A known roller of this kind according to the German utility model 87 00 869.6 U1 has wheels at both ends of a bearing axle between which wheels a two-armed lever as well as a single-armed lever, interacting with each other, are provided in such a manner that when a pedal surface of the two-armed lever is pressed downward clockwise, the single-armed lever with a base is pressed against the travelling plane and at the same time the roller, together with its bearing axle and the housing is raised into an unstable position past dead centre. A slight push against the pedal surface of the two-armed lever, a free actuating end of which protrudes past a external circumferential contour of the wheels, pivots the lever upward (counter-clockwise) to displace it from the unstable position past the dead centre. In addition to its complicated construction which is susceptible to breakdown and apart from its poor appearance, this roller has a relatively small support area under high pressure. For this reason it can be used only for light loads, e.g. in the form of mobile clothes stands for store equipment as stated in this prior publication. These rollers are definitely not suitable to accept greater loads, e.g. from 100 kg to 350 kg per roller, as is the practice in packaging machines.
An object of the invention is to produce a roller which while having a considerably greater load carrying capacity reliably precludes an accidental release of the roller after its fixing and, while having a simple construction, assures a stable supporting device with great load carrying capacity together with a lifting device which is simple to operate.