EP1607187B1 - Device for improving the deactivation response of an electropneumatic percussive tool - Google Patents

Description

The invention relates to degradation devices with electropneumatic drive, in particular to electropneumatic drill and / or chisel hammers. In particular, it relates to a device for improving the shutdown behavior of such mining equipment (see, eg US-A-5,975,217 ).

In devices of the type mentioned, an exciter piston is driven by an electric motor which periodically excites a reciprocating piston, which is coupled via a pressure impact pad (hereinafter "air spring"), to and fro. As a result of the impact of the flying piston on a removal tool held in a tool holder or via an anvil connected therebetween, a shock wave is generated in the tool, which causes the degradation of the substrate.

If the removal tool is lifted off the ground in chisel or hammer drilling mode, the electro-pneumatic impact mechanism should be deactivated as quickly as possible, since after lifting the shock wave generated by the flying piston and running along the tool can no longer be absorbed by the substrate; it is completely reflected. The total shock wave energy in this case must be taken up by the structure of the excavator and the user. Not only the returning shaft, but above all the first shock wave after lifting must be absorbed by the re-storage of the tool holder. As a rule, special damping elements ensure that no damage to the structure occurs due to repeated reference of the flying piston. However, these damping and structural elements of the device are not designed or interpreted so that the entire chisel power could be taken for a long time without permanent damage. The consequences of too slow shutdown of the impact mechanism after lifting off the ground are a relatively high wear of material and of course also unpleasant and harmful vibrations on the arms, joints and overall the body of the user.

1. (a) Das aktive Schlagwerk: Luftablassöffnungen in der Luftfeder werden geöffnet.
2. (b) Das passive Schlagwerk: Die Luftfeder wird beim Abheben des Geräts verlängert und dadurch weich.
3. (c) Das schnelle Abschalten des Antriebs, eventuell unterstützt durch schnelles, aktives Abbremsen des Antriebs.

Basically, the following methods are known to disable an electro-pneumatic percussion mechanism when interrupting or ending a work process and lifting the device from the ground:

1. (a) The active hammer mechanism: Air exhaust holes in the air spring are opened.
2. (b) The passive impact mechanism: The air spring is extended when lifting the unit and thus soft.
3. (c) Quick shutdown of the drive, possibly supported by fast, active braking of the drive.

The method (a) is realized in practice so that when lifting the device from the ground, the tool and the striker move forward by a few millimeters to centimeters from the user. This axial movement is transmitted to a control sleeve, which

Air outlet openings on the guide tube opens. This causes a large leakage in the air spring and thus a pressure equalization to the atmospheric pressure. The excitation piston is now no longer able to generate a negative pressure during the return stroke and to suck in the flying piston again. The hammer mechanism is deactivated.

Also in the method (b), the path of the bonnet or tool when lifting the device from the ground is exploited, but not to control a sleeve, but to extend the percussion or its air spring. The extension of the effective percussion length to the striker path causes the air spring is so soft that the flying piston is not sucked in during the return stroke of the exciter piston.

Method (c) requires a dynamic drive. The most common type of drive in power tools of the type mentioned today is the universal motor. This type of engine can not be actively braked - except by a very complex arrangement by turning the current direction in the stator. As soon as the excavator is lifted off the ground, the engine is switched off. When re-pressing the tool to the ground, the speed is increased again.

All three methods mentioned have in common that a lookup still occurs or at least can occur. Depending on the friction conditions on the wall of the guide tube in the percussion mechanism and on the sealing elements of the flying piston, it can happen in all known methods that the flying piston, after it has been deactivated, several times hits the striker. The kinetic energy contained in the flying mass can only be absorbed and reduced by friction with the lateral surfaces of the guide tube, by collisions with the striker or by compression of the residual content of air. In this respect, these are purely passive procedures. The flying piston loses its kinetic energy through impact or friction.

The invention has for its object to improve the shutdown and in particular Nachschlagverhalten of electropneumatically operated mining equipment, in particular of drilling and / or chipping hammers.

This object is achieved by a mining device according to claim 1.

According to the invention is a mining device with electro-pneumatic percussion, in particular a drill and / or chisel hammer whose percussion has an electrically driven within a guide tube back and forth driven exciter piston which accelerates a piston of this compressed air spring, which in turn held in a tool holder Powered striking tool, characterized by an activatable when lifting the excavator from the degraded surface valve means over which the pressure acting between the flying and the excitation piston pressure in the percussion is increased.

According to the invention, the valve device has a check valve, via which, when the tool is lifted off the ground, the negative pressure arising during the return stroke of the excitation piston between the latter and the flying piston is raised to a higher pressure, in particular ambient pressure. Preferably, the guide tube has at least one bore in the area of the air spring, here also referred to as "puff hole", and the check valve is displaceable relative to the guide tube and arranged so that that it is aligned when lifting the excavator from the ground by an adjustment on the hole.

According to the invention, the check valve is integrated in a control sleeve surrounding the control sleeve, which is displaceable by the adjusting device. Provided - as provided in a preferred embodiment - the air piston operated via the air spring striking acts on a tool holder associated with the beatpiece, the adjusting device for the check valve is preferably actuated by the lifting device when moving forward anvil. In this case, the control sleeve can be formed by the adjusting device relative to the guide tube either axially displaceable or rotatable relative to the guide tube. A spatially favorable because space-saving design embodiment can be realized when the preferably integrated into the control sleeve check valve is a flapper valve or a ball valve. A flap valve integrated into the control sleeve can be formed, for example, by a leaf spring which is clamped on one side and extends transversely to a passage channel in the control sleeve. The solution with integrated in the control sleeve ball valve has the advantage that the bias and thus the trigger pressure of the check valve can be adjusted well via an acting on a compression spring screw.

Another basic embodiment variant of the invention for preventing the refueling of the flyer provides for the use of an accumulator device, which increases the pressure in the percussion mechanism upon activation of the valve device at the time of interruption of work and lifting of the tool. The pressure accumulator may be an actuatable via the exciter piston pump, for example, be actuated by the connecting rod of the exciter piston reciprocating pump. An elegant and space-saving solution results when the pump is realized as an actuated by the drive of the exciter piston eccentric, with an eccentric of the connecting rod drive as a piston and the surrounding housing act as a pump housing.

A further basic embodiment variant of the invention provides to realize the valve means by means of at least one actively switched valve, such as an electromagnetically actuated valve, such as in the form of a dynamic valve sleeve valve. The valve is formed in particular by an electromagnetically actuated control sleeve, which closes at least one guide tube passing through the through hole to the air spring in a switching position and releases in a different switching position. Another proven and advantageous solution for a dynamic pusher sleeve valve is to move the control sleeve relative to the guide tube of the percussion axially by a voice coil actuator whose displaceable core is formed by the control sleeve.

Fig. 1

die Prinzipdarstellung eines Bohr- und/ oder Meisselhammers mit elektropneumatischem Schlagwerk, das erfindungsgemäß mit einer pneumatischen Flugkolbenbremse ausgestattet ist;

Fig. 2 mit Teilfiguren 2A und 2B

die Prinzipdarstellung eines elektropneumatischen Schlagwerks für Geräte der genannten Art mit einer aktiven Flugkolbenbremse, realisiert mittels durch eine Steuerhülse axial verschiebbarer Klappenventile, wobei
Fig. 2A die Position des Klappenventils in der Arbeitsposition des Geräts, also beim Abbau von Untergrund zeigt, während
Fig. 2B das Klappenventil bei vom Untergrund abgehobenem Werkzeug, und damit aktivierter Flugkolbenbremse veranschau- licht;

Fig. 3A

die isometrische Darstellung einer erprobten Steuerhülse mit integrierten Klappenventilen zur Deaktivierung und Aktivierung der Flugkolbenbremse;

Fig. 3B

die Schnittdarstellung der Steuerhülse nach Fig. 3A;

Fig. 4

die Schnittdarstellung einer Steuerhülse mit integrierten Kugelventilen als Rückschlagventile;

Fig. 5

die Prinzipdarstellung eines elektropneu- matischen Schlagwerks, ausgerüstet mit einer Steuerhülse mit Kugelventilen gemäß Fig. 4;

Fig. 6

die Prinzipdarstellung eines elektropneu- matischen Schlagwerks mit aktiver Flug- kolbenbremse gemäß der Erfindung zur Verdeutlichung des Begriffs "effektive Schlagwerkslänge";

Fig. 7 mit Teilfiguren 7A, 7B und 7C

die Prinzipdarstellung eines elektropneumatischen Schlagwerks mit aktiv steuerbarem Rückschlagventil, dargestellt in drei unterschiedlichen Positionen zur Veranschaulichung eines nachfolgend erläuterten Betriebsverhaltens;

Fig. 8

drei zeitkorreliert übereinander dargestell- te Signaldiagramme zur Veranschauli- chung eines Stopp- und Startvorgangs eines elektropneumatischen Schlagwerks mit erfindungsgemäßen Merkmalen bei kurzzeitiger Unterbrechung und Wieder- aufnahme eines Arbeitsvorgangs mit dem Abbaugerät;

Fig. 9

eine zeitlich auseinandergezogene Darstellung der Messsignaldiagramme der Fig. 8 zur Veranschaulichung des Abschalt- bzw. Nachschlagverhaltens eines elektropneumatischen Schlagwerks mit erfindungsgemäßer Flugkolbenbremse;

Fig. 10

die ebenfalls zeitlich auseinandergezogene Darstellung eines Teilabschnitts der Messsignale aus Fig. 8 zur Verdeutlichung des Anlaufverhaltens des Schlagwerks gemäß der Erfindung;

Fig. 11

eine der Fig. 8 entsprechende zeitkorrelierte Darstellung von drei Messsignalen zur Verdeutlichung eines Stopp- und Startvorgangs eines elektropneumatischen Schlagwerks, bei dem zusätzliche Maßnahmen getroffen sind, um einen beim raschen Abbremsen des Flugkolbens erzeugten Überdruck im Schlagwerk rasch abzubauen;

Fig. 12

eine zeitlich gestreckte Detaildarstellung aus der Graphik der Fig. 11 zur besseren Verdeutlichung des Anlaufverhaltens des Schlagwerks bei zusätzlichem Abblasen des für den Abbremsvorgang aufgebauten Druckpolsters;

Fig. 13

eine Ausführungsform der Erfindung, bei der die Flugkolbenbremsung durch Aufbau eines Zusatzdrucks über einen durch eine Hubkolbenpumpe aufladbaren Druckspeicher erfolgt;

Fig. 14

eine andere Ausführungsvariante, bei der ein Druckspeicher über eine vom Pleuel des Erregerkolbens mitbetätigte Exzenterpumpe aufgeladen wird;

Fig. 15

eine Ausführungsvariante der Erfindung, bei der eine Druckerhöhung im Schlagwerk bei Arbeitsunterbrechung über ein schaltbares Ventil, vorzugsweise Zweiwegeventil, erfolgt; und

Fig. 16

eine Ausführungsvariante der Erfindung, bei der eine Steuerhülse zur aktiven Öffnung von Schnauflöchern im Bereich der Luftfeder bei Arbeitsunterbrechung und Abheben des Werkzeugs vom Untergrund durch einen Voice-Coil-Aktor axial hinund hergeschoben wird.

The invention and advantageous details thereof are explained in more detail below with reference to the drawings in exemplary embodiments. Show it:

Fig. 1

the schematic diagram of a drill and / or chisel hammer with electropneumatic impact mechanism, which is equipped according to the invention with a pneumatic air piston brake;

Fig. 2 with sub-figures 2A and 2B

the schematic diagram of an electro-pneumatic percussion mechanism for devices of the type mentioned with an active air piston brake, realized by means of a control sleeve axially displaceable flap valves, wherein
Fig. 2A shows the position of the flap valve in the working position of the device, ie when dismantling underground, while
Fig. 2B illustrates the flap valve when the tool is lifted off the ground, and with this activated air piston brake;

Fig. 3A

the isometric view of a proven control sleeve with integrated flap valves for deactivation and activation of the aircraft piston brake;

Fig. 3B

the sectional view of the control sleeve after Fig. 3A ;

Fig. 4

the sectional view of a control sleeve with integrated ball valves as check valves;

Fig. 5

The schematic diagram of an electropneumatic impact mechanism, equipped with a control sleeve with ball valves according to Fig. 4 ;

Fig. 6

the schematic diagram of an electropneumatic percussion with active piston piston brake according to the invention to illustrate the term "effective percussion length";

Fig. 7 with sub-figures 7A, 7B and 7C

the schematic diagram of an electro-pneumatic percussion with actively controllable check valve, shown in three different positions to illustrate a below-explained operating behavior;

Fig. 8

three time-correlated signal diagrams for illustrating a stop and start operation of an electro-pneumatic percussion mechanism with features according to the invention in the event of brief interruption and re-starting recording a work process with the mining equipment;

Fig. 9

a temporally exploded view of the measurement signal diagrams of Fig. 8 to illustrate the turn-off or Nachschlagverhaltens an electropneumatic percussion with inventive aircraft piston brake;

Fig. 10

the likewise temporally exploded representation of a subsection of the measurement signals Fig. 8 to illustrate the start-up behavior of the striking mechanism according to the invention;

Fig. 11

one of the Fig. 8 corresponding time-correlated representation of three measuring signals to illustrate a stop and start operation of an electro-pneumatic impact mechanism, in which additional measures are taken to rapidly reduce a generated in the rapid deceleration of the air piston overpressure in the percussion;

Fig. 12

a temporally stretched detail from the graph of Fig. 11 for better clarification of the start-up behavior of the percussion mechanism with additional blowing off of the pressure pad constructed for the braking process;

Fig. 13

an embodiment of the invention, in which the air piston brake is done by building up an additional pressure via a pressure accumulator can be charged by a reciprocating pump;

Fig. 14

another embodiment in which a pressure accumulator is charged via a co-operated by the connecting rod of the exciter piston eccentric pump;

Fig. 15

an embodiment of the invention, in which an increase in pressure in the impact mechanism at work interruption via a switchable valve, preferably two-way valve occurs; and

Fig. 16

an embodiment of the invention in which a control sleeve for the active opening of Schnauflöchern in the air spring at work stoppage and lifting the tool from the ground by a voice coil actuator is pushed axially back and forth.

Corresponding components or assemblies are given in all figures with the same references.

The Fig. 1 shows a schematic side sectional view of a mining device with features of the invention, in the example shown a drill and / or chisel hammer 1, the housing is formed by two parts, namely a handle shell 2 and a motor housing shell 3. This division of the housing is not mandatory; There are other one-, two- or multi-part housing enclosures for devices of this kind. In the handle portion of the handle housing shell 2 can be seen a push button 4 for the ON / OFF circuit, which at certain operating modes via a potentiometer switch at the same time to Motordrehzahl- or Torque adjustment can serve. The power is supplied via a connection cable 6. Various operating modes, in particular the preselection for pure drilling, drilling hammer or pure chisel and optionally for fine boring, fine chisels, etc., are possible on a selector switch 8, the default values of an only schematically indicated motor control or control 7 are supplied.

The drive motor is of conventional design and is not shown for reasons of clarity. The excavator has an electropneumatic hammer mechanism 10 with a guide tube 11, in whose rear area an exciter piston 12 by a connecting rod 13 back and forth and is driven back and forth. The excitation piston 12 acts via an air spring 19 on a flying mass 14, which passes on its kinetic energy via a pressure pad 21 to an anvil 15, which in turn axially striking a held in a tool holder 9 tool, in particular a chisel (not shown), acts. In the context of the invention, the pressure pad 21 is not mandatory. In principle, it is also possible for the flying mass 14 to act directly on the tool or directly on the striker 15.

Essential to the invention is a pneumatic air piston brake generally indicated by reference 30 for generating an overpressure between the excitation piston 12 and the flying mass 14, which causes the flying mass 14 is pressed against the striker 15 when depositing the excavation device from the ground. As a result, a negative pressure in the air spring 19 and thus a lookup of the flying piston 14 is avoided during the return stroke of the exciter piston 12.

At the in Fig. 1 only schematically and in the Fig. 2A, 2B More clearly illustrated embodiment is a control sleeve 17, also referred to as "pump-up sleeve", the hammer or chisel operation of the mining equipment in the in Fig. 2A illustrated position in which Schnauflöcher 18 are closed by an annular closed portion of the control sleeve 17. If the excavator is set down from the ground, then the striker 15 slips forward by a length Δx of a few millimeters to a centimeter by 2.5 cm in the direction of the tool. About the coupled with the striker 15 adjusting the control sleeve 17 is also displaced axially forward so that check valves, designed here as flap valves 20 are aligned with the Schnauflöcher 18. If the excitation piston 12 now moves backwards, so that a negative pressure would arise in the space of the air spring 19, then the flap valves 20 open. As a result, the pressure in the air spring 19 does not drop or does not drop substantially below atmospheric pressure. The flying mass 14 is no longer sucked in and stays on or standing in front of the stopper 15.

The isometric representation of Fig. 3A shows an enlarged view of a proven embodiment of the axially displaceable control sleeve 17. This control sleeve 17, which is preferably produced as a plastic molded part consists - like the Fig. 3B can recognize - from a sleeve ring 21 with a number of the Schnauflöcher 18 corresponding plurality of recessed axial chambers 24, in which the flap valves 20 are inserted, and are held by a screw 26 sealingly. The axial chambers 24 are connected via an opening 25 whose number corresponds to the number of Schnauflöcher 18, with the interior of the control sleeve in conjunction. The flap valves 20 essentially consist in each case of a cantilevered leaf spring element 22 which releases or closes an inlet / outlet opening 27 depending on the pressure conditions on one or the other side of the leaf spring element 22. The hardness of the leaf spring element 22 determines the response of the flapper valve 20.

The Fig. 4 shows another proven embodiment of the control sleeve 17. Instead of the flap valves 20 ball valves 28 are here provided which release the openings 25 or close. The response of this type of valve can be adjusted sensitively via a set screw 31, via which the bias of a pressure acting on the ball valve spring 29 is determined. The advantage of this design with ball valves is a simpler manufacturing process, since the control sleeve 17 can be made largely completely as an injection molded part, and a good adjustability of the valve bias and thus the response of the check valves.

The Fig. 5 shows an embodiment of the electro-pneumatic impact mechanism 10, equipped with the ball valve sleeve according to Fig. 4 as a control sleeve 17. Incidentally, the embodiment corresponds to Fig. 5 that of the Fig. 2A or 2B, so that further explanation is unnecessary.

The Fig. 6 , which in turn shows the already explained electro-pneumatic striking mechanism, but in this case only schematically indicated Control sleeve 17, serves to explain a mathematical estimate of the maximum achievable pressure and the effective forces, in Fig. 6 the term l _eff used in the following is registered and illustrated as the "effective percussion length".

In the method on which the invention is based, also referred to as "pump-up method" at the moment of switching off the percussion - as already explained - check valves are connected, which are directly connected to the air spring 19 of the percussion and inflate this, that in the rearward movement of the exciter piston 12, a negative pressure in the air spring 19 is formed. The inwardly directed check valves, such as the flapper valves 20 or the ball valves 28, are opened and air mass is sucked into the interior of the air spring 19. As soon as the excitation piston 12 changes its direction of movement, these check valves are closed and the air is compressed. This creates an overpressure in the striking mechanism, which presses the flying mass 14 forward, in the direction of the striker 15. The air piston 14 thus remains after a short time in the foremost position.

In the following, the mean pressure is to be estimated, which is generated in the percussion mechanism in order to illustrate that the forces are sufficient to accelerate the flying mass 14 forward in the direction of the tool within a short time.

If it is permissible to assume that the check valves close at the time when the excitation piston 12 changes its direction of movement, ie at the rear dead center position, then the maximum pressure generated in the impact mechanism can be estimated. The pressure in the impact mechanism is just as great at this time as the external atmospheric pressure po. The stroke of the exciter piston 12 amounts to h _EK . The air mass in the impact mechanism is compressed around this stroke. It is legitimately assumed that the gas (the air) in the impact mechanism behaves ideally isentropically (adiabatically) with a coefficient κ = 1.4. It applies then: $${\left(\frac{\mathrm{<figure-callout\; id="0"\; label="V\; V"\; filenames="imgf0007.png,imgf0008.png"\; state="\{\{state\}\}">V\; </figure-callout>}}{V_{}}\right)}^{\kappa }={\left(\frac{x}{x_0}\right)}^{\kappa }=\left(\frac{p_0}{p}\right)$$

The maximum pressure is thus given by: $$p_{\mathrm{Max}}={\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="imgf0007.png,imgf0008.png"\; state="\{\{state\}\}">p</figure-callout>}}_0\cdot {\left(\frac{{\mathit{l}}_{\mathit{eff}}\mathit{+}{\mathit{H}}_{\mathit{EK}}}{{\mathit{l}}_{\mathit{eff}}}\right)}^{\kappa }$$

• l_eff: effektive Schlagwerkslänge; (vgl. Fig. 6)
• po: äußerer Atmosphärendruck
• h_EK: Hub des Erregerkolbens
• κ: Isentropen-Koeffizient; κ = 1.4 für Luft.

In this mean:

• l _eff : effective percussion length; (see. Fig. 6 )
• po: external atmospheric pressure
• h _EK : stroke of the exciter piston
• κ: isentropic coefficient; κ = 1.4 for air.

Assuming that the exciter piston stroke corresponds approximately to the effective percussion length, ie h _EK = l _eff , this results in a maximum pressure which is slightly more than twice as high as the external atmospheric pressure p 0: $$p_{\mathrm{Max}}\approx 2^{\kappa }{\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="imgf0007.png,imgf0008.png"\; state="\{\{state\}\}">p</figure-callout>}}_0\approx 2.6\cdot {\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="imgf0007.png,imgf0008.png"\; state="\{\{state\}\}">p</figure-callout>}}_0$$

The force with which the flying mass 14 is accelerated forward is given by: $$F\left(t\right)=A\cdot {\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="imgf0007.png,imgf0008.png"\; state="\{\{state\}\}">p</figure-callout>}}_0\cdot {\left[\frac{{\mathit{l}}_{\mathit{eff}}\mathit{+}{\mathit{H}}_{\mathit{EK}}}{x_{\mathit{EK}}\left(t\right)}\right]}^{\kappa }-\mathrm{<figure-callout\; id="0"\; label="A\; \cdot \; p"\; filenames="imgf0007.png,imgf0008.png"\; state="\{\{state\}\}">A\; </figure-callout>}\cdot p_{}{}_0$$

If the time-dependent instantaneous position of the excitation piston is denoted by x _EK (t), the following applies: $$x_{\mathit{EK}}\left(t\right)=l_{\mathit{eff}}+\frac{{\mathrm{<figure-callout\; id="2"\; label="H\; EK"\; filenames="imgf0001.png,imgf0007.png"\; state="\{\{state\}\}">H\; </figure-callout>}}_{\mathit{EK}}}{2}\cdot \left[1+\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="imgf0001.png,imgf0007.png"\; state="\{\{state\}\}">cos</figure-callout>}\left(2\mathit{\pi ft}\right)\right]$$

It follows from Eq. (4) $$F\left(t\right)=A\cdot {\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="imgf0007.png,imgf0008.png"\; state="\{\{state\}\}">p</figure-callout>}}_0\cdot {\left[\frac{{\mathit{l}}_{\mathit{eff}}\mathit{+}{\mathit{H}}_{\mathit{EK}}}{{\mathit{l}}_{\mathit{eff}}\mathit{+}\frac{x_{\mathit{<figure-callout\; id="2"\; label="EK"\; filenames="imgf0001.png,imgf0007.png"\; state="\{\{state\}\}">EK</figure-callout>}}}{2}\cdot \left[1+\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="imgf0001.png,imgf0007.png"\; state="\{\{state\}\}">cos</figure-callout>}\left(2\mathit{\pi ft}\right)\right]}\right]}^{\kappa }-\mathrm{<figure-callout\; id="0"\; label="A\; \cdot \; p"\; filenames="imgf0007.png,imgf0008.png"\; state="\{\{state\}\}">A\; </figure-callout>}\cdot p_{}{}_0$$

The mean force results from an averaging over a field piston period: $$\tilde{F}=\frac{1}{T}\cdot \underset{0}{\overset{T}{\int }}F\left(t\right)dt=\frac{A\cdot {\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="imgf0007.png,imgf0008.png"\; state="\{\{state\}\}">p</figure-callout>}}_0}{2\pi }\cdot \underset{0}{\overset{2\pi }{\int }}{\left[\frac{{\mathit{l}}_{\mathit{eff}}\mathit{+}{\mathit{H}}_{\mathit{EK}}}{{\mathit{l}}_{\mathit{eff}}\mathit{+}\frac{x_{\mathit{<figure-callout\; id="2"\; label="EK"\; filenames="imgf0001.png,imgf0007.png"\; state="\{\{state\}\}">EK</figure-callout>}}}{2}\cdot \left[1+\cos \left(x\right)\right]}\right]}^{\kappa }dx$$

Therein, A is the end face of the excitation piston and T is the period of an excitation piston cycle.

The integral of equation (7) can not be easily solved analytically because of the exponent κ. Therefore, two simplifications are considered. The first is to remove the exponent from the integrand. You then get: $${\tilde{F}}_1=A\cdot {\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="imgf0007.png,imgf0008.png"\; state="\{\{state\}\}">p</figure-callout>}}_0\cdot {\left(\frac{1}{\pi \sqrt{{\mathit{l}}_{\mathit{eff}}}}\cdot \sqrt{{\mathit{l}}_{\mathit{eff}}\mathit{+}{\mathit{H}}_{\mathit{EK}}}\arctan \left[\frac{\sqrt{{\mathit{l}}_{\mathit{eff}}}\tan \left(x/2\right)}{\sqrt{{\mathit{l}}_{\mathit{eff}}\mathit{+}{\mathit{H}}_{\mathit{EK}}}}\right]{|}_0^{2\pi }\right)}^{\kappa }=A\cdot {\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="imgf0007.png,imgf0008.png"\; state="\{\{state\}\}">p</figure-callout>}}_0\cdot {\left(\frac{{\mathit{H}}_{\mathit{EK}}}{{\mathit{l}}_{\mathit{eff}}}+1\right)}^{\frac{\mathrm{<figure-callout\; id="2"\; label="\kappa "\; filenames="imgf0001.png,imgf0007.png"\; state="\{\{state\}\}">\kappa </figure-callout>}}{2}}$$

This results in an average force of: $$\left\{\tilde{F}={\tilde{F}}_1-\mathrm{<figure-callout\; id="0"\; label="A\; \cdot \; p"\; filenames="imgf0007.png,imgf0008.png"\; state="\{\{state\}\}">A\; </figure-callout>}\cdot p_{}{}_0=A\cdot {\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="imgf0007.png,imgf0008.png"\; state="\{\{state\}\}">p</figure-callout>}}_0\cdot {\left(\frac{{\mathit{H}}_{\mathit{EK}}}{{\mathit{l}}_{\mathit{eff}}}+1\right)}^{\frac{\kappa }{2}}\right\}=m_{\mathit{FK}}\cdot \tilde{a}$$

und eine mittlere Beschleunigung von $$a=\frac{F}{m_{\mathit{FK}}}\approx \frac{0.62\cdot A\cdot p_0}{m_{\mathit{FK}}}$$

Assuming that the stroke of the connecting rod 13 again corresponds to the effective percussion length, ie h _EK = I _eff , the following results: $$\tilde{F}\approx A\cdot {\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="imgf0007.png,imgf0008.png"\; state="\{\{state\}\}">p</figure-callout>}}_0\cdot \left\{{\sqrt{2}}^{\kappa }-1\right\}\approx 0.62\cdot A\cdot {\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="imgf0007.png,imgf0008.png"\; state="\{\{state\}\}">p</figure-callout>}}_0=m_{\mathit{FK}}\cdot \tilde{a}$$

and a mean acceleration of $$a=\frac{F}{m_{\mathit{FK}}}\approx \frac{0.62\cdot A\cdot p_0}{m_{\mathit{FK}}}$$

If the flying mass 14 moves from rest from the rearmost position to the striker 15, this will take approximately: $$\tau =\sqrt{\frac{2l_{\mathit{eff}}}{\tilde{a}}}\approx \sqrt{\frac{2\cdot l_{\mathit{eff}}\cdot m_{\mathit{FK}}}{0.62\cdot A\cdot {\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="imgf0007.png,imgf0008.png"\; state="\{\{state\}\}">p</figure-callout>}}_0}}$$

$${\mathrm{l}}_{\mathrm{eff}}\mathrm{=}\mathrm{35}\mathrm{mm}$$

$${\mathrm{m}}_{\mathrm{FK}}=100g$$

$${\mathrm{p}}_{\mathrm{0}}\mathrm{=}\mathrm{1}\mathrm{bar}\mathrm{=}\mathrm{1}\mathrm{E}\mathrm{5}\mathrm{Pa}$$

Typical numerical values are: $$\mathrm{r}\mathrm{=}\mathrm{15}\mathrm{mm}$$

$${\mathrm{l}}_{\mathrm{eff}}\mathrm{=}\mathrm{35}\mathrm{mm}$$

$${\mathrm{m}}_{\mathrm{FK}}=100\mathrm{<figure-callout\; id="0"\; label="G\; p"\; filenames="imgf0007.png,imgf0008.png"\; state="\{\{state\}\}">G\; </figure-callout>}$$

$${\mathrm{p}}_{}$$$${\mathrm{}}_{\mathrm{0}}\mathrm{=}\mathrm{1}\mathrm{bar}\mathrm{=}\mathrm{1}\mathrm{e}\mathrm{5}\mathrm{Pa}$$

This results in a time constant of about 14 ms, which is sufficient to completely prevent the lookup of the flying piston 14.

A further permissible simplification possibility is to calculate the isentropic coefficient κ in Eq. (7) by the nearest integer fraction, ie: $$\kappa =1.4\approx \frac{3}{2}$$

The integral of Eq. (7) can be solved analytically in this case: $${\tilde{F}}_2=A\cdot {\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="imgf0007.png,imgf0008.png"\; state="\{\{state\}\}">p</figure-callout>}}_0\cdot \frac{2\pi }{\pi }\cdot \frac{\left({\mathit{H}}_{\mathit{EK}}+{\mathit{l}}_{\mathit{eff}}\right)}{{\mathit{l}}_{\mathit{eff}}}\cdot e\left(x\right)\left[\frac{{\mathit{H}}_{\mathit{EK}}}{{\mathit{H}}_{\mathit{EK}}+{\mathit{l}}_{\mathit{eff}}}\right]$$

E denotes the complete elliptic integral of the second kind. Assuming that the connecting rod stroke again corresponds to the effective impact length, the result is: $$\tilde{F}={\tilde{F}}_1-\mathrm{<figure-callout\; id="0"\; label="A\; \cdot \; p"\; filenames="imgf0007.png,imgf0008.png"\; state="\{\{state\}\}">A\; </figure-callout>}\cdot p_{}{}_0\approx A\cdot {\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="imgf0007.png,imgf0008.png"\; state="\{\{state\}\}">p</figure-callout>}}_0\cdot \left[\frac{4e\left(\frac{x}{2}\right)}{\pi }-1\right]=A\cdot {\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="imgf0007.png,imgf0008.png"\; state="\{\{state\}\}">p</figure-callout>}}_0\cdot \left[\frac{\mathrm{04/01/35}}{\pi }-1\right]\approx 0.72\cdot A\cdot {\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="imgf0007.png,imgf0008.png"\; state="\{\{state\}\}">p</figure-callout>}}_0$$

The in Eq. (15) function E (x) is defined as follows: $$\begin{array}{l}e\left(\phi |m\right)=\underset{0}{\overset{\phi }{\int }}\sqrt{1-m\cdot {\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="imgf0001.png,imgf0007.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2\left(\theta \right)d\theta }\\ e\left(m\right)=e\left(\frac{\pi }{2}|m\right)\end{array}$$

Therein θ denotes a general argument for the definition of the complete elliptic integral of the second kind (Eq. It is the integration variable to be integrated after. The argument of E (φ, m) is on the one hand the upper bound of the integral, on the other hand the modulus m. In our case: $$\mathrm{\phi }=\pi /\mathrm{Second}$$

The function E (x) can be evolved around zero into a Taylor series. $$e\left(x\right)=\frac{\pi }{2}-\frac{\pi \cdot x}{2}-\frac{3\pi \cdot x^2}{128}-\frac{5\pi \cdot x^3}{512}+O\left(x^4\right)$$

If only first-order terms are admissibly considered, then a reliable estimate for the average force results: $$\tilde{F}={\tilde{F}}_2-\mathrm{<figure-callout\; id="0"\; label="A\; \cdot \; p"\; filenames="imgf0007.png,imgf0008.png"\; state="\{\{state\}\}">A\; </figure-callout>}\cdot p_{}{}_0\approx A\cdot {\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="imgf0007.png,imgf0008.png"\; state="\{\{state\}\}">p</figure-callout>}}_0\cdot \left[\frac{4}{\pi }\cdot \frac{7\pi }{16}-1\right]=A\cdot {\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="imgf0007.png,imgf0008.png"\; state="\{\{state\}\}">p</figure-callout>}}_0\cdot \left[\frac{7}{4}-1\right]=\frac{3}{4}\cdot A\cdot {\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="imgf0007.png,imgf0008.png"\; state="\{\{state\}\}">p</figure-callout>}}_0$$

This suggests that the maximum pressure that can be generated by the check valves, at about 3/4 of the external pressure p is _0, if it is assumed that the Pleuelweg the length l _eff of the impact mechanism corresponds.

Experiments have shown that the check valves can be considered almost ideal.

The model calculation presented so far, including the behavior of the non-return valves, is subsequently verified by means of a realistic simulation which additionally uses a clear improvement in terms of the operating force of the dismounting device with regard to the required contact pressure by the operator and for a quick start-up behavior.

A mining device of the type mentioned, in particular a drill and / or chisel, is all the more user-friendly, the lower the contact pressure, which must apply the user, so that the device after a business interruption z. B. when settling of underground, starts again quickly and works stably. By generating a higher pressure between the exciter piston 12 and the flying piston 14 when the device is discontinued, the pressing force expended for the restart is increased somewhat.

For example, assuming a maximum overpressure of about 0.6 bar, given an assumed diameter of the guide tube 11 of d = 40 mm, compressive forces of about 24 N, which are to be overcome by the contact force, result.

In order to reduce these opposing forces and to ensure a faster restarting of the percussion mechanism, it is provided according to an advantageous embodiment variant to blow off the excess air mass in the guide cylinder 11 via an intermediate step. This embodiment of the invention will be described with reference to Figs. 7A to 7C described below.

The with the check valve, z. B. the flap valve 20, equipped axially displaceable control sleeve 17 has at a certain axial distance from the flapper valve 20 at least one bore as a discharge opening 32, but preferably a number of Schnauflöcher 18 corresponding plurality of discharge openings 32.

The Fig. 7A shows the working position of the excavation device, in which the Schnauflöcher 18 are closed by the front portion of the control sleeve 17. If the excavation device is set down from the ground, the control sleeve 17 is displaced by the striker 15 slipping forward by the path section Δx ₂ , so that the check valves, for example the flap valve 20, as in FIG Fig. 7C shown aligned with the Schnauflöcher 18. This is the same as in Fig. 2B shown pump-up position in which the flying mass 14 is temporarily stopped. If the operator begins a further degradation process, an intermediate position of the striker 6 or of the control sleeve 17 is achieved when the device is attached, the opposite of the in Fig. 7A working position shown is shifted to a smaller span Ax _1, the so-called discharge position, in which the discharge opening (s) aligned on one of or Schnauflöcher 18 32 (are). As a result, the excess air mass in the striking mechanism is quickly blown off, so that the impact mechanism begins to work again within a very short time.

In the Fig. 8 illustrated time-correlated partial diagrams (a) to (c) illustrate simulation results, with the striking mechanism according to Fig. 2 A / B were carried out.

The abscissa of the three diagrams shows the time in seconds (s). On the ordinates of the three diagrams are in the upper diagram (a) in its upper part diagram 33, the instantaneous position or the path-time curve of the exciter piston 12 and in the lower part of the graph 34, the instantaneous position and the path-time course of the flying piston 14 reproduced.

The middle diagram (b) shows on the one hand in a solid line 35 the total energy consumption and in the lower part of the energy of the individual beats, which are plotted as peaks 36.

Finally, the lowest partial diagram (c) shows the time course of the air mass present in the percussion mechanism during a stopping and starting operation for a striking mechanism according to the invention.

The simulation results of Fig. 8 are to be interpreted as follows:

At t = 0.6 s, the pump-up or control sleeve 17 is activated, ie when placing the device in the in Fig. 2B moved position shown. The percussion comes to a halt within two strokes, which is well from the subdiagram (b) of the Fig. 8 is apparent. At t = 1.2 s, the percussion mechanism is reactivated, it takes, as shown in the partial diagram (c) of the Fig. 8 it can be seen, about 400 ms, until the excess air is broken down in the percussion over the Schnaufloch or the Schnauflöcher 32, and the percussion again starts to work fully.

The three graphical representations of Fig. 9 show a time-prolonged partial excerpt of the simulation results Fig. 8 , It can clearly be seen from this that the flying massile has already reached a rest position after only two individual beats (partial diagram (a)). The exciter piston 12 continues to run and changed accordingly the existing air mass in the percussion pulsating, which is well from the partial diagrams (c) of Fig. 8 and 9 can be seen.

The graphic representation of the Fig. 10 corresponds to a time-extended detailed representation of the graphic after Fig. 8 from the time t = 1.1 s. From the partial diagrams (b) and (c) of Fig. 10 can be read particularly well that without additional draining, as based on the Fig. 10 illustrates that Schlagwerk achieved its full impact performance after about 400 ms. The excess air is degraded via the or the Schnauflöcher although in a tolerable for practice period, but with a noticeable time delay.

The FiG. 11 and 12 show the already explained FIGS. 8 or 10 corresponding graphics or diagrams for a striking mechanism with a pump-up or control sleeve 17 according to Fig. 7 with additional (additional) discharge opening (discharge openings) 32.

According to the Fig. 8 shows Fig. 11 an overview of a stop and start operation of a percussion mechanism by means of a pump-up or control sleeve 17 according to the invention, according to Fig. 7 has additional discharge openings 32. Again, at t = 0.6 s, the control sleeve 17 in the in Fig. 7C shown position. The percussion comes to a halt within two shots. At t = 1.2 s the hammer mechanism is reactivated. Unlike Fig. 8 respectively. Fig. 10 is from the Fig. 11 and 12 It is obvious that the striking mechanism begins to hammer almost immediately, which in both cases Fig. 11 and 12 the partial diagrams (b) and (c) can be recognized well. This favorable start-up behavior of the percussion mechanism is achieved by the additional blow-off via the discharge opening 32. Excess air is rapidly reduced by briefly bleeding the impact mechanism.

Another basic embodiment of the invention using a pump with pressure accumulator is described below with reference to the FIGS. 13 and 14 described.

In this variant of the invention illustrated by two embodiments, the electropneumatic percussion mechanism itself is used to fill an intermediate pressure accumulator 45, which is emptied via a preferably controllable valve 46 into the percussion mechanism, in particular into the air spring 19, as soon as the contact pressure decreases or the extraction unit declines lifted off the ground.

The Fig. 13 shows an embodiment with a driven by the exciter piston additional piston pump 40, which is connected via check valves 41, 42 with the intermediate pressure accumulator 45. The suction sides of the reciprocating pump 40 also have check valves 43, 44. At the accumulator 45, a pressure relief valve 47 may be provided.

As the embodiment according to Fig. 14 shows, it is also possible to use the volume 50 of the eccentric drive 42 for the excitation piston 12 directly as the pump volume, wherein the crankcase serves as a pump housing 51. The check valves 53 and 54 correspond in function to the check valves 41, 42 and 43, 44 at Fig. 13 ,

The advantage of this embodiment of the invention over the variant with pump-up or control sleeve is that the maximum pressure in the impact mechanism are not given by the dimensions of the flying piston travel and / or Exzenterhubs and thus not on the ambient pressure, ie about 1 bar, are limited. It can generate significantly higher pressures, which in principle allows an even more reliable and faster shutdown of the mining equipment when lifting off the ground. It is also advantageous that the pressure at the time of switching off is already available.

A third embodiment variant of the invention is based on the use of fast-switching valves with a sub-variant of a dynamically rapidly displaceable sliding sleeve. Two embodiments are in the FIGS. 15 and 16 shown.

In the embodiment according to Fig. 15 is the function of a check valve compared with the basis of the Fig. 1 to 12 described embodiments replaced by a fast-switching valve 60, which may be a magnetically actuated 2/2-way valve. In order to generate an overpressure in the impact mechanism, the valve 60 is closed as soon as the exciter piston 12 changes its direction of movement at the rear dead center. The air is compressed during the flow of the excitation piston 12 and generates an overpressure. The valve 60 is then opened again each time shortly after the exciter piston 12 has reached the front dead center or reversal point.

This embodiment of the invention has the advantage that after switching off the impact mechanism before the next start by a short opening of the valve 60, the pressure equalization can be made immediately. However, the requirements for the valve 60 are relatively high; Switching frequencies of more than 50 Hz are necessary. Also, the nominal widths of a feedthrough bore on the guide tube 11 (in FiG. 15 not shown) or on the valve itself, must be sized relatively large for rapid gas exchange, z. B. diameters of 3 to 4 mm are required. In particular, electrically operated slide valves or rotary slide valves come into question for this embodiment.

An embodiment of the invention in which a control sleeve itself is used directly as a slide valve, is in Fig. 16 shown. A control sleeve 61, which closes the Schnauflöcher 18 in an end position and releases in a second end position, at the same time forms a bobbin and forms the armature of a voice coil actuator 62, which is placed centrally around the guide tube 11.

Claims (10)

1. Breaker device, in particular hammer drill and/or chipping hammer, the electropneumatic striking mechanism of which comprises an exciter piston (12) which can be driven electrically in a reciprocating manner within a guide tube (II) and which, by means of an air spring (19) compressed thereby, accelerates a free piston (14) which in turn percussively drives a breaker device held in a tool holder (9), the guide tube being provided in the region of the air spring with at least one bore (18) and being surrounded by a control sleeve (17) which can be displaced by an adjusting mechanism (16) which can be actuated when the breaker device is lifted off the ground, characterised in that a non-return valve (20; 28) by means of which the negative pressure produced between the exciter piston (12) and the free piston (14) during the return stroke of the exciter piston when the breaker device is lifted off the ground is increased to a higher pressure is integrated into the control sleeve (17) and is arranged in such a manner that it is aligned with the bore (18) by means of the adjusting mechanism (16) when the breaker device is lifted off the ground.
2. Breaker device according to claim 1, in which the free piston driven by the air spring acts percussively on a plunger (15) associated with the tool holder, characterised in that the valve mechanism (16) for the non-return valve can be actuated by means of the plunger.
3. Breaker device according to claim 2, characterised in that the control sleeve can be displaced axially relative to the guide tube by means of the adjusting mechanism.
4. Breaker device according to claim 2, characterised in that the control sleeve can be rotated relative to the guide tube by means of the adjusting mechanism.
5. Breaker device according to claim 1, characterised in that the non-return valve is a flap valve (20).
6. Breaker device according to claim 5, characterised in that the flap valve (20) is integrated into the circumferential wall of the control sleeve (17).
7. Breaker device according to claim 6, characterised in that the flap valve (20) is formed by a leaf spring (22) extending transversely to an admission port and clamped at one end.
8. Breaker device according to claim 1, characterised in that the non-return valve is a ball valve (28) integrated into the control sleeve (17).
9. Breaker device according to claim 8, characterised in that the preloading of the ball valve can be adjusted by means of an adjusting screw (31) acting on a compression spring (29).
10. Breaker device according to claim 1, characterised by at least one vent (32) traversing the control sleeve (17) for the rapid reduction of excess pressure in the striking mechanism when the hammering or chipping operation is started/resumed.

Images