Information
-
Patent Grant
-
6604936
-
Patent Number
6,604,936
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Date Filed
Wednesday, August 1, 200123 years ago
-
Date Issued
Tuesday, August 12, 200321 years ago
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Inventors
-
Original Assignees
-
Examiners
Agents
- O'Planick; Richard B
- Krawczyk; Nancy T
-
CPC
-
US Classifications
Field of Search
US
- 425 557
- 425 558
- 425 559
- 425 560
- 425 561
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International Classifications
-
Abstract
The injection molding machine has an extruder for providing molding material, a cavity for retaining the molding material prior to injection into a mold, a plunger within the cavity to move the material out of the cavity, and a check valve. The check valve has separate means to permit the material to flow from the extruder to the cavity and from the cavity to an adjacent mold. By having separate flow channels for molding and recharging, the injection molding machine may be recharged on the fly.
Description
FIELD OF THE INVENTION
The present invention is directed to an apparatus for injection molding. More specifically, the disclosed apparatus allows for reduced injection cycle time when injecting rubber.
BACKGROUND OF THE INVENTION
Injection molding presses for injecting molding materials into molds are well known in the manufacturing industry. Molding materials such as rubber composites must typically be cured within their molds under specific temperature and pressure conditions. Prior to the injection of molding material into the mold, the injection press clamps the mold so that the mold is under pressure during the injection operation.
The time required for each molding cycle may be six minutes or more. A molding cycle typically includes the steps of clamping the mold, injecting material into the mold, holding the mold in a clamped condition with the injection nozzle still contacting the mold to initiate curing, and recharging the injection unit with material. Such molding cycle times are required, since the molds must remain under pressure within the press to complete the injection operation, initiate curing, and recharge the injection unit with molding material for the next cycle. Recharging of the unit with material occurs during this time in order to prevent any loss of material from the unit and so that when the next mold is presented to the unit for filling, filling may be immediately begin.
U.S. Pat. No. 5,286,186 discloses an apparatus for injection molding rubber. The apparatus has both a check valve to prevent molding material from passing back into the extruder during injection of the material and a separate shut-off valve to prevent molding material from passing to the injection nozzle during recharging of the internal cavity. The check valve and the shut-off valve do not operate together such that when one is activated the other is automatically operated and material may still pass through one of the valves when not desired.
SUMMARY OF THE INVENTION
The present invention provides a new and improved apparatus for performing a molding process. The apparatus is designed to increase the number of molds processed in a specific time period by permitting recharging of the injection molding machine on the fly.
The injection molding machine has an extruder for providing molding material, a cavity for retaining the molding material prior to injection into a mold, a plunger within the cavity to move the material out of the cavity, and a check valve. The check valve has separate means to permit the material to flow from the extruder to the cavity and from the cavity to an adjacent mold.
The check valve has an injection outlet port to permit flow from the cavity to an injection nozzle and a transfer column to permit flow from the extruder to the cavity. The injection outlet port and the transfer column are spaced from one another.
Movement of the check valve from a recharging position to an injecting position is activated by a hydraulic cylinder. The check valve is moved axially along its centerline to move the valve from an injecting position to a recharging position.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described by way of example and with reference to the accompanying drawings in which:
FIG. 1
is a cross sectional view of the injection apparatus;
FIG. 2
is a cross sectional view of the injection apparatus;
FIG. 3
is a cross sectional view of the check valve; and
FIG. 4
is a perspective view of the injection apparatus.
DETAILED DESCRIPTION OF THE INVENTION
An injection apparatus
10
in accordance with the present invention is illustrated in
FIGS. 1
,
2
, and
4
. The injector
10
has an internal cavity
12
with a plunger
14
to which a charge of molding material is supplied by the extruder
16
. Once the internal cavity
12
is filled with material, the plunger
14
is activated to inject the material into an adjacent mold (not shown). To conserve space, the cavity
12
and the extruder
16
are located adjacent to one another, with the extruder
16
inclined at a low angle relative to the cavity
12
to reduce the distance between the exit port
18
of the extruder and the opening of the cavity
20
.
The extruder
16
includes a barrel
22
with a single extruder screw
24
located within the barrel
22
. An opening (not shown) is provided in the extruder barrel
22
for feeding strips of molding material into the barrel
22
. Preferably, the molding material is rubber. The extruder screw
24
is driven by a reciprocating motor
26
. Since heat is generated within the barrel
22
by mastication of the molding material, coolant flow is provided about the barrel
22
in a coolant flow area
28
. The desired temperature is maintained by a thermal jacket
30
and monitored by thermocouplings located about the barrel
22
.
The internal cavity
12
is located within a housing
32
. After the cavity
12
is filled with material, the material is pushed out of the cavity
12
by the plunger
14
and to the nozzle
34
. The nozzle
34
, at that time, is engaged in a sealing relationship with a sprue opening of a mold. To maintain the desired temperature in the internal cavity
12
, cooling jacket
36
is provided about the cavity housing
32
and coolant is provided similar to the extruder.
Connecting the extruder
16
and the internal cavity
12
and connecting the internal cavity
12
and the nozzle
34
is the check valve
40
. The check valve
40
has a block configuration, see FIG.
3
. The check valve
40
has an injection outlet port
42
and a transfer column
44
. The injection outlet port
42
permits material to flow from the internal cavity
12
to the nozzle
34
and the transfer column
44
permits material to flow from the extruder
16
to the cavity
12
.
The injection outlet port
42
is located at one end of the check valve
40
. The injection outlet port
42
has an internal diameter D
v
equivalent to the diameter D
I
of the nozzle tube
46
. If desired, for the purpose of altering the material flow pressure, the port diameter D
V
may be greater than the diameter D
I
of the nozzle tube
46
. When aligned for use, the injection outlet port
42
connects the nozzle
34
to the internal cavity
12
to allow the molding material to pass from the cavity
12
to the nozzle
34
and into a mold.
Distanced from the injection outlet port
42
is the transfer column
44
. The transfer column
44
connects the extruder
16
and the cavity
12
, permitting material to flow from the extruder
16
to the cavity
12
when the injector
10
is being recharged with molding material. The column
44
has an entrance port
48
and an exit port
50
. When aligned for use, the entrance port
48
connects to the extruder
16
and the exit port
50
connects to the internal cavity
12
. The illustrated column is shown with two bends
52
in the column. For material flow purposes, any bends
52
in the column
44
are preferably constructed to reduce material build up in the bends
52
and the creation of dead zones.
Below the check valve
40
is a hydraulic cylinder
54
for moving the check valve
40
between the injection and the recharging position. The hydraulic cylinder
54
has a position sensor for indicating what position the cylinder
54
is in, and thus, what position the check valve
40
is in. The check-valve
40
is in injection position when the injection outlet port
42
is aligned with the nozzle
34
and the internal cavity
12
, as seen in FIG.
1
. The check valve
40
is in recharging position when the transfer column
44
permits the flow of material from the extruder
16
to the cavity
12
, as seen in FIG.
2
.
As noted, the check valve
40
has a block configuration. The configuration may have an overall circular, square, triangular, or polygonal shape. When the check valve
40
is formed in a non-circular block configuration, it reduces any accidental or incidental radial rotation of the check valve
40
within the apparatus, reducing the possibility of misalignment of the injection outlet port
42
and the transfer column
44
.
The main portion of the transfer column
44
, and the associated portion of the hydraulic cylinder
54
, is illustrated as axially off-center in the check valve
40
. By axially offsetting the column
44
, rotation of the check valve
40
is precluded and prevents misalignment of the check valve
40
. If the configuration of the check valve
40
is non-circular, than the transfer column
44
may also be located along the central axis of the block and rotation of the check valve
40
is precluded by the check valve configuration. Other means of preventing radial rotation of the check valve
40
may be used in addition to or instead of these specific means.
Operation of the apparatus occurs in the following manner. The hydraulic cylinder
54
is activated to move the transfer column
44
to the recharging position, as seen in FIG.
2
. Molding material has been feed into the extruder screw
24
. The material is masticated and conditioned by the screw
24
. The material flows from the screw
24
into the column
44
and then into the internal cavity
12
. As the material flows into the cavity
12
, the plunger
14
is pushed back by the material to a position so that the volume in the cavity
12
is approximately equivalent to the volume of rubber to be injected into the mold.
After the required volume of material is in the internal cavity
12
, the hydraulic cylinder
54
is activated to move the check valve
40
into the injecting position, as seen in FIG.
1
. The plunger
14
is then moved forward to shoot the material into the injection outlet port
42
and then into the nozzle
34
. At this time, the nozzle
34
is in contact with the mold sprue port, and the material passes from the nozzle
34
into the mold.
After all of the material is transferred to the mold, the hydraulic cylinder
54
is activated to return the check valve
40
to the recharging position, closing off any means for further material to continue to flow into the mold. Material that has already been prepared by the screw
24
now flows, via the transfer column
44
, to the internal cavity
12
, recharging the injector
10
and preparing for the next molding operation.
By forming the check valve
40
with two different mechanisms
42
,
44
for injecting the material into the mold and for recharging the cavity
12
, while the injector
10
is recharging, material cannot flow out of the nozzle
34
, and during molding, excess material cannot flow from the screw
24
and into the nozzle
34
. Because material cannot flow out the injector
10
during recharging, it makes it possible to recharge the injector
10
while “on the fly;” that is, the injector
10
may be recharged as either the injector
10
is moved to the next mold or as a new mold is being positioned adjacent to the injector
10
for filling. The disclosed check valve provides the injector
10
with a consistency and reliability that is not present with conventional check valves and shut-off valves.
Variations in the present invention are possible in light of the description of it provided herein. While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the subject invention. It is, therefore, to be understood that changes can be made in the particular embodiments described which will be within the fill intended scope of the invention as defined by the following appended claims.
Claims
- 1. An apparatus for injection molding material into a mold, the apparatus comprising an extruder for providing molding material, a cavity for retaining the molding material prior to injection into a mold, a plunger within the cavity to move the material out of the cavity, a check valve, the check valve being characterized by:the check valve comprising separate means to permit the material to flow from the extruder to the cavity and from the cavity to a mold; the check valve having an external shape that inhibits rotation and misalignment of the check valve.
- 2. An apparatus in accordance with claim 1 wherein the check valve is activated by a hydraulic cylinder.
- 3. An apparatus in accordance with claim 1 wherein the check valve is block shaped.
- 4. An apparatus in accordance with claim 1 wherein the check valve moves axially along its centerline to move the valve from an injecting position to a recharging position.
- 5. An apparatus in accordance with claim 1 wherein the check valve has a radial cross-section configuration selected from the following group of circular, oval, triangular, and polygonal.
- 6. An apparatus for injection molding material into a mold, the apparatus comprising an extruder for providing molding material, an apparatus cavity having an access port for receiving the molding material prior to injection into a mold, a plunger within the cavity to move the material out of the apparatus cavity, a check valve, the check valve being characterized by:(a) an internal transfer column cavity moving axially along a check valve centerline relative to the apparatus cavity access port; (b) an entrance port communicating with the transfer column cavity and allowing passage of the molding material from the extruder to the transfer column cavity; (c) an exit port communicating with the transfer column cavity and allowing passage of the molding material from the transfer column cavity into the apparatus cavity; and (d) an injection outlet port for allowing passage of the molding material from the apparatus cavity through the check valve.
- 7. An apparatus in accordance with claim 6 wherein the check valve moves axially along its centerline to move the valve from an injecting position to a recharging position, the valve entrance port and the valve exit port being closed in the injecting position and open in the recharging position, and the valve injection outlet port being open in the injecting position and closed in the recharging position.
- 8. An apparatus in accordance with claim 7 wherein the check valve moves reciprocally along its centerline between the injecting position to the recharging position to alternatively open and close the entrance port, the exit port, and the injection outlet port.
- 9. An apparatus in accordance with claim 7 wherein the check valve transfer column is transversely oriented relative to the apparatus cavity.
- 10. An apparatus in accordance with claim 6 wherein the injection outlet port extends transversely through the check valve relative to the check valve centerline.
US Referenced Citations (28)