EP2457694A2 - Power tool - Google Patents

Abstract

The tool has a drive shaft (30) displaced in a rotary and partial tangentially striking motion by a tangential striking mechanism (10). The mechanism is driven by a drive e.g. motor and/or gear. The mechanism includes an anvil (60) associated to the shaft, and a hammer (70) associated to the drive. The anvil and the hammer are movable axially under force application of a spring (81), and tangentially and strikingly under twisting of the anvil and the hammer against each other. An auxiliary mass is coupled to a main mass (71) of the hammer and stands under force application of another spring.

Description

Technical area

The invention relates to a hand tool according to the preamble of claim 1.

State of the art

A mechanical Tangentialschlagwerk as in the power tool of the type mentioned, for example, in an impact wrench allows comparatively large torques of the tool holder to provide, with only a comparatively small counter-torque required. This is for example when tightening screw or the setting of screw anchors in particularly solid ground advantage. In particular, in such applications, if appropriate, the tip torque which can be provided by the tangential impactor can far exceed a continuous torque that can be set by the drive of the handheld power tool. The lowest possible counter-torque is of particular advantage to the user, since he usually has to provide the counter-torque on the handle of the hand-held power tool, such as an impact wrench. The lower the counter-torque, the easier it will be to handle the power tool.

Most tangential impact are designed as part of a spring-mass system to a resonant operation thereof, which usually limits the effective operation to a relatively limited torque range. Ultimately, the actual operating point of the power tool in the comparatively narrow torque range is determined by the drive speed of the drive of the power tool.

It is desirable to achieve the widest possible torque range, while maintaining the aforementioned aspects, in which an operation of the power tool is effectively possible. It has been shown that for this purpose a Tangentialschlagwerk the hand tool - similar to a spring-mass system - is adaptable for a resonant operation. For example, it is off DE 198 21 554 B4 a hand tool with a cam known per se, in which a non-rotatably arranged in the housing of the power tool cam against the force of a first spring - and, if necessary, against the force of a deliverable second spring - is axially displaceable. As a result, an increase in the impact strength of the cam mechanism is basically achievable.

Problematic in an adaptation of a Tangentialschlagwerks - basically similar to a slip clutch of the EP 1 862 265 A2 As a spring-mass system can be constructed - is that changing the spring force for the mass of the hammer in Tangentialschlagwerk also leads to a change in the beat frequency, which is noticeable by the user. In the case of use with an impact wrench, this naturally also has an effect on tightening screws or setting anchors. In addition, for example, an increase in a spring force not only leads to an increase in the impact force, but also to a higher release torque of Tangentialschlagwerks, with a corresponding counter-torque is applied by the user on the handle. This deteriorates the handleability of the power tool. In particular, a comparatively low holding torque is particularly desirable, as this is a major advantage of a percussive impact wrench, z. B. compared to a conventional screwdriver represents. In previously known percussion adaptations, it has also been regularly found necessary to adapt an engine speed to the adapted conditions of the striking mechanism in order to achieve an effective operating point in the applicable and adapted torque range.

Presentation of the invention

At this point, the invention begins, the object of which is to provide a hand tool machine in which an applicable torque range can be adapted in an improved manner. In particular, an adaptation of a tangential impact mechanism should be implemented in an improved manner. Particularly advantageously, an adapted torque range should lead to an overall increased applicable torque range.

The task relating to the power tool is achieved by a hand tool of the type mentioned, in the present invention, the features of the characterizing part of claim 1 are provided. According to the hammer of Tangentialschlagwerks on a main mass, the tangential impact additionally provides an additional mass available that is releasably coupled to the main mass and is under the action of a second spring. By coupling the additional mass to the main mass so a hammer is provided, the total mass is composed of the sum of the main mass and additional mass. This increases, if necessary, the deliverable torque of the tangential impact according to the concept of the invention. In addition, the concept of the invention also provides that the additional mass is under the action of a second spring. In this way, in addition to the total mass of the hammer and a total spring force is increased under the force of the spring-mass system of Tangentialschlagwerks stands. As a result, the frequency of impact of the Tangentialschlagwerks in operating conditions with increased total mass of main mass and additional mass at increased total spring force and in other operating conditions, in which only one main mass is under the action of the first spring, kept the same. Thus, while adapted by the concept of the invention, the deliverable torque of the tangential impact, especially in the second operating state with increased total mass of the hammer is advantageously increased, this is nevertheless in a comparatively small way at the expense of increased triggering torque of Tangentialschlagwerks. A holding torque of the user is thus kept relatively low despite increase or adaptation of the delivered torque. The reason for this is that an increase in a spring force for the tangential impact mechanism according to the concept of the invention can be comparatively low due to the increased total mass in the second operating state. Advantageously, a user will thus hardly notice an altered holding torque during the adaptation of the tangential impact mechanism when using the handheld power tool. Nevertheless, a user will be able to adjust the deliverable torque of the hand tool to the required machining environments.

The concept of the invention also has the advantage that due to the largely constant beat frequency when adapting the tangential impact mechanism, an engine speed can also remain relatively constant. This advantageously allows an improved design of the drive both to a first operating state with only the main mass as a hammer and to a second operating state with increased Total mass of the hammer. At most, in the case of using an unregulated motor to drive the power tool when adapting the Tangentialschlagwerks the same speed due to the load also adapt.

In the context of a particularly advantageous development of the power tool, it can thus be operated in a first and a second operating state, it being possible to switch back and forth as required between the operating states mentioned. Advantageously, in a first operating state, the main mass of the hammer and the anvil are axially movable under the action of force of a first spring and, while twisting the same, against each other tangentially against one another. Advantageously, in a second operating state, the main mass and the additional mass of the hammer and anvil under the action of force of the first and second spring axially and while rotating the same against each tangential striking against each other movable.

In a particularly preferred constructional development of the concept of the invention, it is provided that the additional mass can be detachably coupled to the main mass by means of a feed mechanism. The feed mechanism advantageously has a preloaded second spring acting on the additional mass. The feed mechanism is advantageous to operate by the user of the power tool, so that can be switched during operation of the power tool by pressing the feed mechanism between the first and second operating state. By virtue of the prestressed second spring, which already advantageously acts on the additional mass in the feed mechanism, the adaptation of the tangential impact tool with increased total mass and increased spring force is made comparatively simple and effective.

Advantageous developments of the invention can be found in the dependent claims and specify in particular advantageous ways to realize the above-described concept within the scope of the problem and with regard to further advantages.

It is advantageously provided that the feed mechanism is movable along a control link. For example, the delivery mechanism may be movable by a user. Advantageously, the feed mechanism is axially displaceable along a control link. The delivery mechanism may also be rotatable along a control link. Both are possible alone and in combination, for example, to switch between the aforementioned first operating and second operating state of the power tool.

Advantageously, the main mass and the additional mass are positively coupled to one another in a second operating state. This has proven to be a comparatively simple mechanism for increasing the overall mass of the hammer.

In an advantageous constructive development, the feed mechanism has a housing cage, in which said second spring is biased against the additional mass and the housing cage. Such a housing cage is advantageous as a whole freely or according to a control link movable. The feed mechanism thus has an intrinsically compact form which is safe to operate.

Advantageously, the feed mechanism is secured in a first operating state of a securing element against movement. A securing element advantageously serves to prevent unintentional actuation of the feed mechanism. A securing element can be designed to secure the feed mechanism for operation of the handheld power tool both in the first operating state and in a second operating state. For example, a securing element may be designed as a lever lock or the like against whose resistance the feed mechanism is to be actuated or which is also to be actuated by the user before actuation of the feed mechanism.

In principle, it has proved to be advantageous to provide the tangential impact mechanism with a structurally suitable force-transmitting impact gear which acts on the hammer and / or the anvil. A striking mechanism is advantageously used to move the hammer and / or anvil axially against one another according to a control contour and while twisting the same against each other tangentially. Hammer and / or anvil advantageously each have a striking surface over which a Tangentialschlag is transferable to transmit a peak torque between the hammer and anvil. For example, the percussion gear can be formed in the form of a slotted guide with a thread-like control contour, which is formed on a spindle coupling the drive and the hammer. A percussion gear may also be in the form of a knob arrangement with a slanted control contour formed on a cam and anvil coupling cam. Other forms of impact gear are possible and not limited to the aforementioned advantageous developments.

In the context of a particularly preferred first further development variant of the invention, it is provided that the additional mass has a striking surface, which is coupled in the coupling Condition of additional mass and main mass extends axially equal to or beyond an extension of the main mass. In this variant, the impact surface of the additional mass alone or additionally formed to strike against an anvil impact surface for transmitting a Tangentialschlag. This can be used to a larger-scale design of the face of the additional mass and thus lower stress of the additional mass in carrying out the tangential impact.

In a likewise particularly preferred second further development variant of the invention, it is provided that the main mass has a striking surface which extends axially beyond an extension of the additional mass in the coupled state of additional mass and main mass. In this further development variant, the striking surface of the main mass is designed solely to strike against an anvil striking surface. This second variant can advantageously be used to make the striking surfaces, in particular the anvil striking surface comparatively small. This can be used to advantage in reducing the total mass of the tangential impactor.

embodiments

Embodiments of the invention will now be described below with reference to the drawing. This is not necessarily to scale the embodiments, but the drawing, where appropriate for explanation, executed in a schematized and / or slightly distorted form. With regard to additions to the teachings directly recognizable from the drawing reference is made to the relevant prior art. It should be noted that various modifications and changes may be made in the form and detail of an embodiment without departing from the general idea of the invention. The disclosed in the description, in the drawing and in the claims features of the invention may be essential both individually and in any combination for the development of the invention. In addition, all combinations of at least two of the features disclosed in the description, the drawings and / or the claims fall within the scope of the invention. The general idea of the invention is not limited to the exact form or detail of the preferred embodiment shown and described below or limited to an article which would be limited in comparison to the subject matter claimed in the claims. For the given design ranges, values within the stated limits should also be disclosed as limit values and be arbitrarily usable and claimable. For simplicity, below are for identical or similar parts or parts with identical or similar function used the same reference numerals.

• Fig. 1 eine schematische Darstellung einer Handwerkzeugmaschine mit einem Tangentialschlagwerk gemäß dem Konzept der Erfindung;
• Fig. 2A, Fig. 2B ein Tangentialschlagwerk für eine Handwerkzeugmaschine der Fig. 1 in einem ersten Betriebszustand bzw. einem zweiten Betriebszustand, letzterer mit erhöhter Gesamtmasse des Hammers und erhöhter Federkraft des Tangentialschlagwerks zur Verdeutlichung des Konzepts der Erfindung;
• Fig. 3A, Fig. 3B eine erste bevorzugte konstruktiv realisierte Ausführungsform eines Tangentialschlagwerks gemäß der ersten weiterbildenden Variante der Erfindung jeweils in einer axialen und einer Querschnittsdarstellung und für einen ersten bzw. zweiten Betriebszustand;
• Fig. 4A, Fig. 4B eine zweite bevorzugte konstruktiv realisierte Ausführungsform eines Tangentialschlagwerks gemäß der zweiten weiterbildenden Variante der Erfindung jeweils in einer axialen und einer Querschnittsdarstellung und für einen ersten bzw. zweiten Betriebszustand;
• Fig. 5 ein beispielhaft gemessenes Drehmoment als Funktion der Zeit in Folge der Betätigung des Tangentialschlagwerks beim Eindrehen eines Schraubankers in einen festen Untergrund - in Ansicht A unter Nutzung der Handwerkzeugmaschine mit dem Tangentialschlagwerk in einem ersten Betriebszustand und in Ansicht B in einem zweiten Betriebszustand bei erhöhter Gesamtmasse des Hammers und erhöhter Federkraft des Tangentialschlagwerks gemäß dem Konzept der Erfindung.

Further advantages, features and details of the invention will become apparent from the following description of the preferred embodiments and from the drawing; this shows in:

• Fig. 1 a schematic representation of a hand tool with a Tangentialschlagwerk according to the concept of the invention;
• Fig. 2A, Fig. 2B a Tangentialschlagwerk for a hand tool of the Fig. 1 in a first operating state or a second operating state, the latter with increased overall mass of the hammer and increased spring force of the tangential impact mechanism to clarify the concept of the invention;
• Fig. 3A, Fig. 3B a first preferred constructive realized embodiment of a Tangentialschlagwerks according to the first further developing variant of the invention in each case in an axial and a cross-sectional view and for a first and second operating state;
• Fig. 4A, Fig. 4B a second preferred structurally realized embodiment of a Tangentialschlagwerks according to the second further developing variant of the invention in each case in an axial and a cross-sectional view and for a first and second operating state;
• Fig. 5 an exemplary measured torque as a function of time due to the operation of the tangential impact when screwing a screw anchor in a solid ground - in view A using the hand tool with the Tangentialschlagwerk in a first operating state and in view B in a second operating state with increased total mass of the hammer and increased spring force of the tangential impact according to the concept of the invention.

Fig. 1 shows a hand tool 100, which can be held, for example in the form of a striking screwdriver, on a handle 102 formed by the housing 101 and the drive 104 in this case via a trigger 103 in the form of a lever or Push button can be activated. The drive 104 is formed here with a motor 105 in the form of an electric motor having an in Fig. 2 indicated rotational movement 1 transmits via a gear 106 to a spindle 20. The rotational movement 1 of the spindle 20 is about the in Fig. 2 described tangential impactor 10 implemented in a rotating and partially tangential striking movement of the drive shaft 30; this rotating and partially tangential striking movement of the drive shaft 30 is transmitted to a tool not shown in detail in a tool holder of the power tool 100. The same axis 2 as the spindle and drive shaft 20, 30 mounted in the tool holder 40 tool, such as a screwdriver or such is capable of transmitting higher torques than achievable with the continuous torque output of the motor 105 to, for example, a screw. The tangential impactor 10 can be modeled in the context of a simple spring-mass system and is operated here in the resonant range, which optimizes the torque peak transfer to the tool and the screw. A preferred application of an impact wrench shown is z. As the screwing of screws or setting an anchor in concrete or the like hard ground.

Fig. 2A and Fig. 2B schematically show the operation of an adaptive tangential impactor 10, wherein Fig. 2A the adaptive tangential impactor 10 in a first operating state and Fig. 2B shows the adaptive tangential impactor 10 in a second mode of operation. The adaptive tangential impact mechanism 10, which for the sake of simplicity is also referred to as a tangential striking mechanism, has an anvil 60 assigned to the drive shaft 30 and a hammer 70 assigned to the drive 104 Fig. 2A For simplicity, the hammer 70 is merely shown with its main mass 71. In the setting of the adaptive tangential impactor characterizing the first operating state, the main mass 71 of the hammer 70 is movable axially against the anvil 60 solely under the action of a first external spring 81 and tangentially striking the anvil 60 while the main mass 71 is rotated. The first - outboard - spring 81 is part of a in Fig. 2B The first, outer spring 81 is supported against a fixed stop 83 and is biased in this manner against the main mass 71 of the hammer 70. The first outer spring 81 has a first spring constant K1, which is achieved by means of its rigidity. The main mass 71 of the hammer 70 has a weight designated M1.

The adaptive tangential impactor 10 may also be used in a second in accordance with the concept of the invention Fig. 2B shown operating state in which increases the deliverable torque and yet the natural frequency of the spring-mass system of hammer 70 and spring system 80 is kept substantially constant. For this purpose, an additional mass 72 is additionally positively coupled to the main mass 71 of the hammer 70. The weight of the additional mass 72 is referred to herein as M2. The total mass of the hammer 70 is thus in the second in Fig. 2B shown operating state M1 + M2. The equipped with this total mass hammer 70 is under the action of force of the spring system 80, which now in addition to the first, outer spring 81 has a second - extending within the outer spring spring 82. The spring constant K2 of the second spring 82 is determined by its rigidity and may be greater or smaller than the stiffness of the first spring 81. Thus, if required, a spring constant K2 - as well as the mass M2 of the additional mass 72 - be designed to a natural frequency of the spring Mass system of hammer 70 and spring system 80 in the second operating state in comparison to the first operating state to keep largely the same.

Both springs 81, 82 are in turn supported against the stop 83. In the in Fig. 2B shown second operating state is the sum of the weights of the main mass 7 and additional mass 71, 71 of the hammer 70 under the action of the first and second spring 81, 82, so that the hammer 70 is axially and while twisting the same against the anvil 60 tangentially striking movable. The hammer 70 has - in this case shown symbolically on the main mass 71 - hammer cam 73, which are provided for abutment with this also associated symbolically anvil cam 63. To transmit a peak torque at a tangential impact, a hammer cam 73 has a face 74 transverse to the circumferential direction of the hammer 70. Likewise, an anvil cam 63 may have a face 64, which is set transversely to the circumferential direction and is associated with the striking surface 74. The striking surface can also be formed directly on the body of the anvil 60.

The axial and twisting movement of the hammer 70 is realized in the present case by a percussion gear in the form of a not shown in detail slotted guide on the spindle 20. The slotted guide has a thread-like control contour which forcibly guides the hammer 70 with main mass 71 and 72 to a rotary movement under axial feed to the anvil 60, the movement being driven by the spring system 80. Fig. 3A, Fig. 3B show - each in a cross section I and an axial section ll already on Fig. 2A, Fig. 2B explained operating states of a Tangentialschlagwerks 10A according to a particularly preferred first embodiment of the first further developing variant of the invention. For identical or similar parts or parts of identical or similar function, in the present case the same reference numerals as in FIG FIGS. 2A and 2B used. The mode of operation of the first variant of the adaptive tangential impact device 10A corresponds to the mode of operation as described with reference to FIG Fig. 2A, Fig. 2B was explained. In the following, reference is made in particular to the structural details of the tangential impact mechanism 10A and remainder to the description of the Fig. 2A, Fig. 2B directed.

The tangential impactor 10A points in the in FIGS. 3A and 3B illustrated embodiment, a main mass 71 with the weight M1 = 130g and an additional mass 71 with the weight M2 = 160g. In the present case, therefore, the additional mass 72 has a higher weight than the main mass 71. The tangential impactor 10A is in the in Fig. 3A shown first operating mode operated only with the main mass 71, which is under the action of force only the first spring 81 and is moved axially and with rotation of the main mass 71 tangentially striking against the anvil 60. The corresponding cam 73 of the main mass 71 is in the cross-sectional view I of Fig. 3A at the moment of Tangentialanschlags against a cam 63 of the anvil 60, ie the body of the anvil 60 can be seen. The moment of inertia of the main mass 71 in the present case is about ₁ 40 000 gmm ² . The moment of inertia of the additional mass 72 in the present case is about l ₂ 100 000 gmm ² . The spring stiffness K1 of the first spring 81 is presently about 11 kN / m. The spring stiffness K2 of the second spring 82 is present at 36 kN / m. Im in Fig. 3B shown second state, add the weights M1, M2 of the main mass 71 and the additional mass 72 to the total weight M1 + M2 of the hammer 70. Likewise, the spring stiffnesses K1, K2 of the first and second spring add up to a total spring stiffness K1, K2 of the spring system 80th the likewise adding moments of inertia l ₁ , l ₂ , the adaptive tangential impactor 10 A in the second operating state of the Fig. 3B a significantly increased transmissible torque. Nevertheless, the resonantly operable natural frequency of the spring-mass system of the adaptive tangential impactor 10A in the second operating state largely corresponds to that of the first operating state. An effectively selectable beat frequency of the tangential impactor 10A thus remains largely the same although the transmittable torque is increased.

For the structural realization of the coupling and decoupling of an additional mass 72 with the second spring 82, a housing frame 90 which is displaceable along the spindle 20 and rotatably mounted is realized. The housing cage 90 is freely axially displaceable and rotatably mounted along a control link, not shown. That is, by rotating or moving the fixed to the housing cage and the housing 101 of the power tool 100 by cross-wheel 91 can be actuated the delivery mechanism as soon as the unintentional actuation preventing securing elements 92 are unlocked. In the present case, the securing elements 92 are formed in the form of tilting levers against the housing cage 90. Upon actuation of the feed mechanism via the steering wheel 91, the housing cage 90 can be rotated or displaced beyond the resistance of the rocker arms. For this purpose, the tilting levers attached to a housing 101 of the portable power tool are pushed away from the steering wheel 91 toward the housing.

In contrast to the symbolic representation of Fig. 2A, Fig. 2B is in Fig. 3A, Fig. 3B in the case of the adaptive tangential impactor 10A, the first spring 81 here supports an inner spring and against a stop 83.1 fastened to the spindle 20 and prestressed against the main mass 71. In contrast, the second spring 82 is here an outer spring and supported against a formed by the rear wall of the rear housing cage 90 stop 83.2 and biased against the additional mass 72. By turning and moving the housing cage 90 along the control link so both the additional mass 72 and the auxiliary spring 82 to the formation of the hammer 70 and the spring system 80 to the main mass 71 and the first spring 81 is delivered.

The annular designed main mass 71 and additional mass 72 are present in any case partially concentric with each other. The additional mass 72 surrounds the main mass annularly and positively in the second operating state, while the main mass 71 is guided by a control contour of a slotted guide on the spindle 20.

In the present case, the tangential impact mechanism 10A is fastened to the housing 101 of the handheld power tool 100 with screw connections 107. For this purpose, the screw connections 107 hold a bearing block 108, which on the drive side comprises the bearings 109 for the spindle 20.

In the in FIGS. 3A and 3B In the first embodiment of an adaptive tangential impact device 10A according to the first further development variant of the invention, it is provided that the additional mass 72 has a cross-sectional view I of FIG Fig. 3B apparent striking surface 74 on a hammer cam 75 thereof, which extends in the coupled state of additional mass 72 and main mass 71 over an axial extent of the main mass 71 axially out or - in a modification - can extend to the same height thereof. In the present case, at least the striking surface 74 of the additional mass 72 serves - in a modification by the striking surface of the main mass 71 - for abutment against an anvil striking surface on an anvil cam 63.

Both the main mass 71 and the additional mass 72 can therefore have suitable cams 73 with impact surface 74 for the execution of a tangential impact on the anvil 60. According to the presently described first embodiment of an adaptive tangential impactor 10A, the striking surface 74 may be formed by a cam 75 of the additional mass 72 or - in the modification - both by a cam 73 of the main mass and by a cam 75 of the additional mass 72. Especially in the latter case increases the total available impact surface 74 for tangential impact on the anvil 60 so that the tangential impact torque distribution is distributed over a relatively large area. This ultimately leads to less wear of the cams 73, 75 on the main mass 71 and additional mass 72.

In a slightly modified embodiment, the face of the cam 75 of the additional mass 72 projects slightly relative to the cam 73 of the main mass, so that only the cam 75 of the additional mass 72 has contact with the anvil 60 during tangential impact. In both modifications, the main mass 71 and the additional mass 72 are positively connected to each other by the described feed mechanism. Both the main mass and the additional mass 72 and the first spring 81 and the second spring 82 are available for torque transmission at the tangential 10 A in Fig. 3B shown second operating mode available. Accordingly, the deliverable torque increases in the adaptive tangential impactor 10A. Due to the second spring 82, the release torque of the tangential impactor is also increased. However, this holds in a relatively limited range, so that the handling of a hand tool 100 with the adaptive tangential impactor 10 is practically not affected.

Fig. 4A, Fig. 4B show a second embodiment of an adaptive tangential impactor 10B in one FIGS. 3A and 3B analog representation. For the sake of simplicity, identical reference numerals are used herein for identical or similar parts or parts of identical or similar function. The design of the adaptive tangential impactor 10B is broadly similar to that of the adaptive tangential impactor 10A. In the following, only the differences between the two tangential impact devices are referred to. The essential difference is by comparison of the cross-sectional representation I in FIG FIGS. 4A and 4B recognizable. According to the second further development variant of the invention, in the case of the second embodiment of an adaptive tangential impact mechanism 10B, it is provided that the main mass 71 has a striking surface 74 or a cam 73 which is exclusively-that is to say in FIG Fig. 4A shown first operating state as well as in Fig. 4B shown second operating state - Contact with the anvil 60 has Tangentialschlag. In other words, the concentric and form-fitting coupled to each other main mass and additional mass 71, 72 to form the hammer 70 only with the two cams 73 of the main mass 71 are equipped. The additional mass 72 has no cams. Overall, the impact surfaces of the anvil 60 can thereby be carried out to a lesser extent. Also, the entire spring-mass system of the adaptive percussion mechanism 10B can be made smaller in mass.

In detail, the main mass in the present case has a weight of M1 = 135 g and the additional mass 72 has a weight of M2 = 120 g. In the present case, the additional mass 72 thus has a lower weight than the main mass. Accordingly, the moment of inertia difference between the main mass and the additional mass is not as great as in the adaptive tangential impactor 10A. The moment of inertia of the main mass is about ₁ = 40,000 gmm ² . The moment of inertia of the additional mass is about l ₂ = 75 000 gmm ² . The spring stiffness for forming the spring constant K1 of the first spring is selected here with 11 KN / m. The spring stiffness for forming the spring constant K2 of the second spring is presently formed with 24 KN / m. In both the adaptive tangential impactor 10A and the adaptive tangential impactor 10B, the second spring constant K2 in the spring system is thus greater than the first spring constant K1. In both cases, the preferred impact frequency of the tangential impactor 10A, 10B, that is the natural frequency of the total spring-mass system, in the first and second operating state is approximately equal.

Fig. 5 shows on an equal scale the torque peaks transmitted between hammer 70 and anvil 60 over an equal period of time in an adaptive tangential impactor 10A or 10B. In view A, it can be seen that an average amount of transmitted torque peak in the first operating state corresponds to only about half of an average amount of a torque peak in the second operating state. In the first operating state, only the main mass 71 of the hammer 70 is moved tangentially striking the anvil 60 under the force of the first spring 81 while twisting it. In the second operating state, both the main mass 71 and the additional mass 72 of the hammer 70 are moved axially against the anvil 60 by twisting the first and second springs 81, 82, while twisting the same. The illustrations also show that the beat frequency of an adaptive tangential impactor 10A, 10B is substantially equal and fairly constant in the first and second modes of operation.

The choice of the masses M1, M2 described herein, moments of inertia l ₁ , l ₂ and spring stiffnesses K1, K2 are by no means restricted to the abovementioned values. Rather, through measurements, as in Fig. 5 are shown, that the average values of the torque peaks in the first and second operating modes can be adjusted relative to each other and yet a beat frequency can be kept the same in the first and second operating modes. For this purpose, the masses M1, M2, the corresponding moment of inertia l ₁ , l ₂ and spring stiffnesses K1, K2 can be suitably selected and in particular vary in contrast to the abovementioned values.

Claims (12)

Hand tool (100), in particular in the form of a impact wrench, with - One on a drive shaft (30) mounted tool holder for receiving a tool, in particular a screwdriver, wherein - The drive shaft (30) by means of a drive (104), in particular a motor (105) and / or gear (106), drivable Tangentialschlagwerk (10, 10A, 10B) in a rotating and partially tangential striking movement is displaceable, and in which - The Tangentialschlagwerk (10, 10A, 10B) one of the drive shaft (30) associated anvil (60) and the drive (104) associated hammer (70), the force of at least a first spring (81) axially and with rotation thereof against one another tangentially striking against each other are movable, characterized in that - The hammer (70) has a main mass (71), and - To the main mass (71) an additional mass (72) is releasably coupled, which is under the action of a second spring (82). Hand tool (100) according to claim 1, characterized in that in a first operating state, the main mass (71) of the hammer (70) and the anvil (60) alone under the action of the first spring (81) axially and while rotating the same against each tangential striking against each other movable are. Hand tool (100) according to claim 1 or 2, characterized in that in a second operating state, the main mass (71) and the additional mass (72) of the hammer (70) and anvil (60) under the action of the first and second spring (81, 82). axially and with rotation of the same against each tangential striking against each other are movable. Hand tool (100) according to claim 1 or 2, characterized in that the additional mass (72) by means of a feed mechanism to the main mass (71) is detachably coupled, wherein the feed mechanism on the additional mass (72) acting prestressed second spring (82). Hand tool (100) according to one of claims 1 to 4, characterized in that the feed mechanism is movable along a control link, in particular by a user axially displaceable and / or rotatable. Hand tool (100) according to one of claims 1 to 5, characterized in that the Hautpasse (71) and the additional mass (72) are positively coupled in a second operating state. Powered hand tool (100) according to one of claims 1 to 6, characterized in that the additional mass (72) has a striking surface, in the coupled state of additional mass (72) and main mass (71) over an extension of the main mass (71) against the stop an anvil striking surface extends axially equal to or out. Powered hand tool (100) according to one of claims 1 to 7, characterized in that the main mass (71) has a striking surface, in the coupled state of additional mass (72) and main mass (71) over an extension of the additional mass (72) against the stop extending anvil striking surface axially. Hand tool (100) according to one of claims 1 to 8, characterized in that the feed mechanism comprises a housing cage (90) in which the second spring (82) against the additional mass (72) and the housing cage (90) is biased. Hand tool (10) according to one of claims 1 to 9, characterized in that the feed mechanism is secured in a first operating state of a securing element (92) against movement. Hand tool (100) according to one of claims 1 to 10, characterized in that weights of the masses (71, 72) and stiffnesses of the springs (81, 82) are formed such that a resonance frequency of the tangential impact mechanism (10, 10A, 10B) in a first and second operating state is substantially equal. Hand tool (100) according to one of claims 1 to 11, characterized in that the Tangentialschlagwerk (10, 10A, 10B) on the hammer (70) and / or anvil (60) acting force-transmitting impact gear, by means of which the same according to a control contour axially and by twisting the same against each other tangentially striking against each other are movable.

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