Patent GB-623402-A (GB)
Title: Improvements in or relating to telephone instruments
IPC: H04M1/52
Filed: 1946-07-05
Abstract: 623,402. Mechanical switches. TENCH, F. (Automatique Electrique Soc. Anon.). July 5, 1946, No. 20099. [Class 38(v)] [Also in Group XXXIX] Switching mechanism for use in telephone substation apparatus [see Group XXXIX] comprises sets of contact springs, all of which are operated by one key, but which are restored in at least two groups by different subsequent switching operations. For instance, one group may be restored by the operation of a second key, or by the restoration of the first key, or by the replacement of the telephone handset on its cradle. Two types of switch are disclosed, one in which all spring sets are operated together and lock in the operated position, and the other in which the two spring sets are operated sequentially, the first set only locking. The first type is shown associated with the key 15 in Fig. 2, which is a bottom view of.the equipment. Depression of one arm of the L-shaped lever 15 causes its other arm to act on the rollers 22, 23 on the plates 5B, 5D which are riveted to the lever arms 4B, 3B respectively and the resulting movement of these lever arms causes the rollers 24, 25 to engage the operating springs of the spring sets 1B, 2B which are thereby operated. These operating springs are so shaped that a toggle action results between them and the lever arms, which are therefore returned in the operated position until released by the release arm 9 or the member 6. The release arm 9 is arranged between the lever arms 3A and 3B so that if either of them is moved to its operated position, the release arm 9 is rocked about its central pivot and releases the other arm, if operated; while the member 6 is depressed by the replacement of the telephone handset on the cradle, and by means of extensions 6A, 6B releases all operated lever arms. Separate means are provided for releasing the spring set 1B while retaining 1A operated. These means comprise a hook-shaped plate 13 fixed to the lever 15 and arranged so that when the lever is restored to the normal position, the plate 13 engages the pin 12 secured to the plate 5D and restores the lever arm 3B to the unoperated position, thus releasing springs 1B. In the second type of switch which is shown associated with key 14, the connection between the arm 3A and the plate 5C is modified. The plate 5C is pivoted at P, Fig. 4, on the arm 3A and a spring S engages a stop-pin Q on the plate urging the stop-pin against a nose R on the arm. As shown in Fig. 2, 5A and 4A are arranged slightly forward of 5C and 3A by riveting 5A to 4A at an angle different from that between 5C and 3A. During the first-stage operation of the lever 14, plate 5C and arm 3A rotate together, the tension of S being greater than that of the contact springs. When the spring set 1A has been operated and locked, the resistance to movement of 3A increases and on further operation of the lever 14 the plate 5C rotates with respect to 3A, which remains stationary. The lever 14 thus operates the spring set 2A by rotating the plate 5A; but as this spring set is not designed to give toggle action with the arm, this secondstage operation is non-locking. The spring- set 1A is released by release arm 9 or the member 6 as in the case of the first type switch.