U.S. patent application number 11/325761 was filed with the patent office on 2007-07-05 for automatic shutoff and metering device.
This patent application is currently assigned to Honeywell International Inc.. Invention is credited to Nicholas A. Hartney, David C. Henrikson, Winston S. Webb.
Application Number | 20070151621 11/325761 |
Document ID | / |
Family ID | 38223120 |
Filed Date | 2007-07-05 |
United States Patent
Application |
20070151621 |
Kind Code |
A1 |
Hartney; Nicholas A. ; et
al. |
July 5, 2007 |
Automatic shutoff and metering device
Abstract
A method for filling a pressurized container is provided. The
method involves automatically adjusting a shutoff valve between a
supply of a pressurized medium and the pressurized container based
on a weight of the pressurized medium contained in the pressurized
container.
Inventors: |
Hartney; Nicholas A.; (St.
Petersburg, FL) ; Henrikson; David C.; (Seminole,
FL) ; Webb; Winston S.; (Largo, FL) |
Correspondence
Address: |
HONEYWELL INTERNATIONAL INC.
101 COLUMBIA ROAD
P O BOX 2245
MORRISTOWN
NJ
07962-2245
US
|
Assignee: |
Honeywell International
Inc.
Morristown
NJ
|
Family ID: |
38223120 |
Appl. No.: |
11/325761 |
Filed: |
January 5, 2006 |
Current U.S.
Class: |
141/83 |
Current CPC
Class: |
F17C 2250/032 20130101;
F17C 2223/0153 20130101; F17C 2221/017 20130101; F17C 2250/0408
20130101; F17C 2205/0161 20130101; F17C 2205/0332 20130101; F17C
2260/024 20130101; F17C 2205/0326 20130101; F17C 2250/0421
20130101; F17C 2227/04 20130101; F17C 6/00 20130101; F17C 2250/061
20130101; F17C 2270/0509 20130101; F17C 2250/075 20130101 |
Class at
Publication: |
141/083 |
International
Class: |
B65B 3/26 20060101
B65B003/26 |
Claims
1. A method for filling a pressurized container, the method
comprising: automatically adjusting a shutoff valve between a
supply of a pressurized medium and the pressurized container based
on a weight of the pressurized medium contained in the pressurized
container.
2. The method of claim 1, wherein the pressurized medium is one of
a gas or a liquid.
3. The method of claim 1, wherein automatically adjusting the
shutoff valve further comprises: establishing a starting reading on
a scale with a scale linkage positioned to place the shutoff valve
in a fully open position; adjusting a current position of the scale
linkage as the weight of the pressurized container increases; and
once the scale detects that the thermal container is substantially
filled with the pressurized medium, positioning the shutoff valve
in a fully closed position and the scale linkage in a final
position.
4. The method of claim 3, wherein establishing the starting reading
on the scale further comprises taring the scale until the starting
reading is substantially equal to a weight of the thermal container
when the pressurized container does not contain a substantial
amount of the pressurized medium.
5. The method of claim 3, wherein adjusting a current position of
the scale linkage further comprises adjusting a current position of
the shutoff valve.
6. The method of claim 3, wherein the shutoff valve is prevented
from automatically re-opening once the shutoff valve is in the
fully closed position.
7. An apparatus for metering a supply of liquefied gas to a
liquefied gas container, the apparatus comprising: means for
determining a current weight of the liquefied gas container; means,
associated with the means for determining, for allowing liquefied
gas to enter the liquefied gas container; and means, associated
with the means for determining and the means for allowing, for
indicating a current level of liquefied gas contained in the
liquefied gas container.
8. The apparatus of claim 7, wherein the means for determining a
current weight further comprises a scale with adjustments for
liquefied gas containers of varying dimensions.
9. The apparatus of claim 7, wherein the means for allowing
liquefied gas to enter the liquefied gas container further
comprises a shutoff valve mechanically linked to the means for
determining the current weight.
10. The apparatus of claim 7, wherein the means for allowing
liquefied gas to enter the liquefied gas container further
comprises a shutoff valve electrically linked to the means for
determining the current weight.
11. The apparatus of claim 7, wherein the means for indicating a
current level of liquefied gas further comprises one of a
mechanical level gauge and an electronic level meter.
12. A liquefied gas containment system, comprising: a Dewar tank
mounted on a scale and seated within a mobile base; an intake and
relief valve assembly mounted on top of the Dewar tank and coupled
to a main fill line; a shutoff valve coupled between the main fill
line and a removable feed line; a scale linkage connecting the
scale and the shutoff valve; and wherein the scale linkage adjusts
one or more positions of the shutoff valve based on an amount of
the liquefied gas detected in the Dewar tank by the scale.
13. The system of claim 12, wherein an inlet end of the main fill
line is adjustable.
14. The system of claim 12, wherein the scale linkage maintains a
current position of the shutoff valve once the removable feed line
is disconnected from the Dewar tank.
15. The system of claim 12, wherein the scale linkage is a
mechanical linkage between the scale and the shutoff valve.
16. The system of claim 15, wherein the mechanical linkage further
comprises a level gauge link coupled to a level gauge readout.
17. The system of claim 16, wherein the level gauge readout records
a current level of liquefied gas in the Dewar tank.
18. The system of claim 12, wherein the scale linkage is an
electrical linkage between the scale and the shutoff valve.
19. The system of claim 18, wherein the electrical linkage further
comprises a level meter interface coupled to an electronic level
readout.
20. The system of claim 19, wherein the electronic level readout
records a current level of liquefied gas in the Dewar tank.
21. A method for maintaining a level of pressurized medium in a
pressurized container, the method comprising: establishing a
starting level reading by indicating with a level readout that the
pressurized container does not contain a substantial amount of the
pressurized medium; as the pressurized medium enters the
pressurized container, adjusting a shutoff valve as an increase in
weight of the pressurized container is detected; as the weight of
the pressurized container increases, adjusting a current level
reading on the level readout; once the pressurized container is
substantially filled with the pressurized medium, automatically
closing the shutoff valve; and as the pressurized medium is removed
from the pressurized container, updating the level readout to
indicate an adjusted level based on a current weight of the
pressurized container.
22. The method of claim 21, wherein the pressurized medium is one
of a gas or a liquid.
23. The method of claim 21, wherein establishing the starting level
reading further comprises mounting the pressurized container on a
scale.
24. The method of claim 23, wherein mounting the pressurized
container on the scale further comprises adjusting the scale until
the starting reading is substantially equal to a weight of the
container when the pressurized container does not contain a
substantial amount of the pressurized medium.
25. The method of claim 21, wherein the level readout is a digital
measurement of the current level reading, indicated by an
electronic readout.
26. The method of claim 21, wherein the level readout is an analog
measurement of the current level reading, indicated by a level
gauge readout.
Description
BACKGROUND
[0001] The field of cryogenics requires liquefied gases when
conducting experiments and observations. The two types of liquefied
gases used in most cryogenic applications are liquid helium and
liquid nitrogen (LN2). In order to store LN2, for example, special
containers known as Dewar flasks (Dewars) are used. For practical
purposes, the Dewars used are generally about six feet tall and
three feet in diameter. The Dewar is designed to provide very good
thermal insulation. In the case of storing LN2, the leakage of heat
into the extremely cold interior of the flask results in a slow
"boiling-off" of the LN2. A pressure relief valve is provided to
prevent pressure from building up. The excellent insulation of the
Dewar results in the LN2 lasting a long time without the need for
expensive refrigeration equipment.
[0002] When filling the Dewar with LN2, determining when the Dewar
is full is a difficult task that requires constant monitoring. When
the Dewar is overfilled, the LN2 will continue to pour out of a
relief vent and is wasted. This waste of LN2 is expensive and
dangerous. Inhaling LN2 causes minor to severe breathing
difficulty, which is a safety hazard to cryogenic lab personnel.
Additionally, determining the level of remaining LN2 is difficult
when traditional level gauges are mounted on top of the Dewar.
While in use, the top of the Dewar is often covered with frost,
rendering the gauge difficult to read and subject to measurement
inaccuracies.
[0003] Economics also play a role in the storage of liquefied
gases. The ability to provide a readily-available source of
liquefied gas improves the chance of successful studies in a
cryogenic lab. As stated above, the loss of LN2 when filling Dewars
using traditional means results in an accelerated consumption of
purchased liquefied gas. Working environments, such as lab size,
often result in multiple Dewars operating in more than one area at
any given time. Further, each Dewar requires individual servicing
and monitoring.
[0004] For the reasons stated above and for other reasons stated
below which will become apparent to those skilled in the art upon
reading and understanding the present application, there is a need
in the art for an improved method for filling a liquefied gas
container.
SUMMARY
[0005] Embodiments of the present invention address problems with
gas metering and containment and will be understood by reading and
studying the following specification. In one embodiment, a method
for filling a pressurized container is provided. The method
involves automatically adjusting a shutoff valve between a supply
of a pressurized medium and the pressurized container based on a
weight of the pressurized medium contained in the pressurized
container.
[0006] In another embodiment, an apparatus for metering a supply of
liquefied gas to a liquefied gas container is provided. The
apparatus includes means for determining a current weight of the
liquefied gas container and means, associated with the means for
determining, for allowing liquefied gas to enter the liquefied gas
container The apparatus further includes means, associated with the
means for determining and the means for allowing, for indicating a
current level of liquefied gas contained in the liquefied gas
container.
[0007] In yet another embodiment, a liquefied gas containment
system is provided. The system includes a Dewar tank mounted on a
scale and seated within a mobile base, an intake and relief valve
assembly mounted on top of the Dewar tank and coupled to a main
fill line, a shutoff valve coupled between the main fill line and a
removable feed line, and a scale linkage connecting the scale and
the shutoff valve. The system further includes wherein the scale
linkage adjusts one or more positions of the shutoff valve based on
an amount of the liquefied gas detected in the Dewar tank by the
scale.
[0008] In still another embodiment, a method for maintaining a
level of pressurized medium in a pressurized container is provided.
The method involves establishing a starting level reading by
indicating with a level readout that the pressurized container does
not contain a substantial amount of the pressurized medium. As the
pressurized medium enters the pressurized container, the method
involves adjusting a shutoff valve as an increase in weight of the
pressurized container is detected. As the weight of the pressurized
container increases, the method further involves adjusting a
current level reading on the level readout. Once the pressurized
container is substantially filled with the pressurized medium, the
method still further involves automatically closing the shutoff
valve. The method concludes as the pressurized medium is removed
from the pressurized container, and the level readout is updated to
indicate an adjusted level based on a current weight of the
pressurized container.
DRAWINGS
[0009] FIG. 1 is a block diagram of an embodiment of a liquefied
gas containment system in accordance with the present
invention;
[0010] FIG. 2 is a block diagram of another embodiment of a
liquefied gas containment system in accordance with the present
invention; and
[0011] FIG. 3 is a flow diagram illustrating an embodiment of a
method for filling a liquefied gas container in accordance with the
present invention.
DETAILED DESCRIPTION
[0012] In the following detailed description, reference is made to
the accompanying drawings that form a part hereof, and in which is
shown by way of illustration specific illustrative embodiments in
which the invention may be practiced. These embodiments are
described in sufficient detail to enable those skilled in the art
to practice the invention, and it is to be understood that other
embodiments may be utilized and that logical, mechanical and
electrical changes may be made without departing from the spirit
and scope of the present invention. The following detailed
description is, therefore, not to be taken in a limiting sense.
[0013] Embodiments of the present invention address problems with
filling a liquefied gas container. Particularly, in one embodiment,
a method for filling a pressurized container is provided. The
method involves automatically adjusting a shutoff valve between a
supply of a pressurized medium and the pressurized container based
on a weight of the pressurized medium contained in the pressurized
container.
[0014] Although the examples of embodiments in this specification
are described in terms of liquefied gas containment and metering,
embodiments of the present invention are not limited to liquefied
gas containment and metering. Embodiments of the present invention
are applicable to any gas containment and metering activity that
requires continuous knowledge of an amount of a gaseous element
filling a container, and automatically discontinuing a filling of
the gaseous element into the container once a desired level is
reached. Alternate embodiments of the present invention utilize an
automatic Dewar LN2 supply shutoff and metering system
incorporating at least a scale and a shutoff valve linked together.
The system is adapted for use with Dewars of different capacities.
In addition, a gauge mechanism accurately records a remaining level
of LN2 in the Dewar at all times. Moreover, the entire system is
suited for placement on a mobile base.
[0015] FIG. 1 is a block diagram of an embodiment of a liquefied
gas containment system, indicated generally at 100, according to
the teachings of the present invention. System 100 comprises Dewar
tank 102, mobile base 104, and scale 106. Dewar tank 102 further
comprises intake and relief valve assembly 132, mounted on top of
Dewar tank 102 and mechanically coupled to an outlet end of
overhead fill line 130. An inlet end of overhead fill line 130 is
mechanically coupled to an outlet end of main fill line 126 by main
fill line outlet coupler 128. In one embodiment, main fill line
outlet coupler 128 is provided so that one or more lengths of
overhead fill line 130 are adaptable for use in system 100.
Accommodating one or more lengths of overhead fill line 130 allows
one or more Dewar tanks of varying diameters to be incorporated
within system 100. An inlet end of main fill line 126 is
mechanically coupled to an outlet end of shutoff valve 120 by
shutoff valve outlet coupler 124. In one embodiment, the inlet end
of main fill line 126 is constructed of a flexible component. The
flexible component allows one or more Dewar tanks of varying
heights to be incorporated within system 100. Feed line 112 is
mechanically coupled to an inlet end of shutoff valve 120 by
shutoff valve inlet coupler 122. In one embodiment, feed line 112
supplies a liquefied gas to system 100 from a main liquefied gas
supply (not shown). Moreover, the liquefied gas supplied to system
100 consists of one of liquefied nitrogen, liquefied helium, or the
like.
[0016] In one embodiment, Dewar tank 102 is secured on scale 106 by
at least one tank latch 116. Moreover, the at least one tank latch
116 is mechanically mounted on top of scale 106. Scale 106 is
seated within mobile base 104 with scale seat mounts 107.sub.1 to
107.sub.4. In one embodiment, mobile base 104 is constructed with
raised sides to prevent a combination of Dewar tank 102 and scale
106 from sliding off. It is noted that for simplicity in
description, scale seat mounts 107.sub.1 and 107.sub.4 are shown in
FIG. 1. However, it is understood that scale 106 is seated on each
of scale seat mounts 107.sub.1 to 107.sub.4 within mobile base 104.
Mobile base 104 further includes mobile base wheels 108.sub.1 to
108.sub.4. It is noted that for simplicity in description,
mobile/base wheels 108.sub.1 and 108.sub.4 are shown in FIG. 1.
However, it is understood that each of mobile base wheels 108.sub.1
to 108.sub.4 are affixed to a bottom side of mobile base 104. In
one embodiment, the use of each of mobile base wheels 108.sub.1 to
108.sub.4 allows mobile base 104 to transport system 100 to any
necessary and convenient location along surface 110.
[0017] Scale 106 further includes adjustment knob 114 and scale
linkage 134. Adjustment knob 114 is used to tare, or determine a
weight of, an empty Dewar tank 102. The tare value of the empty
Dewar tank 102 is used in the operation of system 100, as further
described below. Including adjustment knob 114 allows the use of
one or more Dewar tanks with varying dimensions, e.g. of one or
more tare values. In one embodiment, scale linkage 134 provides a
mechanical link between scale 106 and shutoff valve 120. Moreover,
scale linkage 134 places shutoff valve 120 in an open position once
scale 106 is tared for the weight of the empty Dewar tank 102. In
another embodiment, scale linkage 134 is mechanically coupled to
level gauge link 136. Moreover, level gauge link 136 provides an
analog measurement to level gauge 118. The operation of level gauge
118 is further described below.
[0018] Prior to operation, adjustment knob 114 is adjusted until a
starting reading of scale 106 is substantially equal to the weight
of Dewar tank 102 when Dewar tank 102 does not contain a
substantial amount of liquefied gas. In one embodiment, once the
starting reading of scale 106 is established, scale linkage 134 is
adjusted to an initial starting position so that a final reading of
scale 106, e.g., a reading of scale 106 when Dewar tank 102 is
filled with liquefied gas, will position shutoff valve 120 in a
closed position. Moreover, current valve positions of shutoff valve
120 will be maintained by current positions of scale linkage 134.
Scale linkage 134 is adjusted to position shutoff valve 120 in a
fully-open position prior to operation. In one embodiment, once
scale linkage 134 is adjusted, feed line 112 is attached to shutoff
valve 120 with shutoff valve inlet coupler 122. Next, a liquefied
gas is supplied to system 100 by feed line 112. As the liquefied
gas enters system 100, the liquefied gas is transported through
main fill line 126 and overhead fill line 128. Eventually, the
liquefied gas enters Dewar tank 102 through intake and relief valve
assembly 132. As the liquefied gas begins to fill Dewar tank 102,
scale 106 begins to detect an increase in weight of Dewar tank 102.
In one embodiment, the increased weight of Dewar tank 102 causes
scale 106 to automatically adjust a current position of scale
linkage 134. An adjusted position of scale linkage 134 begins
closing shutoff valve 120. In one embodiment, the adjusted position
of scale linkage 134 adjusts a current position of level gauge link
136. Moreover, an adjusted position of level gauge link 136 changes
a current reading of level gauge 118. In the case of an increase in
weight of Dewar tank 102, the current reading of level gauge 118
indicates an increase in the amount of liquefied gas, i.e. a
current level, present in Dewar tank 102.
[0019] As additional liquefied gas enters system 100, scale linkage
134 is continually repositioned, adjusting shutoff valve 120 closer
to the closed position. At a time when scale 106 detects that Dewar
tank 102 is substantially filled with the liquefied gas, scale
linkage 134 is in a final position and places shutoff valve 120 in
the closed position. Once shutoff valve 120 is in the closed
position, shutoff valve 120 is prevented from automatically
re-opening. In one embodiment, the final position of scale linkage
134 adjusts level gauge link 136 to change the current reading of
level gauge 118 to indicate that Dewar tank 102 is filled with the
liquefied gas. Moreover, level gauge link 136 and scale linkage 134
remain in operation once system 100 is disconnected from feed line
112. Further, level gauge 118 continues to provide an indication of
the current level of liquefied gas remaining in Dewar tank 102. In
one embodiment, once Dewar tank 102 is filled, feed line 112 is
removed from system 100. System 100 is capable of being transported
via mobile base 104. As the liquefied gas is used, scale 106 will
record a decrease in weight of Dewar tank 102. In response, level
gauge link 136 adjusts the current reading of level gauge 118.
Level gauge 118 will indicate a decrease in the amount of liquefied
gas present in Dewar tank 102.
[0020] Filling a Dewar tank with liquefied gas using the automated
shutoff and metering mechanism described above eliminates a need
for constant manual monitoring of a fill operation. The fill
operation is started and proceeds without additional intervention
required. The amount of liquefied gas used to fill the Dewar tank
is never over-exceeded. Further, the addition of a level gauge near
the bottom of the Dewar tank provides constant indication of the
amount of liquefied gas remaining in the Dewar tank. The placement
of the level gauge near the bottom of the tank eliminates
difficulties in reading the gauge under conditions of frost
accumulation on the top of the Dewar tank.
[0021] FIG. 2 is a block diagram of another embodiment of a
liquefied gas containment system, indicated generally at 200,
according to the teachings of the present invention. System 200
comprises the same Dewar tank 102, mobile base 104, and scale 106
as indicated above in FIG. 1. In one embodiment, system 200 is
identical in every respect to system 100 except that scale linkage
134, level gauge link 136, and level gauge 118 are replaced by
control unit 202 and level meter 208. Moreover, control unit 202
comprises valve control interface 204 and level meter interface
206. Valve control interface 204 is electrically coupled to shutoff
valve 120. In one embodiment, valve control interface 204 is an
electrical interface that controls the operation of shutoff valve
120 based on instructions received from control unit 202. Level
meter interface 206 is communicatively coupled to level meter 208.
In one embodiment, level meter 208 comprises an electronic readout
to indicate a current level of liquefied gas in Dewar tank 102. The
electronic readout is updated with digital measurements received
from level meter interface 206 regarding the current level of
liquefied gas in Dewar tank 102.
[0022] In operation similar to that described with respect to FIG.
1 above, adjustment knob 114 is adjusted so that a starting reading
of scale 106 is substantially equal to the weight of Dewar tank 102
when Dewar tank 102 does not contain a substantial amount of
liquefied gas. In one embodiment, once the starting reading of
scale 106 is established, control unit 202 is adjusted so that an
end reading of scale 106, e.g., a reading of scale 106 when Dewar
tank 102 is filled with liquefied gas, will position shutoff valve
120 in a closed position. Moreover, current valve positions of
shutoff valve 120 will be maintained by valve control interface
204. Prior to operation, control unit 202 is configured to position
shutoff valve 120 in a fully open position. Once shutoff valve 120
is adjusted and feed line 112 is attached to system 200, a
liquefied gas is supplied to system 200 by feed line 112. As the
liquefied gas enters system 200, the liquefied gas is transported
as described above with respect to FIG. 1. In one embodiment, the
increased weight of Dewar tank 102 causes scale 106 to notify
control unit 202 of an increase in the weight of Dewar tank 102.
The notification provided to control unit 202 is further
transferred to valve control interface 204, which automatically
begins closing shutoff valve 120. In one embodiment, the increase
in the weight of Dewar tank 102 is communicated as a meter reading
update to meter interface 206. Level meter 208 receives the meter
reading update from meter interface 206, and the electronic readout
of level meter 208 is updated to indicate a current amount of
liquefied gas in Dewar tank 102. In the case of an increase in
weight of Dewar tank 102, the current reading of level meter 208
indicates an increase in the amount of liquefied gas present in
Dewar tank 102.
[0023] As additional liquefied gas enters system 200, valve control
interface 204 continually adjusts shutoff valve 120 closer to the
closed position. At the time when scale 106 detects that Dewar tank
102 is filled with the liquefied gas, valve control interface 204
has placed shutoff valve 120 in the closed position. Once shutoff
valve 120 is placed in the fully closed position, valve control
interface 204 will no longer change the valve position of shutoff
valve 120. In one embodiment, the closed position of shutoff valve
120 translates to the current reading of level meter 208 to
indicate that Dewar tank 102 is filled with the liquefied gas.
Moreover, control unit 202 remains in operation once system 100 is
disconnected from feed line 112. Further, level meter 208 continues
to provide an electronic indication, e.g., digital readout, of the
amount of liquefied gas remaining in Dewar tank 102. Similar to the
embodiment described above with respect to FIG. 1, system 200 is
capable of being transported via mobile base 104. As the liquefied
gas is used, scale 106 will record a decrease in weight of Dewar
tank 102. In response, control unit 202 adjusts the current reading
of level meter 208. Level meter 208 will indicate a decrease in the
amount of liquefied gas present in Dewar tank 102.
[0024] FIG. 3 is a flow diagram illustrating an embodiment of a
method, according to the teachings of the present invention, for
filling a pressurized container with a pressurized medium. In one
embodiment, the pressurized medium is a one of a gas or a liquid.
In a similar embodiment, the pressurized medium is a liquefied gas.
The method of FIG. 3 begins at block 302. Once the pressurized
container is placed into position, the method of FIG. 3 begins. In
one embodiment, the method of FIG. 3 is designed to fill a Dewar
tank connected to a liquefied gas supply shutoff and metering
system which includes a scale and a shutoff valve linked together.
The system is capable of accommodating Dewars of different
capacities. In addition, a gauge mechanism accurately records a
remaining level of LN2 in the Dewar at all times. Moreover, the
entire system is suited for placement on a mobile base.
[0025] At block 302, the method begins by establishing a starting
reading on a scale with a scale linkage before proceeding to block
304. In one embodiment, establishing the starting reading on the
scale further includes adjusting the scale until the starting
reading is substantially equal to a weight of the container when
the container does not contain a substantial amount of gas.
[0026] At block 304, the method continues by adjusting the scale
linkage to an initial starting position to place a shutoff valve,
attached to the liquefied gas container, in a fully open position
before proceeding to block 306. In one embodiment, adjusting the
scale linkage further includes adjusting for a final reading that
will place the shutoff valve in a closed position. Moreover, the
final reading corresponds to a reading of the scale when the
container is filled with the liquefied gas.
[0027] At block 306, the method attaches a gas feed line to the
shutoff valve before proceeding to block 308. At block 308, as
liquefied gas enters the container, the method detects an increase
in weight of the container. As the weight of the container
increases, adjusting a current position of the scale linkage is
adjusted at block 310. In one embodiment, the current position of
the shutoff valve is maintained by a current position of the scale
linkage. At block 312, the method concludes by positioning the
shutoff valve in a fully closed position and the scale linkage in a
final position once the scale detects that the container is
substantially filled with the liquefied gas. In one embodiment, the
scale linkage is prevented from automatically re-opening the
shutoff valve once the shutoff valve is in the fully closed
position.
[0028] Although specific embodiments have been illustrated and
described herein, it will be appreciated by those of ordinary skill
in the art that any arrangement, which is calculated to achieve the
same purpose, may be substituted for the specific embodiment shown.
This application is intended to cover any adaptations or variations
of the present invention. Therefore, it is manifestly intended that
this invention be limited only by the following claims and the
equivalents thereof.
* * * * *