Tank weigh module with excess motion restraint

Details Tank weigh module with excess motion restraint Tank weigh module with excess motion restraint

2000-01-14

2001-12-18

Gibson, Randy W. (Department: 2859)

Weighing scales

Means holding load-driven element against motion

C177S155000

Reexamination Certificate

active

06331682

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to a tank weigh module that is adapted to receive a load cell and that is provided with restraint features for preventing excess motion of the weigh module or the tank or other vessel mounted on the weigh module.
BACKGROUND INFORMATION
Tank weigh modules are generally known in the art for weighing material storage tanks, bins, hoppers and process vessels, so that the amount of material in the vessel can be determined. Typically, the entire weight of a tank or other vessel will be supported on three or four weigh modules respectively arranged between the three or four supporting legs of the vessel and the shop floor or other supporting platform. A typical tank weigh module is, in effect, a housing and interface adapted to receive a load cell and transmit the weight load of the vessel onto the load cell, which then carries out the weighing function. A conventional tank weigh module includes a base that can be bolted to the supporting floor, and a top plate that can be bolted to the supporting leg of a tank. The load cell is arranged between the base and the top plate to receive and measure the weight load. A rocker pin may be used for load introduction into the load cell while rejecting side or lateral loading.
It is also known to provide various restraining structures and arrangements to check or prevent an excessive motion between the base and the top plate of the weigh module. Such checking or excess motion restraint is necessary for maintaining the structural integrity of the weigh module in the event that an excessive travel or other unusual motion is applied to the top plate of the weigh module by the tank or other vessel. For example, if the vessel is subjected to wind loading, seismic tremors, or other forces that would cause a swaying or tilting of the tank, then the weigh modules arranged on one side of the tank are subjected to an excessive downward travel while the weigh modules arranged on the other side of the tank are subjected to an excessive uplift travel. Under such circumstances, the weigh modules may also be subjected to tilting or twisting motions. If such unusual and excessive motion is not checked or restrained, then the tank or other vessel could tip over. For this reason, conventional tank weigh modules typically include various complicated configurations of overlift restraint bolts, check rods, stay rods, restraining dogs or protrusions, and the like.
The conventional provision of the above mentioned check rods, stays, overlift protection bolts, and the like has caused several disadvantages in the known tank weigh modules. Most importantly, the overall construction of the conventional tank weigh modules has become rather complicated and costly due to the various restraining measures. Furthermore, the installation and servicing of the conventional tank weigh modules has also become complicated for the following reasons. First, the various restraining measures often need to be adjusted or installed after installation of the tank weigh module in its final intended application. Secondly, the restraining measures hinder or prevent access to the load cell, so that replacement of the load cell in the event of a failure requires a complete removal and disassembly of the tank weigh module. Finally, at least some conventional tank weigh modules are regarded as providing inadequate restraint or protection against overlift, tilting, and side loading conditions.
SUMMARY OF THE INVENTION
In view of the above, it is an object of the invention to provide a tank weigh module that has a simplified overall structure in comparison to the prior art tank weigh modules, and that has a simplified and improved structural arrangement for achieving restraint and protection against excess motion in overlift, side load, and tilting situations. It is a further object of the invention to provide an improved and simplified arrangement for mounting and securing a load cell into a weigh module. The invention further aims to avoid or overcome the several disadvantages of the prior art, and to achieve additional advantages, as apparent from the present specification.
The above objects have been achieved in a tank weigh module according to the invention, comprising a top plate member, a bottom plate member, and a stop pin or restraining pin that interconnects the top plate member and the bottom plate member to each other with a desired amount and direction of play between the top and bottom plate members. The plate members are spaced apart from each other and adapted to receive a load cell there-between. Particularly, the top plate member includes a top plate and an upper stop block protruding downwardly therefrom, while the bottom plate member includes a bottom plate and a lower stop block protruding upwardly therefrom. A respective bore hole extends substantially horizontally through the lower stop block and the upper stop block, and the restraining pin is received in the two aligned bore holes. One of the bore holes has an appropriate diameter for receiving the restraining pin in a fixed friction-fitting manner, while the other one of the bore holes has a larger diameter than the restraining pin, so as to provide a free play clearance around the pin. For example, the pin is received in the lower stop block with a tight friction fit, while being received in the upper stop block with a loose fit providing a free play clearance. A second free play clearance is provided laterally between the respective mutually opposed facing sides of the upper and lower stop blocks.
With the above arrangement, the top plate remains freely floating in all directions relative to the bottom plate in a normal operating range of motion, whereby the weight load applied to the top plate is transmitted into the load cell and from the load cell into the bottom plate, so that the load cell can carry out its weighing function. However, if an excessive uplift motion in the vertical direction or an excessive lateral motion in a first horizontal direction is applied to the top plate relative to the bottom plate, in excess of the range of motion allowed by the pin free play clearance, then the restraining pin will positively check and prevent any further motion in these directions by coming into contact with the interior bore walls of the larger diameter bored hole in the associated stop block. An excessive lateral motion in a second horizontal direction perpendicular to the first horizontal direction will be blocked or restrained by the respective upper and lower stop blocks coming into contact with each other.
Excessive tilting motions are restrained either by providing at least two restraining pins received in respective stop blocks in a single weigh module, and/or by the mutual cooperation of at least two tank weigh modules mounted on any given tank, and/or by the restraining interaction of the one or more restraining pins and the associated stop blocks, depending on the particular embodiment or configuration of the weigh module and depending on the direction of the excessive twisting or tilting. Moreover, the free play clearance of the pin in the larger diameter hole in one of the stop blocks, and the free play clearance of the adjacent stop blocks relative to each other allows a side-to-side and back-and-forth free floating of the top plate of the weigh module, for example to accommodate thermal expansion of the tank. However, an excessive side-to-side or back-and-forth motion will be prevented or restrained as described above, in one direction by the restraining pin bearing against the inner wall of the larger diameter hole, and in another direction by the two adjacent stop blocks bearing against each other. The relative positions of the top and bottom plates with respect to each other, within the range of motion allowed by the restraining features, will be regarded as “substantially parallel” herein, which encompasses deviations from true parallelism in the allowed range of motion.
The arrangement of blocks connected respectively to the top and bottom plates, and the

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