GB2500630A

GB2500630A - A lock for an access cover

Info

Publication number: GB2500630A
Application number: GB1205380.7A
Authority: GB
Inventors: Alan Jack Pendleton; John Neil Pickavance; Steven Peter Baldwin
Original assignee: Saint Gobain PAM UK Ltd
Current assignee: Saint Gobain PAM UK Ltd
Priority date: 2012-03-27
Filing date: 2012-03-27
Publication date: 2013-10-02
Anticipated expiration: 2032-03-27
Also published as: GB2500630B; GB201205380D0

Abstract

A lock (10) for an access cover (12) comprises a bolt (13) and housing (14), the bolt can move in a first direction in the housing, and in a second direction between an advanced position in which it protrudes from the housing via a bolt aperture and a further, relatively retracted position. The housing includes a restraint (28, 42, figure 8) with which the bolt is engageable so as to limit movement of the bolt in the second direction; and the lock includes a biasser (27, figure 2) that biases the bolt into the restraint. The housing includes a key aperture (44, figure 5) for receiving a key (29, figure 3) that is engageable with the bolt such that movement of the key is capable of moving the bolt in the first direction against the action of the biasing means and out of engagement with the restraint; and in the second direction between the advanced and further positions.

Description

I

A LOCK

This invention relates to a lock, in particular but not exclusively for an access cover. The invention also relates to an access cover including a lock as defined herein.

Access covers are well known as means of closing off access apertures such as manholes, fire hydrant recesses drain inspection openings and a range of other aperture types.

Access apertures most commonly are formed in roadways and pavements. It is also known to form access apertures, that are closeable by access covers, in bridge decks; the decks of ships, dockyard equipment, oilfgas exploration structures such as drilling platforms and large vehicles such as dragline excavators and other mobile mineral processing equipment; factory/warehouse floors and mezzanines; farmyards, farm sheds and vehicle yards and sheds. The invention relates to locks for covers that are useable in the foregoing and other known types of access aperture.

Typically an access cover is provided as part of an access assembly including a frame that defines a boundary at the upper extremity of an opening in one of the structures indicated above. The access cover is securable to the frame in an openable manner, usually in a way involving seating on a ledge or other support structure(s) defined inside the frame boundary a short distance below its upper edge.

The frame and access cover in many cases are made of metals. A very common material for the frames and access covers is cast iron, including so-called "ductile iron" that is also referred to as spheroidal graphite (SG) iron or nodular cast iron.

Some access covers are made from steel and other metal alloys. In some cases moreover they are made from composite materials, including non-metallic composites.

It is not necessary in all cases for the frame and access cover to be made from the same material and combinations of (for example) steel access covers and cast iron frames are known.

The invention as defined herein embraces within its scope locks that are suitable for use with access covers made from virtually any of the materials from which such covers are known to be manufactured.

Many of the materials from which access covers are made have a high value per tonne when sold as scrap or as a feed to other manufacturing processes. This means that in many countries there exists a problem of theft of the access covers that results in dangerous open apertures in eg. roadways and pavements. The cost of replacing missing access covers can be high and moreover the accident liability represented by access cover loss can be very significant for municipal and highway authorities.

Also it is frequently desired to secure the interior of an aperture against unauthorised access. This may be the case for example when the access cover closes off an underground telecommunications chamber, power equipment chamber, water main or other public utility installation access to which (for reasons of public safety and the security of utility supply) is limited to authorised persons.

In order to prevent illegal or unauthorised acts of access cover removal as outlined above it is known to provide locks for the access covers. Such locks are secured to the access covers using studs, bolts or welds; or sometimes they at least partly are cast integrally with the covers. The locks typically include moveable tongues or bolts that when moved to extended or protruding positions are engageable with features formed in the frames in order to hold the covers in placa In the great majority of cases the locks are secured to the undersides of the access covers and are operable from outside the access openings using simple rotatable keys.

In many installations the access covers include through-going, shaped passages via which shaped, metal keys are partly insertable for the purpose of moving the tongues or bolts between locking and released positions.

The shaping of the keys provides a degree of security to the locks, since the keys normally are made available only to employees of utility companies and other organisations requiring legitimate access inside the apertures.

The keys however sometimes are themselves stolen by or otherwise supplied to unauthorised persons; some of the key designs are relatively easy to replicate eg. using metal fabrication techniques; the shaping of the keys is simple and does not provide for a high degree of lock security; and in any event some key designs can be used in several different types of lock owing to the relatively large dimensions of the key passages.

Simple access cover lock types of the prior art therefore offer limited assistance in preventing unauthorised opening of the cover& A more secure lock mechanism is known from EP-A-1215342.

The improved security in the lock of EP-A-1215342 results from the use of a narrow passage extending through the cover for the purpose of key insertion.

The key is of a design that is alterable between compact and extended configurations, and the passage is sized and shaped so that the key may only pass through it in its compact configuration.

The lock bolt on the other hand is such that it can only be moved by the key when the latter adopts its extended configuration. A lever forming part of the key converts the key between the two configurations from outside the access aperture, once the key has passed through the passage and attained a predetermined location relative to the lock mechanism.

It follows that the lock of EP-A-1215342 offers improved security since the key is harder to manufacture. Moreover the passage accommodates only the reconfigurable keys described in the document, thereby reducing the usefulness of other key designs for illicit aperture opening.

A drawback of the EP-A-121 5342 arrangement however is that the bolt of the lock may be moved without using the key, when the access cover is open or removed from the aperture defined by the frame.

In this regard the bolt is slideable in a slide that guides its movement between extended and relatively retracted positions. A spring-loaded detent is held captive in a wall of the slide so as resiliently to engage recesses formed in the bolt at positions corresponding to extremes of its movement. The detent arrangement retains the lock bolt in either the extended or retracted position following sliding under the rotational influence of the key.

The detent spring provides limited resistance to movement of the bolt away from its end positions, and hence a detectable sensation of the bolt reaching or departing from a desired position that is transmitted via the handle of the key and felt by the user of the lock. The user may with experience use this sensation to know that the key is in one of two positions one of which corresponds to the extended position of the bolt. In this position of the bolt the arrangement permits conversion of the key from the extended to the compact configuration and its removal via the narrow passage.

As a result of a labyrinthine path that the end of the key engaged in the lock must follow s in order to engage and detach from the bolt, the key is not removable when the bolt is in its retracted (unlocked) position. This provides for two effects.

Firstly the bolt may be used to lift the access cover upwardly away from the aperture when the bolt is in the retracted position. The key provides a temporary gripping handle that facilitates such lifting and minimises the risk of injury that the user might otherwise suffer if attempting to lift the typically somewhat heavy access cover without the help of a tool.

Secondly the key provides an indication of the status of the lock bolt. If the key is retained partly protruding from the access cover the user knows that the bolt is retracted and the cover may be lifted away from the frame. On the other hand removal of the key from the cover is intended to signify, notwithstanding the opacity of the closed access cover, that the bolt is in its extended position and the lock is secured.

The resistance to movement of the bolt provided by the spring detent however is not significant. This is because it is necessary for the torque generated by manual rotation of the key for moving the bolt to be within the capability of a human user. Since this torque is limited, the detent in turn must be relatively lightly sprung in order to provide an operational device.

This weakness of the detent means that a user either intentionally or accidentally may move the bolt from its locking (extended) to its unlocked (retracted) position when the key is not engaged with the bolt.

This occurs through a sequence of (i) using the key to release the lock and open the access cover: (ii) while the cover is open, rotating the key so the bolt adopts its extended position (iii) removing the key from the narrow passage and (iv) pushing on the protruding end of the bolt when the key is removed to force it, against the resistance provided by the detent, to its retracted position.

If the access cover is subsequently closed it would falsely appear to the user as a result of separation of the key from the narrow passage that the bolt is in its extended (locking) position. Consequently the access cover may be left in an unlocked configuration, with the attendant risk of security breaches and/or theft of the access cover. Also the bolt might be in an incorrect location for subsequent engagement by a part of the key that is shaped to mate with a formation in the bolt, so the bolt could not then be locked from outside the aperture.

An aim of the invention is to solve or at least ameliorate the above-outlined disadvantage

of the prior art arrangement.

Moreover it is generally desirable for the lock mechanism of an access cover to be robust, simple to install, operate and maintain, resistant to clogging by mud, leaves and other contaminants and above all else cheap to manufacture.

According to the invention in a broad aspect there is provided a lock for an access cover comprising a lock bolt and a housing defining a guide and a bolt aperture, the bolt being received in the guide so as to permit its movement in the guide in a first direction and movement therein in a second direction, that is different from the first direction, between an advanced position in which it protrudes from the housing via the bolt aperture and a further, relatively retracted position; the housing including a restraint with which the bolt is engageable so as to limit movement of the bolt in the second direction; the lock including a biasser that biases the bolt into engagement with the restraint; and the housing having formed therein a primary key aperture for receiving a bolt key that is selectively engageable with the bolt such that movement of the bolt key is capable of moving the bolt in the first direction against the action of the biasser and out of engagement with the restraint; and in the second direction between the advanced and further positions.

The use of a lock bolt that is moveable in two directions in the slide means that the bolt may be advantageously normally biased into engagement with the restraint, and the key used firstly to detach the bolt from the restraint and then, by moving the bolt in a different direction, effect its movement between the extended and relatively retracted positions.

The presence of the restraint prevents step (iv) of the sequence of misuse described in relation to EP-A-1 215342 above from occurring. The bolt normally may only released from engagement from the restraint, that in turn prevents movement to the retracted position, through use of the key.

The need for the bolt to be moved in two differing directions in order to effect its retraction means that if as described below the access cover includes a narrow key passage of the kind disclosed in EP-A-1215342 only a key that is convertible between compact and extended configurations is useable to move the bolt. This in turn means that the number of key types useable to operate the lock is reduced and may be better

controlled than in the prior art arrangements.

The lock of the invention may adopt a simpler construction than the lock in EP-A- 1215342 because the presence of the restraint obviates the requirement, in the prior art, to limit the range of positions of the key in which it may be inserted into the labyrinthine path. This in turn derives from the fact that the bolt by reason of the presence of the restraint would never be in its retracted position when an attempt to insert the key is made.

Preferably the first and second directions of movement of the bolt are mutually perpendicular.

This arrangement advantageously ensures that two distinct movements are needed to move the bolt between the extended and retracted positions. It also means that the lock design is suited for use with a key of the general type disclosed in EP-A-1215342, in which as described below an arm may be pivoted from the compact configuration lying parallel to a shank; and an extended configuration protruding perpendicular to the shank.

Conveniently the bolt is moveable further in the second direction than in the first direction. This means that it can be arranged so that only a relatively small movement in the first direction is needed in order to release it for movement between extended and relatively retracted positions.

Conveniently the restraint and biasser lie within the housing. This means that the restraint and the biasser are protected by the housing against damage that might be caused by rough handling of the lock or of an access cover to which it is secured. Also the locating of the restraint and biasser inside the housing means that these parts of the lock, being the most intricate, are relatively unlikely to become clogged by contaminants.

as In a preferred arrangement of the invention the lock includes a said bolt key, such that the lock and key are supplied as a set. However a lock as defined herein omitting the key is also within the scope of the invention.

Conveniently the bolt is received in the guide on a first side of the housing and the primary key aperture extends through the housing to permit insertion of the bolt key on a second side of the housing that is distinct from the first side and engagement with the bolt adjacent the first side.

This arrangement renders the lock of the invention highly suitable for attachment to an access cover having a key aperture formed therein, since as a result the key may be inserted into the lock from the in-use upper side of the cover; and the lock operated even if the access cover is initially secured in a closed position.

It is also preferable in this regard that the lock includes a secondary key aperture, on the first side of the housing, communicating with the primary key aperture thereby permitting insertion of the bolt key so as to protrude beyond the bolt and permit engagement of the bolt key with the bolt on a side thereof that is remote from the second side of the housing.

The inclusion of the secondary key aperture permits the use, in conjunction with the lock of the invention, of a key that is of the general kind described in EP-A-1215342 that is convertible between compact and extended configurations.

This is because the interior of the housing offers limited space for the conversion operation to take place whereas the secondary aperture permits part of the key after insertion to protrude beyond the housing and thereby undergo conversion in a location that is more spacious.

To this end in preferred embodiments of the invention the bolt key is adjustable between compact and extended configurations in which respectively it is (i) capable of passing through the primary and secondary apertures so as to protrude beyond the bolt and (ii) capable of engaging the bolt following passage through the secondary aperture. As indicated, this is essentially the same bolt design as that proposed in EP-A-1215342.

Desirably the primary aperture is shaped to permit passage of the bolt key in its compact configuration and prevent passage of the bolt key in its extended configuration. As indicated, this improves the security of the lock compared with prior art designs.

The secondary aperture moreover optionally is shaped to permit passage of the bolt key in its extended configuration. This feature permits insertion of the convertible part of the key inside the housing after adopting the extended configuration. This in turn means that part of the key may readily engage the bolt.

Conveniently as indicated the key resembles the key of EP-A-12 15342 and therefore includes a shank; and an arm that is moveable, relative to the shank, between the compact configuration in which the arm lies parallel to the shank and the extended configuration in which the arm protrudes from the shank.

For the purpose of positively engaging the bolt and effecting its movement the arm of the key preferably includes one or more formations that are engageable with a corresponding number of formations of the bolt.

In the preferred version of the key described in more detail below the shank is hollow so as to define a hollow interior and the bolt key includes an actuator secured to the arm so as to extend inside the hollow interior, the actuator being operable from outside the shank at a location spaced from the arm to cause movement of the arm between its compact and extended configurations. It is also preferable that the shank includes an aperture via which a projecting part of the actuator protrudes externally of the shank, the projecting part including a gripping handle permitting manual operation of the actuator.

The foregoing features provide for a key that is robust, reliable, simple to use and cheap to make from common engineering materials such as various steels.

The biasser conveniently is a spring acting between the housing and the bolt in order to urge the bolt into a position permitting engagement with the restraint when the bolt adopts its advanced position. More preferably the spring is a leaf spring secured in the guide between the bolt and the housing on the opposite side of the bolt to the restraint.

Such a spring design is easily retained relative to the housing for example through the use of a fastener acting on an end of the leaf and also is of a type that readily acts as a detent. This is because a leaf spring may be arranged to extend into a detent recess, without becoming trapped.

In practice in preferred embodiments of the invention when in the advanced position the bolt is urged directly into engagement with the restraint. In other versions within the scope of the invention however it is possible for the bolt to be urged to a position that on movement towards the retracted position causes engagement with the recess.

In preferred embodiments of the invention at least part of the length of the guide is or includes a hollow shaft; and the restraint includes a shoulder projecting into the shaft over part of its width so as to define a narrowed portion of the shaft, the thickness of the bolt in the vicinity of the shoulder being less than the width of the narrowed portion such that the bolt may pass along the shaft adjacent the narrowed portion on operation of the bolt key to move the bolt in the second direction.

Preferably the arm includes one or more formations that are engageable with a corresponding number of formations of the bolt.

In a particularly preferred arrangement the arm includes an arm projection and the bolt is includes a recess in which the arm projection is engageable such that movement of the bolt key may cause movement of the bolt in the first direction; although other combinations of formations are possible within the scope of the invention. An advantage of the preferred arrangement is that it permits positive engagement between the arm and the bolt, thereby permitting the arm to move the bolt in two different directions as described.

In one optional embodiment within the scope of the invention the housing includes a cam surface against which the arm bears in use of the bolt key such that movement of the bolt key along the cam surface guides the arm towards engagement with the bolt.

Preferably in order to cause movement of the bolt in the first direction the bolt key is moveable parallel to a longitudinal axis of the bolt key. Further, in order to cause movement of the bolt in the second direction the bolt key preferably is rotatable about an axis extending parallel to a longitudinal axis of the bolt key.

Thus the bolt key is capable in preferred embodiments of the invention of converting rotational movement into longitudinal movement of the bolt resulting in movement of the bolt in the second direction.

The invention also resides in an access cover including secured to or formed integrally with its in-use underside a lock as defined herein in accordance with the invention such that the lock bolt is engageable with a latch for securing the access cover relative to a structure. Such an access cover is more secure than the prior art covers, and achieves improved performance through use of simple, robust, cheap to manufacture features.

Conveniently the access cover includes formed therein a through-going key passage in o register with the primary aperture so as to permit insertion of the bolt key via the in-use upper surface of the access cover.

The listing or discussion of an apparently prior-published document in this specification should not necessarily be taken as an acknowledgement that the document is part of the state of the art or is common general knowledge.

There now follows a description of preferred embodiments of the invention, by way of non-limiting example, with reference being made to the accompanying drawings in which: Figure 1 is a perspective view from underneath of an access cover in accordance with an aspect of the invention and including a lock according to the invention; Figure 2 is a view similar to Figure 1, omitting a lock bar in order to show a biasser forming part of the Figure 1 arrangement; Figure 3 is a perspective view of a bolt key that is an optional feature of the invention, illustrating a moveable arm in a compact configuration of the arm; Figure 4 is a view similar to Figure 3, showing the arm in an extended configuration of the bolt key; Figures 5 and 6 are views similar to Figure 1, showing steps in a process of inserting the bolt key of Figures 3 and 4 so as to engage the bolt of the lock on the underside of the access cover; Figure 7 shows the components of Figures 5 and 6 during movement of the bolt under the influence of the blot key; Figure 8 is a perspective, cross-sectional view of the Figure 7 parts; Figure 9 shows in perspective view the positions of the various parts of the lock and access cover when the bolt occupies a relatively retracted position; and Figure 10 shows in perspective view a second embodiment of lock and access cover combination, including an optional spiral cam surface.

Referring to the drawings there is shown a lock 10 that is secured on the in-use underside 11 of an access cover 12.

The access cover may be of any of the types described herein and may be made from any of the materials known to the worker of skill to be suitable for such components. The access cover 12 is shown inverted compared with its normal usage orientation, in which it occupies and closes off an aperture such as one of the types mentioned above.

The lock 10 includes a lock bolt 13 and a housing indicated generally by numeral 14.

Housing 14 comprises an essentially cuboidal part 14a and a hollow, essentially cylindrical part 14b. The parts 14a and 14b are in the embodiment shown formed integrally with one another by reason of being cast simultaneously from a metal such as cast iron or ductile iron.

The parts of the housing 14 however may in other embodiments of the invention be made in different shapes, and it is not necessary that there are two such parts or that they respectively are cuboidal and cylindrical in shape. Moreover any parts of the housing 14 may be made separately from one another if desired, and joined together using methods known to the worker of skill in the art.

In the preferred embodiment illustrated the housing 14 is cast integrally with the access cover 12, which therefore is made from the same material as the housing 14. This need not necessarily be the case in other embodiments of the invention however.

Cuboidal part 14a of housing 14 is defined by two mutually similar end walls 16a and 1Gb. As best shown in Figure 2 the end waIls 16a and 16b are of the same exterior dimensions and are secured protruding in use downwardly from the underside 11 of access cover 12. The end walls are spaced from and parallel to one another and are aligned with one another so as to define the ends of an elongate, rectangular prism that is the cuboidal part 14a of housing 14.

Each of the end walls 16a, 16b has formed therein a respective through-going aperture 17, 18.

Aperture 17 formed in end wall 16a is rectangular in shape and extends centrally in end wall iSa from a position above the in-use lowermost extent of wall iSa to location only a as short distance below the underside 11 of access cover 12. A short threshold wall IQa connects the terminus of aperture 17 and access cover underside 11.

Aperture 18 formed in end wall 16b is square in shape. Aperture 18 extends generally similarly to aperture 17, but its uppermost extent is less than that of aperture 17. As a result the threshold wall 1 9b connecting the terminus of aperture 18 with access cover underside 11 is deeper than threshold wall 19a.

The apertures 17 and 18 are in register with one another as regards their three sides other than that, in each case, defined by the respective threshold walls 19a and 19b.

The apertures 17, 18 together define a guide for the lock bolt 1& The latter is a bar of (in the preferred embodiment) a hard, rigid metal such as steel that is formed (e.g. by casting and subsequent machining) into a solid rectangular prism.

As illustrated in Figure 1 the lock bolt 13 is receivable in the apertures 17, 18 so as to extend therethrough. The positioning of the lock bolt 13 is described in more detail herein below.

End walls 16a and 16b are interconnected along one side of the rectangular prism by a first side wall 21 that tapers from (at the end of wall 16b) the height of threshold wall 19b to (at the end of wall 16a) the height of threshold wall 19a. Over its entire length therefore first side wall 21 is of considerably less depth than that of the two end walls 16a, 16b.

A second side wall 22 extends along the opposite side of cuboidal part 14a, interconnecting the end walls 16a and 16b. Second side wall 22 is of essentially the same depth over most of its length, and is of the same depth as that of the end walls 16a, 16b. Second side wall 22 is however perforated approximately mid-way along its length by a key retention slot 23 that opens at the free edge of second side wall 22. Key retention slot 23 is also partly defined by a cap plate 24 cast onto the upper surface of second side wall 22 so as to overhang the slot over part of the length of the opening of key retention slot in the free edge of wall 22.

In the space between the threshold walls l9a and 19b the underside 11 of access cover 12 defines an upper wall 26 of cuboidal part 14a. Secured at either end to the upper wall 26 by way of fasteners such as rivets or screws are the ends of a biasser in the form of a leaf spring 27.

The shape of leaf spring 27 is such that it bows into the interior of cuboidal pad 14a.

Leaf spring 27 is made from a metal alloy that is resiliently deformable The result of this arrangement is that the apertures 17, 18 in the end walls 16a, 16b define a guide in which the lock bolt 13 is slideably receivable following insertion of the bolt via aperture 18 and pressing of the leaf spring to permit catching of the end of bolt 13 against the lower edge of aperture 17. The resilient deformability of leaf spring 27 then tends to urge the lock bolt 13 in the in-use downward direction, into contact with the lowermost edges of the apertures 17, 18 formed in the end walls ISa, 16b. Figure 1 shows the bolt 13 in this configuration, following its insertion into the apertures 17, 18 as described.

As best illustrated in Figure 8, the lowermost wall of aperture 17 in end wall 16a is formed to include a restraint in the form of a deadlock step 28.

Deadlock step 28 is formed in the edge of aperture 17 against which the bolt 13 is urged to bear by leaf spring 27. Deadlock step is such that on the side facing aperture 18 the depth of aperture 17 is the same as that of aperture 18; and on the side remote therefrom the depth of aperture 17 below underside 11 is less than its depth on the side described above. A shoulder 42 separates the two sides of the aperture in the vicinity of the deadlock step 28.

Figure 1 shows the lock bolt 13 in an advanced position in which it is retained in the guide defined by apertures 17 and 18 so that a free end protrudes beyond the lateral edge of access cover 12.

The lock bolt 13 is moveable from this position parallel to its longitudinal direction to a relatively retracted position in which it protrudes less far from end wall 1 6b.

so In the extended position the lock bolt 13 is positioned to engage a lock striker formed for example in the frame of a manhole cover assembly; and in the relatively retracted position the lock bolt is disengaged therefrom. In the latter configuration the lock is released and the access cover removable from the frame; and in the former configuration the access cover is securely retained in the frame, closing off the aperture it is intended to cover.

By reason of the presence of the deadlock step 28 and the action of the leaf spring 27 the lock bolt 13 when occupying its extended position is urged into engagement with the lower edge of aperture 16a on the same side of deadlock step 28 as the leaf spring 27.

Any attempt when the lock bolt 13 is extended therefore to push it directly longitudinally towards its relatively retracted position is prevented be engagement of the free end of lock bolt 13 that is remote from the leaf spring with the deadlock step 28.

As a result under normal circumstances it is not possible to push the lock bolt towards the relatively retracted position merely by applying pressure to the exposed end of the io bolt 13. This arrangement therefore obviates the problem apparent in the lock of EP-A-1215342.

The lock bolt 13 however is moveable inside the guide defined by the apertures 16a, 16b towards the access cover 12 in an upward direction perpendicular to the longitudinal axis of the lock bolt.

Such movement takes place against the resilience of the leaf spring 27 and is made possible by reason of the greater depth of aperture 17 than aperture 18.

This depth discrepancy permits the lock bolt 13 when subjected to an upwardly acting force to pivot about the threshold wall 19b of aperture 18 such that the edge of bolt 13 urged by spring 27 into engagement with deadlock step 28 is raised to a level at which it would clear the deadlock step 28. When so positioned the lock bolt 13 is retractable in order to release the lock.

The arrangement of the invention therefore permits movement of the lock bolt initially in a first direction so as to cause it to clear the deadlock step 28 and subsequently in a second direction essentially perpendicular thereto in order to effect retraction of the lock bolt 13.

The application of forces to the lock bolt 13 is made possible by the design of the cylindrical part 14b of the housing 14, and a bolt key 29 which will now be described.

As best illustrated in Figures 3 and 4 the bolt key 29 includes an elongate, hollow, cylindrical shank 31.

At one end the shank has defined therein an n-shaped slot 32 that perforates the wall of the shank 31 and terminates at an opening located at the free end 33 of the shank 31.

Pivotably secured by way of a pin joint in the preferred embodiment in the mouth of slot 32 adjacent the free end 33 of shank 31 is an arm 34 the length of which is slightly less than that of the slot 32. Arm 34 is pivoted adjacent its lowermost end such that it may be rotated from the compact position shown in Figure 3, in which it occupies the slot 32 and is recessed therein so as not to protrude externally of the shank 31, and an extended position as illustrated in Figure 4 and in which the arm 34 extends perpendicular to the free end 33.

An actuator in the form of rod 36 extends along the length of the hollow interior of shank.

An uppermost part of rod 36 protrudes from the shank 31 via a circular opening in the upper end thereof that is visible in Figures 3 and 4.

At this upper end the rod 36 terminates in a gripping handle 38 that in the preferred embodiment shown is a 1-handle, although numerous other designs of handle are possible within the scope of the invention.

At the other end of shank 31 rod 36 is pivotably jointed (e.g. by way of a pin joint or any of a range of other fastenings) to the end of arm 34 that does not protrude from the shank 31.

The position of this pin joint (that is not visible in the drawings) is such that vertical movement of the rod 36 inside the shank 31 effects movement of the arm 34 between its compact and extended configurations. It will thus be apparent that a user of the bolt key may remotely convert the arm 34 between its two possible configurations. This permits such conversion to be effected inside the lock housing 14 from a location above the access cover, in a manner described below.

Movement of the rod 36 is limited by reason of a limit stud 39 that is secured to the rod 36 so as to protrude into a through-going, elongate limit slot 41 that extends parallel to the direction of movement of the rod 36 and hence parallel to the elongate dimension of the bolt key 29. The need for the optional limit stud 39 and slot 41 arrangement is to ensure that the rod 36 does not become over-extended relative to the shank 31 since this could cause jamming of the arm 34 in an extended position.

Referring now to Figures 7 and 8 the deadlock step 28 is shown in further detail.

The apertures 17 and 18 in effect define the guide as a hollow shaft over at least two parts of the distance between the walls 16a and 16b. As is apparent from Figure 8, and as described above, the depth of aperture 17 is greater than that of aperture 18.

Deadlock step 28 defines a shoulder 42 that projects into the shaft in order to reduce its depth in the vicinity of deadlock step 28.

The reduced depth of the hollow shaft in this location however is nonetheless greater than the thickness of the bolt 13 that therefore may be manoeuvred to pass through aperture 17 following its disengagement from the shoulder 42 of deadlock step 28 against which it is urged by the leaf spring 27 when occupying its extended position.

When so disengaged therefore the bolt 13 may be converted between the extended and relatively retracted positions described above.

One version of the cylindrical part 14b of housing 14 will now be described with reference to Figures 5 and 6.

The cylindrical part 14b is defined by an essentially cylindrical wall 43 in turn defining a hollow, through-going shaft 44 the diameter of which is slightly larger than the external diameter of the shank 31 of bolt key 29. Shaft 44 is open on either side of the housing 14.

The shaft 44 is a primary key aperture via which the bolt key 29 is insertable from the in-use upper side of the housing 14 to protrude on the lower side thereof.

Cylindrical wall 43 is essentially tangential to second side wall 22 of cuboidal housing part 14a. As previously described, approximately mid-way along its length the second side wall 22 is perforated by key retention slot 23.

The location and dimensions of the cap plate 24 overlying part of the opening of key retention slot 23 are such as to define a secondary key aperture 46 the width of which is less than the thickness of arm 34. The combined effect of the primary key aperture 44, the secondary key aperture 46 and the key retention slot 23 is to provide a labyrinthine path via which the arm 34 of bolt key 29 may be brought into engagement with the bolt 13 through a sequence described below The cap plate 24 constrains the arm 34 to move in a path involving engagement with the bolt 13, from which the arm 34 may only be released through a reverse of the engagement sequence.

o Adjacent its free end the arm 34 includes a protruding lug 47 that is sized and shaped for engagement with a lug slot 48 formed in one face of the lock bolt 13. The locations of the lug 47 and the lug slot 48 are such that they are mutually engageable when the arm and bolt are correctly juxtaposed relative to one another.

Slot 46 could be replaced in other embodiments of the invention by a bore or any of a range of other shapes of recess, but the oval slot illustrated is particularly suitable since it accommodates tolerance variations in the manufacture of the components of the lock Since the housing 14 is secured (e.g. by welding, integral casting or the use of fasteners) to the underside of access cover 12 it is necessary to provide a through-going key passage, that is in register with the primary key aperture 44, passing through the access cover 12. This permits insertion of the bolt key 29 from the side of the access cover 12 lying remote from housing 14.

Access cover 12 also includes depending downwardly from its underside 11 a cuboidal limit block 49 that preferably is cast integrally with the cover 12. Limit block 49 serves to maintain the exposed end of lock bolt 13 in alignment with a latch member formed in the frame of the access cover assembly of which access cover 12 forms part.

Operation of the lock of Figures 1 to 8 involves the following steps: Assuming the access cover 12 is in place closing off an aperture and the lock bolt 13 is in its advanced position and is engaged with a latch formation of an access aperture frame, the lock bolt by reason of engagement at one end with the shoulder 42 of deadlock step 28 cannot be retracted without use of the bolt key 29. The first step in such use of the key 29 involves inserting its non-handle end into the primary key aperture 44 via the through-going key passage of the access cover The bolt key 29 is in this operation inserted from the upper side of the access cover 12, i.e. from outside the aperture covered by the cover 12. At this stage the bolt key 29 occupies its compact configuration so that it may pass through the key passage into the primary key aperture.

Pushing of the compact configuration bolt key 29 through the primary key aperture results in the in use lowermost end of the bolt key protruding on the underside of housing 14. This situation is illustrated in Figure 5.

The gripping handle 38 is then pulled upwardly relative to the shank 31 of bolt key 29.

The shank 31 may be steadied by hand during this process, which causes the arm 34 to extend out of the slot 32 and protrude at right angles to the shank 31. This condition of the components is shown in Figure 6. The limit stud 39 and limit slot 41 co-operate to ensure that the rod 36 is not over-extended and therefore the arm 34 does not rotate more than 90 degrees out of the slot 32.

Continued pulling on the handle 38 withdraws the bolt key 29 unpwardly in the primary key aperture. As long as the arm 34 is aligned with the entrance to the secondary key aperture 46 it enters that aperture. The secondary key aperture is so located that on entry of the arm 34 into it the lug 47 enters lug slot 48 thereby ensuring positive engagement of the arm 34 and the bolt 13.

Yet further upward pulling on the handle 38 causes the lock bolt 13 to move upwardly by reason of the aforesaid engagement of the arm 34 and lock bolt 13. Such movement amounts to movement in the first direction of the lock bolt as defined herein, and it takes place against the tendency of the leaf spring 27 to urge the lock bolt 13 in a downward direction, into restraining engagement with the deadlock step 28.

This action raises the end of lock bolt 13 that lies adjacent the deadlock step, as shown in Figures 7 and 8, such that the bolt 13 may move longitudinally with clearance over the shoulder 42. Such movement is made possible by reason of the depth of the aperture 17 in end wall 16a being relatively deep and thereby able to accommodate the thickness of the bolt 13 notwithstanding the intrusion of the shoulder 42 of deadlock step 28.

From the position shown in Figure 8 the bolt may be withdrawn towards its relatively retracted position. This is achieved by rotating the handle 38 of bolt key 29 in a direction corresponding to such withdrawal of the bolt 13. Rotation of the handle 38 is transmitted to the bolt partly by reason of the pin jointing of the rod 36 and the arm 34 to the shank 31; and partly because of the interengagement of the lug 47 and the lug slot 48.

The retracted configuration is shown in Figure 9.

Withdrawal of the bolt in this fashion releases it from engagement with the latch formation of the access aperture frame since the lock bolt 13 withdraws to a position inside the perimeter of the underside 11 of cover 12. At this time the lock bolt 13 is disengaged from any latch formation formed in or secured to the frame in which the access cover 12 seats. The access cover may then be freely lifted (or, if ft is pivotably or hingedly secured in the frame, hinged) to expose the aperture.

Such lifting is facilitated by reason of the handle at this time remaining engaged with the bolt 13. This permits the user of the lock 10 to pull upwardly on the handle 38 and thereby raise the whole assembly out of the frame. The key retention slot 23 and cap plate 24 at this time combine to prevent the arm from moving out of engagement with the bolt 13 unless it is positively required for this to happen while the access cover 12 is open.

Should the user wish to remove the bolt key 29 from the access cover 12 while it is open this can only be achieved by rotating the bolt key 29 in the opposite direction to that giving rise to withdrawal of the bolt 13; downward pushing of the bolt key 29 to cause the arm 34 to clear the secondary key aperture 46; further downward pushing of the handle 38 to cause collapsing of the arm 34 to its compact configuration; and, finally, withdrawal of the bolt key 29 upwardly via the primary key aperture and the key passage.

Such a process is relatively complex and can only be completed deliberately. Therefore the risk of accidental removal of the bolt key is virtually zero.

Moreover such bolt key removal steps as are described above result in advancing of the lock bolt 13 to its extended position, which movement necessarily brings the end of the lock bolt 13 that lies inside the housing 14 to the right, in the sense of Figure 8, of the shoulder 42. Once this occurs and any upward force transmitted to the lock bolt 13 via the arm 34 is relaxed the resilient deformability of the leaf spring 27 acts to drive the lock bolt 13 downwardly into engagement with the shoulder 42. As a result the deadlock step 28/shoulder 42 combination prevents retraction of the lock bolt 13 no matter how hard the exposed end of the bolt 13 may be pressed. In consequence it is impossible accidentally (e.g. through rough handling of the access cover 12) to cause retraction of the lock bolt 13 unless the bolt key 29 is correctly in the key retention slot 23.

The arrangement of the invention therefore prevents the problem extant in the prior art of the lock bolt 13 inadvertantly being moved to its withdrawn position and the access cover 12 subsequently being replaced in its aperture without the bolt locking the cover in place.

Moreover should the bolt key 29 be removed through the above-described process while the access cover 12 is open or is removed from its aperture it is impossible to replace or close the access cover 12. This is because the lock bolt 13 in this condition protrudes beyond the edge of the underside 11 of access cover 12. In this condition the access cover 12 cannot be replaced in its aperture because the lock bolt 13 would strike the edge of the frame and prevent closing.

Replacement of the access cover 12 in its aperture therefore can only be effected if the access cover is seated in the frame before the bolt key withdrawal steps, described above, are carried out. In that case the lock bolt 13 would correctly engage a latch is formation forming part of the frame and disposed below its upper rim or edge.

As necessary the access cover and frame may include any of a range of features aimed at ensuring correct alignment of the lock bolt 13 and the latch formation. In the preferred embodiment shown in the drawings this is achieved by reason of the access cover 12 having a shape, as illustrated, that will fit only one way round in a frame defining a similarly shaped aperture. Other features such as shaped projections and recesses, and/or visual markings are possible.

Referring now to Figure 10 a variant on the basic structure of the housing is shown.

In Figure 10 the majority of the components of the lock are the same as their counterparts in Figure ito 9 and therefore have the same reference numerals.

The Figure 10 arrangement however dispenses with the cap plate 24 of Figures ito 9 and as a result the entrance of secondary key aperture 46' is wider. By reason of the absence of cap plate 24 there is no specific key retention slot 23 defined in the Figure 10 version of the cylindrical part i4b of housing 14.

Instead cylindrical waIl 43 includes an upper surface defined as an upwardly inclined spiral cam surface 51.

The cam surface 51 is sufficiently long that following deployment of the arm 34 to its extended position it is easy for the user to manipulate the handle 38 to cause engagement of the arm 34 with the surface 5t From this condition of the components the user may then rotate the handle 38 (thereby causing rotation of the arm 34) in either a clockwise or anticlockwise direction (depending on the direction in which the surface extends) while pulling upwardly on the bolt key 29 The combined rotation and pulling action guides the arm 34 along the surface 51 until it reaches the end 52 identified in Figure 10. Continued rotation and pulling then cause the arm 34 to rise upwardly past end 52 whereupon the lug 47 enters the lug slot 48, the latter being appropriately positioned for this when the lock bolt 13 occupies its advanced (extended) position as shown in Figure 10. Movement of the bolt 13 may then be effected through steps similar to those set out above describing movement of the key 29 and bolt 13 once engagement of the lug 47 in the lug slot has been achieved.

is Other variants on the basic principles of the invention as described herein are possible.

For example the shape of the labyrinthine path that the arm must in the Figures 1 -9 arrangement negotiate in order to engage the bolt 13 may be varied, as may the shapes and sizes of numerous of the parts described herein. As already explained the materials of the lock 10, bolt key 29 and access cover 12 may be varied within wide limits within the scope of the invention.

Overall the lock of the invention provides a reliable yet simple and robust solution to the

drawbacks of prior art access cover locks.

Claims

CLAIMS1. A lock for an access cover comprising a lock bolt and a housing defining a guide and a bolt aperture, the bolt being received in the guide so as to permit its movement in s the guide in a first direction and movement therein in a second direction, that is different from the first direction, between an advanced position in which it protrudes from the housing via the bolt aperture and a further, relatively retracted position; the housing including a restraint with which the bolt is engageable so as to limit movement of the bolt in the second direction; the lock including a biasser that biases the bolt into engagement with the restraint; and the housing having formed therein a primary key aperture for receiving a bolt key that is selectively engageable with the bolt such that movement of the bolt key is capable of moving the bolt in the first direction against the action of the biasser and out of engagement with the restraint; and in the second direction between the advanced and further positions.
2 A lock according to Claim 1 wherein the first and second directions of movement of the bolt are mutually perpendicular.
3. A lock according to Claim 1 or Claim 2 wherein the bolt is moveable further in the second direction than in the first direction.
4. A lock according to any of Claims 1 to 3 wherein the restraint and the biasser lie within the housing.
5. A lock according to any preceding claim including a said bolt key.
6. A lock according to Claim 5 wherein the bolt is received in the guide on a first side of the housing and the primary key aperture extends through the housing to permit insertion of the bolt key on a second side of the housing that is distinct from the first side and engagement with the bolt adjacent the first side.
7. A lock according to Claim 6 including a secondary key aperture, on the first side of the housing, communicating with the primary key aperture thereby permitting insertion of the bolt key so as to protrude beyond the bolt and permit engagement of the bolt key with the bolt on a side thereof that is remote from the second side of the housing.
8. A lock according to Claim 7 wherein the bolt key is adjustable between compact and extended configurations in which respectively it is (I) capable of passing through the primary and secondary apertures so as to protrude beyond the bolt and (ii) capable of engaging the bolt following passage through the secondary aperture.
9. A lock according to Claim 8 wherein the primary aperture is shaped to permit passage of the bolt key in its compact configuration and prevent passage of the bolt key in its extended configuration.
10. A lock according to Claim 8 or Claim 9 wherein the secondary aperture is shaped to permit passage of the bolt key in its extended configuration.
11. A lock according to any of Claims 8 to 10 wherein the key includes a shank; and an arm that is nioveable, relative to the shank, between the compact configuration in which the arm lies parallel to the shank and the extended configuration in which the arm protrudes from the shank.
12. A lock according to Claim 11 wherein the arm includes one or more formations that are engageable with a corresponding number of formations of the bolt.
13. A lock according to Claim 11 or Claim 12 wherein the shank is hollow so as to define a hollow interior and wherein the bolt key includes an actuator secured to the arm so as to extend inside the hollow interior, the actuator being operable from outside the shank at a location spaced from the arm to cause movement of the arm between its compact and extended configurations.
14. A lock according to Claim 13 wherein the shank includes an aperture via which a projecting part of the actuator protrudes externally of the shank, the projecting part including a gripping handle permitting manual operation of the actuator.
15. A lock according to any preceding claim wherein the biasser is a spring acting between the housing and the bolt in order to urge the bolt into a position permitting engagement with the restraint when the bolt adopts its advanced position.
16. A lock according to Claim 15 wherein the spring is a leaf spring secured in the guide between the bolt and the housing on the opposite side of the bolt to the restraint.
17. A lock according to any preceding claim wherein the guide is or includes a hollow shaft along at least pad of its length; and wherein the restraint includes a shoulder projecting into the shaft over part of its width so as to define a narrowed portion of the shaft, the thickness of the bolt in the vicinity of the shoulder being less than the width of s the narrowed portion such that the bolt may pass along the shaft adjacent the narrowed portion on operation of the bolt key to move the bolt in the second direction.
18. A lock according to Claim 11 or any preceding claim depending therefrom, wherein the housing includes a cam surface against which the arm bears in use of the bolt key such that movement of the bolt key along the cam surface guides the arm towards engagement with the bolt.
19. A lock according to any preceding claim wherein in order to cause movement of the bolt in the first direction the bolt key is moveable parallel to a longitudinal axis of the i bolt key.
20. A lock according to any preceding claim wherein in order to cause movement of the bolt in the second direction the bolt key is rotatable about an axis extending parallel to a longitudinal axis of the bolt key.
21. An access cover including secured to or formed integrally with its in-use underside a lock according to any preceding claim such that the lock bolt is engageable with a latch for securing the access cover relative to a structure.
22. An access cover according to Claim 21 including formed therein a through-going key passage in register with the primary aperture so as to permit insertion of the bolt key via the in-use upper surface of the access cover.
23. A lock generally as herein described, with reference to and/or as illustrated in the accompanying drawings.
24. An access cover generally as herein described, with reference to and/or as illustrated in the accompanying drawings.AMENDMENTS TO THE CLAIMS HAVE BEEN FILED AS FOLLOWSCLAIMS1. A lock for an access cover comprising a lock bolt and a housing defining a guide and a bolt aperture, the bolt being received in the guide so as to permit its movement in the guide in a first direction and movement therein in a second direction, that is different from the first direction, between an advanced position in which it protrudes from the housing via the bolt aperture and a further, relatively retracted position; the housing including a restraint with which the bolt is engageable so as to limit movement of the bolt in the second direction; the lock including a biasser that biases the bolt into engagement with the restraint; and the housing having formed therein a primary key aperture for receiving a bolt key that is selectively engageable with the bolt such that movement of the bolt key is capable of moving the bolt in the first direction against the action of the biasser and out of engagement with the restraint; and in the second direction between the advanced and further positions, wherein the biasser is a spring acting between the is housing and the bolt in order to urge the bolt into a position permitting engagement with the restraint when the bolt adopts its advanced position; and wherein the spring is a leaf : spring secured in the guide between the bolt and the housing on the opposite side of the bolt to the restraint. * * *.t**...: 20 2. A lock according to Claim 1 wherein the first and second directions of movement of the bolt are mutually perpendicular. *r 3. A lock according to Claim 1 or Claim 2 wherein the bolt is moveable further in the second direction than in the first direction.4. A lock according to any of Claims 1 to 3 wherein the restraint and the biasser lie within the housing.5. A lock according to any preceding claim including a said bolt key.6. A lock according to Claim 5 wherein the bolt is received in the guide on a first side of the housing and the primary key aperture extends through the housing to permit insertion of the bolt key on a second side of the housing that is distinct from the first side and engagement with the bolt adjacent the first side.7. A lock according to Claim 6 including a secondary key aperture, on the first side of the housing, communicating with the primary key aperture thereby permitting insertion of the bolt key so as to protrude beyond the bolt and permit engagement of the bolt key with the bolt on a side thereof that is remote from the second side of the housing.8. A lock according to Claim 7 wherein the bolt key is adjustable between compact S and extended configurations in which respectively it is (i) capable of passing through the primary and secondary apertures so as to protrude beyond the bolt and (ii) capable of engaging the bolt following passage through the secondary aperture.9. A lock according to Claim 8 wherein the primary aperture is shaped to permit io passage of the bolt key in its compact configuration and prevent passage of the bolt key in its extended configuration.10. A lock according to Claim B or Claim 9 wherein the secondary aperture is shaped to permit passage of the bolt key in its extended configuration.11. A lock according to any of Claims 8 to 10 wherein the key includes a shank; and * an arm that is moveable, relative to the shank, between the compact configuration in * .*e.* which the arm lies parallel to the shank and the extended configuration in which the arm protrudes from the shank. *0* : 20 * *12. A lock according to Claim 11 wherein the arm includes one or more formations * eS that are engageable with a corresponding number of formations of the bolt t. ** * -0 * . 13. A lock according to Claim 11 or Claim 12 wherein the shank is hollow so as to define a hollow interior and wherein the bolt key includes an actuator secured to the arm so as to extend inside the hollow interior, the actuator being operable from outside the shank at a location spaced from the arm to cause movement of the arm between its compact and extended configurations.14. A lock according to Claim 13 wherein the shank includes an aperture via which a projecting part of the actuator protrudes externally of the shank, the projecting part including a gripping handle permitting manual operation of the actuator.15. A lock according to any preceding claim wherein the guide is or includes a hollow shaft along at least part of its length; and wherein the restraint includes a shoulder projecting into the shaft over part of its width so as to define a narrowed portion of the shaft, the thickness of the bolt in the vicinity of the shoulder being less than the width of the narrowed portion such that the bolt may pass along the shaft adjacent the narrowed portion on operation of the bolt key to move the bolt in the second direction.16. A lock according tb Claim 1 or any preceding claim depending therefrom, wherein the housing includes a cam surface against which the arm bears in use of the bolt key such that movement of the bolt key along the cam surface guides the arm towards engagement with the bolt.17. A lock according to any preceding claim wherein in order to cause movement of io the bolt in the first direction the bolt key is moveable parallel to a longitudinal axis of the bolt key.18. A lock according to any preceding claim wherein in order to cause movement of the bolt in the second direction the bolt key is rotatable about an axis extending parallel is to a longitudinal axis of the bolt key. a. * * . **;.**! 19. An access cover including secured to or formed integrally with its in-use underside a lock according to any preceding claim such that the lock bolt is engageable *as with a latch for securing the access cover relative to a structure.*.... 20 * . 20. An access cover according to Claim 19 including formed therein a through-going S...*... key passage in register with the primary aperture so as to permit insertion of the bolt key via the in-use upper surface of the access cover.21. A lock generally as herein described, with reference to and/or as illustrated in the accompanying drawings.22. An access cover generally as herein described, with reference to andfor as illustrated in the accompanying drawings.