EP0026449A1 - Multiple pressure-switch - Google Patents

Abstract

1. A multiple pressure switch, comprising first and second snap switches (10 and 10', respectively) each adopting a starting position under spring bias and comprising first and second points of engagement (68 and 68', respectively) for an actuating member (72) which is supported at a total of three points of engagement (68, 68', 68") located at the corners of an assumed triangle and which first lets the first (10) and then the second snap switch (10') switch over into a final position as an external force (D) acting on the actuating member (72) within the triangle increases gradually, characterized in that, based on a base plane (E) perpendicular to the direction of action of the external force (D), the first point of engagement (68), in its starting position (figs. 4, 5a), is located higher and, in its final position (figs. 5b, c, d), lower than the second point of engagement (68') in its starting position (figs. 5a, b), and in that the second point of engagement (68') is located higher in its starting position (figs. 5a, b) and lower in its final position (figs. 5c, d) than the third point of engagement (68").

Description

The invention relates to a multiple pressure switch with a first and a second snap switch, which each assume a starting position under spring preload and have a first or a second point of attack for an actuator which is supported at a total of three points of attack lying at the corners of an imaginary triangle and at gradual increase of an external force acting on the actuator within the triangle first causes the first and then the second snap switch to snap into an end position.

Such multiple pressure switches generally have a housing which is divided into two chambers by a membrane. A pressure acts on one side of the membrane, which should be monitored; on the other side of the membrane there is a pressure plate to which the membrane transmits the pressure and which in turn is supported on the actuator.

The actuator is generally designed as a three-armed lever and extends with each of its three arms to one of the points of attack, which are at the corners of a triangle, preferably an equilateral triangle. The pressure plate is preferably supported in the center of this Triangle on the actuator. At least two of the points of attack for the actuator are each formed on a snap switch; the third point of attack is either stationary or, if a triple switchover option is required, is formed on a third snap switch.

If, starting from a quiescent state in which the membrane is not loaded with pressure, the external pressure acting on the membrane, and thus the external force acting on the actuator, gradually increases and finally reaches an amount predetermined by the preload on the first snap switch, then the first snap switch, as corresponds to the nature of a snap switch, suddenly snaps from its starting position into its end position. The actuator follows the first point of attack by pivoting about an imaginary axis which is determined by the second and third points of attack. The point of the actuating element that originally lay on the first point of application moves during this pivoting of the actuating element on a circular arc. For reasons of space, it is generally not possible to arrange the first snap switch in such a way that its point of engagement moves on the same circular arc when it is snapped. As a result, a relative displacement takes place between the first point of attack and the actuator when the first snap switch is snapped, in which a frictional resistance must be overcome. This frictional resistance cannot be kept sufficiently constant in series production and changes over time because the sliding, usually very small surfaces either become smoother if the snap switch in question frequently snaps or gradually become rougher due to corrosion. Given the magnitude of the frictional force, the greater the relative displacement between the point of application and the actuator, the greater the energy consumed by friction.

What has been said above in connection with the first snap switch also applies mutatis mutandis to the second snap switch if it snaps over, and to the third snap switch if it is present. However, the greater the frictional energy that is consumed when the individual snap switches are snapped by a relative displacement between their point of application and the actuating element, the lower the accuracy with which a certain switching pressure for each snap switch can be predetermined by adjusting the spring preload of the snap switch concerned.

The invention has for its object to reduce the influence that the friction between the actuator and the individual snap switches exerts on the switching accuracy in a multiple pressure switch of the type described above compared to known generic switches.

The object is achieved in that the first point of attack in its starting position is higher and lower in its end position than the second point of attack in its starting position in relation to a base plane normal to the direction of action of the external force, and in that the second point of attack in its starting position is higher and in its end position is lower than the third point of attack.

In this way, the relative displacement, which takes place between the individual points of attack and the actuating element in each case when a snap switch is snapped, can be kept considerably lower than in the known multiple pressure switch described.

The smallest possible relative displacement achieved when the first snap switch is snapped, given the size of the switching path and the given distance between the points of application one when the second point of attack is in its starting position halfway between the starting and end positions of the first point of attack.

Correspondingly, under otherwise unchanged conditions, the smallest possible relative shift is achieved when the second snap switch is snapped over when the first point of attack in its end position lies halfway between the starting and end positions of the second point of attack.

The third point of attack can be fixed in a known manner if only two snap switches are required. However, the invention can also be used with particular advantage on triple pressure switches, that is to say those pressure switches which, in addition to the first and second snap switches, have a third snap switch at which the third point of application for the actuating element is formed and which gradually increases the external force snapped after the second snap switch. According to the invention, such a multiple pressure switch is further developed in that the third point of attack in its end position is lower than the second point of attack in its end position.

The smallest possible relative displacement between the snap switches and the actuating element when the third snap switch is switched over arises when the second point of attack is in its end position halfway between the starting and end positions of the third point of attack.

• Fig.1 bis 3 Draufsichten eines Dreifach-Druckschalters in verschiedenen Zuständen zunehmender Demontage,
• Fig.4 den Schnitt IV-IV in Fig.1,
• Fig.5a bis 5d den Schnitt V-V in Fig.1 in verschiedenen Schaltzuständen des Dreifach-Druckschalters.

An embodiment of the invention is explained below with reference to schematic drawings. Show it:

• 1 to 3 top views of a triple pressure switch in different states of increasing disassembly,
• 4 shows the section IV-IV in Fig.1,
• 5a to 5d the section VV in Fig.1 in different switching states of the triple pressure switch.

The triple pressure switch shown has a pot-shaped housing 2 with a substantially flat bottom 4 and a circular cylindrical outer wall 6. The housing 2 is closed by a membrane 8 which, in the fully assembled triple pressure switch, covers a housing cover (not shown) and between it and the housing 2 is tightly clamped.

The housing 2 contains three snap switches 10, 10 'and 10 ", which are completely identical in their design and differ from one another only in their arrangement within the housing 2. Therefore, only the snap switch 10 is described in detail below; components of the other two Snap-action switches 10 'and 10 ", which are mentioned below, are provided with the same reference numerals as the corresponding components of the snap-action switch 10 and are distinguished from them by a single or a double index line, depending on whether they belong to the snap-action switch 10' or 10".

As a movable, electrically conductive component, the snap switch 10 has a snap spring 12 in the form of a rectangular leaf spring. The snap spring 12 has two parallel longitudinal slots 14 which delimit a pair of outer legs 16 in such a way that they are connected to one another and to a central part of the snap spring 12 only at their two ends. The middle part consists of two middle legs 18, which were separated from one another when the snap spring 12 was punched out. These two middle legs 18 are welded to a spring support 24 such that the total length of the middle legs 18 and the section of the spring support 24 connecting them is greater than the length of each of the two outer legs 16.

As a result, the two middle legs 18 cannot lie in a common plane with the outer legs 16 gene, but either form a serpentine curve curved upward, then downward and finally upward in relation to the outer legs 16 (FIG. 4) or an arc curved upward in relation to the two outer legs 16. The snap spring 12 attached to the spring support 24 is thus bistable; it can only jump between a first switching position (Fig. 4) and a second switching position under the influence of an external force.

The spring support 24 is fastened to the housing base 4 and has a soldering tab 26 which projects through it to the outside. Further electrically conductive components of the snap switch 10 are two stationary contacts 28 and 30, which are attached to a contact carrier 34 and 36, respectively, opposite one another on both sides of a double-sided switching contact 32 attached to the snap spring 12. The contact carriers 34 and 36 are fastened to the housing base 4 and also each have a solder lug 38 and 40, respectively, which protrude through the latter.

The snap switch 10 thus connects the solder lugs 26 and 38 to one another when the snap spring assumes its switching position, which is referred to below as the starting position. The snap switch 10 can be seen in its initial position in FIG. 4 and partly also in FIG. 5a. On the other hand, when the snap spring 12 assumes its second switching position, hereinafter referred to as the end position, the snap switch 10 connects the solder lugs 26 and 40 to one another. The snap switch 10 is partially shown in its end position in Fig.Sb, c and d.

On each side of the spring support 24, a bearing block 42 is arranged, which is formed in one piece with the housing 2. In the bearing blocks 42, a lever 50 is pivotally mounted about an axis A which is parallel to the plane of the membrane 8 and is approximately radial with respect to the housing 2. The lever 50 engages around the spring support 24 with ample play so that it can be pivoted about the axis A in a wide angular range. To adjust the lever 50, an adjusting member 52 in the form of a cap screw is provided, which engages at the end of the lever 50 remote from the axis A and is screwed into the housing base 4.

The lever -50 has an approximately U-shaped cross section with two flanges 54 which project laterally in a plane parallel to the axis A. Two leaf springs 56 are welded to the two flanges 54 and extend in the same longitudinal direction as the snap spring 12 on both sides thereof. While the snap spring 12 extends between the two bearing blocks 42, the two leaf springs 56 are arranged outside the bearing blocks. The two leaf springs 56 are welded to a flange 58 of a link 60, which is also parallel to the axis A, and together form a bearing for the link 60, which enables this pivoting about the axis A, but no other movement.

A hook 62 is formed on the handlebar 60, on which the one end of the snap spring 12, which is remote from the switching contact 32 and from the lever 50, is fastened. The end 64 of the handlebar itself, which is remote from the lever 50, projects into a recess 66 in the housing wall 6, the upper and lower limits of which each form a stop for the handlebar 60. Between the hook 62 and the end 64, a conical engagement point 68 for an arm 70 of an actuator 72 is formed on the handlebar 60.

Depending on whether the adjusting member 52 is screwed more or less deep into the housing base 4, the end 64 of the handlebar 60 is in the rest position of the snap switch 10 with a more or less large bias against the upper limit of the recess 66 (Fig. 4 and 5a). However, if the actuator 72 exerts with its arm 70 a downward force on the point of application 68, which is a certain amount corresponding to the preload, then this force pushes the handlebar 60 into its lower stop position (Fig.5b, c and d), and on the way there the snap spring 12 jumps around so that its switching contact 32, which in the Starting position on the upper stationary contact 28 has abruptly detached from this and puts on the lower stationary contact 30, whereby the end position of the snap switch 10 is reached. The snap switch 10 remains in its end position until the force exerted by the arm 70 on the point of application 68 again becomes smaller than the pretension generated by the setting element 52 in connection with the leaf springs 56.

The actuator 72 is designed according to Figure 1 as a three-armed lever and has a hollow cone-shaped socket 7.4 in the middle. A mandrel 76 engages in the pan 74, which tapers downward like the pan 74, but at a smaller angle, so that it can tip on all sides within the pan. The mandrel 76 is formed on a pressure plate 78 on which the membrane 8 rests.

In Figure 1, the housing 2 is shown without membrane 8 and pressure plate 78; the uppermost components shown here are the contact carriers 34, 34 'and 34 "and the actuator 72 with its three arms 70, 70' and 70". These components, which are highlighted by thick lines in FIG. 1, have been omitted in FIG. 2, so that the snap springs 12, 12 'and 12 "lie at the top. The snap springs highlighted in FIG. 2 by thick lines 12, 12 'and 12 "are omitted in FIG. 3, so that there the levers 50, 50' and 50", the leaf springs 56, 56 'and 56 "and the links 60, 60' and 60" in all essential details 1 1 to 3 also show intermediate walls 80, 80 'and 80 "which extend essentially radially within the housing 2 and the three snap switches 10, 10' and 10 "separate from each other.

Of the three arms 70, 70 'and 70 "of the actuating member 72, the arm 70 is pan-shaped at its end, which presses on the point of attack 58, as shown in FIGS. 5 a to d, while the arm 70', which cooperates with the point of attack 68 ', is on the bottom The underside of its end has the shape of a notch which is approximately radial with respect to the housing 2, while the arm 70 which cooperates with the point of engagement 68 "is flat on the underside of its end. In this way, the actuating member 70 is located on the three points of attack 68, 68 ' and 68 "supported in a statically clear manner without play.

According to FIG. 5 a, the points of attack 68, 68 'and 68 "in the starting position of the associated snap switch 10 or 10' or 10" lie at different heights above an arbitrarily selected base plane E, which extends normally to the line of action of the pressure force D. The point 68 of the first snap switch 10 has the greatest height H above the base plane E, the point 68 'of the second snap switch 10' has the second greatest height H 'and the point 68 "of the third snap switch 10" has the lowest height _H " Snapping the first snap switch 10, however, the height ratios change according to FIG. 5b in such a way that the point of application 68 now assumes a height that lies between the heights H 'and H ". Corresponding changes in height take place when, according to FIG. 5c, the second snap switch 10 'and according to FIG. 5d, the third snap switch 10 "snaps from its initial position into its end position.

Claims (5)

1.Multi-fold pressure switch with a first and a second snap switch, each assume a starting position under spring preload and have a first or a second point of attack for an actuator which is supported on a total of three points of attack lying at the corners of an imaginary triangle and with gradual increase An external force acting on the actuator within the triangle first causes the first and then the second snap switch to snap into an end position, characterized in that the first point of attack (68) in its starting position (FIGS. 4, 5a) is related to the direction of action of the external force (D) normal base plane E is higher and in its end position (Fig. 5b, c, d) lower than the second point of attack (68 ') in its starting position (Fig.5a, b), and that the second point of attack (68 ') is higher in its starting position (Fig.5a, b) and lower in its end position (Fig.5c, d) than the third attack point nkt (68 "). 2. Multiple pressure switch according to claim 1, characterized in that the second point of attack (68 ') in its starting position (Fig.5a, b) is halfway between the starting and end positions of the first point of attack (68). _3rd Multiple pressure switch according to claim 1 or 2, characterized in that the first point of application (68) in its end position (Fig. 5b, c, d) lies halfway between the starting and end positions of the second point of application ( ₆₈ '). 4. Multiple pressure switch according to one of claims 1 to 3, which additionally has a third snap switch, at which the third point of application is formed for the actuator, and which snaps with a gradual increase in external force after the second snap switch, characterized in that third point of attack (68 ") in its end position (FIG. 5d) is lower than the second point of attack (68 ') in its end position. 5. Multiple pressure switch according to claim 4, characterized in that the second point of attack (68 ') in its end position (Fig.5c, d) is halfway between the starting and end positions of the third point of attack (68 ").

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