EP4021683B1

EP4021683B1 - Power tool for generating an instantaneous torque

Info

Publication number: EP4021683B1
Application number: EP19942829.3A
Authority: EP
Inventors: Li Guo Ma; Jing Feng Zhou; Rui Liang
Original assignee: Techtronic Cordless GP
Current assignee: Techtronic Cordless GP
Priority date: 2019-08-27
Filing date: 2019-08-27
Publication date: 2023-12-20
Anticipated expiration: 2039-08-27
Also published as: WO2021035512A1; EP4021683C0; EP4021683A1; EP4021683A4; CN216067235U

Description

FIELD OF INVENTION

The present invention generally relates to a power tool, and in particularly, to the power tool for generating an instantaneous or a pulsed torque via a hydraulic unit.

BACKGROUND OF INVENTION

In the field of power tools, and in particular power tools for generating an instantaneous or a pulsed torque, e.g., impactor, impact wrench, impact gun, rattle gun, torque gun, and windy gun, it has been proposed to provide a high instantaneous torque output with minimal exertion by a user by generating impacts and periodically delivering it to an output shaft. These power tools are widely used in many industries, such as automotive repair, heavy equipment maintenance, product assembling, major construction projects, and any other instance where high-torque output is required. With the instantaneous torque, it features a reactionless tightening while reducing the nose levels the regular impacts suffer from. These power tools are generally driven by, but not limit to, electric drive, pneumatic drive, and hydraulic drive.
Traditional power tools for generating the instantaneous torque are simply operated via a mechanical drive mechanism which generates greater noises, or via a hydraulic drive mechanism which returns a reaction force or a vibration acts back to the inner components of the hydraulic unit, which makes such inner components and the hydraulic of the power tools become not stable in long term use. EP 1 454 715 represents the closest prior art and discloses a power tool according to the preamble of claim 1.

SUMMARY OF INVENTION

The present invention seeks to mitigate or at least to alleviate the aforesaid problem or shortcoming by providing a power tool with a new or otherwise improved hydraulic unit.
According to the invention, there is provided a power tool according to claim 1, including a transmission mechanism, an output shaft driven by the transmission mechanism, and a hydraulic unit filled with a working fluid. The hydraulic unit is disposed coaxially with the output shaft, and defines a rotatively driving mechanism, a first fluid chamber, and a second fluid chamber. The first fluid chamber is in intermittently fluid connection with the second fluid chamber via a fluid channel. A relative rotation between the hydraulic unit and the output shaft causes the rotatively driving mechanism to axially compress or expand a volume of the second fluid chamber for raising or decreasing a fluid pressure of the second fluid chamber, generating a pressure difference between the first fluid chamber and the second fluid chamber to cause an instantaneous torque to the output shaft.
The rotatively driving mechanism includes an axially extending body protruding from an interior surface of the hydraulic unit. During the relative rotation between the hydraulic unit and the output shaft, the axially extending body pushes a first end wall which defining one edge of the second fluid chamber towards a second end wall which defining another edge of the second fluid chamber downwards at a first position, until the second fluid chamber is decreased to a minimum volume.
More preferably, the hydraulic unit comprises an axially movable member. A first end of the axially movable member forms the first end wall which defining said one edge of the second fluid chamber. A second end of the axially movable member which is axially opposite to the first end of the axially movable member receives the push from the axially extending body.
Preferably, the second end of the axially movable member has a wedge-shape. The second end includes a slope for receiving the push from the axially extending body.
Preferably, the rotatively driving mechanism includes a support assembly comprising a rolling member which rotates radially and synchronously with the axially extending body and a ball moveably received in the rolling member. The end surface of the rolling member forms the second end wall which defining another edge of the second fluid chamber.
More preferably, an axial movement of the ball in the second chamber expands the volume of the second fluid chamber to a maximum by rising the axially movable member after the axially movable member is released by the axially extending body at a second position.
Alternatively, the rolling member includes a groove disposed generally at an edge of the rolling member for moveably receiving the ball. The groove has an arc shape with a deep middle portion and gradually shallower ends.
Alternatively, the radial rotation of the rolling member generates a relatively axial movement between the ball and the second fluid chamber. The ball is adapted to move to a lowest portion of the groove when the volume of the second fluid chamber is decreased to the minimum volume. The ball is further adapted to move to be received by the groove when the axially extending body begins to push a first end wall which defining one edge of the second fluid chamber towards a second end wall which defining another edge of the second fluid chamber downwards at the first position.
Preferably, the rolling member includes a set of slots symmetrical around a center of the rolling member. The set of slots coupling with a set of projections disposed on the axially extending body for receiving a driven force and generating the radial rotation of the rolling member.
Preferably, the fluid channel includes a first fluid passage is in fluid connection with the first fluid chamber, a second fluid passage is in fluid connection with the second fluid chamber. The radial rotation of the rolling member intermittently fluidly communicates the first fluid passage and the second fluid passage.
Preferably, the first fluid passage and the second passage is communicated through the groove.
Preferably, the first fluid passage includes a fluid hole disposed on the output shaft.
Preferably, the second fluid passage includes a trench for receiving the axially movable member.
Preferably, the first fluid passage and the second fluid passage are not in fluid connection between the movements of the axially extending body from the first position to the second position.
Preferably, the first fluid passage and the second fluid passage are in fluid connection after the axially movable member is released by the axially extending body at the second position.
Preferably, the fluid pressure of first fluid chamber generally equals to the fluid pressure of the second fluid chamber when the axially extending body begins to push the first end wall which defining one edge of the second fluid chamber at the first position.
Preferably, a portion of working fluid inside the second fluid chamber is squeezed out from the second fluid chamber to the trench during the push during the axially extending body and the first end wall which defining one edge of the second fluid chamber from the first position to the second position.
Preferably, the working fluid is gas contented hydraulic fluid.
More preferably, the hydraulic unit includes an adjusting screw located coaxially with the output shaft for adjusting the gas content of the working fluid.
Preferably, the working fluid is arranged to flow the fluid channel and hold the first and second fluid chambers.
Preferably, the relatively driving mechanism, the first fluid chamber, and the second fluid chamber are disposed in plural numbers coaxially and rotationally symmetrical to each other.
Preferably, the two rotatively driving mechanisms, two first fluid chambers, and two second fluid chambers are disposed in a relationship rotationally symmetrical by 180° to each other.
The first fluid chamber, the second fluid chamber and the rotatively driving mechanism are disposed inside a generally cylindrical case which is coaxial with the output shaft.
The first fluid chamber is surrounded by an outer side surface of the output shaft, an inner side surface of the case, and both end surfaces of the case.
The second fluid chamber is surrounded by an end surface of the rolling member, the first end of the axially movable member, and an outer side surface of the output shaft, and an inner side surface of the case.
The present invention therefore provides a new or otherwise improved structure of the hydraulic unit which reduce the noises and the reaction force and vibration inside the hydraulic, thus provides a better user experience to the user, and a longer service life of the power tool.

BRIEF DESCRIPTION OF FIGURES

The foregoing and further features of the present invention will be apparent from the following description of preferred embodiments which are provided by way of example only in connection with the accompanying Figures, of which:

Figure 1 shows an outside view of a hydraulic unit and an output shaft of a power tool in accordance with a first embodiment of with the present invention.
Figure 2 shows an exploded perspective view of the main parts of the hydraulic unit and the output shaft of the power tool of Figure 1.
Figure 3 shows a cross-sectional view of the hydraulic unit and the output shaft of the power tool of Figure 1.
Figure 4a shows an external interface of the sleeve of the hydraulic unit of Figure 1.
Figure 4b shows an internal structure of the sleeve of the hydraulic unit of Figure 1.
Figure 5a shows an internal structure of the hydraulic unit of Figure 1.
Figure 5b shows a rear view of the hydraulic unit and output shaft of Figure 1.
Figure 6a shows front a view of a rolling member which forms a part of the hydraulic unit of Figure 1.
Figure 6b shows rear view of the rolling member of Figure 6a.
Figure 7a shows an internal view of a cover which forms a part of the hydraulic unit of Figure 1.Figure 7b shows an external view of the cover of Figure 7a.
Figure 8a shows a top cross-sectional view of the hydraulic unit, which aims to illustrate the status of connectivity between a first fluid chamber and the second fluid chamber inside the hydraulic unit of Figure 1 during a rotation period.
Figure 8b shows a schematic diagram of the projection of the ball, the fluid hole and the blade trench on the rolling member in accordance with a state during a rotation period.
Figure 8c shows a schematic diagram of the status of connectivity between the first fluid chamber and the second fluid chamber inside the hydraulic unit of Figure 1 during a rotation period.
Figure 9a shows the positional relationship of the components inside the hydraulic unit before the axially extending body pushes the axially movable member (Ceta=0° ).
Figure 9b shows a cross-sectional view of the hydraulic unit and the output shaft of Figure 9a.
Figure 10a shows the positional relationship of the components inside the hydraulic unit, after the axially extending body just impacts the axially movable member (Ceta=2° ).
Figure 10b shows a cross-sectional view of the hydraulic unit and the output shaft of Figure 10a.
Figure 10c shows a force analysis diagram of the axially moveable member under ideal conditions during the impacting between the axially extending body and the axially moveable member as shown from Figure 10a to Figure 11a.
Figure 11a shows the positional relationship of the components inside the hydraulic unit, after the axially extending body fully impacts the axially movable member (Ceta=5° ).
Figure 11b shows a cross-sectional view of the hydraulic unit and the output shaft of Figure 11a.
Figure 12a shows the positional relationship of the components inside the hydraulic unit, after the axially extending body fully pushes the axially movable member (Ceta=45° ).
Figure 12b shows a cross-sectional view of the hydraulic unit and the output shaft of Figure 12a.
Figure 12c shows a schematic diagram of the projection of the ball, the fluid hole and the blade trench on the rolling member in accordance with the positional relationship as shown in Figure 12a.
Figure 13a shows the positional relationship of the components inside the hydraulic unit, after the axially movable member is just released from the axially extending body (Ceta=67° ).
Figure 13b shows a cross-sectional view of the hydraulic unit and the output shaft of Figure 13a.
Figure 13c shows a schematic diagram of the projection of the ball, the fluid hole and the blade trench on the rolling member in accordance with the positional relationship as shown in Figure 13a.
Figure 14a shows the positional relationship of the components inside the hydraulic unit, after the axially movable member is released from the axially extending body and the second chamber resumes to the maximum volume (Ceta=90° ).
Figure 14b shows a cross-sectional view of the hydraulic unit and the output shaft of Figure 14a.
Figure 14c shows a schematic diagram of the projection of the ball, the fluid hole and the blade trench on the rolling member in accordance with the positional relationship as shown in Figure 14a.
Figure 15a shows the positional relationship of the components inside the hydraulic unit, after the axially movable member is released from the axially extending body, and the volume of second chamber starts to decrease from the maximum volume (Ceta=135° ).
Figure 15b shows a cross-sectional view of the hydraulic unit and the output shaft of Figure 15a.
Figure 15c shows a schematic diagram of the projection of the ball, the fluid hole and the blade trench on the rolling member in accordance with the positional relationship as shown in Figure 14a.

In the drawings, like numerals indicate like parts throughout the several embodiments described herein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments of the present invention will be readily appreciated that the described features may be applied to any types of power tool which generates an instantaneous or a pulsed torque known in the art, including but not limiting to impactors, impact wrenches, impact guns, rattle guns, torque guns and windy guns.
Embodiments of the present invention now will be described more fully with reference to the accompanying drawings, in which embodiments of the invention are shown. The present invention may however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements throughout this application.
It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., "between" versus "directly between," "adjacent" versus "directly adjacent," etc.).
The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting of the invention. As used herein, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes" and/or "including," when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
The present invention now will be described more fully hereinafter with reference to the accompanying figures, in which embodiments of the invention are shown. However, it should be understood that there is no intent to limit the invention to the particular forms disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the claims.
Referring to Figure 1 to 15 of the drawings, there is a power tool embodying the invention, hereafter referred to as the power tool 10. The power tool 10 generally includes a housing (not shown), a transmission mechanism 12, an output shaft. 14 and a hydraulic unit 16 and an electric motor (not shown) contained within the housing. The motor is configured to drive the transmission mechanism 12, and generate an instantaneous torque onto the output shaft 14 via the transmission mechanism 12 and the hydraulic unit 16. The output shaft 14 is driven by the transmission mechanism 12 and hydraulic unit 16. The output shaft 14 has an output for detachably connecting a tool head, such as a screwdriver head. The hydraulic unit 16 is filled with a working fluid inside, and disposed coaxially with the output shaft 14. The hydraulic unit 16 defines a rotatively driving mechanism 18, a first fluid chamber 20, and a second fluid chamber 22. The first fluid chamber 20 is in intermittently fluid connection with the second fluid chamber via a fluid channel 28, and due to a relative rotation between the hydraulic unit 16 and the output shaft 14. The said relative rotation causes the rotatively driving mechanism 18 to axially compress or expand a volume of the second fluid chamber 22. Therefore, a fluid pressure of the second fluid chamber 22 is either increased or decreasing in accordance with the compressing or expanding the volume of the second fluid chamber 22. The said change of the fluid pressure of the second chamber 22 results in an instantaneous torque to the output shaft 14.
As shown in Figure 4a and 4b, the rotatively driving mechanism 18 includes a sleeve 24 having a pair of axially extending bodies 30a and 30b protruding from a top interior surface 32 of the sleeve 24. The set of axially extending bodies 30a and 30b are located symmetrically around a center of the sleeve 24. The top interior surface 32 of sleeve 24 is divided into two sections, wherein a top 32a is lower than a top 32b. The top 32a is used to restrict an upper end 40 of a blade 36 from above, and further restricting the axial movement of the blade 36. The top 32b constitutes a fluid channel, for keeping the left and right chambers of the first fluid chamber 20 in connection. The sleeve includes an external thread 63 for coupling with an internal thread 100 of a cover 26 to secure the cover 26 to the sleeve 24 with each other.
As shown in Figure 5a and 5b, the hydraulic unit 16 includes an axially movable member 34. The axially movable member 34 is a blade 36. The hydraulic unit 16 includes a pair of blades 36a and 36b which is located symmetrically with each other. A lower end 38 of the blades 36 forms an end wall which defines one edge 42 of the second fluid chamber 22. Meanwhile, the upper end 40 of the blade 36 which is axially opposite to the lower end 38 of the blade 36 is adapted to receive a push and an impact from the axially extending bodies 30. The said push and impact are generated by the relative rotation between the hydraulic unit 16 and the output shaft 14, in particularly by the relative rotation between the sleeve 24 and the blade 36. The said push and impact make the blade 36 moves downwards, and towards another end wall of the second fluid chamber 22. During such relative rotation, the upper end 40 of the blade 36 is pushed by the axially extending body 30 towards the lower end 38 of the blade 36. As the lower end 38 of the blade 36 defines said one edge 42 of the second fluid chamber 22, the volume of the second fluid chamber 22 is decreased in accordance with the push; unit the volume of the second fluid chamber 22 reaches a minimum volume thereof. The working fluid inside the second fluid chamber 22 is squeezed out from the second fluid chamber 22 during the push. As shown in Figure 10, the upper end 40 of the blade 36 has a wedge shape including a slope 46 which is adapted to receive the push and impact from the axially extending body 30. The axially extending body 30 includes an impact surface 146, and a holding surface 148. The impact surface 146 is configured to provide and initially impact and push the slope 46 of the blade 36. The holding surface 148 is configured to restrict the axially movable member 34 from above for a certain distance, after the axially movable member is pushed by the impact surface 146.
As shown from Figure 5a to Figure 6b, the relatively driving mechanism 18 includes a holder 102 and a support assembly 48. The holder 102 is adapted to hold the support assembly 48, a ball 52, the blade 36, and other related components which are shown in Figure 5 and 6. The support assembly 48 is located under the blade 36 and further dynamically supports the axially movement of the blade 36. The support assembly 48 includes a rolling member 50 and a ball 52. The rolling member 50 which has a roughly disc shape rotates radially and synchronously with the axially extending bodies 30a and 30b. The ball 52 is moveably received in the rolling member 50. As shown in Figure 6 and 9, an upper end surface 54 of the rolling member 50 forms an end wall which defines another edge 44 of the second fluid chamber 22. The rolling member 50 comprises a set of grooves 56a and 56b which are disposed generally at an edge of the rolling member 50, and symmetrically with each other. The support assembly 48 includes a set of balls 52a and 52b, located symmetrically with each other. The lower end of the ball 52a and 52b are moveably received in the grooves 56a and 56b, respectively. The grooves 56a or 56b has an arc shape with a deep middle portion and gradually shallower ends. The supporting assembly includes several seal rings 134 and 136 located under the rolling member 50, for seal the rolling member 50 with the cover 26. The sleeve 24, the cover 26, the holder 102, the adjusting screw 120, the sealing ring (128, 136, 140, 142), the blade 36 together constitute the first fluid chamber 20. The first fluid chamber 20 is filled with a certain amount of working fluid. In an embodiment, the working fluid is hydraulic oil which the gas content can be adjusted.
Referring to Figures 2 to Figure 6b, the holder 102 includes a locating shaft 104 located on the upper portion of the holder 102. The locating shaft 104 is inserted into a positioning hole 106 of the sleeve 24 to maintain the coaxiality. An end face 108 is coupled with the sleeve 24 to ensure the perpendicularity of the holder 102 and the sleeve 24. The holder 102 also has a locating shaft 100 for coupling with a hole 102 of the rolling member 48, a cover hole 114, and a bushing of the casing (not shown) to ensure the coaxiality of the holder 102 with the rolling member 48, the cover 26, the output shaft 14. The holder 102 includes a cylindrical bore 116 which inner connects a fluid hole 118 and remains normally open with the same, which constitutes a part of the first fluid chamber 20. The gas content of working fluid inside the first fluid chamber 20 and the second fluid chamber 22 can be adjusted by changing the position of an adjusting screw 120. The adjusting screw 120 is further sealed by a set of seal rings 140 and 142.
A flat surface 79, a side surface 87 and a side surface 69 of the sleeve 24 constitute a blade trench 72 for dynamically receiving the blade 36. The blade 36 includes an inner bore for reducing the blade's weight. As shown, a side surface 85 of the blade 36 is curved to fit the side surface 69 of sleeve 24. The ball 52 moves in the groove 56, and adjusts the axial position of the blade 36 in the blade trench 72 in accordance with the depth of the groove 56. The blade trench 72, a lower end of blade 38, the groove 56, the side surface 69 of the sleeve 24, an end surface of the rolling member 50, and the grooves 56a and 56b form two second fluid chambers 22a and 22b which located symmetrically with the output shaft 14 in radial direction.
As shown in Figure 3, in order to describe the working mechanism of the hydraulic unit 16, the ball 52a and blade 36a are taken as an example for illustration. The ball 52a is received in a cavity 58a of the blade 36a. The blade 36a is configured not moveable with the sleeve 24, so that the ball 52a is also not rotatively moveable in the radial direction with the rotation of the sleeve 24. On the other hand, the radial rotation of the rolling member 50 generates a relatively axial movement between the ball 52a and the second fluid chamber 22, since the bottom of the ball 56a is received in the groove 56a. With such rotation, the groove 56a is adapted to drive the ball 56a in axial direction in accordance with the shape of the groove 56a. As the upper end of the cavity 58a is supported by the ball 52a, the axially movement of the ball 52a causes the synchronous movement of the blade 36a in axial direction, then expand the second chamber 22 after the same being pushed by the axially extending body 30a. Particularly, the ball 52a is adapted to move to a lowest portion of the groove 56a when the volume of the second fluid chamber 22 is decreased to the minimum volume, due to the push from the axially extending body 30a. The ball 52a is further adapted to move to be received by the groove 56a when the axially extending body 30a begins to push the upper end of the blade 36a at the first position.
As shown in Figure 6a and Figure 6b, the rolling member 50 includes a set of slots 60a and 60b which are located symmetrically around a center of the rolling member 50. The set of slots 60a and 60b are configured to couple with a set of projections 62a and 62b disposed on the sleeve 24 for receiving a driven force and generating the radial rotation of the rolling member 50, which is synchronous with the sleeve 24.
As a conclusion, the working mechanism of the second chamber 22 can be concluded as a circulation of firstly, the axially extending body 30 pushes a first end wall which defining one edge of the second fluid chamber 22 towards a second end wall which defining another edge of the second fluid chamber downwards at a first position, until the second fluid chamber 22 is decreased to a minimum volume, and an axial movement of the ball 52 in the second chamber 22 expands the volume of the second fluid chamber to a maximum by rising the axially movable member 34 after the axially movable member is released by the axially extending body 30 at a second position.
The fluid channel 28 includes a first fluid passage in fluid connection with the first fluid chamber, a second fluid passage in fluid connection with the second fluid chamber; and the radial rotation of the rolling member 50 intermittently fluidly communicates the first fluid passage and the second fluid passage.
In an embodiment, the hydraulic unit 16 includes a fluid hole 68 forms as the first fluid passage which punches through the surface 70, and in intermittently communication with the grooves 56a and 56b. The blade trench 72 which receives the blade 36 forms the second fluid passage, which also in intermittently communication with the grooves 56.
The first fluid passage and the second fluid passage is not in fluid connection between the movements of the axially extending body 30 from the first fluid passage and the second fluid passage is in fluid connection after the blade 36 is released by the axially extending body at the second position. The fluid pressure of first fluid chamber 20 generally equals to the fluid pressure of the second fluid chamber 22 when the axially extending body 30 begins to push the blade at the first position. A portion of working fluid inside the second fluid chamber 22 is squeezed out from the second fluid chamber 22 to the blade trench 72 during the push of the axially extending body 30 at the first the first position, and the expanding from the ball 52 at the second position.
In order to increase the rotational torque, referring to Figure 2 and 3, the hydraulic unit 16 includes a reducer unit that is mechanically coupled to an electric motor that provides rotational power and that boosts the output shaft 14. In an embodiment, the reducer unit is a planetary gearing reducer 74. The planetary gearing reducer 74 includes a sun gear 76, at least two planetary gears 78, and a ring gear 80. The sun gear 76 is connected to the electric motor (not shown). The planetary gears 78 are meshed with an outer periphery of the sun gear 78. The ring gear 80 is meshed with an outer periphery of the planetary gears 78. The planetary gears 78 rotate about their planetary gear shaft 82, respectively, and are fixed to the sleeve 24 by a swivel bearing 84. As shown, the sun gear 76, the ring gear 80, the planetary gears 78, and the sleeve 24 are mechanically coupled. By driving with the sun gear 76, the respective rotation of each of the planetary gears 78, and the meshing with the ring gear 80, the planetary gears 78 revolve around the sun gear 76 and further drive the shaft 82 at such revolution speed. The above described components collectively constitute the planetary gearing reducer 74.
In an embodiment, the hydraulic unit 16 further includes a fixed gear case cover 86, and bearing mounting portions 86b, 86c. The gear case cover 86 protects the rotating operation of various parts in the hydraulic unit 16 by preventing the entry of external foreign matters which cause malfunction or acceleration of mechanical loss.
Referring to Figures 2 and 3, a bearing 88 includes an inner ring, an outer ring, a plurality of balls and a cage are (not shown herewith). The outer ring of the bearing 88 is mounted on the bearing mounting portion 86b, and the inner ring is mounted on the bearing mounting portion 86a. The function of the bearing 88 is to ensure that the sun gear 76 rotates coaxial with a rotational center axis 90.
Referring to Figures 2 and 3, the swivel bearing 84 includes an inner ring, an outer ring, a plurality of balls and a cage (not shown herewith). The outer ring of the swivel bearing 84 is mounted on a bearing mounting portion 86c, and the inner ring of the swivel bearing is mounted on a bearing mounting portion 86d. Similarly, the function of the swivel bearing 84 is to ensure that the sleeve 24 rotates coaxial with the rotational center axis 90.
Referring from Figure 2 to Figure 5b, the hydraulic unit 16 further includes a cylindrical hole 92 which reserves a space for receiving the sun gear 76 to prevent the sun gear 76 from colliding with the sleeve 24 in the axial direction. The top of the sleeve 24 has six cylindrical holes 94 which are distributed in a regular hexagon in circumferential direction. The six cylindrical holes 94 are deformed into two groups, one of which is inserted by the planetary gear shaft 82; the other is used as rotating support holes for tightening and loosening the sleeve 24 and the cover 26 of the sleeve 24.
Referring from Figure 6a to Figure 7b, the radial width of a sleeve projection 62 is shorter than the radial width of a slot 60 of the rolling member 50, leaving a certain gap in the inner side of the slot 60. The hydraulic fluid injected from an fluid fill hole 124 flows along an fluid duct 126 of the rolling member 50 and flows into the first fluid chamber 20 from the said slot 60, as the groove 94 is of an arc type with a deep middle portion, and the depth is gradually shallower at both ends.
Referring to Figure 7a and Figure 7b, a slot 99 located in the cover 26 is adapted to mount the sealing ring 128 and the C-ring 55, and the C-ring 55 is used to limit the sealing ring 128. The seal ring 128 is used for static sealing and rotational dynamic sealing of the cover 26 and the holder 102.
Referring to Figure 8a and Figure 8b, the fluid holes 68a, 68b are inner connected with the first fluid chamber 20. The blade trench 72a, 72b are connected with the second fluid chambers 22a and 22b. The blade trench 72a and 72b which intermittently opens and closes the first fluid chamber 20 and the second fluid chamber 22a and 22b. Figure 8a is a cross-sectional view along line A of Figure 3.
Next, the working principle of the above-described hydraulic unit 16 is described. Assuming that the holder 102 is stationary, the planetary gearing reducer 74 drives the sleeve 24 to rotate clockwise. The sleeve 24 rotates clockwise with respect to the holder 102, and the angle of rotation is represented by Ceta. Assuming the moment when the axially extending body 30a or 30b is in contact with the upper end of blade 40a or 40b is Ceta at 0 degree. Then a single running period is represented as Ceta increasing from 0 to 180 degrees. Figure 8b is a schematic diagram of the projection of the fluid hole 68, ball 52 and the blade trench 72 onto the rolling member 50 when Ceta at 0 degree. In this state, the groove 56a or 56b is not in the projection of the fluid hole 68, thus the fluid hole 68 and the blade trench 72 are not in connection, the first fluid chamber 20 and the second fluid chamber 22a and 22b are not in connection either, as shown in Figures 8b and c. Before the impact, as shown in Figure 9a, the pressure difference between the first fluid chamber 20 and the second fluid chamber 6 are equal with each other, thus there is no flow between the two chambers. The axially extending body 30a moves closed to the upper end of blade 40, and ready to impacts the same, and a gap is existed in the axial direction between the lower end of blade 38a and the rolling member end surface 130. The relationship between the changes of Ceta and the connection of the big and second fluid chambers are shown in Figure 8c, wherein the "1" indicates the big fluid chamber is connected with the second fluid chamber, and 0 indicates the non-connection.
Referring to 10c is a force analysis diagram under ideal conditions during in the impacting. After the axially extending body 30a is in contact with the upper end of blade 40a of the blade 36, the sleeve 24 continues to rotate, generating a thrust F1 towards the blade 36. Then, the blade 36is forced to move downwards along the blade trench 72, and the ball 52 is also moved downwards by the blade ball groove 86. At this time, the second fluid chamber 22 and the first fluid chamber 20 are not in connection, and the hydraulic fluid in the second fluid chamber 6 is discharged along the blade trench 72. Under high-speed impacting, when the volume of fluid flowing out of the gap is smaller than the volume swept by the lower end 38 of the blade 36, the hydraulic fluid will generate a large pressure, such pressure is much larger than the inner pressure of the first fluid chamber 20, therefore a pressure difference between the upper end surface 40 of the blade 36 and lower end surface 40 of the blade 36 is generated. The pressure difference will produce a hydraulic force F2. The hydraulic force F2, the inertial force F5, the frictional force F4, and the component force of the thrust F1 in the axial direction are balanced in the axial direction. The blade trench 72 generates a supporting force F3 to the blade 43, which is balanced with the thrust F1 in the circumferential direction. The torque generated by the supporting force F3 on the rotating neutral shaft 4 is transmitted to the output 2.
Referring to Figure 11a and Figure 11b, when Ceta equals to 5 degrees, i.e., when the sleeve 24 is rotated after 5 degrees, the lower end 38 of the blade 36 is supported and restricted by the support assembly 48 and is not able to move downwards again, meanwhile the axially movement of the blade 36 is also restricted by the axially extending body 30 from above.
Referring to Figure 12a, Figure 12b and Figure 12c, the Ceta angle is 45 degrees. It can be seen that the state at this time is similar to the state of Ceta is 5 degrees, and e lower end 38 of the blade 36 is supported and restricted by the support assembly 48, at which time the axially movement of the blade 36 is also restricted by the axially extending body 30 from above. The groove 56 is not connected with the fluid hole 68, and the first fluid chamber 20 and the second fluid chamber 6 are not connected herewith, which is consistent with the Figure 8c.
Referring to Figure 13a, Figure 13b and Figure 13c, it is a state when the Ceta is at 67 degrees. As can be seen from Figure 13a, the axially extending body 30 has already left the upper end 40 of the blade 36, thus the movement of the blade 36 is no longer restricted, the blade 36 returned to the original height. It can be seen from Figure 12c that the groove 56a is connected with the blade trench 72a, and the second fluid chamber 22a and 22b are connected with the first fluid chamber 20. The groove 56 is also rotated to the end where the depth is shallow and the ball 52 is gradually lifted as the rolling member 50 rotates. When the steel ball 52 is raised to a certain height, the upward movement of the blade trench 72 and ball slot 144 is pushed upwards (as shown in Figure 12b), and the hydraulic fluid enters the groove 56a from 56b and then enters the blade trench 87a to complete the fluid return process.
Referring to Figure 14a, Figure 14b and Figure 14c, it is a state when the Ceta is at 90 degrees. As can be seen from Figures 14a, b, at this point the ball 50is already located at the top 88 of the blade trench 72. Meanwhile, the blade 36 has reached the highest axial position.
Figure 15a, Figure 15b and Figure 15c shows the state when the Ceta is at 135 degrees, which is similar to Ceta is at 90 degrees. The next state is as shown in Figure 9, thus the movement in one period is completed. With this arrangement of present transmission assembly, the sleeve 24 outputs two impact torques during each 360 degrees rotation.
Given the foregoing, it should be apparent that the present invention may be embodied in many different embodiments and configurations of these embodiments depending upon the particular use of the present invention. The scope of the present invention is determined by the claims attached hereto and not the foregoing discussion of the preferred embodiments.

Claims

A power tool (10) comprising a transmission mechanism (12), an output shaft (14) driven by the transmission mechanism, and a hydraulic unit (16) filled with a working fluid wherein,
the hydraulic unit is disposed coaxially with the output shaft, and defines a rotatively driving mechanism (18), a first fluid chamber (20), and a second fluid chamber (22);

the first fluid chamber is in intermittently fluid connection with the second fluid chamber via a fluid channel (28); and

a relative rotation between the hydraulic unit and the output shaft causes the rotatively driving mechanism to axially compress or expand a volume of the second fluid chamber for raising or decreasing a fluid pressure of the second fluid chamber, generating a pressure difference between the first fluid chamber and the second fluid chamber to cause an instantaneous torque to the output shaft, characterized in that:
the rotatively driving mechanism comprises an axially extending body (30) protruding from an interior surface (32) of the hydraulic unit; and

during the relative rotation between the hydraulic unit and the output shaft, the axially extending body pushes a first end wall (38) of an axially moveable member (36) which defining one edge (42) of the second fluid chamber towards a second end wall which defining another edge (44) of the second fluid chamber downwards at a first position, until the second fluid chamber is decreased to a minimum volume, and

wherein the first fluid chamber, the second fluid chamber and the rotatively driving mechanism are disposed inside a generally cylindrical case which is coaxial with the output shaft, the first fluid chamber surrounded by an outer side surface (87) of the output shaft, an inner side surface (69) of the case, and both end surfaces of the case, wherein the second fluid chamber is surrounded by an end surface of a rolling member (50), the first end of the axially movable member, and the outer side surface of the output shaft, and the inner side surface of the case.
The power tool of claim 1 wherein, the first end of the axially movable member forms the first end wall which defining said one edge of the second fluid chamber;
a second end (40) of the axially movable member which is axially opposite to the first end of the axially movable member receives the push from the axially extending body.
The power tool of claim 2 wherein, the second end of the axially movable member has a wedge-shape, and comprises a slope (46) for receiving the push from the axially extending body.
The power tool of claim 2, wherein,
the rotatively driving mechanism comprises a support assembly (48) comprising the rolling member which rotates radially and synchronously with the axially extending body and a ball (52) moveably received in the rolling member; and

the rolling member is receiving in a cavity inside the axially movable member.
The power tool of claim 4 wherein, an axial movement of the ball in the second chamber expands the volume of the second fluid chamber to a maximum by rising the axially movable member after the axially movable member is released by the axially extending body at a second position.
The power tool of claim 4 wherein,
the rolling member comprises a groove (56) disposed generally at an edge of the rolling member for moveably receiving the ball;

the groove has an arc shape with a deep middle portion and gradually shallower ends.
The power tool of claim 4 wherein,
the radial rotation of the rolling member generates a relatively axial movement between the ball and the second fluid chamber;

the ball is adapted to move to a lowest portion of the groove when the volume of the second fluid chamber is decreased to the minimum volume; and

the ball is further adapted to move to be received by the groove when the axially extending body begins to push the first end wall which defining one edge of the second fluid chamber towards the second end wall which defining another edge of the second fluid chamber downwards at the first position.
The power tool of claim 7 wherein,
the rolling member comprises a set of slots (60) symmetrical around a center of the rolling member; and

the set of slots couple with a set of projections (62) disposed on the axially extending body for receiving a driven force and generating the radial rotation of the rolling member.
The power tool of claim 2 wherein, the fluid channel (28) comprises a first fluid passage in fluid connection with the first fluid chamber, a second fluid passage is in fluid connection with the second fluid chamber; and the radial rotation of the rolling member intermittently fluidly communicates the first fluid passage and the second fluid passage.
The power tool of claim 9 wherein, the first fluid passage and the second passage is communicated through the groove.
The power tool of claim 9 wherein the first fluid passage comprises an fluid hole (68) disposed on the output shaft.
The power tool of claim 9 wherein the second fluid passage comprises a trench (72) for receiving the axially movable member.
The power tool of claim 9 wherein, the first fluid passage and the second fluid passage are not in fluid connection between the movements of the axially extending body from the first position to the second position.
The power tool of claim 9 wherein the first fluid passage and the second fluid passage are in fluid connection after the axially movable member is released by the axially extending body at the second position.
The power tool of claim 9 wherein, the fluid pressure of first fluid chamber generally equals to the fluid pressure of the second fluid chamber when the axially extending body begins to push the first end wall which defining one edge of the second fluid chamber at the first position.
The power tool of claim 12 wherein, a portion of working fluid inside the second fluid chamber is squeezed out from the second fluid chamber to the trench and the cavity for receiving the rolling member during the push during the axially extending body and the first end wall which defining one edge of the second fluid chamber from the first position to the second position.
The power tool of claim 1, wherein the working fluid is gas contented hydraulic fluid.
The power tool of claim 17, wherein the hydraulic unit comprises an adjusting screw (120) located coaxially with the output shaft for adjusting the gas content of the working fluid.
The power tool of claim 1, wherein the working fluid is arranged to flow the fluid channel and hold the first and second fluid chambers.
The power tool of claim 1, wherein the rotatively driving mechanism, the first fluid chamber, and the second fluid chamber are disposed in plural numbers coaxially and rotationally symmetrical to each other.
The power tool of claim 1, wherein two rotatively driving mechanisms, two first fluid chambers, and two second fluid chambers are disposed in a relationship rotationally symmetrical by 180° to each other.