GB2240500A - Hydraulic torque impulse generator - Google Patents

Abstract

Sealing means 12, 13, 14, 16, 18, 19, 26, 27 on an impulse-receiving rotor 3 and a rotatable mass 1 (defining a hydraulic fluid chamber 2) periodically delimit high and low pressure regions H and L n times per revolution of the mass 1 relative to the rotor 3. The rotor 3 has bypass bores 28, 29 opening at its periphery and cooperating with the periphery of the chamber 2 so as to communicate between the high and low pressure regions (as in Figure 11) n-1 times per revolution, in such a manner that only one torque impulse is generated (as in Figure 13) per revolution. <IMAGE>

Description

HYDRAULIC TOROUE IMPULSE GENERATOR This invention relates to a hydraulic torque impulse generator, e.g. for a power tool, such as a screwdriver or a nut runner driven by an air motor or other motive source.

EP-A-O 243 334 describes a torque impulse generator comprising a hollow mass which is to be driven in rotation and which defines a hydraulic fluid chamber, an impulse-receiving rotor in the chamber, and sealing means on the rotor and mass for periodically delimiting at least one high-pressure region and at least one low-pressure region in the chamber n ( 2) times per revolution of the mass relative to the rotor. In order to ensure that only one torque impulse is generated per revolution, a spindle on the rotor is provided with a peripheral slot or slots which periodically communicate with passages in an end wall of the chamber.

What is desired is an alternative and preferably simpler way of achieving the same effect.

The present invention provides a hydraulic torque impulse generator in which the rotor has one or more passages opening at the periphery of the rotor and cooperating with the periphery of the chamber so as to communicate between the high-pressure regions(s) and the lower-pressure region(s) n-l times per revolution of the mass relative to the rotor, in such a manner that only one torque impulse is generated per revolution.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic axial section through a hydraulic torque impulse generator; Figure 2 is an end view of the impulse generator; Figure 3 is an axial section through a hollow cylinder which forms part of the impulse generator; Figure 4 is a section in line IV-IV in Figure 3; Figure 5 is an end view of the cylinder; Figure 6 shows a rotor which forms part of the impulse generator; Figure 7 is a section on line VII-VII in Figure 6; Figure 8 is a section on line VIII-VIII in Figure 6; Figure 9 is an end view of the rotor; and Figures 10 to 13 are cross-sections through the cylinder and rotor at four equi-angularly spaced positions during a revolution of the cylinder relative to the rotor.

The impulse generator illustrated has a rotatable hollow mass 1 defining a hydraulic fluid chamber 2 accommodating a coaxially rotatable impulse-receiving rotor 3. The mass 1 comprises a hollow cylinder 4 with an integral wall 6 at one end of the chamber 2, and a cap 7 which is screwed onto the cylinder 4 and provides a wall 8 at the other end of the chamber 2. The cap 7 has a coaxial shaft 9 for connection to the output (not shown) of a gear-box or motor of an air-motor-driven power tool having a housing in which the impulse generator is mounted.

The rotor 3, which is generally cylindrical, is journalled in the end walls 6, 8 and is provided with a spindle 11 for connection to a tool bit (not shown) either directly or via intermediate gearing.

The rotor 3 has two diametrically opposed sealing ribs 12, 13 for periodically forming seals with diametrically opposed axially extending sealing surfaces 14, 16 of the chamber 2. At 900 to the ribs 12, 13 the rotor 3 has radial-axial slots 17 containing spring-loaded diametrically opposed sealing blades 18, 19 which continuously make sealing contact with the periphery of the chamber 2. However, except in the angular positions of the cylinder 1 which are shown in Figures 10 to 13, the sealing contact is bypassed by cavities 21-24 (shorter than the chamber 2) formed in the perphery of the chamber 2 between the sealing surfaces 14, 16 and sealing surfaces 26, 27 at an angular spacing of 90 .

Near each end of the rotor 3 there is a pair of bores 28, 29 opening at opposite sides of the periphery of the rotor, the two bores being arranged on opposite sides of (and parallel to) the diametral plane containing the ribs 12, 13, and the axes of the bores lying in a plane normal to the axis of the rotor 3. At one end the bores 28, 29 open into recesses 31 provided on both sides of the rib 13 so that the bores are in constant communication with the hydraulic fluid in the chamber 2.

Referring to Figures 10 to 13 it will be seen that, as the mass 1 rotates relative to the rotor 3, high-pressure regions H and low pressure regions L are delimited by the ribs 12, 13 and the blades 18, 19 in cooperation with the sealing surfaces 14, 16, 26, 27, at two points (Figures 11 and 13) during one revolution.

However, in the relative position shown in Figure 11, the high-pressure regions H communicate with the low-pressure regions L via the bores 28, 29 and recesses 31, so that the pressure is redistributed throughout the hydraulic fluid and therefore no torque impulse is applied to the rotor 3. In the position shown in Figure 13 the lower ends of the bores 28, 29 are closed, with the result that the abruptly increasing pressure differential between the high-and low-pressure regions H and L acts on the rotor blades 18, 19 so that the kinetic energy is transmitted from the mass 1 to the rotor 3, via the hydraulic fluid, as a torque impulse.

The magnitude of the peak torque depends on the resistance to rotation of the rotor 3 and on the rate at which the pressure differential is dissipated. In order to provide adjustability of the latter parameter, and therefore of the final torque, a valve element 32 is arranged in a fluid bleeding path 33 in the cylinder 4 between a region H and a region L.

The chamber 2 is filled with hydraulic fluid through an inlet closed by a screw 34. During use, the fluid undergoes thermal expansion and leaks into an expansion space, between one rotor journal and the cap 7, compressing a resilient insert 36 of closed-cell foam.

Leakage out of the impulse generator is prevent by 0-ring seals 37. After use, as the hydraulic fluid cools and contracts, the resilient insert 36 expands so as to assist in returning the fluid from the expansion space to the chamber 2, which is thereby kept full of hydraulic fluid.

As may be appreciated'from Figure 13, the bores 28, 29 may be closed (at the impulse point) by making the sealing surface 14 wider than the opposite sealing surface 16. However, the fabrication of the cylinder 4 and the mounting of the rotor 3 therein are simplified if the axial length of the bypass cavities 21 and 24 (on either side of the sealing surface 14) is less than that of the cavities 22 and 23 (see Figure 3), so that two wide peripheral valve faces 38 and two narrow peripheral valve faces 39 are defined adjacent respective ends of the cavity 2. Each pair of bores 28, 29 is at an axial location lying between the inner edges of the wide and narrow valve faces 38, 39, so that the bores are periodically closed by the wide valve face 38.

Although a pair of bores has been shown at each end of the rotor, one pair can be omitted. Furthermore, one of the bores- 28, 29 may be omitted, provided that the high-pressure regions H can communicate with each other (e.g. through the slots 17 or through an additional through-bore).

Claims (6)

Claims:

1. A hydraulic torque impulse generator comprising a hollow mass which is to be driven in rotation and which defines a hydraulic fluid chamber, an impulse-receiving rotor in the chamber, and sealing means on the mass and rotor for periodically delimiting at least one high-pressure region and at least one low-pressure region in the chamber n times per revolution of the mass relative to the rotor, where n is at least two, characterised in that the rotor has at least one bypass passage opening at the periphery of the rotor and cooperating with the periphery of the chamber so as to communicate between the high-pressure region and the low-pressure region n-l times per revolution of the mass relative to the rotor, in such a manner that only one torque impulse is generated per revolution.

2. A torque impulse generator as claimed in claim 1, in which the sealing means includes two diametrically opposed axial ribs on the rotor, there being two bypass passages, one of which opens to one side of the ribs and the other of which opens to the other side of the ribs.

3. A torque impulse generator as claimed in claim 1 or 2, in which the or each bypass passage is a straight bore.

4. A torque impulse generator as claimed in any preceding claim, in which the periphery of the chamber has a valve surface which periodically closes one end of the or each bypass passage and which is delimited by cavities in the periphery of the chamber.

5. A torque impulse generator as claimed in claim 4, in which the valve surface is adjacent to one end of the chamber.

6. A power tool incorporating a hydraulic torque impulse generator according to any preceding claim.

6. A hydraulic torque impulse generator substantially as described with reference to, and as shown in, the accompanying drawings.

7. A power tool incorporating a hydraulic torque impulse generator according to any preceding claim.

amendments to the claims have been fled as folows 1. A hydraulic torque impulse generator comprising a hollow mass which is to be driven in rotation and which defines a hydraulic fluid chamber, an impulse-receiving rotor in the chamber, sealing means on the mass and rotor for periodically delimiting at least one high-pressure region and at least one low-pressure region in the chamber n times per revolution of the mass relative to the rotor, where n is at least two, the rotor having at least one bypass passage opening at the periphery of the rotor, and valve means for permitting the high-pressure region and the low-pressure region to communicate with each other via the at least one bypass passage n-l times per revolution of the mass relative to the rotor, in such a manner that only one torque impulse is generated per revolution, characterised in that the valve means comprises a valve surface at the periphery of the chamber, the valve surface periodically closing one end of the at least one bypass passage and being delimited by cavities in the periphery of the chamber.

2. A torque impulse generator as claimed in claim 1, in which the sealing means includes two diametrically opposed axial ribs on the rotor, there being two bypass passages, one of which opens to one side of the ribs and the other of which opens to the other side of the ribs.

3. A torque impulse generator as claimed in claim 1 or 2, in which the or each bypass passage is a straight bore.

4. A torque impulse generator as claimed in any preceding claim, in which the valve surface is adjacent to one end of the chamber.

5. A hydraulic torque impulse generator substantially as described with reference to, and as shown in, the accompanying drawings.