AU2010226950B2 - Improved Post Driver - Google Patents

Abstract

A post driver which includes a vertical support frame and a carriage arranged to 5 move vertically relative to said frame. A high frequency low impact hammer is arranged within the carriage to move relative to the carriage. The hammer impacts a post cap for seating on the top of a post which is held within the lower section of the carriage and a post guide allows for limited movement relative to the carriage. An auger attachment is provided in which the auger carriage is locked to the 10 hammer carriage when in use and is locked to the vertical support frame in its stowed position. 8s 12 72 74 5 76 0

Description

AUSTRALIA Patents Act ORIGINAL COMPLETE SPECIFICATION STANDARD PATENT Application Number: 2010200 Lodgement Date: 5 th October 2010 Nominated Patentee: Brooke and Mackenzie Pty Ltd [A C N 084 285 736] Invention Title: Improved Post Driver The following statement is a full description of this invention, including the best method of performing it known to the applicant.

1 IMPROVED POST DRIVER This invention relates to a an improved post driver particularly for farm fencing Background to the invention. 5 Mechanized post drivers have been proposed. Post drivers are typically mounted on the rear of a truck or tractor or on a trailer and have feet which stabilize the machine on the ground over the post. These devices usually use a drop hammer to impact the top of the post to drive into the ground. The exposed impact zone can be a safety hazard. 10 USA patent 4915180 discloses a 3 sided enclosure for the impact zone of a hammer but it is open at the front. This patent also discloses a tilting mechanism to adjust to post driving on slopes. USA patents 4050526 and 4124081 disclose a hammer slidable within a barrel and a chain driven carriage that carries the anvil and post cap and the hammer lifting 15 mechanism. These patents also disclose preloading of the post prior to driving, using a compression spring and use a spring loaded hammer to achieve acceleration. Safety is still a problem that is only partly addressed by the prior art as it is inconvenient to have a guard that needs to be opened to align the post and then 20 closed to enclose the impact zone. Caps for poles to receive and transmit the impact of the hammer have been disclosed in USA patent 4601349, 4124081 , 5256006 and 4190118. WO/00/31364 discloses a spherical bearing surface with a spike in the pole cap to centralize the cap on the post. None of the prior art patents specifically address the 25 problem of irregularities in the top bearing surface of the post. This can be a problem with farm fencing. Patent WO/00/31364 also discloses maintaining pressure on the cap to ensure that the cap follows the post. This patent also discloses an hydraulic drive raising the mast then using the weight of the mast to apply preload pressure to the cap. An hydraulic accelerator is used to speed the 30 hammer's fall. It is claimed that this allows a lighter weight and a shorter mast to be possible for the post driver. Australian patent 687838 discloses an accelerated hammer which uses an elastic strap to add to gravitational acceleration.

2 All of these post drivers use a large mass and low frequency hammer action. Rock breakers are known and use a hammer mechanism that has a lower impact force and higher frequency of impact. High frequency hydraulic driver performance is limited by the amount of backup mass or down force that is available to be applied to the 5 hammer. When these machines are fitted to conventional agricultural tractors The backup mass or down force on the hammer must be provided by increasing the mass of the linkage mounted machine as most conventional tractors do not have the ability to apply a down force on the linkage. This will result in a very heavy machine mounted of the 10 tractor linkage, forcing an increase in the size / lifting capacity of tractor that the machine can be fitted to. Many of these prior art machines use hydraulic circuits which act on the up and down movements of the hammer. USA patents 5529132 and 6305480 disclose hydraulic circuits specific to pile 15 drivers. A difficulty with hydraulic circuits is that they are usually run from the tractor on which the post driver is mounted. This usually entails relatively long lines from the hydraulic actuators to the system sump which is usually the vehicle or tractor sump. 20 Some post drivers include an auger attachment to drill a pilot hole for the post. Australian patent 746198 discloses an auger attachment that has a stowed position alongside the mast and an operable position underneath the hammer carriage. The auger is lifted with the hammer to its stowed position and is swung under its own weight into the operative position under the hammer. 25 It is an object of this invention to overcome or ameliorate the shortcomings of the prior art. Brief Description of the Invention To this end the present invention provides a post driver for use with a tractor 30 having linkage arms which includes a) a vertical support frame b) a carriage arranged to move vertically relative to said frame 3 c) an accelerated hammer arranged within the carriage to move relative to the carriage d) a pair of hydraulic cylinders that are hydraulically connected in parallel between the post driver linkage mounting frame and the tractor lower linkage arms such that 5 applying hydraulic pressure to the cylinders will cause the cylinders to retract and apply a force that has the effect of attempting to lift the tractor rear axle via the lower linkage arms. e) a post guide and cap for seating on the top of a post and held within the lower section of the carriage and optionally arranged for limited movement relative 10 to the carriage f) an optional auger attachment that is semi automatically adapted to be positioned under the hammer carriage The hammer preferably applies a force using a spring or hydraulics ,additional to 15 gravity and preferably has a high blow frequency, preferably up to 1400 blows per minutes The agricultural post driver of this invention has a vertical mast and carry beam designed to fit to a variety of transport machines including Tractors, Skid steer loaders, excavators. Vehicle or hydraulic motors allow accurate positioning and levelling of the 20 machine. These include positioning along and across the fence line. Tilts are provided to allow levelling of the mast in hilly conditions. In another aspect this invention provides an improvement in linkages to tractors equipment which require a down force. In this aspect there is tractor linkage for a post driver which incorporates a pair of hydraulic cylinders that are hydraulically connected 25 in parallel between the post driver linkage mounting frame and the tractor lower linkage arms such that applying hydraulic pressure to the cylinders will cause the cylinders to retract and apply a force that has the effect of attempting to lift the tractor rear axle via the lower linkage arms. An alternate arrangement is to replace the tractor linkage to the lower arms with a dual action hydraulic cylinder to achieve the same effect. 30 This arrangement applies a controlled force to the tractor lower linkage arms having the effect of applying a down force on the linkage mounted post driver when in post driving mode. This has the effect of transferring a portion of the mass of the tractor to 4 the post driver which is then available to apply greater down force on the hammer thus increasing the hammer driving performance without increasing the total required mass. The machine of this invention has an integrated auger system for drilling pilot holes. The auger is stowed on the mast when not in use and supported by the hammer 5 carriage during hole drilling. The auger, when in it's operating position , operates along the same vertical axis as the hammer and uses the hammer mass to assist in drilling. The auger semi automatically engages and disengages by means of a cam system of the kind disclosed in Australian patent 746198. The contents of that patent are incorporated herein by reference 10 Preferably the hydraulic controls are arranged to allow the mass of the hammer assembly to be applied progressively to the auger assembly to improve digging performance in hard ground. The hydraulic controls preferably allow the application of a portion of the mass of the machine frame and the support vehicle to the hammer assembly to assist in providing 15 backup mass for the hammer thus improving blow energy. Preferably the hammer body is low profile and allows the setting of posts up against existing fences or buildings. Preferably the hydraulic controls allow easy variation of blow frequency and energy for sensitive driving situations The machines uses an enclosed hydraulically accelerated hammer that does not allow 20 any access to the impact producing parts or the impact zone at the post top. Preferably the hammer has a large area anvil that contacts the post continuously thus not allowing access to the hammer impact area. The post guide is mounted on the hammer carriage. The guide uses an adjustable vee for round posts and other shapes for concrete, rail line, and squares. The post is 25 secured loosely in the vee by a chain or similar flexible restraint. This allows relative movement between the post and hammer carriage while still maintaining guiding. The post guide chain is secured to a fixing point that has an over-centering de tensioner to release the chain if it is tight at the end of the post driving. 30 In order to start the post, the carriage is lowered so that the post cap seats on the top of the post and the downward pressure by the carriage ram applies a preload to the post.

5 The logic of the hydraulic circuit ensures that the post is under compression (because the carriage ram is acting downwardly) before the hammer can be actuated (the hammer ram lifts the hammer). In addition with the down force arrangement of this invention the weight of the tractor is also added to the force of 5 the carriage hammer. Detailed description of the invention A preferred embodiment of the invention is illustrated in the drawings in which: Figure 1 is a front view of the post driving attachment of this invention with the 10 hammer carriage down; Figure 2 is a front perspective view of the carriage component of this invention with the hammer carriage up and the post in the start position; Figure 3 is a detailed view of the auger attachment and mechanism for positioning the auger under the carriage 15 Figure 4 is a view illustrating the top of the post prior to fastening in the post guide; Figure is a view of the post guide mechanism; Figure 6 is an exploded view of the post guide mechanism. Figure 7 is a view of the tractor illustrating the linkage points used in a first embodiment of this invention; 20 Figure 8 illustrates a second embodiment of the down force arrangement of this invention. The post driver is an attachment that can be fitted to the rear of a vehicle. The base frame 10 with feet 11 is placed on the ground and the vertical frame 12 is 25 adjusted to its vertical position using the angle ram 15. The carriage 30 moves up and down the vertical frame 12 moved by the hydraulic ram 17 to lift the carriage 30 and then to apply down ward pressure on the carriage when applied to the top of a post. The post 58 is positioned in front of the frame 12 under the carriage 30. 30 The hammer 43 is secured to the hammer slide 40 which moves within the carriage 30.

6 The hammer 43 impacts the anvil 45 which is attached to the post cap 50. The anvil 45 and post cap 50 are held in the base of the carriage 30 covered by the impact zone cover 46. The high frequency hammer is a generic hammer form that is made by a number 5 of manufacturers around the world. There are internal differences in the hammer design between manufacturers, but they all have the same effect of turning a continuous flow of oil into a relatively high frequency high energy blow from the internal hammer piston onto the end of the anvil. The Anvil in has a large area mushroom head that contacts the post top. These hammers are generally used for 10 rock breaking with a pointed anvil. A preferred high frequency hammer is INDECO Model HP500. The post guide system as shown in figures 3 to 6 enables the hammer system to be most effective in post setting. The guide flexibly contains the post allowing the operator to see which way the post is being pushed sideways thus allowing the 15 operator to make early post guiding correction movements with the tilt functions. This results in a faster more accurately driven post in stony ground. The two adjustable guides 52 can be positioned to suit the post diameter. The chain 53 is then brought around the post just below the guides and fixed to the chain lock I detensioner 54. The slack in the chain allows the post to move a bit in the guides. 20 If the driven post has tensioned the chain so that it cannot be released the detensioner handle 55 is pulled. This releases the chain tension allowing the chain 53 to be removed from the detensioner 54. Once the auger 60 is selected the auger carriage 62 is swung into and out of position by being linked to the movement of the hammer carriage 30. As indicated 25 above, the auger 60 is as described in patent 746198. The auger 60 is swung out from under the hammer carriage 30 to a stowed position so that the hammer carriage is free to drive a post into the pilot hole dug by the auger. Figures 7 and 8 illustrates the linkage arrangement that allows some of the weight of the tractor to be applied to the post driver. In figure 7 a conventional tractor linkage is 30 shown with a pair of bottom arms 72 and a fork arm 71. The top mount 70 is adjacent the mount for the fork arm 71. Each bottom arms has terminal pivot points 73 and 76 on the tractor and the post digger frame respectively and intermediate pivot points 74 for the fork arm and 75 for the down force hydraulic rams 85. The down force is 7 achieved by fitting a pair of hydraulic cylinders 85 that are hydraulically connected in parallel between the post driver linkage mounting frame 84 and the tractor lower linkage arms 72 close to the arm lift links. The cylinders 85 are positioned in a substantially vertical attitude to minimise axial loading. Applying hydraulic pressure to 5 the annulus of the cylinder will cause the cylinders 85 to retract and apply a force that has the effect of attempting to lift the tractor rear axle via the lower linkage arms 72. The hydraulic controls are arranged to control the application of this force so that it is only applied when the hammer is required to operate and at all other times both ends of the cylinder are connected to tank, allowing the down force cylinders to act as slaves 10 to any linkage motions. IN the embodiment of figure 8 The linkage arm 71 is replaced by a pair of dual action hydraulic cylinders 88. When down force is needed the cylinders are extended until the fork lifting arms are fully extended upwards. This has the consequence of exerting a downwards force on the lower linkage arms which in turn adds to the applied force of 15 the post driver. The hydraulic design is arranged to limit the maximum value of the down force to prevent overstressing of the tractor linkage components. This can be achieved by adjusting the maximum down force circuit pressure and / or the cylinder annulus area. Those skilled in the art will realize that the post driver of this invention is safe to 20 use as the impact zone is always enclosed. The hydraulic circuit lines and the amount of fluid required can be kept to a minimum using the hydraulic circuit design of this invention. When an auger is required the auger carriage is swung into position using the hammer carriage hydraulics. Those skilled in the art will also realize that this invention can be implemented in 25 embodiments other than those shown without departing from the core teachings of the invention.

Claims (5)

1. A post driver for use with a tractor having linkage arms which includes a) a vertical support frame 5 b) a carriage arranged to move vertically relative to said frame c) an accelerated hammer arranged within the carriage to move relative to the carriage d) at least one hydraulic cylinder that is hydraulically connected to the tractor lower linkage arms such that applying hydraulic pressure to the cylinder will apply a force 10 that has the effect of attempting to lift the tractor rear axle via the lower linkage arms. e) a post guide and cap for seating on the top of a post

2. A post driver as claimed in claim 1 in which the post guide is held within the 15 lower section of the carriage and arranged for limited movement relative to the carriage to allow for the correction of the post alignment during hammering.

3. A post driver as claimed in claim which includes an auger attachment that is semi automatically adapted to be positioned under the hammer carriage 20

4. A post driver as claimed in claim 1 which incorporates a pair of hydraulic cylinders that are hydraulically connected in parallel between the post driver linkage mounting frame and the tractor lower linkage arms such that applying hydraulic pressure to the cylinders will cause the cylinders to retract and apply a force that has the effect 25 of attempting to lift the tractor rear axle via the lower linkage arms.

5. A post driver as claimed in claim I in which at least one dual acting hydraulic cylinder is incorporated between the fork arm mount of the tractor and the lower linkage arms of the tractor such that when the cylinders are extended until the fork 30 lifting arms are fully extended upwards they exert a downwards force on the lower linkage arms.