US3431613A - Sheet material forming machine - Google Patents

Description

Mar h 1969 E. o. ACKER, 5a.. ETAL SHEET MATERIAL FORMING MACHINE Sheet Filed April 17, 1967 AUX/L/AQY VAR/A54 E' OP/ V5 MAIN W i CIT-E S we K m xx 5 m3 w 040 r f 4 5W P M 0 6? Y B Mar 1969 E. o. ACKER, SR.. ETAL 3,431,513

SHEET MATERIAL FORMING MACHINE Sheet Filed April 17, 1967 z-llllllllylllllllllll /@2 /54 a ZNVENTORS EQC 0 Acme 5 few 0, ACKF/Q 5 By POA/ALQ l l/a Acme? 5 5D OQ/VEYS March 11, 1969 E. o. ACKER, sR., ETAL 3,431,613

SHEET MATERIAL FORMING MACHINE Sheet Z of Filed April 17, 1967 CL 07' C H CO/UTPOL E'LL CTPO- MAGNET/C CL UTCH fiEIEr-E TLELEJ f .L E. i i

o INVENTORS 59/6 0. ACKEP 6K2, EQ/"C 0 Aczae L/Q. BY Pox/4L0 m AMA 5e 2as fl zee L3 ifa I J. GL2

ABSTRACT OF THE DISCLOSURE An apparatus for the expansion of sheet material which operates upon sheet stock as it is continually fed to a vertically movable slitting bar which makes a series of diagonally off-set slits across the sheet material; thereafter, the slitted sheet material is stretched at a controlled rate and a tension responsive Wind-up mechanism is employed for finally rolling up the open-mesh material at uniform winding force.

BACKGROUND OF THE INVENTION Field of the invention The invention relates generally to sheet material forming machines and, more particularly, but not by way of limitation, it relates to improved slitting and stretching apparatus for forming open-mesh material from continuous sheet material.

Description of the prior art The prior art includes various types of forming machines wherein initially inserted sheet material is slit or cut and then a subsequent expanding operation is employed to fabricate a form of screen material. Many types of functional and decorative sheet materials are formed in this manner and the mode of formation, i.e., the manner of cutting, elongating, etc., may take various forms. These prior machines have been primarily intended for usage with heavier gauge sheet material to form mesh or lathe panels having relatively high stiffness and rigidity characteristics such that the finished material is handled in sheet form or methods kindred thereto. One of the shortcomings among the prior art disclosures is the absence of slitting and expanding methods and apparatus for forming relatively light, thin gauge sheet material into highly flexible mesh material in a uniform manner with a. minimum of bending and tearing of the finished mesh material.

SUMMARY OF THE INVENTION The present invention contemplates a slitting and expanding forming machine which may be utilized with very thin sheet material to perform a relatively delicate slitting and expanding operation. In a more limited aspect, the invention consists of apparatus for intermittently feeding the sheet material to a slitting position whereupon a novel sliting device, consisting of two, spaced and parallel slitting dies each having a plurality of slitting edges, is reciprocataed vertically at a synchronized rate to make transverse rows of plural slits in the sheet material. Thereafter, the slitted material is passed over a series of rotating rollers under varying tensions and with increasing speed to expand the material by a predetermined amount. The expanded material having selected mesh size and characteristics is then wound-up by a tension sensitive device so that a uniform quantity of open-mesh material is stored on each wind-up roll.

Therefore, it is an object of the present invention to provide a forming machine which may operate upon very 3,431,613 Patented Mar. 11, 1969 thin sheet material to produce a finished mesh material having highly uniform screen characteristics.

It is also an object of the invention to provide a device wherein the degree of stretching or expansion of slitted sheet material is easily controllable by adjusting the differential speed of consecutive rollers,

It is a further object of the present invention to provide apparatus which is capable of expanding thin material of very light substance.

Finally, it is an object of this invention to provide apparatus for forming mesh material through slitting and stretching of sheet material wherein various screen characteristics such as strand size and mesh size can be easily and accurately controlled.

Other objects and advantages of the invention will be evident from the following detailed description when read in conjunction with the accompanying drawings which illustrate the invention.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a functional plan drawing of the present invention;

FIG. 2 is a partial front view of slitting apparatus constructed in accordance with the present invention;

FIG. 3 is a vertical view taken along line 3-3 of FIG. 2;

FIG. 4 is a right-side end view of the FIG. 2 slitting apparatus;

FIG. 5 is a left-side end view as derived from the vertical section taken along lines 5-5 of FIG. 2;

FIG. 6 is a section taken along lines 6-6 of FIG. 2 showing selected timing gear apparatus; a

FIG. 7 is an enlarged sectional view of the slitting device as shown in FIG. 3 which better illustrates a form of sheet material slitting dies;

FIG. 8 is a front view of a portion of the slitting fixtures as shown in FIG. 7;.

FIG. 9 is a pictorial block diagram partially in perspective to illustrate the stretching and wind-up apparatus of the present invention;

FIG. 10 illustrates a section of the slitted sheet material prior to any stretching or wind-up operation;

FIG. 11 illustrates the expanded sheet material after it has been subjected to controlled stretching and wind-up in accordance with the present invention; and

FIG. 12 illustrates in enlarged section an alternative form of slitting die and stripper assembly which may be employed in the forming machine.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 depicts the overall sheet material forming machine 10 which accepts input sheet material of varying weight and substance to form an expanded mesh material. Input material may be selected from various classes of sheet material such as metal foil, plastic sheeting, etc. The material is applied in roll form, such as supply roll 12, and it is maintained on a supply roll axle or support 14 of suitable type. The continuous input material 16 is then fed into a pair of feed rolls 18 and 20 which serve to supply the sheet material 16 to the slitting position 22 at a selected intermittent rate.

The lower roller 18 is a synchronously driven roller and the upper roller 20 is a spring tensioned roller which maintains the sheet material 16 in firm contact with the abiding tangent surface of lower roller 18 such that the sheet material is continuously fed into the slitting position 22. Lower roller 18 is intermittently rotated in synchronism with the slitting apparatus as will be further described.

The slitting position 22 consists of an upper bar 24 which carries a slitting device 26 and it is reciprocally driven vertically to effect successive slitting operations on each down stroke. Vertical reciprocation is effected by a main drive 28 acting through a drive linkage 30. Underneath the sheet material 16 a lower bar 32 supports a stripping assembly 34 for coaction with the slitting device 26 immediately above.

The slitted sheet material 36 emerges continuously (intermittently) from the slitting station 22 to be snubbed around a tensioning bar 38 and then to be led upward and around a constant speed roller 40. The constant speed roller 40 is driven by an auxiliary drive 42 which may consist of a small electric motor providing a rotary drive output 44 and a rubber roller 46 to impart an even, relatively slow speed to the constant speed roller 40.

The slitted material 36 is then taken from the constant speed roller 40 and passed around a stretching roller 48 which is rotated at a selected increased speed as controlled by a variable drive 50 and drive linkage 52. The amount of expansion effected is directly related to the speed increase as caused by the speed of stretch roller 48. The expanded sheet material is then rolled up on a windup roll 54 which is controlled by a constant tension device. Thus, the wind-up roller 54 is driven via a linkage 56 from a tension responsive drive 58 (as will be further described) which can be preadjusted to effect wind-up of the expanded material only within a selected tension limit.

Referring now to FIG. 2 and related figures, the apparatus which is situated in and about the slitting position 22 is rigidly mounted upon a frame plate 60 and various forms of side supporting may be used. For example, vertical side support plates 62 and 64 may be employed along with an outer support plate 66 for supporting certain additional rotary elements as will be described. The main drive 28 (FIG. 1) of the forming machine may be such as a five horsepower electrical motor and it may be mounted with other control and translation equipment in a lower compartment 68 below the main supporting frame plate 60.

Main drive input is provided from the lower compartment 68 by means of an endless belt 70 driving a pulley 72 which turns on a pulley shaft 74 that is suitably journaled in vertical frame plate 62. A second, parallel-disposed pulley wheel 76 is also aflixed to rotate with pulley shaft 74, pulley wheel 76 having a reduced radius from that of pulley wheel 72, and it serves to translate drive energy via a linking endless belt 78 which drives a pulley wheel 80 affixed to a main drive shaft 82 to impart drive rotation thereto. An idler pulley 84 is adjustably secured to the vertical frame plate 62 to control the tension of the endless belt 78.

The main drive shaft 82 extends between the vertical frame plates 62 and 64 through respective journal bearings 84 and 86. A pair of eccentric discs or cam wheels 88 and 90 are rigidly secured to main drive shaft 82 in equi-spaced symmetrical relationship. A pair of bearing blocks or pads 92 and 94 are rigidly secured to the upper surface of the ram or upper bar 24. The pads 92 and 94 are positioned beneath the respective cam wheels 88 and 90 and have respective slot- ways 96 and 98 which provide a good bearing surface for contacting cam wheels 88 and 90.

The upper bar 24 and pads 92 and 94 are maintained upwardly biased at all times due to spring and guide elements 97 and 99 which are situated on each side. That is, referring to FIGS. 4 and 5, the right side of upper bar 24, shaped as an outer extension 100, is rigidly secured above an upper guide plate 102 having vertically aligned holes 104 and 106 disposed therein. Upper guide block 102 is formed to have a cutout portion 108 on its under side for retaining a compression spring 110. The lower end of compression spring 110 is secured centrally on a lower guide block 112 which is secured to the frame plate 60. A pair of guide pins 114 and 116 are secured in vertically upright relationship to said lower guide block 112 to extend through the respective holes 1 4 104 and 106 in the upper guide block 102, thereby to maintain the upward force on upper bar 24 vertically directional.

Similarly, and referring largely to FIG. 5, the left side of the upper bar 24 is constructed in similar manner. Upper bar 24 is formed with an outer extension 120 rigidly secured atop an upper guide block 122 having spaced, parallel-disposed vertical holes 124 and 126, respectively. A compression spring 128 is retained between a cut-out receptacle 130 in the underside of guide block 122 and a lower guide block 132; guide block 132 extends a pair of rigidly afiixed guide pins 134 and 136 upwardly through the respective guide holes 124 and 126 in the upper guide block 122. Suitable adjustment means may be provided with the compression springs 110 and 128 so that the apparatus can be set with a balanced upward bias of the upper bar 24 and bearing pads 92 and 94 against the respective cam wheels 88 and 90.

Drive of an intermittent nature is applied to the driven feed roll 18 and it is derived from the main drive shaft 82, synchronism of action being maintained as will be further described. Referring to FIGS. 2, 5 and 6, a sprocket 140 is rigidly secured to the left-hand end of main drive shaft 82 to drive an endless chain 142 to transfer rotary motion to a sprocket 144 which is rigidly secured to shaft 146 journaled between the vertical frame plate 64 and the outer plate 66. An idler sprocket 148 is adjustably secured on the vertical frame plate 64 to maintain proper tension in the endless chain 144.

The shaft 146 is secured to a cam wheel 150 which is driven rotationally to impart drive motion to an indexing clutch 152. Referring to FIG. 6, the indexing clutch 152 is secured to a drive shaft 154 which is journaled between the vertical frame plate 64 and the outer frame plate 66. The indexing clutch 152 extends an arm 156 which has a cam follower 158 rotationally mounted thereon. The rotation of shaft 146 and cam wheel 150 then cause reciprocal movement of arm 156 and cam follower 158, as shown by arrow 160, and this action is translated by indexing clutch 152 to impart an intermittent clockwise movement to the shaft 154. That is, positive drive is imparted as increasing girth of cam wheel 150 approaches cam follower 158 to force it downward. A retaining spring 162 is suitably afiixed between the arm 156 and a suitable support such as bar 164 to maintain the cam follower 158 in contact with the cam wheel 150.

A particular type of indexing clutch 152 which has been found preferable is a sprag-type clutch which is commercially available from the Formsprag Company of Warren, Mich. The technical disclosure of this type of clutch as employed in a similar machine application may be found in US. Patent No. 3,216,083 entitled Metal Forming Machine.

Referring to FIG. 5, a drive gear 166 is secured at the inner end of shaft 154 such that its intermittent clockwise rotation is transferred to a larger gear 168 as an intermittent counterclockwise motion. The counterclockwise movement of gear 168 is then transmitted to its shaft 170 which extends through vertical frame plate 64 into rigid connection with feed roll 18. The shaft 170 may actually be an integral extension of feed roll 18 as it is rotatably secured within vertical frame plates 62 and 64.

Thus, rotary motion from main drive shaft 82 via chain 142 is translated by indexing clutch 152 into an intermittent rotational motion along shaft 154, gears 166 and 168, and input shaft 170 to drive the feed roll 18. The sizes of the respective sprockets and gears in the drive link is selected so that the input sheet material will be advanced a predetermined amount between each slitting depression of upper bar 24. This control of the advance of input material dictates the width between pairs of slit rows (as will be further described below) and, therefore, the size and character of the expanded material.

The upper feed roll 20 is freely rotating and is merely maintained in pressing relationship against the input material and driven roller 18. Thus, upper feed roller 20 is freely rotatable uon shafts 172 or such as retained in respective pivotal braces 174 and 176. As shown in FIG. 3, the left side brace 176 is rotatable about a pin 178 journaled in vertical frame plate 164 and a spring 180 suitably secured at a rearward position maintains a downward pressure on feed roller 20 against the driven feed roll 18. Similarly, the right side frame 174 is rotatable about a pin 182 and downward tension is maintained by a spring 184.

FIGS. 7 and 8 show the general arrangement of upper bar 24 and lower bar 32 at the slitting position 22. The upper bar 24 is formed in generally rectangular cross section to extend a vertical projection 190 downward along its rearward edge. The projection 190' exposes a flat, vertical face 192 for receiving a pair of slitting dies 194 and 196 in secure vertical positioning therealong. A spacer bar 198 is extended between the slitting dies 194 and 196 and a series of securing bolts 200 provide rigid fastening. The forward slitting die 194 has its lower edge formed with a plurality of slitting edges 202, each of which is slightly beveled forward. The rearward slitting die 196 has equally sized but alternately disposed (laterally shifted) slitting blades 204 which are oppositely beveled rearward.

A passive or stationary spacer die 206 is then secured in an upward projection 208 of the lower bar 32. The spacer die 206 is merely a rectangularly shaped straight edge of the same width as the spacer bar 198 so that depression of upper bar 24 moves the forward and rearward slitting dies 194 and 196 on each side of spacer die 206 in close sliding or shearing relationship. A stripper plate 210 is suitably mounted on a plurality of springs 212 and guide pins 214 along a retaining bar 216 which is secured on shoulder portion 128 of the lower bar 32. The stripper bar 210 extends slightly above the top of the spacer die 206 when at its rest position and it is depressible by at least the distance of overlap of forward slitting die 202 upon spacer die 206 at the point of downward depression of upper bar 24. The retaining bar 216 and lower slitting bar 206 may be secured in position by a plurality of threaded fasteners 220 spaced thereacross. The spring and retaining assembly may be of any conventional construction, for example, the retaining bar 216 may be a U-shaped, inverted member extending bolts 214 upward therethrough into tight threaded engagement in stripper bar 210, springs 212 providing resilient support to stripper bar 210.

The slitted sheet material has the appearance of the section of material in FIG. 10 and, after stretching and wind-up as depicted in FIG. 9, it would have the openrnesh appearance as seen in FIG. 11. Thus, each slitting movement or downward traverse of upper bar 24 results in a pair of spaced slit rows 230 and 232, which consists of rows of serially arranged slits 234 and alternately spaced slits 236, respectively. Connecting lateral spaces 238 of generally equal measure are left between each of the successive slits 234 and 236. Each row of slits 230 and 232 are sequentially spaced a selected distance 239 and an equal distance 240 is interposed between adjacent pairs 242 of slitted rows 230 and 232. The spacing of distances 239 and 240 determines the strand width and thus a predominant characteristic of the mesh pattern.

As shown in FIG. 11, the expended material is stretched into an open-mesh sheeting wherein each individual slit 234 or 236 (FIG. 10) is pulled open by a predetermined amount to form an expanded material made up of spaces 238 and diagonal strands 244 which outline a continuous plurality of diamond-shaped openings 246. 1

Referring to FIG. 9, the slitted sheet material as moved from slitting position 22 is passed under a snubber or tensioning bar 38 and upward over the constant speed roller 40. Constant speed roller 40 is driven by an auxiliary drive 42 which consists of a small electric motor 250 which provides rotational drive on a shaft 252 to a' rubber roller 46 in driving engagement about the surface of constant speed roller 40. The rotational speed of shaft 252 and the size of rubber roller 46 are selected to provide a predetermined surface velocity to the constant speed roller 40. This speed is selected to be approximately the same as the speed at which the slitted sheet material 36 emerges from the slitting position 22.

The slitted material 36 is then passed down around a stretch roller 48 which is rotated at a surface speed which is some selected multiple of that surface speed of constant speed roller 40*. The stretching roller 48 is driven at a selected speed by means of the rotational drive linkage 52 from variable drive 50. Variable drive '50 consists of a D-C motor 254 driving via a mechanical linkage 256 into an associated gear box 258 which provides the rotational output linkage 52. The D-C motor 254 may be controlled by means of speed control 260. One form of variable drive 50 which has been found suitable in this application is the unit known as the Polyspede unit which is commercially available from Power Engineering, Inc., of Dallas, Tex. This assembly consists of a .4 horsepower DC motor which is variable within a wide range of rotational output speeds as realized from its associated gearbox.

The wind-up roller 54 stores the expanded or stretched sheet material 36 under control of the tension responsive drive 58. Tension responsive drive 58 consists of an A-C motor 262 connected via drive linkage 264 to an associated gear box 266, motor 262 and gear box 266 actually constitute what is known as a 60 cycle A-C gear-head motor. The output from gearbox 266 is then provided via rotational linkage 268 to an electromagnetic clutch 270 which, in turn, provides its engaged or positive output on rotational linkage 56 to the wind-up roll 54. A clutch control 272, which is merely a current control, is applied via leads 274 to control the electromagnetic clutch 270 That is, clutch control 272 controls the amount of tension within which electromagnetic clutch 270 will operate, the clutch tending to disengage when exceeding the preset limit. The tension responsive drive 58 may be a commercially available unit known as the Magni-clutch which is manufactured by Vickers, Incorporated, the Electric Products Division, of St. Louis, Mo.

In some applications it may be desirable to include a cork sleeve (not shown) about the stretch roller 48 and/or the constant speed roller 40. This pro-vision of cork about the surfaces tends to provide better gripping of the slitted material 36 about the respective rollers at correspondingly decreased linear tensions. As particularly applied to stretch roller 48, when operating with certain sheet materials, a cork sleeve applied about the roller 48 and only about the center point of contact with the sheet material tends to maintain uniform material stretching across the strip or sheet of slitted material. In effect, this causes a bowed stretching roll.

FIG. 12 depicts an alternative form of slitting device 280 which may be secured in shearing alignment between upper bar 24 and a stationary lower bar 32a. The device 280 employs a similar pair of slitting dies 194 and 196 secured in spaced, parallel relationship on each side of spacer bar 198. However, the lower part of the assembly consists of two stripper bars 282 and 284 resiliently mounted on each side of the spacer die 206. Each of stripper bars 282 and 284 are retained on a respective plurality of leader pins 286 and 288 as supported by springs 290 and 292 on respective retaining bars 294 and 296. Retaining bars 294 and 296 are then secured along with spacer die 206 across the upper surface of lower bar 32a.

This form of slitting apparatus, slitting device 280, is especially useful when operating upon the more brittle types of sheet material to perform serial slitting of precise nature. Thus, input sheet material such as very fine gauge silver, plastics, etc. can be slit with small strand widths such that the stretched, finished material can have very minute, uniform mesh characteristics.

OPERATION The following operational description is carried out with reference to FIG. 1 and other figures at noted. While any of various sheet materials may be supplied as input to the forming machine, the present description proceeds with reference to the treatment of very light gauge metal foil to form open-mesh material similar to that used in air filters.

A bulk roll 12 of the sheet material 16 is operatively positioned to unwind through the feed rolls 18 and 20 into the slitting position 22 of the forming machine 10. The upper feed roll 20- is spring-tensioned against the sheet material 16 and the lower feed roller 18 is synchronously driven at a controlled rate to intermittently insert a predetermined length of sheet material 16 into the slitting position 22. Slitting position 22 includes a ram or upper bar 24 which is vertically reciprocated relative to a lower bar 32 to perform the slitting function.

Referring to FIG. 8, it can be seen that the two slitting dies 194 and 196 have respective slitting edges 202 and 204 which are laterally offset from each other and, that when the upper 'bar 24 is moved a certain distance downward, the rows of slitting edges 202 and 204 can be brought partially down over the upper edge of spacer die 206 (FIG. 7) in shearing relationship to place two rows 230 and 232 of discontinuous slits 234 and 236, respectively, in staggered relationship across the sheet material as shown in FIG. 10.

After the upper bar 24 is with-drawn or reciprocated upward and stripper bar 210 (FIG. 7) urges the sheet material upward and free of the spacer die 206, the feed roll 18 advances the sheet material past the slitting position 22 by another predetermined space which will determine the next ensuing space or distance (strand determination) between consecutive pairs of slit rows 242 (see FIG. 10). Thus, the size of each alternate strand between pairs of slit rows 242 on the slitted sheet material 36 is determined by the intermittent advance caused by driven feed roll 18, while the size of the intersticed strands between individual slit rows 230 and 232 is determined by the thickness of spacer bar 198 (and spacer die 206).

As shown in FIG. 4, main drive applied to pulley 80 is transferred to main drive shaft 82 which carries the main drive cams 88 and 90 (FIGS. 2 and 3). The cams 88 and 90 ride on the pads 92 and 94 and tend to drive the upper bar 24 downward against spring force upon each rotation of main drive shaft 82. This same rotation from main drive shaft 82 is taken off via sprocket 140 (FIG. on the left-hand side of the machine and transmitted by drive chain 142 to a sprocket 144 which provides synchronized drive to the lower feed roll 18. This rotation of sprocket 144 is transmitted along a shaft 146 whereupon another cam 150 (FIG. 6) is driven to reciprocate the cam follower 158 and arm 156 of the sprag-type clutch 152 to impart intermittent clockwise rotation to shaft 154.

It may be noted that each rotation of main drive shaft 82, and therefore each complete slitting cycle of upper bar 24, is accompanied by a complete cycle of sprocket 144, and therefore shaft 146 and cam 150, such that a single segment of advance or ratchet movement of shaft 154 will be applied through gear 168 to the lower feed roll 18. Note too that the movement of lower feed roll 18, the upward release of cam roller 158 and arm 156 of FIG. 6, takes place during the upward excursion of cams 88 and 90 on main drive shaft 82.

Referring now to FIG. 9, the slitted sheet material 36 emerging from the slitting position 22 is passed under tensioning bar 38 and then around a, constant speed roller 40. The constant speed roller 40 while being of metalic surface still maintains enough area of contact such that the slitted sheet material 36 grips sufficiently thereabout. Slight slippage is of no importance and is counteracted in the final stretching and Wind-up stages. The slight slippage about constant speed roller 40 merely tends to maintain a desirable tension along the preceding expanse of sheet material 36 back to the slitting position 22.

The slitted sheet material 36 is then taken off of constant speed roller 40 and wrapped around a stretch roller 48 which is driven at a much higher rate of speed than constant speed roller 40 to thereby expand or stretch the slitted sheet material 36 by some predetermined amount. This is effected by adjusting speed control 260 such that D-C motor 254, gear box 258 and drive linkage 252 rotate the stretch roller 48 such that its surface speed or peripheral rotation is some multiple, e.g., four times, that of the constant speed roller 40. Such a speed differential would result in approximately 400 percent stretch of the slitted sheet material 36.

As shown in FIG. 11, the stretched sheet material 36 is elongated to form a mesh material having a continuous, interlocked pattern of diamond-shaped openings 246. The material forms these openings 246 as outlined by the diagonal strands 244 which are interconnected at each of the continuous, quadrature-arrayed spaces 238. The strand width can be varied by (a) adjustment of the width of spacer die 206 and spacer bar 198, this changing alternate strand row width (e.g., strands 239 of FIG. 10), and (b) adjustment of the indexing assembly or drive to feed roll 18 such that the amount of input sheet material per single advance is changed to set the size of the remaining strands 240.

The stretched and slitted sheet material 36 is then taken from the stretch roller 48 to the wind-up roll 54 where finished rolls are provided for shipment, further processing, or whatever. The wind-up roll 54 is tension responsive and its rotation is controlled by a tension responsive device 58. The tension responsive device 58 consists of an adjustable electromagnetic clutch inserted in the drive linkage 56 such that winding forces in excess of a certain limit will stop the rotary force delivered on linkage 56 and stall the wind-up action of Wind-up reel 54. This is only a momentary condition since further feeding of slitted sheet material 36 lessens the tension below the threshold point such that clutch control 272 can once again energize electromagnetic clutch 270 to impart rotation within the desired tension limits to the wind-up roll 54.

This type of wind-up control is extremely valuable in insuring that the mesh characteristics of stretched sheet material are all even throughout the finished roll of stretched material. Thus, when utilizing constant tension wind-up there is no danger that the shorter radius inner windings will be of different tension, tending to smash or distort the stretched sheet material, and the mesh or screen characteristics can be maintained very even throughout the whole extent of slitted sheet material 36 as it is stretched and wound on wind-up roll 54.

The foregoing discloses novel features of an improved sheet material forming machine which enable formation of mesh material, having highly controllable and accurate characteristics, from sheet material of very light gauge or fine substance. The invention discloses specific slitting apparatus which may perform serial slitting in transverse, discontinuous rows and this operation can be performed on relatively fragile or light gauge sheet material without tearing or unnecessarily crimping the finished output ma terial. The present disclosure also sets forth means whereby such delicate slitted sheet material can be expanded or stretched evenly and wound up under constant tension such that the whole of the reel-stored finish material will have similar mesh characteristics.

Changes may be made in the combination and arrangement of elements as heretofore set forth in the specification and shown in the drawings, it being understood that changes may be made in the embodiments disclosed without departing from the spirit and scope of. the invention as defined in the following claims.

We claim:

1. A machine for forming continuous open-mesh material from sheet material comprising:

means for supplying sheet material;

slitting means for receiving said sheet material and repeatedly placing a transverse array of .slits therein, said array of slits being formed as two spaced rows of discontinuous slits;

first roller means receiving the slitted sheet material from said slitting means and moving it at a first speed;

second roller means receiving the slitted sheet material from the first roller means and moving it at a second speed which is greater than said first speed to stretch the sheet material into a continuous open-mesh ma terial;

wind-up means receiving the open-mesh sheet material from said second roller means; and

tension responsive means controlling the speed of said wind-up means such that it is inoperative when the tension of said open-mesh material exceeds a predetermined force.

2. A machine as set forth in claim 1 wherein said means for supplying comprises:

means holding a supply of sheet material;

first roller means receiving said sheet material thereacross;

second roller means positioned to be placed over said sheet material to bear thereon against said first feedroller means; and

means for driving said first feed roller means in intermittent rotation to supply said sheet material in incremental advances.

3. A machine as set forth in claim 1 wherein said slitting means comprises:

lower bar means positioned transverse to and beneath said sheet material;

upper bar means vertically movably positioned lel to and above said lower bar means;

a pair of slitting dies secured to the under side of said upper bar means;

a spacer die secured to the upper side of said lower bar means in shearing alignment with said slitting dies; and

means for driving said upper bar means in vertically reciprocal motion.

4. A machine as set forth in claim 3 wherein said means for supplying sheet material comprises:

means holding a supply of sheet material;

first feed roller means receiving said sheet material thereacross;

second feed roller means positioned to be placed over said sheet material to bear thereon against said first feed roller means; and

means for driving said first feed roller means in inter mittent rotation to supply said sheet material in incremental advances.

5. A machine as set forth in claim 4 which is further characterized to include:

indexing clutch means connected to supply intermittent rotational output to said first feed roll means; I

means driven in synchronism with said vertically reciprocating drive means for supplying rotational input drive to said indexing clutch means in synchronism 'with the reciprocation of said upper bar means.

6. A machine as set forth in claim 1 wherein said tension responsive means comprises:

drive means providing rotational output;

electromagnetic clutch means receiving said first rotational output and providing a second rotational output to said wind-up means; and

paral- 7 means for applying electrical current to said clutch means.

7. A machine as set forth in claim 3 \wherein said tension responsive means comprises:

drive means providing rotational output;

electromagnetic clutch means receiving said first rotational output and providing a second rotational output to said wind-up means; and

means for applying electrical current to said clutch means.

8. A machine as set forth in claim 1 wherein said second roller means comprises:

stretch roller means:

means providing rotational drive input to said stretch roller means;

means for controlling the speed of said rotational drive input.

9. A machine as set forth in claim 7 wherein said second roller means comprises:

stretch roller means;

means providing rotational drive input to said stretch roller means;

means for controlling the speed of said rotational drive input.

10. A sheet material forming machine, comprising:

a slitting position;

a means continually feeding sheet material to said slitting position;

a first slitting bar means mounted securely to extend across said slitting position and beneath the path of said continually fed sheet material;

a second slitting bar means movably mounted above said sheet material and parallel to said first slitting bar;

drive means for periodically moving said second slitting bar means into discontinuous contact with said first slitting bar means to make a predetermined array of slits through said sheet material;

first roller means moving at a first rotational speed for receiving the slitted sheet material as it emerges from said slitting position;

second roller means moving at a second increased rotational speed and receiving the slitted sheet material therearound such that material leaving the roll is of mesh-like form;

third roller means for receiving and rolling up said sheet material in mesh-like form; and

second drive means connected to rotate said third roller means, said second drive means being tension responsive such that it shuts off with greater than a predetermined tension upon said mesh-like sheet material.

11. A sheet material forming machine as set forth in claim 10 wherein said first and second slitting bar means comprise:

spacer die means secured to said first slitting bar means immediately beneath the path of said continually fed sheet material;

a pair of slitting dies secured to said second slitting bar means transverse to said sheet material and parallel to said spacer die means in shearing alignment.

12. The sheet material forming machine as set forth in claim 11 which is further characterized to include:

stripper means secured along said first slitting bar means and adjacent to the leading edge of said spacer die means.

13. A sheet material forming machine as set forth in claim 10 wherein said drive means comprises:

main drive shaft means supported parallel to and above said second slitting bar means;

cam means secured to rotate with said main drive shaft means in peripheral contact with said second slitting bar means; and

means for providing rotational drive input to said main drive shaft means.

1-4. A sheet material forming machine as set forth in claim 13 which is further characterized to include:

means transmitting rotational drive from said main drive shaft means; indexing clutch means receiving said transmitted rotational drive and providing intermittent rotational output drive; and means connecting said intermittent rotational drive to said means continually feeding sheet material such that said sheet material is introduced to the slitting position in synchronism with the rotation of said main drive shaft means and thus the movement of said second slitting bar means. 15. A sheet material forming machine as set forth in claim 10 wherein said second roller means comprises:

stretch roller means; drive means imparting rotational drive to said stretch roller means; and means for adjusting the speed of said rotational drive. 16. A sheet material forming machine as set forth in claim 10 wherein said second drive means comprises:

motor means providing rotational output; clutch means receiving said rotational output and transmitting rotational output to said third roller means; and tension responsive means controlling said clutch means. 17. A sheet material forming machine as set forth in 5 claim 12 which is further characterized to include:

second stripper means secured along said first slitting bar means and adjacent to the trailing edge of said spacer die means.

18. A sheet material forming machine as set forth in claim 17 wherein said stripper means each comprise:

a stripper bar disposed adjacent the cutting edge of said spacer die means; and

spring means secured to said first slitting bar means and connected to hold said stripper bar so disposed such that said stripper bar can be resiliently dis- I placed along said spacer die cutting edge.

References Cited UNITED STATES PATENTS 3,280,446 10/1966 Borello 296.2

RICHARD- H. EANES, 111., Primary Examiner.

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