US 6,461,142 B1Granted

Injection device

AssigneeMatsushita Electric Industrial Co., Ltd.

InventorsShinji Kadoriku, Takaaki Higashida, Hiroshi Yutani, Tadao Murata

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Abstract

An injection device includes a cylinder, a plunger and a driving device. The cylinder has a port for supplying molding material into the cylinder, and the molding material supplies into the cylinder is compressed by the plunger. The plunger has a groove extending circumferentially around an outer wall of a large-diameter portion of the plunger, and the clearance between the outer wall of the large-diameter portion of the plunger and the inner wall of the cylinder is determined by a specified equation.

Claims8

Dependent claims

An injection molding device comprising:

a cylinder having a first end, a second end, a supply port between said first end and said second end for supplying a molding material into said cylinder, and an injection nozzle at said first end;
a plunger arranged within said cylinder and adapted to slide within said cylinder between a retracted position and a forward position so as to compress the molding material and push the molding material through said injection nozzle and into a cavity of a mold connected to said injection nozzle, said supply port of said cylinder being located between said retracted position of said plunger and said injection nozzle, said plunger having a small-diameter portion, a large-diameter portion, and a stepped surface between said small-diameter portion and said large-diameter portion for guiding the molding material toward said injection nozzle, and having a groove extending in a circumferential direction around an outer wall surface of said large-diameter portion so as to oppose an inner wall surface of said cylinder between said supply port and said second end of said cylinder;
and
a driving device connected to said plunger for sliding said plunger within said cylinder;
wherein a clearance between said outer wall surface of said large-diameter portion of said plunger and said inner wall surface of said cylinder is defined by the following equation:
πP/2ηQ+{(1−k)l1/[(R4−r14)−(R2−r12)/(l1R−l1r1)]}
=kl2/[(R4−r24)−(R2−r22)/(l2R−l2r2)]
+kl3/[(R4−r34)−(R2−r32)/(l3R−l3r3)]
+kl4/[(R4−r44)−(R2−r42)/(l4R−l4r2)]
wherein:
η is a viscosity of the molding material;
P is a back pressure during weighing in kgf/cm2;
Q is a quantity of the molding material to be supplied in cm3/s;
R is an inner radius of said cylinder;
r1 is an outer radius of said small-diameter portion of said plunger;
r2 is an outer radius of said large-diameter portion of said plunger below said groove;
r3 is an outer radius of a bottom surface of said groove;
r4 is an outer radius of said large-diameter portion of said plunger above said groove;
l1 is an axial length of said small-diameter portion of said plunger;
l2 is an axial length of said large-diameter portion of said plunger below said groove;
l3 is an axial length of said groove;
l4 is an axial length of said large-diameter portion of said plunger above said groove;
and
k is a ratio of a flow rate of molding material flowing in an upward direction from said supply port into said cylinder to a flow rate of a total quantity of the molding material flowing from said supply port into said cylinder.

21 more elements

Dependencies are inferred from the claim text.

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Abstract

An injection molding device comprising:

a cylinder having a first end, a second end, a supply port between said first end and said second end for supplying a molding material into said cylinder, and an injection nozzle at said first end;
a plunger arranged within said cylinder and adapted to slide within said cylinder between a retracted position and a forward position so as to compress the molding material and push the molding material through said injection nozzle and into a cavity of a mold connected to said injection nozzle, said supply port of said cylinder being located between said retracted position of said plunger and said injection nozzle, said plunger having a small-diameter portion, a large-diameter portion, and a stepped surface between said small-diameter portion and said large-diameter portion for guiding the molding material toward said injection nozzle, and having a groove extending in a circumferential direction around an outer wall surface of said large-diameter portion so as to oppose an inner wall surface of said cylinder between said supply port and said second end of said cylinder;
and
a driving device connected to said plunger for sliding said plunger within said cylinder;
wherein a clearance between said outer wall surface of said large-diameter portion of said plunger and said inner wall surface of said cylinder is defined by the following equation:
πP/2ηQ+{(1−k)l1/[(R4−r14)−(R2−r12)/(l1R−l1r1)]}
=kl2/[(R4−r24)−(R2−r22)/(l2R−l2r2)]
+kl3/[(R4−r34)−(R2−r32)/(l3R−l3r3)]
+kl4/[(R4−r44)−(R2−r42)/(l4R−l4r2)]
wherein:
η is a viscosity of the molding material;
P is a back pressure during weighing in kgf/cm2;
Q is a quantity of the molding material to be supplied in cm3/s;
R is an inner radius of said cylinder;
r1 is an outer radius of said small-diameter portion of said plunger;
r2 is an outer radius of said large-diameter portion of said plunger below said groove;
r3 is an outer radius of a bottom surface of said groove;
r4 is an outer radius of said large-diameter portion of said plunger above said groove;
l1 is an axial length of said small-diameter portion of said plunger;
l2 is an axial length of said large-diameter portion of said plunger below said groove;
l3 is an axial length of said groove;
l4 is an axial length of said large-diameter portion of said plunger above said groove;
and
k is a ratio of a flow rate of molding material flowing in an upward direction from said supply port into said cylinder to a flow rate of a total quantity of the molding material flowing from said supply port into said cylinder.

21 more elements