U.S. patent application number 09/854823 was filed with the patent office on 2002-11-14 for automatic tamping mechanism control.
Invention is credited to Feucht, Timothy A., Graham, Evant T., Gutzwiller, Timothy M..
Application Number | 20020168226 09/854823 |
Document ID | / |
Family ID | 25319600 |
Filed Date | 2002-11-14 |
United States Patent
Application |
20020168226 |
Kind Code |
A1 |
Feucht, Timothy A. ; et
al. |
November 14, 2002 |
Automatic tamping mechanism control
Abstract
A control system for use with an asphalt paving machine receives
inputs from an operator interface for inputting a desired tamping
frequency or a desired tamping rate (tamps/ft) and a speed sensor
that produces a signal indicative of the speed of the asphalt
paver. The control system includes an automatic mode and when in
automatic mode the system modifies the tamping frequency to better
achieve a desired number of tamps per foot traveled irrespective of
speed.
Inventors: |
Feucht, Timothy A.;
(Edelstein, IL) ; Graham, Evant T.; (Minnetonka,
MN) ; Gutzwiller, Timothy M.; (Peoria, IL) |
Correspondence
Address: |
CATERPILLAR INC.
100 N.E. ADAMS STREET
PATENT DEPT.
PEORIA
IL
616296490
|
Family ID: |
25319600 |
Appl. No.: |
09/854823 |
Filed: |
May 14, 2001 |
Current U.S.
Class: |
404/84.1 ;
404/102; 404/133.2 |
Current CPC
Class: |
E01C 19/407
20130101 |
Class at
Publication: |
404/84.1 ;
404/102; 404/133.2 |
International
Class: |
E01C 023/07; E01C
019/38; E01C 019/34 |
Claims
What is claimed is:
1. A control for a tamping mechanism on an asphalt paver,
including: a speed sensor, said speed sensor sensing the speed of
said asphalt paver; a desired tamping speed input; an electronic
control module that controls the speed of said tamping mechanism as
a function of said tamping speed input and said speed sensor.
2. The control according to claim 1, including: a mode selector
having a manual mode selection and an automatic mode selection; and
wherein said electronic control module controls the speed of said
tamping mechanism in response to said desired tamping speed input
when said mode selector is in said manual mode.
3. The control according to claim 1, wherein: said electronic
control module control increases the speed of said tamping
mechanism in response to an increase in the speed of said asphalt
paver.
4. The control according to claim 1, wherein: said electronic
control module control decreases the speed of said tamping
mechanism in response to a decrease in the speed of said asphalt
paver.
5. An electronic control for an asphalt paver, said paver having a
screed with a tamping mechanism, said electronic control including:
an asphalt paver speed sensor, said sensor outputting a signal as a
function of the speed of said asphalt paver; a mode selector
including a plurality of tamping mechanism mode selections, said
mode selector outputting a signal as a function of the mode
selection; a desired tamping speed selector, wherein said speed
selector outputs a signal indicative of a desired tamping speed
selected by an operator of said asphalt paver; an electronic
controller receiving said speed sensor signal, said mode selector
signal and said desired tamping speed signal and outputting a
tamping mechanism control signal, wherein said tamping mechanism
control signal is a function of said asphalt paver speed sensor
signal, said mode selector signal and said desired tamping speed
signal; said tamping mechanism receiving said tamping mechanism
control signal and controlling the speed of said tamping mechanism
as a function of said tamping mechanism control signal.
6. The electronic control according to claim 5 wherein said mode
selector includes an automatic mode selection, a manual mode
selection and an off selection.
7. The electronic control according to claim 6, wherein: said
electronic control produces said tamping mechanism control signal
as a function of said asphalt paver speed sensor signal and said
desired tamping speed signal when said mode selector is in said
automatic mode selection.
8. The electronic control according to claim 6, wherein said
electronic control produces said tamping mechanism control signal
as a function of said desired tamping speed signal when said mode
selector is in said manual mode selection.
9. The electronic control according to claim 6, wherein said
electronic control produces a tamping mechanism control signal
indicative of no desired movement of the tamping mechanism when
said mode selector is in said off mode selection.
10. The electronic control according to claim 6, wherein: said
electronic control produces said tamping mechanism control signal
as a function of said asphalt paver speed sensor signal and said
desired tamping speed signal when said mode selector is in said
automatic mode selection; said electronic control produces said
tamping mechanism control signal as a function of said desired
tamping speed signal when said mode selector is in said manual mode
selection; and said electronic control produces a tamping mechanism
control signal indicative of no desired movement of the tamping
mechanism when said mode selector is in said off mode
selection.
11. A method of controlling a tamping mechanism on an asphalt
paving machine, said method including the steps of: determining a
velocity of said asphalt paving machine; determining a desired
speed of said tamping mechanism; controlling said tamping mechanism
in response to said velocity of said asphalt paving machine and
said desired speed of said tamping mechanism.
12. The method according to claim 11, wherein said step of
controlling includes: controlling the speed of said tamping
mechanism to be proportional to the speed of the asphalt paving
machine.
13. The method according to claim 11 wherein said step of
controlling includes: controlling said tamping mechanism to provide
a relatively constant number of tamping strokes per unit of
distance traveled by said asphalt paver.
14. The method according to claim 11, wherein said step of
controlling includes: controlling said tamping mechanism in
response to said desired frequency when said asphalt paver is
stationary and increasing the speed of said tamping mechanism in
response to an increasing velocity of said asphalt paver.
Description
TECHNICAL FIELD
[0001] The present invention generally relates to asphalt paving
machines, and more particularly to a control for a tamping
mechanism on an asphalt paving machine.
BACKGROUND
[0002] Asphalt paving machines are used to spread asphalt
relatively evenly over a desired surface. These machines are
regularly used in the construction of roads, parking lots and other
areas where a smooth durable surface is required for cars, trucks
and other vehicles to travel. An asphalt paving machine generally
includes a hopper for receiving asphalt material from a truck and a
conveyor system for transferring the asphalt from the hopper for
discharge on the roadbed. Screw augers spread the asphalt
transversely across the road bed in front of a floating screed,
which is connected to the paving machine by pivoting tow arms or
draft arms. The screed smoothes and somewhat compacts the asphalt
material and ideally leaves a roadbed of uniform depth and
smoothness. The screed is sometimes equipped with an eccentric bar
that rotates and thereby causes the screed to vibrate, which
assists with the compaction. Although the screed compacts the
asphalt material to some degree, it is often desirable to exert
greater compaction force on the asphalt. To do so, some screeds
include a tamping mechanism which often includes a tamping bar,
located in front of the screed, relative to the direction of travel
of the paving machine, and transversely to the direction of travel.
The tamping bar moves up and down, striking the asphalt on each
downward stroke thereby imparting increased compaction force on the
asphalt. The speed with which the tamping bar moves upward and
downward is generally controlled by an operator input device such
as a control knob.
[0003] It is desirable to have the asphalt on the roadbed compacted
uniformly so that the density of the roadbed is consistent from one
place to another. Prior art tamping systems control only the
frequency of the up and down motion of the tamping bar thereby
causing the screed to tamp at a fixed rate. If the asphalt paving
machine is moving at a constant speed the tamping bar will strike
the asphalt the same number of times per unit distance traveled.
Because the tamping bar strikes the asphalt the same number of
times for every foot traveled, it is more likely to produce a
uniformly dense roadbed. However, if the operator changes the speed
of the asphalt paving machine the number of times the tamping bar
strikes the asphalt per foot traveled will change, thereby
increasing the likelihood that the density of the roadbed will be
inconsistent.
[0004] It would be preferable to have an automatic tamping control
that would deliver a uniform number compaction strokes for each
unit distance traveled, irrespective of the speed of the asphalt
paving machine.
SUMMARY OF THE INVENTION
[0005] The present invention includes a control system for use with
a tamping mechanism on an asphalt paver. The control system
preferably includes an electronic control module that is connected
with an operator input device for inputting a desired tamping
frequency. The electronic control module is also connected to a
speed sensor that produces a signal indicative of the speed of the
asphalt paver. The electronic control module controls the speed of
the tamping mechanism as a function of the operator input and the
asphalt paver speed.
[0006] These and other advantages of the present invention will be
apparent upon reading the detailed description in connection with
the drawings and appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The drawings are provided to assist in the understanding of
the present invention and represent a preferred embodiment of
practicing the invention. Other embodiments could be created that
will fall within the scope of the present invention as defined by
the appended claims.
[0008] FIG. 1 is a side view of an asphalt paving machine;
[0009] FIG. 2 is a side view of a screed including a tamping
mechanism associated with the asphalt paving machine of FIG. 1;
[0010] FIG. 3 is a block diagram of a control system of preferred
embodiment of the present invention; and
[0011] FIG. 4 is a flowchart of preferred software control of the
control system of the present invention.
DETAILED DESCRIPTION
[0012] A preferred embodiment of the best mode of practicing the
present invention is described herein. Referring first to FIG. 1, a
typical form of track-laying, floating screed asphalt paver 30 is
shown. In accordance with well known practice, the paver is
provided with push rollers 31 at the front, for engaging and
pushing forwardly on the wheels of a truck loaded with asphalt
paving material. The paving material is arranged to be discharged
progressively from the truck into a hopper 32 at the front of the
paver. Conveyor means (not shown) controllably transport the paving
material to the rear of the paver and deposit it in a mass 33 on
the prepared paving bed 34. Screw augers 35 distribute the paving
material laterally in front of a screed, generally designated by
the numeral 36. The screed is towed behind the paver and connected
thereto by a pair of elongated, forwardly extending tow bars 37
connected at their front ends to the chassis of the paver. In
accordance with known practice, by controlling the elevation of the
tow points 38 and the angle of attack of the bottom surface of the
screed 36, a level, uniform paving mat 39 is laid behind the paver
as it advances forwardly.
[0013] Referring now to FIG. 2, a screed 36 of the type used in
connection with the asphalt paver 30 is shown. The screed 36
comprises a baseplate 100 which is configured to float on paving
material 33 laid upon a prepared paving bed 34 and to "smooth" or
level and compact the paving material on the base surface, such as
for example a roadway or roadbed. The base plate 100 is connected,
preferably by means of a carrier 105, to a vibrating shaft 110
coupled to a vibratory drive (not depicted). As is known to those
skilled in the art, the vibratory shaft 110 generally includes
weights placed eccentrically so that when the vibratory drive
rotates the vibrating shaft 110, the shaft 110 causes the screed 36
to vibrate. The vibrating screed 36 to some degree improves
compaction and quality of the asphalt mat being laid on the
prepared paving bed 34.
[0014] The screed also includes a tamping mechanism 111 which
includes a tamping bar 115 arranged in front of the baseplate 100
and extending generally transversely to the paving direction over
substantially the entire width of the baseplate 100. The tamping
bar 115 is configured to be driven so as to move alternately in
upward and downward directions (i.e., generally toward and away
from the base surface). Preferably, the tamping bar 115 is driven
by an eccentric drive 120 and is configured to be adjustably
displaceable by the amount of an adjustable stroke of the eccentric
drive 120. A speed sensor 290 is preferably located adjacent the
eccentric drive and produces a speed signal on an electrical
connector 300 that is an input to an electronic control module 210,
described in more detail below with reference to FIGS. 3 and 4.
Further, the tamping bar 115 has a lead-in slope 125 located at the
front edge of the bar 115. The angle of the lead-in slope 125 is
preferably between 30 degrees and 70 degrees, so as to ensure an
optimum feed of the paving material.
[0015] The screed 36 has preferably includes a front wall 130
disposed proximal to the screw auger 35 (shown in FIG. 1), the
screw auger 35 functioning to spread paving material falling off
the end of a conveyor mounted on the paver 30 The front wall 130
includes a lower guide portion 135 which is preferably inclined
relative to the tamping bar 115 and which terminates adjacent to
the bar 115, such that the guide portion 135 directs paving
material from the auger 35 to the tamping bar 115. The angle of
inclination of the guide portion 135 preferably corresponds
approximately to the angle of the lead-in slope 125 of the tamper
bar 115.
[0016] Referring now to FIG. 3, a block diagram of a preferred
embodiment of an electronic control system 200 for use with the
tamping mechanism 111 is shown. The electronic control system
preferably includes an electronic control module ("ECM") 210
connected with the various system components shown. A tamper bar
mode selector 230 is connected with the ECM 210. In the drawing,
the tamper bar mode selector is shown as a three position toggle
switch 240. Those skilled in the art will recognize that other
devices, including rotary switches, depressible button switches and
the like could readily and easily be substituted for the three
position switch. As described in more detail below with reference
to FIG. 4, the mode selector 230 preferably includes three
positions corresponding to an off mode, a manual mode and an
automatic mode. The operator of the asphalt paving machine
preferably places the mode selector 230 in a position corresponding
to the desired mode. The mode selector then produces a mode signal
on electrical connectors 250 indicative of the selected mode.
[0017] A tamper bar desired speed input 260 is connected with the
ECM 210 by connector 270. Although this input is described herein
as a desired speed input, it also controls the desired number of
tamps per unit distance when the system is in the automatic mode.
As shown in the drawing, the tamper bar desired speed selector is
shown as a rotary dial 280. Preferably there are markings on the
dial indicating to the operator a general desired tamping bar
rotational velocity (when in manual mode) or a desired number of
tamps per foot (when in automatic mode). The operator of the
asphalt paving machine moves the dial to a position corresponding
to the desired rotational speed of the tamping bar or number of
tamps per foot and the rotary dial 280 produces a signal on
connector 270 indicative of the desired tamping bar speed or tamps
per foot.
[0018] A tamping bar speed sensor 290 is associated with the
eccentric drive 120 of the tamping mechanism 111 and produces a
tamping bar speed signal on connector 300 indicative of the
rotational velocity of the eccentric drive 120. Preferably, the
tamping bar speed sensor is a passive sensor, such as a magneto
restrictive type sensor. However, other types of speed sensors can
be used without deviating from the scope of the present
invention.
[0019] The ECM 210 produces a tamper bar control signal 310 to
control the rotational speed of the shaft eccentric drive 120. As
shown in the drawing, the tamper bar control signal 310 is received
by a solenoid 320 connected with a hydraulic pump 330 associated
with the hydraulic motor 125. The tamper bar control signal 310
controls the flow of hydraulic fluid through conduits 340,350 and
thereby controls the rotational speed of the hydraulic motor 125
and eccentric drive 120 of the tamper bar. Although the preferred
embodiment shows the use of a hydraulic pump 330 and motor 125 to
control the rotational speed of the eccentric drive 120, other
power sources could readily and easily be substituted for the
hydraulic motor without deviating from the scope of the present
invention. For example, in some applications it might be preferable
to replace the hydraulic motor with an electric motor and
controllably power the motor with electric power through associated
power circuitry.
[0020] Also connected with the ECM 210 is a asphalt paving machine
speed sensor 360 that produces a signal on connector 370 indicative
of the speed that the asphalt paving machine is travelling. The
speed sensor is preferably associated with a driveline on the
asphalt paving machine, which connects the engine to the tracks, or
other ground engaging device. The speed sensor produces a signal
indicative of the speed of the track, or other ground engaging
device, which can be readily converted by the ECM 210 to ground
speed. Any of a variety of well known speed sensors could be used
in connection with the present invention.
[0021] Referring now to FIG. 4, a block diagram of a preferred
embodiment of the software control associated with the ECM 210 of
the present invention is shown. Software control begins in block
400 and passes to block 410.
[0022] In block 410 the ECM 210 reads the signal on connectors 250
and determines whether the operator has placed the tamper bar mode
selector 230 in the position corresponding to off mode. If the mode
selected is the off mode then software control returns to block
400. Otherwise, program control continues to block 420.
[0023] In block 420, software control determines whether the
operator has placed the tamper bar mode selector 230 in the
position corresponding to manual mode. If the mode selected is the
manual mode then software control passes to block 430. Otherwise,
software control passes to block 440.
[0024] In block 430, the ECM 210 reads the desired tamping speed
signal on connector 270 produced by the tamping bar desired speed
input 260. Program control then passes to block 470. In block 470,
the ECM produces a tamper bar control signal as a function of the
desired connector 270. In a preferred embodiment of the invention
the speed of the tamper bar shaft 122 is controlled open loop.
However, as will be apparent to those skilled in the art, the ECM
210 could readily and easily use the electrical connector 300 as
feedback to implement a closed loop tamper bar speed control. From
block 470 program control returns to block 400.
[0025] Returning to block 420, as described above if the position
of the mode selector 230 does not correspond to the manual
position, then software control passes to block 440 and the control
system is in automatic mode.
[0026] Software control passes from block 440 to block 450.
[0027] In block 450, the ECM 210 reads the signal on connector 270,
which in the automatic mode corresponds to a desired number of
tamps per foot (or other unit distance) that the asphalt paving
machine travels. Program control then passes to block 460 where the
ECM determines a corresponding desired tamping speed. To do this,
the ECM preferably reads the asphalt paving machine speed signal on
connector 370 and calculates the desired tamping bar speed. In a
preferred embodiment, the control system of the present invention
uses two asphalt paving speed sensors 360 and averages the signals
of those two sensors. Program control then passes to 470.
[0028] As described above, in block 470, the ECM produces a tamper
bar control signal as a function of the desired connector 270. In a
preferred embodiment of the invention the speed of the tamper bar
shaft 122 is controlled open loop. However, as will be apparent to
those skilled in the art, the control could readily and easily use
the electrical connector 300 as feedback to implement a closed loop
tamper bar speed control. From block 470 program control returns to
block 400.
INDUSTRIAL APPLICABILITY
[0029] The control described in the present application permits the
operator of the asphalt paving machine to select between three
modes of tamping: an off mode; a manual mode; and an automatic
mode. In the off mode, the screed will not tamp the asphalt
material. In the manual mode the operator can select a desired
tamping speed which produces a desired tamping rate (i.e., a
desired number of tamps per unit time). In the automatic mode the
operator can select a desired number of tamps per unit distance. In
the automatic mode the control will automatically adjust the
tamping speed as a function of the speed that the asphalt paving
machine is moving. This will allow the operator to better achieve
consistent compaction from the tamper bar with minimum operator
action.
* * * * *