EP3250344B1 - Percussion mechanism device, in particular for an impact wrench - Google Patents

Description

State of the art

From the EP 2168725 A1 is already a Schlagwerkvorrichtung for an impact wrench, with a drivable drive shaft, which has a guide groove, with an output shaft and a beating unit, which includes a rotatably coupled with the output shaft anvil, a hammer and a ball, the hammer over the ball along the Guide groove is mounted on the drive shaft, known. The ball and the groove are easily deformed at a contact surface in operation.

Disclosure of the invention

The invention relates to a percussion device, in particular for an impact wrench, with a drivable drive shaft, which has at least one guide groove, with an output shaft and with a beating unit which comprises a non-rotatably coupled to the output shaft anvil, a hammer and at least one ball, wherein the hammer is mounted on the at least one ball along the at least one guide groove on the drive shaft.

It is proposed that the hammer comprises an at least partially concave curved ball guide surface having at a radially inner point an axial distance to at least one ball, which is greater than a radial distance between the at least one ball and a radially inner point of a concave ball guide surface of the at least one guide groove , This can advantageously a larger contact surface between the at least one ball and the at least one guide groove can be achieved. Thus, a pressure acting on the at least one ball can advantageously spread over a particularly large area. A deformation of the at least one ball can advantageously be kept low. In contrast to the known prior art, a contact surface between the at least one ball and the at least one guide groove can be increased particularly advantageously by about 30%. A lifetime of the percussion device can be advantageously extended. Furthermore, a particularly high impact force can be achieved.

Preferably, the radially innermost point of the curved ball guide surface of the hammer at an axial distance to at least one ball, which is 20% larger, more preferably 50% larger, most preferably twice as large and further advantageously is three times as large as a radial distance between the at least one ball and a radially innermost point of a concave ball guide surface of the at least one guide groove. In this context, a "ball guide surface" is to be understood as meaning, in particular, a surface which is intended to guide the at least one ball. Preferably, the at least one ball guide surface of the guide groove has a continuous curvature. Further advantageous is the at least one ball guide surface of the guide groove free of inflection points and / or flat surfaces.

A "radial distance" should be understood in this context, in particular a distance in a radial direction. A "radial direction" should be understood in this context, in particular a direction which is perpendicular to the axial direction of the drive shaft. An "axial distance" is to be understood in this context, in particular a distance in an axial direction. An "axial direction" should be understood in this context in particular a direction that runs parallel to a main direction of rotation of the drive shaft. Thus, advantageously, a large contact surface between the at least one ball and the ball guide surfaces, in particular with sufficient clearance can be achieved.

In this context, a "radially innermost point" should be understood to mean, in particular, a point which is closest to a main axis of rotation about which the drive shaft executes a main rotational movement in an operating state is and / or that is closest to a rotational symmetry axis of the hammer and / or the drive shaft. Preferably, the at least one ball forms a steel ball. Preferably, the at least one guide groove forms a V-shaped groove. By "intended" is intended to be understood in particular specially designed and / or equipped. The fact that an object is intended for a specific function should in particular mean that the object fulfills and / or executes this specific function in at least one application and / or operating state.

In a further embodiment of the invention, it is proposed that the striking mechanism device has a pressing unit which is provided for radially pressing the at least one ball in the direction of the at least one guide groove. As a result, advantageously, a larger contact surface between the at least one ball and the at least one guide groove can be achieved. The pressing unit preferably exerts a force on the at least one ball in the direction of a main axis of rotation about which the drive shaft executes a main rotational movement in an operating state.

Furthermore, it is proposed that the pressing unit is provided for pressing the at least one ball into the at least one guide groove such that a contact surface extends over at least 2% of a spherical circumference of the ball. As a result, a system pressure between the ball and the at least one guide groove can advantageously be reduced. Preferably, the contact surface extends over at least 5%, more preferably over 10%, most preferably over 20%, further preferably over 24% of a ball circumference of the ball. In this context, a "ball circumference" is to be understood as meaning, in particular, a length of an imaginary great circle of the ball. In this context, a "contact surface" is to be understood as meaning, in particular, a surface on which contact exists between the at least one ball and the at least one guide groove.

Furthermore, it is proposed that the pressing unit comprises a cylindrical inner wall, which is provided for pressing the at least one ball, wherein a diameter of the inner wall at least substantially a double ball diameter plus a smallest possible thickness of the drive shaft corresponds in the region of at least one guide groove. As a result, the pressing unit can be made structurally particularly simple. By "at least substantially" is intended in this context in particular a deviation of less than 0.5 mm, preferably less than 100 microns, more preferably less than 50 microns, more preferably less than 10 microns and most preferably less than 5 microns are understood. Advantageously, a ratio between the double ball diameter plus a smallest possible thickness of the drive shaft and the diameter of the inner wall in the region of at least one guide groove greater than 0.99, more preferably greater than 0.999 and most preferably greater than 0.9999.

In addition, it is proposed that the at least one ball guide surface of the hammer is provided for transmitting a radial contact pressure force to the at least one ball. Thereby, a pressing of the at least one ball can be done in a particularly simple manner. The at least one ball guide surface of the hammer is preferably concavely curved.

In a further embodiment of the invention, it is proposed that the impact mechanism device has at least one spring force element which is provided for exerting the radial contact pressure force on the at least one ball via the at least one ball guide surface of the hammer. As a result, a particularly large contact pressure can be achieved with a structurally small effort. The spring force element preferably forms a helical spring. The spring force element is preferably provided to exert a parallel to the main direction of rotation of the drive shaft extending spring force on the hammer relative to the drive shaft.

Furthermore, it is proposed that the hammer comprises a ball guide surface which, viewed in the circumferential direction, has at least one axial elevation. As a result, a particularly low-wear coupling of the drive shaft can be achieved relative to the hammer in a non-impact operation. Preferably, at least two axial elevations form a central depression of the ball guide surface of the hammer. Further advantageously, the ball guide surface of the hammer forms at least two convex partial surfaces, which extend over a concave partial surface connected to each other.

It is also proposed that the drive shaft comprises at least two guide grooves and that the impact unit has at least two balls, which are mounted at least in an operating state within the at least two guide grooves. As a result, a contact pressure can advantageously be distributed over a particularly large contact area. Preferably, the at least two guide grooves are arranged offset in the circumferential direction by 180 ° to each other.

In addition, it is proposed that the at least one guide groove has a semicircular groove base. As a result, a particularly large contact surface between the at least one ball and the at least one guide groove can be achieved. Preferably, a radial extent of the at least one guide groove is greater than a spherical radius of the at least one ball.

Furthermore, an impact wrench is proposed with an impact mechanism according to the invention. The impact wrench is advantageously designed battery operated. The impact wrench particularly preferably forms a rotary impact wrench or a cordless impact wrench.

The impact mechanism according to the invention should not be limited to the application and embodiment described above. In particular, in order to fulfill a mode of operation described herein, the percussion mechanism according to the invention may have a number deviating from a number of individual elements, components and units mentioned herein.

drawing

Further advantages emerge from the following description of the drawing. In the drawing, an embodiment of the invention is shown. The drawing, the description and the claims contain numerous features in combination. The person skilled in the art will expediently also consider the features individually and combine them into meaningful further combinations.

Fig. 1

eine schematische Seitenansicht eines Schlagschraubers mit einer Schlagwerkvorrichtung,

Fig. 2

die Schlagwerkvorrichtung in einer Schnittdarstellung,

Fig. 3

eine Antriebswelle der Schlagwerkvorrichtung in einer Detailansicht,

Fig. 4

ein Diagramm mit Informationen über eine Anpresskraft in Relation zu einem axialen Versatz und

Fig. 5

eine Detailansicht der Antriebswelle, eines Hammers der Schlagwerkvorrichtung und zweier Kugeln.

Show it:

Fig. 1

a schematic side view of an impact wrench with a percussion device,

Fig. 2

the impact mechanism in a sectional view,

Fig. 3

a drive shaft of the impact mechanism in a detailed view,

Fig. 4

a diagram with information about a contact force in relation to an axial offset and

Fig. 5

a detailed view of the drive shaft, a hammer of Schlagwerkvorrichtung and two balls.

Description of the embodiment

The FIG. 1 shows a hand tool, which is designed as impact wrench 10. The impact wrench 10 has a housing 64 with a handle 66. The impact wrench 10 has a hammer mechanism. The impact wrench 10 is mechanically and electrically connected to an accumulator 68 for mains-independent power supply. The impact wrench 10 is exemplified as a cordless impact wrench. It should be noted, however, that the present invention is not limited to cordless rotary impact wrenches, but rather can be used in different embodiments of impact wrenches, regardless of whether the corresponding impact wrench is network-independent or network-dependent operable. In addition, it should be understood that the present invention is not limited to motor powered impact wrenches but is generally applicable to tools to which the percussion mechanism illustrated in the following figures may find application.

The hammer mechanism is disposed within the housing 64. Furthermore, an electric drive motor 70 supplied with power by the accumulator 68, a gear 72 and a striking unit 20 of the percussion mechanism are arranged in the housing 64. The drive motor 70 can be actuated, for example, via a manual switch 74, that is, switched on and off. The drive motor 70 may be any type of engine, e.g. As an electronically commutated motor or a DC motor. The drive motor 70 is so electronically controlled and / or regulated that both a reversing operation and specifications with respect to a desired rotational speed can be adjusted. The mode of operation and the construction of a suitable drive motor 70 are sufficiently known from the prior art, so that a more detailed description is dispensed with. The drive motor 70 is connected via an associated motor shaft 76 with the gear 72, which converts a rotation of the motor shaft 76 in a rotation provided between the gear 72 and beating unit 20 drivable drive shaft 12 of the percussion device. This conversion is preferably such that the drive shaft 12 rotates relative to the motor shaft 76 with increased torque but reduced rotational speed.

The Schlagwerkvorrichtung forms a rotary and / or rotary impact. The beating unit 20 is intended to generate sudden high-intensity rotational pulses and to transmit them to an output shaft 18 of the percussion mechanism. On the output shaft 18, a tool holder 78 is provided, which is designed for receiving insert tools. The tool holder 78 is both with an insert tool with external coupling, z. B. a screwdriver bit, as well as with an insert tool with internal coupling, z. B. a socket, connectable. In this embodiment, the tool holder 78 is connectable to an insert tool 80 with external polygon coupling.

In the FIG. 2 the hammer mechanism is shown in more detail. The drive shaft 12 has two guide grooves 14, 16. The guide grooves 14, 16 each have a semicircular groove bottom 62, 82. The respective groove bottom 62, 82 deviates from an exact semicircle. The impact unit 20 has two balls 26, 28, which are each guided in one of the guide grooves 14, 16. The guide grooves 14, 16 thus each form a ball guide surface 52, 84. The balls 26, 28 are formed by steel balls. A radius of curvature of the respective groove bottom 62, 82 is slightly larger than a ball radius of the balls 26, 28. In other words, a radial extent of the respective guide groove 14, 16 is greater than a ball radius of the respective ball 26, 28. The balls 26, 28 are thus theoretically at only one point on the ball guide surfaces 52, 84.

The grooves 14, 16 extend in a main extension both in an axial direction 54 of the drive shaft 12 and in a circumferential direction 60 of the drive shaft 12. In this case, the respective groove 14, 16 in the respective main extension to a V-shape. The axial direction 54 is parallel to a main direction of rotation of the drive shaft 12. Since the guide grooves 14, 16 and the balls 26, 28 are the same, is hereinafter for the sake of simplicity, only on the formation of the area around in the FIG. 2 shown upper guide groove 14 and the ball 26 reference.

For transmitting impacts, the impact unit 20 has an anvil 22 rotatably coupled to the output shaft 18. The anvil 22 extends in this view perpendicular to the section plane and is therefore not completely visible. Furthermore, the beating unit 20 comprises a hammer 24. The hammer 24 is cylindrical. Further, the hammer 24 and the drive shaft 12 are arranged coaxially with each other. The output shaft 18 and the drive shaft 12 are arranged coaxially with each other. The hammer 24 is mounted on the drive shaft 12 via the ball 26 along the guide groove 14. The hammer 24 is limited relative to the drive shaft 12 in the axial direction 54 movable. Furthermore, the hammer 24 is limited to rotate relative to the drive shaft 12 limited by a parallel to the axial direction 54 extending main axis of rotation. To guide the ball 26, the hammer 24 has a ball guide surface 44. The ball guide surface 44 is partially concave curved. A radius of curvature of the ball guide surface 44 is greater than a ball radius of the ball 26. The ball 26 is thus theoretically at only one contact point on the ball guide surface 44 of the hammer 24. Like in the FIG. 3 shown, the ball 26 is movably mounted within the guide groove 14.

The percussion device comprises a pressing unit 30, which is provided for the radial pressing of the ball 26 in the direction of the guide groove 14. This results from a deformation of the ball 26 and the guide groove 14, a contact surface 32 to the theoretical contact point. The pressing unit 30 is provided to press the ball 26 into the guide groove 14 such that the contact surface 32 extends over at least 2% of a ball circumference of the ball 26. The pressing unit 30 comprises a cylindrical inner wall 34, which is provided for pressing the ball 26. A diameter 36 of the inner wall 34 substantially corresponds to a double ball diameter 38 of the ball 26 plus a minimum possible thickness 40 of the drive shaft 12 in the region 42 of the guide groove 14. More specifically, the diameter 36 is less than 5 microns larger than the double ball diameter 38 of the ball 26 plus the smallest possible thickness 40 of the drive shaft 12 in the region 42 of the guide groove 14. A ratio between the double ball diameter 38 plus the smallest possible thickness 40 of the drive shaft 12 and the diameter 36 of the inner wall 34 in the region 42 of the guide groove 14th is greater than 0.9999.

In contrast to the known prior art, the contact surface 32 between the ball 26 and the guide groove 14 can be increased by about 30%. The FIG. 4 shows a curve of a total force, which results from the contact of the ball 26 in the guide groove 14 in relation to an axial offset. The ordinate axis represents the total force. The abscissa axis represents the axial displacement of the hammer 24 in one operation. The progression of the total force from a known percussion device is shown in the upper line 86. Due to the small contact surface in the prior art, overall higher loading forces result than in the lower line 88, which represents the total force in the impact mechanism according to the invention.

The percussion device has a spring force element 58. The spring force element 58 is provided for exerting the radial contact pressure on the ball 26 via the ball guide surface 44 of the hammer 24. The spring force element 58 forms a helical spring. The spring force element 58 is provided to exert a parallel to the axial direction 54 of the drive shaft 12 extending spring force on the hammer 24 relative to the drive shaft 12. The hammer 24 comprises a ball guide surface 44 which has two axial elevations in a circumferential direction 60. The two axial protrusions form a central depression of the ball guide surface 44 of the hammer 24. The ball guide surface 44 of the hammer 24 in this case forms two convex partial surfaces, which are connected to one another via a concave partial surface. The ball guide surface 44 of the hammer 24 is provided for transmitting the radial contact pressure to the ball 26. The ball guide surface 44 of the hammer 24 is partially concave curved.

Like in the FIG. 5 shown in more detail, has the partially concave curved ball guide surface 44 of the hammer 24 from a radially innermost point an axial distance 48 to the ball 26, which is greater than a radial distance 50 between the Ball 26 and a radially innermost point of the concave ball guide surface 52 of the guide groove 14. In other words, the concave curved ball guide surface 44 of the hammer 24 in an operating condition of a parallel to a radial direction 90 of the drive shaft 12 extending portion 46 an axial distance 48 to the ball 26, the is greater than a radial distance 50 between the ball 26 and the concave ball guide surface 52 of the guide groove 14 in a parallel to the axial direction 54 extending portion 56. The axial distance 48 from the radially inner point of the curved ball guide surface 44 is more than three times as large as the radial distance 50 between the Ball 26 and the radially innermost point of the concave ball guide surface 52 of the guide groove 14, 16th

Claims (10)

1. Percussion mechanism device, in particular for an impact screwdriver (10), having a drivable drive shaft (12) which has at least one guide slot (14, 16), having an output shaft (18) and having a percussion unit (20) which comprises an anvil (22) coupled to the output shaft (18) for conjoint rotation, a hammer (24) and at least one ball (26, 28), wherein the hammer (24) is mounted on the drive shaft (12) along the at least one guide slot (14, 16) via the at least one ball (26, 28), characterized in that the hammer (24) comprises an at least regionally concavely curved ball guide surface (44) which, at a radially innermost point, exhibits an axial spacing (48) from the at least one ball (26, 28) that is greater than a radial spacing (50) between the at least one ball (26, 28) and a radially innermost point of a concave ball guide surface (52) of the at least one guide slot (14, 16) .
2. Percussion mechanism device according to Claim 1, characterized by a pressing unit (30) which is provided to radially press the at least one ball (26, 28) in the direction of the at least one guide slot (14, 16).
3. Percussion mechanism device according to Claim 2, characterized in that the pressing unit (30) is intended to press the at least one ball (26, 28) into the guide slot (14, 16) such that a contact face (32) extends around at least 2% of a ball circumference of the at least one ball (26, 28).
4. Percussion mechanism device according to Claim 2 or 3, characterized in that the pressing unit (30) comprises a cylindrical inner wall (34) which is intended to press against the at least one ball (26, 28), wherein a diameter (36) of the inner wall (34) corresponds at least substantially to twice the ball diameter (38) plus a smallest possible thickness (40) of the drive shaft (12) in a region (42) of the at least one guide slot (14, 16).
5. Percussion mechanism device according to one of the preceding claims, characterized in that the at least one ball guide surface (44) of the hammer (24) is intended to transmit a radial pressing force to the at least one ball (26, 28).
6. Percussion mechanism device according to Claim 5, characterized by at least one spring-force element (58) which is provided to exert the radial pressing force on the at least one ball (26, 28) via the at least one ball guide surface (44) of the hammer (24) .
7. Percussion mechanism device according to one of the preceding claims, characterized in that the hammer (24) comprises a ball guide surface (44) which, as seen in a circumferential direction (60), has at least one axial elevation.
8. Percussion mechanism device according to one of the preceding claims, characterized in that the drive shaft (12) comprises at least two guide slots (14, 16), and in that the percussion unit (20) has at least two balls (26, 28) which are mounted within the guide slots (14, 16) at least in an operating state.
9. Percussion mechanism device according to one of the preceding claims, characterized in that the guide slot (14, 16) has a semicircular slot bottom (62, 82) .
10. Impact screwdriver (10) having a percussion mechanism device according to one of the preceding claims.

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