US3701275A - Machine for forming piston ring spacer-expanders from strip stock - Google Patents

Abstract

A machine for making spacer-expanders for piston oil rings of the type described in United States Pat. No. 3,477,732. The machine comprises a punch press having a plurality of stations through which strip stock is fed progressively in accurately predetermined increments, the strip stock being worked between dies at each station to transform the strip stock into completed rings. The press includes one or more punching stations where the strip stock is pierced and blanked, one or more forming stations where the pierced and notched strip is bent to form the spring legs of the spacer-expander and then curled into a channel-shaped cross-section, a coiling station where the channel-shaped stock is fashioned into a coil, and a cut-off station where each coil is sheared from the strip to form the semi-finished ring. The press also includes a special transfer apparatus for transferring the semi-finished ring to a final work station wherein the end joints are trimmed and formed to final configuration, after which the finished rings are loaded automatically in stacked relation on a cylindrical mandril.

Description

United States Patent Overway et al. 31, 1972 [54] MACHINE FOR FORMING PISTON [57] ABSTRACT RING SPACER'EXPANDERS FROM A machine for making spacer-expanders for piston oil STRIP STOCK rings of the type described in United States Pat. No. 72 Inventors; R E, O G d H 3,477,732. The machine comprises a punch press hav- Frank win-rick Muskegon, both ing a plurality of stations through which strip stock is f'Mi lfed progressively in accurately predetermined increments, the strip stock being worked between dies at [73] Seal cm'pomtlon each station to transform the strip stock into Muskegon Mlchcompleted rings. The press includes one or more [22] Filed; May 2 7 punching stations where the strip stock is pierced and blanked, one or more forming stations where the [21] PP N 39,499 pierced and notched strip is bent to form the spring legs of the spacer-expander and then curled into a 52 US. Cl ..72/335, 29/l56.6 Channel-shaped cross-section, coiling Station Where 51 Int. Cl. ..B2ld 28/00, B23p /06 the channel-Shaped stock is fashimed a coil and 58 Field of Search ..72/324 335- 29/l56.6 a Statim where e is sheared from the strip to form the semi-finished ring. The press also includes a special transfer apparatus for transferring the [56] References Cited semi-finished ring to a final work station wherein the UNITED STATES PATENTS end joints are trimmed and formed to final configuration, after which the finished rings are loaded auto- Farmer ta k d l d a1 d 2,697,865 12/1954 Norton ..29/l56.6X c yms c 6 onacym Claims, 53 Drawing Figures Primary ExaminerCharles W. Lanham Assistant Examiner-R. M, Rogers Att0rneyBarnes, Kisselle, Raisch & Choate /60 m2 I64 00 [50 H6 H8 H6 H4 8 H6 [/6 I20 I26 4-- [08 I52 /04- /2e- 20: 3 /-3+ 904 I70 I56 Q 220 0,20 m 4/4 4 mmn'fi CoclfrCu'hOff a 2\\ 1J0 5/3 1 3 e s is (K. at 0 "n a m- 2 48 \fl my 0 ion T Stahon 'S'Tfon lmtlor| anon Stahon g 10 f-zoe 54 a a I 213 Stqhon 8 2 4 w gemie 1am; ea, t an, "ear a; at?

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BY FRANK .WARRICK mfll mw ATTORNEYS 4M MACHINE FOR FORMING PISTON RING SPACER- EXPANDERS FROM STRIP STOCK This invention relates generally to a punch press and particularly to an apparatus for punching metal in the form of a strip and forming such punched strip into rings.

More specifically, the invention relates to an apparatus for progressively forming in a continuous operation a flat ribbon metal strip into spacer-expander spring rings of the type commonly located between thin metallic rails in the oil groove of a piston of an internal combustion engine.

An object of this invention is to enable production of such rings accurately, economically and at a high rate.

Another object is to provide an improved machine capable of automatically forming spacer-expanders of the type disclosed in U.S. Pat. No. 3,477,732, particularly in connection with FIGS. 1-5 inclusive and FIGS. 15 and 16 thereof.

A further object is to provide an improved machine capable of performing the improved method of making such a spacer-expander as disclosed in a co-pending application of Frank G. Warrick, Ser. No. 39,264, filed May 21, 1970, entitled Method of Forming a Spacer- Expander, and assigned to the assignee of the present application.

A further object is to provide an improved machine of the above character utilizing certain components and functions of the machine disclosed and claimed in U.S. Pat. No. 2,925,847, assigned to the assignee of the present application, and to improve upon said prior machine.

Other objects, features and advantages of the apparatus of this invention will become apparant from the following detailed description and accompanying drawings wherein:

F IG. 1 is a fragmentary front elevational view of an exemplary but preferred embodiment of the machine of the present invention.

FIGS. 2, 3 and 4 are fragmentary plan views of the strip stock respectively showing the operations performed thereon at the first, second and third punching, blanking and bending stations of the machine.

FIG. 5 is a fragmentary perspective view of the strip stock illustrating the feet and leg bending operations performed thereon successively at stations Nos. 3 and 4 respectively.

FIG. 6 is a fragmentary view partially in vertical elevation and partially in vertical center section through the strip guide infeeding mechanism and leg bending dies of station No. 4.

FIGS. 7 and 8 are fragmentary end elevational and part vertical sectional views taken generally on the line 7-7 of FIG. 6 and respectively illustrating the dies of station No. 4 in their open and closed positions.

FIG. 9 is a fragmentary plan view of the strip infeed guide of station No. 4

FIGS. 10 and 11 are fragmentary enlarged views of the dies as viewed in FIGS. 7 and 8 respectively.

FIG. 12 is a fragmentary front elevational view showing a portion of the die structure shown in FIG. 6 but enlarged thereover and with the dies in closed position.

FIG. 13 is a vertical sectional view taken on the line 13-13 of FIG. 5 but enlarged thereof:

FIG. 14 is a fragmentary front elevational view of the dies of station No. 5 shown partially in vertical center section and with the dies closed.

FIG. 15 is a fragmentary end elevational view of the entrance to station No. 5 taken on the line 15-15 of FIG. 14.

FIG. 16 is a fragmentary vertical sectional view taken on the line 16-16 of FIG. 21 and illustrating the progressive strut bending operation being simultaneously performed by the last sevenof the ten punches and associated dies of station No. 5.

FIGS. 17, 18, 19, 20 and 21 are fragmentary vertical sectional views taken respectively on the line 17-17 of FIG. 14 and lines 18-18, 19-19, 20-20 and 21-21 of FIG. 16.

FIG. 22 is a vertical sectional view taken on the line 22-22 of FIG. 16 illustrating the finished cross-sectional contour of the strip as it emerges from station No. 5.

FIG. 23 is a fragmentary horizontal sectional view taken on the line 23-23 of FIG. 14 illustrating the stationary stripper components in the lower die shoe of station No. 5.

FIG. 24 is a fragmentary horizontal plan view of portion of the structure shown in FIG. 23 with the stationary stripper parts removed to better illustrate the underlying movable stripper and stationary forming dies in the lower die shoe.

FIGS. 25, 26 and 27 are fragmentary vertical sectional views taken respectively on the lines 25-25, 26-26 and 27-27 of FIG. 14.

FIG. 28 is a fragmentary perspective view of the lefthand stripper plate of station No. 5 shown by itself.

FIG. 29 is a fragmentary front elevational view of a portion of the induction heating coil of station No. 6 and also illustrating the coiling and cut-off apparatus of station No. 7 of the machine.

FIG. 30 is a fragmentary front elevational view of the components of station No. 7 with the guide shield and blow-off air tube parts removed to better illustrate details.

FIG. 31 is a fragmentary end elevational view of the entrance guide of station No. 7 looking in the direction of arrow 31 in FIG. 30.

FIG. 32 is a fragmentary vertical sectional view taken on the line 32-32 of FIG. 30.

FIG. 33 is a fragmentary vertical sectional view taken on the line 33-33 of FIG. 30.

FIG. 34 is a fragmentary plan view of the strip stock after it has been severed in the cut-off operation of station No. 7.

FIG. 35 is a fragmentary front elevational view of a portion of station No. 7 illustrating the strip coiling anvil and associated bending pad in the open position thereof.

FIG. 36 is a fragmentary end elevational view of actuating linkage in station No. 7 as viewed on the line 36-36 of FIG. 30.

FIG. 37 is a fragmentary front elevational view of the apparatus of stations Nos. 8 and 9 of the machine.

FIG. 38 is a fragmentary front elevational view of a portion of the station No. 8 apparatus shown in FIG. 37 but illustrating the pusher members in closed position embracing the entrance cone of this station.

FIG. 39 is a side elevational view of the apparatus of station Nos. 8 and 9.

FIG. 40 is a fragmentary horizontal sectional view taken on the line 40-40 of FIG. 37 illustrating a portion of the apparatus of station No. 9.

FIG. 41 is a horizontal sectional view taken on the line 4141 of FIG. 37.

FIG. 42 is a horizontal sectional view taken on the line 42-42 of FIG. 37.

FIG. 43 is a fragmentary horizontal section of the shot pin and slide parts of FIG. 42 but with the shot pin shown in engaged position with the slide.

FIG. 44 is a fragmentary side elevational view illustrating the punch, clamp and die components of station No. 8, FIG. 44 being partially taken in vertical center section and enlarged over FIG. 39.

FIG. 45 is a fragmentary vertical sectional view taken on the line 45-45 of FIG. 44.

FIG. 46 is a fragmentary horizontal sectional view taken on the line 46-46 of FIG. 44 but greatly enlarged thereover.

FIG. 47 is a fragmentary vertical sectional view taken on the line 47-47 of FIG. 46.

FIG. 48 is a fragmentary plan view of a portion of the parts shown in FIG. 46 but with their position changed to illustrate the joint trimming and initial bending actron.

FIG. 49 is a view similar to FIG. 48 showing the parts at the completion of the trim and bending stroke.

FIG. 50 is a fragmentary side elevational view of the left-hand clamp member shown in FIGS. 46, 48 and 49.

FIG. 51 is a fragmentary side elevational view of the right-hand shearing and bending punch shown in FIGS. 46, 48 and 49.

FIG. 52 is an end elevational view of the left-hand forming die shown in FIGS. 46, 48 and 49.

FIG. 53 is a fragmentary perspective view of one end of the spacer-expander illustrating the 'end joints thereof after being trimmed and bent in station No. 8.

For purposes of facilitating description and not by way of limitation, the machine 100 of the present invention is illustrated with the proper dies for forming the piston ring spacer-expander illustrated in the aforementioned U.S. Warrick Pat. No. 3,477,732, particularly the spacer-expander 58 shown and described in conjunction with FIGS. 1-5 inclusive thereof and with the end joint construction shown and described in conjunction with FIGS. 14-16 inclusive thereof, this patent being incorporated herein by reference and hence spacer-expander 58 thereof not being described herein.

GENERAL ARRANGEMENT Machine 100 of the present invention is shown substantially in its entirety in FIG. 1 and generally consists of a punch press similar in part to that shown, described and claimed in the aforementioned U.S. Burns et al Pat. No. 2,925,847, which is incorporated herein by reference for a detailed disclosure of certain portions of the machine identified in more detail hereinafter. Machine 100 has a base 102 which supports a frame 104 and a motor 106 on frame 104 which drives a flywheel 108 through a belt 110. Flywheel 108 is connected by a clutch 112 with the crankshaft 1.14 of the press. Clutch 112 is of the positive drive, electric throw-out type. Shaft 1 14 is journalled on the frame of the machine in bearings 116. A pair of magnetic brakes 118 are arranged around shaft 114 and when electrically energized operate to sieze shaft 114 when the circuit to the brake is closed. Shaft 114 has three crank portions to which the upper ends of connecting rods 120, 122 and 124 are individually pivotally connected. Rods 120, 122 and 123 are connected respectively at their lower ends to associated rams 126, 128 and 130 which are guided for vertical reciprocating movement on frame 104 in ways formed in three sets of guide plates 132, 133 and 134 respectively.

As set forth in more detail hereinafter, ram 126 operates a piercing die assembly 136 of station No. 1 and a blanking and notching die assembly 138 of the station No. 2. Ram 128 operates a foot bending and joint notching die assembly 140 of station No. 3 and a leg bending die assembly 142 of station No. 4. Ram 130 operates a strut bending and strip curling die assembly 144 of station No. 5 and, also, through-a linkage 804, operates a coiling and cut-off die assembly 146 of station No. 7. The end joint trimming and bending die assembly 148 of station No. 8 is powered by pneumatic rams synchronized with the operation of the press by a suitable counting and control mechanism as described in more detail hereinafter.

The end of shaft 114 remote from flywheel 108 carries a disc 150 to which a link 152 is eccentrically connected for driving a strip feeder 154 through a bell crank 156. A suitable commercially available magnetic pick-tip assembly is provided for counting revolutions of shaft 114 to develop one signal per each vertical reciprocation of the rams 126, 128 and 130 through their simultaneous mechanically synchronized working strokes. Pick-up 160 has a rotating part 162 secured to shaft 114 for rotation therewith and a stationary part 164 secured to the stationary structure of the end bearing 116. Pick-up 160 provides the input signal to a suitable counter control (not shown), such as that sold under the trademark DYNAPAR made by the Louis Allis Division of Litton Industries at the Digital Center in Gurnee, Illinois and identified as a Digital Process Controller Type 5X2-5 8-X-l This controller operates through the signals derived from pick-up- 160 to initiate the cut-off operation as well as the air blast at station No. 7. This occurs in response to an output signal developed by storing the number of counts in the digital memory of the controller corresponding to the number of increments of advance of the strip being worked in machine 100 required to pass a given length spacer-expander through the coiling die of station No. 7. Also, this control further provides an output signal for actuating the pusher fingers of station No. 8 after allowing a time delay (corresponding to a given number of counts) for the severed spacer-expander to drop onto the nose cone of station No. 8. The remaining motions in stations Nos. 8 and 9 are controlled by conventional limit switches and solenoid valve circuitry (not shown) associated with the moving parts of this station as described in more detail hereinafter.

The counter control is also adapted to generate a control signal for causing a transverse shuttle motion of die assemblies 136, 138 and 140 of stations Nos. 1, 2 and 3 as an end joint zone of the strip stock being fed therethrough comes into successive registry with the respective die assemblies, as set forth in more detail hereinafter.

In general, the operation of machine 100 is as follows:

Claims (33)

1. A machine for making a spacer-expander, said machine having a plurality of in-line work stations and comprising: 1. means for feeding and guiding a strip of the flat ribbon metal stock with a step-by-step movement past the plurality of stations; 2. means at said stations for blanking said strip to repetitively form successive incremental sections wherein each section comprises two parallel bands extending lengthwise of the strip and defining the side margins thereof, a transverse strut spaced lengthwise of the strip equidistant from the struts of adjacent sections and at least one leg with said leg extending parallel to said strut and offset lengthwise of the strip from said strut, one end of said leg being connected to one of said first and second bands and the free end of the leg terminating short of the opposite one of said first and second bands; 3. means at one of said stations for bending said leg at an angle corresponding to the final free-state inclination of the leg in said spacer-expander relative to its contiguous band; 4. means at another of said stations for bending said struts in a progressive bending operation to impart a channel-shaped configuration to said strip when viewed in radial cross section of the finished spacer-expander, whereby two bends are formed in each strut at the ends of what is to become an intermediate axially extending portion of each strut, said strut bending means having a series of punches and dies operable on successive struts whereby a separate segmental increment of each of said bends of said strut is worked in each stage, said increments in each of said bends being contiguous to define the total curvature of the associated bend; and, 5. means for operating said blanking and bending means simultaneously with One another and in alternation with said strip feeding means.

2. means at said stations for blanking said strip to repetitively form successive incremental sections wherein each section comprises two parallel bands extending lengthwise of the strip and defining the side margins thereof, a transverse strut spaced lengthwise of the strip equidistant from the struts of adjacent sections and at least one leg with said leg extending parallel to said strut and offset lengthwise of the strip from said strut, one end of said leg being connected to one of said first and second bands and the free end of the leg terminating short of the opposite one of said first and second bands;

2. The machine as set forth in claim 1 wherein said strut bending means comprises a row of punch and die means operable simultaneously on each of said bends in each strut in a corresponding row of struts in said strip when registered with said punch and die means, a first series of said punch and die means providing progressively deeper relative penetration therebetween in the direction of strip feed whereby said progressive bending is performed in a first stage on an intermediate one of said bend segments and then in another successive stage on a bend segment disposed outwardly from said first segment, and a second series of said punch and die means following said first series having uniform relative penetration but progressively narrower spacing laterally of said strip whereby in a still further successive stage said progressive strut bending occurs in a bend segment located inwardly of said intermediate bend segment.

2. means for blanking said strip to repetitively form successive incremental sections wherein each section comprises two parallel bands extending lengthwise of the strip and defining the side margins thereof, a transverse strut spaced lengthwise of the strip equidistant from the struts of adjacent sections and first and second legs with the legs extending parallel to said strut and offset lengthwise of the strip, one end of said first leg being connected to said first band and one end of said second leg being connected to said second band and the free ends of the legs terminating short of the opposite band;

3. means for bending said legs at least partially toward the final inclination of the leg relative to its contiguous band in said spacer-expander;

3. The machine as set forth in claim 1 wherein said leg bending means is located in advance of said strut bending means whereby said leg of each section assumes its final position in said spacer-expander as said strip is curled to said channel-shaped configuration by said bending of said struts in said strut bending means.

3. means at one of said stations for bending said leg at an angle corresponding to the final free-state inclination of the leg in said spacer-expander relative to its contiguous band;

4. means at another of said stations for bending said struts in a progressive bending operation to impart a channel-shaped configuration to said strip when viewed in radial cross section of the finished spacer-expander, whereby two bends are formed in each strut at the ends of what is to become an intermediate axially extending portion of each strut, said strut bending means having a series of punches and dies operable on successive struts whereby a separate segmental increment of each of said bends of said strut is worked in each stage, said increments in each of said bends being contiguous to define the total curvature of the associated bend; and,

4. The machine as set forth in claim 1 wherein said strip feeding means is operable to advance said strip intermittently two sections at a time and then is operable to hold said strip stationarily while all of said blanking and bending means simultaneously operate on successive sections.

4. means for bending sail struts at spaced zones to impart a channel-shaped configuration to said strip when viewed in radial cross section of the finished spacer-expander, said feeding means intermittently advancing said strip two sections at a time and then holding it stationary; and,

5. means for operating all of said blanking and bending means simultAneously on successive sections when said strip is stationary.

5. means for operating said blanking and bending means simultaneously with One another and in alternation with said strip feeding means.

5. The machine as set forth in claim 4 wherein said progressive strut bending means comprises an even number multiplicity of successive bending punch and die stations, said punch and die means of said even-numbered stations being operable on one strut and said punch and die means of odd-numbered stations being operable on the next successive strut, said punch and die means being shaped successively in the direction of strip feed to impart a further bend angle to the strut worked therein in each successive station of said multiplicity of stations.

6. The machine as set forth in claim 5 wherein said stations are at least approximately ten in number and the first six of said stations have identical forming punches and bending dies, said dies of said first six stations having strut bending surfaces inclined upwardly in the direction of strip feed such that the first portion of the progression in bending is obtained by progressively deeper penetration of the forming punches between their individually associated pair of laterally spaced forming die shoes in the first six stations, said shoes in the last four stations having progressively more narrowly spaced forming die shoes whereby further bending is imparted by confining said strut progressively between said narrower shoes and the associated strut is struck with said progressively narrower punches associated with said narrower shoes.

7. The machine as set forth in claim 4 wherein said blanking means comprises: a. means for blanking six narrow transversely extending slots in each two adjacent sections of the flat strip whereby, considering the slots as being consecutively numbered one through six in the direction of strip travel, said first slot defines the leading edge of one strut next following said two sections, said third and fourth slots define the trailing and leading edges respectively of the trailing strut of said two sections and said sixth slot defines the trailing edge of the leading strut; b. shuttle punch and die means movable transversely of the direction of strip feed for moving said slot blanking means out of registry with an end joint zone of said strip having a length equal to two sections; c. means in said shuttle means for forming a strip advance slot means in said end joint zone in a portion thereof which is to be subsequently removed and in response to the movement of said slot blanking means oUt of registry with said end joint zone; d. means for removing by blanking two diagonally related portions of said strip between said first and second slots and said second and third slots and likewise removing by blanking two diagonally related portions of said strip between said fourth and fifth slots and said fifth and sixth slots; e. means for bending the free ends of the diagonally related portions remaining after said blanking by said last-mentioned means to thereby form the free ends of four legs at an angle inclined upwardly from the plane of said strip; and, f. wherein said leg bending means is located following said blanking means for bending said legs up from the plane of said strip about a bend line adjacent the associated marginal band.

8. The machine as set forth in claim 7 wherein two successive stations comprise shuttle punch and die means for forming said end joint zone in two blanking stages, the first of said two stations leaving said bands at the margin of said strip uninterrupted and leaving a central longitudinally extending strip connecting the leading and trailing struts of two successive spacer-expander strip lengths adjacent said end zone, the second of said two stations having punch and die means for removing by blanking said bands and leaving said central strip intact.

9. The machine as set forth in claim 1 wherein said blanking and bending means are oriented to move vertically into the surface of said strip which faces the interior of said spacer-expander, said surface facing upwardly throughout travel thereof through said stations, and wherein said blanking and bending means comprise punch means and die means movable vertically relative to one another perpendicular to the plane of said strip.

10. The machine as set forth in claim 9 wherein said leg bending means comprise stationary lower die horns and said legs are formed by being bent upwardly from the plane of said strip by downwardly movable punches, and said strut bending means comprise downwardly movable punches operable on a central portion of each strut and stationary die horns cooperable therewith to bend upwardly the portions of each strut between said central portion and said marginal bands.

11. The machine as set forth in claim 9 further including strip coiling means for coiling said strip into a circle by bending means operable on successive increments of said strip after the same has been worked by said blanking and bending means, said bending means including a movable pad operable to strike the outer periphery of said spacer-expander to impart the coiling curvature thereto.

12. A machine for making a spacer-expander, said machine having a plurality of in-line work stations and comprising:

13. The machine as set forth in claim 12 wherein said blanking means comprises: a. shuttle punch and die means for blanking six narrow transversely extending slots in each two adjacent sections of the flat strip whereby, considering the slots as being consecutively numbered one through six in the direction of strip travel, said first slot defines the leading edge of one strut next following said two sections, said third and fourth slots define the trailing and leading edges respectively of the trailing strut of said two sections and said sixth slot defines the trailing edge of the leading strut; b. means for moving said shuttle means transversely of said strip from a first position to a second position to thereby skip said slot blanking operation in an end joint zone having a length equal to two sections when said zone is registered with said shuttle means; c. means in said shuttle means for forming a strip advance slot means in said end joint zone in response to movement of said shuttle means to said second position; d. means for removing by blanking two diagonally related portions of said strip between said first and second slots and said second and third slots and likewise removing by blanking two diagonally related portions of said strip between said fourth and fifth slots and said fifth and sixth slots; and, e. means for bending the free ends of the diagonally related portions remaining after said blanking to thereby form the free ends of four legs at an angle inclined upwardly from the plane of said strip, and wherein said leg bending means is operable to bend said legs up from the plane of said strip about a bend line adjacent the associated marginal band.

14. The machine as set forth in claim 13 wherein said shuttle punch and die means comprises first and second means located respectively at two of said stations operable to perform said blanking of said end joint zone in two blanking stages, said first means performing the first of said two stages and leaving said bands at the margin of said strip uninterrupted and leaving a central longitu-dinally extending strip connecting the leading and trailing struts adjacent said end zone, said second punch and die means at the successive one of said two stations in the direction of strip feed comprising means for blanking out said bands and leaving said central strip intact.

15. The machine as set forth in claim 14 wherein said strip feeding and guiding means is operable to feed said strip oriented horizontally with the surface thereof which faces the interior of said spacer-expander in its finished form facing upwardly, and wherein said blanking and bending means comprise punch means operating from above said surface in vertical strokes in cooperation with associated stationary die means.

16. The machine as set forth in claim 15 wherein said leg bending means comprises punch and die means operable to bend said legs upwardly from the plane of said strip and wherein said strut bending means is operable upon said struts by punching down a central portion of each strut and bending up the portions of the strut between said central portion and said marginal bands.

17. In a machine for forming flat strip stock into a channel, said machine comprising means for feeding and guiding a strip of the flat ribbon metal stock with a step-by-step movement successively past first and second work stations, means for blanking said strip at said first station to form incremental sections wherein each section comprises two parallel bands extending lengthwise of the strip and defining the side margins thereof and a transverse strut spaced lengthwise of the strip from the struts of adjacent sections, means at said second station for bending said struts in a progressive bending operation to impart a channel-shaped configura-tion to said strip when viewed in cross section trans-verse to strip feed, said strut bending means comprising a row of punches and dies operable on successive struts whereby a separate segmental increment of each of said bends of said strut is worked in each stage, said increments in each of said bends being contiguous to define the total curvature of the associated bend, and means for operating said blanking and bending means in alternation with said strip feeding means.

18. The machine as set forth in claim 17 wherein said strip feeding means is operable to advance said strip intermittently a plurality of sections at a time and then is operable to hold said strip stationary while said blanking means and all of said bending punch and die means simultaneously operate on successive sections.

19. The machine as set forth in claim 17 wherein said strut bending means comprise an upper die shoe and a lower shoe positioned above and below said strip respectively, said punches being mounted in said upper shoe and said dies being mounted in said lower shoe, said punches comprising a first series of punches disposed successively adjacent one another in the direction of strip feed, each of said first series of punches having a uniform cross-sectional profile, the lower ends of said first punches being disposed flush with one another along a horizontal line extending in the direction of strip feed, said dies comprising a first pair of dies disposed respectively facing one another adjacent the path of travel of said first series of punches, each of said first dies having a bending surface extending continuously from upstream of the first punch of said first series to a point downstream of the last punch of said first series, said bending surfaces being inclined upwardly from the horizontal in the direction of strip feed, said first pair of dies having a uniform lateral spacing therebetween, said punches including a second series of punches disposed in a row downstream of said first series of punches, said second series of punches having profiles laterally of the strip which become narrower at their working ends progressively in the direction of strip feed, the lower ends of said second series of punches being horizontally aligned flush with lower ends of said first series of punches, said dies including a second series of dies arranged in laterally spaced pairs disposed with each of said pairs individually adjacent the path of travel of each of said second series of punches, the lateral spacing between each of said pairs of dies being progressively narrower in the direction of strip feed and correlated with the narrowing progression of said second series of punches associated therewith, said second series of dies having their bending surfaces disposed at the same horizontal elevation.

20. The machine as set forth in claim 19 wherein said bending means includes a movable stripper mounted in said lower shoe and having an upper surface extending horizontally in the direction of strip feed adapted to provide a sliding support for a median portion of said strip stock as the same is fed through said shoes, spring means biasing said movable stripper upwardly, stop means limiting upward movement of said movable stripper at a position wherein said upper surface thereof is raised above the elevation of said first and second series of dies, a bottoming support for said movable stripper adapted to limit downward movement thereof to a position wherein the surface of said movable stripper is disposed horizontally and recessed relative to the bending surfaces of said dies, and stationary stripper means mounted above said dies and the path of strip feed and adjacent said punches for clearing the strip stock from the punches during upward opening movement of said upper shoe.

21. The machine as set forth in claim 20 including a paddle forming an extension of said upper surface of said movable stripper upstream of said punches and dies, said paddle being rigidly fixed to said stripper for movement therewith, and entrance guide means flanking said paddle and defining therewith an entrance guideway for said strip in the flat condition thereof Leading into said punches and dies, said entrance guide means being stationarily secured to said lower shoe and having a pair of guiding surfaces overlying the upper surface of said strip closely adjacent the margins of said strip when the same is resting on said paddle in the raised position of said movable stripper.

22. The machine as set forth in claim 21 wherein said entrance guide means comprises a pair of vertical side walls extending along and closely adjacent the margins of said strip and having a vertical dimension extending from the raised to the lowered position of said strip margins when resting on said paddle in the raised and lowered positions of said paddle.

23. The machine as set forth in claim 22 wherein said guide means includes an exit guide mounted on said lower shoe defining an exit guideway aligned in the direction of strip feed with said movable stripper, said exit guideway having a vertical dimension adapted to permit raising and lowering of said strip in response to vertical movement thereof on said movable stripper, said exit guideway having a bottoming wall generally flush with said upper surface of said stripper in the raised position thereof and having a rib extending downwardly between the margins of said strip and extending in the direction of stripper feed for maintaining the channel-shaped strip oriented with its margins upright and said struts below said rib.

24. The machine as set forth in claim 20 wherein said stationary stripper means comprise a pair of stripper plates having a series of overhanging lips projecting horizontally toward the center line of the path of strip feed and being progressively closer thereto in the direction of strip feed, said lips being positioned to engage the margins of said strip as the same are being curled upwardly in progressing from the flat condition of said strip toward the channel-shaped configuration imparted by said punch and die means during working progression of the strip therethrough, and a series of stripper fingers extending horizontally transversely over said strip path in interdigital relation with said second series of punches.

25. The machine as set forth in claim 24 wherein said stationary stripper means includes a pair of guide fingers disposed approximately midway along the path of strip feed through said punch and die means, said guide fingers projecting laterally toward one another and having vertical guiding surfaces against which said strip margins slide during up and down movement of said strip and positioned to center said strip relative to the center line of strip feed.

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