Synchronized piston assembly

Claim 2

A synchronized piston assembly comprising at least two cylinder units each comprising: a drive cylinder having ports adapted for connection with a fluid power control source and a synchronizing cylinder having ports which are cross-connected with respect to the ports of the other synchronizing cylinder; and a piston unit in each cylinder unit having interconnected drive and synchronizing pistons axially reciprocable in the respective cylinders whereby hydraulic actuation of said drive pistons in the respective drive cylinders actuates the respective synchronizing pistons in the respective synchronizing cylinders so that fluid displaced from one end of each synchronizing cylinder to the other end of the other synchronizing cylinder synchronizes the actuation of said drive pistons despite unequal loads on said piston units; each cylinder unit having relief valve means operative to intercommunicate the synchronizing circuit chambers on opposite sides of the synchronizing piston for fluid pressure equalization therein and for continued movement thereof and its drive piston to the end of one stroke in the event that the other piston unit previously reaches the end of one stroke, and to intErcommunicate the synchronizing chambers on opposite sides of the synchronizing piston of said other piston unit to equalize fluid pressures therein each relief valve means being opened by pilot pressure buildup in its decreasing synchronizing chamber during such continued movement of its piston unit to the end of its retract stroke; said pilot pressure opening said other relief valve means for fluid pressure equalization of the synchronizing chambers on opposite sides of the synchronizing piston in said other piston unit.

Claim 3

A synchronized piston assembly comprising at least two cylinder units each comprising: a drive cylinder having ports adapted for connection with a fluid power control source and a synchronizing cylinder having ports which are cross-connected with respect to the ports of the other synchronizing cylinder; and a piston unit in each cylinder unit having interconnected drive and synchronizing pistons axially reciprocable in the respective cylinders whereby hydraulic actuation of said drive pistons in the respective drive cylinders actuates the respective synchronizing pistons in therespective synchronizing cylinders so that fluid displaced from one end of each synchronizing cylinder to the other end of the other synchronizing cylinder synchronizes the actuation of said drive pistons despite unequal loads on said piston units; each cylinder unit having relief valve means operative to intercommunicate the synchronizing circuit chambers on oppostie sides of the synchronizing piston for fluid pressure equalization therein and for continued movement thereof and its drive piston to theend of one stroke in the event that the other piston unit previously reaches the end of one stroke, and to intercommunicate the synchronizing chambers on opposite sides of the sychronizing piston of said other piston unit to equalize fluid pressures therein, each relief valve means being opened by pilot pressure buildup in its decreasing synchronizing chamber which opens the other relief valve means for fluid pressure equalization as aforesaid and for transmission of such pilot pressure to open the first-mentioned relief valve means for fluid pressure equalization in its decreasing and increasing synchronization chambers and for flow of fluid into the increasing synchronizing chamber during such continued movement of its piston unit to the end of its extend stroke.

Claim 4

A synchronized piston assembly comprising at least two cylinder units each comprising: a drive cylinder having ports adapted for connection with a fluid power control source and a synchronizing cylinder having ports which are cross-connected with respect to the ports of the other synchronizing cylinder; and a piston unit in each cylinder unit having interconnected drive and synchronizing pistons axially reciprocable in the respective cylinders whereby hydraulic actuation of said drive pistons in the respective drive cylinders actuates the respective synchronizing pistons in therespective synchronizing cylinders so that fluid displaced from one end of each synchronizing cylinder to the other end of the other synchronizing cylinder synchronizes the actuation of said drive pistons despite unequal loads on said piston units; each cylinder unit having relief valve means operative to intercommunicate the synchronizing circuit chambers on oppostie sides of the synchronizing piston for fluid pressure equalization therein and for continued movement thereof and its drive piston to theend of one stroke in the event that the other piston unit previously reaches the end of one stroke, and to intercommunicate the synchronizing chambers on opposite sides of the sychronizing piston of said other piston unit to equalize fluid pressures therein, each relief valve means being opened by pilot pressure buildup in its decreasing synchronizing chamber which opens the other relief valve means for fluid pressure equalization as aforesaid and for transmission of such pilot pressure to open the first-mentioned relief valve means for fluid pressure equalization in its decreasing and increasing synchronization chambers and for flow of fluid into the increasing synchronizing chamber during such continued movement of its piston unit to the end of its extend stroke.

Claim 5

A synchronized piston assembly comprising at least two cylinder units each comprising: a drive cylinder having ports adapted for connection with a fluid power control source and synchronizing cylinder having ports which are cross-connected with respect to the ports of the other synchronizing cylinder; and a piston unit in each cylinder unit having interconnected drive and synchronizing pistons axially reciprocable in the respective cylinders whereby hydraulic actuation of said drive pistons in the respective drive cylinders actuates the respective synchronizing pistons in the respective synchronizing cylinders so that fluid displaced from one end of each synchronizing cylinder to the other end of the other synchronizing cylinder synchronizes the actuation of said drive pistons despite unequal loads on said piston units; each cylinder unit having relief valve means opened by pilot pressure to intercommunicate the synchronizing chambers on opposite sides of the synchronizing piston for continued movement thereof and its drive piston either to the end of its extend stroke or its retract stroke in the event that the other piston unit previously reaches the end of either of the corresponding strokes, and to intercommunicate the synchronizing chambers on oppostie sides of the synchronizing piston in said other piston unit to equalize fluid pressures therein.

Claim 6

A synchronized piston assembly comprising at least two cylinder units each comprising: a drive cylinder having ports adapted for connection with a fluid power control source and synchronizing cylinder having ports which are cross-connected with respect to the ports of the other synchronizing cylinder; and a piston unit in each cylinder unit having interconnected drive and synchronizing pistons axially reciprocable in the respective cylinders whereby hydraulic actuation of said drive pistons in the respective drive cylinders actuates the respective synchronizing pistons in the respective synchronizing cylinders so that fluid displaced from one end of each synchronizing cylinder to the other end of the other synchronizing cylinder synchronizes the actuation of said drive pistons despite unequal loads on said piston units; each cylinder unit having relief valve means opened by pilot pressure to intercommunicate the synchronizing chambers on opposite sides of the synchronizing piston for continued movement thereof and its drive piston either to the end of its extend stroke or its retract stroke in the event that the other piston unit previously reaches the end of either of the corresponding strokes, and to intercommunicate the synchronizing chambers on oppostie sides of the synchronizing piston in said other piston unit to equalize fluid pressures therein.

Claim 7

The assembly of claim 3 wherein such continued movement toward the end of the retract stroke builds up pilot pressure in the decreasing synchronizing chamber to open its relief valve means for flow into the increasing synchronizing chamber; and wherein such continued movemeNt toward the end of the extend stroke builds up pilot pressure to open the other relief valve means for fluid pressure equalization as aforesaid and for transmission of pilot pressure to open the first-mentioned relief valve means for flow of fluid through the latter in the opposite direction from the then decreasing synchronizing chamber to the then increasing synchronizing chamber.

Claim 8

The assembly of claim 4 wherein each cylinder unit has check valve means to communicate the power circuit with the synchronizing circuit for supply of makeup fluid to compensate for fluid loss in the synchronizing circuit thus to maintain substantially synchronous actuation of said drive pistons.