EP1716979A1 - Percussive tool or drill - Google Patents

Abstract

The electro-pneumatic hammer mechanism (21) and the motor and transmission unit (14) are accommodated inside a housing (12) with a tool (16) attached to the front (15). The hammer mechanism (21) comprises a piston (23) moved axially inside a cylinder (17). The motion is transferred to a hammer ram (25) hitting the striker (26) slightly off center (27) in order to move the tool (16) by the impact. The distance between the striking axis (22) and the point of impact (27) is selected in a specific relation to the length of the striker (26).

Description

Technical area

The invention relates to a drill or chisel hammer with a striking mechanism, referred to in the preamble of claim 1. Art.

State of the art

In a hammer drill or chisel hammer with a percussion means of a percussion along a striking axis impact means via a firing pin, also called an anvil, transmitted impact impulses on a spigot of a set in a tool holder of the drill or chisel hammer tool. Between the firing pin and the impact means a contact point and a counter contact point are provided.

For example, the percussion means is designed as a motor-driven exciter piston, which strikes the transmission of a shock pulse directly on the, the impact means facing the end of the firing pin, wherein the contact point and the mating contact point come into contact.

From the DE 31 21 616 A1 is a striking mechanism with a pneumatically driven percussion piston known. In a cylindrical guide tube, a motor-driven exciter or drive piston and a percussion piston, also called a free piston, is provided, wherein an air cushion is formed between the drive piston and the percussion piston. Due to the reciprocating movement of the drive piston, the percussion piston is displaced in a phase-shifted manner as well, and this acts on the firing pin and the contact point and the counter-contact point come into contact with each other. If the reciprocating motion of the drive piston is stimulated by an electric motor, these impact mechanisms become electropneumatic impactors designated. Electropneumatic impactors are widely used and are used in various performance categories of rotary and chipping hammers.

A disadvantage of the known solution is that when breakthrough of the tool by the machined substrate or when lifting the tool from the ground look up the percussion piston and the firing pin. It should be noted that in the active operating state of the drill or chisel, when the tool is in contact with the ground, the percussion piston and the firing pin cover only a short distance in the guide tube, while in the passive operating state of the drill or chisel, when the tool breaks through the ground or the tool is lifted from the ground, the percussion piston and the firing pin travel a distance in the guide tube, which can correspond to 20 times the distance during the active operating state.

In order to prevent the so-called looking up of the percussion piston, the firing pin and thus also arranged in the drill or chisel tool or at least limit, in a pneumatic percussion a free travel is provided at least for the percussion piston and the firing pin. In the DE 31 21 616 A1 Ventilation openings are provided on the guide tube for this purpose. If the tool z. B. lifted from the ground, the sealing means on the percussion piston passes over these ventilation openings, wherein the air cushion between the percussion piston and the excitation piston is reduced, so that no further impact on the tool.

High performance rotary or chipping hammers are much more likely to look up than lower performance machines, so a relatively long free travel in hammers or chisel hammers with a high single impact energy to prevent lookup must be provided. This requires a correspondingly long design of the drill or chisel hammer, which, however, in particular for ergonomic reasons, for. B. due to the high weight or handling of the drill or chisel hammer, is undesirable.

In addition to the ventilation openings, the kinetic energy of the percussion means, of the firing pin and also of the tool is additionally reduced by friction of the same in their guides. Ideally, the energy of these components is degraded so far that they no longer move the percussion piston from its parking position in which the air cushion is vented, and the ventilation openings are closed again. As has already been stated, stands for constructive and ergonomic reasons Usually there is no adequate way to reduce kinetic energy through friction.

In a very high single impact energy generating drill or chisel hammer therefore additional and structurally complex measures such. As the arrangement of a firing pin brake, a percussion piston brake or catching devices are provided in the percussion to prevent the lookup. From the DE 12 83 769 A1 For example, a firing pin brake is known in which the firing pin is held in the passive operating state in its ineffective position by means of a locking, resilient clamping ring.

A disadvantage of this solution is that such devices represent complex constructions, which for example, due to dirt or wear easily prone to malfunction, which significantly reduces the service life of the drill or chisel hammer.

Presentation of the invention

The object of the invention is to provide a drill or chisel hammer with a percussion, in which a lookup of the percussion means, the firing pin and thus the tool is structurally simple and inexpensive prevented even at high single impact energy of the drill or chisel.

The object is solved by the features of the independent claim. Advantageous developments are set forth in the subclaims.

According to the invention, the contact point is exposed and arranged outside the striking axis.

By the counter contact point spatially nearest and eccentrically arranged contact point act in the operation of the drill or chisel lateral forces on the firing pin and the impact, the energy reduction by the increased friction between the guide and the two components against a firing pin with a centric contact point, positively influenced. Due to the different distances covered by the firing pin and the percussion means in the active operating state and in the passive operating state, the momentum transfer and thus the performance of the drill or chisel is only insignificantly affected despite the eccentric contact point.

Due to the exposed and eccentric contact point, with a comparably short free travel even when drilling or chipping hammers of the upper power class, the lookup can be prevented. The drill or chisel hammer can be made shorter and accordingly has a comparably low total weight. Even if wear should occur in the guides, on the firing pin or on the percussion means, the function of these parts and thus of the drill or chisel hammer over the service life is ensured by the structurally simple design. Overall, the solution according to the invention is very cost-effective, since no additional components or expensive processing steps are required for their realization.

Advantageously, ventilation openings are provided on the guide tube in this percussion mechanism for venting the air cushion in the passive operating state of the chisel hammer.

In this context, contact point and counter contact point do not mean points in the mathematical sense, but contact regions which correspond to the surfaces which are formed when the impact element meets the striker. Outside, an eccentric or offset to the impact axis arrangement of the contact point is based on its center understood, the distance to the impact axis corresponds to an amount that is greater than the usual manufacturing tolerances. It is also conceivable that a region of the contact point, d. H. a part of the contact surface of the percussion means with the firing pin, is penetrated by the striking axis.

In an advantageous embodiment of the drilling and Meisselhammerwerkzeuggerätes the contact point on the firing pin is provided at its, the impact means end facing. For the formation of the contact point, the firing pin, for example, at its end facing the impact means a convex, the impact means facing survey, the culmination point protrudes from a plane defined by a peripheral edge of the firing pin level and is located outside the percussion axis. The survey is z. B. a parabolic curvature of first nutrition. In a variant of this, the contact point is designed as a protruding body over the plane spanned by the peripheral edge of the firing pin, for example as a cylindrical section.

In an alternative, advantageous embodiment of the drill and chisel hammer tool device, the contact point on the impact means is provided on its side facing the firing pin. For the formation of the contact point is the, The firing pin facing side of the impact means, for example, convex, wherein the culmination point of the survey created thereby opposite the peripheral edge of the firing pin facing side of the percussion means plane protrudes and is arranged outside the striking axis. The survey may also have any shape and is z. B. formed as a parabolic curvature first nourishment or as a protruding cuboid portion.

Furthermore, in addition to the contact point, the mating contact point may also be exposed and arranged outside the striking axis, wherein the configuration of the mating contact point does not necessarily have to correspond to the configuration of the contact point.

Preferably, the contact point is arranged at a distance to the impact axis which corresponds to 0.003 to 0.05 times the axial length of the firing pin, whereby an increased friction between the percussion and the firing pin with the corresponding guide for the reduction of kinetic energy, at a negligible compared to a percussion, in which the percussion means centrically strikes on the firing pin is increased is generated. Particularly advantageous in terms of the relationship between the achieved degradation of the kinetic energy, the impairment of momentum transfer and the wear of the guides has proven to be a distance that corresponds to 0.005 to 0.03 times the axial length of the firing pin.

From the following detailed description and the totality of the claims, further advantageous embodiments and feature combinations of the invention result.

Brief description of the drawings

Fig. 1

Einen zeichnerisch vereinfachten Längsschnitt durch den Vorderbereich eines ersten Ausführungsbeispiels eines erfindungsgemässen Meisselhammers;

Fig. 1A

eine Ausschnittsvergrösserung im Bereich IA der Fig. 1;

Fig. 2

eine Seitenansicht eines Schlagkolbens; und

Fig. 3

einen zeichnerisch vereinfachten Längsschnitt durch den Vorderbereich eines zweiten Ausführungsbeispiels eines erfindungsgemässen Meisselhammers.

The invention will be explained in more detail below with reference to two exemplary embodiments. Show it:

Fig. 1

A simplified drawing longitudinal section through the front portion of a first embodiment of an inventive chisel hammer;

Fig. 1A

a detail enlargement in the area IA of Fig. 1;

Fig. 2

a side view of a percussion piston; and

Fig. 3

a simplified drawing longitudinal section through the front portion of a second embodiment of an inventive chisel hammer.

Basically, the same parts are provided with the same reference numerals in the figures.

Ways to carry out the invention

The chisel hammer 11 shown in FIGS. 1 and 1A has a housing 12 in which an electropneumatic impact mechanism 21 and a motor / gear unit 14 are arranged. In the only partially indicated tool holder 15, the insertion end 16 of a tool, not shown, such. B. a latex chisel, held in the chisel hammer 11. The percussion mechanism 21 has an excitation piston 23 which is guided back and forth along the striking axis 22 by means of an eccentric device 13 actuated by the motor / gear unit 14 in a guide tube 17. Due to the reciprocating movement of the exciter piston 23 serving as percussion means 24 percussion piston 25 is also displaced in reciprocating motion, which acts with an exposed and outside the striking axis 22 arranged contact point 27 via a mating contact point 28 on the firing pin 26 on this , The firing pin 26 transmits the impulse generated by the striking mechanism 21 to the insertion end 16 of the tool. The guide tube 17 has for venting the air cushion between the excitation piston 23 and the percussion piston 25 ventilation openings 18.

As can be seen in particular from FIG. 2, the contact point 27 is arranged outside the striking axis 22. The contact point 27 is arranged at a distance D from the impact axis 22 which corresponds to 0.02 times the axial length L of the firing pin 26. If the firing pin 26 has an axial length L of, for example, 100 mm, the distance D is thus 2 mm.

The chisel hammer 31 shown in FIG. 3 is substantially analogous to the chisel hammer 11 and differs only in the design of the percussion mechanism 41. In contrast to the percussion mechanism 21, the percussion mechanism 41 has a percussion piston 45, which is influenced by the excitation piston 43 and serves as percussion means 44 , Wherein this on the firing pin 46 side facing a contact point 47 which acts via a mating contact point 48 on the firing pin 46. The contact point 47 is exposed and arranged outside the striking axis 42. The contact point 47 is arranged at a distance d from the impact axis 42, which corresponds to 0.03 times the axial length l of the firing pin 46. If the firing pin 46 has an axial length l of, for example, 80 mm, the distance d is thus 2.4 mm.

Claims (5)

A hammer or chisel hammer comprising a percussion mechanism (21; 41) which has a percussion means (24; 44) which is moved back and forth along a striking axis (22; 42) and acts on a striking pin (26; 46), wherein between the striking pin (26 26) and the impact means (24; 44) a contact point (27; 47) and a counter contact point (28; 48) is provided, characterized in that the contact point (27; 47) exposed and outside the striking axis (22; 42) is arranged. Drill and chipping tool according to claim 1, characterized in that the contact point (27) on the firing pin (26) at its, the impact means (24) facing the end is provided. Drill and chipping tool according to claim 1, characterized in that the contact point (47) on the impact means (44) on its, the firing pin (46) facing side is provided. Drilling and chipping hammer tool according to one of claims 1 to 3, characterized in that the contact point (27; 47) at a distance (D; d) to the impact axis (22; 42) is arranged, the 0.003 to 0.05 times the axial length (L; I) of the firing pin (26; 46) corresponds. Drill and chipping tool according to claim 4, characterized in that the distance (D; d) to the impact axis (22; 42) corresponds to 0.005 to 0.03 times the axial length (L; I) of the firing pin (26; 46).

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