US3291933A - Electrical switch unit with thin strip mount and sequentially operated snap switches - Google Patents

Description

Dec. 13, 1966 A. T. c. BURROWS 3,291,933 ELECTRICAL SWITCH UNIT WITH THIN STRIP MOUNT AND SEQUENTIALLY OPERATED SNAP SWITCHES 4 Sheets-Sheet 1 Filed Oct. 15. 1965 FIG! U 2666 o o 5 2'7 27 26b 26b 34d Z0 Z0 flvf/wve flew/m? 77/0/1445 4492155 31/220015 Dec. 13, 1966 T c. BURROWS 3,291,933

A. ELECTRICAL SWITCH UNIT WITH THIN STRIP MOUNT AND SEQUENTIALLY OPERATED SNAP SWITCHES Filed 0C(.. 15, 1965 4 Sheets-Sheet 2 MM flag 14AM Dec. 13, 1966 A. T. c. BURROWS 3,291,933

ELECTRICAL SWITCH UNIT WITH THIN STRIP MOUNT AND SEQUENTIALLY OPERATED SNAP SWITCHES 4 Sheets-Sheet 5 Filed Oct. 15. 1965 14 7p A/E Y5 Dec. 13, 1966 A. T. c. BURROWS 3,291,933

ELECTRICAL SWITCH UNIT WITH THIN STRIP MOUNT AND SEQUENTIAL-LY OPERATED SNAP SWITCHES Filed Oct. 15. 1966 4 Sheets-Sheet 4 i/z f/wv/e' Jg THZIE $701 096 flwezas @EFM/ 977- z vfs s United States Patent ()flice 3,291,933 Patented Dec. 13, 1966 ELECTRICAL SWITCH UNIT WITH THIN STRIP MOUNT AND SEQUENTIALLY OPERATED SNAP SWITCHES Arthur Thomas Charles Burrows, Stevenage, England, assignor to Geo. W. King Limited, Stevenage, Hertfordshire, England, a British company Filed Oct. 15, 1965, Ser. No. 496,581 Claims priority, application Great Britain, Nov. 13, 1964, 46,423/ 64 14 Claims. (Cl. 200-76) This invention relates to electrical switch units.

In the case of an electrically operated hoist the electric motor for driving the winding drum will, when the hoist is in its operative position, normally be located at an elevated position out of easy reach of an operator at floor or ground level and it is convenient therefore to provide a so-called pendant switch unit which will hang down from the hoist and will be located at such a level that an operator standing on the floor or ground may readily control the operation of the hoist motor. Since such a switch unit is suspended its weight and facility of operation are features of considerable importance.

It is the primary object of the present invention to provide an improved pendant switch unit which is relatively light in weight and of compact construction such that it will be capable of being readily held in and manipulated by one hand thus leaving the other hand of the operator free for load control or other purposes. It is a further object to provide a switch unit so designed that the risk of wrong actuation by an operator will be reduced to a minimum.

According to the present invention there is provided a switch unit comprising two strip like elements so formed and relatively so arranged as to provide spaced parallel supporting means at least one of which is adapted to support two or more pairs of fixed electrical contacts at spaced locations therealong, two or more plunger members supported in spaced relation by said pressings for sliding movement transversely with respect thereto and a pair of contact carriers pivotally mounted on each plunger member in such a manner as to be disposed in the space between the aforesaid strip like elements, such contact carriers being spring loaded and so arranged on their respective plunger members that upon depression of either plunger member the contact carriers associated therewith will be moved angularly past a dead centre position whereafter the spring will be effective to cause them to snap into a position wherein the contacts carried thereby will bridge the appropriate pair of fixed contacts carried by the aforesaid supporting means. Preferably the plunger members will be actuated through the medium of depressible push button elements appropriately disposed in an outer casing housing the switch mechanism and springs or the like will be associated with said plunger members, which springs will be effective to restore the plunger members, and their associated contact carriers to their initial positions upon release of pressure on said push button elements. Preferably also interlocking means will be incorporated to prevent simultaneous actuation of the plunger members, i.e., when one push button element is depressed the plunger member with which the other push button element is associated will be positively prevented from operative movement.

In order that the nature of the invention may be more readily understood reference will now be made to the accompanying drawings which show one embodiment by way of example and in which:

FIGURE 1 is a front elevational View of a switch assembly partially broken away to permit of illustration of various constructional features,

FIGURE 2 is a sectional view on a horizontal plane,

FIGURE 3 is a longitudinal sectional view, the plane of the section being varied, the better to illustrate constructional details,

FIGURE 4 is a schematic diagram illustrating a switch assembly such as is illustrated in FIGURES 13 connected in the control circuit of a reversible electric motor,

FIGURES 5 and 6 are respectively a side elevational and plan view of a pressing from which switch body components may be produced.

Referring now to the drawings 10, 11 and 12 denote three parts of an outer casing adapted to house the switch mechanism, such parts comprising metal pressings which are provided with a coating of plastic or other dielectric material of the order of .020" thick. Interposed between the aforesaid parts on assembly thereof are annular sealing rings 13 formed of rubber or other appropriate mate-rial. It will be noted that the upper end casing part 10 is formed with an enlarged hole adapted to accommodate a cable sleeve 14 while the central or main part 11 is provided with two depressible switch operating elements 15 each formed of rubber or other appropriate material. Each of the elements 15. conveniently carries a plate 16 marked, as will be clearly seen from FIGURE 1, to indicate the function of the switch, such plate being in turn covered by a transparent disc or the like 17 adapted to constitute a window.

Located within the aforesaid outer casing is the actual switch unit which comprises two steel pressings 18, 19 adapted to support a plurality of contacts 20 which are appropriately disposed in pairs. Supported in the pressings 18, 19 for limited sliding movement transversely with respect thereto are three plunger members 21, 22 and 23 each of which is urged by a separate spring 24 into its normal or at rest position, i.e., is urged to the right as shown in FIGURE 3. The upper and lower members 21, 23 are identical and each is so arranged that one of the depressible operating elements 15 will register and cooperate therewith. Moreover each of the members 21 and 23 is provided with a cantilever projection one of which is indicated at 25 (FIGURE 3) adapted to cooperate with the central plunger member 22 as will be hereinafter more fully described. As shown the member 23 is provided with an upwardly directed projection 25 but it will be appreciated that in the case of the member 21 such projection will be directed downwardly as indicated in FIGURE 1. The centre plunger member 22 while being similar to the members 21 and 23 will not however be provided with any projection such as 25 nor will it cooperate directly with either of the depressible elements 15.

Pivotally mounted on each of the plunger members 21, 22 and 23 are two contact carriers 26 each adapted to support a pair of contacts in the form of rollers 27. As will be seen from FIGURE 1 each of the contact carriers 26 is provided with an upper and a lower arm 26a, 26b respectively such arms being adapted to engage in V- shaped recesses formed respectively in projections 28 and 29 at the upper and lower sides of each plunger member. In FIGURE 2 the aforesaid recesses are shown in the upper projection 29 such recesses being indicated by the reference numeral 30. The contact carriers 26 on each plunger member are connected by a tension spring 31 which serves to hold said carriers in the operative or nonoperative position, it being appreciated that when a pair of carriers is moved angularly from one limiting position such movement will initially tension the spring 31 but as soon as the dead centre position is passed said spring will be effective to snap said contact carriers into the other limiting position.

The fixed contacts 20 are rivetted in pairs on contact holders 32 which are formed of plastic or other appropriate dielectric material and are held in place on the respective pressings 18, 19 by means of nuts and bolts such as are indicated at 33. Associated with each contact is an element 34 which acts as a washer for the rivetted or turned over head of the contact and is formed with a blade like portion 34a to which current supply leads are connected.

The unit illustrated in the drawings is suitable for controlling a two speed reversible electric motor and in this particular case the contact holder 32 mounted on the pressing 18 is fitted with three sets each of four contacts i.e. two pairs of fixed contacts in respect of each of the plunger members 21, 22 and 23. The contact holder carried by the pressing 19 is on the other hand fitted with only one set of four contacts 20 with which the plunger member 22 will cooperate but in order to maintain the geometry of the unit-correctly it is also fitted with two sets of dummy insulating strips 35 with which the rollers 27 on the contact carriers 26 of the plunger members 21 and 23 will be in contact when said plunger members are inoperative.

In order to prevent depression of the other element and actuation of its associated plunger member 21 or 23 when one of such elements is already depressed an interlock device is incorporated which will be effective on displacement of one of said plunger members to be moved thereby into a position wherein it will prevent actuation of said other plunger member. In the embodiment such an interlock device comprises a rod 36 of rectangular section such rod which is slidably supported in guides on the pressing 18 having wedged shaped ends adapted to function as cam surfaces. The shank portion of each plunger 21, 23, carrying a push button element 15 is formed with a slot which provides a cam or beveled surface adapted to cooperate with the cam surface on the appropriate end of the bar 36. When the switch is inoperative the beveled end of the bar 36 will be in engagement with the slot in the shank of the plunger member last inoperativei.e., plunger 23 in FIGURE 3, so that plunger 21 is free to be depressed. On the other hand, if plunger 23 is depressed the bar will move longitudinally until the other beveled end is in its corresponding slot in the shank of plunger 21 leaving plunger 23 free to be depressed. If plunger 21 is then depressed while plunger 23 is depressed, the shank of plunger 23 will prevent axial displacement of the bar 36. Thus, the depression of one of said plunger members 21 or 23 will result in axial displacement of said rod so that it will positively prevent depression of the second member- To avoid loading the current carrying cable to which the switch assembly is attached, a loop 37 is attached to the central portion 11 of the outer casing, such loop allowing for the attachment of a wire rope or chain which will be eifective actually to support the switch assembly, said rope or chain being shorter than the cable so that the latter will always remain slack and not be submitted to any undesirable pulling.

It will be noted that the cable sleeve 14 is so designed that it may readily be cut to suit cables of different diameters. It will be noted that the supply cable introduced through the sleeve 14 will be clamped in place by means of acable clamp 38 which is carried by a bracket 39 attached to the pressings 18, 19.

The assembly above described is adapted to operate as follows:

If either of the elements 15 is depressed the appropriate plunger member 21 or 23 will be moved inwardly against the action of its spring 24 and if the extent of the depression is sufficient the contact carriers 26 associated with that member will be caused to pass over the dead centre position and snap into an operative position wherein the contact rollers 27 will bridge the appropriate fixed contacts 20. As will be seen from the wiring diagram of FIGURE 4 such an operation will result in completion of the circuit for one set of windings of the reversible electric motor which is indicated at 40. As will be seen at this stage the roller contacts 27 associated with the centre plunger member 22 will already be bridging a pair of fixed contacts 20 (i.e. the contacts carried by the pressing 19). Upon further depression of the element 15 the projection 25 on the appropriate plunger member (i.e. the plunger member 21 or 23 which was initially displaced) will engage the middle plunger member 22 and will force the same rearwardly against the action of its spring 24, with resultant snapping over of its contact carriers 26 to bring the respective roller contacts 27 into engagement with the appropriate set of contacts 20 carried by the pressing 18. With the first setof contacts 20 still closed as a result of the action of the plunger member 21 or 23 as the case may be it will be appreciated on reference to the diagram of FIGURE 4 that actuation of the plunger member 22 will result in energisation of the other motor windings and in increase of the motor speed. It is to be understood that the fixed contacts 20 appropriate to the plunger member 21 and the contacts 20 appropriate to the plunger member 23 are respectively so connected that on closure they will cause rotation of the motor in opposite directions. As will be seen from the diagram of FIGURE 4 the brake coil which is designated by 41 will remain energised during change-over from one motor speed to the other whatever the direction of rotation of the motor.

As hereinbefore indicated the switch assembly above described is suitable for control of a two speed reversible motor such as is commonly employed in hoist equipment. Clearly the assembly could readily be adapted for single speed motor control by omitting the central plunger member 22 and its associated components and/or it thought necessary by limiting the travel of the plunger members 21, 23.

Alternatively by appropriately increasing the length of the pressings 18, 19 and of course the casing part 11 it would be possible to provide for an increase in the number of plunger members incorporated in the switch unit. Provision may be made for any number of plunger members up to say eight with the associated fixed contacts and appropriate provision of switch operating elements 15 in the casing part 11. With the construction described it will be feasible to produce the pressings 18, 19 and components of the casing part 11 in relatively long strips from which appropriately dimensionedlengths may be cut off as required. In FIGURES 5 and 6 there is illustrated a pressed strip from which sections of appropriate length may be cut to form the fronts of easing parts 11. The strip of FIGURES 5 and 6 is of channel or U section and is provided with apertures 40 each adapted to accommodate a depressible switch operating element such as 15. To provide for the completion of casing parts 11 a further channel or U section strip will be provided such strip being complementary to that shown in FIGURES 5 and 6 but without the apertures 40. To form a casing part 11 a selected length of the apertured strip shown in FIGURES 5 and 6 will be cut off together with a corresponding length of complementary but unapertured strip whereafter the two cut lengths will be appropriately applied one to the other and welded together to 'form an open ended hollow sleeve which will constitute the required casing part 11. Thus it will be appreciated that switch assemblies incorporating any desired combination of push buttons may readily be produced and since the resulting unit will be relatively slender it will be capable of being readily held and manipulated in and by one hand, thus leaving the other hand of the operator free for load control or other purposes. Furthermore in view of the clear marking of the depressible elements or push buttons it will be readily apparent to any operator which element requires to be depressed to obtain the desired functioning of any motors with which the switch assembly is associated.

What I claim is:

1. A switch unit comprising:

two elongated, relatively thin, strip-like elements, the

"two elements being parallel with their longitudinal faces being spacedly and oppositely disposed from each other;

at least two pairs of fixed electrical contacts mounted on the face of at least one support element at longitudinally spaced positions thereon, each pair of fixed electrical contacts being operatively associated with a pair of contact carriers mounted on a plunger;

means mounted on strip-like elements for supporting at least two plunger members for sliding movement transversely with respect to the faces of the supporting elements;

at least two plunger members supported by the plunger support means; and

a pair of contact carriers, having contacts carried thereby, pivotally mounted on each plunger member in such manner so as to be disposed in the space between the support elements, the contact carriersbeing spring loaded and so arranged on their respective plunger members that upon appropriate depression of either plunger member the contact carriers associated therewith will be moved angularly past a dead center position whereafter the spring will be effective to cause them to snap into a position wherein the contacts carried thereby will bridge the appropriate pair of fixed contacts carried by the support element.

2. A switch unit as in claim 1 wherein the support members, plunger members and associated parts are housed within an outer casing, the outer casing being equipped with at least one depressible element arranged to cooperate with one plunger member.

3. A switch unit as in claim 1 including resilient means associated with each plunger member adapted normally to maintain each plunger member in an initial position such that the contacts carried by the contact carriers will be out of contact with the appropriate pair of fixed contacts, the arrangement being such that depression of the plunger member will take place against the action of said resilient means which will be effective to restore said plunger member to its initial position on removal of pressure from the plunger member.

4. A switch unit as in claim 1 in which one of the plunger members is mounted so as to be operatively connected to the second plunger member, the second plunger member having a lateral projection with its outer free end positioned within the path of movement of the first plunger member, whereby initial depression of the secnd plunger member brings its movable contacts into engagement with the appropriate pair of fixed contacts and brings the projection into engagement with the first plunger member, and further depression of the second plunger member causes the first plunger member to be likewise depressed and effect movement of its movable contacts into engagement with its associated fixed contacts.

5. A switch unit as in claim 1 including an additional plunger member mounted by the support elements and in operative engagement with at least two other plunger members, the additional plunger member having a pair of contact carriers, with contacts carried thereby, pivotally mounted thereon, the contact carriers being spring loaded and so arranged that they are normally adapted to be disposed from a pair of fixed contacts mounted on the support elements, the two other plunger members each having a lateral projection with its outer free end positioned within the path of movement of the additional plunger member, whereby initial depression of either of the two other plunger members brings its movable contacts into engagement with the appropriate pair of fixed contacts and brings its projection into engagement with the additional plunger member and further depression of the initially depressed plunger member causes the additional plunger member to be likewise depressed and effect movement of its movable contacts into engagement with its associated fixed contacts.

6. A switch unit as in claim 5 including interlocking means operatively associated with the two plunger members for positively preventing actuation of one of the two plunger members.

7. A switch unit comprising:

support means comprising at least two parallel faces spacedly and oppositely disposed from each other and facing each other;

at least two pairs of fixed electrical contacts mounted on at least one face of the supporting means at longitudinally spaced positions, each pair of fixed electrical contacts being operatively associated with a pair of contact carriers mounted on a plunger;

means on the support means for supporting at least two plunger members for sliding movement transversely with respect to the faces of the support means;

at least two plunger members supported by the plunger support means, a first plunger member having a lateral projection with its outer free end positioned within the path of movement of the second plunger member and disposed therefrom in its non-operative position; and

a pair of contact carriers, h-aving contacts carried thereby, pivotally mounted on each plunger member in such a manner so as to be disposed in the space between the support means, the contact carriers being spring loaded and so arranged on their respective plunger members that upon appropriate depression of either plunger member the contact carriers associated therewith will be moved angularly past a dead center position whereafter the spring will be effective to cause them to snap into a position wherein the contacts carried thereby will bridge the appropriate pair of fixed contacts carried by the support means, whereby initial depression of the first plunger member brings its moveable contacts into engagement with the appropriate pair of fixed contacts and brings the projection into engagement with the second plunger member and further depression of the first plunger member causes the second plunger member to be likewise depressed and effect movement of its movable contacts into engagement with its associated fixed contacts.

8. The switch unit as in claim 7 wherein the support means comprises two elongated, relatively thin, striplike elements, the two elements being parallel with their longitudinal faces being spacedly and oppositely disposed from each other, and the two pair of fixed electrical contacts being mounted over the face of at least one support element at longitudinally spaced positions thereon.

9. The switch unit as defined in claim 7 additionally comprising a third plunger member identical to the first plunger member and having a projection likewise disposed from and extending into the path of movement of the second plunger member whereby initial depression of either the first or third plunger member brings its moveable contacts into engagement with the appropriate pair of fixed contacts and brings the projection into engagement with the second plunger member and further depression of this plunger member causes the second plung or member to be likewise depressed and effect movement of its moveable contacts into engagement with its associated fixed contacts.

10. The switch unit as in claim 9 including interlocking means extending between the first and third plunger members for positively preventing actuation of one of the plunger members when the other plunger member is depressed.

11. The switch unit as in claim 7 wherein the support means, plunger members and associated parts are housed within an outer casing, the outer casing being equipped with at least one depressible element arranged to cooperate With the plunger member having the projection.

pressible element is made of resilient material.

13. The switch unit as in claim 7 including resilient means associated with each plunger member adapted normally to maintain each plunger member in an initial position such that the contacts carried by the contact carriers will be out of contact with the appropriate pair of fixed contacts, the arrangement being such that depression of the plunger member will take .place against the action of said resilient means which will be effective to restore said plunger member to its initial position on removal of pressure from the plunger member.

8 14. A switch unit as in claim 7 including a second pair of fixed contacts engageable by the contacts of the second plunger member in its normal position, the two pairs of fixed contacts associated with the second plunger member providing for variations in the electrical circuit in which the switch unit is incorporated.

No references cited.

ROBERT K. SCHAEFER, Primary Examiner.

D. SMITH, Assistant Examiner.

Claims (1)

1. A SWITCH UNIT COMPRISING: TWO ELONGATED, RELATIVELY THIN, STRIP-LIKE ELEMENTS, THE TWO ELEMENTS BEING PARALLEL WITH THEIR LONGITUDINAL FACES BEING SPACEDLY AND OPPOSITELY DISPOSED FROM EACH OTHER; AT LEAST TWO PAIRS OF FIXED ELECTRICAL CONTACTS MOUNTED ON THE FACE OF AT LEAST ONE SUPPORT ELEMENT AT LONGITUDINALLY SPACED POSITIONS THEREON, EACH PAIR OF FIXED ELECTRICAL CONTACTS BEING OPERATIVELY ASSOCIATED WITH A PAIR OF CONTACT CARRIERS MOUNTED ON A PLUNGER; MEANS MOUNTED ON STRIP-LIKE ELEMENTS FOR SUPPORTING AT LEAST TWO PLUNGER MEMBERS FOR SLIDING MOVEMENT TRANSVERSELY WITH RESPECT TO THE FACES OF THE SUPPORTING ELEMENTS; AT LEAST TWO PLUNGER MEMBERS SUPPORTED BY THE PLUNGER SUPPORT MEANS; AND A PAIR OF CONTACT CARRIERS, HAVING CONTACTS CARRIED THEREBY, PIVOTALLY MOUNTED ON EACH PLUNGER MEMBER IN SUCH MANNER SO AS TO BE DISPOSED IN THE SPACE BETWEEN THE SUPPORT ELEMENTS, THE CONTACT CARRIERS BEING SPRING LOADED AND SO ARRANGED ON THEIR RESPECTIVE PLUNGER MEMBERS THAT UPON APPROPRIATE DEPRESSION OF EITHER PLUNGER MEMBER THE CONTACT CARRIERS ASSOCIATED THEREWITH WILL BE MOVED ANGULARLY PAST A DEAD CENTER POSITION WHEREAFTER THE SPRING WILL BE EFFECTIVE TO CAUSE THEM TO SNAP INTO A POSITION WHEREIN THE CONTACTS CARRIED THEREBY WILL BRIDGE THE APPROPRIATE PAIR OF FIXED CONTACTS CARRIED BY THE SUPPORT ELEMENT.

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