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CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. provisional application No. 61/243,684 and filing date of Sep. 18, 2009, which is incorporated by reference as if fully set forth. 
    
    
     FIELD OF INVENTION 
     The present invention relates to patching devices, and more particularly, to vehicle mounted patching systems for patching potholes and the like and incorporating method and apparatus for recapturing asphalt emulsion from the feed lines of the patcher for subsequent reuse. 
     BACKGROUND 
     Asphalt patching systems are well known in the art. For example, U.S. Pat. Nos. 5,263,790 issued Nov. 23, 1993 and 5,419,654 issued May 30, 1995, teach a patcher comprising a motor driven, wheeled vehicle having a gravel hopper and a storage tank for liquid emulsion, such as asphalt, as well as pressurized conduits for respectively advancing gravel and asphalt to a mixing head. The asphalt emulsion is delivered from the storage tank to the mixing head by feed lines. The mixing head is arranged to extend from a free end of a swingably mounted, telescoping boom, which is moveable in both horizontal and vertical planes as well as being selectively extendable and retractable to expedite desired positioning of the mixing head above a roadway surface to be patched. The pressurized conduits may also be initially employed to blow debris from the pothole or crevice being patched whereupon an emulsion such as asphalt, with or without aggregate, is delivered to the mixing head. The need for rolling or tamping is eliminated by the use of high-pressure air. 
     The feed lines carrying the asphalt emulsion must be cleaned on a regular basis, typically at least once per day. 
     Present day techniques for repairing a pothole after it is cleared of debris, includes: 
     a) clearing debris from the pothole; 
     b) coating the pothole surface with an emulsion; 
     c) filling pothole with admixed emulsion and a suitable aggregate; and 
     d) coating top surface of the filled pothole with pulverized stone. 
     Due to the need to return roadways to use as quickly as possible after a repair operation, it is nevertheless disadvantageous to use a top coat of pulverized stone since tires of passing vehicles often kick up the pulverized stones into other vehicles causing damage to front, rear or side windows doors, fenders and the like. Also the top layer of crushed stone contrasts with the darker, surrounding road surface. 
     It is therefore desirable to provide method and apparatus for repairing a pothole which enables immediate use of the repaired surface while preventing damage to vehicles passing along the repaired surface. In addition, the apparatus described herein is capable of performing the novel method requiring a minimal amount of operator intervention. 
     In addition, it is also highly desirable to reclaim the emulsion from the conduits for reuse. 
     SUMMARY 
     The present invention is characterized by comprising method and apparatus embodiments for flushing the emulsion feed lines of a patching system and collecting the emulsion for reuse. 
     Feed lines providing asphalt emulsion to a mixing head, which is utilized to mix aggregate and the asphalt emulsion, are selectively fed emulsion and cleaned under control of a pair of four-position valves arranged adjacent to and preferably on opposite sides of the mixing head. The valve pair is remotely operated from the patcher cabin employing an electronic control characterized by a simplified and yet highly reliable design. When moved to a “patching” position, normal patching operations are performed i.e., emulsion is fed to the mixing head to perform patching. 
     By moving both valves to a “clearing” or “blowback” position, and opening a similar valve at the tank holding the asphalt emulsion, the ports of the pair of four-position valves enable high pressure air, preferably derived from the air brake system of the patcher, to enter the asphalt emulsion feed lines that are connected between the tank holding the asphalt emulsion and the mixing head. The pressure in the asphalt emulsion tank is lower than the entering pressure from the air brake system, whereby the asphalt emulsion in the feed lines is forced back to the asphalt storage tank, leaving only a small residue in the asphalt emulsion feed lines. If desired, the patching and clearing operations may be reversed in their order of performance. 
     The next step performed in the procedure is to close the conduit between the emulsion storage tank and the feed lines and place the pair of four-position valves adjacent to the mixing head in a third (“flushing”) position which opens the ports to a conduit connected to a flush tank containing a cleaning agent maintained under pressure. The valve at the asphalt emulsion tank is turned to the flush position, coupling the asphalt emulsion feed lines to the pressurized flush tank, which causes the cleaning agent to move through and flush the feed lines and valves, which feed lines include at least one section of clear hose coupled to a given port of one of the pair of control valves to facilitate observation of the progress of the flushing operation. The cleaning agent flushes the feed lines as well as the pair of valves adjacent to the mixing head and the valve coupling the flush tank to the pair of valves. The cleaning agent then flows out through given ports of the pair of valves and directly into a recovery tank and is maintained in the recovery tank which is preferably positioned above the flushing tank. The cleaning agent is returned from the recovery tank to the flush tank by closing the line between the flush tank and the source of air pressure, venting the flush tank to the atmosphere and opening a valve in the line between the flush tank and the recovery tank when the flush tank is depressurized, enabling the cleaning agent to return by the force of gravity to the flush tank. The flush tank is then sealed from the atmosphere and the air supply valve is then opened to pressurize the flush tank in readiness for a subsequent flushing operation. 
     Pressurized air is drained out of the flush tank by opening an air bleed valve. When the pressure gauge of the flush tank reads “O” psi, the valve in the line coupling the recovery tank to the flush tank is opened to enable the cleaning agent to flow by gravity back into the flush tank. This valve preferably remains open for approximately 2 to 3 minutes and is then closed. The flush valve adjacent to the flush tank is closed and the valve between the flush tank and the air pressure source is opened to re-pressurize the flush tank in readiness to perform a subsequent flushing operation, at which time the cleaning process is completed without removal of either emulsion or cleaning agent from the patching system and thereby providing for recycling of both the emulsion and the cleaning agent. 
     An extract of pine oil is employed as the preferable cleaning agent. The emulsion removed from the interior surfaces of the feed lines by the pressurized cleaning agent passes into the recovery tank and mixes with the cleaning agent. Over a period of time, typically three (3) to five (5) weeks, the amount of emulsion accumulated reaches a concentration which is equivalent to the concentration of emulsion in the emulsion storage tank, enabling the accumulated emulsion to be dispensed through the feed lines and mixing head into a pothole being repaired. This technique makes more efficient use of the emulsion as well as the cleaning agent. The quality and cohesiveness of the emulsion/cleaning agent mixture is as good as the original emulsion dispensed into a pothole being repaired, as well as admixing equally well with the emulsion from the storage tank. 
     The pair of 4-position valves are operated by controls provided in the cab of the patcher. Precision movement of the pair of valves is assured through the use of motor drives under the control of cam-operated control switches, coupled to a single control signal through a diode circuit which prevents feedback of the control signal array when the desired valve positions are not properly aligned. 
     In one preferred embodiment, the cleaning agent is pine oil extract. During a flushing operation, the pressurized pine oil extract removes the emulsion in the feed lines, the emulsion collected by the cleaning agent being delivered to the recovery tank together with the cleaning agent. Assuming that a fresh effusion of the cleaning agent is introduced into the flush tank, either by way of the recovery tank or directly to the flush tank, and assuming regular, daily usage of the patcher, the amount of emulsion collected in the cleaning agent builds up to a level sufficient to be admixed together with emulsion in the heated emulsion storage tank so as to be sufficiently recaptured and used together with emulsion delivered from the heated storage tank to the dispensing head for performing a patching operation, typically within three to four weeks. In order to assure that the emulsion accumulated in the cleaning agent has reached sufficient concentration level, a visual observation may be made by observing the flow of cleaning agent admixed with emulsion by observing a transparent, see-through section of conduit coupled to the feed line of at least one of the pair of multi-position valves. Alternatively, an instrument may be connected in the feed line to measure the amount of emulsion collected in the cleaning agent, such as a viscometer or a pressure differential indicator. Alternatively, the see-through section and the instrument for measuring the emulsion may both be provided as part of the patcher apparatus. 
     The pair of multi-position valves are preferably operated from the patcher cabin through an electronic control utilizing a single switch of novel, simplified design in which power is simultaneously delivered in parallel to electric motors for each multi-position valve to accurately drive each valve to the proper position. 
     A single power source is selectively coupled to both motors through the single switch which is a multi-position switch for selectively connecting power simultaneously to both motors. The lines selectively coupling power to the motors driving the multi-position switches are each provided with a cam-operated switch designed to be normally closed until their switch arms are aligned with a “flat” provided on the respective cams to open the electrical switches when the motors drive the valves to the appropriate position. In order to compensate for any potential differences in the motors during their manufacture, diode arrays are provided for each of the drive motors to prevent the power source from being fed back and coupled through one of the non-selected switch lines to the opposite motor. 
     A gear box provided for each control valve couples the drive from its associated motor to the control valve through an output shaft which simultaneously drives its associated multi-position control valve as well as rotating the cams, each of which opens its associated switch when its control valve reaches the desired control valve position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS AND PREFERRED EMBODIMENTS THEREOF 
       The embodiments of the present invention will be understood from a consideration of the detailed description and drawings, wherein like elements are designated by like numerals, and wherein: 
         FIGS. 1A ,  1 B and  1 C are perspective views of a patching vehicle embodiment utilizing the novel cleaning technique of the present invention. 
         FIGS. 2A and 2B  show the mixing head and boom of  FIGS. 1A and 1B  in greater detail. 
         FIG. 3  is simplified schematic diagram embodying the principles of the present invention and which is useful in describing the cleaning procedure of the present application. 
         FIG. 3A  is a detailed perspective view of one of the multi-position control valves shown in  FIG. 3 . 
         FIG. 3B  is a sectional view of the mixing head looking in the direction of arrows  3 B- 3 B in  FIG. 3 . 
         FIGS. 3C and 3D  are perspective and simplified schematic views of the flush and recovery tanks shown in  FIG. 3 . 
         FIG. 4  shows a simplified perspective view of the drive motors and associated control circuitry for driving the pair of multi-position valves. 
         FIG. 4A  is a view showing the control switches employed for operating the pair of control valves from the patcher cabin. 
         FIG. 4B  is a schematic view showing the control circuitry for operating the motors driving the pair of multi-position control valves. 
         FIG. 4C  is a simplified diagram showing the mechanical components utilized to drive one of the multi-position control valves. 
         FIG. 4D  shows a perspective view of one of the controls shown in  FIG. 4  with the cover removed for purposes of observing the five motor, the gear box coupling the foot shaft of the drive motor to the control valve and the cam shaft driving the cams utilized to control the timing of the electrically switches. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIGS. 1A-1C  are perspective views showing a vehicle (i.e., a “patcher”)  10  for patching roadways and the like, typically through the use of an asphalt-gravel mixture and comprised of a wheeled, self-propelled vehicle including a chassis  12  and a cab,  14  containing the vehicle engine (not shown), which is any suitable engine employing an engine cooling system using liquid coolant (such as water or a water/anti-freeze mixture.) 
     Chassis  12  supports a gravel hopper  16  and an enclosure  18  of substantially hexagonal shape which contains an asphalt emulsion supply tank  20 . The asphalt is normally heated to maintain a temperature of the order of 135 to 160 Degrees F. 
     A front boom assembly  21  is pivotally mounted to the front end of the cab  14  to enable the boom assembly to swing in a horizontal plane by means of pneumatic cylinder  24 , shown in  FIG. 2A . Boom assembly  21  is further swingable in a vertical plane under control of cylinder  26 , detailed views of the boom assembly  21  and activating cylinders  24  and  26  being respectively shown in  FIGS. 2A and 2B . 
     A flexible hose  35  communicates between gravel hopper  16  and a mixing head  34  arranged at the free end of boom assembly  21 . Flexible hose  35  couples gravel hopper  16  to mixing head  34  through a telescoping delivery assembly  36 . 
     The details of the movement of the boom assembly and its various components are set forth in U.S. Pat. No. 5,419,654 which is incorporated herein by reference and further details of the boom assembly and its operation are omitted herein for purposes of simplicity. 
     It is sufficient to understand, however, that a heated asphalt emulsion and aggregate are respectively fed to the mixing head under suitable air pressure as will be described in detail below. 
     The hollow, insulated non-collapsible hose  44  typically contains five (5) different fluid carrying lines as well as electrical wires as will be described below in greater detail. Non-collapsible hose  44  is maintained substantially taut regardless of the expansion or retraction of the telescoping delivery tube assembly  36 , under control of piston cylinder  16 , as is described in detail in the aforementioned issued U.S. Pat. No. 5,419,654. 
       FIG. 1C  shows a rear view of patcher  12  which is provided with an array  50  of red lights mounted upon panel  51  which, when selectively illuminated, appear as left-hand and right-hand arrows to guide vehicles approaching from the rear to either the left or the right (or both the left and right) around the truck as it is performing patching operations. 
       FIG. 3  shows a simplified schematic diagram which is useful in explaining the normal patching operations, including the manner in which the feed lines carrying asphalt emulsion are emptied of emulsion and flushed by a cleaning agent, both of which materials are fully recycled, thereby totally avoiding the need to drain any of the emulsion residue and cleaning agent employed in the flushing operation. In other words, a fully self-contained system is provided for performing the cleaning and flushing operations and no fluids or residue are emitted to the atmosphere nor do they leave the self-contained system during the performance of the air cleaning and flushing operations. 
     As was described above, the aggregate hopper  16  is coupled to the mixing head  34  by means of the telescoping assembly  36  also shown, for example, in  FIG. 2B  and provided at its free end with curved tube  40  joined to the telescoping assembly  36  by coupling collar  41 . Coupling collar  41  and the curved tube member  40  are shown in  FIG. 3  wherein aggregate from hopper  18  passes through coupling  41  and curved tubing  40  and enters into the hollow interior  34   a  of mixing head  34  with the aid of pressurized air. 
     Coolant from the engine cooling system of the patcher  10 , which is typically heated to a temperature in the range of 135-160 and preferably 150 degrees F., enters into a hot water inlet coupling  34   b  and circulates through the hollow interior of the mixing head defined by the inner and outer cylinder walls  34   c  and  34   d , shown in  FIG. 3B , leaving the mixing head by way of coupling outlet  34   e  which returns the cooling fluid through a suitable conduit to the engine radiator, not shown, and forming part of the engine cooling system employed for driving the vehicle which is also not shown for purposes of simplicity. 
     The emulsion storage tank  20  is coupled to an inlet port  102   a  of a multi-port valve  102  having a common outlet port  102   b  which is selectively coupled to one of the ports respectively arranged at 3 o&#39;clock, 6 o&#39;clock, 9 o&#39;clock and 12 o&#39;clock positions about the sidewalls of valve  102 . Valve  102  is preferably enclosed within an insulating jacket  104  having inlet and outlet ports  104   a  and  104   b  for respectively introducing hot water from the engine cooling system into jacket  104  and for returning the hot water to the engine cooling system. The hot water flowing through jacket  104  maintains asphalt emulsion passing through valve  102  in a heated, flowable condition to prevent clogging of the valve  102 . 
     When valve  102  is moved to the position coupling 12 o&#39;clock port  102   a  to common port  102   b , heated asphalt from tank  20  passes through valve  102  and enters asphalt line  106 , which is one of the lines that is enclosed within the hollow, insulated non-collapsible hose  44 , shown in  FIG. 2B . 
     A valve assembly, preferably a one-half inch (0.50″) ball valve assembly  108 , is connected in line  106  and is operated under the control of a custom linear actuator  109  operated under control of an actuator switch  111  located in the patcher cab  14  to provide an adjustable flow rate of the asphalt emulsion through line  106 . Line  106  is split by a T-coupler  110 , providing a first branch  112   a  which is coupled to the common port  114   a  of control valve  114  and a second branch  112   b  coupled to common port  116   a  of control valve  116 . 
     Multi-position control valves  114  and  116 , as well as valve  102 , are substantially identical in design and function, as will be more fully described in connection with  FIG. 3A . Valves  102 ,  114  and  116  are each respectively enclosed within a heating jacket  104 ,  115 ,  117  each of which are electrically heated to maintain the asphalt emulsion in heated, flowable state and thereby prevent freezing of asphalt in these valve structures when patcher  10  is shut down and stored overnight or during weekends, in cold temperature regions, by coupling the electrically operable heating jackets to a suitable power source (not shown). 
       FIG. 3A  is a perspective view of one of the four-position control valves, such as valve  116 , it being understood that both control valves  114  and  116  (as well as valve  102 ) are substantially identical in design and function, and it being further understood that the positions of the outlet ports of valves  114  and  116  in  FIG. 3  are symmetrical about an axis of symmetry which is coaxial with a central axis of mixing head  34 . Only one control valve will be described in detail for purposes of simplicity. 
     The control valve  116  shown in  FIG. 3A  is a substantially solid block provided with ports  116   b ,  116   d ,  116   c  and  116   e , respectively arranged at 12 o&#39;clock, 3 o&#39;clock, 6 o&#39;clock and 9 o&#39;clock positions around the top, right-hand, bottom, and left-hand side surfaces of the control valve. An operating handle  116   f  is mounted along the front face of the control valve and may be selectively positioned in one of the 12, 3, 6 and 9 o&#39;clock positions. The control valve  116  is provided with a common inlet opening  116   a  (not shown in  FIG. 3A ) along its rear surface. By positioning the control valve operating handle so that its tapered shape tip  116   f - 1  is aligned with one of the four (4) given positions  116   b - 116   e , that port communicates with common port  116   a  in accordance with the alignment of the rotatable operating handle  116   f.    
     The valve assembly  116  comprises a hollow housing and is further provided with a pair of openings  116   g  and  116   h  along respective diagonal side surfaces for receiving coolant from the patcher engine cooling system to heat the valve and thereby maintain asphalt passing through the control valve  116  during a patching operation, to be in a heated, flowable state and thereby prevent the control valve  116  (as well as control valves  114  and  102 ) from becoming clogged with cooled emulsion. 
     An air supply line  118  derives air under pressure directly from the air brake supply of the patcher air brake system (i.e., without any reduction in pressure), not shown for purposes of simplicity. Air pressure of the order of 120 psi is supplied to the air line  118 . A T-coupler  120  feeds the pressurized air to branch lines  122   a  and  122   b , each of which are respectively coupled to the 12 o&#39;clock inlet ports  114   b  and  116   b  of multi-position valves  114  and  116 . 
     The 6 o&#39;clock ports  114   c  and  116   c  of multi-position valves  114  and  116  are respectively coupled through one-way valves  122  and  124  to one of the inlets  34   f  and  34   g  which extend through outer and inner jacket walls  34   c  and  34   d  of mixing head  34  (see  FIG. 3B ) in order to introduce asphalt emulsion at diametrically opposed openings provided along the inner and outer jackets  34   c  and  34   d  and thereby introduce asphalt emulsion into the hollow interior of the mixing head  34 . Suitable dispersing members  34   h  and  34   i , shown in  FIG. 3B , are substantially flush with the interior jacket  34   c , to disperse the asphalt emulsion throughout the hollow interior of the mixing head, as shown by arrows A, to coat the aggregate fed into mixing head  34 . 
     As was previously mentioned, the aggregate passes through curved member  40  and into the hollow interior of mixing head  34  where the aggregate is admixed with and coated by the liquid emulsion and then passed through the outlet end, i.e., nozzle,  34   j  of the mixing head  34  for deposit into a pothole or other crevice or recess being coated and/or repaired. As was mentioned above, air under pressure may be introduced into mixing head  34  while the emulsion feed lines and aggregate line are closed, to clean debris from a pothole. Also, air under pressure enters the flexible hose  35  and telescoping assembly  36  to advance the aggregate into the mixing head  34 . 
     Check valves  122  and  124  are preferably respectively coupled between outlet ports  114   c  and  116   c  and couplings  34   f  and  34   g , allowing emulsion to pass in only one direction and enter into the mixing chamber of mixing head  34  while preventing any reverse flow of the asphalt emulsion from the mixing head back into the control valves  114  and  116  through ports  114   c ,  116   c.    
     The one-way check valves  122  and  124  are preferably provided with jackets having inlet and outlet ports similar to the ports  116   g  and  116   h  of valve  116 , as shown in  FIG. 3A , to receive coolant to heat the check valves during patching operations. For simplicity, check valves  122  and  124  are shown as being enclosed within the heating jackets  115  and  117 , but may be provided with their own heating jackets, which maintain any asphalt emulsion within the jackets in the heated, flowable state regardless of the ambient temperature and thereby prevent the one-way valves from becoming clogged with cooled emulsion. Check valves  115  and  117  have a housing provided with inlet and outlet openings similar to the openings  116   g ,  116   h  provided in housing  116  shown in  FIG. 3A , to receive coolant to heat the check valves and hence the emulsion flowing therethrough in the same manner as valve  116 . Heating jackets  115 ,  117  may also electrically heat one-way valves  122  and  124  when not in use. 
     Control valves  114  and  116  are further provided with outlet ports  114   d  and  116   d . Back flush conduits  126  and  128  are coupled between ports  114   d ,  116   d  and recovery tank  130 . Flush tank  132  contains cleaning agent pressurized by air pressure source  118 , to flush the feed lines  106 ,  112   a  and  112   b . Recovery tank  130  is located above flush tank  132  to provide for the flow of cleaning agent by gravity from recovery tank  130  to flush tank  132 , when normally-closed valve  134  is open and flush tank  132  is de-pressurized. Any suitable cleaning agent having cleansing and/or flushing capabilities may be used. In the preferred embodiment pine oil extract is employed as the cleaning agent in order to accumulate the emulsion for use with emulsion delivered from the heated storage tank  20 , as will be more fully described. 
     Patcher  10  operation is initialized by assuring that air pressure provided to the asphalt storage tank  20  and the flush tank  132  are within the range of 50-70 psi and that the air brake system is developing air pressure in the range of 100-120 psi. Valve  136 , coupled near the outlet of the air brake pressure source, is a regulator valve which, when open, regulates the output pressure introduced into the flush tank  132  and the asphalt storage tank  18 , through port  102   c  in valve  102 , to obtain the desired pressure levels mentioned above. Valves  114  and  116  have their operating arms placed in the 12 o&#39;clock position, causing air entering lines  122   a  and  122   b  to enter ports  114   b ,  116   b , pass through valves  114  and  116  and enter into the feed lines  112   a  and  112   b . The air brake pressure source fed to the line  118  bypasses the valve  136  and thus provides maximum pressure (i.e., 100-120 psi) to the 12 o&#39;clock ports  114   b ,  116   b  of valves  114  and  116  to clear lines  112   a ,  112   b  and  106 . Valve  102  is then placed in the 12 o&#39;clock position. The actuator switch  111  in the patcher cab  14  (see  FIG. 3 ) is operated to activate linear actuator  110  and open ball valve  108 . Air blows through the valves  102 ,  114 ,  116 , and feed lines  112   a ,  112   b  and  106 , clearing valves  102 ,  114  and  116  and feed lines  106 ,  112   a  and  112   b  of emulsion and returning the emulsion to tank  20 . The air pressure in the feed lines drops after 1-2 minutes. The pressure is monitored by a pressure gauge (not shown) in cab  14 . The ball valve  108  is then closed by operating switch  111 . Thereafter, the operating arms of both valves  114 ,  116  are moved to the 6 o&#39;clock position in readiness for a patching operation. Emulsion may take approximately 30 seconds to flow to mixing head  34  since air may still be in the feed lines. 
     During a typical patching operation, a pothole in the roadway surface is cleaned by blowing high-volume air into the pothole. Air under pressure is introduced into feed line  106  from port  102   c  and common port  102   b  by placing the operating arm of valve  102  in the 3 o&#39;clock position and placing the operating arms of valves  114  and  116  in the 6 o&#39;clock position, enabling air under pressure to exit through outlet  34   j  of mixing head  34 . Air under pressure is emitted from outlet  34   j  to clear debris from a pothole. 
     In a second step, a tack coat of emulsion may be applied to the area to be treated by coupling the storage tank  20  to inputs  34   f ,  34   g  of the mixing head through valves  102 ,  114  and  116 . 
     In a third step, a mixture of aggregate admixed with heated emulsion is emitted from the mixing head  34  to fill the pothole. The valve  102  is placed in the 12 o&#39;clock position and valves  114  and  116  are placed in the 6 o&#39;clock position to cause emulsion to flow (under pressure) from the supply tank  20  to mixing head  34  through valve  102 , lines  106 ,  112   a ,  112   b , valves  114 ,  116  and one-way valves  122 - 124 . A finished coat of a dry material may then be applied. The 3 o&#39;clock port  102   c  of valve  102  can also receive air to blow out the feed line  106 , if desired. It has been found that sprayed injection patching is the most economical and longest lasting method for pothole repair. 
     In order to clean the internal lines of asphalt emulsion, while at the same time preventing discharge of cleaning agent from the system and completely recycling the asphalt and cleaning agent, control valves  102 ,  114  and  116  are operated in the following manner: 
     A shut-down storage operation is initiated by introducing air into the feed lines by operating switch  111 , located in cabin  14 , to fully close the ball valve  108 . The operating handles of control valves  102 ,  114  and  116  are respectively moved to the 3 o&#39;clock, 12 o&#39;clock and 12 o&#39;clock positions. Ball valve  108  is then opened and maintained open for approximately 1 to 2 minutes until the air pressure in the feed lines drops (monitored by the aforementioned air gauge in cab  14 ) whereupon the ball valve  108  is then fully closed. 
     Valves  114  and  116  have their control arms respectively moved to the 9 o&#39;clock and 3 o&#39;clock positions. Control valve  102  is then moved to 6 o&#39;clock position  102   d , coupling flush tank  132  to feed line  106  through ports  102   d ,  102   b  of valve  102  in readiness to perform a flushing operation. 
     Actuator  109  is operated to open ball valve  108 , enabling solvent in pressurized flush tank  132  to enter the 6 o&#39;clock port of valve  102  and pass through valve  102 , feed lines  106 ,  112   a  and  112   b  and valves  114  and  116  and then to recovery tank  130  through back flush lines  126  and  128 . One of these lines, such as line  128 , is preferably formed of a clear transparent material, enabling an operator to view the cleaning agent as it moves from flush tank  132 , through valve  102 , feed lines  106 ,  112   a ,  112   b , valves  114  and  116  and back flush lines  126 ,  128  and enter into recovery tank  130 , shown in  FIGS. 1C ,  3 ,  3 C and  3 D. The asphalt is removed from lines  106 ,  112   a ,  112   b  and valves  114 ,  116  by the cleaning agent as can be viewed passing through the clear line  128 . The ball valve  108  is then returned to the closed position. 
     The cleaning agent is returned to flush tank  132  from recovery tank  130  by respectively moving the operating arms of valves  114  and  116  to the 3 o&#39;clock and 9 o&#39;clock positions and closing valve  102  (by moving the operating arm of valve  102  to the 9 o&#39;clock, i.e., “plug” position  102   e ). The air supply line to flush tank  132  and to the emulsion tank  20  is closed by closing valve  136 . The air under pressure in flush tank  132  is vented to the atmosphere by opening valve  138  as shown in  FIG. 3C . When the reading of pressure gauge  140  reads “O” (zero) psi, flush tank  132  is now relieved of air pressure. 
     Closed valve  134  is then opened for 2-3 minutes to drain the recycled cleaning agent, delivered by gravity to recovery tank  130  by lines  126  and  128 , back into flush tank  132  and valve  134  is then closed. 
     The air pressure release valve  138  which bleeds air from tank  132  to the atmosphere is closed and valve  136  is opened to repressurize tank  132  and emulsion supply tank  20  from pressure source  118 , completing the back flush operation and retaining all of the solvent and emulsion in the closed system. The connections for the flush operation may be reversed by coupling the flush tank  132  to valves  114  and  116  and coupling the recovery tank  130  to valve  102 , if desired. 
     Asphalt emulsion residing in feed lines  106 ,  112   a  and  112   b  is carried into the recovery tank  130  together with the cleaning agent which is preferably pine oil extract. The residue emulsion is accumulated as the patching operations are performed. It is preferred that the concentration of asphalt emulsion reaches a level of the order of at least 90% and preferably at least 95%. The collected asphalt, admixed with the cleaning agent is utilized during a patching operation and is admixed with asphalt from storage tank  20 , thus making highly efficient use of asphalt collected by the cleaning agent during a flushing operation, for subsequent reuse. A suitable instrument such as an in-line viscometer or a pressure differential indicator is utilized to provide an indication as to when the asphalt emulsion accumulated in the cleaning agent is adequate for use together with fresh asphalt emulsion during the patching operation. When the concentration of the asphalt emulsion is suspended in the cleaning agent is of a sufficient level, preferably of the order of 90%-95%, the cleaning agent admixed with the emulsion may be introduced into the dispensing head through port  102   d  of output  102 , line  106  and lines  112   a ,  112   b  into the mixing head through ports  114   c ,  116   c  of valves  114  and  116 . Thereafter, emulsion from storage tank  20  may be fed to the mixing head to be admixed with the recaptured asphalt emulsion. A fresh supply of the cleaning agent may be introduced into the recovery tank  130  or flush tank  132  by a suitable filler opening, not shown for purposes of simplicity. 
     Making reference to  FIGS. 4 through 4D , operation of the multi-position valves  114  and  116  is electrically operated from the patcher cabin  14  which is provided with a control panel  200  shown in  FIG. 4A  and provided with an On/Off switch  202  and a control valve multi-position selection switch  204  for selecting one of the four ports of the two valves  114 ,  116  to be connected with the common port  114   a ,  116   a  of the control valves.  FIG. 4B  shows switches  202  and  204  in electrically schematic form, switch  202  electrically connecting or disconnecting the voltage source V+ in series with switch arm  204   a  of multi-position switch  204 . Rotatable switch arm  204   a  is selectively movable to engage one of the four stationary contacts  204   b - 204   e . Each contact  204   b - 204   e  is coupled in common to a pair of cam-operated contact switches  205   a - 205   b ,  206   a - 206   d . For example, stationary contact  204   b  is coupled in common to a pair of cam-operated switches  205   a ,  206   a  for respectively controlling the operation of motors  205  and  206 . Switch  205   a  is comprised of a movable switch arm  205   a - 1  and a stationary contact  205   a - 2  is selectively electrically connected to motor  205  through a diode D 1 . Movable switch arm  205   a - 1  is pivotally mounted at  205   a - 3  and is normally biased to move in the clockwise direction and thus be biased toward being disconnected from stationary contact  205   a - 1 . Switch  206   a  has a movable contact  206   a - 1  and a stationary contact  206   a - 2  coupled to motor  206  through diode Dr. Movable contact  206   a - 1  is biased to move in the counterclockwise direction about pivot  206   a - 3 . Each of the remaining switches  205   b - 205   d  for motor  205  and switches  206   b - 206   d  for motor  206  have a similar structure. 
     The output shaft of each motor  205  and  206  is respectively coupled to its multi-position valve through a gear box G 1  and G 2 . The output of each gear box G 1  and G 2 , in addition rotating the operating arm of its associated control valve to couple one of the ports of its associated multi-position valve to the common port, further rotates a common shaft S 1  driven by gear box G 1  for simultaneously rotating four cams C 1 -C 4  arranged along shaft S 1  and four cams C 1 -C 4 ′ arranged along shaft S 2 . Each of the cams C 1 -C 4  and C 1 ′-C 4 ′ has a “flat.” Note, for example, cams C 1  and C 1 ′ having flats C 1   a  and C 1   a ′. Assuming switch  202  is closed and switch arm  204   a  of switch  204  is in contact with stationary contact  204   b , power is provided from source V+ through closed switches  202 ,  204   a - 204   b  and switch arms  205   a - 1 ,  206   a - 1  and diodes D 1 , D 1 ′ to motors M 1  and M 2 , switches  205   a - 1  and  206   a - 1  being closed at the present time due to the fact that switch arms  205   a - 1  and  206   a - 1  engage the curved surfaces of cams C 1  and C 1 ′, which urge  205   a - 1 - 205   a - 2  and  206   a - 1 - 206   a - 2  to the closed position. The motors M 1 , M 2  being energized, rotate their respective output shafts, which are coupled through gear boxes G 1  and G 2  to drive the operating arms of the multi-position valves  114 ,  116  and the shafts S 1  and S 2 , respectively. As the shafts S 1  and S 2  rotate, the cams C 1  and C 1 ′ move to a position having their “flats” C 1   a  and C 1   a ′ aligned with their associated switch arms  205   a - 1  and  206   a - 1 , enabling movable switch arms  205   a - 1  and  206   a - 1  to move away from their associated stationary contacts  205   a - 2 ,  206   a - 2 , and power is disconnected from motors  205 ,  206 . 
     When switches  205   a ,  206   a  are closed, power is delivered through diodes D 1 , D 1 ′ to motors  205 ,  206  but is prevented from being fed through any of the switches  205   b - 205   d  which, although one or more of the other switches may be closed, they are prevented from receiving power from diodes D 1 , D 1 ′ due to the polarities of diodes D 2 -D 4 , D 2 ′-D 4 ′. The diode arrays D 1 -D 4 , D 1 ′-D 4 ′ also prevent any feedback of power to all other closed switches in the event, for example, that switch  205   a  were to open before switch  206   a  (or vice versa), due to the reverse polarities of diodes D 2 ′ through D 4 ′, for example, thereby enabling motor  206  to be energized until the “flat” C 1   a  of cam C 1  is moved to a position aligned with switch arm  206   a - 1 , enabling switch arm  206   a - 1  to open. All of the remaining cams C 2 -C 4  and C 2 ′-C 4 ′ operate in a similar fashion, thus enabling a single power line and one switch to simultaneously provide power to motors  205  and  206  utilizing only a single On/Off switch  202  and multi-position switch  204  to operate the motors  205 ,  206  and provide accurate alignment of the valves  114 ,  116 , even in the event that motors  205 ,  206  have electrical characteristics which differ from one another. 
       FIGS. 4C and 4D  shown one typical electric motor  205  and associated mechanical drive G 1  for operating the multi-position valve  114  and the cams C 1 -C 4 . The housing of motor  205  is directly mounted to one surface of a housing H 3  containing gear box G 1 . The output shaft S serves as a mechanical input drive to gear box G 1  which is provided with a gear assembly to rotate the output shaft S 1  of gear box G 1  at a desired angular speed. Shaft S 1  also drives multi-position valve  114 . Shaft S 1  extends to the left and into the multi-position valve  114 . Shaft S 1  further extends to the right to receive the cams C 1 -C 4 .  FIG. 4  shows the motor drives  205  and  206  enclosed within housing covers H 1  and H 2 , respectively, while  FIGS. 4C and 4D  show motor drive  205 , shafts S and S 1  and cams C 1 -C 4  with the housing cover H 1  removed. Each of the motor drives is provided with a manually operable control arm  206 ,  208  providing a manual override in case of loss of electrical power. 
     The cam arrays C 1 -C 4  and C 1 ′-C 4 ′ may be adjusted so that their angular orientation on the shaft upon which they are mounted assures that the selected port associated with each cam pair is properly aligned.

Summary:
A vehicle mounted patching system for patching potholes and the like and incorporating method and apparatus for removing and flushing asphalt emulsion from the feed lines of the patcher which completely recycles the cleaning agent used to flush the feed lines, as well as eliminating any external discharge of potentially toxic materials. A cleaning agent is used to flush the feed lines. The emulsion is collected in a recovery tank and combined with fresh emulsion delivered from a storage tank when the collected emulsion reaches a given concentration. Electrical controls for operating both motors from a single power source employ arrays of cam-operated switches and a diode array polarized to prevent feedback of power from the power source to assure precision positioning of the multi-position valves to perform a given operation.