US3313002A

US3313002A - Apparatus for heat treating sheet material

Info

Publication number: US3313002A
Application number: US477211A
Authority: US
Inventors: Wyeth Nathaniel Convers
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1965-08-04
Filing date: 1965-08-04
Publication date: 1967-04-11
Anticipated expiration: 1984-04-11
Also published as: DE1635290B2; NL149870B; NL6610916A; DE1635290C3; DE1635290A1

Description

April 11, 1967 N, C, WYET'H 3,313,002

APPARATUS FOR HEAT TREATING SHEET MATERIAL Filed Aug. 4, 1965 United States Patent ilce ansatz 3,313,902 APPTUS FR HEAT TREATING SHEET MATERIAL Nathaniel Conyers Wyeth, Rosedale, Pa., assigner to E. l.

du Pont de Nemours and Company, Wilmington, Del.,

a corporation of Delaware Filed Aug. 4, 1965, Ser. No. 477,211 3 Claims. (Cl. l-lil) This invention relates to an apparatus for the uniform heat-treatment of porous sheet materials. In particular it concerns an apparatus for effecting such heat-treatment while maintaining a restraint on the surface of the sheet thereby preventing or minimizing any change in area dimensions.

The heat-treatment of porous sheet materials, such as non-woven fabric webs or paper like sheet structures, is often required in order to activate a binder material therein, to modify the surface for decorative or smoothing effects, to cause spontaneous elongation of the constituent `fibers thereby developing liber crimp, or for other known purposes. In many instances the heattreatment requires the use of a closely controlled temperature and rapid attainment of that temperature in order to prevent adverse effects upon resulting sheet material. An apparatus designed to achieve these objectives is that described in Huffman U.S. Patent No. 3,192,560. 'It is an object of the present invention to achieve these desirable objectives with a simpler piece of apparatus.

While non-woven fabrics can be bonded by any of the well known solvent, adhesive, or heat-bonding techniques, the latter in which the fibers are self-bonded at a multiplicity of fiber intersection points possesses distinct advantages in terms of cost and the avoidance of the extra steps which are otherwise needed to apply a binder material and remove a volatile carrier should one be used. Moreover, special effects can be often achieved by self-bonding techniques which are not readily attainable by other methods. A noticeable disadvantage of the selfsbonding techniques as heretofore practiced however, has been the lack of equipment which when employed in a continuous operation on a commercial scale will provide a high degree of precision required with respect to temperature control. Thus, if the temperature is not consistently maintained at a suliiciently high level, areas of the fabric may possess an inadequate number of satisfactorily strong bonds. Excessiveiy high temperatures, on the other hand, give rise to overbonding even to the point where the liber structure collapses. Problems have also been experienced in preventing excessive fiber shrinkage during bonding. Certain iibers have been observed to undergo excessive shrinkage even when bonded under carefully controlled conditions. To obtain uniform products therefore, particular care must be exercised to ensure that the fibers in the sheet product are properly restrained during the heating operation.

It is accordingly an object of the invention to provide an apparatus for the uniform heat-treatment of wide sheet materials under closely controlled temperature conditions. Another object of the invention is to provide an apparatus for treating a continuous web of material which is capable of supplying a large quantity of heat at a high rate within a narrow precisely controlled temperature range while the web is under restraint to prevent shrinkage. A still further object of the invention is to provide an apparatus for heat treating a continuous web of material by uniformly heating the web while maintaining restraint and rapidly cooling it after treatment.

The apparatus of this invention is best understood by reference to the following figures in which:

FIGURE l shows a schematic representation of the apparatus in its simplest form.

FGURES 2 and 3 show pneumatic roll embodiments composed of elongated tubular elements arranged parallel to the roll axis and of a plurality of closely spaced tires respectively.

ln FIGURE 1 the bonding apparatus comprises a compressible roll 2 having an outer layer 49 of elastomeric material urged against a perforated rotary drum 1 to provide an extended nip zone. The roll 2 contains coolant passageway ti for removing heat from the elastomeric material 49. Drum 1 is a rigid relatively thick walled hollow cylinder made of a suitable corrosion resistant material such as a stainless steel alloy. At either end of cylindrical drum 1 and tlxedly attached thereto or integral therewith are side members having flanges that may be rotatably journaled, for example, to the outer races of standard commercial type antifriction bearings. Drum 1 may be rotatably driven through force applied to the side members or through other suitable means. A drive shaft connected to a side member and coupled by conventional coupling means to the output of a standard commercial variable speed electric motor drive has been found satisfactory.

Hollow stationary beam 17 is located at the axis of drum l and extends through the side members. Inlet means 7 comprising a pipe located within beam 17 is connected at one end with chamber 3, which is supported by beam 17 and situated within the drum, and at the other with a heated vapor source preferably high pressure steam. One end of the outlet means 8, for the elimination of condensate, connects into the base of chamber 3 and comprises a line carried within the interior of beam 17. The other end of the line extends outside the machine to a suitable condensate removal means. Beam 17 is further modified by opposed side openings 24 into which one end of exhaust ducts 5 connect with beam 17 interior. Beam 17 thus serves as an exhaust conduit which accordingly is suitably connected at some remote point outside the machine to an exhaust blowerV (not shown). The upper ends of ducts 5 are narrow elongated openings which connect with drum apertures that are substantially entirely within the nip. The duct openings extend along the length of chamber 3 and adjacent the inside peripheral surface of drum 1.

Chamber 3 is a shallow rectangular box-like member that is stationary and communicates with certain of the apertures in the drum Wall. The upper face of chamber 3 is formed by a small section of the interior of the drum 1 surface while the perimeter of the upper face of chamber 3 is enclosed by a iloatable seal assembly 4 which frictionally abuts with the internal surface of drum 1. Seal assembly 4 contines the effective area of treatment chamber 3 to a narrow rectangular band of the surface of drum 1 that will ordinarly extend substantially the entire length of the drum and is contained entirely within the nip. against the surface of drum 1 partly by a plurality of spaced compression springs 28 located at the bottom of the recess and by the pressure of the treatment fluid in chamber 3.

Seal assembly 4 is composed of a plurality of flat bars or elements interconnected to form a fluid tight barrier.

Patented Apr. ll, 196? Assembly 4 may be urged,

The elements may be made of a porous carbon composi-l tion impregnated with a fluorocarbon resinous material for low friction, long wear life and high thermal resistance. The elements are modied at their ends by a tongue and groove configuration so thatrwhencoupled together there is ample allowancefor relative movement and deection between individual elements without risk of creating a free path for steam leakage. Seal assembly 4 is retained within a matching recess in chamber 3 wall.

Shaft extensions of roll 2 are rotatably journaled in bearings (not shown). The shaft extensions of roll 2 may be the ends of a rigid tubular steel core 45 t-o which is welded a hollow cylindrical shell 46. Within the shell 46, another cylindrical baffle or wall 47 is affixed that forms the coolant passageway 6 which communicates at one end with the core 45 interior and at the opposite end with an inlet conduit 48. Hydraulic actuators (not shown) operating on the shaft of roll 2 cause movement relative to dmm 1.

Bonded to the external surface of shell 46 is a thick cover 49 of elastomeric material. Any resilient material having high temperature resistance and high fatigue life may be used. A synthetic hydrocarbon rubber manu factured by the Du Pont Company under the trade name Nordel is preferred because of its excellent resistance to wear and high temperature steam. It is preferred for best results that cover 49 be made relatively pliable, the softness ranging from between 45 to 65 Shore A durometer.

The softness of cover 49 determines to a great extent the width of the nip formed between roll 2 and drum 1 and the magnitude of the force urging the rolls together to form the nip. It will be recognized that a cover 49 material excessively resilient will fail to conline the high pressure steam or other heat-treating fluid. Conversely a material too stiff requires tremendous nip pressures and will crush the fibrous product. As previously indicated, large amounts of internal friction heat caused by high intensity flexing of the material rapidly degrades the material. Most of these difficulties, however, may be over-come with a pneumatic roll structure where only a relatively thin membrane or sheath of elastomeric material is subjected to the distortion and flexing action. Moreover, stiffness characteristics of the roll are easily adjusted by a simple regulation of the pneumatic pressure backing the membrane.

FIGURE 2 illustrates an alternative pneumatic roll embodiment utilizing a support shell 50 and sheath 51 composition to enclose a plurality of elongated tubular pneumatic elements S5. The elements are packed closely together parallel to the roll axis and when pressurized expandtightly against each other to form a substantially uniform narrow -cellular pneumatic layer.

FIGURE 3 is a further embodiment of the pneumatic roll concept showing support shell 50 and reinforced sheath 51. The pneumatic portion is composed of a plurality toroidal elements 56 packed tightly side by side. The elements 56 are actually multi-ply auto tires without treads but containing inner tubes.

In operation, a foraminous belt 65 is trained around drum 1 from an upstream web formation area. Belt 65 greatly facilitates transfer of the fragilev sheet material which hereafter is described as web 64 in an essentially non-disturbed condition. Preparatory to actual treatment of product, various adjustments `may be made to the machine to meet end product quality requirements.

At start up, an operator energizes the hydraulic actuators controlling movement of the shaft and lowers the roll 2 closing the nip between the rotary members sufficient to confine the steam to chamber 3. Coolant water is introduced through inlet 48 into passageway 6 to control the maximum temperature of the cover 49 at the operating conditions employed. Drum 1 is driven at Ymachine components some moderate speed, as for example, about six yards per minute. A slightly subatmospheric condition is established in the exhaust ducts 5 by an exhaust blower or some other means. At this point, steam is introduced into treatmentrcharnber 3 slowly so as to allow the cool to attain steam temperatures. Steam pressure is increased at a rate which does not exceed a 46 C. difference in temperature between the steam and the machine parts. It is noted that during the build up of steam, the nip pressure of roll Z is increased proportionately. After the desired operating pressure is attained, final adjustment of nip pressures and drum l speed are made. f

In operation web 64 entering the nip is firmly restrained lnefore communicating with the lsteam treatment zone. rl`he steep vsteam pressure profile subjects the web 64 to rapid heating and cooling. Since significant qualities of steam can be entrapped in the roll apertures and web interstices, the suction of duct 5 on the downstream side of chamber 3 draws off the vap-or and accelerates cooling before the web `64 restraint is released. After emerging from the ni the cooled web 64 is separated from belt 65 under a slight tension and directed to either a take up stand for winding into mill rolls or carried to other downstream processing. If desired, an upper screen belt, not shown, trained around roll 2 from an upstream web formation area and cooperating with belt 65 to sandwich the web while in the nip, may be employed to modify the upper surface of the fibrous structure.

The bonding apparatus of the invention provides a relatively low cost, compact high productivity means for processing wide sheet material. It is capable of handling and processing wide sheet material at high speeds under precisely controlled conditions.

What is claimed is:

1. An apparatus for heat-treating a continuous length of sheet material comprising a compressible roll in rolling engagement with a hollow drum around which is trained a foraminous belt over which a sheet advances between the roll and drum, said drum having its circumferential surface interrupted by perforations and said compressible roll being urged against the drum and deformed thereby so as to form an extended nip zone, and residing within said drum a stationary fluid treatment chamber having an inlet for provision of hot treating fluid, the said chamber opening on the inner surface of the drum and communicating with drum perforations in the nip region to provide a heat-treatment area, seals mounted on said chamber and operatively urged against theinner surface ofthe drum so-that the heat-treatment uid in the chamber is confined to the region of the nip, and exhaust means in the nip region adjacent the heat-treatment area for carrying away uid leakage past the seals and outside of the heat-treatment area.

2. The apparatus of claim 1 wherein cooling means are provided for the compressible roll for removal of internal heat generated in the roll by the operation of said apparatus. n

3. Apparatus for heat-treating a continuous length of sheet material comprising a hollow drum having perforations in the circumferential surface thereof, a roll covered with a layer of resilient material, and a foraminous belt trained around the drum for supporting the sheet material said roll being urged against the drum to provide a nip for receiving and restraining the sheet material as it passes through, the nip being extended by deformation of the resilient outer layer of said roll against the drum, the perforations of`the drum in the region of the nip communicating with a stationary fluid treatment chamber residing within said drum and having fluid inlet means, said chamber having seals urged against the inside surface of the drum for confining the heat-treatment fluid to the nip region perforations of the drum and suction means adjacent to the seals at the inner surface of said drum for carryingl away uid leakage passed the 6 Seals and outside of the heat-treatment area whereby hot 2,952,033 9/ 1960 Goodwin 1S-1 fluid contacts the sheet material substantially only while 3,230,287 1/1965 Caron et al- 18-4 XR the sheet material is engaged by the nip. FOREIGN PATENTS References Cited by the Examiner 5 366920 3/1963 Switzerland UNITED STATES PATENTS References Cited by the Applicant 1,007,137 10/1911 Palmer. UNITED STATES PATENTS 1,880,691 10/1932 Berry. 2,920,406 1/1960 Vlgliarolo.

2,209,760 7/1940 Beffy- 10 WILLIAM J. STEPHENSON, Prima/y Examiner.

Claims

1. AN APPARATUS FOR HEAT-TREATING A CONTINUOUS LENGTH OF SHEET MATERIAL COMPRISING A COMPRESSIBLE ROLL IN ROLLING ENGAGEMENT WITH A HOLLOW DRUM AROUND WHICH IS TRAINED A FORAMINOUS BELT OVER WHICH A SHEET ADVANCE BETWEEN THE ROLL AND DRUM, SAID DRUM HAVING ITS CIRCUMFERENTIAL SURFACE INTERRUPTED BY PERFORATIONS AND SAID COMPRESSIBLE ROLL BEING URGED AGAINT THE GRUM AND DEFORMED THEREBY SO AS TO FORM AN EXTENDED NIP ZONE, AND RESIDIDNG WITHIN SAID DRUM A STATIONARY FLUID TREATMENT CHAMBER HAVING AN INLET FOR PROVISION OF HOT TREATING FLUID, THE SAID CHAMBER OPENING ON THE INNER SURFACE OF THE DRUM AND COMMUNICATING WITH DRUM PERFORATIONS IN THE NIP REGION TO PROVIDE A HEAT-TREATMENT AREA, SEALS MOUNTED ON SAID CHAMBER AND OPERATIVELY URGED AGAINST THE INNER SURFACE OF THE DRUM SO THAT THE HEAT-TREATMENT FLUID IN THE CHAMBER IS CONFINED TO THE REGION OF THE NIP, AND EXHAUST MEANS IN THE NIP REGION ADJACENT THE HEAT-TREATMENT AREA FOR CARRYING AWAY FLUID LEADAGE PAST THE SEALS AND OUTSIDE OF THE HEAT-TREATMENT AREA.