HK1019213B - Lapping head with oscillating toolholders - Google Patents

Description

Grinding head with swing tool clamp

The present invention relates to a grinding head with oscillating tool holder for use in grinding and/or polishing machines, in particular for working stone materials such as marble, granite, sandstone and the like. It is known to those skilled in the art that grinding heads of this type with oscillating tool holders for polishing and grinding stone have a vertical shaft connected at one end to a respective drive shaft and at the other end to a housing for driving it in rotation at a predetermined rate. A stationary reaction flange is provided between the housing and the motor-driven member and is supported by the housing with a plurality of bearings having axes parallel to the shaft. The housing supports a plurality of tool holder components which are adapted to receive respective abrasive tools and which are driven in an oscillating motion about respective axes by a mechanical drive mechanism connected to said drive motor, whereby each abrasive tool is driven in an oscillating motion about the axis of its tool holder and in a rotary motion about the axis of the drive motor. According to another operating technique, machines with cylindrical grinding wheels can also be used. Grinding heads belonging to this type of grinding machine are described, for example, in patents EP-571.340, IT-1.198.798 and IT-FI-96-U-00062.

The kinematic chain that transfers motion from the spindle to each tool holder can be implemented in a variety of ways. For example, it is possible to use a cam with a suitable shape (for example tubular) or an eccentric; it is also known to use specially made connecting rods, or levers, or rockers, on which rollers are arranged to cooperate with associated cam means.

The use of members of the above type can cause uneven swinging of the tool holder because the design of the drive means itself can be a cause of dead time or acceleration when converting the uniform rotational movement of the drive shaft into reciprocating movement of the driven shafts. The occurrence of this phenomenon is detrimental to the grinding process. In addition, with the above-described type of components, problems arise with the use of higher cutting rates, and in particular the use of diamond tools is increasing, which cannot be taken into account.

The main object of the present invention is to provide a grinding head in which the drive shaft drives the tool holder in an oscillating movement, but since the means for transmitting the movement have a plurality of toothed wheels (pivoted on the respective tool holder and a crown wheel driven by being connected to the drive shaft) which are connected to said plurality of toothed wheels by a combination of two toothing, one of which exhibits at least one change in the inclination of a tooth in its developed view; the tool holder is pivoted to said support body so that the tool holder is correspondingly swung when said two toothing systems engage each other according to their portions exhibiting said change of inclination.

The present solution makes it possible to use a higher working rate, resulting in a very uniform tool oscillation without dead times and accelerations that are characteristic of the prior art. In other words, the grinding head can be used for more effectively producing the finished product with better quality.

According to the present invention, there is provided a polishing head having an oscillating tool holder, the polishing head comprising: means for coupling with associated drive means, a drive shaft connected to said coupling means, and a plurality of tool holders connected to a drive motor for movement transmission by the first and second drive means; said first drive means having a first body for supporting the tool holder integral with the drive shaft and rotatable therewith, said second drive means being capable of determining, in response to rotation of said drive shaft, the swinging motion of the identical tool holders about their axes disposed at an angle to said drive shaft; the grinding head is characterized in that said second drive means for transmitting the motion have at least a plurality of first gears pivoted on said plurality of tool holders and a crown gear connected to and driven by the drive motor, said crown gear being in engagement with said plurality of first gears by means of two teeth, one of which exhibits at least one change in inclination in its developed view, said tool holders being pivoted on said supporting body so that said tool holders oscillate when said teeth are engaged according to said portion thereof exhibiting the change in inclination.

The advantages and features of the invention will be better understood by those skilled in the art after reading the following description of a practical but non-limiting example of the invention, given in conjunction with the accompanying drawings. Wherein:

figure 1 is a top perspective view showing an example of a polishing head according to the present invention with a portion cut away to highlight other portions;

FIG. 2 is a top perspective view showing some details of the embodiment of FIG. 1;

fig. 3 is a development view schematically showing the tooth mounting of the crown gear according to the present invention.

The grinding head with oscillating tool holder constructed according to the invention has a drive shaft (1) carrying on its top a flange (2) for coupling to the associated drive means.

In use, the flange (2) enables the grinding head to be fitted to a spindle of a machine, which spindle is not shown in the figures, since it does not form part of the present invention. The grinding head also has a plurality of tool holders (6) attached to the drive shaft (1), the attachment being accomplished by first and second drive means, as will be described below.

The first drive means has a first body (5) supporting a tool holder (6) which is fixed by screws (4) to a flange (3) provided at the lower part of the drive shaft (1) and thus integral with the drive shaft when the latter is rotated.

The purpose of the second drive means is to oscillate the tool holder (6) about its axes (7) in accordance with the rotation of the drive shaft, these axes (7) being arranged at an angle to the drive shaft (1); in particular, the shaft (7) of the tool holder (6) can be arranged radially and substantially perpendicular to the drive shaft (1) -as shown in the non-limiting example, wherein these tool holders are indicated by the unbracketed numeral 6. The second means for transmitting motion generally have: at least a plurality of first gears (15) pivotally supported on the tool holder (6), and a crown gear connected to and driven by the drive shaft (1). As illustrated in the example, a gear train (8, 9) may be provided between the crown gear (12) and the drive shaft (1). As shown, a second gear wheel (8) mounted on the drive shaft (1) drives a third gear wheel (9) which is idle-rotatably pivoted on a second supporting body (17), said second supporting body (17) being located on top of the first supporting body (5).

The third gear wheel (9) has two internal toothing (10, 11) intended to mesh with the first toothing (13) of said second gear wheel (8) and of the crown gear wheel (12), respectively.

In this way it is possible to adjust the rotational movement from the drive shaft (1) according to a predetermined gear ratio for driving the crown wheel (12) and the gears arranged downstream thereof.

The engagement of the crown wheel (12) with the first wheel (15) is achieved by the combination of two loading teeth (14, 15'), one of which exhibits, in its developed view, a variation in the inclination of at least one tooth; in addition, since the tool holder (6) is pivoted to the support body (5), the tool holder can be swung accordingly when the two toothing systems engage according to their portion exhibiting the change in inclination.

The change in the inclination of at least one tooth, which is represented in the developed view of the toothing (hereafter also referred to as special toothing), can be provided both on the crown wheel (12) and on the first toothed wheel (15). In the example shown, the special toothing (14) is formed on the crown wheel (12).

As best seen in fig. 3, the special set tooth (14) has alternating straight and slanted portions.

In particular, with a 360 ° unfolded view, two straight teeth or tooth spaces can be arranged at positions corresponding to the origin (0 ° and 360 ° focal point) and the midpoint. Becoming skewed in the 0 to 90 portion (indicated at 14 a), the maximum slope occurs at 90. After this point, the slope gradually decreases to 180 ° to zero. From 180 deg. to 270 deg. (part 14c) again becomes a helical tooth, but the pitch is opposite to that of parts 14a and 14 b. By 270, the slope is highest, from 270 to 360 (or 0), i.e. at portion 14d, the slope gradually decreases again until it becomes zero.

The swinging of the tool holder (6) is thus obtained thanks to the variation of the inclination of the special toothing (14), which toothing (14), when engaged with the first toothed wheel (15) (straight teeth), causes the corresponding tool holder (6) to tilt differently according to the whole movement of the crown wheel (12) for each rotation.

In field operation, the rate of rotation of the tool holder (6) is determined by the number of divisions of the special toothing (14) and the gear ratio of the gear wheel, which in turn is determined by the second gear wheel (8), the third gear wheel (9) and its two toothing arrangements (10) and (11), and the crown gear wheel (12) and its toothing arrangement (13).

Referring again to the drawings, the first gear (15) may be supported by a pin provided on the tool holder (6) and substantially perpendicular to the shaft (7).

The head advantageously also allows an alternate and continuous radial movement, provided that the special setting tooth (14) is eccentric to the drive shaft (1), or the gear wheel (15) is eccentric to the relative pin (16). The radial movement will be proportional to the change in diameter or the degree of eccentricity of the particular set of teeth (14) (or gears (15)). The radial movement is extremely effective for so-called dressing of the diamond tool.

The shaft (7) can be coupled to the first support body (5) by means of a sleeve (19), which sleeve (19) can be connected to the shaft (7) by means of a connection element with clearance recovery means, such as a spring (20) and a small ball (21) as shown in the figures.

In addition, the support body (5) can be vibrated against the drive shaft (1) by means of spring elements (22) and (23) in order to reduce vibrations and provide a clean and flawless surface. The first support body (5) can be provided with a corresponding bulge (24) in correspondence of the portion intended to face the tool holder (6) so that it coincides with the relative axis of the shaft (7).

In addition, an internal cavity can be provided in the second support body (17) so that it serves as a reservoir for the lubricating fluid.

In practice, all the construction details, such as shape, dimensions, arrangement of parts and nature of the materials used, may be substituted by any equivalent, without thereby departing from the scope of the solution idea underlying the invention and, therefore, remaining within the scope of what should be protected.

Claims (15)

1. A grinding bit having an oscillating toolholder, the grinding bit comprising: -means (2) for coupling with associated drive means, -a drive shaft (1) connected to said coupling means (2), and-a plurality of tool holders (6) connected to the drive motor (1) for movement transmission by the first and second drive means; said first driving means (3, 5) having a first body (5) for supporting a tool holder (6) integral with the drive shaft (1) and rotatable therewith, said second driving means being capable of determining the oscillation of the same tool holder (6) about its axis (7) in response to the rotation of said drive shaft (1), said axis (7) being disposed at an angle to said drive shaft (1); the grinding head is characterized in that said second drive means for transmitting the motion comprise at least a plurality of first toothed wheels (15) pivoted to said plurality of tool holders (6), and a crown wheel (12) connected to and driven by the drive motor (1), said crown wheel being in engagement with said plurality of first toothed wheels (15) by means of two toothing teeth (14, 15'), one of which exhibits at least one change in inclination in its developed view, said tool holders (6) being pivoted to said support body so that said tool holders (6) are oscillated when said toothing teeth are engaged in accordance with said portion exhibiting the change in inclination thereof.

2. The grinding head according to claim 1, wherein said set tooth having at least one change in inclination in its developed view is a set tooth (14) formed on said crown gear (12).

3. The grinding head according to claim 1, wherein said teeth having at least one change in inclination in their developed view are teeth on said plurality of gears (15).

4. The grinding bit of claim 1, wherein said set tooth having at least one change in slope exhibits at least one substantially straight portion alternating with a bevel.

5. The grinding head of claim 4, wherein said loading teeth (14) exhibit a slope that varies in both slope and direction.

6. The grinding head according to claim 1, characterized in that said crown gear (12) has a first set of teeth (13) and a second set of teeth (14) and that a gear train (8, 9) is provided between said drive shaft (1) and said first set of teeth (13) of said crown gear (12) to vary the rotational movement of said drive shaft (1) according to a predetermined gear ratio to drive said crown gear and gears downstream thereof.

7. The grinding head according to claim 6, characterized in that said gear train comprises a second gear wheel (8) keyed on said drive shaft (1) and a third gear wheel (9) idly mounted on a second supporting body (17) fixed to said first supporting body (5), said gear wheel (9) having two internal toothing (10, 11) capable of meshing with said first toothing (13) of said second gear wheel (8) and of said crown gear (12), respectively.

8. The grinding head according to claim 1, characterized in that said first plurality of gears (15) are supported by relative pins (16), which pins (16) are provided on said tool holder (16) and are arranged substantially perpendicular to said shaft (7), said shaft (7) being coupled to said first support by means of a bushing (19), which bushing (19) is connected to the same shaft (7) by means of a coupling member having clearance recovery means.

9. The grinding head according to claim 8, characterized in that said gap-restoring means comprises a spring (20) and a ball (21).

10. The grinding head as claimed in claim 1, characterized in that a spring element (22, 23) which reduces vibrations is provided between the drive shaft (1) and the first carrier body (5).

11. The grinding head as claimed in claim 1, characterized in that a bulge coinciding with the relevant axis of said shaft (7) is provided on said first support body (5) in correspondence of the portion intended to face said tool holder (6).

12. The grinding head according to claim 1, characterized in that it comprises a second support body (17) arranged above said first support body (5), said second support body having an internal cavity for receiving a lubricating fluid.

13. The grinding head according to claim 1, characterized in that said axis (7) of said tool holder (6) is radially disposed and substantially perpendicular to said drive shaft (1).

14. The grinding head according to claim 1, wherein said crown gear (12) has a mounting tooth (14) offset from said drive shaft (1).

15. The grinding head according to claim 1, characterized in that said first gears (15) have mounting teeth (15') offset from the associated pins (16), and the pins (16) support the first gears (15).