FI3879550T3

FI3879550T3 - Switch unit

Info

Publication number: FI3879550T3
Application number: FIEP21171622.0T
Authority: FI
Inventors: Lutz Sommer; Florian Geiser
Original assignee: Schaefer Gmbh
Priority date: 2016-09-29
Filing date: 2017-09-19
Publication date: 2023-03-30
Also published as: EP3301696A3; EP3301696B1; EP3879550A1; EP3301696A2; EP3879550B1; DE102016118430A1; PT3301696T; ES2940920T3; PL3879550T3; DE102016118430B4; PT3879550T; DK3879550T3; PL3301696T3; ES2881799T3; DK3301696T3

Claims

1 21171622.0 SWITCH UNIT

[0001] The invention relates to a switch unit, in particular to a switch unit by which it is possible to detect a wear status or maintenance reguirements.

[0002] Switches and switch units for manually opening and closing circuits are known in principle. For example, US 6,987,233 B2 discloses a switch unit for installation in operator panels, wherein the switch unit contains a housing having an actuation knob and a control lamp, and the actual electrical switch. The switch has three contacts and a closing element, which connects one of the three contacts alternately to one or the other of the two remaining contacts. The actuation is performed by the actuation knob, which is movably held in the housing. The switch housing contains at least one additional conductive path, based on either polymers loaded with metal or carbon particles or intrinsically conductive polymers. This additional conductive path is used for dissipating electrical discharges.

[0003] In addition, US 5,175,214 as well as EP 3 007 196 A1 describes an electrically conductive elastomer which changes its conductivity under pressure. The elastomer can be used to produce a pressure-sensitive switch path.

[0004] US 6,469,267 and US 6,072,130 A constitute further state of the art. US 6,639,159 B2 discloses a contact switch with two deformable elastomer elements arranged one above the other in a dome-like shape, which are arranged centrally above a middle contact. When the outer elastomeric element is pressed down, it first deforms and contacts the dome element underneath, thus closing a first switch circuit. On further depressing, the two elements deform while maintaining their contact until the centre contact is touched, thus closing a second switch circuit. US 2009/0321237 A1 also constitutes state of the art which also has two successively closing switch circuits. A depressible actuating element with conductive coating is held suspended above a snap spring centre contact, which in turn spans a fixed contact. When the actuating element is pressed down, it first contacts the snap spring element and thereby closes a first switch circuit. When the actuating element is pressed down further, the snap spring deforms and contacts the centre contact, closing a second circuit.

[0005] As a result of wear, ageing, corrosion, vandalism or other reasons, switches can suddenly or gradually fail, potentially leading to danger for people or facilities.

2 21171622.0

[0006] The object of the invention is to specify a concept by which danger for people and facilities resulting from switch failures can be reduced or eliminated.

[0007] This object is achieved by a switch unit according to claim 1.

[0008] The switch unit according to the invention has two circuits and thus ensures higher technical availability in line with the redundancy principle. For this purpose, the switch unit according to the invention comprises at least two contact devices and a deformable and/or movably arranged closing element for establishing and breaking an electrical connection between two contact devices. The closing element consists of a thin, laminar, electrically conductive entity, e.g. a thin sheet or dome. Preferably, it is in the form of a catch spring, e.g. by being curved about two axes at an angle to one another.

[0009] In addition, an electrically conductive actuation element is provided and assigned to the closing element. The switch unit thus provides a first switch circuit containing the first contact device, the second contact device and the closing element. In this switch circuit, the current flows lengthways (transversely to the surface normal), i.e. from contact to contact through the closing element. In addition, the switch unit has a second switch circuit containing the actuation element, the closing element and one of the two contact devices. In this switch circuit, the current flows crossways through the closing element, i.e. in the direction of the surface normal of the closing element.

[0010] Upon actuation when wear has occurred, the two switch circuits exhibit characteristic yet different behaviour patterns, from which information can be derived regarding any partial failure and impending total failure of the switch unit. In particular, the switch unit can carry out self-monitoring as a result. For this purpose, it can have a corresponding monitoring circuit, for example in the form of an internal or external microcontroller, which monitors the at least two switch circuits and evaluates the behaviour thereof by collecting data. If irregular behaviour of the switch unit is detected, this can be signalled to the operator or a remote-monitoring unit optically, acoustically or by remote transmission, and a maintenance process can thus be initiated.

[0011] In addition to the two switch circuits, a switch test circuit can be provided, which leads through the first contact device and the closing element. In this way, the integrity of the closing element can be reliably monitored. The switch test circuit can possibly also contain the second contact device.

3 21171622.0

[0012] In addition, a third switch circuit can be provided, which contains the actuation element, the closing element and the first contact device. This circuit flags damage to the closing element before the switch unit becomes entirely unusable.

[0013] By means of said various circuits, which use various combinations of contacts or contact devices of the actuation element and of the closing element, predictive, i.e. prognostic, servicing of the switch unit is possible by using, for example, an evaluation device in the form of an external microcontroller. This is regardless of whether the actuation element is in permanent contact with the closing element or only comes into contact therewith in the event of actuation.

[0014] In preferred embodiments, at least the closing element or the actuation element has contact devices that are electrically connected together. The switch unit thus has a total of at least three contacts, two of which are permanently electrically connected to the closing element. These may be the contacts of one and the same contact device or, in another variant, contacts of the two different contact devices, resulting in further testing options in relation to the integrity of the closing element.

[0015] According to the invention, the actuation element is electrically conductive — based on either polymers loaded with metal or carbon particles or conductive polymers.

[0016] By using a plastics material of this kind having pressure-dependent conductivity as the actuation element, it is possible to detect the actuation force exerted on the switch unit. If contact resistances at the switch gradually increase, for example due to contact corrosion or wear and tear, operators will actuate the switch unit using a higher actuation force on average. An evaluation device associated with the switch unit, for example in the form of an external microcontroller, can detect this and, for example, then provide a maintenance request signal when switch actuations using increased actuation force become more frequent. In addition, by means of the resistance change in the polymer, it is also possible to measure the force or pressure exerted on the actuation element and thus also to log events such as, for example, vandalism incidents or improper operation,

[0017] By forming the actuation element in a manner based on either polymers loaded with metal or carbon particles or intrinsically conductive polymers, a particularly simple switch construction is made possible. In addition, the combination with a closing element made of metal and/or contact devices made of metal leads to a particularly reliable switch unit due to the resistance to corrosion of plastics materials. If a loaded

4 21171622.0 (compounded) plastics is provided as the plastics material, it obtains its conductivity by conductive particles, for example of carbon or metal, being embedded therein. Where necessary, however, the plastics matrix can consist of the same plastics material as the other, electrically insulating switch housing. The mechanical and electrical contact site between the actuation element and the closing element can be optimised tribologically, in which case it is only subject to low mechanical wear.

[0018] In addition, unlike when using other sensors such as piezoelectric components, the electrically conductive actuation element makes it very simple to detect the state of the housing of the switch unit integrated therein. Due to the changing electrical resistance when a force component (pressure) acts on the electrically conductive polymer, information on the position of the switch unit relative to the actuation knob can be derived indirectly. If, for example, a housing breakage occurs, it can generally be assumed that the position of the circuit board comprising the switch unit will change. As a result, if the switch unit is intact, the switching desired by a user is not detected, is detected only sporadically or is detected only in the event of a relatively high actuation force. On the one hand, this state can occur in a creeping manner over a relatively long period of time, which can be detected by a decreasing conductivity of the polymer due to a greater or different distance from the actuation knob. On the other hand, a sudden breakage of the switch housing is also conceivable (for example after vandalism). To diagnose this case too, the inside of the housing of the switch unit can also be made of an electrically conductive polymer. Using a low test current that is not critical in terms of safety and flows through the interior of the housing at regular intervals via the actuation element and the actuation knob without creating any danger for users on the outside, damage to the switch housing can be detected by means of an evaluation device in the form of an external microcontroller in the event that said current path is broken, and a maintenance process can be initiated. Electrically conductive polymers are thus preferably suitable for multi-functional uses and require a significantly simpler evaluation logic compared with piezoelectric sensors, for example for detecting oscillations.

[0019] Further details of advantageous embodiments of the invention are set out in the dependent claims, the drawings and the associated description. In the drawings:

[0020] Figure 1 is a schematic sectional view of a switch unit according to the invention in the non-actuated state,

[0021] Figure 2 shows the switch unit according to Figure 1 in the actuated state,

21171622.0

[0022] Figure 3 shows the faulty switch unit according to Figure 1 in the non- actuated state,

[0023] Figure 4 shows the faulty switch unit according to Figure 3 in the actuated state, 5 [0024] Figure 5 shows a modified embodiment of the switch unit according to the invention in the non-actuated state,

[0025] Figure 6 shows the switch unit according to Figure 5 in the actuated state,

[0026] Figure 7 shows the switch unit according to Figure 1 in the faulty state,

[0027] Figure 8 shows the switch unit according to Figure 7 in the actuated state, Figure 9 and 10 show further switch units that do not constitute embodiments of the present invention,

[0028] Figure 1 is a schematic view of a switch unit 10. This switch unit contains at least one electrical switch arrangement and possibly, where required, an electrical evaluation circuit in order to derive switch signals and possibly also maintenance signals, fault signals or the like from the contact that exists or is lacking in the switch unit 10. The switch unit 10 has a first contact device 11 and a second contact device 12, which is arranged in an electrically insulating housing 13 that preferably consists of plastics material. The housing 13 can, for example, be made from a thermoplastic in an injection moulding technique. This can likewise consist of electrically conductive plastic materials, according to requirements and design.

[0029] The first contact device 11 contains contacts K1a and a second contact K1b, which are arranged immovably in the housing 13 at a distance from one another and are electrically connected together. The second contact device 12 comprises at least one electrical contact K2, which is arranged immovably between the two contacts K1a, K1b of the first contact device 11 and is electrically insulated therefrom. The contacts K1a, K1b, K2 are preferably arranged in a common plane.

[0030] A closing element 14, for example in the form of a metal curved contact element, is supported by its ends on the contacts K1a, K1b and, when in the resting state, is spaced apart from the contact K2. The closing element 14 can be in the form of a catch spring and, for this purpose, be curved in two directions. This is not compulsory, however — the closing element 14 can also be in the form of a metal strip that only has one curvature or is straight. In the latter case, the middle contact K2 can be lower than the

6 21171622.0 two other contacts K1a, K1b. In addition, the closing element 14 can be made of metal or of another suitable electrically conductive material, e.g. polymers compounded with metal or carbon particles, intrinsically conductive polymers, a composite material or the like. The closing element 14 spans the distance between the contacts Kla and K1b, wherein a middle region of the closing element 14 is spaced apart from the contact K2. In this region, the actuation element 15 touches the closing element 14 such that, when pushed down, the closing element 14 presses against the contact K2.

[0031] The switch unit 10 also contains an actuation element 15, which is electrically conductive and which is movably arranged in the housing 13. The actuation element 15 touches the closing element 14 or can be made to touch it. In addition, the actuation element 15 can be accessible for direct manual actuation. For this purpose, it has an actuation surface 16, onto which pressure can be exerted for actuation purposes. The actuation surface 16 can thus be manually accessible or, as preferred, directly or indirectly connected to an actuation knob, an actuation plate or other mechanical actuation means.

[0032] The actuation element 15 can consist of an intrinsically conductive plastics material. However, embodiments having a compounded plastics material that has obtained its electrically conductivity through the addition of electrically conductive particles, for example carbon particles, metal particles or the like, are preferred. In this case, the specific electrical resistance can be set at approximately 500 ohm/cm. To produce or increase the electrical conductivity, the actuation element 15 can also have a metal coating and/or one or more metal inlays. In addition, it is electrically connected to a third contact K3. For this purpose, a flexible contact means proceeding from the contact K3, for example a wire, a litz wire or the like, can be let into the plastics body of the actuation element 15 and connected to the contact K3. Alternatively, the contact K3 can be connected to the contact K3 by means of a flexible conductive plastics web or an electrically conductive plastics membrane. In a particularly advantageous configuration, for connection to the contact K3 the actuation element 15 can be provided with one or more conductor tracks applied, for example, in an additive production process, i.e. a suitable printing process, e.g. the aerosol inkjet process. In that process, the conductor track is formed by a conductive fluid that is hardened after application and is applied, as a conductive ink in the form of an aerosol jet, to the plastics web or membrane which connects the actuation element 15 to the housing 13 and thus to the contact K3.

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[0033] If the actuation element 15 contains a metal inlay, the contact K3 can be connected thereto. The metal inlay can also be exposed on a side facing the closing element 14. Alternatively, the metal inlay can terminate at a certain distance from the contact surface between the actuation element 15 and the closing element 14, such that a plastics-metal contact is established between the actuation element 15 and the closing element 14. This is low-friction and low-wear contact. Furthermore, instead of the conventional metal inlay (e.g. made of nickel-coated stainless steel), nitinol, which generates a switch signal by changing its crystal structure in the event of actuation and thus does not reguire any further contact sites, can preferably be used as the base metal. In addition, this metal is distinguished by a very long service life compared with conventional metal inlays and also enables a function as a sensor element.

[0034] The configuration of the switch unit 10 illustrated in Figure 1 provides multiple switch circuits:

[0035] A first switch circuit S1 is formed by the first contact device 11, the second contact device 12 and the closing element 14.

[0036] A second switch circuit S2 is formed by the actuation element 15, the closing element 14 and the second contact device 12.

[0037] In addition, this second switch circuit can also comprise the third contact K3.

[0038] The switch unit 10 described so far operates as follows:

[0039] In the non-actuated state, the switch unit 10 has the switching state as per Figure 1, in which the two switch circuits S1, S2 are open. If, however, the actuation element 15 is pushed down by an actuation force being applied to its actuation surface 16 counter to the force of a spring (not shown in more detail) and/or counter to the spring force of the closing element 14, such that the closing element 14 touches the second contact device 12, i.e. the contact K2, both the first switch circuit S1 and the second switch circuit S2 close. If the actuation element 15 is permanently low-resistance, in the event of a normal actuation force the switching of the two switch circuits S1 and S2 is detected by the evaluation unit (not shown in more detail) and deemed to be a switch signal.

[0040] As illustrated in the fault scenario in Figures 3 and 4, it is possible to have a fault in which correct contact is not possible in the first switch circuit S1 when the switch unit 10 is actuated. A fault of this kind can, for example, be a breakage of the closing element 14, attrition or oxidation of the contacts K1a, K1b and/or K2, or a similar fault. In this case, the first switch circuit S1 remains open when the actuation element 15 is

8 21171622.0 actuated (see Figure 3 and Figure 4). In the second switch circuit S2, however, contact can still be recorded at least if a certain electrical contact can still be established with the second contact K1, i.e. the second switch circuit S2 closes. The second switch circuit S2 guides the switch current through the closing element 14 as a cross current, whereas the first switch circuit S1 guides the switch current there through as a direct-axis current.

[0041] Since the actuation element 15 consists of conductive plastics material and thus, by definition, has rather higher resistance than a metal part, any contact resistances at the contact K2 play a subordinate role for the second switch circuit. The evaluation device connected to the second switch circuit S2 can report contact for example as early as when the electrical resistance in this switch circuit falls from a value in the mega-ohm range or higher to a resistance in the kilo-ohm range. It is thus possible to generate switch signals even when the switch is in a worn state. However, the evaluation unit can generate a warning signal, a maintenance request signal or the like on the basis of the fact that the first switch circuit S1 no longer closes and the signal comes solely from the second switch circuit 52.

[0042] The switch unit 10 according to Figures 1 to 4 offers further possibilities. For example, in all the embodiments described above and below, the actuation element 15 can be not in contact with the closing element 14 when in the resting state and only come into contact therewith in the event of actuation. This does not change the prescribed functioning.

[0043] Further possibilities result, for example, from evaluating an alternative current path for the first switch circuit, which is denoted by S1’ in Figure 1 to 4. This switch circuit is between the contacts K1b and K2 and is equivalent to the switch circuit S1 formed between the contact K1a and the contact K2.

[0044] In addition, a third switch circuit 53, formed between the actuation element 15, the closing element 14 and the first contact device 11, can be integrated into the evaluation and monitoring. This circuit is always closed when the switch is intact. However, it opens as soon as the electrical connection between the closing element 14 and the contact device 11, or between the actuation element 15 and the closing element, is broken. This may be caused by breakage of the closing element 14 or other faults.

[0045] Overall, the following switching behaviour of the switch unit 10 is produced:

9 21171622.0 k sk k = Intact, non- 1 me A Faulty, non- me A ae k to Po

[0046] “0” denotes an open switch and “1” denotes a closed switch. According to the table, the switch S2 of the second switch circuit can still generate a valid switch signal even if the closing element 14 is faulty. On the basis of the altered behaviour of the first switch circuit S1 in the event of a malfunction, the evaluation circuit can derive a malfunction signal. To increase safety, the behaviour of the third switch circuit S3, which indicates an incipient or existing switch malfunction in both the actuated and non- actuated state, can also be evaluated.

[0047] Figures 5 to 8 show an embodiment of the invention that has been modified further, to which the above description applies mutatis mutandis but with the exceptions described below:

[0048] Unlike the above-described embodiment, the contact K2 of the second contact device is, in this case, not arranged between the contacts K1a, K1b of the first contact device. Instead, the first contact device 11 merely comprises one contact K1, whereas the second contact device 12 comprises two contacts K2a, K2b. In the process, the contact K2a is arranged centrally between the contacts K1 and K2b approximately in the middle below the actuation element 15. The closing element 14 interconnects the contacts K1 and K2b and spans the contact K2a at a distance therefrom. As a result of the actuation element 15 being actuated, the closing element 14 can be pressed against the contact K2a and contact it electrically.

[0049] The first switch circuit S1 is formed between the contacts K1 and K2a. The second circuit S2 is formed between the actuation element 15 and the contact K2a, wherein the second circuit leads via the closing element 14. As in the embodiment according to Figure 1 to 4, in this case the second switch circuit S2 also guides the switch current through the closing element 14 as a cross current, whereas the first switch circuit

10 21171622.0 S1 guides the switch current there through as a direct-axis current. This property is common to all embodiments according to the invention.

[0050] A third switch circuit S3 can optionally be provided, which leads from the actuation element 15 to the first contact K1 via the closing element 14. A test circuit can also be provided, which leads from the first contact K1 to the second contact K2b of the second contact device 12 via the closing element 14.

[0051] When the intact switch unit 10 is in the resting state, the switches $1 and S2 are open, wherein the test circuit ST and the third switch circuit S3 are closed. When the switch unit 10 is actuated (Figure 6), the first and the second switch circuit S1 and S2 close. The test circuit ST and the third switch circuit S3 remain closed.

[0052] In the event of a malfunction, the first switch circuit S1 no longer closes, for example due to a breakage of the closing element 14. However, the second switch circuit S2 continues to operate correctly. However, the test circuit ST and the third switch circuit 53 are often open in both the actuated and non-actuated state. As a result, the fact that the fault has occurred is clearly discernible. Overall, the following switching behaviour is produced: FOR mw Intact, non- 1 1 ow I N Faulty, non- me N N es E k Po

[0053] Once again, “0” denotes an open switch and “1” denotes a closed switch. As can be seen from the table, the switch S2 of the second switch circuit can still generate a valid switch signal even if the closing element 14 is faulty. On the basis of the altered behaviour of the first switch circuit S1 in the event of a malfunction, the evaluation circuit can derive a malfunction signal. To increase safety, the behaviour of the third switch circuit S3 and/or of the test circuit ST, which indicate(s) an incipient or existing switch malfunction in both the actuated and non-actuated state, can also be evaluated.

[0054] By way of example, the switch unit according to the invention can be intended for use in a lift operator panel as a pressure-sensitive switch comprising either

11 21171622.0 polymers compounded with metal or carbon particles or intrinsically conductive polymers. If the conductivity of the actuation element 15 is dependent on the exerted pressure, predictive servicing can be carried out by monitoring the resistance in the second switch circuit. If, for example, the resistance of the second switch circuit S2 decreases over time due to an increase in the operating forces required for actuation, a connected evaluation unit can detect this and, in the first instance, also generate the correct switch signals, but can simultaneously send a signal to the operator, a fault memory or a monitoring control centre to request maintenance or servicing. In this way, a switch unit that detects actuation forces is created in a simple manner, the evaluation unit of which detects the actuation force required and decides, by comparing it with a threshold value, whether the switch unit has reached a wear limit and/or maintenance is required.

[0055] The switch unit according to the invention uses a switch having a movably mounted or deformable closing element 14, which is formed from a laminar, electrically conductive material that is curved once or multiple times. Said element is part of both a first switch circuit S1 and a second switch circuit S2. In the first switch circuit S1, the current flows there through lengthways, i.e. within its plane. In the second circuit S2, the current flows there through crossways, i.e. perpendicular to its plane. The incorporation into different switch circuits S1, S2 and different flow directions makes it possible to detect faults occurring before the total failure of the switch unit 10 and, in the first instance, to maintain operation. In addition, the closing element 14 is moved by an electrically conductive actuation element 15 consisting of plastics material; this has a wear-reducing effect and offers further configuration options, in particular in relation to detecting the actuation force. Reference numerals

12 21171622.0 rr