Patent Publication Number: US-11047095-B2

Title: Variable height offset mold

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to slipform paving machines, and more particularly to offset slipform paving machines using relatively large molds having a variable mold height and variable internal cross-section. 
     2. Description of the Prior Art 
     It is known to use relatively large variable height offset molds for paving or forming variable height concrete barriers adjacent a highway. These molds include at least one form insert that is variable in height relative to a mold frame, as well as two side plates to vary the lower portions of the profile of the mold form. These existing machines vary the profile height of the mold form through the use of the lifting columns which support the paving machine. In some instances, the variable height of the mold exceeds the available leg stroke of the lifting columns. This problem has previously been addressed by stopping the paving operation when a maximum leg stroke is reached, then unbolting the mold from the machine and re-bolting it to the paving machine in a different position so that the legs of the paving machine can be lowered, and paving can be resume. This procedure requires a great deal of manual work. Additionally, when the position of the mold relative to the machine frame is changed, the position of the feeding auger or belt relative to the machine frame must also be changed. 
     A further complication is that it is undesirable to use the entire leg stroke of the paving machine for purposes of adjusting mold height. This is because these relatively large molds are very heavy and thus if the legs are extended to their maximum height, the paving machine may be unstable. Accordingly, only a portion of the leg stroke may be used, and this can require further stages of unbolting and reattaching the mold to the machine frame. 
     These prior art devices have typically required that at least one ground-based operator walk alongside the mold and manually adjust the position of the left and right side form inserts and/or the left and right side plates. In some situations, two ground-based operators may be required, one walking along each side of the form. 
     These existing machines may control the height of the machine frame, and thus the height of the attached offset mold, by following a stringline reference which has been constructed along side the path where the concrete barrier is to be constructed. It is also known to utilize a second stringline reference to control an elevation of one of the form inserts of the offset mold. 
     Accordingly, there is a need for improved slipform paving machines designed to improve the use of large variable height offset molds. 
     SUMMARY OF THE INVENTION 
     In one embodiment a slipform paving machine includes a machine frame, and a plurality of ground engaging units for supporting the slipform paving machine from a ground surface. A plurality of height adjustable machine frame supports may support the machine frame from the plurality of ground engaging units. Each of the machine frames supports may include a machine frame support actuator configured to adjust a height of the machine frame relative to a respective one of the ground engaging units. Each of the machine frame supports may include a machine frame support sensor configured to provide a signal corresponding to the height of the machine frame relative to the respective one of the ground engaging units. The paving machine further includes an offset mold including a mold frame. A mold frame actuator may be configured to adjust a height of the mold frame relative to the machine frame. A mold frame sensor may be configured to provide a signal corresponding to the height of the mold frame relative to the machine frame. An external reference sensor may be provided and configured to provide a signal representative of a position of the slipform paving machine relative to an external reference system. The machine may include a controller configured to receive the signal from the external reference sensor, and to control extension of machine frame support actuators and the mold frame actuator to control a height of the mold frame relative to the ground surface. 
     A conveyor may be included and arranged to discharge material to be molded into the mold. A conveyor actuator may be configured to adjust a position of the conveyor relative to the machine frame. A conveyor sensor may be configured to provide a signal corresponding to the position of the conveyor relative to the machine frame. 
     In any of the above embodiments, the paving machine may further have the controller configured to control an extension of the conveyor actuator at least in part as a function of at least one of the signal from the mold frame sensor and the signal from at least one of the machine frame support sensors. 
     In any of the above embodiments, the slipform paving machine may further be configured such that the external reference sensor includes a stringline sensor. The controller may be configured to control extension of the machine frame support actuators and the mold frame actuator to control the height of the mold frame relative to the ground surface at least in part in response to a signal from the stringline sensor. 
     In any of the above embodiments, the paving machine may be further configured such that the external reference sensor is part of a three-dimensional guidance system, and the controller may be configured to control extension of the machine frame support actuators and the mold frame actuator to control the height of the mold frame relative to the ground surface at least in part in response to the signal from the external reference sensor. 
     In any of the above embodiments the slipform paving machine may have the height adjustable frame supports configured as lifting columns. The machine frame support actuators may include hydraulic piston-cylinder units located within their respective lifting columns. The machine frame support sensors may be integrated in their respective hydraulic piston-cylinder units. The mold frame actuator may include a hydraulic piston-cylinder unit, and the mold frame sensor may be integrated in the hydraulic piston-cylinder unit of the mold frame actuator. 
     In any of the above embodiments, the controller may be configured to control smaller changes in the height of the mold frame relative to the ground surface via the machine frame support actuators, and to control larger changes in the height of the mold frame relative to the ground surface via the mold frame actuator. 
     In any of the above embodiments the mold may further include a first side form assembly and a second side form assembly. The first side form assembly may include a first form insert, a first form insert actuator configured to adjust the height of the first form insert relative to the mold frame, a first form insert sensor configured to provide a signal corresponding to the height of the first form insert relative to the mold frame, a first side plate, and a first side plate actuator configured to adjust a height of the first side plate. Similarly, the second side form assembly may include a second form insert, a second form insert actuator configured to adjust the height of the second form insert relative to the mold frame, a second form insert sensor configured to provide a signal corresponding to the height of the second form insert relative to the mold frame, a second side plate, and a second side plate actuator configured to adjust a height of the second side plate. 
     In any of the above embodiments the first side form assembly may further include a first side plate sensor configured to provide a signal corresponding to the height of the first side plate, and the second side form assembly may further include a second side plate sensor configured to provide a signal corresponding to the height of the second side plate. 
     In any of the above embodiments the controller may be further configured to control a change in position of at least one of the first form insert actuator and the first side plate actuator, and to control a change in position of at least one of the second form insert actuator and the second side plate actuator, in response to a change of height of the mold frame relative to the ground surface. 
     In any of the above embodiments the controller may be configured to provide for a mode of operation wherein for a given change in height of the mold frame relative to the ground surface, on one of the first side form assembly and the second side form assembly the respective form insert actuator position is fixed and the respective side plate actuator provides a corresponding change in position, and on the other of the first side form assembly and the second side form assembly the respective form insert actuator provides a corresponding change in position while the respective side plate actuator remains fixed. 
     In any of the above embodiments the controller may be configured to provide for a mode of operation wherein for a given change in height of the mold frame relative to the ground surface, on each of the first side form assembly and the second side form assembly the respective form insert actuator position is fixed and the respective side plate actuator provides a corresponding change in position. 
     In any of the above embodiments the controller may be configured to provide for a mode of operation wherein for a given change in height of the mold frame relative to the ground surface, on each of the first side form assembly and the second side form assembly the respective form insert actuator provides a corresponding change in position while the respective side plate actuator remains fixed. 
     In any of the above embodiments the controller may be configured such that for a given increase in height of the mold frame relative to the ground surface there is an equal increase in a combined downward extension of the first form insert and the first side plate relative to the mold frame, and there is an equal increase in a combined downward extension of the second form insert and the second side plate relative to the mold frame. 
     In any of the above embodiments each of the first form insert actuator and the second form insert actuator may include a hydraulic piston-cylinder unit, and each of the first form insert sensor and the second form insert sensor may be integrated in the hydraulic piston-cylinder unit of its respective actuator. 
     In any of the above embodiments the left first plate actuator may be configured to adjust a height of the first side plate relative to the first form insert, and the second side plate actuator may be configured to adjust a height of the second side plate relative to the second form insert. 
     In another embodiment of the invention a method is provided for operating a slipform paving machine. The paving machine may include a machine frame, a plurality of ground engaging units supporting the paving machine from a ground surface, and a plurality of height adjustable machine frame supports supporting the machine frame from the plurality of ground engaging units. Each of the machine frame supports may include a machine frame support actuator configured to adjust a height of the machine frame relative to a respective one of the ground engaging units. Each of the machine frame supports may include a machine frame support sensor configured to provide a signal corresponding to the height of the machine frame relative to the respective one of the ground engaging units. The machine may further include an offset mold including a mold frame, a mold frame actuator configured to adjust a height of a mold frame relative to the machine frame, and a mold frame sensor configured to provide a signal corresponding to the height of the mold frame relative to the machine frame. The machine may further include an external reference sensor configured to provide a signal representative of a position of the slipform paving machine relative to an external reference system. 
     The machine may further include a controller. The method may comprise the steps of:
         (a) receiving in the controller the signal from the external reference sensors; and   (b) controlling with the controller extension of the machine frame support actuators and the mold frame actuator to control a height of the mold frame relative to the ground surface.       

     The slipform paving machine may further include a conveyor arranged to discharge material to be molded into the mold, a conveyor actuator configured to adjust a position of the conveyor relative to the machine frame, and a conveyor sensor may be configured to provide a signal corresponding to the position of the conveyor relative to the machine frame, and the method may further include controlling with the controller, extension of conveyor actuator in response to changes in height of the mold frame relative to the ground surface, to maintain an upper end of the conveyor above an inlet of the mold. 
     In any of the above embodiments the mold may further include a first side form assembly and a second side form assembly. The first side form assembly may include a first form insert, a first form insert actuator configured to adjust the height of the first form insert relative to the mold frame, a first form insert sensor configured to provide a signal corresponding to the height of the first form insert relative to the mold frame, a first side plate, and a first side plate actuator configured to adjust a height of the first side plate. Similarly, the second side form assembly may include a second form insert, a second form insert actuator configured to adjust the height of the second form insert relative to the mold frame, a second form insert sensor configured to provide a signal corresponding to the height of the second form insert relative to the mold frame, a second side plate, and a second side plate actuator configured to adjust a height of the second side plate. The method may further include controlling with the controller, one or more of the actuators of each of the first and second side form assemblies so that extension of the side form assemblies corresponds to changes in height of the mold frame. 
     Numerous objects, features and advantages of the present invention will be readily apparent to those skilled in the art upon reading of the following disclosure when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front perspective view of a slipform paving machine including a large offset mold. 
         FIG. 2A  is a schematic front elevation view of the paving machine of  FIG. 1  in a first orientation. 
         FIG. 2B  is a schematic front elevation view of the paving machine of  FIG. 2A  in a second orientation. 
         FIG. 2C  is a schematic front elevation view of the paving of machine of  FIG. 2A  in a third orientation. 
         FIG. 2D  is a schematic front elevation view of the paving of machine of  FIG. 2A  in a forth orientation. 
         FIG. 2E  is a schematic front elevation view of the paving of machine of  FIG. 2A  in a fifth orientation. 
         FIG. 2F  is a schematic front elevation view of the paving of machine of  FIG. 2A  in a sixth orientation. 
         FIG. 3  is a schematic front elevation view of the paving machine as shown in  FIG. 2A  with a further addition of schematic illustration of the various actuators, and with a schematic illustration of the associated control system. 
         FIG. 4  is a schematic illustration similar to  FIG. 3  showing an alternative arrangement of the left side plate actuator and the right side plate actuator. 
         FIG. 5  is a schematic elevation cross section view of a typical hydraulic piston-cylinder unit including an integrated position sensor, which is representative of any of the actuators shown in  FIG. 3 . 
         FIG. 6  is a schematic elevation view of a concrete divider wall formed by the paving machine of  FIG. 1 . 
         FIGS. 7A-7C  illustrate several possible scenarios of varying road height on opposite sides of the barrier wall. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a front perspective view of a slipform paving machine  10 , which may for example be a Wirtgen model SP60 machine. The slipform paving machine  10  includes a machine frame  12  which in the illustrated embodiment includes four swing arms such as  14 . A plurality of lifting columns  16  are attached to the machine frame  12  via the swing arms  14 . A lower portion of each lifting column  16  has a crawler track  18  mounted thereon. The crawler tracks  18  may be referred to as ground engaging units  18  for supporting the slipform paving machine  10  from a ground surface  20 . Alternatively, the ground engaging units may be wheels. 
     Each of the lifting columns  16  may be referred to as a height adjustable machine frame support  16  for supporting the machine frame  12  from one of the ground engaging units  18 . 
     An offset mold  22  is supported from the machine  10 . Mold  22  is of the type commonly referred to as a “large” offset mold. Such large offset molds may weigh on the order of 8 to 12 metric tons. This is contrasted to more conventional offset molds which typically have a weight on the order of 1-2 metric tons. 
     The direction of travel of the paving machine  10  in  FIG. 1  is in the direction of the arrow  24 , and thus with reference to the driver&#39;s viewpoint, in the illustrated embodiment of  FIG. 1  the offset mold  22  is mounted on the left hand side of the machine frame  12 . It will be appreciated that the mold  22  and the paving machine  10  are constructed so that the mold  22  may also be mounted on the right hand side of the machine frame  12  if desired. 
     A conveyor  26  is also mounted on the machine frame  12  and is arranged to discharge a material to be molded, such as concrete, from its upper end  28  into the mold  22 . As will be understood by those skilled in the art, the conveyor  26  may be a belt type conveyor or alternatively it may be an auger type conveyor. A lower end  30  of the conveyor  26  will receive the material to be molded from a supply truck or the like and will convey that material upward to its upper end  28  and thus into the mold  22 . 
       FIG. 3  is a schematic front elevation illustration of the slipform paving machine  10  of  FIG. 1  further illustrating the internal components of the offset mold  22  and further illustrating the various actuators used to control the relative position of the various components of the slipform paving machine  10 . 
     As seen in  FIG. 3 , each of the lifting columns or machine frame supports  16  includes a machine frame support actuator  32  configured to adjust a height of the machine frame  12  relative to a respective one of the ground engaging units  18 . Each of the actuators  32  comprise a hydraulic piston-cylinder unit located within their respective lifting columns  16 . As seen in  FIG. 3 , the machine frame support actuator  32  includes a cylinder portion  34  attached to an upper tubular portion  36  of the lifting column  16 , and a piston portion  38  attached to a lower tubular portion  39  of the lifting column  16 . 
       FIG. 5  further schematically illustrates the internal construction of the actuator  32  and is also representative of the internal construction of the other actuators herein described. In the illustrated embodiment, the actuator  32  is of a type sometimes referred to as “smart cylinder” which includes an integrated sensor  32 S configured to provide a signal corresponding to an extension of the piston member  38  relative to the cylinder member  34  of the actuator  32 . 
     The sensor  32 S includes a position sensor electronics housing  44  and a position sensor coil element  46 . 
     The piston portion  38  of actuator  32  includes a piston  48  and a rod  50 . The piston  48  and rod  50  have a bore  52  defined therein, within which is received the piston sensor coil element  46 . 
     The actuator  32  is constructed such that a signal is provided at connector  53  representative of the position of the piston  48  relative to the position sensor coil element  46 . 
     Such smart cylinders may operate on several different physical principles. Examples of such smart cylinders include but are not limited to magnetostrictive sensing, magnetoresistive sensing, resistive (potentiometric) sensing, Hall effect sensing, sensing using linear variable differential transformers, and sensing using linear variable inductance transducers. 
       FIG. 3  schematically illustrates the sensors associated with each of the actuators by the same number as used for the actuator with the addition of the suffix “S”. Thus, each of the machine frame support actuators  32  include a sensor  32 S. 
     The sensors  32 S associated with the machine frame support actuators  32  may be referred to as machine frame support sensors  32 S configured to provide a signal corresponding to the height of the machine frame  12  relative to the respective one of the ground engaging units  18 . It will be appreciated that the sensor  32 S does not need to directly measure the height of the machine frame relative to the ground engaging units, but instead the change in extension of the actuator  32  is an indirect indication of the height of the machine frame relative to the ground engaging units, because the same change occurs in the height of the machine frame relative to the ground engaging units as is measured in the extension of the actuator  32 . Given the known dimensions and geometry of the other components of the paving machine  10  the desired height may be determined from the sensor signal. 
     Variable Height Offset Mold 
     As schematically illustrated in  FIG. 3 , the offset mold  22  includes a mold frame  54 . A mold frame actuator  56  is connected between the mold frame  22  and the machine frame  12  and is configured to adjust a height of the mold frame  22  relative to the machine frame  12 . A mold frame sensor  56 S is configured to provide a signal corresponding to the height of the mold frame  54  relative to the machine frame  12 . In the same manner as just described with reference to  FIG. 5  for the actuator  32 , the mold frame sensor  56 S is preferably integrated in the mold frame actuator  56 . 
     It will be appreciated that the mold frame sensor  56 S does not need to directly measure the height of the mold frame relative to the machine frame, but instead the change in extension of the actuator  56  is an indirect indication of the height of the mold frame relative to the machine frame, because the same change occurs in the height of the mold frame relative to the machine frame as is measured in the extension of the actuator  56 . Given the known dimensions and geometry of the other components of the paving machine  10  the desired height may be determined from the sensor signal. 
     As schematically illustrated in  FIG. 3 , the slipform paving machine  10  may further include a conveyor actuator  58  configured to adjust a position of the conveyor  26  relative to the machine frame  12 . In the illustrated embodiment, changes in position of the conveyor  26  relative to machine frame  12  may result in a change of the slope angle  60  of the conveyor  26 , such that its lower end portion  30  remains at substantially the same elevation relative to ground surface  20  and such that its upper end  28  is at a suitable elevation so as to discharge material into the upper end of the mold  22 , regardless of the change in height of the mold  22  relative to the ground surface  20 . 
     The conveyor actuator  58  may have a conveyor sensor  58 S integrated therein as schematically represented in  FIG. 3 . The conveyor sensor  58 S may be configured to provide a signal corresponding to the position of the conveyor  26  relative to the machine frame  12 . In the same manner as just described with reference to  FIG. 5  for the actuator  32 , the conveyor sensor  58 S is preferably integrated in the conveyor actuator  58 . 
     It will be appreciated that the conveyor sensor  58 S does not need to directly measure the position of the conveyor  26  relative to the machine frame  12 , but instead the change in extension of the actuator  58  is an indirect indication of the position of the conveyor  26  relative to the machine frame  12 , because the same change occurs in the height of the position of the conveyor  26  relative to the machine frame  12  at pivot point  59  as is measured in the extension of the actuator  58 . Given the known dimensions and geometry of the other components of the paving machine  10  the desired position may be determined from the sensor signal. 
     The paving machine  10  may further include an external reference sensor  60  configured to provide a signal representative of a position of the slipform paving machine  10  relative to an external reference system  62 . For example, the external reference system  62  may be comprised of a stringline  64  constructed on the ground surface  20  adjacent the location where it is desired to form the slipformed structure such as a barrier wall  90 . 
     The external reference sensor  60  may take the form of a conventional wand type sensor arm  68  which engages and follows the stringline  64  as the slipform paving apparatus  10  moves along the ground parallel to the stringline  64 . As will be understood by those skilled in the art, such stringline type external reference systems  62  may provide a reference suitable to guide the direction of the slipform paving machine  10  and also to control an elevation of the slipform paving machine  10  and thus of the attached offset mold  22 . 
     The details of construction of the offset mold  22 , in particular its internal components, are further schematically illustrated in the series of views designated as  2 A- 2 F and in  FIG. 3 . In the series of views designated as  2 A- 2 F the various actuators, such as lifting column leg actuators  32  and the mold frame actuator  56  previously identified are indicated by double headed arrows in the approximate position of the actuator and indicating the general direction of movement of the associated components provided by the actuator. In  FIG. 3 , schematic representations have been provided of the actual actuators in the form of hydraulic piston-cylinder units schematically showing the general physical connections between the actuator and the components to which it is connected. 
     As is seen in both  FIGS. 2A-2F  and  FIG. 3 , the mold  22  includes a first side form assembly  70  and a second side form assembly  72 . With regard to the point of view of the viewer of  FIGS. 2A-2F  and  FIG. 3 , the first side form assembly  70  and second side form assembly  72  might be referred to as left and right side assemblies respectively. On the other hand, from the viewpoint of the operator of the paving machine  10  those left and right side designations might be reversed. In general, it will be understood that designations such as left and right side with regard to the side form assemblies are merely designations of convenience. This is particularly true when one considers that the mold  22  may be mounted either on left or right side of the paving machine  10 . Thus, this further description will simply refer to first and second side form assemblies  70  and  72 , and it will be understood that these could also be referred to as left and right side, or right and left side depending on the viewpoint of the viewer. 
     The first side form assembly  70  includes a first form insert  74  and a first side plate  76 . The second side form assembly  72  includes a second form insert  78  and a second side plate  80 . 
     The first side form assembly  70  further includes a first form insert actuator  82  configured to adjust the height of the first form insert  74  relative to the mold frame  54 . The first form insert actuator  82  has integrally included therein a first form insert sensor  82 S schematically illustrated in  FIG. 3  and configured to provide a signal corresponding to the height of the first form insert  74  relative to the mold frame  54 . 
     The first side form assembly  70  further includes a first side plate actuator  84  configured to adjust a height of the first side plate  76 . 
     As seen in the embodiment of  FIG. 3 , the first side plate actuator  84  is connected between the first form insert  74  and the first side plate  76  and thus is configured to adjust the height of the first side plate  76  relative to the first form insert  74 . 
     However, in the alternative embodiment of  FIG. 4 , the first side plate actuator  84  is connected between the first side plate  76  and the mold frame  54  and is thus configured to adjust the height of the first side plate  76  relative to the mold frame  54 . 
     The first side plate actuator  84  has integrally formed therein a first side plate sensor  84 S which is schematically illustrated in  FIG. 3  and which provides a signal corresponding to the height of the first side plate  76   
     Similarly, the second side form assembly  72  further includes a second form insert actuator  86  configured to adjust the height of the second form insert  78  relative to the mold frame  54 . The second form insert actuator  86  has integrally formed therein a second form insert sensor  86 S schematically illustrated in  FIG. 3  and configured to provide a signal corresponding to the height of the second form insert  76  relative to the mold frame  54 . 
     The second side form assembly  72  further includes a second side plate actuator  88  configured to adjust a height of the second side plate  80 . In the embodiment of  FIG. 3  the second side plate actuator  88  is connected between the second side plate  80  and the second form insert  78  and thus adjusts the height of the second side plate  80  relative to the second form insert  78 . In the alternative embodiment of  FIG. 4  the second side plate actuator  88  is connected between the second side plate  80  and the mold plate  54  and thus is configured to adjust the height of the second side plate  80  relative to the mold frame  54 . 
     The second side plate actuator  88  has integrally formed there in a second side plate sensor  88 S schematically illustrated in  FIG. 3  and configured to provide a signal corresponding to the height of the second side plate  80 . 
     Although in  FIG. 3  only a single mold frame actuator  56  is shown, it will be understood that the mold frame actuator  56  will typically comprise a pair of spaced forward and rearward actuators connected between the machine frame  12  and the mold frame  54 . Similarly, the first form insert actuator  82  will typically be one of a pair of a forward and rearward spaced form insert actuators. The same is true for the first side plate actuator  84 , the second form insert actuator  86 , and the second side plate actuator  88 . 
     In addition to the alternative embodiment of  FIG. 4 , it is also possible to support the side plates directly from the mold frame  54 , and to support the first form insert  74  from the first side plate  76 , and to support the second form insert  78  from the second side plate  88 . 
     In a further embodiment, the first side plate actuator  84  and the second side plate actuator  88  may not include sensors, or the first side plate actuator  84  and the second side plate actuator  88  may be operated in a “floating mode”, such that instead of controlling the specific extension of the first side plate actuator  84  and the second side plate actuator  88 , those actuators may be urged downwardly so that the bottom edges of first side plate  76  and the second side plate  80  slide along the ground  20 . 
     Variable Height Concrete Divider Walls 
     The offset mold  22  is particularly designed for the construction of concrete barrier walls to divide lanes of a highway which are flowing in opposite directions. The general shape of the barrier wall is shown in  FIG. 3  and the barrier wall is designated as  90 . The finished barrier wall  90  apart from the mold  22  is seen in  FIG. 6 . The barrier wall  90  may be described as having a height  92  above the ground surface. It will be understood that the ground surface may in fact be an underlying concrete slab which has been previously been poured. The barrier wall  90  has a first side profile  94  which is defined by the first side form assembly  70  and a second side profile  96  which is defined by the second side form assembly  72 . 
     It is noted that the first side profile  94  includes a first step  98  and the second side profile  96  includes a step  100 . As will be understood by those skilled in the art, for a typical barrier wall the height  92  may need to vary along the path of the highway, and the first and second side profiles  94  and  96  may vary in that the relative heights of their steps  98  and  100  relative to the ground surface  20  may also vary relative to each other. 
       FIGS. 7A, 7B and 7C  schematically illustrate several examples of variations in mold profile. In  FIG. 7A , the barrier  90  is shown in a standard situation wherein two traffic lanes  102  and  104  are at the same level, and the barrier  90  has a symmetric left and right profile. 
     In the example of  FIG. 7B , a left hand curve is shown where the traffic lanes are inclined to the left and the left side or first side barrier profile  94  is higher that the right side or second side barrier profile  94 . 
     Then in  FIG. 7C , a right curve is illustrated wherein the traffic lanes incline to the right, and the right or second side barrier profile  96  is higher than the left or first side barrier profile  94 . 
     In addition to variations in the barrier profiles as shown in  FIGS. 7B and 7C  it may be necessary to change the height  92  of the barrier wall  90 . 
     Control of Mold Height 
     The offset mold  22  disclosed herein is capable of automatically performing all these changes in the height and in the first and second side profiles of the molded barrier wall  90  through the use of a controller  110  which is schematically illustrated in  FIG. 3 . The controller  110  may be a part of the machine control system of paving machine  10 , or it may be a separate control module. The controller  110  could be mounted as part of the offset mold  22 . 
     The controller  110  receives input signals from the machine frame support sensors  32 S, the mold frame sensor  56 S, the conveyor sensor  58 S, the first form insert sensor  82 S, the first side plate sensor  84 S, the second form insert sensor  86 S, the second side plate sensor  88 S and the external reference sensor  60  all as schematically illustrated in  FIG. 3 . 
     The controller  110  may also receive other signals indicative of various functions of the paving machine  10 . The signals transmitted from the various sensors to the controller  110  are schematically indicated in  FIG. 3  by phantom lines connecting the sensors to the controller with an arrowhead indicating the flow of the signal from the sensor to the controller. 
     Similarly, the controller  110  will generate command signals for controlling the operation of the various actuators, which command signals are indicated schematically in  FIG. 3  by phantom lines connecting the controller to the various actuators with the arrow indicating the flow of the command signal from the controller  110  to the respective actuator. It will be understood that the various actuators as disclosed herein may be hydraulic piston-cylinder units and that the electronic control signal from the controller  110  will actually be received by a hydraulic control valve associated with the actuator and the hydraulic control valve will control the flow of hydraulic fluid to and from the hydraulic actuators to control the actuation thereof in response to the command signal from the controller  110 . 
     Furthermore, the controller  110  may control the direction of travel of the slipform paving machine  10  by steering of the ground engaging units  18  via a conventional steering system (not shown). Communication of such steering signals from the controller  110  to the various steered ground engaging units is preformed in a conventional manner. 
     Controller  110  includes or may be associated with a processor  112 , a computer readable medium  114 , a data base  116  and an input/output module or control panel  118  having a display  120 . An input/output device  122 , such as a keyboard or other user interface, is provided so that the human operator may input instructions to the controller. It is understood that the controller  110  described herein may be a single controller having all of the described functionality, or it may include multiple controllers wherein the described functionality is distributed among the multiple controllers. 
     Various operations, steps or algorithms as described in connection with the controller  110  can be embodied directly in hardware, in a computer program product  124  such as a software module executed by the processor  112 , or in a combination of the two. The computer program product  124  can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, or any other form of computer-readable medium  114  known in the art. An exemplary computer-readable medium  114  can be coupled to the processor  112  such that the processor can read information from, and write information to, the memory/storage medium. In the alternative, the medium can be integral to the processor. The processor and the medium can reside in an application specific integrated circuit (ASIC). The ASIC can reside in a user terminal. In the alternative, the processor and the medium can reside as discrete components in a user terminal. 
     The term “processor” as used herein may refer to at least general-purpose or specific-purpose processing devices and/or logic as may be understood by one of skill in the art, including but not limited to a microprocessor, a microcontroller, a state machine, and the like. A processor can also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. 
     With regard to controlling the operations of the offset mold  22 , the control operations may generally be broken down into two categories. First, height of the mold  22  relative to the ground surface  20  and thus the height  92  of the resulting concrete barrier wall  90  is controlled by controlling the height of the machine frame  12  relative to the ground surface  20  via the actuators  32  within the lifting columns  16 , and controlling the height of the mold  22  relative to the machine frame  12  via the mold frame actuator  56 . The project plan will have determined that the barrier wall  90  should be located at a certain location on the earth&#39;s surface and that its height and side profiles should have varying specifications as the construction of the barrier wall proceeds along a predetermined path which is part of the project plan. Thus, the controller  110  will typically receive a signal from the external reference sensor  60 , in response to which the controller  110  will control the extension of the machine frame support actuators  32  and the mold frame actuator  56  to control the height of the mold frame  54  relative to the ground surface  20  and thus control the resulting height  92  of the resulting molded barrier wall  90 . 
     Thus, the controller  110  may be described as being configured to receive the signal from the external reference sensor  60  and to control extension of the machine frame support actuators  32  and the mold frame actuator  56  to control the height of the mold frame  54  relative to the ground surface  20 . 
     Control of Extension of Internal Side Form Assemblies of the Offset Mold 
     The second aspect of the control provided by controller  110  is to control the actuation of the actuators  82 ,  84 ,  86 , and  88  associated with the first and second side form assemblies  70  and  72  to accommodate changes in the height of the mold frame  54  relative to the ground surface  20 , and to accommodate changes in the first and second side profiles  94  and  96  of the molded barrier wall  90 . This control of the internal actuators of the mold  22  generally requires an extension of the overall height of the side form assemblies as the height of the mold  22  increases so the side form assemblies extend all the way downward to the ground surface  20 . Additionally, the relative positions of the form inserts and the side plates may be modified to change the location of the steps  98  and  100  of the barrier wall relative to the ground surface. 
     It will be appreciated that for a given change in height of the mold frame  54  relative to the ground surface  20  there are a number of different combinations of actions of the actuators  82 ,  84 ,  86 , and  88  associated with the interior components of the mold  22 , which may be utilized to provide a corresponding change in the height of the first and second side form assemblies  70  and  72 . 
     There are at least nine possible combinations of actions which may be utilized as shown in the following table and identified as modes 1-9. 
     
       
         
           
               
               
               
               
               
             
               
                   
               
               
                   
                 FIRST 
                 FIRST 
                 SECOND 
                 SECOND 
               
               
                   
                 FORM 
                 SIDE 
                 FORM 
                 SIDE 
               
               
                   
                 INSERT AC- 
                 PLATE AC- 
                 INSERT AC- 
                 PLATE AC- 
               
               
                 MODE 
                 TUATOR 
                 TUATOR 
                 TUATOR 
                 TUATOR 
               
               
                   
               
             
            
               
                 1 
                 Variable 
                 Fixed 
                 Variable 
                 Fixed 
               
               
                 2 
                 Variable 
                 Fixed 
                 Fixed 
                 Variable 
               
               
                 3 
                 Fixed 
                 Variable 
                 Variable 
                 Fixed 
               
               
                 4 
                 Fixed 
                 Variable 
                 Fixed 
                 Variable 
               
               
                 5 
                 Variable 
                 Variable 
                 Variable 
                 Fixed 
               
               
                 6 
                 Variable 
                 Fixed 
                 Variable 
                 Variable 
               
               
                 7 
                 Variable 
                 Variable 
                 Fixed 
                 Variable 
               
               
                 8 
                 Fixed 
                 Variable 
                 Variable 
                 Variable 
               
               
                 9 
                 Variable 
                 Variable 
                 Variable 
                 Variable 
               
               
                   
               
            
           
         
       
     
     Each of these modes of operation may be generally described as having the controller configured to control a change of position of at least one of the first form insert actuator  82  and the first side plate actuator  84 , and to control a change in position of at least one of the second form insert actuator  86  and the second side plate actuator  88 , in response to a change in height of the mold frame  54  relative to the ground surface  20 . 
     Mode 1 from the table above may be described as having the controller  110  configured to provide for a mode of operation wherein for a given change in height of the mold frame  54  relative to the ground surface  20 , on each of the first side form assembly  70  and the second side form assembly  72  the respective form insert actuator provides a corresponding change in position while the respective side plate actuator remains fixed. 
     Modes 2 and 3 from the table above are representative of another preferred control technique. Modes 2 and 3 may be generally described as having the controller  110  configured to provide for a mode of operation wherein for a given change in height of the mold frame  54  relative to the ground surface  20 , on one of the first side form assembly  70  and the second side form assembly  72  the respective form insert actuator position is fixed and the respective side plate actuator provides a corresponding change in position, and on the other of the first side form assembly  70  and the second side form assembly  72  the respective form insert actuator provides a corresponding change of position while the respective side plate actuator remains fixed. 
     Another preferred control technique is that represented by mode 4, which may be described as having the controller  110  configured to provide for a mode of operation wherein for a given change in height of the mold frame  54  relative to the ground surface  20 , on each of the first side form assembly  70  and the second side form assembly  72 , the respective form insert actuator position is fixed and the respective side plate actuator provides a corresponding change in position. 
     It will be appreciated that each of the remaining modes of operations 5-9 provide more complex interactions of the movements of the various actuators wherein on at least one of the left and right side form assemblies  70  and  72  both associated actuators are varied in order to achieve the desired overall extension of the side form assembly and to provide the appropriate change in location of the associated step on the resulting formed concrete barrier wall. 
     In another embodiment of the invention, preferred modes of operation may be selected from the above table, dependent upon the magnitude and/or nature of the change in height and profile of the molded structure  90 . Such selection may also be dependent upon the current state of extension of the lifting columns  16 . 
     As previously noted one result to be achieved in association with any change in height of the offset mold  22  is that the first and second side form assemblies  70  and  72  must be extended or retracted in length to correspond to the change in height of the mold  22  so that the side plates  84  and  88  extend all the way down to or substantially down to the ground surface  20 . This may be described as having the controller  110  configured such that for a given increase in the height of the mold frame  54  relative to the ground surface  20  there is an equal increase in a combined downward extension of the first form insert and first side plate relative to the mold frame, and there is an equal increase in a combined downward extension of the second form insert  78  and the second side plate  80  relative to the mold frame  54 . 
     It will be appreciated that the offset mold  22  with its mold frame actuator  56  is constructed to provide for changes in height of the offset mold  22  relative to the ground surface which are substantially larger that any changes which could be achieved solely through the use of the actuators  32  within the lifting columns  16 . On the other hand, it will be appreciated that relatively small changes in the height of the mold  22  relative to the ground surface  20  may be achieved either through use of the actuators  32  of the lifting columns  16  or through use of the mold frame actuator  56 . For example, typical actuators  32  of the lifting columns  16  may be capable of moving through a leg stroke of a maximum of approximately 42 inches. The mold frame actuator  56 , on the other hand, may be constructed to achieve much larger changes in elevation of the mold frame  54  relative to the machine frame  12 , on the order of as much as nine feet (108 inches). It will further be appreciated that due to concerns for stability of the paving machine  10 , and due to the high weight of the relatively large offset mold  22  it may be desired not to extend the actuators  32  of the lifting columns  16  to their furthest possible extension. Thus, it may be desired to only utilize the actuators  32  within a relatively small range of perhaps 24 inches. 
     The controller  110  may be configured to control smaller changes in height of the mold frame  54  relative to the ground surface  20  via the machine frame support actuators  32 , and to control larger changes in the height of the mold frame  54  relative to the ground surface  20  via the mold frame actuator  56 . 
     Control of the Conveyor 
     For a given height of the offset mold  22  and its mold frame  54  relative to the ground surface  20  as shown for in example in  FIG. 2A , the conveyor  26  will be positioned relative to the machine frame  12  so that its lower end  30  is accessible by a concrete supply truck or the like, and such that its upper end  28  is located above the mold  22  so as to discharge concrete material to be formed into a receiving inlet in the mold  22  for directing the same in between the mold form assemblies  70  and  72  to be formed into the concrete barrier wall structure  90 . As previously described with regard to  FIG. 3 , the position of the conveyor  26  relative to the machine frame  12  is at least in part controlled by a conveyor actuator  58 . Typically, the lower portion of conveyor  26  will be pivotally supported from the machine frame  12 , for example at pivotal connection  57  schematically seen in  FIG. 3 . The conveyor  26  may also have an intermediate point pivotally connected to the conveyor actuator  58  such as at pivotal connection  59  (see  FIG. 3 ). Thus as the machine frame  12  is changed in height relative to the ground surface by actuators  32  and/or as the mold frame  54  is changed in height relative to the machine frame  12  by mold frame actuator  56 , it is necessary to reorient the conveyor  26  relative to the machine frame  12  so that its lower end  30  remains accessible by a concrete supply truck, and so that its upper end  28  remains located above the upper inlet of the mold  22 . This change in orientation is typically accomplished by extension and retraction of the conveyor actuator  58  so as to change the angle  60  of the conveyor relative to the machine frame  12 . 
     The controller  110  may be generally described as being configured to control extension of the conveyor actuator  58  at least in part as a function of at least one of the signal from the mold frame sensor  56 S and the signal from at least one of the machine frame support sensors  32 S. 
     EXAMPLES OF FIGS.  2 A- 2 F 
       FIGS. 2A-2F  schematically show several examples of the modes of control that can be accomplished with the machine  10 . In  FIG. 2A  the mold frame  54  is at a relatively low position relative to the ground and the machine frame  12 . 
     In  FIG. 2B , as compared to  FIG. 2A , the lifting column actuators  32  have been extended thus raising the machine frame  12  and the attached conveyor  26  and mold frame  54 . The side plates  76  and  80  have been extended downward relative to the side form inserts  74  and  78 , to keep the lower edges of the side plates near the ground surface  20 . Note that these changes have resulted in a change in the height  92  of the molded structure  90  as identified in  FIG. 6 . 
     In  FIG. 2C , as compared to  FIG. 2B , the lifting column actuators  32  are still further extended. The mold actuator  56  has lowered the mold frame  54  relative to the machine frame  12 . 
     In  FIG. 2D , as compared to  FIG. 2C , the mold actuator  56  has lifted the mold frame  54  relative to the machine frame  12 . The side plates  76  and  80  have been further extended downward relative to the side form inserts  74  and  78  using actuators  84  and  88 , to keep the lower edges of the side plates near the ground surface  20 . 
     In  FIG. 2E , as compared to  FIG. 2D , the second insert form  78  has been raised relative to the mold frame  54  using actuator  86 , the second side plate  80  has been further extended relative to second insert form  78  using actuator  88 , and the conveyor  26  has been raised using conveyor actuator  58 . Note that these changes have resulted a change in the right side profile  96  of the molded structure  90 , without changing the height  92  of the molded structure  90 . 
     In  FIG. 2F , as compared to  FIG. 2E , the mold frame  54  has been further raised relative to machine frame  12  using mold actuator  56 , the second form insert  78  has been lowered relative to mold frame  54  using actuator  86 , the first side plate  76  has been lowered relative to the first form insert  74  using actuator  84 , and the machine frame  12  has been further raised relative to the tracks  16  using the lifting column actuators  32 . 
     External Reference Systems 
     One form of external reference system which has previously been noted is the use of a stringline  62  which has been constructed on the ground surface  20  adjacent the path of the desired slipform concrete structure  90 . For such an external reference system, the external reference sensor  60  may include a stringline sensor as schematically illustrated in  FIG. 3 . With such a system the controller  110  may be described as being configured to control extension of the machine frame support actuators  32  and the mold frame actuator  56  to control the height of the mold frame  54  relative to the ground surface  20  at least in part in response to the signal from the string line sensor  60 . 
     In connection with the use of a stringline the paving machine  10  may use a cross slope control to control the elevation of the opposite side of the machine from the stringline. 
     When using the stringline type of external reference system, the stringline  62  may convey the information about the desired overall height  92  of the molded structure  90 . Information for the control of the position of the steps  98  and  100  formed by the form inserts  74  and  78  may be communicated to the controller  110  in various ways. One technique is to utilize a second stringline (not shown) constructed alongside the path of the barrier wall  90  which second stringline is used to communicate information regarding the desired position of one or both of the form inserts  76  and  78 . 
     One alternative form of external reference system is the use of a three-dimensional guidance system. As will be appreciated by those skilled in the art such a three-dimensional guidance system may include one or more GPS sensors mounted on or fixed relative to the machine frame  12  or the mold frame  54  and receiving signals from a global navigation satellite system (GNSS) via which the position of the sensors within the three-dimensional reference system may be established. With such a system the external reference sensor may be described as being part of a three-dimensional guidance system and the controller  110  may be described as being configured to control extension of the machine frame support actuators  32  and the mold frame actuator  56  to control the height of the mold frame  54  relative to the ground surface  20  at least in part in response to the signals from the external reference sensors. 
     Another alternative form of external reference system is the use of a total station, which is another type of three-dimensional guidance system. The total station may be placed on the ground at a known location within the external reference system, and one or more reflector prisms may be mounted on the slipform paving machine. The total station measures the distance and direction to the reflectors and thus determines the position and orientation of the slipform paving machine within the external reference system. The total station may transmit a signal to the controller of the slipform paving machine, the signal being representative of the position of the slipform paving machine relative to the external reference system. The reflector prisms, in association with the total station, may be considered to be external reference sensors configured to provide a signal representative of a position of the slipform paving machine relative to the external reference system. 
     With any of the external reference systems described herein, the external reference sensor or sensors may be mounted on the mold frame  54 , or on the machine frame  12 , or elsewhere on the slipform paving machine  10 . What is important is that the position of the mold frame  54  relative to the positions of the external reference sensor or sensors is known or can be determined from the geometry of the slipform paving machine  10  and the known positions of the various actuators. Regardless of the location of the external reference sensor or sensors, the external reference sensor or sensors may be described as being configured to provide a signal representative of a position of the slipform paving machine relative to the external reference system. 
     In combination with the input signals from either the stringline or the three-dimensional guidance system, or the total station, the controller  110  may utilize pre-programed instructions (for example via the software  124 ) to determine the desired overall height of the structure  90  and the desired side profiles  94  and  96  of the slipform structure  90  at various locations along the path of the paving machine  10 . 
     Methods of Operation 
     When constructing a molded barrier wall  90  with the slipform paving machine  10  described above, the controller  110  will perform steps of receiving in the controller  110  a signal from the external reference sensor  60  and then controlling the extension of the machine frame support actuators  32  and the mold frame actuator  56  to control the height of the mold frame  54  relative to the ground surface  20 . 
     In further response to changes in the height of the mold frame  54  relative to the ground surface  20 , the controller  110  may control extension of the conveyor actuator  58  to reorient the conveyor  26  to keep its upper end  28  appropriately situated above the material inlet in the upper end of the mold  22 . 
     Also, concurrently with changing the height of the mold frame  54  relative to the ground surface  20 , the controller  110  may control the various actuators  82 ,  84 ,  86 , and  88  associated with the first and second side form assemblies  70  and  72  so that the extension of the side form assemblies  70  and  72  corresponds to changes to height of the mold frame  54  so that the side form assemblies still extend down substantially to the ground surface  20 . 
     Furthermore, the controller  110  may control the various actuators  82 ,  84 ,  86 , and  88  to situate the form inserts  74  and  78  at appropriate elevations relative to the ground  20  to form the steps  98  and  100  of the slipformed concrete structure  90  at the appropriate elevations as desired by the construction plan. 
     Thus, it is seen that the apparatus and methods of the present invention readily achieve the ends and advantages mentioned as well as those inherent therein. While certain preferred embodiments of the present invention have been illustrated and described for purposes of the present disclosure, numerous changes in the arrangement and construction of parts and steps may be made by those skilled in the art which changes are encompassed within the scope and spirit of the present invention as defined by the appended claims.