U.S. patent application number 11/205850 was filed with the patent office on 2007-03-01 for housing of an electronic device formed by doubleshot injection molding.
This patent application is currently assigned to Apple Computer, Inc.. Invention is credited to Evans Hankey, Jonathan P. Ive, Stephen Paul Zadesky, Rico Zorkendorfer.
Application Number | 20070048470 11/205850 |
Document ID | / |
Family ID | 37804537 |
Filed Date | 2007-03-01 |
United States Patent
Application |
20070048470 |
Kind Code |
A1 |
Zadesky; Stephen Paul ; et
al. |
March 1, 2007 |
Housing of an electronic device formed by doubleshot injection
molding
Abstract
A two shot injection process for forming an enclosure for an
electronic device is disclosed. The two shot injection process
allows for a thinner walled enclosure that uses less materials and
allows for added structural features that would not be possible
using traditional molding techniques. The two shot injection
process generally includes forming one or more walls of an
enclosure with a first shot and thereafter forming the remaining
walls of the enclosure with a second shot. During the second shot,
the walls fuse together thereby forming an integrally molded
enclosure that is one piece.
Inventors: |
Zadesky; Stephen Paul; (San
Carlos, CA) ; Hankey; Evans; (San Francisco, CA)
; Ive; Jonathan P.; (San Francisco, CA) ;
Zorkendorfer; Rico; (San Francisco, CA) |
Correspondence
Address: |
BEYER WEAVER & THOMAS, LLP
P.O. BOX 70250
OAKLAND
CA
94612-0250
US
|
Assignee: |
Apple Computer, Inc.
|
Family ID: |
37804537 |
Appl. No.: |
11/205850 |
Filed: |
August 16, 2005 |
Current U.S.
Class: |
428/35.7 ;
264/328.8; 425/572 |
Current CPC
Class: |
Y10T 428/1352 20150115;
B29C 45/062 20130101; B29C 45/162 20130101 |
Class at
Publication: |
428/035.7 ;
425/572; 264/328.8 |
International
Class: |
B32B 27/08 20060101
B32B027/08; B29C 45/00 20060101 B29C045/00; B29B 7/00 20060101
B29B007/00 |
Claims
1. A method of forming a multiwall enclosure that defines an open
space for placement of internal components via a double shot
injection molding process.
2. The method as recited in claim 1 wherein the multiwall enclosure
is a five wall enclosure with an open end.
3. The method as recited in claim 1 wherein the multiwall enclosure
extends longitudinally from a top to a bottom end of the multiwall
enclosure.
4. The method as recited in claim 1 wherein the double shot
injection molding process comprises: forming one or more walls of
the multiwall enclosure with a first shot; and thereafter, forming
the remaining walls of the multiwall enclosure with a second shot,
the walls of the first shot fusing with the walls of the second
shot during the second shot so as to provide an integrally molded
multiwall enclosure that is one piece.
5. The method as recited in claim 4 wherein a first side of the
multiwall enclosure is formed during the first shot, and the second
half of the multiwall enclosure is formed during the second
shot.
6. The method as recited in claim 5 wherein the first side of the
multiwall enclosure includes a front wall, right side wall, left
side wall and top wall, and the second side of the multiwall
enclosure includes a back wall.
7. The method as recited in claim 1 wherein the inside surfaces of
the multiwall enclosure have limited or no taper, and wherein the
thickness of the walls of multiwall enclosure is substantially
uniform from a top to a bottom end of the multiwall enclosure.
8. An enclosure having multiple walls for enclosing internal
electronic components of an electronic device, the enclosure being
formed by the process comprising: performing a first injection
molding process, the first injection molding process forming at
least a first wall of the enclosure; allowing the at least a first
wall of the enclosure to solidify; thereafter performing a second
injection molding process, the second injection molding process
forming at least a second wall of the enclosure, the at least a
second wall of the enclosure fusing with the at least a first wall
of the enclosure during the second injection molding process, the
at least second wall of the enclosure forming a different side of
the enclosure than the at least first wall of the enclosure; and
allowing the at least a second wall of the enclosure to solidify,
the at least a second wall of the enclosure being integrally formed
with the at least a first wall of the enclosure.
9. The enclosure as recited in claim 8 wherein the first and second
injection molding processes are performed on the same injection
molding machine.
10. The enclosure as recited in claim 8 wherein the first and
second injection molding processes are performed on the same
injection molding machine.
11. The enclosure as recited in claim 8 wherein the enclosure
extends longitudinally from a top to a bottom end of the enclosure,
and wherein the enclosure defines an open space for placement of
internal components.
12. The enclosure as recited in claim 11 wherein the enclosure
includes 5 walls, a front wall, a back wall, a right side wall, a
left side wall and a top wall.
13. The enclosure as recited in claim 12 wherein the first
injection molding process includes forming at least the front wall,
and the second injection molding process includes forming at least
the back wall.
14. The enclosure as recited in claim 13 wherein the first
injection molding process further includes forming the right side
wall, left side wall and top wall.
15. The enclosure as recited in claim 11 wherein the length of the
enclosure is about 8 times the depth of the enclosure.
16. The enclosure as recited in claim 8 wherein the thickness of
each of the multiple walls is substantially uniform, and wherein
the thickness of each of the walls is between about 1 mm to about
1.5 mm.
17. The enclosure as recited in claim 8 wherein at least a portion
of the walls include internal features that are formed during the
first or second injection molding process and without using
mechanical actions.
18. The enclosure as recited in claim 8 wherein the inside surfaces
of the enclosure are formed with no or a minimal amount of taper
during the first and second injection molding processes.
19. The enclosure as recited in 8 wherein the first and second
walls of the enclosure are formed with the same material.
20. The enclosure as recited in 8 wherein the first and second
walls of the enclosure are formed with a different material.
21. The enclosure as recited in 8 wherein the first and second
walls of the enclosure are formed from a plastic material selected
from polycarbonate (PC), ABS or PC-ABS.
22. The enclosure as recited in claim 8 wherein the enclosure is
configured for a miniature electronic device that includes a
connector that extends out of the open end of the enclosure.
23. The enclosure as recited in claim 8 wherein internal features
are formed on the inside surface of the first wall during the first
injection molding process.
24. A method of forming a single opening enclosure, comprising:
performing a first injection mold process, the first injection mold
process forming a front wall, right and left side walls, and a top
wall of the single opening enclosure; and performing a second
injection mold process, the second injection mold process forming a
back wall of the single opening enclosure, the back wall being
integral with the front, right, left and top walls so as to form a
single integral part.
25. The method as recited in claim 24 wherein the front wall, back
wall, right side wall and left side wall extend longitudinally from
a top to an open end of the enclosure.
26. The method as recited in claim 24 wherein the length of the
enclosure is between about 40 to about 70 times the thickness of
the walls.
27. The method as recited in claim 24 wherein at least a portion of
the walls include internal features that are formed during the
first or second injection molding process and without using
mechanical actions.
28. The method as recited in claim 24 wherein the inside surfaces
of the enclosure are formed with no or a minimal amount of taper
during the first and second injection molding processes.
29. The method as recited in claim 24 wherein the inside surfaces
of the front wall, right side wall and left side wall are formed
with zero taper along the longitudinal axis of the enclosure
between the top and bottom ends of the enclosure.
30. The method as recited in claim 24 further comprising: forming
internal features on the inside surfaces of one or more walls
during the first injection molding process.
31. The method as recited in claim 24 further comprising: forming
internal features on the inside surfaces of one or more walls
during the second injection molding process.
32. A double shot injection molding method for producing an
enclosure of an electronic device having five walls and an open
end, the double shot injection molding comprising: providing mold A
and mold B, mold A including a first injecting area and second
injecting area, the first injecting area including a core, the
second injecting area including a cavity and a movable insert for
forming a wall of the enclosure, mold B including a cavity that
cooperates with the core to form multiple walls of the enclosure;
engaging mold A with mold B so that the core of mold A is partially
inserted into the cavity of mold B, the mold cooperating to form a
void associated with a first half of the enclosure; injecting
plastic into the void so as to form a first half of the enclosure;
allowing the first half of the enclosure to cool and solidify;
disengaging mold A and mold B, the first half of the enclosure
remaining in the mold B after disengagement; rotating mold B so
that the first half of the enclosure is aligned with the second
injection area of mold A; engaging mold A with mold B, the movable
insert being inserted into the first half of the enclosure so that
only the edges of the first half of the enclosure are exposed to
the cavity of mold A; injecting plastic into the cavity of mold A
so as to form a second half of the enclosure, the second half of
the enclosure fusing with the first half of the enclosure during
the injection; allowing the second half of the enclosure to cool
and solidify, the second half of the enclosure being integrally
formed with the first half of the enclosure thereby producing the
entire enclosure; removing the insert from the entire enclosure;
disengaging mold A and mold B, the entire enclosure remaining in
mold B after disengagement; and ejecting the entire enclosure from
mold B.
33. The method as recited in claim 32 further comprising: retaining
the first half of the enclosure inside the cavity when plastic is
injected into the cavity to form the second half of the
enclosure.
34. The method as recited in claim 33 wherein the first half of the
enclosure is retained via retention features located inside the
cavity.
35. The method as recited in claim 32 further comprising: cooling
the insert in order to prevent the softening of the first half of
the enclosure when plastic is injected into the cavity to form the
second half of the enclosure.
36. The method as recited in claim 32 wherein the surfaces of the
insert are polished in the pull direction so that the polishing
lines run parallel to the pull direction.
37. The method as recited in claim 32 further comprising: machining
the enclosure to its final form factor.
38. The method as recited in claim 37 wherein the machining step
includes: forming a circle in the front wall to accommodate a
button or wheel; forming a rectangle in the back wall to
accommodate a switch; and removing excess material generated during
the second shot from the bottom edge of the enclosure.
39. A method of forming an enclosure, comprising: forming first
void, the first void forming a first set of walls of the enclosure;
injecting plastic into first void to form first part; allowing
first part to solidify; inserting wedge into first part; forming
second void, the second void forming the remaining walls of the
enclosure; injecting plastic into the second void to form a second
part, the second part fusing with the first part during the
injection thereby forming a final enclosure with integral first and
second parts; allowing the second part to solidify; and removing
the wedge from the final part, the final part having five walls and
an open end.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates generally to methods of
injection molding and housings formed therefrom. More particularly,
the present invention relates to a housing of an electronic device
formed by double shot injection molding.
[0003] 2. Description of the Related Art
[0004] Injection molding is one of the most popular processes for
manufacturing plastic products. The injection molding process
generally includes (1) injecting molten plastic material into a
closed mold, (2) allowing the plastic to cool down and solidify,
and (3) ejecting the finished product from the mold. This process
may for example be used to form enclosures or housings for various
electronic products.
[0005] Referring to FIG. 1, in order to mold a single opening
enclosure for electronic devices using standard injection molding
processes, the mold 10 typically consists of two parts, a first
mold half 12 that includes a cavity 14, and a second mold half 16
that includes a core 18. When the two mold halves 12 and 16 close,
the core 18 is placed inside the cavity 14, and plastic is injected
through a gate into the open space 22 found between the cavity 14
and the core 18 thereby forming a box like part with an open end.
The part is typically formed vertically along its longitudinal axis
24. After allowing the part to cool, the two mold halves 12 and 16
open and the solidified part is ejected out of the mold, and more
particularly the cavity 14 of the first mold half 12.
[0006] In order to allow proper removal of the core 18 when the
mold halves 12 and 16 are opened, the core 18 typically includes a
draft angle 28 on each of its sides (e.g., four sides). The draft
angle 28 is the amount of taper required to allow the proper
removal of the core 18 from the molded part along the axis 24. That
is, the draft angle 28 allows the core 18 to slide out of the
molded part when the molds are opened. The larger the draft angle
28, the easier it is to get the core 18 out of the part. If there
is no draft angle 28 the core 18 may be difficult to remove from
the molded part (the part shrinks around the core). Although the
draft angle depends on the part design, in most cases a 2 degree
draft angle per side is used. However, the minimum requirement is
typically 1 degree and in some cases the draft angle may be as
small as 1/2 degree. However, in elongated parts that extend
longitudinally as shown, the draft angle 28 tends to be on the high
side as for example at least one degree and more likely 2 degrees.
If a large draft angle is not used, the sticktion force between the
part and the core 18 is difficult to overcome. And even if the
sticktion force is overcome, stresses may be induced in the molded
part and/or the part may be damaged during ejection. A large
sticktion force is typically caused by the large surface area
between the part and the core in the direction of the release
(e.g., along the longitudinal axis 24).
[0007] Unfortunately, because of the draft angle 28, the inside
walls of the molded part are also tapered and as a result the
thickness of the molded part is non-uniform. The thickness varies
longitudinally from thin at the open end 30 to thick at the closed
end 32. While this may not be too problematic in low depth parts,
it can be especially problematic in elongated parts, as the
thickness can become very large at the closed end. In enclosures
for electronic devices, especially small handheld electronic
devices, either the outer dimensions of the part have to grow to
provide the internal space necessary for the internal electronics
or the device is left with less room for these components. That is,
the draft either reduces the amount usable space inside the
enclosure or drives the outside of the enclosure larger to create
the same space for the electronic components inside. Neither of
these results is desirable in small handheld devices where the
outer dimensions are highly controlled and the internal space is at
a premium. Furthermore, the thick wall sections may yield cosmetic
issues such as sinks, cooling/flatness issues, etc. and require
additional plastic material that is not needed thereby driving up
the cost of the product.
[0008] In some cases, it may be desirable to place internal
features such as protrusions, recesses, undercuts, on the inside
surfaces of the molded part. In cases such as these, the core may
include a mechanical action. The mechanical action forces the part
off of the core and at the same time causes the part to be lifted
away from the internal feature thereby allowing the core to be
released from the molded part. If the core was not lifted away, the
part would get stuck on the core as its removed along the
longitudinal axis. By way of example, the core may include a lifter
that forms the internal feature on the inside surface and then
moves away from the internal feature in order to provide enough
clearance during removal.
[0009] Unfortunately, mechanical actions require large cores so
they are not possible with smaller parts, especially small parts
that are thin and long (as shown). With parts such as these, there
is simply not enough room inside the part for mechanical actions
such as those created by lifters. This is especially true at the
closed end of the part. Even if a lifter was somehow placed on the
core, it probably wouldn't make too many cycles before it failed.
Because of the small size, the lifter would overheat and self
destruct.
[0010] Injection molding is not limited to forming parts as
described above. In some cases, injection molding may be used to
put decorative features on the outer surfaces of a part. This may
be accomplished using a technique called double shot injection
molding. In double shot injection molding, the molding process
utilizes two injections. One of the injections is used to form the
part (as described above for example), and the second injection is
used to create an outer layer around some or all of the part (or
vice versa). By way of example, double shot injection molding may
be used to place a soft layer on top of a hard layer, a transparent
layer on top of an opaque layer, or create multicolored layers. In
the case of an enclosure as discussed above, double shot injection
molding typically only serves to enhance the look and feel of the
enclosure. It does not help form the enclosure itself, as for
example each of the various walls
[0011] Thus, there is a need for improved approaches for molding
thin elongated enclosures, especially those for small handheld
electronic devices.
SUMMARY OF THE INVENTION
[0012] The invention relates, in one embodiment, to a method of
forming a multiwall enclosure that defines an open space for
placement of internal components via a double shot injection
molding process.
[0013] The invention relates, in another embodiment, to an
enclosure having multiple walls for enclosing internal electronic
components of an electronic device. The enclosure is formed by a
process that includes performing a first injection molding process.
The first injection molding process forms at least a first wall of
the enclosure. The process also includes allowing the at least a
first wall of the enclosure to solidify. The process further
includes performing a second injection molding process. The second
injection molding process forms at least a second wall of the
enclosure. The at least a second wall of the enclosure fuses with
the solidified at least a first wall of the enclosure during the
second injection molding process. The at least second wall of the
enclosure forms a different side of the enclosure than the at least
first wall of the enclosure. The process additionally includes
allowing the at least second wall of the enclosure to solidify. The
at least a second wall of the enclosure is therefore integrally
formed with the at least a first wall of the enclosure.
[0014] The invention relates, in another embodiment, to a method of
forming a single opening enclosure. The method includes performing
a first injection mold process. The first injection mold process
forms a front wall, right and left side walls, and a top wall of
the single opening enclosure. The method also includes performing a
second injection mold process. The second injection mold process
forms a back wall of the single opening enclosure. The back wall is
made integral with the front, right, left and top walls so as to
form a single integral part.
[0015] The invention relates, in another embodiment, to a double
shot injection molding method for producing an enclosure of an
electronic device having five walls and an open end. The double
shot injection molding method includes providing a mold A and a
mold B. Mold A includes a first injecting area and second injecting
area. The first injecting area including a core. The second
injecting area including a cavity and a movable insert for forming
a wall of the enclosure. Mold B includes a cavity that cooperates
with the core to form multiple walls of the enclosure. The method
also includes engaging mold A with mold B so that the core of mold
A is partially inserted into the cavity of mold B. The mold
cooperating to form a void associated with a first half of the
enclosure. The method further includes injecting plastic into the
void so as to form a first half of the enclosure. The method
additionally includes allowing the first half of the enclosure to
cool and solidify.
[0016] Once solidified, the method continues by disengaging mold A
and mold B. The first half of the enclosure remains in the mold B
after disengagement. The method also includes rotating mold B so
that the first half of the enclosure is aligned with the second
injection area of mold A. The method further includes engaging mold
A with mold B. The movable insert is inserted into the first half
of the enclosure so that only the edges of the first half of the
enclosure are exposed to the cavity of mold A. The method further
includes injecting plastic into the cavity of mold A so as to form
a second half of the enclosure. The second half of the enclosure
fuses with the first half of the enclosure during the injection.
The method additionally includes allowing the second half of the
enclosure to cool and solidify. The second half of the enclosure is
integrally formed with the first half of the enclosure thereby
producing the entire enclosure.
[0017] Once formed, the method continues by removing the insert
from the entire enclosure. The method also includes disengaging
mold A and mold B. The entire enclosure remains in mold B after
disengagement. The method further includes ejecting the entire
enclosure from mold B.
[0018] The invention relates, in another embodiment, to a method of
forming an enclosure. The method includes forming first void. The
first void forms a first set of walls of the enclosure. The method
also includes injecting plastic into first void to form a first
part. The method further includes allowing first part to solidify.
The method additionally includes inserting wedge into first
part.
[0019] Moreover, the method includes forming second void. The
second void forms the remaining walls of the enclosure. The method
also includes injecting plastic into the second void to form a
second part. The second part fuses with the first part during the
injection thereby forming a final enclosure with integral first and
second parts. The method further includes allowing the second part
to solidify. The method additionally includes removing the wedge
from the final part. The final part having five walls and an open
end.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The invention may best be understood by reference to the
following description taken in conjunction with the accompanying
drawings in which:
[0021] FIG. 1 illustrates a standard injection molding process.
[0022] FIG. 2 is a perspective diagram of an enclosure for an
electronic device, in accordance with one embodiment of the present
invention.
[0023] FIG. 3 is a flow diagram of a two shot injection method
forming an enclosure of an electronic device, in accordance with
one embodiment of the present invention.
[0024] FIGS. 4A-J illustrate a method for forming an enclosure of
an electronic device, in accordance with one embodiment of the
present invention.
[0025] FIG. 5 is a diagram of a double shot injection molding
apparatus, in accordance with one embodiment of the present
invention.
[0026] FIG. 6 is a flow diagram of a double shot injection method,
in accordance with one embodiment of the present invention.
[0027] FIG. 7A is a diagram of a key-like enclosure, in accordance
with one embodiment of the present invention.
[0028] FIG. 7B is diagram of a finally assembled media player 402
that utilizes the enclosure of FIG. 7A, in accordance with one
embodiment of the present invention.
[0029] FIG. 8 are cross sectional side views showing a side by side
comparison of an enclosure formed via a traditional single shot
process and an enclosure formed via the inventive two shot process,
in accordance with one embodiment of the present invention
DETAILED DESCRIPTION OF THE INVENTION
[0030] The present invention proposes a two shot injection process
for forming an enclosure for an electronic device. The two shot
injection process allows for a thinner walled enclosure that uses
less materials and allows for added structural features that would
not be possible using traditional molding techniques. The two shot
injection process generally includes forming one or more walls of
an enclosure with a first shot and thereafter forming the remaining
walls of the enclosure with a second shot. During the second shot,
the walls fuse together thereby forming an integrally molded
enclosure that is one piece.
[0031] Embodiments of the invention are discussed below with
reference to FIGS. 2-8. However, those skilled in the art will
readily appreciate that the detailed description given herein with
respect to these figures is for explanatory purposes as the
invention extends beyond these limited embodiments.
[0032] FIG. 2 is a perspective diagram of an enclosure 50 for an
electronic device, in accordance with one embodiment of the present
invention. The enclosure 50 includes five walls--a front wall 52, a
back wall 54, a right side wall 56, a left side wall 58 and a top
wall 60. The enclosure 50 also includes an open end 62 at the
bottom of the enclosure 50. The enclosure 50 extends longitudinally
from the top to bottom end of the enclosure 50. The dimensions of
the enclosure 50 are defined by length L, width W, depth D and
thickness t.
[0033] Although the dimensions can be widely varied, in one
particular embodiment, the enclosure 50 is thin and long and
therefore the depth D is small and the length L is large. By way of
example, the length L may be about 8 times the dimension of the
depth D. In one embodiment, the enclosure has a depth of about 8.5
mm, a width of about 24.1 mm, a length of about 68.4 mm and a
thickness t between about 1 mm to about 1.5 mm. It should be noted
however is not a limitation but rather an example of a particular
thin and elongated enclosure. By way of example, this example may
generally correspond to the dimensions of the enclosure used in the
iPod Shuffle manufactured by Apple Computer of Cupertino,
Calif.
[0034] As mentioned in the background, this configuration of an
enclosure (long and thin) presents problems when molding the
enclosure using conventional techniques. For example, large tapers
must be used, and further forming internal features is nearly
impossible. In order to overcome these problems, the present
invention proposes forming the enclosure 50 in two or more
injection molding steps rather than just one injection molding
step. In the first step one or more walls are created, and in the
second step, the remaining walls are created. More particularly, a
first side of the enclosure is formed with the first injection and
a second side of the enclosure is formed with the second injection.
Although done in two steps, all the walls are integrally formed as
the remaining walls fuse with the existing walls during the second
injection molding process. These steps can be performed on the same
machine in the same cycle (double shot) or separate machines
(transfer) in different cycles.
[0035] FIG. 3 is a flow diagram of a two shot injection method 70
for forming an enclosure of an electronic device, in accordance
with one embodiment of the present invention. The method 70 may for
example be used to form the enclosure 50 shown in FIG. 2. The
method 70 includes blocks 72 and 74. In block 72, one or more walls
of an enclosure are formed via a first injection. In block 74, the
remaining walls of the enclosure are formed via a second injection.
During the second injection, the molten plastic that forms the
remaining walls fuses with the solidified walls formed during the
first injection thereby forming a single solid enclosure with
integral walls.
[0036] By utilizing two process steps, the taper that would
normally exist is substantially minimized or completely eliminated
from the inside surfaces of the enclosure. As such, the internal
space of the enclosure is capable of fitting the desired internal
components without increasing the outer dimensions of the
enclosure. Furthermore, internal features can be placed on the
inner surfaces without using a mechanical action. Mechanical
actions for creating internal features are nearly impossible with
enclosures of this type (e.g., thin and long).
[0037] Further advantages can be realized, when you consider that
the two injection processes can use the same or different
materials. In one embodiment, the first and second injections use
the same plastic material. This may be beneficial in that this
typically provides the best bond strength. In another embodiment,
the first and second injection use different materials or the same
materials with different characteristics (e.g., color). The
materials may for example be selected from polycarbonate (PC), ABS
or PC-ABS plastic materials. Polycarbonate has been found to work
particularly well. In one implementation, both injections use
polycarbonate. In another implementation, one of the injection uses
polycarbonate, and the other injection uses ABS. In yet another
implementation, one of the injection uses polycarbonate, and the
other injection uses PC-ABS.
[0038] In one embodiment, and referring to FIGS. 2 and 3, the front
wall 52, side walls 56 and 58, and top wall 60, are formed in the
first injection molding process, and the back wall 54 is formed in
the second injection molding process. This arrangement has been
found to work particularly well. In fact, the inside surface of the
front wall can be made with zero taper, and the inside surface of
the back wall can be made with a limited taper such as
substantially zero. Furthermore, the inside surfaces of the right
and left sides can be made with zero taper along the y axis and
minimal taper in the z direction as for example substantially zero.
As a result, the thickness t of the enclosure can remain
substantially uniform from the top and bottom ends.
[0039] It should be pointed out, however, that although this
embodiment is directed at creating the front, sides and top of the
enclosure in a first process, and the back wall of the enclosure in
a second process, this is not a limitation and that the two or more
process steps may be used to form a different arrangement of walls.
For example, the front wall may be formed in the first step and the
remaining walls may be formed in the second step. Alternatively,
the back and one of the side walls may be formed in a first process
and the front and the remaining side walls may be formed in the
second process (or vice versa).
[0040] FIGS. 4A-J illustrate a method for forming an enclosure of
an electronic device, in accordance with one embodiment of the
present invention. The method may for example be used to form the
enclosure shown in FIG. 2. Each Figure includes both a cross
sectional side view and a cross section top view. FIG. 4A
illustrates a first mold 102 and a second mold 104. The first mold
102 includes a cavity 106 and the second mold 104 includes a core
108.
[0041] In FIG. 4B, the molds 102 and 104 are closed and the core
108 is inserted into the cavity 106 thereby forming a first void
110. The first void 110 provides the space for molding the first
half of the enclosure, particularly, the front, top, and side walls
of the enclosure.
[0042] In FIG. 4C, plastic is injected into the first void 110.
This may be accomplished with a gate located in the second mold
102. In the illustrated embodiment, the plastic is injected through
the core 108 via the gate and thus the plastic flows first into the
area of the void 110 that forms the front wall and then into the
area of the void 110 that forms the top and side walls. By
injecting plastic along the inner surface of the front wall, any
imperfections created at the gate interface may be hidden inside
the enclosure.
[0043] Unlike, the traditional part, the enclosure is formed
horizontally rather than vertically as shown in FIG. 1. That is the
part is laid during molding rather than being upright. As a result,
the long longitudinal surface of the front wall does not include a
taper. Furthermore, because the side and top walls are short, the
walls may or may not include a taper. If a taper is used, it is
typically very minimal because the part is easy to remove since the
depth of the part is small, and/or because the part does not fully
surround the core in the pull direction (e.g., one side is open
thereby alleviating the squeezing caused by shrinkage). Even if a
larger taper is used, the taper does not have a large affect on the
wall thickness because of the shallow depth, i.e., the draft
increases the wall thickness very minimally. As should be
appreciated, the longer the part, the greater the impact of the
draft angle. By way of example, the taper is less than about 0.5
degrees, and more particularly zero or near zero.
[0044] In FIG. 4D, the molds 102 and 104 are opened and the core
108 is removed from the first half of the enclosure 112, which
stays inside the cavity 106. Once the molds 102 and 104 are opened,
the first half of the enclosure 112 is ready for the second shot.
In some cases, the first half of the enclosure 112 remains in the
first mold during the second shot (double shot), and in other cases
the first half of the enclosure 112 is ejected and moved to another
set of molds (transfer). In the illustrated embodiment, the first
half of the enclosure 112 stays with the first mold 102, however it
is moved from one molding area to another molding area. For
example, the first mold 102 may rotate so that the first half of
the enclosure 112 can interface with another part of the second
mold 104 that is configured for forming the remaining portions of
the enclosure.
[0045] In FIG. 4E, the first mold 102 transports the first half of
the enclosure 112 to a second molding area of the second mold 104.
The second molding area of the second mold 104 includes a second
cavity 114 with an insert 116 partially positioned in front of the
second cavity 114. The insert 116 is sized and dimension for
placement inside the first half of the enclosure 112 between the
walls. The insert 116 is configured to protect the existing walls
and form the remaining walls during the second injection
process.
[0046] In FIG. 4F, the molds 102 and 104 are closed and the insert
116 is placed inside the internal space of the first half of the
enclosure 112 thereby leaving the edges of the walls exposed to the
second cavity 114. The insert hits tight against the inside
surfaces of the first half of the enclosure (shuts off the inside
surfaces for the second shot except at the edges where the
remaining walls are connected to the existing walls). The second
cavity 114 in cooperation with the wall edges and the back surface
of the insert 116 form a second void 118. The second void 118
provides the space for molding the second half of the enclosure,
particularly, the back wall of the enclosure.
[0047] In FIG. 4G, plastic is injected into the second void 118.
This may be accomplished with a second gate located in the second
mold 104. In the illustrated embodiment, the plastic is injected at
the bottom edge of the second cavity 114 and thus the plastic flows
first into the bottom of the back wall and then to top of the back
wall and the edges of the exposed front, top and side walls. By
injecting plastic at the bottom edge, any imperfections created at
the gate interface may be easily removed as for example during a
machining operation.
[0048] When the injected molten plastic comes into contact with the
edges of the existing walls, the molten plastic melts the edges of
the existing walls thereby allowing the back wall to fuse with the
other walls. In essence, the plastic of the second shot recombines
with the plastic of the first shot thereby forming a single
integral enclosure 120. After injection, the enclosure 120 is
allowed to solidify.
[0049] Because the first half of the enclosure is frozen and the
second half of the enclosure is molten during the second shot, the
first half of the enclosure may have the tendency to curl up when
the molten material of the second half of the enclosure begins to
cool (as the second half solidifies, it begins to shrink which
squeezes the first half of the enclosure). Unfortunately, this may
adversely affect the structural strength, dimensional tolerances,
and aesthetics of the enclosure.
[0050] Several techniques can be performed to prevent curling
during the second shot. In one embodiment, the first mold includes
one or more retention features that help hold the first half of the
enclosure rigid inside the cavity during the second shot. The
retention features may for example be protrusions that are located
inside the cavity along the front wall. The protrusions increase
the surface area onto which plastic is molded during the first shot
thereby increasing the sticktion force between the cavity and the
part. They also provide pilings that help capture the part thereby
preventing any bowing. For at least these reasons, the first half
of the enclosure is prevented from curling up. In the illustrated
embodiment, the retention features are a pair of spatially
separated but side by side nubs 121. One of the nubs 121 is located
closer to the right side and the other nub 121 is located closer to
the left side thereby creating a more rigid structure on both
sides. In some cases, the nubs 121 may include a slight taper for
helping remove the part from the cavity when the process is
completed. In other cases, the nubs 121 may be strategically placed
at locations where aesthetics are of no concern or alternatively
locations that can be machined or removed altogether. For example,
the nubs may be positioned at locations where an opening will
eventually be created in the enclosure for I/O devices such as
buttons or displays.
[0051] In another embodiment, the insert may include a cooling
feature. The cooling feature prevents the insert from getting to
hot. Because the core is thin (shallow depth), it heats up very
rapidly and the heat may cause the first half of the enclosure to
soften which as a result reduces the enclosures resistance to creep
and bending. The cooling keeps the first half of the enclosure
rigid, which helps prevent the curling effect. In one
implementation, the cooling is provided by one or more cooling
channels that run through the insert and that maintain the
temperature of the insert at an appropriate level. For example,
water can run through the channels.
[0052] In FIG. 4H, the insert 116 is removed from the internal
space 122 of the enclosure 120. This may be accomplished via a
sliding action. Because only the back wall is made with molten
plastic, the side of the insert 116 that helped form the second
void typically does not require a taper or alternatively only
requires a minimal taper in order to remove the insert 116 from the
internal space 122 of the enclosure 120. As should be appreciated,
this is the only place that has any sticktion force as the existing
walls have already solidified and therefore there is substantially
no sticktion between the existing walls and the insert 116. That
is, because the existing walls are already frozen when the insert
is placed therein, the insert does not stick thereto making the
release manageable without a draft. Furthermore, because the
existing walls are solid they do not shrink around the insert. In
essence, the draft can be much less that would normally be used
since its only one side and therefore the sticktion force and
shrinkage force is much less. By way of example, the draft angle of
the insert on the side of the back wall may be less than 0.25
degree, and more particularly, zero or substantially non-zero.
[0053] In some cases, the surfaces of the insert 116, and mainly
the surfaces in contact with the molten plastic, are polished to
make the removal from the enclosure much easier. In one particular
embodiment, the final polishing step used to create the polished
surfaces is performed in the pull direction so that the polishing
lines run parallel to the pull direction. Not only does this help
in the removal, but it also helps prevent mystery or sink marks
from forming on the surfaces during removal of the insert from the
enclosure. It has been found that if the final polishing steps is
performed in a direct transverse to the pull direction, sink marks
may be created on the surfaces of the part when the insert is
pulled out of the enclosure. In some cases, this may even cause the
part to deform.
[0054] In FIG. 41, the molds 102 and 104 are opened. In most cases,
the enclosure 120 stays inside the fist cavity 106 of the first
mold 102.
[0055] In FIG. 4J, the enclosure 120 is ejected from the first mold
102. In some cases, a robot arm with suction cups picks the
enclosure 120 out of the first mold 102 and transfers it to another
area where post molding steps may be performed. For example,
machining steps may be performed as for example to clean up the
edges of the enclosure 120.
[0056] FIG. 5 is a diagram of a double shot injection molding
apparatus 200, in accordance with one embodiment of the present
invention. The double shot injection molding apparatus 200 is
configured to perform two shots in the same machine and using the
same molds--the first shot forming the first half of the enclosure,
the second shot forming the second half of the enclosure and fusing
the second half to the first half. One advantage of double shot is
that the part stays in the mold, and as a result there is less
handling, quicker cycle times and better cosmetics.
[0057] As shown, the molding apparatus 200 includes a mold
positioning mechanism 202 and an injection unit 204. The mold
positioning mechanism 202 includes a clamping unit 206 and a
rotating platen 208. The clamping unit 206 is configured to clamp
first and second molds 210 and 212 together along a clamping axis
214. The rotating platen 208 is configured to rotate the first mold
210 about the clamping axis 214 in order to reposition the first
mold 210 with the second mold 212. The rotating platen 208 may for
example rotate the first mold 210 after the first shot in order to
position the first half of the enclosure for the second shot.
[0058] The injection unit 204, on the other hand, includes a pair
of injectors 216A and 216B and a fixed platen 218. The fixed platen
218 is configured to support the second mold 212 during the
injection processes. The injectors 216 are configured to inject
plastic into the molds 210 and 212 when they are clamped together.
The first injector 216A is configured to produce the first shot and
the second injector 216B is configured to produce the second shot
of the double shot molding apparatus 200. Each injector 216
includes a heating cylinder 220 and a material feed system 222 such
as a hopper. Alternatively, a single material feed system may be
used to feed material to both heating cylinders. The injectors 216
are configured to force molten plastic out of nozzles 224A and 224B
and into gates 226 and 228 found in the second mold 212. The first
gate 226 distributes the molten plastic to a first molding area 230
of the second mold 212, and the second gate 228 distributes molten
plastic to a second molding area 232 of the second mold 212.
[0059] The first molding area 230 includes a core 234 that that
interfaces with a cavity 236 on the first mold 210 during the first
shot. The first gate 226 is positioned through the core 234 so that
plastic can be forced into the void created by the core 234 and the
cavity 236. The second molding area 22 includes a cavity 238 and a
movable insert 240 located in front of the cavity 238. The second
gate 228 exits into the cavity 240 so that molten plastic can be
forced into the void created by the insert 240 and the cavity 238.
This arrangement is configured to interface with a second cavity
242 on the first mold 210 during the second shot. The second cavity
242, which includes the first half of the enclosure, is rotated
into alignment with the insert 240 of the second mold 212 after the
first shot, and the first cavity 236 is rotated into alignment with
the core 234 of the second mold 212 after the second shot and after
the final molded enclosure is ejected from the first mold 210. The
insert 240 is configured for placement in the first half of the
enclosure, which is left in the second cavity 242. The insert 240
protects the existing walls of the first half of the enclosure
while leaving the edges of the existing walls exposed to the molten
plastic of the second shot. The insert 240 is slidably coupled to
the second mold 212. Once the part cools, the insert 240 slides out
of the part in a direction that is transverse to the injection
axis. For example, the insert 240 may slide into or out of the
page.
[0060] FIG. 6 is a flow diagram of a double shot injection method
300, in accordance with one embodiment of the present invention.
The flow diagram may for example be used to operate the apparatus
described in FIG. 5. The method begins at block 302 where
[0061] the first mold 210 closes thereby causing the core 234 of
the second mold 212 to be inserted into the cavity 236 of the first
mold 210. When closed the molds 210 and 212 form a void in the
shape of the first half of the enclosure.
[0062] Thereafter in block 304, plastic is injected into the void
through the second mold 212 so as to form the first half of the
enclosure. The gate 226 is located in the core 234 and injects
plastic in the middle of the void. The molten plastic flows out of
the gate 226 into the area that forms the front wall of the
enclosure and eventually flows into areas that form the side walls
and top wall of the enclosure. Once filled, the first half of the
enclosure is allowed to cool and solidify. The first half of the
enclosure includes an integral front wall, top wall, and left and
right side walls and an open bottom end, and no back wall.
[0063] Following block 304, the method proceeds to block 306 where
the first mold 210 opens. The first half of the enclosure stays in
the first mold 210 after the opening sequence.
[0064] Thereafter, in block 308 the first mold 210 rotates while
the second mold 212 stays fixed. The first mold 210 is rotated so
that the second half of the enclosure can be integrally formed with
the first half of the enclosure. The first half of the enclosure is
rotated until it is aligned with the movable insert 240 of the
second mold 212. The movable insert 240 is configured for placement
in the internal space of the first half of the enclosure.
[0065] Following block 308, the method proceeds to block 310 where
the first mold 210 is closed and the insert 240 is placed into the
internal space of the first half of the enclosure. The insert 240
forms a tight fit against the walls of the first half of the
enclosure so that the walls are protected during the second shot.
The insert 240 does however leave the edges of the walls exposed to
the cavity 238 located behind the movable insert 240.
[0066] Thereafter in block 312, plastic is injected into the cavity
238 from the second mold 212 so as to form the second half of the
enclosure. The plastic flows out of the gate 228 and into the void
that forms the back wall of the enclosure. As it fills the void,
the molten plastic comes into contact with the edge of the walls
thereby fusing the back wall to the side and top walls of the first
half of the enclosure. Once filled, the second half of the
enclosure is allowed to cool and solidify. This forms an enclosure
with an open bottom end and five integrally formed walls.
[0067] Following block 312, the method proceeds to block 314 where
the movable insert 240 is removed. That is, the insert 240 slides
out the open bottom end in a direction that is transverse to the
gate 228 (e.g., radially).
[0068] Thereafter in block 316 the first mold 210 opens. The
enclosure stays in the cavity 242 of the first mold 210 during
opening.
[0069] Following block 316, the method proceeds to block 318 where
the enclosure is ejected from the first mold 210.
[0070] Thereafter in block 320, post molding steps are performed.
For example, the enclosure is machined to final its form
factor.
[0071] In accordance with one embodiment, the enclosure as
described above is configured as a keylike device such as a USB key
or miniature media player. FIG. 7A is a diagram of a keylike
enclosure 400, and FIG. 7B is diagram of a finally assembled media
player 402 that utilizes the enclosure 400. As shown, the enclosure
400 extends longitudinally and includes five walls and an open end.
The five walls are integrally formed as a single part. The front
wall 404 and side walls 406, 408 and 410 are formed in the first
shot, and the back wall 412 is formed in the second shot.
[0072] After the enclosure 400 is formed, various surfaces are
machined to allow access to I/O devices or to remove excess
material. In the illustrated embodiment, a circle 414 is machined
in the front wall 404 to accommodate a button wheel 416 and a
rectangle 416 is machined in the back wall 412 to accommodate a
switch (not show). In one embodiment, the gates are strategically
placed at locations on the enclosure that would normally be
machined to accommodate other parts. In one implementation, the
gate that forms the front wall 404 is located in the region where
the button wheel 416 is located. As such, the surface marks
associated with gate are removed while making space for the button
wheel 416. In another implementation, the gate that forms the back
wall is located at the bottom edge of the back wall so that the
outer surface of the back wall is free from gate imperfections. In
this implementation, the bottom edges are machined to remove excess
material generated at the gate during the second shot.
[0073] Once the surfaces are machined, the internal parts are
positioned inside the enclosure, and the open bottom end is sealed
with a wall 420 that includes a USB or alternatively a Firewire
connector 422. The connector 422 and bottom wall 420 may be
connected to a printed circuit board that includes the electrical
hardware for the media player. The media player may therefore be
assembled with ease, i.e., insert the PCB assembly into the
enclosure while sealing the bottom end.
[0074] FIG. 8 are cross sectional side views showing a side by side
comparison of an enclosure 500 formed via a traditional single shot
process and an enclosure 502 formed via the inventive two shot
process. Each part is designed to provide the volume necessary to
accommodate all of the internal electronic parts inside the
enclosure. Because of the use of a draft angle, the traditional
enclosure 500 includes a large taper 504 along its longitudinal
surfaces. As a result, the wall thickness t increases from the open
end to the close end of the enclosure 500. In order to provide the
internal volume necessary, the depth D of the traditional part 500
is increased to make up for the increased thickness at the closed
end. In contrast, the two shot enclosure 502 of the present
invention does not include any taper along the longitudinal
surfaces and if a taper is needed it is typically very minimal. The
thickness t therefore remains substantially uniform from the bottom
to the top ends. As such, the overall depth D of the part can be
minimized to accommodate the same space as the traditional part
500.
[0075] In one example, the thickness t of the two shot enclosure
502 is a substantially uniform thickness of about 1.2 mm for the
back surface and about 1.5 mm for the front surfaces with an
overall depth D of about 8.5 mm. In contrast, using conventional
techniques, the traditional enclosure 500, includes thickness t
that varies between 1.2 mm at the open end to 2.7 mm at the closed
end with an overall depth of about 11.2 mm. Moreover, the two shot
enclosure 502 includes internal structural features 510 on the
front longitudinal surface whereas the traditional part 500 does
not. The internal features may for example be embossments or
undercuts in the inside surface of the front wall of the enclosure
for helping position and support the button wheel.
[0076] The advantages of the invention are numerous. Different
aspects, embodiments or implementations may yield one or more of
the following advantages. One advantage of the invention is that
the overall size of the enclosure can be reduced while maintaining
the useable space inside the enclosure. Another advantage is that
the thickness of the wall can remain thin and substantially
uniform. This saves material costs and reduces the cosmetic risks
(sink, cooling/flatness issues, etc.). Another advantages is that
the invention additionally allows for placement of structural and
placement features that would be nearly impossible using
traditional molding techniques.
[0077] While this invention has been described in terms of several
preferred embodiments, there are alterations, permutations, and
equivalents, which fall within the scope of this invention. It
should also be noted that there are many alternative ways of
implementing the methods and apparatuses of the present invention.
It is therefore intended that the following appended claims be
interpreted as including all such alterations, permutations, and
equivalents as fall within the true spirit and scope of the present
invention.
* * * * *