GB2342555A

GB2342555A - Ground penetrating implements

Info

Publication number: GB2342555A
Application number: GB9820241A
Authority: GB
Inventors: John Michael Claxton
Original assignee: Digby UK Ltd
Current assignee: Digby UK Ltd
Priority date: 1998-09-18
Filing date: 1998-09-18
Publication date: 2000-04-19
Also published as: AU5871699A; GB9820241D0; WO2000016604A1

Abstract

The digging implement is formed at least in part from a material which is electrically non-conductive. The electrically non-conductive material may be in the form of a heat shrinkable sleeve 21 around the neck of the shaft of the digging implement or in the form of a foot pad (figs 2-8) attachable to the blade of the implement.

Description

2342555 IMPROVEMENTS IN AND RELATING TO GROUND PENETRATING IMPLEMENTS

Field of the Invention

This invention relates to improvements in and relating to ground penetrating 1 implements, in particular, but not exclusively to ground penetrating implements used professionally by those employed by the electricity industries.

Background Art Known to the Applicant

Conventional ground penetrating implements, for example, spades, forks, lawn edgers etc are well known. Figure I illustrates one such ground penetrating implement known as a spade. It is generally referenced 10 and comprises a blade 1, with an upper edge herein termed the top bar 2, a ground penetrating edge 37, a neck 3, a shaft 4 and a handle 5. The term blade I is used herein to desianate the ground penetrating portion of the implement 10 in its normal use and is not intended to refer solely, to the blade I of a spade. Similarly, the reference numeral 10 is intended to be generic and refer to all types of hand-held ground penetrating implements, notjust a spade.

As the ground may be compact, dry and/or house obstacles, such as high voltage cables (buried underground for safety purposes), or stones, the ground engaging edge 37 of the implement 10 needs to be thin enough to be able to cut into the ground and yet thick enough to withstan ' d damage from ground impact. It also has to be robust enough to withstand the torque forces experienced when the implement 10 is in use.

The advent of modern materials, be they for example, laminates, metals, alloys, plastics etc or any appropriate selection or combination thereof, have meant that the blade I of ground penetrating implements 10 can be relatively thin.

0 It is not therefore unusual for the cross-sectional area of the top bar 2, blade I and the ground penetrating edge 37, in practical terms to be substantially the same.

The thin nature of the ground perietrating edge 37, has positive advantages for anyone using the implement 10, as the force per unit area exerted on the ground during the implement 10's normal use, is maximised if the ground penetrating edge 37 is as thin as is practically possible, This could present a problem as the ground penetrating edge 37 can act as a "knife-edge" and could potentially cut its way into any underground high voltage cable.

In use, such implements 10 are held by the user by the handle 5 and the shaft 4, the arch of the user's foot being placed on to the top bar 2, where pressure is then applied, to aid the penetration of the ground penetratinc, edge 37 into the ground.

0 Slightly curving the blade I about its longitudinal axis such that the top bar 2 and the ground penetrating edge 37 are curved, also enhances the structural strength of the blade 1, thereby increasing the amount of torque that the blade I can cope with without damage. Such a strengthening would encourage a user to apply the maximum force possible to the top edge 2 of the blade I with their foot when attempting to penetrate the ground, increasing the "cutting effect" of the "knife Z edge".

During the professional use of such implements 10, purpose built footwear is usually provided which is thick-soled to protect the wearer's foot from damage caused by the repeated downward applied pressure of the foot on to the top bar 2.

Certain "bolt-on" demountable foot-pads are known to alleviate the effect of the top bar 2 cutting into the bottom surface of the footwear - a consequence of Newton's third law of motion - and the reader is referred to PCT patent application number PCT/GB97/02145which should be read in conjunction with this particular patent specification.

Such foot-pads or thick-soled footwear do not, however, protect the user from high voltage electricity when such digging implements 10 are used by for example professionals whose job it is to dig up, maintain and/or replace sections of these high voltage cables. Furthermore, there is always the possibility that the non professional, for example, the DlY garden enthusiast and home builder could, at best, uncover such cables, and at worst, experience severe injury or even death if the digging implements 10 that they were using were to cut into these high voltage cables. This problem becomes even more acute when one considers the fact that more often than not, the preferred footwear of choice used by such non professionals and some professionals is the widely available sports shoe or "trainer". Electrocution in these circumstances is extremely likely if the wearer does actually dig into and cut through the insulated rubber sleeve that surrounds the high volta(,e cable as the sole of this type of footwear is not robust enough to withstand mains voltage electricity.

Although many patents exist that attempt to alleviate the effect of Newton's third law of motion on the foot of the wearer when usina dicaing implements 10, e.g.

UK patent application number 89 23737.4, UK patent application number 83 12968 and US patent number 5,402,853, none of these patent specifications has recognised, let alone dealt with the problem of potential electrocution when using such digging implements 10 near to or when purposely looking for underground high voltage cables, It is an object of the present invention to attempt to alleviate these problems of potential electrocution by the professional and non-professional alike.

Summary of the Invention

According to the present invention in its broadest aspect, there is provided a digging implement for use by an individual formed from (either in part or in its entirety) or otherwise fitted with, in use, a material that is non- electrically conductive, such that, in use, an individual -using the digging implement will not experience an electric shock if the ground penetrating portion of the digging 1_ 1"D implement comes into contact with a source of high voltage electricity.

Preferably, the material is readily demountable, at least in part from the digor'ing implement.

Preferably, the neck and top bar of the digging implement are fitted with such a material in use.

The digging implement is fitted with a foot pad of the type generally described in PCT patent application number PCT/GB97/02145 and preferably, the foot pad is fully electrically insulated.

Preferably, the digging implement is fitted with a heat-shrinkable electrically insulating sleeve around the neck of the shaft of the digging implement.

The invention includes within its scope, a digging implement substantially as C herein described with reference to and as illustrated by any appropriate selection or combination of Figures 2 - 16 of the accompanying drawings.

Brief Description of the Drawing

Preferred embodiments of the invention will now be more particularly described, by way of example only, with reference to the accompanying sheets of drawings wherein:

Figure I illustrates one example of a conventional digging implement that outlines the general features associated with a digging implement.

Figure 2 illustrates a top view of one preferred embodiment of the present invention, that of an electrically insulated foot-pad that insulates both the top bar and neck of the digging implement.

Figure 3 illustrates the underside of Figure 2, T Figure 4 illustrates a side view of the embodiment illustrated in Figures 2 and 3 above.

Figure 5 illustrates a perspective view of the embodiment illustrated in Figures 2 4 above.

Figure 6 illustrates a side view of a second embodiment of the present invention.

Figure 7 illustrates the underside view of the embodiment illustrated in Figure 6.

Figure 8 illustrates a side view of yet a further alternative embodiment of the present invention.

Figure 9 illustrates a digging im plement incorporating an electrically insulated sleeve about the neck of the shaft of the digging implement.

I Figure 10 illustrates a digging implement formed from a completely plastics covered (i.e. an electrically insulating, or otherwise, non-electrically conductive material) conventional digging implement.

Figures I I and 12 show an all plastics digging, implement encasing metal blade Z_ I portions to provide the ground penetrating portion of the digging implement with the necessary structural strength it needs to function.

Figures 13 and 14 illustrate two other all-plastics digging implements, that form alternative embodiments of the present invention.

Figure 15 shows a side view of the embodiment shown in Figure 14.

C Figure 16 shows an alternative design of the digging implement shown in Figures 14 and 15.

Description of the Preferred Embodiments

Throughout this specification, the use of the word "integral" is intended to cover not only something, which is formed from the outset, as one single-entity component, but also, anything which, whilst being assembled from a plurality of

0 initially disparately-produced integers, ends up as one overall and normally non dismantleable structure.

Figure 2 illustrates a top view of a foot-pad generally referenced 6 that comprises a pair of treaded portions 7 that are so sized and shaped as to act as a platform for the foot of a user of a dig ing implement 10. The treaded portion 7 is formed from relatively thick rubber, an electrically insulating (i.e. non- electrically conductive) material. From Figures 4 and 2 it can be seen that the tread 7 is in the form of a series of saw-tooth cut-outs that are substantially parallel to each other, one edce of each respective "repeat-unit - saw-tooth" being substantially vertical, with respect to the platform whilst the remaining edge of each respective repeat unit saw tooth slopes at substantially 45 with respect to the vertical edge. In use, the faces of the vertical edges of the tread 7 face away from the recoanised front face of the digging implement 10.

The foot-pad 6 further comprises a collar 8 that stands vertically proud of the treaded platform 7 in its normal attitude of operation, but is formed of similar material to and is intearal with, the tread 7. The collar 8 is slightly flexible, 0 allowing the collar to fit around a number of necks 3 of digging implements 10 in 17.,;.

such a manner that the inside edge of the majority of the collar 8 is in contiguous 0 contact with a major portion of the neck 3 of the shaft 4 of the digging implement 10, when the foot-pad 6 is fitted to the digging implement 10.

O'D Figure 3 illustrates the underside of the foot-pad 6 which is shown to comprise two pairs of parallel opposing arms 12, each respective pair 12 being, located on either side of the collar 8 in a side by side relationship. Each respective arm is apertured I I and each respective aperture I I is adapted to receive a screw 9. The arms 12 form a channel 13 that is adapted to fit over the top bar 2 of the digging implement 10, the screws 9 being tightened against the blade I in use, to demountably attach the foot-pad 6 to the digging implement 10.

The rear, in use portion, of each respective pair of arms 12 is provided with a reinforcing shoulder 14 to add structural strength to the foot-pad 6 when it is in use. The non-rubberised portion of the foot-pad 6 (i.e. portions 9, 11, 12 and 14) are formed from extruded aluminium as an integral unit. The aluminium underside 9, 11, 12 and 14 of the finished foot-pad 6 is integral with the rubberised portions (i.e. portions 7 and 8) of the foot-pad 6 as a result of the use of rubber-to-metal glue. The top surface of the tread 7 completely spans in a continuous fashion and subsequently overlaps the horizontal top edge 38 of the aluminium underside 9, 11, 12 and 14 of the foot-pad 6 and immediate surrounding edges of the non-rubberised portion of th(, foot-pad 6. The foot-pad 6, because it can be used by either a left-footed or right-footed individual without the need for its removal from the implement 10 possesses a distinct advantage over any other foot-pad that has been described in any of the prior art documents mentioned herein, As can be seen, the foot-pad 6 can be fitted to most forms of ground penetrating I., Z., implements 10 of the type generally referred to in this and the prior art specifications.

Figure 6 shows an alternative embodiment to the foot-pad 6 illustrated in Figures 2 - 5. In this particular embodiment, the foot-pad is generally referenced 17 and comprises a foot-pad 17 of the type generally described in PCT Patent Application Number PCT/GB97/02145, but in this particular embodiment, the treaded portion 7 is formed from extremely thick rubber (extremely thick, being a relative term and meaning sufficiently thick to enable someone to use the foot-pad 17 without the risk of electrocution). The integral underside 9, 12, 14 of the foot- pad 17 is made of steel and is recessed 15 on its top in use surface to receive a complementary rubberised tread 7 to provide a "lock and key" mechanism enabling the one to be integral with the other without the need for metal- to-rubber glue. The edges 16 of the tread 7 extend beyond and again overlap the top surface of the steel underside 11, 12 and 14 to ensure that the working top surface of the foot-pad 17 is always going to be an electrically insulated surface as far as the foot of the user is concerned. Figure 7 shows the underside of the foot- pad 17 shown in Figure 6.

Figure 8 shows yet a further alternative embodiment of the foot-pad which in this particular embodiment is generally referenced 18. In this embodiment, the rubber portion 19 completely surrounds the metal body of the underside of the foot-pad 18. The screws 9 used in this particular embodiment, are also formed from electrically insulating plastics material, in this particular instance, polyurethane.

In the embodiments thus far described, the non-rubberised portion of the foot-pad 6, 17 and 18 could be formed from metals other than steel or aluminium, for example, iron, copper or mild steel or alternatively, it could be formed from alloys such as brass or alternatively it could be formed from man-made polymers or composite materials such as appropriate types of polyurethanes, polyethylenes, polypropylenes and/or copolymers thereof, or it could be formed from a ceramic material. Instead of using rubber for the rubberised portions of the foot- pad 6, 17, 18, other man-made electrically insulating, materials could be used. These are immediately apparent to the person skilled in the art and need not be discussed any further within this specification. It need not be important however, to have a foot-pad 6, 17, 18 that comprises two materials, one adding strength to the other.

Furthermore, the glass-transition temperature of the digging, implement needs to be below minus 30'C as it is conceivable that digging implements 10 using such foot-pads 6, 17 and 18 could be used in countries like Canada where the temperature in the Winter time reaches well below O'C, but work still needs to be done. Therefore, it is extremely important to have an electrically insulating material with a glass transition temperature of such a value that ensures that in use, the rubber or otherwise electrically insulating portion of the foot- pad 6, 17 and 18 remains "rubber-like" and does not become "glass-like".

It is clear from the embodiments just described hereinabove, that individuals using such digging implements 10 whilst employing the foot-pads 6, 17, 18 hereiribefore described, will not suffer any form of electric shock if they were to cut into electricity cables, provided that the handle 5 and the hand gripped portion of the shaft 4 were made of non-electrically conductive material e-g. wood.

Nevertheless, there still exists a possibility of electrocution from other areas of the digging implement 10 that may be gripped or touched inadvertently by the user.

A way around this particular problem is to provide a fully electrically insulating layer to the top bar 2, at least the majority of the neck 3 and possibly the blade 1.

Turning now to Figure 10, the reader is directed to one such embodiment that incorporates such an electrically insulated digging implement that electrically C11) D insulates both the top bar 2 and majority of the neck 3 and it is generally referenced 20.

In this embodiment, the handle 5 and shaft 4 are made from wood that screws into a metal neck 3 of a conventional metal digging implement 20. Prior to screwing the shaft 4 to the neck 3, an insulated heat shrinkable tube 21 is rolled onto the neck 3 of the digging implement 20. The heat shrinkable tube 21 is made from electrically insulating material, and may in certain circumstances, constitute the same material that forms the electrically insulating material in the hereinbefore described foot-pads 6, 17, 18. The shaft 4 is then screwed on to the neck 3 and the heat shrinkable tube 21 is then fully unfurled to cover the neck 3 and a portion of the shaft 4 of the digging implement 20. Heat shrinking is then effected so that the tube 21 firmly bonds to the implement 20 to form an integral unit with the implement 20. Of course, the tube 21 does not need to cover any portion of the wooden shaft 4 and can simply cover all, or a majority of the neck 3 region of the digging implement 20. Furthermore, the tube 21 could in principle, be fitted to the shaft 4 initially, before the shaft 4 is fitted to the neck 3. In this situation, the tube 21 would then be "rolled" down the shaft 4 and on to the neck 3.

Alternatively, the tube 21 could be so sized and shaped as to cover the entire, or majority of the neck 3 and shaft 4 of the digging implement 20. Once heat shrinking has been effected, any one of the foot-pads 6, 17, 18 hereinbefore described could be fitted to the top bar 2 of the digging implement 20 to provide a 0C. I= further form of electrically insulated digaing implement.

Figure 10 shows a further modification to that which has just been described and illustrated in Figure 9. Figure 10 illustrates an "improved" Figure 9 that dispenses with the need for the foot-pads 6, 17, 18 herein described.

Figure 10 illustrates a digging implement generally referenced 22 that employs a heat shrunk tube 21 of the type hereiribefore described, however, in this particular embodiment, the blade I portion of the digging implement 22 has been modified.

The metal portion 24 of the blade I is covered in its entirety on both sides with a rigid electrically insulating plastics continuous sheet 25, 26. The metal portion 24 of the blade I serves the purpose of adding structural integrity to the plastics sheets 25, 26 enabling such plastics sheets 25, 26 to be used. Integral with the plastics sheets 25, 26 is a moulded plastics platform 23. The method by which the plastics sheets 25, 26 and moulded platform 23 are to be fitted to the blade I are known generally pe7' se and will not be discussed any further in this speclfication The plastics material used will be of sufficient thickness and type to prevent electrocution, i.e. it will be an electrical insulator.

In the embodiments just described, i.e. Figures 9 and 10, the tube 21 could be formed by hot dipping the neck 3, for example, into a container filled with the liquefied electrically insulating, material, then the neck 3 could be removed from the hot dip and allowed to dry. In this way a coating of the electrically insulating material could be applied to the neck 3 of the implement 20. Furthermore, in alternative embodiments not illustrated, the tube 21 could be cold sprayed to form an even coating of material about the neck 3 to form a sleeve of electrically insulating material 21. It is clear that the thickness of the tube 21 formed by either method would need to be sufficient to withstand, for example, 25, 000 volts and a number of experiments would need to be carried out by the person skilled in the art to ensure that the thickness of the tubing 21 would be sufficient to enable this criteria to be fulfilled. This criteria would also apply to the manufacture of the foot-pads 6, 17, 18. With respect to the hot dip method, the neck 3 may need to be dipped several times, once each respective "coat" of electrically insulated material 21 has dried. Similarly, cold spraying would require more precision to ensure that an even thickness of tubing 21 had been achieved.

Figures I I and 12 comprise a further development of the technolog described in gy Figures 9 and 10.

Figure I I comprises an improved spade that is generally referenced 27. This digging implement 27 comprises a steel blade I denoted by the dotted lines 29.

Figure I I actually shows two embodiments, one where the steel blade tapers 29, towards the ground penetrating edge 37 and one where the blade I essentially is the full width 33 of the digging implement 27. In this embodiment, the handle 5, shaft 4, neck 3, platform 32 and majority of the blade 29, 33 is coated with or otherwise formed from an electrically insulating material, exposing only a little more than the ground penetrating edge 37 of the implement 27 as bare steel. In this way, the structural rigidity of the blade I possesses the requisite torque strem,th that is achieved with a coating/moulding, formed as one integral unit that C.

has to be resistant to for example the passage of current associated with 25,000 volts.

Similarly, Figure 12 illustrates a variant of Figure 11, in so far as that Figure 12 illustrates a fork generally referenced 28, whose sole metallic components are a plurality of tines 3 1 linked towards their distal end (with respect to the handle 5), by a metallic bar as illustrated in Figure 12. Every other component is essentially identical to that described for Figure 11.

The platforms 32 span the entire width of the digging implements 27, 28, but there is no reason why they could not form platforms as illustrated in Figure 10 that are discontinuous. Each respective type of platform 32 and 23 is provided with a shoulder 30 to reinforce the load bearing potential of each type of platform 32, 23).

In embodiments not illustrated, the top, in use, surface of the platforms 23, 32 could also be ribbed or otherwise supplied with a treaded surface. This treaded surface could be provided by the same rubber material used to form the foot-pads 6, 17, 18 and could simply glued on to the top surface(s) of the platforms 23, 32 using a suitable adhesive.

Turning now to Figure 13, this digaing implement 10 is in the form of a fork generally referenced 34 and comprises a platform 36 that is integral with the top surface of the blade 1, the neck 3 of the shaft 4 of the implement 34 being integrally connected to the blade I through the use of a yoke 35. The central point of the platform 36 is co-axial with the longitudinal axis of the shaft 4 of the implement 34 and when the implement is used, because of the location of the platform 36, a user of the implement 34 experiences no "tilting" of the blade I as the ground penetrating edge 37 enters the ground. For example, there will be a tendency for the right hand side of the ground penetrating edge 37 to sink preferentially into the ground if a conventional diccring implement 10 is used by In for example a right-footed person. With the embodiment illustrated in Figure U, a more even pressure is applied throughout the length of the ground penetrating edge 37, thereby ensuring a minimal to non-existent "tilting" effect. For the 0 purposes of this specification, the implement 34 is cast as a one piece unit from electrically insulating material and is likely to be a rigid plastics material.

Figure 14 shows a similar implement also referenced 34, but as the reader can see, this particular implement 34 is a spade Figure 15 shows the side profile view of Figure 14 which also corresponds to the side profile view of Figure 13 and it demonstrates the "swan-neck" of the yoke 35 to avoid the possibility of a user's knee hitting the shaft 4 of the implement 34 when using the implement. Figure 16 shows a side profile of an alternative fixing of the yoke 3 5 to the blade I and in this particular instance, instead of the yoke 5 10 forming a continuous sweeping integral linkage with the outer edges of the blade 1, the yoke 35 is formed as an integral unit with the front face of the blade 1. Of course, the embodiments 13 16 that have just been described, need not necessarily be formed solely from an electrically insulating material and could be formed from steel and coated with a continuous or discontinuous barrier of 15 electrically insulating material in the manner herein described.

-13

Claims

I A digging implement for use by an individual, the digIging implement 1.) C- I I ID Z.) being formed from, either in part or in its entirety, or otherwise fitted with, in use, a material that is non-electrically conductive, such that, in use, an individual using the digging implement either will perceive no electric shock or will experience only an attenuated shock if the ground penetrating portion of the digging implement comes into contact with a source of electricity.
2. A digging implement according to claim I wherein, the material is readily C) demountable, at least in part from the digging implement.
3. A digging implement according to any claim I or claim 2, having a neck I and a top bar over which the material is fitted.
4. A digging implement according to any one of the preceding claims, in which the digging implement is fitted with a foot pad mounted directly on Z.

or adjacent to its ground penetrating portion, the foot pad in use spreading the force of the ground penetrating implement over an increased area of the sole of a user, the foot pad being insulating in respect of electricity.
5. A digging implement according to claim 4 in which the foot pad is I I contracted of a resistant, durable, electrically insulating material having sufficient insulating properties to substantially prevent shock from a I source of 25,000 volts.
6. A digging implement according to any preceding claim, the digging 0 C implement being fitted with a heat-shrinkable electrically insulating sleeve around the neck of the shaft of the digging implement.
7. A digging implement substantially as herein described with reference to and as shown in Figures 9 to 16 of the accompanying drawings.
8. A foot pad for use with a digging implement substantially as herein =D Z-) described with reference to and as shown in Figures 2-8.
9. A foot pad having a horizontal top edge, the foot pad being adapted for use on a ground penetrating implement, the foot pad comprising at least one tread portion, so sized and shaped as to act as a platform for the foot of a user of the digging implement, wherein the tread portion is electrically insulated.
10. A foot pad according to claim 9, which comprises a collar to fit around the neck of the digging implement.

0
11. A foot pad according to claim 10, in which the collar is integral with the tread portion.
12. A foot pad according to any of claims 9 to 11, wherein the tread overlaps the ends of the horizontal top edge.
13. A foot pad according to any of claims 8 to 12, in which the tread extends around the underside of the foot pad.
14. A ground penetrating implement comprising a ground penetrating portion, a neck of a shaft, the central point of the ground penetrating portion I I being co-axial with the longitudinal axis of the shaft, the shaft being connected to either end of the ground penetrating portion.