A control assembly for controlling the rotation of a turnstile comprising a rotary shaft (1) with barrier arms (2) spaced over an angle of x° from one another, which control assembly comprises:
- a frame (7);
- a hub (8) on which the turnstile is adapted to rotate and which is rotatably mounted onto said frame (7);
- a torque-restoring mechanism (13) defining 360/x home positions of said turnstile and restoring torque, which has been exerted onto the turnstile during substantially a first half of a part-rotational movement of the turnstile from one of said home positions to a next home position, during substantially a second half of said part-rotational movement so as to assist the rotation of the turnstile to said next home position;
- and
- a hydraulic damper (26) for damping the movement of the said turnstile during the second half of said rotational movement, which damper (26) comprises a cylinder-piston mechanism which contains a hydraulic fluid,
- characterised in that
- the cylinder-piston mechanism of the hydraulic damper (26) is a double cylinder-piston mechanism which comprises:
- a first piston (27) reciprocating in a first cylinder (28) and defining with the first cylinder (28) a first cylinder cavity (32) having a maximum size at the beginning of a first stroke of the first piston (27), a minimum size at the end of this first stroke and a maximum size at the end of a subsequent second stroke of the first piston (27);
- and
- a second piston (29) reciprocating in a second cylinder (30) and defining with the second cylinder (29) a second cylinder cavity (33), the second piston (29) being coupled to the first piston (27) to reciprocate simultaneously with the first piston (27) so that said second cylinder cavity (33) has a minimum size at the beginning of said first stroke of the first piston (27), a maximum size at the end of said first stroke and a minimum size at the end of said subsequent second stroke of the first piston (27),
- in that the first and second pistons (27, 29) are operatively connected to said hub (8) via a motion converting transmission (50-57) converting said part-rotational movement of the turnstile over x° between two successive home positions into a reciprocating motion of the first piston (27) starting substantially in the middle of one of said first and said second strokes and ending substantially in the middle of the other one of said first and second strokes;
- in that the first cylinder cavity (32) has a first inlet (58) which is provided with a first one-way valve (59) allowing flow of hydraulic fluid into the first cylinder cavity (32) during said second stroke of the first piston (27) and the second cylinder cavity (33) has a second inlet (60) which is provided with a second one-way valve (61) allowing flow of hydraulic fluid into the second cylinder cavity (33) during said first stroke of the first piston (27);
- in that the first cylinder (28) has a first damping outlet (45) allowing a restricted flow of hydraulic fluid out off the first cylinder cavity (32) at least during a first part of said first stroke of the first piston (27);
- in that the second cylinder (30) has a second damping outlet (47) allowing a restricted flow of hydraulic fluid out off the second cylinder cavity (33) at least during a first part of said second stroke of the first piston (27);
- in that the first cylinder (28) is provided with a first by-pass channel (39) having an inlet (40) and an outlet (41) ending both in said first cylinder cavity (32) at the beginning of said first stroke of the first piston (27), the first by-pass channel (39) allowing flow of hydraulic fluid out off the first cylinder cavity (32) when the first piston (27) has passed the outlet (41) of the first by-pass channel (39) during a second part of said first stroke of the first piston (27);
- and
- in that the second cylinder (30) is provided with a second by-pass channel (42) having an inlet (43) and an outlet (44) ending both in said second cylinder cavity (33) at the beginning of said second stroke of the first piston (27), the second by-pass channel (42) allowing flow of hydraulic fluid out off the second cylinder cavity (33) when the second piston (29) has passed the outlet (44) of the second by-pass channel (42) during a second part of said second stroke of the first piston (27).