Rapid-action mold closer

Claim 1

A mold-closing apparatus for an injection-molding machine having a movable mold-carrying plate, said apparatus comprising: a fixed main cylinder; a main piston connected to said plate and displaceable in said cylinder along a predetermined axis, said main piston forming in said cylinder a rear chamber and spaced axially toward said plate therefrom a front chamber, whereby pressurizing of said rear chamber with simultaneous depressurizing of said front chamber displaces said piston and plate forward to close a mold; a rapid-action cylinder formed and extending axially in said main piston; a rapid-action piston in said rapid-action cylinder and having an axially forwardly directed face forming therein a rapid-action chamber; a positioning cylinder fixed on said main cylinder; a positioning piston in said positioning cylinder and having therein a rearwardly directed face larger than said face of said rapid-action piston and forming with said positioning cylinder a pressurizable positioning chamber, said positioning piston being axially fixed on and integral with said rapid-action piston, said rapid-action piston being formed with a piston passage extending between and opening at its said face and at said face of said positioning piston, said main cylinder being formed with a large-diameter fill passage opening axially forward into its said rear chamber; a valve element integral with and fixed axially to said rapid-action and positioning pistons and displaceable between a rear closed position engaged with and blocking off said fill passage and an open position forward therefrom and exposing said fill passage; a fluid reservoir connected to said fill passage; drive means for supplying fluid under pressure; and control means including valves connected between said reservoir, drive means, and chambers for, in a rapid-action closing position, supplying fluid under pressure to said positioning chamber while venting said front chamber to said reservoir and thereby moving said positioning piston, rapid-action piston, and valve element forward with displacement of the latter into said open position, whereby said rapid-action chamber is pressurized through said piston passage to move said main piston rapidly forward and said rear chamber is connected to said large fill passage to fill rapidly, in a mold-closing position, supplying fluid under pressure to said rear chamber while venting said front and positioning chambers for moving said valve element back into said closed position, whereby said main piston is urged forward by pressure in said rear chamber, and in a rapid-action opening position, supplying fluid under pressure to said front chamber while blocking flow out of said positioning chamber to move said element into said open position and vent said rear chamber through said fill passage into said reservoir.