INDEXING HEAD WITH TWO ROTATING AXES

Abstract

Indexing head with two rotating axes, with a first rotating axis A perpendicular to the fixing position with regard to the mode of operation of the head, and with a second rotating axis B in the axis of the fixing direction, in turn defining an upper part of the fixed head in relation to the B axis and a lower part of the head, which moves in relation to axes A and B; and which has a principal servomotor A (40) and a position locking mechanism on the A axis arranged on the part of the lower head; and a principal servomotor B (21) for rotation on the B axis with a position locking mechanism on the B axis arranged on said upper part of the head.

Description

OBJECT OF THE INVENTION

The object of the invention is an indexing head with two rotating axes which makes it possible to move objects connected to it, such as an optical scanner, for example, and whose distinctive feature lies in the fact that it has two independent mechanisms to control locking of the two rotating axes.

STATE OF THE ART

Indexing heads are heads with an ability to repeat the position determined by the user as many times as required. Heads used nowadays are directed electronically.

U.S. Pat. No. 5,088,337 describes a head which can be used to position a probe mounted on a coordinate positioning machine. This head is mounted on the machine using a fixed support. The head has a rotor which rotates around a vertical axis, according to the plane of the drawing, and a rotating element, which houses the probe and performs a second rotation around an axis orthogonal to the first. The different positions are fixed by means of an array of ball bearings and cooperating rollers, arranged circumferentially around the two rotating axes. The locking and unlocking of a given position is carried out by a manual mechanism common to both axes. This mechanism consists of a right angle bracket which pivots on a support because of the retraction of a bar, located in the vertical rotating axis, which pushes the rotating element to couple with the side wall of the rotor. The bar is moved manually using a wheel which rotates a lever, the rotation of which displaces a bar, joined transversally to the bar. This movement is the one which causes the coupling and uncoupling of the rotor with regard to the fixed portion or support, thus also locking and unlocking the first rotation.

Meanwhile, the UK patent document GB2298488A operates according to principles similar to the above, with the difference that the movement of the right angle bracket is produced by a locking motor. This motor rotates an axis between two predetermined angular positions, which correspond to locking and unlocking of the head. A cable passes around a pulley, mounted on the base, and is connected by its end furthest from the axis to the right angle bracket-shaped drive device, similar to the one described earlier. When the motor operates, it rotates the axis, pulling the locking lever (part of the right angle bracket) upwards and withdrawing the rotor from its indexed position, pushing another rotor upwards to couple with the base. On the other hand, reverse rotation of the axis would have the opposite effect on the rotors indicated.

DESCRIPTION OF THE INVENTION

The object of the invention, as indicated in the description thereof, refers to an indexing head with two principal rotating axes referred to as A and B for the sake of simplicity. The rotating axis A corresponds to the rotating axis perpendicular to the fixing position with regard to the operating mode of the head in the measuring machine, whereas rotating axis B corresponds to the axis of the head fixing position.

The head indexing relates to the ability to repeat the position. The repetition of the position is achieved as a result of the following process:

• • a) Unlocking of the initial position on axes A and B.
  • b) Rotation of axes A and B to a position determined by the user.
  • c) Locking of rotating axes A and B in the new position.

When the system is locked, it means that the rotating axis has no degree of freedom for movement, which is achieved by using an array of cylindrical rollers and ball bearings. On both the rotating axis A and B, the ball bearings are placed in a circumference, in an ordered fashion, with a 5° separation between them. Meanwhile, there are three pairs of rollers, separated from each other by an angle of 120°, in a part which moves in relation to the fixed parts which house the ball bearings. In a second practical embodiment, the aforementioned part will be formed of two sloping ramps, which replace the rollers.

Considering that the rotating axes are mobile, and once the motors responsible for rotating the head on both A and B axes reach the position determined by the user, the upper locking mechanism (locking on the B axis) and lower locking mechanism (locking on the A axis) are activated to fix the established position. This means that the motors are only working during the process of securing and releasing, guaranteeing the position mechanically, and also providing a saving in energy, consumption and useful life of the motors, as they only work when in movement and not when the desired position is reached.

Meanwhile, on axis A (perpendicular to the fixing position) a rotation range of ±105° is guaranteed. This means that rotation on the A axis is sufficient to reach these positions without activating the locking/unlocking of the B axis and, consequently, reducing wear and tear on the mechanical components of the B axis and improving its durability. Meanwhile, the locking/unlocking system on the B axis returns to its initial position thanks to the force exercised by two springs in the axial direction of the rotating axis B. The force applied by these springs can be regulated using a mechanism designed for the purpose, as the force to be applied may vary depending on the component which has to be moved.

Throughout the description and the claims, the word “comprises” and variants thereof are not intended to exclude other technical characteristics, additions, components or steps. For experts in the subject, other objects, advantages and characteristics of the invention will be gleaned in part from the description and in part from the practice of the invention. The following examples and drawings are provided for illustrative purposes, and are not intended as a restriction on this invention. In addition, this invention covers all the possible combinations of particular and preferred embodiments indicated here.

BRIEF DESCRIPTION OF THE DRAWINGS

Below is a very brief description of a series of drawings which help to understand the invention better and which are expressly related to an embodiment of said invention presented as a non-restrictive example thereof.

FIG. 1—Shows an image of the head which is the subject of the invention, showing the two rotating axes A and B.

FIG. 2—Shows the cross section of the locking mechanism on axis B in the unlocked position.

FIG. 3—Shows a first view in detail of the locking mechanism on axis B in the unlocked position.

FIG. 4—Shows the cross section of the locking mechanism on axis B in the locked position.

FIG. 5—Shows a first view in detail of the locking mechanism on axis B in the locked position.

FIG. 6—Shows a detail of the rest areas and gear stop.

FIG. 7—Shows a detail of the system which guarantees return to the initial position.

FIG. 8—Shows a detail of the rotating operation of the rotating axis B.

FIG. 9—Shows a detail of the guiding areas in the lower casing structure.

FIG. 10—Shows the cross section of the locking mechanism on axis A in the unlocked position.

FIG. 11—Shows the cross section of the locking mechanism on axis A in the locked position.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

As can be seen in FIG. 1, the head has two principal rotating axes called A and B. The rotating axis A corresponds to the rotating axis perpendicular to the fixing position with regard to the operating mode of the head in the measuring machine, whereas rotating axis B corresponds to the axis of the head fixing position. The name indexing head refers to the ability of the head to repeat the position determined by the user. The repetition of the position is achieved as a result of the following process:

• • a) Unlocking of the initial position on rotating axes A and B.
  • b) Rotation of the axes to a determined position.
  • c) Locking of the A and B rotating axes in the new position.

With reference to FIG. 2, it is possible to see the locking mechanism on the B axis (the one which corresponds to the fixing direction) in the unlocked position. The upper base (1) is considered the reference part, as it is a part which does not move in any way. In the unlocked position, the part which holds the lower casing (5) which houses the gears for the rotating axis B (11) is in its natural position, supported solely by a supporting axis (7) and resting on the ring (9) which the part supporting the lower casing (5) has on its upper part.

Located in the lower casing (5) is an array of ball bearings (38) which are arranged in a circumference, in an ordered manner and with a separation of 5° between them on both rotating axes A and B. Meanwhile, there are three pairs of cylindrical rollers (37), separated from each other by an angle of 120°, in a part which moves in relation to the fixed parts which house the ball bearings.

FIG. 4 shows the locking position. This figure shows how the rotation of the part called the anchor gear (2), because of a lever which it incorporates, causes the group formed by the supporting axis (7), the part which supports the lower casing (5), an L-shaped part (8) and the gear on the rotating axis B (11) to move upwards, moving a referenced distance such as (D), reaching a locking position where the ball bearings in the lower casing (5) and the rollers come into contact, preventing any degree of freedom.

The operation of the locking system on the rotating axis B is relatively simple. Rotation of the anchor gear (2) causes the L-shaped part (8) to slide along the lever of the aforementioned anchor gear (2). The sliding occurs on two ball bearings (30) which the L-shaped part (8) incorporates to reduce friction, rest on a single point and facilitate rotation. The lever forces the L-shaped part (8) to rotate on its transverse axis, raising the supporting axis (7) and, consequently, the entire lower part of the head which is the object of the invention.

The lever incorporated in the anchor gear and controlled rotation thereof causes the lower part of the head to move vertically until it blocks any permitted movement.

Observe the difference between the initial and final positions of the critical components which make up the mechanism shown in FIGS. 2 to 4. In FIGS. 2 and 3, the anchoring mechanism is in its initial position, i.e. in an unanchored or unlocked position, whereas in FIGS. 4 and 5 the anchor gear (2) has rotated, raising the L-shaped part (8) together with the supporting axis (7), the part which supports the lower casing (5), the gears on the rotating axis B (11) and consequently the lower part of the head with all its associated parts.

Rotation of the anchor gear (2) is controlled by a secondary servomotor on axis B (14), which is activated when it receives a signal from the controller. This secondary servomotor on axis

B (14) is associated with a reduction gear (13) which reduces the output speed of the servomotor and at the same time increases the torque. This reduction gear is connected to a transmission system (15) which is what causes the anchor gear (2) to rotate and consequently lock or unlock the whole, preventing or allowing rotation of axis B.

For rotation of the anchor gear (2) to be more effective, the part is guided by ball bearings (3) which in turn are inserted in a part called the positioning disc (10).

To allow the mechanism to stay in the anchor position, the lever on the anchor gear (2) has two flat areas (16), perpendicular to the direction in which the force is applied, and where there is no danger of the system returning to its initial position. In addition, to prevent the system returning to the initial position in the same rotation direction, the anchor gear has stops (17) at the end of the lever. All of this can be seen to better effect in FIG. 6.

To enable the system to return to its initial position, two springs (18) are incorporated, with a pre-load capacity to apply greater or lesser force to the L-shaped part (8) in the releasing process and in the axial direction of rotating axis B. These springs are preloaded by means of two set screws (23) which screw into openings (19) which can be seen in FIG. 7. Depending on how tightly they are screwed in, the springs (18) will be preloaded to a greater or lesser extent.

As can be seen in FIG. 8, once the anchor system of rotating axis B has released the lower part, the principal servomotor B (21) receives a signal to rotate the head to the position desired by the user for axis B. This principal servomotor B (21), as with the secondary servomotor B (14), is associated with a reduction gear (22) which reduces the output speed of the principal servomotor B (21) while at the same time increasing the output torque. A pinion (20) which this reduction gear (22) has at the output of its own rotating axis is meshed with the rotating axis B (11) gear of the part supporting the lower casing (5). Consequently, the whole of the lower part rotates to the desired position.

Having explained both the anchoring/releasing mechanism and the operation of rotating axis B, an explanation will now be given of the anchoring/releasing mechanism and the operation of rotating axis A.

FIG. 10 presents a cross section of the lower part of the head in the unlocked position. Meanwhile, FIG. 11 presents a cross section of the lower part of the head in the locked or anchored position. As can be seen, the only variation consists of the longitudinal movement (D1) experienced by the anchoring of the external casing (24) on the rotating axis A (crosswise to the locking direction).

To lock the rotation of the external casing (31), as presented previously in reference to the locking system, the anchoring part (24) of the external casing (31) has an array of ball bearings (39) which allow the external casing to be positioned, and three pairs of rollers with a separation of 120° between them, in a position determined every 5°.

Having explained the locking system for rotating axis A, an explanation will now be given of the positioning and rotating system for axis A.

The rotating operation and the positioning of the external casing (31) are identical to the system used on rotating axis B. On the one hand, rotation is carried out by a principal servomotor A (26) attached to a reduction gear (25) which, by means of a transmission system using gears, formed of the pinion (29) and the gears (12), rotates the external casing (31).

As far as the locking/unlocking mechanism for rotation of axis A is concerned, the mechanism is completely independent of the locking/unlocking mechanism for rotation of axis B.

Its principal characteristic is its simplicity. The secondary servomotor A (33) incorporates a part called a threaded shaft A (28) at the shaft output. This part is inserted in the threaded hole in the anchoring part (24) of the external casing (31).

Once the secondary servomotor a (33) begins to operate, the rotation direction will determine whether the anchoring part (24) of the external casing (31) moves forward or backwards, locking or unlocking the rotation of the external casing (31). So that the anchoring part (24) of the external casing (31) can only move forwards or backwards and not rotate, until the distance referred to as (D1) has disappeared, the structure of the internal casing (32) has two guide areas (34) in which the anchoring part (24) of the external casing (31) can slide with no possibility of rotation.

One of the differences in the locking/unlocking mechanism for rotating axis B is that, while the positioning ball bearings on the rotating axis B (39) are fixed to the upper base (1), which is a static part, the positioning ball bearings on the rotating axis A have relative movement, as these positioning ball bearings on the rotating axis B (39) are fixed to the anchoring part (24) of the external casing (31) with the ability to move forwards or backwards. By ensuring that the anchoring part (24) of the external casing (31) cannot rotate, the ball bearings can repeat their position even though they have relative movement.

To avoid all the weight which has to be supported by the head falling on the cover, the gears (35) in the internal casing (32) and the anchoring axis (27) of the internal cover have been designed so that the effort is distributed along the circumference forming the part resting on the structure of the internal casing (32).

Claims

1. An indexing head with two rotating axes, with a first rotating axis A perpendicular to a fixing position with regard to a mode of operation of the head in a measuring machine, and with a second rotating axis B in the axis of a fixing direction, in turn defining an upper part of the head that is fixed with regard to the B axis and a lower part of the head, which moves in relation to axes A and B; the indexing head comprising: a principal servomotor A (26) for rotation on the axis A and a locking mechanism for the position on the axis A arranged in said lower part of the head; and a principal servomotor B (21) for rotation on the axis B with a locking mechanism for the position on the axis B arranged on said upper part of the head;the locking mechanism on the axis B comprising an anchor gear (2) connected to a transmission system (15) of a secondary motor B (14) which rotates an L-shaped part (8) caused by the anchor gear (2) sliding on a lever in such a way that it raises the lower part of the head; andwhere the locking mechanism on the axis A comprises an anchoring part (24) of an external casing (31) which has an array of ball bearings which allow said external casing (31) to be positioned and in turn moved forwards or backwards to lock the rotation of said external casing (31) depending on the rotational direction of a secondary servomotor A (33).

2. The head according to claim 1, wherein the locking mechanism for axis B comprises an upper base (1), in such a way that, in an unlocking position, the part which supports a lower casing (5) houses a gear for rotating axis B (11) which is in its natural position, supported solely on a supporting axis (7) and resting on a ring (9) which the part supporting the lower casing (5) has on its upper part.

3. The head according to claim 1, wherein a lever on the anchor gear (2) has two flat areas (16), perpendicular to a direction in which a force is applied, and stops (17) at the end of the lever.

4. The head according to claim 1, including two springs (18) which can be preloaded to apply greater or lesser force on the L-shaped part (8) in the unlocking process and in the axial direction of the rotating axis B; and in which the springs are preloaded by means of two set screws (23) which are screwed into openings (19).

5. The head according to claim 1, wherein the anchor gear (2) is guided by a ball bearing system (3) which is in turn inserted in a positioning disc (10).

6. The head according to claim 1, wherein the principal servomotor B (21) is associated with a reduction gear (22); and in which a pinion (20) which said reduction gear (22) has at the output of its own rotating axis meshes with the gear on the rotating axis B (11) of the lower casing (5).

7. The head according to claim 1, wherein the principal servomotor A (26) meshes with a gear (12), also solidly attached to an external casing (31), and in which both components are fixed to an internal gear (35), while said part is also screwed to the structure of the internal casing (32).