1. Field of the Invention
This invention relates to a suction cup device, more particularly to a suction cup device which defines a volume-variable space to produce an adjustable reduced pressure with a desired suction strength.
2. Description of the Related Art
FIG. 1 shows a conventional suction cup device 10 disclosed in U.S. Patent Publication No. US 2010/0116954 A1, which is adapted to be attached to a flat wall 1, and which includes a suction cup 13 with a rack 14 connected to the center thereof, a mount body 11 attached to the suction cup 13 by virtue of a pressing ring 12, and a lever 15 pivotably mounted on the mount body 11 and provided with a pinion 152 meshing with the rack 14. By turning the lever 15, a central part of the suction cup 13 can be pulled away from the flat wall 1 to produce a reduced pressure in an enclosed space between the flat wall 1 and the suction cup 13 for holding the suction cup device 10 against the flat wall 1. However, in the conventional suction cup device 10, the strength of suction force generated as a result of movement of the central part of the suction cup 13 is constant, and cannot be increased after a period of use, thereby resulting in undesired disengagement of the suction cup device 10 from the flat wall 1.
Another conventional suction cup device is disclosed in U.S. Pat. No. 7,021,593 B1, which includes a suction lock/release disposed on a lever and deep scoops disposed on the mount body to lock the lever at a fixed angle so as to adjust the suction strength of a suction cup. However, assembly of the suction lock/release to the lever is troublesome. Besides, manual operation of the suction lock/release is required to lock or unlock the lever, thereby rendering the adjustment complicated.