GB2292059A - Hand held power tiller - Google Patents

Abstract

A hand-held power tiller (2) includes two independently driven tines (10, 12) which, in use, are arranged to rotate in opposite senses about generally vertical axes. This provides a more controllable tiller than conventionally available. Each of the tines (10, 12) has forks (24a, b, c) which are angled to drag the tiller (2) down into the earth being tilled. Each set of tines 10, 12 is driven by an electric motor 14, 16, which may be powered by batteries stored in the handle 4. <IMAGE>

Description

POWER TILLER The present invention relates to power tillers and has particular, although not exclusive, relevance to power tillers arranged to be hand-held for use in a domestic garden environment.

Power tillers are known which comprise a drive unit, such as a diesel engine, coupled to rotatable tine means. The tine means are disposed for rotation about a generally horizontal axis such that their rotation not only tills the earth, but also causes the power tiller to be dragged across the earth. Thus the provision of wheels or other means for enabling the power tiller to be moved whilst it tills is obviated because the tine means themselves achieve this.

A problem with this known type of power tiller is that controlling the tiller can be somewhat difficult. Because the tine means themselves provide for motion of the tiller across the land whilst they are tilling the earth, a very uneven movement is achieved. Turning the tiller can be problematical whilst the tines are rotating because they will actually be at least partially in the earth and thus resist a turning force. If the tines are stopped to allow the tiller to be turned, then the tines will need to be lifted out of the earth.

Furthermore, in a domestic garden environment in particular, there will rarely be the need for such a powerful and cumbersome machine to till only a relatively small area of land. Thus, should the user only wish to till the earth in respect of light work, such as removing weeds, then this known type of tiller is far from ideal.

Thus the provision of a more manageable tiller than has hitherto been available is an attractive proposition and it is thus an object of the present invention to at least alleviate the problems mentioned above.

Hence, according to the present invention there is provided a power tiller including: a plurality of tine means, each tine means of the plurality arranged for rotation about a respective axis; electrically powered drive means coupled to the tine means for enabling rotation of the tine means about said respective axes and wherein the tiller is arranged such that, in use, said respective axes are generally orthogonal with respect to the earth to be tilled. In this way, by enabling the tine means to rotate about an axis which is normal to the plane of the earth being tilled, a power tiller is proposed which may be more easily controlled than the known device because the rotating action of the tine means causes only tilling of the earth and does not set out to also achieve movement of the tiller.

Preferably each tine means of the plurality is individually coupled to a respective electrically powered drive means and advantageously each of the respective electrically powered drive means is powered independently. This means that, should one of the tine means become stuck in the earth due to an obstruction, say, then the other tine means may carry on rotating and thus may even dislodge the obstacle preventing rotation of the stuck tine means.

Additionally or alternatively each of the tine means of the plurality may comprise a plurality of individual forks, each of which forks may be arranged and configured such that, on rotation, the tine means are urged into the earth being tilled. Thus there is no need for the user of the power tiller to exert undue force in order to urge the tine means into the earth, as the forks themselves achieve this. Such a feature is particularly advantageous in cases of very hard earth or where the user of the power tiller has little strength himself.

The present invention will now be described, by way of example only and with reference to the accompanying drawings, of which: Figure 1 shows a perspective view of a power tiller in accordance with the present invention; Figure 2 shows a perspective view of the tine means and associated parts of the power tiller of Figure 1; Figure 3 illustrates schematically an electrically powered drive means and an associated tine means in accordance with the present invention; Figure 4 illustrates schematically a circuit diagram for the tiller of Figure 1; and, Figure 5 shows a perspective view of an alternative power tiller to that of Figure 1.

Referring firstly to Figure 1, a power tiller in accordance with the present invention is shown generally as 2. The tiller 2 comprises a handle 4 by which an operator may hold and use the tiller 2, a shaft 6 and an operating platform 8 connected to the end of the shaft 6 remote from the handle 4.

The operating platform 8 supports and houses a plurality of tine means, in this example two rotatable tines 10 and 12 (see also Figure 2).

Each of the tines 10 and 12 is coupled to a respective electrically powered drive means, in this example a low-speed high-torque electric motor 14, 16.

The power supply for each of the electric motors 14 and 16 may be from any suitable source such as mains or transformed mains. In this example, however, the power supply is via nickel-cadmium batteries (not shown) stored within the shaft 6.

Referring now particularly to Figure 3, it can be seen that the motor 14 and its associated tine means 10 is shown more clearly. The motor 14 receives power via supply cable 18. The underside of the motor 14 is rigidly mounted on operating platform 8, which has a hole therein through which an output spindle 20 of the motor 14 passes.

In this example motor 14 is only able to rotate the spindle 20 in one sense - as shown by the arrows. The spindle 20 is coupled to a tine means 10 which, in this example, comprises a supporting disc 22 on the underside of which are mounted a plurality of individual forks, here three 24a,b, and c.

Considering Figure 1 again, the operation of the tiller 2 will be explained in detail. The user holds the tiller by handle 4, attached to which is a switch (not shown) which, when activated supplies the motors 14,16 with power from the batteries (not shown) held within shaft 6. The motors 14,16 are arranged for rotation in opposite senses, for reasons which will be explained hereafter. It can thus be seen that each tine means rotates about an axis which is parallel to the axis of rotation of the other tine means.

The user next allows the forks 24a,b,c, of each tine means 10,12 to engage the earth to be tilled such that the axes of rotation of the tine means are generally vertical with respect to the earth. It will be seen from Figures 1 - 3 that the forks 24a,b,c are arranged and configured such that on rotation they tend to drag their respective tine means down into the earth. This is achieved here by angling the ends of the forks 24a,b,c remote from supporting disc 22 to face the direction of rotation of the tine means but at around 45" to the vertical. By such an arrangement of the forks 24a,b,c, the user need not exert undue force upon the tiller 2 in order to achieve efficient tilling, because the tiller will tend to urge itself into the earth. This feature, although not essential, is particularly advantageous to the present invention.

Furthermore it can be seen that the tips of the forks face inwards with respect to the circumference of the circle defined by the rotation of the tine means 10 or 12. Hence the tips of the forks do not project out beyond this circumference. This feature ensures that the tine means must engage the earth to be tilled in a generally orthogonal attitude thereto, otherwise the tips of the forks will not engage the earth effectively. If, for example, the tine means were attempted to be used in a horizontal axis with respect to the earth to be tilled, then clearly none of the forks would engage the earth.

It will be understood that it is also advantageous for the motors 14,16 to be contra-rotating. This then means that a minimising effect on the movement felt about the point 24 where the shaft 6 joins the operating platform 8 is achieved. This makes for a comfortable feeling for the user during operation of the tiller 2 as there is no need to fight to maintain the position of the tiller on the earth being tilled.

In order to further minimise any moment about the point 24, it can be seen that this point has been chosen to lie midway between the two motors 14 and 16. It will, however, be appreciated that this is not an essential feature.

Figure 4 shows a preferred form of electrical connection between the motors 14 and 16 and their supply. The supply 26 in this case provides a source of d.c. to which a parallel coupling of the motors 14 and 16 is made.

If, during operation of the tiller 2 one of the motors 14 or 16 stalls due to, say, the forks 24 becoming lodged in rocks or the like, then due to the parallel nature of their coupling to the supply 26, the other motor 16 or 14 may continue to rotate. In fact, this continuing rotating motor may cause its associated tine means to dislodge the obstruction of the stalled motor.

It is advantageous that, should a motor stall, a current limiter 28 be in series therewith in order to prevent an overload of current therefor which could burn out the motor. This could happen because, when a motor stalls, there is no longer any back-emf associated therewith and so it draws more current than when it was running.

Referring now to Figure 5, an alternative tiller to that of Figures 1 - 4 is shown. It will be seen that similar features to those previously described are numbered correspondingly. It will also be seen that the salient difference between the previously described embodiment and that shown in Figure 5 is that, in the latter embodiment one motor 14 drives a plurality of tine means, here four 10,12,30,32, by itself. The precise manner in which this driving occurs is not germane to the present invention but here each of the four tine means is driven from the motor 14 by a set of intermeshing cogs (not shown).

It will be appreciated by those skilled in the art that any number of individual tine means may be employed in the present invention, although if an even number are employed, then it is advantageous if the same number which rotate in one sense are matched by an equal number which rotate in the other sense. In this way net moments about the shaft 6 can be reduced. Thus with reference to Figure 5, two of the tine means rotate clockwise and two others rotate anticlockwise.

Thus the present invention, by providing a power tiller designed to engage the earth to be tilled in a direction, generally orthogonal respect to the plane of the earth has envisaged a more controllable and manageable tiller than has hitherto been available. It will be understood that the present invention provides a portable device capable of hand-held operation and which may be either mains or battery powered.

Claims (10)

1. A power tiller including a plurality of tine means, each tine means of the plurality arranged for rotation about a respective axis; electrically powered drive means coupled to the tine means for enabling rotation of the tine means about said respective axes and wherein the tiller is arranged such that, in use, said respective axes are generally orthogonal with respect to the earth to be tilled.

2. A power tiller according to claim 1 wherein each tine means of the plurality is individually coupled to a respective electrically powered drive means.

3. A power tiller according to claim 2 wherein each of the respective electrically powered drive means is powered independently.

4. A power tiller according to any one of the preceding claims wherein each tine means of the plurality comprises a plurality of individual forks.

5. A power tiller according to claim 4 wherein each of the forks is arranged and configured such that on rotation, the tine means are urged into the earth being tilled.

6. A power tiller according to any one of the preceding claims wherein there are an even number of tine means in the plurality of tine means and for every tine means of the plurality which rotates in one sense about its respective axis, another tine means of the plurality rotates in the opposite sense about its own respective axis, thereby enabling substantially no net moment to occur about the power tiller.

7. A power tiller according to any one of the preceding claims arranged for hand-held operation.

8. A power tiller comprising: a planar platform supporting a plurality of tine means; a handle coupled to the platform and angled with respect thereto, the handle including a power source; a drive means coupled to the power source for driving the tine means; wherein the drive means are on one side of the platform and the tine means are on the other side.

9. A power tiller substantially as hereinbefore described and with reference to Figure 1 - 4.

10. A power tiller substantially as hereinbefore described and with reference to Figure 5.