Bag Machine

Abstract

The bag machine of the present disclosure is of the type which can produce bags made of various thermoplastic sheet material and can be adapted to make side weld or bottom weld bags. The following description will, however, be confined to the production of side weld bags. A roll of plastic web is mounted on an unwind stand and traverses a folding board constraining the web to fold along its longitudinal median or along a line spaced from and parallel to the longitudinal median in the event it is desired to produce wicketed bags having a lip with a pair of holes in which is inserted a U-shape wire called a wicket. Downstream of the folding board a gusseter is provided to produce a fold which permits greater expansion at the bottom of the bag. The folded and gusseted web thence comes under the influence of a reciprocating transversely disposed seal and cutter bar which divides the web, at longitudinally spaced intervals, to produce individual bags. The bags are then transported to a table which is provided with devices for arranging the bags into a stack.

Parent Case Text

This application is a division of U.S. application Ser. No. 760,048, filed Sept. 16, 1968 now U.S. Pat. No. 3,663,338.

Description

BACKGROUND OF THE INVENTION

In order to attain a production rate of 200 or more quality thermoplastic bags per minute it is essential to design the bag making machine with features that provide: a) positive control of the film during its unwinding from the parent roll; b) maintenance of a fixed positional relationship between the parent roll supporting stand and the infeed frame of the bagging machine; c) when desired, a gusseting mechanism which provides a minimum drag to the film while insuring a gusset of constant depth; d) web draw rolls whose nip pressure is evenly distributed and has the ability to apply a differential nip pressure from one end of the rolls to the other; e) mechanism which will release the nip pressure in the event film movement is stopped to prevent the creation of flat spots on the film; f) a seal bar which will maintain a uniform evenly distributed temperature throughout its length and one that is shielded to prevent heat loss to the film; g) a seal bar drive arranged for a manual or automatic lift when desired or when web feeding is interrupted for any reason; h) mechanisms to vary the length of the bag being produced while the machine is operating to correct or change the size of the bags accurately under operating conditions with no down time and; i) a bag transporting conveyor, which conventionally runs at higher speed than the film, including an easily adjustable positive control arrangement whereby adjustments can be made under operating conditions to insure that the trailing end of the bag is engaged by a conventional bag slow down mechanism to stack the bags so that their margins are in registration.

In accordance with the present invention means are provided for controlling the speed of the bag transporting conveyor to effect separation of the bags downstream of the seal bar so as to prevent contact between the seals of adjacent bags and thus avoid possible sticking. With the increase in velocity problems are encountered in constraining the bags to produce neat stacks since the stiffness of the film is not sufficient to overcome an abrupt stop against fences mounted on the stacking table. The bag machine of this invention makes use, therefor, of a conventional bag slow down device which momentarily grasps the trailing end of the bag prior to its encountering the bag stacking fences. To insure grasping of the bag at its trailing end the present invention provides a direct current drive motor for the bag transporting and indexing conveyor which can be accurately adjusted to synchronize its speed with the slow down device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B, when viewed together along the break line R show the bag machine of the present invention in longitudinal section wherein the path of the web is shown by a broken line and the direction of web feed is indicated by arrows applied thereto.

FIGS. 2A and 2B, considered together along the break line S, illustrates the bag machine in plan view.

FIG. 3 is a simplified diagrammatic perspective of the drive train of the bag machine.

FIG. 4 is a schematic of the circuit for regulating the speed of the index conveyor of the bag machine.

DESCRIPTION OF THE PREFERRED EMBODIMENT

GENERAL ARRANGEMENT

With reference to FIGS. 1A, 1B, 2A and 2B it will be noted that the bag machine of the present invention is generally indicated by the numeral 20 and it comprises an unwind stand 22 (FIG. 2A) rotatably supporting core shafts 24 which in turn support film rolls 26. The web, designated by the letter W, unwound from the roll 26 is folded along a line parallel to its ends by a folding board or a V-board 28. When so called even edged bags are made the fold line is located at the longitudinal median of the web while the fold line for lipped bags is spaced from and parallel to the longitudinal median. FIG. 2A shows the V-board set up for producing lipped bags since the left hand margin of the web, identified by L. H., is laterally spaced from the right hand margin R. H. downstream from the V-board 28. The web then comes under the influence of a gusseting mechanism 30 which forms an inwardly directed fold on that portion of the web which defines the bottom of the completed bag. The fold is shown by a dotted line in FIG. 2A and is identified by numeral 32.

Referring to FIG. 1A it will be seen that the gusseting mechanism 30 is mounted on support arms 34 pivotally connected to a transverse rod 36 mounted to and extending between laterally spaced infeed frame members 38. Rotatably supported on the transverse rod 36 is a roller 40 which directs the web between a first set of infeed rolls of 42 connected to conventional nip pressure regulating means 43. The web is thence trained about a plurality of idler rollers 44, mounted on dancer arms 46, and rollers 48 extending between and rotatably mounted on the infeed frame members 38. The length of web accumulated in the path defined by the rollers 44 and 48 serves to provide a temporary supply which automatically increases or decreases in response to transient values of web tension. This arrangement tends to produce a constant value of web tension.

The bag machine frame comprises a base plate 50 having mounted thereon transversely spaced upwardly projecting side frame members 52 located substantially at the midportion of the machine. At the discharge end, outfeed frame members 54 are also mounted on the base plate 50 and served to support bag discharge control devices explained in detail hereinafter.

Referring again to FIG. 1A it will be observed that between the infeed frame members 38 and the mid-frame members 52 a horizontal accessory platform 56 is connected therebetween and it serves to support hole punching assemblies 58 mounted on a base plate 60. As shown in FIG. 2B the base plate 60 is mounted on a rectangular frame 62 and is transversely adjustable on this frame. It is held in a selected transverse position by a lock screw 64. Longitudinal adjustment of the rectangular frame 62 carrying the hole punch assemblies 58 is accomplished by racks 66 and pinions 68. As shown diagrammatically in FIG. 2B the racks 66 are fixed to the inner surfaces of the side rails 56 while the pinions 68 are keyed to a transversely extending shaft 70 rotatably mounted in the rectangular frame 62. On one end of the shaft 70 a knob 71 is keyed for rotating the shaft 70 and consequently adjusting the longitudinal position of the hole punching assemblies 58.

Downstream of the hole punching assemblies 58 an electronic web registration device 72 commonly referred to as a scanner, is likewise mounted for longitudinal and transverse adjustment. Longitudinal adjustment is accomplished by pinions 74 (FIG. 1A) in mesh with the racks 66. The pinions 74 are mounted on a transverse shaft 76 rotatably carried in generally L-shaped in frames 78. On the upright legs of the L frames 78 a transverse bar 79 is secured. Slidably mounted on the bar 79 is the scanner 72 which can be locked in any transverse position by a lock screw 80. On the horizontal leg of the L frame 78 a transverse bar 82 is mounted and it will be observed, by inspection of FIG. 1A, that its upper surface is in substantially the same plane as the web line. In order to insure repeated response of the scanner the upper surface of the transverse bar 82 is white in color so as to provide good contrast for detection of the printed registration mark. As is conventional the scanner is electrically connected to the control circuit of the bag machine to deenergize the clutch and simultaneously energize the brake thereby arresting the movement of the web for a sufficient period of time to allow the transverse seal bar to operate and thereby make the side weld for two longitudinally adjacent bags. After the seal bar completes its function the control circuit is then conditioned to release the brake and engage the clutch commencing web movement.

As shown in FIG. 1B downstream of the scanner the web passes between intermittently operating draw rolls 84 associated with upper and lower sets of the stripper fingers 86 and 88, respectively, detachably mounted on transverse bars 90 and 91. The draw rolls are connected, as hereinafter will be more particularly described, with means, generally indicated by the numeral 92, for controlling the nip pressure the draw rolls exert on the film and for removing the nip pressure when required, either selectively or automatically.

To resist the deflection of the draw rolls, particularly at their midportion and thereby insure an even value of nip pressure along the length of the draw rolls, a back-up roll 94, in rolling contact with the lower draw roll, is provided. The back-up roll 94 is rotatably mounted in a yoke 96 having a link extension 98 which forms one link of a parallel linkage mechanism 100. The vertical position of the back-up roll 94 and accordingly the back-up force it will apply to the draw rolls 84 can be selected by adjusting a screw jack 102.

Immediately downstream of the draw rolls there is provided a vertically reciprocating sealing mechanism 104, cooperating with an intermittently rotating seal roll 106 for making the transverse seals in the folded web. These seals constitute the lateral margins of the bags. The seal mechanism is reciprocated by a pair of cams 108 (one of which is shown in FIG. 1B) keyed to a shaft 110.

After the web passes the seal mechanism individual bags are at that time produced and they are received by a continuously operating belt conveyor 112. The index conveyor comprises a series of transversely spaced and aligned upper and lower sets of belts, 114 and 116 respectively, moving in a direction indicated by the arrows in FIG. 1B. Those reaches of the belts which are traveling from left to right, as viewed in FIG. 1B, are in contact for the purpose of gripping the bags discharged from the sealing mechanism and transporting them to a stacking table 118 provided with adjustable stop plates 120 for collecting the bags in a stack.

The upper belts 114 of the index conveyor 112 pass around an idler shaft 122 rotatably supported on linkages 124 mounting a cam follower roller 126 which is held in engagement with a cam 128 by a spring 130. As shown in FIG. 1B the cam 128 is mounted on a shaft 132 and during operation the linkages 124 are oscillated raising and lowering the idler shaft 122 which serves the purpose of accommodating any over travel of the bags as they issue from the sealing and cutting mechanism 104 and thus prevent wrinkling of the bag.

Before the bags are discharged to the stacking table 118 they come under the influence of conventional corrugating rollers 134 which serve to stiffen the bag in the direction of movement so as to prevent distortion thereof as it is ejected to the stacking table 118. Before being discharged to the stacking table the trailing end of the bag is momentarily gripped by a slow down mechanism 136 of known construction.

In order to synchronize the speed of the belt conveyor so that bags discharged therefrom are momentarily gripped at or adjacent their trailing edge, an electrically adjustable direct current drive arrangement 138 is provided. While the details of construction of the direct current drive will be explained in greater detail in connection with showings of FIGS. 3 and 4, preliminarily it is to be observed that FIG. 3 shows a variable speed DC motor 140 driving a belt 141 trained about a pulley 142 which is keyed to a shaft 143. The shaft 143 has an adjustable pitch pulley 144 at its opposite end which drives a belt 145 trained about a pulley 146 mounted on a shaft 147. The shaft 147 provides power for the corrugating rollers 134. For purposes of adjusting the pitch of the adjustable pulley 144, a tightener pulley 148 tensions the belt 145 and is carried by a stub shaft 150 mounted on an adjustable arm 152. For driving the index conveyor 112, a pulley 142 on the shaft 143 drives a belt 530 which is trained around a pulley 532 on an upper drive shaft 534 of the index conveyor 112. The lower drive shaft 536 of the index conveyor is powered via gears 538 on the upper and lower shafts 534 and 536.

SLOW DOWN AND D.C. DRIVE

In accordance with the present invention means are provided for accurately adjusting the speed of the belt conveyor 112 to insure that the bag slow down mechanism momentarily grips the trailing edge of each bag before it is discharged to the stacking table 118. The particular means employed to produce the indicated result comprises course and fine adjustment potentiometers 496 and 500 respectively (FIG. 4). As a matter of convenience the potentiometer 496 is located at the main control panel of the machine which is approximately in the area of the seal mechanism 104. The fine adjustment potentiometer 500 is located within reach of the position the operator takes at the stacking table 118, either to observe the bags as a stack is being produced or to remove a completed stack of bags.

As shown in FIG. 4 the potentiometers 496 and 500 are electrically connected to the D.C. motor 140 which is connected to the line by a switch 502. The motor 140 has a pulley 504 keyed on its shaft. The belt 141 transfers the torque of the motor 140 to the double grooved pulley 142 mounted on the shaft 143 which also has keyed thereto the adjustable pitch pulley 144 driving the belt 145 trained about the pulley 146 keyed to the shaft 147. The shaft 147, in addition, carries another pulley 514 driving a belt 516 trained about an idler pulley 518 and pulleys 520 and 522 keyed, respectively, to shafts 524 and 526 which mount the corrugating wheels 528.

The other groove of the pulley 142 engages the previously mentioned belt 530 trained about the pulley 532 which is keyed to the shaft 534; shaft 534 drives the upper belts 114 of the belt conveyor 112, and shaft 536 drives the lower belts 116. Due to the above described organization of structure it will be seen that the DC motor 140 provides the drive for the belt conveyor 112 and the corrugating rolls 134.

To adjust the speed of the motor 140 the fine adjustment potentiometer 500 is set to its midposition while the course adjustment potentiometer is adjusted to regulate the motor 140 so that the bags issuing from the corrugating rolls 134 are gripped by the slow down 136 in the vicinity of their trailing edge. Accurate adjustment of the index conveyor 112 is then accomplished by closely observing where contact with the bags is made by the slow down 136 and adjusting the potentiometer 500, from its previously set mid-position, to change the speed of the motor 140 so that the bags are momentarily gripped at the trailing end before being discharged to the stacking table 118.

The remaining parts of the bag machine drive shown in FIG. 3 comprise a main motor 540 driving the shaft 110 through pulley 542, keyed on the motor shaft, and pulley 544, keyed on shaft 110, and having a belt 546 extending therebetween. Also keyed on the shaft 110 is a reduced diameter pulley 548 driving a belt 550, which in turn drives the shaft 132 by a pulley 554.

On the shaft 132 there is mounted the cam 128, for oscillating the idler shaft 122, through the linkages 124. The pulley 554 is provided with an additional belt groove in which is disposed a belt 556 for driving a shaft 558 by a pulley 560 supporting the lower bar of the slow down 136. As shown, the upper bar of the slow down 136 is driven by gears 562. To maintain proper tension of the belt 556 an idler tension pulley 563 is provided and it is mounted on a shaft 564.

Since the draw rolls 84 and the seal roll 106 are intermittently driven, the input torque to the pulley 460 is received through a shaft 566 mounting a clutch 568 and a brake 570. The belt 462 is trained on a pulley 572 mounted on the shaft 566. The degrees of rotation imparted to the shaft 566 is controlled by the development change device, generally indicated by the numeral 574, which determines the throw of the crank 322 and, of course, the angle through which the segment gear 326 oscillates.

In view of the above it should be apparent that the bag machine drive of the present invention provides a high degree of flexibility by independently controlling the bag belt conveyor to insure proper engagement of the bag by the slow down 136.

Although the best mode contemplated for carrying out the present invention has been herein shown and described, it will be apparent that modification and variation may be made without departing from what is regarded to be the subject matter of the invention as set forth in the appended claims.

Claims

I claim:

1. In a bag machine of the type for making bottom or side weld bags of thermoplastic web material, said machine having a drive train operable to intermittently feed the web which is transversely severed and sealed during its period of repose thereby producing an individual bag, the bag so produced being transported by conveyors, running faster than the average speed of the web, to effect separation of the bags, the discharge end of said conveyor being associated with a bag decelerating device operable to momentarily grip the trailing end of the bag before it is received on a stacking table, the improvement in said bag transporting conveyor comprising a variable speed drive for said transport conveyor, means for adjusting said drive independently of the drive train of the bag machine for controlling the speed at which the bags are transported by said conveyor, said drive being adjusted so that the trailing edges of the bags is momentarily engaged by the bag decelerating device.

2. The apparatus according to claim 1 wherein said variable speed device comprises independently operable nominal and fine adjusting means.

3. The apparatus according to claim 1 wherein said means for driving the bag transporting conveyor is an electric motor whose speed is infinitely adjustable to synchronize the speed of said conveyor with the bag decelerating device so that the trailing end of the bag is momentarily engaged.

4. The apparatus according to claim 3 wherein said electric motor is of the direct current type which is electrically connected to potentiometers adjustable to produce nominal and fine adjustments of said motor.

5. An apparatus for synchronizing the speed of a bag machine belt conveyor with the operation of a bag slow down device which makes momentary contact with bags before being discharged to a stacking table, said apparatus comprising a direct current motor for driving the belt conveyor, means for preliminarily adjusting the speed of said motor to deliver the bags to the slow down so that contact with the bag is made at or near its trailing edge, and means for finally adjusting the speed of said motor so that bags transported by the belt conveyor are engaged at their trailing edge by said slow down device.