Abstract:
A locking manhole insert to be placed under a conventional manhole cover to prevent unauthorized access to the manhole. The insert includes a plate-shaped disc with a plurality of locking radial arms mounted to its undersurface. The locking radial arms are securable in the extended position using a conventional padlock. The insert further includes apparatus for suspending equipment, such as pollution monitoring units, within the manhole opening.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a locking manhole insert and more specifically to a locking manhole insert designed to be placed under an existing manhole cover for the security of any equipment which might be placed thereunder. 
     To monitor for unauthorized effluent pollutants, environmental monitoring equipment often is installed through manholes into sanitary sewer and stormsewer pipes. The monitoring equipment is typically left in a single location for an extended period of time (e.g. one week) and then removed for data extraction. Such equipment is generally well known in the environmental testing art. 
     Unfortunately such equipment sometimes is tampered with since it is left unattended by authorized personnel for many days. Tampering may be for the purpose of intentionally affecting (e.g. improving) the acquired data. Tampering may also occur by curious people who want to see what was placed in the hole. Obviously, any tampering is undesirable. 
     Applicant is not aware of any commercially available device for securing the testing equipment within the manhole. However, Applicant is aware that locking manhole covers are shown in the patent literature. 
     One such locking manhole cover is disclosed in U.S. Pat. No. 5,082,392, issued Jan. 21, 1992, to Marchese. The Marchese cover has radial locking arms mounted on the underside of an otherwise generally conventional manhole cover. These radial arms are retracted and extended by rotating an actuating disc that is accessible through a vent hole in the cover. A key is provided that extends through the vent hole and is used to rotate the disc. 
     A second locking manhole cover is disclosed in U.S. Pat. No. 4,964,755, issued on Oct. 23, 1990, to Lewis et al. The Lewis cover also has radial locking arms attached to an actuating disc that is mounted on the underside of an otherwise generally conventional manhole cover. The actuating disc is spring-biased upwardly toward the cover and has a series of locking pins that engage holes in the cover. The actuating disc is accessed through a vent in the cover using a special key. To turn the actuating disc, one must use the special key to force the plate downward, so as to disengage the locking pins from the cover, and rotate the disc. 
     Marchese and Lewis suffer from a series of shortcomings. First, both inventions are designed to be used in place of an existing manhole cover. Therefore, they must meet the structural requirements of a conventional manhole cover. This makes them expensive to fabricate and, as a result of their weight, burdensome to use. Second, both locking manhole covers require a special key to actuate the locking mechanism. This means that an individual who gains access to a single key can unlock and remove all covers. In this sense, the covers are not truly secure. Third, if the locking mechanism malfunctions, or the key is misplaced, it may be necessary to damage or destroy the locking cover in order to remove it from the manhole frame. 
     SUMMARY OF THE INVENTION 
     The aforementioned problems of manhole security are overcome by the present invention wherein a locking manhole insert is provided which may be installed underneath a conventional manhole cover to restrict access to any equipment which might be temporarily located within the manhole. 
     The manhole insert includes a plate-shaped body that fits within a conventional manhole frame. A series of locking radial arms are attached to an actuating disc mounted on the underside of the insert body. The body includes a peripheral lip and a floor that supports the insert within the manhole frame opening by resting upon the manhole frame support flange. The floor of the plate-shaped disc is recessed below the lip, defining a void. Portions of the locking and/or actuating mechanism are located within the void on the floor of the insert body and under the conventional manhole cover. 
     The rotating disc includes an actuating handle extending through the insert and accessible from the top of the manhole insert. The radial arms are retracted and extended by operating the handle. A fixed ear is secured to the insert floor. The handle is aligned with the fixed ear when the radial arms are in the extended position, enabling the handle to be padlocked to the fixed ear and prevent the radial arms from being retracted. 
     In a preferred embodiment, chains are mounted to the undersurface of the manhole insert. These chains can be used to suspend equipment, such as a pollution monitoring sampling unit, within the manhole opening. Once installed and locked, the manhole insert prevents access to the manhole opening and any equipment suspended therein. 
     The present insert is relatively simple and inexpensive to fabricate. The insert need not meet all the structural requirements of a conventional manhole cover, which is reinstalled over the insert. 
     A structure that permits the use of conventional padlocks enables a different lock for each manhole insert. Use of a conventional padlock is also less expensive than incorporating a key-lock mechanism into each manhole insert. Further, if the padlock key is lost or misplaced, the padlock can be cut rather than damaging or destroying the manhole insert. 
     These and other objects, advantages, and features of the present invention will be more fully understood and appreciated by reference to the detailed description of the preferred embodiment and the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a preferred embodiment of the present invention suspending a pollution monitoring unit; 
     FIG. 2 is a top view of a preferred embodiment of the present invention; 
     FIG. 3 is a bottom view of a preferred embodiment of the present invention; and 
     FIG. 4 is a sectional view of the present invention installed in a conventional manhole frame and suspending a pollution monitoring unit. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A locking manhole insert 1 constructed in accordance with the preferred embodiment of the present invention is generally illustrated in FIGS. 1 and 2, and includes a plate-shaped body 10 having a plurality of radial locking arms 18 attached to a rotating disc 20 concentrically mounted on the undersurface of the insert. When installed, the body fits underneath a conventional manhole cover to prevent unauthorized access. The body is easily installed and locked, and also unlocked and removed. 
     The plate-shaped body 10 includes a circular, planar floor 14, a circumferential wall 16, and a peripheral lip 12. The floor 14 is disc-shaped and has a diameter slightly smaller than the internal diameter of the support flange 62 in the manhole frame 60. The circumferential wall 16 extends axially upward from the outer edge of the floor 14. The lip 12 extends radially outward from the top of the circumferential wall 16 and has an external diameter substantially identical to the diameter of a conventional manhole cover 64. The floor defines an arcuate slot to receive the actuating handle as will be described. A fixed ear or lug 28 is secured, for example, by welding to the floor 14 adjacent one end of the slot 26. The ear defines a hole 34 for receiving a padlock 36. A fixed ring or eye 32 is fixedly secured to the top surface of the floor 14, for example, by welding (see FIG. 2). This ring 32 is used in installing and removing the plate-shaped insert 10. The circumferential wall 16 creates a space between the lip 12 and floor 14, so that the manhole cover 64 may be seated upon the lip 12 without interference from any elements that may extend above or lie upon the floor 14. 
     A pivoting actuating disc 20 with a diameter substantially smaller than the floor 14 is concentrically mounted to the underside of the plate-shaped body 10. One end of each of the locking radial arms 18 is pivotally attached to the rotating disc 20 in a radially symmetric manner. A fixed guide 22 is radially aligned with each locking radial arm 18 and is attached to the underside of the plate-shaped body 10. Each locking radial arm 18 slidably passes through its corresponding fixed guide 22. The fixed guide 22 provides a fixed point through which each locking radial arm 18 must pass when being retracted or extended. 
     An L-shaped actuating handle 24 is fixedly attached, for example, by welding to the rotating disc 20 (see FIG. 1). The long leg 38 of the handle 24 extends radially from the rotating disc 20. The short leg 40 of the handle 24 extends upward through the arc-shaped slot 26 in the floor 14 of the plate-shaped body 10 (see FIG. 3). The short leg 40 defines a hole 42 for receiving a padlock 36. The holes 34 and 42 are aligned to receive the padlock when the insert 1 is locked in position. The slot 26 defines the range of motion for the handle 24. The rotating disc 20 is rotated by moving the handle 24 back and forth along the arc-shaped slot 26. Rotating this disc 20 in turn retracts or extends the radial locking arms 18. The handle 24 abuts the fixed ear 28 when the radial arms 18 are in the extended position. When the handle 24 is secured to the fixed ear 28 the locking radial arms 18 can not be retracted. 
     As shown in FIG. 1, a plurality of fixed rings 44 are attached to the undersurface of the plate-shaped body 10 in a radially symmetric manner. A chain 30 is attached to each of these fixed rings 44 for use in suspending equipment, such as environmental monitors, below the plate-shaped body 10 (see FIGS. 3 and 4). 
     When a sampling device is to be placed in a manhole, the conventional manhole cover is removed, and the sampling unit 70 is suspended from the insert 1 on the chains 30. The unit 70 and insert with the locking arms 18 retracted are then lowered into the manhole 60, optionally using the suspension ring 32. Upon complete installation, the peripheral lip 12 sits upon the support flange 62 of the manhole frame 60. The floor 14 and circumferential wall 16 extend below the plane of the lip, and the sampling unit 70 is suspended below. To secure the plate-shaped body 10, the actuating handle is moved to the end of slot 26 adjacent the locking ear 28 to extend the locking radial arms 18. A padlock 36 is installed through the lug 28 and handle 24 to lock the arms in the extended position. Finally, the conventional manhole cover 64 is reinstalled on top of the plate-shaped body 10. As discussed above, the floor 14 is sufficiently recessed below the lip 12 to allow a manhole cover 64 to be seated upon the lip 12 above the padlock, actuating handle 24, and fixed ring 32. The process is reversed to remove the insert and sampling unit from the manhole. 
     The above description is that of a preferred embodiment of the invention. Various changes and alterations can be made without departing from the spirit and broader aspects of the invention as set forth in the appended claims, which are to be interpreted in accordance with the principles of patent law, including the doctrine of equivalents.