US3584178A

US3584178A - Can body welding machine

Info

Publication number: US3584178A
Application number: US814549A
Authority: US
Inventors: Louis H Huber; James E Kelly; James F Mcdonald; Leon M Patarini
Original assignee: National Can Corp
Current assignee: Rexam Beverage Can Co
Priority date: 1969-04-09
Filing date: 1969-04-09
Publication date: 1971-06-08
Anticipated expiration: 1988-06-08

Abstract

A can body welding machine which includes a mandrel, a device for wrapping a can body blank about the mandrel, and roller electrodes for welding overlapped edges of the blank to form the side seam of the can body. A sensing device is used to control the initiation and termination of welding current flow.

Description

United States Patent n 13,5s4,17s

Louis 11. Huber l-linsdale;

James E. Kelly, Justice; James F. McDonald; Leon M. Patarini, Chicago, all oi,1ll.

Apr. 9, 1969 June 8, 1971 National Can Corporation Chicago, Ill.

lnventors Appl. No. Filed Patented Assignee CAN BODY WELDING MACHINE 10 Claims, 16 Drawing Figs.

US. Cl 219/59, 219/64 Int. Cl 823k 31/06 Field of Search 219/59, 64,

[56] References Cited UNITED STATES PATENTS 1,321,463 10/1913 Lloyd 219/60 2,307,089 1/1943 Winters 219/64 2,578,832 12/1951 Pearson 219/64 2,635,573 4/1953 Taylor.... 219/60 3,005,901 10/1961 King 219/131 3,085,146 4/1963 Ferrervela 219/60 Primary Examiner-J. V. Truhe Assistant Examiner-R. Skudy Attorney Robert J. Doherty ABSTRACT: A can body welding machine which includes a mandrel, a device for wrapping a can body blank about the mandrel, and roller electrodes for welding overlapped edges of the blank to form the side seam of the can body. A sensing device is used to control the initiation and termination of welding current flow.

PATENTED JUN 8l97l 3584', 178

I saw 2 or 8 KM; wax- $3M PATENTED Jun 8 as?! SHEET 5 0F 8 INVEN TORS:

Lam's/ Huge-R fines E- AE Y IAN/Es FM DMMLD,

Leo M wank/w PATENTED JUN 8197] 3584.178

sum 7 OF 8 Irma 5. Kelly, Imps F. HcDwnw By Lev M- BTW/YA,

W9. 901114;, EH 5 SHEET 8 [IF 8 N l/E N T0195. LOU/5 H. HUBER, JAMES E. KELLK JAMES F. Ma DONALD, LEON M. PATAR/N/ WJ e?! 3 17: 5

CAN BODY WELDING MACHINE This invention relates to an improved can body welding machine in which metal can body blanks are shaped into tubular form with overlapping edges and thereafter the overlapped edges are welded to form a continuous longitudinal side seam.

Metal cans which are formed from rectilinear blanks and which have welded side seamsas contrasted to hammered seams are advantageous because they are asthetically pleasing and there is more surface area on which copy can be printed. The present invention provides a machine for forming welded side seams of cans in a very efficient manner.

The welding machine of the present invention includes a mandrel and means for wrapping a sheet metal body blank about the mandrel and for holding the adjacent'edges of the blank in overlapping relation. Means are provided for feeding the wrapped blank to a welding station. A pair of roller electrodes are located atthe welding station for welding the overlapping edges together along a continuous longitudinal seam that constitutes the side seam of the can body. The roller electrodes are positioned on opposite sides of the seam, one of the roller electrodes being supported by the mandrel and the second roller electrode being supported by a carrier.

In the illustrative embodiment of the invention, photoelectric cells are provided for initiating and terminating the flow of current through the roller electrodes in response to predetermined positions of the can body relative to the electrodes.

Resilient means are provided for biasing the roller electrode carrier away from the overlapped edges of the blank, and adjustable means, operable in opposition to the resilient means, are provided for biasing the second roller electrode against the overlapped edges.

In the illustrative embodiment, the second roller electrode is driven at a lineal velocity that is greater than the velocity of the means driving the can blank toward the welding station. When the second roller electrode engages'the can blank, the blank will be advanced by the roller electrodes during the welding operation, rather than by the means feeding the wrapped blank to the welding station.

A more detailed explanation of the invention is provided in the following description and claims, and is illustrated in the accompanying drawings, in which:

FIG. 1 shows a side elevational view of a body maker unit for manufacturing container bodies according to the present invention;

FIG. 2 is an enlarged side elevational view with portions broken away,;showing a spot welder for spot welding edge portions ofa can body together to hold it during a subsequent side seam welding operation;

FIG. 3 is an enlarged end view, with portions broken away, partly elevational and partly in section, of the spot welder of FIG. 2 taken along lines 3-3 thereof;

FIG. 4 is an enlarged side elevational view of one embodiment of the welding wheel assembly ofthe present invention;

FIG. 5 is an enlarged vertical sectional view, taken along lines 5-5 of FIG. 4, showing the welding wheel assembly, support means therefor, and the body mandrel of this invention;

FIG. 6 is a top plan view of a portion ofa welding wheel apparatus of FIG. 4, on a reduced scale, showing driving means for the welding wheel;

FIG. 7 is an end elevational view, on a reduced scale, of the welding wheel and mandrel portions of the welding apparatus ofthe invention;

FIG. 8 is a vertical sectional view taken along lines 8-8 of FIG. 5 showing support means for the welding wheel assembly;

FIG. 9 is a top plan view of a portion of the bodymaker wings and other elements of the invention used to form the can body;

FIG. 10 is a fragmentary end elevational view of the bodymaker wing elements of FIG. 9; v FIG. 11 is a fragmentary side elevational view, with portions broken away, showing an embodiment of the invention which includes a movable welding wheel and a cantilevered, fixed mandrel; H

FIG. 12 is a top plan view of the embodiment of FIG. 11 showing the movable position welding wheel and means for moving it;

FIG. 13 is a fragmentary vertical sectional view of the embodiment of the welder shown in FIG. 11 along line 13-13 thereof;

FIG. 14 is a vertical sectional view of portions of a bodymaker mechanism for use with the welder shown in FIG. 11;

FIG. 15 is a perspective view of the mandrel shown in FIG. 14; and

FIG. 16 is a perspective view ofa portion ofthebodymaker wings shown in FIG. 14.

Referring now to FIG. I, a welding apparatus 30 is shown to comprise a plurality of stations, each of which is provided to perform a particular operation on the can bodies. This embodiment shows a sheet feeding station 32, a body forming and tack welding station 34, a body pickup station 36, a side seam welding station 38, and a can body discharge station 40. Current supply control means for supplying welding current is provided, housed in a suitable cabinet 42, and the power supply is connected to an output cable 44 and a current return cable 46.

The body forming and spot welding station 34 includes a spot welder support assembly 48, and the side seam welding station 38 includes a welding wheel support assembly 50. The individual stations will now be described in greater detail.

A sheet feed station 32 is provided for advancing flat or preflexed body blanks to the body forming station. This sheet feeding means comprises a table for supporting body blanks and reciprocating means for advancing each body blank separately to the body forming station. Such a feeder is described, for example, in the Renard US Pat. No. 2,944,498. It will be understood, however, that only one feed station is necessary for use with this invention, since, as will be discussed later, body blanks are completely rectangular and have no notches, slits, folds, or cutouts therein. Thus, the Renard US Pat. No. 2,944,498 illustrates a plurality of feed dogs moving the body through six different stations before it presents a body to the forming horn, whereas in the present invention only one such station is necessary since the blanks are not notched or edged as shown, for example, in FIG. 14 of the Renard patent. Drawings of this part of the mechanism are omitted for clarity in illustrating other parts of the invention.

At a body forming station 34, a can body B is formed by wrapping a body blank B around a mandrel 52 by means of body forming wings 54. As shown in FIGS. 9 and 10, the wings 54 pivot about lower shafts 56 and move up to surmount the mandrel 52 when the connecting rods 58 are moved by driving wheels 60, as from a power gear 62. Lower wheel journals 64 and upper wing pins 66 serve as pivots for the connecting rods 58.

In use, the wings 54 converge first onto and then outwardly from the mandrel 52, substantially simultaneously, except that it is preferred that the right-hand wing 54, as shown in FIG. 10, close upon the mandrel slightly in advance of the left-hand wing, so that the lower marginal edge 68 of the blank B is in position touching the mandrel when the upper overlapping edge 70 of the blank B is moved into position. In this way, the

edges

68, 70 do not strike each other as they are being moved into their positions surrounding the mandrel 52. As can be seen in FIG. 9, the wing knives 72, that is, the outer edge portions of the wings 54, include end portions 74 and inside, recessed edges 76, so that when the wings 54 are holding a body blank in position, the end portions 74 abut each other. The recessed edges 76 are spaced apart about a quarter of an inch, for example, so that spot welding electrodes may move downwardly into contact with the overlapping

edges

68, 70 through the aperture formed between the edges 76.

Once the body blank Bjhas bee n positioned around the body mandrel 52, the spot welder assembly 78 (FIGS. 2 and 3) is used to spot weld the

edge portions

68, 70 of the blank B together. The spot welder 78 comprises a fixed vertical support member 80 attached to the body maker frame F and surmounted by a horizontal support member 82. The movable electrode holder 84 contains a plurality (in the present instance four) of electrodes-86 ending in sharp points 88 which are each electrically connected by suitable cable means 90 to the holder 84. The electrodes 86 are resiliently held downwardly in a desired position under the influence of springs 92.

Guide rods 96 are fixedly attached to the electrode holder 84 and extend upwardly through openings in the horizontal support member 82 to guide and locate the movement of the holder 84 when the piston 94 pushes downwardly on the holder 84. The piston 94 is activated from an air supply line 98 (FIG. 1) in which the pressure is kept at a desired level by a regulator 100. The supply of air to the piston 94 is turned on and off by a switch 102 which is suitably connected so as to be activated by the movement of the wings 54 which hold the body blank B in place.

As the wings 54 assume a closed position closely surrounding the mandrel 52 and wrapping a body blank tightly around the mandrel 52, and as the switch 102 is activated, the piston 94 moves the electrode holder 84 downwardly causing tips 88 of the electrodes 86 to contact the blank B in the area where the

edges

68, 70 overlap each other. The springs 92 control the tension placed-on the seam formed by the overlapping edges, and afford a means of maintaining constant mechanical pressure on the seam. When the electrodes 86 contact the seam, electric switch means 104 (FIG. 1) allow the passage of current which then flows briefly, for example, for about 200 milliseconds through the lap seam and spot welds the body blank B into a cylindrical shape. The current, in a preferred embodiment, is about 1,000 amperes.

A body pickup and transfer station 36 comprises means for moving a can body from the station 34 at which it is formed, to the discharge station 40 at the end of the mandrel 52, in the form of an endless chain 106 on which are disposed a plurality of feed dogs 108. The chain is afflxed to front and rear shafts 114 supported by bearing blocks 116 resting on braces 118. One or more idler or tension rollers 120 may be provided for the chain 106. A double-row roller-type construction is preferred for the chain 106 of the invention. The dogs 108 extend upwardly into a groove 122 extending longitudinally in the mandrel 52. The chain 106 is driven by motor means (not shown) and is designed to engage and slide a can body along the can body mandrel 52 at a desired rate. The relative speed of the feed dogs 108 and chains 106 will be discussed further herein.

Referring to FIGS. 4-8, the welding station generally comprises a welding wheel support assembly 50, and a rotary electrode or welding wheel proper 124, which is secured by bolts 126 to a rotatably mounted shaft 128. The shaft 128 rides in support bearings 130, contained inside a brass, electrically conductive outer carrier 132, which is in turn supported by upper and lower retainers 134 held in place by locating bolts 136. The bolts 136 secure the outer carrier 132 to the pressure pad 138, which is supported by pistons 140 operating within cylinders 142 which rest upon the frame F. Inside the cylinders 142 are coil springs (not shown) which urge the welding wheel assembly 50 upwards against a downward pressure, preferably pneumatic, acting on piston 146 through a cylinder 148. A desired amount of pressure is maintained in the cylinder 148 by means of the regulator 150 connecting a pressure supply (not shown) to the cylinder 148.

The springs inside the cylinders 142 bias the welding wheel 124 slightly upwardly so that, for example, when the force in the line 152 reads 16 pounds on the gauge 154, the actual effective force under the welding wheel 124 is that resulting from putting 16 pounds on the cylinder 148 (a 2 inch diameter cylinder, for example) which, in turn, moves the 4 inch diameter welding wheel 124 downwardly against the body blank B in the area ofthe lap seam. The edge ofthe wheel normally has a somewhat rounded edge, as opposed to a knife-type edge, the radius of curvature thereof normally being about three thirtyseconds of an inch, it being understood that some pressure is required to equalize the upward force placed on the pressure pad 138 by the springs contained in the cylinder 142. At any rate, the force or pressure brought to bear on the lap seam is only enough to hold the

edges

68, 70 in close contact and is not sufficient to amount to a forging or like operation. The four cylinders 142 and pistons are designed to maintain precise alignment of the parts when the carrier 132 and the parts associated therewith moved vertically.

The stranded ends 13? of the output cable 144 are connected to terminals 137 of the carrier 132. Electrical contact between the welding wheel 124 and the output cable 44 is achieved by filling the opening between the rotatably mounted shaft 128 and the carrier 132 with liquid mercury, in the space axially inside of the bearings 130, which also serve as seals. Thus, the shaft 128 is free to rotate within the carrier 132 and a sound electrical connection is maintained, which is capable of carrying several thousand amperes of current. Likewise, brushes may be used to make contact, other liquid metals or alloys may be used, or sliprings of a silver-impregnated carbide may also be used in place of the liquid mercury.

A lower welding wheel 156 is disposed inside of the mandrel 52. As shown in FIG. 5, this wheel 156 is disposed directly beneath the upper welding wheel 124 with the top surface of the wheel 156 extending upwardly through an opening 158 in the mandrel 52. Combination seal and bearing units 160 support the shaft 162 which is integrally formed with the wheel 156. Outwardly of the ends of the shaft 162 on either side, are mercury-filled cylindrical openings 164, sealed at the end thereof by plugs 166. In this manner, electrical contact is made between the lower wheel 156 and the mandrel 52, through the mercury in the opening 164 which contacts the ends of the shaft 162. The bearing and seal units 160 prevent the mercury from running into the wheel well 168. The lower wheel assembly may also employ the substitute construction referred to above, in place of the liquid mercury. In order to prevent possible accidental contact between the parts being welded and the edges surrounding the opening 158, this area is protected by an insert of a lubricous nonconductive plastic material such as a fluorocarbon polymer (Teflon). The mandrel 52 is electrically connected to the return cable 46 but is preferably insulated from the rest of the machine.

The welding station 38 has leftand right-hand photoelectric cells (electric eyes) 172 and 174 (FIGS. 4 and 5) which are adapted to start and stop welding current flow from the upper wheel 124 through the body blank B and into the lower wheel 156. Each of the cells receives a reflected beam of light from a conventional light source, preferably a source located within the same housing as each cell. The reflected beam of light changes when it is reflected from the blank, causing the photoelectric cell resistance to change.

Thus, when the reflected beam to the left-hand cell 172 is changed due to the position of the forward edge of the blank, a switch in the welding current supply circuit is closed starting the flow of current, and when the reflected beam coming to the right-hand cell 174 is changed due to the position of the forward edge of the blank, the switch is opened and the current is shut off. A new blank B breaking the beam from the left-hand eye" initiates a repeat cycle. The left-hand eye" is arranged so that current starts to flow substantially immediately when the body blank has progressed to a point directly under the center of upper wheel 124, and the righthand eye 174 turns the current off when the blank B has reached an imaginary vertical centerline drawn through the wheel 124. During the period when the welding current is on the overlapped edges of the blank B will pass between the electrode wheels 124, 156 and weld a continuous side seam on the can body.

A single photoelectric cell could be utilized to start and stop welding current in response to the resistance change of the cell due to the position of the forward or leading edge of the blank and its resistance change clue to the position of the rear or trailing edge of the blank.

In some embodiments, however, there may be a small weldfree area left at either end of the can body to reduce possible arcing and to avoid annealing the metal just outwardly to either side-of the joint, where head conductivity away from the weld is not good. If the metal adjacent the seam has been unduly annealed, bending the ends of the body into a flange and body hook may cause occasional failure of the body in this area. It is not necessary that such weld-free area be left in most cases, but if the weld has a tendency to anneal the metal beside the weld itself, a few thousandths of an inch of scam may be left unwelded and, provided this ultimately becomes the body hook portion of the can body, the can will be satisfactorily pressure tight. Thus, the exact location of the

photoelectric cells

172, 174 is, to a certain extent, a matter of preference.

Referring now to FIG. 6, it will be seen that the driving means for the upper welding wheel 124, which contacts the body blank B, and therefore drives the lower wheel 156, comprises a welding wheel driven pulley I76 driven by a belt 178 running around a driving pulley 180 rotating on shaft 182. A second drive belt 184 engages a driving wheel 186 which is disposed at the opposite end of the shaft 182. Suitable bearing blocks 188, or the like, attach this portion of the mechanism to the frame F. The second belt 184 is driven by a conventional electric motor (not shown). The sizes of the pulleys are appropriately selected so that the upper and lower welding wheels 124, 156 have a peripheral lineal velocity of between and SOinches per second.

In a preferred embodiment, the lineal velocity of the wheels 124, 156 is about 10 percent faster than the velocity of the feed dogs 108, since driving the dogs 108 is fast or faster than the wheels 124, 156, tends to cause undesirable sliding and slipping of the blank B relative to the wheels 124, 156, resulting in an inferior quality weld. Thus, it is preferred to have the blank B advanced by the wheels 124, 156 during the welding operation, rather than by the dogs 108. However, when the weld is completed, the dogs, which are only fractions of an inch behind the trailing edge of the blank B, catch up therewith in a fraction of a second and continue to advance the cylinders formed from the blank B.

FIGS. 11 to 16 inclusive show an embodiment in which a different arrangement of can bodymaker parts is made, so that the body blank remains stationary after being formed into a cylinder and themovable welding wheel rotates and traverses the length of the body, while the body is being held stationary to weld the body side seam. In this case, the elements ofithe bodymaker are the'same, and a so-called crossfeed station is used, namely one in which the body blanks are fed from one side of the mandrel area to an area directly beneath the mandrel as described above. Since such crossfeed mechanisms for bodymakers are known in the art, they are not described herein.

Referring now to FIGS. 11 through 13, a frame member F is shown, to which are attached a welding wheel unit 124a secured by cap screws 126a to a rotary shaft 128a housed inside a housing 132a, which is fixedly supported by shaft cap 134a and held in place by vertical capscrews or studs 140a. Studs 140a rest in a welding wheel carrier unit 320 which reciprocates longitudinally on guide rods 322 (FIG. 12) secured to the frame F by mounting brackets 324. Two openings are formed in the wheel carrier 320 which accommodate bearing units 326 of a circulating ball type for providing smooth and accurate movement of the carrier 320 back and forth over the guides 322. A double-acting pneumatic cylinder 328 containing a piston rod 330 is attached to the carrier 320 by a wrist pin 332 and is provided for moving the carrier 320 and the parts attached thereto back and forth. Fittings 334 are provided on either end of the cylinder 328 for admitting air thereto from hoses receiving air from a constant shaft 128a is run over a stationary rack 338 affixed to the frame F by capscrews 340. A shock absorbing buffer 324 for preventing accidental damage thereto, especially in case of failure of the pressure in the return side of the cylinder 328. Thus, in operation, the carrier 320 is rapidly reciprocated on the guide rods 322 causing the wheel to be moved back and forward along a fixed axis and rotated by the action of the

gears

336, 338.

The electrical connection between the power supply cabinet 42 (FIG. 1) and the welding wheel 124a comprises the cable 44 (FIG. 1) which is subdivided into a number of strands 139a which are fastened at terminals 137a by capscrews 141a wheel to the housing 132a which supports the welding wheel 124a. Plugs 143a are provided for allowing a filling of liquid mercury 1300 to be placed between the housing 132a and the shaft 128a inwardly of the support bearings 145a which also function as seal members. Since the shaft 128a is always in direct electrical contact with the metallic liquid mercury, current is carried from the cable 44 to the wheel 124a and thence to the body blank B and the mandrel 52a.

The body blank receiving mandrel 52a is supported by a front block 342 and a rear block 344, with the nose or end portion 346 of the mandrel 52a being free from support means, or cantilevered outwardly past the front support block 342. The support blocks 342, 344 rest on a lower portion of the frame F. Another principal assembly is the can body stripper, which contains an appropriate number,- say two or four, stripper bars 348 which operate in grooves 350 in the mandrel 52a and which are moved longitudinally of the mandrel 520 by a cylinder 352 which supports the stripper bars 348. The cylinder 352 is driven by a pneumatically actuated shaft 354 which is also operated from the air supply which operates the cylinder 328.

When the wheel 124blank is passed over the outer or forward edge 346 of the mandrel 52a, or when the wheel 124a has finished welding the can body and returned to the position of FIG. 11, the cylinder 352 and stripper bars 348 move forward as a unit in the grooves 350 and the leading edges of the stripper bars 348 engage the back edge of the body blank B pushing it off the end ofthe mandrel where it is picked up and conveyed to other equipment for flanging and end seaming, etc. Further description ofthe piston operating the shaft 354 is omitted, since the operation is identical to the operation of the pneumatic cylinder 328, that is, the cylinder 352 and the stripper bar reciprocate as a unit in exactly the same manner as the cylinder 328 causes reciprocation of the piston rod 330 and the carrier unit 320 attached thereto. The stripper bars 348 are somewhat longer than the can body, so that the cylinder 352 which rides outside the mandrel 52a need not pass under the welding wheel 124a even if it is in its rearmost position, that is, in the position shown in FIG. 11.

In the operation of this embodiment of the invention it is preferred that workflow proceed from a stack of flat body blanks through a roll preflexer and that the blanks are then crossfed under the mandrel 52a where bodymaker wings 54a having the action shown in FIGS. 9, l0, 14 through 16 wrap them around the mandrel where they are held in position for the welding wheel 124a to pass over the side seam thus formed.

FIGS. 14, 15 and 16 show variations of the bodymaker components shown in FIGS. 9 and 10 and used in the embodiment of the welder shown in FIGS. 11 through 13 inclusive. Referring to FIG. 14, it is desired to have a space for the welding wheel 124a to pass over and in contact with the side seam formed by the overlap of the lower and upper edges 28a, 70a of the body blank B. Thus, unlike the embodiment in which the cylinder is first spotwelded and in which the ends of the blank may be completely surrounded by bodymaker wings, the embodiment shown in FIGS. 11 through 13 requires that the overlapped

edges

68a, 70a be supported throughout entire length, since the welding wheel traverses the entire length of the body while it is being held only by the wings 54a. Therefore, the outer edges of the wings 54a include front and rear locking lugs 356 which engage corresponding openings 358 in the mandrel 52a. Insulation means 360 may be provided on the inner edges of the wings 54a to prevent undesired current flow therethrough. The lugs 356 on the upper portions of the wings 54a are shown as being integral with the wings 54a, but it will be understood that these parts may-be made separately in order to simplify the construction and shaping of the lugs 356 andthe openings 358.

In the operation of this unit, the wing 54a and wing knife edges 362 tightly clamp a body blank B to a mandrel 52a, and the welding wheell24a passes over the

edges

68a, 70a of the blank B forming the plurality of. overlapping spot welds described above.

Another detail modification which is possible with the embodiment of the invention shown in FlGS. 11-16 inclusive involves the elimination of the mercury 130a which is disposed between the housing 132a and shaft 128a. If the welding wheel 124a is made relatively large, say 6 to 9 inches in diameter, for example, and the body to be welded is a beer can body having a side seam length of 4 13/16 inches, it is obvious that the wheel 124 will have an outside circumference of somewhat,

greater than 18 to 27 inches, and, accordingly, will have to rotate even less than one-half of a complete turn while in contact with a body blank which is less than inches in length. Accordingly, if the strands 139a of the cable 44 are somewhat flexible, they may be bolted directly, as by the screws 126a, to the welding wheel, thereby establishing direct contact between the cable 44 and the wheel 124a. Since the strands 139a will typically be large woven copper cables or straps, they will undergo several million cycles of moderate flexing under thesefconditions and still deliver satisfactory performance. This construction simplifies the construction of the unit, decreases the cost thereof, and minimizes the electrical resistance in the welding current circuit.

Return of the current supply to the welding wheel 124a is by way of the bus bars 364 which serve to support the mandrel 52a and which extend longitudinally therethrough as shown in FIGS. 11 through l3. Current flowing therethrough is returned to' the frame F of the unit either by way of a return cable, such as that shown at 46 in HO. 1, or through the support blocks 342, 344.

The current supplied to the

weld wheels

124, 124a for the seam welding operation may be AC or a pulsating DC. The characteristics of the current may be such as to form the seam by a number of overlapping spot welds resulting from the pulse of current passing through the seam. The current for spot welding of the can body through the electrodes 86 may be supplied through a transformer and controlled by relays, all in a manner known in the art.

lt is understood that the invention is not limited to the precise constructions herein shown, the same being merely illustrative of the principles of the invention.

What we claim is:

1. In a can body making machine having a mandrel for receiving a tubular body blank with overlapped edges: means for welding said overlapped edges together along a seam, said means including a first roller electrode in the mandrel and projecting beyond the surface thereof; a second roller electrode; a carrier upon which said second roller electrode is rotatably mounted; resilient means for biasing the carrier and said second roller electrode away from said overlapped edges; adjustable means operable in opposition to said resilient means for biasing said second roller electrode against said overlapped edges, and means for initiating and terminating the flow of current through the roller electrodes in response to predetermined position of the can body relative to the electrodes.

2. A can body making apparatus which comprises: a mandrel; means for wrapping a sheet metal body blank about said mandrel and holding adjacent edges of the blank in overlapping relation; means for spot welding said overlapped edges together at longitudinally spaced regions to hold the body in a cylindrical shape on the mandrel; means for welding said overlapped edges together along a continuous longitudinal seam that constitutes the side seam of the can body; said seam welding means'comprising a pair of roller electrodes on opposite sides of the seam, one of said roller electrodes being supported by said mandrel; a carrier; the other ofsaid roller electrodes being rotatable on said carrier; resilient means biasing said carrier away from the overlapped edges; adjustable means operable in opposition to said resilient means for biasing said other roller electrode against the overlapped edges; and means for moving the spot welded body with respect to the roller electrodes.

3. A can body making apparatus as described in claim 2, including photoelectric means for initiating and terminating the flow of current through the roller electrodes in response to predetermined positions of the body relative to the electrodes.

4. ln a can body making machine having a mandrel, body forming means for wrapping a sheet metal body blank about the mandrel and holding the adjacent edges of the blank in overlapping relationship, said body forming means having coacting wing members with edge portions thereof that are spaced apart when holding said overlapped edges, a plurality of spot welding electrodes for welding said overlapped edges together; a carriage'for supporting said spot .welding electrodes; means for moving the carriage to position said electrodes against said overlapped edges and in the space between said wing member portions; means on the mandrel and cooperating with said electrodes for supporting said overlapped edges during said welding; a first roller electrode carried by the mandrel for disposition within the can body; a second carriage having a second roller electrode for engagement with the exterior of the overlapped edges and cooperating with saidfirst roller electrode for welding a continuous longitudinal seam that constitutes the side seam of the body; feed means for advancing the spot welded body to said roller electrodes for engagement thereby; and means for rotating the second roller electrode to advance the body during the seam welding.

5. In a can body making machine as described in claim 4, resilient means biasing said second carriage away from the overlapped edges; and adjustable means operable in opposition to said resilient means for biasing said second roller electrode against the overlapped edges.

6. In a can body making machine as described in claim 4, photoelectric means for initiating and terminating the flow of current through the roller electrodes in response to predetermined positions of the body relative to the electrodes.

7. ln a can body making apparatus comprising a mandrel; means for wrapping a sheet metalbody blank about said mandrel and holding adjacent edges of the blank in an overlapping relationship, said wrapping means having coacting wing members with edge portions thereof that are spaced apart when holding said overlapped edges; means for feeding said wrapped blank to a welding position; means for welding said overlapped edges together along the seam, said welding means including a roller electrode in the mandrel and projecting beyond thesurface thereof, and a second roller electrode; means for biasing said second roller electrode against said overlapped edges; and means for driving said second roller electrode at a velocity that is greater than the velocity at which said feed means feeds said wrapped blank to said welding position, whereby engagement of said second roller electrode with said wrapped blank will cause said blank to be advanced by said second roller electrode during the welding operation.

8. A can body making apparatus as described in claim 7, including photoelectric means for initiating and terminating the flow of current through said roller electrodes in response to predetermined positions of said wrapped blank relative to said electrodes.

9. A can body making apparatus as described in claim 7, the lineal velocity of said second roller electrode being about ten percent greater than the velocity of said feed means.

10. A can body making apparatus comprising a mandrel; means for wrapping a sheet metal body blank about said mandrel and holding the adjacent edges of the blank in overlapping relationship, said wrapping means having coacting wing members with edge portions thereof that are spaced a part when holding said overlapped edges; means for spot welding said overlapped edges together at longitudinally spaced regions to hold the body in a cylindrical shape on the mandrel; a first roller electrode carried by said mandrel for disposition within the can body; a carriage having a second roller electrode for engagement with the exterior of the overlap and cooperating with said first roller electrode for welding a continuous longitudinal seam that constitutes the side seam of the body; feed means for advancing the spot welded body to the roller electrodes for engagement thereby; resilient means biasing the carriage away from the overlapped edges; adjustable means operable in opposition to said resilient means for biasing said second roller electrode against the overlapped edges; means for driving said second roller electrode at a lineal velocity that is greater than the velocity of said feed means; and photoelectric means for initiating and terminating the flow of current through the roller electrodes in response to predetermined positions of the body relative to the electrodes.

Claims

2. A can body making apparatus which comprises: a mandrel; means for wrapping a sheet metal body blank about said mandrel and holding adjacent edges of the blank in overlapping relation; means for spot welding said overlapped edges together at longitudinally spaced regions to hold the body in a cylindrical shape on the mandrel; means for welding said overlapped edges together along a continuous longitudinal seam that constitutes the side seam of the can body; said seam welding means comprising a pair of roller electrodes on opposite sides of the seam, one of said roller electrodes being supported by said mandrel; a carrier; the other of said roller electrodes being rotatable on said carrier; resilient means biasing said carrier away from the overlapped edges; adjustable means operable in opposition to said resilient means for biasing said other roller electrode against the overlapped edges; and means for moving the spot welded body with respect to the roller electrodes.

4. In a can body making machine having a mandrel, body forming means for wrapping a sheet metal body blank about the mandrel and holding the adjacent edges of the blank in overlapping relationship, said body forming means having coacting wing members with edge portions thereof that are spaced apart when holding said overlapped edges, a plurality of spot welding electrodes for welding said overlappEd edges together; a carriage for supporting said spot welding electrodes; means for moving the carriage to position said electrodes against said overlapped edges and in the space between said wing member portions; means on the mandrel and cooperating with said electrodes for supporting said overlapped edges during said welding; a first roller electrode carried by the mandrel for disposition within the can body; a second carriage having a second roller electrode for engagement with the exterior of the overlapped edges and cooperating with said first roller electrode for welding a continuous longitudinal seam that constitutes the side seam of the body; feed means for advancing the spot welded body to said roller electrodes for engagement thereby; and means for rotating the second roller electrode to advance the body during the seam welding.

7. In a can body making apparatus comprising a mandrel; means for wrapping a sheet metal body blank about said mandrel and holding adjacent edges of the blank in an overlapping relationship, said wrapping means having coacting wing members with edge portions thereof that are spaced apart when holding said overlapped edges; means for feeding said wrapped blank to a welding position; means for welding said overlapped edges together along the seam, said welding means including a roller electrode in the mandrel and projecting beyond the surface thereof, and a second roller electrode; means for biasing said second roller electrode against said overlapped edges; and means for driving said second roller electrode at a velocity that is greater than the velocity at which said feed means feeds said wrapped blank to said welding position, whereby engagement of said second roller electrode with said wrapped blank will cause said blank to be advanced by said second roller electrode during the welding operation.