Motors: spring – weight – or animal powered – Spring – With winding means
Reexamination Certificate
1998-11-16
2001-03-13
Bucci, David A. (Department: 3682)
Motors: spring, weight, or animal powered
Spring
With winding means
C185S037000
Reexamination Certificate
active
06199664
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to spring motors and, more particularly, to a spring motor for delivering constant torque for driving an electric power generator.
There has been a recent interest in development of power systems for electronic devices such as flashlights and radios which can obtain electrical power from mechanical sources. These systems are of particular interest for use in emergency kits in which storage batteries may be depleted or in remote locations where access to electric generators is limited.
U.K. Patent Specification No. 9516144.4 describes a radio which is powered from an electric generator driven by a spring motor. The spring motor comprises a strained steel band which is wound on a torque drum and is then allowed to unwind onto a storage drum. The torque drum is mounted on a shaft which rotates with the drum and is connected to drive an electric power generator. The spring force of the wound spring is released at a constant angular rate so as to drive the generator at a constant speed and produce a constant voltage output. However, although the spring force is constant, the torque developed by the spring motor, which is a product of the spring force and the radius of the spring on the torque drum, varies as the spring unwinds. Since the power developed by the spring motor is proportional to the product of torque and angular frequency, the power output varies as the spring unwinds from the torque drum. When such a variable power source is used to drive a generator, the electric power output of the generator will likewise vary and affect operation of devices receiving the electric power.
Notwithstanding the above described power variation, it is desirable to assure that the power available from the spring motor, even in the last few turns, is sufficient to provide the minimum amount of power necessary to operate electrical devices connected to the electric power generator. Typically, this would be achieved by oversizing the spring motor to produce the desired torque at t he last few turns. Such design, however, will produce excess torque at all other spring conditions and lead to wasted power and extra cost. Accordingly, it is desirable to provide a spring motor which can produce constant torque at any winding state of the spring.
SUMMARY OF THE INVENTION
A spring motor is provided which produces a constant torque and produces a desired torque at any winding state without producing excess torque when fully wound. In at least one embodiment, the invention is described in conjunction with a drive system for an electric power generator in which the drive system includes a spring motor coupled to the generator through a gear train so that each revolution of the spring motor drive shaft produces multiple revolutions of the generator rotor. The spring motor includes a spring in which the spring width varies generally or approximately linearly from one end of the spring to the opposite end, with the narrowest end being at the outer radial position when the spring is fully wound on a torque or crank-up drum or spool. Since the spring force is proportional to the spring width, and the generated torque is proportional to the product of spring force and radius, the resultant motor generates constant torque at all spring winding states.
In still another embodiment, the spring force is transferred to an output shaft which is driven directly from the unwinding spring rather than by the shaft of the crank-up spool. This drive method assures that the spring force is applied at constant radius and results in constant torque. In order to prevent slippage, the spring may be further embodiment uses an idler wheel in contact with the moving spring, with the drive shaft being driven by contact with the periphery of the idler wheel. The idler wheel may include sprocket or gear teeth to prevent slippage on the spring or on contact with the drive shaft. This latter embodiment allows the drive shaft to be fixed in position while the idler wheel accommodates the displacement caused by the change in radius of the spring on the crank-up drum as the spring unwinds.
REFERENCES:
patent: 2063799 (1936-12-01), Fornelius et al.
patent: 3194343 (1965-07-01), Sindlinger
patent: 3308907 (1967-03-01), Bodkin
patent: 3342998 (1967-09-01), Anderson
patent: 4427163 (1984-01-01), Kondziola
patent: 4719992 (1988-01-01), Elward et al.
patent: 9823561 (1998-11-01), Toti
patent: 0677638 (1995-03-01), None
patent: 0942337 (1998-08-01), None
patent: 2262324 (1992-11-01), None
patent: 2304208 (1997-03-01), None
Tiemann Jerome Johnson
Tkaczyk John Eric
Bucci David A.
General Electric Company
Hansen Colby
Snyder Marvin
Stoner Douglas E.
LandOfFree
Spring motor for generating constant torque does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Spring motor for generating constant torque, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Spring motor for generating constant torque will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2439449