Power tools equipped with hydraulic pulse units

Abstract

This specification relates to an impulse tool including a hydraulic pulse unit arranged to intermittently transmit torque pulses to a tool output shaft, the hydraulic pulse unit having an inertial drive member including a hydraulic fluid chamber and intermittently coupled to the output shaft via a hydraulic pulse generating mechanism that divides the hydraulic fluid chamber into a low-pressure chamber and a high-pressure chamber. A bypass passage is provided for transmitting hydraulic fluid between the high-pressure chamber and the low-pressure chamber, and the hydraulic pulse generating mechanism further includes a first check valve arranged to allow a first flow from the low-pressure side to the high-pressure side, and a second check valve arranged to allow a second flow from the low-pressure side to the high-pressure side. This specification also relates to a combined valve unit and bushing used in the valve unit of the pulse tool.

Description

[Technical Field]

[0001] The present invention relates generally to power tools for tightening threaded fasteners, and more particularly to impulse-type power tools having a hydraulic pulse unit. [Background technology]

[0002] Power tools for tightening are known to be used in a variety of industrial fields, for example, impulse-type power wrenches equipped with hydraulic pulse units are commonly used in continuous mass production.

[0003] The hydraulic unit of such a tool is filled with oil. In such a pulse tool, torque pulses can be supplied to the output shaft by a pulse generating mechanism that divides a fluid chamber into a low-pressure side and a high-pressure side, and during operation, fluid can flow between the low-pressure side and the high-pressure side.

[0004] However, such fluid flow is often accompanied by losses that significantly affect the efficiency of the pulse tool.

[0005] To alleviate some of the problems, solutions have been proposed that include various designs and combinations of fluid passages and / or valves arranged to allow fluid flow between the low pressure side and the high pressure side, however, known problems with pulse tools that include this type of design include increased complexity and reduced durability. Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, a need exists for improvements in the field of power tools with hydraulic pulse units. [Means for solving the problem]

[0007] It would therefore be desirable to provide a pulse tool in which losses due to flow restriction are kept low. In particular, it would be desirable to provide such an improved pulse tool in a less complex and more durable manner. In order to better solve one or more of these problems, a pulse tool and a valve unit are provided according to the independent claims. Preferred embodiments are defined in the dependent claims.

[0008] According to a first aspect of the present invention, there is provided a pulse tool comprising a motor, an output shaft, and a hydraulic pulse unit coupled to the motor and arranged to intermittently transmit torque pulses to the output shaft. The hydraulic pulse unit comprises an inertial drive member connected to the motor, the drive member comprising a hydraulic fluid chamber, an impulse receiving portion of the output shaft extending coaxially within the hydraulic fluid chamber, the impulse receiving portion being intermittently coupled to the drive member via a hydraulic pulse generating mechanism that divides the hydraulic fluid chamber into at least one low-pressure chamber and at least one high-pressure chamber, a bypass passage providing fluid communication between the high-pressure chamber and the low-pressure chamber, and the hydraulic pulse generating mechanism further comprising a first check valve arranged to allow a first flow from the low-pressure side to the high-pressure side and a second check valve arranged to allow a second flow from the low-pressure side to the high-pressure side.

[0009] According to a first aspect, an impulse tool (or pulse tool, power wrench, power tool or fastening tool, these terms are used interchangeably throughout this specification) provides an inventive solution to the above-mentioned problems by virtue of its design incorporating fluid passages designed to ensure the desired flow between the low pressure side and the high pressure side.

[0010] More specifically, the dual check valve design allows for greater flow from the low pressure side to the high pressure side, thus reducing losses in the pulse unit, significantly improving the performance of the power tool.

[0011] The referenced pulse tool may be an electrically driven pulse tool or a pneumatically driven pulse tool. The pulse tool may further include a housing having a front end and a rear end, and the output shaft may be located at the front end of the housing. Furthermore, the high and low pressure chambers may also be referred to as high and low pressure compartments, high and low pressure sides, or high and low pressure sections.

[0012] The first and second check valves can be positioned to facilitate sufficient flow from the low pressure side, for example, in one embodiment, they can be positioned on opposite sides of the chamber, i.e., 180 degrees apart.

[0013] In one embodiment, the impulse receiver can be formed as an integral part of the output shaft and can extend into the fluid chamber through a central opening in the front end wall of the inertial drive member. The output member can further comprise a transverse cylinder bore in which a movably guided piston is disposed. The piston can be reciprocated in the cylinder bore by a cam with two cam lobes formed on the inner wall of the fluid chamber, for example, which acts on the piston via rollers to drive the hem inward, thereby generating pressure peaks. A central cam spindle can be rotatably supported on the output member to return the piston and roller to their outward positions.

[0014] According to one embodiment, the bypass passage is separate from the first and second flows. For example, the bypass passage or leak flow can be located at a different location from the first and second check valves. In some embodiments, the leak flow is provided by a separate component.

[0015] According to one embodiment, the bypass passage and at least a part of one of the first and second check valves are formed by a single component. For example, the first and / or second check valves can be valve units, and the bypass passage can be formed in (or extend through) one of these units. This makes it possible to ensure a sufficient flow in a particularly compact way.

[0016] According to one embodiment, the single component comprises a body having a central bore for permitting hydraulic fluid flow, a valve body arranged to selectively close the central bore, and a bypass passageway for communicating fluid between the high pressure chamber and the low pressure chamber through the single component.

[0017] In one embodiment, the body has a cylindrical shape.

[0018] According to one embodiment, at least one bypass passage extends axially through said body, for example, the bypass passage may extend along the axis of the cylindrical body.

[0019] In one embodiment, the flow through the bypass passage may flow substantially parallel to the flow through the check valve.

[0020] According to one embodiment, the bypass passage is disposed radially outward of the central hole, where radial refers to the radius of the central hole.

[0021] According to one embodiment, at least two bypass passages are equally spaced along the circumference C1 of said central bore, along which should be understood as along a part of the body adjacent to said circumference C1.

[0022] According to one embodiment, the at least one central hole forms part of a conical valve seat, and the at least one bypass passage is disposed along a portion of the conical valve seat adjacent to the outer periphery C2, i.e., along a portion of the body adjacent to the circumference C2.

[0023] According to one embodiment, the bypass passage is formed by at least one leak hole for allowing a leak flow through said single component, a leak hole being understood as a small hole that allows a small flow from the high pressure side to the low pressure side during the pulse.

[0024] According to one embodiment, the single component is a combined bushing and valve unit having a cylindrical outer shape.

[0025] According to one embodiment, the body is a cylindrical bushing body having a central bore for permitting hydraulic fluid flow, and the at least one leak hole is a hole for permitting leak flow through the bushing body forming a bypass passage. In one embodiment, the body can therefore be described as a combined valve unit and leak hole bushing, comprising a check valve assembly and one or more leak holes.

[0026] According to one embodiment, components are removably arranged within the pulse unit, which is advantageous in that modularity is achieved and servicing / replacement of the unit is easy.

[0027] Such bushings may further comprise means for engaging a screwdriver or the like to facilitate assembly and / or maintenance and replacement. Such means may be adapted to engage any tool tip shape, such as a Torx, Hex, etc.

[0028] According to one embodiment, the bypass passage is provided in a separate element having a central bore for permitting leakage flow therethrough, the central bore forming part of the bypass passage. The element may comprise, for example, a body, such as a cylindrical bushing body, having the central bore formed therein. In one embodiment, the separate element has substantially the same dimensions as the first and second valve units.

[0029] According to one embodiment, the first and second check valves are ball-type check valves each having a ball and a valve seat. The valve seat can be formed in the valve body and, together with the ball, form a valve unit. The first and / or second check valves can be formed in the first and second valve units and can be removably disposed in the pulse unit.

[0030] According to yet another aspect of the present invention, there is provided a combined valve unit and bushing for a pulse tool, comprising a body with a central bore for permitting hydraulic fluid flow, a ball arranged to selectively close the central bore / fluid flow, and at least one leak hole for permitting leak flow through the single component, thereby forming a bypass passage. The objects, advantages and features of the valve unit contemplated within the scope of the second aspect of the present invention will be readily understood from the above description referring to the first aspect of the present invention.

[0031] Further objects, features, and advantages of the present invention will become apparent upon review of the following detailed disclosure, drawings, and appended claims. Those skilled in the art will appreciate that different features of the present invention can be combined to create embodiments other than those described below.

[0032] The present invention is described in the following illustrative and non-limiting detailed description of exemplary embodiments with reference to the accompanying drawings. [Brief explanation of the drawings]

[0033] [Figure 1] FIG. 1 is a perspective view of an exemplary pulse tool. [Figure 2a] 1 is a cross-sectional view of an exemplary pulse unit of a power tool according to one embodiment. [Figure 2b] 10 is a cross-sectional view of an exemplary pulse unit of a power tool according to another embodiment. [Figure 3a] FIG. 2 is a cross-sectional view of an exemplary pulse unit according to one embodiment. [Figure 3b] FIG. 2 is a cross-sectional view of an exemplary pulse unit according to one embodiment. [Figure 4a] FIG. 1 is a perspective view of a combined bushing and valve unit according to an exemplary embodiment; [Figure 4b] FIG. 1 is a perspective view of a combined bushing and valve unit according to an exemplary embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0034] All figures are schematic and not necessarily to scale, and generally only parts necessary to elucidate the invention are shown, other parts may be omitted or merely suggested.

[0035] FIG. 1 shows an exemplary pulse tool 1 according to one embodiment, in this case a pistol-type tool comprising a housing 100 having a front end 100a and a rear end 100b in which a motor and hydraulic pulse unit are disposed, and further having a square-ended output shaft 10 extending to the front end of the housing.

[0036] 2 illustrates an exemplary hydraulic pulse unit 20 according to one embodiment. The pulse unit or impulse unit is coupled to a motor and is arranged to intermittently deliver torque pulses to an output shaft.

[0037] The hydraulic pulse unit comprises an inertial drive member 21 including a cylindrical front element 25 and an end element 24. The rear or end element 24 is formed with a motor coupling for connection to a motor. The inertial drive member consequently comprises a hydraulic fluid chamber 26, in this case an oil chamber, surrounded by the front and end elements, into which extends the impulse receiver 11 of the output shaft 10. In the embodiment shown, the impulse receiver is formed in one piece with the output shaft 10 and extends into the fluid chamber through a central opening in the front end wall of the inertial drive member.

[0038] The impulse receiving output is intermittently coupled to the drive member via a hydraulic pulse generating mechanism 30 which, in use, divides the hydraulic fluid chamber into at least one low pressure chamber 31 and at least one high pressure chamber 32 (shown in cross section in Figure 2b).

[0039] To generate the pressure pulse, the output shaft of this embodiment has a transverse cylinder bore in which a piston is arranged movably guided. The piston is reciprocated in the cylinder bore by a cam with two cam lobes formed on the inner wall of the fluid chamber, which acts on the piston via rollers to drive the hem inward, thereby generating a pressure peak. However, the operation of the impulse mechanism itself is known in the art and will not be described in further detail. Similar mechanisms have been previously described, for example, in U.S. Pat. No. 6,110,045 and U.S. Pat. No. 13,697,107.

[0040] Multiple fluid flows are provided to enable fluid communication between the high-pressure and low-pressure chambers. Figures 3a and 3b show two exemplary embodiments illustrating these fluid flows. For example, a bypass passage 40 is provided to enable flow between each chamber, and the hydraulic pulse generating mechanism further includes a first check valve 51 arranged to enable a first flow from the low-pressure side to the high-pressure side, and a second check valve 52 arranged to enable a second flow from the low-pressure side to the high-pressure side. Both valves (valve units) have a cylindrical outer shape and are removably located within the pulse unit.

[0041] During operation of the impulse unit, the inertial drive member is rotated by the motor, achieving a torque impulse on the output shaft 10, which, as described above, is achieved by the piston being reciprocated by the cam, thereby causing a pressure rise. As the pressure rises, oil flows from the high-pressure side to the low-pressure side via the bypass passage 40 described above, causing the piston to move inward, thus allowing the cam to pass the roller and accelerating the output shaft. To return the piston and roller to their outward positions, a central cam spindle is rotatably supported on the output member (not shown). As the central cam spindle rotates to return the piston and roller, oil is sucked back into the high-pressure chamber through the first and second check valves 51, 52, allowing a high oil return flow rate.

[0042] In the embodiment shown in Figure 3a, the bypass passage 40 is provided separately from the first and second flows provided by the first and second check valves 51, 52. More specifically, the bypass passage 40 is provided in a separate cylindrical bushing body 60 having a central bore 61 for allowing bypass or leakage flow through the bushing body, thus forming the bypass passage.

[0043] Each of the first and second check valves 51, 52 is a ball-type check valve comprising a valve body 54 having a valve seat 55 disposed therein that interacts with a respective ball 56. As can be seen in Figure 3a, the separate cylindrical bushing body 60 of the illustrated embodiment has substantially the same dimensions as the first and second valve bodies 51, 52.

[0044] 3b shows another embodiment of a pulse unit, in which the bypass passage 40 and, in this case, the second check valve 52 are formed in a single component 70. In the embodiment shown, this is in the form of a combined bushing and valve unit 70, or leak hole and bushing unit 70, which has a cylindrical outer shape and is removably positioned within the pulse unit.

[0045] 4a-b, the bushing unit 70 comprises a bushing body 71 having a central bore 72 for allowing the flow of hydraulic fluid and forming part of a conical valve seat 73 interacting with a ball. In this case, the bypass passage is formed by three leak holes 41, 42, 43 arranged along or equidistantly spaced from the circumference C1 of the central bore, i.e., adjacent to the outer periphery C2 of the conical valve seat 73 and thus adjacent to the radially outer side of the central bore 72.

[0046] Thus, both the fluid passage for the bypass or leak flow, as well as the fluid passage for the first flow, are provided in the same bushing body 70 in a single component to transmit fluid between the high pressure chamber and the low pressure chamber.

[0047] Figure 4b shows means 74 on the bushing body for engaging a screwdriver or the like, in this case a Torx screwdriver.

[0048] Similar to the embodiment disclosed above, the first check valve 51 is a ball-type check valve comprising a ball and a valve seat.

[0049] While the present invention has been shown and described in detail in the drawings and the foregoing description, such illustration and description is to be considered illustrative or exemplary and not restrictive, and the invention is not limited to the disclosed embodiments. Those skilled in the art will understand that many modifications, variations and changes are possible within the scope defined by the appended claims. In addition, variations to the disclosed embodiments can be understood and effected by those skilled in the art, from a study of the drawings, the disclosure and the appended claims, in practicing the claimed invention. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope of the claims. [Explanation of symbols]

[0050] 10 Output shaft 11 Impulse receiving part 20 Hydraulic pulse unit 21 Inertial drive member 26 Hydraulic fluid chamber 30 Hydraulic pulse generating mechanism 31 Low-pressure chamber 32 Hyperbaric Chamber 40 Bypass Passage 51 First check valve 52 Second check valve

Claims

1. A motor; An output shaft (10); a hydraulic pulse unit (20) coupled to the motor and arranged to intermittently transmit torque pulses to the output shaft; A pulse tool comprising: The hydraulic pulse unit comprises an inertial drive member (21) connected to the motor; The inertial drive member includes a hydraulic fluid chamber (26); an impulse receiving portion (11) of the output shaft extending coaxially within the hydraulic fluid chamber, the impulse receiving portion being intermittently coupled to the drive member via a hydraulic pulse generating mechanism (30) that divides the hydraulic fluid chamber into at least one low-pressure chamber (31) and at least one high-pressure chamber (32); a bypass passage (40) for transmitting fluid between the high pressure chamber and the low pressure chamber; The hydraulic pulse generating mechanism includes: a first check valve (51) arranged to allow a first flow from the low pressure side to the high pressure side; a second check valve (52) positioned to allow a second flow from the low pressure side to the high pressure side; Further provided is a pulse tool.

2. The pulse tool according to claim 1 , wherein the bypass passage is provided separately from the first flow and the second flow.

3. The pulse tool of claim 1 , wherein the bypass passage and at least a portion of one of the first check valve and the second check valve are formed from a single component (70).

4. 4. The pulse tool of claim 3, wherein the single component comprises a body (71) having a central bore (72) for permitting hydraulic fluid flow, and a valve body (54) arranged to selectively close the central bore, and the bypass passage is arranged to communicate fluid between the high pressure chamber and the low pressure chamber through the single component.

5. The pulse tool of claim 4 , wherein the bypass passage extends axially through the body.

6. The pulse tool according to claim 4 or 5, wherein the bypass passage is disposed radially outward of the central hole.

7. A pulse tool according to any one of claims 4 to 6, comprising at least two bypass passages equally spaced along the circumference C1 of the central hole.

8. 8. The pulse tool according to claim 4, wherein the at least one central hole forms part of a conical valve seat (73), and the at least one bypass passage is arranged along a part of the conical valve seat adjacent to an outer periphery C2 of the conical valve seat.

9. A pulse tool according to any one of claims 3 to 8, wherein the bypass passage is formed by at least one leak hole (41; 42; 43) for allowing a leak flow through the single component.

10. A pulse tool according to any one of claims 3 to 9, wherein the single component is a combined bushing and valve unit having a cylindrical outer shape.

11. 11. The pulse tool according to claim 10 when dependent on claim 9, wherein the body is a cylindrical bushing body having a central hole for allowing hydraulic fluid flow, and the at least one leak hole is a hole for allowing leakage flow through the bushing body forming the bypass passage.

12. 12. A pulse tool according to any one of claims 3 to 11, wherein the single component is removably arranged on the pulse unit.

13. 3. The pulse tool of claim 2, wherein the bypass passage is provided in a separate element having a central hole for allowing leakage flow through the element, the central hole forming part of the bypass passage.

14. 14. The pulse tool according to claim 1, wherein the first check valve and the second check valve are ball-type check valves each having a ball and a valve seat.

15. 1. A combined valve unit and bushing for use in a pulse unit of a pulse tool, the valve unit comprising: a body having a central bore for permitting flow of hydraulic fluid; a ball arranged to selectively close the central bore; and at least one leak hole for permitting leakage flow through a single component, thereby forming a bypass passage.

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