Percussive Tool

The present invention relates to a percussive tool, and more particularly to a magnetically operated percussive tools.

Known percussive tools include housing means, a tool member reciprocable in the housing means and surrounding the tool member, and a member which imparts impacts to the tool member under the action of magentic flux generated by a source. In the known tool the tool casing is fixedly connected with the housing means whereby the latter is subjected to impacts during the operation which are transmitted to the user's hand. Still another disadvantage of the known construction is that when the impacting element strikes against a trailing end of the tool member it also strikes against a trailing end of the tool casing so that the latter is prematurely destroyed.

Accordingly, it is an object of the present invention to provide a percussive tool which avoids the disadvantages of the prior art.

More particularly, it is an object of the present invention to provide a percussive tool in which impacts are not or substantially not transmitted from a tool casing to a housing of the tool.

Still another feature of the present invention is to provide a percussive tool in which a member imparting strikes to a tool member does not strike against a tool casing surrounding the tool member.

In keeping with these objects and with others which will become apparent hereinafter one feature of the present invention resides, briefly stated, in a percussive tool in which spring means is provided between a tool casing and a housing so that impacts are substantially not transferred from the tool casing to the housing. On the other hand, a trailing end of the tool casing is provided with a recess having such as axial length that when the spring means urges the tool casing toward an impact imparting member the latter being received into the recess, does not strike the tool casing and admits magnetic flux from the tool casing.

The novel features which are considered to be characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

FIG. 1 is a view showing a percussive tool in accordance with the present invention; and

FIG. 2 is a section taken through line II--II of FIG. 1.

A percussive tool in accordance with the present invention includes a tool member 1, and a member imparting impacts to the tool member, such as a piston 2 The tool member 1 is located in a tool casing 3 with interposition of a bushing 4. A spring 5 is located between a portion of the tool casing 3 and an abutment of the tool member 1 and is operative for urging the latter toward the piston 2.

The tool casing 3 is provided at a trailing end thereof with a recess 6 which is bounded by a circumferential wall 6'. An electromagnet 7 having a body and a winding is accommodated in housing means including a housing 8 which is closed by a magnetoconductive cover 9. A cap 10 is provided forwardly of the cover 9. The latter has several axial projections extending into the interior of the cap 10, as shown particularly in FIG. 2. The projections 9' bound therebetween a plurality of circumferential gaps 11.

Spring means are accommodated in the gaps 11. The spring means include first springs 12 and second springs 13 which abut against a projection 14 at opposite sides thereof. The projection 14 substantially radially extends from the tool casing 3. The tool casing 3 is movable relative to the housing means in an axial direction. A permanent magnet 15 with a pole 16, and a spring 17 located between the latter and a washer 18 is provided.

The percussive tool in accordance with the present invention operates in the following manner. A magnetic flux generated by the electromagnet 7 is transmitted to the tool casing 3 through the cover 9 whereby the tool casing pulls by a magnetic force the impacting member 2 toward the tool member 1. The springs 12 are somewhat relaxed whereas the springs 13 serve for absorbing purposes. The impacting member 2 strikes the tool member 1. At the same time, impacts are transmitted to the tool casing 3, the latter moves forwardly and compresses the springs 12 which serve now for absorbing purposes. After the strike the permanent magnet 15 returns the impacting member 2 to its initial position. The spring 5 urges the tool member 1 toward the impacting member 2, and the springs 13 urge the tool casing to its initial position. The recess 6 has such an axial length that when the tool casing 3 is moved to its initial position which is proximal to the impacting member 2, the wall 6' radially outwardly surrounds a leading end portion of the impacting member 2. Thereby, the magnetic flux is effectively transmitted in optimum manner from the tool casing 3 to the impacting member 2.

It will be understood that each of the elements described above may also find a useful application in other types of tool differing from the type described above. Various modifications and structural changes may be mademade without departing in any way from the spirit of the present invention. The foregoing so fully reveal the gist of the invention that others by applying current knolegde can readily adapt it for various applications without omitting features, that from standpoint of the prior art, fairly constitutes essential chracteristics of the generic or specific aspects of the invention.