US3069983A - Method of laying roads and apparatus therefor - Google Patents

Description

` Dec. 25, 1962 P. PIZZAROTTI ETAL METHOD OF LAYING ROADS AND APPARATUS THEREFOR Filed April 10. 1958 5 Sheets-Sheet l Dec. 25, 1962 P. PlzzARoTTl ETAL METHOD OF LAYING ROADS AND APPARATUS THEREFOR Filed April l0, 1958 Dec. 25, 1962 P. PlzzARoTTl ETAL 3,069,983

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Dec. 25, 1962 P. PlzzARoTTl ETAL 3,059,983

METHOD oF LAYING RoADs AND APPARATUS THEREFOR Filed April 1o, 1958 5 sheets-sheet 5 A T A llited States Patent frce 3,069,933 Patented Dec. 25, 1962 3,l69,)33 ME'HD 0F LAYNG RSAES AND APPARATUS THERE-,FR Pietro Pinzarotti, Camillo lntonneei, and Giovanni Leoncini, Parma italy, assignors to Impresa Pizzarotti 31 C. Sami., Parma, italy, a company of Italy Filed Apr. 10, i958, Ser. No. 727,684 Claims priority, application itaiy .lune 18, i957 2 Claims. (Cl. Std-d6) The present invention relates to a method of laying roads and to the apparatus for practicing the method.

More particularly, this invention has to do with an improved method for laying road mats of bituminous mix by employing asphalt finishing machines or tampingleveling finishers. The machines of this kind have given a remarkable contribution towards the solution of the problem of properly laying, on road bases, airstrip bases, turnpike road bases and the like, a uniform, compact and level mat of bituminous mix.

Said asphalt finishers or tamping-leveling finishers, are only capable of smoothing or minimizing short-wave ripples, whereas they are almost inefficient if it is desired to suppress variations in transverse grade variations and wavy irregularities of the road base having a wavelength exceeding four yards approximately, since the finishing machines referred to above are generally designed to lay road bases, surface base courses, or surface courses of a uniform preselected thickness.

As it is well known to all those familiar with the art of roadmaking, the asphalt finishing machines receive motive power from a tractor unit through crawlers or wheels traveling on the road base, and comprise, in their general constructional outline, a receiving hopper for the bituminous mix located in the front portion of the machine, a spreading mechanism for said bituminous mix, a tamping unit, generally of vibratory type (in some cases a relatively bulky tamper is provided which is vertically reciprocated at a somewhat low rate), and a mechanism for controlling the thickness of the finished pavement.

It is an object of the present invention to obtain the maximum possible fidelity of a bituminous mat, particularly of the surface base course or binder course, to a preselected grade line.

Broadly stated, the method according to this invention comprises the steps of providing at least a reference line parallel to a preselected theoretical grade line, and of continuously adjusting the mat thickness control member of a nishing machine so that the profile of the bituminous mat being laid by the machine is in every instant of time parallel to said reference line, and, consequently, parallel to the grade line desired. According to preferred embodiments of the process of the invention, said reference line consists either of a beam of luminous rays or a line of sight such as provided by a surveying instrument.

it is possible, in general, to arrange two of said reference lines, that is, one for each side of the asphalt finishing machine. In the detailed description to follow, however, a single one of these reference lines will be referred to, in order to simplify the disclosure.

According to a preferred embodiment of the process of the invention, the reference line parallel to the grade line is the axis of a beam of luminous rays provided by illuminating means external to the finishing machine and placed ahead of the machine, photoelectric means being provided aboard the machine, which are responsive to the displacements of a fixed point of the machine relatively to the axis of said beam of luminous rays, said photoelectric means operating a servomechanism intended for actuating the members adapted to control the thickness of the bituminous mat.

According to a less expensive embodiment of the invention, it is possible to install on the asphalt finishing machine a screen, for example a translucent screen of the so-called Reflex type, adapted to collect the trace of the beam of luminous rays referred to above, said screen having fiducial lines or marks thereon, adapted to individualize and check the displacements of a fixed point of the screen relative -to the luminous spot formed by the luminous beam, the axis of which, fixed in the space, defines the desired grade line. An observer checking the luminous spot on the screen is enabled to immediately appreciate by what distance the profile of the bituminous mat being laid departs from the grade line, and to readily intervene by manipulating the mat thickness control members with which an asphalt finisher is conventionally equipped.

It is essential that the Reflex screen (or the photoelectric cells, if a servomechanism, for actuating the mat thickness control members, is adopted) be solidly aixed to the mat thickness control members of the asphalt finishing machine.

According to a further embodiment of the method of the instant invention, the reference line parallel to the preselected grade line is a line of sight provided by a surveying instrument placed ahead of the traveling asphalt finisher and at suitable distance, for example from to 150 yards therefrom. Such a line of sight provided by the cross-hairs of a telescope of a suitable surveying instrument, such as for example a level or a theodolite, will be put in collimating relationship with a vertical sigh-ting stake placed in a convenient location on the finishing machine. In such a case, the attendant Will not be aboard the machine, but will take readings with the sighting instrument.

Taking readings of the coincidence of the optical axis of the instrument with the center of the sighting stake on the machine, permits obtaining a remarkable accuracy of measurement, and the operator is enabled to intervene, if this coincidence is lacking or the established allowances are being departed from, by means of a telecontrol mechanism, on the mat thickness control members of the asphalt finisher. Telecontrol can be effected either by an electric cable or by radio. In the former case, the operator who attends to taking readings of the surveying instrument has a pushbutton panel available, which is connected, by means of a fiexible electric cable, to the servo-mechanis for example an electric servomotor, so that the operator himself can actuate the mat thickness control members of the machine. In the latter case, the control pulses are transmitted by the operator by means of a pushbutton set controlling a small radio transmitter placed near the surveying instrument and are received by a small receiving set installed on the asphalt finisher; and these pulses are amplified to actuate the servomechanism for controlling the mat thickness control members of the asphalt finisher.

The invention is illustrated but not limited by the detailed description following, aided by the accompanying drawings.

In the drawings:

FIG. 1 diagrammatically represents an asphalt finishing machine equipped according to one embodiment of this invention with an apparatus comprising a training reticle and with photoelectric cells for controlling a servoinotor on the machine, a source of luminous rays for actuating the control mechanism being also shown;

FIG. 2 shows in front elevation, partly in section, the reticle and the photoelectric cells;

FIG. 3 is a cross-sectional view taken along the line III-III of FIG. 2;

FIG. 4 is a cross-sectional view taken along the line IV-IV of FIG. 2;

FIG. 5 is a wiring diagram of the control circuit for the servomotor shown in FIG. l;

FIG. 6 shows in a somewhat diagrammatic fashion an asphalt finishing machine equipped according to another embodiment of this invention with a radio telecontrol apparatus;

FIG. 7 is a wiring diagram of the transmitter unit of the apparatus shown in FIG. 6;

FIG. 8 is a wiring diagram of the receiver unit of apparatus shown in FIG. 6;

FIG. 9 shows m a somewhat diagrammatic fashion an asphalt finishing machine equipped according to still another embodiment of this invention with a cable telecontrol apparatus; and

FIG. l() shows in .some detail this servomotor control circuit.

Having, at first, reference to FIG. l a tamping-leveling asphalt finisher, generally designated by the reference character VF, can be seen.

As it is well known, machines of this kind, commonly in use, comprise, proceeding `from the front portion to the rear portion of the machine, a receiving hopper i. for the bituminous mix, a spreading mechanism 2, a tamper 3 and a pressure member 4 (also called a screed or leveling shoe) whose height is adjustable in order that the thickness of the bituminous mat being laid might be controlled.

This mat thickness control member is generally formed by a screw 5 connected to the leveling shoe 4 and actuated, for example via a handwheel, by an attendant aboard the machine. According to the invention to the leveling shoe or screed 4 a base piece 6 is connected which protrudes from one side of the machine VF, said base piece 6 being intended to support, for example by means ot a mounting pillar 7 affixed thereto, a control and sighting unit 8 comprising a translucent screen 9, for example of the Reflex type, and one pair of photoelectric cells 10 and I0.

FIGURES 2, 3 and 4 of the accompanying drawings clearly show the translucent screen and the two photoelectric cells as well. The translucent screen 9 is employed whenever it is desired to control the thickness of the bituminous mat by the manual control method. If this is the case, the luminous spot provided by the instrument l1, comprising a proiector Il (fed by a battery B, FlG. l) and a training telescope 11, is projected on the screen 9. When the luminous spot impinges in the area 9 at the center of the reticle provided on the screen 9, the attendant is assured that the asphalt finisher is following the preselected grade line within the prescribed tolerances.

The adjustment of the instrument 11i with respect to the screen 9 is effected, before starting to work with the asphalt finisher, by collimating with the telescope l1" on the fiducial line 9 of the screen 9, since the distance between 9 and 9 is equal, by construction, to the distance between 11' and Il. At one side of the screen 9 the two photoelectric cells 10 and l0 are mounted, as shown in FIG. 2. These photoelectric cells are in use when it is desired to adopt the automatic operation of the mat thickness control members 4 and 5 by means of a servomechanism, as will be explained more, in detail hereinafter.

The two photoelectric cells 10 and I0 are electrically connected to a unit i?. which, in turn, controls a servomotor 13. The servomotor i3 actuates, for example via a Cardan joint 14 and a worm-and-wheel gearing comprising a worm i5 and a worm wheel l5', the elevation screw S of the leveling shoe 4.

Obviously, the worm wheel 1S will be keyed to the shaft of the screw 5. Thus, when the two photoelectric cells in and itl" are equally illuminated, there is no potential difference between the terminals x, y of the bridge circuit (FIG. 5) and the machine VF will follow the preselected grade line. When, conversely, the beam of luminous rays coming from the projector lli' illumistates the two photoelectric cells unevenly, there will be :a potential difference between the terminals x and y (FIG.

the

5) and this potential difference, amplified in the circuit of FIG. 5, will actuate the servomotor i3, thereby lifting or depressing the leveling shoe 4, according to the sign of the potential difference. FIG. 5 shows in `some detail the control circuit which is not itself a part of the present invention. The two cells l() and itl are bridged, and the terminals x, y of the bridge circuit are connected to an amplifying stage DA and, via a polarized relay IBR, control the switch unit i2 and therethrough the servo-motor i3. Obviously, the sense of rotation of the servo-motor 13 will dependl upon the sign of the difference of potential existing at the bridge output, so that lifting or depressing of the leveling shoe or screed t takes place accordingly.

On examining FIG. 4 again, together with FIG. 2 (on the right) it will be seen that, as the asphalt finisher is lowered with respect to the axis of the luminous beam provided from the projector lll', position I-i of FIG. 4, the servomechanism will act to lift the screed 4, whereas, if the asphalt finisher is lifted with respect to the axis of the luminous beam, as shown by L FIG. 4, the servomotor will effect a depressional movement of the screed 4. The line K of FIG. 4 represents the conditions in which the luminous beam coming from the projector l' provides an even illumination of the two photoelectric cells it) and 10'. In these circumstances there is no difference of potential between the two cells; the servomechanism controlling the motor i3 is inoperative, that is, the bituminous mat is being laid according to the preselected grade line.

FIG. 5 actually represents the position the circuit assumes when there is no difference of potential between the terminals x, y, and the polarized relay PR is in its inoperative or rest position. AV is a vibrator feed-er such as those extensively used in the power packs of autoradios and other portable equipment.

FIG. 6 shows the arrangement to be adopted when it is desired to employ the radio telecontrol method for actuating the thickness control members, the reference line being a line of sight.

On the asphalt finishing machine VF is installed a radio-receiver, generally connoted by the symbol RR, connected to a control unit l2 whose wiring diagram is very much similar to that of the unit 12 of the diagram of FIG. 5. The servo-motor 13 and the mechanical means adapted to connect it to the screed 4 are in this case very much the same as described in connection with FIG. l. On the finishing machine VF a vertical sighting stake VS is also installed and is borne by a pillar 7 connected to the basepiece 6 solidly affixed to the creed 4. Thus, the vertical displacements of a reference or fiducial mark traced on the sighting stake VS accurately reproduce the vertical displacements of the screed 4. At a distance comprised in the range from a minimum of about l0-l5 yards to 50-15() yards ahead of the machine VF, a surveying instrument, for example a level or a theodolite, is placed and provides a line of sight, visible in the drawing, parallel to the preselected grade line. The attendant at the surveying instrument actuates, through a pushbutton set PB, a small radio-transmitter RT whose signals are received by the receiving set RR on the machine VF. Thus, when the attendant, collimating with the telescope of the instrument I6, sees that the displacements vertically in either direction of the reference mark on the sighting stake VS are such as to exceed the permitted tolerance, he can intervene by sending through the transmitter RT, signals which, received by the station RR on the machine VF, are amplified and actuate the servo-motor i3 until such a time as the profile of the bituminous mat is brought within the permitted tolerances again.

FIGURES 7 and 8 show the transmitting and receiving circuits of the apparatus shown in FIG. 6.

These diagrams are disclosed herein for better illustration only but are not themselves a part of the present invention.

FIG. 7 illustrates the transmitter circuit. The two push-buttons F and G, shown in FIG. 6 also, are shown and serve to close the circuit. Said circuit comprises a 60 kHz. oscillator OSC, a 65 kHz. oscillator OSC', a modulating stage (with a cathode follower) MOD-CF and a 30 kHz. oscillator OSC".

The circuit is fed by a vibrator AV and a 6 v. battery. The antenna is a semi-dipole (1A lambda).

The push buttons F and G actuate either of the oscillators OSC, OSC' at 60 and 65 kHz. respectively. Either of these frequencies provides a screen-grid modulation, through the cathode-follower modulating stage, for the 30 MHz. frequency generated by the oscillator OSC.

FIG. 8 shows the receiver circuit which comprises a semi-dipole (1A lambda), a 30 MHz. detect unit DU generating either 60 or 65 kHz. signals, an aperiodic ampliiier AMP amplifying said signals, two band-pass filters BPF, BPF tuned to 60 and 65 kHz. respectively, two detectors D' and D at 60 and 65 kHz. respectively, two power amplifiers PA, PA', a vibrator AV and two relays R', R" actuated by the nal power stages PA, PA respectively.

The circuits brietiy described in the foregoing need not any further illustration since they can be readily understood by all those skilled in the art.

FIG. 9 shows the arrangement which is adopted when it is desired to employ the telecontrol by electric iiexible cable. The general arrangement is that described in connection with FIG. 6 unless, obviously, the two radio sets are lacking, and the control push-button set PB is directly connected by a cable to the unit 12' (FIG. 6) for actuating the servo-motor 13. The readings on the instrument 16 are taken in very much the same way as described in connection with FIG. 6 and the attendant at the instrument manipulates the push-buttons F and G of the push-button set PB just as already described.

FIG. represents still more in detail the control circuit for the servomotor 13. The servo-motor 13, is preferably, a direct-current reversible series motor, i.e. a motor having two exciting windings coiled in reverse senses.

The simple circuit diagram shows the two relays 20 and 21, for lifting and depressing the leveling shoe 4, respectively. Two pilot lamps 20 and 21', shunted to the coils of the relays 20 and 21, respectively, are also shown in the drawing.

On examining the circuit diagrams of FIGS. 5, 8 and 10 it will be appreciated that the terminals A, B, C of the servo-motor 13 can be connected to a three-leg plug, for example A"", B"", C" (FIG. 5) of the control system employing photoelectric cells, or to a three-leg plug A, B", C" (FIG. 8) of the control system employing radio waves, or also to a three leg plug A', B', C (FIG. 10) of the control system by cable. It is therefore possible to pass from one to any other system among those herenbefore described, without particular adaptations of the apparatus since itis possible to provide a servo-motor 13 and a control unit such as 12 (or 12') adapted to iit all three systems for controlling the leveling shoe 4.

We wish it to be understood that a number of modifications may be introduced in the invention, as can be envisaged by anyone skilled in the art without therefore departing from the scope of the invention as delined in and by the appended claims.

What we claim is:

1. A method for laying a road mat according to a grade line with a road finishing machine equipped with a road leveling member, means for adjusting said member vertically to control the thickness of said mat and the location of its upper surface, and an electrical circuit for actuating said adjusting means comprising the steps of irst providing a fixed reference line of sight extending parallel to said grade line from a stationary point ahead of the finishing machine to a second point on the machine which is in iixed relation to said leveling member, continuously checking during the operation of said machine the position of said reference line with respect to said second point by sighting along said reference line from said stationary point toward said second point, and manually controlling said circuit for actuating said adjusting means remotely from said second point to maintain said second point in said reference line with said reference line in constant parallel relationship with the grade line.

2. A method for laying a road mat according to a grade line with a road finishing machine equipped with a road leveling member and with radio-wave telecontrol-operated means for adjusting said member vertically to control the thickness of said mat and the location of its upper surface, comprising the steps of first setting up a telescope in a stationary position at a point spaced ahead of said machine within a distance of approximately yards, adjusting said telescope so that a reference line extending between the cross-hairs thereof is parallel to said grade line, providing a second point on the machine which is in fixed relation to said leveling member and coincident with said reference line when said member is in its desired vertical position relative to said grade line, continuously checking during the operation of said machine the position of said reference line with respect to said second point by sighting through said telescope along said reference line toward said second point, and manually controlling the transmission of radio waves from a position adjacent said telescope for selectively controlling the operation of said adjusting means to thereby maintain said second point coincident with said reference line as said machine approaches said telescope.

References Cited in the iile of this patent UNITED STATES PATENTS 2,295,519 Millikin et al. Sept. 8, 1942 2,441,532 Millikin et al. May 11, 1948 2,491,275 Millikin Dec. 13, 1949 2,591,502 Bohannan et al Apr. 1, 1952 2,601,277 Green June 24, 1952 2,796,685 Bensinger June 25, 1957 2,844,882 Earley et al July 29, 1958 2,916,836 Stewart et al Dec. 15, 1959 FOREIGN PATENTS 457,829 Italy February 1951

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