Abstract:
A cask transporter for engaging, lifting and safely transporting casks containing nuclear waste material. The cask transporter comprises a gantry structure including a plurality of extendible telescoping boom assemblies coupled to a beam. A platform is coupled to and supports the gantry structure and couples the gantry structure to a driven tread mechanism. Couplers couple the beam to a cask to be transported, and cushioned restraints restrain a cask from colliding with the cask transporter.

Description:
REFERENCE TO A RELATED APPLICATION 
     This application is a continuation of Ser. No. 08/250,378, filed May 27, 1994 and entitled CASK TRANSPORTER, now U.S. Pat. No. 6,017,181. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to mobile lifting equipment and, more particularly, to a mobile gantry for transporting casks for nuclear power facilities. 
     Safe storage of spent fuel rods for nuclear power facilities is a problem of increasing magnitude. In the past, spent fuel rods were typically housed in storage facilities which carefully controlled the storage environment. Steadily increasing volumes of this radioactive waste have led to a search for more cost effective storage alternatives. A leading alternative is a system using a specially designed storage casks to house significant amounts of radioactive waste. These containers are designed to withstand the elements, and can therefore be stored outside without requiring the precise control systems of expensive storage facilities. 
     While the cask storage system has significant benefits, this approach has led to a need for a reliable vehicle design capable of transporting casks weighing up to 135 tons. Substantial lifting capacity is not the only feature of an ideal cask transporter. A compact design which does not damage nuclear power facility floors while safely transporting heavy casks is also desirable. 
     In view of the foregoing, it is a general object of the present invention to provide a new and improved vehicle for transporting casks for nuclear power facilities. 
     It is a further object of the present invention to provide a new and improved mobile gantry for transporting casks that is compact and does not damage nuclear power facility floors. 
     It is a further object of the present invention to provide a new and improved cask transporter capable of safe and smooth traverse of uneven ground. 
     SUMMARY OF THE INVENTION 
     The invention provides a mobile gantry for transporting casks for the nuclear power facilities. The gantry comprises telescoping boom assemblies coupled to a beam. Coupling devices connect the beam to the cask for transport. The gantry is connected to a platform which carries an engine and a control console. The engine powers a hydraulic pump which provides pressurized hydraulic fluid to hydraulic motors and to hydraulic cylinders which extend the boom assemblies. The hydraulic motors are coupled to tread mechanisms. The tread mechanisms greatly reduce the floor loading concentrations and allow the vehicle to traverse uneven ground smoothly. A restraining mechanism is provided which prevents uncontrolled swinging of the cask. A cam-locking mechanism prevents unexpected retraction of the boom assemblies, increasing the safety of the design. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. The invention, together with the further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings, wherein like reference numerals identify like elements, and wherein: 
     FIG. 1 is a front view of the cask transporter system embodying various features of the invention. 
     FIG. 2 is a side view of the cask transporter shown in FIG.  1 . 
     FIG. 3 is a top view of the cask transporter shown in FIG.  2 . 
     FIG. 4A is a front sectional view of the boom assembly with a lift cylinder in an upright orientation, and FIG. 4B is a front sectional view of the boom assembly with a lift cylinder in an inverted orientation. 
     FIG. 5A is a detailed side view of a cam locking mechanism shown in FIGS. 1 and 2 and FIG. 5B is a detailed front view of the cam locking mechanism shown in FIGS. 1,  2  and  5 A. 
     FIG. 6 is a front view of a cam engaging a boom assembly. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the figures, and, in particular, to FIG. 1, a cask transporter system  10  includes a gantry  12 , a platform  14  and two tread mechanisms  16 . The cask transporter system  10  generally comprises a self-propelled vehicle that lifts, transports and positions radioactive waste storage casks. The gantry  12  is connected to the platform  14 , which is connected to the tread mechanisms  16 . The tread mechanisms  16  are spaced apart by the platform  14  and the gantry  12  and are driven by conventional hydraulic motors  18 . 
     The gantry  12  includes two extendible boom assemblies  20 , a beam  22  and a restraining system  24 . The beam  22  is connected by pin joints  26  at the tops of the boom assemblies  20  to allow for slight variance in the extension of the two boom assemblies  20 . The joints  26  provide excellent lateral stiffness while allowing extension discrepancies to take place without fatigue or failure of the beam  22 . 
     Conventional couplers  28  such as chains, cables or other conventional rigging equipment are used to connect a cask  30  to the beam  22  for transporting as shown in FIG.  2 . As can be seen in the drawings, the cask  30  is a substantially cylindrical, vertically orientated cask. The cask can be 17 feet high and weigh up to 135 tons. The cask  30  is coupled to the beam  22  when the boom assemblies  20  are fully retracted. The boom assemblies  20  must then be extended to lift the cask  30  off the ground with the beam  22  and the couplers  28 . 
     The boom assemblies  20  each comprise an outer support section  32  and an inner telescoping section  34  slidably received within the outer support section  32 . The outer support section  32  is securely connected to the platform  14  by support structures  36 . It will be apparent to one of ordinary skill in the art that a wide variety of support structures can be used equivalently to support the extendable boom assemblies  20 . However, angled structures  38  connected to the platform  14  as shown in FIGS. 1 and 3 are preferably used. 
     A hydraulic cylinder  40  is connected to the outer support section  32  and is disposed within the inner telescoping section  34  of each boom assembly  20 . The hydraulic cylinder  40  is supplied with pressurized hydraulic fluid by a hydraulic pump  42  driven by a propane engine  44  mounted on the platform  14 . The flow of the pressurized hydraulic fluid is controlled by a conventional valve  46  mounted in the control console  48 . The valve  46  can be controlled from the control console  48  or from an auxiliary pendant control  50  which enables remote operation of the system  10 . All of the hydraulic components are coupled by a conventional hydraulic system in a manner which will be apparent to one of ordinary skill in the art. 
     The inner telescoping section  34  in each boom assembly  20  is extended under power from the hydraulic cylinder  40  when the pressurized fluid is directed through the valve  46  to the hydraulic cylinder  40 . The ram  52  of the hydraulic cylinder  40  extends upward (in the upright configuration shown in FIG. 4A) to contact the upper plate  54  of the inner telescoping section  34 , thereby extending the inner telescoping section  34  as well. The hydraulic cylinder  40  can also be mounted in an inverted position as shown in FIG.  4 B. 
     Because the outer support section  32  is securely connected to the platform  14  and the tread mechanism  16 , and because the boom assemblies  20  are connected to the beam  22 , the beam  22  extends upward coordinately with the boom assemblies  20 . The connection between the cask  30  and the beam  22  using the couplers  28  lifts the cask  30  coordinately with the beam  22 . In this way, the cask  30  is raised to a transport position. If additional lifting height is desired, multiple stage boom assemblies such as the assemblies shown in U.S. patent application Ser. No. 07/971,333, filed Nov. 4, 1992 (and assigned to the assignee of the present application), now U.S. Pat. No. 5,865,327 can be used. 
     In order to improve the security of a raised cask  30 , the boom assemblies  20  are provided with cam-locking mechanisms  56  shown in FIGS. 5 and 6. Each cam-locking mechanism  56  comprises a toothed cam  58  as shown in FIG.  6 . The cam-locking mechanism  56  is mounted on a support  60  that allows rotation of the cam-locking mechanism  56  about the support  60 . It will be apparent to one of ordinary skill in the art that a wide variety of mounting techniques for the cam-locking mechanism  56  can be used, provided the technique enables frictional engagement of the toothed cam  58  with the inner telescoping section  34  of the boom assembly  20 . The cam-locking mechanism  56  is retained in its disengaged position A by hydraulic pressure. When the hydraulic pressure drops to a level where the hydraulic cylinder  40  might begin to retract unexpectedly, the cam-locking mechanism  56  rotates under pressure from spring  57  to engage the boom assembly  20  to which it is mounted. This engagement prevents retraction of the hydraulic cylinder  40 , thus preventing unexpected lowering of the cask  30 . The unlocking cylinder  61  is pressurized to release the cam-locking mechanism  56  from its fictionally engaged configuration. 
     The platform  14  and the tread mechanism  16  enable the cask  30  to be transported over uneven ground and through buildings with minimum floor loading concentrations. The platform  14  comprises a substantially C-shaped structure as shown in FIG.  3 . This shape of the platform  14  allows the cask transporter system  10  to be driven over and around the cask  30  for engagement therewith. Gussets  62  are provided to strengthen the corners of the platform  14 . The gantry  12  is located midway along the platform  14  and is rigidly connected thereto as described hereinbefore. While various materials can be used for all of the components referred to herein, preferably steel or other durable materials are used. 
     The platform  14  is carried by the tread mechanism  16  as coupled thereto. The tread mechanism  16  comprises a left track  64  and a right track  66  mounted on guide rollers  68  and drive sprockets  70  in a conventional manner. The left track  64  and right track  66  are held in a desired spaced relationship by the platform  14  and its connections to the left track  64  and right track  66 . The tread mechanism  16  provides substantial surface area over which the weight of the cask  30  being carried by the gantry  12  can be distributed, thereby minimizing floor loading concentrations. 
     The restraining system  24  is coupled to the gantry  12  to prevent the cask  30  from swinging and adversely affecting the stability of the cask transporter system  10 . Through various types of restraining systems can be used, preferably a damped system comprising cushion hydraulic cylinders  72  coupled in a conventional manner to an accumulator  74  is used. This damped restraint enhances the stability of the cask transporter system  10 , allowing quicker and safer braking. 
     While a particular embodiment of the invention has been shown and described, it will become obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.