Hydraulic torque wrench and control system for a hydraulic torque wrench

A hydraulic torque wrench comprises a ratchet link, a power head, and a signal carrying connector for connection to a controller. The ratchet link includes a housing and a drive plate mounted for rotation about an axis within the housing, the drive plate mounting one part of a first part of a ratchet drive. A socket is mounted for rotation within the housing, the socket providing a second part of the ratchet drive. During rotation of the drive plate in one direction the first and second part of the ratchet drive engage each other to cause rotation of the socket with the drive plate and during rotation of the drive plate in a second direction one of the first and second parts of the ratchet drive rides over the other such that the socket remains stationary while the drive plate rotates. The power head includes a piston and cylinder and hydraulic connections adapted for connection to a source of pressurised hydraulic fluid. The torque wrench mounts a proximity sensor connected to the signal carrying connector and configured to detect maximum extension of the piston. When maximum extension of the piston is detected the proximity sensor emits an electrical signal.

FIELD OF THE INVENTION

The present invention relates to a hydraulic torque wrench and in particular to a control system for powering and controlling the operation of a hydraulic torque wrench.

BACKGROUND OF THE INVENTION

Torque wrenches are used in many situations for tightening and slackening fasteners including nuts, bolts and screws. Typically, the hydraulic torque wrench is operated by a person controlling a valve. When the valve is configured to allow pressurised hydraulic fluid to move through the hydraulic torque wrench, a piston is caused to move by the pressurised hydraulic fluid until the piston reaches the end of its stroke. The operator configures the valve, for example by releasing lever, to de-pressurise the hydraulic fluid behind the piston. A spring then causes the piston to return to its retracted state. A ratchet mechanism in the hydraulic torque wrench allows the lever to follow the piston to a start position. The process of introducing pressurised hydraulic fluid into the cylinder behind the piston and releasing the hydraulic pressure to allow the piston and lever to return the start position is repeated until the operator considers the bolt to be tightened to the desired torque. The may include observing whether the faster is moving for example.

Where the magnitude of the torque is critical, for example in aircraft applications, a torque indicator may be provided so that the operator can continue to tighten the fastener until the desired torque is reached. The torque indicator may be a hydraulic pressure gauge. Torque may be correlated to hydraulic fluid pressure. Where such an apparatus is provided the operator cycles the hydraulic torque wrench until the hydraulic fluid pressure reaches an indicated threshold, and the fastener is observed not to move.

The above described apparatus requires the operator to look at objects in two different positions, namely the hydraulic torque wrench and fastener to which it is attached and the hydraulic pressure monitor. Furthermore, it is possible that the fastener will not be tightened to the desired torque. The fastener may be over tightened or under tightened simply because it is difficult for the operator to cease tightening at the exact desired hydraulic fluid pressure.

It would be desirable to provide an improved hydraulic torque wrench and an improved apparatus for operating and controlling such a hydraulic torque wrench.

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided a hydraulic torque wrench comprising a ratchet link, a power head, and a signal carrying connector for connection to a controller, wherein the ratchet link includes a housing and a drive plate mounted for rotation about an axis within the housing, the drive plate mounting one part of a first part of a ratchet drive, and wherein a socket is mounted for rotation within the housing, the socket providing a second part of the ratchet drive, wherein during rotation of the drive plate in one direction the first and second part of the ratchet drive engage each other to cause rotation of the socket with the drive plate and during rotation of the drive plate in a second direction one of the first and second parts of the ratchet drive rides over the other such that the socket remains stationary while the drive plate rotates, and wherein the power head includes a piston, a cylinder and hydraulic connections adapted for connection to a source of pressurised hydraulic fluid, and wherein the torque wrench mounts a proximity sensor connected to the signal carrying connector and configured to detect maximum extension of the piston, and wherein when maximum extension of the piston is detected the proximity sensor emits an electrical signal.

The proximity sensor may be mounted in a wall of the housing and wherein when the piston is at its maximum configuration a surface of the drive plate is directly adjacent the proximity sensor and the proximity sensor sense the presence of the drive plate.

The piston may have a top surface and bottom surface, the cylinder includes a first port for introducing pressurised fluid in to the space defined by the walls of the cylinder and the top surface of the piston and a second port for introducing pressurised hydraulic fluid into the space defined by the walls of the cylinder and the bottom surface of the piston for extension and retraction of the piston under pressure.

Preferably, the piston is attached to the drive plate by attachment means, wherein the attachment means is adapted to take up relative movement between the piston and the drive plate as the piston moves linearly and the drive plate rotates.

The attachment means may include a pin and a slot.

The hydraulic torque wrench may further comprise an electronic identifier programmed with information selected from the group comprising: tool serial number; tool type; required tool operating pressure; and pressure torque ratio (the value at which when multiplied by the pressure, the torque applied is calculated).

The electronic identifier may be a micro chip.

According to a second aspect of the invention there is provided a combination comprising a hydraulic torque wrench according to the first aspect of the invention and a hydraulic power pack configured to generate pressurised hydraulic fluid and connected hydraulically to the hydraulic connections of the power head for delivering pressurised hydraulic fluid to the power head and for receiving hydraulic fluid from the power head, wherein the hydraulic power pack includes an electronic controller and wherein the signal carrying connector is connected to the electronic controller, and wherein upon receiving a changed signal from the proximity sensor the electronic controller causes the direction of flow of pressurised hydraulic fluid to be reversed.

Preferably, the hydraulic power pack is configurable such that the hydraulic fluid pressure is matched to the hydraulic fluid pressure of the connected hydraulic torque wrench.

Advantageously, the hydraulic torque wrench further comprises an electronic identifier programmed with information selected from the group comprising: tool serial number; tool type; required tool operating pressure; and pressure torque ratio (the value at which when multiplied by the pressure, the torque applied is calculated) and the electronic controller reads the identifying information from the electronic identifier and sets the hydraulic fluid pressure to match the requirements of the identified hydraulic torque wrench.

The combination may further comprise a hand operated control device for controlling the flow of pressurised hydraulic fluid pressure to the power head.

The hand operated control device may include an on/off switch, wherein in the on position pressurised hydraulic fluid flows to the power head and in the closed position pressurised hydraulic fluid does not flow to the power head.

The hand operated control device may include an indicator indicating that the required torque has been reached.

The piston of the power head may be cycled between extended and retracted positions until the electrical signal from the proximity sensor does not change.

The combination may further comprise a data logger, the data logger configured to record one or more of: the torque applied when the electrical signal from the proximity sensor does not change (the last torque applied); pressure achieved; the identifying information of the hydraulic torque wrench; the time and date; the operator; identifying information associated with the object the hydraulic torque wrench is being used on.

The combination may further comprise a human machine interface.

Preferably, the data logger and/or the human machine interface are located in the hydraulic power pack.

The hydraulic power pack may include a hydraulic pressure sensor and wherein the electronic controller is configured to increase the duty cycle fo the hydraulic pump if the sensed hydraulic fluid pressure is less than the hydraulic fluid pressure required by the connected hydraulic torque wrench.

Preferably, the hydraulic power pack includes a hydraulic fluid cooler.

Advantageously, the hydraulic power pack includes a hydraulic fluid temperature sensor, the hydraulic fluid cooler includes a fan and wherein the fan is switched on when the sensed temperature exceeds a threshold temperature.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now toFIG.1, the hydraulic torque wrench1comprises two parts, a ratchet link2and a power head3.

The ratchet link2includes a housing5and a drive plate4mounted in the housing5. The drive plate4mounts a ratchet drive pawl6, the drive pawl6having a series of teeth6a, which engage with external teeth7aof a socket7when the drive plate4rotates in a clockwise direction. When the drive plate4is rotated counter clockwise the respective angles of the surfaces of teeth6a,7acause the teeth6aof pawl6to ride over the teeth7aof socket7.

The power head3includes a housing10in which a cylinder11is formed. A piston12is mounted in the cylinder11. The piston12mounts a piston head13which has a curved surface14. The curved surface14engages with a corresponding curved surface4aof the ratchet lever4. The curved surfaces14,4aprovide for relative movement between the piston head13and drive plate4as the piston moves linearly and the drive plate4rotates.

FIG.2shows the revers side of the ratchet link2and power head3. It can be seen from this drawing that the piston head13includes plate13awhich extends behind the ratchet lever4. The plate13aincludes a slot shaped opening13b. A pin13cpasses through the slot13band is attached to the ratchet lever4. The slot takes up the differential movement between the piston12and the ratchet lever4as the piston moves linearly and the ratchet lever rotates.

The cylinder11has two hydraulic fluid ports15,16, the port15provides for the passage of hydraulic fluid into the space between the top surface12aof piston12and the cylinder11. The port16provides for the passage of hydraulic fluid into the space defined by the bottom surface12bof the piston12and the walls of cylinder11.

A proximity sensor20is mounted in the wall of housing5such that when the piston12is in its fully extended configuration the surface4bof the drive plate4is directly adjacent the proximity sensor20.

The function of the proximity sensor20is to detect the presence of the drive plate4. As the drive plate4approaches the position shown inFIG.1the electronic signal emitted by the proximity sensor20changes, indicating that the maximum extension of the piston12has been reached. The electronic signal from the proximity sensor is used to reverse the flow of hydraulic fluid in the bores15,16. Hydraulic fluid is caused to flow into the port15, filling the space defined by the top surface12aof the piston12and the walls of cylinder11. At the same time, hydraulic fluid is forced out of the space defined by the bottom surface12bof piston12and the walls of cylinder11through the port16.

In the illustrated example, the flow of hydraulic fluid into port15is controlled by a timer. The volume of hydraulic fluid required to move the piston12between its fully extended and fully retracted configurations is known, and hence with knowledge of the flow rate of the hydraulic pump, the time required to return the piston12to its retracted position may be calculated.

Alternatively, another proximity sensor may be provided to detect the position of the drive plate4relative to the housing5or the piston head13relative to the housing10. The change in status of such a proximity sensor would change the direction of flow of hydraulic fluid.

The drive plate4is therefore cycled back and forth without the need for the operator to do anything other than depress an actuator which activates the hydraulic pump. The control of direction of flow is controlled electronically according to the output of the proximity sensor20and the timer described above. A relatively low hydraulic fluid pressure can be used to cycle the drive plate back and forth until the point where the socket7needs to tighten the fastener it is connected to.

The fastener to which the socket7is attached is tightened to the required torque when the drive plate4does not move with the hydraulic fluid pressure set to match the desired torque. This absence of movement of the drive plate is detected by the signal from the proximity switch. When the fastener is tight, the drive plate4will stop moving and hence will not come to the position showingFIG.1.

Referring now toFIG.3, the hydraulic torque wrench1is connected both hydraulically and electrically to a hydraulic power pack30by means of hydraulic hoses31,32and electrical cable33. A control device40is connected electrically to the hydraulic power pack30by means of electrical cable41.

FIG.4illustrates the components illustrated inFIG.3in detail. The hydraulic power pack30comprises a set of components36for generating pressurised hydraulic fluid, including a pump unit36a(which includes an electric motor), a cooler36b, a proportional pressure limiting valve36cand a pressure relief valve36d. The set components36provide pressurised hydraulic fluid which is directed to the hydraulic torque wrench1by a hydraulic circuit34which includes a solenoid operated valve35a. In one configuration of the hydraulic circuit34pressurised hydraulic fluid is directed to the hydraulic torque wrench1via hydraulic hose31, the hydraulic fluid returning through hydraulic hose32, through solenoid operated valve35b, which is open, and via port35eto the cooler36b. In the other configuration of the hydraulic circuit34the solenoid valve35bis closed and solenoid operated valve35ais closed. Pressurised hydraulic fluid is directed to the hydraulic torque wrench1via hydraulic hose32causing the piston12to retract, the hydraulic fluid returning through hydraulic hose31, through solenoid operated valve35a, through the non-return valve35dand via port35eto the cooler36b. The hydraulic circuit34is provided with a pressure gauge35c.

The cooler36bmay include a temperature sensor and a fan, the temperature sensor being configured to detect when the hydraulic fluid temperature exceeds a threshold temperatures, for example 20 C and cause the fan to operate to keep the hydraulic fluid temperature below a second threshold temperature, for example 30 C.

An electronic controller38is connected to various components of the set of components36and the hydraulic circuit34, as described below. The controller38includes a processor38and a programmable logic controller38b. The function of the controller38is to set the components to which it is connected so that hydraulic fluid is supplied at the correct pressure and flow rate to the particular tool1being used.

The controller38is connected electrically to the control device40and the hydraulic torque wrench1. The electrical connection to the hydraulic torque wrench includes one connection to the proximity switch20and a second to a microchip21. The micro chip21carries information that identifies the connected hydraulic torque wrench and the parameters of operation thereof. The PLC38bthen sets the proportional pressure limiting valve36cto match the requirements of the connected hydraulic torque wrench1. The electrical connections to the controller40and the hydraulic torque wrench1, namely the electrical cables33and41are provided within a single cable51which includes both electrical cables33and41.

The control device40includes trigger44for operating the hydraulic torque wrench, emergency stop45and indicator light46.

The hydraulic hoses31,32and electrical cables33,41may be attached to a reel50, which provides for convenient storage of the hoses and cables.

The hydraulic cabinet is also provides with a human machine interface37, which includes touch screen display37a, a data logger37f, an emergency stop37b, a hydraulic fluid high temperature indicator37c(which illuminates when the hydraulic fluid temperature exceeds the threshold temperature), a pump trip switch37dand a socket37e, which is a USB data socket in the illustrated example, for connection to other computer devices for example and which allows data recorded on the data logger to be exported from the data logger.

FIG.5illustrates the embodiment of the control device40as a pistol grip hand held device comprising a housing43providing a hand grip and mounting a trigger44, which is moved towards the housing43to cause the hydraulic power pack30to send pressurised hydraulic fluid to the hydraulic torque wrench1. The electrical cable41enters the housing43through the base thereof. The housing also mounts an emergency stop button45and an indicator light46.

In operation, when the hydraulic torque wrench1is connected to the controller38by cable33, the identity of the hydraulic torque wrench1is read and the required settings for the hydraulic pump36aare downloaded from a database of settings. With the apparatus configured for the connected hydraulic torque wrench, depressing the trigger44initiates cycling of the piston12within the cylinder11begins. Each time the piston is extended such that the surface4bof the drive plate4becomes proximate the proximity sensor20the direction of flow of hydraulic fluid in the hoses31,32is reversed to return the piston12to its retracted position in cylinder11. Cycling of the piston runs down the fastener to which the hydraulic torque wrench is connected to a point where the fastener begins to tighten. Cycling of the piston continues while the trigger44is depressed and until the surface4bof the ratchet drive does not become proximate the proximity sensor, which indicates that the fastener is tight.

The PLC38bis programmed so that hydraulic fluid is pumped into the space defined by the cylinder11and the upper surface of the piston12asuch that the piston retract time is a short period, for example 0.5 seconds.

The PLC38bis programmed so that a torque achieved time, which may be 5 seconds, is required before torque achieved lamp on the control device40is illuminated.

The PLC38bis programmed with a pump idle time which switches off the motor/pump38awhen the pump has been idling for a period of time, which may be 5 seconds.

The PLC38bis programmed with a pressure required not reached time. This may be set at 7 seconds. If the required hydraulic fluid pressure as sensed by the hydraulic fluid pressure sensor35fis not reached for the time period, the duty cycle of the pump38ais increased to increase the hydraulic fluid pressure.

The PLC38bis programmed with a duty cycle increase rate. An increase in the duty cycle is required where the required pressure is not reached. The duty cycle increase rate is set at 3 seconds. This means that if a duty cycle increase rate is required because the required pressure has not been reached, the duty cycle is increased and the pump is operated at that increased duty cycle for a period of 3 seconds before the duty cycle is increased again, if the required pressure is still not reached.

The apparatus of the invention allows fasteners to be set to a torque automatically, with the operator needing only to operate an on/off switch and without the requirement to watch for rotation fo the fastener whilst also watching a pressure dial. Furthermore, the apparatus may use less energy because it is not necessary to operate at full hydraulic pressure until the fastener starts to tighten.