U.S. patent application number 11/627440 was filed with the patent office on 2007-08-02 for keep for doctor blade holder.
This patent application is currently assigned to Kadant Web Systems. Invention is credited to Christopher Borradaile, Michael DeJesus, David Gardiner, Robert Reid.
Application Number | 20070174990 11/627440 |
Document ID | / |
Family ID | 37964752 |
Filed Date | 2007-08-02 |
United States Patent
Application |
20070174990 |
Kind Code |
A1 |
DeJesus; Michael ; et
al. |
August 2, 2007 |
KEEP FOR DOCTOR BLADE HOLDER
Abstract
An injection molded keep is disclosed that includes a
thermoplastic material and a reinforcement material. The keep is
positioned adjacent a top plate in a doctor blade holding apparatus
and provides a slot opening between the keep and the top plate for
receiving an end of a doctor blade in the slot opening.
Inventors: |
DeJesus; Michael; (Charlton,
MA) ; Reid; Robert; (Charlton City, MA) ;
Gardiner; David; (Paxton, MA) ; Borradaile;
Christopher; (Medway, MA) |
Correspondence
Address: |
GAUTHIER & CONNORS, LLP
225 FRANKLIN STREET, SUITE 2300
BOSTON
MA
02110
US
|
Assignee: |
Kadant Web Systems
Auburn
MA
|
Family ID: |
37964752 |
Appl. No.: |
11/627440 |
Filed: |
January 26, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60763518 |
Jan 31, 2006 |
|
|
|
Current U.S.
Class: |
15/256.51 |
Current CPC
Class: |
B05C 11/044 20130101;
D21G 3/005 20130101 |
Class at
Publication: |
15/256.51 |
International
Class: |
B21B 45/02 20060101
B21B045/02 |
Claims
1. An injection molded keep comprising a thermoplastic material and
a reinforcement material, said keep being positioned adjacent a top
plate in a doctor blade holding apparatus and providing a slot
opening between said keep and said top plate for receiving an end
of a doctor blade in said slot opening.
2. The keep as claimed in claim 1, wherein said thermoplastic
material includes at least one of a polyetheretherketone,
polyphenylene sulfide, polyphthalamide polyvinyl chloride,
polyethylene and polypropylene.
3. The keep as claimed in claim 1, wherein said reinforcement
material includes a plurality of fibers.
4. The keep as claimed in claim 3, wherein each of said fibers is
formed of at least one of glass, carbon, aramid, ceramic and a
thermoplastic material.
5. The keep as claimed in claim 3, wherein each of said fibers has
a largest dimension of between about 0.25 mm and about 15 mm.
6. The keep as claimed in claim 3, wherein each of said fibers has
a largest dimension of between about 0.5 mm and about 3 mm.
7. The keep as claimed in claim 1, wherein said reinforcement
material includes a plurality of particles.
8. The keep as claimed in claim 7, wherein each of said particles
is formed of at least one of glass, silicon, carbide and calcium
carbide.
9. The keep as claimed in claim 7, wherein each of said particles
has a diameter of between about 1 nm to about 1 mm.
10. The keep as claimed in claim 7, wherein each of said particles
has a diameter of between about 10 nm to about 100 nm.
11. The keep as claimed in claim 1, wherein said keep includes at
least one gusset for providing additional structural rigidity.
12. The keep as claimed in claim 1, wherein said keep includes
cavities that are positioned to provide a more uniform
cross-sectional area that would exist on the keep without the
cavities.
13. The keep as claimed in claim 1, wherein said keep includes a
relieve in a surface for providing that a portion of the keep
adjacent a fastening screw hole maintains contact with the top
plate when the keep is secured to the top plate.
14. An injection molded thermoplastic keep that is positioned
adjacent a top plate in a doctor blade holding apparatus and
provides a slot opening between said keep and said top plate for
receiving an end of a doctor blade in the slot opening, said keep
comprising a thermoplastic material and relief features in said
thermoplastic keep, said relief features including at least one
gusset that provides additional structural rigidity, at least one
cavity that is positioned to provide a more uniform cross-sectional
area that would exist on the keep without the cavity, and a relieve
in a surface for providing that a portion of the keep adjacent a
fastening screw hole maintains contact with the top plate when the
keep is secured to the top plate.
15. The keep as claimed in claim 14, wherein said keep provides a
flat portion of a surface that contacts the top plate, wherein said
flat portion has a flatness tolerance of at least 0.250 inches per
inch.
16. The keep as claimed in claim 14, wherein said keep provides the
slot opening with a flat portion having a flatness tolerance of at
least 0.250 inches per inch.
17. The keep as claimed in claim 14, wherein said thermoplastic
material includes at least one of a polyetheretherketone,
polyphenylene sulfide, polyphthalamide polyvinyl chloride,
polyethylene and polypropylene.
18. The keep as claimed in claim 14, wherein said keep further
includes a plurality of reinforcement fibers formed of at least one
of glass, carbon, aramid, ceramic and a thermoplastic material.
19. The keep as claimed in claim 14, wherein said keep further
includes a plurality of reinforcement particles formed of at least
one of glass, silicon, carbide and calcium carbide.
20. An injection molded thermoplastic keep that is positioned
adjacent a top plate in a doctor blade holding apparatus and
provides a slot opening between said keep and said top plate for
receiving an end of a doctor blade in the slot opening, said keep
comprising a nut retaining and anti-rotation cavity for receiving a
nut that may be fastened to a screw that passes through the top
plate.
21. The keep as claimed in claim 20, wherein nut is received with
said cavity in a snap-fit arrangement.
22. The keep as claimed in claim 20, wherein said nut is adhered to
the keep within the cavity.
Description
PRIORITY
[0001] This application claims priority to U.S. Provisional Patent
Application Ser. No. 60/763,518 filed on Jan. 31, 2006.
BACKGROUND OF THE INVENTION
[0002] This invention relates generally to doctor blade holders,
and is concerned in particular with improved mounting structures
(or keeps) for such holders.
[0003] A doctor blade holder generally holds a doctor blade in a
desired position with respect to a rotating roll in a manufacturing
process. For example, doctor blades in papermaking machines are
generally employed to remove accumulated debris from a roll in the
papermaking machine. In certain systems, the doctor blade may
further be employed to shed a portion of a sheet of paper. Many
such roll cleaning and sheet shedding applications in paper
machines and other web handling applications involve blade support
devices that are commonly referred to as doctor blade holders.
Typically, a doctor blade holder is mounted on a heavy-duty beam,
and includes a top plate with a mounting structure called a keep
along its underside. Each keep coacts with the top plate to define
a slot, and the rear edge of a doctor blade is received in the slot
of each keep. The doctor blade then becomes captured between the
top plate and the keeps.
[0004] The doctoring process often involves exposing the blade
holder to high steady-state loads in combination with impact loads.
It is imperative that holder components, including the keeps, be of
robust design so as to safely accommodate such conditions.
[0005] In addition to the mechanical loading, the blade holder may
be exposed to a wide range of caustic chemicals and high operating
temperatures. For this reason, the selection of appropriate
materials is of the utmost importance and often involves the use of
very expensive corrosion resistant metals such as type 316
Stainless Steel.
[0006] The metal keeps are conventionally produced by a process
known as investment casting whereby molten stainless steel is
poured into a ceramic mold. After solidification of the stainless
steel, the ceramic mold is broken apart to remove the keep. The
mold is not reusable.
[0007] The casting process is labor intensive and therefore quite
expensive. Since a typical blade holder requires many keeps (often
several hundred), the total cost of the keeps amounts to a very
significant percentage of the holder cost. Stainless steel is also
difficult and costly to machine. Each keep requires the machining
of two tapped holes that receives screws used to mount the keep to
the top plate. This operation further adds cost to the already
expensive part.
[0008] An objective of the present invention is to provide an
improved keep design that addresses the major issues of structural
integrity, chemical resistance, and hi-temperature endurance.
SUMMARY
[0009] In accordance with an embodiment, the invention provides an
injection molded keep that includes a thermoplastic material and a
reinforcement material. The keep is positioned adjacent a top plate
in a doctor blade holding apparatus and provides a slot opening
between the keep and the top plate for receiving an end of a doctor
blade in the slot opening.
[0010] In accordance with another embodiment, the invention
provides an injection molded thermoplastic keep that is positioned
adjacent a top plate in a doctor blade holding apparatus and
provides a slot opening between the keep and the top plate for
receiving an end of a doctor blade in the slot opening. The keep
includes a thermoplastic material and relief features in the
thermoplastic keep. The relief features include at least one gusset
that provides additional structural rigidity, at least one cavity
that is positioned to provide a more uniform cross-sectional area
that would exist on the keep without the cavity, and a relieve in a
surface for providing that a portion of the keep adjacent a
fastening screw hole maintains contact with the top plate when the
keep is secured to the top plate.
[0011] In accordance with a further embodiment, the invention
provides an injection molded thermoplastic keep that is positioned
adjacent a top plate in a doctor blade holding apparatus and
provides a slot opening between the keep and the top plate for
receiving an end of a doctor blade in the slot opening. The keep
includes a nut retaining and anti-rotation cavity for receiving a
nut that may be fastened to a screw that passes through the top
plate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The following description may be further understood with
reference to the accompanying drawings in which:
[0013] FIG. 1 is a side view of a doctoring apparatus, with a keep
in accordance with the present invention included in the doctor
blade holder;
[0014] FIG. 2 is a top perspective view of the keep;
[0015] FIG. 3 is a bottom perspective view of the keep;
[0016] FIGS. 4, 5, 6, and 7 are top, front, bottom, and side views
respectively of the keep; and
[0017] FIG. 8 is an enlarged partially sectioned view of the keep
attached to the top plate.
[0018] The drawings are shown for illustrative purposes only and
are not to scale.
DETAILED DESCRIPTION
[0019] Applicants have discovered that a thermoplastic material may
be formed by an injection molding process that is suitable for use
in securing a doctor blade to a top plate in accordance with
various embodiments of the invention.
[0020] With reference initially to FIG. 1, a doctoring apparatus 10
is shown adjacent to the surface of a roll 12. The roll rotates
about an axis A.sub.1, and the doctoring apparatus includes a
doctor back 14 that is rotatable about an axis A.sub.2 that is
parallel to the axis A.sub.1. A doctor blade holder 16 is shown
supported on a beam 18 forming part of the doctor back. The holder
is formed of a generally conventional design, having a top plate 20
mounted for pivotal movement about an axis A.sub.3. A plurality of
keeps 22 in accordance with the present invention are spaced along
the underside of the top plate 20. The keeps 22 coact with the top
plate 20 to define slots receiving the rear edge of a doctor blade
24. The rear edge of the doctor blade is captured between the top
plate and the keeps, and its forward edge is applied to the surface
of the roll 12 to effect doctoring. The top plate 20 is pivoted
about axis A.sub.3 by means of inflatable loading and unloading
tubes 26, 28 in a manner that is well known to those skilled in the
art. A piston/cylinder unit 30 acts via a crank arm 32 to rotate
the doctor back 14 about axis A.sub.2 in order to load the blade 24
against the roll surface.
[0021] The keep 22 is a one piece component that is molded from a
variety of thermoplastics including engineered thermoplastic
materials. Such engineered plastics include, but are not limited to
polyetheretherketone (PEEK), polyphenylene sulfide (PPS),
polyphthalamide (PPA), polyvinyl chloride (PVC), polyethylene (PE)
and polypropylene (PP).
[0022] PPA, as a base resin, combines excellent chemical and
thermal resistance. When used in combination with fiber
reinforcement, the mechanical properties are greatly enhanced in a
variety of environments. A preferred reinforcement is discontinuous
carbon fiber wherein the term discontinuous refers to the size of
fibers relative to the keep. The small fibers may be injection
molded resulting in random orientation. This random orientation
leads to isotropic properties. The fibers may be formed of glass,
carbon, aramid, ceramic and thermoplastic material. The fibers may
be between about 0.25 mm and about 15 mm, and may preferably be
between about 0.5 mm and about 3 mm in length. Other potential
reinforcement materials may include non-fiber elements formed of
glass, ceramic, or plastic as well in continuous or discontinuous
size distributions. In further embodiments the reinforcement
material may include a plurality of particles that are formed of
glass, silicon carbide and calcium carbide, and may have a diameter
of between about 1 nm to about 1 mm, and preferably may have a
diameter of between about 10 nm and about 100 nm.
[0023] With reference additionally to FIGS. 2-7, it will be seen
that the keep 22 comprises a base 34 grooved along its rear edge at
36, with a forwardly projecting ledge 38 having an upturned lip 40.
The top surface of the base forms an elongated boss having through
holes 42 at the opposite ends thereof. Each hole 42 leads to a
hexagonal recess 44 in the bottom surface of the base 34. The
hexagonal recess 44 provides a nut-retaining recess for receiving a
nut that engages a screw that passes through the top plate. The nut
may be adhered to the keep within the recess or may be received
within the recess in a snap-fit arrangement in various embodiments.
The hexagonal recess 44 also provides an anti-rotation recess that
prevents the nut from rotating when screw is rotated.
[0024] The keep also includes a plurality of engineered relief
features. For example, mutually spaced parallel strengthening
gussets or ribs 46 are located between the recesses 44 and extend
rearwardly from the ledge 38 along the underside of the base 34.
The gussets provide additional structural rigidity. The relief
features also include at least one cavity 52 that is positioned to
provide a more uniform cross-sectional area that would exist on the
keep without the cavity, and a relieve 54 (as also shown in FIG. 5)
in a surface for providing that a portion of the keep adjacent a
fastening screw hole maintains contact with the top plate when the
keep is secured to the top plate.
[0025] The keep also provides that the slot opening is partially
defined by a slot flat portion 56 that has a flatness tolerance of
at least 0.250 inches per inch. The keep further provides a top
plate flat portion 58 that contacts the tope plate, and the top
plate flat portion has a flatness tolerance of at least 0.250
inches per inch.
[0026] As shown in FIG. 8, the keep 22 is attached to the underside
of the top plate 24 by means of a pair of screws 48 (only one being
shown) and coacting hexagonal nuts 50. The screws 48 project
downwardly through holes in the top plate and the holes 42 in the
keep for threaded engagement with the nuts, the latter being
received in and rotatably fixed in the hexagonal recesses 44.
[0027] With this arrangement, there is no need to drill and tap
holes in the keep. The use of mass produced threaded nuts as an
alternate to a machining operation further reduces cost.
[0028] The nuts 50 are prevented from rotating by the matching
molded recesses 44 in the keep. Thus, when the two screws are
tightened, there is no need to use a wrench to hold the nuts at the
underside of the keep. This simplifies the assembly operation
further reducing the overall cost of the blade holder.
[0029] Those skilled in the art will appreciate that numerous
modifications and variations may be made to the above disclosed
embodiments without departing from the spirit and scope of the
invention.
* * * * *