GB2179576A

GB2179576A - Formation of coating by electrical means

Info

Publication number: GB2179576A
Application number: GB08521645A
Authority: GB
Inventors: Tashko Iliev Tashkov; Fillip Raykov Fillipov; Toma Lyubenov Popov
Original assignee: ZENTRALEN MASH I
Current assignee: ZENTRALEN MASH I
Priority date: 1985-08-30
Filing date: 1985-08-30
Publication date: 1987-03-11
Also published as: GB2179576B; DE3530249A1; JPS6260880A; CH668569A5; GB8521645D0

Abstract

There is disclosed method and apparatus for the formation of a coating on a workpiece (24) by electrical means and using a multi-disc electrode assembly (1). The workpiece (24) is mounted on a table (23), and the electrode assembly (1) is rotated by a horizontal drive shaft (2) as it is advanced over the surface of the workpiece which is to be coated. Intermittent contact takes place between the discs (1) and the workpiece surface by providing an arrangement for imparting vibration to the table (23), this comprising an eccentric (26) driven by a motor (28) via a cogged belt drive (27). <IMAGE>

Description

SPECIFICATION The Formation of a Coating on a Workpiece by Electrical Means This invention relates to a method and apparatus for the formation of a coating on a workpiece by electrical means.

The invention has particular, though not exclusive, application in the surface deposition of electrically conductive materials on parts and instruments for general and special use, and particularly in the construction of machines.

The invention is particularly concerned with a method and apparatus for the formation of a coating on a workpiece by electrical means, which involves so-called electrosparking weld padding (EWP).

A method for electrosparking weld padding of metals and alloys is known according to which an electrode assembly performs a rotative and forward motion and is simultaneously subjected to vertical vibrations. Due to the vibrations, the electrode assembly intermittently contacts a static surface of a workpiece which is to be coated (padded).

A device is known for implementing the above method, comprising a disc-type electrode assembly mounted on a flexible shaft which is connected with a horizontal D.C. electric motor.

A disadvantage of the known method and the device for implementing the same is that the parallel use of more than one electrode disc is not possible because the proper contact of more than one disc with the surface which is being padded cannot be provided, the result of which is low efficiency.

Another disadvantage is the requirement for the direct participation of an operator in the padding process, which results in a deterioration of the surface quality.

The present invention seeks to provide a method and apparatus for electrosparking weld padding which are highly efficient due to the automation of the weld padding process as a result of which an even surfacing with high mechanic characteristics is achieved.

According to one aspect of the invention there is provided a method for the formation of a coating on a workpiece by electrical means using a rotatable disc type electrode, comprising the steps of advancing the rotating electrode over the surface of the workpiece which is to be coated while making intermittent contact with said surface, and imparting vibration to the workpiece so as to produce the intermittent contact with the electrode.

According to a further aspect of the invention there is provided apparatus forthe formation of a coating on a workpiece by electrical means and comprising: a rotatable disc-type electrode; a table for mounting the workpiece so that a surface of the workpiece which is to be coated is presented to the electrode; means for rotating the electrode and for advancing the rotating electrode over the surface of the workpiece; and means for imparting vibration to the table so that the workpiece surface can make intermittent contact with the electrode during its movement over the workpiece surface.

In a preferred embodiment of apparatus according to the invention, the following advantages can be achieved: surfacing of a workpiece with an even thickness and density, without requiring any special skill on the part of the operator; and high efficiency due to the possibility of using more than one electrode disc at a time and because of the automatic compensation in the feeding of the electrode assembly relative to the surface which is to be coated, as the electrodes wear, as a function of the change in the difference between the amplitude of movement of the idle table (i.e. without the workpiece) and the amplitude with optimum electrode force when the workpiece is on the table.

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic side view of apparatus according to the invention; and Figure 2 is a section on the line A-A in Figure 1.

As will become evident from the detailed description of the preferred embodiment of the invention, there is disclosed herein a method and apparatus forthe formation of a coating on a workpiece by electrical means using a rotatable disc type electrode. Means is provided for advancing the rotating electrode over the surface of the workpiece which is to be coated while making intermittent contact with such surface, and means is also provided for imparting vibration to the workpiece so as to produce the intermittent contact with the electrode.

Referring now to the drawings, the apparatus comprises an electrode assembly with more than one electrode disc 1 mounted on a shaft 2 connected with a horizontal D.C. electric motor 3, which is mounted on a base 4, fixed to a drive screw 5. The apparatus is used in so-called electrosparking weld padding (EWP) to apply a coating on a workpiece.

The drive screw 5 is connected via a drive nut 6 with a stepping electric motor 7 situated on a carriage 8.

A nut 9 with a screw 10 is mounted on the carriage 8.

The screw 10 is connected with an upper electric motor 11 and with a ratchet mechanism 12 with a limiting screw 13 mounted on guides 14. On the ratchet mechanism 12 there are mounted an electromagnet 15, a pawl 16 with lobes G1 and an end switch K1. The carriage 8 with the end switches K2 is connected with a body 17 with lobes G2 which is mounted on a longitudinal carriage 18 with end switches K3 and K4. The longitudinal carriage 18 is placed on the guides 14 with lobes G3 and an electromagnet 19 with a lobe G4. The longitudinal carriage 18 is connected with a lower electric motor 21 by means of a rack and pinion gear 20. The electrode assembly with discs 1 is connected with pulse generators 22. A table 23 with a workpiece 24 to be coated is arranged under the discs 1, the table being mounted on flat or leaf springs 25.Mounted on the table 23 is an eccentric 26 connected with a vertical D.C. electric motor 28 by means of a cogged belt transmission 27. The table 23 is also connected with a correcting device 29 which is mounted on the longitudinal carriage 18.

The operation of the apparatus illustrating also the gist of the method is as follows: The horizontal D.C. motor 3, the vertical D.C.

motor 28, the lower motor 21 and the pulse generators 22 are activated and the apparatus begins its automatic cycle. Each double pass of the longitudinal carriage 18 is accompanied by a transverse translational feeding by means of the ratchet mechanism 12. The reciprocating motion is effected by means of reversing the direction of rotation of the lower motor 21, which receives signals from the end switches K3 by means of the lobes G3. At the end of the coating or padding cycle the lobe G2 on the body 17 presses the end switch K2 which sends a signal to the electromagnets 15 and 19. The electromagnet 19 activates lobe G4 and at the end of the double pass of the carriage 1 8 the lower motor 21 gets locked while the horizontal D.C.

motor 3 and the vertical D.C. motor 28 stop. The activated electromagnet 15 attracts the pawl 16 of the ratchet mechanism 12 and the screw 10 is released, whereas the end switch K2 switches on the upper motor 11 which moves the carriage 8 back to its initial position.

With the placing of a new workpiece on the table 23, the machine is ready for a new automatic cycle For maintaining a constant clearance within certain limits between the electrode assembly and the surface which is being coated or padded, a correcting device 29 is used, registering any change in the difference between the idle table amplitude and the table amplitude when padding is being carried out. When a certain preset value for the change in the difference is reached, the correcting device 29 transmits a signal to the stepping electric motor 7 which moves the drive nut 6, the drive screw 5 and the electrode assembly 1 downwards and restores the proper clearance.

Claims

1. A method forthe formation of a coating on a workpiece by electrical means using a rotatable disc type electrode, comprising the steps of advancing the rotating electrode over the surface of the workpiece which is to be coated while making intermittent contact with said surface, and imparting vibration to the workpiece so as to produce the intermittent contact with the electrode.

2. A method according to claim 1, in which the electrode comprises a plurality of axially spaced electrode discs mounted on a common driving shaft.

3. A method according to claim 1 or 2, in which a correcting device monitors wear of the electrode and automatically adjusts the position of the electrode relative to the workpiece surface, to compensate for such wear.

4. A method according to claim 1 and substantially as hereinbefore described with reference to, and as shown in the accompanying drawings.

5. Apparatus for the formation of a coating on a workpiece by electrical means and comprising: a rotatable disc-type~electrode; a table for mounting the workpiece so that a surface of the workpiece which is to be coated is presented to the electrode; means for rotating the electrode and for advancing the rotating electrode over the surface of the workpiece; and means for imparting vibration to the table so that the workpiece surface can make intermittent contact with the electrode during its movement over the workpiece surface.

6. Apparatus according to claim 5, in which the workpiece comprises a plurality of axially spaced electrode discs mounted on a common driving shaft.

7. Apparatus according to claim 5 or 6, including a correcting device arranged to monitor wear of the electrode and to provide automatic adjustment of the position of the electrode relative to the workpiece surface, in order to compensate for electrode wear as it occurs.

8. Apparatus for carrying out a method according to claim 1 and comprising: an electrode assembly having a plurality of electrode discs (1) mounted on a common driving shaft (2) provided on a first horizontal D.C. electric motor (3); a drive screw (5) coupled with said first motor (3) and connected by means of a drive nut (6) with a second stepping electric motor (7) for adjusting the position of the electrode discs (1) relative to the workpiece surface;; a carriage (8) on which said second motor (7) is mounted and connected by means of a nut (9) with a screw (10) which is connected with a ratchet mechanism (12) provided with a limiting screw (13), an electromagnet (15) and a pawl (16), the ratchet mechanism (12) being fixed to a body (17) which is mounted on a longitudinal carriage (18) placed on guides (14) and connected by means of a rack and pinion gear (20) with a third lower electric motor (21); a table (23) for mounting the workpiece (24) adjacent to the electrode discs (1); an eccentric (26) coupled with the table (23) in order to impart vibration to the workpiece (24) so that the latter makes intermittent contact with the electrode discs (1); a cogged belt transmission (27) coupled with said eccentric (26) and with a fourth vertical D.C. electric motor (28); and a correcting device (29) arranged to monitor electrode disc wear and coupled with said table (23) and with said longitudinal carriage (18).

9. Apparatus according to claim 5 and substantially as hereinbefore described with reference to, and as shown in the accompanying drawings.