GB2300874A - Release units - Google Patents

Abstract

A release unit which may be hydrostatically actuated for launching liferafts comprises a part 12 secured within a casing 28, 30 by a latch member 14 which is movable to permit release of the part 12, the latch member 14 being held in engagement with the part 12 by securing means comprising for example a spring 34 and an elongate body 40 slidably received in a part of the casing 38. The spring 34 is held in tension between the body 40 and the part 12, the body 40 being held fixed in the casing part 38 by a detent 42 attached to a diaphragm 48 so as to be movable under the influence of hydrostatic pressure to release the body 40. Following its release the body 40 is propelled by the spring 34 to strike the latch member 14 and disengage it from the part 12. Alternatively the securing means may comprise a toggle linkage 110 and the detent 42 a slidable and rotatable cam 118 (Figs. 6, 7 and 9 not shown).

Description

RELEASE UNITS This invention concerns release units which firmly but releasably secure a part in place, and which may be actuated by minimal force or movement to release the part. Such release units may be actuated manually, or by changes in ambient pressure to form for example parachute release mechanisms, bomb fuses or hydrostatic release units (HRU's) for liferafts. The invention is particularly described in relation to HRU's, but is not limited to such use.

The invention aims to provide a release unit of simple construction and high reliability. These are important requirements for HRU's, which are subjected to corrosive brine spray and in accordance with internationally agreed safety standards must be overhauled at regular service intervals. The present invention enables the construction of inexpensive, simple and reliable HRU's, which in some constructions may be disposable at the end of each service interval.

In accordance with the present invention there is provided a release unit comprising a part secured within a casing by a latch member movable to permit release of the part, the latch member being held in engagement with the part by securing means held fixed in the casing by a detent movable under the influence of an actuating force to release the securing means for movement within the casing. By this means only a relatively small actuating force is required to move the detent through only a small distance in order to release the part, which prior to application of the actuating force is firmly secured in place by the latch.

The part and latch member may each comprise an external connection point mutually disengaged upon operation of the unit. In this way forces exerted between the connection points are transmitted directly between the part and latch member. Consequently the casing may be made of relatively weaker material, e.g. cheap and corrosion-resistant plastics.

Alternatively external connection points may be provided on the part and casing.

To ensure a positive release action, resilient means may be arranged to cause the securing means to strike against and release the latch from the part upon movement of the detent.

Alternatively or additionally, resilient means may be arranged to eject the part from the casing upon its release by the latch member. In one embodiment, the resilient means is arranged to cause the detent to contact and eject the part from the casing. The or each resilient means is preferably kept in a deformed state when the securing member is held fixed within the casing.

For actuation by pressure changes, the detent may be connected to a resiliently biassed diaphragm exposed to variable pressure. The resilient bias is advantageously provided by a sealed chamber closed by the diaphragm. If used as an HRU, the chamber is preferably sealed against the ingress of water but is air permeable, e.g. by providing an aperture communicating with the exterior surroundings and sealed against water ingress by a sintered plug. The plug permits air to flow into or out of the chamber with changes in temperature, so avoiding possible false releases.

For mutual engagement/disengagement, the latch member and part may be provided with series of co-operating teeth lying along a line extending obliquely to the direction of a loading force applied to the part, the teeth having substantially flat flanks lying normal to said direction and rounded tips, whereby when the teeth are fully engaged a relatively small force applied by the securing means will serve to hold the latch member and part in engagement, but when the securing means are released and the teeth are partially disengaged, the loading force will separate the part and latch means.

The securing means may comprise a body slidable within the casing and releasably held fixed therein by the detent.

In one possible arrangement, the body is connected to the latch member by resilient means. In another arrangement, the body directly contacts the latch member to hold it in engagement with the part. In a third arrangement, the body is connected to the latch member by a toggle linkage. A pair of such latch members may be connected to the body by a pair of such linkages.

The detent may comprise a cam manually rotatable between a position in which it holds the securing means fixed in the casing and a position in which the securing means are released. Advantageously, the cam is slidably mounted upon a manually rotatable drive spindle and is held fixed against such sliding movement by engagement with a pressure actuated releasable pin aligned with the spindle, whereby the securing means may be released by such manual cam rotation, or by pressure actuation of the pin allowing the cam to slide on the spindle and release the securing means.

Further preferred features and advantages of the invention will be apparent from the following illustrative embodiments described with reference to the drawings in which: Fig. 1 is a sectional view of an HRU embodying the present invention, shown in the secured condition; Fig. 2 is a view on arrow A of the releasable part (upper eye) and latch member (lower eye) of the HRU of Fig.

1; Fig. 3 is a sectional view similar to Fig. 1 but showing the HRU in the released condition; Fig. 4 is a sectional view of an alternative embodiment of HRU shown in the latched condition; Fig. 5 is a front view of another HRU embodiment shown in the secured condition; Fig. 6 is a view similar to Fig. 5, but showing the HRU with a front cover removed; Fig. 7 is a sectional view on line VII-VII in Fig. 5; Fig. 8 is a view similar to Fig. 5 but showing the HRU in a manually released condition; Fig. 9 is a view similar to Fig. 6, but again in the manually released condition; Fig. 10 is a view similar to Fig. 6, but in the pressure released condition; and Fig. 11 is a view similar to Fig. 7, but in the pressure released condition.

As shown in Figs. 1 and 2, an HRU comprises a releasable part 12 secured by engagement with a latch member 14. Part 12 forms an upper eye to which a rope or strap can be fastened, e.g. to secure a liferaft container in a deck cradle. The latch member 14 forms a lower eye which may be similarly secured to the deck cradle. Part 12 and latch member 14 each include pairs of parallel limbs 16 and 18 respectively (only one limb of each pair being visible in Fig. 1). Co-operating surfaces of the pairs of limbs 16, 18 are provided with series of interengageable teeth 20, 22 by which part 12 may be releasably secured to latch member 14.

The limbs 18 of latch member 14 are interconnected by an upper cross-member 24 and a lower cross-member 26. The limbs 16 and 18 are received within a plastics casing having an upper part 28 secured to a lower part 30 by spaced peripheral screws 32 (only one such screw being shown in Fig.

1). A rubber gaiter 33 seals the part 12 to the upper casing part 28, protecting the casing interior from rain and sea spray.

One end of a tension spring 34 is secured to latch member 14 by an insert 36 which spans the gap between crossmembers 24 and 26. The other end of spring 34 is secured to a lug 38 upstanding from an elongate body 40 slidingly received within the housing upper part 28. Together the spring 34, insert 36 and body 40 comprise securing means for holding the latch member 14 firmly in engagement with the releasable part 12. To this end, spring 34 is held in tension by engagement of a detent 42 in an aperture 44 provided in body 40.

The casing lower part 30 includes a chamber 46 closed by a diaphragm 48 whose periphery is clamped between a rim 50 of the chamber wall and a cover 52 secured to the casing lower part 30 by screws 54. The detent 42 protrudes through central apertures formed in the cover 52 and the diaphragm 48 and is formed with a diaphragm supporting flange 56. The detent 42 also includes a tubular extension 58 telescopingly received with a clearance fit over a boss 60 upstanding from the centre of the bottom of chamber 46. A depth-setting compression spring 62 whose stiffness is selected in accordance with the required release pressure surrounds the boss 60 and tubular extension 58 to act between the bottom of chamber 46 and the flange 56. Diaphragm 48 seals about the protruding portion of detent 44.

When the HRU is submerged, water is admitted into the casing upper part 28, e.g. via the aperture 64 through which the eye of the latch member 18 emerges from the casing lower part 30. The casing upper part 28 may also be provided with one or more air vents 66. Hydrostatic pressure acts on the upper surface of diaphragm 48 via an aperture 68 in the cover 52, against the resilient bias provided by spring 58 and air trapped within chamber 46, forcing the detent to move downwardly. The detent 42 is thus released from the aperture 44 in body 40 such that the latch member 14 is no longer firmly held in engagement with the releasable part 12.

At the same time tension spring 34 propels the body 40 rapidly to the right as shown, causing an end surface 70 of body 40 to strike against the lower cross member 26 of the latch member 14. Latch member 14 is pivotally retained in downward extensions 72 of the lower casing part 30. The spring 34 is made stiff enough and body 40 is made sufficiently massive for the momentum transferred by its impact with cross-member 26 to rotate the latch member 14 in the clockwise direction as shown and disengage the latch member teeth 22 from the corresponding teeth 20 of part 12.

Held compressed between upper cross-member 24 and a lower surface 75 of part 12 is a spring 74 which, when teeth sets 20 and 22 are disengaged, causes the part 12 to be ejected from the upper casing part 28.

It should be noted that the teeth 20, 22 are arranged along a line extending obliquely to the direction of any tensile force arising between latch member 14 and part 12 and, as shown in Fig. 3, have flat flanks 76 lying normal to the direction of tensile force, and rounded tips 78. This tooth shape and arrangement ensures that only a relatively small tension in spring 34 is sufficient to hold the latch member 14 firmly in engagement with part 12, permitting the transmission of considerable tensile force applied between the eyes of latch member 14 and part 12. Moreover, it ensures that following a small rotation of the latch member 14 resulting in partial disengagement of the teeth sets 20, 22, tensile force (e.g. arising from the buoyancy of a submerged liferaft container and/or the action of spring 74) will cause the teeth to completely disengage, releasing the part 12.Thus spring 74 is only required when tensile force applied to the eyes is low or absent.

To ensure that the HRU is not released by changes in ambient temperature, the boss 60 includes an aperture 80 closed by a sintered plug 82, e.g. of polyethylene or polytetrafluoroethylene which is air permeable to maintain atmospheric pressure in chamber 46, but which is impermeable to water so preventing the application of hydrostatic pressure to the interior of chamber 46 via the aperture 82.

Fig. 4 shows an HRU forming an alternative embodiment of the invention, similar to the embodiment of Figs. 1-3, with the following significant modifications. Spring 34 is a compression spring rather than a tension spring, and acts between a flange 84 of the upper casing 28 and a head portion 86 of body 40. Lower cross-member 26 of the latch member 14 is replaced by a pin 88 extending through a longitudinal slot 90 in body 40, and the relative positions of limbs 16 and 18 are reversed. Upon release of the detent 42 from the aperture 44, spring 34 propels body 40 rapidly to the left as shown, causing an end 92 of slot 90 to strike pin 88, thereby rotating latch member 18 in the anti-clockwise direction to disengage it from the part 12.

Referring to Figs. 5-11, there is shown yet another HRU embodying the invention. It includes an upper casing part or cover 28 having a generally circular recess 94 in which is housed a knob 96 rotatable through 90" between a secured or set condition (Fig. 5) and a free or released condition (Fig.

8). A part 12 provided with a first fastening eye 98 is releasably secured in a lower casing part 30 having an integrally cast or moulded second fastening eye 100. For this purpose the part 12 has a shank with circumferential grooves 102 engaged by teeth 22 carried at the ends of a pair of latch members 14 housed within the lower casing part 30.

Part 12 can therefore swivel to adjust the orientation of the eye 98 relative to the eye 100. The latch members 14 are guided for pivotal movement on part-circular bearing surfaces 104 co-operating with corresponding surfaces 106 formed in the lower casing part 30. The latch members 14 may additionally pivot on pins 108 engaged between the upper and lower casing parts 28, 30. The other ends of the latch members 14 are connected to securing means comprising toggle linkages 110 and a body 40 guided by a keel portion 114 for sliding movement in a track 112 formed on the inside of the upper casing part 28. The body 40 is held in an outermost position by a detent 42 comprising the knob 96, a drive spindle 116, a cam 118 and a release pin 120. Cam 118 comprises a longitudinal keel 122 flanked by cut-away edge portions 124.Cam keel 122 engages in a transverse slot 126 formed in an end face of the drive spindle 116 and is normally prevented from sliding in slot 126 by engagement of the release pin in a circular depression 128 formed on a face of the cam 118 opposite keel 122. Rotation of knob 96 will cause the drive spindle 116 to rotate the cam 118, pivoting it on the release pin 120 from a position in which it holds the body 40 in the outermost position (Figs. 6 and 7) to a position in which the body 40 is allowed to move towards an inner position (Fig. 9) under the influence of a spring 130. This allows the ends of the latches 14 attached to the toggle links 110 to move towards one another, causing the opposite ends of latches 14 to pivot apart, resulting in manual release of the part 12.

For pressure-actuated release of the member 12, release pin 120 is attached to a pressure sensitive diaphragm 48 and chamber 46 arranged to operate in the same manner as chamber 46 and diaphragm 48 of the previously described embodiments.

Exposure of aperture 68 to an increase in hydrostatic pressure causes the release pin to withdraw from the circular depression 128 against the bias of spring 62 and of the air in chamber 46. Withdrawal of the release pin 120 frees the cam 120 to slide in the transverse slot 126 on the drive spindle 116, again allowing the body 40 to move inwardly (Figs. 10 and 11), resulting in release of the part 12. To aid ejection of the part 12 from the casing lower part 30, a face 132 of the cam 118 is pressed against the part 12 by the spring 130.

Claims (19)

CLAIMS:

1. A release unit comprising a part secured within a casing by a latch member movable to permit release of the part, the latch member being held in engagement with the part by securing means held fixed in the casing by a detent movable under the influence of an actuating force to release the securing means for movement within the casing.

2. A unit as defined in claim 1 wherein the part and latch member each comprise an external connection point mutually disengaged upon operation of the unit.

3. A unit as defined in claim 1 or claim 2 wherein resilient means are arranged to cause the securing means to strike against and release the latch from the part upon movement of the detent.

4. A unit as defined in claim 1 or claim 2 wherein resilient means are arranged to cause the detent to contact and eject the part from the casing.

5. A unit as defined in any preceding claim wherein resilient means are arranged to eject the part from the casing upon its release by the latch member.

6. A unit as defined in claim 3, 4 or 5 wherein the or each resilient means is kept in a deformed state when the securing means is held fixed within the casing.

7. A unit as defined in any preceding claim wherein the detent is connected to a resiliently biassed diaphragm exposed to variable pressure.

8. A unit as defined in claim 7 wherein the resilient bias is provided by a sealed chamber closed by the diaphragm.

9. A unit as defined in claim 8 for use as a hydrostatic release unit, wherein the chamber is sealed against the ingress of water but is air permeable.

10. A unit as defined in claim 9 wherein the chamber communicates with its exterior surroundings via a sintered plug providing a seal against water ingress.

11. A unit as defined in any preceding claim in which the latch member and part are provided with series of cooperating teeth lying along a line extending obliquely to the direction of a loading force applied to the part, the teeth having substantially flat flanks lying normal to said direction and rounded tips, whereby when the teeth are fully engaged a relatively small force applied by the securing means will serve to hold the latch member and part in engagement, but when the securing means are released and the teeth are partially disengaged, the loading force will separate the part and latch means.

12. A unit as defined in any preceding claim wherein the securing means comprises a body slidable within the casing and releasably held fixed therein by the detent.

13. A unit as defined in claim 12 wherein the body is connected to the latch member by resilient means.

14. A unit as defined in claim 12 wherein the body directly contacts the latch member to hold it in engagement with the part.

15. A unit as defined in claim 12 wherein the body is connected to the latch member by a toggle linkage.

16. A unit as defined in claim 15 comprising a pair of said latch members connected to the body by a pair of said linkages.

17. A unit as defined in claim 15 or 16 wherein the detent comprises a cam manually rotatable between a position in which it holds the securing means fixed in the casing and a position in which the securing means are released.

18. A unit as defined in claim 17 wherein the cam is slidably mounted upon a manually rotatable drive spindle and is held fixed against such sliding movement by engagement with a pressure actuated releasable pin aligned with the spindle, whereby the securing means may be released by said manual cam rotation or by pressure actuation of the pin, allowing the cam to slide on the spindle and release the securing means.

19. A release unit substantially as described with reference to or as shown in the drawings.