Improvements in or relating to ground surface access assemblies

Abstract: An assembly including a cover (2) and a frame (1) including a plurality of generally straight sides in plan configuration, in which the cover is adapted to be mounted within the frame by means of complementary and mating support surfaces (19, 20, 21, 22) of a non-wedging configuration and angled at or adjacent or about a first side (in plan view) of the assembly, and by means of complementary and mating pairs (7, 8, 9, 10) of wedging support surfaces of the cover and frame at or adjacent or about a second side of the assembly opposing the first side, the wedging surfaces being downwardly inclined in a direction across the second side and inwardly towards the first side.

Description: This invention relates to ground surface access assemblies by which is meant covers and frames for openings in a pavement, road or flooring or similar surfaces serving as an access opening to water hydrants, sewers, access pits, wiring conduits and similar below surface cavities and installations. More especially, but not exclusively, the invention relates to access assemblies of polygonal configuration or of any convenient regular four sided plan such as rectangular, square or trapezium for example, and of a relatively small plan size (of the order of 250 x 400 mm for example) of the kind frequently used to cover a valve fitting such as a fire hydrant valve fitting which may need to be operated quickly in an emergency and to which access is therefore correspondingly required on a rapid basis. A common form of design of such access assemblies (see, for example, GB-A-664 152) employs a solid single piece cover having wide V-shaped wedging seatings on each of the opposing short sides of the cover which fit matching recessed seatings in the frame. Such a design is simple, and perfectly adequate for supporting vehicular loading without lateral movement or rocking, since, despite having four seating faces (i.e. each of the sloping faces of the two wedges at each side) the jamming action of the loading usually automatically creates its own stability of the cover within the frame. However, a disadvantage of such an assembly is that after a substantial period of load bearing, the cover becomes tightly wedged within its frame, which inhibits speedy removal, which in an emergency (when a required fire hydrant fitting for example is located therebeneath), creates a serious disadvantage. It is an object of the present invention to provide an access assembly which overcomes the above mentioned problem and disadvantage. In accordance with one aspect of the present invention there is provided a ground surface access assembly including a cover and a frame including a plurality of generally straight sides in plan configuration, in which the cover is adapted to be mounted within the frame by means of complementary and mating support surfaces of a non wedging configuration and angle at or adjacent or about a first side (in plan view) of the assembly, and by means of complementary and mating pairs of wedging support surfaces of the cover and frame at or adjacent or about a second side of the assembly opposing the first side, the wedging surfaces being downwardly inclined in a direction across the second side and inwardly towards the first side. The complementary and mating pairs of wedging support surfaces may be located in sides of the frame and cover disposed so that one extends from each end of said second side inclined in plan view of the second side. Wedging support surfaces may be disposed adjacent the ends of the second side, and may additionally be disposed away from the ends of the second side. In one embodiment of the invention the assembly may be generally four sided and in accordance with another aspect of the present invention there is provided a ground surface access assembly including a cover and a frame of generally four sided plan configuration, in which the cover is adapted to be mounted within the frame by means of complementary and mating support surfaces of a non wedging configuration and angle at a first side (in plan view) of the assembly, and by means of complementary and mating pairs of wedging support surfaces at or adjacent a second side of the assembly opposing the first side, the wedging surfaces being disposed at or adjacent each of the corners of the second side and being downwardly inclined across the second side and inwardly inclined towards the first side, the frame being provided between the first side and third and fourth sides of the frame, with corner cutting wall portions inclined in plan view to the line of the first side, and the cover being provided with complementary surfaces (or pads) for mating with the inclined frame corner cutting wall portions. The cover and frame may be of generally regular four sided plan configuration and in a preferred form of the invention, the cover and its supporting frame are generally rectangular or square in plan view. The configuration of the corner cutting portions on the frame may in this case be at 45° to the first side of the frame, and the complementary mating surfaces or pads on the cover may be at a corresponding angle to the sides of the cover. It is to be noted that these angles may vary significantly from this specified angle without rendering ineffective the operation of the invention. Preferably the complementary and mating support surfacesof a non wedging configuration and angle are located generally centrally of said first side. By way of the explanation of the invention it is to be noted that with the provision of non-wedging support at the first side of the frame and cover, it becomes in practice an easy matter to prise the cover away from the frame by providing a prising slot for example at the centre of the first side of the cover. However, by providing simple wedging supports only at the second side of the frame and cover, lateral movement of the cover relative to the frame could occur away from that second side (for example in the case of a vehicle braking on the cover) both in the direction between the first and second sides, and transversely thereto. Such movement is possible in practice because of the inevitable gap between the cover periphery and the frame due to casting tolerances. By providing mutually engaging wedging surfaces at the second side of the frame which are downwardly inclined across the second side (for simple wedging) and inwardly towards the first side, movement of the cover in the direction between the first and second sides is prevented, and by providing the two pads on the cover and the mating inclined wall portions on the frame at the ends of the first side thereof (in addition to the inclination of the wedging faces at the second side, across that side), movement transverse to this direction is also prevented. Thus, these features ensure that irrespective of manufacturing tolerance on length and width, the cover is caused to be held immovably between the angled wedge seatings and the two pad assemblies. In effect, by means of the invention, particularly where this relates to a square or rectangular cover and frame, there is provided a cover which seats on a non wedging seating located preferably centrally at one end, and forms, in conjunction with the angled seatings at or near the corners of the opposite end an approximate three point suspension arrangement. Furthermore by means of the inclined cover pads at the plane seating end, the cover is securely held in the frame and yet can be easily removed by a removing tool such as a prising bar (for example) operated at that end. The cover may be provided at the first side of the assembly with a groove extending downwardly from the top surface thereof to provide a slot between the cover and frame at the first side for the insertion of a prising bar between the frame and the cover. The groove may have an upper lip for leverage by the prising bar for assistance in removal of the cover. In one embodiment of the invention, the first and second sides are opposing short sides (in plan view) of the assembly. The non-wedging support surfaces may be plane surfaces and may be horizontal (in use) or may be inclined at any convenient angle, provided an angle at which wedging between the cover and frame can occur is not approached. By means of the invention a cover of a reasonable range of manufacturing tolerances can be located firmly within its associated frame, tolerance variations between the first and second sides of the assembly being accommodated by the cover fitting at a different level upon the complementary wedging support surfaces of the cover and frame, the inclinations of these surfaces causing the cover under normal usage from traffic to move down the wedging support surfaces and towards the first side to the extent caused by the relative tolerances of the cover and frame, until the cover and frame engage via the cover pads and frame inclined wall portions adjacent the first side of the assembly, at which point all side to side and end to end movement of the cover in the frame is prevented. It will be apparent that it is necessary to ensure that tolerance ranges in dimension across the width of the first and second sides need to be such that the cover will always, at maximum tolerance divergence, fit within the frame. In alternative embodiments of the invention the cover and frame may be of polygonal plan configuration, the first side and the second side facing one another. The cover and frame may be of hexagonal configuration. Sides carrying the wedging support surfaces may extend (inclined in plan view) from each end of the second side, and sides (having complementary frame and cover bearing surfaces) may extend (inclined in plan view) one from each end of the first side. In order that the invention may be more readily understood, one embodiment thereof will now be described by way of example with reference to the accompanying drawings in which:- Figure 1 is a isometric view showing one embodiment of a cover and frame according to the invention; Figure 2 is a schematic plan view showing the wedge short side of the assembly of Figure 1 with varying manufacturing tolerance differences between the frame and cover; Figure 3 is a schematic elevation of the arrangement illustrated in Figure 2; Figure 4 is a scrap plan view of one corner of the cover and frame; and Figure 5 is a plan view, partly broken away, of a second embodiment of a cover and frame according to the invention. Referring now to the drawings, and particularly to Figure 1, it is to be seen that the access assembly comprises a frame 1 and cover 2 of generally rectangular plan configuration. The dimensions of the assembly illustrated will be approximately 250 mm x 450 mm in plan, and the assembly is of the kind commonly used to cover hydrants or similar water valves. The cover is supported within the frame at the opposing short sides thereof (the first and second sides 3, 4 of the assembly). At the first side 3 the cover is supported by means of a downwardly protruding foot 5 generally centrally of that side of the cover having a generally horizontal lower surface which is adapted to engage upon a shoulder 6 having corresponding upwardly generally horizontal surfaces extending from the side wall of the frame. The short side 3 of the frame 1 is connected to adjacent long sides 15 and 16 by means of wall portions 19 and 20 which, in plan, are inclined to the respective adjacent walls at 45°. In a similar manner short side 3 of the cover 2 is connected to adjacent long sides 17 and 18 by means of angled faces carrying pads 21 and 22 correspondingly inclined (in plan) to the respective adjacent sides at an angle of 45°. At the second side 4 of the assembly, the frame is provided with wedging support surfaces 7, 8 adjacent each corner, which wedge surfaces are inclined downwardly and inwardly both across to the second side 4, and towards the first side 3. Corresponding and matching inclined wedging support surfaces 9, 10 are provided at the corresponding second side 4 of the cover. In operation, on engagement of the cover 2 within the frame 1, the non wedging support surfaces 5 and 6 at the first side 3 of the assembly of the cover and frame engage. At the same time the wedging surfaces 7, 8, 9, 10 at the second side 4 also engage, and allow the cover at the second side 4 to move downwardly on the engaging wedge surfaces 7, 8, 9, 10 so that the cover 2 is located centrally within the frame with respect to side 4, and is also pushed towards the first side 3 for firm engagement between the pads 21, 22 of the cover and the corresponding inclined wall portions 19, 20 of the frame, as illustrated in Figure 4. As can be seen from Figures 2 and 3, the left hand part of the figure shows a situation where manufacturing tolerances are such that the cover is a few mm shorter than the frame, so that the cover 2 is located, at second side 4 both away from the second side of the frame, and below the level of the frame by a few mm. On the right hand side an alternative position is shown where the cover is a few mm longer than the frame, and in this case the cover at the second side 4 extends beyond and above the frame, in each case by a few mm. As can be seen in Figure 4 the use of the pads 21, 22 of the cover and the corresponding inclined wall portions 19, 20 of the frame enables the satisfactory and firm accommodation of a cover smaller by a few mm in each direction than the frame. It will be appreciated also that movement either between the short sides 3, 4 of the frame, or transverse thereto is prevented by the engagement of pads 21, 22 on wall portions 19, 20. In the embodiment illustrated the wedging angle of inclination 11 of the wedging support surfaces is of the order of 15°, whilst the seating face angle 12 is of the order of 28°. As can be seen in Figure 1 the cover is provided with a groove 13 having a lip 14 at its upper inner edge which enables a prising tool (not shown) to be inserted between the cover and the frame at the first side 3 of each when the cover 2 is in situ in the frame 1 for removal thereof. It is a simple matter at that time, by prising by means of a crow bar or similar device inserted into the groove 13 and turned under the lip 14 to distort the frame sufficiently (if necessary), to cause the cover 2 to be lifted from the frame 1 at this first side 3. This causes the wedging support surfaces at the second side 4 to free for rapid and easy removal of the cover from the frame. The embodiment of the invention illustrated in Figure 5 comprises a hexagonal manhole cover 30 and complementary frame 31. The operational surfaces and features of the assembly of Figure 5 correspond closely to those of the rectangular cover and frame of Figures 1 to 4. A first side 32 of the frame and cover assembly is provided with complementary non wedging support surfaces (shown at 33, 34 on the frame) of generally horizontal disposition. A second side 35, opposite to the first side 32, has no support surfaces, but adjacent sides 36 and 37 carry complementary wedging surfaces (shown at 38, 39 and 40, 41 respectively on the frame) inclined inwardly of the assembly and providing in combination a wedging action on the cover 30 in the direction of assembly side 32, inhibiting movement in that direction and transverse thereto. As with the embodiment of Figures 1 to 4, removal of the cover 30 is by means of a prising tool (not shown) which can be inserted between the cover and the frame in the groove 42 in the side 32 of the assembly. It is to be understood that the foregoing is merely exemplary of access assemblies in accordance with the invention and that modifications can readily be made thereto without departing from the scope of the invention as defined by the appended claims.

Claims: A ground surface access assembly including a cover (2) and a frame (1) including a plurality of generally straight sides in plan configuration, in which the cover is adapted to be mounted within the frame by means of complementary and mating support surfaces (5,6) of a non-wedging configuration and angle at or adjacent or about a first side (3) (in plan view) of the assembly, and by means of complementary and mating pairs of wedging support surfaces (7,8,9,10) of the cover and frame at or adjacent or about a second side (4) of the assembly opposing the first side, the wedging surfaces being downwardly inclined in a direction across the second side and inwardly towards the first side. An assembly as claimed in claim 1 in which the complementary and mating pairs of wedging support surfaces are located in sides of the frame and cover disposed so that one extends from each end of said second side inclined in plan view of the second side. An assembly as claimed in claim 2 wherein wedging support surfaces are disposed adjacent the ends of the second side. An assembly as claimed in claim 2 or 3 wherein wedging support surfaces are disposed away from the ends of the second side. Apparatus as claimed in any one of the preceding claims wherein the cover and frame are of polygonal plan configuration, the first side and the second side facing one another. An assembly as claimed in claim 5 wherein the cover (30) and frame (31) are of hexagonal plan configuration. An assembly as claimed in claim 5 or 6 wherein sides carrying the wedging support surfaces extend (inclined in plan view) one from each end of the second side (35), and sides (having complementary frame and cover bearing surfaces) extend (inclined in plan view) one from each end of the first side (32). An assembly as claimed in any one of claims 1 to 4 wherein the cover and the frame are generally of four sided plan configuration, and in which the cover is adapted to be mounted within the frame by means of complementary and mating support surfaces of a non-wedging configuration and angle at a first side (in plan view) of the assembly, and by means of complementary and mating pairs of wedging support surfaces at or adjacent a second side of the assembly opposing the first side, the wedging surfaces being disposed at or adjacent each of the corners of the second side and being downwardly inclined across the second side and inwardly inclined towards the first side, the frame being provided between the first side and third and fourth sides of the frame, with corner cutting wall portions (19,20) inclined in plan view to the line of the first side and the cover being provided with complementary surfaces (or pads) (21,22) for mating with the inclined frame of the corner cutting wall portions. An assembly as claimed in claim 8 in which the cover and frame are generally of rectangular configuration in plan view. An assembly as claimed in claim 9 in which the configuration of the corner cutting portions on the frame are at 45° to the first side of the frame and the complementary mating surfaces or pads on the cover are at a corresponding angle to the sides of the cover. An assembly as claimed in any one of claims 8 to 10 in which the cover is provided at the first side of the assembly with a groove (13) extending downwardly from the top surface thereof to provide a slot between the cover and frame at the first side for the insertion of a prizing bar between the frame the cover. An assembly as claimed in claim 11 in which the groove is provided with an upper lip (14) for leverage by the prizing bar for assistance in removal of the cover. An assembly as claimed in any one of claims 8 to 12 in which the first and second sides are opposing short sides (in plan view) of the rectangular assembly. An assembly as claimed in any one of claims 8 to 13 in which the non-wedging support surfaces are planar and disposed in a horizontal disposition.

Inventors: BATEMAN TERENCE, GREATOREX CYRIL BARRIE, BATEMAN, TERENCE, GREATOREX, CYRIL BARRIE
Applicants: STANTON PLC
Application year: 1990
Main classification: E02D29
IPC codes: E02D29