Control valve for a hydraulic elevator

Abstract: Control valve for a hydraulic elevator, provided with a speed regulating plug (2) which moves with the flow of the hydraulic fluid and whose position determines the flow of hydraulic fluid into the actuating cylinder of the elevator. At each end of the speed regulating plug, the valve is connected to a system 1 of hydraulic channels (1) in which the hydraulic fluid flows and which communicates with the main hydraulic circuit. Besides a throttle (9), an additional channel (10) is connected to the hydraulic channel system (1), said additional channel being provided with a flow resistance component comprising a capillary throttle (12).

Description: The present invention relates to a control valve arranged in a main hydraulic fluid flow between a pressure supply and an hydraulic cylinder of an hydraulic elevator, the control valve being provided with a speed regulating plug moving in a cylindrical chamber which is connected to leads of the main hydraulic fluid flow, the position of the speed regulating plug in the chamber determining the amount of the main fluid flow and being controlled by a hydraulic channel system connecting both ends of the cylindrical chamber and comprising a throttle for delimiting the hydraulic fluid flow through the channel system, the channel system being in communication with the main fluid flow The viscosity of oil, which is the hydraulic fluid most commonly used in hydraulic elevators, is reduced by about a decade as the oil is heated from the lowest working temperature to the highest working temperature. In the case of an elevator provided with a pressure-controlled ON-OFF-type control valve, this involves an increase in deceleration with an increase in temperature, because the control valve is closed faster due to a reduced kinetic resistance of the speed regulating plug. A problem in this case is that the elevator, when working at "normal operating temperature", has an excessively long creeping time when arriving at a landing. This is because the distance of the deceleration vanes in the hoistway from the landing must be adjusted for the lowest oil temperature to avoid overtravel. In principle, the deceleration is based on a hydromechanical time reference. After the supply of electricity to the magnetic valve has been interrupted, a spring pushes the plug of the control valve towards the closed position while a throttle in the hydraulic circuit retards the closing of the valve. It is important to notice that the closing speed depends on the viscosity of the oil even in the case of a fully viscosity-independent throttle, because the kinetic resistance of the valve plug depends on the viscosity. As the resistance diminishes, the pressure difference across the throttle increases, involving an increase in the flow towards the speed regulating plug and therefore an increase in the plug speed. DE application publication 2908020 proposes a device for decelerating a hydraulic elevator by means of throttles and valves controlling the open position of the by-pass valve. The adjustment depends on the temperature of the hydraulic fluid. However, the device has the disadvantage that it uses a magnetic valve, necessitating a connection to the electrical system, thus rendering the solution too complex. GB-A 2 204 362 discloses a control valve for regulating the actuating velocity of the hydraulic cylinder of an hydraulic elevator. This control valve comprises three by-pass check valve, a circulating valve and a setting valve which are connected by a channel system. The control of the valve is performed by means of solenoids and according to the adjustment of throttles to provide three different actuating velocities of the hydraulic cylinder. However, the adjustments and setting points of this control valve are influenced by changes of the viscosity of the hydraulic fluid, which may occur as result of a temperature rise of the hydraulic fluid during use. The object of the present invention is to create a control valve for a hydraulic elevator which achieves compensation of variations in the viscosity of the hydraulic fluid in a simple manner so as to keep the creeping distance essentially constant all the time. The control valve of the invention is characterized in that, that an additional channel (10) is provided, ending in the channel system (1) between the throttle (9) and one end (2b) of the cylindrical chamber, and that a flow resistance component (12-15) is provided in that additional channel, the flow resistance thereof being based on the internal friction of the fluid. The other embodiments of the control valve of the invention are characterized by what is presented in the subclaims. The invention has the advantage that it provides a control valve for hydraulic elevators that is independent of variations in the viscosity of the oil, thus ensuring a reliable deceleration of the elevator and making it more comfortable for the passengers. In the following, the invention is described in detail by the aid of examples of preferred embodiments, reference being made to the drawing attached, wherein: Fig. 1 presents a diagram of a part of a conventional control valve for a hydraulic elevator, said part comprising a speed regulating plug and a hydraulic channel system. Fig. 2 presents the same as Fig. 1, with the difference that the hydraulic channel system is provided with an additional branch as provided by the invention. Fig. 1 shows part of the conventional hydraulic channel system 1 of the control valve of a hydraulic elevator, comprising a speed regulating plug 2 which moves in an essentially closed space 3 provided for it. The hydraulic fluid in the main flow channel flows through this space 3, from the inflow channel 4 to the outflow channel 5, which leads to the actuating cylinder of the elevator. The middle part of the speed regulating plug is of an essentially conical form. Thus, when the plug moves longitudinally to the left (as seen in Fig. 1), it throttles the flow 4, 5. The flow is largest when the plug is in its extreme right position. The elevator speed decreases when the spring 8 pushes the speed regulating plug 2 towards the closed position, i.e. to the left in Fig. 1. As a result of this movement of the speed regulating plug, the oil used as hydraulic fluid will pass the plug by its left-hand end and flow in the hydraulic channel system 1 through the distributing valve 6 and the throttle 9 choking the mass flow into the spring space to the right of the plug. Thus, the speed of the plug movement is determined by the throttle 9. In the position shown in Fig. 1, the 3/2-way distributing valve 6 provided in the hydraulic channel system 1 permits a fluid flow towards the speed regulating plug. In this situation, the elevator is being decelerated. As the temperature of the hydraulic fluid rises during use, its viscosity is reduced, thus reducing the kinetic resistance of the speed regulating plug. Consequently, the pressure difference Δp₁ increases, increasing the flow V₁. Therefore, the speed control valve is closed faster, resulting in a greater rate of deceleration of the elevator. The change in the flow across the throttle 9 between the extreme positions is about 30 %, and the variation in deceleration in previously known solutions is proportional to this. This variation in deceleration is one of the drawbacks of previously known solutions. In the other position of the distributing valve 6, the hydraulic fluid is allowed to flow into the tank 7 until the speed regulating plug 2 has reached its fully open position and the elevator is travelling at full speed. Fig. 2 illustrates the solution of the invention, in which the hydraulic channel system 1 comprises, besides a distributing valve 6 and a throttle, an additional channel 10. The first end 10a of the additional channel is connected to the hydraulic channel system 1 at a point where the pressure is the same as the pressure at the first end 2a of the speed regulating plug 2. This pressure is designated p₀ in this context. Similarly, the other end 10b of the additional channel is connected to the hydraulic channel 1 at a point where the pressure is the same as the pressure at the other end 2b of the speed regulating plug 2. This pressure is designated p₁. In the embodiment described here, the first end of the additional channel is connected to a point between the first end 2a of the speed regulating plug 2 and the distributing valve 6, whereas the other end of the additional channel is connected to a point between the other end 2b of the speed regulating plug and the throttle 9. The additional channel is provided with a flow resistance component consisting of a capillary throttle 12 choking the volume flow, a cylinder 13, an auxiliary piston 14 moving in it, and a spring 15 connected between the cylinder and the auxiliary piston, said spring acting in the direction of movement of the auxiliary piston. The capillary throttle 12 is connected in series with the cylinder-piston-spring assembly 13-15. The action of the viscosity-compensated system of the invention during deceleration of the elevator is as follows. The flow V₁ from the throttle 9 to the speed regulating plug 2 is divided into two components, one V₂ of which flows to the speed regulating plug and the other V₃ to the flow resistance component 12-15 in the additional channel. The capillary throttle is a tubular choker based on the internal friction of the fluid. The flow through the capillary throttle is inversely proportional to the viscosity of the fluid, so that if the viscosity is reduced e.g. to 1/10, the flow in the capillary throttle is increased to an almost tenfold value. By contrast, throttle 9 chokes the mass flow, and the mass of oil does not change much with rising temperature and falling viscosity. The following example makes this clear. The hydraulic fluid typically used in hydraulic elevators is oil, whose temperature varies between 10° - 60° during use. The viscosity of warm oil is 10 times lower than that of cold oil. Due to the size of the speed regulating plug, the volume flow V₁ is 16 units of volume (uv)/second for cold oil and 25 uv/s for warm oil. The flow resistance component 12-15 is so dimensioned that when the oil is cold and volume flow V₁ is 16 uv/s, volume flow V₃ will be 1 uv/s and the volume flow V₂ going to the speed regulating plug will be 15 uv/s. As the temperature rises to the maximum value of 60°, volume flow V₁ increases to a value of 25 uv/s. The oil, whose viscosity has been reduced to 1/10, now flows at a tenfold rate through the capillary throttle 12, .i.e. V₃ is 10 uv/s, which means that volume flow V₂ is still 15 uv/s. In this way, volume flow V₂ has been rendered independent of variations in the viscosity of the oil used as hydraulic fluid. Therefore, a constant closing speed of the regulating plug 2 is maintained. If desired, even a diminishing closing speed with rising temperature can be achieved. This makes it possible e.g. to compensate the effect of pump leakage. It is obvious to a person skilled in the art that the invention is not restricted to the examples of its embodiments described above, but that it may instead be varied within the scope of the following claims.

Claims: Control valve arranged in a main hydraulic fluid flow (4,5) between a pressure supply and an hydraulic cylinder of an hydraulic elevator, the control valve being provided with a speed regulating plug (2) moving in a cylindrical chamber which is connected to leads (4,5) of the main hydraulic fluid flow, the position of the speed regulating plug (2) in the chamber determining the amount of the main fluid flow (4,5) and being controlled by a hydraulic channel system (1) connecting both ends of the cylindrical chamber and comprising a throttle (9) for delimiting the hydraulic fluid flow through the channel system (1), the channel system (1) being in communication with the main fluid flow (4,5), characterized in that an additional channel (10) is provided, ending in the channel system (1) between the throttle (9) and one end (2b) of the cylindrical chamber, and that a flow resistance component (12-15) is provided in that additional channel, the flow resistance thereof being based on the internal friction of the fluid. Control valve according to claim 1, characterized in that the first end (10a) of the additional channel (10) is connected to the hydraulic channel system (1) at a point where the pressure (p₀) is the same as the pressure at the first end (2a) of the speed regulating plug (2), and that the other end (10b) of the additional channel is connected to the hydraulic channel (1) at a point where the pressure (p₁) is the same as the pressure at the other end (2b) of the speed regulating plug (2). Control valve according to claim 1 or 2, characterized in that the flow resistance component consists of a capillary throttle (12) choking the volume flow, a cylinder (13), an auxiliary piston (14) moving in it, and a spring (15) connected between the cylinder and auxiliary piston, said spring acting in the direction of movement of the auxiliary piston, and that the capillary throttle (12) is connected in series with the cylinder-piston-spring assembly (13-15).

Inventors: PELTO-HUIKKO RAIMO, PELTO-HUIKKO, RAIMO
Applicants: KONE ELEVATOR GMBH
Application year: 1990
Main classification: B66B1
IPC codes: B66B1, B66B9