Patent Application
20080240849
The present invention relates to a shaft collar, and similar mechanical components, that are secured snugly around a shaft in a slip-free manner, without marring the surface of the shaft.
Known shaft collars, and similar mechanical components, such as gears, pulleys, hex nuts, handles, and the like, usually include a cylindrical body with a centrally located bore; the bore fits over the outer diameter, or periphery, of an elongated cylindrical shaft. The shaft collar is secured to the shaft by tightening radially spaced set screws. The inner end or tip of each screw presses against the outer diameter of the shaft, and retains the collar in fixed position upon the shaft.
Such known shaft collars, however, have caused burrs or marring, of the shaft, so that the shaft can not be used indefinitely, and must be replaced, periodically, leading to increased maintenance costs, delays or failures in system operation. Additionally, known shaft collars have proven to be unreliable during high torque operations, for the tips of the set screws gouge the metal shaft, in a point-to-point manner and slip thereabout.
In response to the known problems of marring of shafts, and/or slippage of the shaft collar in high torque applications, diverse improved shaft collars have been proposed. The improved shaft collars rely upon relatively broad contact areas in the shaft collar to more efficiently distribute the forces applied by the set screws.
To illustrate, U.S. Pat. No. 3,463,520, Turro, discloses a combination collar-clamp and shaft coupling (20) which clamps around shaft (30) without creating a burr or disfigurement on the shaft. A split clamping ring (38) is retained in recess (36) in the body of the collar clamp, as shown in
U.S. Pat. No. 3,740,085, Evans, discloses a set collar (1) adapted to be mounted on a shaft. The collar includes a radially disposed set screw (3) which presses a plate-like insert (4) against the outer diameter of a shaft. More than one set screw may be employed, as shown in
Although the holding strength of the clamps disclosed by Turro and Evans represented an advance over prior shaft collars, and marring of the shaft may be reduced, the cost and inconvenience of properly locating a metallic spring insert within the body of the collar introduced additional cost and complexity into the manufacturing and assembly process.
Consequently, with the deficiencies of known shaft collars clearly in mind, the present invention pertains to an inexpensive, yet reliable, shaft collar, with increased gripping ability, that does not burr, mar, gouge, or otherwise harm or degrade, the surface of the shaft to which the collar is clamped. The increased gripping ability is sufficient to avoid relative motion between the collar and the shaft, even under high torque conditions.
Furthermore, applicant's shaft collar relies upon a slot, in the body of the collar, to receive a set screw. The radially oriented set screw is advanced inwardly to press against the lower wall of the slot; the wall flexes and presses an arcuate segment defined in the body of the coupling against the outer surface of the shaft. The set screw does not contact the shaft, and the force of the set screw is distributed over a broad contact area, which does not burr, mar, or gouge the shaft.
The slot may assume the form of a straight or elliptical slot, an arcuate slot, or a round hole. The lower, or inner, wall of the slot is spaced from the surface of the shaft by a narrow arcuate segment of material which may be metallic or molded plastic. The amount of flexure of each segment is controlled by the radially inward advance of each set screw.
The narrow arcuate segment of resilient material is bowed or flexed radially inwardly, within its elastic limit. The resilient material may be flexed several times, thus insuring a long operational life, and successful operation, over an extended period of time, for the shaft collar.
Additionally, applicant's shaft collar is simple and relatively inexpensive to manufacture and/or mold, contains a minimum number of components, is relatively light in weight, and can function satisfactorily over a wide range of operating speeds.
Other advantages realized by applicant's shaft collar, vis-à-vis known shaft collars, will become readily apparent to the skilled artisan when the appended drawings are construed in harmony with the ensuing specification. As noted previously, the principles that applicant has applied to the novel shaft collar, find ready application to gears, gear and hub units, pulleys, hexagonal nuts, handles, etc.
Set screw 18 is advanced, in the radial direction, through slot 16. The inner tip 20 of set screw 18 contacts the wall defining the base of slot 16, and exerts an inwardly, radially directed force thereupon. The base deflects and presses arcuate segment 22 against the outer diameter of shaft 14 to lock collar 10 in fixed position on the shaft. The collar remains in locked position, until set screw 18 is withdrawn from contact with the base of slot 16. Set screw 18, made of metal, does not contact shaft 14, and arcuate segment 22 is deflected, within its elastic limit, so that the collar may be used repeatedly, without loss of effective holding power.
Set screw 38 is advanced, in the radial direction, through slot 36. The inner tip 40 of set screw 38 contacts the wall defining the base of slot 36, and exerts an inwardly, radially directed force thereupon. The base deflects and presses arcuate segment 42 against the outer diameter of shaft 34 to lock collar 30 in fixed position on the shaft. Collar 30 remains in locked position, until set screw 38 is withdrawn from contact of the base of slot 36. Set screw 38, made of metal, does not contact shaft 34, and arcuate segment 42 is deflected, within its elastic limit, so that the collar may be used repeatedly, without loss of effective holding power.
Set screw 58 is advanced, in the radial direction, through aperture 56. The inner tip, or base, 60 of set screw 58 contacts the wall defining the base of aperture 56, and exerts an inwardly, radially force thereupon. The base deflects and presses arcuate segment 62 against the outer surface of shaft 54 to lock collar 50 in fixed position on the shaft. Collar 50 remains in locked position, until set screw 58 is withdrawn from contact with the base of the aperture.
Slot 118 extends along the longitudinal, or axial, extent of hub 112. Set screw 120 is advanced radially through slot 118 to press against the lower wall, or base, of slot 118 and thereby deflects segment 122 against the outer diameter of shaft 114. Radial undercut 124 intersects slot 118 to increase the flexibility of segment 122.
As shown in
Numerous revisions and modifications to the several embodiments of applicant's shaft collar may occur to the skilled artisan. The shape of the collar, as well as the shape of the aperture, such as elliptical, round, or arcuate, may be varied, and the axial extent of each aperture may also be modified, without departing from the scope of applicant's invention. The forming of the aperture in the shaft collars may be achieved by molding same, or by machining same, or some combination of both techniques. Accordingly, the appended claims should be broadly interpreted in a manner consistent with applicant's contribution to the useful arts and sciences, and should not be limited to their literal terms.
