Method for operating emergency brake unit for motor-driven tool, monitoring unit and emergency brake unit

Abstract

A method for operating an emergency braking unit (26) for a motor-driven tool is described. The emergency braking unit (26) comprises an actuator (34) having an actuating element (36), and at least one electrical energy storage unit (52). Electrical energy stored in the energy storage unit (52) can be used to selectively act on the actuating element (36). The method comprises detecting an energy storage unit state parameter (Z1) characterizing a state of the energy storage unit (52). Alternatively or additionally, an actuating element state parameter (Z2) characterizing a state of the actuating element (36) is detected. A blocking signal is triggered if at least one of the energy storage unit state parameter (Z1) and the actuating element state parameter (Z2) is outside the respective associated standard range. Furthermore, a monitoring unit (50) for monitoring a state of the emergency braking unit (26) and the emergency braking unit (26) are provided.

Description

Technical Field

[0001] The invention relates to a method for operating an emergency brake unit for a motor-driven tool. The emergency brake unit has an actuator and at least one electrical energy storage unit, the actuator having an actuating element, the at least one electrical energy storage unit being electrically coupled to the actuating element via an electrical switching element, so that the actuating element can be selectively supplied with electrical energy stored in the energy storage unit by actuating the switching element.

[0002] The invention also relates to a monitoring unit for monitoring the state of an emergency brake unit of a motor-driven tool. The emergency brake unit has an actuator and at least one electrical energy storage unit, the actuator having an actuating element, the at least one electrical energy storage unit being electrically coupled to the actuating element via an electrical switching element, so that the actuating element can be selectively supplied with electrical energy stored in the energy storage unit by actuating the switching element.

[0003] The invention also relates to an emergency brake unit for a motor-driven tool having a monitoring unit of this type. Background Art

[0004] Motor-driven tools with emergency brake units are known in the art. The same applies to the emergency brake units. These emergency brake units are used to bring the cutting element (e.g., saw blade) of the tool to a standstill if user contact with the cutting element is imminent or is detected during operation. In this way, injury is prevented or the severity of injury is reduced.

[0005] In this case, an actuating element is understood to be an element of an actuator by means of which the movement required by the actuator is generated in order to act on the system actuated by the actuator, in this case a braking system. Actuating elements of a known type include shape memory alloys. Their function is based on a thermally activated lattice transformation of the shape memory alloy, which leads to a change in the length of the actuating element. Actuating elements comprising shape memory alloys are usually formed as wires, which are shortened due to the thermally activated lattice transformation. Another known type of actuating element is a lifting magnet, in which a plunger can be displaced by electrically controlling a magnetic coil.

[0006] This type of actuator is preferably used in a reversible emergency brake unit, in other words, an emergency brake unit that can be used multiple times to stop the cutting element. It should be understood that in a reversible emergency brake unit, the actuator must be able to be actuated multiple times with a consistently high reliability. Summary of the invention

[0007] It is therefore an object of the present invention to further improve the known emergency brake units.

[0008] This object is achieved by a method for operating an emergency brake unit of a motor-driven tool. The emergency brake unit has an actuator and at least one electrical energy storage unit, the actuator has an actuating element, the at least one electrical energy storage unit is electrically coupled to the actuating element via an electrical switching element, so that the actuating element can be selectively supplied with electrical energy stored in the energy storage unit by actuating the switching element. The method comprises:

[0009] - detecting an energy storage unit state parameter characterizing the state of the energy storage unit and / or an actuating element state parameter characterizing the state of the actuating element,

[0010] - comparing the detected energy storage unit state parameter with an energy storage unit threshold value, and / or comparing the detected actuating element state parameter with an actuating element threshold value, said energy storage unit threshold value limiting a standard range assigned to said energy storage unit state parameter, said actuating element threshold value limiting a standard range assigned to said actuating element state parameter (Z2),

[0011] If at least one of the detected state parameter of the energy storage unit and the detected state parameter of the actuating element is outside the respectively assigned standard range, a blocking signal is triggered.

[0012] Thus, by means of the method according to the invention, the state of at least one of the energy storage unit and the actuating element is monitored. Only when the energy storage unit state parameter or the actuating element state parameter describing the state is within the corresponding associated standard range (which may also be referred to as the normal range), can the actuator of the emergency brake unit and therefore the emergency brake unit as a whole be operated. Otherwise, the operation of the actuator and therefore the operation of the emergency brake unit are blocked. In this way, the reliability of the emergency brake unit is improved, because it can only be operated when the corresponding state of at least one of the energy storage unit and the actuating element has been detected. This is particularly applicable if the emergency brake unit is an emergency brake unit that can be triggered multiple times. In this variant, it is ensured that at least one of the energy storage unit and the actuating element is in a suitable state each time it is triggered. In the case of an emergency brake unit that can be triggered multiple times, in this case, it can also be said that the aging state or wear state caused by the triggering that has occurred is monitored. It should be understood that the emergency brake unit can only be operated according to the state parameters actually detected or previously received. There are several alternatives for triggering the blocking signal. In a first alternative, this type of blocking signal is actively triggered when the energy storage unit state parameter and / or the actuator state parameter are outside the corresponding assigned standard range. This type of blocking signal is not triggered when all detected state parameters (in other words, the energy storage unit state parameter and / or the actuator state parameter) are within the standard range. Optionally, in this case, an active or explicit release signal can be triggered. In a second alternative, when all detected state parameters (in other words, the energy storage unit state parameter and / or the actuator state parameter) are within the standard range, an active release signal is always triggered. The blocking signal can be triggered simply by no longer triggering the release signal. It should also be understood that, depending on the type of state parameter, the assigned threshold value can limit the normal range upward and / or downward.

[0013] The tool may be a handheld tool, which may also be referred to as a hand tool, a semi-stationary tool, or a stationary tool.

[0014] In a preferred embodiment, the tool is a saw. It can be a hand saw, a semi-stationary saw or a stationary saw. An example of a hand saw is a portable circular saw. An example of a semi-stationary saw is a mobile table saw. An example of a stationary saw is a panel saw.

[0015] The actuating element may comprise a lifting magnet or a shape memory alloy, for example in the form of a wire.

[0016] The electrical energy storage unit may be a capacitor or a battery. It does not matter whether the electrical energy storage unit (in other words, capacitor or battery) is constructed as a component of the actuator or as a component of the tool. What is important is that the electrical energy storage unit is electrically coupled to the actuating element.

[0017] In one variation, the actuator comprises a biasing element. The method may then additionally comprise:

[0018] - detecting a bias element state parameter indicative of a state of the bias element,

[0019] - comparing the bias element state parameter to a bias element threshold value, said bias element threshold value limiting a standard range assigned to the bias element state parameter,

[0020] - Trigger a lock signal when the bias element state parameter is outside the normal range.

[0021] The biasing element is particularly designed to transfer the actuating element to a predetermined position or location, or to hold it there when the actuating element is not actuated. The biasing element is designed, for example, as a spring. Thus, in this variant, the state of the biasing element is monitored. This ensures that the actuator and the emergency brake unit equipped with the actuator are only operated when the biasing element is in the appropriate state. Thus, the reliability of the emergency brake unit is improved.

[0022] The biasing element state parameter may describe the conductivity of the biasing element and the biasing element threshold value may describe the minimum permissible conductivity. The conductivity of the biasing element is conveniently measured between the two ends of the biasing element. In this example, the biasing element may also be designed as a spring, in particular a helical spring or a leg spring made of an electrically conductive material such as metal. In this case, a reduced or zero conductivity may be understood as an indication of structural damage to the biasing element. In this case, operation of the actuator and therefore of the emergency brake unit is prevented. An illustrative example of this is a broken helical spring made of metal, the conductivity of which is greatly reduced or no longer exists due to the break.

[0023] The energy storage unit state parameter may also describe the number of actuation processes of the energy storage unit that have occurred, and the energy storage unit threshold value may describe the maximum permissible number of actuation processes. Alternatively or additionally, the actuation element state parameter may describe the number of actuation processes of the actuation element that have occurred, and the actuation element threshold value may describe the maximum permissible number of actuation processes. Thus, the actuation processes of the energy storage unit and / or the actuation element are counted and compared to the maximum number.

[0024] The maximum number may be specified by the manufacturer of the actuator or emergency brake unit as a fixed maximum number. This value is therefore fixed and cannot be changed directly or indirectly by the user.

[0025] Alternatively or additionally, the maximum number can be calculated according to one or more state parameters of the actuating element and / or the energy storage unit. This produces a maximum number of scenarios that depends on the specific aging and / or wear of the actuator and / or the emergency brake unit. This may be at least indirectly affected by the use behavior. The state parameter that can be used for this purpose is the energy storage capacity of the energy storage unit or the resistance of the actuating element (e.g., a wire made of a shape memory alloy) comprising a shape memory alloy. In another alternative, the maximum number is not directly calculated according to one or more state parameters of the actuating element and / or the energy storage unit, but is calculated by means of a model that calculates the maximum number based on one or more state parameters of the actuating element and / or the energy storage unit. This type of model can be constructed based on empirical data from the operation of the actuator and / or the emergency brake unit as a whole. The empirical data include, for example, the number of previous triggers, the historical current intensity of historical triggers and the current application period, the downtime of the emergency brake unit to stop operating, and / or the downtime between two safety tests of the emergency brake unit. In all variants, it is ensured that the emergency brake unit acts or triggers a blocking signal with a high degree of reliability.

[0026] It should be understood that the threshold value defining the maximum allowed actuation number may also be determined as the smaller maximum allowed actuation number between the fixed maximum number and the contextual maximum number.

[0027] In one variant, the actuator element state parameter describes the position or position difference of the actuator element, and the actuator element threshold value describes the target position or target position difference. The position difference is, for example, the stroke of the actuator element. The position can be an initial position or a zero position of the actuator element. By monitoring the position, it can be determined whether the actuator element is aged or worn, so that a decision can be made as to whether reliable operation of the emergency brake unit is still possible. In the case where the actuator element comprises a lifting magnet, the position of the associated plunger can be determined via the inductance of the magnetic coil.

[0028] Alternatively or additionally, the actuator element state parameter may describe the resistance of the actuator element and the actuator element threshold value may describe the maximum permissible resistance. The resistance is considered to be an indicator of wear and / or aging. This applies in particular to the case where the actuator element comprises a shape memory alloy. Here, structural fatigue of the shape memory alloy can be derived from the increase in resistance. The influence of temperature on the resistance can be computationally eliminated. In the case where the actuator element comprises a lifting magnet, damage to the electrical wires, such as a cable break, can be detected via the increased resistance.

[0029] In one embodiment, the actuator state parameter describes the actuation delay of the actuator, and the actuator threshold describes the maximum allowed actuation delay. The actuation delay is understood as the time between the closing of the switch element and the actuator element starting to move or reaching a defined position. The defined position is, for example, a target position. In the case where the actuator element includes a shape memory alloy, functional fatigue is characterized by the loss of shape memory, and is generally characterized by a significant increase in the transition temperature, which is represented by the extended time interval (in other words, length change) between the start of current flow and the start of phase change. The time when the length change of the shape memory alloy wire begins can be determined, for example, by the maximum value of the resistance of the shape memory alloy wire. Therefore, the degradation of the response of the actuator can be determined in a simple manner.

[0030] Furthermore, the actuator element state parameter can describe the voltage drop across the actuator element, and the actuator element threshold value can describe the maximum permissible voltage drop. Several variants are conceivable here. On the one hand, the voltage drop itself can be used as an indicator of the aging or wear state. This is particularly the case if the associated current is only subject to slight fluctuations or is known. Alternatively, it is conceivable to use the voltage drop to calculate the resistance.

[0031] In one variant, the actuating element state parameter describes the actuating force of the actuating element, and the actuating element threshold value describes the minimum permissible actuating force. Alternatively or additionally, the biasing element state parameter describes the biasing force of the biasing element, and the biasing element threshold value describes the minimum permissible biasing force. This ensures that the actuating element and / or the biasing element have an actuating force or biasing force sufficient for reliable operation of the emergency brake unit, or to trigger a blocking signal. Overall, the emergency brake unit is highly reliable.

[0032] In another variant, the energy storage unit state parameter describes the storage capacity of the energy storage unit and the energy storage unit threshold value describes the minimum permissible storage capacity. As previously mentioned, the energy stored in the energy storage unit is used to supply the actuating element. This ensures that the storage capacity, which may be affected by aging or wear, is sufficient for reliable operation of the emergency brake unit.

[0033] At least one of the energy storage unit state parameter, the actuation state parameter and the biasing element state parameter may be detected during the test routine. Alternative terms for the test routine are test operation, test sequence, verification routine and self-test. The test routine is to be distinguished from the operation of the emergency brake unit. The test routine is performed before the actual operation or before a predetermined part of the operation to ensure that the corresponding detected state parameter is within the normal range. Otherwise, the operation cannot be carried out. The test routine is performed, for example, after each activation of the emergency brake unit, after each use of the tool, before each use of the tool or regularly during work breaks or temporary interruptions in the operation of the tool.

[0034] As part of the test routine, the energy storage unit can be fully or partially charged and then discharged again. In this way, the storage capacity of the energy storage unit can be determined.

[0035] In the case where the actuating element comprises a shape memory alloy in the form of a wire, a relatively small current (in other words, a relatively low energy) can be applied to the shape memory alloy as part of a test routine and the travel or voltage drop can be measured after a certain time. These values ​​can be compared with respectively assigned target values.

[0036] The test routine may also include checking whether a cutting element is installed in the tool. As mentioned above, the cutting element is, for example, a saw blade.

[0037] The test routine may also include checking the wear of the mechanical components of the emergency brake unit. In this case, for example, the wear state of the brake pads of the emergency brake unit can be determined. The wear state of one or more brake pads can be determined, for example, by applying the brake to a capacitively coupled saw blade. The thickness of the brake pad influences the capacitive coupling between the saw blade and the brake, so that conclusions can be drawn about the wear of the brake pad.

[0038] In a variant, the method also includes providing the user with at least one of the energy storage unit state parameters, the actuator element state parameters and the biasing element state parameters. An overall state aggregated by at least two of the energy storage unit state parameters, the actuator element state parameters and the biasing element state parameters can also be provided. This can be provided via an interface that cannot be directly read by humans, such as via Bluetooth or WLAN. For this purpose, a smart phone or another electronic device can be coupled to the interface of the emergency brake unit. Alternatively, a human-readable communication interface, such as a display, can be provided on the emergency brake unit or on a tool equipped with the emergency brake unit. In an illustrative example, the user can be notified in this way of the triggering of the emergency brake unit that has occurred and / or the triggering that is still available. On this basis, the user can plan his work well with the tool. In addition, confidence in the reliability of the emergency brake unit and the tool equipped with the emergency brake unit is enhanced.

[0039] The method may further comprise triggering a warning signal if at least one of the energy storage unit state parameter, the actuating element state parameter and the biasing element state parameter is within a respectively assigned standard range and within an assigned warning range. In particular, the warning range is at one end of the standard range, which corresponds to relatively high wear or relatively high aging. Users of the emergency brake unit and of a tool equipped with the emergency brake unit thus receive a warning that the emergency brake unit may soon no longer be able to be operated and can therefore prepare for this.

[0040] Furthermore, the object of the present invention is achieved by a monitoring unit for monitoring the state of an emergency brake unit of a motor-driven tool. The emergency brake unit has an actuator and at least one electrical energy storage unit, the actuator having an actuating element, the at least one electrical energy storage unit being electrically coupled to the actuating element via an electrical switching element, so that the actuating element can be selectively supplied with electrical energy stored in the energy storage unit by actuating the switching element. The monitoring unit comprises at least one state sensor, which is designed to detect an energy storage unit state parameter characterizing the state of the energy storage unit. Alternatively or additionally, the state sensor is designed to detect an actuating element state parameter characterizing the state of the actuating element. In addition, the monitoring unit comprises a storage unit, on which at least one of an energy storage unit threshold value and an actuating element threshold value is stored, the stored energy storage unit threshold value and the actuating element threshold value limiting the corresponding assigned standard range. The monitoring unit also comprises a calculation unit, which is designed to compare the energy storage unit state parameter detected by the state sensor with the energy storage unit threshold value. Alternatively or additionally, the calculation unit is designed to compare the detected actuating element state parameter with the actuating element threshold value. The monitoring unit also includes a communication interface for triggering a blocking signal. Therefore, the monitoring unit can be used to monitor the state of at least one of the energy storage unit and the actuating element. Only when the state parameter describing the state is within the associated standard range (also referred to as the normal range), can the actuator of the emergency brake unit be operated and therefore the emergency brake unit as a whole be operated. Otherwise, the operation of the actuator is blocked and therefore the operation of the emergency brake unit is blocked. In this way, the reliability of the emergency brake unit is improved, because it can only be operated when the corresponding state is detected within the corresponding assigned standard range for all state parameters to be detected. This is particularly applicable if the emergency brake unit is an emergency brake unit that can be triggered multiple times. In this variant, it is ensured that the emergency brake unit is in a suitable state each time it is triggered. In the case of an emergency brake unit that can be triggered multiple times, in this case, it can also be said that the aging state or wear state caused by the previous trigger is monitored. As far as the triggering blocking signal is concerned, the alternatives that have been explained in conjunction with the method according to the present invention are still available. In general, the monitoring unit improves the reliability of the associated emergency brake unit.

[0041] If the state to be detected by the monitoring unit relates to an actuation process of the energy storage unit, the state sensor can be a current sensor or a voltage sensor, which detects the current flowing through the system boundary of the energy storage unit over time or the voltage dropped across the energy storage unit. Current and voltage curves of this type can be evaluated to determine the number of actuation processes. In the case of a detected current, the direction of the current can also be taken into account. In this case, for example, crossings exceeding a certain threshold are counted and used as an indicator of an actuation process.

[0042] If the state to be detected by the monitoring unit relates to the storage capacity of the energy storage unit, the state sensor may be a current sensor which detects the current flowing through the system boundary of the energy storage unit over time. To determine the storage capacity, the energy storage unit may be fully charged once and fully discharged once, for example as part of a test routine. The storage capacity may be determined from the resulting current curve.

[0043] If the state to be detected by the monitoring unit involves a voltage drop across the actuating element, the state sensor may be a voltage sensor which detects the voltage drop across the actuating element over time.

[0044] If the state to be detected by the monitoring unit concerns the resistance of the actuating element, the state sensor can be a combination of a current sensor and a voltage sensor. This means that the current flowing through the system boundary of the actuating element and the voltage dropped across the actuating element over time can be detected. These values ​​can be used to calculate the resistance.

[0045] If the state to be detected by the monitoring unit relates to an actuation process of the actuating element, the state sensor can also be a current sensor or a voltage sensor, which detects the current flowing through the system boundary of the actuating element over time or the voltage dropping across the actuating element. Current and voltage curves of this type can be evaluated to determine the number of actuation processes. In this case, for example, over-limit behaviors exceeding a certain threshold are counted and used as an indicator of the actuation process. Alternatively or additionally, the current and voltage curve can be used to determine the aging state of the actuating element, for example by counting over-limit behaviors exceeding a certain current or voltage threshold and using them as an indicator of the aging of the actuating element.

[0046] If the state to be detected by the monitoring unit relates to the position or position difference of the actuating element, the state sensor can be a position sensor. This includes position sensors that can detect absolute positions and position sensors that can only detect relative positions.

[0047] If the state to be detected by the monitoring unit relates to the actuation force of the actuation element, the state sensor can be a force sensor.

[0048] If the state to be detected by the monitoring unit relates to an actuation delay of the actuating element, the state sensor can also be a current sensor or a voltage sensor which detects the current flowing through the system boundary of the actuating element over time or the voltage dropped across the actuating element. These current and voltage curves can be used to determine the actuation delay. Alternatively, the above-mentioned position sensors and / or force sensors can also be used.

[0049] Alternatively or additionally, the state sensor may be a trigger control unit for detecting contact of the user with the saw blade or imminent contact of this type, which comprises, for example, a capacitive sensor. In this way, for example during a test routine, the time period from triggering of the emergency brake unit to contact of the brake, in particular the brake cam, with the saw blade, in other words, the actuation delay of the emergency brake unit as a whole, can be determined.

[0050] The monitoring unit may further comprise a state sensor configured to determine a state of a biasing element of an actuator of the emergency brake unit.

[0051] If the state to be detected by the monitoring unit relates to the conductivity of the biasing element, the state sensor may be a current sensor detecting the current flowing through the system boundary of the biasing element.The conductivity may be determined based on the magnitude of the measured current.

[0052] If the state to be detected by the monitoring unit relates to the biasing force of the biasing element, the state sensor may be a force sensor.

[0053] It should be understood that the state sensor may also include any combination of the mentioned sensors.

[0054] The above-mentioned purpose is also achieved by an emergency brake unit of a motor-driven tool. The emergency brake unit includes a monitoring unit according to the present invention. Therefore, the state of at least one of the energy storage unit and the actuating element can be monitored, in other words, the functional core elements of the emergency brake unit can be monitored. Only when the state parameter describing the state is within the associated standard range (which can also be referred to as the normal range) can the actuator of the emergency brake unit and therefore the emergency brake unit as a whole be operated. Otherwise, the operation of the actuator and therefore the operation of the emergency brake unit is prevented. In this way, the reliability of the emergency brake unit is improved.

[0055] It should be understood that the effects and advantages mentioned with respect to any one of the method of the present invention, the monitoring unit of the present invention and the emergency braking unit of the present invention also apply to any other one of the method of the present invention, the monitoring unit of the present invention and the emergency braking unit of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The present invention is explained below with reference to various embodiments shown in the accompanying drawings, in which:

[0057] Figure 1 A sawing device is shown having an emergency brake unit according to the invention, which is equipped with a monitoring unit according to the invention and an actuator, which emergency brake unit can be operated by a method according to the invention,

[0058] Figure 2 Shows Figure 1 A sawing device, wherein the housing part and the protective cover are omitted,

[0059] Figure 3 It passes along plane III Figure 2 The cross section of the sawing device,

[0060] Figure 4 Along the Figure 2 The view in direction IV shows the emergency brake unit separately,

[0061] Figure 5 Corresponding to Figure 3 The figure shows an alternative embodiment of the emergency brake unit,

[0062] Figure 6 Corresponding to Figure 3 The figure shows another alternative embodiment of the emergency brake unit, and

[0063] Figure 7 is a schematic diagram of an emergency brake unit according to the invention and its actuator and a monitoring unit according to the invention. DETAILED DESCRIPTION

[0064] Figure 1 and Figure 2 A motor-driven tool 10 is shown, which in the example shown is a sawing device 12 , more precisely a miter saw.

[0065] The sawing device 10 comprises a base 14 having a support surface 16 for a workpiece 18. The workpiece 18 is to be understood as being exemplary.

[0066] The sawing device 12 further has a pivot device 20 which is hingedly mounted at a first portion 20a on the base 14. A disc-shaped saw blade 22 is mounted on a second portion 20b spaced apart from the first portion 20a. A handle 24 is also provided on the second portion 20b.

[0067] Thus, a user of the sawing device 12 can use the handle 24 to cause the saw blade 22 in a rotating state to interact with a workpiece 18 mounted on the support surface 16 so that the workpiece is sawed or cut.

[0068] The sawing device 12 , in other words the motor-driven tool 10 , is also equipped with an emergency brake unit 26 .

[0069] The emergency brake unit 26 is designed to brake the saw blade 22 to a standstill if it detects that a user has come into contact with the saw blade 22 or that such contact is about to occur while the saw blade 22 is rotating.

[0070] In this case, the saw blade 22 acts as a capacitive sensor element, in other words, the capacitance of the saw blade 22 is continuously detected. In the case where the capacitance is outside a predetermined normal range, contact is detected. This example should be understood to be exemplary. Other methods for detecting that a user has made contact with the saw blade 22 or that this type of contact is about to occur, such as optical methods, are also conceivable.

[0071] exist Figures 3 to 6 The emergency brake unit 26 can be seen in detail in several variants of FIG.

[0072] In all variants, the emergency brake unit 26 has a brake caliper 28 which engages on the edge of the saw blade 22 such that a pressure element 30 provided on the brake caliper 28 is arranged on a first axial side of the saw blade 22 and a brake cam 32 rotatably mounted on the brake caliper 28 is arranged on a second axial side of the saw blade 22.

[0073] The braking cam 32 is coupled to an actuator 34 , by means of which the braking cam 32 can be selectively rotated so that it presses the saw blade 22 against the pressure element 30 and thus brakes it to a standstill.

[0074] exist Figure 3 and Figure 4 In a variant of the embodiment of the present invention, the actuator 34 comprises an actuating element 36, which comprises a shape memory alloy 38. In particular, the actuating element 36 is designed as a wire made of the shape memory alloy 38.

[0075] The actuating element 36 is fastened at a first end 36a to a fastening receptacle. The fastening receptacle may be part of the brake caliper 28 or part of a holding structure fixed to the brake caliper 28. The other end 36b of the actuating element 36 is fastened to a carriage 40 which is mounted so as to be displaceable in translation relative to the brake caliper 28. The carriage 40 is subjected to a force in a direction corresponding to the tensile load on the actuating element 36 via a biasing element 42. In the present case, the biasing element 42 is designed as a helical spring.

[0076] Furthermore, the carriage 40 is coupled to the brake cam 32 via an actuating pin 44 .

[0077] If the actuating element 34 is supplied with a current of sufficient magnitude, a thermally induced lattice transformation of the shape memory alloy 38 occurs and causes the actuating element 36 to shorten. This causes the carriage 40 and the actuating pin 44 to move in a Figure 3 In other words, it is opposite to the bias of the biasing element 42. As a result, the brake cam 32 engages with the saw blade 22 and brakes it to a standstill.

[0078] Figure 5 An alternative embodiment of an actuator 34 is shown. In this embodiment, a first end 36 a of an actuating element 36 , which is designed as a wire made of a shape memory alloy 38 , is generally fixed relative to the brake caliper 28 .

[0079] However, with Figure 3 and Figure 4 Unlike the variant of , the second end 36b is directly attached to the brake cam 32. The brake cam 32 is subjected to force via the biasing element 42. The loading direction also corresponds to the tensile loading direction of the actuating element 36.

[0080] The biasing element 42 is also a coil spring.

[0081] exist Figure 5 In a variation of , if the actuating element 36 is supplied with a current of sufficient magnitude, a thermally induced lattice transformation of the shape memory alloy 38 occurs and causes the actuating element 36 to shorten. This causes the brake cam 32 to rotate so that it engages with the saw blade 22 and brakes it to a standstill. Figure 5 In the embodiment of the present invention, when the emergency brake is triggered, the brake cam 30 rotates clockwise.

[0082] Figure 6 Another variation is shown, in which the brake cam 32 corresponds to Figure 3 The brake cam 32 is provided.

[0083] and Figures 2 to 5 The essential difference of the variant of is that the actuating element 36 is now designed as a lifting magnet 46 , the plunger 48 of which acts directly on the brake cam 32 .

[0084] In this variant, if the actuating element 36 (in other words, the lifting magnet 46) is supplied with a current of sufficient magnitude, the plunger 48 is moved in Figure 6 This causes the brake cam 32 to move to the right. Figure 6 2 is rotated clockwise in the illustration so that it engages with the saw blade 22 and brakes it to a standstill.

[0085] In all variants, the emergency brake unit 26 comprises a monitoring unit 50 which is only Figures 3 to 6 This can be shown schematically in Figure 7 The other components of the actuator 34 are seen in detail.

[0086] The emergency brake unit 26 (whose actuating element 36 is in Figures 3 to 6 ) also includes an electrical energy storage unit 52, which can be designed as a battery or a capacitor.

[0087] The electrical energy storage unit 52 is coupled to the actuating element 36 via the electrical switching element 54, so that the actuating element 36 can be selectively supplied with the electrical energy stored in the energy storage unit 52 by actuating the switching element 54. In other words, according to this embodiment, the wire or lifting magnet 46 made of the shape memory alloy 38 is energized by actuating the switching element 54. The amount of charge provided in the energy storage unit 52 is used for this purpose.

[0088] The monitoring unit 50 is designed to monitor the state of the emergency brake unit 26 .

[0089] For this purpose, the monitoring unit 50 comprises a first state sensor 56 a which is designed to detect an energy storage unit state parameter Z1 which characterizes the state of the energy storage unit 52 .

[0090] In the embodiment shown, the monitoring unit 50 further comprises a second state sensor 56 b which is designed to detect an actuating element state parameter Z2 which is characteristic of the state of the actuating element 36 .

[0091] Furthermore, in the present example, the monitoring unit 50 comprises a third state sensor 56 c which is designed to detect a biasing element state parameter Z3 which is characteristic of the state of the biasing element 42 .

[0092] All state sensors 56 a , 56 b , 56 c are signal-coupled to a computing unit 58 of the monitoring unit 50 .

[0093] The calculation unit 58 is also signal-coupled to a storage unit 60 .

[0094] In this case, the calculation unit 58 is designed to receive the energy storage unit state parameter Z1 , the actuating element state parameter Z2 and the biasing element state parameter Z3 detected by the respectively assigned state sensors 56a, 56b, 56c.

[0095] Furthermore, the calculation unit 58 is designed to receive from the storage unit 60 an energy storage unit threshold value S1 assigned to the energy storage unit state parameter Z1, an actuating element threshold value S2 assigned to the actuating element state parameter Z2, and a biasing element threshold value S3 assigned to the biasing element state parameter Z3.

[0096] The energy storage unit threshold S1 , the actuation element threshold S2 , and the biasing element threshold S3 are stored on the storage unit 60 .

[0097] The energy storage unit threshold value S1 limits the standard range of the energy storage unit state parameter Z1. The actuation element threshold value S2 limits the standard range of the actuation element state parameter Z2. The biasing element threshold value S3 limits the standard range of the biasing element state parameter Z3.

[0098] In addition, the calculation unit 58 is designed to compare the energy storage unit state parameter Z1, the actuating element state parameter Z2 and the biasing element state parameter Z3 detected by means of the corresponding assigned state sensors 56a, 56b, 56c with the corresponding associated thresholds among the energy storage unit threshold S1, the actuating element threshold S2 and the biasing element threshold S3.

[0099] Furthermore, the monitoring unit 50 comprises a communication interface 62 which is signal-coupled to the computing unit 58 .

[0100] As will be explained in more detail below, a blocking signal may be triggered via the communication interface 62 , which results in the actuator 34 and, therefore, the emergency brake unit 26 being inoperable.

[0101] In the example shown, the first state sensor 56a includes a current sensor and a voltage sensor. Thus, the current flowing through the system boundary of the energy storage unit 52 and the voltage dropped across the energy storage unit 52 can be detected over time.

[0102] Based on these current and voltage curves, the number of actuation processes can be determined by the calculation unit 58. In this case, the crossings of the measured current above a certain threshold value provided by the storage unit 60 are counted and used as an indicator of an actuation process.

[0103] Furthermore, the calculation unit 58 is designed to determine the storage capacity of the energy storage unit 52 based on the detected current distribution.

[0104] The second state sensor 56 b also includes a current sensor and a voltage sensor. Thus, the current flowing through the system boundary of the actuator element 36 and the voltage dropped across the actuator element 36 can be detected over time.

[0105] In this case, the voltage drop itself can be used to monitor the state of the actuating element 36 .

[0106] Furthermore, the resistance of the actuating element 36 can be calculated based on the determined voltage curve and the determined current curve and can be used as the actuating element state parameter Z2 .

[0107] As explained above in conjunction with the energy storage unit 52 , the number of actuation processes of the actuation element 36 can also be determined by the calculation unit 58 based on the current and voltage curve.

[0108] In the embodiment shown, the second state sensor 56 b also comprises a position sensor, by means of which the position of the second end 36 b of the actuating element 36 in the form of a wire made of shape memory alloy 38 can be detected. Figure 6 ), the position of the plunger 48 can be detected by means of a position sensor.

[0109] Furthermore, the second state sensor 56 b comprises a force sensor, by means of which the actuation force of the actuation element 36 can be detected.

[0110] The current sensor or voltage sensor can also be combined with a position sensor or a force sensor to detect the actuation delay of the actuation element 36. The start of the desired actuation in the form of a voltage change or a current change is detected by means of the voltage sensor or the current sensor. The actual start of the movement of the actuation element 36 is detected by means of the position sensor or the force sensor. The time period in between is the actuation delay. In this case, the calculation unit 58 is designed to perform the above steps to calculate the actuation delay.

[0111] Alternatively, the actuation delay can be determined with the aid of a state sensor, which is or comprises the trigger control unit 55. It is designed to detect during operation that a user has come into contact with the saw blade 22 or that such a contact is about to occur. The trigger control unit 55 comprises, for example, a capacitive sensor. The capacitive sensor is used to detect contact or proximity of a conductive medium, for example the skin of a user of the emergency brake unit 26. Thus, the trigger control unit 55 can assume a "triggered" and "untriggered" state. This can be regarded as a trigger control unit state parameter Z4.

[0112] The trigger control unit state parameter Z4 can also be used as part of a test routine. In this case, the trigger control unit 55 is switched from the "untriggered" state to the "triggered" state in a defined manner by means of a test trigger, without the capacitive sensor detecting contact with the saw blade 22. Instead, the capacitive sensor is used to detect contact between the brake (in particular the brake cam 32) and the saw blade 22. In this way, during the test routine, the time period from the test triggering of the emergency brake unit 26 (in other words, from the time when the trigger control unit state parameter Z4 switches from "untriggered" to "triggered") to the contact of the brake (in particular the brake cam 32) with the saw blade 22 (in other words, from the time when the trigger control unit switches from "untriggered" to "triggered") can be determined, in other words, the actuation delay of the emergency brake unit 26 as a whole can be determined.

[0113] The third state sensor 56c may also include a current sensor. If the current value detected in this way is compared with the biasing element threshold value S3 stored in the storage unit 60, the conductivity of the biasing element 42 may be determined.

[0114] In addition, the third state sensor 56 c includes a force sensor so that the biasing force of the biasing element 42 can be detected.

[0115] The monitoring unit 50 is also equipped with a user interface 64 that is signal-coupled to the computing unit 58. Each of the energy storage unit state parameter Z1, the actuating element state parameter Z2, and the biasing element state parameter Z3 can be provided to the user of the tool 10 via the user interface 64. The energy storage unit threshold value S1, the actuating element threshold value S2, and the biasing element threshold value S3 can also be optionally provided to the user. In the present example, the user interface 64 is designed as a display.

[0116] In addition, the monitoring unit 50 includes a warning unit 66 which is also signal-coupled to the computing unit 58. The warning unit 66 can emit a warning signal. In this example, the warning unit 66 is designed as a speaker. However, it should be understood that this is only an example.

[0117] Alternatively, the warning unit 66 and the user interface 64 may be formed by a shared display. In this example, the warning unit 66 is designed to output an optical warning signal.

[0118] The actuator 34 may be operated by a method for operating an actuator of an emergency brake unit of a motor-driven tool.

[0119] As part of the method, an energy storage unit state parameter Z1 is detected, which characterizes the state of the energy storage unit 52 .

[0120] Furthermore, an actuating element state parameter Z2 is detected which characterizes the state of the actuating element 36 .

[0121] Furthermore, a biasing element state parameter Z3 is detected, which characterizes the state of the biasing element 42 .

[0122] Subsequently, an energy storage unit threshold value S1 assigned to the energy storage unit state parameter Z1 , a state parameter threshold value S2 assigned to the actuating element state parameter Z2 , and a biasing element threshold value S3 assigned to the biasing element state parameter Z3 are obtained from the storage unit 60 .

[0123] Furthermore, by means of the calculation unit 58 the energy storage unit state parameter Z1 is compared with the energy storage unit threshold value S1 , the actuating element state parameter Z2 is compared with the actuating element threshold value S2 , and the biasing element state parameter Z3 is compared with the biasing element threshold value S3 .

[0124] Thus, the energy storage unit threshold value S1 is assigned to the energy storage unit state parameter Z1 , the actuating element threshold value S2 is assigned to the actuating element state parameter Z2 , and the threshold value S3 is assigned to the state parameter S3 .

[0125] The energy storage unit threshold value S1 limits the standard range of the energy storage unit state parameter Z1 , the actuation element threshold value S2 limits the standard range of the actuation element state parameter Z2 , and the biasing element threshold value S3 limits the standard range of the biasing element state parameter Z3 .

[0126] In order to reliably operate the emergency brake unit 26, each of the energy storage unit state parameter Z1, the actuating element state parameter Z2, and the biasing element state parameter Z3 must be within a correspondingly assigned standard range.

[0127] Thus, if one of the energy storage unit state parameter Z1 , the actuating element state parameter Z2 and the biasing element state parameter Z3 is outside the normal range, a blocking signal is triggered by this method. The emergency brake unit 26 cannot then be operated.

[0128] In case one of the energy storage unit state parameter Z1, the actuating element state parameter Z2 and the biasing element state parameter Z3 is within the standard range but also within the associated warning range, the method provides for a warning signal to be issued by the warning unit 66. The warning range is selected within the respectively assigned standard range such that the energy storage unit state parameter Z1, the actuating element state parameter Z2 and / or the biasing element state parameter Z3 lying within the warning range indicates an imminent loss of reliability.

[0129] Additionally, as part of the method, the determined energy storage unit state parameter Z1 , the determined actuation element state parameter Z2 , and the determined biasing element state parameter Z3 are provided to a user of the tool 10 via the user interface 64 .

[0130] The energy storage unit threshold S1 , the actuation element threshold S2 , and the biasing element threshold S3 are also provided to a user of the tool 10 via the user interface 64 .

[0131] As explained previously in conjunction with the monitoring unit 50, the energy storage unit state parameter Z1 characterizing the state of the energy storage unit 52 may be the number of actuation processes of the energy storage unit 52 that have occurred and / or the storage capacity of the energy storage unit 52. The energy storage unit threshold value S1 accordingly describes the maximum permissible number of actuation processes and / or the minimum permissible storage capacity.

[0132] As explained previously in conjunction with the monitoring unit 50, the actuator state parameter Z2 characterizing the state of the actuator element 36 may be the number of actuation processes of the actuator element 36 that have occurred, the position of the actuator element 36, the resistance of the actuator element 36, the actuation delay of the actuator element 36, the voltage drop across the actuator element 36 and / or the actuation force of the actuator element 36. The actuator threshold value S2 accordingly describes the maximum permissible number of actuation processes of the actuator element 36, the target position, the maximum permissible resistance, the maximum permissible actuation delay, the maximum permissible voltage drop and / or the minimum necessary actuation force.

[0133] As also explained previously in connection with the monitoring unit 50, the biasing element state parameter Z3 characterizing the state of the biasing element 42 may be the conductivity of the biasing element 42 and / or the biasing force of the biasing element 42. The biasing element threshold S3 describes the minimum allowed conductivity and / or the minimum allowed biasing force, respectively.

[0134] In the present example, the method is performed as part of a test routine that is run when the tool 10 is switched on. During the test routine, an energy storage unit state parameter Z1 characterizing the state of the energy storage unit 52, an actuating element state parameter characterizing the actuating element 36, and a biasing element state parameter Z3 characterizing the biasing element 42 are detected. The emergency brake unit 26 can only be operated if the energy storage unit state parameter Z1, the actuating element state parameter Z2, and the biasing element state parameter Z3 are all within the respectively assigned standard ranges.

[0135] In the above example, the monitoring unit 50 includes a large number of state sensors. Therefore, a large number of state parameters can be detected. It should be understood that the monitoring unit 50 can also only include a selection including one or more of the above sensors. Therefore, only one or more of the above state parameters can be monitored. Therefore, the method for operating the actuator can also be performed using only a selection of state parameters including one or more state parameters.

[0136] The above explanation relates to a sawing device 10 in the form of a miter saw. However, it should be understood that the design as a miter saw is only one example and the above description also applies to sawing devices of other designs, such as a band saw.

[0137] Reference numerals list

[0138] 10 Tools

[0139] 12 Sawing device

[0140] 14 Base

[0141] 16 Support surface

[0142] 18 Workpiece

[0143] 20 Pivot device

[0144] 20a Part 1

[0145] 20b Part 2

[0146] 22 Saw Blade

[0147] 24 Handle

[0148] 26 Emergency brake unit

[0149] 28 Brake caliper

[0150] 30 Pressure element

[0151] 32 Brake cam

[0152] 34 Actuator

[0153] 36 Actuating element

[0154] 36a First end

[0155] 36b Second end

[0156] 38 Shape memory alloy

[0157] 40 Slide

[0158] 42 Bias element

[0159] 44 Actuating pin

[0160] 46 Lifting Magnet

[0161] 48 Piston

[0162] 50 Monitoring Units

[0163] 52 Electrical energy storage unit

[0164] 54 Electrical switch element

[0165] 55 Trigger control unit

[0166] 56a First state sensor

[0167] 56b Second status sensor

[0168] 56c Third state sensor

[0169] 58 computing units

[0170] 60 storage units

[0171] 62 Communication interface

[0172] 64 User Interface

[0173] 66 Warning Unit

[0174] S1 Energy storage unit threshold

[0175] S2 Actuator Threshold

[0176] S3 Bias Element Threshold

[0177] Z1 Energy storage unit status parameters

[0178] Z2 actuator state parameters

[0179] Z3 Bias element state parameters

[0180] Z4 trigger control unit status parameters

Claims

1. A method for operating an emergency brake unit (26) for a motor-driven tool (10), wherein the emergency brake unit (26) has an actuator (34) and at least one electrical energy storage unit (52), the actuator (34) having an actuating element (36), the at least one electrical energy storage unit (52) being electrically coupled to the actuating element (36) via an electrical switching element (54), so that the actuating element (36) can be selectively supplied with electrical energy stored in the energy storage unit (52) by actuating the switching element (54), the method comprising: - detecting an energy storage unit state parameter (Z1) characterizing the state of the energy storage unit (52) and / or an actuating element state parameter (Z2) characterizing the state of the actuating element (36), - comparing a detected energy storage unit state parameter (Z1) with an energy storage unit threshold value (S1), and / or comparing a detected actuating element state parameter (Z2) with an actuating element threshold value (S2), said energy storage unit threshold value (S1) limiting the standard range assigned to said energy storage unit state parameter (Z1), said actuating element threshold value (S2) limiting the standard range assigned to said actuating element state parameter (Z2), - triggering a blocking signal if at least one of the detected energy storage unit state parameter (Z1) and the detected actuating element state parameter (Z2) is outside a respectively assigned standard range.

2. The method of claim 1, wherein the actuator (34) includes a biasing element (42), and wherein the method comprises: - detecting a biasing element state parameter (Z3) characterizing the state of the biasing element (42), - comparing the bias element state parameter (Z3) with a bias element threshold value (S3), the bias element threshold value (S3) limiting a standard range assigned to the bias element state parameter (Z3), - When the bias element state parameter (Z3) is outside a normal range, a blocking signal is triggered.

3. The method of claim 2, wherein the biasing element state parameter (Z3) describes the conductivity of the biasing element (42) and the biasing element threshold value (S3) describes a minimum allowed conductivity.

4. The method according to any one of the preceding claims, wherein the energy storage unit state parameter (Z1) describes the number of actuation processes of the energy storage unit (52) that have occurred and the energy storage unit threshold value (S1) describes the maximum permissible number of actuation processes, and / or The actuating element state parameter (Z2) describes the number of actuating operations of the actuating element (36) that have occurred, and the actuating element threshold value (S2) describes the maximum permissible number of actuating operations.

5. A method according to any one of the preceding claims, wherein the actuator element state parameter (Z2) describes the position or position difference of the actuator element (36), and the actuator element threshold value (S2) describes the desired position or the desired position difference.

6. The method according to any of the preceding claims, wherein the actuating element state parameter (Z2) describes the resistance of the actuating element (36) and the actuating element threshold value (S2) describes a maximum permissible resistance.

7. The method according to any of the preceding claims, wherein the actuating element state parameter (Z2) describes an actuation delay of the actuating element (36) and the actuating element threshold value (S2) describes a maximum permissible actuation delay.

8. The method according to any of the preceding claims, wherein the actuator element state parameter (Z2) describes the voltage drop across the actuator element (36) and the actuator element threshold value (S2) describes a maximum allowed voltage drop.

9. The method according to any of the preceding claims, wherein the actuating element state parameter (Z2) describes the actuating force of the actuating element (36) and the actuating element threshold value (S2) describes a minimum permissible actuating force, and / or The biasing element state parameter (Z3) describes the biasing force of the biasing element (42), and the biasing element threshold value (S3) describes a minimum allowed biasing force.

10. The method according to any of the preceding claims, wherein the energy storage unit state parameter (S1) describes the storage capacity of the energy storage unit (52) and the energy storage unit threshold value (S1) describes a minimum allowed storage capacity.

11. The method according to any of the preceding claims, wherein at least one of the energy storage unit state parameter (Z1), the actuating element state parameter (Z2) and the biasing element state parameter (Z3) is detected during a test routine.

12. The method according to any of the preceding claims, further comprising providing at least one of the energy storage unit state parameter (Z1), the actuation element state parameter (Z2) and the biasing element state parameter (Z3) to a user.

13. The method according to any one of the preceding claims, further comprising: If at least one of the energy storage unit state parameter (Z1), the actuating element state parameter (Z2) and the biasing element state parameter (Z3) is within a respectively assigned standard range and within an assigned warning range, a warning signal is triggered.

14. A monitoring unit (50) for monitoring the state of an emergency brake unit (26) for a motor-driven tool (10), wherein the emergency brake unit (26) has an actuator (34) and at least one electrical energy storage unit (52), the actuator (34) having an actuating element (36), the at least one electrical energy storage unit (52) being electrically coupled to the actuating element (36) via an electrical switching element (54), so that the actuating element (36) can be selectively supplied with electrical energy stored in the energy storage unit (52) by actuating the switching element (54), the monitoring unit (50) comprising: at least one state sensor (56a, 56b) designed to detect an energy storage unit state parameter (Z1) characterizing the state of the energy storage unit (52) and / or to detect an actuating element state parameter (Z2) characterizing the state of the actuating element (36), a storage unit (60) on which at least one of an energy storage unit threshold value (S1) and an actuating element threshold value (S2) is stored, said energy storage unit threshold value (S1) and said actuating element threshold value (S2) limiting a respectively assigned standard range, a calculation unit (58) designed to compare the energy storage unit state parameter (Z1) detected by means of the state sensor (56a, 56b) with the energy storage unit threshold value (S1) and / or to compare the detected actuating element state parameter (Z2) with the actuating element threshold value (S2), and - a communication interface (62) for triggering a blocking signal.

15. An emergency brake unit (26) for a motor-driven tool (10), comprising a monitoring unit (50) according to claim 14.

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