Measuring and testing – Volumetric content measuring
Reexamination Certificate
2001-12-18
2004-01-13
Raevis, Robert R (Department: 2856)
Measuring and testing
Volumetric content measuring
Reexamination Certificate
active
06675643
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a device for measuring the volume of containers such as jars or bottles for quality control purposes, and a method for measuring the volume of the same.
BACKGROUND OF THE INVENTION
Containers are formed by various methods of production and from various materials. Plastic containers can be formed by introducing a desired amount of material into a mold and then blowing air into the material to force it against the walls of the mold (blow molding) or by pulling a vacuum between the mold and the material to pull the material to the wall (thermoforming). Alternately, containers can be made by the injection molding process, or rotomolding. For glass containers, glass blowing is frequently used, as is well known and discussed in the patent art. Containers can also be fabricated from metal or other materials by various methods.
In the container manufacturing industry, it has been the practice to maintain consistency in the production of containers to assure that they meet the targeted volume capacity. For example, for molded containers, quality control techniques have been developed to determine whether the container material is adequately conforming to the walls of the mold. Meeting these requirements depends on whether certain process parameters, such as the temperature of the material and the conditions of the forming operation, are within tolerable limits. It has been found that measuring the volume of the resulting containers not only provides verification of this important parameter, but also provides an excellent way to determine whether the containers are adequately conforming to the mold walls and whether the containers will meet the targeted volumetric content when filled to a predetermined fill line.
Two different volume measurements are of concern when dealing with containers. The first is the ultimate, brimful volume of the containers, normally referred to as the OverFlow Capacity (OFC). The OFC includes the volume up to the upper rim of the opening. The second measurement is the Fill Line Volume (FLV), which is the volume to a fill line plane to which the container is intended to be filled. Thus, when the properly sized container is filled with liquid such that the surface of the liquid resides in the fill line plane when the container is upright, the volume of liquid equals the FLV. The FLV must meet the packaging target of such containers, and normally becomes a specified amount on the label of most products sold in containers. For monitoring production, once standard production parameters have been established, it is sufficient for quality control purposes to measure and control the OFC of the containers.
The standard method for determining the volume is to fill the container with water and weigh the container with and without the water, using the net water weight and its density to calculate the volume. This method requires filling the container consistently to a particular fill height, as well as making accurate measurements of both weight and temperature, the latter to compensate for changes in the water density. When performed manually, the method is very labor intensive and is subject to operator limitations, making repeatability problematic.
An alternative approach for determining volume is taught in U.S. Pat. No. 5,319,957, which teaches the use of a piston to compress air in the container being tested. The pressure in the container is sensed and the volume determined from the change in pressure. While this approach eliminates the need to fill the container precisely with liquid, it is extremely complicated and requires complex equipment and calculations to obtain the volume measurement. An additional problem is that many containers are sufficiently thin and flexible that the volume may change as the pressure inside the container is increased. Further, this method cannot be used for the determination of the volume to the fill line level.
Thus, there is a need for a simple device and method for measuring the volume of containers which does not require complex equipment or calculations, and which is independent of the exact volume of fluid employed for measuring.
SUMMARY OF THE INVENTION
The present invention provides a device and a method for measuring the volume of containers having a rim. The method is easily executed and the container volume measuring device is simple in structure and provides reliable results. The container volume measuring device has a reservoir of known volume having an upper bounding surface. Preferably, the known volume is comparable to but slightly larger than the volume of the containers to be measured.
A measuring tube is also provided. The measuring tube has a first end and a second end, and has a measuring tube passage which passes therebetween. The measuring tube passage has a passage volume greater than the difference in volume between the known volume of the reservoir and the volume range of the containers to be tested. The measuring tube is positioned such that the first end is sealably attached with respect to the reservoir such that the measuring tube passage communicates with the reservoir. It is preferred that first end of the measuring tube be at the bounding surface of the reservoir, since such will leave the known volume unobstructed. The measuring tube is also attached to a container mount which is configured to sealably engage the rim of the container. The container mount is attached to the measuring tube such that the measuring tube passage communicates with the container at the second end of the measuring tube when the container is attached to the container mount. The measuring tube passage is preferably configured such that the height of liquid in the measuring tube can be correlated to the volume of liquid contained therein. More preferably, the measuring tube passage has a constant cross section such that the height of liquid therein varies linearly with the volume of liquid residing in the measuring tube.
Means are provided for measuring the volume of liquid residing in the measuring tube. When the height of liquid in the measuring tube is correlated to the volume of liquid contained in the measuring tube passage, such means can be provided with various means for measuring the height of the liquid. In one embodiment, the measuring tube is provided with a window of sufficient size to allow the height of the liquid in the measuring tube to be viewed independently of whether the reservoir or the container is beneath the tube. The window in turn has indicia thereon, allowing an operator to visually measure the height of liquid in the measuring tube which is correlatable to the volume of the liquid in the measuring tube. When the tube passage has a constant cross section, the height of the liquid in the measuring tube will be directly proportional to the volume and the indicia can be used to read the volume directly.
The measuring tube is mounted to a support, which allows the measuring tube to be pivoted between two measuring orientations. Preferably, in each of the two measuring orientations the measuring tube is substantially vertical. In the first measuring orientation, the first end of the measuring tube is lower than the second end, while in the second measuring orientation, the first end is elevated above the second end. Preferably, stops are provided on the support to limit the motion of the measuring tube to prevent the measuring tube from being pivoted beyond the two measuring orientations.
When the measuring tube is oriented such that the first end of the measuring tube is lower than the second end, the reservoir and the measuring tube are filled with liquid such that the liquid partially fills the measuring tube. The volume of liquid is selected to be at least as great as the maximum volume of container anticipated. The volume of the liquid in the measuring tube is the excess volume of liquid equal to the difference in volume between the total volume of liquid and the known volume of the reservoir, and is defined as a first excess volume, which is ass
Raevis Robert R
Semprebon Jeffrey E.
Weins Michael J.
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