WO2008049159A1

WO2008049159A1 - Post driver

Info

Publication number: WO2008049159A1
Application number: PCT/AU2007/001613
Authority: WO
Inventors: Rodney Brooke
Original assignee: Brooke & Mackenzie Pty Ltd
Priority date: 2006-10-25
Filing date: 2007-10-24
Publication date: 2008-05-02
Also published as: AU2007308744B2; AU2007308744A1

Abstract

A post driver which includes a vertical support frame and a carriage arranged to move vertically relative to said frame by means of a dual action hydraulic ram. A hammer is arranged within the carriage to move relative to the carriage by means of a lifting ram on the upstroke and gravity on the down stroke. 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 arranged for limited movement relative to the carriage. A surge chamber is located adjacent and in communication with the return line of the hydraulic cylinder for the hammer to accommodate the increased fluid flow when the hammer falls. Springs are associated with the hammer and the hydraulic ram lifts the hammer against the force of the springs so as to provide a spring accelerated fall for the hammer. The hydraulic circuit for the two hydraulic rams includes a check valve to ensure hammer is not able to be lifted until the carriage ram is acting downwardly. An auger attachment is provided in which the auger carriage is locked to the hammer carriage when in use and is locked to the vertical support frame in its stowed position. The auger frame seats on a pivot pin on the carriage frame when in use and is transferred to a fixed pivot on the vertical frame when the hammer carriage is raised to its stowed position.

Description

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1

POST DRIVER

This invention relates to a an improved post driver particularly for farm fencing and roadside barriers. Background to the invention. Mechanised 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. 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 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 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 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 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. 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 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.

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.

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 which includes a) a vertical support frame b) a carriage arranged to move vertically relative to said frame by means of a dual action hydraulic ram c) a hammer arranged within the carriage to move relative to the carriage by means of a lifting ram on the upstroke and gravity on the down stroke d) a post cap for seating on the top of a post and held within the lower section of the carriage and arranged for limited movement relative to the carriage e) wherein the hydraulic circuit for the two hydraulic rams is arranged to ensure that the hammer is not able to be lifted until the carriage ram is acting downwardly.

This arrangement enables the carriage to carry a cover that encompasses the impact zone. Access to the impact zone is not necessary because the post cap that engages the top of the post is below the impact zone. Access to the impact zone between the hammer and post cap is not possible because the cover which is preferably an integral cover, covers the impact zone during driving and the post cap does not separate from the top of the post during driving. Because the post cap moves relative to the carriage the impact force of the hammer on the post cap is not transmitted to the carriage. 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.

The post cap incorporates a pivoted securing means that adapts to the top surface of the post and ensures that the hammer blow is transferred into the vertical line of the post. For regular shaped posts this may not be necessary but for rough farm posts the cap needs to ensure that the force transferred to the post by the impact of the hammer on the post cap does not result in the post being skewed to the vertical. 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). The valve in the hammer circuit which, when open, allows the hydraulic fluid to flow from the ram and allow for a fast fall of the hammer may be a pressure valve actuated by a predetermined pressure being exceeded or an electrically actuated valve. When an electric actuated valve is used the control may also include an adjustable timer switch to control the period that the hammer valve is open. This enables the height to which the hammer is raised to be adjustable which in turn determines the stroke force of the hammer. Thus to initiate hammering or to control the height of the post the timer can be adjusted so that a lower impact force is applied. Where speed is important the time that the valve is closed can also be adjusted relative to the time that is opened so that the valve is closed long enough for the hammer to have impacted the post cap. The use of an electric actuated valve and timer is an inexpensive means of semi automation of the control of the hammer. When the hammer valve is closed it is necessary to evacuate the hydraulic cylinder as quickly as possible so that the fall of the hammer is not retarded. This is achieved by opening a blocking valve when the hammer valve is closed. The blocking valve opens into a surge chamber or dashpot which is connected by a line leading back to the sump or the hydraulic inlet line. In order to accelerate the fall of the hammer it is preferred to provide coil springs in the carriage biased (for compression or tension) against the hammer so that the hammer ram raises the hammer against these springs. This also avoids the need to provide a damper in the hydraulic circuit to guard against excessive hydraulic pressure in raising the hammer.

A supply side accumulator is preferably incorporated in the hydraulic circuit for the hammer as it reduces the peak oil flow and power required from the pump and enables the required pump size to be reduced. This also reduces the heating in the circuit caused by over pressure relief. The post driving machine may optionally include a digger carriage with an auger that is able to be swung under the hammer carriage so that a pilot hole for the post can be drilled. The auger carriage is locked to the hammer carriage when in use and is locked to the vertical support frame in its stowed position and the auger frame seats on a pivot pin on the carriage frame when in use and is transferred to a fixed pivot on the vertical frame when the hammer carriage is raised to its stowed position.

Detailed description of the invention

A preferred embodiment of the invention is illustrated in the drawings in which: Figure 1 is a front perspective view of the post driving attachment of this invention;

Figure 2 is a rear perspective view of the post driving attachment of this invention;

Figure 3 is a front perspective view of the carriage component of this invention;

Figure 4 is an exploded view of the carriage component of figure 3;

Figure 5 A is an assembled view and 5 B is an exploded view of a first embodiment of the hammer hydraulic ram of this invention;

Figure 6 A is an assembled view and 6 B is an exploded view of a second embodiment of the hammer hydraulic ram of this invention;

Figure 7 shows the hydraulic circuit for the post driver of this invention;

Figure 8 shows the hydraulic circuit for the post driver with auger attachment of this invention;

Figures 9 to 14 show the sequential movement of the optional auger carriage 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 adjusted to its vertical position using the angle ram 15. The carriage 30 moves up and down the vertical frame 12 moved by the dual acting 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 is positioned in front of the frame 12 under the carriage 30. The hammer 43 is secured to the hammer slide 40 which moves within the carriage 30 . The carriage 30 has the channel guides 47 to accommodate the hammer slide 40 which has slide blocks 44 adapted to move within the guides 47 and guide the hammer 43.

The hammer 43 impacts the post cap 50 which is held in the base of the carriage 30 covered by the impact zone cover 46. The cap 50 is composed of two parts the hammer impact plate 51 and the post cap 55. The impact plate 51 has a flange 52 which seats the cap 50 on a corresponding flange on the carriage 30 to locate the impact plate 51 within the covers 46. To improve the transfer of impact force from the hammer 43 to the impact plate, particularly with concrete posts, a resilient pad 54 is located on the impact plate upper surface. The post cap 55 is secured to the bottom of the body 53 of the impact plate 51 by the fasteners 56 and extends beyond the body to form flange 57 which limits the upward movement of the post cap 50 by abutting the flange in the carrier. The height of the body 53 which is the distance between the flanges 52 and 57 is designed to be greater than the maximum relative movement between the carriage 30 and the hammer 43 when the hammer falls at a faster rate than the carriage. The under surface of the post cap 55 is shaped to provide maximum transfer of the impact to the top of the post. When the post is preloaded the flange 57 is forced up to contact the bottom flange of the carriage 30. The preloading of the post with the weight of the carriage ensures that the cap 55 fits tightly to the top of the post. For rough farm posts the under surface may incorporate a pivoted hemispherical cap that can adapt to the top surface of the post. It may also include a spike that prevents the post from sliding or skewing under impact.

The hammer ram 60 pushes the rod 61 upwards. The rod 61 is secured by nut 63 to the top plate 48 of the hammer slide 40 and extends through an opening in the bottom plate of hammer slide 40. Within the carriage hammer guide channels 47 springs 72 are held and these springs are compressed as the slide blocks 44 on hammer slide 40 move upward with the hammer slide as it is raised by the ram 60. The ram 60 is fixed to carriage 30 and includes the ram tube 62 the ram rod 61 and the surge chamber or accumulator 64. The manifold block 65 includes the directional valve 67, the pilot check valve 68 and the hydraulic fluid inlet and outlets 66. Figure 6 illustrates a double acting cylinder 81 used in a second embodiment of the invention adapted for driving agricultural posts where additional down ward force from the hydraulic cylinder is desirable. It includes an addition hydraulic line 82 for exerting the down ward pressure on the rod 61 A The hydraulic circuits shown in figure 7 and 8 are designed so that the machine may operate with either a fixed or variable displacement hydraulic pump which may operate from a tractor remote hydraulic unit or with a dedicated power pack. The embodiment of figure 7 is for a roadside guard rail post driver which has a single acting cylinder 60 as shown in figure 5, and no auger attachment. Referring to figure 7, oil is supplied to the main valve bank with an inbuilt over pressure relief valve PR1. Valves V1 V2 V3 are used to operate the machine positioning functions operated by cylinders C1 (Side shift ) , C2 (Fore/ Aft tilt), C3 (Side tilt). The valve V4 is used to operate the carriage cylinder 17. The

Checked flow control FC1 allows unrestricted upward movement of cylinder 17 but restricted down ward movement. The limit is set at the factory. Pressure reducing relief valve PR2 in combination with the fixed flow control FC2 limits the pressure that can be applied to the carriage cylinder 17 annulus that limits the down force that can be applied to the post by the carriage 30. This is set to limit the proportion of the main frame mass that is utilized to react preload and hammer acceleration forces to maintain machine stability. When V4 is opened to move, via cylinder 17, the hammer carriage 30 downwards, oil is supplied to the hammer enable directional valve V5. This has the effect that the hammer 43 will only work when the hammer carriage is preloaded on a post.

The hammer enable directional valve V5 is used to initiate and stop hammer operation. An electrical switch contact built into V5 starts and stops the hammer electronic timer . The hammer timer alternately applies power to the hammer solenoid directional valve 67. When solenoid directional valve 67 is energized oil is supplied via valve 67 to the hammer cylinder 60. The hammer then rises against gravity and the springs 72. While this is occurring pilot check valve 68 is closed. When the timer de-energises valve 67, it switches the supply oil from the hammer cylinder 60 to the pilot on valve 68. This opens pilot check valve 68 and allows oil to flow from the hammer cylinder through both valves 67 and 68 to tank via hammer enable directional valve V5. When valve V5 is operated pressure is also applied to the pilot of pilot check valve CV1 , opening valve CV1 to provide an alternate low resistance path for the oil from under the piston of hammer carriage cylinder 17. This permits the hammer carriage 47 to fall at a maximum rate to follow the post as it is driven into the ground.

A supply side accumulator ACC1 is placed upstream of the hammer enable directional valve V5. The supply side accumulator acts as a flow averaging device to maintain relatively constant pressure to the hammer carriage cylinder 17 and hammer cylinder 60, while absorbing unused oil flow or discharging oil to the circuit when required. This has the effect that very little or no oil passes across the system pressure relief valve PR1 during hammer operation despite being supplied by a constant volume of oil while the loads require highly impulsive flows. The return accumulator or dashpot 64 is placed in the return line at the hammer cylinder manifold 65. As shown in figures 5 and 6 the hammer cylinder 60 is fixed directly to the manifold 65 to minimize flow path lengths between cylinder 60, hammer solenoid directional valve 67, pilot check valve 68, and return accumulator 64. Return accumulator or dashpot 64 acts during the down stroke or fall of the hammer 43 to absorb the very high but short duration flow from cylinder 60. This prevents excessive back pressure building up in the long return line and path to the tank, thus maximizing the impact velocity of hammer 43. The hammer timer has an operator adjustable on time. This allows the operator to adjust the height that the hammer is lifted to during operation, therefor resulting in higher or lower energy as required. In figure 8 the embodiment is for an agricultural post driver using a double acting cylinder as shown in figure 6 and also includes an auger attachment. An extra valve slice V3A is added to the main manifold to operate the hole digging auger drive MT1. This may be fitted between V3 and V4. Compared to the circuit of figure 7 the single acting cylinder 60 is replaced by the double acting cylinder 81 illustrated in figure 6. The piston 61A diameter is the same as the rod 61 diameter in the single acting cylinder 60. Port 4 of hammer solenoid directional valve 67 in the manifold 65 is connected to the annulus or rod end of cylinder 81 , as is the pilot check valve 68. This allows oil pressure and flow to assist in accelerating the hammer 43 down wards, to achieve a higher impact velocity and consequently higher blow energy.

Because the flow requirement for the hammer is relatively low and the flow requirement of the auger drive is relatively high a variable displacement pump is the most efficient pump for the agricultural hydraulic circuit shown in figure 8. A new auger swing attachment for the Agricultural post driver (figures 6 and 8) is schematically illustrated in figures 9 to 14. Once the Auger is selected it is swung into and out of position by being linked to the movement of the hammer carriage 30. Figures 9 to 14 illustrate the movement of the auger carriage 90 relative to the hammer carriage 30 as the auger 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.

In figure 9 the digger carriage 90 is resting on and aligned with the moving pivot 92 which is attached to the hammer carriage 30and is positioned for engagement with the tube 96 of fixed pivot 95 attached to the machine frame 12. At this stage the auger carriage is latched to the hammer carriage 30.

In figure 10 the auger carriage 90 has been unlatched from the hammer carriage 30 and is rising with the hammer carriage 30 so that the tube 93 on digger carriage 90 is beginning to slide within the tube 96 of the fixed pivot 95. The fixed flat section of the fixed spiral flute 97 inside tube 96 is just engaging the set of rollers 94 in the top of the tube 93 of the auger carriage 90.

As shown in figures 11 and 12 the auger frame 90 swings away from the hammer carriage 30 as the auger carriage tube 93 moves further into the fixed pivot tube 96 and the rollers 94 react against the spiral flute 97. In figure 13 the digger carriage 90 is fully raised and has swung away from the hammer carriage 30. The cam rollers 94 are engaged with the top flat section of flute 97 to hold the auger carriage in its stowed position. At this point the auger carriage 90 in its stowed position is latched to the frame 12. As shown in figure 14 the carriage frame 30 is now able to move down to its operative position on the post.

When the next hole is to be drilled the sequence operates in reverse with the carriage frame rising so that the pivot 92 on the hammer carriage 30 mates with the auger carriage 90. The auger carriage 90 is unlatched from frame 12 and as the hammer carriage 30 and the auger carriage 90 descend the auger carriage swings back into position below the hammer carriage and is latched to the hammer carriage again as in figure 9.

Those skilled in the art will realize that the post driver of this invention is safe to 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 embodiments other than those shown without departing from the core teachings of the invention.

Claims

-10CLAIMS

1. A post driver which includes a) a vertical support frame b) a carriage arranged to move vertically relative to said frame by means of a dual action hydraulic ram c) a hammer arranged within the carriage to move relative to the carriage by means of a lifting ram on the upstroke and gravity or on the down stroke d) a post cap for seating on the top of a post and held within the lower section of the carriage and arranged for limited movement relative to the carriage e) wherein the hydraulic circuit for the two hydraulic rams includes is arranged to ensure that the hammer is not able to be lifted until the carriage ram is acting downwardly.

2. A post driver as claimed in claim 1in which hammer is moved relative to the carriage by a dual acting hydraulic ram which lifts the hammer on the upstroke and is additional to gravity on the down stroke.

3. A post driver as claimed in claim 1 or 2 in which a surge chamber is located adjacent and in communication with the return line of the hydraulic cylinder for the hammer to accommodate the increased fluid flow when the hammer falls.

4. A post driver as claimed in anyone of claims 1 to 3 which includes an electrically operated valve in the return line of the hammer lifting ram with an associated timer to set the time that the valve is closed and the lifting ram is lifting the hammer and the time that the valve is open when the hammer is allowed to fall.

5. A post driver as claimed in claim in anyone of claims 1 to 4 in which springs are associated with the hammer and the hydraulic ram lifts the hammer against the force of the springs so as to provide a spring accelerated fall for the hammer. A post driver as claimed in claim 1 in which the post cap is arranged to guide the top of the post so that it is driven vertically.

A post driver as claimed in claim 5 in which the post cap incorporates a pivoted securing means that adapts to the top surface of the post and ensures that the hammer blow is transferred into the vertical line of the post.

A post driver which includes a. a vertical support frame b. a carriage arranged to move vertically relative to said frame by means of a dual action hydraulic ram c. a hammer arranged within the carriage to move relative to the carriage by means of a lifting ram on the upstroke and gravity on the down stroke d. a post cap for seating on the top of a post and held within the lower section of the carriage e. where in a surge chamber is located adjacent and in communication with the return line of the hydraulic cylinder for the hammer to accommodate the increased fluid flow when the hammer falls.

A post driver as claimed in claim 8 in which hammer is moved relative to the carriage by a dual acting hydraulic ram which lifts the hammer on the upstroke and is additional to gravity on the down stroke.

A post driver as claimed in claim 8 or 9 which includes an electrically operated valve in the return line of the hammer lifting ram with an associated timer to set the time that the valve is closed and the lifting ram is lifting the hammer and the time that the valve is open when the hammer is allowed to fall. A post driver as claimed in any one of claims 8 to 10 in which springs are associated with the hammer and the hydraulic ram lifts the hammer against the force of the springs so as to provide a spring accelerated fall for the hammer.

A post driver which includes a. a vertical support frame b. a carriage arranged to move vertically relative to said frame by means of a dual action hydraulic ram c. a hammer arranged within the carriage to move relative to the carriage by means of a lifting ram on the upstroke and gravity on the down stroke d. a post cap for seating on the top of a post and held within the lower section of the carriage e. an electrically operated valve in the hydraulic return line of the hammer lifting ram with an associated timer to set the time that the valve is closed and the lifting ram is lifting the hammer and the time that the valve is open when the hammer is allowed to fall.

A post driver as claimed in claim 10 in which springs are associated with the hammer and the hydraulic ram lifts the hammer against the force of the springs so as to provide a spring accelerated fall for the hammer.

A post driver as claimed in claim 10 or 11 in which a surge chamber is located adjacent and in communication with the return line of the hydraulic cylinder for the hammer to accommodate the increased fluid flow when the hammer falls. An auger attachment for a post driver as claimed in any of the previous claims in which the auger carriage is locked to the hammer carriage when in use and is locked to the vertical support frame in its stowed position wherein the auger frame seats on a pivot pin on the carriage frame when in use and is transferred to a fixed pivot on the vertical frame when the hammer carriage is raised to its stowed position.