EP1662523A1

EP1662523A1 - Push button switch

Info

Publication number: EP1662523A1
Application number: EP04425896A
Authority: EP
Inventors: Antonio Coppola
Original assignee: Signal Lux MDS Srl
Current assignee: Signal Lux MDS Srl
Priority date: 2004-11-26
Filing date: 2004-11-26
Publication date: 2006-05-31

Abstract

A push button switch comprises at least three electric terminals (4) suitable for connection with at least two electric circuits, a conductive element (8) provided with a first end (8a) in engagement with one of the electric terminals (4), and a first movable contact (9) having a first end (9a) permanently in electric contact with one of the electric terminals (4). The conductive element (8) is defined by an elastic conductive wire wound up at least partly like a helical spring (11). The first movable contact (9) is movable upon operation of a command key (2), between a first operating position, at which a second end (9b) of the first movable contact (9) lies in contact with the conductive element (8), and a second operating position, at which the second end (9b) is moved apart from the conductive element (8).

Description

The present invention relates to a push button switch of the type comprising the features set out in the preamble of claim 1.
In particular, the present invention falls within the field of change-over switches, the function of which is to change connections between two or more electric circuits.
Preferably, the switch of the present invention is adapted to be mounted on household appliances, such as coffee-making machines, to control, by way of example and in a manner known by itself, the heating circuit for steam production and the on-off valve for steam cut-off.
It is known that a change-over switch of the push button type comprises a box-shaped holding body having an opening close to which a control push button is housed which is movable between at least two operating positions.
Four electric terminals partly project from the box-shaped body and are suitable for connection with two electric circuits. The push button is operatively connected with a movable contact carrier disposed at the inside of the box-shaped body that, upon operation of the push button, is able to move between two operating positions corresponding to closure of either of the two circuits. To this aim, the contact carrier is defined by a plate connected to the push button so as to carry out translation between a first and a second positions. In the first position, each of the opposite ends of the plate comes into contact with a respective terminal belonging to a first pair of terminals connected to the first circuit. In the second position, each of the opposite ends of the plate comes into contact with a respective terminal belonging to a second pair of terminals connected to the second circuit.
Disadvantageously, due to the mutual position to be taken by the components of the switches of the above described type and to the sizes of the plates that must be able to withstand passage of a predetermined current intensity, usually up to 16 amp, the sizes of the box containing them cannot be reduced to a great extent.
Therefore, due to bulkiness of the switch of known type, mounting of same on the device for which it is designed is made difficult and the available space for other elements of the device itself is reduced.
The Applicant has found that the switches of the above described type can be improved under different points of view, in particular in terms of reduction in bulkiness, construction simplicity and production cost.
Accordingly, it is an aim of the present invention to propose a push button switch of limited sizes which however enables currents up to 16 amp to be dealt with.
The above and still further aims that will become more apparent in the course of the following description are achieved by a switch comprising the features set out in claim 1 and in the claims depending thereon.
Further features and advantages will be best understood from the detailed description of a preferred but not exclusive embodiment of a switch in accordance with the present invention.
This description will be set out hereinafter with reference to the accompanying drawings, given by way of non-limiting example, in which:

Fig. 1 shows a first embodiment of the switch in accordance with the present invention with some parts removed for a better view of others;
Fig. 2 shows the switch in Fig. 1 devoid of a further element, for better illustrating the contact structure;
Fig. 3 shows a variant of the first embodiment of the switch in Fig. 2;
Fig. 4 shows a second embodiment of the switch of the invention with some parts removed for a better view of others; and
Fig. 5 shows a variant of the second embodiment of the switch in Fig. 4.

With reference to the drawings, a push button switch in accordance with the present invention has been generally identified by reference numeral 1.
Switch 1 comprises a box-shaped element, known by itself and therefore not shown or described, which is provided with an opening for housing a command key 2 movable between at least two operating positions. In the accompanying drawings, to make representation simpler and facilitate understanding of the figures, only the bearing structure 2a of the command key 2 has been shown, said structure in the completed switch being preferably enclosed in a covering element known by itself. The key is of the type known as "push button", i.e. it carries out a translation without tilting or rocking, and is able to control, by means of a contact carrier 3a defined by a body of plastic material shown in Fig. 1, a set of contacts 3. The contact set 3 acts on at least three electric terminals 4 projecting from the box-shaped element and suitable for connection with at least two electric circuits.
Each of the electric terminals 4 is preferably defined by a cut-away plate carrying a contact board 6 perpendicular to the plate, at a first end 5 thereof internal to the box-shaped element. The contact board 6 delimits a contact and electric-transmission surface 7.
The contact set 3 further comprises a conductive element 8 provided with a first end 8a in engagement with one of the electric terminals 4. The conductive element 8 rests on and is joined preferably by electric welding to the surface 7 of the contact board 6 of the respective terminal 4.
The conductive element 8 extends away from the contact board 6 of the respective terminal 4, until it partly overlaps a first movable contact 9. The conductive element 8 is defined by a wire 10 of a conductive material, which is advantageously elastic and preferably consists of a metal material, copper or iron-based alloys for example, at least partly wound up like a helical spring 11. A second end 8b of the conductive element 8 extends away from the helical spring 11, to overlap the first movable contact 9.
The cross section of wire 10, that is selected based on the current intensity designed to pass through the conductive element 8, preferably has a diameter included between 0.2 mm and 1.5 mm.
The first movable contact 9 has a first end 9a thereof permanently in electric contact with one of the electric terminals 4. In particular, the first end 9a of the first movable contact 9 is shaped into a convex surface resting in a seat 12 conforming in shape to said surface and defined by the contact surface 7 of the contact board 6. This solution enables the first movable contact 9, upon the action of the command key 2, to rotate on the electric terminal 4 with which it is permanently in engagement, for displacement between a first and a second operating positions. In the first operating position, a second end 9b of the first movable contact 9 opposite to the first end 9a, lies in contact with the second end 8b of the conductive element 8 to close one of the two circuits. In the second operating position, corresponding to closure of the second one of said circuits, the second end 9b of the first movable contact 9 is moved apart from the conductive element 8.
In a first embodiment shown in Figs. 1 and 2, the switch 1 comprises a first electric terminal 4a permanently in electric contact with the first movable contact 9, a second electric terminal 4b carrying the conductive element 8 and a third electric terminal 4c lying in side by side relationship with the second terminal 4b. The second end 8b of the conductive element 8 extends until over the contact board 6 of the third electric terminal 4c. In particular, the second end 8b of the conductive element 8 has a first rectilinear stretch 13 perpendicular to the contact board 6 and connected to a second rectilinear stretch 14 parallel to said contact board 6 and oriented towards the third electric terminal 4c. Finally, a third rectilinear stretch 15 of the conductive element 8 extends from the second stretch 14 and is oriented towards the first electric terminal 9.
The first movable contact 9 extends until over the third electric terminal 4c and the second end 9b thereof is positioned between the contact board 6 of the third electric terminal 4c and the third rectilinear stretch 14 of the conductive element 8. The first movable contact 9 is therefore movable between the first position, at which it is in contact with the third rectilinear stretch 15 of the conductive element 8 and the second position, at which it is in contact with the third electric terminal 4c. In the first operating position, the conductive element 8 and the first movable contact 9 allow current passage between the first 4a and second 4b electric terminals. In the second operating position, the first movable contact 9 allows current passage between the first 4a and third 4c electric terminals.
Advantageously, as clearly visible in Fig. 1, the third rectilinear stretch 15 of the conductive element 8 is inclined relative to the contact board 6 so that it appears to be parallel to the first movable contact 9 when the latter is in the first operating position. The second end 8b of the conductive element 8 and second end 9b of the first movable contact 9 therefore delimit a mutual-coupling surface enabling passage of current at an intensity as high as 16 amp. To this aim, the switch further comprises a plate 16 positioned on the second end 9b of the first movable contact 9 and set to come into contact with the second end 8b of the conductive element 8. Located on the second end 9b of the first movable contact 9, on the opposite side from plate 16, is a small disk 17 that when the first movable contact 9 is in the second position comes into contact with a small disk 18 located on the contact board 6 of the third terminal 4c.
In a variant of the first embodiment of Fig. 1, shown in Fig. 3, the switch 1 further comprises a fourth electric terminal 4d and a signal light 19 permanently in electric contact with the fourth electric terminal 4d and the first movable contact 9. Connection between the fourth electric terminal 4d is obtained through a second movable contact 20 having a first end 20a permanently in contact with the fourth electric terminal 4c. The second movable contact 20 is movable, upon operation of the command key 2, together with the first movable contact 9. In the same manner as the first movable contact 9, the first end 20a of the second movable contact 20 is shaped like a convex surface resting in a seat 12 conforming in shape to said surface and defined in the contact board 6 of the fourth terminal 4d. Power supply to the signal light 19 is ensured by deformable spring elements 21, of a type known by itself, connecting the signal light 19 to the first and second movable contacts 9, 20.
In a second embodiment, shown in Fig. 4, the switch 1 comprises a first electric terminal 4a permanently in electric contact with the first movable contact 9, a second electric terminal 4b carrying the conductive element 8, a third electric terminal 4c, permanently in electric contact with a second movable contact 20, and a fourth electric terminal 4d.
Each of the first ends 9a, 20a of both the first and second movable contacts 9, 20 is shaped as previously described as regards the first embodiment (Figs. 1, 2 and 3). Both the movable contacts 9, 20 rotate together, upon operation of the command key 2, on the respective electric terminals 4a; 4c, for movement between the first and second operating positions.
The first movable contact 9 extends towards the second electric terminal 4b. The second end 8b of the conductive element 8 is defined by a single rectilinear stretch 22 substantially parallel to the contact boards 6 and extending towards the first electric terminal 4a. The first movable contact 9 is movable between the first operating position, at which its second end 9b lies in contact with the second end 8b of the conductive element 8, and the second operating position at which its second end 9b is moved away from the second end 8b of the conductive element 8.
The second movable contact 20 extends towards the fourth electric terminal 4d and its second end 20b lies in superposed relationship with the contact board 6 of said fourth electric terminal 4d. The second movable contact 20 is movable between the first operating position at which its second end 20b is moved apart from the fourth electric terminal 4d, and the second operating position at which its second end 20b lies in contact with the fourth electric terminal 4d. In the first operating position, the conductive element 8 and the first movable contact 9 enable passage of current between the first 4a and second 4b electric terminals. In the second operating position, the second movable contact 20 enables passage of current between the third 4c and fourth 4d electric terminals.
In a variant of the second embodiment of Fig. 4, shown in Fig. 5, switch 1 further comprises a signal light 19 permanently in electric contact with the first and the second movable contacts 9, 20. Power supply to the signal light 19 is ensured by the same deformable spring elements 21 as used for the variant of the first embodiment (Fig. 3).
The present invention achieves the intended purposed and offers important advantages.
First of all, the switch in accordance with the present invention enables a reduction in sizes as compared with the change-over switches of known type and therefore it can be mounted more easily on the household appliances with which it is associated.
In addition, the particular construction solution of the switch in accordance with the present invention allows a reduced cost of the different components and an easy assembly. In fact, the conductive element in the form of a cylindrical spring can be easily found as a standard component, to a low cost, which enables the final cost of the switch to be reduced.
The elasticity of said conductive element further ensures the electric contact with the terminals, even in the presence of vibrations when the appliance on which it is mounted is being operated.
Finally, the conductive element can be easily chosen and/or sized, based on the current intensity that the switch must handle.

Claims

A push button switch, comprising:
- at least three electric terminals (4) adapted for connection with at least two electric circuits;

- a command key (2);

- a conductive element (8) provided with a first end (8a) in engagement with one of said electric terminals (4);

- a first movable contact (9) having a first end (9a) permanently in electric contact with one of said electric terminals (4) and a second end (9b) opposite to the first one (9a); the first movable contact (9) being movable, upon operation of the command key (2), between a first operating position at which the second end (9b) lies in contact with the conductive element (8) to close at least a first one of said at least two circuits, and a second operating position, corresponding to closure of at least a second one of said at least two circuits, wherein the second end (9b) is moved away from said conductive element (8);
characterised in that the conductive element (8) is defined by an elastic conductive wire wound up at least partly like a helical spring (11).
A switch as claimed in claim 1, wherein the conductive element (8) has a second end (8b) extending away from the helical spring (11), to come into contact with the second end (9b) of the first movable contact (9).
A switch as claimed in claim 1, wherein the conductive wire (10) has a cross section of a diameter included between 0.2 mm and 1.5 mm.
A switch as claimed in claim 1, wherein the conductive wire (10) is electrically welded to the respective electric terminal (4).
A switch as claimed in claim 2, wherein in the first operating position the second end (8b) of the conductive element (8) and the second end (9b) of the first movable contact (9) delimit a mutual-coupling surface.
A switch as claimed in claim 2, further comprising a plate (16) positioned on the second end (9b) of the first movable contact (9) and set to come into contact with the second end (8b) of the conductive element (8).
A switch as claimed in claim 1, wherein the first movable contact (9) rotates on the electric terminal (4) with which it is permanently in contact, for movement between the first and second positions.
A switch as claimed in claim 1, wherein said at least three electric terminals (4) comprise a first electric terminal (4a) permanently in electric contact with the first movable contact (9), a second electric terminal (4b) carrying the conductive element (8) and a third electric terminal (4c); in the second operating position, the first movable contact (9) being in contact with the third electric terminal (4c) to close the second circuit.
A switch as claimed in claim 8, further comprising a fourth electric terminal (4d) and a signal light (19) permanently in electric contact with said fourth electric terminal (4d) and the first movable contact (9).
A switch as claimed in claim 8, further comprising a second movable contact (20) that, upon operation of the command key (2), is movable together with the first movable contact (9) and has a first end (20a) permanently in electric contact with the fourth electric terminal (4d).
A switch as claimed in claim 1, wherein said at least three electric terminals (4) comprise a first electric terminal (4a) permanently in electric contact with the first movable contact (9), a second electric terminal (4b) carrying the conductive element (8); a third electric terminal (4c); a fourth electric terminal (4d); a second movable contact (20) having a first end (20a) permanently in electric contact with the third electric terminal (4c) and a second end (20b) opposite to the first one (20a); the second movable contact (20) being movable, upon operation of the command key (2), between the first operating position at which its second end (20b) is moved apart from said fourth electric terminal (4d) and the second operating position at which its second end (20b) lies in contact with the fourth electric terminal (4d).
A switch as claimed in claim 11, wherein the second movable contact (20) rotates on the third electric terminal (4c) for movement between the first and second operating positions.
A switch as claimed in claim 11, further comprising a signal light (19) permanently in electric contact with the first movable contact (9) and the second movable contact (20).