Die closing unit for injection molding machine

Claim 2

A push-type die closing unit for an injection molding machine, serving to open and close the die halves of an injection molding die in a reciprocating motion along the longitudinal center axis of the unit, the die closing unit comprising in combination: a stationary die carrier plate to which the stationary half of the injection molding die is attachable and which extends transversely to the unit center axis; a stationary head plae likewise extending transversely to the unit center axis, on the other side of the emplacement of the injection molding die and at a distance therefrom; a movable die carrier member to which the movable half of the injection molding die is attachable and which is arranged axially between the stationary die carrier plate and the staionary head plate; means for guiding the movable die carrier member and attached die half in relation to the stationary die carrier plate and head plate for opening and closing movements along the unit center axis between a forward closed position and a rearward open position; and a hydraulic linear actuator mounted axially behind the stationary head plate, said actuator including: a power cylinder enclosing a power piston having valve means for selectively hydraulically bypassing the power piston, an auxiliary cylinder extending coaxially to the rear of the power cylinder and enclosing an auxiliary piston, a piston rod carrying both said power piston and said auxiliary piston and extending in the unit center axis, the forward extremity of the piston rod being connected to the movable die carrier member for the transmission thereto of opening and closing forces, including elevated closing pressures; and wherein the movable die carrier member defines, in the area immediately surrounding the unit center axis between the movable die half and the piston rod, a central space for the accommodation, at least in part, of an ejector device or other accessory device; and the piston rod has a hollow forward portion accommodating therein an accessory drive in the form of an accessory hydraulic linear actuator to which said accessory device is connectable.

Claim 3

A die closing unit as defined in claim 1, wherein said accessory hydraulic linear actuator includes a cylindrical bore inside the forward end portion of the piston rod, an accessory drive piston with a forwardly extending accessory drive piston rod cooperating with said bore, and a forward end flange in the form of an enlarged thrust plate interposed between and rigidly connecting together the piston rod and the movable die carrier member.

Claim 4

A die closing unit as defined in claim 2, wherein the thrust plate between the piston rod and the movable die carrier member includes in its body hydraulic connections, including connections for two channels which open into said bore in the piston rod on opposite axial sides of the accessory drive piston; and the movable die carrier member further includes a number of clamping bolts reaching axially through the thrust plate and into the wall of the hollow piston rod portion.

Claim 5

A die closing unit as defined in claim 1, wherein the means for guiding the movable die carrier member includes a plurality of parallel tie rods extending between said two stationary plates and rigidly connected thereto so as to define with them a rigid guide frame; and the movable die carrier member includes axially extending guide sockets engaging the tie rods.

Claim 6

A die closing unit as defined in claim 4, wherein the movable die carrier member is a rigid die carrier frame, having a die mounting wall on the forward axial side thereof, a pressure transfer wall spaced axially to the rear of the die mounting wall and connected to the piston rod, and pressure transfer means rigidly connecting the die mounting wall to the pressure transfer wall; the guide sockets constitute at least part of said pressure transfer means; and the central space for the accommodation of an accessory device is arranged inside said die carrier frame.

Claim 7

A die closing unit as defined in claim 5, wherein said accessory hydraulic linear actuator includes an accessory drive piston with an accessory drive piston rod extending forwardly into said central space of the die carrier frame; the forward portion of the accessory drive piston rod carries a contact arm moving with said piston rod inside said central space; the die carrier frame includes two axially adjustable stationary end switches cooperating with the contact arm so as to adjustably delimit the stroke of the accessory drive piston.

Claim 8

A die closing unit as defined in claim 6, wherein said contact arm extends radially from the accessory drive piston rod, being guided to move along an axial path; the two switches are proximity switches responding to the approach of the outer radial extremity of the contact arm; and the proximity switches are clampingly held against axially aligned clamping surfaces of the movable die carrier frame, in relation to which they are adjustable axially.

Claim 9

A push-type die closing unit for an injection molding machine, serving to open and close the die halves of an injection molding die in a reciprocating motion along the longitudinal center axis of the unit, the die closing unit comprising in combination: a stationary die carrier plate to which the stationary half of the injection molding die is attachable and which extends transversely to the unit center axis; a stationary head plate likewise extending transversely to the unit center axis, on the other side of the emplacement of the injection molding die and at a distance therefrom; a movable die carrier member to which the movable half of the injection molding die is attachable and which is arranged axially between the stationary die carrier plate and the stationary head plate; means for guiding the movable die carrier member and attached die half in relation to the stationary die carrier plate and head plate for opening and closing movements along the unit center axis between a forward closed position and a rearward open position; and a hydraulic linear actuator mounted axially behind the stationary head plate, said actuator having a piston rod extending in the unit center axis and being rigidly connected to the movable die carrier member for the transmission thereto of opening and closing forces, including elevated closing pressures; and wherein: the hydraulic linear actuator includes: a power cylinder rearwardly adjoining the stationary head plate, a smaller-diameter auxiliary cylinder coaxially adjoining the rear extremity of the power cylinder, and a mounting flange connecting and centering the two cylindrs; the piston rod extends through the power cylinder and into the auxiliary cylinder, carrying a matching double-acting power piston inside the former and a matching single-acting auxiliary piston inside the latter; the piston rod portion between the power piston and auxiliary piston extends sealingly through the mounting flange between the two cylinders with a diameter which is smaller than the diameter of the piston rod portion extending forwardly from the power piston; the piston rod further has a hollow forward end portion for the accommodation therein of a drive for an accessory device, said drive being an accessory hydraulic linear actuator; and the power piston includes at least one bypass channel extending from one axial side thereof to the other side, and hydraulically operated valve means for selectively opening and closing the bypass channel, so that the piston rod in the power cylinder acts as a differential piston, producing a rapid die closing motion, when the power cylinder is pressurized with the bypass channel held open, and the auxiliary piston produces a rapid die opening motion, when the forward side of the auxiliary piston is pressurized with the power piston bypass channel held open, while the power piston produces an elevated closing pressure, when its rear side is pressurized with the bypass channel closed.

Claim 10

A push-type die closing unit for an injection molding machine, serving to open and close the die halves of an injection molding die in a reciprocating motion along the longitudinal center axis of the unit, the die closing unit comprising in combination: a stationary die carrier plate to which the stationary half of the injection molding die is attachable and which extends transversely to the unit center axis; a stationary head plate likewise extending transversely to the unit center axis, on the other side of the emplacement of the injection molding die and at a distance therefrom; a movable die carrier member to which the movable half of the injection molding die is attachable and which is arranged axially between the stationary die carrier plate and the stationary head plate; means for guiding the movable die carrier member and attached die half in relation to the stationary die carrier plate and head plate for opening and closing movements along the unit center axis between a forward closed position and a rearward open position; and a hydraulic linear actuator mounted axially behind the stationary head plate, said actuator having a piston rod extending in the unit center axis and being rigidly connected to the movable die carrier member for the transmission thereto of opening and closing forces, including elevated closing pressures; and wherein: the hydraulic linear actuator includes: a power cylinder rearwardly adjoining the stationary head plate, a smaller-diameter auxiliary cylinder coaxially adjoining the rear extremity of the power cylinder, and a mounting flange connecting and centering the two cylindrs; the piston rod extends through the power cylinder and into the auxiliary cylinder, carrying a matching double-acting power piston inside the former and a matching single-acting auxiliary piston inside the latter; the piston rod portion between the power piston and auxiliary piston extends sealingly through the mounting flange between the two cylinders with a diameter which is smaller than the diameter of the piston rod portion extending forwardly from the power piston; the piston rod further has a hollow forward end portion for the accommodation therein of a drive for an accessory device, said drive being an accessory hydraulic linear actuator; and the power piston includes at least one bypass channel extending from one axial side thereof to the other side, and hydraulically operated valve means for selectively opening and closing the bypass channel, so that the piston rod in the power cylinder acts as a differential piston, producing a rapid die closing motion, when the power cylinder is pressurized with the bypass channel held open, and the auxiliary piston produces a rapid die opening motion, when the forward side of the auxiliary piston is pressurized with the power piston bypass channel held open, while the power piston produces an elevated closing pressure, when its rear side is pressurized with the bypass channel closed.

Claim 11

A die closing unit as defined in claim 8, wherein the stationary head plate serves as a forward end flange for the power cylinder, having an axial centering recess on its rear side; the power cylinder is a tubular section, engaging with its forward extremity said axial recess of the head plate; the mounting flange between the two cylinders is integrally attached to the smaller auxiliary cylinder, having an axial centering recess on its forward side engaged by the other extremity of the power cylinder; and the linear actuator further includes a number of cylinder tie rods extending axially between the head plate and the mounting flange, clamping the power cylinder between them.

Claim 12

A die closing unit as defined in claim 9, wherein the mounting flange between the power cylinder and the auxiliary cylinder includes hydraulic connections for both cylinders.

Claim 13

A die closing unit as defined in claim 8, wherein the power piston has a plurality of angularly spaced bypass channels and further includes, as part of its valve means, an annular valve seat surrounding the openings of said channels on the rear side of the power piston; the valve means further includes an annular valve plunger arranged on the rear side of the power piston, the valve plunger being sealingly movable along the piston rod towards and away from said valve seat, thereby opening and closing the bypass channels; and the valve means still further includes hydraulic linear actuator means cooperating with the valve plunger so as to move the latter, and a central hydraulic flow channel extending through a length portion of the piston rod to said plunger actuator means.

Claim 14

A die closing unit as defined in claim 11, wherein the rigid connection between the forward extremity of the piston rod and the movable die carrier member includes an intermediate radially enlarged thrust plate and a number of clamping fasteners traversing said member and said plate axially; and the outside connection for said central hydraulic flow channel of the power piston valve means is arranged on said thrust plate.

Claim 15

A push-type die closing unit for an injection molding machine, serving to open and close the die halves of an injection molding die in a reciprocating motion along the longitudinal center axis of the unit, the die closing unit comprising in combination: a stationary die carrier plate to which the stationary half of the injection molding die is attachable and which extends transversely to the unit center axis; a stationary head plate likewise extending transversely to the unit center axis, on the other side of the emplacement of the injection molding die and at a distance therefrom; a plurality of tie rods extending between the two plates, parallel to and radially spaced from the unit center axis, and connected to said stationary plates so as to define with them a rigid elongated guide frame; a rigid movable die carrier frame to which the movable half of the injection molding die is attachable, the die carrier frame being engaged by the tie rods for guided movement therealong between a forward closed position and a rearward open position; and a hydraulic linear actuator mounted axially behind the stationary head plate, said actuator having a piston rod extending in the center axis of the die closing unit and connected to the movable die carrier frame for the transmission thereto of opening and closing forces, including elevated closing pressures; and wherein the movable die carrier frame includes: a die mounting wall on the forward axial side thereof; a pressure transfer wall which is substantially continuous in the transverse direction and spaced axially to the rear of said die mounting wall, and to which is connected the forward extremity of the piston rod; a plurality of tie rod embracing guide sockets defined by said die mounting and pressure transfer walls; and pressure transfer ribs extending between and rigidly connecting said two walls in the area located radially inside the guide sockets, while leaving free a central space between said walls, for the accommodation therein of an accessory device; the piston rod of the hydraulic linear actuator includes, at its connected forward extremity, a thrust plate with which it engages the rear side of the pressure transfer wall in a central area whose radial extent is greater than the minimum radial distance of the pressure transfer ribs on the opposite side of the pressure transfer wall; and the hydraulic linear actuator further includes: a power cylinder enclosing a power piston seated on the piston rod; valve means associated with the power piston for selectively hydraulically bypassing the power piston; and an auxiliary cylinder extending coaxially to the rear of the power cylinder and enclosing an auxiliary piston seated on the same piston rod.

Claim 16

A push-type die closing unit for an injection molding machine, serving to open and close the die halves of an injection molding die in a reciprocating motion along the longitudinal center axis of the unit, the die closing unit comprising in combination: a stationary die carrier plate to which the stationary half of the injection molding die is attachable and which extends transversely to the unit center axis; a stationary head plate likewise extending transversely to the unit center axis, on the other side of the emplacement of the injection molding die and at a distance therefrom; a plurality of tie rods extending between the two plates, parallel to and radially spaced from the unit center axis, and connected to said stationary plates so as to define with them a rigid elongated guide frame; a rigid movable die carrier frame to which the movable half of the injection molding die is attachable, the die carrier frame being engaged by the tie rods for guided movement therealong between a forward closed position and a rearward open position; and a hydraulic linear actuator mounted axially behind the stationary head plate, said actuator having a piston rod extending in the center axis of the die closing unit and connected to the movable die carrier frame for the transmission thereto of opening and closing forces, including elevated closing pressures; and wherein the movable die carrier frame includes: a die mounting wall on the forward axial side thereof; a pressure transfer wall which is substantially continuous in the transverse direction and spaced axially to the rear of said die mounting wall, and to which is connected the forward extremity of the piston rod; a plurality of tie rod embracing guide sockets defined by said die mounting and pressure transfer walls; and pressure transfer ribs extending between and rigidly connecting said two walls in the area located radially inside the guide sockets, while leaving free a central space between said walls, for the accommodation therein of an accessory device; the piston rod of the hydraulic linear actuator includes, at its connected forward extremity, a thrust plate with which it engages the rear side of the pressure transfer wall in a central area whose radial extent is greater than the minimum radial distance of the pressure transfer ribs on the opposite side of the pressure transfer wall; and the hydraulic linear actuator further includes: a power cylinder enclosing a power piston seated on the piston rod; valve means associated with the power piston for selectively hydraulically bypassing the power piston; and an auxiliary cylinder extending coaxially to the rear of the power cylinder and enclosing an auxiliary piston seated on the same piston rod.

Claim 17

A die closing unit as defined in claim 13, wherein the tie rods are four in number and their axes pass through the four corners of a regular square whose center coincides with the unit center axis; and the movable die carrier frame includes four guide sockets integrally connecting both of said frame walls and enclosing the tie rods.

Claim 18

A die closing unit as defined in claim 14, wherein each guide socket includes an elongated axial bore with two axially spaced guide bushings pressed into it which slidably engage the associated tie rod with minimal clearance; and the axial distance between the guide bushings in the guide socket bores is at least equal to the diameter of the associated tie rods.

Claim 19

A die closing unit as defined in claim 14, wherein the pressure transfer ribs extend radially inwardly from the four guide sockets, the inner edges of the pressure transfer ribs being located at approximately mid-distance between the tie rod axes and the unit center axis; and the four pressure transfer ribs are interconnected in pairs by axially shallow connecting ribs on the forward side of the pressure transfer wall.

Claim 20

A die closing unit as defined in claim 13, wherein the tie rods engage said axially spaced stationary plates through smooth bores in said plates of a diameter equal to the diameter of the tie rods with which they guide the movable die carrier frame; each tie rod has end portions on both extremities extending a distance beyond the associated plate bores; and the tie rod tensions created by said closing pressures are transmitted to the stationary plates by abutment means on said tie rod end portions bearing against the outer sides of the stationary plates.

Claim 21

A die closing unit as defined in claim 17, wherein the guidance diameter of tie rods is also their maximum diameter; each tie rod includes in its protruding end portions an abutment groove; said groove having a substantially planar abutment face oriented toward the associated plate; each tie rod connection includes a split abutment ring seated in said abutment groove and having one axial end face bearing against said abutment face and the other axial end face bearing against the associated plate in the area surrounding the plate bore; and the tie rod connections further include means for retaining the abutment rings inside their grooves and means for axially preloading the tie rods against said plates in the sense of said abutment connections.

Claim 22

A die closing unit as defined in claim 18, wherein said retaining means and said clamping means are constituted by clamping caps which enclose the protruding tie rod end portions and their abutment rings and bear against the extremities of the tie rods under the action of clamping fasteners pulling the clamping caps against the stationary plates.

Claim 23

A die closing unit as defined in claim 13, wherein the hydraulic linear actuator is directly attached to the stationary head plate, the latter serving as the forward end flange for the power cylinder of the actuator; and the hydraulic linear actuator further includes an intermediate flange mounted between the power cylinder and the auxiliary cylinder and a plurality of cylinder tie rods clamping the power cylinder between the head plate and the intermediate flange.