Rough terrain hydraulic mower attachment

A rough terrain hydraulic mower, with dual blades, attached in a non-rigid manner to a backhoe boom mounted on the towing tractor by way of a three point hitch arrangement.

BACKGROUND--FIELD OF THE INVENTION 
This invention provides an improved means of cutting grass, underbrush, and 
small trees growing on the side of levees, waterways, and ditches. The 
invention consists of a successful hydraulic circuit with two hydraulic 
motors driving two separate cutting heads with the mower deck modified to 
trail the tractor, while riding on the ground, mounted on a backhoe boom 
to permit improved vehicular maneuverability. 
BACKGROUND--DESCRIPTION OF PRIOR ART 
A patent search was conducted in Class 56, sub-classes 10.9, 11.9, 15.2, 
and 15.5. The folowing patents were discovered: 
______________________________________ 
3,045,413 07/24/1959 Sheffer 
2,997,835 08/29/1961 Stewart 
3,462,925 08/26/1969 Lanier 
3,665,685 05/30/1972 Allard 
3,729,910 05/01/1973 Hardee 
3,949,539 04/13/1976 Cartner 
4,048,789 09/20/1977 Cartner 
4,206,580 06/10/1980 Truax et al 
4,502,269 03/05/1985 Cartner 
4,769,977 09/13/1988 Milbourn 
4,802,327 02/07/1989 Roberts 
4,996,830 03/05/1991 Davison 
5,201,350 04/13/1993 Milbourn 
5,174,098 12/29/1992 Emery 
______________________________________ 
It is necessary to keep trees from growing on river levees, or else the 
tree root systems become extensive and weaken the levee, providing leakage 
paths for the water contained by the levee. To date, there has not been a 
good way to do this. Conventional mechanical mowers are not very 
maneuverable and don't mow the young trees and underbrush as well or as 
quickly as is desired. A common practice is to drag a bar or weighted beam 
across the levee to break down the trees. This is not very satisfactory 
either. This inventor did not start out to invent a better means of 
cutting the underbrush, trees and grass off the river levees. This 
inventor tried to buy a commercial mowing means to accomplish the above, 
and was informed by the "Woods" brand brush cutting mower manufacturer, 
that a hydraulic version of their type of mower did not exist, and was not 
practical for this application. So the inventor purchased a "Woods" brand 
dual spindle PTO shaft driven "bush hog" and proceeded to modify it to do 
the job. This inventor obtained, from a prominent Indiana based fluid 
power distributor, hydraulic motors, pumps, and other components that were 
supposed to do the job in a conventional way. The conventional, state of 
the art approach did not work. At that point the inventor improved on the 
state of the art approach until it worked very well, for the intended 
purpose. i.e. mowing heavy grass, underbrush, and small trees on levees 
and waterways and in ditches at several miles per hour. 
There are reasons why no one has come up with a feasible tractor attachment 
for heavy duty rough terrain mowing to date. The hydraulic systems on 
agricultural tractors are usually sized for raising and lowering a tool. 
They are seldom sized for running hydraulic motors. (American Society of 
Agricultural Engineers, St. Joseph, Mich. Paper #921604, #Eliminate 
Agricultural Tractor PTO Driveline Accidents . . . ", George H. Morgan, 
Appendix C, 3rd par.) The tractor hydraulic system on the "Ford 8730 Power 
Shift" tractor, which is a large tractor, was adequate for operating the 
backhoe boom, but an additional hydraulic system had to be added to the 
vehicle to operate the mower. Where to hang the pump is a problem. Mobile 
hydraulic pumps typically operate most efficiently in the 2,000/3000 rpm 
range. The faster the rpms, the smaller the pump required for a given 
flow. However, there are only two places to put the pump. One is off the 
front crankshaft of the engine. The other is off the power take off, which 
is popularly known as the PTO. There are major problems, outlined in the 
above Appendix C, to hanging the pump off the front crankshaft. The 
typical PTO operates at either 540 rpm or 1,000 rpm. Those are not 
volumetricly or mechanically efficient speeds for gear pumps or axial 
piston pumps. The mower the inventor modified was a Woods, Division of 
Hesston Corporation, a manufacturer located in Oregon, Ill., Model 121 
commercial two spindle mower. The recommended blade speed range was 730 or 
1000 rpm, depending on whether the customer used a 540 rpm or a 1,000 rpm 
PTO speed according to their published literature. That recommended blade 
speed range is not an efficient range for gear motors or axial piston 
motors. As it is on the high side of the speed range of gerotor motors up 
to this time, making a hydraulic system work for this application is not 
as simplistic as portrayed by the patents uncovered to date. There has 
been some development of orbital gerotor motors as pumps to work in the 
540 rpm range (Ref. ASAE Paper 921604 previously mentioned) but the 
manufacturer has only acheived relatively light applications to date. A 
gear pump with two gear motors and a valve type flow divider was the 
original recommendation by the hydraulic components supplier for 
converting the "Woods" mower from mechanical to hydraulic drive. 
The valve type flow divider to split the flow between the two gear motors 
operating in parallel is the common type of flow divider in agricultural 
circles. But, it was a factor in the excess heat generated in the initial 
mowing trials. An explanation for this problem is found in Appendix A, of 
the Paper #911596 "Gerotor Rotary Flow Divider" by George H. Morgan, P. 
E., published by the American Society of Agricultural Engineers, St. 
Joseph Mich. Replacing the valve type flow divider with a gerotor rotary 
flow divider during the redesign improved system efficiency. 
The original installation ran exessively hot so an oil cooler was added. 
Even with the oil cooler, the top mowing speed for the intended purpose 
was in the order of approximately one half mile per hour, which was not a 
feasible attainment, considering the equipment involved and the costs 
incurred. After two mowing seasons, this inventor revised the design and 
the resulting invention now is speed limited by the terrain, not the 
hydraulic system, to a mowing speed of several miles per hour. 
In reviewing the above patents, boom mounts seem quite common. However, in 
the boom mounts covered in the above patents, the mowers are suspended 
from the boom so the operator needs to constantly monitor the height of 
the mower with respect to the ground being mowed. The mower doesn't travel 
on the ground, it is suspended from the boom, requiring constant attention 
by the operator. This is not practical for mowing the heavy grass, 
underbrush and small trees on a levee or in a ditch or waterway at a speed 
of several miles per hour. 
U.S. Pat. No. 3,045,413 by Sheffer is shows a dual mowing approach. 
However, the circuit shown doesn't work. With none of the valves open, the 
hydraulic pump, if sufficiently powered, would break, unless a relief 
valve was added. If both valves to both motors were opened, whichever 
motor that was the least loaded would use all the oil, and the most loaded 
motor would stall. There is no arrangement to divide the flow between the 
motors. If only one valve operated at a time, it is no longer a tandem 
mowing mechanism. Sheffer mentions water as one of the fluids for 
operation. To date, none of the agricultural tractor hydraulic systems 
work on water. Sheffer's patent is dated 1962. 
U.S. Pat. No. 3,665,685 by Allard also shows a dual mowing approach. He 
proposes two hydraulic mowers in series. The circuit he discusses would 
work for relatively light mowing tasks, such as trimming grass around 
fences, but he does not have relief valves in his circuit. When two 
hydraulic motors are in series, the pressure from the pump equal the sum 
of the pressure drops across each of the two motors. An excess pressure 
surge, say from the last hydraulic motor in the series hitting an 
obstacle, could damage that motor, plus the upstream motor in series, plus 
the original pump. Using hydraulic motors in series, where one can expect 
to run into obstacles, without relief valves, is an invitation to 
disaster. In the series circuit, all the pumped oil goes through each of 
the two motors, with the pressure available divided up between the motors. 
In a parallel circuit, the oil would be split between the motors, and the 
pump pressure no longer has to equal the total of the pressure drops 
across the motor. 
This inventor's solution to the inadequate attempts by Sheffer and by 
Allard will be detailed in this application. 
The present invention is a dual mowing arrangement, with two side by side 
blades, each blade driven by a hydraulic motor, with an improved means of 
insuring more or less equal blade speeds, independent of blade loading, 
with the mowing arrangement riding on the ground with minimal operator 
attention. i.e. as the tractor is mowing, the operator can concentrate on 
where he is going, and not need to constantly monitor and adjust the boom 
arrangement. The boom arrangement permits off-set mowing, while the 
boom/mower connection is such that the mower deck can rise or fall with 
respect to the boom, so the mower's position with respect to the ground is 
determined by the wheels and the deck height adjustment. As the present 
invention allows the mower to follow the contour of the ground being mowed 
which is different than the ground the tractor wheels are traversing, in 
rough terrain, the operator is not required to moniter and adjust the boom 
constantly to allow for changes in relative slope or ground elevation with 
respect to the vehicle. In the sales literature this inventor has seen, 
showing boom mounted mowing decks in operation, the operator, when shown, 
is looking at the mower deck instead of where he is going. That seems an 
unsafe mowing condition. In the present invention, the operator can focus 
on where he is going, as opposed to continually monitoring and adjusting 
the boom so the mower deck is at a proper elevation and orientation with 
respect to the ground. 
There are additional societal benefits far beyond the immediate task at 
hand. "More than 25,000 people were treated at hospital emergency rooms 
last year (1991) for injuries related to farm equipment. That was an 11 
percent increase over 1990. The majority of 1991 farm injuries were 
related to tractors, silo loaders, tillage equipment, posthole drivers, 
mowers, hay processing equipment, and wagons." U.S. Consumer Products 
Safety Commission. (From the Evansville (Indiana) Courier, Saturday, Aug. 
29, 1992, p.3A. Discover column. "25,000 Injured in Farm Accidents Last 
Year.") "A Sentry Insurance spokesman who insures Farm Equipment 
Manufactuers Association members said that 90% of his payouts are split 
between drive line accidents and feed grain auger incidents." The source 
of these facts is the previously mentioned Amercan Society of Agricultural 
Engineers Paper No. 921604. 
In the present invention, the pump is close coupled to the tractor PTO 
drive shaft, said pump within the three point hitch to which the boom 
attaches. This arrangement is an improvement over the long exposed drive 
shaft one so frequently sees on mowers along the side of the highway. 
An additional benefit of a hydraulic driven mower, is that hydraulic drives 
can have safety interlocks such that if an operator falls off the tractor 
seat, the hydraulics are shut off. There are sad mowing accidents, on 
occasion, where the operator fell off the tractor, survived the fall, only 
to be killed by being run over by mechanically driven mower attachment. 
SUMMARY 
The invention starts with a Woods, Division of Hesston Corporation, Oregon, 
Ill. Model 121 commercial two spindle "bush hog" type mower. The PTO drive 
shaft as well as two drive shafts on the mower, and the gearing 
arrangements for driving the spindles which drive the mowing blades are 
removed. A hydraulic motor is directly mounted over each of the two 
spindles. In this aplication, all pumps and motors referred to are 
hydraulic pumps and motors. 
A relief valve is installed at or in the motor to protect the motor in the 
event of the blade hitting an obstruction. 
A major obstacle to a dual blade hydraulic mower was lack of an efficient, 
economic way to keep the dual blades, driven by hydraulic motors, at 
approximately equal speeds. 
Three alternatives considered for the present invention are: 
1) A"Gerotor" rotary flow divider splitting the flow between the two 
hydraulic motors operating in parallel; 
2) operating the two motors in series, where all the flow from the pump 
goes through each of the two motors in series; and 
3) using a double section pump, each section of equal displacement, each 
section driving one motor. 
The purpose of these alternatives is to insure that in the event one motor 
is more heavily loaded than the other, the relative blade speeds are more 
or less equal, until a motor sees sufficient pressure to open a relief 
valve in or adjacent to the given motor. Otherwise, in a parallel circuit, 
i.e. where the pump flow is split between two motors, in the event one 
motor is under more load than the other, the motor with the heavier load 
tends to stall while the other motor tends to overspeed. Operating the 
motors in series can cause excessive cumulative pressure drop which causes 
problems in heavy duty operating conditions. 
As the pressure and speed characteristics of gear motors and gear pumps are 
similar, the parallel circuit with the "Gerotor" flow divider is a 
balanced design. As the most efficient pressure operating ranges of 
orbiting "Gerotor" motors is typically approximately half that of gear 
pumps, (Ref. Eaton Fluid Power Products, Eaton Corp., 15151 Highway 5, 
Eden Prairie, Minn. 55343, Form no. 11-850-120, February 1980, for typical 
optimum pressure and speed ranges. Later literature does not convey the 
information as well. Also ref. Permco, Inc. 1500 Frost Road, Streetsboro, 
Ohio 44241-0829 Design Engineer's Handbook for typical hydraulic gear pump 
and motor performances.) using a gear pump, with two orbiting gerotor 
motors in series, thereby eliminating the "Gerotor" rotary flow divider is 
also a balanced design. The trade off is that at the 754 to 1000 rpm blade 
speed listed in the specifications sheet for the "Wood's" 121 mower, the 
gear motors would be running below their optimum speed for volumetric and 
mechanical efficiency, and the orbiting gerotor motors would be running at 
the high end of their recommended speed range for optimum life but have a 
higher volumetric efficiency. Also, orbiting gerotor motors have a very 
high mechanical efficiency at dead stop start ups as compared to gear 
motors. This is desirable in start-ups under load conditions. In the 
series circuit, relief valves would be highly desirable at or in each of 
the motors. In the parallel circuit with the gear motors, relief valves 
are highly desirable at or in each of the gear motors to protect each 
motor and also at or in the pump to protect the pump. Closed loop 
hydrostatic drives also can be made to work but are not as economically 
feasible at the present time. 
The preferred embodiment of the present invention employs a double section 
vane pump, with each of the sections equal in displacement, each section 
powering an orbiting "Gerotor" motor, each motor having an integral relief 
valve. The Woods mower literature recommends a blade speed of 1,000 rpm. 
This is at the upper limit of the recommended speed of an orbiting gerotor 
motor. Such motors are catagorized in the trade as low speed, relatively 
high displacement hydraulic motors. Vane motors are typically catagorized 
as relatively high displacement low pressure as compared to gear pumps. 
So, by going with a vane pump, double section, each section powering an 
orbiting gerotor motor, with the displacement of the pump such that the 
motors are sized to keep the pressure down, the result is an efficient 
hydralic circuit driving the mower blades at the required rpm. The 
integral relief valve in the motor simplifies the circuitry by eliminating 
hoses and connections. 
The mower is further modified by adding a dual front wheel arrangement with 
an eye that serves as the attachment point for the clevis pinned in one 
end of the backhoe. The hydraulic hoses are then run from pump to the 
motors and then from the motors back to a return line filter then to a 
reservoir. In one of the emboidiments, a "Gerotor" flow divider is 
upstream of the motors. There are a variety of hydraulic circuitry 
arrangements for providing oil flow at the pressure required. For running 
the hydraulic motors in parallel, a rotary gerotor flow divider divides 
the flow more or less equally between the two hydraulic motors so the 
blades speeds are more or less equal from one hydraulic motor to the next. 
In one of the embodiments, to be discussed in the detailed description, a 
double section vane pump is used as an alternative to using the gerotor 
flow divider for a parallel flow arrangement. An added advantage of the 
vane pump is that they are more efficient than a gear pump at 1,000 rpm. 
Vane pumps are rarely used on mobile hydraulic applications as the 
pressure ratings are less than those of gear pumps. The vane pump is used 
on the preferred embodiment of the invention as its operating 
characteristics matched those of the orbiting "Gerotor" motors and the 
combination was more efficient than any alternatives considered. 
It is important to minimize heat in the circuitry. The initial circuitry, 
state of the art, from a prominent Indiana fluid power distributor, did 
not work, because of excess heat generation encountered in the types of 
vegetation encountered on levees and in ditches and waterways. Refinements 
beyond the initial circuitry were required. 
An important factor was using SAE rated engine oil as opposed to the 
recommended hydraulic oil. The better oil, with higher temperature 
ratings, was a factor in success. Hydrdaulic oil seems to be formulated on 
the assumption that the hydraulic system is going to be running at around 
120 degrees Fahrenheit. As the present invention ran hotter than that with 
the general purpose type hydraulic oil, the additives were cooking out, 
the system efficiency decreased, and the oil got even hotter. Switching to 
an SAE engine oil, which has a much higher temperature rating, helped the 
system efficiency, reducing the heat generated. 
A valve type flow divider was recommended as state of the art to divide the 
flow between the two motors in parallel so as to have approximately equal 
blade speeds from one motor to the next. According to the circuit 
proposer, with the valve type flow divider, the blades would stay at equal 
speeds in the event one blade was more heavily loaded than the other. What 
the circuit proposer didn't or couldn't say, was that in the event of 
unequal blade loads, heat would be generated. Excess heat was encountered. 
So a "Gerotor" rotary flow divider was used, that was considerably more 
efficient. Apparantly, no one had ever been successful with a heavy duty 
rough terrain twin spindle hydraulic mower before because they believed 
the experts on how to do it. 
An extension to the front of the mower frame was added. This extension 
included two additional wheels, bringing the wheel total to four wheels. 
Two wheels were on the leading edge of the mower and two were on the 
trailing edge of the mower. 
The backhoe boom was mounted on the "Ford" tractor by way of a thre point 
hitch arrangment and the modified mower deck was attached to the backhoe 
boom with a loose, non rigid connection. This connection consisted of an 
eye on the mower deck extension and a clevis on the end of the backhoe 
boom. This connection had sufficient play that the mower deck could ride 
on the ground, and the ground elevation and slope with respect to the 
vehicle could vary, without the operator having to adjust the boom. 
The backhoe boom does several things. It improves total vehicle 
maneuverability, providing short turning radii to permit turns on the top 
of the levee as well as minimizing the necessity of driving onto farmland 
adjacent to the levee. The backhoe boom also permits off-set mowing, which 
is advantageous at times when mowing levees, ditches, and waterways. The 
backhoe boom connection arrangements to the mower permit the operator to 
focus on where he is going, and to concentrate on driving on the rough 
terrain, dragging the mower directly behind him. The backhoe boom was 
modified to match the three point hitch used on the tractor. This inventor 
does not know of anyone else every mounting a backhoe boom on a tractor 
with a three point hitch. 
The problem of timing the blades, so they would not interfere which each 
other, was solved by cutting the tips off, so the blades were short enough 
so the blade tips wouldn't hit each other. Even though there is some 
clearance between the blade tips, the normal bounce and jounce associated 
with rough terrain mowing on levees, in ditches, and on waterways, as a 
practical matter there was not a noticeable line of uncut grass. The 
blades were left long enough the grass still was cut properly. The only 
limit to the speed was the operator's judgement on what was a safe speed 
on the rough levee, waterway, or ditch terrain. Normally this worked out 
to several miles an hour. 
The inventor discovered, from the field trials a smaller tractor than the 
"Ford 8730 Powershift" was unable to drag the mower attachment through the 
underbrush.

REFERENCE NUMERALS IN DRAWINGS 
1. rough terrain mower assembly 
2. backhoe boom 
2A. clevis pin 
3. blade 
4. mower 
6. motor 
8. relief valve 
10. coupling 
12. oil reservoir 
14. pump 
15. double section vane pump 
16. intake line filter 
18. return line filter 
20. drive shaft 
22. hydraulic pressure line 
24. hydraulic return line 
25. pump intake line 
26. oil cooler 
28. eye 
30. clevis 
32. frame extention 
34. leading wheel 
36. trailing wheel 
38. flow divider 
40. mower leading edge 
43. tractor 
44. three point hitch 
DETAIL DESCRIPTION WITH RESPECT TO DRAWINGS 
Referring to FIG. 1, the preferred embodiment of the invention, is shown as 
a rough terrain mower assembly 1, which includes a backhoe boom 2, a mower 
4, and a variety of hydraulic components which will be discussed in the 
description that follows. 
The mower 4 includes a frame extension 32 which includes leading wheels 34. 
The frame extension 32 with the leading wheels 34 is an addition to the 
original Woods twin spindle mower. 
The backhoe boom 2 is modified to attach to a three point hitch 44, said 
three point hitch 44 as typically used with agricultural tractors and not 
in in itself inventive. While there is nothing unique about mechanically 
adapting anything to fit said three point hitch 44, the idea of attaching 
a backhoe boom 2 to the three point hitch 44 is novel and not something 
the inventor has seen done before. A clevis 30 attaches to the backhoe 
boom 2 by means of a clevis pin 2A. 
The mower 4 includes an eye 28, which accepts the clevis 30 which attaches 
to the backhoe boom 2 by means of the clevis pin 2A. This means of 
attachment permits some slack which allows the mower 4, which includes 
trailing wheels 36 as well as the frame extension 32 which includes the 
leading wheels 34, to ride on the ground as opposed to the mower 4 being 
rigidly mounted to, and suspended from, the backhoe boom 2. This is an 
important detail. This allows the operator in the tractor to watch where 
he is going, as opposed to having to look back over his shoulder, or to 
one side, to monitor the height of a mower with respect to the ground 
while constantly adjusting a boom elevation to adjust for changing ground 
contours. 
The backhoe boom 2 has all the degrees of movement associated with backhoe 
booms, up and down, in and out, and left to right, which permits placement 
of the mower 4 on either side of the towing tractor or behind the tractor. 
This permits quite of variety of mowing cuts, including ditches, levees, 
and roadways. While the backhoe boom 2 in itself is not inventive, its 
connection to the mower 4 as well as the connection to the tractor 43 by 
way of the three point hitch 44 does seem inventive to this inventor. The 
joining of the backhoe boom 2 to the three point hitch 44 forms a 
protective frame around a double section vane pump 15 which is connected 
to a drive shaft 20 by a coupling 10. 
Refer to FIG. 4. for the preferred embodiment of the hydraulic system. Each 
section of a two section vane pump 15, drives a motor 6. Each motor 6 
contains a relief valve 8. In the preferred embodiment an HB series 
orbiting "Gerotor" motor with integral relief valve as manufactured by 
White Hydraulics of Hopkinsville, Ky. is used to power each blade 42. An 
oil cooler 26 is optional, as is an intake line filter 16 and a return 
line filter 18. There is also an oil reservoir 12. Pump intake lines 25 
and hydraulic return lines 24 are shown with arrows indicating direction 
of oil flow. There are also hydraulic pressure lines 22 in FIG. 4. 
FIG. 1 illustrates the locations of these components, except for an intake 
line filter 16 and a return line filter 18, both of which can be located 
in a variety of places, including the oil reservoir 12. 
FIG. 2 shows an alternate embodiment that differs from FIG. 4 in that a 
pump 14, which is a single section pump, drives two motors 6 in parallel. 
As said motors 6 are in parallel, some means of dividing the flow is 
required. Otherwise, the motor with the lightest load will tend to 
overspeed while the motor with the heaviest load will tend to stall. A 
rotary flow divider, 38 solves this problem. A "Gerotor" rotary flow 
divider as manufactured by White Hydraulics of Hopkinsville, Ky. was used 
in this alternate embodiment as a replacement for a valve type flow 
divider, which was the heretofore state of the art. A rotary flow divider 
divides the horsepower as required by the differing loads on the motors. A 
valve type flow divider doesn't. This turned out to be quite critical in 
successful operation of the hydraulic system as shown in FIG. 2. FIG. 2 
includes the the intake line filter 16, the return line filter 18, the 
hydraulic pressure line 22, the hydraulic return line 24, the pump intake 
line 25, the oil cooler 26, relief valves 8, and the reservoir 12. 
Directional arrow heads indicate the direction of oil flow to assist in 
understanding the circuit. 
FIG. 3 shows an alternate embodiment that differs from FIG. 2 in that two 
motors 6 are run in series, to eliminate the rotary flow divider as used 
in the FIG. 2 embodiment. The cumulative pressure drops across the motors 
6, in series, makes the FIG. 3 embodiment of the present invention less 
desirable than preferred embodiment as shown in FIG. 4. 
The state of the art in tractor hydraulics is gear pumps and gear motors. 
They don't work very efficiently at the speeds involved. The drive shaft 
20 operates at 1,000 rpm, which is not an optimum speed for hydraulic gear 
pumps or motors. Most tractors have an alternative drive shaft speed with 
a 540 rpm range. This is even less desirable than a 1,000 rpm range. A 
vane pump works much more efficiently at 1,000 rpm a gear pump, which is 
why it is the choice in the preferred embodiment. By using a double pump, 
a flow dividing arrangment such as is used in FIG. 2 is avoided in FIG. 4. 
FIG. 5 illustrates the preferred embodiment of the invention where a mower 
leading edge 40 is at twice the height of a blade 3. The mower leading 
edge 40 bends the grass forward, putting the grass in tension, which 
reduces the torque required by the blade 3 to cut the grass. That has not 
been seen on previous mowers by this inventor. 
The backhoe boom 2 is operated by the tractor hydraulic system, including 
typical directional valves. This is not novel so such operation is not 
detailed. 
The drive shaft 20, which powers the pump 15 through the coupling 10 is 
from the tractor PTO which is a part of the tractor which is not 
inventive, so is not given a reference number. 
Hydraulic pressure lines 22, hydraulic return lines 24, and pump intake 
lines 25 are indicated in the various figures, along with direction 
indicators where appropriate to assist in understanding the embodiment of 
the invention shown. 
Although the description above contains many specificities, these should 
not be construed as limiting the scope of the invention but as merely 
providing illustrations of some of the presently preferred embodiment of 
this invention. For example, a back hoe boom, modified by removing the 
bucket is used to drag the mower through the grass and trees. A similar 
boom, that wasn't a surplus backhoe boom would serve the same purpose. 
While gear pumps are referred to as a specificity, piston pumps would also 
do the job. 
Thus the scope of the invention should be determined by the appended claims 
and their legal equivalents, rather than by the examples given.