US 3266216 A
Description (OCR text may contain errors)
Aug. 16, 1966 G. VAN DEN 808 3,266,216
DRIVING MECHANISM FOR ADJUSTABLE UP-AND-DOWN ACTIVATION OF THE SEALING JAWS OF A PACKAGING MACHINE Filed Dec. 19, 1963 United States Patent 8 Claims. ci. 53-189) This invention relates to packaging machines of the type which produce filled and sealed packages from a tube of heat-scalable packaging material.
In these machines, a continuous web of packaging material is pulled over a forming element which surrounds a filling pipe. The forming element forms the web into a tube with the longitudinal margins of the web in overlapping relation. A heated tool may cooperate with the filling pipe for fusing the overlapping margins to form a continuous longitudinal seam. Successive charges of merchandise to be packaged are introduced into the tube through the filling pipe. A pair of heated sealing jaws operate on opposite sides of the tube below the filling pipe, the jaws being movable in a direction transverse to the longitudinal axis of the tube between an open and a closed position, in order to form successive transverse seals in the tube. In addition, the jaws are movable downwardly, while in closed position, in order to advance the tubular material through the machine, and upwardly while in open position, preparatory to formation of the succeeding seal. Each sealing operation of the jaws provides a top seal for the filled package at the lower end of the tube, and a bottom seal for the next package to he filled. If desired, the sealing mechanism may also be provided with means for severing the tube in the sealed region in order to separate the bags from one another.
Machines of the type described above are well known. The present invention relates particularly to the drive mechanism which effects the upward and downward movements of the sealing jaws.
The general ojbect of the invention is to provide a mechanical drive, for effecting the up-and-down movements of the sealing jaws, which permits the length of the stroke of the up-and-down movement to be adjustably varied, even during continued running of the machine. Advantageously, the location of the uppermost end of the stroke of movement of the jaws, i.e., the end lying nearest to the point of formation of the web into a tube and the filling pipe, should remain constant, in which case the alteration of the length of stroke involves only a varia' tion in the location of the opposite end of the stroke.
For the accomplishment of this general objective, according to this invention, one end of a flexible cable or chain is fastened to the jaws and their associated mechanism and the cable or chain is guided over a special combination of rollers or sprocket wheels. These include a fixed sprocket, an adjustable sprocket, and a reciprocaible sprocket, the chain being anchored to the periphery of the reciprocable sprocket. The latter is mounted on a rod having one end pivoted on a fixed axis for swinging movements of said reciprocable sprocket along a circular arc. The reciprocable sprocket or roller is moved back and forth along this are by means of a driving means having a constant reciprocating stroke. The invention also involves the mounting of said adjustable sprocket on a rod which has one end anchored to a fixed pivot, and an adjusting mechanism by means of which this rod can be secured in any selected setting. The adjustable sprocket may therefore be brought closer to or further away from the center of arcuate swing of 3,266,216 Patented August 16, 1966 the reciprocable sprocket. The are along which said adjustable sprocket may be moved by the adjusting mechanism is centered on the arc of swinging movement of the reciprocaible sprocket, and the adjustable sprocket can be shifted between a point near the fixed axis about which said reciprocable sprocket swings and a point which lies on the arc of swinging movement of said reciprocable sprocket.
In a preferred embodiment of the invention a chain or cable extends from a point on the periphery of said reciprocahle sprocket to a point on the periphery of a disk or wheel mounted in coaxial relation to the pivot axis of the rod on which said third sprocket is mounted, said wheel or disk being rigidly secured to the framework of the machine.
Details of the invention will become clearer after a reading of the following description of a preferred embodiment of the mechanism illustrated in the accompanying drawings.
The figure is a schematic representation of a drive mechanism of the present improved character.
The transverse sealing jaw unit is designated in the drawing by the reference numeral 20. It is mounted on a movable carrier 21 appropriately guided in hearings or guides 211 fixedly associated with the framework of the packaging machine. At the upper end of the carrier 21 one end of a chain or cable 22 is secured. Although the present description refers to a chain 22, this element may be a cable, cord, belt, or the like. It extends over a wheel or sprocket 23 mounted on a fixed axis, and from there it extends around another fixed sprocket 2-8, thence to and around an adjustable sprocket 33, thence to a reciprocalble sprocket 25. The chain 22 is secured at 24 to a point on the periphery of the sprocket 25. Although the present description refers to sprockets, these elements may be wheels, rollers, pulleys, or the like.
The sprocket 25 is pivot-ally mounted on the end of a rod 39 whose opposite end is pivoted upon an axis 391 afforded by a fixed bear-ing 29 3. A wheel or disk 29 is secured to the framework of the machine on the axis 391. A chain 30 extends from a point 32 on the sprocket 25 to a point 31 on the periphery of the wheel or disk 29. In series with the chain is a protective spring 300 which serves to prevent injury to the mechanism in case any unyielding obstruction should accidentally hecome interposed between the unit 20 and the guides 211 during the upward movement of the unit 20. Thus, should the upward movement of the unit 20 be prevented, the sprocket 25 will rotate in a counterclockwise direction in the figure to stretch the spring 300 and effectively lengthen the chain 22.
A driving wheel 27, which may be rotated by a suitable motor, in timed relation to the packaging machine, is pivoted on a fixed axis on the framework of the machine. It is adapted to rotate in the direction of the arrow 271. Secured to an eccentric point on the wheel 27 is a connecting rod 26 whose opposite end is articulated to the axis of the swingahle sprocket 25. The connections at the opposite ends of the rods 26 are of a pivotal character, and the wheels 27 and rod 26 serve the function of a crank and connecting rod to impart a reciprocating swinging motion of fixed stroke to the axis of the sprocket 25. j
The sprocket 33 is mounted for free rotation upon the end of a rod 35. The opposite end of this rod is pivotally mounted on a fixed axis 351 on the framework of the machine. An adjusting mechanism is provided for shifting the angular disposition of the rod 35, and by way of illustration an adjusting screw 38 is shown mounted for rotation within a fixed part 40 of the housing of the machine, this rodbeing in threaded engagement with an internally threaded articulation 382 slidably mounted on the rod 35. A hand wheel 381 or equivalent device permits the rod 38 to be rotated, thus serving to adjust the angular disposition of the rod 35, and with it the setting of the sprocket 33. The sprocket 33 can be adjusted to any desired setting along the arc 34.
While the drawing shows a relationship of parts in which the pivot axis 351 of the rod 35 appears to be coaxial with thesprocket 25, it is to be understood that the alignment shown occurs only at one point of the arcuate swinging movement of the sprocket 25 along the arc 392. The pivot axis 351 may be at any selected point along the are 392 and is advantageously at or relatively close to the uppermost end of the swinging movement of the sprocket The drive mechanism according to this invention operates as follows: As the drive wheel 27 rotates in the direction of the arrow 271, a reciprocating movement is imparted to the sprocket 25 by means of the rod 26. The movement is constrained, by the rod 39, to remain on the are 392. The extent of swinging movement of the sprocket 25 along the are 392 is thus constant. During this swinging movement, the sprocket 25 moves alternately closer to and further from the sprocket 33. When the sprocket 25 moves closer to the sprocket 33, the chain 22 is played out around the sprocket 33, whereby the carrier 21 and the sealing mechanism 2%) carried by it slides or travels downwardly, e.g., by its own Weight. On the other hand, when the sprocket 25 moves away from the sprocket 33, the carrier 21 is drawn upwardly. The length of the up-and-down stroke of the carrier 21 is thus dependent upon the extent to which the sprocket 25 moves toward and away from the sprocket 33. The extent of this movement can be adjusted by means of the adjusting screw 38. If the screw 38 is manipulated to swing the rod 35 upwardly, i.e., to bring the sprocket 33 nearer to the pivot axis 391, the extent of movement of the sprocket 25 toward and away from the sprocket 33 becomes smaller and smaller. Conversely, if the adjusting mechanism 33 is manipulated to move the rod 35 away from the axis 391 so as to bring the sprocket 33 to a setting further away from the axis 391 and nearer to the are 392, the differential of movement between the sprockets 25 and 33 during the reciprocating movements of the sprocket 25, becomes appreciably greater, as a result of which the length of the up-anddown stroke of the sealing jaw mechanism is correspondingly greater.
As hereinbefore stated, the adjustment of the screw 38 moves the sprocket 33 along an are 34, the arrow 37 indicating that direction in which the differential of movement between the sprockets 25 and 33 becomes smaller, thus decreasing the length of the stroke of the sealing jaw unit; and the arrow 36 indicates the direction in which the differential of movement between the sprockets 25 and 33 becomes greater with corresponding increase in the length of the stroke of the sealing jaw mechanism. It is important to note that the adjustment of the screw 38 by means of the wheel 381 can be achieved during continued operation of the machine as a whole.
As a result of the provision of the chain 30, the upper end of the stroke of movement of the sealing jaws becomes independent of the length of the stroke of the sealing jaws, and therefore the location of the jaws at the upper end of the stroke can be caused to be constant or substantially so. This is because the distance between the axes 391 and 351 of the wheel 29 and sprocket 25, respectively, remains constant, and because, at the uppermost point of the swing of the sprocket 25 (i.e., when the carrier 21 is at or near its upper end of movement) the section of chain 22 between sprockets 28 and 33 is substantially parallel to the section of chain between the sprockets 33 and 25. The desired result (maintaining the location of the jaws constant at the upper end of their stroke) is ac ieved to maximum advantage when the axis 351 coincides with the uppermost end of the arc of movement (392) of the sprocket 25. Under these circumstances, the distance between the sprockets 25 and 33 is always the same, at the upper end of swinging movement of sprocket 25, regardless of the setting of the sprocket 33 along the are 34. In other words, at the uppermost point of movement of sprocket 25 the chain length between the points 31 and 32, and the chain lengths between sprockets 25 and 33, and 33 and 28, respectively, are always the same; and the result is that the uppermost position of the mechanism 20 remains constant.
This invention has been illustratively depicted in connection with a packaging machine in which the sealing jaw mechanism moves vertically, and in which the downward movement could be brought about by the inherent weight of the sealing unit. It goes without saying, however, that it is within the scope of the invention to employ an appropriate spring or the like in place of the force of gravity, and under these circumstances the invention could obviously be used in a packaging machine in which the transverse sealing mechanism does not travel in a vertical reciprocation, but along a horizontal or other path.
What is claimed is:
1. In a packaging machine in which a tube of heatsealable material is filled with successive charges of merchandise and provided with longitudinally spaced-apart transverse heat seals between said charges in order to form individual merchandise-filled packages, said heat seals being created by a pair of spaced-apart heated jaws arranged on either side of said tube, said jaws being movable toward each other to clamp said tube between them and thereby form a seal in said tube, then downwardly to advance said tube, then away from each other to release said tube, and then upwardly to their initial position preparatory to the formation of another seal in said tube:
an adjustable drive mechanism for effecting the upward and downward movements of said sealing jaws comprising a roller rotatable about an axis fixed with respect to the machine frame, a roller rotatable about an axis adjustable in an arcuate path with respect to a fixed axis on the machine frame, and a roller rotatable about an axis reciprocable in an arcuate path with respect to a fixed axis on the machine frame, all of said axes being parallel, a cable fastened at one end to said sealing jaws and extending over said fixed roller and adjustable roller and having its other end secured to said reciprocable roller, means for reciprocating said reciprocable roller through a swing of constant length in order to impart upward and downward movement to said sealing jaws, and means for adjusting the position of said adjustable roller between the fixed point about which said reciprocable roller swings and the arcuate path along which said reciprocable roller swings, in order to vary the upward and downward stroke of said sealing jaws.
2. In a packaging machine, the elements defined in claim 1 including a disk secured to the machine frame, the axis of said disk coinciding with the axis about which the axis about which said reciprocable roller swings, and a cable having one end secured to a point on the periphery of said reciprocable roller and its other end secured to a point on the periphery of said disk.
3. In a packaging machine, the elements defined in claim 2 including a protective spring in series with said last-named cable.
4. In a packaging machine, the elements defined in claim 1 wherein said axis about which said adjustable roller is adjustable lies on the are along which the reciprocable roller swings.
5. In a packaging machine, the elements defined 'in claim 1 wherein said axis about which said adjustable roller is adjustable passes through substantially the uppermost end of the are along which the reciprocable roller swings.
6. In a packaging machine, the elements defined in claim 1 wherein said axis about which said reciprocable roller swings lies on the arc along which said adjustable roller is movable.
'I. In a packaging machine, the elements defined in claim 1 wherein said means for reciprocating said reciprocable roller comprises a crank, means operating in timed relation to the packaging machine for rotating said crank, and a connecting rod extending between said crank and the axis of said reciprocable roller.
8. In a packaging machine, the elements defined in claim 1 wherein said means for adjusting said adjustable roller comprises a screw threadably mounted in the machine frame, a rod pivoted at one end at the axis about References Cited by the Examiner UNITED STATES PATENTS 1/1942 Kelly. 2/1961 Bennett 744O FRANK E. BAILEY, Primary Examiner.
S. ABEND, Assistant Examiner.