WO2010060974A1

WO2010060974A1 - Plug gauge and checking system for checking dimensions and/or form deviation of a hole

Info

Publication number: WO2010060974A1
Application number: PCT/EP2009/065938
Authority: WO
Inventors: Fabrizio Bettazzoni
Original assignee: Marposs Societa' Per Azioni
Priority date: 2008-11-27
Filing date: 2009-11-26
Publication date: 2010-06-03

Abstract

Plug gauge (1;61) and checking system for checking dimensions and/or form deviation of a hole including: a main body (2; 62) which has a longitudinal axis and is adapted to be inserted into the hole; at least a feeler (7; 7', -67) which is mounted on the main body so as to be radially movable and is adapted for touching a surface of the hole to be checked; and at least a position transducer (4; 64) which is adapted for detecting the radial position of the feeler and has components that are independently supported by the main body, in particular a movable component (5; 65) mechanically connected to the feeler and a stationary component (6; 66) carried by the main body and coupled to the movable component.

Description

DESCRIPTION

«PLUG GAUGE AND CHECKING SYSTEM FOR CHECKING DIMENSIONS AND/OR FORM DEVIATION OF A HOLE»

Technical field

The present invention relates to a plug gauge and a checking system for checking dimensions and/or form deviation of a hole.

Background art

For checking dimensions and/or form deviation of a hole it is known to use checking systems, in particular a plug gauge which is inserted into the hole and is implemented, for example, as described in the US patent US-4, 339, 879-A1. This plug gauge includes an elongate main body which supports a plurality of sensors with corresponding movable arms carrying mechanical feelers. Each sensor comprises a position transducer which typically includes a movable component mechanically connected to the feeler and a stationary component coupled to the movable component and adapted to detect the radial position of the feeler. The position transducer can be for example of the inductive type; in this case the stationary component includes windings connected to power supply and processing devices, and the movable component consists of a ferromagnetic core coupled to the windings. Each sensor comprises a support element, which is fixed (e.g. screwed) to the main body and supports both the stationary component and the movable component of the position transducer and the movable arm, too . In a known plug gauge of the type previously described, for changing size (that is, for adapting the plug gauge to the diameter measure of a hole having a different shape/nominal dimension) it is not always sufficient to substitute only the feelers. It could be also necessary to substitute the sensors currently mounted with fresh sensors that are proper for the shape/nominal dimension of the hole to be measured. This operation takes a long time and is especially expensive, since the substitution of each sensor causes the concurrent substitution of different elements, such as the movable arm and the whole transducer, i.e. both the stationary component and the movable component. Moreover, the substitution of a whole sensor is needed even in the case of breakage of just one element. In particular, if the movable arm - which is one of the most exposed parts - breaks down, it is necessary to replace the whole sensor, and thus both the components of the position transducer. Hence, in order to meet the need of substitutions - due to changes of nominal dimensions to be checked or to breakages it is necessary to plan the availability of a not negligible number of whole sensors, so involving associated high costs of storage.

Disclosure of the invention

Object of the present invention is to provide a plug gauge and a checking system for checking dimensions and/or form deviation of a hole which overcome the aforementioned inconveniences and can be concurrently easily and cheaply implemented.

The present invention provides a plug gauge and a checking system for checking dimensions and/or form deviation of a hole according to what is claimed in the accompanying claims.

Brief description of the drawings

The present invention is now described with reference to the enclosed sheets of drawings, given by way of non limiting example, wherein: figure 1 is a perspective simplified view, with some parts removed for the sake of clarity, of a plug gauge implemented according to the present invention; figure 2 is a cross-sectional view shown in an enlarged scale of a detail of a position transducer of the plug gauge of figure 1 ; figure 3 is a perspective view, with some parts removed for the sake of clarity, of a movable arm carrying a component of the position transducer of figure 2 ; - figure 4 is a perspective exploded view, with some parts removed for the sake of clarity, of components of the position transducer of figure 2 ; figure 5 is a perspective simplified view of the plug gauge of figure 1, with an additional component and few modified components; figure 6 is a side view, partially cross-sectioned, of a plug gauge according to a different embodiment of the present invention; and figure 6A in an enlarged view of a detail of the plug gage of figure 6.

Best mode for carrying out the invention

In figures 1 and 5, the reference number 1 indicates, on the whole, a checking system, more specifically a plug gauge, for checking diametral dimensions and/or form deviation of a hole.

The plug gauge 1 includes a main body 2 having the shape of a parallelepiped with a rectangular cross-section, e.g. square, and a substantially cylindrical casing 52 (that is shown in figure 5, only), has a longitudinal axis 3, and is adapted to be inserted into the hole for measuring the diameter of the hole at several points. Moreover, the plug gauge 1 includes a plurality of sensor assemblies, or sensors, with position transducers 4, that are assembled in four groups arranged along the main body 2. Each group comprises four sensors with position transducers 4, that - A -

are reciprocally aligned on a same transversal position and are arranged in the four sides of the main body 2 for checking radial dimensions at four points of the same transversal section, spaced apart one from another so as to form a 90° angle. According to an alternative embodiment, for a different type of checking, the groups or some of them, can be composed of a different number of sensors with position transducers 4, for example two mutually facing sensors . According to what is illustrated in figure 2, each position transducer 4 includes components that are independently supported by the main body 2, more specifically a movable component 5 and a stationary component 6, the latter being coupled to the movable component 5 and being connected to power supply and processing devices for detecting changes in the radial position of the movable component 5. More specifically, the stationary component 6 of each position transducers 4 is coupled without contact to the corresponding movable component 5 and is adapted to provide signals depending on the mutual position between said movable component 5 and stationary component 6. The power supply and processing devices - per se known - are, for instance, included in an electrical control unit 30. The position transducer 4, per se known, can be for example an inductive transducer, as it will be also hereinafter described, of the HBT (Half Bridge Transducer) or LVDT

(Linear Variable Differential Transformer) type, wherein the stationary component 6 is implemented by electrical windings, and the movable component 5 includes a ferromagnetic core. A feeler 7 is associated with the position transducer 4 of each sensor. The feeler 7 is radially movable with respect to the main body 2, is adapted to touch a surface of the hole to be checked, and is mechanically connected to the movable component 5 of the position transducer 4 by means of a movable arm 8 placed between the feeler 7 and the transducer 4. More specifically, each movable arm 8 mechanically supports both the movable component 5 and the feeler 7.

The stationary component 6 of each position transducer 4 is not mechanically connected to the movable component 5 and is mechanically fixed to the main body 2 independent of the movable component 5. The movable component 5 of each position transducer 4 is mechanically fixed to the relevant movable arm 8 independent of the stationary component 6, in such a way that it is electromagnetically coupled to the stationary component 6.

According to what is illustrated in figures 2 and 3, each movable arm 8 is substantially stiff and is hinged at one end to the main body 2 for performing limited rotations with respect to the main body 2 about a rotation axis 9. A hinge or fulcrum 10 placed between each arm 8 and the main body 2 is implemented, for instance, by an elastically deformable lamina, which has one end integral with one end of the arm 8, and the other end connected to the main body 2 by means of elements such as screws 11 allowing an easy coupling and an easy removal when necessary. Besides forming the hinge or fulcrum 10 between the arm 8 and the main body 2, each lamina can serve - if properly formed and arranged - to elastically urge the arm 8 radially towards the outside of the main body 2. According to different embodiments, herein not illustrated, each arm 8 supporting the movable component 5 is connected to the main body 2 by means of hinges or fulcra implemented in different ways, for instance by suitably machining an area of the arm 8 near an end thereof or using an articulated parallelogram structure of a known type. Furthermore, there can be springs or other elastic thrust devices for elastically urging the arm 8 radially towards the outside of the main body 2. The arm 8 of each sensor with the associated fulcrum 10, movable component 5 of the position transducer 4 and feeler 7 defines a checking assembly which is integrally connected to the main body 2, and can be easily removed by acting on the screws 11.

In the event transducers of the LVDT or HBT type are used, as previously mentioned and illustrated in the figures, each movable component 5 includes a ferromagnetic core, for example a cylindrical shaped permanent magnet, which is connected to an intermediate portion of the corresponding arm 8, for instance by means of a screw 12, so as to be integral with the arm 8 in a position which is radially adjustable and protrudes from the arm 8 towards the main body 2.

According to the preferred embodiment shown in figures 2 and 4, the stationary component 6 of each position transducer 4 includes a support element 13, which is inserted into a housing seat 14 having an elongated shape, the corresponding arm 8 being coupled to the main body 2 so that the former substantially covers the relevant housing seat 14. In each support element 13 there is defined a transducer seat 15 which is cylindrical shaped, is radially arranged, and is adapted for receiving in its inside the movable component 5. The movable component 5 of each position transducer 4 radially protrudes towards the main body 2 so as to enter at least partly the transducer seat 15. As previously stated, according to a preferred embodiment each position transducer 4 is of the inductive type and the stationary component 6 of each position transducer 4 includes electric windings 16 arranged at the transducer seat 15. The movement of the movable component 5 inside the transducer seat 15 of each position transducer 4 modifies the inductance of the electric windings 16, and by estimating such inductance or its variation it is possible to trace back to the position or the displacement amount of the movable component 5. Each support element 13 includes a locking plate 17 which has a central through hole located at the transducer seat 15, rests on an external surface of the main body 2, and is screwed into the main body 2. More specifically, each locking plate 17 has two side through holes 18 that are arranged at opposite sides of the central hole and are passed through by two screws 19, that are screwed into corresponding threaded blind holes located across the main body 2.

According to the preferred embodiment shown in figures 1 and 5, the main body 2 includes a central channel 20 which communicates with the housing seats 14, comes out in a collector 21 arranged at one end of the main body 2, and houses electrical coupling cables 22 (schematically illustrated in figure 4) of the position transducers 4. The collector 21 preferably includes an electrical connector which is connected to all the terminals of the electrical coupling cables 22, and is used for rapidly implementing an electrical connection between the plug gauge 1 and the electrical control unit 30 including the above mentioned power supply and processing devices. When assembling one of the sensors with position transducer 4 to the main body 2, at first the support element 13 of the stationary component 6 is inserted into the housing seat 14. The housing seat 14 is longitudinally elongate so as to easily insert the support element 13 and especially the electrical coupling cables 22 of the electrical windings 16 carried by the support element 13. Afterwards, the support element 13 is screwed into the main body 2, and thus the checking assembly with the arm 8 is arranged in such a way as to partly overlap the stationary component 6 so that the movable component 5 integral with the arm 8 can enter the transducer seat 15. Finally, the arm 8 is screwed into the main body 2 so completing the assembly of the position transducer 4 to the main body 2. When disassembling a position transducer 4 from the main body 2, the above described assembly operations must be inversely performed.

As shown in figure 5 the plug gauge 1 further includes the substantially cylindrical casing 52, that, at one end is coupled to the main body 2 by means of screws 51, and at the other end carries a closure plate 53. The casing 52 has protective and centering function, and includes lateral openings 50 through which feelers 7' protrude, and which allow limited access to carry out possible adjustments, e.g. in connection with the radial position of the movable component 5 of any position transducer 4, or the substitution of the feelers 7' with the feelers 7 of figures 1 and 3, or with feelers having a different shape, that can be proper for the specific part to be checked.

The above described plug gauge 1 has many advantages as it can be easily and cheaply implemented. Moreover, it can enable to rapidly adapt the configuration of the sensors to a different size (i.e. to the checking of a new hole having different shape/nominal dimensions) . In particular, it can be possible to adapt the configuration of the sensors to a different size and for doing so it is sufficient, by simply reaching the plug gauge 1 from the outside after having removed the casing 52, to disassemble from the main body 2 each arm 8 (the latter carrying the movable component 5 and the feeler 7) , and replace it by assembling to the main body 2 a fresh arm 8 (the latter carrying a fresh feeler 7 and a fresh movable component 5) which is adapted to the new size, while the stationary component 6 of each position transducer 4 remains the one previously assembled to the main body 2. Finally, a new casing 52 is mounted, for properly centering the plug gauge 1 with respect to the new hole to be checked. The disassembly/assembly of arms 8 is particularly rapid as it is enough to unscrew/screw the corresponding screws 11 placed in positions which can be easily reached.

In other words, in case it is required to adapt the plug gauge 1 to carry out dimensional and/or shape checkings of a hole having different shape/nominal dimension, it is not necessary to entirely substitute the various sensors currently mounted, but it is sufficient to substitute just the arms 8 with the movable components 5 and the feelers 7 integral with the arms 8. This operation is quite rapid, simple and cheap since for each position transducer 4 it is necessary to substitute just the movable component 5 and not the stationary component 6. In this regard, it should be noted that the most expensive and complex part of each position transducer 4 is the stationary component 6 (in the illustrated case: the electrical windings 16 connected to the power supply and processing devices by means of the cables 22) , whereas the movable component 5 carries or includes just a pin made of ferromagnetic material having limited cost. Moreover, the arms 8 and the feelers 7 are essentially metal pieces of simple shape with limited dimensions that involve very reasonable costs. The possibility of carrying out simple and rapid substitution operations is very important mainly in case of breakages. In fact, in the event the arm 8 breaks down, it is not necessary to substitute the entire corresponding sensor including the position transducer 4, but only the arm 8 carrying the movable component 5 and the feeler 7, by performing, in this case too, simple operations from the outside of the plug gauge 1.

Figures 6 and 6A show a plug gauge 61 according to a different embodiment of the invention. The plug gauge 61 includes a main body 62 having an elongated shape with a longitudinal axis and a rotational symmetry external surface having variable diametral dimensions. Checking assemblies similar to the ones of figures 1 to 3 include each an arm 68 with a movable element 65 of a position transducer 64 and a feeler 67, and are arranged each in a proper recess 60, so that just the feeler 67 partially protrude with respect to the external surface of the main body 62. The arms 68 are connected to the main body 62 by means of screws 71 and include each a fulcrum 70 that, in the embodiment shown in figure 6 and 6A, is obtained by lightening a portion by means of a suitable - and per se known - machining operation. Springs 69 elastically urge the arms 68, more specifically the feelers 67 radially towards the outside of the main body 2. In the example of figure 6, the plug gauge 61 includes three groups of sensors with position transducers 64, each group comprising two sensors with diametrically opposed relevant feelers 67. Stationary components 66 of the position transducers 64 include each a support element 73 coupled to the main body 62 at an housing seat or opening 74 between the recess 60 and a central channel 80, similar to channel 20 of figure 1. Each support element 73 defines a transducer seat and carries electric windings 76 arranged in the transducer seat which cooperate with a ferromagnetic core included in the movable component 65 of the relevant position transducer 64. The plug gauge 61 of figure 6 has substantially the same features and advantages already set forth in connection with the plug gauge 1 of figure 1. In this case, too, for instance, the stationary components 66 of the position transducers 64 are connected to power supply and processing devices (not shown in the figures) for detecting changes in the radial position of the movable components 65. However, the plug gauge 61 does not need any additional centering casing, in view of the particular shape of the main body 62. The structure of the plug gauges according to the present invention is particularly advantageous in terms of flexibility. In fact, the same structure can be also used for implementing plug gauges including position transducers of different types and in particular exploiting different technologies. For instance, they can have components of pneumatic, optical or other type, working by contact or contactlessly, that can be used in place of the ferromagnetic core included in the movable component 5 and of the electrical windings 16 housed in the housing seat 14 of the main body 2. Alternative embodiments of the invention can differ from what has been herein described and illustrated in the figures as regards a different number or a different arrangement of the sensors with the position transducers 4.

Claims

1. Plug gauge (1;61) for checking dimensions and/or form deviation of a hole including: a main body (2; 62) which has a longitudinal axis (3) and is adapted for being inserted into the hole; and at least a sensor with a position transducer (4;64), which is carried by the main body (2; 62) and includes a movable component (5; 65) and a stationary component (6; 66) that is coupled to the movable component (5; 65) and is adapted to provide signals depending on the radial position of the movable component (5; 65); and a feeler (7; 7'; 67) which is mounted on the main body

(2; 62) so as to be radially movable, is mechanically connected to the movable component (5; 65) of the position transducer (4; 64) and is adapted to touch a surface of the hole to be checked; the plug gauge (1;61) is characterized by the fact that: the stationary component (6; 66) of the position transducer (4; 64) is mechanically fixed independent of the movable component (5; 65) to the main body (2; 62); and the movable component (5; 65) of the position transducer (4; 64) is mechanically fixed to the feeler (7; 7'; 67) independent of the stationary component (6; 66) for being coupled to the stationary component (6; 66) .

2. Plug gauge (1;61) according to claim 1, wherein said at least one sensor includes an arm (8; 68) which supports the movable component (5; 65) and the feeler (7;7';67), and is hinged to the main body (2; 62) by means of a fulcrum (10; 70) for performing limited rotations with respect to the main body (2; 62) .

3. Plug gauge (1;61) according to claim 2, wherein said arm (8;68) together with said fulcrum (10;70), movable component (5; 65) of the position transducer (4; 64) and feeler (7; 7',-67) defines a checking assembly which is adapted for being removably connected to the main body (2; 62) .

4. Plug gauge (1;61) according to claim 2 or claim 3, wherein the stationary component (6; 66) of the position transducer (4;64) includes a support element (13;73), in which there is defined a transducer seat (15) that is radially arranged and is adapted for receiving in its inside the movable component (5; 65); the movable component (5; 65) radially protrudes towards the main body (2; 62) so as to at least partly enter the transducers seat (15) .

5. Plug gauge (1;61) according to claim 4, wherein the stationary component (6; 66) of the position transducer (4;64) includes electric windings (16;76) that are arranged at the transducer seat (15) .

6. Plug gauge (1;61) according to claim 5, wherein the movable component (5; 65) includes a core of ferromagnetic material.

7. Plug gauge (1) according to any one of claims 4, 5 or 6, wherein the support element (13) includes a locking plate (17) which has a central through hole located at the transducer seat (15) , rests on an external surface of the main body (2) and is screwed into the main body (2) .

8. Plug gauge (1) according to any one of claims 3 to 7, wherein the main body (2) includes housing seats (14) which have elongated shape, the support elements (13) being housed in said housing seats (14) and corresponding arms (8) substantially covering said housing seats (14) .

9. Plug gauge (1;61) according to any one of claims 1 to 8 and including a plurality of sensors that are located along the main body (2; 62) .

10. Plug gauge (1;61) according to claim 9, wherein the main body (2; 62) includes a central channel (20; 80) which comes out in a collector (21) arranged at one end of the main body (2; 62), and houses electrical coupling cables

(22) of the stationary components (6; 66) of the position transducers (4;64) .

11. Plug gauge (1;61) according to any one of claims 1 to

10, wherein the stationary components (6; 66) of the position transducers (4; 64) are connected to power supply and processing devices (30) .

12. Plug gauge (1;61) according to any one of claims 1 to

11, wherein each of said stationary components (6; 66) of the position transducers (4; 64) is coupled without contact to the corresponding movable component (5; 65) and is adapted to provide signals depending on the mutual position between said movable component (5; 65) and said stationary component (6; 66) .

13. Checking system for checking dimensions and/or form deviation of a hole including: a main body (2; 62) which has a longitudinal axis (3) and is adapted for being inserted into the hole; a plurality of arms (8; 68), each of them carrying a feeler (7; 7'; 67) adapted to touch a surface of the hole to be checked; and a plurality of position transducers (4; 64) connected to the main body (2; 62), each of them including a movable component (5; 65) connected to an arm (8; 68) of said plurality of arms (8; 68) and a stationary component (6; 66) which is coupled to the movable component (5; 65) and is adapted to provide signals depending on the radial position of the movable component (5; 65); the checking system is characterized by the fact that: the main body (2; 62) defines a plurality of housing seats (14; 74) adapted for housing the stationary components (6; 66) of said plurality of position transducers (4;64); and the arms (8; 68) of said plurality of arms (8; 68) are removably connected to the main body (2; 68) .

14. Checking system according to claim 13, wherein each arm (8; 68) of said plurality of arms (8; 68) includes a fulcrum (10;70); each assembly composed of the arm (8;68) and the respective fulcrum (10;70), movable component (5; 65) and feeler (7; 7',-67) defines a checking assembly which is adapted for being removably connected to the main body (2; 62) .