WO1993003323A1

WO1993003323A1 - Micrometer

Info

Publication number: WO1993003323A1
Application number: PCT/CH1992/000161
Authority: WO
Inventors: Jacques Thouanel; Raymond Girardier; Nicolas John Michael Watson
Original assignee: Airgiss S.A.
Priority date: 1991-08-05
Filing date: 1992-08-05
Publication date: 1993-02-18
Also published as: JPH06507719A; FR2680238A1; EP0551472A1

Abstract

A micrometer comprising a pistol-shaped body (10) contains an electric motor (15) connected to a coder (21) driving an endless screw (19), coupled to a measuring pin (26) rigidly fixed to a spring (27), by means of an endless screw (107), a shaft (108) and a helical screw (109). Said spring (27) stores mechanical energy and restores it as a bearing force exerted by sensors (28) via a cone (30) on the surface of the part to be measured. A coder (33) outputs a pulse for each micron of measuring pin movement, which moves the cone (30) and spaces the sensors (28) apart.

Description

MICROMETER

The present invention relates to a display micrometer comprising a body containing measuring members and carrying means for displaying the results of these measurements, this body being equipped with a head arranged to receive a measuring piece suitable for measuring either external dimensions. of a surface, either of the internal dimensions of a cavity or of a bore, or of the depths, said measurement piece being removable and interchangeable and comprising a bearing surface, and said means for performing the measurements comprising an axis of axially movable measurement powered by an electric motor.

We already know the micrometer that was the subject of the European patent

N ² 0 236 371 by the same holder. This micrometer has many advantages over the prior art. However, if we want to be able to guarantee a high accuracy of the measurement, that is to say the reproducibility of this measurement with very high accuracy, it is necessary to provide means for applying a predetermined permanent pressure on the probes , even when these have come to a stop and the drive motor has stopped. Indeed, it may happen that during a measurement the measurement part is not arranged exactly in the axis of the part to be measured, so that the support of the probes is not uniform. In this case, the indication displayed is incorrect even though the motor has brought the probes to a stop. To overcome this drawback, it would be conceivable to provide a friction member which makes it possible to absorb the motor torque while applying to the feelers a given force sufficient to ensure precise positioning of the measurement piece, if it is moved slightly in different directions transverse to its axis.

However, this solution consumes energy and is only hardly compatible with a supply by electric batteries or rechargeable batteries. The same would be true if the friction member were replaced by any torque limiter or the like.

Other measuring devices are, for example, known from the Japanese publication JP-A-57 128 808 which describes a digital micrometer in which the measurement is triggered by a pressure detector constituted by a conductive rubber, the Japanese publication JP- A-58-.41301 which describes a measuring device applying a controlled pressure on glass parts, the Japanese publication JP-A-61 026 802 which describes a "clutch mechanism adaptable to a measuring instrument, in which the measurements are carried out under constant pressure, the Japanese publication JP-A-61 219 819 which describes a digital caliper in which the measurement is triggered by a pressure detector, and the European publication EP-A-287 506 which describes a foot traditional slide valve fitted with a compression spring to apply constant pressure to the workpiece.

None of the devices described uses the principle of energy accumulation which allows very high measurement accuracy

The present invention therefore proposes to overcome the drawbacks of the prior art by making a micrometer in which a permanent pressure is applied to the probes - to guarantee their uniform support on the surface of a part to be measured and thereby obtain a high accuracy of the measurements made.

For this purpose, the micrometer according to the invention is characterized in that said means for carrying out the measurements further comprises a member arranged to accumulate mechanical energy and to release this energy, by applying a predetermined force to said measuring piece .

According to a preferred embodiment, said member arranged to accumulate mechanical energy comprises at least one spring. According to a first embodiment, said spring is a compression spring.

According to other embodiments, said spring can be of the barrel type, or constituted by a stack of Belleville washers or by a block having elastomeric properties.

Advantageously, said spring is mounted between a measurement axis with axial displacement coupled to said measurement piece and a member arranged to cause the displacement of this axis;

Preferably, the member for moving the measuring axis comprises an endless screw driven in rotation by an electric motor and said spring is coupled to said endless screw to generate a predetermined torque tending to advance said measuring axis. .

In the preferred embodiment of the invention, the micrometer comprises a microprocessor, this microprocessor being arranged to, on the one hand control the motor and cause the displacement of the measurement axis until the probe reaches the stop mobile forming part of the measurement piece and for, on the other hand controlling this motor after said arrival in abutment, so as to arm said member arranged to accumulate mechanical energy.

Advantageously, the micrometer may include a console arranged to ensure the recharging of electrical supply batteries contained in the body of the device.

This console can be equipped with a transceiver arranged to ensure the wireless transfer of measurement data to similar consoles or peripheral equipment.

To ensure the transfer of measurement data to peripheral equipment, the micrometer may include a transceiver, this transceiver being of the infrared type. In another embodiment, the means for carrying out the measurement comprise a movable measurement axis carried by two bearings, a sliding carriage traversed by this measurement axis, an electric motor arranged to move said carriage, and a first coaxial compression spring to the measurement axis and arranged to couple this carriage to this axis and to accumulate energy when the measurement axis is in abutment.

Advantageously, to accumulate energy when the measurement axis is in abutment, the spring is designed to bear on the one hand against the carriage and on the other hand against a first fixed fixed stop ring of the measurement axis.

Preferably, the carriage carries a first microswitch and the measurement axis carries a screw serving as a stop, these two elements being arranged to cooperate and provide an engine stop signal when the carriage is driven forward while the measurement axis is stopped.

The carriage can also carry a second microswitch arranged to cooperate with the screw and stop the motor when the carriage is driven backwards and the measurement axis is stopped.

In this embodiment, the measurement axis carries a second compression spring arranged to cooperate with a second fixed stop ring and allow limited relative movement of the carriage towards the rear relative to the measurement axis.

The present invention will be better understood with reference to the description of an embodiment and the appended drawing in which:

FIG. 1 represents a schematic view of the digital micrometer according to the invention,

FIG. 2 represents a view in axial section of this micrometer, ^• Figure 3 shows schematically the transfer of data from a part to be measured to a printer,

FIG. 4 * schematically illustrates the transfer of data in a control installation comprising several micrometers placed on a console, and

Figures 5 and 6 show schematic views partially in section illustrating another embodiment of the micrometer according to the invention. .

With reference to FIG. 1, the micrometer shown comprises a body 10 in the form of a pistol equipped with a control trigger 11 which the operator actuates at the time of the measurement. On one side of this micrometer appears a keyboard 12 provided with a number of function keys 13, and a screen 14 on which the results of the measurements are displayed. Inside the body are mounted the mechanical and electrical equipment necessary for the measurements. An electric motor 15, powered by a battery (not shown) and controlled by a microprocessor 16 coupled to a random access memory 17 and to a read-only memory 18, drives a worm 19. On the axis 20 of this worm is mounted an encoder 21 which comprises a cylindrical drum 22 carrying a predetermined number of marks 23, and an optical transceiver 24. connected to the microprocessor 16. The screw 19 meshes a nut 25 which advances or moves back in the direction of the double arrow A depending on the direction of rotation of the motor 15. The nut 25 is mechanically coupled to a measuring axis 26, by means of a spring 27. This spring 27 constitutes said member arranged to accumulate mechanical energy and for restore this energy in the form of a pressing force exerted by the feelers 28 on the surface of the part to be measured, by means of a rod 29 and a cone 30. The measurement axis 26 cooperates with a reference stop 31 and por te a set of pins 32 arranged to cooperate with an axial position encoder 33 which is also coupled to the microprocessor 16. The measurement axis 26, the rod 29, the cone 30 and the feelers 28 are identical or equivalent, functionally, to the corresponding elements illustrated by the figures of the European patent cited in the preamble.

From the point of view of operation, the initial position is defined by the reference stop 31 which corresponds to the zero point of the measurement axis 26. This measurement measurement axis is advanced by the screw 19 driven by the motor 15 and l position encoder 33 provides a pulse for each micron of movement of the measurement axis. The axial displacement of the measuring axis has the effect of displacing the cone 30 and spreading the feelers 28. When these feelers come into contact with the surface of the part to be measured, the advance of the measuring axis measure 26 stops. This stop is detected by the microprocessor 16 by the absence of pulses from the position encoder 33. However, this microprocessor gives the motor 15 the order to continue to run by performing a predetermined number of revolutions. This number of revolutions is detected by the encoder 21 of the motor. The desired result is the arming of the spring 27 which generates a thrust on the measurement tax corresponding to a constant measurement force.

If, following improper centering of the probes 28 inside the part to be measured, the force accumulated by the spring 27 causes a slight displacement of the measurement axis 26, detected by the encoder 21, the motor 15 is reactivated to ensure adequate resetting of the spring 27 so that the measurement pressure is kept constant until the end of the measurement. In other words, if the measurement axis moves axially by a given length, detected by the position encoder 33 of the measurement axis, under the effect of the spring, the motor 15 resets the spring 27 in such a way that its state is identical to that in which it was before the aforementioned movement of the measuring axis 26. In this way the measuring pressure of the probes is constant and the spring 27 has stored sufficient force for the probes 28 can still move under the pressure of this spring in the event that improper centering would have resulted in a blockage premature said probes in a position where they would not exert a uniform and identical thrust at the support points of these probes. It will be noted that the measurement pressure exerted by the probes at the various support points is defined by the number of pulses that the microprocessor 16 receives from the transmitter 24 after a first stop of the measurement axis 26. Each number of pulses correspond to a particular arming of the spring 27 which ultimately defines a pressing force of the feelers 28.

FIG. 2 illustrates a sectional view of the actual construction of the micrometer shown diagrammatically in FIG. 1. In this construction we find the body 10 in the form of a gun, the electric motor 15, the worm 19 coupled to the axis of measure 26, the cone 30 which ensures the displacement of the feelers 28, and the member 27 arranged to accumulate mechanical energy and to release this energy by applying a predetermined force on the measurement piece. In the diagrammatic view of FIG. 1, this member was represented in the form of a helical spring mounted between the endless screw 19 and the measurement axis 26. In the construction represented by FIG. 2 this member is constituted by a barrel spring which is directly mounted on the endless screw 19, or more exactly on an axial extension of this screw. Since this worm is directly coupled to the measuring axis, a torque applied to this screw automatically generates an axial force on the measuring axis.

The other components of the micrometer shown are for the most part identical to those which appear in FIGS. 7, 8 and 9 of the European patent mentioned above. These are in particular the endless screw 107 mounted on the drive shaft 108 of the motor 15, the helical wheel 109 which engages the endless screw 107, and the head 105 intended to receive a measuring piece 106 The drive shaft 108 carrying the endless screw 107 is extended by a rod 200 which carries the encoder 21 of the motor. The encoder 33 of the measurement axis 26 is mounted on the body 10 of the housing. The coupling between the measurement axis and the cone 30 takes place by means of a rigid coupling segment 201, arranged axially, around which a spring is coaxially mounted. recall 202 whose function is to ensure the recall of the probes after use.

It is understood that this construction is not rigid but can possibly be modified, certain components being able to be replaced by others having equivalent functions. Among these components is in particular the member capable of accumulating mechanical energy which can be in the form of a helical spring, a barrel spring or which could also be replaced by an elastomer block or by a stacking of washers of the Belleville washer type or by any other mechanism capable of accumulating and restoring mechanical energy.

FIG. 3 illustrates another interesting characteristic of the micrometer described above and which includes means for transferring, without the aid of cables, the data which it has stored to peripheral units. This micrometer 300 is equipped with a measuring head 301 making it possible to measure the external dimensions of a ball or of an axis 302, coupled by means of an infrared beam 303 to one. peripheral member 304 which, in the example illustrated, is a printer. It is obvious that this peripheral member 304 could also be a computer or any other device equipped with a receiver capable of converting the data transmitted by a transmitter and contained in the micrometer, and of using them.

Figure 4 illustrates another characteristic of the micrometer described above. In the use shown, there are four micrometers 300 equipped with various measuring heads, each of these micrometers being placed on a console 310 to which it is connected by a flexible connection 311. The different consoles are connected together by beams data transmission which are for example infrared beams transmitted and received by a transceiver housed in their base. These beams are cascaded so that the first micrometer transmits its data via its console to the console of the second micrometer, the second micrometer transmits via its console both the data of the first micrometer and its own data to the console of the third micrometer which transmits to the console of the fourth micrometer the data coming from the first and second micrometer as well as its own data. The console of the fourth micrometer is then connected to a peripheral member such as for example a computer 320. Each console is further designed to ensure rapid charging of the accumulators contained in the micrometer.

With reference to FIGS. 5 and 6, the micrometer shown comprises, as before, a body 10 in the form of a gun, the handle of which

40 is provided with two switches 41 and 42 whose role will be defined below. This handle contains a drive motor 43 and one or more rechargeable batteries or batteries 44 to power this motor, the output axis of which carries a pinion 45. The latter is engaged with a rack 46 secured to a movable carriage 47 This carriage is provided with two lateral guides 48, 49 which guide the carriage in its movements along the double arrow 50. It is crossed by a longitudinal rod 51 called the measurement axis, which is carried by two fixed bearings 52 and 53 This measurement axis carries a screw 54 which passes through an oblong opening 55 formed in the upper wall of the carriage 47. On either side of this screw are positioned two microswitches 56 and 57 which are carried by the carriage. A first compression spring 58 is placed on the front part of the measurement axis 51 which carries a fixed stop ring 59. A second compression spring 60 is placed on the rear part of the measurement axis which also carries a fixed stop ring 61.

The measured values are read on a commercial comparator 62 which may be of the mechanical, electronic, digital or analog type adapted to the rear of the device. At the front of this device is mounted a measuring head 63 of the type described above. This measuring head comprises a rod 64 for actuating the probes 65. This rod bears against the measurement axis 51 and moves axially at the same time as it. To use this micrometer, for example, as before, the measuring head is introduced into an appropriate bore (provided of course that the measuring head used is suitable for this type of measurement) and the motor 43 is started by means of the switch 41. The motor drives the pinion 45 and moves the carriage 47 forwards (on the left in FIG. 6) by acting on the rack 46. In the absence of resistance at the feelers, the carriage drives the measuring axis 51 to which it is coupled via spring 58. As soon as the probes meet resistance, the measuring axis is stopped, but the motor continues to run and continues to move the carriage forwards, this which results in arming the compression spring 58. This phenomenon continues until the microswitch 57 abuts against the screw 54 secured to the measurement axis. When the contact is made, this microswitch stops the rotation of the motor 43. If the probes are repositioned and allow the advance of the measurement axis, the contact in abutment of the microswitch 57 against the screw 54 is interrupted, which has the effect restart the motor 43 and the cycle advances the carriage, advances the measuring axis, etc. , can resume.

The measurement consists in determining the deviations from a reference measurement carried out with the same device on a standard ring or any other element considered as reference. These differences are indicated by the comparator, for example in the form of the display of a numerical value.

After this measurement, the operator presses the switch 42 to reverse the direction of the motor 43. As before, the carriage driven by the pinion 45 acting on the rack 46 drives the measurement axis 51 until that the fixed stop ring 61 encounters resistance. The carriage continues to move back towards the rear of the device, which has the effect of compressing the spring 60 until the microswitch 56 abuts against the screw 54. The power supply to the motor 43 is then interrupted and the carriage remains stopped in this position. The device is ready for a new measurement. The present invention is not limited to the embodiments described but can undergo different modifications and come in various variants obvious to those skilled in the art.

Claims

1. Display micrometer comprising a body containing measuring members and carrying means for displaying the results of these measurements, this body being equipped with a head arranged to receive a measuring piece suitable for measuring either the external dimensions of a surface, either of the internal dimensions of a cavity or of a bore, or of the depths, said measurement part being removable and interchangeable and comprising a bearing surface, and said means for performing the measurements comprising an axially movable measurement axis actuated by an electric motor, characterized in that said means for carrying out the measurements further comprises a member arranged to accumulate mechanical energy and to release this energy, by applying a predetermined force to said measuring piece.

2. Micrometer according to claim 1, characterized in that said member arranged to accumulate mechanical energy comprises at least one spring (27).

3. Micrometer according to claim 2, characterized in that said spring (27) is a compression spring.

4. Micrometer according to claim 2, characterized in that said spring (27) is of the barrel type.

5- Micrometer according to claim 2, characterized in that said spring (27) consists of a stack of Belleville washers.

6. Micrometer according to claim 2, characterized in that said spring (27) consists of a block having elastomeric properties.

7. Micrometer according to claim 2, characterized in that said spring (27) is mounted between a displacement axis (26) axial coupled to said measurement piece and a member arranged to generate this displacement of this axis.

8. Micrometer according to claim 7, characterized in that the member for moving the measurement axis comprises an endless screw (19) driven in rotation by an electric motor (15).

9. Micrometer according to claim 8, characterized in that said spring (27) is coupled to said worm (19) to generate a predetermined torque tending to advance said measurement axis (26).

10. Micrometer according to claim 1, characterized in that it comprises a microprocessor (16), this microprocessor being arranged to, on the one hand control the motor (15) to generate the displacement of the measurement axis up to the arrival at stop of movable feelers (28) forming part of the measurement piece and for, on the other hand, controlling this motor after said arrival at stop, so as to arm said member arranged to accumulate mechanical energy.

11. Micrometer according to claim 1, characterized in that it comprises a console (310) arranged to ensure the recharging of electrical supply batteries contained in the body of the device.

12. Micrometer according to claim 11, characterized in that the console (310) is equipped with a transceiver arranged to ensure the wireless transfer of measurement data to similar consoles or peripheral equipment (320).

13. Micrometer according to claim 1, characterized in that it comprises a transceiver for ensuring the transfer of the measurement data to peripheral equipment (304).

14. Micrometer according to claims 12 and 13, characterized in that the transceiver is of the infrared type.

15. Micrometer according to claim 1, characterized in that the means for carrying out the measurement include a movable measurement axis (51) carried by two bearings (52, 53), a sliding carriage (47) crossed by this measurement axis, an electric motor (43) arranged to move said carriage, and a first compression spring (58) coaxial with the measurement axis (51) arranged to couple this carriage to this axis, this spring and to accumulate energy when the measuring axis is in abutment.

16. Micrometer according to claim 15, characterized in that, to accumulate energy when the measurement axis is in abutment, the spring is arranged to bear on the one hand against the carriage (47) and on the other part against a first fixed stop ring (59) integral with the measurement axis.

17. Micrometer according to claim 15, characterized in that the carriage carries a first microswitch (57) and in that the measuring axis carries a screw (54) serving as a stop, these two elements being 'arranged to cooperate and give an engine stop signal (43) when the carriage is driven forward while the measuring axis is stopped.

18. Micrometer according to claim 17, characterized in that the carriage carries a second microswitch (56) arranged to cooperate with the screw (54) and stop the motor (43) when the carriage is driven backwards while the measurement axis is stopped.

19. Micrometer according to claim 18, characterized in that the measuring axis carries a second compression spring (60) arranged to cooperate with a second fixed stop ring (61) and allow limited relative movement of the carriage towards the rear with respect to the measurement axis.