Combination hydraulic and pneumatic door closer
A door closer capable of adjusting door closing speed, includes a pneumatic cylinder on the door frame, a hydraulic cylinder on the door, and a lever. One end of the lever is movably connected to the pneumatic cylinder, and the other end is connected to the hydraulic cylinder. The pneumatic cylinder includes a sliding rail, and a sliding member cooperated with the sliding rail. A hermetic chamber is formed by the sliding member and the sliding rail. An adjusting valve, for adjusting the air exhaust of the hermetic chamber, is provided on a wall of the hermetic chamber.
1. A closer for a screen door pivotally mounted in a door frame for movement between open and closed positions, the closer comprising:
a hydraulic cylinder;
a pneumatic cylinder;
one of the cylinders being mounted to the door frame and the other of the cylinders being mounted to the screen door;
a rigid arm extending between the cylinders;
the pneumatic cylinder having a first piston, and the arm having a first end pivotally connected to the first piston;
the hydraulic cylinder having a second piston acting on a cam for controlling movement of the second piston, and the arm having a second end connected to the cam.
2. The closer of claim 1 wherein the hydraulic cylinder is mounted in the door frame and pneumatic cylinder is mounted in the screen door.
3. The closer of claim 1 further comprising an adjustable valve on the pneumatic cylinder to control exhaust from the pneumatic cylinder during closing of the screen door.
4. The closer of claim 1 wherein the hydraulic cylinder includes a spring to bias the second piston towards a door-closing position.
5. The closer of claim 4 wherein the spring is compressed when the door is opened and decompressed when the door is closed.
6. The closer of claim 1 wherein the cylinders are mounted in the door and in the door frame.
7. A method of closing a screen door mounted in a door frame, comprising:
mounting a hydraulic cylinder in one of the screen door and the door frame, the hydraulic cylinder having a first piston acting on a cam for controlling movement of the first piston;
mounting a pneumatic cylinder in the other of the screen door and the door frame, the pneumatic cylinder having a second piston;
connecting of the hydraulic and pneumatic cylinders with an arm, the arm having a first end connected to the second piston and a second end connected to the cam; and
biasing the door towards the closed position, when the door is open, with the hydraulic cylinder; and
controlling closing speed of the door with the pneumatic cylinder.
8. The method of claim 7 further comprising adjusting venting of the pneumatic cylinder with an adjustable valve.
9. The method of claim 7 further comprising drawing air into the pneumatic cylinder when the door opens and expelling air from the pneumatic cylinder when the door closes.
10. The method of claim 7 wherein the pneumatic cylinder prevents bouncing of the pneumatic cylinder while the door closes.
11. The method of claim 7 wherein the hydraulic cylinder is unbiased when the door is in the closed position.
12. The method of claim 7 wherein the biasing force is hydraulic pressure in the hydraulic cylinder.
13. The method of claim 7 wherein the biasing force is spring pressure in the hydraulic cylinder.
14. The method of claim 7 wherein the pistons retract when the door opens and extend when the door closes.
15. The method of claim 7 wherein the arm is rigid.