Title of Invention

" A COMPRESSOR SYSTEM ADAPTABLE TO SUPPLY COMPRESSED AIR FOR PNEUMATIC DRILLING OF SOIL AND/ OR ROCK"

Abstract

Compressor installation and control system applied thereby. Compression installation comprising a compressor element (2) which is driven by a motor (4) , provided with an air inlet (5) with a controlled throttle valve (9) and a compressed air outlet (6) which is connected to a compressed air receiver (7), whereby the motor (4) is provided with a control system (10) for the rotational speed which is connected, via a first control line (15) and a regulating valve (16) for supplying a first control pressure (Prl), to the compressed air receiver (7), whereby the compressed air receiver (7) is connected to the control system (10) for supplying a second control pressure (Pr2) via a second control line (21), and whereby the motor (4) is controlled on the basis of the first and second control pressure (Prl and Pr2). Figure 1.

Full Text

1 Compressor installation and control system applied thereby. The present invention concerns a compressor installation and a control system applied thereby. In particular, the invention concerns a compressor installation of the type provided with a compressor element driven by a motor which is designed to supply compressed air to a drilling gear for carrying out soil drillings and/or rock drillings by means of pneumatic hammer drillings, whereby the above-mentioned compressor element is provided with an air inlet in which is provided a pneumatically controlled throttle valve and a compressed air outlet which is connected to a compressed air receiver, whereby the above-mentioned motor is provided with a pneumatic control system to control the rotational speed and whereby said control system as well as the above-mentioned throttle valve are connected together, via a first control line and a regulating valve for supplying a first control pressure to said control line, to the above-mentioned compressed air receiver. In the known compressor installations, the above-mentioned motor consists of a combustion engine whose fuel supply is connected to the above-mentioned control system via a mechanical coupling, made in the shape of a pneumatic valve which consists of a single-acting compressed air cylinder which is controlled by the above-mentioned control pressure. 2 While using the drilling gear which is connected to such known compressor installation, three different modes are passed through, namely drilling, washing and idling. The technique applied with such a drilling gear is known as hammer drilling and implies that, while drilling, a pulsating hammer motion is exerted on the drill chuck. To this end, the drilling gear requires that compressed air is supplied during the drilling at a certain set pressure value and flow rate, whereby the motor of the compressor installation rotates at an average rotational speed. The washing with compressed air aims to discharge drilling waste from the borehole, without further deepening the borehole, and this is done at a relatively low compressed air pressure and a high compressed air flow, such that the motor of the compressor installation has to rotate practically at its maximum rotational speed. Finally, during idling, the drill can be replaced for example, or the drill can be extended by applying extension pieces, such that during these operations, no compressed air supply is required and the motor of the compressor installation can rotate at minimal speed. While the drilling gear is operational, there will be an alternation of drilling and washing, such that the motor of the compressor installation will have to keep switching between two different points of operation, which is 3 realised by means of the above-mentioned control system, as a function of the load. A disadvantage of such a known compressor installation is that during the transition from washing to drilling, the operating pressure increases rapidly from for example 16 to almost 25 bar, while the motor is still turning at its maximum rotational speed. At that moment, the motor is fully loaded, as a result of which it will decelerate under the influence of the load, which has a negative influence on the life of the motor. Another disadvantage of the known compressor installations is that, as soon as the drilling equipment has worn out and/or when leaks occur in the drilling system, the compressor installation will try to compensate this by increasing the engine speed so as to maintain the operating pressure at the value set in the regulating valve. It is clear that, due to this increase of the rotational speed of the motor, the load of the motor increases, which is also disadvantageous to the life of this motor. It is easy to get round these disadvantages by installing a powerful motor with sufficient excess power. However, this is less favourable from an economical point of view, due to the higher cost price of the motor, the higher fuel consumption and the possibly larger and heavier design. 4 The present invention aims to remedy one or several of the above-mentioned and other disadvantages. To this end, the present invention concerns a compressor installation of the above-mentioned type, whereby the compressed air receiver is also connected via a second control line to the above-mentioned control system for supplying a second control pressure, whereby a switching device with an adjustable pressure and hence a reversible shut-off valve are provided in the second control line and whereby the rotational speed of the above-mentioned motor is adjusted on the basis of the above-mentioned first and second control pressure as a function of the operating pressure in the above-mentioned compressed air receiver. An advantage of such a compressor installation according to the invention is that the motor speed can be adjusted on the basis of the above-mentioned first control value between a minimum value for idling and an average value for drilling, and that it can be switched on the basis of the above-mentioned second control value between the above-mentioned average value and a maximum rotational speed for washing, as a result of which a controlled deceleration of the motor speed can be realised during the transition from washing to drilling, without thereby fully loading the motor. Another advantage of such a compressor installation according to the invention is that, as soon as the drilling equipment wears out and/or as soon as leaks occur in the drilling system, the motor can keep on turning at a 5 constant rotational speed until the operating pressure has dropped to a pressure value set in the switching device, such that the life of the above-mentioned motor can be considerably extended. The present invention also concerns a control system which can be applied in a compressor installation of the above-mentioned type, whereby this control system is provided with two compressed air connections, a connection for the above-mentioned first control line and a connection for a second control line respectively, which is also connected to the above-mentioned compressed air receiver and in which are provided a switching device with an adjustable pressure and hence a reversible shut-off valve, and whereby this control system regulates the speed of the motor on the basis of the first and second control pressure. In a preferred embodiment, the control system is made in the shape of a pneumatically controlled valve with two connections, a connection for the above-mentioned first control line and a connection for the above-mentioned second control line respectively, whereby this pneumatic valve is preferably provided with a piston body which is connected via a mechanical coupling to the fuel supply of the above-mentioned motor and which is provided in a housing in a sliding manner, and against which a spring pushes on either side which determines a rest position of the piston body, whereby the fuel supply is adjusted such that the motor turns at an average rotational speed (Nmid) which is lower than the maximum rotational speed (Nmax) of this motor. 6 In order to better explain the characteristics of the present invention, the following preferred embodiments of an improved control device according to the invention are given as an example only without being limitative in any way, as well as a control system applied thereby, with reference to the accompanying figures in which: figure 1 schematically represents an existing compressor installation; figure 2 represents the control characteristics of a compressor installation according to figure 1; figure 3 represents a possible torque/rotational speed characteristic of the motor in a compressor installation according to figure 1; figure 4 represents a compressor installation according to the invention; figure 5 represents the control characteristics of a compressor installation according to figure 4. Figure 1 represents an existing compressor installation 1 which is made as a mobile screw-type compressor installation which is in this case provided with an oil-injected compressor element 2 which is driven by a thermal motor via a transmission 3. The above-mentioned compressor element 2 is provided with an air inlet 5 for drawing in a gas to be compressed, and with a compressed air outlet 6 which is connected to a compressed air receiver 7 of a known type. 7 Via a compressed air line 8 which is connected to the above-mentioned compressed air receiver 7, compressed gas can be taken at a specific operating pressure Pw by compressed air users, for example to drive a drilling gear which is not represented in the figures. In order to control the flow through the screw-type compressor 1, a pneumatic throttle valve 9 of a known type is provided at the air inlet of the compressor element 2. Further, the compressor installation 1 comprises a pneumatic control system 10 to regulate the rotational speed of the above-mentioned motor 4, which control system 10 is made in the shape of a pneumatic valve 11 which consists of a single-acting compressed air cylinder which is connected in the known manner via a mechanical coupling 12 to a fuel supply 13 of the above-mentioned thermal motor 4 and which is pushed in a rest position by means of a spring 14, whereby the fuel supply 13 is adjusted such that the motor 4 turns at its maximum rotational speed Nmax. The above-mentioned control system 10 and the above-mentioned throttle valve 9 are connected together, via a control line 15 and a control valve 16 in this control line 15, to the above-mentioned compressed air receiver 7. As is known, the above-mentioned regulating valve 16 is provided with an input 17 which is directly connected to the compressed air receiver 7, whereby, thanks to this regulating valve 16, a control pressure Pr is supplied to an output 18 of said regulating valve 16 which is directly 8 connected to the above-mentioned throttle valve 9 and the control system 10, and whereby the above-mentioned control pressure Pr is a function of the operating pressure Pw at the above-mentioned input 17 of the regulating valve 16. The above-mentioned regulating valve 16 is bridged in the known manner by a bypass 19 in which is provided a load valve 2 0 which is made for example in the shape of a usually closed valve which can be electromagnetically opened or closed. The use and working of such a known compressor installation 1 is well known and as follows. Depending on the type of drilling gear that needs to be driven with the compressor installation 1 and, depending on the condition of the medium to be drilled, such as for example the hardness of the medium, a threshold value A must be set for the operating pressure Pw in the regulating valve 16. As is known, as soon as the operating pressure Pw has exceeded this threshold value A, a control pressure Prl will be built up at the output 18 of the regulating valve 16 which increases in proportion to the increasing operating pressure Pw. As is schematically represented by means of the curve N in figure 2, the pneumatic valve 11 is situated, at an operating pressure Pw which is lower than the above-mentioned value A, in such a position that the fuel supply 9 to the motor 4 is entirely open and the motor 4 consequently turns at its maximum rotational speed Nmax. In practice, this operational condition will occur while the bore hole is being washed by means of the drilling gear that is driven by the compressor installation 1, whereby a major compressed air flow is supplied. As soon as the operating pressure Pw rises above the above-mentioned threshold value A, the above-mentioned control pressure Prl is built up, and the pneumatic valve 11 is controlled against the spring force, such that the motor speed drops in proportion to the rising control pressure Prl. As soon as the operating pressure Pw has reached a specific value B which is larger than the above-mentioned threshold value A, the pneumatic valve 11 will be such that the motor speed becomes minimal. Via the above-mentioned control line 15, the control pressure Prl is sent from the above-mentioned outlet 18 of the regulating valve 16 to the above-mentioned throttle valve 9 on the one hand, and to the pneumatic valve 11 on the other hand. When the value of the pressure in the compressed air receiver 7 increases further, and thus the value of the operating pressure Pw increases further as well, the throttle valve 9, as is schematically represented by the curve P which represents the inlet pressure Pi of the 10 compressor element 2 as a function of the operating pressure Pw, will start to throttle the air drawn in by the compressor element 2, such that the inlet pressure Pi of the compressor element 2 will decrease in proportion to the increasing operating pressure Pw until the latter reaches a value C. When the throttle valve 9 is entirely closed and the rotational speed Nmin of the motor 4 is minimal, the drilling gear is in a idling mode, whereby the drilling tools can be replaced for example. Depending on the selection of the motor 4, one can make sure that the point of operation D is situated at an average rotational speed Nmid while drilling, as represented in figure 3, between the point of operation E during idling with a minimal rotational speed Nmin and the point of operation F for washing at a maximum rotational speed Nmax. A disadvantage of such a known compressor installation 1 is that, during a transition from the point of operation F for washing to the point of operation D for drilling, the operating pressure Pw rises fast from for example 16 to almost 25 bar, whereas the motor 4 is still turning at its maximum rotational speed Nmax. At that moment, the motor 4 is fully loaded, as a result of which it will slow down under the influence of the load, which has a negative influence on the life of the motor 4. 11 A compressor installation 1 according to the present invention has an almost identical construction as the above-described known compressor installation 1, but, as represented in figure 4, apart from the above-mentioned control line 15 which now forms a first control line, it also has a second control line 21 which connects the above-mentioned compressed air receiver 7 to the above-mentioned control system 10. In this second control line 21 is provided a switching device 22 with an adjustable pressure value G and hence a reversible shut-off valve 23. The above-mentioned control system 10 is in this case made in the form of a double-acting pneumatic valve 24 which is provided with two connections, a first connection 25 for the above-mentioned first control line 15 and a second connection 26 for the above-mentioned second control line 21 respectively. By means of two springs 27 and 28, which are provided on either side of a piston body 29 of the valve 24 which can slide in a housing, this valve 24 is kept in a central position when in rest. The working of a compressor installation 1 according to the invention is very simple and as follows. The regulating valve 16, the throttle valve 9 and the load valve 2 0 have the same function as in the known compressor installations. 12 As is represented by the curve N in figure 5, the above-mentioned switching device 22 is in an open position and the shut-off valve 23 is open as long as the operating pressure Pw is smaller than the above-mentioned set pressure value G, such that between this shut-off valve 2 3 and the valve 24 is built up a second control pressure Pr2 whose value depends on the throttle adjustment in said shut-off valve 23. Under the influence of the second control pressure Pr2, the piston body 29 of the valve 24 is pushed into a position, against the force of the spring 27, in which the rotational speed of the motor 4 is maximal. This mode of operation will occur during the washing with the drilling gear, whereby a large flow of compressed air is required and whereby the operating pressure Pw is low. When the pressure in the compressed air receiver 7 rises above the set value G, the switching device 22 and thus also the shut-off valve 23 are shut off, such that the second control pressure Pr2 flows away via a blow-off valve and the valve 24 goes back into its position of rest, whereby the motor speed assumes an average value Nmid. In this position of equilibrium, which is created during the drilling, the compressor installation 1 has to deliver a smaller flow rate than during the washing. 13 When the operating pressure Pw further increases above a set value H, the first control pressure Prl is built up, by-means of the regulating valve 16, which will push the piston body 29 of the valve 24 in the opposite sense of the control pressure Pr2, against the spring force of spring 28, such that the motor speed decreases in proportion to the increase of said operating pressure Pw. As soon as the operating pressure Pw has reached a value I, the rotational speed of the motor 4 will remain minimal, as is the case in the known compressor installation, whereas, as represented by means of the curve P in figure 5, the inlet pressure Pi of the compressor element 2 decreases in proportion to the increasing operating pressure Pw up to the point of operation J, whereby the drilling gear is situated in an idling mode. As is further clear from the curve N in figure 5, the switching device 22 in this case has a built-in hysteresis function, such that we can prevent the valve 24 from continuously switching between the position of rest with an average rotational speed Nmid and the extreme position with a maximum rotational speed Nmax when the operating pressure Pw is exactly equal to the set value G. As these control pressures Prl and Pr2 are taken into account to control the motor 4, a controlled deceleration of the motor 4 becomes possible with a compressor installation 1 and control system 10 according to the invention when switching from washing to drilling, as a 14 result of which the motor 4 is not maximally loaded and its life is extended. Preferably, the above-mentioned set value G can be adjusted on the basis of the working conditions, such as the depth of the borehole or the amount of dirt and/or liquid in this borehole. In a preferred embodiment of compressor installation 1, the valve 24 is provided with mechanical positioning means, not represented in the figures, which make it possible to place this valve 24 in a correct manner on the motor 4, such that the position of rest of this valve 24 provides the required average rotational speed Nmid. In the given example, the above-mentioned pneumatic control system is made in the form of a double-acting pneumatic valve 24, but the invention is not restricted as such. Indeed, the above-mentioned control system 10 can also be made in the form of a pressure sensor which can measure the above-mentioned first and second control value Prl and Pr2 and generates an electric signal on the basis thereof which is transmitted to an electronic control module for controlling the motor 4. The above-mentioned electronic control module transforms the above-mentioned electric signal, coming from the pressure sensor, into another electric signal forming the set desired value of the motor's rotational speed. 15 A software hysteresis function can in this case be provided to prevent the continuous switching between the maximum rotational speed Nmax and the motor's average rotational speed Nmid. The present invention is by no means restricted to the embodiments given as an example and represented in the accompanying drawings; on the contrary, such an improved compressor installation according to the invention and a control system applied thereby can be made in all sorts of shapes and dimensions while still remaining within the scope of the invention. 16 Claims. 1.- Compressor installation which is provided with a compressor element (2) driven by a motor (4) which is designed to supply compressed air to a drilling gear for carrying out soil drillings and/or rock drillings by means of pneumatic hammer drilling, whereby the above-mentioned compressor element (2) is provided with an air inlet (5) in which is provided a pneumatically controlled throttle valve (9) and a compressed air outlet (6) which is connected to a compressed air receiver (7) , whereby the above-mentioned motor (4) is provided with a pneumatic control system (10) to control the rotational speed and whereby said control system (10) as well as the above-mentioned throttle valve (9) are connected together, via a first control line (15) and a regulating valve (16) for supplying a first control pressure (Prl) to said control line (15) , to the above-mentioned compressed air receiver (7) , characterised in that the compressed air receiver (7) is also connected via a second control line (21) to the above-mentioned control system (10) so as to deliver a second control pressure (Pr2), whereby a switching device (22) with an adjustable pressure (G) and hence a reversible shut-off valve (23) are provided in the second control line (21) , and in that the rotational speed of the above-mentioned motor (4) is adjusted on the basis of the above-mentioned first and second control pressure (Prl and Pr2) as a function of an operating pressure (Pw) in the above-mentioned compressed air receiver (7). 17 2.- Compressor installation according to claim 1, characterised in that the above-mentioned pneumatic control system (10) is made in the form of a pneumatically-controlled valve (24) with two connections (25 and 26) , a connection (25) for the above-mentioned first control line (15) and a connection (26) for the above-mentioned second control line (21) respectively. 3.- Compressor installation according to claim 2, characterised in that the above-mentioned pneumatic valve (24) is provided with a piston body (29) which is provided in a sliding manner in a housing and against which a spring (27, 28 respectively) pushes on either side, pushing the piston body (29) in a rest position. 4.- Compressor installation according to claim 3, characterised in that the above-mentioned motor (4) is a thermal motor, in that the above-mentioned piston body (29) is connected, via a mechanical coupling (12) , to a fuel supply (13) of the above-mentioned motor (4) and whereby the above-mentioned rest position of the above-mentioned piston body (29) controls the fuel supply (13) such that the motor (4) turns at an average rotational speed (Nmid) which is lower than the maximum rotational speed (Nmax) of this motor (4). 5.- Compressor installation according to claim 4, characterised in that the above-mentioned pneumatic control system (10) is such that between a certain value (H) of the operating pressure (Pw) and a higher value (I) thereof, the 18 rotational speed of the motor (4) decreases in proportion to an increase of this operating pressure (Pw). 6.- Compressor installation according to claim 1, characterised in that the above-mentioned shut-off valve (23) is provided with a throttle, such that in an open position, the incoming compressed air is throttled up to the above-mentioned second control pressure (Pr2). 7.- Compressor installation according to claim 1, characterised in that the above-mentioned switching device (22) is made such that, when the operating pressure (Pw) rises above the above-mentioned predetermined value (G) , it will close the above-mentioned shut-off valve (23). 8.- Compressor installation according to claim 1, characterised in that the above-mentioned switching device (22) is provided with a hysteresis function to prevent the continuous opening and closing of the shut-off valve (23) when the operating pressure (Pw) is practically equal to the above-mentioned adjustable pressure (G). 9.- Compressor installation according to claim 1, characterised in that the above-mentioned pneumatic control system (10) is made in the form of a pressure sensor which is connected to an electronic control module which regulates the rotational speed of the above-mentioned motor (4) . 10.- Compressor installation according to claim 9, characterised in that the above-mentioned electronic 19 control module is provided with a hysteresis function to prevent the continuous opening and closing of the shut-off valve (23) when the operating pressure (Pw) is practically equal to the above-mentioned adjustable pressure (G) . 11.- Control system which can be applied in a compressor installation (1) which is provided with a compressor element (2) driven by a motor (4) which is designed to supply compressed air to a drilling gear for carrying out soil drillings and/or rock drillings by means of pneumatic hammer drilling, whereby the above-mentioned compressor element (2) is provided with an air inlet (5) in which is provided a pneumatically controlled throttle valve (9) and a compressed air outlet (6) which is connected to a compressed air receiver (7) , whereby the rotational speed of the above-mentioned motor (4) is controlled by said control system, and whereby this control system (10) as well as the above-mentioned throttle valve (9) are connected together, via a first control line (15) and a regulating valve (16) for supplying a first control pressure (Prl) to said control line (15) , to the above-mentioned compressed air receiver (7) , characterised in that this control system (10) is provided with two compressed air connections (25 and 26) , a connection (25) for the above-mentioned first control line (15) and a connection (26) for a second control line (21) respectively, which is also connected to the above-mentioned compressed air receiver (7) and in which are provided a switching device (22) with an adjustable pressure (G) and hence a reversible shut-off valve (23) , and in that the above-mentioned control system (10) adjusts 20 the speed of the motor (4) on the basis of the first and second control pressure (Prl and Pr2). 12.- Control system according to claim 11, characterised in that it is made in the form of a pneumatically controlled valve (24) with two connections (25 and 26) , a connection (25) for the above-mentioned first control line (15) and a connection (26) for the above-mentioned second control line (21) respectively. 13.- Control system according to claim 11, characterised in that the above-mentioned pneumatic valve (24) is provided with a piston body (29) which is provided in a sliding manner in a housing and against which a spring (27, 2 8 respectively) pushes on either side, determining a position of rest of the piston body (29) whereby the fuel supply (13) is adjusted such that the motor (4) turns at an average rotational speed (Nmid) which is lower than the maximum rotational speed (Nmax) of this motor (4). 21 Compressor installation and control system applied thereby. Compression installation comprising a compressor element (2) which is driven by a motor (4) , provided with an air inlet (5) with a controlled throttle valve (9) and a compressed air outlet (6) which is connected to a compressed air receiver (7), whereby the motor (4) is provided with a control system (10) for the rotational speed which is connected, via a first control line (15) and a regulating valve (16) for supplying a first control pressure (Prl), to the compressed air receiver (7), whereby the compressed air receiver (7) is connected to the control system (10) for supplying a second control pressure (Pr2) via a second control line (21), and whereby the motor (4) is controlled on the basis of the first and second control pressure (Prl and Pr2). Figure 1. FORM -2 THE PATENTS ACT, 1970 (39 OF .1970) & The Patents Rules, 2003 COMPLETE SPECIFICATION (See section 10 and rule 13) 1. Title of the Invention : COMPRESSOR INSTALLATION .AND CONTROL SYSTEM APPLIED THEREBY 2, Appiicant(s) Name. Nationality & Address ; ATLAS COPCO AIRPOWER, NAAMLOZE VENNOOTSCHAP Boomseststeenweg 957, B-2610 Wilrijk Belgium. 3. Preamble to the description : COMPLETE : The following specification particularly describes the invention and the manner in which is to be performed

Documents:

00311-kol-2006 abstract.pdf

00311-kol-2006 claims.pdf

00311-kol-2006 correspondence others.pdf

00311-kol-2006 description(complete).pdf

00311-kol-2006 drawings.pdf

00311-kol-2006 form-1.pdf

00311-kol-2006 form-2.pdf

00311-kol-2006 form-3.pdf

00311-kol-2006 form-5.pdf

00311-kol-2006 others.pdf

00311-kol-2006 priority document.pdf

00311-kol-2006-correspondence others-1.1.pdf

00311-kol-2006-form-26.pdf

311-KOL-2006-(10-04-2012)-ABSTRACT.pdf

311-KOL-2006-(10-04-2012)-CLAIMS.pdf

311-KOL-2006-(10-04-2012)-DESCRIPTION (COMPLETE).pdf

311-KOL-2006-(10-04-2012)-EXAMINATION REPORT REPLY RECEIVED.pdf

311-KOL-2006-(10-04-2012)-FORM-1.pdf

311-KOL-2006-(10-04-2012)-FORM-2.pdf

311-KOL-2006-(10-04-2012)-FORM-3.pdf

311-KOL-2006-(10-04-2012)-FORM-5.pdf

311-KOL-2006-(10-04-2012)-OTHERS.pdf

311-KOL-2006-(14-08-2012)-CORRESPONDENCE.pdf

311-KOL-2006-CORRESPONDENCE.pdf

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