[0044] The side of the motor housing end cover 18 that faces the gear housing end cover 21 has a convex shape that matches the concave side of the gear box housing, such as will be explained in the following. Accordingly, said side of the motor housing end cover 18 exhibits a third shelf 61, FIG. 6, which in the assembled drilling machine 1 abuts against the planar end surface or edge 42 of the gear housing end cover 21, a fourth cylindrical or slightly conical wall portion 62, which abuts against the first wall portion 44 of the gear housing end cover, a fourth shelf 63 at a slight distance from the first shelf 45 of the gear box housing, and a fifth cylindrical or slightly conical wall portion 64, which abuts a short distance against the second wall portion 46 of the gear housing end cover.

 [0045] Concentrically with the countersinking 49 of the gear housing end cover, the motor housing end cover 18 exhibits a projecting, stepped, tapering portion 66 on its convex side. Between the projecting portion 66 and the peripheral portions of the gear housing end cover, the gear housing end cover 18 exhibits a waist at a considerable distance from the bottom 47 of the gear housing end cover 21. The projecting portion 66 on the motor housing end cover is, by its front steps, inserted in the countersinking 49 of the gear housing end cover. Accordingly, a sixth cylindrical or slightly conical wall portion 68 abuts against the cylindrical wall in the hole 53 in the gear housing end cover, a fifth shelf 69 abuts against said second shelf 52 in the countersinking 49 of the gear housing end cover, while a seventh cylindrical or slightly conical wall portion 70 abuts against the third wall portion 51 of the countersinking 49. An eighth cylindrical wall portion 71, that is concentric with the other wall portions of the projecting portion 66 of the motor housing en cover, follows thereafter and has a slightly larger diameter than the just mentioned seventh wall portion 70. 

 [0046] A disc-shaped room 79 is formed on the concave side of the motor housing end cover 18, serving as a fan chamber and housing a fan 80 for the cooling of the electrical motor 14. Inlet and outlet air openings 81a in the fan chamber 79 are arranged in the wall of the motor housing end cover, communicating with recesses in both sides of the gear housing end cover.

 [0047] The motor housing end cover 18 is in contact with the gear housing end cover 21, in the circumferential area where the annular edge 65 of the motor housing end cover 18 abuts against the gear housing end cover, as well as in the central area where the surfaces 68, 69, 70 of the wall and shelf portions of the motor housing end cover abut against the wall of the hole 53, said second shelf 52 and said third wall portion 51 in the gear housing end cover 21. Between said peripheral and central contact areas there is accordingly formed, between the motor housing end cover 18 and the gear housing end cover 21, i.e. between the rear 2 and front 4 units of the drilling machine 1, an annular space 82 that is to be water-filled when the drilling machine is in operation. 

 The water chamber 82 has a bore inlet 83 that extends obliquely through the bottom of the gear housing end cover 21, FIGS. 3 and 4, and mouths in the bottom portion of the annular water chamber, which means the part of the water chamber close to the underside of the drilling machine 1, when the drilling machine is oriented with its drilling shaft horizontal. A moulded channel 84 extends to the inlet 83, in an axial direction in the bottom of the gear housing end cover 20, and a distance further through the gear housing end cover 21 and up to the inlet portion 83, and a nipple 85 extends to the channel 84, to which nipple the water hose 7 is connected. A connecting hose for the tap 87 is denoted 86. The water hose extends through the downwardly directed part of the hand protector bow 5 and below the hand protector bow there is a tap 87 for connection and disconnection and for control of the water flow. The oval, annular shape of the water chamber enables the water chamber to have a considerable vertical extension between the rear unit and the front unit. This also means that the channels that extend through the lower part of the machine have a very short vertical extension, which is favourable from a constructional point of view. 钻孔机英文文献和中文翻译(5):http://www.youerw.com/fanyi/lunwen_56212.html