US3369296A

US3369296A - Line cutter

Info

Publication number: US3369296A
Application number: US520138A
Authority: US
Inventors: Albert T Takahashi; Ronald E Gardner
Original assignee: Hi Shear Corp
Current assignee: Hi Shear Corp
Priority date: 1966-01-12
Filing date: 1966-01-12
Publication date: 1968-02-20
Anticipated expiration: 1985-02-20

Description

United States Patent 3,369,296 LINE CUTTER Albert T. Takahashi, Torrance, and Ronald E. Gardner,

Lomita, Califi, assignors to Hi-Shear Corporation, Torrance, Califi, a corporation of California Filed Jan. '12, 1966, Ser. No. 520,138 6 Claims. (Cl. 30-228) ABSTRACT OF THE DISCLOSURE This invention relates to a line cutter in which a body has a bore with an axis along which a cutter plug can be fixed to cut a line which passes transversely through the bore. A choke is disposed in the path of the cutter plug to decelerate the same by extrusion, or change of cross-section. However, the choke is not contacted by the cutter plug until the trailing edge of the cutter plug passes an edge of -a port through which the line enters the bore, whereby the propellant gases are vented before the cutter plug is clecelerated.

This invention relates to a cutter for severing lines such as nylon reefing lines, and electrical wiring.

There are numerous situations in which it is desirable to cut a line upon receiving a signal for that purpose. One example is found in cutting reefing lines of parachutes so as to release a cargo. Another is to sever an electrical wire at a preselected time so as to break a circuit. It is an object of thisinvention to provide a reliable device of this type.

An optional object of this invention is to provide a device of this type which can utilize an explosive charge, and which is essentially self-contained both before and after actuation.

A cutter according to this invention comprises a body having an internal bore with an axis and with a line passage extending transversely through the body and the bore to receive a line to be cut. A cutter plug makes a fluid-sealing, slidable fit in the bore to one side of the line passage. A charge is provided for releasing gas into the bore on the opposite side of the plug from the line passage, whereby gas pressure from the charge propels the plug to sever a line that is passed through the line passage by shearing the line between the plug and the body at the line passage.

According to a preferred but optional feature of this invention, a choke is formed internally in the bore on the opposite side of the line passage from the plug whereby the plug is extruded by the choke after the line is severed, thereby to decelerate and retain the plug in the body.

According to still another preferred but optional feature of the invention, the charge is an explosive material.

The above and other features of this invention will be fully understood from the following detailed description and the accompanying drawings in which:

FIG. 1 is an axial cross-section of the presently preferred embodiment of the invention;

FIG. 2 is a perspective view of a portion of FIG. 1;

FIG. 3 is a righthand end view of FIG. 1;

FIG. 4 is a fragmentary cross-section of the device of FIG. 1 after actuation; and

FIG. 5 is a side elevation of the device of FIG. 1 after actuation.

As can best be seen in FIG. 1, a cutter according to the invention includes a body 11 having an internal bore 12. The bore has a central axis 13 and is preferably cylindrical. A line passage 14 includes first and

second ports

15, 16, so that a line 17 can be passed through the line passage and through the bore. Preferably the line passage intersects the central axis at right angles.

A cutter plug 18, preferably of extrudable material such as nylon or other plastic material, is placed in the bore adjacent to an intern-a1 chamfer 19'. The cutter plug includes a chamfer 20 to abut chamfer 19. The plug makes an interference fit so that it makes a fluid-sealing, slidable fit with the wall of the bore. It is axially slidable therein.

A choke 25 is formed at open end 26 of the bore. A choke is by definition a reg-ion of lesser lateral dimension than the bore. It may be formed by staking in a lip 27 (or lips) or it might be formed by a machined shoulder. The choke need not be completely peripheral but preferably it is. The object of the choke is to cause the plug to be extruded through a region of a lesser lateral dimension than its own, thereby to dissipate the kinetic energy of the plug and to prevent its expulsion from the body. This type of deformation dissipates the energy in such a way as to prevent the plug from making a sharp blow on the body. Energy dissipated in deformation is not transmitted to the body as a shock load. This is advantageous, because there will then be a lesser reaction on the body and on surrounding structure.

Energy for severing the line is provided by means of a source of gas under pressure. The preferred source is a squib 30 which comprises a charge of explosive material. The squib is placed in the bore adjacent to chamfer 19 and is packed against a ceramic header 31 which closes the left-hand end of the bore. The header is potted in place by an epoxy barrier 31a. The header supports a bridgewire 32 which is in contact with the explosive material 33. Two electrodes 34, 35 are provided so that the squib can be connected to a source of electrical energy for firing the same. They extend through the header and the barrier. A threaded neck 36 protects the electrodes and provides means for attachment of the electrodes. A pair of

external grooves

37, 38 is provided to aid in attaching the reefer cutter to other structure such as by tying it to said other structure with wire, clamps, or other fastening means.

The device is shown in FIG. 1 in its repose condition, the line to be cut having been threaded through the transverse line passage. The cutter plug makes a complete environmental seal for the squib so that .no further care need be taken as to the squib itself. So long as the device remains in this condition, the line remains continuous and the line cutter simply remains in place.

When a firing current is passed through the bridgewire, the explosive material generates a quantity of gas under pressure and fires the plug to the right in FIG. 1. The plug shears off the line at the two points of intersection of the ports and the wall of the bore. The portion of the line which is cut out is simply pushed ahead of the plug, but because it is light, it does no harm if it leaves the body. The plug continues to move to the right. After it passes the line passage, the gas pressure behind it is released. The kinetic energy of the plug is dissipated by extrusion at the choke, the result of which is shown in FIGS. 4 and 5 where a neck 39 has been formed on the plug. Thus the fast-moving plug cannot leave the device to strike and perhaps damage adjacent structure.

Line 40 as shown in FIG. 5 is severed into two

pieces

41, 42, which will easily fall away from the cutter because there is nothing to hold it in place. It is evident that it is only necessary to provide suflicient strength in the plug and sufiicient energy in the gas-generating charge to exercise a shearing action on the line. The force required is determined by the material which is to be cut. This can readily be determined by a few trials. Overdesign of the explosive charge will do no harm because of the retention effect of the choke. Any gas-generating source is suificient, but a good example of a suitable squib will be found in United States Patent No. 3,135,200 issued to Jackson on June 2, 1964. In addition to explosive charges, gas-release cartridges and the like may also be used.

This device has many advantages, one being that a circular plastic cutter may be used instead of the usual steel chisel blade and anvil utilized in line cutters. In blades and anvils the resulting percussive effect is often undesirable and, furthermore, the compression of the material between the chisel .blade and the anvil sometimes interferes with the actual severance thereof. A good environmental seal is provided by the plug, thereby rendering the squib quite reliable. The temperature range of the device is great. The device has been operated over the range from 65 to +200 F.

This invention is not to be limited by the embodiment shown in the drawings and described in the description which is given by way of example and not of limitation, but only in accordance with the scope of the appended claims.

We claim:

1. A cutter for severing a flexible line, comprising: a body having a bore with an axis and a line passage passing transversely through the body and the bore, thereby forming two aligned ports in the body, the passage having a first and a second end, the ports lying between the ends; a cutter plug of extrudable material making a fluidsealing slidable fit in said bore and adapted initially to be placed between the first end and the ports; a source for supplying gas under pressure to the bore at the first end in order to propel the cutter plug against a line passing through the ports and bore by shearing the same at the junctions of the ports and the wall of the bore; and a choke comprising a reduction in at least one lateral dimension of the bore such as to change the cross-section of at least a portion of the cutter plug as this portion passes through the choke, the cutter plug having a dimen- 4; sion of length of its portion making said fluid seal, and the choke being axially spaced from the edge of the ports nearest the first end by a distance which is no less than said dimension of length, whereby the end of the fluidsealing portion of the cutter plug nearest the first end passes the said edge of the ports and releases the gas pressure on the cutter plug no later than the time the cutter plug engages the choke, whereby gas pressure on the cutter plug is relieved while the choke decelerates the cutter plug, the bore being clear to the lateral dimensions of the choke for a suificient distance to leave axially unobstructed the portion of the cutter plug which is extruded.

2. A cutter according to claim 1 in which the plug makes an interference fit with the bore.

3. A cutter according to claim 1 in which the source is an explosive material.

4. A cutter according to claim 1 in which the choke comprises an inwardly extending portion of the body.

5. A cutter according to claim 1 in which the bore is open at its end on the other side of the line passage from the plug.

6. A cutter according to claim 1 in which the plug is made of an extrudable plastic material.

References Cited UNITED STATES PATENTS 2,140,214 12/1938 Temple.

2,920,532 1/1960 McBride.

2,924,147 2/1960 Bohl et al.

OTHELL M. SIMPSON, Primary Examiner.

WILLIAM FELDMAN, Examiner.

I. C. PETERS, Assistant Examiner.