U.S. patent application number 09/840321 was filed with the patent office on 2001-08-16 for keypad for portable telephone and manufacturing method thereof.
This patent application is currently assigned to You Eal Electronics Co., Ltd Korea corporation. Invention is credited to Yang, Yoon-Hong.
Application Number | 20010014152 09/840321 |
Document ID | / |
Family ID | 36746280 |
Filed Date | 2001-08-16 |
United States Patent
Application |
20010014152 |
Kind Code |
A1 |
Yang, Yoon-Hong |
August 16, 2001 |
Keypad for portable telephone and manufacturing method thereof
Abstract
A keypad for a portable telephone and manufacturing method
thereof is disclosed. The method comprises the steps of printing
characters on a transparent, planar film; pre-forming the planar
film through a pressing process such that the planar film has a
predetermined shape including a plurality of depressions; punching
slits in the pressed planar film around the depressions; filling
liquid silicone rubber into the depressions of the pressed planar
film; forming a keypad by pressing the silicon rubber in a metal
mold so as to fabricate an integrated keypad in which keys are
interconnected; and trimming an outer periphery of the formed
keypad according to a predetermined keypad shape.
Inventors: |
Yang, Yoon-Hong; (Seoul,
KR) |
Correspondence
Address: |
Y. ROCKY TSAO
Fish & Richardson P.C.
225 Franklin Street
Boston
MA
02110-2804
US
|
Assignee: |
You Eal Electronics Co., Ltd Korea
corporation
|
Family ID: |
36746280 |
Appl. No.: |
09/840321 |
Filed: |
April 23, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09840321 |
Apr 23, 2001 |
|
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09470272 |
Dec 22, 1999 |
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Current U.S.
Class: |
379/422 ;
156/227; 379/442 |
Current CPC
Class: |
Y10T 156/1051 20150115;
H01H 2219/028 20130101; Y10T 156/1062 20150115; H01H 13/702
20130101; H01H 2231/022 20130101; H01H 2219/03 20130101; H01H
2229/047 20130101; B29K 2083/005 20130101; Y10T 156/108
20150115 |
Class at
Publication: |
379/422 ;
156/227; 379/442 |
International
Class: |
B31F 001/00; H04M
009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 31, 1998 |
KR |
98-63310 |
Oct 29, 1999 |
KR |
99-47619 |
Claims
What is claimed is:
1. A method for manufacturing a keypad, comprising the steps of:
printing characters on a transparent, planar film; pre-forming the
planar film through a pressing process such that the planar film
has a predetermined shape including a plurality of depressions;
punching slits in the pressed planar film around the depressions;
filling liquid silicone rubber into the depressions of the pressed
planar film; forming a keypad by pressing the silicon rubber in a
metal mold so as to fabricate an integrated keypad in which keys
are interconnected; and trimming an outer periphery of the formed
keypad according to a predetermined keypad shape.
2. The method as recited in claim 1, wherein the characters are
printed on a rear side of the planar film.
3. The method as recited in claim 1, wherein in the step of
pre-forming the planar film, a hot press is used, the hot press
being heated to a predetermined temperature such that a uniform
film thickness is maintained and a distortion of the characters
caused by film expansion is prevented.
4. The method as recited in claim 1, wherein in the step of
pre-forming the planar film, grooves are formed in the planar film
in which light emitting devices are located.
5. The method as recited in claim 1, wherein in the step of
punching the slits, non-cutting, connecting portions are left
between the slits such that the film is maintained as a single-body
structure.
6. A keypad for a portable telephone, comprising: a printed circuit
board having a plurality of contacts; a plurality of dome switches
disposed on the printed circuit board; a plurality of keys for
pushing the plurality of dome switches; and a plurality of light
emitting devices, displaced between the plurality of keys, for
backlighting, wherein grooves are formed between the plurality of
keys to enable the placing of the plurality of light emitting
devices thereon.
7. The keypad as recited in claim 6, wherein slits are punched
around the plurality of keys so that the keys are prevented from
interfering with each other.
8. The keypad as recited in claim 7, wherein non-cutting,
connecting portions are formed between ends of the slits, so that
the keys are not separated from the keypad, the connecting portions
having a predetermined width.
Description
BACKGROUND OF THE INVENTION
[0001] (a) Field of the Invention
[0002] The present invention relates to a keypad for a portable
telephone and a manufacturing method thereof. More specifically,
the present invention relates to a keypad in which film and
silicone rubber are integrated in a single-body structure to
manufacture the keypad.
[0003] (b) Description of the Related Art
[0004] Certain types of electronic equipment such as calculators,
telephones or a portable telephone require a means of inputting
data. A common structure providing this capability is comprised of
a front housing and a keypad, the keypad being assembled into the
housing such that buttons, or keys, of the keypad protrude through
holes provided in the front housing.
[0005] A conventional keypad used in a portable telephone has dome
switches which contact a printed circuit board in response to key
operation. The conventional keypad may be made of plastics (film
type keypad) or silicone rubber (silicone rubber type keypad).
[0006] The silicone rubber type keypad is formed by an injection
molding process in which silicone rubber is used. After injection
molding, characters such as numerals, letters and symbols are
printed on an outer surface of the keypad. A drawback of the
silicone rubber type keypad is the likelihood that the characters
will discolor or rub off after a period of use.
[0007] The film type keypad is formed by an injection molding
process in which plastics are used. After injection molding, a film
on which characters are printed is attached to the keypad. Since
characters are printed on an interior surface of the film, they do
not discolor or rub off with use. However, because the film type
keypad is made of hard plastics, it is not as agreeable to the
touch as a keypad made of a pliant material such as silicone
rubber.
[0008] The inventor of this application disclosed a keypad and
method for overcoming the aforementioned problems in Korean Patent
Application No. 98-63310 filed on Dec. 31, 1999. In the method of
this patent application, after a film, which is pre-formed into a
key shape, is coated with epoxy, the film is filled with silicone
rubber. However, after the epoxy is cured, the epoxy becomes overly
hard such that the keys are difficult to operate. It also takes
long time to fabricate the keypad.
SUMMARY OF THE INVENTION
[0009] In view of the prior art described above, it is an object of
the present invention to provide a keypad and a manufacturing
method thereof in which a time for fabricating the keypad is
minimized by extruding a film and silicone rubber in a single
mold.
[0010] It is another object of the present invention to provide a
keypad and a manufacturing method thereof in which slits are
provided around keys to provide enhanced operation feel to the user
and prevent keys adjacent to the user-targeted key from being
depressed.
[0011] To achieve these objects, as embodied and broadly described
herein, the invention comprises the steps of
[0012] printing characters on a transparent, planar film;
[0013] pre-forming the planar film through a pressing process such
that the planar film has a predetermined shape including a
plurality of depressions;
[0014] punching slits in the pressed planar film around the
depressions;
[0015] filling liquid silicone rubber into the depressions of the
pressed planar film;
[0016] forming a keypad by pressing the silicon rubber in a metal
mold so as to fabricate an integrated keypad in which keys are
interconnected; and
[0017] trimming an outer periphery of the formed keypad according
to a predetermined keypad shape.
[0018] In the pre-forming process, grooves are formed in the planar
film in which light emitting devices are located. It is preferable
to use a hot press in the pre-forming process, which is heated to a
predetermined temperature such that a uniform film thickness is
maintained and a distortion of the characters caused by film
expansion is prevented.
[0019] Also, to achieve these objects, the present invention
provides a keypad for a portable telephone, comprising a printed
circuit board having a plurality of contacts; a plurality of dome
switches disposed on the printed circuit board; a plurality of keys
for pushing the plurality of dome switches; and a plurality of
light emitting devices, displaced between the plurality of keys,
for backlighting.
[0020] In the keypad, grooves are formed between the plurality of
keys to enable the placing of the plurality of light emitting
devices thereon.
[0021] Both foregoing general description and the following
Detailed Description are exemplary and are intended to provide
further explanation of the invention as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The accompanying drawings provide a further understanding of
the invention and, together with the Detailed Description, explain
the principles of the invention. In the drawings:
[0023] FIG. 1 is a flow chart of a method for manufacturing a
keypad for a portable telephone according to a preferred embodiment
of the present invention;
[0024] FIGS. 2A-2D are cross-sectional views of a keypad according
to a preferred embodiment of the present invention as the keypad
undergoes sequential manufacturing processes;
[0025] FIGS. 3A-3B are exploded perspective views of the keypad
shown in FIG. 2D, a front housing, a dome switch assembly, and a
printed circuit board; and
[0026] FIG. 4 is a cross-sectional view of the keypad, front
housing, dome switch assembly, and printed circuit board shown in
FIGS. 3A and 3B in an assembled state.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0027] The present invention will be described in detail with
reference to the accompanying drawings.
[0028] Referring to FIG. 1, a method for manufacturing a keypad for
portable telephones according to a preferred embodiment of the
present invention will be explained.
[0029] First, characters such as numerals, letters and symbols are
printed on a transparent, planar film in step S1. The characters
are printed on a rear side (interior surface) of the planar film in
step S1. Accordingly, the user does not directly contact the
printed characters, thereby avoiding discoloring and effacing
problems.
[0030] Next, the rear side of the film is coated with adhesive in
step S2 such that silicone rubber can adhere to the rear side of
the film in a process to follow. Subsequently, the film is pressed
into predetermined key shapes by a press in step S3. This step is
referred to as a film pre-forming process and is performed by a hot
press which is heated up to a predetermined temperature or by the
direct heating of the film. Both these methods allow a uniform film
thickness to be maintained and prevent a distortion of the
characters due to film expansion. When performing the pre-forming
process of step S3, dome-shaped grooves are also formed between
keys to enable positioning of light emitting diodes (LEDs) which
are used for backlighting.
[0031] Following the above step, slits are formed around each key
on the film in step S4 in order to avoid difficulty of operation
due to the hardness of the film. In particular, two slits are
punched around each key, so as to prevent a key(s) adjacent to the
user-targeted key from being unintentionally depressed and to
improve comfort of operation. That is, a pair of slits are
preferably formed at a predetermined length around a circumference
of each key such that two non-cut portions remain between ends of
the slits at each key. Accordingly, each key is not separated from
the film and the film maintains a single-body structure. The
non-cut portions between the ends of the slits have a predetermined
width.
[0032] The pre-formed film with the predetermined key shapes is
inserted into a first metal mold which has the same shape as the
film, then each key is filled with liquid silicone rubber by a
filling machine in step S5. In step S5, an amount of the silicone
rubber filled in each key is such that the silicone rubber slightly
overflows each key (i.e., a volume of the silicone rubber filled in
each key is slightly larger than a volume of each key). Following
the filling process of step S5, a second metal mold is placed over
the first metal mold then pressed, thereby obtaining a completed
keypad shape in step S6. This step is referred to as a keypad
forming process. Because the volume of silicone rubber in each key
is slightly larger than that of each key, silicon rubber is spread
between the keys when the second metal mold is pressed onto the
first metal mold. Therefore, the keys are interconnected, resulting
in a single-body structure with the film. Also, because the film is
applied with adhesive in step S2 as described above, the silicone
rubber tightly adheres to the film, further enhancing and ensuring
the single-body structure with the film.
[0033] After the keypad forming process of step S6, the silicone
rubber is cured for a predetermined time. After allowing the keypad
to cure, trimming or profiling is performed, in which the formed
keypad is cut to its final shape in step S7, thereby completing the
manufacture of the keypad. In this step, external edges of the
keypad are cut and holes needed to fix the keypad to a front
housing of a portable telephone are formed. FIGS. 2A-2D are
cross-sectional views of a keypad according to a preferred
embodiment of the present invention as the keypad undergoes
sequential manufacturing processes.
[0034] Referring first to FIG. 2A, characters are printed on a
surface 4 of a transparent, planar film 2, the planar film 2 having
a thickness of about 0.25-0.5 mm. Next, an adhesive is coated on
the printed surface 4 to form an adhesive layer 6.
[0035] The film 2 can be made of a synthetic resin such as
polycarbonate, or of any material having a predetermined strength
and flexibility. It is preferable that the adhesive layer 6
provides good adhesion between the film 2 and silicone rubber, and
is coated with a minimum thickness, as long as a predetermined
level of adhesion is obtained.
[0036] As shown in FIG. 2B, a hot press (not shown), heated to a
predetermined temperature, is used to press the film 2, the printed
surface 4 and the adhesive layer 6 into a predetermined shape. That
is, the film pre-forming process is performed in which the film 2,
the printed surface 4 and the adhesive layer 6 are pressed by the
hot press such that a plurality of key-shaped depressions 7 are
formed.
[0037] Also formed during the film pre-forming process are
dome-shaped grooves 8. The dome-shaped grooves 8 are formed between
the depressions 7, and are used to position LEDs such that back
lighting is provided to the keypad. Since the LEDs are at least
partially placed on the grooves 8, the amount of space in the
portable phone occupied by the LEDs is reduced, resulting in a
compact portable telephone.
[0038] After the pre-forming process is completed, slits 10 are
punched around each depression 7 (or key) as shown in FIG. 2C. The
slits 10 prevent a key(s) adjacent to a user-targeted key from
being unintentionally depressed.
[0039] When the slits 10 are formed, two non-cut portions remain
between ends of each pair of slits 10 at each depression 7.
Accordingly, each depression 7 is not separated from the film 2 and
the film 2 maintains a single-body structure together with the
printed surface 4 and the adhesive layer 6. The non-cut portions
between the ends of the slits 10 have a predetermined width.
[0040] Subsequently, the film 2 is inserted into a first metal mold
which has the same shape as the film 2. Next, as shown in FIG. 2D,
the depressions 7 are filled with liquid silicone rubber. At this
time, an amount of the silicone rubber filled in each depression 7
is such that the silicone rubber slightly overflows each depression
7 (i.e., a volume of the silicone rubber filled in each depression
7 is slightly larger than that a volume of each depression 7.
[0041] After the above, a second metal mold is placed over the main
metal mold. The second metal mold shapes a rear side of the keypad.
By pressing the second metal mold onto the first metal mold,
completed keys 17 are formed. Three sides of each key 17 are
defined by the depressions 7 of the pre-formed film 2, printed
surface 4 and adhesive layer 6; and on the rear side of the keypad,
resulting from filling the depressions 7 with silicon rubber and
pressing the second metal mold onto the first metal mold, each key
17 comprises an interior 12, a contact projection 14 and a skirt
16. The contact projection 14 extends in a direction opposite the
direction the depressions 7 are formed and from a center of each
key interior 12. The skirt 16 is formed around a circumference of a
proximal end of each contact projection 14. The skirts 16 provide
elasticity to each key 17 to enhance operation comfort and to help
restore the keys 17 to their original position after they are
pushed.
[0042] Since the volume of silicone rubber filled in each
depression 7 is slightly larger than the volume of each depression
7, the pressing of the second metal mold onto the first metal mold
spreads the silicon rubber between depressions 7. Therefore, rubber
connecting parts 19 are also formed between the keys 17. Each key
17 is connected through the rubber connecting parts 19, thereby
forming an integrated, single-body keypad. Also, holes 18 are
formed through the rubber connecting parts 19 at areas
corresponding to the grooves 8 of the pre-formed film 2. This
allows for the positioning of LEDs on the grooves 8. Finally, outer
peripheries of the keypad are cut, and a plurality of fixing holes
20 is formed through both the rubber connecting parts 19 and the
film 2 (i.e., the film 2, the printed surface 4 and the adhesive
layer 6). The fixing holes 20 are formed at predetermined positions
and are used to fix the keypad to a front housing of a portable
telephone. Because the film 2 is coated with the adhesive layer 6,
the interior 12 of each key 17 and the rubber connecting parts 19
are securely adhered to the film 2. That is, the film 2 is
integrated with the silicone rubber such that a single-body
structure is obtained. Therefore, it is easy to assemble the keypad
to a housing of a portable telephone.
[0043] Referring to FIGS. 3A-3B and 4, the fabricated keypad is
assembled into a portable telephone. The keypad is inserted into a
front housing 22 of a portable telephone, each key 17 being placed
in a corresponding opening 24 formed in the front housing 22.
[0044] A printed circuit board 26 is located below the keypad.
Further, dome switches 32 are displaced between the printed circuit
board 26 and the keypad Both the printed circuit board 26 and the
dome switches 32 are supported by projections 28 formed in the
front housing 22 as shown in FIG. 4. Supporting bars 30, integrally
formed extending from the front housing 22, also buttress the
printed circuit board 26 and the dome switches 32 through the
fixing holes 20 of the keypad.
[0045] When assembled, the contact projection 14 of each key 17
contacts a corresponding dome switch 32 on the printed circuit
board 26. When one of the dome switches 32 is pressed by a
corresponding contact projection 14 of the key 17, it contacts a
contact point (not shown) on the printed circuit board 26. The dome
switches 32 are preferably selected from a material having a
predetermined degree of elasticity such that the dome switches 32
can return to their original shape after the user releases pressure
on the keys 17.
[0046] When the user pushes a key 17, the contact projection 14
presses a dome switch 32, which causes the dome switch 32 to
contact the printed circuit board 26 such that a key input signal
is generated. When the user stops pushing, the dome switch 32 and
key 17 restore to their original positions.
[0047] Preferably, the elements of the keypad have suitable
strengths and elasticities to enable them to perform their
particular functions as described.
[0048] It will be apparent to those skilled in the art that various
modifications and variations can be made to the device of the
present invention without departing from the spirit and scope of
the invention. The present invention covers the modifications and
variations of this invention provided they come within the scope of
the appended claims and their equivalents.
* * * * *