Joints and connections – Interfitted members – Radially interposed shim or bushing
Reexamination Certificate
1999-09-30
2003-07-29
Browne, Lynne H. (Department: 3679)
Joints and connections
Interfitted members
Radially interposed shim or bushing
C403S016000, C403S004000, C403S374300, C403S374400, C403S374100, C403S370000
Reexamination Certificate
active
06599052
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the field of power transmission systems, such as gear reducer systems employing hubs and shafts coupled to one another for input or output of torque. More particularly, the invention relates to a technique facilitating assembly and disassembly of shafts mounted in support hubs, such as an output hub of a gear reducer or similar equipment.
2. Description of the Related Art
A wide range of applications exist for rotary drive systems, throughout all aspects of industry, material handling, agriculture, and transportation, to mention just a few fields. In general, many such systems are based upon the generation of rotary motion which is transmitted to various machine elements through couplings, gear drives, transmissions, and so forth. In systems where a prime mover, such as an electric motor or an internal combustion engine, rotates at a speed other than that desired at the actual application, gear reducers or variable speed drives are typically employed to reduce or increase the speed and torque to the desired range.
The input and output elements of power transmission components must interface with one another to transmit mechanical power reliably, and to withstand loading likely to be encountered in use. Input and output in such systems is often provided by rotating shafts which may be coupled to one another via couplings, sheaves, belts, or similar techniques. In specific applications, however, it is often useful to interface a shaft within a hub designed to receive the shaft, and to transmit power either from the shaft to the hub or vice versa. By way of example, certain gear reducers are designed with an input shaft and an output hub internally coupled to one another via intermeshing gears and pinions. The machine is designed to be secured firmly to an output shaft which is inserted in the hub. A range of coupling and support configurations have been designed and are presently in use for insuring reliable power transmission in such arrangements, while offering resistance to additional loading provided by the coupling system itself.
In one known mounting and coupling arrangement for rotational power transmission systems, a tapered bushing inserted between a shaft and a hub serves to lock the shaft and hub with respect to one another when the system is fully assembled. The tapered bushing may interface directly with corresponding tapered portions of the hub or the shaft, and is generally wedged axially into tight engagement therebetween by axial displacement of the hub, the shaft, the bushing, or more than one of these elements. For machines designed to be hung onto output or input shafts, such as shaft-mounted gear reducers and torque arms, a pair of tapered bushings may be employed at either end of the hub, or at one end and an intermediate position, to provide adequate support for the hub on the shaft. Single tapered bushing arrangements have also been developed for this purpose.
While mounting and coupling arrangements of the type described above provide excellent power transmission capabilities and good mechanical support, they are not without drawbacks. For example, in hub-mounted gear reducers systems, tapered bushings may be pressed between the hub and the shaft during assembly, or the shaft may be directly interfaced with a tapered portion of the hub at one end. Flanged arrangements with threaded fasteners are then typically employed for forcing tight engagement of the tapered surfaces with one another. For subsequent servicing, however, the tight engagement of the tapered surfaces, and the tight wedged engagement of the tapered bushing between the shaft and hub make disassembly extremely time consuming and difficult. In practice, various hand tools, hoists, pullers, and the like may be employed in an attempt to separate the machine elements from one another, sometimes resulting in damage or destruction of one or more of the elements, leading to additional down time and cost.
There is a need, therefore, for an improved technique for assembling and disassembling mechanical components such as a hub and shaft. There is, at present, a particular need for a simple and straightforward system which can be retrofitted into existing power transmission systems, or installed in new systems to facilitate both assembly and disassembly. Such a technique would advantageously build from certain existing product configurations, reducing the overall system redesign, particularly in retrofitted systems.
SUMMARY OF THE INVENTION
The invention provides a novel technique for assembling hubs and shafts in mechanical power transmission systems designed to respond to these needs. The technique employs a tapered bushing approach to the mechanical support of the hub and shaft with respect to one another. A tapered bushing may be positioned between the hub and shaft at least one end of the system. A similar tapered bushing may be provided at the opposite end, or a tapered region of the shaft may be directly interfaced with a tapered portion of the bushing. The system is drawn into tight engagement by a fastener secured through a retaining or keeper plate which interfaces with the tapered bushing. The keeper plate and fastener arrangement form a low-profile structure which may facilitate reduction of overhung loads in the power transmission arrangement.
The technique facilitates uncoupling and removal of the shaft and hub in a straightforward manner. In a preferred arrangement, the retaining structure may interface with fasteners which urge the shaft and hub out of engagement with one another following removal of the securement fastener. The retaining plate structure may be reversible, such that it serves to maintain a retaining fastener in tension during normal operation, while supporting removal fasteners in compression during removal of the shaft and hub from one another for servicing. The system thus permits the shaft and hub to be solidly supported via taper locking arrangements during use, and removed from one another in a simple and controlled manner when desired.
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Browne Lynne H.
Garcia Ernesto
Gerasimow Alexander M.
Reliance Electric Technologies LLC
Walburn William R.
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