Abstract: A telescopic column includes at least two linearly movable telescopic elements and a drive system. The drive system includes a drive unit having a first clutch element and an output unit having a shaft, a windable connecting element and a second clutch element connected to the shaft such that the clutch element and the shaft rotate together. The drive system includes a brake unit configured to transmit a retaining force onto the second clutch element and configured such that applying a drive moment to the first clutch element reduces the retaining force and allow the telescopic elements to move relative to each other. The brake unit is further configured such that applying an output-side torque to the second clutch element increases the retaining force acting on the second clutch element.

Abstract: A drilling motor assembly can include a housing, a shaft, and a pawl which selectively engages a recess, the pawl having an axis of rotation and a generally planar engagement face which engages a generally planar engagement face of the recess when relative rotation between the housing and the shaft is prevented. The engaged engagement faces can be oblique relative to a radius extending from the axis of rotation to the engaged engagement faces. A method of drilling a wellbore can include flowing a fluid through a drilling motor assembly, thereby rotating a shaft relative to a housing, and rotating the housing, thereby engaging a pawl with a recess and preventing relative rotation between the housing and the shaft, the pawl and recess each having a generally planar engagement face, whereby the engaged engagement faces prevent relative rotation between the shaft and the housing.

Abstract: A pneumatically striking hand-held power tool is controlled by the following steps. An acceleration (a) along a striking axis (8) of the hand-held power tool (1) is detected. A driving power is reduced if the detected acceleration (a) is greater than a threshold value (A), the threshold value (A) being selected to be greater than maximum acceleration values (a1, a2) that occur on a workpiece during the striking operation of the hand-held power tool (1).

Abstract: A method for controlling a fluid operated percussive device, which inside an axially extending cylinder room (3) of a housing (2) of the percussive device includes a to and fro moveable percussive piston (1), which is adapted for performing strikes in a striking direction (A) and which includes a signal portion (4) for controlling a main valve (5), which is adapted to intermittently transmit pressure fluid to at least one driving chamber (7) for the percussive piston. An auxiliary valve (9) is controlled for transmitting fluid contact between at least one auxiliary channel means (13,14) with a channel opening in the cylinder room (3), and the main valve (5) over the signal portion (4), for switching the main valve (5) before the percussive piston, in operation, has reached at least one of said regions. The invention also concerns a percussive device and a rock drilling machine.

Abstract: The design of the free-mass in an ultrasonic driller/corer (USDC) has been refined in order to improve the performance and operational reliability of the system. In one embodiment, the improvements in performance and operational reliability include decreasing the impact surface area of the free-mass to increase the transfer of impact energy from the piezoelectric transducer and reductions in the likelihood that the system will jam.

Abstract: A vibratory mechanism for a pile driver com-prises a static part and a dynamic part. The dynamic part is movable with respect to the static part. The static part is provided with a drivable crankshaft and the dynamic part comprises a housing and a vibration member. The vibration member is drivably coupled to the crankshaft through a connecting rod and linearly movable with respect to the housing in a direction of vibration. The housing is resiliently coupled to the vibration member.

Abstract: A pneumatically striking hand-held power tool is controlled by the following steps. An acceleration (a) along a striking axis (8) of the hand-held power tool (1) is detected. A driving power is reduced if the detected acceleration (a) is greater than a threshold value (A), the threshold value (A) being selected to be greater than maximum acceleration values (a1, a2) that occur on a workpiece during the striking operation of the hand-held power tool (1).

Abstract: A portable power tool includes a housing, and an impact mechanism movably supported in the housing and having a front opening for receiving a working implement and a hammer piston for delivering hammer blows to the working implement. The impact mechanism is supported in the housing by a pivot device in a point located between the forward and rear ends of the impact mechanism and allowing longitudinal and pivotal movements but preventing in the support point radial and rotational movements of the impact mechanism relative to the housing. A resilient device is located at a distance from the pivot device and is arranged to bias the impact mechanism to a neutral position relative to the housing and to absorb vibration movements of the impact mechanism to protect the housing against such vibration movements.

Abstract: A method and software product for controlling a percussion device belonging to a rock-drilling machine, and a percussion device. The impact frequency of the percussion device is set so that the percussion device forms a new compression stress wave to the tool always when reflected waves from the previous compression stress waves reach a first end of the tool. This requires that the impact frequency be set proportional to the propagation time of the stress wave, whereby the length of the used tool and the propagation velocity of the stress wave in the tool material are to be noted.

Abstract: A hand-guided vibration tamper, which is driven by a motor laterally cantilevered on the tamper head, is provided with guard plates covering its underside and lateral sides. The underside and lateral guard plates are connected to a housing for the motor, and the underside guard plate is fastened near its free end to the motor and/or an air circulation hood for the motor. Preferably, the underside guard plate is a thick-walled aluminum plate screwed together with the lateral guard plates and extends beyond to protect the air circulation hood with its extension. Advantageously, the motor is also protected by a substantially closed, upper covering connected to the lateral guard plates.

Abstract: The present invention relates to a drilling tool for percussive drilling by means of a top hammer unit, which unit gives compressive pulses. The tool comprises at least one drill tube (12) and a drill bit (11), which cooperates via a connection. The drill bit comprises a bit head (13) provided with crushing means (15) and a shank (17). A shoulder (20) is provided in connection with the bit head, said bit portion having a first abutment surface (21) facing towards a free end of the tube. The free end of the tube facing towards the drill bit is povided with a second abutment surface (23), said top hammer unit being provided to tannsfer compressive pulses to the tube. Each compressive pulse is transferred to the drill bit via the impact surfaces (21, 23). The tube and the drill bit comprise cooperating device (19, 24, 25) for driving and retaining. The tool is defined by that it has a relation between the length of the shank and the length of the bit head that is 5 or more.