Measuring head

Abstract

There is provided a measuring head comprising a supported frame, an arm extending along a trajectory between at least a first end and a second end and comprising at least one probe arranged at the first end and adapted to be in contact with an external object, and a restraint device configured to loosely couple the frame with the arm, the arm is movable relative to the frame such that the arm is rotatable relative to the frame about a rotation axis transverse to the trajectory, the rotation being proportional to a displacement defined by the interaction of the probe and the object; the measuring head includes a differential capacitive sensor including a transmitter integrally formed with the frame and disposed near the second end, a receiver integrally formed with the second end, and a computer operably connected to the receiver, the computer is configured to determine a position parameter of the receiver relative to the transmitter from a predetermined reference position value, thereby determining a displacement of the probe.

Description

Technical Field

[0001] The invention relates to a measuring head.

[0002] In particular, the invention relates to a measurement head configured to determine the relative displacement between a probe (eg a probe moved by interaction with an object) and a fixed support frame. Background Art

[0003] As we all know, a measuring head is an instrument for measuring roughness and imbalance. In more common terms, a measuring head is an instrument that uses a moving probe in contact with an object to measure the displacement of an object.

[0004] The touch probe is usually attached to a swing arm relative to a fixed frame. Thus, the displacement of the touch probe relative to the object interference can be determined by the sensor.

[0005] The sensor medium commonly used is basically an inductive displacement sensor, also known as a LVDT.

[0006] These sensors essentially consist of a tube consisting of three windings with parallel axes, surrounding a ferromagnetic cylindrical core that moves parallel to the axes. Furthermore, the cylindrical core is usually characterized by a high magnetic permeability.

[0007] Specifically, the central winding is called the primary winding and is connected to an AC voltage generator, while the other two windings are called secondary windings, allowing the output voltage to be measured at the ends of the secondary windings to obtain a variable related to the core displacement.

[0008] The electrical signal is therefore substantially proportional to the linear displacement of the core, and thus the information can be transmitted to an external processor which converts the proportional signal back into the found displacement value.

[0009] The described prior art suffers from some major disadvantages.

[0010] In particular, LVDT sensors are expensive and therefore economically disadvantageous.

[0011] Furthermore, no matter how sensitive an LVDT sensor is, it typically has its own range and contains mechanical obstructions that substantially limit the available travel. Summary of the invention

[0012] In this context, the technical task of the present invention is to design a measuring head capable of substantially eliminating at least some of the above-mentioned disadvantages.

[0013] Within this technical task, an important aim of the invention is to obtain a measuring head which is simple and inexpensive to manufacture.

[0014] Another important object of the invention is to achieve a measuring head that is not affected by mechanical limitations or obstacles and that allows longer travels, ie enables longer estimates of displacements.

[0015] Furthermore, a further object of the invention is to provide a measuring head having reduced mechanical dimensions having the above-mentioned advantages.

[0016] Finally, another object of the invention is to realize a measuring head allowing a linearization of the measurements.

[0017] The technical task and the specific aims are achieved by a measuring head as described in the present application.

[0018] Preferred technical solutions are emphasized in this application. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The features and advantages of the present invention will be explained below through a detailed description of preferred embodiments of the present invention with reference to the accompanying drawings, in which:

[0020] Figure 1 shows a schematic side view of a measuring head according to the invention, wherein a cursor is located at a predetermined reference position value of a composite signal returning to zero;

[0021] Figure 2 A rear cross-sectional view showing a differential capacitance sensor of a measuring head according to the present invention;

[0022] Figure 3 is a schematic side view of a measuring head according to the invention, wherein the cursor is located at a minimum position value, wherein the cursor is located only in the second emission zone and defines a composite signal with a maximum amplitude and a determined phase; and

[0023] Figure 4 A schematic side view of a measuring head according to the invention is shown, wherein the cursor is at a minimum position value, wherein the cursor is only located in the first emission zone and defines a composite signal with a maximum amplitude, which is the same as the composite signal formed by Figure 3 The measuring head defines the signal inversion. DETAILED DESCRIPTION

[0024] In this document, when associated with terms such as "approximately" or other similar terms such as "almost" or "substantially", measurements, values, geometric shapes and references (such as perpendicularity and parallelism) should be understood to exclude measurement errors or inaccuracies due to production and / or manufacturing errors and, most importantly, exclude slight deviations from the associated values, measurements, shapes or geometric references. For example, when associated with a value, these terms preferably mean a deviation of no more than 10% of the stated value.

[0025] Furthermore, terms such as "first," "second," "upper," "lower," "primary," and "secondary" when used do not necessarily denote an order, relationship priority, or relative position, but may simply be used to more clearly distinguish different components from one another.

[0026] Unless otherwise indicated in the following discussion, terms such as "process," "compute," "determine," "calculate," and the like are deemed to refer to the action and / or process of a computer or similar electronic computing device that manipulates and / or transforms data represented as physical quantities, such as electronic quantities in a computer system's registers and / or memories, and similarly other data represented as physical quantities in a computer system, registers, or other information storage, transmission, or display device.

[0027] Unless otherwise stated, the measurements and data reported in this paper should be deemed to have been made in the ICAO International Standard Atmosphere (ISO 2533:1975).

[0028] With reference to the accompanying drawings, a measuring head according to the invention is indicated generally by numeral 1 .

[0029] The measuring head 1 is an instrument primarily suitable for detecting and quantifying displacements experienced by a component, for example displacements associated with surface features or movements of the object 10 .

[0030] The object 10 may be a fixed object, a flat object or a squat object or an object of any other shape. Alternatively, the object 10 may be a rotating body, such as a cylinder, having its own roughness and possibly being in an unbalanced state.

[0031] Overall, the measuring head 1 therefore comprises at least one frame 2 .

[0032] The frame 2 is essentially a supporting frame. Therefore, the frame 2 is configured to support the overall structure of the frame of the measuring head 1.

[0033] For example, the frame 2 can be a structure fixed to the ground or a plane or other supporting elements. Therefore, the frame 2 can be supported by the ground or a plane or a wall, or attached to the ground or a plane or a wall.

[0034] Furthermore, the measuring head 1 comprises at least one arm 3 .

[0035] The arm 3 is essentially a movable part of the measuring head 1. In particular, preferably and as explained more fully below, the arm 3 is a part of the measuring head 1 which oscillates or swings relative to the interference of the measuring head 1 with the object 10.

[0036] Furthermore, preferably, the arm 3 is substantially an elongated element, such as a rod or a bar or the like. In fact, the arm 3 preferably extends along a track 3a.

[0037] The track 3a can be a straight track or a curved track. Alternatively, the track 3a can also be more tortuous, possibly segmented into linear parts. In this case, the arm 3 can be defined as an L-shape or a U-shape in whole or in part.

[0038] In any case, preferably, the arm 3 extends along a trajectory 3 a at least between a first end 30 and a second end 31 .

[0039] Ends 30, 31 are understood to be substantially opposite portions of the arm 3. The ends may coincide exactly with the opposite free ends of the arm 3, or the ends may be opposite but intermediate portions, ie not coinciding exactly with the free ends.

[0040] The arm 3 thus comprises a probe 32. The contact probe 32 is a part of the arm 3, and thus of the measuring head 1, adapted to come into contact with an external object 10. The probe 32 is thus preferably arranged at one of the ends 30, 31, for example in particular at the first end 30.

[0041] Specifically, the contact probe 32 may be integrated into the first end portion 30, or the probe 32 may be restrained at the first end portion 30. Preferably, the contact probe 32 may be removably restrained at the first end portion 30.

[0042] Furthermore, the probe 32 is configured to move laterally relative to the first end 30 along a positioning axis 32a in a controlled manner.

[0043] The positioning axis 32a is substantially transverse to the track 3a. Therefore, the contact probe 32 can be constrained so that the probe 32 can move relative to the arm 3. For example, the arm 3 can include a threaded groove and the contact probe 32 can include a screw that translates along the positioning axis 32a by rotation.

[0044] Alternatively, other configurations known in the art may be employed.

[0045] Generally, and preferably, the contact probe 32 has a blunt tip suitable for interacting with the object 10. Furthermore, the probe 32 defines, together with the arm 3, a kind of hammer.

[0046] As mentioned above, the arm 3 is the oscillating part of the measuring head 1 .

[0047] Preferably, in order to achieve this, the measuring head 1 comprises a constraining device 4. The constraining device 4 is basically configured to loosely constrain the frame 2 and the arm 3 so that the arm 3 can rotate relative to the frame 2.

[0048] Specifically, the arm 3 is preferably rotatable relative to the frame 2 about the rotation axis 4 a.

[0049] The rotation axis 4a is preferably transverse to the trajectory 3a. Furthermore, the rotation axis 4a is preferably located between the ends 30, 31. In particular, the rotation axis 4a can be located exactly at a point equidistant from the ends 30, 31. Alternatively, preferably, the distance between the second end 31 and the rotation axis 4a and the distance between the first end 30 and the rotation axis 4a define a ratio, respectively, which is between 0.76 and 0.86. More advantageously, the ratio can be 0.81.

[0050] Therefore, the restraining device 4 may include a mechanical hinge defining the rotation axis 4a, or may include a deformable element capable of allowing the arm 3 to rotate by elastic deformation, or may include a plurality of elastic elements, such as springs, connected between the frame 2 and the arm 3 at multiple points, which are separated in such a way as to still allow the arm 3 to rotate relative to the frame 2 at least around the rotation axis 4a.

[0051] Alternatively an elastomeric element may be provided.

[0052] In any case, generally, the arm 3 rotates relative to the frame 2 about the axis of rotation 4 a , said rotation being proportional to the displacement defined by the interaction of the contact probe 32 with the object 10 .

[0053] Advantageously, the measuring head 1 comprises additional elements.

[0054] In particular, the measuring head 1 comprises a capacitive sensor 8 .

[0055] The capacitive sensor 8 is of the differential type. Thus, it is configured to exploit the transmission of a variable signal related to the capacitance of the elements of the sensor 8, these elements being essentially similar to capacitors.

[0056] Capacitive sensor 8 therefore comprises at least one transmitter 5 and one receiver 6 .

[0057] The transmitter 5 is preferably formed integrally with the frame 2. In addition, the transmitter 5 is disposed near the second end 31. According to the following description, the term "near" means that the transmitter 5 is not in contact with the second end 31, but is close enough to electrically interact with the second end 31 or with an object connected or coupled to the second end 31.

[0058] In particular, the emitter 5 preferably defines a first emission area 5a and a second emission area 5b. The emission areas 5a and 5b perform substantially the same function.

[0059] Preferably, the first emitting area 5a and the second emitting area 5b are configured to emit a power signal. Specifically, the electrical signal is preferably a sinusoidal signal. In addition, the electrical signal advantageously defines equal frequency and amplitude for each emitting area 5a, 5b.

[0060] However, it is still advantageous if the source signals of the emission areas 5a, 5b are in anti-phase with respect to each other.

[0061] However, from a structural point of view, the emission regions 5a, 5b are separated from each other, parallel or distributed along a main direction 5c.

[0062] Preferably, the main direction 5c is transverse to the trajectory 3a. Furthermore, in particular, due to the oscillation of the arm 3 about the rotation axis 4a, the main direction 5c is preferably tangential to the trajectory defined by the second end 31 during the oscillation, or interferes with the trajectory in another way. In other words, the emission zones 5a, 5b are located near the oscillation zone of the second end 31 and overlap and separate from each other.

[0063] More specifically, in order to realize the emission areas 5 a , 5 b , the emitter 5 may include a support 50 .

[0064] Preferably, the support member 50 is a flat element. Therefore, the support member 50 can be a plate or a baffle located near the second end 31 .

[0065] Furthermore, preferably, the support 50 extends parallel to the track 3a, ie at least partially on the side of the arm 3, for example Figure 2 In addition, the support member 50 also extends parallel to the main direction 5c.

[0066] Therefore, the support member 50 includes a first armature 50a and a second armature 50b.

[0067] The first armature 50a and the second armature 50b are basically capacitor armatures. Therefore, when there are additional armatures on both sides, the first armature 50a and the second armature 50b can transmit electrical signals.

[0068] The first armature 50a substantially defines the first emitting area 5a. The second armature 50b substantially defines the second emitting area 5b.

[0069] Thus, the armatures 50 a , 50 b extend on the support 50 and may be part of the support 50 or constrained to the support 50 .

[0070] The transmitter 5 also preferably includes a generator 51 .

[0071] The generator 51 is essentially an electrical generator. In detail, it is a generator of a sinusoidal signal and thus a generator of a source signal. Therefore, preferably, the generator 51 is operably connected to each armature 50a, 50b. In addition, the generator 51 is configured to provide a source signal to the armature 50a, 50b.

[0072] Preferably, the receiver 6 is formed integrally with the second end portion 31 .

[0073] In particular, the receiver 6 may be integrated into the second end portion 31 , or it may be coupled to the second end portion 31 , or it may be removably coupled to the second end portion 31 .

[0074] For example, in the latter configuration, the receiver 6 may comprise a strip that may be constrained into a slot formed at the second end 31 of the arm 3 by conventional connecting means such as screws and bolts or other similar means.

[0075] Advantageously, the receiver 6 is configured to capacitively (ie contactlessly) receive the source signal when passing through one or more emission zones 5a, 5b. Furthermore, the receiver 6 is configured to define from the source signal a resultant signal proportional to its position relative to the emission zones 5a, 5b.

[0076] Each composite signal can be simply defined by the arithmetic sum of the contributions of each source signal.

[0077] From a structural point of view, this is achieved by the receiver 6 comprising a third armature 60 .

[0078] Like the other armatures 50a, 50b, the third armature 60 is essentially a capacitor armature. In addition, the third armature 60 extends parallel to the armatures 50a, 50b. Therefore, the receiver 6 oscillates stably at the second end 31, and the third armature 60 moves between the armatures 50a, 50b, which defines a plurality of positions, in which the third armature 60 interacts differently with the armatures 50a, 50b, essentially forming a capacitor structure.

[0079] In other words, the third armature 60 defines a mobile armature capacitor together with each armature 50a, 50b. Of course, this movement has an effect on the capacitance and therefore on the amplitude of the source signal transmitted from the transmitter 5 to the receiver 6, specifically locally from each transmitting area 5a, 5b.

[0080] In order to improve the detection accuracy, the measuring head 1 may further include two supporting members 50. If there are two supporting members 50, the supporting members 50 are formed as mirror images of each other. Therefore, preferably, the receiver 6 further includes two third armatures 60.

[0081] In particular, it is preferred that the third armatures 60 are located at opposite sides. Therefore, the third armatures 60 each face the corresponding support member 50.

[0082] Furthermore, the distance between the first armature 50a and the second armature 50b is preferably smaller than the extension defined by the third armature 60 along the main direction 5c.

[0083] In this manner, the distance is no greater than the third armature 60, and when between the armatures 50a, 50b, the third armature 60 may preferably not simultaneously define a non-interacting region with both.

[0084] Advantageously, the capacitive sensor 8 also comprises a computer 7 .

[0085] The computer 7 is an electronic device which is basically able to receive and process electrical signals in order to return signals or output data useful to an operator (for example using the measuring head 1 ).

[0086] The computer 7 may include a computing device, a computing apparatus, a simple circuit board, and generally any device capable of performing electronic calculations. In particular, the computer 7 includes at least one oscilloscope, or is part of at least one oscilloscope, or is operated by at least one oscilloscope.

[0087] In particular, the computer 7 is preferably operatively connected to the receiver 6 .

[0088] Therefore, the computer 7 is configured to determine a position parameter of the receiver 6 relative to the transmitter 5. In particular, the computer 7 determines the position parameter based on a predetermined reference position value.

[0089] The predetermined reference position value is substantially a starting value or a zero value of the measuring head 1. In other words, when the receiver 6 is at the predetermined reference position value, the arm 3 is substantially at rest.

[0090] The computer 7 is then configured to determine the displacement of the contact probe 32 by evaluating the position parameter of the receiver 6 relative to the reference position value.

[0091] More specifically, in this regard, the computer 7 is configured to determine a position parameter of the receiver 6 in proportion to the resultant signal (ie, the signal derived from the source signal).

[0092] Furthermore, preferably, but not necessarily, the predetermined reference position value is defined at the position between the emission zones 5a, 5b at which the receiver 6 defines a substantially zero composite signal. Of course, this last feature corresponds to possibly different calibration choices.

[0093] Generally speaking, this configuration is advantageous and corresponds to a value position where the cursor 6 is located substantially between the armatures 50a, 50b, exactly at the midpoint between the armatures 50a, 50b, because the source signal is an anti-phase signal with equal amplitude and frequency, so when the interaction between the receiver 6 and the first transmitting area 5a is equal to the interaction between the receiver 6 and the second transmitting area 5b, they cancel each other out and produce a zero signal, or, in other words, when the surfaces of the third armature 60 and the first armature 50a facing each other are substantially equal to the surfaces of the third armature 60 and the second armature 50b, they cancel each other out and produce a zero signal.

[0094] The operation of the measuring head 1 described above in terms of structure is as follows.

[0095] Essentially, when the probe 32 is moved by the object 10, for example due to surface irregularities or due to the movement of the object 10 itself, or even due to an imbalance during the rotation of the object 10, the arm 3 oscillates, rotating about the axis of rotation 4a proportional to the movement of the probe 32. In turn, the second end 31 and thus the receiver 6 move relative to the transmitter 5. Thus, a capacitance difference is generated in the receiver 6 relative to the transmitting areas 5a, 5b, which causes a variation of the source signal and therefore of the resultant signal.

[0096] For example, when computer 7 is Figure 3 When measuring the movement of the receiver in the case of , the cursor 6 interacts only with the second emission area 5b, so the resulting signal corresponds only to the source signal of the second emission area 5b with the largest amplitude.

[0097] On the contrary, when computer 7 is Figure 4 When measuring the movement of the receiver in the case of , the cursor 6 interacts only with the first emission area 5a, so that the resulting signal corresponds only to the source signal of the first emission area 5a with the largest amplitude.

[0098] In all intermediate cases, the different amplitudes produced by the capacitance changes between the third armature 60 and the armatures 50a, 50b produce a composite signal in which the different phase components (with respective amplitudes) of the source signals are added (and therefore subtracted).

[0099] The computer 7 is then configured to convert the resulting composite signal into a linear measurement substantially representative of the movement of the contact probe 32 interacting with the object 10 .

[0100] The measuring head 1 according to the invention has important advantages.

[0101] In fact, the measuring head 1 is simple to manufacture and can be produced at low cost.

[0102] Furthermore, the measuring head 1 is not subject to any mechanical limitations or obstacles and allows greater strokes, i.e. the measurement of greater displacements, since any arm 3 having an even greater distance between the first end 30 and the axis of rotation 4a can be used, and thus greater strokes can be measured simply by balancing the weight of the various arm 3 parts.

[0103] Furthermore, the measuring head 1 has reduced mechanical dimensions.

[0104] Finally, due to the way in which the signal is received, the measuring head 1 allows the measurement to be linearized in a simple manner.

[0105] The invention is susceptible of variations within the inventive concept defined by the claims.

[0106] Throughout this document, all the details may be replaced by equivalent elements, and the materials, shapes and dimensions may be any.

Claims

1. A measuring head (1), comprising: Supporting frame (2), an arm (3) extending along a track (3a) at least between a first end (30) and a second end (31), the arm (3) comprising at least one probe (32) arranged at the first end (30) and adapted to come into contact with an external object (10), A restraining device (4) configured to loosely couple the frame (2) to the arm (3) so that the arm (3) can rotate relative to the frame (2) about a rotation axis (4a) transverse to the trajectory (3a), the rotation being proportional to the displacement defined by the interaction of the probe (32) and the object (10), and characterized in that The measuring head (1) comprises: A differential capacitance sensor (8), comprising: a transmitter (5) formed integrally with the frame (2) and arranged near the second end (31), a receiver (6) formed integrally with the second end portion (31), and A computer (7) is operatively connected to the receiver (6) and is configured to determine the position parameter of the receiver (6) relative to the transmitter (5) based on a predetermined reference position value, thereby determining the displacement of the probe (32).

2. The measuring head (1) according to claim 1, wherein: The transmitter (5) defines at least a first transmitting area (5a) and a second transmitting area (5b), wherein the first transmitting area and the second transmitting area are distributed separately from each other parallel to or along a main direction (5c) transverse to the trajectory (3a), and are configured to transmit sinusoidal power signals with equal frequency and amplitude and opposite phases. The receiver (6) is configured to receive the source signal in a capacitive manner when passing through one or more transmitting areas (5a, 5b), thereby defining a composite signal proportional to its position relative to the transmitting areas (5a, 5b), and the computer (7) is configured to determine the position parameter of the receiver (6) proportional to the composite signal.

3. The measuring head (1) according to claim 2, wherein: The transmitter (5) comprises at least one flat support (50) and an electrical generator (51) of a sinusoidal signal; the support (50) extends parallel to the track (3a) and comprises a first armature (50a) defining the first emission area (5a) and a second armature (50b) defining the second emission area (5b), the first armature (50a) and the second armature (50b) extending on the support (50); the electrical generator (51) is operably connected to each armature (50a, 50b) and is configured to feed the source signal to the armatures (50a, 50b).

4. The measuring head (1) according to claim 3, wherein: The receiver (6) includes a third armature (60) extending parallel to the armatures (50a, 50b).

5. The measuring head (1) according to claim 4, comprising two said supports (50) facing each other in mirror image, and the receiver (6) comprises two said third armatures (60) on opposite sides, and each third armature (60) faces the corresponding said support (50).

6. The measuring head (1) according to claim 3 or 4, wherein: A distance between the first armature (50a) and the second armature (50b) is smaller than an extension defined by the third armature (60) along the main direction (5c).

7. The measuring head (1) according to any one of the preceding claims, wherein The predetermined reference position value is defined at a position between the transmitting areas (5a, 5b) at which the receiver (6) defines a substantially zero composite signal.

8. The measuring head (1) according to any one of the preceding claims, wherein The receiver (6) is removably coupled to the second end portion (31).

9. The measuring head (1) according to any one of the preceding claims, wherein: A contact probe (32) is removably constrained to the first end (30) and is configured to translate in a controlled manner relative to the first end (30) along a positioning axis (32a) transverse to the trajectory (3a).

10. The measuring head (1) according to any one of the preceding claims, wherein The distance between the second end (31) and the rotation axis (4a) and the distance between the first end (30) and the rotation axis (4a) respectively define a ratio, and the ratio is between 0.76 and 0.86.

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