Abstract:
A sealing assembly and method of manufacturing a sealing assembly for a spring brake actuator having a dynamic center seal for sealing a first surface to a second surface. The sealing assembly has dynamic sealing elements that seal in a smooth hole or bore, where the sealing element or element stack is retained in the hole or bore on each end by a bearing for the center pushrod or center tube.

Description:
FIELD OF THE INVENTION 
     This invention relates to a sealing assembly for a spring brake actuator having a dynamic center seal for sealing a first surface to a second surface. 
     BACKGROUND OF THE INVENTION 
     Air brake systems for a vehicle such as a bus, truck, trailer and other heavy-duty vehicles or the like typically include a brake shoe and drum assembly which is actuated by means of an actuator assembly operated by the selective application of compressed air. Conventional air brake actuators have both a service brake actuator for actuating the brakes under normal driving conditions by the application of compressed air and also a spring-type emergency brake actuator which causes actuation of the brakes when air pressure has been released. The emergency brake actuator includes a strong compression spring which forces application of the brake when air is released. This is often referred to as the spring brake. 
     When applying the parking brakes, the spring brake actuator pressure is discharged from the pressure chamber and the large force compression spring pushes the spring piston and the diaphragm toward the dividing wall between the spring brake actuator and the service brake actuator. In this position, the actuator rod connected to the spring piston is pushed forward extending into the service section through the dividing center wall applying the parking or emergency brakes and thus forcing the vehicle to stop or remain parked. To release the parking brake, the pressure chamber is closed to the atmosphere and pressurized air is introduced into the pressure chamber of the spring brake actuator which expands the pressure chamber, moving the diaphragm and spring piston toward the opposing end of the spring brake actuator housing, thereby compressing the strong compression spring. 
     U.S. Pat. No. 6,006,651 (Pierce et al.) teaches a spring brake having an actuator with an opening provided with a bearing having at least one annular recess which accommodates at least one O-ring seal. U.S. Pat. No. 5,377,579 (Pierce) teaches a spring brake having an actuator with one or more O-ring seals through which the spring brake actuator rod reciprocates. 
     U.S. Pat. No. 3,977,308 (Swander, Jr. et al.) teaches a brake actuator having an opening where a retainer ring is positioned which retains a nylon and small seal or O-ring positioned in said opening. U.S. Pat. No. 3,813,994 (Swander, Jr. et al.) teaches a spring brake actuator having a seal and guide bushing retained by a ring. United States Patent Application No. 2008/0083325 A1 (Scheckelhoff et al.) teaches a spring brake actuator having bearings and seals for fluid reciprocation of the connecting shaft within the aperture. United States Patent Application No. 2007/0034465 A1 (Thompson et al.) teaches a flexible bushing assembly for a spring brake push rod seal having a sealing member to engage the push rod. Thompson et al. also teach a threaded section. United States Patent Application No. 2007/0131498 A1 Li et al. teaches a sealing member of one or more O-ring seals positioned around a push rod. 
     However, none of the above mentioned patents teaches a spring brake center seal design which involves dynamic sealing elements that seal in a smooth hole, bore or cavity, where the sealing element or element stack is retained in the hole, bore or cavity on each end by a bearing for the center pushrod or center tube. 
     Furthermore, none of the above mentioned patents teach a spring brake center seal design which has a sealing element separator between two sealing elements, such that less complicated machining is required to achieve a proper surface finish for sealing with the smooth hole or bore or cavity design since it is a through hole rather than in a groove. 
     As none of the prior art teaches such a design, it is desirable to provide such a sealing assembly and method for making such a sealing assembly. 
     It is further desirable to provide a spring brake center seal design which involves dynamic sealing elements that seal in a smooth hole or bore, where the sealing element or element stack is retained in the hole or bore on each end by a bearing for the center pushrod or center tube. 
     It is further desirable to provide a spring brake center seal design which has a sealing element separator between two sealing elements, such that less complicated machining is required to achieve a proper surface finish for sealing with the smooth hole or bore design since it is a through hole rather than in a groove. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a sealing assembly and method for making such a sealing assembly that has a dynamic center seal for sealing a first surface to a second surface. 
     It is another object of the present invention to provide a sealing assembly and method for making such a sealing assembly that overcomes the problems of the prior art. 
     It is another object of the present invention to provide a spring brake center seal design which involves dynamic sealing elements that seal in a smooth hole or bore, where the sealing element or element stack is retained in the hole or bore on each end by a bearing for the center pushrod or center tube. A bore, hole or cavity may be used interchangeably throughout the application. 
     It is another object of the present invention to provide a spring brake center seal design which has a sealing element separator between two sealing elements, such that less complicated machining is required to achieve a proper surface finish for sealing with the smooth hole or bore design since it is a through hole rather than in a groove. 
     It is another object of the present invention to provide a spring brake actuator having such a sealing assembly. 
     It is another object of the present invention to provide a sealing assembly having a hole located between a first sealing surface and second sealing surface and also having two sealing elements located within the hole and one sealing element separator located within the hole and between the two sealing elements. 
     These and other objectives are achieved by providing an assembly for forming a seal in a spring brake actuator comprising: a first component having a first surface, a second component having a second surface, a cavity, the cavity located between the first surface and the second surface, one or more sealing elements located within the cavity, and one or more retaining elements located within the cavity, the one or more retaining elements retaining the one or more sealing elements within the cavity, and the one or more sealing elements providing a seal, so as to seal the first surface to the second surface. 
     The diameter of the one or more sealing elements may be greater than the distance between the first and second sealing surfaces. 
     The assembly may further comprise one or more sealing element separators. 
     The one or more sealing element separators may separate the one or more sealing elements from one another. The combined width of the one or more sealing element separators, the one or more sealing elements and the one or more retaining elements may be greater than the width of the cavity. 
     The cavity may be circular and may have an equal diameter throughout. The one or more retaining elements may be located along the ends of the cavity. 
     The one or more sealing element separators may be free floating or retained in the cavity. The cavity may be smooth. The first surface of the component may also be smooth. The second surface may also be smooth. 
     The one or more sealing elements may be selected from a group consisting of a square-ring, O-ring, quad-ring, lip seal, or a combination thereof. The one or more retaining elements may be bearings. 
     The seal formed may be dynamic. The cavity may be a through hole and may be made by a drill, mill, lathe, or other similar machine. 
     The first component may be a pushrod. The second component may be a center body. 
     Other objectives of the invention are achieved by providing a spring brake actuator for applying parking brakes of a vehicle comprising: a housing including a first end wall, a second end wall opposing the first end wall, and a side wall extending between the first and second end walls, the first end wall, the second end wall and the side walls together defining an cavity therein; a diaphragm spanning the cavity, and dividing the cavity into a spring chamber located between the diaphragm and the first end wall, and a pressure chamber located between the diaphragm and the second end wall, the diaphragm being in a first position when the pressure chamber is pressurized with fluid and in a second position when the pressure chamber is exhausted; a pushrod, wherein when the diaphragm is in the second position the pushrod is positioned to apply the parking brake, and when the diaphragm is in the first position the pushrod is positioned to release the parking brake; and an assembly for sealing the pushrod to a center body, the assembly comprising: a first surface located on the center body, a second surface located on the pushrod, a cavity, the cavity located between the first surface and the second surface, one or more sealing elements located within the cavity, one or more retaining elements located within the cavity, the one or more retaining elements retaining the one or more sealing elements within the cavity, and the one or more sealing elements providing a seal, so as to seal the first surface to the second surface, wherein upon sealing the first surface to the second surface the pushrod is sealed to the center body. 
     The diameter of the one or more sealing elements may be greater than the distance between the first surface and the second surface. 
     The assembly of the spring brake actuator may further comprise one or more sealing element separators and the one or more sealing element separators may separate the one or more sealing elements from one another. 
     The combined width of the one or more sealing element separators, the one or more sealing elements and the one or more retaining elements may be greater than the width of the cavity. 
     The cavity may be circular and has an equal diameter throughout. The one or more sealing element separators may be free floating or retained in the cavity. 
     Other objectives of the invention are achieved by providing an assembly for sealing a spring brake actuator comprising: a first component having a first surface, a second component having a second surface, a cavity, the cavity located between the first surface and the second surface, two sealing elements located within the cavity, one sealing element separator located within the cavity and between the two sealing elements, and two retaining elements located within the cavity, the two retaining elements retaining the two sealing elements within the cavity, and the two elements providing a dynamic seal, so as to seal the first surface to the second surface. 
     The combined width of the two sealing elements and sealing element separator may be greater than the distance between the two retaining elements. 
     The diameter of each of the two sealing elements may be greater than the distance between the first surface and the second surface. 
     The cavity may be circular and has an equal diameter throughout. The cavity may be made by a drill, mill, lathe, or other similar machine. 
     The one sealing element separator may be free floating or retained in the cavity. 
     Other objectives of the present invention are achieved by providing a spring brake center seal design which involves dynamic sealing element(s) that seal in a smooth hole or a smooth bore, being a hole made by a drill, mill, lathe, or other similar machine. The smooth hole is a through hole with an equal diameter throughout. The sealing element or element stack is retained in the hole on each end by a bearing for the center pushrod or center tube. If a sealing element stack is used, the sealing element separator(s) may be either free floating or retained in the hole. Inside the hole, the only necessary machined features would be those used for retaining the bearings and/or sealing element separator(s). The sealing element(s) may be any commercially available seal (such as a square-ring, O-ring, quad-ring, lip seal) in any quantity and/or combination thereof. 
     The use of a smooth hole in place of machined gland groove(s) reduces the amount of material removed during machining and the amount of time required for machining. If the parent material is cast, this design has the added benefit of reducing the chance of machining into porosity since less parent material is removed and a thinner wall section is initially cast. Machining into porosity has the result of an ineffective seal and a scrapped part. 
     Less complicated machining is required to achieve a proper surface finish for sealing is with the smooth hole or bore design since it is a through hole rather than a groove. Measuring the surface finish of a through hole is also less complicated than in a groove. 
     The smooth hole or bore design allows for easier installation of sealing elements. Since the bore diameter is close to the outer diameter of the sealing element, there is less chance of rolling or twisting the sealing element during assembly which could lead to premature failure of the seal. 
     The invention also relates to methods of making such a sealing assembly. The invention relates to a method of manufacturing said sealing assembly. The method of manufacturing such sealing assembly involves the steps of manufacturing the individual elements of the sealing assembly. 
     The invention also relates to methods for installation and/or assembly such a sealing assembly involving the steps for putting the elements of such sealing assembly together in the proper arrangement. 
     Other objects of the invention and its particular features and advantages will become more apparent from consideration of the following drawings and accompanying detailed description. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-section view of the sealing assembly of an embodiment of the present invention; 
         FIG. 2  is an exploded view of the sealing assembly of claim  1 ; 
         FIG. 3  is a cross-section view of the sealing assembly of an embodiment of the present invention utilizing quad-rings; 
         FIG. 4  is a perspective view of a quad-ring; 
         FIG. 5  cross-section view of the sealing assembly of an embodiment of the present invention utilizing square-rings; 
         FIG. 6  is a perspective view of a square ring; 
         FIG. 7  is cross-section view of the sealing assembly of an embodiment of the present invention where more than one sealing element separator is provided; 
         FIG. 8  is a cross-section view of the sealing assembly of an embodiment of the present invention where the hole is circular and has an equal diameter throughout. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , sealing assembly  100  of the present invention is shown. Here, actuator pushrod  110  is shown having a dynamic sealing surface  120 . The actuator pushrod  110  runs through center body  160 , which separates the spring side  180  from the service side  190  of the spring brake actuator. 
       FIG. 1  also provides the sealing assembly  100  of the present invention whereby the sealing elements  140 ,  145  are shown. Here, retainer bearings  130  and  135  are shown having sealing elements  140  and  145  present between retainer bearings  130  and  135 . Sealing element separator  150  is present between sealing elements  140  and  145 . 
     Also shown in smooth bore sealing surface  170  of the center body  160 . The bore or hole is filled by retainer bearings  130  and  135 , sealing elements  140  and  145 , and sealing element separator  150 . These elements allow for the dynamic center seal of the spring brake actuator to be provided. The dynamic center seal allows for sealing a first surface to a second surface. The dynamic center seal assembly allows the pressure within the chamber to be retained or released depending upon the application. This overcomes the problems in the prior art that have failed to achieve such a dynamic sealing assembly that provides advantages with regards to the dynamic sealing of a spring brake actuator. 
       FIG. 2  shows and exploded view of the sealing assembly of  FIG. 1 . Here, the sealing assembly is shown having pushrod  110 , retainer bearings  130  and  135 , sealing elements  140  and  145  present between retainer bearings  130  and  135 , and sealing element separator  150  present between sealing elements  140  and  145 . 
     The retainer bearings  130  and  135  have edges  230  and  235  respectively. These edges  230  and  235  fit into holes  210  and  215  respectively, allowing for the retainer bearings  130  and  135  to be retained in the bore  250 . However, the retainer bearings may be of a different design that allows the retainer bearings  130 ,  135  to be retained in the bore  250 . 
     The retainer bearings  130  and  135  also have edges  232  and  237  respectively, which line up with the bore sealing surface  222  and  227  respectively. The bore sealing surface  222  and  227  is smooth in preferred embodiments. 
     The smooth surface of bore  220  interacts with sealing elements  140  and  145  to form a seal. 
     The sealing elements may be any commercially available seal such as an O-ring, square ring, quad-ring, and/or lip seal in any quantity and/or combination thereof. Other such sealing elements known in the art may also be used. 
     The use of a smooth bore in place of machined gland groove(s) reduces the amount of material removed during machining and the amount of time required for machining. If the parent material is cast, this design has the added benefit of reducing the chance of machining into porosity since less parent material is removed and a thinner wall section is initially cast. Machining into porosity has the result of an ineffective seal and a scrapped part. 
     Less complicated machining is required to achieve a proper surface finish for sealing with the smooth hole or bore design since it is a through hole rather than a groove. Measuring the surface finish of a through hole is also less complicated than in a groove. 
     The smooth hole or bore design allows for easier installation of sealing elements. Since the bore diameter is close to the outer diameter of the sealing element, there is less chance of rolling or twisting the sealing element during assembly which could lead to premature failure of the seal. 
     Other embodiments are referred to in  FIG. 3 , where, sealing assembly  300  of the present invention is shown. Here, actuator pushrod  310  is shown having a dynamic sealing surface  320 . The actuator pushrod  310  runs through center body  360 , which separates the spring side  380  from the service side  390  of the spring brake actuator. 
       FIG. 3  also provides the sealing assembly  300  of the present invention whereby the sealing elements  340 ,  345  are shown. Here, retainer bearings  330  and  335  are shown having sealing elements  340  and  345  present between retainer bearings  330  and  335 . Sealing element separator  350  is present between sealing elements  340  and  345 . Sealing elements  340  and  345  are provided and shown as a quad-ring. 
     Also shown is smooth bore sealing surface  370  of the center body  360 . The bore or hole is filled by retainer bearings  330  and  335 , sealing elements  340  and  345 , and sealing element separator  350 . These elements allow for the dynamic center seal of the spring brake actuator to be provided. 
       FIG. 4  show a perspective view of a quad ring  400  that is used as sealing elements  340  and  345 . 
     Other embodiments are referred to in  FIG. 5 , where, sealing assembly  500  of the present invention is shown. Here, actuator pushrod  510  is shown having a dynamic sealing surface  520 . The actuator pushrod  510  runs through center body  560 , which separates the spring side  580  from the service side  590  of the spring brake actuator. 
       FIG. 5  also provides the sealing assembly  500  of the present invention whereby the sealing elements  540 ,  545  are shown. Here, retainer bearings  530  and  535  are shown having sealing elements  540  and  545  present between retainer bearings  530  and  535 . Sealing element separator  550  is present between sealing elements  540  and  545 . Sealing elements  540  and  545  are provided and shown as a square-ring. 
     Also shown in smooth bore sealing surface  570  of the center body  560 . The bore or hole is filled by retainer bearings  530  and  535 , sealing elements  540  and  545 , and sealing element separator  550 . These elements allow for the dynamic center seal of the spring brake actuator to be provided. 
       FIG. 6  show a perspective view of a quad ring  600  that is used as sealing elements  540  and  545 . 
     Other embodiments are referred to in  FIG. 7 , where, sealing assembly  700  of the present invention is shown. Here, actuator pushrod  710  is shown having a dynamic sealing surface  720 . The actuator pushrod  710  runs through center body  760 , which separates the spring side  780  from the service side  790  of the spring brake actuator. 
       FIG. 7  also provides the sealing assembly  700  of the present invention whereby the sealing elements  740 ,  745  and  748  are shown. Here, retainer bearings  730  and  735  are shown having sealing elements  740 ,  745  and  748  present between retainer bearings  730  and  735 . Sealing element separators  750  and  755  are present between sealing elements  740 ,  745  and  748 , respectively. Sealing elements  740 ,  745  and  748  are provided and shown as an O-ring, however, square-rings, quad-rings and another other such sealing elements known in the art may be used. 
     Also shown in smooth bore sealing surface  770  of the center body  760 . The bore or hole is filled by retainer bearings  730  and  735 , sealing elements  740 ,  745  and  748 , and sealing element separators  750  and  755 . These elements allow for the dynamic center seal of the spring brake actuator to be provided. 
     Other embodiments may be provided where additional sealing element separators (3 or more) and sealing elements (4 or more) may be provided. 
       FIG. 8  provides sealing assembly  800  of the present invention. Here, the actuator pushrod and dynamic sealing surface are not shown.  FIG. 8  shows bore  810  having an equal diameter throughout as shown via element A-A.  FIG. 8  shows center body  860 , which separates the spring side  880  from the service side  890  of the spring brake actuator. 
       FIG. 8  also provides the sealing assembly  800  of the present invention whereby the sealing elements  840 ,  845  are shown. Here, retainer bearings  830  and  835  are shown having sealing elements  840  and  845  present between retainer bearings  830  and  835 . Sealing element separator  850  is present between sealing elements  840  and  845 . Sealing elements  840  and  845  are provided and shown as O-Ring(s), however square-rings, quad-rings and another other such sealing elements known in the art may be used. 
     Also shown in smooth bore sealing surface  870  of the center body  860 . The bore or hole is filled by retainer bearings  830  and  835 , sealing elements  840  and  845 , and sealing element separator  850 . These elements allow for the dynamic center seal of the spring brake actuator to be provided. 
     The invention also calls for methods and manufacturing and assembly of such a dynamic sealing assembly. 
     While the invention has been specifically described in connection with certain specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation and that various changes and modifications in form and details may be made thereto, and the scope of the appended claims should be construed as broadly as the prior art will permit. 
     The description of the invention is merely exemplary in nature, and thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.