US20120255397A1

US20120255397A1 - Rotary indexing table

Info

Publication number: US20120255397A1
Application number: US13/501,427
Authority: US
Inventors: Uwe Weiss
Original assignee: Weiss GmbH
Current assignee: Weiss GmbH
Priority date: 2009-10-16
Filing date: 2010-10-15
Publication date: 2012-10-11
Also published as: US9868183B2; WO2011045078A1; CN102712068B; EP2475498A1; CN102712068A; WO2011045077A1; WO2011045078A8; EP2475497A1; EP2475498B2; EP2475498B1; EP2475497B1; CN102712069A; US20120266721A1

Abstract

The present invention relates to a rotary indexing table comprising a plate and at least two motors for driving the plate to carry out a rotational movement. The motors are drivingly connected to the plate by means of at least one cam barrel. The cam barrel comprises a drive groove with which drivers engage that are associated with the plate, wherein the drive groove has a constant pitch.

Description

The present invention relates to a rotary indexing table having a plate and at least two motors for driving the plate to make a rotational movement.
Rotary indexing tables are widely used, inter alia in assembly technology and automation technology. They usually have a turntable which is arranged vertically or also horizontally and on which a workpiece can be spanned to carry out machining work/assembly steps at the workpiece in different positions or at the rotating workpiece. Since larger and larger workpieces are today machined in an automated manner, there is a need for reliable rotary indexing tables which can cope with the strains which occur in so doing.
It is therefore an object of the present invention to provide a rotary indexing table which can also reliably cope with large loads and can position them precisely. In addition, the rotary indexing table should be able to be used flexibly.
This object is satisfied by a rotary indexing table having the features of claim 1.
As already initially mentioned, the rotary indexing table in accordance with the invention has a plate and at least two motors for driving the plate to make a rotational movement. The motors are drive-operatively connected to the plate via at least one barrel cam. The barrel cam has a driving groove into which drivers engage which are associated with the plate. The driving groove has a constant gradient.
In other words, the rotary indexing table in accordance with the invention utilizes at least two motors in order also to ensure a reliable rotational movement of the turntable under large strains. Any desired number of motors can generally be provided to take account of the respective application profile present. The drive can take place directly or indirectly. An indirect drive is to be understood as the interposition of a transmission between the respective motor and the barrel cam.
The transmission of the driving torque of the at least two motors to the plate takes place in a generally known manner via at least one barrel cam, i.e. the plate has drivers which engage into the driving groove of the barrel cam so that, on a rotation of the barrel cam, a rotational movement of the plate is generated (driving groove/driver coupling). As already stated above with respect to the motors, the number of barrel cams can likewise be selected in accordance with the respective conditions present.
To be able to use the rotary indexing table as flexibly as possible, i.e. to be able to adapt the rotational movement of the turntable to the respective demands, the driving groove has a constant gradient. A stepped operation of the plate is thus not generated by a latching step—a section of the driving groove without gradient—but rather by a corresponding control of the drive power of the motors. A barrel cam having a driving groove with a constant gradient can as a rule be manufactured less expensively than barrel cams having a varying gradient in which the movement of the turntable is “coded” by the shape of the driving groove and the driving torque provided to the barrel cam is substantially constant in time.
The rotary indexing table in accordance with the invention having any desired number of motors (at least two) and any desired number of barrel cams (at least one) can be used with high performance and flexibly. The motors and/or barrel cams can in particular be designed as modular components to lower the costs. No replacement of mechanical parts (barrel cams) is necessary on a change of the demand profile on the movement of the turntable due to the provision of a driving groove with a constant gradient. Only the control of the motors has to be matched.
Further advantageous embodiments of the invention are described in the description, in the drawings and in the dependent claims.
In accordance with an advantageous embodiment of the rotary indexing table in accordance with the invention, it has at least one further barrel cam having a driving groove into which the drivers of the plate engage, wherein a motor is drive-operatively associated with the barrel cam and the further barrel cam. In other words, in this embodiment, at least two barrel cams are provided which are each driven by at least one motor.
The described embodiment reduces the forces acting on the respective driving groove or drivers—compared with embodiments having only one barrel cam—and thus allows a more efficient torque transmission. In addition, the wear of the named components of the drive of the plate is reduced.
The most varied combinations of motors and barrel cams can generally be realized. Provision can, for example, also be made to associate two motors with at least one of the barrel cams, but in particular with each barrel cam.
A variant of the rotary indexing table in accordance with the invention of particularly simple design provides that the barrel cam and the motor respectively associated with it are arranged coaxially. If two motors are associated with a barrel cam, both motors can also be arranged coaxially to the barrel cam.
The motors are preferably asynchronous motors which are in particular connected to one another such that performance differences or performance fluctuations of the asynchronous motors are automatically compensated. Such an automatic compensation can be realized in a simple manner in that the asynchronous motors are connected in parallel and can be controlled by a common control device. The control device is in particular a single amplifier which supplies the motors with electric energy.
The above-described embodiments allow a simpler synchronization of the motors to avoid an unwanted tensioning of the drive components of the rotary indexing table.
It is of advantage for specific uses of the rotary indexing table in accordance with the invention if at least one of the motors is a torque motor which directly drives the barrel cam. A torque motor is—in simplified terms—a direct drive without a transmission with a relatively high driving torque and a relatively small driving speed in comparison with usual electric motors. Since transmissions, which can only be built with small clearance at high cost, are omitted, the manufacturing costs for such a rotary indexing table fall. In addition, inter alia, higher dynamics of the rotary indexing table and a higher precision of the turntable positioning are achieved.
The barrel cam can preferably be driven by two torque motors which are each arranged at a respective one of the end faces of the barrel cam coaxially to the barrel cam.
In accordance with a further development of the embodiments of the rotary indexing table, the barrel cam has a prolongation which substantially has the diameter of the barrel cam and which has the functional components of the torque motor. The drive of the barrel cam thus does not take place via a drive shaft of the barrel cam, but the barrel cam itself is driven. Functional components of the torque motor are those elements which are required for an operation of the motor, such as coils and magnets. In other words, this embodiment provides that the barrel cam with a section—which is preferably designed without a driving groove—itself forms an element of the motor, whereby the motor is particularly efficient and generates a high torque. The named barrel cam section is thus the rotor of the torque motor which is integrally connected to the section of the barrel cam provided with the driving groove.
The above-described embodiments do not preclude that different types of motors (synchronous motors, asynchronous motors, torque motors) are combined with one another to allow a drive of the rotary indexing table adapted to the respective situation. The number of motors and of barrel cams is generally arbitrary to the extent that at least two motors and one barrel cam are provided. Any desired number of motors can respectively be associated with the barrel cam or with the barrel cams.
The invention furthermore relates to a method of operating a rotary indexing table having at least two motors.
The problem occurs with such rotary indexing tables that the motors have to be synchronized with one another to avoid tensions of the components of the drive of the rotary indexing table.
It is thus a further object of the invention to provide a method which allows a reliable operation of a rotary indexing table of the aforesaid kind.
This object is satisfied by a method having the features of claim 11 or of claim 12.
The first approach variant relates to rotary indexing tables which have two or more asynchronous motors. In accordance with the invention, the asynchronous motors have a common working current applied by a common control device, in particular an amplifier, so that an equal power output of the asynchronous motors is automatically adopted.
The fact is made use of in this respect that with asynchronous motors which are connected in parallel and which are associated with a single amplifier, an automatic compensation of the power output takes place between the motors. A complex control circuit is therefore not required.
The second approach variant is not restricted to specific types of motors. In accordance with the invention, a respective separate motor is associated with the motors, with data being transmitted from one of the control devices to the other control device in order to adapt a control of the motor associated with the other control device using the data. This variant thus provides a master/slave configuration in which a control device takes over a master function. It controls a primary motor which is responsible for the positioning of the turntable. The primary control device transmits data to a secondary control unit which is associated with a secondary motor. The secondary control unit reacts on the basis of these data and controls the secondary motor such that it applies assisting driving torque. In figurative terms, the primary motor “pulls”, while the secondary motor additionally “pushes”. It is understood that a plurality of secondary control units/secondary motors can be provided. A plurality of secondary motors can also be controlled by a common secondary control unit.

The invention will be described in the following purely by way of example with reference to advantageous embodiments and to the drawings. There are shown:

FIGS. 1 a to 1 c an embodiment of the rotary indexing table in accordance with the invention;

FIGS. 2 a and 2 b a further embodiment of the rotary indexing table in accordance with the invention;

FIG. 3 a further embodiment of the rotary indexing table in accordance with the invention;

FIG. 4 a schematic representation of a further embodiment of the rotary indexing table in accordance with the invention;

FIG. 5 a section through a barrel cam and its direct drive by two torque motors; and

FIG. 6 a circuit diagram for a rotary indexing table in accordance with the invention which is driven by two asynchronous motors.

FIG. 1 a perspectively shows a rotary indexing table 10 which has a ring-shaped turntable 12 which is driven to make a rotational movement by two motors 14. The turntable 12 surrounds a central opening 16 in which, for example, one or more machining tools can be arranged for machining workpieces fastened on the turntable 12.
FIG. 1 b substantially shows the embodiment of FIG. 1 a in a plan view, with drivers 18 being able to be recognized which are drawn by dashed lines and which are arranged—in the position of use—at the lower side of the turntable 12. Only the motors 14 have different dimensions than those shown in FIG. 1.
As can be seen from FIG. 1 c, the drivers 18 engage into driving grooves 20 which are formed at barrel cams 22. The barrel cams 22 are each driven to make a rotational movement by one of the motors 14. The drivers 18 engaging into the driving grooves 20 running spirally around the barrel cams 22 are taken along by the rotational movements of the barrel cams 22, whereby the turntable 12 is driven to make a rotational movement.
The motors 14 and the barrel cams 22 are generally arranged coaxially. In the present embodiment, however, a transmission (not shown) is interposed to step down a drive speed of the motors 14 (indirect drive).
Any kind of motors can generally be used. The use of asynchronous motors is associated with the advantage that their synchronization can be realized comparatively simply. The two motors 14 are for this purpose connected in parallel and supplied with current by a common amplifier (not shown). An equal power output of the two motors is automatically adopted in this arrangement due to the properties inherent to asynchronous motors which thus contribute “with equal priority” and to an equal extent to the drive of the turntable 12.
FIG. 2 a shows a further embodiment 10′ of the rotary indexing table in a plan view. The turntable 12 in this embodiment has a smaller central opening 16 than in the embodiment shown in FIGS. 1 a to 1 c. This admittedly reduces the free space for the arrangement of further devices at the center of the rotary indexing table 10′; however, the area of the turntable 12 is accordingly larger. This is advantageous in specific embodiments, e.g. the fastening of larger workpieces is facilitated.
The rotary indexing table 10′ is also driven by two motors 14. They are, however, not arranged at different sides of the rotary indexing table 10′ (anti-parallel arrangement, see FIGS. 1 a and 1 b), but on the same side. In other words, the two barrel cams 22 of the rotary indexing table 10′ are supplied with driving torque from the same side.
The rotary indexing table 10′ substantially has a similar structure to the rotary indexing table 10 of FIGS. 1 a to 1 c. It can be recognized that a respective transmission 24 is arranged between the motors 14 and the barrel cams 22. The transmission 24 includes at the side of the barrel cam a gear ring 26 which is rotationally fixedly placed onto a barrel prolongation 28. At the motor side, the transmission 24 includes a spur gear 30 which is rotationally fixedly connected to an output shaft of the respective motor 14 and which meshes with the gear ring 26. The two components 26, 30 described form a step-down together.
FIG. 2 b shows the rotary indexing table 10′ in a vertical section. The sectional view shows that the axes of rotation R_Mof the motors 14 are admittedly arranged at the same level in the rotary indexing table 10, but lie beneath the plane spanned by the axes of rotation R_Kof the barrel cams 22.
A further special feature of the rotary indexing table 10 is a plate 32 which is present in addition to the turntable 12 and which is fixedly fastened to a central element 34 which is in turn fixedly connected to a housing 36 of the rotary indexing table 10′. The plate 32 thus does not move on operation of the rotary indexing table 10′. Assembly devices or machining tools can, for example, be arranged on it to manipulate or machine the workpieces arranged on the turntable 12.
A further embodiment 10′ of the rotary indexing table is shown in FIG. 3. The motors 14 here are, unlike the embodiment of FIGS. 1 a to 1 c, not arranged behind or in front of the barrel cam 22, but the motors 14 and the barrel cams 22 respectively associated with them lie offset in parallel next to one another with respect to a direction perpendicular to the axes of rotation R_Kof the barrel cams 22. This embodiment also has transmissions 24 between the motors 14 and the respective barrel cams 22. The turntable 12 is not shown in FIG. 3 to allow a view into the interior of the rotary indexing table 10″.
FIG. 4 schematically shows a further variant of how the drive of the turntable 12 can be designed. In the embodiment 10′ of the rotary indexing table, three barrel cams 22 are provided, with the axes of rotation R_Kof two adjacent barrel cams 22—viewed from above—including an angle of approximately 60° C. so that the barrel cams 22 are arranged in the form of an isosceles triangle. Two of the barrel cams 22 are driven by a respective motor 14. The third barrel cam 22 is in drive-operative contact with two motors 14. One of the motors 14 is—as in the barrel cams with a respective motor 14—arranged coaxially to the barrel cam 22, i.e. its driving torque is directly transmitted to the barrel cam 22. The driving torque of the second motor 14 which is associated with this barrel cam 22 is transmitted to the barrel cam 22 via the transmission 24, with the transmission 24 of FIG. 3 being able to be used, for example. The rotary indexing table 10′″ is intended to illustrate by way of example that any desired number of motors 14 and of barrel cams 22 can be combined in the different arrangements to be able to provide an ideal drive of the turntable 12 for the respective application.
FIG. 5 shows a section through a barrel cam 22′ which is driven directly by two torque motors 38 which are arranged at the two end faces of the barrel cam 22′. A drive shaft is not provided. The magnets 40 required for the operation of the torque motors 38 are arranged directly at the barrel cam 22′. The magnets 40 cooperate with coils 42 to generate a driving torque of the barrel cams 22′. The magnets 40 are arranged at extension sections A of the barrel cam 22′ which are not provided with the driving groove 20. The driving groove 20 is restricted to a section B of the barrel cam 22′ between the two extension sections A.
The extension sections A and the section B substantially have the same diameter. A large driving torque can thereby be provided in a simple manner. It moreover simplifies the manufacture of the barrel cam 22′. The above-described type of drive represents the “most direct” form of a direct drive of the barrel cam 22′. Drive losses and positioning inaccuracies are minimized in an advantageous manner by the omission of interposed components.
A synchronized control of the motors 14 can in particular be effected by a master/slave configuration in variants of the rotary indexing table 10, 10′. 10″, 10′″ in which no asynchronous motors connected in parallel are used for the automatic synchronization. This provides that a separate control device (not shown) is associated with each motor 14. One of the control devices takes over the master function, i.e. it controls a primary motor 14 which is responsible for the movement profile of the turntable 12. The further motor or motors 14 (slave(s)) serve for the assistance of the primary motor 14. To synchronize their assisting power with the drive power of the primary motor, the control devices associated with the secondary motors 14 are supplied with data which the primary control device outputs. The secondary drive units (slaves) are thus dependent on the instructions of the primary unit (master). This hierarchical structure facilitates the control and ensures a precise control of the turntable 12.
As already stated, the rotary indexing table 10, 10′, 10″, 10′″ can be operated by at least two asynchronous motors 14′. FIG. 6 illustrates a parallel connection of two asynchronous motors 14′ which are only connected to a single amplifier 44 (power part). I.e. the supply of the motors 14′ with electric energy (three-phase current) takes place via lines U, V, W which emanate from the amplifier 44. The amplifier 44 is in turn connected via lines L1, L2, L3 to corresponding lines which supply other components of the rotary indexing table 10, 10′, 10″, 10′″ with energy or to an external power grid. Lines PE serve for the grounding of the named components.
The parallel connection of the motors 14′ results in an automatic adaptation of their power output. The motors 14′ are thus coupled in a compulsory manner. Complex apparatus and special adaptations for the synchronization of the motors 14′ are therefore omitted.
To monitor the status of the system, a position encoder G is provided which monitors the location of a drive shaft of one of the motors 14′ and transmits the measured data to the amplifier 44. The data are used there to control and optionally adapt the drive power of the motors 14′. As already explained above, only the monitoring of one of the motors 14′ is necessary to obtain reliable information on the drive of the rotary indexing table 10, 10′, 10″, 10′″ due to the automatic synchronization of the motors 14′ inherent to the parallel connection of the motors 14′.

REFERENCE NUMERAL LIST

10, 10′, 10″, 10′″ rotary indexing table
12 turntable
14 motor
14′ asynchronous motor
16 opening
18 driver
20 driving groove
22, 22′ barrel cam
24 transmission
26 gear ring
28 barrel prolongation
30′ spur gear
32 plate
34 central element
36 housing
R_M, R_Kaxis of rotation
38′ torque motor
40 magnet
42 coil
44 amplifier
A extension section
B groove section
G position encoder
U, V, W, L1, L2, L3 electric line
PE ground line

Claims

1. A rotary indexing table having a plate (12) and at least two motors (14) for driving the plate (12) to make a rotary movement wherein the motors (14) are drive-operatively connected to the plate (12) via at least one barrel cam (22, 22′);

wherein the barrel cam (22, 22′) has a driving groove (20) into which drivers (18) engage which are associated with the plate (12); and

wherein the driving groove (20) has a constant gradient.

2. A rotary indexing table in accordance with claim 1, wherein

the rotary indexing table has at least one further barrel cam (22, 22′) having a driving groove (20) into which the drivers (18) of the plate (12) engage, with at least one respective motor (14) being drive-operatively associated with the barrel cam (22, 22′) and the further barrel cam (22, 22′).

3. A rotary indexing table in accordance with claim 1, wherein

two motors (14) are associated with the barrel cam (22, 22′).

4. A rotary indexing table in accordance with claim 1, wherein

the barrel cam (22, 22′) and the motor (14) respectively associated with the barrel cam are arranged coaxially.

5. A rotary indexing table in accordance with claim 1, wherein

the motors (14) are asynchronous motors.

6. A rotary indexing table in accordance with claim 5, wherein

the asynchronous motors are connected to one another such that power differences of the asynchronous motors are automatically compensated.

7. A rotary indexing table in accordance with claim 5, wherein

the asynchronous motors are connected in parallel and can be controlled by a common control device.

8. A rotary indexing table in accordance with claim 1, wherein

at least one of the motors is a torque motor (38) which directly drives the barrel cam (22′).

9. A rotary indexing table in accordance with claim 8, wherein

the barrel cam (22′) can be driven by two torque motors (38) which are arranged coaxially to the barrel cam at a respective one of the end faces of the barrel cam (22′).

10. A rotary indexing table in accordance with claim 8, wherein

the barrel cam (22′) has a prolongation (A) which has substantially the diameter of the barrel cam (22′) and which has the functional components (40) of the torque motor (38).

11. A method of operating a rotary indexing table having a plate (12) and at least two motors (14) for driving the plate (12) to make a rotary movement, wherein the motors (14) are drive-operatively connected to the plate (12) via at least one barrel cam (22, 22′), the barrel cam (22, 22′) has a driving groove (20) into which drivers (18) engage which are associated with the plate (12), the driving groove (20) has a constant gradient, and the motors (14) are asynchronous motors, the method comprising:

supplying, by a common control device, a common working current to the asynchronous motors so that an equal power output of the asynchronous motors is automatically adopted.

12. A method of operating a rotary indexing table having a plate (12) and at least two motors (14) for driving the plate (12) to make a rotary movement, wherein the motors (14) are drive-operatively connected to the plate (12) via at least one barrel cam (22, 22′), the barrel cam (22, 22′) has a driving groove (20) into which drivers (18) engage which are associated with the plate (12), the driving groove (20) has a constant gradient, and a respective separate control device is associated with the motors, the method comprising:

transmitting data from one of the control devices to the other control device in order to adapt a control of the motor associated with the other control device using the data.

13. A rotary indexing table in accordance with claim 3, wherein two motors are associated with each barrel cam (22, 22′).

14. A method in accordance with claim 11, wherein the asynchronous motors are acted on by an amplifier.