Power tool comprising hydraulic pulse unit

Abstract

The present specification relates to an impact tool comprising a hydraulic pulse unit arranged to intermittently transmit torque pulses to a tool output shaft, the impact tool comprising an inertial drive member, the inertial drive member includes a hydraulic fluid chamber and is intermittently coupled to the output shaft via a hydraulic pulse generating device that divides the hydraulic fluid chamber into a low pressure chamber and a high pressure chamber. A bypass passage is provided for fluid communication between the high pressure chamber and the low pressure chamber, where the hydraulic pulse generating mechanism further comprises 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. The present specification also relates to a combination valve unit and bushing for use in a pulse unit of a pulse tool.

Description

Technical Field

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

[0002] Known electric tools for tightening are used in various industries. For example, impulse wrenches including a hydraulic pulse unit are typically used in continuous mass production.

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

[0004] However, such fluid flow is generally associated with losses and thus has a great impact on the efficiency of the impulse tool.

[0005] To alleviate these problems, some solutions have been proposed, including various designs and combinations of fluid paths and / or valves that are arranged to allow fluid to flow between the low-pressure side and the high-pressure side. However, such impulse tools with such designs have known problems, including increased complexity and reduced durability.

[0006] Therefore, there is a need for improvement in the field of power tools including a hydraulic pulse unit. Summary of the Invention

[0007] Therefore, it is desirable to provide an impulse tool that keeps losses due to flow restrictions low. In particular, it is desirable to provide such an improved impulse tool in a less complex and more durable manner. To better solve one or more of these problems, an impulse tool and a valve unit according to the independent claims are provided. Preferred embodiments are defined in the dependent claims.

[0008] According to a first aspect of the present invention, there is provided an impulse tool comprising: a motor; an output shaft; and a hydraulic pulse unit coupled to the motor and arranged to intermittently transmit a torque impulse to the output shaft. The hydraulic pulse unit includes an inertia drive member connected to the motor, wherein the drive member includes a hydraulic fluid chamber; wherein an impact receiving portion of the output shaft extends coaxially into the hydraulic fluid chamber, and the impact receiving output portion is 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; wherein a bypass channel is provided to allow fluid communication between the high-pressure chamber and the low-pressure chamber, and wherein 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.

[0009] According to a first aspect, an impulse tool (or pulse tool, power wrench, power tool or tightening tool, these terms being used interchangeably in this specification) provides a creative solution to the above problems by combining a fluid path design that is designed to ensure the required flow between the low-pressure side and the high-pressure side.

[0010] More specifically, a design with two check valves allows for a greater flow from the low-pressure side to the high-pressure side, thereby reducing losses in the pulse unit. As a result, the performance of the power tool can be significantly improved.

[0011] The mentioned pulse tool can be an electric pulse or a pneumatic pulse tool. The pulse tool can further include a housing having a front end and a rear end, wherein an output shaft can be arranged at the front end of the housing. In addition, the high-pressure chamber and the low-pressure chamber can also be referred to as the high-pressure chamber and the low-pressure chamber, the high-pressure side and the low-pressure side, or the high-pressure zone and the low-pressure zone.

[0012] The first check valve and the second check valve can be arranged in a manner that facilitates sufficient flow from the low-pressure side. For example, in one embodiment, the valves can be arranged on opposite sides of the chamber, i.e., at an angular distance of 180 degrees.

[0013] In one embodiment, the impact receiving portion can be formed integrally with the output shaft and extend into the fluid chamber through a central opening in the front end wall of the inertial drive member. In addition, the output member can include a transverse cylinder bore in which a movably guided piston is arranged. The piston can reciprocate in the cylinder bore by means of a cam that includes two cam lobes formed on the inner wall of the fluid chamber and acts on the piston via, for example, rollers to drive the piston inwardly, thereby generating a pressure peak. A central camshaft can be rotatably supported in the output member to return the piston and the rollers to their outer positions.

[0014] According to one embodiment, the bypass channel is provided separately from the first flow and the second flow. For example, the bypass channel or the leakage flow can be provided at a position separated from the first check valve and the second check valve. In some embodiments, the leakage flow is provided by a separate component.

[0015] According to one embodiment, at least a portion of the bypass channel and one of the first check valve and the second check valve are formed as a single component. For example, the first valve and / or the second valve can be a valve unit, and the bypass channel can be formed in (or extend through) one of these units. Thus, sufficient flow can be ensured in a particularly compact manner.

[0016] According to one embodiment, a single component includes a body, wherein a central hole is provided in the body to allow the flow of hydraulic fluid, wherein a valve body is arranged to selectively close the central hole, and wherein a bypass passage is provided to enable fluid communication between a high-pressure chamber and a 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 the 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 be substantially parallel to the flow through the check valve.

[0020] According to one embodiment, the bypass passage is arranged radially outside the central hole. Radially refers to the radius of the central hole.

[0021] According to one embodiment, at least two bypass channels are equidistantly arranged along the circumference C1 of the central hole. Along should be understood as along the part of the body adjacent to the circumference C1.

[0022] According to one embodiment, at least one central hole forms part of a conical valve seat, and wherein the at least one bypass passage is arranged along the part of the conical valve seat adjacent to the outer circumference C2 of the conical valve seat. That is, along the part of the body adjacent to the circumference C2.

[0023] According to one embodiment, the bypass passage is formed by at least one leakage hole for allowing leakage flow through the single component. The leakage hole should be understood as a small hole that allows a small flow from the high-pressure side to the low-pressure side during a 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 hole for allowing the flow of hydraulic fluid, wherein at least one leakage hole is a hole in the bushing body for allowing leakage flow through to form the bypass passage. In one embodiment, the body can thus be described as a combined valve unit and leakage hole bushing including a check valve assembly and one or more leakage holes.

[0026] According to one embodiment, the component is detachably arranged in the pulse unit. This is advantageous because modularity can be achieved and it facilitates the repair / replacement of the unit.

[0027] Such bushings may further include means for engaging a screwdriver or the like to facilitate assembly and / or repair and replacement. Such means may be adapted to engage any tool tip shape, e.g., Phillips, hexagon, etc.

[0028] According to one embodiment, a bypass passage is provided in a separate element having a central bore for allowing leakage flow through the element, the central bore forming part of the bypass passage. The element may include a body, e.g., a cylindrical bushing body in which the central bore is formed. In one embodiment, the separate element has substantially the same dimensions as the first valve unit and the second valve unit.

[0029] According to one embodiment, the first check valve and the second check valve are spherical check valves including respective spheres and valve seats. The valve seats may be formed in the valve body and together with the spheres form valve units. The first check valve and / or the second check valve may be formed in the first valve unit and the second valve unit which may be removably arranged in the pulse unit.

[0030] According to another aspect of the present invention, there is provided a combined valve unit and bushing for a pulse tool, the combined valve unit and bushing including a body having a central bore therein for allowing the flow of hydraulic fluid, a sphere arranged to selectively close the central bore / fluid flow; and at least one leakage hole for allowing leakage flow through a single component thereby forming a bypass passage. By the above discussion with reference to the first aspect of the present invention, the purpose, advantages and features of the valve unit conceivable within the scope of the second aspect of the present invention can be readily understood.

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

[0032] The present invention will be described in the following illustrative and non - limiting detailed description of exemplary embodiments with reference to the accompanying drawings, in which

[0033] Figure 1 is a perspective view of an exemplary pulse tool.

[0034] Figure 2a is a cross - sectional view of an exemplary pulse unit of a power tool according to one embodiment.

[0035] Figure 2b is a cross - sectional view of an exemplary pulse unit of a power tool according to another embodiment.

[0036] Figure 3aIs a cross-sectional view of an exemplary pulse unit according to an embodiment.

[0037] Figure 3b Is a cross-sectional view of an exemplary pulse unit according to an embodiment.

[0038] Figure 4a And Figure 4b Are different perspective views of a combined bushing and valve unit according to an exemplary embodiment.

[0039] All the drawings are schematic, not necessarily drawn to scale, and generally show only the components necessary to illustrate the invention, where other components may be omitted or only suggested. Detailed Description

[0040] Figure 1 Shows an exemplary pulse tool 1 according to an embodiment. In this case, the pistol-type tool includes a housing 100 having a front end 100a and a rear end 100b. In the housing 100, a motor and a hydraulic pulse unit are arranged. The housing 100 further has an output shaft 10 with a square end extending at the front end of the housing.

[0041] FIG. 2 shows an exemplary hydraulic pulse unit 20 according to an embodiment. The pulse unit or impact unit is adapted to be coupled to the motor and is arranged to intermittently transmit torque pulses to the output shaft.

[0042] The hydraulic pulse unit includes an inertia drive member 21, and the inertia drive member 21 includes a cylindrical front member 25 and an end member 24. The rear portion 24 or the end member 24 is formed with a coupling portion for connecting to the motor, and this coupling portion is for connecting to the motor. This inertia drive member further includes a hydraulic fluid chamber 26 surrounded by the front member and the end member. In this case, it is an oil chamber, and the impact receiving portion 11 of the output shaft extends into the oil chamber. In the shown embodiment, the impact receiving portion is integral with the output shaft 10 and extends into the fluid chamber through a central opening in the front end wall of the inertia drive member.

[0043] This impact receiving output portion is intermittently coupled to the drive member during use via a hydraulic pulse generating mechanism 30, and the hydraulic pulse generating mechanism 30 divides the hydraulic fluid chamber into at least one low-pressure chamber 31 and at least one high-pressure chamber 32 (as Figure 2b shown in the cross-sectional view).

[0044] To achieve a pressure pulse, the output shaft in this embodiment includes a transverse cylinder bore in which a piston is movably guided. The piston reciprocates in the cylinder bore by means of a cam, which includes two cam lobes formed on the inner wall of the fluid chamber and acts on the piston via rollers to drive the piston inwardly, thereby generating a pressure peak. However, the operation of the impact 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. Patent No. 6,110,045 and U.S. Patent No. 13,697,107.

[0045] To allow fluid communication between the high-pressure chamber and the low-pressure chamber, several fluid flows are provided. Figure 3a and Figure 3b Two exemplary embodiments showing these fluid flows are shown. For example, a bypass channel 40 is provided to allow flow between the chambers. The hydraulic pulse generating mechanism further includes a first check valve 51 and a second check valve 52. The first check valve 51 is arranged to allow a first flow from the low-pressure side to the high-pressure side, and the second check valve 52 is arranged to allow a second flow from the low-pressure side to the high-pressure side. The two valves or valve units have a cylindrical shape and are detachably arranged in the pulse unit.

[0046] During the operation of the impact unit, the inertia drive member rotates by means of a motor, and a torque impact is achieved in the output shaft 10, which, as described above, is achieved by the reciprocating movement of the piston by means of the cam, resulting in an increase in pressure. As the pressure increases, oil flows from the high-pressure side to the low-pressure side via the above-mentioned bypass channel 40, thereby allowing the piston to move inwardly and thus causing the cam to pass over the roller, thereby allowing the acceleration of the shaft. To return the piston and the roller to their outer positions, the central camshaft is rotatably supported in the output member (not shown). When the central camshaft rotates to return the piston and the roller, the oil is sucked back into the high-pressure chamber again via the first check valve 51 and the second check valve 52, thereby allowing a high return flow of oil.

[0047] In Figure 3a the embodiment shown, the bypass channel 40 is separately provided from the first flow and the second flow via the first valve 51 and the second valve 52. More specifically, the bypass channel 40 is provided in a separate cylindrical bushing body 60, which has a central hole 61 for allowing the bypass or leakage flow to pass through the bushing body, thereby forming the bypass channel.

[0048] The first check valve 51 and the second check valve 52 are spherical check valves, and each check valve includes a valve body 54 in which a valve seat 55 interacting with a corresponding sphere 56 is arranged. As Figure 3a shown, the separate cylindrical bushing body 60 in the embodiment shown has substantially the same dimensions as the first valve body 51 and the second valve body 52.

[0049] In Figure 3b there is shown another embodiment of the pulse unit. In this embodiment, the bypass channel 40 and in this case the second check valve 52 are formed as a single component 70. In the embodiment shown, it is in the form of a combined bushing and valve unit 70 or a leak hole bushing unit 70, having a cylindrical outer shape and being removably arranged in the pulse unit.

[0050] Figures 4a to 4b The bushing unit 70 shown in detail in

[0051] includes a bushing body 71 having a central hole 72 to allow the flow of hydraulic fluid and forming part of a conical valve seat 73 that interacts with the sphere. In this case, the bypass channel is formed by three leak holes 41, 42, 43 which are equidistantly arranged along or with respect to the circumference C1 of the central hole (i.e., along the part of the conical valve seat 73 adjacent to the outer circumference C2 of the conical valve seat and thus located radially outside the central hole 72).

[0052] Figure 4b There is shown a means 74 provided in the bushing body for engaging a screwdriver or the like, which in this case is adapted to engage a Phillips screwdriver.

[0053] Similar to the above embodiment, the first check valve 51 is also a spherical check valve including a sphere and a valve seat.

[0054] Although the invention has been shown and described in detail in the drawings and the foregoing description, such illustration and description shall be regarded as illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Those skilled in the art will understand that many changes, variations and alternatives can be conceived within the scope defined in the appended claims. In addition, those skilled in the art can understand and implement various modifications to the disclosed embodiments after practicing the claimed invention, studying the drawings, the disclosure and the appended claims. In the claims, the wording "comprising" does not exclude other elements or steps, and the wording "a" or "an" does not exclude a plurality. The fact that certain measures are stated in mutually different dependent claims does not mean that a combination of these measures cannot be used advantageously. Any reference signs in the claims should not be construed as limiting the scope of the claims.

Claims

1. A pulse tool, comprising: a motor, an output shaft (10); and a hydraulic pulse unit (20) coupled to the motor and arranged to intermittently transfer torque pulses to the output shaft, wherein the hydraulic pulse unit includes an inertia drive member (21) connected to the motor, wherein the inertia drive member includes a hydraulic fluid chamber (26); wherein an impact receiving portion (11) of the output shaft extends coaxially into the hydraulic fluid chamber, and the impact receiving portion is 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); wherein a bypass passage (40) is provided to enable fluid communication between the high-pressure chamber and the low-pressure chamber, and wherein the hydraulic pulse generating mechanism further includes: a first check valve (51) arranged to permit a first flow from the low-pressure side to the high-pressure side, and a second check valve (52) arranged to permit a second flow from the low-pressure side to the high-pressure side.

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

3. The pulse tool according to claim 1, wherein, At least a part of the bypass passage and one of the first check valve and the second check valve form a single component (70).

4. The pulse tool according to claim 3, wherein, The single component includes a body (71), wherein a central hole (72) is provided in the body to permit the flow of hydraulic fluid, wherein a valve body (54) is arranged to selectively close the central hole, and wherein the bypass passage is arranged to enable fluid communication between the high-pressure chamber and the low-pressure chamber through the single component.

5. The impulse tool according to claim 4, wherein, The bypass passage extends axially through the body.

6. The impulse tool according to any one of claims 4 or 5, wherein, The bypass passage is radially arranged outside the central hole.

7. The pulse tool according to any one of claims 4 to 6, including at least two bypass passages equidistantly arranged along the circumference C1 of the central hole.

8. The impulse tool according to any one of claims 4 to 7, wherein The at least one central hole forms part of a conical valve seat (73), and wherein the at least one bypass passage is arranged along a part of the conical valve seat adjacent to the outer circumference C2 of the conical valve seat.

9. The impulse tool according to any one of the preceding claims 3 to 8, wherein, The bypass passage is formed by at least one leakage hole (41; 42; 43) for permitting a leakage flow through the single component.

10. The impulse 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. The impulse tool according to claim 10, dependent on claim 9, wherein, The body is a cylindrical bushing body having a central hole for permitting the flow of hydraulic fluid, and wherein the at least one leakage hole is a hole in the bushing body forming the bypass passage for permitting a leakage flow through the bushing body.

12. The impulse tool according to any one of claims 3 to 11, wherein, The single component is detachably arranged in the pulse unit.

13. The impulse tool according to claim 2, wherein, The bypass passage is provided in a separate element having a central hole for permitting a leakage flow through the element, and the central hole forms part of the bypass passage.

14. The impulse tool according to any one of the preceding claims, wherein, The first check valve and the second check valve are spherical check valves including respective spheres and valve seats.

15. A combined valve unit and bushing for use in a pulse unit of a pulse tool, the unit comprising a body provided with a central bore to allow the flow of hydraulic fluid, a sphere arranged to selectively close the central bore, and at least one leakage hole for allowing leakage flow through a single component to form a bypass channel.

Images