WO1991005639A1

WO1991005639A1 - A cutting device

Info

Publication number: WO1991005639A1
Application number: PCT/NO1990/000155
Authority: WO
Inventors: Svein Danielsen
Original assignee: Svein Danielsen
Priority date: 1989-10-19
Filing date: 1990-10-18
Publication date: 1991-05-02
Also published as: NO170263B; NO894171L; NO170263C; NO894171D0

Abstract

A cutting device comprises a carrier means (5), in which two substantially circular disks (1, 2) are provided, which disks have cutting edges and are mounted to be freely rotatable. At least one of said disks has at least one axially through recess (7) along its circumference, which recess extends radially inwards from the circumference. Said disks comprise portions which cover each other in an axial projection of the disks, and the planes comprising the cutting edges of the respective disks extend at a slight mutual distance. Said recesses are adapted to the diameter of the object (6) to be severed, the edge of the recess also being designed to be a cutting edge. An edge portion of the recess of one of the disks extends substantially in parallel with an adjacent edge portion of the other disk, when the object to be severed is introduced into said recess, so that mutual rotation of disks (1, 2) as a consequence of the fact that object (6) is urged in a direction towards the connecting line between said disks will cause both disks to exert substantially oppositely directed shear forces against the object (6).

Description

A cutting device

The invention relates to a cutting device which comprises a carrier means, in which two substantially circular disks are provided, which disks have cutting edges, and are mounted in the carrier, being freely rotatable about their respective axes which extend in parallel and at a mutual distance through circle centres, normal to the disk planes, with at least one disk along its circumference having at least one axially through recess extending radially inwards from the circum¬ ference.

From US-PS 2 402 057 a device is known for severing mooring cables or chains for mines, comprising two freely rotating disks with coincident central rotational planes which comprise the cutting edges of the disks. The cutting edges have evenly distributed recesses along the circumference. When this device is towed through the water and, e.g. catches a cable, said cable is squeezed between the disks and is either completely or partially severed. The edge of recesses not being designed to be a cutting edge and the recesses being small, the object is probably a reduction of the length of the cutting edge, so that the surface pressure against the cable is increased and the remaining cutting edge may be forced further into the cable with the same power being exerted against it. However, severing depends on the surface pressure being higher than the resistance to pressure of the material of the cable. If the sharp cutting edge of the disks is blunted, which happens to a higher degree the sharper this edge is, however, the exerted surface pressure will be reduced, which may prevent the cutting edge of the disks from being forced far enough into the cable, so that severance of the cable does not occur.

It is an object of the invention to provide a cutting device of the above mentioned kind which does not show the above mentioned disadvantages.

The cutting device according to the invention is distinguished by the characterizing features as stated in the claims.

The invention is disclosed in more detail below with reference to the drawing, in which an embodiment of a cutting device according to the invention is diagrammatically shown.

Figure 1 shows a section through a cutting device along line I-I in Figure 3, where the disks and the object to be severed are in a first mutual position; Figure 2 is a view similar to that of Figure 1, but with disks and the object to be severed in a second mutual position; Figure 3 is an elevational view of the cutting device shown in Figures 1 and 2, as seen in the direction of arrow III in Figure 1.

As will appear from Figure 1 two plate-shaped disks 1, and 2, respectively, are mounted freely rotatable on a shaft 3, and 4, respectively, which shafts are, in turn mounted in a frame or a carrier means 5, which may also constitute a surrounding casing, e.g. a divisible casing.

The shafts 3, 4 may be attached to the carrier means 5 and extend in parallel, normal to the plate plane of disks 1, 2, and through the centres of the respective circular disks. As will appear especially from Figure 3, the disks 1 and 2 are mutually displaced in the axial direction, and the distance between the shafts 3, 4 is slightly less than the sum of the disk radii, so that the disks 1, 2 comprise overlapping portions which are close to each other and may, but must not, touch each other.

Along their circumferences the disks are provided with axially through recesses 7, and 8, respectively, which extend radially innwards and the edge of which may, as shown, have the shape of a segment of a circle. The diameter of recesses 7, 8, however, must be slightly larger than the diameter of the cables 6, or the like which are to be severed by the device, so that they may be received by a recess.

The cutting device according to the invention will function as follows, assuming that it is to severe a stationary cable, which extends normal to the surface plane of the disks 1, 2. At the beginning the cutting device is, thus, moved towards the cable 6, until the latter is between the disks and is partly surrounded by one recess 7, 8 of each disk 1, 2, as shown in Figure 1.

When the cutting device is made to contact the cable 6, the latter will exert a force C which is directed towards the cutting device, and a corresponding turning moment is exerted against each of the disks 1, 2. This turning moment will, in turn, cause forces D and E to be exerted towards the cable. The magnitude of said forces may be changed by varying the diameter of the disks 1, 2, the distance between the rotating shafts 3, 4, and the size of the recesses 7, 8. Thus, the forces D and E may be increased maintaining the same force C if, e.g. the diameter is increased. The forces will cause the cable to be cut in single sheer and rotation of the disks relative to the carrier means in the direction of the arrows.A,B, e.g. to the position as shown in Figure 2.

The disk portions causing the severance pass each other and may in a manner known per se have surfaces extending normal to the surface plane of the disks or, enclosing an acute angle with the normal on said planes.

Continued mutual movement of the cutting device and the cable will cause continued rotation of the disks and increasing severance of the cable, until the latter is completely severed or is cut so deeply that the tension of the cable will cause it to be severed.

It was mentioned above that the cable extends normal to the surface plane of the disks. This is advantageous if the cable is thick. If the cable is relatively thin, it may, however, extend at an acute angle relative to the surface plane. Furthermore, a coaxial toothed wheel may be mounted on each disk, and said toothed wheels may mesh so that the movement of the disks is synchronized and the recesses of the respective disks are in a mutually correct position.

A cutting device of the above disclosed kind is especially suitable for mounting on the front portion of the roof of helicopters, so that in case of a collision between the helicopter and, e.g. an air cable it can severe the cable and prevent the helicopter from being wrecked. To this aim frame 5 may be firmly connected with the helicopter fuselage, and the cutting device may additionally be provided with an upper and a lower hoop or hook, which may also be firmly connected with the helicopter fuselage or, e.g. with frame 5, so that both hooks together form a guiding means which diverges in a forward direction and may guide the cable towards the disks. In this connection the upper hook may extend upwards, approximately to the main rotor, so that cables which would have hit relatively high on the main rotor shaft may be guided into the cutting device.

The device according to the invention may also be used in other connections, e.g. for cutting mine mooring cables, barbed wire, reinforcing steel, wire cloth, textiles, etc. It may be said that the device is in principle useful when the device and the object to be severed are moved relative to each other. It may also be used in connection with manual tools.

In a practical embodiment both disks will preferably be provided in a casing, which may be divided in the cutting plane of the device and in which one disk is provided and mounted in each of the casing halves. This provides for an especially simple design and mounting.

The cutting means are disclosed to have straight - or obtuse - angled cutting edges, but the edges may also be designed like knife-edges, which is especially desirable for cutting flexible or pliable cables. The edges should be made from hardened steel.

Claims

CLAIMS :

1. A cutting device for external mounting on helicopters, and for severing cables and the like in case of a collision between a cable and the helicopter in flight, c h a r a c t e r i z e d i n that it comprises a carrier means (5) known per se, in which two substantially circular disks (1,2) are mounted to be freely rotatable, the rotational axes of which disks extend substantially normal to the direction of flight and mutually in parallel, and at a mutual distance through the circle centres, normal to the surface plane of the disks, with said disks being provided with a continuous row of axially through recesses (7) , the edges of which are designed to severe the cable, said recesses being adapted to the cross section of the cable, and extending radially inwards from the circumference, and with said disks, furthermore, being provided with peripheral portions which cover each other in an axial projection of the disks, the planes which comprise the cutting edges of the respective disks extending close to each other, and with recesses (7,8) being designed successively during rotation of the disks in pairs to form a substantially U-shaped opening facing away from the disks, in the direction normal to the connecting line between the disk centres, so that a cable which is forcibly introduced towards the bottom of the opening in this direction will cause rotation of the disks, and portions of the opening which at first constituted its sides will cause severance of the cable.

2. A cutting device according to claim 1, c h a r a c t e r i z e d i n that the disks (1, 2) are mounted in a casing, which is divisible along the cutting plane, with a disk (1 or 2) being provided and mounted in each of the casing halves.

3. A cutting device according to claim 1 or 2, c h a r a c t e r i z e d i n that the angle between the side of a disk which is to face the other disk and the surface of the recesses of the disk is 90°.

4. A cutting device according to claim 1 or 2, c h a r a c t e r i z e d i n that the angle between the side of a disk which is to face the other disk and the surface of the recesses of the disk is acute.