Electrical switch

Abstract

The invention relates to an electrical switch (10) for an electrical device, in particular for manually operated electrical tools having at least one electric motor and having a set of electronics which controls the movement of the at least one electric motor and thus of the tool by open-loop and / or closed-loop control. Also provided are a housing (11), which entirely or partially encloses the components of the switch (10), and a spring-loaded actuator (20), which can be operated from the outside by an operating person, wherein the actuator (20) is movable within the housing (11) counter to the force of the spring (21). A movement of the actuator (20) causes the rotational speed and / or the torque of the at least one electric motor to change. The invention proposes that a detection element (30) be provided, which at at least one of its ends (31) is indirectly or directly fixed to the housing (11) and which at at least one other end (32) is movably supported, wherein the at least one other, movable end (32) of the detection element (30) is indirectly or directly operatively connected to the actuator (20), and in the event of a movement of the actuator (20) is also moved. The detection element (30) consists of a pseudoelastic material which changes its electrical resistance and / or its electrical capacitance when deformed. The resistance and / or the capacitance of the detection element (30) is monitored, and the rotational speed and / or the torque of the at least one electric motor is changed if the resistance and / or the capacitance changes.

Description

[0001] Electrical switch

[0002] The invention relates to an electrical switch, in particular for hand-operated electrical tools with electric motors, such as drills, cordless screwdrivers, hammer drills, and the like. Such tools usually have, in addition to the electrical circuit, which can be switched by an externally actuated actuator, a control and regulation of the speed or torque. Rotary or slide potentiometers are typically used for this purpose.

[0003] DE 2014 112 982 A1, for example, describes a switch of this type. Here, contacts are guided via potentiometer tracks, similar to a sliding contact, which detects the movement of the contact and thereby controls or regulates the electric motor. However, over the switch's lifetime, the contacts or potentiometer tracks become subject to wear and tear, ultimately leading to malfunctions or even destruction of the switch. To better maintain the potentiometer tracks, they must be lubricated and protected against moisture ingress, which entails additional costs.

[0004] The object of the invention is therefore to avoid these disadvantages and to provide a switch that is significantly more durable and, moreover, maintenance-free, as well as very space-saving and compact in design. This object is achieved by the characterizing features of claim 1, which are of particular importance as follows.

[0005] A detection element is provided which is fixed directly or indirectly to the housing at at least one of its ends and is movably mounted at at least one other end. The at least one other movable end of the detection element is directly or indirectly operatively connected to the actuator and is also moved when the actuator moves. This creates a relative movement between the one or more fixed ends and the at least one other movable end of the detection element. The detection element is made of a material with pseudo-elastic properties which changes its electrical resistance and / or electrical capacitance upon deformation, in particular upon stretching or compression. In a preferred embodiment, the detection element undergoes a structural transformation during deformation. The resistance orThe capacitance of the detection element is monitored, and if the resistance or capacitance changes, the torque or speed of the electric motor is also adjusted. This adjustment preferably takes place depending on the magnitude of the change in capacitance or resistance. The materials used for the detection element are smart materials. The switch according to the invention no longer requires a sliding contact, which can become faulty due to material removal. Instead, the electric motor is actuated by a movement, in particular by stretching the material of the detection element. This prevents wear on the switch, and the switch is very small, maintenance-free, and significantly longer-lasting. Preferably, the recovery of the detection element supports the movement of the actuator to its initial state, which is driven by the spring.Depending on the design of the detection element and the actuator, the rebound of the detection element may be sufficient for the return movement of the actuator and the use of an additional spring may be omitted, since the detection element then acts as a spring.

[0006] In a preferred embodiment, a control cam is provided directly or indirectly on the actuator, wherein the other movable end of the detection element moves along the control cam when the actuator moves. In the process, the detection element deforms, in particular due to stretching. Of course, a kinematic reversal is also encompassed by the inventive concept, in which the other movable end of the detection element moves, the actuator being arranged in a stationary manner and the detection element moving along the control cam. The deformation of the detection element changes its electrical property, namely the capacitance or the resistance, with a greater deformation causing a greater change. As a result, the speed and / or torque of the electric motor can then be controlled and / or regulated.

[0007] A particularly simple type of detection element is achieved by arranging it in the form of a loop. In this case, for example, both ends can be mounted in fixed bearings on the housing, while the other movable end forms the apex of the loop and interacts with the actuator, also moving when the actuator moves.

[0008] It is particularly advantageous if the fixed bearings, in which the ends of the detection element are located, provide not only the mechanical but also the electrical connection of the detection element. This includes both the electrical coupling for measurement purposes and an electrical connection if additional functions are present, such as heating the detection element or similar.

[0009] It is also possible to use the two fixed ends of the detection element as temperature sensors. Here, too, the electrical connection can preferably be made via the fixed bearings at the ends.

[0010] In a preferred embodiment, the actuator is designed as a linearly movable slide. Other, particularly rotary, configurations are also conceivable, for example, as a lever or a rotary cam disk or similar. The movement of the actuator can also be additionally supported or guided, for example, by one or more grooves, rails, or similar.

[0011] In a further preferred embodiment, a guide is provided for the other movable end of the detection element, in which the latter is guided and held in place in order to reliably measure even minor deformations of the detection element. This guide can then preferably be arranged stationary in the housing and only move vertically along the control curve of the actuator. In this case, the movable end of the detection element is also moved and stretched, thereby changing the capacitance and / or electrical resistance of the detection element. The guide protects the detection element from accidental deformations or stretches that could otherwise occur when the tool is moved.

[0012] Furthermore, additional electronics can preferably be provided which has further functions in addition to the control or regulation of the electric motor. This can be arranged on the same or a separate circuit board as the electronics for controlling or regulating the electric motor. A wide variety of functions are conceivable for the additional electronics, such as additional sensors or further influences on the detection element or on other components of the switch. For example, the additional electronics can convert the current resistance value of the detection element into a signal for a specific value for an electrical voltage. It is also conceivable for the electronics to influence the detection element in such a way that it heats it and thereby changes the mechanical properties such as the elasticity of the material of the detection element.Furthermore, the additional electronics can also decrease or increase the current used to measure the electrical resistance or capacitance, which also leads to a change in the mechanical properties of the material of the detection element. Furthermore, the additional electronics can also include a resistance bridge with an amplifier or similar components to adjust or amplify the signal characteristics. Beyond the application examples mentioned, other functions of the additional electronics are also possible and encompassed by the inventive concept.

[0013] It is also possible to process the pseudoelastic material of the detection element so that it exhibits a modified haptic response when the actuator is moved by an operator. For example, several discrete haptically perceptible switching steps can be provided here. If a shape memory alloy such as Nitinol is used as the pseudoelastic material, the different haptic properties can be induced by temperature treatment of the material. Such shape memory alloys obtain their special properties through an allotropic transformation of the lattice structure of the crystal lattice, usually from an austenitic to a martensitic structure and back again. This structural transformation can be induced by mechanical stress. Depending on how the crystal structure of the material of the detection element is adjusted, various haptically perceptible switching steps or other haptic effects can be induced.

[0014] It is also possible to provide a detent in the actuator's actuation path, which represents the actuator's absolute end-of-travel position. This detent can be provided, for example, as a detent lug, detent recess, or detent projection and can be characterized by a sudden increase in resistance, capacitance, or voltage in the material of the detection element. By detecting this sudden increase, at least one absolute end-of-travel position is identified.

[0015] The detection element can be made of various materials. A first preferred embodiment uses shape memory alloys such as Nitinol. Another possibility is electroactive polymers such as dielectric elastomers. The exact material used depends on the specific application and the desired properties.

[0016] Further advantages and embodiments of the invention will become apparent from the dependent claims, the following description, and the drawings. The invention is illustrated in two exemplary embodiments in the figures. They show:

[0017] Fig. 1: the internal structure of a switch according to the invention in the non-actuated position, Fig. 2: the internal structure of the switch from Fig. 1 in the actuated position,

[0018] Fig. 3: the individual components of another switch according to the invention,

[0019] Fig. 4: the switch from Fig. 3 in assembled state.

[0020] Figs. 1 and 2 show the internal structure of a switch 10 according to the invention. The actuator 20, designed as a slide 23, is shown in its rest position in Fig. 1; in Fig. 2, the actuator has been displaced by the distance ds since it was actuated.

[0021] The spring 21, which supports the actuator 20 against the housing 11, can be seen. The spring 21 strives to bring the actuator 20 into the position shown in Fig. 1. Furthermore, the detection element 30, which here has the shape of a wire, can be seen. The detection element 30 has the approximate shape of a loop 33, with both first ends of the loop 33 being designed as ends 31 fixed to the housing 11, while the apex 34 of the loop 33 is provided as a movable end 32 in a guide 35. The fixed ends 31 are each arranged in fixed bearings 36, which can also serve as temperature sensors. Additional electronics 40 is also provided near the fixed bearings 36.

[0022] The actuator 20 has a control cam 22 that is operatively connected to the guide 35 of the detection element 30. The guide 35, and thus the detection element 30, can only move vertically along the control cam 22 and are otherwise rigidly arranged in one location in the housing 11. If the actuator 20 is now moved, the control cam 22 pushes the guide 35 upward and thus also the detection element 30, which is thereby stretched. This stretching causes a change in the electrical resistance or capacitance of the detection element 30 and thus a control or regulation of the electric motor. A second embodiment of the switch 10 according to the invention is shown in Fig. 3 and 4. In Fig. 3, the individual components of the switch 10 are shown separately, while Fig. 4 shows the assembled switch 10.

[0023] In this exemplary embodiment, the housing 11 and the actuator 20, which here too is designed as a carriage 23, can be seen again. From Fig. 3, it can be seen that the actuator 20 moves on a rail in the housing 11. The detection element 30 is also designed here as a loop 33, with two ends that are provided as fixed ends 31 and an apex 34 of the loop 33 that serves as a movable end 32. The detection element 30 is also arranged here in a guide 35. In this embodiment, a receptacle is provided for the guide 35 of the detection element 30, which is additionally arranged in the housing 11, as shown in Fig. 4. From Fig. 4 it can also be seen that two openings are provided in order to lead the fixed ends 31 of the detection element 30 out of the housing 11 and to contact them and to connect them mechanically and / or electrically.

[0024] Finally, it should be noted that the embodiments presented here are merely exemplary embodiments of the invention. This is not limited to them. Rather, modifications and variations are possible. Even if the preferred movement of the detection element upon movement of the actuator is an extension or compression, other movements are possible and encompassed by the inventive concept. The housing does not have to be completely closed, but can also consist of several parts or can even be partially open. List of reference symbols:

[0025] 10 Electrical switch

[0026] 11 housings

[0027] 20 Actuator 21 Spring

[0028] 22 Control curve

[0029] 23 sleds

[0030] 30 detection element

[0031] 31 Fixed end of 30 32 Movable end of 30

[0032] 33 loop

[0033] 34 vertices of 33

[0034] 35 lead out of 30

[0035] 36 Fixed bearing 40 Additional electronics

Claims

AMENDED CLAIMS received by the International Bureau on 23 October 2024 (23.10.2024) New patent claims:

1. An electrical switch (10) for an electrical device, in particular for hand-operated electrical tools with at least one electric motor, comprising electronics that control and / or regulate the movement of the at least one electric motor and thus of the tool, comprising a housing (11) that completely or partially encloses the components of the switch (10), comprising a spring-loaded actuator (20) that can be operated externally by an operator, wherein the actuator (20) is movable within the housing (11) against the force of the spring (21), and wherein a movement of the actuator (20) causes a change in the speed and / or torque of the at least one electric motor, characterized in that a detection element (30) is provided, which is fixed directly or indirectly to the housing (11) at at least one of its ends (31) and is movably mounted at at least one other end (32),wherein the at least one other movable end (32) of the detection element (30) is connected to the actuator (20) directly or indirectly in, AMENDED SHEET (ARTICLE 19) operative connection, and is also moved when the actuator (20) moves, that the detection element (30) consists of a pseudo-elastic material, namely a metallic shape memory alloy such as nitinol, which changes its electrical resistance and / or its electrical capacitance when deformed, and that the resistance or capacitance of the detection element (30) is monitored, and when the resistance or capacitance changes, a change in the speed and / or torque of the at least one electric motor is brought about.

2. Electrical switch (10) according to claim 1, characterized in that at least one control cam (22) is provided directly or indirectly on the actuator (20), wherein the at least one other movable end (32) of the detection element (30) moves along the control cam (22) of the actuator (20) during a movement of the actuator (20) and is deformed, in particular stretched, in the process.

3. Electrical switch (10) according to claim 1 or 2, characterized in that the detection element (30) forms a loop (33), wherein both ends (31) of the loop (33) are mounted on the housing (11) in a fixed bearing (36) and the apex (34) of the loop (33) forms the movable other end (32) of the detection element (30) and also moves when the actuator (20) moves.

4. Electrical switch (10) according to claim 3, characterized in that both the mechanical and the electrical connection of the detection element (30) is effected by the fixed bearing (36). AMENDED SHEET (ARTICLE 19) 5. Electrical switch (10) according to claim 3 or 4, characterized in that the two fixed ends (31) of the detection element (30) serve as a temperature sensor.

6. Electrical switch (10) according to one of claims 1 to 5, characterized in that the actuator (20) is designed as a linearly movable slide (23).

7. Electrical switch (10) according to one of claims 2 to 6, characterized in that a guide (35) is provided for the detection element (30), on which guide the movable end (32) of the detection element (30) can be arranged and which is arranged stationary in the housing (11) and is in operative connection with the control cam (22) of the actuator (20), wherein the guide (35) moves along the control cam (22) of the actuator (20) only in its height and in the process the movable end (32) of the detection element (30) moves with it, whereby the detection element (30) is stretched.

8. Electrical switch (10) according to one of claims 1 to 7, characterized in that additional electronics (40) are provided.

9. Electrical switch (10) according to claim 8, characterized in that the additional electronics (40) converts the resistance value of the detection element (30) into a signal for a specific value for an electrical voltage.

10. Electrical switch (10) according to claim 8 or 9, characterized in that the additional electronics (40) can heat the detection element (30) in order to change the mechanical properties such as the elasticity. AMENDED SHEET (ARTICLE 19) 11. Electrical switch (10) according to one of claims 8 to 10, characterized in that the additional electronics (40) decreases or increases, as needed, the current used to measure the electrical resistance or capacitance of the detection element (30), thereby changing the mechanical characteristics of the pseudoelastic material of the detection element (30).

12. Electrical switch (10) according to one of claims 8 to 11, characterized in that the additional electronics (40) has at least one resistance bridge with amplifier in order to adjust and / or amplify the signal characteristics.

13. Electrical switch (10) according to one of claims 1 to 12, characterized in that the pseudo-elastic material of the detection element (30) is adjusted so that a modified haptic is achieved during the movement of the actuator (20) by an operator, in particular that several discrete haptically detectable switching stages are present during the movement of the actuator (20).

14. Electrical switch (10) according to one of claims 1 to 13, characterized in that at least one detent is provided in the actuating path of the actuator (20), which represents at least one absolute end position of the actuator (20). AMENDED SHEET (ARTICLE 19)

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