U.S. patent application number 10/489934 was filed with the patent office on 2004-12-16 for fusers and intermediate transfer members.
Invention is credited to Romem, Ilan.
Application Number | 20040250985 10/489934 |
Document ID | / |
Family ID | 11043112 |
Filed Date | 2004-12-16 |
United States Patent
Application |
20040250985 |
Kind Code |
A1 |
Romem, Ilan |
December 16, 2004 |
Fusers and intermediate transfer members
Abstract
Drum intermediate transfer member or fuser apparatus, for use in
a printer or copier, comprising: a drum having a drum surface and
including a liquid-containing region in the interior of the drum
thermally connected to the drum surface, such that the liquid is
capable of heating and cooling the drum surface; and a liquid
transfer system including a hot liquid reservoir, a cold liquid
reservoir, at least one pump, pipes and optionally at least one
valve arranged to selectively pump liquid between the
liquid-containing region and the hot liquid reservoir, and between
the liquid-containing region and the cold liquid reservoir.
Inventors: |
Romem, Ilan; (Ramat
Hasharon, IL) |
Correspondence
Address: |
William H Dippert
Reed Smith
599 Lexington Avenue
29th Floor
New York
NY
10022-7650
US
|
Family ID: |
11043112 |
Appl. No.: |
10/489934 |
Filed: |
March 16, 2004 |
PCT Filed: |
November 6, 2001 |
PCT NO: |
PCT/IL01/01033 |
Current U.S.
Class: |
165/58 |
Current CPC
Class: |
G03G 15/161 20130101;
G03G 15/2053 20130101 |
Class at
Publication: |
165/058 |
International
Class: |
F25B 029/00 |
Claims
1. Drum intermediate transfer member or fuser apparatus, for use in
a printer or copier, comprising: a drum having a drum surface and
including a liquid-containing region in the interior of the drum
thermally connected to the drum surface, such that the liquid is
capable of heating and cooling the drum surface; a liquid transfer
system including a hot liquid reservoir, a cold liquid reservoir,
at least one pump, pipes and optionally at least one valve arranged
to selectively pump liquid between the liquid-containing region and
the hot liquid reservoir, and between the liquid-containing region
and the cold liquid reservoir; and including one or both of: an
accumulator in the hot liquid reservoir which allows the volume of
liquid in the hot liquid reservoir to change substantially without
a commensurate change in liquid pressure: and an accumulator in the
cold liquid reservoir which allows the volume of liquid in the cold
liquid reservoir to change substantially without a commensurate
change in liquid pressure.
2. Apparatus according to claim 1 wherein the liquid-containing
region and the liquid transfer system are sealed from the outside,
and are substantially free of gas.
3. Apparatus according to claim 1 wherein the liquid-containing
region does not rotate when the drum rotates.
4. Apparatus according to claim 1 and comprising at least one
rotating seal used to transfer liquid into and out of the
liquid-containing region.
5. Apparatus according to claim 1 wherein the optional at least one
valve comprises a three-way valve and including an outlet pipe
connecting the liquid-containing region directly or indirectly to
the three-way valve, controllable to direct liquid leaving the
liquid-containing region into either the hot liquid reservoir or
the cold liquid reservoir.
6. Apparatus according to claim 1 wherein the optional valve
comprises a three-way valve and including an input pipe connecting
the liquid-containing region directly or indirectly to a three-way
valve, controllable to direct liquid from either the hot liquid
reservoir or the cold liquid reservoir into the liquid-containing
region.
7. Apparatus according to claim 1 and including a heating element
in the hot liquid reservoir.
8. (Cancelled)
9. Apparatus according to claim 7 and including a temperature
sensor in the hot liquid reservoir.
10. Apparatus according to claim 9 wherein the temperature in the
hot liquid reservoir is maintained in a certain range by using
feedback from the temperature sensor to control the heating
element.
11. Apparatus according to any of the preceding claims claim 1 and
including a refrigerating element in the cold liquid reservoir.
12. (Cancelled)
13. Apparatus according to claim 11 and including a temperature
sensor in the cold liquid reservoir.
14. Apparatus according to claim 13 wherein the temperature in the
cold liquid reservoir is maintained in a given range by using
feedback from the temperature sensor to control the refrigerating
element.
15. Apparatus according to claim 1 and including an accumulator in
the hot liquid reservoir which allows the volume of liquid in the
hot liquid reservoir to change substantially without a commensurate
change in liquid pressure.
16. Apparatus according to claim 1 and including an accumulator in
the cold liquid reservoir which allows the volume of liquid in the
cold liquid reservoir to change substantially without a
commensurate change in liquid pressure.
17. Apparatus according to claim 15 and including an accumulator in
the cold liquid reservoir which allows the volume of liquid in the
cold liquid reservoir to change substantially without a
commensurate change in liquid pressure.
18. Apparatus according to claim 17 wherein the accumulator in the
hot liquid reservoir is linked to the accumulator in the cold
liquid reservoir, so that when one reservoir increases in volume,
the other reservoir decreases in volume by the same amount.
19. Apparatus according to claim 18 wherein the accumulators
comprise a movable sealed barrier between the hot liquid reservoir
and the cold liquid reservoir.
20. Apparatus according to claim 1 and including an accumulator in
the liquid-containing region which allows the volume of liquid in
the liquid-containing region to change substantially without a
commensurate change in liquid pressure.
21. (Cancelled)
22. Apparatus according to claim 1 wherein the liquid-filled region
is largely drained of liquid of one temperature, before it is
filled with liquid of a different temperature.
23. Apparatus according to claim 1 wherein the liquid-containing
region heats and cools the surface of the drum indirectly through a
separate thin region which also contains liquid.
24. Apparatus according to claim 56 wherein the liquid in the thin
region is volatile and increases the gas pressure in the thin
region when the liquid therein is heated.
25. Apparatus according to claim 56 wherein different liquids are
used in the liquid-containing region and in the thin region.
26. Apparatus according to claim 1 wherein the liquid in the
liquid-containing region has low volatility in the operating range
of temperature.
27. (Cancelled)
28. Apparatus according to claim 56 wherein the liquid in the thin
region is volatile and increases the gas pressure in the thin
region when the liquid therein is heated.
29-31. (Cancelled)
32. Apparatus according to claim 56 and including a pressure sensor
in the thin region.
33. (Cancelled)
34. Apparatus according to claim 1 and including a pressure sensor
in the liquid-containing region or in the liquid transfer system,
and including a controller that controls one or more of said at
least one pump and at least one valve, wherein the controller
causes hot liquid to flow out of the liquid-containing region
and/or causes cold liquid to flow into the liquid-containing
region, if the pressure in the liquid-containing region or in the
liquid transfer system rises higher than a given value.
35. Apparatus according to claim 56 and including an overflow valve
in the liquid-containing region or in the liquid transfer system,
wherein the valve opens and relieves the pressure in the
liquid-containing region or in the thin region, if the pressure
rises higher than a given value.
36. Apparatus according to claim 1, and including an overflow valve
in the liquid transfer system or the liquid-containing region that
allows excess liquid to leave the liquid transfer system or the
liquid-containing region.
37. Apparatus according to claim 57 wherein the overflow valve is
forced open mechanically when the liquid pressure rises higher than
a given value.
38. Apparatus according to claim 1, and including a pressure sensor
in the liquid-containing region or in the liquid transfer
system.
39. (Cancelled)
40. Apparatus according to claim 57, and including an overflow
reservoir, wherein excess liquid that flows through the overflow
valve enters the overflow reservoir, and liquid can flow from the
overflow reservoir into the liquid transfer system or the
liquid-containing region when the pressure falls below a given
value.
41-42. (Cancelled)
43. Apparatus according to claim 56, wherein at least part of the
boundary between the liquid-containing region and the thin region
is flexible, so that an increase in pressure in the thin region
will lead to an increase in pressure in the liquid-containing
region.
44-46. (Cancelled)
47. Apparatus according to claim 36 wherein the overflow valve is
forced open mechanically when the liquid pressure rises higher than
a given value.
48-49. (Cancelled)
50. Apparatus according to claim 34, wherein the controller
receives data from the pressure sensor and opens the overflow valve
when the pressure rises higher than a given value.
51. Apparatus according to claim 34, and including an overflow
reservoir, wherein excess liquid that flows through the overflow
valve enters the overflow reservoir, and liquid can flow from the
overflow reservoir into the liquid transfer system or the
liquid-containing region when the pressure falls below a given
value.
52. Apparatus according to claim 1, and including a controller that
controls one or more of said at least one pump and said at least
one valve, thereby to control selective pumping.
53. Apparatus according to claim 1, and including a bleed valve for
removing unwanted gas from the apparatus.
54. Apparatus according to claim 1, and including a shut-off valve
closable to prevent liquid from flowing into the liquid-containing
region.
55. Drum intermediate transfer member or fuser apparatus, for use
in a printer or copier, comprising: a drum having a drum surface
and including a liquid-containing region in the interior of the
drum thermally connected to the drum surface, such that the liquid
is capable of heating and cooling the drum surface; and a liquid
transfer system including a hot liquid reservoir, a cold liquid
reservoir, at least one pump, pipes and optionally at least one
valve arranged to selectively pump liquid between the
liquid-containing region and the hot liquid reservoir, and between
the liquid-containing region and the cold liquid reservoir, wherein
the liquid-filled region is largely drained of liquid of one
temperature, before it is filled with liquid of a different
temperature.
56. Drum intermediate transfer member or fuser apparatus, for use
in a printer or copier, comprising: a drum having a drum surface
and including a liquid-containing region in the interior of the
drum thermally connected to the drum surface, such that the liquid
is capable of heating and cooling the drum surface; and a liquid
transfer system including a hot liquid reservoir, a cold liquid
reservoir, at least one pump, pipes and optionally at least one
valve arranged to selectively pump liquid between the
liquid-containing region and the hot liquid reservoir, and between
the liquid-containing region and the cold liquid reservoir; wherein
the liquid-containing region heats and cools the surface of the
drum indirectly through a separate thin region which also contains
liquid.
57. Drum intermediate transfer member or fuser apparatus, for use
in a printer or copier, comprising: a drum having a drum surface
and including a liquid-containing region in the interior of the
drum thermally connected to the drum surface, such that the liquid
is capable of heating and cooling the drum surface; a liquid
transfer system including a hot liquid reservoir, a cold liquid
reservoir, at least one pump, pipes and optionally at least one
valve arranged to selectively pump liquid between the
liquid-containing region and the hot liquid reservoir, and between
the liquid-containing region and the cold liquid reservoir; and an
overflow valve in the liquid-containing region or in the liquid
transfer system, wherein the valve opens and relieves the pressure
in the liquid-containing region, transferring excess liquid outside
the liquid containing region and the liquid transfer system.
58. Drum intermediate transfer member or fuser apparatus, for use
in a printer or copier, comprising: a drum having a drum surface
and including a liquid-containing region in the interior of the
drum thermally connected to the drum surface, such that the liquid
is capable of heating and cooling the drum surface; a liquid
transfer system including a hot liquid reservoir, a cold liquid
reservoir, at least one pump, pipes and optionally at least one
valve arranged to selectively pump liquid between the
liquid-containing region and the hot liquid reservoir, and between
the liquid-containing region and the cold liquid reservoir; a
pressure sensor in the liquid-containing region or in the liquid
transfer system; and a controller that controls said at least one
pump, wherein the controller causes hot liquid to flow out of the
liquid-containing region and/or causes cold liquid to flow into the
liquid-containing region, if the pressure in the liquid-containing
region or in the liquid transfer system, measured by the pressure
sensor, rises higher than a given value.
Description
FIELD OF THE INVENTION
[0001] The present invention is related to the field of printers
and copiers and more particularly to fusers, intermediate transfer
members, and/or elements that function as both fusers and
intermediate transfer members and to printers or copiers that
utilize the same.
BACKGROUND OF THE INVENTION
[0002] Printers and copiers are well known. Modern copiers that
utilize powder or liquid toners comprising toner particles to form
visible images generally form a latent electrostatic image on an
image forming surface (such as a photoreceptor), develop the image
utilizing a toner (such as the aforementioned powder or liquid
toners) to form a developed image and transfer the developed image
to a final substrate. The transfer may be direct, i.e., the image
is transferred directly to the final substrate from the image
forming surface, or indirect, i.e., the image is transferred to the
final substrate via one or more intermediate transfer members.
[0003] In general, the image on the final substrate must be fused
and fixed to the substrate. This step is achieved in most copiers
and printers by heating the toner image on the substrate. In some
copiers and printers the fusing and fixing of the image is
performed simultaneously with the transfer of the image to the
substrate. This is achieved by utilizing a heated intermediate
transfer member to perform the transfer and by pressing the
intermediate transfer member against the final substrate. This
combination of heat and pressure softens the toner particles and
fixes them to the substrate. In other copiers and printers, the
image is first transferred to the final substrate, and then fused
by a separate fuser. Once the transferred image has been fused, it
is desirable for the surface of the intermediate transfer member or
fuser to cool below a certain temperature while it is still in
contact with the final substrate, so that none of the toner sticks
to it.
[0004] In several prior art devices, a drum used as an intermediate
transfer member or fuser contains water or another liquid in its
interior. These include devices described in PCT Publication WO
00/31593, EP 0 772 100 A2, JP Publication 08320625, U.S. Pat. No.
4,172,976, PCT Application PCT/IL00/00652 filed Oct. 13, 2000, and
a PCT Application titled "Fusers and Intermediate Transfer Members"
filed Oct. 30, 2001 at the Israel Patent Office by Ilan Romem of
Indigo N. V., the disclosures of all of which are incorporated
herein by reference. There are two reasons for including liquid
inside the drum. The first reason is that the liquid can keep the
outer surface of the drum at a uniform temperature. This is
important for obtaining good image quality, and especially for
avoiding "short-term memory" effects, in which an image can be
affected by the previous image. Such short-term memory effects are
believed to be caused by lower surface temperatures in regions
where the drum previously had liquid toner, which cools the surface
locally when it evaporates. Having liquid inside the drum has been
found to practically eliminate short-term memory. The second reason
for using liquid, described in WO 00/31593, is that when the liquid
gets hot, the vapor pressure of the liquid inside the drum can
support a thin membrane, allowing it to conform slightly to the
surface of the substrate that it is in contact with, when
transferring images or fixing images. That could also be
accomplished by maintaining air under pressure inside the drum, or
by including a layer of compliant spongy material underlying the
outer surface of a drum whose interior is rigid. But maintaining
air under pressure inside the drum would require a pumping system,
and a spongy layer can easily become damaged, and thermally
insulates the surface from the source of heat inside the drum.
Another advantage of using a thin membrane supported by gas
pressure is that the heat capacity on transfer is low, so the image
cools and hardens during transfer.
[0005] There are some disadvantages to using a drum with liquid in
it, particularly a drum whose outer surface is a thin membrane
supported by gas pressure. The liquid can have a high heat
capacity, and hence take a long time to heat up. This means there
may be a long waiting time when the copier or printer is first
turned on, until it is ready to print. To avoid waiting, the drum
may be kept hot all the time, but this can be dangerous, because
someone inadvertently touching the drum could be burned, and
because the drum could explode if the gas pressure inside gets too
high. Also, toner particles on the drum could be burnt onto the
drum. If the surface of the drum is a thin somewhat flexible
membrane, then it cannot be built to withstand very high pressure.
Using liquid with high heat capacity also means that, if the gas
pressure does get too high, it will take a long time to bring the
pressure down by cooling off the liquid. The heating problem is
especially acute if a large amount of liquid is used.
SUMMARY OF INVENTION
[0006] An aspect of some embodiments of the invention is concerned
with rapidly changing the temperature of a drum containing a liquid
used as an intermediate transfer member or fuser, in a printer or
copier.
[0007] An aspect of some embodiments of the invention is concerned
with rapidly heating such a drum, in order to bring it up to the
temperature required for printing, and rapidly cooling the drum
once the printing is completed.
[0008] An aspect of some embodiments of the invention is concerned
with rapidly cooling such a drum, in order to reduce the gas
pressure, if it gets too high.
[0009] An embodiment of the invention comprises a reservoir of hot
liquid and a reservoir of colder liquid, and pipes connecting the
reservoirs to the interior of the drum. The embodiment also
comprises valves which can be opened and closed, to control the
flow of liquid between the interior of the drum and the reservoirs.
When the printer or copier is idle, the drum contains colder
liquid, so that it is safe to touch, and there is no danger of
explosion or fusing toner to the drum. Before the printer or copier
begins to print, the colder liquid is pumped out of the drum back
to the colder liquid reservoir, and hot liquid is pumped from the
hot liquid reservoir to the drum, which transfer heats up the drum
very quickly, especially if the drum has a cylindrical surface
formed of a thin membrane.
[0010] Once printing is done, hot liquid is pumped out of the drum
back to the hot liquid reservoir, and colder liquid is pumped into
the drum from the cold liquid reservoir. If the drum becomes too
hot and the gas pressure gets too high in the middle of printing,
and/or if there is a paper jam, the gas pressure and temperature
can be quickly reduced to a safe level by pumping at least some of
the hot liquid out of the drum, and/or pumping some colder liquid
into the drum. This is particularly true when the cylindrical
surface is thin so that the heat capacity of the liquid is much
higher than that of the cylinder, but it is not necessary for the
surface to be thin. The valves can be arranged so that this
transfer of liquid is done automatically, and in a fail-safe way,
whenever the gas pressure gets too high. The colder liquid need not
be colder than room temperature, it could be room temperature or
even hotter than room temperature.
[0011] In an embodiment of the invention, a heater within the drum
is used to replace heat transferred to the final substrate and
other rollers of the system. Alternatively or additionally, this
heat is provided by the heater in the reservoir, for example, in
response to a temperature measurement of the drum surface and/or
the temperature of the liquid in the drum.
[0012] The volatile liquid used to produce gas pressure in the drum
in some embodiments need not be the liquid that is being pumped
into and out of the drum to heat and cool the drum. The liquid
transfer system which is used to pump the liquid into and out of
the drum will work best if it uses a non-volatile liquid, free of
gas. The volatile liquid used to produce gas pressure could be in a
thin outer region just beneath the outer surface of the drum. The
liquid being pumped into and out of the drum could fill a separate,
more central portion of the drum, below the outer region, sealed
off from the outer space but in good thermal contact with it.
[0013] In some embodiments, the hot liquid reservoir has a heating
element and thermostat, and/or the cold liquid reservoir has a
refrigeration element and a thermostat, to maintain the hot liquid
and the cold liquid at the desired temperature. The hot liquid
reservoir, unlike a drum with a thin membrane, can be kept well
insulated thermally, and it can be kept some distance away from the
parts of the printer or copier that require frequent handing (for
example, to remove paper jams), so there will be little danger that
someone will be burned by touching it. The hot liquid reservoir can
also be designed to withstand much higher gas pressure than a drum
using a thin membrane, since it can have thick walls, so there will
be little danger of it exploding. It can also be kept at a higher
temperature than the desired final temperature of the liquid, so
that the final temperature, after the change of liquid in the drum,
will be the desired final temperature. For both these reasons, it
will be safe to keep the liquid in the hot liquid reservoir heated
all the time. Having good thermal insulation around the hot liquid
reservoir and the cold liquid reservoir also means that it will not
require much power to maintain the hot liquid and the cold liquid
at their desired temperatures.
[0014] There is thus provided, in accordance with an embodiment of
the invention, a drum intermediate transfer member or fuser
apparatus, for use in a printer or copier, comprising:
[0015] a drum having a drum surface and including a
liquid-containing region in the interior of the drum thermally
connected to the drum surface, such that the liquid is capable of
heating and cooling the drum surface; and
[0016] a liquid transfer system including a hot liquid reservoir, a
cold liquid reservoir, at least one pump, pipes and optionally at
least one valve arranged to selectively pump liquid between the
liquid-containing region and the hot liquid reservoir, and between
the liquid-containing region and the cold liquid reservoir.
[0017] In an embodiment of the invention, the liquid-containing
region and the liquid transfer system are sealed from the outside,
and are substantially free of gas.
[0018] In an embodiment of the invention, the liquid-containing
region does not rotate when the drum rotates.
[0019] In an embodiment of the invention, there is at least one
rotating seal used to transfer liquid into and out of the
liquid-containing region.
[0020] In an embodiment of the invention, the optional at least one
valve comprises a three-way valve and including an outlet pipe
connecting the liquid-containing region directly or indirectly to
the three-way valve, controllable to direct liquid leaving the
liquid-containing region into either the hot liquid reservoir or
the cold liquid reservoir.
[0021] In an embodiment of the invention, the optional valve
comprises a three-way valve and including an input pipe connecting
the liquid-containing region directly or indirectly to a three-way
valve, controllable to direct liquid from either the hot liquid
reservoir or the cold liquid reservoir into the liquid-containing
region.
[0022] In an embodiment of the invention, there is a heating
element in the hot liquid reservoir.
[0023] In an embodiment of the invention, there is a temperature
sensor in the hot liquid reservoir.
[0024] Optionally, the temperature in the hot liquid reservoir is
maintained in a certain range by using feedback from the
temperature sensor to control the heating element.
[0025] In an embodiment of the invention, there is a refrigerating
element in the cold liquid reservoir.
[0026] In an embodiment of the invention, there is a temperature
sensor in the cold liquid reservoir.
[0027] Optionally, the temperature in the cold liquid reservoir is
maintained in a given range by using feedback from the temperature
sensor to control the refrigerating element.
[0028] In an embodiment of the invention, there is an accumulator
in the hot liquid reservoir which allows the volume of liquid in
the hot liquid reservoir to change substantially without a
commensurate change in liquid pressure.
[0029] In an embodiment of the invention, there is an accumulator
in the cold liquid reservoir which allows the volume of liquid in
the cold liquid reservoir to change substantially without a
commensurate change in liquid pressure.
[0030] Optionally, the accumulator in the hot liquid reservoir is
linked to the accumulator in the cold liquid reservoir, so that
when one reservoir increases in volume, the other reservoir
decreases in volume by the same amount.
[0031] Optionally, the accumulators comprise a movable sealed
barrier between the hot liquid reservoir and the cold liquid
reservoir.
[0032] In an embodiment of the invention, there is an accumulator
in the liquid-containing region which allows the volume of liquid
in the liquid-containing region to change substantially without a
commensurate change in liquid pressure.
[0033] Optionally, the liquid-filled region is largely drained of
liquid of one temperature, before it is filled with liquid of a
different temperature.
[0034] In an embodiment of the invention, the liquid-containing
region heats and cools the surface of the drum indirectly through a
separate thin region which also contains liquid.
[0035] In an embodiment of the invention, the liquid in the thin
region is volatile and increases the gas pressure in the thin
region when the liquid therein is heated.
[0036] In an embodiment of the invention, different liquids are
used in the liquid-containing region and in the thin region.
[0037] In an embodiment of the invention, the liquid in the
liquid-containing region has low volatility in the operating range
of temperature.
[0038] In an embodiment of the invention, there is a pressure
sensor in the thin region.
[0039] In an embodiment of the invention, at least part of the
boundary between the liquid-containing region and the thin region
is flexible, so that an increase in pressure in the thin region
will lead to an increase in pressure in the liquid-containing
region.
[0040] In an embodiment of the invention, there is a pressure
sensor in the liquid-containing region or in the liquid transfer
system, and a controller that controls one or more of said at least
one pump and at least one valve, wherein the controller causes hot
liquid to flow out of the liquid-containing region and/or causes
cold liquid to flow into the liquid-containing region, if the
pressure in the liquid-containing region or in the liquid transfer
system rises higher than a given value.
[0041] In an embodiment of the invention, there is an overflow
valve in the liquid-containing region or in the liquid transfer
system, wherein the valve opens and relieves the pressure in the
liquid-containing region and in the thin region, if the pressure
rises higher than a given value.
[0042] In an embodiment of the invention, there is an overflow
valve in the liquid transfer system or the liquid-containing region
that allows excess liquid to leave the liquid transfer system or
the liquid-containing region.
[0043] Optionally, the overflow valve is forced open mechanically
when the liquid pressure rises higher than a given value.
[0044] In an embodiment of the invention, there is a pressure
sensor in the liquid-containing region or in the liquid transfer
system.
[0045] In an embodiment of the invention, there is an overflow
reservoir, wherein excess liquid that flows through the overflow
valve enters the overflow reservoir, and liquid can flow from the
overflow reservoir into the liquid transfer system or the
liquid-containing region when the pressure falls below a given
value.
[0046] In an embodiment of the invention, there is a controller
that controls one or more of said at least one pump and at least
one valve, wherein the controller causes hot liquid to flow out of
the liquid-containing region and/or causes cold liquid to flow into
the liquid-containing region, if the pressure in the thin region
rises higher than a given value.
[0047] In an embodiment of the invention, the controller receives
data from the pressure sensor and opens the overflow valve when the
pressure rises higher than a given value.
[0048] In an embodiment of the invention, there is a controller
that controls one or more of said at least one pump and said at
least one valve, thereby to control selective pumping.
[0049] In an embodiment of the invention, there is a bleed valve
for removing unwanted gas from the apparatus.
[0050] In an embodiment of the invention, there is a shut-off valve
closable to prevent liquid from flowing into the liquid-containing
region.
BRIEF DESCRIPTION OF THE DRAWING
[0051] Exemplary embodiments of the invention are described in the
following section with reference to the drawing. The drawing is
generally not to scale.
[0052] FIG. 1 is a schematic diagram showing the elements of an
embodiment of the invention.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0053] The embodiment shown in FIG. 1 has a drum 10, with a region
12 filled with a liquid. Optionally, there is a thin outer region
11, between region 12 and the outer surface of drum 10, which
contains its own liquid, optionally a different liquid more
volatile than the liquid in region 12, which maintains gas pressure
supporting the outer surface when the drum is hot. Generally, the
liquid in region 12 need not be replaced when the temperature of
the drum is to be changed. Region 12 is connected to a liquid
transfer system 13, consisting of pipes, connectors, valves, and
reservoirs. An outlet 14 of region 12 connects region 12 to a
return pipe 16. In those embodiments where there is an outer region
11 between region 12 and the outer surface of drum 10, region 12
optionally remains fixed in place while drum 10 is rotating. In
this case, outlet 14 is optionally an ordinary pipe connector. If
region 12 rotates with the outer surface of drum 10, then outlet 14
optionally comprises a rotating seal. Return pipe 16 is optionally
connected to a three-way valve 18, with connections to both a hot
liquid reservoir 20 and a cold liquid reservoir 22. The three-way
valve 18 can be electrically controlled by a controller 19, to
allow liquid from the return pipe 16 to flow into either the hot
liquid reservoir 20 or the cold liquid reservoir 22. The hot liquid
reservoir has a heating element 24 and a thermostat 26. The cold
liquid reservoir has a refrigeration element 28, and optionally
also has a thermostat. Controller 19 optionally maintains the hot
liquid reservoir and/or the cold liquid reservoir at desired
temperatures by using feedback from the thermostats to control the
heating element and refrigeration element. Hot liquid reservoir 20
has an outlet 30, and cold liquid reservoir 22 has an outlet 32,
which both connect to a three-way valve 34, which also connects to
a pump 36. Three-way valve 34 can be electrically controlled by
controller 19, to selectively control the pump to pump liquid out
of either the hot reservoir 20 or the cold reservoir 22. Controller
19 can also turn the pump on and off. The outflow of pump 36
connects to a pipe 38, which connects to an inlet 40 to drum 10.
Pipe 38 has a bleed valve 42 somewhere along its length, which
allows trapped air or other gas to be removed from liquid transfer
system 13. Trapped gas in the liquid transfer system may make it
operate less efficiently, or, in an extreme situation, not operate
at all. Pipe 38 also has a shut-off valve 43 somewhere along its
length, which can be used to prevent liquid from flowing into
region 12. Pipe 38 also has an overflow valve 44 somewhere along
its length, which allows liquid from the liquid transfer system to
flow into an overflow reservoir 46 and relieve the pressure, if the
liquid pressure gets too high. Overflow valve 44 can also allow
liquid transfer system 13 to draw liquid from overflow reservoir
46, if the liquid pressure gets too low. The overflow valve can
allow liquid to flow in each direction automatically, when the
pressure difference exceeds some value. Alternatively, a pressure
sensor 47 in pipe 38, or elsewhere in liquid transfer system 13,
triggers controller 19 to open overflow valve 44. In some
embodiments, pressure data is not used by the controller for this
purpose; it may still be used to notify an operator of a problem.
Too high a pressure could lead to leaking or even catastrophic
failure of the liquid transfer system. Too low a pressure could
lead to cavitation, which would adversely affect the performance of
the pump. Even before those extreme conditions are reached, the
shape of the drum can be distorted, or the compliance of the drum
can be less than or greater than optimal, if the pressure is too
high or too low.
[0054] Because, in a desired operating range of pressures, the
liquid is essentially incompressible, and it is generally desirable
not to have any trapped gas in the liquid transfer system, hot
reservoir 20 and cold reservoir 22 optionally change their volumes
as liquid is pumped into and out of them. One way to do this,
illustrated in FIG. 1, is to have a movable barrier 48 between hot
reservoir 20 and cold reservoir 22. In response to a small
difference in pressure between hot reservoir 20 and cold reservoir
22, barrier 48 moves to increase the volume of one reservoir and
decrease the volume of the other reservoir by the same amount. With
this configuration, cold liquid preferably flows into region 12 at
the same rate as hot liquid is being pumped out, and vice versa.
This can lead to some mixing of hot and cold liquid in region 12,
when both hot and cold liquid are present there.
[0055] An alternative scheme is to have separate accumulators in
region 12, hot reservoir 20, and cold reservoir 22. Each
accumulator independently changes the volume of its region or
reservoir in response to a small change in pressure. Each
accumulator may consist of a gas-filled balloon or bellows, or any
other kind of accumulator known to the art. In this scheme, it is
possible to largely or completely empty the hot liquid from region
12 before starting to pump in the cold liquid, and vice versa.
Also, because barrier 48 between hot reservoir 20 and cold
reservoir 22 is not necessarily movable, it might be easier to make
the barrier a better thermal insulator, and to avoid having liquid
leak past it. In this embodiment, hot reservoir 20 and cold
reservoir 22 do not have to be adjacent to each other, which makes
it even easier to thermally insulate them, and to prevent liquid
leaking from one reservoir into the other.
[0056] Another alternative scheme is to have separate accumulators
in hot reservoir 20 and cold reservoir 22, but not in region 12.
Like the first scheme, this scheme may require that when liquid is
pumped from region 12 to one reservoir, an equal volume of liquid
is pumped from the other reservoir into region 12. However, in this
scheme the hot and cold reservoirs could be some distance apart,
and better insulated from each other. A disadvantage of this
scheme, compared to the first scheme, is that there will be larger
transient increases in pressure if the pumping starts suddenly,
which can lead to noise and vibrations that could damage the liquid
transfer system.
[0057] In some embodiments, drum 10 has a thin outer region 11
between region 12 and the outer surface of the drum, containing a
volatile liquid which produces gas pressure to support the outer
surface when the drum is hot. The boundary between outer region 11
and region 12 could either be rigid or flexible. If the boundary is
flexible, then raising the gas pressure in outer region 11 will
also cause the liquid pressure to rise in region 12. This
relationship is optionally used to prevent the gas pressure from
getting too high or too low. For example, raising the liquid
pressure in region 12 above a given level could force open a valve
at outlet 14, allowing liquid from region 12 to flow through pipe
16, past the 3-way valves, reservoirs and pump, and through
overflow valve 44, even without the pump running. The resulting
increase in volume of outer region 11, as the flexible boundary
expands at the expense of region 12, would immediately decrease the
gas pressure. (Having a flexible boundary between region 12 and
outer region 11 might not work, however, if region 12 had its own
accumulator, since this would tend to prevent the gas pressure in
the outer blanket from changing.) Alternatively or additionally, a
pressure sensor in outer blanket 11 or region 12 optionally
triggers the pump to draw hot liquid out of region 12 and to pump
cold liquid into region 12, if the pressure exceeds a given value,
or the pressure sensor triggers the pump to pump more hot liquid
into region 12 if the pressure falls below a given value. Pressure
sensor 47, even it is located in pipe 38 or elsewhere in liquid
transfer system 13, optionally is used for this purpose.
[0058] The invention has been described in the context of the best
mode for carrying it out. It should be understand that not all
features shown in the drawing may be present in an actual device,
in accordance with some embodiments of the invention. Furthermore,
variations on the method and apparatus shown are included within
the scope of the invention, which is limited only by the claims. As
used herein, the terms "have", "include" and "comprise" or their
conjugates mean "including but not limited to."
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