U.S. patent application number 12/857665 was filed with the patent office on 2011-03-31 for deposition source.
This patent application is currently assigned to Samsung Mobile Display Co., Ltd.. Invention is credited to Chang-Soon Ji, Do-Sung Kwon, Jong-Woo Lee, Hye-Yeon SHIM.
Application Number | 20110076399 12/857665 |
Document ID | / |
Family ID | 43780672 |
Filed Date | 2011-03-31 |
United States Patent
Application |
20110076399 |
Kind Code |
A1 |
SHIM; Hye-Yeon ; et
al. |
March 31, 2011 |
DEPOSITION SOURCE
Abstract
A deposition source with uniform deposition characteristics
includes a crucible in which a deposition material is disposed; a
heat transfer member disposed on upper portions of the deposition
material in the crucible; and an accommodation member for
accommodating the heat transfer member and including a mesh
plate.
Inventors: |
SHIM; Hye-Yeon;
(Yongin-city, KR) ; Ji; Chang-Soon; (Yongin-city,
KR) ; Lee; Jong-Woo; (Yongin-city, KR) ; Kwon;
Do-Sung; (Yongin-city, KR) |
Assignee: |
Samsung Mobile Display Co.,
Ltd.
Yongin-city
KR
|
Family ID: |
43780672 |
Appl. No.: |
12/857665 |
Filed: |
August 17, 2010 |
Current U.S.
Class: |
427/248.1 ;
118/726 |
Current CPC
Class: |
H01L 51/56 20130101;
H01L 51/001 20130101; C23C 14/30 20130101; C23C 14/26 20130101;
C23C 14/243 20130101; C23C 14/24 20130101 |
Class at
Publication: |
427/248.1 ;
118/726 |
International
Class: |
C23C 16/448 20060101
C23C016/448; C23C 16/00 20060101 C23C016/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 25, 2009 |
KR |
10-2009-0091144 |
Claims
1. A deposition source comprising: a crucible in which a deposition
material is disposed; an accommodation member comprising a mesh
plate and which is disposed adjacent the deposition material; and a
heat transfer member disposed within the accommodation member and
separated from an upper portion of the deposition material by the
mesh plate.
2. The deposition source of claim 1, wherein the heat transfer
member comprises a thermo ball.
3. The deposition source of claim 1, wherein: the accommodation
member comprises a bottom portion disposed between the heat
transfer member and the upper portion of the deposition material,
and a side portion extending from the bottom portion and forming a
side surface of the accommodation member, the bottom portion
comprises the mesh plate, and the side portion comprises another
mesh plate.
4. The deposition source of claim 3, wherein: the accommodation
member further comprises a top portion that is parallel to the
bottom portion and is connected to the side portion such that the
heat transfer member is disposed between the top and bottom
portions, and the top portion comprises a further mesh plate.
5. The deposition source of claim 4, wherein the top portion is
connected to the side portion by welding.
6. The deposition source of claim 3, wherein: the accommodation
member comprises a cover portion disposed on upper portions of the
heat transfer member, and the cover portion comprises a further
mesh plate and is detachable from the side portion.
7. The deposition source of claim 3, further comprising supports
disposed on the side portion and connected to the bottom
portion.
8. The deposition source of claim 7, wherein the supports comprise
titanium (Ti).
9. The deposition source of claim 1, wherein the accommodation
member has a shape formed to correspond to an inner circumferential
surface of the crucible.
10. The deposition source of claim 1, wherein the mesh plate is
formed so that the heat transfer member does not escape from the
accommodation member.
11. The deposition source of claim 1, wherein the heat transfer
member comprises particles having a diameter greater than a size of
openings in the mesh plate.
12. The deposition source of claim 1, wherein the heat transfer
member comprises silicon (Si) powder.
13. A deposition material holder for use in a crucible holding a
deposition material source, the holder comprising: a housing having
openings which allow the deposition material when in a gaseous form
to pass through the housing and which is shaped to be accommodated
in the crucible; and a heat transfer member disposed within the
housing and comprising particles having a diameter greater than a
size of the openings, the particles being non-reactive with the
deposition material and having a good heat transfer efficiency
property and a high heat-resistance property.
14. The holder of claim 13, wherein the heat transfer member
comprises silicon (Si) powder.
15. The holder of claim 13, wherein: the housing comprises a top
and a bottom connected by a side to form a space which accommodates
the particles, and each of the top and bottom comprise the
openings.
16. The holder of claim 15, wherein a shape of the bottom is
substantially a circumferential shape of the crucible at an upper
surface of the deposition material.
17. The holder of claim 15, wherein top is connected to the side by
welding.
18. The holder of claim 15, wherein the top is removable from the
housing.
19. The holder of claim 18, further comprising a protrusion which
extends from the top and supports the top when the top is
removed.
20. A method of performing deposition comprising: accommodating a
deposition material holder in a crucible holding a deposition
material source, the holder comprising: a housing having openings;
and a heat transfer member disposed within the housing and
comprising particles having a diameter greater than a size of the
openings, the particles being non-reactive with the deposition
material and having a good heat transfer efficiency property and a
high heat-resistance property; and heating the crucible and the
particles to transform the deposition material into a gas which
passes through the particles and openings to a substrate.
21. The method of claim 20, further comprising: disposing the
particles within the deposition material holder; and covering the
particles within the deposition material holder with a cover having
the openings.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of Korean Patent
Application No. 10-2009-0091144, filed Sep. 25, 2009 in the Korean
Intellectual Property Office, the disclosure of which is
incorporated herein by reference.
BACKGROUND
[0002] 1. Field
[0003] Aspects of the present invention relate to a deposition
source, and more particularly, to a deposition source with uniform
deposition characteristics.
[0004] 2. Description of the Related Art
[0005] Electronic devices include a fine thin film and use various
methods to form the fine thin film. Particularly, flat display
devices are manufactured by forming a plurality of thin films.
Thus, in order to improve the characteristics of flat display
devices, the characteristics of the plurality of thin films need to
be improved.
[0006] Organic light-emitting display apparatuses, among flat
display devices, have a larger viewing angle, better contrast
characteristics, and a faster response rate than other flat display
devices, and thus have drawn attention as a next-generation display
device. An organic light-emitting layer that emits visible rays
from an organic light-emitting display apparatus, and organic
layers disposed around the organic light-emitting layer are formed
using various methods. Particularly, vacuum deposition, which is a
simple process, is frequently used to form the organic layers. In
vacuum deposition, a deposition material in a powder form is put in
a crucible used in a deposition process, and is heated to form a
deposited film in a desired portion.
[0007] A dotted deposition source, a linear deposition source or a
plate-shaped deposition source is used in the vacuum deposition.
Specifically, in vacuum deposition, a deposition material in a
powder form is put in a crucible. The crucible is heated so that
gas particles may be moved towards a substrate and the deposition
material is deposited on the substrate to form a deposited
film.
[0008] In this process, heat is non-uniformly transferred to the
deposition material. As such, the deposition material may be
non-uniformly vaporized. Also, a splash phenomenon can occur, where
the deposition material forms into a mass and splashes out of the
deposition source while it is being vaporized. As such, deposition
characteristics of the deposition source are lowered, and there is
a limitation in forming a desired deposited film.
SUMMARY
[0009] Aspects of the present invention provide a deposition source
with improved deposition characteristics.
[0010] According to an aspect of the present invention, there is
provided a deposition source including: a crucible in which a
deposition material is disposed; a heat transfer member disposed on
an upper portion of the deposition material filled in the crucible;
and an accommodation member for accommodating the heat transfer
member and including a mesh plate.
[0011] According to an aspect of the invention, the heat transfer
member may be a thermo ball.
[0012] According to an aspect of the invention, the accommodation
member may include a bottom portion disposed facing the deposition
material and a side portion that is connected to the bottom portion
and forms a side surface of the accommodation member, where the
bottom portion and the side portion are formed in a shape of the
mesh plate.
[0013] According to an aspect of the invention, the accommodation
member may further include a top portion that is parallel to the
bottom portion and is connected to the side portion, where the top
portion is formed in a shape of the mesh plate.
[0014] According to an aspect of the invention, the top portion may
be connected to the side portion by welding.
[0015] According to an aspect of the invention, the accommodation
member may include a cover portion disposed on upper portions of
the deposition material, and the cover portion may be formed in the
shape of the mesh plate.
[0016] According an aspect of the invention, supports may be
disposed on the side portion, and the supports may be connected to
the bottom portion.
[0017] According to an aspect of the invention, the supports may
include titanium (Ti).
[0018] According to an aspect of the invention, the accommodation
member may be formed to correspond to an inner circumferential
surface of the crucible.
[0019] According to an aspect of the invention, the mesh plate may
be formed so that the heat transfer member does not escape from the
accommodation member.
[0020] Additional aspects and/or advantages of the invention will
be set forth in part in the description which follows and, in part,
will be obvious from the description, or may be learned by practice
of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The above and other features and advantages of the present
invention will become more apparent by describing in detail
exemplary embodiments thereof with reference to the attached
drawings in which:
[0022] FIG. 1 is a schematic front view of a deposition device
including a deposition source according to an embodiment of the
present invention;
[0023] FIG. 2 is a cross-sectional view taken along line II-II of
FIG. 1;
[0024] FIG. 3 is a schematic perspective view of an accommodation
member of FIG. 2;
[0025] FIGS. 4A and 4B are perspective views of an accommodation
member of a deposition source according to another embodiment of
the present invention;
[0026] FIG. 5 is a schematic front view of a deposition device
including a deposition source according to another embodiment of
the present invention;
[0027] FIG. 6 is a cross-sectional view taken along line VI-VI of
FIG. 5;
[0028] FIG. 7 is a schematic perspective view of an accommodation
member of FIG. 6; and
[0029] FIG. 8 is a perspective view of an accommodation member of a
deposition source according to another embodiment of the present
invention.
DETAILED DESCRIPTION
[0030] Reference will now be made in detail to the present
embodiments of the present invention, examples of which are
illustrated in the accompanying drawings, wherein like reference
numerals refer to the like elements throughout. The embodiments are
described below in order to explain the present invention by
referring to the figures.
[0031] FIG. 1 is a schematic front view of a deposition device 1000
including a deposition source 100 according to an embodiment of the
present invention, FIG. 2 is a cross-sectional view taken along
line II-II of FIG. 1, and FIG. 3 is a schematic perspective view of
an accommodation member 130 of FIG. 2.
[0032] Referring to FIG. 1, the deposition device 1000 includes a
chamber 101 and a deposition source 100 disposed in the chamber
101. A substrate 103 is disposed in the chamber 101 facing the
deposition source 100. The substrate 103 is a region on which a
deposition material is to be deposited. A deposition process may be
performed after the substrate 103 is fixed in the deposition device
1000 with a clamp or a support (not shown), but aspects of the
invention are not limited to specific fixing devices.
[0033] At least one pump (not shown) is connected to the chamber
101 to keep the chamber 101 in a vacuum state or under low
pressure. Also, an outlet 102 is disposed at a side surface of the
chamber 101. The substrate 103 is transferred between the inside
and outside of the chamber 101 through the outlet 102. While shown
as a single outlet 102, it is understood that multiple outlets can
be used to provide multiple pathways between the inside and outside
of the chamber 101.
[0034] As shown in the embodiment in FIG. 2, the deposition source
100 includes a crucible 110, an accommodation member 130, and a
heat transfer member 150. The crucible 110 is filled with a
deposition material 120. The shown deposition source 100 is of a
point type and includes a rectangular crucible 110. However, the
present invention is not limited thereto, and the deposition source
100 may include a crucible 110 having, for example, a circular
cross-section. The crucible 110 may be formed of material such as
metal or conductive ceramics, but the invention is not limited
thereto.
[0035] The deposition material 120 is heated by a heating unit (not
shown), and is changed to a gaseous state. The deposition material
120 in the gaseous state leaves the crucible 110, and moves to the
substrate 103 on which the deposition material is deposited to form
a layer of the deposition material. The heating unit may heat the
crucible 110 by using electron beam heating or resistive heating,
but the invention is not limited thereto.
[0036] The accommodation member 130 accommodates the heat transfer
member 150. The accommodation member 130 is disposed in the
crucible 110 to cover the deposition material 120 such that the
deposition material 120 in the gaseous state moves through the heat
transfer member 150. The heat transfer member 150 allows heat to be
uniformly transferred to the deposition material 120 when the
crucible 110 is heated, so that uniformity of deposition is
improved. The heat transfer member 150 may be heat transfer
particles like thermo ball, but the invention is not limited
thereto.
[0037] The heat transfer member 150 includes material that does not
affect the deposition material 120 and has good heat transfer
efficiency and high heat-resistance properties so that the heat
transfer member 150 is not damaged even at a high temperature. In
detail, the heat transfer member 150 may include a silicon (Si)
powder having an appropriate diameter, but the invention is not
limited thereto.
[0038] When the deposition material 120 is an organic material, a
splash phenomenon can occur where the deposition material 120 is
locally heated and the organic material forms into a mass and
splashes out of the deposition source 100. The heat transfer member
150 is disposed on the deposition material 120, and vaporized gas
particles of the deposition material 120 pass through the heat
transfer member 150 and are discharged to the substrate 103. In
other words, the gas particles when in a mass form do not pass
through the heat transfer member 150. Thus, the splash phenomenon
may be efficiently prevented.
[0039] The heat transfer member 150 is disposed in the
accommodation member 130. The accommodation member 130 includes a
bottom portion 131, a side portion 132, and a top portion 133. The
bottom portion 130, the side portion 132, and the top portion 133
are formed in the shape of a mesh plate. In detail, the bottom
portion 130, the side portion 132, and the top portion 133 have a
mesh that is smaller than the size of particles of the heat
transfer member 150 so that the heat transfer member 150 may not
escape from the accommodation member 130. While shown as square, it
is understood that the accommodation member 130 can be other shapes
depending on the shape of the deposition material 120 and the
crucible 110. Further, the side portion 132 can have a single
continuous side as opposed to separate sides as shown, such as
where the crucible 110 has a round cross section, and the side
portion 132 need not be of a mesh and can be a solid surface
without openings. Lastly, while described as a mesh plate, it is
understood that the surfaces can be of any material having
openings, and the openings need not be of uniform size.
[0040] The bottom portion 131, the side portion 132, and the top
portion 133 of the accommodation member 130 are formed of metal
having heat-resistance properties. However, the present invention
is not limited thereto. The bottom portion 131, the side portion
132, and the top portion 133 of the accommodation member 130 may be
formed of various materials having high durability so as to
efficiently accommodate the heat transfer member 150.
[0041] The accommodation member 130 further includes supports 134.
The supports 134 are disposed on corner edges of the side portion
132. The supports 134 connect the bottom portion 131 and the top
portion 133 so that durability of the accommodation member 130 is
improved. The supports 134 may include titanium (Ti) having high
durability, but the invention is not limited thereto.
[0042] The accommodation member 130 accommodates the heat transfer
member 150 so that the heat transfer member 150 is uniformly
distributed above the deposition material 120. The heat transfer
member 150 is in the form of particles and needs to be uniformly
distributed over the deposition material 120 so that heat is
uniformly transferred to the deposition material 120 and the splash
phenomenon of the deposition material 120 is efficiently
prevented.
[0043] The particles of the heat transfer member 150 can become
concentrated in one direction from an upper portion of the
deposition material 120 due to shaking of the crucible 110 or a
change of distribution of pressure in the crucible 110. However,
with the heat transfer member 150 is disposed in the accommodation
member 130, the particles of the heat transfer member 150 are
uniformly disposed on the upper portion of the deposition material
120. Particularly, when the accommodation member 130 is completely
filled with the heat transfer member 150 so that there is no space
in the accommodation member 130, the heat transfer member 150 may
be uniformly and more efficiently disposed on the upper portion of
the deposition material 120. However, it is understood that other
mechanisms can be used to ensure uniformity such that the
accommodation member 130 need not be completely filled with the
particles.
[0044] Also, the accommodation member 130 may be formed to
correspond to an inner circumferential surface of the crucible 110.
Thus, the accommodation member 130 may not be shaken in the
crucible 110 but may be stably disposed on the upper portion of the
deposition material 120. In this case, the bottom portion 130, the
side portion 132, and the top portion 133 of the accommodation
member 130 are formed in the shape of a mesh plate having a mesh
that is smaller than the size of particles of the heat transfer
member 150 so that the heat transfer member 150 may be easily and
stably accommodated in the accommodation member 130 and allows
vaporized gas particles to proceed therethrough. As such, a uniform
deposition process may be easily performed.
[0045] In the shown embodiment, the accommodation member 130
includes the top portion 133. The top portion 133 of the
accommodation member 130 is separated from the accommodation member
130 before the heat transfer member 150 is disposed in the
accommodation member 130, and after the heat transfer member 150 is
disposed in the accommodation member 130, the top portion 133 may
be connected to the side portion 132 of the accommodation member
130 through welding. However, it is understood that the top portion
133 could be otherwise connected. Further, in order to ensure the
particles are uniformly distributed, the top portion 133 could be
movable relative to a bottom portion 131 to change an internal
volume of the accommodation member 130 to allow for different
amounts of the heat transfer member 150, such as by using a screw
to adjust the height of the top member 133.
[0046] FIGS. 4A and 4B are perspective views of an accommodation
member 230 of a deposition source according to another embodiment
of the present invention. For convenience of explanation, only a
difference between the present embodiment and the previous
embodiment will now be described. Specifically, only the features
of the accommodation member 230 that are different from those of
the previous embodiment will now be described.
[0047] A heat transfer member 250 is disposed in the accommodation
member 230. The accommodation member 230 includes a bottom portion
231, a side portion 232, and a cover portion 233. Also, supports
234 are disposed on the side portion 232. The bottom portion 230,
the side portion 232, and the cover portion 233 are formed in the
shape of a mesh plate. Specifically, the bottom portion 230, the
side portion 232, and the top portion 233 are formed in the shape
of a mesh plate having a mesh that is smaller than the size of
particles of the heat transfer member 250 so that the heat transfer
member 250 may not escape from the accommodation member 230.
[0048] In the shown embodiment, the accommodation member 230
includes a cover portion 233. The cover portion 233 is not bonded
to the side portion 232 by welding. Referring to FIG. 4A, after the
heat transfer member 250 is disposed in the accommodation member
230, the heat transfer member 250 is covered by the cover portion
233 and is fixed in the accommodation member 230, as illustrated in
FIG. 4B. The cover portion 233 includes protrusions 233a that allow
the cover portion 233 to be easily moved and support the cover
portion 233.
[0049] The accommodation member 230 according to the present
embodiment includes the cover portion 233 that is separated from
the accommodation member 230, unlike the accommodation member 130
according to the previous embodiment. Thus, the heat transfer
member 250 may be easily disposed in the accommodation member 230
and may be easily removed therefrom. Also, the amount of the heat
transfer member 250 disposed in the accommodation member 230 may be
differently adjusted according to various deposition process
conditions.
[0050] FIG. 5 is a schematic front view of a deposition device 2000
including a deposition source 300 according to another embodiment
of the present invention, and FIG. 6 is a cross-sectional view
taken along line VI-VI of FIG. 5, and FIG. 7 is a schematic
perspective view of an accommodation member 330 of FIG. 6. For
convenience of explanation, only a difference between the present
embodiment and the previous embodiment of FIG. 1 will now be
described.
[0051] Referring to FIG. 5, the deposition device 2000 includes a
chamber 201 and the deposition source 300 disposed in the chamber
201. A substrate 203 is disposed in the chamber 201 facing the
deposition source 300. Also, an outlet 202 is disposed at a side
surface of the chamber 201 and is through which the substrate 203
is transferred between the outside and the inside of the chamber
201.
[0052] The deposition source 300 is of linear type in which the
deposition source 300 extends from a lengthwise direction of the
substrate 203. The deposition source 300 extends in one direction,
and the width of the deposition source 300 in another direction is
smaller than the length of the substrate 203.
[0053] Since the deposition source 300 is of linear type in which
the deposition source 300 extends from the lengthwise direction of
the substrate 203, the deposition source 300 may be moved so that
the deposition process may be performed in the entire area of the
substrate 203. A moving portion 305 that moves in one direction or
multiple directions is disposed on the bottom end of the deposition
source 300. The deposition source 300 is moved by the moving
portion 305 in a straight direction so that the deposition process
may be uniformly performed on the substrate 203. While depicted as
a wheel, it is understood that the moving portion 305 is not
limited thereto.
[0054] The deposition source 300 includes a rectangular crucible
310 in which a deposition material 320 is disposed, an
accommodation member 330, and a heat transfer member 350. The
accommodation member 330 accommodates the heat transfer member 350
and is disposed in the crucible 310. The heat transfer member 350
allows heat to be uniformly transferred to the deposition material
320 when the crucible 310 is heated, so that uniformity of
deposition is improved. The heat transfer member 350 may be a
thermo ball, but the invention is not limited thereto.
[0055] The accommodation member 330 includes a bottom portion 331,
a side portion 332, and a top portion 333. The bottom portion 331,
the side portion 332, and the top portion 333 are formed in the
shape of a mesh plate. In detail, the bottom portion 331, the side
portion 332, and the top portion 333 have a mesh that is smaller
than the size of particles of the heat transfer member 350 so that
the heat transfer member 350 may not escape from the accommodation
member 330.
[0056] The accommodation member 330 further includes supports 334.
The supports 334 are disposed on corner edges of the side portion
132. The supports 334 connect the bottom portion 331 and the top
portion 333 so that durability of the accommodation member 330 is
improved. The supports 334 may include titanium (Ti) having high
durability, but the invention is not limited thereto.
[0057] The accommodation member 330 accommodates the heat transfer
member 350 so that the heat transfer member 350 may be uniformly
distributed over the deposition material 320. In other words, due
to the accommodation member 330, the particles of the heat transfer
member 350 are not concentrated in one direction but are uniformly
disposed on upper portions of the deposition material 320.
Particularly, when the accommodation member 330 is completely
filled with the heat transfer member 350 so that there is no space
in the accommodation member 330, the heat transfer member 350 may
be uniformly and more efficiently disposed on the upper portions of
the deposition material 320. However, it is understood that other
mechanisms can be used to ensure uniformity such that the
accommodation member 330 need not be completely filled with the
heat transfer member 350 in all aspects of the invention.
[0058] Also, the accommodation member 330 may be formed to
correspond to an inner circumferential surface of the crucible 310.
Thus, the accommodation member 330 may not be shaken in the
crucible 310 but may be stably disposed on the upper portions of
the deposition material 320.
[0059] In the shown embodiment, the accommodation member 330
includes the top portion 333. The top portion 333 is separated from
the accommodation member 330 before the heat transfer member 350 is
disposed in the accommodation member 330, and after the heat
transfer member 350 is disposed in the accommodation member 330,
the top portion 333 may be connected to the side portion 332 by
welding.
[0060] FIG. 8 is a perspective view of an accommodation member 430
of a deposition source according to another embodiment of the
present invention. For convenience of explanation, only a
difference between the present embodiment and the previous
embodiment will now be described. Specifically, only the features
of the accommodation member 430 that are different from those of
the embodiment shown in FIGS. 5 through 7 will now be
described.
[0061] A heat transfer member 450 is disposed in the accommodation
member 430 including a bottom portion 431, a side portion 432, and
a cover portion 433. Also, supports 434 are disposed on the side
portion 432. The bottom portion 430, the side portion 432, and the
cover portion 433 are formed in the shape of a mesh plate.
Specifically, the bottom portion 430, the side portion 432, and the
top portion 433 have a mesh that is smaller than the size of
particles of the heat transfer member 450 so that the heat transfer
member 450 may not escape from the accommodation member 430.
[0062] In the shown embodiment, the accommodation member 430
includes the cover portion 433. The cover portion 433 is not bonded
to the side portion 432 by welding. Referring to FIG. 8, after the
heat transfer member 450 is disposed in the accommodation member
430, the heat transfer member 450 is covered by the cover portion
433 and is fixed in the accommodation member 430. The cover portion
433 includes protrusions 433a that allow the cover portion 433 to
be easily moved and support the cover portion 433.
[0063] The accommodation member 430 according to the present
embodiment includes the cover portion 433 that is separated from
the accommodation member 430, unlike the accommodation member 330
according to the previous embodiment of FIG. 6. Thus, the heat
transfer member 450 may be easily disposed in the accommodation
member 430 and may be easily removed therefrom. Also, the amount of
the heat transfer member 450 disposed in the accommodation member
430 may be differently adjusted according to various deposition
process conditions.
[0064] As described above, in a deposition source according to
aspects of the present invention, deposition characteristics of the
deposition source can be improved.
[0065] Although a few embodiments of the present invention have
been shown and described, it would be appreciated by those skilled
in the art that changes may be made in this embodiment without
departing from the principles and spirit of the invention, the
scope of which is defined in the claims and their equivalents.
* * * * *