DD145243A5 - DRILLING AND CHISEL HAMMER WITH INTERNAL COMBUSTION ENGINE DRIVE - Google Patents

Abstract

The invention aims to improve the power/weight ratio of a two-stroke engine employed as the prime mover in a drilling and chiselling hammer 1 (sometimes also known as a percussion tool) of the kind in which percussion impacts are transmitted to a tool holder 3 of the tool by way of a percussion piston 9 which is reciprocated by the engine, thereby to enable the tool to be lighter, so that it can more readily be manipulated in the case of a hand-held tool. To achieve this improved efficiency, crank 7 of the percussion piston 9 is accommodated in a chamber 1a into which air is drawn by way of a non- return valve 11 upon movement of the piston 9 towards the top dead-centre position and from which air is displaced, under compression, through a pipeline 13 to an entry slot 1e of the cylinder 1c of the engine. <IMAGE>

Description

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Drilling and chiselling hammer with internal combustion engine drive

Field of application of the invention:. ·

The invention relates to a drill and chisel hammer with percussion and internal combustion engine, wherein the crankshaft of the engine is coupled to a drive piston of the percussion mechanism via a connecting rod in a reciprocating motion offset crank.

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' ^ Characteristic of the known techn. Solutions; : Drill and chisel hammers of the type mentioned above are mainly used for higher mining performance. In the internal combustion engines serving the drive are usually so-called 2-stroke engines. This design has the advantage over a 4-stroke engine the advantage of a simpler structure and thus a lower weight at comparable performance. 2-stroke engines are therefore common for weight and price reasons for hand-held devices and machines.

The 2-stroke engine must be purged with a gasoline-air mixture after each working hump, ie the flue gases present in the cylinder are displaced by the mixture and a new, ignitable charge is supplied to the engine. However, a pump is necessary for the mixture to flow into the cylinder. In virtually all 2-stroke small engines, the crankcase of the engine is used as a scavenge pump. However, this is associated with a significant disadvantage. The bearing shafts of the crankshaft and the connecting rod as well as the cylinder wall must be sufficiently lubricated. Through the gasoline-air mixture, the lubricating oil is washed out in a short time, so that the machine would be destroyed without countermeasures within the shortest possible time. To remedy this, a gasoline-oil mixture is used in 2-stroke engines. It falls to the OeI the task to lubricate the engine. Gasoline is the source of energy for combustion.

Since the OeI entering the combustion chamber only incompletely burns during the combustion of the gasoline-air mixture, it appears as a troublesome, blue exhaust smoke.

Furthermore, the efficiency of conventional 2-stroke engines is usually lower than that of a comparable 4-stroke engine. The lower efficiency is mainly due to the flushing losses when flushing the combustion chamber. For larger, stationary or in-vehicle engines

sometimes operated a considerable effort for flushing the combustion chamber. For example, turbo blowers, rotary vane blowers or piston pumps are known. For portable devices, such as drilling and Meisseihämmern such measures, however, ruled out for weight reasons from the outset.

Aim of the invention; ·.

The invention has for its object to provide a drilling and Meisseihammer with internal combustion engine, the engine thanks to good flushing achieved high efficiency and the hammer has a total of favorable power to weight ratio.

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Explanation of the essence of the invention:

According to the invention, this object is achieved in that the crank des.Schlagwerkes is arranged in a relation to the other parts of the hammer separated space having an inlet valve and is connected via an outflow opening with the combustion chamber leading inlet slots of the engine in connection.

If the crankcase of the striking mechanism is separated from the other parts of the hammer, this can be used as a rinsing pump for the engine. Since the stroke volume of the impact mechanism for a given 2-stroke engine corresponds approximately to the stroke volume of the engine, the percussion crankcase is best suited as a rinsing pump for the engine. The bearing of the crankshaft is usually arranged in the engine crankcase and the drive piston is usually lubricated by the striking mechanism ago. The rod bearings of the impact mechanism can be easily carried out with dense, grease-lubricated bearings. Lubrication of the Sphlagwerkkurbelkastens is therefore not necessary. Since the crankcase of the engine with the fuel-air mixture in a carburettor engine or with the intake air in an injection engine does not come into contact, the lubrication of the crankshaft bearings, Pleuellagerüngen and the cylinder surface of the engine can be designed for optimal considerations. For example, "one

Dipping or oil mist lubrication can be used. The aspirated fuel-air mixture thus has no special lubrication functions to meet. It is thus possible to operate the device without oily two-stroke mixture - which has a favorable effect on the operating costs and the exhaust gases.

The known 2-stroke machines have another disadvantage. During purging, part of the fuel-air mixture passes as flushing losses through the exhaust slots over the muffler into the open air. This is practically unavoidable with 2-stroke engines. The consequences are a high fuel consumption, as this fuel in the combustion process no longer participates and a high proportion of unburned, mostly toxic gases that escape from the exhaust. In the case of the so-called injection engines, this is prevented by flushing with "clean air." As soon as the piston has covered the control slots and the combustion chamber is thus sealed, fuel is injected by means of a high-pressure injection nozzle Subsequent injection of the fuel noticeably increases the performance, significantly reduces fuel consumption and improves the exhaust gas quality considerably.The flushing mechanism according to the invention with the striking mechanism crankcase is suitable for both carburettor and injection engines.

Through the inlet valve, a flammable mixture is sucked in via a known carburetor, or pure air via an air filter. Although this system is especially suitable for a working according to the two-stroke principle internal combustion engine, so that, for example, in a four-stroke engine so-called charging and thus an increase in performance can be achieved. The inventive solution is particularly simple and needed

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compared to a known, driven by an internal combustion engine drill and chisel hammer only an inlet valve and a connecting line from the discharge opening of the separated space to the inlet slots of the engine. The inventive measures thus have practically no increase in weight result.

For a simple construction of the device, it is expedient that the connecting rod facing the end face of the drive piston forms a wall portion of the separated against the other parts of the hammer space. In particular, in a pneumatic percussion no additional measures are necessary because the reciprocating in a cylinder drive piston is already sealed against the arranged between the drive piston and a percussion piston air cushion. The compression of the sucked air or the mixture in the separated space can be optimally determined by setting the crank stroke and the dead space within certain limits regardless of the drive motor.

By separated from the other parts of the hammer space arise over a known device in which the crank of the hammer mechanism and the crank of the drive motor are arranged in the same space, new possibilities. In a conventional two-stroke engine, the air-fuel mixture is sucked into the crankcase of the engine and precompressed during the expansion phase of the combustion chamber in the crankcase. Shortly before reaching the bottom dead center, the overflow channels are released by the piston and the pre-compressed mixture can flow from the crankcase into the combustion chamber. As the crank continues to rotate, however, the pressure in the crankcase as well as the overflow channel decreases again, so that the influx into the combustion chamber

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space is slowed down. For this reason, only an incomplete flushing of the combustion chamber is possible. On the other hand, if the purge pressure is increased by reducing the crankcase, there is a risk that too much of the ignitable mixture escapes unburned through the exhaust slots as a purge loss, which in turn leads to increased fuel consumption. In order to be able to optimally adapt the flushing pressure to the flushing process, it is advantageous that the crank of the impact mechanism is offset from the crankshaft of the engine in such a way that the percussion mechanism lags behind the engine with a crank offset of 10 to 60. Thus, it is possible that, starting from the bottom dead center position of the engine piston, upon further rotation of the crankshaft sufficient scavenging pressure is present until the inlet or ÜBfeerströmschlitzeded by the piston are covered again. Since the hammer mechanism is coupled to the crankshaft, this crank offset always remains the same.

In practice, it has proven to be expedient that the crank offset is 40 °. As a result, at a given position, the intake or overflow slots will cause sufficient scavenging pressure to be present until the intake or overflow slots are closed, preventing backflow of scavenging air and allowing much better scavenging than is achievable with crankcase scavenging. On the other hand, when opening the inlet slots, the pressure gradient between the scavenging pressure and the pressure in the combustion chamber is low, so that a StröHSMag can form in the combustion chamber and the newly inflowing mixture largely displaces the burned gases through the exhaust slots. Ausfuhrun ^ sbeispiele; · ......

The invention will be explained below with reference to the example reproducing drawings. Show it :

Fig. 1 an inventive drill and chisel hammer, partially in section, shown.

Fig. 2 The engine parts of the percussion and the

Motors in the top dead center position of the drive piston, according to the line A-A in Fig. 1st

Fig. 3 The engine parts in the bottom dead center position of the drive piston.

The apparent from Fig. 1 drill and chisel hammer consists essentially of a generally designated 1 housing. At the rear end of the housing 1, a handle 2 is attached. On the opposite side of the handle 2 of the housing 1, a tool holder 3 is arranged. In the housing 1, a generally designated 4 crankshaft of the engine is rotatably mounted. A connecting rod 5 is rotatably mounted on a crank arm 4a. The connecting rod 5 is in turn connected to a piston 6. The piston 6 is in turn guided in a cylinder Ic. At the upper end of the crankshaft 4, a crank, generally designated 7, is connected to the crankshaft 4 via a thread 4b. On a crank pin 7a, a connecting rod 8 of the striking mechanism is attached. The connecting rod 8 is in turn connected to a drive piston 9, for example, for a pneumatic percussion. The drive piston 9 is guided in a bushing 10. The impact mechanism is thus coupled with the combustion engine. On the housing 1 in the areas of the crank 7, a total of 11 designated inlet valve is arranged. In the inlet valve, a ball lla is pressed by means of a spring 11b against a valve seat lic-. The intake valve II thus has the function of a check valve or one-way valve. When the drive piston 9, moves in the direction of the tool holder 3, is characterized by the

Inlet valve 11 air or possibly a fuel-air mixture in a space la, in which the crank 7 and the connecting rod move sucked. The space la is sealed off from the remaining parts of the housing 1 by a seal 12. The space la also has an outflow opening Id. A; Piping leads from the outflow opening Id to an inlet slot Ie in the cylinder Ic. When the drive piston 9 changes direction and moves again against the handle 2, the space la is reduced in size and the air sucked therein or the fuel air mixture is expelled through the pipeline 13. When the piston 6 releases the vertical slot Ie, the air can flow into the combustion chamber Ib. In this case, the burned exhaust gases contained in the combustion space Ib after ignition are displaced by an exhaust slot If. This process is referred to in the jargon aucti as irrigation. In a so-called carburetor engine is flushed with an ignitable fuel-air mixture. This in itself has the disadvantage that a part of the mixture can also escape through the exhaust ports If and the efficiency of the internal combustion engine is reduced. In the case of the so-called injection engine, on the other hand, it is flushed with clean air. The fuel is injected through a nozzle into the combustion chamber Ib only when both the inlet slot Ie and the exhaust slot If are closed. This in turn has a favorable effect on the efficiency. At the lower end of the crankshaft 4, a conventional in internal combustion engines' flywheel 14 is arranged. The flywheel 14 serves on the one hand as a balance between the power output of the engine and the power consumption of the engine during the compression phase and the impact work of the striking mechanism. In addition, the flywheel is additionally used as a generator for generating the ignition voltage and as a fan for a cooling air flow, which is sucked through a cover 15 and blown past the cylinder ic.

From the apparent in Fig. 2 section through the device according to the line AA in Fig. 1, the main engine parts of the device can be seen. The drive piston 9 is in its upper dead center position. With regard to the direction of rotation D, however, the piston 6 has already exceeded its top dead center position. The crank pin 7a of the percussion mechanism is thus offset from the crank arm 4a of the internal combustion engine by an angle ω, the percussion mechanism lags the internal combustion engine by this angle ω. As the crank 7 continues to rotate, the space lla is reduced again and the air or air contained therein Fuel jet mixture ejected through the discharge opening Id. This lagging of the percussion mechanism relative to the internal combustion engine has compared to a conventional two-stroke engine, in which the crankcase of the engine acts as a rinsing pump has the advantage that during the entire rinsing the rinsing pressure is above that in the combustion chamber, so that Backflow is prevented.

Fig. 3 shows the same engine parts as Fig. 2, but in the bottom dead center of the drive piston 9. The piston 6 is already moving away from the crank 7 again. In this case, the fuel-air mixture which has passed from the space 1a through the outflow opening Id and the inlet slot Ie into the combustion space is compressed. In this position, the power requirement of the impact mechanism is low. The stored energy in the flywheel can thus be used virtually fully for the compression of the fuel-air mixture contained in the combustion chamber Ib. Thus, the phase shift between percussion and combustion engine also has a favorable effect.

Claims (4)

invention claims 1. Drilling and chipping hammer with percussion and internal combustion engine, wherein the crankshaft of the engine is coupled to a drive piston of the percussion mechanism via a connecting rod in a reciprocating motion offset crank, characterized geke η ζ ic e ic h.η et that the crank (7) of the percussion mechanism is arranged in a space (1a) separated from the remaining parts of the hammer, "having an inlet valve (11) and via an outflow opening (Id) with the combustion chamber (Ib) leading inlet slots (Ie) of the engine is in communication. 2. Drill and chisel hammer on point \ _f characterized in that the connecting rod (8) facing the end face of the drive piston (9) forms a wall portion of the separated against the other parts of the hammer space (la). 3. Drilling and chipping hammer according to one of the points ± or 2, characterized in that the crank (7) of the impact mechanism to the crankshaft (4) of the engine is offset such that the percussion gear with respect to the engine with a crank offset of 10 to 60 ° lags. 4. Bohr ^ · and chisel hammer after point j _f characterized in that the crank offset is 40. Hteni_! ^ JSeften Zeidimmgen -P Uli !, -iü I is - - i '\