U.S. patent application number 10/762717 was filed with the patent office on 2005-10-27 for spruing assembly.
Invention is credited to Lee, Kwang H..
Application Number | 20050236551 10/762717 |
Document ID | / |
Family ID | 35135494 |
Filed Date | 2005-10-27 |
United States Patent
Application |
20050236551 |
Kind Code |
A1 |
Lee, Kwang H. |
October 27, 2005 |
Spruing assembly
Abstract
An improved spruing assembly utilized in the investment process
in the making of investment mold castings. The spruing assembly
comprising a base unit engaged to a casting ring to define a
receptacle for receiving investment material, and a sprue holding
member connecting to the base unit within said receptacle and
supporting thereon one or more sprues for holding a wax structure
formed in a pattern to be cast. The sprue having a first end
connecting to the wax structure and a curved adapter disposed at
the second end for quick locking onto the sprue holding member.
Inventors: |
Lee, Kwang H.; (Burbank,
CA) |
Correspondence
Address: |
Jerry H. Noh
Suite 2741
3435 Wilshire Blvd.
Los Angeles
CA
90010
US
|
Family ID: |
35135494 |
Appl. No.: |
10/762717 |
Filed: |
January 22, 2004 |
Current U.S.
Class: |
249/54 ;
249/105 |
Current CPC
Class: |
B22C 9/082 20130101;
B22C 9/04 20130101 |
Class at
Publication: |
249/054 ;
249/105 |
International
Class: |
B22C 009/08 |
Claims
What is claimed as being new and therefore desired to be protected
by Letters Patent of the United States is as follows:
1. In a spruing assembly comprising: a runner bar for connecting to
a base unit surrounded by a casting ring; at least one sprue
connected at a second end to the runner bar, said sprue having an
opposed first end for connecting to at least one wax structure
formed in a pattern to be cast, the improvement comprising: a
curved adapter disposed at the second end of the sprue, said
adapter being sized and shaped to lock onto said runner bar in a
secure engagement.
2. The spruing assembly as described in claim 1 wherein the adapter
has a radius of a first predetermined length, and the runner bar
has a radius of a second predetermined length which is longer than
the first predetermined length.
3. The spruing assembly as described in claim 1 wherein said sprue
has a reservoir formed thereon.
4. The spruing assembly as described in claim 1 wherein at least
the first end of said sprue is hollow.
5. In a spruing assembly comprising: a base unit removeably engaged
to a casting ring to define a receptacle for receiving investment
material for the making of castings; a sprue holding member
connected to the base unit inside said receptacle; said improvement
comprising: at least one wax structure formed in a pattern to be
cast; at least one sprue having a first end and a second end, said
first end connected to the wax structure; and, a curved adapter
disposed at the second end of the sprue, said adapter of the second
end connected to said sprue holding member; said adapter being
sized and shaped to lock onto said sprue holding member in a secure
engagement.
6. The spruing assembly as described in claim 5 wherein the adapter
has a radius of a first predetermined length, and the sprue holding
member has a radius of a second predetermined length which is
longer than the first predetermined length.
7. The spruing assembly as described in claim 6 wherein the sprue
holding member is a single elongated runner bar having an arcuate
cross-section.
8. The spruing assembly as described in claim 6 wherein the sprue
holding member is a runner bar formed in the shape of a ring having
a central plug and a plurality of radial bars extending from the
central plug and connected to the ring, said central plug is
connected to said base unit, said runner bar has an arcuate
cross-section.
9. The spruing assembly as described in claim 5 wherein said sprue
has a reservoir formed thereon.
10. The spruing assembly as described in claim 5 wherein at least
the first end of said sprue is hollow.
11. In a spruing assembly comprising: a base unit removeably
engaged to a casting ring to define a receptacle for receiving
investment material for the making of castings; a sprue holding
member connected to the base unit inside said receptacle; said
improvement comprising: at multi-unit wax structure formed in a
pattern to be cast; each unit of said multi-unit wax structure
having a sprue connected thereto, each sprue having a first end and
a second end, said first end connected to the corresponding unit of
said multi-unit wax structure; and, a curved adapter disposed at
the second end of each sprue, each adapter of each second end
connected to said sprue holding member; each adapter being sized
and shaped to cover at least half of the circumference of the sprue
holding member in locking onto said sprue holding member in a
secure engagement.
12. The spruing assembly as described in claim 11 wherein each
adapter has a radius of a first predetermined length, and the sprue
holding member has a radius of a second predetermined length which
is longer than the first predetermined length.
13. The spruing assembly as described in claim 12 wherein the sprue
holding member is a single elongated runner bar having an arcuate
cross-section.
14. The spruing assembly as described in claim 12 wherein the sprue
holding member is a runner bar formed in the shape of a ring having
a central plug and a plurality of radial bars extending from the
central plug and connected to the ring, said central plug is
connected to said base unit, said runner bar has an arcuate
cross-section.
15. The spruing assembly as described in claim 11 wherein each
sprue has a reservoir formed thereon.
16. The spruing assembly as described in claim 11 wherein at least
the first end of each sprue is hollow.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to investment casting and, more
particularly, this invention relates to an improved spruing
assembly in the making of investment mold castings.
[0003] 2. Description of the Prior Art
[0004] The casting of miscellaneous items by both jewelry and
dental technicians utilize the lost wax process. For dental
technicians, the lost wax process is used for several dental
restoration procedures including crown restorations, inlays,
bridges, and coping. For a typical crown restoration, an impression
of the patient's teeth is taken by a doctor, and a model of the
teeth is made from the impression. One or more layers of wax are
built-up onto the model to an exact replication of the crown or the
substructure. The finished wax structure of the crown is removed
from the model and placed for investing in a casting ring. Sprues
are utilized to support the wax structure in a sprue holding member
attached to a base unit of the casting ring. It is common to attach
one end of the sprue onto the wax structure to remove the wax
structure from the model and attach the opposed free end of the
sprue to the sprue holding member. The casting ring is then filled
with investment material which solidifies. The solidified
investment material is removed from the casting ring and base unit
and heated to burn out the wax structure, sprues, and sprue holding
member. Thereafter, a metal is melted down and cast into the void
created by the burned out structures. After the metal is cooled,
the investment material is removed to expose the cast structure and
assembly.
[0005] One of the problems arising in this process is the potential
for movement of the sprue at the attachment point to the sprue
holding member of the base unit. Typically, sprue holding members
can be a chunk of wax, a runner bar, or a runner wheel. The sprues
are commonly made of wax or plastic. For sprues made of wax, the
sprues are attached to the sprue holding member by heating a
portion of the tip of the sprue and immediately connecting the
heated portion onto the holding member. For sprues made of plastic,
the sprue is connected to the sprue holding member by melting a
piece of wax with a waxing tool between the sprue end and the
holding member and allowing the wax to harden. In multi-wax unit
structures, a sprue connects each unit to the sprue holding member.
It is important in such multi-unit structures that each sprue does
not shift, even slightly, along its connection with the holding
member; otherwise, slight shifting can negatively affect the
precise fitting of the final dental product. However, with the
conventional method of connection as described, there can be a
tendency for a slight shift resulting from the investing process
because wax has inherit memory which can cause expansion and
contraction with heat change occurring in the investing
process.
[0006] Another problem with the typical lost wax process is the
time consuming nature of the step of connecting the sprue to the
sprue holding member, especially for connecting multi-unit wax
structures. Currently, the dental technician must have one hand
holding the wax structure with the sprue and a waxing tool in the
other hand to attach the end of the sprue to the sprue holding
member. This can be tedious and time consuming when attaching
multiple sprues at multiple angles for a multi-unit structure. In
addition, in multi-unit structures, each sprue must be connected at
a proper angle, and this may require bending of wax sprues, or
reattachment of plastic sprues to form the proper angle of
connection of each sprue. A problem with bending of wax sprues in
multi-unit wax structures is the potential for shifting which may
exert a slight pressure on the corresponding unit of wax structure,
which in turn may affect the precise fit of the finished
product.
[0007] Thus, it is an object of the present invention to provide an
improved spruing assembly which provides a secure connection
between the sprue and the sprue holding member. It is another
object of the present invention to provide a spruing assembly which
provides quick and adjustable connection between the sprue and the
sprue holding member. It is another object of the present invention
to provide a spruing assembly for producing precise castings of
multi-unit wax structures.
SUMMARY OF THE INVENTION
[0008] The present invention is an improved spruing assembly
utilized in the investment mold process for the making of castings.
The spruing assembly comprising a base unit engaged to a casting
ring to define a receptacle for receiving investment material, and
a sprue holding member connecting to the base unit within said
receptacle and supporting thereon one or more sprues for holding a
wax structure formed from a stone model in a pattern to be cast.
The sprue has a first end connecting to the wax structure and a
second end for connecting to the sprue holding member. A curved
adapter is placed at the second end of the sprue for quick locking
of the second end of the sprue onto the sprue holding member. The
curved adapter allows for a secure connection which will allow the
sprue to rotate at the second end with the application of a
predetermined amount of force; however, the connection is
sufficiently strong enough so that the sprue will not move nor
rotate during the entire investment process. The sprue holding
member can be a runner bar formed of one or more elongated bars or
a ring having a central plug with a plurality of radial bars
extending from the plug to the ring. The wax structure, sprues, and
sprue holding members are all made of materials which will burn out
during the investment process.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a perspective view of a multi-unit wax structure
connected by sprues to a runner bar as the structure is being
removed from the model formed from a dental impression;
[0010] FIG. 2 is an isolated view of a sprue and runner bar of the
present invention;
[0011] FIG. 3 is an isolated view of an embodiment of a sprue and
runner bar of the present invention;
[0012] FIG. 4 is an isolated side view of and an end the sprue and
runner bar;
[0013] FIG. 5 is an isolated view of an embodiment of a runner bar
of the present invention;
[0014] FIG. 6 is a side view of the runner bar of FIG. 5;
[0015] FIG. 7 is an isolated view of another embodiment of a runner
bar of the present invention;
[0016] FIG. 8 is a side view of the runner bar of FIG. 7; and,
[0017] FIG. 9 is a sectional, partially broken view of the spruing
assembly of the present invention filled with investment
material.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0018] The present invention illustrated in FIGS. 1 to 9 is a
spruing assembly 10 comprising a base unit 15 engaged to a casting
ring 17 to define a receptacle. The casting ring 17 is formed to be
removeably connected to the base unit 15. Furthermore, the base
unit 15 shown in the illustration has a channel 20 in a ring
pattern forming a slot for receiving the bottom edge 22 of the
casting ring 17 for a secure fit so that the receptacle is suitable
for receiving investment material 25 therein without leakage. In
the embodiment shown in FIG. 9, the casting ring 17 is tapered. The
vertical cross-sectional shape of the casting ring can be
elliptical, circular, or any other shape known in the art suitable
for fitting over and housing the sprue holding member 28, sprues
30, and wax structures 33.
[0019] Also, the spruing assembly 10 comprises a sprue holding
member 28 connected to the base unit 15 inside the receptacle. The
sprue holding member 28 is made of a material which will burn out
during the heating process along with the wax structure 33 and
sprues 30. In the embodiment shown in FIG. 9, the sprue holding
member 28 is a runner bar 36 formed as an elongated bar. The runner
bar 36 can have a plug 38 attached thereto for connection into a
hole formed in the base unit 15. The plug 38 can be a preformed
plastic structure or a suitable mass of wax. FIG. 5 shows an
alternative embodiment of the sprue holding member 28 formed as
three elongated runner bars attached to a plug 38. FIG. 6 shows
another alternative embodiment of the sprue holding member 28
formed as a ring 40 having a central plug 38 and a plurality of
radial bars 42 extending from the central plug 38 and connecting to
the ring 40. In each embodiment of the runner bars, the
cross-section of each runner bar is arcuate. The plug 38 in each
embodiment also is made of a material which will burn out during
the heating process. In the embodiments shown in FIGS. 1-9, each
sprue holding member 28 has a circular cross-section.
[0020] Supported on each sprue holding member 28 is a sprue 30
connecting to a wax structure 33 formed in a pattern to be cast.
FIG. 9 shows a 3 unit wax structure 33b having a separate sprue 30
connecting each unit of wax structure 33 to the sprue holding
member 28. Two embodiments of suitable sprues 30 are shown in FIGS.
1 and 2. FIG. 3 shows a sprue 30 having a first end 47, which is
the end connecting to the wax structure 33, and a second end 49
which has an adapter 50 formed thereon for locking onto the sprue
holding member 28. The adapter 50 is curved generally in a
semi-circular shape to define an opening for receiving therein the
sprue holding member 28. That is, the adapter 50 is sized and
shaped to grip sufficiently around the sprue holding member 28 to
lock onto the sprue holding member 28 in a secure engagement. Also,
the adapter 50 is sized and shaped to cover at least half of the
circumference of the sprue holding member 28. The radius R1 of the
adapter can be adjusted relative to the size of the sprue holding
member 28 to control the strength of the force with which the
adapter 50 locks onto the sprue holding member 28. For multi-unit
wax structures, it can be desirable that the angle of the sprue 30
on the sprue holding member 28 be adjustable, which requires that
the sprue 30 rotate at the connection to the sprue holding member
28 with the exertion of at least a predetermined amount of force on
the sprue 30. Although rotatable, it is important that the adapter
50 be sufficiently locked onto the sprue holding member 28 so that
the sprue 30 will not rotate nor move during the investment
process. FIG. 4 shows an isolated side view of the adapter 50 of
the sprue above a side view of the a runner bar 36. The adapter 50
has a radius R1 of a first predetermined length, and the sprue
holding member has a radius R2 of a second predetermined length
which is longer than the first predetermined length. The adapter
also has a depth R3 of a third predetermined length. For a
rotatable yet secure fit which will not rotate during the
investment process, it has been found for an adapter which is made
of plastic that the second predetermined length R2 is in the range
of 9.2% to 11.4% longer than the first predetermined length R1, and
the third predetermined length R3 is in the range of 29% to 48%
longer than the first predetermined length R1. To effectuate a
gripping force on the sprue holding member 28, the adapter 50 is
relatively flexible. FIG. 2 shows a sprue 30 having a reservoir 53
formed between the first and second ends 47, 49 thereof. The sprue
30 along with the adapter 50 and any reservoir 53 formed thereon is
made of a material which will burn out in the heating process, and
common materials in the art for sprues include wax and plastic.
Sprues can be hollow or solid. In the embodiment shown, at least
the first end of the sprue is hollow. A sprue being hollow at the
end connecting to the wax structure provides an advantage in
allowing for increased surface area of connection between the sprue
30 and the corresponding wax structure 33. This is because a sprue
having a hollow end when connected to the waxing tool using a
waxing tool has the entire circumference of inner and outer sides
of the end of the sprue connecting to the wax structure; whereas,
in a solid sprue end, only the circumference of only the outer side
of the end of the sprue connects to the wax structure.
[0021] Using the present sprue assembly, a wax structure is first
formed from the stone model formed from the dental impression. For
a single unit wax structure, the first end of a sprue is connected
using a waxing tool to the wax structure. Thereafter, the wax
structure is then removed from the stone model and snapped onto the
sprue holding member which is placed onto the base unit. It is also
possible to have the second end of the sprue first snapped onto the
sprue holding member prior to attaching the first end of the sprue
onto the wax structure for removal of the wax structure from the
stone model. After the sprue holding member is set onto the base
unit, the casting ring is placed on the base unit and investment
material is poured into the receptacle to cover the sprue holding
member, sprue, and wax structure. For making many separate single
unit wax structure casts in a single investment process, sprue
holding members shown in the embodiments of FIGS. 5 and 6 are
desireable for its ability to hold many single unit wax
structures.
[0022] For a multi-unit wax structure, the present invention allows
for the sprues to be first snapped onto the sprue holding member.
For multi-unit structures, a sprue holding member being a single
elongated or curved runner bar is preferred. Once the sprues are
snapped onto the runner bar, the length of each sprue can be cut
and the angle of each sprue can be adjusted by rotating the sprue
at the adapter so that each sprue can be in optimal position for
connection to the corresponding unit of wax structure. After each
sprue has been optimally aligned and sized, each sprue is connected
to each corresponding unit of wax structure. As an additional step,
to ensure that an adapter will no longer rotate after the sprue is
connected to the wax structure, the user can bond a piece of melted
wax between the adapter and the sprue holding member.
[0023] Although embodiments of the invention have been described
and illustrated for purposes of clarity and example, it should be
understood that many changes, substitutions and modifications to
the described embodiment will be apparent to those having skill in
the art in light of the foregoing disclosure without departing from
the scope and spirit of the present invention which is defined by
the claims which follow.
* * * * *