Abstract:
A composite seal including multiple seal elements is disclosed along with corresponding methods and seal structures. In one embodiment, the composite seal may include a first, substantially annular seal element having an upper body portion, a neck portion, and an axial protrusion. The upper body portion includes opposing inclined surfaces extending toward the neck portion defining a first angle. The axial protrusion includes opposing inclined surfaces extending towards an axial end of the axial protrusion defining a second angle, wherein the first angle and the second angle are substantially similar. The composite seal may further include a second, substantially annular seal element having a mouth portion, a neck portion and a recess portion, wherein the axial protrusion is configured to be complementarily engaged with the recess portion in an interlocking manner.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates generally to seals and structures used to effect a fluid seal between multiple mechanical or structural elements and, more particularly, to composite seals and structures used to effect fluid seals between mechanical or structural elements which may be relatively movable with respect to one another wherein the seal is effective in both low and high pressure applications.  
         [0003]     2. State of the Art  
         [0004]     Seals are conventionally used to maintain a substance, such as a fluid or gas, located in one area or zone from escaping to another area or zone while allowing relative movement of two or more mechanical components with one of the mechanical components traversing through both areas or zones. Such seals may also be used in keeping contaminants, such as dirt, dust or other particulate-type materials, from entering into a specified area or zone. For example, it may be desirable to maintain a lubricant in a specified area or zone while keeping dust or other particulates from entering into the same zone and contaminating the lubricant.  
         [0005]     As will be appreciated by those of ordinary skill in the art, the ability to maintain adequate lubrication between to relatively movable machine components, as well as the ability to limit contaminants from entering between the two relatively movable machine components, greatly enhances the working efficiency of the machine components and also greatly reduces wear of such components, thereby increasing the usable life thereof. Additionally, the ability to keep a fluid within a specified zone, sometimes while exhibiting elevated pressures relative to other areas adjacent the zone, may be essential to the proper operation of the machine, device or structure in which the seal is disposed.  
         [0006]     One common example of mechanical components that move with respect to one another is a piston and bore (which may also be referred to as a rod and cylinder). For instance, a piston may have an outer surface that is complementary and generally coaxial with the inner surface of a bore in which the piston moves axially, with or without rotation. It is usually desirable that no fluid flow around the piston, so that pressure within the bore may cause the piston to move. Moreover it is also preferred that the piston remain relatively centered within the bore, to prevent the surfaces of the piston and the bore from contacting one another.  
         [0007]     Seals take various forms and are made of numerous types of materials depending on their intended of service and anticipated working environment. O-rings are an example of a simple type of seal. Another type of seal conventionally used in conjunction with two or more relatively moving machine components are lip seals. Generally, lip seals exhibit a more complex cross-sectional geometry than O-rings and are correspondingly more complex to manufacture. O-rings and lip seals are relatively simple in their installation and operation as will be appreciated by those of ordinary skill in the art.  
         [0008]     Another type of available seal may be referred to as a composite seal. Examples of composite seals are described in U.S. Pat. No. 3,848,880, issued to Tanner, and U.S. Pat. No. 4,635,945, issued to Beck, the disclosures of each of which patents are incorporated by reference herein in their entireties. Generally, composite seals include two or more seal elements or components that cooperatively and interdependently define and maintain the separation of multiple zones or areas such as discussed hereinabove. The two different seal elements may include two substantially annular, or ring-like, members formed of different materials so as to take advantage of the different sealing or other structural characteristics offered by such different materials. For example, one of the seal elements may be formed of a first specified material and configured to provide an efficient seal at relatively low pressures while another of the seal elements may be configured of a substantially different material and configured to provide an efficient seal when subject to elevated pressures.  
         [0009]     Sometimes composite seals may be configured such that a portion of one seal element cooperatively engages and interlocks with a portion of another seal element such as described with the aforementioned Tanner and Beck patents. However, such cooperative and interlocking structures are often difficult to properly assemble. Moreover, composite seals will oftentimes become separated during installation between, for example, two relatively movable machine elements requiring removal and reassembly of the seal elements.  
         [0010]     For example, referring to  FIG. 1 , a cross section of a composite seal  10  is shown that is generally similar to that described by the Beck patent. The seal  10  includes a first seal element  12  and a second seal element  14 . The second seal element  14  exhibits a cross-sectional geometry that defines a throat  16  and a recess  18  that is radially enlarged relative to the throat  16 . The first seal element  12  includes a protrusion  20  that exhibits a cross-sectional geometry that is complementary to the recess  18  of the second seal element  14 . Adjacent the throat  16  is a pair of angled surfaces  22  which define an angle θ1 that is approximately 60° as such surfaces toward the throat  16 . On the opposite side of the throat  16  is a pair of angled surfaces  24  which define an angle θ2 that is approximately 40° as they extend away from the throat. The first seal element  12  includes surfaces that complementarily mate with the angled surfaces  22  and  24  of the second seal element  14 .  
         [0011]     While the geometric configuration of the seal  10  may provide a relatively effective interlock between the first seal element  12  and the second seal element  14  (i.e., by way of the enlarged recess  18  as compared to the throat  16  and the cooperatively mating protrusion  20 ), the same configuration has made it difficult to assemble (or reassemble) the first and second seal elements  12  and  14 . For example, the radially enlarged portions of the protrusion  20  (i.e., the portion configured to matingly engage the recess  18 ) may not become entirely inserted or installed within the recess  18  as intended. Rather, one of the radially extending edges of the protrusion  20  may get caught on an edge of the throat  16  and not become entirely disposed within the recess  18 . In another example, air may become trapped between the protrusion  20  and the recess  18  such that the first seal element  12  is not entirely seated within second seal element  14  as intended. The partial seating of one component relative to the other can have a deleterious effect on the performance of the composite seal  10 .  
         [0012]     It is, therefore, desirable to provide a composite seal which provides effective sealing between multiple machine elements under varying conditions which is also simple to manufacture, assemble and install.  
       BRIEF SUMMARY OF THE INVENTION  
       [0013]     In accordance with one aspect of the present invention, a composite seal is provided. The composite seal includes a first, substantially annular seal element having an upper body portion, a neck portion, and an axial protrusion. The upper body portion includes opposing inclined surfaces extending toward the neck portion defining a first angle. The axial protrusion includes opposing inclined surfaces extending towards an axial end of the axial protrusion defining a second angle, wherein the first angle and the second angle are substantially similar. The composite seal further includes a second, substantially annular seal element having a mouth portion, a neck portion and a recess portion, wherein the axial protrusion is configured to be complementarily engaged with the recess portion in an interlocking manner.  
         [0014]     In accordance with another aspect of the present invention, a method of forming a seal is provided. The method includes forming a first, substantially annular seal element including defining an upper body portion, a neck portion and an axial protrusion. Opposing inclined surfaces are formed on the upper body portion to extend toward the neck portion and define a first angle. Opposing inclined surfaces are also formed on the axial protrusion that extend towards an axial end of the axial protrusion and define a second angle that is substantially equal to the first angle. A second, substantially annular seal element is also formed to include a mouth portion, a neck portion and a recess portion. The axial protrusion of the first seal element is disposed in the recess portion of the second seal element in an interlocking manner to form the composite seal.  
         [0015]     In accordance with yet another aspect of the present invention, a seal structure is provided. The seal structure includes a first machine element and a second machine element, wherein the first machine element and second machine element are configured to accommodate relative movement of one with respect to the other. A substantially annular cavity formed in the first machine element and a composite seal is disposed in the substantially annular cavity. The composite seal includes a first, substantially annular seal element having an upper body portion, a neck portion, and an axial protrusion. The upper body portion includes opposing inclined surfaces extending toward the neck portion defining a first angle. The axial protrusion includes opposing inclined surfaces extending towards an axial end of the axial protrusion defining a second angle, wherein the first angle and the second angle are substantially similar. The composite seal further includes a second, substantially annular seal element having a mouth portion, a neck portion and a recess portion, wherein the axial protrusion is configured to be complementarily engaged with the recess portion in an interlocking manner. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0016]     The foregoing and other advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings in which:  
         [0017]      FIG. 1  is a partial cross-sectional view of a prior art composite seal;  
         [0018]      FIG. 2  is a sectional perspective view of a composite seal in accordance with an embodiment of the present invention;  
         [0019]      FIG. 3  is an enlarged cross-sectional view of a portion of the composite seal shown in  FIG. 2 ;  
         [0020]      FIGS. 4A and 4B  show the cross-sectional profiles of seal elements of the seal shown in  FIG. 2 ;  
         [0021]      FIG. 5  is a cross-sectional view of a composite seal installed in a device or structure having relatively movable machine elements in accordance with an aspect of the present invention; and  
         [0022]      FIG. 6  is a partial cross-sectional view of a composite seal in accordance with another embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0023]      FIGS. 2 and 3  depict a composite seal  100  in accordance with an embodiment of the present invention.  FIG. 2  shows a perspective view of the seal  100  with a section removed to show cross-sectional details of various seal components.  FIG. 3  shows an enlarged cross-sectional view of the seal components shown in  FIG. 2 . The seal  100  is formed as a generally ring-like, or annular, structure and, in the embodiment described with respect to  FIGS. 2 and 3 , is a continuous structure. In other embodiments the seal may include a split structure wherein two matching ends meet at, for example, an angled or a stepped interface as will be appreciated by those of ordinary skill in the art.  
         [0024]     The seal  100  includes a first seal element  102  and a second seal element  104 . The first seal element  102  matingly engages the second seal element  104  such that the two seal elements  102  and  104  are effectively interlocked with one another and may generally function as a single unit when installed in a machine or structure as shall be described in a greater detail below. In one embodiment, the first seal element  102  may be formed of a relatively softer material than that of the second seal element  104 . For example, the first seal element  102  may be formed of a material such as synthetic rubber or other synthetic elastomers including thermoset or thermoplastic materials, while the second seal element  104  may be formed of a material such as relatively harder elastomers or rubber, or plastics such as polyurethanes and polyamids. Of course various other embodiments may incorporate different materials depending, for example, on the intended applications and environments in which the seal  100  is expected to be utilized.  
         [0025]     As noted hereinabove, the seal elements  102  and  104  work together to cooperatively define the seal  100 . However, each seal element  102  and  104  includes features that help to enable their complementary and cooperative nature.  FIGS. 4A and 4B  depict cross-sectional profiles of the first seal element  102  and second seal element, respectively, in unassembled condition to better describe some of the features associated with such seal elements  102  and  104 . Referring first to  FIG. 4A  in conjunction with  FIGS. 2 and 3 , the first seal element includes an upper body portion  110 , an area of reduced cross sectional width referred to as a neck portion  112 , and a lower body portion or what may be termed an axial protrusion  114 . The upper body portion  110  includes a radially outer lip  116  and a radially inner lip  118 . The radially outer lip  116  is disposed a distance from the radial inner lip  118  an axial distance “X.” The axial distance X between the two lips  116  and  118  helps to provide stability to the seal  100  when installed in an intended environment as will become more apparent upon further reading of the description.  
         [0026]     The upper body portion  110  includes two opposing inclined surfaces, a radially inner surface  120 A and a radially outer surface  120 B, that extend towards the neck portion  112 . The two opposing inclined surfaces  120 A and  120 B of the upper body portion define an angle α1 therebetween. In one embodiment, the angle α1 may be approximately 60° or greater. In one particular embodiment, the angle α1 may be approximately 85°. Additionally, in one embodiment, the angle α1 may be congruent about an axis  121  extending in the axial direction.  
         [0027]     The axial protrusion  114  includes two opposing inclined surfaces, a radially inner surface  122 A and a radially outer surface  122 B, that extend away from the neck portion  112  and which define an angle β. In one embodiment the angle β may be approximately 90° or greater. In one particular embodiment, the angle β may be approximately 98°. As with angle α1, angle β may be congruent about the axial axis  121 .  
         [0028]     The axial protrusion  114  further includes two opposing inclined surfaces, a radially inner surface  124 A and a radially outer surface  124 B, that extend towards a generally flat bottom  126  of the axial protrusion  114 . The two inclined surfaces  124 A and  124 B define an angle α2 therebetween that is substantially similar to angle α1. In other words, radially inner surface  120 A is substantially parallel with radial inner surface  124 A and radially outer surface  120 B is substantially parallel with radially outer surface  124 B.  
         [0029]     Referring now to  FIG. 4B  in conjunction with  FIGS. 2 and 3 , the second seal  104  includes what may be termed a mouth portion  130 , an opening of reduced cross-sectional width which may be referred to as a throat portion  132  and a recess  134  exhibiting a cross-sectional width that is greater than that of the throat portion  132 . The second seal element  102  includes two opposing inclined walls, including a radially inner wall  140 A and a radial outer wall  140 B, which extend from the mouth portion  130  to the throat portion  132  and define an angle α1. In other words, the radially inner and outer walls  140 A and  140 B define an angle similar to that defined by radially inner and outer walls  120 A and  120 B of the first seal element  102  so as to provide a complementary fit between the two seal elements  102  and  104  at such locations (see  FIGS. 2 and 3 ).  
         [0030]     Opposing inclined walls, including radially inner wall  142 A and radially outer wall  142 B, extend from the throat portion  132  into the recess  134  and define an angle β that is substantially similar to the angle defined by radially inner and outer walls  122 A and  122 B of the first seal element  102 . Additionally, opposing inclined walls, including radially inner wall  144 A and  144 B, extend within the recess  134  toward a flat bottom  136  thereof and define an angle α2 which is substantially similar to the angle defined by radially inner and outer walls  126 A and  126 B of the first seal element  102 .  
         [0031]     The second seal element  104  also includes a radially inner lip  148  and a radially outer lip  150  at the axially end which engages with the first seal element  102 . An additional protrusion  152  may be formed to extend radially inwardly from the inwardly-most radial wall of the second seal element  104 .  
         [0032]     Referring to  FIGS. 2, 3 ,  4 A and  4 B, the first and second seal elements  102  and  104  cooperatively engage one another to define the composite seal  100 . The angle α1 defined between the surfaces  140 A and  140 B extending from the mouth portion  130  to the throat portion  132 , being approximately 60° or greater, improves ease of assembly of the first seal element  102  with the second seal element  104  enabling the protrusion  114  to more easily align with the throat portion  132 . Moreover, the angle α2 being substantially similar to the angle α1 enables the opposing surfaces  124 A and  124 B of the first seal element  102  to engage and align with the opposing surfaces  140 A and  140 B of the second seal element  104  during assembly prior to the axial protrusion  114  being disposed through the neck portion  132  of the second seal element  102  and into the recess  134 . Once the axial protrusion  114  is disposed within the recess  134  of the second seal element  104 , an interference occurs between the radially extending portions of the axial protrusion  114  and the throat portion  132  of the second seal element  104  to effect the interlock between the first and second seal elements  102  and  104 . The angle β being approximately 90° or greater provides an effective interlock between the seal elements  102  and  104  and reduces the possibility of the two seal elements  102  and  104  from inadvertently separating during installation of the seal  100  in a machine element.  
         [0033]     In the embodiment shown and described with respect to  FIGS. 2, 3 ,  4 A and  4 B, and when assembled as a seal  100 , the opposing surfaces  120 A and  120 B of the first seal element  102  engage with the opposing surfaces  140 A and  140 B of the second seal element  104  over an axial distance which is approximately one third (i.e., the upper one third as shown in  FIGS. 2 and 3 ) of the overall axial length of the second seal element  104 . Additionally, the axial protrusion  114  of the first seal element  102  engages with the recess  134  of the second seal element over an axial distance of approximately one third (i.e., the middle one third as shown in  FIGS. 2 and 3 ) of the over all axial length of the second seal element  104 . These relationships again help to enable simple and effective assembly of the first and second seal elements  102  and  104  while also providing a stable and effective resulting seal  100 .  
         [0034]     Referring now to  FIG. 5 , a cross-sectional view is shown of a seal  100  installed in a machine environment. The machine environment may include a first machine element such as, for example, a piston or a rod  160  and a second machine element such as, for example, a bore or a cylinder  162 . The rod  160  is disposed within the cylinder  162  such that a substantially annular space  164  is defined therebetween. A substantially annular cavity  166  may be defined within the cylinder  162  and the seal  100  disposed within the cavity  166 . In another embodiment, the annular cavity  166  may be formed in the rod  160  as will be appreciated by those of ordinary skill in the art. In operation, the rod  160  may rotate relative to the cylinder  162 , may be axially displaced along longitudinal axis  168  relative to the cylinder  162 , or both.  
         [0035]     The radially outer lip  116  of the first seal element  102  contacts a wall of the cavity  166  forming a fluid seal therewith and the radial inner lip  118  of the first seal element  102  contacts a surface of the rod  160  forming a fluid seal therewith. The lips  116  and  118  of the first seal element  102  may be displaced radially towards one another (as indicated by dashed lines) such that the first seal element  102 , or at least a portion thereof, is generally placed in radial compression. Similarly, the radial outer lip  150  of the second seal element  104  may contact the wall of the cavity  166  and the radial inner lip  148  of the second seal element  104  may contact the surface of the rod  160  to provide additional fluid seals. The radial protrusion  152  may also contact the surface of the rod  160  to provide an additional fluid seal, to provide stability of the seal  100  in its installed configuration, or to act as both a fluid seal and a stabilizing structure.  
         [0036]     Referring now to  FIG. 6 , a seal  200  in accordance with another embodiment of the present invention is shown. The seal  200  includes a first seal element  202  and a second seal element  204  which are configured substantially similar to the seal elements  102  and  104  of the seal  100  shown and described with respect to  FIGS. 2 and 3 . However, the axial protrusion  214  of the first seal element  202  (and the corresponding recess  234  of the second seal element  204 ) does not exhibit a substantially flat bottom but, rather, exhibits a substantially arcuate peak  226  that transitions between opposing inclined surfaces  224 A and  224 B.  
         [0037]     While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.