Power tools equipped with pulse units

Abstract

This specification relates to a handheld power tool (1) that supplies pulsed torque, the handheld power tool (1) comprising an elongated housing (10), an angle head (20) and a power transmission device (30) located at the front end of the housing, the power transmission device (30) comprising a motor (31) located within the housing, a bevel gear (33) located within the angle head, and a pulse unit (40) arranged to be driven by the bevel gear. The power transmission device further comprises a torsion spring assembly (50) arranged to transmit power between a first component and a second component of the power transmission device, the elasticity of which allows for limited relative rotation between the two components.

Description

Technical Field

[0001] The present invention generally relates to power tools for screw fastening, and more particularly to an angle-type power tool equipped with a hydraulic pulse unit.

Background Art

[0002] Electric tools for screw fastening are known to be used in various industries. For example, an impulse-type power wrench equipped with a hydraulic pulse unit is widely used in continuous mass production.

[0003] In such pulse tools, torque is intermittently transmitted to the output shaft by a pulse generating mechanism, that is, in a pulsed manner. Since the pulse is very short, there is almost no reaction force on the handle, and only a much lower motor torque is transmitted to the operator's hand. In addition, there is less vibration and noise compared to an impact wrench. However, for example, when compared with impact tools, although the vibration during operation is considerably reduced, the problem of vibration still remains.

[0004] Examples of general impact tool usage are well known. Japanese Patent Publication No. 2004-255544 discloses a handheld tool with an angled head configuration in which vibration is minimized by using a first washer elastically held by an O-ring on the top of the spindle and a second washer holding a second bevel gear.

[0005] Another angle head drill hammer tool, known from Japanese Utility Model Publication No. 03-117572U, is a medium-sized drill hammer in which the impact mechanism and drive motor are arranged perpendicular to each other, and a suitable gear reduction ratio results in a compact and easy-to-handle structure.

[0006] One particularly problematic application is when the pulse unit is used in an angle tool. An angle tool is a tool equipped with an angle head attachment mechanism and is mainly used for reasons of accessibility. Generally, these are constructed as straight tools with an angle head attachment mechanism, and in some applications, the pulse unit is attached to the angle head.

[0007] Specifically, since the pulse unit stops between each pulse, the motor of the tool that rotates at high speed also stops, and particularly intense vibrations occur, which are transmitted to the operator.

Summary of the Invention

Problems to be Solved by the Invention

[0008] Therefore, there is a need for improvement in the field of angle-type power tools equipped with hydraulic pulse units. [Means for solving the problem]

[0009] Therefore, it is desirable to provide an improved angle-type pulse tool. More specifically, it is desirable to provide a tool with reduced vibration levels. To address at least one of these challenges, a power tool according to independent claim 1 is provided. Preferred embodiments are defined in the dependent claims.

[0010] According to a first aspect of the present invention, a handheld power tool is provided that supplies pulsed torque. The tool comprises an elongated housing, an angle head positioned at the front end of the housing, and a power transmission device, the power transmission device comprising a motor positioned within the housing, a bevel gear positioned within the angle head, and a pulse unit, the pulse unit being positioned to be driven by the bevel gear, the power transmission device further comprising a torsion spring assembly positioned to transmit power between a first component and a second component of the power transmission device, the elasticity of which allows limited relative rotation between the two components.

[0011] According to a first aspect, a power tool (or impulse tool, pulse tool, power wrench, fastening tool; these terms are used interchangeably throughout this specification) provides an inventive solution to the above-mentioned problem by incorporating a torsion spring assembly between two components of a power transmission device when viewed in the direction of power transmission.

[0012] More specifically, a design in which the two components of a power transmission device are operatively connected or coupled by a torsion spring assembly allows for limited relative motion between the motor and the pulse unit, so that the motor can continue rotating in the driving direction during a pulse (against the biasing or elasticity of the spring assembly) instead of stopping with each pulse. Thus, the motor can rotate at a nearly constant speed when pulses are supplied. This results in a constant or at least substantially constant torque transmitted to the operator, significantly reducing the vibration experienced by the operator.

[0013] To be positioned or placed between two components of a power transmission device should be understood as the torsion spring assembly being positioned to operatively connect or link the two components of the power transmission device, that is, being positioned between the two components in the power transmission direction of the power transmission device.

[0014] The two components can be any components of a power transmission device. For example, they could be two components positioned between a motor and a pulse unit when viewed in the power transmission direction. These could also be two components positioned adjacent to each other (in a conventional power transmission device) when viewed in the power transmission direction. In some embodiments, one of the two components can be a motor and / or pulse unit that also constitutes part of the power transmission device.

[0015] The housing can be an elongated, substantially cylindrical housing, and the angle head can be attached to the front end of the housing (fixed or detachable), and the power transmission device can be at least partially located in the space (i.e., inside) formed by the housing and the angle head, and can extend through that space. The angle head can be attached to the front end of the housing and supports the output shaft of a bevel gear to which the pulse unit can be operably coupled in a laterally extended position. The angle head may further comprise a casing.

[0016] The referenced power tool or pulse tool may be an electrically powered pulse tool or a pneumatically powered pulse tool for fastening screw fasteners. According to one embodiment, the power tool is a handheld power tool. According to one embodiment, the power tool is a battery-powered power tool.

[0017] According to one embodiment, the power transmission device further comprises a planetary gear unit. The planetary gear unit is positioned, for example, between a motor and a bevel gear unit in the power transmission direction, and can operatively couple them.

[0018] According to one embodiment, the torsion spring assembly is positioned between the planetary gear unit and the bevel gear unit in the power transmission direction of the power transmission device.

[0019] According to one embodiment, the torsion spring assembly is positioned between the planetary gear unit and the motor in the power transmission direction of the power transmission device.

[0020] According to one embodiment, the torsion spring assembly is positioned between the bevel gear and the pulse unit.

[0021] According to one embodiment, the torsion spring assembly comprises a torsion spring element, such as a torsion spring. In some embodiments, the torsion spring is a torsion coil spring. The stiffness of the torsion spring element is preferably selected to be stiff enough to transmit sufficient torque from the motor to the pulse unit, but flexible enough to allow sufficient relative rotation between pulses. In one embodiment, the number of turns of the torsion coil spring is in the range of 10-40, in one embodiment, the number of turns is in the range of 15-35, and in one embodiment, the number of turns is in the range of 25-30.

[0022] In one embodiment, the torsion spring of the torsion spring assembly is a clock spring, and may be a progressive clock spring. In some embodiments, the torsion spring assembly can include a torsional resistance screw mechanism. In one embodiment, the torsion spring assembly includes a compression spring actuated by an element including a cam surface arranged to compress the compression spring. In some embodiments, the cam surface further includes a groove, and a ball or roller arranged to compress the compression spring can be disposed in the groove. The compression spring can be a disc spring or a leaf spring.

[0023] According to one embodiment, the torsion spring assembly includes a torsion bar.

[0024] According to one embodiment, the torsion spring assembly further includes a centering shaft assembly around which a torsion coil spring is wound. Thereby, the spring is centered and undesirable bending or buckling of the spring is prevented.

[0025] According to one embodiment, the shaft assembly includes a shaft element attached to a first component and a tube element attached to a second component, and at least a part of the shaft element extends into the tube element. The coil spring can be attached to the shaft element at a first end and to the tube element at a second end.

[0026] According to one embodiment, the power tool is configured to supply torque pulses in the range of 100 - 300 Nm, for example in the range of 150 - 250 Nm. Since the vibration level increases in tools used for high-torque fastening, the present invention can be particularly advantageous when implemented in such tools.

[0027] According to one embodiment, the pulse unit is a hydraulic pulse unit. According to one embodiment, the hydraulic pulse unit includes an inertial drive member coupled to the output shaft of the spur gear and rotatable about the rotation axis, an oil chamber surrounded by the inertial drive member, and impulse generating means arranged to intermittently transmit kinetic energy to the impulse receiving portion of the output shaft housed in the oil chamber.

[0028] According to one embodiment, the power tool is a tool with a transducer, that is, it includes one or more sensors for acquiring data related to the operation of the tool. According to one embodiment, the power tool includes a torque transducer or sensor, and / or a current sensor. For example, the sensor can be arranged to measure the angular velocity of the pulse unit, and the introduction torque can be obtained from the derivative value of the speed. Since the present invention not only reduces the friction that may affect the measurement but also makes it more uniform, it is particularly advantageous when implemented in a tool with a transducer.

[0029] The further objects, features and advantages of the present invention should become apparent by considering the following detailed disclosure, drawings and appended claims. Those skilled in the art can understand that various features of the present invention can be combined to create embodiments other than those described below.

[0030] The present invention will be described in an exemplary and non-limiting detailed description of the following exemplary embodiments with reference to the accompanying drawings.

Brief Description of Drawings

[0031] [Figure 1a] It is a perspective view of an exemplary power tool. [Figure 1b] It is a cross-sectional side view of an exemplary power tool. [Figure 2a] It is a perspective view of an exemplary power tool. [Figure 2b] It is a cross-sectional side view of an exemplary power tool. [Modes for carrying out the invention]

[0032] All drawings are schematic and not necessarily to scale. Generally, only the parts necessary to clarify the invention are shown, and other parts may be omitted or merely suggested.

[0033] Figure 1a shows an exemplary pulse tool 1 according to one embodiment, in which case it is an electrically powered handheld angle tool 1 comprising an elongated cylindrical housing 100 having a front end 100a.

[0034] As can be seen from Figure 1b, the power transmission device 30 is partially located in the space formed between the housing 100 and the angle head 20, and therefore extends through this space. The power transmission device comprises a motor 31 located at the rear 100b of the housing, a planetary gear unit 32 operatively coupled to the motor 31, a bevel gear 33 located within the angle head 20, and a pulse unit 40 operatively coupled and positioned to be driven by the laterally extending output end of the bevel gear 33. The pulse unit 40 extending to the angle head output forming section of the power transmission device 30 is a hydraulic pulse unit 40 comprising an inertial drive member coupled to the output shaft of the bevel gear 33 and rotatable around the rotation axis, an oil chamber surrounded within the inertial drive member, and an impulse generating means arranged to intermittently transmit kinetic energy to an impulse receiving section of the output shaft housed within the oil chamber. The operation of such impulse mechanisms is already known, so a detailed explanation will be omitted. Similar mechanisms have already been described, for example, in U.S. Patent No. 6,110,045 and U.S. Patent No. 13,697,107.

[0035] Furthermore, the power transmission device of the illustrated embodiment includes a torsion spring assembly 50 that is positioned between the planetary gear unit 32 and the bevel gear unit 33 and operably coupled to them when viewed in the driving direction of the power transmission device.

[0036] The torsion spring assembly 50 comprises a centering shaft assembly 52 around which a torsion coil spring 51 is wound. In the illustrated embodiment, the shaft assembly 52 comprises a shaft element 52a attached to a planetary gear unit 32 and a tubular element 52b attached to a bevel gear 33. The coil spring 51 is attached to the shaft element at a first end and to the tubular element 52b at a second end and extends for most of the length of the shaft assembly. The shaft element 52a extends into the tubular element 52b, and these two overlapping elements can rotate relative to each other against the biasing force of the torsion spring 51. In the illustrated embodiment, the shaft assembly 52 is attached to the planetary gear unit 32 and the bevel gear 33 via splines.

[0037] As a result, the torsion spring assembly 50 is positioned to transmit power between the planetary gear unit 32 and the bevel gear unit 33 in a manner that allows for a limited relative rotation between them due to the elasticity of the torsion spring assembly 50. This allows the motor 31, which is operatively coupled to the planetary gear unit 32, to rotate a limited distance relative to the pulse unit 40, which is operatively coupled to the bevel gear 33. Consequently, the motor 31 can continue to rotate forward even during pulse operation in which the pulse unit 40 intermittently stops.

[0038] Figure 2a shows an exemplary pulse tool 1 according to another embodiment, and, similar to the embodiments in Figures 1a and 1b, the electric handheld angle tool 1 comprises an elongated cylindrical housing 100 having a front end 100a. The angle head 20 is positioned at the front end of the housing 100a.

[0039] As can be seen from Figure 2b, the power transmission device 30 is partially located in the space formed between the housing 100 and the angle head 20, and therefore extends through this space. The power transmission device comprises a motor 31 located at the rear 100b of the housing, a planetary gear unit 32 operatively coupled to the motor 31, a bevel gear 33 located within the angle head 20, and a pulse unit 40 operatively coupled and positioned to be driven by the laterally extending output end of the bevel gear 33. The pulse unit 40 is the hydraulic pulse unit described in Figure 1.

[0040] Furthermore, the power transmission device of the illustrated embodiment includes an offset gear assembly 60 positioned between the bevel gear unit 33 and the pulse unit 40, and operably coupled to them, when viewed in the driving direction of the power transmission device. As can be seen from Figures 2a and 2b, the orientation of the pulse unit 40 is reversed compared to the embodiment in Figure 1, which allows for a convenient compact design.

[0041] Similar to the embodiments shown in Figures 1a and 1b, the power transmission device 30 in the illustrated embodiment further comprises a torsion spring assembly 50 which is positioned between the planetary gear unit 32 and the bevel gear unit 33 and operably coupled to them when viewed in the driving direction of the power transmission device.

[0042] The design and function of the torsion spring assembly 50 shown in Figure 2b are basically the same as those of the embodiment shown in Figure 1b.

[0043] Although the present invention is illustrated and described in detail in the drawings and the above description, such illustrations and descriptions are illustrative or exemplary and not limiting, and the present invention is not limited to the disclosed embodiments. A person skilled in the art will understand that many modifications, variations, and changes are conceivable within the scope defined in the appended claims. In addition, variations of the disclosed embodiments can be understood and implemented by a person skilled in the art when carrying out the claimed invention by examining the drawings, the disclosure and the appended claims. In the claims, the term “equipped with” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude the plural. The fact that certain means are described in different dependent claims does not mean that these means cannot be combined and used advantageously. Any reference numerals in the claims should not be construed as limiting the scope of the claims. [Explanation of Symbols]

[0044] 1. Handheld power tools 10. Long and slender housing 20 Angle Head 30 Power transmission device 31 Motor 33 Bevel gear 40 pulse units 50 Torsion spring assembly

Claims

1. A handheld power tool (1) that supplies pulsed torque, A long, slender housing (10), An angle head (20) positioned at the front end of the housing, Power transmission device (30), The power transmission device (30) is equipped with, A motor (31) is located inside the housing, A bevel gear (33) is positioned inside the angle head, A pulse unit (40) is arranged to be driven by the bevel gear, Equipped with, A handheld power tool, wherein the power transmission device further comprises a torsion spring assembly (50) arranged to transmit power between a first component and a second component of the power transmission device, and the elasticity of the torsion spring assembly (50) allows for limited relative rotation between the first component and the second component.

2. The handheld power tool according to claim 1, wherein the power transmission device further comprises a planetary gear unit (32).

3. The handheld power tool according to claim 2, wherein the torsion spring assembly is disposed between the planetary gear unit and the bevel gear unit.

4. The handheld power tool according to claim 2, wherein the torsion spring assembly is positioned between the planetary gear unit and the motor.

5. The torsion spring assembly is positioned between the bevel gear and the pulse unit, as described in claim 1.

6. The torsion spring assembly comprises a torsion coil spring (51), as described in any one of claims 1 to 5.

7. The handheld power tool according to claim 6, wherein the torsion spring assembly further comprises a centering shaft assembly (52) on which the torsion coil spring is wound.

8. The handheld power tool according to claim 7, wherein the shaft assembly comprises a shaft element (52a) attached to the first component and a tubular element (52b) attached to the second component, and at least a portion of the shaft element extends into the tubular element.

9. The torsion spring assembly comprises a torsion bar, as described in any one of claims 1 to 4.

10. The handheld power tool according to any one of claims 1 to 9, wherein the power tool is a handheld electric power tool.

11. The handheld power tool according to claim 9, wherein the power tool is a battery-powered tool.

12. The handheld power tool according to any one of claims 1 to 11, wherein the power tool is configured to supply torque pulses in the range of 100-300 Nm, for example, in the range of 150-250 Nm.

13. The handheld power tool according to any one of claims 1 to 12, wherein the pulse unit is a hydraulic pulse unit.

14. The handheld power tool according to claim 13, wherein the hydraulic pulse unit comprises an inertial drive member coupled to the output shaft of the bevel gear and rotatable around the rotation axis, an oil chamber surrounded by the inertial drive member, and an impulse generating means arranged to intermittently transmit kinetic energy to an impulse receiving portion of the output shaft housed in the oil chamber.

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