Patent ID: 8397833

Claim:
Construction apparatus comprising: an extendable mast with an upper mast element and a lower mast element coaxial with the upper mast element, wherein the upper mast element is longitudinally displaceable relative to the lower mast element between an extended mast position and a retracted mast position, a linear drive for longitudinal displacement of the upper and lower mast elements relative to each other, wherein the linear drive has a lower drive part and an upper drive part coaxial with the lower drive part, the upper drive part being actuatable in a linear manner relative to the lower drive part of the linear drive, and a locking device for locking the two mast elements in the extended mast position, wherein the upper drive part of the linear drive is fixed to the upper mast element, the lower drive part of the linear drive is displaceably secured to the lower mast element for displacement of the upper mast element relative to the lower mast element, the lower drive part of the linear drive is displaceable from the lower mast element and displaceable longitudinally of the lower mast element when the upper mast element is fixed relative to the lower mast element, and a securing device is provided on the lower mast element, for displaceably securing the lower drive part to the lower mast element, the upper mast element being displaceable relative to the lower mast element when the lower drive part is secured to the lower mast element by the securing device.