LOW-PRESSURE STARTING DEVICE FOR PNEUMATIC PUMPS

Description

[0001] The present invention refers to a low pressure starting device for pneumatic pumps with a pivoting directional air control valve which uses a low pressure starting system consisting of a piston driven by a variable tension spring which exerts force on the shaft of the pivoting element of the directional valve body, during start-up, in one of the operating positions at either end. It is used to control the operation of a double diaphragm pump or pneumatic piston pump.

[0002] The main body of the directional valve has inlet and outlet ports. The pivot element is placed inside the directional valve and moves freely between the two limit positions and has two surfaces that adapt to close the air ports in either the two end positions. Once the pivoting directional control valve is set in motion to control the diaphragm or piston pump, the low-pressure starting system is retracted by the double diaphragm or piston pump's own operating pressure. The operation of the pivoting directional control valve also requires the use of pneumatic pilot sensors that detect the limit positions of the diaphragms of the double diaphragm pump to allow the reversal of the movement of the pivoting directional control valve itself.FIELD OF APPLICATION THE INVENTION

[0003] This invention has its application within the sector of the pneumatic pump industry for the transfer of fluids and / or fluids containing solids or particles in suspension and / or powders and / or fluids which are chemically aggressive or difficult to handle, such as hydrocarbons, chlorinated hydrocarbons, acids, bases and other chemical products used in industrial processes.BACKGROUND TO THE INVENTION

[0004] There are many pneumatic double diaphragm or piston pumps on the market driven by air motors that control the reciprocating motion of the pumps for normal operation.

[0005] Air motors can take various forms and generally consist of an air steering device or slide although a pivoting drive can also be used instead. The present invention has its application in air motors for driving pneumatic devices which have a pivoting drive element. In these cases, to improve the start-up of devices controlled at very low pressures, the low-pressure start-up system described in this patent will be used.

[0006] The applicant company holds Patent No. ES20100000633 (PCT / ES2011 / 000162) for a central flow double diaphragm pump with a low friction pivoting directional spoiler valve, however, the present invention is a substantial improvement to the starting system of the aforementioned low-pressure pumps. It is not known of any type of pneumatically operated motor with a pivoting device incorporating a low-pressure starting device consisting of a piston driven by a spring of variable force and which allows the device to start at low pressures and retract automatically when the set normal operating pressure is reached.

[0007] On the other hand we find WO 99 / 25999, EP 0524820 and DE 15 28 505.

[0008] Regarding WO 99 / 2599 describes a pivoting valve.

[0009] The valve described in this patent includes one inlet port and two outlet ports.

[0010] On the other hand, this patent does not address the issue of starting at low pressures because it is not a pneumatic motor, it is a description of a passage valve used to control the passage of fluids other than air.

[0011] The aforementioned patent describes a pivot valve but the actuation system is completely different as it is actuated by magnets to ensure the tightness of the valve.

[0012] Regarding EP 0524820 describes a diaphragm pump with its fluid chambers, check valves and bleed system. The bleed system refers to grooves that are made in the fluid check valves that allow the passage of fluid when required. The fluid flow from the purge system can be internal or external. The described diaphragm pump incorporates an air motor with a different technology based on slide valves which are completely different from pivoting valves. The slide valve described in this patent shows mechanisms formed by shafts and O-rings for sealing, which have a reciprocating but not pivoting movement.

[0013] Regarding DE 15 28 505 describes a system for increasing the pressure of fluid media and more specifically refers to a mechanism for increasing the pressure of a fluid whose application requires high pressures.DESCRIPTION OF THE INVENTION

[0014] For the description of the present invention, the following terminology is used and is confirmed to be commonly accepted in the field to which it refers. The meaning of each piece of terminology is given below for the purposes of its understanding. AIR / COMPRESSED AIR= compressed air or any other driving fluid. FLUID = pumped material which could be a liquid, a liquid with suspended particles, or air with suspended dust. PIVOTING VALVE = pivoting directional valve with a replaceable inlet and outlet drum LSD = Low Start Device

[0015] The present invention consists of a special design of the pneumatically driven air motor equipped with a pivoting valve which works via the introduction of a piston thrust device which allows the starting of the pump which it controls to take place even with very low pressure.

[0016] The low pressure starting device (3) consists of the following elements: Main thrust piston with its sealing ring (3.4) Spring (may be an elastomer) Spring stop (3.3)

[0017] This device is located in the air motor chamber for driving double diaphragm or piston pneumatic pumps, where the pivoting valve is housed. Its function is to distribute the compressed air to the two chambers of the pump to produce its alternating movement, the present invention provides a low pressure starting device comprising of a piston, a sealing ring (3.4), a spring and a spring stop (3.3) which hold the pivoting valve in its starting position until the required minimum starting pressure is reached. Once this minimum starting pressure is reached, the low-pressure starter system is pulled back against the spring pressure and held in this position due to the working pressure in the chamber until the air motor pressure is released due to the air motor being switched off, at which point the air motor returns to its starting position.

[0018] The push piston is positioned so that the end of the main push piston strikes the pivot valve at its inlet arm in such a way that it holds it in the initial start position, even if the system is not pressurised. The point of contact on the pivoting valve shall be such that the force exerted by the piston spring allows the pivoting valve to be held in the standby position regardless of the state of the air motor.

[0019] Once the air pressure is allowed into the air motor through the motor inlet and once it reaches the set start pressure, the air pressure exerts a force on the LSD piston which causes it to pull backwards eliminating the support it had on the pivot valve. At this point the working pressure is reached and the pivoting valve starts to work without being disturbed by the LSD thrust piston and sends air alternately to both chambers through the air inlet ports.

[0020] Once the air pressure is lost due to the device stopping, the pressure in the inlet chamber of the air motor disappears and the LSD piston is automatically pushed by a spring or by any pressure system used for this purpose, it returns to its initial position by pushing the pivoting valve and holding it in its starting standby position ready to start the work cycle again.

Claims

1. Low-pressure starting device for a pneumatic double-diaphragm pump or piston pump with a pivoting air directional control valve, which has two defined working positions located at the opposite ends of its range of motion, wherein in one position, it applies pressure to the pivoting air directional control valve, and in the other position, it is fully retracted, comprising a low-pressure starting system comprising a retractable push piston (3.1),a sealing gasket (3.4),a variable-tension spring (3.2), and a spring stop (3.3), wherein the retractable push piston is driven by the variable-tension spring, which exerts force on the pivoting air directional control valve during startup, and the spring stop retains the pivoting air directional control valve in its start position until the minimum starting pressure is reached, once this minimum starting pressure is achieved, the low-pressure starting device retracts against the spring force and remains in the retracted position until the air motor pressure is released upon shutdown of the air motor, at which point it returns to its initial position, and a pressure regulation system is included, enabling adjustment of the minimum starting pressure of the pivoting air directional control valve, and wherein, optionally, in the low-pressure starting device, the function of the spring (3.2) can be performed by an electronic pressure control system, which allows automatic adjustment of the starting pressure.

2. Low pressure starting device for pneumatic pumps with pivoting directional air control valve according to claim 1 which can have a driving fluid other than compressed air but which is equally suitable for driving pneumatic devices such as double diaphragm pneumatic pumps or piston pumps.

3. Low-pressure starting device for pneumatic pumps with pivoting directional air control valve, according to claim 1 wherein the spring (3.2) can be an elastomer whose elastic properties allow the retractable piston to be operated.

4. Low pressure starting device for pneumatic pumps with pivoting directional air control valve, according to claim 1 wherein the retractable piston can be operated by means of air or pressurised hydraulic fluid instead of the spring (3.2).

5. Low pressure starting device for pneumatic pumps with pivoting directional air control valve, according to claim 1 wherein the pivoting valve is provided with an inlet drum and an outlet drum which distribute the compressed air to the pump chambers to be driven alternately and both drums are replaceable.