Patent GB-730720-A (GB)
Title: Improvements relating to hand-operated electric selector switches
Inventor: DELL RICHARD CHRISTOPHER
IPC: G05G9/047
Filed: 1952-07-02
Abstract: 730,720. Retractive switches. DOWTY EQUIPMENT, Ltd. Oct. 2, 1953 [July 2, 1952], No. 16691/52. Class 38 (5). A switch intended for aircraft trim control comprises a mushroom-shaped stem 12 secured by a screw 11 to an insulating base 10 and housing a spherical bearing 20 rockable by a rod 23 about two mutually perpendicular axes determined by a cross-shaped gate 37 in a plate 34. The rod 23 is also rotatable about its longitudinal axis and the rocking and rotational movements may be performed simultaneously. A part-spherical insulating member 24 secured to the rod 23 carries on its periphery two wire-like ring contacts 39, 41 which, on rocking of the rod 23, co-operate with pairs of fixed contacts angularly spaced therearound at 90 degrees corresponding to the arms of the gate 37, two of the contact pairs 50, 51 and 52, 53 mounted on spring arms 54, being shown in Fig. 1. The distance between contact 39 and contacts 50, 52 is less than that between 41 and 51, 53 so that if, for example, the member 24 is rocked clockwise by the knob 38, contact 39 engages contact 52 and then on further movement of the rod 23 limited by the gate 37, contact 41 engages contact 51, the contacts 39, 52 remaining engaged. A similar switching action takes place for each rocking direction of the knob 38. Rocking of the knob 38 in the plane of the drawing has no effect on the two pairs of fixed contacts not shown, and, similarly, rocking of the knob perpendicularly to the plane of'the drawing has no effect on the contact pairs 50, 51 and 52, 53. The member 24 also carries a longitudinal wire-like contact 42 soldered to the ring contact 39, but insulated from the ring contact 41, and a similar contact 43 soldered to the contact 41 but insulated from the contact 39, the contacts 42, 43 being connected by coiled wires 47, 48 to terminals 45, 46. Further longitudinal contacts 56, 57 disposed on a diameter at right angles to that of contacts 42, 43 are respectively soldered to the contacts 41, 39 and insulated from the contacts 39, 41. The contacts 42, 56 are doubled to provide contact over a greater angular extent of rotation of the knob 38. The contacts 42, 43, 56, 57 co-operate with contacts 58, 59, 61, 62 mounted on spring arms 63, biased inwardly against stops 64. On, for example, clockwise rotation of the knob 38, contact 42 first engages contact 62 and then on further rotation contact 43 engages contact 59, the contacts 42, 62 remaining engaged, the contacts 56, 57, 58, 61 being similarly operated on counter-clockwise rotation of the knob. Rotation of the knob does not operate ring contacts 39, 41 and, similarly, rocking of the knob does not operate longitudinal contacts 42, 43, 56, 57, but these contacts may be operated conjointly by simultaneously rotating and rocking the knob. The knob is centralized from a rocking displacement by a spring-loaded ball 22 co-operating with a central detent in a bush 15, the detent comprising a hole 68 surrounded by an inner conical recess 65 separated from an outer conical recess 66 by a step 67. The step 67 corresponds to the displacement of the knob in which the contacts such as 50 or 52 are engaged by the ring 39 but before the contacts such as 51 or 53 are engaged by the ring 41. For centralizing the knob from a rotational displacement the stem 12 carries spring-pressed balls 72 which normally rest in grooves 74 formed in the member 24. An inclined surface 75 is formed on either side of the grooves 74 and bounded by a step 76 leading on to a cylindrical surface 77. The steps 76 correspond to the rotational displacement of the knob in which the contacts 62, 58 are engaged by the contacts 42, 56, but before the contacts 59, 61 are engaged by the contacts 43, 57. Abutments 78 limit the rotation of the knob. The rod 23 passes sealingly through a rubber diaphragm 36 and a rubber joint ring 31 is interposed between the body 29 and base 10, the connecting wires passing through sleeves 83 of a rubber grommet 82.