US 2077335 A
Description (OCR text may contain errors)
April 13, 1937.
APPARATUS FOR MAKING CIRCULAR BUSHINGS 2 Sheets-Sheet 2 Filed Nov.` :25, 1931 if '/0/ d l fm mm;
J. c. LEMMING l 2,077,335
Patented Apr. 13, 1931 APPARATUS Fon MAKING CIRCULAR BUSHINGS l John C. Lemming, Dayton, Ohio, assignor, by
mesne assignments, to General Motors Corporation, Detroit, Mich.. a corporation of Delaware Application November z5, 1931, 'serial No. 577,246
5 claims. (ci. 153-49) This invention relates to .an apparatus for forming circular bushings or circular forms from iiat metal stock and has particular reference to forming circular bearing bushings fromflat strip bronze stock.
An object of the invention is to provide a simple and eilic'ient apparatus for producing circular bushings having uniformly exact finished dimensions and which will have uniformly smooth and 'emcient interior bearing surfaces.
A feature of this invention is the reduction in diameter of the bushing in the final forming operation, whereby any tendency for the formed bushing to spring open slightly at the butt joint is avoided, and whereby such cold working of the metal improves the bearing qualities of the interior surface of the bushing.
Furtherobjects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred embodiment of one form of the present invention is clearly shown.
In the drawings:
Fig. 1 shows a fiat blank of strip bronze or other metal from which the bushing is to be formed.
Fig. 2 shows the at 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 upper halfdie. Here the bottom ends of the U-form have been bent inwardly under the floating arbor and caused saidarbor to-be raised somewhat to .per-- mit theends of the U-form to come together easily. f
Fig. 5 shows the completion `of the down stroke of the upper half-die shown inFigs., 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 butthe reduction indiameter is exaggerated to enable it to be shown. Here the metal of the bushing walls is flowed slightly under the high pressure of the exterior half-dies to form the bushing to exact dimensions and give themetal a permanent set. l
Fig. 7 is a section on line 'I-'I of Fig. 6 and Fig. 5 and shows the successive forming operations of those two figures.
Fig. 8 is a section on line 8-8 of Fig. 6 and Fig. 5.
Similar reference characters refer to similar parts throughout the several views.
The drawings and vfollowing description refer to a method of making bearing 'bushings according to this invention.
The at metal blank I is preferably sheared off from the end of a continuous strip 9 of flat stock of bronze or vother suitable bearing "metal 4 by the edge 8 of the reciprocating die I2.. If desired, oil grooves, holes and/or trade-marks may be stamped in the blank yIII by suitable dies prior to the stroke of the die 'I2 which shears off blank III. The blank I0 is then bent into the U-form II by the continued down-stroke of the reciprocating die I2 over the stationary central die I3. I4 is a stationary stripper bar which aids in guiding the fiat blank 'I0 into proper position between dies I2 fand I3, and prevents the next following upsstroke ofv die1^I2 from dragging the U-form II up with it, all as will be clearly understood from viewing Fig. 2.
The Uform II next is passed endwise from its position on die I3 to the position shown in Fig. 3 where 'its lower ends I5 rest by gravity upon the curved surface I6 of the stationary lower half-die 20, the upper half-die 2i 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 aprojecting end shank I! (see Figs. '7
and il)y so that it may be easily moved vertically.
upward a small distance bythe ends I of the U- form II as they are forced together as *shown in Fig. 4. Floating arbor 22 has cylindrical sur faces 23, 24 and flat sides to enable it to properly clear the sides of U-form II which at lthis timev are much closer together than the full inside diameter of the'bushing to be formed. Now when-v vthe upper half-die 2l descends it compresses the U-form Il between dies 2| and 2l) and causes the lower ends yI5 of the U-form to rst cam nwardly on the semi-cylindrical surface I6 of die 20 until they pass under the Ifreely oating arbor 22 and raise it upwardly by buckling atthe pointsv 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 30 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 Il and this causes the flat sides of the U-form to always and uniformly buckle outwardly rather than inwardly even though said ilat sides are spaced bearing qualities of bronze metal.
other Yver'y important function of the floating arbor 22 is to prevent the formation of a raised internal bead in the formed bushing 30 where the two ends I of the U-form I I 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 2| moves up again on its up-stroke. Since arbor 22 is floating, that is, it is not held in xed position but may be moved upward freely for a short distance, the pressure of 'bushing 30 upon the lower halfdie 20 is immediately released when die 2I starts on its upstroke and hence this feature also permits easy endwise movement of bushing 30 from arbor 22.
For the nal forming operation shown in Fig. 6 the bushing 3D 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 floating arbor 22 and hence arbor 42 is also floating (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 4U and 4I are formed integral with the half-dies 20 and 2| 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 40 to such an extent that the metal thereof is'ilowed 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 At the next up-stroke of upper half-die 4I the finally formed bushing 3U is slipped endwise 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. This movement to the left (as seen in Figs. 7 and 8) of both bushings 30 and 3| is done by automatic meansk not shown since it form 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 correspondingl to these three stations.
The bushings coming from the third station,4
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.
While the form of embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.
What is claimed is as follows:
1. Apparatus for making a circular bushing from a U-form metal blank comprising: two relatively reciprocating dies have coacting forming cavities which engage and compress said Uform blank therebetween and force same to buckle outwardly into circular form, and a flattened floating arbor positioned between said coacting cavities and having such cross section dimensions that said U-form blank may be passed thereabout prior to its being formed into circular shape, said floating arbor having surfaces which engage portions 0f the inside surface of the bushing as said cavities which engage and compress said U-form blank therebetween and force same to buckle outwardly into circular form, and a flattened floating arbor located within said die cavities when in closed position and having parti-cylindrical surfaces which engage the inside surface of the bush.- ing while it is being formed into circular shape.
3. Apparatus for making a circular bushing from a U-form metal blank comprising: two relatively reciprocating dies having coacting forming cavities which receive and compress said U-form blank therebetween and bend same into circular form, and a flattened central arbor having diametrically opposed parti-cylindrical surfaces which engage portions of the inside surface of the bushing being formed, said arbor having a sectional width less than its dimension across said parti-cylindrical surfaces whereby it may lie freely within said U-form blank prior to its bending into circular shape.
4. 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 out-l wardly into substantially cylindrical form, and a floating arbor positioned between said coacting dies and having a width materially less than the inside diameter of the bushing to be formed so that said U-form blank may pass thereabout prior to its being buckled outwardly by 'said coacting dies.
5. In an apparatus for making a circular bushing from a U-form metal blank. inv 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 floating arbor located between said coactingv dies and movable relative to both of said dies to permit the opposed ends of said U-form blank to pass therearound while being bent into circular shape, said arbor having a width materially less than the inside diameter of the bushing to be formed and I JOHN C. LEMMING.