Hedge Trimmer

Abstract

A hedge trimmer having a pole 12 and a body 14 mounted to the pole, a first blade and a second blade mounted to the body, a motor 24 connected to at least one of the blades for driving the blade to mo

Description

FIELD OF THE INVENTION This invention relates to a hedge trimmer. Notwithstanding that the generally-used name for devices such as that of the present invention is a “hedge trimmer”, as with the known devices of this type the device of the present invention can be used for trimming and cutting foliage other than hedges. The hedge trimmer of the present invention is designed as a gardening implement for manual operation, i.e. to be carried by a user during use to trim garden hedges, bushes and the like. It is therefore distinct from industrial machines which are typically carried by a tractor and suited to trimming hedgerows bordering fields for example. The hedge trimmer is also distinct from garden strimmers and chainsaws which have different structures and operations, notwithstanding that both of those could be used to trim hedges. BACKGROUND TO THE INVENTION A hedge trimmer has first and second elongate blades which lie close to each other and which can slide relative to each other. The blades have cooperating rows of teeth. One or both of the blades is driven to move reciprocally so that the rows of teeth slide towards and across each other. Branches and leaves are cut by a scissor action between the teeth of the blades. The teeth of the first blade have relatively sharp leading and trailing edges, which leading and trailing edges alternate as the blade reciprocates. The teeth of the second blade may be substantially identical to the teeth of the first blade, but often the form of the respective teeth differ. In particular, the teeth of the second blade may not have sharpened edges, the teeth of the second blade effectively comprising means to hold the branches and leaves as they are cut by the teeth of the first blade. In some hedge trimmers the second blade is stationary relative to a body of the hedge trimmer. In many hedge trimmers, however, the second blade also moves reciprocally, in the opposite direction to the first blade. One benefit of having both blades moving in opposing directions is that the stroke of the first blade (i.e. the total distance by which the first blade must move relative to the body) is reduced. Another benefit is that there are no stationary teeth which might become stuck on a branch during use. Hedge trimmers may be powered by mains electricity, by battery, or by an internal combustion engine. The present invention is designed to be powered by batteries but the invention is also applicable to the other power sources. A first design of hedge trimmer has a body with handles for a user to hold with two hands. An end of the first blade, and an end of the second blade, are connected to the body. A motor is located in the body and is connected to the blades by driving elements such as cams and / or connecting rods which convert the rotary output of the motor into opposing reciprocating movement of the blades. The body carries an actuating switch or trigger by which the user can actuate the motor. During use of this first design of hedge trimmer the user may approach a section of hedge to be trimmed and manipulate the body by way of the handles so that the blades are moved in a sequence of swinging arc-like movements, either generally in the up / down directions or generally in the left / right directions (or more typically a combination of these general directions) across the branches and leaves of the hedge. The user can stand in a suitable location close to the hedge whilst a section of hedge is trimmed to the desired degree, with the blades being moved by the user’s arms so that the arc-like movements are generally centred around the user’s shoulders. When the section of hedge has been trimmed the user can move the blades away from the hedge before moving along the hedge to trim a new section. A hedge will therefore typically be trimmed in a sequence of relatively small sections, with the size of each section largely being determined by the reach of the user. This method of operation is represented in Fig. 1 with the arrows representing the path of movement of the blades across the hedge as a chosen section of the hedge is trimmed. Alternatively, the user can walk slowly along the hedge, trimming the areas within reach, raising his or her arms to reach higher foliage and bending to reach low foliage. It is noted that raising and lowering the users arms and bending to cut low foliage is in itself tiring; with the addition of the weight of the trimmer itself, the process is often exhausting for the average non-professional gardener. To enable the hedge trimmer to cut foliage in whichever direction the blades are being moved across the hedge, the first and second blades each have a row of teeth along both of their opposing edges. The cooperating rows of teeth along one of the edges can therefore be used to cut foliage when the hedge trimmer is being moved to the left (for example) and the cooperating rows of teeth along the opposing edge can be used to cut foliage when the hedge trimmer is being moved to the right (for example). Another design of hedge trimmer is a pole hedge trimmer. This design differs from the hedge trimmer described above in that the body containing the motor is mounted to one end of an elongate rod or pole. The pole is typically around 1 metre or more in length and it is intended that the user holds and manipulates the hedge trimmer by way of the pole. The actuating switch or trigger for the motor is therefore typically mounted to the pole. A handle may also be mounted to the pole, although in many pole hedge trimmers the user grasps the pole directly in a chosen position and there is no dedicated handle. Pole hedge trimmers are generally used in similar methods to those described above. However, the pole increases the user’s reach and thereby increases the size of the sections of hedge which can be trimmed without the user having to move along the hedge. The pole also enables the user to reach higher up a hedge, and in many cases the user can reach the top of a hedge which could only be reached with the first design of hedge trimmer by way of a ladder. Pole hedge trimmers are typically electrically operated, and many are battery powered. In a battery powered pole hedge trimmer the battery pack can be located at the opposite end of the pole to the body and blades in order to better balance the weight of the hedge trimmer along the pole, and thereby better balance the weight relative to the user’s grip. In the first design of hedge trimmer described above the orientation of the blades is typically fixed relative to the body and to the handles. It is therefore necessary for the user to adjust the orientation of the whole hedge trimmer in order to adjust the orientation of the blades relative to the hedge. Some pole hedge trimmers have an articulating joint whereby the angle of the blades relative to the pole can be adjusted. The ability to adjust the angle of the blades relative to the pole can make it significantly easier to trim some parts of the hedge. The articulating joint is typically located between the pole and the body. In one design of pole hedge trimmer the range of articulation is a little over 90°. In order to enable many years of effective use, the blades of most hedge trimmers are necessarily robust and therefore relatively heavy. The weight of the blades in particular is increased by the requirement to have a row of teeth along both of the blades’ opposing edges. The weight of the blades can be reduced by reducing their length but that directly reduces the height to which the hedge can be trimmed without a ladder, and also reduces the size of the sections of hedge which can be trimmed without the user moving along the hedge. In both cases this can increase the time taken to trim a hedge. There is therefore a compromise between increasing the length of the blades in order to reduce the time taken to trim a hedge, and reducing the length of the blades to make the hedge trimmer lighter and easier to hold and manipulate. The user necessarily has to support the weight of the hedge trimmer as it is being used. The user also has to control the orientation of the blades accurately during use so that the hedge is trimmed by a consistent and desired amount. Controlling the orientation of the blades is made more difficult because most or all of the weight of the blades and most or all of the weight of the body are offset from the grip of the user. Whilst some of that weight can be balanced by the battery pack in a battery powered pole hedge trimmer, the user must still control a significant weight, often for a significant period of time, as the hedge trimmer is manipulated during use. Most of that support must typically be provided by the arms and shoulders. Fatigue, particularly in the arms and shoulders, is a major factor in determining the length of time for which many users can use a hedge trimmer, especially when the hedge trimmer is lifted towards or over head-height. SUMMARY OF THE INVENTION It is an object of the invention to provide a pole hedge trimmer which is easier and more comfortable to use for extended periods of time. It is another object of the invention to provide a hedge trimmer in which the weight is better balanced at the pole and therefore at the grip of the user. It is another object of the invention to provide a hedge trimmer having an articulating joint, in which the range of articulation is significantly greater than that provided by the known hedge trimmers. It is another object of the invention to provide a hedge trimmer which is suited to a different method of use than that described above, and in particular to a method of use which is expected to reduce or slow the onset of fatigue for many users. According to a first aspect of the invention there is provided a hedge trimmer having a pole and a body mounted to the pole, a first blade and a second blade mounted to the body, a motor connected to at least one of the first blade and the second blade for driving the respective blade to move, the first blade and the second blade having respective ends, in which the first blade and the second blade are mounted to the body between their respective ends. Alternatively stated, the blades are not mounted to the body in cantilever as is the case with the known hedge trimmers, but instead the mounting locations of the first blade and the second blade are each spaced away from the respective ends of the blades. Mounting the blades to the body in this way can reduce the offset weight of the blades relative to the body, and also relative to the longitudinal axis of the pole. This has a particular benefit when the blades are articulated as the offset weight is less (or in some cases is not) dependent upon the angle of articulation. In this respect it will be understood that when the known pole hedge trimmers are used with the blades aligned substantially with the pole the centre of gravity of the blades acts at a point which is at or close to the longitudinal axis of the pole. However, when the blades are adjusted to a large angle of articulation their centre of gravity is a relatively large distance from the longitudinal axis of the pole. The offset weight of the blades seeks to twist the pole substantially about its longitudinal axis and that twisting moment must be countered directly by the user’s grip upon the pole; this can cause significant and rapid fatigue, in particular in the user’s forearms. With the present invention, however, the centre of gravity of the blades can remain at or close to the longitudinal axis of the pole for all angles of articulation. Preferably, the mounting locations of the first blade and the second blade are located substantially mid-way between the ends of the blades. Such a mounting location minimises the movement of the centre of gravity relative to the pole as the blades are articulated. Notwithstanding the significant benefits which are described above in relation to blades which can be articulated, the invention can be used in a hedge trimmer without an articulating joint if desired. Preferably, however, the first and second blades are mounted by way of an articulating joint. Preferably also, the range of articulation at the articulating joint is greater than 180°, and desirably is greater than 210°, and ideally is around 230°. It will be appreciated that such ranges of articulation far exceed the range of articulation available with known hedge trimmers, and help to facilitate the new method of operation as described below. The motor is preferably mounted to the body. Whilst mounting the motor to the body (and thereby immediately adjacent to the blades) is a common design feature it is not universal and in some pole hedge trimmers the motor is located at one end of the pole with the body and blades at the other end of the pole. In such arrangements the motor is connected to the blades by way of a drive shaft which runs along the pole. A bevel gear can be provided at the pivot axis to accommodate the articulation of the blades. The present invention can utilise a similar arrangement if desired. Desirably, the first blade has a row of teeth along only one of its opposing edges and the second blade has a row of teeth only along its corresponding edge. Alternatively stated, the blades have teeth along only one of their edges and can therefore trim foliage when moving only in one direction across the hedge. Whilst it may be considered that the ability to cut foliage in one direction only is disadvantageous, this is suited to the new method of operation described below, and has many practical benefits as also described below. One practical benefit is that the motor can be located to “follow” the blades as they are moved across the hedge. It will be understood that the motor will often occupy a large proportion of the body of the hedge trimmer and the location and size of the motor will usually determine the location and size of the body. The motor (and consequently the body) is generally wider and more bulky than the cutting blade and can hinder the blade from passing freely through the hedge as foliage is cut. Alternatively stated, with the known hedge trimmers it is often necessary to push a part of the body through the hedge as foliage is cut. Providing blades with teeth along only one edge enables the motor (and consequently much of the body) to be offset from the blades, and in particular to be located alongside the opposing edge of the blades (i.e. the edge without teeth). It can thereby be arranged that the teeth of the blades will always lead the motor (and much of the body) as they cut foliage. The blades can therefore pass freely through the uncut foliage with the motor and body trailing behind. In order to cut foliage in the opposite direction the user can simply turn the hedge trimmer around so the blades lead the body in the opposite direction. Another practical benefit is that it can be easier to balance the weight of the blades relative to the longitudinal axis of the pole if the blades have only one row of teeth. In particular, it can be arranged that the weight of the motor acts to one side of the longitudinal axis of the pole and the weight of the blades acts to the other side of the longitudinal axis. The combined weight of these relatively heavy components can thereby be better balanced relative to the pole and their combined centre of gravity can be relatively close to (or coincident with) the longitudinal axis of the pole, which can reduce the fatigue of the user. This benefit can be felt whether or not the blades can articulate. Another practical benefit is that the avoidance of two rows of teeth along both of the opposing edges of the blades can reduce the weight of the blades and therefore directly contribute to making the hedge trimmer lighter and easier to manipulate (and also reducing the fatigue of the user). It is also easier to balance the weight of lighter blades with the weight of the motor at or close to the longitudinal axis of the pole. A further practical benefit is that the avoidance of two rows of teeth can reduce the friction which the blades generate as they move relative to each other. It will be understood in particular that removing a row of teeth from the first and second blades can directly reduce the friction between the blades. Also, with rows of teeth along both of the opposing edges of the blades, all of the teeth generate friction when they are cutting and not cutting (i.e. when they are leading and trailing); at any point in time only one of the two rows of teeth of each blade is being used to cut foliage and for approximately half of the total period of use one row of teeth on each blade is creating friction without cutting any foliage. Avoiding the rows of teeth along one of the opposing edges of the blades can thereby reduce the frictional load upon the motor, enabling the use of a smaller and lighter motor, and if desired also a smaller and lighter battery pack. Preferably, the first blade and the second blade are mounted for opposing reciprocal movement relative to the body. Thus, whilst it will be understood that most of the benefits of the invention will apply to a hedge trimmer in which the first blade reciprocates relative to a fixed second blade, providing two oppositely movable blades is beneficial for the reasons set out above. A recognised disadvantage of two oppositely movable blades is that two sets of drive elements are required to convert the rotary drive of the motor into reciprocating movement of the blades. Two sets of drive elements are necessarily heavier than the single set of drive elements required for a single movable blade. However, in embodiments of the present invention which have rows of teeth along only one edge of the blades, the weight saved by removing the opposing rows of teeth is expected to be significantly greater than the weight penalty of adding a second set of drive elements. In addition, the increased weight of two sets of drive elements can be balanced with an offset motor and blades as discussed above. Preferably, the body has a pivotable part which pivots with the blades as the blades articulate, the pivotable part moving about a pivot axis which provides the articulating joint for the blades. Desirably, the motor is located in the pivotable part of the body and therefore pivots as the blades articulate. This enables the motor to move with the blades as the blades articulate and avoids the requirement for a complex drive connection between the motor and the blades. Preferably, the centre of gravity of the pivotable part is located at or close to the pivot axis. It will be understood that the weight of the pivotable part comprises the combined weight of the blades and other components which are mounted to the pivotable part (including the motor in preferred embodiments). Since those components move together as the blades articulate they have a single combined centre of gravity. If the centre of gravity is located at or close to the pivot axis the centre of gravity will move by only a small distance (if at all) as the blades articulate. The offset weight which the user must support therefore remains consistent as the blades articulate. Preferably, the centre of gravity of the body is located at or close to the longitudinal axis of the pole. It will be understood that locating the centre of gravity of the body close to the longitudinal axis of the pole minimises the offset weight which the user must support through their grip upon the pole. It is therefore highly desirable for the centre of gravity to be at or close to the longitudinal axis of the pole, preferably for all angles of articulation of the blades. Ideally therefore, the user has to counter or support only a small offset weight at most, and that offset weight is substantially consistent for all angles of articulation of the blades. In common with the known hedge trimmers, the motor has a drive shaft which is connected to drive elements which convert the rotary movement of the drive shaft into linear reciprocating movement of the blades. Preferably, a cam is mounted to the drive shaft. The cam desirably has a substantially circular periphery which is located in a substantially circular recess at one end of a connecting rod, the other end of the connecting rod being connected to a blade. The centre of the cam is offset from the drive shaft whereby when the drive shaft rotates the cam rotates eccentrically. The blade is guided to move linearly whereby the complex reciprocating movement of the connecting rod is converted into linear reciprocation of the blade. In preferred embodiments in which both of the blades move relative to the body, there are two cams mounted to the drive shaft with their centres offset in opposing directions, and a separate connecting rod for each of the blades. Desirably, the body has a mounting part for connection to the pole. In known fashion, the pole is preferably releasably mounted to the mounting part. The ability to remove the body from the pole is primarily for ease of packaging and transportation and it is not intended that the hedge trimmer will be used with the pole disconnected from the body. In practical applications the motor is an electric motor and the battery pack for the motor is preferably located at the end of the pole opposing the body whereby operation is prevented when the pole is removed. In addition, mounting the relatively heavy battery pack at the opposing end of the pole enables the hedge trimmer to be better balanced along the length of the pole. Preferably, the articulating joint is located between the pivotable part of the body and the mounting part. There are two convenient options for adjusting the articulation angle of the blades. Firstly, the articulating joint may incorporate a locking mechanism, which when operated by the user allows the angle of the blades relative to the pole to be adjusted. Secondly, the articulating joint can be adjusted remotely, for example by way of a control handle mounted to the pole. In one embodiment of the second option the articulating joint has a pulley which is engaged by a pivot belt. Preferably the pivot belt extends along the pole, ideally internally of the pole. Preferably, a pivot handle is movably mounted to the pole and the pivot belt is connected to the pivot handle. It can thereby be arranged that movement of the pivot handle relative to the pole causes rotation of the pulley and pivoting of the pivotable part of the body relative to the mounting part. Desirably, the pivot belt is a continuous loop. Preferably, the pivot handle is movable along the longitudinal axis of the pole. The pivot handle can have a continuous range of movement relative to the pole. Preferably, however, the pivot handle has a series of discrete locations at which it can be positioned relative to the pole whereby to define a number of discrete articulation angles for the blades. The discrete locations are preferably defined by detent positions of the handle. As above stated, it is a particularly beneficial feature of the invention that the articulating joint is at the centre of gravity of the body and the longitudinal axis of the pole, which ensures that the weight is evenly balanced regardless of the angle of articulation of the blades. Unlike the known hedge trimmers therefore, the hedge trimmer according to the present invention is as easy and comfortable to use with the blades perpendicular to the longitudinal axis as it is with the blades parallel with the longitudinal axis (and is similarly easy and comfortable to use for all angles of articulation). This enables the user to trim a hedge in a different method to that described above. In particular, the user can set the blades at a suitable angle of articulation to trim a chosen portion of the hedge (for example the bottom portion of the hedge) and can move along the hedge trimming the chosen portion of the whole length of the hedge in one continuous run. The user can then set the blades at another suitable angle of articulation for trimming another portion of the hedge (for example the portion immediately above the bottom portion) and can move back along the hedge trimming the chosen portion of the whole length of the hedge in a second continuous run. The user can repeat the procedure until the whole hedge has been trimmed, and can of course trim the same portions of the hedge repeatedly if that is desired. This method of operation is represented in Fig.2, with the arrows showing the path of movement of the blades across the hedge as the hedge is trimmed. Accordingly, whereas the conventional way to trim a hedge is by way of repeated arc-like movements across a chosen section of hedge, the present hedge trimmer enables an alternative method in which the hedge is trimmed in substantially horizontal strips or layers, with the hedge trimmer being adjusted (i.e. the blades being articulated) as required only when a chosen strip of the whole hedge has been trimmed. An unexpected benefit of this new method of hedge trimming is the creation of stripes in the hedge, similar to the stripes which are visible on a freshly cut lawn when cut by a lawnmower with a roller. The stripped effect can be appealing to users and unique to this new hedge trimmer. It has been found that this striped effect is more enduring than those seen in a lawn, remaining clearly visible for several weeks. It will be understood that since the hedge trimmer is not being used to trim separate sections in arc-like movements as with the known hedge trimmers, it is not required to have rows of teeth along both of the opposing edges of the blades, and one edge of the blades can remain the leading edge throughout the above procedure. The user can choose to move along the hedge in the left-to-right direction to trim a particular strip of the hedge, and in a right-to-left direction to trim the same or a different strip of the hedge, setting the angle of articulation accordingly; the large range of articulation which is provided for the blades enables the toothed edge of the blades to remain the leading edge for both directions of travel. It will also be understood that the above method of use avoids the user having to lift and lower the hedge trimmer repeatedly during use which significantly reduces the effort required, especially by the user’s arms and shoulders. In practice, the user can articulate the blades to a position which is suitable for the chosen strip of hedge to be trimmed and at which the user can hold the pole comfortably, without needing to extend their arms. As the user walks along the hedge trimming the chosen strip of the hedge it is not necessary to move the arms relative to the user’s body so that the fatigue in the user’s arms and shoulders is minimised. It will be understood that the user will likely have to hold the body of the hedge trimmer above head height in order to trim higher strips of the hedge, as is the case with the known hedge trimmers. Notwithstanding that supporting a weight above head height can quickly cause fatigue, the ability for the user to adopt the most comfortable position for their arms as the higher strips of hedge are trimmed will reduce the fatigue as compared to the known methods of operation. The manufacturers of many of the known battery powered hedge trimmers appreciate that it is not necessary for the battery to contain sufficient energy for more than 20-30 minutes or so of use as few users remain comfortable holding and manipulating the hedge trimmer in the known arc-like movements for greater periods of time. It is appreciated that the reduction in fatigue which the present invention can provide might require a larger battery pack but since the battery pack is preferably located at the end of the pole opposed to the body a heavier battery pack would likely have less significance for users of this new design of hedge trimmer. According to a second aspect of the invention there is provided a hedge trimmer having a pole and a body mounted to the pole, a first blade and a second blade mounted to the body, a motor connected to at least one of the first blade and the second blade for driving the respective blade to move, the first blade and the second blade being mounted for articulating movement relative to the pole, the angle of articulation being greater than 180°. Embodiments according to this second aspect share the benefits of the greater articulation which are described in the application, some of which benefits apply to hedge trimmers in which the blades are mounted in cantilever. According to a third aspect of the invention there is provided a hedge trimmer having a pole and a body mounted to the pole, a first blade and a second blade mounted to the body, a motor connected to at least one of the first blade and the second blade for driving the respective blade to move, the first blade and the second blade each having teeth along only one of their respective opposing edges. Embodiments according to this third aspect share the benefits of the single rows of teeth which are described in the application, some of which benefits apply to hedge trimmers in which the blades are mounted in cantilever, and also to hedge trimmers in which the blades do not articulate. The optional features which are described in relation to the first aspect of the invention can also be utilised in the second and / or third aspects of the invention where compatible. Those optional features are not repeated for the second and / or third aspects to avoid unnecessary repetition. BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will now be described in more detail, by way of example, with reference to the accompanying drawings, in which: Fig.1 represents a known method of trimming a hedge with a known hedge trimmer; Fig.2 represents a method of trimming a hedge for which the present hedge trimmer is particularly suited; Fig.3 represents a hedge trimmer according to the present invention with the blades at a first angle of articulation for cutting a strip of the hedge in the method of Fig.2; Fig.4 represents the hedge trimmer of Fig.3 with the blades at a second angle of articulation for cutting a higher strip of the hedge in the method of Fig.2; Fig.5 shows the hedge trimmer of the present invention with the blades at the first angle of articulation; Fig.6 shows the hedge trimmer of the present invention with the blades at the second angle of articulation; Fig.7 shows a perspective view of the hedge trimmer of Fig.6; Fig.8 represents the longitudinal axis of the pole and the articulation of the blades of the hedge trimmer; Fig.9 shows a perspective view of the hedge trimmer; Fig.10 shows an enlarged view of the body and blades of the hedge trimmer; Fig.11 shows a view similar to that of Fig. 10 but with the blades articulated at a different angle and with the protective shroud for the drive elements removed; Fig.12 shows the motor, drive elements and blades of the hedge trimmer; Fig.13 shows a part of the hedge trimmer in sectional view; Fig.14 shows another part of the hedge trimmer in sectional view; Fig.15 shows a part of the hedge trimmer with the blades at one end of their range of articulation; Fig. 16 shows the part of the hedge trimmer with the blades at the other end of their range of articulation; Fig.17 shows the whole hedge trimmer with the blades articulated as in Fig.16; Fig.18-20 represent the longitudinal axis of the pole and the offset weight of the body and blades at different angles of articulation. DETAILED DESCRIPTION Figs. 1 and 2 represent two methods of trimming a hedge. Fig.1 represents the known, widely used, method which is described above. Fig.2 represents an alternative method and whilst this alternative method could be utilised with the known hedge trimmers, it is especially suitable with the present invention and offers significant advantages as described herein. In the method of Fig.1 the user manipulates the hedge trimmer (not shown) so that the blades are moved in a sequence of swinging arc-like movements 1 across a chosen section of the hedge 2. In Fig.1 the arc-like movements 1 are generally in the left / right directions but the user may also move the blades in the up / down directions (or more typically a combination of these general directions). The user will typically stand still until the chosen section of hedge has been trimmed to the desired degree. In Fig.1 the chosen section of the hedge 1 is the left-hand end of the hedge and the user can reach to the top of the hedge without a ladder whereby the user can trim the full height of the chosen section of hedge before moving along the hedge to the right to trim the next section in a similar way. It will be understood that the arrows 1 do not necessarily show the precise path of the blades across the hedge and are intended solely to represent the series of arc-like movements which are typical of this known method. It will be understood that the arc-like movements 1 which are represented in Fig. 1 will be extended if the user also moves along the hedge 2 as the hedge is being trimmed. Nevertheless, cutting the hedge 2 in a series of relatively short sections as is represented in Fig. 1 is a widely recognised method of use of a conventional hedge trimmer. In the method of Fig.2, on the other hand, the user trims the hedge 2 in a series of substantially horizontal portions or strips 4,5 along the complete length of the hedge. The strips 4 are trimmed with the user walking along the hedge from left-to-right whereas the strips 5 are trimmed with the user walking along the hedge from right-to-left. Clearly, the user can choose to trim less than the complete length of the hedge in one strip if desired, but Fig.2 represents the significant difference between the two methods of use. It will be understood that a user could decide to use a known hedge trimmer, including a known pole hedge trimmer, in a method of use similar to that represented in Fig.2, but that would be unusual and the known hedge trimmers are primarily used in the method represented in Fig. 1. A hedge trimmer 10 according to the present invention in use trimming the hedge 3 is shown in Figs. 3 and 4, and also in Figs. 5 and 6. The hedge trimmer 10 has a pole 12, a body 14 mounted to the pole 12 and a pair of blades 16, 18 mounted to the body 14. It will be seen that the blades 16, 18 are mounted to the body 14 between their respective ends, i.e. the blades 16, 18 project in opposing directions from the body 14. It will also be seen that the blades 16, 18 can articulate or pivot relative to the pole 12, Figs.3 / 5 and Figs.4 / 6 showing two of the possible angles of articulation. The user is not shown in Figs. 3 and 4 but it will be understood that the user will hold the pole 12 in two hands during use and will support and manipulate the hedge trimmer by way of their grip upon the pole 12. The user chooses the suitable angle of articulation of the blades as shown in Fig.3 in order to enable the comfortable trimming of the bottom portion of the hedge 3. The user can grip the pole 12 in the orientation shown in Fig.3 and walk along the hedge to trim a bottom strip 4 of the hedge 3 such as that represented in Fig.2. The user chooses another suitable angle of articulation of the blades as shown in Fig.4 in order to enable the trimming of a higher portion of the hedge 3. Accordingly, the user is able to grip the pole 12 in the orientation shown in Fig.4 and to walk along the hedge to trim a higher strip 4 of the hedge 3 such as that represented in Fig.2. The hedge trimmer 10 is shown in side view in Figs. 5 and 6 in greater detail, with the blades 16, 18 at the angles of articulations of Figs. 3 and 4 respectively. The hedge trimmer 10 is also shown in Fig.7 in perspective view with the blade at the angle of articulation of Fig.4. It will be seen from Fig.7 that the blades 16, 18 have teeth 20 along only one of their opposing edges. In Figs. 3-6 the teeth are facing out of the page towards the viewer. It will be understood that to trim the hedge 3 the blades must be moved across the hedge with the teeth 20 leading, so that the toothed edge will be the leading edge of the blades 16, 18 in use. Unlike the known hedge trimmers therefore, the blades 16, 18 have no teeth on their opposing, trailing, edge. Figs. 3 and 4 therefore show the hedge trimmer 10 trimming a strip 4 of the hedge in the method represented in Fig.2, i.e. with the user moving along the hedge from left-to-right in Fig.2 and towards the viewer in Figs. 3 and 4. To trim a strip 5 of the hedge when moving right-to-left as represented in Fig.2 it is necessary to reorient the hedge trimmer 10 so that the teeth 20 are leading in that direction. The curved arrow in Fig.8 represents a portion of the range of articulation of the blades 16, 18 relative to the pole 12. The total range of articulation of one design of hedge trimmer is shown in Figs. 15 and 16. Specifically, Fig.15 shows one extreme end of the range of articulation, and in this embodiment the angle between the longitudinal axis A-A of the pole and the cutting line C-C of the blades (see Fig.17) is 13°. Fig.16 shows the other extreme end of the range of articulation, and in this embodiment the angle between the longitudinal axis A-A and the cutting line C-C is 243°. It will be understood that such a large range of articulation readily enables the user to choose a suitable angle of articulation for trimming a particular strip 4 or 5 of the hedge 3, with the teeth 20 leading, in a chosen walking direction along the hedge. In practical hedge trimmers the teeth 20 of the blades 16, 18 may be identical or not identical but the form of the teeth is incidental to the present invention and the same reference numeral is therefore used for the row of teeth on each of the blades. Fig.9 shows another perspective view of the hedge trimmer 10, including more detail upon the pole 12 and the body 14. In known fashion, the battery pack 22 is located at the end of the pole 12 opposed to the body 14. The battery pack 22 is removable to facilitate recharging and replacement if required. The motor 24 is mounted in the body 14 and is connected to the blades 16, 18 by drive elements as described below. A protective shroud 26 protects the user from the moving drive elements, and also helps to prevent cut foliage and sap from engaging and perhaps fouling the drive elements. A trigger 28 to actuate the motor 24 is located adjacent to the battery pack 22, the motor being connected to the battery pack and trigger by wires running along the inside of the hollow pole 12. Importantly, the body 14 has a mounting part 30 (see also Fig.7) and a pivotable part 32. The body is mounted to the pole 12 (in this embodiment removably mounted to the pole) by way of the mounting part 30 and when mounted the mounting part 30 is firmly secured to the pole 12. The pivotable part 32 can pivot relative to the mounting part 30 about a pivot axis P-P, to provide an articulating joint for the blades 16, 18. In this preferred embodiment the motor 24, driving elements and blades 16,18 are all mounted to the pivotable part 32 and pivot together as the blades articulate. A pivot handle 34 is mounted to the pole 12 and can move along the pole between a number of defined positions, the positions being defined by a detent mechanism (not seen). The detent mechanism can be released by the user to enable the handle position to be adjusted. As seen in Fig.13, a (continuous) pivot belt 36 passes around a pulley 38. The pulley 38 is mounted to the pivotable part 32 of the body 14. The pivot belt 36 also passes around a pulley 40 located inside the pole 12. The pivot handle 34 is connected to one run of the pivot belt 36 inside the pole 12. It will be understood from Figs. 13 and 14 that movement of the pivot handle 34 along the pole 12 causes the pivot belt 36 to move and to drive the pulley 38 to rotate relative to the mounting part 30. The pulley 38 is centred at the pivot axis P-P and rotation of the pulley drives the pivotable part 32 to pivot and the blades 16,18 to articulate. Figs. 11 and 12 show the drive elements which connect the drive shaft 48 of the motor 24 to the blades 16, 18. In this embodiment both of the blades 16, 18 reciprocate relative to the body 14 and are guided for linear sliding movement by bolts or pegs (not shown) which pass through slots 42 in the blades in known fashion. Two cams 44 (only one of which can be seen) are eccentrically mounted to the drive shaft 48, the centres of the cams 44 being offset in opposing directions. One end of a respective connecting rod 46 is mounted to each of the cams 44 and the other end of the connecting rods are mounted to respective blades 16, 18. Fig.17 shows the whole of the hedge trimmer 10 with the blades 16, 18 at the extreme angle of articulation of Fig. 16. The hedge trimmer 10 could be used in this orientation if desired, but it will be understood that in this orientation the user will need to push much of the body 14 through the hedge during use (it will be seen that much of the body projects 14 to the right beyond the cutting line C-C at which the hedge will be trimmed). It is therefore much more likely that the user will reorient the blades 180° counterclockwise from the position shown in Fig. 17 so that only a much smaller part of the hedge trimmer projects beyond the cutting line as shown for example in Figs. 5 and 6. It will be understood from Figs. 7, 9 and 18 that much or all of the blades 16,18 are located to one side of the longitudinal axis A-A of the pole 12, and much of the body 14 is located to the other side of the longitudinal axis. Fig.18 in particular shows that the teeth 20 of the blades 16, 18 will always lead the body 14 as the hedge is being cut. The parts of the hedge trimmer 10 which must be pushed through uncut parts of the hedge can thereby be minimised. This arrangement enables another significant benefit of the present invention, namely that the combined weight of the blades 16, 18, the drive elements 44,46 and the motor 24 (and which together make up a large proportion of the total weight of the hedge trimmer 10) can be better balanced relative to the longitudinal axis of the pole, i.e. with a much smaller or zero weight offset. It is another significant benefit that this better balance can be maintained regardless of the angle of articulation of the blades 16, 18. In particular, the present invention enables the centre of gravity of the blades, driving elements and motor to remain at or close to longitudinal axis A-A of the pole for all angles of articulation. These benefits are provided firstly by mounting the blades 16, 18 to the body substantially mid-way between the opposing ends of the blades. Secondly, since a row of teeth is provided only along one edge of each of the blades, the weight of the blades 16, 18 can be offset to one side of the longitudinal axis A-A and the weight of the motor 24 can be offset to the other side of the longitudinal axis. Thirdly, mounting the motor 24 in the pivotable part 32 of the body 14 enables the designer to offset the weight of the motor to one side of the pivot axis P-P in order to balance the offset weight of the blades and driving elements at the other side of the pivot axis. It is thereby possible to balance the weight of the pivotable part 32 and all of the attached componentry at (or at least close to) the pivot axis so that the balance of the hedge trimmer 10 is not changed (or is changed little) as the blades articulate. Furthermore, by arranging the pivot axis P-P close to the longitudinal axis A-A of the pole the offset weight of the hedge trimmer which must be countered by the user’s grip is relatively small and consistent for all angles of articulation. Figs. 18-20 show the longitudinal axis A-A of the pole 12 at which the user grips the hedge trimmer. Also shown is the axis W-W along which the weight of the body 14 acts. The weight of the body 14 comprises the weight of the mounting part 30 and its componentry, plus the weight of the pivotable part 32 and its componentry. The centre of gravity of the body 14 therefore lies upon the axis W-W. It will be noted that the axis W-W is very close to the longitudinal axis A-A so that the user’s grip only has to counter a relatively small offset weight during use. Such a small offset weight is expected to be easy to support for most users, but in alternative embodiments it can be arranged that the weight axis W-W is coincident with the longitudinal axis A-A. In addition, it will be seen from Figs. 19 and 20 that the location of the weight axis W-W is unchanged whether the blades 16,18 are aligned with the longitudinal axis A-A or articulated to a perpendicular orientation. This is because the centre of gravity of the pivoting part 32 (comprising the blades 16, 18, motor 24, drive elements 44,46 and associated componentry which all move together as the blades articulate) is centred at the pivot axis P-P and therefore does not move as the blades articulate. The offset weight which the user’s grip must counter during use is therefore consistent for all angles of articulation.

Claims

1. A hedge trimmer having a pole and a body mounted to the pole, a first blade and a second blade mounted to the body, a motor connected to at least one of the blades for driving the at least one of the blades to move, the first blade and the second blade having respective ends, in which the first blade and the second blade are mounted to the body between their respective ends, the body having an articulating joint by which the blades can articulate relative to the pole, the articulating joint having a pivot axis, the body having a mounting part and a pivoting part with the articulating joint between the mounting part and the pivoting part, in which the blades are mounted to the pivoting part and in which the centre of gravity of the pivoting part is located at or adjacent to the pivot axis.

2. A hedge trimmer according to claim 1 in which the first blade and the second blade are mounted to the body substantially mid-way between their respective ends.

3. A hedge trimmer according to claim 1 or claim 2 in which the pole has a longitudinal axis, and in which the centre of gravity of the body is located at or adjacent to the longitudinal axis.

4. A hedge trimmer according to any one of claims 1-3 in which the range of articulation of the blades is greater than 180°.

5. A hedge trimmer according to claim 4 in which the range of articulation of the blades is around 230°.

6. A hedge trimmer according to any one of claims 1-5 in which the pole has a longitudinal axis, and in which the centre of gravity of the body is located at or adjacent to the longitudinal axis throughout the range of articulation of the blades.

7. A hedge trimmer according to any one of claims 1-6 in which the mountingpart is configured for releasable connection to the pole.

8. A hedge trimmer according to any one of claims 1-7 in which the motor is mounted to the pivoting part.

9. A hedge trimmer according to any one of claims 1-8 in which the pole has a longitudinal axis, and in which the pivot axis is located at or adjacent to the longitudinal axis.

10. A hedge trimmer according to any one of claims 1-9 in which the blades can be articulated remotely.

11. A hedge trimmer according to claim 10 in which the blades can be articulated by way of a control handle mounted to the pole.

12. A hedge trimmer according to claim 10 or claim 11 in which the body has a pulley which is engaged by a pivot belt.

13. A hedge trimmer according to claim 12 in which the pivot belt extends along the pole.

14. A hedge trimmer according to claim 12 or claim 13 in which the control handle is movably mounted to the pole and the pivot belt is connected to the control handle.

15. A hedge trimmer according to any one of claims 1-14 in which the first blade and the second blade each have teeth along only one of their respective edges.

16. A hedge trimmer according to any one of claims 1 -15 in which the first blade and the second blade are mounted for opposing reciprocal movement relative to the body.s

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