interior floating arbor, just prior to the descent of the upper halfdie.

Fig. 4 shows what happens during the first portion of the down stroke of the Vupper half-die. Here the bottom ends of the U-form have been bent inwardly under the floating arbor and caused said arbor to be raised somewhat to permit the ends of the U-form to come together easily; V

Fig. 5 -shows the completion of the down stroke of the upper half-die shown in Figs. 3 and 4. Here the U-form -has been buckled out into approximately circular form'by the dies and the central floating arbor has been forced to its down position and aids in causing the bushing to buckle out into substantially circular form though this circular form is not exact.

Fig. 6 shows another station where the bushing is being reformed to a more exact circular form and to slightly smaller inside and outside diameters which are its final dimensions. The dotted lines indicate the original size before reforming but the reduction in diameter is exaggerated to enable it to be shown. Here the metal of the bushing walls isV flowed slightly under the high pressure of the exterior half-dies to form the bushing to exact dimensions and give the metal a permanent set.

Fig. 7 is a section on line 'l-l of Fig. 6 and Fig. 5 and shows the successive forming operations of those two figures. p

Fig. 8 is a section on line 8-8 of Fig. 6 and Fig. 5.

Figs. 9 to 1,2'i1lustrate the iniprovements'herein disclosed but not disclosed in said prior application.

Fig. 9 is similar to Fig. 3 but shows the inwardly projecting abutment'key fixed to the lower halfdie.

Fig. 10 is similar to Fig. 4 and shows whatV forming of the bushing by an interior cylindrical arbor and the final closing of the spaced scam shown in Fig. 11.

Similar reference characters refer to similar parts throughout the several views. First there will be described the means and method illustrated in Figs. 1 to 8.

The flat metal blank ID is preferably sheared off from the end of a continuous strip 9 of flat stock of bronze or other suitable bearing metal by the edge 8 of the reciprocating die I2. If

desired, oil grooves, holes and/or trade-marks' may be stamped in the blank I by suitable dies prior to the stroke of the die I2 which shears off blank IU. The blank I is then bent into the U-form II by the continued down-stroke of the reciprocating die |2 over the stationary central die I3. I4 is a stationary stripper bar which aids in guiding the flat blank l0 into proper position between dies I2 and I 3, and prevents the next following up-stroke of die I2 from dragging the U-form I I up with it, all as will be clearly understood from viewing Fig. 2.

The U-form II next is passed endwise from its position on die I3 to the position Vshown in Fig. 3

where its lower ends IE rest by gravity upon the curved surface iii of the stationary lower halfdie 20, the upper half-diefl2l being at that time at a higher position than as shown in Fig. 3 to provide proper clearance between it and the top of U-form II. An interior floating arbor 22 is suitably supported in the position shown in Fig. 3 by a projecting end shank I9 (see Figs. 7 and 8) so that it may be easily moved vertically upward a small distance by the ends I of the U-form II as they are forced together as shown in Fig. 4. Floating arbor 22 has cylindrical surfaces 23, 24 and flat'sides to enable it to properly clear the sides of U-form II which at this time are much closer together than the full inside diameter of the bushing to be formed. Now when the upper half-die 2I descends it compresses the U-form II between dies 2I and and causes the lower ends I5 of the U-form to rst cam inwardly on the semi-cylindrical surface of die 20 until they pass under the freely floating arbor 22 and raise it upwardly by buckling at the points 25, all as clearly shown in Fig. 4. From this point, further down movement of 'the upper half-die 2| rounds out the U-form II into the nearly circular form as shown in Fig. 5. During this forming, the cylindrical surfaces 23 and 24 of arbor 22 aid materially in rounding out the top and bottom portions of the U-form I I and` this causes the flat sides of the U-form to always `and uniformly buckle outwardly rather than inwardly even though said flat sides are spaced some distance from the interior arbor 22. Another very import'antV function of the floating arbor 22 is to prevent the formation of a raised internal bead in the formed bushing where the two ends I5 of the U-form II abut at high pressure when die 2I descends as described above. The diameter of the circular surfaces of arbor 22 is preferably several thousandths of an inch less than the inside diameter of bushing 30, formed as above described, to permit said formed bushing 30 to be easily slipped endwise from arbor 22 after the upper half-die 2I moves up again on its upstroke. Since arbor 22 is floating, that is, it is not held in fixed position but may be moved up- Ward freely for a short distance, the pressure of bushing 30 upon the lower half-die 20 is immediately released when die 2I starts on its up-stroke and henc'e this feature also permits easy endwise movement of bushing 30 from arbor 22.

For the final forming operation shown in Fig. 6 the bushing 30 is slipped endwise from the flatted arbor 22 onto the slightly smaller but full cylindrical arbor 42. This cylindrical arbor 42 is mounted upon a bolt 43 screwed into the end of fioating arbor 22 and hence arbor 42 is also fioating (see Figs. 7 and 8). Preferably there is a small clearance 44 between the central aperture in arbor 42 and bolt 43 so that arbor 42 can move slightly relative to arbor 22, in order that the forming operation of Fig. 6 will be substantially' independent of that of Fig. 5 even though the' exterior half-dies and 4I are formed integral with the half-dies 20 and 2I as clearly shown in Figs. '7 and 8. During this final forming operation of'Fig. 6 all small bumps or irregularities in bushing 30' are smoothed out and the walls of said bushing are compressed under high pressure between the half-dies 40, 4I and the central arbor 42 to such an extent that the metal thereof is flowed slightly to cause it to permanently set in its formed exact dimensions. The cold working given the metal by the described reduction in diameter of the bushing at the station shown in Fig. 6 also improves the bearing qualities of bronze metal. At the next up-stroke of upper half-die 4| the finally formed bushing 30' is slipped end- Wise from the end of arbor 42 by the movement to the left (as seen in Figs. '7 and 8) of the succeeding bushing 30 as it is moved to its position on arbor 42. Since arbor 42 is slightly smaller in diameter than the cylindrical portion of arbor 22, bushing 30 slides easily to its position upon arbor 42. lI'his movement to the left (as seen in Figs. '7 and 8) of both bushings 30 and 30' is done by .automatic means not shown since it forms no essential part of this invention.

It is to be understood that the operations described above preferably are continuous, that is, the U-form II is made at one station, the initial forming of bushing 30 is done at a second station, and the final forming of bushing 30' is done at a third station, all at one down stroke of the punch press carrying the dies corresponding to these three stations.

The bushings coming from the third station, that is, from arbor 42 may later have their ends cut smooth or chamfered in a suitable trimming machine if it is so desired, but otherwise these bushings are ready to be mounted as bearings in the machine in which they are to be used.

The operation of the means shown in Figs. 9 to 12 will now be described. In Figs. 9, 10 and 11' the lower half-die 20' has a longitudinally extending flat key fixed thereto and extending up into the forming cavity as clearly shown. The fiattened floating arbor 22' has a longitudinal slot 5| therein which fits snugly upon key 50 with an easy slip fit. Thus clearance for key 50 is provided when dies 28' and 2i' close (as shown in Fig. 11) and also key 50 serves as a suitable guide for the small vertical motion of the floating arbor 22'. Otherwise the parts shown in Figs. 9 to 12 are exactly as described above for Figs. 3 to 6.

In operation, the U-form blank I i is first passed to the position shown in Fig. 9 where its lower ends I5 rest by gravity upon the curved surface IS of the stationary lower die 22'. The upper die 2I' is shown partly descended in Fig. 9 until it engages the upper curved end of the U-form I I. Further downward movement of die 2I' now causes vthe ends I5 of U-form II to first cam incil.

wardly on the cylindrical surface [6 until they pass under the floating arbor 22' and raise it upwardly a slight amount by buckling at the points 25, as shown in Fig. 10. The end surfaces |5 of U-form ll abut against opposed sides of the inwardly projecting flat key 50 (rather than against each other as in the form of the invention described above) and are thus prevented from scoring or grooving each other. Further downward movement of die 2l' rounds out the bushing blank into the nearly circular form 60 shown in Fig. 11. During this forming the cylindrical surfaces 23' and 24' of arbor 22' aid materially in rounding out the top and bottom portions of the blank I l and thus cause the flat sides of the U-form to always buckle outwardly rather than inwardly. Also an important function of arbor 22' is to prevent any thickening of the ends |5 by a flow of the metal due to the high pressure With which they abut the flat key 50 during the forming shown in Fig. 11.

The circular form BU With the spaced seam therein (due to the ends l5 being spaced apart by the thickness of key 50) is easily slipped endwise from the arbor 22' and onto the circular arbor 42' after the upper die 2l' moves up again on its up-stroke in the same manner as described above for the bushing 30. The final forming of bushing 60' is done by the floating circular arbor 42' and the two half-dies 40' and 4l' as shown in Fig. 12, the operation being substantially the same as described above for the final forming of bushing 30' shown in Figs. 6 and 8. During this final forming of the bushing the spaced seam 35 shown in the form 60 in Fig. 11 is fully closed by the dies since the flat key 50 extends only throughout the length of the forming surface of die 20'. Of course the diameters of the dies 40' and 4I' and of circular arbor 42' are sufiiciently smaller than the diameters of dies 20' and 2l' and of arbor 22' to provide for the complete closing of the open seam in bushing 60. Such reduction of diameters of the dies in the final forming stage readily permits the partially formed 45 bushing 60 to be easily slipped endwise from the arbor 22' to its final forming stage where it surrounds circular arbor 42'. Floating arbors 22' and 42' are attached by pin 43' and both move upwardly together a short distance by a yielding 50 spring action to the position shown in Fig. 9 immediately upon the up-stroke of the integral upper dies 2l' and 4l'. This floating action of the arbors greatly facilitates the endwise movement of bushing 60 to its final forming position and also the endwise ejection of the final bushing 60' from the end of the circular arbor 42', as described above.

While the embodiment of the present invention as herein disclosed, constitutes a preferred 60 form, it is to be understood that other forms ity and rigidly fixed to one of said dies and forming an immovable abutment for the opposed edges of said U-form blank during the forming operation.

2. In an apparatus for making a circular bushing from a U-form metal blank, in combination, two relatively reciprocating dies having coacting substantially semi-cylindrical forming cavities which engage and compress said U-form blank therebetween and force same to buckle outwardly into substantially cylindrical form, and a thin longitudinal key fixed to one of said dies and projecting inwardly at the center line of one of said semi-cylindrical cavities and forming an immovable abutment for the opposed edges of said U-form blank during the forming operation, and a central arbor located Within said die cavities when in closed position and having a cutout recess for clearing said inwardly projecting key.

3. In an apparatus for making a circular bushing from a U-form metal blank, in combination, two relatively reciprocating dies having coacti-ng forming cavities which engage and compress said U-form blank therebetween and force same to buckle outwardly into substantially circular form, and a longitudinal key projecting into the forming die cavity from one of said dies and forming an abutment for the opposed edges of said. U- form blank during the forming operation, and a floating arbor positioned between said coacting cavities and having a reduced width such that said U-form blank may pass thereabout prior to being formed into circular shape, said floating arbor having a slot therein vfor receiving the inner portion of said key projecting beyond the wall thickness of the formed bushing.

4. In an apparatus for making a circular bushing from a U-form metal blank, in combination, two relatively reciprocating dies having coacting forming cavities which engage and compress said U-form blank therebetween and force same to buckle outwardly into substantially circular form, and a. longitudinal key projecting into the forming die cavity from one of said dies and forming an abutment for the opposed edges of said U- form blank during the forming operation, and a floating arbor located between said coacting dies and movable relative to both of said dies toper- Vmit the opposed ends of said U-form blank to pass therearound while being bent into circular shape, said arbor having a slot therein for receiving the inner portion of said key.

5. In an apparatus for making a circular bushing from a U-form metal blank, in combination, two relatively reciprocating dies having coacting forming cavities which engage and compress said U-form blank therebetween and force same to buckle outwardly into substantially circular form,

JOH'N C. LEMMING.

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