HIGH-PRECISION SEALED-CONTACT LIMIT SWITCH Russian patent published in 2007 - IPC H01H36/00 

FIELD: electrical engineering; checking and controlling electromechanical drives and high-precision locks.

SUBSTANCE: proposed switch has rectangular plastic case with internal lugs that accommodates sealed printed-circuit board copper-plated on one side. Non-copper-plated side of mentioned board mounts sealed switching contact with magnetically soft ferromagnetic screen in the form of cylindrical tube section disposed between its leads. This sealed switching contact is spaced apart from external surface of case effective edge through distance "Δ"; operating distance "L_op" for linear displacement of cylindrical bar magnet in plane crossing longitudinal symmetry axes of case effective edge and magnet is found from equation where d_m and L_m is bar magnet diameter and length, respectively; L_s, d_s, and h_s is length, diameter, and wall thickness of tubular ferromagnetic screen, respectively; a is degree of overlapping of sealed-contact members in pair being closed; b is width of movable sealed-contact member; F_max(A) is high value of admissible operating magnetomotive force range; F_i(A) is operating magnetomotive force current value for sealed contact used in switch; Δ is distance between outer surface of case effective edge and projection of sealed-contact cylinder longitudinal symmetry axis onto plane incorporating longitudinal symmetry axis of case effective edge which is disposed in parallel with printed-circuit board plane, limitations being imposed by following expressions: 2 ≤ L_m/D_m ≤ 3.5 and 0.9 < L_s/l_δ < 1.2, where l_δ is sealed-contact glass cylinder length for magnets with poles N and S disposed at bar end, permissible difference in magnetic flux densities B_N and B_S being limited on ends by expression 0.9 < B_N/B_S < 1.1.

EFFECT: facilitated operation and maintenance, reduced travel of differential.

1 cl, 6 dwg