Abstract:
A method for detaching a manhole frame ( 7 ) that is embedded in a road surface, wherein the manhole frame ( 7 ) is cut horizontally starting from the inside, without significant exposure of the outside area surrounding the manhole frame ( 7 ), by using a horizontally oriented rotating cutting blade ( 15 ) that performs eccentric circumferential runs along the inside of the manhole frame.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based on and claims the priority date of European Patent Application No. 02 012 068.9, filed on May 31, 2002. 
     BACKGROUND OF THE INVENTION 
     The invention relates to a method and an associated apparatus for detaching an embedded manhole frame. 
     To replace the manhole frames of manhole covers, e.g., in case of damage, the prior art calls for breaking up the asphalt or concrete road surface in which the manhole frame is embedded, preferably with pneumatic tools, until the manhole frame is easily accessible with the tools. After separating the manhole frame from the asphalt or concrete road surface and detaching it from the manhole cone or brickwork, the manhole frame can be lifted out manually, often piece-by-piece. The manhole cone can be damaged easily during this operation as a result of scraping, which reduces its load-carrying capability. For a high-quality reconstruction, the area where the road surface is broken up must be freed up to the manhole cone and the manhole cone must then be reconstructed, starting with the upper cone edge. The large area of repair and the considerable expenditure for the repair is a disadvantage. 
     Accordingly, it is the object of the present invention to provide a method for detaching an embedded manhole frame and a device that is particularly suitable for realizing this method. The method calls for a quick and low-cost removal of the manhole frame, without having to free a larger area around the manhole frame and the manhole cone, and without damaging the manhole cone section adjacent to the manhole frame. The method and device should lend themselves to a high degree of automation. 
     SUMMARY OF THE INVENTION 
     The above object generally is achieved according to a first aspect of the invention by a method for detaching a manhole frame embedded in a road surface wherein the manhole frame is horizontally detached, starting from the inside, with the aid of a rotating cutting blade that performs eccentric circumferential runs along the inside of the manhole frame. 
     As a result of the horizontal cut made to the manhole frame from the inside, which is realized with a rotating cutting blade that performs circumferential runs around the circumference at increasing depth up to the manhole frame cone wall on the outside, the manhole frame section can be cut off quickly without having to free it on the outside. There is no danger of damage to the remaining manhole cone due to the smooth cutting, so that the reconstruction is made easier. Since the manhole frame is not cut into smaller pieces, it can then be lifted out in one piece with the aid of a machine once it has been separated on the outside from the connection to the asphalt/concrete road surface. It is particularly advantageous if the manhole frame is separated from the asphalt/concrete road surface and the deeper layers by drilling concentrically around the outside of the manhole frame, up to the depth of the horizontal cut and, if necessary, slightly past it. As a result, uncontrolled retractions and expansions in the asphalt road surface are avoided during this operation. The manhole frame can be replaced without considerable preliminary work or a subsequent reworking of a construction site surrounding the manhole frame and a repaired frame can be released immediately for road traffic. 
     Preferably, the horizontal cut into the manhole frame is made during several successive circumferential runs of the cutting blade, meaning partial cuts with increasing depth toward the outside of the manhole frame. The cutting depth of each partial run can be adjusted for the essentially circumferential run along the cylindrical inside space of the manhole frame. 
     The above object generally is achieved according to a second aspect of the invention by a device for detaching an embedded manhole frame, according to the above-mentioned method, with the device generally comprising a rotating cutting blade that is mounted on a turntable such that it can be adjusted horizontally eccentric to the axis of the turntable and that also can be adjusted vertically adjustable. The turntable mounted for rotation on a mounting support with fastening elements that are suitable for locking in place the mounting support inside the manhole frame. 
     The device can have a compact enough design to be deposited easily with a truck-mounted loading crane at the place of use, above a manhole frame. The detaching device thus requires little road space. If the cutting blade is operated, e.g., made to rotate, preferably with a hydraulic drive motor, the hydraulic system of the truck, which otherwise functions to activate the loading crane, can be used for driving the cutting blade. In further detail, the detaching device with its mounting support is placed over the manhole frame onto the asphalt/concrete road surface, such that the manhole frame is positioned concentrically within the preferably round mounting support. The mounting support is then attached with its fixation or fastening elements to the manhole frame, wherein an additional centering can occur. The cutting blade is subsequently lowered into the manhole frame up to the intended location of detachment from the manhole cone or brickwork. The cutting blade is adjusted eccentrically with respect to the turntable that is mounted for rotation on the mounting support, wherein the cutting blade pushes from the inside against the manhole cone or the brickwork. Flushing water is preferably fed into the rotating cutting blade, and the rotating cutting blade performs a circumferential run along the cylindrical inside wall of the manhole cone or brickwork via the turntable, in particular via a simple manual guide rod assembly. In the process, the cutting blade cuts into the manhole cone or the brickwork. The circumferential runs of the cutting blade along the inside wall are repeated with constant readjusting of the cutting blade until the manhole frame/cone wall is cut through completely up to the outside edge. Several circumferential runs of the cutting blade are thus made with increasing cutting depth toward the outside. With this device for detaching the manhole frame, the above-described functions can be realized reliably. The device is distinguished by its simplicity and robustness and can be automated, in particular for adjusting the cutting blade. 
     Since the detaching device with the cutting blade is placed against the inside wall of the manhole cone or brickwork, it is not necessary to expose the manhole frame, the manhole cone or the brickwork on the outside. 
     The subsequent exposure of the manhole frame outside can be reduced to a minimum, so that the manhole frame that is horizontally detached in one piece, or the drill chips, can be lifted out of the pit with the aid of a hoisting device. Thus, the exposure is required only up to the depth of the horizontal cutting location. A hydraulic drill can be used for this reduced exposure, which is suitable for drilling a clearance space around the outside circumference of and concentric to the manhole frame. 
     It must further be emphasized here that the detaching device does not damage the regions of the manhole cone or brickwork below the cutting location because of the horizontal cutting or detaching method. No repair or reconstruction work on the upper cone edge is therefore necessary. 
     Details of the features of the detaching device, with its uncomplicated design, generally include a rotating positioning of the cutting blade mounted in a vertically oriented spacer tube, a pivoting arm provided with a first section and, at a distance thereto, a second section, a vertical adjustment of the spacer tube on a first section of the pivoting arm and the positioning of the second section of the pivoting arm such that it can pivot on the turntable for adjusting the eccentricity at the cutting location. The spacer tube in this case is advantageously provided with a device for locking in place the height or depth adjustment of the cutting blade. By pivoting the pivoting arm around its bearing location on the turntable, the eccentricity of the spacer tube and thus the cutting blade is adjusted, so that the cutting blade fits under pressure against the inside or brickwork of the manhole cone. 
     According to a further feature of the invention, a simple and robust threaded rod is provided for adjusting the eccentricity. This rod, on the one hand, is engaged in a member on the second section of the pivoting arm and, on the other hand, has one end pivotally mounted on the turntable. The threaded rod can be adjusted simply by turning it, thus eccentrically adjusting the pivoting arm as well as the spacer tube and the cutting blade. While lowering the cutting blade, meaning during the height adjustment, this blade is oriented nearly concentric inside the manhole frame. At the operating depth, the cutting blade is then moved eccentrically against the inside wall of the manhole cone or the brickwork. 
     A hydraulic adjustment of the pivoting arm is also possible, which can furthermore occur automatically. 
     For a sensitive, but also strong guidance during the circumferential run of the cutting blade for the horizontal cutting operation, a manual guide rod assembly is attached in an uncomplicated manner to the turntable. The guide rod assembly can be designed, for example, to resemble a nearly reversed U-shape, which is bent at an angle to form a lever arm that can be used to manually exert a torque onto the turntable. 
     According to a further feature of the invention, the turntable can be prevented from turning in one rotational or circumferential run direction by using at least one detent pawl that is positioned on the mounting support for the turntable and engages a toothed edge of the turntable. Even a high torque exerted by the cutting blade during the cutting operation onto the turntable can be absorbed safely in this manner. 
     The rotational direction of the cutting blade can be reversed, for example, with a hydraulic control unit for a quick realization of the horizontal cut with increasing cutting depth. 
     According to a still further feature, the mounting support that carries the turntable comprises, in an uncomplicated manner, a ring that can be secured with screws inside the manhole frame and on which the turntable is positioned for concentric rotation. 
     The invention is explained in the following with the aid of an exemplary embodiment of the detaching device and with the aid of seven Figures. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic illustration of a first cutting position of the detaching device, according to the invention, seen in a sectional view of the side of the manhole frame. 
     FIG. 2 is a sectional view through the detaching device in the cutting plane II—II shown in FIG.  1 . 
     FIG. 3 is a view from the side of the detaching device in a second position. 
     FIG. 4 is a view from the side of a detail of the detaching device, namely the cutting blade connected to a hydraulic drive motor and positioned inside a spacer tube. 
     FIG. 5 is a view from above of the detail according to FIG.  4 . 
     FIG. 6 is a cutout view from the side of another detail of the detaching device, namely the pivoting arm and the elements connected thereto. 
     FIG. 7 is a cutout view from above of the additional detail according to FIG.  6 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In FIGS. 1 to  3 , the number  1  refers to a ring for a mounting support on which a generally annular turntable  2  is positioned so as to rotate concentrically with the ring. Four fixing or fastening elements in the form of fixing screws  3  to  6  are located evenly spaced in circumferential direction on the ring  1 . These screws are used to secure the ring  1  inside a manhole frame  7 . For a better view, the fixing elements  4  and  5  are shown somewhat offset in FIGS. 1 and 3. A detent pawl  8  that engages ratchet teeth  25  on the turntable, preferably on the circumferential surface, is furthermore pivotally positioned on the ring  1 , which permits the turntable to turn only in the direction of arrow  9 . 
     Attached to the turntable  2  for turning it is an essentially inverted U-shaped manual guide rod assembly  10 . This guide rod assembly  10  is bent toward the side on the top and out of the drawing plane at bending locations B, B to generally form a handle for manually turning the turntable  2 . 
     A pivoting arm  11  has a first end or section  27  mounted on the turntable  2  for pivotal movement about a vertical axis  19 . The other end, or section  12 , of the arm is disposed at a distance from the turntable, and is provided with a collar  26  in which a spacer tube  13  is disposed for axial displacement. The spacer tube  13  can be moved vertically inside the collar  26  of section  12  of pivoting arm  11 , and can be locked in place at the specified height with a locking screw  14  disposed in the collar  26 . Preferably, the spacer tube  13  is provided with a non-circular shape, e.g., hexagonal, as shown, and the interior of the collar  26  is provided with a mating shape to prevent rotation of the spacer tube  13  relative to the collar  26 . 
     A horizontally oriented cutting blade  15  is positioned at the lower end of the spacer tube  13 , and is mounted for rotation about the spacer tube  13 . The cutting blade is made to rotate with the aid of a drive motor  16 , preferably a hydraulic drive motor, as shown, mounted at the upper end of spacer tube  13 . The motor  16 , and consequently the cutting blade  15 , can rotate in one of two possible rotational directions, shown with double arrow  18 , depending on the adjustment of a control unit  17 , e.g., a hydraulic control unit, as shown. The cutting blade  15 , the hydraulic drive motor  16 , and the spacer tube  13  are shown separately in FIGS. 4 and 5 for a better illustration. Via a threaded rod  28 , the pivoting position of pivoting arm  11 , and thus the eccentricity of spacer tube  13  and cutting blade  15  mounted thereon, relative to the turntable  2  and thus the manhole frame  7 , can be adjusted within broad limits when the turntable  2 , via ring  1  of the mounting support, is placed onto the manhole frame  7 . 
     FIGS. 6 and 7 show the position in which pivoting arm  11  can pivot around the pivoting axis  19  that is arranged on the turntable  2 . The pivoting is adjusted with a threaded rod  28 . One end  20  of this rod  27  is also mounted on the turntable  2  for pivotal as well as rotational movement, while a section  21 , at a distance from the end  20 , engages in a threaded member  22  that is pivotally located on the section  12  of the pivoting arm  11 . FIGS. 6 and 7 furthermore clearly show the locking screw  14  located in the collar  26  for locking in place the vertical height and depth adjustment of the spacer tube  13 . 
     When fitting the detaching device onto the manhole frame  7 , meaning its ring  1  of the mounting support, the spacer tube  13  and thus the cutting blade  15  are initially centered in the ring  1  and turntable  2 , as shown in FIG.  1 . The placed-on ring  1  is then secured to the frame  7  in a centered orientation with the fastening elements  3  to  6 . 
     Following this, the structural component comprising the spacer tube  13 , the cutting blade  15  and the hydraulic drive motor  16  is lowered, as indicated with double arrow  23 , with the locking screw  14  loosened, as indicated with double arrow  23 . The component is lowered until the cutting blade  15  is at the desired cutting height, as shown in FIG. 3, and then the screw  14  is tightened to secure the cutting blade  15  in the desired position. 
     Subsequently, the pivoting arm  11  is pivoted by activating the threaded rod  28 —see double arrow  24 —until the cutting blade  15  is pushed at the desired cutting height against the inside wall of frame  7 . At the same time or following this, the drive motor  16  starts the rotation of cutting blade  15  in one of two rotational directions of double arrow  18 , depending on the position of the hydraulic control unit  17 . The cutting blade  15  cuts into the manhole cone or the brickwork, and the complete horizontal cut is realized by rotating the turntable  2  with guide rod assembly  10  across the entire circumference of the inside wall. The circumferential runs are repeated with increasing cutting depth until the horizontal cutting operation reaches at least the non-designated outside edge of the manhole frame  7 , or the manhole cone, or the brickwork. The direction for the circumferential run can be alternately changed as a result of the use of the non-designated hydraulic feed lines. The detent pawl  8  is inactivated for one of the two circumferential directions. Depending on the direction of the turntable  2 , the rotational direction for cutting blade  15  can also be reversed with the hydraulic control unit  17 , as shown with double arrow  18 , to obtain an optimum cutting operation. 
     The drive motor  16  is subsequently turned off and the cutting blade is reset to the center of the manhole by turning the threaded rod  28 . After loosening the fastening elements  3  to  6 , the detaching device can subsequently be lifted off the manhole frame  7  and removed with a loading crane. 
     To remove the detached manhole frame  7 , an area must then be drilled concentrically from above around the outside of this frame  7 , concentric down to the height of the horizontal cut. The exposed manhole frame  7  can then be removed by lifting it as a whole from the manhole with a hoisting device. 
     While this invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.