RU2138107C1 - Compound for manufacturing current collectors - Google Patents

Abstract

FIELD: electrical engineering; current collectors for trolley buses. SUBSTANCE: known compound composed of 67-75 mass percent of graphite, 5-12 mass percent of hardened coke, 11-20 mass percent of phenol formaldehyde resin, and 0.5-2.0 mass percent of zinc stearate is doped, in addition, with 0.5-5.0 mass percent of polytetrafluoroethylene. EFFECT: improved density of load current collected. 1 tbl

Description

 The invention relates to electrical engineering and relates to a composition for the manufacture of current collectors, for example inserts for current collectors of trolley buses.

 A known composition for the manufacture of a sliding part, containing 30-80 weight. % graphite powder, 0.5-30 wt.% lead-containing powder, 15-45 wt. % organic polymer binder (US Pat. US N 4316834, Ml. C 08 L 6/06, Ncl 260-38, 1982).

 The disadvantage of this composition is the formation of lead dust during the operation of products, which is environmentally hazardous for the atmosphere of the city.

 A known composition for the manufacture of current collectors, containing in wt.%: Electrographite (graphite powder of high purity with an ash content of not more than 0.3%) - 60-90, a binder - phenol-formaldehyde resin, 10-40, 0.5-5 aluminum granules and 0.05-0.5 granular silicon carbide added to graphite powder (US Pat. Japan N 60-13382, Ml. H 02 K 13/00, H 01 B 43/12, 1985).

 A disadvantage of the known composition is the uneven distribution of silicon carbide in it, which, in turn, leads to uneven grinding properties of the material, wear of the contact wire.

 Closest to the claimed composition is a composition for the manufacture of current collectors, containing in wt.%: Electrographite 67-75, calcined coke 5-12, phenol-formaldehyde resin 11-20, aluminum 0.5-5, zinc stearate 0.5-2.0 (Pat. RF N 1809725, MKl. H 01 B 39/20, 1993 - prototype).

 Current collectors made from the known composition work both in dry and in wet conditions.

 The disadvantage of the composition is that on paired trolley buses, where the density of the removed current load is much higher than on ordinary trolley buses, the current collectors (inserts) begin to chip, forming transverse cracks, the bulk of the inserts are removed from service without fulfilling the required resource.

 In addition, aluminum oxide formed under conditions of high humidity (rainy weather, marine climate) is an abrasive, which over time leads to increased wear of the contact wire.

 The aim of the invention is to expand the range of applicability of the carbon insert by increasing the density of the removed current load.

 This goal is achieved by the fact that in the known composition containing in wt.%: Electrographite 67-75, coke calcined 5-12, phenol-formaldehyde resin 11-20, zinc stearate 0.5-2.0, additional polytetrafluoroethylene (fluoroplast-40 ) in an amount of 0.5-5 wt.%.

 Common features of the invention and the prototype is the content of electrographite, calcined coke, phenol-formaldehyde resin and zinc stearate.

 A distinctive feature is the introduction of polytetrafluoroethylene (fluoroplast-40) into the composition.

 The use of polytetrafluoroethylene as an additive is known in brushes in order to reduce wear (Av. St. USSR N 233783, Ml. H 01 R 39/24, 1968), in order to increase the durability of the brushes and improve the collector properties (US Pat. Japan N 24763 / 67, N. 55 A 0/33, 1967).

 In the proposed technical solution, polytetrafluoroethylene additive is used to expand the range of applicability of current collectors (inserts) by increasing the density of the removed current load.

 Thus, the proposed solution has a novelty and inventive step.

 The industrial applicability of the technical solution is undeniable. The inserts made of the carbon composition taken as a prototype are operated on trolleybus lines in Russian cities. They provide high mileage of trolley buses and, very importantly, do not wear out the contact wire, which is made of copper.

But the inserts work well only on single trolley buses, where the density of the removed current load is 18 A / cm ² , on paired trolley buses, where the density of the removed current load reaches 35 A / cm ² , the inserts from the known composition practically do not work.

 The proposed technical solution makes it possible to manufacture carbon inserts operating at high current densities, and at the same time not wear out the wire.

 The invention consists in the following.

 The carbon insert is a fine anti-friction material, but fragile. When operating trolley buses, the inserts experience large shock loads, especially at the joints of wires. They chip, cracks form. Under the influence of current, high local temperatures arise in the body of the insert, which increase crack formation.

 The higher the density of the removed current load, the greater the tendency to crack formation. The insert is removed from service not because of its deterioration, but because of the formation of cracks. Such an insert as a conductive material can no longer work.

On conventional trolley buses, the current load is 18 A / cm ² , but at the time of stopping and starting it increases to 28 A / cm ² . As a rule, at these moments, the insert undergoes the strongest current. Especially, this phenomenon progresses with the operation of inserts on twin trolleybuses (trolleybus trains), where the current load increases to 35 A / cm ² . On trolleybus trains, an insert from a known composition practically does not work.

 In the present invention, in order to expand the applicability of the inserts by increasing the density of the removed current load, polytetrafluoroethylene (fluoroplast-40) is additionally introduced into the composition.

 Ftoroplast-40, introduced into the composition, improves the wettability of the filler, increases the adhesion of the binder to the filler, increases the elasticity of the spatial lattice during the curing of phenol-formaldehyde resin.

 The material has a more perfect structure, which is characterized by greater elastic properties, greater impact strength.

 This, in turn, makes it possible to obtain an insert that can withstand large shock and current loads without destruction; the number of inserts with virtually no cracks producing a full resource increases significantly.

 The following are specific examples of the manufacture of compositions.

 Example 1 (prototype).

 Electrographite (TU 48-4802-20-90), calcined coke (TU 14-7-80-86), crushed and sieved through a sieve 07, in the ratio (wt.%) 71: 8 were averaged in a Z-shaped mixer for 30 min.

To the averaged filler was added a binder in the amount of 17 wt.% - phenol-formaldehyde resin of the SFP0IIL brand and was again mixed for 40 minutes. The mass was unloaded from the mixer and plasticized in a 2-screw mixer CH-100 at a temperature of 100-120 ^o C.

The processed and cooled mass was ground in a DM-300 mill, sieved through a 045 mesh. 3 wt.% Aluminum powder and 1 wt.% Zinc stearate were introduced into the obtained powder. The mixture was stirred for 40 minutes in a Z-shaped mixer and discharged. From the obtained powder was pressed on a 63-ton press at beats. a pressure of 900 kgf / cm ² , a temperature of 175-185 ^o C and a shutter speed of 60 seconds insert size 88 x 28 x 14.5 mm In the insert, the dynamic elastic modulus (GOST 30262-95) and the impact strength on the pile swingarm (GOST 7853-84) were determined.

The inserts were subjected to operational testing on the route with the following characteristics:
Contact wire brand - MF-85
Suspension Type - Chain
The number of intersections with tram lines - 12
The number of intersections with trolleybus lines - 5
Contact network length -9.72 km
Humidity 80% at a temperature of 20-22 ^o C
The test results of the inserts obtained in example 1 are given in the table.

 Example 2

 Electrographite (TU 48-4802-20-90) and calcined coke (TU 14-7-80-86) crushed and sieved through a sieve 07, in the ratio (wt.%) 71: 8 were averaged in a Z-shaped mixer for 30 min

 A binder - 17 wt% - phenol-formaldehyde resin of the SFPIIII brand (TU 6-05-1370-90) and 3 wt% fluoroplast-40 (GOST 14906-77) was added to the averaged filler and mixed again for 40 minutes.

The mass was unloaded from the mixer and subjected to plasticization in a 2-screw mixer SN-100 at a temperature of 100-120 ^o C.

 The processed and chilled mass was ground in a DM-300 mill, sieved through a 045 mesh. 1 wt.% Zinc stearate was introduced into the obtained powder. The mixture was stirred for 40 min in a Z-shaped mixer.

From the obtained powder was pressed on a 63-ton press at beats. a pressure of 900 kgf / cm ² , a temperature of 175-185 ^o C and a shutter speed of 1 min insert size 88x28x14.5 mm.

The insert was tested for impact strength (GOST 7853-84), dynamic modulus of elasticity (GOST 30262-95) and subjected to operational tests on the route with the following characteristics:
Contact wire brand - MF-85
Suspension Type - Chain
The number of intersections with tram lines - 12
The number of intersections with trolleybus lines - 5
Contact network length - 9.72 km
Humidity 80% at a temperature of 20-22 ^o C
The test results of the inserts of example 2 are given in the table.

 Example 3

 Electrographite and coke calcined, crushed and sieved through a sieve 07, in a ratio of 75:12 were averaged in a Z-shaped mixer for 30 minutes. To the averaged filler was added a binder in an amount of 11 wt.% - phenol-formaldehyde resin of the brand SFPOIIL and 0.5 wt.% Fluoroplast-40 and was again mixed for 40 minutes

 Further processing and testing were carried out according to example 2.

 Example 4

 Electrographite and coke calcined, crushed and sieved through a sieve 07, in a ratio (wt.%) Of 67:10 were averaged in a Z-shaped mixers for 30 minutes. A binder in the amount of 17 wt.% - phenol-formaldehyde resin of the SFPIIII brand and 5 wt.% Fluoroplast-40 was added to the averaged filler and again mixed for 40 minutes.

 Further processing and testing was carried out according to example 2.

 Example 5

 Electrographite and coke calcined, crushed and sieved through a sieve 07, in the ratio (wt.%) 75:12 were averaged in a Z-shaped mixer for 30 minutes. To the averaged filler was added a binder in an amount of 11 wt.% - phenol-formaldehyde resin of the SFPOIIL brand and 0.4 wt.% Fluoroplast-40 and was again mixed for 40 minutes.

 Further processing and testing was carried out according to example 2.

 Example 6

 Electrographite and coke calcined, crushed and sieved through a sieve 07, in the ratio (wt.%) Of 67: 9 were averaged in a Z-shaped mixer for 30 minutes. A binder in the amount of 18 wt.% And 5.2 wt.% Of fluoroplast-40 was added to the averaged filler and mixed again for 40 minutes.

 Further processing and testing was carried out according to example 2.

From the analysis of the results presented in the table, it follows that when operating the inserts from the known composition, the resource without destruction at the current load (conventional trolley buses) of 18 A / cm ² passes only 70% of the inserts; 30% of the inserts are decommissioned due to the formation of cracks and chips. With an increase in current load up to 35 A / cm ^{2, the} number of inserts that have not worked out their resource increases even more.

 The proposed technical solution (examples 2-4) can significantly increase the elastic properties and impact strength of the material (1.5-2 times), increase the density of the removed current load, while the number of inserts working out the resource significantly increases.

At a current load of 35 A / cm ² , the number of inserts removed due to cracks and chips from operation is reduced to 21%, and at a load of 18 A / cm ² - up to 5%.

The content of fluoroplast-40 should not be less than 0.5 wt.%, Since with a lower content (example 5) the results are almost the same as is typical for the known composition. But it was not painful to 5 wt.%, Since with a higher content of fluoroplast-40 (Example 6), although the toughness continues to increase, the number of inserts that withstand a current load of 35 A / cm ² decreases. This is due to the fact that fluoroplast-40, introduced into the composition in an amount of more than 5 wt.%, Begins to reduce the conductivity of the material, the electrical resistivity of the inserts increases, the inserts begin to overheat and collapse.

Claims (1)

 Composition for the manufacture of current collectors containing 67 to 75 wt.% Electrographite, 5 to 12 wt.% Coke calcined, 11 to 20 wt.% Phenol-formaldehyde resin, 0.5 to 2.0 wt.% Zinc stearate, characterized in that it additionally contains polytetrafluoroethylene in an amount of 0.5 to 5 wt.%.

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