GB2279600A

GB2279600A - Electrode tip dresser

Info

Publication number: GB2279600A
Application number: GB9413396A
Authority: GB
Inventors: Hiroyuki Kizaki; Kazuo Arai; Sadao Kamei; Toyoji Yamada; Takeshi Okubo; Kenji Takahashi; Yukihiro Yaguchi; Tadashi Takeo
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 1991-04-26
Filing date: 1992-04-01
Publication date: 1995-01-11
Anticipated expiration: 2012-04-01
Also published as: GB2279601B; GB2279600B; GB9413397D0; GB9413396D0; GB9413395D0; GB2279601A; GB2279599A; GB2279599B

Description

2279600 ELECTRODE TIP DRESSER This invention relates to an electrode tip

dresser which dresses or reforms an electrode tip for a resistance welding machine, and to a cutter for use in the electrode tip dresser.

An electrode tip dresser is constructed in the following manner. Namely, a cutter is held by a cutter holder which is rotatably held in a dresser main body. The cutter holder is rotated while an electrode tip is urged against the cutter so that the front end portion of the electrode tip is cut and dressed by the cutter.

Conventionally, this kind of cutter comprises a central column-like block and a plurality of cutter blades which radially extend from the block. A flat portion which faces the front end surface of the electrode tip is made up by an end surface of the column-like block, and a rising portion around the flat portion is made up by each of the cutter blades. Cutting teeth for cutting the front peripheral portion of the electrode tip are formed in the rising portion. A plurality of cutting teeth which extend from the center of rotation of the cutter holder radially towards each of the cutter blades are formed in the flat portion so that the front end surface of the electrode tip 1 can be cut by these plurality of cutting teeth. However, if the plurality of cutting teeth are formed in the flat portion, the cutting teeth at the central portion at which they meet each other form a chisel edge, resulting in a disadvantage in that the central portion at the front end surface of the electrode tip cannot be cut well.

The applicant's co-pending British patent application number 9207195.0, serial number 2255302 includes subject matter disclosed in this application and has claims directed to a cutter for use in an electrode tip dresser and to an electrode tip dresser, which overcome the above and other disadvantages.

There is conventionally known an electrode tip dresser in which a cutter having upper and lower cutting teeth for cutting a pair of upper and lower electrode tips of a welding gun is mounted on a cutter holder so that simultaneous dressing of both electrode tips can be performed by pinching the cutter by the pair of electrode tips. In this electrode tip dresser, it is normal practice to vertically fixedly mount the cutter in the cutter holder. Therefore, even if the upper and lower electrode tips become different in cutting depth in the process of dressing work each of the electrode tips is independently dressed, resulting in different cutting depth between the two electrode tips.

According to the present invention, there is provided an electrode tip dresser for simultaneously dressing a pair of upper and lower electrode tips of a resistance welding apparatus, comprising:

a cutter holder which is rotatably driven and is mounted on a stationary dresser main body; and a cutter which is held by said cutter holder and comprises a cutting member having upper and lower cutting teeth for cutting a front end portion of each of the electrode tips extending from the centre to a 1 peripheral region of each tip, wherein said cutter is supported so as to be movable relative to said dresser main body in a direction substantially parallel to a line extending between the 5 upper and lower electrode tips.

It is advantageous to make the cutter vertically movable for the following reasons. Namely, when the cutting reaction force increases due to an increase in the cutting depth in one of the upper and the lower electrode tips, the cutter is pushed by the cutting reaction force and will move towards the other electrode tip. As a result, the cutter is held in a position in which the cutting depth of the upper and the lower electrode tips are balanced, so that the cutting depth of both electrode tips become equal.

For a better understanding of the present invention and to show how it may be carried into effect reference will now be made by way of example to the accompanying drawings, in which:

Fig. 1 is a plan view of an electrode tip dresser according to the invention; Fig. 2 is a sectional view taken along the line XVII-XVII in Fig. 1; Fig. 3 is a plan view of a cutter and a supporting plate to be used in the electrode tip dresser; Fig. 4 is a sectional view taken along the line XIX-XIX in Fig. 3; Fig. 5 is a sectional view taken along the line XX-XX in Fig. 3; Fig. 6 is a sectional view taken along the line XXI-MI in Fig. 3; Fig. 7 is a sectional view taken along the line XXII-XXII in Fig. 3; Fig. 8 is a sectional view of another example corresponding to Fig. 4; and Fig. 9 is a diagram explaining the movement of a cutter holder.

Pigs. 1 and 2' show a stationary type electrode tip dresser in which a pair of electrode tips W, W to be mounted on a robot or the like are dressed or reformed. The electrode tip dresser comprises a dresser main body 102 having a mounting base 101 which is f ixed on an unillustrated apparatus frame, and a cutter holder 103 which is rotatably supported from three sides inside the dresser main body 102 by a driving gear 104 which meshes with a gear 103b on the periphery of the cutter holder 103 and two supporting gears 105, 105. The cutter holder 103 is provided with a supporting plate 103c which is contained inside a concave portion 103a. A single-plate cutter 106 which has upper and lower cutting teeth is fit into a diametrically longitudinal slit-like groove 103d formed as shown in Fig. 3. An upper guide plate 107, a holding plate 108 for holding the cutter 6 and a supporting plate 103c are tightened together. In addition, a lower guide plate log is bolted to the lower surface of the cutter holder 103. A a pair of electrode tips Wt W are thus made, by the closing movement of the welding gun. to abut the upper and the lower cutting teeth of the cutter 6 through guide holes 107a, 109a provided in each of the guide plates 107, 109.

The upper and the lower cutting teeth of the cutter are formed so as to be in plane-symmetry with each other. The construction of the upper and the lower cutting teeth is explained in detail hereinbelow with reference to Figs. 3 and 4.

In this embodiment, the above-mentioned groove 103d is so arranged that its widthwise center line is parallel with a predetermined diametrical line of the supporting plate 103 and is slightly offset in a widthwise direction. That central point 0 of the cutter 106 which coincides with the axis of rotation of the cutter holder 103 is thus offset to one side from the thickness-wise center of the cutter 106. The lengthwise central portion of the cutter 6 is concaved to form therein a flat portion 106a. which faces the front end surface of the electrode tip as well as rising portions 106b, 106b on both ends thereof. Out of the rising portions, the one 106b whose one side surface having a smaller thickness-wise distance from the central point 0 looks towards the rotational direction of the cutter (clockwise 'direction in pig. 3), is formed with a cutting tooth 106c which is provided, as shown in Fig. 5, with a rake face 106c, on one side and a flank 106C2 on its upper side. The other rising portion 106b is formed with a cutting tooth 106c which is provided, as shown in Fig. 6 with a rake face 106c, formed on a front side in the rotational direction and a flank 106C2 on its upper side. The front peripheral portion of the electrode tip is thus cut with both cutting teeth 106c, 106c.

In the flat portion 106a there is formed, as shown in Fig. 7, a cutting tooth 106d having a face 106d, in the form of a notch formed on the abovementioned one side surface as well as a flank 106d2 on its upper sider such that the cutting tooth 106d diametrically extends from the central point 0 as an origin towards the starting end of the cutting tooth 106c of the above-mentioned one of the rising portion 106b and, an origin portion of the cutting tooth 106d extends to the opposite side beyond the central point 0. The front end surface of the electrode tip W is thus cut with the cutting tooth 106d and, like in the above-mentioned embodiment, the oppositely extended portion 106e prevents the center portion of front end surface of the electrode tip from being left uncut.

In case the above-mentioned groove 103d is formed along the diametrical line of the supporting plate 103c and the central point 0 is located in the thickness-wise center of the cutter 3, each of the cutting teeth 106c, 106d will have to be formed such that the rack faces thereof lie along the thickness-wise center line of the cutter 106. As a 6 1 consequence, the thickness of each of the cutting teeth 1 06c, 106d will become about half that of the cutter 106. if, on the other hand, the central point 0 is made closer to one side surface of the cutter 106 as in this embodiment. it is advantageous in that the thickness of each of the cutting teeth, 106c, 106d can be maintained rather thick even if the width of the cutter 106 is not increased. The groove 103d may be f ormed such that the central point 0 coincides with one side of the cutter 106. In this arrangement, however, the cutting tooth 106c to be f ormed on the other rising portion 106b, the other side surface of which looks towards the f ront of the direction of rotation, must be largely inclined towards the above-mentioned one side surface approaching the central point 0. As a consequencei the thickness of the cutting tooth 106c is decreased. Therefore. it is preferable to form the groove 103d so that the central point 0 is positioned in a slightly inside of one side surface, as in this embodiment. In Fig. 3, numeral 103e denotes chip-discharging holes which are formed in the supporting plate 103c. In the chip-d is charging hole 103e on one side of the groove 103d, there is integrally formed an opening portion 103f for receiving therein chips by the cutting tooth 106d. Here, by making the groove 103d to offset relative to the diametrical line of the supporting plate 103c, it becomes possible to form on the abovementioned one side of the groove 103d a larger chip- 7 discharging hole 103e having the opening portion 103f. This leads to an improved chip discharging efficiency..

In addition, the cutter 106 is fit into the groove 103d to allow for a slight sliding in a vertical direction. Therefore, when the cutting depth of one of the upper and the lower electrode tips becomes larger. the cutter 106 is pushed towards the other of the electrode tips by the cutting reaction force so that the cutter 106 can be automatically adjusted in its position to have an equal amount of cutting depth. As another embodiment, the cutter holder 103 may be vertically movably supported on the dresser main body 102 so that the cutter 106 is vertically movable.

Each of the above-mentioned cutting teeth 106c is inclined rearwards in the direction of rotation relative to the line "a" drawn to connect the end edge on the side of the flat portion 106a and the central point 0. The biting of the cutter into the electrode tip is thus minimized so that the electrode tip can be cut in a smooth manner.

The above-mentioned embodiment refers to one in which the longitudinal central portion of the cutter 106 is concaved to form therein the flat portion 106a and the rising portions 106b, 106b, thereby dressing the front end portion of the electrode tip into a truncated cone. In case the end shape of the electrode tip is different from that in the abovementioned embodiment, the cutter 106 may be formed 8 into a concave having a continuous curve to conform to the end shape of the electrode tip.

As shown in Fig. 8 r the following embodiment may also be employed. Namely, a notched portion 106f is provided in such a corner in the longitudinal direction of the cutter 106 as will lie in the bottom side when the cutter 106 is normally inserted into the groove 103d as illustrated. A projection 103g which conforms to the notched portion. 106f is provided on the side of the supporting plate 103c. In. this manner, when the cutter 106 is tried to be inserted in a longitudinally opposite direction or upside down against the normal condition, the cutter 106 is unable to be set in position, thereby preventing the cutter 206 from being wrongly assembled at the time of setting.

The above-mentioned pair of supporting gears 105, 105 are rotatably supported by the dresser main body 102 via an eccentric bush 110 as shown in Figs. 1 and 2. By rotatably adjusting the bush 110, the backlashes of the above-mentioned driving gear 104 and each of the supporting gears 105 relative to the gear 103b on the periphery of the cutter holder 103 are adjusted so that the cutter holder 103 can be movable within a predetermined range.

As an example of a moving range of the cutter holder 103, an explanation is made with reference to Fig. 9, in which each of the gears 104, 105 is shown by its center, numeral 0 denotes the center of rotation of the cutter 9 holder 103 and Ll through L3 denote the distances between the center 0 and the center of each of the gears: In the above-mentioned embodiment, the number of teeth of the driving gear 104 and the gear 103b of the cutter holder is set to be 36, and that of each of the supporting gears 105 is set to be 18. The module is set to be 2 and the pressure angle is set to be 200. Therefore, Ll becomes 72mm and L2 and L3 both become 54mm. Normally, the amount of backlash is set to a minimum value within a range in which each of the gears is rotatable; for example, the backlash is set to be 25pm - SOAAm according to the above-mentioned specification. In this embodiment, however, the amount of backlash is set to be SOAAm - 100AAm which is double the amount of normal backlash. As a result# since each of the dimensions Ll - L3 can be shortened by 1 46A m 292,U m as compared with the case in which the backlash is zero, the center of rotation 0 can be movable within an approximately equilateral triangles having each side of O.Smm - 1.0mm.

Consequently, the offset between the cutter holder 103 and the electrode tip W is automatically adjusted by the radial movement of the cutter holder 103, and the electrode tip can thus be accurately dressed.

1 P It is readily apparent that the above-mentioned electrode tip dresser have the advantage of wde commercial utility. It should be understood that the specific form of the invention hereinabove described is intended to be representative only, as certain modifications within the scope of these teachings will be apparent to those skilled in the art.

Accordingly, reference should be made to the following claims in determining the full scope of the 10 invention.

The applicant's co-pending British Patent Application No., Serial No. discloses an electrode tip dresser as described herein. The claims of this co-pending application are directed to an electrode tip dresser having a cutter holder which is supported by two supporting gears and a driving gear. This allows radial movement of the cutter holder and prevents chattering.

Furthermore, the applicant's co-pending British Patent Application No.. Serial No. discloses an electrode tip dresser in which the dresser main body is provided with a slide groove in which a guide plate is engaged in one direction, and having a lock pin for retaining the guide plate. This enables various types of electrode tips to be machined in different ways as desired.

Claims

CLAIMS 1. An electrode tip dresser for simultaneously dressing a pair of

upper and lower electrode tips of a resistance welding apparatus, comprising: 5 a cutter holder which is rotatably driven and is mounted on a stationary dresser main body; and a cutter which is held by said cutter holder and comprises a cutting member having upper and lower cutting teeth for cutting a front end portion of each of the electrode tips extending from the centre to a peripheral region of each tip, wherein said cutter is supported so as to be movable relative to said dresser main body in a direction substantially parallel to a line extending between the upper and lower electrode tips.