U.S. patent application number 11/462574 was filed with the patent office on 2006-11-30 for milling machine.
This patent application is currently assigned to D4D TECHNOLOGIES, L.P.. Invention is credited to Branko Bem, Rod Duncan, Basil Haymann, Jeffrey Prince, Henley Quadling, Mark Quadling, Kirk Ray, Anthony Starfield, Joel Witt, Rui Xu.
Application Number | 20060269373 11/462574 |
Document ID | / |
Family ID | 35800700 |
Filed Date | 2006-11-30 |
United States Patent
Application |
20060269373 |
Kind Code |
A1 |
Duncan; Rod ; et
al. |
November 30, 2006 |
MILLING MACHINE
Abstract
The improved milling machine makes use of individually
controlled x-axis, y-axis, and z-axis carriages. These carriages
provide positive and precise control of the position of the cutting
tools and the blank to be cut. A tool changer allows the tools to
be changed to accommodate other materials. A camera is used to
detect wear on the tools.
Inventors: |
Duncan; Rod; (Plano, TX)
; Witt; Joel; (Dallas, TX) ; Quadling; Mark;
(Plano, TX) ; Quadling; Henley; (Dallas, TX)
; Prince; Jeffrey; (Grass Valley, CA) ; Bem;
Branko; (Plano, TX) ; Xu; Rui; (Plano, TX)
; Ray; Kirk; (Plano, TX) ; Haymann; Basil;
(Dallas, TX) ; Starfield; Anthony; (St. Paul,
MN) |
Correspondence
Address: |
CARSTENS & CAHOON, LLP
P O BOX 802334
DALLAS
TX
75380
US
|
Assignee: |
D4D TECHNOLOGIES, L.P.
Richardson
TX
|
Family ID: |
35800700 |
Appl. No.: |
11/462574 |
Filed: |
August 4, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10917069 |
Aug 12, 2004 |
|
|
|
11462574 |
Aug 4, 2006 |
|
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Current U.S.
Class: |
409/64 |
Current CPC
Class: |
Y10T 409/30 20150115;
A61C 13/0009 20130101; Y10T 409/301792 20150115; Y10T 409/303976
20150115; A61C 13/0004 20130101; Y10T 483/1733 20150115 |
Class at
Publication: |
409/064 |
International
Class: |
B23Q 1/28 20060101
B23Q001/28 |
Claims
1-12. (canceled)
13. A method of milling a blank using an improved milling machine
comprising the steps of: (a) inserting a blank into the milling
machine; (b) selecting a contour for the blank; (c) milling the
blank to match the contour using three tools that are manipulated
on an x-carriage, a y-carriage, and a z-carriage.
14. The method of claim 13 wherein the step of inserting the blank
comprises fixing the blank by means of a mandrel into a mandrel
socket.
15. The method of claim 13 wherein the step of selecting a contour
for the blank comprises the steps of receiving data from an
intra-oral digitizer.
16. The method of claim 13 wherein the step of milling the blank
comprises selecting a first and second tool for milling.
17. The method of claim 16 wherein the step of milling the blank
further comprises inserting the first and second tool into a first
and second spindle coupled to the x-axis carriage.
18. The method of claim 17 further comprises advancing spindles
along the the x-axis into contact with the blank.
19. The method of claim 17 further comprises positioning the blank
using the y-axis and z-axis carriages.
Description
TECHNICAL FIELD OF THE INVENTION
[0001] The present invention relates to an improved milling machine
that is used to mill a crown or dental implant from a blank. The
milling machine is adapted to receive instructions from a separate
scanner that provides a memory in the milling machine with data on
the outer and inner contours for the milled crown.
BACKGROUND TO THE INVENTION
[0002] One of the most common procedures for a dentist is the
repair of a broken tooth. When a tooth is broken, a portion of the
enamel comes off, exposing the dentin underneath. The dentin must
be covered to prevent the dentin from becoming infected. The
dentist will grind a portion of the remaining enamel away to
prepare the tooth for a crown. Once the grinding procedure is
complete, a reduced stump remains and a mold of the stump is made
with a quick setting mold material. Further a mold of the adjacent
teeth and the opposing teeth are also made. Then a temporary crown
in placed on the stump. The temporary crown has been partially
customized to fit over the stump and to mesh with the opposing
teeth. However, due to traditional time constraints, the temporary
crown rarely feels as natural as the original tooth. Further, the
temporary crown must be affixed to the stump with a temporary
fixative.
[0003] With the mold as a guide, an outside laboratory will prepare
a permanent crown. The permanent crown may be made of porcelain,
gold, ceramic, or other metal or substance. This process usually
takes at least three weeks to complete. During this time, the
patient must function with the temporary crown. Unfortunately,
there is a risk that the temporary crown may loosen and be
swallowed or otherwise lost by the patient. Even if it only
loosens, bacteria can gain access to the dentin for a time and
cause more serious dental health issues. Also, once the permanent
crown is available for placement, the temporary crown must be
removed. This requires the dentist to twist the temporary crown off
the stump, exerting a significant torque to the roots. Even then,
if the permanent crown is misshaped, then it may need to be removed
again and remade.
[0004] A need exists for a method of improving the speed of
producing a permanent crown for a patient. Indeed, if the crown
could be produced while the patient waited, it would be a great
savings for the patient and the dentist both. Moreover, it would
also be beneficial to eliminate the need to make a temporary crown
at all.
[0005] Sirona Dental Services GmbH, of Bensheim Germany produces a
milling machine specifically for producing porcelain crowns. It is
disclosed in U.S. Pat. No. 6,394,880 discloses one aspect of this
milling machine. It allows for the use of two milling bits to
simultaneously work a blank to form it into a permanent crown. The
mill bits are located on opposite sides of the blank and can move
in an x-, y-, and z-plane. However, the bits can not be changed on
demand to accommodate a different blank material. Also, there is no
method disclosed for determining the bit wear to warn the dentist
that the crown's dimensions may be skewed due to bit wear.
[0006] The Sirona patent illustrates a portion of a larger milling
machine known as the CEREC. The CEREC has several other drawbacks.
First, it has only a wireless connection with an intraoral
digitizer used to make the measurements of the stump and adjacent
teeth. Once the measurements are made, the intraoral digitizer
cannot be used until the crown is finished. Therefore, a need
exists for a milling machine that includes a memory that can store
the required data thereby freeing the intraoral digitizer to be
used again. Further, the CEREC device is flawed in its failure to
minimize vibration that affects the quality of the milling. Even
minor vibration can create many microns of error on the surface of
the crown.
SUMMARY OF THE INVENTION
[0007] The present invention overcomes many of the defects of the
prior art and allows the dentist to mill a superior permanent crown
or other dental inlay while the patient waits. This reduces the
amount of time for the patient in the dentist chair, thereby
allowing the dentist to schedule more patients. Further, it is a
significant time savings for the patient. The milling machine can
be located at the dentist office. However, it could also be located
at a traditional dental lab. In this event, the lab would receive
the data outlining the contours for the crown or the inlay. It
would still be able to supply a superior crown or inlay in less
time than traditionally experienced.
[0008] The present milling machine is characterized by a robust and
sturdy frame that minimizes any vibration. This helps ensure the
highest quality end product. Further, the spindles that rotate the
milling bits are located on a common rail, giving the device the
ability to move the tools in the x-axis. The blank is releasably
attached to a mandrel. The mandrel is secured to a subassembly that
allows motion in the y-axis and the z-axis. The milling machine
includes a CPU and memory for storing the data on the contour of
the crown or inlay. Further, the milling machine has a water
reservoir for settling any particulate that becomes entrained in
the water used to cool and rinse the blank during milling.
[0009] Tools used to mill the blank can be changed using a novel
automatic tool changer. The ability to engage different tools also
allows for the use of different blank materials, from hardened
metals to ceramics to porcelain to gold. Further, a camera or other
sensing device can be used to monitor wear experienced by the
tools. The blank is held by a mandrel that engages a frame within a
work area that is easily accessible to a technician or the dentist.
While this disclosure focuses on the production of crowns, it
should be understood that this term is being used broadly. Indeed,
while a crown is one of the preferred items for milling, this
improved milling device could be used to produce inlays, onlays,
coping, framework, bridges, implants, implant abutments, veneers,
and overlays.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The novel features believed characteristic of the invention
are set forth in the appended claims. The invention itself,
however, as well as a preferred mode of use, further objectives and
advantages thereof, will best be understood by reference to the
following detailed description of an illustrative embodiment when
read in conjunction with the accompanying drawings, wherein:
[0011] FIG. 1 is a perspective view of a milling machine that
embodies the present invention;
[0012] FIG. 2 is perspective showing the carriage that controls the
x-axis movement of the spindles;
[0013] FIG. 3 is a cut-away view of the spindle showing the collet
that engages the cutting tool and the cooling fluid delivery
path;
[0014] FIG. 4 is a perspective view of the subassembly that
controls the y-axis and z-axis of the device;
[0015] FIG. 5 is an enlarged view showing the automatic tool
changing machine and the digital camera used to detect tool wear
and axial calibration;
[0016] FIG. 6 is an enlarged perspective showing the engagement
between the tool in a spindle and the automatic tool changer;
[0017] FIG. 7 is a perspective view of a tool that can be used in
the present embodiment;
[0018] FIG. 8 is an exploded view of the mandrel and blank.
DETAILED DESCRIPTION OF THE DRAWINGS
[0019] This inventive milling machine is sized to fit on the
countertop of a dentist office or in a lab. Its generally compact
size however does not mean that the quality of end product is
diminished. Instead, the milling machine is built so robustly that
it will produce the highest quality crowns and inlays. An
intra-oral digitizer is used to measure the dimensions of the
prepared tooth, as well as the adjacent and opposed teeth. Software
within the digitizer constructs an outer contour that meshes with
the adjacent and opposing teeth. The design is approved by the
dentist and then conveyed to the milling machine.
[0020] FIGS. 1 and 2 provide perspective views of the milling
machine 100. It includes a cover 102 that protects the operator
from the moving parts within. A blank 10 is held within a work area
that is accessible through door 104. The x-axis carriage 110 is
used to move the tools back and forth into engagement with the
blank 10. The carriage 110 includes a first and second frame that
both slide on rails on subframe 112. The subassembly 140 is used to
control the y-axis and z-axis movement of the mandrel and blank. A
reservoir is also located at the bottom of the machine 100. The
CPU, memory and other electronics are located in compartment 107.
These can be controlled, or activity displayed on display 106.
[0021] FIG. 2 is an isolated view of the x-axis carriage 110. It
includes a first frame 114 and a second frame 116. In one
embodiment, these frames are formed from a single block of metal,
having no seems to decrease their stiffness. A first and second
spindle 118, 120 are coupled to these frames 114, 116. The frames
114, 116 move on a single pair of rails 122 to ensure absolute
alignment. Each frame is coupled to a first and second spindle,
wherein each spindle has a central axis. The central axis of each
spindle are aligned. Tools 128 and 130 are accepted into the
spindles along this axis. The spindles rotate the tools so that a
cutting surface on the tool can carve away material from the blank
as desired. Of course, this process generates heat and carvings. A
fluid stream emits from the spindle ports 126 as well to wash and
cool the blank during milling. This effluent exits to a reservoir
where particulate matter can settle. Motors 124 are used to supply
the power to move the frames along the rails and to rotate the
tools within the spindles.
[0022] FIG. 3 provides a more detailed view of the spindle 120 and
the tool 130. Water, or other cooling fluid, is fed into the
spindle through supply 124. Water passes through passages 132 into
a collar 136. This collar supplies the water into several tubes 138
that carry the water to the front of the spindle. The water is
sprayed from the tips of the tubes 138 and directed toward the tip
of the tool 130. At least one o-ring is used to seal and separate
the spindle's motor from the water.
[0023] The complex outer contour of the damaged tooth is reproduced
by the present milling machine. This requires an accurate
understanding of exactly the location of the tip of the tools and
the x, y, z coordinates of the blank. Thus the shape and length of
the mandrel 160 holding the blank must be precise. Very precise
motors are used to move the carriages shown in FIG. 3. This same
level of precision is reproduced for the y and z axes. However,
rather than move the spindles, the mandrel is moved in the y and z
axes by the subassembly 140 shown in FIG. 4. In FIG. 4, the y-axis
is controlled by moving a carriage along rails. A separate z-axis
carriage 142 includes the frame for engaging the mandrel 160 and
automatic tool changer 130. This view also illustrates the location
of the mandrel 160 and blank 10 to be milled. It is located on the
z-axis carriage. A cam 162 is used to secure the mandrel in place.
The mandrel and blank will be shown in greater detail below. The
automatic tool changer 150 is also attached to the z-axis carriage.
The tool changer can carry several additional tools 128, 130 for
placement into the spindles. The tool changer 150 also includes at
least one open port 154 for accepting the tool in the spindle. An
electronics package 152 can be located on the end of the tool
changer 150.
[0024] FIG. 5 provides an even more detailed view of the tool
changer 150, blank 10, and tools. In this view, the y-axis carriage
has moved the blank 10 above the tool 128. In this position, a
camera 170 can be used to inspect the condition of the tip of tool
128. Note that the tool 128 is co-axially located within the
spindle 118. Further, note that the nozzles 126 are angled to
direct a cooling spray of fluid onto the tip of the tool 128.
[0025] One of the important advances of the present invention is
the ability to substitute tools as required. For example, a tool
for grinding a contour onto a ceramic is different than a tool for
grinding a contour onto a blank of gold. The prior art has never
addressed the need for a lab to be able to quickly deal with blanks
of differing materials. The present invention can allow a
technician to simply enter the desired material. The milling
machine will engage the appropriate tool for the material. The
camera 170 will inspect the tool for wear and if necessary, select
a backup tool for the process. Alternatively, if the tool is too
worn and no back-up is available, the technician will be alerted.
The ability to engage and disengage the tools is shown in FIG. 6.
The tool changer 150 is positioned with the y-axis carriage to a
position in between the spindles. The selected tool is positioned
in co-axial relationship with the spindle using the z-axis
carriage. A collet on the spindle is opened to engage the distal
end of the tool, for example tool 130. The tool is releasably
secured in the tool changer 150 with a spring loaded ball 172 or
other means for securing the tool. Ball 172 presses against a
central portion of the tool between a first and second flange. When
the tool is engaged in the spindle, its collet closes. The tool
changer 150 is then lowered with the y-axis carriage. This forces
the ball 172 against pin 174 and compressed spring 176. The force
on spring 176 can be adjusted using the set screw 178.
[0026] FIG. 7 provides a more detailed illustration of the tool
130. It includes a distal end 130a that is engaged within the
spindle. At least 25% of the length of the tool is engaged within
the spindle to ensure stability and to minimize and bending of the
tool. The proximal end 131 of the tool can vary based on the
material to be milled. For example, the grinding tip shown is for a
ceramic. However, another tip might be used for grinding away a
metal blank. Flanges 130b and 130c define a central portion that is
used to engage the tool to the tool changer 150. However, the
flanges serve the additional purpose of assisting with the
registration of the tool and the blank. In other words, even though
the exact length of the tool is known, the x, y, z coordinates of
its tip must still be known exactly. When the tool is engaged into
the spindle, the flange acts as a travel limit and thus defines the
distance between the tip and the spindle. Thus, when the spindle
moves along the x-axis, the position of the tip of the tool will be
known.
[0027] In addition to knowing the exact x, y, and z coordinates of
the tool tips, it is also essential to know the exact position for
the blank. This requires that the mandrel and blank be consistently
placed into the machine. The mandrel and blank engage a mandrel
socket 164 that in turn engages the z-axis carriage. FIG. 8 shows
the mandrel socket in more detail. The mandrel 160 has a distal end
that enters a similarly shaped socket 164. As shown the mandrel has
a generally circular cross-section that engages the generally
cylindrical socket. A groove 166 near the distal end of the socket
provides an engagement surface for a cam 162. The cam 162 is
rotated to a first position to allow insertion of the mandrel 160.
The cam 162 is then rotated to a second position that engages the
groove and secures the mandrel within the socket. A pin 168 is used
to prevent the accidental rotation of the cam. While a cylindrical
mandrel is shown, its cross-section could be any suitable shape.
Note that the socket has an opening on both ends. This allows for
debris to be pushed through the socket rather than allow it to
build up within the socket.
[0028] While various embodiments of the invention have been
described, it will be apparent to those of ordinary skill in the
art that many more embodiments and implementations are possible
within the scope of the invention. Accordingly, the invention is
not to be restricted except in light of the attached claims and
their equivalents
* * * * *