referring first to fig1 and 2 , the tool shown has an angled head 1 with a sole plate 2 extending substantially horizontally . the head accommodates two cultivating blades 3 , 4 projecting from the end of the head at an acute angle to the sole plate , as shown in fig2 . the upper portion 5 of the head extends upwardly at an angle of approximately 45 ° to the sole plate 2 and receives one end of a shaft in the form of a tubular stem 6 at the other end of which is located the handle 40 of the tool . the length of the stem 6 is such that , when the tool is held by the handle by an operator standing up , the tool blades 3 , 4 can be used to carry out surface cultivation of the soil . the blades 3 , 4 are driven by a motor 26 mounted in the head 2 within a casing 7 which is of clam shell construction and extends upwardly from the head perpendicular to the sole plate 2 . the end portions of the blades 3 , 4 are generally fork - shaped , each having three diverging prongs 8 . the blades are located one on top of the other and pivotally mounted within the housing formed by the casing 7 and sole plate 2 as described below for movement about an axis perpendicular to the plane of the blades 2 : the position of the axis is indicated at 9 in fig2 . the whole of a cultivating blade , removed from the tool , is shown in fig5 . the prongs 8 extend from a main body 11 of the blade in which , proceeding towards the other end of the blade , are formed a dome 43 , an aperture 12 , then a portion 13 of reduced width and finally , at the other end of the blade , an elongated aperture 14 . the aperture 12 which , as shown in fig5 is located on the longitudinal centre line of the blade , is used for the pivotal mounting of the blade within the tool head 1 . each blade has the same shape but one is turned over before being placed on top of the other with the aperture 12 in alignment . referring now also to fig3 and 4 , the motor 26 is attached to a gear housing 24 and has a drive shaft 44 which meshes with a gear 25 rotatably mounted in the housing 24 . fixed to the gear 25 are two cams 30 , 31 which are mounted on opposite sides of the axis of rotation of the gear 25 . each cam 30 , 31 is circular and is located within the elongated aperture 14 of its respective blade . the blades 3 , 4 are pivotally mounted on the gear housing 24 being pivotable about a bushing 45 passing through the aperture 12 in the blades and secured to the gear housing by a screw 46 . as a result , when the motor 26 is operated , the cams 30 , 31 will cause the blades 3 , 4 to reciprocate in antiphase relationship to one another about the bushing 45 ( see fig4 ) as indicated by the arrow 10 in fig3 . the sole plate 2 is secured by screws ( not shown ) to the casing 7 and the blades 3 , 4 are sandwiched between projecting portions of the sole plate 2 and the gear housing 24 . the forked end portions of the blades 3 , 4 project from the casing 7 through a slit 27 in the front end of the casing . the narrowed portion 13 of the blades ensure adequate clearance between the blades and adjacent parts of the tool head during reciprocal movement . in a central position the blades 3 , 4 are aligned with one another while at either end of their reciprocating stroke ( one end being shown in fig3 ) the relative movement of the prongs 8 of the two blades is about half the separation of adjacent prongs of the same blade . the tubular stem 6 of the tool is received in an aperture at the upper end of the tool head casing 7 and secured in any suitable manner . the other end of the stem 6 is similarly received and secured in an aperture in a downward - extending portion 33 of the tool handle 40 which is of clam shell construction . the stem 6 comprises , in the example illustrated , a metal tube 47 with a plastics insulating sleeve 48 . the tool handle resembles that of a garden spade , being generally rectangular with a central aperture , but mounted at right angles to the conventional direction . the power supply cord enters the tool through an aperture in the lower part of the handle , fitted with a cord protector 34 and the supply of power to the motor is controlled by a switch housed within the handle 40 and operated by an actuating member in the form of a switch bar or bar 35 on an upper tubular portion ( i . e . the grip ) of the handle . the longitudinal axis of the tubular portion of the handle 40 lies in the same plane as the longitudinal axis of the stem 6 . fig6 shows further details of the handle and indicates the location of a switch 36 within the handle and a pivotal mounting 37 of the bar 35 such that , by squeezing the handle grip , the bar 35 can be moved further into the tubular portion of the handle to operate the switch and actuate the motor 26 . the bar 35 is resiliently biased downwardly away from the tubular portion of the handle by an integral leaf spring 50 which extends perpendicular to the bar 35 and engages an inclined surface 51 within the handle . outward movement of the bar 35 is limited by engagement of the free end of the bar with a shoulder 52 formed on the handle . when the pressure on the handle grip is released , the switch bar 35 moves back to its original position and the switch 36 operates to disconnect the motor . the handle also incorporates an interlock arrangement to prevent accidental operation of the tool . more particularly , the handle houses a resiliently - biased lock off member 38 which extends across the top of the handle and has a downwardly extending portion 38a which in the neutral position of the member co - operates with the switch bar 35 to prevent operation of the bar . the lock off member 38 is provided with a pair of integral leaf springs 53 which engages bosses 54 inside the handle and bias the member 38 into its central , neutral position . operating buttons 39 are provided at each end of the member 38 and project at each end of the tubular portion of the handle so that the member 38 can be displaced from its central position by an operator pressing inwardly on whichever button is more convenient . when the bar 35 is released , the member 38 returns , under the action of the resilient bias , to its original position . normal operation of the tool is illustrated in fig1 . an operator wishing to cultivate soil 55 containing weeds 56 grips the tubular portion of the handle 40 with one hand and may grip the stem 6 with the other hand . with the tips of the blades 3 , 4 resting on the top of the soil the operator shifts one of the operating buttons 39 with the thumb of the hand gripping the handle and squeezes the handle thereby moving the switch bar 35 into the handle and operating the switch 36 . the motor 26 then reciprocates the blades 3 , 4 and as a result of the force exerted by the tool &# 39 ; s own weight , the blades 3 , 4 penetrate into the soil and thoroughly disturb it . weeds 56 in the vicinity of the blades will be freed from the soil as a result of the disturbances caused by the blades . any small roots in the path of the blades 3 , 4 will be cut by the blades . the operator can manoeuvre the tool with the blades remaining in the soil or can lift the tool away from the soil and set it down in another location to be weeded or otherwise cultivated . if the operator wishes to cut the tops off weeds , or the like above ground level the tool can be operated resting on its sole plate 2 with the blades 3 , 4 just clear of the ground . in this case the blades will cut off the vegetation with a shearing action . the tool can also be used to weed between paving stones or to trim the edge of a lawn . in these applications the tool is held in the orientation shown in fig7 with the blades 3 , 4 in vertical planes . the arrangement of the handle 40 enables the tool to be held comfortably in this orientation also . the blades 3 , 4 described above pivot about apertures 12 provided on the longitudinal centre line of the tool . it is however possible for the apertures 12 to be offset from the centre line as indicated by the dotted line position 12a in fig4 . this would enable the throw of the blades to be increased . the exact shaping of the forked ends of the blades can be varied : for example , fig8 shows an alternative form of blade in which the prongs 8 are less spread out and whereas the prongs of the blade shown in fig5 have rounded points at their ends those shown in fig8 have cut - off ends in which are formed small recesses 41 . the blades may be formed from mild steel and typical dimensions for the blade shown in fig5 are as follows : the dimensions of the blades shown diagrammatically in fig8 are similar except that the prongs are shorter ( typically , 4 . 5 cm ) and the angle between them is smaller ( typically , 10 °).
a cultivating tool comprises a housing , an electric motor mounted within the housing , a pair of soil working members which project from the housing , an elongate shaft connected at one end to the housing , and a handle at the other end of the shaft . the soil working members are of generally lamellar construction and arranged to be reciprocated relative to one another transverse to the direction from which they project from the housing and in adjacent parallel planes . the tool handle incorporates a switch with a lock off mechanism . in normal use of the tool the soil working members penetrate into soil to be cultivated and disturb the soil .