EP1137029A2 - Apparatus for proximity switching of an electrical contact and pressure measuring apparatus - Google Patents

Abstract

The arrangement has a switch element (14) which exerts the switching force and a flat spring (38) clamped on one side at a clamping point (C). The switching element engages the spring to move it from a rest position to a switching position (48'). The spring forms the switching force threshold when in the rest position. An arrangement (58) for altering the position of the clamping point varies the threshold by altering the clamping point. Independent claims are also included for the following: a pressure measurement device.

Description

• einem Schaltglied, mittels dessen die Schaltkraft ausgeübt wird,
• einer an einer Einspannstelle einseitig eingespannten Blattfeder, wobei das Schaltglied zum Schalten an der Blattfeder angreift, um die Blattfeder von einer Ruheposition in eine Schaltposition zu bewegen, wobei die Blattfeder in der Ruheposition so angeordnet ist, daß deren Federkraft die vorbestimmte Schaltkraftschwelle bildet.

The present invention relates to an arrangement for contactless switching of an electrical contact by means of a switching force exceeding a predetermined switching force threshold

• a switching element by means of which the switching force is exerted,
• a leaf spring clamped on one side at a clamping point, the switching element for switching engaging the leaf spring to move the leaf spring from a rest position into a switching position, the leaf spring being arranged in the rest position so that its spring force forms the predetermined switching force threshold.

The invention further relates to a pressure measuring device with at least a pressure chamber separated by a membrane and with a such an arrangement for contactless switching of an electrical Contact.

Such an arrangement for the contactless switching of a electrical contact and such a pressure measuring device are known from GB-1,139,162.

Pressure gauges with non-contact switching arrangement are also known under the term pressure can.

In a pressure cell, when the pressure changes in the pressure-elastic chamber, which is usually rubber-elastic. The membrane is coupled to the switching element and switches electrical contact due to the bulging process.

In practice, the electrical contact is switched predominantly by mechanical means. Here is the switching element immediately provided with an electrical contact that at Bulging the membrane touches another contact and thereby closes an electrical circuit.

Such switching arrangements are known from US-A-3,585,328 and from DE 42 02 144 A1.

In the switching arrangement of DE 42 02 144 A1 there is a leaf spring provided to influence a switching force threshold. A Adjustment screw engages a central portion of the leaf spring to change the switching force threshold.

Furthermore, mechanical load switches of this type suffer from the known ones Disadvantages such as corrosion, sparking, etc.

However, pressure cans are also known in practice in which the electrical contact is switched without contact. The Electrical contact is often a reed contact in these pressure sockets. The rubber-elastic membrane is on its underside designed with a membrane plate on one side clamped leaf spring rests. From the bottom of the Leaf spring presses against an adjustable conical coil spring the leaf spring to form the switching force threshold. At the The end region of the free end of the leaf spring is a permanent magnet attached so that it is diagonally above the reed contact is arranged.

When the pressure increases, a force is counteracted using the membrane exerted the pressure force of the conical coil spring. As soon as the switching force threshold set up by means of the coil spring is exceeded, the membrane is deflected so far that the leaf spring with the attached permanent magnet so gets close to the reed contact that it switches.

DE 91 08 159 U1 is a further switching arrangement for contactless switching of an electrical reed contact known. This arrangement is in the usual way on A switching magnet at the end of a leaf spring clamped on one side arranged. Serve to set up a switching force threshold two permanent magnets with the same polarity. The one permanent magnet is attached to a central section of the leaf spring. The other permanent magnet is fixed to the housing. The permanent magnets therefore replace the conical mentioned above Coil spring for setting the switching force threshold. The disadvantage here is that the switching force threshold is not adjustable and the magnetic spring set up in this way is a strong one has progressive characteristic.

From the GB-1,139,162 mentioned above is a pressure-operated Magnetic switch known. A solenoid for actuating a Reed contact is attached directly to a membrane. To set up a switching force threshold is an elastic one Element provided that acts on the switching magnet from above. The preload of the elastic element should be adjustable to change the switching force threshold. However, it is not explained how this adjustability can be solved should.

The pressure cells can also be designed as differential pressure cells two pressurized media e.g. Gases, are separated by the membrane. Use cases are e.g. Heating heaters in which the pressure cell by recording the pressures before and after a fan detects whether there is excess or There is negative pressure.

The switching force threshold should be differential pressures in the range from a few pascals to a few hundred pascals. At such low pressures and consequently low ones Switching force thresholds (the membrane of a typical pressure cell for Heiztherme has a diameter of about five centimeters and consequently an area of approximately 20 square centimeters, which makes Switching forces in the range of 0.001 N are transmitted) are the individual structural elements, especially the spring devices, very delicate and delicate. The setting the switching force threshold occurs at the one described above Pressure can in several stages. It is both the location and consequently preload of the conical coil spring adjustable as well as the relative position of the reed contact to the permanent magnet.

Against this background, it is the object of the invention, a Arrangement for the contactless switching of an electrical contact and to specify a pressure measuring device equipped with it, the high demands on the simple construction Switch sensitivity correspond.

This task becomes contactless in the arrangement mentioned at the beginning Switching an electrical contact solved by that means to change the position of the clamping point are provided so that by changing the position of the clamping point the switching force threshold can be set, in particular can be adjusted finely.

With the pressure measuring device mentioned at the outset, the task is thereby solved that such a switching arrangement is included, wherein the membrane is coupled to the switching element.

By the measure, the switching force threshold by changing the To make the position of the clamping point of the leaf spring adjustable, the conditions are created to a high To achieve switching sensitivity with a simple construction. In particular, the preload of the leaf spring can be changed, without having to touch the leaf spring itself. Hence the preload can be adjusted without additional friction losses are generated.

According to a further aspect of the invention is to achieve a high switching accuracy an arrangement for contactless Switching an electrical contact by means of a created switching force exceeding predetermined switching force threshold, which is a switching element by means of which the switching force is exercised, and has a movable leaf spring, wherein the switching element for switching engages the leaf spring to the To move the leaf spring from a rest position into a switching position, the leaf spring being arranged in the rest position is that the spring force alone the predetermined switching force threshold does not form an additional spring like one Coil spring still repelling permanent magnets provided become.

The fact that only one for setting the switching force threshold Spring, namely the movable leaf spring is provided the overall design is simplified. Because of the lesser The total number of mechanical components friction hysteresis occurring due to bearing and clutch of the components lower. As a result, there is a high one Switching accuracy.

The following preferred configurations can be applied to both Apply above aspects of the invention.

It is particularly preferred if the leaf spring is in the rest position is biased by a fixed stop.

In this way, on the one hand, it becomes a fixed and precise resting position the leaf spring set up.

It is particularly preferred if the leaf spring by means of the fixed stop is biased so that the leaf spring in its rest position essentially no force on the Switching element exercises.

In this way, the switching element is not in the rest position preloaded. When used in a pressure can is thus avoided that the membrane with a constant Bias is applied, as is the case with the bias due to the conical coil spring described above is.

Overall, it is particularly preferred if the leaf spring is frictionless is movably mounted, so when there is a deflection by the switching element essentially no frictional forces are to be overcome. As a result, essentially not The friction hysteresis that occurs is very high overall high switching accuracy.

It is further preferred if the leaf spring is clamped on one side and if the electrical contact is close to hers free end is arranged.

This results in a simple construction of the clamping the leaf spring. This can therefore be based on the principle of a simply clamped bending beam can be dimensioned. The Movement of such a spring joint is generally smooth.

It is particularly preferred if the leaf spring at the clamping point at an acute angle> 0 ° to a transverse plane is clamped, which is approximately perpendicular to the direction of movement of the Switching element is aligned.

In this way, one can be generally perpendicular to the Transversely aligned pressure can comparatively simply a Set up preload for the leaf spring.

According to a further preferred embodiment, the Switching arrangement, with essentially unchanged construction, can be manufactured with different clamping blocks clamp the leaf spring at a different angle, so that switching arrangements with different switching force threshold can be produced by selecting the setting block.

In this way, with a single basic construction Switching arrangements for different areas of application create, each area of application a different switching force threshold owns. The switching force thresholds can Pressure differences in the range from a few Pascals to correspond to several hundred pascals. Expressed differently, can by the choice of the adjustment block and consequently the Roughly preselect the switching force threshold. The means of Changes in the position of the clamping point are then used for fine adjustment.

Furthermore, it is particularly preferred if the end region of the free end of the leaf spring approximately parallel by means of a stop is aligned to the transverse plane.

In this way, the stop can be constructive integrate particularly easily into the arrangement. On the other hand be achieved that the switching element under an almost attack vertical angle on the leaf spring.

According to a further preferred embodiment, the clamping point is the leaf spring at the free end of a cantilever arranged elastic support element.

This results in the adjustability the switching force threshold by means of the leaf spring is the greatest possible Flexibility.

It is particularly preferred if the spring rate of the support element is much greater than the spring rate of the leaf spring.

This ensures that for setting up the switching force threshold required force essentially alone the spring rate of the leaf spring is decisive.

Furthermore, it is particularly preferred if the support element is an electrical circuit board.

A circuit board is in a non-contact arrangement Switching an electrical contact and especially in one Pressure gauges generally available anyway. Furthermore, one such a board with a material thickness in the range of a few Millimeters a much larger spring rate than a typical one Leaf spring.

It is particularly preferred if the free end of the Leaf spring and the free end of the support element or the circuit board point in opposite directions.

In this way, the arrangement can be made particularly compact become.

It is further preferred if the arrangement has means for adjusting has the deflection of the free end of the support element, so as to change the position of the clamping point to the switching force threshold adjust.

In this way, the bias of the leaf spring can be particularly simple way indirectly by adjusting the deflection adjust the free end of the support element.

According to an overall preferred embodiment, the agents designed to change the position of the clamping point, to pivot the clamping point about an axis.

Although it is generally also possible to use the clamping point to move suitable means linearly, in particular parallel to Switching force direction, the inventors found that a Swiveling the clamping point offers constructive advantages.

It is particularly preferred if the clamping point is like this is pivotable that the position of the portion of the leaf spring, on which the switching element acts, essentially unchanged remains.

In this way, frictional influences between the switching element and leaf spring can be minimized. Furthermore, the starting point of the switching element, which is also particularly true for pressure sockets is movably attached to a membrane by the change the bias is not affected.

According to a further preferred embodiment, the leaf spring is provided with a recess in the area of the clamping point, preferably with one on the central axis of the leaf spring arranged hole.

This "weakening" of the clamping point of the leaf spring determines the spring rate of the leaf spring, in particular the switching behavior and the on-off hysteresis.

In other words, the remaining portion of the leaf spring the width of a spring joint in the area of the recess. A central hole or a central bore is opposite lateral recesses preferred because of a higher torsional rigidity is achieved at the clamping point. In this way the spring rate of the leaf spring can be adjusted in particularly fine increments and specify particularly precisely.

It is also preferred if the leaf spring means for contactless Switching the electrical contact has.

It is generally conceivable that the leaf spring itself their deflection an electrical contact without contact switches. However, there is preferably a permanent magnet on the leaf spring provided that e.g. switch a reed contact can. In this case, the leaf spring material should not be magnetic.

According to a further preferred embodiment, the leaf spring is clamped on one side and the switching element engages in the area between the end area of the free end and the clamping point on.

In this way, the switching arrangement as a whole can be special be compact, especially with pressure cans, at which the switching element, i.e. the diaphragm plate, usually centrally is arranged.

Further advantages result from the description and the attached one Drawing.

It is understood that the above and those below Features to be explained not only in each case specified combination, but also in other combinations or can be used alone, without the scope of to leave the present invention.

Fig. 1

eine schematische Schnittansicht einer erfindungsgemäßen Schaltanordnung;

Fig. 2

eine schematische Schnittansicht entlang der Linie II-II von Fig. 1;

Fig. 3

eine perspektivische, teilweise weggeschnittene Ansicht einer Druckdose mit einer erfindungsgemäßen Schaltanordnung von schräg oben; und

Fig. 4

eine perspektivische Ansicht der Druckdose der Fig. 3 von schräg unten;

Fig. 5

eine weitere schematische Darstellung der erfindungsgemäßen Schaltanordnung;

Fig. 6

eine Detailansicht einer bevorzugten alternativen Ausführungsform; und

Fig. 7

eine Detailansicht einer weiteren alternativen Ausführungsform.

Exemplary embodiments of the invention are shown in the drawing and are explained in more detail in the following description. The drawings show:

Fig. 1

is a schematic sectional view of a switching arrangement according to the invention;

Fig. 2

is a schematic sectional view taken along line II-II of Fig. 1;

Fig. 3

a perspective, partially cut-away view of a pressure can with a switching arrangement according to the invention obliquely from above; and

Fig. 4

a perspective view of the pressure cell of Figure 3 obliquely from below.

Fig. 5

a further schematic representation of the switching arrangement according to the invention;

Fig. 6

a detailed view of a preferred alternative embodiment; and

Fig. 7

a detailed view of a further alternative embodiment.

In Fig. 1 is an arrangement for non-contact switching a electrical contact generally designated 10.

The switching arrangement 10 is used for the contactless switching of a electrical reed contact 12, which is arranged stationary.

A switching process is triggered by means of a switching element 14, which is preferably made of plastic. The switching element 14 is shown in Fig. 1 as a membrane plate 14 with a elastically deformable membrane 16 is connected. The membrane 16 separates a pressure chamber 18 from a pressure chamber 20. Das Switching element 14 is on the membrane 16 on the pressure chamber 20th facing side set.

As soon as the pressure in the pressure chamber 18 is greater than in the pressure chamber 20, the membrane 16 and thus the switching element 14 to Pressure chamber 20 deflected out. This is schematic in Fig. 1 indicated by an arrow 17 indicating the direction of movement of the switching element 14, as well as the switching force, which due to the area of the membrane on the switching element 14 is exercised.

The arrangement 10 also has a stationary support 22, which can be formed, for example, by a housing.

A printed circuit board 24 is fixed on the carrier 22.

The reed contact 12 is on the top of the circuit board 24 fixed and electrically with conductor tracks of the circuit board 24 connected (not shown). It is understood that the circuit board have further electrical components and circuits can to open and close the reed contact 12th evaluate appropriately. Alternatively, the circuit board can also be used only connect to external contacts like it will be explained below.

The circuit board 24 is clamped in the manner of a one-sided Beam (cantilever) set.

A free end 32 of the circuit board 24 can consequently be pivoted, as indicated by an arrow 25.

The circuit board 24 has in the area of the clamping point 26 Hole 28 or another weakening recess. Hereby becomes a fulcrum 30 for the free end movements 32 set up close to the clamping point 26.

At the top of the end portion of the free end 32 of the circuit board 24 is a clamping block 34, which is preferably is made of plastic. The top 36 of the chuck 34 is at an angle 37 of 2 ° to 45 °, in the illustrated Embodiment inclined, for example, by approximately 5 °. By selecting different clamping blocks 34 with different ones Angle of the top 36 can be otherwise unchanged design parameters of the switching arrangement 10, Create suitable components for different applications. In other words, by choosing the angle of the top 36 of the clamping block 34 a basic prestress towards it fastening leaf spring 38 can be selected.

On top 36 there is a single layer, approximately in plan view rectangular leaf spring 38 clamped on one side. The free end 40 of the leaf spring 38 points in the opposite direction like the free end 32 of the circuit board 24.

The one set by the one-sided clamping of the leaf spring 38 Mobility is shown schematically at 41.

In a central region 42 of the free end 40 is the Leaf spring 38 provided with a central hole 44. By the Hole 44 engages a downward pin 46 of the switching element 14. The underside of the switching element 14 is also conical tapered so that the top of the leaf spring 38 is touched only in dots or circles.

An end region 48 of the free end 40 of the leaf spring 38 lies in a rest position, which is shown in solid lines in Fig. 1st is shown on the underside of a fixed stop 50 on. The stop 50 can be made in one piece with the stationary support 22 be formed.

The position of the stop 50 is chosen so that the leaf spring 38 is biased in the rest position. The top is also located of the central area 42 of the leaf spring in the rest position directly below the underside of the switching element 14, in such a way that the membrane 16 is relaxed against it Basic position is not deflected.

At the bottom of the end portion 48 is a permanent magnet 52 set.

In the rest position of the leaf spring 38 is the bottom of the Permanent magnets 52 from the top of the reed contact around a switching distance 54 spaced.

As shown in Fig. 2, the center of the reed contact is located 12 from the center of the permanent magnet 52 µm offset a distance 62. Due to the lateral offset 62 it is ensured that the reed contact 12 is always from field lines of the magnetic field of the permanent magnet 52 of a predetermined one Direction is applied.

If the switching element 14 is offset in the direction of movement 17 becomes the free end 48 from the rest position shown in FIG. 1 moved to the switching position 48 'shown in dashed lines. The the distance traveled is shown at 56.

In switch position 48 ', permanent magnet 52 is so close to brought the reed contact 12 that the latter switched becomes.

To move the leaf spring 38 from the rest position in the Switch position 48 'must have a force 17 by means of the membrane 16 be applied, the force 51 (= switching force threshold) exceeds that established by the bias of the leaf spring 38 is. This avoids a switching operation even with minimal pressure differences between the pressure rooms 18, 20 or unintentionally triggered by vibrations etc. becomes.

On the carrier 22, an adjusting screw 58 is mounted on the bottom of the free end 32 of the circuit board 24 attacks. By turning the adjusting screw 58 in direction 59 the free end 32 of the circuit board 24 depending on the direction of movement 25 moved up or down. This will make the clamped side of the leaf spring 38 relative to the pivot point 30 offset to the stop 50.

In other words, by adjusting the adjusting screw 58 adjust the preload of the leaf spring 38 as it is explained in detail below with reference to FIG. 5. The rest position of the end region becomes due to the stop 50 48 of the free end 40 of the leaf spring 38 is not changed. When the free end 32 pivots about the pivot point 30 becomes the central region 42 of the free end 40 of the Leaf spring 38 also hardly or not at all in its axial position change. As a result, the preload is adjusted the leaf spring 38 does not change substantially Initial loading of the membrane 16. Thus, by adjusting the bias of the leaf spring 38, the kinematics of Switching arrangement 10 otherwise not changed.

As shown in FIG. 2, the leaf spring 38 is also in the area provided with side recesses 60 at their clamping point. The size and arrangement of the recesses 60 are influenced the spring rate of the leaf spring 38 consequently a basic spring rate and consequently a certain basic preload the leaf spring 38 is set in the rest position. The bias of the leaf spring 38 can, starting from the Basic preload, finely adjusted using the adjusting screw 58 become.

3 and 4 each show a pressure measuring device in the form of a Pressure cell 70 with a switching arrangement according to the invention. Elements, which have the same function as the schematic Representation of a switching arrangement in FIGS. 1 and 2, are provided with the same reference numbers.

The pressure cell 70 has an upper part 72 and a lower part 74 between which the membrane 16 is clamped. Hence becomes an upper between the upper part 72 and the membrane 16 Pressure room 18 set up. Is located below the membrane 16 the second pressure chamber 20. The upper part 72 and the lower part 74 are plastic injection molded parts. The lower part 74 forms the stationary support 22 and the stop 50.

It can also be seen that the adjusting screw 58 as a simple Grub screw is formed, which is screwed into the lower part 74 and from the outside, i.e. when assembled, can be moved. This enables a fine adjustment of the switching point possible in the assembled pressure can 70.

Recesses are also provided on the lower part 74, opposite which are protruding from two contacts 76, which are connected to conductor tracks of Printed circuit board 24 are connected (not shown).

It can also be seen that the leaf spring 38 in its end region 48 with locking means 78 for receiving the permanent magnet 52 is provided. As a result, the permanent magnet 52 is in a locked position. The arrangement 10 according to the invention and the pressure cell 70 can be installed fully automatically and adjust.

The position of the permanent magnet 52 is preferably determined by a characteristic of switching distance 54 over center offset 62 the arrangement of permanent magnet 52 and reed contact 12th

If there is no stop 50, an adjustment is made the adjusting screw 58 of the permanent magnet 52 on the free End 40 of the leaf spring 38 either approximates the reed contact 12 or moved away from it. This allows the switching distance 54 can be reduced or enlarged. So that the Switching force threshold or switching pressure in a simple way to adjust.

The pivot point of the free end 32 of the circuit board 24 can be by the location of the hole 28 (or by the location corresponding side recesses) and consequently by narrowing the Set joint width. Depending on the distance of the fulcrum 30 from the adjustment screw 58, the adjustment sensitivity is low or high.

As mentioned above, the recesses 60 determine the spring rate the leaf spring 38. For different applications the same starting leaf spring by providing different large recesses 60 (or a corresponding hole) is used become. As a result, the switching characteristics of the Pressure cell 70 can be adapted to the particular circumstances.

The coupling between switching element 14 and leaf spring 38 can also be done so that instead of a hole 44 in the leaf spring 38 a trough is provided in which the as a tip bearing trained pin 46 engages.

In general, the entire assembly of leaf spring 38, Permanent magnet 52, clamping block 34, and the free end 32 the circuit board 24 move substantially smoothly. Further is the adjusting screw for setting the switching force threshold 58 provided. The reed contact 12 is on the other hand Printed circuit board 24 fixed.

Overall, the pressure can 70 according to the invention can be extremely few components. Therefore, no kick Friction or coupling hysteresis. The switching arrangement 10 can be adjusted with only a single adjusting screw 58 and fine-tune. This is based on an optimal relative position between permanent magnet 52 and reed contact 12, how they are characterized by a characteristic of switching distance 54 Center offset 62 can be determined.

Fig. 5 shows in schematic form the arrangement from the free end 32 of a carrier, clamping block 34 and leaf spring 38 in schematic form and serves to explain the setting of the Pretension by swiveling the clamping block 34.

By exerting a force B on the free end 32, for example by means of the adjusting screw 58, the free end can be 32 around the pivot point A (corresponding to the reference symbol 30 in Fig. 1) pivot.

A starting position is in solid lines in FIG. 5 shown. A swivel position is through dash-dot lines shown.

In the starting position, the clamping point C is in a position C ₁ . When a force F ₁ (at 17) is exerted on a central region of the leaf spring 38, for example by means of the switching element 14, the point D is deflected by a path S * ₁ .

Accordingly, the end 40 _{1 of} the leaf spring 38 is pivoted from a position E ₁ to a position from which the reed contact 12 switches. This position is shown as a threshold in FIG. 5. The path of the free end 40 ₁ into the position shown at 40 ₁ 'is S ₁ .

With a spring rate c = ΔF / ΔS, F ₁ = C x S ₁ * applies. By pivoting the free end 32 about the pivot point A, the clamping point C moves to the position C ₂ . Consequently, the free end 40 _{2 of} the leaf spring 38 is at a position E ₂ . The free end 40 ₂ therefore only has to cover a distance S2 up to the working point, shown at 40 ₂ '. This requires a force F ₂ at point D that is less than F ₁ . Because in order to achieve the path S ₂ at the end 40 ₂ , the point D only has to cover a path S ₂ * which is smaller than the path S ₁ * mentioned above.

In other words, in the construction shown, the operating point (switching force threshold _{) is} reached at a lower force F ₂ when the free end 32 is raised. On the other hand, lowering the free end 32 means that the operating point is only reached at a higher force 17.

In Fig. 5 is also at the extreme end of the free end 32 alternative pivot point A 'shown. In this alternative embodiment would be the mounting block 34 so that it around the pivot point A 'is pivotable. With such a A configuration would pivot the clamping block 34 out the solid position shown in a swivel position upwards by means of a force B the switching force threshold increase.

It is understood that when using such switching arrangements setting up a lower switching force threshold in a pressure cell means that the pressure can is at a lower Pressure difference switches.

FIG. 5 also shows that the free end 40 of the leaf spring 38 does not necessarily have to be pretensioned by a stop 50, as shown in FIG. 1. The stop 50 essentially serves to avoid vibrations of the system of membrane 16 and leaf spring 38 with a force 17 of essentially 0 Newton or a pressure difference of essentially 0. The prestressing path realized by the stop 50 should then be 5 example shown may be greater than the difference S ₁ - S ₂ . In other words, the stop 50 should be approximately at the level of E ₂ . Then the switching function is not influenced despite the stop 50 over the setting range of the clamping block 34.

A variant of a recess 60a in the form of one on a center line the leaf spring hole is shown in Fig. 6. Such a hole 60a is opposite the side recesses 60 of FIG. 2 is preferred since the leaf spring 38 is then more torsionally rigid is stored.

7 shows a further variant in which the leaf spring 38 provided without a hole 44 for a pin of the switching element 14 is. In this case, the lower end of the switching element is 14a rounded and lies on the leaf spring 42a and can Reduction in friction, for example coated with Teflon his.

Claims (16)

Arrangement (10) for the contactless switching of an electrical contact (12) by means of a switching force (17) exceeding a predetermined switching force threshold, with a switching element (14) by means of which the switching force (17) is exerted, a leaf spring (38) clamped on one side at a clamping point (C), the switching element (14) engaging for switching on the leaf spring (38) in order to move the leaf spring (38) from a rest position into a switching position (48 '), wherein the leaf spring (38) is arranged in the rest position so that its spring force (51) forms the predetermined switching force threshold, characterized in that
Means (58; B) for changing the position (C ₁ , C ₂ ) of the clamping point (C) are provided so that the switching force threshold can be set by changing the position (C ₁ , C ₂ ) of the clamping point (C). Arrangement according to claim 1, characterized in that the leaf spring (38) is pretensioned in the rest position by means of a fixed stop (50). Arrangement according to claim 2, characterized in that the leaf spring (38) is biased by means of the fixed stop (50) in such a way that the leaf spring (38) exerts essentially no force on the switching element (14) in its rest position. Arrangement according to one of claims 1-3, characterized in that the leaf spring (38) is clamped at the clamping point (C) at an acute angle (37) greater than 0 ° to a transverse plane which is approximately perpendicular to the direction of movement (17) of the switching element (14) is aligned. Arrangement according to claim 4, characterized in that the switching arrangement (10), with an otherwise essentially unchanged construction, can be produced with different clamping blocks (34) which clamp the leaf spring (38) at a different angle (37), so that switching arrangements (10) with different switching force threshold can be produced by selecting the setting block (34). Arrangement according to one of claims 1-5, characterized in that the end region (48) of the free end (40) of the leaf spring (38) is aligned approximately parallel to the transverse plane by means of a stop (50). Arrangement according to one of claims 1-6, characterized in that the clamping point (C) of the leaf spring (38) is arranged at the free end (32) of a projecting elastic support element (24). Arrangement according to claim 7, characterized in that the spring rate of the support element (24) is substantially greater than the spring rate of the leaf spring (38). Arrangement according to claim 7 or 8, characterized in that the support element (24) is an electrical circuit board (24). Arrangement according to one of claims 7-9, characterized in that the free end (40) of the leaf spring (38) and the free end (32) of the support element (24) point in opposite directions. Arrangement according to one of claims 7-10, characterized by means (58) for adjusting the deflection of the free end (32) of the support element (24) so as to change the position (C ₁ , C ₂ ) of the clamping point (C), to set the switching force threshold. Arrangement according to one of Claims 1 to 11, characterized in that the means (58; B) for changing the position (C ₁ , C ₂ ) of the clamping point (C) are designed to move the clamping point (C) around an axis (A ) to pivot. Arrangement according to claim 12, characterized in that the clamping point (C) can be pivoted such that the position of the section (D) of the leaf spring (38) on which the switching element (14) acts remains essentially unchanged. Arrangement according to one of claims 1-13, characterized in that the leaf spring (38) is provided in the region of the clamping point (C) with a recess (60; 60a), preferably with a hole () arranged on the central axis of the leaf spring (38). 60a). Pressure measuring device with at least one pressure chamber (18, 20) separated by a membrane (16), characterized by an arrangement (10) according to one of claims 1-14, wherein the membrane (16) is coupled to the switching element (14). Apparatus according to claim 15, characterized in that the predetermined switching force threshold can be in the range corresponding to a pressure difference from a few pascals to a few hundred pascals.

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