US3762076A

US3762076A - Hoeing scraper control system

Info

Publication number: US3762076A
Application number: US00213362A
Authority: US
Inventors: L Eftefield
Original assignee: Caterpillar Tractor Co
Current assignee: Caterpillar Inc
Priority date: 1971-12-29
Filing date: 1971-12-29
Publication date: 1973-10-02
Anticipated expiration: 1990-10-02

Abstract

An electro-hydraulic circuit provides semi-automatic control of movements of a hoeing apron loading device in a scraper vehicle. The system uses a combination of position sensing means and timing devices to cycle hydraulic jacks which manipulate the apron in a selected pattern of hoeing motions to load material into the scraper and also to position the apron for closing the bowl in preparation for transporting loaded material. The system, which may be overridden by manual controls, greatly simplifies the operator''s task and thereby increases the efficiency of scrapers equipped with hoeing aprons.

Description

United States Patent 1 Eftefield [4 1 Oct. 2, 1973 HOEING SCRAPER CONTROL SYSTEM Larry G. Eftefield, Brussels, Belgium [73] Assignee: Caterpillar Tractor Co., Peoria, 111.

[22] Filed: Dec. 29, 1971 [2]] Appl. No.: 213,362

[75] Inventor:

[52] US. Cl 37/4, 37/124, 214/500,

.74/D1G. 2, 137/624.l5, 91/459, 91/412 [51] Int. Cl 860p 1/00 [58] Field of Search 37/4.8, 124, 126,

37/129; 91/411-414, 361, 459, 275; 60/52 R; 137/624.11624.2; 74/2, 471 R, DIG. 2; 1 214/275, 500

[56] References Cited I UNITED STATES PATENTS 3,495,662 2/1970 Welch 172/3 3,294,178 12/1966 Lawson et al... 172/6 X 3,126,653 3/1964 Bourgeous 172/45 3,636,325 1/1972 Chytil 37/116 3,589,242 6/1971 Peterson 91/413 3,016,804 1/1962 Zawkl et al. 91/414 X 3,198,083 8/1965 Farr et al. 1 91/414 X 3,570,243 3/1971 Comer et a1. 60/52 R 3,477,152 11/1969 Ask 37/129 Primary Examiner'Robert E. Pulfrey Assistant Examiner-Eugene H. Eickholt Attorney-Donald J. McRae et a1.

[57] ABSTRACT An electro-hydraulic circuit provides semi-automatic control of movements ofa hoeing apron loading device in a scraper vehicle. The system uses a combination of position sensing means and timing devices to cycle hydraulic jacks which manipulate the apron in a selected pattern of'hoeing motions to load material into the scraper and also to position the apron for closing the bowl in preparation for transporting loaded material. The system, which may be overridden by manual controls, greatly simplifies the operators task and thereby increases the efi'iciency of scrapers equipped with hoeing aprons.

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I NVENTOR LARRY C EFTEFXELD ATTORNEYS HOEIN'G SCRAPER CONTROL SYSTEM BACKGROUND OF THE INVENTION This invention relates to control systems for load manipulating devices which are mounted on vehicles and more particularly to a self-cycling system for causing the apron of a scraper to execute predetermined hoeing motions to assist the movement of material into the bowl of the scraper.

Under many working conditions the bowl of a scraper cannot be fully loaded by relying solely on the forward thrust produced by the drive wheels of the vehicle. To avoid the need for employing supplementary pusher tractors, a variety of loading assist mechanisms have been developed to aid in moving earth or the like over the cutting edge of the scraper and up into the bowl. A very efficient advantageous form of loading assist mechanism employs an apron which may be forceably pivoted relative to support arms which in turn may be forceably pivoted relative to the scraper bowl whereby the apron may be made to undergo a hoeing or raking movement to draw material into the bowl. Hoeing scrapers of this general type are disclosed in U.S. Pat. No. 3,471,952 and in co-pending application Ser. No. 21,369 of Larry G. Eftefield filed Mar. 20, 1970 for HOEING APRON MECHANISM FOR SCRAPERS.

The operator of a hoeing apron scraper must perform the conventional control functions associated with driving the vehicle, such as steering, transmission shifting, braking and the like and in addition has heretofore been required to perform taxing additional control functions for causing the apron to undergo the desired motions. As the apron motions are complex, this has greatly increased the demands made on the operator in terms of complicated hand motions and diversion of attention from more conventional scraper control functions. As a practical matter, operation of such a scraper has proved to be very tiring and has required an individual possessing unusual dexterity and stamina. This adversely affects the general efficiency of hoeing scrapers inasmuch as the capabilities of the operator, rather then those of the machinery, tend to be the limiting factor insofar as rate of material handling is concerned.

SUMMARY OF THE INVENTION The present invention provides a semi-automatic control system for cycling the apron of a hoeing scraper which system may be selectively activated by the operator as an alternative to manual control of the several different motions of the apron and which may be overridden by the manual controls when necessary. The several fluid motors or the like which provide apron movement are actuated and stopped at appropriate times by electrical signals originating in a control circuit which, in a preferred form, utilizes position sensors and timing devices to eflect any selected one of a plurality of predetermined patterns of apron movement. The task of operating the hoeing scraper is thereby greatly simplified and made less demanding.

Accordingly it is object to this invention to simplify the task of controlling the operations of a hoeing scraper.

It is another object of this invention to provide means whereby the apron of a hoeing scraper may be caused to self cycle through any selected one of a plurality of repetitive apron movements.

It is still another object of the invention to increase the effectiveness and efficiency of hoeing scrapers by reducing dependence on complex and tiring control manipulations by the operator.

The invention, together with further objects and advantages thereof, will best be understood by reference to the following description of preferred embodiments taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings:

FIG. 1 is a side elevation view of a hoeing scraper together with a schematic diagram of the electrical and hydraulic circuit of the present invention;

FIG. 2 is a broken out view of a portion of the bowl of the scraper of FIG. 1 including the hoeing apron mechanism thereof and illustrating a first pattern of loading movement of the apron;

FIG. 3 is a broken out view of a portion of the bowl of the scraper including the hoeing apron mechanism showing a second pattern of apron movement which may be employed in the course of loading;

FIGS. 4 to 7 illustrate successive stages of apron motion in the course of loading of the scraper under semiautomatic control by the present invention; and

FIGS. 8 to 11 illustrate successive positions of the apron in the course of a semi-automatic apron closing movement provided by the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring initially to FIG. 1 of the drawing, a scraper 11 of the form equipped with a hoeing apron loading assist mechanism 12 typically has a bowl 13 with a cutting edge 14 at the open forward end thereof and is supported at the forward end by tractor means 16 including front wheels 17 powered by a front engine 18. Tractor means 16 is coupled to the bowl through a gooseneck 19 and draft arms 21 which are pivoted to the side walls of the bowl. Hydraulic jacks 22 connected between the tractor means 16 and the front end of bowl 13 provide for selectively raising and lowering the bowl by pivoting movement about the axis of rear wheels 23 which support the back end of the bowl and which are powered by a separate rear engine 24. The scraper is loaded with earth or the like by lowering the bowl 13 until cutting edge 14 engages the ground whereby a layer of earth is guided upwardly into the bowl when the scraper is driven forward.

l-Ioeing apron mechanism 12 is caused to undergo a hoeing or raking motion to assist the movement of earth over the cutting edge 14 to avoid a need for additional tractive power and to assure full loading of the scraper. For this purpose the hoeing apron mechanism 12 may consist of a pair of bail arms 26 disposed adjacent opposite side walls of bowl l3 and each having a lower end pivoted thereto whereby the upper ends of the bail arms may be swung forward and backward by motor means such as hydraulic bail jacks 27 connected between each bail arm and a more forward point on the bowl 13 by pivot means. The apron 28 extends transversely relative to bowl l3 and has an extension arm 29 at-each side which connects to the upper end of the bail arm 26 at that side and is coupled thereto for pivoting motion relative to the bail arm. Such pivoting movement of the apron 28 relative to bail arms 26 is provided for by additional motor means such as a pair of apron jacks 31 extending therebetween and pivotally attached to each thereof.

Dashed outline 32 of FIG. 2 illustrates one typical pattern of movement of the lower end of the apron 28 in the course of loading of the scraper. This hoeing motion depicted by outline 32 assists the movement of earth over the cutting edge 14 and into bowl 13 and serves the further purpose of retaining material which has already been loaded. Typically, several such hoeing movements 32 are required in the course of a single filling of the bowl. It may be desirable to shorten certain phases of the movement defined by dashed outline 32 during difierent loading operations because of differences in the characteristics of the earth or other material being loaded or during different stages of a single loading operation as the bowl fills. Accordingly dashed outline 32' of FIG. 3 illustrates a suitable alternate apron movement pattern which may be desirable under such conditions and which differs from the apron movement depicted in FIG. 2 principally by a shortening of the extent of the vertical and horizontal motions of the lower end of the apron. This alternate pattern of movement 32' may be desirable, for example, after material has been heaped relatively high in bowl 13 in order to reduce loss of loaded material during the stage when the apron is extended forwardly.

Heretofore, the necessary extensions and contractions of the

jacks

27 and 31 are needed to produce the above described motions of the apron 28 have been manually initiated and stopped by the operator who must also tend to driving the vehicle. A suitable manual control system for this purpose is disclosed in U.S. Pat. No. 3,589,242 of Robert A. Peterson issued June 29, 1971 and entitled SINGLE LEVER CONTROL FOR HOEING SCRAPER COMPONENTS.

Considering now the system of the present invention by which the operator of a scraper may be freed of much of the task of controlling apron movement, reference should again be made to FIG. 1. The jacks 27 which manipulate bail arms 26 are operated by high pressure fluid from a pump 33 drawing from a suitable fluid reservoir 34. Fluid from pump 33 is transmitted to the jacks 27 through a three position pilot operated valve 36. Valve 36 has a fluid input line 37 receiving fluid from pump 33 and a drain line 38 to reservoir 34, a relief valve 39 being connected across

lines

37 and 38 to maintain a maximum predetermined pressure in line 37. Output lines 41 and 42 from valve 36 connect with the head and rod ends respectively of bail jacks 27. Valve 36 is of the form which assumes a center or Hold position when pilot pressure is applied to both ends of the valve through

pilot lines

43 and 44 and at this position outputs 41 and 42 are both blocked and 'thus the jacks 27 are immobilized. Release of pressure from pilot line 43 causes valve 36 to shift to a Hail Forward position at which pressure is transmitted to outlet 42 while outlet 41 is vented to drain 38 thereby causing the bail jacks 27 to contract and pivot bail arms 26 forward. Release of pilot pressure from the other pilot line 44 causes valve 36 to shift to a Bail Back position at which pressurized fluid from input 37 is transmitted to the head ends of bail jacks 47 while the rod ends thereof are vented to drain 38.

When the hoeing apron mechanism 12 is under manual control, the pilot pressure signals for actuating valve 36 are produced by operator manipulation of a manual control valve 46. Control valve 36 receives fluid under pressure from an additional pump 47, that draws from a fluid reservoir 48, and has a drain line 49 back to the reservoir, a relief valve 51 being connected between the output of pump 47 and reservoir 48 to maintain a predetermined maximum fluid pressure at the input to control valve 36. Manual control valve has a centered Hold position at which output pressure from pump 47 is transmitted to both of the

pilot pressure lines

43 and 44 of valve 36 through solenoid controlled valves 52 and 53 respectively which will hereinafter be described in more detail. Thus at the Hold position of the manual control valve 46, both

pilot lines

43 and 44 are pressurized and bail jacks 27 are immobilized provided that solenoid valve 52 and 53 are both unenergized at that time. Manual control valve 46 may be shifted to a Bail Forward position at which pilot line 44 is pressurized while pilot line 43 is vented thereby causing valve 36 to shift to start contraction of bail jacks 27. Manual control valve 46 may also be shifted to a Bail Back position at which pressure is directed to pilot line 43 while pilot line 44 is vented causing valve 36 to shift to the position at which bail jacks 27 extend.

With the manual control valve 46 in the Hold position at which pressure is transmitted to both

pilot lines

43 and 44, the solenoid valves 52 and 53 provide an alternate means for controlling the bail jacks 27. In particular, electrically energizing an input conductor 54 to solenoid valve 52 causes valve 52 to shift to a position at which pilot line 43 is vented to the reservoir thereby causing valve 36 to shift to contact jacks 27. Similarly, energizing of an input conductor 57 to solenoid valve 53 depressurizes pilot line 44 causing valve 36 to shift to extend bail jacks 27 Accordingly, automatic control of the bail jacks 27 may be realized by electrically energizing solenoid

valve input conductors

54 and 57 as necessary as will hereinafter be described.

An essentially similar fluid circuit provides for alternate manual or automatic control of the apron jacks 31. In particular, a manually operated apron control valve 59 receives fluid from a reservoir 61 through a pump 62 and has a drain line 63 back to the reservoir. To maintain a predetermined pressure at control valve 59, a relief valve is connected across the outlet of pump 62 and reservoir 61. Manual control valve 59 has a pair of outlets which communicate with pilot lines 64 and 65 of a pilot operated apron jack control valve 66 through

solenoid valves

67 and 68 respectively. Manual control valve 59 has a Hold position at which fluid pressure from pump 62 is transmitted to both pilots 64 and 65 of valve 66. Valve 66 receives pressurized fluid from an additional pump 67 and has a drain line 68 to return fluid to the reservoir 69 from which the pump draws fluid, a relief valve 71 being connected across the output of pump 67 and drain line 68 maintains a predetermined maximum pressure. Valve 66 has a pair of outlets 72 and 73 communicating with the rod end and head end respectively of the apron jacks 31. With manual control valve 59 at the Hold setting described above the resultant pressurization of both pilots 64 and 65 causes valve 66 to assume a centered position at which both outlets 72 and 73 are blocked thereby immobilizing the apronjacks 31. Manual control valve 59 may be shifted to a Raise Apron position at which pressure from pump 62 is supplied to pilot 64 of valve 66 while pilot 65 is vented. This causes valve 66 to shift to supply pressure from pump 67 to the rod ends of apron jacks 31 while venting the head ends thereof and thereby pivots the apron 28 upward relative to bail arms 26. Similarly, manual control valve 59 maybe shifted to a Lower Apron position at which pressure from pump 62 is transmitted to pilot 65 of valve 66 while pilot 64 is vented. This causes valve 66 to shift to transmit pressure from pump 67 to the head end of apron jacks 31 while venting the rod ends thereof and thereby pivots the apron 28 downward relative to bail arms. 26.

With the manual control valve 59 in the center or Hold position, wherein pilots 64 and 65 are both pressurized, the same actions may be realized by energizing one of the

solenoid valves

67 or 68. Electrical energization of an input conductor 74 of solenoid valve 67 causes valve 67 to release pressure from pilot 64. Under this condition valve 66 shifts to extend the apron jacks 31 and thereby lower the apron 28. Similarly electrical energization of an input conductor 77 to solenoid valve 68 causes valve 68 to depressurize pilot 65. This causes valve 66 to shift to contract apron cylinders 61 and thereby raise the apron 28.

Thus automatic control of the movements of the apron 28 may be realized by appropriately timed electrical energization of the four

solenoid valves

52, 53, 67, and 68.

Considering now the electrical circuit which controls the four solenoid valves for the above described purpose, power from a suitable DC source 79 which may be the vehicle battery'is transmitted to the four

solenoid valve conductors

54, 57, 74, and 77 at appropriate times through an operators control console represented by dashed rectangle 81 in FIG. 1 and through a rotary stepping switch 82. Stepping switch 82 in this example is of the form having four bank levels 82-1, 82-2, 82-3, and 82-4, each having a set of ten stationary contacts designated by numerals l to at each level in FIG. 1. At each bank level, a three armed rotating contact 83 is provided and is permanently connected to an input terminal designated by numeral 0. Each stepping of the rotating contacts 83 successively connects the input contact 0 at each bank level with contacts 1 to 10 thereat. The rotating contacts 83 at each bank level 82-1 to 82-4 are shifted one step each time a driver solenoid 84 is operated by means to be hereinafter described. Solenoid operated rotary stepping switches 82 of this form are well known to the art and thus the detailed mechanical structure of the switch will not be described herein.

The first bank level 82-1 of stepping switch 82 controls the operation of the apron jacks 31 and for this purpose input conductor 74 of solenoid valve 67 is connected to each of contacts 1, 2, 5, 6 and 7 of bank level 82] while input conductor 77 to solenoid 68 is connected to contacts 3 and 4 of bank level 82-1. The final three contacts 8 to 10 of bank level 82-1 are not utilized. The second bank level 82-2 controls operation of the bail jacks 27 and for this purpose input conductor 57 of solenoid valve 53 is connected to contacts 2 and 6 of bank level 82-2. The input conductor 54 of solenoid valve 52 connects with contacts 4 and 7 of bank level 82-2, the remaining contacts being unutilized.

The third bank level 82-3 controls the timing of successive steps of the stepping switch 82 in the course of loading of the scraper while the fourth bank level 82-4 controls the timing during an automatic closing movement of the apron at the end of the loading operation and the connections to the contacts of these two bank levels for this purpose will be hereinafter described.

To energize the driver solenoid 84 of the stepping switch 82 at variable intervals in order to cause the several rotating contacts 83, to advance successive steps at predetermined times, a pulse generator circuit 86 is provided. Pulse generator 86 has a power input conductor 87 connected to the positive side of battery 79 through a protective fuse 88 and key operated switch 89 located in the operators control console 81. Power input conductor 87 connects with a positive terminal 91 of solenoid 84 through a set of normally closed interrupter contacts 92 which are opened by energization of the solenoid coil. Thus the solenoid coil can be energized only briefly without interruption inasmuch as each energization of the coil, which advances the stepping switch contacts 83 one step, is immediately terminated by the resultant opening of contacts 92. To control the timing of successive energizations of solenoid coil 84 the negative terminal 91 thereof is connected to ground through an SCR (silicon controlled rectifier) 93 and thus the solenoid coil 84 will transmit current each time the SCR 93 is made conductive with the current transmission acting as described above to open contact 92 and thereby deenergize the coil which action also restores the SCR 93 to the non-conductive state. I r

A capacitor 98 is connected between ground and a control signal conductor 97, through a resistor 94, and firing of SCR 93 is initiated when the charge on the capacitor reaches a predetermined value. The emitter of a unijunction transistor 95 is connected to the ungrounded side of the capacitor 98 while one base of the transistor connects with power input conductor 87 through resistor 95a and the other base connects with ground through a resister 95b and with the control electrode of SCR 93 through resistor 95c. Accordingly when capacitor 98 is charged to a predetermined value through control signal conductor 97, unijunction transistor 95 conducts to discharge the capacitor and to simultaneously gate SCR 93 into conduction thereby pulsing solenoid 84. A diode 92a is connected across contacts 92 to protect the contacts against voltage spikes arising from de-energization of solenoid 84.

Bank levels 82-3 and 82-4 of stepping switch 82 act to establish a predetermined amount of resistance between battery 79 and capacitor 98 at each step of the rotary switch 82 so that the time required for capacitor 98 to charge to a value sufficient to trigger SCR 93 and energize solenoid 84 is appropriate to that particular step in the cycle of operation of the system.

For this purpose control signal conductor 97 is connected directly to each of contacts 5, 6, 7, 8 and 9 of bank level 82-3 and also to contacts 1, 2, 3, 4, 8, 9'and 10 of bank level 82-4, the functional significance of these connections being hereinafter discussed in connection with the description of the operation of the system. Control signal conductor 97 connects to contact 1 of bank level 82-3 through a variable resistor 99 and to contact 3 of the same bank level through an additional variable resistor 101, the variable resistors providing for an adjustable predetermined delay time between energizations of stepping solenoid 84 at certain specific steps as will hereinafter be described in more detail. Control signal conductor 97 connects with contact 2 of bank level 82-3 through a normally open limit switch 102 and normally open contacts 103 of a Cycle One selector switch 104. Control signal conductor 97 also connects with contact 2 of bank level 82-3 through an additional limit switch 106 and normally open contacts 107 of a Cycle Two selector switch 108. Control signal conductor 97 connects to contact 4 of bank level 82-3 through a pair of normally open limit switches 109 and 11 1 in series. Still further connections to control signal conductor 97 include a variable resistor 112 connected between contact 5 of bank level 82-4 and conductor 97 and another variable resistor 113 connected between conductor 97 and both contacts 6 and 7 of bank level 82-4. The final contact 10 of bank level 82-3 connects with the control signal conductor 97 through a second set of normally open contacts 114 of Cycle One selector switch 104 and also through a second set of normally open contacts 116 of Cycle Two selector switch 108.

The above described Cycle One selector switch 104 and Cycle Two selector switch 108 are preferably located at the operators console 81. Within console 81 a normally open On-Off switch 117 provides for connection of contacts 0 of bank levels 82-1 and 82-2 to the positive side of battery through fuse 88 and key switch 89. To indicate when the system is energized by closing of key switch 89, an indicator lamp 118 at console 81 is connected to the positive side of battery 79 through fuse 88 and the key switch. Console 81 also has a two position Operation Selector switch 119 which at one position connects contact 0 of bank level 82-3 to positive battery through fuse 88 and key switch 89 and at the alternate position connects contact 0 of bank level 82-4 with positive battery through the fuse and key switch. As will be discussed in connection with the operation of the system, the first described position of switch 119 conditions the system to perform loading operations while the alternate position of the switch 119 conditions the system to automatically close the apron at the conclusion of a loading cycle. A Rapid Home switch 121 is provided at the control console for the purpose of restoring stepping switch 82 to the start position if it is necessary to interrupt an automatic loading cycle. Closing of the Rapid Home switch 121 connects control signal conductor 97 with each of contacts 2, 3, and 4 of bank level 82-3 thereby by-passing the resistances and limit switches heretofore described as connected between such contacts and the control signal conductor.

Considering now the operation of the above described electrical circuit, it will first be assumed that key switch 89 and On-Off switch 117 are both closed by the operator to energize the system and that the several rotating contacts 83 of stepping switch 82 are at the home position wherein contacts 0 and 10 are electrically connected at each bank level. It will further be assumed that Operation Selector switch 119 is in the Load position at which input contact 0 of bank level 82-3 is energized while input contact 0 of bank level 82-4 is unenergized. As illustrated in FIG. 4, the apron 28 of the scraper is at what is termed the start position at which both the apron jacks 31 and the bail jacks 27 are fully contracted. At this position the apron 28 is situated forward and upward from cutting edge 14. The previously described limit switch 109 associated with contact 4 of bank level 82-3 is situated on the bowl 13 side wall in position to be closed by abutment of one of the bail arms 26 thereagainst when the apron is at the above described start position. Similarly, the previously described limit switch 111 connected in series with limit switch 109 is situated on apron arm extension 29 in position to be closed by a bracket 26 at the top of bail arm 26 when the apron 28 is at the described start position. Under these start conditions, a first pattern of automatic hoeing motions of the apron may be initiated by the operator by closing the Cycle One selector switch 104 of FIG. 1.

Upon closing of the Cycle One selector switch 104, the control signal conductor 97 of pulse generator 86 is connected to positive battery through contacts 114 at switch 104,

contacts

10, 83 and 0 of bank level 82-3, Operation Selector switch 119 and fuse 88 and key switch 89. As this circuit path contains relatively little resistance, capacitor 98 of pulse generator 86 charges rapidly to gate on SCR 93 and thereby pulse solenoid 84. Solenoid 84 immediately de-energizes due to opening of contacts 92 but the brief energization results in advancement of contacts 83 of the stepping switch 82 by one step to energize contact 1 at each bank level. The momentary conduction through unijunction transistor 95 removes the charge from capacitor 98 in preparation for the next charging cycle.

At this position of stepping switch 82, the Lower Apron solenoid valve 67 is energized through conductor 74. This causes the hydraulic system to initiate extension of the apron cylinders 31 as previously described causing the apron 28 to be pivoted rearwardly and downwardly from the position shown in FIG. 4 to that illustrated in FIG. 5. Bail jacks 27 are immobile during this stage of the hoeing motion and it should be observed that bracket 26 moves away from limit switch 111 enabling that limit switch to assume the normally open condition.

The extent to which apron 28 pivots downward and backward during this phase of the loading cycle is determined by the resistance of the variable resistor 99 associated with contact 1 of bank level 82-3. Once the stepping switch 82 has been stepped to energize the contact 1 at bank level 82-3, voltage is transmitted to capacitor 98 through the variable resistor 99 and thus the time interval required for the capacitor 98 to charge sufficiently to initiate another step of the stepping switch 82 is determinable by appropriate adjustment of the resistor 99. This time is selected to initiate a second step of the stepping switch 92 after the apron 28 has moved from the position depicted in FIG. 4 to that shown in FIG. 5.

At the second position of stepping switch 82, contact 2 of bank level 82-1 is energized and this holds the Lower Apron solenoid 67 energized to continue the extension of apron jacks 31. However, the apron movement now differs from that described above in that contact 2 of bank level 82-2 is also energized and this energizes the Bail Back solenoid 57 to cause extension of the bail jacks 27 through the hydraulic circuit action hereinbefore described. Accordingly, with both sets of

jacks

31 and 27 in the process of extending, the apron 28 moves from the position shown in FIG. 5 towards the position depicted in FIG. 6. Extension of the apron jacks 31 is completed before full extension of the bail jacks 27 and thus the apron undergoes a predominately backward movement followed by a predominately upward movement at this stage as best seen by reference to FIG. 2.

The previously described limit switch 102 is situated on the side wall of bowl 11 position to be closed by abutment of a bail arm 26 against the switch 102 when the bail jacks 27 have reached maximum extension as shown in FIG. 6. Referring again to FIG. 1, closing of limit switch 102 applies positive battery voltage to control signal conductor 97 through a low resistance path which includes contact 103 of Cycle One selector switch 104 and contacts 2, 83 and of bank level 82-3. Capacitor 98 of the pulse generator circuit 86 therefore charges immediately and solenoid 84 is momentarily energized to advance the rotating contacts 83 of the stepping switch to the third step position. At the third step position, bank level 821 has de-energized the Lower Apron solenoid 74 and energizes the Raise Apron solenoid valve 68 through contact 3. Accordingly the hydraulic circuit shifts to cause the apron jacks 31 to contract. At this third position of the stepping switch 82, neither of the

bail solenoid valves

53 and 54 are energized and thus the bail arms 26 do not undergo movement. Accordingly, at this stage the apron 28 pivots forward and upward from the position depicted in FIG. 6 to the position depicted in FIG. 7. The extent of this apron movement is determined by the variable resistor 101 associated with contact 3 of bank level 82-3 inasmuch as voltage is applied to control signal conductor 97 through this resistor at this time. Accordingly, capacitor 98 of the pulse generator circuit 86 recharges at a rate determined by the value of resistor 101 and eventually terminates the apron mo tion under discussion by briefly energizing solenoid 84 to advance the contacts 83 of stepping switch 82 to the fourth step position. As contact 4 of each bank level is energized at the fourth step position, the Raise Apron solenoid valve 68 continues to be energized through bank level 82-1 thereby causing apron jacks 31 to continue contracting. However bank level 82-2 now energizes Bail Forward solenoid valve 52 at this fourth step position and thus the apron proceeds from the position shown in FIG. 7 towards the start position depicted in FIG. 4. As best seen in FIG. 2, this movement has two distinct stages including a predominately forward motion followed by a predominately downward movement inasmuch as contraction of apron jacks 31 is completed prior to contraction of bail jacks 27. This final portion of the hoeing motion is terminated when the bail arms 26 reach the full forward position depicted in FIG. 4 and close limit switch 109. Limit switch 111 closed previously when apron jacks 31 fully contracted. With both of the series connected limit switches 109 and 111 closed, capacitor 98 charges immediately through bank level 82-3 and pulses driver solenoid 84 to step contacts 83 at each bank level to the fifth step position.

It may be observed that the apron mechanism 12 has now executed one complete hoeing motion and has returned to the initial starting position. As contacts through 9 of bank level 82-3 are each connected to control signal conductor 97 to apply battery voltage to the control signal conductor through a low resistance path, the stepping switch 82 repeatedly steps without delay until the original or Home position is reached. Provided that the Cycle One selector switch 104 remains closed, this initiates another identical hoeing motion of the apron mechanism 12 and this cycling continues until such time as the operator opens Cycle One selector switch 104 which is preferably of the latching push-button type.

The modified pattern of hoeing motion depicted by dashed outline 32' in FIG. 3 can be initiated by closing the Cycle Two selector switch 108 shown in FIG. 1. This initiates cycling of the system in a manner similar to that previously described for the Cycle One movement with the exception that the above described rearward movement of the bail arms 26, by extension of bail jacks 27, is not limited by the limitswitch 102 as in cycle one but is limited instead by closing of limit switch 106 which is situated on the side wall of bowl 13 in position to be closed by contact of the one of the bail arms 26 thereon prior to the time that the bail arm reaches the full rearward position. Closing of limit switch 106 in this manner directs battery voltage to control signal conductor 97 through a low resistance path and thus causes the stepping switch driver solenoid 84 to step contacts 83 from the second step position to the third position while the bail arms 26 are at an intermediate stage of rearward travel. This foreshortening of rearward motion of the bail arm is the only control difference between the cycle two movement pattern 32 depicted in FIG. 3 and the cycle one movement pattern 32 depicted in FIG. 2.

Rapid Home switch 121 is utilized when the operator interrupts automatic cyling while a hoeing motion is in progress in order to exert manual control over the apron through the

manual control valves

46 and 59. Closing of the rapid home switch 21 connects each of contacts 2, 3, and 4 of bank level 82-3 directly with control signal conductor 97 thereby bypassing the limit switches and timing resistors associated with those contacts which otherwise delay stepping of the stepping switch. Thus upon closing of the Rapid Home switch 121, the stepping switch 82 steps immediately to the home position at which all four solenoid valves 53, S4, 67 and 68 are unenergized and do not interfere with manual control of the hoeing apron mechanism.

When the bowl 13 has been fully loaded, the apron 28 must be brought into a closed position where the lower edge of the apron is adjacent cutting edge 14 in order to retain the loaded material in the bowl while the scraper is driven to the discharge site. The movement of the apron 28 to the close position is generally initiated when the apron is at its most forward stage of the hoeing motions described above and shown in FIG. 4. It is usually undesirable to move the apron directly to the close position by the shortest path as the weight of a very sizable amount of loaded earth may be acting against the apron to resist the closing movement and since excessive bulldozing of additional earth in front of the apron may occur. Accordingly it is preferable that the apron execute one or more abbreviated hoeing motions in the course of progressing from the start position to the closed position. Dashed outline 122 of FIG. 8 illustrates a suitable pattern of movement of the lower end of the apron in the course of closing.

Referring again to FIG. 1, the operator may initiate an automatic closing movement of this kind by shifting Operation Selector switch 119 to the alternate position at which battery voltage is disconnected from stepping switch bank level 82-3 and is connected to bank level 824 at contact 0 thereof. Shifting of Operation Selector switch 119 to this alternate position transmits battery current to control signal conductor 97 through

contacts

0, 83 and 10 at bank level 82-4 causing capacitor 98 to charge immediately and pulse driver solenoid 84 whereby the stepping switch is shifted to the first step position. As each of the contacts 1, 2, 3 and 4 at bank level 82-4 are connected directly to control signal conductor 97 without resistors, the stepping switch 82 progresses immediately to the position at which contacts of bank levels 82-1, 82-2 and 82-4 are energized. The stepping switch then dwells at this position for a predetermined period required to charge capacitor 98 through variable resistor 112. At this position Lower Apron solenoid valve 67 is energized through bank level 82-1 while neither of the bail solenoid valves 52 and 53 are energized. Accordingly bail arms 26 remain stationary while the apron 28 is pivoted rearwardly and downwardly from the position shown in FIG. 8 to that shown in FIG. 9. At the position shown in FIG. 9, the stepping switch is again stepped, since capacitor 98 has now charged through resistor 1 12, to the sixth step position at which contacts 6 at the several bank levels are energized. Capacitor 98 must now recharge through variable resistor 113 and thus the period during which the stepping switch remains at the sixth step position is determined by the resistor 1 13. At this position Lower Apron solenoid valve 67 remains energized through bank level 82-1 and apron cylinders 31 therefore continue to pivot the apron towards the bail arms 26. However at this position Bail Back solenoid valve 53 is now energized through bank level 82-2 and thus the bail arms 26 move backward concurrent with the above described motion of the apron so that the apron now moves from the position depicted in FIG. 9 towards the position shown in FIG. 10. When this motion is terminated by charging of capactor 98 through resistor 113, solenoid 84 shifts stepping switch 82 to the seventh step position at which contacts 7 are energized at bank levels 82-1, 82-2 and 82-4. The dwell time of stepping switch 82 at the seventh step position is again determined by resistor 113 through which bank level 82-4 again transmits battery current to capacitor 98. At this position the Lower Apron solenoid valve 67 again remains energized however Bail Back solenoid valve 53 is de-energized at bank level 82-2 while Bail Forward solenoid valve 52 is energized. Accordingly apron cylinders 31 continue to extend while bail cylinders 27 now contract causing apron 28 to move from the position depicted in FIG. to that shown in FIG. 11 which is the desired closed position. Inasmuch as contacts 8 and 9 at bank level 82-4 are both connected to control signal conductor 97 without resistors, the stepping switch 82 progresses immediately to the home position and the automatic closing operation is now completed.

The several motion timing resistors 99, 101, 112 and 113 in this embodiment are variable resistors in order to allow for adjustments of the duration of the apron motion determined by each resistor. It will be apparent that predetermined fixed resistances may be used if desired. Similarly, the

limit switches

102, 109 and 111 are of the form which are closed at the limits of travel of

jacks

27 or 31 by contact of some moving element with the switch however limit switches may be employed which are of the fluid pressure operated form that respond to the rise of fluid pressure at a jack which has reached the limit of travel. It will also be apparent that various other apron motions, such as other patterns of hoeing movement or closing motion may be provided by adding bank levels to the rotary switch 82 with appropriate resistances and position sensing switches to determine the extent of the several motions which are required. Accordingly while the invention has been described with respect to a single exemplary embodiment it is not intended to limit the invention except as defined in the following claims:

What is claimed is: 1. In a scraper vehicle having a bowl for receiving and transporting material and an apron disposed at the front region of said bowl, and support means for said apron which provides for forward and backward movements of said apron relative to said bowl and upward and downward movement of said apron relative to said bowl to accomplish hoeing motions the combination comprising:

motor means coupled to said support means for moving said apron in any of said forward and backward and upward and downward directions relative to said bowl in response to control signals, and

circuit means for generating a first predetermined sequence of said control signals for causing said apron to execute a first predetermined pattern of hoeing motion to assist movement of said material into said bowl, said circuit means having means for selectively generating a second predetermined sequence of said control signals to cause said apron to execute a modified pattern of hoeing motion, and manual means for conditioning said circuit means to produce any selected one of said sequences of control signals.

2. The combination defined in claim 1 wherein said circuit means has means for generating a third predetermined sequence of said control signals for causing said apron to move to a closed position at said forward region of said bowl to retain loaded material therein.

3. The combination defined in claim 2 wherein said circuit means for generating said third sequence of said control signals has means for causing said apron to move upward and backward simultaneously and then downward and backward simultaneously at least once in the course of movement towards said closed position.

4. The combination defined in claim 1 further comprising an electrical power source and wherein said circuit means comprises a stepping switch connected between said power source and said motor means and having a plurality of step positions with means for transmitting predetermined ones of said control signals to said motor means at predetermined successive ones of said step positions, said stepping switch further having drive means for stepping said stepping switch through said sequence of step positions, and a pulse generator connected between said power source and said drive means of said circuit means for transmitting a sequence of pulses to said drive means to sequentially progress said stepping switch through said sequence of step positions thereof.

5. The combination defined in claim 4 further comprising means for delaying the transmission of successive pulses from said pulse generator to said drive means at predetermined ones of said step positions to control the extent of movement of said apron during corresponding portions of said hoeing motion thereof.

6. The combination defined in claim 5 wherein said pulse generator produces said pulses in response to charging of a capacitor to a predetermined voltage level and wherein said stepping switch transmits a voltage from said power source to said capacitor at said step positions and wherein said time delay means at at least one of said step positions comprises a resistor connected between said stepping switch and said capacitor at said one stepping position to delay charging of said capacitor to said predetermined value for a predetermined time period.

7. The combination defined in claim wherein said pulse generator produces said pulses in response to charging ofa capacitor to a predetermined level and wherein said stepping switch transmits voltage from said power source to said capacitor at each of said step positions and wherein said time delay means comprises a normally open limit switch connected between said stepping switch and said capacitor at at least one of said step positions of said stepping switch to charge said capacitor to said predetermined value only after said limit switch is closed, and means for closing said limit switch when said apron reaches a predetermined position in said hoeing motion thereof.

8. In a scraper having a bowl with an opening at the forward end for receiving material and having a pair of bail arms on opposite sides of said bowl which are pivotally attached to said bowl at the lower end of said bail arms and having at least one fluid pressure operated bail motor connected between said bowl and one of said bail arms for pivoting said bail arms forward and backwards and having an apron pivotally carried by said bail arms and having at least one fluid pressure operated apron motor coupled between said apron and one of said bail arms for pivoting said apron upward and downward relative to said bail arms the combination comprising:

first electrically controlled valve means for actuating said bail motor to pivot said bail arms forward,

second electrically controlled valve means for actuating said bail motor to pivot said bail arms backward,

third electrically controlled valve means for actuating said apron motor to pivot said apron upwardly, fourth electrically controlled valve means for actuating said apron motor to pivot said apron downward,

an electrical power source,

a stepping switch having at least three banks of output contacts and having an input contact for receiving voltage from said power source and having drive means for sequentially connecting said input contact with successive ones of said output contacts at each bank in response to successive step pulses,

step pulse generator means for transmitting said step pulses to said stepping switch in response to an input voltage of predetermined magnitude,

conductor means connecting predetermined ones of said output contacts of said stepping switch with predetermined ones of said first, second, third, and fourth electrically controlled valves to cause said bail motor and said apron motor to move said apron through a predetermined pattern of movement as successive ones of said output contacts of said stepping switch are energized, and

means transmitting said input voltage to said pulse generator through an individual one of said output contacts of said stepping switch at successive ones of said step positions thereof and having means for delaying rise of said voltage to said predetermined magnitude at predetermined ones of said step positions to predetermine the extent of specific movements in said predetermined pattern of movement of said apron.

9. The combination defined in claim 1 wherein said circuit has position sensing means for initiating predetermined ones of said sequence of control signals in response to completion of an apron movement initiated by preceding ones of said control signals, and has timing means for initiating others of said signals a predetermined time after initiation of preceding ones of said signals.

Claims

1. In a scraper vehicle having a bowl for receiving and transporting material and an apron disposed at the front region of said bowl, and support means for said apron which provides for forward and backward movements of said apron relative to said bowl and upward and downward movement of said apron relative to said bowl to accomplish hoeing motions the combination comprising: motor means coupled to said support means for moving said apron in any of said forward and backward and upward and downward directions relative to said bowl in response to control signals, and circuit means for generating a first predetermined sequence of said control signals for causing said apron to execute a first predetermined pattern of hoeing motion to assist movement of said material into said bowl, said circuit means having means for selectively generating a second predetermined sequence of said control signals to cause said apron to execute a modified pattern of hoeing motion, and manual means for conditioning said circuit means to produce any selected one of said sequences of control signals.

7. The combination defined in claim 5 wherein said pulse generator produces said pulses in response to charging of a capacitor to a predetermined level and wherein said stepping switch transmits voltage from said power source to said capacitor at each Of said step positions and wherein said time delay means comprises a normally open limit switch connected between said stepping switch and said capacitor at at least one of said step positions of said stepping switch to charge said capacitor to said predetermined value only after said limit switch is closed, and means for closing said limit switch when said apron reaches a predetermined position in said hoeing motion thereof.

8. In a scraper having a bowl with an opening at the forward end for receiving material and having a pair of bail arms on opposite sides of said bowl which are pivotally attached to said bowl at the lower end of said bail arms and having at least one fluid pressure operated bail motor connected between said bowl and one of said bail arms for pivoting said bail arms forward and backwards and having an apron pivotally carried by said bail arms and having at least one fluid pressure operated apron motor coupled between said apron and one of said bail arms for pivoting said apron upward and downward relative to said bail arms the combination comprising: first electrically controlled valve means for actuating said bail motor to pivot said bail arms forward, second electrically controlled valve means for actuating said bail motor to pivot said bail arms backward, third electrically controlled valve means for actuating said apron motor to pivot said apron upwardly, fourth electrically controlled valve means for actuating said apron motor to pivot said apron downward, an electrical power source, a stepping switch having at least three banks of output contacts and having an input contact for receiving voltage from said power source and having drive means for sequentially connecting said input contact with successive ones of said output contacts at each bank in response to successive step pulses, step pulse generator means for transmitting said step pulses to said stepping switch in response to an input voltage of predetermined magnitude, conductor means connecting predetermined ones of said output contacts of said stepping switch with predetermined ones of said first, second, third, and fourth electrically controlled valves to cause said bail motor and said apron motor to move said apron through a predetermined pattern of movement as successive ones of said output contacts of said stepping switch are energized, and means transmitting said input voltage to said pulse generator through an individual one of said output contacts of said stepping switch at successive ones of said step positions thereof and having means for delaying rise of said voltage to said predetermined magnitude at predetermined ones of said step positions to predetermine the extent of specific movements in said predetermined pattern of movement of said apron.