Apparatus and method for manufacturing rubber-wrapped spiral wound gaskets

A spiral wound gasket made of an elongate band with a portion of the elongate band jacketed by a resilient filler material, the jacketed elongate band wrapped in a plurality of overlapping turns to define a radially thick reinforcing member with the band in each turn enclosed by resilient filler material that abuts contactingly to the resilient filler material in an adjacent turn, the overwrapped portions of the elongate band defining opposing sealingly resilient lateral surfaces, with a leading portion and a trailing portion of the elongate band lacking the jacketing resilient filler material and adjacent turns of the leading portion secured together to fix an inner diameter and adjacent turns of the trailing portion secured together to fix an outer diameter. A method and apparatus is disclosed to wind an elongate band jacketed by a filler material around the perimeter of a die until a desired radially thick spiral wound gasket is formed.

TECHNICAL FIELD

The present application relates to gasket manufacturing apparatus and processes. More particularly, the present invention is directed to apparatus and methods for manufacturing rubber spiral wound gaskets.

BACKGROUND OF THE INVENTION

Spiral wound gaskets made of rubber-derivative materials are used typically for oil seal connections in industrial processing applications. The rubber-based spiral wound gaskets are typically formed by rolling a thin sheet of rubber material in overlapping relation to form a tube. The overlapping layers of the rubber sheet define the radially-thick gasket having an inner diameter and an outer diameter for being received in a sealing application. A cross-section is cut through the tube to form a disc-like gasket of a selected thickness, having the selected inner diameter and outer diameter. The disc is pressed in a mold having an inner and outer diameter lip material for sealing. A primer encapsulates the windings of the rubber material with the lip material.

While these processes have resulted in rubber-based gaskets suitable for oil sealing and other applications, there are drawbacks to the apparatus and methods of manufacturing such gaskets. It is cumbersome to hold the sheet while rollingly winding the sheet into a tube. The tube must be held rolled while gaskets are cut, and the cut gaskets also must be held from unwinding. Further, the tube often can not be completely cut to form gaskets. The ends loosen and generally a portion of the tube must be scrapped.

Accordingly, there is a need in the art for an improved method and apparatus for manufacture for rubber-based spiral wound gaskets. It to such that the present invention is directed.

BRIEF DESCRIPTION OF THE PRESENT INVENTION

The present invention provides an apparatus and method for manufacturing rubber-based spiral wound gaskets. The spiral wound gasket comprises an elongate band with a portion of the elongate band jacketed by a resilient filler material, the jacketed elongate band wrapped in a plurality of overlapping turns to define a radially thick reinforcing member having a plurality of plys with the band in each turn enclosed by resilient filler material that abuts contactingly to the resilient filler material in an adjacent turn, the overwrapped portions of the elongate band defining opposing sealingly resilient lateral surfaces, with a leading portion and a trailing portion of the elongate band lacking the jacketing resilient filler material and adjacent turns of the leading portion secured together to fix an inner diameter and adjacent turns of the trailing portion secured together to fix an outer diameter.

Objects, features, and advantages of the present invention will become apparent from a reading of the following detailed description of the invention and claims in view of the appended drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now in more detail to the drawings, in which like numerals indicate like parts throughout the several views,FIG. 1is a perspective schematic view of an apparatus10for manufacturing rubber-based spiral wound gaskets according to the present invention. The apparatus10includes a band supply section12, a gasket forming section generally14, and a gasket discharge section16.

The band supply section12includes a supply20of an elongate band22. In a preferred embodiment, the elongate band22is a narrow fiber web. The band22passes between a pair of opposing guide rollers24.

Adjacent the guide rollers24is a housing30for a sealing material bath34that holds a fluidial mixture of a sealing material to be coated onto the elongate band. The sealing material is preferably rubber-based. Spaced-apart rollers38,40, and42guide the elongate band into and through the solution contained within the bath34for coating with the sealing material. The sealing material dries rapidly upon the continued travel of the elongate band out of the bath34. A return roller44in the housing30directs the elongate band22to an outlet46.

In an alternate embodiment, the sealing material is applied by passing the elongate band past a plurality of spray nozzles that communicate with a supply of the sealing material. The spray nozzles are selectively actuated to apply sealing material to at least a length of the elongate band.

A pair of pivotally mounted wire brushes70are disposed on opposing sides of the travel path for the elongate band22near the exit from the housing30. The wire brushes70mount on pivotable bases72in order to move from a first position spaced-apart from the elongate band22to a second position with the wire brushes70in contact with the respective face of the elongate band. The wire brushes70are rotatable such as by a pneumatic motor74which rotates the shaft on which the wire brushes70mount.

A treatment station75includes spray nozzles76which communicate with a supply of a treating solution. A tray77collects the overspray. The sprayer76in the treatment section75applies a spray coating to the jacketed portion of the elongate band. In a preferred embodiment, the spray is an acid bath to provide increased temperature range for the gasket having the jacket of a rubber sealing material. The treatment solution is selected from the group of phosphoric acid, aluminum hydroxide, silicone carbonate, and boron.

An idler arm80connects by a pivot82to the frame for the apparatus10. The arm80is biased by a spring. A roller86attaches to a laterally extending distal portion of the arm80. The roller86guides the band22into a cutter assembly90.

The cutter assembly90mounts to a movable frame92. The frame92moves from a retracted position to an extended position as operated by a motor-driven screw assembly93. The cutter90includes a pivotable knife94. The knife94moves from a first position away from an opening in the cutter assembly90to a cutting position whereby the band22passing through the opening is severed. A table96reciprocally mounts to the cutter assembly90. The table96moves between a first position adjacent the cutter assembly90and a second position spaced-apart from the cutter assembly. In the first position, the table96firmly bears against the band22in the cutter assembly90to hold the band secure during the cutting operation of the knife94. The table96drops to the second position during the winding process for forming the spiral wound gasket of the present invention, as discussed below.

The gasket forming section14includes a rotatable die100. The die100in the illustrated embodiment is an annular disc in which at least one slot102is formed. The slot extends inwardly from a perimeter edge104of the die100. The perimeter edge104conforms in cross sectional shape to the surface defined by the crimp rollers24whereby the metal band22is matingly held to the perimeter edge104of the die100. A tracking roller106mounts to a frame108that is spring biased to a support column110. The support column includes a potentiometer112to measure the movement of the support frame108in the support column110.

A welding apparatus120is disposed opposing the tracking roller106. The welding apparatus120connects to a reciprocal member122in order to move the welding apparatus120from a first position spaced-apart from the die100to a second position in which a pair of welding members124are in contact with portions of the elongate band22on the die100. The welding members124provide for securing positions of elongate band together, such as by sonic welding, adhesive, hot contact securing, and other suitable rapid securing mechanisms.

The gasket discharge section16includes a tapping apparatus130. The tapping apparatus130has a pneumatic cylinder132from which a piston extends and retracts. A tapper134attaches to the distal end of the piston of the cylinder132. In the illustrated embodiment, the tapper136is a bronze disc. The cylinder132mounts to an arm136that encloses a screw rod138. The screw rod138attaches to the end of the arm136. The opposing end of the screw rod138defines a roller140. A motor142connects to a driver roller146. A belt148extends between the driver roller146and the roller140.

FIG. 3is a cross-sectional view of the elongate band22after exiting the sealing material housing30. The elongate band22is enclosed in a jacket180of the rubber sealing material with opposing thick regions generally182,184on the side faces of the band22and opposing thin regions186,188on the relatively thin sides of the band22.

FIG. 2is a partial view of the gasket forming section14showing details of the gasket formed on the die100in the forming section14. The die100is illustrated with a plurality of turns of the coated elongate band22wound around the perimeter104to form the gasket according to the present invention. The welding apparatus120is illustrated spaced-apart from the radially thick cross-sectional view of the gasket, prior to moving into position for securing portions of the elongate band22together.

With reference toFIG. 1, the apparatus10of the present invention is operated in order to form a spiral wound gasket. The roll of the narrow thin elongate band22is attached to a rotatable mandrel in the band supply section12to provide a supply of the elongate band for winding into the spiral wound gasket. The elongate band22feeds through the opposing guide rollers24over the rollers38,40and passes through a cleaner bath solution held in the bath32. The cleaner solution removes the contaminants, such as oils and other materials left on the elongate band22during manufacturing. The rubber-based sealing material is then applied to the elongate band22. The band22, guided by the rollers42, passes into the bath34for application of the rubber-based sealing material held in the bath. The coated band22passes over the roller44and the roller48and exits from the housing30through the opening46.

At the treatment station75, the spray nozzle76communicates the treating solution to the jacketed elongated band22. Overspray collects in the tray77.

Periodically, the wire brushes70are pivoted from the spaced-apart position to the contact position whereby the wire brushes70are brought into contact with the jacketed elongate band22. The motors74operate in order to rotate the wire brushes70which bear against the opposing broad faces of the elongate band22. The wire brushes remove the rubber jacket180from the portion of the elongate band22on which the brushes are brought into contact. The purpose of removing the rubber sealing material from a portion of the elongate band22is to provide band surfaces for welding and for being exposed on the inner diameter and outer diameter of the completed spiral wound gasket, as discussed below. The elongate band22passes under the idler roller86attached to the idler arm80. The elongate band22is held in the cutter assembly90. The table96reciprocates from the first position to the second position bearing the elongate band against the cutter assembly90. In the spaced-apart position of the table96the elongate band22is spaced apart from the cutter assembly90, as discussed below.

With reference toFIG. 3, the cutter assembly90moves between the retracted position whereby the cutter assembly90is spaced-apart from the die100and the extended position in which the cutter assembly90is brought close to the perimeter edge104of the die100. In this position, the elongate band22is held between the table96and the cutter assembly94. A distal portion180of the band22is fed into the slot108in the disc100. The disc100is rotated in order to start winding the elongate band22about the perimeter104of the die100. As the initial portion of the elongate band reaches the tracking roller106, the table96is released and drops to the second spaced-apart position. The idler arm80moves downwardly as the table96moves downwardly. The table96moves out of the way, and the roller92guides the travel of the elongate band22as it moves longitudinally towards the die100.

The apparatus10is configured whereby the elongate band22defines a tangent to the die100, in order to avoid bending the elongate band22as it wraps around the perimeter104of the die. One and one half revolutions of the die100are made. The die100stops rotating. The welding apparatus120moves from its retracted position to the engagement position placing the welding tips124against the elongate band22opposing the tracker roller106. The welding apparatus120is operated to secure the overlapping band22together. In the illustrated embodiment, the welding tips124are electrodes. An electric current communicated between the electrodes through the metal elongate band22spot welds the outer wrap to the inner wrap. The welding apparatus120then moves to its retracted position spaced apart from the die100. The die100resumes rotating in order to wind a plurality of overlapping layers of the elongate band onto the die100and thereby form a radially increasing thickness of a gasket.

The tracker roller106is biased to the support column110. The potentiometer112measures the change in the position of the tracker roller106relative to the support column110. This provides a measure of the increasing radial thickness of the spiral wound gasket being formed on the die100. At an appropriate time, depending on the outer diameter of the gasket being formed, the wire brushes70are pivoted from the retracted position to a position where the wire brushes bear against the wide faces of the elongate band22. The wire brushes70are rotated by the motors74in order to brush away the rubber sealing material covering a portion of the elongate band22. The length of the portion for which the jacket180is removed is a length sufficient to provide at least one and a half ending wraps of the elongate band around the gasket being formed, as well as to provide one and a half leading wraps of the elongate band22for the next gasket to be formed. It is to appreciated that this portion includes the short distal portion180received in the slot108.

When the final one and a half wraps of the unjacketed elongate band22are made, the rotation of the die100stops. The welding apparatus120moves from the retracted position to a contacting position with the welding tips124in contact with the exterior surface of the elongate band on the die100. The welding apparatus120is actuated to spot weld the distal end of the gasket being formed on the die100. The welding apparatus120then retracts.

The motor142is operated to drive the belt148so that the screw138rotates. This moves the arm136laterally towards an alignment position relative to the die100. When the tapper134is aligned with an arcuate portion of the die100and the gasket wrapped around the perimeter edge104, the motor142stops. The table96moves to its elevated position in order to hold the elongate band22firmly in the cutter assembly90. The knife94is pivoted to sever the gasket on the die100from the supply of the elongate band22.

The pneumatic cylinder132is actuated to drive the tapper134strikingly against the side face of the die100. The tapper134bears forcingly against the die100and the gasket formed thereon, and this sharp hit taps the gasket free of the die100.

The pneumatic cylinder132then retracts the tapper134. The motor142is reversed to move the arm136from its extended position to the retracted position spaced apart from the die100.

FIG. 4illustrates a cross-sectional view of the gasket190made with the apparatus10. The gasket190defines an inner face192on the inner diameter of the gasket190and an outer face194on the outer diameter of the gasket. An inner portion196has a wrap and a half of the unjacketed band22. Similarly, an outer diameter portion198has a wrap and a half of the unjacketed band22. The wraps for the inner portion196and the wraps for the outer portion198are each secured by welds to hold the gasket together. An intermediate section200includes a plurality of turns of the jacketed elongate band22. As the band22is wound around the perimeter of the die100, the rubber sealing material in the opposing high density regions generally122,184become more densely packed. The low density regions186,188, however, do not become more densely packed as the winding continues to form the gasket. Accordingly, the resulting gasket has opposing faces202,204of a low-density sealing material which contact the faces of the flange in the connection being sealed. The low density provides a relatively low minimum seat to affect the seal. The high density sealing material182,184, allow the gasket to resist interbuckling. The rubber-based spiral wound gasket can subsequently be placed in a mold with an inner diameter core and an outer diameter wrap and encapsulated in a covering material, if desired. The core and the wrap are especially selected for the service tasks required these surfaces.

The present invention accordingly provides an apparatus and method for forming improved rubber-based spiral wound gaskets. The principles, preferred embodiments, and modes of operation of the present invention have been described in the foregoing specification. The invention is not to be construed as limited to the particular forms disclosed because these are regarded as illustrative rather than restrictive. Moreover, variations and changes may be made by those skilled in the art without departure from the spirit of the invention as described by the following claims.