RU2497673C2 - Method of high-frequency processing of polyamide parts and device to this end - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to high-frequency processing of roller bearing polyamide cage. Proposed method comprises embracing the part by high-potential and earthed electrodes of operating capacitor connected to high-frequency generator and applying pressure thereto. Note here that said part is embraced over top, bottom and inner side surfaces of plates to create spatial circuit 2×n of operating capacitors and simultaneously, connection to generator is made. This makes the potential difference between top high-potential plate and electrodes connected via bottom contact group to bottom earthed plate and bottom earthed plate and electrodes connected via top contact group to top high-potential plate. Heating is performed to polyamide recrystallisation start temperature. Then, generator is switched off on turning the part about its axis by one electrode to heat unprocessed surfaces.

EFFECT: recovery of durability of bearing cage made of polyamide.

6 cl, 3 dwg, 1 tbl, 1 ex

Description

The proposed method and device for its implementation relates to the processing of parts from plastics, in particular from polyamide.

80% of emergency stops of the rolling stock of Russian Railways is related to the failure of the axle boxes, one of the main elements of which are bearings with polyamide cages.

The problem of separators made of polyamide is their hydrophilicity, water absorption reaches several percent (in some cases up to 8%) and significantly affects the strength and toughness. The deformation-strength characteristics of polyamides are restored after drying of the samples (see the book “Technical properties of polymeric materials”: Uch.-sp., Village / V.K. Kryzhanovsky, V.V. Burlov, A.D. Panimatchenko, Yu. V. Kryzhanovskaya. - St. Petersburg, publishing house "Profession", 2003, pp. 43-44, 110).

Therefore, the task is to create an effective technology for drying polyamides, using high-frequency processing, ensuring the restoration of the necessary mechanical properties of critical structural products, including bearing cages made of polyamide.

A similar drying method is presented in patent RU No. 2338135, IPC F26B 7/00 (claimed on November 7, 2008, publication date: November 10, 2008).

This patent describes a method for drying sodium iodide.

The essence of the method includes: preliminary dehydration of the feedstock to a mass fraction of moisture of 5-7%, cooling to a temperature of 60-65 ° C and final drying with the supply of electromagnetic field energy and a medium pressure of 25-30 mm. Hg The final vacuum drying is carried out in an atmosphere of carbon tetrachloride vapor.

It is possible to develop a similar method for removing high humidity from polyamide separators in vacuum when applying electromagnetic field energy, but the cost of the installation will be very high, and the high costs of operation and maintenance will make it uncompetitive.

It is also known "Device for dielectric heating of long material" (patent RU No. 2073315 MAK Н05В 6/46, filed March 11, 1993, publication date: February 10, 1997).

The essence of the device is that for dielectric heating of a long material, containing two identical long flat electrodes between which there is a heated material, two output terminals, a high-frequency generator, located opposite the middle of the length of the electrodes symmetrically relative to them and two identical groups of conductors connecting the output terminals generator, one of which is connected to a common bus, with the corresponding long electrodes. They are connected in an identical way symmetrically with respect to the ends of the electrodes and at equal distances along the length of the electrodes, while the distance from the ends of the electrodes to the nearest ends of the conductors is half the distance between adjacent ends of the conductors. The conductors are made in the form of a symmetric, relative to the common bus, n-step m-channel branching system with identical parameters of the conductors in each step. Two conductors of the first branching stage are located symmetrically relative to the additional conductor shielding them from the common bus, both ends of which and the middle of one conductor of the first branching stage are connected to the common bus

An inductive element is connected between the middle of another conductor of the first stage connected to the output terminal of the generator that is not connected to the common bus and the middle of the said additional conductor.

It is practically impossible to use this method and device for drying separators made of polyamide due to the bulkiness of the installation and the complexity of its manufacture. During operation, this installation requires a lot of time for preparatory work, adjustment of equipment and fixtures.

Closest to the proposed invention relates to "A method for high-frequency welding of plastic parts and a device for its implementation" (Patent RU No. 2396171 IPC В29С 65/04, filed December 22, 2008, publication date: August 10, 2010).

The essence of this method

To seal the cover-case connections of plastic batteries with compartments formed by a partition inside the case, the parts to be connected are covered around the perimeter by high-potential and grounded electrodes of the working capacitor connected to the high-frequency generator, while applying pressure. A second working capacitor is formed inside the housing, the potential difference is created due to the induced EMF and at the same time, the potential difference in the second working capacitor is regulated.

This method solves the problem of sealing the connection "cover - housing" made of plastics. In our case, the task is to restore the strength characteristics of products made from polyamide using high-frequency processing.

The aim of the invention is the restoration of the strength characteristics of a bearing cage made of polyamide.

The goal is achieved by the fact that they produce high-frequency processing of a roller bearing cage made of polyamide by covering parts with high-potential and grounded electrodes of a working capacitor connected to a high-frequency generator, while applying pressure, while covering the workpiece with electrodes is carried out on the upper, lower and inner side surfaces of the partitions, creating a spatial scheme of 2 × n working capacitors (where, n is the number of electrodes), simultaneously connect to a high frequency generator, thereby forming a potential difference between adjacent electrodes and between the upper high potential plate and electrodes connected through the lower contact group to the lower grounded plate and the lower grounded plate and electrodes connected through the upper contact group to the upper high potential plate. Heating is carried out to the temperature at which polyamide recrystallizes, which is determined by the occurrence of a step in the anode current readings on an ammeter mounted on a high-frequency generator, after which the high-frequency generator is turned off. Since the parts of the upper and lower rims located under the contacts of the upper and lower contact groups are not heated, the treatment cycle is repeated by turning the part (for example, the separator) around the axis by one electrode.

The pressure of the press is carried out by connecting contact groups with electrodes and high-potential and grounded plates.

A device for high-frequency processing of parts (separator) made of polyamide, containing high-potential and grounded electrodes, a working capacitor, a high-frequency generator, while on the lower grounded plate and on the upper high-potential plate installed contact groups connecting the electrodes respectively to the lower grounded and upper high-potential plate, moreover, one of the contacts of the upper or lower group of contacts is connected to each electrode, moreover, metal electrodes are used as electrodes s body rolling bearings.

The contacts of the upper and lower contact group tightly fit part of the outer surface of the electrodes.

The invention is illustrated by drawings.

The figure 1 presents a diagram of a device for high-frequency processing of parts made of polyamide

The figure 2 presents a diagram of a device for high-frequency processing of parts made of polyamide (type A). (The bottom grounded plate and part of the electrodes are not shown).

The figure 3 presents a diagram of a device for high-frequency processing of parts made of polyamide (with the upper high-potential plate lowered)

In Fig. 1, Fig. 2, the device contains a movable upper high-potential plate (1) and a lower grounded plate (2), they are installed: on a movable upper high-potential plate - an upper contact group (3), on a lower grounded plate - a lower contact group (four).

The separator (5) consists of partitions (6), the upper rim (7) and the lower rim (8). Electrodes (9) are inserted into the separator (5). Press (10) is in a raised state.

Figure 3 shows the working capacitors and potential differences on them, formed as a result of a technological device for high-frequency processing of parts assembled and connected to a high-frequency generator (press (10), is in the lowered, working state).

The working capacitor C _v and the potential difference on it U _v - are formed between the upper movable high-potential plate (1) and the lower grounded plate (2).

The working capacitors of the partitions (6) C _{per1 ... n} , and the potential difference on them U _{per1 ... n} , are formed between the electrodes (9) connected to the upper high-potential plate (1) and the electrodes (9) connected to the lower ground stove (2).

The working capacitors of the upper rim (7) C _{о1 ... n} and the potential difference on them, U _{о1 ... n} , are formed between the upper high-potential plate (1) and the electrodes (9) connected to the lower grounded plate (2). The working capacitors of the lower (8) rim are formed between the lower grounded plate (2) and the electrodes (9) connected to the upper high-potential plate (1).

Thus, all the working capacitors C _v , C _{ob1 ... n} and C _{pep1, .. n} are connected in parallel, which allows processing of all construction elements of the separator connected to the electrodes in one cycle.

The processing of parts made of polyamide is as follows. Between the movable upper high-potential plate (1) and the lower grounded plate (2), a workpiece (an example is a polyamide cage (5), a roller bearing) with electrodes inserted into it (9) is installed on the lower contact group (4). Top set the upper contact group (3). The press (10) is lowered onto the assembled technological device and the generator is turned on. The processing mode is controlled by the anode current indicator of the ammeter installed on the high-frequency generator. The tight fit of the upper (3) and lower (4) contact groups to the electrodes (9) ensures the design of the contacts of the contact group (curvature radius R) and the pressure on the contact groups by the press (10).

After connecting the device to the high-frequency generator at the points of contact with the electrodes (9) on the product surfaces, potential differences U _{per1 ... n are formed} on the baffles (6) of the separator and U _{ob1 ... n} on the rims of the separator (5) in the capacitors C _{per1. ..n} and C _{about ... n} . The electric field in the capacitors leads to heating of the structural elements of the partitions (6) and the upper (7) and lower (8) rims of the separator (5), respectively. To heat parts of the upper (7) and lower (8) rims located directly under the contacts of the upper (3) and lower (4) contact groups, it is necessary to repeat the processing process by turning the part (separator) around the axis by one electrode. After which the part is removed and goes to the assembly.

The high-frequency processing method provides the evaporation of moisture from parts, thereby increasing the dielectric constant of the material. Given that the dielectric constant of materials is proportional to humidity, heating continues until increased humidity is maintained. Due to the low thermal conductivity of the polyamide when heated to the temperature of the onset of recrystallization, the bulk of the material will not be removed from the crystalline or glassy state.

A series of experiments was carried out on drying the polyamide at the UZP 2500 installation in accordance with the described methodology and technological device.

Separators and electrodes (rollers) of bearings of model 2726 of JSC Stepnogorsk Bearing Plant (former GP3-16) were used, with an operating time of more than 50,000 km (dismantled during the overhaul period, when conducting a full audit of axle boxes in LCChD-7, Irkutsk, Russian Railways Railways) . Bearing cages material - Armamide PA SV 30-1ETM. The processing time varied from 60 to 120 seconds, with a nominal anode current of 0.6-0.7A, controlled by an ammeter installed on a high-frequency generator.

The results are presented in table 1

Table 1 Drying time, s 0 60 80 one hundred 120 Relative humidity% 5,6 2.05 1,6 1.75 0.7 Tensile strength, MPa 136.7 137.2 139.3 141.4 144.3 Anode current, A 0.65 0.7 0.7 0.7 0.6

From the above data it can be seen that the relative humidity at the initial values of 5.6% after treatment decreased to 0.7%, and the strength characteristics increased by 7.6%, which allows us to conclude the practical significance of this technique.

Claims (6)

1. The method of high-frequency processing of a part, which is a polyamide cage of a roller bearing, by covering the part with high-potential and grounded electrodes of a working capacitor connected to a high-frequency generator, while applying pressure, characterized in that the workpiece is covered by electrodes along the upper, lower and inner side to the surfaces of the partitions, creating a spatial scheme of 2 × n working capacitors, where n is the number of electrodes connected to high-frequency potential generator, a potential difference is formed between adjacent electrodes and between the upper high potential plate and electrodes connected through the lower contact group to the lower grounded plate, and the lower ground plate and electrodes connected through the upper contact group to the upper high potential plate, heating is performed to the temperature of the onset of recrystallization polyamide, after which the high-frequency generator is turned off, the part is rotated around the axis by one electrode and the raw surfaces are heated. 2. The method of high-frequency processing of a polyamide part according to claim 1, characterized in that the part is heated until a step occurs in the anode current readings on the ammeter. 3. The method of high-frequency processing of parts made of polyamide according to claim 1, characterized in that the pressure is carried out when connecting the contact groups with the electrodes and high-potential and grounded plates. 4. Device for high-frequency processing of a part, which is a polyamide cage of a roller bearing, containing high-potential and grounded electrodes, a working capacitor, a high-frequency generator, characterized in that contact groups are connected to the lower grounded plate and to the upper high-potential plate, connecting the electrodes respectively to the lower grounded and the upper high-potential plates, moreover, one of the contacts of the upper or lower group of contacts is connected to each electrode. 5. The device for high-frequency processing of parts made of polyamide according to claim 1, characterized in that the metal rolling elements of the bearings are used as electrodes. 6. The device for high-frequency processing of parts made of polyamide according to claim 1, characterized in that the contacts of the upper and lower contact groups tightly fit part of the outer surface of the electrodes.

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