In order to provide the necessary level of protection and redundancy in current systems, a great deal of mechanical and electrical complexity must be incorporated into the system design. These additional systems and components, in turn, provide multiple points of potential failure that must be monitored, reinforced and/or otherwise protected. Points of failure may, among other things, include the electrical and control circuitry and wiring, the mechanical drive and lift components, and the wires utilised for supporting and lifting the container or other loads.
Fig 1 – an illustration of one embodiment of a known crane system. Fig 2 – an exploded view of a crane system constructed in accordance with the teaching disclosed herein.
It would be desirable to provide a lifting or crane system that could provide for high lifting capacity and/or failure proof hold capabilities while simultaneously utilising a simplified mechanical and control system.
The disclosed crane system may be configured to support a load during a seismic event that could cause the load to momentarily and dynamically increase by a factor of five to ten. One disclosed embodiment is an overheard crane system that includes a trolley which incorporates a support span and carries a drive system on the support span. The drive system may be, in turn, configured to translate the trolley between a first position and a second position.
The crane system may further include a lift mechanism carried by the support span and configured to releasably translate a chain between a support position and a lift position. One exemplary lift mechanism may include a fixed latch configured to engage a first link of the chain, the fixed latch having an open position and a positive closed position, and a travelling latch movably aligned relative to the fixed latch and configured to engage a second link of the chain, the travelling latch having an open position and a positive closed position.
In operation, while the fixed latch is in the open position and the travelling latch is in the positive closed position, the lift mechanism can translate between the support position and the lift position. Similarly, while the fixed latch is in the positive closed position and the traveling latch is in the open position, the lift mechanism can translate between the lift position and the support position. Thus, regardless of the direction of travel of the load or the chain, one of the latches (fixed or travelling) is always in the positive closed position thereby supporting and holding the load.
Fig 3 – a perspective view of an embodiment of a trolley that may be utilised in conjunction with the crane system disclose herein. Fig 3a – top view of the trolley shown in Fig 3.
Technical illustrations
Fig 2 illustrates an exemplary embodiment of a bridge or gantry crane system (200) that may be utilised to transport materials and/or equipment in a conventional manner with a high safety factor utilising mechanical friction brakes or stops in cooperation with a wire rope hoist system (discussed below). For example, in a nuclear power plant the transportation of a reactor head, a reactor vessel, fuel cask or other potentially radioactive or otherwise hazardous load must be conducted in compliance with regulations and laws provided and/or enforced by entities such as the Nuclear Regulatory Commission (NRC). Thus, it is desirable for the crane system to be designed to lift and transport a load while maintaining, for example, a 10:1 lift capacity or ratio to support that load throughout a catastrophic event.
While the likelihood of a dynamic or seismic event occurring during a lift or transport operation is extremely low, the ability to prevent a catastrophic failure is desirable.
The gantry or movable gantry, in turn, supports a trolley (202) configured to carry one or more hydraulic lift mechanisms (204, shown in an exploded perspective view in Fig 2).
The trolley (202) may further include a support deck (210) that spans the distance between the transverse beams (106). The support deck or support span (210) can be configured to carry the hydraulic lift mechanisms (204) and/or any control or hydraulic equipment required to operate the same. The support deck or span may be fixedly attached to the trolley (202), or may be shiftable relative to the trolley structure to allow for precise positioning of the hydraulic lift mechanisms (204). The hydraulic lifts, in one exemplary embodiment, releasably engage a chain (212) that extends through the support deck. The chain includes a plurality of links individually identified by the reference numeral (214). The chain (212), in turn, may be secured to a load (L).
Figs 4 and 4A illustrate an enlarged view of the hydraulic lift that may be utilised in conjunction with the crane systems and trolleys disclosed herein. The hydraulic lift, in this exemplary embodiment, includes a pair of hydraulic cylinders (400) each having an extendable rod (402) and hydraulic cylinder head (disposed within the cylinder and therefore not shown). The extendable rods being hydraulically shiftable between a support or retracted position adjacent to the hydraulic cylinders and a lift or extended position. The extendable rods each include a rod end (404) configured to support and carry a travelling cross arm (406). In this exemplary embodiment, the lift or hydraulic cylinders are substantially vertically lined and arranged in a parallel manner with the respect to each other. Moreover, it will be understood that one or more flow valves (not shown) in fluid communication between the hydraulic cylinders and the hydraulic generation and control equipment (308) may regulate and balance the flow/pressure provided to each of the cylinders.
Fig 4 – view of a lift mechanism that may be utilised in conjunction with the crane system shown in Fig 2 and the trolley shown in Figs 3 and 3A. Fig 4A – a plan view of the lift mechanism that may be cooperatively engaged to a chain.
A fixed cross arm (408) ties together a top or base portion (410) of the hydraulic cylinders. Similar to the travelling cross arm, the fixed cross arm spaces apart and secures the hydraulic cylinders while providing additional rigidity and stability to the overall hydraulic lift. Both the travelling cross arm and the fixed cross arm each support and carry a pair of latches, wherein each pair of latches is individually identified as traveling latches (412) and fixed latches (414), respectively. The latches are one-way latches which allow movement in a single direction and prevent movement in the opposite direction. In this exemplary embodiment, the latches allow vertical movement in the direction indicated by the arrow A1 and prevent movement in the direction indicated by the arrow A2.
In operation, the chain is oriented and aligned substantially in the direction indicated by the arrow A1 and positioned through the slots (416) provided within the travelling cross arm and a fixed cross arm, respectively. The links (214) of the chain (212) are alternately and individually engaged by the traveling latches (412) and the fixed latches (414).
In one exemplary embodiment, each hydraulic cylinder may be a six inch diameter hydraulic cylinder configured to receive 5,200 pounds per square inch (PSI) of hydraulic pressure from the hydraulic generation and control equipment (308).
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About the patent
This article is an edited version of US Patent application 20080159831, published on July 3 2008 and filed on December 31 2006. The inventor is Julian Davis of West Union, South Carolina, USA.
