Patent Application
20150298354
The present invention relates to a power tool with a spraying device for binding dust, according to the generic part of claim 1.
The term “power tool” as set forth within the scope of the present invention encompasses all power tools that drive a processing tool in a rotating direction around an axis of rotation during the processing of a workpiece, whereby the axis of rotation is arranged relative to the workpiece surface at an angle that differs from 90°. Typical examples of such power tools are a wall saw, a disc grinder, an angle grinder and a circular saw.
Processing concrete workpieces, ceramic construction workpieces (roof tiles, bricks, floor tiles, wall tiles), mineral workpieces (sandstone, porous concrete stones), etc. with power tools gives rise to dust that contains not only larger dust particles but also fine dust particles. The term “fine dust” refers to particles in the air that do not sink to the ground immediately but rather, remain in the atmosphere for a certain period of time. Fine dust is divided into fractions, depending on the particle size. The most important fractions are the fraction that can be inhaled (I-fraction) and the fraction that can enter the alveoli (A-fraction). An inhalable fraction refers to fine dust particles that are deposited and settle primarily in the nasal and pharyngeal passages, whereas the expression “fraction that can enter the alveoli” refers to fine dust particles that get all the way into the pulmonary vesicles, the so-called alveoli.
The inhalation of fine dust particles has a detrimental effect on the health of humans. In this context, it holds true that the smaller the fine dust particles are, the greater the risk of harm to health. Smaller fine dust particles penetrate further into the respiratory tract than larger fine dust particles and they get into areas from which they are not expelled during exhalation, as a result of which they are particularly harmful to health. Studies have shown that there is no fine dust particle concentration below which no health-hazardous consequences can be expected.
For this reason, it is not only elevated concentrations of fine dust particles that have a negative effect on health, but rather, even low concentrations of fine dust particles are already detrimental to health, especially when they are present over a prolonged period of time. Therefore, the fine dust burden should be as low as possible in order to minimize the risk of damage to the health of humans.
Familiar power tools with a spraying device for binding dust comprise a processing tool that is driven around an axis of rotation by a drive means and that covers a processing plane perpendicular to the axis of rotation, a protective hood that partially surrounds the processing tool, and the spraying device with at least one spray nozzle which produces a jet along a spraying direction.
European patent specification EP 1 349 714 B1 discloses a power tool configured as a handheld disc grinder with a spraying device for binding dust and for cooling the grinding disc. The spraying device comprises a pump that operates within the pressure range of 2 bar to 4 bar, and one or more spray nozzles arranged on the side of the grinding disc that enters the workpiece (entry side). The pump is driven by means of at least one drive component of the drive means. The pump of the spraying device, which operates within the pressure range of 2 bar to 4 bar, and the arrangement of the spray nozzles on the entry side of the grinding disc have proven to be unsuitable for binding fine dust particles, especially the fraction of the fine dust that can enter the alveoli.
International patent application WO 2004/0000501 A1 discloses another power tool configured as an angle grinder with a spraying device. The spraying device comprises a first spray nozzle for binding dust and a second spray nozzle for moistening the workpiece that is to be processed. The first spray nozzle produces a first jet along a first spraying direction and is arranged in the protective hood on the side of the grinding disc that exits the workpiece (exit side). The second spray nozzle produces a second jet along a second spraying direction and is arranged in the protective hood on the entry side of the grinding disc. The spraying device is implemented in two configurations that differ from each other in terms of the arrangement of the first and second spray nozzles and their spraying directions. In the first configuration, the first and second spray nozzles are located outside of the diameter of the processing tool configured as a grinding disc. The spraying directions run perpendicular, that is to say, at an angle of approximately 90°, relative to the axis of rotation, and the first and second jets strike perpendicularly onto the workpiece that is to be processed. In the second configuration, the first and second spray nozzles are located inside of the diameter of the grinding disc. The spraying directions of the first and second spray nozzles are each oriented at an angle of approximately 66° relative to a plane that is perpendicular to the processing plane and parallel to the axis of rotation of the workpiece that is to be processed, and slanted in the processing plane in the direction of the axis of rotation. The angle grinder does not have a pump to convey the liquid. A non-return valve to which a water line is connected is screwed into the protective hood of the angle grinder. The amount of liquid is likewise regulated by the non-return valve. The pressure of the liquid as it enters the spraying device is at least 3 bar so that the spray nozzles can generate a functional first and second jet.
The orientation of the jets relative to the processing tool as well as the pressure build-up in the spraying device described in international patent application WO 2004/0000501 A1 are disadvantageous for binding fine dust particles, especially the fraction of the fine dust that can enter the alveoli. The spraying device also has the drawback that the liquid is supplied via a water line of an external pipe system, so that the spraying device of the power tool can only be employed if a functioning pipe system is available.
It is an object of the present invention to provide a spraying device for a power tool by means of which the fine dust burden is reduced for the operator during the processing of a workpiece using the power tool. In this context, particularly the fraction of the fine dust that can enter the alveoli and that is hazardous to health is to be reduced. Moreover, the amount of liquid needed for binding the dust should be as small as possible.
The present invention provides that the pump generates a minimum pressure of 5 bar in the first connection line. Especially preferably, the pump generates a pressure between 5 bar and 8 bar in the first connection line. A minimum pressure of 5 bar is necessary to create liquid drops. The high pressure and a corresponding first spray nozzle generate a first jet that can bind the fraction of the fine dust that can enter the alveoli.
Preferably, the throughput rate of the first spray nozzle is between 8 and 12 liters per hour. A suitable arrangement and orientation of the first spray nozzle and a minimum pressure of 5 bar in the first connection line to the first spray nozzle markedly reduce the amount of liquid needed for binding the dust. Instead of the usual throughput rates of several liters per minute, the throughput rate for the first spray nozzle in the spraying device according to the invention is merely a few liters per hour. This low throughput rate means that the contents of the reservoir last longer before it needs to be refilled, which is advantageous especially at construction sites without external supply lines. Moreover, the workpiece that is to be processed is not exposed to water unnecessarily.
Especially preferably, the first spray nozzle produces the first jet with liquid drops measuring between 40 μm and 150 μm. The fraction of the fine dust that can enter the alveoli can be bound by means of liquid drops measuring between 40 μm and 150 μm, in addition to which the demand for liquid is reduced in comparison to jets having larger liquid drops. Since the binding of the fraction that can enter the alveoli is bound by the first jet, the fine dust burden for the operator is reduced during the processing of the workpiece. Bound fine dust particles are not inhaled by the operator and are not deposited in the alveoli.
In a preferred embodiment, the first spraying direction is arranged at an angle of up to ±10° relative to a plane perpendicular to the processing plane and parallel to the axis of rotation. In this context, the first spraying direction is especially preferably arranged essentially parallel to the axis of rotation and thus perpendicular to the processing tool. Thanks to the virtually perpendicular arrangement of the first jet relative to the processing tool, the fraction of bound fine dust particles, particularly the fraction that can enter the alveoli, is higher than with jets that are oriented, for instance, perpendicular to the workpiece that is to be processed.
In a preferred embodiment, the spraying device has at least a second spray nozzle that produces a second jet along a second spraying direction, whereby the second spray nozzle is arranged on the side of the processing tool that enters the workpiece (entry side). The second spray nozzle can be advantageously used for diamond-tipped processing tools, for example, diamond saw blades or diamond grinding discs. The processing speed as well as the service life of diamond-tipped processing tools are increased by cooling the processing tool. Since the second spray nozzle is arranged on the entry side, the processing tool is cooled and lubricated before the processing tool enters the workpiece. Part of the liquid is drawn into the slit together with the processing tool and transported to the processing site of the processing tool. Cooling and lubricating the processing tool in the vicinity of the processing site serve to enhance the processing and the processing speed.
In addition to cooling and lubricating the processing tool, the second spray nozzle can promote the binding of the dust. If the liquid drops in the second jet are of an appropriate size, then fine dust particles that were not bound by the first jet can be bound by the second jet at the entry side. Since the processing tool is rotated around the axis of rotation, at least some of the fine dust particles that were not bound by the first jet are conveyed via the protective hood to the entry side. The second jet binds additional fine dust particles and reduces the burden caused to the operator by fine dust particles.
Preferably, the pump is connected to the second spray nozzle via the second connection line and it generates a minimum pressure of 5 bar in the second connection line. Especially preferably, the pump generates a pressure between 5 bar and 8 bar in the second connection line.
Particularly preferably, the throughput rate of the second spray nozzle is between 13 and 17 liters per hour. The arrangement and the orientation of the second spray nozzle and a minimum pressure of 5 bar in the second connection line leading to the second spray nozzle markedly reduce the amount of liquid needed for cooling and lubricating the processing tool.
Especially preferably, the second spray nozzle produces the second jet with liquid drops measuring between 40 μm and 150 μm. Small liquid drops measuring between 40 μm and 150 μm have the advantage that, when the cold liquid drops strike the heated processing tool, they evaporate and the resulting evaporation cold intensifies the cooling of the processing tool. Owing to the evaporation cold, along with the increased cooling effect, the amount of liquid needed is reduced in comparison to spray nozzles that generate larger liquid drops. Liquid drops measuring between 40 μm and 150 μm in the second jet are suitable not only to cool and lubricate the processing tool but also to bind fine dust particles that were not bound by the first jet. Some of the fine dust particles that were not bound by the first jet are conveyed to the entry side by the rotation of the processing tool around the axis of rotation, and are then bound by the second jet. The second jet captures additional fine dust particles, thus further reducing the fine dust burden for the operator.
Preferably, the second spraying direction is arranged at an angle of up to ±10° relative to a plane perpendicular to the processing plane and parallel to the axis of rotation. In this context, the second spraying direction is especially preferably arranged essentially parallel to the axis of rotation and thus perpendicular to the processing tool. The virtually perpendicular orientation of the second jet relative to the processing tool ensures that the liquid drops strike the processing tool and that the processing tool is thoroughly cooled.
In a preferred embodiment, the pump is driven by at least one drive component of the drive means. Driving the pump via the drive means has the advantage that there is no need for separate drive components for the pump. Dispensing with an electric drive component—whose installation would require an electrician—simplifies the retooling of the spray device in a power tool. The spraying device can be installed or replaced by an operator without any special skills
Especially preferably, the pump is driven by means of a crankshaft that is non-rotatably joined to a drive motor. Implementing the drive via the crankshaft has the advantage that driving the pump and thus feeding the liquid to the spray nozzles are coupled to the drive of the processing tool. Between the drive motor and the crankshaft, there is a centrifugal clutch that only transmits the driving motion of the drive motor to the crankshaft once a limit rotational speed has been exceeded. Liquid is fed to the spray nozzles whenever the processing tool is rotating, and this is interrupted when the processing tool is not being driven. Coupling the liquid feed to the drive of the processing tool reduces the amount of liquid needed since no unnecessary liquid is sprayed. On the other hand, it is ensured that liquid is sprayed during processing in order to bind dust and/or to cool and lubricate the processing tool.
Especially preferably, a transmission unit is arranged between the pump and the crankshaft. In this context, the transmission unit is especially preferably configured as a planetary gear train with a transmission ratio between 2 to 1 and 4 to 1. The transmission unit between the pump and the crankshaft reduces the high rotational speeds of the drive motor to a lower speed range that is permissible for the pump. The transmission unit is necessary in order to prevent damage to the pump due to the high rotational speeds of the drive motor. A planetary gear train is particularly well-suited to reduce the rotational speed as well as to adapt the transmission ratio of the planetary gear train to the rotational speeds of the drive means and to the maximum rotational speeds of the pump.
In a preferred embodiment, the pump and the transmission unit are fastened as a module to a mounting plate. Owing to this configuration as a module that can be fastened to a mounting plate that is provided, the pump and the transmission unit can be easily replaced. Moreover, a power tool can be retrofitted with the module as an accessory. The mounting plate is provided as a standard option with every power tool, so that each power tool lends itself to being retrofitted. Since the pump is driven via the drive means and since there is no need for an electrician to install the pump, the module with the pump and the transmission unit can be installed by the operator. The mounting plate simplifies the retrofitting for the operator.
Embodiments of the invention will be described below with reference to the drawing. The drawing does not necessarily depict the embodiments true-to-scale, but rather, the drawing—where necessary for the sake of elucidation—is shown in schematic and/or slightly distorted form. Regarding any additions to the teaching that can be gleaned directly from the drawing, reference is hereby made to the pertinent state of the art. Here, it should be kept in mind that many modifications and changes relating to the shape and to details of an embodiment can be made without departing from the general idea of the invention. The features of the invention disclosed in the description, in the drawing as well as in the claims can be essential for the refinement of the invention, either individually or in any desired combination. Moreover, all combinations of at least two of the features disclosed in the description, in the drawing and/or in the claims fall within the scope of the invention. The general idea of the invention is not limited to the exact form or detail of the preferred embodiment shown and described below nor is it limited to a subject matter that would be limited in comparison to the subject matter put forward in the claims. At given rated ranges, values that fall within the specified limits are also disclosed as limit values and can be used and claimed as desired. For the sake of clarity, identical or similar parts or else parts with an identical or similar function are designated by the same reference numerals below.
The following is shown:
For the operation of the disc grinder 10, a first handle 22 is provided which has an actuator 23 and which is configured as a rear handle in the embodiment shown in
When a workpiece 26 is processed by means of the handheld disc grinder 10, the disc grinder 10 is moved by the operator along a feeding direction 27 over the workpiece 26 that is to be processed. Due to the rotation of the grinding disc 12 in the rotational direction 14 around the axis of rotation 15 and due to the movement of the disc grinder 10 along the feeding direction 27, a slit 28 is created in the workpiece 26. The grinding disc 12 digs into the workpiece 26 on an entry side 31 and exits the workpiece 26 on an exit side 32. In the case of the power tool 10 shown in
The spraying device 11 serves, among other things, to bind dust that is generated during the processing of the workpiece 26 using the disc grinder 10. In this context, the spraying device 11 is configured in such a way that the fine dust concentration, especially the fraction that can enter the alveoli, is reduced. The fraction of the fine dust that can enter the alveoli is particularly harmful to health since the minute fine dust particles of the fraction that can enter the alveoli pass through the upper respiratory tract and reach the air vesicles in the lung (alveoli). The spraying device 11 comprises a reservoir 34 filled with a liquid 33, a supply line 35, a pump 36 and a first spray nozzle 37 that is connected to the pump 36 via a first connection line 38. The pump 36 is configured in the form of a diaphragm pump. A diaphragm pump is impervious to dirty water and is thus well-suited for use in gasoline-powered disc grinders that become very soiled during operation. Moreover, a diaphragm pump does not run dry and it is impervious to excess pressure from an external line system.
When it comes to diamond-tipped processing tools, for example, in the form of diamond saw blades or diamond grinding discs, it is advantageous to cool the processing tool 12, which is done by supplying a cooling liquid. Cooling improves the processing and prolongs the service life of the processing tool. When diamond-tipped processing tools are employed, the spraying device 11 has a second spray nozzle 39 to cool the processing tool 12. The second spray nozzle 39 is connected to the pump 36 via a second connection line 41. If necessary, the liquid 33 can be cleaned by means of one or more filter elements 42, whereby the filter elements 42 can be provided on the reservoir 34, in the supply line 35 and/or in the pump 36.
The requirements made of the first spray nozzle 37 differ from the requirements made of the second spray nozzle 39. The first spray nozzle 37 serves to bind the dust generated during grinding, while the second spray nozzle 39 serves to cool and lubricate the grinding disc 12 during grinding. Moreover, the first and second spray nozzles 37, 39 are installed on different sides of the grinding disc 12. The first spray nozzle 37 is arranged on the exit side 32 while the second spray nozzle 39 is arranged on the entry side 31 of the grinding disc 12. The arrangement of the first spray nozzle 37 on the exit side 32 has the advantage that the dust can be bound directly at the site where it is generated and the dust can be largely prevented from spreading. Owing to the arrangement of the second spray nozzle 39 on the entry side 31, the grinding disc 12 is cooled and lubricated before it enters the workpiece 26. Some of the liquid 33 is drawn into the slit 28 along with the grinding disc 12 and then transported to the processing site of the grinding disc 12. The cooling and lubrication of the grinding disc 12 in the area of the processing site improve the processing and increase the grinding speed.
The first and second spray nozzles 37, 39, as shown in
The liquid 33 is conveyed from the pump 36 via the connection lines 38A, 38B, 41A, 41B to the first and second spray nozzles 37A, 37B, 39A, 39B. The first spray nozzles 37A, 37B each generate a first jet 45A, 45B, which spreads out along a first spraying direction 46A, 46B, while the second spray nozzles 39A, 39B each generate a second jet 47A, 47B, which spreads out along a second spraying direction 48A, 48B. The first spraying directions 46A, 46B are arranged at angles αA, αB relative to the axis of rotation 15 or at an angle of 90°-αA, 90°-αB relative to the grinding plane 44 that runs perpendicular to the axis of rotation 15. The second spraying directions 48A, 48B are arranged at angles βA, βB relative to the axis of rotation 15 or at an angle of 90°-βA, 90°-βB relative to the grinding plane 44. In the embodiment shown in
The first jets 45A, 45B bind the dust generated during the grinding. In order to bind the fine dust particles, especially the fraction of the fine dust that can enter the alveoli, by means of the first jets 45A, 45B, first spray nozzles 37A, 37B are used which create liquid drops measuring between 40 μm and 150 μm. In this process, the size of the liquid drops is set via the nozzle geometry of the first spray nozzles 37A, 37B, especially the diameter, and via the pressure in the first connection lines 38A, 38B. The pressure generated by the pump 36 is at least 5 bar. This minimum pressure is necessary in order to create liquid drops of the desired size. The first spray nozzles 37A, 37B are configured as full-cone nozzles which generate the first jets 45A, 45B at angles γA, γB approximately 75°. A large jet angle has the advantage that the first jets 45A, 45B strike a large volume area and can bind many dust particles.
The second jets 47A, 47B cool the grinding disc 12 during the grinding. In order to cool the grinding disc 12, the second spray nozzles 39A, 39B direct the second jets 47A, 47B along the second spraying direction 48A, 48B onto the grinding disc 12, whereby the second spraying direction 48A, 48B is directed at the grinding disc 12 essentially parallel to the grinding plane 44. In order to properly cool and lubricate the grinding disc 12, second spray nozzles 39A, 39B are employed which, like the first spray nozzles 37A, 37B, create liquid drops measuring between 40 μm and 150 μm. Small liquid drops ensure that, when the cold liquid drops strike the heated grinding disc 12, they evaporate and the resulting evaporation cold intensifies the cooling of the grinding disc 12. Owing to the evaporation cold, along with the increased cooling effect, the amount of liquid needed is reduced in comparison to spray nozzles that generate larger liquid drops. The second spray nozzles 39A, 39B are configured as full-cone nozzles which generate second jets 47A, 47B at angles δA, δB of approximately 75°. A large jet angle has the advantage that the second jets 47A, 47B, which are directed onto the grinding disc 12, strike and cool a surface area of the grinding disc 12. The more effectively the grinding disc 12 is cooled in the area of the processing site, the higher the grinding speed of the disc grinder 10.
For the second jets 47A, 47B, there is a need for a throughput rate that is higher than that of the first jets 45A, 45B.
The pump 36 is driven by the crankshaft 53. Due to the high rotational speeds of the drive motor 17, the pump 36 is not arranged directly on the crankshaft 53, but rather, a transmission unit 57 is installed between the crankshaft 53 and the pump 36. In the embodiment shown in
The pump 36 is switched on and off by means of the centrifugal clutch 52 that actuates the drive of the grinding disc 12. The driving movement of the drive motor 17 is only transmitted via the centrifugal clutch 52 to the grinding disc 12 once a limit rotational speed has been exceeded. The drive of the pump 36 feeds liquid to the spray nozzles 37A, 37B, 39A, 39B only when the grinding disc 12 is being driven around its axis of rotation 15. As soon as the limit rotational speed of the centrifugal clutch 52 has been exceeded, the centrifugal clutch 52 transmits the drive force of the drive motor 17 via the belt drive 19 to the grinding disc 12 and via the planetary gear train 57 to the pump 36. Consequently, the drive of the pump 36 and thus the liquid feed to the spray nozzles 37A, 37B, 39A, 39B are coupled to the drive of the grinding disc 12.
The pump 36 is connected via a connection line 72A, 72B to the second spray nozzle 39A, 39B that is connected via an extension line 73A, 73B to the first spray nozzle 37A, 37B. The liquid 33 is transported via the connection line 72A, 72B to the second spray nozzle 39A, 39B and some of the transported liquid 33 is transported from the second spray nozzle 39A, 39B via the extension line 73A, 73B to the spray nozzle 37A, 37B.
If long lines are being used, a pressure drop that increases with the length of the line can occur. For this reason, in the case of the spraying device 71, the liquid 33 is first conveyed via the connection lines 72A, 72B to the second spray nozzles 39A, 39B, which have a higher throughput rate than the first spray nozzles 37A, 37B. Subsequently, the liquid is conveyed via the extension lines 73A, 73B to the first spray nozzles 37A, 37B. If the pressure in the lines between the pump 36 and the spray nozzles 37A, 37B, 39A, 39B is virtually constant, then the sequence in which the liquid 33 is fed to the spray nozzles 37A, 37B, 39A, 39B is of secondary importance. In this case, the pump 36 can at first be connected via connection lines to the first spray nozzles 37A, 37B, and subsequently, extension lines can connect the first spray nozzles 37A, 37B to the second spray nozzles 39A, 39B.
The separate supply of the first and second spray nozzles 37A, 37B, 39A, 39B is advantageous whenever different requirements are being made of the first and second spray nozzles 37A, 37B, 39A, 39B. Instead of two parallel connection lines 86A, 86B which connect the first pump 83 to the first spray nozzles 37A, 37B, a connection line and an extension line can be provided, whereby the connection line connects one of the first spray nozzles 37A, 37B to the first pump 83, and the extension line connects the first spray nozzles 37A, 37B to each other. Analogously, the second spray nozzles 39A, 39B can be connected via a connection line and via an extension line to the second pump 85. Another alternative consists of using Y-lines that connect the first pump 83 to the first spray nozzles 37A, 37B and the second pump 85 to the second spray nozzles 39A, 39B.
In an alternative embodiment to
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2012 221 273.6 | Nov 2012 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2013/074148 | 11/19/2013 | WO | 00 |
