WO1996027818A1

WO1996027818A1 - Xy-drive

Info

Publication number: WO1996027818A1
Application number: PCT/NL1996/000098
Authority: WO
Inventors: Hans Georg Jerie
Original assignee: United Overseas Technology Limited
Priority date: 1995-03-03
Filing date: 1996-03-04
Publication date: 1996-09-12

Abstract

The invention relates to a combination of a carriage and a drive device for driving this carriage independently in two mutually perpendicular directions (x, y) in one plane, which device comprises: a frame; a carriage movable relative to this frame; guide means for guiding the carriage independently in each of the two directions (x, y); and drive means for driving the carriage independently in each of the two directions (x, y). The drive device according to the invention is characterized by two elongate drive rollers (12, 13) which are mounted rotatably round their respective axes relative to the frame and drivable rotatably by respective motor drives and which are each provided with a helical toothing for driving co-action with corresponding gear racks arranged on the carriage (2); which drive rollers (12, 13) are placed mutually parallel such that at least one of the two drive rollers engages on two gear racks (4, 5) present on the carriage (2) at a mutual distance; such that the drive rollers (12, 13) are the guide means and also form part of the drive means; wherein the rotation directions and rotation speeds of the rollers determine the direction and the speed of the displacement of the carriage (2) in said plane.

Description

XY-DRIVE

The invention relates to a combination of a carriage and a drive device for driving this carriage independently in two mutually perpendicular directions (x, y) in one plane, which device comprises:

a frame;

a carriage movable relative to this frame;

guide means for guiding the carriage independently in each of the two directions (x, y); and drive means for driving the carriage independently in each of the two directions (x, y).

Such a drive device is known in many embodiments and in many applications.

A microfiche reader can be envisaged as an example of a possible application. Such an apparatus is adapted to cause a transparent photo of for instance a text and/or images to be supported by the carriage. The fiche carries the information in greatly reduced form. A lighting device illuminates the transparent image from the one side while a projection device arranged on the other side thereof can for instance project a picture onto a screen. In order to show a desired portion of the fiche the carriage is directed to the relevant desired coordinates by driving the associated drive means.

The carriage can for instance be driven in one direction by means of a motor relative to an auxiliary frame which is in turn drivable in transverse direction by means of a motor, whereby a displacement is possible in both independent directions in the plane defined by both directions x, y.

The object of the invention is to provide a drive device which enables a maximum displacement in both directions while occupying the smallest possible space. A further object of the invention is to embody a drive device such that both motors can be arranged stationary relative to the frame, whereby the mass for displacement is smaller, the system can react more rapidly and lighter motors can be applied.

In order to realize these and other objectives the drive device according to the invention is

characterized by two elongate drive rollers which are mounted rotatably round their respective axes relative to the frame and drivable rotatably by respective motor drives and which are each provided with a helical

toothing for driving co-action with corresponding gear racks arranged on the carriage;

which drive rollers are placed mutually

parallel such that at least one of the two drive rollers engages on two gear racks present on the carriage at a mutual distance;

such that the drive rollers are the guide means and also form part of the drive means;

wherein the rotation directions and rotation speeds of the rollers determine the direction and the speed of the displacement of the carriage in said plane.

For the greatest possible accuracy, wherein the carriage can be guided in both directions, the variant is recommended in which the one roller engages on two gear racks and the other roller engages on only one gear rack. In this way any possible jamming due to tilting is effectively prevented, while due to the three engagement zones the drive system is not mechanically over-defined as would be the case if both drive rollers were to engage onto two gear racks located at mutual distance. In such a case, which theoretically could only function with perfect dimensional stability, there is the possibility of the system jamming, for example due to ageing phenomena, effects of temperature. The system according to the above described embodiment is inherently stable, reliable and can moreover be embodied less expensively. Use is preferably made of an embodiment in which the orientations of the helical toothings of the two respective rollers are opposed. It has been found that the simplest and lowest-friction drive is realized herewith. When the drive rollers have equivalent but opposing helical toothings, forces can then be exerted on the carriage by driving the rollers in opposing

directions such that the carriage moves in the direction of the axis of the rollers. When the rollers are driven in the same direction a driving takes place wherein the carriage moves in transverse direction relative to the rollers.

Attention is further drawn to the fact that the simplest embodiment is such that the axes of the mutually parallel rollers extend in one of the main directions x, y.

The embodiment is recommended in which a drive roller is driven by the motor drive via a worm present on the shaft of the motor drive.

It is generally noted that everywhere where drive elements mutually co-act the transmission must take place such that it takes place with the lowest possible friction and clearance. In general the shapes of teeth will be dimensioned with a view to this criterion.

A specific embodiment within the latter context is that in which the shaft of the motor drive forms an angle with the helical toothing at the position of the point of contact between the worm and the drive roller of a magnitude of 90' corrected with the pitch angle of the worm.

For this purpose use can also be made of an embodiment in which the motor is arranged spring-loaded on the frame such that the worm is urged toward the drive roller.

in order to avoid second-order displacement effects and thus bring about the greatest possible displacement accuracy, use can be made of an embodiment in which the motor is pivotable on a pivot axis which is parallel to the axis of the drive roller and defines together with the effective point of contact between worm and drive roller a plane which is parallel to said plane (x, y) in which the carriage is movable.

In a particular embodiment the combination has the further characteristic that at least one of the two drive rollers is urged toward the carriage by spring load.

The invention will now be elucidated with reference to the annexed drawings. Herein:

Figure 1 shows an exploded view of a combination according to the invention embodied as microfiche projection apparatus;

Figure 2 shows a perspective view of the assembled combination according to figure 1; and

Figure 3 shows the microfiche according to figures 1 and 2 in perspective view and on enlarged scale.

Figure l shows a microfiche projection device 1 embodied as a combination of a drive device and a

carriage according to the invention.

A microfiche 2 is provided with a toothing along its entire standing peripheral edge 3. Figure 3 in particular shows this clearly. The edge parts 4 and 5 have a toothing in the same direction. The edge part 6 has a toothing in a different direction, while edge part 7 has a toothing which can be regarded as a

superimposition on the toothings of the edge parts 4, 5; 6.

Figure 1 shows why this configuration has been selected. A drive device comprises two drive rollers 12, 13 drivable by motors 8, 9 via respective worms 10, ii. Both rollers 12, 13 are provided with a helical toothing. Roller 12 haβ a toothing which extends over the entire length of the roller. This toothing can co-act with the edge parts 4 and 7. Roller 13 has a toothing which extends over roughly half the effective length of the roller. This roller co-acts only with edge part 7. This makes clear why edge part 7 is provided with a toothing which forms a superimposition on the two types of toothing. It must after all co-act with the toothing of both rollers 12, 13 which have opposing orientations but which are otherwise the same.

It will also be apparent herewith that by driving rollers 12, 13 in the same direction a movement of the microfiche in the y direction can occur, while through oppositely orientated driving of rollers 12, 13 a displacement of microfiche 2 in the x direction can occur. Rollers 12, 13 ar» supported by a frame 14. By means of a spring-loaded guide roller 15 which is

disposed rotatably relative to frame 14 by means of a bracket, the microfiche 2 is urged toward rollers 12, 13 by driving thereby.

The motors 8, 9 are also supported by the frame 14.

The worms 10 and 11 press with some force against rollers 12, 13 for driving thereof. Each worm is arranged such that it makes an angle with the axis of the associated drive roller 12, 13 of a magnitude of 90* minus the pitch angle of the worm 10, 11. A clearance- free and low friction driving contact between the worm 10, 11 and the associated roller 12, 13 is hereby

ensured.

The frame 14 further supports a lighting unit 17. This illuminates the microfiche 2, which is embodied as transparency information carrier or as carriage in which such an information carrier is accommodated. A lens system 18 placed on the other side acts optically to form an image of the relevant illuminated part of microfiche 2 for projection. For example via optional mirrors and a projection screen.

The motors 8, 9 can be controlled by means of known means which do not form part of the invention. Use can be made for this purpose of known digital control units. The motors can be stepping motors or be provided with other means with which the angular positions of worms 10, 11 can be determined. Alternatively, a

detection can also take place of a reference position pre-recorded on the microfiche. Whether this is necessary depends on the application. The described positioning means are superfluous for particular applications.

Aβ shown in figure 3, the microfiche 2 is embodied as a transparent plastic carriage which has an input opening 19 via which an information carrier can be inserted. Such a transparency information carrier may for instance carry map information.

Focussing of the lens system 18 can take place in the manner shown in figure 2 by means of an adjusting wheel 20 which via a shaft 21 drives a worm 22 which co-acts with a gear rim 23 which can set the lens system 18 into rotation and into corresponding axial movement via screw-threaded means.

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Claims

1. Combination of a carriage and a drive device for driving this carriage independently in two mutually perpendicular directions (x, y) in one plane, which device comprises:

a frame;

a carriage movable relative to this frame;

guide means for guiding the carriage independently in each of the two directions (x, y); and drive means for driving the carriage independently in each of the two directions (x, y),

characterized by

two elongate drive rollers which are mounted rotatably round their respective axes relative to the frame and drivable rotatably by respective motor drives and which are each provided with a helical toothing for driving co-action with corresponding gear racks arranged on the carriage;

which drive rollers are placed mutually

2. Combination as claimed in claim 1, wherein the one roller engages on two gear racks and the other roller engages on only one gear rack.

3. Combination as claimed in claim 1 , wherein the orientations of the helical toothings of the two respective rollers are opposed.

4. Combination as claimed in claim 1, characterized in that a drive roller is driven by the motor drive via a worm present on the shaft of the motor drive.

5, Combination as claimed in claim 4, character!.red ia that the shaft of the motor drive forms an angle with the helical toothing at the position of the point of contact between the worm and the drive roller of a magnitude of 90' corrected with the pitch angle of the worm.

6. Combination as claimed in claim 4, characterised in that the motor is arranged spring-loaded on the frame such that the worm is urged toward the drive roller.

7. Combination as claimed in claim 6, characterised in that the motor is pivotable on a pivot axis which is parallel to the axis of the drive roller and defines together with the effective point of contact between worm and drive roller a plane which is parallel to said plane (x, y) in which the carriage is movable.

8. Combination as claimed in claim 1, characterlied in that at least one of the two drive rollers is urged toward the carriage by spring load.

9. Drive device adapted and evidently intended for use as part of the combination as claimed in any of the claims 1-8.

10. Carriage adapted and evidently intended for use as part of the combination as claimed in any of the claims 1-8.

11. Carriage as claimed in claim 10, characterised by an information carrier present thereon.

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