Tool extension attachment

Abstract: A tool extension attachment particularly for electrically powered tools comprises a main spar (10) carrying at its forward end a cradle (12) on which a tool such as a hedge trimmer (14) can be detachably mounted and having towards intermediate its ends a handle (20) on or adjacent which an on/off switch (22) is provided. A control arm (16) coupled by control rods (18) or levers or cables to the cradle, enables the tool to be adjusted in pan and tilt. A counterweight (28) is mounted at or near the rear end of the spar 10. The positions of the handle (20) and counterweight (28) are adjustable as in the weight of the counterweight to accommodate different tool weights. A shoulder strap 30 or a shoulder pad/harness 53 is provided to allow the weight of the equipment to be at least in part transferred to the shoulder of a user.

Description: Field of the invention This invention relates to an attachment according to the pre-characterising portion of claim 1 for a tool, (typically a power tool) to extend the normal range of operation to an increased distance from the user, especially in height. Such an attachment is known from US-A-4207675. The invention is of particular application to a power pruning saw or more especially a hedge trimmer, but is not limited to such devices which are mentioned by way of example only. Background to the invention In use of a domestic or an industrial hedge trimmer, the range of operation is normally limited to a height of the order of the height of a operator. Where trimming of a high hedge is required, ladders or steps have to be employed to enable the operator to access the higher parts of the hedge. Sometimes, as when a hedge is sited on top of a bank, the erection of some form of scaffolding is necessary. The same problem can arise with a power pruner or saw for cutting the overhead branches of trees, and with any powered tools such as drills, buffing and sanding tools, paint spraying apparatus, grinding tools and the like. US-A-4,760,646, DE-A-3904964 and CH-A-196896 disclose prior art embodiments of tool extension attachments which attempt to allow for trimming of high branches and the like. US-A-4,207,675 provides an extension handle for an electrically powered hand tool. It is an object of this invention to provide a solution to the aforesaid problem, whereby the use of ladders, steps or scaffolding is rendered unnecessary when using powered tools such as when using a hedge trimmer for trimming or cutting up to a certain level above the normal maximum possible height. The invention According to one aspect of the present invention, there is provided a power tool extension attachment comprising a main spar, a cradle pivotally mounted at a forward end of the main spar for detachably holding the tool, handle means joined to the spar at a position intermediate the ends thereof, control means on or adjacent the handle means for controlling operation of the power tool, control arm means mounted for movement relative to the main spar and force transfer means interconnecting the control arm means and the tool cradle, characterised in that the control arm means is pivotally mounted so that at least the angle of tilt of the axis of the tool is adjustable relative to the axis of the main spar by pivotal movement of the control arm means relative to the spar. Preferably, the cradle and the control arm are pivotally mounted relative to the main spar and interconnected so that not only the tilt but also the pan of for example a cutting blade driven by the tool can be adjusted, i.e. the angle of orientation of the cutting blade to the tool about its axis can be adjusted. Tilt of the tool cradle is preferably controlled by pivotal forward and backward movement of the control arm relative to the length of the main spar, whilst pan may be controlled by rotation of the control arm about the main spar. This control can be enabled by use of two force transfer means interconnecting the control arm and the cradle. The control means may for example control the supply of electrical power to an electrically powered tool from the region of the handle, where a socket may be provided for connection of a power supply lead. In use, the in-built power switch on the tool may be fixed in the "on" condition, and a power connecting lead extending from the handle region through the said control means will plug into the in-built power supply socket on the power tool. This connecting lead may incorporate a coiled section to accommodate expansion and reduction in length when the power tool is adjusted in position. The degree of tilt available will preferably be at least 90 degrees so that, in the case of a hedge trimmer for example, the horizontal flat top of a high hedge can be trimmed as well as its vertical sides. Preferably, behind the handle, the rear end of the main spar is adapted to carry a counterweight. A shoulder strap may be provided for assistance in supporting the weight of the equipment. Alternatively a shoulder pad or harness may be fitted to the spar between the handle means and the rear end of the main spar, so that the latter can be supported on the shoulder of a user. In this event the control arm preferably extends laterally on opposite sides of the spar and includes downward extensions forming two handles on opposite sides of the main spar, to be gripped by both hands of the user in much the same way as a bicycle handlebar is held by a cyclist, to enable the user to both lift, control and steer the main spar and the tool hand grips may be provided on the lower ends of the downwardly extending handles. The position of the control arm and/or handle means along the length of the spar may be adjustable, as may be the position and/or weight of the counterweight, to enclose different tool weights to be balanced. The force transfer means may comprise rods or cables or levers or any combination thereof. The control arm may for example comprise a lever pivotally mounted on the spar on the handle means or a pistol grip and trigger likewise mounted. Quick release locking means may be provided to allow the control means and/or the control arm to be secured in a desired position. The invention also extends to a kit of parts for construction of the afore-described power tool extension attachment. Thus, in accordance with a further aspect of the invention there is provided a kit of parts comprising a main spar which can be assembled from two or more spar lengths, means for assembly of a tool cradle and for mounting said cradle to a forward end of the main spar, handle means mounted on or mountable on the main spar intermediate the ends thereof said handle incorporating a control means for controlling operation of a power tool carried by the cradle, and either comprising or having mounted near thereto control arm means movable relative to the main spar and at least one force transfer means interconnectable between the control arm means and the cradle to enable at least the tilt of a tool carried thereon to be adjusted. While not limited thereto, the invention has particular applicability to an extension attachment for a hedge trimmer but any power tool may be fitted to an extension attachment embodying the invention. Description of embodiments An extension attachment in accordance with the invention will now be described by way of example with reference to the accompanying drawings, in which:- Figures 1 and 2 show a first embodiment of the attachment of the invention, with a power hedge trimming tool mounted thereto, in respective side views mutually at right angles; Figures 3 to 5 show details of a handle assembly, cradle assembly and control arm assembly, respectively; Figures 6 and 7 show the attachment and hedge trimmer mounted thereto, when in use for trimming the vertical side of a high hedge; Figure 8 shows the attachment and hedge trimmer mounted thereto, when in use for trimming the horizontal top of a high hedge; Figure 9 shows an alternative embodiment of the attachment of the invention with alternative handle assembly supported by means of a shoulder harness, when in use for trimming a high hedge; and Figure 10 shows details of the alternative handle assembly The illustrated and described embodiment supports an electrically powered hedge trimmer to enable the trimming of vertical sides of hedges up to about 3.8 metres high, and the trimming of flat tops of hedges up to about 3 metres high. The attachment provides for both tilt and pan adjustment, but pan adjustment is generally required only when trimming a vertical hedge side, enabling the operator to traverse sideways whilst maintaining the trimmer blade width parallel to the face being trimmed. The drawings illustrate the principle of the device, and a simple method of construction possible with minimum special tooling. This method of manufacture is merely an example, and improvements may be made for volume production by replacing fabricated assemblies with, e.g., injection mouldings or diecastings. The device is especially intended to be supplied in a part-assembled form, so that the packaged product is no longer than 1250 mm, for convenience of palleted transport, and easy display on shop shelving. The drawings show a typical and commonly used model of hedge trimmer, but the device is adaptable to enable a range of different models to be mounted thereto. Referring to Figures 1 and 2, the device or attachment comprises a main spar 10, a cradle 12 for the trimmer 14 pivotally mounted at the front end of the main spar, a control arm 16, two thrust transmitting means such as rods 18 interconnecting the control arm 16 and the cradle 12, a handle 20, an on/off switch 22 on the handle, a cable 24 connecting a power input socket 26 on the handle with a power input socket on the trimmer 14, a counterweight carrier 28 and a shoulder strap 30. These parts are illustrated in Figures 3 to 5 and now briefly described with reference thereto. The main spar 10 is made of tube, in three pieces that fit inside each other, and bolted together by the user, of strong, lightweight material, e.g. heat treated aluminium alloy or carbon fibre composite. The trimmer cradle 12 is a fabricated assembly made up of an inverted "U", of a channel section 32, that fits over the cross handle of the trimmer. Aircraft type rigging pins 34 with sprung ball detents are inserted through holes in this U member, to allow quick attachment or removal of the trimmer. Holes in different positions as necessary can be used for different models of trimmer. Extended side plates are permanently attached to the U member, and have pivots for a tubular axle beam 35, and clevis bearings 36 for control rods at the top. The axle beam has an offset clevis bracket, which is attached to the main spar pivotally at right angles to the axle. The control arm 16 is a bent tube of inverted "L" shape, fitted with a cycle type handgrip 38, that is mounted pivotally and axial vertically in a trunnion 40 that is pivotally attached to the main spar, in a direction parallel to the trimmer cradle axle. The position of this pivot is approximately two thirds of the way along the main spar, from the trimmer end. Above the trunnion, a cross tree beam 42 is pivotally mounted parallel to the trunnion axis, which carries a control rod clevis at each end. The thrust transmitting rods 18 are preferably also made of tube, each in two main parts, bolted together by the strong material, e.g. aluminium alloy. A through hole is drilled near to each end, parallel in axis. A domed plastics insert fits in each end, and is secured by the pivot pin fitted through the clevises at the control arm and trimmer cradle assemblies. The clevises form universal joints, with horizontal "U" members that pivot around their respective axles and plastics shoulder bushes, retained by pivot pins, with the domed inserts bearing against the axles, as indicated at 44. The thrust transmitting rods 18 may be replaced by levers or cables, typically a Bowden cable or cables. The handle 20 is made of non-conducting material for electrical safety, and is typically a two part injection moulding. The handle 20 is bolted to the main spar 10 a short way behind the control arm, and incorporates a momentary action push button switch 22, a standard garden appliance connector 26, internal cable clamp 46, and a grommeted cable outlet 48. Internal wiring connects the connector to the switch, where the outlet cable is also connected, and clamped before its outlet through the grommeted hole at the front. The cable 24 is routed from the handle around the main spar to a cable clamp on the bottom surface, and thence to the trimmer, terminating in a standard garden appliance connector. It can thus be seen that the supply cable lead can conveniently be plugged directly into the trimmer for independent use, or into the handle of the extension arm for use in that mode. The outlet cable has part of its length formed into a lightly sprung coiled length 50, which helps to tidily manage the variance in distance between the trimmer and the control arm during operation. The counterweight carrier 28 is a formed tray, mounted to the extreme end of the main spar, and is proportioned to accept a weight to counterbalance the moment of the front extension with the trimmer attached. This weight can conveniently be, e.g., two house bricks, which are commonly available. An elastic strap retains the bricks properly in place. The shoulder strap 30 is a golf bag type strap, suitably padded for comfort, and pivotally connected to an eye-bolt on the main spar, between the control arm and the handle, at the notional centre of gravity of the assembled device. In use the integral switch on the hedge trimmer is set to permanently on and, for safety, before the supply cable lead is plugged into the handle of the extension arm device. Some trimmers cannot be switched permanently on, so a supplied plastic clamp would be used in this case. With the strap over one shoulder, the device should approximately balance horizontally for the most convenient use. When the control arm is moved forwards or backwards, the trimmer tilts in the same direction. When the control arm is turned, the trimmer will also turn. The operations shown in Figures 6, 7 and 8 can therefore be achieved in a more convenient time and fashion than possible without the device. When the mode is for trimming the extremes in height, the user has to lift the device via the handle, to obtain extra reach. The effort in doing this is more than for the lower areas, as the benefit of support from the shoulder strap is lost, but would be occasional, not continuous effort. The overall weight of the device with trimmer and counterbalance is approximately the same as a full set of golf clubs, and for the average hedge, the time spent trimming would be minutes rather than hours. In an alternative embodiment as shown in Figure 9 spar 10' of the extension attachment is supported on a padded shoulder harness 53, with a quick release compliant pivot at its longitudinal centre of gravity. Operation of the attachment is achieved by use of the handle assembly 55 as shown in Figure 10. The handle assembly 55 includes dual control arms 57, 57' with hand grips 38, 38' connected by a torsion bar 59. Differential fore and aft movement of the arms 57, 57', enables pan adjustment. The arms 57, 57' spring back to their neutral position on relase due to the torsion bar. Movement of the arms for levers fore and aft, equally, enables simple tilting of the trimmer. A switch 62 is provided on the handle assembly to control the supply of power to the tool. This embodiment of the invention provides greater reach due to the pivot point being on the shoulder, less chance of the counterbalance weight hitting the ground due to increased elevation of the pivot point, and greater control as all functions are controlled by dual handles. The opposed ends 64, 66 of the two control lever arms 57, 57' are received in a bearing tube 68 which is carried transversely relative to the spar 10' by a bracket 70 to which is secured a clamp 72 for clamping around the tubular spar 10'. The ends 64, 66 are hollow to allow the strip torsion bar 59 to extend therethrough as shown in Figure 10. Pins 74, 76 driven through holes in the tubular lever ends 64, 66 and through aligned holes in the ends of the torsion bar 59, not only key the lever arms to the bar, but also retain the lever in the sleeve (tube) 68. The ends of the two rods (18', 18'') (one of which is visible in Figure 9 and is identified by reference numeral 18'), which are joined by the lever arms 57, 57', are attached thereto by pivoting joints 78, 80. The tool may be electrically powered as illustrated herein, or air-line powered or self-powered for example by an internal combustion engine or by any other known power means. Various modifications of the above described and illustrated arrangement are possible within the scope of the invention as defined in the appended claims.

Claims: Claims for the following Contracting States : DE, FR, NL A power tool extension attachment comprising a main spar (10, 10'), a cradle (12) pivotally mounted at a forward end of the main spar for detachably holding the tool (14), handle means (20, 57) joined to the spar at a position intermediate the ends thereof, control means (22, 62) on or adjacent the handle means for controlling operation of the power tool, control arm means (16; 57, 57') mounted for movement relative to the main spar and force transfer means (18) interconnecting the control arm means and the tool cradle, characterised in that the control arm means is pivotally mounted so that at least the angle of tilt of the axis of the tool is adjustable relative to the axis of the main spar by pivotal movement of the control arm means relative to the spar. An attachment according to claim 1, in which the force transfer means comprises a control rod (18; 18). An attachment according to claim 1 or claim 2, wherein tilt of the tool cradle is controlled by pivotal forward and backward movement of the control arm means relative to the length of the main spar. An attachment according to claim 1, or claim 2 or claim 3, wherein the cradle and the control arm means are pivotally mounted relative to the main spar and interconnected so that not only the tilt but also the pan of the tool is adjustable. An attachment according to claim 4, wherein pan of the tool cradle is controlled by rotation of the control arm means about the main spar. An attachment according to claim 4 or claim 5, wherein tilt and pan control as aforesaid is enabled by use of two force transfer means interconnecting the control arm means and the cradle. An attachment according to claim 6, in which the two force transfer means comprise a pair of parallel connecting rods. An attachment according to any of claims 1 to 7, in which the tool is electrically powered and electric current therefor is supplied for the control means through a cable, part of which is coiled to accommodate expansion and reduction in length when the tool is adjusted in position. An attachment according to any of claims 1 to 8, wherein behind the handle means, the main spar is adapted to carry a counterweight. An attachment according to any of claims 1 to 9, wherein support means is provided for transferring at least some of the weight of the equipment to the shoulder of the user. An attachment according to any of claims 1 to 10, wherein the control arm means comprises two control arms (57, 57') which extend laterally on opposite sides of the main spar and downward extensions thereof comprise the handle means (57, 57') and hand grips (38, 38') are provided thereon to enable the handle means to be gripped by the user using both hands, in use. An attachment according to claim 11, in which the control arms and force transfer means are so arranged that differential fore and aft movement of the control arms (57, 57') causes the tool to pan, whilst equal fore and aft movement of the control arms (57, 57') adjusts said angle of tilt. A kit of parts of a power tool extension attachment according to any of the preceding claims. comprising a main spar which can be assembled from two or more spar lengths, means for assembly of a tool cradle and for mounting said cradle to a forward end of the main spar, handle means mounted on or mountable on the main spar intermediate the ends thereof, said handle incorporating a control means for controlling operation of a power tool carried by the cradle, and either comprising or having pivotally mounted near thereto control arm means pivotally moveable relative to the spar and at least one force transfer means interconnectable between the control arm means and the cradle to enable at least the tilt of a tool carried thereon to be adjusted. Claims for the following Contracting State : GB A power tool extension attachment comprising a main spar, (10, 10') a cradle (12) pivotally mounted at a forward end of the main spar for detachably holding the tool (14), handle means (20, 57) joined to the spar at a position intermediate the ends thereof, control means (22, 62) on or adjacent the handle means for controlling operation of the power tool, control arm means (16; 57, 57') mounted for movement relative to the main spar and force transfer means (18) interconnecting the control arm means and the tool cradle, characterised in that the control arm means is pivotally mounted so that at least the angle of tilt of the axis of the tool is adjustable relative to the axis of the main spar by pivotal movement of the control arm means relative to the spar, the control arm means comprising two control arms which extend laterally on opposite sides of the main spar and downward extensions thereof comprise the handle means (57, 57') and hand grips (38, 38') being provided thereon to enable the handle means to be gripped by the user using both hands, in use. An attachment according to claim 1, wherein the cradle and the control arm means are pivotally mounted relative to the main spar and interconnected so that not only the tilt but also the pan of the tool is adjustable. An attachment according to claim 2, in which the control arms and force transfer means are so arranged that differential fore and aft movement of the control arms (57, 57') causes the tool to pan, whilst equal fore and aft movement of the control arms (57, 57') adjusts said angle of tilt. An attachment according to claim 2 or 3, wherein tilt and pan control as aforesaid is enabled by use of two force transfer means interconnecting the control arm means and the cradle. An attachment according to claim 4, in which the force transfer means comprise a pair of connecting rods. An attachment according to any of claims 1 to 5, in which the tool is electrically powered and electric current therefor is supplied for the control means through a cable, part of which is coiled to accommodate expansion and reduction in length when the tool is adjusted in position. An attachment according to any of claims 1 to 6, wherein, behind the handle means, the main spar is adapted to carry a counterweight. An attachment according to any of claims 1 to 7, wherein support means is provided for transferring at least some of the weight of the equipment to the shoulder of the user. A kit of parts of a power tool extension attachment according to any of the preceding claims, comprising a main spar which can be assembled from two or more spar lengths, means for assembly of a tool cradle and for mounting said cradle to a forward end of the main spar, handle means mounted on or mountable on the main spar intermediate the ends thereof, said handle incorporating a control means for controlling operation of a power tool carried by the cradle, and either comprising or having pivotally mounted near thereto control arm means pivotally moveable relative to the spar and at least one force transfer means interconnectable between the control arm means and the cradle to enable at least the tilt of a tool carried thereon to be adjusted.

Inventors: BAILEY PETER J D, BAILEY, PETER J.D.
Applicants: BAILEY PETER J D, BAILEY, PETER J.D.
Application year: 1993
Main classification: B25G1
IPC codes: A01G3