Contour measuring probe for measuring aspects of objects

An exemplary contour measuring probe (10) includes a tip extension (16) and two driving members (13). The tip extension is configured for touching a surface of an object. The driving members are configured for driving the tip extension linearly moving along a first direction. The driving members are tapered and a diameter of each driving member increases along the first direction. The driving members are driven to move by gas pressure acting on an outer side surface thereof.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to nine co-pending U.S. patent applications, which are: application Ser. No. 11/611,724, filed on Dec. 15, 2006, and entitled “DISTANCE MEASURING PROBE WITH AIR DISCHARGE SYSTEM”, application Ser. No. 11/843,664, filed on Aug. 23, 2007, and entitled “CONTOUR MEASURING DEVICE WITH ERROR CORRECTING UNIT”, applications Ser. Nos. 11/966,951 and 11/966,952 and both entitled “CONTOUR MEASURING PROBE”, applications Ser. Nos. 11/966,957 and 11/966,956, and both entitled “CONTOUR MEASURING METHOD FOR MEASURING ASPECTS OF OBJECTS”, application Ser. No. 11/966,964, and entitled “MEASURING DEVICE FOR MEASURING ASPECTS OF OBJECTS”, application Ser. No. 11/966,961, and entitled “MEASURING DEVICE AND METHOD FOR USING THE SAME”, and application Ser. No. 11/966,959, and entitled “BASE AND CONTOUR MEASURING SYSTEM USING THE SAME”. In Ser. No. 11/611,724, Ser. Nos. 11/843,664 , 11/966,951 , 11/966,957, and 11/966,956, the inventors are Qing Liu, Jun-Qi Li, and Takeo Nakagawa. In Ser. Nos. 11/966,961, 11/966,964, 11/966,959, and 11/966,952, the inventors are Qing Liu and Jun-Qi Li. In Ser. No. 11/611,724 and Ser. No. 11/843,664, the assignee is Hon HAI PRECISION INDUSTRY CO. LTD and FINE TECH Corporation, and the assignee of other applications is HONG FU JIN PRECISION INDUSTRY (ShenZhen) CO., LTD and Hon HAI PRECISION INDUSTRY CO. LTD. The disclosures of the above identified applications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to contour measuring probes for coordinate measuring machines (CMMs); and more particularly to a contour measuring probe using a relatively small, steady measuring force for contact-type contour measuring devices.

2. Discussion of the Related Art

Manufactured precision objects such as optical components (for example, aspherical lenses) and various industrial components need to be measured to determine whether manufacturing errors of the objects are within acceptable tolerance. Manufacturing errors are the differences between design dimensions of the object and actual dimensions of the manufactured object. Measured dimensions of the manufactured object are usually regarded as the actual dimensions. Precision measuring devices are used to measure the objects; and the more precise the measuring device, the better. Generally, the precision objects are measured with a CMM, which has a touch trigger probe that contacts the objects. A measuring force applied to the touch trigger probe of the coordinate measuring machine should be small and steady. If the measuring force is too great, a measuring contact tip of the touch trigger probe may easily be damaged resulting in measuring errors. If the measuring force is not steady, a relatively large measuring error may occur.

As indicated above, a contact-type coordinate measuring device is commonly used to measure dimensions of precision objects such as optical components and certain industrial components. A measuring force is applied to the touch trigger probe by the coordinate measuring device. However, if the object has a slanted surface, the contact tip of the touch trigger probe may bend or deform by a counterforce acting on the touch trigger probe, thereby causing a measuring error. Therefore, the touch trigger probe is not ideal for measuring precision lenses having slanted surfaces.

Nowadays, two methods are generally used to reduce a measuring force on the touch trigger probe. In a first method, the contact tip is obliquely arranged so that a component force of gravity acting on the measuring contact tip is regarded as a measuring force. The contact tip is very light, so the measuring force is very small accordingly. However, if an oblique angle of the contact tip changes during measuring, the measuring force will also change, which makes the measuring force difficult to control. In a second method, the touch trigger probe is configured with a spring. An elastic force of the spring is regarded as a measuring force. However, when the contact tip moves upward and downward along the surface of the object being measured, a vibration of the upward and downward movement may cause the spring to resonate and deform. Therefore, the measuring force varies with the deformation of the spring. Thus both methods are subjected to errors in the measurement results.

In another kind of probe, a measuring force is provided by an air pump. However, the air pump provides pulsed pressure. Therefore, the air pump cannot provide a small, steady measuring force.

Therefore, a contour measuring probe employing a relatively small, steady measuring force is desired.

SUMMARY

An exemplary contour measuring probe includes a tip extension and two driving members. The tip extension is configured for touching a surface of an object. The driving members are configured for driving the tip extension linearly moving along a first direction. The driving members are tapered and a diameter of each driving member increases along the first direction. The driving members are driven to move by gas pressure acting on an outer side surface thereof.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1andFIG. 2shows a contour measuring probe10of a first embodiment of the present invention. The contour measuring probe10includes a base11, a tube guide12, two hollow tubes13, a first fixing member14, a second fixing member15, a tip extension16, a linear measuring scale17, a displacement sensor18, and a plurality of pipes19.

The base11is substantially a flat rectangular sheet. It should be understood that the base11may alternatively be any other shapes. The tube guide12is securely mounted onto the base11. The tube guide12includes a front end and a rear end. The tube guide12defines two tube chutes121extending from the front end to the rear end correspondingly. The tube chutes121are spaced apart from, and aligned parallel to, each other. A sidewall for defining each tube chute121defines a ring-shaped slot122communicating with the tube chutes121. A porous film123is disposed inside each tube chute121of the tube guide12and between the slot122and the corresponding tube chute121. The films123are generally made of carbon having a plurality of micro holes allowing gas to spread therethrough. The hollow tubes13are hollow frustums of a cone. Each hollow tube13is received through a corresponding tube chute121of the tube guide12, and a diameter of the hollow tubes13increases from the front end to the rear end of the tube guide12. A gap (not labeled) is defined between each film123and the tube guide12, such that a gas bearing can be formed when gas is injected into the tube chutes121. The pipes19are inserted into the tube guide12and are spaced from each other. The pipes19are communicated with the slots122so as to inject gas into the slots122.

The first fixing member14and the second fixing member15are correspondingly fixed to two opposite ends of the hollow tubes13. The hollow tubes13are slidable in the tube guide12in a direction parallel to a direction defined by a line joining the front end to the rear end of the tube guide12. The hollow tubes13are non-rotatable relative to the tube guide12. The tip extension16is needle-shaped, and has a contact tip (not labeled) that touches a surface of an object when the contour measuring probe10is used for measuring the object. The tip extension16is fixed on the first fixing member14so that the tip extension16is linearly movable together with the first fixing member14and the hollow tubes13. The linear measuring scale17is fixed on the second fixing member15such that it moves (displaces) linearly when the tip extension16moves. The displacement sensor18is mounted on the base11corresponding to the linear measuring scale17. The displacement sensor18is used for reading displacement values of the linear measuring scale17. Alternatively, the positions of the linear measuring scale17and the displacement sensor18may be exchanged.

The contour measuring probe10further includes a cover102that engages with the base11and completely seals other various components of the contour measuring probe10except the base11and a part of the tip extension16. The cover102defines a through hole (not labeled) for allowing an end portion including the contact tip of the tip extension16to extend out from the through hole. The gas is injected into the slots122to form the gas bearing via the pipes19mounted to the cover102.

When gas is injected into the pipes19, gas fills in the slots122of the tube guide12. With gas continually injected into the slots122, a pressure in the slots122increases. Meanwhile, gas spreads into and fills the gaps between the hollow tubes13and the films123of the tube guide12, thereby forming a gas bearing. Also referring toFIG. 3, a plurality of pressure forces Fn acts on an outer side surface of each hollow tube13, because gas enters the gap between the hollow tube13and the films123and the hollow tubes13are taper-shaped. The forces Fn have a direction perpendicular to the outer side surface of each hollow tube13. Each force Fn can be divided into a force Fn1having a direction parallel to an axis of each hollow tube13and a force Fn2having a direction perpendicular to the axis. A plurality of forces Fn2are such that a force, in a direction perpendicular to the axis of each hollow tube13, acting on each hollow tube13is 0. A composition of forces caused by the forces Fn1pushes the hollow tube13to move in the direction from the rear end to the front end of the tube guide12. In addition, gas is continually injected out from the gaps between the hollow tubes13and the film123of the tube guide12. Therefore, a gas pressure of gas in the gap remains relatively small. Thus, the composition of forces pushing the hollow tubes13is relatively small. Accordingly, a measuring force acting on the tip extension16is relatively small. It can be understood that, the measuring force can be changed by changing a tapered angle of the hollow tubes13.

Alternative embodiment, the contour measuring probe10includes only one hollow tube13or more than two hollow tubes13. In such embodiments, the tube guide12defines only one tube chute121or more than two tube chutes121corresponding to the number of the hollow tubes13. The hollow tubes13may be other shaped driving member such as a solid cylinder or have other shapes, such as a cuboid.

When manufacturing precision components such as optical lenses, the optical lenses generally need to be re-machined if they do not have required shape and size. Referring toFIG. 4, the contour measuring probe10is applied in an ultraprecise equipment100for manufacturing optical lenses. The optical lenses are measured on the ultraprecise equipment100immediately after being machined. Therefore, error caused by releasing the optical lenses from a machining equipment and reclamping the optical lenses on a measuring machine is eliminated. In addition, much time can be saved. The contour measuring probe10is mounted on a slidable platform of the ultraprecise equipment100.

In use, the contour measuring probe10is placed near the object. The pipes19communicate with a gas chamber (not shown), and gas is injected into the slots122of the tube guide12. Then the gas spreads through the films123and enters the tube chutes121. Gas pressure acts on the hollow tubes13and pushes the hollow tubes13to move towards the object, thereby pushing the tip extension16to move towards the object. When the contact tip of the tip extension16touches the object, the hollow tubes13together with the tip extension16stops moving, and the tip extension16always gently touches the surface of the object. When the tip extension16carries the linear measuring scale17to move from one position to another position, the displacement sensor18detects and reads a displacement of the linear measuring scale17. That is, a displacement value of the tip extension16is measured. The displacement sensor18connected to a processor (not shown) sends the displacement value of the tip extension16to the processor.

Referring toFIG. 5, a contour measuring probe30according to a second embodiment alternative to the first embodiment of the present invention is shown. The contour measuring probe30is similar in principle to the contour measuring probe10except that tube guides32A,32B for holding hollow tubes33A,33B are offset from each other in the contour measuring probe30. That is, the tube guide32A is set at a front portion of the base31, and the tube guide33B is set at a back portion of the base31. Because the tube guides32A,32B are offset from each other, the tube guides32A,32B collectively hold the hollow tubes33A,33B along a longer length in a direction coinciding with an axis of movement of the tip extension (not labeled), compared with a corresponding length along which the tube guide12holds the tip extension16in the contour measuring probe10. Thereby, the tip extension of the contour measuring probe30moves very steadily forward and backward with little or no lateral displacement. Alternatively, only one of the hollow tubes33A,33B is tapered and gas is injected into one of the hollow tubes33A,33B. Thereby, the contour measuring probe30is further simplified.