US3889961A

US3889961A - Molded type heat insulating gasket

Info

Publication number: US3889961A
Application number: US434871A
Authority: US
Inventors: Robert G Farnam
Original assignee: F D FARNAM Co
Current assignee: FD FARNAM Inc; Colt Industries Operating Corp; F D FARNAM Co
Priority date: 1974-01-21
Filing date: 1974-01-21
Publication date: 1975-06-17
Anticipated expiration: 1992-06-17
Also published as: CA1027605A

Abstract

A heat insulating gasket structure with a molded body, and having bolt holes passing through raised bosses, is provided with a fluid passageway encircled by sealing members of packing material of a greater height than the raised bosses and having a plan area substantially less than that of the body. Sealing and heat insulation are accomplished by drawing mating flanges together to compress the sealing members to the height of the bosses and insulating air gaps result between the mating flanges and the molded body.

Description

United States Patent Farnam MOLDED TYPE HEAT INSULATING GASKET Inventor: Robert G. Farnam, New Lisbon,

Wis.

[73] Assignee: F. D. Farnam Co., New Lisbon, Wis.

22 Filed: Jan. 21, 1974 21 Appl. No.: 434,871

[52] US. Cl. 277/166 [51] Int. Cl. Fl6j 15/10 [58] Field of Search 277/166, 211, 235 B [56] References Cited UNITED STATES PATENTS 3,191,950 6/1965 Hiltner 277/211 3,655,210 4/1972 Farnam et a]. 277/235 B 3,889,961 [451 June 17, 1975 Primary Examiner-Robert I. Smith Attorney, Agent, or Firm-Mann, Brown, McWilliams & Bradway ABSTRACT A heat insulating gasket structure with a molded body, and having bolt holes passing through raised bosses, is provided with a fluid passageway encircled by sealing members of packing material of a greater height than the raised bosses and having a plan area substantially less than that of the body. Sealing and 'heat insulation are accomplished by drawing mating flanges together to compress the sealing members to the height of the bosses and insulating air gaps result between the mat-' ing flanges and the molded body.

4 Claims, 3 Drawing Figures MOLDED TYPE HEAT INSULATING GASKET BACKGROUND OF THE INVENTION This invention pertains to insulating gaskets, particularly those of the type that are used between a carburetor and the engine manifold.

There has been disclosed in Farnam et a]. US. Pat. No. 3,655,210 a heat insulating gasket, which has been successfully used in automotive engines between the carburetor body and the intake manifold, but, as engine temperatures increase, due to many factors relating to environmental control, there is a need for heat insulating gaskets which can withstand even higher temperatures.

Also, in smaller internal combusion engines, where the size of the gasket does not justify the cost involved with the type of insulating gasket shown in said earlier patent, there is a need for a simpler construction which can be produced at relatively low cost.

Molded insulators have been used in the past to attempt to solve the gasketing problems in these smaller engines, but they have not been altogether satisfactory, due to the fact that the clamping loads necessary to bring the flange parts together to seal them were generally such that they cause the parts to crack under stress, and this condition was further aggravated by the fact that the flange surfaces are often uneven because of the expense involved in machining these parts as smooth as might be desired.

In larger internal combustion engines, such as normally found in todays high-powered automobile, the economics of the part are a real problem, as well as the technical problems due to the high temperature generated in the manifold area of the engine, this often being in the range of 350 to 400F, and sometimes even higher. The heat conducted from the manifold to the carburetor through the throttle bowl joint causes a high evaporative loss of the fuel in the throttle bowl. These temperature increases are further hampered by the trend of design toward low profile automobiles which provide for very cramped engine compartments, with low hood lines. The use of sound dampening material to reduce the noise level in the remainder of the automobile is a further complication to the problem because this material is heat insulating, prevents rapid dissipation of the engine heat to the ambient atmosphere, and keeps the heat of the engine at a higher level longer. Any steps which can be taken to minimize the heat buildup in the throttle bowl, and therefore prevent vaporization of the fuel contained therein not only improve the performance and the economy of the automobile engine, but also reduce the ecological problems with unburned petroleum fuels. The fuel evaporated may condense inside the engine compartment and drip back down onto the hot engine to be further vaporized and partially burned, causing a particulate matter to be suspended in the atmosphere.

BRIEF SUMMARY OF THE INVENTION It is an object of this invention to provide a heat insulating gasket structure which will be particularly effective in extremely high temperature conditions. It is an additional object to provide that the insulator gasket structure may be drawn into sealing configuration without undue distortion of the gasket structure or the mating flanges of the conduit being sealed. It is also an object to provide a gasket structure that is economical to manufacture, so that it may be used in small engine applications, where the cost heretofore has been a deterrent to proper gasketing techniques. It is an aim of this invention to provide a structure which is more resilient than previously known structures so as to permit greater tolerances as far as the flatness and alignment of the mating surfaces. It is a further object to provide an air gap between the mating flanges and the gasket body to take advantage of the great insulating value of air.

DESCRIPTION OF THE DRAWINGS j ,In the drawings:

FIG. 1 is a plan view of an embodiment of the invention;

FIG. 2 is a partial perspective view of the embodiment depicted in FIG. 1; and

FIG. 3 is a sectional view along the lines 3--3 of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION Referring to the drawings where like numerals of reference will designate like elements throughout, and referring specifically to FIG. 1, an improved heat insulating gasket structure 10 is shown. The structure 10 is composed ofa molded body portion 12 with a fluid passageway 14 passing therethrough. Raised bosses 16 with bolt holes 18 coaxial with the bosses are located, in this case, at the extremities of the structure 10. Sealing members 20 of packing material encircle the fluid passageway 14 in the body 12. The members 20 are of a thickness greater than the-overall thickness of the bosses 16.

As seen generally in FIGS. 2 and 3, the gasket structure has three levels or tiers on each mating face. The facesof the body 12 are the main planes of reference from which all other heights are determined. The bosses 16 project from the surfaces of the faces 12, and the sealing members 20 are affixed to the faces of the body 12 so as to encircle the fluid opening I4 at a distance greater than the projection of the bosses 16. This relationship is specifically illustrated with the primed reference numerals in FIG. 3. The distance A is the thickness of the molded body portion 12 between points 12'12'. The distance B is the thickness of the raised boss portion 16 between points 16I6'. The distance C is the free standing thickness of the gasket structure 10 taken between points I0'--I0'. The thickness of the packing or sealing members 20, as here shown, would be (C A )/2. Certain limitations exist to make this three-tiered structure effective. The bosses must project at least 0.005 inch above the molded body portion of the gasket structure and may project possibly 0.030 inch above the body portion. Normally the bosses 16 would project on both sides of the gasket structure but a particular application may necessitate bosses on one side so that in any event the bosses will project on at least one side of the molded body portion 12.

The height of the bosses is dependent on the gasket thickness necessary to maintain a seal and this includes provision for the degree of compaction required as well as the practicability of the thickness selected. A typical thickness of the gasket would approximate 0.020 inch with a boss height above the molded body portion of about0.0l5 inch, keeping in mind that the total height over the bosses, including the molded body thickness,

the boss height at each side and the sealing gaskets, which may be on one or both sides, all require tolerances which must be considered in arriving at the specifications for a particular gasket structure.

The sealing members must be at least 0.002 inch above the plane of the bosses 16. Here too the member 20 normally is disposed on both sides of the gasket structure but always on at least one side. The width of the sealing member should normally be no more than ten times its height, with a minimum of 0.075 inch and a maximum of 0.200 inch with typical sealing member being in the range of 0.090 to 0.200 inch. A typical body portion would be 0.250 inch thick, and the bossed would protrude about 0.020 inch on each side of the body portion. The sealing members of packing material would be approximately 0.025 inch high and approximately 0.075 inch in width encircling the fluid opening. The sealing members would be compressed when the mating parts were drawn together upon the raised bosses to a thickness of 0.020 inch approximately on each side, or be approximately 20 percent compressed. The gasket with the compressed sealing member and the flanges resting upon the raised bosses is then in position with an air gap on each side of the body portion of approximately 0.020 inch. In other cases, the air gap might be as little as 0.005 inch since the bosses 16 must be at least 0.005 inch above the level of the molded body portion 12. This air gap serves to insulate the carburetor throttle bowl, which may be on one side of one flange from the intake manifold, which would be on the other side of the structure on the other flange. The insulating value of this air gap, even when small, far exceeds any detrimental conductivity through the bossed portions of the body of the gasket.

While the factor of these bossed portions may be higher than would be suitable for the entire gasket, the fact that the area in contact with the flanges is as minimal as it is, as well as the fact that the area of the packing material of the sealing member is minimal compared to the plan area of the flanges being sealed, provide for a very good insulation of the joint sealed.

The materials used in making the body portion of the insulating gasket structure of this invention will generally be moldable materials such as asbestos phenolic molding compounds. These materials are phenolic resins to which asbestos fibers have been added to give additional strength and resilience. Typical of the commercially available compounds that have been found useful for making the body portion are Gene] 4300 from the General Electric Co. and No. 25398 from Reichhold Chemical. The molds will ordinarily be such that the cavity provides that the bosses protrude the same distance above and below the faces of the body portion. Other materials and molding techniques known to the art may be used.

The sealing members will be compactible and compressible packing materials. The specific material is selected for its compatibility with the environment of use. Factors of prime importance are temperature ranges, corrosiveness of fluid, and clamping pressure. The packing materials known in the art, such as curable nitrile rubber, acrylonitrile rubber, neoprenes, and chloroprenes may be suitable. I prefer asbestos rubber sheet packing, such as Kaobestos 66013, sold by the F. D. Farnam Co., for the reasons that it provides good sealing of a wide range of fluids over a broad temperature range, and the material is very stable at the high temperatures which are contemplated in the field of use.

A typical heat insulating gasket structure may be assembled as follows: A sheet of Kaobestos 66013 is coated on one side with an elastomer adhesive resin, such as Farnam l800l-XR, and dried. This adhesive, which is particularly suitable for the gasket structure environment, is a water dispersion of curable neoprene and a phenolic resin emulsion of the type disclosed in Farnam et al. US. Pat. No. 3,158,526. The sealing elements 20 are then die-cut to the desired configuration. The die-cut pieces are then put into an auto feed device to be indexed upon the preheated faces of the molded body portion. The molded body portion is preheated to about 200F., and the dried adhesive coated faces of the sealing elements become tacky upon contact with the preheated insulator. These elements are pressed over a dwell time of one to five seconds. The bond lines of the structures are cured in an oven over a period of 10 to 15 minutes at temperatures of about 325 to 350F. The finished parts are removed to cool, and then will be inspected and packaged.

The size, shape and assembly conditions have a hearing on the selection of the flange width, which may be of uniform width over the entire area or the width may be variable. The primary purpose of the invention includes the provision of a minimum gasket area under clamp load, thereby increasing unit loading and minimizing distortion, or bending of the mounting flanges, while gaining an insulating air gap and keeping the width of the sealing member at a minimum.

The embodiments in which an exclusive property or privelege is claimed are defined as follows:

1. A heat insulating gasket for use between mating flanges of an internal combustion engine conduit or the like, said gasket comprising a unitary molded core member of insulating material having a body portion of given thickness, having bolt holes and a fluid passageway therethrough, bosses coaxial with said bolt holes projecting from the surfaces of said body portion to a greater thickness than the. thickness of said body portion, die-cut sheet packing material on said body portion of said core surrounding said fluid passageway projecting further from said body portion than said bosses project, the total plan area of said packing material being less than 33 /3 percent of the plan area of the core member, whereby when the gasket structure is clamped between said mating flanges, said packing material will be compressed to the level of said bosses forming a seal between said flanges and substantial air spaces will be provided between said flanges and said core member for heat insulating purposes.

2. The heat insulating gasket structure as set forth in claim 1 wherein the said packing material projects at least 0.002 inch further from said core member on each side than do said bosses.

3. The heat insulating gasket structure as set forth in claim 1 wherein said air spaces will be at least 0.005 inch thick.

4. A heat insulating gasket structure for use between mating flanges of an internal combustion engine conduit, said gasket comprising a unitary core of insulating material having a body portion of given thickness, having a fluid passageway and bolt holes, raised bosses coaxial with said bolt holes projecting at least 0.005 inch from the surfaces of the body portion, die-cut sheet packing material mounted on said body portion of said 6 said mating flanges, said packing material will be compressed to the level of said bosses thereby forming a seal between said flanges and substantial air spaces will be provided between said flanges and said core member for heat insulating purposes.

Claims

1. A heat insulating gasket for use between mating flanges of an internal combustion engine conduit or the like, said gasket comprising a unitary molded core member of insulating material having a body portion of given thickness, having bolt holes and a fluid passageway therethrough, bosses coaxial with said bolt holes projecting from the surfaces of said body portion to a greater thickness than the thickness of said body portion, diecut sheet packing material on said body portion of said core surrounding said fluid passageway projecting further from said body portion than said bosses project, the total plan area of said packing material being less than 33 1/3 percent of the plan area of the core member, whereby when the gasket structure is clamped between said mating flanges, said packing material will be compressed to the level of said bosses forming a seal between said flanges and substantial air spaces will be provided between said flanges and said core member for heat insulating purposes.

4. A heat insulating gasket structure for use between mating flanges of an internal combustion engine conduit, said gasket comprising a unitary core of insulating material having a body portion of given thickness, having a fluid passageway and bolt holes, raised bosses coaxial with said bolt holes projecting at least 0.005 inch from the surfaces of the body portion, die-cut sheet packing material mounted on said body portion of said core surrounding said fluid passageway projecting at least 0.002 inch further from said body portion on each side than said bosses project, the width of said packing material being no more than ten times its thickness, the total plan area of said packing material being no more than 33 1/3 percent of the plan area of said core member, whereby when the gasket structure is clamped between said mating flanges, said packing material will be compressed to the level of said bosses thereby forming a seal between said flanges and substantial air spaces will be provided between said flanges and said core member for heat insulating purposes.