A control valve device includes a valve main body formed to have an actuator port connected to an actuator, a communication passage formed in the valve main body and configured to allow the actuator port to communicate with a drain port, and an on/off valve provided between the communication passage and the drain port, and the on/off valve includes a seat member assembled to the valve main body, an orifice provided in the seat member, and a poppet member configured to open and close a seat portion of the seat member.

A hydraulic system for controlling bleed down and retraction of a boom within a safety envelope includes a backup battery power supply, and at least a first boom lift hydraulic cylinder configured to raise and lower the boom. The first boom lift hydraulic cylinder includes a solenoid bleed valve electrically connected to the backup battery power supply. The hydraulic system also includes an input device controllable by an operator of the boom. The input device may, for instance, be used by the operator to initiate bleed down and retraction of the boom from an elevated position. To accommodate independent failsafe features of the system, the input device is configured to selectively actuate the solenoid bleed valve using electrical power supplied from the backup battery power supply.

A pneumatic control device includes a functional assembly that has an interruption valve device for the selective opening or interruption of at least one main working channel used for the pneumatic control of a pneumatic actuator. The functional assembly also contains a manually actuatable valve device that is connected to the interruption valve device by means of at least one auxiliary working channel and which enables manual pneumatic control of the connected actuator, if the at least one main working channel is interrupted by the interruption valve device at the same time. A process control device can also be equipped with a control device of this type.

A back-up load retention system includes a retention line which is connected to a load, a counterweight unit which is connected to the retention line, and a double-acting hydraulic cylinder which is connected to the counterweight unit. The counterweight unit maintains a tension force in the retention line. The double-acting hydraulic cylinder brakes and/or stops the load in a case of a failure in a main lifting system.

A control handle of a photography support stand and a photography support stand are provided. The control handle is configured to unlock or lock a support leg locking assembly of the photography support stand, and includes a handle housing and a hydraulic cylinder arranged in the handle housing. The hydraulic cylinder includes a cylinder body and a first piston. The cylinder body is defined with a hydraulic chamber for storing hydraulic fluid and a through hole that is communicated with the hydraulic chamber and configured to allow the hydraulic fluid to enter and exit the hydraulic chamber. The through hole is communicated with the support leg locking assembly. The first piston is slidably arranged in the hydraulic chamber and configured to expel the hydraulic fluid in the hydraulic chamber through the through hole or draw the hydraulic fluid back into the hydraulic chamber through the through hole.