US2401774A

US2401774A - Process for treating plastic tubing

Info

Publication number: US2401774A
Application number: US423746A
Authority: US
Inventors: Frank H Reichel
Original assignee: Sylvania Industrial Corp
Current assignee: Sylvania Industrial Corp
Priority date: 1941-12-20
Filing date: 1941-12-20
Publication date: 1946-06-11
Anticipated expiration: 1963-06-11

Description

June 1946. F. H. REICHEL PROCESS FOR TREATING PLASTIC TUBING Filed Dec. 20, 1941 2 Sheets-Sheet 1 N) INVENTOR FRANK H. REICHEL ATTO R N EY June 1946. F. H. REICHEL PROCESS FOR TREATING PLASTIC TUBING 2 Sheets-Sheet 2 Filed Dec. 20, 1941 v INVENTOR FRANK H. REICHEL B ZOE/4K9. x04

ATTORNEY atented June 11, 1946 V UNITED STATES PATENT OFFICE lfROCESS FOR TREATING PLASTIC H. Reichel, Fredericksburg, Va., assignor to Sylvania Industrial Corporation, Fredericksburg, Va., a corporation of Virginia Application December 20, 1941, Serial No. 423,746

. at some point in its production so as to test the tubing and so that the tubing will have a predetermined circumference after drying and/or after rewetting. In some instances, the tubing has been expanded during drying as by maintaining the tubing expanded with air during the drying operation so that when dry it will have a predetermined dry size.

This procedure has created many problems, however, since when the tubing is maintained in an expanded condition during drying without having been preexpanded, the expanded length of tubing is required to simultaneously undergo expansion, drying and shrinking. It is diflicult to control all three of these operations satisfactorily because one is inevitably influenced by the other. Also, it is impossible as a practical matter to expand a tubing sufliciently to test it and at the same time dry it to its proper size during the same operation. This is because the tubing cannot shrink to its proper dry size if maintained under an expansion pressure which adequately tests the casing, that is, expands -it to a sizeat least equal to and preferably greater than the maximum expanded size it will assume during stufling, cooking, curing and other processing operations. I

For the purpose of overcoming the difflculties presented by the simultaneous expansion and drying process, the operation of expanding the tubing prior to the drying operation has been adopted. The expanding has been accomplished either by the use of a gas such as air or a liquid such as water, and the expansion has usually been brought about by positioning a body of fluid within a casing between two pairs of squeeze rollers and suitably adjusting the volume-of the fluid so as to expand the tubing the desired amount transversely between the two pairs of squeeze rollers which serve to seal oil the part of the tubing between the squeeze rollers from the. remainder of the tubing and maintain the fluid in position within the tubing as the tubing is the tubing with a gas such as air until the tubing @l 12 Claims. (01. 18-57) to partake of set. This has necessitated some support for the tubing such as a moving belt or the like because the static weight of the tubing and the fluid between the squeeze rollers, particularly when a liquid is used as the expanding fluid, imposes additional tensile stress on the tubing over and above that naturally caused by the expansion of the tubing and creates extraneous stresses which frequently cause breakage of the tubing even when the tubing would be fully capable of withstanding the expansion incidental to stufiing, curing, cooking and the like.

I The use of such supports has had some unsatisand the supports which causes the tubing to befactory aspects due largely to the fact that the supports collect dust and some inevitable slippage takes place between the expanded tubing abraded and scuffed so as to make it unsightly and in some cases even punctured. Also, the part ofthe tubing which is in contact with the support'is not free to expand to the same extent as the tubing which is not in contact with any solid surface, so that unequal expansion of the vide a process for expanding tubing which overcomes all of the aforementioned difilculties.

It is another object of the present invention to provide a'process of expanding tubing uniformly throughout the area of the tubing while supporting the tubing on a liquid which does not abrade nor restrict expansion of the tubing.

It is a further object of the present invention to provide a process of producing tubing which involves the expansion of wet tubing while supported on a liquid and the subsequent drying of the'tubing.

Other objects and advantages'of the invention will be apparent to those skilled in the art from recourse to the following detailed description of what are now considered the preferred embodiments of the invention.

The process of the invention in general comprises supporting a length of tubing on the surface of a body of :water or other liquid, filling is expanded to the amount desired, permitting the tubing to remain in the expanded condition for the time necessary for it to take a permanent set to the desired wet size while, if desired,

maintaining the entire surface of the tubing wet by a fluid spray, and thereafter drying the tubing either while inflated or deflated.

The invention accordingly comprises the sev- I tion reference i made to the attached drawings, throughout the figures of which the same elements are represented by the same reference numerals and in which:

' Fig. 1 is a side-elevational view of one form of apparatus for carrying out the process of the invention;

Fig. 2 is a vertical sectional view taken on' the plane indicated by line 2- -2 of Fig. 1 and looking in the direction of the arrows, and

Fig. 3 is a cross-sectional view taken substantially on the plane indicated by line 3-3 of Fig. 1 and looking in the direction of the arrows but with certain parts of the apparatus deleted for the sake of more clearly disclosing the feature to which Fig. 3 relates.

The reason for expanding tubing formed of flexible nonflbrous material, for example, regenerated cellulose, when such tubing is to be used as artificial casings for sausages and other food products, is that the casing are subjected to considerable expanding pressures when the food products and the like are filled into the casing during the stufling operation and when the food products swell during cooking and curing. The high pressures involved frequently cause the casing to burst with a resultant waste of filling material as well a loss of time incidental to clearing away the debris caused by the failure. It has been found that such losses can be minimized by expanding tubing'so used during its manufacture to a size at least equal to the tubing is expanded during stufiing or curing operations for the dual purpose of testing the tubing and sizing the tubing so that lower stuffing pressures can be employed than were heretofore possible. During the preexpansion of such tubing, however; it is preferable that the tubing be uniformly wet over its entire area so as to insure that the tubing be uniformly expanded instead of overexpanded over the wet areas and underexpanded over the dry areas. It is also necessary that the expanding medium have a little static weight as possible so that the tubing is not called upon to support this unnecessary weight during the expanding operation as previously explained. In view of the fact that the tubing is of a relatively fragile nature, it is also necessary that it not be subjected to abrasion incidental to sliding it over supporting surfaces.

It has been found that relatively long lengths of tubing, for example, fifty to several hundred feet, can be supported on a, relatively shallow body of water during expanding as well as moved without harming the tubing by pulling it through the body of water incidental to placing the tubing -on the body of water and removing it therefrom.-

of the tank ID to provide the necessary support. The uprights l4 at the left end of the tank In as viewed in Fig. 1 support frame members it which have a roller I 8 mounted for rotation thereon in suitable bearings 20.

At the left end of the tank I0 as viewed in Fig. 1, a roller 22 is suitably mounted for rotation on a pair of the uprights l4. The roller 22 is contacted by a roller 28 suitably supported for rotation in a frame 28 pivoted at 80 to the same pair of uprights [4. The end of the frame 28 opposite from the pivotal point 30 is provided with a cross bar 29 which serves as an operating handle by means of which the frame 28 and the roller 26can be raised away from the roller 22 to provide for the insertion of tubing between the rollers. The shaft of the roller 22 carries a pulley 32 for rotation therewith and the pulley 32 i connected by means of a belt or chain 34 with a pulley 38 of a driving motor M.

A roller 40, similar to the roller 22, is mounted for rotation on a pair of uprights l4 at the right end of thetank III as viewed in Fig. 1. The roller 40 is contacted by a roller 42 suitably mounted for rotation in a frame 44 pivoted at 46 to the same pair of uprights. The end of the frame 44 opposite from the pivotalpoint 46. is provided with a cross bar 48 which serves as an operating handle by means of which the roller 42 can be raised away from the roller "to provide for the insertion of tubing between the rollers.

the belt 52 with pulley W is connected by means plication Serial No. 399,560, filedon June 24, v

1941, inthe name of Frank H. Reichel.

Referring to the drawings, one form of apparatus capable of use in practicing the .process of the present invention is illustrated in Fig. 1 and comprises a relatively shallow tank l0 which is supported by means of cross-pieces l2 carried v by uprights M. The uprights' I 4 are placed at each end of the tank and, if desired, maybe placed at any desired interval along the length of belt 58 with pulley 58 connected through a suitable friction mechanism (not shown) with a winding drum W suitably mounted for rotation in a supporting frame 60.

The uprights l4 at the right end of the tank It as viewed in Fig. 1 carry frame members 62,

which rotatably support an idler pulley 64 by means of suitable bearings 86.

Tubing T is supplied by a reel R or any other suitable supply source. The reel It may be supported at the left end of the machine by a suitable supporting frame 38.

In the practice of the process of the present invention tubing T is removed from the supply roll R, passed over the idler roller l8, down between the rollers 22-26, along the liquid L in the tank Hi to the opposite end of the machine, and inserted between the second pair of pinch rollers 4042. A supply of expanding fluid, for example air, is inserted within the tubing lying between the two pairs of pinch rollers by raising th frame 44 and inserting a fluid supply nozzle or other fluid-supplying device into the open end .of the tubing and holding th tubing tightly about the nozzle or the like to prevent leakage of the fluid and thereby injecting suflicient fluid into the interior of the tubing T to expand it transversely to the desired diameter between the two pairs ,of pinch rollers. The frame 44 is then lowered to permit the pinch rollers 40-42 to collapse the tubing therebetween and seal an isolated substantially constant quantity of the expanding fluid within the tubing between the two pairs of pinch rollers. The motors M and M are'then started to feed the tubing T through the two pairs of feed rollers and horizontally along the liquid in the tank It). The free end of the tubing T is F a then passed up over the idler roller 04 and down to the wind-up reel W. The speeds of the motors M and M are regulated by any well-known type of speed controllers (not shown) so that the rate of passage of the'tubing T out from between the rollers 40-42 is exactly equal to the rat of passage of the tubing T into the rollers at the left-hand end of the machine. This does not necessarily mean that the speeds of the motors M and M are exactly equal since the tubing may undergo some longitudinal stretching during the transverse expanding. The external diameter of the tubing is suitably measured from time to time by the use of calipers or some other suitable measuring device. If desired, an automatic calipering device may be employed to stop-the machine if the tubin increases above or falls below a predetermined expanded size. When air is needed to bring the tubing to the desired diameter. the machine is stopped and a cut is made in the tubing behind the pinch rollers t042 through which th fluid supply nozzle may be inserted and air may be added by raising the frame 46 to separate the'rollers ie- 32 until the tubing expands to the desired size. The air may, of course, be added in front of the pinch rollers 22-28 instead of after the pinch rollers flit-4? if desired.

In the event it is desired to expand the tubing discontinuously, the tubing '1 is either severed just in advance of the rollers 22-- -2t or is slit sutflciently to permit the insertion of an air or other gas-supplying nozzle and the frame 28 is raised to permit the gas to pass into the tubing supported on the surface of the liquid L and to expand the tubing to the desired amount as indicated by the external size of the tubing by measuring with calipers or any other suitable measuring device. When the tubing '1 reaches the desired size the frame 28 is lowered to permit the rollers 222t to pinch and seal the tubing which is maintained in expanded conditionbetween'the rollers 22-28 and 66-42. After a suitcient time has elapsed to permit the tubing to undergo the desired amount of permanent set as determined by trial, and this time factor will vary with difierent tubing materials, the frame 28 is again raised and the motor M only is suitably nergized to pull the tubing along the water from which it is wound up onto the winding reel W.

In this case the motor M may be suitably disconnected from the roller 22 by any well-known type of declutching device (not shown).

In the event the tubing was severed to permit the insertion of the air nozzle, th ends of the tubing are suitably connected so that the tubing being removed from the surface of th liquid supporting bath will draw additional tubing to be expanded onto the liquid support and subsequent lengths of tubing are expanded in the same manner. Each subsequent length of tubing is preferably joined to the immediately preceding length of tubing in any desired manner so as topermit the gas from the expanded tubing to flow into th tubing to be expanded to thereby at least partially fill the tubing to be expanded with theexhaust gas as it passes onto the liquid support.

In view of the fact that the tubing expands over wet areas more readily than over the dry areas, it is desirable that the tubin be maintained uniformly wet throughout the area being expanded, and to this end a suitable sprayhead 3 may be positioned above the tubing along the length of the tank ill to keep the tubing wet over the entire area undergoing expansion. The water added by the spray S may be exhausted from the 6 tank at any desired outlet or any m' 'nber of outlets llla. In addition to maintaining the tubing wet, the spray and supporting liquid L act as a was}; for the tubing and thereby wash out any materials remaining in the tubing from the form ing operation.

The process of the present invention may be employed in connection with tubing formed from all of the materials set forth in the above-mentioned patent applications.

The tubing may be plasticized or softened before, during or after expansion but before drying. It is preferred to expand the casing while in a wet state but befor plasticizing, since by deferring the plasticlzing step until after the expanding step, the loss of plasticizer is avoided in the event that the tubing breaks while expanding. Also, the thinner wall of the expanded tubing facilitates the plasticizing step in that less time is required for the plasticizer to penetrate entirely through the walls of the tubing. Any p'asticizer or softener agent appropriate to the nature of the tubing material may be used. For example, with cellulose hydrate tubing, the plasticizer may be an aqueous solution of glycerine, a glycol, sorbitol, or th like The tubing may be plasticized by passing it in a fiatcondition through a tank containing the plasticizing solu tion. For example, as by festooning it over a plurality of rolls so that at least the lower portions of the loops oi the tubing pass into the plasticizin solution;. or the tubing may have a plasticizing solution included on the interior of the tubing as well as on the exterior; or the plasticizing solution may be restricted to the interior of the tubin only so as to avoid the for-. mation of deposits of excess plasticizer on the exterior of the tubing and place the majority of th plasticizer on the interior of the tubing where it facilitates stufing and later removal of the easing from the stuffed product. The absence of free glycerine deposits on the externalsurface permits printing inks to spread uniformly and adhere tenaciously to the surface.

Tubing treated in accordance with the present invention may either be wet following the process of forming the tubing or may be rewet after 4 once having been dried.

Casings which have been -dried before being expanded by the present process may be conditioned for such expansion by first treating them with a'suitable wetting agent having regard for the nature of the casing material. For example, dried cellulose hydrate tubing may be placed in a wet state by soaking in an aqueous solution of a wetting agent such, for example, as tergltol, aerosol, monopole oil or other wetting agent. Casings which have become wrinkled or otherwise distorted may be reshaped so as to remove the distortion and/0r sized or resized at the same time by the process of the present invention.

It is to be understood that all expansion of the casing according to the present invention is independent of and distinct from any stretching to which the casing may have been subjected prior to denitration or prior to regeneration, as the case may be, for example, as disclosed in U. S. Patent No. 2,176,925. Any stretching of the tubing which is carried out before denitration or regeneration does not accomplish the novel results produced by expanding the casing after denitration or regeneration in accordance with the present invention.

in any well-known manner, but preferably the tubing to be expanded by the present invention is produced according to said U, 5. Patent no. 2,176,925.

Following expansion of the tubing while supported on the liquid bath it may be dried in a flattened condition, for example, in accordance with the disclosure of patent application, Serial No. 397,552, orin an expanded condition, for exover the stuffing horn of any desired type of stufling machine. While the casing is so held tightly about the horn by one hand of the operator, the latter .operates a pedal or the like to release the product to be filled into thecasing from the stufiing machine. The product, such assausage meat, is ejected from the machine under pressure and is forced into the casing to fill the same and to expand the casing the small amount only which is necessary to insure that the casing closely conforms to the product intro-- duced into the casing without wrinkles or bulges. When the end of the casing is reached, the operator stops the flow of the sausage meat from the stuffer and twists the casing 'to close the open end. While holding the twisted end of the casing, the operator then ties the twisted end or clips it in accordance with the usual procedure to close the casing. The stuffed food product is then passed for further smoking and curing operations in accordance with well-known prior art practices.

The small amount which it is necessary for thesausage meat to expand the casing in accordance with the present invention relieves the operator of the effort heretofore required to hold thecasing against a high pressure. For example, while stuffing prior art casings, it has frequently been necessary to expand the casing in excess of 40 per cent. During stufllng of the casing of this particular modification of the present invention, an expansion of to 18 per cent is all that is required to maintain the casing in tight contact with the casing filling at all times.

When the casing is expanded to the proper extent while supported on the liquid and is later dried in an expanded condition to produce a tubing of the type described in patent application, Serial No. 399,560, the predetermined diameter to which the casing is expanded is ascertained by trial and is-selected so that the casing, after drying and rewetting, will have a circumference smaller than the circumference to which it will be stufied. The difference between the rewetted circumference and the circumference immediately after stuffing is made assmall as possible,

7 having regard for the wall thickness of the easing and the physical characteristics of the material from which it is formed, so as to require a .minimum stuffing pressure and, at the same time,

cause theelastic forces exerted by the casing the casing did not exert any pressure on the stufling material during and subsequent to stuffing. An expansion to a diameter from 5 to 40 per cent greater than the diameter after stuffing has been found to be satisfactory.

When the casings are to be wet prior to stuffing, they are usually tied at one end and then soaked in water or some liquid which wets the casing material. The casings will then shrink when the stresses are relieved which were set in the casing by drying while in an expanded condition. The amount which the casing so shrinks is determined by the magnitude of the predetermined diameter to which the casing was expanded in the drier, and the rewet diameter will be just sufflciently smaller than the diameter to which the casing is to be stuffed to enable the casing to exert the necessary pressure upon the material stuffed into the casing to hold the material firmly in position and prevent bulging and wrinkling of the casing. I

When the casing is stuffed while dry, one end of each of the dry casings as received by the .stufier is closed as by tying or clipping and the material to be filled into the casing is merely poured in from a suitable container or from a suitable spigot, nozzle or the like, while at atmospheric pressure. When the dry casing is thus filled in the same manner as one would pour any product into an open bag or the like, the upper end is closed as by gathering the casing and tying it or clipping it, and the stuffed casing is set aside for a short period. During this period the moisture within the filling material wets the casing and causes it to shrink in the same manner that the casing shrank when rewet prior to stuffing. The shrinkage of the casing while stuifed causes the casing to compress the filling material and force it into a compact, shapely mass which is ,of substantially uniform size throughout its area. The stuffed product is then passed for further treatment in accordance with well-known practices.

Tubing may be expanded while supported on open without stretching the tubing transversely by an internally applied fluid pressure, for example, by an apparatus such as that disclosed in patent application, Serial No. 399,560. In this 'manner the cylindrical shape of the tubing is maintained during drying;

All of the specific examples set forth in the two aforementioned patent applications for the production of tubing are to be understood as applying to the process of the present invention.

The process of the present invention makes it possible to support tubing over a considerable area instead of merely a line contact as is the case when tubing is supported on a conveyor belt or a stationary surface, andat the same time the tubing is supported so as to make it impossible to abrade or in any way scratch the tubing. Also, the tubing is permitted to expand -or contract during transverse expansion and in so doing move over the'surface of the water without putting longitudinal stress Within the tubing because of the .ease with which the tubing can move over the surface of the water as contrasted to the friction which would be present if the tubing were resting on a solid surface such as aconveyor belt.

Since certain changes may be made in carrying out the above process without departing from the scope of the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed is: 1

1. In a process of continuously expanding a fllm-forminghydrophilic organic plastic tubing to a predetermined size prior to drying, the steps comprising placing said tubing in the wet gel state, continuously advancing and expanding successive sections of the wet tubing to the predetermined size' with an isolated substantially constant volume of a fluid and supporting the expanded section of the tubing horizontally on the surface of a body of liquid while so advancing the tubing.

2. In a process of continuously expanding a film-forming hydrophilic organic plastic tubing to a predeterminedsize prior to drying, the steps comprising placing said tubing in the wet gel state, continuously advancing the wet tubing while expanding it to the predetermined size by trapping an isolated substantially constant volume of gas inside successive sections of the tubing and floating the expanded section horizontally on the surface of a body of liquid while so advancing the tubing.

3. In a process of continuously expanding a film-forming hydrophilic organic plastic tubing to a predetermined size prior to drying, the steps comprising placing said tubing in the wet gel state, continuously advancing the wet tubing while expanding itto the predetermined size by trapping an isolated substantially constant volume of gas inside successive sections of the tubing, floating the expanded section horizontally on the surface of a body of liquid while so advancing the tubing, and continuously moistening the surfaces of the expanded section which are not in contact with said body of liquid.

4. In a process of continuously expanding a film-forming hydrophilic organic plastic tubing to a predetermined size prior to drying, the steps comprising placing said tubing in the wet gel state, continuously advancing the wet tubing while expanding it to the predetermined size by trapping an isolated substantially constant volume of gas inside successive sections of the tubing, floating the expanded section horizontally on the surface of a body of liquid while so advancing the tubing, and continuously flattening the expanded tubing.

5. In a. process of continuously expanding a film-forming hydrophilic organic plastic tubing to a predetermined size prior to drying, the steps comprising placing said tubing in the wet gel state, continuously advancing the wet tubing while expanding it to the predetermined size by trapping an isolated substantially constant volume of gas inside successive sections of the tubing, floating the expanded section horizontally on the surface of a body of liquid while so advancingthe tubing, and thereafter drying the tubing.

6. In a process of continuously expanding a film-forming hydrophilic organic plastic tubing to a predetermined size prior to drying, the steps comprising placing said tubing in the wet gel state, continuously advancing'the wet tubing while expanding it to the predetermined size by to a predetermined size prior to drying, the steps comprising placing said tubing in the wet gel state, continuously advancing the wet tubing between spaced pairs of pressure rollers, expanding the section of tubing to the predetermined size between said rollers with an isolated substantially constant volume of a fluid, and supporting the expanded section between said rollers horizontally on the surface of a body of liquid while so advancing the tubing.

8. In a process of continuously expanding a film-forming hydrophilic organic plastic tubing to a predetermined size prior to drying, the steps comprising placing said tubing in the wet gel state, continuously advancing the wet tubing between spaced pairs of pressure rollers, expanding the section of tubing to the predetermined size between said rollers with an isolated substantially constant volume of a gas, and floating the expanded section horizontally on the surface of a body of liquid while so advancing the tubing.

9. In a process of producing artificial sausage casings formed of a hydrophilic organic plastic material, the steps comprising placing said tubing inthe wet gel state, continuously advancing a length of wet tubing while expanding it to a predetermined size by trapping an isolated substantially constant volume of a gas inside successive sections of the tubing, floating the expanded section horizontally on the surface of a body of liquidwhile so advancing the tubing, maintaining the expanded section in a moist condition, continuously flattening the tubing, and drying the flattened tubing.

10. In a process of continuously expanding to a predetermined size regenerated cellulose tubing formed by the denitration of nitrocellulose tubing in'the course of which the tubing is subjected to a liquid treatment, the steps comprising continuously advancing a length of the tubing while it is in the wet gel state resulting from said liquid treatment, expanding successive sections of the wet tubing to the predetermined size with an iso-' lated substantially constant volume of a gas, and floating the expanded section of the tubing horizontally on the surface of a body of liquid while so advancing the tubing.

11. In aprocess of continuously expanding to a predetermined size regenerated cellulose tubing formed from viscose by coagulation and regeneration, in the course of which the tubing is subjected to a liquid treatment, the steps comprising continuously advancing a length of the tubing an isolated substantially constant volume of a gas, and floating the expanded section of the tubing'horizontally on the surface of a. body of liquid while so advancing the tubing.

12. In a process of continuously expanding to a predetermined size a regenerated cellulose tubing, which during formation, is subjected to a liquid treatment, the steps comprising continuously advancing a length of the tubing while it is in the wet gel state resulting from said liquid treatment, expanding successive sections of the wet tubing to the predetermined size with an isolated substantially constant volume of a gas, and floating the expanded section of the tubing horizontally on the surface of a body of liquid while so advancing the tubing.

FRANK H. REICHEIQ.