Spring clamp with clamped condition holding device

A spring clamp with a clamped condition holding device comprising:

• a housing (A) having an axis;
• a clamping actuation member (B) having a first end and a second end and being supported by said housing (A) in a movable manner in the direction of said axis;
• a clamping spring (3) adapted to urge said actuation member (B) to a clamping position (X) on the side of said first end;
• an unclamping actuation means (D) adapted to actuate said actuation member (B) to an unclamping position (Z) on the side of said second end against said clamping spring (3);
• a clamped condition holding device (8) adapted to change over between such a locked condition (R) as to hold said actuation member (B) in the clamping position (X) and such an unlocked condition (U) as to cancel the holding, said clamped condition holding device (8) being provided with a cylinder (10) extending in the direction of said axis, a piston (11) liquid-tightly slidably inserted into said cylinder (10) and a liquid sealing chamber (12) formed on the second end side of said piston (11), said piston (11) being connected to said actuation member (B);
• a changeover device (9) adapted to change over said clamped condition holding device (8) between said locked condition (R) and said unlocked condition (U), said changeover device (9) being provided with a liquid supply/discharge chamber (13) connected in communication to said liquid sealing chamber (12), a liquid sealing valve (15) interposed between both these chambers (12) (13) and an operation means (19) adapted to open and close said liquid sealing valve (15);
• wherein, when said liquid sealing valve (15) is so closed by means of said operation means (19) as to seal a liquid (L) within said liquid sealing chamber (12), said clamped condition holding device (8) being changed over to the locked condition (R), and when said liquid sealing valve (15) is so opened by means of said operation means (19) as to connect said liquid sealing chamber (12) to said liquid supply/discharge chamber (13), said clamped condition holding device (8) being changed over to the unlocked condition (U).