Pressure detecting device for torque control wrench

Abstract: A pressure detecting device for a torque control wrench which is simple in construction and yet carries out precise detecting. This device has such advantage that it dispenses with the timer control, equalizes tightening torque and carries out pressure detecting precisely.

Description: This invention relates to a device for detecting pressure in a torque control wrench which is simple in construction and yet carries out precise detecting. A shut-off mechanism by which when a set pressure is reached, air supply to a motor is suspended to stop the wrench, is adopted generally in torque control wrenches. In one form of shut-off mechanism, a small hole communicating with a high pressure chamber of a liner is made at an upper lid of the liner, a piston is moved inside the upper lid of the liner by rise of pressure in the liner chamber upon generation of pulse, a detecting valve of self-holding type is worked in linkage with the piston, a timer circuit is worked in response to the working of the detecting valve and a main valve is shut after the lapse of a certain period of time preset so as to stop working of the wrench. However, when the above piston is moved by rise of pressure, spring pressure for returning is always acting on the piston and internal pressure at the time of pulse is high and it is difficult to work out a spring design to cope with such internal pressure. Theoretically, it is possible to change timing of oil pressure detection by regulation of a spring but substantially, regulation of timing is impossible. Since a timer is worked after a preset pressure is reached, tightening torque varies with variation of the state of tightening work and accordingly tightening torque becomes unbalanced. Moreover, it becomes necessary to regulate tightening time by means of output regulation by a relief valve shaft and a timer. In another torque wrench disclosed in EP-A-70325 and corresponding to the preamble of claim 1, the maximum pressure of the working fluid acts on a piston which in turn actuates a shut-off valve, and a relief valve operates to relieve said pressure when it exceeds a predetermined value. EP-A-0309625 describes a relief valve provided in a passage interconnecting the port of the high-pressure chamber and the port of the low-pressure chamber. This relief valve is provided solely to adjust the output of the torque control wrench. There is no description of how the function of the relief valve may be adjusted. According to the present invention there is provided a torque wrench having a rotary liner incorporating a pressure detecting device for adjusting the output of the wrench and adjusting the pressure at which a relief valve of the wrench opens, comprising a relief valve shaft having a passage connected to a port of a high-pressure chamber, a spring-loaded relief valve element co-operating with the relief valve shaft, a shut-off valve, a piston and cylinder device operated by a pressure of the working fluid, and a rod interconnecting the piston and the shut-off valve, characterized by the passage interconnecting the port of the high-pressure chamber with a port of a low-pressure chamber, a branch passage leading from a location intermediate the ends of the passage in the relief valve shaft and opening to a chamber at one end of the shaft, the relief valve element being spring-loaded into engagement with the open end of the branch passage and arranged to allow fluid to flow from the passage in the valve shaft into the chamber when said pressure exceeds a predetermined pressure to relieve the pressure in the passage in the relief valve shaft, the cylinder of the piston and cylinder device being in permanently open communication with the chamber, and the relief valve shaft comprising a main body part and a regulating rod screw-threadedly connected to the main body part, the main body part having a pin in an axial slot connected to the liner whereby rotation of the regulating rod causes the axial position of the main body part to be adjusted. The present invention has for its object to dispense with the timer control, to provide improved control of tightening torque by means of improved detection of pressure. In order to attain the above object, one embodiment of the present invention has the following construction. A passage in which a part of pressure oil on the side of the liner high pressure chamber flows is formed in a relief valve shaft inserted adjustably in the liner. An opening surface of this passage is formed at an end of the relief valve shaft and a relief valve which is biassed by a spring is provided at this end surface so as to open the passage at a set pressure. This relief valve communicates with a cylinder through the medium of a relief valve inserting hole made in the liner and a passage formed at an upper lid of the liner. A piston provided at a forward end of a rod which passes through a rotor shaft is put in a cylinder inside the upper lid of the liner and a shut-off valve mechanism is provided at the other end of the rod. The invention will now be described in more detail with reference by way of example to the accompanying drawings in which: Figure 1 is a sectional elevation of a torque control wrench according to the invention, the regulating rod of the relief valve being left out for clarity reasons, Figure 2 is a sectional view of part of the wrench of Figure 1 on a larger scale, the regulating rod of the relief valve being left out for clarity reasons, Figure 3 is an end view on the section line 3-3 of Figure 2, Figure 4 is a sectional elevation of the relief valve shaft shown in Figures 1 to 3, Figure 5 shows a modified form of relief valve shaft, Figure 6 is a sectional end view on the line 6-6 of Figure 5, Figure 7 is a view corresponding to Figure 3 but incorporating the modified relief valve shaft, Figure 8 shows an alternative form of shut-off valve mechanism to that shown in Figure 1, Figure 9 is a view corresponding to Figure 2 but having the relief valve shaft in an alternative position, and Figures 10 and 11 are sectional end views on the lines 10-10 and 11-11 respectively of Figure 9. Referring first to Figures 1 to 4 of the drawings, reference numeral 1 denotes the main body of an oil pressure type torque wrench, in which a main valve 2 to effect supply and stoppage of supply of high pressure air and a valve 3 for switching between forward and reverse operation are provided. A rotor 4 is provided in the main body 1 so that high pressure air from the above valves generates rotational torque. The main body 1 has the motor construction of a general pneumatic tool. An oil pressure type impulse torque generator 5 which converts rotational torque of the rotor 4 into impulse torque is provided in a front casing 6 which is provided projects forward from the main body 1. The oil pressure type impulse torque generator 5 has a liner 8 whose inner calibre is eccentric to a main shaft 7 within a liner casing 12, which liner is rotatably mounted on the main shaft 7. Working oil for generating torque in the liner 8 fills the liner, which is sealed. Two opposing blade receiving grooves 7b are formed on a diametrical line passing through the centre of the main shaft 7. Inserted in the grooves 7b are two respective blades 9 having a thickness smaller than the width of the groove, which are biassed by a spring S to project radially outwardly toward the outer circumference of the main shaft 7. Seal points (surfaces) 7a, which project slightly from the outer end surface of the main shaft 7, are formed at the outer circumferential surface between the two blades 9. A straight line connecting the two seal points 7a is shifted by a certain spacing from a straight line which is in parallel with it and passes through the centre of the main shaft, so that a desired angle may be formed between the centre line and a straight line connecting the centre of the main shaft and a seal point. The liner 8 in which is fitted the main shaft 7 carrying the two blades 9 in such a fashion that they project in opposite directions, forms liner chambers of eyebrow-shape in cross section, as shown in Figure 3. The liner circumferential surfaces of these opposing constricted portions are projected in cone-shapes from the inner circumferential surfaces of other portions so as to form seal points 8a, 8b. The liner has internally thereof two seal ribs 8a provided at the ends of the minor axis of the generally elliptical cavity, and two seal ribs 8b are disposed at opposite ends of the major axis of the cavity which passes through the axis of rotation of the main shaft. The two seal points 8a however are disposed on a straight line which is shifted by a certain spacing from the line of the minor axis passing through the center of the cavity and is in parallel with it. It is so determined that a required angle is formed by the line of the minor axis of the cavity and a straight line connecting the center of the cavity and the seal point 8a. Therefore, regarding the space between seal points 8a and 8b (in the direction of cavity circumference), corresponding spaces between seal points on both sides of the line of apsides are equal but corresponding spaces between seal points on both sides of the line of the minor axis are unequal. When the liner 8 revolves around the outer circumferences of the main shaft 7 inserted in the liner chamber, the seal point 8a makes contact with or approaches the seal point 7a of the main shaft 7, whereby the liner chamber is divided into two, which are sealed hermetically, by the seal points 7a and 8a. Formed intermediately of the opposing seal points 8a are cone-shaped seal points 8b which divide temporarily the liner chamber into two or four chambers by contacting with an extreme end of the blades 9. These seal points 8b are provided opposite to each other with their centers on a straight line passing the center of the liner chamber. An output adjusting valve inserting hole 10 is made at one of the seal point 8b parts of the liner 8, in parallel with the liner chamber, i.e., in parallel with the axis of rotation of the liner. Ports P₁ and P₂ are formed at the innermost part of the hole 10 so that at least two chambers divided by the seal points 8a of the main shaft 7 and the blades 9 communicate with each other. A relief valve shaft 11 and a relief valve B which effect output regulation are fitted adjustably in the hole 10. As shown most clearly in Figure 4, the relief valve shaft 11 comprises a main body part 11A and a regulating part 11B in screw-threaded engagement in the main body part, and a pin 11N which is fixed relative to the liner engaged in an axial slot 11h in the part 11A, so that rotation of the regulating part moves the body part axially and so adjusts the pressure control of the relief valve B by adjusting the spring pressure on the valve. The relief valve shaft 11 is fitted in a lower lid 14 of the liner and the regulating part is adjustable for rotation from the outside of the lower lid 14. Flats 11a are formed at the outer circumference of the relief valve shaft 11, between a diametrical passage 11p extends, and a branch passage 11b extends axially from passage 11p and opens to an end surface of the valve shaft 11. A relief valve B disposed in a chamber engages the opening in the end surface of the relief valve shaft and is pressed in engagement with the opening by spring pressure. This relief valve B is biassed to the side of the relief valve shaft 11 by a spring 11c fixed in a chamber 13a made in the upper lid 13 of the liner. A hole extends along the axis of rotation of the rotor 4 and a rod 15 is inserted slidably in this hole. A piston 16 provided at a forward end of the rod 15 is fitted in a cylinder 17 provided inside the upper lid of the liner. A forward end of the piston 16 is opposed to an end surface of the main shaft 7 which is opposite to the upper lid 13 of the liner. The end surface of the main shaft 7 is inserted in a cavity 13c of the upper lid of the liner and a minute gap is formed between the inner bottom surface of the cavity 13c and the end surface of the main shaft and thus a cylinder 13d for pressure detecting is formed. A small passage 13b is made to connect the cylinder 13d with the cavity 13a of the upper lid of the liner. Provided at the other end of the rod 15 is a shutoff valve mechanism 18 which is worked by the movement of the rod 15. Under the above construction, when pressure air is introduced into the rotor chamber in the main body 1 by operation of the main valve 2 and the switch valve 3, the rotor 4 revolves at high speed. The rotational force of the rotor 4 is transmitted to the liner 8 provided at the rotor shaft. This liner 8 is supported rotatably at its outer circumference by a tubular liner casing 12. The upper lid 13 and the lower lid 14 of the liner are provided at both end surfaces of the casing 12 so that working oil filled in the liner chamber is hermetically sealed. By the rotation of the liner 8, the cross-sectional shape of the liner chamber changes. At the time of impulse, the seal points 7a of the main shaft and the blades 9 respectively contact the seal points 8a and 8b of the liner 8, the liner chamber is divided into two chambers, left and right, with the opposing blades 9 therebetween, and the left chamber and the right chamber are further divided vertically into a high pressure chamber H and a low pressure chamber L by the contacting seal points 7a and 8a. Thus, the high pressure chamber H and the low pressure chamber L are formed substantially at both sides of the blade. With the rotation of the liner 8 by the rotation of the rotor 4, of the two chambers divided by the seal points 7a of the main shaft 7 and the seal points 8a on the liner side, a high pressure chamber H decreases in volume but a low pressure chamber increases in volume, just before the moment of impulse, and when the two chambers with blades therebetween are put in a perfectly sealed state, high pressure is generated at the high pressure chamber and such oil pressure presses momentarily the side of the blade 9 to the side of the low pressure chamber, whereupon such impulse is transmitted to the main shaft in which blades are fitted and thus the desired intermittent torque is generated at the main shaft, which is rotated to effect the required work. After the torque is generated at the main shaft 7 by the impulse of the blade 9, further rotation of the liner makes the high pressure chamber H and the low pressure chamber L communicate with each other to define one chamber. Thus, the overall liner chambers are divided only into two chambers of the same pressure and no torque is generated in the main shaft but the liner rotates further by the rotation of the rotor. When the liner rotates further by 90 degrees, namely, rotates through 180 degrees from the time of the impulse, a gap is caused between the seal points 7a and 8a because the opposing seal points 8b of the liner 8 and the seal points 7a of the main shaft are shifted by several decrees from the straight line passing through the center and the liner chamber is divided into two chambers, right and left, by the main shaft and upper and lower blades 9. At this time, the change in pressure is observed throughout the whole chamber and the liner rotates freely. The state in which further rotation of the liner through 90 degrees or 270 degrees from the time of the impulse, is substantially the same as the state in which the liner rotated through 90 degrees. Only the position of the output regulating valve is turned upside down. If the liner turns further than this state, the liner chamber which was divided into two, right and left, with each blade therebetween is divided further into four, by each blade and the seal points 8b on the liner side and also by contact of both seals 7a and 8a on the liner side, namely, into two high pressure chambers and two low pressure chambers with a blade therebetween. Thus, there is caused the difference in pressure between the two, whereby an impulse is generated at each rotation of the liner. In this way, each rotation of the liner produces one impulse. In the oil pressure type impulse torque generator 5, when high pressure is generated by rotation of the liner 8 working oil flows from the high pressure chamber H to the low pressure chamber L via the port P₁, the relief valve B in the hole 10 and the port P₂. At this time, the relief valve B is pressed against the end surface of the relief valve shaft by spring pressure until the pressure in the high pressure chamber H reaches the preset pressure and this pressure is not detected. However, when the pressure rises up to the level of preset pressure and pulse is generated, the pressure in the high pressure chamber which has risen to the level of preset pressure flows from the port P₁ to the port P₂ and a part of such pressure opens the relief valve against the force of spring, whereby a part of working oil is introduced into the cylinder 13d via the passage 11b and 13b and the pressure acts on the piston 16, with the result that the rod 15 is moved, the shut-off valve mechanism 18 is worked and set pressure is detected. Regulation of impulse is effected by regulating pressing force of the relief valve B (which is biassed by the spring). In order to provide good regulation, the relief valve shaft 11 is divided into a main body 11A and a regulating rod 11B so that even if the regulating rod 11B is turned, the main body side of the relief valve shaft does not rotate but only reciprocates. In the examples illustrated in Figure 4 and in Figures 5 and 6, a slot groove 11h is made in axial direction at the main body side 11A and a knock pin 11N on the regulating rod 11B is inserted in the groove 11h, whereby the main body side 11A is prevented from rotating in rotational direction. In the machine of low output type and the machine of small type, branched pressure from high pressure to low pressure is generally low. In order to improve it, as shown in Figures 5 and 6 an orifice 11p whose opening calibre is large at one side and small at the other side may be provided. Figure 8 shows an alternative form of shut-off valve mechanism with its actuating rod 15. Referring now to Figures 9 to 11, in which corresponding components are indicated by the same reference numerals, it is possible to provide the relief valve shaft 11 inside the upper lid of the liner on the rear end side of the torque generator as shown in Figures 9 and 10. By providing the relief valve shaft inside the upper lid of the liner, it becomes possible to lessen the outside diameter of the liner and also concentricity of relief valve shaft holes of the lower lid of the liner becomes unnecessary. Application of the above device for pressure detecting is not limited to two-blade type oil pressure impulse torque. In the arrangements described above, a passage in which a part of pressure oil on the side of the liner high pressure chamber flows is formed in a relief valve shaft inserted adjustably in the liner. An opening surface of this passage is formed at an end of the relief valve shaft and a relief valve which is biassed by a spring is provided at this end surface so as to open the passage at a set pressure. This relief valve communicates with a cylinder through the medium of a relief valve inserting hole made in the liner and a passage formed at an upper lid of the liner. A piston provided at a forward end of a rod which passes through a rotor shaft is put in a cylinder inside the upper lid of the liner and a shut-off valve mechanism is provided at the other end of the rod. Under the above construction, pressure to be detected is not high and the spring design is easy because of small hole diameter of the passage. Moreover, even if the state of tightening work changes, a tool does not stop until a set torque is reached and precision of tightening torque can be maintained. Regulation of torque can be done only by the relief valve shaft and therefore a timer controller is not necessary. Thus, miniaturization and lighter weight of the machine can be realized. Although the relief valve shaft is slidable in the direction of the line of apsides in the passage made inside the liner or the upper lid of the liner, it is so designed that the relief valve shaft does not rotate and therefore the flowing direction of branched oil can be kept constant in relation to the flow of oil for detecting. Also, in the modified arrangements of Figs. 5 and 6, since the orifice which serves as a passage for signal oil and is made in the relief valve shaft has a calibre which is larger on its high pressure side than its low pressure side, it is possible to keep branched oil pressure at the required detectable pressure and thus accurate detecting can be carried out. Moreover, even if air pressure used on the tool side changes, output (torque) does not change and thus detecting precision is improved.

Claims: A torque wrench having a rotary liner (8) incorporating a pressure detecting device for adjusting the output of the wrench and adjusting the pressure at which a relief valve (B) of the wrench opens, comprising a relief valve shaft (11) having a passage (11p) connected to a port (P1) of a high-pressure chamber (H), a spring-loaded relief valve element (B) co-operating with the relief valve shaft (11), a shut-off valve (18), a piston (16) and cylinder (17) device operated by a pressure of the working fluid, and a rod (15) interconnecting the piston (16) and the shut-off valve (18), characterized by the passage (11p) in the relief valve shaft (11) permanently interconnecting the port (P1) of the high-pressure chamber (H) with a port (P2) of a low-pressure chamber (L), a branch passage (11b) leading from a location intermediate the ends of the passage (11p) in the relief valve shaft (11) and opening to a chamber (13a) at one end of the shaft (11), the relief valve element (B) being spring-loaded (11c) into sealing engagement with the open end of the branch passage (11b) and arranged to allow fluid to flow from the passage (11b) in the valve shaft into the chamber (13a) when said pressure exceeds a predetermined pressure to relieve the pressure in the passage (11p) in the relief valve shaft, the cylinder (17) of the piston and cylinder device being in permanently open communication with the chamber (13a), and the relief valve shaft (11) comprising a main body part (11A) and a regulating rod (11B) screw-threadedly connected to the main body part, the main body part having a pin (11N) in an axial slot (11h) connected to the liner (8) whereby rotation of the regulating rod (11B) causes the axial position of the main body part (11A) to be adjusted. A torque wrench as claimed in claim 1 wherein the area of the port (P1) between the branch passage (11b) and the high pressure chamber (H) is greater than the area of the port (P2) between the branch passage (11b) and the low pressure chamber.

Inventors: TATSUNO KOJI C O URYU SEISAKU, TATSUNO, KOJI, C/O URYU SEISAKU, LTD.
Applicants: URYU SEISAKU LTD, URYU SEISAKU, LTD.
Application year: 1990
Main classification: B25B21
IPC codes: B25B21, B25B23