JACK JETTING

JACK Cric; V rin

Equipment and Tools

1. A lifting tackle or pushing device used to displace loads a short distance.

   The two main jacks used are:

   • rack-and-pinion jack or lever jack ( le cric cr maill re), machine intended mostly for lifting a load, acting by pushing or by traction. The driving of this machine takes manually by the agency of a crank that sues after reduction of the rack whose base is equipped of a paw or a horn. This type of jack is also used in horizontal position to perform sliding along operations;

   • hydraulic jack ( le cric hydraulique), device for lifting loads through a piston hydraulically moved. The hydraulic pressure is obtained by pumping.

2. An apparatus used to lift objects of great weight with little physical effort. It has great thrusting and tensile power as well. Syn. with LIFTING JACK

JACK ARCH Vo tain

Construction

In some road or railway bridges with steel deck, small surbased vault, generally made of bricks or sheet metal, leaning on the metal elements of the framework (on the distance pieces generally). All the jack arches constitute the cover. According to whether they lean on stringers or transverse girders, they are longitudinal or transverse. Jack arches only lie in the former works. See Figure 1

JACK ARCH

Figure 1

JACK HAMMER DRILL Marteau perforateur

Equipment and Tools

A pneumatic or hydraulic tool, heavier than the pick-hammer, in which the tool (borer) undergoes a rotation of a fraction of...