Abstract:
A directional control valve having three positions controls the direction of flow through an asphalt distributor. The directional control valve is interposed between a pump and a feed line assembly to a spray bar. The directional control valve has a first position in which flow is recirculated through the pump, a second position in which flow is delivered to the spray bar and a third position providing for handspray and transfer operations. A pressure relief valve is provided for controlling return flow of asphalt from the spray bar to the tank. The pressure relief valve is open in spray bar circulation mode and is closed during a spraying mode. According to the preferred embodiment the directional valve and pressure relief valve are contained within a modular control valve assembly. The directional control valve eliminates the need to reverse the flow in one of the individual feed lines and feed line assembly connecting the modular control valve assembly to the spray bar. The feed line assembly includes a delivery and return line running coaxial or otherwise adjacent for heat transfer therebetween. The directional control valve reduces the quantity and lengths of exposed valving and plumbing associated with prior asphalt distributors.

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to asphalt distributors and more particularly relates to control valves in the circulating systems of asphalt distributors. 
     BACKGROUND OF THE INVENTION 
     Asphalt distributors apply hot liquid asphalt to road and other surfaces in a variety of paving applications. Upon cooling, asphalt material becomes more viscous and eventually “freezes” to provide a binder material for pavement. Although it is desired that asphalt freezes upon spray application, it is important to prevent cooling of the asphalt material before spraying, while the asphalt is in the distributor. If asphalt freezes in the distributor, the asphalt can cause serious operating problems such as plugging the system and decreasing uniformity of the spray application. 
     Asphalt distributors conventionally include a tank, a pump, a spray bar and the plumbing network for communicating asphalt from the tank through the pump to the spray bar. The tank, pump and spray bar are conventionally supported directly by a vehicle such as a truck or supported by a detachable trailer pulled behind the vehicle. The plumbing network of an asphalt distributor preferably performs a number of desired functions, including loading of asphalt into the tank, off-loading asphalt out of the tank, transfer to handspray operations, circulating asphalt in the tank during initial asphalt heating, spraying of asphalt, and circulating asphalt through the spray bar while not spraying to prevent freezing of asphalt therein. 
     A prior attempt of providing an asphalt distributor is exemplified by Hill, U.S. Pat. No. 4,274,586. Hill provides a circulating system that includes dual feed lines connecting the pump to the spray bar, each feed line being connected near one end of the spray bar. In Hill, flow through one feed line is positive or one directional while the flow through the other feed line is positive or negative (bi-directional) depending upon whether spraying or circulation through the bar is desired. During normal spraying operations, flow through both feed lines is positive to deliver asphalt flow to the spray bar. However, when the distributor is stopped, flow through the bi-directional feed line is typically reversed to circulate asphalt through the spray bar and back to the tank to continuously move the asphalt through the feed lines and spray bar and prevent asphalt from freezing therein. Switching the flow is accomplished with an intermediate conduit having an on/off valve therein selectively connecting the feed lines, an adjustable pressure relief valve in the bi-directional feed line, and a pair of on/off valves in the spray bar. 
     Problems existing in the art relate to the complexity and cost of providing the circulating network in the asphalt distributor. Prior attempts have typically required complex and multiple valves and extensive lengths of circulating plumbing to reverse the flow of asphalt in one of the feed lines and provide the desired operating functions of an asphalt distributor, while all the time preventing asphalt from freezing and plugging the system. Not only are complex valves expensive but the multiple valve locations which are dictated by the routing of interconnecting plumbing do not provide easy operation or straightforward understanding of operation. For manually operated valves, this requires extra worker training and presents a potential safety hazard. The multiple connections can be prone to assembly difficulties and leaks, and the multiple lengths of exposed plumbing result in excessive heat loss from the asphalt which can lead to freezing or plugging of the system. 
     SUMMARY OF THE INVENTION 
     It is therefore the general aim of the present invention to provide an improved approach of directing asphalt flow through the circulating system of an asphalt distributor. 
     It is another general aim to centralize the control of asphalt flow through the circulation system of an asphalt distributor. 
     It is another general aim of the present invention to reduce the cost of providing control valving for the circulating system of an asphalt distributor. 
     It is therefore objects of the present invention to reduce the complexity of valving in a circulating system of an asphalt distributor while providing for multiple desire operating features. 
     It is a further objective of the present invention to provide a circulating system in an asphalt distributor that is easier to use, and therefore which is safer to workers. 
     It is a subsidiary object of the present invention to reduce the lengths of exposed plumbing in a circulating system of an asphalt distributor. 
     It is another subsidiary object of the present invention according to a preferred embodiment to eliminate the need to reverse the flow in one of the feed lines to the spray bar in the circulating system of an asphalt distributor. 
     It is therefore a feature of the present invention to provide a directional control valve that has three positions corresponding to four different operating modes of an asphalt distributor. The directional control valve includes an inlet receiving asphalt from a pump, a first outlet to the tank and a second outlet to the spray bar. Control means is provided for selectively positioning the directional control valve. The directional valve includes the first position connecting the inlet to the first outlet for recirculation mode, a second position connecting the inlet to the second outlet for spraying and spray bar circulation modes, and a third position in which the inlet is disconnected from both outlets. 
     It is an aspect of the present invention that the directional control valve provides a third outlet to a transfer line for operating as off-loading and/or handspray operations. This allows asphalt to continually flow through the directional control valve during transfer operations so as to further prevent freezing of asphalt in the directional control valve. 
     It is another aspect of the present invention that the directional control valve does not switch the flow through the feed line assembly which delivers asphalt to and from the spray bar. According to the preferred embodiment, the feed line assembly includes a delivery line for one directional delivery flow to the spray bar and a return line for one directional return flow back to the tank. The return line runs coaxially or otherwise adjacent to the delivery line to form a heat exchanger so that static asphalt in the return line is heated by the delivery line to prevent asphalt freezing therein. 
     It is another feature of the present invention to provide a modular control valve assembly which includes a directional control valve and a pressure relief valve housed in the same valve body. The valve body includes an inlet to the pump, a recirculating outlet for recirculating asphalt to the tank, a delivery outlet for delivering asphalt to the spray bar and a return inlet connected to the spray bar for receiving circulated asphalt from the spray bar. The directional control valve has three positions for alternatively connecting the inlet to the recirculating and delivery outlets. The pressure relief valve is interposed between the return inlet and the recirculating outlet. The pressure relief valve has open and closed positions corresponding to spraying and spray bar circulating modes. During the spraying mode the pressure in the spray bar is low because nozzles on the spray bar are open for discharging asphalt. During spray bar circulation mode, the pressure in the spray bar increases as the nozzles are closed. This causes the pressure relief valve to open thereby allowing asphalt to circulate through the manifold return line and recirculating outlet back to the tank. 
     It is an aspect of the present invention that the delivery line and return line of the feed line assembly which connects the modular control valve assembly to the spray bar are coaxial or otherwise run adjacent to provide a heat exchanger means for heat transfer therebetween. During the spraying mode, heat is transferred from the delivery line to the return line to prevent freezing of residual or remaining asphalt therein. 
     These and other objects and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic illustration of a coaxial feed line assembly and improved circulating system according to a preferred embodiment of the present invention. 
     FIGS. 2A,  2 B,  2 C(i) and  2 C(ii) are schematic flow diagrams illustrating the multiple positions and alternative flow paths in the circulating system of FIG.  1 . 
     FIG. 3 is a side view of a modular control valve assembly and cross sectional view of a spray bar assembly with a coaxial feed line assembly connecting assemblies according to a preferred embodiment. 
     FIG. 4 is a cross-sectional view of the modular control valve assembly of FIG. 3 taken about line  4 — 4  showing a coaxial outlet connection to a coaxial feed line assembly. 
     FIG. 5 is a top view of parts of the spray bar shown in FIG.  3 . 
    
    
     While the invention is susceptible of various modifications and alternative constructions, certain illustrative embodiments thereof have been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the invention to the specific forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions and equivalents falling within the spirit and scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     For purposes of illustration and referring to FIG. 1, a modular control valve assembly  20  in an asphalt circulating system  21  of a vehicular asphalt distributor is illustrated in accordance with a preferred embodiment of the present invention. The modular control valve assembly  20  includes a directional control valve  22  and a pressure relief valve  24  for controlling the alternative flow paths of asphalt through the system  21 . 
     The circulating system  21  includes a pump  26  for pumping asphalt through the system, a spray bar  28  for discharging asphalt, and plumbing and valving therebetween to provide for several operating modes as will be explained. As shown, the pump  26  is preferably bi-directional so that asphalt flow may be reversed and sucked back from the circulating system  21  after a worksite or workday is completed. The pump  26  is connected by a supply line  27  to an asphalt tank  30  and by a pump output conduit  32  to an inlet  34  of the directional control valve  22 . Disposed along the supply line  27 , are a strainer  36  for removing frozen asphalt chunks and large impurities which could clog the circulating system  21 , a quick disconnect coupling  38  for tank filling operations, and a tank valve  40  for selectively shutting off flow from the tank  30 . Within the modular control valve assembly  20 , the directional control valve  22  and pressure relief valve  24  have return outlet ports  42 ,  43  that are connected to form a single return or recirculating line  44  to the asphalt tank  30 . The directional control valve  22  includes a transfer outlet  45  connected to a transfer line  46  for handspray and/or asphalt off-loading operations. Flow through the transfer line  46  and to handspray and off-loading outputs is selectively controlled by on/off type valves  47 ,  48 . The modular control valve assembly  20  is connected by a feed line assembly  50  to the spray bar  28  for transferring asphalt to and from the spray bar  28 . The directional control valve has a delivery outlet  52  and a return inlet  54  connected with the feed line assembly  50 . As shown, the feed line assembly  50  is generally disposed transversely between the tank  30  and the spray bar  28  and connects preferably near the center of the spray bar  28  and orthoganally thereto. The feed line assembly  50  includes a delivery conduit  53  for delivering asphalt to the spray bar and a return conduit  55  for returning asphalt therefrom. The spray bar  28  includes an inlet  29  connected to the delivery conduit  53  and an outlet  31  connected to the return conduit  55 . The spray bar  28  also has a plurality of solenoid actuated on/off type nozzles  56  linearly aligned between manifold ends  28 A,  28 B for uniformly discharging asphalt over a selected surface area. As schematically shown in FIG. 1, the spray bar  28  provides adjacent flow passages with a first top passage  58  from the delivery conduit  53  to the ends  28 A,  28 B of the spray bar  28  and a second bottom passage  59  from the ends  28 A,  28 B of the spray bar  28  to the return conduit  55 . This provides for continuously positive flow through the spray bar  28  without the need to reverse the flow of asphalt therein. In a preferred embodiment, the bottom passage  59  and outlet  31  are disposed vertically below the top passage  58  and inlet  29  as can be seen better in FIG.  3  and as will be later described in further detail. By connecting the delivery conduit  53  near the center of the spray bar  28  as schematically shown, the pressures at the ends  28 A,  28 B are substantially equal pressures throughout the length of the spray bar thereby providing for substantially uniform spraying. 
     In accordance with the aim of centralizing the control of asphalt flow through the circulation system of an asphalt distributor, and referring to FIGS. 2A,  2 B,  2 C(i) and  2 C(ii), the directional control valve  22  has three positions for directing the flow of asphalt through circulating system  21 . In the first position shown in FIG. 2A, the pump  26  is connected to the transfer line  46  and is disconnected from the delivery conduit  53  and the recirculating line  44  for off-loading and handspray operations. In this position, workers can selectively operate valves  47 ,  48  for handspray and off-loading operations. 
     In the second position shown in FIG. 2B, the directional control valve  22  connects the pump  26  to the recirculating line  44  while disconnecting the pump from the delivery conduit  53  for tank recirculation mode and tank loading operations. During recirculation mode, asphalt is pumped from the tank  30  to the directional control valve  22  and back to the tank  30  without going through the spray bar  28 . Recirculation mode is normally done during initial startup to heat the asphalt and warm up a portion of the circulating system  21  and is also used for handspray operations. During tank loading operations, an external supply line is connected to the quick disconnect coupling  38  whereby the pump  26  delivers asphalt to the tank through the directional control valve  22  and return line  44 . 
     In the third position shown in FIGS.  2 C(i) and  2 C(ii), the directional control valve  22  connects the pump  26  to the delivery conduit  53  while disconnecting the pump from the recirculating line  44  for spray bar circulating and asphalt spraying modes. During spray bar circulation mode shown in FIG.  2 C(i), the nozzles  56  are closed which raises the pressure of asphalt in the spray bar  28  and thereby the pressure at the pressure relief valve  24  causing it to open past its cracking point. This allows the asphalt to flow from the return conduit  55  through the recirculating line  44  and back into the tank  30 . Spray bar circulation mode is typically used during initial warming up of the spray bar  28  and nozzles  56  as well as during standby or breaks in operation as when the asphalt distributor is stationary. During the spraying modes shown in FIG.  2 C(ii), the directional control valve  22  is in the same position as for the spray bar circulation mode. However, the nozzles  56  are open for discharging the asphalt over a selected surface. With the nozzles  56  open, the pressure in the spray bar  28  is released thereby lowering the asphalt pressure causing the pressure relief valve  24  to close. The cracking point of the pressure relief valve  24  is set between the respective asphalt pressures corresponding to the spray bar circulation and the spraying modes. 
     In viewing FIG.  2 C(ii) of the preferred embodiment, it can be seen that asphalt does not readily flow through the return conduit  55  during the spraying mode. Recalling that asphalt is prone to freeze and cause problems if left to cool, the preferred embodiment prevents asphalt freezing by running the delivery conduit  53  coaxial or otherwise adjacent with the return conduit  55 . More specifically, residual asphalt remaining in the return conduit  55  during the spraying mode is heated through heat transfer from the delivery conduit  53  by the asphalt flowing therethrough. Although the coaxial conduits  53 ,  55  are the preferred way to prevent freezing of asphalt in the return line, other methods may work as well including draining the return conduit  55  during spraying mode or otherwise preventing the asphalt from freezing therein. It is an advantage that the directional control valve  22  does not need to reverse the flow of asphalt in either of the conduits  53 ,  55  of the feed line assembly  50  during the operating modes. It is another advantage that the directional control valve  22  reduces the amount of valving and external plumbing while providing for numerous desired operating modes of the asphalt distributor. The directional control valve and modular control valve assembly also reduce the costs of providing an asphalt circulating system on an asphalt distributor while also reducing the potential for asphalt freezing and leaks. 
     Turning now to FIGS. 3 and 4, a preferred mechanical implementation of the modular control valve assembly  20  is shown. The modular control valve assembly  20  provides an elongate tube-like valve body  60  with a directional control valve generally indicated at  22  and a pressure relief valve generally indicated at  24 , both housed therein. The valve body  60  has various pipes welded or otherwise fixed to the body to provide an inlet  34  for receiving pumped asphalt from the pump  26  (FIG.  1 ), an outlet  44  for returning asphalt to the tank  30  (FIG.  1 ), a delivery outlet  52  connected to the delivery conduit  53  for delivering asphalt to the spray bar  28  (FIG.  1 ), and a return inlet  54  connected to the return conduit  55  for receiving circulated asphalt from the spray bar  28  (FIG.  1 ). An extension line  62  extends the bar feed return inlet  54  to the pressure relief valve  24 . In the preferred embodiment, the extension line includes two metal pipes  62   a ,  62   b  and a temperature resistant flexible hose  62   c  clamped therebetween to allow for thermal expansion or misalignments. Fixed on the ends of the valve body  60  are flange like shaft mounting plates  64 ,  65 , with valve seating plates  66 ,  67 ,  68  linearly and parallelly spaced and fixed therebetween. Connecting adjacent shaft mounting plates  64 ,  65  and valve seating plates  66 ,  67 ,  68  are tubular body segments  60   a ,  60   b ,  60   c , and  60   d  which may be formed relatively cheaply from sheet steel with radially outward flange ends abutted against their respective plates  64 - 68 . Each body segment  60   a - 60   d  contains a respective fluid chamber  70 ,  71 ,  72 ,  73 . Running through the shaft mounting plates  64 ,  65  and the valve seating plates  66 - 68  on the outside of the valve body  60  is a tie rod assembly  75  that includes several nuts and bolts, which ties or clamps the modular control valve assembly  20  together, preferably along with gaskets (not shown) disposed between the body segments  60   a - 60   d  and adjacent plates  64 - 68  for preventing leakage. As shown in FIG. 4, the fluid chambers  70 - 73  are in fluid communication with the delivery outlet  52 , the inlet  34 , the recirculating outlet  44  and return inlet  54 , respectively. Each valve seating plate  66 - 68  defines an annular flow orifice  76 ,  77 ,  78  for selectively connecting the chambers  70 - 73 . 
     To control the flow through the directional control valve  22 , the preferred embodiment provides two annular valve members  80 ,  81  or other movable operator for selectively plugging the respective flow orifices  76 ,  77 . The two valve members  80 ,  81  are slidably mounted over a linearly translatable screw drive shaft  82 . A centering spring  84  concentrically disposed over the shaft  82 , or other resilient means, urges the valve members  80 ,  81  in opposite directions against there respective seating plates  66 ,  67 . In the preferred embodiment, each of the valve members  80 ,  81  includes a plate portion  86  for seating against the respective seating plates  66 ,  67  and an axially projecting stem portion  87  that is received into a respective flow orifice  76 ,  77  for partially plugging the respective flow orifices  76 ,  77 . Each stem portion  87  includes an outer groove  88  and an inner groove  89 . Disposed between the valve members  80 ,  81  and the seating plates  66 ,  67  are disc shaped gaskets  90  for sealing off the inner chamber  71  from the outside chambers  70 ,  72  of the directional control valve  22 . The gaskets  90  are held in place by retainer discs  91  and snap rings  92  or other such retaining means. The snap rings  92  are fitted in the outer periphery groove  88  to hold the retainer discs  91  and gaskets  90  against the valve members  80 ,  81 . A ring gasket  93  is carried in the inner groove  89  to prevent leakage between the drive shaft  82  and the valve members  80 ,  81 . 
     The position of the drive shaft  82  determines the position of the valve members  80 ,  81 . A pair of spring pins  95  or other radially projecting members are linearly spaced and fixed on the drive shaft  82  for selectively engaging the valve members  80 ,  81  as the drive shaft  82  moves. As the shown and oriented in FIG. 4, neither of the spring pins  95  are engaging the valve members  80 ,  81  which keeps the flow orifices  76 ,  77  closed and the inlet  34  disconnected from the recirculating and delivery outlets  44 ,  52 , thereby providing for asphalt flow diagrammed in FIG.  2 A. As the drive shaft  82  moves to the right, the left spring pin  95  engages the left valve member  80  lifting it off the seating plate  66  and compressing the centering spring  84 , which provides for asphalt flow diagrammed in FIGS.  2 C(i) and  2 C(ii), depending upon the state of the nozzles  56 . Likewise, as the drive shaft  82  moves to the left, the right spring pin  95  engages the right valve member  81  lifting it off the seating plate  67  and compressing the centering spring  84 , which provides for asphalt flow diagrammed in FIG.  2 B. As the drive shaft  82  linearly translates, the centering spring  84  engages the valve members  80 ,  81  to close the open valve member before allowing the other valve member to open, thereby providing a third position in which the valve members  80 ,  81  close both flow orifices  76 ,  77 . 
     Although two different controls and other control means may alternatively be used for each valve member of the directional control valve  22 , the preferred embodiment, provides a single control generally indicated at  96  for controlling the position of the drive shaft  82  to thereby provide for the three positions of the directional control valve  22 . It is an advantage that providing a single control  96  reduces the complexity of the circulating system which increases worker understanding of how to operate the circulating system  21 , and in turn increases worker safety. From the above discussion and the drawings, it will be appreciated to those in the art that the preferred embodiment minimizes the amount of machine tooling and casting to provide the various valve components, thereby keeping cost at a minimum, while providing the various desired operating mode features. 
     In the preferred embodiment, the control  96  comprises a manually operated wheel  97  coupled to the drive shaft  82  outside the valve body  60 . The drive shaft includes a threaded portion  82   a  which is received in a corresponding rotationally fixed threaded sleeve portion  98  of the actuator mounting plate  64 . As the wheel  97  and drive shaft  82  rotate, the threads  82   a  of the drive shaft  82  engage the threads of the sleeve portion  98  causing the drive shaft  82  to linearly translate. The sleeve portion  98  also carries a scraper  99  and a ring gasket  100  to prevent asphalt from interfering with the rotation of the drive shaft  82  relative to the sleeve portion  98 . In an alternative embodiment, a single control  96  is provided by a single three position pneumatic cylinder (not shown) or other fluid or electrical actuator for linearly translating a drive shaft without rotation. It is an advantage of the alternative embodiment that the control may be remotely controlled. 
     Also shown in FIGS. 3 and 4 is that directional control valve  22  includes a transfer outlet  45  and conduit  46  connected to the intermediate fluid chamber  71  and thereby the inlet  34  for continuously connection to pump  26  (FIG. 1) during all three positions of the directional control valve  22 . Although the transfer line outlet conduit  46  may alternatively be placed upstream of the directional control valve  22 , connecting the transfer line  46  directly to the directional control valve  22  has the advantage of increasing heat transfer to other portions of the directional control valve  22  and modular control valve assembly  20  when both valve members  80 ,  81  are in the closed positions. The increased heat transfer prevents freezing of asphalt in the modular control valve assembly  20  during transfer operations. 
     In furtherance of the objects of reducing the potential for asphalt leaks and freezing or clogging of the circulation network, the preferred embodiment configures the directional control valve  22  with the pressure relief valve in the same valve body  60  to form the modular control valve assembly  20 . In particular, heat transfer through the valve body  60  prevents asphalt freezing in the pressure relief valve  24  when it is not open. Also, the pressure relief valve  24  and directional control valve  22  share intermediate return chamber  72  and the recirculating outlet and line  44 , thereby further reducing the lengths of plumbing needed to provide for the circulating system  21 . 
     In the preferred embodiment, the pressure relief valve  24  comprises a valve member  105  mounted on a linearly translatable retaining shaft  107  for engaging the valve seating plate  68  and plugging the respective flow orifice  78 . Like the directional control valve  22 , associated with the valve member are a disc gasket  90 , a retainer disc  91 , a snap ring  92 , and a inner gasket  93 , whose function at this point is understood from the above discussion. A spring pin  95  fixed on the retaining shaft  107  continuously engages the valve member  105 . More specifically, a spring  108  engages a nut  110  on the retaining shaft  107  to bias the retaining shaft  107  and valve member  105  against the valve seating plate  68 . The spring  108  is compressed between the nut  110  and a mounting sleeve portion  112  of the mounting plate  65  for determining the cracking point at which the valve member  105  will open. Also shown in FIG. 4 are a scraper  99  and gasket  100  carried by inner sleeve  112  for preventing asphalt from interfering with the smooth linearly translation of the retaining shaft  107 . 
     As described above, the pressure relief valve  24  opens during spray bar circulation mode and closes during spraying mode. To provide for this, the cracking point of the pressure relief valve  24  is determined by pre-setting the compression in the spring  108 . The nut  110  can be tightened or loosened as desired to control the spring compression and thereby the cracking point of the pressure relief valve  24 . It is an advantage that during normal operation of switching between spraying and spray bar circulating modes, the spring compression or cracking point does not need to be adjusted. However it will be appreciated that operating conditions can be different on different days. For example, colder weather often causes an increase in asphalt viscosity which may change the pressure applied to the pressure relief valve  24  in different modes. This may require a minor adjustment of the spring compression or cracking point to compensate for changes in operating pressures. 
     The modular control valve assembly  20  also has a coaxial inlet/outlet connection generally indicated at  120  that connects with the coaxial feed line assembly  50 . In the preferred embodiment, the connection  120  includes the outlet pipe  52  and the return inlet body  54 . The extension line  62  connects the return inlet body  54  with the pressure relief valve  24 . The delivery conduit  53  of the feed line assembly is closely and slidably fitted over the outlet pipe  52  while the return conduit  55  and the return inlet body  54  includes respective flange portions  121 ,  122 ,  123  that are tied together by a tie rod assembly  75  disposed on the outside of the return inlet body  54 . The return and delivery conduits  53 ,  55  of the feed line assembly  50  are preferably built from flexible metal tubing such as commercially available tar and asphalt hose. Advantageously, the preferred embodiment forms a heat exchanger by coaxially disposing the return and delivery conduits  53 ,  55  to preserve heat therein. As used herein, coaxial means that one conduit is housed inside the other conduit and not necessarily that the conduits have a common center. In the preferred embodiment a common center for the return and delivery conduits  53 ,  55  does not necessarily exist because of the preferred flexible nature and inherent play in the coaxial feed line assembly which also allows for thermal expansion and small misalignments. 
     Referring to FIGS. 3 and 5, the spray bar  28  also includes a coaxial inlet/outlet connection generally indicated at  125  that is preferably located in proximity to the center of is longitudinal axis of the spray bar  28 . As shown, the spray bar  28  includes a divider  28   a  therein which splits the spray bar up into the upper and lower flow passages  58 ,  59 . The coaxial connection  125  generally includes a inner duct  126  disposed within an outer duct  128 . In greater detail, the inner duct  126  is welded or otherwise fixed to the spray bar  28  in fluid communication with the upper flow passage  58 . The delivery conduit  53  is closely fitted into the inner duct  126  to connect the delivery conduit  53  with the upper flow passage  58 . The outer duct  128  welded or otherwise fixed between two flanges  129 ,  130  to provide a chamber  132 . The first flange  129  is fixed to the spray bar  28  and includes an flow aperture  134 . A hollow body structure  136  is fixed between the first flange  129  and the spray bar  28  for connecting the flow aperture  134  to the bottom flow passage  59  thereby to provide for the spray bar outlet  31 . The second flange  130  is fastened to a corresponding flange  138  of the return conduit  55  to connect the return conduit  55  to the outlet  31  and couple the feed line assembly  50  and spray bar  28 . 
     Thus, there has been provided a DIRECTIONAL CONTROL VALVE AND VALVE ASSEMBLY IN AN ASPHALT DISTRIBUTOR which fully satisfies the objects, aims, and advantages set forth above. While the invention has been described in connection with a specific embodiment thereof, it is evident that may alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations that fall within the spirit and broad scope of the appended claims.