US 2440861 A
Description (OCR text may contain errors)
May 4, 1948.
A. H. LAMB RELAY CIRCU IT Am) RELAY Filed Sept. 25, 1944 Patented May 4, 1948 RELAY CIRCUITS Anthony E. Lamb, Hillside, N. 3., assignor to Weston Electrical Instrument Corporation, Newark, N. 3., a corporation of New Jersey Application September 25, 1944, Serial No. 555,696
9 blaims. i
This invention relates to relay circuits and relays, and particularly to relay circuits and relays in which a closure of the relay contacts is positively prevented until a definite operative step is taken to condition the relay for a circuitclosing operation.
It is desirable in certain instances to complete some or all of the relay circuit connections during the installation of a relay system but, for various reasons, it may be necessary to prevent an inadvertent closure of the controlled circuit or circuits from rough handling or shaking of the relay, from an accidental current supply to the relay coil, or from any other casual cause prior to the completion of the installation and the establishment of definite safety operating conditions. This problem may arise, for example, in relays for marine mines that are to be fired by remote control or automaticallyupon the occurrence of a preselected condition.
Objects of this invention are to provide relay circuits and relays that are full safety or positively blocked against circuit closure unless and until a predetermined operative step is taken to condition the relay circuit and relay for normal operation. An object is to provide relays in which the moving contact arm is positively held out of engagement with the fixed contact or contacts by blocking members that may be rendered inoperative, if and when desired, by closing an auxiliary or safety-release circuit. More specifically, an object is to provide a sensitive instrument type relay having a resilient blocking member or members initially positioned to prevent engagement of the relay contact arm with a fixed contact or fixed contacts, the blocking member or members being biased for movement out of the path of the relay contact arm but initially held in blocking position by a fusible connection that may be melted by a preselected current through the same. A further object is to provide a relay with thermally releasable blocking members of the character above described that are spaced apart to permit a limited movement of the relay contact arm for continuity and/or other tests of the relay circuit. Another specific object is to provide a. relay with initially operative blocking mechanism of the type stated, the blocking mechanism being mounted on a cover plate that may be removed and replaced without disturbing the basic relay circuit connections.
These and other objects and advantages of the invention will be apparent from the following specification when taken with the accompanying drawings in which:
' which certain relay elements are illustrated as viewed in section on the plane indicated by section line 2-2 of Fig. 1;
Fig. 3 is a plan view of an instrument relay that includes another form of blocking mechanism; and
Fig. 4 is a fragmentary perspective view, on a.
larger scale, of the blocking mechanism of the Fig.3relay.
In Figs. 1 and 2 of the drawing, the reference numeral l identifies the contact arm carried by the relay moving coil 2 for cooperation with a low" contact 3 and/or a high contact 4. The coil 2 is mounted for angular movement in the interpolar space of a permanent magnet 5 in response to the current established through the coil by a primary control circuit that is shown schematically as including a current source 6, a switch I and a variable impedance device 8. The controlled circuit or circuits of the relay are connected between the movable contact arm I and the fixed contacts 3 and/or 4, and include a current source 9 and signal or control elements in, H of any desired type between the fixed contacts,3. 5 respectively and the current source.
The several relay and relay circuit elements as so far described may be of any conventional or desired type. In accordance with this invention, safety mechanism is incorporated in the relay to prevent an inadvertent closure of the controlled relay circuit or circuits prior to the deliberate release of the safety mechanism. The safety mechanism, as illustrated in Figs. 1 and 2, comprises a. pair of spring members l2, l3, of hairpin form in unstressed condition, at opposite sides of the contact arm I. The spring members each have one arm mounted on the relay base It, the other arms of the spring members are turned upwardly and retained in substantially vertical position bya connecting link l5 of fine fuse Wire that is soldered to the spring members. The fuse wire I5 is in series with a current source l6 and switch i! that may be closedmanually to send current through the fuse Wire to melt the same, thereby permitting the blocking arms to rotate into inoperative positions, as shown in dotted line in Fig. 2, to permit free movement of the relay contact arm I.
The blocking members I2, I3 prevent a closure of the relay contacts through shock, vibration or current in coil 2 so long as the members I2, is are tied to each other by the fusible link l5.
The inadvertent completion of the controlled relay circuit or circuits is therefore initially prevented, and the relay system may be set up and all circuit connections completed and checked without danger of a premature energization of the controlled device or devices III, II.
A preferred embodiment of the invention, as illustrated in Figs. 3 and 4, includes a pair of resilient blocking members fixed to circuit terminals l8 mounted on and extending through an insulating cover plate 19, preferably transparent as shown, that is bolted to the relay casing 20. The blocking members are of fine spring wire of approximately-L-shape, as viewed in side elevation, with horizontally extending arms 21, 2| that terminate in downwardly extending arms 22, 22'. The spring members are normally retained infixed spaced relation by a fuse wire 23 that is soldered to the resilient members. The vertical arms 22, 22 are spaced apart to permit angular movement of the contact arm I through a limited angle a that is not sufficient to permit engagement of the contact arm with either of the fixed contacts 3, 4. Movement of the contact arm I within this restricted range permits testing of the relay circuit for continuity, and the angular displacement of the contact arm I under the test conditions may be observed through the transparent cover plate I9 to check the sensitivity of the relay. The safety system may be removed from the relay as a unit, and without disturbing the relay circuit connections, by unbolting and removing the plate I9 that carries the blocking members. The magnetic structure, moving coil, and all electrical connections of the relay circuits are'mounted in the usual manner on the relay base, not shown.
In order to render the relay operative, the fuse Wire 23 is caused to melt by passage of a current of electricity therethrough from a source of current (not shown) connected to the fixed circuit terminals i8-I 8'. Upon melting of the fuse wire, the blocking members spring apart, owing to the inherent resilience of the wire from which they are made, and the vertical blocking arms 22-22 assume positions outside of the sector of swing of the contact arm I, thus permitting normal functioning of the relay.
The invention is not restricted to the embodiments herein illustrated and described as there is considerable latitude in the design and mounting of the blocking members within the scope of the invention as set forth in the followingclaims.
1. In a relay circuit, the combination with a relay having a moving contact arm cooperating with a relatively fixed contact, a primary circuit for energizing said relay to displace said contact arm towards said contact, and a controlled cir cuit including said contact arm and contact, of safety means normally preventing engagement of said contact arm with said contact, said safety means including a blocking member initially in the path of movement of said contact arm, means biasing said blocking member for movement to a position outside the path of movement of said contact arm, a fuse wire normally retaining said blocking member in the path of movement of said contact arm, and means for establishing a current through said fuse wire to melt the same.
2. A relay having a contact arm movable to' engage a fixed contact, electric motor means including a pivoted coil and a moving said contact arm, mechanical means normally positioned to block movement of said contact am into engagement with the fixed contact, said mechanical means including means biasing the same towards movement out of said blocking position, and fusible means normally retaining said mechanical means in said blocking position.
3. A relay as recited in claim 2 wherein said mechanical means comprises a spring arm, and said fusible means comprises a fusible wire normally retaining said spring arm in the path of movement of said contact arm.
4. A relay as recited in claim 2 wherein said mechanical means comprises a pair of spring members atopposlte sides of said contact arm, and said fusible means comprises a fusible link mechanically retainingmortions of said spring members in blocking position, the resilience of said spring members biasing said blocking portions for movement out of the path of said contact arm.
5. A relay as recited in claim 2 wherein said mechanical means comprises a pair of spring members of hairpin shape when in unstressed condition.
6. A relay as recited in claim 2 wherein said mechanical means comprises a pair of spring wires of approximately L-shape.
7. In a relay, the combination with a magnetic structure, a moving system, said moving system including a contact arm cooperating with a fixed contact, and a casing housing said magnetic structure and moving system; of safety means comprising a resilient arm biased for movement out of the path of said contact arm, fusible means normally retaining said resilient arm in the path of said contact arm to prevent engagement of the same on said fixed contact, and circuit terminals carried by said casing and connected electrically to said fusible means, whereby a current may be established through said fusible means to melt the same and release said resilient arm for movement out of the path of the contact arm.
8. In a relay, the invention as recited in claim 7, wherein said casing includes a transparent cover on which said circuit terminals are mounted, and said safety means comprises a pair of resilient wires carried by said circuit terminals.
9. In a relay, the invention as recited in claim 7, wherein said casing includes a transparent cover on which said circuit terminals are mounted, said safety means comprises a pair of resilient wires carried by said circuit terminals, and said resilient wires have portions normally retained in spaced positions at opposite sides of said contact arm by said fusible'means.
ANTHONY H. LAMB.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS fixed magnet for