US3470672A - Equipment for packaging machines comprising a sealing ring - Google Patents

Description

A. TUMA Oct. 7, I969 EQUIPMENT FOR PACKAGING MACHINES COMPRISING A SEALING RING Filed June 5. 1967 3 Sheets-Sheet 1 A. TUMA EQUIPMENT FOR PACKAGING MACHINES COMPRISING A SEALING RING Filed June 5. 1967 3 Sheets-Sheet P V /f fy/ Fig. 2

A. TUMA Oct. '7, I969 EQUIPMENT FOR PACKAGING MACHINES COMPRISING A SEALING RING Filed June 5. 1967 3 Sheets-Sheet Fig.3

United States Patent Ofifice 3,470,672 Patented Oct. 7, 1969 US. Cl. 53-59 5 Claims ABSTRACT OF THE DISCLOSURE Apparatus for forming a continuous tubular container from a web of packaging material in which the overlapping seams are sealed longitudinally and a filler pipe disposed axially of said tubular container delivers a viscous liquid thereinto. A bell-shaped sleeve member is tightly atfixed to said filler pipe at a point below the sealing means and the skirt of said sleeve member slidingly and sealingly engages the wall of said container whereby the level of the liquid introduced into the container and the inside of the sleeve form a closed space and variations of pressure inside said space are used to control the flow of viscous liquid through said filler pipe.

The present invention relates to the packaging art and more closely to an equipment for the control of the filling material level for the kind of packaging machines working with a packaging web material that is shaped into a tube, which is longitudinally sealed and partially filled with a preferably viscous filling material and formed into separate packages; the filling material being supplied to the tube through a filling pipe submerged in said tube.

The control of filling material level in packaging machines of the said special kind has long constituted a difficult technical problem. In cases where the filling material consists of a liquid of low viscosity, such as for example, milk, wine, juice or similar, the control problems could be solved with the aid of a level :pipe submerged in the filling material. By sensing the air pressure above the liquid level in the level pipe, and letting this operate throttle valves in the filling material supply line, the so-called filling pipe, the material level in the tube has been able to be arbitrarily controlled.

When the filling material is a viscous substance such as, for example, clotted milk, yogurt, fruit-juice jelly or the like, however, the difficulties cannot be overcome only by arranging a level pipe in the tube. It is true that even in these cases the differences between filling material levels in the tube and the level pipe will create a certain pressure in the level pipe, but due to the inertia of the filling material, the reaction of a change in level is suppressed considerably. Thus the system will be both insensitive and slow, and does not therefore meet the demands raised on a packaging machine control unit.

One object of the invention is therefore to produce a control equipment that will comply with the requirements stipulated even in cases where the filling material is viscous. As before, this equipment includes a level pipe of the kind stated, which is supplemented by a pressure amplifying sealing member by which means much greater and more rapid reaction in the level pipe will be obtained after a change in level in the tube. Possibly the level pipe can be eliminated if instead the pressure is sensed directly in the filler pipe.

As previously mentioned, the invention is intended to be used for packaging machines that work with a packaging web material, which is folded over to form a tube that is longitudinally sealed and filled with material through the filling pipe. The longitudinal joint is produced by placing both the edges of the web material so that they overlap each other, whereafter heat is supplied to the overlapping area so that the plastic material with which the web is coated will melt and stick together, so that a welded tube is obtained. In order for the joint to be durable, however, it must be allowed to stabilize .itself for at least a short interval of time. It is obvious, therefore, that high stresses in the newly-formed tube must 'be avoided if possible. Thus the internal compressive stresses in the tube constitute a considerable risk factor that must be eliminated. It is therefore an additional object of the invention to eliminate the detrimental effect of the internal pressure amplification that occurs with the present level control method, and this can be obtained principally by a special design of the sealing member.

The invention is thus characterized in that a sealing member is fitted around the filler pipe in the form of a sleeve, which makes sealing contact with the inside of the movable tube and tightly encloses the filling pipe, by which means a closed space is obtained defined at the top by the said sleeve and at the bottom by the upper level of the filling material in the tube, whereby the volume of the space is determined by the level of filling material in the tube, i.e. the level that is intended to be controlled.

The invention will now be more closely described in the following with reference to the accompanying draw ings, showing by way of example an embodiment of the invention, and in which FIG. 1 is a schematic view of a packaging machine, to which it is intended to apply the principles of the invention;

FIG. 2 shows, partly in section, a sealing element according to the invention; and

FIG. 3 shows in section a tube and its filling material together with a level-pressure diagram.

In FIG. 1 a packaging web material is designated 1 and is of the kind that, at least on the side that is intended to form the inside of the finished packages, has a surface of heat-scalable plastic. The web material 1 is unwound from a supply roll, passes a guide roller and a folder, and is shaped with the aid of a tube forming element, not shown in more detail, into a tube 3. The overlapping longitudinal edges are sealed to each other by means of a welding element 4, so that a longitudinal joint 2 is obtained. The tube is pressed together at its lower part with the aid of transverse sealing jaws, which are not shown. When these jaws are heated, the compressed plastic surfaces will stick together and, in this way, a transverse seal 5 is obtained. If consecutive transverse seals 5' and 5 are made at right angles to each other, packages 6 of tetrahedral shape will be obtained.

8 designates a pipe for the supply of filling material to the tube 3. The filling material, which is assumed to consist of a viscous substance such as, for example, clotted milk, or yogurt, will rise in the tube to a filling material level N which it is required to maintain at a certain constant value. The mouth of a level pipe 9 arranged inside the filler pipe 8, is essentially on a level with the lower end of the filler pipe. The level pipe 9 is open at its lower end, so that it communicates with the tube 3. The filling material will thereby rise in the level pipe to a level N which, as a result of a certain overpressure being maintained in the level pipe above the level N will be slightly below the level N in the tube 3. 10 designates a relay unit that is arranged, dependent on the pressure in the level pipe 9, to control a throttle valve 11 arranged in the filler pipe 8 or its supply line. It is also possible entirely to eliminate the level pipe if the pressure in the filler pipe is permitted, via a pressure sensing member, to control directly a throttling element, for example 3 a reducing diaphragm. The pressure sensing member in this case may be an impulse diaphragm.

12 in FIG. 1 finally designates a bell-like sealing member, which as to its function defines a sleeve seal. How

this member is intended to be designed for a projected embodiment is shown in more detail in FIG. 2.

The sealing member 12, which in FIG. 2 has been shown partly in section, has three principal parts, namely a neck portion 2% with a considerable wall thickness, an intermediate portion 21 with first a rather great but then diminishing wall thickness, and finally a flexible cylindrical portion 22 with a thin wall thickness. The cylindrical portion 22. makes a sealing contact with the inside of the movable tube 3. The neck portion 26 is pressed securely against the filling pipe 8 by means of a hose clip 23, so that sealing is obtained also here. The sealing body 12 is suitably manufactured of a rather elastic material with a low friction value so that no harmful friction can occur against the thin plastic surface of the tube 3. A suitable material for this purpose is the plastic substance polytetrafiuoroethylene, i.e. the material that is marketed under the name Teflon. It is obvious that the sealing sleeve may be given a shape that differs from that shown in the figure. Thus it is not essential that the part 2.2 is wholly cylindrical. Instead, it might be more advantageous to make it slightly enlarging downwards, so that it will press against the wall of the tube, whereby a good initial sealing may be obtained.

In FIG. 3 a tube filled with filling material is shown schematically in cross section. If the tube is not fitted with a sleeve seal specific for the invention, the filling material will rise to a considerable height before the pressure in the level pipe 9 becomes sufiiciently high for it to react by reducing, via a throttling element, the supply of filling material through the filler pipe 8. A particu lar disadvantage is also that the thick, viscous material in the peripheral parts of the tube is brought into motion downwards by the downward-moving package material, whilst the filling material in the central part of the tube, after a considerable rise in level, will be left suspended on the wall of the filler pipe. How the pressure p in the level pipe 9 depends on the filling material level 11, in the case when there is no sealing member in the tube, is shown by the upper curve in the diagram.

By instead arranging a sealing member 12 in the tube, as in accordance with the invention, which demarcates a closed space 31, a means will be obtained of controlling the filling material level within considerably closer limits. If the filling material 3% rises in the tube 3, the volume of space 31 will be reduced with a consequent pressure amplification. Naturally this pressure will act on the upper surface of the filling material and force up the filling material in the level pipe 9, so that the pressure therein will increase. When the filling material is viscous, this factor is predominant for the creation of the pressure in the level pipe, since the pressure factor that is dependent on the difference in levels between the levels in tube and level pipe, defined liquid column, is appreciably reduced by the high viscosity of the filling material. The greater dependence of the pressure p on the filling material level, in the case when a closed space has been created above the filling material level with the aid of the sealing member 12-, is shown by the lower curve in the diagram.

There are above all two reasons why it is important that the filling material in the tube will rise above the lower edge 32 of the sleeve 12, viz on one hand because it creates a self-sealing of the volume 31, and on the other hand because the newly-formed longitudinal joint 2 is prevented from being exposed to pressure from the air volume 31. Instead the longitudinal joint 2 will be brought into contact with the filling material 30, but as this is rather cold it will act on the contrary as a stabilizing factor for the joint by cooling it.

In certain cases the occurrence of air bubbles in the filling material supplied to the tube is considerable. There is therefore a risk that these will collect into an ever increasing air cushion above the surface of the liquid in the tube, whereby the volume 31 will become larger and larger. This risk can be eliminated, however, in that the sleeve 12 is perforated by a ring of small apertures in the area of transition between parts 21 and 22.

It should be appreciated that the invention is not limited to the embodiment shown. For example, it is possible to vary the control capacity of the air volume 31 in several ways. Thus the throttling members in the filling pipe, which according to the embodiment shown are controlled by the volume 31, could possibly be eliminated completely, and instead permit the pressure in the volume 31 to counteract by its force the pumping means that force down the filling material through the filler pipe, i.e. make the system fully self-controlling without exterior control members. Other modifications are also conceivable, as well regarding the level controlling capacity of the sealing sleeve, as its abiiity of supporting the longitudinal joint. In order to improve the latter factor, it is possible for example, to permit the sleeve to work together with an outer sleeve; with specially designed trans verse sealing jaws; or with other members intended further to support the pressurized tube. It should be appreciated, therefore, that the invention is only limited by the following claims.

I claim:

1. In apparatus for packaging viscous liquid materials which includes means for forming a continuous tubular container from a web of packaging material, means for forming a continuous longitudinal seam along the wall of said tubular container, a filler pipe disposed axially of said tubular container for introducing liquid material into said tubular container and means for forming separate compartments in said filled tubular container, the improvement comprising a bell-shaped sleeve member of resilient, flexible material secured in sealing relation about said filler pipe, the circumferential skirt of said sleeve member slidingly and sealingly engaging the inner wall of said tubular container to form a closed space defined by the inside of the sleeve member and the level of viscous liquid above the bottom edge of the skirt of the sleeve member and means responsive to the pressure in said closed space for controlling the rate of introduction of viscous liquid through said filler pipe.

2. Apparatus as claimed in claim 1 wherein the bellshaped sleeve is disposed below said sealing means whereby the longitudinal seal along the wall of said tubular container is stabilized before coming in contact with the viscous liquid as the continuous tubular container is continuously filled.

3. Apparatus as claimed in claim 1 wherein the thickness of the circumferential bell-shaped sleeve member diminshes toward the lower edge thereof to improve the sliding and sealing engagement with the wall of said tubular container.

4. Apparatus as claimed in claim 1 wherein the upper portion of said bell-shaped sleeve member is provided with vents to permit exhausting excess pressure from said closed space caused by air bubbles introduced with said viscous liquid.

5. Apparatus as claimed in claim 1 wherein the bellshaped sleeve member is composed of polytetrafluoroethylene.

References Cited FOREIGN PATENTS 511,594 6/1952 Belgium.

THERON E. CONDON, Primary Examiner E. F. DESMOND, Assistant Examiner US. Cl. X.R.

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