Patent GB-1297691-A (GB)
IPC: G04F3/02
Filed: 1970-02-23
Abstract: 1297691 Timed control of electric circuits ROBERTSHAW CONTROLS CO 23 Feb 1970 [24 Feb 1969] 8475/70 Heading G3T [Also in Division H1] A time switch has a contact set which may be subjected to timed actuation, to manual retractive actuation or to manual retained set actuation. The time switch comprises a rotatable knob 94 carrying a time scale 104 to which is secured a shaft 31 which is rotatable during timed operation by a spiral spring 36. Mounted centrally in knob 94 is a push button 106, biased outwardly by spring 111 and retained slidingly in the knob 94 by the snap fitting co-operation of tongues 109 of legs 108 of the button 106 with the back of knob 94. The push-button 106 rotates with knob 94. The push button legs 108 co-operate with a rectilinearly guided plate 112 which abuts against the left hand end 118 of a plunger 75 biased by spring 81 to the left. The right-hand end 84 of plunger 75 co-operates with normally open contact set 85. The plunger 75 has an enlargement 79 which co-operates with a latch member 54, Fig.12. Timed actuation of contact set 85 is prevented even though the spring 36 is fully wound, if a gear train 40, 43, 45, 46, 47, 48, 50, Fig.8, connected to the shaft 31 by a friction clutch 38, is restrained from movement by a ratchet member 53 which is normal timed running is rocked by the camming teeth 51 of gear 50. An angled latch member 54 pivoted near its angle can be moved into restraining engagement with ratchet member 53 to prevent the timing actuation. The latch member 54 is biased anti-clockwise by a spring 57 away from ratchet member 53 but is restrained from such movement by the engagement of a cam portion 60 of a cam 61 with the arm 59 of latch member 54. The spring 57 is attached to cam 61 to bias it anti-clockwise. A cam 66 carried by shaft 31 co-operates with a tang 65 of cam 61. A further cam 68 loosely mounted on shaft 31 and biased clockwise by spring 70 has a high side 69 which may co-operate with the tang 65 of the cam 61 to move the latch member 54 out of engagement with ratchet member 53 into latching engagement with the enlarged portion 79 of plunger 75. When it is desired to close the contact set 85 retractively, push button 106 is pushed inwardly whilst knob 94 is in its angular off position, and the plate 112 and plunger 75 move to the right. The contacts open when the push button is released. If it is desired to close the contact set 85 continuously the knob 94 is rotated anti-clockwise to a manual position. During this rotation, cam 66 rotates anti-clockwise from its Fig.12 position and through its engagement with a tang 74 of cam 68 drives cam 68 anti-clockwise against spring 70 to cause its tang 71 to rotate cam 61 clockwise away from arm 59 of latch 54 so that spring 57 tends to rotate the latch 54 anti-clockwise. However the latch 54 cannot release ratchet member 53 because the side of enlargement 79 of plunger 75 is in the way. When the push button 106 is depressed, plate 112 and plunger 75 are moved to the right to actuate contact set 85 and at the same time the enlargement 79 clears the latch to permit it to clear ratchet member 53 and move to a position behind the enlargement 79 whereby it holds the plunger 75 depressed and maintains contact set 85 closed. The contact set 85 is opened by rotating knob 94 clockwise back to its off position such movement returning cam member 66 to its Fig.12 position, spring 70 rotating cam 68 with cam member 66 so that spring 57 can cause anti-clockwise rotation of cam 61 to move latch 54 out of locking engagement with enlargement 79 to allow the spring return of plunger 75. When it is desired to cause timed actuation of contact set 85, knob 97 is rotated clockwise to the desired time setting. This causes clockwise rotation of cam 66 to cause it to cam against  tang 65 and rotate cam 61 clockwise a distance sufficient for the high portion 69 of cam 68 to engage the back of tang 65 hold cam 61 in a position which stresses spring 57 in a sense tending to move the latch member 54 against plunger 75. Enlargement 79 prevents latch member 54 releasing ratchet member 53 for timed actuation until the push button 106 is depressed. When it is depressed the ratchet member 53 is released and the plunger 75 is retained by the engagement of its enlargement 79 with latch 54. As spring 36 drives shaft 31 back to the off position, cam 66 rotating clockwise, will engage a tang 74 of cam 68 and drive its high portion 69 out of engagement with tang 65 of cam 61. When the tang 65 is released, spring 57 will move cam 61 to its Fig.12 position and latch member 54 will release plunger 75 and re-engage ratchet member 53. Carried on shaft 31 is a wiper contact 133 sweeping over angularly spaced printed contacts serially connected to contact set 85 so that a pulsed output can be obtained during timed operation.