Patent Application
20120061150
There are no cross-related applications.
The present invention generally relates to scales and weighing apparatus employing load cells and having means to prevent damage of the load cell due to an overload, and more particularly to rotary carousel scales.
Many checkout stations in retail establishments embody a rotary platform on which is mounted a series of bag racks. Each bag rack contains a stack of plastic bags, the front one of which can be opened in order to pack goods after scanning them prior to making payment. Since the bag racks are arranged in a circular fashion, successive bags can be brought to the front for packing by rotating the platform.
On self-checkout versions of these stations, in which customers do their own scanning and packing, a means is necessary for checking that the items placed in the bags are the same as scanned, to detect for possible fraud. Weight can be used for this check and when this is required, a rotating platform can be constructed so as to weigh the bags and contents. In common with static types of scale used for this purpose, the scale requires a high resolution and fast response. When a round, rotary platter is required, the easiest method of support is a centrally mounted “single-point” load cell designed to support such a rotary platter when fitted with a bottom and top frame.
Rotary carousel scales can be constructed using a single, centrally mounted load cell with bottom and top frames. The bottom frame fits inside the scale housing and supports the scale while the top frame is fitted with a centrally mounted shaft which holds the rotary platter in position; wheels mounted on the extremities support the rotary platter and allow it to rotate freely. This arrangement, whilst providing adequate strength and performance, is expensive to construct and awkward to transport.
A much lower cost solution is to mount four load cells at the platform support points and tie their upper load application points together with a sub-frame which in turn supports four or more wheels. A shaft is mounted at the center of this sub frame to hold the platform in position. Overload protection for the load cells can be incorporated internal to the load cell mounts or be external, as part of the frame. The assembly has a much lower overall cost, is highly accurate and can be shipped as a complete assembly or as a kit, saving space and shipping cost.
The aforesaid and other objectives of the present invention are realized by generally providing a rotary carousel scale comprising a rotary platter mounted on a shaft, the shaft being located at the center of the rotary platter, the rotary platter being free to rotate along the shaft; at least three load cells comprising loading points; a plurality of resilient mounts, the resilient mounts being connected to the loading points of the load cells; a frame disposed on the resilient mounts; a plurality of wheels, the wheels being disposed on the frame, the rotary platter being disposed on the wheels, and the rotary platter rotating on the wheels.
The invention described herein provides a rigid frame attached to a plurality high-accuracy load cells.
In a preferred embodiment, the rotary platter is mounted on a rigid frame attached to four high-accuracy load cells. The load cells can be mounted on a frame which is part of the structure of the checkout counter, whilst the rotary platter provides the base on which the bag racks are attached. Since the load cells are adjusted to all have the same output, the scale weighs objects placed on it with high accuracy, regardless of their position on the platform.
In a still preferred embodiment, the frame is rigidly attached to the resilient mounts. The rotary carousel scale may further comprise an overload protection device comprising a body and a stop portion, the stop portion being adapted to stop a downward movement of the frame. In a still preferred embodiment, each of the load cells is installed underneath one of the wheels.
One of the objectives in this particular design is cost. The use of very low cost load cell assemblies with a light frame to support the wheels and platform result in a cost-effective solution that also eases shipment and service.
The rotary carousel scale of the present invention supports a rotary platter in such a way that it is free to rotate while weighing items placed anywhere on the rotary platter with a high degree of accuracy.
The rotary carousel scale of the present invention allows several load cells to be coupled together at their loading points in such a way that their individual and joint accuracy is not impeded.
The rotary carousel scale of the present invention provides a stable mounting surface for the wheels that support the rotary platter, which sufficient strength to support the full gross weight of the rotary platter and load.
The rotary carousel scale of the present invention either allows the load cells' built-in overload protection to function or provides external overload protection for the load cells.
The features of the present invention which are believed to be novel are set forth with particularity in the appended claims.
The above and other objects, features and advantages of the invention will become more readily apparent from the following description, reference being made to the accompanying drawings in which:
A novel rotary carousel scale will be described hereinafter. Although the invention is described in terms of specific illustrative embodiment(s), it is to be understood that the embodiment(s) described herein are by way of example only and that the scope of the invention is not intended to be limited thereby.
It is to be noted that the rotary carousel scale described in the present application is not limited to supermarket application. Indeed, the invention described can be used with almost any application involving a rotary carousel scale.
Self-serve checkout station preferably includes a computer which may be configured similar to known microprocessor-based computers and has a CPU, a plurality of storage devices and an I/O interface. The storage devices may include program memory, RAM, non-volatile memory (such as ROM, EEPPROM, etc.), and any or a combination of the mass storage devices known conventionally in the art, such as floppy disk, optical disk, hard disk and/or tape cartridge drives, plus appropriate device drivers. A product lookup database may be stored in the storage devices. The CPU communicates via the I/O interface with the load cells (not shown in
The rotary platter 101 shown in
According to the present invention, the rotary carousel scale comprises three, four or more load cells 101 that support a frame or plate 102 which in turn supports a plurality of wheels 103, mounted in suitable brackets. The wheels 103 are in contact with the bottom surface 120 of the rotary platter 105. In the embodiment shown in
The use of resilient mounts eliminates side loading and moment forces from affecting the load cells.
It is to be noted that the wheels may be mounted on the frame directly over or close to the load cell support points or not. However, when each of the load cells are mounted underneath one of the wheels which supports the rotary platter, it results in a rigid assembly with faster response to weight changes. Fastest response is an important criterion when assessing suitability for use in some retail situations.
The use of a rigid frame joining the load cell loading points and supporting the wheels prevents side loading or moment forces from reaching the load cells, which could reduce accuracy or possibly damage the load cells if sufficiently high in value.
In a preferred embodiment, the rotary carousel scale utilizes typically four load cells of either planar-beam or single-point type, fitted with the frame and the wheels to support the rotary platter. A planar beam load cell type, when compared with the average single-point load cell, has a more linear response or, putting it another way, the error over the range from zero to full scale is lower.
The planar beam load cells used in this application are calibrated to be equal in output, with a small margin of error. They are either connected in parallel, which has the effect of giving the numerical average of the outputs of all the load cells within a very tight margin, or connected separately to different inputs on a signal conditioner or transmitter which sums the separate inputs, allowing them to be combined into a value that is translated into lb or kg for use. They work in combination to give an equal reading when a weight is placed anywhere on the rotary platter. Each load cell used is preferably adjusted during factory calibration to give the same output, measured in millivolts, when the same load is applied. The allowable error is preferably +/−0.1% of reading.
The frame can be attached through rubber ‘vibration mounts’ which have either threaded studs or female threaded inserts at their top and bottom. The rubber allows enough lateral movement to ensure accuracy but only a small amount of vertical movement, preserving rigidity and maximizing speed of response. Equally well, rubber ‘bumpers’ (similar to the rubber feet found on many appliances) can be used provided that some form of horizontal location is provided.
Typical ‘vibration mounts’ made from rubber are available from hardware supply houses such a Spae-Naur. The rubber is vulcanized onto an upper and lower metal plate onto/into which the threaded restraint is mounted.
While illustrative and presently preferred embodiment(s) of the invention have been described in detail hereinabove, it is to be understood that the inventive concepts may be otherwise variously embodied and employed and that the appended claims are intended to be construed to include such variations except insofar as limited by the prior art.
