Abstract:
A hub is mounted or dismounted by the use of hydraulic pressure with the hub being the only movable member. Either of two seals of different diameters are used in conjunction with a third seal of an intermediate diameter so as to establish a differential annular area between the two seals in use. Depending upon which pair of seals is used, hydraulic pressure tends to either force the hub onto or off of the shaft.

Description:
BACKGROUND OF THE INVENTION 
     The present invention is directed to a shaft coupling, with or without a key, which may be mounted or removed through the use of hydraulic pressure. 
     In the rotary machine art, it is common practice to move the hub of a coupling, impeller or the like onto a shaft over which the hub has been preliminarily applied or to displace a hub from such a mounted position. Such couplings use a number of parts which can be combined in different arrangements for mounting and dismounting the hub. 
     SUMMARY OF THE INVENTION 
     According to the present invention, a hub is moved into or out of a force-fit on a shaft by hydraulic pressure. Either of two annular seals of different diameters are used to establish a seal between the hub and a lock nut. A third annular seal of an intermediate diameter is used to establish a seal between the hub and the shaft and together with either one of the two annular seals between the hub and the lock nut defines an annular chamber for receiving pressurized hydraulic fluid. A differential area is established on the hub which, depending upon which of the two seals is used, tends to move the hub onto or off the shaft responsive to hydraulic pressure acting on the differential area. 
     It is an object of this invention to provide a method and apparatus for moving the hub of a coupling, wheel, propeller, impeller or the like into and out of a force-fit position on a shaft to which the hub may be keyed. 
     It is a further object of this invention to provide a simplified mounting and removal of a hub for a shaft of a rotary machine. 
     It is an additional object of this invention to provide a mechanism for mounting and removing a hub wherein the hub is the only movable member. These objects, and others as will become apparent hereinafter, are accomplished by the present invention. 
     Basically, either of two seals of different diameters, depending upon the step to be taken, is placed between the hub to be moved and the lock nut which is threaded to the shaft and thereby integral therewith. Each of these seals defines a differential area on the hub relative to a seal of an intermediate diameter located between the hub and the shaft. Thus, depending upon which of the two seals is in place, hydraulic pressure supplied to the cavity formed between the shaft and the hub will act on the hub to tend to move the hub onto or off of the shaft. If desired, a key may be used between the hub and the shaft. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a fuller understanding of the present invention, reference should now be made to the following detailed description thereof taken in conjunction with the accompanying drawings wherein: 
     FIG. 1 is an exploded sectional view of a coupling; 
     FIG. 2 is a partial sectional view showing the assembly arrangement of the coupling; 
     FIG. 3 is a partial sectional view showing the disassembly arrangement of the coupling; and 
     FIG. 4 is a partial sectional view of a modified coupling in the assembly arrangement. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As best shown in FIG. 1, the coupling 100 is made up of shaft 10, key 20, seal 30, hub 40, seals 60 and 70 and lock nut 80. Shaft 10 has a first tapered portion 12 with a groove 13 therein for receiving seal 30, a step portion 14, a second tapered portion 16 having a keyway 17 therein for receiving key 20, and a threaded portion 18. Hub 40 is bored complementarily to shaft 10 and has a first tapered bore section 42, a hub step 44 and a second tapered bore section 46 having an annular groove 45 and a keyway 47 for receiving key 20. While hub 40 can be the hub of a wheel, impeller or the like, it is illustrated as a coupling having a flange 48 which is adapted to be secured to a similar coupling affixed to a second shaft to thereby establish a string. An annular recess 50 is formed in one end of hub 40 and has a groove 51 in inner annular surface 52 for receiving seal 60. Tapped hole 54 and drilled passageway 56 form a fluid path through the wall of hub 40 terminating in annular groove 45 and bore 46. Lock nut 80 has a threaded bore portion 82 for sealingly engaging threaded portion 18 of shaft 10 and has an annular projection 84 which is adapted to be received in complementary annular recess 50 of hub 40. A groove 85 for receiving seal 70 is formed on outer surface 86 of projection 84. If desired a second annular projection can be formed on lock nut 80 to limit the axial movement of key 20. 
     The assembled coupling 100 is illustrated in the assembly arrangement in FIG. 2 and in the disassembly arrangement in FIG. 3. The only structural differences in these two Figures is the use of seal 70 in the FIG. 2 arrangement and the use of seal 60 in the FIG. 3 arrangement. Because hub 40 is the only moving part, fluid pressure supplied to the annular cavity 90 formed between shaft 10, hub 40 and lock nut 80 acts on the differential area defined by the annular area between seal 30 and seal 70 for the assembly arrangement of FIG. 2 and the annular area between seal 30 and seal 60 for the disassembly arrangement of FIG. 3 to tend to move hub 40. 
     Referring now to FIG. 2, hub 40 is placed over shaft 10 with key 20 in place in keyway 17 and keyway 47 aligned therewith to prevent relative rotational movement of hub 40 and shaft 10 in the event that design torque is exceeded. Alternatively, key 20 can be inserted after hub 40 is placed over shaft 10. Hub 40 is slid onto shaft 10 so that seal 30 sealingly engages tapered bore 42. Seal 70 is placed in groove 85 and lock nut 80 is threaded onto threaded portion 18 of shaft 10 so that annular projection 84 enters into recess 50 and seal 70 sealingly engages surface 53 of annular recess 50. Threaded portion 18 of the shaft 10 and threaded bore portion 82 of lock nut 80 provide at least a nominal sealing structure. However since bore portion 82 does not go through lock nut 80, an oil collecting cavity 89 is formed between the shaft 10 and lock nut 80 to prevent the leakage of oil to atmosphere, and the loss of hydraulic pressure. Pump 92 is serially connected to cavity 90 via line 94, valve 96, fluid tight connection 98, passage 56 and annular groove 45. Fluid pressure, which is indicated by stippling, is supplied by pump 92 via groove 45 to cavity 90 and acts on a differential area defined on hub 40 by 
     
         π(D.sub.1.sup.2 -D.sub.2.sup.2)/4 
    
     where D 1  is the diameter of seal 70 and D 2  is the diameter of seal 30. The force acting on hub 40 to force-fit it on shaft 10 is Pπ(D 1   2  -D 2   2 )/4 where P is the fluid pressure. The fluid pressure acting radially on hub 40 tends to increase the inner diameter of all portions of the hub 40 exposed to the fluid pressure. Similarly, fluid pressure acting radially on shaft 10 tends to reduce the diameter of the portion of the shaft exposed to fluid pressure. The net result of the fluid pressure acting on the members causes hub 40 to move further onto shaft 10. Upon the removal of the fluid pressure, a force-fit will be established between tapered portion 12 and tapered bore 42 as well as between tapered portion 16 and tapered bore 46. Step portions 14 and 44 can remain separated as will end 58 of the hub and lock nut 80 as a function of the desired hub interference with the shaft after the hydraulic pressure is removed. The axial position of the hub relative to the shaft determines the final interference fit. This can be measured in a conventional manner or a reference can be provided as in the FIG. 4 configuration. Lock nut 80 would then be tightened until surfaces 59 and 88 engage so as to prevent movement of the hub 40. 
     Referring now to FIG. 3, lock nut 80 is removed from shaft 10 and seal 60 is placed in groove 51 of hub 40. Seal 70 is preferably removed from groove 85 but may be left in place since its sealing function is obviated by the presence of seal 60. Lock nut 80 is threaded onto threaded portion 18 of shaft 10 so that annular projection 84 enters into recess 50 and seal 60 sealingly engages surface 87 of annular projection 84. Surfaces 59 and 88 are spaced so that hub 40 can be moved by the fluid pressure and the movement measured and/or detected. As in the FIG. 2 arrangement, fluid pressure, indicated by stippling, is supplied by pump 92 via groove 45 to cavity 90 and acts on a differential area which is now defined on hub 40 by 
     
         π(D.sub.2.sup.2 -D.sub.3.sup.2)/4 
    
     where D 3  is the diameter of seal 60. The force acting on hub 40 to remove hub 40 from shaft 10 is Pπ(D 2   2  -D 3   2 )/4. As explained above, fluid pressure also acts radially to separate the members. If the members are initially in a fluid-tight interference fit, pressure supplied to annular groove 45 progressively spreads the hub 40 and shaft 10 until fluid communication is established with cavity 90. The net result is that fluid pressure acting on the differential area of hub 40 causes hub 40 to tend to move off of shaft 10. Disassembly movement is limited by the engaging of surface 59 of hub 40 with surface 88 of lock nut 80. In this position, however, there is no longer a force-fit between the hub 40 and shaft 10 so that hub 40 can be easily removed. 
     The coupling 100 may be modified by eliminating the key 20 and related structure. The resultant coupling 100&#39; is illustrated in FIG. 4 where all modified structure is indicated by a prime. Coupling 100&#39; is the same as coupling 100 except that key 20, keyway 47 and steps 14 and 44 have been eliminated. Additionally, tapered shaft portions 12 and 16 of shaft 10&#39; have been replaced with a single, steeper sloped shaft portion 12&#39; and tapered bore portions 42 and 46 of hub 40&#39; have been replaced with a single steeper sloped bore 42&#39; complementary to tapered portion 12&#39;. Annular flange 11 has been added to shaft 10&#39; to provide a reference point for determining the interference fit of hub 40&#39; on shaft 10&#39;. Except for the key and its function, coupling 100&#39; would be assembled and disassembled the same as coupling 100. Although preferred embodiments of the present invention have been illustrated and described, other changes will occur to those skilled in the art. For example, the bores may be made cylindrical rather than tapered. It is therefore intended that the scope of the present invention is to be limited only by the scope of the appended claims.