EP3169485A1

EP3169485A1 - Friction bearing between rotor and anvil in an impact wrench

Info

Publication number: EP3169485A1
Application number: EP15719676.7A
Authority: EP
Inventors: Adrian Vogt; Anatoli Pankraz
Original assignee: C&E Fein GmbH and Co
Current assignee: C&E Fein GmbH and Co
Priority date: 2014-07-04
Filing date: 2015-04-27
Publication date: 2017-05-24
Also published as: DE102014109412B3; US20170165817A1; WO2016000843A1; CN106660196A

Abstract

The invention relates to an impact wrench (100) comprising: - a housing (110); - a motor-driven driveshaft (120); - an output shaft (130) for securing a tool, and - a percussion mechanism (140) which couples the driveshaft (120) to the output shaft (130) in order to transmit a torque. A first bearing torque is provided between the output shaft (130) and the housing (110), said bearing torque acting opposite the rotational direction of the output shaft (130), and a second bearing torque is provided by the percussion mechanism (140) between the output shaft (130) and the driveshaft (120) when the driveshaft (120) is not coupled to the output shaft (130), said bearing torque acting opposite the rotational direction of the drive shaft (120). The invention is characterized in that the first bearing torque is smaller than the second bearing torque.

Description

Friction bearing between runner and anvil in a hammer blower

The present invention relates to an impact wrench, in particular a

Tangential impact wrench, and further a method for releasing and / or securing a screw with a tangential impact driver.

From EP 1 510 394 B1 an impact wrench is known, which periodically and briefly provides a large tightening torque for tightening screw connections or for setting screw anchors.

In general, tangential impact wrenches are suitable for inserting screws into a wide range of materials of varying hardness, such as cellular concrete, sand-lime brick, brick, stone or concrete. It is a percussion used for this purpose, in which two impactors, hammer and anvil, are accelerated against each other and impulsively transmit kinetic energy upon contact.

An object of the invention is to provide an impact wrench, which has a lower wear of the striking mechanism. Another task of

Invention is a method for the operation of a impact wrench

to provide a threshold more accurate and faster achievable.

The objects are achieved by an impact wrench or a method having the features of the independent claims. Advantageous developments can be found in the dependent claims. Thus, an impact wrench with a housing, a motor-driven drive shaft, an output shaft for mounting a tool, and a percussion gear, which couples the drive shaft to the output shaft for transmitting a torque, wherein a first bearing torque between the

Output shaft and the housing is present, which acts against the direction of rotation of the output shaft, wherein a second bearing torque between the output shaft and the drive shaft, in particular in non-coupling of the drive shaft to the output shaft by the hammer mechanism, is present, which acts against the direction of rotation of the drive shaft, characterized characterized in that the first bearing torque is smaller than the second bearing torque.

Further proposed is a method for releasing and / or fastening a screw connection with a tangential impact driver with the following steps:

Performing impact cycles wherein, within one beat cycle, a runner of a striking mechanism is engaged with an anvil alternately in a first time interval and disengaged in a second time interval, and provides a

Torque on the screw, especially during the second

Time interval, wherein the torque is in the range of 10 mNm to 500 mNm, preferably in the range of 50 mNm to 400 mNm, more preferably in the range of 250 mNm to 350 mNm.

Still further proposed is a method for operating a

Tangential impact wrench comprising the steps of: attaching a plug-in tool to an output shaft of a tangential impact driver; Producing an engagement of the plug-in tool with a corresponding to the plug-in tool fastening means; Performing impact cycles being within one

Impact cycle of a striker of an impact mechanism with an anvil of the percussion engaged alternately in a first time interval and in a second

Time interval is disengaged and providing a damping means for

Reduction of a game against the direction of rotation of the output shaft between the fastener, the plug-in tool and the output shaft. By means of a friction bearing between the output shaft or the anvil and the drive shaft, the output shaft can also between the individual

Tangential impacts are driven in the direction of rotation with a low torque. Turning back the output shaft is prevented and thus

ensures that the next blow is introduced as completely as possible into the screw.

The torque transmission according to the invention between the drive shaft and the output shaft, and an anvil of the output shaft with higher bearing torque or higher storage torques, higher torques of individual shocks as well as smaller torque fluctuations can be achieved from beat to beat. It is thus advantageous to provide a more effective impact use and less time required to achieve a certain screwing or to solve a screw, in particular a screw. This results in a lower wear of the impact mechanism by the aforementioned shortened

Screwing times.

It has been found that the torque transmitted during impact depends significantly on the angular position between the anvil, the tool, usually a nut, and the screw connection or the screw anchor. In particular, the impact strength, which ultimately acts on a screw, ie the impact of the hammer on the anvil further transmitted via a nut on the screw kinetic energy depends essentially on the rigidity and the backlash of

Connection of the last three components. The less torsional backlash between the screw, the nut and the output shaft or the anvil formed thereon, the higher peak moments can be transmitted.

The bearing moment is defined here as the sum of all moments which exist between the elements mentioned in the claims in this connection. Common to these moments that they are directed opposite to the respective direction of rotation of the motor drive of the impact wrench, which is considered in the prior art as basically undesirable, the invention, however advantageously recognizes and exploits. In particular, it is found that the bearing torque is not limited to the moments that have rolling bearings, but all moments should be included, which are caused by sliding friction, rolling friction or a frictional connection, as can be done by a slip clutch. The bearing moments are known to have in common that they vary depending on parameters such as the speed, the temperature, the surface roughness of Lagerwälzkörper, etc. In a sufficient approximation and without limitation, for example, a bearing moment, averaged over a

Period of one second, at 20 degrees Celsius room temperature and a speed of 2000 rpm, the drive spindle sspindel as storage torque in the sense of the present invention are considered.

It has proven to be particularly advantageous for effective impact utilization if the first bearing moment is in the range from 5 mNm to 200 mNm, preferably in the range from 10 mNm to 100 mNm, more preferably in the range from 20 mNm to 70 mNm. Furthermore, it has proven to be favorable for an effective impact utilization that the second bearing moment is greater by at least 1, 1-fold, in particular at least 2-fold, preferably at least 5-fold greater than the first bearing moment.

In general, an improvement in the impact utilization is to be expected if the second bearing moment by at least 10 mNm, better at least 50 mNm, preferably by at least 100 mNm, more preferably by at least 200 mNm greater than the first bearing moment.

The impact wrench can be further developed in one embodiment in that the first bearing moment of at least one bearing, in particular a rolling bearing is formed, wherein the rolling bearing between the output shaft and the housing of the impact wrench is arranged. Further bearings, in particular further rolling bearings, can likewise be arranged here between the output shaft and the housing and likewise make a contribution to the first bearing torque with their respective moments. At this point it is noted that the bearing moments do not form a constant size but usually vary depending on, for example, the temperature, the rotational speed and furthermore the signs of wear. However, although the variance may be comparatively low and only a few 10 mNm may be, therefore, the bearing moment in each case with a range must be specified or otherwise be understood as an average.

At the higher second bearing torque results according to the invention an improved impact utilization. However, the engine of the tangential impact wrench is loaded accordingly at a higher second bearing moment, which results in an upper limit for the second bearing torque, which should not be exceeded for reasons of economy. In one embodiment, it is provided that the second bearing torque is formed by at least one O-ring. The O-ring is preferably used braced in one of the waves or in both to achieve the relatively higher second bearing torque. The advantage of using an O-ring to achieve the second bearing torque lies in the low production costs of this component.

In a further embodiment, the second bearing torque can be formed by at least one friction bearing or a preloadable rolling bearing, in particular a needle bearing or a ball bearing. In particular, the rolling bearing may in this case be designed as a friction bearing known per se, that generates a friction torque approximately over entangled rolling elements. The bias voltage can be applied for example via a corrugated spring.

In a further embodiment, the second bearing torque can be applied by at least one slip clutch.

Furthermore, the second bearing torque may be formed in a further embodiment of a socket connection between the drive shaft and the output shaft. By a fit or press fit forms the socket connection Sliding torque, which can correspond to the bearing moment, or a part of the bearing torque applies.

A further development of the impact wrench can still consist in that the first and / or the second bearing moment is formed by a plurality of bearing elements.

In the following the invention will be explained in more detail by means of exemplary embodiments. It shows:

Fig. 1 is a sectional view of the front part of a striking screwdriver;

Fig. 2 of the striking screwdriver of Figure 1 in a sectional view.

Fig. 3 is a diagram of a torque measurement in an impact wrench according to the prior art;

4 shows a diagram of a torque measurement in an impact wrench according to FIGS. 1 and 2.

FIG. 1 shows a tangential impact driver 100 according to the invention, still completely shown in FIG. 2 with a motor 170, with a sectional view of its front part.

In a housing 110 of the Tangentialschlagschraubers 100 is an electric motor driven drive shaft 120 and further arranged thereon by means of a striking mechanism 140 output shaft 130 is arranged. On the drive shaft 120 there are two helically running around scenes indicated by dashed lines 122 in each of which a ball 124 runs. The two balls 124 are in contact with a rotor 142. On the rotor 142, a hammer 126 is further formed. The hammer 126 is here in contact with an anvil 132, which is connected to the

Output shaft 130 is integrally connected and ends. Furthermore, one attacks Return spring 150 in a recess 144 of the rotor 142 a. A first

Bearing moment is determined by a bearing torque of a rolling bearing 160, which is formed between the housing 110 and the output shaft 130 and another

Storage torque of a Teflon disk 162, which is formed between the housing 110 and the anvil 132 of the output shaft 130 is formed. A second

Bearing moment is formed by a friction bearing 164. For the first mentioned

Bearing moment was at a speed in idle mode of a

Tangential impact wrench according to the invention, a mean value of about 0.03 Nm or 30 mNm detected by measurement. The difference between the recorded maximum and minimum values of the bearing moments was about 90 mNm.

Starting from the initial position shown, the rotor 142 is by means of a hammer 126 in engagement with the anvil 132 and thus with the output shaft 130. The rotor 142 is through the anvil 132 prevented to rotate in the direction of rotation of the drive shaft 120. Instead, the link 122 forces the rotor 142 to move in the direction of the axis of rotation out of engagement with the anvil 132. Out of engagement with the anvil, the rotor 142 may rotate relative to the anvil 132 and to the drive shaft 120. The anvil 132 and the hammer 126 come back into a position in which they interlock. The return spring 150 drives the rotor 142 back to the anvil 132. The rotor is thereby accelerated in the direction of the longitudinal axis and receives by the forced operation of the gate 122 a

Rotational motion with a corresponding angular momentum. The rotational movement of the rotor 142 is stopped by the lateral abutment of the hammers 126 of the rotor 142 on the anvil 132 and the angular momentum is almost completely transmitted to the anvil 132 and the tool, not shown here in the form of a nut and the screw connection, also not shown. The system is back in the starting position and another beating cycle begins.

The first bearing torque, which is present between the output shaft 130 and the housing 110, acts against the direction of rotation of the output shaft 130 and a second Bearing moment is especially in non-coupling of the drive shaft 120 with the output shaft 130 by the hammer 140 between the output shaft 130 and the drive shaft 120 and also acts against the direction of rotation of the drive shaft 120. The second average bearing torque, for example, about 50 mNm be greater than that first mean bearing moment. This will be the

Output shaft 130 through the friction bearing 164, which forms the second bearing torque, still driven with a small drive torque from the drive shaft 120 between the individual above-described Tangentialschlagzyklen. As a result, a reverse rotation of the output shaft 130 is prevented and ensures that the next shock is introduced as completely as possible in the screw or other fasteners.

FIG. 3 shows the torque of a tangential impact wrench known from the prior art over time. The scaling is 20 Nm for the torque and 0.5 seconds for the time. In Figure 4 with identical

Scaling the torque of this tangential impact driver 100 is plotted over time, with a conventional bearing has been replaced by a friction bearing 164.

As can be seen, the torque in FIG. 4 is more uniform and at a considerably higher level with a plateau of peak amplitudes of more than 150 Nm.

LIST OF REFERENCE SIGNS

100 tangential impact wrench

110 housing

120 drive shaft

122 backdrop

124 ball

126 hammer

130 output shaft

132 anvil

140 percussion

142 runners

144 recess

150 return spring

160 rolling bearings

162 Teflon disk

164 friction bearings

170 engine

Claims

Impact screwdriver (100) with:

a housing (110);

a motor-driven drive shaft (120);

an output shaft (130) for mounting a tool and a percussion mechanism (140) connecting the drive shaft (120) with the

Output shaft (130) for transmitting a torque couples, wherein a first bearing torque between the output shaft (130) and the housing (110) is present, which acts against the rotational direction of the output shaft (130),

wherein a second bearing torque when non-coupling the drive shaft (120) to the output shaft (130) by the hammer mechanism (140) between the output shaft (130) and the drive shaft (120) is present, which acts against the rotational direction of the drive shaft (120), characterized characterized in that the first bearing torque is smaller than the second bearing torque.

Impact wrench (100) according to claim 1, wherein the first bearing moment in the range of 5 mNm to 200 mNm, preferably in the range of 10 mNm to 100 mNm, more preferably in the range of 20 mNm to 70 mNm.

Impact wrench (100) according to claim 1 or 2, wherein the second

Storage torque in at least 1.1 times, in particular at least 2 times, preferably at least 5 times greater than the first bearing moment.

Impact wrench (100) according to claim 1 or 2, wherein the second

Storage moment by at least 50 mNm, preferably by at least 100 mNm, more preferably by at least 200 mNm greater than the first

Bearing moment.

Impact wrench (100) according to one of the preceding claims, wherein the first bearing torque of at least one bearing (160), in particular a rolling bearing is formed, wherein the rolling bearing between the

Output shaft and the housing is arranged.

6. impact wrench (100) according to one of the preceding claims, wherein the second bearing torque of at least one friction bearing (164), at least one O-ring, at least one preloadable rolling bearing, in particular a needle bearing or a ball bearing, by a socket connection between the drive shaft and the output shaft, and / or is formed by at least one slip clutch.

7. impact wrench (100) according to any one of the preceding claims, wherein the first and / or the second bearing torque of a plurality of

Bearing elements is formed

8. Method for releasing and / or fastening a screw connection with a tangential impact driver (100) comprising the steps:

Execution of impact cycles, wherein within a beat cycle a runner (142) of a hammer mechanism (140) is engaged with an anvil (132) alternately in a first time interval and disengaged in a second time interval,

Providing a torque to the screw connection, in particular during the second time interval, wherein the torque is in the range of 10 mNm to 500 mNm, preferably in the range of 50 mNm to 400 mNm, more preferably in the range of 250 mNm to 350 mNm.

9. A method of operating a Tangentialschlagschraubers (100) with the

steps:

- Attaching a Aufsteckwerkzeugs on an output shaft (120) of a tangential impact driver;

- Making an engagement of the Aufsteckwerkzeugs with a for

Attachment tool corresponding fastener;

- Implementation of impact cycles within a beat cycle, a runner (142) of a striking mechanism (140) with an anvil (132) of the Striking mechanism (140) is engaged alternately in a first time interval and disengaged in a second time interval,

- Providing a damping means (164) for reducing a backlash against the direction of rotation of the output shaft (130) between the

Fastening means, on the plug-in tool and the output shaft (120).