An adaptive intelligent control lip seal device based on a spool valve mechanism

Abstract

The application discloses a kind of self-adapting intelligent regulation and control lip seal device based on slide valve mechanism, device includes sealing ring body, air spring, rigid skeleton, main air passage, slide valve mechanism, secondary lip O-ring, secondary lip air passage, radial air passage and pressure sensor of spoke type.The slide valve mechanism responds to the pressure fluctuation monitored by pressure sensor, dynamically controls the flow of gas between main air passage, radial air passage and secondary lip air passage, realizes the adaptive adjustment of main lip part holding force: when overpressure caused by vibration, exhaust to secondary lip mouth to enhance sealing and active chip removal;When low pressure caused by wear, air supply restores holding force.Working mode includes normal cut-off state and automatic adjustment cycle, and slide valve mechanism is automatically reset after pressure balance.The device is evenly arranged along the circumferential direction Control unit, monitor and respond to non-uniform pressure individually, form "exhaust-seal-self-cleaning" synergistic effect, significantly improve the sealing reliability, dynamic stability and service life.

Description

Technical Field

[0001] This invention belongs to the technical field of rotary shaft lip seal devices, specifically relating to an adaptive intelligent control lip seal device based on a slide valve mechanism. Background Technology

[0002] Lip seals are among the most widely used components in rotary shaft dynamic seals. They rely on the interference fit between the elastic lip and the shaft surface to generate radial contact pressure, forming an effective barrier at the sealing interface to prevent leakage of lubricating oil and other media from the cavity and to prevent the intrusion of external contaminants. However, lip seals must withstand the combined effects of complex friction conditions, shaft end vibration, and contaminant intrusion over extended periods. Especially during shaft end vibration, the lip contact pressure and contact gap constantly change instantaneously. On the side with a larger contact gap, the lip contact pressure decreases, significantly increasing the possibility of leakage; conversely, on the side with a smaller contact gap, the lip contact pressure increases sharply, leading to increased local frictional heat and accelerated wear. Furthermore, during operation, after prolonged friction and wear between the lip and the rotating shaft surface, the lip seal faces problems such as gradually decreasing interference fit, reduced sealing performance, and the adhesion and even jamming of wear debris. This performance degradation is an irreversible process, and its failure is further accelerated with prolonged operation.

[0003] Therefore, the core technical challenge lies in how to effectively maintain the dynamic fit between the lip and the shaft during long-term operation, and how to achieve intelligent control and dynamic compensation for the degradation of sealing performance caused by shaft end vibration and lip wear, so as to ensure the reliability and stability of the rotary shaft sealing system during long-term service.

[0004] While existing technologies employ chambers pre-filled with pressurized fluid to provide constant sealing pressure, these solutions struggle to adapt to dynamic changes under complex operating conditions. Specifically, after lip wear occurs, the constant sealing pressure is insufficient to maintain an effective seal; furthermore, when shaft vibration intensifies, this approach not only fails to provide cushioning but may also damage the seal ring due to the inability to release pressure in a timely manner. Therefore, there is an urgent need for an intelligent compensating lip seal device that can adaptively adjust the sealing pressure according to changes in operating conditions, possessing both automatic compensation capabilities after wear and buffering / pressure relief functions under vibration conditions. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide an adaptive intelligent control lip seal device based on a slide valve mechanism. This device can dynamically adjust the radial clamping force of the sealing lip in real time according to changes in operating conditions and wear. By coordinating pressure regulation, it enhances the auxiliary sealing and active chip removal functions of the secondary lip, thereby significantly improving the long-term operational reliability and service life of the lip seal.

[0006] To solve the above technical problems, the technical solution adopted is:

[0007] An adaptive intelligent control lip sealing device based on a slide valve mechanism is installed on a rotating shaft and includes a sealing ring body, an air spring, a rigid frame, a main air passage, a slide valve mechanism, a secondary lip O-ring, a secondary lip air passage, a spoke-type radial air passage, and a pressure sensor.

[0008] The main lip of the sealing ring body is interference-fitted with the surface of the rotating shaft to form the main sealing barrier. An air spring is circumferentially embedded in the outer groove of the main lip to provide adjustable radial clamping force. A rigid skeleton is embedded inside the sealing ring body to provide structural support, including a main lip skeleton, a secondary lip skeleton, and a reinforcing ring for connecting the main and secondary lip skeletons. The main air passage is located on the reinforcing ring for introducing an external air source. A spool valve mechanism connects the main air passage and the secondary lip skeleton, including a valve sleeve, a valve core, a pressure diaphragm, and a spring. The valve core can slide within the valve sleeve to dynamically control gas flow in response to pressure changes. The secondary lip O-ring is installed in the annular groove of the secondary lip skeleton. To achieve auxiliary sealing, the secondary lip air passage is located within the secondary lip side frame, connecting the slide valve mechanism and the secondary lip O-ring. The spoke-type radial air passage is evenly arranged circumferentially, connecting the air spring and the slide valve mechanism to construct a low-flow-resistance pressure transmission network. Pressure sensors are located on the spoke-type radial air passage and the main air passage for real-time pressure monitoring. The slide valve mechanism is configured to respond to pressure fluctuations detected by the pressure sensor, controlling the flow of gas between the main air passage, the spoke-type radial air passage, and the secondary lip air passage to achieve adaptive adjustment of the main lip clamping force. At the same time, excess pressure is guided to the secondary lip O-ring area to synergistically enhance the auxiliary sealing and active chip removal functions.

[0009] Furthermore, the spool valve mechanism includes valve core air passage one and valve core air passage two, which are connected to the external air passage through air passage interface one, air passage interface two, air passage interface three, air passage interface four and air passage interface five. The sliding of the valve core is adjusted by the deformation of the pressure diaphragm and the preload of the spring, realizing the switching between the initial cut-off state and the air intake and exhaust state, in order to cope with the pressure changes caused by shaft end vibration or lip wear.

[0010] Furthermore, the spoke-type radial air passage includes an inlet passage and an outlet passage. The inlet passage and the outlet passage are evenly inclined around the circumference to form a pressure distribution network with a fast response, which avoids valve core jamming or response lag. The inlet of the inlet passage is connected to the valve core air passage one through air passage interface one, and the outlet branch is connected to the air spring and air passage interface three. The inlet of the outlet passage is connected to the air spring, and the outlet branch is connected to air passage interface two and air passage interface four.

[0011] Furthermore, the proximal outlet of the secondary lip air passage is oriented towards the compression deformation direction of the secondary lip O-ring, so that the exhaust airflow simultaneously acts to enhance the sealing force of the O-ring and to purge wear debris and contaminants.

[0012] Furthermore, the pressure sensor includes a first pressure sensor and a second pressure sensor, which are respectively installed on the air outlet and the air inlet and the main air passage, respectively, to monitor the pressure and provide feedback to control the gas flow in the air passage.

[0013] Furthermore, the slide valve mechanism, spoke-type radial air passage, and pressure sensors are evenly distributed in 3-12 groups along the circumference, each group being able to monitor and control independently to cope with the non-uniform pressure distribution in the circumference.

[0014] Furthermore, the device operates in the following manner:

[0015] During normal operation, the slide valve mechanism is in the closed state, and the main lip is sealed by the preload of the air spring;

[0016] When the shaft end vibration causes excessive local pressure, the first pressure sensor triggers the slide valve mechanism to exhaust gas, directing the excess gas to the secondary lip air passage, releasing the overpressure and enhancing chip removal.

[0017] When the lip is worn or the pressure is too low, the second pressure sensor triggers the air replenishment mechanism, which introduces an external air source to increase the pressure through the slide valve mechanism and restores the clamping force of the main lip.

[0018] After each adjustment cycle, the spool valve mechanism automatically resets once the pressure returns to equilibrium.

[0019] The beneficial effects of this invention are as follows:

[0020] This invention integrates a slide valve mechanism, a spoke-shaped multi-channel air passage structure, and a high-precision sensing system to construct an adaptive intelligent control lip seal device. It can respond in real time to pressure fluctuations caused by shaft end vibration or sealing pressure attenuation due to lip wear. Through dynamic differential pressure adjustment and adaptive control of the air supply passage, it maintains the optimal sealing force of the main lip and prevents local overpressure, while avoiding leakage caused by sudden drops in contact pressure. This significantly improves the dynamic stability and overall reliability of the sealing interface, greatly extending its service life. Innovatively, it throttles and guides excess pressure from the main lip to the secondary lip, actively blowing away accumulated wear debris or contaminants while tightening the O-ring to enhance auxiliary sealing and buffering shaft vibration impact. This achieves efficient reuse of excess pressure, forming a synergistic effect of "exhaust-sealing-self-cleaning." Furthermore, by integrating the slide valve mechanism, sensor, and actuator within the sealing ring skeleton, it forms a compact, responsive, and highly resistant built-in intelligent control system. Attached Figure Description

[0021] Figure 1 This is an axisymmetric structural diagram of a lip seal device;

[0022] Figure 2 This is a schematic diagram of the installation of a lip seal device on a shaft.

[0023] Figure 3 This is a schematic diagram of the initial closed state of the slide valve mechanism;

[0024] Figure 4 A schematic diagram of the intake and exhaust states of the slide valve mechanism;

[0025] Figure 5 This is a schematic diagram of the O-ring at the secondary lip.

[0026] In the diagram: 1. Sealing ring body; 11. Main lip; 2. Air spring; 3. Rigid frame; 31. Main lip side frame; 32. Secondary lip side frame; 321. Annular groove; 33. Reinforcing ring; 4. Main air passage; 5. Slide valve mechanism; 51. Valve sleeve; 511. Air passage interface one; 512. Air passage interface two; 513. Air passage interface three; 514. Air passage interface four; 515. Air passage interface five; 52. Valve core; 53. Pressure diaphragm; 54. Spring; 55. Valve core air passage one; 56. Valve core air passage two; 6. Secondary lip O-ring; 7. Secondary lip air passage; 8. Spoke-type radial air passage; 81. Inlet passage; 82. Outlet passage; 9. Pressure sensor; 91. First pressure sensor; 92. Second pressure sensor. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited thereto.

[0028] like Figure 1 and Figure 2 As shown, an adaptive intelligent control lip sealing device based on a slide valve mechanism includes a sealing ring body 1, an air spring 2, a rigid frame 3, a main air passage 4, a slide valve mechanism 5, a secondary lip O-ring 6, a secondary lip air passage 7, a spoke-type radial air passage 8, and a pressure sensor 9.

[0029] The sealing ring body 1 is molded from wear-resistant elastic materials such as fluororubber and has a main lip 11, which forms a seal through an interference fit with the shaft. An air spring 2 is embedded circumferentially in the groove on the outer side of the main lip 11. A rigid frame 3, as the core load-bearing component, is embedded inside the sealing ring body to provide structural support. It includes a main lip frame 31, a secondary lip frame 32, and a reinforcing ring 33. The proximal side of the main lip frame 31 extends to the main lip 11. The proximal side of the secondary lip frame 32 has an annular groove 321. The reinforcing ring 33 has a main air passage 4, which includes an inlet pipe and an outlet pipe. The main air passage 4 extends radially inward and connects to the slide valve mechanism 5. The secondary lip O-ring 6 is installed in the annular groove 321 and forms an auxiliary seal through an interference fit with the shaft.

[0030] like Figure 3 and Figure 4As shown, the spool valve mechanism 5 includes a valve sleeve 51, a valve core 52, a pressure diaphragm 53, and a spring 54. The valve sleeve 51 is fixed to the middle of the secondary lip side frame 32. The valve core 52 can slide within the valve sleeve 51. The distal side of the valve core 52 is fitted into the groove of the valve sleeve 51 with a clearance fit. The proximal side is achieved by the deformation of the pressure diaphragm 53 and the pre-tightening of the spring 54 to realize the real-time sliding of the valve core 52. The valve sleeve 51 and the valve core 52 are respectively bounded by the middle cavity wall to form a valve core air passage 1 55 on the left and a valve core air passage 2 56 on the right. Air passage interface 1 511, air passage interface 2 512, air passage interface 3 513, air passage interface 4 514, and air passage interface 515 are opened on the side wall of the valve sleeve 51. The pressure diaphragm 53 is connected to the tail end of the valve core 52 by fasteners, and the edge of the pressure diaphragm 53 is fixed to the inner wall of the valve sleeve 51. It is adjusted by the pressure of the valve core air passage 2 56 and the spring force of the right spring 54.

[0031] The secondary lip airway 7 is located within the secondary lip side frame 32. The distal side of the secondary lip airway 7 is connected to the valve core airway 55 via airway interface 515. Figure 5 As shown, the proximal side is radially aligned with the center of the secondary lip O-ring 6 and faces the compression deformation direction of the O-ring.

[0032] The spoke-type radial air passage 8 includes an inlet passage 81 and an outlet passage 82, which are evenly inclined along the circumference. The inlet of the inlet passage 81 is connected to the valve core air passage 55 via the air passage interface 1 511. The two branches of the outlet are connected to the air spring 2 and the air passage interface 3 513, respectively. The inlet of the outlet passage 82 is connected to the air spring 2. The two branches of the outlet are connected to the air passage interface 2 512 and the air passage interface 4 514, respectively. This creates a low-flow-resistance, fast-response pressure transmission network, improves the sensitivity and stability of the valve core under differential pressure drive, and avoids valve core jamming or response lag caused by uneven pressure distribution.

[0033] The main air passage 4, slide valve mechanism 5, spoke-type radial air passage 8, air spring 2, and secondary lip air passage 7 constitute an internal air passage network, which is used to introduce external compressed air and dynamically regulate gas flow.

[0034] The pressure sensor 9 includes a first pressure sensor 91 located at the air inlet of the exhaust duct 82 and a second pressure sensor 92 located on the main air duct 4, which together constitute a pressure detection module. The first pressure sensor 91 monitors the exhaust pressure P1 in real time to identify overpressure or underpressure states and initiate protective exhaust or replenishment; the second pressure sensor 92 continuously monitors the intake pressure P0 to provide feedback signals for maintaining system pressure stability.

[0035] The slide valve mechanism 5, the spoke-type radial air passage 8, and the pressure sensor 9 are all arranged in 3 to 12 groups evenly along the circumference, and each can be independently monitored and controlled.

[0036] See Figure 3The arrow indicates the direction of fluid flow. During operation, an external air source (pressure P0) is connected to the main air duct 4. During initial installation, the air spring 2 is pre-charged with a certain pressure.

[0037] During normal operation, valve core 52 is in Figure 3 In the cutoff state shown, the valve core flow channel 1 55 and valve core flow channel 2 56, the spoke radial air channel 8 and the air spring 2 inside the slide valve mechanism 5 are in a balanced state. The main air channel 4 and the secondary lip air channel 7 are not connected to the slide valve mechanism 5. Under the clamping force applied by the air spring 2 and the interference of the shaft load, the main lip 11 is tightly fitted to the shaft surface, providing a stable radial force to form the main sealing barrier. At the same time, the secondary lip O-ring 6 achieves auxiliary sealing through its own pre-tightening force.

[0038] When vibration occurs at the shaft end, the main lip 11 experiences non-uniform contact pressure along the circumference, manifested as a sharp increase in pressure near the eccentric side and a significant decrease in pressure on the far eccentric side. This device achieves independent monitoring and control through the circumferentially uniform arrangement of the slide valve mechanism 5, the spoke-type radial air passage 8, and the pressure sensor 9.

[0039] On the near-eccentric side, the air spring 2 experiences a large radial pressure, causing its internal air pressure to rise. The first pressure sensor 91 at the air inlet of the outlet 82 detects that the pressure exceeds a set threshold, and some of the gas in the air spring 2 is discharged, entering the valve core air passage 1 55 and valve core air passage 2 56 via the outlet 82, air passage interface 2 512, and air passage interface 4 514, respectively. Subsequently, under the combined action of inertial force and air pressure difference, the pressure diaphragm 53 elastically bulges to the right, compressing the spring 54 and driving the valve core 52 to move to the right. Figure 4 In the indicated state, at this valve position, the flow area between the valve core 52 and the valve sleeve 51 at the second airway interface 512 decreases, generating a throttling and pressure-reducing effect, initially dissipating the energy of the overpressured gas. Simultaneously, the valve core airway 55 connects to the secondary lip airway 7 via the fifth airway interface 515, guiding excess gas towards the secondary lip O-ring 6 area. This exhaust process effectively releases the overpressure risk of the air spring 2 at the main lip 11, improving system reliability, and also enhances the sealing force of the secondary lip O-ring 6, suppressing vibration effects and optimizing the auxiliary sealing effect. Simultaneously, the airflow promptly removes accumulated wear debris and contaminants from the secondary lip area, maintaining a clean sealing interface. On the other hand, the valve core airway 55 connects to the main airway 4 via the third airway interface 511, introducing gas to provide pressure stabilization and compensation. When the pressures of the first pressure sensor 91 and the second pressure sensor 92 return to equilibrium, and the system pressure stabilizes within the set range, external air supply pressure replenishment stops, and the valve core 54 moves to the left under the spring's restoring force, resetting to its original position. Figure 3 The initial state is used to complete one complete adaptive adjustment cycle.

[0040] On the far eccentric side, the air spring 2 experiences a smaller radial pressure, resulting in a decrease in its internal air pressure and insufficient sealing pressure. The first pressure sensor 91 at the air inlet of the outlet 82 detects that the pressure is below a set threshold. The external air supply device increases the supply pressure, pushing the valve core to move to the right against the spring preload. This connects the main air passage 4 to the valve core passage 55 and then to the inlet 81 via the air passage interface 511, ultimately delivering pressurized gas to the air spring 2 for supply and pressurization. This causes the main lip 11 to re-adhere to the shaft surface, effectively compensating for the decrease in sealing pressure caused by eccentricity, thereby restoring and maintaining its stable radial clamping force. Simultaneously, the valve core air passage 55 connects to the secondary lip air passage 7 via the air passage interface 515, guiding some gas to the secondary lip O-ring 6 area, enhancing the sealing force and chip removal effect of the secondary lip O-ring 6. When the pressures of the first pressure sensor 91 and the second pressure sensor 92 are restored to equilibrium, and the system pressure stabilizes within the set range, the external air supply pressure replenishment is stopped, and the valve core 52 moves to the left under the action of the spring restoring force, resetting to its original position. Figure 3 The initial position is determined, and a complete adaptive adjustment cycle is completed.

[0041] During continuous operation of the lip seal, the main lip inevitably wears due to dynamic friction with the surface of the rotating shaft, which gradually reduces the initial interference between the shaft and the lip, leading to an overall decrease in the radial contact pressure of the lip and a deterioration in performance.

[0042] When the first pressure sensor 91 at the air inlet of the outlet 82 detects that the pressure is lower than the set threshold, the external air supply device increases the air supply pressure, pushing the valve core 52 to move to the right against the spring preload force. This connects the main air passage 4 to the valve core passage 55 and then to the inlet 81 via the air passage interface 511, ultimately delivering the pressurized gas to the air spring 2 to achieve air supply and pressurization. This causes the main lip 11 to re-adhere to the shaft surface, effectively compensating for the decrease in sealing pressure caused by wear, thereby restoring and maintaining its stable radial clamping force. Simultaneously, the valve core passage 55 connects to the secondary lip passage 7 via the air passage interface 515, guiding some gas to the secondary lip O-ring 6 area, enhancing the sealing force and chip removal effect of the secondary lip O-ring 6. When the pressures of the first pressure sensor 91 and the second pressure sensor 92 return to equilibrium, and the system pressure stabilizes within the set range, the external air supply pressure is stopped, and the valve core 52 moves to the left under the spring restoring force, resetting to its original position. Figure 3 The initial position is determined, and a complete adaptive adjustment cycle is completed.

Claims

1. An adaptive intelligent control lip sealing device based on a slide valve mechanism, mounted on a rotating shaft, characterized in that, It includes a sealing ring body (1), an air spring (2), a rigid frame (3), a main air passage (4), a slide valve mechanism (5), a secondary lip O-ring (6), a secondary lip air passage (7), a spoke-type radial air passage (8), and a pressure sensor (9). The main lip (11) of the sealing ring body (1) is press-fitted with the surface of the rotating shaft to form the main sealing barrier. The air spring (2) is circumferentially embedded in the groove on the outside of the main lip (11) to provide adjustable radial clamping force. The rigid frame (3) is embedded inside the sealing ring body (1) to provide structural support. It includes the main lip side frame (31), the secondary lip side frame (32), and the reinforcing ring (33) for connecting the main lip side frame (31) and the secondary lip side frame (32). The main air passage (4) is located on the reinforcing ring (33) to introduce external air source. The slide valve mechanism (5) connects the main air passage (4) and the secondary lip side frame (32). It includes the valve sleeve (51), the valve core (52), the pressure diaphragm (53), and the spring (54). The valve core (52) can slide in the valve sleeve (51) to dynamically control the gas flow in response to pressure changes. The secondary lip O-ring (6) is installed on the secondary lip. The annular groove (321) of the lip skeleton (32) is used to achieve auxiliary sealing. The secondary lip air passage (7) is opened in the secondary lip skeleton (32) and connects the slide valve mechanism (5) and the secondary lip O-ring (6). The spoke radial air passage (8) is evenly arranged in the circumference and connects the air spring (2) and the slide valve mechanism (5) to build a low flow resistance pressure transmission network. The pressure sensor (9) is set on the spoke radial air passage (8) and the main air passage (4) to monitor the pressure in real time. The slide valve mechanism (5) is configured to respond to the pressure fluctuation detected by the pressure sensor (9). By controlling the flow of gas between the main air passage (4), the spoke radial air passage (8) and the secondary lip air passage (7), the clamping force of the main lip (11) is adaptively adjusted. At the same time, the excess pressure is guided to the area of ​​the secondary lip O-ring (6) to synergistically enhance the auxiliary sealing and active chip removal functions.

2. The adaptive intelligent control lip sealing device based on a slide valve mechanism as described in claim 1, characterized in that, The slide valve mechanism (5) includes valve core air passage one (55) and valve core air passage two (56), which are connected to the external air passage through air passage interface one (511), air passage interface two (512), air passage interface three (513), air passage interface four (514) and air passage interface five (515). The sliding of the valve core (52) is adjusted by the deformation of the pressure diaphragm (53) and the preload of the spring (54), realizing the switching between the initial cut-off state and the air intake and exhaust state, so as to cope with the pressure changes caused by shaft end vibration or lip wear.

3. The adaptive intelligent control lip sealing device based on a slide valve mechanism as described in claim 1, characterized in that, The spoke-type radial air passage (8) includes an inlet passage (81) and an outlet passage (82). The inlet passage (81) and the outlet passage (82) are arranged evenly in the circumferential direction to form a pressure distribution network with fast response, so as to avoid the valve core (52) from getting stuck or responding late. The inlet of the inlet passage (81) is connected to the valve core air passage (55) through the air passage interface one (511), and the outlet branch is connected to the air spring (2) and the air passage interface three (513). The inlet of the outlet passage is connected to the air spring (2), and the outlet branch is connected to the air passage interface two (512) and the air passage interface four (514).

4. The adaptive intelligent control lip sealing device based on a slide valve mechanism as described in claim 1, characterized in that, The proximal outlet of the secondary lip air passage (7) faces the compression deformation direction of the secondary lip O-ring (6), so that the exhaust airflow simultaneously acts to enhance the sealing force of the O-ring and to blow away abrasive contaminants.

5. The adaptive intelligent control lip sealing device based on a slide valve mechanism as described in claim 3, characterized in that, The pressure sensor (9) includes a first pressure sensor (91) and a second pressure sensor (92), which are respectively installed on the air inlet of the outlet (82) and the main air passage (4). The pressure is monitored and feedback is provided to control the gas flow in the air passage (4).

6. The adaptive intelligent control lip sealing device based on a slide valve mechanism as described in claim 1, characterized in that, The slide valve mechanism (5), the spoke radial air passage (8), and the pressure sensor (9) are evenly distributed in 3-12 groups along the circumference. Each group can be independently monitored and controlled to cope with the non-uniform pressure distribution in the circumference.

7. The adaptive intelligent control lip sealing device based on a slide valve mechanism as described in claim 5, characterized in that, The device operates in the following ways: During normal operation, the slide valve mechanism (5) is in the closed state, and the main lip (11) is sealed by the preload of the air spring (2); When the shaft end vibration causes the local pressure to be too high, the first pressure sensor (91) triggers the slide valve mechanism (5) to exhaust the gas, guide the excess gas to the secondary lip air passage (7), release the overpressure and enhance chip removal; When the lip is worn or the pressure is too low, the second pressure sensor (92) triggers the air replenishment mechanism, which introduces an external air source to increase the pressure through the slide valve mechanism (5) and restores the clamping force of the main lip (11); After each adjustment cycle, the slide valve mechanism (5) automatically resets after the pressure returns to equilibrium.

Images