GB2178234A - An electrical switch - Google Patents

Abstract

In an electrical switch of the kind which includes an operating key 12 pivotally mounted in a housing 10, a fixed contact 14, a moveable contact pivotally mounted for movement by the operating key 12 from a first position in which it is spaced from the fixed contact 14 to a second position in which it engages the fixed contact 14, and a spring which urges the moveable contact towards its first position and which also acts to return the operating key 12 to a rest position, the pivotally mounted moveable contact comprises a generally U-shaped member which may be formed from wire and which includes a fixed contact engaging portion 19 to which one end of the spring is attached. The fixed contact 14 is of generally planar form arranged so that its plane extends transversely with respect to the pivotal axis 23 of the moveable contact, and is shaped to provide a recess through which the portion 19 of the moveable contact extends, one side of the recess forming a ledge 25 which is engageable by the peripheral surface of the portion 19 of the moveable contact. <IMAGE>

Description

SPECIFICATION An electrical switch This invention relates to an electrical switch of the kind including a housing, an operating key pivotally connected at one end thereof to the housing for angular movement relative to the housing between a rest position and an operating position, a fixed contact mounted in the housing, a movable contact pivotally mounted in the housing for movement by the operating key from a first position in which the movable contact is spaced from the fixed contact, to a second position in which the movable contact engages the fixed contact, and a spring which urges the movable contact towards its first position and which acts to return the operating key to its rest position after operation of the key.

One example of an electrical switch of the kind specified is described in our prior patent No. 2064223B. In the switch which is described in this patent specification there is provided an angularly movable contact which is arranged in one position to engage an upper fixed contact and in another position to engage a lower fixed contact. Each of these fixed contacts is formed with a bent-over portion or flange which are thus alternatively engaged by the movable contact as the latter moves between its two alternative positions, the portion of the movable contact which is so engageable with either of the aforesaid two fixed contacts being connected to one end of the spring.A part of the movable contact remote from the aforesaid portion adapted to engage the upper and lower fixed contacts also engages further fixed contact means which are also formed with bent-over portions or flanges which engage and form seatings for the adjacent parts of the movable contact. It has been found in practice however that in some circumstances relatively poor electrical contact is made between the movable contact on the one hand and at least some of the fixed contacts on the other hand and it is one object of the present invention to provide a modified construction of electrical switch of the kind specified in which the efficiency of the electrical contact between the moving contact and the various fixed contacts is improved.

In accordance with the present invention there is provided an electrical switch of the kind including a housing, an operating key pivotally connected at one end thereof to the housing for angular movement relative to the housing between a rest position and an operating position, a fixed contact mounted in the housing, a movable contact pivotally mounted in the housing for movement by the operating key from a first position in which the movable contact is spaced from the fixed contact, to a second position in which the movable contact engages the fixed contact, and a spring which urges the movable contact towards its first position and which acts to return the operating key to its rest position after the operation of the key, wherein the pivotally mounted movable contact comprises a loop which includes a fixed contact engaging portion which is remote from the pivotal axis of the movable contact and to which one end of said spring is attached, said fixed contact comprising a member of generally planar configuration arranged so that its plane extends transversely with respect to said pivotal axis of the movable contact, the fixed contact being shaped to provide a recess within which said portion of the movable contact extends, one side of said recess forming a ledge which is engaged by the peripheral surface of said portion of the movable contact when the latter is in its second position corresponding to the operating position of the operating key.

There may be provided a second fixed contact which also comprises a member of generally planar configuration and which is also formed with a recess through which said portion of the movable contact extends, said second fixed contact recess providing at one side a second ledge which is engageable with said portion of the movable contact when the latter is in its first position corresponding to the rest position of the operating key. In this case, the aforesaid two fixed contacts are preferably disposed so that they extend in two parallel planes.

The loop which forms the movable contact may be of open generally U-shaped form with its free ends turned inwardly so that they are co-axial and generally parallel with the aforesaid fixed contact engaging portion of the movable contact. Said ends of the movable contact may then form pivots which respectively pivotally engage in apertures or recesses formed in two further fixed contacts which may also each be formed from a generally planar member, the two further fixed contacts being disposed in a pair of parallel planes which lie in planes which are coincident with the planes in which the first two mentioned fixed contacts are disposed.

The invention will now be more particularly described with reference to the accompanying drawings wherein Figure 1 is a plan view of part of the housing of an electrical switch constructed in accordance with the invention, Figure 2 is a section taken along the line 2-2 of Fig. 1, Figure 3 is a section taken along the line 3-3 of Fig. 1, Figure s 4 and 5 show respectively alternative forms that can be used for two of the four contacts seen in Figs. 1-3, Figures 6 and 7 show respectively alternative forms that can be used for another of the contacts seen in Figs. 1-3, and Figures 8 and 9 show respectively alternative forms that can be used for the remaining contact seen in Figs. 1-3.

Referring now to the drawing the electrical switch shown therein comprises a housing which is conveniently formed from two parts 10 and 11, each moulded in a synthetic resin material. There is also provided an operating key 12, also moulded in a synthetic resin material, and pivotally connected to the housing part 10. Such connection may be formed by means of a pair of opposed outwardly extending pivot posts 9 formed integrally on the housing part 10 which are adapted to be engaged respectively with a pair of laterally spaced slotted arms (not shown) which are inregrally connected to the operating key 12 so as to depend therefrom. Such pivotal connection between the operating key and the housing is more particulary described in our prior Patent No. 2064223B but this connection forms no part of the present invention.

Located within the housing part 10 is a movable contact 13 which comprises a loop of generally U-shaped configuration formed from wire which may be, as shown, of circular cross-section. Also located within the housing part 10 are a plurality (in this case four) fixed contacts indicated respectively by reference numerals 14, 15, 16 and 17. There is also provided a coiled spring 1 8 which is attached at one end to a part of the housing and at the other end to a portion of the movable contact 13 which acts as a fixed contact engaging portion and which is indicated by reference numeral 19.The aforementioned operating key 12 is integraily formed with a spigot 20 which extends through a suitable aperture formed in the housing part 11 and which is adapted to engage said spring 18 at a position intermediate its ends, said spigot 20 extending in a direction which is generally transverse to the axis of said spring.

The aforesaid fixed contacts 16 and 17 are of identical form and each comprise planar metallic portions formed so that a leg of each portion will project through the housing part 10 to form a pin which provides a terminal of the switch. Fig. 4 shows a view of the fixed contact 1 7 (and similarly the fixed contact 16) which is used in Figs. 2 and 3, such form including an aperture 21 arranged so that the two apertures thus provided in said contacts 16 and 17 are respectively adapted to receive the inturned ends 22 and 23 of the wire loop forming the movable contact 13.Said inturned ends 22 and 23 are co-axial and the aforementioned apertures 21 are slightly larger in diameter than the diameter of the wire forming said loop 13 so that said wire loop can freely pivot on the pivots which are provided by said inturned ends 22 and 23 turning within the apertures 21. Fig. 5 however indicates an alternative form for the fixed contact 17 and the fixed contact 16 in that as shown in Fig. 5 and indicated by reference numeral 17a, the aperture 21 is replaced by a generally V-shaped notch 22a in which the aforesaid inturned ends 22 and 23 of the wire loop 13 will be firmly seated by reason of the pressure applied in use by the spring 18. In this case also therefore the wire loop 13 will be able freely to pivot on the fixed contacts 16 and 17.

Each of the other two fixed contacts 14 and 15 is also formed from a planar piece of metallic material and each again is formed so as to have a leg which projects throught the housing part 10 to form two further terminals of the switch. Furthermore each of said fixed contacts 14 and 15 is formed with a recess which in the case of fixed contact 14 is indicated by reference numeral 23 and in the case of fixed contact 15 by reference numeral 24.

Fig. 6 shows separately the particular shape of fixed contact 14 which is also seen in Figs.

2 and 3 and as will be seen from Fig. 6 the aforementioned recess has a lower side 25 which forms a ledge which slopes outwardly and downwardly relative to the upper edge 26 of said contact 14. In the alternative version of contact 14, seen in Fig. 7 and indicated by reference numeral 14a, the aforementioned ledge 25 is replaced by a ledge 27 which is generally parallel to said upper edge 26 of the contact.

In the case of fixed contact 15, Fig. 8 shows separately this contact which is in the same form as is used in Figs. 2 and 3 and in this case the aforesaid recess 24 is bounded by a lower side or ledge 28 which is relatively inclined to the adjacent edge 29 of the contact together with an upper side 30. Fig. 9 shows an alternative form of this fixed contact (indicated by reference numeral 15a) and in this case the aforesaid recess 24 is bounded on its lower side by a ledge 31 which is generally parallel to the adjacent edge 29.

Fig. 2 shows a rest condition of the switch in which the operating key 12 is in a relatively open position in which its outer end is spaced from the adjacent surface of the housing part 11. Said operating key 12 will be have been moved to this position by engagement betweenthe coiled spring 1 8 and the free end of the spigot 20 formed on said key whilst at the same time said spring 18, acting on said fixed contact engagig portion 19 of the wire loop 13 will have moved said portion 19 into a position in which it is spaced from the ledge 25 formed on the fixed contact 14. The position of said movable contact 13 is indicated in full lines in Fig. 2 and it will be seen therefrom that said portion 19 of the movable contact 13 engages the ledge 28 of the fixed contact 1 5.

If now however the operating key 12 is depressed so that its outer end engages the adjacent surface of the housing part 11 as seen in Fig. 3 the free end of the aforemen tioned spigot 20 will engage the coiled spring 18 and deform it so as to push the aforementioned portion 19 of the movable contact away from the aforesaid ledge 28 on contact 15 and snap it over into engagment with the ledge 25 formed on fixed contact 14 as indicated in full lines in Fig. 3. The dashed lines in Fig. 2 indicate the position of the movable contact 13 when the operating key 1 is in its operating position as seen in Fig. 3 whereas the dashed lines in Fig. 3 indicate the position of said movable contact 13 when the operating key is in its rest position as shown in Fig.

2.

It will be seen from the drawing that the two fixed contacts 14 and 17 (which are each formed from a planar piece of metal) lie in the same plane which extends substantially perpendicularly both to the portion 19 and the inturned ends 22 and 23 of the movable contact 13. Similarly the fixed contacts 15 and 16, which are also formed from a planar piece of metal, lie in a common plane which extends substantially perpendicularly to the portion 19 and inturned ends 22 and 23 of the movable contact 13. Further, as stated above, in the rest position shown in Fig. 2 said portion 19 of the movable contact is disengaged from the ledge 25 of fixed contact 14 (whilst being engaged with the ledge 28 of fixed contact 15) whereas in the operating position shown in Fig. 3 said portion 19 is engaged with the ledge 25 of fixed contact 14 whilst being disengaged from the ledge 28 of fixed contact 15. It will of course be realised that the ends 22 and 23 are at all times in electrical contact with the fixed contacts 16 and 17 but where engagement between the portion 19 of the movable contact is made either between the ledge 25 or the ledge 28 a good and efficient electrical conductive path will be established by engagement of a part of the periphery of said portion 19 with either of said ledges. Such engagement will be firm and positive and will thus permit the required electrical current to flow between the movable contact 13 and either of the fixed contacts 14 and 15 depending upon the position of said movable contact.

Claims (11)

1. An electrical switch of the kind including a housing, an operating key pivotally connected at one end thereof to the housing for angular movement relative to the housing between a rest position and an operating position, a fixed contact mounted in the housing, a moveable contact pivotally mounted in the housing, a movable contact pivotally mounted in the housing for movement by the operating key from a first position in which the movable contact is spaced from the fixed contact, to a second position in which the movable contact engages the fixed contact, and a spring which urges the movable contact towards its first position and which acts to return the operating key to its rest position after operation of the key, wherein the pivotally mounted movable contact comprises a loop which includes a fixed contact engaging portion which is remote from the pivotal axis of the movable contact and to which one end of said spring is attached, said fixed contact comprising a member of generally planar configuration arranged so that its plane extends transversely with respect to said pivotal axis of the movable contact, the fixed contact being shaped to provide a recess through which said portion of the movable contact extends, one side of said recess forming a ledge which is engaged by the peripheral surface of said portion of the movable contact when the latter is in its second position corresponding to the operating position of the operating key.

2. An electrical switch as claimed in claim 1 wherein there is provided a second fixed contact which also comprises a member of generally planar configuration and which is also formed with a recess through which said portion of the movable contact extends, said second fixed contact recess providing at one side a second ledge which is engageable with said portion of the movable contact when the latter is in its first position corresponding to the rest position of the operating key.

3. An electrical switch as claimed in claim 2 said two fixed contacts are disposed so that they extend in two parallel planes.

4. An electrical switch as claimed in any one of the preceding claims wherein the movable contact is of open generally U-shaped form with its free ends turned inwardly so that they are co-axial and generally parallel with the aforesaid fixed contact engaging portion of the moveable contact.

5. An electrical switch as claimed in claim 4 wherein said free ends of the movable contact form pivots which respectively pivotally engage in apertures or recesses formed in two further fixed contacts.

6. An electrical switch as claimed in claim 5 wherein said two further fixed contacts are also each formed from a generally planar member, the two further fixed contacts being respectively disposed in a pair of parallel planes which lie in planes which are coincident with the planes in which the first two mentioned fixed contacts are disposed.

7. An electrical switch as claimed in claim 2 wherein each of said ledges is of planar configuration and wherein said fixed contact engaging portion of the movable contact loop is of circular configuration in cross-section.

8. An electrical switch as claimed in claim 2 or claim 7 wherein one or each of said ledges is arranged so that the associated recess is of outwardly flared configuration.

9. An electrical switch as claimed in claim 5 or claim 6 wherein each of said two further contacts is formed with an aperture with which the associated free end of the movable contact is pivotally engaged.

10. An electrical switch as claimed in claim 5 or claim 6 wherein each of two further fixed contacts is formed with a recess with which the associated free end of the movable contact is pivotally engaged.

11. An electrical switch of the kind specified substantially as hereinbefore described with reference to and as shown in Figs. 1, 2 and 3 of the accompanying drawings.