Microswitch assembly which can be associated to a gas cock, in particular for cooktops and the like

Abstract

 The microswitch unit (10) can be associated with a gas supply control tap (14), in particular for cooking hobs and the like, and comprises a fixed casing and an actuating member. The fixed casing houses a fixed contact strip (20) and a movable contact strip (22) facing each other. The actuating member has a base portion mounted slidably inside the casing and provided with means able to cause engagement/disengagement of the contact strips (20, 22) with/from each other, and a top portion provided with means able to snap-engage with a stem (12) of the tap (14).

Description

[0001] The present invention relates to a microswitch unit which can be associated with a gas supply control tap, in particular for cooking hobs and the like.

[0002] Microswitch units of this kind are typically used to operate electric components of the cooking hob and for sending signals to control boards.

[0003] According to a known technology, the microswitch unit is associated with a stem of the tap by means of an external spring and an elastic circlip using an assembly procedure which is fairly complex and costly.

[0004] In order to overcome this drawback of the prior art, the present invention relates to a microswitch unit comprising: a fixed casing, which houses a fixed contact strip and a movable contact strip facing each other, and an actuating member having a base portion, mounted slidably inside said casing and provided with means able to cause engagement/disengagement of said contact strips with/from each other, and a top portion provided with means able to snap-engage with a stem of the tap.

[0005] The microswitch unit according to the invention may be easily associated with a gas supply control tap by engaging the snap-engaging means of the top portion of the actuating member with a circumferential groove which is typically present on the outer surface of the stem of a tap.

[0006] The microswitch unit according to the invention also has the further advantages of the low cost of its component parts and the suitability for adaptation to gas supply control taps of the most varying type and size.

[0007] Further advantages and characteristic features of the present invention will emerge from the detailed description which follows, provided by way of a non-limiting example, with reference to the accompanying drawings in which:

Figure 1 is a perspective view of a microswitch unit according to the invention associated with a gas supply control tap,

Figure 2 is an exploded perspective view of components of the microswitch unit according to the invention and a tap stem,

Figure 3 is a schematic elevation view of the microswitch unit according to the invention, in which the associated electric circuit is in the open configuration,

Figure 4 is a view similar to that of Figure 3, in which the electric circuit is in a closed configuration,

Figure 5 is a cross-sectional view along the line V-V in Fig. 3,

Figure 6 is a view, on a larger scale, of some components of the microswitch unit according to the invention, and

Figure 7 is a schematic perspective view of a series of microswitch units according to the invention.

[0008] A microswitch unit 10 is associated (Fig. 1) with a stem 12 of a gas supply control tap 14, in particular for cooking hobs and the like. The exploded view of Fig. 2 shows various components of the unit 10 and in particular: a fixed casing formed by a hollow body 16 and by a cover 18, a fixed contact strip 20 and a movable contact strip 22 facing each other, a first and a second electric wire 24, 26, a resilient recall member such as a helical spring 28 and an actuating member such as a bush 30.

[0009] The body 16 of the casing is shaped substantially in the form of a parallelepiped and the cover 18 is mounted on the upper side of the body 16. The upper surface of the body 16 and the cover 18 have respective openings 32a, 32b which are able to allow, as described in detail below, the displacement of the bush 30.

[0010] The perimeter of the opening 32b formed on the cover 18 is surrounded by an annular shoulder 34 so as to prevent the penetration of liquids inside the casing, which for example are produced by condensation of vapour or are accidentally spilled on the cooking hob.

[0011] The body 16 has, moreover, respective seats 36 for housing the first and second electric wire 24, 26 which co-operate with ribs 38 of the cover 18, preventing closure thereof if the wires 24, 26 are not correctly positioned inside the respective seats 36.

[0012] The movable contact strip 22 is shaped substantially in the form of a U and has a first fixed arm 40, provided with an incision 42 for insertion of the first electric wire 24 with cutting of its insulating sheath, and a second arm 44 movable towards the fixed contact strip 20. The movable arm 44 has moreover a protuberance 46 directed towards the bush 30.

[0013] The fixed contact strip 20 has a first portion 48, provided with an incision 50 for the insertion of the second electric wire 26 with cutting of its insulating sheath, and a second portion 52 arranged alongside the first portion 48 and facing the movable arm 44 of the movable contact strip 22.

[0014] The bush 30 has a circular base portion 54 which is slidably mounted inside the casing and a top portion 56 with a frustoconical shape formed by a ring of inclined elastic lugs 58 alternating with slits 60. The lugs 58 act as means for snap-engagement with a circumferential groove 62 present on the outer surface of the stem 12 of the tap 14. Spacers 64 projecting internally inside the bush 30 (Fig. 5) ensure that the latter and the stem 12 are coaxial.

[0015] The helical spring 28 is arranged between a flat piece 66 radially projecting from the bottom end of the base portion 54 of the bush 30 and a bottom surface of the casing so as to be coaxial with respect to the stem 12 of the tap 14.

[0016] The base portion 54 has, in addition to feet 68 for guiding its sliding movement inside the casing, a bottom lug 70 formed by a flat piece 72 having, protruding radially therefrom, a stud 74 able to bias the outer surface of the movable arm 44 of the movable contact strip 22. The outer surface of the flat piece 72 also has, at one of its bottom ends, a chamfer 76 able to interact with the protuberance 46 of the movable contact strip 22.

[0017] Figure 3 shows the microswitch unit in the rest configuration with the associated electric circuit open. In this configuration, the stud 74 pushes upwards the outer surface of the movable arm 44, keeping it disengaged from the fixed contact strip 20.

[0018] When the user pushes the stem 12 downwards, by operating a top knob not shown, the engagement of the ends of the lugs 58 inside the groove 62 causes the simultaneous displacement of the bush 30 (cf. arrow 78 in Figures 4 and 5), such that the movable arm 44, which is no longer opposed by the stud 74 which has moved downwards, touches the fixed contact strip 20, closing the electric circuit (Figure 4). It should be noted that, after closing of the electric circuit has been performed, the downwards displacement of the bush 30 does not cause any further substantial biasing of the fixed contact strip 20 by the movable arm 44, in the direction perpendicular thereto, which could in the long run cause a damaging deformation of the contact strips 20, 22. On the other hand, following interaction between the chamfer 76 of the flat piece 72 and the protuberance 46 of the movable arm 44, the latter slides on the fixed contact strip 20 (cf. arrow 80 in Figure 5), exerting a cleaning action which removes impurities which may have been deposited thereon and ensures that good electric conductivity properties are maintained over time.

[0019] The downwards displacement of the bush 30 is opposed by the spring 28 which is progressively compressed against the bottom of the body 16 of the casing. Consequently, as soon as the user releases the top knob of the stem 12, the spring 28 pushes again the bush 30 into the position shown in Figure 3 and the electric circuit is opened again, since the stud 74 pushes upwards the outer surface of the movable arm 44, disengaging it from the fixed contact strip 20.

[0020] It is possible to associate several microswitch units of the type described above with respective gas supply control taps present on a same cooking hob. In this case, the electric wires may be the same for the various microswitch units which are arranged longitudinally staggered. Figure 7 shows by way of example four microswitch units 10 arranged in succession along the wires 24, 26 having at their end a faston or dedicated connector 82. For greater clarity, Figure 7 does not show the gas supply control taps.

[0021] Obviously, without modifying the principle of the invention, the constructional details and the embodiments may vary widely with respect to that described purely by way of example, without thereby departing from the scope claimed. In particular, the various components of the microswitch unit may be manufactured with forms and dimensions such as to adapt to the most varied range of configurations and sizes of tap stem.

Claims

1. Microswitch unit (10) which can be associated with a gas supply control tap (14), in particular for cooking hobs and the like, said unit (10) comprising: a fixed casing, which houses a fixed contact strip (20) and a movable contact strip (22) facing each other, and an actuating member having a base portion mounted slidably inside said casing and provided with means able to cause engagement/disengagement of said contact strips (20, 22) with/from each other, and a top portion provided with means able to snap-engage with a stem (12) of the tap (14).

2. Unit (10) according to Claim 1, comprising means able to cause relative sliding of said contacts (20, 22) during engagement/disengagement with/from each other, so as to exert a cleaning action which removes any impurities which may have been deposited thereon.

3. Unit (10) according to any one of the preceding claims, in which said movable contact strip (22) is shaped substantially in the form of a "U" and has a first fixed arm (40) and a second arm (44) movable towards the fixed contact strip (20), one of the two arms (40, 44) also having a protuberance (46) able to interact directly or indirectly with the base portion (54) of the actuating member.

4. Unit (10) according to any one of the preceding claims, in which said actuating member is shaped in the form of a bush (30) having a circular base portion (54) and a top portion (56) with a frustoconical shape formed by a ring of inclined elastic lugs (58) alternating with slits (60) so as to act as means for snap-engagement with a groove (62) formed on the stem (12) of the tap (14).

5. Unit (10) according to Claim 4, in which said base portion (54) has a bottom lug (70) formed by a flat piece (72) which has, projecting radially therefrom, a stud (74) able to bias the outer surface of the movable arm (44) of the movable contact strip (22).

6. Unit (10) according to Claim 5, in which the outer surface of the flat piece (72) has at one of its bottom ends a chamfer (76) able to interact with said protuberance (46) of the movable contact strip (22).

7. Unit (10) according to any one of the preceding claims, comprising a resilient recall member, such as a helical spring (28), arranged between a flat piece (66) of the bottom end of the base portion (54) of the actuating member and a bottom surface of the casing.

8. Unit (10) according to any one of the preceding claims, in which said casing is formed by a hollow body (16) substantially shaped in the form of a parallelepiped and by a cover (18) mounted on the upper side of said hollow body (16), the upper surface of the body (16) and the cover (18) having respective openings (32a, 32b) able to allow displacement of the base portion (54) of the actuating member.

9. Unit (10) according to Claim 9, in which the perimeter of the opening (32b) formed on the cover (18) is surrounded by an annular shoulder (34) so as to prevent the penetration of liquids inside the casing.

10. Unit (10) according to Claim 8 or 9, in which said body (18) has respective seats (36) for housing a first and a second electric wire (24, 26), which co-operate with ribs (38) of said cover (18).

Drawing