WO1998001624A1

WO1998001624A1 - Method and device for metal workpiece allowance grinding

Info

Publication number: WO1998001624A1
Application number: PCT/CH1997/000254
Authority: WO
Inventors: Jacques Hentsch
Original assignee: E F S A
Priority date: 1996-07-08
Filing date: 1997-06-27
Publication date: 1998-01-15
Also published as: FR2750632A1; FR2750632B1; EP0851952A1

Abstract

A device for carrying out a method for removing an allowance from the surface of a metal workpiece, particularly along a railway track rail weld, is disclosed. The device comprises a rotary circular grinding wheel with an electrical contact element (40) built into said wheel (11), and means for sensing contact between said element and said metal workpiece (13) in the area of the allowance (12) and optionally in an adjacent allowance-free area used as a reference surface (R). Said electrical contact element (40) comprises a conductive member (40a) housed in an insulating sheath (40b) and parallel to the rotational axis of the grinding wheel (11).

Description

METHOD AND DEVICE FOR GRINDING A THICKNESS OF A METAL PART

The invention relates to a grinding method for flattening an excess thickness of a surface of a metal part, in particular of a railroad track at the location of a weld, by means of a rotary circular grinding wheel.

It also relates to a grinding device for flattening an excess thickness of a surface of a metal part, in particular of a railroad track, at the location of a weld, by means of a rotary circular grinding wheel, for the implementation of the above method.

When welding metal parts, the weld bead which is deposited at the junction of the parts creates an excess thickness which it is then necessary to eliminate by appropriate machining. When the parts are small and can be assembled in the workshop, on machining machines such as levelers or others, the planarization of the additional thickness poses no problem. On the other hand, when grinding must be carried out on the site, which is the case with railway rails, the problem is much more complex. Very often, the operation, which is long and tedious, is carried out by hand, which can lead to an imprecise finish. For high-speed train rails in particular, the finish must necessarily reach a precision that is difficult to achieve manually repeatedly. For this reason, automatic grinding machines have been developed which do not, however, include simple and effective detectors capable of determining with precision the end of the grinding operation, that is to say the moment when the excess thickness has completely disappeared. .

The invention proposes to fill this gap by producing a grinding device and by developing an appropriate method for grinding the excess thicknesses of a metal part, and in particular the weld seams on rail tracks, this device being arranged to detect with precision and in a simple and effective manner the moment when the excess thickness has completely disappeared.

This object is achieved by the method according to the present invention, characterized in that the end of the grinding operation is automatically detected by means of an electrical circuit comprising an electrical contact element integrated in said rotary circular grinding wheel, and means for detecting the closure of this circuit following contact of said electrical contact with said metal part in the area of the allowance and / or in an adjacent area which constitutes a reference surface.

According to a first embodiment of the method, the grinding operation is automatically stopped when two electrical contacts are detected per revolution of the grinding wheel, one of these contacts corresponding to the contact of said electrical contact element with said metal part. in the area of the additional thickness and the other contact corresponding to the contact of said electrical contact element with said metal part in said adjacent area.

According to a second embodiment of the method, the area of the additional thickness and at least one adjacent area is scanned, and the contacts between said electrical contact element and said metal part are detected only in said adjacent zone, said grinding operation being interrupted at the time of this detection.

In all embodiments, to grind a cylindrical surface of any cross section, the procedure is by grinding of adjacent facets covering the area of the allowance.

This object is also achieved by the device for implementing the method according to the invention, characterized in that it comprises an element of electrical contact integrated in said rotary circular grinding wheel, and means for detecting the contacts of this element with said metal part in the area of the allowance, on the one hand and, if necessary, in an adjacent area free of allowance which constitutes a surface reference.

In an advantageous embodiment, said electrical contact element comprises a conductive member mounted in the thickness of a cup wheel, this conductive member being arranged parallel to the axis of rotation of the wheel.

In an alternative embodiment, said electrical contact element may comprise a conductive member mounted in the thickness of a flat grinding wheel, this conductive member being arranged radially and opening out at the periphery of this grinding wheel.

In this variant, the device comprises a collecting brush connected to said contact element, and a conductive bar arranged to cooperate with said collecting brush to constitute an electrical circuit in which are included said metal part and a device for detecting an electrical signal, said conductive bar being electrically interrupted in the area of the allowance. The interruption of the busbar can for example be carried out by means of an insulating cursor adjustable in position.

Preferably, the conductive member, which is integrated in the grinding wheel and which may consist of a graphite rod, is housed in an insulating sheath comprising a fibrous material constituting at least one layer peripheral to the conductive member. Said fibrous material may include paper.

In all embodiments, the conductive member and the insulating sheath must be arranged to wear out at the same speed as the grinding wheel. The invention will be better understood with reference to the detailed description of exemplary embodiments and to the accompanying drawings, in which:

FIG. 1 schematically represents a first embodiment of the device according to the invention,

FIG. 2 schematically represents a second embodiment of the device according to the invention,

FIG. 3 schematically represents the operation of a signal generator associated with the device according to the invention, and

FIG. 4 represents a graph illustrating the signals coming from the generator of FIG. 3, used within the framework of the embodiment of the device corresponding to FIG. 1.

With reference to FIG. 1, the grinding device 10 represented comprises a rotary grinding wheel 11, which is the grinding tool intended to flatten an extra thickness 12 of a surface of a metal part 13, such as a track rail railroad. In the example shown, the grinding wheel is a cup, cup-shaped grinding wheel having a U-shaped cross section, the active surface being annular.

This wheel is mounted on a carriage 14 arranged to move along the double arrow A on a transverse beam 15, by means of four guide rollers 16. This transverse beam is carried by two end supports 17 comprising a threaded sleeve 18 in which is engaged an endless screw 19. The two endless screws 19 arranged on either side of the transverse beam 15 each carry a drive pinion 20 which meshes respectively with a drive pinion 21 disposed at 90 ° and secured to a rotary drive shaft 22. The pinions 20 and 21 constitute two pairs of gears arranged to drive the screws 19 and to ensure a displacement in translation along the double arrow B, of the transverse beam 15. The pairs of gears 20, 21 are made integral with two uprights 23 and a crosspiece 24 of a frame which carries the entire device and which allows the latter to be mounted on a reference plane R of the metal part 13, by means of fixing flanges 25. The grinding wheel 11 is driven by an electric motor 26 carried by the carriage 14 and supplied by a suitable cable 27, housed in a support or cable tray 28 which is connected to a connection box 29 itself coupled to an electrical panel 30.

The movement of the carriage 14 according to the double arrow A is effected by means of a pneumatic cylinder 31 without rod, which is supplied with fluid compressed by products 32 and 33 which end in a supply unit 34 also carrying a pneumatic reverser 35 arranged to alternately reverse the direction of movement of the carriage 14.

The drive of the shaft 22 can be done by means of a crank 36, or any other manual or mechanized means.

The grinding wheel 11 comprises an electrical contact element 40 comprising a conductive member 40a integrated in an insulating sheath 40b housed in a bore 42 formed through its entire thickness. This electrical contact element is connected by a cable to a slip ring 43 which cooperates with a detector working on an angular sector of the order of 90 °.

When the grinding wheel is in rotation, as long as the additional thickness 12 remains, a single electrical signal appears for each revolution of this grinding wheel. As soon as the excess thickness has disappeared, the electrical contact element 40 arrives at each revolution of the grinding wheel in contact on the one hand with the excess thickness zone and, on the other hand, with the reference surface R, so that two signals appear at each turn of the grinding wheel. The device 50 according to FIG. 2 differs from the previous embodiment in that the grinding wheel 51 is of the disc grinding wheel type and in that the part 52 is movable relative to the grinding wheel. As before, the grinding wheel has an electrical contact element 53 comprising a conductive member 53a integrated in an insulating sheath 53b which is housed in a radial bore 54 formed in the thickness of the grinding wheel. The axis 55 of the grinding wheel carries a slip ring 56 which cooperates with contact brushes 57 carried by a support 58 secured to a fixed console 59 which carries the motor of the grinding wheel.

The part 52 is carried by a magnetic plate 60 which is integral with a movable table 61 of a workshop leveler 62 or the like. An electrically conductive bar 63 is mounted on the movable table 61 and an insulating slider 64 is linked to this bar to which it is fixed by means of a locking screw 65. The insulating slider is arranged substantially vertical to the area to be grind 12 of part 52. The bar 63 is electrically linked to the movable table.

A collecting brush 66 fixed relative to the movable table 61 is preferably mounted on the frame of the workshop leveler 62. A power supply unit 67 provides the electrical supply as well as the distribution of the supply current to the system detection. A cable 68 connects this power supply unit 67 to the contact brushes 57 and another cable 69 connects the housing 67 to the collecting brush 66. The housing 67 is supplied with electrical energy by a cable 70.

In this embodiment, the console 59, which carries the grinding wheel 51, is fixed, the part 52 being movable relative to this grinding wheel. The workpiece moves alternately on either side of a substantially vertical axis passing through the axis of the grinding wheel. In this way, the area to be ground 12, that is to say the excess thickness due to a weld is scanned from left to right and from right to left. The electrically conductive bar 63 moves at the same time as the movable table. Since the insulating cursor is placed at the vertical of the zone which covers the zone to be ground when the grinding wheel is located in this zone, no electrical signal is transmitted to a detector (not shown) via the electrical contact element 53 and the collecting brush 66 When the grinding wheel is offset from the area to be ground, two cases may occur

either the periphery of the grinding wheel is located at the height of the protuberance and does not touch the reference surface R of the part on either side of this protuberance and, in this case, the circuit is not closed and no signal appears even though the collecting brush 66 is in contact with the conductive bar 63 on either side of the insulating cursor 64,

- either the periphery of the grinding wheel is located at the height of the reference surface R, because the protuberance is completely ground and, in this case, the circuit is closed on either side of the part 52 and a signal of end of grinding is emitted by the device

FIG. 3 illustrates the principle of detecting the end of grinding. The electrical contact element of the grinding wheel is constituted by the conductive member 40a and its insulating sheath 40b in the example of embodiment of FIG. 1 and of the electrical contact element 53 consisting of the conductive member 53a embedded in its insulating sheath 53b in the embodiment of the figure

2 The conductive member is preferably constituted by a rod of more or less hard graphite, such as for example a pencil lead, and the insulating sheath can be made of a winding of paper or of a sleeve made of a brittle material which does not clog the grinding wheel, this sheath advantageously being made at least partially of a more or less soft fibrous material depending on the graphite used. The electrical contact element is positioned so that it exceeds by a few tenths of a millimeter the surface of grinding and wears out at roughly the same speed as the grinding wheel

The detector D provides a signal DR to a microcontroller 80 A cam 81 arranged to rotate with the axis of the grinding wheel, cooperates with an optical or capacitive detector 82 or the like to supply a signal ME to the microprocessor. The cam has a notch 83 of a quarter circle, which makes it possible to define a time base which determines a measurement window of 180 °.

The workpiece 13, for example a rail, is connected to earth 84 of the microcontroller. The supply voltage is connected to terminal 85. An alarm 86 is provided to signal the contact of the detector with the reference surface of the workpiece. A QA signal called "alarm receipt" is transmitted to the microcontroller.

Figure 4 illustrates the shape of the system signals. The signal ME defines a time measurement corresponding to a 90 ° angle of the grinding wheel and a corresponding measurement time. The signal DR corresponds to pulses from detector D. The pulses are only taken into account in the measurement window. The signal MC illustrates the first signal DR which is maintained during the time of 90 ° of rotation of the grinding wheel. The signal AL defines the alarm order when a second signal DR appears in the measurement window. The QA signal corresponds to the receipt and cancellation of the order. The system measures the travel time of the grinding wheel at an angle of 90 ° and stores this time. It is used as a reference to create 90 ° immunity upon detection of contact with the part. It is also used to define a 180 ° measurement window to detect a second possible contact point which identifies the end of grinding and the triggering of the alarm. Without an alarm, and at the end of the measurement window, the system waits for a new first DR signal.

Claims

1 Grinding method for smoothing an excess thickness of a surface of a metal part, in particular of a rail track at the location of a weld, by means of a rotary circular grinding wheel, characterized in that the the end of the grinding operation is automatically detected by means of an electrical circuit comprising an electrical contact element integrated in said rotary circular grinding wheel, and of means for detecting the closure of this circuit following the contact of said electrical contact with said part metallic in the area of the allowance and / or in an adjacent area which constitutes a reference surface

2 Method according to claim 1, characterized in that the grinding operation is automatically stopped when two electrical contacts are detected per wheel revolution, one of these contacts corresponding to the contact of said electrical contact element with said metallic piece in the area of the additional thickness and the other contact corresponding to the contact of said electrical contact element with said metallic piece in said adjacent area

3 Method according to claim 1, characterized in that one proceeds to a scanning of the area of the allowance and at least one adjacent area, and in that one detects the contacts between said electrical contact element and said metal part only in said adjacent zone, said grinding operation being interrupted at the time of this detection

4 Method according to any one of the preceding claims, characterized in that, to grind a cylindrical surface of any section, one proceeds by grinding of adjacent facets covering the area of the allowance

5 Grinding device for smoothing an excess thickness of a surface of a metal part, in particular of a railroad track, at the location of a weld, by means of a rotary circular grinding wheel, for the implementation of the method according to claim 1, characterized in that it comprises an electrical contact element (40, 53) integrated in said rotary circular grinding wheel ( 11, 51), and means for detecting the contacts of this element with said metal part (13, 52) in the area of the allowance (12) on the one hand and, if necessary, in an adjacent area free of allowance which constitutes a reference surface (R).

6. Device according to claim 5, characterized in that said electrical contact element (40) comprises a conductive member (40a) mounted in the thickness of a cup wheel (1 1), this conductive member being arranged parallel to the 'axis of rotation of the grinding wheel.

7. Device according to claim 5, characterized in that said electrical contact element (53) comprises a conductive member (53a) mounted in the thickness of a flat grinding wheel, this conductive member being disposed radially and opening out at the periphery of this wheel.

8. Device according to claim 7, characterized in that it comprises a collecting brush (66) connected to said contact element (53), and a conductive bar (63) arranged to cooperate with said collecting brush to constitute an electrical circuit in which include said metal part (52) and a device for detecting an electrical signal, said conductive bar being electrically interrupted in the region of the allowance.

9. Device according to claim 8, characterized in that the interruption of the busbar is obtained by means of an insulating slider (64), adjustable in position.

10. Device according to claim 5, characterized in that the conductive member (40a, 53a) integrated in the grinding wheel (11, 51) is housed in an insulating sheath (40b, 53b).

11. Device according to claim 10, characterized in that the conductive member (40a, 53a) is constituted by a graphite rod.

12. Device according to claim 10, characterized in that the insulating sheath (40b, 53b) comprises a fibrous material constituting at least one layer peripheral to the electrical contact element (40, 53).

13. Device according to claim 12, characterized in that said fibrous material comprises paper.

14. Device according to claim 10, characterized in that the conductive member (40a, 53a) and the insulating sheath (40b, 53b) are arranged to wear out at the same speed as the grinding wheel.