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  1. 1. * GB780200 (A) Description: GB780200 (A) ? 1957-07-31 Improvements in and relating to mechanical rotary motion coupling means Description of GB780200 (A) We, THE BRITISH THOMSON-HOUSTON COMPANY LIMITED, a British Company, having its registered office at Crown House, Aldwych, London, W.C.2, do hereby declare S the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: - This invention relates to mechanical coupling or transmission of motion and aims at providing a means for deriving from a more or less constant or continuously variable speed rotation a successively retarded and accelerated rotational output movement which may serve for a step-by-step drive. Such drive is often required to change the position of a device in discrete steps. For instance, the setting of certain aircraft instruments requires adjustment in discrete steps according to the changing altitude zones in which the aircraft is operating. The present invention makes it possible to produce a step-by-step rotation or angular position changes at predetermined intervals of a continuous (as opposed to step-by-step) rotational input. Furthermore the invention ensures operational stability by providing a predetermined separation of the points at which the acceleration, that is discrete changes of position, occur if the rotation of the input is in one direction, from those associated with the other direction of rotation, if such rotation must be expected in both directions. Accordingly this invention resides in a rotary motion transmitting device comprising driving and driven members rotating about a common axis and interconnected by a resilient member arranged to be loaded when the two members are angularly dis[Price 3s. 6d.] placed, a catch supported by a stationary member being biased for movement into the path of a stop of the driven member, and cams associated with the
  2. 2. driving member being provided to control the movement of the catch into and out of the path of the stop, wherein the driving and driven members comprise circular discs, and the resilient member comprises a loop-shaped spring interconnecting tongues which project from the discs at right angles thereto, and are radially aligned with each other in their rest or neutral position. In a preferred embodiment the catch is formed by a pawl riding on the peripheral surface of the driving member and springbiased towards the axis of rotation. A. portion in the periphery of the driving disc is cut away so that the pawl when it coincides with this recessed portion is allowed to move towards the axis of rotation. The stop is formed by a second tongue that is a projection on the driven disc, and on contacting this projection the pawl arrests the motion of the driven disc for a period, during which energy is stored in the coupling spring, until the pawl is moved out of the recess of the driving disc by means of a tapered end of the said recess. The coupling spring which has been stressed by the relative angular movement between the two discs during said period, then causes the driven disc to rotate at a higher speed until it is again in phase with the driving disc and follow its rotation at the slower normal speed of the input motion. The driven disc may be connected through a shaft to an intermittent movement, such as that used in a revolution counter, or any other suitable mechanism which responds only to the higher speed of the disc and disregards the intermediate low speed rota780,200 PATENT SPECIFICATION Inventor:-BERNARD ROY TUPPEN. i&% Date of Jlli'ng Complete Specification: Aug. 11, 1955. Application Date: Aug. 12, 1954. No. 23462/54. / CoCmplete Specification Published: July 31, 1957. Index at Acceptance:-Class 80(2), 02F4D(3: 5). International Classificationr:-Ee6d. COMPLETE SPECIFICATION. Improvements in and relating to Mec liicga RotRJY Motion Coupling Means. 2 78( tion. The output of this movement. therefore, is a series of discrete steps or rotation occurring at predetermined intervals while the driving disc rotates miore or less uniformly. Assuming that the input rotation is of constant speed, and that there is only one peripheral recess, or that several such recesses are equally spaced, then the steps must occur at equal time intervals. These conditions are assumed only for illustration. The speed of the driving disc need not be constant, and several recesses can be differently spaced from one another along the periphery of the driving
  3. 3. disc. As the projection which is engaged by the pawl has a finite width, there will be an angular, and therefore a time, displacement between the said steps corresponding to the two directions of rotation of the driving disc. This is a further feature of the invention, suitable tQ eliminate points.of instability in operation when the input rotation is reversed. The width of the projection can be designed so as to afford a separation of the operating points' corresponding to each direction of rotation by a desired amount. The invention will now be described more fully with reference to the dlrawings accompanying the ProVisional Specification, in which:Fig. i shows an end elevation; and Fig. 2 shows a side elevation of a preferred embodiment.' A driving disc 1 mounted on an input shaft 2 has a peripheral recess 3. This disc carries a tongfie 4 which at its rest or centre position coincides angularly witli a tongue carried by a driven disc 6, the coincidence of ihe two tongues being resiliently maintained by a pretensioned coupling spring 7 which engages both. Also carried by the driven disc 6 is a second tongue 8, which normally lies in the centre of recess 3 of the disc I.' 'Riding on the periphery of the disc 1 is a pawl 9, which is biased towards the shaft 2, so that when it coincides with the cut away portion, that is the recess 3 of the disc 1 it moves towards the centre of rotation. The pawl extends laterally and on further rotation of the two discs it engages the tongue 8, and arrests the motion of the driven 'disc 6 thereby loading the spring 7 until the pawl 9 is lifted by the suitably shaped cam portion at the end of the recess to disengage the tongue 8. The accumulated power of spring 7 then causes the driven disc to accelerate and rotate rapidly until the tongues 4 and 5 are re-aligned, whereupon the disc 6 rotates with disc 1, is arrested again by the pawl 9, and so on in 12-00 repeated succession as long as disc 1 rotates. ThDiedriidi'sc 6 is connected by means of a shaft 10 to an intermittent movement 11 of any type known in the art, the output of which comprises step-by-step rotational displacements synchronised with the occurrences of the high speed displacement of the driven disc 6. * Sitemap * Accessibility * Legal notice * Terms of use * Last updated: 08.04.2015
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