Patent GB-968408-A (GB)
Abstract: 968,408. Cam-actuated switches. OAK MANUFACTURING CO. Jan. 26, 1961 [Jan. 27, 1960], No. 3084/61. Heading H2B. [Also in Divisions F2 and G3] A variable-speed mechanism for use in a timer controlling electric switches in the circuits of a refrigerator &c. comprises an input carrier mounting one planet pinion having a single set of teeth meshed by two sun gears having slightly different numbers of teeth, and a clutch to lock-up the two sun gears &c. As shown, a synchronous motor 21, Fig. 23, drives a pinion 24 meshing a drive gear 26 upon which is rotatably mounted a planetary pinion 34. Two sun gears 30, 31, Fig. 7, lying adjacent to the drive gear 36, are of the same diameter but are provided with a slightly differing number of teeth, e.g. one tooth in forty-five, the arrangement being such that both the sun gears are meshed by the planetary pinion 34. The sun gear 31 is provided with two symmetrically arranged axial holes 41, 42 and the sun gear 30 is provided with a single hole 38 at an equal radial distance from its centre, a cam path 39 leading up from the hole 38 to the face of the gear. The drive gear 26 is provided with several recesses 29 at the same radial distance from its centre to line-up with the holes 41, 42, 38. The three gears 26, 30, 31 are mounted upon the hub of a switch-actuating cam-block 46 itself rotating about a fixed pin 48. The cam block 46 contains two axially slidable clutch pins 52, 53, Fig. 8, which are aligned with the holes 41 &c. in the three gears. The outer ends 54 of the pins 52, 53 engage in slots 63, Fig. 23, in a ring-shaped spring 60 fast upon the cam-block 46. A cam plate 66 carried by the housing of the timer coacts with extending edges 62 of the ring-shaped spring as the latter rotates, to withdraw the pins 52, 53 from engagement with the hole 38 in the sun gear 30 and the recesses 29 in the drive gear 26. The cam block 46 is provided with a peripheral cam surface 72, Fig. 9, which actuates two sets of spring switch contacts 75. In the position shown in Fig. 8, rotation of the motor 21 drives the gears 24, 26 which are clutched solidly by the pin 52 to the cam block 46, so that the latter turns and through its cam surface 72 actuates the switch contacts 75. When the edge 62 of the ring-shaped spring 60 engages the cam 66, the pin 52 is withdrawn from the hole 38 in the sun gear 30 and from the corresponding recess 29 in the drive gear 26. The friction of the load applied to the cam block 46 holds the latter, together with the sun gear 31, stationary. As the drive gear 26 and the planetary pinion 34 continue to rotate, the different numbers of teeth on the two sun gears 30, 31 cause the sun gear 30 to turn slowly relatively to the sun gear 31, so that the hole 38 is moved out of alignment with the holes 41, 42 in the sun gear 31. Accordingly engagement of the clutch pins 52, 53 with the holes 38 &c. is prevented. After continued rotation of the drive gear 26 and the planetary pinion 34, the hole 38 in the sun gear 30 ultimately lines-up with one or other of the holes 41, 42 in the sun gear 31 and with one or other of the several recesses 29 in the drive gear 26. The ring-shaped spring 60 is then able to project the corresponding pin 52, 53 axially into the hole 38 for re-engagement of the clutch, the cam block 46 begins to turn again and the switch contacts 75 are again actuated.