Telescopic support caps, e.g. for use in mining

In a support cap of telescopic construction, the combination of the following means assembled together:

• a main element in the form of a generally straight beam having one end, referred to as the support end, and another end, referred to as the extensible end,
• a straight bar adapted to slide relative to the main element and having one end slidingly connected to the main element and another, free end projecting outwardly of the main element on the side of the extensible end,
• a crank with two ends, a pivot with a transverse axle connecting one end of the crank to the main element by being fixed thereto adjacent the said support end at a distance from the latter which is less than the length of the crank, the other end of the crank being a free end shaped for bearing on an auxiliary element, such as a timber prop, without other connecting means,
• and a jack connectable to a source of pressure-fluid and pivotally supported, on the one hand, on a point of the bar and, on the other hand, on a point of the crank intermediate the pivotal axis of the crank on the main element and its free end,
• the arrangement being such that the cap in use is buttressed on actuating the jack to extend the cap by the free end of the bar on the one hand, and by the combination of the main element and the crank, on the other hand.