Power tool equipped with a hydraulic pulse unit

Abstract

The present specification relates to an impulse tool comprising: a motor; an output shaft; an inertial drive member coupled to the motor and rotatable about a rotation axis, an oil chamber surrounded by the inertial drive member, and a hydraulic pulse unit arranged to intermittently transmit kinetic energy to the output shaft, wherein the inertial drive member further comprises an end portion having a transverse wall, the impulse tool further comprises a disc-shaped element arranged to at least partially define a receiving space in fluid communication with the oil chamber, the receiving space being formed between the disc-shaped element and the transverse wall, the impulse tool further comprises a compressible insert arranged to be in fluid communication with the receiving space, the compressible insert comprising a foam comprised of a closed cell foam, the compressible insert being arranged in the insert space formed in the end portion.

Description

Technical Field

[0001] The present invention generally relates to a power tool for fastening a screw, and more particularly to an impulse type power tool having a hydraulic pulse unit and a compressible insert disposed within the unit.

Background Art

[0002] Power tools for fastening are known to be used in various industries. For example, impulse type power tools equipped with a hydraulic pulse unit are commonly used in continuous mass production.

[0003] The hydraulic units of such tools are filled with oil. However, these units need to be designed to accommodate the thermal expansion of the oil since the oil is heated during operation. To absorb this thermal expansion, a solution has been proposed to introduce a small amount of air into the oil. However, in this type of power tool, a known problem necessarily involves filling the pulse unit with a precisely accurate amount of oil, so that a sufficient amount of air to absorb the expansion of the oil remains in the pulse unit.

[0004] To mitigate some of these problems, attempts have been made to provide an air volume in communication with the oil chamber to accommodate thermal expansion. For example, when the oil expands, a small amount of oil can flow into such an air space, so that the air within this space is compressed, and when the pulse unit cools, the oil is drawn back into the oil chamber. However, when the oil is drawn back, there is a risk that air from the air volume is introduced into the oil chamber, compromising efficiency.

[0005] Another solution that has been proposed relates to using elastic elements to compensate for thermal expansion, whereby the pulse unit can be completely filled without leaving any air in the oil volume.

[0006] However, such elastic elements tend to undergo residual deformation, air is expected to enter the oil chamber and the efficiency decreases, and furthermore, in many cases, it leads to a bulky and complex design and / or affects the inertia, thus remaining the problem of adversely affecting the operation of the pulse unit.

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] Therefore, there is a need for improvement in the field of power tools equipped with hydraulic pulse units.

MEANS FOR SOLVING THE PROBLEMS

[0008] Therefore, it would be desirable to provide an impulse tool in which the measures for ensuring a low air ratio in the oil volume are more efficient. Specifically, it would be desirable to provide an impulse tool in which such measures are provided in a way that does not affect the operation of the pulse unit and the complexity of the tool. To better address one or more of these problems, an impulse tool is provided with a compressible insert as defined in the independent claims. Preferred embodiments are defined in the dependent claims.

[0009] According to a first aspect of the present invention, an impulse tool is provided, the impulse tool comprising a hydraulic pulse unit including a motor, an output shaft, an inertia drive member coupled to the motor and rotatable about a rotational axis, an oil chamber surrounded by the inertia drive member, and impulse generating means arranged to intermittently transmit kinetic energy to the output shaft, the inertia drive member further comprising a distal end portion having a transverse wall, the impulse tool further comprising a disc-shaped element arranged to at least partially define a receiving space in fluid communication with the oil chamber, the receiving space being formed between the disc-shaped element and the transverse wall. The impulse tool further comprises a compressible insert arranged in fluid communication with the receiving space, the compressible insert including a foam composed of a closed cell foam, the compressible insert being arranged in an insert space formed in the distal end portion.

[0010] According to a first aspect, an impulse tool (or power tool or fastening tool, these terms being used interchangeably throughout this specification) provides an inventive solution to the above-described problems by means of a design incorporating a compressible insert. More specifically, this design enables a relatively large insert that can accommodate the thermal expansion of the oil by means of elastic deformation only, i.e., without permanent deformation and without impairing the efficiency of the pulse unit, as described below, thereby ensuring the proper functioning of the compressible insert.

[0011] The compressible insert of the present invention is made of a closed-cell foam material, i.e., a material having separated air bubbles, so that air is trapped within the insert, ensuring that it does not interfere with the operation of the pulse unit, and as a result, the performance of the power tool can be significantly improved. The compressible insert can be formed by a single uniform foam or can comprise one or more separate foams joined to each other. The insert can further comprise a skin surrounding the foam.

[0012] Furthermore, the compressible insert is adapted to be disposed within the pulse unit during assembly before the unit is filled with oil. In the stopped state of the tool, i.e., the cooled state, the compressible insert is unstressed and the oil fills the internal space of the unit. When the impulse unit operates and the oil is heated and expands, the compressible insert is compressed in the adjacent insert space. However, when the tool stops, the oil is cooled again and the compressible insert expands and returns to the uncompressed state.

[0013] The disc-shaped separating element separates the oil chamber from the receiving space and, in some embodiments, can comprise an opening that allows oil to flow between the oil chamber and the receiving space, enabling fluid communication. Thus, providing a separate receiving space in which the compressible insert is disposed for fluid communication is advantageous in that the compressible insert is protected from rapid pressure fluctuations (as opposed to slow temperature fluctuations). Protecting the insert from rapid fluctuations can potentially improve fatigue life. Accordingly, the compressible element is, in some embodiments, disposed in a chamber separate from the main oil chamber and, in some embodiments, is connected via a fluid opening or orifice, such orifices further contributing to attenuating rapid pressure fluctuations. The disc-shaped structure should be understood to have a substantially circular circumference and a thickness much smaller than the diameter, but does not necessarily have to be a perfectly flat surface.

[0014] The impulse tool referred to can be a hand-held pneumatic impulse tool or a power tool, such as a battery-powered tool.

[0015] According to one embodiment, the insert space is disposed adjacent to the receiving space. Thereby, the oil can act directly on the insert when expanding, and since the insert is disposed outside the oil chamber, the influence on the pulse unit can be minimized.

[0016] According to one embodiment, the insert space extends axially from the receiving space over at least two-thirds of the length of the end portion. In one embodiment, the insert space extends between the receiving space and the end wall opposite the end portion. A longer design allows for a smaller radius and thus less influence on inertia.

[0017] In some embodiments, the compressible insert extends along the entire length of the insert space. According to one embodiment, the outer boundary surface of the compressible insert and the insert space are congruent, and the compressible insert in the uncompressed state is adapted to fill the entire insert space. Thereby, effective utilization of space is achieved.

[0018] The shape of the compressible insert (and / or insert space) of the present invention can preferably be selected so as to minimize the influence on the strength and operation of the pulse unit. More specifically, it is selected so as not to affect materials that are subject to high stress and / or materials that contribute significantly to the moment of inertia. This can be achieved, for example, by keeping the radius as small as possible. In some embodiments, the element is further designed such that the axial length of the element has an elongated shape that is greater than the radius. The length can be, for example, at least twice the radius. Further, the insert can be rotationally symmetric.

[0019] According to one embodiment, the compressible insert is rotationally symmetric with respect to the central axis A-A of the pulse unit, and the radius of the compressible insert R2 is less than or equal to half of the radius of the end portion along the length of the insert chamber. Rotational symmetry refers to the overall shape of the element, ignoring, for example, slits for facilitating attachment. R1 is less than or equal to half of the radius of the end portion along the length of the insert chamber. Rotational symmetry refers to the overall shape of the element, ignoring, for example, slits for facilitating attachment.

[0020] According to one embodiment, at least one of the radius of the compressible insert R2 and the varying radius of the end portion R1 varies along the length of the insert chamber.

[0021] According to one embodiment, the insert space extends between the receiving space and the oil inlet formed at the end portion, the oil flow path is formed in the compressible insert, and fluidly connects the receiving space and the oil inlet to form a fluid passage. Thereby, the flow of oil can pass through a part of the insert, and it becomes easy to fill the pulse unit after the insert is arranged in the unit.

[0022] According to one embodiment, the oil flow path is an oil flow path for filling the pulse unit, and the oil flow path extends along the central axis of the compressible insert. Such an oil inlet can be an inlet formed in the end wall on the opposite side of the end portion.

[0023] According to one embodiment, the oil flow path is an oil flow path extending in a direction orthogonal to the central axis of the compressible insert for filling the pulse unit. Such an oil inlet can be an inlet formed in the side wall of the end portion.

[0024] The volume of the insert can preferably be selected to be large enough to ensure only elastic deformation, but this may depend on the material used for the foam and the properties of the oil used for the pulse unit. In any case, preferably, each volume needs to be selected such that the thermal expansion of the oil corresponds to an appropriate compression level of the insert, and appropriate means, in some embodiments, a level that allows only elastic deformation, that is, a level at which no permanent deformation of the insert occurs or only a small permanent deformation is allowed.

[0025] For example, according to one embodiment, the volume V of the insert f is in the range of 10 - 30% of the total volume V of the combined oil chamber and receiving space. Therefore, the total volume V corresponds to the total volume of oil that fills the pulse unit during use.

[0026] According to one embodiment, the volume V of the insert fis in the range of 10 - 25% of the combined total volume V, preferably 10 - 20%, more preferably 10 - 15%.

[0027] The material of the foam should preferably be oil-resistant, able to withstand high temperatures, and able to withstand fatigue damage.

[0028] According to one embodiment, the closed-cell foam is a foam material that can withstand a compression of 20 - 50%, preferably 20 - 30%, more preferably 22 - 27% without permanent deformation.

[0029] According to one embodiment, the cell diameter of the closed-cell foam is in the range of 0.15 - 0.35 mm, preferably 0.2 - 0.3 mm, more preferably 0.25 - 0.28 mm.

[0030] According to one embodiment, the gas fraction of the closed-cell foam is in the range of 85 - 99%.

[0031] The correctly selected cell diameter and gas fraction of the foam are important to ensure the proper elastic behavior of the compressible insert.

[0032] According to one embodiment, the closed-cell foam is made of polyvinyl fluoride. Other examples include, for example, silicone rubber.

[0033] According to a second aspect of the present invention, there is provided a compressible insert adapted to be disposed in an impulse tool according to any of the above embodiments. The objectives, advantages, and features of the compressible insert contemplated within the scope of the second aspect of the present invention can be readily understood from the above description referred to in the first aspect of the present invention.

[0034] Further objects, features and advantages of the present invention will become apparent upon review of the following detailed disclosure, drawings and appended claims. Those skilled in the art will appreciate that different features of the present invention can be combined to create embodiments other than those described below.

[0035] 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]

[0036]

Figure 1

Figure 2a

Figure 2b

Figure 3a

Figure 3b

[0037] All drawings are schematic and not necessarily to scale, and generally only those parts necessary to clarify the invention are shown, other parts may be omitted or merely suggested.

[0038] The exemplary impulse tool shown in Figure 1 is a pistol-type tool consisting of a housing 100 with a handle 110. For output control, the tool is provided with a trigger button 140. Further provided within the housing is a hydraulic pulse unit 20 having a motor (not shown) and a square ended output shaft 10.

[0039] As shown in FIG. 2a (and FIG. 3a), the impulse unit is connectable to the motor, rotatable about the axis of rotation (A-A), and further includes an inertial drive member 21 that surrounds the oil chamber 22. The inertial drive member 21 includes a rear portion 24, i.e., a distal end portion 24, adapted to be coupled to the motor. The output shaft 10 has an impulse receiving portion extending into the oil chamber 22 and is intermittently coupled to the drive member 21 via an impulse generating mechanism. Since the operation of the impulse mechanism itself is known in the art, it will not be described in further detail. Similar mechanisms have been described conventionally, for example, in U.S. Patent No. 6,110,045 and U.S. Patent No. 13,697,107.

[0040] The disc-shaped element 31 defines a receiving space 27 formed between the element 31 and the transverse wall 24a of the distal end portion 24. The receiving space 27 is in fluid communication with the oil chamber 22 (e.g., by a fluid opening provided in a disc-shaped element not shown) and can be described as a chamber into which oil can flow from the oil chamber 22 when thermal expansion occurs.

[0041] In the illustrated embodiment, the insert space 60 is disposed adjacent to the receiving space 27, and the compressible insert 50 is disposed within this insert space 60. Accordingly, the insert 50 is in fluid communication with the oil within the pulse unit, i.e., the oil acts on the compressible insert 50 and compresses the compressible insert 50, for example, during thermal expansion. In the illustrated embodiment, the insert space 60 extends axially from the receiving space 27 to an oil inlet 70 formed in the distal end portion.

[0042] In the illustrated embodiment, the compressible insert, in a stress-free state, fills the entire insert space, i.e., the outer boundary surface of the compressible insert 50 and the insert space 60 are congruent. Further, the oil flow path 51 extends along the central axis of the compressible insert and forms a fluid passage connecting the receiving space and the oil inlet, so that the pulse unit can be filled with oil.

[0043] Figure 2b shows the insert in detail in a perspective view. It can be seen that the insert has an overall rotationally symmetric structure except for the slit 51 provided to facilitate assembly. The shape of the compressible insert 50 (and thus the mating space 60) is further selected in the illustrated embodiment to realize the largest possible insert while minimizing the impact on the operation of the pulse unit. By giving the insert an elongated shape, the variable radius R2 of the rotationally symmetric insert 50 is kept small in order to minimize the influence on the stress region at the end portion and the influence on inertia.

[0044] In the illustrated embodiment, the volume of the compressible insert 50 is approximately 15% of the total volume of the oil chamber and the receiving space (corresponding to the total volume of the oil in the system during use). This can make the deformation when the oil expands relatively small, and as a result, although there is a difference, complete elastic deformation of the insert is guaranteed (i.e., no permanent deformation occurs).

[0045] The illustrated insert is made of a closed-cell foam material, illustratively polyvinyl fluoride.

[0046] Figures 3a - 3b show a second embodiment of the present invention. Similar to the first embodiment, the insert space 60' is arranged adjacent to the receiving space 27, and the compressible insert 50' is arranged within this insert space 60'.

[0047] In this exemplary embodiment, the insert space extends over most of the end portion 24 but does not necessarily reach the rear end wall 24b. The compressible insert also fills the entire insert space in this exemplary embodiment when no stress is applied.

[0048] Figure 3b shows the insert 50' in detail in a perspective view. Different from the insert shown in Figure 2b, the insert 50' is not rotationally symmetric, and a different approach is shown to realize the largest possible insert while minimizing the impact on the operation of the pulse unit. This is achieved by reducing the amount of material at a large distance from the center of the insert as much as possible. The notch, or recess 52', forms an oil flow path extending in a direction perpendicular to the central axis of the insert in this case. This enables the flow of oil from the oil inlet 71' through the inlet 50'.

[0049] During the operation of the impulse unit, the inertial drive member 21 is rotated by the motor, and a torque impulse is achieved on the output shaft 10. When the oil is heated and expands, some of the oil will enter the receiving space 27 from the oil chamber 22 through a fluid opening (not shown), and as a result, the compressible inserts 50; 50' are compressed within the adjacent insert spaces 60; 60'. However, when the tool stops, the oil cools, and the compressible inserts can expand and return to an uncompressed state.

[0050] Although the present invention has been illustrated and described in detail in the drawings and the above description, such illustration and description should be considered as exemplary or illustrative and not restrictive, and the present invention is not limited to the disclosed embodiments. Those skilled in the art will understand that many modifications, variations, and changes are possible within the scope defined by the claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain means are described in mutually different dependent claims does not indicate that a combination of these means cannot be used advantageously. Any reference signs in the claims should not be construed as limiting the claims.

Claims

1. A motor, an output shaft (10), an inertial drive member (21) coupled to the motor and rotatable about a rotation axis (A - A), an oil chamber (22) surrounded by the inertial drive member, and impulse generating means arranged to intermittently transmit kinetic energy to the output shaft, a hydraulic pulse unit (20); An impulse tool comprising: The inertial drive member (21) further comprises an end portion (24) having a transverse wall (24a); The impulse tool further comprises a disc-shaped element (31) arranged to at least partially define a receiving space (27) in fluid communication with the oil chamber. An opening provided in the disc-shaped element allows oil to flow between the oil chamber and the receiving space through the opening, and the oil chamber and the receiving space (27) are in fluid communication. The receiving space is formed between the disc-shaped element and the transverse wall; The impulse tool further comprises a compressible insert (50) arranged in fluid communication with the receiving space; The compressible insert includes a foam composed of a closed-cell foam; The compressible insert is arranged in an insert space (60) formed in the end portion (24). The insert space is arranged adjacent to the receiving space and extends between the receiving space and an oil inlet (70) formed in the end portion. An oil flow path (53) is formed in the compressible insert to form a fluid passage that fluidly connects the receiving space and the oil inlet and allows the flow of oil to pass through a part of the compressible insert. An impulse tool.

2. The impulse tool according to claim 1, wherein the insert space extends axially from the receiving space over at least 2 / 3 of the length of the end portion.

3. The impulse tool according to claim 1, wherein the outer boundary surface of the compressible insert and the insert space are congruent, and the compressible insert in an uncompressed state fills the entire insert space.

4. The impulse tool according to claim 1, wherein the oil flow path is an oil flow path for filling the pulse unit with oil, and the oil flow path extends along the central axis of the compressible insert.

5. The oil flow path is an oil flow path for filling the pulse unit with oil, and the oil flow path extends in a direction orthogonal to the central axis of the compressible insert. The impulse tool according to claim 1.

6. The volume (V f ) of the insert is in the range of 10 - 30% of the total volume (V) of the oil chamber and the receiving space combined, the impulse tool according to claim 1.

7. The volume (V f ) of the insert is in the range of 10-25%, preferably 10-20%, more preferably 10-15% of the combined total volume (V), of the impulse tool according to claim 6.

8. The closed-cell foam is a foam material that can withstand compression of 20 - 50%, preferably 20 - 30%, more preferably 22 - 27% without permanent deformation. The impulse tool according to claim 1.

9. The cell diameter of the closed-cell foam is in the range of 0.15 - 0.35 mm, preferably 0.2 - 0.3 mm, more preferably 0.25 - 0.28 mm. The impulse tool according to claim 1.

10. The gas fraction of the closed-cell foam is in the range of 85 - 99%. The impulse tool according to claim 1.

11. The closed-cell foam is made of polyvinyl fluoride. The impulse tool according to claim 1.

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