Importance

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Abstract

A wheeled roadway planing machine in which the wheels are pivotable by individual hydraulic rams for steering purposes. Each ram is controlled by a rotary, blocked-center valve and the valves are simulataneously actuated by a linkage which establishes a pattern of off-center displacements of their valve members to initiate pivoting of the wheels. The valves are mounted on pivotable wheel representation members which pivot with the wheels, via cables connecting the representation members to support shafts upon which the wheels are mounted, to return the valves to their blocked-center positions as the wheels pivot to a pattern of positions on the chassis of the machine similar to the pattern of displacements of the valve members resulting from operation of the linkage. A cutting drum is mounted on the chassis to form a cut in the roadway, such cut having a shape determined by the position of the chassis on the support shafts. Such position and the depth of each side of the cut are shown by scales, mounted on the chassis near each end of the drum and near the rear end of the chassis, and pointers mounted on rods positioned by the roadway surface. String lines, extending between supports pivotally attached to the ends of the chassis, provide a grade reference for control of the position of the chassis relative to the roadway. Portions of the supports which engage the roadway are laterally positionable on the chassis for selection of a grade line. SUMMARY OF THE INVENTION The present invention relates generally to construction machines and, more particularly, but not by way of limitation, to construction machines having a cutting tool for forming a cut in the surface of a paved work surface as the machine is driven therealong. In the past it has been common practice to repair blemishes in paved surfaces, such as potholes, cracks and the like in roadways, by the addition of asphalt concrete to the surface. This addition has, in some cases, taken to form of patching the surface and, in other cases, has taken the form of repaving; that is, of overlaying an existing, blemished surface with a new layer of asphalt. It has been found that better results of repair can be achieved, in either case, by preparing the surface for the addition of asphalt by planing away a portion of the surface prior to the addition of new asphalt. A machine for planing such surfaces has been disclosed in U.S. Pat. No. 4,139,318, issued Feb. 13, 1979 to Jakob, et al., and assigned to the assignee of the present invention. A number of problems are encountered in the use of machines of this type and these problems vary with the circumstances under which machines are used. A very common problem occurs when a machine is used to plane a roadway or the like wherein are located relatively small obstacles, such as manholes, which must be avoided in the planing operation. It is desirable that the machine be large in order that obstacle-free areas can be planed as rapidly as possible and this size has, in the past, resulted in difficulty in the maneuvering of machines about such small obstacles. While linkages, for connecting and turning wheel and track assemblies for turning a machine, are known which will provide various types of machines with a reasonable degree of maneuverability, such linkages are generally unsuited for a planing machine because of the weight and size the planing machine must have to carry out the planing operation. On the other hand, where the machine is guided by servomechanisms, known servomechanisms have not, in the past, been able to provide the machine with the maneuverability required to avoid small obstacles. For example, a known servomechanism includes a master-slave system wherein one track assembly supporting a machine, the master track, is positioned by opening a valve to a ram which turns the master track assembly and providing a means for repositioning the case of the valve to close the valve as the master track assembly reaches a selected position and a similar valve and repositioning means for causing the slave track assembly to follow the master track assembly. While such a servomechanism is capable of steering a heavy machine, such as a planing machine, the turning of track assemblies by equal amounts does not provide a machine with the degree of maneuverability required in many of the applications of a machine used to plane a paved surface. In the present invention, this problem is solved via a linkage which is connected between representations of the transporters rather than between the transporters themselves. The linkage is utilized to open a plurality of valves mounted on the representation members and a feedback assembly, connecting the transporters to the representations thereof is utilzed to cause the representations to pivot with the transporters to close the valves as the transporters assume desired positions for steering the machine. It is common in machines of this type to mount the tool used to form a cut in the work surface on the chassis of the machine and to control the position of the tool relative to the work surface by positioning the chassis of the machine relative thereto. Problems arise both in the control of the position of the chassis during a planing operation and in the initial positioning thereof at the commencement of a planing operation. In general, machines of this type are provided with some means for establishing a reference for the chassis with respect to the work surface and a control circuit which senses the position of the reference relative to the chassis of the machine and provides control signals for extablishing the attitude of the chassis from the reference. A common reference is the average grade of an interval of the work surface containing the machine and various types of grade averaging assemblies have been developed to permit such an average grade to be used as a reference. In the past, a problem which has arisen in many cases is that portions of the work surface engaged by a grade averaging assembly have been severely blemished with the result that overcontrol of the chassis of the machine has been affected to leave a cut surface with undesirable undulations. The present invention includes a novel stringline support assembly, attachable to the ends of the construction machine for supporting the ends of a stringline utilized for averaging control, which permits a selection of a wide range of lines, fore and aft of the chassis of the machine, along which the average grade of the work surface is to be measured. For this purpose, the stringline support assembly has a pivot arm which is attached to the end of the chassis and a walking beam which is attached to the pivot arm via a walking beam support arm which is slidable laterally on the pivot arm. Where control of the attitude of the chassis is accomplished during a planing operation via automatic controls, such controls must be set at the commencement of the planing operation and it is desirable that the controls be set as quickly as is feasible. In the past, it has been found that such setting can be facilited by mounting scales on portions of the chassis adjacent the transporters which move the machine along the work surface and to support pointers by the transporters to indicate the positions of the transporters with respect to the chassis. The pointers are zeroed when the cutting tool grazingly contacts the work surface so that the attitude of the chassis can be established for a desired depth of cut by means of manually raising and lowering the chassis on the transporters while observing the position of the pointers on the scales. While such scales and pointers have been found useful for establishing the position of the chassis of the machine when automatic control of the attitude of the chassis is to be carried out, a problem has arisen where, as is often the case, the attitude of the machine is to be controlled manually. For example, a common type of contract for a planing operation will call for a particular depth of the work surface to be removed. Often, such removal is most conveniently carried out by manually positioning the chassis of the machine during the cutting oeration provided that the position of the cutting tool is known with respect to the work surface. The present invention provides the ease of setting of automatic controls which has heretofore been provided by mounting pointers on the transporters of the machine and further permits for manual control of the attitude of the chassis by utilizing pointers which are positioned by uncut portions of the work surface mounted on the chassis of the machine. By this means, the depth of the cut, at each side thereof, is measured directly and such information is visually displayed to the operator of the machine. A third pointer which is supported by one of the transporters of the machine of the present invention and which rides in the cut made by the cutting tool, overlays a third scale on the chassis of the machine so that the three scales and three pointers can be utilized, at the commencement of a planing operation wherein automatic control of the attitude of the chassis of the machine is to be carried out, to permit rapid positioning of the chassis for setting the automatic controls. An object of the present invention is to provide a planing machine with a high degree of maneuverability while avoiding the use of heavy linkages between transporters which support the machine on a work surface and move the machine therealong. Another object of the present invention is to provide a planing machine having the capability of grade averaging control utilizing a selection of lines longitudinal of the chassis of the machine for establishing the control grade. Yet a further object of the present invention is to provide a planing machine with a scale assembly which permits gauging of the cut made by the machine in a work surface for manual control of the position of the chassis of the machine relative to the work surface, at such times that is desirable to employ manual control, while further permitting the rapid positioning of the chassis of the machine for the setting of devices utilized to automatically control the cut made in the work surface. Other objects, features and advantages of the present invention will become apparent from the following detailed specification when read in conjunction with the attached drawings and appended claims.

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First Claim