LOCKING DEVICE FOR WELL COVERS

Abstract: The invention relates to a locking device to be mounted in the space between a cover (11) or grate and a surrounding frame (12) in openings in water and sewage systems and that prevents unauthorised opening. The locking device comprises two first elements (1), identical and put inverted to each other and on one side provided with friction element (5) of resilient material. In their lower edge the metal elements have outwardly bent flanges (3), extending to half the width of the element, which catch under the lower edge of respective elements when they are put together and inserted in the space. The upper part of the elements is bent outwardly to a second flange (4) in the opposite direction to the first flange (3). A second metal element (6) is inserted between the two first elements and expands the device, whereby the friction elements are compressed and cause extensive friction force against the walls of the space (11, 12).

Description: Locking device for well covers. The present invention relates to a locking device to be mounted in the space between for instance cover or grate and surrounding frame in openings of sewage and draining systems and thereby prevent unauthorised access to wells and culverts, comprising elements of stainless metal and friction element of resilient material. Devices are known who have a tube with a plate in the upper end that keeps the well cover down and a device being operated through the tube gripping the walls of the well. The gripping device is operated through the tube with a special tool. The device does not provide any greater security against unauthorised opening and is also complicated and thereby expensive. There are also well designs with slightly wedge shaped covers who fit the frame relatively good making the cover be wedged up and they are removed with a tool with the shape of a sliding hammer. However such a cover doesn't look too difficult to remove in another way. A design known through patent application SE 1812487-2 comprises a rubber detail in a holder of metal, placed on at least one side of the cover or grate, inside the surrounding frame. The rubber detail is forced to expand by inserting a metal piece, a wedge, whereby the friction against the edges of the cover and the frame provides locking. The rubber detail has a complicated shape with longitudinal ridges in the wedge slot and outer transversal grooves or rifles on one side. The detail has a recessed back for mounting of a metal holder having an outward bent part, which will bear against the upper side of the cover or the frame. The rubber detail rests in a u-shaped lower part of the metal holder. To open a cover the whole device is pulled up from the space by applying a tool under the device itself. Thus the device is pulled up under full friction against the rubber detail, which then runs a great risk to be damaged. Since one side of the device, with the metal holder makes contact with the cover or the frame, such high friction is not obtained as if the metal holder would have been provided with a rubber back. The spaces between covers and frames are not the same from make to make and to overcome this, rubber details of different dimensions must be available. This leads to that more tools with different dimensions must be used for manufacturing of the details. A different embodiment is disclosed comprising only the rubber detail, which is forced to expand. To make such a device effective the rubber detail would be equilateral and thereby a further variant is required and another tool for manufacturing. An object with the present invention is to provide a device for securing covers or grates for wells in surface water and sewage systems that have a reliable and simple design with few and simple details being easy to manufacture without complicated tools and thereby cheap. The device should be easy to apply in spaces of different width and must provide so high friction against cover and frame that an unauthorised removal is exceedingly difficult. Besides the device should be easy to remove and able to re-use. The object is achieved by a device characterised in that the metal elements are three in number of which the two first ones are identical, towards each other inverted elements with a plane rectangular web, whose lower edges have a first flange, bent perpendicular to the element, extending to half the width of the element and whose upper part is bent in the opposite direction forming a second flange, preferably perpendicular to the element, whereby their first flanges catch under the edge of the opposite element and secure the elements to each other when the elements are positioned inverted to each other so that when one of them is subjected to a lifting force, the force is transferred to the second element, and that the third metal element is plane and of less length and width than the two elements and which in its upper part, a small distance from the upper edge, is provided wits cuts for applying a removing tool and that the friction elements of resilient material are two in number and fixed to the first elements so that they cover the web under the second flanges and have a thickness adapted to the width of the space between the well cover and the frame, whereby the device expands and the elements of resilient material compress and secure the well cover to the frame when the third element is pressed down between the two first metal elements. A preferred embodiment of the invention will now be described with reference to the attached drawings, on which Fig.1 shows a first metal element in perspective with a glued friction element of resilient material. Fig. 2 shows a plane view of a second metal element. Fig. 3 shows the application of the locking device in a well. In fig. 1 a first metal element is depicted with a web 2 and an outwardly bent first flange 3 in the lower part, extending to half the width of the web. The upper part of the element is bent outwardly perpendicular to the web forming a second flange 4 in the opposite direction to the first flange 3. On the back of the element the whole web is covered with a plate 5 of resilient material, preferably synthetic rubber of a relatively hard quality. The plate is cut or punched from rubber sheets of standard size. The thickness of the plate is adapted to the application in question and is for instance fixed to the web with a double adhesive tape. The plate can also be glued. In fig. 2 a second metal element 6 is depicted, which has length and width slightly less than those of the first element do. The upper corners have a chamfering 7, and at a short distance from the upper edge cuts 8 with a horizontal upper part 9 are made. These form a holder for a retraction tool. The lower edges of the element have a slight chamfering 10 to facilitate inserting between the two first elements. To further facilitate the insertion the second element can be wedge shaped in the lower part. Fig. 3 shows how the locking device is applied in the space between a drain cover 11 and its surrounding frame 12. The two identical first metal elements 1 are provided with rubber plates with a thickness that the space is completely filled out when the two metal elements are put together with their webs against each other and the upper flanges pointing from each other. The elements are pushed down in the space so that the flanges bear against cover and frame respectively. The second metal element 7 is pressed or punched down between the two first elements, whereby the rubber plates 5 are compressed and will be pressed strongly against the edges of the cover and the frame respectively. The metal element 7 is punched down until its upper edge lies slightly lower than the upper side of the flanges 4. A very high friction force arise keeping the device and thereby the well cover in place and a force of the size of 1 ,5 kN is required to pull or press up a cover out of its frame. Results from testing at the Swedish National Testing and Research Institute are presented in the following extract from the test report. "In the test the well cover and frame was fixed to a horizontal bed. The load was applied with a hydraulic cylinder by a pulling force acting on the cover (grate). The load was increased by a continuous increase of the deformation with 10 mm/minute. Results from testing with cover and frame of type A1 with two locking devices are shown in table 1. The test was performed both with centric and eccentric load. Eccentric load was applied in the middle of one long side. Results from testing of cover and frame of type A1 with hinges at one short side locked with one locking device are shown in table 2. The test was only carried out with centric load as eccentric load makes opening impossible. The force was applied at the short side where the locking device was mounted. Table 1 Result with cover and frame type A1 Table 2 Result with cover and frame A1 with one locking device and hinges at one short side of the cover. To remove the locking device a tool of a special shape is applied to the cuts 9 and 10 in the second metal element and this is pulled up whereby the rubber plates expand and the friction force disappears. The invention is not limited to the described embodiment but can be made in different ways within the scope of the claims, for instance as locking device for other sealing devices than just covers and grates for wells in sewage and draining systems. As examples can be mentioned covers and doors that need not be opened very often and do not need quickly operated locking devices of prevalent design. In a variant of the device the backside of the webs of the two first elements have a cut surface or is provided with ridges that eliminate the need to glue or tape the friction element.

Claims: Claims 1. Locking device to be mounted in the space between for instance cover or grate and surrounding frame in openings of sewage and draining systems and thereby prevent unauthorised access to wells and culverts, comprising elements of stainless metal and friction element of resilient material, characterised in that two first elements (1) with a plane, rectangular web (2) and a first flange (3) at its lower edge, bent perpendicularly to the element and extending to half the width of the element and an upper part bent in the opposite direction, preferably perpendicular to the element forming a second flange (4), are positioned inverted to each other so that their first flanges (3) catch under the edge of the opposite element and secure the elements to each other, whereby the force is transferred to the opposite element when one of them is subjected to a lifting force, and that a second metal element (6), which is plane and of slightly less length and width than the first two elements, in its upper part, a small distance from the upper edge, has cuts (8, 9) for applying a removing tool and that the friction elements (5) of resilient material are fixed to the first elements so they cover the web (2) below the first flanges (4) and has a thickness adapted to the space between the drain cover and the frame, whereby the device expands and the elements of resilient material are compressed and secure the well cover to the frame when the third element (6) is pressed down between the two first metal elements (1). 2 • Locking device according to claim ^characterised in that the surface below the flange (4) on the web on the two first elements is rifled or cut. 3 • Locking device according to claim ^characterised in that the second element (6) has a wedge shaped lower part. AMENDED CLAIMS [received by the International Bureau on 18 January 1999 (18.01.99); original claims 1 - 3 replaced by new claims 1-4(1 page)] 1. Locking device to be mounted in the space between for instance cover or grate and surrounding frame in openings of sewage and draining systems and thereby prevent unauthorised access to wells and culverts, comprising elements of stainless metal and friction elements of resilient material, 2. characterised in that two first, identical elements (1) with a plane, rectangular web (2) and a first flange (3) at its lower edge, bent perpendicularly to the element and extending to half the width of the element and an upper part bent in the opposite direction, preferably perpendicular to the element forming a second flange (4), are positioned inverted to each other so that their first flanges (3) catch under the edge of the opposite element and secure the elements to each other, whereby the force is transferred to the opposite element when one of them is subjected to a lifting force, that a second metal element (6), which is plane and of slightly less length and width than the first two elements, in its upper part, a small distance from the upper edge, has cuts (8, 9) for applying a removing tool and that the friction elements (5) of resilient material are fixed to the first elements so they cover the web (2) below the first flanges (4) and has a thickness adapted to the space between the drain cover and the frame, whereby the device expands and the friction elements (5) of resilient material are compressed and secure the well cover to the frame when the second element (6) is pressed down between the two first metal elements (1). 3. Locking device according to claim ^characterised in that the surface below the flange (4) on the web on the two first elements (1) is rifled or cut. 4. Locking device according to claim ^characterised in that the second element (6) has a wedge shaped lower part.

Inventors: JOHANSSON SVEN-ERIK, JOHANSSON, SVEN-ERIK
Applicants: JOHANSSON SVEN ERIK, JOHANSSON, SVEN-ERIK
Application year: 1998
Main classification: E02D29
IPC codes: E02D29, E03F5