Thermoforming apparatus

Claim 2

Thermoforming apparatus comprising a first mold having a female cavity; a second mold through which fluid under pressure is admitted to act on a heated plastic sheet adapted to be clamped between said molds to deform the sheet against said female cavity; mold-actuating mechanism including linkage means for relatively moving said molds to closed and locked position with the heated sheet in such locked position being clamped therebetween; and means for conducting fluid under pressure to said second mold comprising valve means operative when opened to conduct fluid under pressure to said second mold, and valveoperating means actuated by said linkage means to open said valve means prior to the time that said linkage means reaches such mold-locking position and thereafter.

Claim 3

The apparatus of claim 1 wherein a double-acting lock cylinder operatively connected to said linkage means is so arranged that at the same cylinder-actuating fluid pressure the mold-unlocking force exerted thereby is greater than the mold-locking force.

Claim 4

The apparatus of claim 1, wherein said linkage means includes a double toggle linkage having a first pair of toggle linkages disposed between a fixed member on said thermoformer and one of said molds, said first pair of toggle linkages in their locking position constituting struts between said fixed member and said mold, and having a second toggle linkage which, during movement to said locking position, spreads apart said first pair of linkages toward locking position.

Claim 5

The apparatus of claim 3, wherein a lock cylinder on said one mold has its piston rod connected to said second linkage to actuate the latter and said first pair of linkages between locking and unlocking positions.

Claim 6

Thermoforming apparatus comprising an arrangement of vertical tie bars having upper and lower heads affixed thereto; upper and lower platens between said heads vertically movably guided on said bars; upper and lower molds on said platens; actuating mechanisms between the respective heads and platens to lock said molds together in clamping relation to a heated plastic sheet therebetween for deformation thereof into a cavity in one of said molds by fluid under pressure admitted through the other one of said molds; each mechanism including at least one actuating cylinder between each head and platen operative to move the latter to a position in which the molds are closely adjacent, a first pair of toggle linkages pivotally connected to the respective head and platen, a second toggle linkage between said first pair of toggle linkages, and actuating means between said second toggle linkage and the respective platen operative to move said second toggle linkage to locking position to spread apart said first pair of toggle linkages to locking position thus to move said molds into locking position, to securely lock the respective platen against movement toward the respective head, and to preload said bars to preclude mold separation during forming of the heatEd sheet.

Claim 7

Thermoforming apparatus comprising an arrangement of vertical tie bars having upper and lower heads affixed thereto; upper and lower platens between said heads vertically movably guided on said bars; upper and lower molds on said platens; actuating mechanisms between the respective heads and platens to lock said molds together in clamping relation to a heated plastic sheet therebetween for deformation thereof into a cavity in one of said molds by fluid under pressure admitted through the other one of said molds; each mechanism including at least one actuating cylinder between each head and platen operative to move the latter to a position in which the molds are closely adjacent, a first pair of toggle linkages pivotally connected to the respective head and platen, a second toggle linkage between said first pair of toggle linkages, and actuating means between said second toggle linkage and the respective platen operative to move said second toggle linkage to locking position to spread apart said first pair of toggle linkages to locking position thus to move said molds into locking position, to securely lock the respective platen against movement toward the respective head, and to preload said bars to preclude mold separation during forming of the heatEd sheet.

Claim 8

The apparatus of claim 5 wherein said actuating means comprises a lock cylinder on each platen having a piston rod pivotally connected to said second toggle linkage to actuate said linkages to platen locking and unlocking positions, said lock cylinder being in idling condition when said actuating cylinders are moving said molds to said closely adjacent position.

Claim 9

The apparatus of claim 6 wherein said lock cylinders are double acting and are so arranged that at the same cylinder actuating fluid pressure the mold unlocking force exerted thereby is greater than the mold locking force.

Claim 10

The apparatus of claim 5 wherein valve means when opened conducts fluid under pressure into said other mold; and wherein valve-operating means actuated by one of said first pair of toggle linkages opens said valve means prior to the time that said first pair of toggle linkages and said second toggle linkage reach mold-locking position and thereafter.

Claim 11

The apparatus of claim 1 wherein said valve means comprises a solenoid-operated valve; and wherein said valve-operating means comprises a switch which is closed by said linkage means to energize the solenoid of said valve and thus open said valve as aforesaid.

Claim 12

Thermoforming apparatus comprising a first mold having a female cavity; a second mold through which fluid under pressure is admitted to act on a heated plastic sheet adapted to be clamped between said molds to deform the sheet against said female cavity; mold-actuating mechanism including linkage means for relatively moving said molds from opened and unlocked position whereat a deformed sheet may be withdrawn from between said molds and a heated sheet positioned therebetween to closed and locked position with the heated sheet in such locked position being clamped therebetween; valve means operative when opened to conduct fluid under pressure to said second mold and when closed to vent such fluid under pressure therefrom; and valve-operating means actuated by said linkage means to open and close said valve means respectively prior to the time that said linkage means reaches such mold-locking position and after said linkage means commences to relatively move said molds to opened and unlocked position.

Claim 13

Thermoforming apparatus comprising a first mold having a female cavity; a second mold through which fluid under pressure is admitted to act on a heated plastic sheet adapted to be clamped between said molds to deform the sheet against said female cavity; mold-actuating mechanism including linkage means for relatively moving said molds from opened and unlocked position whereat a deformed sheet may be withdrawn from between said molds and a heated sheet positioned therebetween to closed and locked position with the heated sheet in such locked position being clamped therebetween; valve means operative when opened to conduct fluid under pressure to said second mold and when closed to vent such fluid under pressure therefrom; and valve-operating means actuated by said linkage means to open and close said valve means respectively prior to the time that said linkage means reaches such mold-locking position and after said linkage means commences to relatively move said molds to opened and unlocked position.