Weighing assembly

Details Weighing assembly Weighing assembly

1999-04-23

2001-11-20

Gibson, Randy W. (Department: 2859)

Weighing scales

Structural installation

C177S126000, C177SDIG009

Reexamination Certificate

active

06320142

ABSTRACT:

This invention relates to improvements in weighing of objects, and in particular to an improved assembly for mounting a load cell.
It is known to measure the weight of a container or tank by placing the container or tank onto a load cell. Often, more than one cell is used and the combined total of the weights measured by the multiple cells is used as an indication of the overall weight. The load cell typically comprises a beam which is fixed at one end onto a mounting assembly and supports a load on a button at an opposing end. The load acting on the button deflects the beam, inducing stresses which can be measured. Of course, many other arrangements of load cell are known.
In order to correctly transfer the weight of the container or tank (and its contents) onto the load cell, it is known to provide a mounting assembly comprising a base onto which the load cell can be affixed and a movable platform. The mounting assembly is installed usually underneath the object to be weighed and the movable platform is secured to the object. The load cell is mounted onto the mounting assembly in such a manner that the weight of the object acts down onto the load cell through the platform. The mounting assembly steadies the load as well as locates it onto the load cell.
With large and heavy objects (up to 20 tonnes or more), there is considerable engineering expertise required to install the mounting assembly and the load cell in position relative to the load. As all the weight must be accurately guided onto the load cell, the object must first be lifted prior to inserting the mounting assembly. The object must then be lowered down onto the platform, which in turn is compressed onto the load cell.
It is known to provide a mounting assembly which can be installed prior to installation of a load cell. This comprises a base defining a support for a load cell, a moveable support member adapted to be moved relative to the base, and a moveable platform. The platform sits on top of the moveable support member, and in the installation (non-working) position, the support member is locked to the base in a first position. This allows the platform and support to be slid under the object. A load cell is then inserted into the mounting assembly below the platform. Finally, the support frame is lowered, causing the platform and the object to drop down onto the load cell. Eventually, the support is lowered sufficiently that all the load and platform is supported on the load cell. Thus, the load cell can be easily installed after the initial steelwork is complete and the mounting assembly has been set in position.
Whilst the prior art mounting assembly is advantageous in that it allows the load cell to be removed and inserted at any time after the mounting assembly has been installed, it is not without its problems. The moveable support member for the platform which can be raised and lowered relative to the base is complex to engineer, and must withstand high loads.
In accordance with a first aspect, the invention provides a mounting assembly for use in combination with a load cell adapted to measure the weight of an object comprising:
a fixed portion comprising a base means and a support means; and
a moveable platform adapted to be supported by the support means when in its installation (non-working) position, in which the platform is adapted to be raised from its non-working position to a working position by means of a lever, and in which the moveable platform is adapted to be supported by the load cell in this working position.
The lever may comprise a load cell. Thus, the mounting assembly may be adapted to be moved into position relative to the object in its installation (non-working) position and a load cell may then be used to raise the moveable platform to its working position.
The support means may comprise a support member spaced from the base means by a support frame to define a cavity. The support member may be fixed relative to the base means. The load cell may be located at least partially within the cavity.
The fixed portion may include one or more threaded mounting holes adapted to receive a respective threaded bolt for securing a load cell onto the base means. The support frame may be fixed relative to the base.
The load cell may comprise a shear-beam type cell, or any other known kind of load cell.
The support member may comprise a substantially planar element integral with the support frame and having an opening therein through which a portion of the moveable platform is passed.
The moveable platform may comprise a plate like member having an upper surface adapted to engage the load or object and a lower surface from which an extending portion projects. The extending portion may be adapted to be accommodated in the opening in the support member.
The support member may be provided with a raised protrusion or wall around the opening on its upper face. This may be adapted to contact the lower face of the moveable platform in the non-working installation position.
The raised protrusion may be a continuous or discontinuous wall having a substantially conical cross-section fixed around the opening in the support member. The top or peak of the wall may be machined flat. The raised wall is advantageous as it holds the platform slightly proud of the surface of the upper face of the support member. Any dirt or foreign bodies collecting on the support member fall off the sides of the wall onto the support members surface.
The extending portion of the moveable platform may be a loose fit within the opening in the support member. Thus, the platform is allowed to move in a plane parallel to the surface of the support member by an amount equal to the clearance between the extending portion of the platform and the opening.
A spacer portion may be provided on the free end of the extending portion of the platform. It may be held onto the extending portion by an O-ring which is provided around a circumference of the extending portion and is accommodated within a complementary recess in an upper face of the spacer portion.
The spacer portion may be provided with an elongate slot on a lower face which is adapted to accommodate a button of the load cell. The slot acts to locate the spacer onto the load cell. The spacer portion (and hence slot) may be free to rotate relative to the extended portion to allow the slot to be oriented in a preferred alignment relative to the extended portion.
According to a second aspect, the invention provides a mounting assembly according to the first aspect in combination with a load cell, in which a securing means may be provided whereby as the load cell is secured to the mounting assembly using the securing means, the load cell is adapted to pivot relative to the base means of the fixed portion to act as a lever to move the platform from the installation (non-working) position to its working position.
The securing means may comprise one or more bolts having a head and a threaded shank adapted to pass through one or more respective openings in the load cell to engage one or more respective threaded holes in the base means. The base means may have a stepped profile whereby a portion of the base means directly below the support member may be lower than a portion containing the threaded holes for the securing means, with a step defined between the two portions. The load cell may therefore extend across both portions and pivot about the step as the bolts are tightened, the bolt heads applying a downward force onto the load cell. Alternatively, shims may be used to raise one end of the load cell from the base or alternatively the load cell mounting face may be stepped instead of providing a stepped base.
The bolts may have an outer diameter of the threaded portion so dimensioned relative to the inner diameter of the respective hole in the load cell so that when the bolts are only partially tightened in the holes in the base means the load cell may pivot relative to the axis of the bolts and the base means yet when the bolts are fully tightened the load cell is prevented from moving.

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