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Velocity Limiter and Decelerator for Spring Driven Device

IP.com Disclosure Number: IPCOM000076701D
Original Publication Date: 1972-Apr-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 3 page(s) / 55K

Publishing Venue

IBM

Related People

Bishop, RE: AUTHOR [+2]

Abstract

A spring-driven device is accelerated to a predetermined constant velocity and then decelerated to a very low velocity at its final position by the addition of a pneumatic cylinder. A step-type retarding force is applied at some point during the motion of the device. In another version, a controlled velocity with minimum variation is established.

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Velocity Limiter and Decelerator for Spring Driven Device

A spring-driven device is accelerated to a predetermined constant velocity and then decelerated to a very low velocity at its final position by the addition of a pneumatic cylinder. A step-type retarding force is applied at some point during the motion of the device. In another version, a controlled velocity with minimum variation is established.

A paper-cutting knife on a copy machine is an example of a spring-driven device which must be accelerated to a velocity, perform the paper-cutting function, and then be decelerated back to zero velocity. In some cases, this operation is performed by a spring-driven link which impacts a rubber bumper on completion of the cutting stroke. The impact causes noise, loosening of set screws, and even copy smearing in certain cases. Any lowering of this impact velocity has obvious advantages. Also it has been shown that the knives will cut when slightly dulled if the cutting velocity is lower than that of the spring-driven mechanism. Therefore, there is a motivation to limit the maximum velocity, as well as to decelerate to zero velocity at the end of the cutting stroke.

The mechanism in Fig. 1 accomplishes both tasks with a single pneumatic cylinder. The system is actually a rotary system but the linear system illustrated shows the principle.

One pneumatic cylinder coupled to the spring-driven mass can cause both a limiting velocity and a controlled deceleration at the end of the stroke.

During the acceleration portion from 1 to 2 of the stroke, the pressure force created at the suction side of the piston builds up to equal the spring force. During the velocity-limited portion 2 to 3, the spring force and pressure forces are equal. (This also is the paper cutting portion. The effect of the paper cutting force will not be discussed at this point in order to understand the action of the pneumatic cylinder more clearly). At the start of deceleration portion at 3, the piston extension A starts covering the major portion of the cylinder hole B which in turn activates the compression end of the cylinder by allowing the air to escape at a rate which causes a pressure increase to decelerate the mass. The suction and exhaust orifices are sized to cause the desired limiting velocity and deceleration characteristic.

The same characteristic cannot be obtained by simply using the compression part of the cylinder. Computer programs have been written which calculate the dynamic motion of the mass and the dynamic pressure in the cylinder.

The knife is subjected to a step-type retarding force during its stroke due to the force required to cut the paper. Velocity limiting with minimum velocity ...