GB2116885A

GB2116885A - Clamping head for a drill-grinding machine

Info

Publication number: GB2116885A
Application number: GB08306283A
Authority: GB
Inventors: Hans Schmid
Original assignee: Fritz Gottstein
Current assignee: Fritz Gottstein
Priority date: 1982-03-09
Filing date: 1983-03-08
Publication date: 1983-10-05
Also published as: CH655035A5; DE3307935C2; FR2523015B1; GB8306283D0; DE3307935A1; FR2523015A1

Abstract

A drill (18) to be resharpened is chucked in a clamping chuck (16) of a clamping head (14), in order to undergo either conical grinding or four-surface grinding on the plane surface (48) of the grinding wheel (26). A crank handle (70) serves as a drive element for executing the various movements required especially for conical grinding. The crank handle (70) can be engaged in an initial position by means of a lever (90). To grind the drill (18), it is necessary for its cutting surfaces to assume a very specific angular position in the initial position of the crank handle (70). Consequently, to make chucking easier, there is, located in the clamping head (14) between the crank handle (70) and the clamping chuck (16), an electromagnetically actuable coupling which is engaged after the chucked drill (18) has previously been brought into the angular position provided, as a result of rotation of the clamping chuck (16). <IMAGE>

Description

SPECIFICATION Clamping head for a drill-grinding machine The invention relates to a clamping head for a drill-grinding machine.

Clamping heads having a clamping chuck to receive a drill to be resharpened are well known. To achieve, for example, a conically ground surface, it is necessary for the clamping chuck to execute three different types of movement which have to be co-ordinated with one another, namely a to-and-fro pivoting movement, a rotary movement about the axis of the drill and an axial feed movement towards and away from the grinding wheel.

Swiss Patent Specification 330,589 discloses such a clamping head, but it is one which involves clamping the drill in a very specific angular position.

In addition, it is necessary for an exactly predetermined length of the drill to project from the clamping chuck. This length depends on the diameter of the drill, so that the surface of the cone envelope to be ground is geometrically correct in relation to the tip of the drill. To achieve these conditions during chucking, it is possible to use, in the known clamping head, a laterally fastened gauge the end of which extends at an angle up to the drill tip. Chucking by means of such a gauge is complicated and demands a high degree of skill from the operator. If accuracy is neglected, it is not possible for the cutting edges of the drill tohave the desired geometry envisaged, and the result can be a shorter service life, while it is also possible that a clean cut cannot be obtained by means of a drill which has been ground inaccurately.

To achieve the desired conical surface during grinding, it is essential for the three types of movement to be co-ordinated precisely with one another. Since the axial advance must be carried out at a precise rate when each cutting edge of the drill is ground, cam discs are conventionally used for controlling the advance. For example, cam discs acting in an axial direction are known, these being arranged on a shaft extending parallel to the axis of the clamping chuck. Since the clamping chuck has to be rotated simultaneously about its axis, for which purpose the same drive element is conventionally used, it is advantageous, for reasons of gearing, if all the axes extend in the same direction and parallel to one another.However, the disadvantage of a cam disc acting in an axial direction isthatfora left-hand cutting drill, a cam disc directed in the opposite direction is required. Although it is also known to use radially acting cam discs which, by being reversed, can also be employed for left-hand cutting drills, such cam discs are, however, arranged on shafts which extend transversely to the axial direction of the clamping chuck. The outlay in terms of gearing is increased as a result of such an arrange ment, for example because bevel wheels are needed.

According to the present invention there is provided a clamping head for a drill-grinding machine including a rotatably mounted clamping chuck to receive a drill to be ground and which is connected to a drive element with an electromagnetically actuable coupling located between the drive element and the clamping chuck.

With the invention, it is not necessary to clamp the drill to be resharpened in the clamping chuck in the correct angular position. When the coupling is disengaged, the clamping chuck can rotate freely, whilst the drive element is stationary. In this way, it is possible to rotate the drill, as a result of rotation of the clamping chuck, into the correct angular position after chucking has been carried out. The electromagnetically actuable coupling can then be engaged in order to make the drive connection between the drive element and the clamping chuck. Chucking is thereby substantially simplified, but nevertheless it is possible to position the drill accurately in the correct angular position.

Preferably the head includes a magnifying glass having a reticule to be aligned with the cutting edge of a drill to be clamped in the clamping chuck, the magnifying glass being pivotable in the direction of the drill axis by means of a scaled precision drive.

This makes it substantially easier to clamp the drill to the correct length and align it, as mentioned above, by rotating the clamping chuck, with the coupling disengaged.

Preferably, also, the clamping chuck is mounted to be pivotable about a first pivot axis, is arranged to be rotatable about its chuck axis, which coincides with the axis of a drill to be ground, and can be fed towards a grinding wheel in the direction of the chuck axis, and wherein the drive element is for causing the three said types of movement, and wherein the drive element has a drive axle which is parallel to the chuck axis and on which is located a radially acting cam disc, following which are located in series two follower elements of which the first senses the cam disc and the second transmits to the clamping chuck the movement sensed by the first, such movement being converted to an axial movement for carrying out said feed movement.As a result, it is possible to use cam discs which can be used both for right-hand cutting and for left-hand cutting drills, although all the axes of rotation of the gear extend parallel to one another.

Preferably, the clamping chuck has a hollow shaft which is connected axially, but not rotationally, to a pin which is adapted to sense the pivoting movement of the plate and the pin is adjustable towards and away from the plate so as to vary the amount of axial movement transmitted. This allows the axial movement of the clamping chuck to be set, starting from zero, up to a maximum value, without the cam disc having to be changed.

In orderthatthe invention may be more clearly understood, the following description is given by way of example only with reference to the accompanying drawings, in which: Figure 1 shows, in a plan view, a drill-grinding machine; Figure 2 shows the three movement actions of a drill to achieve a conically ground surface; Figure 3 shows, in a side view, the clamping head of the drill-grinding machine according to Figure 1; Figure 4 shows the arrangement of an electromagnetically actuable coupling, Figure shows, in a front view, the arrangement of a cam disc with follower members, and Figure 6shows, in an axial section, a view according to Figure 5.

The drill-grinding machine illustrated in Figure 1 has a baseplate 10 with a cross slide 12 located on it.

A clamping head 14 is arranged pivotably on the cross slide 12. The clamping head 14 has a clamping chuck 16 in which a drill 18 to be resharpened is clamped. The clamping chuck 16 is preferably a six-jaw chuck so as to guarantee that even drills with a large diameter and a large pitch can be clamped exactly centrally. Two legs 20 and 22 extend vertically upwards from the baseplate, and between them a support 24 is arranged so as to be pivotable about a horizontal axis B. A large grinding wheel 26 and a small grinding wheel 28 are mounted in the support 24.

Located on the baseplate 10 is a first guide 30 on which a second guide 34 is adjustable along a Y-axis as a result of actuation of a handwheel 32. On the second guide 34, the cross slide 12 is adjustable along the X-axis by means of a further handwheel 36, inasmuch as a reversing lever 38 located on the second guide 34 on the side opposite the handwheel 36 is brought into the position I. When the reversing lever 38 is in the position II illustrated, the cross slide 12 can move to and fro along the X-axis as a result of actuation of a pivoting lever 40. When the reversing lever 38 is in the zero position located between the two positions I and II, the cross slide 12 is freely movable by hand along the X-axis.

Whilst the handwheel 36 provided with a scale 42 serves for fine adjustment, the pivoting lever 40 serves to move the cross slide 12 to and fro smoothly when, for example, the tip of the drill 18 is to undergo surface grinding. The zero position of the reversing lever 38 serves for bringing the cross slide 12 into another position quickly, for example in front of the small grinding wheel 28. A scale 44 is assigned to the handwheel 32 as well as to the handwheel 36.

The two scales 42 and 44 serve, on the one hand, for controlled fine adjustment and, on the other hand, for reproducing specific settings. To guarantee reproducibility, it is possible to actuate the reversing lever 38 into position I or II only when the cross slide 12 is in specific positions along the X-axis.

The large grinding wheel 26 driven by a first motor 26 has a plane end face 48. The small grinding wheel 28 driven by a second motor 50 is rounded at its outer edge and is conical both on the inside and on the outside. The plane end face 48 of the large grinding wheel 26 must be located exactly on the pivot axis B. To satisfy this condition, the large grinding wheel 26 is adjustable along its axis D by means of a handwheel 52. A handwheel 54 located near the small grinding wheel 28 serves for adjusting the height of this grinding wheel.

Afurther handwheel 56 serves for pivoting the support 24 about the pivot axis B. The pivoting angle can be read off roughly on a scale 58. A further scale 60 assigned to the handwheel 56 allows very accurate fine adjustment of the pivoting angle.

The clamping head 14 is arranged to carry out three movement actions simultaneously, in order, when the drill 18 is resharpened, to grind conical surfaces on the drill tip. With reference to Figure 2, the three movement actions are indicated by arrows.

C denotes the axis of the drill which coincides with the axis of the clamping chuck 16 and is designated below as the chuck axis. An arrow 62 indicates the first movement action in which the drill 18 is pivoted about the point 64 located on a first axis A extending vertically. The distance between the first axis A and the horizontal second axis B already mentioned depends on the diameter of the drill 18 to be resharpened. To maintain the necessary distance between the first, vertical pivot axis A and the second, horizontal pivot axis B, the drill 18 must be clamped in the clamping chuck 16 over the appropriate length.

The second movement action to obtain conical surfaces is the rotation of the drill 18 about its axis C, this movement action being indicated by the arrowed line 66. The third movement action is the feed movement of the drill 18 in the direction of the grinding wheel 26 along the chuck axis C. In the case of a double-edged drill, this feed movement must take place twice per revolution. Each feed movement is followed by a retraction. This movement action is designated by the double arrow 68.

The clamping chuck 16 mounted in the clamping head 14 is designed to execute simultaneously the movement actions explained with reference to Figure 2, when a crank handle 70, serving as a drive element, is rotated. The clamping head 14 has an intermediate plate 72 which is pivotable about the first pivot axis A and is lockable on the cross slide 12 by means of a locking screw 74. The tip angle of the drill to be resharpened can be set on a scale 76. A guide groove 78 having a radius is located in the cross slide 12 for guiding the intermediate plate 72.

The pivoting movement 72 (Figure 2) is executed by the clamping head 14 in relation to the intermediate plate 72. The feed movement 68 (Figure 2) is executed by the clamping chuck 16 in relation to the clamping head 14.

An adjusting wheel 80 arranged laterally on the clamping head 14 serves for changing over a step gear located between the crank handle 70 and the clamping chuck 16, so that it is possible to change over from double-edged to triple-edged drills and, if appropriate, to multiple-edged drills.

A cam disc 82 connected to the crank handle 70 via the above-mentioned gear is sensed by a first follower element 84. The cam disc 82 and the follower element 84, which is preferably a roller, are the first members of a transmission mechanism for converting the rotary movement generated by the crank handle 70 into the axial movement 68 (Figure 2). The cam disc 82 can be exchanged or reversed by loosening a knurled nut 86. Reversal makes it possible to resharpen left-hand cutting drills. For this purpose, the clamping head 14 must be pivoted to the right-hand side of the cross slide 12 by loosening the locking screw 74.

Afurther adjusted wheel 88 on the clamping head 14 serves for adjusting the stroke for the feed movement 68 (Figure 2). This stroke can be adjusted from zero up to a maximum.

The two levers 90 and 92, each having a ball handle, serve for locking the clamping chuck 16 in predetermined angular positions. The right-hand lever 90 is intended for right-hand cutting drills and the left-hand lever 92 is intended for left-hand cutting drills. In position I, the clamping chuck 16 is locked in the initial position which is intended for clamping and aligning the drill 18. In position II, locking is effected to grind the tip of the drill 18 on the small grinding wheel 28. In the zero position, the lock is released.

The vertical pivot axis A mentioned forms a centre for the scale 76 and the guide groove 78. The horizontal chuck axis C intersects the first pivot axis A at right angles. The second pivot axis B extends at right angles to the first pivot axis A, but without intersecting the latter. The grinding-wheel axis D of the larger grinding wheel 26 intersects the second pivot axis B at right angles. In the basic position of the support 24 and consequently of the grinding wheel 26, the plane grinding surface 48 of the large grinding wheel 26 in parallel to the first pivot axis A.

The second pivot axis B lies in the plane of the grinding surface 48 and intersects the chuck axis C, so as to make it possible to carry out, instead of the conical grinding described, surface grinding, for example four-surface grinding of a double-edged drill, without rechucking the drill. To make it possible also to grind the tips of drills on the small grinding wheel 28 in the same chucking position, the lower edge of the small grinding wheel 28 is located in the region of the second pivot axis B.

Figure 3 illustrates the clamping head 14 connected to the intermediate plate 72, from its righthand side. It is especially evident from this Figure that a magnifying glass 100 directed to the tip of the drill 18 is supported on the clamping head 14. This magnifying glass 100 having a reticule is adjustable along the chuck axis C on an adjustment element 102 which has a precision drive. The scale of the adjusting element 102 can be provided, for example, with diameter values for the drill to be ground.

Figure 4 shows an electromagnetically actuable coupling 104 which is located between two shafts 106 and 108. A first engaging means ll0iscon- nected, fixed against rotation, to the shaft 106, and a second engages means 112 is connected, fixed against rotation, to the shaft 108. An electrical coil 114 serves for generating a magnetic field. As soon as a magnetic field is present when the coil 114 is switched on, the two engaging means 110 and 112 are held against one another by means of a frictional connection. As a result, the two shafts 106 and 108 are coupled to one another. Coupling is possible in any angle of rotation of the two shafts 106 and 108 relative to one another. When the coupling is not energised, the two engaging means 110 and 112 slide away from one another.

One shaft 106 is connected to a drive element which, in the exemplary embodiment illustrated, is the crank 70 according to Figure 1. The driven shaft 108 is connected, via a gear not shown, to the shaft of the clamping chuck 16 illustrated in Figures 1 and 3. This shaft of the clamping chuck 16 is conventionally a hollow shaft, so that the shank of the drill to be resharpened is accommodated in it.

Consequently, this electromagnetically actuable coupling 104 separates the clamping chuck 16 from the drive element 70. The purpose of this coupling is to make it easier to chuck the drill 18 to be resharpened, because it is merely necessary to ensure, during chucking, that the drill projects the cross length from the clamping chuck 16 in relation to the first pivot axis A. This is necessary to achieve the desired geometry of the conical surfaces during grinding. The length of the drill 18, projecting from the clamping chuck 16, is adjusted using the magnifying glass 100, since specific points on the cutting edges of the drill must coincide with the transverse line of the reticule in the magnifying glass previously adjusted to the appropriate drill diameter.After the drill has been chucked over the correct length, the clamping chuck 16 can be rotated easily into the angular position provided, with the coupling disengaged. Not only the appropriate length, but also the angular position provided before engagement is evident in the reticule centre of the magnifying glass 100. During this adjusting operation, the drive element 70 is locked in its initial position by the lever 90. When the coupling is engaged, the rotary connection between the drive element 70 and the clamping chuck 16 is made in the exact angular position relative to one another. The locking of the drive element 70 can then be cancelled by moving the lever 90 into the zero position.

Figure 5 illustrates, in a front view, the cam disc 82 already shown in Figure 1.The follower element 84 which senses the periphery of the cam disc 82 may likewise be seen again. The follower element 84 is designed as a roller, for example as a ballbearing.

The cam disc 82 is a radially acting cam disc, as emerges clearly from Figure 5. It is fastened on a shaft 116 which is connected to the drive element 70 via gear elements (not shown). The roller 84 acting as a follower element is connected to a slide 120 guided linearly on a rod 118. The slide 120 is prestressed towards the cam disc 82 by a spring 122.

The slide 120 has an inclined guide 124 in which a second follower element 126, designed as a roller or ball bearing, is guided. The second follower element 126 is located on a plate 130 pivotable about a pivot axis 128. The plate 130 is provided in its centre with a recess 132 through which the hollow shaft 134 of the clamping chuck 16 (Figure 1) extends.

Figure 6 illustrates, in a longitudinal section through the clamping head, some of the elements illustrated in Figure 5. It is especially evident from this Figure how the second follower element 126 is guided in the inclined guide 124. The pivotable plate 130 can also be seen again. The pivoting movement of this plate 130 is converted into an axial movement by means of a pin 136. The pin 136 is located in a disc, for example a gear wheel 138, which is mounted freely rotatably on the hollow shaft 134.

The gearwheel 138 acts via an axially acting needle bearing 140 against a shoulder 142 located on the hollow shaft 134.

The gear wheel 138 meshes with a further gear wheel 144 (Figure 5) which is connected to the adjusting wheel 88 (Figure 1), in order to adjust the axial stroke of the hollow shaft 134 and consequently of the clamping chuck 16. The axial stroke is adjusted by displacing the sensing point of the pin 136 to another point on the pivotable plate 130.

By means of the arrangement described, the stroke of the clamping chuck 16 can be adjusted continuously between zero and a maximum during actuation by the drive element 70. The cam disc 82 fastened to the shaft 116 by means of the knurled nut 86 can be exchanged for cam discs with a different pitch curve. It also becomes possible, by means of such an arrangement, for one and the same cam disc to be used for grinding or resharpening right-hand cutting and left-hand cutting drills.

Claims

1. A clamping head for a drill-grinding machine including a rotatably mounted clamping chuck to receive a drill to be ground and which is connected to a drive element with an electromagnetically actuable coupling located between the drive element and the clamping chuck.

2. A clamping head according to claim 1, wherein the coupling is located between two shafts of which one is connected via a gear to the clamping chuck, the other shaft being connected to the drive element and being lockable in an initial preselected position.

3. A clamping head according to claim 1 or2, wherein the coupling can be continuously engaged.

4. A clamping head according to claim 1,2 or 3, wherein the coupling has a fixed electromagnetic coil.

5. A clamping head according to any preceding claim, including a magnifying glass having a reticule to be aligned with the cutting edge of a drill to be clamped in the clamping chuck, the magnifying glass being pivotable in the direction of the drill axis by means of a scaled precision drive.

6. A clamping head according to claim 5, wherein the scale of the precision drive has diameter values for drills to be ground.

7. A clamping head according to any preceding claim, wherein the clamping chuck is mounted to be pivotable about a first pivot axis, is arranged to be rotatable about its chuck axis, which coincides with the axis of a drill to be ground, and can be fed towards a grinding wheel in the direction of the chuck axis, and wherein the drive element is for causing the three said types of movement, and wherein the drive element has a drive axle which is parallel to the chuck axis and on which is located a radially acting cam disc, following which are located in series two follower elements of which the first senses the cam disc and the second transmits to the clamping chuckthe movement sensed by the first, such movement being converted to an axial movement for carrying out said feed movement.

8. A clamping head according to claim 7, wherein the first follower element is spring-loaded against the cam disc and is connected to an inclined guide which extends in the sensing direction and which interacts with the second follower element.

9. A clamping head according to claim 8, wherein the second follower element is a roller which is located on a plate pivotable about an axis extending transversely to the chuck axis and transversely to the direction of movement of the first follower element.

10. A clamping head according to claim 9, wherein the clamping chuck has a hollow shaft which is connected axially, but not rotationally, to a pin which is adapted to sense the pivoting movement of the plate.

11. A clamping head according to claim 10, wherein the pin is adjustable towards and away from the plate so as to vary the amount of axial movement transmitted.

12. A clamping head according to claim 11, wherein the pin is located on a braked disc surrounding the hollow shaft, and the pivotable plate has a centrally arranged recess through which the hollow shaft extends.

13. A clamping head according to claim 12, wherein the disc is a gear wheel which meshes with adjusting means, and an axially acting needle bearing is located between this gear wheel and a shoulder of the hollow shaft.

14. A clamping head according to any one of claims 7 to 13, wherein the cam disc is fastened so as to be exchangeable and reversible.

15. A clamping head for a drill-grinding machine including a clamping chuck which is mounted to be pivotable about a first pivot axis, is arranged to be rotatable about its chuck axis, which coincides with the axis of a drill to be ground, and can be fed towards a grinding wheel in the direction of the chuck axis, a drive element for causing the three said types of movement, and wherein the drive element has a drive axle which is parallel to the chuck axis and on which is located a radially acting cam disc, following which are located in series two follower elements of which the first senses the cam disc and the second transmits to the clamping chuck the movement sensed bythefirst, such movement being converted to an axial movement, for carrying out said feed movement.

16. A clamping head according to claim 15, wherein the first follower element is spring-loaded against the cam disc and is connected to an inclined guide which extends in the sensing direction and which interacts with the second follower element.

17. A clamping head according to claim 16, wherein the second follower element is a roller which is located on a plate pivotable about an axis extending transversely to the chuck axis and transversely to the direction of movement of the first follower element.

18. A clamping head according to claim 17, wherein the clamping chuck has a hollow shaft which is connected axially, but not rotationally, to a pin which is adapted to sense the pivoting movement of the plate.

19. Aclamping head according to claim 18, wherein the pin is adjustable towards and away from the plate so as to vary the amount of axial movement transmitted.

20. A clamping head according to claim 19, wherein the pin is located on a braked disc surrounding the hollow shaft, and the pivotable plate has a centrally arranged recess through which the hollow shaft extends.

21. A clamping head according to claim 20, wherein the disc is a gear wheel which meshes with adjusting means, and an axially acting needle bearing is located between this gear wheel and a shoulder of the hollow shaft.

22. A clamping head according to any one of claims 15 to 21, wherein the cam disc is fastened so as to be exchangeable and reversible.

23. A clamping head for a drill-grinding machine substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

24. A drill-grinding machine including a clamping head according to any preceding claim.