EP2826599A1 - Control method and hand tool machine - Google Patents

Abstract

The hand tool (1) for setting a nail (2) has a user operable safety mechanism (10) and an actuatable button (11) for triggering a setting of the nail. In a combustion chamber (4), a mixture of combustible gas and air is ignitable. A piston (6) is movably arranged in the combustion chamber to be accelerated by the combustion gases in the setting direction (3). A plunger (7) on the piston is provided for propelling the nail. A compressor (17) for compressing the air in the combustion chamber is directly connected to the combustion chamber via a duct (20). A valve (22, 23) connecting the duct or combustion chamber to the environment is opened between the actuation of the safety mechanism and the actuation of the button.

Description

FIELD OF THE INVENTION

The present invention relates to a hand-held machine tool, such as, for example, from US 2010/108736 A or US 2004/134961 A are known. A combustion chamber with a piston is filled with air and a combustible gas. The gas mixture is ignited, whereupon the combustion gases accelerate the piston. The kinetic energy of the piston is used to drive a nail into a workpiece. A piston compressor compresses the air and feeds it into a reservoir. The combustion chamber is fed from the reservoir. The increased air pressure makes it possible to feed the same amount of air for combustion in a smaller combustion chamber. However, the additional compressor and the energy source required for it lead to increased weight and size of the setting device.

DISCLOSURE OF THE INVENTION

The hand tool according to the invention for setting a nail has a user-operable safety mechanism and an actuatable button for triggering a setting of the nail. In a combustion chamber, a mixture of combustible gas and air is ignitable. A piston is movably disposed in the combustion chamber to be accelerated by the combustion gases in the setting direction. A plunger on the piston is provided for propelling the nail. A compressor for compressing the air in the combustion chamber is directly connected via a channel to the combustion chamber. A valve connecting the duct or combustion chamber to the environment is opened between the actuation of the safety mechanism and the actuation of the button.

The hand tool is provided with a bypass, which dissipates the air conveyed by the compressor into the environment. Due to the open bypass, there is a significant loss of air delivered by the compressor. Overall, the losses amount to over 30%. Nevertheless, this proves to be helpful in making the compressor smaller and more fragile. The compressor, which preferably consists of a rapidly rotating electric motor and a fan, is during the acceleration phase from standstill lower mechanical loads exposed. The compressor is preferably switched on from the actuation of the safety mechanism, previously switched off.

One embodiment provides that the open valve is designed to discharge an air flow of at least 1000 cc per second of the compressor into the environment. The size of the combustion chamber is preferably in the range of 200 cc and 500 cc.

One embodiment provides that the valve is closed after pressing the button.

A control method for a nailing machine hand tool having a combustion chamber, a compressor, a passage connecting the compressor to the combustion chamber, a valve, a safety mechanism, and a user-operable button has the following steps. The compressor is turned on in response to actuation of the safety mechanism. The air supplied by the compressor flows into the compressor connecting to a combustion chamber channel. The channel opens in the combustion chamber. The valve is opened. The valve now connects the duct or combustion chamber to the environment so that at least a portion of the air delivered by the compressor drains into the environment. The valve closes in response to a pushbutton actuation. A combustible gas is introduced into the combustion chamber. The gas mixture is ignited when a pressure of the air in the combustion chamber reaches a predetermined value. The compressor is turned off when a pressure of the air in the combustion chamber reaches the predetermined value.

An embodiment provides that the compressor has an electric motor and a fan. The electric motor is accelerated to a speed of at least 75% of an operating speed with actuation of the safety mechanism. In response to the actuation of the button, the electric motor is accelerated to the operating speed of at least 2,000 revolutions per second.

BRIEF DESCRIPTION OF THE FIGURES

Fig. 1

ein Setzgerät für Nägel

Fig. 2

ein Steuerungsdiagramm für das Setzgerät,

Fig. 3

ein Verlauf der Drehzahl eines Kompressors,

Fig. 4

ein Verlauf der Strom bzw. Leistungsaufnahme eines Elektromotors,

Fig. 5

ein Blockdiagramm einer Motorsteuerung für den Elektromotor

The following description explains the invention with reference to exemplary embodiments and figures. In the figures show:

Fig. 1

a setting tool for nails

Fig. 2

a control diagram for the setting tool,

Fig. 3

a curve of the speed of a compressor,

Fig. 4

a course of the current or power consumption of an electric motor,

Fig. 5

a block diagram of a motor control for the electric motor

Identical or functionally identical elements are indicated by the same reference numerals in the figures, unless stated otherwise.

EMBODIMENTS OF THE INVENTION

Fig.1 1 shows as an example of a hand-held machine tool schematically a combustion-driven setting tool 1 for nails 2. The setting tool 1 presses the nail 2 in setting direction 3 in a workpiece. The energy required for this purpose is provided by burning a gas mixture in a combustion chamber 4 of the setting device 1 . The user can hold and guide the setting tool 1 during operation, ie when setting the nails 2 , by means of a handle 5 . The setting tool 1 is correspondingly compact and lightweight.

The combustion chamber 4 is closed in the setting direction 3 by a piston 6 which is movable parallel to the setting direction 3 . The piston 6 is accelerated by the expanding combustion gases in the setting direction 3 . The piston 6 is provided with a punch 7 , which projects into a barrel 8 . A nail 2 can be inserted into the barrel 8 , individually by hand or automated by a magazine. 9 The moving with the piston 6 stamp 7 presses the nail 2 out of the barrel 8 , into the workpiece.

The user initiates the setting process by actuating a safety button 10 and a release button 11 . A device control 12 fills the combustion chamber 4 with the gas mixture in response to the actuation and ignites the gas mixture by means of a fuze 13 in the combustion chamber 4 .

The gas mixture is composed of a combustible gas and air. The combustible gas preferably contains volatile, short-chain hydrocarbons. The combustible gas is preferably provided by means of a cartridge 14 . The cartridge 14 is arranged in a receptacle in the housing 15 . The cartridge 14 is removable and exchangeable for a full cartridge 14 or the cartridge 14 is refillable. A controllable Metering valve 16 is disposed between the cartridge 14 and the combustion chamber 4 . The device control 12 opens and closes the metering valve 16 and thus meters the amount of combustible gas which is fed into the combustion chamber 4 for a setting process.

The combustion chamber 4 is actively filled with air by a compressor 17 . The air provides the oxygen necessary for combustion. The compressor 17 includes a fan 18 and a brushless electric motor 19 . The fan 18 is designed as a radial fan, which sucks the air along its axis and blows out in the radial direction. The fan 18 promotes one revolution less than 5 cc, for example between 0.5 cc (cubic centimeters) and 2 cc. The operating speed is greater than 2,000 (two thousand) revolutions per second (120,000 rpm) to achieve an air flow between 2,000 cc and 10,000 cc per second.

The compressor 17 feeds the combustion chamber 4 directly. Between the compressor 17 and the combustion chamber 4 no buffer is arranged, which would be charged by the compressor 17 , and from which, if necessary, the combustion chamber 4 would be filled. A continuous channel 20 starts at the compressor 17 and ends at the combustion chamber 4 . The channel 20 opens into an inlet valve 21 of the combustion chamber. 4 The inlet valve 21 is controlled by the device controller 12 . The channel 20 has a bypass valve 22 in the illustrated embodiment. The air flow generated by the compressor 17 can flow through the opened bypass valve 22 into the housing 15 , ie, into the environment. The device controller 12 may close the bypass valve 22 , whereupon the air flow completely flows into the combustion chamber 4 . Alternatively or additionally, a bypass valve 23 may be provided in the combustion chamber 4 . The air flow flows into the combustion chamber 4 , and can escape through the open bypass valve 23 . The bypass valve 22 , 23 , possibly including further lines, is designed to open an air flow of at least 1000 cc per second into the environment.

The electric motor 19 of the compressor 17 is fed from a battery 24 . The battery 24 preferably contains battery cells based on a lithium-ion technology. The battery 24 may be permanently disposed in the housing 15 adjacent the combustion chamber 4 and the compressor 17 , alternatively, the battery 24 may be detachably attached to the housing 15 .

The setting process is explained with reference to the control scheme in Fig. 2 and the time course in Figure 3 explained. The setting device 1 is initially T01 in an idle state S01 . The combustion chamber 4 is vented, in the combustion chamber 4 is essentially only air under ambient pressure. The compressor 17 is turned off and does not deliver air. The piston 6 is preferably in its the combustion chamber 4 minimizing the starting position.

The user presses the barrel 8 against the workpiece. The exemplary barrel 8 is displaceable against a spring 25 in the housing 15 . The safety button 10 is actuated T02 . The device controller 12 continuously checks S02 whether the safety button 10 is kept pressed. If the user releases the safety button 10 by the setting tool 1 is no longer pressed against the workpiece, the device control 12 interrupts the setting process and transfers the setting device 1 in its idle state S01 .

In response to the actuation of the safety button 10 , the compressor 17 is turned on S03 . The speed 26 of the electric motor 19 is accelerated from initially zero to an intermediate value 27 . The intermediate value 27 is for example over 2 500 revolutions per second. The intermediate value 27 is preferably between 50% and 90% of the operating speed 28 . The device control 12 opens S04, the bypass valve 22, 23 is preferably at the beginning or during the acceleration to the intermediate value 27th The inlet valve 21 of the combustion chamber 4 can be opened. If the bypass valve 23 is disposed in the combustion chamber 4 , the intake valve 21 is opened with the bypass valve 23 . After reaching T03 of the intermediate value 27, the electric motor 19 keeps the rotational speed 26 at S05. The bypass valves 22, 23 remain fully open. The apparatus controller 12 waits S06 for the operation of the release button 11. If the release button 11 does not turn on within a predetermined period after the operation of the safety button 10 , the compressor 17 is turned off. The setting device 1 returns to the idle state S01.

The user presses the release button 11 (T04) after the safety button 10 . The device controller 12 checks S07 whether the safety button 10 is still operated, otherwise the setting process is aborted. In response to the actuated safety button 10 , the compressor 17 accelerates S08 to its operating speed 28. The operating speed 28 is greater than 2,000 revolutions per second (180,000 rpm). The capacity of the compressor 17 reaches a value of 3 liters per second to 10 liters per second.

The bypass valve 22 is closed in response to the actuation of the trigger button 11 S09. The closing S09 preferably takes place with the start T04 of the acceleration, can also during the acceleration or when T05 reaches the Operating speed 28 . The air flow now flows completely into the combustion chamber 4 . The combustion chamber 4 is not hermetically sealed, but allows a drain between 0.3 and 0.8 liters per second. For example, the bypass valve 23 may remain open or only partially closed. The tiny radial fan can only build up a small static pressure difference. The operation permanently requires a high air flow, even if the target pressure has already been reached substantially. The pressure in the combustion chamber 4 increases due to the higher inflow than outflow to a target value between 1.3 and 3.5. The set value (compression) is indicated unitarily as the pressure ratio of the air in the combustion chamber 4 to the surroundings. The compression is specified by the device controller 12 . The device controller 12 determines the compression based on the ambient temperature and the ambient pressure. The device controller 12 determines S10 a duration (time T06 ) which the compressor 17 needs to reach the compression in the combustion chamber 4 . Until then, the compressor 17 is operated at the operating speed 28 S11 .

After the bypass valves 22, 23 are closed, the combustible gas is injected into the combustion chamber 4 S12 . The amount of combustible gas determines the implement controller 12 based on the ambient temperature and the ambient pressure. The amount of combustible gas and the amount of air are matched to achieve a desired set energy. The timing of the injection of the combustible gas is tuned to the use of the type of the bypass valve 22 , 23 . In the bypass valve 23 behind the combustion chamber 4, it proves to be advantageous to inject the combustible gas into the combustion chamber 4 only shortly before reaching the compression. For example, the pressure in the combustion chamber 4 should already have reached more than 75% of the target pressure. In the bypass valve in front of the combustion chamber 4, it proves to be advantageous to feed the combustible gas early, when substantially no pressure is built up in the combustion chamber 4 . The combustion chamber 4 is not designed pressure-tight. Airflow from the combustion chamber 4 is desirable because the high speed compressor 17 requires a permanent airflow. However, it should not be rinsed with the precious fuel gas. However, the combustible gas should be fed before reaching the compression. With closing of the inlet valve 21 , the pressure drops rapidly, for example at least 0.1 bar per 100 ms (milliseconds).

As soon as the device controller 12 determines S13 that the duration has elapsed T06, ie, the target pressure has been reached, the inlet valve 21 is closed S14 and the compressor 17 is switched off S15. Alternatively or additionally, a pressure sensor 29 may be provided in the combustion chamber 4 , which determines the achievement of the compression.

Once the inlet valve 21 is closed T06, the combustible gas is ignited S16. The device controller 12 transmits a corresponding control signal to the detonator 13. The duration T04-T06 between the actuation of the trigger button 11 by the user and the ignition S15 is in the range of 50 ms to 150 ms. Duration T04-T06 is short in terms of safety requirements. The user should not be able to lift the setting tool 1 from the workpiece during this time. The piston 6 is accelerated as described and drives the nail 2 in the workpiece. The cooling of the combustion gases leads to a negative pressure in the combustion chamber 4, which retracts the piston 6 in its initial position. The inlet valve 21 is closed, as is the bypass valve 23.

The compressor 17 and the battery 24 for the supply of the compressor 17 are additional components that contribute with their weight to the total weight of the setting tool 1 . However, the compression of the air makes it possible to make the combustion chamber 4 smaller because the same amount of oxygen is introduced in the smaller volume. The volume and weight of the combustion chamber 4 can be reduced. The effective weight reduction is probably only for a compression ratio between 1.3 and 3.5 feasible. The weight change of the combustion chamber 4 for a compression ratio of less than 1.3 does not yet weigh the additional components. Although a compression ratio of more than 3.5 allows a very light combustion chamber 4, but the advantage is offset by the weight of the compressor or problems with the fatigue strength of the compressor. With a compression between 1.3 and 3.5, a reduction in the total weight can be achieved when the compressor 17 is designed with a high speed 26 and a small radial fan. The speed 26 should be over 2,000 revolutions per second. If compression [K] greater than 1.3 is required, an increase in speed [D] 26 of at least 67 revolutions per second is required for each percentage point of compression: D = 6,700 (K-1).

The electric motor 19 is powered by a battery pack 24 . The high acceleration values of the electric motor 19 lead to high peak currents, which in particular significantly burden conventional battery cells based on lithium-ion technology. The electric motor 19 is therefore provided with a motor control 30 , which achieves the high acceleration under moderate load of the battery pack 24 . The motor controller 30 regulates the line receptacle 31 of the electric motor 19 during the acceleration phase to a target power 32 from. The peculiarity of the regulated power consumption is that initially a high current 33 in the still dormant Electric motor 19 is fed and the current 33 is reduced with increasing speed of the electric motor 19 . With the speed 26 increases above the electric motor 19 falling voltage 34, which multiplied by the current 33 defines the power consumption 31 .

The motor controller 30 preferably regulates the speed 26 of the electric motor 19 to a desired value 35. The desired value 35 may be the intermediate value 27 or the operating speed 28 , depending on the phase of setting. The exemplary motor controller 30 is shown in the block diagram of FIG Fig. 5 shown. The electric motor 19 is provided with a sensor 36 for determining the current actual rotational speed 26 . The sensor 36 may include, for example, a Hall sensor or determine the speed based on the periodically varied induced voltage in the motor coils. Other sensors commonly used with brushless motors can also be used. A comparator 37 compares the target speed 35 with the actual speed 26 and outputs a corresponding actuating signal 38 . The control signal 38 is a measure of the current which is to be fed into the electric motor 19 . A limiter 39 compares the control signal 38 with a permissible limit value and reduces the control signal 38 to the limit value when the limit value is exceeded. The limited actuating signal 40 is fed to a control loop 41 , which adjusts the current 33 in the electric motor 19 with a comparator 42 to the limited actuating signal 40 . The control loop 41 can, for example, change the voltage 34 applied to the electric motor 19 , a pulse width ratio etc. for controlling the current 33 .

The speed control of the motor control 30 is supplemented by a feedback of the actual speed 26 in the limiter 39 to the power control during acceleration. During the acceleration of the electric motor 19 , the still large deviation of the actual rotational speed 26 leads from the desired rotational speed 35, in addition to the fact that the limiter 39 limits the actuating signal 38 to the limit value. The limiter 39 adjusts the limit [G] in inverse proportion to the actual speed [D] 26 : G = a / D. The threshold is initially high at low actual speed 26 , thereby requiring a correspondingly high current from the control signal 38 33 is impressed in the electric motor 19 . The highest current 33 results when accelerating out of the rest. A proportionality factor [a] is preferably chosen such that when accelerating out of rest, the maximum allowable power of the battery 24 is retrieved. The proportionality factor can be fixed. Preferably, the proportionality factor is determined as a function of the state of charge of the battery 24 . The proportionality factor is reduced with decreasing state of charge. Furthermore, the proportionality factor can be reduced with decreasing ambient temperature. With increasing actual speed 26 , the limit decreases and also the current flowing in the electric motor 19 current 33th If the Electric motor 19 has reached the target speed 35 , the control signal 38 is low and no longer affected by the limit. The power control is no longer active.

The engine control 30 can equally be used for a motor 43 , which returns the piston 6 in the combustion chamber 4 against the setting direction 3 in the basic position. The motor 43 may be connected via a gear 44 to the piston 6 . The gear 44 preferably has a freewheel which decouples the motor 43 when the piston 6 moves in the setting direction 3.

The setting tool 1 has a temperature sensor 45 to determine the temperature of the environment. The device controller 12 determines, based on the temperature, the amount of combustible gas and the amount of air to set the nail 2 with the desired set energy. The support table contains for different temperatures and for different set energies the associated amounts of combustible gas and air or pressure in the combustion chamber 4. The compression of the air is reduced with decreasing temperature, also the amount of combustible gas in the combustion chamber 4 is reduced.

The setting device 1 may have an adjusting element 46 , which allows the user to set the setting energy. A variation of the set energy is advantageous, for example, to optimize the setting in different ground or to allow the setting of a nail 2 with a soft silicone washer. The device controller 12 detects the set set energy and determined by means of tables, the necessary amount of combustible gas and to be reached in the combustion chamber 4 pressure. The latter sets the amount of oxygen in the combustion chamber 4 . The individual values can be determined in advance by test series and stored in a table. The engine controller 30 preferably adjusts the operating speed 28 in response to the pressure to be achieved, and at reduced pressure, a lower speed 26 is sufficient.

Claims (7)

Hand tool (1) for setting a nail (2) with: a user operable safety mechanism (10) and an actuatable button (11) for triggering setting of the nail (2); a combustion chamber (4) in which a mixture of combustible gas and air is ignitable; a piston (6) which is arranged in the combustion chamber (4) of combustion gases in the setting direction (3) movable; a punch (7) disposed on the piston (6) for propelling the nail (2); a compressor (17) for compressing the air in the combustion chamber (4), a passage (20) connecting the compressor (17) to the combustion chamber (4), characterized by a valve (22, 23) connecting the channel (20) or the combustion chamber (4) to the atmosphere, the valve (22, 23) being opened between the actuation of the safety mechanism (10) and the actuation of the button (11) is. Powered hand tool (1) according to claim 1, characterized in that the compressor (17) is switched on from the actuation of the safety mechanism (10). Powered hand tool (1) according to claim 1 or 2, characterized in that the valve (22, 23) is designed to discharge an air flow of at least 1000 cc per second of the compressor (17) into the environment. Powered hand tool (1) according to one of the preceding claims, characterized in that the valve (22, 23) after actuation of the button (11) is closed. Powered hand tool (1) according to one of the preceding claims, characterized in that the compressor (17) has an electric motor (19) and a fan wheel (18). Control method for a hand tool (1) for setting nails, comprising a combustion chamber (4), a compressor (17), a passage (20) connecting the compressor (17) to the combustion chamber (4), a valve, a safety mechanism (10) and a user-operable button (11), comprising the following steps: Energizing the compressor (17) in response to actuation of the safety mechanism (10), wherein air conveyed by the compressor (17) flows into the compressor (17) with a passage (20) connecting a combustion chamber (4), Opening the valve (22, 23) which connects open the channel (20) or the combustion chamber (4) with the environment so that at least a part of the air supplied by the compressor (17) flows into the environment, Closing the valve (22, 23) in response to an actuation of the button (11), Feeding a combustible gas into the combustion chamber (4), Igniting the gas mixture when a pressure of the air in the combustion chamber (4) reaches a predetermined value, and Turning off the compressor (17) when the pressure of the air in the combustion chamber (4) reaches the predetermined value. A control method according to claim 6, characterized in that the compressor (17) comprises an electric motor (19) and a fan wheel (18), the electric motor (19) operating at a speed (26) of at least 75% of an operating speed (28) the safety mechanism is accelerated and in response to actuation of the button (11) to the operating speed (28) of at least 2,000 revolutions per second is accelerated.

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