Geometrical instruments – Miscellaneous – Light direction
Reexamination Certificate
1999-07-06
2001-02-20
Fulton, Christopher W. (Department: 2859)
Geometrical instruments
Miscellaneous
Light direction
C033S227000, C033S121000, C356S370000
Reexamination Certificate
active
06189223
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to a volumeter.
Devices of this type are suitable for measuring the volume of items with a surface which cannot be measured by simple geometric outlining and/or a surface which has individual structures such as straps, strings, layers of packaging paper, etc., or which is deformable. The device serves primarily but not exclusively to determine the volume of packages or similar items which are to be sent through the mail.
In addition, the invention pertains to a self-service postal station which is equipped with a volumeter of this type.
2. Description of the Related Art
Self-service postal stations of this type are known (see, for example, WO 92/17,861 and EP No. 643,374). At these postal stations, however, it is primarily the weight and not the volume of the postal item which is used to determine the amount of postage required. Only the maximum dimensions of the postal item are limited by mechanical devices (size of the feed slot). Additional light-optic sensors monitor the positioning of the postal item within the acceptance space and its required minimum dimensions. In another known system (Zuhlke Engineering AG, Schlieren-Zurich, Publication No. 66, “Developing New Products and Production Processes with Automation”), a linear light barrier determines the thickness of the item to be mailed (a letter), which is merely inserted into the receiving slot, and an electronic camera determines the surface area of the item. The volume of the letter is then calculated from these two values. To improve the measurement racy, a Fresnel lens is swung between the camera lens and the item being mailed so that the focal points of the camera lens and the Fresnel lens coincide. This solution is expensive, and the measured volume is also negatively affected by various features specific to the item being mailed (material projecting beyond the surface of the item such as flaps of packaging paper, strings, etc.).
The transport costs of an item, however, must often be determined not only on the basis of weight but also on the basis of the volume of the item. It has now been shown that, for a wide variety of reasons (cost, technical complexity, avoidance of damage to the item, etc.), volumes should be measured by means of contactless measuring methods (e.g., light-optic, ultrasonic sensors, etc.). In these measurement methods, however, the disadvantage is that a correct measurement can be disadvantageously affected by the structure and nature of the item. For example, projecting folds or edge reinforcing strips on items wrapped in packaging paper or loosely attached string can cast shadows and thus easily fool the device into concluding the item is larger than it really is. Items which rock back and forth or which fail to come to rest in some other way during the measurement are also measured incorrectly.
SUMMARY OF THE INVENTION
The task was therefore to create a volumeter which does not suffer from the disadvantages described above.
In addition, a self-service postal station is to be created, in which the volumes of all the submitted objects (packages, thick letters, etc.) are detected in a repeatable and defined manner so that the correct postage can then be calculated. It should also be possible for the device to be integrated into postal mailing stations operated by the customer himself or herself without a great amount of effort with respect to construction or operation. It should also be possible for the device to be protected against natural and intentional damage and contamination.
In accordance with the present invention, the volumeter is characterized in that the item to be measured can be acted on in at least one of the three main spatial directions by a surface which can be moved in this direction.
Preferably, the surface is the surface of a solid or grid-like plate, which can be pressed down onto the item by a movable holder at a force or at a constant pressure produced by this force, i.e., under a load which is independent of the surface area of the item acted on by the plate and in that the item to be measured rests on a support surface essentially parallel to the surface.
The two other main spatial directions can be measured by means of an optical camera acting through the surface.
The camera is mounted on the carrier at a fixed distance from the surface and can be moved along the surface.
An illuminating device is provided which is mounted in such a way that no light reflections on the surface or on the carrier of the surface which could interfere with the measurement are visible to the camera and/or in that a polarizing filter is present, by means of which the reflections detected by the camera can be filtered out.
In the area of the surface, a mirror, which moves with the surface, is provided, which projects the coding of a height measurement scale into the lens of the camera, the scale being mounted in a stationary manner with respect to the support surface and oriented in the direction in which the surface moves.
The surface is part of a transparent glass or plastic plate or of a wire or bar grate.
The surface has, for example, a replaceable protective layer or the surface is hardened.
In accordance with the invention, a self-service postal station equipped with the above described volumeter is characterized in that the holder of the surface is connected to a closing device for closing and opening a mail feed slot and/or is driven by it.
The surface which can be laid on the item to be measured stabilizes the item and smooths/conditions the surface of the item in direct contact with the surface.
Optimum results are achieved when the applied force is in the range of only 1-10 N. Because most packages consist of pairs of parallel surfaces, the surface which supports the item is preferably parallel to the surface which presses down on the item. By adjusting the above-cited force, it is possible, of course, to keep the pressure applied to packages of different surface areas constant. In this way, both large and small packages can be subjected to the same specific load.
Of course, this last-mentioned method of applying pressure means that the pressing force must be controlled as a function of the surface area or cross-sectional area of the package. As shown in the following, however, the volumeter has suitable means for determining this area even before the plate presses down on the package. This means that the system which controls the device must be designed in such a way that as soon as the volume-measuring process begins or shortly after it has been initiated, the camera detects a first cross-sectional image of the package, and the computer then converts this image into the (approximate) surface area of the top of the package. On the basis of this area, the computer then calculates the required force to be applied to achieve the desired applied pressure. By means of a simple force-measuring device such as a strain gauge bridge or some other conventional method, this force can be measured in situ after the plate has been set onto the item. The signal thus obtained can be sent as an actual-value signal to a force control unit in the best way available. Because the cross-sectional area of the package required to calculate the force to produce a given applied pressure is determined before the plate makes contact, a (usually) small error in the area can result, but as a rule this is can be readily tolerated. But it is also conceivable, as a way of avoiding this error, to allow the plate to make light, initial contact with the package at a small preliminary pressure. The actual determination of the package volume is then made at a greater applied pressure. Thus the difference between the first-cited, less precise, method and the more precise method explained second can consist in the more complicated programming of the device's computer.
In principle, the dimensions of the item can be detected in all three primary dimensions of space by any desired measuring devices such as mechanical feelers, u
Fulton Christopher W.
Kueffner Friedrich
LandOfFree
Device for measuring volume does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Device for measuring volume, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Device for measuring volume will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2566006