Hilti Aktiengesellschaft

Franz Chromy

Rolf Bereiter

A hammer drill has a cylinder within a housing with the cylinder forming a piston chamber. A drive piston is reciprocally mounted within the piston chamber and is displaced by a motor. A percussion piston is located within the piston chamber with an air cushion space located between the two pistons. As the drive piston reciprocates, it moves the percussion piston back and forth by way of the air cushion located between them. One of the pistons has a conduit open at one end to the air cushion space and at the other end to the exterior of the cylinder. A closure plug is located in the one end of the conduit and closes off air flow from the air cushion space into the conduit at regular operating temperatures. If the temperature in the air cushion space rises due to air leakage from the space, the closure plug melts and connects the conduit with the air space so that the reciprocation of the percussion piston stops before the pistons strike against one another and cause damage.

Hammer drill with pneumatically driven percussion piston

In a motor driven drilling or chipping device, a housing forms a sealed housing space containing a gear arrangement and an air cushion propulsion mechanism driven by the gear arrangement. The housing space is partially filled with lubricating oil. A pressure equalizing nozzle has a bore connecting the interior of the housing space to the ambient atmosphere outside the housing. The port at the end of the nozzle bore communicating with the housing space is enclosed by wall members forming a stilling chamber. The stilling chamber is in communication with the sealed housing space and is arranged so that regardless of the position of the drilling or chipping device, it is not flooded by the lubricating oil and the lubricating oil does not flow out of the stilling chamber through the nozzle bore.

Motor driven drilling or chipping device

A hammer drill is arranged to rotate and also apply percussive force to a tool receptacle. The percussive force is transmitted from a shaft to a drive piston which, in turn, reciprocates a percussion piston which drives the tool receptacle. The hammer drill includes a housing and a bearing rotatably mounted in the housing. The shaft is rotatably mounted in the bearing and its axis extends perpendicularly of the axis of rotation of the bearing. The bearing supports a contact rim which is in meshed engagement with the shaft. The contact rim is displaceably into frictional contact with a brake member for holding the contact rim against rotation while the bearing rotates carrying with it the shaft. Due to its meshed engagement with the contact rim, the shaft rotates about its own axis causing the drive piston to reciprocate.

Hammer drill

In a hammer drill, a drive piston is reciprocated by a motor, and, over a pneumatic buffer, the reciprocating motion is transmitted to a percussion piston. A throttle valve regulates the flow of a fuel mixture to the motor for controlling its operation. A membrane switch connected to and operated by the pressure conditions within the pneumatic buffer controls the throttle valve.

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Levis, Austria

Franz Chromy