Release unit

Details Release unit Release unit

1999-02-22

2001-05-01

Swinehart, Ed (Department: 3617)

Buoys, rafts, and aquatic devices

Buoy

Marker buoy

C114S367000

Reexamination Certificate

active

06224442

ABSTRACT:

This application claims the priority of Great Britain patent application GB 9803571.0, filed Feb. 21, 1998, the entire disclosure of which is hereby incorporated by reference.
FIELD OF THE INVENTION
This invention relates to a device which releasably connects an ancillary unit to an object, such as, for example, a ship or an aircraft. More particularly, this invention relates to a hydrostatic release device.
BACKGROUND OF THE INVENTION
It is essential that ancillary equipment, such as for example, safety equipment such as life jackets, life buoys, life rafts and emergency position indicating radio beacons (“EPIRB”), are rapidly released when an object, such as a ship or aircraft sinks under water. During normal use however, the mechanism which retains an ancillary unit with an object, must be sufficiently strong and efficiently reliable in order that the ancillary unit will only be disengaged under the appropriate emergency conditions.
Typically, mechanisms for retaining and deploying ancillary units at sea have comprised a link which is secured at one part to the ancillary unit, and at another part to a release device which is associated with an object. Upon submergence, the release device triggers the release of the unit, for example by cutting the link connecting the device and the unit.
Hydrostatic release units are commonly used to trigger the release of safety equipment. Hydrostatic release units respond to the change in ambient pressure that occurs when they become submerged under water. Each unit has a pressure-sensing means, usually a pressure-sensitive diaphragm, that reacts to the increase in pressure and triggers the release of the ancillary unit.
EP-A-0676 327, for example, describes a hydrostatic release unit wherein a change in ambient pressure opens a liquid-filled chamber, thereby releasing a hydrostatic pressure behind a reciprocable member; as a result, the reciprocable member facilitates the release of an ancillary unit
GB-A-2,300,874 describes a release unit wherein an increase in pressure triggers a pressure-sensitive spring mechanism to open a latch and release a life raft.
Similarly, U.S. Pat. No. 5,365,873 describes a mechanism wherein an increase in pressure results in the displacement of a slider which releases a life-raft or the like.
Another known hydrostatic release unit comprises a pressure-sensitive diaphragm which triggers a spring-loaded block. On release of the spring at a predetermined pressure, a blade cuts a rope which links the ancillary unit to the release device and the ancillary unit is then free to float to the surface. In an alternative mechanism, depression of a pressure-sensitive diaphragm allows water to flood into a compartment containing a soluble tablet which retains a releasing means, such as a blade for example, in position. Once the tablet has dissolved, the blade is released to sever the rope.
Most of the hydrostatic release units presently available, however, suffer from a number of disadvantages. The use of a soluble tablet for instance, can be unreliable and prone to accidental release under the typically moist and damp conditions that inevitably co-exist with seafaring vessels. Spring mechanisms also suffer detriment under moist conditions which may affect their mechanical operation. Moreover, larger and more powerful springs are needed in order to generate the force required to cut through increasingly thick linking ropes or ropes made from tougher material and the size of a hydrostatic release unit must be increased accordingly to accommodate the necessary increase in power required. This is increasingly impractical in light of the small size of life buoys and EPIRBs that are currently available.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a device for releasably linking an ancillary unit to an object, such as, for example, a ship or an aircraft, so that the ancillary unit is released when the object is submerged under water. It is also an object of the invention to provide a device that is simple to construct, economical to manufacture and highly reliable. It is a further object of the present invention to provide a device that is substantially resistant to the corrosive effects of sea water spray.
Accordingly, in one aspect, the invention provides a device for releasably connecting a first object to a link with a second object, such as an ancillary unit; the device comprising a body with holding means for securing the body to the link, and releasing means for releasing the link from the body, the releasing means being actuable in response to a change in ambient pressure; the device being characterized in that the releasing means is actuated by a pyrotechnic composition, igniting means being provided for igniting the pyrotechnic composition in response to a change in ambient pressure.
The first object may, for example, be a ship, an aircraft or any other object that has the potential to sink in water.
The second object (e.g., an ancillary unit) may for example, be such safety equipment as life jackets, life buoys, life rafts and emergency position indicating radio beacons (EPIRBs), or any other object that needs to be released upon submergence in an emergency situation.
The link between the first object and the second object (e.g., ancillary unit) may for example, be a securing bolt, a rope, a cable, or the like.
The releasing means may, for example, comprise a cutting mechanism, wherein activation of the releasing means severs the link to the second object. The releasing means may comprise a retractable means, wherein activation of the releasing means results in the retraction of a holding means, which may, for example, be a securing pin, a bolt, or the like, to release the link to the second object.
Accordingly, in one embodiment of the invention, the releasing means may comprise a cutting blade, which upon activation, cuts through the link. Preferably, the cutting blade has a curved or oblique cutting edge. Most preferably, the cutting blade has an oblique cutting edge, as this requires less force than a straightedged blade in order to provide the same cutting efficacy.
In a preferred embodiment, the releasing means may be a sliding member having a cutting blade at a leading end thereof. The sliding member may be moveable within a channel in the body, the channel lying between the igniting means and the link with the second object (e.g. an ancillary unit).
The sliding member may, for example, be a piston. It is preferred that the pyrotechnic composition is contained in a recess in the trailing end of the piston. The pyrotechnic composition may, for example, comprise gunpowder and a binding agent, such as, for example, nitrocellulose.
In a preferred embodiment, the piston contains a resilient seal about its perimeter. The resilient seal may for example, be an ‘O’-ring seal, such as a plastics ‘O’-ring, such as, for example, a Neoprene™ ‘O’-ring. The ‘O’-ring seal prevents the escape of noise or gas from the device and ensures that the body remains a sealed, non-hazardous unit.
The igniting means may, for example, take such forms as an electrical stimulus, a percussive stimulus, a piezoelectric stimulus, a friction-induced stimulus or a chemically-induced stimulus.
Accordingly, in one embodiment of the invention, the igniting means may, for example, be an electrical squib. The electrical squib may comprise a standard commercial Type A squib that comprises an insulating plate surrounded by two conducting plates that are joined by a bridging wire. Accordingly, the igniting means may be activated by electricity, for example, such as by an electrical circuit activated by a switch. In one embodiment, the switch may be activated by a pressure-sensing means wherein the pressure-sensing means detects changes in ambient pressure. Preferably, the switch is activated by an increase in pressure. Here, an increase in pressure causes the pressure-sensing means to activate the switch and thereby complete the electric circuit.
In one embodiment, the switch may be activated at a pressure correspondi

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