Film Heating System

Abstract

A mechanism includes a series of half-shells pivotally interconnected to form an endless chain of elements and forms a series of half-sections from a film drawn by vacuum into the pivotally interconnected half-shells and such half-sections are secured to another series of similarly formed half-sections to envelop a plurality of primary packages. The pairs of half-sections are then sealed together and tightened about the primary packages and are subsequently severed from each other. In order to condition the film for lining the half-sections, it is necessary to apply heat thereto and such heating is effected by supplying fluid such as heated air at a constant temperature and a at a rate which varies in accordance with variations in the velocity of movement of the film through the heating station, such movement being a function of the speed of operation of the mechanism itself.

Description

In order to form a series of interconnected half-sections from a continuous strip of plastic film by means of vacuum, it is necessary first to heat the film and then preferably to apply vacuum thereto in such a way as to draw the film into the interconnected shells. Obviously the temperature of the film must be properly controlled and the heating action must be correlated with the speed of movement of the film in order to prevent improper heating of the film.

According to this invention, a strip of plastic film moving along a predetermined path is heated by conduit means arranged to direct a flow of heated fluid at a substantially constant temperature toward the film, and regulating means for controlling the rate of flow of the fluid is provided and is coordinated with the velocity of movement of the film itself.

For a better understanding of the invention, reference may be had to the following detailed description taken in conjunction with the accompanying drawings in which

FIG. 1 is a side view of a packaging machine which incorporates a film heating system constructed according to this invention;

FIG. 2 is a top view of the arrangement shown in FIG. 1;

FIG. 3 is a perspective view of a heating mechanism disposed atop the packaging machine and which is constructed according to this invention;

FIG. 3A is a cross-sectional view taken along the line designated 3A--3A in FIG. 3;

FIG. 3B is a cross-sectional view taken along the line designated 3B--3B in FIG. 3A;

FIG. 3C is a cross-sectional view taken along the line designated 3C--3C in FIG. 3A;

FIG. 4 is a cross-sectional view taken along the line designated 4--4 in FIG. 2;

FIG. 5 is a cross-sectional view taken along the line designated 5--5 in FIG. 1;

FIG. 5A is a view generally similar to FIG. 5 but which depicts by arrows the direction of flow of fluid such as air for heating the film strip according to this invention;

FIG. 6 is a cross-sectional view taken along the line designated 6--6 in FIG. 5;

FIG. 7 is a schematic view of the control system for the packaging machine and the associated film heating system.

In the drawings, a pair of corner posts 1 and 2 are provided and are observable in FIG. 1. While only two posts are observable in FIG. 1, it will be understood that a vertical post is disposed at each corner of the machine. Transverse horizontally disposed beams 3 and 4 are provided as is apparent in FIG. 2 and are supported by the corner posts. Longitudinally disposed beams 5 and 6 are provided and constitute elements of the frame of the machine together with the beams 3 and 4 and the corner posts. As is apparent in FIG. 1, side plate 7 is mounted in any suitable manner on the frame of the machine and cover plates 8 and 9 overlie portions of the moving parts as is schematically shown in FIG. 2.

A first group of half-shells generally designated by the numeral 10 are pivotally interconnected by pins one of which is designated at 11 to form an endless chain. Disposed alongside this endless chain is a strip of film designated F1. Film F1 is heated by oven section 12 which is constructed according to this invention and the film F1 is held into close contact with the half-shells 10 by means of endless element 13. A series of shells 10 forming an endless chain are supported at the lefthand end as shown in FIG. 2 by a rotatable sprocket mechanism 14 and in similar fashion at the other end the chain is supported by sprocket 15. Endless element 13 is supported at its ends by rotatable sprockets 16 and 17.

On the other side of the machine, a similar arrangement is provided wherein film strip F2 is fed alongside a series of half-shells not shown in the drawing but which are movably mounted on sprockets 18 and 19.

The two series of interconnected half-sections are formed from the strips F1 and F2 by drawing the film strip into the half shells. Primary packages schematically represented by the letter P are fed in onto the platform schematically shown and designated by the numeral 20 and are enveloped in the region of the numeral 21 by the two cooperating mating half-sections as is more fully disclosed in U.S. Pat. Application Ser. No. 31,687 filed Apr. 24, 1970.

The film such as F1 and F2 must be heated before being drawn into the half-shells 10. Toward this end, the oven section 12 is disposed over and alongside the film F1 while a corresponding oven section 22 is disposed over and alongside the film F2. Oven sections 12 and 22 are interconnected by a center hood section generally designated by the numeral 23.

The oven and its two heating sections can best be seen in FIGS. 3, 3A, 3B and 3C as a unit apart from the associated packaging machine.

Generally speaking, ambient air is circulated by a fan F driven by motor M mounted atop the hood 23. This air follows the directions indicated by the arrows in FIG. 3A downwardly through the central supply conduits S and into the two oven sections 12 and 22 and thence transversely toward the film strips through nozzles designated by the numerals 24-30 forming a part of oven section 12 and through corresponding nozzles such as are designated by the numerals 24A and 25A. Heat is imparted to the circulating air by means of heater elements 31 and 32 which are thermostatically controlled by means not shown and through which the return air flowing from the point of use adjacent oven sections 12 and 22 through return conduits R into fan F. Fan F directs the heated air transversely and downwardly through suitable conduit means into the nozzles and thence into contact with the film such as F1 and F2. As is apparent in FIGS. 3B and 3C, air is fed downwardly through the central supply conduit S and is returned through the outer return conduits designated at R.

As is more fully explained in the aforementioned U.S. Application Ser. No. 31,687 now U.S. Pat. No. 3642414 and is generally shown in FIG. 4, the chain of buckets or half shells as represented by the numeral 10 in FIG. 4 is provided with rollers 33 and 34 which ride on tracks 35 and 36 affixed to support elements 37 and 38 respectively. Support elements 37 and 38 are secured by bolts such as 39 and 40 to brackets 41 and 42 which in turn are provided with slots 43 and 44 by which lost-motion connections from left to right are established between the brackets 41 and 42 and the fixed elements 45 and 46 by virtue of bolts 47 and 48 which are disposed within the slots 43 and 44. Pressure fluid supplied into flexible conduits 49 and 50 thus urges brackets 41 and 42 toward the left and holds the buckets such as 10 into secure contact with film F1 which on its lefthand surface is held against transverse movement by support plates 51 and 52 on which rollers 51A and 51B are mounted. Thus the film F1 is securely held between the contacting surfaces of the shells 10 and support plates 51 and 52 and associated structure all as is more fully disclosed in the aforementioned U.S. patent application.

As is apparent from FIGS. 4, 5 and 5A, hot air supplied downwardly through supply conduit S is fed horizontally through horizontally disposed conduit C and outwardly through the nozzles such as 24-30 and into contact with the film F1.

In accordance with a principal facet of this invention, this heated air is supplied at a constant temperature and at a rate which varies in coordination with variations in the speed of movement of the film F1.

In order to effect progressive variations in the rate of flow of heated air through conduit C, a slidably mounted gate valve 53 is provided with a series of apertures 54-60 which, as is obvious from FIG. 6, are variable in cross-sectional area. Thus movement of gate valve 53 from its closed position represented in FIGS. 5 and 6 toward the left first causes aperture 54 to coincide with the horizontal passage through nozzle 30 and in this manner a flow of heated air is established through nozzle 30 and into contact with film F1. For slow velocities of movement of Film F1, it is possible that valve 54 alone can supply sufficient heating action properly to condition the film F1 for subsequent manipulation by the packaging machine. As the velocity of movement of film F1 increases, valve gate 53 automatically moves toward the left and at such time as aperture 55 partially or completely overlies the opening through nozzle 29, an increasing flow of heated air at a constant temperature is supplied to film F1. In like fashion, a coincidental relationship between apertures 56-60 and nozzles 28-24 is established as the velocity of movement of the film such as F1 is increased.

Should the packaging machine stop either by design or through inadvertence, it is necessary to shut off the flow of air through the nozzles 24-30 and toward this end gate valve 53 is closed automatically. This operation is accompanied by a simultaneous opening of by-pass valves 61 and 62 which allow the air within conduit C to flow through valves 61 and 62 upwardly through return conduits R and to circulate through the heaters 31 and 32 and fan F without coming into direct contact with the film such as F1. This operation keeps the oven warm and the temperature of the air constant and hence when the machine is restarted, the temperature is correct and operation is correctly and immediately resumed.

Automatic operation of the gate valve 53 and of the by-pass valve 61 and 62 is insured because of the general control system represented in a highly schematic fashion in FIG. 7. In FIG. 7, a source of high pressure operating air is indicated by the numeral 63. This fluid is supplied through conduits 64, 65 and 66 to main machine operating device 67 and to oven control operating devices 68 and 69. Main machine operating device 67 is simply arranged to vary the speed of the packaging machine and in turn the movement of the film strips F1 and F2 depending upon the accumulating of backlog and the rate of infeed of primary packages P into the machine all as described and claimed in U.S. Pat. No. 3,465,869 issued Sept. 9, 1969 in which packages or containers C correspond to packages designated P herein. The schematic device designated at 67 in FIG. 7 together with motor M correspond to FIG. 6 of U.S. Pat. No. 3,465,869 wherein the motor designated M corresponds in structure and function to the motor designated M herein. In U.S. Pat. No. 3,465,869, the arrangement of FIG. 6 serves to vary the effective diameter of a driving pully mounted on the shaft of motor M. Devices 68 and 69 are similar to devices 67 and simply control impart sliding movement to the operating arms 68A and 69A and in turn the gate valves such as 53 and 53A for the two oven sections designated by the numerals 12 and 22. Control pressure is supplied from source CP to the main operating device 67 and to the gate operating elements 68 and 69 through control conduit 70, 71 and 72. In U.S. Pat. No. 3,465,869 as shown in FIG. 3, control pressure is derived from relay AR and is supplied to conduit L5 which corresponds to conduits 70, 71 and 72 herein. It is apparent from FIG. 7 that the same initial conditions which cause changes in the speed of operation of the packaging machine as reflected by operation of device 67 also cause changes in the operation of the devices 68 and 69. By this means, a constant temperature supply of heated air is available and the degree of heating imparted to the film such as F1 and F2 is dependent upon the rate of flow of heated air supplied to the film in accordance with a principal facet of this invention.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A system for heating a moving element comprising conduit means for directing a flow of heated fluid at a substantially constant temperature toward said element, regulating means for controlling the rate of flow of said fluid in coordination with the velocity of movement of the element, said regulating means including aperture means disposed along the path of movement of the element to be heated, and means for varying the effective open cross-sectional area of said aperture means as a function of the velocity of movement of the element.

2. A system for heating a moving element comprising conduit means for directing a flow of heated fluid at a substantially constant temperature toward said element, regulating means for controlling the rate of flow of said fluid in coordination with the velocity of movement of the element, said regulating means comprising a series of spaced nozzles disposed along the path of movement of the element and arranged to direct a flow of fluid toward said path, and a slidable gate valve member having apertures therein corresponding to said nozzles and movable in a direction generally parallel to said path thereby to regulate the flow of fluid through said nozzles by varying the degree of registry of said apertures and their associated nozzles.

3. A system for heating a moving element comprising conduit means for directing a flow of heated fluid at a substantially constant temperature toward said element, regulating means for controlling the rate of flow of said fluid in coordination with the velocity of movement of the element, and by-pass valve means forming a part of said conduit means and arranged to accommodate flow of fluid to the entry end of said conduit means when said regulating means prevents a flow of fluid to the element.

4. A system according to claim 1 wherein said aperture means is progressively opened from the region of the outfeed end of the path of movement of the element toward the infeed end thereof as a direct function of an increase in the velocity of movement of the element.

5. A system according to claim 2 wherein movement of said gate valve member toward the infeed end of said path increases the rate of flow of the fluid.

6. A system according to claim 2 wherein the cross sectional area of said apertures increases from one aperture to the next in a direction toward the outfeed end of said path.