[0055] In an alternative embodiment for the water supply, the supply and the discharge of water to and from, respectively, the water chamber 82 could at least partly be arranged by a channel inside the motor shaft 16, i.e. the shaft 16 driven by the motor. This can be arranged by instead connecting the water hose 7 to the rear part of the drilling machine and by providing a channel that leads to a water chamber that encircles a portion of the rear part of the motor shaft. One or two radial lip seals prevent leakage along the motor shaft. The channel inside the motor shaft leads the water to the front part of the motor shaft, where it is transferred to the water chamber 82. This can take place e.g. by one or more radial holes arranged in front of the seal 96 but behind a similar additional seal that connects to the channel inside the motor shaft. Naturally, the channel ends after the latter connection, such that all water is led out between the two seals and further to the water chamber 82.

 [0056] In the end of the motor shaft 16 that projects into the gear box housing 20, through the two end covers 18 and 21, there is a driver 106 in the form of a small cog wheel arranged via a sliding clutch to drive a transmission shaft 108 parallel with the drilling shaft 8 and part of the gear box/transmission 22, as is known per se. The gear box has three gears. Without describing the known design of the transmission in detail, it should be mentioned here that the drilling shaft, as seen from the front, has a first cog wheel 111 for the first gear, a second cog wheel 112 for the second gear and a third cog wheel 113 for the third gear, FIGS. 2 and 4. The cog wheel 112 of the second gear is connected to the motor shaft via a cotter joint and is by a handle 115 on the outside of the drilling machine displaceable between the cog wheels 111 and 113 of the first and the third gear, respectively, FIG. 1, FIG. 4. Depending on the position of the handle 115, the torque of the motor shaft is transmitted via the sliding clutch and the transmission shaft 108 and the cog wheels of the transmission shaft, to the cog wheels of the first, second and third gears, respectively, in order to rotate the drilling shaft at a desired rotation speed. It is typical for this known transmission that the drilling shaft forms an integral part of the transmission and that it has a stepped decreasing diameter with the smallest diameter in the rearmost section 57, a circumstance that is utilised according to the invention in order to lead water all the way through the drilling shaft, thereby to cool the gear box, at the same time as the sealing problems can be satisfactorily solved, also for the bearings that might be exposed to a chance of water penetrating into the bearing/bearings. In use, water is led in via the water hose 7 that extends through the front portion 10 of the hand protector bow 5, via the nipple 85 into the channel 84 and the inlet 83 into the lower part of the annular water chamber 82, between the motor housing end cover 18 of the rear unit and the gear housing end cover 21 of the front unit 4. From the water chamber 82, the water is pressed into the channel 78 inside the tubular rotary drilling shaft 8, in order finally to discharge into the front end of the drilling shaft where a tool, preferably a core drill steel, is attached.

本发明涉及一种钻孔机，其包括一个钻孔轴，电机壳体，齿轮箱，驱动电机和延伸到齿轮箱壳体的驱动电机，以及在齿轮箱壳体的发送和钻孔。轴由电动机驱动，钻井轴之间的轴以所希望的旋转速度旋转。

本发明涉及到钻孔机的工作部分，其中包括被布置在操作过程中要被提供给该工具的芯钻头。

本发明的背景

钻孔机在行业内被广泛使用，为了在墙壁，屋顶和/或地板的情况下钻孔。通常，这发生在钻井轴通道中。以往，水被引导到钻井轴通过齿轮箱壳体的前部的通道。这有一些相当大的缺点，首先，在钻井轴力大，这部分的传输意着，径向唇密封件是必要的，以防止水的渗漏，这反过来又使密封更加困难，导致密封磨损相对较快，由于在密封部的钻孔轴的圆周速度高，其次，齿轮箱拆除大部分，钻孔轴和/或齿轮箱壳体通常是需要密封以交换。 钻孔机英文文献和中文翻译(7):http://www.youerw.com/fanyi/lunwen_56212.html