PUMPING MACHINE OR COMPRESSOR AND SYSTEMS USING SUCH UNITS

The present invention relates to a pump and/or a compressor for pumping, respective compressing a fluid, such as air, gases or liquids, comprising a cylinder wherein two pistons are configured to reciprocate, the pistons being connected to crankshafts driven by at least one motor. The cylinder may in addition be provided with a suction valve and a discharge valve. US Patent Specification No. 1,689,419 describes a pump or compressor which, via a motor and two worm gears on a shaft drives two reciprocating pistons in a cylinder. The reciprocation is obtained by means of a shaft and a crank fixed on the shaft, together with a connecting rod which is pivotally arranged on the crank. The purpose of the solution described in US 1,689,419 is to provide a pump or a compressor free of valves. The cylinder is for this purpose provided with two openings, arranged on the same side in the cylinder. According to US 1,689,419, the inlet and outlet of the cylinder are arranged on each side of the middle section of the cylinder, the openings being arranged in such way that at least one opening always will be closed by one of the pistons. The openings according to US 1,689,419 are arranged in a position wherein one of the openings is placed in the region of the inner dead point of one of the pistons, while the other opening is arranged in the region of the inner dead point of the other piston. The movement pattern of the pistons with respect to each other is locked, i.e. the synchronous angles cannot be changed. Although US 1,689,419 does disclose use of two reciprocating pistons in a cylinder, the pistons are not configured to function as a double acting piston engine, since compression only may be achieved by relative motion

of one piston with respect to the other.

An object of the invention is to increase the capacity and the effect of a pump or a compressor without having to increase the pump weight or dimensions to any degree .

Another object of the invention is to be able to vary the capacity or the effect and efficiency of a pump or a compressor for pumping and/or compressing a fluid, such as a gas or a liquid, without having to make specific or substantial modifications to the pump or the compressor. "

A still further object is to provide a pump or a compressor where it is not required to make specific adaptations if the medium to be pumped or to be compressed is a gas or a liquid, or if the pump or compressor in addition is to be used as an emergency compressor.

A still further object of the invention is to provide a solution where it is possible by means of stepless electronical and programmed control, to regulate speed, i.e. revolutions per minute, capacities, pressure and deadvolume in a simple manner.

Yet a further object of the invention is to provide well balanced pump and/or compressor, such unit being able to run at high speed and providing a high capacity utilization, higher efficiency and a low level of vibration. Yet another object of the invention is to provide a pump or a compressor with small dimensions and low weight, without head gasket and made up of a limited number of dependable and simple components.

Another object of the invention is to obtain a pump or compressor equipped with a simple cooling system for the movable parts as well as for the exit air.

A still further object of the invention is to provide a pump or compressor which may be coupled in series or in parallel .

The objects according to the invention are achieved by a pump system or compressor as further defined in the preamble of the independent claims and the characterizing parts. Additional embodiments are defined in the dependent claims .

The invention is based on a synchronized piston technology comprising two reciprocating pistons which may reciprocate independent of each other in the same cylinder. The invention may for example be driven by two motors with stepless electronical and programmed control for regulating the speed, i.e. the number of revolutions per minutes, and the capacity, and which also provides possibilities for regulating the dead volume by adjusting the synchronous angle on one of the crankshaft up to 180° with respect to the other piston, and with subsequent electronical locking of the synchronous angle position. In such manner, the pressure and also the capacity may be regulated. The solution according to the invention, comprising two opposing reciprocating pistons, provides for the possibilities of a proper balancing, which again makes it possible to run at speed with high capacity output and higher efficiency. This opens up for reducing the dimensions and lowering the weight of the unit. The construction according to the invention does not have a cylinder head and consists of few parts. Because of the counter moving pistons in the same cylinder, the unit may also operate at very high pressures. For all embodiments, by using two pistons in a cylinder, a compression corresponding to double stroke length of a conventional compressor is obtained. The dead volume of the compressor may consequently be substantially reduced. As a consequence, a high compression pressure may

be achieved through one stroke, while at the same time good venting of the medium in the cylinder is obtained, reducing the temperature and increasing the efficiency. This means that the compressor may produce a high air pressure in one compression stroke. Due to its construction, the compressor provides possibilities for improved cooling of the moveable parts as well as of the exhaust air. The unit may be designed for cooling by both water and/or oil cooling and air cooled. The unit may also be constructed for pressure oil lubrication, splash lubrication or as an oil free solution.

A still further advantage of the solution according to the invention is that the synchronous angle, which basically may be in a locked state, may be unlocked ans changed wireless, for example via internet, telephony, change of chips or the like.

According to the invention the following advantages are obtained:

Reduced weight compared to capacity - Reduced number- of parts

Reduced level of vibration - A more simple construction Reduced production cost Reduced material consumption - More simplicity in production and more simple to install Programmable pressure and capacity control due to use of stepless, adjustable synchronous angle (dead volume) . One and the same compressor may, subsequent to delivery from manufacturer to a customer, easily be adjusted in order to deliver different capacities, such adjustment being made by using a coding system, for example delivered via internet.

Further, with a solution in accordance with the invention, the following is possible to achieve:

It is possible to avoid detrimental resonance and natural frequencies in the various ranges for rotational speed.

The unit may be run as an emergency compressor by using simple means and without substantial mechanical modify- cations, simply by locking of one of the crankshafts when the piston is at its top position, whereby only the other cylinder is functioning in a conventional manner as a compressor. - Larger efficiency because of smaller dead volume compared with conventional compressors.

Based on calculations and tests with a suitable prototype, an efficiency of up to about 90% or more is documented. This implies that the solution according to the invention may deliver approximately six times more air per weight unit, or alternatively may weigh down towards 1/6 of units having a corresponding pump capacity.

Different embodiments of the invention shall now be described in further details, referring to the accompa- nying drawings, where the same reference numbers are used for identical construction parts, wherein:

Figure 1 shows schematically and principally a section through a compressor in its simplest form, indication the directions of rotation and the direction of suction and exhaust;

Figure 2 shows a corresponding embodiment as shown in Figure 1, where the positions are powered by separate motors;

Figure 3 shows a single step compressor with two cylinders run in parallel, where the fluid is sucked in through a valve in each cylinder and exhausted through an adjacent valve on each cylinder; and

Figure 4 shows a corresponding compressor as shown in Figure 3, where the cylinders are arranged in series, i.e.

the compressed air delivered from the exit of one cylinder is delivered to the suction side of the second cylinder.

Figure 1 shows schematically a cross section through a compressor and/or a pump 10 according to the present invention, comprising one cylinder 11. Two pistons 12,12' are reciprocally arranged in the cylinder 11. The reciprocation of the pistons 12,12' in the cylinder 11 is obtained by means of a motor 13 (not shown in Figure 1) , crankshafts 14,14' rotatably arranged on the output shafts 14,14' of the motor 13, and a pivotably arrange connecting rod 16,16', which opposite ends also are pivotably arranged on the pistons 12,12'. As indicated in Figure 1 one of the crankshafts 15' rotates in clockwise direction, while the opposite crankshaft 15 rotates in an anti- clockwise direction, so that the two pistons 12.12' moves toward each other and away from each other in the course of a complete revolution of the shaft 14,14'. The pistons 12,12' are in conventional manner equipped with piston rings 17. According to the embodiment shown in Figure 1, the pistons 12,12' are configured in such manner that the synchronous angle of the pistons 12,12' is 0°.

At its mid-portion the cylinder 11 is equipped with a suction valve 18 and a discharge valve 19. According to the position of the pistons 12,12' shown in Figure 1, a dead zone 21 is formed in the cylinder 11 between the pistons 12,12' when the pistons are in their inner top position.

The valves 18,19 are configured in such way that the fluid is drawn in when the pistons 12,12' moves away from each other, or move away from the inner position of the pistons in the cylinder, while the fluid is pressed out of the cylinder 11, when the pistons 12,12' move toward each other, or when the pistons moves inwards in the cylinder 11. During the suction phase, i.e. when the pistons move

away from their top position, the discharge valve 19 is kept closed, while the suction valve is open. When the pistons 12,12' moves inwards in the cylinder, the suction valve 18 is kept closed, while the exhaust valve 19 opens when the required pressure is reached.

Figure 2 shows an embodiment where two motors 13,13' power the crankshaft 15,15', the connecting rods 16,16' and the pistons 12,12'. The crankshafts 15,15' may rotate in opposite direction of rotation, or in same direction of rotation.

Figure 3 show a compressor/pump 10 comprising two cylinders 11. Each compressor/pump 10 comprises a pair of pistons 12,12'. Each piston 12,12' is made to reciprocate in the cylinder by its motor 13,13', connecting to the crankshaft 15,15' and the connecting rod 16,16'. Each crankshaft 15,15' shown is configured in such way that the corresponding piston in each cylinder either is at its top, inner point or at its opposite bottom point. According to the embodiment shown in Figure 3, the two cylinders 11,11' are arranged in parallel, i.e. as a single stroke compressor 10, the fluid being drawn in through the suction valves 18,18' and is pressed out through the discharge valve 19,19' for each cylinder, the air which is pressed out of the discharge valves 19,19' may be fed to a common manifold (not shown) .

Figure 3 shows the cylinders with the pair of pistons 12,12' in their two most extreme positions, one pair with a minimum of dead volume 21, and the other pair with a maximum dead volume 21'. Figure 4 shows an alternative embodiment of the compressor or the pump 10, shown in Figure 3, wherein the cylinders 11,11' are coupled in series, i.e. where the fluid is compressed in two steps. In the first step the compressed fluid leaves the discharge valve 19 and is fed

into the suction valve 18' of the second unit via a supply- pipe (not shown) . In the second cylinder 11 ' , the compressed air is compressed even further, leaving the second cylinder 11' through the discharge valve 19' at a higher pressure than the pressure of the fluid leaving the first stage.

It should be appreciated that even though the figures only show two cylinders 11,11', the number of cylinder according to the invention may be higher. The number of cylinders and number of steps are governed by what is considered to be feasible from a practical point of view.

Further, it should be appreciated the embodiments according to Figures 1, 2, 3, and 4 may be run in optional directions .

Area of application

A single cylinder model with two motors is shown in Figure 2. Two cylinders with a common outlet (one step) are shown in Figure 3. Two cylinders pressurizing the fluid in several steps are shown in Figure 4. The cylinder (s) of the compressor (s) may also be supplied with pre-compressed air produced by means of a turbo unit or a fan, on order to achieve higher discharge pressure. All units may be equipped with PLS (programmable logical control) for complete remote control of the unit and possibly also for surveillance of the rate of wear. For these embodiments a hardware system lock may be used when selling the machine, thus delivering units, meeting requirements of different and specific capacities or pressures. Alternatively, printed circuit board or circuit elements or a coded system, programmable via internet, may be used. Since the synchronous angle may be regulated, it is possible to regulating dead volume also. Such feature opens up for the possibility of reprogramming the product

at a later stage, thus upgrading the capacity or pressure, one or ^' several times.

The pistons may move independent of each other in one and the same cylinder, and the motion of the cylinders may be controlled electronically and/or mechanically with respect to each other. By using electronic control the capacity and the pressure may be regulated more or less stepless during normal running of the unit.

For the contra-rotating running of the crankshaft, the vibration resultants will be inclined in longitudinal direction, whilst the vibration resultant will be minimal when the crankshafts rotate in same direction, compared with the conventional piston compressors.

Compared to prior art compressors, a compression corresponding to double stroke length, or a compression produced by two cylinders, is obtained due to the use of two pistons in a common cylinder. The result is that even a single cylinder concept of the present invention may function as a high pressure compressor, if the compressor is given all necessary dimensions to enable such effect. It is also possible to pre-pressurize the pressure of input fluid by 1-5 bars by means of a turbo-supercharger with separate or speed governed running, and hence achieve a delivered pressure, for example in the order of 60 bars, or doubling a volume of air delivered by a low pressure compressor by two till five times.

The synchronous angle may be adjusted electronically via an operator panel, a personal computer (PC) or the like. The angle is adjusted from a top dead point, i.e. when the pistons both are at their top dead point, and stepless and down to the lower dead point, i.e. when a piston is in its upper dead point position (UP) , and the other piston is in its lower dead point position (LD) . Such operation may be performed for a quick release or

loading upon demand and dependent upon pressure or pressure drop in the tanks. Such operation may also be used for stepless regulation of the compression pressure and the capacity of the pump or the compressor. Since the capacity and pressure depend on the angle between the upper dead point position and the angular displacement of crankshaft of the counter moving piston, and since said angle may be locked electronically, it is provided for the possibility of selling the unit capacity several times. Different pressure and different supplied volumes requires different capacities and different requirements, due to the constructions different possibilities for delivering stepless pressures and capacities in a stepless controlled manner. This provides electronical re-programming (changing capacity or pressure) around the world via internet, telephony, chips or the like.

In order to adjust the synchronous angle up to 180 degrees, the following method may be used:

Piston 12 is brought to its upper dead point position (UP) . The piston 12' may now be stepless adjusted electronically up 180 degrees with respect to the upper dead point position of the piston 12, providing the possibility of adjusting the capacity for all revolution ranges from = to full capacity. In order to reach the extreme position, i.e. a 0 degree angular displacement, the position of the piston 12' is adjusted such that the piston 12 and the piston 12' at the same time are in their inner top point position, as shown in Figure 2. Such positions give maximum pressure and maximum capacity.

In order to obtain the opposite extreme position, i.e. 180 degrees angular displacement, the piston 12 is set in its inner extreme position, i.e. as far into the cylinder as possible; while the piston 12' is placed at

its extreme outer position. Such individual placement of the pistons with respect to each other, results in that the distance between the pistons 12.12' always will be constant and the two pistons will always move in the same direction. Hence, independent of speed, no change in volume will occur.

The locking mechanism used for locking of the synchronous angle may be of any known, conventional and suitable type, well known by the person skilled in the art.

By locking one of the pistons in its upper dead point and by letting the other piston run as normal, the solution according to the invention may function as a emergency compressor without taking any other action and without having to implement any dismantling. The alternative would have been to remove the piston and plug the cylinder using seals extending into the cylinder extending up to the top dead point of said removed cylinder or use an additional compressor. Hence, according to the present invention, it is possible to obtain approval from certifying bodies without having to install any separate, additional compressors for use as an emergency compressor. Due to the design of the solution it is also possible to use a simplified cooling system which effectively will be able to cool down the cylinders as well as the valves.

The solution according to the invention will have a weight, which subject to choice of material and required effect, in any case will be substantially lighter than existing prior art compressors or pumps having the same capacity. The weight may for example be 1/3 or less of the weight of said conventional units.