LIFTING DEVICE

Abstract: A lifting device comprises a rotatable pawl with arm held in a pawl sleeve. The pawl has an open position in which a rope may be freely adjusted in tightening or loosening direction, and a close position in which the rope is lockably engaged between the pawl and the pawl sleeve. The pawl has a pawl arm against which the locked rope may be directed to rotate the pawl into an open position. The lifting device also includes a pulley for mechanical advantage, and a base for mounting to a surface.

Description: LIFTING DEVICE The present invention claims the priority of U.S. Provisional Application No. 60/181,272, filed February 9, 2000. Field of the Invention: The present invention relates to a lifting device for holding and locking rope under tension. More particularly, the present invention relates to a lifting device having a self locking feature upon release of a first end of a line, so that a load on the second end of the line will not be freed, except by operation of the first end of the line when placed under tension. Background of the Invention: Cam cleats for releasably clamping and holding ropes are well known in the art, with prior art patents dating back over a century. For particular rope holding and adjusting applications, however, even the populous prior art has left various problems unresolved. Cam cleats are widely used on sailing vessels and the like, and generally comprise one or more spring loaded pawls which serve to releasably lock a line or rope in one direction, namely the direction of the load on the line. The free end of the line can be pulled manually through the cam jaws or pawls, and the line is locked when tension is released on the free end of the line. The line can be disengaged only by manually lifting the line out of engagement with the pawl. It is also generally known to provide a retaining member above the pawls to constrain the line after it has been released, which facilitates re-engagement of the line with the cam. Many examples of known cam cleats are described in the 1999 Harken Yacht Fittings catalog published by Harken, Inc., Pewaukee, WI. Cam cleats having a lever arm on one of the cams are also known. The free end of the line can be deflected against the lever arm to release the associated cam. Notwithstanding past development, however, there presently exists a need for a fail safe device for raising and lowering heavy objects. As an example, for storage in the ceiling space of a garage. The present invention solves these and other problems that remain otherwise heretofore unresolved. Objects of the Invention: It is an object of the invention to provide a lifting device having a mechanical advantage and a releasable cleat to enable fail safe raising and lowering of objects. Summary of the Invention: The present invention comprises a lifting device having a rotatable pawl. The pawl has a rope locking surface, and a pawl arm, and is rotatably mounted in a pawl sleeve. The sleeve has an endwall with a rope engaging surface. A rope is removably locked between the pawl locking surface and the pawl sleeve engaging surface when the pawl is in a closed position. Urging the rope against the pawl arm rotates the pawl into an open position, wherein the rope may be slidingly adjusted in either a tightening or loosening direction through the sleeve between the sleeve engaging surface and the pawl locking surface. The pawl rotates into a closed position under the force of a spring once the rope is no longer urging the pawl arm into an open position. Thus upon releasing the free end of the rope, the pawl closes with the rope thereby locked in place. The lifting device of the present invention further comprises a pulley in combination with the pawl and sleeve. The pulley provides for mechanical advantage, and comprises a sheave rotatable about a central hub, with bearings rotatably engaged between the sheave and hub. The hub is held between opposing side cheeks, with the side cheeks connected to the pawl sleeve. The rope passes from the cam cleat to engagement with the pulley sheave. Preferably, the pawl sleeve is substantially U-shaped, with the sleeve endwall comprising the closed end of the U-shape. The sleeve rope engaging surface comprises the interior arc of the closed U-shape end. The pawl is rotatably mounted between the opposing ends of the U-shaped sleeve. The above brief description sets forth rather broadly the more important features of the present disclosure so that the detailed description that follows may be better understood, and so that the present contributions to the art may be better appreciated. There are, of course, additional features of the disclosure that will be described hereinafter which will form the subject matter of the claims appended hereto. In this respect, before explaining a preferred embodiment of the disclosure in detail, it is to be understood that the disclosure is not limited in its application to the details of the construction and the arrangements set forth in the following description or illustrated in the drawings. The present invention is capable of other embodiments, of being practiced and carried out in various ways, as will be appreciated by those skilled in the art. In addition, it is to be understood that the phraseology and terminology employed herein are for description and not limitation. Brief Description of the Figures: Fig. 1 is a side view, partially in cross section, of an embodiment of the lifting device of the invention, with the pawl in the open position. Fig. 2 is an end view of the pawl and pawl sleeve of Fig. 1, viewed along the line 2-2 of Fig. 1. Fig. 3 is an end view, partially in cross section, of the embodiment of Figs. 1 and 2 viewed along the line 3-3. Fig. 4 is a side view, partially in cross section, of the same embodiment of the lifting device illustrated in Fig. 1, with the pawl in the closed position. Detailed Description: Turning now to the drawings, Fig. 1 is a side view of a preferred embodiment of the lifting device of the invention. The preferred lifting device generally comprises rotatable pawl 2 with rope locking surface 4 and arm 6. Pawl 2 is rotatable about a pawl hub 8. As used herein, "rotatable" is not intended to refer to only a condition of full 360° rotation, but also include partial rotation. Indeed, preferred pawl 2 is "rotatable" only along a partial circumference of pawl hub 8. A torsion spring 10 preferably operates between pawl 2 and hub 8 to urge pawl 2 into a closed position, as illustrated in Fig. 4 (pawl 2 is illustrated in Fig. 1 in an open position). Pawl 2 is mounted within pawl sleeve 12, having an endwall 14 with an inside rope engaging surface 16. Preferred rope engaging surface 16 has a plurality of locking ridges to increase gripping power. Pawl rope locking surface 4 faces sleeve rope engaging surface 16, with a rope 18 passing through a gap therebetween. As best seen in Fig. 2, pawl sleeve 12 is substantially U-shaped. Sleeve end wall 14 is represented by the closed end of the U-shape, with the interior arc of the closed U- shape end wall comprising sleeve rope engaging surface 16. Pawl 2 is rotatably mounted within the opposite, open end of the U-shape between opposing sleeve end members 19. It is noted that Fig. 2 is illustrated with pawl 2 rotated to an open position, with the gap between pawl locking surface 4 and sleeve engaging surface 16 enlarged so that rope 18 may pass freely. The preferred pawl 2 of the invention thus advantageously allows for locking of rope 18 in place with only a single moving member, providing for savings in manufacturing and assembly costs. Referring once again to Fig. 1, rope 18 passes from pawl sleeve 12 to pulley 20. In operation, pawl 2 and sleeve 12 are "upstream" of pulley 20, with rope 18 having a "free end" closer to pawl 2, and an opposite end attached to a load nearer to pulley 20. Pulley 20 provides significant mechanical advantage to the lifting device of the invention. Preferred pulley 20 comprises sheave 22 rotatable about central hub 24, with a plurality of ball bearings 26 rotatably engaged between hub 24 and sheave 22. As best seen in the end view of Fig. 3, pulley 20 further comprises opposing side cheeks 28, which are connected to pawl sleeve 12. Most preferably, , pawl sleeve 12 and side cheeks 28 are integral with one another. (It is noted that rope 18 has been omitted from the view of Fig. 3.) As used herein "integral" is intended to refer to a condition of being a single, unitary construction, as opposed to separate parts connected by connectors or the like. As an example, should side cheeks 28 and pawl sleeve 12 be comprised of metal, they may be made integral by welding, or by being molded as a single part. Likewise if the respective elements should be comprised of a moldable polymer such as a thermoplastic, they may be made integral with one another if, for example, they are formed together in a single mold. As illustrated in Fig. 4, when pawl 2 is rotated into a closed position, locking surface 4 moves towards engaging surface 16 thereby decreasing the size of the gap therebetween. Rope 18 is thus firmly gripped and locked in place between the respective surfaces. This will occur, for instance, as a load pulls downward on rope 18 in the direction of the "LOAD" arrow of Fig. 4. To urge pawl 6 into an "open" position, rope 18 is engaged against pawl arm 6, as has been illustrated in Fig. 1, with the "RELEASING FORCE" arrow indicating the direction of the required force. As rope 18 engages pawl arm 6 in this direction, pawl 2 is disengaged from rope 18 with pawl locking surface 4 moving away from sleeve engaging surface 16. Once in this open position, rope 18 may be adjusted in either a downward or upward direction (i.e. tightening or loosening as indicated by the arrow of Fig. 1). This may be accomplished by pulling rope 18 in the direction of RELEASING FORCE, and then tightening or loosening while orienting rope 18 in the direction of RELEASING FORCE so it passes over pawl arm 6. Thus the lifting device of the present invention may be operated with a single hand, with either tightening or loosening possible. This is an important advantage over cam cleats of the prior art, many of which do not allow for two way adjustment. Should the rope be released, either intentionally or accidentally, pawl 2 will quickly rotate back to the closed position of Fig. 4 under the urging of spring 10, as well as friction of rope 18 on rope locking surface 4. This provides for fail safe operation, as accidental release of rope 18 free end will not result in a load on the opposite end of rope 18 being dropped. In this closed position, pawl arm 6 preferably extends substantially across rope 18 centerline (shown as dashed line "CENTER" in Fig. 4) when rope 18 is held between locking surface 4 and engaging surface 16. Such orientation advantageously provides for ease of urging pawl arm 6 into an open position when desired. Referring once again to Fig. 1, the preferred lifting device of the invention further comprises base 40 for attachment to a surface, such as a vertical wall (illustrated in dashed line in Figs. 1 and 4). Base 40 has apertures through it for attaching to the vertical surface by use of screws 42. As illustrated in Figs. 1 and 3, base 40 is substantially flat with a plane of orientation that is substantially parallel to a central axis of rotation of pulley 20. In addition, when mounted on a vertical surface such as a wall, pawl 2 is preferably located spaced farther horizontally from the vertical surface than pulley 22, and located below pulley 22. It has been discovered that such an orientation provides for advantageous use of the lifting device of the invention in many applications, including by way of example for raising loads to be stored along a wall. It is to be understood, however, that the lifting device of the present invention is not limited to such an orientation. Indeed, other embodiments of the lifting device of the invention may orient the base so that the lifting device can be mounted to an overhead surface such as a ceiling. The advantages of the disclosed invention are thus attained in an economical, practical, and facile manner. While a preferred embodiment has been shown and described, it is to be understood that various further modifications and additional configurations will be apparent to those skilled in the art. It is intended that the specific embodiment herein disclosed is illustrative of the preferred and best modes for practicing the invention, and should not be interpreted as limitations on the scope of the invention as defined by the appended claims.

Claims: Claims: What is claimed is: 1. A lifting device with a rope adjustably held therein; the lifting device comprising: a) a pawl, said pawl rotatable, a spring urging rotation of said pawl towards a closed position; said pawl having a rope locking surface; a pawl arm connected to said pawl; b) a pawl sleeve, said pawl sleeve having an endwall, said endwall having a surface for engaging the rope; said pawl rotatably mounted in said pawl sleeve with said pawl rope locking surface movably facing said sleeve endwall engaging surface; wherein the rope is lockably engageable between said pawl locking surface and said endwall when said pawl in said closed position, and wherein urging said rope against said pawl arm causes said pawl to rotate to an open position wherein said rope may be slidingly adjusted between said pawl locking surface and said sleeve engaging surface in a tightening or loosening direction through said sleeve; and c) a pulley, said pulley comprising opposing side cheeks connected to said pawl sleeve, a central hub held between said opposing side cheeks, a sheave rotatable about said central hub, bearings rotatably engaged between said sheave and said hub; the rope passing from said pawl and said pawl sleeve and over said sheave. 2. A lifting device as in claim 1, further comprising a base for mounting the lifting device to a surface, said base attached to said pulley opposing side cheeks. 3. A lifting device as in claim 2, wherein said base having a plane of orientation for engaging the surface, said pulley having a central axis of rotation; said base plane of orientation substantially parallel to said pulley rotation axis. 4. A lifting device as in claim 1 wherein said pulley side cheeks are integral with said pawl sleeve. 5. A lifting device as in claim 1, wherein said sleeve having an axial centerline, the rope passing substantially along said centerline, and wherein said pawl arm extends beyond said centerline when said pawl in said closed position, the rope passing through said sleeve and over said pawl arm. 6. A lifting device as in claim 1, wherein said pawl sleeve is substantially U- shaped, said endwall comprising the closed U-shape end, said endwall rope engaging surface comprising the interior arc of the closed U-shape end; said engaging surface having a series of locking ridges, said pawl rotatably mounted between opposing members of the open end of said U-shaped sleeve. 7. A lifting device as in claim 1, wherein said spring comprises a torsion spring. A lifting device with a rope adjustably held therein; the lifting device for attachment to a surface, the lifting device comprising: a) a pawl, said pawl rotatable, a torsion spring urging rotation of said pawl towards a closed position; said pawl having a rope locking surface; a pawl arm connected to said pawl; b) a substantially U-shaped pawl sleeve, said pawl rotatably mounted between opposing ends of said U-shaped sleeve; an endwall at the closed end of said U-shaped sleeve, said endwall having an inside rope engaging surface comprising the interior arc of the closed U-shape end, said rope engaging surface having a plurality of locking ridges; said pawl locking surface movably facing said sleeve endwall engaging surface; c) a pulley comprising a pair of opposing side cheeks; said side cheeks connected to said pawl sleeve; a central hub held between said opposing side cheeks; a sheave rotatable about said central hub, bearings rotatably engageable between said sheave and said hub; the rope passing from said pawl and over said sheave, said side cheeks integral with said pawl sleeve; d) a base for mounting the lifting device to the surface, said base attached to said opposing side cheeks; e) wherein the rope is lockably engageable between said pawl locking surface and said pawl sleeve rope engaging endwall when said pawl in said closed position, and wherein urging said rope against said pawl arm causes said pawl to rotate to an open position in which said rope may be adjusted in a tightening or loosening direction through said sleeve, the rope passing over said pulley sheave. 9. A lifting device as in claim 8, wherein the surface for mounting said base is a substantially vertical surface, the vertical surface having a plane of orientation, and wherein when said base attached to said vertical surface, said pulley having an axis of rotation substantially parallel to said vertical surface, said pawl being oriented below said pulley so that the rope may operate in a substantially vertical direction to raise and lower loads. 10. A lifting device as in claim 9, wherein said pulley is located horizontally closer to the vertical surface than said pawl, and wherein said pawl is located vertically below said pulley, with the rope passing over said sheave and passing freely downward between said pawl and the vertical surface.

Inventors: LOB CHARLES J, MILLMAN JOHN S, LOB, CHARLES, J., MILLMAN, JOHN, S.
Applicants: HARKEN INC, HARKEN, INC.
Application year: 2001
Main classification: B66D
IPC codes: B66D3