GB2184890A

GB2184890A - A push-button switch having sealed switching chambers

Info

Publication number: GB2184890A
Application number: GB08630537A
Authority: GB
Inventors: Werner Schmalenbach
Original assignee: Brown Boveri und Cie AG Germany; BBC Brown Boveri France SA
Current assignee: BBC Brown Boveri AG Germany; BBC Brown Boveri France SA
Priority date: 1985-12-23
Filing date: 1986-12-22
Publication date: 1987-07-01
Also published as: DE3545879C2; GB2184890B; ES2003982A6; DE3545879A1; GB8630537D0

Abstract

The switch has a push-button 25, a switch base 1 and a latch lever 32 running in a slideway 42. In order to seal the switching chambers 21, 22 of the push-button switch to exclude solid or liquid foreign substances adequately and in such a way as to meet the demands of automated assembly and a compact slim construction, an insertable, pre- assembled insert member 36 is provided in the push-button 25 and an insert member 13 formed of one material throughout is provided in the housing wall 11 attachable to the switch base 1. <IMAGE>

Description

SPECIFICATION A push-button switch having sealed switching chambers and capable of being automatically assembled The invention relates to a push-button switch.

Push-button switches are known, for example from West German Patent Specification 2 606 551, in which a push-button and switch base enclose between them a switching chamber, which also accommodates a cam-controlled latch mechanism for holding the push button in or out, that is to say on or off or vice versa.

Known push-button switches of this kind are unsuitable for automatic assembly, and/or do not provide for adequate sealing of the interior against liquid or soiid foreign matter for example sand, dust, moisture, which might interfere with operation. By way of example, such a switch is described in unpublished German Patent Specification P 35 45 938.7; this switch is suitable for automatic assembly but does not provide sealing against foreign substances.

An object of the invention is to provide a push-button switch of a compact, slim design and to satisfy the requirements of automated assembly in respect of simplification and reduction in the number of assembly units, in such a way that its switching chambers are sealed to exclude liquid or solid foreign substances.

This invention provides a push-button switch comprising a switch base, a push-button slidable on the switch base, a latch mechanism operable by depression of the push-button and having two stable conditions in which respectively the push-button is in a stable "out" position relative to the switch base and the push-button is in a stable "in" position relative to the switch base and is held in by the latch mechanism, and switch contacts operable by movement of the pushbutton between its "in" and "out" positions, and in which the base is provided with an upstanding outer wall, and upstanding inner wall spaced from the outer wall by a channel, a guide projection within the inner wall for guiding the movement of the push-button, and webs extending between the inner wall and the guide projection, defining within the inner wall an enclosed switch chamber containing said contacts at one side of the guide projection and an enclosed latch chamber containing said latch mechanism at the opposite side of the guide projection, and the push-button has a skirt slidably received in the channel and has an internal guide well slidably seated on the guide projection, and a return spring acting to urge the push-button to its "out" position; whereby the said chambers are substantially sealed from the environment.

A preferred embodiment resides in a pushbutton switch with a push-button and a switch base, a latch lever and a latch slideway with a closed control curve, the slideway being provided with an inner slideway guide surface situated inside the control curve and an outer slideway guide surface situated outside the control curve, a follower mounted on the latch lever being alternately in a stable "off" position or a stable "on" position along the control curve describing the slideway guide, and the push-button being held in the "on" position by co-operation with the inner slideway guide surface and in the "off" position by co-operation with portions of the switch base, characterised in that a first insert member is mounted inside a housing wall, an encircling channel being formed between the inside wall surface of the housing wall and the outside wall surface of the first insert member, webs extend between the outside wall surface of the first insert member and the inside wall surface of the housing wall and between the inside wall surface of the first insert member and the generated surface of the push-button guide sleeve, in such a way that channel regions and switching chamber regions are physically separated in themselves and relative to one another, the housing wall can be fixed to the switch base, and the push-button has a second insert member on which there are formed a push-button guide cylinder with a guide sleeve receiving well, the slideway, and at least one well for receiving a contact bridge compression-spring with a space to allow movement of the contact bridge.

By means of these features foreign substances are substantially prevented from penetrating into the switching chambers. Any substances which do enter can be ducted away through openings in the side of the encircling channel. One advantage is that the arrangement and design of the components allow both satisfactory central guiding of the pushbutton and an extremely slim design of pushbutton switch (for example dimensions 15 x 41 mm; height without plug-in portion 28 mm; push-button size 12 x 38 mm). Also, the switch design facilitates automated assembly.

Thus, for example, the insert member for the push-button is readily accessible for pre-assembly and insertion into the push-button. Application of the housing wall to the switch base (also affording ease of access for preassembly), insertion of the push-button return spring and application of the push-button are the only steps required to complete the assembly process.

Preferred features of the invention are detailed in the sub-claims.

An embodiment of the invention will now be described and explained in more detail with reference to the drawings, in which: Figure 1 is a side view showing a pushbutton switch embodying the invention, in section on a line I-I and in the direction indicated by arrows in Figure 3; Figure 2 is an endwise cross-section through the push-button switch on a line Il-Il in Figure 1; Figure 3 is a plan view of the push-button switch without the push-button, with a Cshaped guide extension of the push-button shown in section at one side; Figure 4 is an endwise cross-section through the push-button switch a line IV--IV in Figure 3; and Figure 5 is a plan view of the switch base for the push-button switch.

Figures 1 to 5 illustrate an embodiment of the push-button switch in accordance with the invention by way of example.

As shown in Figure 1 a switch base 1 contains fixed contact members 3, 4, 5 anchored in corresponding recesses in the switch base floor 2. The contact members 3, 4 are placed over support blocks 6 of equal heights, integral with the floor 2, and are physically nested in one another with double right angles to give a narrow gauge for the switch base's plug-in portion (formed by the contact members 3/5, trapezoidal side wall members 7 and connecting walls 8).

Triangular guide protuberances 9 are formed on the connecting walls 8 parallel to the side wall members 7 in the central plane of the switch. The fixed contact member 5, which serves to connect a lamp 10, is bent and lies on the switch base floor 2. The lamp 10 may be connectable to a series resistance and can be used for continuous or status-dependent lighting, as desired. A frame-like first insert member 13, of one material throughout, is formed in and integral with a housing wall 11 which can be fitted to the switch base 1 by means of retaining elements 12. The wall 11 is rectangular in plan and similar.in size and shape to the switch base. The insert member 13 is similarly rectangular but is discontinuous with gaps in the middle of its long sides.

As Figure 3 shows, an encircling channel 14 is thus formed between the inside wall surface of the housing wall 11 and the outside wall surface of the first insert member 13, integral webs 1 6 being formed across the channel between the outside wall surface of the first insert member 13 at the ends of the latter, and the inside wall surface of the housing wall 11, and between the inside wall surface of the first insert member 13 and the generated surface of a-for example, cylindrical integral push-button guide sleeve 15, in such a way that channel regions 17, 18, 19, 20, and switching chamber region 21, and latch chamber 22, which serve respectively to receive a bridge contact connection 3, 4, 43 or to receive a latch device 32, 42 and the lamp 10, are physically separated in themselves and relative to one another.The floor of the channel 14 is at the same level, higher than the switch base floor 2, in all of its regions 17/20 except for deeper end regions 23.

These deeper regions 23 extend down to the switch base floor 2 and are designed to receive C-section guide projections 24 on the ends of a push-button 25.

As Figure 2 shows, bevels 26 are formed in the channel regions 18, 20 at the integral transition (without change of material) between the push-button guide sleeve 15 and the webs 16. These bevels 26 lead to rectangular side openings 27 in the wall 11 through which any foreign substances which have penetrated into the central channel regions 18, 20 can escape.

The deeper end regions 23 of the channel regions 17, 19 lead (Figure 1) to rectangular end openings 28 left at the level of the switch base floor 2, also to allow foreign substances to escape. The end openings 28 also serve to guide and retain the push-button, by co-operating with projections 24 which have snap-fit retaining nibs 29. Respective stop edges 30 at the tops of the end openings 28 define an upper end stop for the push button 25.

The contact surfaces 31 of the fixed contact members 3, 4 are mounted on the switch base floor 2 in the switching chamber region 21. The latch chamber region 22 houses, in addition to the lamp 10 and contact member 5 which are also mounted on the floor 2 (Figure 5), a latch lever 32 anchored in portions of the housing wall 11 (Figures 1 and 3).

Connection of the lamp 10, which is held between guide ribs 33, is, as Figure 5 shows, on the one hand by way of a first lead wire 62 (Figure 5) urged onto the contact member 4 by a push-button return compression spring 35 held in a well 34; and on the other hand in that a second lead wire 63 is urged onto the contact member 5 by the metal latch lever 32 or is soldered to the contact member 5, or a metal latch lever 32 previously connected to the second lead wire 63 is urged in turn onto the contact member 5.

The push-button 25 has a second insert member 36 (Figures 1 and 2), which is mounted in the underside of the button surface 37 of the push button 25 by means of snap-fit connections 46, 47 and a plug-in connection 48, 49. The snap-fit connections 46, 47 have retaining nibs 46 formed on a pushbutton guide cylinder 38 and retaining apertures 47 formed in the sides of the pushbutton 25. The plug-in connection 48, 49 has a pin 48 formed in the underside of the button surface and engaging in a corresponding hole 49 in the second insert member 36 with an interference fit.The push-button guide cylinder 38 with a guide sleeve receiving well 39, a slideway 42 and a cylindrical well 40 receiving a contact bridge compression spring 44 with a space 41 to allow movement of the contact bridge are formed on the second insert member 36, in such a way that the sli deway 42 is formed on one side region of the outer generated surface of the push-button guide cylinder 38, and the well 40 with, below it, the space 41, is formed in a region diametrically opposite. A contact bridge 43, supported on abutments 45 and slidable along the inside walls of the space 41, compresses the compression spring 44 in the well 40. The longitudinal axis of symmetry of the contact bridge 43 here lies in the plane defined by the central axes of the coil springs 35, 44.The push-button guide sleeve 15 is shaped to fit, and is slidable in, the receiving well 39 of the cylindrical push-button guide cylinder 38. Inside the guide sleeve 15, in turn, the pushbutton return spring 35 is received in its well 34 in such a way that it supports itself on the contact member 4 and on the floor of the well 39 of the push-button guide cylinder 38.

As Figure 4 shows, a latch lever 32 perma neatly and resiliently anchored in base portions of the first insert member 13 engages by way of its guide or follower pin 53 in the slideway guide 50 of the slideway 42 formed on the push button guide cylinder 38. The slideway 42 comprises an inner slideway guide or cam surface 51 lying inside a heartshaped control curve, and an outer slideway guide or cam surface 52 lying outside the control curve. A light guide 54 is formed in the button surface 37 of the push-button 25 to illuminate a central identification symbol 55 from lamp 10.

Operation of the push-button switch embodying the invention will now be described.

In the "out" position of the push-button, shown in the drawings, the push-button return spring 35 is compressed and the retaining nibs 29 abut on the upper end stops 30 in the end openings 28, the push-button 25 is held in a stable "off" position A, with contact bridge 43 raised clear of fixed contacts 3, 4.

The latch lever 32 is in the "off" position A (Fig. 4), being positively guided by a deflector cam 58 in an oblique position (in which it is under stress due to its resilience) in readiness for the next switching stroke.

During depression of the push-button 25 in opposition to the push-button return spring 35 (switch-on process) the contact bridge 43, bridging the contact members 3, 4, comes to bear on the latter, while the guide pin 53 of the switch lever 32 slides upwards on a bevel 56 on the inner slideway guide surface 51 under the influence of the resilient pre-tension resulting from its oblique position of readiness in the "off" position A. During further depression of the push-button 25, as far as contact of the guide pin 53 with a first lower stop 57 in opposition to the contact bridge compression spring 44, which now also has effect, the contact pressure between the contact bridge 43 and contact members 3, 4 reaches its maximum.If the push button 25 is now released the guide pin 53 engages in a recess 59 in the inner slideway guide surface 51 in the "on" position E, the contact pressure falling slightly below its maximum.

When the push-button 25 is pressed again (switch-off process) the guide pin 53 slides to a second lower stop 60, in which position it is to one side of the inner guide cam 5', and then, when the push button 25 is released again, along the deflector 58 on the outer slideway guide surface 52 to the "off" position A, in readiness for the next switching stroke.

Meanwhile, resilient pre-tension, which is at a maximum in the "off" position A, builds up in the resiliently mounted lever 32.

During the entire on/off switching cycle the push-button 25 slides on its guide sleeve 15 by way of its guide cylinder 38 and slides between the housing wall 11 and first insert member 13 by way of an encircling push-button skirt 61 which descends into the channel 14. The maximum depth to which the pushbutton 25 descends (determined by the lower stops 57, 60) and the height of the webs 16 are so matched relative to one another by means of recesses (not shown) formed in the push-button 25 and second insert member 36 and positively engaging the webs 16 that the switching chamber regions 21, 22 are physically separate from the channel regions 17/20 throughout the switching cycle.

Claims

1. A push-button switch comprising a switch base, a push-button slidable on the switch base, a latch mechanism operable by depression of the push-button and having two stable conditions in which respectively the push-button is in a stable "out" position relative to the switch base, and the push-button is in a stable "in" position relative to the switch base and is held in by the latch mechanism, and switch contacts operable by movement of the push-button between its "in" and "out" positions, and in which the base is provided with an upstanding outer wall, an upstanding inner wall spaced from the outer wall by a channel, a guide projection within the inner wall for guiding the movement of the push-button, and a connection between the inner wall and the guide projection, defining within the inner wall an enclosed switch chamber containing said contacts at one side of the guide projection and an enclosed latch chamber containing said latch mechanism at the opposite side of the guide projection, and the push-button has a skirt slidably received in the channel and has an internal guide well slidably seated on the guide projection, and a return spring acting to urge the push-button to its "out" position; whereby the said chambers are substantially sealed from the environment.

2. A push-button switch as claimed in claim 1 in which the said connection comprises webs.

3. A push-button switch as claimed in claim 1 or 2 in which the said walls, guide projection, and webs are integral parts of a member separate from the switch base and mounted on the switch base by a push-on fit.

4. A push-button switch as claimed in claim 3 in which the said member is secured on the switch base by snap-fit retaining means.

5. A push-button switch as claimed in claim 1, 2, 3 or 4 in which the push-button has an insert member fitted in it, which insert member integrally comprises a guide sleeve within which is the guide well, means defining a further well for a spring acting on a contact bridge carrying movable switch contacts, and means defining a cam track of the latch mechanism.

6. A push-button switch as claimed in claim 5 in which the said insert member is secured in the push-button by snap-fit retaining means.

7. A push-button switch as claimed in any preceding claim in which the outer wall is penetrated by at least one aperture level with the base of the channel.

8. A push-button switch as claimed in any preceding claim in which webs extend across the channel adjacent the guide projection and the region of the channel defined between these webs, the aforementioned connection or webs, and the exterior of the guide projection, is provided with an aperture through the outer wall and level with the base of the channel.

9. A push-button switch with a push-button and a switch base, a latch lever and a latch slideway with a closed control curve, the slideway being provided with an inner slideway guide surface situated inside the control curve and an outer slideway guide surface situated outside the control curve, a follower mounted on the latch lever being alternately in a stable "off" position or a stable "on" position along the control curve describing the slideway guide, and the push-button being held in the "on" position by co-operation with the inner slideway guide surface and in the "off" position by co-operation with portions of the switch base, characterised in that a first insert member is mounted inside a housing wall, an encircling channel being formed between the inside wall surface of the housing wall and the outside wall surface of the first insert member, webs extend between the outside wall surface of the first insert member and the inside wall surface of the housing wall and between the inside wall surface of the first insert member and the generated surface of the push-button guide sleeve, in such a way that channel regions and switching chamber regions are physically separated in themselves and relative to one another, the housing wall can be fixed to the switch base, and the push-button has a second insert member on which there are formed a push-button guide cylinder with a guide sleeve receiving well, the slideway, and at least one well for receiving a contact bridge compression-spring with a space to allow movement of the contact bridge.

10. A push-button switch as claimed in claim 9, characterised in that the push-button guide cylinder is slidable on a push-button guide sleeve which is shaped to fit it, and which houses the push-button return spring.

11. A push-button switch as claimed in claim 9 or 10 characterised in that the second insert member is mounted on the push-button by means of snap-fit connections and a plugin connection.

12. A push-button switch as claimed in claim 11, characterised in that the snap-fit connections have retaining nibs formed on the push-button guide cylinder and retaining apertures in the sides of the push-button.

13. A push-button switch as claimed in claim 11 or 12 characterised in that the plugin connection has a pin formed in the underside of the button surface of the push-button and engaging in a corresponding hole in the second insert member with an interference fit.

14. A push-button switch as claimed in any of claims 9 to 13, characterised in that the slideway is formed in a region of the generated surface of the push-button guide cylinder, and the contact bridge compression-spring receiving well with, below it, the space to allow movement of the contact bridge, is formed in a region diametrically opposite.

14. A push-button switch as claimed in any of claims 8 to 13, characterised in that side openings are provided in the sides of the housing wall and end openings in the ends of the housing wall at the respective level of the floor of the channel.

15. A push-button switch as claimed in any of claims 8 to 14, characterised in that the switch lever is anchored in portions of the first insert member, preferably resiliently.

16. A push-button switch as claimed in any of claims 8 to 15, characterised in that the plane defined by the central axes of the coil springs is parallel to the longitudinal axis of the contact bridge.

17. A push-button switch substantially as herein described with reference to the accompanying drawings.