Patent Application
20120312105
The present invention relates to a mechanism for transforming circular motion from, for example, the shaft of an electric motor or an internal combustion engine or the like to a translation movement for driving the pistons of a gas compressor, preferably a compressed natural gas (CNG) compressor.
Particularly it is related to a drive mechanism of a lubricated-type reciprocating gas compressor that receives a circular driving motion through an engine's shaft and becomes a linear drive motion to move the pistons of a compressor without using prior art rod-type systems, as will be explained in detail later.
Reciprocating compressors are already widely used in different industries, and are one of the oldest compressor designs, but remains being the most versatile and highly effective ones. This type of compressor drives a piston forward in a cylinder via a connecting rod and a crankshaft. If only one side of the piston is used for compression, it is described as a single action compressor. If both sides of the piston are used, top and bottom, it is called double action compressor.
The versatility of reciprocating compressors has no limits. It compresses both air and gases, with small modifications. The piston compressor is the only design capable of compressing air and gas to high pressures, such as breathing air applications.
The configuration of a piston compressor can be from a single cylinder for low pressure/low volume applications to a multi-stage configuration capable of compressing fluids to very high pressures. In the later case, air is compressed in stages, increasing the pressure before entering the next stage to compress also high pressure air.
Typical applications for this type of compression includes natural gas (CNG, nitrogen, inert gas, landfill gas), high pressure (breathing air for diving cylinders, seismic surveys, air injection circuits), PET bottling, boot motors, etc.
The mechanism for converting the circular motion of the driving motor shaft to a linear motion of the piston compressor commonly used in such compressors is the connecting rod-crank type. The most common current example of this type is found in the internal combustion engine of a car, where the linear movement of the piston is transmitted to the rod by the explosion of gasoline and becomes circular motion in the crankshaft.
But this mechanism is older than the automobile and was used in steam locomotives, although in this case it was for the inverse function, that is to say converting the linear motion of piston driven by high-pressure steam to a circular movement which drives the wheels of the locomotive. In schematic form, this mechanism is created with two “bars” joined together by a union of revolute. One end of the bar that rotates (the handle) is attached to a fixed point, the fulcrum, and the other end is attached to the rod. The remaining end of the rod is attached to a piston that moves in a straight line.
The reciprocating compressors operate on the adiabatic principle by which gas is introduced into the cylinder by the inlet valves; it is retained and compressed in the cylinder and exits through the exhaust valves, against the discharge pressure. These compressors are rarely used as individual units, unless the process requires intermittent operation. The reciprocating compressors have contact parts such as piston rings to cylinder walls, springs and valve plates or disks that are attached to their seats and between the gasket and rods. All these parties are subject to wear by friction. That is why they can be lubricated or non-lubricated. If the process allows it, it is preferable to have a lubricated compressor, because the pieces will last longer.
The reciprocating compressors should have, preferably, low-speed direct link engines, especially if they have more than 300 HP and work at constant speed.
Alternative piston compressors are classified according to the compression phase in single phase or dual phase. Single phase or single direction compressors are those which piston performs a single stage of compression (compression action is executed by only one side of the piston). Dual phase, biphasic, double effect or reciprocal compressors are those which piston performs a dual compression (compression action is performed by both sides of the piston).
The reciprocating compressors range from a very small capacity to about 3,000 PCMS and are used for high pressure and at a rather low cost. The number of stages or cylinders must be chosen in relation to the discharge temperatures, space available for the cylinders and load on the compressor body or rod.
Rather small size compressors, of up to about 100 HP, usually use a simple action cylinder, air cooling, and can allow the oil vapors in the tank (sump) to be mixed with air or compressed gas. These ones are desirable only in special modified designs.
Larger compressors for air or gas have two or more cylinders. In most facilities, the cylinders are arranged horizontally and in series so that they perform two or more stages of compression. The number of stages of compression depends largely on how much the temperature rises on each stage, usually limited to about 120° C. But is also depends on the load the rod that can handle and, occasionally, on the total pressure increase in one stage related to the design of the compressor valves, which usually support less than 1,000 psi.
The total compression ratio is determined to have an initial idea about the number of compression stages necessary. If the ratio is very high, between 3.0 and 3.5 for a single stage, then the square root of the overall relationship will be equal to the ratio per stage for the two stages, the cube root for three stages, etc. The inter-stage pressure and the ratio of actual stages will be modified after taking into account the pressure drop in inter-coolers, inter-stage pipeline, separators and pulsation dampers, if used.
Piston compressors compress gases and vapors in a cylinder through a piston in a rectilinear movement and are used for driving pneumatic tools (6 to 7 kg/cm2), ammonia refrigeration plants (up to 12 kg/cm2), supply gas transmission (up to 40 kg/cm2), liquefaction of air (up to 200 kg/cm2), compressed air locomotives (up 225 kg/cm2) and hydrogenation and synthesis under pressure (more than 1000 kg/cm2).
From the above it is clear that the linear-displacement reciprocating compressors driven by electric motors or internal combustion engines are already widely known in the art, but the object of this invention is to improve the mechanisms used to transform said circular motion from the engines to a linear driving motion applied to a compressor piston. As previously explained in detail, known compressors use a linkage system that although it has proven to be efficient for decades, due to the physical characteristics of the pieces involved, it is very difficult to miniaturize.
At present, reciprocating compressors without rod systems to transform the movement of the engine are not known. It is precisely an object of this invention to avoid these traditional rod mechanisms and replace them with a system to reduce the size of the set with significant benefits to manufacturing and maintenance applications.
The present invention relates to a driving mechanism of a lubricated reciprocating gas compressor that receives circular motion from a motor shaft and converts it into a linear driving motion to move the pistons of a compressor. The purposed invention does not use traditional rod systems, but a rectangular driving piece that sits, on a linearly movable way, inside a chamber and is coupled to a crankshaft. When the crankshaft rotates the rectangular piece tries to rotate too, but divides the rotational movement in an up-down movement within the aforementioned camera and a horizontal linear movement of the right-left type. As the aforementioned camera has in turn the ends of the piston rods of the compressor linked, they cause the linear displacement thereof, as will be explained in detail later.
The purposed invention replaces the traditional rod systems with a simple mechanism that simplifies the set and their maintenance, and allows miniaturization.
In the description that follows we will not focus on the overall operation of the compressor since it is not part of this invention, but we will rather focus on the mechanism that receives the rotating movement of any engine and transforms it into a linear movement that drives the pistons of the compressor. The rest of the operation of the compressor is of the traditional type, that is to say that the entire sequence of suction, compression and exhaust, and the operation of the pistons, valves, lubrication, etc. are very well known in the art and they are included in some of the attached drawings for the sole purpose of drawing the whole equipment and therefore we will not describe its operation and are not part of the proposed inventive concept.
These and other aspects, features, and advantages of the present invention will become more readily apparent from the attached drawings and the detailed description of the preferred embodiments, which follow.
To the sole purpose of giving an overview of the compressor equipment in which the proposed mechanism is applied, but without entering into technical details thereof, we will start from
At one end of the housing a shaft 7 extends and defines the nose of the crankshaft which is coupled, as usual, to an engine (not illustrated) that will be responsible for driving the compressor. At the end of said crankshaft, there is a wheel 7′.
Referring now to
To complete this series of perspective figures which provide an overview of the whole compressor set where the proposed mechanism is applied, without limiting the application of this invention to this particular embodiment (it can be applied to any type of compressors) we now refer to
Finally we refer to
We shall now make a detailed description of the compressor which includes the proposed mechanism, making quick and superficial references for the conventional parts of the compressor and detailed references for the proposed mechanism.
Compressor 1 has the tip of crankshaft 7 coupled to a motor (not shown) that can be an electric motor or internal combustion engine. This motor causes the rotation of crankshaft 9 and the subsequent turn of main gudgeons and counterweights 21. Being said rectangular piece 19 attached to the counterweight 21 of the crankshaft 9, when the crankshaft 9 rotates the driving rectangular piece 19 is also rotated. But said rectangular piece 19 cannot rotate as the counterweight because on one side it can move in an ascending-descending way inside the parallelepiped housing 10 and also the camera 10 moves linearly in a horizontal way 22 defined by the housing 3. Therefore when the crankshaft rotates and the counterweights 21 are moving in a circle around the longitudinal axis 23 the driving part 19 decomposes the circular motion in two linear motions, one up-down motion inside the parallelepiped housing 10 and another horizontal linear motion within the camera 22. As the end 16′ of the connecting rod 16 is linked to the lateral aspect of the aforementioned housing 10 through the plate 18, when it moves horizontally it also moves the rod horizontally, and consequently the piston 14.
Through a structurally and functionally simple construction as the receptacle 10 and the rectangular piece 19, the use of traditional rods can be avoided, which imply less wear and maintenance, but also the possibility of reducing the compressor size to achieve special applications, especially in the field of compressed natural gas compressors. Indeed, without limiting the scope of protection of the present invention, a preferred application of the proposed mechanism is on compressed natural gas (CNG) compressors.
While the preferred embodiments of the invention have been described above, it will be recognized and understood that various modifications can be made in the invention and the appended claims are intended to cover all such modifications which may fall within the spirit and scope of the invention
