US3512278A

US3512278A - Control systems for earthmoving scrapers

Info

Publication number: US3512278A
Application number: US666033A
Authority: US
Inventors: William H Bechman
Original assignee: Westinghouse Air Brake Co
Current assignee: Westinghouse Air Brake Co
Priority date: 1967-09-07
Filing date: 1967-09-07
Publication date: 1970-05-19
Anticipated expiration: 1987-05-19

Description

' May 19, 1970 w. -H.. B.ECHMAN v CONTROL, SYSTEM FOR EARTHMOVING SCRAPERS med'se t. '7, 1967 2 Sheets-Sheet 1 INVENTOR WILLIAM H. BECHMAN BYI ANDREW J. BECK ATTORNEY May 19, 1970' WQH- BECHMAN 5' 3,512,278

' CONTROL SYSTEM FOR EARTHMOVING SCRAPERS Filed Sept. v, 1967 1 2 Sheets-Shet 2 FIG.2 v

M46 INVENTOR WILLIAM H. BECHMAN US. Cl. 37-8 6 Claims ABSTRACT OF THE DISCLOSURE A tractor scraper including a hydraulic control system comprising a plurality of valves for controlling movable elements of a scraper. The valves have a common manifold and are mounted directly on the scraper to minimize the number of hydraulic lines directed from a tractor, by the pivotal connection between the tractor and scraper, to hydraulic cylinders for each of the movable scraper elements. A hydraulically motivated, valve actuation system including valve modulation means is provided to permit accurate, remote control of the valves. As a safety feature, an alternate source of fluid under pressure for the valve actuation system is provided by connection to a scraper bowl hoist cylinder to permit dropping the bowl as an emergency braking measure upon failure of the primary source of fluid under pressure. When utilized in a tandem scraper arrangement, the present control system may include a ground contacting sensing element operatively connected to the valve actuation system to control the depth of cut of the second scraper dependent upon variations of the actual depth of cut of the first scraper.

Field of invention This invention relates to excavating scrapers, and, more specifically to control systems therefor.

Description of the prior art In recent years, hydraulic controls for standard and elevating-type earthmoving scrapers have gained favor in the earthmoving industry. Hydraulically controlled scrapers may include appropriate circuitry and cylinders for control of the scraper bowl, ejector, apron, or, in some instances, a retractable bowl floor and elevating conveyor. Control valves for actuation of each of the cylinders for these scraper elements conventionally are mounted on the tractor and a pair of flexible lines from each valve is directed from the tractor, through the pivotal connection between the tractor and scraper, to the remote cylinders for each scraper element. In some instances, as many as four or more pairs of relatively large diameter lines are so directed. Because the scraper is usually connected to the tractor for relative pivotal movement about three axes, design or maintenance of such hydraulic lines has been complicated or troublesome. From a safety standpoint, rupture of such lines, as induced by repetitive flexing, has been a serious hazard in that large quantities of hot hydraulic oil under substantial pressure may erupt adjacent the operators compartment. Various solutions to this problem have been suggested but the alternative arrangements have been structurally complicated, sometimes unsafe, and have not always permitted accurate control of the scraper elements because of an inability to modulate or feather the control valves. This problem has been magnified, in some respects, when such scrapers, particularly those of the elevating type, are utilized in tandem.

Sum-mary of the invention It is a general object of the present invention to provide a hydraulic control system for earthmoving scrapers United States Patent 3,512,278 Patented May 19, 1970 adapted to be utilized in tandem, the system minimizing the problems heretofore noted.

In achieving this general object, the present invention provides a hydraulic control system for a tractor-scraper wherein the various movable scraper elements are controlled by valves mounted directly on the scrap r, the valves being remotely actuated by an operator positioned on the tractor. A single pair of lines are directed from a tractor-mounted hydraulic pump and reservoir, by the pivotal connection between the tractor and scraper, to a manifold serving all the valves.

To accurately control the scraper elements, the present invention provides a valve actuation system including modulation means utilizing fluid under pressure to position the valves in any position between fully open and closed.

As a safety feature, the present invention provides an alternate source of fluid under pressure for the valve actuation system by connecting the same to the pressure side of a scraper bowl hoist cylinder. In this manner, th bowl may be dropped as an emergency braking measure in spite of failure of the primary source of fluid under pressure.

In a tandem scraper operation, the present invention additionally provides a sensing means for controlling the elevation of the second scraper bowl in accordance with variations of the actual depth of cut of the first scraper.

Brief description of the drawings In describing the invention, reference will be made to the accompanying drawings in which:

FIG. 1 is a schematic illustration of a pair of earthmoving scrapers connected in tandem and including a hydraulic control system according to the present system; and

FIG. 2 is a schematic diagram of a valve actuation system adapted to actuate the control valves for the various movable elements of the scrapers shown in FIG. 1.

Detailed description of the invention Referring in more detail to FIG. 1 of the drawings, a hydraulic control system, as shown therein, is adapted to be used with conventional scrapers of either the standard or elevating type. Such scrapers include a wheeled tractor unit 10 pivotally connected for relative movement about three axes to a scraper unit 11 including a gooseneck 12. Fixed on the rear end of the scraper gooseneck 12 is a draft tube 14 the lateral ends of which are provided with draft arms 16. A scraper bowl 18 is supported at its rear end by rear wheels 20, and at its intermediate portion on the rear ends of the draft arms 16. The bowl 18 includes a cutting edge 21 at its forward lower end, these elements being elevationally adjustable by actuation of a pair of double acting, hydraulic bowl hoist cylinders 22 connected between the forward end of the bowl and the draft tube 14. In a scraper of the el vating type, an'elevating conveyor assembly 24, which may be electrically, mechanically or hydraulically motivated, is provided to assist in moving material excavated by the cutting edge 21 upwardly and rearwardly in the bowl. To facilitate ejection of materials from the bowl, an ejector or tailgate 28 is movably positioned at the rear of the bowl, the ejector being adapted to be moved longitudinal in the bowl by a double-acting, hydraulic ejector cylinder 30. Additionally, the bowl 18 includes a slidable floor section 31, movable by a pair of double-acting, hydraulic floor cylinders 32 to expose an opening through which material may be ejected.

In a tandem operation, a second or rear scraper unit 33 of the same basic construction as the first or forward scraper unit 11, may be universally connected to the rear end of the first scraper by attachment of the second scraper gooseneck 34 adjacent the first scraper rear wheels 20.

To control the various movable elements of the scrapers, a hydraulic pump 35 is mounted on the tractor 10. The pump is of substantial capacity such as providing an output of approximately 70 g.p.m., is driven by the tractor engine 36, and is connected to a hydraulic fluid reservoir 38. Pressure and return conduits 40 and 42, a portion of which may be flexible lines, are connected to the pump output and reservoir, respectively, and are directed by the pivotal connection between the tractor and first scraper, over the scraper gooseneck, to a valve assembly 44 mounted directly on the scraper gooseneck 12 and draft tube 14.

The valve assembly 44 may include three conventional spool valves mounted in series for independent actuation of the bowl hoist cylinders 22, the ejector cylinder 30, and the bowl floor cylinders 32. It should be appreciated that as many valves may be provided as are required for actuation of each of the movable scraper elements, the hydraulic cylinders of which are connected thereto by suitable lines, not shown. Referring to FIG. 2, a spool valve 46 for actuation of the bowl hoist cylinders 22. is therein shown. The spool valves for actuation of the ejector and floor cylinders, while not shown, are substantially the same as the bowl hoist valve 46 and are connected by common manifolds (not shown) to the pressure and return lines 40 and 42 of the pump and reservoir. The spool valve 46 includes a housing 49 in which is movably mounted a spool 50 for directing hydraulic fluid through

ports

51 and 52 to the rod or head ends of the hoist cylinders 22 for controlling the elevation of the bowl.

To permit accurate control of the position of the spool 50 and to permit modulation or feathering thereof, the present invention includes a modulating valve actuation system 53, schematically illustrated in FIG. 2, for each of the valves of the valve assembly 44. The valve actuation system 53 for the spool valve 46 includes a flexible fluid jet tube 54 mounted in a housing 56 adjacent the upper end of the spool 50, the flexible tube adapted to be deflected in a vertical plane as will be discussed hereinafter. The input end of the fluid jet tube 54 is connected to a manifold 58 serving the other valve actuation systems. The manifold is connected to a conduit 60, of a relatively small diameter compared to the conduits 40 and 42. This conduit 60 is in fluid communcation with the pressure side of a pilot pump 61 mounted adjacent the pump 34. The pilot pump, supplied by reservoir 38, is engine driven and is of a. relatively small capacity providing approximately 6 g.p.m. An output end 62 of the fluid jet tube 54 is positioned within the housing 56 so that fluid therefrom will impinge upon an area of a plug 64 between a pair of vertically spaced

ports

66 and 68, schematically illustrated in FIG. 2. A suitable return line 69 (FIG. 1) is provided to return flow from all of the valve actuation systems to the reservoir 38. The port 66 is in fluid communication with a conduit 70 directed through the

housings

56 and 49 to a chamber 71 at the lower end of the spool 50. The port 68 is in fluid communication with a chamber 72 at the upper end of the spool 50. Plug 64 is embraced by a pair of adjustable springs 73 providing a self-centering function.

To meter the flow by actuation of the spool 50, an electromagnet assembly 74 is provided. This assembly includes an electromagnet solenoid core 75, the lower end of which is positioned in a coil 76 fixedly connected to the valve housing. The coil 76 is electrically connected by leads 78 to a rheostat switch means 79, including means to reverse polarity mounted on the instrument panel of the tractor in a position for convenient manual control by the tractor operator. Depending upon the direction of current flow through the coil 76,.the core and jet tube are moved in an upwardly or downwardly direction, as shown in FIG. 2. Such movement causes the output end 62 of the jet tube 54 to be aligned with one of the

ports

66 and 68. Fluid flow from the jet tube is thereby directed to one of the chambers 71 and 72 resulting in movement of the spool 50. It is important to note that spool move ment may be finely adjusted, modulated, or feathered because movement of the jet tube 54 may be closely regulated.

As a safety feature, the present invention provides an alternate source of fluid under pressure to the jet tube manifold upon interruption of pilot pump output, such as occasioned by stalling of the tractor engine. To achieve this function, a fail-safe system 80, schematically shown in FIG. 2, is provided. This system includes a fluid pressure responsive switch 82 which is electrically connected to a servo-motor 84. Upon reduction of fluid pressure in the conduit 60, an electric circuit is closed thereby actuating servo-motor 84 which in turn opens a valve 86 for directing fluid in a conduit 88 from the pressure or rod end of one of the scraper bowl hoist cylinders 22, to the conduit 60, and the jet tube 54. The fluid in the rod end of the cylinder 22 is under substantial pressure because the weight of the bowl is supported thereon. Conventional check valves 90 are positioned in the conduits 60 and 38 to permit fluid flow from the cylinder 22 only in the direction to the jet tube 54. This alternate source of fluid pressure thereby makes it possible to drop the bowl as an emergency braking measure when the tractor engine stalls, and the pilot pump 61 ceases operation.

When utilized in a tandem scraper operation, the present control system offers substantial advantages as to accuracy of control and a reduction of the number of iarge diameter hydraulic lines which must be strung between the tractor and the two scrapers. Additionally, to eliminate the necessity of an operator manually controlling the depth of cut of the second scraper, the present invention provides a sensing means 92 for controlling the elevation or depth of cut of the second scraper relative to its starting position in accordance with variations in the depth of cut of the first scraper. The sensing means 92 includes a ground contacting wheel 94 pivotally mounted on the second scraper bowl 96 by an arm 98 so as to trail in the path of cut made by the first scraper. Any suitable vertical adjustment means such as an extensible threaded connection 100 may be provided between the wheel 94 and the arm 98. Adjacent the rear end of the arm 98, a pair of limit switches 102 may be positioned on the bowl. The second scraper includes a valve assembly 104, substantially like the valve assembly 44 for the first scraper, which is connected thereto by suitable pressure and return lines 106. A second valve actuation system, like the valve actuation system 53 for the first scraper, is also provided. The limit switches 162 are electrically connected so as to direct current in either direction through a coil, like coil 76, of the valve actuation system for the hoist cylinders of the second scraper.

In operation, an operator may adjust the initial position of the sensing means 92 relative to the cutting edge of the second scraper by adjustment of the extensible connection 100. During operation, the operator need only manually control the depth of cut of the first scraper while the sensing means 92 governs the cut of the second scraper to excavate a predetermined depth below the actual cut of the first scraper. Such an arrangement is particularly beneficial in a tandem scraper operation because the cutting edge of the second scraper is often obscured from the view of the tractor operator. Close control of the cut of the second scraper, either manually or automatically, is made possible. Further, utilization of the present invention with tandem scrapers of the elevating type is particularly advantageous for the following reason. When utilizing standard scrapers, the primary limitation on depth of cut is tractor power and traction. However, when utilizing elevating scrapers, additional care must be taken not to overload and stall the elevating conveyor by making too great a cut. For example, assume a total cut of 8 inches is desired, each scraper taking a bite of 4 inches. Further assume that because of operator inattention or the like, the first scraper cuts merely 2 inches. In such a condition, if a sensing element did not trail in a path of the cut of the first scraper, as in the present invention, but rather senses ground level to either side of the tandem'scrapers, then the second scraper might take a 6 inch cut. Such an increase in depth of cut might well overload the conveyor of the second scraper thereby stalling the same and prohibiting further loading without clearing the conveyor.

Although the present invention has been disclosed as incorporating a sensing means including a ground contacting wheel, certain of the advantages afforded by this aspect of the present invention may be achieved by utilization of other sensing means. For example, a photoelectric or other energy sensing systems, having sending and receiving elements adjustably positioned in opposed relation and at approximately axle height on the front and rear scraper bowls, might be utilized. In this way, the second scraper cutting edge could be maintained at a predetermined depth below the actual cut of the first scraper.

By utilization of plurality of scraper mounted valves having a common pressure and return manifold, the number of hydraulic lines which are directed by or through the pivotal connection between the tractor and scraper may be minimized. But of further benefit is the aspect of the present invention wherein the hydraulic lines between the valves and pump which are of a substantial length and which must of necessity be directed adjacent the operators compartment, are not subjected to shock loads imposed thereon by loads on the various cylinders in any fixed position. For example, a momentary increase in the fluid pressure in the bowl hoist cylinders 22, as may be induced by the scraper hitting a bump during travel, is blocked by the valve assembly 46 thereby insulating lines 40 and 42 from the same.

In describing the present control system, reference has been made to a preferred embodiment. However, it should be appreciated by one skilled in the art that various additions, deletions, and modifications may be made which fall into the scope of the present invention which is to be ascertained from the following claims.

What is claimed is:

1. a tractor-scraper comprising:

a prime mover including engine means;

a Wheeled scraper including a bowl and draft frame means pivotally connecting said prime mover and said bowl;

motor means connecting said draft frame means and said bowl for controlling the elevation of said bowl;

control actuating means for actuating said motor means;

power means for motivating said control actuating means; and

fluid pressure delivery means for motivating said control actuating means upon failure of said power means, said fluid pressure delivery means including said motor means and said motor means comprising fluid jack means.

2. A tractor-scraper vehicle according to claim 1 wherein said power means includes pump means mounted on said prime mover and driven by said engine means, and conduit means connecting said pump means and said control actuating means.

3. A tractor-scraper according to claim 1 having aligned with, and connected to, the rear of said wheeled scraper, a second wheeled scraper having a bowl, the bowl of each scraper having a cutting edge adjacent the forward lower end thereof, and modulating control means controlling the depth of cut of said second scraper relative to its initial position in accordance with variations in the depth of actual cut of said first scraper.

4. A tractor-scraper according to claim 3, said modulating control means further comprising ground contacting sensing means positioned on one of said scrapers aligned with, and rearwardly of the cutting edge of said first scraper.

5. A tractor-scraper arrangement according to claim 4 further comprising elevating conveyor means positioned in at least the bowl of said second scraper above the cutting edge thereof.

6. A tractor-scraper according to claim 2, wherein said alternate power delivery means further comprises pressure responsive means responsive to reduction of fluid pressure in said first conduit means for directing flow from said fluid jack means to said control actuating means for actuating said motor control means.

References Cited UNITED STATES PATENTS 2,858,849 11/1958 Griffith 91-459 2,985,147 5/ 1961 Rockwell.

3,129,645 4/ 1964 Olmsted 91-461 3,233,349 2/1966 Becton 37-124 3,272,234 9/1966 Parker 91-459 3,282,283 11/1966 Michio Takeda 91-390 3,386,343 6/1968 Gray 91-461 3,401,601 9/1968 Velicer et al. 91-390 3,434,390 3/1969 Weiss 91-459 2,567,107 9/1951 Gobeil 172-4 2,665,637 l/1954 Lauck 103-4 2,755,721 7/1956 Rusconi 172-4 2,935,951 5/1960 Forster 103-4 3,196,599 7/1965 Meiners et al. 172-4 3,233,680 2/1966 Arzoian et al. 172-4 3,304,633 2/1967 Hein et al. 37-129 3,346,972 10/ 1967 Johnson 37-8 3,364,824 1/1968 Rood 37-129 3,394,474 7/1968 Rockwell 37-129 ROBERT E. PULFREY, Primary Examiner E. H. EICKHOLT, Assistant Examiner U.S. Cl. X.R.