GB2505899A

GB2505899A - Hatch assembly having an actuation mechanism using camming surfaces

Info

Publication number: GB2505899A
Application number: GB1216350.7A
Authority: GB
Inventors: Ashley Clayton Alastair
Original assignee: Individual
Current assignee: Individual
Priority date: 2012-09-13
Filing date: 2012-09-13
Publication date: 2014-03-19
Anticipated expiration: 2032-09-13
Also published as: GB201711111D0; GB201216350D0; GB2550300A; GB2505899B; GB2550300B

Abstract

Hatch assembly 2 includes a hatch 6 and an actuation mechanism 4 configured to firstly open and close the hatch and secondly lock the hatch in a closed position. The hatch has two opposed sides 8 each bearing two spaced hatch camming surfaces 38, the actuation mechanism including a linkage 46 adjacent each side of the hatch. Each linkage is connected to the adjacent side of the hatch for opening and closing the hatch and bearing linkage camming surfaces (68 and 76, Fig 7) are arranged to engage the hatch camming surfaces, to effect locking of the hatch. The application also discloses a hatch assembly that includes a cover (112, Fig 10) with a frame assembly including an outer frame (120, Fig 10) and an inner frame (124, Fig 10) situated radially inwardly of the outer frame and releasably secured thereto by releasable securing means (130, Fig 10) wherein release of the securing means allows the outer frame to be released from other parts of the hatch assembly to allow the hatch assembly to be opened while leaving the outer frame secured.

Description

HATCH

[0001] The present invention relates to a hatch such as a hatch typically installed in the deck of a yacht to permit entrance to and exit from an interior of a hull of the yacht.

[0002] Historically, such hatches, for closing a hatch aperture, have simply been connected to a deck of the yacht along one edge of the hatch by a hinge or hinges and include handles located adjacent to an opposite edge which are rotatable so as to engage complementary parts mounted to an edge of the hatch aperture. Rotation of the handle draws the hatch downwards so as to effect a seal between a perimeter of the hatch and a perimeter of the hatch aperture. With the ever increasing trend to automate yacht eguipment, hatches have been designed which use remotely actuable actuation means to open and close such hatches. There exists a problem however with such automatic hatches in that the actuation mechanism that they use for opening and closing of the hatches do not effect good sealing of the hatch against the perimeter of the hatch aperture. Either a separate mechanism needs to be provided for drawing the hatch downwards with sufficient force to effect sealing and to lock the hatch or the actuation mechanism is undesirably complex.

[0003] A first object of the invention is to overcome at least one of the above disadvantages.

[0004] According to the invention there is provided a hatch assembly including a hatch and an actuation mechanism configured to firstly open and close the hatch and secondly lock the hatch in a closed position, the hatch including two opposite sides each bearing two spaced hatch camming surfaces, the actuation mechanism including a linkage adjacent each side of the hatch, each linkage being connected to the adjacent side of the hatch for opening and closing the hatch and bearing linkage camming surfaces arranged to engage the hatch camming surfaces to effect locking of the hatch.

By providing the camming surfaces on the linkages which move the hatch between its opened and closed positions, wlvich engage complementary hatch camming surfaces, the linkages can provide a dual function and not only move the hatch between its opened and closed positions but also provide a camming action which can draw the hatch downwardly into sealing engagement with a perimeter surrounding an opening that the hatch closes and lock the hatch in a closed and sealed configuration.

[0005] Preferably each linkage includes first and second links, first ends of which are connected by a pivotable interconnection and the actuation mechanism includes a support means adjacent each side of the hatch which rotatably supports opposite second ends of the links. This arrangement provides robust and stable support for the hatch during its opening and in its final opened configuration.

[0006] Preferably at each side of the hatch the pivotable interconnection of the first ends of the links is connected to the adjacent side of the hatch.

[0007] Preferably, at each side of the hatch, the second ends of the links are translatably supported by the associated support means.

[0008] The actuation mechanism preferably includes linear actuation means connected to linearly displace the second ends of the first links. Since the second ends of the first links are translatably supported by the associated support means, the actuation means can be conveniently accommodated below deck level and accordingly in a position where it will be protected from impact, damage and exposure to salt water and other aggressive agents.

[0009] Preferably the actuation meohanism inoludes an individual linear actuator connected to linearly displace the second end of the first link of each linkage. This arrangement permits an individual actuator to be neatly aocornmodated, together with the linkage and other oomponents at each side of the hatch, thereby minimising the extent to which the hatch assembly impinges on an interior space closed by the hatch assembly.

[0010] Preferably, at each side of the hatch, the support means is configured to permit translation of the second end of the first link by a first distance in order to displace the hatoh between opened and closed positions.

[0011] Preferably, at each side of the hatch, the pivotable interconnection between the first ends of the first and second links is connected to the adjacent side of the hatch so as to be translatable by a second distance in order to displace the linkage camining surfaces into and out of engagement with the hatch camming surfaces. This arrangement provides a convenient means by which each linkage can be displaced to allow camming interaction between the linkage camming surfaces and the hatch camming surfaces and in addition permits the linkages to effect displacement of the hatch between its opened and closed positions.

[0012] Preferably the first distance is greater than the second distance.

[0013] Preferably, at each side of the hatch, the actuation mechanism is configured such that displacement of the linear actuation means in a first opening direction, firstly displaces the linkage so that the linkage camming surfaces disengage from the hatch camming surfaces and then secondly reconfigures the linkage so that the hatch is opened.

[0014] Preferably, at each side of the hatch, the actuation mechanism is configured such that, after disengagement of the camming surfaces, displacement of the pivotable interoonnection between the first ends of the first and second links is arrested by an abutment which causes the commencement of the reconfiguring of the linkage to open the hatch. After disengagement of the camming surfaces, translation of the linkage may be arrested by an abutment which causes the commencement of the reconfiguring of the linkage to open the hatch. The use of such an abutment has been found to be a convenient means of switching the actuation mechanism from its first function to disengage the camming surfaces to its second function to reconfigure the linkages to open the hatch.

[0015] Preferably, at each side of the hatch, the actuation mechanism is configured such that displacement of the linear actuation means in a second closing direction firstly reconfigures the linkage so that the hatch is closed and secondly displaces the linkage so that the linkage camming surfaces engage the hatch camming surfaces to lock the hatch in its closed position.

[0016] Preferably, at each side of the hatch, the actuation mechanism is configured such that the first and second links become at least substantially aligned with each other when the hatch reaches its closed position, whereafter further displacement of the linear actuation means in the second closing direction displaces the linkage so that the linkage camming surfaces engage the hatch camming surfaces to lock the hatch in its closed position. The alignment or substantial alignment of the first and second links of each linkage have been found to provide a convenient and automatic switching of the actuation mechanism from its function of moving tTne batch to its closed posi ti on to its funoti on of causing the linkage and hatch camming surfaces to inter-engage.

[0017] Preferably the hatch includes a peripheral portion configured to sealingly engage around a hatch aperture. With such an arrangement, the seal can be arranged such that it keeps seawater and rain away from internal parts of the hatch assembly and in particular away from the actuation mechanism.

[0018] A danger associated with the automatic opening and closing of a hatch, used for example on a yacht, is that if an associated actuation mechanism becomes disabled for some reason it is possible that the hatch may not be easily openable which poses a safety hazard. Such disabling could occur for example in the event of a loss of electrical or hydraulic power and/or an actuator jamming. Even for a hatch which is opened and closed manually, if catches used to hold the hatch closed are lockable then the non-availability of means to unlock the catches could also provide a safety hazard.

[0019] A second separate object of the invention is to provide a hatch which overcomes the above problems.

[0020] Thus according to a second aspect of the invention there is provided a hatch assembly having an interior surface arranged to face an interior of a space closed by the hatch assembly, the hatch assembly including a cover with a frame assembly including an outer frame configured to be drawn in a direction that the interior surface faces and secured to secure the hatch in a closed position, the frame assembly also including an inner frame situated radially inwardiy of the outer frame and releasably secured thereto by releasable securing means wherein release of the securing means aiLlows the outer frame to he rd eased from other parts of the hatch assembly to allow the hatch assembly to be opened while leaving the outer frame secured.

[0021] It should be noted that the first and second aspects of the invention can be used in combination with each other or independently.

[0022] raith the hatch assembly according to the second aspect of the invention, regardless of how the hatch is secured in its closed position and regardless of whether any hatch actuating mechanism has become disabled for any reason, it will be possible for a person in the space closed by the hatch to escape from the hatch by releasing the securing means and opening the majority of the hatch, including the cover, while leaving the outer frame in its closed position.

[0023] Preferably the hatch assembly includes at least one hinge connected, directly or indirectly, to that cover but not directly connected to the outer frame.

[0024] In order to facilitate rapid release of the outer frame from other parts of the hatch assembly, preferabty the outer frame is only connected to other parts of the hatch assembly by means of the releasable securing means.

[0025] Preferably the releasable securing means comprises plural screw-threaded fasteners which will allow the securing means to be easily re-installed to connect the inner and outer frames back together if this is required after their release has been effected. Furthermore, such release means can be easily released by someone not having knowledge of any particular release techniques and possibly under difficult circumstances.

[0026] Conveniently each screw-threaded fastener passes through a clearance hole in the inner frame and engages a screw-threaded hole in the outer frame. With this arrangement, engagement of the screw-threaded fastener in the clearance hole in the inner frame will automatically aiign the screw-threaded fastener with the screw-threaded holLe in the outer frame thereby facilitating its engagement therewith.

[0027] Preferably the cover includes a peripheral sealing region situated radially outwardly of an interface between the inner frame and the outer frame. This will keep rain and seawater away from an interface between the inner and outer frames and mean that no seal will need to be provided therebetween.

[0028] More preferably the peripheral sealing region is situated outwardly of the outer frame in order that parts of the hatch assembly positioned outwardly of the outer frame (such as a hatch actuating mechanism) can also be protected from rain and seawater.

[0029] Preferably the peripheral sealing region is situated radially outwardly of a hatch actuation mechanism whereby sealing of the sealing region against a complimentary sealing surface prevents access of water to the hatch actuation mechanism.

B

[0030] Preferably the cover comprises a sheet to an interior surface of which the inner frame is secured. This prcvides a robust construction which can be easily assembled and enables the cover to be made economically from material normally supplied in the form of large sheets. More preferably, the sheet from which the cover is made of is of substantially nf1exh1e matera1 sucTi as glass or a slght1y flexh1e acrylic material. This will ensure that good sealing of the cover can be achieved. Even more preferably, the sheet is at least partially transparent in order that the hatch assembly can let light into the space closed by the hatch.

[0031] Preferably a seal is connected to the interior surface of the sheet adjacent a periphery thereof. This means that the seal can be attached to the hatch assembly in a factory environment and can be attached easily and securely since it is being connected to an at least substantially flat surface.

[0032] The inventions will now be described by way of example only with reference to the attached drawings in which: [0033] Fig. 1 is a top plan view of a hatch assembly according to a first embodiment of the invention; [0034] Fig. 2 is a cross-section on the line -A of the hatch assembly shown in Fig. 1; [0035] Fig. 3 is a view of the area marked B in Fig. 1 showing an actuation mechanism at one side of the hatch used to open and close the hatch with the hatch in its closed but unlocked configuration; [0036] Fig. 4 is a view along the line C-C of Fig. 3 showing part of the actuation mechanism; [0037] Fig. 5 is a cross-section on the line E-E of the part of the actuation mechanism shown in Fig. 4; [0038] Fig. 6 is a side view of the hatch and actuation mechanism shown in Fig. 3 except with the hatch in its closed and locked configuration; [0039] Fig. 7 is a view similar to Fig. 6 except with the hatch in its closed but unlocked configuration, as shown in Fig. 3; [0040] Fig. 8 is a view similar to Fig. 6 except with the hatch in its opened configuration; [0041] Fig. 9 is a top plan view of a hatch assembly according to the second aspect of the invention; [0042] Fig. 10 is a cross-section on the line F-F in Fig. 9 of the hatch assembly in its closed and locked configuration; [0043] Fig. 11 is a view similar to Fig. 10 except with the hatch assembly in its normal opened configuration; and [0044] Fig. 12 is a view similar to Fig. 10 except with the hatch assembly in its emergency opened configuration.

[0045] A hatch assembly 2 according to a first aspect of the invention is shown in Fig. 1 and Fig. 2 shows a cross-section on the line A-A in Fig. 1. An actuation mechanism 4, for opening and closing a hatch 6 of the assembly is situated at each side 8 of the hatch 6 but omitted from Figs. 1 and 2 for the sake of clarity. The area occupied by the actuation mechanism 4 on the right-hand side of the hatch, as seen in Fig. 1, is designated by the dotted line marked B. A similar actuation mechanism will be provided on the left-hand side of the hatch 6 also. The hatch includes a leaf 10, which may be made of plastics material and may be transparent. The leaf has a top surface 12 and a bottom surface 14. A frame 16 is connected to the bottom surface 14 by means which are not shown but could include screw-threaded fasteners and/or adhesive. The frame may be made from metal such as stainless steel or anodised aluminium. The frame has a hollow box-secticn cross-section but other forms could be used. The frame includes a frame side 18 positioned inwardly of each side 8 of the hatch. While the frame shown in Fig. 1 is a closed frame extending continuously around the bottom surface 14, the frame 16 need not extend along all four sides of the hatch 6 and could for example extend around only three sides and not along a side of the hatch to which hinges 20 are connected for connecting the hatch to a hatch coaming 26 surrounding an aperture 22 that the hatch is designed to close. Each hinge 20 is provided with first fasteners 28 for connecting the hinge to the leaf 10 and/or the frame 16 and second fasteners 30 for connecting the hinge to the hatch coaming 26. An elongate sealing member 24, preferably of an elastomeric material, is connected to the bottom surface 14 and extends around the hatch for forming a seal between the leaf 10 and the hatch coaming 26.

[0046] Fig. 3 shows a top plan view of the actuation mechanism 4 with the hatch in its closed but unlocked configuration. The leaf 10 has been omitted from Fig. 3 for reasons of clarity. Figs. 4 and 7 show views on the lines C-o and D-D in Fig. 3 of the hatch in the same configuration.

Fig. 5 shows a view on the line E-E in Fig. 4. The components of the actuation mechanism 4 will first be described with particular reference to Figs. 3, 4, 5 and 7.

-i--i- [0047] On an outer surface of the frame side 18, a pair of spaced wedges 32 are provided. These wedges 32 are mcunted on wedge plates 34 which are screwed to the frame side 18 by machine screws 36. An upper surface of each wedge 32 has an inclined surface which constitutes a hatch camming surface 38. The wedges 32 are positioned adjacent ends of the associated frame side 18.

[0048] Approximately centrally positioned between the wedges 32 is a hatch driving plate 40 which is connected to the frame side 18 by machine screws 42. The hatch driving plate 14 includes a hatch slot 44. The hatch slot 44 extends in a direction which is parallel to the leaf 10.

[0049] As shown in Fig. 3, a linkage 46 is situation outwardly of the wedges 32 and the hatch driving plate 40.

The linkage 46 includes a first link 48 and a second link 50.

The first 48 and second 50 links have first ends 52 and 54 respectively which are rotatably interconnected by a hatch pivot 56. The hatch pivot 56 extends into and is slidable back and forth in the hatch slot 44. As shown in Fig. 3, the hatch pivot 52 comprises a nut 58 and bolt 60. The first 48 and second 50 links have second ends 53 and 55 respectively.

The first link 48 is plate-like in form and h-shaped and includes a relatively long main leg 62 and a relatively short leg 64 which projects perpendicularly from the main leg 62.

A first link cam member 66 is connected to and projects from the short leg 64 towards the frame side 18. A lower surface of the first link cam member 66 constitutes a first link camming surface 68. The second link 50 is similarly formed and includes a main leg 70, a short leg 72, a second link cam member 74 and a second link camming surface 76.

[0050] On the first link 48, where the short leg 64 meets the main leg 62 at the second end 53, and on the opposite side of the first link 48 to that from which the first link cam member 66 projects, a first link pivot 78 projects. A second link pivot 80 extends in a like manner and from a like position from the second link 50.

[0051] As shown in Fig. 3, a support means 82 is provided whioh extends along the frame side 18 and supports the first 78 and second 80 link pivots. As shown in Figs. 4 and 5, the support means 82 has an inverted U-shape. An inner limb 84 and an outer limb 86 of the support means 82 include aligned first slots 88 through which the first link pivot 78 extends.

The inner limb 84 also includes a second slot 90 through which the second link pivot 80 extends. A linear actuator 92 is mounted with a longitudinal axis aligned with a longitudinal axis of the support means 82. As shown in Figs. 3 and 4, a main body 94 of the actuator 92 projects from one end of the support means 82. A displaceable ram 96 of the actuator 92 extends from the main body 94 along an interior of the support means 82 and is connected to the first link pivot 78 inside the support means 82.

[0052] The manner in which the actuation mechanism 4 opens and closes the hatch will now be described. Figs. 6, 7 and 8 show the three main stages of actuation. In Fig. 6 the hatch assembly is closed and locked, in Fig. 7 the hatch assembly is closed but not locked and in Fig. 8 the hatch assembly is open. Slots 88 and 90 in support means 82 have been shown in broken lines in Figs. 6, 7 and 8 to show their positions relative to link pivots 78 and 80 despite the fact that they would not be visible in section D-D.

[0053] In the closed and locked configuration shown in Fig. 6, downward force, exerted by the camming surfaces 68 and 76 of the link cam members 66 and 74 on the hatch camming surfaces 38, hold the hatch in a closed and locked configuration with the sealing member 24 held firmly against the hatch ccaming 26.

[0054] First the ram 96 is retracted a short second distance L2 in a first or opening direction labelled 0. As this occurs, the first 78 and second 80 link pivots slide to the left along the first 88 and second 90 slots of the support means 82 and the hatch pivot 56 slides to the left in the hatch slot 44. As this happens, the first 66 and second 74 link cam members are displaced to the left and out of engagement with the wedges 32. When the linkage 46 reaches the configuration shown in Fig. 7 the second link pivot 80 is arrested by contacting an abutment 98 constituted by an end of the second slot 90 and the hatch assembly is unlocked.

Abutment may alternatively be provided by the hatch pivot 5 abuting against an abutment 100 constituted by an end of the hatch slot 44.

[0055] As a consequence of the above described abutment, continued retraction of the ram 9 in the direction C results in further displacement cf the first link pivot 78 alcng the first slot 88 a first distance Li. This causes the hatch pivot 5 to bear against an interior surface of the hatch slot 44 and raise the hatch to the opened position shown in Fig. 8. By selecting the lengths of the slots and links appropriately, the extent to which the hatch can be opened can be determined. By altering the relative lengths of the first link 48 and the second link 50 the speed of opening and the mechanical advantage provided by the actuation mechanism can be altered. Fcr example, when the hatch is heavier than normal, it may be advantageous for the first link 48 to be shorter than the second link 50. This will decrease the speed of cpening and increase the mechanical advantage.

[0056] Closing and locking of the hatch will comprise reversal of the steps described above by extending the ram in a second or closing direction C. [0057] Cf particular note is the final locking stage in whioh the aotuation meohanism moves from the oonfiguration shown in Fig. 7 to that shown in Fig. 6. As this occurs, the hatch pivot 56 moves to the right in the hatch slot 44 and the link cam members 66 and 74 cammingly engage the wedges 32 to draw the hatch down into its final locked and sealed configuration.

[0058] Due to the fact that the short legs 64 and 72 of the linkage 46 projeot substantially upwardly when the hatoh assembly is in its closed and locked configuration, as the links 48 and 50 are rotated to the open configuration shown in Fig. 8, the short legs 54 and 72, and thus the linkage cam members are rotated so as to project upwardly to a lesser extent thereby reducing the possibility of them snagging on items etc. being passed through the hatch aperture 22. The design of the actuation mechanism allows the hatoh assembly to have a low profile so that the cover can be arranged flush with a surrounding deck area while not projecting downwardly to an undesirable extent.

[0059] While the first 48 and second 50 links in the embodiment shown are of egual length, they could be selLected to have different lengths.

[0060] While the linear aotuator extends from the first link pivot away from the hinges 20, it could extend in the opposite direction in which case ram retraction would effect closing and looking of the hatoh assembly.

[0061] It will be understood that an actuation mechanism as described above will be provided on each side of the hatch 6.

The actuator(s) can be of any suitable type such as hydraulic cr of an electric motor actuated screw thread type.

[0062] One important advantage of the actuation mechanism described is that the sequence of movements of the linkage is determined purely mechanically. For this reason, delicate electronic sensors and the like are not required to control changes from one part of the sequence to another. In an aggressive marine environment this is highly advantageous.

[0063] A hatch assembly according to a second aspect of the invention will now be described with reference to Figs. 9 to 12. Fig. 9 shows the hatch assembly from above in its closed configuration. Fig. 10 shows a cross-section on the line F-F of the closed hatch shown in Fig. 9 and Fig. 10 shows a similar cross-section with the hatch in its normally opened configuration. Fig. 11 shows a similar cross-section with the hatch in its emergency opened configuration.

[0064] The hatch 110 includes a cover 112 in the form of a sheet which may be of plastics material and may be transparent. The cover 112 has an interior surface 114 adapted to face an interior 116 of a space closed by the hatch 110. The cover 112 has an edge 116 inwardly of which a seal 118 of elastomeric material is connected to the interior surface 114. Inwardly of the seal 118 is an outer frame 120.

The outer frame 120 extends around the cover in the region of its edge 116 and is connected to the cover 112 by any suitable means such as threaded fasteners and/or adhesive.

The outer frame 120 may be continuous as shown or may extend around less than four sides of the cover, for example around three sides of the cover. Adjacent a radially inner surface 122 of the outer frame 120 is an inner frame 124. In the embodiment shown, the inner frame 124 is a closed frame which is a sliding fit inside the outer frame 120. clearance holes 126 extend through the inner frame 124 and a screw-threaded hole in the outer frame is aligned with each clearance hole 126 in the inner frame 124. A screw-threaded fastener 130, constituting a releasable securing means, is provided which extends through each clearance hole to engage the corresponding screw-threaded hole in the outer frame 120.

Each screw-threaded fastener 130 has a head 132 configured to permit unscrewing by hand without the use of any hand tool.

Both lateral sides of the inner frame 124 are secured by a pair of screw-threaded fasteners 130. A different number and/or type of releasable fastener may however be used and they may be situated in different locations. For example the releasable fasteners may simply comprise push-fit pins with an appropriate head for facilitating manual extraction. The pins would be a friction fit in aligned holes in the inner and outer frames.

[0065] Hinges 134 are provided to connect one side of the hatch to a hatch coaming 136. On the opposite side of the hatch to the hinges, one or more catches 138 are provided to secure the outer frame 120 to the hatch coaming 136. In the embodiment shown, two catches 136 are provided, each comprising an engagement member 140 which is selectively engagable with a slot 142 in the hatch coaming 136. Each engagement member 140 is rotatable by means of a handle 144 about a securing member 146 which is connected to the outer frame 120.

[0066] Normal opening of the hatch will be effected by first rotating each engagement member 140 from the position shown on the left in Fig. 9, in which it engages its associated slot 142, to the position shown on the right in Fig. 9, in which the engagement member does not engage its associated slot. Then the hatch 110 will be pushed upwardly as shown in Fig. 11. During normal opening, the inner frame 124 remains secured to the outer frame 120 by the fasteners 130.

[0067] Should the catches 138 be locked in the engaged position, as shown on the left in Fig. 9, and means of unlocking them not be readily available then it may be necessary, in an emergency situation, to open the hatch using an emergency opening method. Such a requirement would also arise if, instead of having oatohes 138 such as those shown, the hatch included an automatic actuation mechanism, such as that described in connection with the first embodiment described above and hydraulic and/or electrical power was not available to effect opening of the hatch or if the actuator became jammed. In such situations emergency opening of the hatch can be effected by unscrewing and removing the fasteners 130 to release inner frame 124 and the cover 112 from the outer frame 120. When this has been done, the inner frame 124 and the cover 112 can be rotated about hinges 134 leaving the outer frame 120 in its secured position as shown in Fig. 12. This will permit emergency access through the hatch. If and when required, the inner frame 124 can be realigned with the outer frame 120 and re-secured thereto by means of the fasteners 130.

[0068] It should be noted that the position of the seal 118, radially outwardly of the outer frame 120, will mean that there will be no requirement for an interface between the inner and outer frames to be sealed. Furthermore, if a peripheral sealing region 148 of the cover 112 bearing the seal 118 extends far enough, it can be configured to cover, and seal against the ingress of water, a region in which a hatch actuation mechanism, such as the one described above, is accommodated.

[0069] While particular embodiments of the inventions have been described it will be understood that modifications may be made thereto without departing from the scope of the appended claims.

Claims

Claims 1. Hatch assembly including a hatch and an actuation mechanism configured to firstly open and close the hatch and secondly lock the hatch in a closed position, the hatch including two opposed sides each bearing two spaced hatch camming surfaces, the actuation mechanism including a linkage adjacenc each side of the hatch, each linkage being connected to the adjacent side of the hatch for opening and closing the hatch and bearing linkage camming surfaces arranged to engage the hatch camming surfaces to effect locking of the hatch.
2. The hatch assembly of claim 1 wherein each linkage includes first and second links, first ends of which are connected by a pivotable interconnection and the actuation mechanism includes a support means adjacent each side of the hatch which rotatably supports opposite second ends of the links.
3. The hatch assembly of claim 2 wherein, at each side of the hatch, the pivotable interconnection of the first ends of the links is connected to the adjacent side of the hatch.
4. The hatch assembly of claim 2 of 3 wherein, at each side of the hatch, the second ends of the links are translatably supported by the associated support means.
5. The hatch assembly of claim 2, 3 or 4 wherein the actuation mechanism includes linear actuation means connected to linearly displace the second ends of the first links.
6. The hatch assembly of claim 5 where in the actuation mechanism includes an individual linear actuator connected to linearly displace the second end of the first link of each linkage.
7. The hatch assembly of claim 4 wherein, at each side of the hatch, the support means is configured to permit translation of the second end of the first link by a first distance in order to displace the hatch between opened and closed positions.
8. The hatch assembly of claim 3 wherein, at each side of the hatch, the pivotable interconnection between the first ends of the first and second links is connected to the adjacent side of the hatch so as to be translatable by a second distance in order to displace the linkage camming surfaces into and out of engagement with the hatch camming surfaces.
9. The hatch assembly of claims 7 and 8 wherein the first distance is greater than the second distance.
10. The hatch assembly of claim 5 or any claim depending thereon wherein, at each side of the hatch, the actuation mechanism is configured such that displacement of the linear actuation means in a first opening direction firstly displaces the linkage so that the linkage camming surfaces disengage from the hatch camming surfaces and then secondly reconfigures the linkage so that the hatch is opened.
11. The hatch assembly of claims 2 and 10 wherein, at each side of the hatch, the actuaticn mechanism is configured such that after disengagement of the camming surfaces, displacement of the pivotable interconnection between the first ends of the first and second links is arrested by an abutment which causes the commencement of the reconfiguring of the linkage to open the hatch.
12. The hatch assembly of claim 5 or any claim depending thereon wherein, at each side of the hatch, the actuation mechanism is configured such that displacement of the linear actuation means in a second closing direction firstly reconfigures the linkage so that the hatch is closed and secondly displaces the linkage so that the linkage camming surfaces engage the hatch camining surfaces to look the hatch in its closed position.
13. The hatch assembly of claim 12 wherein, at each side of the hatch, the actuation mechanism is configured such that the first and second links become at least substantially aligned with each other when the hatch reaches its closed position whereafter further displacement of the linear actuation means in a second closing direction displaces the linkage so that the linkage camming surfaces engage the hatch camming surfaces to lock the hatch in its closed position.
14. The hatch assembly according to any proceeding claim wherein the hatch includes a peripheral portion configured to sealingly engage around a hatch aperture.
15. Hatch assembly having an interior surface arranged to face an interior of a space closed by the hatch assembly, the hatch assembly including a cover with a frame assembly including an outer frame configured to be drawn in a direction that the interior surface faces and secured to secure the hatch in a closed position, the frame assembly also including an inner frame situation radially inwardly of the outer frame and releasably secured thereto by releasable securing means wherein release of these curing means allows the outer frame to be released from other parts of the hatch assembly to allow the hatch assembly to be opened while leaving the outer frame secured.
16. The hatch assembly of claim 15 including at least one hinge connected to the cover but not directly connected to the outer frame.
17. The hatch assembly of claim 15 or 16 wherein the outer frame is only connected to other parts of the hatch assembly by means of the releasable securing means.
18. The hatch assembly according to claims 15, 16 or 17 wherein the releasable securing means comprises plural screw-threaded fasteners.
19. The hatch assembly of claim 18 wherein each screw-threaded fastener passes through a clearance hole in the inner frame and engages a screw-threaded hole in the outer frame.
20. The hatch assembly of any of claims 15 to 19 wherein the cover includes a peripheral sealing region situated radially outwardly of an interface between the inner frame and the outer frame.
21. The hatch assembly of claims 20 wherein the peripheral sealing region is situated outwardly of the outer frame.
22. The hatch assembly of claim 21 wherein the peripheral sealing region is situated radially outwardly of a hatch actuation mechanism whereby sealing of the sealing region against the complementary sealing surface prevents access of water to the hatoh aotuation meohanism.
23. The hatch assembly according to any of claims 15 to 22 wherein the cover comprises a sheet, to an interior surface of which the inner frame is secured.
24. The hatch assembly according to claim 23 wherein the sheet is substantially inflexible.
25. The hatch assembly according to claim 23 or 24 wherein the sheet is at least partially transparent.
26. The hatch assembly according to claim 23, 24 or 25 wherein a seal is connected to the interior surface of the sheet adjacent a periphery thereof.