GB2100398A - Vacuum drying machines - Google Patents

Abstract

In a continuous vacuum drying machine for open width fabric, a roller sealing arrangement at the inlet (6) for fabric or outlet for fabric from the vacuum chamber (2) includes a set of resilient rollers (10,12) for sealingly gripping the fabric in a nip (14), hard rollers (28,30) bearing against the set (10,12) so as to provide sealing contact, and sealing strips (34,36) in turn bearing against the rollers (28,30) extending tangentially thereto and drawn against the rollers (28,30) by the vacuum inside the chamber (2). <IMAGE>

Description

SPECIFICATION Vacuum drying machines The invention relates to vacuum drying machines in which fabrics and other materials in sheet form are drawn continuously through a chamber where a subatmospheric pressure is produced so that water evaporates from the fabric.

The invention provides a vacuum drying machine having a vacuum drying chamber, means for creating a vacuum in the chamber, and an inlet and outlet for fabric to the chamber each including a pair of resilient friction rollers formirig nip for advancing fabric into or out of the chamber, a pair of hard sealing rollers each resting on one side against the respective friction rollers, and a pair of low friction sealing strips mounted resiliently and sealingly on the chamber at one side and extending substantially tangentially towards the sealing rollers, so that when a vacuum exits inside the chamber the strip is urged by vacuum onto the sealing roller sealingly to engage it.

The resulting seal reduces the ingress of air, and maintains vacuum. High friction rollers can be used for positive non-slip fabric advancement whilst efficient sealing is created by the strips bearing on the sealing rollers aided by the internal low pressure in the machine. Wear of the strip is compensated automatically.

Preferably a strip of plastics material is sandwiched between rubber strips at its mounting side. In this way movement of the strip to establish or maintain efficient sealing is facilitated and relatively hard and low friction materials may be used for the strips.

Efficient end sealing can be obtained by arrangements in which a low friction sealing material is urged against the ends of the rollers and moist air is directed onto the roller ends for cooling. Preferably then all rollers are driven and the roller ends are grooved to facilitate the circulation of air and cooling.

The sealing material can then be urged strongly against the roller ends while a satisfactory seal life is obtained.

Drawings Figure 1 shows a side view of an inlet arrangement for a vacuum drying machine according to the invention; Figure 2 shows a part front view of the arrangement of Figure 1; Figure 3A and 3B show a top view, partly in section of the arrangement of Figure 1; Figure 4 shows schematically a section through a drying machine according to the invention; Figure 5 shows schematically a possible vacuum and liquid circulation arrangement for use with the drying machine of Figure 4; and Figure 6 shows a similar arrangement in more detaii.

With reference to Figure 4, a drying chamber 2 encloses a series of heatable rollers 4 over which fabric passes from an inlet arrangement 6 to an outlet arrangement 8.

Each inlet and outlet arrangement (see Figures 1, 2, 3A and 3B) includes a pair of resilient, high friction rubber covered rollers 10 and 1 2. The rollers 10 and 12 are pressed towards one another and from a nip 14 in which fabric is gripped to convey it in or out of the chamber 2.

The rollers 10 and 12 have axles 1 6 located in bearing blocks 1 8 which can be adjusted by means of screws and nuts at 20 in the fabric feed direction of side plates 22.

The side plates 22 also mount bearing blocks 24 for axles 26 of hard metal sealing rollers 28 and 30 whose surfaces bear against the rollers 10 and 12.

L-section members 32 mounting a sealing strip arrangement which includes a polythene strip 34 sandwiched between rubber strips 36 by means of a metal strip 38 bolted to the members 32. The strip 34 extends tangentially to the rollers 28 and 30.

A plate 40 of polytetrafluorethylene is located between the plates 22 at each end of the rollers and the rollers 10, 12 and 28, 30. The ends of the rollers have annular grooves 42 passing over the plates 40 (See Figure 3A). Air nozzles (not shown) direct moist air into the grooved roller ends.

A pulley and gear arrangement indicated at 44 rotates all the rollers simultaneously. The resilient compression of the rollers 10 and 12 seals off and reduces ingress of air at the nip 14. The contact between the rollers 10 and 28 and 12 and 30 respectively prevent ingress of air over or under the rollers 10 and 12 without frictioning as both surfaces are rotated simultaneously. The strips 34 slide over or under the rollers 28 and 38 at low friction because of the nature of the material forming the strips 34 and the smoothness of the rollers 28 and 30. The vacuum inside the chamber 20 pulls the strips 34 onto the rollers 28 and 30 and reinforces the sealing effect.

The flow of air onto the grooved roller ends cools the rollers reducing thermal distortion and also wear and heating of the polytetrafluorethylene plates 40. The airflow also cleans the roller ends.

With reference to Figure 5, it can be seen how the drying chamber and sealing arrangement described previously can be used in an overall system wherein steam 50 from a boiler enters heating rollers 4 to heat the fabric and wherein the cooled steam from the heating rollers 4 and the steam generated by drying of the fabric are both condensed at 52 by injection of cold water at 54. The liquid formed in the condenser 52 contains the heat of condensation of the steam and can be used as a source of hot water for use in boilers etc. Due to the efficient sealing, ingress of air is reduced to such an extent that the condensation process can proceed satisfactorily whilst helping to maintain a low pressure or vacuum inside the chamber 2.

Figure 6 shows two chambers 2 in series, and how liquid formed in the condenser 52, is transferred by a condensate pump 56 to a trap 58 having a vent 60. A vacuum pump 62 is applied to the top of the condenser 52, is connected to the mains water inlet 54, and returns pump water to the trap 58. Steam condensate also is returned by a line 64 from the chambers 2 to the trap 58.

From the trap 58, hot water is discharged by a pump 66 to processing or other end use.

Claims (filed on 12 May, 1982) 1. A vacuum drying machine having a vacuum drying chamber, means for creating a vacuum in the chamber, an inlet and outlet for permitting fabric to run into and out of the chamber each inlet and outlet including a set of opposed, resilient friction rollers forming a nip for fabric therebetween, hard sealing rollers one on each side of the set of resilient friction rollers, each hard roller resting on one side of the resilient rollers facing the hard rollers, and low friction sealing strips, one on each side of the assembly formed by the resilient rollers and hard rollers, each mounted resiliently and sealingly on the chamber on one side of the strip and extending tangentially to the side of the adjacent hard roller opposite the side which engages the resilient roller so that when a vacuum exists inside the chamber the strip is urged by the vacuum towards the hard roller to sealingly engage it.

2. A vacuum drying machine as claimed in claim 1 wherein each of the low friction sealing strips include rubber strips on the side of the strip mounted on the chamber and a strip of plastics material between the rubber strips for engaging the hard roller.

3. A vacuum drying machine as claimed in claim 1 in which a pair of flanges mount between them the resilient and hard rollers at the inlet and outlet, each flange including low friction resilient material, the rollers have ends with axially orientated annular grooves, the flanges have cut aways to expose the roller ends, and means are provided for directing moist air on to the roller ends at the cut aways to cool the roller ends and the low friction resilient material bearing against the roller ends.

4. A vacuum drive machine as claimed in claim 1 in which drive means provided for rotating each roller, individually adjustment means are provided for the set of resilient rollers to move it in the direction of fabric movement and the hard rollers are off-set in the direction of movement of the fabric so that the sealing pressure between the respective resilient and hard rollers can be varied.

5. A vacuum drying machine according to claim 1 in which a plurality of fabric engaging hollow guide rollers are mounted to extend through the drying chamber to provide a convoluted fabric path, means are provided for supplying steam to and exhausting it from the interior of the guide rollers and means are provided to condense exhaust steam from rollers and the vapour from the vacuum chamber by the use of cold water to thereby assist in the maintenance of the chamber vacuum and permit use of the condensate for a secondary end-use.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. how liquid formed in the condenser 52, is transferred by a condensate pump 56 to a trap 58 having a vent 60. A vacuum pump 62 is applied to the top of the condenser 52, is connected to the mains water inlet 54, and returns pump water to the trap 58. Steam condensate also is returned by a line 64 from the chambers 2 to the trap 58. From the trap 58, hot water is discharged by a pump 66 to processing or other end use. Claims (filed on 12 May, 1982)

1. A vacuum drying machine having a vacuum drying chamber, means for creating a vacuum in the chamber, an inlet and outlet for permitting fabric to run into and out of the chamber each inlet and outlet including a set of opposed, resilient friction rollers forming a nip for fabric therebetween, hard sealing rollers one on each side of the set of resilient friction rollers, each hard roller resting on one side of the resilient rollers facing the hard rollers, and low friction sealing strips, one on each side of the assembly formed by the resilient rollers and hard rollers, each mounted resiliently and sealingly on the chamber on one side of the strip and extending tangentially to the side of the adjacent hard roller opposite the side which engages the resilient roller so that when a vacuum exists inside the chamber the strip is urged by the vacuum towards the hard roller to sealingly engage it.

2. A vacuum drying machine as claimed in claim 1 wherein each of the low friction sealing strips include rubber strips on the side of the strip mounted on the chamber and a strip of plastics material between the rubber strips for engaging the hard roller.

3. A vacuum drying machine as claimed in claim 1 in which a pair of flanges mount between them the resilient and hard rollers at the inlet and outlet, each flange including low friction resilient material, the rollers have ends with axially orientated annular grooves, the flanges have cut aways to expose the roller ends, and means are provided for directing moist air on to the roller ends at the cut aways to cool the roller ends and the low friction resilient material bearing against the roller ends.

4. A vacuum drive machine as claimed in claim 1 in which drive means provided for rotating each roller, individually adjustment means are provided for the set of resilient rollers to move it in the direction of fabric movement and the hard rollers are off-set in the direction of movement of the fabric so that the sealing pressure between the respective resilient and hard rollers can be varied.

5. A vacuum drying machine according to claim 1 in which a plurality of fabric engaging hollow guide rollers are mounted to extend through the drying chamber to provide a convoluted fabric path, means are provided for supplying steam to and exhausting it from the interior of the guide rollers and means are provided to condense exhaust steam from rollers and the vapour from the vacuum chamber by the use of cold water to thereby assist in the maintenance of the chamber vacuum and permit use of the condensate for a secondary end-use.