Electric switch for speed control of motors.

The invention relates to an electrical switch for speed regulation of motors, particularly electric motors on electric hand tools according to the preamble of claim 1.

An electric hand tools, such as drills, screwdrivers, etc.., Switches are frequently arranged, allow an adjustment of the rotational speed between zero and a maximum speed. For this purpose, the actuator can be adjusted to different extents, with the respective position of the actuator is appropriate speed on the electric motor set and kept largely constant by means of an electronic circuit. Such a switch is shown in the DE-OS 41 21 264th

In some cases, such as the drilling or screwdriver operation, it is desirable that the rotational speed only up to a preselected largest speed is adjustable, but the one hand, smaller or equal to the maximum speed of the electric hand tool and on the other hand, larger or equal to one of the switch interpretation dependent minimum speed of the electric hand tool is. For this purpose these have switch means for presetting a maximum speed, which limit the displacement path of the actuating member at a distance which is smaller or equal to the maximum possible adjustment. In most cases, such switches have an additional mechanical locking device with which the actuator can be found in about the corresponding one of said preselected greatest speed position. Then, the user needs the actuating member of the switch in the continuous operation of the electric hand tool not hold. Such a locking device is known from DE-OS 24 10 871st

For example, the user can when drilling the greatest speed which is adapted to the material being drilled, first preset on the switch. can then gently drilled and the drill speed can be increased up to this preselected greatest speed by movement of the actuator. In the position of the preselected greatest speed the actuator can then be locked so that the user no longer has to hold longer the actuator during further drilling.

Common power tools can be operated in two opposite directions of rotation, ie they have a right and left rotation. For example, can be in screwdriver operation then screws in a material both single and unscrew. To switch between the forward and reverse rotation, an additional switch is located on the switch, which is preferably operated by a disposed near the actuator operating lever.

With electric hand tools generally called universal motors are used. These universal motors, the brushes that feed the armature current via the collector, adjusted with a certain angle from the neutral position to achieve an increase of the torque and thus the power in a clockwise direction. If such an electric motor, however, operated in reverse, so this brush position is extremely unfavorable and can lead to the so-called brush sparking, which can lead to the destruction of the brushes and the collector and hence to premature failure of the entire engine at full power. However, because the CW is generally operating at an electric hand tool, you do not want to renounce the agreement reached by adjustment of the brushes increase performance in general.

To avoid the unfavorable sparking it is known per se, not to operate the electric motor in reverse at full power, but there to reduce power consumption to a harmless size. This is achieved with a device for limiting the speed in reverse, with the help of the largest adjustable speed in reverse is limited so that it is smaller than the maximum speed in a clockwise direction. Such a device for limiting the speed in reverse is shown in the DE-OS 33 42 412 and consists of an effective counter-clockwise rotation stop on the actuating member, which means the stop the magnitude of the adjustment of the actuator in the counterclockwise rotation is correspondingly reduced. In general, the size of the adjustment is chosen such that the clockwise rotation limitation is present half the maximum speed of the right barrel to about.

As is apparent from the DE-OS 24 10 871, the locking device has a user-operable spring-loaded bolt which can engage in a recess on the device for presetting a maximum speed when the actuating member in the this maximum speed is brought appropriate position. When actuated locking the bolt then the actuator stops in this position. It has been shown that in the event that the pre-selected at the device to preset a maximum speed speed is less than the maximum speed, the reverse operation with speed limitation in the actuated locking an indissoluble entanglement may occur. In such a case, then neither a lock nor a solution of the off of the switch is possible, which the switch will eventually unusable. It is also immediately evident that then they are caused considerable risk of accidents from not disconnectable by the switch electric hand tool.

Starting from this prior art, the invention aims to improve the electrical switch for speed regulation of motors so that an indissoluble entanglement of locking in an anticlockwise direction with speed limitation can no longer occur.

This object is achieved in a generic electrical switch by the characterizing features of claim 1.

Further embodiments of the invention are subject of the subclaims.

It has been found that the associated with conventional switches in an anticlockwise direction in certain positions of the actuator and actuated locking unsolvable entanglements are due to the fact that due to the effective stroke in the actuator, which is located in the device for limiting the speed in reverse, the game deleted between the bolt of the locking device and the notch on the device for presetting a maximum speed or at least is so small that the bolt can no longer be released from the recess. The invention is assuming based on the idea that the locking of the actuator is prevented in an anticlockwise direction. Thus, the advantages achieved with the invention in particular that due to the achieved prevention of entanglements of the locking device in an anticlockwise direction with speed limitation otherwise possible becomes useless the switch can no longer occur and the associated risks of accidents are effectively banned.

Conventional switches for speed control with a clockwise rotation effective, available on the actuator stop for speed limitation tend to tilt the actuator for concern at this attack, bringing an unwanted fluctuation of speed associated. This tilting is greatly reduced when inventive switch. Next also tolerances in the assembly of the switch for the right-left run and the actuating lever to act in a conventional switch to the speed limit. Such tolerances are largely eliminated in the invention.

As in another embodiment of the invention, only one additional part is used over traditional switches, which is also simple in design, it is a cost-effective solution. This additional part is designed such that it is in the Backoff speed-limiting position of the actuator is supported on a surface of the switch housing so that even large exerted by the user on the actuator forces can not lead to premature deterioration of this part.

An embodiment of the invention is shown in the drawings and will be described in more detail below. Show it <dl id="dl0001"><dt>Fig. 1</dt><dd>a schematic representation of a switch of the invention in perspective and partly cut view, the switch for the right-left run for clarity is omitted,</dd><dt>FIG. 2</dt><dd>the switch also partially cut with slide switch for the right-left run in side view according to the direction A in Fig. 1,</dd><dt>Fig. 3</dt><dd>a plan view of the switch in the anti-clockwise position corresponding to the direction B in Fig. 1,</dd><dt>Fig. 4</dt><dd>a plan view of the switch shown in Fig. 3, but in clockwise rotation position,</dd><dt>Fig. 5</dt><dd>a section of the locking device in side view,</dd><dt>Fig. 6</dt><dd>a section along the line 6-6 of Fig. 5 in not locked position</dd><dt>Fig. 7</dt><dd>a section as in Fig. 6, but in locked position,</dd><dt>Fig. 8</dt><dd>a plan view of the present in the device for preventing locking in reverse lever in an enlarged representation,</dd><dt>Fig. 9</dt><dd>the present in the anti-clockwise position switch in side view according to the direction A of FIG. 1 and partially cut, wherein the means for setting a maximum speed to maximum speed is set,</dd><dt>Fig. 10</dt><dd>a plan view according to the direction B of Fig. 1 to the switch in the position of FIG. 9,</dd><dt>Fig. 11</dt><dd>an enlarged side view of the locking device in the position of the switch according to Fig. 9 and</dd><dt>Fig. 12 to 14</dt><dd>located in the anti-clockwise rotation position switches in the Figs. 9 to 11 corresponding views, wherein the means for presetting a maximum speed is set to a minimum speed.</dd></dl>

It is the invisible levers of the device for preventing locking in left rotation shown in Figs. 3, 4, 10 and 13 to be in solid lines for reasons of clarity.

An electrical switch 1 for speed control of electric motors, which is used particularly in electric hand tools with right and left rotation, such as drills, rotary hammers, u. Like., Is shown in Fig. 1 schematically. The switch 1 has a switch housing 2, in which a printed circuit board 3 is disposed. On the circuit board 3 are the electrical and electronic components 4 a circuit arrangement for controlling the speed of the electric motor. In this circuit, there may be a known phase angle control, as described for example in DE-OS 29 14 496th

The illustrated in Fig. 1 switch 1 has further designed as a handle 5 actuating member which is mounted adjustably on the switch housing 2, and secured thereto, into the interior of the switch 1 leading actuating plunger 6. The handle 5 can be performed manually in the direction of arrow 7 'be moved against a compression spring, not shown, so that it returns to release back into the starting position according to the arrow. 7

In switch 1 there is a contact rocker 8, which helps to operate the trigger 5, an electrical contact is made. In the unactuated state of the push button 5 is a befindlicher on the actuating tappet 6 switching cam 9 acts on the one end 10 of the contact rocker arm 8, so that the contact connection between the other end 10 'of the contact rocker arm 8 and the connecting contact 11 is opened. Upon actuation of the trigger 6 of the switch cams the end 10 of the contact rocker 8 are 9-free and a tension spring 12 pulls the other end 10 'of the contact rocker 8 to the terminal contact 11, so that the electrical connection is now closed.

Inside the switch 1 a projection 13 with a grinder attached thereto 14 is arranged on the actuating plunger. 6 This grinder 14 slides with one end on an on the circuit board 3 resistance path 15, whereby the slider 14 and the resistance path 15 together form a potentiometer sixteenth By moving the pusher 5 of the grinder 14 is moved linearly on the resistance path 15, thereby changing the position of the potentiometer 16th The of the respective position of the potentiometer 16 corresponding electrical resistance, which thus is in correlation to the respective position of the pusher 5, is used for speed setting and regulation of the electric motor by means of the circuitry located on the circuit board. 3

The respective speed of the electric motor depends on the position of the pusher 5 and can be set to a maximum speed corresponding to the maximum possible displacement of the pusher 5 in the direction 7 'and in the full voltage on the electric motor is applied. In some cases it is desirable to be able to vary the rotational speed only up to a preselected largest speed which is on the one hand equal to or less than the maximum speed and on the other hand is greater than or equal to one of the switch interpretation dependent minimum speed. This may be the case with drilling machines, for example in screwdriver operation where the speed when screwing of zero is increased up to a preselected greatest speed, said preselected largest speed depends on the material of the workpiece, the size of the screw u. The like. However, in the generally is much lower than the maximum speed. For this purpose, the electric switch 1 has a device for presetting a maximum speed which is between the minimum and maximum speed.

This means for presetting a maximum speed has a rotatably mounted at the front of the trigger 5 setting wheel 21 which allows rotational adjustment by the code of the greatest speed. As shown in more detail in Fig. 2, may be established by the adjusting wheel 21 a provided with a stop cam 23 slide 22 which is guided in a recess 26 on a side surface of the switch housing 2, linear-adjust. For this purpose a into the interior of the pusher 5 protruding threaded screw 24 is connected to the setting wheel 21, which in a befindliches where the pusher 5 facing the end of the slider 22 thread counterpart 25 of the slider 22 engages. By rotating the control wheel 21 then the slider 22 and therefore also the stop cam 23 in the direction of the arrows can be adjusted 7 and 7 '.

When the handle 5 is moved manually in the direction of arrow 7 ', so is the slider 22 which moves in the direction of arrow 28 in the recess 26 through the threaded screw 24 and the thread counterpart 25 is connected to the handle 5. The handle 5 may then insofar move until the stop cam 23 comes to rest against the front face 44 of the switch housing. 2 In this position, the electric motor runs at the preselected by thumbwheel 21 greatest speed.

is is the thumbwheel 21 adjusted so that the stop cam bears 23 remote with its switch housing 2 surface to an inner surface of the pusher, as shown in FIG. 2, the handle can 5 when operating the full adjustment through to the stop cam 23 to rest comes to the front surface 44 of the switch housing second With this setting, the setting wheel 21 thus the preselected largest speed is just the maximum speed. If the stop cam 23 by means of the adjusting wheel 21 of the inner surface of the pusher 5 to be set off in the direction of the switch housing 2, the handle 5 may be only a part of its full displacement path until it abuts the stop cam 23 on the front surface 44 of the switch housing through 2 so that the preselected largest speed is less than the maximum speed. The minimum speed that can be adjusted with the setting wheel 21 is thus determined by the extent to which the stop cam 23 is adjustable in the direction of the switch housing 2 by means of the adjusting wheel 21st

The electric switch 1 further has a Arretiereinrichhtung for mechanically locking the actuating member in the position corresponding to the preselected largest speed. The locking device consists of a shown in more detail in FIGS. 2 and 3 Arretierdrücker 30 which cooperates with the slider 22, and a guide sleeve 29.

The guide sleeve 29 26 is arranged on the side surface 45 of the switch housing 2 in the region of the pusher 5 end facing the recess, that the recess 26 overlaps, so that the slide 22 without hindrance by the guide sleeve 29 in the recess 26 is movable. The Arretierdrücker 30 is movably supported in the guide sleeve 29 against the force of a compression spring, not shown, in the direction perpendicular to the side surface 45 of the switch housing 2 direction and has one of the recess 26 facing mandrel 32 which terminates in a thickened end 33, as shown in Figures . 6 and 7 can be seen. The slide 22 in turn is provided with a recess 31, which is currently located at movement of the pusher 5 to the pre-selected by means of the adjusting wheel 21 greatest speed in the guide sleeve 29th As a result, 32 engage in the recess 31, which is shown in FIGS. 5 and 6 by pressing the Arretierdrückers 30 of the mandrel. If the handle 5 is now released, so tried this with the slider 22 due to the spring pressure again to move back in the direction of arrow 7, however, said hooking the thickened end 33 in the recess 31 as shown in Fig. 7 is closer to see, and so completed the further movement of the pusher fifth In this position, the lever 5 is then locked and the motor runs at the preselected biggest speed without the pusher 5 must be manually held.

If the locked switch 1 will be switched off again, the pusher 5 again 'pressed, whereby the slider 22 is also in the direction of arrow 7' in the direction of arrow 7 is moved as shown in FIG. 7, which is possible, since the recess 31 by a suitable overrun 35 is made larger than the size of the mandrel 32nd Due to the pressure exerted on the Arretierdrücker 30 spring pressure of the thickened end 33 thereby leaps out of the recess 31, whereby the locking is released so that the lever 5 can be moved back again freely in the direction of arrow 7 (see Fig. 1 or 2).

On the top 17 of the switch housing 2, a switch 18 for the right-left run of the electric motor is further lockably mounted, as shown in FIG. 2 is closer to see. This switch 18 has a switch lever 19 which projects slightly above the pusher fifth The switching lever 19 is movable in two positions, namely in a first for the clockwise rotation and in a second for the reverse operation. According to the respective position of the switching lever 19 of the circuit is so connected to the electric motor via supply lines which are connected to the plug contacts 20 in that the electric motor is running on the right or left.

The brush of the electric motors, which are used particularly in electric hand tools, are usually set for clockwise from the neutral position in a preferred direction, whereby an increase in torque is achieved in a clockwise direction. This, however, decreases in reverse achievable without overloading the electric motor power. To avoid an excessive load on the motor in the reverse operation of the electric switch 1 further has a device for limiting the speed in left-hand running to a speed which is less than the maximum speed, namely usually at a speed which is approximately half the maximum speed. This device has a stroke-limiting stop 36 which is fixed in the interior of the pusher fifth

Integrated into this facility for limiting the speed in reverse is the device for preventing locking in left rotation. Here, the stroke-limiting stop 36 and the stop projection 23 acts in reverse with retained on the device for preventing locking in left rotation corresponding stops, which consist of a projecting lug 42 and a stop pin 43, together, as will be explained in more detail below, so that the maximum displacement of the pusher 5 is limited anticlockwise to preferably about half of the clockwise rotation maximum adjustment travel. Consequently, thus a reduction of the maximum speed is reached in the counter-clockwise rotation.

The device for preventing locking in left running consists of a lever 37 which is rotatably mounted in a recess 40 at the top 17 of the switch housing 2 by means of engaging in a hole in the switch housing 2 pin 38th Of course, conversely, a pin may be attached to the top side 17 of the switch housing 2 and engage said pin in a hole in the lever 37th The lever 37 has two parallel to the top 17 of the switch housing 2 in the recess 40 extending lever arms, the first lever arm 34 in the said push-piece 5 facing away from the direction and the second lever arm 34 'in which the lever 5 facing direction is arranged (see also Figure . 8th). At the end of the first lever arm 34 of the lever 37 is a protruding cam 39, which in turn engages in an oblong hole 46, which is located in the remote side of the actuating arm 47 of the switching lever 19th Here it is again possible, the protruding cam 39 and the slot to exchange 46th Thus, the lever 37 upon actuation of the switch 18 for the right-left run by the change lever 19 between two positions swung back and forth, where a position is assigned to the right and the other the reverse operation. The position of the lever 37 in a clockwise direction can be seen in Fig. 4 and that in the counter-clockwise rotation in FIG. 3.

The second lever arm 34 'of the lever 37 terminates at the side opposite the pin 38 side is approximately at the front edge of the switch case 2. At this end is approximately a 90 degrees angled, parallel to the front surface 44 of the switch housing 2 extending arm 41 from (see also Fig. 2). This arm 41 has a projecting lug 42 which is approximately located at the same height as the limiting device 36 and runs parallel to the second lever arm 34 'of the lever 37 substantially. On projecting approach is further a stop pin 43, which runs parallel to the arm 41 substantially and is located approximately at the level of the stop 23 of the slide 22nd

The approximately rectangular cross-section of the bent arm 41 includes an angle α with the second lever arm 34 'of lever 37 a, as shown in FIG. 8 can be removed. Preferably, this angle α at about 120 to 150 degrees. This has the advantage that the angled arm 41 is completely secured in the anti-clockwise position with its switch housing 2 facing surface on the front surface of the switch housing 2 and can be supported there (compare to Fig. 2 and 3).

Next, the operation of the device for limiting the speed in reverse along with the integrated device for preventing locking in an anticlockwise direction with reference to FIG. 9 is to be explained in more detail to 14.

In FIGS. 9 to 11, the changeover switch 18 is set to reverse and the thumbwheel 21 is in one extreme position, namely preset maximum speed, whereby the stop cam 23 is in its closest to the handle 5 facing position on slide 22. Now, when the pusher 5 moves according to the direction of arrow 7 ', the limiting device comes 36 into contact with the projecting lug 42 of the lever 37. As a result, the handle can be 5 stop moving and the largest, 5 adjustable by pressing the trigger speed is in clockwise rotation limited to a lower speed than the maximum speed. Preferably, the size of Hubbegrenzungsanschlags 36 and the upstanding projection 42 is selected so that this largest-clockwise rotation adjustable speed is about half the maximum speed. As shown in Figs. 9 and 11 is further seen, the pusher 5, which represents the largest adjustable speed in reverse operation, the stop cam 23 is removed from the stopper pin 43 on the slide 22 in this position. The recess 31 on the slide 22 is not yet in the area of ​​the mandrel 32 of Arretierdrückers 30 so that an intervention of the thickened end 33 in the recess 31 and thus locking in reverse is not possible.

In FIGS. 12 to 14 is now the other extreme position seen in reverse, namely the position in which the adjusting wheel 21 is set to minimum speed, with the stop cam 23 of the slide 22 in its furthest from the pusher 5 remote position is , Now, when the pusher 5 moves according to the direction of arrow 7 ', so the stop cam 23 of the slider 22 comes into contact with the stop pin 43 of the lever 37. This also allows the pusher 5 stop moving and the adjustable speed thereby the links running again limited to a lower rotational speed than the maximum speed. As shown in Figs. 12 and 14 is further seen, the pusher 5, which represents the largest adjustable speed reverse, the travel limiting device 36 is removed from the projecting lug 42 in this position. Also, the recess 31 on the slider 22 is in turn not yet completely in the area of ​​the mandrel 32 of the Arretierdrückers 30 so that engagement of the thickened end 33 in the recess 31 and thus locking in reverse is precluded.

Since the minimum speed already far is generally below the maximum speed, it is the size of the stop pin 43 preferably chosen so that on the one hand the minimum speed in reverse is only slightly reduced and on the other hand intervention of the thickened end 33 in the recess 31 just not possible. Thus, effective prevention of locking in reverse is achieved even at a preselected minimum speed.

Is the thumbwheel 21 in an intermediate position between these two, in Figs. 9 and 12 shown extreme positions preset so when located in the direction of arrow 7 'moving handle 5 clockwise rotation of either the stop cam 23 of the slide 22 on the stop pin 43 of the lever 37 (see FIG. 12) or of the stroke-limiting stop 36 on the projecting lug 42 of the lever 37 (see Fig. 9). In certain positions of adjustment of the adjusting wheel 21, it may also happen that applied in reverse of the stop cam 23 on the stop pin 43 and at the same time the travel limiting device 36 at the protruding neck 42nd This reduction of the largest adjustable by means of the pusher 5 Backoff speed to a speed ensuring less than the maximum speed in all cases. As described with reference to FIGS. 9 to 14, the thickened end 33 of the mandrel 32 of the Arretierdrückers 30 in any of these positions can be further engaged in the recess 31 on the slider 22, whereby a locking of the locking device in all presettable positions of the adjustment wheel 21 in an anticlockwise effective is prevented. Advantageously, thus can then also in the counter-clockwise rotation no unsolvable hooking the locking occur in any of the adjustable on the dial 21 positions.

In the clockwise position associated with the switching lever 19, the lever 37 is pivoted into the reverse operation is remote position, which is closer to see in Fig. 4. In this position, the angled arm 41 of the lever 37 is disengaged for the stroke-limiting stop 36 and the stop cams 23, which are located asymmetrically to the center line 48 of the switch housing 2 at the anti-clockwise position associated side of the switch housing. 2 Thus, neither the travel limiting device 36 nor the stop cam 23 of the slider 22 during movement of the pusher 5 in the direction of arrow 7 'into contact with the projecting lug 42 and stop pin coming 43rd The size of Hubbegrenzungsanschlags 36 is tuned so together with the projecting lug 42 for the reverse operation, that the travel limiting device 36, the front surface of the switch housing 2 is not touched for maximum speed in reverse at position 5 of the pusher or possibly just touches. A reduction in speed due to the Hubbegrenzungsanschlags 36 thus can not occur in a clockwise direction and the maximum adjustment of the pusher 5 is determined only by the system of the stop 23 on the front surface 44 of the switch housing 2, as already described above.

Numeral list:

<dl id="dl0002"><dt>1:</dt><dd>Electric switch</dd><dt>2:</dt><dd>switch housing</dd><dt>3:</dt><dd>circuit board</dd><dt>4:</dt><dd>Components (on the board)</dd><dt>5:</dt><dd>handle</dd><dt>6:</dt><dd>actuating ram</dd><dt>7, 7 ':</dt><dd>Directional arrows (manual operation)</dd><dt>8th:</dt><dd>contact rocker</dd><dt>9:</dt><dd>switching cam</dd><dt>10,10 ':</dt><dd>End of contact rocker</dd><dt>11:</dt><dd>connection contact</dd><dt>12:</dt><dd>mainspring</dd><dt>13:</dt><dd>Approach (the actuating ram)</dd><dt>14:</dt><dd>grinder</dd><dt>15:</dt><dd>resistance path</dd><dt>16:</dt><dd>potentiometer</dd><dt>17:</dt><dd>Top (of the switch housing)</dd><dt>18:</dt><dd>Switch for right-left run</dd><dt>19:</dt><dd>Switching lever</dd><dt>20:</dt><dd>plug contact</dd><dt>21:</dt><dd>thumbwheel</dd><dt>22:</dt><dd>pusher</dd><dt>23:</dt><dd>stop cam </dd><dt>24:</dt><dd>screw</dd><dt>25:</dt><dd>Threaded counterpart</dd><dt>26:</dt><dd>deepening</dd><dt>28:</dt><dd>Directional arrow (for moving slide)</dd><dt>29:</dt><dd>guide sleeve</dd><dt>30:</dt><dd>Arretierdrücker</dd><dt>31:</dt><dd>Recess (in slider)</dd><dt>32:</dt><dd>Dorn (the Arretierungsdrückers)</dd><dt>33:</dt><dd>thickened end (the mandrel)</dd><dt>34, 34 ':</dt><dd>first, second lever arm (the lever)</dd><dt>35:</dt><dd>Stopping distance (in recess of the slider)</dd><dt>36:</dt><dd>limiting device</dd><dt>37:</dt><dd>lever</dd><dt>38:</dt><dd>spigot</dd><dt>39:</dt><dd>cam</dd><dt>40:</dt><dd>Depression (in top of the switch housing)</dd><dt>41:</dt><dd>bent arm</dd><dt>42:</dt><dd>projecting approach</dd><dt>43:</dt><dd>stop pin</dd><dt>44:</dt><dd>front face (of the switch housing)</dd><dt>45:</dt><dd>Side surface (of the switch housing)</dd><dt>46:</dt><dd>Slot (located behind switching)</dd><dt>47:</dt><dd>Arm (the change lever)</dd><dt>48:</dt><dd>Center line (of the switch housing)</dd></dl>