WO1997039857A1

WO1997039857A1 - Hyraulic power wrench

Info

Publication number: WO1997039857A1
Application number: PCT/EP1997/001949
Authority: WO
Inventors: Joachim Hauenstein; Klaus Rüssmann; Thomas Beyert
Original assignee: Wagner, Paul-Heinz
Priority date: 1996-04-20
Filing date: 1997-04-18
Publication date: 1997-10-30
Also published as: DE29607207U1; DE59704463D1; EP0904178B1; EP0904178A1

Abstract

The invention relates to a hydraulic power wrench (10) with a drive section containing a piston, and an operational part which is contained in a housing (12), has a ratchet lever driven by the drive section and drives by way of the ratchet lever a rotatably mounted shaft insertable into the housing (12). One end of said shaft has a tool holder (32). To observe with greater ease the predetermined tightening torque when producing a screw connection with the hydraulic power wrench (10), the invention proposes that the shaft is in the form of a measuring shaft (30) with a measuring section (40) adjacent the tool holder device (32), and it has a torsion sensor (41) arranged in the measuring section (40).

Description

Hydraulic power wrench

The invention relates to a hydraulic power screwdriver.

The reliability of a screw connection depends crucially on the fact that when the screw connection is tightened a tightening torque specified by the construction is maintained, i.e. reached and is not exceeded within the permissible tolerance.

To tighten a screw connection with a small torque, screwdrivers and other tools are used. With these screw connections, the tightening torque can be set by means of a torque wrench. Screw connections with a high tightening torque cannot be produced in this way.

Hydraulic power wrenches are used to produce screw connections with a high tightening torque. Such power screwdrivers (DE 41 11 631 AI) sen on a reciprocating piston, which is slidably arranged in a cylinder space of a drive part. This piston drives a ring piece via a ratchet lever, which transmits a torque to the screw connection via an insert shaft. Thanks to the ratchet lever and high pressures acting on the piston, such a hydraulic power wrench can even achieve torques in the range of 4500 Nm.

In the case of such hydraulic power screwdrivers, the setting of a torque has hitherto been carried out by setting the pressure of the hydraulic oil which acts on the working piston of the oscillating power screwdriver. However, the pressure of the hydraulic oil is only a measure of the force that is exerted on the ratchet lever of the hydraulic power wrench at a changing angle. The tightening torque depends not only on the pressure of the hydraulic oil in the cylinder space of the power wrench, but also on the type of support of the power wrench. For this reason, tables have been used so far from which a tightening torque for a given hydraulic pressure and a given support geometry could be seen. However, since it is impossible to make calculations in advance for all possible support variants of the hydraulic power wrench and to document them in a table, this known method of determining the tightening torque is not only cumbersome, but also in the case of unknown support conditions inaccurate.

The invention is based on the object of maintaining a predetermined tightening torque during the production of a screw connection with a hydraulic one To facilitate power wrench, which is driven by a reciprocating working piston.

This object is achieved according to the invention with the features of claims 1, 8 and 9.

In order to facilitate the measurement of a torque or the achievement of a predetermined tightening torque, the invention provides for the torque not to be determined retrospectively or indirectly, but instead to be measured immediately and directly on the screw or nut. For this purpose, the shaft on the hydraulic power wrench is designed as a measuring shaft with a measuring section adjacent to the tool holder device. A torsion of the measuring shaft occurring in this measuring section is detected by a torsion sensor arranged in the measuring section. Since the torsion (torsion) is a measure of the torque at this point, the tightening torque can be determined directly on the screw connection with the measuring shaft. The tightening torque can then be reliably maintained by monitoring the torsion or the torque.

An essential advantage of the invention results from the fact that the components required for determining the tightening torque have no influence on the structure of the power wrench in other respects, ie on the drive and functional part. The measuring device is arranged exclusively on or in the measuring shaft. The advantages of the invention can therefore also be achieved with an old hydraulic power wrench if it has been modified by using a measuring shaft. Because the hydraulic power screw requires no modifications other than on the measuring shaft. In addition, sophisticated constructions of known power screwdrivers can be adopted unchanged in their technology, thereby ensuring high operational reliability.

The pluggability of the shaft also has the advantage that if the measuring section or the torsion sensor is damaged, the hydraulic power wrench can be repaired quickly by simply replacing the measuring shaft. In addition, the pluggability of the measuring shaft facilitates the calibration of the torsion sensor when the measuring shaft is removed.

In order to increase operational reliability, the torsion sensor preferably has a signal output which is arranged on the end of the shaft opposite the tool holding device. In such an embodiment, the housing of the hydraulic power wrench lies between the signal output and the tool holder device and thereby shields the signal output. In addition, with such a configuration, the hydraulic power wrench in the area of the tool remains free of attachments which, under certain circumstances, would hinder the attachability of the hydraulic power wrench to a screw connection.

The measuring shaft is preferably designed in such a way that all the connections of the torsion sensor required for energy and / or signal transmission are guided contactlessly to the rotating shaft or the rotating part of the shaft. In this way, sliding contacts tending to errors can be avoided.

There are special advantages if the invented hydraulic power wrench according to the invention is used together with a hydraulic pump unit and contains a control device on which a desired torque can be set, the control device receiving signals from the torsion sensor of the measuring shaft and the supply of hydraulic oil to the power wrench upon receipt of the desired torque corresponding signal interrupts. Since the torsion (torsion) is coupled to the torque prevailing in the measuring section via known material and geometry variables, the torsional moment can be determined from the torsion on the one hand without problems and on the other hand just as easily a target torque from a target torque Torsion. Due to the fact that the hydraulic pump unit automatically interrupts the pressure medium supply upon receipt of a signal corresponding to the desired torque, the screw connection is reliably prevented from being tightened, in particular preventing human error.

The pump unit can also be simplified by controlling the hydraulic pump unit via the signals from the measuring shaft. In particular, a pressure adjustment valve and a manometer can be saved on the pump unit. The pump set only needs to be switched on and off and can always remain set to maximum pressure. Only a pressure relief valve is still required for safety reasons.

Further advantages result if the hydraulic power wrench can be connected to an evaluation device as an alternative or in addition to the connection to a hydraulic pump unit. Such an evaluation device, for example a battery-powered torque Display device in breast pocket format, or a data processing system for assembly control with a measurement log printer, allow the moments applied during the production of a screw connection to be determined with high accuracy and, if necessary, documented.

Further advantageous refinements and developments of the invention result from the subclaims and from the drawings in connection with the description. In the drawings relating to two preferred embodiments of the invention:

1 shows a hydraulic power wrench according to a first embodiment with an evaluation unit and a hydraulic pump unit in an exploded view,

2 shows the hydraulic power wrench in FIG. 1 in a side view in a simplified representation,

Fig. 3 shows a section through the power screwdriver in Fig. 2, and a shaft inserted into the power screwdriver according to the line III-III in a simplified representation, and

4 shows a section through a power wrench according to a second embodiment, as shown in FIG. 3.

The in Figs. 1-3 shown hydraulic power screwdriver 10 according to the first embodiment has a one-piece housing 12 in which a drive part 14 and a functional part 16 are contained. The drive Part 14 has a piston 20 which can be axially displaced in a cylinder space 18 and which drives a ratchet lever 24 via a piston rod 22. The ratchet lever 24 has a spring-loaded ratchet element (not shown) which takes along a ring piece 26 arranged on the end opposite the piston rod articulation end of the ratchet lever 24 during a working stroke of the piston 20.

For receiving a measuring shaft 30 which can be inserted into the hydraulic power wrench 10, the ring piece 26 has an insertion channel 28 provided with internal teeth, which extends coaxially with an insertion opening 28 for a measuring shaft 30 which extends transversely through the housing 12.

The measuring shaft 30 has a square at one end as a workpiece receiving device 32. The tool holder 32 serves to hold a plug-in socket (not shown). In order to mount the measuring shaft 32 in the housing 12 of the hydraulic power wrench 10, a first bearing section 34 and a second bearing section 36 are formed on the measuring shaft 30, which are part of a sliding bearing for the measuring shaft 30. Between the first and the second bearing section 34, 36, the measuring shaft 30 has a toothing section 38 with a serration complementary to the serration of the ring piece 26. Via this toothed section 38, a force exerted by the piston 20 via the piston rod 22 on the ratchet lever 24 is transmitted as a moment to the tool holder 32 and from there transmitted into a screw connection to be tightened. In order to be able to determine the tightening torque which occurs when the screw connection is tightened, the measuring shaft 30 of the tool holder device 32 has a measuring section 40 immediately adjacent, in which a plurality of strain gauges 42 (FIG. 3) are arranged. To accommodate the strain gauges 42, the measuring shaft 30 has a flat annular groove 44, which then extends to a measuring shaft collar 46 to support the measuring shaft 30 on the housing 12 over almost the entire length of the measuring section 40. To determine the torque, the strain gauges 42 are glued to the measuring shaft 30 in the annular groove 44 at 45 ° to the longitudinal axis of the measuring shaft 30 and cast with a sealing compound 48, so that the strain gauges 42 become detached due to moisture or mechanical stress Environmental influences is prevented. In order to also secure the strain gauges 42 against impacts, a sleeve 50 is provided which completely covers the annular groove and which ends flush with the measuring shaft collar 46 in the radial direction.

For signal transmission from the strain gauges 42 to the end of the measuring shaft 30 opposite the tool holder 32 there are in the measuring shaft 30 a centrally arranged connecting bore 52 running in the axial direction and a connecting bore extending obliquely from the connecting bore 52 to the annular groove 44 54 provided. A connecting cable 56 runs through the bores 52, 54 to an electronic amplifier element 60 arranged in a plug-receiving space 58. The amplifier element 60 is designed as a circuit board on the rear side of a connector 62 which is inserted or screwed into the measuring shaft 30. To the Connector 62, which is designed as a plug, can be connected to a connecting cable 66 provided with a connecting socket 64 (FIG. 1), which leads to an evaluation unit 68 provided with a power supply for the torsion sensor 41. In this embodiment, the connector 62 rotates with the tool holder device 32 and thus twists the connecting cable 66; however, such a twisting is acceptable since, in general, only a few revolutions of the measuring shaft take place until the tightening torque is reached. The simple and robust design of the connection, on the other hand, is a great advantage.

In order to be able to secure the measuring shaft 30 which can be plugged through the housing 12 of the hydraulic power screwdriver 10 in the housing 12 against falling out, a securing sleeve 70 is provided which can be plugged onto the measuring shaft 30 in the region of the second bearing section 36 and the measuring shaft 30 locked in the housing 12.

The hydraulic power wrench 110 according to the second embodiment (FIG. 4) differs from the hydraulic power wrench 10 according to the first embodiment only with regard to the design of the measuring shaft 130. For this reason, reference numerals are used in the power wrench 110 according to the second embodiment are increased by "100" compared to the reference signs in the power wrench 10 according to the first embodiment. In this regard, reference is made to the description of these parts in connection with the first embodiment.

The hydraulic power wrench 110 according to the second embodiment has compared to the hydraulic power Screwdriver 10 according to the first embodiment has the advantage that the connector 162 for connecting the measuring shaft 130 to an evaluation unit can be freely rotated relative to the tool holder device 132, that is to say does not rotate when screwing. In order to ensure this rotatability, the measuring shaft 130 has a carrier projection 180 which protrudes from the housing 112 on the side of the power screwdriver 110 opposite the tool holding device 32 and is equipped with a bearing device for mounting a rotary cap 182. This bearing device preferably consists of two axially spaced ball bearings 184, 186. The ball bearings 184, 186 ensure that the rotating cap 182 can freely rotate about the carrier projection 180.

In order to supply the torsion sensor 141 with energy, the rotary cap 182 has an electronics unit 188 which is located in a chamber 192 which extends coaxially to the rotary cap 182 and is delimited by a container wall 190. The container wall 190 of the chamber 192 is immersed in a transmission chamber 194 formed in the carrier projection 180 and running coaxially to the measuring shaft 130.

The electronics unit 188, which is supplied with 9 V direct current by the connector 162, converts the direct current into high-frequency energy (60 kHz), which is supplied to a first coil 198 (primary coil) via a high-frequency line 196. The primary coil 198 is arranged coaxially to the measuring shaft in the rotary cap 182 and connected to it in a rotationally fixed manner. Radially inside the first coil 198 (primary coil), a second coil 200 (secondary coil) is provided, leaving an annular gap free, which is connected to measuring electronics 202 and forms a transformer together with the primary coil 198.

The measuring electronics 202 are arranged in a rotating space 204 which is delimited in the axial direction by the ball bearing 184 and the primary and secondary coils 198,200 and in the radial direction by the carrier projection 180 and the rotating cap 182. In order to protect the measuring electronics 202 from damage when the rotary cap 182 is removed, an annular holding cup 210 made of amanetic material, e.g. Aluminum, provided, the inner radial wall 206 of which also fixes the ball bearing 184 on the carrier projection 180, acts as a support surface for the secondary coil 200 and defines the distance between the first ball bearing 184 and the second ball bearing 186. The outer wall 208 of the holding cup 210 serving to protect the measuring electronics 202 is connected to the inner wall 206 via a radial web. The holding cup 210 is open on one side in the axial direction before it is installed, the measuring electronics 202 preferably being cast in the holding cup 210.

The measuring electronics 202, on the one hand, supplies the strain gauges 142 with energy and, on the other hand, receives from the strain gauges 142 via a signal line 214 measurement signals which are converted into a high-frequency, frequency-modulated signal and via a diode line 216 to an optical transmitter 218 (infrared - transmitter) are transmitted. The transmitter 218 transmits the frequency-modulated signals, which are modulated at a carrier frequency of approximately 8 kHz +/- 2 kHz, to a receiver 220 which, like the transmitter 218, is arranged on the axis of the measuring shaft 130 and is located at the front end of the container wall 190 formed on the rotary cap 182. The signals received by the receiver 220 are processed by the electronics unit 188 in the rotary cap 182 and transmitted to an evaluation unit via the connector 162. Since both the signal transmission and the energy transmission take place without contact, the hydraulic screwdriver 110 operates reliably according to the second embodiment, transmission errors being able to be excluded in particular because of the frequency-modulated signal transmission.

The diameter of the rotary cap 182 shown in FIG. 4 is smaller than that of the internal toothing of the ring piece. The measuring shaft 130 can therefore be pushed through the housing 112 of the power screwdriver. However, the measuring shaft can also be designed to be divisible, so that in such an embodiment a rotary cap is only inserted into the rotating part after the rotating part of the measuring shaft has been pushed through the housing 112. Such a rotary cap then preferably also serves to axially fix the measuring shaft.

The operation of the two power wrenches 10, 110 described is described below with reference to the power wrench 10 of the first embodiment. Power wrenches 10 are used in that the power wrench 10 is first attached to the screw connection after a socket has been attached. A support foot 72 of the power screwdriver is then brought into a favorable support position on the housing 12 by adjustment. By turning on a hydraulic pump unit 74, the power wrench 10 is then supplied with pressure oil via a flexible hydraulic line 76. The pressure oil supply causes the measuring shaft 30th is turned and thus the screw connection is tightened. The torque prevailing on the screw connection during tightening can be read off on the evaluation unit 68. The evaluation unit is preferably designed such that the supply of hydraulic oil to the power wrench 10 is automatically interrupted when the torsion sensor 41 receives a signal corresponding to the desired torque.

The invention has been described above as a hydraulic power wrench. However, the invention is also implemented if a measuring shaft as described above is prepared for installation in a hand-operated power multiplier or a ratchet is prepared or is installed in such a power multiplier or such a ratchet.

Claims

PATENT CLAIMS

1. Hydraulic power wrench with a drive part (14), in which a piston (20) can be displaced, and a functional part (16) contained in a housing (12, -112), one of which is steep from the drive ( 14) has a driven ratchet lever (24) and, via the ratchet lever (24), drives a rotatably mounted shaft which is interchangeably inserted into the housing (12, -112) and has a tool holder (32, -132) at one end, characterized in that the shaft is designed as a measuring shaft (30; 130) with a measuring section (40; 140) adjacent to the tool holding device (32; 132) and a torsion sensor (41, -141) arranged in the measuring section (40; 140) having.

2. Hydraulic power wrench according to claim 1, da¬ characterized in that the torsion sensor

(41, -141) has a signal output which is arranged on the end of the shaft opposite the tool holding device (32; 132).

3. Hydraulic power wrench according to claim 2, characterized in that the signal output of the torsion sensor (41) leads to a connector (62) which is arranged on the measuring shaft (30) with the tool holder (32) rotating .

4. Hydraulic power wrench according to claim 2, characterized in that the signal output of the Torsion sensor (141) is guided to a connector (162) which is arranged on a rotating cap (180) which is freely rotatable relative to the tool-holding device (132) of the measuring shaft (130).

Hydraulic power wrench according to claim 4, characterized in that the connector (162) can be connected to an external power source and is connected to a transformer arranged in the interior of the rotating cap (180), the primary coil (198) of which is non-rotatable on the rotating cap (180) is arranged and its secondary coil (200) is arranged in a rotationally fixed manner relative to the tool holding device (132).

Hydraulic power wrench according to Claim 4 or 5, characterized in that measuring electronics (202) convert the signals from the torsion sensor (141) into frequency-modulated signals which are transmitted from a transmitter (218) rotating with the tool holder device (132) of the measuring shaft (130) to one Receivers (220) arranged in a rotationally fixed manner on the rotary cap (180) are transmitted.

Hydraulic power wrench according to one of claims 1 to 6, characterized by a control device on which a desired torque can be set and which receives the signals from the torsion sensor (41; 141) of the measuring shaft (30; 130) and upon receipt of one If the signal corresponding to the desired torque switches off the pump unit supplying the power screwdriver. Measuring shaft for a power screwdriver, with a first shaft end, a second shaft end, a tool holder (32) provided on the first shaft end and a measuring section (40) arranged between the shaft ends, in which a torsion sensor (41) is arranged , characterized in that a decoupling device for outputting the signals of the torsion sensor to an external display device is arranged on the second shaft end.

Hydraulic pump unit for a hydraulic power wrench (10) according to claim 7, characterized in that, instead of a control valve at the pressure outlet, an interrupter device which shuts off the hydraulic supply at the pressure outlet is provided.