The present invention relates to a powered cutting tool and in particular to a remotely operated hydraulic cutting tool primarily but not exclusively for use underwater, for example in submarine conditions by attachment of the tool to a manipulator arm of a remotely operated vehicle.

Underwater powered cutting tools are designed for cutting wire ropes, armoured telecommunication cables, power cables and hydraulic lines. Typically such a tool comprises a bifurcate body between the arms of which is slidably mounted a hydraulically powered guillotine blade. The tool is manipulated so that the cable or rope to be severed is located between the arms of the body. The tool is then powered so that an anvil pin is moved across the open end of the body to trap the cable or rope therein whereupon the guillotine blade is hydraulically driven down the arms, through the cable or rope and against the anvil pin. Once the cable or rope is severed, the blade is returned and the anvil pin retracted ready for the next cutting operation.

The main problem with cutting tools of this type arises if the anvil pin does not seat adequately when it is moved across the open end of the body then the movement of the blade is not checked by the anvil at the appropriate time. As the hydraulic operating pressures are high, if the movement of the blade is not correctly checked, it can travel too far down the body, seriously damaging the connection between the anvil pin and the body and jamming the cable or rope within the body without severing it. Such a problem is expensive to sort out as a diver may have to be deployed to manually cut through the cable or rope to free the damaged cutting tool and the remotely operated vehicle. Unfortunately, because such cutting tools are operated remotely in hostile submarine environments, it is relatively easy for the seat for the anvil to become clogged by sand, grit and other debris which it is difficult to detect by a controller operating the cutter and which prevents the anvil pin from being adequately seated. The object of the present invention is to overcome or substantially mitigate the aforementioned problem.

According to the present invention there is provided a powered cutting tool comprising a bifurcate body with spaced first and second arms; an anvil pin reciprocable through the first arm between a first position wherein an item to be cut can be located in the body between the first and second arms and a second position wherein it seats in the second arm thereby to trap the item within the body; a blade slidable between the arms of the body to contact the anvil pin when the anvil pin is in its second position; and means for powering the movement of the anvil pin and the blade by means of a pressurizing fluid; characterised in that a valve is provided to control the flow of pressuring fluid for operation of the blade, actuation of the valve being trigged to allow the flow of the pressuring fluid to power the blade only when the anvil pin has seated in the opposite side of the body.

In the present invention, the use of a valve to control the flow of pressurizing fluid for operation of the blade means that adequate seating of the anvil pin in the body can be ensured prior to blade operation. This obviates the problem encountered in the prior art.

Preferably, an actuator for the valve operates synchronously with the movement of the anvil pin.

Preferably also, the actuator comprises a plunger which reciprocates in a first bore through which pressurizing fluid can flow when the valve is open to power the blade, the plunger reciprocating between a first, retracted position wherein the valve is biased closed and a second, actuating position at the end of its stroke wherein the plunger acts to open the valve against the force of the bias. Advantageously, the plunger and the anvil pin are connected to and reciprocated synchronously by a lever pivotally mounted on the body.

Preferably also, rotation of the lever is powered by a piston which reciprocates in a second bore formed within the body, the bore defining a first pressure chamber on one side of the piston and a second pressure chamber on the other side of the piston, first and second inlet/ outlet ports being provided into the first and second pressure chambers respectively through which pressurizing fluid can flow into or out of the first or second chamber to cause the piston to move one way or the other within the bore dependent on the chamber that is pressurized to move the lever towards or away from the body and thereby move respectively the anvil pin and the plunger from their first positions into their second positions and vice versa.

Preferably also, a side of the valve opposite the plunger is pressurized by the pressurized fluid at the same time as the first pressure chamber is pressurized whereby on opening of the valve by the actuator pressurized fluid can immediately flow to means for operating the blade.

Movement of the blade is preferably powered by a pressure intensifier mounted on the body and to which the flow of pressuring fluid is permitted when the valve is opened.

Preferably also, the valve comprises a spring-loaded ball valve.

Advantageously, the anvil pin reciprocates through a guide located in the first arm and seats in a seating cavity defined in the second arm. In addition, preferably longitudinally orientated parallel grooves are provided in the arms along which the blade slides as it travels between the arms.

Preferably also, the grooves are formed in strengthening guide plates attached to the inside of the arms. An example of the present invention will now be described by way of example with reference to the accompanying drawings in which;-

Fig. l is a perspective view of an embodiment of hydraulically powered cutting tool in accordance with the present invention;

Fig. 2 is a side elevation of the tool shown in Fig. i;

Fig. 3 is a plan view of the tool shown in Figs, i and 2;

Figs 4 and 5 are cross-sectional views along the lines IV-IV and V-V respectively in Fig. 3.

The embodiment of powered cutting tool 1 shown in the drawings comprises a bifurcate body 2 with first and second arms 3 and 4 between which is a substantially U-shaped aperture 5. An anvil pin 6 is reciprocable through a guide 7 located in the first arm 3 between a first position, wherein an item to be cut can be located in the aperture 5 between the first and second arms 3 and 4, and a second position wherein it seats in cylindrical seating cavity 8 formed in the second arm 4. In this second position the anvil pin 6 bridges the arms 3 and 4 and thereby traps an item located between the arms 3 and 4 within the body 2. In the drawings, the anvil pin 6 is shown in a position part way between its first and its second position so that it does not bridge the arms 3 and 4 but it in a position projecting part of the way across the aperture 5.

A hardened steel guillotine blade 9 is mounted within the body 2 so that it can slide between the arms 3, 4 to contact the anvil pin 6 when the pin 6 is in its second position. In this way the blade 9 can be driven down the body 2, through any trapped item and against the anvil pin 6 to sever the item. The blade 9 is driven by a hydraulic ram located within a housing 10 attached to the body 2, a pressure intensifier, which is also located in the housing 10, being used to build up a high pressure feed for the ram. Located at the top of the body 2 are first and second inlet/outlet ports ii and 12 through which pressurizing fluid can flow into or out of the body 2 to power movement of the anvil pin 6 and to charge the pressure intensifier which powers movement of the blade 9. As is described below, a valve 13 is provided within the body 2 to control the flow of fluid to the pressure intensifier, opening of the valve 13 to allow flow of the fluid only occurring when the anvil pin 6 has seated fully in the cavity 8.

The anvil pin 6 is moved by a lever 14 to which it is pivotably connected and which is itself pivotally connected by a link 15 to the top of the body 2 adjacent the first arm 3. The lever 14 is rotated by a hydraulic piston arrangement. As shown in Fig. 4, a piston 16 is located in and can reciprocate within a bore 17 formed within the body 2. A piston rod 18, which is integrally formed with the piston 16, passes out of the bore 17 through a fluid seal 19 and is connected to one side of the lever 14. The bore 17 defines a first pressure chamber 20 on one side of the piston 16 and a second pressure chamber 21 on the other side of the piston 16. The first and second inlet/ outlet ports 11 and 12 are respectively linked to these chambers 20 and 21 via respective connecting bores 22 and 23. Plugs 24 close off the free ends of these bores at the exterior of the body 2 that were necessary to enable their machining during manufacture. It will be appreciated that by pressurizing either the first or the second pressure chamber 20 or 21 with hydraulic fluid, the piston 16 is forced to move one way or the other within the bore 17 to rotate the lever 14 towards or away from the body 2. This, in turn, moves the anvil pin 6 from its first position into its second position and vice versa.

Connected to the opposite side of the lever 14 but at the same level as the piston arrangement is an actuator 25 controlling operation of the valve 13. As shown in Fig. 5, the actuator 25 comprises a plunger 26 that is located in and can reciprocate within a bore 27 formed within the body 2. The plunger 26 reciprocates for most of its length within a guide 28 located in the bore 27 and passes out of the bore 27 through a fluid seal 29 where it is connected to the lever 14. The bore 27 is constricted at a location near its centre but in a position closer to the second arm 4 than the first arm 3 to form a valve seat 30 for the valve 13. In this embodiment, the valve 13 comprises a ball valve member 31 which is biased closed against the seat 30 by a spring loading 32. The plunger 26 is arranged so that its free end only makes contact with the valve member 31 to move it against the bias of the spring loading 32 to open the valve 13 as it nears the end of its stroke into the bore 27. In addition, the location of the valve seat 30 in the bore 27 and the length of the plunger 26 are determined so that the opening of the valve 13 can only take place when the lever 14 has been rotated sufficiently to ensure that the anvil pin 6 has adequately seated in the seating cavity 8 in the second arm 4.

The inlet/outlet port 11 is also linked to the bore 27 on the side of the valve 13 opposite the plunger 26 by connecting bores (not shown). The side of the bore 27 on the opposite side of the valve is linked via other connecting bores (not shown) to the pressure intensifier for the blade 9 that is located within the housing 10. Hence, when the pressure chamber 20 is pressurized by the pressurizing fluid to move the piston 16 and thereby the anvil pin 6 towards its seating cavity 8, the side of the valve 13 opposite the plunger 26 is also pressurized by the pressurizing fluid. This means that as soon as the plunger 26 has travelled sufficiently far into the bore 27 to open the valve 13, the pressurizing fluid can immediately flow through the valve seat 30 to commence charging of the pressure intensifier for operation of the blade 9. The blade 9 will commence its travel down the body 2 between the arms 3, 4 to contact the anvil pin 6 as soon as the pressure intensifier has built up the requisite high pressure feed for the hydraulic ram that powers it. Such pressures are typically up to 700 bar.

The blade 9 is guided as it slides between the arms 3, 4 in longitudinally orientated parallel grooves 33 formed in strengthening guide plates 34 attached to the inside of the arms 3, 4. The grooves 33 continue in the arms 3, 4 themselves below the level of the seating cavity 8 to allow the blade 9 to be removed from the tool for maintenance or replacement, when necessary.

In use, the cutting tool 1 is attached to equipment with which it is to be used, for example to a manipulator arm of a remotely operated underwater vehicle and hydraulic fluid supply/return hoses are attached to the inlet/outlet ports 11 and 12. In its standby or rest condition, the anvil pin 6 is in maintained in its first position with the aperture 5 open and the blade 9 is in a retracted position within the body 2 at the top of the aperture 5. The body 2 can then be manipulated so that the item to be cut is located in the aperture 5 between the arms. Typically, the item is a wire rope, cable or the like and has an diameter up to around 300 mm. Once the item to be cut has been captured between the arms 3, 4 in the aperture 5, the tool 1 can be powered to sever it. Pressurizing fluid is therefore pumped through the inlet/outlet port 11 to pressurize the pressure chamber 20 and the bore 27 on the side of the valve 13 opposite the plunger 26. The pressurizing fluid moves the piston 16 inwardly along the bore 17 to rotate the lever 14 towards the body 2 which in turn moves the anvil pin 6 from its first position into its second position and pushes the plunger 26 deeper into the bore 27. As the piston 16 reaches the end of this stroke, the anvil pin 6 starts to seat in the seating cavity 8 and assuming the cavity is unobstructed, the anvil pin 6 will enter fully into the cavity 8 and seat correctly. Only when the anvil pin 6 has seated adequately in the seating cavity 8 towards the very end of the stroke of the piston 16 will the plunger 26 reach a position wherein it contacts the ball valve member 31 and moves it against the spring loading 32 to open the valve 13. This allows the pressurizing fluid to flow through the bore 27 to the pressure intensifϊer to power the blade 9. It will be appreciated that during charging of the pressure intensifier, the pressurizing fluid continues to be pumped through the port 11 and while there is no further fluid flow into the chamber 20 as the piston 16 will have reached the end of its stroke, both the piston 16 and the plunger 26 are maintained in their position while the pressure intensifier is charged. Once charging is complete, the pressure intensifier powers the hydraulic ram to slide the blade 9 down between the arms 3, 4 and through the item trapped in the aperture 5. Once the blade 9 has severed the trapped item its movement is checked by contact with the anvil pin 6. Once this occurs it is automatically retracted back into the body 2. Pressurizing fluid is then pumped into the body 2 through the port 12 into the chamber 21 and exits the body 2 via the port 11 in order that the piston 16 and the plunger 26 move in the opposite direction. This rotates the lever 14 away from the body 2, allowing the valve 13 to close under the bias of the spring loading 32 and retracting the anvil pin 6 from its seating cavity 8 and back to its first position ready for the next cutting operation.

It will be appreciated that should the cavity 8 be obstructed so that the anvil pin 6 is unable to seat adequately, the piston 16 will be prevented from completing its stroke. The resulting increase in pressure of the pressurizing fluid will operate a cut-out mechanism to stop fluid being pumped through the port 11. In this circumstance, the plunger 26 is also prevented from completing its stroke and is unable to open the valve 13. This means that the pressure intensifier is not charged and operation of the blade 9 does not take place. Hence, in the present invention the blade 9 is never operated unless the anvil pin 6 has seated adequately.

In most circumstances it is expected that the cutting tool of the present invention will be powered hydraulically using oil, as described above. However, it will be appreciated that it could also be operated pneumatically with suitable changes as would be obvious to a man skilled in the art.