Solid material comminution or disintegration – Processes – With application of fluid or lubricant material
Reexamination Certificate
1999-07-20
2001-11-06
Rosenbaum, Mark (Department: 3725)
Solid material comminution or disintegration
Processes
With application of fluid or lubricant material
C241S030000, C241S031000, C241S033000
Reexamination Certificate
active
06311904
ABSTRACT:
BACKGROUND OF THE INVENTION
(i) Field of the Invention
The present invention relates to an apparatus for grinding containers that contain a powder, such as, for example, cartridges of toner for photocopiers or laser printers, this apparatus including a grinder placed in an enclosure for confinement of the powder released during grinding.
(ii) Description of Related Art
For the purpose of recycling emptied photocopier toner cartridges, one technique commonly employed consists in grinding them in a grinding apparatus which includes a grinder placed in a confinement enclosure and in sucking out the residual powder released during grinding through one or more openings made in the wall of the confinement enclosure by means of a suction system in order to recover the toner powder.
However, in known apparatuses, the toner powders, which generally have a particle size of less than 500 micrometers, are mixed with the ambient air and are partly in suspension in the confinement enclosure, thus creating, under certain conditions, a flammable and/or explosive mixture.
At the present time, in order to prevent the risks of a fire and/or an explosion, there is a requirement to limit the amount of cartridges ground per unit time and to equip the known apparatuses with a powerful, and costly, ventilation system. Furthermore, before grinding, the cartridges usually undergo a preliminary manual step of draining off the residual toner.
Despite these efforts, it has been found that the risks of an explosion and/or a fire are not fully under control.
SUMMARY OF THE INVENTION
The invention is aimed at alleviating these various drawbacks by proposing a grinding apparatus which is safer in operation and allows a larger number of containers to be treated per unit time, while eliminating the preliminary manual step of draining the containers.
For this purpose, the subject of the invention is an apparatus for grinding containers that contain a powder, which includes a grinder placed in an enclosure for confinement of the powder released during grinding, this apparatus furthermore conditioning the atmosphere in the confinement enclosure with an inert gas whose nitrogen content is greater than approximately 90% by volume.
The grinding apparatus according to the invention may also include one or more of the following characteristics:
the nitrogen content of the inert gas is approximately 95% by volume;
the oxygen content of the inert gas is less than approximately 5% by volume;
the atmosphere is conditioned using a supply of the inert gas and a conduit for introducing the inert gas into the confinement enclosure;
the inert gas supply is preferably a plant for producing nitrogen by a membrane-type air separation process;
the plant for producing the inert gas by a membrane process comprises, apart from a membrane-type air separator feeding a buffer tank from which the confinement enclosure is fed with inert gas, a backup tank of liquid nitrogen;
a throttling device, configured so as to be normally open in operation (an expression familiar to those skilled in the art, meaning the the device, for example a solenoid valve, is open, i.e., fluid can flow- should there be no electricity), is placed in the gas line connecting the buffer tank to the confinement enclosure;
the confinement enclosure includes an inlet for the containers and an outlet for the ground containers in order to allow continuous grinding, and the apparatus furthermore includes, by the inlet, an airlock for introducing the containers so as to prevent the ambient air from entering the confinement enclosure and, at the outlet, a suction device for extracting the powder released during grinding;
the containers are introduced into the confinement enclosure via a conveyor, the airlock surrounding the conveyor and including injectors, for injecting the inert gas, which are placed on each side of the conveying belt of the conveyor;
a sensor which measures the oxygen content of the atmosphere in the confinement enclosure and a regulator which regulates the flow rate of inert gas introduced by the supply depending on the oxygen content measured by the sensor;
a comparator which compares the oxygen content of the atmosphere in the confinement enclosure, measured by the sensor, with a predetermined threshold and an alarm actuated by the comparator when the measured oxygen content of the atmosphere in the confinement enclosure exceeds a predetermined threshold.
The invention also relates to a process for grinding containers that contain a powder, using a grinder placed in an enclosure for confinement of the powder released during grinding, and further comprising the step of conditioning the atmosphere in the confinement enclosure with an inert gas whose nitrogen content is greater than approximately 90% by volume.
The process according to the invention may also adopt one or more of the following characteristics:
the oxygen content of the inert gas is less than approximately 5% by volume;
the conditioning step is carried out by supplying the confinement enclosure from a supply of inert gas, which supply is a plant for producing nitrogen by a membrane-type air separation process;
the membrane-type nitrogen production plant comprises, apart from a membrane-type air separator feeding a buffer tank from which the confinement enclosure is fed with inert gas, a backup tank of liquid nitrogen;
the confinement enclosure is fed with inert gas from the buffer tank via a throttling device located in the gas line connecting the buffer tank to the confinement enclosure, which throttling device is configured so as to be normally open in operation;
if the grinder has to be suddenly stopped in an emergency, the confinement enclosure continues to be fed with inert gas from the buffer tank because of the fact that the throttling device is configured so as to be normally open in operation;
the oxygen content of the atmosphere in the confinement enclosure is measured and the oxygen content of the atmosphere thus measured is compared with a predetermined threshold, and an alarm is provided which is capable of being actuated, depending on the result of the comparison, when the measured oxygen content of the atmosphere in the confinement enclosure exceeds a predetermined threshold;
the oxygen content of the atmosphere in the confinement enclosure is measured and the flow rate of inert gas introduced is regulated depending on the oxygen content thus measured;
the confinement enclosure is fed according to the following procedure;
i) under normal operating conditions, the confinement enclosure is fed with inert gas at a maintain flow rate Q
m
from the buffer tank;
ii) the oxygen content of the atmosphere in the confinement enclosure is measured continuously;
iii) as soon as a limit threshold S
1
for the measured oxygen content is exceeded, the containers to be ground stop being introduced into the grinder and the confinement enclosure is fed with inert gas at a purge flow rate Q
p
from the backup tank of liquid nitrogen so as to be able to bring the measured oxygen content in the confinement enclosure back down to the S
1
level or below it, Q
p
being greater than Q
m
;
iv) as soon as the measured oxygen content in the confinement enclosure has returned to the S
1
level or below it, normal operating conditions are resumed in which the confinement enclosure is fed with inert gas at the maintain flow rate Q
m
from the buffer tank and the containers to be ground start being introduced into the grinder again;
v) if application of the purge flow rate Q
p
does not succeed in bringing the measured oxygen content in the confinement enclosure back down, as described in step iv), the grinder is then stopped.
It will be understood that, like in any industrial plant, the grinder may suddenly stop for many reasons, including the fact that, for one reason or another, the electricity on the site is or has to be cut off.
Further characteristics and advantages of the invention will emerge from the following description, given by way of example, and the drawings, without a limiting character.
Leturmy Marc
Pioger Frederic
Soula Richard
Burns Doane Swecker & Mathis L.L.P.
L'Air Liquide, Societe Anonyme pour l'Etude et l'
Rosenbaum Mark
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