US3749534A

US3749534A - Apparatus for the production of sheets or films from liquid material having poor mechanical stability and not susceptible of being directly pumped

Info

Publication number: US3749534A
Application number: US00099869A
Authority: US
Inventors: D Matthews
Original assignee: Res & Dev Co Ltd
Current assignee: Res & Dev Co Ltd; Research & Development Co Ltd gb
Priority date: 1969-12-30
Filing date: 1970-12-21
Publication date: 1973-07-31
Anticipated expiration: 1990-07-31
Also published as: GB1326541A; CA974715A

Abstract

An apparatus for producing sheets or films from mixtures of water and natural or synthetic rubber latex, and other gas having poor mechanical stability and therefore not susceptible of being directly pumped. A conveyor is arranged to receive the liquid mixture from a depositor having a linear outlet extending transversely of the conveyor. The conveyor is arranged to pass through a heating chamber after it has received the liquid mixture. The depositor is fed with liquid from a supply container, a supply conduit extending from the lower part of the container to the depositor. A displacement conduit extends between the upper part of the supply container and a displacement reservoir. The displacement gas reservoir is arranged to receive a supply of a displacement gas under pressure and a displacement liquid supply reservoir is arranged to supply displacement liquid to the displacement gas reservoir, to displace gas therefrom. Displacement liquid fed through the displacement conduit to the supply container forces liquid material from the supply container through the supply conduit to the depositor.

Description

United States Patent 11 1 Matthews 1 July 31, 1973 1 APPARATUS FOR THE PRODUCTION OF SHEETS OR FILMS FROM LIQUID MATERIAL HAVING POOR MECHANICAL STABILITY AND NOT SUSCEPTIBLE OF BEING DIRECTLY PUMPED [75] Inventor: David Ernest Matthews, Cranleigh,

England [73] Assignee: Research & Development Company Limited, Leatherhead, Surrey, England [22] Filed: Dec. 21, 1970 [21] Appl. No.: 99,869

[30] Foreign Application Priority Data Dec. 30, 1969 Great Britain 63,219/69 [52] [1.5. CI 425/92, 425/376, 264/162, 264/216 [51] Int. Cl 529d 7/20 [58] Field of Search ..18/15 R, 15 F, 15 S, 18/4 B; 164/87, 276; 264/50, 162, 216, 217

[56] References Cited UNlTED STATES PATENTS 2,051,201 8/1936 Davidson 264/217 X 2,576,317 11/1951 Toulmin 18/55 2,841,827 7/1958 Crownover.... 18/15 F X 2,951,305 9/1960 Seymour 264/162 X 3,040,381 6/1962 Pioch 18/15 F X 3,216,878 11/1965 Newnharn et a1 264/216 X 451,407 4/1891 LloLyd 164/1 19 FOREIGN PATENTS OR APPLICATIONS 647,140 8/1962 Canada 18115 R Primary Examiner-R. Spencer Annear Attorney1a'nes & Chapman [57] ABSTRACT An apparatus for producing sheets or films from mixtures of water and natural or synthetic rubber latex, and other gas having poor mechanical stability and therefore not susceptible of being directly pumped. A conveyor is arranged to receive the liquid mixture from a depositor having a linear outlet extending transversely of the conveyor. The conveyor is arranged to pass through a heating chamber after it has received the liquid mixture. The depositor is fed with liquid from a supply container, a supply conduit extending from the lower part of the container to the depositor. A displacement conduit extends between the upper part of the supply container and a displacement reservoir. The displacement gas reservoir is arranged to receive a supply of a displacement gas under pressure and a displace ment liquid supply reservoir is arranged to supply dis placement liquid to the displacement gas reservoir, to displace gas therefrom. Displacement liquid fed through the displacement conduit to the supply container forces liquid. material from the supply container through the supply conduit to the depositor.

6 Claims, 5 Drawing Figures Patented July 31, 1973 3 Sheets-Sheet 1 FIN P Patented Jul 31, 1973 3 Sheets-Sheet 2 APPARATUS FOR THE PRODUCTION OF SHEETS OR FILMS FROM LIQUID MATERIAL HAVING POOR MECHANICAL STABILITY AND NOT SUSCEPTIBLE OF BEING DIRECTLY PUMPED BACKGROUND OF THE INVENTION It is well known to produce films or sheets of natural or synthetic rubber latex by depositing a mixture of such material and water or a suitable support and then causing the liquid to solidify, usually by the application of heat. An object of the present invention is to provide an improved way of producing such films or sheets.

BRIEF SUMMARY OF THE INVENTION The invention provides an apparatus for producing sheets or films comprising a conveyor, a depositor having a linear outlet extending transversely of the conveyor and arranged to deposit liquid on the conveyor, means for heating liquid deposited on the conveyor, and feeding means for supplying liquid to the depositor, the said feeding means including a supply container for liquid to be deposited, a supply conduit extending between the lower portion of the supply container and the depositor, a displacement reservoir for a displacement gas, a displacement conduit extending between the upper portion of the supply container and the displacement reservoir, and means by which displacement liquid can be supplied to the displacement reservoir under pressure.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS FIG. 1 is a sectional diagram of an apparatus for producing sheets or films constructed in accordance with a preferred embodiment of the invention;

FIG. 2 is a detail view of, part of a depositor forming part of the apparatus,

FIG. 3 is a sectional diagram of the depositor, and,

FIGS. 4 and 5 are schematic drawings of a modified construction.

DESCRIPTION OF A PREFERRED EMBODIMENT In the embodiment of the invention illustrated in FIGS. 1 to 3, a liquid is spread on to a moving endless conveyor belt 1, gelled (i.e. set by application of heat) and dried to produce a film or sheet of uniform thickness and, if necessary, heated further to vulcanise or cure.

The coveyor l is made of stainless steel or of a woven or non-woven coated fabric. It is passed over rollers 2, to provide a horizontal upper run. One of the rollers 2a is driven by an electric motor 3 through a variable speed transmission unit.

The upper run of the conveyor travels through a heating chamber or oven 4 in which the liquid deposited on the upper run is dried and solidified. The heat ing chamber 4 is conveniently arranged at a temperature of 95C.

The liquid is a water'based natural or synthetic rubber latex and can be pre-vulcanised. Preferably, the liquid consists of about 60 percent rubber and about 40 percent water, the constituents not being exactly in these percentages since small quantities of additives such as stabilisers, sulphur, vulcanising accelerators and zinc oxide are also included. The liquid can be heat-sensitised by any of the well known methods, but preferably by the addition of 0.5 2.0 percent polyvinyl-methyl-ether with adjustment of pH so that it can be gelled or set by the application of fairly intense heat for say 2-3 minutes before drying. This enables thick sheets, say up to 0.040 inch thick, to be deposited continuously in one operation.

The liquid is deposited on the conveyor by a depositor 5 arranged at one end of the upper run. The thickness of the dried sheet is determined by the quantity of liquid deposited and this can be controlled by varying the speed of the conveyor. This depositor 5 comprises an elongated container 6, preferably made of aluminium, for liquid arranged transversely of the conveyor. The container 6 is constructed so as to form a structural beam. At the bottom of the container is a nozzle 7 with a linear outlet slot 8 through which liquid can pass on to the conveyor 1. The nozzle 7 is conveniently of stainless steel, glass or plastics and consists of two strips clamped together with spacers 9 arranged between them at suitable intervals. If the viscosity of the liquid is in the range 30 to 56 centipoises, the outlet slot 8 preferably has a width of 0.015 inch. If desired, the depositor can be provided with heat insulation and with cooling means.

Liquid is supplied to an open top of the depositor 5 by a feed pipe or conduit 10. This feed pipe 10 can either be stationary or, as illustrated, it can be arranged to move from one end of the depositor container to the other on a powered carriage 10a. The liquid, which has poor mechanical stability and therefore cannot be directly pumped, is supplied to the depositor 5 by a displacement system which includes a supply container 11 for liquid to be deposited, a pair of gas reservoirs 12 from which gas is displaced by liquid, and a liquid supply tank 16 from which liquid such as water is fed to the gas reservoirs 12 to displace the gas. The feed pipe 10 to the depositor 5 extends to the bottom of this supply container. A displacement gas conduit 13 extends from the top of the supply container 1 l to the top of the two displacement reservoir 12. The supply container 11 and the displacement reservoirs 12 are both pressurised with air supplied through a line 14 and communicated through the line 13 to the top of the supply container 11, the air pressure being sufficient to force liquid through the feed pipe or conduit 10 into the depositor 5. Water to displace the air in the displacement reservoirs 12 is pumped into the displacement reservoirs 12 through the line from the variable speed pump 15 to the top of the displacement reservoirs l2. l5 drawing water from a constant head supply such as a tank 16, or is gravity fed through a flow meter (not shown). As the water is pumped into the reservoirs 12, it displaces air therefrom, which is communicated through line 13 to the top of tank 11, thereby to maintain a constant flow of liquid latex to the depositor.

The sheet or film produced by the drying of the liquid in the heating chamber is taken off the end of the upper run remote from the depositor 5 on to a spool 17. A thin blade 18 rests on a take-off conveyor 19 in front of the spool 17 and dusting powder, preferably talc, is heaped on the conveyor 19 in front of the blade 18. A rotary brush 20 driven by an electric motor 21 is arranged between the blade and the spool and removes some of the dusting powder from the upper surface of the film or sheet on the take-off conveyor 19 and applies it to the lower surface of the film or sheet exposed on the spool 17.

The heating of the heating chamber 4 is effected by electric heating elements 22 and hot air is caused to circulate inside the chamber by air circulation 23.

A gel heater, i.e. a pre-heater, 24 is arranged between the depositor 5 and the heating chamber 4 to gel the liquid before it enters the heating chamber.

If desired, the apparatus can be modified to produce thicker sheets by means of several deposits, in such cases the take off spool and blade are not used until the sheeting is to be removed.

If desired the apparatus can be a cantilever structure having a removable side frame, making possible the removal of complete endless sheets. The take-off spool 17 and blade 18 are not included in this modified apparatus.

As shown in FIGS. 4 and S the apparatus include a stationary flat, level and smooth bed 25 over which the depositor 5 is arranged on a traversing beam 26. The beam 26 supports a rail 27 on which is a carriage 28 for the pipe 10. The depositor 5 is supported on wheels 31 running on a track 29 at each side of the bed 25. A variable speed geared electric motor 30 drives the wheels 28. The gel heater 24 is movable with the depositor.

I claim:

1. An apparatus for producing sheets or films from a liquid material having poor mechanical stability and therefore not susceptible of being directly pumped, comprising, in combination, a conveyor; a depositor having a linear outlet extending transversely of the conveyor and arranged to deposit such liquid material on the conveyor in the form of a relatively uniform film; means for heating such liquid material deposited on the conveyor; and feeding means for supplying such liquid material to the depositor, the said feeding means including a supply container for such liquid material to be deposited; a supply conduit extending between the lower portion of the supply container and the depositor; a displacement reservoir for a displacement gas; a displacement gas conduit extending between the upper portion of the supply container and the displacement reservoir; and means by which displacement liquid can be supplied to the displacement reservoir to displace gas therefrom to the supply container under pressure, thereby displacing such liquid material through the supply conduit to the depositor.

2. An apparatus as claimed in claim 1 wherein the depositor comprises an elongated container and a nozzle into which liquid can pass from the container, the said nozzle including two plates arranged to define the linear outlet slot, the plates being clamped together with spacers between them.

3. An apparatus as claimed in claim 1 comprising a feeding means which includes a supply container for liquid to be deposited, a supply reservoir for a displacement liquid, a pump for drawing liquid from the supply reservoir and supplying it to the displacement reservoir, a line through which air under pressure can be supplied to the displacement reservoir, and a line through which air under pressure can be communicated from the displacement reservoir to the supply container to displace liquid therefrom, as displacement liquid is supplied to the displacement reservoir.

4. An apparatus as claimed in claim 3, comprising a heating chamber through which the conveyor can travel after receiving liquid from the depositor, a takeoff spool arranged to receive film or sheet from the conveyor after it has emerged on the conveyor from the heating chamber, a blade arranged to contact the film or sheet before it reaches the spool and a rotatable brush arranged to brush the film or sheet as it passes between the blade and the spool.

5. An apparatus as claimed in claim 4 wherein a preheater is arranged between the depositor and the heating chamber to heat liquid on the conveyor before it enters the heating chamber. 6

6. An apparatus as claimed in claim 1, wherein the conveyor is arranged to pass over a flat bed and the depositor is arranged on a traversing beam above the bed, the depositor being supported on the beam and being mounted on wheels so that it can be driven along the bed by an electric motor.

Claims

4. An apparatus as claimed in claim 3, comprising a heating chamber through which the conveyor can travel after receiving liquid from the depositor, a take-off spool arranged to receive film or sheet from the conveyor after it has emerged on the conveyor from the heating chamber, a blade arranged to contact the film or sheet before it reaches the spool and a rotatable brush arranged to brush the film or sheet as it passes between the blade And the spool.

5. An apparatus as claimed in claim 4 wherein a pre-heater is arranged between the depositor and the heating chamber to heat liquid on the conveyor before it enters the heating chamber.