US3196817A

US3196817A - Apparatus for fabricating sheet metal joints

Info

Publication number: US3196817A
Application number: US234107A
Authority: US
Inventors: Fraze Ermal Cleon
Original assignee: Individual
Current assignee: Individual
Priority date: 1962-10-30
Filing date: 1962-10-30
Publication date: 1965-07-27
Anticipated expiration: 1982-07-27

Description

E. c. FRAZE 3,196,817

APPARATUS FOR FABRICATING SHEET METAL JOINTS July 27, 1965 15 Sheets-'-Sheet 1 Filed Oct. 30, 1962 July 27, 1965 E. c. FRAZE 7 APPARATUS FOR FABRICATING SHEET METAL JOINTS Filed 001:. 30, 1962 15 Sheets-Sheet 2 Ema M. CLEO TTORNEYS RAZE y 1965 E. c. FRAZE EJQfil APPARATUS FORFABRICATING SHEET METAL JOINTS Filed 001:. 30, 1962 15 Sheets-Sheet 3 I T 1% 1 1 LQ' 2 INVEN TOR. Emmu Luau YRfim E. c. FRAZE 3,196,817

APPARATUS FOR FABRICATING SHEET METAL JOINTS July 27, 1965 15 Sheets-Sheet 4 Filed 001:. 30, 1962 INVENTOR.

Cm YER LL 6% July 27, 1965 E. c. FRAZE 9 APPARATUS FOR FABRICATING SHEET METAL JOINTS Filed Oct. 30, 1962 15 Sheets-Sheet 5 23 2. 5% INVENTOR.

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E. c. FRAZE. 39 9 7 APPARATUS FOR FABRIGATING SHEET METAL JOINTS July 2, 1965 15 Sheets-Sheet 6 Filed 001;..30, 1962 E. m m {a M Ekmm. Luann l I l ll llllll 1| ll ll l I III E. c. mam

APPARATUS FOR FABRICATING SHEET METAL JOINTS FRAZE l5 Sheets-Sheet 7 Filed Oct 30, 1962 INVENTOR. Cum 1mm wwumu@m III ,3 BY ZQS Jmfly 27, 1965 E. c. FRAZE 9 3 APPARATUS FOR FABRICATING SHEET METAL JOINTS Filed Oct. 50, 1962 15 Sheets-Sheet 8 INVENTOR. swam Fmza Q'wwamvms APPARATUS FOR FABRICATING SHEET METAL JOINTS Filed Oct. 30, 1962 E. C. FRAZE July 27, 1965 15 Sheets-Sheet 9 OnP w INVENTOR. EflRL axis V2911 qw-vomaws July 27, 1965 E. c. FRAZE 3,196,817

APPARATUS FOR FABRICATING SHEET METAL JOINTS Filed Oct. 30, 1962 15 Sheets-Sheet 10 Fuh- A INVENTOR.

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July 27, 1965 E. c. FRAZE 3,196,817

APPARATUS FOR FABRICATING SHEET METAL JOINTS Filed Oct. 30, 1962 15 Sheets-Sheet 11' l N VEN TOR. Eva-m; Cm Fzwua.

3,196,817 APPARATUS FOR FABRIGATING SHEET METAL JOINTS Filed Oct. 30, 1962 E. C. FRAZE July 27, 1965 15 Sheets-Sheet 12 INVENTOR. 11mm QJ-Lon FERZE.

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APPARATUS FOR FABRICATING SHEET METAL JOINTS July 27, 1965 15 Sheets-Sheet 13 Filed Oct. 30, 1962 I NVEN TOR. Eknfik. CLEO VER'LE.

QTY QRNEHB YRS-55 July 2%,]965 c. FRAZE 3,196,817

APPARATUS FOR FABRICA'IING SHEET METAL JOINTS Filed 001:. 30, 1962 15 Sheets-Sheet 14 I NVEN TOR. EEMRL CLEO VY-QZE.

T T OYDAEYS E c. FRAZE 3, 7 APPARATUS FOR FABRICATING SHEET METAL JOINTS July 27, 1965 15 Sheets-Sheet 15 Filed 001:. 50, 1962 l NVEN TOR. Elna; m VLQZE BY 'twozgua United States Patent C) 3,196,817 APPARATUS FOR FABRICATING SHEET METAL JOINTS Ernral Cleon Fraze, 355 W. Siroop Road, Dayton, Ohio Filed Set. 30, 1962, Ser. No. 234,107 Ciaims. (Cl. 113-4) This application is a continuation-in-part of my pending application, Serial No. 193,060, filed May 2, 1962, for Sheet Metal Joint and Method and Means of Fabrication, now abandoned, which, in turn, in a continuationin-part of my application, Serial No. 130,884, filed August 11, 1961, now abandoned.

This invention relates to a high speed multiple-stage apparatus for attaching devices to sheets of deformable material, and, more particularly, is directed to such an apparatus that fabricates the joints without using any fasteners whatsoever and without breaking the continuity of the sheets. While the invention is widely applicable for its purpose of attaching a member to a deformable sheet, it has special utility for those applications in which the sheet of deformable material is a fluid-confining wall. Since the continuity of the fluid-confining wall is not broken, the invention eliminates the problem of making the joint fluid-tight.

The invention has been initially embodied in an apparatus for the rapid continuous production of metal can tops that have manually removable tear strips whereby sealed cans incorporating the tops may be opened without the use of tools. This particular practice of the invention has been selected by way of example for the purpose of the present disclosure and will provide adequate guidance for those skilled in the art who may have occasion to apply the underlying principles to other specific purposes.

lt is highly desirable to provide sealable cans, for example cans for fruit juices, beverages and various food products and articles subject to deterioration by the atmosphere, with the can tops or end walls scored to provide tear strips and with tabs attached to the tear strips to serve as handles for severing the tear strips to permit the can tops or end walls to be removed without the use of a can opener or like tools.

The problem of attaching the tab to the tear strip of a can top in a dependable manner without any possibility of incurring leakage at the joint is solved by forming a small part of the sheet metal of the tear strip into a hollow rivet element. The hollow sheet metal rivet element is inserted into an aperture of the tab and is then deformed into positive engagement with the tab. Since containers of this type must be produced at exceedingly low cost, the pressing requirement is to provide a completely automatic apparatus to convert blank can tops into finished can tops and simultaneously to produce the required tabs from sheet metal stock. More specifically, the requirement is to provide a fully automatic apparatus capable of carrying out the sequence of steps at the operating stations shown in the following flow chart:

3,196,817 Patented July 27, 1965 g"- Ce STA TION A Partially blank tab S TA TI ON B Form ribs in tab STATION 1 Form a dimple in a blank STATION 0 can top Punch aperture in tab S TA TI ON 2 STA TI ON D Form the dimple into a 1101- low rlvet element Coin radius in rim of tab aperture STA TI ON 8 STA TI ON E Score the can top to form the tear strip Sever tab STA TI ON 4 Place the tab on the hollow rivet element and spread the hollow rivet element slightly to hold the tab in position STA TI ON 5 Deform the hollow rivet element into permanent en gagement with the tab It will be readily apparent to those skilled in the art that various well known types of conveyor mechanisms may be used to advance the can tops by stages through the sequence of can top operations and at the same time synchronously advance material for the tabs by stages through the seqeunce of tab operations. For example, a turntable may be used for either or both of the sequences, the turntable being rotated intermittently to carry the work in process from operating station to operating station.

In the particular embodiment of the invention selected for the present disclosure, the can tops, blanked out and formed in advance, are fed to one end of a straight line conveyor to progress through the successive operating stations for the can tops. At the same time strip material for the tabs progresses through a second series of operating stations in a second straight line that intersects the first straight line at Station 4 where the tabs and the can tops are brought together.

The conveyor system for the can tops comprises a series of workholders carried by a pair of parallel continuous conveyor chains which move intermittently to shift the workholders through Stations 1 to in sequence. Each workholder carries two can tops and two sets of dies at each station operate on the two can tops simultaneously. In the meantime a strip of metal for the tabs advances step by step through progressive dies to produce the required tabs for each successive pair of can tops arriving at Station 4.

As will be explained, the invention solves the problem of positioning the workholders accurately at the different processing stations where high precision is essential and solves all of the other problems involved in carrying out both the can top cycle and the tab cycle at high speed in a continuous automatic operation. These other problems include: feeding the blank can tops to the workholder; safeguarding the apparatus from damage by faulty operation; operating the dies and conveyor chains in synchronism; indexing the conveyor chains for accurate intermittent movement of the workholders from station to station; using close fitting positioning jigs for the workholders where required without any possibility of the close fitting workholders sticking in the jigs; employing a progressive die for operating on a single strip of metal to produce two tabs simultaneously spaced to arrive simultaneously at Station 4; transferring the finished tabs to the can tops at Station 4; and discharging the finished can tops from the workholders at the end of the conveyor line.

The features and advantages of the invention may be understood from the following detailed description and the accompanying drawings.

In the drawings, which are to be regarded as merely illustrative:

FIG. 1 is a fragmentary perspective view of a can equipped with a tear strip as produced by the present apparatus;

FIG. 2 is a plan view of a blank can top after the first step of forming a dimple;

FIG. 3 is a plan view of a can top after the second step of forming the dimple into a hollow rivet;

FIG. 4 is a plan view of a can top after the third step of scoring the can top to form the tear strip;

FIG. 5 is a diagrammatic plan view showing how a tab is initially placed on the hollow rivet;

FIG. 6 is a plan view of the finished can top with the hollow rivet swaged into permanent connection with the tab;

FIGS. 7 to 11 are sectional views corresponding to adjacent FIGS. 2 to 6 respectively, FIG. 7 being taken along the line 77 of FIG. 2, FIG. 8 being taken along the line 8-8 of FIG. 3, FIG. 9 being taken along the line 99 of FIG. 4, FIG. 10 being taken along the line 1010 of FIG. 5 and FIG. 11 being taken along the line 1111 of FIG. 6;

FIG. 12 is an enlarged sectional view showing how dies cooperate at Station 1 to form a dimple in a blank can p;

FIG. 13 is a similar view showing how dies cooperate at Station 2 to form the dimple into a hollow rivet element;

FIG. 14 is a perspective view of the lower die in FIG. 13;

FIG. 15 is an enlarged fragmentary sectional view showing how the metal of a can top is scored at Station FIG. 16 is an enlarged sectional view showing how dies cooperate to spread the hollow rivet element slightly into temporary engagement with a tab at Station 4;

FIG. 17 is a similar view showing how dies cooperate at Station 5 to swage the hollow rivet element into permanent engagement with the tab;

FIG. 18 is a fragmentary sectional view showing how retractible fingers function to release blank can tops one at a time from a stack of can tops in a supply chute:

FIG. 19 is a simplified fragmentary elevational view showing a rack and eccentric assembly of the mechanism for actuating the fingers in FIG. 18;

FIG. 20 (first sheet) is a perspective view of a workholder and adjacent portions of two associated conveyor chains for carrying pairs of can tops through Stations 1 to 5;

FIG. 20a is a fragmentary sectional view of a portion of a workhoider taken along the line Zita-2.0a of FIG. 12 and showing the construction of one of the retractible fingers for releasably holding a can top in the workholder;

FIG. 21 is a sectional taken along the line 21-21 of FIG. 29 showing how each successive workholder fits releasably into an accurate positioning jig at each of Stations 1 to 3;

FIG. 22 is a fragmentary sectional view showing how a shuttle plate reciprocates lower rams at Stations 4 and 5;

FIG. 22:: is a perspective View of the shuttle plate of FIG. 22;

FIG. 22b is a fragmentary perspective view of a cam member that is mounted on the lower end of each of the lower rams in FIG. 22;

FIG. 23 is a fragmentary sectional view showing one of the three yielding pawls that supports a stack of the finished can tops in a discharge chute;

FIG. 24 is a side elevational view of the selected embodiment of the apparatus;

FIG. 25 is an end elevation of the apparatus as seen along the line 2525 of FIG. 13;

FIG. 26 is an enlarged transverse section along the line 2626 of FIG. 24 showing the mechanism for feeding blank can tops to the successive worltholders;

FIG. 27 is a horizontal section as seen from below along the line 27-27 of FIG. 26 showing a portion of the mechanism for controlling the retractible fingers for feeding blank can tops to the successive workholders;

FIG. 28 is an enlarged fragmentary longitudinal section of the apparatus showing one of the sets of dies at each of the Stations 1 to 3 FIG. 29 is an enlarged transverse section along the line 23-29 of FIG 24 showing the two sets of dies at Station 1;

FIG. 30 is a similar transverse section along the line 3)30 of FIG. 24 showing the two sets of dies at Station FIG. 31 is a similar transverse section along the line g131 of FIG. 24 showing the two sets of dies at Station FIG. 32 is a horizontal section taken along the line 32-32 of FIG. 24 as well as along line 32 32 of FIG. 33 showing the progressive dies for forming the tabs at Stations A to E;

FIG. 33 is a longitudinal section along the line 33-33 of FIG. 32 showing the progressive dies at Stations A to E for forming the tabs;

FIG. 34 is a greatly enlarged portion of FIG. 33 showing a pair of cooperating coining dies at Station D for rounding the edges of the aperture in a tab;

FIG. 35 is a sectional view along line 35-35 of FIG. 24 showing the mechanism for transferring the finished can topsto two discharge chutes and also showing the mechanism for intermittently feeding strip material to the progressive dies for forming the tabs;

FIG. 36 is a transverse section along the angular line 36-36 of FIG. 24 showing the two lower rams at Station 4 and mechanism for actuating the shuttle plate to reciprocate the rams;

FIG. 37 is a longitudinal section along the line 3737 of FIG. 36 showing the same mechanism and also showing the dies at Stations 4 and 5 and FIG. 38 is a fragmentary perspective view showing how a nipping die at Station E transfers a finished tab to a can top at Station 4.

The successive operations on the can tops and labs FIG. 1 shows a can with a metal top, generally desig nated T, as produced by the apparatus of the present embodiment of the invention. The can top T is scored along a pair of lines to form a tear strip 42 in a spiral-like formation circumscribing the periphery of the top so that removal of the tear strip in effect severs the top from the can. The tear strip 42 has a leading end indicated at 44 in FIG. 4 and one end of a thin tab 45 of a suitable metal is attached to the leading end of the tear strip to serve as a handle for manual removal of the tear strip.

The tab 45 is normally positioned in face-to-face engagement with the can top so that it does not interfere with normal stacking of the cans for shipment or display. The tab 45 is formed with a plurality of longitudinal ribs 48 to stiffen the tab and permit the tab to function as a relatively rigid lever for prying the leading end of the tear strip from the can top. Thus lifting the tab by its free end causes its opposite end to serve as a fulcrum for initiating the tearing action.

The tab 45 is formed with an aperture 59 as indicated in FIG. 5 to receive a hollow rivet element 52 that is formed in the sheet metal of the leading end of the tear strip 42, the hollow rivet element being best shown in FIGS. 3 and 8. Preferably, the aperture 5%? is surrounded by an embossed rib 54 (FIGS. 16 and 17) which reinforces the rim of the aperture. It will be noted that both the aperture of the tab and the hollow rivet element 52 are of elongated or non-circular configuration. In the finished can top T shown in FIGS. 1 and 6, the hollow rivet element 52 extends through the aperture 56 of the tab and is flattened and swaged outwardly to form a rivet head as best shown in FlG. 17 for permanent and positive engagement of the leading end of the tear strip with the tab.

At Station 1, a relatively large circular dimple 56, shown in FIGS. 2 and 7, is formed in the blank can top T by the pair of dies shown in FIG. 12 comprising an upper female die 58 with a circular recess 6t and a lower male die 62 having a suitably tapered nose 64. The lower male die 62 is surrounded by a pressure pad 65 which clamps the metal of the can top against the upper die 58 with sufiiciently light pressure to permit the sheet metal to creep radially inward towards the male die. The resulting dimple 56 which is much larger in area than the subsequently formed hollow rivet element 52 is only slightly thinner than the surrounding sheet metal of the can top.

At Station 2, the dimple 56 is formed into the hollow rivet element 52 by die means shown in FIGS. 13 and 14 comprising an upper female die 66 and a lower male die 68. The upper female die 66 has a cavity 70 and a leading face '72 and is surrounded by a pressure pad '74. The pressure pad 74 is under sufficient spring pressure to cooperate with a lower die block 75 to resist creepage of the sheet metal of the can top radially outward from the female die 66. The cavity 70 which is of the elongated cross-sectional configuration of the desired hollow rivet element 52 is dimensioned in depth to avoid restraining the upper surface of the transverse wall 76 that forms the top or outer end of the hollow rivet element 52.

The lower male die 68 serves as a forming mandrel so that when the two dies 66 and 68 close together they convert the relatively large dimple 56 into the smaller steepshouldered hollow rivet element 52, the side walls of the rivet element being substantially perpendicular to the plane of the can top.

In the forming operation the two dies 66 and 63 function somewhat in the manner of conventional shrink dies to cause the metal of the previously formed dimple 56 to flow radially inward to result in thickening of the central portion of the dimple that is not restrained by the telescoping die surfaces. Thus the transverse wall '76 of a hollow rivet element 52 is increased in thickness as indit5 cated in FIG. 13, the thickness in this instance being substantially equal to the thickness of the tab 45.

At Station 3 an upper die '73 shown in FIG. 15 cooperates with a lower die 80, the upper die including a scoring element 82 to thin the metal of the can top along the pair of lines at) to form the desired tear strip 42. The lower die 34 serves as an anvil with a fiat upper surface to support the can top against the action of the scoring element 82. If the thickness of the can top T is of the order of 0.008 inch thick, the metal may be scored to a depth of 0.005 inch. At the same station, the upper die 73 cooperates with the lower die to offset a portion of the sheet metal of the can top downward to form an elongated recess in the upper surface of the can top, which recess is designated 84 in FIG. 4. The parallel side walls of the recess 84 stiffen the sheet metal of the can top locally to facilitate the initial separation of the leading end of the tear strip from the can top by the leverage of the tab 45.

At Station 4 where a finished tab 45 is placed on the hollow rivet element 52 as indicated in FIG. 5, an upper nipping die 88 which severs a finished tab from a metal strip carries the finished tab downward to place the tab on the hollow rivet element 52. As best shown in FIG. 16, a can top T at Station 4 rests on a lower die block 85 which surrounds an upwardly protruding anvil member 86 that is dimensioned to fit snugly into the hollow rivet element 52. The upper nipping die 83 in FIG. 16 is cut away to conform to the embossed rib 5 of the tab 45 and incorporates a central ram member 90 that cooperates with the lower anvil member 86 to spread the rivet element 52 slightly in all radial directions for light engagement with the tab 45 to hold the tab in place as the can top is conveyed to Station 5.

At Station 5 the can top T with the tab 45 lightly engaged therewith is processed by a pair of dies in the manner indicated in FIG. 17. In FIG. 17 the can top T rests on a lower die block 92 that incorporates an anvil member 94 that protrudes upward into the interior of the hollow rivet element 52 in abutment with the inner surface of the transverse wall 7% of the hollow rivet. An upper die block 55 in FIG. 17 is cut away to clear the embossed rib 54 of the tab 45 and incorporates an upper ram member 96 to cooperate with the lower anvil member 9 for swaging the hollow rivet element 52 radially in all directions. The upper ram member 96 is driven forcibly against the transverse wall 76 of the rivet element 52 to squeeze and force the metal of the transverse wall outwardly by extrusion to form the previously mentioned rivet head 55 for firmly uniting the tab with the can top. Since the height of the hollow rivet element 52 is somewhat greater than the thickness of the tab 45 the die operation also tends to here the side wall of the hollow rivet element 52 radially in all directions to force the side wall of the rivet element into pressural engagement with the outer rim of the aperture 50 of the tab. Preferably so-much of the metal of the transverse wall 76 of the hollow rivet element is displaced radially by extrusion that the resultant peripheral bead or rivet head 55 is thicker than the final thickness of the transverse wall. Thus at Station 5 the can top is completed to provide the finished can top shown in FIGS. 6 and 11.

With reference to the fabrication of the tabs 45, a narrow strip of metal 98 is fed into the apparatus transversely thereof in the manner indicated in FIG. 35 and is processed by progressive dies at Stations A to E which are indicated by corresponding letters in FIGS. 32 and 33. At Station A spaced dies partially blank out two tabs 45 simultaneously leaving the two tabs connected to the metal strip 98 by narrow tongues so that the metal strip may serve as means to transport the tabs to the remaining Stations C to E in sequence.

At Station C the apertures 50 are punched in the tabs and at Station D the rims of the apertures 50 are coined or rounded. At Station E the previously mentioned nip- '2 ping dies 88 complete the blanking operation to sever the finish-ed tabs from the metal strip and at this station the nipping dies carry the finished tabs downward to the previously mentioned Station 4 and serve as die means at Station 4 for lightly spreading the hollowurivet elements 52 into light or temporary engagement with the tabs.

General description of the apparatus As shown in FIG. 24, the framework of the apparatus includes a base structure, generally designated 1%, four columns 162 extending upward from the base structure to support fixed structure associated with Stations 1 to 3 for processing the can tops and four additional columns 1M extending upward for supporting the four corners of fixed structure associated with Stations 4 and 5 for processing the can tops and associated with Stations A to E for processing the tabs.

For the purpose of moving can tops in pairs firom a feed station under a pair of 'feed chutes 105 through Stations 1 to 5 to a discharge station under a pair of discharge chutes 106, a series of dual workholders 111 of the construction shown in FIG. 20 are mounted at evenly spaced points on a pair of parallel conveyor chains 112. An upper run of the two conveyor chains extending from a pair of upper sprockets 114 to a pair of upper sprockets 115 forms a straight conveyor line through Stations 1 to 5, the return run of the two continuous conveyor chains extending from a lower pair of sprockets 116 to a cooperating lower pair of sprockets 113.

As shown in FIG. 20, each of the workholders 111 may be in the form of a relatively heavy rectangular plate with two circular apertures 120 formed with circumferential ledges or flanges 122 to serve as seats for a pair of the can tops. Each of the circular seats 120 18 provided with a plurality of circumferentially spaced spring-loaded fingers 124 which serve the purpose of yieldingly retaining the can tops in the seats during the operations at Stations 1 to 5. The blank can tops are forced into the circular seats 120 at the feed station and are forced upward out of the seats at the discharge station. The operating Stations 1 to 5 are spaced five inches apart measured from center to center and the two conveyor chains are intermittently moved five inches to move the can tops to the five stations in succession.

At Stations 1 to 3 the upper dies of the previously mentioned die sets are fixedly mounted on an upper platen 125 that is supported by the tour columns 162 and the corresponding lower dies are mounted on a lower reciprocative platen 126 that is slidingly guided by the four columns. At Stations 4 and 5 the previously described lower dies are mounted on upwardly extending rams comprising a pair of rams 128 (FIG. 36) for Station 4 and a similar pair of rams 130 (FIG. 37) for Station 5. The upper dies at Stations 4 and 5, as well as the upper d es at Stations A to E are mounted on an upper reciprocative platen 132 which is slidingly guided by the upper ends of the four columns 104. The lower reciprocative platen 126 for Stations 1 to 3 and the upper reciprocative platen 132 for Stations 4 and 5 and for Stations A to E are all actuated by a lower drive shaft 134 that extends longitudinally of the apparatus.

As shown in FIG. 24, a first sensing means in the form of a pair of photoelectric devices 135 is positioned between the feed station and Station 1 to sense whether or not a traveling workholder has an empty seat, a second sensing means 136 of the same character is positioned between Stations 3 and 4 for the same purpose and a third sensing means 138 in the form of a pair of microswitches is located between Station 5 and the discharge station at the chutes 106 to detect whether or not tabs are assembled to the can tops as they approach the discharge chutes. If either of the first two sensing means detects that a workholder i110 lacks a can top or if the third sensing means ascertains that a tab is missing rom a can top, the drive shaft 134 is immediately stopped.

All of the upper dies for progressively forming the tabs at Stations A to E are mounted on the reciprocative upper platen 132 as shown in FIG. 33 and the lower dies for these stations are mounted on fixed structure between the lower rams 128 and and the upper reciprocative platen 132.

The metal strip 98 for forming the tabs 45 is supplied in a large roll and is fed intermittently to the apparatus in a well known manner by the mechanism shown in FIG. 35. An upper idler roller 14!) under pressure from a coil spring 142 cooperates with a lower drive roller 144 that is driven at a constant speed by an individual motor (not shown). The drive roller 144 is journalled on an eccentric member (not shown) having an arm 145 for oscillation to move the drive roller into and out of driving contact with th underside of the metal strip 98. Thus the drive roller 144 periodically drives the metal strip by periodic upward pressure against the metal strip in opposition to the pressure of the idler roller 140.

The operating arm 145 is connected by a link 146 to a lever 148 that rocks on a central fulcrum 150. The lever 148 is connected by a connecting rod 152 to a crank 154 on a sprocket 155, the sprocket 155 being driven from a sprocket 156 (FIGS. 24 and 35) on the drive shaft 134 by means of a sprocket chain 158. The radial position of the crank 154 on the sprocket 155 is adjustable to adjust the throw of the crank and thereby adjust the length of the metal strip 98 that is advanced into the apparatus for each rotation of the drive shaft 134. FIGS. 24 and 35 also show a second sprocket 160 on the drive shaft 134 which drives a pump 162 by means of a sprocket chain 164 for circulating lubricant throughout the apparatus.

Considering the length of the metal strip 98 as divided into steps just long enough for blanking out one tab 45, the crank 154 is adjusted on the sprocket 155 for the drive roller 144 to advance the metal strip two steps on each of the revolutions of the drive shaft 134 that causes reciprocation of the various dies. Referring to FIG. 33, two upper punches 165 at Station A for partially blanking the tabs out of the metal strip 98 are two steps apart, i.e., considering the first of the two upper punches as operating on the first step along the length of the metal strip 98, the second punch operates on the fourth step. At Station B two sets of dies for forming ribs 48 on the tabs operate on two contiguous steps along the length of the metal strip 9 8. In like manner the dies at Station C for punching the apertures 50 in the tabs and the dies at Station D for coining or rounding the rims of the apertures 50 operate on two contiguous steps of the metal strip. The two nipping dies 83 at Station E are spaced apart with six intervening steps, the two nipping dies being thus spaced apart by the distance between the two hollow rivet elements 52 on the two can tops respectively on the workholder at Station 4. Pilot holes 166 (FIG. 32) are punched in the metal strip 93 at Station A to be used by suitable pilot pins (not shown) for accurately registering the metal strip with the dies at the remaining Stations B to E.

With the described arrangement of the progressive tab fabricating dies, finished tabs are punched out of all of the successive steps of the metal strip 98. Beyond Station E the remaining material of the metal strip is cut away two steps at a time by a punch 167 (FIGS. 33 and 36) and the pieces of scrap fall through an inclined chute 168 to a scrap box (not shown).

The mechanism for actuating the various dies As shown in FIGS. 24 and 25, the drive shaft 134 which is journalled in suitable bearings 170 is driven by a variable specd motor 172 through the medium of a belt 174 and what is known commercially as a Fawick Fly Wheel Drive which includes a fly wheel 175 and an assembly comprising an air brake 176 and a clutch 173. The fly wheel 17 5 and the air brake-clutch assembly are mounted on the drive shaft 134 with an inclined link 180 (FIG. 25)

9 anchoring the brake shoes (not shown). Upon receiving a signal from any one of the three sensing means 135, 136 and 138, the clutch 178 is disengaged to relase the drive shaft 134 from the fly wheel 175 and the air brake 176 is simultaneously actuated to bring the drive shaft to an instant stop.

Referring again to FIG. 24, the reciprocative lower platen 125 for Stations 1 to 3 is operated in a well known manner by two spaced eccentric assemblies 182 on the drive shaft 134 the reciprocative platen being connected to the two eccentric assemblies by two corresponding connecting rods 184 which pivot on a cross pin 185 of the platen.

To actuate the upper reciprocative platen 132 an overhead walking beam 185 is fulcrumed by a pivot 183 on fixed structure above the fixed platen 125 and is actuated by a yoke 1% which functions in the manner of a pull rod. As shown in FIG. 35 the upper end of the yoke 19% is connected to the walking beam 186 by pivot means 192 and its lower end is pivotally connected by a cross pin 1% to an eccentric assembly 195 on the drive shaft 134. The reciprocative platen 132 is operatively connected to the beam 126 by a pair of connecting rods 1% (FIGS. 24 and 35), the upper end of each connecting rod being pivotally connected to the walking beam by a corresponding pin 197 and the lower end of each connecting rod being connected to the platen 132 by a ball joint 1%. As may be seen in FIG. 35, the yoke 190 straddles the upper runs of the two conveyor chains that carry the workholders 110 so that the yoke exerts balanced downward pressure on the die sets at Stations '4 and 5.

Referring again to FIG. 24 an intermittent drive means or indexer, generally designated 2%, drives a shaft 292 carrying the two previously mentioned sprockets 114 for intermittently advancing the two conveyor chains 112 by increments of five inches on each revolution of the main drive shaft 134. The indexer 206 may be what is known commercially as a Ferguson Drive and may be driven by means of three sprocket chains 2114 which connect three corrsponding sprockets 205 on the drive shaft 134 with three sprockets 2% on the indexer.

The two

lower rams

128 and 130 at Stations 4 and 5 respectively, are actuated by a drive means shown in FIGS. 22, 22a, 22b, 36 and 37. An upright lever 2117 mounted on a central fulcrum 263 is oscillated by the upper reciprocative platen 132. For this purpose the upper end of the lever carries a follower 2119 in the form of a roller that rides in an angular cam slot 216 that moves with the platen 13-2. The lower end of the upright lever 2117 is connected by a short link 2111 with a shuttle plate 212. By this arrangement the shuttle plate 212 makes one reciprocation for each reciprocation of the upper platen 132.

Each of the four lower rams 123, 1311 has an inclined cam surface 213 on its lower end and each ram is provided on its lower end with a downwardly extending axial belt 214 of stepped configuration which mounts a narrow cam block 215 on the lower end of the ram. As shown in FIG. 22b, each of the cam blocks 215 is formed with a pair of inclined cam surfaces 216 on its opposite sides respectively. Preferably suitable compression springs 21'? (FIG. 36) act on the four bolts 214 to urge the four lower rams downward.

As shown in FIGS. 22a and 36 the shuttle plate 212 has a longitudinal slot 218 that straddles the cam blocks 215 of the two lower rams 128 and a second similar slot 219 that straddles the cam blocks 215 of the two lower rams 13%. The shuttle plate 212 has two transverse inclined cam surfaces 2211 and 221 on its upper side to cooperate with the cam surfaces 213 of the four lower rams to lift the rams when the shuttle plate is moved to the right as viewed in FIGS. 22, 22a and 36. In like manner, the underside of the shuttle plate 212 is formed with two transverse inclined cam surfaces 222 and 223 to contact the inclined cam surfaces 216 of the four cam blocks 215 to to lower the four rams with the assistance of the four compression springs 217.

The workholders and their operation As best shown in FIG. 20 each of the rectangular workholders that is carried by the pair of parallel conveyor chains 112 is mounted on skids 231) at its opposite ends respectively. Each of the two skids 230 is recessed as shown at its opposite ends for engagement and retention in a loose manner by two pairs of pins 232 that extend laterally from the two conveyor chains 112 respectively. By this arrangement the various workholders are held captive by the two conveyor chains but have substantial freedom for movement relative to the chains to permit the workholders to be lifted into operating positions at Stations 1 to 5.

As may be seen in FIG. 26 the opposite ends of the workholders 111i rest on the two conveyor chains 112 and the two conveyor chains in turn ride along parallel rails 23 1 as the workholders shift from station. On the return run of the two conveyor chains at the bottom of the apparatus the inverted workholders 110 ride along fixed rails 235 as shown in FIG. 25 and the two conveyor chains ride on two corresponding fixed rails 236.

Referring to FIGS. 20 and 20a, a ring 233 is mounted around the rim of each of the circular seats to guide the blank can tops into the seats, each of the rings being tapered to form an inner circumferential guide surface 246. Each of the springloaded fingers 124 is mounted in a radial guideway 242 under the ring 238 and is formed with a retaining pin 244 that extends upward through a corresponding short radial slot 245 in the ring. In the absence of a can top in a circular seat 120 of a workholder 110, the fingers 124 are held at their radially inward limit positions by a garter spring 246 that is common to all three of the fingers. When a can top '1 is forced downwardly into a circular seat 120 of a workholder 116 the rim of the can top is guided by the guide surface 24-19 of the ring 238 to make contact with inclinded cam surfaces 248 at the ends of the fingers 124. The can tops T act on the cam surfaces 248 to retract the three fingers 124 and then drop below the cam surfaces to be frictionally retained in the workholder seat by the fingers 124 under the pressure exerted by the garter spring 246. Thus the blank can tops T may be mounted on the successive workholders 110 by merely forcing the can tops downward to seat on the inner circumferential ledges 122 of the workholders.

At each of the Stations 1 to 5, the successive workholders 110 are lifted from the two conveyor chains 112 into seats that locate the workholder accurately relative to the dies at the station. At Stations 1 to 3 where exceedingly high accuracy is required in the positioning of the can tops, high precision jigs receive the workholders with close fit.

As shown, for example, in FIG. 31 illustrating Station 3, each of the positioning jigs includes an upper rectangular base plate 252 which is attached to the upper reciprocative platen 125. Two downwardly extending jig arms 2541 at the opposite ends of the base plate 252 are spaced apart to confine with close fit the opposite ends of the successive workholders 110. In like manner as indicated in FIG. 21, two pairs of jig arms 255 extending downward from the base plate 252 make close fit with the opposite longitudinal sides of each successive workholder 119. The lower end of each of the six downwardly extending jig arms is cut away as shown in FIG. 31, to form a shoulder 256 for abutting the upper surface of a workohlder and to form an adjacent shoulder 258- to fit against the edge of the workholder so that the six jig arms cooperate to form an accurately dimensioned and closely fitted rectangular jig seat. The lower end of each of the six downwardly extending

jig arms

254 and 255 is additionally tapered as shown at 260 to guide the successive workholders into the jig seat.

Claims

1. IN AN APPARATUS OF THE CHARACTER DESCRIBED FOR FORMING A HOLLOW RIVET IN A SHEET-LIKE MEMBER TO SERVE AS MEANS FOR ATTACHING THE SHEET-LIKE MEMBR TO AN APERTURE OBJECT, THE COMBINATION OF: MEANS TO ADVANCE THE MEMBER THROUGH A SEQUENCE OF OPERATING STATIONS; A FIRST FORMING MEANS AT ONE OF SAID STATIONS TO FORM A DIMPLE IN SAID MEMBER; A FIRST HOLDING MEANS AT SAID ONE STATION HOLD THE MEMBER DURING THE DIMPLE-FORMING OPERATION AND TO PERMIT SLIPPAGE OF THE MATERIAL OF THE MEMBER RADIALLY INWARDLY TOWARD THE DIMPLE AREA TO MINIMIZE THINNING OF THE MATERIAL IN THE DIMPLE-FORMING AREA; A SECOND FORMING MEANS AT A SUBSEQUENT STATION TO SHRINK SAID DIMPLE INTO A HOLLOW RIVET HAVING A TRANSVERSE WALL OF SUBSTANTIALLY SMALLER AREA THAN THE DIMPLE WITHOUT PRESSURE ON THE AREA OF THE TRANSVERSE WALL; AND A SECOND HOLDING MEANS AT SAID SUBSEQUENT STATION TO SURROUND THE DIMPLE AREA TO CLAMP THE MEMBER UNDER PRESSURE DURING THE SHRINKING OPERATION TO PREVENT SLIPPAGE OF THE MATERIAL RADIALLY OUTWARD AWAY FROM THE DIMPLE AREA TO PROMOTE THICKENING OF THE MATERIAL OF THE HOLLOW RIVET IN THE AREA OF SAID TRANSVERSE WALL.