[0014] By introducing the water required for the core drill steel in the rear end of the drilling shaft and letting it flow all the way through the gear box, the simultaneous effect is achieved that the gear box is chilled, which is an additional beneficial effect.

 [0015] The inner part of the gear box housing, which is oil filled, and said water filled room, are separated from each other by the gear box housing end cover that according to the embodiment is detachably mounted, by screws, at the main part of the gear box housing. The rear portion of the drilling shaft as well as the front portion of the motor shaft extends through this end cover and into the water filled room and the oil filled gear box housing, respectively. According to one aspect of the invention, the gear box housing with its drilling shaft, gear box and gear box housing end cover, hereby forms a machine front unit that can be detached in its entirety from the rear portions of the drilling machine, comprising the motor and the motor housing. This will among other things result in the advantage that said radial lip seal(s) on the rear portion of the drilling shaft is/are easy to access without having to open the gear box housing.

 [0016] According to another aspect of the invention, also the motor part of the drilling machine, comprising a motor housing with a motor, is made as a machine unit, more particularly forming a rear machine unit, whereby also the inner part of the motor housing is covered by an end cover, here called motor housing end cover, that is detachably mounted by a screw joint, i.e. analogous with the conditions for the gear box housing and its gear box housing end cover. According one aspect of the invention, the outgoing shaft driven by the motor extends through the motor housing end cover and the gear box housing end cover (in the following called gear housing end cover) and into the gear box housing and the transmission arranged therein. This means that according to one aspect of the invention, the water filled room can be formed between the motor housing end cover and the gear box housing end cover. According to this aspect of the drilling machine according to the invention it is thus in summary characterised in

that the motor housing has a front, detachably mounted, motor housing end cover,

that the gear box housing has a rear, detachably mounted, gear housing end cover,

that the motor housing including its assembled motor housing end cover forms a rear machine unit,

that the gear box housing including its assembled gear housing end cover forms a front machine unit in which all cog wheels are positioned after assembly, i.e. they are all positioned in front of the gear housing end cover,

that the rear machine unit and the front machine unit can be interconnected, with said two machine end covers bearing against each other, and

that the machine can be split by separating the two machine units from each other without disconnecting any of the end covers from its respective housing.

 [0023] The water filled room according to the first aspect of the invention is preferably arranged between the motor housing end cover and the gear housing end cover. It is realised that this arrangement will additionally improve the possibility of servicing either one of the front machine unit and the rear machine unit without having to dismantle the unit that is not to be serviced at that particular occasion.

 [0024] According to one aspect of the invention, the motor housing end cover and the gear housing end cover are in contact by peripheral contact surfaces that form a peripheral limit for the water filled room, in the following also called the water chamber, as well as by a central area in which the lead-through of the shaft driven by the motor is arranged. This means in other words that the water chamber is annular. By the motor housing end cover and the gear housing end cover being in mutual contact in the area of the lead-through, it is also possible to extend the motor-driven shaft through the end covers without contacting water, which in turn means that there is no need for a radial lip seal against water leakage on the shaft in question. Hence, the number of radial lip seals in order to prevent water leakage can be reduced only to the or those radial lip seals that are arranged to prevent water from flowing from the water chamber, along the drilling shaft and into the bearing of the drilling shaft in the area of the rear section of the drilling shaft and/or into the oil filled gear box housing.