GB2220690A

GB2220690A - Post driver assembly

Info

Publication number: GB2220690A
Application number: GB8915878A
Authority: GB
Inventors: Geoffrey Jones
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-07-14
Filing date: 1989-07-11
Publication date: 1990-01-17
Anticipated expiration: 2009-07-11
Also published as: GB8915878D0; GB2220690B; GB8816787D0

Abstract

A post driver assembly for driving a post in a downward direction comprises a post receiving member (12) adapted to receive the upper part of a post (2), and releasable securing means (45) associated with the receiving member (12) for securing the post (2) in the receiving member. The receiving member (12) is arranged to locate in use a guide (6') for a tup (6) so as to align the tup with an end of the post (2) for impact therewith. This arrangement is advantageous in that it allows the assembly to be portable. The assembly may include tup biassing means, such as a coiled compression spring acting between the tup and the guide for urging the tup towards an end of the post. <IMAGE>

Description

POST DRIVER ASSEMBLY This invention relates to a post driver assembly and particularly to a portable post driver assembly which is sufficiently compact to enable it to be manoeuvred and operated by one or two operatives.

I consider that there is a need for a post driver assembly which can be carried by an operative to its position of use to drive in a post, such as a fence post, and then carried to the next position at which a further post is to be driven into the ground. Ideally the post driver should not require any substantial supporting legs or framework which would add to the weight and make it difficult to manoeuvre.

It is an object of the present invention to provide a post driver assembly which is portable and sufficiently light and compact to enable it to be manoeuvred and operated by one or two operatives.

According to the present invention there is provided a post driver assembly for driving a post in a downward direction, which assembly comprises a post receiving member adapted to receive the upper part of a post, and releasable securing means associated with the post receiving member for securing the post in the receiving member, the receiving member being arranged to locate in use a guide for a tup so as to align the tup with an end of the post for impact therewith.

The apparatus can be laid horizontally on the ground, a post then being placed in and secured to the post receiving member, and the apparatus and post then brought to an upright or inclined position by lifting the apparatus to tilt it about the foot of the post.

The securing means preferably comprises a flexible ligament which can be passed around the post, and tensioning means for drawing the ligament taut around the post. Conveniently the tensioning means comprises a ratchet mechanism, means being provided to disengage the ratchet when it is desired to release the tension in the ligament for removing the post driver assembly from the post.

The post driver assembly may include tup biassing means acting between the tup and the guide for urging the tup towards the end of the post. The biassing means preferably comprises a coiled compression spring.

The post driver assembly may include a continuous chain one leg of which runs substantially parallel to the longitudinal direction of the tup guide, and a chain drive means, the chain carrying a chain abutment adapted to engage with a tup abutment when the tup is towards the lower end of its travel in the guide, such that the tup is then carried in use towards the upper end of the guide by the chain until the chain path takes the chain abutment out of engagement with the tup abutment, thereby to release the tup for downward movement.

Thus the chain is driven continuously during a post driving operation, and any suitable rotary drive means may be employed. This could be an electric motor or flexible shaft for example, but preferably it is a hydraulic motor. The hydraulic motor can be powered by a portable hydraulic power pack (possibly wheel, skid or trailer mounted) to provide a self-contained post driving system, or from any machine or vehicle having a suitable hydraulic power system, such as a farm tractor, dumper truck or Land Rover (T.M.).

The path of the chain in approaching the leg running parallel to the longitudinal direction of the guide is preferably so arranged that the abutments will not engage with one another when the tup is in its lowermost position.

The chain preferably passes around a pair of vertically spaced sprockets one of which is driven by the drive means.

Preferably the upper sprocket is the driven sprocket.

The lower sprocket is preferably positioned adjacent to the lower end of the guide means, and the upper sprocket is preferably spaced downwards from the upper end of the guide means.

The guide means is preferably an elongate guide tube, the tup is preferably a slug which is freely movable within the tube, and the tup abutment is preferably constituted by a pair of spaced lug members which project radially outwards of the tube through a longitudinal slot in the wall of the guide tube for engagement by the chain lug, the leg of the chain path being positioned in a cavity defined between a pair of elongate parallel guide plates fixed to the tube and positioned to either side of the slot, the guide plates being slidably engageable by the respective lugs.

The chain abutment preferably then comprises a pair of chain lugs extending in opposite directions from a chain link for respective abutment with the tup lugs.

Alternatively, the guide means may be an elongate guide tube, the tup may be a slug which is freely movable within the tube, and the tup abutment may be constituted by a lug member which projects radially outwards of the tube through a longitudinal slot in the wall of the guide for engagement by a chain lug which extends between a pair of chains which run in parallel.

The assembly may include an operating handle attached to a driver casing, the arrangement being such that, with a post secured in the receiving member, when a downwards force is applied to the handle, the tup is raised from its lowermost position to a striking position in which the top of the post contacts the driver casing and the chain abutment and the tup abutment are able to engage with each other.

Preferably, the post is slidably mounted to allow the tup to be urged to the striking position. The operating handle may be movable downwards relative to the driver casing until the handle comes into contact with a positive stop and is biassed to resist further downwards movement. The operating handle may operate an ON/OFF control in which the control moves to the ON position prior to contacting the positive stop. It is accordingly necessary to the tup to be moved upwards relative to the guide from its lowermost position before the chain can drive the tup upwards for commencing a post driving operation. This can provide an important safety feature since otherwise an accidental switching-on of the hydraulic motor could cause the tup to be driven and cause injury to the operator.

The post driver assembly may incorporate stop means for the tup which includes a resilient buffer which is compressed on impact between the tup and the stop means.

A post driver assembly in accordance with the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a schematic view of the assembly in its position of use mounted on a fence post which is about to be driven into the ground; Figure 2 is a schematic view showing the position of the apparatus for securing a new post in the post receiving member; Figure 3 is a side elevation of the lower half of the apparatus showing in particular the details of the receiving member with associated tensioning mechanism, the column carried by the receiving member being shown partially sectioned in a vertical plane; Figure 4 is an enlarged underplan view of the assembly shown in Figure 3; Figure 5- is an enlarged section on the line 5-5 of Figure 3 but omitting the spring rod within the column;; Figure 6 is a side elevation, on a similar scale to Figure 3, of the upper half of the apparatus, the tup being shown in its lowermost position; Figure 7 is a vertical cross-section on a larger scale than Figure 6 of the upper half of the apparatus, but omitting the uppermost portion of the guide tube, the tup being shown in full outline in a partially raised position; Figure 8 is an enlarged cross-sectional view on the line 8-8 of Figure 7; Figure 9 is a side view of the lower end of the tup body; Figure 10 is a side view and plan view of one of the tup lugs; Figure 11 is a side view of the tup lower end piece; and Figure 12 is a vertical section of the valve assembly in the inoperative condition.

With reference to Figure 1, the post driver assembly 1 is shown as a self-contained unit, preferably without any stabilising legs which would add to the weight, which is adapted to be supported on a post 2 to be driven in a downard direction into the ground 3. It is necessary for the operative to hold onto the horizontal handgrip 4 of a substantially T-shaped handle assembly 5 to maintain the post and attached post driver vertical, or in any other direction of driving, during the early stages of the driving operation and, as will be explained in more detail, downward movement of the handle is used to control the driving operation.

The apparatus comprises a tubular guide 6' for a cylindrical tup assembly 6 of which the lower end piece 7 projects downwards below a base plate 8 of the tup guide 6' prior to operation of the assembly. The guide 6' is rigidly carried by a tubular column 9 of square section. The column 9 extends slidably through a pair of spaced shoes 10,11 of a post receiving member in the form of a cradle assembly 12 which comprises a pair of spaced V-shaped cradle members 13,14 which embrace the upper part 15 of the post 2 and are secured to post by flexible ligaments in the form of tension wires 45. The post 2 could be round or square or of irregular cross-section. Cradle members 13,14 may be shaped to fit a particular shape of post cross-section. For example, the cradle members could be of channel section to fit a rectangular motorway post.

It will be appreciated that the engagement of the cradle 12 with the post provides the means for substantially aligning the guide tube 6' with the axis of the post, and no auxiliary legs are required to support the assembly.

The use of the cradle assembly, rather than for example a tubular socket, to receive the post enables a post to be readily secured to the assembly, and furthermore enables the assembly to be removed easily from a driven post, and to be used for posts of different cross-sections and shapes.

Figure 2 shows how the assembly can be laid horizontally on the ground and the upper part of a post positioned in the cradle 12 for securing of the wire retainer. The operative can then grasp the handgrips 4 and raise the post and driver assembly to a vertical or other driving position, simply by pivoting everything about the lower end of the post.

Details of the cradle assembly will be described with reference to Figures 3 to 5. The cradle members 13,14 are welded to the upper and lower ends respectively of a pair of tubular cradle spacers 15a, through one of which extends the drive shaft 16 of a wire tensioning arrangement. The hexagonal upper end 17 of shaft 16 carries a wire tensioning spool 18 and the lower end 19 co-operates with a ratchet mechanism 20, arranged such that the shaft 16 can normally be turned in one direction only by application of a suitable handle to the end 17. However, the lower extremity 21 of the shaft 16 is of round cross-section to enable the lower end portion of the shaft 16 to be disengaged from a hexagonal ratchet member 22, Figure 4, to release the wire tension simply by driving the lower end 21 of the shaft 16 upwards with a hammer or wooden mallet, to overcome the ratchet mechanism.

A single length of wire 45, Figure 1, is wrapped around the post adjacent to both the upper and lower cradle members 14,13, the wire extending from upper rotatable spool 18, Figure 3, around the post adjacent to cradle 14, around lug 18' down the post to lug 19', Figure 4, then around the post adjacent to cradle 13 to a looped end 45' secured to fixed spool 19, such that when the shaft 16 is rotated the spool 18 is turned to tighten the wire and clamp the post firmly to both cradle members 13,14.

In a modification, not shown, the drive shaft 16 carrying rotatable spool 18 extends transversely through the spacers 15a, and is located adjacent to one of the cradles 13,14.

As shown in Figures 6 and 7, the lower end of the tup guide carries the base plate 8 which holds the tup members captive to the guide. In the circumstances that the device is rapidly stopped it may happen that the tup is arrested largely by the base plate and not by impact with the post, which might damage the base plate or its connection with the guide if such connection were to be a rigid connection, and to the production of a metallic noise. For these reasons, stop means comprising an upper annular plate 60, a lower annular plate 61, an intermediate resilient member such as a rubber buffer 62, and a plurality of bolts 63 securing the annular plates and the resilient member to the base plate 8. The lower annular plate 61 is secured, for example by welding, to the guide tube 6' and on impact between the tup and the base plate the rubber buffer 62 is compressed axially.

With reference to Figures 6 and 7 the tup 6 is reciprocable in the guide tube 6' against the biassing force of a pre-loaded coiled compression spring 23 of which the lower end bears on an enlargement 24 on the tup, and the upper end bears against the closed upper end 25 of the guide tube 6'.

It is the spring 23 together with gravity, which provides the driving force on the tup, and the spring 23 is further compressed by raising the tup 6 upwards inside the guide tube 6' this being accomplished by a chain mechanism 26 shown in Figures 7 ci 8.

Chain mechanism 26 comprises a continuous chain 27 which passes over a driving sprocket 28 and an idler sprocket 29 and is tensioned by a spring biassed plastics tensioner 30.

One leg 29' of the path of the chain extends parallel to the guide tube longitudinal axis and radially outwards of a wide longitudinal slot 31 in the tube which extends circumferentially between a pair of parallel elongate side plates 32, Figures 3 and 8, by which the guide tube 6' is rigidly connected to the upper part of column 9.

The tup 6 is mainly of mild steel but carries a pair of projecting abutment lugs 33 of hardened steel which can be engaged by a corresponding pair of lugs 34, Figure 8, carried by the chain 27, the chain lugs 34 extending in opposite directions from a link of the chain and parallel to the link pivotal axis.

The lowermost positions of the tup end 7 and tup lugs 33 are indicated at 7' and 33' respectively in Figure 7, and it should be noted that the chain lugs cannot come into engagement with the tup lugs when the tup is in this position. It will be seen that the tup must be raised to bring the tup lugs to the position 33", adjacent to sprocket 29, before it is possible for the chain to drive the tup upwards.

Figures 9,10 and 11 illustrate the arrangement for securing the tup lugs 33 to the tup, the tup 6 being formed as a mild steel tup body 6' and a separate lower end piece 7 which is secured in use to the body 6' by an axial screw. The body 6' has a spigot 37 on its lower end which is received in a complementary recess in the upper face of end piece 7. A pair of slots 38 are provided in the end piece 7 to receive the respective lugs 33, and the lugs are provided with respective arcuate cut-outs 39 for locking engagement with the spigot 37, to ensure that the lugs 33 are firmly anchored to the tup.

A suitable hydraulic drive motor 35 (Figures 1,6), is mounted on the upper end of one of the sideplates 32 for directly driving the driving sprocket 28 (Figure 7), and the hydraulic fluid supply to motor 35 is controlled by a valve assembly 36 which is operated by the inner ends 37 of a pair of handle limbs 5', the two limbs 5' being pivoted at an intermediate position on pivot pins 38 which are secured to projecting lugs, not shown, carried by the respective side plates 32. The hydraulic fluid supply to motor 35 is via the valve assembly 36 which is of the piston type.The valve assembly 36 in the inoperative condition provides a substantially unrestricted fluid connection between fluid supply and return lines connected to the valve assembly 36, such lines taking the form of flexible high pressure hoses 46, Figure 1, which are connected to a farm tractor or other source of high pressure fluid. When the valve assembly 36 is operated said fluid connection is shut off, and fluid is supplied to the motor 35 by way of send and return pipes, 50,51 extending between motor 35 and valve assembly 36. The valve assembly 36, shown in Figure 12, employs a spool valve member 47.

Valve assembly 36 is operated to supply fluid to motor 35 when the lever handle 4 is moved downwards to the horizontal position of Figure 6, but movement of the handle is resisted by a strong compression spring 40, Figure 3, housed within the lower part of column 9. The inner ends 37 of handle arms 5', as well as being connected to the actuator of valve assembly 36 are connected to a rod 41 which carries an adjustable spring abutment washer 42 on its lower end, the spring 40 acting between washer 42 and a fixed abutment 43 within column 9. The lower end of rod 41 is threaded and carries an adjuster nut 44 for controlling the pre-loading of spring 40.

It will be realised that the totally enclosed position of spring 40 protects the spring and rod 41 from damage, and that column 9 provides also a guard for the chain drive assembly.

When a post to be driven into the ground has been secured to the driver as in Figure 2 and brought to a vertical or other driving position as shown in Figure 1, the handle 5 is initially in the inclined position shown. The pre-loading of spring 40 relative to the pre-loading of tup spring 23 is pre-adjusted, with nut 44, such that downward pressure on handle handgrip 4 by the operative does not initially result in pivoting of the handle 5. Instead the tup lower end 7 is urged inwardly of the tup guide 6', the column 9 and tup guide 6' moving downwards relative to the post, as facilitated by the sliding of column 9 through shoes 10,11.

This brings plate 8 into engagement with the top of the post, such that the tup lugs 33 adopts the position 33" of Figure 7 to enable the lugs 33 to be engaged by the chain lugs when the chain is operated. The drive motor 35 will not, however, be supplied with hydraulic fluid until further downward pressure has been applied to the handle handgrip 4, whereupon the handle 5 will pivot against the biassing of spring 40, to operate the valve assembly 36.

When the valve member 47 Figure 12 reaches its fully actuated position, the pin 37, Figure 1, will contact a positive stop, not shown, formed on the side plates 32, and the downwards force exerted on the handgrip 4 will be transmitted directly to the guide tube 6' via pivots and support lugs at 38, Figure 1. The top face of the post 2 will be in contact with the face of base plate 8, and a downwards force applied to the handle will thus also be applied to the top of the post to assist driving. For small posts a piece of timber can be inserted between the top of the post and base plate 8.

This downwards force will also be transmitted via the guide tube 6' to its closed upper end 25, Figure 6, to resist the reaction of the biassing force from coil spring 23, Figure 7.

This sequence of operations which are necessary before the drive motor 35 is operated makes it substantially impossible for the tup to be driven without the apparatus being brought to a vertical or other driving position, with a post in position.

The illustrated assembly has been designed for fabrication from readily available plate steel material, and from commercially available components.

The motor is capable of providing about 120 blows per minute when supplied with fluid from a supply of 20 litres per minute at 1500 psi.

It will be appreciated that in the illustrated device most moving parts have been enclosed to eliminate possible accidental damage through rough handling, and to prevent injury to an operator.

Claims

1. A post driver assembly for driving a post in a downward direction, which assembly comprises a post receiving member adapted to receive the upper part of a post, and releasable securing means associated with the post receiving member for securing the post in the receiving member, the receiving member being arranged to locate in use a guide for a tup so as to align the tup with an end of the post for impact therewith.

2. A post driver assembly as claimed in claim 1, wherein the securing means comprises a flexible ligament which can be passed around the post, and tensioning means for drawing the ligament taut around the post.

3. A post driver assembly as claimed in claim 2, wherein the tensioning means comprises a ratchet mechanism, means being provided to disengage the ratchet when it is desired to release the tension in the ligament for removing the post driver assembly from the post.

4. A post driver assembly as claimed in any preceding claim and including tup biassing means acting between the tup and the guide for urging the tup towards the end of the post.

5. A post driver assembly as claimed in claim 4, wherein the tup biassing means comprises a coiled compression spring.

6. A post driver assembly as claimed in any preceding claim and including a continuous chain one leg of which runs substantially parallel to the longitudinal direction of the tup guide, and a chain drive means, the chain carrying a chain abutment adapted to engage with a tup abutment when the tup is towards the lower end of its travel in the guide, such that the tup is then carried in use towards the upper end of the guide by the chain until the chain path takes the chain abutment out of engagement with the tup abutment, thereby to release the tup for downward movement.

7. A post driver assembly as claimed in claim 6, wherein the path of the chain in approaching the leg running substantially parallel to the longitudinal direction of the guide is so arranged that the abutments will not engage with one another when the tup is in its lowermost position.

8. A post driver assembly as claimed in claim 6 or 7, wherein the guide means is an elongate guide tube, the tup is a slug which is freely movable within the tube, and the tup abutment is constituted by a pair of spaced lug members which project radially outwards of the tube through a longitudinal slot in the wall of the guide tube for engagement by the chain lug, the leg of the chain path being positioned in a cavity extending in the axial direction of the guide tube and defined between a pair of elongate parallel guide plates fixed to the tube and positioned on either side of the slot, the guide plates being slidably engageable by the respective lugs.

9. A post driver assembly as claimed in clain 6 or 7, wherein the guide means is an elongate guide tube, the tup is a slug which is freely movable within the tube, and the tup abutment is constituted by a lug member which projects radially outwards of the tube through a longitudinal slot in the wall of the guide tube for engagement by a chain lug which extends between a pair of chains which run in parallel.

10. A post driver assembly as claimed in any one of claims 6 to 9 and including an operating handle attached to a driver casing, the arrangement being such that, with a post secured in the receiving member, when a downwards force is applied to the handle, the tup is raised from its lowermost position to a striking position in which the top of the post contacts the driver casing and the chain abutment and the tup abutment are able to engage with each other.

11. A post driver assembly as claimed in claim 10, wherein the post is slidably mounted to allow the tup to be urged to the striking position.

12. A post driver assembly as claimed in claim 10 or 11, wherein the operating handle is movable downwards relative to the driver casing until the handle comes into contact with a positive stop and is biassed to resist further downwards movement.

13. A post driver assembly as claimed in claim 12, wherein the operating handle operates an ON/OFF control in which the control moves to the ON position prior to contacting the positive stop.

14. A post driver assembly as claimed in any preceding claim wherein stop means for the tup includes a resilient buffer which is compressed on impact between the tup and the stop means.

15. A post driver assembly substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.