GB2306094A

GB2306094A - Agricultural hand tool

Info

Publication number: GB2306094A
Application number: GB9520668A
Authority: GB
Inventors: Colin Raymond Ashford; Benito Magnani
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-10-10
Filing date: 1995-10-10
Publication date: 1997-04-30
Anticipated expiration: 2015-10-10
Also published as: GB9520668D0; GB2306094B

Abstract

The present invention provides a spade blade 1 having a plurality of tines 2 extending axially from the leading edge of the blade 1 characterised in that: a. there are from 3 to 6 tines extending from the blade; b. the tines: 1. are tapered at their distal end and the taper has an overall included angle of from 1 to 30{, preferably 5 to 20{, and 2. have a maximum transverse dimension, D, at the junction with the leading edge of the blade, their proximal end, of from 0.75 to 1.5 cms, and 3. have a length, L, between their proximal and distal ends of from 2.5 to 7.5 cms, and 4. have an L:D ratio of from 5:3 to 5:1, preferably of from 3:1 to 5:1; and b. the ratio of the length L of the tines to the spacing, S, between the tines at the leading edge of the blade is from 2:1 to 1:2. The tines 2 are welded to the underside of the blade 1 and are formed from hardened tool steel.

Description

TITLE: DEVICE The present invention relates to a device, notably to a spade blade having axially projecting tines.

BACKGROUND TO THE INVENTION: Conventional spade blades present a wide edge to the ground and require considerable effort to drive the blade into hard ground or ground having a high stone content.

In order to overcome these problems, it has been proposed to form the leading edge of the blade with a serrated or toothed edge. However, this has not overcome the problem and, furthermore, does not cause break up of the soil when the spade blade is worked in the soil. It has also been proposed to form the spade blade with axially extending sharpened teeth to cut into roots encountered as the spade is driven into the soil. However, such teeth rapidly become blunted in use and are no longer effective in cutting roots. Furthermore, such teeth do not significantly assist penetration of the spade blade into the soil.

We have now devised a form of blade which overcomes the above problems. Due to its design, the blade of the invention is remarkably effective in penetrating the soil and in breaking up the soil into a tilth when the blade is worked in the soil.

SUMMARY OF THE INVENTION: Accordingly, the present invention provides a spade blade having a plurality of tines extending axially from the leading edge of the blade, characterised in that: a. there are from 3 to 6 tines extending from the blade; b. the tines: 1. are tapered at their distal end and the taper has an overall included angle of from 1 to 300, preferably 5 to 200, and 2. have a maximum transverse dimension, D, at the junction with the leading edge of the blade, their proximal end, of from 0.75 to 1.5 cms, and 3. have a length, L, between their proximal and distal ends of from 2.5 to 7.5 cms, and 4. have an L:D ratio of from 5:3 to 5:1, preferably of from 3:1 to 5:1; and b. the ratio of the length L of the tines to the spacing, S, between the tines at the leading edge of the blade is from 2:1 to 1:2.

Preferably, the ratio of the length of the tines L to the total length of the blade and tines L1 is from 1:5 to 1:10. Such a ratio ensures that a spade assembled by attaching the blade to a conventional handle is correctly balanced. Preferably, the ratio is about 1:6 to 1:8.

The tines are formed from a hard material capable of resisting rapid wear in use. Preferably, the tines are made from a hardened tool or other steel. However, it is within the scope of the present invention to form the tines from a mild steel and to harden the tines during manufacture of the blade of the invention. Thus, the tines will usually be secured to the blade by welding and some tempering of the steel will take place during welding and/or when the hot welded construction is water or oil quenched. For convenience, the invention will be described hereinafter in terms of the use of hardened tool steel tines.

The tines present a sharp tip to the soil so as to assist penetration of the tines into the soil and breaking up of clods or stones encountered as the blade penetrates into the soil. Whilst the tines may be formed initially with a sharp point, this will become blunted during use. It is therefore necessary to form the tines with a taper so that a high point load can be achieved even where the tines tips have been blunted during use. The taper can be a fine taper, ie. with a low included angle, but this may lead to the formation of a substantially squared tip during use. Where the taper is large, the point loading will be rapidly reduced as the tines wears. We have found that the use of a taper with an overall included angle of from 2 to 300 provides satisfactory results.It is particularly preferred to use a taper having an overall included angle of from 10 to 15 since such a taper preserves the high point loading at the tip of the tine after substantial wear.

The term overall included angle is used herein to denote the included angle of the cone within which the tapered portion of the tine is congruent, ignoring the blunted tip of the tine.

The tines have a maximum transverse dimension D at their proximal end of from 0.75 to 1.5 cms. We have found that tines which have D greater than 1.5 cms present too great a frontal area to permit ready penetration of the tine into the soil. On the other hand, if the tines have D less than about 0.75 cms, the tine flexes during working of the blade in the soil and negates use of the blade to break up the soil. Preferably the tines have a maximum transverse dimension of about 1 cm.

The tines can have any suitable cross section, for example round, squared, triangular or polygonal. However, we have found that, if the transverse dimension of the tine in the plane of the blade is too great, the tines present an excessive area to movement through the soil as the blade is worked backwards and forwards in the soil. As a result, excessive effort is required to use such working of the spade in the soil to cause break up of the soil.

We therefore prefer that the ratio of the maximum transverse dimension R1 to the minimum transverse dimension R, both dimensions measured from the longitudinal axis of the tine to an adjacent edge or corner of the cross section of the tine, be not more than 2:1, preferably about 1:1. The use of a circular cross section tine, ie. one in which R:R1 is 1:1, is preferred since the wear on such a tine during use will usually be symmetrical about the longitudinal axis of the tine. For convenience, the invention will be described hereinafter in terms of the use of a tapered circular cross section tine.

As with the transverse dimensions of the tine, we have found that the length of the tine must fall within predetermined values if the tine in not to be too flexible or too short to be capable of achieving any useful break up of the soil as the blade is worked in the soil. Thus, the length L of the tines is to be from 2.5 to 7.5 cms and the ratio of L to D is to fall within a value of from 5:3 to 5:1. Furthermore, the tines need not all be of the same length, since we have found that in some hard grounds it may be desirable to have the tips of the tines in the central area of the edge of the blade axially forward of those at the edge of the blade. Alternatively, the leading edge of the blade can be curved so that the tips of tines of the same length mounted thereon present a curved arc to the ground.Typically, the central tip is from 0.25 to 1 cm axially in advance of the tips at each edge and the curved arc they present is symmetrical about the centre line of the blade. However, it may be desirable in some cases, for example where the blade is to be used close to a wall or other vertical obstruction in the ground, for the tip of the edge tine to be axially in advance of the other tines.

The leading edge of the blade causes a chiselling action upon the soil which significantly assists break up of the soil. However, we have found that if the length of the leading edge between adjacent tines is excessive, the initial soil break up caused by the penetration of the tines does not extend adequately across the space between the tines. As a result, the leading edge of the blade encounters unbroken soil and the force required to drive the leading edge into the soil is not significantly less than that required when no tines are present. It is therefore necessary to space the tines within prescribed limits to achieve ease of penetration of the leading edge of the blade into the soil. Thus, the tines are spaced apart at their proximal ends by from half to twice their axial length, preferably by about their axial length. As a result, for most widths of spade blades there will be four to five tines evenly space across the length of the leading edge of the blade. The use of five tines is particularly preferred for a blade having a leading edge from 20 to 25 cms long since we have found that this number of tines is unexpectedly effective in assisting penetration of the blade into the soil and subsequent break up of the soil as the blade is worked within the soil.

In a particularly preferred form of blade for use in the manufacture of a man's digging spade the tines are formed from tool steel, have a taper of about 15 , a length of about 4 cms, a diameter at their proximal end of about 1 cm, are spaced about 4.5 cms from each other along the length of the leading edge of the blade and are secured to a blade having a length of about 23 cms and a width of about 20 cms. For a ladies spade, the weight and dimensions of the blade and tines will be less than those quoted above.

The blade of the invention is conveniently made by welding the appropriate number of tines extending from the leading edge of the blade. The tines are preferably located at uniform spacings along the leading edge. However, in some cases, for example when working adjacent a wall or other structure, it may be desired to have a closer spacing between the tines adjacent the lateral edges of the leading edge of the blade. The tines can be welded to the top or bottom face of the blade with rearwardly extending portions of the tines extending onto the face of the blade. Typically, the tines extend for from 4 to 10 cms, eg. 6 to 8 cms, onto the blade to provide a secure anchorage of the tine to the blade.If desired, the leading edge of the blade can be cut with axial slots to receive the foot of the tines or the tines can be provided with axial slots into which the leading edge of the blade is received. Where the blade is to be used to break up heavily compacted or stony ground, we have found that it is advantageous for the tines to be mounted below the plane of the blade with their exposed lower face ground away to follow the line of the lower surface of the blade and for the blade to be a substantially flat blade. Where the blade is to be used in ground which has already been broken up, for example in a garden, it is preferred that the blade be of a transversely dished shape.

The blades of the invention find use wherever it is desired to break up ground. By virtue of the number, shape and spacing of the tines, the user can insert the blade to its full spit depth into the soil with less effort than a conventional spade blade or a blade with tines which do not meet the requirements of the invention.

Once inserted into the soil, the blade can be worked to and fro in the soil to break up the soil. The blade can then be removed from the soil carrying a load of broken up soil on the planar part of the blade where the spade is used for digging as well as for breaking up the soil.

Surprisingly, we have found that the blade of the invention is remarkably effective in breaking up hard clods and stones in the soil as compared to either a conventional fork, where stones can become jammed between the tines, or a conventional spade where the blade can be thrown off line when it strikes a stone. The blade of the invention is thus of especial use in the construction industry or in breaking up compacted stony ground.

Furthermore, it can achieve with a single tool what would hitherto have required the use of a conventional fork and/or pickaxe in conjunction with a conventional spade to achieve. The invention may thus reduce the number of tools which a repair crew or site preparation gang are required to carry.

DESCRIPTION OF THE DRAWINGS: The invention will now be described by way of illustration only with respect to the accompanying drawings in which Figure 1 is a plan view from above of a blade of the invention for a man's spade; Figure 2 is a side view of the blade of Figure 1; Figure 3 is a plan view from below of the blade of Figure 1; and Figure 4 is a plan view of a blade having a curved leading edge.

DESCRIPTION OF THE PREFERRED EMBODIMENT: The blade of the invention comprises a generally planar portion 1 and the tines 2 extending axially from the distal end of portion 1. Extending axially from the proximal end of portion 1 is a conventional handle socket 3 into which is fitted a metal or wooden handle (not shown).

The tines 2 are made from hardened tool steel and extend about 4 cms from the leading edge 4 of portion 1 and extend axially onto portion 1 for about 7 cms. The rearwardly extending portions 5 of the tines 2 are welded to portion 1 and the exposed lower faces of portions 5 are ground away so that the lower face of the tines follows the line of the lower face of portion 1. If desired, portion 1 can have axial cut outs extending rearwardly of leading edge 4 top receive portions 5 of the tines so that grinding away of the tine surfaces is reduced or obviated.

The tines 2 have a generally circular cross section tapering from about 1 cm at the leading edge 5 of portion 1 to about 2 mms immediately adjacent the sharpened tip 6, giving an included angle for the cone of the taper of about 140. Five of such tines are welded at approximately 4.5 cm spacing along the leading edge 4.

Such a blade can readily be driven into compacted gravelly ground and worked in the ground to break up the ground to enable a hole or trench to be dug. Surprisingly, stones within the ground were readily shattered by the tines, enabling a comparatively smooth sided hole or trench to be formed.

By way of comparison, when a conventional spade was used, it could not be driven into the ground, despite the user apply his full weight to the blade. It was necessary to break up the ground first with a pickaxe and/or a heavy duty fork, thus requiring two or three tools where a single blade of the invention can be used. Even then the hole or trench had uneven sides due to deflection of the spade blade by stones in the ground.

Where a blade having only three tines was used, so that the spacing between the tines at the leading edge 4 of the blade is approximately 9 cms and the ratio of the length of the tines to the spacing is 1:2.25, the blade could not easily be driven into the ground beyond the depth of the tines and break up of the soil was difficult to achieve.

Where a blade having nine tines spaced at 2.25 centres along the leading edge of the blade is used, the tines would present such a combined total frontal area to be driven into the ground that it would require excessive force to achieve penetration of the tines into the soil.

Also the blade would now be excessively nose heavy and the balance of the assembled spade would be adversely affected.

As shown in Figure 4, the leading edge of the blade can be curved so that the tips of the tines follow a curved profile. In this way, all the user's weight can be applied initially to the ground through the central tine so as to apply a high point load to assist penetration of the tine into hard ground. Once the first tine has penetrated the ground, the blade can be worked in the ground to break it up and assist penetration of the other tines of the blade. Typically, the central tine tip is about 0.75 to 1.5 cms, eg. about 1 cm, ahead of the tips of the tines at the edges of the blade and the tips present a symmetrical curved profile as shown. However, the leading edge of the blade can be straight as shown in Figure 1 and the tines of different lengths to achieve the same effect. Alternatively, the profile presented by the tine tips can be angled as shown dotted in Figure 4 to enable the blade to be used close up against a wall.

Claims

CLAIMS: 1. A spade blade having a plurality of tines extending axially from the leading edge of the blade, characterised in that: a. there are from 3 to 6 tines extending from the blade; b. the tines:

1. are tapered at their distal end and the taper has an overall included angle of from 1 to 300, and

2. have a maximum transverse dimension, D, at the junction with the leading edge of the blade, their proximal end, of from 0.75 to 1.5 cms, and

3. have a length, L, between their proximal and distal ends of from 2.5 to 7.5 cms, and

4. have an L:D ratio of from 5:3 to 5:1, preferably of from 3:1 to 5:1; and b. the ratio of the length L of the tines to the spacing, S, between the tines at the leading edge of the blade is from 2:1 to 1:2.

2. A blade as claimed in claim 1, characterised in that the taper to the tines has an included angle of from 5 to 20 .

3. A blade as claimed in either of claims 1 or 2, characterised in that the tines have an L:D ratio of from 3:1 to 5:1.

4. A blade as claimed in any one of the preceding claims, characterised in that the ratio of the length of the tines L to the total length of the blade and tines L1 is from 1:5 to 1:10.

5. A blade as claimed in claim 4, characterised in that the ratio of L to L1 is about 1:6 to 1:8.

6. A blade as claimed in any one of the preceding claims, characterised in that the tines are made from a hardened tool steel.

7. A blade as claimed in any one of the preceding claims, characterised in that the ratio of the maximum transverse dimension R1 of the tine to the minimum transverse dimension R of the tine, both dimensions measured from the longitudinal axis of the tine to an adjacent edge or corner of the cross section of the tine, is not more than 2:1.

8. A blade as claimed in claim 7, characterised in that the ratio of R1:R is about 1:1.

9. A blade as claimed in any one of the preceding claims, characterised in that the tip of at least one of the tines in the central portion of the blade is axially forward of those at the lateral edges of the blade by from 0.25 to 1 cm.

10. A blade as claimed in any one of the preceding claims, characterised in that the ratio of S:L is about 1:1.

11. A blade as claimed in any one of the preceding claims, characterised in that the tines are welded to the underside of the blade and extend axially rearwardly of the leading edge of the blade for from 4 to 10 cms.

12. A blade as claimed in any one of the preceding claims, characterised in that the tines are formed from tool steel, have a taper of about 15 , a length of about 4 cms, a diameter at theirproximal end of about 1 cm, are spaced about 4.5 cms from each other along the length of the leading edge of the blade and are secured to a blade having a length of about 23 cms and a width of about 20 cms.

13. A blade as claimed in claim 1, substantially as hereinbefore described with respect to and as shown in any one of the accompanying drawings.

Amendments to the claims have been filed as follows 1. A blade for a hand operated ground working tool, which blade has a plurality of tines extending axially from the leading edge of the blade, characterised in that: a. there are from 3 to 6 tines extending from the blade; b. the tines are made from a wear resistant material and:

1. are tapered at their distal end and the taper has an overall included angle of from 1 to 30 , and

4. have an L:D ratio of from 5:3 to 5:1; and b. the ratio of the length L of the tines to the spacing, S, between the tines at the leading edge of the blade is from 2:1 to 1:2.

5. A blade as claimed in claim 4, characterised in that the ratio of L to L1 is from 1:6 to 1:8.

8. A blade as claimed in claim 7, characterised in that the ratio of R1:R is substantially 1:1.

10. A blade as claimed in any one of the preceding claims, characterised in that the ratio of S:L is substantially 1:1.

12. A blade as claimed in any one of the preceding claims, characterised in that the tines are formed from tool steel, have a taper of substantially 15 , a length of substantially 4 cms, a diameter at their proximal end of substantially 1 cm, are spaced substantially 4.5 cms from each other along the length of the leading edge of the blade and are secured to a blade having a length of substantially 23 cms and a width of substantially 20 cms.