Abstract:
Gasket stock is disclosed having a rectangular metal core that is readily bendable in one direction and a deformable rubberized jacket coextruded with and encasing the metal core. A method of fabricating the gasket stock through a coextrusion process is disclosed. A method also is disclosed for forming a press-in-place gasket with the method including obtaining bendable gasket stock, incrementally advancing the gasket stock to predetermined positions in a bender, and bending the gasket stock at the predetermined positions along its length to form a desired shape of the press-in-place gasket. The bender is controlled by a computer to form the shape of the gasket according to a CAD or other electronic file. Finally, a method of supplying press-in-place gaskets and accommodating design changes of such gaskets is disclosed.

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 61/727,759, filed on 19 Nov. 2012, and entitled “Press-in-place Gaskets and Fabrication Methods”, which application is incorporated by reference in its entirety herein. 
    
    
     TECHNICAL FIELD 
     This disclosure relates generally to gaskets for creating a seal between a pair of facing mating surfaces and more particularly to so-called press-in-place or spaghetti gaskets configured to be pressed into a groove formed in one or more of the mating surfaces. 
     BACKGROUND 
     Press-in-place gaskets are well known for sealing between a pair of flanges that are secured together in face-to-face relationship with bolts or the like. Such gaskets, sometimes referred to as spaghetti gaskets, generally are relatively thin bands of rubber or similar material that are injection molded to have a shape corresponding to that of a groove formed in the surface of one (or both) of the flanges to be sealed. The press-in-place gasket, as its name implies, is pressed into the groove before the flanges are joined and bolted together. A cross-sectional profile of the gasket may be configured to hold the gasket in place within the groove and to control the compression of the gasket as the flange and its mating flange are bolted together, whereupon the gasket forms a seal between the mating surfaces. Some press-in-place gaskets are made with a metal core to, among other things; help the gaskets hold their shape before and during installation. These metal core gaskets generally are fabricated in an injection mold wherein a metal core in the shape of the gasket is placed in the injection mold. The rubberized gasket material is then injection molded around the metal to form the gasket. 
     Prior press-in-place gaskets, and methods of making them, have exhibited inherent problems and shortcomings. For example, the cost of an injection mold for molding press-in-place gaskets can be exceedingly expensive and generally requires weeks of time for its production. This also means that there can be no substantive changes in the shape or configuration of the gasket once the mold maker begins the task of making the mold. Further, a modification in the gasket before or after the mold is finished usually requires that a new mold be created, taking time and consuming substantial financial resources. It often is useful for a designer of power train components to have access to prototypes of gaskets to be used in power train components in order to test and refine the components and surfaces to be sealed. Unfortunately, it is problematic to provide prototypes of press-in-place gaskets since the injection molding process by which they are made is expensive, slow, and does not lend itself readily to rapid prototyping techniques. 
     A need exists for a press-in-place gasket and a method of making press-in-place gaskets that addresses these and other problems of the prior art. It is to the provision of such a gasket and method that this disclosure is primarily directed. 
     SUMMARY 
     Briefly described, a method of fabricating press-in-place gaskets includes extruding a rubberized gasket material around a central core made of a malleable material such as aluminum to form a continuous elongated strand of gasket stock. The gasket stock has a predetermined outer profile and may be wound onto storage reels for storage and/or shipment. The method further includes incrementally moving the gasket stock through a computer controlled bender having heads that bend the gasket stock into a desired programmed shape corresponding to the shape of a groove in a flange. When the bending is complete the strand is cut and the resulting free ends may be bonded together to form a continuous closed press-in-place gasket. Press-in-place gaskets having unique characteristics according to the invention and press-in-place gaskets formed by the unique method of the invention are also within the scope of the invention. Once fabricated, the press-in-place gaskets can be used in a manner similar to traditional injection molded press-in-place gaskets by pressing them into a groove formed in a mating surface and clamping the corresponding mating surface to the first mating surface. 
     The method of the invention eliminates the requirement to form an injection mold in which to mold press-in-place gaskets. Further, a press-in-place gasket of virtually any shape can be fabricated in an exceedingly short time since the shape of the gasket is determined in a digital profile such as a CAD or other electronic file. Significant also is the fact that changes can be made to a gasket design at any time in the process, and those changes can be implemented simply by revising the digital profile in the computer and “bend forming” the new gasket. Prototypes having perhaps various different shapes can be delivered in short order to power train component designers for research and development purposes and for a fraction of the cost of traditional injection molded press-in-place gaskets. Accordingly, press-in-place gaskets and methods of fabricating them are now provided that address the problems above and provide other benefits and advantages not possible with traditional injection molding techniques. These and other aspects, features, and advantages will be better appreciated upon review of the detailed description set forth below taken in conjunction with the accompanying drawing figures, which are briefly described as follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective partially sectioned view of a press-in-place gasket that embodies principles of the invention in one preferred form. 
         FIG. 1 a    is a cross sectional view of a press-in-place gasket having an alternate exterior profile according to an aspect of the invention. 
         FIG. 2  is a cross-sectional view of a cross-head injection molding apparatus configured to extrude press-in-place gasket stock according to methods of the invention. 
         FIG. 3  is a simplified schematic of a bending apparatus forming a press-in-place gasket from the extruded stock according to principles of the invention. 
         FIG. 4  is an enlarged view of a computer controlled bender head of the bender illustrating control of the head to bend the press-in-place gasket stock to form a press-in-place gasket of a desired shape. 
         FIG. 5  is a plan view illustrating one technique for bonding cut ends of a press-in-place gasket to form a continuous gasket according to the invention. 
         FIG. 6  is a cross sectional view showing a press-in-place gasket according to the invention disposed between a pair of mating surfaces forming a seal therebetween. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now in more detail to the drawing figures, wherein like reference numerals indicate like parts throughout the several views,  FIG. 1  illustrates a length of press-in-place gasket stock that embodies principles of the invention on one preferred form. The gasket stock  11  comprises a core  12  that is made of a malleable or bendable material that holds its shape when bent. In the preferred embodiment, the material of the core can be aluminum; however, other materials such as mild steel, copper, other metals, or non-metals such as polymers and composites may be used so long as the core can be bent and retains its bent shape after bending. The core  12  in the illustrated embodiment has a rectangular cross sectional profile so that it is readily bendable in a direction transverse to the long dimension of the core but resists bending in a direction transverse to the short dimension of the core. In  FIG. 1 , for instance, the core is readily bendable in the direction indicated by arrows  15 . It also is possible that the core be substantially square in cross section so that it is bendable along two orthogonal axes perpendicular to adjacent sides but resists bending in directions between these. Indeed, the core can be shaped to bend readily in more than two directions if desired for a particular gasket. In this way, press-in-place gaskets configurations in more than one plane can be formed. All such configurations are within the scope of the invention even though the exemplary embodiment is readily bendable in only one direction. 
     The core is encased in a jacket  13  made of gasket material. The gasket material may be any compressible material suitable for use as a press-in-place gasket including, without limitation, a thermoset rubber, a polymer, an acrylic, a polyacrylic, an elastomer, a composite, or combinations thereof. As detailed below, the jacket  13  is extruded around the core  12  and is formed to exhibit an exterior profile of a desired shape. In the embodiment of  FIG. 1 , for instance, the profile has a base  16 , side ribs  14 , and a top portion  17 . When pressed into a groove of a mating surface, the side ribs may compress against the walls of the groove to hold the gasket in place in the groove as the mating flange is secured against the mating surface. The gasket also may be formed with any other suitable exterior profile. For example, in  FIG. 1 a   , a gasket  21  has a core  22  embedded within a jacket  23 . The jacket  23  is extruded to have an exterior profile with a bottom protrusion  26 , a top protrusion  27  formed of a pair of upwardly projecting ribs  28 , and side ribs  24 . In this embodiment, the side ribs  24  help hold the gasket in a groove while the bottom protrusion  26  and the upwardly projecting ribs bear against mating surfaces to form a seal. These and many other profiles of the gasket are possible depending upon application specific requirements, and all such profiles are intended to be within the scope of the invention. 
       FIG. 2  illustrates a preferred methodology for forming press-in-place gasket stock according to an aspect of the invention. The gasket may be formed using a traditional cross-head extruder  31 . Such extruders are generally understood by the skilled artisan, and so need not be described in detail here. In general, however, the extruder  31  has a central opening through which a length of core material  32  is moved in the direction of arrow  29 . Jacket material, which may be a thermoset material, is fed, usually in strips, from a hopper (not shown) through the barrel  33  of an extruder by a screw  34 . In the process, the jacket material is heated until it becomes flowable. The jacket material is forced by the extrusion screw  34  through channels  38  in the extruder and through aligned channels in an extruder die  37  until it intersects with and encases the moving core  32 . In this regard, the rate of movement of the core  32  is controlled to correspond to the rate at which the jacket material moves through the die to minimize shear and promote good bonding between the jacket material and the material of the core. 
     The die is formed to shape the jacket material with a desired exterior profile, such as those shown in  FIGS. 1 and 1   a  for example, to form the metal core gasket stock of the invention. As the gasket stock leaves the die, it can be cooled by known methods to cure the thermoset jacket material. Alternatively, the gasket stock can be passed through a temperature controlled bath of hot salt water or other liquid so that the jacket material is not completely set or cured at this stage. With this alternative, gaskets later formed from the gasket stock as described below can be cured by annealing or otherwise after they are formed. In either event, the resulting gasket stock may be wound onto a bulk reel for storage and transport. 
       FIG. 3  is a simplified schematic of an apparatus for forming press-in-place gaskets from gasket stock according to the methodology of the invention. The apparatus  41  is fed with gasket stock  43  as described above from a reel  42  or other bulk store from which gasket stock can be drawn. The stock  43  extends through a vice  44  that can be computer controlled to grip and release the gasket stock and, when gripping it, to move predetermined distances in a back and/or forth direction as indicated by arrow  46 . In this way, the gasket stock  43  can be controllably fed from the reel  42  through the apparatus in predetermined increments of predetermined sizes. The gasket stock  43  is fed by the vice through an alignment block  47 , which holds the stock straight as it is fed downstream to the right in  FIG. 3 . Straightening rollers also may be incorporated in the alignment block or elsewhere to straighten the gasket stock  43  as it is drawn from the spiral reel. 
     A bending head  48  is disposed just downstream of the alignment block  47  and the gasket stock  43  extends from the alignment block through the bending head  48 . With reference to  FIG. 4 , the bending head in the illustrated embodiment comprises a rotatable platter  50  to which is attached a pair of arcuate bending dogs  52  and  53 . The bending dog  52  has an end  58  and the bending dog  53  has an end  59 . The platter  50  is controllably rotatable in the directions indicated by arrows  49  and the rotation of the platter is controlled by the computer or other controller that controls the vice  44 . A cylindrical anvil  51  is axially aligned with and is stationary with respect to the platter  50 . A slot  57  extends through the anvil  51  and each wall of the slot terminates in a downstream edge  55 . The slot  57  is sized to receive gasket stock  43  in such a way that the gasket stock is snug within the slot  57  but nevertheless moveable therethrough as the closed vice  44  advances the gasket stock incrementally as indicated at  46 . 
     Referring to  FIG. 4 , as the platter  50  and its bending dogs rotate in, for example, a counterclockwise direction indicated in  49  with a length of gasket stock  43  projecting from the slot  57  of the anvil  51 , the end  58  of bending dog  52  engages the gasket stock. As the platter  50  rotates further, the bending dog  52  causes the gasket stock to bend at the edge  55  of the slot  57 . The rectangular metal core of the gasket stock is oriented transverse to the direction of the bend. Thus, bending of the gasket stock in the direction shown in  FIG. 4  (and the opposite direction as in bend  56 ) occurs readily and the resulting bend keeps its shape after the bending. The platter  50  and its bending dogs  52  and  53  are controllably rotatable in either direction and through any degree of arc so that a bend in the gasket stock of virtually any angle can be accomplished. 
     To fabricate a press-in-place gasket of desired configuration, the desired finished shape of the gasket is established in a CAD or other electronic file. This file is received into the computer that is programmed to control the apparatus  41  and the computer carries out its program instructions to form the gasket according to the specification in the electronic file. More specifically, the computer controls the vice  44  to grip the gasket stock  43  and to move the stock in the downstream direction until the location of a desired bend in the stock aligns with the edges  55  of the anvil  51 . With the gasket stock so located, the computer then controls the platter  50  and thus the bending dogs  52  and  53  to rotate in the direction of the desired bend in the gasket stock. As the end of a bending dog engages the gasket stock, it begins to bend the gasket stock as shown in  FIG. 4 . The computer rotates the platter through the appropriate arc to form a bend in the gasket stock having the angle specified in the electronic file. The bend may be slight or may be ninety degrees or more as required to conform to a flange slot into which the finished gasket is to be pressed. 
     The vice is then controlled to move the gasket stock to the incremental location of the next desired bend and the platter and bending dogs form the next bend in a similar manner. It will thus be seen that a press-in-place gasket  54  is progressively formed having multiple bends that define a shape that corresponds to that specified in the CAD or electronic file. This is exemplified in  FIG. 3 , for instance, where the press-in-place gasket  54  is seen taking shape with bends  56  of various angles having been created at the proper locations. 
     Once the gasket shape is completed, the gasket stock is cut at the appropriate place to form a free end. This free end can then be joined to the opposite free end of the formed gasket to complete the continuous press-in-place gasket  61  as illustrated in  FIG. 5 . Any appropriate technique of joining the free ends  62 ,  63  can be used including bonding with adhesives, bonding with solvents, bonding with heat or, as in  FIG. 5 , bonding through sonic welding. In the case of  FIG. 5 , the free ends  62 ,  63  may be cut at an angle to increase the surface areas of the ends in contact when brought together. In the illustrated embodiment, an ultrasonic welding head  66  of an ultrasonic welder (not shown) can then apply ultrasonic energy to the ends to weld or fuse the gasket material together. It has been found that welding the jacket material and not joining the ends of the internal metal core helps to compensate for the differences in coefficients of expansion between the two materials when the gasket is in service. 
     Regardless of the bonding technique, the result is a continuous press-in-place gasket that is ready to be pressed into a matching shape groove in a surface to form a seal, as shown in  FIG. 6 . In this simplified example, part  71  has a surface  73  and part  72  has a mating surface  74 . The mating mating surface  74  is formed with a groove  77  having a shape determined by the part designer to seal the region between the two mating surfaces  73  and  74 . A press-in-place gasket previously formed by the methodology of the present invention has a shape that matches that of the groove  77 . Prior to bolting the parts  71  and  72  together, the press-in-place gasket is pressed into the groove  77  in the mating surface  74  of part  72 . The parts  71  and  72  are, in this example, bolted together with bolts  76 . As the surface  73  is tightened toward engagement with the mating surface  74 , the jacket  82  of the press-in-place gasket  79  is compressed and deformed so that the gasket forms a seal between the two surfaces. The metal core of the press-in-place gasket is sized so that it does not interfere with the compression of the jacket material. 
     In view of the forgoing discussion, it now will be understood by the skilled artisan that press-in-place gaskets of virtually any shape and configuration can be formed quickly, reliably, and without the need to make injection molds in which to form the gaskets. Test gaskets of various configurations can be made to order and be immediately available to power train designers and others for testing various designs and gasket configurations for a particular purpose. Further, power train designers are now free to make changes in the designs of mating surfaces to be sealed right up until production; and press-in-place gaskets to accommodate these changes can be fabricated and made immediately available to designers at very little cost. This level of flexibility simply has not been available to power train designers and others in the past. 
     The invention has been described herein in terms of preferred embodiments and methodologies that exemplify the invention and are considered by the inventors to represent the best modes of carrying out the invention. The skilled artisan will understand, however, that a wide gamut of additions, deletions, and substitutions, both subtle and gross, might well be made to the illustrated embodiments without departing from the spirit and scope of the invention, which is determined only by the claims. For example, while the disclosure is particularly applicable to gaskets for power trains of vehicles and other equipment, it may be applied to the formation of gaskets for virtually any press-in-place application. Such gaskets may be useful in the pluming industry, for sealing oil and gas pipeline sections, and many other applications. Thus, the invention is not limited to any particular end application. The particular bending head configuration illustrated herein is an example only and is not limiting. Bending devices of other configurations are within the scope of the invention so long as they meet the requirements detailed above for forming the press-in gasket stock into desired shapes. These and other modifications, both subtle and gross, are possible without departing from the scope of the invention exemplified above.