Patent Application
20080283260
1. Field of the Invention
The present invention relates to a hand-held power tool and, in particular, to a percussion power tool with a lubricated air spring-percussion mechanism assembly and, specifically, to a combination hammer or chisel hammer.
2. Description of the Prior Art
In percussion hand-held power tool, the axially reciprocating parts of the air-spring-percussion mechanism assembly and guide elements are subjected to high tribological stresses. In order to prevent an excessive wear, at least separate parts of the percussion mechanism are lubricated, and the penetration of an abrasive dust into the lubricated percussion mechanism is prevented where possible.
German Publication DE 30 39 617 discloses a percussion power tool in which an anvil is arranged between an air spring-driven percussion piston and an end surface of the working tool. The anvil is sealed by an O-ring with respect to its guide sleeve in a sealing plane, dust-tightly and lubricant-tightly sealing the lubricated percussion mechanism with a percussion piston relative to a dust-loaded working tool holder.
According to German Publications DE 100 30 962 and DE 100 19 071, an anvil, which is displaceable in a widened tool guide, is sealed by two axially offset seals that, thus, form two, axially offset sealing planes. No free space is available between the two seals.
An object of the present invention is to further improve the sealing of a lubricated air spring-percussion mechanism assembly of a hand-held power tool.
This and other objects of the present invention, which will become apparent hereinafter, are achieved by providing a hand-held power tool a percussion mechanism of which has an anvil, guide means for the anvil, at least two, axially offset relative to each other, sealing elements for dust-tightly and lubricant-tightly sealing the anvil with respect to the anvil guide means, a lubricant chamber formed between the at least two sealing elements for receiving a barrier lubricant, and a percussion piston for applying blows to the anvil and driven by air spring of hand-held power tool.
The barrier lubricant forms a barrier against dust at the working tool side of the percussion mechanism and against percussion mechanism lubricant at the percussion piston side. Dust, which can possibly penetrate into the barrier lubricant chamber at the working tool side, and/or percussion mechanism lubricant (e.g., a synthetic gear oil), which can possibly penetrate in the barrier lubricant chamber at the percussion piston side, becomes bonded with the barrier lubricant. The barrier lubricant, which is contaminated with the dust and the percussion mechanism lubricant, can be easily replaced during servicing of the power tool.
Advantageously, the barrier lubricant consists of grease, advantageously, of a rolling bearing grease. The grease insures a reliable bonding of the penetrated dust and/or lubricant.
Advantageously, at least one of the at least two sealing elements is formed of a centering ring fixedly secured in the guide means (e.g., in the guide sleeve for the working tool or percussion piston), and a dynamic seal arranged in the centering ring coaxially therewith. In this case, the tribological stress takes place excessively between the anvil and the centering ring. Both parts are considered to be wearable, and can be economically replaced after being weared in excess of a predetermined amount.
Advantageously, the centering ring is formed of two annular discs assembled axially together and fixedly connected with each other, advantageously radially pressed into each other. An axially sealing, dynamic O-ring is arranged coaxially therebetween in a space between the two discs. This insures a technologically simple manufacturing of the centering ring.
The centering ring further advantageously includes a coaxial outer static seal such as, e.g., a lamella seal. Thereby, a possible coaxial outer, with respect to the guide sleeve, open bypass is sealed.
The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiments, when read with reference to the accompanying drawings.
The drawings show:
An axially percussion hand-held power tool 1, which is shown in
According to
Though the present invention was shown and described with references to the preferred embodiment, such is merely illustrative of the present invention and is not to be construed as a limitation thereof and various modifications of the present invention will be apparent to those skilled in the art. It is therefore not intended that the present invention be limited to the disclosed embodiment or details thereof, and the present invention includes all variations and/or alternative embodiments within the spirit and scope of the present invention as defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2007 000 255.8 | May 2007 | DE | national |
