RU2423620C2 - Metering gear pump - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: metering gear pump comprises a body with an input and an output holes, a driving shaft, an upper plate of a gear mechanism, a stator of a gear mechanism, a lower plate of a gear mechanism, a master gear, a slave gear, a master gear axis, a pressing plate, a clamping bolt with a nut, an upper and a lower bushings of the shaft. Pump gears are made of a self-lubricating composite material with a polyimide matrix with a plasticiser - lecithin. On the driving shaft, where the shaft is in contact with the upper and the lower plates, there are bushings installed made of the self-lubricating composition. The gap between the inner surface of the stator and the gear diameter makes 8…10 mcm. The gap between the driving shaft and the inner diameter of the master gear makes 5…7 mcm. The gap between the axis and the master gear makes 5…7 mcm.

EFFECT: reduced speed of wear in pump components that are friction pairs, and simplified technology of pump manufacturing.

1 dwg

Description

The invention relates to mechanical engineering, in particular to metering gear pumps with external gearing, and can be used for dosing chemically active liquid media, as well as in spinning machines that form chemical fibers in a wet and dry-wet way.

One of the main reasons for the deterioration in the metering characteristics of gear pumps pumping chemically active solutions is the rapid wear of the materials of their tribological conjugations, since, basically, these pumps were made for dosing liquids with a relatively low aggressiveness to metals. Wear leads to an increase in optimal gaps between the rubbing parts, inadmissible fluid flows from the suction chamber to the discharge chamber. In this case, the metering characteristics of the pumps change and they are removed from the machine.

Therefore, the main task of increasing the durability of metering pumps for chemically active environments is to reduce the processes of corrosion-mechanical and hydrogen wear of its parts. This is achieved by manufacturing parts of metering pumps from materials chemically resistant in these environments that do not create macro- and galvanic couples that are sources of electrochemical dissolution of metals.

A gear pump is known [Patent No. 2278300], the casing of which is made of a self-lubricating composite material with a polyamide matrix, including (wt.%): Plastic lubricant based on aviation sulphate cleaning oil No. 158 - from 12 to 16, graphite C-1 - from 6 to 10, lecithin - from 1 to 2 and polyhexamethylene sebaciamide - the rest [Patent No. 2241722]. The use of a self-lubricating composite material with a phospholipid - lecithin, which is an inhibitor of metal corrosion, as a casing made it possible to reduce the processes of anodic dissolution of the metal from which the pump drive shaft is made, which is in contact with the casing, which in turn increased its wear resistance and increased pump life. However, during friction of the metal surface of the intermediate sleeve, on which the pinion gear is located on the metal surfaces of the upper cover and the lower support plate, and also when the metal surface of the pinion gear is rubbed on the metal surface of the axis on which the gear is located, corrosion-mechanical wear of friction pairs occurred . As a result, unacceptable gaps appeared in these friction zones, fluid flows began, the pump lost the required dosing characteristics and was removed from the machine.

The closest in technical essence and the achieved result is a gear metering pump [Patent No. 2307260]. To prevent metal contact of the shaft with the surface of the lower and upper plates and the contact of the driven gear and its axis, an antifriction coating was applied to the surface of the shaft and axis, i.e. galvanic couples on the surfaces “metal shaft - metal plates” and “metal gear - gear axis” were practically eliminated. This design allowed to reduce the corrosion-mechanical wear in these tribological conjugations. However, the technology of applying and precision processing a three-layer coating was a complex and lengthy process, which significantly reduced the efficiency of coating use and increased the cost of the pump itself. Moreover, in the design of the pumps, both in the analogue and in the prototype, there are friction pairs “metal gears - metal stator” and “metal gears - metal plates”, which are most actively subjected to corrosion-mechanical wear. Even if these pump parts are made of a stainless steel of the same brand, they have different electrode potentials, which, when contacted during friction, leads to the formation of macro galvanic couples and, accordingly, to the processes of electrochemical dissolution of metals, depending on what is the anode or cathode in tribological conjugation .

The problem to which the present invention is directed, is to reduce the wear rate of the pump parts, representing the friction pairs "pinion gear - stator", "pinion gear - stator", "pinion gear - lower and upper plates", "pinion gear - lower and upper plates ”and simplification of pump manufacturing technology.

The technical result is to increase the durability of the operating life of the metering gear pump.

The above technical result is achieved by changing the design of the drive shaft of the pump, and the gears of the pump are made of composite material with a polyimide matrix with a plasticizer - lecithin.

The metering gear pump shown in the drawing contains a pump housing 1, a drive shaft 2, an upper plate of a gear mechanism 3, a stator of a gear mechanism 4, a lower plate of a gear mechanism 5, a drive gear 6, a driven gear 7, an axis of the driven gear 8, a pressure plate 9 , coupling bolts 10 with nuts 11, upper and lower bushings 12, inlet channel 13, outlet channel 14.

Distinctive features of the analogue and prototype are its following features.

1. The driving gear 6 and the driven gear 7 of the pump are made of a composite self-lubricating material with a polyimide matrix. The plasticizer in this material is phospholipid - lecithin;

2. The antifriction three-layer coating removed earlier on the drive shaft 2 and axis 8 was removed from the pump design;

3. The design of the pump drive shaft has been changed. In places where there is a contact of the shaft 2 with the upper 3 and lower 5 plates, sleeves 12 of a self-lubricating composition are installed [Patent No. 2241722], which are additional bearings of the drive shaft 2.

The optimal clearances in the pump mates are:

- the diameter of the inner surface of the stator - the outer diameters of the gears 8 ... 10 microns.

- axis diameter - inner diameter of the driven gear 5 ... 7 microns

- diameter of the drive shaft - the inner diameter of the drive gear 5 ... 7 microns.

The indicated ranges are determined taking into account an increase or decrease in the dimensions of parts and, accordingly, gaps with temperature. The dosing gear pumps under consideration are pumping and dosing chemically active solutions under the conditions of production of chemical threads for 12 months or more. During this period of time, the temperature of the pumps can vary between 10 ... 15 ° C. Accordingly, the gaps in the pump also change. This is because the pumps are in contact with the surrounding cold or warm air in the workshop, and also because the dosing solution, passing through the pipelines, is also cooled or heated. By mathematical, technological calculations and pilot tests, it was found that the operation of pumps with a reduced clearance between the inner surface of the stator and the outer surface of the gear below the above limits (7 μm or less) can lead to pump seizure in this tribological coupling with increasing temperature. At the same time, with an increase in the gap above the indicated limits (11 μm or more), the pump productivity and its dosage characteristics change sharply, which should remain constant throughout the entire life of the pump. Reducing the gap between the inner diameter of the driven gear and the axis (4 μm or less) can lead to jamming of the gear on the axis with increasing temperature. With an increase in this gap (8 μm or more), the metering characteristics of the pump also change due to the shift of the gear towards the engagement between the gears and, accordingly, the increase in the gap between the driven gear and the stator. Reducing the gap between the diameter of the drive shaft and the inner diameter of the pinion gear (4 μm or less) can lead to jamming (impaired self-installation of the gear during operation of the pump), since the gear should have free movement along the axis of the shaft. With an increase in this gap (8 μm or more), the dosage characteristics also change due to the shift of the gear in the direction of engagement between the gears and, accordingly, an increase in the gap between the drive gear and the stator.

Production tests confirmed the operability of metering gear pumps with the indicated clearances and their unreliability in case of their change.

The pump operates as follows.

The rotation of the drive shaft 2 is transmitted to the drive gear 6 and the pumped liquid is supplied through the channel 13 in the housing 1 to the suction area of the gear mechanism. From the suction region, the liquid enters the discharge region of the pump gear mechanism in the volumes formed by the tooth cavities of the pinion gear 6 and the driven gear 7 and the stator 4. From the pump region, the fluid is removed from the pump through channel 14. The drive shaft 2 rotates with the bushings fixed to it in the housing 1, which is simultaneously a self-lubricating bearing for the shaft. Driven gear 7 made of self-lubricating material rotates on axis 8.

During the operation of the driving and driven gears during friction on the surface of the stator, axis and plates, as a result of the difference between the internal and contact temperatures, a plasticizer — lecithin — is released from the gear in microvolumes, which creates constantly restored films on the contacting surfaces of the stator, axis and surfaces of the plates, interfering with their corrosion-mechanical wear.

The test results of a gear metering pump with an increased service life on spinning machines of Kamenskvolokno OJSC allow us to judge the high efficiency of the described construction. The service life of the gear metering pump in comparison with the service life of the known design increased by 2 ... 3 times. There is no longer any need for anti-friction coatings on the shaft and axis of the pump.

Claims (1)

Dosing gear pump, consisting of a housing with an inlet and outlet, a drive shaft, an upper gear plate, a gear stator, a lower gear plate, a pinion gear, a driven gear, a driven gear axis, a pressure plate, a coupling bolt with a nut, an upper and the lower shaft bushings, characterized in that the pump gears are made of a self-lubricating composite material with a polyimide matrix with a plasticizer - lecithin, and on the drive shaft, where ct shaft with upper and lower plate, bushings of a self-lubricating composition are installed, while the gap between the inner surface of the stator and the diameter of the gears is 8 ... 10 μm, the gap between the drive shaft and the inner diameter of the pinion gear is 5 ... 7 μm, the gap between the axis and the driven the gear is 5 ... 7 microns.

Images