US3107460A - Method and apparatus for removing highway traffic lines - Google Patents

Description

Oct. 22, 1963 R. H. STAEHLIN 3,107,460

METHOD AND APPARATUS FOR REMOVING HIGHWAY TRAFFIC LINES Filed Feb. 15, 1961 2 Sheets-Sheet 1 791 n 4/ 9o //2 I I 39 7/ //VVEN7'OR RALPH H-STAEHL/N By Ant-611.).Edal

HIS AT TOR NE Y Oct. 22, 1963 R. H. STAEHLIN 3,107,460

METHOD AND APPARATUS FOR REMOVING HIGHWAY TRAFFIC LINES Filed Feb. 15, 1961 2 Sheets-Sheet 2 INVENTOR RALPH H- STAEHL/N H/5 ATTORNEY United States Patent 3,107,460 METHOD AND APPARATUS FOR REMOVING HIGHWAY TRAFFIC LINES Ralph H. Staehlin, 2719 Crescent Blvd, Kettering, Dayton 9, Shin Filed Feb. 15, 1%1, Ser. No. 89,414 28 Claims. (Cl. 51-176) This invention relates to a self-propelled abrading ma fhine particularly designed to remove highway traflic mes.

It is among the objects of the present invention to provide a self-propelled abrading machine capable of abrading a continuous or an interrupted, straight or deviating path along a surface.

A further object of the present invention is to provide an abrading machine capable of lightly or more heavily to abrade a selected continuous or interrupted, straight or deviating path upon a surface.

More particularly, it is an object of the present invention to provide a machine capable of erasing traflic directing lines or markings placed upon a highway or road bed without leaving undesirable grooves or furrows in the road bed.

Another object of this invention is to provide a method of removing a marking stripe from a road surface to which the stripe has been attached which comprises rubbing the stripe by means of a wheel rotated by power means, said wheel having an elastic stripe removing surface rotated in contact with said stripe progressively and continuously along the length of the stripe, and with such wheel held free to maintain the wheel surface in continuous contact with the stripe on a relatively rough surface, while simultaneously restraining forward movement of the wheel by applying an adjustable restraining force on said road surface, said force being adjusted independently of said wheel.

Further objects and advantages of the present invention will be apparent from the following description, reference being bad to the accompanying drawings which schematically illustrate a preferred form of construction.

In the drawings:

FIG. 1 shows a side view of the complete machine.

FIG. 2 is a fragmentary plan view of the machine at a larger scale than FIG. 1, and a modified arrangement of the manually operable control devices shown in FIG. 1.

FIG. 3 schematicallyillustrates the propulsion opposing mechanism of the machine provided on the pilot vehicle.

As shown in the drawings, the machine of the present invention consists of a plurality of units cooperatively combined in an assembly which consists of:

(1) A carriage having a frame supporting a power driven abrading wheel.

(2) A pilot vehicle to which said carriage is adjustably attached, said pilot vehicle being propelled by the abrading wheel.

(3) Means on the pilot vehicle, operative to oppose or restrain the propulsion of the vehicle by the abrading wheel, thereby causing the wheel to rotate slidably relatively to the engaged surface and effect abrasion thereof.

(4) Two actuators connected between the frame and pilot vehicle, one to raise and lower said frame so that the abrading wheel is respectively disengaged from or pressed upon the surface to be abraded. The second actuator for shifting the frame transversely in either direction relating to the pilot vehicle for limited guiding purposes.

(5) An abrasive containing dispense-r for applying abrasive material upon the surface in the path ahead of the abrading wheel.

(6) And suitable, manually operable control devices,

3,l7,4%ll Fatented Got. 22, 1963 "ice carried by the pilot vehicle for controlling the operation of the propulsion restraining means, the two actuators, and the action of the abrasive dispensing mechanism.

This machine is primarily designed and constructed to be operative over a highway or street for the elimination of continuous or interrupted traflic control lines painted upon the surface thereof. Such lines, although consisting generally of a hard, wear resisting paint, is completely eifaced substantially without the usual groove or shallow rut resulting from the use of grinding or wire brush wheels.

Referring to the drawings, the machine is shown consisting of a carriage portion 15 having a frame 20 to which is secured a gear box 21, housing a suitable speed reducing gearing mechanism. The extremity gears 23 and24, the only ones of this mechanism illustrated, are respectively connected to the drive shaft of the abrading wheel 22 and the pulley or sprocket 25 outside the gear box. Wheel 22 is attached to the drive shaft 26 which is journalled in a suitable bearing carried by frame 29, and is secured to gear 23 of the speed reducing gearing. An inflatable tire 27 is provided on and is part of wheel 22. A source of power shown in the form of an internal combustion engine 30 is mounted on frame 20, the drive pulley or sprocket 28 of the engine being drivingly connected to pulley or sprocket 25' by a belt or chain 29.

A fluid pressure pump 31 is mounted upon frame 2%, adjacent to the engine 30. This pump 31 is driven by the engine through a belt or chain 32. Pump 31 may take its fluid from a reservoir which may be a separate compartment in the gear box 21 and discharge said fluid under pressure from the four exhaust ports 35, 3 6, 37 and 38, from which conduits 39, 40, 41 and 42 lead to control valves as will later be described. Thus the pump 31 and the abrading wheel 22 are simultaneously driven by engine 30.

At the end of carriage frame 20, opposite the engine and abrading wheel, a cross arm 45 is provided, said arm having enlarged head portions 46 and?! at its respective ends. These head portions provide journal bearings which rotatably and slidably fit upon a cross shaft 48.

Another unit of the machine, termed the vehicle portion 50, is illustrated as a standard automotive truck equipped with an engine 51 for operating the driving wheel-s 52 of the truck through a transmission gearing 53, having a power take-off 54. Two brackets 54- and 55 extend from the rear end of the vehicle or truck 50' and carry cross shaft 48 upon which the frame 20 may be rotatably and slidably moved. Thus the carriage 15 is coupled to the vehicle 50- and both are propelled by the engine driven abrading wheel 22 when said wheel is in contact with the surface 104] to be abraded. Continued abrasion of the surface upon which the vehicle and carriage roll will not obtain, if the propulsion of the vehicle portion 50 by the abrading wheel is not opposed, for eventually the vehicle portion will be propelled at the rolling speed of said engine driven wheel. However if the vehicle portion Sli is equipped predeterminately to oppose the pro pulsion thereof by the abrading wheel 22 of the carriage portion 15, then the engine driven wheel will be forced to slip rotatably relatively to the surface engaged by the wheel, and abrade said surface. The propulsion restraining force presented by the vehicle portion 50 must be properly proportioned to the propelling force of the engine driven wheel in order to attain the proper wheel slippage and the desied abrasion of the contacted surface area.

As has previously been stated, the means coupling the carriage 15 to the vehicle 50 permits movement of said carriage upwardly and downwardly of the surface till) upon which the machine is adapted to roll and also transversely to move in either direction relatively to the vehicle 56.

An hydraulic ram 60 of any suitable standard construction has one of its movable parts hingedly secured to a bracket 61 secured to the vehicle 50 the other relatively movable part being hingedly attached to the bracket 62 secured to the frame 29 of the carriage 15. This hydraulic ram 60 is actuated by fluid under pressure emitting from exhaust port 35 of the fluid pressure pump 31. This fluid pressure is directed through conduit 39 to the manually operable control valve 70 which may be actuated selectively to direct the fluid pressure flow into and through the conduit 71 into the hydraulic ram 60 for actuating it to lift the carriage so that the abrading wheel is moved out of contact with the surface 109, or to direct the fluid pressure flow into and through the conduit 72 into the ram 60 for actuating it to move the carriage 15 so that the abrading wheel 22 is urged upon the surface 100 at a predetermined pressure. When so pressed upon said surface, the contacting face of the inflated tire 27 of said wheel becomes a flat ovate shaped surface. Satisfactory test results have been attained where said ovate shaped contact area of the tire was substantially 6 inches long, and for traflic line erasure, at least four inches wide. The abrading Wheel is lifted out of engagement with surface tee by ram 60 to permit the machine to be transported from one location to another.

A second, similar hydraulic ram 75 has its one movable portion attached to the vehicle bracket 54, and its other relatively movable member to the bracket 76 on the frame 20 of the carriage 15. Like ram 60, fluid pressure is directed from pump 31, through exhaust port 36 and communicating conduit 40 to manually operable control valve 77 which selectively directs the fluid pressure to one or the other end of the ram through conduits 78 or 79 respectively. This slidably actuates the carriage 15 and its frame 24 in either direction transversely of the vehicle 50, facilitating keeping the abrading wheel in contact with the desired area of the surface to be abraded, more specifically the traflic line on a street or highway. If the traflic line is continuous, the ram 60 is energized to press the abrading wheel 22 into substantially constant contact with the road bed or surface 100. However, if the traflic line on the road bed is of the interrupted type or alternate painted and unpainted areas, then, to avoid abrading the unpainted areas, fluid flow restricting valve 84 may be completely opened which will permit substantially unopposed propulsion of the vehicle portion 50 of the machine by the abrading wheel. Under these circumstances the abrading wheel will not slip rotatably relatively to the road bed surface 100 and abrasion thereof will not take place. When the wheel 22 again reaches a painted portion valve 84 is again actuated predeterminate-ly to restrict fluid flow therethrough, thereby again establishing opposition to propulsion of the vehicle portion 50 of the machine by the abrading wheel and thus reestablishing its abrading function.

The machine illustrated uses any suitable abrasion material which is spread upon the surface 100 ahead and in the path of the abrading wheel tire 27 which, in contact with said surface, propels the pilot vehicle 50 over said surface. Satisfactory results have been attained with abrasive material consisting of substantially hard crushed stone providing small particles having substantially flat facets presenting sharp edges and points which tem-s porarily imbed themselves and frictionally adhere to the inflated tire as it passes over the abrasive on the surface engaged. The rotating slippage of the tire over this surface will rub said abrasive over said surface and the flat surfaces of the abrasive particles will scrape the painted traflic line and eliminate it.

The abrading material is contained in a hopper 1.01

carried by the carriage frame 20. The discharge chute 1&2 of the hopper is adjacent to and in front of the tire 27 on the abrading wheel 22 so that the abrasive material may be spread in controlled amounts on surface 100 in the path of said wheel. This control mechanism 103 is rendered effective by the actuation of the control valve 9% which is operatively connected to the discharge port 37 of the fluid pressure pump 31 through conduit 41 and into the mechanism 103 by conduit 91.

As has been previously stated, the effort of the abrading wheel 22 to propel the vehicle 50 must predeterminately be opposed or restrained to effect continuous rotatable slippage of said wheel on the engaged surface 160, for abrading purposes. This propulsion opposition is provided by the vehicle, and is effected by mechanism consisting of a fluid pressure pump 80 driven by the standard power take-off 54 from the transmission gearing unit 53. This pump 80 has fluid inlet and outlet conduits 81 and 82 respectively, forming a fluid circuit from and back into a fluid reservoir 83. Any standard fluid pressure actuated, flow restricting valve 84 is connected in the discharge conduit 82 of this circuit, and may be actuated to restrict fluid flow from the pump 30 to any desirable degree and thereby oppose predeterminately, the operation of said pump 86, the power take-off 54' from the transmission gearing unit 53 and the driving wheels 52 of the vehicle which are actuated in response to the propulsion effort of the engine driven abrading wheel 22. The fluid from restricting valve 84 is adjustably actuated by fluid pressure through conduit 85 connected to the manually operated control valve 86. This valve 86 is connected to the discharge port 38 of the fluid pressure pump 31 by conduit 42.

The several control valves 70, 77, 86 and 99 are shown in FIG. I mounted on a side panel 110 on vehicle 50. FIG. 2 shows another arrangement where the panel 112 lies in a horizontal plane at the rear of vehicle 50 so that all valves are easily accessible and operative by the vehicle attendant.

If the machine is operated down a hill of the road or highway, propulsion of the vehicle will be accelerated and consequently the attendant must operate the regulating valve 86 to cause the fluid flow restricting valve 84 to increase restriction through conduit 82 and thereby increase the opposition to such propulsion. This again establishes the necessary proportion between the propulsion effort by the wheel and the opposition to said propulsion, thereby maintaining the proper slippage of said wheel on the engaged surface for abrading purposes. When the machine is operated up hill, the fluid restriction by valve 84 must necessarily be reduced to obtain the proper balance between the opposing forces, propulsion and restraint.

Instead of dropping abrasion material upon surface ahead of the abrading wheel, the tire of said wheel may have any suitable abrading agent applied to or secured in the peripheral tread of the tire for the intended purpose. Also any suitable cover or boot having its outer surface provided with an abrasive coating or elements may be removably attached to the tire.

Fuel for the engine 30 may be taken from the fuel supply tank of the vehicle 50 which transports the idle carriage from one location to the other when the said carriage is in its raised position.

The carriage portion 15 and control panel 112 may be detached as a unit from the pilot vehicle or truck 50,

thereby rendering said truck available during intervals in which no required.

It is thus to be seen that method of removing a marking stripe from a road surface to which the stripe has been attached which comprises rubbing the stripe by means of a wheel 22 rotated by power means 30, said wheel having an elastic stripe removing surface 27 rotated in contact with said stripe for other uses abrading operations are this invention provides a progressively and continuously along the length of the stripe, and with such wheel held free to maintian the wheel surface in continuous contact with the stripe on a relatively rough surface, while simultaneously restraining forward movement of the wheel by applying an adjustable restraining force at driving wheels 52 on said road surface, said force being adjusted at valve 86 independently of said wheel 22.

Because the following units of the machine, the engine 39, fluid pressure pump 31 speed reduction gearing in box 21, actuating rams 60 and 75, fluid pressure receiving and distributing control valves 70, 77, 86 and 90, fluid pressure pump 80 and pressure actuated fluid flow restricting valve 84 are all of standard construction, purchasable on the open market, no detail constructions thereof have been illustrated.

What is claimed is as follows:

1. A machine to be propelled over a road surface for erasing marks on said road surface, said machine comprising in combination, a power driven erasing wheel having a yieldable elastic surface engageable with one portion of said road surface, pressure means for exerting a continuous pressure on said elastic surface creating a propelling force against said machine over said road surface; restraining means engaging another portion of said road surface, said restraining means being operative adjustably to oppose said propelling force to cause constant slippage of said wheel relative to the engaged road surface to effect abrasion thereof and means for actuating said restraining means independently of said erasing wheel.

2. A machine for erasing marks on a road surface, said machinecornprising in combination, a carriage supported by a power driven erasing Wheel having a yieldable elastic surface operative to exert a propelling force against said carriage over the road surface to be abraded; pressure means for exerting a continuous pressure on said elastic surface; a restraining member attached to said carriage propelled therewith over said road surface; and controllable means on said restraining member, operative adjustably to restrain the propulsion of said restraining member by the wheel, causing constant slippage of said wheel on said road surface to effect progressive erasure of marks thereon, and means for actuating said restraining member independently of said wheel.

3. A road surface erasing machine comprising in combination, a carriage equipped with a power driven wheel having a yieldable elastic surface for propelling said carriage over the road surface desired to be erased; pressure means for exerting a continuous pressure on said elastic surface; loading means for adjusting the amount of said continuous pressure; a member secured to said carriage and propelled thereby over said surface; propulsion restraining means on said member operative adjustably to oppose the propulsion of said member by said wheel driven carriage, causing the erasing wheel to slip rotatably relatively to the surface engaged thereby and effect erasure thereof and means for actuating said restraining means independently of said erasing wheel.

4. A road surface erasing machine, comprising in combination, a carriage supported by an erasing wheel having a yieldable elastic surface; an engine on said carriage operatively connected to the wheel for driving it to roll over the road surface to be erased; a vehicle coupled to said carriage and propelled over said road surface to be erased by said engine operated wheel; resistance means on the vehicle operative adjustably to oppose propulsion of the vehicle by said wheel, and to cause constant slippage of said wheel relative to said road surface engaged thereby to effect erasure thereof and means for actuating said resistance means independently of said erasing wheel.

5. A'road abrading machine, comprising in combination, a carriage supported by an abrading wheel having a yieldable elastic surface; an engine on said carriage operatively connected to the wheel for driving it to roll over the road surface to be abraded; a vehicle coupled to said carriage and propelled over said road surface to be abraded, by said engine operated wheel; and resistance means on the vehicle operative adjustably to oppose propulsion of the vehicle by said wheel, and to cause constant slippage of said wheel relative to said road surface engaged thereby to effect abrasion thereof, in which the said resistance means, operative to oppose propulsion of the vehicle by the engine driven wheel, consists of a fluid pressure pump, actuated by the vehicle in response to its propulsion, said pump being operative to circulate fluid through a circuit including a fluid reservoir; and a control valve operative adjustably to restrict fluid flow through said circuit, thus providing opposition to the propulsion of the vehicle.

6. A surface abrading machine, comprising in combination a carriage provided with an abrading Wheel; an engine on said carriage operatively connected to the wheel for driving it to roll over the surface to be abraded; a vehicle coupled to the carriage and propelled over the surface to be abraded by the said engine operated wheel; and means on the vehicle operative predeterminately to oppose propulsion of the vehicle by the wheel, thereby causing the wheel to slip rotatably relative to the surface engaged thereby and effect abrasion thereof; in which the vehicle consists of a standard automotive truck having an engine, operative to actuate the driving wheels of the truck through transmission gearing providing a power take-off; a fluid pressure pump driven by said power take-off, said pump being operative to circulate fluid through a fluid reservoir; and a fluid flow restricting valve in said circuit, operable selectively to vary the restriction to fluid flow through said circuit and predeterminately oppose the propulsion of the truck by the abrading wheel.

7. A road surface abrading machine, comprising in combination, a carriage supported by an abrading wheel having a pneumatic tire with a yieldable elastic surface; an engine on said carriage, operatively connected to said abrading Wheel for driving it; a vehicle coupled to the carriage and propelled by said abrading wheel over the road surface engaged by said abrading wheel; a fluid pressure pump operative to circulate fluid through a hydraulic circuit in response to propulsion of the said vehicle; a control valve in said hydraulic circuit operative to vary the restriction of the fluid flow through said hydraulic circuit thereby providing adjustable opposition to the propulsion of the vehicle by the abrading Wheel, resulting in a rotating slippage of said wheel on said road surface and abrasion thereof.

8. A machine in accordance with claim 7 in which the coupling between the carriage and vehicle provides for transverse and vertical movements of the carriage relatively to the vehicle, and means for selectively moving said carriage transversely and vertically to cause the abrading wheel to make and break abrading contact with selected areas of the surface over which the vehicle passes.

9. A surface abrading machine, comprising in combination, a carriage provided with an engine driven abrading Wheel having an inflatable tire with a yieldable elastic surface; a vehicle adjustably attached to said carriage so that said carriage may be moved vertically and transverse- 1y relatively to the said vehicle; and two actuating means connected between the carriage and vehicle, one of said means being operative to selectively lift said carriage with said abrading wheel off the surface to be abraded and to urge the carriage downwardly to press said wheel into engagement with said surface at a predetermined continuous pressure, the other said means being operative to shift said carriage transversely of said vehicle in either direction; and manually actuated control means, operative to render said actuating means active.

10. A machine in accordance with claim .9, in which a fluid presure pump is provided on said carriage and driven by the engine thereon, fluid pressure from said pump being operative hydraulically to actuate either of said actuating means in response to operation of selected control valves mounted on said machine.

11. A machine in accordance with claim 9, in which a hopper for an abrading material is mounted on said carriage, said hopper having a discharge chute adjacent to the abrading wheel for spreading a controlled supply of abrading material upon said surface ahead and in the path of said wheel.

12. A machine in accordance with claim 9, in which the carriage supports a hopper for abrading material, said hopper having a discharge chute adjacent to and aligned with said abrading wheel and a discharge control device in said chute, and manually actuated control means operative to effect operation of said discharge control device.

13. For removing paint such as a painted highway traffic line from a paved surface, the combination comprising an apparatus having a power driven wheel with an elastic paint-removing surface, power means on said apparatus for rotatin said wheel, a supporting structure between said wheel and said apparatus subject to propelling force exerted by said abrading wheel, and free to maintain said wheel in continuous contact with said paved surface, and restraining means effective between said apparatus and said paved surface independently of said wheel with adjusting means independent of said wheel and operative adjustably to restrain said propelling force of said wheel to cause controlled slippage of said. wheel and controlled abrasion of the paved surface supporting said wheel in proportion to variation in the restraint exerted by said restraining means upon said propelling force.

14. For removing paint such as a painted highway traflic line from a paved surface, the combination comprising an apparatus having a power driven wheel with an elastic paint-removing surface, power means on said apparatus for rotating said wheel, a supporting structure between-said wheel and said apparatus to support said wheel in a position normal to the paved surface and which exerts the continuous pressure of a gravitational load upon said wheel in a manner to maintain said wheel in continuous contact with said paved surface, said wheel under said gravitational load being capable of exerting a propelling force upon said supporting structure when operated under power, and restraining means effective between said apparatus and said paved surface independently of said wheel with adjusting means independent of said wheel and operative adjustably to restrain said propelling force of said wheel to cause controlled slippage of said wheel relative to said paved surface and controlled abrasion of said paved surface in proportion to variation in the restraint exerted on said propelling force by said restraining means.

15. A device as claimed in claim 14 having means for varying the gravitational load exerted by said supporting structure upon said wheel.

16. The method of removing a marking stripe from a road surface to which said stripe has been attached which comprises rubbing said stripe by means of a wheel rotated by power means, said wheel having an elastic stripe removing outer wheel surface rotated in contact with said stripe progressively and continuously along the length of said stripe, and with said wheel held free to maintain said wheel surface in continuous contact with said stripe on a relatively rough road surface, and simul taneously restraining forward movement of said Wheel by applying an adjustable restraining force on said road surface, said force being adjusted independently of said wheel.

17. The method of removing a marking stripe from a road surface to which said stripe has been attached which comprises rubbing said stripe with an elastic surface of an elastic tire frictionally rotated by power means, with said tire in contact with said stripe progressively and continuously along the length of said stripe, and with said wheel held free to maintain said wheel surface in continuous contact with said stripe on a relatively rough road surface, and simultaneously restraining forward movement of said tire by applying an adjustable restraining force on said road surface, said force being adjusted independently of said tire.

18. The method of erasing a marking stripe froma paved road surface to which said stripe has been attached which comprises rubbing said stripe with a stripe removing elastic outer wheel surface rotated by power means in contact with said stripe progressively and continuously along the length of said stripe, guiding and exerting gravitational pressure on the wheel carrying said wheel surface from a supporting structure which supports said wheel normal to said paved road surface and which is subject to propulsion by the propelling force resulting from the traction of the rotating wheel, adjustably restraining the propulsion of said supporting structure independently of said wheel to control the slippage and abrasive action of said wheel as said wheel is guided progressively along said stripe, and with said Wheel held free to maintain said wheel surface in continuous contact with said stripe on a relatively rough road surface.

19. A combination according to claim 13 in which said paint removing surface is formed by a pneumatic tire.

20. A combination according to claim 14 in which said paint removing surface is formed by a pneumatic tire.

References Cited in the file of this patent UNITED STATES PATENTS 976,627 Boynton Nov. 22, 1910 1,354,470 Lamping Oct. 5, 1920 1,557,747 Wagner Oct. 20, 1925 2,059,950 Johnson Nov. 3, 1936 2,062,232 Pogue Nov. 24, 1936 2,319,520 Ryphema May 18, 1943 2,529,197 Stor'oerg Nov. 7, 1950 2,585,219 Boyle Feb. 12, 1952 2,601,048 Monger June 17, 1952 2,673,725 Coates Mar. 30, 1954 2,684,558 Harris et al July 27, 1954 2,701,134 Klicpcra Feb. 1, 1955 2,791,412 Hatcher May 7, 1957 2,870,582 Raske Ian. 27, 1959 2,874,948 Bjorkman et al Feb. 24, 1959 2,909,383 Nanfeldt Oct. 20, 1959 2,951,474 Wayland Sept. 6, 1960 2,990,660 Hatchet July 4, 1961

Claims (1)

1. A MACHINE TO BE PROPELLED OVER A ROAD SURFACE FOR ERASING MARKS ON SAID ROAD SURFACE, SAID MACHINE COMPRISING IN COMBINATION, A POWER DRIVEN ERASING WHEEL HAVING A YIELDABLE ELASTIC SURFACE ENGAGEABLE WITH ONE PORTION OF SAID ROAD SURFACE, PRESSURE MEANS FOR EXERTING A CONTINUOUS PRESSURE ON SAID ELASTIC SURFACE CREATING A PROPELLING FORCE AGAINST SAID MACHINE OVER SAID ROAD SURFACE; RESTRAINING MEANS ENGAGING ANOTHER PORTION OF SAID ROAD SURFACE, SAID RESTRAINING MEANS BEING OPERATIVE ADJUSTABLY TO OPPOSE SAID PROPELLING FORCE TO CAUSE CONSTANT SLIPPAGE OF SAID WHEEL RELATIVE TO THE ENGAGED ROAD SURFACE TO EFFECT ABRASION THEREOF AND MEANS FOR ACTUATING SAID RESTRAINING MEANS INDEPENDENTLY OF SAID ERASING WHEEL.

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