Oil pressure type impulse torque generator for wrench

Abstract: In the oil pressure type impulse torque generator for a wrench, either one of both seal surfaces on the main shaft side and the liner side is made variable type by floating in order to eliminate "burning" and wear at the seal surfaces.

Description: This invention relates to an oil pressure type impulse torque generator for a torque wrench and the like, which is entirely free from "burning phenomenon" at the seal surfaces of a main shaft and a liner. Torque wrenches which are pneumatic tools used in bolt tightening operations and the like generate impact by a mechanical method based on the turning power of a rotor and such impact is converted into the desired torque. As the impact torque obtained by this mechanical method involves high impact noise, it can cause noise pollution. Also, there is a risk of operators being affected by Steinbrocken syndrome or Raynaud's phenomenon due to vibration caused by impact. With this in view, torque wrenches which use oil pressure for obtaining impact torque to prevent noises and vibration have been developed. Such torque wrenches have an oil pressure type torque generator with one blade or a plurality of blades at a main shaft (four blades in the case of Japanese Patent Publication Gazette No. 41-5800). In the case of the former or the single blade construction, oil pressure in a rotatable liner through which a main shaft is put, namely, oil pressure of the impact torque generator becomes higher, for which a more precise and stronger sealing construction is required. In the case of the latter or the construction using plural blades, an impact is generated at least twice in each revolution of the liner. Moreover there are types in which the seal surface is realised simply as a floating type such as in DE-A-3347016 and US-A-3263449 for example, but they have a problem with the working efficiency and the durability because of a large sliding resistance. Although the number of impacts generated in one revolution of the liner differs with the number of blades, the oil pressure type impulse torque generator will have better sealability if a clearance between seal surfaces of the liner and the main shaft is made smaller and as a result, internal pressure rises and accordingly output also rises. However, due to the rise of internal pressure "burning" at the seal surfaces of the liner and the main shaft is liable to take place. In EP-A-268715 there is provided an oil pressure type impulse torque generator for generating an intermittent torque at a main shaft disposed in an oval-shaped cavity in a liner which is rotatable by a rotor about the main shaft, the liner having first and second seal surfaces provided on its inner circumferential surface and the shaft having first and second seal surfaces said second shaft seal surface being provided by a blade means biased into contact with the liner and able periodically to seal with respect to both liner seal surfaces and said first shaft seal surface being able to seal periodically only with respect to the first liner seal surface. According to the present invention said first shaft seal surface is formed by a roller provided in a dovetail-shaped groove provided on the main shaft,said roller being movable and rotatable in said groove and being urged outwardly by spring means such that the roller is able to engage the first liner seal surface. The nature and advantages of the present invention will become apparent from the following description made with reference to the accompanying drawings, in which: Fig. 1 is a cross sectional view of an oil pressure type torque generator; Fig. 2 is a cross section, on an enlarged scale, of the seal surface on the major shaft side which is of roller type; Fig. 3 (A), (B) and (C) show respectively an embodiment of a different seal surface on the major shaft side; Fig. 4 (A), (B), and (C) show respectively an embodiment of a different seal surface on the liner side; and Fig. 5 is a cross section of an oil type wrench in which the present invention is incorporated. DETAILED DESCRIPTION OF THE INVENTION (Embodiment) An explanation is made below about the present invention on the basis of an embodiment illustrated in the drawing. Reference numeral 1 designates a main body of a wrench having therein a main valve 2 which carries out supply and stoppage of supply of high pressure air, a switchover valve 3 (normal and reverse turning) and a rotor 4 which causes high pressure air fed from the above valve group to generate turning torque. Thus, the wrench according to the present invention has a motor construction of general pneumatic tools. An oil pressure type impulse torque generator which converts turning torque of the rotor 4 into impulse torque is provided in a front case 6 which projects at a top end portion of the main body 1. The oil pressure type impulse torque generator 5 has in its liner case 12 a liner 8 which is rotatable about a main shaft 7 and has an inside caliber eccentric to the main shaft 7 and working oil for generating torque is filled and tightly sealed in the liner 8. Two blade insertion grooves 7b, opposite to each other, on a diametrical line which passes the center of the main shaft 7 are provided in the main shaft 7. A blade 9 is fitted in each of the two grooves 7b in such a fashion that the two blades 9 are always forced to project reciprocally in the outer circumferential direction of the main shaft 7 by a spring S. The thickness of the blade 9 is made smaller than the width of the groove 7b and seal surfaces 7a of floating and variable types are formed at the outer circumferential surface of the main shaft 7 between the two blades. These seal surfaces 7a are provided in such a fashion that they project a little from the outer end surface of the main shaft and are on the axial line which crosses at a right angle to the straight line connecting two blade insertion grooves 7b. Formation of this seal surface 7a of floating and variable type is carried out as follows. As shown in Fig. 2, a groove 71 of dovetail shape is made in the main shaft 7. A roller 72 is inserted in the groove 71 in such a fashion that it does not fly off in a radial direction of the main shaft 7 even by centrifugal force at the turning of the main shaft. This roller 72 is freely rotatable within the groove 71 and is movable within the range allowed in the groove by the centrifugal force and spring pressure. Thus, projection of the roller 72 from the outer circumferential surface of the main shaft 7 is made variable. A leaf spring 73 or a spring of other type is interposed between the roller 72 and the bottom of the groove 71. The seal surface 7a formed in floating type on the main shaft 7 is available in various shapes, namely, in parallel with the shaft center in lengthwise direction of the main shaft as shown in Fig. 3 (A), or, the shaft center b with a certain inclined angle with respect to the shaft center a in lengthwise direction as shown in Fig. 3 (B), or, in crank shape as shown in Fig. 3 (C). When two seal surfaces 7a are formed with respect to one main shaft, in the developed drawing each seal surface 7a is arranged in such a fashion that it is dissymmetrical to the axial line a. The liner 8 in which the main shaft 7 having two blades 9 projecting opposite direction and seal surfaces 7a are fitted forms a liner chamber of oval shape in section, as shown in Fig. 1. The inner circumferential surfaces of the opposite constricted parts of the liner 8 are protruded from the inner circumferential surface of the other part of the liner 8 and such protrusions are made seal surfaces 8a which intersect a straight line a passing the center of the liner 8. In the case where the seal surface 7a on the main shaft side is of floating type, the seal surfaces on the liner side is to be of conventional fixed type and in the case where the seal surface 8a on the liner side is of floating type, the seal surface on the main shaft side is to be of fixed type. At any rate, either one of the seal surfaces 7a (on the main shaft side) and the seal surface 8a (on the liner side) may be of floating type. The seal surface 8a on the liner side is formed selectively in any one of the shapes shown in Fig. 4 (A), (B) and (C). The seal surface 8a and the seal surface 7a at the liner and the main shaft respectively are formed correspondingly. Under this arrangement, when the liner 8 turns around the outer circumference of the main shaft 7 put in the liner chamber, the seal surface 8a makes contact with or gets near the surface 7a of the main shaft 7 and when both seal surfaces coincide completely with each other, hermetical sealing is done as if the liner chamber was divided into two by the seal surfaces 7a, 8a. At the middle position between both seal surfaces at the inner circumferential surface of the liner 8, seal surfaces 8b which make contact with top ends of the blades 9 and cause the two blades 9 and both seal surfaces 7a, 8a to divide temporarily the liner chamber into two rooms or four rooms are formed. These both seal surfaces 8b are opposite to each other, with their centers coinciding with a straight line passing the center of the liner chamber. An output adjust valve inserting hole 10 is made at one of the seal surfaces 8b of the liner 8 in parallel with the liner chamber or in parallel with an axial center of the liner. At the innermost recess of the hole 10, ports are made so that each of the at least two rooms partitioned by the seal surface of the main shaft and the blade may communicate with the output adjust valve inserting hole 10. An output valve 11 is fitted adjustably in said hole 10. When pressure air is introduced into a rotor room in the main body 1 by operating the main valve 2 and the switchover valve 3, the rotor turns at a high speed. Turning force of this rotor is transmitted to the liner 8 provided at a rotor axis. This liner 8 is supported rotatably at its outer circumference by a cylindrical liner case 12. The liner upper lid 13 and the liner lower lid 14 are provided at both end portions of the case 12 so that working oil filled in the liner chamber is hermetically sealed. In the state where pulse or impact force is generated, the seal surfaces 7a of the main shaft and the blades 9 make contact with the seal surfaces 8a and the seal surfaces 8b of the liner respectively and the liner chamber is divided into two rooms (right and left) with the opposite two blades on a straight line therebetween. Each of the right and left rooms is further divided into an upper room (high pressure room H) and a lower room (low pressure room L) by seal surfaces 7a, 8a. Substantially, the high pressure room H and the low pressure room L are formed on both sides of the blades. When the liner 8 is rotated further by rotation of the rotor 4, at immediately before the moment of impulse the volume of the high pressure room H is decreased but the volume of the low pressure room L is increased and when the two rooms with the blades therebetween are completely in confined state, high pressure is generated at the high pressure room H and the side of the blade 9 is pressed in a moment to the low pressure room L side by this oil pressure and such impulse force is transmitted to the main shaft in which the blades are inserted and thus the desired intermittent torque is generated at the main shaft and the desired operation is carried out. When the liner further turns 90° after torque was generated at the main shaft the high pressure room H and the low pressure room L with the blades therebetween communicate with each other and turn one room. Thus, the liner chamber as a whole is divided into two rooms of the same pressure and no torque is generated at the main shaft. Under this condition, the liner turns 90° by the rotation of the rotor, namely, the liner turns 180° from the time of impulse. In this state, since the seal surfaces 8b of the liner and the seal surfaces 7a of the main shaft, opposite to each other, intersect the axial line a passing the center, clearance is generated between both seal surfaces 7a, 8a and the liner chamber is divided into right and left two rooms by the main shaft and the upper and lower blades. This is substantially the same state as the state when the liner turns 90° from the time of impulse, namely, no pressure change is generated and the whole liner room is under the same pressure. Therefore, the liner rotates freely. The state of the liner when it further turns 90°, namely, turned 270° from the time of impulse, is substantially the same as the state when the liner turned 90° and the only difference is that the position of the output adjust valve is turned upside down. If the liner further turns from this state, the liner chamber which has been divided into right and left two rooms is divided into four rooms, namely, two high pressure rooms and two low pressure rooms, by the contact of the blades with the seal surfaces 8b and the contact of both seal surfaces 7a, 8a on the main shaft side and on the liner side with each other. Thus, pressure difference is generated between rooms on both side with the blades therebetween and impulse force is generated. In this way, strong impulse is generated once in each one revolution of the liner. Adjustment of this impulse force is done by the output adjust valve 11 by the conventional method. The above embodiment refers to two-blade type but is applicable to one-blade type. According to the present invention, in the case where rise of internal pressure is obtained by hermetical sealing between the seal surfaces of the liner and the seal surfaces of the main shaft and pulse is generated by oil pressure, either one of both seal surfaces is made a variable type by floating and therefore following the distortion of the liner, the seal surfaces vary and as a result, neither "burning" nor wear takes place. Moreover, as the seal surfaces of the main shaft and the liner vary, even if "burning" due to distortion of the liner is prevented by enlarging the tolerance of the liner inside diameter or the main shaft outside diameter, high pressure can be obtained without impairing sealability at both seal surfaces. Moreover, except when the oil pressure is increased with the seal surface on the inner circumferential face of the liner and the seal surface on the outer circumferential face of the main shaft to generate pulses, the projection quantity of the floating type seal surface is restricted so that the floating type seal surface may not get in touch with other members. This makes it possible to not only improve the working efficiency and the durability of the system but also keep the heat generation by friction at a low level by reducing the sliding resistance of the seal surface.

Claims: An oil pressure type impulse torque generator for generating an intermittent torque at a main shaft (7) disposed in an oval-shaped cavity in a liner (8) which is rotatable by a rotor (4) about the main shaft (7), the liner having first and second seal surfaces (8a, 8b) provided on its inner circumferential surface and the shaft having first and second seal surfaces, said second shaft seal surface being provided by a blade means (9) biased into contact with the liner and able periodically to seal with respect to both liner seal surfaces (8a, 8b) and said first shaft seal surface (7a) being able to seal periodically only with respect to the first liner seal surface (8a) characterised in that said first shaft seal surface (7a) is formed by a roller (72) provided in a dovetail-shaped groove (71) provided on the main shaft (7), said roller (72) being movable and rotatable in said groove (71) and being urged outwardly by spring means such that the roller (72) is able to engage the first liner seal surface (8a).

Inventors: TATSUNO KOJI C O URYU SEISAKU, TATSUNO, KOJI C/O URYU SEISAKU, LTD.
Applicants: URYU SEISAKU LTD, URYU SEISAKU, LTD.
Application year: 1989
Main classification: B25B21
IPC codes: B25B21, B25D15