Hand-held machine tool comprising a sealing ring disposed in the tool holder

Abstract

A low-wear sealing ring, which assures a favorable sealing action that prevents the escape of lubricants from the transmission chamber of the machine tool and prevents the entry of dust into the transmission chamber, has a number of sealing lips (6, 7) that rest against a percussion bolt (3) in the machine tool. At least on its lateral flank oriented toward the machine, the sealing ring (4) is provided with one or more radially extending recesses (8, 9). This lends the sealing lips (6, 7) a high degree of flexibility, allowing them to easily follow the movements of the percussion bolt (3), as a result of which the sealing ring (4) has a low susceptibility to wear and assures a high degree of impermeability.

Description

PRIOR ART

[0001] The current invention relates to a hand power tool with a tool holder, which can be driven in a rotary and percussive fashion and in which a percussion bolt is supported so that it can move axially, in which the tool holder contains at least one sealing ring that encompasses the percussion bolt.

[0002] DE 197 24 532 A1 has disclosed a drilling and hammering machine tool of this kind. The percussion bolt must be sealed in relation to the tool holder in such a way that on the one hand, no lubricant escapes from the transmission chamber of the machine tool and on the other hand, no dirt from the outside gets into the transmission chamber of the machine through the tool holder. To that end, in the known machine tool, sealing rings (O-rings) are inserted into two radially extending grooves of the percussion bolt, which seal the gap between the percussion bolt and the inside of the tool holder.

[0003] In a percussive machine tool, the percussion bolt moves in the axial direction, for example with a frequency of 65 to 85 Hz and an amplitude of 1 to 10 mm. In addition, the percussion bolt also moves in the radial direction depending on component tolerances and a thermal expansion of the materials. Under these circumstances, a seal inserted between the percussion bolt and the tool holder experiences a relatively high amount of wear. The object of the invention, therefore, is to produce a sealing ring, which experiences the least amount of wear possible due to the motion of the percussion bolt and therefore assures a high degree of impermeability over a long operation time of the machine tool.

ADVANTAGES OF THE INVENTION

[0004] The stated object is attained with the features of claim 1 by virtue of the fact that the sealing ring has a number of sealing lips that rest against the percussion bolt and that at least on its lateral flank oriented toward the machine, the sealing ring is provided with one or more radially extending recesses. This particular formation of the sealing ring lends the sealing lips a very high degree of flexibility so that they can easily follow the axial and radial movements and the thermal expansion of the material without a large amount of wear and consequently produce a reliable sealing of the percussion bolt in the tool holder.

[0005] Because one or more radially extending recesses are provided on the lateral flank of the sealing ring oriented toward the machine, the penetration of lubricant (oil or grease) from the transmission chamber into the at least one recess causes the sealing lip oriented toward machine to experience an increased pressure against the percussion bolt and consequently increases the impermeability against an escape of lubricant from the transmission chamber of the machine tool. If the lateral flank of the sealing ring oriented toward the tool is also provided with one or more radially extending recesses, this also lends the sealing lip oriented toward the tool a high degree of flexibility, allowing it to easily follow the axial and radial movements of the percussion bolt as well as thermal expansions of the material and consequently produces an effective seal of the transmission chamber of the machine tool against penetration of dust through the tool holder.

[0006] Advantageous modifications of the invention can be inferred from the dependent claims.

[0007] It is useful to provide both lateral flanks of the sealing ring with one or more recesses in order, as mentioned above, to produce a seal that prevents both the penetration of dust and the escape of lubricant.

[0008] The sealing ring preferably has a cross-sectional form that is symmetrical with regard to a radial central plane thus preventing a laterally reversed insertion of the sealing ring.

[0009] A favorable adhesion of the sealing ring in the tool holder is achieved by virtue of the fact that the sealing ring is fitted with its side oriented away from the percussion bolt into a radially extending groove in the tool holder.

DESCRIPTION OF AN EXEMPLARY EMBODIMENT

[0010] The invention will be explained in detail below in conjunction with an exemplary embodiment shown in the drawing.

[0011] The sole FIGURE of the drawing shows a longitudinal section through the front part of a rotating and hammering hand power tool, namely a percussive drill or a hammer drill. Freed of all parts of the hand power tool that are unnecessary for the explanation of the invention, the drawing shows a tool holder 1 with a receiving bore 2 for a tool, for example a drill bit, a chisel, or the like. This tool holder transmits a rotary motion from a drive mechanism that is not shown to a tool that is inserted into it. A percussion bolt 3 is supported so that it can move axially in the tool holder 1. A drive mechanism moves this percussion bolt 3 back and forth axially in the tool holder 1 with a frequency of 65 to 85 Hz and an amplitude of 1 to 10 mm and transfers this motion to a tool inserted into the tool holder 1.

[0012] A sealing ring 5, which encompasses the percussion bolt 3, is inserted into an annular groove 4 on the inside of the tool holder 1. The purpose of this sealing ring 5 on the one hand is to prevent an escape of lubricant (grease or oil) from the transmission chamber of the machine tool into the tool holder 1 and on the other hand to prevent the penetration of dust from the tool holder 1 into the transmission chamber. Fulfilling these high sealing requirements for the longest possible operating time of the machine tool is problematic because the percussion bolt 3 encompassed by the sealing ring 5 moves not only in the axial direction, but also moves in the radial direction due to component tolerances and thermal expansion of the materials. In order, even with these movements of the percussion bolt 3, to minimize the wear susceptibility of the sealing ring 5 and therefore a slackening of its sealing action, the sealing ring 5 has two parallel sealing lips 6 and 7 in the axial direction of the percussion bolt 3. The sealing lip 6 oriented toward the interior of the machine seals the transmission chamber against the escape of lubricant and the sealing lip 7 oriented toward the tool produces a seal preventing the penetration of dust from the tool holder 1. The sealing ring 5 is thus formed so that separate sealing lips 6 and 7 perform the two sealing functions. The sealing ring 5 can also have more than two sealing lips.

[0013] A rapid wear of the sealing ring 5 and therefore a loss of sealing action can be counteracted by giving the sealing lips 6 and 7 a high degree of flexibility so that they can easily follow the axial and radial movements of the percussion bolt 3. A high degree of flexibility of the sealing lips 6 and 7 is achieved by virtue of the fact the sealing ring 5 is provided with recesses 8 and 9 that extend radially around the sealing ring on both of its lateral flanks above the sealing lips 6 and 7. This gives the sealing ring 5 a waist above the sealing lips 6 and 7, which make these sealing lips very mobile.

[0014] In contrast to the exemplary embodiment shown, a recess 8, 9 does not have to be provided on each lateral flank of the sealing ring 5. However, it is advantageous to provide at least one recess 8 on the lateral flank oriented toward the machine. This recess 8 would namely have the effect that lubricant from the transmission chamber of the machine tool could penetrate into this recess and, due to the pressure of the lubricant in the recess 8, the sealing lip 6 disposed underneath it would be pressed against the percussion bolt 3 with a greater pressure.

[0015] The size and depth of the recesses 8 and 9 and depending on them, the thickness of the sealing lips 6 and 7, influence the flexibility of the sealing lips 6 and 7 and their contact force against the percussion bolt 3. The flexibility of the sealing lips 6 and 7 could be further increased by providing not only one recess 8, 9 on each lateral flank of the sealing ring 5, but a number of radially extending recesses that are offset from one another.

[0016] The ends of the sealing lips 6 and 7 resting against the percussion bolt 3 are rounded so that they can slide as well as possible against the moving percussion bolt 3.

[0017] The sealing ring 5 is preferably comprised of an elastomer material.

[0018] If, as shown in the drawing, a sealing ring 5 is used, which has a cross-sectional form that is symmetrical with regard to a radial central plane 10, no particular insertion direction of the sealing ring 5 needs to be maintained.

[0019] The region of the sealing ring 5 oriented away from the percussion bolt 3 fills the annular groove 4 in the tool holder 1 over its entire width and rests flush in the groove. As a result, the outer region of the sealing ring 5 has a high degree of stability and a favorable adhesion in the tool holder 1 so that the ring is secured against sliding in the axial direction and against rotating around the tool holder axis.

Claims

1. A hand power tool with a tool holder (1), which can be driven in a rotary and percussive fashion and in which a percussion bolt (3) is supported so that it can move axially, in which the tool holder (1) contains at least one sealing ring (5) that encompasses the percussion bolt (3), characterized in that the sealing ring (5) has a number of sealing lips (6, 7) that rest against the percussion bolt (3) and that the sealing ring (5), at least on its lateral flank oriented toward the machine, is provided with one or more radially extending recesses (8, 9).

2. The hand power tool according to claim 1, characterized in that the sealing ring (5) is provided with one or more radially extending recesses (8, 9) on each of its two lateral flanks.

3. The hand power tool according to claim 1 or claim 2, characterized in that the sealing ring (5) has a cross-sectional form that is symmetrical in relation to a radial central plane (10).

4. The hand power tool according to claim 1, characterized in that with its side oriented away from the percussion bolt (3), the sealing ring (5) is fitted into a radially extending groove (4) in the tool holder (1).