Power tool including a hydraulic pulse unit

Abstract

The present invention relates to a pulse tool, comprising a motor, an output shaft and a hydraulic pulse unit, wherein the hydraulic pulse unit comprises an inertial drive component connected to the motor and rotatable about a rotation axis, an oil chamber enclosed in the inertial drive component and a pulse generating device arranged to intermittently transfer kinetic energy to the output shaft, wherein the inertial drive component further comprises an end piece having a transverse wall, and the pulse tool further comprises a disc-shaped element, which is arranged to at least partially define a receiving space fluidly connected to the oil chamber, the receiving space being formed between the disc-shaped element and the transverse wall, and a compressible insert being arranged to be fluidly connected to the receiving space, wherein the compressible insert comprises a foam body, the foam body comprises a closed-cell foam, and wherein the compressible insert is arranged in an insertion space formed in the end piece.

Description

Technical Field

[0001] The present invention generally relates to power tools for tightening screws, and more particularly, to a pulse-type power tool having a hydraulic pulse unit and a compressible insert disposed in the unit. Background Art

[0002] Power tools for tightening are known to be used in various industries. For example, pulse-type power tools including hydraulic pulse units are generally used for continuous heavy 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 as it heats up during operation. Solutions have been proposed to introduce a small amount of air into the oil to absorb this thermal expansion. However, in power tools of this type, a known problem consists in filling the pulse unit with precisely the right amount of oil so that enough air will remain inside the pulse unit to absorb the expansion of the oil.

[0004] To alleviate some of these problems, attempts have been made to provide an air volume arranged in communication with the oil chamber to accommodate thermal expansion. For example, as the oil expands, a small amount of oil may be allowed to escape into such an air space, thereby compressing the air in the space, and as the pulse unit cools, the oil is sucked back into the oil chamber. However, as the oil is sucked back, there is a risk that air in the air volume is introduced into the oil chamber, resulting in reduced efficiency.

[0005] Another solution proposed involves the use of elastic elements to compensate for the heat-related expansion, which allows the pulse unit to be completely filled without leaving any air in the oil volume.

[0006] However, there remains the problem that such elastic elements are susceptible to residual deformations, allowing air to enter the chamber, resulting in reduced efficiency and also often leading to a more bulky and complex design and / or adversely affecting the inertia and therefore the operation of the pulse unit.

[0007] Therefore, there is a need for improvements in the field of power tools including hydraulic pulse units. Summary of the invention

[0008] It is therefore desirable to provide a pulse tool in which the measures for ensuring a low percentage of air in the oil volume are more effective. In particular, it is desirable to provide a pulse tool in which such measures are provided in a manner that does not affect the operation of the pulse unit and the complexity of the tool. In order to better address one or more of these problems, there is provided a pulse tool comprising a compressible insert as defined in the independent claim. Preferred embodiments are defined in the dependent claims.

[0009] According to a first aspect of the present invention, there is provided a pulse tool comprising a motor, an output shaft and a hydraulic pulse unit, the hydraulic pulse unit comprising an inertial drive member connected to the motor and rotatable about a rotation axis, an oil chamber enclosed in the inertial drive member and a pulse generating device arranged to intermittently transfer kinetic energy to the output shaft, wherein the inertial drive member further comprises an end piece having a transverse wall, the pulse 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. wherein the pulse tool further comprises a compressible insert arranged to be in fluid communication with the receiving space, wherein the compressible insert comprises a foam body, the foam body comprising a closed-cell foam, and wherein the compressible insert is arranged in an insertion space formed in the end piece.

[0010] According to a first aspect, a pulse tool (or power tool or tightening tool, these terms are used interchangeably throughout the specification) provides an inventive solution to the above-mentioned problems by incorporating a compressible insert design. More specifically, the design ensures proper functioning of the compressible insert by allowing a relatively large insert to be able to accommodate thermal expansion of the oil by elastic deformation only (i.e. without permanent deformation) and without loss of efficiency of the pulse unit, as shown below.

[0011] The compressible insert of the present invention is made of a closed cell foam material, i.e., a material with isolated gas bubbles, ensuring that the air is contained in the insert and does not interfere with the operation of the pulse unit, thus significantly improving the performance of the power tool. The compressible insert may be formed of a single uniform foam body, or may include one or more separate foam bodies bonded together. The insert may further include an outer skin of closed foam.

[0012] During assembly, the compressible insert is further adapted to be arranged in the pulse unit before the unit is filled with oil. In a static state of the tool (i.e., a cold state), the compressible insert and the oil in an unstressed state thus fill the inner space of the unit. During operation of the pulse unit, as the oil heats up, expansion occurs, causing the compressible insert to compress in the adjacent insert space. However, as the tool stops, the oil cools again and the compressible insert can expand back to its uncompressed state.

[0013] The disc-shaped separator element separates the oil chamber from the receiving space and in some embodiments may include an opening through which oil can flow between the oil chamber and the receiving space providing fluid communication. An advantage of the arrangement in which the compressible insert is arranged in fluid communication with such a separate receiving space is that the compressible insert is protected from rapid fluctuations in pressure (as opposed to slower changes in temperature). By protecting the insert from rapid fluctuations, fatigue life can be improved. Therefore, in some embodiments, the compressible element can be described as being arranged in a chamber separated from the main oil chamber, and in some embodiments, the chamber is connected to the main oil chamber via a fluid opening or orifice, wherein such an orifice will further help to suppress rapid pressure changes. Disc-shaped should be understood as a structure having a substantially circular circumference and whose thickness is significantly less than the diameter, but not necessarily a completely flat surface.

[0014] The pulse tool referenced may be a hand-held pneumatic pulse tool or an electric tool, such as a battery-powered tool.

[0015] According to one embodiment, the insertion space is arranged adjacent to the receiving space. This allows the oil to act directly on the insert when expanding and allows the insert to be arranged outside the oil chamber, thereby minimizing the impact on the pulse unit.

[0016] According to one embodiment, the insertion space extends from the receiving space in the axial direction over at least 2 / 3 of the length of the end piece. In one embodiment, the insertion space extends between the receiving space and the opposite end wall of the end piece. A longer design allows a smaller radius and therefore a smaller effect on inertia.

[0017] In some embodiments, the compressible insert extends along the entire length of the insertion space. According to one embodiment, the outer boundary surface of the compressible insert and the insertion space are consistent, so that the compressible insert in an uncompressed state fills the entire insertion space. Thus, efficient use of space is achieved.

[0018] The shape of the compressible insert (and / or the insertion space) of the present invention can preferably be selected to minimize the impact on the strength and operation of the pulse unit. More specifically, a material is selected that does not affect the ability to withstand high stresses and / or significantly contribute 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 as an elongated shape in which the axial length of the element is greater than the radius. The length can, for example, be at least twice the radius. The insert can further be rotationally symmetric.

[0019] According to one embodiment, the compressible insert is rotationally symmetric with respect to the central axis AA of the pulse unit, and wherein the radius R2 of the compressible insert along the length of the insertion chamber is less than or equal to half the radius R1 of the end piece. Rotational symmetry refers to the overall shape of the element, without taking into account slits for facilitating installation, etc.

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

[0021] According to one embodiment, the insert space extends between the receiving space and an oil inlet formed in the end piece, and wherein an oil channel is formed in the compressible insert, forming a fluid path fluidly connecting the receiving space and the oil inlet. Thus, oil flow is allowed through a portion of the insert, which facilitates filling the pulse unit after the insert is arranged in the unit.

[0022] According to one embodiment, the oil channel is an oil channel extending along the central axis of the compressible insert for filling the pulse unit.Such an oil inlet may be an inlet formed at an opposite end wall of the end piece.

[0023] According to one embodiment, the oil channel is an oil channel for filling the pulse unit extending in a direction perpendicular to the central axis of the compressible insert.Such an oil inlet may be an inlet formed at a side wall of the end piece.

[0024] The volume of the insert may preferably be chosen to be large enough to ensure only elastic deformation, which may depend on the material used for the foam and the properties of the oil used in the impulse unit. In any case, the corresponding volume should preferably be chosen so that the thermal expansion of the oil corresponds to a suitable degree of compression of the insert - in some embodiments, suitable can be understood as a degree that only elastic deformation is allowed, i.e. the insert should not undergo permanent deformation, or only undergo minor permanent deformation.

[0025] For example, according to one embodiment, the volume V of the insert f In the range of 10-30% of the combined total volume V of the oil chamber and the receiving space. The total volume V is therefore equal to the total volume of oil filled into the pulse unit in use.

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

[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 capable of withstanding 20-50% compression, preferably 20-30%, more preferably 22-27% deformation 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] Correct selection of the cell diameter and gas fraction of the foam is important to ensure 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 invention, there is provided a compressible insert suitable for arrangement in an impulse tool according to any of the above embodiments. The objects, advantages and features of the compressible insert which may be envisaged within the scope of the second aspect of the invention may be readily appreciated from the above discussion with reference to the first aspect of the invention.

[0034] Further objectives, features and advantages of the present invention will become apparent when studying the following detailed disclosure, the drawings and the appended claims.Those skilled in the art realize that different features of the present invention can be combined to form embodiments other than those described in the following. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The invention will be described in the following illustrative and non-limiting detailed description of exemplary embodiments with reference to the accompanying drawings, in which:

[0036] Figure 1 is a side view of an exemplary power tool according to one embodiment.

[0037] Figure 2a is a cross-sectional view of a hydraulic pulse unit according to one embodiment.

[0038] Figure 2b is a perspective view of an exemplary compressible element according to one embodiment.

[0039] Figure 3a is a cross-sectional view of a hydraulic pulse unit according to one embodiment.

[0040] Figure 3b is a perspective view of an exemplary compressible element according to one embodiment.

[0041] All the figures are schematic, not necessarily to scale, and generally only show parts which are necessary in order to elucidate the invention, wherein other parts may be omitted or mentioned briefly. DETAILED DESCRIPTION

[0042] Figure 1 The exemplary pulse tool shown is a pistol-style tool comprising a housing 100 with a handle 110. For power control, the tool is provided with a trigger button 140. A motor (not shown) and a hydraulic pulse unit 20 with a square-ended output shaft 10 are further provided in the housing.

[0043] like Figure 2a (and Figure 3a ), the pulse unit includes an inertial drive member 21, which can be connected to the motor and can rotate around the rotation axis (AA) and close the oil chamber 22. The inertial drive member 21 includes a rear portion 24 or an end piece 24 suitable for connection to the motor. The output shaft 10 has a pulse receiving portion, which extends into the oil chamber 22 and is intermittently connected to the drive member 21 by a pulse generating mechanism. The operation of the pulse mechanism itself is not described in further detail because it is known in the art. Similar mechanisms have been previously described in, for example, U.S. Patents 6,110,045 and 13,697,107.

[0044] The disc-shaped element 31 defines a receiving space 27 formed between the element 31 and the transverse wall 24a of the end piece 24. The receiving space 27 is in fluid communication with the oil chamber 22 (e.g., via a fluid opening provided in the disc-shaped element, not shown), and can be described as a cavity into which oil can flow from the oil chamber 22 when thermal expansion occurs.

[0045] In the embodiment shown, the insertion space 60 is arranged adjacent to the receiving space 27 and the compressible insert 50 is arranged in the insertion space 60. The insert 50 is thus in fluid communication with the oil in the pulse unit, i.e. the oil acts on the compressible insert 50, for example during thermal expansion, causing the compressible insert 50 to compress. In the embodiment shown, the insertion space 60 extends in the axial direction from the receiving space 27 to an oil inlet 70 formed in the end piece.

[0046] The compressible insert in the illustrated embodiment in an unstressed state fills the entire insertion space - i.e., the outer boundary surface of the compressible insert 50 and the insertion space 60 are congruent. In addition, the oil channel 51 extends along the central axis of the compressible insert, forming a fluid path connecting the receiving space and the oil inlet, and thus allowing oil to fill into the pulse unit.

[0047] Figure 2bThe insert is shown in detail in a perspective view. It can be seen that the insert has an overall rotationally symmetrical design, without taking into account the slits 51 provided to facilitate assembly. In the embodiment shown, the shape of the compressible insert 50 (and therefore the conforming space 60) is further selected to achieve as large an insert as possible while minimizing the impact on the operation of the pulse unit. This is achieved by giving the insert an elongated shape, wherein the varying radius R2 of the rotationally symmetrical insert 50 is kept small to minimize the impact on the stress area of ​​the end piece and the impact on the inertia.

[0048] In the illustrated embodiment, the volume of the compressible insert 50 is approximately 15% of the combined total volume of the oil chamber and the receiving space (corresponding to the total volume of oil in the system in use) - this allows relatively small deformation to occur when the oil expands, thereby ensuring that the insert deforms almost completely elastically (i.e., no permanent deformation occurs).

[0049] The insert shown is made of a closed cell foam material, in the exemplary case polyvinyl fluoride.

[0050] Figure 3a-Figure 3b A second embodiment of the invention is shown.Similar to the first embodiment, an insertion space 60' is arranged adjacent to the receiving space 27 and a compressible insert 50' is arranged in the insertion space 60'.

[0051] In this exemplary embodiment, the insertion space extends over a large portion of the end piece 24, but does not completely reach the rear end wall 24b. In this illustrated embodiment, the compressible insert in its unstressed state also fills the entire insertion space.

[0052] Figure 3b The insert 50' is shown in detail in a perspective view. Figure 2b In contrast to the insert shown, the insert 50' is not rotationally symmetrical, which illustrates a different approach to achieving the largest possible insert while minimizing the impact on the pulse unit operation. This is achieved by minimizing the amount of material at a large distance from the center of the insert. The cutout or groove 52' forming the oil passage in this case extends in a direction perpendicular to the center axis of the insert. This allows oil to flow from the oil inlet 71' through the inlet 50'.

[0053] During operation of the pulse unit, the inertial drive member 21 is rotated by the motor and a torque pulse is achieved in the output shaft 10. As the oil heats up and expands, some oil will enter the receiving space 27 from the oil chamber 22 via the fluid opening (not shown), causing the compressible insert 50; 50' to compress in the adjacent insert space 60; 60'. However, as the tool stops, the oil cools down and the compressible insert can expand back to its uncompressed state.

[0054] Although the present invention has been elaborated and described in detail in the drawings and the above description, such elaborated and described should be considered as illustrative or exemplary rather than restrictive; the present invention is not limited to the disclosed embodiments. Those skilled in the art understand that many modifications, changes and variations can be envisaged within the scope defined by the appended 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 fact that certain means are recited in mutually different dependent claims does not indicate that a combination of these means cannot be used to advantage. Any figure mark in the claims should not be interpreted as limiting the scope of the claims.

Claims

1. A pulse tool comprising a motor, an output shaft (10) and a hydraulic pulse unit (20), the hydraulic pulse unit comprising an inertial drive member (21) connected to the motor and rotatable about a rotation axis (AA), an oil chamber (22) enclosed in the inertial drive member and a pulse generating device arranged to intermittently transfer kinetic energy to the output shaft, wherein: The inertial drive member (21) further comprises an end piece (24) having a transverse wall (24a), The pulse tool further comprises a disc-shaped element (31) arranged to at least partially delimit a receiving space (27), the receiving space (27) being in fluid communication with the oil chamber via an opening provided in the disc-shaped element, through which oil can flow between the oil chamber and the receiving space, the receiving space being formed between the disc-shaped element and the transverse wall, The pulse tool further comprises a compressible insert (50), the compressible insert being arranged in fluid communication with the receiving space, wherein the compressible insert comprises a foam body, the foam body comprises a closed cell foam, and wherein the compressible insert is arranged in an insert space (60) formed in the end piece (24), wherein the insert space is arranged adjacent to the receiving space, wherein the insert space extends between the receiving space and an oil inlet (70) formed in the end piece, and wherein an oil passage (53) is formed in the compressible insert forming a fluid path fluidly connecting the receiving space and the oil inlet, thereby allowing oil to flow through a portion of the insert.

2. The pulse tool according to claim 1, wherein: The insertion space extends from the receiving space in the axial direction over at least 2 / 3 of the length of the end piece.

3. The pulse tool according to any one of the preceding claims, wherein: An outer boundary surface of the compressible insert and the insertion space are conformable such that the compressible insert in an uncompressed state fills the entire insertion space.

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

5. The pulse tool according to claim 1, wherein: The oil passage is an oil passage for filling the pulse unit with oil, and the oil passage extends in a direction perpendicular to a central axis of the compressible insert.

6. The pulse tool according to claim 1, wherein: The compressible insert is rotationally symmetric relative to a central axis (AA) of the pulse unit, and wherein a radius (R2) of the compressible insert along a length of the insertion chamber is less than or equal to half a radius (R1) of the end piece.

7. The pulse tool according to claim 6, wherein: At least one of a radius (R2) of the compressible insert and a radius (R1) of the end piece varies along a length of the insertion chamber.

8. The pulse tool according to claim 1, wherein: The volume of the insert is in the range of 10-30% of the combined total volume of the oil chamber and the receiving space.

9. The pulse tool according to claim 8, wherein: The volume of the insert is in the range of 10-25% of the total volume of the combination.

10. The pulse tool according to claim 9, wherein: The volume of the insert is in the range of 10-20% of the total volume of the combination.

11. The pulse tool according to claim 10, wherein: The volume of the insert is in the range of 10-15% of the total volume of the combination.

12. The pulse tool according to claim 1, wherein: The closed-cell foam is a foam material that can withstand 20-50% compression deformation without permanent deformation.

13. The pulse tool according to claim 12, wherein: The closed-cell foam is a foam material that can withstand 20-30% compression deformation without permanent deformation.

14. The pulse tool according to claim 13, wherein: The closed cell foam is a foam material that can withstand 22-27% compression deformation without permanent deformation.

15. The pulse tool according to claim 1, wherein: The pore diameter of the closed-cell foam is in the range of 0.15-0.35 mm.

16. The pulse tool according to claim 15, wherein: The pore diameter of the closed-cell foam is in the range of 0.2-0.3 mm.

17. The pulse tool according to claim 16, wherein: The pore diameter of the closed-cell foam is in the range of 0.25-0.28 mm.

18. The pulse tool according to claim 1, wherein: The gas fraction of the closed cell foam is in the range of 85-99%.

19. The pulse tool according to claim 1, wherein: The closed-cell foam is made of polyvinyl fluoride.

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