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 generally relates to a power tool for tightening a screw fastener, and more particularly to an impulse type power tool having a hydraulic pulse unit.

Background Art

[0002] It is known that electric power tools for tightening are used in various industrial fields. For example, an impulse type power wrench equipped with a hydraulic pulse unit is generally used for continuous mass production.

[0003] The hydraulic unit of such a tool is filled with oil. In such a pulse tool, a torque pulse 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, the fluid can flow between the low-pressure side and the high-pressure side.

[0004] However, such fluid flow often involves losses, which greatly affects the efficiency of the pulse tool.

[0005] To mitigate some 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 in pulse tools including this type of design include further complexity and low durability.

Summary of the Invention

Problems to be Solved by the Invention

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

Means for Solving the Problems

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

[0008] According to a first aspect of the present invention, a pulse tool is provided 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 coupled to the motor, the drive member comprising a hydraulic fluid chamber, an impulse receiving portion of the output shaft extending coaxially into 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 for communicating fluid 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 problem by incorporating a fluid passage designed to ensure a desired flow between a low-pressure side and a high-pressure side.

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

[0011] The pulse tool referred to may be an electrically driven pulse tool or a pneumatically driven pulse tool. The pulse tool may further comprise 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-pressure chamber and low-pressure chamber may also be referred to as the high-pressure compartment and low-pressure compartment, the high-pressure side and the low-pressure side, or the high-pressure section and the low-pressure section.

[0012] The first and second check valves can be positioned to facilitate sufficient flow from the low-pressure side. These valves can be positioned, for example, on the opposite side of this chamber, i.e., at an angular distance of 180 degrees, in one embodiment.

[0013] In one embodiment, the impulse receiving section can be formed integrally with the output shaft and may further extend into the fluid chamber through a central opening in the front end wall of the inertial drive member. Furthermore, this output member may comprise a lateral cylinder bore in which a movably guided piston is arranged. The piston reciprocates within the cylinder bore by a cam, which has two cam lobes formed in the inner wall of the fluid chamber that act on the piston, for example via rollers, to drive a hem inward, thereby generating a pressure peak. A central cam spindle may be rotatably supported on the output member to return the piston and rollers to their outer positions.

[0014] According to one embodiment, the bypass passage is provided separately from the first and second flows. For example, the bypass passage or leak flow may 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 portion of one of the first and second check valves are formed from a single component. For example, the first and / or second check valves can be valve units, and the bypass passage can be formed in one of these units (or extend through these units). This ensures sufficient flow in a particularly compact manner.

[0016] According to one embodiment, a single component comprises a body having a central bore for allowing the flow of hydraulic fluid, a valve body arranged to selectively close the central bore, and a bypass passage provided to transmit fluid 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 a cylindrical body.

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

[0020] According to one embodiment, the bypass passage is located radially outward from the central hole. Radial direction refers to the radius of the central hole.

[0021] According to one embodiment, at least two bypass passages are arranged at equal intervals along the circumference C1 of the central hole. "Along the" 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 the at least one bypass passage is arranged along a portion adjacent to the outer circumference C2 of the conical valve seat. That is, it is along a part 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 the single component. A leak 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, and the at least one leak hole is a hole for allowing a leak flow through the bushing body forming the bypass passage. In one embodiment, thus, the body can 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, the component is removably arranged within the pulse unit. This is advantageous in that modularization is achieved and servicing / replacement of the unit is facilitated.

[0027] Such a bushing can further comprise means for engaging with a screwdriver or the like to facilitate assembly and / or servicing and replacement. Such means can be adapted to engage with some tool tip shape such as torx, hex, etc.

[0028] According to one embodiment, the bypass passage is provided in a separate element, which has a central hole for allowing a leakage flow through this element, and the central hole forms part of the bypass passage. This element can comprise a body such as a cylindrical bushing body in which the central hole is formed. In one embodiment, this 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 check valves each comprising a respective ball and valve seat. The valve seat is formed within the valve body and can form a valve unit together with the ball. The first and / or second check valve can be formed in the first and second valve units and can be removably arranged in the pulse unit.

[0030] According to yet another aspect of the invention, a combined valve unit and bushing for a pulse tool is provided, which comprises a body having a central hole for allowing a flow of hydraulic fluid, a ball arranged to selectively close the central hole / fluid flow, and at least one leak hole for allowing a leakage flow through a single component, thereby forming a bypass passage. The purposes, advantages and features of the valve unit contemplated within the scope of the second aspect of the invention are readily understood from the above description referring to the first aspect of the invention.

[0031] Further objects, features and advantages of the invention will become apparent upon consideration of the following detailed disclosure, drawings and appended claims. Those skilled in the art will understand that different features of the 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 Description of the Drawings

[0033] [Figure 1] It is a perspective view of an exemplary pulse tool. [Figure 2a] This is a cross-sectional view of an exemplary pulse unit of a power tool according to one embodiment. [Figure 2b] This is a cross-sectional view of an exemplary pulse unit of a power tool according to another embodiment. [Figure 3a] This is a cross-sectional view of an exemplary pulse unit according to one embodiment. [Figure 3b] This is a cross-sectional view of an exemplary pulse unit according to one embodiment. [Figure 4a] This is a perspective view of a unit combining a bushing and a valve according to an exemplary embodiment. [Figure 4b] This is a perspective view of a unit combining a bushing and a valve according to an exemplary embodiment. [Modes for carrying out the invention]

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

[0035] Figure 1 shows an exemplary pulse tool 1 according to one embodiment, in which the pistol-type tool comprises a housing 100 having a front end 100a and a rear end 100b, in which a motor and a hydraulic pulse unit are housed, and further comprises a corner-end output shaft 10 extending from the front end of the housing.

[0036] Figure 2 shows an exemplary hydraulic pulse unit 20 according to one embodiment. The pulse unit or impulse unit is connected to a motor and is positioned to intermittently transmit torque pulses to the output shaft.

[0037] The hydraulic pulse unit comprises an inertial drive member 21, which includes a cylindrical front element 25 and end elements 24. The rear element 24 or end element 24 has a motor coupling portion formed therein, which is connected to a motor. The inertial drive member consequently comprises a hydraulic fluid chamber 26, in this case an oil chamber, enclosed by the front and end elements, into which the impulse receiving portion 11 of the output shaft extends. In the illustrated embodiment, the impulse receiving portion is formed integrally with the output shaft 10 and extends into the fluid chamber through a central opening provided in the front end wall of the inertial drive member.

[0038] This impulse receiving and output unit is intermittently coupled to the drive member during use via a hydraulic pulse generation mechanism 30 that divides the hydraulic fluid chamber into at least one low-pressure chamber 31 and at least one high-pressure chamber 32 (shown in the cross-sectional view of Figure 2b).

[0039] To generate a pressure pulse, the output shaft of this embodiment comprises a transverse cylinder bore in which a piston guided to move within is positioned. The piston reciprocates within the cylinder bore by a cam having two cam lobes formed in the inner wall of the fluid chamber, acting 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. Patent No. 6,110,045 and U.S. Patent No. 13,697,107.

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

[0041] During operation of the impulse unit, the inertia drive member is rotated by the motor, and a torque impulse is achieved on the output shaft 10, which, as described above, is achieved by a piston reciprocated by a cam, thereby causing a pressure increase. As the pressure increases, oil flows from the high-pressure side to the low-pressure side through the bypass passage 40 described above, causing the piston to move inward, and thus allowing the cam to pass the rollers, enabling acceleration of the output shaft. A central cam spindle (not shown) is rotatably supported on the output member to return the piston and rollers to their outer positions. As the central cam spindle rotates to return the piston and rollers, oil is drawn back into the high-pressure chamber through the first and second check valves 51, 52, thus enabling a high return flow rate of oil.

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

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

[0044] Figure 3b shows another embodiment of the pulse unit. In this embodiment, the bypass passage 40 and, in this case, the second check valve 52 are formed by a single component 70. The illustrated embodiment is in the form of a combined bushing and valve unit 70, or leak hole bushing unit 70, having a cylindrical shape and being removablely arranged within the pulse unit.

[0045] The bushing unit 70, shown in detail in Figures 4a-b, comprises a bushing body 71 having a central hole 72 for allowing the flow of hydraulic fluid and forming part of a conical valve seat 73 that interacts with a ball. In this case, the bypass passage is formed along the circumference C1 of the central hole, or by three leak holes 41, 42, 43 arranged equally spaced thereto, i.e., along the outer circumference C2 of the conical valve seat 73 and thus along the radially outward portion adjacent to the central hole 72.

[0046] Therefore, both the fluid passage for the bypass or leak flow, and the fluid passage for the first flow, are provided within 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 a means 74 provided on the bushing body for engaging with a screwdriver or the like, and in this case, it is designed to engage with a Torx screwdriver.

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

[0049] Although the present invention is illustrated and described in detail in the drawings and the above description, such illustrations and descriptions are illustrative and not restrictive, 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 possible within the scope defined in the appended claims. In addition, variations to the disclosed embodiments can be understood and achieved by a person skilled in the art by examining the drawings, disclosure, and appended claims when carrying out the claimed invention. In the claims, the term “comprising” does not exclude other elements or steps, and the indefinite articles “a” or “an” do not exclude plurals. The mere fact that certain means are described in different dependent claims does not indicate that combinations of these means cannot be used advantageously. No reference numeral in the claims should be construed as limiting the claims. [Explanation of Symbols]

[0050] 10 Output shaft 11 Impulse receiving section 20 Hydraulic pulse unit 21 Inertia drive member 26 Hydraulic fluid chamber 30 Hydraulic pulse generation mechanism 31 Low-pressure chamber 32 High-pressure chamber 40 Bypass passage 51 First check valve 52 Second check valve

Claims

1. Motor and, 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 equipped with, The hydraulic pulse unit comprises an inertial drive member connected to the motor, The inertia drive member includes a hydraulic fluid chamber, The impulse receiving portion (11) of the output shaft extends coaxially into the hydraulic fluid chamber, and the impulse receiving portion is intermittently coupled to the inertial drive member via a hydraulic pulse generation 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) is provided to allow the flow of hydraulic fluid from the high-pressure chamber to the low-pressure chamber. The hydraulic pulse generation mechanism is A first check valve (51) is arranged to allow a first flow from the low-pressure chamber to the high-pressure chamber, A second check valve (52) is arranged to allow a second flow from the low-pressure chamber to the high-pressure chamber, A pulse tool that is further equipped with these features.

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 according to 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 by a single component (70).

4. The pulse tool according to claim 3, wherein the single component comprises a body (71) having a central hole (72) for allowing the flow of hydraulic fluid, and a valve body (54) arranged to selectively close the central hole, and the bypass passage is provided to transmit hydraulic fluid between the high-pressure chamber and the low-pressure chamber via the single component.

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

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

7. The pulse tool according to claim 4 or 5, further comprising at least two bypass passages arranged at equal intervals along the circumference (C1) of the central hole.

8. The pulse tool according to claim 4 or 5, wherein the central hole forms part of the conical valve seat (73), and the 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 pulse tool according to claim 4 or 5, wherein the bypass passage is formed by at least one leak hole (41; 42; 43) for allowing leak flow through the single component.

10. The pulse tool according to claim 9, wherein the single component is a combined bushing and valve unit having a cylindrical outer shape.

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

12. The pulse tool according to any one of claims 3 to 5, wherein the single component is detachably disposed in the hydraulic pulse unit.

13. The pulse tool according to any one of claims 1 to 5, wherein the first check valve and the second check valve are ball-type check valves each comprising a ball and a valve seat.

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