Shaft and rotatable machine element assembly

#The present invention relates to a shaft and rotatable machine element assembly and more particularly to a unique structural arrangement for a shaft and gear assembly wherein the hub of a gear is slidably mountable upon a rotatable shaft having a radially extending projection member, the hub being restrained from rotational movement on the shaft through a fastening arrangement cooperable between the hub and projection member.

#It has been long known in the machine design art to fasten a gear (or other rotatable machine element such as a disk or sheave); slidably mountable on a rotatable shaft by either passing a pin member through aligned apertures or lateral recesses in the hub of a gear and in the shaft on which the gear has been mounted or by threading a pin in the form of a set screw through an aperture in the shaft hub with the end of the pin or set screw engaging tightly against the peripheral wall of the shaft when the threaded set screw is rotated in a preselected direction. Both of these well known aforedescribed arrangements often require stress-inducing drilling in the gear hub or other complex steps to provide the aperture in the hub with load accommodating characteristics being limited by the relative geometry, location and manner of engagement between pin and hub. Further, the frictional engagement arrangement of the threaded pin or set screw end against the shaft surface has resulted in problems of rotational slippage. Moreover, in the arrangement where a pin extends through aligned apertures in the hub and shaft, accurate drilling and aligning steps have been required in manufacture and assembly, these steps being comparatively time-consuming and expensive.

#Recognizing these problems of past arrangements, the unique structural arrangement of the present invention provides a shaft and gear assembly which is straightforward and economical in both manufacture and assembly, requiring a comparative minimum of steps in both operations. Further, the novel structural arrangement of the present invention minimizes past problems of aperture alignment between hub and shaft without sacrificing the ability of the assembly to accommodate both bi-directional axial and torsional loads and, in fact, serve to optimize the distribution and accommodating capacity for axial and torsional loads. In addition, the structural assembly arrangement of the present invention integrates a novel spacer structure into the assembly, allowing for compact axial adjustment of a preselected number of interlocking spacers in accordance with usage demands. Further, the structural features of the present invention can be effectively and efficiently employed with various configurations and sizes of gear and shaft arrangements, allowing for quick and efficient interchange of the several parts of the structural assembly.

#Referring to the drawings which disclose one advantageous embodiment of the invention and a variation thereof:

#FIG. 1 is an exploded isometric view of a rotatable shaft with gear, pin and spacer mounted thereon in accordance with one advantageous embodiment of the present invention;

#FIG. 2 is an end elevational view of the spacer of FIG. 1 taken in a plane through line 2--2 of FIG. 1;

#As can be seen in FIG. 1 of the drawings, the inventive assembly 2 includes a rotatable shaft 3. Shaft 3 which can be a typical steel shaft or which can be made from some other suitable rigid material is provided with an aperture 4 extending radially therethrough to receive cylindrical pin 6 of greater length than the diameter of shaft 3 to provide a pair of shaft protruding pin sections which serve as projection members arranged to extend radially from the periphery of rotatable shaft 3. Advantageously, pin 6 is sized in diameter to be press fit through aperture 4 in shaft 3. It is to be understood that it also would be possible to have pin 6 slidably engage in aperture 4, the pin being restrained from axial movement by the nesting gear and interlocking spacer assembly described herein. Further, it is to be understood that the present invention is not to be considered as limited to the cylindrical pin configuration shown but that other radial projection member configurations also could be utilized.

#As can also be seen in FIG. 1, slidably mounted on shaft 3 on either side of the projection member in facing relation is a gear 7 and interlocking spacer 8. Referring particularly to FIGS. 6-8, gear 7, which can be formed from any one of a number of suitable tough, strong materials such as plastic or compacted powdered metals, is provided with a hub portion 9 joined to the gear ring by a web member. Hub 9 has a suitably sized aperture 11 therein to permit slidable mounting of gear 7 on shaft 3. Extending radially from either side of aperture 11 in hub 9 are laterally open-ended recesses 12 terminating within hub 9 in curved surfaces 15 and surrounded in part by spaced longitudinal protrusions or flanks 10 extending from the web face of gear 7. As can be seen in FIGS. 8 and 9 of the drawings, open-ended recesses 12 are contoured as at 15, dimensioned and sized in hub 9 to nest in curvilinear facing contact with only one corresponding pair of curved side faces of the radially protruding cylindrical pin sections of cylindrical pin 6 which extends through shaft 3 so that the longitudinal rotating axis of pin 6, when the curved side faces of the pin sections are so nested in contacting relation with the curved surfaces 15 of recesses 12, falls in a plane Y-Y extending normal to the rotational axis of hub 9 halfway between the extremities of the hub width. This engagement of the curved extremities 15 of recesses 12 of hub 9 with corresponding curved side faces of the cylindrical pin sections of pin 6 restrains rotational movement of gear 7 relative the shaft 3 with the contacting curved surfaces and location of contact substantially centrally within the hub width serving to optimize the distribution and accommodating capacity for axial and torsional loads.

#Referring to FIGS. 1-5 of the drawings, it can be seen that slidably mountable on shaft 3 on the other side of the projection member or pin 6 is spacer 8 with pin 6 sandwiched between opposed faces of spacer 8 and gear 7. Spacer 8, like gear 7, also can be molded from a suitable, tough strong material such as plastic or compacted powdered metal to include a pair of rib-like protrusions 13 radially extending from one face thereof from an aperture 14 through which shaft 3 passes for slidable mounting thereon. Protrusions 13 have radially extending open-ended curved recesses 16. These protrusions 13 with curved recesses 16 are contoured and sized so that protrusions 13 of spacer 8 nest and interlock with the open-ended recesses 12 in hub 9 of gear 7 with the open-ended recesses at the opposite faces of gear 7 and protrusions 13 nesting with opposite corresponding pairs of the curved side faces of the pin sections of pin 6 extending from the shaft 3 to maximize surface contact so that pin 6, spacer 8 and gear 7 are in interlocking engagement with maximized surface contact between spacer and gear and optimized load distribution.