Hydraulic torque impulse generator

Abstract: A hydraulic torque impulse generator, comprises a motor driven drive member (10) with a fluid chamber (23), an output spindle (11) connectable to a work piece and extending into the fluid chamber (23), two diametrically opposite seal elements (12, 13) movably supported in axial slots (32, 33) in the output spindle (11) for sealing cooperation with seal lands (24, 25) on the fluid chamber wall, axially extending seal ribs (27-30) on both of said fluid chamber wall and said output spindle (11), and a cam spindle (40) drivingly coupled to the drive member (10) and extending into a coaxial bore (34) in the output spindle (11) for engagement with the seal elements (12, 13) and moving the latters outwardly towards the fluid chamber wall in two relative angular positions between the drive member (10) and the output spindle (11). The cam spindle (40) has two diametrically opposite and differently shaped cam means (41, 42) for alternative engagement with high and low lift cam following portions (45-50) on the seal elements (12, 13) such that in one of the relative positions between the drive member (10) the output spindle (11) the seal elements (12, 13) are moved outwardly into sealing engagement with the seal lands (24, 25) and in the other of the relative positions between the drive member (10) and the output spindle (11) the seal elements (12, 13) are moved to positions where no sealing cooperation with the seal lands (24, 25) is obtained, thereby ensuring a single torque impulse only to be generated during each full revolution of the drive member (10) relative the output spindle (11).

Description: This invention concerns a hydraulic torque impulse generator of the type, comprising a motor driven drive member with a fluid chamber, an output spindle connectable to a work piece and extending into the fluid chamber, two diametrically opposite seal elements movably supported in axial slots in the output spindle for sealing cooperation with seal lands on the fluid chamber wall, axially extending seal ribs on both of said fluid chamber wall and said output spindle, and a cam spindle drivingly coupled to the drive member and extending into a coaxial bore in the output spindle for engagement with the seal elements. In previously known torque impulse generators of the above type valve means have been incorporated to short circuit the impulse generating seal means every second time they coincide to avoid more than one torque impulse being generated per each relative revolution between the drive member and the output spindle. In U.S. Patent No. 4,884,995 there is shown a hydraulic torque impulse generator of the above type (according to the preamble of claim 1) in which the cam spindle is provided with passage forming grooves which in cooperation with radial openings in the output spindle form short circuiting passages between the high and low pressure compartments of the fluid chamber. One problem concerned with this prior art impulse generator is that the valve means on the cam spindle and the output spindle create leakage points which require a very tight fit between the cam spindle and the output spindle to avoid reduced impulse magnitudes due to leakage. Extra passage forming means on the cam spindle and the output spindle as well as a very accurate fit between these elements cause increased manufacturing costs for the impulse generator. The above problem is solved by the invention as it is defined in claim 1. Hereinafter, a preferred embodiment of the invention is described in detail with reference to the accompanying drawings. On the drawings: Fig 1 shows a longitudinal section through an impulse generator according to the invention illustrating the seal elements in their impulse generating seal positions. Fig 2 shows a cross section along line II-II in Fig 1. Fig 3 shows an exploded view of the cam and cam following means on the spindle and the seal elements, respectively, illustrating the high lift engagement position of the cam means as in Fig 1. Fig 4 is similar to Fig 1, but illustrates the seal elements in their free running positions, Fig 5 shows a across section along line V-V in Fig 4. Fig 6 is similar to Fig 3, but illustrates the low lift position of the cam means. The hydraulic torque impulse generator shown in the drawing figures comprises a drive member 10, an output spindle 11 with a square end portion, and two movable T-shaped seal elements 12, 13. The drive member 10 includes a cylindrical main portion 15, a front end wall 16 with a central opening 17 for the output spindle 11 and a rear end wall 18 which is rotationally locked relative to the main portion 15 by a stud 19 (See Figs 3 and 4). The rear end wall 18 is formed with a stub axle 22 for connection to a drive motor (not shown) and is fixed to the main portion 15 by means of a ring 20 threaded into the main portion 15. The stub axle 22 may be square or hexagonal in cross section or be provided with splines for intercoupling with a corresponding female coupling means on the motor shaft. The drive member 10 further includes a cylindrical fluid chamber 23 into which the rear portion of the output spindle 11 extends. On the circumferential wall of the fluid chamber 23 there are two parallel, axially extending seal lands 24, 25 for sealing cooperation with the seal elements 12, 13, and two parallel, axially extending seal ribs 27, 28 for sealing cooperation with two corresponding seal ribs 29, 30 on the output spindle 11. The output spindle 11 comprises two radially extending axial slots 32, 33 in which the seal elements 12, 13 are movably supported. Moreover, the output spindle 11 is formed with an axial bore 34 extending from its rear end and having radial openings 35, 36 for receiving the central stem portions 37, 38 of the T-shaped seal elements 12, 13. A cam spindle 40 extends into the bore 34, and is at its rear end positively coupled to the drive member 10 for corotation therewith. The cam spindle 40 is formed with two differently shaped and diametrically opposite cam means 41, 42. One of the cam means is basically the opposite of the other. As mentioned above, the seal elements 12, 13 are formed with central stem portions 37, 38 which extend into the bore 34 through the radial openings 35, 36 to engage the cam means 41, 42 of the cam spindle 40. Each of the seal element stem portions 37, 38 has a cam following portion 43, 44 for engagement with the cam means 41, 42. On one of the seal elements 12 the cam following portion 43 comprises a central low lift surface 45 surrounded by two high lift surfaces 46, 47, whereas the cam following portion 44 of the other seal element 13 comprises a central high lift surface 48 surrounded by two low lift surfaces 49, 50. See Fig 3. For cooperation with the cam following portions 43, 44 of the seal elments 12, 13, the cam means 41, 42 of the cam spindle 40 are formed with cam lobes of a configuration corresponding to the high and low lift surfaces of the cam following portions 43, 44. Accordingly, one of the cam means 41 comprises a central cam lobe 51 surrounded by two clearance grooves 52, 53, whereas the other cam means 41 comprises two cam lobes 54, 55 surrounding a central clearance groove 56. The cam lobes 51 and 54, 55, respectively, have all the same radial extent, but depending on which of the high or low lift surfaces on the cam following portions 43, 44 they actually engage they accomplish a sealing cooperation between the seal elements 12, 13 and the seal lands 24, 25 on the fluid chamber wall or free running positons of the seal elements 12, 13. In Figs 1,2, and 3, there is illustrated the impulse generating phase in which the seal elements 12, 13 are brought into contact with the seal lands 24, 25. This is obtained by a cooperation between the cam lobe 51 and the high lift surface 48 on the seal element 13 and between the cam lobes 54, 55 and the high lift surfaces 46, 47 on the seal element 12. In this phase, the low lift surfaces 45 and 49, 50 coincide with the clearance grooves 56 and 52, 53, respectively. See Fig 3. When a relative rotation of 180° has occurred between the drive member 10 and the output spindle 11 the free running phase takes place. This is illustrated in Figs 4, 5, and 6. In this phase, the cam lobes 51 and 54, 55 engage the low lift surfaces 45 and 49, 50, respectively, whereas the high lift surfaces 48 and 46, 47 coincide with the clearance grooves 56 and 52, 53, respectively, on the cam spindle 14. See Fig 6. In both phases, however, sealing cooperation is obtained between the seal ribs 27, 28 on the fluid chamber wall and the seal ribs 29, 30 on the output spindle 11. The cam operation of the seal elements 12, 13 according to the invention is advantageous in that no extra valve forming means is needed to accomplish a single torque impulse per relative revolution between the drive member 10 and the output spindle 14. It is to be noted that the invention is not limited to the above described embodiment but can be varied within the scope of the claims. For example, the cam lobes of the cam spindle cam means as well as the cam following surfaces of the seal elements may be disposed otherwise. It is important to note though that the camming engagement between the cam spindle and the seal elements takes place symmetrically on the latters to avoid tilting and jamming thereof.

Claims: Hydraulic torque impulse generator, comprising a drive member (10) connected to a rotation motor and including a fluid chamber (23) with a cylindrical circumferential wall, an output spindle (11) connectable to a work piece and having a rear portion extending into said fluid chamber (23) in a coaxial relationship with said drive member (10), said rear spindle portion having two diametrically opposite axial slots (32, 33) supporting radially movably seal elements (12, 13) for sealing cooperation with two seal lands (24, 25) on said fluid chamber wall, and a first set of two axially extending seal ribs (29, 30) on said spindle (11) for sealing cooperation with a second set of two axially extending seal ribs (27, 28) on said fluid chamber wall, a cam spindle (40) drivingly coupled to said drive member (10) and extending into a coaxial bore (34) in said output spindle (11) and arranged to engage said seal elements (12, 13) via radial openings (35, 36) in said output spindle (11) to move said seal elements (12, 13) outwardly towards said circumferential wall in two relative angular positions between said drive member (10) and said output spindle (11), characterized in that said cam spindle (40) comprises two differently shaped cam means (41, 42) located diametrically opposite one another, that said seal elements (12, 13) have correspondingly shaped inner cam following portions (43, 44) for cooperation with said cam means (41, 42) such that in one of said two relative positions between said drive member (10) and said output spindle (11) said cam means (41, 42) cooperate with said cam following portions (43, 44) to move said seal elements (12, 13) outwardly into positions well out of sealing cooperation with said seal lands (24, 25), and that in the other of said two relative positions said cam means (41, 42) cooperate with said cam following portions (43, 44) to move said seal elements (12, 13) outwardly into positions in which a sealing cooperation with said seal lands (24, 25) is obtained. Impulse generator according to claim 1, wherein said two differently shaped cam means (41, 42) comprise a first cam means (41) and a second cam means (42), said second cam means (42) is diametrically opposite said first cam means (41), each of said first and second cam means (41, 42) includes one or more cam lobes (54, 55), said cam lobe or lobes (54, 55) of said first cam means (41) are axially separated from said cam lobe or lobes (51) of said second cam means (42), each of said seal elements (12, 13) has a high lift cam following means (46-48) and a low lift cam following means (45, 49, 50) separated from each other in the axial direction of said output spindle (11), said high lift cam following means (46, 47) of one of said seal elements (12) is axially separated from said high lift cam following means (48) of the other seal element (13) but is axially aligned with said cam lobe or lobes (54, 55) of said first cam means (41), whereas said high lift cam following means (48) of the other of said seal elements (13) is aligned with said cam lobe or lobes (51) of said second cam means (42), and said low lift cam following means (45) of said one of said seal elements (12) is axially separated from said low lift cam following means (49, 50) of the other seal element (13) but is axially aligned with said cam lobe or lobes (51) of said second cam means (42), whereas said low lift cam following means (49, 50) of the other seal element (13) is axially aligned with said cam lobe or lobes (54, 55) of said first cam means (41). Impulse generator according to claim 1 or 2, wherein one of said cam means (41, 42) comprises a central cam lobe (51) surrounded by two clearance grooves (52, 53), whereas the other of said cam means comprises two cam lobes (54, 55) surrounding a central clearance groove (56), and one of said seal elements (13) has a cam following portion (44) with a central high lift surface (48) surrounded by two low lift surfaces (49, 50), whereas the other of said seal elements (12) has a cam following portion (43) with two high lift surfaces (46, 47) surrounding a central low lift surface (45). Impulse generator according to claim 1, 2 or 3, wherein said seal elements (12, 13) comprise T-shaped vanes having their central stem portion (37, 38) extending into said coaxial bore (34) through said radial openings (35, 36) in said output spindle (11) and being formed with said cam following portions (43, 44).

Inventors: SCHOEPS KNUT CHRISTIAN, SCHOEPS, KNUT CHRISTIAN
Applicants: ATLAS COPCO TOOLS AB, ATLAS COPCO TOOLS AB, NACKA
Application year: 1993
Main classification: B25B21
IPC codes: B25B21, F16D31