Sheet metal container making – Method – Assembling receptacle with closure
Reexamination Certificate
2000-05-30
2003-09-23
Hong, William (Department: 3725)
Sheet metal container making
Method
Assembling receptacle with closure
C413S006000, C413S031000, C413S040000, C413S041000
Reexamination Certificate
active
06623230
ABSTRACT:
TECHNICAL FIELD
This invention relates to can closing machines. Specifically this invention relates to a double seam forming can closing apparatus which identifies defects and rejects cans with improper seams. This invention further relates to a double seam forming can closing apparatus in which the seam forming parameters may be set up more rapidly and reliably.
BACKGROUND ART
Canning equipment and processes are commonly used in a variety of industries. Canning processes are often used to preserve food products because such products can be processed and promptly hermetically sealed within a can. Canning operations may be performed at high speed and at a reasonable cost. The sealing of cans is important because an improper seal may result in the infiltration of air to the interior of the can. This may result in bacterial growth and premature spoilage.
Can closing machines are known in the prior art. One type of can closing machine secures an end to a can body after the product has been placed in the can by formation of a folded double seam. An example of a double seam forming machine which secures top ends to can bodies is shown in U.S. Pat. No. 3,465,703. The disclosure of this Patent is incorporated herein by reference.
The goal of a double seam forming machine is to produce a perfect seam which extends about the circumference of every can that passes through the machine. Unfortunately this is not always possible. Undesirable conditions may occur due to defects in either the can body or the can end. Such defects may include undesirable variances in dimensions in which the ends do not perfectly “fit” the can bodies. Variations in metal thicknesses may also occur which impacts the ability to form a proper double seam.
Other conditions which may cause imperfect seams include cracks or tears in the can bodies or can ends. Such defects may result in loose or open spaces in the seam. Similarly, defective manufacture of the ends or bodies may result in folds or areas having excessive metal thickness. Such defects in the area of the seam also prevent proper seam formation.
Defects in the chucks or rolls which are used to form the seams can also result in defective can seams. Such defects may include the accumulation of metal on a chuck or roll. The accumulated material causes irregularity in the tooling surface in contact with a seam as it is being formed and can result in an improper seam. Alternatively the-chucks or rolls used to form the seam may crack, producing a gap. The seam is not properly formed in the area of the gap which results in improper can closure.
Double seam can closing machines generally include several stations where cans are formed. They include multiple associated sets of chucks and rolls which perform the same operations. If a tooling problem occurs at one chuck or roll, it will not be readily apparent because only cans that have been acted upon by the defective tooling will exhibit an improper seam. Double seam forming machines typically operate at very high production rates. It is therefore difficult to detect a problem as soon as it occurs. Hundreds or thousands of cans that are potentially defective could be closed before a problem is noticed.
In an effort to improve the inspection of can seams produced by a double seam can closing machine, others have developed devices to monitor seam quality. An example of such a device is shown in U.S. Pat. No. 4,600,347, the disclosure of which is incorporated herein by reference. This Patent discloses a modification to a standard can closing machine in which force sensors are installed on a stationary cam. Cam followers move around the stationary cam in engaged relation therewith. The cam followers are in connection with the rolls which contact the can ends and chucks which form double seams. The contour of the cam moves the cam followers, which in turn move the rolls to form the seams.
In the prior art device the sensors on the stationary cam detect the force applied by the cam followers during the final ironing turn of the can seam before the can leaves the machine. The force applied to the stationary cam by each cam follower during this operation corresponds to the configuration of the formed can seam about its circumference. The prior art device works on the principle that by monitoring the force applied by the cam follower for each station as it performs the final ironing turn on the seam, certain defects can be identified. Common defects include situations where the seam is either too tight or too loose. Such defects may arise in the form of a consistently high or low force or a transient force “spike”. A high transient force spike indicates excessive metal on either the can seam, forming roll or a tooling chuck. Alternatively, a transient low spike may be indicative of a cracked tooling roll or chuck, or a gap or tear in a can seam.
While the device shown in U.S. Pat. No. 4,600,347 represents a significant advance in the detection of seaming problems, it suffers from several drawbacks. These drawbacks include the fact that double seam forming can closing machines generally include many stations. The tooling associated with each can closing station is somewhat different. This results in variation of the force that is applied by each cam follower as it moves across the force-sensing portion of the stationary cam. As a result, the amount of force associated with a “good” seam in different stations can vary significantly. The prior art devices cannot account for this variation in normal loading between the various machine stations. Rather, the prior art generally compares the applied seam force to a single high limit or low limit for all the stations. These limits must have a range that accommodates the force at all machine stations. An improper fault indication may result if the limits are set too narrowly. However, if the limits are set too widely then defective cans may be allowed to pass.
A further drawback associated with the prior art is that force variations that result from excess metal or a broken seam or chuck, are only detected if the corresponding spike is sufficiently “high” or “low” to extend beyond the limits which are established for a tight or a loose seam. Spikes or breaks that occur within the limits may be indicative of a developing tooling problem and/or have adverse consequences for the seam. However, in the prior art such conditions may go undetected.
A further drawback associated with the prior art is that developing problems with tooling, can bodies and can ends often go undetected until one of the limits is exceeded. Dimensional changes in the seam may begin moving the seam tolerances toward a limit. Such movement of seam conditions away from the optimum, increases the risk of seam failure. It may be advisable to correct such problems before they result in a fault condition. Unfortunately because the prior art devices cannot account for variations from station to station, such trends are difficult to detect.
Can seamers usually run at high speeds. As a result if a single can exhibits a fault condition, it is necessary to either shut the machine down or to locate the defective can among a large population of good cans. Stopping the machine delays production which increases costs and requires a set-up person's attention for restart. Alternatively, not shutting the machine down while attempting to locate the can that is defective may be very time consuming. Visual inspection often may not readily distinguish a defective can which further complicates the problem.
A further drawback associated with the prior art systems is that they may be subject to false triggering. Vibration or other conditions may result in short-term “noise” from the sensors on the stationary cam. This noise may produce a signal which falls outside the high and low limits, which causes a fault indication to be given. Considerable effort may then be expended in an effort to locate a problem that does not exist.
A further drawback associated with such prior art systems is the time necessary to set up the system. Gener
Bagheri Ali
Bernstein Jeffrey K.
Hong William
Jocke Ralph E.
Pneumatic Scale Corporation
Walker & Jocke
Wasil Daniel D.
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