A telescopic lifting unit with a first segment, a second segment, and a third segment. The first and second segments may be displaced relative to one another, and the second and third segments may be displaced relative to one another. The first and second segments may be moved relative to one another by a motor unit, and the second and third segments may be moved relative to one another by a cable hoist.

A telescopic lifting unit with a first segment, a second segment, and a third segment. The first and second segments may be displaced relative to one another, and the second and third segments may be displaced relative to one another. The first and second segments may be moved relative to one another by a motor unit, and the second and third segments may be moved relative to one another by a cable hoist.

A linear jack includes an outer sleeve, an inner sleeve disposed at least partially within the outer sleeve, and an inner screw disposed at least partially within the inner sleeve. The outer sleeve is threadedly coupled to an outer diameter surface of the inner sleeve. The inner screw is threadedly coupled to an inner diameter surface of the inner sleeve. A thread pitch of the outer sleeve is greater than a thread pitch of the inner screw.

According to an aspect of some embodiments of the present invention there is provided a piston mounted on and fixedly fastened to a ball screw nut, the nut threaded onto a ball screw. By mechanically rotating the piston and preventing the ball screw from rotating, the balls screw nut rotates, thereby raising or lowering the ball screw, thereby raising or lowering the piston, thereby raising or lowering a casing, for example a bollard, mounted on the piston. The casing may be raised or lowered by attaching a handle to the piston and rotating the handle.

According to an aspect of some embodiments of the present invention there is provided a piston mounted on and fixedly fastened to a ball screw nut, the nut threaded onto a ball screw. By mechanically rotating the piston and preventing the ball screw from rotating, the balls screw nut rotates, thereby raising or lowering the ball screw, thereby raising or lowering the piston, thereby raising or lowering a casing, for example a bollard, mounted on the piston. The casing may be raised or lowered by attaching a handle to the piston and rotating the handle.

A jack apparatus has a main jack body defined by telescopically engaged outer and inner tubes, a selectively positionable clamp assembly positioned along the jack body for selective engagement with the object to which a force is to be applied, and a drive assembly located on and within the jack body. In a further related aspect a retainer is configured for being mounted on the object to be moved or lifted and for positively engaging a receiver on the clamp assembly so as to effectively lock the jack to the object being lifted such as a vehicle for safe and effective operation.

A jack apparatus has a main jack body defined by telescopically engaged outer and inner tubes, a selectively positionable clamp assembly positioned along the jack body for selective engagement with the object to which a force is to be applied, and a drive assembly located on and within the jack body. In a further related aspect a retainer is configured for being mounted on the object to be moved or lifted and for positively engaging a receiver on the clamp assembly so as to effectively lock the jack to the object being lifted such as a vehicle for safe and effective operation.

A lifting column includes a drive unit, a lifting tube, and a transmission assembly. The lifting tube includes a first tube, a second tube, a third tube, a fourth tube, and a fifth tube. The transmission assembly includes a first screw rod, a second screw rod, a third screw rod, and a fourth screw rod. The drive unit is in transmission fit with the first screw rod and drives the first screw rod to rotate. A lower end of the second screw rod has a first nut in transmission with the first screw rod, a lower end of the third screw rod has a second nut in transmission with the second screw rod, a lower end of the fourth screw rod has a third nut in transmission with the third screw rod, and a lower end of the first tube has a fourth nut in transmission with the fourth screw rod.

A lifting column includes a drive unit, a lifting tube, and a transmission assembly. The lifting tube includes a first tube, a second tube, a third tube, a fourth tube, and a fifth tube. The transmission assembly includes a first screw rod, a second screw rod, a third screw rod, and a fourth screw rod. The drive unit is in transmission fit with the first screw rod and drives the first screw rod to rotate. A lower end of the second screw rod has a first nut in transmission with the first screw rod, a lower end of the third screw rod has a second nut in transmission with the second screw rod, a lower end of the fourth screw rod has a third nut in transmission with the third screw rod, and a lower end of the first tube has a fourth nut in transmission with the fourth screw rod.

A low-profile trailer jack reduces the height of the jack above the trailer a-frame by over 50% eliminating pickup tailgate interference when lowered by a vehicle operator. This is accomplished using a two-stage concentric lead screw design rather than a single screw as described in prior art. The two-stage design also allows for increased lowering and raising speed of the jack foot by using the first stage, which is a larger outer screw with larger pitch, generating a faster speed when no load is present. The second stage inner screw is engaged when a load is present and a slower speed with greater mechanical advantage is required.