Abstract:
A universal joint assembly has a housing and a universal joint in a chamber within the housing. A diaphragm seal in the housing forms a wall of the chamber. The chamber is substantially sealed to exclude entry of foreign elements. The diaphragm seal is flexible to allow for expansion and contraction of the chamber due to changes in temperature to prevent any substantial increase or decrease in the pressure within the chamber.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to universal joints and more particularly to a sealed universal joint. 
     BACKGROUND OF THE INVENTION 
     The internal temperature of a constant velocity universal joint changes due to the moving internal components and the influence of the external environment. These temperature fluctuations tend to cause changes in the internal pressure of the joint. However, it is important to keep the internal pressure more or less equal to the outside atmospheric pressure because if the internal pressure changes, the boot, which closes the sealed chamber in which the joint operates, may deform and cause a failure of the seal. In the past, internal pressure equalization has been accomplished by adding one or more vent holes to the outer race or grease cap, or placing a groove in the mating interface between the inner race stub shaft and the boot. The drawback of these attempts at pressure equalization is that the joint can ingest contaminates through the vent holes, often resulting in joint failure. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, a diaphragm seal is added to the chamber in which the joint operates. The diaphragm seal is capable of expanding and contracting to minimize pressure fluctuation and maintain the internal pressure more or less equal to the external pressure. As the temperature within the joint increases, the diaphragm seal will expand, allowing an increase in the volume of the chamber without significantly changing the internal pressure. Likewise, when the temperature within the joint decreases, the diaphragm seal will contract, allowing a decrease in the internal volume without material change in the internal pressure. Therefore, as the internal temperature increases and decreases, the diaphragm seal will “breathe” to maintain an equalized pressure with the atmosphere. 
     Further, in accordance with the invention, the diaphragm seal separates the internal chamber from a vent space, with a vent hole or holes from the vent space. As a result, the diaphragm seal can expand and contract more freely. 
     The diaphragm is preferably made of a flexible or stretchable elastomeric material. In one embodiment of the invention, the diaphragm seal includes a flexible sheet having a plurality of concentric circular portions of progressively increasing radius measured from a centerpoint of the sheet, with alternate circular portions having a generally U-shaped cross-section opening toward the chamber and the remaining circular portions having a generally U-shaped cross-section opening away from the chamber. In another embodiment of the invention, the diaphragm is a flat sheet of flexible, stretchable, elastomeric material. 
     One object of this invention is to provide a universal joint having the foregoing features and capabilities. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiments 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 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a longitudinal sectional view of a sealed constant velocity universal joint having a diaphragm seal and constructed in accordance with the invention; 
         FIG. 2  is a view of the diaphragm seal taken on the line  2 — 2  in  FIG. 1 ; 
         FIG. 3  is a perspective view of the diaphragm seal with parts broken away; 
         FIG. 4  is a sectional view of a sealed universal joint of modified construction, also constructed in accordance with the invention; and 
         FIG. 5  is a perspective view of the diaphragm seal in  FIG. 4 , with parts broken away; 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application or uses. 
     Referring now more particularly to the drawings and especially to  FIGS. 1–3 , a universal joint assembly  10  is shown comprising a universal joint  12  operable in a chamber  14  provided in a housing  16 . 
     The universal joint  12  comprises an inner spherical race  18 , an outer spherical race  20 , a spherical cage  22  between the inner and outer races  18  and  20 , and balls  24  in slots  26  of the cage engaged in axially extending grooves  28  in the inner race  18  and axially extending grooves  30  in the outer race  20 . 
     The housing  16  includes a bell-shaped hollow block  32  which has the outer race  20  formed as a part thereof. The block  32  has a tubular extension  34  which is splined or otherwise secured to a shaft  36 . A shaft  38  is splined or otherwise secured to the inner race  18 . 
     As is typical in constant velocity universal joints, the speed of rotation of the shafts  36  and  38  is always the same no matter what the relative angular adjustment of the two shafts may be. 
     The chamber  14  is sealed at one side of the universal joint  12  by a boot  40  and an annular boot can  42 . The boot  40  is generally tubular and at one end  44  encircles and seals against the shaft  38 . The other end of the boot is turned radially outwardly and folded back and has a sealed connection to one end of the boot can  42 . The boot can  42  at its opposite end encircles and is sealed to the outer surface of the bell-shaped block  32 . 
     The chamber  14  at the opposite side of the universal joint  12  is sealed by a diaphragm seal  46 . The diaphragm seal  46  actually forms a wall of the chamber  14 . The diaphragm seal  46  has a circular supporting ring  47  secured and sealed by any means such as a suitable adhesive to a counter-bore  48  in the bell-shaped block  32 . 
     The diaphragm seal  46  includes a flexible sheet  50  which is surrounded by and marginally secured to the supporting ring  47 . The sheet  50  has a wavy or sinuous configuration with a plurality of concentric annular, circular portions  52  of progressively increasing radius measured from a centerpoint  53  of the sheet. Alternate circular portions  54  have a generally U-shaped cross-section opening toward the chamber  14  and the remaining circular portions  56  have a generally U-shaped cross-section opening away from the chamber. 
     The entire diaphragm seal  46  including the flexible sheet  50  and the supporting ring  47  is of integral one-piece construction, and preferably made of natural or synthetic rubber or other suitable, flexible, stretchable elastomeric material which is imperforate to completely seal the chamber  14  from the outside environment. 
     The diaphragm seal  46  separates the chamber  14  from a vent space  58 . One or more vent holes  60  in the block  32  provide communication between the vent space and the outside environment. 
     Outwardly of the diaphragm seal  46 , the vent space  58  is closed by a Welch plug  62  or the like. 
     The chamber  14  is completely sealed off from the outside environment. Pressure changes in the chamber  14  due to changes in temperature are at least significantly reduced if not entirely eliminated by the diaphragm seal  46  which is capable of expanding to prevent an increase in pressure or contracting to prevent a decrease in pressure so that the pressure within the chamber remains virtually the same without the need for venting the chamber. The vent space  58  and vent hole  60  enable the diaphragm seal to flex inwardly or outwardly more freely. 
       FIGS. 4 and 5  show a universal joint system  64  of modified construction having a universal joint  66  operable in a chamber  68  provided in a housing  70 . 
     The universal joint  66  comprises an inner spherical race  72 , an outer spherical race  74 , and a spherical cage  76  between the inner and outer races  72  and  74 , and balls  78  in slots  80  of the cage engaged in axially extending grooves  82  in the inner race  72  and axially extending grooves  84  in the outer race  74 . 
     The housing  70  includes a bell-shaped hollow block  86  to which the outer race  74  is secured by fasteners  88 . The block  86  has a tubular extension  90  which is splined or otherwise secured to a shaft  92 . A shaft  94  is splined or otherwise secured to the inner race  72 . 
     The chamber  68  is sealed at one side of the universal joint  66  by a boot  96  and a boot can  98 . The boot  96  is generally tubular and at one end  100  encircles and seals against the shaft  94 . The other end of the boot  96  is turned radially outwardly and folded back and has a sealed connection to one end of the boot can  98 . The boot can  98  at its opposite end encircles and is sealed to the outer surface of the bell-shaped block  86 . 
     The chamber  68  at the opposite side of the universal joint  66  is sealed by a diaphragm seal  102 . The diaphragm seal  102  actually forms a wall of the chamber  68 . The diaphragm seal  102  has a circular supporting ring  104  secured and sealed by any means such as a suitable adhesive to one end of an annular grease cap  106 . The other end of the grease cap  106  is clamped and sealed between the block  86  and the outer race  74 . 
     The diaphragm seal  102  includes a flexible sheet  108  which is substantially flat and is surrounded by and marginally connected to the supporting ring  104 . The entire diaphragm seal  102  including the supporting ring  104  and the flexible sheet  108  is of integral one-piece construction, and preferably made of natural or synthetic rubber or other suitable, flexible, stretchable elastomeric material which is imperforate to completely seal the chamber  68  from the outside environment. 
     As in the first embodiment, the diaphragm seal  102  separates the chamber  68  from a vent space  110 . One or more vent holes  112  in the block  86  provide communication between the vent space and the outside environment. 
     Outwardly of the diaphragm seal  102 , the vent space  110  is closed by a Welch plug  112  or the like. 
     As in the embodiment of  FIGS. 1–3 , the chamber  68  is completely sealed off from the outside environment with the advantage, due to the diaphragm seal  102 , of enabling the chamber to expand and contract and thereby minimize if not virtually eliminate pressure changes within the chamber. Also, as in the first embodiment, the vent space  110  and vent holes  112  enable the diaphragm seal to flex inwardly and outwardly more freely. 
     It should be understood that, if desired, in  FIG. 1  the diaphragm seal  46  could be replaced by the diaphragm seal  102 , and in  FIG. 4  the diaphragm seal  102  could be replaced by the diaphragm seal  46 . 
     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.