Reciprocating screw injection molding machine cylinder head with integral spreader and automatic nozzle

Claim 2

In a reciprocating screw type injection molding machine having a mold and an injection assembly including a heating cylinder having an injection nozzle engageable with said mold, a feed screw rotAtable and axially reciprocable in said heating cylinder, and drive means operative to rotate said feed screw in said heating cylinder to deposit material fed thereto and plasticized thereby into a collecting chamber in said heating cylinder as said feed screw is retracted by progressive enlargement of said collecting chamber, and to axially advance said feed screw in said heating cylinder to inject the plasticized material from said collecting chamber through an orifice in said nozzle into said mold, the improvement which comprises a heating cylinder head to which said nozzle is secured and which has an integral spreader operative to subdivide plasticized material into a plurality of streams of progressively decreasing cross-section area during the course of the flow of plasticized material from said collecting chamber to said nozzle; said spreader being hollow and said head having a lateral opening communicating the space within said spreader with the atmosphere; said spreader having a bore leading into such space and disposed coaxially with respect to said orifice; a valve member axially slidably sealed in said bore for movement into and out of engagement with a seat at the upstream end of said orifice; said valve member having an area exposed to pressure of plasticized material upstream of said seat tending to move said valve member out of engagement with said seat; and spring means in said spreader bearing on said valve member to permit yielding movement of said valve member out of engagement with said seat upon predetermined increase in pressure exerted on the plasticized material during axial advance of said feed screw in said heating cylinder; said nozzle having screw threaded engagement with said head; and said seat being at the upstream end of said orifice and having radial float in said nozzle to compensate for eccentricity of the interengaged threads of said nozzle and head.

Claim 3

In a reciprocating screw type injection molding machine having a mold and an injection assembly including a heating cylinder having an injection nozzle engageable with said mold, a feed screw rotatable and axially reciprocable in said heating cylinder, and drive means operative to rotate said feed screw in said heating cylinder to deposit material fed thereto and plasticized thereby into a collecting chamber in said heating cylinder as said feed screw is retracted by progressive enlargement of said collecting chamber, and to axially advance said feed screw in said heating cylinder to inject the plasticized material from said collecting chamber through an orifice in said nozzle into said mold, the improvement which comprises a heating cylinder head to which said nozzle is secured and which has an integral spreader operative to subdivide plasticized material into a plurality of streams of progressively decreasing cross-section area during the course of the flow of plasticized material from said collecting chamber to said nozzle; said spreader being hollow and said head having a lateral opening communicating the space within said spreader with the atmosphere; said spreader having a bore leading into such space and disposed coaxially with respect to said orifice; a valve member axially slidably sealed in said bore for movement into and out of engagement with a seat at the upstream end of said orifice; said valve member having an area exposed to pressure of plasticized material upstream of said seat tending to move said valve member out of engagement with said seat; and spring means in said spreader bearing on said valve member to permit yielding movement of said valve member out of engagement with said seat upon predetermined increase in pressure exerted on the plasticized material during axial advance of said feed screw in said heating cylinder; said spreader defining with a circular cross-section passage in said head diametrically opposite passages for flow of plasticized material, said passages being of segmental cross-section shape of progressively decreasing chord widths in a direction from the upstream end of said spreader toward said nozzle.

Claim 4

In a reciprocating screw type injection molding machine having a mold and an injection assembly including a heating cylinder having an injection nozzle engageable with said mold, a feed screw rotatable and axially reciprocable in said heating cylinder, and drive means operative to rotate said feed screw in said heating cylinder to deposit material fed thereto and plasticized thereby into a collecting chamber in said heating cylinder as said feed screw is retracted by progressive enlargement of said collecting chamber, and to axially advance said feed screw in said heating cylinder to inject the plasticized material from said collecting chamber through an orifice in said nozzle into said mold, the improvement which comprises a heating cylinder head to which said nozzle is secured and which has an integral spreader operative to subdivide plasticized material into a plurality of streams of progressively decreasing cross-section area during the course of the flow of plasticized material from said collecting chamber to said nozzle; said spreader being hollow and said head having a lateral opening communicating the space within said spreader with the atmosphere; said spreader having a bore leading into such space and disposed coaxially with respect to said orifice; a valve member axially slidably sealed in said bore for movement into and out of engagement with a seat at the upstream end of said orifice; said valve member having an area exposed to pressure of plasticized material upstream of said seat tending to move said valve member out of engagement with said seat; and spring means in said spreader bearing on said valve member to permit yielding movement of said valve member out of engagement with said seat upon predetermined increase in pressure exerted on the plasticized material during axial advance of said feed screw in said heating cylinder; said spreader defining with a circular cross-section passage in said head diametrically opposite passages for flow of plasticized material, said passages being of segmental cross-section shape of progressively decreasing chord widths in a direction from the upstream end of said spreader toward said nozzle.

Claim 5

The machine in claim 2 wherein said segmental passages from the points of minimum chord width are yet of segmental cross-section with the arcuate portions being of progressively decreasing diameter so that said passages converge toward each other as the material flows toward said nozzle.

Claim 6

A spreader, valve, and nozzle assembly for a reciprocating screw type injection molding machine comprising a cylinder head adapted to be secured at the end of the heating cylinder of such machine and having a passage at one end registering with the bore of said heating cylinder and a nozzle at the other end having an orifice through which plasticized material flows through said passage into a mold engaged by the said nozzle; a spreader integral with said head and defining with said passage two flow passages for transforming a cylindrical body of plasticized material into two segmental streams of progressively decreasing area as the plasticized material flows toward said nozzle; said spreader being hollow and being communicated with the atmosphere via a lateral passage extending through said head between said segmental flow passages; said spreader having a central axial bore which is coaxial with said orifice and which leads into said spreader; a valve member slidably sealed in said bore; said nozzle having a valve seat smaller than said bore; and spring means in said spreader biasing said valve member into engagement with said seat except when the pressure of the plasticized material acting on the differential area of said bore and seat is sufficient to overcome the biasing force of said spring, at which time, said valve member is urged away from said seat for flow of plasticized material through said orifice.

Claim 7

A spreader, valve, and nozzle assembly for a reciprocating screw type injection molding machine comprising a cylinder head adapted to be secured at the end of the heating cylinder of such machine and having a passage at one end registering with the bore of said heating cylinder and a nozzle at the other end having an orifice through which plasticized material flows through said passage into a mold engaged by the said nozzle; a spreader integral with said head and defining with said passage two flow passages for transforming a cylindrical body of plasticized material into two segmental streams of progressively decreasing area as the plasticized material flows toward said nozzle; said spreader being hollow and being communicated with the atmosphere via a lateral passage extending through said head between said segmental flow passages; said spreader having a central axial bore which is coaxial with said orifice and which leads into said spreader; a valve member slidably sealed in said bore; said nozzle having a valve seat smaller than said bore; and spring means in said spreader biasing said valve member into engagement with said seat except when the pressure of the plasticized material acting on the differential area of said bore and seat is sufficient to overcome the biasing force of said spring, at which time, said valve member is urged away from said seat for flow of plasticized material through said orifice.

Claim 8

The assembly of claim 4 wherein said segmental passages converge to an annular passage defined between said valve member and a surrounding bore of said nozzle upstream of said orifice.

Claim 9

The assembly of claim 4 wherein said seat comprises a ring having radial float in said nozzle to accommodate eccentricity of said orifice with respect to said spreader bore.

Claim 10

The assembly of claim 4 wherein said nozzle is detachably secured to said head whereby, upon detachment of said nozzle, said valve member may be withdrawn from said spreader bore for conditioning of the spreader bore and exterior surface of said valve member to maintain a smooth sliding seal of said valve member in said spreader bore.

Claim 11

The assembly of claim 4 wherein said spreader extends diametrically across said head; and wherein said lateral passage in said head extends diametrically through said head between the surfaces of said spreader which form the chords of said segmental passages.

Claim 12

The assembly of claim 4 wherein said spring means comprises a coil spring inserted into said spreader from an end of said lateral passage in said head to a position coaxial with said spreader bore with said valve member having a shoulder engaging one end of said spring so as to be biased thereby into engagement with said seat.