US3381105A - Modular high current switch - Google Patents

Description

April 30, 1968 v. A. MORTENSON 3,381,105

MODULAR HIGH CURRENT SWITCH Filed Feb. 14, 1966 4 Sheets-Sheet l INVENTOR. VICTOR A. MORTENSON W W %A April 1968 v A. MORTENSON 3,381,105

MODULAR HIGH CURRENT SWITCH Filed Feb. l4, 1966 4 Sheets-Sheet 2 .7% FIG. 2

INVENTOR.

VICTOR A. MORTENSON BY W, W QM April 30, 1968 v. A. MORTENSON 3,381,105

MODULAR HIGH CURRENT SWITCH Filed Feb. 14, 1966 4 Sheets-Sheet 5 FIG. 3

INVENTOR.

VICTOR A. MORTENSON BY W, mew

April 1968 v. A. MORTENSON 3,381,105

MODULAR HIGH CURRENT SWITCH Filed Feb. 14, 1966 4 Sheets-Sheet a 42&

INVENTOR.

V l CTOR A. MORTENSON BY W, 641 4 PW United States Patent 3,381,105 MODULAR HIGH CURRENT SWITCH Victor A. Mortenson, Stoughton, Mass., assignor to Anderson Power Products, Inc., Boston, Mass., a corporation of Massachusetts Filed Feb. 14, 1966, Ser. No. 527,162 4 Claims. (Cl. 200164) ABSTRACT OF THE DISCLOSURE A modular, high current switch having two stationary, spaced, coplanar electrically conductive plates and at least one movable contact assembly for establishing or interrupting a conductive path between the plates. Each contact assembly has a pair of spaced, parallel, substantially planar electrically conductive bars which are leaf spring biased. The contact assembly is in movable, electrical contact with one of the stationary plates in both the open circuit and closed circuit positions.

This invention relates to electrical switches and more particularly to a modular, high current pressure switch that provides maximum switching density per unit volume without compromising the generally accepted mechanical and electrical design requirements for high amperage switching equipment.

The design parameters of high current switching equipment of the type employed, for example, in the electrochemical industry, are well known to those skilled in the art, The switching equipment must have a high electrical efiiciency in order to reduce costly power losses. Such efiiciency can be obtained only by reducing contact resistance to an absolute minimum. Generally, this is accomplished by employing high unit pressures between mating contact surfaces in conjunction with mechanical abrasion to remove dirt and corrosion from the contact surfaces. In addition, such equipment should combine the requisite high electrical efiiciency with ease of operation and economy in a physically compact and readily accessible design.

It is accordingly a specific object of the present invention to prove a high current switch which fulfills the above-mentioned design requirements.

It is a specific object of the invention to provide an electrical switch having positive means for applying and releasing high unit clamping pressure between mating contact surfaces without requiring a high operating torque.

It is another object of the invention to provide modular, leaf-spring biased, movable contact assemblies that have a thin profile to permit maximum switching density per unit volume.

It is a feature of the invention that each contact assembly can be independently spring biased to control the clamping pressure between the contact surfaces of the movable assembly and two stationary contact plates.

It is still another object of the invention to provide separate, initial engagement, bearing surfaces and final, closed circuit contact surfaces on each movable contact assembly.

It is a further object of the invention to provide a readily accessible, modular design which facilitates routine maintenance, including replacement of individual contact assemblies or any component therein.

It is a still further object of the invention to provide a modular design which permits simple and economical variations in switch capacity even after initial installation.

These objects and other objects and features of the invention will best be understood from the following description of a preferred embodiment of the invention, se-

lected for purposes of illustration, and shown in the accompanying drawings in which:

FIGURE 1 is a perspective view of a ganged, two element, modular, high current switch constructed in accordance with the present invention and shown with the movable contact assemblies in the open circuit position;

FIGURE 2 is a view in side elevation of the high current switch showing the movable contact assemblies in the closed circuit position;

FIGURE 3 is a front elevation of the switch showing the movable contact assemblies in the closed circuit position;

FIGURE 4 is an enlarged cross-sectional view taken along line 4-4 in FIGURE 3 showing one movable contact assembly in the open circuit position;

FIGURE 5 is an enlarged cross-sectional view also taken along line 4-4 in FIGURE 3 showing the movable contact assembly in initial engagement with one of the stationary contact plates;

FIGURE 6 is a similarly enlarged cross-sectional view showing the movable contact assembly in the closed circuit position;

FIGURE 7 is an enlarged view in perspective of an alternative embodiment of a contact bar having a compoundly curved contact member;

FIGURE 8 is an enlarged cross-sectional view of an arc confining member secured to one stationary contact plate and the corresponding arc confining contact bar; and,

FIGURE 9 is an isometric view of an alternative embodiment of the arc confining member.

Turning now to the drawings, and particularly to FIG- URES 1, 2 and 3 thereof, there is shown in perspective view and side and front elevation, respectively, a two element, modular switch constructed in accordance with the present invention and identified generally by the reference numeral 10. Since both switching elements 12 and 14, indicated by the dashed dividing line in FIGURE 2, have identical components, the following description is applicable to either switching element and to any other switching element which may be added to the switch module 10 as hereinafter described.

Looking at FIGURES 1, 2 and 3, the switching element 12 has two stationary, electrically conductive contact plates 16 and 18 that are held in spaced, coplanar relation by two electrically insulating supports 20 and 22. Suitable countersunk fasteners 24 are employed to structurally tie together the plates 16 and 18 and supports 20 and 22 to form a rigid, rectilinear structure. Both stationary plates are provided with means for electrically and mechanically securing the plates to an external circuit component, such as, for example, a bus bar. As shown in FIGURES l and 3 of the drawings, the securing means comprises a plurality of stud mounting holes 26 located at spaced intervals along the outer edges 28 and 30, respectively, of plates 16 and 18. The elongated, oval configuration of the stud mounting holes 26 affords a certain degree of flexibility in positioning the switching elements to compensate for any slight misalignment of the switching elements and the external circuit components. Other mounting means can, of course, be used to electrically and mechanically connect the plural switching element, modular switch It to the external circuit.

Each switching element 12 electrically comprises a single pole, single throw switch in which the stationary plates 16 and [18 are electrically bridged by a movable contact assembly, indicated generally in FIGURES 1 and 3 by the reference numeral 32. It can be seen from these figures that five individual contact assemblies 32 are utilized to establish or interrupt a corresponding number of conductive paths between the stationary plates 16 and 18. The contact assemblies 32 are moved in unison by a mechanical linkage which is indicated generally in FIG- URE 1 by the reference numeral 34 and which will be described hereinafter in greater detail.

The number of individual contact assemblies is governed by the desired current carrying capability of the switching element. For example, in one construction of the present invention, each contact assembly handles 1000 amps and the total current carrying capability of the switch can be increased in 1000 ampere increments by adding a modular contact assembly 32 for each additional 10 amps of current. Other ampacities can obviously be obtained by altering the design parameters of the stationary plates and contact assemblies in addition to increasing the number of contact assemblies in each switching element.

The modular design of the present invention greatly facilitates the replacement of any contact assembly or any component therein during normal, routine maintenance operations. This constructional feature will be apparent from an examination of FIGURES 4, 5 and 6 which shows the contact assembly 32 in an enlarged cross-sectional view. The figures depict, respectively, the

movable contact assembly in the open circuit position, in

initial engagement with stationary plate 18 and in the closed circuit position in electrical contact with plates 16 and 18.

Referring to FIGURE 4, the contact assembly 32 com prises two, spring loaded, electrically conductive contact bars or fingers 36 and 38 having corresponding convex contact members 40a and 40b and 42a and 42b, respectively, located at the ends thereof. The contact bars 36 and 38 are positioned on opposite sides of a contact assembly carrier bar 44 with the convex contact members facing each other. The lateral and longitudinal placement of the contact fingers 36 and 38 with respect to the carrier bar 44 are controlled by a press-fitted pin 46 that extends outwardly from opposite sides of the carrier bar. It can be seen in FIGURE 3 that the longitudinal axis of the contact bars 36 and 38 are normal to the longitudinal axis of the carrier bar 44 While the transverse axis of the contact bars are parallel to the carrier bar axis.

Leaf springs 48 and 50 provide the requisite spring loading or biasing for contact bars 36 and 38. The amount of spring biasing can be individually adjusted for each contact assembly 32 by varying the position of locknut 52 along the threaded portion of carriage bolt 54. The integrally formed contact bar shoulders 56 and 58 serve 'a dual function in the present invention: primarily, they are employed to control the alignment of leaf springs 48 and 50 with respect to the longitudinal axes of the contact bars and, secondarily, to limit the outward extension of the leaf springs as locknut 52 is advanced toward the head of carriage bolt '54.

The simplified construction and relatively few components of the movable contact assembly 32 greatly facilitates the repair or replacement of the entire contact assembly or any components therein. By utilizing the physical locking characteristic of the carriage bolt 54, it is possible to service or replace an entire contact assembly even though only one side is accessible, e.g. the front or locknut side as shown in FIGURE 1.

Turning back now to FIGURES 1, 2 and 3, it will be remembered that each contact assembly 32 is removably mounted on 'a carrier bar 44 and that the contact assemblies are moved in unison by a mechanical linkage, indicated generally as 34. The function of the mechanical linkage 34 is to convert bidirectional rotary motion into corresponding reciprocatory linear motion. Expressed in terms of the switch components, the rotary motion of shaft 60 produced by the operators movement of switch handle 62 is converted into linear motion which causes carrier bar 44 to move within slots 64 defined by the opposite surfaces of plate supports 20 and 22.

The rotary to linear conversion is accomplished in the following manner. As shaft 60 rotates, it carries with it bell cranks 66 which transmit the rotary motion to links 68 through intermediate connecting pins 70. The other ends of links 68 are drilled to provide journals for the turned end portions 72 of carrier bar 44. Since the movement of the carrier bar is restricted to up and down motion within slots 64 (as viewed in FIGURES 1, 2 and 3), the movement of links 68 produced by the rotation of bell cranks 66 causes the carrier bar 'and, hence, the contact assemblies, to move reciprocatorally between an open circuit position (FIGURE 1) and a closed circuit position (FIGURES 2 and 3). The limit of the travel in the closed circuit position is controlled by a stop member.

74 which engages link 68 and prevents further movement of the carrier bar 44.

In the stop position, the bell cranks 66 and links 68 are knuckled beyond the dead center to lock in the linkage against vibration. The over dead center relationship of the bell cranks and links also allows a certain amount of rotational momentum to be built up before the carrier bar and contact assemblies are moved by the linkage.

The movement of the contact assemblies 32 between an open circuit position and a closed circuit position and vice versa, is best illustrated by the operational sequence depicted in FIGURES 4, 5 and 6. As mentioned previously, FIGURE 4 shows the contact assembly in the open circuit position with carriage bolt 54 abutting the edge of the first stationary plate 16. It should be noted that in this position, the spacing between the opposed convex contact members 40a and 42a is less than the thickness of the second stationary plate 18. Thus when the contact assembly is moved to the position shown in FIGURE 5, the sharply curved leading portions of contact bars 36 'and 38 initially engage plate 1 8 at a predetermined point along the double inclined plane 76. Further movement of the contact assembly causes the contact members to ride up the inclined plane thereby spreading the contact bars 36 and 38.

It will be appreciated that this configuration permits high unit clamping pressure to be exerted immediately upon initial engagement with the second stationary plate 18. The high unit clamping pressure continues as the contact members ride up the double inclined Plane 76 and onto the fiat surfaces of plate 18 thereby providing a wiping action that abrades any dirt or corrosion which may have formed on the contact members 40a and 42a or on the inclined plane or flat surfaces of plate 18. A similar wiping action also occurs as the other contact members 40b and 42b slide across the first stationary plate 16.

It has already been mentioned that the contact assemblies 32 are positioned on the carrier bar 44 so that the longitudinal axes of the contact bars are normal to the axis of the carrier bar and that the transverse axes are parallel to the carrier bar axis. Furthermore, it should be noted that each one of the convex contact members 40a-40b and 42a-42b has a generally semi-cylindrical shape with the axis thereof parallel to the transverse axis of the contact bar. Given these physical relationships and the rectilinear structure of plates 16 and 18 and supports 20 and 22, it will be apparent that as the carrier bar 44 moves within slots 64 the longitudinal axes of the contact bars 36 and 38 or the extensions thereof will be normal to the contact member engaging edge of plate 18 and therefore each contact member will slidably engage stationary plate 18 in a line contact.

Looking at FIGURES 5 and 6, it can be seen that the initial bearing surface of the contact member, as it strikes the inclined plane, does not form the final closed circuit plate contacting portion of the contact member. The physical separation of these surfaces greatly increases the longevity of the contact bar because all of the mechanical stresses involved in switch opening and closing are borne by the plate engaging portion of the contact member rather than by the closed circuit plate contacting portion.

As depicted in the above-discussed figures, the convex contact member has a generally semi-cylindrical shape with a single radius of curvature. However, even greater physical separation of the initial bearing surface and the closed circuit contacting surface can be obtained by using a compoundly curved contact member as shown in the alternative embodiment depicted in FIGURE 7. In this embodiment, the leading edge 78 of the convex contact member has a shorter radius of curvature than the trailing edge 80 which forms the closed circuit plate contacting portion of the contact member. Since the distance between the initial bearing portion on leading edge 78 and the plate contacting portion on trailing edge 80 has been increased there will be a concomitant increase in the longevity of the contact bar.

In the switching of high amperage currents, contact arcing can be a serious problem especiallyif the switched circuit contains a substantial amount of inductance. Preferably, the damage caused by arcing should be confined to a predetermined number of contact bars that can be easily replaced when necessary. In the present invention, contact arcing can be confined to the predetermined number of contact bars and a small portion of the second stationary plate 18 by either of the arrangements shown in FIGURES 8 and 9.

Referring, first to FIGURE 8, an arcing member 82 is removably secured to stationary plate 18 in a position so that the leading edge of the arcing member extends outwardly from the contact member engaging edge of plate 18. Thus the first make and last break of the circuit will occur between the arcing member 82 and the one contact bar 84. The mating surfaces of arcing member 82 and contact bar 84 can have a brazed arcing alloy 86 if further longevity is desired.

The alternative arrangement depicted in FIGURE 9 employs an arcing member 88 whose surfaces are flush with the surfaces of the stationary plate 18. The contact bar positioned opposite to the arcing member 88 is replaced with a longer contact bar (not shown) so that all arcing is confined to the arcing member 88 and the longer contact bar. The brazed arcing alloy 86 can also be employed in this arrangement, if greater longevity is desired. It will be appreciated that in both are confining arrangements the modular design of the present invention greatly simplifies the replacement of the arcing member and/ or contact bar.

For purposes of illustration, the arc confining arrangement has been depicted with respect to a single contact bar. However, it should be understood that additional arcing members and contact bars can be used if desired.

Although the preceding discussion has been limited to the components of switching element 12, the identical components are used in switching element 14 and any other switching element which may be added to switch 10 even after initial installation. Referring to FIGURES 1, 2 and 3 it can be seen that switching element 14 is physically secured to element 12 by means of tie plates 90 and fasteners 92. When the two switching elements are properly secured together, stationary plates 16 and 18 are in parallel, opposed relation to the corresponding first and second stationary plates 16a and 18b, respectively, in switching element 14. The rotational movement of hell crank 66 is transmitted to a corresponding bell crank 66a through connecting links 94. Subsequent movement of links 68a and the corresponding carrier bar, is the same as previously described in connection with switching element 12. Thus it can be seen that switching elements 12 and 14 operate in unison when shaft 60 is rotated by the operators movement of switch handle 62.

It will be appreciated that the relatively low profile of the leaf spring biased contact assembly allows a very narrow modular stacking height, as illustrated in FIG- URE 2, by the distance d. In addition to the parallel stacking of switching elements 12 and 14, as shown in 6 FIGURES 1, 2 and 3, the modular switch of the present invention can also be gauged on a common shaft merely by increasing the length of shaft 60 to accommodate another switching element.

As mentioned previously, the ampacity of the modular switch can be incrementally increased simply by adding contact assemblies. Similarly, the breakdown voltage rating can be raised by increasing the spacing between the two stationary plates 16 and 18, The longer air gap between the plates requires a different bell crank to provide a longer stroke and, of course, correspondingly longer contact bars. However, it is important to note that the modular design of the present invention permits an increase in the breakdown voltage rating without requirin a corresponding increase in the stacking height of the switching element.

From the foregoing description it will now be apparent to those skilled in the art that numerous minor variations of the preferred embodiments of my invention herein shown, are possible, and accordingly, it is not my intention to confine the invention to the precise form shown herein, but rather to limit it in terms of the appended claims.

Having thus described and disclosed a preferred embodiment of my invention, what I claim is new and desire to secure by Letters Patent in the United States is:

1. An electric switch comprising: first and second stationary, spaced, coplanar, electrically conductive plates; at least one movable contact assembly for establishing or interrupting a conductive path between said plates, said assembly comprising a pair of substantially planar electrically conductive bars each having convex contact members at the ends thereof, said bars being positioned in parallel, spaced relation with the convex contact members of the two bars facing each other, and means for leaf spring biasing each of said contact bars; and means for linearly moving said contact assembly between an open circuit position in which a first pair of the convex contact members grips both sides of the first stationary plate in electrical contact therewith and a closed circuit position in which a second pair of contact members slidably engages and grips both sides of the second stationary plate in electrical contact therewith while said first pair of contact members remains in electrical contact with said first plate thereby establishing or interrupting the conductive path between said plates.

2. The electrical switch of claim 1 further characterized by said second stationary plate having a straight contact member engaging edge; said convex contact members each having a generally semi-cylindrical configuration with the axis thereof normal to the longitudinal axis of the contact bar; and said moving means moving the contact assembly in a direction parallel to the longitudinal axis of said contact bars and normal to the straight edge of said second stationary plate so that said pair of contact members slidably engages and remains in electrical contact with said second plate in a line contact in the closed circuit position While the other pair of contact members slides across said first stationary plate in a line contact therewith.

3. An electrical switch comprising: first and second stationary, spaced, coplanar, electrically conductive plates; a plurality of movable contact assemblies removably secured to a carrier bar in parallel, side-by-side relation for establishing or interrupting a corresponding plurality of conductive paths between said plates, said assemblies each comprising a pair of substantially planar electrically conductive ba-rs each having convex contact members at the ends thereof, said bars being positioned in parallel, spaced relation with the convex contact members of the two bars facing each other, and independent means for leaf-spring biasing the pair of contact bars; and means for uniformly moving said carrier bar between an open circuit position in which a first pair of the convex contact members in each assembly grips both sides of the first stationary plate in electrical contact therewith and a closed circuit position in which a second pair of convex contact members in each assembly slidably engages and grips both sides of the sec- 0nd stationary plate in electrical contact therewith while said first pair of contact members remains in electrical contact with said first plate thereby establishing or interrupting the conductive paths between said plates.

4. A ganged electrical switch comprising: at least two switching elements operable in unison, said switching elements each comprising first and second stationary, spaced,

coplanar, electrically conductive plates, a plurality of movable contact assemblies removably secured to a carrier bar in parallel, side-by-side relation for establishing or interrupting a corresponding plurality of conductive paths between said plates, said assemblies each comprising a pair of substantially planar electrically conductive bars each having convex contact members at the ends thereof, said bars being positioned in parallel, spaced relation with the convex contact members of the two bars facing each other, and independent means for leaf-spring biasing the pair of contact bars; means for supporting said switching elements so that the first and second stationary plates of any one switching element are in parallel, opposed relation to the corresponding stationary plates of any other switching element; means for uniformly moving said-carrier bars in unison between an open circuit position in which a first pair of the convex contact members in each assembly grips both sides of the first stationary plate in electrical contact therewith and a closed circuit position in which a second pair of convex contact members in each assembly slidably engages and grips both sides of the second stationary plate in electrical contact therewith while said first pair of contact members remain in electrical contact with said first plate thereby establishing or interrupting the conductive paths between the stationary plates in each switching element.

References Cited UNITED STATES PATENTS 929,041 7/1909 Sontag 200-446 2,198,277 4/ 1940 Schellenger 200-146 2,679,567 5/ 1954 Kradel 200-169 2,751,471 6/ 1956 Wills 200-164 2,918,541 12/ 1959 Waite 200-166 3,143,622 8/ 1964 Fischer 200----146 FOREIGN PATENTS 667,031 7/ 1963 Canada. 926,739 4/ 1955 Germany.

ROBERT K. SCHAEFFER, Primary Examiner.

H. BURKS, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,381,105 April 30, 1968 Victor A. Mortenson It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, lines 40 and 42, "axis", each occurrence, should read axes Signed and sealed this 14th day of October 1969.

(SEAL) \ttest:

WILLIAM E. SCHUYLER, JR.

Commissioner of Patents Edward M. Fletcher, I r. testing Officer

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