Patent Application
20090291793
The present invention is generally related to a pulley and more particularly is related to a pulley apparatus for retaining an object in a stationary position.
It is well known to at least partially offset the weight of a movable object that is to be raised and lowered within a range of movement. If precisely balanced, the object remains in place when positioned, rather than tending to fall because due to gravity, or rise because of an excessive offset force. An operator or the like need only exert the force needed to move the object from one position to another, and need not offset the weight of the object itself. To avoid the need for accommodating a counterbalancing deadweight, the weight of the object is advantageously offset with a spring. Familiar examples of spring-counterbalanced weights are window sashes, garage doors, movable-panel blackboards, and supporting carriages for vertically movable equipment.
Spring force varies as a function of deflection of the spring; however, the weight of the movable object is fixed. In order to compensate for the additional force exerted by a counterbalancing spring when the spring is deflected (e.g., as a window sash is being lowered), it is known to provide a compensating pulley that converts a linearly varying spring force to a constant force. A flexible cord, cable, wire, rope or the like connects the spring and the supported weight via a conical or spiral pulley. The spiral pulley defines a radius for the cord that varies linearly with displacement of the ends of the spring, and thus defines a linearly varying moment arm to compensate for the variation in spring force over the range of movement of the object. This idea is workable for various types of springs in extension or retraction, and for various weights and other constant force exerting conditions.
Some devices in the prior art use a helical coil spring for producing force varying linearly with spring deflection, namely compression and extension of the spring along the central axis of the helix. This form of spring obviously requires a housing at least as long as the full extension length of the spring. A more compact form of spring is possible, wherein the spring is wound spirally in a plane. The inner end of the spring can be fixed, and the outer end can be rotated around the fixed inner end or pulled outwardly along a tangent. Similarly, the outer end can be fixed and the inner end arranged to rotate a shaft. The movable end of the spring is connected to rotate a conical pulley relative to the fixed end. This spiral form of spring, known as a power spring or clock spring, is relatively compact.
It is axiomatic that the force exerted by a resilient structure defining a spring in extension or compression varies linearly with the relative displacement of the ends of the spring. The same is true of torsional (twisting) displacement of the ends of a resilient object. Wherein the pulley carrying the cord is conical, a linear relationship or “spring constant” is assumed for the spring as a whole, with the spring force compensated in an amount directly proportional to displacement. However, in a power spring, the force exerted by the spring as a whole is not linear, i.e., not directly proportional to displacement. The effectiveness of known power spring balances is thus limited. Various modifications of power spring apparatus have been suggested to improve operation, but persons skilled in the art have continued to assume that a power spring should be compensated in the same manner as an extension spring.
Thus, a heretofore unaddressed need exists in the industry to address the aforementioned deficiencies and inadequacies.
Embodiments of the present invention provide a pulley apparatus for retaining an object in a stationary position system. Briefly described, in architecture, one embodiment of the system, among others, can be implemented as follows. The pulley apparatus includes a conical pulley rotateable about an axis. An exterior surface of the conical pulley has a convex shape. A pulley cable is in communication with the exterior surface. An angular biasing mechanism applies a torquing force to the conical pulley.
The present invention can also be viewed as providing a method for retaining an object in a stationary position. In this regard, one embodiment of such a method, among others, can be broadly summarized by the following steps: raising an object connected to a pulley cable, the pulley cable attached to a conical pulley; rotating the conical pulley about an axis, the conical pulley having a convex exterior surface; and retaining the object at a raised position with an angular biasing mechanism.
Other systems, methods, features, and advantages of the present invention will be or become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the present invention, and be protected by the accompanying claims.
Many aspects of the invention can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present invention. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
The pulley apparatus 10 also includes an exterior surface 24 with a convex shape. The convex shape may be defined as an outward curve seen in the profile of the pulley structure 12 with respect to a central portion 21 of the pulley structure 12. In
The exterior surface 24 may be integral with the pulley structure 12. For example, the pulley structure 12 and exterior surface 24 may be machined, forged or molded out of a single material such that there is no boundary between the pulley structure 12 and the exterior surface 24. The exterior surface 24 and the pulley structure 12 may be made of different materials and bonded together. In this exemplary embodiment, there may be a boundary between the exterior surface 24 and the pulley structure, 12 but the two materials may be integral and function as one structure. Additionally, the exterior surface 24 may be detachably affixed to the pulley structure 12. The means of detachably affixing the exterior surface 24 to the pulley structure 12 may be any technique or design known to those having ordinary skill in the art capable of providing successful use of the pulley apparatus 10. Detachably affixing the exterior surface 24 may allow a single pulley structure 12 to be adapted with a plurality of exterior surfaces 24 that may have different shapes. Furthermore, this may allow a means for convenient replacement of the exterior surface 24 if there is a significant amount of wear and tear to the pulley apparatus 10.
The pulley apparatus 10 further includes a pulley cable 28 or a plurality of pulley cables 28. The pulley cable 28 is in communication with the exterior surface 24 of the pulley structure 12. A first end 30 of the pulley cable 28 may be fixed to the exterior surface 24 of the pulley apparatus 10. The first end 30 of the pulley cable 28 may be fixed directly to the pulley structure 12 (not shown). During use of the pulley apparatus 10, the pulley cable 28 may be wound on the exterior surface 24 of the pulley structure 12. The pulley cable 28 may be any material capable of providing successful use of the pulley apparatus 10, including but not limited to rope, chain, metallic wire and synthetic cable. The specific materials suitable to make a successful pulley cable 28 may be known to those having ordinary skill in the art.
An angular biasing mechanism 38 known to those having ordinary skill in the art is a spring coil.
In accordance with the first exemplary embodiment, the pulley structure 12 may be disposed within a pulley casing 40. The pulley casing 40 may be a fixed point that provides a housing structure for the pulley structure 12. The recoiling shaft 36 may be attached to the pulley casing 40 or to another fixed point. As shown in
With reference to
During use of the pulley apparatus 10, the object 34 may be raised or lowered. To accomplish this, a user may exert a slight force on the object 34 in the desired direction to initiate movement of the object 34. For example, if the user desires to raise the object 34, he or she will only have to exert a slight upward force. Only a small force is needed because the user will only be lifting a small percentage of the mass of the object 34. The pulley apparatus 10 will lift the remaining mass of the object 34 by transferring the rotational force of the angular biasing mechanism 38 to the pulley structure 12, thereby changing the rotational force into a linear force within the pulley cable 28. If the recoiling shaft 36 is situated to partially support the object 34, the pulley apparatus 10 may also cause the recoiling shaft 36 to extend. The object 34 and the recoiling shaft 36 may be situated to move in correspondence to a rotation of the pulley structure 12.
When the object 34 is at the desired height, the user may let go of the object 34, leaving it in a stationary position. The object 34 will remain motionless because the force of gravity acting on the object 34 may be approximately equal to the tension of the pulley cable 28. The rotational force of the angular biasing mechanism 38 may remain continuously transferred to the pulley cable 28, securing the object 34 in the stationary position for a period of time. The rotational force needed may vary in relation to the mass of the object 34 and the shape and dimensions of the pulley structure 12. In general, the movement of the recoiling shaft 36 and the object 34 may be substantially in the vertical direction, due to the forces of gravity. However, one having ordinary skill in the art will recognize that movement of the recoiling shaft 36 and the object 34 may occur in a direction other than a substantially vertical direction, subject to the chosen design and implementation.
As is shown by block 102, an object 34 connected to a pulley cable 28 is raised, where the pulley cable 28 is attached to a conical pulley 12. The conical pulley 12 rotates about an axis 14, where the conical pulley 12 has a convex exterior surface 24 (block 104). The object 34 is retained at a raised position with an angular biasing mechanism 38 (block 106).
It should be emphasized that the above-described embodiments of the present invention, particularly, any “preferred” embodiments, are merely possible examples of implementations, merely set forth for a clear understanding of the principles of the invention. Many variations and modifications may be made to the above-described embodiments of the invention without departing substantially from the spirit and principles of the invention. All such modifications and variations are intended to be included herein within the scope of this disclosure and the present invention and protected by the following claims.
