Patent GB-1429137-A (GB)
Title: Electromagnetic linear motion device
IPC: G21C7/14
Filed: 1974-04-08
Abstract: 1429137 Ratchet mechanism WESTING- HOUSE ELECTRIC CORP 8 April 1974 [17 April 1973] 15409/74 Heading F2Q [Also in Division H1] In a fail-safe electromagnetic vertical stepping device, e.g. for the part length central rods of a nuclear reactor, capable of vertical up or down incremental motion while restrained from descent under gravity on interruption of the energizing power supply, a system is provided similar to that of U.S.A. Specification 3,158,766 wherein (Figs. 1, 2, placed end-to-end; Figs. 3, 4, cross-section in planes III, IV of Fig. 1) magnet coils 13, 14, 15, secured to non-magnetic pressure housing 10 threaded to the housing of a system to be operated, are selectively energized to provide incremental motion to a linearly movable element. Coil 13 actuates annular lift pole 16 and annular movable gripper pole 17 so that on energization the latter moves axially to contact the former. Coil 14 actuates gripper pole 17 and annular movable gripper latch pole 18 so that on energization the latter moves to pivot latch arm 19 to engage movable linear element 20. On sequential energization of coils 14, 13 latch arm 19 grips linear element 20 for linear incremental axial movement of the element 20, gripper pole 17, latch pole 18, and latch arm 19 as a unit. Coil 15 energizes annular gripper pole 21 and latch pole 22 of magnetic material; pole 21 being fixed relative to the linear motion device while pole 22 is axially movable. Pole 22 then moves axially to contact pole 21 and rotate latch arm 23 to engage linear element 20; and on de-energization due to power failure coils 13, 14, 15 release latch arms 19, 23 from linear element 20 which is then free to fall axially under gravity, unless restrained according to the invention by latch arm lock ring 30 interposed between latch arms 19 and gripper latch pole 18. A similar latch arm lock ring 31 is positioned round latch arms 23; the surfaces of latch arms 19, 23 being L-notched at 32, 33 (Fig. 5, not shown) so that on disengagement from linear element 20 the notch legs are disposed vertically and horizontally; thus allowing relative axial movement between latch arm and lock ring. Look ring 30 is linked to latch pole 22 by circumferentially spaced straps 34 (Fig. 6) of laterally curved profile to fit the circumference of the device, which are clipped and pinned to the locking 30 at 36, 37 while bolted to latch pole 22 through holes 35. Lock ring 31 is similarly but invertedly linked to gripper pole 17 through straps 40 (Fig. 7, not shown). In operation in a lifting sequence (Fig. 8) linear element 20 is held stationary by gripper latch 23 with coils 13, 14 de-energized, coil 15 energized, and gripper pole 17 locating locking ring 31 below notch 33 of gripper latch arm 23. On power interruption, coil 15 releases latch arm 23 which is retained by lock ring 31 in engagement with linear element 20, which is thus held. On de-energization of coil 13 and energization of coils 14, 15 (Fig. 9) latch arms 19, 23 engage linear element 20 and gripper pole 17 is lifted together with lock ring 31, while lock ring 30 engages notch 32 of latch arm 19. Power interruption de-energizes coils 14, 15 whereby latch arm 19 disengages from linear element 20, but gripper arm 23 is held engaged with linear element 20 by lock ring 31, while coil 14 releases gripper pole 17 and lock ring 31 to move downwards into the locking position. Lock ring 30 prevents latch arm 23 from disengaging linear element 20, so that the latter is retained against axial descent. On energization of coil 14 only (Fig. 10, not shown) latch arm 19 supports linear element 20, and on power interruption gripper pole 17 is restrained from downward movement by lock ring 31 engaging notch 33 of latch arm 23, so that latch arm 19 supports linear element 20. On energization of coils 13, 14 and de-energization of coil 15 (Fig. 11, not shown) linear element 20 is moved incrementally upwards and on power interruption lock ring 30 holds latch arm 19 engaged; latch pole 22 and ring 30 being held in their downward position by de-energization of coil 15. De-energization of coil 13 on power interruption releases linear element 20 restrained by gripper latch 19, for one increment of downward movement to the position of Fig. 10 (not shown). On energization of coils 13, 14, 15 (Fig. 12, not shown) latch arm 23 retains linear element 20, and latch arm 19 is disengaged so that on power interruption linear element 20 is lowered by one increment to the position of Fig. 10 (not shown). In the final stage of the lifting sequence linear element 20 is supported by latch arm 23, and latch arm 19 is disengaged by de-energization of coil 14 in preparation for its sequential descent by one increment. On power interruption linear element 20 is retained by either of latch arms 19, or 23 in the position of Fig. 8 or of Fig. 10 (not shown) and the linear element 20 is subsequently lifted one increment at a time by repetition of the sequence commencing with the position of Fig. 8. Linear element 20 may similarly be lowered one increment at a time in a reverse sequence with similar protection against gravity descent on power interruption (Figs. 14 to 19, not shown) in which release of the linear element by simultaneous disengagement of all latch arms is impossible.