A ground surface access assembly locking system

Abstract

A GSAA lock (10) comprising a bolt (14), slidably mounted upon a base plate (20); located adjacent a blade-shaft guide member (16), connected to base plate (20); wherein, upon insertion of a key shaft (S) into the upper open end (22) of the guide member (16), the key blade (B) abuts against an upper top-face portion (24) of open end (22) preventing full insertion of the shaft (S) and blade (B) within the lock, until the key (K) is further partly turned, when it drops into a lower face portion (26) of open end (22), thereby allowing the blade (B) to enter / engage a tapered bolt recess / slot (28) located on an upper face of the bolt (14); so that on further turning of the key (K), blade (B) abuts against a sidewall (6, 8) of slot (28), and pushes the bolt from an extended position to retracted / unlocked position or vice-versa.

Description

Technical Field

[0001] The present invention relates to a robust lock for securing a hinged Ground Surface Access Assembly cover to a surrounding frame.Background

[0002] Conventionally, Ground Surface Access Assemblies (GSAAs) comprise a frame defining an opening with one or more covers located within the frame opening. The one or more covers are typically hinged to the frame, or removable, to permit access to underground services via the opening.

[0003] Typically, the GSAA frame and covers are formed of cast iron, and the covers locate and are held in the frame by a combination of the depth of insertion and self-weight. Unlocked covers, although heavy and difficult to remove, are vulnerable to theft. Importantly, in certain traffic conditions, or if the frame and / or the cover has become corroded, the cover tends rock or lift within the frame. This is undesirable; in particular resulting in wear / damage to the GSAA frame.

[0004] For GSAAs located in trafficked road surfaces any locking device must be capable of enduring loads imposed by traffic, which will include cyclic loading and shear loading. Such GSAA locks should ideally be resistant to corrosion; resistant to clogging by silt and debris; and capable of operating after long periods in-situ.

[0005] In the UK, the Loss Prevention Certification Board publishes "Loss Prevention Standards", which require that to achieve specified security ratings, a product must be able maintain structural integrity for a specified period under extreme attempts to force-open. This standard provides a benchmark for a wide range of GSAA products.

[0006] Conventionally, it should be noted that for GSAAs the term "lifting key" is used to denote a relatively large / strong hand tool which only facilitates engaging and thereby lifting of a cover or grating. Such "lifting keys" are not able to function as a lock-key.

[0007] In this specification the term "cover" is used to include: covers which have a closed / continuous upper surface that is substantially waterproof; and also an upper surface defining a plurality of waterway apertures, such as gratings.

[0008] In this specification, the terms inner, outer, inwardly and outwardly under above etc, when used in relation to the GSAA, cover and frame, are used with respect to the opening; which is inward of the cover / frame; and the terms upward and downward are used in relation to the, in-use orientation of a ground surface access assembly, in which downward means towards the ground.Summary of Invention

[0009] An aim of the present invention is to provide a robust GSAA lock resistant to transient heavy loads imposed by heavy vehicles, and the like, passing thereover. A further aim is to provide a GSAA lock that can be used with a lifting-key that may both open the lock and lift the cover. Another aim is to provide a GSAA lock that is not easily blocked by debris and is resistant to corrosion during prolonged use. A further aim is to provide a lock that can be internally washed by both hosed water and rain-water; to clear any debris within the mechanism. Another aim is to provide a robust GSAA lock that is difficult to "pick" (open without a key).

[0010] In a first aspect the invention relates to a Ground Surface Access Assembly lock (10,110), for use with a lock-key (K) comprising a handle (H), a shaft (S) and a key-blade (B); said lock (10,110) comprising: a plurality of stacked members, housing: a bolt member (14,114) slidably mounted upon a base plate member (20,120), with a side face thereof located adjacent a short tubular blade-shaft guide member (16,116); having one end fixed to, or extending upwardly from said base plate (20,120), and an upper open end (22,122) with an upper top-face portion (24,124); wherein, upon insertion of said lock-key (K) shaft and blade through a keyhole located above or within said lock, said key shaft (S) enters said blade shaft guide member (16,116) before an underside portion of the key blade (B / Bn) abuts against said upper top-face portion (24,124) of the tubular blade-shaft guide member (16,116): thereby preventing full insertion of the shaft (S) and blade (B) within the lock until the lock-shaft (S) is partly rotated causing said underside of key-blade (B) to descend / fall, over an edge (19,119), onto a lower top face portion (26,126) of the tubular blade-shaft guide member (16,116), and then enter / engage a tapered bolt recess / slot (28,128) located on the upper face of said slidably mounted bolt member (14,114); subsequently, on further turning the lock-shaft (S) through an acute angle, said key-blade (B) first abuts against a first sidewall (8,108) of said tapered bolt recess / slot (28,128), and then pushes the bolt member (14,114) from an extended / locked position to retracted / unlocked position.

[0011] Preferably, said acute angle is approximately 45°.

[0012] The lock is opened by reversing the key shaft / blade movements recited above; except that to push the bolt member from a retracted / unlocked position an extended / locked position said key-blade (B) abuts against a second sidewall (6,106) of said tapered bolt recess / slot (28,128).

[0013] Preferably, the lock (10,110) further comprises an annular blade-guide member (42,142): comprising, an annular shaped plate (44,144) and an adjoining centrally located tubular collar (46,146); wherein said tubular collar (46,146) is rotatably mounted around said tubular blade-shaft guide member (16,116) to allow restricted partial rotation; said annular blade-guide member (42,142) further comprising adjoining slots (48 and 50, 148 and 150); forming an angled slot (52, 152) within part of the annular plate (44,144) and part of the tubular collar (46,146); in use, said key blade (B) engages said angled slot (52, 152) allowing only partial rotation of annular guide member (42,142) and key-shaft (S) during locking / unlocking, as the key shaft (S) is turned. Preferably, the extent that the blade-guide member (42) can be turned / rotated is limited by an end stops (56a, 56b) on the periphery thereof; abutting against a corresponding protrusion (60) on an upper plate member (19).

[0014] Preferably, the lock (10,110) also further comprises an initial key entry zone (202, [21,23,25,27]) located below a plate / member or cover (C) providing a lock keyhole; which in use allows the key-shaft (S) and blade (B) to be inserted within the lock, but prior to further turning shaft (S) through a first angle prevents the key blade (B) and shaft (S) being inserted deeper / further, to allow a bottom edge of the key blade (B) to abut against the upper top-face portion (24,124) of said tubular blade-shaft guide member (16,116). Preferably, the key shaft (S) has to be turned through said first angle of before it can align with said annular guide member slot (48 / 50, 148 / 50) thus allowing the bottom edge of the key blade (B) to abuts against the top-face portion (24,124) of said tubular blade-shaft guide member (16,116). Preferably, this first angle is approximately 90°.

[0015] Preferably, in use a key (K) is first partially inserted through said keyhole; the key shaft it then turned allowing the bottom edge of the key blade (B) be further inserted and to abuts against the top-face portion (24,124) of said tubular blade-shaft guide member (16,116); subsequently allowing full insertion of the shaft (S) and blade (B), when the key shaft (S) is further partly turned through said acute angle and drops / falls into / within the tapered bolt recess / slot (28,128); allowing said key-blade (B) to abut against the first sidewall (8,108) or the second sidewall (6,106) of said tapered bolt recess / slot (28,128), and thereby push said bolt member (14,114) from an extended / locked position to retracted / unlocked position or vice-versa.

[0016] Preferably, a key blade slot / notch (Bn), located proximal the shaft (S) on an underside portion of the key-blade (B) is dimensioned to loosely engage the upper top-face portion (24,124) and the lower top-face portion (26,126) of said tubular blade-shaft guide member (16,116).

[0017] Preferably, the width of the tapered bolt recess / slot (28,128) increases as it approaches the tubular guide member. Preferably, the tapered bolt recess / slot (28,128) extends from a first side-face of the bolt (14,114) to the second side-face. Most preferably, the tapered bolt recess / slot (28,128) comprises a (first) straight side edge (8,108) and a (second) curved side edge (106).

[0018] In another aspect the invention comprises a method of unlocking a Ground Surface Access Assembly lock (10,110), for use with a lock-key (K) comprising a handle (H), a shaft (S) and a key-blade (B); said lock (10,110) comprising: a plurality of stacked members, housing: a bolt member (14,114) slidably mounted upon a base plate member (20,120), with a side face thereof located adjacent a short tubular blade-shaft guide member (16,116); having one end fixed to, or extending upwardly from said base plate (20,120), and an upper open end (22,122) with an upper top-face portion (24,124); wherein, upon insertion of said lock-key (K) shaft and blade through a keyhole located above or within said lock, said key shaft (S) enters said blade shaft guide member (16,116) before an underside portion of the key blade (B / Bn) abuts against said upper top-face portion (24,124) of the tubular blade-shaft guide member (16,116): thereby preventing full insertion of the shaft (S) and blade (B) within the lock until the lock-shaft (S) is partly rotated causing said underside of key-blade (B) to descend / fall onto a lower top face portion (26,126) of the tubular blade-shaft guide member (16,116), to then enter / engage a tapered bolt recess / slot (28,128) located on the upper face of said slidably mounted bolt member (14,114); subsequently, on further turning the lock-shaft (S) through an acute angle, said key-blade (B) first abuts against a first sidewall (8,108) of said tapered bolt recess / slot (28,128), and then pushes the bolt member (14,114) from an extended / locked position to retracted / unlocked position; said method comprising the following steps: a) Inserting a lock-key (K) through a keyhole located above or within said lock (10,110), until a portion of the lower face of the key blade (B / Bn) engages the upper top-face portion (24,124) of the tubular blade-shaft guide member (16,116); b) Partly turning said key-shaft (S) until the key blade (B) drops / falls over an edge (19, 119) onto the lower top face portion (26,126) causing said portion of the lower face of the key blade (B / Bn) to enter / engage a tapered bolt recess / slot (28,128) located on an upper face of said slidably mounted bolt member (14,114); and c) Further turning of the lock-shaft (S) so that a portion of the key blade (B) abuts against a first sidewall (8,108) of said tapered bolt recess / slot (28,128) and thereby pushes bolt member (14,114) from an extended / locked position to retracted / unlocked position.

[0019] Preferably, during unlocking the key shaft (S) is progressively turned anti-clockwise.

[0020] In another aspect the invention comprises a method of unlocking a Ground Surface Access Assembly cover lock (10,110) according to a first aspect of the invention (as detailed above) comprising the following steps: (a) Turning of the lock-shaft (S) so that the key blade (B) abuts against the second curved sidewall (6,106) of said tapered bolt recess / slot (28,128) and thereby pushes bolt member (14,114) from a retracted / unlocked position to an extended / locked position. (b) Lifting key-blade (B) clear of said tapered bolt recess / slot (28,128) and onto the upper top-face portion (24,124) of a tubular blade-shaft guide member (16,116); (c) Further turning lock-shaft (S) until key-blade aligns with keyhole allowing withdrawal of lock key (K).

[0021] Preferably, during locking the key shaft (S) is progressively turned clockwise.Brief Description of Drawings

[0022] The present invention is illustrated by the following diagrammatic figures in which: Figure 1 illustrates a sectioned side elevation view of a first embodiment of the lock of the present invention (10), secured by bolts to the underside of a partial view of the associated GSAA cover (C) and frame (F), and in a locked position; Figure 2 illustrates side and end elevation views of a locking key (K) suitable for use with the present invention, which may also be used to lift the unlocked GSAA cover; The construction of the above lock (10) is relatively complex and so for clarity Figures 3 to 7 illustrate selected key component parts of the first embodiment; in particular: Figures 3 illustrates a perspective view of the lock (10), partially disassembled, and shows a lock-bolt, with a tapered recess, slidably mounted on a base plate (in a partly opened position) adjacent a tubular guide member; Figure 4 illustrates an underside perspective view of the annular key-blade guide member that guides the key shaft and key-blade during lock opening and closing, limiting the degree of key shaft rotation, and providing additional security; Figure 5 illustrates a perspective view of the lock (10), partially disassembled and shows the annular key-blade guide illustrated in Figure 4, rotatably mounded upon and around a tubular blade-shaft guide member; Figures 6a and 6b show, partly using two side elevation views, the vertical downward movement / fall of the key-blade (B) necessary to engage a recess located on the upper surface of the lock-bolt and also using two corresponding plan views, the angular position of the key-shaft / blade. The key bolt is not shown for clarity purposes: Figures 7a and 7b show plan views of the lock-bolt when, during opening, part of the key blade has engaged a tapered slot, located on the top face of the bolt, both at the start and end of the bolt movement, and in particular how the key blade, after falling within the key-bolt tapered slot then moves the bolt from a closed position (Figure 7a) to an open position (Figure 7b) as the key shaft is turned through a further acute angle of about 45°; Figures 8 to 14 illustrate further features of this first embodiment of the GSAA lock, of the present invention, and in particular how the prime component parts illustrated above interact with other parts within the lock ; Figure 8 shows a sectioned side view through the entire assembled lock showing all of the stacked plate members, the lock-bolt, the blade-shaft guide member, and the annular blade-guide member, but (for clarity) not a key-blade; Figure 9 shows a perspective top-side view of the lock (10), partially disassembled with the slidably mounted bolt sandwiched between an upper and lower pair of stacked plate members; Figure 10 includes all of the component parts of Figure 9 plus additional plate members 17 and 19, illustrated in Figure 8; Figure 11 includes all the components of Figure 10 plus the rotatably mounted annular blade guide, and shows a part-sectioned view of a key blade; Figure 12 includes all of the lock component parts of Figure 11 plus 4 additional plate members 21,23,25 and 27, illustrated in Figure 8, that in combination define an initial key entry zone; Figure 13 illustrates a perspective top-side view of stacked plate members 11,20, 13,15,17,19 and 21; Figure 14 is a perspective sectioned side view corresponding to Figure 11 when the key bolt (B) (again shown partly sectioned) is about to drop / fall over an edge onto a lower top-face portion of the tubular blade-shaft guide member before engaging the bolt tapered slot. Figures 15 to 27 illustrate a preferred (second) embodiment of the lock of the present invention, in particular: Figure 15 shows an underside perspective view of the lock secured to part of (a circular portion) of an associated GSAA cover (C); Figure 16 shows a perspective view (from above) of the base member; Figure 17 (like Figure 3) shows a plan view or a bolt member slidably mounted on the base member; Figure 18 shows a plan view of the guide member housing member mounted on the base member and above the bolt; Figures 19 and 20 show underside elevation and an underside perspective view respectively of the annular blade guide member; Figure 21 shows a plan view of the annular blade guide member rotationally mounted upon the base plate blade-shaft guide member in addition to the component parts illustrated in Figure 18: Figures 22 and 23 show topside and underside perspective views of the key-entry member; Figures 24 and 25 show topside and underside perspective views of the guide member housing; Figure 26 shows an underside elevation view of the base member; and Figure 27 shows an underside elevation of the bolt member. Detailed Description

[0023] Two embodiments of the present invention will be described.

[0024] Figure 1 illustrates a sectioned side view of a first embodiment of the GSAA lock (10), bolted onto the underside of an associated GSAA cover; the associated GSAA comprising: said cover (C) and a frame (F); where only part of the cover (C) and frame (F) are illustrated. In particular, it shows a slidably mounted locking bolt (14), that forms a vital part of the GSAA lock, in an extended / locked position, such that a side flange (Fs) of the GSAA frame (F) prevents vertical opening / lifting or hinged opening of the GSAA cover (C).

[0025] Figure 2 illustrates a lock-key (K) required to lock / unlock both the first and second embodiments of the present invention, and comprises a key Handle (H); key-shaft (S); and attached key-blade (B). The key-blade (B) is "L-Shaped" and presents a blade notch (Bn), located adjacent the key-shaft, having an abutment surface that extends in a direction perpendicular to the shaft axis. The distance from the central axis of the key-shaft to the extremity of the key-blade (Rb) is significant relating to lock security (see latter).

[0026] The first embodiment of the GSAA lock casing (12) comprises ca. 10 stacked plates / members that would typically be manufactured from steel using a laser printer. The construction of this above embodiment is relatively complex, and Figures 3 to 7 illustrate selected prime component parts of the present lock.

[0027] Figures 3 illustrates a perspective view of a slidably mounted bolt (14), in a partly opened position, mounted on a base plate (20), located adjacent a short tubular blade-shaft guide member (16) attached to said base plate (20); located closely adjacent to a side-face guide recess (18), having two curved portion faces (18a, 18b) configured to approximately match the curvature of the outer wall of said tubular blade-shaft guide member (16). This guide recess (18), in use, limits the longitudinal travel of the bolt (14) relative to the base plate (20). In use, the bolt (14) slides along a track guided / restrained by a plurality of cylindrical guide members (32) that are rotatably mounted upon said base plate (20). Figure 3 illustrates 4 such guide members each comprising an outer sleeve (34) surrounding a pin (36) attached to said base plate (20). Thus, the outer tubular sleeve (34) is free to rotate around the fixed pin (36). In addition, one or more spacer members (38) that have the same height as said cylindrical guide members are in use held to said base plate by a bolt (not shown). The combination of said plurality of guide members (32) and one or more spacer members (38) support the remaining stacked members of the lock mechanism, and in use, allow unimpeded traverse of the slidably mounted bolt (14).

[0028] The slidably mounted bolt (14) has a tapered recess / slot (28) on the upper surface that comprises a straight first sidewall (8) and a curved second sidewall (6) defining a recess / slot (28) that widens as it nears said adjacent short tubular blade-shaft guide member (16). In use, this tapered recess / slot configuration allows a lower portion of key blade (B) to abut against a first sidewall (8) or a second sidewall (6) and upon turning of a key move the bolt (14) from a locked to unlocked position, or vice-versa.

[0029] The short blade-shaft guide member (16) is attached to the base plate (20) in such a way that it cannot rotate, preferably by engaging a threaded circular aperture / hole in the base plate, or similar means. This type of connection advantageously also allows rainwater and flushing / cleaning water, that enters through the keyhole etc. to exit the lock mechanism via the associated tubular blade-shaft guide member aperture (see also Figure 14).

[0030] The upper open end (22) of the tubular blade-shaft guide member (16) is defined by: an upper top-face portion (24) that extends around most of the upper annular surface of the tubular blade-shaft guide member (16); and lower top face portion (26) that defines the remainder of the tubular blade-shaft guide member (16).

[0031] Following insertion of the key shaft (S) within upper open end (22) of the tubular blade-shaft guide member (16) an underside portion of the blade (B / Bn) abuts against the upper top-face portion (24) of said tubular blade-shaft guide member (16). The key shaft (S) is then partly turned (anti-clockwise), until the underside off blade (B) descends / falls onto lower top-face portion (26) of the tubular blade-shaft guide member (16); allowing the blade (B) to fall-within / engage the bolt tapered recess / slot (28); such that on turning the shaft (S) through a further acute angle; the blade (B) abuts against a first sidewall (8) of said tapered bolt recess / slot (28) and thereby pushes said bolt member (14) from an extended / locked position to retracted / unlocked position. In this illustration, during this unlocking process, the key-blade (B) falls over a vertical edge (19) defining the transition from / between the upper and lower top face portions (24, 26) of the tubular blade-shaft guide member (16).

[0032] Figure 4 illustrates an annular blade (B) guide member (42) that comprises an upper generally annular plate (44) with an adjoining short tubular collar (46) located on the underside of said annular plate (44). The annular blade guide (42) further comprises a horizontal slot (48) formed in the upper annular portion (44) and an adjoining vertical slot (50) formed in the short annular collar (46). The resulting, angled slot (52) comprising slots 48 and 50 is dimensioned to allow the key blade (B) to just pass therethrough. The short tubular collar (46) of the annular blade guide (42) is rotatably mounted around short tubular blade-shaft guide member (16). The annular plate (44) comprises two sections that have a slightly different radius. The smaller radius portion (54) has at each end a buffer (56a, 56b) that in use cooperates with another lower-positioned stack member (not shown - see below) to restrict the angle through which the guide member can pivot / rotate.

[0033] This guide member (42) also provides additional security. When the cover is closed and locked without any key inserted, the short tubular collar (46) largely obscures sight of the slidably mounted bolt member (14) and access to said tapered recess / slot (28). Thus, when in the locked position, the key blade (14) tapered recess / slot (28) is almost completely concealed to a person looking downwardly into the tubular blade-shaft guide member (16) through the keyhole. Any unauthorised person trying to engage a side-face of the tapered recess / slot (28) with say a L-shaped tool via the narrow angled-slot (52) will likely fail if the length of the blade dimension (Rb) relative to the internal diameter (D) of the short tubular collar (46) of the guide member (42) (see Figure 2) is appropriately selected (see below).

[0034] Figure 5 shows the annular blade guide (42) illustrated in Figure 4 rotatably mounded around said tubular blade-shaft guide member (16), but omits 4 thin plate sections (13,15,17, and 19, illustrated in Figure 8) the functions of which are described below. This illustration shows the angled slot (52) aligned with the start of lower top face portion (26) of the tubular blade-shaft guide member (16).

[0035] Figures 6a and 6b show, partly using two side elevation views, the progressive vertical downward movement / fall of the key-blade (B) necessary to engage a tapered recess (28) located on the upper surface of the lock-bolt; and two corresponding plan views, showing corresponding the angular position of the key shaft (S) and blade (B).

[0036] In particular, Figures 6a and 6b show the vertical downward movement of the key-blade (B) as it falls over an edge (19); separating the upper top-face portion (24) and lower top face portion (26); to engage a tapered recess / slot (28) located on the upper surface of lock-bolt 14 (not shown - for clarity - see also Figure 14)

[0037] The upper (plan view) portion of Figure 6a shows the key shaft (S) and blade (B) located in the angled slot (52) of the annular blade guide (44,46), just before unlocking movement of the key-blade (B), with the key-blads (B) notch abutment face (Bn) resting upon upper top-face portion (24) of tubular blade-shaft guide member (16) just before it falls over the edge 19 onto the lower surface recess / slot (26) of tubular blade-shaft guide member (16).

[0038] Figure 6b shows how the blade (B) and Key shaft (S) descend / fall to their lowest position in the lock. At this point the lower part of the key blade B has engaged the tapered recess / slot (28) located of the upper surface of the slidably mounted bolt (14).

[0039] Figures 7a and 7b show plan views of the key-bolt (14) and key blade (B) located within the tapered recess / slot (28), at the start and end of the lock opening step. In particular, Figures 7a and 7b show how the key blade, after initially falling within the tapered recess / slot (28) abuts against a first straight sidewall (8) and then moves the bolt from a closed position (Figure 7a) to an open position (Figure 7b) as the key shaft is turned through a further acute angle, preferably of ca 45°.

[0040] Figures 8 to 15 illustrate further features of this first embodiment of the GSAA lock, of the present invention, and in particular how the key component parts illustrated above interact with other parts within the complete lock.

[0041] Figure 8 is a sectioned view through the entire assembled lock that shows all of the stacked plate members (apart from optional keyhole plate), and in particular the base plate member (20); key-bolt (14) with tapered slot (28); and the blade-shaft guide member (44,46); and

[0042] Figure 9 shows a perspective view of the slidably mounted blade (14) sandwiched between a lower pair of plate members (11,20) and an upper pair of plate members (13,15); that present an aligned (approximately 135°) partial-arcuate slot (70) that in use limits how far the key shaft and blade (K,B) can (in total) be rotated, once inserted within the lock.

[0043] Figure 10 shows a perspective view of the slidably mounted blade sandwiched between a lower pair of plate members and four upper stacked members (13,15,17 and 19). Annular blade guide (42) (not shown) is supported by 3 plate members (13, 15 and 17) that are rest supported by said plurality of guide members (32) and one or more spacer members (38), as mentioned in the description of Figure 3 above. Plate member (19) houses and closely surrounds the annular plate (44) of the annular blade guide (42), and along with plate member 17 presents a partial-arcuate (plan view) space (72), which spans an included angle of approximately 90°.

[0044] The plate members (11,20,13,15,17,19,21 and 23) are held together by a nut and bolt (68). Adjustable (threaded) spring-biased ball- bearing bias units (62) abut against the lower surface of the slidably mounted bolt (14) partly engaging semi-hemispherical recesses (66) located in the lower surface of said bolt (14) thereby further limiting movement of the bolt. Figure 8 illustrates 2 such bearing modules (62) and 4 hemispherical recesses (66).

[0045] Figure 11 includes all of the component parts of Figure 10 and in addition annular blade guide (42). A sectioned view (only) of the Key blade (B) is also shown. The rim of annular plate (44) is closely surrounded by a generally circular aperture within plate member (19) that also provides a stop protrusion (60) that limits the angle through which the annular blade guide (42) can rotate. In use, during opening / closing of the lock annular plate (44) buffer members (56a,56b) abut against an inwardly extending protrusion (60) of blade guide housing member (19); thereby limiting the extent that the annular blade guide (42) can partially rotate during engaging the bolt tapered slot (28). Annular blade guide (42) also presents an internal keyhole (74) through which the key blade must fall in order to exit the initial key entry space / zone (72) - see below.

[0046] Figure 12 includes all of the component parts of Figure 11 plus 4 additional plate members (21,23,25,27) illustrated in Figure 8, which define an initial key entry space / zone (72) that presents a partial-arcuate (in plan view) space which spans an included angle of approximately 90°. The key shaft has to be turned through the above included angle of approximately 90° before the key blade (B) can exit the initial key entry space / zone, via internal keyhole (74).

[0047] Figure 13 Includes all of the plate members shown in Figure 8 and in addition an optional keyhole plate (29) that allows the lock to be operated detached from a fame cover (C); thus, it is an alternative to item (C) of Figure 1; that contains a similar keyhole (not illustrated).

[0048] Figure 14 is a perspective sectioned side view corresponding to Figure 11 when the key bolt (B) (again shown partly sectioned, without shaft S) is about to drop / fall onto the lower top face portion (26) of the tubular blade-shaft guide member (16) and hence engage the bolt tapered slot (not shown).

[0049] A second and preferred embodiment of the GSAA lock (110) is illustrated in Figures 15 to 27.

[0050] Figure 15 illustrates a perspective view of a preferred (2 nd< ) embodiment of the lock (110) of the present invention secured to the underside of a partial (just a circular portion) view of the associated GSAA cover (C) that includes a keyhole (not shown). The lock (110) comprises 5 principal parts: a base member (PART 1, 120); a slidably mounted bolt (PART 2, 114); guide member housing (PART 3, 200); annular blade guide member (PART 4, 142); and key entry member (PART 5, 202). All of these parts are preferably formed of cast-iron. The lock (110) will normally be attached to the underside of a GSAA cover (C), in a similar way to that described above for the first embodiment of the invention, and will also provide a suitably aligned keyhole and also a roof for the key entry member (202).

[0051] The construction of this preferred embodiment is much simpler than that described above for the first embodiment; but (importantly) shares the same basic functional features recited in the "Statement of Invention" and attached claims.

[0052] Figure 16 is a perspective view that illustrates the base member (PART 1, 120). This combines items 16, 20, 22, 24, 26 and 38 of the first embodiment. Again, a slidable bolt (114) is supported by the base member (120). The base member (120) has an integrally formed short tubular blade-shaft guide member (116).

[0053] Figure 17 illustrates a plan view of the locking bolt (PART 2, 114) slidably mounted upon said base member (120), with a side face located closely adjacent the tubular blade-shaft guide member (116). The upper open end (122) of the tubular blade-shaft guide member (116) is defined by: an open end (122): an upper top-face portion (124) that extends around most of the upper annular surface of the tubular blade-shaft guide member (116); and lower top face portion (126) that defines the remainder of the tubular blade-shaft guide member (116).

[0054] Again, the slidable bolt (114) has a tapered recess / slot (128) on the upper surface that comprises a first straight sidewall (108) and an adjacent second curved sidewall (106) to provide a slot that widens as it nears said adjacent short tubular blade-shaft guide member (116). In use, this tapered configuration allows a lower portion of a key blade (B) (not shown) to abut against a sidewall (106,108), and upon turning of a key, to move the bolt (114) from a locked to unlocked position, or vice-versa.

[0055] Comparing Figures 17 and Figure 3 shows that both embodiments use a key blade to move (a slidably mounted) bolt (B) relying upon, near the point of full insertion, the key-blade descending / falling over an edge (119) between portion upper and lower top face portions (124, 126) of the open end (122) of tubular blade-shaft guide member (116), prior to the lower end of the key-blade (B, Bn) engaging the tapered recess / slot (128) of the bolt (114). Thus, Figure 17 includes all of the significant features illustrated in Figure 3. (first embodiment).

[0056] Figure 18 shows the bolt (PART 2, 114) sandwiched between the base member (120) and the underside of guide member housing (PART 3, 200). PART 3 combines items 13, 15 17 and 19 of the first embodiment.

[0057] The lock bolt (114) can slide within the aperture (side view) defined by items 120, 200, 116 and an inner sidewall (204) of the base member. Again, the slidably mounted bolt (114), in use, is moved when the tuning the shaft (S) of a fully engaged lock-key (K) causes a lower portion of a key-blade (B / Bn) to abut / push against a sidewall (106, 108) of the tapered recess / slot (128) during both opening and closing of the lock.

[0058] Figures 19 and 20 illustrate an annular blade guide member (PART 4, 142) comprising an annular shaped plate (144) and a centrally located (integrally formed) tubular collar (146); wherein the tubular collar (146) is rotatably mounted upon / around said tubular blade-shaft guide member (116); the annular blade guide member (142) further comprising a pair of adjoining slots (148,150), that define an angular slot (152), formed within part of the annular plate (144) and part of the tubular collar (146). In use, the key blade (B) engages the angular slot (152) during locking / unlocking as the key-shaft (S) is turned.

[0059] The guide member housing (PART 3, 200) houses the annular blade guide member (142) and limits the angle through which it can be turned / partially-rotated by mean similar to that described above for the first embodiment.

[0060] Figures 21 illustrates a plan view of the annular key-blade guide member (PART 4, 142) rotatably mounted / housed within the guide member housing (PART 3, 200).

[0061] Figures 22, 23 are perspective upper and lower views (respectively) of key entry member (202, PART 5). The purpose of this member is to provide an initial key entry space that requires the key shaft (S) and blade (B), following initial insertion, to be turned through an angle of ca. 90° before the key blade and shaft (B, S) can be further inserted through internal keyhole 174 within the lock so that the lower surface of the blade (B / Bn) rests upon key-shaft tubular blade-shaft guide member (116). PART 5 combines items 21,23,25,and 27 of the first embodiment. It also includes 6 bolt holes 3 of which (176) are threaded and co-operate with 3 threaded bolts that hold PARTS 1, 2, 3 and 5 together. The other 3 bolt holes (178) are used to attach the lock (110) to the underside of a GSAA cover (C), using bolts that engage threaded holes in the underside of a cover (C).

[0062] Figures 24 and 25 are perspective views that illustrate the topside and underside (respectively) of the guide housing member (PART 3, 200). This guide housing member (200) combines the function of items 13, 15, 17 and 19 of the first embodiment (illustrated in Figure 8 above).

[0063] PARTS 1-5 of the above 2 nd< embodiment of the invention are preferably constructed of cast-iron.

[0064] The GSAA lock of the present invention is extremely robust; resistant to corrosion; and not easily blocked by debris as the annular blade guide member (42,142) obscures entry of debris into the vicinity of the slidable bolt (14,114), and the relatively wide key-shaft aperture favours effective flushing out of any debris that may accumulate within the remainder of the mechanism, both by rainwater and hosed water.

[0065] The lock of the present invention is difficult to open without the key (K). When in the locked position the key blade (14,114) tapered recess slot (28,128) is almost completely concealed to a person looking downwardly into the tubular blade-shaft guide member 116 through the keyhole. An unauthorised person trying to engage a side-face of the tapered recess slot (28,128) with say a L-Shaped tool will likely fail if the length of the blade dimension (Rb) relative to internal diameter (D) of the tubular blade-shaft guide member (42, 142) is greater than approximately unity. (i.e., Rb / D > 1.0)

[0066] Advantageously, the "lock key" disclosed / used in the present invention once engaged within the GSAA lock can, at the end of the unlocking operation, also be used to assist an operative raising a, typically heavy, cover member. In addition, the key cannot be detached / removed during any such lifting stage, which is an advantageous safety feature; it can only be removed when locked.

Claims

1. A Ground Surface Access Assembly lock (10,110), for use with a lock-key (K) comprising a handle (H), a shaft (S) and a key-blade (B); said lock (10,110) comprising: a plurality of stacked members, housing: a bolt member (14,114) slidably mounted upon a base plate member (20,120); said bolt member (14,114) having a side face located adjacent a short tubular blade-shaft guide member (16,116); said tubular guide member (16,116) having a lower end fixed to, or extending upwardly from said base plate (20,120), and an upper open end (22,122) with an upper top-face portion (24,124); wherein, upon insertion of said lock-key (K) shaft and blade through a keyhole located above or within said lock, said key shaft (S) enters said blade shaft guide member (16,116), before an underside portion of the key blade (B) abuts against said upper top-face portion (24,124) of the tubular blade-shaft guide member (16,116): thereby preventing full insertion of the key-shaft (S) and key blade (B) within the lock until the key-shaft (S) is partly rotated causing said underside of key-blade (B) to initially descend / fall onto a lower top face portion (26,126) of the tubular blade-shaft guide member (16,116) and then / subsequently enter / engage a tapered bolt recess / slot (28,128), located on an upper face of said slidably mounted bolt member (14,114); subsequently, on further partial rotation of the key-shaft (S) through an acute angle, said key-blade (B) abuts against a first sidewall (8,108) of said tapered bolt recess / slot (28,128), and thereby pushes the slidably mounted bolt member (14,114) from an extended / locked position to retracted / unlocked position.

2. A lock according to Claim 1 further comprising an annular blade-guide member (42,142) comprising an annular shaped plate (44,144) and a centrally located tubular collar (46,146); wherein said tubular collar (46,146) is mounted to allow restricted partial rotation upon / around said blade-shaft tubular member (16,116); said annular guide member (42,142) further comprising adjoining apertures / slots (48 / 50, 148 / 150) formed within part of the annular plate (44,144) and part of the tubular collar (46,146); in use, said key blade (B) engaging said slots (48 / 50,148 / 150) allowing only partial rotation of annular guide member (42,142) during locking / unlocking as the key shaft (S) is turned / partially-rotated.

3. A lock according to Claim 2 wherein the extent that the blade-guide member (42) can be turned / rotated is limited by end stops (56a, 56b) on the periphery of the blade-guide member (42) that, in use, abut against, at last one, corresponding protrusion (60) on an upper plate member (19).

4. A lock according to any preceding claim further comprising an initial key entry zone (202, [21,23,25,27]) located below a plate / member or cover (C) that provides a lock keyhole; which in use allows the key-shaft (S) and key-blade (B) to be inserted within the lock, but prior to further turning shaft (S) through a first angle prevents the key blade (B) and shaft (S) being inserted deeper / further, to allow a bottom edge of the key blade (B) to abut against the upper top-face portion (24,124) of said tubular blade-shaft guide member (16,116).

5. A lock according to Claim 4 wherein the key shaft (S) has to be turned through said first angle of before it can align with said annular guide member slot (48 / 50, 148 / 50) thus allowing the bottom edge of the key blade (B) to abuts against the top-face portion (24,124) of said tubular blade-shaft guide member (16,116).

6. A lock according to Claim 4 or 5 wherein said first angle is approximately 90°, and / or the acute angle is approximately 45°.

7. A lock according to any preceding claim wherein in use a key (K) is first partially inserted through a keyhole; the key shaft (S) it then turned allowing the bottom edge of the key blade (B) be further inserted and abut against the top-face portion (24,124) of said tubular blade-shaft guide member (16,116); subsequently allowing full insertion of the shaft (S) and blade (B), when the key shaft (S) is further partly turned through an acute angle and drops / falls into / within the tapered bolt recess / slot (28,128); allowing said key-blade (B) to abut against the first sidewall (8,108) or the second sidewall (6,106) of said tapered bolt recess / slot (28,128), and thereby, upon further / final partial rotation of said key shaft (S), slide / push said bolt member (14,114) from an extended / locked position to retracted / unlocked position, or vice-versa.

8. A lock according to any preceding claim wherein a key-blade slot / notch (Bn), located within the key blade (B), proximal the shaft (S); loosely engages the top-face portion (24,124) of said tubular blade-shaft guide member (16,116).

9. A lock according to any preceding claim wherein the width of the tapered bolt recess / slot (28,128) increases as it approaches the tubular blade-shaft guide member (16,116).

10. A lock according to any preceding claim wherein the bolt recess / slot extends from a first side-face of the bolt (14,114) to the opposite second side-face.

11. A lock according to any preceding claim wherein the tapered bolt recess / slot (28,128) comprises a straight side edge (8,108) and a curved side edge (106).

12. A lock according to any preceding claim wherein during locking said key-blade (B) abuts against a curved edge (6, 106) of said tapered bolt recess / slot (28,128), and thereby, on partial rotation of said key-shaft (S), slides / pushes said bolt member (14,114) from a retracted / unlocked position to an extended / locked position.

13. A method of unlocking a Ground Surface Access Assembly lock (10,110), for use with a lock-key (K) comprising a handle (H), a shaft (S) and a key-blade (B); said lock (10,110) comprising: a plurality of stacked members, housing: a bolt member (14,114) slidably mounted upon a base plate member (20,120); said bolt member (14,114) having a side face located adjacent a short tubular blade-shaft guide member (16,116); said tubular guide member (16,116) having a lower end fixed to, or extending upwardly from said base plate (20,120), and an upper open end (22,122) with an upper top-face portion (24,124); wherein, upon insertion of said lock-key (K) shaft and blade through a keyhole located above or within said lock, said key shaft (S) enters said blade shaft guide member (16,116), before an underside portion of the key blade (B) abuts against said upper top-face portion (24,124) of the tubular blade-shaft guide member (16,116): thereby preventing full insertion of the key-shaft (S) and key blade (B) within the lock until the key-shaft (S) is partly rotated causing said underside of key-blade (B) to initially descend / fall onto a lower top face portion (26,126) of the tubular blade-shaft guide member (16,116) and then / subsequently enter / engage a tapered bolt recess / slot (28,128), located on an upper face of said slidably mounted bolt member (14,114); subsequently, on further partial rotation of the key-shaft (S) through an acute angle, said key-blade (B) abuts against a first sidewall (8,108) of said tapered bolt recess / slot (28,128), and thereby pushes the slidably mounted bolt member (14,114) from an extended / locked position to retracted / unlocked position; comprising the following steps: (a) Inserting a lock-key (K) through a keyhole located above or within said lock (10,110), until a portion of the lower face of the key blade (B) engages the upper top-face portion (24,124) of the tubular blade-shaft guide member (16,116); (b) Partially rotating said key-shaft (S) until the key blade (B) drops / falls within a lower top face portion (26,126) of the blade-shaft guide member (16,116) causing a lower portion of said key-blade (B) to enter / engage a tapered bolt recess / slot (28,128) located on an upper face of said slidably mounted bolt member (14,114); and (c) Further partially rotating the lock-shaft (S) so that the key blade (B) abuts against a first sidewall (8,108) of said tapered bolt recess / slot (28,128) and then slides / pushes bolt member (14,114) from an extended / locked position to a retracted / unlocked position.

14. A method of locking a Ground Surface Access Assembly cover lock (10,110) according to any of Claims 1 to 11 comprising the following steps: (a) Partially-rotating / Turning the key-shaft (S) so that the key blade (B) abuts against a second sidewall (6,106) of said tapered bolt recess / slot (28,128) and then slides / pushes the bolt member (14,114) from a retracted / unlocked position to an extended / locked position. (b) Lifting key-shaft (S) clear of said tapered bolt recess / slot (28,128) and onto a top-face portion (24,124) of a tubular blade-shaft guide member (16,116); (c) Further partially rotating key-shaft (S) until key-blade aligns with the lock keyhole allowing withdrawal of the lock key (K).

15. A Method according the Claim 14 wherein during locking the key shaft (S) is progressively turned clockwise.

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