Tool driving or impacting – Impacting devices – Hammer head driven by pulsating fluid pressure
Patent
1999-06-30
2000-09-19
Smith, Scott A.
Tool driving or impacting
Impacting devices
Hammer head driven by pulsating fluid pressure
173118, 173212, B65D 1104
Patent
active
061197963
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a pneumatic spring percussion mechanism in accordance with the preamble of patent claim 1 and to a percussion hammer and/or hammer drill in which a pneumatic spring percussion mechanism of this type is used.
2. Description of the Related Art
Pneumatic spring percussion mechanisms, in particular for use in percussion hammers and/or hammer drills, are generally known. In a pneumatic spring percussion mechanism of this type a driving piston is set into an oscillating axial movement by a suitable drive, for example a crank assembly connected to an electric motor. In a particularly advantageous design, the driving piston is hollow. A percussion piston is inserted into the cavity in the driving piston with a pneumatic spring forming at least between an end surface of the percussion piston and the cavity in the driving piston. Owing to the inertia of the percussion piston, the movement of the driving piston initially produces a positive pressure in the pneumatic spring, which pressure is used to drive the percussion piston in the direction of a tool fastened on the hammer/drill. After the percussion piston has struck against the tool or against a riveting set arranged between the percussion piston and tool, it rebounds. In the pneumatic spring the reverse movement of the driving piston, which movement is produced by the crank assembly, causes suction to be exerted on the percussion piston, the suction assisting the recoil produced during the blow and exerted on the percussion piston whereupon the percussion piston moves away from the tool. After the upper dead center of the driving piston is reached, said driving piston again moves in the opposite direction toward the tool, retards the percussion piston, which is still in the reverse movement, and accelerates it again onto the tool in order to carry out the next blow.
Apart from the single-sided pneumatic spring percussion mechanisms which have just been described, percussion mechanisms having a double pneumatic spring are also known in which a pneumatic spring is formed between the percussion piston and driving piston not just behind the percussion piston--as seen in the percussion direction but also in front of the percussion piston. A two-sided pneumatic spring percussion mechanism of this type permits reliable starting and idling behavior.
FIG. 5 shows an example of a conventional percussion mechanism having a double pneumatic spring. A percussion piston 2 is inserted in a driving piston 1 which can be moved axially to and fro, for example, by a crank assembly (not shown) in a percussion mechanism housing (not shown). A front pneumatic spring 3 is formed in front of the percussion piston 2 and a rear pneumatic spring 4 is formed behind the percussion piston 2. The front and the rear pneumatic springs 3, 4 are supplied with air via a ventilation slot 5, which leads to the surroundings or into the crank housing, in the driving piston 1.
Owing to its inertia the percussion piston 2 follows the oscillation movement of the driving piston 1 with a constant time delay. As a result, during the forward movement of the driving piston 1 (direction of movement to the left in FIG. 5) an air pressure builds up in the rear pneumatic spring 4, which pressure finally likewise drives the percussion piston 2 in a forward direction where the percussion piston 2 strikes against a tool (not shown) or against a riveting set (not shown) and carries out the blow. Subsequently, because of the action of the crank assembly the driving piston 1 passes into a reverse movement (to the right in the figure), as a result of which a positive pressure builds up in the front pneumatic spring 3, which pressure likewise drives the percussion piston 2 in the reverse movement and reinforces the recoil produced by the blow. During each stroke movement of the percussion piston 2 a connection is produced between the ventilation slot 5 and one of the respectively unstressed pneumatic springs 3, 4, which makes it possible to
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Smith Scott A.
Wacker-Werke GmbH & Co. KG
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