JPH03168488A - Water hammer buffering device - Google Patents

Abstract

PURPOSE:To prevent the second pressure wave from being generated by collision by setting the spring force of a spring which forces a piston in a cylinder chamber which buffers water hammer to a communicating opening side at such strength as the piston stops before it comes into contact with the rear edge part of the cylinder chamber with water pressure. CONSTITUTION:When a venturi tube 18 is installed inside a water flow passage, and when flow is generated, a low pressure part occurs in a throttling part 20 and a piston 34 in a cylinder 26 fully goes down. After the water flow is suddenly stopped, the water flow of high pressure passes through the hole 22 of the throttling part 20. Then the piston 34 is raised to absorb water hammer. The spring force of a spring 38 which forces the piston 34 is set at such strength as the piston 34 stops before it collides with a cap 32 at the rear edge part of the cylinder. It is thus possible to absorb water hammer by retracting the piston 34, and prevent the piston from colliding with the cap 32 at the time of retraction, and the second pressure wave from being generated by collision.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention alleviates the so-called water hammer phenomenon that occurs when the valve part of a faucet is suddenly closed, and improves the quality of faucet equipment, piping, etc. Water S prevents damage and also suppresses noise generation
Regarding shock absorbers. (Issue 8 to be solved by the prior art and the invention) In recent years, screw-type faucets have been replaced by screw-type faucets, which open and close the valve part by rotating the handle and screwing the valve body in the axial direction. As a result, lever-type faucets, which open and close the valve part by rotating the lever, are rapidly becoming popular. This type of lever-type faucet has the advantage of being easy to operate and use, such as being able to quickly close the valve from fully open, but on the other hand, the sudden opening of the valve causes large water hammer in the piping system. Easy to do. In other words, when the valve of a faucet is suddenly closed to a place where water or hot water (hereinafter simply referred to as water) is flowing at a flow rate V in the pipe, the following equation (A) ΔP=ρCV... (A ) (ρ: density of fluid; C: propagation speed of pressure wave) A sudden pressure increase ΔP occurs, which causes a large wood strike phenomenon in the pipe. To be more specific, if the pipe wall does not expand even if the pressure increases, C = 1400 m/s, and the flow velocity in the pipe when the faucet is fully opened is V'; 2 m/s.
That's about it. Therefore, these detectives and ρ= 1 0 0
Substituting the value of 0 kg/m3 into the above formula (^), the pressure rise when the faucet is suddenly closed is ΔF' = 2 8 0 0
It reaches an extremely high value of KPa' = 28 kgf/cm2, which causes a large water hammer phenomenon inside the pipe. If such a wood impact phenomenon occurs, impact may occur and faucet equipment, piping, etc. may be damaged. Various devices have been devised to buffer against such water hammer, but the reality is that none have been provided that are fully satisfactory. (Means for Solving the Problems) The water hammer shock absorber of the present invention has been devised to solve the above problems, and its gist is (a) that it is arranged on a water supply flow path so that the water flow is A venturi part that lowers the pressure at the constriction part to generate a low pressure part when the pressure is generated, (a) a cylinder that communicates the internal cylinder chamber with the constriction part of the venturi part through a communication port, and (c) a cylinder that slides into the cylinder. With a piston that can be fitted together. (2) having a spring that urges the piston toward the communication port of the cylinder chamber;
The spring force of the spring pushes the piston to the front end of the cylinder when a water flow occurs in the flow path, and when a sudden pressure increase occurs in the flow path and pushes the piston back, the spring force pushes the piston toward the front end of the cylinder. The piston is sized to stop the piston before it touches the end. (Actions and Effects of the Invention) In the device of the present invention. When the valve part of the faucet is closed and there is no water flow in the flow path, the piston is pushed back a certain distance from the front end of the cylinder due to the water supply pressure, that is, it is pushed back against the biasing force of the spring. is in a state. When the valve part of the faucet is opened in this state and a flow is generated in the flow path, a pressure drop occurs at the constriction part of the venturi part, and the water in the cylinder passes through the communication port and passes through the flow path due to the action of the low pressure part created there. At the same time, the piston is pushed out to the front end of the cylinder by the biasing force of the spring. On the other hand, when the valve of a faucet is suddenly closed and a sudden pressure rise occurs in the flow path, the piston at the front end of the cylinder moves back against the biasing force of the spring, and along with this, the water in the flow path flows into the cylinder through the communication port. This absorbs the pressure increase that occurs within the flow path. At this time, the spring that pushes the piston deforms more and more as the piston retreats, increasing the elastic force, and before the piston reaches the rear end of the cylinder, the elastic force, that is, the push-back force, acts on the piston. The piston stops when the pressure is balanced. This is because the biasing force (spring force) of the spring is set to such a magnitude in advance. That is, when the piston collides with the rear end of the cylinder, a secondary pressure wave is generated at that time, so in the present invention, this is stopped before the piston hits the rear end of the cylinder. This prevents the generation of secondary pressure waves. Now, the piston is pushed back by the sudden pressure.
Next, it is pushed toward the front end of the cylinder by the biasing force of the spring, and stops at a position where the biasing force and the water supply pressure acting on the piston are balanced. When the next water flow occurs, it is moved forward again to the front end of the cylinder and waits to absorb the next sudden pressure rise. In this way, the water hammer shock absorber of the present invention has the feature of effectively absorbing pressure increases by making the piston work effectively through the action of the venturi section. In other words, if such a venturi section is not provided, even if water flow occurs in the flow path, the piston will be pushed back by a certain amount inside the cylinder by the water supply pressure, and therefore the faucet valve section will not suddenly open. When a sudden pressure rise occurs in the flow path due to closure, the effective stroke that can be retreated for pressure absorption becomes shorter and pressure absorption is not performed effectively. However, in the device of the present invention, Based on the action of the venturi, the piston retreats from the front end of the cylinder and absorbs pressure, making it possible to effectively suppress pressure rise. In addition, the device of the present invention has the advantage that the cylinder can be downsized, and the entire 'Ilc device can therefore be constructed compactly. This is because the venturi allows the piston to work effectively, which means that the capacity of the cylinder can be used without waste for pressure absorption. This venturi section has the effect of reducing the pressure at the constriction section and then immediately restoring the pressure downstream, and therefore has the advantage of keeping the flow resistance low when this device is installed. When the low pressure section is generated by a venturi section according to the present invention, there is an advantage that the maximum flow rate can be limited when the water supply pressure is particularly high. If the water supply pressure is particularly high like this, the flow rate when the faucet valve is fully open will be unnecessarily large, and in this case, the water hammer will be extremely large when the valve is fully closed from fully open. It is actually extremely difficult to prevent this, but if a venturi section is installed on the flow path, cavitation will occur at the constriction section of the venturi section, and even if the valve section of the faucet is fully opened, water will not exceed a certain flow rate. The water does not flow and the water flow rate is restricted. Therefore, the occurrence of water hammer when the valve part is fully closed can be sufficiently suppressed. (Example) Next, an example of the present invention will be described in detail based on the drawings. In FIG. 1, numeral 10 denotes a water hammer shock absorber, which is an example of the present invention, and has a cylindrical part 2. Pipes 1 are installed at both ends of the cylindrical portion l2.
7 is provided, and each connection part 4
On the inner surface thereof, there is a female threaded portion l6 for threaded connection with the pipe 17.
is provided. A penturi tube l8 is provided inside the cylindrical portion l2. A through hole 22 is formed in the constricted portion 20 of the Venturi tube l8, and the inside of the Penturi tube l8 communicates with an external communication chamber 24 through the through hole 22. Note that the inner diameter d of the constricted portion 20 is suppressed to about <, d=0.3D, which is much smaller than the pipe inner diameter D, and the divergence angle θ is set to about 7e, which causes the least loss.
There is no large pressure loss when water flows through this area. 26 is a cylinder provided integrally with the cylindrical portion l2, and a communication port 28 is provided at one end, and the internal cylinder chamber communicates with the communication chamber 24 and the inside of the constricted portion 20 of the Venturi tube l8 through the communication port 28. It is being done. The opening on the other end side of the cylinder 26 has an atmosphere introduction hole 30.
A cylinder M32 having a diameter is fixed by a screw connection. A piston 34 is slidably fitted inside the cylinder 26. An annular structure is formed on the outer peripheral surface of the piston 34, and an O-ring 36 is installed in the annular groove.
The piston 34 and the cylinder 2 are connected by this O-ring 36.
6 The fitting part with the inner surface is sealed watertight. A compression coil spring 38 is interposed between the piston 34 and the cylinder M32. spring 38
One end is brought into contact with the cylinder M32, and the other end is brought into contact with the rear surface of the piston 34. Note that the piston 34 has a cylindrical portion 40 formed therein, and a spring 38
A part of the cylindrical portion 40 is housed inside the cylindrical portion 40. In the device shown in the example of a tree, when a tree is generated in the flow path, the piston 34 comes into contact with the lower end (front end) of the cylinder 26 in the figure.
In addition, a sudden pressure increase occurs in the flow path, causing the piston 34 to
The spring force of the spring 38 is set so that the piston 34 stops just before it comes into contact with the cylinder lid 32 when it is retracted. Next, we will explain the function of this device. In the device shown in the wooden example, when the valve part of the faucet is closed, the piston 34 is pushed back a certain amount upward in the figure by the water supply pressure, and the spring 38 that biases it in the opposite direction is pushed back by the water supply pressure. Stops at the position where the urging force of +h L
,ing. In this state, when the valve part is opened and a water flow is generated in the flow path, the water that has entered the cylinder chamber is drawn into the flow path by the action of the low pressure part generated at the constriction part 20 of the venturi pipe 18 and the biasing force of the spring 38. As well as being sucked out,
The piston 34 is pushed out to the lower end (front end) in the figure. Next, when the faucet valve section is suddenly closed, a sudden pressure increase ΔP=ρC■ defined by the above formula (A) occurs in the same section and propagates within the piping flow path. Then, based on the pressure increase, the water in the flow path pushes up the piston 34 and pushes up the passage hole 22 and the communication chamber 2.
4. It flows into the sill 26 through the communication port 28.
That is, the water in the flow path escapes into the cylinder 26, thereby absorbing the pressure increase and avoiding the occurrence of water hammer. At this time, the piston 34 moves back to the vicinity of the rear end of the cylinder 26 while deflecting the spring 38, and at the same position, the pressure acting on the piston 34 and the spring force of the spring 38 are balanced, and the piston 34 temporarily stops there. Now, once the piston 34 has retreated to the vicinity of the rear end of the cylinder 26, it is continued to be pushed out by the spring 38,
It stops at a position where the urging force and the water supply pressure acting on the piston 34 are balanced. Then, when a water flow is generated in the flow path again, it is moved forward by the action of the venturi tube 18, and when a sudden pressure rise occurs in the flow path, it retreats inside the cylinder 26 to its full capacity again to absorb the pressure rise. Incidentally, even when the venturi tube 18 is not provided as described above and the cylinder chamber is simply communicated with the flow path, the pressure increase in the flow path can be absorbed to some extent. However, various inconveniences occur in this case. For example, if the Venturi tube l8 is not provided and the same spring 38 as described above is used, the piston 34 will not advance to the front end of the cylinder 26 even if a water flow occurs in the flow path.
It stops at a position set back a certain distance from the front end of the cylinder 26, that is, at a position where the water supply pressure and the biasing force of the spring 38 are balanced. When a sudden pressure rise occurs in the flow path, the pressure rise is absorbed by retreating from that position. The movement stroke at this time is small, and therefore the amount of wood flowing into the cylinder 26 is also small, making it impossible to absorb the pressure increase effectively. On the other hand, in the device of the present invention, the piston 34 moves back almost the entire stroke of the cylinder 26 to absorb pressure, so that the increase in pressure within the flow path can be effectively suppressed. In addition, the device of this example makes full use of the cylinder chamber to absorb the pressure increase, so even a small cylinder can serve the purpose well. ! The shock absorber can be configured compactly. In the case where the venturi tube 18 is not provided, by setting the spring in a precompressed state, the piston 34 can be moved forward to the front end of the cylinder 26 even when water flow is generated in the flow path. [In this case, there is no low pressure part, so
Does the piston 34 move forward to the front end of the cylinder 26 regardless of the presence or absence of water flow? ). However, in this case, the following inconvenience occurs. In order to effectively absorb the pressure increase due to water hammer, the following conditions are satisfied: (a) When water is flowing, the piston 34 advances to the front end of the cylinder 26, and as the pressure increases, it retreats to the rear end of the cylinder 26. Therefore, more water in the flow path can flow into the cylinder 26. (U) When the piston 34 stops at the backward end, it should stop as gently as possible. (c) The shear stress acting on the spring is small, and the maximum value of ■8 is less than or equal to the allowable shear stress τa. It is necessary to satisfy the following conditions. Therefore, as shown in FIG. 2, the diameter of the cylinder chamber is DC, the length of the cylinder chamber is lc, the average diameter of the spring is Da, and the wire diameter is da. -4i If the effective number of turns is n and the length when installed is Mata, then
The shear stress and spring constant k are as follows. ? Here, G is the transverse elastic modulus, which is 7 5 in the case of stainless steel wire.
It is about 0 0 kgf/mm2. Also, the maximum value wmax of the compressive force W in equation (1) is W man = Yi/
4 s D c7P may -- given by (3). Here, P■8 is the maximum pressure generated by water hammer, which acts on the piston 34. Now, if the spring is precompressed to overcome the water supply pressure and bring the piston 34 into contact with the front end of the cylinder 26, the spring constant of the spring will be smaller than when no precompression is applied. That is, in either case, if the piston 34 retreats almost to the rear end of the cylinder 26 due to the pressure increase, the maximum compression force of the spring at that time is W aX = kx. Here, X is the amount of displacement from the free state, and the amount of displacement is naturally larger when precompression is applied than when no precompression is applied. Therefore, the value of k becomes smaller when precompression is applied. Therefore, if the value of k becomes small, from equation (2), if n and Da are equal, da
> da ′ (if da is given precompression, below, those without precompression will be indicated with ′), and (1)
From the formula, τ becomes τ′. In other words, when precompression is applied, a large shear stress is generated in the spring. On the other hand, τ when the piston 34 reaches the retreating end is τ. 8 and equal to the allowable reconnaissance τa of τ, then if D6 = aDc and insert this into equation (1) together with W = W @aw = π/4・Dc2Psax, d4 /Dc ='i5Pm
ax / 1"J -------(a). Here, for example, α = 0.7, Psax = 7 kgf/
cm. 2, τa = 90 kgf/am2
Then, d a /D c =0. 1
becomes. On the other hand, the diameter Da of the spring is . If DC is given, it is better to make it as large as possible within that range.5 Therefore, this is also D.
It is determined depending on the value of c. Therefore, when precompression is applied to the spring, the effective number of turns n of the spring must be set to a large value according to equation (2) (the value of k is smaller than when no precompression is applied). If the number of turns n is increased, the maximum stroke nda of the piston 34 becomes smaller, and less water can be taken into the cylinder 26 when the piston 34 retreats. In other words, the pressure absorption effect during water hammer is smaller than when no precompression is applied to the spring. In other words, by providing the venturi tube l8 as in this example, water hammer can be more effectively buffered. FIG. 3 shows another embodiment of the invention. In this example, a pole valve body 42 and a weak spring 44 are installed in the cylinder chamber.
A small check valve 48 consisting of a support member 46 and a support member 46 is provided. In the case of this example, an air chamber 50 is formed between the piston 34 and the cylinder M32, and the air sucked and trapped inside the air chamber 50 acts as an air spring when the piston 34 retreats, so that the piston 34 Prevents collision with cylinder M32. Since the air trapped in the air chamber 50 rapidly increases the elastic force as the piston 34 retreats to prevent the piston 34 from colliding, there is an advantage that the spring force of the spring can be set to a correspondingly weaker value. ．． As shown in FIG. 3, a convex portion 52 is provided in the cylindrical portion 40 to form an air chamber 50 when the piston 34 is retracted.
It is advantageous to make the volume as small as possible because the compressibility of the air becomes higher and the elastic force of the air spring becomes stronger. Although the embodiments of the present invention have been described in detail above, the present invention can be modified and modified in various ways based on the knowledge of those skilled in the art without departing from the spirit thereof.

[Brief explanation of the drawing]

Figure 1 shows an embodiment of the present invention. FIG. 2 is an explanatory diagram for explaining the advantages of the device, and FIG. 3 is a cross-sectional view of the water hammer impact device, which is another embodiment of the present invention. be. lO: Water hammer #11II device l8: Venturi tube 2
0: Throttle part 26: Cylinder 28 two communication ports
34: Piston 38: Spring Fig. 2

Claims (1)

[Claims] (a) a venturi section which is arranged on the water supply flow path and which lowers the pressure at the throttle section to generate a low pressure section when water flow occurs;
(b) a cylinder that communicates the internal cylinder chamber with the throttle part of the venturi section through a communication port; (c) a piston that is slidably fitted into the cylinder; (d) a piston that connects the piston to the throttle part of the venturi section and a spring that biases toward the communication port, and the spring force of the spring pushes the piston to the front end of the cylinder when a water flow occurs in the flow path, causing a sudden burst into the flow path. 1. A water hammer shock absorber, characterized in that the size of the piston is set such that when the piston is pushed back due to an increase in pressure, the piston is stopped before it comes into contact with the rear end of the cylinder.