| 摘要 |
A pneumatic drive means for propelling a cleaning brush through a tubular channel, comprising a long external casing (10) provided at one end with an attachment (16) for a cleaning brush and at the other end with a blast-air inlet (17) connectible to a blast-air hose. The drive means shows a plunger (24) displaceable therein arranged to cooperate with operating chambers (26, 27) located one on each side of the plunger (24) means being provided to cause the plunger (24) to move to and fro in said bore. The plunger (24) is therefor provided with at least one pair of longitudinal channels (28, 29) aligned with each other with outer ends facing away from each other and opening into one each of the two operating chambers (26, 27), and inner ends facing each other shaped in the form of seats (30, 31) for a valve body (32) which is movable to and fro between them in an intermediate space (33) in the plunger (24), said space communicating permanently with the blast-air inlet, and that the means is provided with at least one outlet opening (42, 43) for each operating chamber (26, 27) arranged in the casing (10) or in an element (42, 43) rigidly joined thereto, the plunger (24) being designed to alternatively close and expose said opening during its so and fro movement in the bore, the outlet openings (42, 43) pertaining to the different operating chambers (26, 27) being located at such a distance in relation to each other in the longitudinal direction of the means that only one operating chamber (26, 27) at a time is able to communicate with an outlet opening (42, 43). <IMAGE> |
