Note: Descriptions are shown in the official language in which they were submitted.
~OTO~ G~ADER BROOM
Field of the Invention
This invention relates to road grading and maintenance
equipment, and more specifically to road graders having mold
boards or blades for grading a surface9 and vehicles having
rotary sweepers for brushing debris from a surface.
Back~round of the Invention
Motor graders having a mold board or blade for scraping
a surface are commonly known and extensively used in highway
and airport construction and maintenance. In many road con-
struction projects, the grader blade is passed over a surface
with the mold board smoothing and scraping off irregularities --
to provide a finished surface which may then be either paved or
coated with oil or asphaltic material to provide a smooth hard
surface. A separate piece of equipment having its own operator
and mounting a rotary broom is then passed over the finished
surface to clear away the finer debris left behind once the
construction is completed. In other situations shoulder repair
work may be required on existing paved surfaces. In these
situations, a motor grader blade is used to provide a reworked
shoulder surface. This procedure may also require other earth
moving equipment in the area creating a need for general clean
up of the road surface for safety reasons as well as
appearance. Thus specialized pieces of equipment and skilled
operators are needed in most instances, which contributes
significantly to the overall cost. Most road and highway
maintenance organi7ations do in fact need both a grader and a
broom.
At present, there is no single apparatus which satis-
factorily combines the functions of the motor grader and the
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rotary broom in such a way that the mold board or the broo~ can
be u6ed, separately or together as desired, without time con-
suming and complicated broom removal or mounting procedures.
The need exists therefor for a combined grader and broom in
which the mold board and the broom may be independently verti-
cally adjustable 50 that each may be used alternately or
together ~7ithout interference from the other. Preferably, such
a device should not be significantly more complicated to
operate than a grader alone or a broom alone and would include
automatic side shiEting of the broom independently or and
concurrently with the blade as well as vertical adjustment of
the broom to avoid its interference with the structure of the
motor grader in ay position of operation. A prescribed con-
stant downward pressure exerted by the broom as well as its
speed and direction of rotation should also be automatically
controlled.
Brief Description of the Invention
The present invention includes a rotary broom assembly
mounted in conjunction with a mold board on a conventional
circle arrangement commonly used in motor graders. The broom
assembly may be mounted parallel to the mold board on the
circle of the grader for movement therewith. Additionally, the
broom assembly is capable of vertical adjustmeDt and sideways
movement or "side shifting" independently of the mold board.
For independent vertical adjustment, the broom assembly in one
of the illustrated embodiments includes a longitudinal crossbar
which passes through a pair of collars on the blade mountiDg
arms which descend from the circle and act as a pivotal axis
for vértical pivoting of the broom assembly. In this embodi-
ment a hydraulic ram may be affixed at one end to the circle,
and at the other end to any such means as a slide bar or the
like mounted on the shield or hood which oYerlies the broom.
The broom assembly thus may be raised and lowered by action of
the conventional vertical adjustment of the circle or relative
thereto by the hydraulic ram. In a second embodiment vertical
adjustment of the broom assembly is accomplished by linear
movement. In this embodiment pin and slot connector members
are mounted directly to the blsde mounting arms. The pin and
slot connectors carry the broom assembly and may be raised and
lowered relative to the blade by means of a double hydraulic
ram arrangement acting between the circle and the connectors.
In some cases it may be desirable or necessary to use multiple
sets of lift cylinders to accomodate or share the load of the
broom as it is shifted laterally.
~or independent side shifting, a horizontal ram may be
mounted to act between one of the blade mounting arms and the --
broom shield in the first embodimPnt described to shift the
broom assembly sideways relative to the mold board and or
circle. In the second embodiment the side shift ram may be
connected to act between one of the pin and slot connectors and
the broom hood.
Feelers or sensor arms positioned on the ends of the
broom assembly are used to close switches upon contact with
obstacles such as posts, stakes, or curbs, causing the
horizontal hydraulic ram to automatically side shift the broom
away from the obstacle. This method may also be used to side
shift the mold board to avoid such obstacles. ~imit switches
mounted on the structure of the motor grader may be used as
sensors which close when contacted by the broom assembly,
causing the vertical or horizontal ram to automatically pivot
or shift the broom away from the motor grader structure so as
to avoid interference between the two when the blade is angled,
raised or lowered. Likewise, of course, position sensor
mounted in conjunction with the vertical and side shift link-
ages of the circle may be used to signal the movement of the
broom assembly to avoid interference with the motor grader
structures.
The number of rotations of the broom per foot of travel
of the device is held constant or settable at different
preselected speeds by a broom rotation speed control circuit,
and the downward pressure of the broom is controlled by a broom
pressure control circuit.
Thus a combined grader and broom is provided whicb has
the convenience of automatic position adjustment found in
conventional graders, with the additional utility of indepen-
dently operational grader and broom as~emblies.
Brief Description of the Drawin~s ---
Figo 1 is a perspective view of a preferred embodiment
of the invention;
Fig. 2 is a side elevational view of the grader and
broom assemblies of the embodiment of Fig. 1 with certain parts
broken away;
Fig. 3 is a top plan view of the grader and broom
assemblies of the embodiment of Fig. l;
Fig. 4 is a schematic diagram showing vertical adjust-
ment of the broom asssembly relative to the grader assembly;
Figs. 5 and 6 are schematic top plan views showing
angular positions of adjustment of the grader and broom assem-
blies in a horizontal plane;
Figs. 7 and 8 are schematic rear elevation views show-
ing angular positions of adjustment of the grader and broom
assemblies in a vertical plane;
Fig. 9 is a side elevational view of a modification of
the broom assembly mounting structure;
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Fig. 10 is a perspect;ve view of the modified mounting
structure of Fig. 9;
Fig. 11 is a functional block diagram of the broom
rotation speed control circuit;
Fig~ 12 i8 a schematic diagram of the automatic broom
side shifting mechanism;
Fig. 13 i8 a schematic diagram of the automatic broom
lowering mechanism; and,
Figo 14 is a functional bloc~ diagram of the broom
pressure control circuit.
Detailed Description of a Preferred Embodiment
Referring to Figs. 1-3, the motor grader broom device 1
of a preferred embodiment may be conventional in all respects,
the operation and control of which are well known in the con-
struction arts. According to the present invention, the device
includes a rotary broom assembly 2 mounted parallel to the
conventional grader assembly 3 on a circle 6 of a well-known
design, for movement therewith. The grader assembly 3 includes
a mold board 4 mounted in front of the broom assembly 2, in a
conventional manner on the circle 6. As illustrated in Fig. 3,
the circle is rDtated by a drive pinion 7, so as to rotate the
mold board 4 and, in the present embodiment, the broom assembly
2 in a horizontal plane. The cross angle of the blade or mold
board is thus adjusted relative to the direction of travel of
the machine to control the width of cut and the windrow the
material scraped. The mold board support assembly 8 also
provides sideways adjustment of the position of the mold board
4 in response to well known automatic control means, and the
side shift cylinder 5. Conventional operator-actuated controls
are provided to pivot the circle 6 along a horizontal axis
transverse to the length of the mold board 4, as shown in Fig.
7, and also to raise and lower the circle as shown in Fig. 8.
It will be understood that the structural details of the
described controls for the blade 4 are conventional and form no
part of the present invention except as they relate
functionally with the rotary broom assembly.
The broom assembly 2 includes a horizontal rotary broom
9 mounted on a rotary shaft 11. A curved shield or hood 12
overlies the broom 9 and prevents debris from flying into the
surrounding mechanism in a conventional manner. Referring to
Figs. 3 and 11, the broom assembly 2 may be driven by a conven-
tional reversible hydraulic motor 13 at a speed which is
preferably held to a constant number of rotations per foot of
forward travel or preselected speeds of the motor grader 1 by a
speed adjustment circuit. This circuit includes a speed trans-
ducer 14 which produces an output voltage proportional to the
speed at which the motor grader is traveling. The output from
the speed transducer 14 is connected to a speed adjustment
potentiometer 16, which the operator can set to a resistance
proportional to the desired number of broom rotations per foot
of travel, to produce a result~nt voltage Vt proportional to
the desired target rotational speed of the broom 9, while a
rotational speed transducer 17 produces a voltage Va propor-
tional to the actual rotational speed of the broom 9.
An error amplifier 18 amplifies the difference between
the voltages Va and Vt, and an error integrator 19 integrates
the output from the amplifier 18~ ~hen the difference between
Va and Vt is zero, no correction to the rotational speed of the
broom 9 is needed, and the output voltage Yi from the
integrator 19 remains constant. If the difference between Va
and Vt increases to a non-zero value, then Vi changes at a rate
determined by the resistor Rl, and capacitor Cl, in the in-
tegrator 19, to supply the desired voltage to the motor 13~ A
buffer 21 boosts the voltage Vi as needed to drive the motor
13.
y~ (
Referrin~ again to Figs. 1-3, brackets 22 on the oppo-
site ends of shield 12 support a crossbar 23 parallel to the
broom 9. The crossbar 23 passes through collars 26 mounted the
pair of blade mounting arms 27 which normally extend from and
are fixed to the circle 6. The cross bar is slidably received
in the collars for linear movement. A horizontally disposed
hydraulically actuated ram 28 of conventional design has one
end fixed to one of the arms 27, and the other to the shield 12
for shifting the broom assembly 2 sideways. A generally verti-
cal ram 29 is mounted with one end fixed to the circle 6 and
the other end slideably mounted on a slide bar 31 on the shield
12 to pivot the broom assembly 2 about the crossbar 23 in a
generally vertical position. The slide bar 31 allows the
piston rod to travel therealong during side shifting of the
broom.
Referring now to Figs. 12 and 13, the hori~ontal and
vertical rams 28, 29 in the present embodiment are
automatically controlled by three limit switches 32, 33, 34 on
the body of the device 1 which close on contact with the broom
assembly 2. ~ach of the first two limit switches 32, 33 i6
positioned to contact an end of the broom assembly 2 as it
rotates or pivots with the circle 6 in the manner sho~n in
Figs. 5 and 7. It will be understood that the position of the
limit switches may be chosen so as to provide the optimum
functionality for any particular road grader frame design and
degree of movement of the broom desired. On contact, either of
these limit switches 32, 33 activates the horizontal ram 28 to
shift the broom assembly 2 to the opposite side so that it will
not contact either the wheels or frame of the device 1 or other
surrounding structure. It will be understood also by those
skilled in the art that other rotational controls may be
devised such as a limit switch or the like mounted on the
p~
circle or any relatively moving parts of the rotary frame. Any
such modification is considered to be withiD the the scope of
the present invention.
The third limit switch 34 may preferably be positioned
on the undercarriage of the device 1 to contact the circle 6
when it is raised beyond a predetermined point where the broom
assembly 2 might hit the surrounding structure of the motor
grader device at any given position of horizontal rotation.
When this contact occurs, the third limit switch 34 will
activate the vertical ram 2 to pivot the broom assembly 2
downward, if it is not already in a dropped position, so that
it will clear the undercarriage of the device 1 as the broom
and grader assemblies 2, 3 are raised along with the circle 6.
To avoid damage to the broom assembly 2 from obstacles
on the sides of its path, a feeler 36 as sho~n in Fig. 12 may
be mounted to each end of the broom assembly 2. Each of the
two feelers 36 will close a switch on contact with an obstacle
in a well known manner, to activate the horizontal ram 28 for
shifting the broom assembly 2 away from the obstacle.
Referring now to Figs. 4 and 14, when a sweeping opera-
tion is desired, the mold board 4 is raised by the conventional
control means of the grader to an elevation several inches
above the surface to be swept. In most cases a clearance of S
to ~ inches above the surface will be sufficient to allow the
material being swept by rotary action of the broom to be th}own
forwardly under the blade edge. With the broom and blade in
the angled position shown in Fig. 5 for instance, the material
will work its way to one side off of the roadway or to be
windrowed and picked up later. The blade positioned in front
of the broom will, of course, remove any large obstacles from
the path of the broom and prevent any large build up of
material as the machine advances. When dirt is windrowed, the
broom ~sfiembly may be raised and the blade theu used in its
Dormal fashion to remove and di~tribute the material. The
broom 9 is positioned to contact the ground by any well-Xnown
manual, electrical or other valve means controlled by the
machine operator for activating the vertical lift ram 29. The
downward pressure of the broom 9 is held constaDt by an
electrical pressure control circuit which maintains a
predetermined pressure in the hydraulic cylinder or lines. In
this manner only a predetermined proportion~of the broom weight
is allowed to rest on the surface. This is determined, of
course, by the amount of lift pressure maintained in the
hydraulic line. As shown in Fig. 14, the control circuit
includes a pressure transducer 37 which produces a voltage Yu
proportional to the upward force oE the vertical ram 29. A
pressure adjustment potentiometer 38 and zero adjustment poten-
tiometer 39, which are initially adjusted by the operator,
produce a voltage Vd, proportional to the desired pressure of
the broom 9. In a manner similar to that of the rotation speed
control circuit, an error amplifier 41 am~lifies the difference
between Yu and Vd, and an error integrator 42 integrates this
difEerence to produce an integrator output voltage Vi, which
drives an electric valve 43 through a buffer 44, to supply the
amount of hydraulic pressure, to the vertical ram 29 necessary
to apply the predetermined amount of lift on the broom 9 to
allow it to bear against the road surface with the desired
amount of downw~rd pressure.
Referring to Fig. 11, it is preferrable that the down-
ward pressure of the broom 9 is ceased, and the broom 9 lifted
from the road surface when the motor grader travels in reverse.
To accomplish this, a reverse speed comparator 46 receives the
voltage Vt representing the rate of travel of the device 1, and
activates the vertical ram 29 when the polarity of Yt is
reversed from it~ normal state. A bu~fer ~7 raises the output
voltage from the comparator 46 as needed to drive the vertical
ram 29.
It will be understood, of course, that in addition to
the automatic control of the the position of the broom assembly
2 just described, operator-actuated controls are provided to
selectively lift or lower the broom assembly 2 relative to the
mold board 4 which i6 equipped with independent lift controls.
Thus the broom and mold board may be lifted and lowered
independently or in unison, as desired.
Figs. 9 and 10 illustrate a modified mounting structure
for the broom assembly which provides for linear vertical
adjustment of the broom assembly relative to the blade rather
than the pivotal vertical adjustment of the Figs. 1-4 embodi-
ment. It will be understood, of course, that the overall
function of the broom assembly and automatic controls remain
the same for both embodiments, the primary difference being in
the positioning and functioning of the "side shift" and
"vertical lift" rams of the broom assembly. For this reason
identical reference numerals will be used to describe the
various structural members of Figs. 9 and 10 which are
identical to the Figs. 1-4 embodiment.
As seen in Figs. 9 and 10 the blade support arms 27
which are fixed to the circle 6 are each provided with brackets
48. The brackets 48 may be welded or otherwise fixed to the
lower portions of the arms 27 or other suitable locations and,
in the embodiment illustrated, are preferably located on the
outside surfaces of the arms. Each bracket 48 is provided vith
an elongated substantially vertical slot 49 with the slots
being transversely aligned on the blade arms. The transversely
extending broom hood 12 is provided with an elongated rail or
slider bar structure 51 which is located on one side of the
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hood adjacent to the brackets 48 and includes the side flsnges
52 and 53. The slider bar structures may be made from bar
stock and conviently ~elded or otberwise fixed to the hood. A
connector frame serves to connect the broom assembly to the
brackets 48 and includes the end plates 54 which may be
identical and are rigidly connected together by a cross tie bar
56 to form the connector frame. Each end plate is provided with
two vertically aligned pins 57 which engage the respective
slots 49 in the brackets 48 to form a pin and slot connertion
to guide vertical lift movement of the connector frame and boom
assembly. The vertical lift ram means in this embodiment is
connected between the circle 6 and the cross tie bar described.
In order to gain travel the lift ram means may be
comprised of two independent double acting hydraulic cylinders
58 and 59 coupled in a manner illustrated in Fig. 9 so as to
substantially double the reach capacity of a single ram. When
fixed together in this manner they may be made to operate
sequentially so as to provide both a rough and fine adjustment
as will be apparent to those skilled in the art. As previously
mentioned, laterally spaced multiple lift rams may be desirable
in some instances to ensure stability as the weight of the
broom assembly shifts laterally during "side shifting".
For side shift adjustment a single horizontal ram 61 is
connected between one of the end plates 54 and a suitable
connector on the hood 12 as illustrated in Fig. 10. The advan-
tage of the Figs. 9-10 mounting will lie in its use in those
situations when space constraints require a more compact struc-
ture and operator.
Although the invention has been described with respect
to specific preferred embodiments, further modifications to
these embodiments are considered to be within the scope of the
invention.
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