Patent Application
20220097152
This application claims priority of European patent application no. 20 198 401.0, filed Sep. 25, 2020, the entire content of which is incorporated herein by reference.
The disclosure relates to a handheld work apparatus and a method for operating a handheld work apparatus.
Cutoff machines having a drive motor and having a tool are known, wherein the tool is driven via a belt drive. Cutoff machines of this type are complex work apparatuses which are subject to regular maintenance intervals. The work apparatus can be put into a service state, in which service routines are carried out. Here, the exchange of information between the work apparatus and the operator is also necessary.
It is an object of disclosure to provide a handheld work apparatus wherein transmission of information between operator and work apparatus in a straightforward manner is made possible.
The aforementioned object can, for example, be achieved by a handheld work apparatus including: a tool; a drive motor configured to drive the tool; a mechanical braking device for the tool; an actuating lever; the braking device being configured to be adjusted between a braked position and a released position by an operator via the actuating lever; an electromagnet; an armature configured to cooperate with the electromagnet; the electromagnet being configured to hold the braking device in the released position; and, a control device configured to ascertain a position of the armature with respect to the electromagnet so as to determine a position of the braking device.
A work apparatus according to the disclosure includes a drive motor, wherein the drive motor drives at least one tool. The work apparatus has a mechanical braking device for the tool, wherein the braking device can be adjusted between a braked position and a released position by the operator via an operating element. The work apparatus includes an electromagnet and an armature cooperating with the electromagnet. The electromagnet is configured to hold the braking device in its released position. The work apparatus has at least one control device, wherein the at least one control device is configured to ascertain the position of the armature with respect to the electromagnet to determine the position of the braking device. In the released position of the braking device, the drive motor can drive the tool. In the braked position, the drive of the tool via the drive motor is prevented by the braking device.
If the operator actuates the operating element, the armature is moved relative to the electromagnet, wherein the control device detects the position of the armature, in particular in the released position and the braked position of the braking device.
By using specific operating patterns, the operator can thus transmit information to the work apparatus, wherein the control device determines the position of the armature, analyzes the operating pattern and processes the transmitted information. Thus, for example, a service state can be acknowledged without having to provide additional sensors or user interfaces on the work apparatus.
Provision can advantageously be made for the mechanical braking device to include a brake band, wherein the brake band acts on a clutch drum driving the tool. The clutch drum is part of a centrifugal clutch.
Preferably, the operating element mechanically actuates a lever, wherein in particular the armature is arranged on the lever. Advantageously, a spring unit acts on the lever in such a way that the armature is tensioned via a tensile force in the direction away from a yoke of the electromagnet. When the operating element is actuated, the armature is guided onto the electromagnet via the lever, counter to the tensile force. If the operator releases the lever with the electromagnet inactive, the lever will pull the armature away from the electromagnet via the tensile force of the spring unit. The electromagnet is in particular configured in such a way that when the electromagnet is energized in the released position of the braking device, the armature is held on the yoke of the electromagnet, counter to the tensile force. If the electromagnet is not energized, the armature is drawn away from the electromagnet via the lever via the tensile force, by which means the braking device brakes the clutch drum and therefore also the tool.
Provision is advantageously made for the position of the armature with respect to the electromagnet to be determined by a test voltage being applied to the electromagnet and the resultant current flow being ascertained. Depending on the position of the armature with respect to the electromagnet, the inductance of the coil of the electromagnet also changes. If the armature is resting on the electromagnet, the inductance is higher than when the yoke of the electromagnet is open. As the inductance increases, the current intensity measured on the coil of the electromagnet reacts to the voltage signal with an increased delay. Conclusions about the position of the armature can be drawn by the control device on the basis of the measured current intensities.
The test voltage is in particular configured in such a way that the magnetic force of the electromagnet which results from the test voltage is lower than the tensile force acting on the armature. Accordingly, the test voltage is sufficiently low that when the test voltage is applied the armature cannot be held on the electromagnet. As a result, the test voltage has no influence on the position of the braking device. The test voltage can preferably correspond to individual voltage pulses. As a result, simple evaluation of the current intensity is possible.
Provision can preferably be made for the position of the armature with respect to the electromagnet to be ascertained by a signal from an additional sensor or an electronic switch being evaluated.
It is a further object of the disclosure to provide a method for operating a handheld work apparatus which permits transmission of information between operator and work apparatus in a straightforward manner.
The aforementioned further object can, for example, be achieved by a method for operating a handheld work apparatus, wherein the work apparatus includes a tool, a drive motor configured to drive the tool, a mechanical braking device for the tool, wherein the braking device is configured to be adjusted between a braked position and a released position by an operator via an actuating lever, the work apparatus further includes a control device and an electromagnet configured to hold the braking device in the released position. The method includes: repeatedly ascertaining whether the braking device is in the braked position or in the released position through a position of the armature with respect to the electromagnet over a period of time.
According to a method according to the disclosure, the control device ascertains the position of the braking device through the position of the armature with respect to the electromagnet repeatedly over a predetermined time period. As a result, it is possible to detect specific operating patterns, which are used for the transmission of information.
Provision can preferably be made for the control device to apply test voltage pulses and to ascertain the resultant current flow on the electromagnet. The current flow or the current intensity varies as a function of the position of the armature relative to the electromagnet because of the variable induction. The current flow through the electromagnet rises over a certain time period, in a manner braked by the inductance. If the inductance is increased, for example by the armature resting on the electromagnet, the rise of the current flow is slowed, as a result of which the maximum current value over the corresponding time period is likewise reduced. As the inductance becomes lower, for example as a result of a remote position of the armature, the rise in the current flow takes place more quickly, and therefore the maximum current value over the corresponding time period increases.
Preferably, to ascertain the position of the braking device, the control device compares the current flow with reference values. Preferably, the control device can ascertain the reference values in the braked position of the braking device. In the braked position of the braking device, the distance between the armature and the yoke of the electromagnet is at a maximum, as a result of which the inductance is at a minimum. When setting up the reference value in the braked position, the current flow reaches a global maximum current value because of the reduced inductance. The subsequently measured current intensities are compared with the reference values, by which means the position of the armature and therefore the position of the braking device are determined.
Provision is advantageously made for the control device to ascertain a pattern of the actuation of the operating element. Via such patterns, a multiplicity of items of information can be transmitted. Preferably, the control device compares the detected pattern of the actuation of the operating element with a stored pattern. Depending on the stored pattern, further method steps which influence the state or the further operation of the work apparatus can be initiated. The control device in particular changes the state of at least one component of the work apparatus when the detected pattern matches the stored pattern.
A pattern can, for example, consist of multiple attempts of the operator to attempt to move the braking device into the braked position in a predefined time period.
The invention will now be described with reference to the drawings wherein:
The cutoff machine 1 has an outrigger 7 which, in the embodiment, is fixed to the housing 2. At the free end of the outrigger 7, a cutting disk 8 is supported such that it can rotate about a rotational axis 58. The cutting disk 8 is the tool of the cutoff machine 1 and is driven by the drive motor 10 via a belt drive. Another drive of the cutting disk 8 may also be advantageous. The belt drive is implemented as a two-stage belt drive in the embodiment and includes a first drive belt 12 and a second drive belt 13. To tension the drive belts 12 and 13, tension rollers 14 are provided, one of which is shown in
The cutting disk 8 is covered over part of its circumference by a protective hood 9. During operation, when the cutting disk 8 is used for cutting rock, a large quantity of dust arises. In order to bind the dust and to cool the cutting disk 8, a liquid supply, in particular a water supply, can be provided. The liquid supply includes a liquid connector 100 to be connected to an external liquid feed. The liquid connector 100 is connected via a liquid line 101 to at least one feed valve 106, in particular a feed nozzle, on the protective hood 9. To control the quantity of liquid supplied, a valve 102, which is electrically controlled, is provided. The quantity of liquid to be supplied which is desired by the operator can be set via an operating panel 107 (
A control device 103 for the valve 102, which activates the valve 102 appropriately, is provided. In the embodiment, the control device 103 is arranged on the underside of the housing 2. In the embodiment, the control device 103 is not arranged in the housing 2 but outside the housing 2 and is covered at the bottom by a separate cover 104. The control device 103 is advantageously potted, so that via the potting and the cover 104, the result is dual protection against contaminants or liquid.
The cover 104 is fixed to the housing 2, advantageously via snap-in connections and/or screw connections. The control device 103 is advantageously located at a distance in the cover 104. A defined distance between the control device 103 and the cover 104 can be achieved, for example, via ribs between the control device 103 and the cover 104. In a preferred configuration, the cover 104 has at least one outlet opening on its underside, which is arranged on the bottom thereof in normal operation, so that moisture or dirt can escape from the cover 104. It may be advantageous to support the control device 103 with respect to the cover 104 via at least one damping element.
To control the drive motor 10, an additional control device 105 is advantageously provided, which is configured separately from the control device 103 and in particular is arranged in the upper region of the housing 2 on the drive motor 10 itself. Another arrangement of the additional control device 105 or the arrangement of a further control device for activating the drive motor 10 may also be advantageous. The control of the electromagnet 33 (
The cutoff machine 1 has a braking device 15. To trigger the braking device 15, a rate of rotation sensor is advantageously provided. In the embodiment, provision is made for the rate of rotation sensor likewise to be arranged in the control device 103. The rate of rotation sensor is advantageously aimed at the rotational axis 58 of the cutting disk 8. An axis of measurement of the rate of rotation sensor is preferably located parallel to the rotational axis 58.
The outrigger 7 has a longitudinal direction 37 which, in the embodiment, forms the straight connecting line between the drive axis and the output axis of the belt drive in a side view in the direction of the drive axis. In the embodiment, the drive axis coincides with a rotational axis 25 of a crankshaft 24 (
As
The arrangement of the actuating lever 16 is also shown in
The braking device 15 advantageously has a toggle lever arrangement 31, which acts on the brake band 17. When the pivoting lever 28 is pivoted out of the released position 40, shown in
To actuate the braking device 15, the electromagnet 33 is switched off. As a result, the armature 36 is released from the electromagnet 33, and the pivoting lever 28 pivots into the braked position 41 shown in
If the electromagnet 33 is switched off, then the trigger spring 32 displaces the lever 44. In the process, the pivot axis 46 moves further away from the toggle lever plane 49. The toggle lever joint toggles, and the trigger spring 32 is able to pivot the lever 44, as a result of which the brake band 17 is tensioned. In the braked position 41 of the braking device 15, the pivot axis 46 and the hook-in point of the trigger spring 32 on the lever 44 are also located on opposite sides of the toggle lever plane 49. In the embodiment, irrespective of the position of the braking device 15, the pivot axis 46 is always located on one side, below the toggle lever plane 49 in the illustration in
The output disk 27 of the belt drive is also shown in
To displace the braking device 15 from the braked position 41 of the pivoting lever 28, shown in
As shown in
As
The control device 103 is configured in such a way that it is able to ascertain the position of the armature 36 with respect to the electromagnet 33 to determine the position of the braking device 15.
Provision can advantageously be made for the additional control device 105 to be configured in such a way that it is able to ascertain the position of the armature 36 with respect to the electromagnet 33 to determine the position of the braking device 15.
In addition, the control device 103 is advantageously configured in such a way that transmission of information between the operator and the work apparatus in a straightforward manner is possible. Such a transmission of information is important in particular when the work apparatus is in a service state. In such a state, the operator can, for example, be requested to replace or to service certain components. The operator must then confirm the procedure carried out.
In the embodiment, the operator can input operating patterns 50 via the actuating lever 16. For this purpose, the control device 103 detects the position of the armature 36 with respect to the electromagnet 33. As already explained above, the armature 36 is mechanically coupled with the pivoting lever 28. Ascertaining the position of the armature 36 is described in more detail below with reference to the flowchart shown in
After the work apparatus has been started up, the control device 103, 105 checks whether the service state has been activated. The service state can be triggered, for example, depending on a minimum number of operating hours, on ventilation processes of the braking device 15 or the like since a previous maintenance interval. If the service state is deactivated, the normal operation of the work apparatus 1 continues. If the service state has been activated, the determination of the position of the armature 36 and therefore also the determination of the position of the braking device 15 are carried out.
In order to be able to determine the position of the armature 36 with respect to the electromagnet 33, the control device carries out current intensity measurements on the coil of the electromagnet 33, wherein the current intensity is different as a result of the induction changing as a function of the position of the armature 36. The inductance causes a braking action on the current flow through the electromagnet 33. If the inductance is high, the current values rise only slowly because of the braking action on the current flow. If the inductance is low, the current values rise correspondingly quickly.
As shown in
Once the control device 103 has ascertained the reference values, further current curves 71′ as a response to the voltage pulses 70 are measured. If, in the service state, the actuating lever 16 is actuated by the operator, the braking device 15 is in the released position 40. In this released position 40, the distance between the armature 36 and the yoke 34 of the electromagnet 33 is at a minimum. The armature 36 preferably lies directly on the yoke 34. Consequently, the induction is at a maximum, as a result of which the current flow is braked and only low current values are produced within the voltage pulse 70. Such current values in the released position 40 of the braking device 15 preferably lie at around 35 mA. The control device 103, 105 compares the ascertained current values with the previously determined reference values and detects whether the distance between the armature 36 and the electromagnet 33 is large or small or whether the braking device 15 is in the fixed position 41 or in the released position 40.
Of course, the control device 103, 105 provides appropriate tolerances during the determination of the position of the armature 36. Thus, a released position 40 of the braking device 15 is assumed even if there is a deviation of the current curve 71 of less than 20%, in particular of less than 10%, as compared with the expected reference value.
Stored in the control device 103, 105 are operating patterns 50, which take into account a dependence of time period and number of switching operations of the braking device 15 with the operating lever 16 from the braked position 41 into the released position 40 and back again. Depending on the operating pattern 50, a corresponding item of information can be transmitted from the operator to the work apparatus 1. The control device 103, 105 compares the previously stored operating pattern 50 with the operating patterns 50 carried out by the operator and measured by the control device 103. Depending on the operating pattern 50 detected, a procedure is triggered which, for example, acts on the state of a component of the work apparatus 1 and changes the latter. The service state is finally ended. The work apparatus 1 is again in the operating state.
In an alternative embodiment of the work apparatus 1, it may be expedient to provide an additional positioning unit 72 which determines the position of the armature 36. Such a positioning unit 72 is illustrated schematically in
It is understood that the foregoing description is that of the preferred embodiments of the invention and that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20 198 401.0 | Sep 2020 | EP | regional |
