Electric switch

The invention relates to an electric switch according to the precharacterizing clause of patent claim

1

,

2

or

3

, and to a method for adjusting the switch point of an electric switch of this type according to the precharacterizing clause of patent claim

12

or

13

.

In small-scale electric switches, such as quick-action switches, microswitches or the like because of the small dimensions, production tolerances in the contact system have a particularly pronounced effect on the switch point of the latter. It may therefore be necessary, in switches of this type to adjust the switch point at a later date.

DE-A 31 50 210 discloses a quick-action switch with a contact system consisting of fixed contacts and of movable contact tongues. One end of the quick-action springs is operatively connected to the contact tongues. The other end of the quick-action springs is mounted on a body which, in turns is arranged in a movable actuating member. By virtue of this mounting, the actuating member, when being moved, acts on the quick-action springs in order to change over the contact system. The body is longitudinally displaceable in the actuating member by means of a screw, so that the bearing for the quick-action springs can be set in the direction of movement of the actuating member. As a result of this setting, the quick-action switch point of the quick-action springs and therefore, in turn, the changeover point of the contact tongues can be adjusted.

In this switch, therefore, although the changeover point can be adjusted at a later date, the design of the adjusting arrangement is complicated, since a multiplicity of additional parts are necessary for this purpose. The adjusting arrangement therefore incurs increased costs for the switch and the susceptibility of the adjusting arrangement to faults also increases. The actual adjusting operation is complicated and has to be carried out manually. Adjustment is consequently time-consuming and also cost-intensive. It is not possible for the adjusting operation to be automated, so that, at all events, this switch does not seem to be suitable for mass production.

The object on which the invention is based is to design an electric switch in such a way that the switch point of tile contact system can be adjusted at a later date in a simple way. In particular, the adjusting operation is also to be suitable for largely automated mass production of the switch.

In a generic electric switch, this object is achieved by means of the characterizing features of claim

1

,

2

or

3

. A method for adjusting the switch point is specified in more detail by the features of patent claim

12

or

13

.

In the solution according to the invention, the bearing for the contact tongue of the contact system and/or the contact tongue itself and/or the fixed contact of the contact system and/or part of the actuating member is capable of being set in the direction of movement of the actuating member. This setting of the bearing and/or of the fixed contact and/or of the contact tongue and/or of part of the actuating member is preferably carried out by means of mechanical or thermal deformation, in particular permanent deformation, which is introduced during or after the fitting of the contact system to a carrier receiving the bearing or the fixed contact, or the contact tongue or part of the actuating member. This deformation may be plastic deformation. The subclaims relate to further refinements of the invention.

The connection, designed as a carrier, between an electric terminal of the switch and the bearing may possess a first portion which runs approximately transversely to the direction of movement of the actuating member. This portion may have adjoining it a second portion running approximately in the direction of movement of the actuating member. The first and second portions then form, on the carrier for the bearing, a protuberance shaped essentially perpendicularly to the direction of movement of the actuating member. This protuberance is approximately U-shaped, half-S-shaped, in the form of a question mark or else S-shaped.

The setting of the bearing for adjusting the changeover point may be carried out by means of a tool which acts on the carrier for the bearing and in the direction of the bearing. It is appropriate for the tool to have a wedge-shaped design. In order to set the bearing, this tool is then displaced approximately transversely to the direction of movement of the actuating member, with the result that the tool acts on the carrier first portion running transversely to the direction of movement of the actuating member, the consequence of which is that the protuberance on the carrier is widened. If appropriate, a further tool with a supporting surface may also be used, in which case, during setting, the supporting surface bears supportingly on the second portion running in the direction of movement of the actuating member.

In a further design, the tool may also be an embossing tool. By means of the embossing tool, at least one embossing can be introduced into the carrier for the bearing. This deformation introduced into the carrier by the embossing causes the bearing to be displaced in the direction of movement of the actuating member. Furthermore, for adjustment, an embossing or other mechanical deformation may also be introduced into the contact carrier for the fixed contact of the contact system or into a switching lever which, as part of the actuating member, acts on a tappet leading into the housing of the switch.

In a preferred version, the carrier receiving the bearing, the contact carrier receiving the fixed contact, the switching lever or another functionally relevant structural part of the switch consists at least partially of a thermally deformable material. For adjustment, thermal action of this kind takes place, so that the carrier, the contact carrier, the switching lever or the other structural part experiences deformation, the deformation having a component in the direction of movement of the actuating member. Furthermore, it is preferred to carry out the thermal action by means of the individual pulses of laser beams, with the result that the size of the deformation can be accurately controlled. If action is to take place on the carrier, located inside the housing, for the bearing or the contact carrier for the fixed contact or the contact tongue, it is expedient for a window transparent to the laser beams to be provided on the housing of the switch.

So that the adjusting operation can also be carried out in a way which is capable of being automated, the following procedure is appropriate. Taking into account the maximum tolerances which occur, the contact system is dimensioned in such a way that, after fitting, the contact system initially does not yet reach the switch point during the associated actuating travel of the actuating member. During subsequent adjustment, the actuating member is then shifted by the amount of the associated actuating travel and the action of the adjusting tool then takes place on the carrier for the bearing, the contact carrier, the contact tongue or the switching lever, in that the wedge-shaped tool is advanced in a direction transverse to the direction of movement of the actuating member, the embossing tool introduces corresponding embossings or thermal heating by laser beams or the like. As a result of these actions, deformation takes place which causes setting in the direction of movement of the actuating member. The action then takes place until the contact tongue kicks over. Kickover can be detected in a simple way by the opening, closing or changeover of the contact system, if the switch is connected with its electric terminals to an electric circuit during adjustment. The adjusting operation by means of the adjusting tool can likewise be terminated when the bearing, the fixed contact, the switching lever or another functionally relevant structural part of the switch has reached a predetermined position. An optical monitoring device, for example a light barrier, can detect when this position is reached.

In a preferred embodiment, the switch possesses electric terminals which are designed in the manner of contact surfaces. These contact surfaces run, essentially plane, approximately parallel to the underside of the switch housing. The switch can consequently be fitted to a printed circuit board by the SMD technique (SMD=Surface Mounted Device).

The advantages achieved by means of the invention are, in particular, that it becomes possible to adjust the switch point and the differential travel for the switch as well as the contact position or the contact clearance for the contact system by means of a simple and cost-effective arrangement which is not susceptible to faults. Adjustment takes place in a simple way, avoids adjustment problems and is capable of being automated. A switch of this kind is therefore also suitable particularly for mass production. The invention can be implemented particularly advantageously in small-scale switches, such as quick-action switches or microswitches, as well as in SMD switches. These can be produced with much narrower tolerances than hitherto as regards to the switch point of the contact system or the differential travel for the actuating member, without the dimensional tolerances for the individual parts of the contact system having to be restricted excessively. On the contrary, the influence of the tolerances of the individual parts is largely eliminated As a result, the follow-up travel of the switch can, in turn, be increased, this being desirable in many instances of use of the switch. Even switches not conforming to the specifications can also be adjusted at a later date, so that the rejection rate in the production of the switch is reduced.

Exemplary embodiments of the invention are illustrated in the drawings and are described in more detail below.

In the drawings:

FIG. 1

shows a side view of an electric switch,

FIG. 2

shows the electric switch from the direction II in

FIG. 1.

,

FIG. 3

shows a section along the line

3

—

3

in

FIG. 2

,

FIG. 4

shows the electric switch from the direction IV in

FIG. 3

,

FIG. 5

shows an enlarged detail from

FIG. 3

in the region of the bearing,

FIG. 6

shows a switch, as in

FIG. 3

, during the adjustment of the switch point, the switch being connected to an indicating and adjusting device shown diagrammatically,

FIG. 7

shows a section, as in

FIG. 3

, according to a further embodiment,

FIG. 8

shows a section along the line

8

—

8

in

FIG. 7

,

FIG. 9

shows an electric switch, as in

FIG. 1

, according to a further embodiment, and

FIG. 10

shows a section, as in

FIG. 3

, in yet another embodiment.

An electric switch

1

designed in the manner of a microswitch and having a housing

2

can be seen in

FIGS. 1 and 2

. On the top side

3

of the housing

2

, an actuating member

5

designed as a tappet projects and is capable of being moved essentially in a direction

20

,

20

′ running perpendicularly to the top side

3

. In order to move the actuating member

5

, a switching lever

7

acts, in turn, on the latter, so that the actual actuation of the switch

1

takes place via the switching lever

7

. The actuating member

5

is provided with an elastic sealing cowl

6

in order to protect the interior of the housing

2

.

As may also be gathered from

FIG. 3

, a contact system

9

is arranged in the interior of the housing

2

, where the contact system may be designed as a break, make or changeover. The contact system

9

consists of at least one fixed contact

10

, of a movable contact tongue

12

as a switching contact and of a spring

13

operatively connected to the contact tongue

12

. In the present case, the contact system

9

also contains a further fixed contact

11

., so that the contact system

9

acts as a changeover. The fixed contacts

10

,

11

are arranged on carrier parts

14

,

15

. The contact tongue

12

is arranged so as to be movable in its longitudinal direction approximately transversely to the direction of movement

20

,

20

′ on a bearing

18

which is designed in the manner of a knife-edge bearing. The bearing

18

is located on a part which is designed in the manner of a carrier and which thus constitutes a carrier part

16

. The carrier part

16

runs, in the region of the bearing

18

, approximately parallel to the direction of movements

20

,

20

′. The spring

13

, designed as a tension spring, is suspended at one end in the contact tongue

12

and at the other end in a further carrier part

17

. The carrier parts

14

,

15

,

16

, and

17

are fastened to the base

24

of the housing

2

.

As may be gathered, in particular, from

FIG. 4

, electric terminals

8

a

,

8

b

,

8

c

,

8

d

project on the underside

4

of the housing

2

, said underside being assigned to the base

24

. The terminals

8

a

,

8

b

,

8

c

and

8

d

are designed in the manner of contact surfaces. The contact surfaces, in turn, run essentially parallel to the underside

4

of the housing

2

and are flat or plane on the base

24

of the housing

2

. As a result, the switch

1

can be fitted to a printed circuit board by the SMD technique (SMD=Surface Mounted Device) and can therefore be further processed by means of an assembly machine.

As is apparent from

FIG. 3

, the contact system

9

is electrically connected to the terminals

8

a

,

8

b

,

8

c

and

8

d

via the carrier parts

14

,

15

,

16

and

17

, respectively. Here, the terminals

8

a

and

8

b

are assigned the carrier parts

14

and

15

for the fixed contacts

11

and

10

, the terminal

8

c

is assigned the carrier part

16

for the bearing

18

and the terminal

8

d

is assigned the carrier part

17

. When the actuating member

5

is in the position of rest, shown in

FIG. 3

, the contact tongue

12

bears on the fixed contact

11

. Consequently, in this first switching position of the contact system

9

, an electric connection is made between the terminals

8

a

and

8

c

. In order to change over the contact system

9

, the actuating member

5

is moved in the direction

20

, the actuating member

5

acting on the spring

13

. The switch point of the contact system

9

, at which the contact tongue

12

kicks over, is reached when the effective line

19

of the spring

13

coincides approximately with the longitudinal direction of the contact tongue

12

. The switch point is thus assigned a specific actuating travel in the direction

20

which the actuating member

5

executes by moving out of the position of rest until the switch point is reached. After the switch point has been exceeded, the contact tongue

12

bears on the fixed contact

10

, and, in this second switching position of the contact system

9

, an electric connection is made between the terminals

8

b

and

8

c

. When the contact system

9

is changed over again, the actuating member

5

is moved back into the position of rest the actuating member

5

likewise being assigned an actuating travel in the direction

20

′ until the switch point is reached. The differential travel is the difference between the size of the actuating travel in the direction

20

and of that in the direction

20

′.

The desired size of the actuating travel and consequently the tolerances for the switch point and the differential travel are determined, as a rule, by the use of the switch

1

. On account of production tolerances which occur, in particular, during the mass production of switches of this type of small overall size, however, the actuating travel actually obtained often fluctuates considerably from switch to switch. In order to adapt the actuating travel to the size determined, in a first version of the switch

1

the switch point, which again is assigned to the actuating travel, is designed to be capable of being adjusted as a result of a shift of part of the contact system

9

in the direction of movements

20

and

20

′ of the actuating member

5

. For this adjustment of the switch point, according to the invention the bearing

18

is designed to be capable of being set in the direction of movement

20

and

20

′ of the actuating member

5

. Of course, in order to adjust the switch point, a shift of the point of suspension of the spring

13

on the carrier part

17

in the direction of movement

20

and

20

′ may be carried out alternatively or else additionally. In other alternatives, the carrier part

14

and

15

serving as a contact carrier for the fixed contact

10

and

11

, the switching lever

7

or another structural part functionally relevant to the contact system and located on the switch

1

are designed to be capable of being set in the direction of movement

20

and

20

′. Various embodiments of a switch capable of being set in this way will be described in more detail below.

In the embodiment shown in more detail in

FIGS. 3 and 5

, the carrier part

16

for the bearing

18

possesses a first portion

21

which runs approximately transversely to the direction of movement

20

and

20

′ of the actuating member

5

. It is appropriate, in particular, to arrange the first portion

21

approximately perpendicularly to the direction of movement

20

and

20

′. The first portion

21

has adjoining it a second portion

22

which runs approximately in the direction of movement

20

and

20

′ of the actuating member

5

. The second portion

22

has adjoining it furthermore, a third portion

23

which runs approximately parallel to the first portion

21

and is fastened in the base

24

of the housing

2

. The third portion

23

contacts the terminal

8

c

. By virtue of this refinement, the first and second portions

21

and

22

form a kind of protuberance on the carrier part

16

for the bearing

18

, said protuberance being shaped approximately perpendicularly to the direction of movement

20

and

20

′ of the actuating member

5

. For example, this protuberance could also be designated as being approximately half-S-shaped, in the form of a question mark or else U-shaped, the “U” being arranged horizontally.

The setting of the bearing

18

is carried out during the fitting of the contact system

9

, or after its fitting, before the housing

2

is closed. Of course, an orifice, not shown any further, may also be provided in the housing

2

in order to allow adjustment at a later date. As may be seen diagrammatically in

FIG. 5

, for the actual setting operation a tool

25

acts on part of the bearing

18

in such a way that a component of the effective direction of the tool

25

is aligned in the direction of movement

20

and

20

′ of the actuating member

5

and therefore with the bearing

18

. During action by the tool

25

, permanent deformation of the carrier part

16

is carried out, so that the setting of the bearing

18

can no longer change by itself at a later date. The deformation expediently consists of a plastic deformation of the carrier part

16

.

The tool

25

may be designed to be approximately wedge-shaped on the side facing the bearing

18

. The tool

25

then acts with this wedge-shaped side on the first portion

21

of the carrier part

16

, said first portion running approximately transversely to the direction of movement

20

and

20

′ of the actuating member

5

. For this purpose, the tool

25

is displaceable approximately transversely to the direction of movement

20

and

20

′ of the actuating member

5

, that is to say in the direction of the arrow

26

, during the setting operation. During this displacement, the wedge-shaped side of the tool

25

then comes into contact with the portion

21

and, with the advance continuing, presses the latter ever further upward in the direction

26

, so that widening of the protuberance occurs and the bearing

18

is shifted in the direction of movement

20

′ of the actuating member

5

. The advance of the tool

25

in the direction

26

and consequently the setting operation are terminated as soon as the bearing

18

has assumed the position which is correct for the desired actuating travel of the actuating member

5

. In order to ensure that widening occurs only in the direction of movement

20

′ and undesirable bending of the second portion

22

is prevented, the second portion

22

may be supported by a tool

29

with a supporting surface

30

during the setting operation, as indicated by broken lines in FIG.

5

. If necessary, of course, a tool may also act on the first portion

21

in such a way that the protuberance is compressed, with the result that the bearing

18

is shifted in the direction of movement

20

of the actuating member

5

.

In a method for adjusting the switch point of such an electric switch

1

in order to achieve the desired associated actuating travel, the kickover of the contact system

9

is utilized for terminating the adjusting operation. Taking into account the tolerances occurring during the production of the individual parts, the contact system

9

is dimensioned in such a way that, after fitting, the switch point of the contact system

9

is initially not yet reached in the case of the actuating travel determined for the actuating member

5

. After fitting, the actuating member

5

is shifted by the amount of the actuating travel determined, and the setting of the bearing

18

is carried out, as described above, until the contact tongue

12

kicks over.

The kickover of the contact tongue

12

may be detected optically by means of a light barrier or the like or else, preferably, by the electric breaking, making or changeover of the contact system

9

, depending on its design. For this purpose, it is merely necessary to connect the switch

1

with its terminals

8

a

,

8

b

and

8

c

and, if appropriate,

8

d

to an electric circuit. When the contact tongue

12

kicks over, the switching signal of the switch

1

then changes, and this, in turn, may be utilized as a trigger for stopping the tool

25

.

An adjusting method using this principle is described in more detail with reference to FIG.

6

.

After or during fitting, the switch

1

is introduced for adjustment into an adjusting device

40

, indicated merely diagrammatically in

FIG. 6

, and the electric terminals

8

a

,

8

b

and

8

c

of the switch

1

are connected to an indicating device

36

. The indicating device

36

contains a voltage source

37

which is connected to the terminal

8

c

. Furthermore, in the indicating device

36

there are light-emitting means, for example a green light-emitting diode

38

contacting the terminal

8

b

and a red light-emitting diode

39

contacting the terminal

8

a

. Since the switch

1

is in the first switching position in which the contact tongue

12

bears on the fixed contact

11

, the red light-emitting diode

39

lights up.

A plunger

41

of the adjusting device

40

thereafter acts on the actuating member

5

in such a way that the latter covers exactly the determined actuating travel in the direction of the arrow

20

and is retained in this position. Due to the dimensioning of the contact system

9

, however, the switch point is not yet reached, with the result that the contact system

9

remains in the first switching position and the red light-emitting diode

39

continues to light up.

The action of the adjusting tool

25

of the adjusting device

40

subsequently takes place on part of the bearing

18

, specifically, as already described, due to the advance of the wedge-shaped tool

25

in the direction

26

, the bearing

18

being shifted in the direction of the arrow

20

′. This advance of the tool

25

is then continued until the contact tongue

12

kicks over into the second switching position, with the result that the contact tongue

12

comes to bear on the fixed contact

10

. At the same time, the red light-emitting diode

39

is extinguished and the green light-emitting diode

38

lights up. As soon as the green light-emitting diode

38

lights up, the switch point of the contact system

9

is correlated with the determined actuating travel of the actuating member

5

and the adjusting operation is terminated. If appropriate, the advance of the wedge-shaped tool

25

is also to be continued somewhat beyond this switch point, in order to take into account a spring-back of the first portion

21

on the carrier part

16

.

A switch

1

′ in a second embodiment, which can be seen in more detail in

FIG. 7

, possesses a somewhat modified contact system

9

′, parts comparable to the switch

1

being given the same reference symbols. In this switch

1

′, the actuating member

5

movable in the direction of movement

20

and

20

′ acts on a first lever arm of a two-armed inner lever

28

. Suspended on the second lever arm of the inner lever

28

is one end of a spring

13

which, in turn, is suspended at its other end on a contact tongue

12

. The contact tongue

12

is movably mounted in a bearing

18

which is illustrated in

FIG. 7

in a part section through the spring

13

. The bearing

18

is located on a carrier part

16

′ making an electric connection with a terminal

27

a

. The two fixed contacts

10

and

11

are arranged on contact carriers

34

and

35

which, in turn, make a connection with the electric terminals

27

c

and

27

b

of the switch which are designed as plug terminals. The movable actuating member

5

is consequently operatively connected to the contact tongue

12

via the inner lever

28

and the spring

13

for the changeover of the contact system

9

′.

In this version, instead of the bearing

18

or else in addition to the bearing

18

, another part of the contact system

9

′, specifically the fixed contacts

10

and

11

, can be set in the direction of movements

20

and

20

′ of the actuating member

5

, with the result that the contact position and the contact clearance are adjusted. A tool designed as an embossing tool may be used for setting.

By means of the embossing tool, at least one indentation or embossings

32

and

33

are is introduced into the contact carrier

35

and/or

34

for the fixed contacts

10

and

11

respectively as may be seen particularly clearly in FIG.

8

. As a result of the embossings

32

and

33

, the contact carriers

34

and

35

are stretched plastically and the fixed contacts

10

and

11

are thereby displaced in the direction of movements

20

and

20

′ of the actuating member

5

. If the displacement achievable by means of embossings

32

and

33

is not sufficient, then, of course, a plurality of embossings

32

and

33

may also be introduced or the depth of penetration of the embossings

32

and

33

may be varied. However,

FIGS. 7 and 8

show only one embossings

32

and

33

in the contact carriers

34

and

35

respectively. The action of the adjusting tool and consequently the embossing in the contact carrier

34

and

35

takes place until the fixed contacts

10

and

11

has reached a predetermined position, so that the contact clearance of the fixed contacts

10

and

11

has the desired size. Optical monitoring of the position assumed by the fixed contacts

10

and

11

may be adopted in order to detect when this position is reached. For optical monitoring, it is possible, for example, to use a light barrier which, when the predetermined position is reached, emits a signal which, in turn, is utilized in order to terminate the embossing.

The bearing

18

for the contact tongue

12

, the carrier parts

14

and

15

or the contact carriers

34

and

35

for the fixed contacts

10

and

11

, the switching lever

7

or other structural parts functionally relevant to the contact system

9

can be set mechanically in the way described. It is particularly preferable also to have an adjusting operation which takes place essentially contactlessly and which will be explained in more detail by means of the following exemplary embodiment.

As shown in

FIG. 9

, the setting of the actuating travel for the switch

1

is carried out by means of thermal deformation on the switching lever

7

. For this purpose, the switching lever

7

consists at least partially of a material which is permanently deformable thermally. For example, the material may be copper alloys, steel or the like. Pulses of laser beams

31

act on one side of the switching lever

7

by means of a laser. The location on the switching lever

7

at which the laser beams

31

impinge is thereby heated on one side and the material of the switching lever

7

expands at this location. By being heated on one side, the switching lever

7

undergoes warping with a component in the directions

20

and

20

′, so that the switching lever finally permanently assumes the position designated by reference symbol

7

′. By appropriate control of the power of the laser beams

31

or of the number of pulses of laser beams

31

, thermal deformation of the desired size can be generated, so as to result in the corresponding setting of the actuating travel for the switch

1

. Heating may, of course, also take place in another way, for example inductively or the like.

According to an exemplary embodiment shown in

FIG. 10

, the parts of the contact system

9

which are located inside the housing

2

of the switch

1

, such as the carrier

16

receiving the bearing

18

, the contact carriers

14

and

15

receiving the fixed contacts

10

and

11

, the contact tongue

12

or the like, can also be set by means of thermal deformation. For this purpose, a window

42

transparent to the laser beams

31

is affixed to the housing

2

. The laser beams

31

pass through this window

42

into the interior of the housing

2

virtually without any loss. In

FIG. 10

, the laser beams are directed onto the contact tongue

12

, so that deformation

43

, depicted by broken lines, is generated on the contact tongue

12

. By virtue of the size of the deformation

43

, it is possible, in turn, to set the switch point at which the contact tongue

12

changes over and, consequently, the switch point of the contact system

9

. As is immediately apparent, the switch

1

can be fitted complete and setting can be carried out thereafter, since contactless setting can also take place inside the housing

2

via the window

42

. Of course, metal coatings and other aids may also be arranged on or in the housing

2

, in order to align the laser beams

31

with that structural part of the switch

1

which is to be set.

The invention is not restricted to the exemplary embodiments described and illustrated. On the contrary, it also embraces all developments within the scope of the concept of the invention which are within the ability of a person skilled in the art. If necessary, adjustment of a plurality of parts, for example of the bearing for the contact tongue and/or of the fixed contacts and/or of the switching lever and/or of other structural parts functionally relevant to the contact system, may also be carried out at the same time on a switch. Furthermore, the invention can be used advantageously not only on small-scale electric switches, but also on other switches, sensors or the like.