Torque limiter having automatic reset function

Details Torque limiter having automatic reset function Torque limiter having automatic reset function

1993-05-28

1997-09-30

Stodola, Daniel P.

Rotary shafts, gudgeons, housings, and flexible couplings for ro

Overload release coupling

Torque transmitted via resiliently biased positive drive...

192 45, F16D 702

Patent

active

056721102

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL BACKGROUND

This invention relates to a torque limiter having an automatic reset function.


BACKGROUND ART

In ordinary industrial machines, various means are used to transmit power by rotation, such as belts, pulleys, gears and shaft coupling. In order to increase the reliability of the entire machine and to prevent any fatal accident, an increasingly greater number of machines are provided with safety devices for preventing excessive loads on critical parts thereof.
It is especially important to provide a propeller engine of a small ship or a compression circuit in a compressor for a refrigerator with a safety device for cutting off torque transmission from the engine if the driven side is subjected to an excessive load.
A shear pin shown in FIG. 20 is one of such safety devices. This shear pin 71 is inserted between a driving shaft 72 and a driven member 75 (propeller in the illustrated example). If the driven member is subjected to an excessive load, the pin 71 is broken, allowing the driving shaft 72 to run idle.
But such a shear pin has to be replaced with a new one every time the driven member is repaired. Such a replacement is troublesome. If such a shear pin is used for a propeller shaft of a small ship, pins have to be replaced while on the sea. Such a job thus involves a lot of trouble and danger.
A safety device of the type having an automatic reset function and thus usable repeatedly is known as a torque limiter, as shown in FIG. 21. This torque limiter has balls 82 held in position by a hub 81 coupled to a driven member and received in pockets 85 formed in a driving flange 84. Springs 83 are provided to bias the balls 82 against the pockets 85. If the hub 81 is subjected to an excessive load, the balls 82 get out of the pockets 85, thus cutting off torque transmission. As the driving flange 84 further rotates, each ball 82 will get into another pocket 85. The torque limiter is thus automatically reset and the hub 81 resumes its function.
With this type of torque limiter, automatic resetting occurs too soon before the driving side member and the driven side member make one rotation relative to each other. Thus, even if the torque limiter should stop due to some malfunction of the driven side, it will be automatically reset repeatedly at very short time intervals as far as the driving side is rotating at a high speed. For example, if the driving flange 84 is rotating at 1800 rpm, the balls 82 will repeatedly come into and out of the pockets at the rate of 350 times or more per second to restart torque transmission. This will not only wear the contact parts markedly but the device at the driven side will also be subjected to undue forces because it is restarted soon after it has failed.
It is therefore an object of this invention to provide a torque limiter which is adapted to reset not immediately but after a predetermined long period of time after clutch has disengaged due to some malfunction at the driven side.


DISCLOSURE OF THE INVENTION

In order to solve the above problems, there is provided, as a first means of this invention, a torque limiter having an automatic reset function comprising two bearing rings fitted one on the other, one of the bearing rings being connected to a driving side and the other to a driven side, the bearing rings having surfaces opposed to each other, one of the opposed surfaces being a cylindrical surface, the other of the opposed surfaces being engaging surfaces, a cage formed with a plurality of pockets and mounted between the bearing rings, engaging elements each received in the pockets and adapted to engage the cylindrical surface and the engaging surfaces, one of the cylindrical surface and the engaging surfaces having their portions to be brought into contact with the engaging elements made elastically deformable, and a decelerating means coupled to the cage for transmitting the rotation of the bearing ring connected to the driving side to the cage after decelerating it.
In the second means of this invention, the engaging surfaces form a polygo

REFERENCES:
patent: 2637987 (1953-05-01), Hill et al.
patent: 2668428 (1954-02-01), Hoover
patent: 3877253 (1975-04-01), Yeague
patent: 4344306 (1982-08-01), Citron
patent: 4610340 (1986-09-01), Helmes et al.

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