Abstract:
A muffler is disclosed. In the muffler a throttling device that is controlled by the energy of the airflow to be muffled is provided in a pipeline of the airflow that needs to be muffled. The muffler is adjusted by itself according to random variety of the pulsing airflow, and can eliminate or reduce effectively the pulsation of the airflow and the related noise in the range of the low frequency and the middle frequency. The muffling effect of the muffler has no correlation with the volume of the muffler, and therefore the volume of the muffler can be reduced.

Description:
This is a nationalization of PCT/CN03/000689 filed Aug. 19, 2003 and published in Chinese. 
   FIELD OF THE INVENTION 
   This invention relates to a muffler, more particularly, to a muffler for eliminating or reducing effectively the gas flow pulsation and the noise caused thereby. 
   DESCRIPTION OF THE RELATED ART 
   A muffler is used to reduce noise by utilizing mainly aerodynamic attenuating principle, such as sound absorption, expansion, resonance and so on, the level of researches and development associated with the structures and the principles of the muffler is very high. By patent searching it is found that Only in China the number of the patents associated with mufflers is more than 600. The mufflers in these patents are various, but they have a common ground, that is, the structures of the mufflers are unchangeable so that they can&#39;t be provided with a mechanism which is capable of realizing self-adjustment automatically with respect to change of the pulsating gas flow, now although there are some adjusting devices provided for them, these devices only can be adjusted manually. Sound-deadening characteristic of the mufflers having the unchangeable structure is unchangeable, but variation of pulsation of gas flow is random and the mufflers having the unchangeable structure are therefore always in a passive state in operation, anechoic effect can not be perfect. At present, it still has not found a muffler which can change positively with respect to the pulsating gas flow and realize self-adjustment. In practice, the muffler is normally used to reduce noise of discharging gas of reciprocating engines and gas compressors, which are originated from pulsation of discharging gas. Generally, it is more difficult to reduce or eliminate the pulsation in low-frequency and medium-frequency than that in high-frequency. At present, it still can not provide a novel, light-weighted and small-sized muffler which can reduce effectively gas flow pulsation in low-frequency. 
   SUMMARY OF THE INVENTION 
   To solve the problems in the art, the object of the invention is to design a muffler which can not only realize self-adjustment with respect to the random change of the pulsating gas flow but eliminate or reduce effectively the gas flow pulsation in low-frequency and medium-frequency and the noise caused thereby. 
   In order to realize the object, the invention is to provide a muffler which comprises a casing within which is a gas inlet, a gas chamber and a gas outlet, a throttling device which is located in gas flow route and controlled by the pressure of gas flow. The throttling device controlled by pressure of gas flow is a pressure reducing valves structure. The pressure reducing valves structure includes an adjusting device and a throttling device. The adjusting device comprises a manual adjusting device, a spring, an energy sensor member and a connection lever which are connected in series. The throttling device comprises an open and close member and a fixture. 
   Compared with the conventional muffler, the muffler according to the invention has significantly advantages and positive effects as follows: 1. It can realize self-adjustment with respect to the random change of the pulsating gas flow. 2. It can eliminate or reduce effectively the pulsation of gas flow in low-frequency and medium-frequency which is difficult to eliminate and the noise caused thereby. 3. It can reduce the volume of the muffler because the anechoic effect is not much dependent on it. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the invention will now be further described with reference to the accompanying drawing. 
       FIG. 1  is schematic viewing showing structural principle of a muffler according to the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   As shown in  FIG. 1 , a muffler casing  14  is divided into a gas inlet chamber  2  communicated with a gas inlet  13  and a gas outlet chamber  4  communicated with a gas outlet  5  by a partition  3 , one throttling device is constructed of an open and close component  1  and a fixture  12  on the partition  3 , when the open and close component  1  moves upwardly as shown in the FIGURE, the area of the flow cross-section will decrease, whereas it will increase. The muffled gas flow flows into the gas chamber  2  through the gas inlet  13 , and is throttled by the throttling device and into the outlet chamber  4 , then discharges from the gas outlet  5 . In this embodiment, the adjusting device consisting of a manual adjusting device  9 , a spring  8 , an energy sensor member  7  and a connection lever  6  which are connected in turn is located on the upper portion of the casing. The energy sensor member  7  is a diaphragm in this embodiment and sensible for potential energy of the muffled gas flow chiefly. The energy sensor member  7  also can be selected from a piston, a bellows etc. The gas outlet chamber  4  is located on the lower portion of the energy sensor member  7  and a spring chamber  11  is located on the upper portion thereof and communicated with atmosphere through a balancing hole  10 . The energy sensor member  7  in the gas outlet chamber  4  is connected with the open and close member  1  and fixed thereon by the connection lever  6  and in the spring chamber  11  is connected with the end of the spring  8 . The other end of the spring  8  is connected with the manual adjusting device  9  fixed on the casing  14 , which adjusts the spring force acted on the energy sensor member  7  by the spring  8  in a manner that the predetermined compressive value of the spring  8  can be adjusted. Now analyze the force of the energy sensor member  7  at the balancing position, if P is represented for the gas pressure in the gas outlet chamber  4 , S is for the effective area of the diaphragm (energy sensor member  7 ), F is for the spring force and G is for the gravity, and because the amount of the deformation force of the diaphragm and the fluid force at throttled point is relatively small, they can be ignored, the force applied by the gas flow in gas outlet chamber  4  is equal to the spring force plus gravity, P*S=F+G, P=(F+G)/S, the gas pressure in the gas outlet chamber  4  is dependent on the amount of the spring force, so that the pressure at the balancing point can be set by the spring force adjusted by the manual adjusting device  9 . The amount of displacement of the open and close member  1  is very small in operation so that the change of the spring force is small and the change of the gas pressure in the gas outlet chamber  4  is also small. The energy sensor member  7  is located on its undermost position under the action of the spring force and gravity when the muffler is not in operation, where the area of the flow cross-section of throttling device is the largest. After the pulsating gas flow enters the muffler, gas energy in the gas outlet chamber  4  increases, the pressure therefore increases, once the gas force is larger than the spring force, the movement of the energy sensor member  7  drives the open and close member  1  to move upwardly, the throttling device starts to work and is therefore controlled by the muffled gas self-energy. When the muffler is in the balancing position, if the energy of the muffed gas flow continues to increase, the pressure keeps up increasing, then the open and close member  1  is driven by the energy sensor member  7  to move upwardly, the area of the flow cross-section decreases, the pressure decreases, which leads to a trend that the pressure in gas outlet chamber  4  decreases to the pressure at balancing point, whereas when energy decreases, the pressure decreases, the open and close component  1  moves downwardly, then the area of the flow cross-section increases, which leads to a trend that the pressure in the gas outlet chamber  4  recovers to the pressure at the balancing point. It can be determined that the pressure fluctuation of the gas outlet chamber will be very small. Since the discharge duct is fixed, the gas flow discharged is continuous, stable and no pulsation. It can be analyzed from the point of the pulsating gas flow, the pulse waveform whose pressure is greater than the pressure at the balancing point will be intercepted, the energy intercepted will be stored in the gas inlet chamber  2  and previous ducts so that the pulsating energy whose pressure is lower than the pressure at the balancing point increases, and when it cooperates with the method of increasing the area of the flow cross-section, the energy of the gas flow will be much more uniform than before, which corresponds with the case that pulse waveform of gas flow is commutated to be approximately a line. The pressure in the gas outlet chamber  4  at the balancing pressure can be considered comprehensively so as to be set according to the factors, such as the average value of the pulsating gas flow, the continuity and stability of the muffed gas flow required and gas resistance. It can be made out that the anechoic effect is not much dependent on the volume of the muffler on the basis of the working principle thereof. The open and close member  1 , the diaphragm (energy sensor member  7 ) and the spring  8  can be regarded as a mass-spring vibrating system having its nature frequency, for which the pulsation of the gas flow is a stimulant force, when the pulsation of the gas flow is in low-frequency and medium-frequency, the vibrating system consisting of the open and close member, the diaphragm and the spring can be substantially in response to said frequency and carry out the adjustment, the response of the system is relatively small when in the high-frequency, so that the adjusting function is relatively weak, the muffler is more effective when the gas flow is in low-frequency than in high-frequency. 
   The gas inlet  13  and gas outlet  5  in the embodiment as above said can be exchanged each other, accordingly, the gas inlet chamber  2  and the gas outlet chamber  4  can be exchanged each other, too, the working principle is similar to above-mentioned embodiment, and it can obtain the same effect. 
   In addition, as shown in  FIG. 1 , the structure of the open and close member  1  is characterized in that a cross sectional area of its first surface subjecting to gas pressure from the gas inlet  13  is larger than a cross sectional area of its second surface that is opposite to the first surface and exposes to the gas outlet  5 . 
   The means according to the invention can be used in series to further improve stability of gas flow and reduce noise; the parallel usage of the means can enhance flowing capacity, and it also can be used with common mufflers cooperatively.