U.S. patent application number 13/125101 was filed with the patent office on 2011-10-27 for vacuum processing apparatus.
This patent application is currently assigned to P2I LIMITED. Invention is credited to Charles Edmund King.
Application Number | 20110259455 13/125101 |
Document ID | / |
Family ID | 40133725 |
Filed Date | 2011-10-27 |
United States Patent
Application |
20110259455 |
Kind Code |
A1 |
King; Charles Edmund |
October 27, 2011 |
VACUUM PROCESSING APPARATUS
Abstract
The present invention relates to an apparatus (10) for vacuum
processing articles (12). The apparatus comprises a processing
region (14) in which articles can be vacuum processed at a
processing pressure and a loading region (18) into which articles
can be loaded into the apparatus at ambient pressure. A plurality
of article carriers (20) are provided for carrying articles from
the loading region to the processing region along an enclosed
passage (24) so that articles can be vacuum processed. The carriers
(20) comprise respective sealing means (26) for sealing against an
inner surface of the passage when carrying articles along the
passage. The sealing means (26) resist the flow of gas or vapour
past the sealing means along the passage from the loading region to
the processing region so that articles loaded at ambient pressure
in the loading region and carried to the processing region can be
vacuum processed at processing pressure.
Inventors: |
King; Charles Edmund;
(Kidlington, GB) |
Assignee: |
P2I LIMITED
Abingdon
GB
|
Family ID: |
40133725 |
Appl. No.: |
13/125101 |
Filed: |
October 19, 2009 |
PCT Filed: |
October 19, 2009 |
PCT NO: |
PCT/GB09/02499 |
371 Date: |
July 1, 2011 |
Current U.S.
Class: |
137/565.23 |
Current CPC
Class: |
A43D 95/10 20130101;
Y10T 137/86083 20150401; A43D 95/06 20130101; C23C 14/566 20130101;
A43B 7/12 20130101 |
Class at
Publication: |
137/565.23 |
International
Class: |
F04F 3/00 20060101
F04F003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 23, 2008 |
GB |
0819474.8 |
Claims
1-31. (canceled)
32. Apparatus for vacuum processing articles, comprising: a fluid
passage adapted to receive at least one carrier at a loading region
at atmospheric pressure; carriers having at least one seal whereby
in use an intermediate volume is defined within which one or more
articles are received for processing; a processing region defined
in said passage, whereat the pressure is low or high with respect
to atmospheric pressure; a means to displace carriers along the
passage, from the loading region to the processing region and
subsequently to an exit region; and at least one pump or pressure
differential means which, in use, is in fluid communication with
the passage and which is operative to reduce or increase the
internal pressure of carriers within the passage intermediate said
loading region and said exit region, wherein the at least one seal
comprises a flexible material sandwiched between two discs so as to
reveal an annulus of flexible material which conforms to the cross
section of the fluid passage.
33. Apparatus as claimed in claim 32, wherein the seal is disc
shaped in order to conform with a pipe with a circular cross
section.
34. Apparatus as claimed in claim 32, wherein seals are formed from
pneumatic "U", "T" or "V" type seals extending around a first end
and a second end of the carrier, whereby in use, a pressure
differential is created across the flange.
35. Apparatus as claimed in claim 32, wherein the seal comprises a
flexible material compounded with or laminated with a
fluoro-polymer such as poly-tetrafluroethane (PTFE) or molybdenum
disulphide, so as to reduce friction between the seals and the
wall, whilst in use still maintaining an airtight (or near
airtight) seal.
36. Apparatus as claimed in claim 35, wherein the seal is protected
from a process environment by a flexible inert covering, so as to
reduce contamination of the process by the seal material, whilst in
use still allowing the seal to maintain a gas tight (or near
gas-tight) seal.
37. Apparatus as claimed in claim 32, wherein the walls are coated
with a material, such as poly-tetrafluroethene (PTFE), so as to
reduce friction between the seals and the wall, whilst in use still
maintaining an airtight (or near airtight) seal.
38. Apparatus as claimed in claim 32, wherein valves are located at
intervals, in the wall of the fluid passage and which are connected
to the or each pump, thereby acting to reduce the pressure within
the volume defined between the seals of a carrier and the wall of
the fluid passage.
39. Apparatus as claimed in claim 32, wherein a control means is
provided that operates so as to actuate pumps and/or valves in
synchronism with the means to displace the carriers, whereby on
displacement of one or more carriers from a first location to a
second location, pumps and/or valves are energised so as to at
least maintain the pressure differential between a location within
a carrier, (as defined by the walls of the fluid passage and the
volume intermediate the seals of the carrier), with respect to a
location outside the carrier.
40. Apparatus as claimed in claim 32, wherein the processing region
is selected from the group consisting of a plasma processing
region, a vacuum deposition region, a desiccation region, an
infusion region and a freeze drying region.
41. Apparatus as claimed in claim 32, wherein carriers are
cylindrical shaped and hollow with an open aperture for
loading.
42. Apparatus as claimed in claim 32, wherein the means to displace
carriers includes actuators from the group comprising: an hydraulic
ram; a pneumatic ram; an electro-magnetic actuator; a ball or
roller screw actuator; one or more motorized conveyors; and a
direct mechanical engagement means.
43. Apparatus as claimed in claim 32, comprising: an unloading
region from which articles can be unloaded from the apparatus at
ambient pressure; and a second enclosed pre-conditioning passage
along which said carriers can carry new un-processed articles to
the loading region.
44. Apparatus as claimed in claim 43, wherein said sealing means of
said carriers seals against an inner surface of said second
enclosed pre-conditioning passage so that when carrying articles
along the second passage, said sealing means resist the flow of gas
or vapour past said sealing means along said second passage from
the unloading region to the processing region so that articles are
pre-conditioned at processing pressure and carried to the loading
region for loading at ambient pressure.
45. Apparatus as claimed in claim 43, wherein said second
pre-conditioning passage comprises an intermediate pressure region
adapted to be maintained at a pressure between ambient pressure and
processing pressure so that a pressure differential across the
sealing means of carriers in said second passage is less than the
pressure differential between ambient and processing pressure.
46. Apparatus as claimed in claim 45, wherein said intermediate
pressure region comprises a plurality of sub-regions adapted to be
maintained at respective pressures from one sub-region to the next
along said passage towards said processing region.
47. Apparatus as claimed in claim 32, wherein enclosed passages
form a circuit along which said carriers circulate between ambient
pressure regions in which articles can be loaded and unloaded and
processing region at processing pressure in which articles can be
processed.
48. A method of processing articles, comprising the steps of:
loading a carrier with one or more articles to be processed and
placing the carrier in a passage at a loading region at atmospheric
pressure, said carrier having first and second seals defining an
intermediate volume within which one or more articles are received
for processing; urging carriers along the passage from a region of
a first pressure to a region of lower pressure until the carrier
arrives at a processing region that is substantially a vacuum;
processing said articles that are located in the carrier at the
processing region; displacing carriers from the processing region
to an exit region.
Description
FIELD OF THE INVENTION
[0001] This invention relates to an apparatus for processing an
article in a vacuum or under very low pressure conditions, but can
also be applied to any differential pressure process.
BACKGROUND OF THE INVENTION
[0002] Low pressure or vacuum processing is widely applied in
manufacturing to process or to modify characteristics of
material(s) e.g. sputtering of aluminium onto polyester film,
nitriding of steels to increase hardness, sputter coating of indium
tin oxide onto glass to form transparent electrodes, cold plasma
processing to increase reactivity towards adhesives, to apply
chemicals to materials or so as to perform some other process to
materials or items under low pressure conditions, such as for
example, freeze drying them. Examples of above atmosphere
processing include sterilizing, pasteurization, rendering,
speciality chemical production and the like.
[0003] In order to vacuum process products, or interim materials,
it is necessary to transfer the products from a holding region at
ambient pressure to a treatment chamber at a processing pressure.
One way in which transferal can be achieved is simply by placing a
product (or batch of products) in a treatment chamber and then
evacuating the chamber to processing pressure. Following treatment,
the chamber pressure is increased to ambient pressure and the
product can be removed. Such a process is inefficient as the
pressure in the chamber must be cycled between ambient and
processing for each product or batch of products being treated.
Cycling pressure requires energy and is time intensive; and
therefore product throughput is low unless large and expensive
chambers are used. Large chambers with high product density can
also be detrimental to uniform processing.
[0004] The process can be improved by incorporating one or more
load lock chambers in which the pressure cycles between ambient and
processing. Products may be transferred from the load lock to the
treatment chamber when the load lock chamber is at processing
pressure. Products may be transferred to and from the load lock
chamber when the load lock chamber is at ambient pressure. This
latter process has the advantage that the treatment chamber can be
maintained at processing pressure which allows relatively
continuous treatment to be achieved. However, in this process the
load lock chamber must be cycled between ambient and processing
pressure and gate valves with automated carousel movement are
required enabling transfer between chambers which increases
complexity, cost and potential for faults
[0005] If the products are planar, or 2-D (e.g. thin flexible
sheets or hard rigid semi-continuous sheets), the products can be
transferred to and from the treatment chamber through a number of
seals which allow evacuation of the treatment chamber. The seals
seal against the flat surface of the planar products when the
products pass through the seals. Whistling or labyrinth seals are
commonly used for this purpose, which rely on the flatness of the
product and consist of multiple, sometimes flexible, seals which
press against the product during transfer or are close enough to
the product so as to limit ingress of gas from high pressure
regions into low pressure regions. Such a process is not suitable
for treatment of 3-D products which are not planar, may have
irregular shape, be porous or may be easily deformed.
PRIOR ART
[0006] U.S. Pat. No. 5,425,264 (Grenci et al) discloses a method
for making vacuum components from plastic material, and in
particular, PVC and CPVC, where the plastic component is exposed to
a high vacuum or ultra high vacuum for an extended period of time,
at which time the outgas rate drops considerably to levels that are
well within required limits for high vacuum and ultra high vacuum
applications.
[0007] US-A-2005/0111936 describes a multi-chamber system in which
load-lock chambers transfer samples from air into vacuum and robots
move samples from one chamber to another. The intention is to
reduce footprint, increase throughput, reduce vacuum volume and
enable the system to be expanded.
[0008] International Patent Application WO-A-2005/0111936 teaches
the use of conventional vacuum gates and carriers combined with
robotics in a circular arrangement.
[0009] Japanese Patent application JP-A-2001196437 also describes a
system for transferring substrates using conventional load-locks
with vacuum gates and robotic arms. JP-A-2001196437 intends to
reduce damage to substrates caused by excessive handling.
SUMMARY OF THE INVENTION
[0010] According to a first aspect of the invention there is
provided an apparatus for vacuum processing articles
comprising:
[0011] a fluid passage adapted to receive at least one carrier at a
loading region at atmospheric pressure;
[0012] carriers having at least one seal which in use defines an
intermediate volume within which one or more articles are received
for processing;
[0013] a processing region defined in said passage, whereat the
pressure is low with respect to atmospheric pressure;
[0014] a means to displace carriers along the passage, from the
loading region to the processing region and subsequently to an exit
region; and
[0015] at least one pump which, in use, is in fluid communication
with the passage and which is operative to reduce the internal
pressure of carriers within the passage intermediate said loading
region and said processing region and is operative to increase the
internal pressure of carriers within the passage intermediate said
processing region and said exit region.
[0016] Ideally carriers have two seals one positioned at each end
thereof.
[0017] It is apparent therefore that a gradual reduction in
pressure is experienced by the carriers (and their contents) as
they pass from the loading region to the processing region. When
the carriers arrive at the processing region very low pressure or
vacuum processing is able to be performed on articles contained in
each carrier. Following processing the carriers are urged to the
exit region, which is also at atmospheric pressure, and from where
articles are able to be removed from the carriers.
[0018] The passage is ideally defined by a wall whose cross section
conforms to the seal of the carrier.
[0019] Preferably the seals are formed from a deformable flange
portion extending around a first end and a second end of the
carrier, whereby in use, a pressure differential is created across
the flange. The seal, which is ideally disc shaped in order to
conform with a pipe with a circular cross section, but can also be
cup shaped, is advantageously in the form of a flexible material
sandwiched between two flat discs so as to reveal an annulus of
flexible material. Seals may be loosely or firmly laminated to
provide a combination of characteristics e.g. pressure sealing,
ablation resistance, lubricity, material compatibility with
processing atmospheres.
[0020] Inner walls of the passage are ideally smooth, polished and
optionally may be coated with a material, such as
poly-tetrafluroethene (PTFE), so as to reduce friction between the
seals and the wall, but still maintain an airtight (or near
airtight) seal. However reduced friction may also be imparted by
micro-roughening of smooth walls. In this instance inner walls so
roughened must be in regions where pressure differentials are small
i.e. less than 500 mbar and more preferably less than 10 mbar.
[0021] Although reference has been made to vacuum or very low
pressure processing, it is understood that the invention may be
modified for use with pressures above atmospheric pressure.
[0022] Thus according to a second aspect of the present invention
there is provided an apparatus for processing articles at an
elevated pressure, comprising:
[0023] a processing region in which articles can be processed at a
an elevated processing pressure;
[0024] a loading region into which articles can be loaded into the
apparatus at ambient pressure; a plurality of article carriers for
carrying articles from the loading region to the processing region
along an enclosed passage so that articles can be processed at
elevated pressure;
[0025] wherein said carriers comprise respective sealing means for
sealing against an inner surface of the passage when carrying
articles along the passage, said sealing means resisting the flow
of gas or vapour past said sealing means along said passage from
the loading region to the processing region so that articles loaded
at ambient pressure in the loading region and carried to the
processing region can be processed at the processing pressure.
[0026] An advantage of the invention is the lack of need for
automated control valves to adjust pressure, because the fluid
passage length may be adjusted such that pressure is reduced (or
increased) at a desired rate towards the processing region and is
allowed to increase (or decrease) at a desired rate towards the
exit region. A further advantage is that one or more processes may
be carried out in parallel and kept separate one from another, by
the seals on each of the carriers.
[0027] However valves may be located at intervals, in the wall of
the fluid passage and which are connected to one or more pumps
which act to reduce the pressure within the volume defined between
the seals of a carrier and the wall of the fluid passage.
[0028] A control means is optionally provided that operates so as
to actuate pumps and/or valves in synchronism with the means to
displace the carriers, whereby on displacement of one or more
carriers from a first location to a second location, pumps and/or
valves are energised so as to at least maintain the pressure
differential between a location within a carrier, (as defined by
the walls of the fluid passage and the volume intermediate the
seals of the carrier), with respect to a location outside the
carrier.
[0029] Preferably the pressure differential between a location,
within a carrier, with respect to a location outside the carrier is
increased as a carrier is displaced towards the processing
region.
[0030] The processing region may be a plasma processing region.
Alternatively other low pressure processes may be carried out in
the processing region and these include: vacuum deposition and/or
etch processes, desiccation, infusion or freeze drying, or any
combination that may be useful
[0031] Carriers are ideally formed from a rigid material capable of
withstanding high compressive forces, typically those created by
pressure differentials in excess of 0.1 Mega Pascals (MPa).
[0032] Ideally carriers are cylindrical and are adapted to fit
inside a pipe or tubular passage and are hollow and shaped to
receive items to be treated or processed. The carriers have a seal
located around a periphery which is advantageously formed from a
material that takes up the shape of the passage and conforms
thereto, so that it deforms only to a small extent when the carrier
is displaced long the passage. It being understood that an optimum
size exists for a given combination of seal type and material, the
material forming the wall and a particular pressure regime.
[0033] One example of a suitable material that deforms when
subjected to a force is polyurethane, which if placed as a flange
of thickness of between 2 mm to 10 mm, creates an efficient seal.
More complex seals may also be used for example composite
cross-section polyurethane discs with flexible edges and thicker
and stiffer centre sections, or cup-like discs, or composite
material seals to reduce friction e.g. polyurethane and PTFE
laminate or lubricant doped polyurethane. In all instances seals
will interfere with the pipe or tubular passage inner diameter by
way of their diameter which is typically between 101% to 107%
greater than inner diameter of the passage.
[0034] The means to displace carriers includes: an hydraulic or
pneumatic ram arranged to push a train of abutting carriers, an
electro-magnetic actuator; a ball-screw or similar actuator, one or
more motorized conveyors; and a direct mechanical engagement means,
such as inter engaging hooks, taught wire or a rack and pinion
system.
[0035] Advantageously, the carriers containing articles or product
to be processed are arranged so that, in use, one is in direct
contact with another, thereby defining a series of carriers or a
chain of carriers that are urged along the enclosed passage from
the loading region, to the processing region and thence to the
exit. This is ideally achieved by application of a uniaxial force,
for example from an hydraulic ram that is transmitted from one
carrier to an adjacent carrier.
[0036] Other preferred and/or optional features of the invention
are defined in the accompanying claims.
[0037] The invention will now be described, by way of examples
only, with reference to the drawings, in which: --
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] FIG. 1 shows a vacuum processing apparatus;
[0039] FIG. 2 shows a carrier of the vacuum processing apparatus
shown in FIG. 1;
[0040] FIG. 3 shows an alternative vacuum processing apparatus;
[0041] FIG. 4 shows in diagrammatical form an alternative
embodiment of a linear version of the apparatus; and
[0042] FIG. 5 shows a further alternative embodiment of the
apparatus within a closed circuit or loop.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
[0043] Referring to FIGS. 1 and 2, apparatus 10 is shown for vacuum
processing articles, or product, 12. The processing apparatus is
suitable for processing articles at differential pressure to
ambient atmosphere up to pressure differential of 3 Bar including
low pressure or vacuum, for instance, at pressures in the region of
133 Pa to 0.1 Pa, although pressures outside this range are also
applicable. Vacuum processing includes techniques for
functionalizing a surface of the articles, such as sputtering,
modifying articles (for example by nitriding steels to increase
hardness, plasma processing or applying chemicals to articles), as
well as desiccating or freeze drying items, such as,
pharmaceuticals, foodstuffs and edible items.
[0044] Apparatus 10 is particularly suitable for techniques where
it is required or desirable to process many articles quickly.
[0045] The apparatus 10 comprises a processing region 14 in which
articles can be vacuum processed at a very low or near vacuum
processing pressure. The processing region is evacuated through
vacuum ports 15 by one or more vacuum pumps 16. In addition other
pumps or a balanced air extraction system controlled by one or more
valves, acts to gradually reduce (or increase) the pressure from an
inlet or loading regions (which is at atmospheric or ambient
pressure) to the processing region, which is at very low pressure
or at vacuum.
[0046] The processing region may consist of a vacuum chamber,
having openings through which unprocessed articles can be
transferred into the chamber and processing articles can be removed
from the chamber; alternatively it may be at a high air (or other
gas) pressure. The processing region 14 can be generally maintained
at a required processing pressure throughout processing of many
articles, since as described in more detail below, articles can be
transferred to the chamber and removed therefrom without
significantly changing the pressure in the processing region.
[0047] Articles 12 are loaded into the apparatus 10 at ambient
pressure at loading region 18. In this regard, a plurality of
article carriers 20 are provided (shown in greater detail in FIG.
2) for carrying articles from the loading region 18 to the
processing region 14. The carriers 20 comprise respective
compartments 22 into which articles to be processed 12 can be
loaded. As shown, the carriers are generally elongate, right
circular cylinders, but can be any structure with closed ends and
whose walls and sides have a strong rigidity. Compartment 22 is
formed along a lateral extent of the carrier spaced from each end.
The compartments 22 are dimensioned and arranged to comfortably
receive articles for processing with sufficient space round the
article so that vacuum processing of a large surface area of an
article can be achieved in the processing region.
[0048] The apparatus 10 is suitable for carrying so-called 3-D
articles (i.e. articles which are not planar such as sheets of
glass or metal). The carriers are dimensioned and arranged so that
the articles typically fit fully within the compartment 22 and
therefore do not extend beyond an outer lateral extent of the
carrier. It will be appreciated that if an article extends beyond
an outer lateral extent of the carrier it may interfere with the
inner surface of the passage and prevent sealing by the sealing
means (described below).
[0049] The carriers 20 carry loaded articles from the loading
region 18 to the processing region along an enclosed passage 24. In
this embodiment, the enclosed passage 24 is a tube having a
generally cylindrical inner surface.
[0050] Referring to FIG. 2, the carriers 20 comprise respective
sealing means 26 for sealing against the inner surface of the
passage 24 when the carriers are moved along the passage. Hence,
the sealing means provide an obturation in the passage which moves
with the carrier from the loading region to processing region and
beyond.
[0051] The sealing means 26 may comprise one or more seals, such as
friction seals, which resist the flow of gas or vapour past the
sealing means 26 along the passage from the loading region to the
processing region. Accordingly, the sealing means of the carriers
enable significant evacuation of the processing region so that
articles loaded at ambient pressure in the loading region and
carried to the processing region can be vacuum processed at
processing pressure.
[0052] It will be appreciated that some limited leakage of gas in
to the processing region may occur past the sealing means
(depending on the quality of the seals). Further, when a carrier
enters the processing region the processing region may rise
slightly in pressure since, just prior to entry into the processing
region, the carrier may be at a pressure greater than the
processing pressure. The pressure change is a function of the
outgassing characteristics of the product and may also be
controlled by choice of the length of the intermediate regions 28
and 42 and quality and number of seals 26.
[0053] In FIG. 2, the sealing means comprises two seals 34, 36. The
first seal 34 is positioned forward of the compartment 22 and seals
against the passage forward of the compartment with respect to a
direction of travel (shown by arrows in FIG. 2). The second seal 36
is positioned rearward of the compartment and seals against the
passage rearward of the compartment. Accordingly, seals 34, 36
maintain pressure in the compartment 22. Each seal extends around
an outer lateral periphery of the front and rear of the carrier so
that the seals can engage the inner surface of the passage 24. If
the inner surface of the passage 24 is generally cylindrical (as
shown) the seals are generally circular and are preferably 101% to
107% of the inner diameter to correspond with the internal shape of
the passage.
[0054] To maintain concentricity and so effectiveness of seals 26,
at least two portions of outer diameter of carrier 20 may be made
between 95% and 99% of the inner diameter of the passage 24.
Alternatively a semi rigid spacer disc of similar dimensions may be
included in the group of seals 26 which seals are otherwise 101% to
107% of passage 24 inner diameter.
[0055] In an alternative arrangement, each carrier 20 may comprise
a single seal positioned either forward or rearward of the
compartment. In this case, the pressure of a compartment of a
carrier is maintained by one seal on that carrier and another seal
on an adjacent carrier.
[0056] The passage 24 shown in FIG. 1 comprises an intermediate
pressure region 28 adapted to be maintained at a pressure between
ambient pressure and processing pressure. In this regard, the
passage has vacuum ports 30, 31 for connection to one or more
vacuum pumps 32. Pumps 32 and 16 may be integral and in this case
vacuum ports 30, 31 may be connected to an intermediate inlet of
the vacuum pump whilst the processing region is connected to the
main inlet of the pump.
[0057] The intermediate regions provide a more gradual decrease (or
increase) in pressure from the loading region to the processing
region. In this way, the pressure differential across the sealing
means of carriers in the passage is less than the pressure
differential between ambient and processing pressure. Accordingly,
the provision of several intermediate region(s) between ambient
pressure and the processing region means that each seal has to
resist a relatively smaller pressure differential. If the
processing region is maintained at 13.3 Pa and the loading region
at atmosphere, the intermediate region may be maintained at 133 Pa
to 13.3 Pa.
[0058] The intermediate pressure region 28 comprises two
sub-regions at different pressure. A first sub-region is evacuated
through vacuum port 31 to a pressure which is higher than a second
sub-region which is evacuated through vacuum port 30 so that the
pressure in passage 24 decreases in stages towards the processing
region. More than two sub-regions may be provided. In general the
first sub-region e.g. evacuated through vacuum port 31 will remove
the bulk of the air and be independently pumped by a pump 33.
[0059] The carriers 20 are arranged in contact one with an adjacent
carrier to form a series or chain of carriers along the passage so
that movement of one carrier along the passage causes movement of
the other carriers in the chain along said passage. The carriers
may comprise spacing means for spacing apart the carriers, if
required. The carriers can be moved, or pushed, along the passage
by for instance a hydraulic ram, located at ambient pressure.
Alternatively, the carriers can be connected and pulled along the
passage.
[0060] Apparatus 10 further comprises an unloading region 38 from
which articles 12 can be unloaded from the apparatus at ambient
pressure. A second enclosed passage 40 extends from the processing
region 14 to the unloading region 38. The second enclosed passage
is similar to passage 24 and like features will not be described in
detail again for the sake of brevity. Carriers 20 can be moved
along the second passage carrying processed articles from the
processing region to the unloading region.
[0061] Sealing means 26 of the carriers seal against an inner
surface of the second enclosed passage 40 when carrying articles
along the second passage. The sealing means resists the flow of gas
or vapour past the sealing means along the second passage from the
unloading region to the processing region so that articles
processed at processing pressure and carried to the unloading
region can be unloaded at ambient pressure. In this way, the
processing region can be maintained generally at processing
pressure whilst processed articles are removed from the
apparatus.
[0062] It will be appreciated that the sealing means in the first
passage 24 resist the flow of gas or vapour from the unloaded
region to the processing region (i.e. to the right hand side of
FIG. 1) and in the second passage 40 resist the flow of gas or
vapour from the unloading region to the processing region (i.e. to
the left hand side of FIG. 1). Accordingly, sealing means 26 must
be suitable for restricting flow in both directions with respect to
the direction of travel of the carriers 20.
[0063] Similarly to the first passage 24, the second passage 40
comprises an intermediate pressure region 42 adapted to be
maintained at a pressure between ambient pressure and processing
pressure so that a pressure differential across the sealing means
26 of carriers in the second passage 40 is less than the pressure
differential between ambient and processing pressure.
[0064] The intermediate pressure region 42 may comprise a plurality
of sub-regions adapted to be maintained at respective pressures
from one sub-region to the next along said passage towards said
processing region. In this regard, the second passage can be
evacuated through vacuum ports 44 and 46. The sub-region associated
with port 46 is maintained at a higher pressure than the sub-region
associated with port 44 so that pressure in passage 40 is increased
in stages from the processing region to the unloading region 38.
The second passage 40 may be evacuated by vacuum pump 32.
[0065] In a preferred embodiment the intermediate region 42 is not
actively pumped except perhaps for one vacuum port adjacent to the
processing region 14. In this way any process effluent may be
removed from the carriers/product e.g. through vacuum port 44. A
gradual rise in pressure will naturally occur in region 42 as
carriers progress towards the unloading region 38. The rise in
pressure being controlled by the length of the intermediate region
42 and number of seals and carriers. A controller may be arranged
to evacuate the passage in synchronism with a stroke of an actuator
so that regions either side of seals are pumped efficiently as
those regions pass a valve.
[0066] Apparatus 10 will now be described in use.
[0067] Carriers 20 are positioned as shown in FIG. 1 along the
first passage 24, through the processing region 14 and along the
second passage 40. The sealing means 26 of the carriers 20 seal the
processing region from the loading region 18 and the unloading
region 38. Vacuum pumps 16, 32 and 33 are operated to evacuate the
processing region 14 and passages 24, 40 respectively so that the
processing region is at processing pressure and the first and
second passages are at an intermediate pressure. Articles 12 are
loaded into the compartments 22 of one or more carriers 20 at the
loading region 18.
[0068] The carriers are then moved along the passages. When the
first seal 34 of a carrier passes over vacuum port 31 in the first
passage, gas or vapour is evacuated from between the first seal 34
and the second seal 36 thereby reducing pressure in the compartment
22 to a first intermediate pressure (e.g. 150 Pa). When the first
seal 34 passes over vacuum port 30 in the first passage, gas or
vapour is evacuated from between the first seal 34 and the second
seal 36 thereby reducing pressure in the compartment 22 from the
first intermediate pressure to a second intermediate pressure (e.g.
15 Pa). Continued movement of the carrier 20 causes the first seal
34 to enter the processing region, at which time gas or vapour is
evacuated from between the first seal 34 and the second seal 36
thereby reducing pressure in the compartment from the second
intermediate pressure to a processing pressure (e.g. 13 Pa).
[0069] Vacuum processing of the articles is conducted in the
processing region. The carriers 20 may move continuously or
semi-continuously and the length of the processing region must be
selected to allow sufficient residence of a carrier in the
processing region for processing to be conducted. Alternatively,
the carriers 20 may be caused to stop in the processing region for
a duration while processing is conducted.
[0070] There may be several processing sub-regions along the length
of the enclosed passage and each region may have a chosen length so
that the residence time of a carrier in each region is sufficient
for the appropriate process to be completed. Because all such
processes, including loading and unloading of product, are carried
out in parallel, the time taken to process a product is dependent
substantially on the length of the enclosed passage. The longer the
enclosed passage the shorter the process time for any one carrier
containing product and so the faster the overall throughput.
[0071] Following processing, and assuming no waste gasses are to be
removed from carriers the carriers are moved along the second
passage 40. When the first seal 34 moves past vacuum port 44, gas
or vapour enter between the first seal 34 and the second seal 36
raising the pressure in the compartment 22 to the second
intermediate pressure (e.g. 500 Pa). When the first seal 34 moves
past vacuum port 46, gas or vapour enters between the first seal 34
and the second seal 36 raising the pressure in the compartment 22
to the first intermediate pressure (e.g. 1000 Pa). When the first
seal 34 moves into the unloading region, gas or vapour enters
between the first seal 34 and the second seal 36 raising the
pressure in the compartment 22 to the ambient pressure (e.g.
atmosphere) allowing articles to be unloaded.
[0072] A preferred method of operation is not to actively evacuate
any of the carriers in the second passage 40, except perhaps to
remove waste gases through vacuum port 44. Thereafter in the second
passage 40 with no active pumping seals 34 and 36 gradually leak
air from the unloading region. The length of passage 40 is chosen
so that the leak rate is small and approximately zero leak is seen
in the process region.
[0073] In an alternative arrangement shown in FIG. 3, the enclosed
passages 24, 40 form a circuit along which the carriers 20 can
circulate between an ambient pressure region 48 in which articles
can be loaded and unloaded and the processing region 14 maintained
at processing pressure in which articles can be processed.
[0074] FIG. 5 shows an apparatus that comprises a linear closed
circuit or loop processing system, in which like parts bear the
same reference numerals and which has an automatic off loader 25
and an automatic loader 27. Carriers 20 are urged from an
atmospheric entrance or loading position 18 into a passage 24
through which carriers pass to a processing region 14, which is at
vacuum or very low pressure. After the items 12 within carriers 20
have been processed, carriers pass to regions of increasing
pressure 42 to an exit position 38. At the exit position the
passage is cut away and/or a slight incline or some other actuator
is provided which causes or permits carriers to move away from the
processing passage and to roll or to pass onto a conveyor 50. At
the exit region 38 product that has been processed is removed and
new, un-processed product is placed into carriers which now pass to
region 58 of the conveyor 50.
[0075] The conveyor may incorporate any method of conveying
carriers back to region 18, e.g. a ram system, wherein carriers are
maintained end-to-end and so push one another along the conveyor,
or are transported by a belt, air-pressure, or other such movement
system where there may be a gap between carriers. Advantageously
the conveyor may be enclosed and incorporate one or more
pre-conditioning processes that may be applied to product in
carriers, e.g. drying, heating, coating, spraying, etc. For vacuum
processing of products in region 14 a particularly useful
pre-condition step that may be applied along the conveyor 50 is
vacuum drying in region 52.
[0076] There may be several low pressure stages along the conveyor
which separate atmosphere in region 58 to low pressure in region 56
and back to atmosphere in region 25. To effect low pressure in
region 56, vacuum ports 54 may be connected to a single pump or
multiple pumps 70 to effect outgassing of product as it traverses
the conveyor 50. At the exit position 25 the passage is cut away
and/or a slight incline or some other actuator is provided which
causes or permits carriers 20 to move away from the conveyor
passage 50 and to roll or to pass onto the loading region 18 and
the cycle starts again.
[0077] Advantageously the contents 12 of the carriers--that is
items that have been processed--are either presented to someone who
removes the items from the carriers at region 38 (for example for
packing); or a mechanical means is provided in order to remove the
items. Advantageously new items to be processed may replace
processed items so that load and unload occur at the same
location.
[0078] Other variations of a system for performing vacuum
processing include a simple linear process line an example of which
is shown in FIG. 5.
[0079] FIG. 4 shows an apparatus that comprises a linear processing
system, in which like parts bear the same reference numerals and
which has a loading position 18 and an unloading position 38.
Carriers 20 are urged from an atmospheric entrance or loading
position 18 into a passage 24 through which carriers pass to a
processing region 14, which is at very low pressure. After the
items 12 within carriers 20 have been processed, carriers pass to
regions of increasing pressure 42 to an exit position 38 where
carriers are removed from the passage 40 and processed product 12
is removed from carriers. Carriers are then transported back to the
loading position 18. New un-processed product 12 is placed into the
carrier aperture 22 and the cycle starts again.
[0080] The following example further illustrates the present
disclosure:
Example 1
[0081] With reference to FIG. 4 and FIG. 2, samples 12 of cotton
cloth 24 cm.times.24 cm were placed one each into carriers.
Carriers 20 are made from polyvinylchloride (PVC) and are 97% of
the passage inner diameter and 42 cm in length. Polyurethane disc
seals 34 FIG. 2, 102% of the passage inner diameter are situated at
either end of each carrier. Eighteen carriers 20, each containing a
sample of cotton cloth were placed consecutively into the loading
region 18 and urged into the passage 24 by a ram. A vacuum was
applied by three pumps whereby a pressure of 133 PA was held at the
first vacuum port 33, 250 Pa at the first intermediate region 28
and 10 Pa in the process region 14. With vacuum achieved a plasma
was struck in region 14 using external electrodes; a 13.56 MHz
source and a fluoro-monomer was introduced into the same region.
Further carriers containing cotton cloth samples were consecutively
fed into the loading station and pushed along the length of the
passage 24 and also removed from the exit region 38. After 8
carriers had emerged from the exit region, the first "processed"
carrier, i.e. having seen plasma and process chemical was pushed
out of the exit region 38.
[0082] The cotton samples showed hydrophobic effects. Subsequently
a further eight carriers were caused to traverse the passage and
were satisfactorily processed. The pressure in the process region
14 maintained at approximately 10 Pa.
Example 2
[0083] Shoes are made from materials that typically outgas water
and solvents when placed in a vacuum chamber and this outgassing
can interfere with CVD and PECVD processes. With reference to
regions shown in FIG. 5, fifty pairs of sports (training) style
shoes were placed one pair each into the carriers and fed to the
load station of a closed circuit continuous machine of the present
invention. Carriers containing a pair of shoes traveled first
through region 52 of the pre-treatment conveyor in which a vacuum
of approximately 1200 Pa was dynamically applied. Carriers remained
in this vacuum drying region for around 6.5 minutes.
[0084] Regions 25 and 18 are at atmospheric pressure and are
connected and enclosed containing clean, dry air so avoiding water
absorption in transferring carriers from the conveyor 50 to the
process line regions 28, 14, 42. Carriers were then urged into the
process line region 28 and through the process region 14 and so on
to the exit region 38. The cycle time for a pair of shoes was 30
seconds and a pressure of 18 Pa was maintained in the process
region 14. A good uniform process effect was achieved.
[0085] Shoes from the same batch were processed using a batch
machine and pre-drying shoes using dry air for 10 hours. Process
pressure achieved was 30 Pa and process cycle time for a pair was
90 seconds. A variable process effect was achieved.
[0086] The invention has been described by way of several
embodiments, with modifications and alternatives, but having read
and understood this description further embodiments and
modifications will be apparent to those skilled in the art. All
such embodiments and modifications are intended to fall within the
scope of the present invention as defined in the accompanying
claims.
[0087] For example, although reference has been made to processing
at very low pressure or vacuum the apparatus may be modified for
processing at high pressures. Likewise items other than clothing
and sports footwear may be processed. For example, solid items may
be processed such as laboratory equipment, such as glassware and
other items such as pipettes, tubes and narrow conduits or fluid
pathways, where wetting is disadvantageous.
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