Description:
BACKGROUND OF THE INVENTION
This invention relates to an improvement in the design of electromechanical relays and, more particularly, to an improved self-holding remanent reed relay.
For many years the mainstay of switching and logic circuits has been, and in all probability will continue to be the well-known electromechanical relay which consists of a magnetic flux-producing coil of wire and at least one contact pair operable in response to the generation of the magnetic flux. In order to achieve the operational speeds necessary to make relays compatible with transistor circuitry, special types of relays, namely, reed relays, have been designed having a pair of make contacts (reeds) inside a glass-enclosed vessel, the reeds being of a magnetically soft material. Such a relay is disclosed in U. S. Pat. No. 2,995,637 issued on Aug. 8, 1961 to A. Feiner, C. A. Lovell, T. N. Lowry and P. G. Ridinger.
Numerous improvements have been made to such reed relays to improve time-response characteristics and to provide for self-holding capability where a current pulse through the wire coil causes the relay to operate and to remain operated until a second current pulse is applied. One type of self-holding relay has contacts made from a magnetic material which, when exposed to a magnetic flux, will assume a magnetic state and will remain in that state until exposed to a magnetic flux of an opposite direction. These relays are called remanent reed relays, or remreed relays for short. An example of such a relay is taught by U. S. Pat. No. 3,037,085 issued to T. N. Lowry on May 29, 1962.
Although remreed relays are beginning to find wide acceptance among circuit designers, a problem exists with the currently available relays; namely, the fact that the current pulse which operates the relay (closes the contact pair) must, in fact, be a dual pulse applied to two windings concurrently. This results from the fact that the application of current to a single winding of the relay causes the relay to release. Thus, from a circuit design standpoint, provision must be made for supplying two simultaneous pulses of current. While in certain applications, such as in selectable matrix arrays, it may be desirable to operate a relay only upon coincidence of pulses, in logic circuitry such a result is difficult and costly to achieve.
Accordingly, it is one object of our invention to provide a self-holding remanent reed relay capable of single-pulse selective operation.
A further problem exists in that, with remanent reed relays, the pulse magnitude is critical. For example, if the relay is operated and a current pulse is applied to a release winding, the pulse must enable the release of the relay without remagnetizing the remanent magnetic material and causing the relay to reoperate. The Lowry patent referred to above is directed, inter alia, to just such a problem by teaching the use of two windings wound in opposite directions and connected together in series to form a pair of control windings. The two windings of each pair have different magnetic flux densities generated and are wound in opposition to each other so that a single current pulse always produces a constant resultant magnetic flux. Under this arrangement, a magnetic shunt plate is necessary between the windings to insure that the magnetic flux generated by the respective windings folds back around the associated contact of the contact pair. The use of such a shunt is costly from a materials standpoint, adds unwanted weight to the relay, and increases the assembly time.
Accordingly, it is another object of our invention to provide a remanent reed relay having magnetic flux-producing windings which prevent over-demagnetization while at the same time eliminating the need for shunt plates between the windings.
SUMMARY OF THE INVENTION
These and other objects of our invention are achieved by arranging one or more pairs of remanent reed contacts with a matched pair of magnetic flux-producing windings with one winding over each contact of the contact pair. The windings are separated from each other by an air gap and connected together in series so that an applied current pulse causes a magnetic field to be produced around one contact in one direction and around the other contact in the other direction. The resultant magnetic flux is such that the free ends of the contact pair (or pairs) are magnetized to the same magnetic pole and thus separate.
The magnitudes of the flux produced by the windings are equal so that the magnetic field produced by one causes the magnetic field produced by the other to fold back around the associated contact. Accordingly, in our arrangement each magnetic field becomes, in effect, a barrier to the magnetic field of the other, thereby eliminating the need for an actual physical shunt plate between the windings.
Each relay also contains a third winding wound in association with one of the other two windings and wound in a manner to produce a magnetic flux magnitude greater than the magnetic flux generated by the associated other winding and having a flux direction opposite to the flux direction produced by the associated other winding. The relay is designed so that a single current pulse flowing through the operate winding as well as through the release windings causes the relay contacts to close while a current pulse flowing only through the release windings causes the relay contacts to separate. Thus, the relay is capable of single-pulse destructive operation.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an overall view of one embodiment of our relay showing the cover removed;
FIG. 2 is a schematic representation of our relay showing one contact set in conjunction with two release windings and an operate winding;
FIG. 3 is a schematic representation of our relay showing the direction of the magnetic flux fields produced by each of the release windings; and
FIG. 4 is a schematic representation of our relay showing the magnetic flux fields produced by the release windings in conjunction with the operate winding.
DETAILED DESCRIPTION
As shown in FIG. 1, a plurality of reed contact sets or pairs 103, 104, 105 and 106 are shown surrounded by the magnetic flux-producing release windings 22 and 23, which windings are separated by an air gap 107. Also shown, and wound in conjunction with one of the release windings, 23, is the operate winding 24. Each reed bottle, such as bottle 103, contains two reed contacts, 20 and 21, and any number of such bottles may be positioned within the magnetic flux-producing windings. Each bottle contains a pair of reed contacts, such as reed contacts 20 and 21, extending through opposite ends of the bottle. Each reed contact consists of a remanent magnetic material exhibiting a plurality of stable magnetic states. These states are established exclusively by the magnetic flux fields produced by the associated winding coils. When the magnetic flux fields surrounding both reed contacts 20 and 21 are in the same direction, the free ends of the reed contacts have opposite polarities, thereby attracting each other and closing an electrical path through the relay. When the magnetic flux fields surrounding the reed contacts are in the opposite direction, the free ends of the reed contacts have the same polarities, thereby repelling each other and opening the electrical path through the relay.
Cover 10, which is shown removed, is ideally made from a highly magnetic material so that the flux produced by the operate winding 24 returns through the cover, thereby reducing the magnetic reluctance and so increasing the generated magnetic flux around the associated contact. Although the cover is not necessary for operation, increased sensitivity results dependent upon the magnetic permeability of the cover material. In situations where it is desired to eliminate the magnetic cover, such as in instances where it is desired to encapsulate the relay in plastic, the connecting wires or posts running lengthwise of the coil, such as post 108, can be constructed from iron wire so that they act as a return path for the magnetic fields generated.
In FIG. 2, there is shown a single contact bottle or vessel 103 having two reed contacts 20 and 21. When the reed contact pair is operated, the free ends of the contacts move together thereby closing the electrical path through the reed package. As shown, the uppermost release winding 22 is wound from left to right from terminal 32 to terminal 33. The lower release winding begins at terminal 33 and is wound from right to left, terminating at terminal 34. Thus, in a manner to be described hereinafter, a current pulse applied at terminal 32 creates a magnetic field in one direction around reed contact 20 and this same current pulse creates a magnetic field in the opposite direction around reed contact 21. If no other magnetic influence were to be exerted at this point, the free ends of reed contacts 20 and 21 would then separate, thereby opening or releasing the relay contact pair.
Operate winding 24 is shown in conjunction with lower release winding 23 and lower reed contact 21, and wound in a direction from left to right, which is opposite to the winding direction of release winding 23. Operate winding 24 extends from terminal 30 to terminal 31 and the application of a current pulse at terminal 30 causes a magnetic flux field to be generated around reed contact 21 in the same direction as the magnetic flux field produced by release winding 22. Thus, when release windings 22 and 23 are pulsed concurrently with the pulsing of operate winding 24, the magnetic flux field produced around each reed contact 20 and 21 is such that the free ends of the reeds will attract, thereby closing the contacts and operating the relay.
In one embodiment of our invention, release windings 22 and 23 would each consist of three layers of 32 gauge copper wire, each layer having 49 turns. Operate winding 24 would consist of six layers of 32 gauge copper wire, each layer having 49 turns. The operate winding should, of course, be separated from the release winding by suitable insulation.
Turning now to FIG. 3, the magnetic fields produced during the release operation of the relay will be described. Current applied from signal source 301 to terminal 32 of the relay flows from left to right through release windings 22 and 23 to ground applied via terminals 34 and 35. The current flow through release winding 22 generates a magnetic flux field 221 in a clockwise direction with respect to reed contact 20, thereby creating magnetic poles N and S, as shown. The current flowing through release winding 23 produces a magnetic flux field 231 and, with respect to reed contact 21, produces magnetic poles N and S, aS shown. Since the free ends of both reed contacts have the same polarity, they repeal each other, thereby separating. This separation prevents current from flowing through the reed contacts.
It should be noted that the magnetic flux field 221 produced by release winding 22 and the magnetic flux field 231 produced by release winding 23 are of equal magnitude and opposite in direction. Therefore, each magnetic flux field acts as a magnetic barrier to the other, thereby causing the other to loop around the associated contact, in the manner shown, with only an air gap between them. Because the magnetic flux fields are equal in magnitude, neither overpowers the other and, thus, magnetic shunt plates are not necessary.
As shown in FIG. 4, when ground is moved from terminal 35 to terminal 30, the current produced by signal source 301 passes through operate winding 24 as well as through release windings 22 and 23. The current passing through release windings 22 and 23 produces magnetic flux fields 221 and 231, respectively, in the manner discussed above. However, current flowing through operate winding 24 produces magnetic flux field 241 which, as shown, is produced in a direction opposite to the direction of magnetic flux field 231 produced by associated release winding 23. Since magnetic flux field 241 has a magnitude greater than the magnitude of magnetic flux field 231, the resultant magnetization of reed contact 21 is clockwise, thereby producing magnetic poles S and N, as shown. Since the free ends of reed contacts 20 and 21 are now magnetized to opposite magnetic polarities they attract, thereby operating the relay so as to allow current to pass through reed contacts 20 and 21.
It will be remembered that since reed contacts 20 and 21 are constructed of a remanent magnetic material each contact retains its last-set magnetic state so that at the termination of any current pulse the reeds will either remain open or closed dependent upon their last magnetic orientation.
Of course, the relay can be designed to operate on a long pulse or on a continuous-current basis if sufficient copper wire is used to provide the necessary flux density and to dissipate the resulting generated heat. However, since the advantage of the remanent reed concept is that the flux density to magnetize or reverse magnetize the reeds need exist only long enough to change the remanent magnetization of the reeds, the required flux density can so be obtained with a comparatively large current through a nominally small number of turns of wire. This wire should be only large enough in cross section to carry the current for a short time and thus the relay may be made smaller than continuous-current relays.
In conclusion, because of the diverse applications to which this relay may be applied, numerous physical structures can be devised by one skilled in the art taking advantage of the operational principles we have described without departing from the spirit and scope of our invention. In addition, it should be borne in mind that although our relay has been described with reference to a single contact, any number of contacts may be arranged in association with the release and operate windings. Also, the operate winding may have a different percentage relationship of magnetic flux with respect to the release windings from that detailed herein, again without departing from the spirit and scope of our invention.