Power plants – Pressure fluid source and motor – Having a mechanical clutch or brake device in the power train
Reexamination Certificate
1999-06-18
2001-11-13
Look, Edward K. (Department: 3745)
Power plants
Pressure fluid source and motor
Having a mechanical clutch or brake device in the power train
C060S494000, C091S044000
Reexamination Certificate
active
06314728
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to industrial door operators, and particularly to a hydraulic control system for the door operator which provides for different speeds in opening and closing the door and provides for the engagement and disengagement of a brake that holds the door against unwanted movement.
Door operators are used to open and close doors that are mounted for swinging or sliding movement between open and closed positions, or for doors that are mounted to unroll and roll up for closing and opening door openings. The industrial doors may be used for a variety of purposes such as closing the entry ways to cold storage environments. The industrial doors are typically driven between open and close positions by a reversible motor connected to a door drive mechanism.
Hydraulic systems for door operators have been proposed. Examples of hydraulic door operators are found in U.S. Pat. No. 4,296,570 issued Oct. 27, 1981 to George C. Balbach, et. al. and assigned to the assignee of this invention. In such hydraulic systems, a reversible hydraulic pump driven by an electric motor is connected by a closed loop to a reversible hydraulic motor which in turn drives the mechanical drive for the door.
The speed of operation of the door is important. When the doors are used in a cold storage environment, they should be kept open for the shortest possible duration consistent with safety. Typically, the door will be driven open at a very rapid speed and will be closed at a second, slower speed to ensure pedestrian and vehicle clearance through the door opening before closing occurs. U.S. Pat. No. 5,410,842 issued May 2, 1995 to Joel W. Watson, and assigned to the assignee of this invention, discloses a two-speed hydraulic door operator in which the speed of closing the door is slower than that of opening the door. This is accomplished by the use of a bypass valve assembly connected between the pump and hydraulic motor and operative to bypass a portion of the fluid flow from the pump to the motor when the pump is driving the motor to close the door. The bypass flow is returned to the pump. The bypass valve is disconnected from operation by a check valve when fluid flows from the pump to the hydraulic motor in a direction to drive the motor to open the door so that full fluid flow is directed to the motor during opening. This approach allows the use of an inexpensive single speed electric motor for two-speed operations and eliminates the need for a restrictive orifice in a connection between the pump and the motor which can generate heat.
The present invention is directed to a simplified two-speed hydraulic control system that also controls the disengagement of a brake that normally holds the door against movement.
SUMMARY OF THE INVENTION
According to the invention, a flow control valve is connected between one hydraulic control line leading from the reversible pump to the reversible motor connected to the door. The flow control valve leads to the hydraulic fluid reservoir that feeds the pump. A hydraulic control line leads from each side of the pump to a corresponding side of the motor and each hydraulic control line includes a counter balance valve piloted by pressure from the other control line. The flow control valve is connected to the one hydraulic control line at a point between the pump and the counter balance valve. Preferably, the flow control valve is a pressure compensated, adjustable flow control valve.
Further in accordance with the invention, an actuatable valve is disposed between the source of fluid pressure for a hydraulically releasable brake and the fluid reservoir. The actuatable valve normally connects the hydraulic release mechanism for the brake to the reservoir but is actuated to block the connection thereby providing fluid flow from either one of the hydraulic control lines to release the brake. Preferably, the actuatable valve is a poppet-style solenoid valve.
It is a principal object of the invention to provide a simplified mechanism for a two-speed operation of a hydraulic door operator.
It is also an object to provide a hydraulic door operator including a simple mechanism for controlling the release of a brake normally holding the door against movement.
The foregoing and other objects and advantages of the invention will appear in the detailed description which follows. In the description, reference is made to the accompanying drawing which illustrates a preferred embodiment of the invention.
REFERENCES:
patent: 4296570 (1981-10-01), Balbach et al.
patent: 4941320 (1990-07-01), Kersten et al.
patent: 5410842 (1995-05-01), Watson
patent: 5771636 (1998-06-01), Mathis
Evans Harry C.
Schilling Ronald A.
ASI Technologies, Inc.
Lazo Thomas E.
Look Edward K.
Quarles & Brady LLP
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