US3518588A - Microminiature relay - Google Patents

Description

United States Patent 3,518,588 MICROMINIATURE RELAY Roscoe A. Norton, Jr., Batesburg, S.C., assignor to Westinghouse Air Brake Company, Swissvale, Pa., a corporation of Pennsylvania Filed June 4, 1968, Ser. No. 734,307 Int. Cl. H01h 6'7/02 US. Cl. 335-424 18 Claims ABSTRACT OF THE DISCLOSURE My invention relates to a microminiature relay and more particularly to an improved transistor size of electromagnetic relay which is virtually impervious to frictional wear, is substantially free of adjustments after assemblage, is effectively protected against contamination, is relatively inexpensive, is readily controllable in regard to its electromagnetic characteristics, and is efficient and reliable in operation.

With the ever increasing advancements and developments in our aerospace program, the need for new and improved electromechanical as well as electronic hardware is in constant demand. In the electromechanical field, there is a continual requirement for smaller, lighter and better electromagnetic relays which will succeed in meeting the rigorous standards necessary in mil-spec applications. In addition to the ability to withstand extreme inertial forces caused by shock, vibration, acceleration, deceleration and gravitational changes, the relays must be possessed of various other required attributes which insure satisfactory operation even under the most extreme environmental conditions. For example, it is desirable from the standpoint of size and weight reduction to decrease the number of relay parts by combining the functions of separate members. In addition, it is advantageous to preferably employ an all-welded construction since mechanical fasteners not only require additional space but also are time consuming. In relays having bearing type pivoted armatures, it has been found that lubrication or lubricating vehicles cause contamination to occur so that it is generally advisable to employ improved bearing surfaces to prevent contamination and also to minimize frictional Wear and, therefore, to maximize mechanical life. Further, it has been found that an insulator type pivot bearing surface arrangement permits more operating power to be utilized for the contact transfer function rather than overcoming frictional drag and also serves as an insulator to facilitate relay assembly by welding. Further, it will be appreciated that the spacing of parts in a microminiature relay allows little, if any, available room for adjustments, and, therefore, it is highly advantageous to completely eliminate and dispense with any adjustments after final internal assemblage. A further desired feature in microminiature relays is the ability to control and vary the dropout and pickup current ratio without altering or exchanging any of the parts of the relay.

Accordingly, it is an object of my invention to provide a new and improved microminiature relay which en- 3,518,588 Patented June 30, 1970 compasses all of the above-mentioned features and advantages.

A further object of my invention is to provide an improved transistor type relay which does not require any adjustments after final assemblage.

Another object of my invention is to provide a unique electromagnetic relay which employs an improved bearing arrangement having minimum wear and long mechanical life for pivotally supporting the relay armature.

Yet another object of my invention is to provide an improved electromagnetic relay which allows an allwelded construction to be employed.

Yet a further object of my invention is to provide a unique microminiature relay which requires a minimum number of parts due to the employment of a multiple function principle.

Still another object of my invention is to provide an improved microminiature relay having a controllable dropout current characteristic.

Still yet another object of my invention is to provide a unique transister type of electromagnetic relay having a pivotal armature which is preselectively positioned in relation to the electromagnetic pole pieces to establish a. predetermined dropout-to-pickup current ratio.

Still yet a further object of my invention is to provide a new and improved electromagnetic relay that is extremely small, light and compact, that has low frictional wear, that is immune to shock and vibrations, that has low power consumption, and that has improved operational characteristics.

Yet still another object of my invention to to provide a new and improved microminiature relay which is simple in construction, economical in cost and efficient and reliable in operation.

Further objects, features and advantages of my invention will become more apparent as the following description proceeds and the ingenuity and novelty which characterizes my invention will be pointed out particularly in the appended claims which form part of my specification.

Generally, my invention relates to a microminiature relay comprising a header and contact assembly having a plurality of insulated contact pins including external terminal portions and internal stationary and movable contact portions. An electromagnetic assembly has an energizable coil and a magnetic frame including a first pole piece and a pair of depending elongated legs fixedly secured to the header. A magnetic core member extends through the coil and has one end secured to the magnetic frame and has a second pole piece formed on the other end thereof and is spaced from the first pole piece. A split retaining plate is disposed intermediate the pole pieces and the adjacent surface of the coil for holding the coil in proper relationship. A bearing assembly includes a pair of bearing support plates fixedly secured at preselected points along the elongated legs. Each of the hearing support plates has a jeweled bearing press fit into suitable apertures therein. An armature assembly includes a flat armature member and a pivoted shaft secured thereto and has the ends of the shaft journaled in the jeweled bearings so that a first air gap exists between the first pole piece and the adjacent surface of the armature and a second air gap exists between the secand pole piece and the adjacent surface of the armature member. Contact actuating means are carried by the armature assembly and are adapted to engaged the movable contact portions for providing a transfer switching action between the :movable and stationary contact portions. A biasing spring is carried by the header and urges the armature member against the split retaining plate when the coil is deenergized, thereby limiting the rotational movement of the armature assembly. A cover completely encloses the internal structure and is securely fastened to the header for providing a hermetically sealed microminiature relay.

A better and more complete understanding of my invention will be had by reference to the drawings, in which similar characters of reference refer to similar parts throughout the several views and in which:

FIG. 1 is an actual size perspective view of a relay, with the cover on, constructed in accordance with the present invention.

FIG. 2 is a side elevation, partly in section, greatly enlarged of the relay of FIG. 1.

FIG. 3 is a cross-sectional view of FIG. 2 taken along lines 'III--III.

FIG. 4 is a side elevation view of the header and contact assembly shown in FIG. 3 with the cover removed.

FIG. 5 is a side elevational view, partially in section, of the relay in its deenergized condition, the cover and header and contact assembly being omitted.

FIG. 6 is a cross-sectional view of FIG. 5 taken along a line substantially corresponding to line VII-VII of FIG. 5.

FIG. 7 illustrates a detailed partial cross-section in magnified form of a pivotal journal bearing of the relay.

FIG. 8 is a cross-sectional view of FIG. 5 taken along a line substantially corresponding to line VIIIVIII of FIG. 5.

FIG. 9 is a partial side elevational view of the relay in its energized condition, the cover and header and contact assembly being omitted.

FIG. 10 is a perspective view, partially in section, of the armature assembly.

Referring now to the drawings, there is shown in FIG. 1 the actual size of a transistor type of relay in accordance with the present invention. The various internal assemblies which make up the relay are completely enclosed and hermetically sealed by the cover C which is preferably welded to an associated flange of the header assembly H so that the relay is impervious to dust, moisture and other contaminants which may be present in the operating environment. The various electrical circuit connections are made through the connecting leads or connector pins 17, which will be described in greater detail hereinafter.

As shown in FIG. 2, the relay simply consists of five principal parts, namely, a header and contact assembly H, an electromagnetic assembly B, an armature assembly A, a bearing assembly B, and a cover C, all of which will now be described.

The header and contact assembly H, which is best shown in FIGS. 2, 3, and 4, comprises a circular base plate or header disk 11 having a peripheral flange 12 and a central table portion 13. As previously mentioned, the flange portion 12 is designed to cooperate with the lower rim portion 14 of the cover C which is telescoped over the internal relay assemblies and is welded in cooperative association therewith as is shown in FIG. 2. A guide tab 15 extends laterally from the flange portion 12 and provides an indexing position or point of reference for facilitating plug mounting or wiring of the relay. The base plate 11 also includes a pair of notches 16a and 16b for receiving a pair of supporting legs of the electromagnetic assembly E, as will be described in greater detail hereinafter. The plurality of circularly disposed connector pins or leads 17 protrude outwardly from the header plate 11 and afford external connections with the inner contacts of the relay. Each of these connector pins or leads is secured in place by being embedded in a mass of suitable insulating material 18, such as glass, which fills each of the openings 19, as best shown in FIG. 3. Thus, an air tight bond exists between external terminal portions on one side of the header plate 11 and the internal contact assembly which performs the various switching functions on the other side of the header plate 11. The contact assembly includes a pair of movable contacts or switch blades 20a and 20b, the inner ends of which are suitably secured, such as by welding to the connector pins 17a and 17b, respectively. The movable contacts or blades 20a and 20b are suitably disposed and normally biased into cooperative association with a pair of flattened upper and lower stationary contacts 21a-22a and 21b-22b respectively. The stationary contacts 21a and b and 22a and b are integrally formed and bent at substantially right angles so that they are parallel with respect to the upper surface of the table portion 13. Further, each pair of stationary contacts are also arcuately bent to overlap each other so that the outer free ends of movable contacts 20a and 20b provide a make-and-break contact arrangement for selectively performing the desired switching functions. Thus, as shown in FIGS. 3 and 4, the stationary and movable contacts form two independent double-throw switches each having two positions. While a multiple DPST switching arrangement is illustrated in the drawings, it is readily understood that a single DPST switching arrangement or a multiple SPST as well as a single SPST contact arrangement may be equally employed in practicing the present invention. The inner portions and 17d of the two remaining connector pins are employed for providing the necessary electrical connection between the electromagnetic coil and a suitable source of electrical power, as will be described in greater detail hereinafter.

In addition, the header assembly carries an elongated biasing spring 25 which has one end securely fastened to the upper surface of the header table 13, such as by spot welding, as indicated at 26 in FIG. 3. As will be described in greater detail hereinafter, the purpose of spring 25 is to engage the armature assembly and to bias the armature member in a particular given direction.

The electromagnetic assembly E, which is best illustrated in FIGS. 2, 5, 6, 8 and 9, includes a stamped magnetic frame 30, a cylindrical magnetic core member 31 and a prewound energizable coil 32 which is electrically connected by wires or leads 33 and 34 to inner connecting portions 170 and 17d, respectively. The magnetic frame 30 includes a depending portion 35 which terminates into a turned-in arcuate magnetic pole face 36. The magnetic frame 30 also includes a pair of diametrically opposed depending supporting legs 37 and 38 which as previously mentioned are received within the appropriate recesses 16a and 16b for securing the frame to the base or header. The energizable coil 32 is preferably suitably disposed in partial surrounding relationship with the magnetic frame 30 and includes a pair of dielectric end flanges 39 and 40 disposed at the top and bottom thereof for insulation purposes. As shown in FIG. 5, the cylindrical core member 31 extends through the axial center of the coil 32 and includes an upper reduced portion which is preferably rigidly secured, such as, being peened, to the top of the magnetic frame 30. The projecting end of the core member 31 is jointed 'to a second magnetic pole piece 42 which is suitably spaced from the first magnetic pole piece 36. A split retaining ring 43 is suitably disposed between the bottom surface of the coil, namely, the underside of the insulating end flange 40 and the upper surface of the pole piece members 36 and 42 for securely holding the coil in proper spaced relationship thereto. The split retaining plate 43 fits snugly around the circumference of the core piece member, and the slit 44 effectively reduces eddy current losses due to induced currents. The retaining plate also includes a pair of oppositely facing tabs 43a and 43b which extend downwardly and engage the respective sides of the pole piece 42 for holding it in place.

The armature assemblage A, which is best illustrated in FIGS. 2, 5, 6, 9 and 10, comprises an armature member 45 consisting of a flat piece of suitable magnetic material. As shown, one end of the armature 45 is provided with a curved surface 46 which agrees with the arcuate shape of the pole piece extension portion 35. The other end of the armature member 45 is provided with a projection 47 which cooperates with the under surface of the split retaining plate 43 to operate as a stop member for limiting the amount of clockwise rotation of the armature member 45 when the coil 32 is deenergized, as will be described in greater detail hereinafter. The armature assembly also includes a pivotal shaft or pin 48 which is securely fastened to the underside viewing FIGS. 2, 5, and 9, of the armature member 45 by means of a T-shaped pivotal mounting bracket or plate 49. As shown, the bracket 49 is suitably attached to the armature member 45 by means of depression type spot welds 50, 51 and 52 which are situated on opposite sides of the pivot pin 48. Accordingly, the pivot pin 48 is securely fastened between the bracket 49 and the armature member 45. As shown, the width of the bracket or plate 49 is preferably greater than the armature width so that it extends slightly beyond the sides of the armature member 45, the purpose of which will be described in greater detail hereinafter. Further, a pair of contact actuating members or pusher arms 53 and 54 are suitably fastened, such as by spot welding, to the retainer plate 49. Each of the actuating members 53 and 54 is terminated with nonconducting spheres, such as glass balls 55 and 56, or other suitable insulating material. As will be described in greater detail hereinafter, the insulating balls 55 and 56 are arranged to engage and to transfer the movable contact blades a and 20b from stationary contacts 21a and 21b to 22a and 22b, respectively. It will be appreciated that the glass insulating spheres are employed to provide the necessary isolation and insulation between the various sets of electrical contacts.

The bearing assembly B, which is best shown in FIGS. 2, 5, 6, 7, 8, and 9, comprises a pair of press fitted assemblies B each including bearing support plates 57 and 58 and suitable jeweled bearings 59 and 60 disposed therein. Each of the jeweled bearings 59 and 60 is preferably constructed of a suitable gem, such as a synthetic sapphire, which is forced into suitably size apertures in the respective bearing support plates such as hole 57a, shown in FIG. 7. Each bearing is a circularly-shaped apertured disc having a central concaved portion 61, such as shown in FIG. 7, which facilitates insertion of the end of the pivotal pin and also reduces the contact area between the bearings and ends of the mounting bracket 49 thereby decreasing the frictional wear therebetween. That is, the bearings 59 and 60 preferably protrude beyond the inner surface of the bearing plates 57 and 58, respectively, so that a portion of the low-frictional bearing surface remains exposed. Accordingly, such an arrangement insures that when any lateral movement of the armature assembly causes the outer extremities of the mounting bracket or plate 49 to engage the protruding portions of the bearings 59 and 60, reduced wear and drag are achieved thereby enhancing the overall operation of the relay.

As shown in FIGS. 2, 6, and 8, the bearing plates 57 and 58 are preferably spot welded to the respective supporting legs 37 and 38 at preselected points to provide the necessary pivotal journals for the armature assembly A. That is, each bearing assembly B is welded at a point such as 64 along the longitudinal axis illustrated by dashed line 65 of the elongated supporting leg 37 as shown in FIG. 2. Further, it will be noted in FIG. 2 that the supporting leg 37 is received within the notch 16a and is secured at a point 66 such as by spot welding. Similarly, the supporting leg 38 is received within notch 16b and is securely attached thereto. Such construction results in a highly compact yet rigidly stable assembly which needs no standard type of fasteners such as screws, bolts, rivets, etc., and as previously mentioned, requires no adjustment after the assemblage is completed. The entire structure when assembled may be completely enclosed within the metallic cover C which has the rim 14 tightly fitted against the flange 12 and preferably welded thereto. If it is desired, the inside of the relay may be evacuated, charged with a suitable gas, such as dry nitrogen which prevents electrical breakdown and arcing and reduces the possibility of corrosion and contamination.

In operation, the parts of the relay normally assume a position that is shown in FIG. 2 when the electromagnetic coil 32 is not energized. Under this condition, the armature is released and the spring 25 constantly urges the projection 47 against the underside of the retaining plate 43 so that a predetermined air gap exists between the magnetic frame pole face 36 and the adjacent surface of the armature member 45. It will be noted that a separate or ancillary stop member for limiting the downward movement of the armature is not required since the projection 47 and the retaining plate 43 mutually cooperate to inherently limit the amount of rotational movement of the armature. With the armature in its released position, the insulating contact balls 55 and 56 permit the movable switch blades 20a and 20b to electrically contact and engage the upper stationary contacts 21a and 21b, respectively. Accordingly, a completed circuit path exists between movable contact 20a and stationary contact 21a and also between movable contact 20b and stationary contact 21b. By integrally forming the stationary contacts 20a, 20b, 21a and 21b from the connector leads or pins 17, a better and more reliable electrical contact is realized since previously the individual contact members which were fixedly secured to the connector leads were susceptible to breakage or crystallization thereby impairing the integrity of the relay. In addition, the use of contact buttons is not required since the connector leads and the stationary contact members as well as the movable contacts may be suitably plated with highly conductive materials for reducing the contact Wear and improving the current carrying capabilities.

Now when the electromagnetic coil 32 is energized by connecting the coil leads Or pins and 17d to a source of current, the armature member 45 is attracted and the armature assembly A is caused to rotate about its pivotal axis, namely, shaft or pin 48 in a counterclockwise direction, as viewed in FIG. 2. That is, the energization of the coil 32 causes the free end of the armature to be drawn toward the pole face 36 so that the armature member 45 assumes the position, as shown in FIG. 9, namely, with the upper face of the armature 45 engaging the pole face 36. It will be appreciated that the required amount of electromagnetic force and, in turn, the pickup current characteristic of the relay is a direct function of the length of the air gap existing between the pole face 36 and the upper adjacent surface of the armature member 45. The counterclockwise rotational movement and picking up of the armature 45 and, in turn, the downward movement of the spherical insulating balls 55 and 56 causes the movable contact blocks 20a and 20b to break contact with the upper stationary contacts 21a and 21b and to make contact with the lower stationary contacts 22a and 22b so that the circuits common to the stationary contacts 21a and 21b are interrupted and the circuits common to the stationary contacts 22a and 22b are established. In reviewing FIGS. 5 and 9, it will be noted that a second air gap exists between the core member pole piece 42 and the adjacent surface of the armature 45. The length of this second air gap determines the dropout current characteristics of the relay. That is, when the relay is picked up, it shortens the magnetic circuit air gap, which permits a smaller magnitude of coil current to keep the relay picked up than was required to pick it up. It has been found that the drop-out value, namely, the current level which allows the relay to release the armature and to transfer the electrical contacts may be effectively controlled by varying the air gap between the armature 45 and the core member pole piece 42. Accordingly, by selectively varying the positions at which the bearing support plates 57 and 58 are securely fastened along the longitudinal axis 65 of the supporting plates 37 and 38, the pivotal axis of the armature assembly may be raised and lowered in accordance therewith. It will be appreciated that the lowering of the pivotal axis causes an increase in the air gap dimension to exist between pole face 42 and adjacent surface of the armature 45 which in turn increases the current value at which the relay will release. Conversely, by slightly raising the bearing support plates in relation to the longitudinal axis of the supporting legs the air gap between the magnetic core pole piece 42 and the adjacent surface of the armature member 45 is decreased so that the maxi-mum value of drop-out current is proportionally decreased. Accordingly, the drop-out to pick-up current characteristic ratio may be accurately controlled simply by preselectively determining the positions of the bearing support plates in regard to the longitudinal axis of each of the supporting legs. However, it will be noted that the particular disposition of the bearing support plates does not appreciably influence the pick-up current characteristic of the relay due to the stopping action achieved by the armature projection 47 and split retaining plate 43. It is readily evident that the biasing spring 25 also effectively limits the maximum dimension of the air gap between the pole piece 36 and the armature 45. Thus, without the need of any special adjustments or supplemental parts, any given relay or a group of relays designated for a particular environment or project which necessitates a particular drop-out to pick-up current characteristic may be readily produced and available by simply varying the position of the bearing plates in regard to the longitudinal axis of the supporting legs. Hence, an optimum operation and great versatility by a standard relay employing standard parts is achieved.

It has been found that after final assemblage, namely, the fabrication of the internal parts of the relay, adjustments of a microminiature relay are not only difiicult and laborious but in many cases impossible due to the minuteness of the structure. For example, standard relay adjusting tools are too large and bulky to be manipulated within the confined spaces of the relay proper. In addition, the limited amount of space does not permit ready access for accurate gage measurements and the minuteness of parts within the confined spaces does not allow accurate visual adjustment. Thus, it is highly desirous in a microminiature assembly to dispense with all final adjustments after assemblage of the internal parts of the relay so that increased savings in overall manufacturing costs may be realized. It will be appreciated that the presently described relay does not require any adjustments after it has been assembled.

Further, it will be appreciated that the relative simplicity of the structure described makes it possible to readily assemble the various parts while they are held in a predetermined position in assembly jigs, thus insuring that uniformity of assemblage is achieved.

In addition to the qualities of reducing friction and, in turn, wear on the pivoted journaled surfaces as well as on the adjacent surfaces of the armature mounting plate, the jeweled bearings eliminate contamination previously caused by lubricating vehicles and in the present case facilitates assembly by welding. For example, the insulated qualities of the jeweled bearings prevents minute particles from adhering thereto during welding, which could' result in increased wear to the point of complete failure, as was possible in prior structures employing noninsulating pivotal arrangements.

Thus, it is apparent that the new and improved relay of the present invention employs new and improved features which result in a more compact, smaller, lighter, more economical, durable and efficient microminiature relay. Because of the unique all welded construction, a sturdier and less costly relay is realized. Because of the jeweled bearing pivotal arrangement, the problem due to lubricating vehicle contamination has been eliminated.

Because of the integrally formed stationary contacts and the elimination of a separate stop member, a reduction in the space between the header and magnetic core frame is achieved. Because of the selectivity of positioning the bearing support plates and in turn the pivotal axis of the armature assembly, the electromagnetic characteristics of the relay is effectively controlled, and because of all of this the need for final adjustment after assemblage has been eliminated.

While my invention has been described with reference to a single embodiment thereof, it should be understood that numerous other embodiments and numerous variations may be made by those skilled in the art that will fall in the spirit and scope of my invention. Therefore, it is understood that the invention is not to be limited to the exact details described herein but is to be accorded the full scope and protection of the appended claims.

Having thus described my invention, what I claim is:

1. An electromagnetic relay comprising, a header and contact assembly, an electromagnetic assembly, an armature assembly, a bearing assembly and a cover, said electromagnetic assembly including a magnetic frame having a first pole face and having a pair of elongated supporting legs secured to said header, an e ectrically energizable coil partially surrounded by said magnetic frame, and a magnetic core extending through said coil and having a second pole face formed on one end and having the other end secured to said magnetic frame, said bearing assembly including a pair of bearing support plates each having a jeweled bearing, each of said bearing support plates secured at a preselected position along the longitudinal axis of each of said elongated supporting legs, said armature assembly including an armature member and a pivot pin the ends of which are journaled in said jeweled bearings so that a first air gap exists between said first pole face and the adjacent surface of said armature member and a second air gap exists between said second pole face and the adjacent surface of said armature member.

2. An electromagnetic relay as defined in claim 1, wherein the axis of said armature pivot pin is normal to said longitudinal axis of said supporting legs so that the preselected position at which said bearing plates are secured to said elongated supporting legs determines the size of said second air gap and, in turn, the drop-out current characteristic of the relay.

3. An electromagnetic relay as defined in claim 1, wherein each jeweled bearing comprises a circularly shaped synthetic sapphire press-fit into a suitable aperture in each bearing support plate.

4. An electromagnetic relay as defined in claim 1, wherein said header and contact assembly including a circular base plate, a plurality of insulated connecting leads extending through said base plate, said connecting leads having terminal portions protruding from one side of said base plate and having contact portion-s protruding from the other side of said base plate, said contact portions including a plurality of integrally formed fixed contacts and having at least one movable contact attached to one of said contact portions in cooperative association with said integrally formed fixed contacts, said energizable coil electrically connected to a separate pair of said contact portions.

5. An electromagnetic relay as defined in claim 4, wherein said base plate includes a flange portion with which said cover cooperates to hermetically seal the internal assemblies of the relay.

6. An electromagnetic relay as defined in claim 4, wherein a biasing spring is secured to said circular base plate for urging said armature away from said pole faces.

7. An electromagnetic relay as defined in claim 6, when a coil retaining plate is disposed between said energizable coil and said pole pieces for holding said energizablecoil in place, said coil retaining plate cooperating with said armature member for limitingsaid first air gap dimension and, in turn, the pick-up current characteristic of the relay.

8. An electromagnetic relay as defined in claim 4, wherein said armature assembly includes contact actuating means for engaging and operating said at least one movable contact into and out of engagement with selected ones of said integrally formed fixed contacts.

9. An electromagnetic relay as defined in claim 4, wherein said elongated supporting legs are welded to said circular base plate.

10. An electromagnetic relay as defined in claim 2, wherein said bearing plates are welded to said elongated supporting legs.

11. A microminiature relay comprising, a header plate having a plurality of insulated contact means including external terminal portions and internal stationary and movable contact portions, an electrically energizable coil, a magnetic frame having a pole face and having a pair of supporting legs fixedly secured to said header plate and partially surrounding said coil, a core member extending through said energizable coil, said core member having one end secured to said frame and a pole face formed on the other end thereof, a bearing plate having a lowfriction bearing selectively secured to each of said supporting legs at preselected points, an armature having a pivot pin journaled in said low-friction bearings so that one side of said armature is disposed adjacent to said pole faces thereby establishing a first air gap between said magnetic frame pole face and said one side of said armature which determines the armature pick-up characteristic and a second air gap between said magnetic core pole face and said one side of said armature which determines the armature drop-out characteristic, contact actuating means disposed on the other side of said armature and adapted to engage said movable contacts, a return spring having one end secured to said header plate and having the other end engaging and biasing said armature away from said magnetic frame pole face, and a cover securely attached to said header plate for providing a sealed enclosure.

12. A microminiature relay as defined in claim 11, wherein a split retaining plate holds said energizable coil in proper relationship with said magnetic frame and said core member and limits the distance said armature is biased away from said magnetic frame pole face.

13. A microminiature relay as defined in claim 11, wherein each of said low-friction bearings is a synthetic gem press-fit into an aperture in each of said bearing plates.

14. A microminiature relay as defined in claim 11, wherein said stationary contact portions are arcuately bent and integrally formed from selected ones of said plurality of said insulated contact means.

15. A microminiature relay as defined in claim 11, wherein said contact actuating means comprises a pusher arm and an insulated ball on one end thereof.

16. A microminiature relay as defined in claim 11, wherein the relay is an all-welded construction which is free of any necessary adjustment after assemblage.

17. An electromagnetic relay which is substantially free of any adjustments after assemblage comprising:

(a) a header and contact assembly,

(b) an electromagnetic assembly,

(c) a bearing assembly,

(d) an armature assembly,

(e) and a cover,

said header and contact assembly including a flanged base plate, a plurality of insulated connector pins extending through said base plate, said connector pins having terminal portions on one Side of said base plate and having contact portions in the form of arcuate stationary, elongated movable contacts on the other side of said base plate, and a biasing spring carried by said base plate,

said electromagnetic assembly including an electrically energizable coil, a magnetic frame and a magnetic core, said magnetic frame having a first magnetic pole piece and a pair of supporting legs partially surrounding said coil and having the free ends of said supporting legs securely fastened to said flanged base plate, said magnetic core extending through said coil and having one end secured to said magnetic frame and having a second magnetic pole piece formed on the other end thereof, a split retaining plate disposed between said magnetic pole pieces and said energizable coil for securely holding said coil in place,

said bearing assembly including a pair of bearing plates, each of said bearing plates having a jeweled bearing mounted'thereon, each of said bearing plates selectively positioned at a predetermined location along each of said supporting legs,

said armature assembly including an integrally constructed armature member, a pivot pin, a retaining plate and contact actuating means, said pivot pin having its ends journaled in said jeweled bearings so that an air gap is defined between said magnetic core pole piece and the adjacent surface of said armature member, the dimensional length of said air gap determines the drop-out characteristic of the relay and is dependent upon the given position at which said bearing plates are secured to said supporting legs, said biasing spring engaging said armature assembly and urging one end of said armature member away from said pole pieces to a point Where the other end of said armature member engages said retaining plate, said contacting actuating means engaging said movable contacts and causing one end of said elongated movable contacts to effect a make and break action with said arcuate stationary contacts,

said cover securely fastened to said flanged base plate for providing a sealed enclosure for said assemblies.

18. An electromagnetic relay as defined in claim 17,

wherein the relay is an all-welded assembly.

References Cited UNITED STATES PATENTS 3,042,775 7/1962 Jordan 335- 3,154,653 10/1964 Rowell 335125 3,202,782 8/1965 Mathison 335--202 3,253,095 5/1966 Richert 335-125 3,255,327 6/1966 Wood 335-124 3,321,722 5/1967 Cohen 335-128 BERNARD A. GILHEANY, Primary Examiner I-I. BROOME, Assistant Examiner

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