WO1994012321A1

WO1994012321A1 - Method and means for lifting a ground hole coverplate

Info

Publication number: WO1994012321A1
Application number: PCT/AU1992/000632
Authority: WO
Inventors: Thomas Armore Schwerdt
Original assignee: Thomas Armore Schwerdt
Priority date: 1992-11-26
Filing date: 1992-11-26
Publication date: 1994-06-09
Also published as: AU2936892A

Abstract

An apparatus for lifting a ground hole coverplate including means to impart an upwardly directed shock loading on the ground hole coverplate. Such means can take the form of a slide hammer or a pneumatic hammer. Either of these is coupled to a coverplate engaging tip having engagement surfaces for engagement with the coverplate keyhole, so that said tip can transmit an upward force to the coverplate. The apparatus preferably includes a spring to hold the engagement surfaces against the coverplate keyhole when in use.

Description

METHOD AND MEANS FOR LIFTING A GROUND HOLE COVERPLATE

BACKGROUND OF THE INVENTION

This invention relates to an apparatus and a method for lifting a ground hole coverplate and in particular to the lifting of such plates that have become jammed in position.

In order to provide access to an underground facility which is beneath a road surface or pathway, it is common to provide an assembly comprising an access hatch having a metal cover and a frame into which the cover fits, that is located in the road or pathway surface. A typical example is the use of disc shaped covers for fire hydrants in roadway surfaces. The edge portion of such disc shaped covers is chamfered or tapered so as to provide a locking fit into the correspondingly tapered roadway frame. Such coverplates are provided with a central key-hole for the engagement of a tool to aid in the removal of the coverplate. Such keyholes normally comprise a disc shaped cavity having a slot shaped access hole into which a T-shaped tip can be inserted. Upon inserting the T-shaped tip, it is rotated through 90° thereby allowing the transmission of an uplifting force to the coverplate.

Due to the use of a tapered edge portion, and also because of the ingress of dirt and moisture around the edge portion, the coverplates readily become jammed in position. Obviously, in the case of a fire hydrant cover it is essential that the cover can readily be removed, and without any delay. However, in the past, it has been found that great force is required to remove coverplates which have become jammed, and that delays result. Furthermore, where direct effort by a person is required, injury to the back of the person may result.

In the past, various mechanisms have been devised to extract jammed coverplates. One such device has made use of a lever arm with a coverplate engagement tip pivotally connected to it. Even given the significant mechanical advantage the lever provides, it has been found insufficient in some cases to dislodge a jammed coverplate. A further device has been a coverplate engagement tip attached to a threaded portion, which is engaged within a frame that is supported by the road surface around the coverplate. A threaded nut is engaged on the threaded section above the tip, and bears against the frame, whereby rotation of the nut places an uplifting force upon the coverplate. Although such an arrangement, if properly set up and positioned, will provide the necessary force to extract the jammed coverplate, such an arrangement is not able to be quickly set up, and results in a significant delay in removing the coveφlate. Such apparatuses are also large, cumbersome and somewhat difficult to manoeuvre.

The jamming of such coverplates not only results in frustration and delays, but may also endanger human life when the cover to a fire hydrant cannot be quickly removed.

It is an object of this invention to provide a lifting means and method for removin jammed coveφlates which will obviate or minimise any one of the foregoing disadvantages in a simple yet effective manner or at least provide the public wit a useful choice.

SUMMARY OF THE INVENTION

In a broad form the invention could be said to reside in an apparatus for lifting a ground hole coverplate including means to impart an upwardly directed shock loading on the ground hole coveφlate coupled by a shaft to a covβφlate engag tip having engagement surfaces for engagement with the covβφlate keyhole, s that said tip can transmit an upward force to the coveφlate and the apparatus including means to hold the engagement surfaces against the coveφlate keyho when in place.

In one form the means to impart an upwardly directed shock loading force is pneumatically driven.

In another form the invention could be said to reside in an apparatus including a slide hammer, said slide hammer including a weight slidable along a vertical shaft, and having a stop means for stopping the vertical movement of the weight, and the coveφlate engaging tip is coupled to the lower end of the vertical shaft said coverplate engaging tip having engagement surfaces for engagement with the coveφlate keyhole, such that the said tip can transmit an upward force to the coverplate, on the slide hammer making contact with the stop, and the apparatus including means to hold the engagement surfaces against the coverplate keyhole when in use.

In the above form the slide hammer may be hand driven.

In a further form the invention could be said to reside in a ground hole coverplate removing apparatus comprising a slide hammer, and a coverplate engaging tip coupled to the lower end of the slide hammer having engagement surfaces for engagement with the coverplate keyhole, such that the said tip can transmit an upward force to the coveφlate and the apparatus including means to hold the engagement surfaces against the coverplate keyhole when in use.

Preferably, the means to hold the engagement surfaces against the coverplate keyhole, comprises a spring means located between the coveφlate engagement tip and the slide hammer, which is compressed as the said tip is engaged with the coverplate keyhole, thereby forcing the tip upwardly, and holding it against the upper surface of the keyhole when the tip is engaged such that there is no relative movement between the tip and the keyhole upon operation of the slide hammer.

The use of a slide hammer results in a shock loading which is sufficient to dislodge most jammed coverplates. In the past, attempts at striking the coveφlates by swinging a hammer onto the surface, have only resulted in further jamming of the covβφlate, and it is therefore necessary that any shock loading be provided in an upward direction, normal to the surface of the coverplate.

The use of a spring as described above results in the coveφlate engagement tip being forced upwardly such that the upper engagement surfaces of the tip are held against the keyhole so that there will be no relative movement between the tip and the keyhole upon operation of the slide hammer. This maximises the impact force transmitted to the coverplate, and also prevents damage that might be caused with the tip striking against the keyhole surfaces.

In an alternative form the invention could be said to reside in a method of removing a ground hole coverplate using any embodiment apparatus as in any one of the preceding claims comprising the step of inserting the tip into a slot of a keyhole, and rotating the tip for engagement of the engagement surfaces with the keyhole coveφlate, transmitting an upward force onto the coveφlate to loosen the coveφlate from a support of the coveφlate, and lifting the coverplate from said support of the coverplate.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be clearly understood and readily carried into effect, a embodiments will now be described, by way of example and with reference to the accompanying illustrations wherein:

FIG. 1 is a perspective view of a first embodiment of the invention,

FIG. 2 is a part cross sectional view of the first embodiment in position within a key hole of a covβφlate with the weight of the slide hammer in a lower position, and

FIG. 3 is a part cross sectional view similar to the one shown in FIG. 2 except that the weight is shown in the raised position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Similar reference characters indicate corresponding parts throughout the several views of the drawings.

Dimensions of certain of the parts as shown in the drawings may have been modified and/or exaggerated for the puφoses of clarity of illustration.

The apparatus comprises generally a means to impart an upwardly directed shock loading 1 to a coverplate 2 through a coveφlate engaging tip 3. The means to impart the shock loading in the illustrated embodiment takes the form of a slide hammer. The slide hammer comprises a cylindrical weight 4 the central hollow 5 of which encircles a vertical rod 6, an upper stop 7 takes the form of a collar welded to the rod. The tip 3 is welded to the lowermost end of the rod and is transversely of an elongate dimension so that it can fit through the generally rectangular keyhole 8 of the coverplate. The rod extends upwardly from the collar 7, and is connected at its uppermost portion to a handle 12. The uppermost surface 9 of the tip is flat so that it can effectively bear against an underneath surface of the keyhole 10 to thereby transfer a upwardly transmitted shock force. The lowermost surface of the tip is curved so as to be complementary to the shape of the keyhole, however it is not desired that there be a tight fit, by reason of the fact that debris tends to collect in such keyholes and too tight a fit would make insertion somewhat difficult.

A lower stop 13 is provided in the form of a collar, and the weight generally rests on the lower stop, unless it is supported otherwise. A spring 14 is positioned beneath the lower stop and around the rod and has beneath it an annular support ring 15, which support ring can slide along the rod. When in place the support ring 15 is urged against an upper surface of the coverplate, and thereby braces the uppermost surface of the tip against the underneath surface 10 of the keyhole. This allows for the apparatus to be self supporting on the coverplate, and more importantly has the advantage of preventing the tip from being sheared off on the impact of the hammer.

In use then the tip is inserted into the keyhole, and turned half a circle to engage the body of the coverplate. The apparatus is steadied, and the weight of the slide hammer brought rapidly upwards to strike against the undersurface of the collar. The force of the weight upon the collar is transmitted to the tip, the uppermost surfaces of which bear against the undersurface of the keyhole, whereby to loosen the fit of the coveφlate from the keyhole. The coveφlate can thereafter simply be lifted up.

In an alternative embodiment of the apparatus having a sliding hammer, the lifting means comprises a slide hammer having a rod including a pair of stopper plates secured at each end of the rod, and a sliding weight slidably mounted to the rod and positioned between the two stopper plates. The coveφlate engagement tip comprises an elongate shaft member with a tip portion for engagement within a coverplate keyhole. In this embodiment, the tip comprises a "spear" shaped head, with the surfaces extending perpendicularly from the shaft of the elongate member forming the surfaces which engage the coverplate keyhole upon an uplifting force being applied. The elongate shaft portion of the coverplate engagement tip is secured to the lower end of the slide hammer either by welding or by a threaded coupling. In this embodiment, a threaded coupling is used such that replacement of the tip or the use of various shaped tips is facilitated. The spring member comprises a helical spring attached to the lower stopper plate and extending along the elongate shaft to a position at least adjacent the tip member. The upper end of the slide hammer is provided with a transverse handle member which allows for convenient handling of the lifting means and allows for easy handling of the coverplate when the lifting means is engaged. The handle comprises an elongate bar member which is positioned transverse to the longitudinal axis of the slide hammer.

In operation of the lifting means the tip is inserted within the coverplate keyhole, and by rotating the lifting means through 90°, the tip is engaged with the coverplate keyhole. In inserting the tip into the keyhole, the helical spring is compressed, and the tension of the spring is such that it lifts the lifting means vertically and holds the tip against the keyhole. The sliding weight is then grasped and from the lower position moved rapidly to the upper position whereupon it will strike the upper stopper plate. This will provide the necessary shock loading which will remove a jammed coveφlate.

In a further embodiment the apparatus includes a tip to engage the coverplate keyhole and may take any of the forms discussed above. The rod to which the tip is connected however could be coupled to a pneumatically driven hammer, so that the tip creates a upwardly lifting shock force, by reason of the hammer.

As can be seen from the above description, the invention readily provides a quick and convenient means for removing jammed coveφlates, and in the case of fire hydrant covers avoids the frustration and danger to human life that may result from delays in removing such a coveφlate.

Claims

CLAIMS:

1. An apparatus for lifting a ground hole coverplate including means to impart an upwardly directed shock loading on the ground hole coverplate coupled to a coverplate engaging tip having an engagement surface for engagement with the coveφlate keyhole, such that said tip can transmit an upward force to the coveφlate and the apparatus including means to hold the engagement surfaces against the coveφlate keyhole.

2. An apparatus as in claim 2 wherein the means to impart an upwardly directed shock loading is coupled by a shaft to the coverplate engaging surface against the coveφlate is supported on said shaft.

3. The apparatus as in claim 2 wherein a compression spring constrained is positioned on said shaft between the means to impart the upwardly directed shock loading and the tip so as to bear down on an uppermost surface of the coverplate when in use, so as to hold the engagement surfaces against the coverplate keyhole.

4. The apparatus as in claim 3 wherein the apparatus includes a slide hammer, said slide hammer including a weight slidable along said shaft, and having a stop means for stopping the vertical movement of the weight , and the coveφlatθ engaging tip is coupled to the lower end of the shaft, said coveφlate engaging tip having engagement surfaces for engagement with the coveφlate keyhole, such that the said tip can transmit an upward force to the coveφlate, on the slide hammer making contact with the stop.

5. The apparatus as in claim 4 wherein means a lowermost collar is fixed to the shaft to limit the extent to which the compression spring can slide on the shaft and the stop means for the weight comprises a second collar fixed onto the vertical rod and spaced apart from the lowermost collar.

6. The apparatus as in either claim 2 or 3 wherein the means to impart the upwardly directed shock loading includes a pneumatic vibratory motor, positioned for vibrating the tip upwards.

7. The apparatus as in any one of the preceding claims wherein the tip is removable from the apparatus.

8. A ground hole coverplate removing apparatus comprising a slide hammer, and a coverplate engaging tip coupled to the lower end of the slide hammer having engagement surfaces for engagement with the coverplate keyhole, such that the said tip can transmit an upward force to the coverplate, and including a biasing means positioned to hold the engagement surfaces against the coverplate keyhole.

9. Method of removing a coverplate using an apparatus as in any one of the preceding claims comprising the step of inserting the tip into a slot of a keyhole, and rotating the tip for engagement of the engagement surfaces with the keyhole coverplate, transmitting an upward force onto the coverplate to loosen the coverplate from a support of the coverplate, and lifting the coverplate from said support of the coverplate.