EP2140976A1 - Impact wrench - Google Patents

Abstract

The wrench has an actuating unit (23) i.e. axially displaceable setting ring (22), for switching an impact mechanism between an operating mode in which the mechanism is switched on, and an operating mode in which the mechanism is switched off. The actuating unit is in rotationally fixed engagement with a drive shaft (30) or a hammer (20), or is not engaged with the hammer or the shaft, when the mechanism is switched on. The actuating unit is in rotationally fixed engagement with the hammer and the shaft, when the mechanism is switched off, and is axially movable to switch the mechanism.

Description

The invention relates to an impact wrench for screwing and drilling with a rotary impact mechanism wherein such impact wrench are used inter alia to produce or solve high-strength threaded connections. Impact wrenches have been known in the art for many years, the function of the rotary impact mechanism being based on the idea of temporarily storing the drive energy of an engine and periodically applying it to an output shaft within a very short working phase. These periodically emitted angular momentum produce a significantly higher resulting depending on the pulse duration Drive torque as possible with a constant torque curve. From the drive side, the system receives kinetic energy in the form of torque and speed, which is cached in an assembly, for example in a spring or a rotating mass. The storage process takes each time until a control mechanism ensures that the stored energy is delivered via a hammer on an anvil. For this purpose, both the anvil and the hammer of the impact mechanism on impact jaws, wherein the hammer comprises a flywheel, which is formed by the massive part of the hammer, which is accelerated by this mass, the kinetic energy is transferred to the anvil. The anvil is in a rotationally fixed connection to the output, so also for screwing. The control mechanism provides for the time-limited delivery of energy to the anvil, so that the compound dissolves again when the stored energy is released.

There are two working phases in the striking mechanism, whereby in phase 1 the energy is collected and stored and in phase 2 the stored energy is released again. The energy stored in phase 1 is determined by the input quantities of torque, speed and stroke rate. The higher the stroke rate, the shorter Phase 1 is in terms of time and the less energy can be stored, because the engine can only apply a given torque and thus the duration of the storage process is crucial.

In the second phase also decides the duration of the energy tax. If the stored energy is delivered to the output in a shorter time, ie the duration of the stroke is shorter, the resulting torque peak will be higher than with a longer duration of the stroke.

Basically, the typical torque curve of an impact wrench is created by temporarily storing energy over a longer period of time, which is delivered abruptly to the output in a very short period of time.

In the case of impact no torque is generated at the output between the torque peaks. Due to this design high tightening and loosening moments in a compact design are possible. Nevertheless, the moment of reaction which the worker has to absorb with the impact wrench is only the moment that is necessary to accelerate the rotating hammer mass in the impact mechanism or to tension the spring. It is comparatively low compared to the output torque.

An impact wrench is for example in the DE 43 01 610 A1 described above.

In this case, it may be desirable to provide a device which can provide a switchover between a type of operating mode with a percussion mechanism switched on and a mode with a striking mechanism switched off in which the screwdriver can be used as a simple screwdriver without a rotary impact or as a drill.

It is from the DE 43 01 610 A1 Already previously known form a shutdown device for the impact mode, in which case the racket is axially fixed by means of a manually operable actuator, without preventing the rotary drive of the output shaft. In this way, the axial movement of the racket or hammer and thus clamping of the impact energy storage means, which is formed as a spring in the prior art, is prevented.

Furthermore, for example, from the EP 1 574 294 A2 a design known for an impact wrench, wherein here an axially displaceable ring is provided, which cooperates in a first beating mode with the hammer and in a second mode of operation connects the hammer with the anvil, wherein the ring with both the hammer and the anvil cooperates and so provides a rotationally fixed connection between the hammer and anvil.

Finally, out of the EP 1 762 343 A2 also a device for switching on and off the impact function of a wrench known, wherein a pin is provided which is axially displaceable in a groove and blocked in one of the end positions in the output-side direction, the mobility of the hammer in the axial direction. This keeps the hammer constantly engaged with the anvil and the impact function is blocked. It is also known from this document to provide a further wave, which bypasses the power flow on the percussion. This second wave is brought in the deactivation of the impact function via a switching element with both the drive and the output side in rotational connection. At the same time the connection of the drive to the striking mechanism is released.

The object of the invention is therefore to provide an actuating means for switching on and off of the impact mechanism, which has an alternative constructive solution and at the same time enables a particularly simple switching between an operating mode with and a mode with the impact mechanism switched off.

The invention is achieved by an impact wrench with the features of claim 1, namely a Impact wrench with a drive motor for driving a drive shaft and a coupled with a tool holder output shaft and a percussion mechanism, wherein the percussion includes an output shaft coupled to the anvil and a hammer which is guided on the drive shaft and rotates with this non-stop rotation and relative to the drive shaft in the case of impact performs at least a limited rotational movement, wherein an actuating means is provided for switching the percussion between a mode with and a mode with switched-off percussion, wherein the actuating means with activated percussion in a first position in a rotationally fixed engagement with the drive shaft or the hammer or without engagement with one of the two components, hammer or drive shaft, is and with the impact mechanism switched off in a second position in a rotationally fixed engagement with the hammer and drive shaft, wherein the actuating means for scarf th is axially movable. Such an impact wrench is suitable in addition to the screws for drilling.

It can be provided that rotates in a first non-impact case of the hammer with the anvil and the drive shaft, the impact jaws of anvil and hammer abut against each other and are engaged, that is, overlap in the axial direction, this operation is done with activated percussion until the maximum torque of the screwdriver is reached without hitting. This usually means until it comes to a first blockage of the screw. For further tightening of the screwed connection, a transition to impact mode then takes place automatically when the percussion mechanism is activated, with the anvil and the hammer, with their percussion jaws, being arranged on hammer and anvil faces facing one another in percussive operation, against one another no longer permanently, as in the screw, abut, but are separated from each other during energy storage, and then in the energy discharge and thus the impact in the circumferential direction collide against each other and so to provide a momentarily greater torque.

In this case, the hammer can perform an axial movement relative to the drive shaft in case of impact in addition to the relative rotation to the drive shaft. The axial movement can be oscillating.

It is to shutdown the percussion to ensure a pure screwing or drilling operation without the percussion is automatically switched on, the drive shaft connected by axial displacement of the actuating means with the hammer. In this case, the actuating means is coupled in a first position only with the drive shaft or the hammer or is engaged with the two and in a second position hammer and drive shaft are coupled together so that there is no relative rotation between them and thus also in the axial direction oscillatory motion is prevented. In this way, no energy storage and no overlapping of the impact jaws.

If the actuating means with the hammer and the drive shaft is engaged, it blocks the rotational relative movement between the hammer and the drive shaft, which allows the impact function in addition to the axial relative movement.

Such a configuration with an axially displaceable actuating means, in a first position and mode either without engagement or in engagement is only with drive shaft or hammer and is in a second mode with switched Schlagwerk in engagement with the hammer and drive shaft, manufacturing technology is particularly easy to implement, being particularly preferred that the switching operation can be done independently of the relative angle of the components hammer and drive shaft to each other. This switching independently of the relative arrangement of the two components to one another can be achieved by the design of the impact mechanism, for example as V-Nutenschlagwerk that always has the same position of hammer and drive shaft to each other at a standstill, but it can also be achieved by the actuating means is designed accordingly.

Particularly preferred is an axially displaceable adjusting ring or an axially displaceable pin, wherein the adjusting ring may in particular have one or more grooves or ribs, which are engageable with grooves or ribs in the drive shaft and / or the hammer and along the Nutlängsrichtung, which runs in the axial direction, can be moved. Also conceivable are spirally arranged grooves, via which a rotationally-axially displaceable actuating means in engagement with one or both of the components can be brought.

The actuating means can be actuated via a slide switch but also via a rotational movement on a ring in an axial-rotational movement. In addition, as a member with which the actuating means is moved, a rotary handle may be provided which allows a corresponding guide a translational movement or a coupled translationally rotational movement of the actuating element.

It can be provided in particular that for actuating the actuating means a protruding through a housing opening slide switch is provided, which is connected to the adjusting ring, wherein the slide switch is guided in particular in a circumferential groove around the adjusting ring and rotates in the groove around the adjusting ring, if the adjusting ring rotates with the drive shaft.

Particularly preferably, it may be provided that the impact mechanism is designed as a V-groove impact mechanism, wherein the hammer performs an axially oscillatory rotational movement with respect to the drive shaft in case of impact. Under an axial oscillatory movement is to be understood here that the hammer in case of impact, both an axial relative movement, wherein the hammer on the drive shaft alternately axially toward the drive-side end of the drive shaft and the output side end of the drive shaft is reciprocated in a groove , wherein the groove is V-shaped and performs the tip of the V in the direction of the output side of the shaft, wherein caused by the axial movement due to the V-shape of the grooves at the same time also a relative rotational movement of the hammer to the drive shaft. The hammer can be guided over a ball guide in the V-grooves, wherein preferably two V-grooves are arranged diametrically opposite to the drive shaft.

A V-groove striking mechanism works as follows: Before an impact event occurs, the anvil turns over its impact jaws which abut against the hammer's jaws, together with the hammer and the drive shaft without any relative movement between the individual components. When concerns a larger torque, it now comes from the fact that this torque is not due to the normal torque of the impact wrench can be applied between anvil and hammer to decouple the impact jaws. The rotation of the drive shaft, which is transferred to the hammer and the counter-support of the anvil, causes the hammer to move on the drive shaft in the V-grooves. By providing the V-grooves, the hammer is moved away from the anvil at the same time as the rotation relative to the drive shaft in the axial direction, and it comes to a catch in the axial direction of the impact jaws of the hammer and the anvil. By releasing the hammer from the anvil, the hammer can move freely in a rotational direction and is accelerated by the stored energy, which is stored in a spring by the axial movement of the hammer in the drive direction until it is at the end of its rotational movement and axial movement against striking the impact jaws of the anvil with its impact jaws and so performs a blow in the circumferential direction, which leads to a further tightening or loosening of the machined Schraubfalls. After impact the tensioning of the percussion mechanism takes place by axial and radial movement of the hammer again.

According to a first embodiment it can be provided that in the drive shaft and the hammer, a groove or a rib are provided, wherein generally also a plurality of circumferentially distributed grooves or ribs may be provided, which cooperate with a corresponding rib or groove of the actuating means. By distributing the force over several ribs, these can be better distributed and the elements designed to be adjusted accordingly.

In principle, on the actuating means, if it is a sleeve or a ring, a toothing be mounted, which cooperates with a corresponding toothing on the outer circumference of the drive shaft and hammer.

According to a particularly preferred embodiment, it may be provided that the hammer consists of a separate flywheel and a separate control part, wherein the control part interacts with the anvil in case of impact and the flywheel and the control part rotatably, but are axially connected to each other movable. In Providence of a V-groove impacting particular only the control part is axially movable relative to the drive shaft. By dividing the hammer into two elements, namely the flywheel and the control part, which are positively rotatably but axially slidably coupled together, there is the advantage that by the fact that the flywheel performs no axial movement, no vibrations in this direction are caused. Only the control part performs the axial oscillation. Since the mass of the control part is significantly lower in comparison to the entire flywheel mass, the vibration excitation in the direction of the axis of rotation is reduced considerably.

In addition, it can preferably be provided that a torque adjustment is realized, which takes place in particular via variations of the biasing force of the spring of the V-groove impaction.

According to another preferred embodiment, it can be provided that the impact wrench is a cordless wrench, with cordless tools generally having the advantage of being easier to use at any location and even in difficult applications. In addition, the impact function is particularly advantageous in cordless tools, since in devices with direct electrical connection, the torque design can be such that higher Torques can be achieved so that, if necessary, can be worked without an additional impact function.

Further advantages and features of the invention will become apparent from the remaining application documents. The invention will be explained in more detail below with reference to a drawing.

Figur 1

ein Schlagwerk in montierter Form,

Figur 2

ein Schlagwerk in teilweise auseinandergezogener Darstellung

Figur 3

eine Antriebswelle

Figur 4

einen Hammer

Figur 5

einen Stellring eines Betätigungsmittels

Figur 6

eine geschnittene Darstellung durch das Schlagwerk bei abgeschaltetem Schlagwerk

Figur 7

einen Schnitt durch das Schlagwerk bei zugeschaltetem Schlagwerk

Figur 8

eine alternative Ausgestaltung des Schlagwerks bei zugeschaltetem Schlagwerk

Showing:

FIG. 1

a striking mechanism in assembled form,

FIG. 2

a percussion in partially exploded representation

FIG. 3

a drive shaft

FIG. 4

a hammer

FIG. 5

a collar of an actuating means

FIG. 6

a sectional view through the percussion with the impact mechanism switched off

FIG. 7

a section through the percussion mechanism with activated Schlagwerk

FIG. 8

an alternative embodiment of the impact mechanism with activated percussion

FIG. 1 shows a striking mechanism of an impact wrench comprising an output shaft 10 which is connectable at its output end 12 with a tool, in particular a screwdriver and at its drive end has an anvil 14 having two impact jaws 16 which are formed diametrically opposite each other in the radial direction wherein the striking surfaces are substantially radially extending surfaces. The rectangular impact jaws 16 of the anvil 14 cooperate with cake-piece-like impact jaws 18 of a hammer 20, wherein the impact jaws 18 of the hammer 20 have striking surfaces which face the striking surfaces of the striking jaws 16 of the anvil 14 against each other issue. The hammer 20 forms on the one hand a flywheel and serves as another control means for the control of a beating process. In addition, the percussion includes a collar 22 as an actuating means 23 having a circumferential groove 24 in which a slide switch 26 is guided, which passes through an opening in a housing of the impact wrench, wherein by movement of the slide switch 26 in the axial direction 28 there is a shift the adjusting ring 22 comes in the axial direction, wherein the adjusting ring 22 is coaxial with the output shaft 10 and the drive shaft 30 and the drive shaft 30 and the hammer 20 at least partially and at least partially surrounds.

In this case, a groove 32 is formed in the hammer 20, in which a rib 34 of the adjusting ring 22 engages, and so ensures a positive connection between the adjusting ring 22 and hammer 20.

FIG. 2 now shows an exploded view of the striking mechanism, in which case the adjusting ring 22 has been removed. In this case, the adjusting ring 22 has two diametrically opposed ribs 34, each engaging in a groove 32 of the hammer 20, wherein also in the drive shaft 30 in an integrally connected to the drive shaft 30 flange 36 grooves 38 are provided, in which also the ribs 34 can intervene. The drive shaft 30 is in this case coupled with its drive-side end 40 with a drive motor, in particular a planetary gear (not shown) between the drive motor and the drive shaft 30 can be interposed to translate the speed of the drive motor and to vary.

In addition, a spring 42 is provided, which cooperates with its output end with the hammer 20 and with its drive-side end 44 bears against the flange 36 of the drive shaft 30. By an axial movement in the direction 46 of the hammer 20, the spring 42 between the hammer 20 and flange 36 tensioned and thereby energy stored in the spring 42.

FIG. 3 now shows the drive shaft 30 with the flange 36 and the grooves 38 and another flange 46 for connection to a transmission or the drive motor, wherein in the drive shaft 30, two V-shaped grooves 48 are provided at the output end 50 of the drive shaft 30 and the V -shaped groove for controlling the axial oscillatory rotational movement of the hammer 20 relative to the drive shaft 30 is used. The two V-grooves 48 are arranged opposite one another. In the grooves 48 of the hammer 20 via ball guides (not shown) out.

The hammer 20 alone is here in FIG. 4 shown.

FIG. 5 now shows the adjusting ring 22 with the ribs 34 for axial guidance and positive connection, in particular with the drive shaft 30 and the hammer 20 or both the drive shaft 30 and the hammer 20th

FIG. 6 represents a section through the percussion, in which case the adjusting ring 22 engages with its ribs 34 both in the groove 32 of the hammer 20 and in the groove of the flange 36 of the drive shaft 30 and so the drive shaft 30 rotatably and positively connected to the hammer 20 , By this combination of hammer 20 and drive shaft 30, the relative rotational movement of the hammer 20 to the drive shaft 30 to enable the impact process is prevented and the hammer 20 always rotates together with the drive shaft and thus remains constantly with its impact jaws 18 with the impact jaws 16 of the anvil 10 in Contact. In this way, a pure screwing or drilling function can be made possible.

FIG. 6 also shows the ball guide 50 in the V-grooves 48 of the drive shaft 30 and the spring 42, which serves to store the energy that discharges later in the blow. In addition, a bearing 52 is arranged in the interior of the hammer 20, so that only an axial load on the spring 42 takes place, but no rotational load is applied to the spring 42.

FIG. 7 shows an operating mode in which the impact wrench is in an operating state with activated Schlagwerk, in which case the adjusting ring 22 engages with its rib 34 only in the groove 32 of the hammer 20, but not in the groove 38 of the flange 36 of the drive shaft 30. Auf In this way, the hammer 20 can move in the direction of the drive shaft 30 both in the predetermined by the V-grooves dimensions rotationally and axially in the direction 44, so that it comes to a separation of the striking jaws 16 and 18 of the anvil 10 and hammer 20 and thus to a latching of the impact jaws 16 and 18 and to a subsequent relaxation of the spring 42 and to an acceleration of the hammer 20 in the axial direction, which is here designated by the arrow 56. With fully tensioned spring 42 is due to the lack of contact with the anvil 10 and the guide in the V-grooves to a rotational movement of the hammer 20 with simultaneous axial movement of the hammer 20 in the driven direction, which then by the meeting of the striking jaws 18 of the hammer 20 on the impact jaws 16 of the anvil 14 are stopped and imparted a shock to the striking jaws 16 of the anvil 14, which then results in a momentary torque peak which may be used for further tightening or loosening a threaded connection.

FIG. 8 Finally, shows a further embodiment, in which case the adjusting ring 22 is only in contact with the groove 38 of the flange 36 of the drive shaft 30 and thus also a relative movement in rotational terms between the hammer 20 and drive shaft 30 and an axial movement coupled thereto is made possible.

In principle, it can also be provided that the adjusting ring 22 is neither in engagement with the drive shaft 30 still engaged with the anvil 14 and in this way a striking position is made possible.

In the manner described above, a connection and disconnection of an impact mechanism of a striking screwdriver can be achieved particularly easily in terms of production technology. Moreover, by blocking the relative rotational movement and providing axially extending coupling elements, e.g. by the ribs in the adjusting ring 22, the force on the adjusting ring 22 are distributed over a relatively large area and over the circumference, so that the life of the device can be increased.

Claims (9)

Impact wrench with a drive motor for driving a drive shaft (30) and an output shaft (10) which can be coupled to a tool holder and a percussion mechanism, the percussion mechanism comprising an anvil (14) coupled to the output shaft (10) and a hammer (20) acting on the drive shaft (30) is guided and rotates with the latter in the non-impact case and relative to the drive shaft (30) in case of impact rotational movement, wherein an actuating means (23) is provided for switching the percussion between an operating mode with and a mode with switched off Impact mechanism, characterized in that the actuating means (23) with the percussion mechanism in a first position in a rotationally fixed engagement with the drive shaft (30) or the hammer (20) or without engagement with the hammer (20) or drive shaft (30) is and at is turned off in a second position in a rotationally fixed engagement with the hammer (20) and drive shaft (30) wherein the actuating means (23) is axially movable for shifting. Impact wrench according to claim 1, characterized in that the actuating means (23) is an axially displaceable adjusting ring (22). Impact wrench according to one of the preceding claims, characterized in that the impact mechanism is designed as a V-groove impact mechanism, wherein the hammer (20) in the case of impact performs an axial-oscillatory rotational movement with respect to the drive shaft (30). Impact wrench according to claim 3, characterized in that the drive shaft (30) has at least one V-groove (48) and the hammer (20) in the V-grooves (48) of the drive shaft (30) is guided. Impact wrench according to one of the preceding claims, characterized in that the hammer (20) and anvil (14) each have two diametrically opposed impact cams, which rest against each other in the non-impact case and transmit the rotation and perform in the case of impact relative rotation and in particular axial movement and meet each other at the beat. Impact wrench according to one of the preceding claims, characterized in that in the drive shaft (30) and the hammer (20) at least one groove (32, 38) or a rib is provided with at least one corresponding rib (34) or groove of the actuating means (23) cooperates. Impact wrench according to one of the preceding claims, characterized in that the hammer (20) comprises a flywheel and a control part, wherein the control part cooperates with the anvil (14) in the impact case and the flywheel and the control member rotatably, but axially connected to each other movable are. Impact wrench according to one of the preceding claims, characterized in that the actuating means (23) by means of one with the actuating means (23) connected through a housing opening of a housing projecting slide switch (26) is actuated. Impact wrench according to one of the preceding claims, characterized in that the impact wrench is a cordless device.

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