The present invention relates to lead screws generally and, more particularly, but not by way of limitation, to a novel, one degree of freedom diaphragm coupling for a lead screw.
In order to create linear motion from a rotary motor, a lead screw is often used. This lead screw is rotated and a nut translates motion from rotary to linear. The attachment of the lead screw can be done by several methods.
One method is the use of an integral threaded shaft. This method is suitable for relatively short travel lengths. For longer shafts, it often becomes impractical to employ this method and making the shaft from one piece often adds unnecessary cost. In addition, packaging and shipping problems are presented.
Another method is the use of a rigid coupling. This method may be used to simplify the shaft and allow for a longer threaded section. For long shafts, an end bearing support may be used. This system presents the problem that extremely close alignment of the motor and end bearing is required, since the system is rigid. Because of manufacturing tolerances, it is often difficult to maintain shaft alignment with the motor unless made with the utmost precision. These systems are prone to binding and misalignment as well as fatigue.
A further method is the use of a compliant coupling. This method often is used in order to alleviate misalignment problems. These couplings allow angular misalignment, but, because of their design, are not stiff axially and may not maintain the centerline of the motor and the threaded shafts. This requires the use of a second bearing support.
Some designs, such as a universal joint, are stiff axially and maintain a common shaft centerline, but are not designed for the high axial loads a threaded shaft can produce and often are mechanically complex.
Accordingly, it is a principal object of the present invention to provide a coupling for a lead screw that overcomes the above disadvantages.
It is a further object of the present invention to provide such a coupling that can withstand high axial loads.
It is another object of the present invention to provide such a coupling that allows for angular shaft misalignment.
It is an additional object of the present invention to provide such a coupling that is axially stiff in both directions.
Yet a further object of the present invention is to provide such a coupling that generally maintains a common shaft centerline.
Yet another object of the present invention is to provide such a coupling that can transmit torque.
Yet an additional object of the present invention is to provide such a coupling that is mechanically simple.
Other objects of the present invention, as well as particular features, elements, and advantages thereof, will be elucidated in, or be apparent from, the following description and the accompanying drawing figures.
The present invention achieves the above objects, among others, by providing, in a preferred embodiment, an apparatus, comprising: a diaphragm coupling member; said diaphragm coupling member having a generally ball shaped central portion; said ball shaped central portion having a first surface engaging a complementarily shaped portion of a cover plate; said ball shaped central portion having a second surface engaging a complementarily shaped portion of a drive plate; and said cover plate and said drive plate being co-engaged such as to remove any clearance between said ball shaped central portion and said complementarily shaped portion of said cover plate and said complementarily shaped portion of said drive plate.
Understanding of the present invention and the various aspects thereof will be facilitated by reference to the accompanying drawing figures, provided for purposes of illustration only and not intended to define the scope of the invention, on which:
Reference should now be made to the drawing figures, provided for purposes of illustration only, and on which the figure numerals in parentheses (when used) refer the reader to the figure in which the element(s) being described are more fully shown, although the element(s) may be shown on other figures also.
Diaphragm coupling member 110 has a first shoulder 130 formed thereon which engages a complementarily shaped surface on a cover plate 132 and a second shoulder 134 formed thereon which engages a complementarily shaped surface on a drive plate 136. As shown on
Diaphragm coupling member 110 is preferable formed of a soft plastic by injection molding. The stiffness of diaphragm coupling member 110 depends on geometry and flexure required. Cover plate 132 and 136 are formed of a harder material than diaphragm coupling member 110, such as a metallic material.
When the web portion is an elastomeric material, it is constructed of an elastomeric material in the Shore A range of about 60 to about 100. When the web portion is a metallic material, it's thickness is less that about one-half millimeter and is highly elastic, such as spring steel or stainless steel, and it's hardness is in the HRC range of about 30 to about 50. Some non-ferrous materials, such as beryllium copper, will also work, but that is often cost prohibitive. Soft materials, such as aluminum and certain copper alloys would not be suitable.
“Slight misalignment” refers to an angle of about two-and-one-half degrees per side or five degrees of total sweep. “Axial stiffness” refers to an axial displacement of up to about twenty-five microns under load.
In the embodiments of the present invention described above, it will be recognized that individual elements and/or features thereof are not necessarily limited to a particular embodiment but, where applicable, are interchangeable and can be used in any selected embodiment even though such may not be specifically shown.
Spatially orienting terms such as “above”, “below”, “upper”, “lower”, “inner”, “outer”, “inwardly”, “outwardly”, “vertical”, “horizontal”, and the like, when used herein, refer to the positions of the respective elements shown on the accompanying drawing figures and the present invention is not necessarily limited to such positions.
It will thus be seen that the objects set forth above, among those elucidated in, or made apparent from, the preceding description, are efficiently attained and, since certain changes may be made in the above construction and/or method without departing from the scope of the invention, it is intended that all matter contained in the above description or shown on the accompanying drawing figures shall be interpreted as illustrative only and not in a limiting sense.
It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/US2006/033660 | 8/29/2006 | WO | 00 | 2/27/2009 |