US2491075A - Magnetic switch - Google Patents

Description

C. BELSKY MAGNETIC SWITCH Dec. 13, 1949 Filed May 3, 1945 Patented Dec. 13, 1949 UNITED STATES PATENT OFFICE new; I

. MAGNETIC swrron Charles Belsky, Detroit,Mich., assignor, by mesne assignments, to'Robot Appliances, Ine., Detroit, Mich., a. corporation of Michigan Application Mays, 1945, Serial No. 591,688

The. invention relates to magnetic switches.v One object of the invention is to provide an improved magnetic switch of the type which is responsive to. changes in the distribution of flux resulting from an approaching automobile. for controlling an electrical circuit for operating an electrically actuated door operating mechanism 'or other electrically operable means.

Another object of the invention is to .provide an improved switch of this type which is adapted to be installed in the ground.

Another object of the invention is to provide an improved magnetic switch which is simple in construction and can be economically fabricated.

- Another object of the invention is to provide'a n improved switch of this type which comprises simple and inexpensive means for positioning the switch-casing in a box while it is filled with pitch or other suitable mass for excluding moisture from the switch.

Another object of the invention is to provide an improved switch which may be placed in a multiplicity of positions for operation.

Other objects of the invention will appear from the detailed description.

.proofing mass.

' Fig. 4 is a perspective of the switch-lever and the magnet thereon.

Fig. 5 is a perspective of the annular electric conductor which contacts the pool of mercury in the casing and connected to one of the conductors of the circuit controlled by the switch.

Fig. 6 is a perspective of a portion of one of the casing sections. The magnetic switch comprises a box [0 which 3 Claims. (Cl. 200112).

retain the switch-casing inthe box so that it will be completely surrounded by the mass Hi, particularly while the mass in a fluid state is poured into the box around the assembled switch and after the conductors to the circuit to be controlled by the switch have been connected to the switchelements in the casing. This retainer, generally designated 15, consists of a single strip of material, such as heavy kraft paper or cardboard of sufiicient stiffness to support the casing, bent to fit in the box and provided with openings for receiving and retaining the switch-casing. This strip is bent to form a pair of V-shaped sides [6 and I1 and a V-shaped bridge I8. The lower members of the sides l6, I1 and the V-shaped bridge 18 form diagonal legs which extend into the lower corners of the box and the upper members of the sides l6 and I! extend diagonally from the legs to the upper portions ofv the sides of the box. The side edges of the strip fit the sides of the box.

Slots 20 are out in the inner portions of the V-shapecl sides i6 and I! and a slot is cut in the upper portion of bridge l8, into which the 25 casing fits and whereby the casing will be posiis adapted to be buried in the ground or roadway,

and in which the casing containing the switchparts is embedded, in a suitable mass or filling M, such as pitch, for excluding moisture from the in side of the casing. The box may be formed of a single piece of suitable material, such as sulphate kraft paper, bent to form the ends and sides and infolded and overlapping integral flanges H and I! which form the bottom of the box.

In practice, it is advantageousto position and tioned in the central portion of the box where it will be completely surrounded by the filler mass M. V-shaped notches 22 are cut in the upper members of the V-shaped sides [6, l1 and notches 23 are cut in the lower members of sides W, H and the upper portion of the bridge If; to provide passages through which the pitch will flow under and around all sides of the switch-casing.

The switch-casing comprises a pair of generally circular cup- shaped sections 25 and 26 with sides and inwardly extending confronting rims 27 and 28 and is formed of plastic insulating material, such as bakelite. The rims 21, 28 of sections 25, 26 are formed to interfit and overlap and are sealed together. The mating faces of rims 21, 28 are chamfered to form a V-shaped substantially angular groove which is filled with a plastic adhesive 29 for forming a tight seal between, and also securing together, the casing sections. This avoids the use of screws for securing the casing sections together. The lower portion of the chamber in the casing contains a pool of mercury 30. vA conductor-ring 3|, preferably formed of stainless non-magnetic steel, has its outer marginal portion fitting and confined between the faces of the interfitting portions of rims 2?, 23 and its inner portion projects into the chamber in the casing for contacting the pool 30 of mercury. Ring 3| is provided with an outwardly projecting lug or extension 32 which extends through a notch 33 cut in the rim of casing section 26 for connection to a terminal clip 34 of a conductor 35. A screw 36 extends through the terminal, a hole in lug 32 and into an integral outward extension 38 on casing section 26. Ring 3| forms an electric conductor between the mercury 3|] and terminal clip 34. g V v A lever, .generallyifdesignated fifl ifsgipref efrahly formed of stainless sheet steel, "and is centrally pivoted on a pin 48 so it will be in balanced suspension over the pool of mercury 30. A permanently magnetized bar 4| is secured enilevei' 40, for shifting it. Switch lever40 comprises -a strip 42 which underlies the magnerbar "4|,

upstanding integral tongues43between-whieh;

bar 4| is confined against transverse movement,

tongues 44 bent around and ever the ends*of bar 4| for holding said bar against endwi-se movement on the lever 40, central upstanding tongues 4 which are provided with co-axial holes 46 through whichiulcrum pin 48 extends "for pivotally supporting the lever, an'djpointed depen'd n-g tongues 41, Olleidf which, when the lever "49 lsftilted' in either 'direetioii," Will dip into the pool of mercury for clos'nig'th switch. Pin "'48,

'd'uctor 53 of the circuit to be controlled by the v twitch. Cap 50 'hasjits 'inner' en'dispun to'ho'ld it in' casing section 25' a'nd'is sealed in saids'ec tion with a plasticadhesive. The adhesive 29 "extends into notch 33in casing section- 26 wine outer face of ring 3 In fabricatingthe's'witch, eap5il is secured in the casing-section 25 with the terminal f5] confined between the cap and said section. The pin'48 is inserted through tongue's45" to connect the lever 40 to section '25. Thef rnerci1ry130is poured into section 26 while it is horizontal and sections 25 and 2B are as'sembled'together with ring 3 between them. Thecasing is then-closed "by placing the plastic adhesive 29 or sealing {material in the peripherabV-shaped"groove bee tween said sections-so they will be secured and sealed together. The terminal-0111134; maytheii the secured by screw 36 in "contact with thee'xtension 32 on casing se'ctionifi. 'Thefretaine'r I5 is then placed around the casing so it will be confined in slots 20 'andfZ'I of'the retainer arid the assembled casing andretain'er are placed iii the box. The casing will becentrally positioned the box. The pitchisthenfpo ired into the box until it is filled. Th'epitc'h will flow 'con'r-f pletely around'the'switch casing, the terminal clips 34,- and the portions of the eonductors :alfid53 in the bOX to protect the swi tch froin moi's ture-in the ground inwhich the box is usually installed.

"The operationof the switch is 'as'foubws: "The balanced bar-magnet 4] and lever 4|! are'nor inally freely suspended from 'p'ivotrpiinw, 'fo'r swinging movement, in 'oppositedirctions from their horizontal position and both'offlthe'coh tact-points 4! are then withdrawn from the pool 30. The circuit'between outside-comm tors 3'5 and 53 will then .be'interrupteclbetween pool 30'an'd contact pointsffl. v

"The =bar magnet 4 is surrounded "by'a "poweb r111 magnetic field projectinginto the-space above ground level. When a vehicle which is made in part, of magnetic material, approaches the switch, it affords a low resistance path for this magnetic field through its metal parts and thereby creates an attraction between itself and one end of the bar-magnet. This attraction causes lever to swing from its normal horizontal positiony until one'or the ether yer e-contact points 'di'ps'iiito' the pool 6f mercury. "The end 0f the bar-magnet 4| nearest the approximate magnetic center of the vehicle, will be lifted, while-the opposite end of the lever 40 is lowered to shift its contact 41 into the pool of mercury. will close the following circuit: conductor 35, clip'34, ring 3|, cap 50, clip 5| and conductor 53. The balanced magnet and lever are freely an d centrally suspended, so that one of their endsis-movable upwardly while their opposite end moves downwardly. As a result, either end of the bar-magnet may be attracted upwardly bythevehicleto lower thecontactpoifif'fl at theopposite end into the pool,"to' Cl'osetheir cuit. In this construction, the single "leveraiid m'agnetwill function to close'th'e s'witch whe'n a vehicle is travelling in the magnetic fieldfiat either side of the switch, or is -approachi'r1. z"a'n" d travelling away from the switch. The leveranfd .bar being :balanced and suspended fro'm'pin 48, are extremely sensitive to the 'attra'ctionpf'the 'vehicle. The lever in wnirmam shirted an'd keep this circuit closed until themov'in'g'vehlcile passes out of the-magnetic'field, whereupen "the attraction between the vehicle and the barnagnet will cease and lever 40' and saidmagnet will swing back to theinbalanced or horizontal position and withdrawthe submerged contact point t! from the pool bf mercury to open-ssh circuit.

The switch is particularly adapted for iriistalla tion in the ground for operation responsive lyto 'theapproa'ch of a vehicle-which is made inpart, of-a magnetic material. A characteristicof the invention is that the sw'iteh box, with the casing *therein, need not be installed in the ground-with accuracy to maintain the casmg-m 'a veamh "plane, for the movement -of the switc'ah lever by gravity and maintaining its'operative "relation with the pool of mercury. "For examplejtheb'ox may be installed in difierent angular positions in the groundwhile its'sides are vertical or the axis of pin 48 remainshor-i'z'on-tal, because'the operative relation of the mercury-and'le ver will sbe maintained, because the pool of 'Inerc'ury'is free to flow by gravity circumferentially'tothe lowest portion of the chamber in the casing-and lever 40 will remain free to swing by gravity into parallelism with the top surface of thepool-of mercury in different circumferential proportions of-said chamber. This relationship "will be maintained even if the box is installe'dso the-conductors 35, 53 lead laterally to the boxer-the sides of the box extend horizontally -in the ground so long as the axis of pin 48 remains substantially horizontal. In-all positionsthe lever 4|) will be pivotally suspended-so it will normally "remain parallel with the surface of theliquid, and the contact points'd'l will be positioned for closing the circuit between the lever and the mercury when magnet 4| isinfiuenced by attraction from an external source. The box may also'be positioned in "the ground "with limited transverse angular variation. For example, until the box is angularl'y' disposed inthei'groiind "so the axis of pivot pin"48isincliriedfro th'e'ho'rizo'ntal nearly 30 "degrees, the =1ever-wln-r nam free for pivotal movement to its normal position by gravity and to close the circuit when the magnet 41 is attracted out of its balanced or normal position. These attributes are advantageous, particularly when the box is installed under a concrete roadway through a small tunnel or elongated opening where inaccessibility and necessity for packing the soil around the box make it difiicult to accurately position the box in the ground. Furthermore, after installation, the box is sometimes displaced by frost or other ground conditions, and when this occurs, the Operative relation of the switch-lever and mercury will be maintained.

The invention exemplifies a magnetic ground switch with a casing formed of sections sealed together with a conductor-ring between them. The invention includes a retainer for the casing with a filler mass poured into the box to completely surround the casing. The switch-lever may be formed of sheet metal and with integral contacts and magnet retaining tongues. The invention also exemplifies a magnetic switch of this type which is simple in construction and is effectively protected against short circuiting by seepage of moisture from the ground from which the switch is embedded.

The invention is not to be understood as restricted to the details set forth, since these may be modified within the scope of the appended claims without departing from the spirit and scope of the invention.

Having thus described the invention, what I claim as new and desire to secure by Letters Patent is:

1. A switch comprising: a casing including a pair of sections having sides and annular mating, substantially cylindrical rims secured together, defining a closed, substantially cylindrical chamber containing a pool of conductor liquid; a pivot pin co-axial with, and substantially horizontally disposed in, the chamber; a balanced lever pivotally supported by said pin and free, for tilting movements in opposite directions from its normal horizontal position and provided with contacts at its opposite ends normally out of and movable respectively into the liquid upon swinging movements of the lever in opposite directions, a balanced, permanent magnet on the lever respongether, defining a closed, substantially cylindrical chamber containing a pool of conductor liquid; a pivot pin co-axial with, and substantially horizontally disposed in, the chamber; a balanced, freely suspended lever pivotally supported by said pin, for tilting movements in opposite directions from its normal position and provided with contacts at its opposite ends, normally out of and movable respectively into the liquid upon swinging movements of the lever in opposite directions, a balanced, permanent magnet on the lever responsive to attraction caused by magnetic objects approaching the switch in different directions and adapted to shift the lever in opposite directions, a conductor ring extending into the liquid in said chamber and confined between the rims of the casing sections, and provided with an integral extension to the outside of the casing, said pin and lever being connected for electrical conduction, an annular seal between the rims of the casing sections outwardly of the ring, a conductor connected to said extension, a second electrical conductor on the outside of the casing and electrically connected to the pivot pin, the conductor element extending circumferentially around the chamber for maintaining operative contact between said element and the liquid, when the switch is installed with the pool in differential circumferential positions in said chamber.

3. In a magnetic switch, a pair of easing sections forming a chamber, a liquid electric conductor in said chamber, an electric conducting member extending into said casing, an electric a conducting switch member pivotally supported on sive to attraction caused by magnetic objects ap- U proaching the switch in difierent directions and adapted to shift the lever in opposite directions, an annular conductor element extending into the liquid in said chamber and confined between the casing sections, and provided with a connection to the outside of the casing, said pin and lever being connected for electrical conduction, a conductor connected to said connection. a second electrical conductor on the outside of the easing and electrically connected to the pivot pin, the annular element extending circumferentially around the chamber for maintaining operative contact between said element and the liquid, when the switch is installed with the pool in different circumferential portions of the chamber.

2. A switch comprising: a casing including a pair of sections having sides and annular mating, substantially cylindrical rims secured tosaid conductor member within said chamber, a bar magnet carried by said switch member, said bar magnet normally being balanced on said conductor member above the level of said electric conducting liquid, a downwardly directed contact carried by said switch member on each side of the fulcrum thereof, and an electric conductor ring held by and between said casing sections in contact with said liquid conductor and in the plane of tilting of said pivoted switch member.

CHARLES BELSKY.

REFERENCES CITED UNITED STATES PATENTS Number Name Date 613,794 Brown Nov. 8, 1898 1,293,441 Housekeeper Feb. 4, 1919 1,333,004 Vaugh Mar. 9, 1920 1,558,277 Phelan Oct. 20, 1925 1,564,840 Faber Dec. 8, 1925 1,725,291 Moore Aug. 20, 1929 1,992,214 Katz Feb. 26, 1935 2,052,911 Weathers Sept, 1, 1936 2,101,092 Payne Dec. '7, 1937 2,149,998 Jones Mar. 7, 1939 2,337,468 Hilger Dec. 21, 1943 FOREIGN PATENTS Number Country Date 117,634 Switzerland Nov. 16, 1926 119,086 Great Britain Sept. 19, 1918

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