Implements or apparatus for applying pushing or pulling force – Apparatus for hauling or hoisting load – including driven... – Device includes rotatably driven – cable contacting drum
Reexamination Certificate
1999-09-24
2001-04-03
Matecki, Katherine A. (Department: 3653)
Implements or apparatus for applying pushing or pulling force
Apparatus for hauling or hoisting load, including driven...
Device includes rotatably driven, cable contacting drum
C254S270000, C033S734000, C033S743000
Reexamination Certificate
active
06209852
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a chain hoist position encoder assembly which may be removably attached externally on the casing of a chain hoist to track the movement of the load carried by the chain hoist relative to a fixed location.
2. Description of the Prior Art
Chain hoists are utilized in many different applications to raise and lower loads suspending from overhead supports. A chain hoist is comprised of a heavy-duty motor housed within a rugged casing and having at least one chain access opening in the casing. A chain may be suspended from an overhead support or from the chain hoist itself to carry a load. In either case the chain is routed around a chain drive gear located within the chain hoist casing. The chain drive gear within the casing is driven by the chair hoist motor. The slack portion of the chain, after passing around the drive gear within the casing, is routed back out through the chain opening and hangs from the chain hoist casing as a slack end having a length that varies with the position of the chain hoist casing relative to the overhead support or with the position of the load relative to the chain hoist casing.
The chain hoist motor, through the internal chain drive gear within the casing, pulls either the load or the motor casing vertically upward, or allows the load or chain motor casing to travel vertically downward. The travel of the chain hoist casing or the load vertically up and down is controlled by switches located remotely from the chain hoist casing and coupled to the chain hoist motor by means of an electrical control cable. One or more hooks that are attached to the chain motor casing suspend a load beneath the chain hoist casing. This load is raised and lowered, under the control of the chain hoist operator switches, by the upward and downward travel of the load or the chain hoist along the portion of the chain which is under tension and from which the chain hoist is suspended or by pulling chain in and playing chain out from the casing. One such conventional chain hoist is described in U.S. Pat. No. 2,991,976, while another is described in U.S. Pat. No. 3,960,362.
Chain hoists are utilized extensively and in widely differing applications. They are used in shops, factories, warehouses, shipyards, and numerous other types of commercial and industrial establishments. In many applications of commercially available chain hoists the position of the chain hoist motor and casing relative to the length of the suspended chain upon which it travels or the position of the chain which travels relative to it may be controlled merely by observing either the chain hoist itself, or the load suspended from it. Adjustments to the vertical position of the chain or chain hoist may be performed merely by providing manual inputs to the chain hoist control switches. Indeed, a simply manually operated control is sufficiently accurate for many, many chain hoist applications that do not require precise position control.
On the other hand, there are some applications in which precision control of the chain hoist is required. In the theatrical industry stage sets and props are often moved vertically utilizing general purpose chain hoists, but this movement must be controlled with great precision. For example, different portions of a stage prop may be moved vertically relative to the stage and relative to each other in a closely controlled and intricate sequence and at precise speeds in order to produce special theatrical effects. Precision control of general purpose chain hoists is often necessary in other applications as well. For example, precision control of a general purpose chain hoist may likewise be required at trade shows and expositions in order to create special effects or in order to move interdependent loads in a complex manner. Where precision control of a chain hoist is necessary, visual observation and corresponding adjustment utilizing manual controls is very inadequate and unacceptable.
To provide the necessary precision control for specific applications of general purpose chain hoists, various position-encoding systems have been devised. However, all of these prior position-encoding systems have involved modifications to the chain hoist within the structure of the chain hoist casing. For example, some conventional position-encoding systems for chain hoists have involved the installation of an optical or magnetic encoder within the casing of the chain hoist to sense the rotation of the chain hoist motor or the gear that engages the chain and which is driven by the chain hoist motor within the casing. The internally installed encoder provides corresponding electrical position output signals.
While such conventional position-encoding systems do provide the required positional information, they have significant disadvantages. For one thing, they can be installed within a chain hoist casing only by a person who has extensive knowledge of the internal operations of the components of a chain hoist. The services of such individuals are expensive and often are not readily available.
A further significant disadvantage of such conventional chain hoist encoder systems is that once the chain hoist casing is opened, the manufacturer's warranty for the chain hoist is voided. This is only reasonable since if a person without sufficient expertise attempts to install a position encoder within the casing of a chain hoist, connections can easily be made or broken that will cause permanent damage to the chain hoist and cause it to malfunction. Moreover, tampering with the internally protected components of a chain hoist by persons lacking sufficient expertise can result in alterations to the chain hoist that can cause vary hazardous malfunctions. This can lead to significant property damage and personal injury when the chain hoist is thereafter operated.
SUMMARY OF THE INVENTION
The present invention involves the provision of a position encoder assembly for a general purpose chain hoist that can be attached to and detached from the chain hoist casing, and which requires no internal connections within the chain hoist casing. Moreover, the position encoder assembly of the invention is readily removable and may be attached to and removed from the exterior of the chain hoist casing in merely a matter of seconds. Nevertheless, it provides highly accurate encoded position information that meets or exceeds the accuracy of position encoders that are internally wired within the casing of a chain hoist.
The present invention has significant advantages over conventional systems in that no particular knowledge of the internal operation of the chain hoist is required in order to properly mount the position encoder assembly of the invention on the casing of the chain hoist. Installation and removal may be performed by virtually any unskilled laborer.
A further very significant advantage of the present invention is that the position encoder assembly of the invention may be removably installed upon the casing of a chain hoist totally externally of the operating mechanism of the chain hoist. As a consequence, installation does not require the chain hoist casing to be opened, nor does it require any internal connections to the operating components of the chain hoist. As a result, the installation of the position encoder assembly of the invention on a chain hoist does not void or in any way affect the warranty provided by the chain hoist manufacturer.
A further advantage of the position encoder assembly of the invention is that all exposed components are highly rugged and durable and not readily susceptible to damage. Nevertheless, the position encoder assembly of the invention produces encoded position and direction signals which are highly precise and which may be provided as inputs to a computer-controlled system, thereby enabling a high degree of precision control of the operation of the chain hoist.
A further advantage of the removable position encoder assembly of the invention is that it is readily adaptable for instal
Booth Thomas G.
Bracegirdle Glenn R.
Fry Robert A.
George David W.
Guth Christopher E.
George & Goldberg Design Assoc.
Matecki Katherine A.
Thomas Charles H.
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