Material or article handling – Apparatus for moving material between zones having different... – Including trap chamber having horizontal axis of rotation
Reexamination Certificate
1999-02-05
2001-07-10
Werner, Frank E. (Department: 3652)
Material or article handling
Apparatus for moving material between zones having different...
Including trap chamber having horizontal axis of rotation
C422S297000, C422S300000, C426S521000, C432S239000, C053S091000, C198S605000, C198S608000
Reexamination Certificate
active
06257820
ABSTRACT:
TECHNICAL FIELD
The present invention relates to rotary sterilizer vessels and transfer valves therefor and, more particularly, to an atmospheric rotary feed and discharge valve for delivering and receiving containers into and out of an atmospheric rotary sterilizer.
BACKGROUND ART
Atmospheric rotary sterilizers are used to sterilize containers of food products that are high in acid content, while pressure sterilizers are used for food products low in acid, which require more heating to achieve thorough sterilization of the food. Atmospheric sterilization is advantageous over pressure sterilization from an equipment standpoint because atmospheric pressure levels greatly simplify equipment design and operation. With pressure sterilizers, pressure levels as high 45 psi and more are used to sterilize food containers, which requires that transfer valves be sealed to maintain the high pressure levels within the sterilization vessels. Sealed transfer valves require greater power inputs to operate, which complicates associated drive systems. In fact, pressurized transfer valves can utilize up to 80% of the power requirements of a rotary sterilizer system. The high power inputs to transfer valves require complex gearing and precise valve positioning in order to rotate the transfer valves, which complicates design of the drive system machinery and significantly adds to its cost. Complex gearing also limits a sterilizers ability to handle different size containers due to the specific timing requirements of different sized containers.
A disadvantage of atmospheric rotary sterilizers is the upper temperature limits of these machines. Typically, an atmospheric rotary sterilizer is limited to process temperatures of 206 to 210 degrees Fahrenheit, depending on elevation. Pressure sterilizers, of course, can achieve significantly higher temperatures and, thus require shorter processing times.
A rotary sterilizer, either pressure of atmospheric, operates generally as follows. Filled containers enter a processing line by means of a positive feed device, which synchronizes the cans with the rest of the line. From the feed device, the containers are transferred to a rotary valve on the sterilizer vessel, which, in the case of a pressure sterilizer, is designed to prevent the escape of steam from the vessel shell. Inside the vessel shell, containers are positively conveyed by a spiral and reel mechanism. The reel rotates and pushes the containers along the spiral. The containers are then ejected from the reel to a rotary discharge valve and into the next sterilizing vessel or cooling vessel, as the case may be.
Within the sterilizer vessel, containers are heated by steam from a trough on the bottom of the vessel. Uniform distribution of steam is ensured by a manifold steam supply system feeding the trough along the entire length of the vessel. Bleeders are placed at frequent intervals along the top of the vessel and in the transfer valves of pressure sterilizers. Such continuous air removal ensures uniform temperature control, as required by safety regulations.
The rotor in each transfer valve is constructed with equally spaced sprockets on the valve's periphery. Each pocket is designed to hold one can and is mechanically timed with the station on the reel. At the discharge end, a star wheel mounted within the reel gently ejects the containers into the discharge valve for removal from the vessel.
Atmospheric rotary sterilizers typically feed containers directly onto the sterilizer's reel within its vessel. The containers are fed by a free roller feed or a feed chute through an inlet opening in the vessel shell. Due to low steam pressures within the vessel and also due to the size of the opening relative to the size of the cans, a minimal amount of steam and air escapes through the inlet opening.
The present invention is designed to provide a low pressure sterilizer and transfer valve mechanism that achieves advantages of the both atmospheric and pressure sterilizers.
DISCLOSURE OF INVENTION
Briefly described, the transfer valve of the present invention is positioned adjacent an inlet or discharge opening in a sterilizer vessel, and includes a plurality of radially outwardly facing pockets for receiving the containers and transferring them to the inlet opening or away from the discharge opening, into and out of the vessel. The pockets are circumferentially spaced apart to provide gaps between the pockets, and the transfer valve further includes an arcuate transfer valve saddle extending from opposite sides of the inlet opening around a portion of the circumference of the rotary transfer valve. The saddle is positioned so that the pockets are substantially sealed against the saddle prior to and during movement over the inlet or discharge opening. In operation, most of the air and steam escaping the atmospheric rotary vessel at the inlet or discharge opening escapes through the inlet opening between the pockets and the saddle.
According to an aspect of the invention, each pocket may be biased radially outwardly against the saddle by a spring mechanism. The biasing of the pockets allows for wear of the contact surfaces between the pockets and the saddle while maintaining a seal between the pockets and the saddle. Preferably, the rotary transfer valve includes side plates, one on each lateral side of the pockets, for supporting the pockets as they are biased against the saddle.
According to another aspect of the invention, gaps are provided between the pockets and the saddle, and the size of the gaps between the pockets allows for sufficient air and steam to escape in order to maintain a suitable low steam-to-air ratio within the vessel. Preferably the saddle extends only around a portion of the circumference of the transfer valve, so that a portion of the pockets are exposed to the exterior of the vessel as they rotate around the transfer valve. In addition, the interior of the transfer valve is open to the gaps between the pockets, so that air and steam escaping through the inlet opening enters the interior of the transfer valve and can subsequently escape the transfer valve to the exterior of the vessel through the gaps between the pockets moving around the exposed portion of the transfer valve.
According to another aspect of the invention, the size of the gaps between the pockets is narrow enough to maintain a raised pressure within the rotary vessel. The raised pressure within the rotary vessel is at least 2 psi above atmospheric pressure. Preferably, the raised pressure within the rotary vessel is at least 3 psi.
The present invention also includes an atmospheric rotary steam vessel assembly that includes a rotary atmospheric steam vessel for heating containers, the steam vessel including an inlet opening for receiving containers to be heated and an outlet opening to eject heated containers, and a rotary feed transfer valve adjacent the inlet opening, with a plurality of radially outwardly facing pockets for receiving the containers and transferring them to the inlet opening and into the vessel. The pockets are circumferentially spaced apart to provide gaps between the pockets. The steam vessel assembly further includes an arcuate transfer saddle extending from opposite sides of the inlet opening around a portion of the circumference of the rotary transfer valve and is positioned so that the pockets are substantially sealed against the saddle prior to and after moving over the inlet opening. In operation, most of the air and steam escaping the atmospheric rotary vessel at the inlet opening escapes through between the pockets and the saddle.
According to an aspect of the invention, the assembly further comprises a timing device for delivering containers to the transfer valve in a manner that places one container into each pocket. The assembly also may include a rotary discharge transfer valve adjacent the outlet opening. The discharge transfer valve includes a plurality of radially outwardly facing pockets for receiving the containers from the vessel, the pockets being circumferentially
Flehr Hohbach Test Albritton & Herbert LLP
FMC Corporation
Werner Frank E.
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