Source: {"pile_set_name": "USPTO Backgrounds"}

The present invention relates to a plug connection for drilling or boring tubes, pipes and worms of earth boring equipment or the like in accordance with the preamble of claim 1.
A known plug connection for boring tubes is provided at one tube end with a male part and at the opposite tube end with a female part. One half of a radial and an axial coupling is in each case constructed on the male and female part. The radial coupling half on the male part is positioned at a point which is set back with respect to its front end and comprises uniformly external circumferentially distributed wedges or keys and the half of the axial coupling on the male part comprises an external circumferentially fitted annular slot with tapped holes in the slot bottom arranged on a front portion with respect to the radial coupling. On its front end portion, the female part is directly provided with recesses passing through the entire female part wall and these are shaped in complementary manner to the wedges formed on the male part. The radial coupling for transferring the torque is formed by a V or claw coupling. At a set back point on the inner circumference of the female part is provided an annular slot, which in the coupled state comes to rest directly over the all-round slot formed in the male part, so that the two recesses form a circumferentially extending annulus or annular space. The annular slot in the femal part is accessible from the outside via several, e.g. three openings, which essentially have the same axial extension as the annular slot and which directly issue into the latter. At the said openings, it is possible to pass through the complete wall thickness of the female part. For the positive coupling of male and female parts, a locking device is necessary and comprises several units, which have to be individually fitted through the openings into an annulus portion. Such a locking unit comprises two wedges or keys, which are inserted in the opposite circumferential direction through the opening into the annulus. The two wedges must then be prevented from falling out by an additional securing means, e.g. a spring clip and a screw. The screw must be turned into tapped holes formed in the annular slot on the male part.
It is a disadvantage of the known procedure for forming a positive axial coupling between the male and female parts that the locking device comprises several locking units, whereof each is constituted by several loose parts and whereof each must be separately fitted and dismantled. It is also disadvantageous in the known coupling device that each locking unit must be brought into coupling engagement through a separate opening. Thus, several openings or windows uniformly distributed over the circumference of the female part are required, so that the cross-section for femal part force transfer is considerably weakened.
It is also disadvantageous that in the case of the known locking units, it is necessary in each case to provide a securing means, which prevents the inserted parts or mating parts from falling out.