Note: Descriptions are shown in the official language in which they were submitted.
3541
,. E
RESONANTLY DRIVEN PAVEMENT CRUSHER
The present invention relates to a vertical impact
system, and in particular to a resonantly driven system for
breaking up a pavement surface using a specially adapted
pavement breaking tool.
A variety of different pavement breaking and other
types of surface impact tools are in use at the present
time. Typically, such tools employ a heavy weight which is
lifted and allowed t~ fall to provide the power stroke of
the tool. Lifting of the weight for each stroke is gen-
erally inefficient, but more efficient solutions have not
been available to date where large forces are necessary.
Pneumatic and hydraulic tools are often used, but such tools
are limited as to the amount of force that can be applied
because the reaction forces on the tool are e~ual to those
applied to the surface.
In the patent literature, the patent to Gettelman,
U.S. Patent No. 1,841,802, discloses a pick or tamping tool
located at the end of a leaf spring supported at its center.
This flexible spring, however, is insufficient to generate
sufficiently large forces to break up most pavement, or
provide a sufficient tamping action. Also, the large ampli-
tudes involved render the device hard to control, and appli-
cant has no knowledge that the Gettelman device has ever
been successfully applied in practice.
Theoretical advantages in using resonant systems
to apply large forces have been disclosed in the patent
literature, as illustrated in U.S. Patent Nos. 3,232,669 and
3,367;716, to Bodine. However, such resonant techniques
apparently have not been successfully applied to vertical
impact tools such as the type disclosed herein.
The present invention provides a surface impact
system including a pavement breaking tool particularly
3 ~ 1
adapted to function with a resonant drive system. A
resonant beam having anti-nodes at each end and one or more
nodes therebetween is supported at said node(s) on a mobile
carrier vehicle. An oscillator is fixed to an input anti-
node o. the beam to vibrate the beam at at least near itsresonant frequency. The pavement breaking tool is rigidly
attached to the output anti-node of the beam, located at one
end thereof. The tool can be a pick or other sharpened
implement designed to penetrate the pavement. Alternatively
and preferably, the tool includes a substantially flat
surface oriented parallel to the beam and lying substantial-
ly in the horizontal plane. An upwardly-inclined flange
projects forward (with respect to the direction of travel)
of the horizontal surface and is contiguous thereto. The
preferred angle of inclination depends on the angle of
motion of the tool relative to the ground, as will be
described thoroughly hereinafter. The width of the tool may
vary depending on the desired width of the swath to be cut.
As it is reciprocated by the beam, the tool moves
at an angle relative to the pavement determined by its
location relative to the forward node of the beam, the
forward node acting as a center of rotation. The tool is
located both forward and downward with respect to the node,
and as the forward distance increases relative to the down-
ward distance, the angle of motion approaches vertical.Typically, the tool strikes the pavement at an angle in the
range from about 30 to 60 relative to the plane of the
work face, more usually in the range from 35 to 55.
Since the forward flange is also inclined relative
to the plane of the work face (typically horizontal), as the
tool is reciprocated the forward flange strikes the ground
at a "closing angle" which depends on both the angle of
inclination of the flange and on the angle of motion of the
tool. Selection of a closing angle in the range from 6 to
18, preferably from 8 to 16, assures that the tool will
break off the edge of the pavement, resulting in a far more
efficient fracturing of the pavement. Moreover, it has been
found that the horizontal surface also aids in crushing the
'7~
broken fragments of pavement or concrete and moving them
away from the area where breaking is taking place. Such
corhir.ation of hish b~eal~iny forc a.,d c~ to clcar the
work area leads to a highly efficient pavement breaking
system.
The closing angle is defined as the difference
between the angle of motion of the tool and the angle of
inclination of the flange. With both angles measured from
horizontal, the angle of motion will always be greater than
the angle of inclination so that the flange impacts the
pavement on the downstroke. The amount greater (i.e., the
size of the closing angle~ is selected to maximize the
breaking action of the tool.
Typically, the beam is mounted to the carrier
vehicle at a node near the input end of the beam. A weight
is superimposed over the beam at a node near the output end,
and has a bearing surface adapted to bear downwardly against
the beam at that node. The weight is coupled to the vehicle
to control the vertical position of the weight. A tool
depends from the output end of the beam, and strikes the
surface on which the vehiclè rests at the vibration fre-
quency of the beam as the tool vibrates responsively to
vibrations of the beam. The reaction force generated by the
tool is substantially absorbed by the weight and not trans-
mitted to the carrier vehicle.
In theory, resonant systems are supported at theirnodes so that the input oscillatory forces are not trans-
mitted to the supporting frame. However, the impact forces
of the tool attached to the resonant system causes a reac-
tion force which, at the resonant freguencies employed, issubstantially constant. In typical past systems, the reac-
tion force is transmitted directly to the supporting frame.
The transmission of such a force to the frame i6 unaccept-
able for the relatively large forces generated by a surface
impact tool such as that disclosed herein. However, the
weight provided in the system of the present invention
substantially absorbs the reaction force so that it is not
11~79~41
transmitted to the frame. Preferably, the weight is suppor-
ted by a single acting cylinder to further isolate reaction
forces from the carrier vehicle.
In the present invention, it is preferred that the
weight be significantly less than the input forces of the
oscillator. Accordingly, if the tool encounters an obstacle
which it is unable to penetrate, the weight will be lifted,
moving the forward node position upwardly and allowing the
system to continue to vibrate in a resonant mode. This
flexibility avoids a forced vibration mode resulting in trans-
mission of the oscillator forces directly to the frame withpotential catastrophic consequences. In the preferred embodi-
ment of the present invention, the oscillator motor is mounted
on a frame which pivots along with the beam to preserve
proper alignment.
Typically, the tool will include a second flange
similar to the first but attached to the opposite side of
the horizontal surface. The second flange, which lies at
the rear of the tool as the vehicle is driven forward, does
not contribute to the breaking action. Rather, it is pro-
vided so that the mounting of the tool may be reversed toextend its useful life. The novel features which are characteristic of the
invention, as to organization and method of operation, to-
gether with advantages thereof will be better understood
from the following description considered in connection with
the accompanying drawings in which a preferred embodiment of
the invention is illustrated by way of example. It is to be
expressly understood, however, that the drawings are for the
purpose of illustration and description only and are not
intended as a definition of the limits of the invention.
In the drawings:
Fig. 1 is an elevation view of a preferred embodi-
ment of the vertical impact system of the present invention;
Figs. 2 is a plan view of the embodiment of Fig.
l;
Fig. 3 is an elevation view of the embodiment of
Figs. 1 and 2 with portions broken away to illustrate the
resonant system.
Fig. 4 is a side elevation view of a first embodi-
ment of the work tool of the present invention.
Fig. 5 is a front elevation view of the first
embodiment of the work tool illustrated in Fig. 4.
Fig. 6 is a side elevation view of a second em-
bodiment of the work tool of the present invention.
Fig. 7 is a front elevation view of the second
embodiment of the work tool illustrated in Fig. 6.
Fig. 8 is a schematic view illustrating the work
tool in motion.
Figs. 9A and 9B are schematic views which illus-
trate the effect of varying the inclination of the flangedsurface of the tool.
The preferred embodiment 10 of the present inven-
tion i6 illustrated generally by way of reference to Figs. 1
and 2 in combination. Impact system 10 includes a carrier
vehicle with a forward frame 12 connected to a rear frame 14
by an articulating joint 16 ~Fig. 2). ~ydraulic actuators
17, 18 extend between forward and rear frames 12, 14 to
control articulation of the vehicle. The carrier vehicle
rides on wheels 20 over a paved surface 22 comprised of
concrete, asphalt, cement or the like. The vertical impact
forces applied by the impact system 10 are intended to break
up the pavement, typically to facilitate its removal.
An engine 24 is mounted on rear frame 14. Engine
24 dxives a hydraulic output 26 (Fig. 2) operating three
hydraulic pumps 28, 29, and 30. A reservior 32 for
hydraulic fluid i8 provided adjacent pumps 28-30. One of
the pumps 28-30 drives wheel6 20 to propel the vehicle, one
of the pumps is used to control the vehicle and operate its
articulating cylinders 17, 18 and other control systems, and
the third pump operates an eccentric weight oscillator to be
described hereinafter.
'7~S~
The forward portion 12 of the vehicle includes a
large fuel tank 34 located remote from engine 24. The
ope.ator of the vehicle ride~ in a cor.trol c~ 36 projectirlg
forwardly and to one side of the remainder of the vehicle.
A solid, homogeneous resonant beam 38, typically
steel, is supported by the carrier vehicle, as depicted in
more detail by way of reference to Fig. 3. Beam 38 has a
resonant frequency with forward and aft nodes spaced inward-
ly from its ends, and anti-nodes (locations of maximum
amplitude) at its opposite ends and approximately at its
center.
Resonant beam 38 is supported at its aft node by a
shaft 40 penetrating the beam transversely at the location
of the aft node. Shaft 40 is fixed to beam 38 and thus
rotates with the beam. Shaft 40 is supported by resilient
members such as 42 on opposite sides of the beam to isolate
vibrations of the beam at the node from the surrounding
frame. Resilient supports 42 are mounted on an extension 44
from forward frame 12 ~f the carrier vehicle which projects
rearwardly beyond articulating joint 16.
Eccentric weight oscillator 46 (Figs. 1 and 3) is
attached to the aft end of beam 38 by plates 48. A motor
mount 50 is rotatably mounted to shaft 40, and projects
rearwardly to a position to the side of oscillator 46. A
hydraulic motor 52, powered by one of the pumps 28-30 is
supported by motor mount 50, and drives eccentric oscillator
46 to apply eccentric forces to resonant beam 38.
Typically, motor 52 drives oscillator 46 at a
freguency slightly below the resonant frequency of the beam.
As eccentric weight oscillator 46 rotates, it applies a
force to beam 38 which moves in a rotational fashion about
the axis of the oscillator. The components of force applied
axially to beam 38 are absorbed by the weight of the beam.
Components of force normal to the axis of beam 38 cause the
aft end of the beam to vibrate in an up and down motion,
inducing a near resonant vibration of the entire beam about
its node locations.
11~7~541
A massive weight 54 is superimposed over beam 38
toward its forward end. An aperture 56 is provided in the
weight through which beam 38 passes. weign~ 54 includes a
bearing surface 58 bearing downwardly on the beam at its
S forward node location. The weight of the beam is supported
by a transverse resilient strip 60 on the bottom surface of
aperture 56.
Weight 54 is mounted on a pivot arm 62 pivotably
mounted to forward frame 12 on shaft 64. Shaft 64 is fixed
to arm 62 and rotates therewith. The vertical position of
weight 54 is controlled by a single acting hydraulic cylin-
der 66 (Figs. 2 and 3) suspended from support 68 projecting
upwardly from forward frame 12. Hydraulic cylinder 66 is
single acting in that it is capable of supporting weight 54,
bùt incapable of transmitting forces from the weight to
support 68.
A bell crank arm 70 (Figs. 1 and 3) is nonrotat-
ably mounted to shaft 64 supporting pivot arm 62. A similar
bell crank arm 72 is nonrotatably mounted to motor mount 50.
A rod 74 interconnects bell crank arms 70 and 72 so that the
rotational positions of môtor mount 50 and shaft 64 coupled
to the forward node of the beam by weight 54 are interdepen-
dent. As a result, vertical movement of the forward node of
resonant beam 38 is transmitted through arm 74 to rotate
motor mount 50 to maintain motor 52 aligned with the axis of
oscillator 46.
A tool 76 is supported on a shank 78 terminating
in a flange 80. Flange 80 is bolted to a corresponding
flange 82 depending from the underside of the forward end of
resonant beam 38. At the neutral or rest position of tool
76, it is slightly above surface 22.
The tool 76 of the present invention is specially
adapted for breaking pavement, such as cement, concrete,
asphalt and the like, to facilitate pavement removal in a
variety of circumstances. Referring now particularly to
Figs. 4 and 5, the specific structure of a first embodiment
76a of the pavement breaking tool 76 will be described in
detail. The tool 76a is typically bolted to the lower end
ii'7~S41
of the shank 78 and comprises a plate having a central
section 84 which lies substantially parallel to the ground
22 (Figs. 1 and 3) when the resonan~ beam 38 i8 at rest, a
forward flanged portion 86 inclined generally upward from
the central section 84 and a rear flanged portion 88 also
inclined generally upward from the central section 84. The
forward flanged portion 86 is inclined upward at an angle a
relative to the horizontal, where a lines in the range from
approximately 25 to 35, with a presently preferred orien-
tation of approximately 30. Typically, the rear flangedportion 86 will be inclined upward at an angle ~ which is
equal to ~. The angle ~ does not have to e~ual a and, in
fact, the rear portion of the tool 76a need not be inclined
upward at all. A rear flange 88 is provided only so that
lS the tool 76a may be reversed as the forward flange 86
suffers wear.
While the dimensions of the tool 76a may vary
within relatively wide limits, the contact area between the
lower surfaces of the tool, particularly the horizontal
surface 84 and the forward flanged surface 86, should be
large enough to break a substantial swath in the concrete so
that the job may be completed in a reasonable time yet not
so large that the applied force per unit area is reduced
beyond that necessary to break the pavement. A tool having
an overall length Q (Fig. 4) of approximately 16" and a
width w (Fig. 5) of approximately 12" has been found suc-
cessful with a constant input force of approximately 10,000
pounds.
Figs. 6 and 7 illustrate an alternate embodiment
76b of the tool 76 specially adapted for cutting pavement,
concrete and the like along a relatively narrow line. As in
the first embodiment (Figs. 4 and 5), the cutting tool 76b
is bolted to the lower end of the shank 78 and comprises a
central section 90, a forward flange 92 inclined upward at
an angle ~ from the plate of the central section 90, and a
rear section 94 inclined upward at an angle ~ from the plane
of the central section 90.
11~79S41
The width w (Fig. 7) of the cutting tool 76b will
be substantially less than that of the breaking tool 76a.
Otherwise, ~e dimension6 may be simiiar. Tne overaii
length Q (Fig. 6) may vary within wide limits, as can the
relative lengths of the sections so, 92 and 94. The angle
preferrably lies in the range from 20 to 35, while the
angle ~ will normally be equal to a so that the tool 76b may
be reversed.
Either embodiment 76a or 76b of the tool of the
present invention would function in the absence of the rear
flanged portion (88 and 94, respectively). It is desirable
to provide the rear flange, however, so that the mounting of
the tool may be reversed when the leading portion, i.e., the
region between sections 84 and 86 or sections 90 and 92,
becomes worn. In that case, the angle ~ should equal a as
selected for best performance.
A situation to be avoided in the operation of a
resonant system is one which downward movement of tool 76
relative to its neutral position is prevented, such as when
system 10 encounters an upwardly inclined surface. If tool
76 cannot move downwardly from its neutral position, it
essentially becomes locked in place, converting the forward
end of beam 38 to a node and changing the vibrational char-
acteristics of the beam. To prevent this situation from
occurring, the size of weight 54 is significantly less than
the input forces of oscillator 46. Accordingly, when tool
76 encounters such an obstacle, the reaction forces will
overpower weight 54, causing the weight to lift, shifting
the forward node location upwardly and allowing the resonant
beam to continue to vibrate in its near resonant mode.
In operation, oscillator 46 supplies forces to
resonant beam 38 to cause the resonant beam to vibrate at
least near its resonant frequency. At that frequency, the
beam exhibits two nodes, an aft node at the location of
support shaft 40, and a forward node underlying bearing
surface 58 of weight 54. Tool 76 vibrates vertically about
its neutral position, and strikes the underlying surface 22
on its downward stroke to perform the desired function.
-- 11'79~41
In viewing Fig. 3 it is evident that resonant beam
38 is supported only at two positions, namely, at its aft
node on shaft 40 and at its fo~ard ncdc by ~eight 5~.
Since the node locations are basically stationary when the
beam is operating in its near resonant mode, the fact that
the beam is vibrating does not cause significant vibrational
forces to be transmitted from the beam to the supporting
vehicle.
The impact of tool 76 on underlying surface 22
results in the application of an upwardly directed reaction
force on beam 38. These reaction forces are transmitted
almost entirely to weight 54 by way of bearing surface 58.
These reaction forces are substantially absorbed by the
weight, and are not transmitted to the frame through single
acting cylinder 66. As a result, operation of the resonant
system is substantially isolated from the carrier vehicle,
and large impact forces can be exerted on surface 22 without
corresponding reaction forces being exerted on the carrier
vehicle.
The operation of the tool 76 ~including both
embodiments 76a and 76b) in breaking or cutting pavement may
be understood by reference to Figs. 8, 9A and 9B. As ex-
plained above, the tool 76 reciprocates about a neutral
position which corresponds to the position of the tool when
the resonant beam 38 is stationary. The motion of the
tool 76, however, is not truly vertical and depends on the
length of the portion of the resonant beam 38 forward of the
forward node, shown generally as distance dl on Fig. 8,
relative to the length of the tool sleeve 78 shown generally
as distance d2. Typically, the lengths dl and d2 be sub-
stantially equal 60 that the motion of the tool 76 will
describe an arc having an angle of motion, indicated by tan-
gent 100 at the neutral position, lying at approximately 45
to the plane of the work face which is typically horizontal.
The angle of motion may vary, however, as dl and d2 are
adjusted for particular applications. The resulting angle
of motion may vary widely, typically within the range from
20 to 70, more usually between 30 to 60, relative to the
41
plane of the work face without degrading the performance of
the system, so long as the proper closing angle is main-
tained, as discussed herei.,after.
Selection of the value of the angle ~ (Figs. 4 and
6) formed by the forward section (86 or 92) is important to
the proper operation of the tool 76. If the forward section
were not flanged (i.e, a = 0 ), the force per unit area
imparted by the tool to the pavement would be greatly re-
duced, reducing the ability of the tool to break the pave-
ment. As ~ increases, the forward flange applies force overa much smaller area and the pavement is more easily broken.
As the orientation of the forward flange approaches the
angle of motion of the tool, however, the surface of the
flan~e becomes nearly parallel with the direction in which
it is moving and the flange is unable to break the pavement.
Referring now to Figs. 9A and 9B, the closing
angle is defined as (y - ~), which is the difference between
the angle of motion (~) of the tool and the angle of incli-
nation (y) of the flange. As stated hereinbefore, so long
as (y - 0) lies in the range between 6 and 18, preferably
from 8 to 16, more preferably at approximately 12, opera-
tion of the pavement breaker will be successful. The
reasons for such successful operation will now be set forth.
The action of the forward flange (86 or 92) is
best understood in reference to Figs. 9A and 9B. In Fig.
9A, the forward flange (86 or 92) is inclined upward at y
from the central section (84 or 90). The junction between
the flange and the central portion of the tool 76 strikes
the pavement 22, on the downstroke, at point a. Since the
angle of motion ~ of the tool 76 is less thhn y (by 15 as
illustrated), as the tool continues its downward movement,
contact between the flange and the pavement moves forward to
point a'. Thus, an incremental portion b of pavement will
be broken by each downstroke. It should be noted that the
distance between a and a' results only in small part from
the forward movement of the vehicle 10. Rather, the
distance depends on the relative inclinations of the surface
'3~4~
of the flange and the tangential direction of motion of the
tool 76.
As the orientatior of ~e forwaLd Llange (~6 os
92) approaches the angle of motion (i.e., ~' ~ y'), the
situation approaches that illustrated in Fig. 9B. There,
the contact point a" between the flange and the pavement
remains virtually stationary as the tool is driven downward.
Thus, no breaking at all occurs. In that event, the leading
edge of the central portion (84 or 9O) of the tool 76 will
encounter unbroken pavement as the vehicle lO is driven
forward. Since the force per unit area applied by the
central portion is so low, the central portion will be
unable to break the pavement and the tool will not function.
With the breaking tool 76a, by driving the vehicle
forward at a relatively slow speed in the range from 0.5 to
l foot per second, the pavement is typically broken into
very small chunks which can easily be reused in making
concrete and other composite materials. It is possible,
however, to drive the vehicle at a much higher rate, in the
range from 1 to 3 feet per second when it is desired to
complete the job rapidly. The broken pieces resulting from
the latter method of operation are much larger and must be
broken down further prior to reuse.
It has also been found that with the breaking
tool 76a of the present invention, the pavement may be
broken by running the machine over parallel, spaced-apart
strips with substantial fracturing occurring in the areas
between said strips without the direct application of force.
With the cutting tool 76b, the vehicle may be
driven at a rapid rate, typically in excess of 1 foot per
second, without any deterioration in the cut achieved.
While a preferred embodiment of the present inven-
tion is illustrated in detail, it is appartent that modifi-
cations and adaptations of that embodiment will occur to
those skilled in the art. However, it is to be expressly
understood that such modifications and adaptations are
within the spirit and scope of the present invention, as set
forth in the following claims.
