U.S. patent application number 11/176626 was filed with the patent office on 2007-01-11 for mold knife preservation system and method.
This patent application is currently assigned to Graham Packaging Company, L.P.. Invention is credited to Edwin Beck, David A. Kesselman, Bernie Klingenmaier, Roy N. Krohn.
Application Number | 20070006682 11/176626 |
Document ID | / |
Family ID | 37434353 |
Filed Date | 2007-01-11 |
United States Patent
Application |
20070006682 |
Kind Code |
A1 |
Beck; Edwin ; et
al. |
January 11, 2007 |
Mold knife preservation system and method
Abstract
A system for preserving a cutting knife can include an actuator
for moving a first knife from an engaged to a removed position, at
which the first knife does not contact a second knife when a first
mold half, to which the actuator is connected, and a second mold
half, to which the second knife is connected, move from an open to
a closed position.
Inventors: |
Beck; Edwin; (York, PA)
; Kesselman; David A.; (York, PA) ; Klingenmaier;
Bernie; (York, PA) ; Krohn; Roy N.;
(Wrightsville, PA) |
Correspondence
Address: |
VENABLE LLP
P.O. BOX 34385
WASHINGTON
DC
20043-9998
US
|
Assignee: |
Graham Packaging Company,
L.P.
York
PA
|
Family ID: |
37434353 |
Appl. No.: |
11/176626 |
Filed: |
July 8, 2005 |
Current U.S.
Class: |
425/531 ; 451/11;
451/45 |
Current CPC
Class: |
B26D 5/04 20130101; B26D
5/02 20130101; B26F 2210/06 20130101; B26F 1/40 20130101; B29C
49/50 20130101; B29C 49/4817 20130101 |
Class at
Publication: |
076/082 ;
451/045; 451/011 |
International
Class: |
B24B 51/00 20060101
B24B051/00; B24B 1/00 20060101 B24B001/00; B21K 11/00 20060101
B21K011/00 |
Claims
1. A system for preserving a cutting knife, comprising: a first
mold half and a second mold half; an actuator connected to the
first mold half; a first knife connected to the actuator; a second
knife connected to the second mold half; wherein the first mold
half and the second mold half have an open position and a closed
position; wherein the actuator moves the first knife from an
engaged position to a removed position at which the first knife
does not contact the second knife when the mold halves move from
the open position to the closed position.
2. The system of claim 1, wherein the first knife is a bed knife,
and the second knife is a cutting knife.
3. The system of claim 1, wherein the first knife is a cutting
knife, and the second knife is a bed knife.
4. The system of claim 3, wherein the actuator comprises a cylinder
capable of admitting a fluid for fluid coupling to a fluid supply
and a piston within the cylinder and wherein the piston is
connected to the cutting knife.
5. The system of claim 4, wherein the fluid is a gas.
6. The system of claim 4, further comprising an actuator valve
fluidly coupled to the cylinder and for fluidly coupling to the
fluid supply.
7. The system of claim 6, further comprising a valve toggle for
manually opening the actuator valve.
8. The system of claim 6, further comprising an automatic control
device for automatically opening the actuator valve.
9. The system of claim 3, further comprising an automatic control
device connected to the actuator, wherein the automatic control
device comprises a parison sensor.
10. The system of claim 3, further comprising a spring connected to
the cutting knife and connected to the first mold half.
11. The system of claim 3, further comprising a knife holder,
wherein the knife holder is connected to the actuator and the
cutting knife is held by the knife holder.
12. The system of claim 3, further comprising: a fulcrum connected
to the first mold half; and a knife holder, wherein the cutting
knife is held by the knife holder and the fulcrum contacts the
knife holder during at least part of the motion of the cutting
knife from the engaged position to the removed position.
13. The system of claim 3, further comprising: a fulcrum connected
to the first mold half; a lever connected to the cutting knife;
wherein the actuator moves the lever to move the cutting knife from
the engaged position to the removed position and wherein the
fulcrum contacts the lever during at least part of the motion of
the cutting knife from the engaged position to the removed
position.
14. The system of claim 3, wherein the cutting knife comprises a
cutting edge and the bed knife comprises a sharpening surface.
15. A system for self-sharpening a cutting knife, comprising: a
first mold half and a second mold half; a first knife connected to
the first mold half; and a second knife connected to the second
mold half, wherein the first mold half and the second mold half
have an open position and a closed position, the first knife comes
into sliding contact with the second knife when the mold halves
move from the open position to the closed position, the first knife
is a cutting knife and the second knife is a bed knife, and the
cutting knife comprises a cutting edge and the bed knife comprises
a sharpening surface.
16. The system of claim 15, wherein the sharpening surface
comprises a sharpening stone.
17. The system of claim 15, wherein the sharpening surface
comprises a monocrystalline diamond coating.
18. The system of claim 15, the bed knife further comprising a
substrate, wherein the substrate is a metal.
19. The system of claim 15, wherein the cutting knife has a length
and the length of the cutting knife is positioned at a non-zero
angle with respect to the sharpening surface, so that the cutting
edge slides along the sharpening surface when the mold halves move
to the closed position.
20. A method for preserving a cutting knife, comprising moving a
first knife from an engaged position to a removed position at which
the first knife does not contact a second knife when a first mold
half to which the first knife is connected and a second mold half
to which the second knife is connected move from an open position
to a closed position.
21. The method of claim 20, the moving a first knife comprising
triggering an actuator to move the first knife from the engaged
position to the removed position, wherein the first knife is a
cutting knife, and the second knife is a bed knife.
22. The method of claim 21, the triggering an actuator comprising
deactivating the actuator to relieve force on the cutting
knife.
23. The method of claim 21, the triggering an actuator comprising
activating the actuator to impose force on the cutting knife.
24. The method of claim 23, the triggering an actuator comprising
forcing a fluid into a cylinder of a fluid actuator, so that the
fluid moves a piston within the cylinder, wherein the piston is
connected to the cutting knife, and the piston moves the cutting
knife from the engaged position to the removed position.
25. A method for self-sharpening of a cutting knife, comprising
moving a first mold half connected to a first knife and a second
mold half connected to a second knife from an open position to a
closed position, wherein the first knife is a bed knife and the
second knife is a cutting knife or the first knife is a cutting
knife and the second knife is a bed knife, and a cutting edge of
the cutting knife slides along a sharpening surface of the bed
knife.
26. The method of claim 25, further comprising moving the first
mold half and the second mold half from the closed position to the
open position, so that the cutting edge slides along the sharpening
surface to create a sharp burr on the cutting edge.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a mold knife preservation
system, which can be used in conjunction with a mold system for the
formation of objects, and a method. More particularly, the
invention relates to using an actuator, a first knife, and a second
knife with a first mold half and a second mold half.
DESCRIPTION OF THE RELATED ART
[0002] A molding apparatus can form a part by introducing a parison
of molding material between mold halves, closing the mold, and
separating the parison in the mold from the parison material
outside of the mold, for example, separating the parison in the
mold from another parison in a following mold. The part formed can
be, for example, a container. The parison can be separated by, for
example, cutting by mold knives. For example, a first knife can be
connected to a first mold half, and a second knife can be connected
to a second mold half. The knives can be configured, so that when
the mold halves close, the knives slide over each other, trapping
and cutting the parison material between them. For example, the
first knife can be a cutting knife with a sharp edge for contacting
and cutting the parison material. The second knife can be a bed
knife, for holding the parison material so that the sharp edge of
the cutting knife can cut through the parison material.
[0003] It can be important for the mold knives to be sharp, so that
the parison is cut cleanly. When a parison is between the mold
halves, so that the mold knives contact and cut the parison
material when the mold halves close, the parison material, for
example, a thermoplastic, can act to lubricate the knives. It is
thought that the lubrication by the parison material can prevent
the mold knives from coming into contact with each other. Thus a
mold knife can contact soft parison material, rather than another
mold knife, and retain its sharpness for an extended period of
time.
[0004] However, the mold halves can close with no parison material
between them. This can occur, for example, when the molding
apparatus is being tested or calibrated or if there is an
interruption in the parison material being supplied to the molding
apparatus. In this case, there is no parison material to serve as a
lubricant, and the mold knives can contact each other. For example,
the mold knives can contact each other when sliding over each
other, or, if there is a slight misalignment of the mold knives,
impact each other. Contact of one hard mold knife with another hard
mold knife can lead to rapid dulling of the sharp surface or
surfaces of a mold knife and/or lead to damage of the mold
knife.
[0005] When the mold knives become dull or damaged, the cutting of
the parison by the mold knives can be such that a less than clean
cut results; this can result in uncontrolled drop of the part,
which can disrupt the molding cycle, for example, the molding cycle
of a molding wheel. Therefore, when a mold knife becomes dull or
damaged, it must be replaced. Such replacement requires shutting
down the molding apparatus. The downtime and resultant interruption
of production has a high associated economic cost. Furthermore, the
frequent replacement of mold knives increases maintenance costs.
The problem of premature dulling or damage of a knife can be a
problem in any machine in which knives cut material and the machine
is on occasion run without being fed material.
[0006] If a molding apparatus is run so that there is always a
parison between the mold halves, dulling and wear of mold knives,
for example, a cutting knife, is delayed; the parison material is
understood to act as a lubricant between, for example, a cutting
knife and a bed knife. However, even in such a case, the mold
knives do eventually become dull and worn, so that the molding
apparatus must be shut down and the mold knives replaced. Eventual
dulling or wear of a knife will occur in any machine in which
knives cut material.
[0007] There thus remains an unmet need for a mold knife
preservation system and method to prevent knives from being
prematurely dulled by mold closure without the presence of a
parison. There further remains an unmet need for a self-sharpening
arrangement and method in which a knife is continually sharpened in
a mold closure and cutting step, rather than being continually worn
in a mold closure and cutting step.
SUMMARY OF THE INVENTION
[0008] It is therefore an object of the present invention to
provide a mold knife preservation system and method to prevent
knives from being prematurely dulled by mold closure without the
presence of a parison. It is a further object of the present
invention to provide a self-sharpening arrangement and method in
which a knife is continually sharpened in a mold closure and
cutting step, rather than being continually worn in a mold closure
and cutting step.
[0009] A system for preserving a cutting knife can include a first
mold half and a second mold half. An actuator can be connected to
the first mold half; and a first knife can be connected to the
actuator. A second knife can be connected to the second mold half.
The first mold half and the second mold half can have an open
position and a closed position. The actuator can move the first
knife from an engaged position to a removed position. At the
removed position, the first knife does not contact the second knife
when the mold halves move from the open position to the closed
position.
[0010] A system for self-sharpening a cutting knife can include a
first mold half and a second mold half. A first knife can be
connected to the first mold half, and a second knife can be
connected to the second mold half. The first mold half and the
second mold half can have an open position and a closed position.
The first knife can come into sliding contact with the second knife
when the mold halves move from the open position to the closed
position. The first knife can be a cutting knife, and the second
knife can be a bed knife. The cutting knife can include a cutting
edge, and the bed knife can include a sharpening surface.
[0011] A method for preserving a cutting knife can include moving a
first knife from an engaged position to a removed position. At the
removed position, the first knife does not contact a second knife
when a first mold half, to which the first knife is connected, and
a second mold half, to which the second knife is connected, move
from an open position to a closed position.
[0012] A method for self-sharpening of a cutting knife can include
moving a first mold half connected to a first knife and a second
mold half connected to a second knife from an open position to a
closed position. The first knife can be a bed knife and the second
knife can be a cutting knife. Alternatively, the first knife can be
a cutting knife and the second knife can be a bed knife. A cutting
edge of the cutting knife can slide along a sharpening surface of
the bed knife.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a side cross-sectional view of a mold knife
preservation system.
[0014] FIG. 2 is a side cross-sectional view of a mold knife
preservation system.
[0015] FIG. 3 is a side cross-sectional view of a mold knife
preservation system.
[0016] FIG. 4 is a side cross-sectional view of a mold knife
preservation system.
[0017] FIG. 5 is a side cross-sectional view of a portion of a mold
knife preservation system.
[0018] FIG. 6 is a side cross-sectional view of a portion of a mold
knife preservation system.
[0019] FIG. 7 is a top view of a portion of a mold knife
preservation system.
[0020] FIG. 8 is a top view of a portion of a mold knife
preservation system.
[0021] FIG. 9 is a side cross-sectional view of a portion of a mold
knife preservation system.
[0022] FIG. 10 is a side cross-sectional view of a portion of a
mold knife preservation system.
[0023] FIG. 11 is a side cross-sectional view of a mold knife
self-sharpening system.
[0024] FIG. 12 is a side cross-sectional view of a mold knife
self-sharpening system.
DETAILED DESCRIPTION
[0025] Embodiments of the invention are discussed in detail below.
In describing embodiments, specific terminology is employed for the
sake of clarity. However, the invention is not intended to be
limited to the specific terminology so selected. A person skilled
in the relevant art will recognize that other equivalent parts can
be employed and other methods developed without parting from the
spirit and scope of the invention. All references cited herein are
incorporated by reference as if each had been individually
incorporated.
[0026] An embodiment of a system for preserving a cutting knife can
include the following, as shown in FIGS. 1 and 2. The system can
include a first mold half 2, of which a portion is shown, and a
second mold half 4, of which a portion is shown. An actuator 6 can
be connected to the first mold half 2, and a first knife can be
connected to the actuator 6. A second knife can be connected to the
second mold half 4. The first mold half 2 and the second mold half
4 have an open position for which the first mold half 2 and the
second mold half 4 are not in contact, as shown in FIGS. 1 and 2.
The first mold half 2 and the second mold half 4 have a closed
position for which the first mold half 2 and the second mold half 4
are in contact, or nearly in contact, as shown in FIGS. 3 and 4.
The actuator 6 can move the first knife from an engaged position as
shown in FIG. 1 to a removed position as shown in FIG. 2. In the
engaged position, the first knife contacts, or nearly contacts the
second knife when the mold halves 2 and 4 move from the open
position, as shown in FIG. 1, to the closed position, as shown in
FIG. 3. In the removed position, the first knife does not contact
the second knife when the mold halves 2 and 4 move from the open
position, as shown in FIG. 2, to the closed position, as shown in
FIG. 4. By open position and closed position, the relative
positions of a first mold half 2 and a second mold half 4 are
described; that is, in moving from the open position to the closed
position the first mold half 2 may move, the second mold half 4 may
move, or both the mold half 2 and the mold half 4 may move. The
first mold half 2 and the second mold half 4 can be components of,
for example, a molding apparatus, such as an extrusion blow molding
machine. As used in this text, the term "connected" can either mean
directly connected, for example, a part A being directly connected
to a part B; or the term "connected" can mean indirectly connected,
for example, a part A being connected to a part C, with part A
being directly connected to a part B and part B being directly
connected to a part C.
[0027] When parison material is not between the first mold half 2
and the second mold half 4, the first knife can be moved to the
removed position, so that the first knife does not contact the
second knife, when the first mold half 2 and the second mold half 4
move to the closed position. Because the first knife and the second
knife do not contact each other, the sharpness of the first knife
and the second knife is preserved and the first knife and the
second knife are not prematurely worn.
[0028] In an embodiment, not shown in the Figures, the first knife
is a bed knife 10 and the second knife is a cutting knife 8. In
other embodiments, shown in FIGS. 1-10, the first knife is a
cutting knife 8 and the second knife is a bed knife 10.
[0029] The system for preserving a cutting knife can be used, for
example, with a mold forming apparatus. A parison can be forced
between the first mold half 2 and the second mold half 4. The
cutting knife 8 can be in the engaged position. When the first mold
half 2 and the second mold half 4 close, the cutting knife 8 can
move so that a cutting edge 24 of the cutting knife 8 contacts the
parison and separates the parison inside the mold from parison
material outside the mold. The cutting knife 8 can come into
sliding contact with the bed knife 10 to separate the parison
inside the mold from parison material outside the mold. Sliding
contact between the cutting knife 8 and the bed knife 10 can be
useful, for example, if the parison material is resistant to
cutting, or tends to form strands. The parison material can
include, for example, a thermoplastic, such as polypropylene,
high-density polyethylene, or another type of polyethylene. For
example, when the parison material is high-density polyethylene,
the first knife, e.g., the cutting knife 8, and the second knife,
e.g., the bed knife 10, can be positioned so that they have a
separation from each other in the range of from about 0.005 to
about 0.010 inches when the first knife is in the engaged position
and the first mold half 2 and the second mold half 4 are in the
closed position. For example, when the parison material is
polypropylene, which can have a tendency to smear when cut instead
of cutting cleanly, the first knife, e.g., the cutting knife 8, and
the second knife, e.g., the bed knife 10, can be positioned so that
they have no separation from each other, that is, they are in
sliding contact, when the first knife is in the engaged position
and the first mold half 2 and the second mold half 4 are in the
closed position. The wall of the parison can be formed of a single
layer of material, or multiple layers of material.
[0030] As shown in FIGS. 5 and 6, the actuator can be a fluid
actuator 36, which can include a cylinder 12 capable of admitting a
fluid. FIG. 5 is a side cross-section, along section A-A of FIG. 7,
of a portion of a system for preserving a cutting knife 8, with the
cutting knife 8 in the engaged position, shown in top view in FIG.
7. FIG. 6 is a side cross-section, along section C-C of FIG. 8, of
a portion of a system for preserving a cutting knife 8, with the
cutting knife 8 in the removed position, shown in top view in FIG.
8. The cylinder 12 can be for fluid coupling to a fluid supply, and
the fluid actuator 36 can include a piston 14 within the cylinder
12. The piston 14 can be connected to the cutting knife 8. The
piston 14 can be directly connected to the cutting knife 8.
Alternatively, the piston 14 can be indirectly connected to the
cutting knife 8; for example, the piston 14 can be connected to a
rod 30 which can act on a lever 22, the lever 22 can be connected
to a knife holder 18, and the knife holder 18 can hold a cutting
knife 8, as shown in FIGS. 5 and 6. The fluid which the cylinder 12
can admit, can be a gas, as, for example, in the case of a
pneumatic cylinder; alternatively, the fluid can be a liquid, as,
for example, in the case of a hydraulic cylinder. In the case of a
gaseous fluid, for example, air, nitrogen, or any other gas, the
cylinder 12 can be for fluid coupling to a supply of pressurized
gas. In the case of a liquid fluid, the cylinder 12 can be for
fluid coupling to a supply of pressurized liquid. For example, one
hose and one fitting can be fluidly coupled to the cylinder 12 and
fluidly coupled to a supply of pressurized air, to supply the
cylinder 12 with air.
[0031] The system can include an actuator valve fluidly coupled to
the cylinder 12 and for fluidly coupling to the fluid supply. The
actuator valve can be fluidly coupled to a single cylinder 12
associated with a single mold, or the actuator valve can be fluidly
coupled to multiple cylinders 12 associated with multiple molds. A
valve toggle can be included for manually opening the actuator
valve. Alternatively, an automatic control device can be included
for automatically opening the actuator valve.
[0032] In an embodiment, the system includes an automatic control
device connected to the actuator 6. The automatic control device
can include a parison sensor, which detects the presence of a
parison between the first mold half 2 and the second mold half 4.
The parison sensor can include, for example, a light source that
projects a beam of light across a region a parison occupies when a
parison is present between the first mold half 2 and the second
mold half 4 and a photodetector that can receive the beam of light.
The photodetector not detecting the beam of light can be indicative
of the presence of the parison; the photodetector detecting the
beam of light can be indicative of the absence of the parison. For
example, the parison sensor can be connected to control circuitry,
which can in turn be connected to a solenoid. The solenoid can be
connected to a valve toggle that can open or close an actuator
valve.
[0033] The system can include a spring 16 connected to a first mold
half 2 and connected to a cutting knife 8. The system can include a
knife holder 18. The knife holder 18 can be connected to the
actuator 6, and the cutting knife 8 can be held by the knife holder
18. For example, the system can include a spring 16 connected to
the first mold half 2 and connected to a knife holder 18 that holds
the cutting knife 8, as shown in FIGS. 9 and 10. FIG. 9 is a side
cross-section, along section B-B of FIG. 7, of a portion of a
system for preserving a cutting knife 8, with the cutting knife 8
in the engaged position, shown in top view in FIG. 7. FIG. 10 is a
side cross-section, along section D-D of FIG. 8, of a portion of a
system for preserving a cutting knife 8, with the cutting knife 8
in the removed position, shown in top view in FIG. 8.
[0034] The system can be configured so that the cutting knife 8 is
normally in the engaged position. Alternatively, the system can be
configured so that the cutting knife 8 is normally in the removed
position. Furthermore, the system can be configured so that the
actuator 6 is activated, for example, supplied with fluid under
pressure, or activated in another manner, when the cutting knife 8
is in the normal position; or the system can be configured so that
the actuator 6 is deactivated, for example, not supplied with fluid
under pressure, or deactivated in another manner, when the cutting
knife 8 is in the normal position.
[0035] For example, the embodiment shown in FIGS. 5 and 6 can be
configured so that the cutting knife 8 is normally in the engaged
position, shown in FIG. 5, when the fluid actuator 36 is normally
deactivated, by setting the spring 16, shown in FIG. 9, to be under
compression. The force imposed by the spring 16 on the cutting
knife 8 can act to maintain the position of the cutting knife 8
when the first mold half 2 and the second mold half 4 move to the
closed position, so that the cutting knife 8 properly cuts through
the parison material. The fluid actuator 36 shown in FIGS. 5 and 6
can be deactivated when the cylinder space to the left of the
piston 14, which can be capable of admitting fluid through an inlet
port 32, is not under fluid pressure.
[0036] Or, the embodiment shown in FIGS. 5 and 6 can be configured
so that the cutting knife 8 is normally in the removed position,
shown in FIG. 6, when the fluid actuator 36 is normally activated,
by setting the spring 16, shown in FIG. 10, to be under
compression. The fluid actuator 36 shown in FIGS. 5 and 6 can be
activated when the cylinder space to the left of the piston 14,
which can be capable of admitting fluid through the inlet port 32,
is under fluid pressure.
[0037] In the embodiment shown in FIGS. 5 and 6, the fluid actuator
36 includes a cylinder 12 that admits fluid on a side of the piston
14, so that fluid pressure will act through the piston 14 to force
the cutting knife 8 to the removed position; i.e., the cylinder 12
has an inlet port 32 for fluid on the left side of the piston 14.
In alternative embodiments, the fluid actuator 36 includes a
cylinder 12 that admits fluid on a side of the piston 14, so that
fluid pressure will act through the piston 14 to force the cutting
knife 8 to the engaged position. The devices shown in FIGS. 5 and 6
could be modified to such an alternative embodiment by, for
example, having the inlet port 32 in the cylinder 12 on the right
side of the piston 14 and including a link between the rod 30 and
the lever 22 so that the piston 14 can pull the lever 22 to the
left and thus force the cutting knife 8 to the engaged position.
Such an alternative embodiment can be configured so that the
cutting knife 8 is normally in the engaged position when the fluid
actuator 36 is normally activated, by setting the spring 16 to be
under tension. The fluid actuator 36 can be activated when the
cylinder space to the right of the piston 14, which can be capable
of admitting fluid through an inlet port 32, is under fluid
pressure. Or, such an alternative embodiment can be configured so
that the cutting knife 8 is normally in the removed position when
the fluid actuator 36 is normally deactivated, by setting the
spring 16 to be under tension. The fluid actuator 36 can be
deactivated when the cylinder space to the right of the piston 14,
which can be capable of admitting fluid through an inlet port 32,
is not under fluid pressure.
[0038] Thus, at least two modes of operation are possible with the
embodiment shown in FIGS. 5 and 6. At least two additional modes of
operation are possible with an embodiment in which the inlet port
32 is placed to allow fluid to enter to the right of the piston 14
and there is a link between the piston 14 and the lever 22, so that
the piston 14 can pull the lever 22 to the left.
[0039] For a system for which the cutting knife 8 is normally in
the engaged position, as shown in FIG. 5, when the fluid actuator
36 is deactivated, a parison sensor can act to trigger the
activation of the fluid actuator 36 when no parison is detected.
The fluid actuator 36 can then move the cutting knife 8 to the
removed position. And, for example, when the parison sensor later
detects the presence of a parison, the parison sensor can act to
trigger the deactivation of the fluid actuator 36, so that the
cutting knife 8 can return to the engaged position; for example,
when the fluid actuator 36 is deactivated, a spring 16 under
tension can act to return the cutting knife 8 to the engaged
position.
[0040] For a system for which the cutting knife 8 is normally in
the removed position, as shown in FIG. 6, when the fluid actuator
36 is activated, a parison sensor can act to trigger the
deactivation of the fluid actuator 36 when a parison is detected.
For a system for which the cutting knife 8 is normally in the
engaged position when a fluid actuator 36 is activated, a parison
sensor can act to trigger the deactivation of the fluid actuator 36
when no parison is detected. And for a system for which the cutting
knife 8 is normally in the removed position when a fluid actuator
36 is deactivated, a parison sensor can act to trigger the
activation of the fluid actuator 36 when a parison is detected.
[0041] The system can include a fulcrum 20 connected to the first
mold half 2; the fulcrum 20 can contact the cutting knife 8 or a
knife holder 18 holding the cutting knife 8 during at least part of
the motion of the cutting knife 8 from the engaged position to the
removed position, as shown in FIGS. 5 and 6. A lever 22 can be
connected to the cutting knife 8 or to a knife holder 18 holding
the cutting knife 8; a fluid actuator 36 can move the lever 22 to
move the cutting knife 8 from the engaged position to the removed
position; and a fulcrum 20, connected to the first mold half 2, can
contact the lever 22 during at least part of the motion of the
cutting knife 8 from the engaged position to the removed position.
FIGS. 5 and 6 show an embodiment in which the piston 14 can be
driven by a pressurized fluid in the cylinder 12 to move a rod 30;
the rod 30 can contact and exert force on a lever 22; the lever 22
can be connected to a knife holder 18 holding a cutting knife 8;
and the lever 22, knife holder 18, and cutting knife 8 can tilt
about a fulcrum 20 which can contact the knife holder 18.
[0042] The fulcrum 20 can be formed from a pin and socket. For
example, the fulcrum 20 can include a pin on a knife holder 18, a
cutting knife 8, or a lever 22 which fits into a socket on the
first mold half 2, or into a socket on a part connected to the
first mold half 2. Or, the fulcrum 20 can include a socket or hole
in the knife holder 18, the cutting knife 8, or the lever 22 into
which a pin protruding from the first mold half 2, or from a part
connected to the first mold half 2 fits. Alternatively, a fulcrum
can include a portion jutting from the first mold half 2, or from a
part connected to the first mold half 2 about which a cutting knife
8, a knife holder 18, or a lever 22 can tilt. Such a jutting
portion is not shown in FIG. 5 or 6.
[0043] The system for preserving a cutting knife 8 presented herein
can be readily adapted to a range of machinery in which a cutting
knife cuts material.
[0044] A system for self-sharpening a cutting knife can include a
first knife connected to a first mold half 2, and a second knife
connected to a second mold half 4. The first knife can come into
sliding contact with the second knife when the mold halves move
from an open position, shown in FIG. 11, to a closed position,
shown in FIG. 12. The first knife can be a bed knife, and the
second knife can be a cutting knife. Alternatively, as shown in
FIGS. 11 and 12, the first knife can be a cutting knife 8, and the
second knife can be a bed knife 10. The cutting knife 8 can include
a cutting edge 24, and the bed knife can include a sharpening
surface 26. In an embodiment, not shown in FIGS. 11 and 12, the bed
knife 10 is entirely formed of a sharpening surface 26. The cutting
edge 24 can contact and cut a parison when the first mold half 2
and the second mold half 4 move from the open position to the
closed position. The sharpening surface 26 can include, for
example, a sharpening stone or a monocrystalline diamond coating.
The bed knife 10 can include a substrate 28, as shown in FIGS. 11
and 12. The substrate 28 can be, for example, a metal. The cutting
edge 24 of the cutting knife 8 and the sharpening surface 26 can be
positioned with respect to each other, so that when the first mold
half 2 and the second mold half 4 move to the closed position, the
cutting edge 24 slides along the sharpening surface 26, so that the
sharpening surface 26 sharpens the cutting edge 24. For example,
the length of the cutting knife 8 can be positioned at a non-zero
angle, e.g., a small angle, with respect to the sharpening surface
26, so that the cutting edge 24 slides along and is sharpened by
the sharpening surface 26 when the first mold half 2 and the second
mold half 4 move to the closed position.
[0045] A force forcing the cutting edge 24 into contact with the
bed knife 10 or with a sharpening surface 26 of a bed knife 10 when
the cutting knife 8 is in the engaged position and the first mold
half 1 and the second mold half 2 move to the closed position can
be imposed on the cutting knife 8. Such a force can ensure contact
between the cutting edge 24 and the bed knife 10 or the sharpening
surface 26 in order to, for example, more effectively cut the
parison material and/or ensure sharpening of the cutting edge 24 by
the sharpening edge 26. For example, the cutting knife 8 can have a
fulcrum, and a spring can be connected to the cutting knife 8 and
to the first mold half 2 in order to impose such a force on the
cutting knife 8 (not shown in FIGS. 11 and 12). Alternatively, the
cutting knife 8 can be held by a knife holder 18; the knife holder
18 can have a fulcrum; and a spring can be connected to the first
mold half 2 and to the knife holder 18; so that force is imposed on
the cutting knife 8 to force the cutting edge 24 into contact with
the sharpening surface 26 when the cutting knife 8 is in the
engaged position and the first mold half 2 and the second mold half
4 move to the closed position (not shown in FIGS. 11 and 12).
[0046] This system for self-sharpening can prolong the retention of
a sharp edge by the cutting edge 24, and thereby increase the
period between shut down of the molding apparatus for cutting knife
8 replacement. This system for self-sharpening can be readily
adapted to a range of machinery in which a knife cuts material.
[0047] The system for self-sharpening can be combined with a system
for preserving a cutting knife in which bed knife 10 or the cutting
knife 8 can be moved from an engaged position to a removed
position. For example, in FIGS. 1-4, the bed knife 10 can include a
sharpening surface 26. When the cutting knife 8 is in the engaged
position, shown, for example, in FIG. 1, and the first mold half 2
and the second mold half 4 move from the open position, e.g., as
shown in FIG. 1, to the closed position, e.g., as shown in FIG. 3,
the cutting knife 8 can come into sliding contact with the bed
knife 10, and the cutting knife 8 can be sharpened by the bed knife
10.
[0048] A method for preserving a cutting knife can include moving a
first knife from an engaged position, as shown in FIG. 1, to a
removed position, as shown in FIG. 2. In the removed position, the
first knife does not contact a second knife when a first mold half
2, to which the first knife is connected, and a second mold half 4,
to which the second knife is connected, move from an open position,
such as shown in FIG. 2, to a closed position, such as shown in
FIG. 4. The first knife can be a bed knife 10 and the second knife
can be a cutting knife 8. Alternatively, the first knife can be a
cutting knife 8 and the second knife can be a bed knife 10, as
shown in FIGS. 1-4.
[0049] The method can include triggering an actuator 6 to move the
cutting knife 8 from the engaged position, as shown in FIG. 1, to
the removed position, as shown in FIG. 2. Triggering an actuator 6
can include activating the actuator 6 to impose force on the
cutting knife 8; this can result in the actuator 6 forcing the
cutting knife 8 from a normally engaged position, as shown in FIG.
1, to a removed position, as shown in FIG. 2. For example,
triggering an actuator 6 can include forcing fluid into a cylinder
12 of a fluid actuator 36, so that the fluid moves a piston 14
within the cylinder 12; and the piston 14, connected to the cutting
knife 8, moves the cutting knife 8 from the engaged position to the
removed position. For example, a rod 30 can be connected to the
piston 14, and the rod 30 can be forced against a lever 22
connected to a knife holder 18 which holds the cutting knife 8. The
force imposed by the piston 14 on the knife holder 18 can overcome
the force imposed by a spring 16, and move the cutting knife 8 from
the engaged position, shown in FIG. 5, to the removed position,
shown in FIG. 6. Forcing fluid into the cylinder 12 can include
opening an actuator valve connected to the cylinder 12 and for
fluidly connecting to a fluid supply.
[0050] Or, triggering an actuator 6 can include deactivating the
actuator 6 to relieve force on the cutting knife 8; this can result
in the actuator 6 allowing the cutting knife 8 to return from a
normally engaged position, as shown in FIG. 1, to a removed
position, as shown in FIG. 2.
[0051] Alternatively, the method can include triggering an actuator
6 to move the cutting knife 8 from a removed position, as shown in
FIG. 2, to the engaged position, as shown in FIG. 1. Triggering an
actuator 6 can include activating the actuator 6 to impose force on
the cutting knife 8; this can result in the actuator 6 forcing the
cutting knife 8 from a normally removed position, as shown in FIG.
2, to an engaged position, as shown in FIG. 1.
[0052] Or, triggering an actuator 6 can include deactivating the
actuator 6 to relieve force on the cutting knife 8; this can result
in the actuator 6 allowing the cutting knife 8 to return from a
normally removed position, as shown in FIG. 2, to an engaged
position, as shown in FIG. 1.
[0053] A method for self-sharpening of a cutting knife 8 can
include moving a first mold half 2, connected to a first knife, and
a second mold half 4, connected to a second knife, from an open
position to a closed position. The first knife can be a bed knife
10 and the second knife can be a cutting knife 8. Alternatively,
the first knife can be a cutting knife 8 and the second knife can
be a bed knife 10, as shown in FIGS. 1 and 3. During the motion of
the first mold half 2 and the second mold half 4 from an open
position to a closed position, the cutting edge 24 of the cutting
knife 8 can slide along a sharpening surface 26 of the bed knife
10. FIG. 11, showing the open position, shows that the cutting edge
24 of the cutting knife 8 can contact the sharpening surface 26
when the first mold half 2 and the second mold half 4 move to the
closed position, shown in FIG. 12.
[0054] A method for self-sharpening of a cutting knife 8 can
include moving the first mold half 2 and the second mold half 4
from the closed position to the open position, so that the cutting
edge 24 slides along the sharpening surface 26. This sliding during
moving from the closed position to the open position can create a
sharp burr on the cutting edge 24. This sharp burr can be
advantageous, because it can act to cut a parison when the first
mold half 2 and the second mold half 4 move from the open position
to the closed position. For example, the first mold half 2 and
second mold half 4, shown in the closed position in FIG. 12, can
move to the open position shown in FIG. 11.
[0055] The embodiments illustrated and discussed in this
specification are intended only to teach those skilled in the art
the best way known to the inventors to make and use the invention.
Nothing in this specification should be considered as limiting the
scope of the present invention. All examples presented are
representative and non-limiting. The above-described embodiments of
the invention may be modified or varied, without departing from the
invention, as appreciated by those skilled in the art in light of
the above teachings. It is therefore to be understood that, within
the scope of the claims and their equivalents, the invention may be
practiced otherwise than as specifically described.
* * * * *