POWER WRENCH COMPRISING A HYDRAULIC PULSE UNIT

Abstract

A power wrench includes a hydraulic pulse unit that includes an impulse generator. A separating arrangement is provided to extract air from oil. The separating arrangement includes a disc-shaped separator element and a sealing arrangement arranged to provide a seal between the disc-shaped separator element and a receiving space in fluid communication with the oil chamber. The disc-shaped separator element provides a passageway between the oil chamber and the receiving space by a fluid opening. The separating arrangement also includes a partitioning element arranged in the receiving space, such that first and a second partial volumes are formed on sides of the partitioning element. The first and second partial volumes are in fluid communication, and the fluid opening is arranged on the first side of the partitioning element.

Claims

1-15. (canceled)

16. A power wrench comprising: a motor; an output shaft; and a hydraulic pulse unit including an inertia drive member connected to the motor and rotatable about a rotation axis, an oil chamber enclosed in the inertia drive member, and an impulse generator arranged to intermittently transfer kinetic energy to the output shaft, wherein the inertia drive member comprises an end piece having a transverse wall, wherein a separating arrangement is provided for extracting air from oil, the separating arrangement comprising a disc-shaped separator element and a sealing arrangement configured to provide a seal between the disc-shaped separator element and the transverse end wall, thereby partly delimiting a receiving space therebetween in fluid communication with the oil chamber, the disc-shaped separator element providing a passageway between the oil chamber and the receiving space by a fluid opening located at a first radial distance from the rotation axis, wherein the separating arrangement further comprises a partitioning element arranged in the receiving space, such that a first partial volume is formed on a first side of the partitioning element and a second partial volume is formed on a second side of the partitioning element, wherein the first and second partial volumes are in fluid communication and wherein the fluid opening is arranged on the first side, wherein the fluid communication between the first and second partial volumes is provided by a fluid passageway at least partly formed by the partitioning element, wherein the sealing arrangement comprises an outer seal and an inner seal, and wherein the inner seal forms the partitioning element such that the fluid passageway is provided by a channel delimited by the outer seal and the inner seal.

17. The power wrench according to claim 16, wherein the fluid passageway constitutes the first volume portion.

18. The power wrench according to claim 17, wherein the fluid passageway extends at the first radial distance from the rotation axis following a path defined by a shape of a portion of a circumference of the disc-shaped separator element.

19. The power wrench according to claim 16, wherein the fluid passageway extends at the first radial distance from the rotation axis following a path defined by a shape of half of a circumference of the disc-shaped separator element.

20. The power wrench according to claim 16, wherein the fluid opening is arranged approximately in the middle of the fluid passageway, measured lengthwise.

21. The power wrench according to claim 16, wherein the outer seal extends following a curvature of a circumference of the disc-shaped separator element at a second radial distance from the rotation axis and is adapted to bear against the transverse wall and form a fluid-tight seal therebetween, wherein the second radial distance is larger than the first radial distance, and wherein the inner seal extends following the curvature of a portion of the circumference at a third radial distance from the rotation axis and is adapted to bear against transverse wall and form a fluid-tight seal therebetween, wherein the third radial distance is smaller than the first radial distance, such that the fluid passageway is formed between the inner and outer seals.

22. The power wrench according to claim 16, wherein the partitioning element comprises a protruding shoulder.

23. The power wrench according to claim 16, wherein the partitioning element comprises a tubular element such that the fluid passageway is provided therein.

24. The power wrench according to claim 16, wherein the partitioning element forms part of the disc-shaped separator element.

25. The power wrench according to claim 16, wherein the partitioning element forms part of the transverse wall.

26. The power wrench according to claim 16, wherein the wrench is an electric wrench.

27. The power wrench according to claim 16, wherein the wrench is a pneumatic wrench.

28. A disc-shaped separator element for use in a separating arrangement in a power wrench that includes a motor, an output shaft, and a hydraulic pulse unit including an inertia drive member connected to the motor and rotatable about a rotation axis, the disc-shaped separator element comprising: a fluid opening located at a radial distance from the rotation axis; and a partitioning element configured such that a first partial volume is formed on a first side of the partitioning element and a second partial volume is formed on a second side of the partitioning element; an outer seal; and an inner seal which forms the partitioning element, wherein the first and second partial volumes are in fluid communication, wherein the opening is arranged on the first side of the partitioning element, and wherein the fluid passageway is provided by a channel delimited by the outer seal and the inner seal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The invention will be described in the following illustrative and non-limiting detailed description of exemplary embodiments, with reference to the appended drawing, on which

[0031] FIG. 1 is a perspective view of an exemplary power wrench according to one embodiment.

[0032] FIG. 2 is a cross sectional view of a hydraulic pulse unit according to one embodiment.

[0033] FIG. 3a is a perspective view of an exemplary disc shaped separator element according to one embodiment.

[0034] FIG. 3b is a front view of an exemplary disc shaped separator element according to one embodiment.

[0035] FIGS. 4a-d show the functionality of the separating arrangement at different rotational positions.

[0036] All 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 merely suggested.

DETAILED DESCRIPTION

[0037] The power wrench shown as an example in the drawings is a pistol type wrench which comprises a housing 100 with a handle 110. For power control, the wrench is provided with a trigger button 140. In the housing there is further provided a non-illustrated motor, and a hydraulic pulse unit 20 with a square ended output shaft 10.

[0038] As illustrated in FIG. 2 the impulse unit comprises an inertia drive member 21 including a cylindrical front piece 25 and an end piece 24 and enclosing an oil chamber 22. The rear part 24, or end piece 24, is formed with a coupling portion for connection to the motor. The output shaft 10 has an impulse receiving portion which extends into the oil chamber 22 and is intermittently coupled to the drive member 21 via an impulse generating mechanism 23. The operation of the impulse mechanism per se is not described in any further detail since it is known in the art. Similar mechanisms has been previously described for example in U.S. Pat. Nos. 6,110,045 and 13,697,107.

[0039] The separating arrangement 30 is provided between the oil chamber 22 and a receiving space 27, or air chamber 27, and comprises a disc shaped separator element 31, a sealing arrangement 32 arranged to provide a seal between the disc and a transverse wall 24a of the end piece, or rear part 24, such that the receiving space 27 is formed there between. This receiving 27 space, at room temperature, contains a mixture of approximately 60% oil and 40% air, and may be described as a chamber into which oil may flow from the oil chamber 22 when heat expansion occurs whereby the air in the receiving space is compressed correspondingly in order to accommodate this oil volume. In order to allow this flow, the disc shaped separator element 31 comprises an oil outlet opening 33 at a distance a1 from the axis A-A, shown in FIG. 3.

[0040] The disc shaped element 31 will now be described in greater detail with reference to FIGS. 3a and 3b. From FIG. 3 it may be recognized that in the illustrated embodiment, the surface 31a of the disc shaped element which faces the receiving space 27 has a slightly conical shape. The disc shaped element further comprises an outer seal 32a and a partitioning element 34 in the form of a protruding shoulder 34. The outer seal 32a extends along the circumference of the disc shaped element at a radial distance a2 from the rotation axis A-A and is adapted to bear against the transverse wall 24a of the rear part. The partitioning element 34 is in the illustrated embodiment formed by an inner seal and extends following the curvature of a portion of the circumference at a radial distance a3 from the rotation axis A-A and is also adapted to bear against transverse wall 24a. Accordingly the inner and outer seal have the same shape and thus a constant width channel C is formed there between, in the illustrated embodiment a channel C having the shape of half a circle.

[0041] As the disc shaped element 34 is arranged between the oil chamber 22 and the receiving space 27 a first volume portion V1 and a second volume portion V2 are formed partly delimited from each other by the partitioning element 34, the corresponding areas of the disc shaped element 31 are indicated in FIG. 3. The partitioning element 34 is however designed such that the first and second volume portion remain in fluid communication. The oil outlet opening 33 is in FIG. 3 shown at an upper portion of the disc. In the illustrated embodiment, the distance a1 is slightly less than the radius R of the disc shaped element 31. More particular, a1 is approximately equal to the radius of the disc minus the radial thickness of the outer seal 32a. This fluid channel C delimited by the outer and inner seal also provides a fluid passageway from the second volume to the first volume and consequently to the fluid opening 33, the fluid opening being arranged in the first volume portion.

[0042] During operation of the impulse unit the inertia drive member is rotated by the motor and a torque impulse is accomplished in the output shaft 10. The separating arrangement co-rotates with the inertia drive member.

[0043] As the oil heats up and expansion occurs, some oil will enter from the oil chamber 22 via the opening 33 into the receiving space 27, resulting in compression of the air volume in this space. As the tool halts however, the oil is cooled again and the oil is sucked back into the oil chamber 22.

[0044] However, due to the difference in density between air and oil, in an exemplary use case where the output shaft 10 extends in parallel to a horizontal surface and the disc shaped separator element 31 is positioned substantially vertically, the air moves to the upper part of the receiving space 27, whereas the heavier oil collects at the bottom of the space. The position of the flow opening 33 is on the other hand changed as the separating arrangement rotates and is arbitrary as the tool may be stopped at any time.

[0045] Turning to FIG. 4a-d, the functionality of the partitioning element 34 will be described. In FIG. 4a, the opening 33 is positioned at what will be referred to as a top position. Here, the partitioning element 34 acts both as a barrier preventing the air from reaching the opening 33, in a sense trapping the air in the pocket formed by the (arched) partitioning element, but also together with the outer seal 32a forming a fluid channel C through which the oil may flow into the opening 33. In FIG. 4b, the same disc is shown rotated 45°, the air is still trapped in the pocket or “air trap” formed by the partitioning element 34 and the oil flows through the same channel C. In FIG. 4c, showing the disc shaped element 31 rotated an additional 45° i.e. a total of 90° compared to FIG. 4a, the oil level is still well above the opening 33 and the air remains at the upper portion, and is not allowed to enter into the oil chamber 22 via the opening 33 due to the oil forming a barrier. Finally, in FIG. 4d, since the opening 33 is at the lowest position, the oil level is above both ends of the channel C and only oil enter the channel also at this position.

[0046] The element 34 is hence designed such that the oil is guided to form a barrier between the air and the opening 33 in the disc shaped separator element 31, regardless of the rotational position at halt. Or, in other words, at least one end of the channel is always below oil level, thus always providing a fluid connection for the oil to the opening and thus the chamber.

[0047] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiment. The skilled person understands that many modifications, variations and alterations are conceivable within the scope as defined in the appended claims. Additionally, variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, form a study of the drawings, the disclosure and 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 mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope of the claims.