GB732306A - Improvements relating to sewing machines - Google Patents

Abstract

732,306. Mechanical switches, without quick action. SCHWAB, M. June 22, 1953 [June 20, 1952], No. 17303/53. Addition to 732,295, [Group VII]. Class 38 (5). [Also in Group VII] A three-contact switch for controlling operations of a sewing-machine at the end of a seam as described in the parent Specification and thus requiring a normal off position followed by a cycle of three positions in which successively two contacts are connected, all are disconnected, and all three are connected, is formed as a rotary member with contact pieces arranged so that several cycles of connection are completed in one revolution, the member being actuated by a knee-lever through ratchet gear of such stroke that one cycle of connections corresponds to one tooth of the ratchet and thus to one complete movement of the lever. In the form shown, the rotary member 4, Fig. 2, is of insulating material and the contact pieces are formed.by rods 10 embedded therein ; the fixed contacts are in the form of spring members 22 arranged side by side, their ends being shaped to engage the rods 10 and ridges 16 formed between the rods so as to locate the member 4 in its successive positions. Alternate rods 10 span all three contacts and only two of them, the member 4 being formed with a plain cylindrical surface for that part of its length corresponding to the third contact at parts of its periphery adjacent to the short rods 10; the member 4 is preferably formed in two parts, one of the lengths corresponding to the short rods and the other making up the remainder. The spindle 28, Fig. 4, is geared to a wheel 29 integral with a ratchet-wheel 31 and free on a spindle 30, and the knee-lever 32 is also free on this spindle and carries the ratchet pawl 34; the lever is biased by a spring 35 to the position A in which all the contacts are disconnected. To carry the member 4 through its cycle, the lever is moved successively to positions B (short .rod under the contacts), C (ridge under contacts), and D (long rod under contacts), and finally to E, which corresponds to the off position at the beginning of a new cycle ; the lever is now released to position A (the member 4 remaining stationary) and the pawl engages the next tooth of the ratchet-wheel 31.