US 2870287 A
Description (OCR text may contain errors)
United States Patent ELECTRICAL DEXICE Howard E. Corhitt, M0nrovlr.=,-Ralph M. Hill, Jr., Azusa, and David H. Bozarth, Downey, Calili, assignors to Aerojet-General. Corporation, Azusa, Califl, a corporation of Ohio Applicationi ebrnary 13, 1956, Serial No. 565,000
5. Claims. (Cl. ZOO-87) This invention relates to electrical relay switches and moreparticularly to relays of the type comprising magnetic reed contacts.
Switching devices are known in, which the switch contacts are-composed of reeds of magnetic material sealed within a tube or envelope such as glass, the reeds being operable by a coil around the envelope.
lt'is'oftendesirable to encapsulate such an envelope in a solid potting compound to protect it from moisture, breakage or other damage. Such a compound is ordinarily a resin which upon setting produces a strain of the envelope, thereby undesirably changing the relative posi- .tions. of the contacts.- Furthermore the encapsulating resinordinarily develops strains and volumetric changes with changes of temperature which produce corresponding undesirable strains of the envelope and contacts.
in accordance with the present invention, the envelope, or at least the ends where the contacts are supported, are encased or coated by a resilient or rubber-like compound having enough resilience to yield without bending the envelope. The encapsulating or potting material is applied over the envelope as it is already covered by the rubber-like material. By this construction much of the undesirable stresses which would otherwise operate to strain the envelope and move the reed contacts out of adjustment, are absorbed by the rubbery material; so that the adjustment of the reeds may easily be maintained.
The foregoing and other features of the invention will be better understood from the following detailed description and the accompanying drawings of which:
Fig. 1 is a cross-section View of an envelope containing magnetic reeds, taken at line 11 of Fig. 3;
Fig. 2 is a cross-section view taken at line 2-2 of Fig. l; and
Fig. 3 is a cross-section view showing the envelope of Figs. 1 and 2 with a coil around it and encapsulated in accordance with the present invention.
Referring to the drawings, there is shown an elongated closed substantially rigid envelope it), generally cylindrical in form and tapering at its ends. The envelope is preferably of substantially rigid material such as glass through the opposite ends of which there are sealed electrlcal conducting rods 11 and 12 aligned with each other coaxial with the longitudinal axis of the envelope. Electrical leads l3 and 14 are connected with the respective rods 11 and 32. Inside the envelope, reeds 15 and 16 of electrically conducting magnetic material are connected, as by soldering or welding, to the respective rods 11 and 12, the free ends of the reeds overlapping each other at about the central portion of the envelope and being somewhat spaced from each other. The envelope may, if desired be evacuated of air or other gas to permit sensitive movement of the reeds.
A coil 17 having terminals 20 and 21 is placed around the cylindrical portion of the envelope so that it surrounds the overlapping portions of the reeds.
The ends of the envelope have applied to them a coat- Patented Jan. 26, 1959 ing of a resilient rubber-like material 18 and 18a respectively. This may be done by dipping the ends of the envelope into a liquified compound or composition of a material which will solidify or harden'sornewhat in place, and be adherent to the surface of the envelope. This application of material 18 and 1811 should be sufficient to cover not only the ends oi the -envelope including rods 11 and 22, out also the ends of the coil. The composition 1.3 and 18:: may, for example, be a plastic material such as polymerized polyvinyl chloride. By dipping the envelope into the liquid monomer, enough of the material can be applied so that upon subsequent polymerizati'on there will be formed a substantial coating of material 18, 181:, having a consistency which is rubbery and re,- silient. While polyvinyl chloride is suggested as an efie'otive substance, 'it will be understood that other rubbery substances such as rubber itself or synthetic rubber or rubber-like plastic may be used instead so long as they have similar rubber-like and resilient physical properties.
After the substance 18, 18a has solidified, the entire assembly is encapsulated in a conventional manner in a suitable encapsulating or potting compound. The potting of electrical elements in this manner is well known and neens no further description here. Any of the well known potting compounds or substances may be used for the material 39. Suitable potting compounds for this purpose are, for example, the conventional epoxy type resins such as Epon 828, manufactured by the Shell Oil. Company, and Scotchcast Embedding Resin No. 2, ma-nufac tured by the Minnesota Mining and Manufacturing Company. This may be applied to the unit in any suitable manner as for example by dipping it into a container of the compound in a semiliquid form which will harden in place on the unit.
unit operates in a well known manner. The application of a voltage across the coil terminals 20, 21, produces a magnetic field which passes through the magnetic reeds l5 and 16, causing them to be attracted and to contact with each other. Such contact of the reeds can be used to close a circuit in a well known manner through the leads 13 and 14 which may be connected into any circuit as may be desired.
It will be recognized that by this invention there is provided a self-contained relay unit which is impervious to moisture and largely protected from shock, by reason of the encapsulating compound and coatings 18, 18a. The encapsulating medium 19 provides a mount for the relay coil 17 and the envelope which does not require the use of other mechanical supporting means. Thus, the weight of the relay is uniformally distributed rather than being supported at specific separated points which might produce strains which could get the reeds out of adjustment.
it has been the experience that the process of encapsulation has produced strains of the envelope due to stresses set up by the solidification of the potting compound. This has caused some distortion between the reed contacts. Such strains and consequent distortions has produced malfunctioning of the switch and has even made the switch contacts inoperative. Further cause of strains of the envelope is change of ambient temperature, which will strain the encapsulating material enough to strain the envelope.
The use of the rubber-like coating 18 and 18a, towards the ends of the envelope prevents the strains from the encapsulating compound from being transmitted to the envelope at 19. The resilience of compound 18, 18a is sufiicient to absorb such strain. Thus, the envelope itself is maintained free of strains which thereby enables the reeds to maintain their proper relative positions to each other to make and break contact properly. It has been found that the device can be maintained operative over temperature ranges of as much as minus 65 to plus F.
Particular advantages of this invention are had when the unit forms part of the system incorporating such elements as diodes, vacuum tubes, resistors, capacitors and the like. In such systems the encapsulated units may be made an integral part of the entire assembly rather than a separate sub-component. This greatly reduces bulk and Weight and results in improved reliability.
The invention is not limited to the particular form shown in the drawings which is given by way of illustration rather than of limitation, and is only limited in accordance with the scope of the appended claims.
' We claim:
1. An encapsulated relay switch comprising an elongated enclosed envelope, a pair of electrically conducting magnetic reed contacts supported within the envelope in overlapping but normally non-contacting relationship so that application of a magnetic field to the reeds causes them to contact each other, a pair of electrical leads passing through the envelope and in electrical contact with the respective reeds, a'coil around the exterior of the envelope, a coating of resilient rubber-like material adherent to the portions of the envelope at which the leads pass through, and a potting substance around the envelope, coil and rubber-like material.
' 2. An encapsulated relay switch according to claim 1 in which the rubber-like material is adherent to and covers at least a portion of the coil as well as the ends of the envelope.
3. An encapsulated relay switch according to claim 1 in which the rubber-like material is a polymer of polyvinyl chloride.
4. An encapsulated relay switch according to claim 3 in which the potting material is an epoxy type resin.
5. An encapsulated relay switch comprising a rigid elongated enclosed envelope, a pair of electrically conducting magnetic reed contacts supported within the rigid envelope in overlapping but normally non-contacting relationship so that application of a magnetic field to the reeds causes them to contact each other, a pair of electrical leads passing through the rigid envelope and in electrical contact with the respective reeds, a current carrying coil around the exterior of the rigid envelope, a coating of resilient rubber-like material adherent to portions of the rigid envelope at which the leads pass through, and a potting substance around the rigid envelope, current carrying coil and rubber-like material.
References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Modern Plastics Magazine, October 1952, pages 91 and 92.
Electronic Equipment Magazine, January 1956, pages 48-61.