Abstract:
A rotary fluid union comprises a rotor having a sealing surface and mounted into a rotary member, and a stator having a sealing face and mounted in a stationary housing, the rotor and stator being mechanically disconnected other than by the sealing faces thereof being abutted. The sealing faces are abutted to define a gapless sealing interface, normally disposed in a plane perpendicular to the axis of rotation, but inclined to the axis of rotation in situation where the rotary member deflects radially from coincidence with the axis of rotation, whereby the sealing interface plane is at an angle to the perpendicular plane.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     This invention relates to a fluid tight rotary mechanical fluid coupling between a pair of relatively rotatable seal members in which the fluid sealing occurs between rotating axial mating faces, and more particularly to an arrangement wherein a non-rotating floating seal member is mounted in a housing separate from a rotating seal member and the axial sealing faces are biased into sealed engagement. 
     Fluid coupling apparatus that incorporates a rotating fluid seal between the axial mateable sealing faces of a pair of relatively rotatable parts thereof is known. Typical of such apparatus is rotary union of the kind used for effecting the transfer of fluid from a stationary fluid source to a fluid conduit in the form of a rotating spindle, shaft, clutch hub or other such device into which fluid is to be fed. Illustrative is &#34;Rotating Union with Replaceable Sealing Assembly&#34; shown in U.S. Pat. No. 4,817,995, issued Apr. 4, 1989 to Deubler et al. wherein a rotor seal member and a stator seal member are assembled in concentric relation in a common housing for relative rotation and passing fluid. The stator and rotor are axially biased towards one another such that the axial seal faces thereof are in engagement and define a rotating seal interface in the housing that is perpendicular to the axis of rotation. The rotor seal member is journalled on a bearing for rotation relative to the housing and includes a threaded shaft which extends from the housing to be affixed to the rotating spindle for rotation therewith. 
     Fluid conducting rotating unions give satisfactory service when operated at low or moderate speeds, such as about 2,000 rpm, but when operated at relatively high speeds, such as between 4,000 to 6,000 rpm and higher, encounter difficulties, typified by bearing failure, rapid wear, overheating, etc. Likewise, these rotating fluid unions give satisfactory service when conducting fluids at low or moderate pressures, but are oftentimes incapable of holding high pressures, or encounter operating difficulties under high pressures. 
     While the reasons for failure either at high speed, or high pressure, or combinations of both, are not completely understood, it is generally believed important that the respective rotor, stator, and spindle axes be maintained concentric with the axis of rotation during operation. Vibration and wobble can be produced if the spindle end is not accurately machined, or is damaged, or if the mass of the fluid union is not coaxial with the axis of the spindle. 
     However, the end face of the threaded rotor shaft and end face of the spindle (or mounting shoulder of the device mounted to) are typically very small, particularly in relationship to the mass and overall geometrical size of the complete fluid union housing which must be cantilevered at the end of the spindle, which can set up a mechanical disadvantage. When installing the union, the spindle end portion must be cleaned of chips and inspected for burrs or dents, such as would prevent accurate engagement between the axial end faces of the spindle and rotor. 
     Notwithstanding these precautions, at spindle speeds in the 2,500 rpm range and higher, harmonic vibrations can be induced if the mounting surfaces are not perfectly abutted and maintained in a plane perpendicular to the axis of rotation of the spindle to which fluid is to be supplied. These induced vibrations cause bearing failures in the fluid union itself. More seriously, these vibrations can lead to bearing failures in the spindle, or in the item to which the fluid union is mounted. Ultimately this can lead to quality problems and failures in the output operation of the spindle assembly. 
     The failures, as listed above, are also believed to result in part from the fluid supply hose being supported to the fluid union. The fluid supply hose is typically mounted to a fluid inlet at one end of the housing inlet, whereby to communicate fluid to the stator. Unless supported, this supply hose will place a load on the bearing. 
     Also, it is believed that tension forces placed on the fluid union in order to support the hose, which forces are countered only by bearings in the fluid union, will produce the same failures. 
     As is now appreciated, more pressure on the rotating seal interface to maintain axial contact between the sealing faces correlates into more friction, higher torque and thus more wear. A floating seal would be desirable to compensate for possible axial misalignment and wear. 
     At present, no one-piece fluid coupling unit is believed capable of meeting the demands and loads to which the marketplace is exposing these fluid couplings. 
     In accordance with this invention, a rotary fluid coupling for effecting the transfer of fluid from a stationary fluid source to a rotary member, such as a spindle, comprises a stationary housing assembly having an interior chamber, a stator assembly including a plunger non-rotatably mounted in the chamber, and a rotor assembly including a sleeve anchored to the spindle for rotation therewith, the rotor and stator assemblies each including a sealing member having a seal face facing axially. The sealing members are mounted, respectively, in the plunger and sleeve such that the sealing faces are engaging. Cooperating flats on the plunger and in the housing prevent the plunger from rotating relative to the chamber but allow the plunger axis to shift or be slightly inclined to the axis of rotation as a result of misalignment of the axis of the spindle end under rotation. 
     A biasing arrangement in the chamber acts against the plunger to maintain the sealing faces of the two members in abutted engagement to form a gapless rotary sealing interface. The housing assembly comprises an L-shaped bracket having an opening, and a cup-shaped member projecting axially from the bracket and forming therewith the interior chamber and positions the opening adjacent to the rotor. The forward end of the plunger which mounts the seal member thereof is positioned in the opening and is configured so a not to rotate relative to the housing but to permit minor movements of the plunger axis transversely to the spindle axis and as well as axially rearward from the opening along the axis. 
     The two-piece design wherein the rotor assembly is mounted to the spindle but mechanically separate from the stator assembly, advantageously eliminates the need of costly bearings to support the rotor assembly. 
     Advantageously, because of its two-piece construction, the fluid coupling herein is smaller, lighter, uses fewer parts, and uses no bearings. 
     Advantageously, mounting the stator plunger such that the sealing end face thereof &#34;floats&#34; relative to the housing axis and axis of rotation allows the sealing interface to maintain sealed engagement under high rotational speeds without placing forces and movements on bearings. 
     The rotor assembly herein advantageously mounts to the spindle to allow for a more liberal tolerance to the mounting specifications required of the spindle manufacturer. 
     The rotor and stator assembly herein advantageously allows the sealing interface to compensate for the spindle axis shifting from coincidence with the rotation axis. 
     These and other advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a longitudinal side elevational section view of a fluid-tight rotary coupling assembly embodying the principles of the present invention. 
     FIG. 2 a section view taken along line II--II of FIG. 1. 
     FIG. 3 is an enlarged side view in section of a sealing interface of the rotary coupling assembly shown in FIG. 1. 
     FIG. 4 is an enlarged side view in section, similar to FIG. 3, showing misalignment of the sealing interface which could result from high speed rotation or a mass imbalance in the driving elements. 
     FIG. 5 is a view of the sealing interface taken along line V--V of FIG. 4. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now the drawings, FIGS. 1-5 show apparatus in the form of a fluid coupling arrangement, generally indicated by the reference numeral 10 for effecting transfer of fluid from a fluid source, generally indicated by the fluid hose 12, to a rotating fluid conveying conduit, shown in the form of a rotating spindle 14, and such stationary device 16 into which fluid is to be fed. Spindle 14 is generally cylindrical and has a partially threaded axial bore 17 extending axially inward from a forward axial end face 18 thereof. The spindle extends axially outwardly from stationary device 16 and is mounted for rotation about a primary axis 20, the axis of rotation and geometric axis of the spindle being substantially concentric when not rotating. 
     The fluid coupling arrangement 10 includes a housing assembly 22, a rotor assembly 24, and a stator assembly 26. Housing assembly 22 includes an L-shaped bracket 28 and a cylindrical cup member 30 connected to the bracket whereby to define a chamber 32. Bracket 28 includes a mounting base 34 and a vertical support wall 36 having a cylindrical opening 38 therethrough. Preferably, as shown, bracket 28 is rigidly mounted by base 34 to stationary device 16 and is adapted to position opening 38 of support wall 36 adjacent to the outwardly extended end portion of spindle 14. 
     Cup 30 includes a cylindrical body 31 having at opposite respective ends an annular, flange 40 and an end wall 42. The interior wall of the body 31 is annularly stepped to form a first and second cylindrical counterbore 44 and 46 axially inwardly from flange 40. A cylindrical mounting flange 48 is fastened to cup flange 40, such as by fasteners 50, and is affixed to support wall 36, such as by fasteners 52. End wall 42 is provided with a threaded bore 54, whereby to receive a fluid connector 56 to receive fluid hose 12 and form a fluid inlet to communicate fluid into the chamber 32. 
     Cylindrical mounting flange 48, shown best by reference to FIGS. 1 and 2, includes forward and rearward axial end faces 58 and 60, and a central cylindrical bore 62 extending therethrough, end face 58 being adapted to abut cup flange 40. Extending axially inwardly of end face 60 is a cylindrical counterbore 64, and an oval-shaped counterbore 66, the bore 62 and counterbores 64 and 66 being defined about an axis adapted to be aligned with the axis of rotation 20. Oval counterbore 66 includes a pair of parallel flat portions 66a to aid in positioning and maintaining the stator assembly relative to the rotor assembly, in a manner to be described hereinbelow. 
     The rotor assembly 24 comprises an axial sleeve 68 having a bore 70 extending coaxially between forward and rearward axial end faces 72 and 74, a medial annular shoulder 76 having an axial face 78 adapted to abut end face 18 of the spindle, and a counterbore 80 extending axially inwardly from forward end face 72. The rearward end portion of the sleeve is provided with external thread to enable the sleeve to be threadably anchored into the spindle bore 16 whereby to bring axial face 78 thereof into abutment with the axial end face 18 of the spindle. 
     Stator assembly 26 is non-rotatably mounted in the chamber 32 and includes an axial plunger 82, a coil spring 84, a seal washer 86, a seal ring 88, and an elastomeric seal 90. The plunger 82 is generally cylindrically-shaped and has a center axis 83 adapted to be coincident with the axis of rotation 20. Plunger 82 includes a forward end portion forming an oval-shaped collar 92 and defining a forward axial end face 94, a reduced diameter rearward end portion 96 defining a rearward axial end face 98, and a bore 100 extending between the end faces 94 and 98 thereof. Collar 92 includes a counterbore 102 that extends axially inwardly from forward end face 94, and is shaped to include a pair of cylindrical sectors 104 and pair of parallel flats 106 sized to permit snug receipt within oval counterbore 66. The flats 66a cooperate to engage flats 106 whereby to prevent rotation of the plunger relative to the collar. The flats 66a and 106 cooperate to allow the collar 92 to translate within the counterbore 66, both in a direction transverse to the axis of rotation, and in a direction generally along the axis of rotation 20 (i.e., axially rearward relative to the flange 48). 
     Spring 84 has a rearward end abutting the end wall 42 of cup 30 and a forward end engaging rearward end face 98 whereby to urge the plunger 82 axially towards flange 48 and maintain collar 92 within the oval counterbore 66. Although a coil spring is shown for biasing the plunger, the bias member could be other. The spring force is preferably selected to provide only the minimum bias force needed, regardless of fluid pressure, resulting in a freer turning. 
     Seal washer 86 is generally cylindrical, comprised of steel, aluminum or other durable wearing material, and is mounted within counterbores 44 and 64. Washer 86 includes a cylindrical bore 108 of a diameter slightly greater than oval collar 92 and mounts about the collar in a manner such that slight tilting motion of the collar outer periphery and axis thereof relative to the bore 108 is permitted. Such tilting results in the axis 83 (and the plunger 82) being inclined to the axis of rotation 20. 
     Seal ring 88 is generally cylindrical, and comprised of steel, aluminum or other durable wearing material. Ring 88 mounts within bore 44 of cup 30 and is in encircling relation about rearward end portion 96 of the plunger. 
     A hat-shaped seal member 110 and 111 is mounted, respectively, into the counterbore 80 of the rotor sleeve 68 and counterbore 102 of the stator plunger 82. Seal member 110 is provided with a central bore 112 that extends between forward and rearward end faces 114 and 116 and includes a cylindrical body portion 48 adapted to non-rotatably affix the seal member into the counterbore 80. Seal member 111 is provided with a central bore 113 that extends between forward and rearward end faces 115 and 117 and a cylindrical body portion 119 to non-rotatably affix the seal member into the counterbore 102. When mounted into the respective counterbores, forward end faces 114 and 115 face axially outwardly with each of the faces being generally disposed in a plane that is perpendicular to the axis of rotation 20. This plane defines a sealing interface generally indicated by the letter &#34;S&#34;. The axes of the bores 112 and 113 are coincident with the axis of rotation prior to rotation. The seal member 111 in the stator assembly 26 is adapted to be positioned in the opening 38 of vertical wall 36. 
     The sealing members 110 and 111 are comprised of a material which provides long wear. Preferably, one member is comprised of a material such as tungsten carbide and silicon carbide, and abutted against the other member comprised of carbon graphite. The seal faces 114 and 115 are micro-lapped to maintain substantially perfect mating of the seal faces (i.e., evacuate the space between the faces and form an axially gapless interface whereby to substantially effect a hydraulic suction). Such interface allows the stator and rotor assemblies to rotate smoothly and easily with minimum friction to assure long life and still not leak. 
     FIG. 3 shows the sealing interface, generally indicated by the letter &#34;S&#34;, when the rotor assembly is not rotating or rotating at low speeds. The sealing interface &#34;S&#34; is defined by the seal faces 114 and 115 being biased together and is normally perpendicular both to the axis of rotation 20, and to the geometric axis 83 of the plunger and to the axis 69 of the sleeve. 
     FIGS. 4 and 5 show that during rotation, slight imperfections in the mass distribution of the spindle, may cause the spindle to deflect and the spindle axis to deflect radially, or otherwise shift, from being coincident with the axis of rotation. If so, the sealing interface &#34;S&#34; defined by the seal faces 114 and 115 thereof can become inclined at an angle &#34;A&#34; to the axis of rotation 20. The seal faces remain in complete engagement during this rotation because the oval-shaped collar and counterbore 66, respectively, of the plunger and flange 48, and the seal washer 86 bore 108, are dimensioned such that the plunger can both fit into the opening 38, axially retract relative to the counterbore 66, and move slightly transversely (e.g., radially) from alignment the axis of rotation. That is, the plunger axis 83 can be tilt slightly at the angle &#34;A&#34; relative to axis of rotation. The seal face 115 of the stator assembly seal member 111 can &#34;float&#34; relative to the axis of rotation whereby to maintain planar contacting relation the seal face 114 of the rotor assembly seal member 110. 
     In the above-described bearingless fluid seal, the failures associated with the prior art are not believed capable of happening because of the following: (1) the mass of the union is separated from the rotating device and is held positive to some form of bracket which is fixed to a rigid component on the machine; therefore, the hose tension has no influence on the union; and (2) the mounting of the union to the rotating equipment only affects the small single adapter portion of the union; and, hence does not require a perfect mounting face to function without influencing the whole union. Further, the bearingless fluid union can run at higher speeds than units used with bearings thereby giving product manufacturers far more flexibility to reach the new technically advanced manufacturing limits. Also, great amounts of manufacturing downtime are saved due to the decreased failures. 
     While the above description constitutes the preferred embodiment of the invention, it will be appreciated that the invention is susceptible to modification, variation, and change without departing from the proper scope or fair meaning of the accompanying claims.