Plastic article or earthenware shaping or treating: apparatus – Means applying electrical or wave energy directly to work
Reexamination Certificate
2000-05-26
2001-12-04
Heitbrink, Tim (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Means applying electrical or wave energy directly to work
C264S069000, C264S478000, C425S207000, C425S564000
Reexamination Certificate
active
06325612
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to an injection molding machine, and more particularly to an apparatus for applying vibrational repetitive movements to a melt of molding materials held inside the heating cylinder of an injection molding machine so as to improve the moldability of the melt.
2. Description of the Related Art
One of the present inventors has proposed an improved screw injection molding system in which low frequency vibrations are applied to a melt of molding materials to lower the viscosity of the melt, as disclosed in Japanese Patent Laid-open Publication No. HEI-11-170318. The disclosed screw injection molding system includes a needle valve mechanism which includes, as shown here in
FIG. 8
, a guide
32
engaged in a block
19
connecting a heating cylinder
11
and a discharge nozzle
18
, a primary cylinder
34
connected to the guide
32
via a bracket
33
, a primary piston
35
slidably disposed interiorly of the primary cylinder
34
, a secondary cylinder
37
formed integrally with the primary piston
35
, a secondary piston
38
slidably disposed interiorly of the secondary cylinder
37
, front and rear piston rods
41
and
41
extending from the secondary piston
38
in a forward-and-rearward direction, an elongated rod
44
received in the front and rear piston rods
41
,
42
and fixed to the latter via bushes
43
,
43
, a needle
31
formed at a distal end of the elongated rod
44
, and an amplitude adjusting nut
46
mounted to a proximal end of the elongated rod
44
and locked in position by a lock nut
47
. In
FIG. 8
numeral
12
denotes a screw slidably and rotatably received in the heating cylinder
11
.
In
FIG. 8
, the needle
31
of the needle valve mechanism
30
is placed in an open position in which the nozzle
18
of the heating cylinder
11
is opened. When the primary piston
35
is advanced or moved in the direction of the arrow a relative to the primary cylinder
34
, the needle
31
moves to a closing position in which the nozzle
18
is closed. By thus moving the primary piston
35
back and forth relative to the primary cylinder
34
, the nozzle
18
can be opened and closed by the needle
31
.
While the needle
31
is held in the open position of
FIG. 8
, the secondary piston
38
is moved reciprocally (back and forth) in the direction of the arrow b relative to the secondary cylinder
37
. In this instance, the needle
31
never closes a flow path of a molten material in its fully advanced position. In its half-open position, the needle
31
thus vibrates the molten material, thereby lowering the viscosity of the molten material. The amplitude of vibration of the needle
31
is determined by the distance h between the secondary cylinder
37
and the amplitude adjusting nut
46
, which can be varied by turning the amplitude adjusting nut
46
rightwardly or leftwardly.
By thus moving the needle
31
reciprocally in the direction of the arrow b, low frequency vibrations can be applied from the tip of the needle
31
to the melt of molding materials. However, since the application of vibrations to the melt in the prior arrangement relies on minute reciprocal movement of the secondary piston
38
controlled hydraulically, a controller requires a servo valve installed in a hydraulic circuit. The servo valve is expensive per se and requires a complicated control circuit. This may render the controller complicated in construction and highly expensive to manufacture.
In addition, the frequency of vibrations must be changed according to the sort of molten materials used. This requirement may enhance the difficulties in achieving servo control of the secondary piston.
SUMMARY OF THE INVENTION
It is accordingly an object of the present invention to provide a vibration applying apparatus which is simple in construction, can be manufactured at a relatively low cost, is easy to control and is able to change the frequency of vibrations easily and reliably.
To achieve the foregoing object, the present invention provides a vibration applying apparatus associated with an injection molding machine for applying vibrational repetitive movements to a melt of molding materials to improve the moldability of the melt while the melt is held within a heating cylinder of the injection molding machine. The vibration applying apparatus comprises a rod having one end received inside the heating cylinder and disposed in the proximity of a nozzle of the heating cylinder, a stationary guide supporting the rod such that the rod is movable back and forth, a rotating shaft being orthogonal to the rod, a drive motor for rotating the rotating shaft, and a cam mechanism acting between the rotating shaft and the rod so as to convert rotary motion of the rotating shaft into linear reciprocal motion of the rod, whereby vibrational repetitive movements are applied from the one end of the reciprocating rod to the melt of molding material.
Preferably, the cam mechanism is comprised of an eccentric cam provided on the rotating shaft, and a cam follower connected to the other end of the rod and held in contact with the eccentric cam. In one preferred form, the cam is a circular disk set off center on the rotating shaft, and the cam follower is a ring strap rotatably receiving therein the circular disk. The cam mechanism may further include a bearing disposed between the ring strap and the circular disk.
It is preferable that the drive motor is a variable-speed motor so that the frequency of vibrational repetitive movements created by the one end of the reciprocating rod is variable with the rotational speed of the drive motor. The amplitude of vibrational repetitive movements is constant and is two-times the eccentricity of the eccentric cam.
In another preferred form of the present invention, the rod serves also as a nozzle shut-off valve member movable between a valve opening position in which the one end of the rod is opening the nozzle, and a valve closing position in which the one end of the rod is closing the nozzle. The vibration applying apparatus further includes a cylinder actuator disposed between the rod and the cam mechanism and operable to move the nozzle shut-off valve member between the valve opening position and the valve closing position. The nozzle shut-off valve member is disposed in the valve opening position while the cam mechanism is operating. The cylinder actuator includes a cylinder connected to the cam follower and a piston mounted to the other end of the rod and slidably received interiorly of the cylinder. The nozzle shut-off valve member and the cylinder actuator jointly form a nozzle shut-off mechanism which is formed as an integral part of the vibration applying apparatus. The injection molding machine equipped with such vibration applying apparatus is compact in size and can be manufactured at a low equipment cost as compared to the conventional injection molding machine in which a vibration applying apparatus and a nozzle shut-off mechanism are provided separately at different positions.
The above and other objects, features and advantages of the present invention will become manifest to those versed in the art upon making reference to the following description and accompanying sheets of drawings in which preferred structural embodiments incorporating the principle of the invention are shown by way of illustrative examples.
REFERENCES:
patent: 5145694 (1992-09-01), Brams
patent: 5160466 (1992-11-01), Allan et al.
patent: 5766654 (1998-06-01), Groleau
patent: 5770131 (1998-06-01), Bubel et al.
patent: 6190601 (2001-02-01), Nakamura
patent: 6203747 (2001-03-01), Grunitz
patent: 11-170318 (1999-06-01), None
Matsubayashi Koichi
Nakamura Nobuyuki
Okubo Kazuyuki
Heitbrink Tim
Merchant & Gould P.C.
Nissei Plastic Industrial Co. Ltd.
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