US2686982A

US2686982A - Road working machine

Info

Publication number: US2686982A
Application number: US146335A
Authority: US
Inventors: Chester P Leliter
Original assignee: Allis Chalmers Corp
Current assignee: Allis Chalmers Corp
Priority date: 1950-02-25
Filing date: 1950-02-25
Publication date: 1954-08-24
Anticipated expiration: 1971-08-24

Description

Aug, 24, 1954 c. P. I -ELITER 2,586,982 ROAD WORKING MACHINE Filed-Feb. 25, 1950 2 Sheets-Sheet l /aMXO/a @Mmm c. P. LELITER 2,686,982

ROAD WORKING MACHINE Aug. 24, 1954 Filed Feb. 25, 1950 2 Sheets-Sheet 2 Patented Aug. 24, 1954 Tsar orFicE ROAD WORKING MACHINE Chester P. Leliter,

springfield, 111., assigner to Allis-Chalmers Manufacturing Company, Mill waukee, Wis.

Application February 25, 1950, Serial No. 146,335

6 Claims. l

The invention relates to road working machines, and it is concerned` more particularly with the `provision of suitable apparatus for performing two principal road working operations namely, rst, breaking up an existing road surface or the like by scarifying, -and second, nishing or refinishing an existing road surface or the like by grading.

Motor graders, that is, selfpropelled machines which are' equipped for road grading operations have been in general use during the pastand such machines as usually constructed incorporate an engine and propelling unit at the rear, a dirigible wheel unit at the front, a vehicle frame between the front and rear units, and a grader unit including a mold board in the space between the front and rear wheels of the machine. It has also been usual to mount a scariiier unit, in addition to the grader unit, in the space between the front and rear wheels of the mac'hine, the preferred location of the scarier unit being directly behind the front `wheels and forwardly of the mold board circle frame so that the ripping teeth of the scariier unit may operate to break up aroad surface ahead of the mold board upon propulsion of the machine in a forward direction, and so that the mold board may operate to grade a road surface in rear of the ripping teeth upon propulsion of the machine in said forward direction.

Scarifying, as is well known in the art, is the most severe operation to be performed by machines of the mentioned character, calling for maximum propelling power and considerable downward load on the ripping teeth in order to force them into the usually hard road surface. When the machine is to be steered during scarifying, incident lateral movement of the ripping teeth is strongly opposed by the material in which the teeth operate, and if the machine is constructed according 'to the heretofore preferred practice so that the ripping teeth operate rearwardly of dirigible front wheels and s forwardly of the mold board, the machine responds poorly or not at all to steering adjustment of the front wheels during scarifying, as is well known in the art.

Steering diiiiculties` during scarifying are also apt to be caused by the development of `an upwardly directed load component which tends to lift the end of the machine on which the dirigii ble wheels are mounted.

Generally, it is an object of the invention to provide an improved self-propelled road working machine fhaving a mold board and ripping teeth between longitudinally spaced dirigible and supporting wheels, and which machine will properly respond to steering adjustment of the dirigible wheels during scarifying.

Another object of the invention is to provide an improved road working machine of the above mentioned character in which` the ripping teeth may be subjected to the necessary downward thrust in order to force them into a hard road surface without subjecting either end of the machine to an objectionable upward thrust.

A further object of the invention is to provide an improved machine of the above mentioned character which during scarifying will develop an increased downward load upon driving wheels at one end of the machine, and thereby afford increased traction of such driving wheels at a time when it is most needed.

A further object of the invention is to provide an improved machine of the above outlined character which in addition to developing an increased downward loadupon driving wheels at one end of the machine as stated, will also develop at the same time another but smaller increased downward load upon dirigible wheels at the other end of the machine.

A further object of the invention is to provide an improved scarier mounting for self-propelled road working machines.

The foregoing and other objects and advantages are attained by the present invention various novel features of which will be apparent from the description herein and the accompanying drawings, disclosing an embodiment of 4the invention, and will be more particularly pointed out in the appended claims.

Referring to the drawings:

Fig. 1 is a side view of a self-propelled road working machine including a forward grader unit i and a rearward scarier unit;

Fig. 2 is a top View of the machine shown in Fig. l; i

Fig. 3 is an enlarged fractional top view of frame and scarii'ler parts at the rear end of the machine shown in Figs. 1 and 2; and

Fig. 4 is a sectional View, on an enlarged scale, of a hydraulic jack for raising and lowering the scarier unit shown in Fig. 1.

The machine shown in Fig. 1 incorporates a rearward engine and propelling unit, a backbone type vehi-cle frame and a steerable front wheel unit, and in these respects it is generally similar to a well known type of road working machine as disclosed, for instance, in U. S. Patent i 2,287,438, June 23, 1942, H. W. Lindsay, Brake Mechanism.

The rearward engine and propelling unit, as

shown in Figs. 1 and 2, comprises a pair of tandem wheels I and 2 at the right side of the machine, anot'her pair of tandem wheels 3 and d at the left side of the machine, a transverse axle housing Ii (Fig. 2), an internal combustion engine 'land a transmission unit S which has an upper `portieri secured to the -forward end of the engine 'l and a lower portion secured to the axle housing 6. A casing 3 which mounts the right tandem wheels I and 2 is rockably mounted on the right end of the axle housing E, and another casing II which mounts the lefttandem wheels 3 and 4 is rockably mounted on the left end of the axle housing 3. The housing of the transmission unit 8 and the tandem casings Il and II enclose suitable mechanism (not shown) for transmitting propelling power from the engine "I to the tandem wheels I, 2 and 3, d.

Connected to the rearward engine and propelling unit is a rigid vehicle frame which comprises a pair of longitudinally extending transversely spaced side members I2 and i3 (Fig. 3) at the rear of the machine, front and rear cross members Id and I6 connecting the side members I2 and I3 at their forward and rearward ends, respectively, and an arched tubular backbone or reach member Il which is rigidly connected at its rear end with the forward cross member I4 and extends in a forward direction therefrom centrally of the machine. I9 at the forward side of the cross member Ifl are rigidly secured to the latter and to opposite sides of the reach member Il at the rear end of the latter, as by welding, for bracing purposes.

The forward end of the reach member I'I is supported on a steerable front wheel unit which comprises an axle ZI, Fig. 2, and right and left

front wheels

22 and 23 which are steerably mounted on opposite ends of the axle 2|. izontal plate '24 ,(Fig. 1) is secured to the forn ward end of the reach member Il and has a pair of depending lugs 26 between which the axle fil is pivotally mounted at its center for transverse rocking movement in conformity with established 4;

practice. The plate 24 extends rearwardly under the reach member I'I, and side plates 2l (Fig. 1) and 28 (Fig. 2) are secured to opposite sides, respectively, of the reach member I'I at the for ward end of the latter and to the rearwardly extending portion of the plate 2d to provide a pocket under the reach member I1. The

front wheels

22 and 23 .may be adjusted for steering by means of a steering linkage 2Q of conventional construction and a worm and gear unit (not shown) which is mounted in the pocket under the reach member Il and is operatively connected with a hand wheel 3l, Fig. 1, at the rear of the machine by means of flexible shafting 32 part of which extends through the reach member I'I as indicated in Fig. 1.

The rearward section of the vehicle frame comprising the side members I2, I3 and cross members I4, I6 is supported on the rear axle housing 6 by means of a pillow block 33 at the right side of the machine and by means of a corresponding pillow block, not shown, at the left side of the machine, the pillow blocks berigidly secured to and extending downwardly from the frame side members I2 and I3. The housing of the transmission unit has a forwardly extending lug 34 which is rigidly secured centrally between the side members I2 and I3 to a cross frame member 3E as shown in Fig. 3, and another cross frame member 3l under- Filler pieces I3 and A horf- 4 lying a rearward portion of the engine has a mounting pad 38 which is rigidly connected by a pair of bolts to a suitable lug on the engine midway between the side frame members I2 and I3.

An operators station forwardly of the engine 'I' comprises a seat 39 and a iloor plate li (Fig. 3) which extends between and is rigidly secured to the undersides of the side frame members I2 and I3.

A grader unit underlying the reach member I'I intermediate the forward and rear ends of the latter comprises a subframe, generally designated by the reference character t2, and which is of generally conventional construction in that it comprises a tubular drawbar 43 and a circle frame lill at the rear end of the drawbar. The forward end of the drawbar t3 has a ball and socket connection 46 with the rear end or the plate 2li, and an adjusting mechanism for the grader unit 42 comprises two hydraulic jacks lil (Fig. 1) and d8 (Fig. 2) which are mounted at opposite sides of the reach member Il and are operatively connected at their lower ends, respectively, with the circle frame it at diametrin cally opposite portions of the latter. As shown in Fig. 2, the hydraulic jack 41 is mounted at the outer end of a side arm to which is secured to the reach member Il at the right side of the latter and the hydraulic jacli i3 is similarly mounted on a side arm 5I which is secured to the reach member I'I at the left side of the latter. Also mounted on the side arms lle and 5I are head lamps 52 and 53, respectively. A side shift mechanism for the circle frame Ml comprises a transverse link 5e which is connected at its opposite ends with the circle frame le and with a bracket Se on the reach member Il' and which may be shortened and lengthened to adjust the circle frame 44 laterally relatiye to the reach member Il.

A mold board 5l of the grader unit d2 is mounted on the circle frame e4, in conventional manner, for up and down adjustment with the circle frame relative t-o the reach member I? and for rotary adjustment relative to the drawbar d3.

A hydraulic control unit 58 at the operators station is connected by hose lines 53 with upper and lower cylinder ports of the hydraulic jack M, and another pair of hose lines 3i (Fig. 2)

similarly connect the hydraulic control mechanism 58 with upper and lower cylinder ports of the hydraulic jack 48. The hydraulic control unit 58 has a hand lever S2 which controls admission of pressure fluid to and emission of fluid from the hydraulic jack d1. Adjustment of the hand lever 32 to a neutral position in which it is shown in Fig. 1 locks the piston rod 63 of the hydraulic jack 41 against upward and downward movement. Forward adjustment of the hand lever 62 from its neutral position causes downward movement of the piston rod G3 and consequent downward movement of the right side of the circle frame (It, and rearward movement of the control lever 62 from its neutral position causes upward movement of the piston rod 63 and consequent upward movement of the right side of the circle frame 44. The hydraulic jack (i8 at the left side of the machine is similarly controlled by a hand lever 64 of the hydraulic control unit 58.

A scarii-ler unit generally designated by the reference character 66 is mounted on the machine in underlying relation to the vehicle frame and rearwardly of the grader unit 42. It comprises a V-shaped scarifier block 61, best shown in Fig. 3, and a plurality of transversely spaced ripping teeth 68 mounted on the scarifler block.

A pair of

push beams

69 and 1| for the scarierblock 61 are pivoted, respectively, at their rear ends on the rearward section of the vehicle frame.

As shown in Figs. 1 and 3, an angle bracket 12` at the right side of the machine has a horizontal flange underlying the floor plate 4| and secured thereto by a pair of bolts 13, and a vertical depending ilangev on which the push beam 69 is pivoted by means of a bolt 14. The push beam 1| (Fig. 3) is similarly connected with an angle bracket 16 underlying the floor plate 4| at the left side of the machine, the angle bracket 16 having a horizontal flange secured to the floor plate 4| by means of a pair of bolts 11 and a vertical depending ilange on which the push beam 1| is pivotally mounted at its rear end by means of a bolt 18.

A rearwardly and upwardly extending bracket plate 19 is rigidly secured tothe scarier block 61 at the right end of the latter, the bracket plate 19 being positioned at the right side of and connected to a forward portion of the push beam 69 yby means of a pair of bolts 8| and 82. The bolt 8| is passed through a forward hole in the plate 19 and through a registering forward hole in the push beam 69, and the bolt 82 is passed through a rearward hole in the plate 19 and through a registering rearward hole in the push beam 69. Nuts on the bolts 8| and 82 are drawn up tightly to rigidly secure the push beam 69 and the bracket plate 19 together. Referring to Fig. l, the bracket plate 19 has another 'rearward hole 83 above the bolt 82 which in the position of the parts as shown in Fig. l registers with another rearward hole in the push beam 89. The purpose of the additional hole 83 and of the additional rearward hole in the push beam 69 is to provide for pivotal adjustment of the scarier block 61 relative to the push beam 69 about the center of the bolt 8|.

At the left end of the scarier block 61, a bracket plate 84 corresponding to the bracket plate 19 is rigidly secured to the scarier block and connected tothe forward end of the push beam 1| by means of bolts 86 and 81 in the same manner as explained hereinbefore in connection with `the bracket plate 19 and the push beam 69,

except that` the bracket plate 84 overlaps the push beam 1| at the inner side of the latter, as compared with the bracket plate 19 which overlaps the push beam 89 at the outer side of the latter. i i

The ripping teeth 6B are secured to thescarier block 81 in conventional manner and are each provided with a forwardly and downwardly inclined tip sectionwhich will dig into the ground when the scarier is adjusted to an operative position, as shown in Fig. 1.

An adjusting mechanism for the scarier unit comprises `a single hydraulic jack 88 which is mounted on `the rear end of the reach member 1 at the right side of the latter and is operatively connected with a forwardly and `upwardly extending bracket plate 89 on the scarii'ler block 81.

Referring to Fig. 4 which shows a vertical section through the hydraulic jack 88, a collar 9| is rigidly secured to the cylinder part 92 of the` jack and has a spherical surface in cooperative engagement with complementary spherical Surfaces on a supporting bracket 93 and on a cap member 94 to form a ball and socket support for the cylinder 92. The bracket 93, as shown in Fig. 4, is suitably secured, as by welding, to the reach member |1 at the right side of the latter, and the cap member 94 is suitably secured to the bracket 93 by bolts, not shown. Y

The reciprocable part ofl the jack 88 comprises a piston rod 96 and a piston 91 on the upper end of the rod 96 within the cylinder 92, upward movement of the piston being limited by engage-` ment of a nut 98 with the closed upper end of the cylinder 92. A bearing cap 99 is rigidly connected with the lower end of the piston rod 95, and the lower end of the cylinder 92 is sealed by a stuiiing box 10|. A port |02 at the upper end of the cylinder 92 and a `port |03 at the lower end of the cylinder are connected by` hose lines |04 and |06, respectively,` with the hydraulic control unit 58, and admission of pressure fluid to and emission of fluid from the cylinder 92 is controlled by a hand lever |01 (Fig. 2) of the control unit 58.' The hand lever |01 may be adjusted to three positions, namely, a neutral position in which fluid above and below the piston 91 will betrapped within the cylinder, a raising position in which pressure iluid isadmitted to the port |03 and in which the port |02 is vented, and to a lowering position in which pressure fluid is admitted to the port |02 and in which the port |83 is vented. When the hand lever |01 is moved to neutral after the piston rod has been raised or lowered to anydesired vertically adjusted position, the piston rod will be positively,

locked against vertical movement from such adjusted position due to the mentioned trapping of iluid within the cylinder above and below the piston 91. The bearing cap 99 and a complementary bearing cap cooperate with a ball element |08 on the bracket plate 89 to universally connect the piston rod 96 at its lower end with the scarier block 61 intermediate the opposite ends of the latter.

`Considering now various desirable features which are attained by the herein disclosed a1'- rangement and constructionlof component parts of a road working ,machine and more particularly by the herein disclosed arrangement of a scarifler unit rearwardly of a grader unit as compared with the usual forward scarier arrangement, the following should be noted.

When the machine is traveling without doing any road work, that is, with the grader unit and scarifier unit both elevated to inoperative positions, steering adjustment of the

front wheels

22 and 23 will cause turning of the machine to the right or left about a virtual center which according to well known principles lies at the rear and to the right or left of the machine depending' on the direction in which the turn is to be made. Obviously, when the ripping teeth 68 are in the ground, that is, when the scariiier unit is` adjusted to an operative position and the grader unit is in an elevated position, as 'shown in Fig. l, straight ahead movement of the machine is opposed by the ground resistance encountered by the ripping teeth, and which resistance may be considered as being concentrated at a single point representing the virtual center `of tooth resistance.

Assuming now that during propulsion of the machine with the scariiier unit in operative position, and the grader unit in inoperative position, as shown in Fig. 1, the front wheels are angled for a turn to the right or left, the front wheels will then tend to travel on horizontal arcs of predetermined radii about the virtual turning center, but movement of the machine as a whole about the virtual` turning center will beopposed by the scarier teeth, or more strictly speaking by an opposing lateral force acting horizontally at the virtual center of tooth resistance. Under certain conditions, as when the ground in which the ripping teeth operate is soft, the opposing lateral force at the virtual center of tooth resistance may be relatively light, but in road work, and particularly when such work requires breaking up road surfacing material, such as gravel, which has previously been compacted, the opposing lateral force is relatively strong and considerable eiortwill be required to overcome it.

One of the principal advantages of the herein disclosed roadtworking machine resides in its ability to eiiiciently overcome the mentioned strong lateral opposing force at the center of tooth resistance when the machine is steered to the right or left during scarifying in hard ground. The radii of the arcs on which 'the

front wheels

22 and 23 tend to move about the virtual turning center are substantially longer than the horizontal distance of the virtual center of tooth re sistance from the virtual turning center, and a suiciently large mechanical advantage is thus afforded for overcoming a considerable lateral opposing force at the virtual center of tooth resistance, and for insuring proper response of the machine to steering adjustment of the front Ywheels 22 and 23 during scarifying in hard ground.

The construction and arrangement of the component parts of the machine which insure the mentioned advantageous relation between the turning radii of the front wheels and the virtual center of tooth resistance, are further significant from another aspect, namely, the requirement of applying a maximum amount of downward pressure to the ripping teeth at the commencement of a scarifying operation. It is desirable, particularly in road working machines of relatively low horsepower rating and corresponding light construction, that most or all of the total weight of the machine, including the weight of the grader unit, be available to load the ripping teeth for proper ground penetration. in the herein disclosed road working machine the principal weight producing component parts, that is, the engine and propelling unit, vehicle frame, steering wheel, grader and scarifier units,

are so constructed and arranged as to take care of the mentioned loading requirements of the ripping teeth in a practical and entirely satisfactory manner. ,The arrow W in Fig. l indicates the total weight of the machine which is effective at the center of gravity, and the point |09 in Fig. l indicates the approximate location at which the center of gravity may be expected in a machine of the herein disclosed construction. The virtual center of rear support afforded by the right and left tandem wheel units coincides with the axis of the rear axle housing 6, and the line X in Fig. 1 indicates a vertical plane through the center of gravity of the machine. It will be noted that in the operative position of the scarier unit as shown in Fig. 1, the ripping teeth are located to break up a road area in proximity to the plane X, that is, in a desirable close horizontal relation to the center of gravity.

When the scarier unit is lowered to an operative position at the commencement of a scarifying operation, admission of pressure fluid to the port H52 of the hydraulic jack 88 will subject the ripping teeth 68 to downward pressure which is taken up on the vehicle frame at the mounting bracket 93 for the jack 88 and at the

angle brackets

12 and 16 for the push beams 69 and l l. When the downward pressure applied to the ripping teeth in the mentioned manner is gradually increased more and more weight of the machine is transferred from the driving and steering wheels to the ripping teeth, and the limit of load application to the ripping teeth will be reached when most or all of the weight of the machine is carried by the ripping teeth. For traction purposes, a certain amount of weight will have to be retained on the rear wheels, and the operator may readily regulate the downward pressure on the ripping teeth at the beginning of a scarifying operation by manipulation of the hand lever |01.

A still further aspect of the herein disclosed construction and arrangement of the component parts of the machine will be noted from a consideration of the loads to which the driving wheels at the rear end of the machine and the steering wheels at the front end of the machine become subjected during propulsion of the machine with the scarifier unit in operative, and the grader unit in inoperative position, as shown in Fig. l. As pointed out hereinbefore, the tip sections of the ripping teeth are forwardly and downwardly inclined, and as a result the scarifier unit will become subjected to a rearwardly and downwardly inclined force indicated by the arrow R in Fig. l at the virtual center of tooth resistance, when the machine is advanced forwardly with'the scariiier unit in operative position. The angle ,a at which the force R is inclined relative to the horizontal is subject to variation, depending on the character of the material in which the ripping teeth operate, and the angle a will be relatively small when the ripping teeth operate in soft ground. However, in road work, and particularly in breaking up road surfacing material such as gravel which has previously been compacted, the inclination of the force R relative to the horizontal will be appreciable, and it has thus been shown in Fig. l for purposes of exemplication and analysis. The

horizontal and vertical components of the force R are designated in Fig. l by the reference characters H and V, respectively, and it will be noted that the component V represents a downwardly directed force which is transmitted to the vehicle frame by the hydraulic jack B8 if the latter is locked against expansion and contraction as explained hereinbefore, and by the push beams (i9 and 1I. Designating the wheel base of the machine, that is, the distance between the virtual centers of rear and front support as shown in Fig. l, by the reference character a, the distance between the virtual centers of rear support and tooth resistance by the reference character b, and the distance between the virtual center of rear support and the vertical plane X through the center of gravity by the reference character c, the following relations will be readily apparent:

wherein D represents the total downward load acting upon the driving wheels l, 2 and 3, 4 during scarifying in hard ground; and

S-EW-l-EV (Z) wherein S represents the total downward load acting upon the

front wheels

22 and 23 under the same conditions, the letters W and V in each formula representing the total weight of the machine and the vertical component of the force R, respectively, as pointed out hereinbefore.

`The rst summand in Formula l `represents that part of the total weight of the` machine to which the driving wheels I, 2 and 3, `4 become subjected when the machine is in a condition in which the grader unit and scarier unit are entirely supported by the frame, or in other words when the grader and scarier units are in an elevated condition of adjustment. The second summand in Formula 1 represents an additional load to which the driving wheels i, 2 and 3, `l become subjected during scarifying. rThe second summand may assume appreciable magnitude during scarifyingin hard ground, with the result that an additional downward load of appreciable magnitude will be imposed upon the driving wheels when it is most needed in order to prevent spinning of the driving wheels.

Similarly, the first summand in Formula 2 represents that part of the total weight of the machine to which the

steering wheels

22 and 23 become subjected when the grader and scarier unit are in an elevated condition of adjustment, and the second summand in Formula 2 represents an additional load to which the steering wheels become subjected during scarifying.

Assuming the following representative dimensions for purposes of exemplification:

1:167 inches; 17:65 inches; 0:54 inches and the value of S as determined by Formula 2 hereinbefore will be Evaluating these relations in `practical terms with reference to a machine of the herein disclosed construction and dimensioned in accordance with the stated assumption,` it will be seen that 68 per cent of the total weight of the machine and 61 per cent of the vertical component V will be imposed upon the driving wheels during scarifying in hard ground, and that 32 per cent of the total weight of the machine and 39 per cent of the vertical component V will be imposed upon the steering wheels under the same conditions. The relatively heavy loading of the driving wheels is highly desirable for traction purposes, as has been pointed out hereinbefore, and the relatively light additional loading of the steering wheels is also desirable for insuring proper response of the machine to angular steering adjustment of the front wheels fying.

From a practical standpoint, it may further be noted that the mounting of the hydraulic jack at the rear end oi the reach member l1 affords relatively short hose connections with the hydraulic control unit 58, and in that respect the herein disclosed machine has a further adduring scarivantage over road working machines as hereto-` fore used in which the scarier unit is mounted ahead of the grader unit, and relatively long control connections are required for the scarier unit.

It will further be noted that a rearward location of the scariiier unit as disclosed herein,

brings the weight of the scarifier block, ripping teeth and push beams close to the driving wheels and in that respect contributes to the attainment of the various advantageous results which have been discussed in detail hereinbefore.

In general terms, the herein disclosed road working machine comprises longitudinally spaced steering and supporting Wheels represented, respectively, by the

wheels

22, 23 and l, 2, 3, 4; a vehicle frame extending between and connected at opposite ends thereof in supported relation pendently of each other on the vehicle frameV and including two adjusting mechanisms supported on the vehicle frame and operatively connected, respectively, with said subframe and scarier block, one of such adjusting mechanisms being represented in the illustrated embodiment of the invention by the hydraulic jacks il and 48, and the other being represented by the hydraulic jack 88; a mold board 51 mounted on the subframe 42 and operable to grade a road area in advance of the scarier block upon forward propulsion of the machine; and ripping teeth 68 mounted on the scarier block and operable to break up a road area in rear of the mold board 51 upon said forward propulsion of the machine.

Designating the engine 'l and transmission unit 8` as a power unit, it will be noted that such power unit is mounted in rearwardly spaced relation to the

front wheels

22, 23 so as to impose most or all of its weight upon the rear wheels 2, 3 and 4. First thrust transmitting means including the ball and socket joint 46 and the hydraulic jacks 4l and 48 are operatively interposed between the vehicle frame and the grader unit for advancing the mold board 51 in operative position, and second thrust transmitting means including the brace structure represented by the push beams 59, 'll and the hydraulic jack 88 are operatively interposed between the vehicle frame and the scariiier unit 61, 68 for advancing the ripping teeth68 of the soarier unit in operative position upon forward propulsion of the machine. i

It should be understood that it is not intended to limit the invention to the hereinabove described forms and details, and that the invention includes such other forms and modications as are embraced by the scope of the appended claims. i

It is claimed and desired to secure by Letters Patent:

l. A self-propelled road working machine comprising, in combination, rearward driving wheels; steerable front wheels; a rigid vehicle frame supported at its rearward and forward ends on said driving and front wheels, respectively; a power unit connected in driving relation with said driving wheels and fixedly secured to said rearward end of said frame; a grader unit including a mold board intermediate said `driving and front wheels; a soarier unit uni1 board in operative position upon forward propulsion of the machine by said driving wheels, said iirst thrust transmitting means including an adjusting mechanism mounted on said vehicle frame and operatively connected with said grader unit independently of said scariiier unit for raising and lowering said grader unit; and second thrust transmitting means operatively interposed between said vehicle frame and said scariiier unit for mounting the latter independently of said grader unit and for advancing said ripping teeth in operative position upon said forward propulsion of the machine, said second thrust transmitting means including another adjusting mechanism mounted on said vehicle frame and operatively connected with said scariiier unit independently of said grader unit for raising and lowering said scariiier unit.

2. A self-propelled road working machine as set forth in claim l, in which said scarier unit comprises a mounting block for said scarifler teeth; in which said second thrust transmitting means include a brace structure extending rearwardly from said mounting block, and pivot means rearwardly of said mounting block connecting said brace structure with said vehicle frame for up and down swinging movement of said mounting block on a center in proximity to said driving wheels; and in which said other adjusting mechanism comprises a vertically adjustable lifting element mounted on said vehicle frame rearwardly of said adjusting mechanism for said grader unit and connectedin supporting relation with said mounting block at a portion of the latter forwardly of said pivot means.

S. A self-propeller road working machine comprising, in combination, rearward driving wheels, steerable front wheels, a rigid vehiclel frame, a power unit xedly secured to the rearward end of saidvehicle frame, and road working equipment, all combined to form an operative assembly in which the virtual center of rear support afforded by said driving wheels is spaced a predetermined rearward distance from a vertical plane through the center of gravity of said assembly, and in which the virtual center of front support aiioided by said front wheels is spaced a predetermined forward distance from said plane larger than said rearward distance; said road working equipment comprising a grader unit mounted in said vehicle frame in vertically adjustable relation thereto rearwardly of said front wheels, a scariiier unit positioned between said grader unit and said center of rear support, means mounting said scarifier unit in- 'aesaese 12 dependently of said grader unit for swinging movement on a pivot center at a portion of said vehicle frame rearwardly of said plane, and ripping teeth secured to said scariier unit for breaking up a road area in proximity to said plane; and an adjusting mechanism mounted on said vehicle frame forwardly of said pivot center and operatively connected with said scariiier unit for raising and lowering the latter relative to said vehicle frame independently of said grader unit. 4. A self-propelled road working machine comprising, in combination: a steerable front wheel unit; a rearward engine and propelling unit including a pair of tandem driving wheels at each of its lateral sides; an elongated rigid vehicle frame supported at its forward end on said steerable front wheel unit and 'iixedly secured adjacent its rearward end to said engine and propelling unit in supported relation to said driving wheels; a grader unit connected to and underlying said vehicle frame; an adjusting mechanism mounted on said vehicle frame and operatively connected with said grader unit for raising and lowering the latter relative to saidV vehicle frame; a scariiier unit pivotally connected to said vehicle frame independently of said grader unit and having ripping teeth adapted to penetrate a road surface in an area forwardly of said driving wheels and rearwardly of said grader unit; and vertically adjustable lift means mounted on said vehicle frame independently of said grader unit and adjusting mechanism and operatively connected with a portion of said scarier unit forwardly of its pivot connection with said vehicle frame.

5. A road working machine as set forth in claim 4 in which said scariier unit includes a pair of longitudinally disposed push beams pivotally connected at their rearward ends to said vehicle frame to swing into and out of a forwardly and downwardly inclined position.

6. A road working machine as set forth in claim 5 in which a single lift element for said scarier unit, forming part of said lifting means, is operatively connected with said scarifier unit.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 823,872 Jones June 19, 1906 1,829,728 Beatty et al, Nov. 3, 1931 2,085,944 Best July 6, 1937 2,287,438 Lindsay June 23, 1942 2,475,710 McCauley July 12, 1949 2,488,016 Lado Nov. 15, 1949