Rotary indexing table with power-optimized drive

Abstract

Disclosed is a rotary indexing table (10) having an output flange (12) which is suitable for receiving a workpiece, mounted on a housing (14) of said rotary indexing table (10) for rotation about an axis of rotation (A) and drivingly connected to at least one drive element (24) which engages a driving groove (22) in a cylindrical cam (20) which can be driven by a motor, the cylindrical cam (20) being disposed asymmetrically to the axis of rotation (A) of the output flange (12).

Claims

1. A rotary indexing table having an output flange for receiving a workpiece, the output flange being supported rotatably about an axis of rotation at a housing of the rotary indexing table, and the output flange being drivably connected to at least one entrainer, the at least one entrainer engaging into a drive groove of a barrel cam that is drivable, wherein a drive effective section of the barrel cam, extending along a rotational axis of the barrel cam over an axial extent of the drive groove from a location where the at least one entrainer enters the drive groove to a location where the at least one entrainer exits the drive groove, is arranged asymmetrically in axially offset relation along the rotational axis relative to the axis of rotation of the output flange.

2. The rotary indexing table in accordance with claim 1, wherein a length of the drive effective section of the barrel cam is defined by an axial length section of the drive groove extending along the rotational axis of the barrel cam.

3. The rotary indexing table in accordance with claim 2, wherein the drive effective section of the barrel cam is axially offset along the rotational axis of the barrel cam with respect to the axis of rotation of the output flange by approximately 5 to 30% of the length of the drive effective section of the barrel cam.

4. The rotary indexing table in accordance with claim 3, wherein the drive effective section of the barrel cam is axially offset along the rotational axis of the barrel cam with respect to the axis of rotation of the output flange by approximately 7 to 25% of the length of the drive effective section of the barrel cam.

5. The rotary indexing table in accordance with claim 4, wherein the drive effective section of the barrel cam is axially offset along the rotational axis of the barrel cam with respect to the axis of rotation of the output flange by approximately 10 to 20% of the length of the drive effective section of the barrel cam.

6. The rotary indexing table in accordance with claim 5, wherein the drive effective section of the barrel cam is axially offset along the rotational axis of the barrel cam with respect to the axis of rotation of the output flange by approximately 15% of the length of the drive effective section of the barrel cam.

7. The rotary indexing table in accordance with claim 1, wherein the output flange is supported at the housing of the rotary indexing table by means of a ball bearing supported stewing ring.

8. The rotary indexing table in accordance with claim 7, wherein the ball bearing supported stewing ring is designed as a four-point bearing.

9. The rotary indexing table in accordance with claim 1, wherein the output flange is supported at the housing of the rotary indexing table by means of a bearing supported stewing ring and the bearing supported stewing ring is designed as a cross roller bearing.

10. The rotary indexing table in accordance with claim 1, wherein the at least one entrainer enters the drive groove at a first angle of rotation and exits the drive groove at a second angle of rotation, wherein the first angle of rotation is different from the second angle of rotation.

11. The rotary indexing table in accordance with claim 10, wherein the first angle of rotation has a greater absolute value than the second angle of rotation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be explained in the following purely by way of example with reference to the drawings, in which:

(2) FIGS. 1a-1c show an embodiment of a rotary indexing table in accordance with the invention in different views;

(3) FIG. 2 illustrates the effective lever arm relationships of a conventional rotary indexing table having a symmetrically arranged barrel cam; and

(4) FIG. 3 illustrates the effective lever arm relationships of a rotary indexing table in accordance with the invention having an asymmetrically arranged barrel cam.

DETAILED DESCRIPTION OF THE INVENTION

(5) FIG. 1a perspectively shows a rotary indexing table 10 in accordance with the invention that in the embodiment specifically shown here has an annular output flange 12 formed as a turntable 11 to receive workpieces to be machined (not shown). The output flange 12 or the turntable 11 is here supported rotatably about an axis of rotation A at a housing 14 of the rotary indexing table 10 so that the output flange 12 can be rotationally moved from one position of rest into a second position of rest. In the embodiment shown here, the output flange 12 is annular and surrounds a central opening 16 in which, for example, one or more machining tools (not shown) can be located to machine workpieces located on the turntable 11.

(6) The rotary indexing table 10 or its output flange 12 is driven by a motor, not shown here, whose shaft can be coupled to a drive shaft 18 of the rotary indexing table 10. The drive shaft 18 here drives a barrel cam 20 that is rotatably supported in the housing 14 of the rotary indexing table 10. For this purpose, a spirally peripheral drive groove 22 is formed in the barrel cam 20 and the entrainers 24 that are drive effectively connected to the drive flange 12 at its side that is lower—in the position of use—engage into said drive groove 22. The entrainers 24 are here designed as roller pins having cam rollers 26. The entrainers 24 engaging into the drive groove 22 are thus dragged along by the rotational movement of the barrel cam 20, whereby the output flange 12 is driven to make a rotational movement in the desired manner.

(7) As can be seen from FIG. 1c, the output flange 12 is supported in accordance with the invention by means of a ball bearing supported slewing ring 28 designed as a four point bearing at the housing 14 of the rotary indexing table 10, whereby the bearing friction can be minimized in the desired manner in favor of the reduction of the required drive power for the rotary indexing table 10.

(8) As can be seen from FIG. 1a and in particular from FIG. 1b, the barrel cam 20 and in particular its drive effective section, that is defined by the axial extent of the drive groove 22, is arranged asymmetrically to the axis of rotation A of the output flange 12 in favor of the optimization of the effective lever arm length via which the output flange 12 is driven by the barrel cam 20. In the embodiment shown here, the drive effective section of the barrel cam 20 is here offset with respect to an arrangement that is symmetrical with respect to the axis of rotation A of the output flange 12 by an offset amount V that approximately corresponds to 15% of the length of the drive effective section of the barrel cam 20. The specific offset amount V, however, depends on the geometry of the respective rotary indexing table and is preferably in the region between 10 and 20% of the length of the drive effective section of the barrel cam 20.

(9) The effect of the asymmetrical arrangement of the barrel cam 20 in accordance with the invention on the effective lever arm length will be explained in the following with reference to FIGS. 2 and 3. FIG. 2 here explains the effective lever arm length in a conventional rotary indexing table 10′ having a symmetrically arranged barrel cam 20′ as is schematically illustrated in the left hand representation of FIG. 2. The right hand representation of FIG. 2 here illustrates the effective lever arm length in dependence on the angle of rotation of the output flange, that is not shown here. As can be seen from this representation, the individual entrainers 24′ enter into the drive groove 22′ of the barrel cam 20′ at an angle of rotation ψ of approximately −31°, whereupon they are dragged along by the drive groove 22′ as a result of the rotational movement of the barrel cam 20′ and exit the same again at an angle ψ of approximately 31°. The effective lever arm length here increases during this engagement region from a starting value of approximately 270 mm to a maximum value of approximately 275 mm before the effective lever arm length subsequently continuously reduces down to a minimal lever arm length of approximately 190 mm at that point in time at which the entrainers 24′ leave the drive groove 22′ again. The effective lever arm length can be determined here in that the radial spacing of the respective entrainer 24′ from the axis of rotation A at every angle of rotation ψ of the output flange is split into two vectors which are perpendicular to one another and of which the one vector is perpendicular on the border of the drive groove 22′. The other vector then represents the effective lever arm length.

(10) If corresponding considerations are made for a rotary indexing table 10 having an asymmetrically arranged barrel cam, the relationships result such as are shown with reference to FIG. 3. As can here be seen from the right hand diagram of FIG. 3, the entrainers 24 already enter into the drive groove 22 at an angle of rotation ψ of approximately −45° due to the asymmetrical arrangement of the barrel cam 20, with a lever arm length of 230 mm resulting. The effective lever arm length here also increases up to a value of approximately 275 mm, with this maximum effective lever arm length being adopted at an angle ψ of approximately −14° from where the effective lever arm length continuously reduces down to a minimal value of 230 mm at an angle ψ of approximately +15°.

(11) In contrast to the symmetrical arrangement of the barrel cam in accordance with FIG. 2, the minimal effective lever arm length is thus 40 mm larger (230 mm with the asymmetrically arranged barrel cam with respect to 190 mm with a symmetrically arranged barrel cam), whereby the maximum strain on both the entrainers 24 and the barrel cam 20 can be reduced. Due to the larger minimal effective lever arm length, less torque is furthermore also required for the drive of the output flange 12, whereby the drive power required for the drive of the rotary indexing table 10 can be minimized.