US2729270A - Pressure sealing apparatus - Google Patents

Description

D. E. PRENVEILLE ETAL PRESSURE SEALING APPARATUS Filed March 24, 1954 5 Sheets-Sheet l FIE 1 o I4| o 2 207 IF'IE 2 INVENTORS DONALD E. PRENVEILLE ALVIN H. STORCH, JR.

ATTORNEY Jan. 3, 1956 D. E. PRENVEILLE ET AL 2,729,270

PRESSURE SEALING APPARATUS Filed March 24, 1954 5 Sheets-Sheet 2 IE'IE EI INVENTORS DONALD E. PRENVEILLE ALVIN H. STORCH, JR.

BY A a/ow 1 ATTORNEY Jan. 3, 1956 b. E. PRENVEILLE ETAL 2,729,270

PRESSURE SEALING APPARATUS 5 Sheets-Sheet 4 Filed March 24, 1954 INVENTORS DONALD E. PRENVEILLE ALVIN H. STORCH, JR.

ATTORNEY Jan. 3, 1956 D. E. PRENVEILLE ETAL 0 PRESSURE SEALING APPARATUS Filed March 24, 1954 5 Sheets-Sheet 5 as )IZQ zls F'IE: E

INVENTORS DONALD E. PRENVEILLE ALVIN H. STORGH,JR.

United States Patent PRESSURE SEALING APPARATUS Application March 24, 1954, Serial No. 418,438 22 Claims. (Cl. 1s4 4z This invention relates to machines for fabricating articles such as bags by uniting sheets composed of or coated with pressure sensitive material, and more particularly to apparatus for applying pressure to such sheets to seal them together.

An object of the invention is to provide novel means for applying pressure to sheet material in performing a sealing operation thereon.

Many of the plastic sheet materials now commonly employed in the manufacture of bags, require control within relatively narrow limits, of the pressure with which they are engaged by sealing members such as the pressure shoes of a bag making machine. This is particularly true in the case of heated sealing shoes used in forming bags by welding together sheets of a thermo-setting plastic such as Vinylite or polyethylene.

it is, therefore, another object of the present invention to provide actuating means, for bag making pressure shoes, adapted to automatically exerta force of predetermined magnitude in applying a pressure shoe to the sheet material.

Another object is to provide heated pressure shoe actuating means regulable to permit predetermination within close limits of the pressure exerted by the same.

Another object is the provision of actuating mechanism for a pressure-sealing shoe, characterized by uniformity in the force exerted by the mechanism throughout the entire range of movement of the same.

Another object is to provide means for adjusting the pressure shoe actuating mechanism over a range sufiiciently wide to adapt it for use in connection with scalable materials whose optimum sealing pressures differ from one another to a considerable extent.

Other objects and advantageous features of the invention will become apparent from the following description and the drawings in which: 7

Figure 1 is a plan of a bag forming machine employing pressure shoe actuating means constructed in accordance with the present invention.

Figure 2 is a side elevation chine of Fig. 1.

Figure 3 is an enlarged fragmentary section taken along the line 33 of Fig. 1.

Figure 4 is a fragmentary perspective of one of the longitudinal sealing members and the actuating mechanism therefor viewed in the direction of the arrow 4 of Fig. 1.

Figure 5 is an elevation, partly broken away, of the transverse sealing member and the actuating mechanism therefor, taken along the line 55 of Fig. 1.

Figure 6 is a diagrammatic perspective of the machine of Figs. 1 and 2.

Figure 7 is an enlarged fragmentary perspective detail view.

Figure 8 is a diagram of the compressed air supply and regulating system.

The inveniton contemplates actuating mechanism for the pressure shoes of a machine for fabricating articles from of the bag forming ma verse sealing means to seal the gears 25 and 26, 25a and 26a (Figs. 5 and 6) for 12, so that the web pressure sensitive sheets, and is illustrated for exemplary purposes in operative association with a machine for fabricating bags from two superimposed, continuous Webs of sheet material by welding the sheets together along appropriately positioned seam lines and, upon completion of the requisite seam or seams, shearing the webs to sever the completed bag from its parent stock. The stock may be of flattened tubular form, presenting bag stock comprising two plies integrally joined along both lateral edges, in which case it is necessary only to provide transplies together along the line corresponding to the bottom of each completed bag. Alternatively, two separate sheets of parent stock may be used, requiring, in addition to the end-defining transverse seal, two longitudinal seals having their web-engaging portions spaced apart by a distance corresponding to the width of the completed bags, and whose function it is to seal the lateral edges of the bags. The stock may be composed of, or may be coated with, a suitable pressure sensitive material; and if this material is of the thermo-setting variety, such as Vinylite or polyethylene, the plies can readily be caused to adhere to each other along the desired seam lines, and only at those locations, by applying heat andpressure to the stock along those lines without the necessity The pressure shoe actuating mechanism has been illustrated in the drawings in operativeassociation with a machine for making bags from two separate superimposed sheets of heat scalable, materiahsuch as polyethylene. Inasmuch as the constructional and operational de tails of the web-advancing portions of the bag making The bag making machine is indicated in its entirety at 10. Asillustrated in Figs. 1 and 2 it comprises a frame 11 supportinga horizontal bed plate 12 across the upper surface of which is drawn a web 13 composed of two continuous, superimposed plies 14 and 15 of heat scalable material supplied'from rolls 16 and 17 respectively, rottatably supported from an extension 18 of the frame 11,

by mandrels 19 and 20. As illustrated diagrammatically in Fig. 6 the web advancing means comprises two spaced sets 21 and 21a of draw rolls 23 and 24, and 23a and 24a, respectively. The upper and lower rolls 23 and 24; 23a and 24a of each set 21, 21a, are interconnected by simultaneous rotation in opposite directions, so that the web 13, engaged between the rolls 23 and 24, and between the rolls 23a and 24a, will be advanced in accordance with the operation of the rolls. The rolls 23 and 24 of the first set are rotatably supported from opposed side plates 27 rigid with the frame 11 adjacent the after end of the bed plate 12, and are so arranged that the webengaging surfaces of the rolls are substantially in horizontal alignment with the upper surface of the bed plate 13, in being drawn across the bed plate, lies flat on the upper surface of the same. The rolls 23a and 24a of the second set 21a are rotatably mounted in an extension 28 of the frame 11 at the de- 1 cally actuated to advance the web 13 intermittently, the distance through which the web 13 is advanced during for making provision to prevent adhesion at other contacting areas of the plies.

each period of activity of the rolls corresponding to the desired length of the completed bags. The roll actuating mechanism, indicated in its entirety at 35 (Figs. 5 and 6) comprises a power shaft 36 driven at suitable constant speed by a speed reduction mechanism 37 which receives its motivating power by a belt 38 and pulleys 39 and 40 from a motor 41. A crank 42 rigid with one end of the power shaft 36 imparts reciprocatory motion to a bar 43 having thereon rack teeth 44 constantly enmeshed with a pinion 45 carried by the input shaft 46 (Fig. 5) of a unidirectional clutch 47, the output shaft 48 of which is rigid with the lower feed roll 24 of the first feed roll set 21. The clutch 47 is constructed and arranged to impart rotation to the shaft 48, and through it and the gears 25 and 26, and the gears 25a and 26a, to the feed rolls 23, 24, 23a, and 24a in a manner to advance the web 13, as the bar 43 is retracted by the crank 42; but when the bar 43 is propelled, the rolls 23, 24, 23a and 24a, and consequently the web 13, remain motionless.

The web severing mechanism for shearing each completed bag from the web 13 comprises upper and lower cutter blades 51 and 52, respectively, mounted in posi: tion for the web 13 issuing from the second set 23a of draw rolls to pass between the blades. The upper blade 51 is rigid with the frame extension 28, while the lower blade 52 is mounted by suitable guiding means (not shown) for vertical reciprocation in operative relation to the stationary blade 51. Each end of the reciprocable blade 52 is provided with a pin 53 extending therefrom, and each pin 53 is engaged in a slot extending longitudinally in an arm 54, the two arms 54' being rigidly affixed to a rock shaft 55 suitably journaled adjacent and parallel to the blade 52.

A third arm 56 rigid with the rock shaft 55 is pivotally connected to one end of a rod 57 the other end of which is operatively connected to a cam follower 58 held against a cam 59 on the power shaft 36 by a spring 60. The cam 59 is so shaped and is so positioned on the power shaft 36 that the follower 58 enters a depression 61 of the cam during each idle period of the draw rolls, permitting the spring 60 to move the rod 57 and thereby turn the shaft 55 to raise the lower cutter blade 52 to effect shearing from the web 13 the completed bag which issued from between the rolls 23a and 2411 during the preceding operation thereof. The cam 59 is so proportioned that the follower 58 leaves the depression 61 and climbs onto a higher portion 62 of the cam, and thus effects retraction of the cutter blade 53 to clear the Way for advance of the web 13, prior to the next succeeding period of activity of the draw rolls.

In its advance along the bed plate 12, the web 13 traverses first a longitudinal sealing station A, and thereafter, a transverse sealing station B (Figs. 1 and 2). At the former, two longitudinally extending sealing shoes 70 and 71 are mounted in transversely spaced, parallel re-. lation above the bed plate 12. Both shoes 70 andI71 are supported from a shaft 72 (Figs. 3 and 4) rotatably carried by upright brackets 73 and 73a (Figs. 1 andl) rigid with and extending upward from the bed plate 12 at the lateral edges thereof. A bracing arch 74 interconnects the two brackets 73 and 73a; and an auxiliary bracket 75 suspended from the center of the arch 74 rotatably supports the shaft 72 above the longitudinal center line of the bed plate.

Approximately half the length of the shaft 72 is of reduced diameter, as indicated at 76 (Fig. 4), and the shoulder 77 between the portion 76 of smaller diameter and the portion 78 of larger diameter, abuts against one lateral face of the auxiliary bracket 75 and thereby restrains the shaft from shifting to the right as viewed in Fig. 4. A tubular shaft or quill 79 is rotatably fitted on the portion 76 of the shaft, and extends from the other lateral face of the auxiliary bracket and through the upright bracket 73. The smaller portion 76 of the shaft 72 extends through and beyond the outboard end of the quill 79, where it carries a dog (Figs. 2 and 6) slidably engaging the end of the quill and thereby restraining the' shaft 72 from shifting to the left as viewed in Fig. 4, and the quill from shifting to the right.

A radially split collar (Figs. 1, 3 and 4) is clamped to the quill 79 by a screw 86 interconnecting the parts of the collar on opposite sides of the split; and a similar collar 87 (Fig. 1) is similarly clamped to the portion 78 of the shaft 72 between the side bracket 73a and the intermediate bracket 75. Each collar 85, 87, is provided with a cylindrical portion 88, 89 (Fig. 1), respectively, disposed eccentrically with respect to the quill 79 or shaft 72, as the case might be, to which it is secured. Each of the sealing shoes 70 and 71 is provided with an upstanding web 91. The shoe 70 is operatively connected to the quill 79 to be raised and lowered in response to rotative movement thereof by a horizontal cylindrical sleeve 92 journaled on the eccentric 88. A snap ring 93 (Fig. 4) seated in a circumferential groove 94 in the eccentric retains the sleeve against lateral displacement from the eccentric. The shoe 71 is similarly operatively connected to the shaft 72 by a sleeve 95 (Fig. l) journaled on the eccentric 89.

Each collar 85, 87 and its associated eccentric 88, 89 are positively locked against rotation with respect to the actuating quill 79 or shaft 72, respectively, by a key 96, 97 (Fig. 4) seated in a keyway 98, 99 in the quill 79 or shaft 72, respectively, and slidably engaged within a relatively loosely fitting keyway in the bore of the associated collar and eccentric. Each of the keys 96 and 97 is elongated to permit the associated collar and eccentric to be shifted laterally after loosening the associated clamping screw 86, so as to accommodate the sealing shoes 70 and 71 to the width of web 13 to be converted' to' bags.

Each of the sealing shoes 70 and 71 is provided with a pressure foot 100 secured to its lower edge by screws 101 (Fig. 4) extending through a horizontal flange 102 at the lower edge of the web 91. Each pressure foot 100 has an electrically insulated resistance element 103 therewithin to heat the pressure foot to suitable sealing temperature by passage therethrough of electrical energy automatically controlled by a thermostat concealed within a housing 104(Figs. 1, 2, and 3) mounted on the associated'pressure shoe and carrying an adjusting knob 105 whereby the temperature of the pressure foot is regulable.

A collar 111 (Fig. 4) having a lever 112 extending therefrom is afiixed to the quill 79 adjacent the side bracket 73. The outboard end of the key 96 is seated within a keyway 113 in the bore of the collar 111 to positively lock the collar 111 to the quill 79 to prevent rotary movement of the one with respect to the other. Resilient pressure is exerted against the lever 112 in the direction causing the quill 79 to effect downward motion of the pressure shoe 91. For this purpose, a pneumatic cylinder 114 having a piston 115 reciprocable therein, is mounted'by means of a clamp 116 on the side bracket 73 directly above the collar 111, in position for the cupped lower end 117 of the piston rod 118 actuated by pressure within the cylinder 114 to bear against a ball 119 seated in a cup 120 resting on the upper surface of the lever 112. A shank 121 integral with the cup 120 extends downward into a socket 122 in the lever 112, the socket 122 being of slightly greater diameter than the shank 121-to permit a sufiicient amount of movement of the cup 120 to prevent binding of the parts otherwise apt to develop as the result of the arcuate motion of the lever 112 in response to straight line motion of the piston'rod 118.

The pressure shoe 71 on the other side of the ma chine 10 is similarly actuated by the rod 126 of a piston (not shown) reciprocable in a pneumatic cylinder 127 (Fig. 3) mounted by a clamp 128 on the side bracket 73a; The piston rod 126 likewise is provided with a cupped lower end pressing a ball downward against. a cup, which details are not. shown but are similar in design and arrangement to the corresponding items described in connection with the actuating mechanism for the pressure shoe 76. Figure 6, however, reveals the manner in which the piston rod 126 exerts its downward resilient pressure, derived from pneumatic pressure within the cylinder 127, against a lever 129 extending from a clamp 130, to urge the shaft 72 to rotate in that direction which effects downward motion of the sealing shoe 70.

Both cylinders 114 and 127 are continuously supplied with compressed air at uniform, regulated pressure by tubes 131 and 132, respectively, both of which lead from a supply tank 133 (Figs. 2 and 8), the capacity of which is ample to avoid any appreciable fluctuation in pressure in the tank133 and cylinders 114 and 127 in response to motion of the pistons therein. Therefore, at all times during practical operation of the machine 14) a constant and uniform downward pressure is imposed on both levers 112 and 129, which pressure is translated thereby into torque in the shaft 72 and the quill 79, respectively. Thus, the two sealing shoes 70 and '71 are both pressed downward, with constant and substantially identical resilient pressure, toward the bed plate 12 which serves as a fixed, lower pressure sealing member or shoe, cooperating with both upper, movable pressure sealing members 71 and 72 to impose sealing ressure on the web 13 while heat is being applied to the same by the electrically heated pressure feet 100 in two parallel lines spaced apart by a distance corresponding to the desired bag width. 6

.A pressure gauge. 134 mounted on the fitting 135 by which the tube 132 is connected to the cylinder 127, in-

dicates the air pressure within both cylinders 114 and 127 above their respective pistons 115.

Means are provided for lifting the pressure members 70 and 71 to permit advance of the web 13 engaged between each shoe and the bed plate 12. Such raising of the pressure members 70 and 71 occurs at the proper time with relation to the operation of the feed roll actuating means 35, and is accomplished by turning the shaft 72 and quill 79 in the reverse direction, i. e., against the yieldable pressure imposed pneumatically upon the levers 112 and129. The end of the quill 79 beyond which an end of the shaft 72 extends, as described hereinbefore, extends outboard beyond the side bracket 73 far enough to receive thereon a clamp 136 formed integrally with a release lever 137 (Figs. 1, 2, 4, and 6). The clamp 136 is rigidly atfixed to the shaft in adjusted position with relation thereto, by a nut 138 tightened on a bolt 139 extending across a radial slot 140 (Fig. 6) in the clamp 136. A cam follower roller 141 on the outer end of the release lever 137 is pressed against'a cam 142 on the shaft 36, due to the torque maintained on the shaft 72 by the pneumatic pressure within the cylinder 127. The cam 142 is so located with respect to the feed roll actuating crank 42 that the follower 141 rides onto the high lobe 143 of the cam 142 a brief interval before the crank 42 starts to retract the rod 43, i. e., just before the feed rolls are activated. I

The clamp 136 is provided with a lateral extension 144 which carries an abutment screw 145 threaded therethrough in position to engage the aforementioned dog 80 on the shaft 72 and thereby impart like rotary motion to the shaft 72 when the quill 79 and clamp 136 are turned in pressure member liftingrotation. The abutment screw 145 is preferably adjusted to, and retained by a lock nut 146 in, that position wherein the screw 145 is spaced slightly from the dog when both pressure mentbers 70 and 71 are in their fully lowered position. The

clearance thus established between the screw and e the dog 80 permits the two pressure members 70 and 71 to press against the web 13 independently of each other, assuring that the full force of each pneumatic cylinder 114, 127 will be imposed upon the individually associated pressure members 70, 71, respectively. This assists, therefore, in causing both pressure shoes to exert identical pressure against the web 13.

The parts are so proportioned and arranged that as the low lobe 147 of the rotating cam 142 approaches the follower roller 141, both pressure members 70 and 71 engage the web 13, which, since it is supported on the bed plate 12, arrests the downward stroke ofthe shoes 71 and 70 shortly before the portion 148 of the cam 142 of least radius reaches the follower roller 141. As a consequence, clearance is established between the cam 142 and the follower 141 for an interval ineach operational cycle of the machine 10, and throughout this interval the pressure shoes 70 and 71 exert their full force, as determined by the pneumatic pressure within the two cylinders 114 and 127, against the web 13. Hence, the described arrangement of lifting cam 141 and lever 137 is an important factor contributing toward uniformity in the quality of the sealed material produced by the machine 10.

At the transverse sealing station E, opposed upper and lower pressure sealing shoes 148 and 149, respectively, are provided (Figs. 3, 5, and 6). Each of these pressure shoes 148 and 149 comprises a rigid backing member 150, 151, respectively, to which a heat and pressure applying head 152, 153 is secured by screws 154, 155, respectively (Fig. 3). Each of the heat and pressure applying heads 152, 153 is heated to sealing temperature by an electrical resistance element 156, 157, respectively, the

temperature of whichis automatically controlled by a thermostat concealed within a housing 158, 159 adjustable by a knob 160, 161 (Fig. I).

The upper and lower sealing shoes 148 and 149, respectively, are mounted adjacent the first set 21 of draw rolls 23, 24, in position for the web 13 to pass between the shoes 148 and 149 immediately after passage between said rolls. Both shoes 148 and 149 extend transversely of the machine 10 and both are mounted for independent, vertical reciprocatory movement by having their ends 162, 163, respectively, slidably mounted on vertical pins 164 (Figs. 3 and 7). One such pin is rigidly supported from each of the side plates 27 within an opening 165 in the plate of sufiicient size to permit freedom of movement of the shoes 148 and 149 Without engagement of their ends 162 and 163 with the side plates. Preferably, however, a hardened slipper block 166 is seated within each of the openings 165 between the end 163 of the lower sealing shoe 149 and one side of the opening 165 to resist the side thrust imposed on the lower shoe 161 by its actuating mechanism, as will become apparent from the description to follow. The upper end of each guide pin 164 is threadedly engaged with a bracket 167 bridging the top of the opening 165 and rigidly secured to the associated side plate 27 by screws 168. A collar 169 is fitted to each pin 164 for sliding movement thereon, and is adapted to be anchored in selected position of vertical adjustment by a set screw 170. The two collars are set in such positions on their respective pins 164 that they prevent downward movement of the upper sealing shoe 148 beyond that position in which the lowermost portion of the heat and pressure applying head 152 is substantially in horizontal alignment with the upper face of the bed plate 12 and with the contacting faces of the feed rollers 23 and 24.

pneumatically actuated means are provided for yieldably pressing the upper sealing shoe 148 downward to its lower limit of motion. For this purpose, a pneumatic cylinder 176 having a piston 177 reciprocable therein (Fig. 3) is mounted by a clamp 178 on each of the brackets 167. The rod 179 of each of the pistons 177 exerts downward pressure against the outer end of a lever 130 through an anti-friction ball 181 seated in the cupped lower end 182 of saidrod and in a cup 183 engaged upon the lever in a manner similar to that in which each of the cups 120 is seated on its associated lever 112, as

hereinabove described. The opposite end of each of the levers 180 is pivotally supported from: the associated bracket 167 by a pin 184; and'both levers bear'downward against the top ofthe upper sealing shoe-148 at'points between the outer ends of the levers-180 and their pivot pins 134. Preferably, the point on' each lever 1S0'where it engages the; sealing shoe 148 is relatively close to the associated. pivot pin 184-, thus' gaining a considerable mechanical. advantage and making possible the exertion of the necessary pressure of the sealing shoe 148 against theweb 13 with relatively low pneumatic'pressure in the cylinders 176. Both cylinders 176 are adapted to receive air under. regulated pressure from an accumulator tank 186. (Figs. 2 and 8) continuously connected to the upper ends of both cylinders 176 by tubing 187. As in the case of the tank 1'33, theaccumulator tank 186 is of sufficient volumetric capacity to prevent any material fluctuation in the: pressure of its contents in response to movement of the pistons-177 within their cylinders 176. A pressure gauge 188connected to the fitting 189 by which the tubing 187 is connected to oneof'the cylinders 176 gives a constant reading'of the air pressure-within both cylinders 176 above their respective pistons 177.

The lower sealing shoe 149 is intermittently forced upwardto press the web 13 against the heated head 152 of the upper shoe 148 by an actuating mechanism indicated in-its entirety at 190. This is accomplished by cranks 191operatively connected to the ends of the lower shoe 149 by connecting rods 192 pivoted'as at 193 to the cranks and at 194 to the shoe 149 (Fig. 6). Both cranks 191 are rigidly secured to a rock shaft 195 suitably journaled in the sideplates 27. One end ofanarm 196 is clamped rigidly to the rock shaft 195 intermediately of the side plates 27 by clamping screws 197 (Figs. 3 and 5) and the other end of the arm 196 is pivoted by a pin 198 to one end of a two-part follower rod' 199 slidably journaled'in a bracket 200 rigid with and extending downward from the bed plate 12. One part 201 of the follower rod 199' is threaded into a socket in an end of the other part 202, to which it is locked in selected position of longitudinal extension by a lock nut 203. The opposite end of the part 202 is pivotally connected by a pin 204 to a link 205 pivotally suspended from a bracket 206 on the underside of the bed plate 12, so that a spring 207, under compression between the bracket 200 and a collar 20:; on the follower rod 199, holds a follower roller 209 rotatably mounted on the link, against a earn 210 rigid with the powershaft 36.

The cam 210 is so positioned on the power shaft 36- that'the high lobe 21.1 of the cam propels the follower roller 209'and rod 199 to the right as viewed in Figs. 2,

3 and 6, at the same time that the low lobe 147 of the cam 142 is approaching the follower roller 141 on the longitudinal seal releasing lever 137. Consequently, at the same time that the lever 137 is released to permit the two longitudinal sealing shoes 70 and 71 to be carried downward, the rock shaft 195 is turned clockwise as viewed in Figs. 2, 3 and 6, causing the cranks 191 and connecting rods 192 to force the lower transverse sealing shoe 149 upward. The construction and realtive proportionsof the parts involved in this operation are such that-the lower shoe 149 is raised far enough to not only press the web 13 against the: sealing head 152 onthe upper shoe 149 upward. The construction and relative propor- 169. In this manner, it is assured that the web 13 will be squeezed between the upper and lower transverse sealing shoes 148 and 149 with a'force whose magnitude is determined by the pneumatic pressure within the cylinders 176; and this force remains constant regardless of the height to whichthe upper shoe 148 is lifted, provided only that it is notraised high enough for'its ends 162 to encounter the brackets .167.

In addition to the hereinbefore mentioned longitudinal seal accumulator tank 133 and the transverse seal accumulator tank 186, the air supply and pressure" regulating system (Figs. 2 and 8) includes an air compressor 216 driven by a suitable motor (not shown) and a receiver tank 217. The compressor is connected by tubing 218 accumulator tank 133 through tubing 219, and with the transverse seal accumulator tank 186 through tubing 220. The tubing 220 leads to the transverse seal accumulator tank 186 through a manually adjustable pressure reducing valve 221; but inasmuch as the eccentrics 88 and 89 develop a considerably greater mechanical advantage in applying the force of the pneumatically actuated pistons to the sealing shoes 70 and 71 than do the levers 180 in applying such force to the sealing shoes 148 and 149, equalization of the pressures exerted by all the sealing shoes is facilitated by providing two pressure reducing valves 222 and 223 connected in series with each other between the receiver tank 217 and the longitudinal seal accumulator tank 133. The tubing 219 leads from the receiver tank 217 first to the reducing valve 222 which is adjustable to deliver air at pressures within a relatively high range, say, between 125 and 250 p. s. i. From the reducer valve 222, the tubing 219 leads to the reducing valve 223, which is adjustable todeliver air at pressures within a lower range, say, between 0 and 125 p. s. i. From the lower stage pressure reducer 223, the tubing leads to the longitudinal seal accumulator tank 133.

Under certain circumstances, however, it may be desirable to provide air for the cylinders 114 and 127 of the longitudinal seal, at pressure within the range of the first stage reducer 222; and for that reason a by-pass 224 is provided around the second stage reducer 223, and a shut-off valve 225 in the by-pass 224 may be opened to permit pressure within the range of the first stage reducer 222 to build up in the longitudinal seal accumulator tank 133 and cylinders 114 and 127.

In practical operation of the bag making machine, a two-ply web 13 of heat and pressure scalable material is engaged between the feed rolls 23 and 24, and between the feed rolls 23a and 24a. Both sets 21 and 21a of draw rolls are periodically actuated by the crank 42 and rod 43, to advance the web 13 through a distance corresponding to the desired bag length during each period of activity of'the rolls. Upon termination of each such period and while the web 13 is motionless, the cam 142 turns its low lobe 147 to the'foliower roller 141, permitting the pistons 115 of both cylinders 114 and 127 to force the two longitudinal sealing shoes 70 and 71 downward. The web 13 is thus engaged between the bed plate 12 and the heated pressure feet of both shoes 70 and 71 in two parallel lines defining the width of the bag being formed. The force of'such engagement is proportional to the pneumatic pressure within the cylinders 114 and 127 and the longitudinal seal accumulator tank 133. This pneumatic pressure is established by proper setting of one or both of the reducing valves 222 and 223 and appropriate adjustment of the by-pass shut-off valve 221, as explained hereinbefore.

Substantially simultaneously with lowering of the iongitudinal sealing shoes 70 and 71, the cam 210 presents its high lobe 211 to the follower roller 209, thereby effecting raising of the lower longitudinal sealing shoe 149 to press-the web upward against the upper longitudinal sealing shoe 148 and, as explained hereinabove, lifting the upper shoe 148 off the collars 169. Thus the web 13 is engaged between the'heated heads 152 and 153 of the upper and lower pressure shoes 148 and 149, respectively, with a force proportional to the pneumatic pressure within both cylinders 176 and the transverse seal accumulator tank'18'6, where the pressure is established by proper setting of the reducing valve 221.

Whereas the reducer valves 221, 222 and 223 are of any suitable conventional type, they should be of such design and construction that they are capable of maintaining the pressure within each of the accumulator tanks 133 and 186 constant Within quite close limits, although pressure within one tank may be difierent from that within the other. Once the temperature and pressure requirements of the particular heat sealing material to be employed have been ascertained, the apparatus can be arranged to cause each of the pressure shoes 70, 71, 148 and 149 to exert the optimum pressure every time they operate, by a simple adjustment of the reducer valves 221, 222 and 223; and proper manipulation of the thermostatadjusting knobs 105, 160 and 161 results in heating theweb-engaging portions 100, 152 and 153 to the optimum temperature for the material of the web. Moreover, having once been set to effect engagement of the web by sealing members heated to precisely the proper temperature and with force of precisely the proper magnitude, the web-engaging portions of the sealing members will remain at that temperature, and the web 13 will be engaged by the sealing members at that same pressure at each operation thereof over an indefinite operational period.

While we have illustrated and described a particular embodiment of the present invention, it will be understood that varous changes may be made in the details thereof without departing from the scope of the invention as defined in the appended claims.

Having thus described the invention, what we claim and desire 'to protect by Letters Patent is as follows:

1. A pressure sealing apparatus comprising two pposed sealing members, means yieldably pressing one of said sealing members toward the other with substantially unvarying force, and means operable to force said sealing members apart.

2. A pressure sealing apparatus comprising two opposed sealing members, pneumatic means yieldably pressing one of said sealing members toward the other with force of constant predetermined magnitude, and means operable to force said sealing members apart.

3. Pressure sealing apparatus comprising two opposed sealing members, means mounting at least one of said sealing members for reciprocatory motion toward and away from the other, means yieldably pressing one of said sealing members toward the other, means operably associated with one of said sealing members for withdrawing the same from the other sealing member, and means maintaining uniform the magnitude of the force exerted on said one sealing member by the pressing means.

4. Pressure sealing apparatus comprising opposed sealing members, means mounting at least one of the sealing members for movement toward and away from the other, pneumatically operable means for yieldably pressing one of the sealing members toward the other, means constantly supplying the pressing means with actuating fluid under uniform pressure, and means operatively associated with one of the sealing members for temporarily moving the same away from the other.

5. Pressure sealing apparatus comprising opposed sealing members, means mounting at least one of the sealing members for movement toward and away from the other, pneumatic means yieldably pressing a movably mounted one of the sealing members toward the other with pressure substantially uniform throughout the operational cycle of the sealing apparatus, regulating means operably associated with said pneumatic means and adjustable to vary the pressure imposed thereby on said yieldably pressed sealing means, and means operatively associated .with a movably mounted one of the sealing members for temporarily moving the same away from the other.

6. Pressure sealing apparatus comprising relatively movableyopposed sealing members adapted to receive therebetween superimposed webs of material to be sealed, fluid operated means operatively associated with one of said sealing members to press the same into sealing engagement with webs interposed between the sealing members, powered mechanism operatively associated with one of said sealing members to temporarily force the same away from the other sealing member to release the webs, and means independent of said powered mechanism for supplying the fluid operated means with actuating fluid under pressure.

7. In apparatus for forming a seal between superimposed webs, including relatively movable sealing members disposed at opposite sides of webs to be sealed and means for intermittently advancing the webs, the combination therewith of yieldable means continuously and uniformly pressing one of said sealing members toward the other to impose sealing pressure on the webs, and means operatively associated wth one of thet sealing members and operable prior to operation of the web-advancing means to space the sealing members apart and there by release the webs therefrom.

8. In apparatus for forming a seal between superimposed webs, including relatively movable sealing members disposed at opposite sides of webs to be sealed and means for intermittently advancing the webs, the combination therewith of yieldable means continuously pressing one of said sealing members toward the other to impose sealing pressure on the webs, means limiting movement of said yieldably pressed sealing member by saidpressing means, and means operatively associated with one of the sealing members and operable prior to operation of the web-advancing means to space the sealing members apart and thereby release the webs therefrom.

9. Sealing mechanism comprising opposed sealing members adapted to receive therebetween a web of material to be sealed, means mounting one of the sealing members for reciprocatory movement toward and away from the other, means yieldably pressing said movably mounted sealing member toward the other into sealing engagement with a web interposed between said sealing members, and means operatively associated with said movable sealing member for moving the same away from the other sealing member against the urgency of said pressing means to release the web.

10. In a sealing machine having two opposed sealing members, one of the sealing members being mounted for rec'iprocatory movement toward and away from the other,

the combination therewith of pneumatic mechanism continuously and yieldably pressing the movable sealing member toward the other, powered mechanism for retracting the movable sealing member from the other sealing member against the urgency of said pneumatic mechanism, and means for periodically disabling said retracting means temporarily to permit advance of the movable sealing member to sealing relation with the other sealing member.

11. In apparatus for uniting plies of sealable material including two opposed sealing members adapted to receive therebetween superimposed plies to be united, means mounting one of the sealing members for reciprocative motion toward and away from the other, and means for intermittently advancing superimposed plies of sealable material extending between the sealing members, the combination therewith of pneumatic means arranged in cooperative association with the movable sealing member to continuously urge the same toward the other sealing member with a force of predetermined magnitude, and powered mechanism operatively connected to the movable sealing member and operable prior to each operation of the ply advancing means to retract the movable sealing member against the urgency of said pneumatic means and operable upon completion of each operation of said ply advancing means to release the movable sealing member for the same to be advanced by said pneumatic means to sealing relation with-the other sealing member.

12. A heat sealing machine comprising a stationary sealing member, a rotatably mounted shaft disposed in spaced relation to said stationary sealing member, an eccentricdisc rigid with said shaft, a movable sealing member including a presser shoe and a flange upstanding therefrom having a circular opening therein, said eccentric disc being fitted to and seated within said circular opening to advance the movable sealing member to scaling relation with said stationary sealing member when saidshaft turns in one direction and to retract the movable scaling member when the shaft turns in the other direction, means" for heating the operative face of one of said sealing members to'heat sealing temperature, a lever rigid with and extending radially from said shaft, a pneumatic cylinder fixedly mounted adjacent said shaft, a plunger reciprocable in said cylinder and extending therefrom into'operative engagement with said lever to impart sealing member advancing rotation to said shaft upon movement of said plunger by pneumatic pressure within said cylinder, means maintaining predetermined pneumatic pressure within said cylinder, and means operable periodically to turn said shaft in sealing member retracting rotation against the urgency of said plunger.

13. Pressure sealing apparatus comprising two opposed sealing members,means mounting one of said sealing members in fixed position, means mounting'the other of said sealing members for movement to and from sealingrelation with said fixed sealing member, a shaft journalled on said fixed sealing member mounting means, an

eccentric disc affixed to said shaft and fitted to a circular opening in said movable sealing member to advance said movable sealing member to sealing relation with said fixed sealing member when the shaft turns in one direction and to retract the movable sealing member whenthe shaft turns in the opposite direction, a crank lever'rigid with said shaft, a pneumatic cylinder supported from said fixed sealing member mounting means, a plunger reciprocable in said cylinder and engaging said crank lever so as to impart sealing member advancing rotation to said shaft upon movement of said plunger in response to pressure within said cylinder, means connecting said cylinder with a supply of gas under pressure, a second crank lever rigid with said shaft, a cam follower carried by said second crank lever, a cam having a high lobe, said cam being rotatably mounted in cooperative relation with said second lever and cam follower to impart sealing member retracting rotation to said second lever and shaft as said high lobe approaches the follower, and means for rotating the cam.

14. Pressure sealing apparatus comprising two opposed sealing members, means mounting one of said sealing members in fixed position, means mounting the other of said sealing members for movement to and from sealing relation with said fixed sealing member, a shaft jour nalled on said fixed sealing member mounting means, an eccentric disc affixed to said shaft and fitted to a circular opening in said movable sealing member to advance said movable sealing member to sealing relation with said fixed sealing member when the shaft turns in one direction and to retract the movable sealing member when the shaft turns in the opposite direction,- a crank lever rigid with said shaft, a pneumatic cylinder supported from said fixed sealing member mounting means, a plunger reciprocable in said cylinder and engaging said crank lever so as to impart sealing member advancing rotation to said shaft upon movement of said plunger in response to pressure within said cylinder,

means connecting said cylinder with a supply of gas" under pressure, a second crank lever rigid with said shaft, a cam follower carried by said second crank'l'ever", a cam having a high lobe and at low lobe and rotatably mounted in cooperative relation to said second level and cam follower to impart sealing member retracting" rotation to said second lever and shaft as said high lobe approaches the follower, said low' lobe being spaced from lower limit of movement, means connecting said sealing member to said shaft to lower said sealing member in response to turning. of said shaft in one direction and toraise said sealing member in response to turning of said shaft in the opposite direction, pneumatically operated means continuously and yieldably urging said shaft to turn in. sealing member lowering direction, a crank lever rigid with said shaft, a cam follower carried by'said crank lever, a cam having a high lobe and a low lobe and rotatably mounted in cooperative relation to said lever and cam follower to turn said lever and shaft in sealing member raising direction as the high lobeappreaches the follower, said low lobe being spaced from the axis of rotation of the cam by a distance less than the distance of said follower from said axis when said sealing member is at its lower limit of movement, and means for turning said cam.

16. A pressure sealing machine comprising a bed plate adapted to support a web to be sealed, at spindle shaft rotatably mounted in spaced relation above saidbed plate, a quill shaft rotatably mounted on said spindle shaft coaxially therewith with said spindle shaft extending beyond both ends of the quill shaft, a pressure shoe associated with each of said shafts, means connecting each of said pressure shoes to its associated shaft to raise said shoes when the associated shaft turns in one direction, independent means associated with each of said shafts for continuously and yieldably turning the same in the opposite direction, a crank lever rigid with one of said shafts, means for periodically turning said lever to turn the associated shaft in shoe raising direction, a dog rigid with the other of said shafts, and means on said lever for engaging said dog to turn said other shaft in shoe raising direction in response to turning of said lever inshoe raising rotation.

17. 'A pressure sealing machine comprising. a bed plate adapted to support a web to be sealed, a spindle shaft rotatably mounted in spaced relation above said bed plate, a quill shaft rotatably mounted on said spindle shaft coaxially therewith with said spindle shaft extending beyond both ends of the quill shaft, a pressure shoe associated with each of said shafts, means connectingeach of said pressure shoes to its associated shaft to be raised thereby when the associated shaft turns in one direction, independent means associated with each of said shafts for continuously and yieldably turning the same in the opposite direction, a crank lever rigid with one of" said shafts, means for periodically turning said lever to impart to the associated shaft shoe raising rotation, a dog rigid with the other of said shafts, and means on said lever for engaging said dog to impart to said other. shaft shoe raising rotation in response to turning of said lever in shoe raising direction, said dog and said dog-engaging means being spaced apart when said shoes are at the lower limits of their respective motions to free said shafts from each other for independent actuation ofsaid pressure shoes by their respectively associated yieldable shaft turning means.

18. Pressure sealing apparatus comprising two opposed sealing member's, means mounting each of said sealing.

' ing members toward the other, means limiting movement of said yieldably pressed sealing member toward the other, and means operatively associated with said other sealing members for positively advancing the same toward the yieldably pressed sealing member until the yieldably pressed sealing member is displaced from the position thereof determined by said limiting means.

19. A pressure sealing machine comprising two opposed sealing members, means mounting said sealing members for movement toward and away from each other, pneumatic means yieldably pressing one of said sealing members toward the other, abutment means constructed and arranged to interrupt movement of said yieldably pressed sealing member toward said other member, and means connected to said other sealing member and periodically operable to temporarily advance said other sealing member toward said yieldably pressed sealing member far enough to displace the same against the urgency of said pneumatic means from the position thereof determined by said abutment means.

20. In apparatus for uniting plies of sealable material, including two opposed sealing members adapted to receive therebetween superimposed plies to be united, means mounting each of said sealing members for movement toward and away from the other, and means for intermittently advancing superimposed plies of sealable ma terial extending between the sealing members, the combination therewith of pneumatically actuated means operably connected to one of the sealing means to continuously press the same toward the other sealing means, means limiting movement of said continuously pressed sealing member by said pressing means; and mechanism operably connected to the other sealing member and operable between successive periods of advance of said plies to move said other sealing member toward the yieldably pressed sealing member far enough to squeeze the plies between the sealing members with sealing pressure and operable to retract said other sealing member to release the sealed plies from said sealing members.

21. A heat sealing machine comprising opposed sealing members, means mounting said sealing members for reciprocative movement toward and away from each other, a pneumatic cylinder supported from said mounting means, a plunger including a piston reciprocable in said cylinder and a rod extending therefrom, means connecting said cylinder to a source of gas under pressure, means connecting one of the sealing members to said rod to be yieldably pushed thereby toward the other sealing memher in response to pneumatic pressure imposed on the piston within the cylinder, means limiting movement of said yieldably pushed sealing member by said rod, and means operably connected to said other sealing member and operable to advance the same into sealing relation with said yieldably pushed sealing member and to retract said other sealing member from said yieldably pushed sealing member.

22. A heat sealing machine comprising opposed sealing members, means mounting said sealing members for reciprocative movement toward and away from each other, a pneumatic cylinder supported from said mounting means, a plunger including a piston reciprocable in said cylinder and a rod extending therefrom, means maintaining substantially constant predetermined pneumatic pressure within said cylinder, means connecting one of the sealing members to said rod to be yieldably pushed thereby toward the other sealing member in response to pneumatic pressure imposed on the piston within the cylinder, means limiting movement of said yieldably pushed sealing member by said rod, and means operably connected to said other sealing member and operable to advance the same into sealing relation with said yieldably pushed sealing member and to retract said other sealing member from said yieldably pushed sealing member.

References Cited in the file of this patent UNITED STATES PATENTS 1,628,203 Stein May 10, 1927 2,476,629 Salfisberg July 19, 1949 2,500,874 Salfisberg Mar. 14, 1950 2,533,832 Monroe Dec. 12, 1950 2,646,105 Langer July 21, 1953;

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