Post driver assembly

Abstract

A post driver assembly for positioning and driving a post (4) into the ground, comprising mechanical parts moveable only within a rotatable flat plane of operation, comprising: a mast part (2), moveable about a generally vertical orientation within the flat plane, and alongside which a post to be positioned and driven into the ground is mountable; the mast being pivotally attached at mast pivotal attachment points to at least two generally horizontal strut parts (35,36), that are pivotally attached to at least two generally vertical strut parts (37,38), that are pivotally attached to a rotatable shaft part (22), the orientation of the mast within the plane of operation being adjustable by induced movement of the strut parts.

Description

[0001]1495.  01 / H Post Driver Assembly Technical Field 5  The present invention relates to a post driver assembly for a post driver vehicle, for positioning and driving a post into the ground particularly but not exclusively for use in the fencing industry where there is a requirement to align posts to a predetermined fence line. 0  Background and Prior Art Post drivers are devices that are used for the driving of a vertical post, beam or rod vertically downwards into a supporting surface, such as the surface of the earth, and are well-known. They typically comprise a post driver assembly attached to a post driver5  vehicle that provides transport and a main supporting framework for mounting the assembly thereon. They typically operate by lifting a weight, or pile, followed by releasing the pile to fall under gravity to collide with and drive the post, beam or rod into the earth. A particular type of post driver assembly drives posts into the ground using a weight or0  force that is guided by a mast. The mast is usually upright, however posts may be ‘knocked in’ at an angle, for example as supports for corner posts where the fence wires can exert greater sideways forces. Such devices are commonly used in the fencing industry and the solar panel industry. 5  Typically, an intended position is predetermined for the post and the post driver assembly is manoeuvred to approach that position. A post is placed beside the mast of the post driver with the weight in an elevated position. In moving to a new post position the post driver vehicle will often travel over uneven ground, and the post driver assembly will typically be at some arbitrary orientation and requires alignment to vertical. Alignment for0  vertical is then required and when adjustment is made to the vertical position the point where the post points to ground level moves laterally and off the fence line due to the nature of the pivots connecting the mast to the driver framework. This requires further adjustment of the mast position over the fence line and can in turn move the post away from vertical, requiring an iterative procedure of alignment, and being very time5  consuming.   Typically, a post driver will be mounted at right angles to the travel of the powered vehicle on which it is mounted or connected, and at right angles to the fence line so that the powered vehicle drives parallel to the fence line and the post driver protrudes from the side of the powered vehicle. It is common that the post driver assembly swings to other positions in relation to the powered vehicle for example where a post needs to be placed in the corner of a field. Further improvements in this area would therefore be useful. Brief Description of the Invention In a first aspect, the invention relates to a post driver assembly for positioning and driving a post into the ground, comprising mechanical parts moveable only within a rotatable flat plane of operation, comprising: a mast part, moveable about a generally vertical orientation within the flat plane of operation, and alongside which a post to be positioned and driven into the ground is mountable; the mast being pivotally attached at mast pivotal attachment points to at least two generally horizontal strut parts, that remain parallel to each other when moving within the flat plane of operation, and being pivotally attached to at least two generally vertical strut parts, that remain parallel to each other when moving within the flat plane of operation, and being pivotally attached to a rotatable shaft part, rotatable about an axis within and parallel to the flat plane of operation and inclinable to an angle to horizontal, the rotation of which rotates the flat plane of operation about the axis of the rotatable shaft, the orientation of the mast within the plane of operation being adjustable by induced movement of the strut parts, and wherein   the assembly defining a post insertion point located on the surface of the ground, at the point where the axis of the rotatable shaft meets the line that passes through the mast pivotal attachment points the mast being arranged such that when a post is positioned alongside the mast, the post is positioned on a line substantially passing through the post insertion point. In this way, the inventor has found that the post insertion point does not move when the parts move within the flat plane of operation, meaning that a post can be more accurately placed in a vertical position at the post insertion point. The invention comprises a mast and a weight or force guided by the mast which acts on the post. Typically, the weight drops quickly onto the top of the post and is lifted by a hydraulic ram and rope mechanism. A series of blows are made until the post is at the correct height. Other types of force could be used. Preferably the movement of at the strut parts within the rotatable flat plane of operation is constrained, such that when the rotatable shaft rotates the flat plane of operation, the mast rotates only in a vertical plane (which is generally parallel to the fence line). This provides the additional benefit that when the flat plane of operation is rotated, the mast does not move away from vertical, which may have already been partially established by movement of the mechanical parts within the flat plane of operation. Thus, a post can be accurately placed at the post insertion point in two steps and there is no need to have continuous readjustment. Preferably the post driver assembly comprises a foot surrounding a post insertion target region through the centre of which the line through the mast pivotal attachment points passes. This may be attached to the mast, or another part of the assembly. Preferably it is mechanically coupled to the rotatable shaft. Preferably at least one of the generally vertical strut parts comprises an extended portion that extends beyond the rotatable shaft part, and the movement of the strut parts within the plane of operation is constrained by constraining the extended portion. This may be   carried out by the end of the extended portion being constrained to move in a vertical circle. Other methods of constraining the movement of the strut parts are possible. The rotatable shaft part may be hingedly attached to a main frame of a post driver vehicle. This can provide a wider variety of movement of the flat plane of operation, giving greater flexibility to position the post insertion point at the intended location. In a second aspect, the invention relates to a post driver vehicle comprising a main frame, wheels tracks or legs for movement over the ground surface, and comprising a post driver assembly as described herein. In a third aspect, the invention relates to method of operating a post driver vehicle according to the second aspect, the method comprising the steps of: a) positioning a post alongside the mast, b) identifying an intended post insertion point on the ground located on a fence line, c) manoeuvring the post driver vehicle such that the post insertion point is located at the intended post insertion point, d) orienting the mast within the flat plane of operation to be located above the fence line, e) before or after step d) rotating the flat plane of operation until the flat plane of operation is vertically oriented, f) driving the post into the ground at the post insertion point located at the intended post insertion point. The invention will now be illustrated, with reference to the following figures, in which: Figure 1 is a perspective view of a post driver assembly according to the present invention. Figure 2 is a side view of the post driver assembly shown in figure 1. Figure 3 is a side view of a second post driver assembly according to the present invention. Figure 4 is a side view of a third post driver assembly according to the present invention.   Figures 5A is a side view showing detail of a foot attachment arrangement for use with a post driver assembly according to the present invention. Figure 5B is a plan view in section as seen from line A-A in figure 5A. Figures 1 and 2 show a first post driver assembly according to the present invention, comprising a mast part 2 and a weight or force 1 that acts on a post 4 (the central axis of which only is shown). The mast part 2 is pivotally attached to two generally horizontal strut parts 35, 36 by attachment points 6, 7, which are, in turn, pivotally attached at points 8, 9, 12, 13 to two generally vertical strut parts 37, 38, the four strut parts thereby forming a parallel linkage 5. The parallel linkage 5 is connected to a rotatable shaft part 22 that is rotatable about axis 23. The mast part 2, the parallel linkage 5 and the rotatable shaft part 22 are all located within a single flat plane of operation. The mast pivotal attachment points 6, 7 are located such that that the line that passes through mast pivotal attachment points 40 passes through the intended location of post insertion, called the post point 3. The rotatable shaft part 22 is rotatable about axis 23, and also passes through the intended location of post insertion, called the post point 3. The rotatable shaft part 22 is rotatably attached to a supporting frame 27 which may be connected to further swinging frame (not shown) or an extending frame (not shown) as is common with post drivers. One of the generally vertical strut parts 37 comprises an extended portion 11 that extends beyond the rotatable shaft part 22. Connected at the end of the extended portion 11 to the extended portion 35 is a hydraulic ram 18 which can move the parallel linkage 5 within the flat plane of operation. Also provided is a second hydraulic ram 24 to induce rotation of the rotatable shaft 22, although other mechanisms are possible. Because the axis 23 of the rotatable shaft 22 is in line with the post insertion point 3, and in this instance the ground is horizontal, it is necessary that the axis 23 is inclined at an angle to the horizontal. Note that if the ground is not horizontal, such as a slope, it may   be possible for the axis 23 to be horizontal. A foot 32 is provided mechanically coupled to the rotatable shaft 22, and thereby connected to the fixed frame 27, that helps locate the post insertion point and position the mast 2 and maintains the required height for the parallel linkage to be effective around the post point 3 and centre line 23. In use, a post 4 is positioned along axis 4 supported by mast 2. The assembly is moved into position so that the axis 23 points to the post insertion point 3 located on a fence line 33. In this condition, the mast 4 is generally at an angle to vertical, although the flat plane of operation may be vertically aligned. Because of this angle the rotation of the rotatable shaft 22 around axis 23 takes the mast away from the fence line 33. However, the ram 18 that operates the parallel linkage 5 is connected to the main frame 27 via an adjustable link 21 with swivel ends 19, 20 such that when the rotatable shaft 22 rotates about axis 23 the ram 18 is off-centre and is pulled towards the mainframe 27 as the swivel link 21 travels in an arc in either direction, thus pulling the ram 18 and linkage, and therefore the mast 2 is constrained to rotate only in a vertical plane parallel to the fence line 33. Thus, maintaining an alignment of the mast 2 with the fence line 33 despite the rotation around an angled rotational housing centre line 23. Thus, the post 4 can be aligned vertically within the flat plane of operation, and then subsequently, the flat plane of operation can be rotated parallel with the fence line 33 without the post insertion point 3 moving, ensuring accurate placement of the post in the ground. The arrangement is particularly advantageous because it allows for the movement of the mast 2 to a wide range of positions including but not restricted to 28, 29, 30 and 31 and could including a position that may allow automatic loading of a post onto the mast where an adjustable post clamp 34 might be used to automatically hold the post to the mast in a loading position and move to the correct position to knock the post into the ground without an operator handling the post. The rotation of the mast 2 may be outside of the angles 28, 29, 30 and 31 in order to help facilitate such automatic loading or knocking a post into the ground at a steep angle.   This may be coupled with a system to automatically bring the mast to a vertical position in each new post position. The centre line of the post 4 and the point at which it enters the ground 3 will be typically on average 70 mm from the face of the mast 2 allowing for an average 100-150mm post diameter. In order for the mast 2 to tilt in line with the fence line 33 where the fence line is at 90° to the housing centre line 23 it is important that there is a relationship between the angle of the rotational housing centre line 23 from horizontal and the distance apart of the adjustable fixed swivel link pivot points 19 and 20 and the distance between the parallel linkage pivot points 10 to ram pivot point 11. The relationship regarding the angle and lengths 19, 20 and 10, 11 are such that these distances allow the mast move in line with the fence line when the centre line 23 is at 90° to the fence line. In this embodiment, it is essential that the tilt ram 18 remains in line with the parallel linkage 5 and thus the ram pivot point 16 is kept in line via a yoke 17 connected to the rotational housing at pivot point 15. Alternatively, as shown in figures 3 and 4, the link 21 could be replaced by the ram 18 and no yoke 17 would be needed. The ram would be connected to the main frame 27 via swivel joints to the parallel linkage 5. A similar effect of alignment of the mast to the fence line would occur. Figure 5A shows a side view showing detail of a foot attachment arrangement 50 for positioning the foot 32 on the ground. Figure 5B shows a plan view in section viewed from line A-A. The rotatable shaft is connected to a rotation coupling 51 which in turn is rigidly attached to an adapter plate 52. Rigidly attached to the foot 32 is two semi-circular arches 54. The adapter plate 52 is attached to the two semi-circular arches 54 via carriages 56. In use, the carriages 54 can be urged to move along the semi-circular arches 54 when locating the post insertion point 3 on the ground. Thus, the foot 32 is mechanically coupled to the rotatable shaft 22 and is capable of relative rotation therewith.

Claims

Claims 1. A post driver assembly for positioning and driving a post into the ground, comprising mechanical parts moveable only within a rotatable flat plane of operation, comprising: a mast part, moveable about a generally vertical orientation within the flat plane of operation, and alongside which a post to be positioned and driven into the ground is mountable; the mast being pivotally attached at mast pivotal attachment points to at least two generally horizontal strut parts, that remain parallel to each other when moving within the flat plane of operation, and being pivotally attached to at least two generally vertical strut parts, that remain parallel to each other when moving within the flat plane of operation, and being pivotally attached to a rotatable shaft part, rotatable about an axis within and parallel to the flat plane of operation and inclinable to an angle to horizontal, the rotation of which rotates the flat plane of operation about the axis of the rotatable shaft, the orientation of the mast within the plane of operation being adjustable by induced movement of the strut parts, and wherein the assembly defining a post insertion point located on the surface of the ground, at the point where the axis of the rotatable shaft meets the line that passes through the mast pivotal attachment points the mast being arranged such that when a post is positioned alongside the mast, the post is positioned on a line substantially passing through the post insertion point.

2. A post driver assembly according to claim 1, wherein the movement of the strut parts within the plane of operation is constrained, such that when the rotatable shaft rotates the plane of operation, the mast rotates only in a vertical plane.

3. A post driver assembly according to claim 1 or claim 2, which comprises a foot surrounding a post insertion target region through the centre of which the line through the mast pivotal attachment points passes.

4. A post driver assembly according to claim 3, wherein the foot is mechanically coupled to the rotatable shaft.

5. A post driver assembly according to claim 4, wherein the mechanical coupling provides relative rotation between the foot and the rotatable shaft.

6. A post driver assembly according to any one of the preceding claims, wherein at least one of the generally vertical strut parts comprises an extended portion that extends beyond the rotatable shaft part, and the movement of the strut parts within the plane of operation is constrained by constraining the extended portion.

7. A post driver assembly according to claim 6, wherein the end of the extended portion being constrained to move in a vertical circle.

8. A post driver assembly according to any one of the preceding claims, wherein the rotatable shaft part is hingedly attached to a main frame of a post driver apparatus.

9. A post driver vehicle comprising a main frame, wheels, tracks or legs for movement over the ground surface, and comprising a post driver assembly according to any one of the preceding claims.

10. A method of operating a post driver vehicle according to claim 8, the method comprising the steps of: a) positioning a post alongside the mast, b) identifying an intended post insertion point on the ground located on a fence line, c) manoeuvring the post driver apparatus such that the post insertion point is located at the intended post insertion point, d) orienting the mast within the flat plane of operation to be located above the fence line,e) before or after step d) rotating the flat plane of operation until the flat plane of operation is vertically oriented, f) driving the post into the ground at the post insertion point located at the intended post insertion point.

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