WO1990006672A1

WO1990006672A1 - Rotary cultivator tool

Info

Publication number: WO1990006672A1
Application number: PCT/SE1989/000731
Authority: WO
Inventors: Stig Andersson
Original assignee: Stig Andersson
Priority date: 1988-12-15
Filing date: 1989-12-14
Publication date: 1990-06-28
Also published as: AU4749190A; SE8804529D0; SE8804529L; SE462733B

Abstract

A soil cultivator tool (18) comprises an attachment portion (19) for securing the tool to a motor-driven spindle of a soil cultivator, and an operating portion (20) formed of a wire which is spirally curved about an axis (C) of rotation of the tool extending through or located near the attachment portion (19). The operating portion (20) is in the shape of a spiral when viewed in the direction of the axis (C) and is connected to the attachment portion (19) at the inner end of the spiral. A hand-held motorized soil cultivator comprises a motor-driven spindle to which the soil cultivator tool (18) is removably attached with the axis (C) of rotation of the tool coinciding with the axis of the spindle.

Description

Rotary cultivator tool

This invention relates to a soil cultivator tool and, m particularly, a soil cultivator tool comprising an attachme portion for attaching the tool to a motor-driven spindle, a an operating portion which is secured to the attachment por tion and formed of a spring wire, the spring wire being coi about an axis of rotation of the tool extending through or located near the attachment portion.

The invention also relates to a soil cultivator compris such a soil cultivator tool.

In a soil cultivator tool of the kind defined above (WO88/02981) , which is intended for use in a hand-held moto ized soil cultivator, the spring wire which constitutes the operating portion of the tool forms a cylindrical coil (hel the axis of which is substantially parallel to the ground i operation of the tool. An embodiment of the tool comprises halves or sections which are coiled in opposite directions project in cantilever fashion from opposite ends of a spind driven by a motor through an intermediate shaft perpendicul to the spindle and an angular gear.

An object of the present invention is to provide an im¬ proved soil cultivator tool of the kind defined above for u in a hand-held motorized soil cultivator and particularly useful for relatively light cultivation work, e.g. in flowe beds, plots of vegetables, ground areas between and under bushes, and so on. A further object is to provide such a so cultivator tool which is efficient in operation and yet is prone to damaging flowers, vegetables, bushes or other utili plants growing in the soil to be cultivated. These and other objects are accomplished according to th invention in a soil cultivator tool of the kind defined abov which is characterised in that the operating portion is in t shape of a spiral when viewed in the direction of the axis o rotation and is connected to the attachment portion at the inner end of the spiral.

In the soil cultivator tool according to the invention t wire constituting the operating portion of the tool thus is bent along a line which is curved about the axis of rotation of the tool and, starting from the attachment portion, i.e.. from or near the axis of rotation, gradually increases its distance from the axis of rotation with increasing distance (as measured along the line) from the attachment portion. Instead of only forming a flat spiral shape, the spirally curved line may additionally increase gradually its axial distance, i.e. the distance as measured parallel to the axi of rotation, from the attachment portion so that it forms a conical or substantially conical coil, the extension of the operating portion as measured parallel to the axis of rotat then being smaller than its extension as measured perpendic larly to the axis of rotation.

In operation, the tool is rotated about the axis of rot tion in the direction which corresponds to the direction of the orbiting movement of a point which travels from the ra- dially outer end of the operating portion towards the attac ment portion so that this end of the operating portion cons tutes the trailing end.

According to the invention there is also provided a han held motorized soil cultivator. Preferably, the soil cultiv tor, which comprises a soil cultivator tool according to th invention, is designed such that the person who operates th soil cultivator may carry out the cultivation in a substan¬ tially upright position. For example, the soil cultivator m comprise an operating unit, which includes a supporting and protective tube enclosing a coaxial rotatable spindle one e of which protrudes from the tube and carries the cultivator tool, and a driving and control unit which is secured to th end of the tube remote from the cultivator tool and driving connected with the other end of the spindle. The driving an control unit includes a suitable motor, such as an electric motor or an internal combustion engine, and a handle provid with a motor control member. In operation, the operator hol and manipulates the soil cultivator with one hand gripping handle and the other hand gripping the supporting and prote tive tube or a second handle attached to it.

Other designs of the soil cultivator are also possible. For example, the driving motor may be disposed adjacent the soil cultivator tool on one end of a supporting tube or bar the other end of which is provided with a handle and a moto control member. A further handle may be attached to the sup porting tube or bar or, possibly, on the housing of the dri ing motor.

In operation of the soil cultivator, the rotating culti vator tool is engaged with the ground with the axis of rota tion of the tool perpendicular to or at an acute angle with the ground surface. The spirally curved operating portion o the cultivator tool is resiliently deformed in the directio of the axis of rotation as a consequence of the engagement subsequent movements of the soil cultivator so that the too tills the soil down to a certain depth. The spiral shape of the operating portion coupled with its flexing movements results in an agitation of virtually all soil particles con tained in the volume of soil swept by the operating portion Accordingly, the soil is cultivated very thoroughly, and th cultivation can be carried out down to a depth which can be chosen almost at will within practical limits, the cultivat depth being chosen by applying a suitable pressure to the cultivator tool. The movements of the soil cultivator and, hence, of the cultivator tool may be composed as desired of vertical and horizontal components. If the wire from which the operating portion of the tool is made is smooth, as is preferred, the operating portion may be allowed to engage well-rooted plan both above and below the surface of the ground; because of spiral shape and the smooth surface of the operating portio there is no substantial danger of mutilating the plants. Naturally, contact with unprotected parts of the human body the rotating tool should be avoided but is not particularly dangerous. Children may therefore be permitted to use a soi cultivator provided with a soil cultivator tool according t the invention.

The invention is described in greater detail below with reference to the accompanying drawing. Fig. 1 is a side view of a hand-held motorized soil cul vator provided with a soil cultivator tool embodying the invention;

Fig. 2 is an enlarged side view of the end of the soil cultivator of Fig. 1 which carries the soil cultivator tool; Fig. 3 is a plan view of the soil cultivator tool as se in the direction of the axis of rotation (from above) ;

Fig. 4 is a side view of a modified embodiment of the s cultivator tool. As shown in Fig. 1, the hand-held soil cultivator com- prises a driving and control unit 11, which includes a variable-speed electric motor (not shown) having a power supply cord 12 and a handle 13 with a motor control switch and an operating unit 15, which is releasably interconnecte with the driving and control unit 11. The driving and contr unit 11 may be adapted for use also with other kinds of ope rating units.

The operating unit 15 comprises a straight, rigid prote tive tube 16 one end of which is attached to the driving an control unit 11 and which surrounds a coaxial, rotatably journalled spindle 17. One end of the spindle 17 is driving connected to the motor and the other end protrudes from the lower end of the protective tube 16 and carries a soil cult vator tool 18 embodying the invention. The tool 18 is remov ly secured to the spindle 17 by means of a clamping device

17' , the details of which are not shown but which is design such that it can accommodate the tool 18 only if the tool i turned the right way round.

An axis of rotation of the tool 18 is represented by a phantom line C. When the tool 18 is properly secured to the spindle 17, the axis C coincides with the axis of the spind 17 and the axis of the protective tube 16.

The cultivator tool 18 is a planar structure formed of spring wire, preferably a steel spring wire, and comprises central attachment portion 19, which is bent to substantial circular shape about the axis C, and an operating portion 2 which is spirally curved about the attachment portion. One end, the inner end, of the operating portion is integrally connected with the attachment portion 19, whereas the other outer end is free. The operating portion 20 merges with the attachment portion 19 without any distinct transition and comprises slightly more than two full spiral turns. As show in Fig. 3, the outer or end segment of the outermost turn gradually approaches the next inner turn so that the outer free end 21 of the operating portion 20 engages or is posi¬ tioned adjacent the last-mentioned turn. Accordingly, the shape of the outermost turn of the operating portion 20 de¬ viates only slightly from the true circular shape. The number of spiral turns of the operating portion 20 vary, but preferably the operating portion comprises at lea a full spiral turn. Generally, a number of spiral turns ex¬ ceeding three is not to be recommended, and a preferred max mum number of spiral turns is two and a half. The spiral shape of the operating portion 20 may vary b preferably the shape is chosen such that the radial distanc separating adjacent spiral turns is roughly constant throug out the major portion of the length of the spiral curve. The wire diameter and the "diameter" of the operating portion 20, e.g. the largest dimension D (see Fig. 3) of th operating portion 20, as measured in a plane perpendicular the axis C (the plane of the spiral) may vary within fairly wide limits and should be matched with the power rating of driving unit and the general character of the soil to be cultivated in order that optimum operation of the tool 18 m be realized. Generally, the wire diameter should be within range of 2,5 to 4 mm and the dimension D should be within t range of 50 to 80 mm. The preferred operating speed is from 600 to 3500 rpm. Referring to Fig. 4, when viewed in the direction of th axis C, the modified soil cultivator tool 18A has the same spiral shape as the tool 18, i.e. the shape shown in Fig. 3, and the tool 18A differs from the tool 18 only in that the spring wire forming the operating portion 20A, which is like wise integral with the attachment portion 19A, is coiled not only spirally, but also helically, so that the wire is in th shape of a substantially conical helix. The axial extension height H of the operating portion 20A, which for practical purposes is equal to the total axial extension or height of the entire cultivating tool 18A, is smaller than the above- mentioned dimension D.

The modified embodiment of Fig. 4, in which the wire is coiled with a certain axial pitch, may be preferred when the number of spiral turns is smaller than 1.2 to 2. In the embodiments of the cultivator tool illustrated in the drawing, the wire is circular in cross-section and smoot as is preferred, but it is within the scope of the invention to use a wire of non-circular, e.g. square or rectangular, cross-section and/or having a surface provided with projec¬ tions or other irregularities rendering the operation of the tool more effective. If the cross-section of the wire is non-circular, the wire may be twisted about its axis to have helically extending ridges or flutes.

Claims

1. A soil cultivator tool (18,18A) comprising an attac ment portion (19,19A) for attaching the tool to a motor-dri spindle (17), and an operating portion (20,20A) which is secured to the attachment portion and formed of a spring wi the spring wire being coiled about an axis (C) of rotation the tool extending through or located near the attachment portion, characterised in that the operating portion (20,20 is in the shape of a spiral when viewed in the direction of the axis (C) of rotation and is connected to the attachment portion (19,19A) at the inner end of the spiral.

2. A soil cultivator according to claim 1, characteris in that the spring wire is in the shape of a substantially conical helical coil and in that the extension (H) of the operating portion (20A) as measured parallel to the axis (C) of rotation is smaller than its extension (D) as measured perpendicularly to the axis (C) of rotation.

3. A soil cultivator tool according to claim 1 or 2, characterised in that the end section of the outermost turn the operating portion (20,20A) gradually approaches the nex inner turn in the radial direction.

4. A soil cultivator tool according to any one of clai 1 to 3, characterised in that the operating portion (20,20A) comprises at least one full spiral turn.

5. A soil cultivator tool according to any one of clai 1 to 4, characterised in that the operating portion (20,20A) comprises at least one full spiral turn and not more than three spiral turns, preferably not more than two and a half spiral turns.

6. A soil cultivator tool according to any one of claim 1 to 5, characterised in that the attachment portion (19,19A and the operating portion (20,20A) are formed of a single length of spring wire.

7. A soil cultivator tool according to any one of claim 1 to 6, characterised in that the largest dimension (D) of t operating portion (20,20A) as measured perpendicularly to th axis (C) of rotation is in the range of 50 to 80 mm and that the diameter or largest transverse dimension of the spring wire is in the range of 2.5 to 4 mm.

8. A soil cultivator, comprising a motor-driven spindle (17) and a soil cultivator tool (18,18A) according to any on of claims 1 to 7, the soil cultivator tool (18,18A) being releasably secured to the spindle with the axis (C) of rota- tion substantially coinciding with the axis of the spindle (17).