US2995156A

US2995156A - Automatic grid machine

Info

Publication number: US2995156A
Application number: US736925A
Authority: US
Inventors: Stanley J Gartner; Jr Charles E Smith
Original assignee: Sylvania Electric Products Inc
Current assignee: GTE Sylvania Inc
Priority date: 1958-05-21
Filing date: 1958-05-21
Publication date: 1961-08-08
Anticipated expiration: 1978-08-08

Description

.Aug` 8, 1961 s. J. GARTNER ET AL 2,995,156

AUTOMATIC GRID MACHINE Original Filed Sept. 3. 194'? 5 Sheets-Shea?l l IN V EN TORS arles Sm, di.'

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AUTOMATIC GRID MACHINE Original Filed Sept. 3. 1947 5 Sheets-Sheet 4 Aug- 8, 1961 s. J. GARTNER ET AL 2,995,156

AUTOMATIC GRID MACHINE 5 Sheets-Shea?I 5 Original Filed Sept. 3. 1947 nr @im y wwf Nza r @ma d m u m34 M 6 mimi.

United Stat Patent AOfce l Patented Aug. v8, 1961 .Continuation of `application Ser. No. 771,996, Sept. 3,

'1947. This application May 2.1, 1958, Ser. No. 736,925

42 Claims. (Cl. Mtl-71.5)

This invention relates to machines for making grids for electron discharge devices and the like and to feeding, `stretching and severing devices for like machines. This 1s a continuation of application Serial No. 771,996, led September 3, 1947, entitled, Automatic Grid Machine.

In a companion application iiled concurrently herewith by Stanley J. Gartner, a novel machine for forming a strip of grids in a continuous and automatic fashion is described, with principal emphasis on the forming end of the machine. The form of grid involved includes one or more side rods to which multiple spaced turns of line wire are secured. The feeding of the grid strip during its formation, accomplished by drawing the side rods past forming devices, should be uniform and reliable to the end that the helical turns of tine wire may be accurately spaced in accordance with design specifications.

It has become accepted practice to stretch the side rods of formed strips of grids, either cold or hot, in order that `the grids may be uniform and straight when completed.

It is also necessary to divide strips into individual grids. These operations are commonly effected as separate operations, in a discontinuous procedure, following the forming of a strip of grids.

Accordingly it is the principal object of this invention to provide a novel grid-making machine having devices to enable grid strips to be formed very accurately, and to be processed into completed grids in a continuous manner in the forming machine. It will be apparent as the description proceeds that the various features of the illustrative machine described herein may be employed according to my invention without others of the features, but when integrated into a single machine, especially with the grid-forming devices in the above companion application, a grid-making machine of notable characteristics is obtained.

In usual machines the grid lateral is helically wound about the side rods at a constant rate. As a result the spacing between the helical turns is determined by the rate of side-rod feed. Usually the turns of a grid are to be uniformly spaced and the side rods are drawn past the forming devices at a uniform rate. It is nevertheless advisable to advance the side rods very rapidly at the endV of each grid-winding cycle so that the number of gridlateral turns left unsecured, between the wound and secured grid laterals, may be held to a minimum to limit the amount of unsecured grid-lateral wire that is waste. Furthermore it is often necessary to vary the mutual spacing between the secured turns and to accelerate the feed during winding of the widely-spaced loose turns. Accordingly a specific object of the present invention is to devise a feeding mechanism that can be made to cyclically vary the rate of feed of grid side rods according to an arbitrary schedule. A further object in this connection is to provide such feed mechanism in the grid machine that the organization is readily susceptible to change for manufacturing grids of different length and diiferent grid-lateral distribution and spacing.

Another feature of the improved grid machine is the incorporation of an automatic stretching arrangement to straighten the grid side rods without disturbing the continuous cyclic operation. Still another feature is the incorporation of a severing device to divide the strip into separate grids, and to remove the side-rod material deformed by the gripping faces in the feeding and stretching heads. A further feature is concerned with novel feedjaw construction for reliably engaging the grid strip, without disturbing the feed rate as would be occasioned by elongation of the strip incidental to ordinary deformation by the feed jaw.

The invention will be better understood from the following specific description of an illustrative embodiment of the invention shown in the attached drawings wherein:

FIG. 1 is a plan view of the preferred embodiment with certain parts broken away and others omitted for clarity.

FIG. 1A is the elevation of an operating cam and hydraulic valve detail.

FIG. 2 is an elevation of the structure in FIG. 1 with parts lbroken away and omitted for clarity, showing a wiring detail in addition.

FIG. 3 is a longitudinal sectional detail of the mechanism for stretching the side rods.

FIG. 4 is an elevation of the second feed head and operating mechanism, being illustrative of the` threeother four-motion heads in the machine.

FIG. 5 is a plan view of a portion of the mechanism in FIG. 4.

FIGS. 6 and 7 are alternative forms of grid that .can be made with the illustrative machine.

FIG. 8 is a diagram of the hydraulic system for operating various mechanisms in the presently preferred machine.

FIG. 9 is an elevation of the feed jaws of the second feed head, being illustrative of the jaws in the first feed head and the stretch head.

FIG. lO is a fragmentary sectional view of the feed jaws along the line 10--16 in FIG. 9.

FIGS. 11 and 12 are enlarged sectional detail views of successive feed jaws according to alternative embodiments.

FIG. 13 is a cam chart, corresponding closely vto a timing chart of the important' operations in the improved grid machine. v

GENERAL Referring now to FIGS. l and 2 the side rods R are drawn to the right by the feed mechanism, to be described, through guide tube 10 and laterally supported by mandrel 12 iixed to the end of tube 10. Grid-lateral wire L from reel 14 is directed by guide 16 to the exact point along mandrel 12 where the grid lateral is to be laid. Reel 14 and guide 16 form part of Winding head 18 that is rotated about tube 10.

A pair of sharp-edged notehing discs 20 are reciprocable in alternation against rods R on mandrel 12 and in ad- Vance of the point where guide 16 lays grid lateral L. A pair of blunt-edged peem'ng discs 22 are also reciprocable against mandrel 12, in alternation with each other and in alternation with the adjacent notching disc, to secure the grid-lateral wires in place immediately after they are wound by guide 16 on head 18. Rods R are gradually drawn to the night while the notching, winding and gridlateral-securing operations take place to form a series of secured turns of grid lateral wire on side rods R, either evenly spaced or unevenly spaced as in the completed grids of FIGS. 6 and 7. At the completion of each sequence of secured turns, the contact between discs 20 and 22 with side rods R is interrupted while the winding of grid-lateral wire continues. During this time the side rods R yare advanced to the right more rapidly than usual and several loose turns of grid lateral L are wound. The winding of the loose turns is for the purpose of maintaining continuity of grid lateral L between the sequence of secured turns that are to form the grid in FIGS. 6 and 7, during those intervals when side rods R are drawn past the grid-forming devices without having grid-lateral wire attached, The rapid side-rod feed provides the necessary lengths of side-rod material for grid terminals and locating extensions, and fordeform-ation incidental to the feeding operations.

A pair of blades 24 and 26 (FIG. 1) and a mechanical picker 27 (FIG. 2) are jointly effective to separate the loose turns from the secured turns and to remove the separated turns from the machine. As a result the uncompleted strip G` of grids is drawn to the right beyond the grid forming tools, having groups of secured turns spaced by lenths of bare side-rod wire R.

The devices described to this point are more fully disclosed in U.S. Patent No. 2,759,499 of August 2l, 1956, assigned to the assignee of the present invention.

The strip of grid material G is continuously drawn through the machine by a pair of feeding heads 28 and 30 each of which operates in 'a four-motion path to grip the material, draw it along the machine, release it, and return for a renewed feeding stroke. The timing of the four-motion strokes is such that there is continuous feeding through the machine without a disturbance such as would otherwise cause erratic spacing of the grid-lateral turns. An additional head 32 is provided for stretching the side rods and, optionally, for heating them electrically during the stretching operation. A fourth head 34 divides the grids from each other to yield individual grids, and to cut out the portions of side-rod material that have been deformed by the feeding and stretching heads.

The first feeding head 28 fis carried by bracket 36 on shaft 38 which is axially reciprocated parallel to the travel of grid strip G and completes one cycle of reciprocation for each completed grid. Cutting head 34 is also secured to shaft 38 by bracket 49. A second shaft 42, parallel to but laterally spaced from shaft 38, carries bracket 44 for supporting the second feed head 3G. Stretching head 32 is carried on head 30 by a pair of threaded

shafts

46 and 48, but is cyclically movable along the strip of grids in relation to head 30 by hydraulic pistons described below.

Each

shaft

38 and 42 is axially reciprocable by cam mechanism for effecting longitudinal movements of the

several heads

28, 30, 32 and 34 parallel to the travel of the grid strip and in the restoring direction. Hydraulic actuators are used for effecting gripping and separating motions of the maws within the several heads. Hydraulic cylinders S0, 52 and 54 for this purpose are shown in FIG. 2. The axially reciprocated shafts and the hydraulic actuators are timed to close the jaws of the head of the grid strip, move with the strip, separate and then return, in a four-motion path.

Head travel The mechanism to operate

shafts

38 and 42 axially for moving the feeding, stretching and cut-ting heads parallel to the grid-strip will now be described. Shaft 38 is supported in a pair of

bearings

56 and 58 which are secured to the bed plate 60 of the machine. Shaft 42 is similarly carried by bed plate 60 in

bearings

58 and 62. At the right extremes of

shafts

38 and 42 are a pair of fixed abutment rods 64 and 66 having enlarged ends as 68 on -rod 64 (FIG. 2) which is s'lidable in the bored end of shaft 38. A spring 70 acts between the end of the bore in shaft 38 and enlargement 68 yto urge shaft 38 constantly to the left. A similar enlarged end, bore and spring construction urges shaft 42 constantly to the left. Shaft 38 carries cam follower 72, maintained in contact with cam 74 by spring 70. Cam follower 72 is adjustable along shaft 38 by means of capstan nut 76, threaded and shouldered rod 78, and abutment Sil which is xed to shaft 38. By rotating nut 76 when cam 74 is stationary it is possible to adjust the position of the first feeding head 28 and of cutting head 34 along the grid strip. By Virtue of these adjustments the feeding heads can be caused to engage grid strip G accurately between the lengths of side rods R to which the grid lateral L is secured, and each of the heads can be made to register with the deformation formed by the preceding head. Cutting head 34 can be adjusted relative to iirst feeding head 28 by loosening the bracket by which it is carried on shaft 38. Cam follower 82 on cam 74, spaced 180 from cam follower 72, is adjustably carried by shaft 42 and reciprocates

heads

30 and 32 along the grid strip.

Cam 74 is rotated -by cam shaft 84 which is supported in split bearing 86, 88 depending from bed plate 60. Shaft 84 is rotated once for each complete grid cycle by gear 90 driven in turn by pinion 92 on drive shaft 94.

At its left extreme, shaft 84 carries a cam follower 96 which-is held against rotation with that shaft by an arm 9S, and -is provided with a thrust bearing. Arm 95 is slidable in fixed grooved plate 97. Cam follower 96 is urged against cam 98Vby the same springs, as '70, that maintain

cam followers

72 and 82 against cam 74. Cam 98 on shaft 108 iis driven from shaft 94 through spiral gears 102 and 104 :to reciprocate shaft 84 axially once each grid cycle. Shaft and gear 102 are carried in housing 106 supported from bed plate 60.

Operation of jaws in heads Before considering the effect of

cams

74 and 98 on the various feeding, stretching and cutoff heads, the nature of an individual head will first be described. For this purpose the second feeding head 3) shown in FIG. 4 is taken as typical. The other heads have the same type of operating linkage and frame construction, although frame detaiis are varied among the heads in order to meet space requirements.

Second feeding head 30 is supported on shaft 42 by bracket 44 including clamping portion 44a. This head comprises a frame 168 having a grooved face-portion 110 for laterally guiding a pair of

slides

112 and 114 carrying the maws to grip the strip of grid material G. A pair of

gibs

116 and 118 are secured to frame 108 to guide and retain

slides

112 and 114 against face-portion 110.

Slides

112 and 114 have similar operating linkages, and are reciprocated toward and away from each other by a common hydraulic actuator. Hydraulic fluid is alternately admitted to

lines

120 and 122 supplying cylinder 52 for reciprocating piston 124. This reciprocatory drive is transmitted to connector 126 by link 128 to operate a pair of bell cranks 130 and 132 which are pivoted on frame 108. The operative stroke of connector 126 is transmitted through these bell cranks to

links

134 and 136 respectively which are secured by

eccentrics

138 and 140 to

slides

112 and 114. The eccentrics can be locked in any adjusted position in a suitable manner.

The strokes of

jaws

112 and 114 are enforced cyclically by hydraulic pressure, being limited by the excursion of piston 124 in cylinder 52. The ultimate positions of

slides

112 and 114 in engagement with grid strip G are determined by adjustment of

eccentrics

138 and 140 and by fixing the length of connector 126 at adjustable portion 142.

The second feeding head 3i) differs notably from the first head 28 and fourth head 34 in that it supports a pair of cylinders and pistons for supporting and operating the third or stretching head 32. In addition, because of the long space between shaft 42 which supports head 30 and the center of mass of the head, a plate 144 is provided on head 3ft for sliding in guide 146 carried by arm 148 rigidly secured to bed plate 60.

Heads

30 and 32 are guarded by this plate and guide construction against pivoting downward about shaft 42.

Stretching head The mechanism for operating stretching head 32 is best shown in FIGS. 3, 4 and 5. The stretching of grid strip G is to be effected while the side rods are cold tion as shown.

or, opitonally, while the siderods are electrically heated. For this purpose the heads are electrically insulated apart, as will appear, and a voltage applied between the heads is impressed on the strip.

In FIG. 3 cylinder 150 is shown supported in frame 108 and carrying a piston 152 at the left end of rod 46. Frame 108 of stretching head 32 is adjustably secured to threaded shaft 46. When hydraulic iluid is admitted to cylinder 150, the stroke of piston 152 carries stretching head 32 away from the second feed head 30 at a time when the jaws of `both

heads

30 and 32 are closed on grid strip G. Second feeding head 30 actually travels along bed plate 60 in drawing the grid strip past the forming devices including the forming head; but piston v152 moves head 32 faster in the feeding direction and `stretches the portion of grid strip gripped between

heads

30 and 32.

The extent of stretch is determined by the mechanical .stops limiting the stroke of piston 152 in cylinder 150. At the left end, the wall of cylinder 50 forms a stop. At the right end, collar 154 limits the stroke. Collar 154 is adjustably screwed on the outside of cylinder 150 and is externally uted for engagement by ball detent '156 secured to frame 108. Shaft 46 is provided with .a keyway 158 and is held against rotation with respect '1o cylinder 150 by key 160. The latter is secured to a plug 162 within cylinder 150 by means of a screw 164 'the head of which abuts collar 154. A compression coil :spring 166 reacts between piston 152 and plug 162 to maintain screw 164 in contact with collar 154 in all its positions of axial adjustment.

When hydraulic uid is admitted to cylinder 150 from line 168, piston 152 is urged to the right extreme as limited by plug 162 which in turn is arrested by collar 154. Upon release of the hydraulic pressure in line 168, piston 152 is restored by spring 166 to its left-hand posi- Collar 154 is externally provided with a calibrated scale 170 (see FIG. 5) so that extent of -stretch of the grid side rods can be accurately changed without trial-and-error procedure.

The structure for operating the second shaft 48, parallel to shaft 46, is identical with that shown in FIG. 3 and both are energized by a common hydraulic supply.

For the purpose of heating the side rods electrically during the stretching operation, a controlled voltage is ,applied between

heads

30 and 32, and for this reason these two heads are electrically insulated apart. The connection of shaft 46 to frame 108 includes nut 172 spaced from frame 108 by an insulating washer 174, and bushing 176 on the opposite side of frame 108 is spaced from the frame by an insulating bushing 178. Bushing 176 is held against rotation in relation to insulating bushing 178 by means of key 180 that extends into keyway 158. Nut 182 on threaded shaft 46 tightens bushings 176 and 178 against frame 108', confined by nut 172. .Electrical lines 184 and 186 are connected respectively to

heads

30 and 32 and are energized by an appropriate portion of secondary winding 188 of a transformer having a selector tap switch 190. The primary 192. of this transformer is energized from the usual power supply line through a control relay 194, switch 196, and cam switch 198 the purpose of which is to time the start and duration of heating of the side rods. When it is not desired to utilize the hot-stretch provision, switch 196 is opened and grids can then be made according to the cold-stretch procedure. The hydraulic

lines feeding cylinders

52 and 54 of

heads

30 and 32 are of nonrnetallic materials and do not short-circuit the hot-stretch electrical circuit.

Hydraulic system and timing chart From the foregoing, it will be apparent that the longitudinal travel of the first and second feed heads and of the cutting head are eiected by

cams

74 and 98. The stretching head 32 travels with head 30, but is given an 8 augmentedexcursion by means of hydraulic mecha'- nism including 150. The jaws in the several heads are all operated, for closing on the grid strip and for opening, by hydraulic mechanism including a cylinder carried by each of the heads and exible lines leading to them.

The complete hydraulic system `for the entire machine is diagrammatically shown in FIG. 8.

Cylinders

50, 52, 54 and 186 for operating the jaws of

heads

28, 30, 32 and 34 are alternately supplied with high-pressure fluid at opposite ends, and are connected foi return of the low-pressure uid to the supply hy means of a series of two-way valves 189. High-pressure supply line 191 is connected to all of these valves, and it in turn is supplied fby pump 193 and pressure regulator 195 which has a return line 197 to sump 199. Hydraulic motor 200 with its control valve 202 for operating the entire machine is also shown in this diagram. Valves 189 are connected for return of low-pressure fluid through

lines

204 and 206 to sump 199. A second regulator 208 is provided for reducing the available hydraulic pressure to `a suitable level for operating the stretching mechanism, including hydraulic cylinder 150. This mechanism is spring-restored rather than restored by hydraulic pressure. For this reason a slightly different valve 210 is utilized for connecting cylinder 150 alternately for input from regulator 208 and `for discharge to return line 206. Picker 27 is hydraulically operated from the high-pressure lines, as indicated, just as in the case of the jaws in the various heads.

Valves 189 are cam-operated as indicated in FIG. 1A. Plural cams 212 are secured to shaft 214 which is rotated once for each grid cycle, in time with cam-

shafts

84 and 100. Cams are also provided on shaft 214 for operating valve 210 of the stretching head, and for hot-stretch switch 198 shown in FIG. 2. The cam-operated valve detail is naturally subject to wide variation, but the relative timing among the several valves is of importance.

rIlhe timing of the various operations will -be understood from FIG. 13. While this figure is actually a cam chart it is a close approximation of a timing chart as well. It will be seen from the top section of the chart that cam 74 has portions for causing a gradual uniform forward or feeding stroke of the first and second feeding heads, and a fast return stroke, the division being about 260 and 100 and the return strokes are spaced by 180. Between zero and and between 180 and 260 botth heads Amove in unison and in thesame direction. From the second and third sections of the diagram it is apparent that the jaws of both

heads

28 and 30 are in engagement with grid strip G during a part of these corncurrent feeding strokes of

heads

28 and 30, and the jaws of one feeding head grip the strip at other times. It therefore follows that Ithe grid strip will be smoothly advanced past the winding and forming devices atvthe left of FIGS. l and 2, and uniform grids will be produced, The lead, or the extent of feed in a grid cycle, is controlled by the extreme limits of cam 74 which is therefore termed the lead cam.

Cam 98, it will be seen from the fourth portion yof FIG. 13, incorporates a long, very gradual sloping portion and a relatively abrupt return portion. IThis cam simply varies the feeding rate of the grid strip that would be caused by cam 74, the abrupt portion serving to impart a fast, long feeding stroke `during the winding of the loose turns. The remainder of the cycle of cam 98 modifies the feeding rate of cam 74 during the winding of secured turns. Where this long portion of cam 98 is straight, the pitch of the grids will be uniform from end to end. The spacing bre-tween the successive secured turns of the grid can be varied from one end of the grid to the other (FIG. 7) by properly curving cam 98. Therefore cam 98 is termed the pitch cam.

When the machine is tobe changed from operati-on on one type of grid -to production of another type, cam 74 need not be removed if the length of the'new grid is the same as the old one. Cam 98 need not be replaced if `7 the distribution of the secured turns' and the lengthY of the loose-turn zone are not changed.

Comparing the fourth and fifth sections of FIG. 13 it is apparent that the fast-feeding operation that occurs simultaneously with the winding of unsecured turns occurs previous to the stroke of loose-turn picker 27. This is because the grid strip should advance to cutters 24 and 25 before the loose turns are parted from the secured turns. Therefore loose-turn picker 27 is lowered at a later time in the grid cycle, after the winding of a number of secured turns.

Comparing the third and sixth sections of FIG. 13 it can be seen that the jaws of stretching head 32 engage the grid strip shortly `after the jaws of head 34.1 grip the strip. Similarly the stretching-head jaws release the grid strip shortly before the strip is released by the jaws of head 30. The engagement and release of both jaws take place in the region of 190 to 200 and 40 to 50, respectively. Comparison of the seventh section of FIG. 13 with the sixth section shows that the stretching operation, effected by cylinder 156, takes place after the jaws of streaching head 32 grip the strip and that the piston in cylinder 150 is restored after the jaws of head 32 have released the grid strip. The electrical heating of the side rods is lcommenced and completed after the grid strip is gripped by both the second feeding head and the stretching head, and the heating is interrupted shortly after pressure is admitted to the stretching cylinders, as 150, after which the strip is supported during cooling.

The loperation of cutting head 34 corresponds to that of the first feeding h-ead 28. The cutting head, positioned beyond the stretching head, is not in engagement with the grid strip during the initially effective part of the stretching operation as `controlled by cylinder 150. The cutolf head, however, acts to support the end of grid strip G after the previous grid is parted, so that the grid strip will not sag while the jaws of stretching head 32 close to grip the strip.

In FIGS. 9 to l2 there are shown several feed-jaw details which contribute signicantly to the excellence of the feeding mechanism. As is apparent from the foregoing, and especially in connection with the overlap in the feeding strokes of the first and second heads, it is desirable that there be no interruption in the smooth travel of the side rods past the forming devices. It is likewise desirable that the feed jaws in the first and second heads do not change the length of those side rods in firmly gripping them, for this would defeat the careful arrangement directed to uniform feeding. One fonrn of feed-jaw detail is shown in FIGS. l and 10 as comprising a blade 216 fixed to slide 112 (compare with FIG. 4) and a pressure pad 218 having portions on opposite faces of blade 216. Pad 218 is spring-loaded by compression spring 22h and button 222 to contact grid strip G in advance of blade 216 and to strip the side-rods from blade 216 4during the return stroke of slide 112. A positive-acting backup block 224 is secured to slide 114 below grid strip G. As previously mentioned in connection with the mechanism of FIG. 4, sli-

des

112 and 114 are operated to precisely determined end-points, so that blade 216 will penetrate the side rods R of grid strip G to an accurate extent. The jaws of two successively `acting heads are shown, enlarged, in FIG. 11. These are illustrative of the first and second feeding heads and of the second feeding head and the stretching head. The surface of blade 216 is formed to cause essentially transverse plastic flow of the side-rod material, thereby causing no elongation of the rod. Similarly shaped blade 216' is arranged in the following head to take a new bite into the side rod R, still without causing elongation of the side rod. The blades have lateral surfaces that are essentially perpendicular to the side-rods and embody a Y groove between them for accommodating the lateral fiow of side-rod material. l

An alternative form of feeding-jaw detail is shown 1n FIG. 12, wherein a positively operated blade 226, flanked by a pressure pad 228, offsets a portion of the side-rod material without foreshortenng or elongating that side rod. The lateral surfaces of blade 226 are essentially perpendicular to the grid strip. The pressure block of FIG. 11 is modified in FIG. 12 to comprise positive-acting portions 230` and -a resilient stripping pad 232 between portions 230. This construction also accommodates the later-al flow of side-rod material. The offset formed in the first feed jaw can be reliably used for feeding without further deformation in the arrangement shown by having a narrow positive-acting blade 218 register with the forward edge of the previously formed depression.

The foregoing specication includes a detailed description of an illustrative embodiment of the invention, this embodiment incorporating several closely related features which coact to facilitate and improve the manufacture of grids. However it will be recognized that the particular embodiment is susceptible to a wide latitude of modication and substitution and portions of it are separately useful in improving similar machines. Therefore the following claims should be interpreted broadly, within the spirit of the invention.

What we claim is:

l. In a machine of the type described including means for modifying a strip of material, a feeding mechanism for moving the strip of material past said modifying means according to a cyclic feed-rate schedule, comprising a pair of four-motion feeding heads operable to grip the strip alternately, lead cam mechanism reciprocating said heads along said strip in an alternating relationship through a predetermined stroke, and additional cam mechanism operatively connected to said lead cam mechanism for cyclically modifying the feeding rate that would otherwise be effected by said lead cam.

2. ln a machine of the type described including means for modifying a strip of material, a feeding mechanism for moving the strip of material past said modifying means according to a cyclic feed-rate schedule, said feeding mechanism comprising a pair of four-motion feeding heads, a rst cam, a pair of spaced cam followers on said cam, one of said lfollowers being operatively connected to each of said feeding heads for reciprocating said feeding heads, and a second cam for cyclically adjusting said first-mentioned cam to modify the feeding rates that would normally be caused by said first cam.

3. A grid-making machine having devices for winding and securing grid-lateral wire about one or more side rods, said machine including a first feeding head and a second feeding head, means for operating each of said first and second feeding heads in alternation in a fourmotion path to grip and advance the strips past the winding and forming devices to effect continuous feeding, a cutting head having grid strip engaging jaws, and means for actuating said cutting head in substantial synchronisrn with the first feeding head to bring said jaws into engagement with the formed grid strip for dividing the formed grid strips into individual grids, the actuating means for said cutting head maintaining said jaws in engagement with the formed grid strip during the return stroke of said second feeding head for supporting the grid strip against deflection during the return stroke of said second feeding head, said second feeding head being positioned between said first feeding head and said cutting head.

4. A grid-forming machine having forming devices for winding and securing grid-lateral wire about one or more side rods, said machine including a feeding mechanism having a four-motion feeding head, means operatively connected to said feeding head for reciprocating said feeding head in `a path parallel to the travel of the formed grid strip, and a stretching head carried by said feeding head, means for engaging said stretching head with the grid strip during feeding thereof by said feeding head whereby saidstretching head is reciprocable parallel to the travel of the formed grid strip and means for recipro- 9 cating said stretching head through a longer stroke than said feeding head during feeding for stretching the side rod material.

5. A grid-forming machine having rst and second four-motion feeding heads, forming devices for winding and securing grid-lateral wire about one or more side rods, said side rods being continuously advanced past said forming devices by said feeding heads, and a four-motion stretching head located beyond said heads in the feeding direction and carried by one of said heads and means for cyclically operating said four-motion stretching head generally in the same sequence as one of said feeding heads and at a greater rate during its engagement with lthe formed grid strip to stretch the side-rod material.

6. A grid-making machine comprising devices for winding and securing grid-lateral wire about one or more side rods to form a strip of grid material, a first and a second four-motion feeding head reciprocable to draw the grid strip continuously at predetermined rates past the gridforming devices, and a four-motion stretching head carried by said second feeding head and means for reciproeating said stretching head at a rate relative to said second feeding head for stretching the grid strip during engagement of the second feeding head and the stretching head with the grid strip.

7. Apparatus according to claim 6 wherein piston and hydraulic cylinder are operatively connected to said stretching head to effect relative travel between said second feeding head and said stretching head.

8. A grid-making machine having devices for forming a helical grid about one or more side rods, said machine having a feeding mechanism including first and second four-motion feeding heads reciprocable parallel to the travel of the formed grid strip and each arranged to engage the grid strip during the respective feeding strokes thereof, hydraulic actuating mechanisms including flexible uid lines respectively connected to said heads, a stretching head for engaging the grid strip during the feeding thereof by said second feeding head, and hydraulic actuating mechanisms including a flexible fluid line for causing the stretching head to operate through a longer stroke than said second feeding head for stretching the side rods.

9. A grid-making machine comprising devices for winding and securing grid-lateral wire about one or more side rods to form a strip of grid material, first and second four-motion feeding heads reciprocable to draw the grid strip continuously at a cyclic rate schedule past said grid-forming devices, a four-motion stretching head carried by said second feeding head, means for moving said stretching head away from said second feeding head and through a prescribed stroke for stretching the gridstrip during engagement of the second feeding head and the stretching head with the grid strip, means electrically insulating said stretching head from said feeding head, an electrical supply connected to said second head and said stretching head for heating the portion of the grid strip gripped between the latter heads, and hydraulic mechanism including electrically non-conducting liuid supply lines for causing at least one of said latter heads to grip said strip.

l0. A grid-making machine including devices for winding and securing helical turns to one or more side rods with predetermined spacing between the turns controlled by the feed-rate of the side-rods past said devices, said machine having a pair of sequentially effective four-motion feeding heads for reliably feeding the side rods according to a predetermined rate schedule, the first head comprising jaws having parallel surfaces with edges arranged to penetrate the side-rod material substantially perpendicularly, said jaws incorporating a recess between said edges for accommodating the transverse ow of siderod material, and a pair `of jaws in the second head for engaging the side rods in registry with the zone previously penetrated.

ll. A machine adapted to modify strip material passed through said machine, and including means past .which said strip progresses and where operations are performed upon said material, a first and a second gripping head', means operatively connected to said first and second gripping heads to alternately reciprocate said heads back and forth along the path of travel of said strip material, each of said heads having jaws to engage said strip ma: terial, means to alternately operate said jaws to continuously draw said material through said machine, and a stretching head carried by the second of said heads; means for mounting said stretching head for movement relative to said second head, said stretching head having jaws to engage said material, meansto engage the jaws of said stretching head when the jaws carried by said second head are closed, and means for increasing the spacing between said second head and said stretching'. head, while the jaws carried by said heads are closed whereby said material is stretched.

l2. A machine having strip material feeding means in'- cluding a pair of sequentially effective four-motion feeding heads reciprocable along the line of travel of said material through said machine, the first of said heads having material clamping jaws with parallel surfacesand edges arranged to penetrate said material perpendicularly, and a recess between said edges for accommodating transverse flow of said material, the second of said heads including material clamping jaws with parallel surfaces and edges arranged to penetrate said materiai perpendicularly `at each side of the points of penetration of said first jaws, the flow of material caused by the clamping yof said second jaws taking place into the depressions formed by said rst jaws without causing a change of length of said strip material.

13. A grid making machine comprising devices for winding and securing grid lateral wire about one or more side rods to form a strip of grid material, first and second four-motion feeding heads, means for alternately reciprocating said feeding heads to draw said grid strip material continuously at a cyclic rate schedule past said grid forming devices, a four-motion stretching head carried by said second feeding head and having gripping means yarranged to clamp said grid strip simultaneously with said second head, means for engaging said gripping means during feeding by said second head, means for reciprocating said stretching head relative to said second head whereby said grid strip is stretched, a cutting head beyond said stretching head and carried by said first head, and means to operate said cutting head to engage said strip simultaneously with said first head to sever the portion of said grid material beyond said cutting head and to support the grid strip between said first feed head and said cutting head.

14. A machine of the type described including means for modifying la strip of material, and a feeding mechanism for moving the strip of material past said modifying means accord-ing to a cyclic feed rate schedule, comprising a pair of feeding heads disposed one after the other along the path of travel of said strip of material, lead cam mechanism for reciprocating said heads along said strip in an alternating relationship through a predetermined stroke, clamping jaws on each head, means operatively connected to the respective jaws to close the jaws at one end of each stroke and to open the jaws at the other end of said stroke, and additional cam mech-anism operating on said lead cam mechanism for cyclically modifying the rate of travel of said heads.

l5. A machine of the type described including means for modifying a strip of material, and a feeding mechanism for moving the strip of material past said modifying means according to a cyclic feed rate schedule, comprising a pair of feeding heads disposed one after the other along the path of travel of said strip of material, a cam follower for each of said feeding heads, a lead cam ,engaging said cam followers for reciprocating said heads along said strip in an alternating relationship through a predetermined stroke, clamping jaws on each head, means operatively connected to the respective jaws to close the jaws at one end of each stroke and to open the jaws at the other end of said stroke, and additional cam mechanism operating on said lead cam for cyclically modifying the rate of travel of said heads, said cam followers being mutually spaced about said lead cam.

16. A machine of the type described including means for modifying a strip of material, and a feeding mechanism for drawing a strip of material cyclically past said operating means according to a predetermined feed rate schedule, said feeding mechanism comprising a pair of feeding heads disposed one after the other along the path of travel of said strip of material, each feeding head having a cam follower for reciprocating it along the path of the strip and lead cam mechanism having a cylindrical cam engaging said cam followers for reciprocating said heads along said strip in an alternating relationship through a predetermined stroke, clamping jaws on each head, means operatively connected to the respective jaws to close the jaws at one end of each stroke and to open the jaws at the other end, and additional cam mechanism operating on said lead cam for cycl-ically modifying the rate of travel of said heads.

17. A machine of the type described including means for modifying a strip of material, and a feeding mechanism for moving the strip of material past said modifying means according to a cyclic feed rate schedule, comprising a pair of feeding heads disposed one after the other along the path of travel of said strip of material, lead cam mechanism for reciprocatingV said heads along said strip in an alternating relationship through a predetermined stroke, clamping jaws on each'head operated to close at one end of each stroke and to open at the other end of said stroke, and additional cam mechanism operating on said lead cam mechanism for cyclically modifying the rate of travel of said heads, one of said heads carrying a set of stretching clamp jaws, means for cyclically causing said stretching jaws to grip said strip while the clamping jaws on said one head are closed, and means for moving said stretching jaws with relation to the clamping jaws on said one head to stretch said strip of material.

18. A machine of the type described including means for modifying a strip of material, and a feeding mechanism for moving the strip of material past said modifying means according to a cyclic feed rate schedule, comprising a pair of feeding heads disposed one after the other along the path of travel of said strip of material,

each feeding head having a cam follower associated i therewith, a lead cam engaging said cam followers for reciprocating said heads along said strip in an alternating relationship through a predetermined stroke, clamping jaws on each head operated to close at one end of each stroke and to open at the other end of said stroke, and

additional cam mechanism operating on said lead cam for cyclically modifying the rate of travel of said heads7 said cam followers being mutually spaced about said lead cam, one of said heads carrying a set of stretching clamp jaws, means for cyclically causing said stretching jaws to grip said strip while the clamping jaws on said one head are closed, and means for moving said stretching jaws with relation to the clamping jaws on said one head to stretch said strip of material.

19. A grid forming machine having rst and second feeding heads disposed one after the other along the path of travel of said grid, clamping jaws on each head, means connected to said clamping jaws to close at one end of each stroke and to open at the other end, forming devices for winding and securing grid lateral wire about one or more side rods, means for reciprocating said feeding heads such that said side rods are continuously advanced past said forming devices by the alternate reciprocating 'action -of said feeding heads, and a stretching head located beyond said heads in the feedingdirection and carried by one of said heads and including clamping jaws, means for cyclically operating said clamping jaws of said stretching head in the same sequence as the jaws of one of said feeding heads, and means for moving said clamping jaws of said stretching head with respect to said one of said feeding heads.

20. A machine of the type described including means for modifying a strip of material, and a feeding mechanism for moving the strip of material past said modifying means according to a cyclic feed rate schedule, comprising a pair of feeding heads disposed one after the other along the path of travel of said strip of material, cam mechanism for reciprocating said heads along said strip in an alternating reltaionship through a predetermined stroke, clamping jaws on each head, means operatively connected to the jaws on the respective heads to close the jaws at one end of each stroke and to open the jaws at the other end of said stroke, said jaws having lateral surfaces substantially transverse of said strip of material and incorporating a recess between said surfaces for accommodating transverse flow of said material.

2l. A machine of the type described including means for modifying astrip of material, and a feeding mechanism for moving the strip of material past said modifying means according to a cyclic feed rate schedule, comprising a pair of. feeding heads disposed one after the other along the path of travel of said strip of material, cam mechanism for reciprocating said heads along said strip in an alternating relationship through a predetermined stroke, clamping jaws on each head, means operatively connected to the jaws on the respective heads to close the jaws at one end of each stroke and to open the jaws at the other end of said stroke, the jaws of the r trst of said heads including a blade for deforming the strip of material laterally while maintaining its length constant, and the second of said heads having jaws registering with the deformation previously affected by jaws of said rst head.

22. A machine of the type described including means for modifying a strip of material, and a feeding mechanism for moving the strip of material past said modifying means according to a cyclic feed rate schedule, comprising a pair offeeding heads disposed one after the other along the path of travel of said strip of material, cam mechanism for reciprocating said heads along said strip in an alternating relationship through a predetermined stroke, clamping jaws on each head, means operatively connected to the jaws on the respective heads to close the jaws at one end of each stroke and to open the jaws at the other end of said stroke, the jaws of the first of said heads having parallel surfaces with edges arranged to penetrate a strip of material substantially perpendicularly of the length of said strip, said jaws incorporating a recess between said edges for accommodating transverse ow of said material, and the jaws in the second of said heads engaging the strip of material in registry with the zone previously penetrated by the jaws of said first head.

23. A machine of the type described including means for modifying a strip of material, and a feeding mechanism for moving the-strip of material past said modifying means according to a cyclic feed rate schedule, comprising a pair of feeding heads disposed one after the other along the path of travel of said strip of material, cam mechanism for reciprocating said heads along said strip in an alternating relationship through a predetermined stroke, clamping jaws on each head operated to close at one end of each stroke and to open at the other endof said stroke, the clamping jaws on each head including a blade mounted transversely of the strip of material gripped thereby, the blade of the clamping jaws of the rst of said heads acting to ofset a portion of the strip of material gripped thereby and the blade in the clamping jaws of the second of said heads being adjusted i3 to clamp said strip of material in the offset formed by the blade in the first of said heads, the blade in the second of said heads being narrower than the blade in the first of said heads to prevent the clamping operation from modifying the length of said strip of material.

24. A machine of the type described including means for modifying a strip of material, and a feeding mechanism for moving the strip of material past said modifying means according to a cyclic feed rate schedule, comprising a pair of feeding heads disposed one after the other along the path of travel of said strip of material, lead cam mechanism for reciprocating said heads along said strip in an alternating relationship through a predetermined stroke, clamping jaws on each head operated to close at one end of each stroke and to open at the other end of said stroke, one of said heads carrying a set of stretching clamp jaws, means for cyclically causing said stretching jaws to grip said strip while the clamping jaws on said one head are closed, and means for moving said stretching jaws with relation to the clamping jaws on s aid one head to stretch said strip of material.

25. A machine of the type described including means for modifying a strip of material, and a feeding mechanism for moving the strip of material past said modifying means according to a cyclic feed rate schedule, comprising a pair of feeding heads disposed one after the other along the path of travel of said strip of material, lead cam mechanism for reciprocating said heads along said strip in an alternating relationship through a predetermined stroke, clamping jaws on each head, means operatively connected to the jaws on the respective heads to close the jaws at one end of each stroke and to open the jaws at the other end of said stroke, one of said heads carrying a set of stretching clamp jaws, means for cyclically causing said stretching jaws to grip said strip while the clamping jaws on said one head are closed, and means for moving said stretching jaws with relation to the clamping jaws on said one head to stretch said strip of material, means for insulating said stretching clamp jaws from the one of said heads carrying said stretching clamp jaws and means for applying an electrical potential differvence between said one of said heads and said stretching clamp jaws.

26. In a machine having a feeding mechanism operable for moving a strip of material through said machine, said feeding mechanism including a pair of heads each having material gripping jaws constructed and arranged to firmly grip said material in succession at the same point, the first one of said gripping jaws being recessed whereby a portion of said material strip is deformed into said recess, the second one o-f said jaws being arranged to engage said strip of material at each side of the zone 4of engagement of the first jaws.

parting stretch to said side rods, and means for moving said stretching device with said gripping means engaging said side rods along said path at a rate in excess of said predetermined feed rate, whereby a stretching and straightening action is exerted on said side rods.

28. In a grid-forming machine, means for performing an operation on a grid, and a feeding mechanism for moving said grid according to a cyclic feed-rate schedule, said feeding mechanism including a pair of four-motion feeding heads, a first cam, a pair of cam followers engaging said cam, one of said followers being operatively connected to each of said feeding heads for reciprocating id said feeding heads, a second cam, and a cam follower engaging said second cam and operatively connected lto said first cam for cyclically shifting said first cam.

29. In a grid-making machine, means for Winding and securing grid-lateral wire about one or more side rods in a grid strip, a first feeding head, a second feeding head, means for moving each of said feeding heads in a fourmotion feed path having a forward stroke for gripping and advancing said grid strip and a return stroke, means for moving said feeding heads in alternation to effect continuous feeding, a cutting head, means for operating said cutting head in substantial synchronism with said first feeding head for dividing said grid strip into individual grids, said cutting head being operative to support said grid strip against deflection during the return stroke of said second feeding head.

30. A grid-forming machine including means for modifying -a strip of material, and a feed mechanism for moving the strip of material past said modified means according to a cyclic feed rate schedule, said feeding mechanism comprising a pair of heads disposed along the path of travel of said strip of material, mechanisms for moving said heads along said path of travel in alternate relationship and through a predetermined stroke, feeding clamp jaws on each of said heads arranged to close at a predeteilmined point along said stroke, a set of stretching clamp jaws, means for mounting said stretching clamp jaws on one of said heads for normal movement therewith and for movement relative thereto, means for 4cyclically causing said stretching clamp jaws to grip said strip while said feeding clamp jaws on said one head are closed, and means for moving said streching clamp jaws with relation to said feeding clamp jaws on said one head to stretch said strip of material.

3l. A grid-forming machine including -means for modifying a strip of material, and a feed mechanism for moving the strip of material past said modifying means according to ya cyclic feed rate schedule, said feed mechanism comprising a pair of heads disposed along a path of travel of said strip of material, feeding clamp jaws on each of said .feed heads operated to periodically close `for gripping said strip of material, one of the feeding clamp jaws of the first of said heads having a notch therein transverse of said strip of material, said one of the feeding clamp jaws of the first of said heads acting in clamping to provide notches transverse to the length of said strip of material, the vfeeding clamp jaws of the second of said heads having a notch therein transverse to the length of said strip of material, said notch being broader than the notch in said first named feeding clamp jaws whereby the feeding clamp jaws of the second of said heads in clamping on said strip of material deforms the material of said strip into the notches formed by the first named lfeeding c-lamp jaws.

32. `In a grid-making machine, means along a predetermined path for modifying a grid strip, and feeding mechansms operative along said predetermined path for moving said grid strip past said modifying means according to a cyclic feed-rate schedule, said feeding mechanisms including first and second heads each mounted for reciprocating movement along said predetermined path, stripengaging means on each of said heads, means operative at selected intervals in said feed-rate schedule for moving said strip-engaging means into gripping engagement with said grid strip, a first cam, first and second cam followers under control of said first cam, means connecting said first follower to said first head, means connecting said second follower to said second head, and means including a second cam operatively connected to said first cam for cyclically adjusting said first cam in relation to said first Iand second cam followers to modify the feeding rates of said first and second heads as normally determined by said first cam.

33. In a grid-making machine, means along a predetermined path for modifying a grid strip, and Ifeeding mechanisms operative along said predetermined 4path for movf ing said grid strip past said modifying means according to a cyclic feed-rate schedule, said feeding mechanisms including first and second heads each' mounted for reciproeating` movement along said predeter-mined path,vstrip engaging jaws on each of said heads, means operative at selec-ted intervals -for moving said jaws toward each other and into engagement with said grid strip, a first cam, first and second cam fol-lowers mutually spaced about and under control of said rst cam, means connecting said first follower to said first head, means vconnecting said second follower to said second head, said first cam and said first and second cam followers being arranged to time 4the reciprocation of said first and second heads whereby during the return stroke of one head, the other head is driven through its feed stroke, and means -Yincluding a second cam operatively connected tojsaid first cam for axially shifting said first cam to modify the feeding rates of said first and second heads as normally determined by saidfirstcam. ,l

34. In a grid-making machine, means lalong a predetermined path for winding and securinga grid lateral about side rods in a grid strip, feeding mechanisms operative along said predetermined path for moving said grid strip past the winding and securing means according to a cyclic feed-rate schedule, said feeding mechanisms including iinst'and second feeding lheads each mounted for reciprocating movement in alternation along' sa-id predetermined path, strip-engaging jaws on each o-f said feeding heads, meansoperative during the forward feeding stroke of the respective feeding heads for closing said jaws into engagement with said grid strip, respective drive means operatively connected to said rst and second feeding heads for moving said first and second -feeding heads in alternation, a cutting head'operatively connected to said rst feeding head for reciprocation therewith; cuttingV jaws on said cutting head, means operative -in substantial synch'ronism with the closing of the jaws of said first .feeding head lfor closing said cutting jaws on said grid strip toV divide said grid strip into individual grids, said cutting jaws remaning closed during the returnY stroke of said second feeding heads to support said grid strip against deflection, a stretching head operatively connected to said second feeding head for reciprocation therewith, stretching jaws on said stretching head, means operative insubstantial synchronism with the closing of the jaws of said second feeding head for closing said stretching jaws on said grid strip, and means operatively connected to said stretching head for -moving said stretching head away from said second feeding head during the forward feeding stroke of said second feeding head.

35. A grid-forming machine including means `along a predetermined path for modifying a strip of material, and a feed mechanism for moving said strip past said modied means according to a cyclic feed rate schedule, said feeding mechanism comprising a pair of feeding heads disposed along the path of travel of saidV strip, driving mechanisms for moving said feeding heads along said path of travel in alternate relationship, strip-engaging means on each of said feed-ing heads arranged to close on said strip, a stretching head operatively connected to one of said `feeding heads, strip-engaging means on said stretching head arranged to close on saidv strip, means for closing the strip-engaging means of said stretching head on said strip while said strip-engaging means on said one feeding head is closed on said strip, and means `for moving said stretching head through a longer stroke than said onepfeeding head whilevthearespective strip-engaging means are closed to stretch said strip of material. Y Y

36. In a grid-making machine, means along Aa predetermined path Vfor modifying a grid strip of the type including side rods and a grid lateral wound about said side rod's`,"and feeding mechanisms including at least one head operative along Said 'predeterminedlvpathfor moving said grid strip past said modifying means according toa cyclic feedarate schedule, strip-engaging jaws on said head movable into engagement along the length of said Vside rods of said grid strip, said strip-engaging jaws being coustructed and arranged to cause transverse flow of the material of said side rods within the limits of said strip-en.- gaging jaws whereby said side rods are reliably gripped without elongation of said side rods, said strip-engaging jaws havingv lateral surfaces extending substantially transverse `of said side rods, there being a recess formed between said lateral surfaces for accommodating said transverse liow of the material of said side rods.

`3,7. In a grid-making machine, means along a predetermined path for modifying a grid strip of the type including side rods and -a grid lateral wound about said side rods, and feeding mechanisms operative along said predetermined path for moving said grid strip past said modifying means according toa cyclic feed-rate schedule, said feeding mechanism including .first and second heads each mounted for reciprocating movement along said predetermined path, strip-engaging means on each of said heads movable into engagement along the length of said side rods of said gri-d strip, the respective strip-engaging means being constructed and arranged to defor'm saidside rods and to cause transverse flow of the material of said side rods within the limits of the strip-engaging means whereby said side rods are reliably gripped without elongation of said rods, the strip-engaging'means on said first head including a blade deforming thermaterial of the side rods laterally, the strip-engaging means on said secondhead including jaws registering with the deformation caused by said blade. v a

38. In a machine for modifying a strip of material passing along a path of travel through said machine, means along said path for performing operations on said strip, first and second gripping heads,means operatively connected to said gripping heads for alternately reciprocating said gripping heads backv and forth'alon'g said path, movable jaws on each of said gripping heads for gripping said strip, means operatively connectedy to said jaws for alternatelyoperating said jaws to continuously draw said strip through said machine, a stretching head carried `by said second gripping head, means mounting said stretching head for movement relative to said'second gripping head, movable jaws on said stretching head, means operatively connected to the jaws of said gripping'he'ad for closing same when the jaws of said second gripping head are closed, means operatively connected between said second gripping head and said stretching head for increasing the spacing between said second gripping head and said stretching head when the jaws on the respectiveheads are closedwhereby said strip'is stretched, and means for passing a current through said 4strip during stretching, the jaws of each of said heads being constructed and formed to grip said strip without changing the length of said strip.

39. In a machine for modifying a strip of material passing along a path of travel through said machine, means along said path for performing operations on said strip, first and second gripping heads, meansoperatively connected to said gripping heads 'for alternately reciprocating said gripping heads back and forth along said path, movable jaws on each of said gripping heads for gripping said strip, means operatively connected to said jaws for alternately operating said jaws to continuously draw said strip through said machine, a stretching Ihead carried by said second gripping head, means mounting said stretching head for movement relative to said second gripping head, movable jaws on saidstretching head, means operatively connected to the jaws of said gripping head for closing same when the jaws of said second grippinghead are closed, means operatively connected between .said second gripping head rand said stretching 'head 4for increasing the spacing between said second gripping head and said stretching head when the jaws on the respective 17 heads are closed whereby said strip is stretched, and means for heating said strip as said strip is stretched.

40. A machine comprising strip material feeding mechanisms including first and second feeding heads each mounted for reciprocating movement along the line of travel of said strip material through said machine, each of said feeding heads including a movable jaw having a blade provided with lateral surfaces substantially per pendicular to said line of travel and pressure pads ilanking said blade and abutting said lateral surfaces, and a fixed jaw including a back-up member cooperating with said pressure pads and a spring-mounted stripper member depressible to accommodate lateral ow of said strip material, the blade of said second feeding head being arranged to register in the depression formed in said strip material by 4the blade of said first feeding head.

41. A machine comprising strip material feeding mechanisms including sequentially effective first and second feeding heads each mounted for reciprocating movement along the line of travel of said strip material through said machine, each of said feeding heads including a movable jaw having a blade provided with lateral surfaces substantially perpendicular to said line of travel and edges arranged to penetrate said strip material, said blade being formed with a recess between said edges for accommodating transverse flow of said strip material, pressure pads flanking said blade and abutting said lateral surfaces, and a fixed jaw including a back-up member cooperating with said movable jaw, the edges of the 18 blade of said second feeding head being arranged to penetrate said strip material at points outwardly of the points of penetration of the edges of the blade of said rst feeding head whereby the transverse ow of strip material brought about by gripping of said second feeding head takes place into depressions formed by said first feeding head.

42. In a grid-making machine, means along a predetermined path for modifying a grid strip, feeding mechanisms operative along said predetermined path for moving said grid strip past said modifying means according to a cyclic feed-rate schedule, rotary lead cam means in a normal operative position, driving connection including cam followers between said lead cam means and said feeding mechanisms for mo'ving said feeding mechanisms, means for mounting said rotary lead cam means for movement relative to said normal operative position, additional cam means, and additional driving connections between said lead cam means and said additional cam means whereby said additional cam means shifts said lead cam means for cyclically modifying the feed rate that would otherwise be affected by said lead cam means,

References Cited in the file of this patent UNITED STATES PATENTS