Method and apparatus for leak testing plastic containers
a leak testing and plastic container technology, applied in the direction of measurement devices, structural/machine measurement, instruments, etc., can solve the problems of imposing a limit on the through-put of containers being produced, high cost, and complicated conventional leak testers
Inactive Publication Date: 2003-12-18
MCCORMICK JOHN
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- Application Information
AI Technical Summary
Benefits of technology
[0010] The method and apparatus of the invention provide a number of significant advantages over prior art leak testers. A primary advantage is that the leak tester does not restrict the speed of container production. The test station can be positioned downstream from the first (air pressurization) station at whatever distance is required to allow time for the pressure within the container to stabilize and be measured. In prior art systems, the speed of travel of the containers must be restricted so that the containers remain within the loop of the leak tester for sufficient time to complete testing.
[0011] In the invention, there is no need for air hoses connecting the containers to the pressure source, or power supply wiring. The containers are momentarily connected to the pressure source at the first station and then sealed. The test heads are battery powered so that no wiring is required. The heads are energized only momentarily when a pressure reading is to be taken, so that battery life can be maximized.
Problems solved by technology
It will be appreciated from the foregoing description that conventional leak testers are quite complex and expensive.
Not only that, but the leak tester may impose a limit on the through-put of containers being produced, since each container must remain in the leak test loop for a period of time sufficient to complete the pressure test.
Method used
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[0020] Referring first to FIG. 1, a blow moulded plastic container is shown at 20 undergoing a typical leak testing cycle. Air is introduced into the container under pressure from a source 22, through a test head 24 that is sealingly engaged with the mouth of the container. A pressure transducer 26 is also connected to the test head and provides to a programmable logic controller 28, a signal representative of the pressure within the container. Typically, the pressure of the source 22 is slightly above atmospheric pressure, for example, 0.6 psi over atmospheric pressure.
[0021] FIG. 2 is a graph showing the pressure in the container 20 with respect to time. It will be seen that the pressure rises to a peak P as the container expands slightly, and then drops off as the container relaxes. If there is no leak, the pressure in the container will stabilize at a lower value than the peak value. That value is indicated at S in FIG. 2. If there is a leak, the pressure will drop off to a lowe...
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A method and apparatus for leak testing moulded plastic containers in which the containers are conveyed seriatim along a linear path. Each successive container is pressurized at a first station along the path and then sealed to maintain pressurization while being disconnected from the source of pressure. A test station is provided a distance downstream along the path from the first station selected to allow pressure in the container to stabilize if there is no leak. At the test station, the pressure in each successive container is momentarily determined and a signal is provided if a container is determined to be leaking. The apparatus includes battery-powered test heads that are brought into engagement with successive containers at the first station and momentarily energized by an optical transmitter when a pressure reading is to be taken, so that battery power is conserved.
Description
[0001] This invention relates generally to leak testers for moulded plastic containers.[0002] In the blow moulding art, for example, it is normal to route containers leaving a blow moulding machine through a leak tester in which each container is pressurized with air to test for leaks.[0003] Since the containers have some elasticity, the pressure in the container will rise to a peak as the container expands slightly under pressure, and then drop off as the container relaxes. If there is no leak, the pressure in the container will stabilize at a value lower than the peak value. The period of time required for the pressure to stabilize is determined for the particular containers being tested and the pressure in each container is monitored for that period, from initial pressurization. If the pressure is below the defined level at the end of the period, the container has a leak and is rejected.DESCRIPTION OF THE PRIOR ART[0004] In a typical conventional leak tester, the containers are c...
Claims
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IPC IPC(8): G01M3/32
CPCG01M3/3209G01M3/3236G01M3/3218
Inventor MCCORMICK, JOHN
Owner MCCORMICK JOHN