Adjustable latch for a relay

Abstract

A magnetic latch for use with relay is provided. In one embodiment of the invention, a latch which can be assembled to a standard relay in the field is provided for latching the relay in a predetermined position. The latch is magnetically biased toward a latching position to follow the movement of the movable contact in the relay and to latch the relay when in the selected position. A spring can be added to bias the latch towards a latching position. The movable contacts of a standard relay are spring biased by a force which is less than that provided by the disclosed magnetic latch. An electric coil is provided for opposing the magnetic flux generated in the latch permitting the spring provided in the standard relay to move the magnetic latch to an unlatched position. In a second embodiment of the invention a magnetic latch for a relay is provided which is latched by a permanent magnet in the open or closed position. The latch includes an armature which is held in the open or closed position by means of two permanent magnets. A coil disposed around the armature can be energized to change the position of the magnetic latch. The direction of movement of the armature is determined by the direction of current flow through the coil and this is controlled by a diode switching arrangement.

Description

BACKGROUND OF THE INVENTION

This invention is related to a magnetic latch for use with an electric relay. More particularly, this invention is concerned with a magnetic latch utilizing permanent magnets to seal the latch in a predetermined position and an electric coil to overcome the magnetic flux generated by the permanent magnets permitting the latch to change positions.

Standard low voltage relays require a latch which can follow the rectilinear motion of their operator. It is desirable that the position of the latch be capable of being rapidly switched. Rapid switching operation has been a problem with prior art relay latches. For standardization and field assembly applications, it is desirable that the magnetic latch be adjustable to fit a variety of standard relays. In some applications it is desirable that the magnetic latch sense the position of the movable contacts in the standard relay and latch in the desired position. it is also desirable that the latch be of a simple reliable construction having a minimum number of parts.

SUMMARY OF THE INVENTION

In one embodiment of the invention a latch for use with an electric relay is provided having a housing formed of a magnetizable or ferromagnetic material with a core formed also of a ferromagnetic material being disposed within the housing. The core is movable between a latched position in contact with the housing and an unlatched position where the core does not contact the housing. The permanent magnet is disposed within the housing between the housing and the core so as to form a magnetic circuit through the core and housing when the core is in contact with the housing. This magnetic circuit securely latches the core to the housing. The permanent magnets bias the core toward a latched position in contact with the housing. A spring may also be provided to aid in biasing the core towards a latched position in contact with the housing. An electric coil which when energized opposes the flux generated by the permanent magnet is disposed around a portion of the core. When the electric coil is energized, the core is freed from contact with the housing and can be moved to the unlatched position. This latch is particularly adaptable for use on a standard relay consisting of a series of moving and stationary contacts in which the position of the moving contacts are controlled by a spring loaded cross bar which is moved electromechanically to the open or closed position. The disclosed magnetic latch is provided with a latch arm which extends from the core and can follow the movement of the spring loaded cross bar used in the standard relay. When the standard relay moves to a position where the core of the magnetic latch contacts the housing, the magnetic latch latches and the standard relay is held in this position. When the coil is energized, the force of the permanent magnets is bucked and the core will move due to the force generated by the cross bar return spring provided in a standard relay.

The core has a threaded opening formed therein which is engaged by a threaded portion provided on the latch arm. Thus, the length of the latch arm can be adjusted by threading the latch arm in or out. An extension can be provided on the latch arm which can be rotated to adjust the length of the latch arm. The disclosed magnetic latch is capable of rapid operation. The disclosed latch also has a low power consumption in that only a short current pulse is required to unlatch the disclosed magnetic latch.

In another embodiment of this invention, a magnetic latching relay is provided. In this embodiment, the movable contacts of the relay are latched by permanent magnets in the open position and in the closed position. A movable core is supported for rectilinear motion inside a ferromagnetic housing. The movable contacts of the relay are connected to the core to change positions in response to core movement. The core is held in the open or closed position by permanent magnets which are disposed in the housing between a portion of the core and the housing. A coil is wrapped around the core and movement of the core between the open and closed position is accomplished by applying current, of the proper polarity, to the coil. The direction of throw of the coil is dictated by the direction of the current flow through the coil. A pair of diodes serving as a directional switch are provided to select the direction of current flow and thus determine the direction of movement of the core, coil and contact assembly. When the coil is not energized, the core is sealed in either the open or closed position by the permanent magnets.

It is an object of this invention to provide a magnetic latch for use with an electric relay which is capable of rapid repeated operation.

It is a further object of this invention to provide a magnetic latch of a simple rugged construction which is adjustable to be mounted on a variety of standard relay configurations.

A still further object of this invention is to provide a latch which can be sealed in position by permanent magnets and which requires a small amount of energy for release.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, reference may be had to the preferred embodiments exemplary of the invention shown in the accompanying drawings, in which:

FIG. 1 is a top view of a magnetic latch utilizing a teaching of the present invention with portions broken away for clarity;

FIG. 2 is a side sectional view of the magnetic latch shown in FIG. 1 in the latched position;

FIG. 3 is a view similar to FIG. 2 with the magnetic latch in the unlatched position;

FIG. 4 is a side sectional view of a relay utilizing another embodiment of the invention; and

FIG. 5 is a view similar to FIG. 4 with the relay in the open position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings and FIGS. 1, 2 and 3 in particular, there is shown a magnetic latch 10 utilizing the teaching of the present invention. The magnetic latch 10 comprises a core 12 which is supported for movement along its longitudinal axis and a housing 14 which partially surrounds the core 12. The core 12 and the housing 14 are both constructed from a ferromagnetic material. A pair of permanent magnets 16 are disposed within housing 14. Permanent magnets 16 are disposed with one pole, formed along side 15, facing housing 22 and the other pole, formed along side 17, facing core 12. The poles formed along side 17 facing core 12 are of the same polarity--either both north poles or both south poles. When magnetic latch 10 is in the latched position as seen in FIG. 2, the permanent magnets 16 set up a magnetic flux path through magnetizable ferromagnetic core 12 and magnetizable housing 14, to securely hold core 12 to housing 14. An electric coil 18 is provided surrounding a portion of core 12. Electric coil 18 when energized generates magnetic flux through core 12 in opposition to the magnetic flux provided by permanent magnet 16. This permits the magnetic latch 10 to be moved to the unlatched position.

Housing 14 has a generally U-shaped configuration with two leg portions 20 and 22 and a bight portion 24 connecting leg portions 20 and 22. An opening 26 is provided through bight portion 24. A portion of latch arm 28 extends through the opening 26 formed in bight portion 24. The magnetic latch 10 can be connected to a standard relay 50, a portion of which is schematically indicated with phantom lines. Standard relay 50 includes a set of stationary contacts 52, a pair of movable contacts 54 which engage stationary contacts 52 and a bridging member 56 which support contacts 54. Bridging member 56 is connected to an insulating cross bar 58. Cross bar 58 is spring biased by spring 60 toward an open position. Standard relay 50 can be closed by an electromechanical operator (not shown). When standard relay 50 moves to the closed position as shown in FIG. 2, latch arm 28 follows the movement of cross bar 58 so that when contacts 52 and 54 engage magnetic latch 10 is sealed with core 12 in engagement with housing 14. The force with which permanent magnets 16 latch core 12 to housing 14 is greater than the force provided by cross bar biasing spring 60 and the standard relay 50 is thus held in the closed position. When coil 18 is energized, the force of magnets 16 is bucked and the core 12 will now move up due to the dominant force generated by the cross bar return spring 60.

Latch arm 28 is provided with a threaded portion 30 which engages a threaded portion 32 of core 12. The threaded engagement between core 12 and latch arm 28 permits the distance which latch arm 28 extends from the bight portion 24 of housing 14 to be adjusted. This allows magnetic latch 10 to be used with various standard relays 50 which require different lengths of operating arm 28.

A top cover plate 40 having an opening 42 formed therein is provided. Cover plate 40 is formed from a non-magnetic material such as brass or an electric insulator. Cover plate 40 is secured to flange portion 44 extending from housing 14. Screws 46 can be used to secure cover plate 40 to housing 14. A spring 34 seated at one end against cover plate 40 and at the other end against core 12 may be provided to urge core 12 toward the latched position. Since cover plate 40 is made from a non-magnetic material, permanent magnets 16 will generate a force component in core 12 urging core 12 toward the latched position. Permanent magnets 16 give a force in the downward direction and a small biasing spring 34 is not necessary when latch 10 is new but after several million operations due to wear it may be desirable to have a biasing spring 34 to assure that core 12 will rapidly and accurately follow cross bar 58. Coil 18 is wound on a spool 36 having a generally rectangular-shaped passage 38 extending therethrough. Core 12 has a generally rectangular outer periphery of a size slightly smaller than the rectangular opening 38 through spool 36. When the magnetic latch 10 is thus assembled, with a portion of core 12 extending into the rectangular passage 38 through spool 36, core 12 is effectively held against rotary motion with respect to housing 14. An extension 61 is connected to the threaded portion 30 of lever arm 28 and extends through opening 42 formed in end plate 40. The distance which latch arm 28 extends from the housing 14 can thus be varied by rotating extension 61. A slot 62 is provided in extension 61 for easy adjustment of latch arm 28. This adjustability feature permits the magnetic latch 10 to be used with a variety of standard relays 50.

Magnetic latch 10 requires a small amount of power for operation. The operating speed of magnetic latch 10 is very rapid. Magnetic latch 10 has been experimentally verified to have an operating speed of over 180 operations per minute. Extension 61 permits magnetic latch 10 to be manually latched or unlatched. The forces generated by permanemt magnets 16 and electric coil 18 when energized are equal and in opposition. Cross bar biasing spring 60 then moves core 12 to the unlatched position. Core 12 is biased by magnetic flux and in some cases spring 34 to follow and sense the position of contacts 54 and 52. Two magnets 16 and 18 set up two separate magnetic loops through a single pole core 12. The hold strength of the disclosed magnetic latch 10 is a function of a variable air gap. This helps magnetic latch 10 to achieve a far superior operating speed upon unlatching than that of the prior art. Tests have shown this magnetic latch 10 to accomplish an excess of 180 latches and unlatches per minute.

Referring now to FIGS. 4 and 5, there is shown a latching relay 70 illustrating another embodiment of this invention. A movable core 72 is disposed within a housing 74. Movable core 72 is movable along its longitudinal axis between a latch closed position shown in FIG. 4 and a latched open position shown in FIG. 5. Movable core 72 and housing 74 are formed from ferromagnetic or magnetizable material. A spool 76 formed from a non-magnetizable material partially surrounds the core 72. Core 72 is held in the open or closed position by permanent magnet 78. Permanent magnet 78 forms a magnetic path through core 72 and housing 74 to latch core 72 in the open or closed positions. A coil 80 is wound around spool 76. Movement of core 72 from the open to the closed position or vice versa may be accomplished by application of power to coil 80. Core 72 is connected to a bridging member 156 made of non-magnetic material which supports movable contacts 54. The bridging member 156 thus completes a circuit between movable contacts 54. In the closed position movable contacts 54 engage stationary contacts 52. Diodes 82 and 84 are provided for selecting the direciton of current flow through coil 80. The direction of the throw caused by coil 80 will be dictated by the direction of current flow through coil 80. The force generated by coil 80 when energized overcomes the force due to permanent magnet 78 and switches the position of core 72. Core 72 is then latched in the switched position by permanent magnet 78. Direction of current flow, through coil 80, as permitted by diode 82 or 84 will determine the position of core 72. An extension 88 of non-magnetic material is provided extending from core 72 to permit manual operation of relay 70. Relay 70 is constructed for rapid switching operations.

Claims

We claim:

1. A latch comprising:

a housing formed of a magnetizable material;

an elongated core formed of a magnetizable material disposed within said housing and being movable between a latched position wherein said core is in contact with said housing and an unlatched position wherein said core is not in contact with said housing;

a magnet disposed within said housing between said housing and said core so as to form a magnetic circuit through said core and said housing when said core is in contact with said housing to securely hold said core to said housing;

said magnet disposed with the north-south pole of said magnet aligned substantially perpendicular to the longitudinal axis of said core;

biasing means for biasing said core towards the latched position;

an electric coil, disposed in said housing, which when energized opposes the magnetic circuit formed through said core by said magnet permitting said core to be moved to the unlatched position;

said housing has a generally U-shaped cross-section with a bight portion connecting the two legs of said U-shaped housing;

said core disposed within said housing for movement along its longitudinal axis between a latched position in engagement with the bight portion of said U-shaped housing and an unlatched position spaced from the bight portion of said U-shaped housing;

an end plate formed from non-magnetic material connecting the free ends of the legs of said U-shaped housing;

said housing having an opening formed in the bight portion;

a latch arm extending from said core through the opening in the bight portion of said housing;

said latch arm being secured to said core to move in unison with said core;

said core having a longitudinal threaded opening formed therein; and

said latch arm includes a threaded portion which engages the threaded opening formed in said core so that the distance which said latch arm extends from said latch can be varied.

2. A latch comprising:

a housing formed of a magnetizable material;

an elongated core formed of a magnetizable material disposed within said housing and being movable between a latched position wherein said core is in contact with said housing and an unlatched position wherein said core is not in contact with said housing;

a magnet disposed within said housing between said housing and said core so as to form a magnetic circuit through said core and said housing when said core is in contact with said housing to securely hold said core to said housing;

said magnet disposed with the north-south pole of said magnet aligned substantially perpendicular to the longitudinal axis of said core;

biasing means for biasing said core towards the latched position;

an electric coil, disposed in said housing, which when energized opposes the magnetic circuit formed through said core by said magnet permitting said core to be moved to the unlatched position;

said housing has a generally U-shaped cross-section with a bight portion connecting the two legs of said U-shaped housing;

said core disposed within said housing for movement along its longitudinal axis between a latched position in engagement with the bight portion of said U-shaped housing and an unlatched position spaced from the bight portion of said U-shaped housing;

an end plate formed from non-magnetic material connecting the free ends of the legs of said U-shaped housing;

said housing having an opening formed in the bight portion;

a latch arm extending from said core through the opening in the bight portion of said housing;

said latch arm being secured to said core to move in unison with said core;

said core having a threaded longitudinal opening formed therethrough;

said end plate having an opening formed therein;

said latch arm includes a threaded portion which engages the threaded opening formed in said core so that the distance which said latch arm extends from said latch can be varied; and,

an extension extending from the threaded portion of said latch arm through the opening in said end plate whereby the distance which said latch arm extends from said latch can be varied by rotating said extension.

3. A latch as claimed in claim 2 wherein:

said electric coil surrounds a portion of said core.

4. A latch as claimed in claim 3 including:

a spool having a generally rectangular opening therethrough around which said coil is wound;

said core having a generally rectangular cross-section which fits in the generally rectangular opening in said spool to prevent relative rotational movement of said core with respect to said spool; and,

said spool is fixed with respect to said housing.

5. A latch as claimed in claim 4 wherein:

said spring is of the coil variety and is disposed around said extension; and,

said magnet is of a flat rectangular shape.

6. A latch comprising:

an elongated core formed from a ferromagnetic material and being movable between a latched and an unlatched position;

biasing means urging said core towards the latched position;

magnetic sealing means, comprising a flat rectangular permanent magnet disposed with the north-south magnetic axis perpendicular to the longitudinal axis of said core, to form a magnetic flux path through said core when said core is in the latched position to magnetically retain the latch in the latched position;

an electric coil disposed so as to buck the magnetic flux path in said core formed by said magnetic sealing means when energized allowing said core to be moved to the unlatched position;

a housing having a generally U-shaped cross section formed from a ferromagnetic material and containing said core and said magnetic sealing means within the confines defined by said housing;

said coil disposed around a portion of said core and being fixed relative to said housing; and,

a latch arm adjustably secured to said core and extending from said housing.

7. A latch as claimed in claim 6 wherein:

said latch arm is threadably secured to said core; and,

an extension rigidly secured to said latch arm and extending from said housing so that the distance said latch arm extends from said latch can be varied by rotating said extension.