Abstract:
A tool quick changing device includes a main body constrainable to an outside handling system, a blocking disk housed in the main body and rotating with respect to the latter on a rotation axis between a blocking position and a releasing position, driving means of the blocking disk, and a male portion designed to be fastened to a tool to be handled. The main body is provided with a housing seat in which the male portion can be inserted by a translatory movement. The blocking disk, in the releasing position, does not intercept the housing seat of the male portion, therefore the latter remaining free for being inserted and drawn out; on the contrary, in the blocking position the blocking disk intercepts at least partially the housing seat in order to hold the male portion therein which, cannot be drawn out and separated from the main body.

Description:
INCORPORATION BY REFERENCE 
       [0001]    This Patent Application claims the priority of Italian Application No. BS2014A000129, filed on Jul. 15, 2014 and 102015000015702, filed on May 19, 2015, the entire contents of which are incorporated by reference herein as if fully set forth. 
       FIELD OF THE INVENTION 
       [0002]    The present invention refers to a tool quick changing device, specifically an electrically supplied and especially compact tool changing device. 
       BACKGROUND 
       [0003]    In the industrial automation field the use of tool changing devices allowing a robotized manipulator, for example an articulated arm, to take and handle on case-by-case basis the tool needed for a given machining is known. 
         [0004]    In different environments the needs are not so different. 
         [0005]    For example, in the medical field machineries are known which are provided with a plurality of diagnostic instruments that must be selectively handled from a non-use position and a use position. 
         [0006]    In order to be able to take the desired tool or instrument on case-by-case basis, manipulators are provided with a tool changing device; object of the present invention is an electrically operated tool changing device. 
         [0007]    Broadly speaking, the currently available devices comprise a male portion intended for being fastened to the tool or instrument to be taken and handled, and a main body intended for being fastened permanently to the manipulator, for example by means of screws, in its turn provided with a female portion arranged to receive and hold the male portion for the necessary time. 
         [0008]    Members intended for reversibly blocking the male portion in the female portion are housed in the body of the tool changing devices. Traditionally, “tool quick changing devices” mean those tool changing devices in which the blocking members move at high speed for rapidly catching and releasing the male portion, for example in less than 1 second, and therefore the tool or instrument. 
         [0009]    Electrically or pneumatically operated tool changing devices are available, depending on whether the driving members are operated by an electric motor or else a pressurized fluid. 
         [0010]    For example, the German Company SCHUNK GmbH &amp; Co KG makes a plurality of electrically or pneumatically operated tool changing devices. 
         [0011]    An electrically operated tool changing device is commercialized with the trade name ‘Quick Change system EWS’, described in detail in the technical form available at the following Internet link: http://www.schunk.com/schunk_files/attachments/EWS_Highlights — 2013-11_EN.pdf. 
         [0012]    The Applicant found that known tool changing devices usually have a complex structure, are bulky, heavy and expensive to be made. 
         [0013]    The weight is a strongly significant aspect, because a tool changing device is normally handled together with the tool or the instrument and therefore concurs to increase the inertia of moving masses. 
         [0014]    Size of tool changing devices is important too. As the bulk increases the versatility similarly decreases, since the operation range of the manipulator on which the tool changing device is assembled is limited. Obviously, a tool changing device having great size will not be used for taking tools or instruments in tight spaces. 
         [0015]    It is moreover desirable simplifying the structure of tool changing devices as much as possible also for minimizing manufacturing and maintenance costs thereof and the power needed for the respective operation. 
         [0016]    Another drawback of known solutions is that, usually, they do not allow detecting precisely the occurrence of blocking or releasing of the male portion. In other words, they do not allow verifying simply and reliably during time if the tool has been caught or released. 
       SUMMARY 
       [0017]    Object of the present invention is to provide a tool changing device solving the drawbacks of the conventional solutions, which is structurally simple, compact, quite lightweight, reliable and inexpensive. 
         [0018]    A particular object of the present invention is to provide a tool changing device that allows verifying with extreme believability and reliability when the tool has been caught or released. 
         [0019]    It is a further object of the present invention to provide an improved tool changing device, able to block the male portion with a very low friction. 
         [0020]    Another object of the present invention is to provide a tool changing device guaranteeing a lifetime as long as possible also in aggressive working environments, for example in presence of aggressive chemical agents. 
         [0021]    Therefore the present invention concerns a tool changing device, quickly operated, according to claim  1 . 
         [0022]    In particular, the device comprises:
       a main body, for example having a box shape, constrainable to an outside handling system;   a blocking disk housed in the main body and rotating with respect to the latter, in the two clockwise and counterclockwise ways, on a rotation axis between a blocking position and a releasing position, which will be defined hereinafter;   driving means of the blocking disk for driving the rotations; and   a male portion designed to be fastened to a tool to be handled.       
 
         [0027]    The main body is provided with a housing seat of the male portion along said rotation axis, meaning that the male portion can be inserted in the corresponding housing seat by a translatory movement along the rotation axis of the blocking disk. 
         [0028]    The blocking disk, in the releasing position, does not intercept the housing seat of the male portion, therefore the latter remaining free for being inserted and drawn out; on the contrary, in the blocking position the blocking disk intercepts at least partially the housing seat in order to hold the male portion therein which, in this case, cannot be drawn out and separated from the main body. In this way the reversible coupling of the male portion to the main body of the device is achieved. 
         [0029]    The tool changing device according to the present invention can be defined “tool quick changing device” as a very little, and therefore quick, rotation of the blocking disk is sufficient for holding the male portion in the corresponding housing seat. 
         [0030]    The suggested solution offers several advantages. 
         [0031]    First of all, the tool changing device is particularly compact: the axial extent of the male portion and the corresponding housing seat can be minimized, because the blocking disk is a substantially thin member in itself. For example, the blocking disk can have a thickness comprised between 2 mm and 6 mm and the male portion can extend axially for 1 cm-3 cm. This allows the axial bulk of the main body of the device to be limited to less than 4 cm. With respect to the average of the tool changing devices available on the market, the device according to the present invention can be considered “flat”. Also the bulk in the radial direction can be limited, for example less than 12 cm. 
         [0032]    Another advantage is that the device structure is strongly simple. The number of components is limited and the respective arrangement allows assembling and disassembling the device rapidly and with high simplicity, without having necessarily to use specific tools. 
         [0033]    Preferably, for example, the blocking disk is not supported in the main body through apposite bearings, but simply it is supported along its own circumference by the inner surfaces of the seat defined in the same body for the disk. 
         [0034]    Having a simple structure, the device is also lightweight if compared to traditional solutions. This plays a key role in managing inertias by the handling system the device is combined with. For example, a device according to the present invention can be implemented with the blocking disk made of hardened steel, the box-shaped body made of aluminum and the driving means made partially of brass and having a total weight lower than 1 kg; the device with all these features can rise tools or instruments whose weight is equal to 15 kg and higher. 
         [0035]    The afore mentioned features concur in rendering the tool changing device particularly versatile and adapted to be used not only in the industrial automation field in the factory but, for example, also in medical, diagnostic and laboratory device fields. For example, the tool changing devices can be used in ophthalmological diagnostic apparatuses equipped with a plurality of diagnostic instruments that must be selectively taken and handled by an appropriate system for their user provisioning. 
         [0036]    In the preferred embodiment the blocking disk is provided with a toothing next to at least part of its perimeter, i.e. a circumferential toothing. The driving means engage such a toothing to impart the clockwise or anticlockwise rotation. This feature is particularly advantageous for what concerns the inner layout of the device, since the driving means can be positioned substantially tangential to the blocking disk, thereby favoring the compactness of the device on the whole. 
         [0037]    In general, different arrangements of the driving means can be provided. 
         [0038]    In the preferred embodiment the driving means comprise a reversible electric motor, i.e. able to rotate alternately in the two ways depending on the polarity of the power-line voltage, and a worm. The electric motor and the worm are both housed in the main body. The worm is constrained to the shaft of the electric motor and meshes directly the toothing of the blocking disk. In practice, the worm is keyed to the shaft of the electric motor and meshes the circumferential toothing of the blocking disk. Clockwise rotations of the worm cause anticlockwise rotations of the blocking disk and vice versa. 
         [0039]    Alternatively, the reversible electric motor can be assembled outside the main body and a transmission element, for example a steel cable, operatively connects the shaft of the electric motor to the worm housed in the main body. This solution can be adopted, for example, when the tool changing device must be particularly compact and the power necessary for the blocking disk rotation is minimal. 
         [0040]    In both solutions the worm is positioned substantially tangential with respect to the blocking disk and on the same lying plane. 
         [0041]    Preferably, the worm meshes directly the blocking disk and is directly constrained to the electric motor, with no interposition of a reduction gear. 
         [0042]    Still alternatively, the driving means can comprise a cylinder and piston assembly, which is pneumatically driven and wherein the piston is constrained to the blocking disk. This solution is adapted for applications in which high powers are required for the blocking disk rotation, for example when the items to be handled are particularly heavy. 
         [0043]    In the preferred embodiment the male portion comprises two or more side projections, for example two or more pins protruding laterally, so that when the male portion is inserted into the respective housing seat, the side projections extend radially with respect to the rotation axis of the blocking disk. The housing seat in the main body has a substantially complementary shape with respect to the male body. This allows a plurality of male portions of corresponding shape having scaled size to be accommodated. 
         [0044]    Preferably, the male portion is substantially cylindrical and can be coaxially inserted into the housing seat and the projections are pins radially arranged with angles at the center of about 120°. 
         [0045]    In an embodiment the blocking pins are rotating on themselves in the respective seats obtained in the male portion, so that the friction generated with the blocking disk when the latter is rotating is of rolling and not sliding type. Therefore a more gentle operation of the device can be achieved and less starting power is required by the electric motor, or in general the driving means are subjected to less stresses with respect to a solution having fixed pins and sliding friction. 
         [0046]    The blocking disk is provided with a lobate through-hole coaxial with the rotation axis and in which the male portion can be inserted. Through the lobes, i.e. through the nick provided around the through hole, the projections of the male portion are inserted into the housing seat. In practice, the housing seat of the male portion is defined both by the surfaces of the main body and the edge of the lobate through-hole of the blocking disk. 
         [0047]    Preferably, the side of the blocking disk facing the part opposed to the male portion, when it is inserted into the housing seat, has at least one circumferential taper, or an inclined plane, in the proximity of each lobe, so that:
       the rotation of the blocking disk in the blocking position makes the tapers or inclined planes intercept the respective projections (the pins) of the male portion and generate an axial thrust onto the same tapers that blocks the male portion on the main body, and   the rotation of the blocking disk in the releasing position makes the tapers or inclined planes not intercept the respective projections of the male portion, therefore the latter being free of escaping from the housing seat.       
 
         [0050]    Preferably, the male portion and the blocking disk together define a substantially bayonet coupling, even if in this case the male portion does not rotate in the housing seat but the blocking disk does, rotating around the male portion inserted in the seat. 
         [0051]    Preferably, the blocking disk is positioned in the main body at the median plane of the housing seat of the male portion. When the male portion is inserted in the accommodating seat, the blocking disk is in a plane in-between the projections of the male portion and the part of the male portion intended to be fastened to the tool or instrument. 
         [0052]    In the preferred embodiment the tool changing device further comprises a magnetic proximity sensor arranged to generate a signal when the male portion is correctly inserted into the housing seat. A control unit, also a remote one, acquires the signal generated by the sensor and prevents the blocking disk from being operated if the male portion is not correctly inserted in the housing seat. 
         [0053]    Preferably, the device further comprises an encoder housed in the main body and arranged in order to each time detect the rotation amplitude the blocking disk really made. For example, the encoder detects (counts) the number of teeth of the blocking disk that pass in front of the encoder itself when the blocking disk is rotating. 
         [0054]    In an alternative embodiment the device comprises an encoder different from the previous one, which comprises a sensor detecting the strength of the magnetic field generated by one or more permanent magnets mounted on board of the blocking disk. The strength changes as the distance among the sensor and the magnets on the blocking disk changes. Therefore, the rotation of the blocking disk causes a corresponding variation of the strength of the magnetic field the sensor can detect. Each strength value of the magnetic field is indicative of the angular position of the blocking disk. 
         [0055]    In an embodiment, two permanent magnets are fastened to the blocking disk at a nick obtained along its circumference. The magnets are aligned to each other and they are arranged along a direction parallel to the tangent of the blocking disk. The sensor is assembled as stationary in the box-shaped body and faces the edge of the blocking disk. With this arrangement, the strength of the magnetic field the sensor can detect, when the blocking disk is rotating, has a trend with at least three thresholds corresponding to the disk in the releasing position, the disk in the blocking position and the disk in the intermediate position. 
         [0056]    An electronic circuit connected to the encoder and to electric driving means, for example the control unit described above, is programmed to detect a possible current peak in the driving means and to receive the signal generated by the encoder, the signal being indicative of the rotation amplitude the blocking disk made. When necessary, i.e. when the disk rotation has been enough to achieve an effective clamping effect of the projections of the male portion, the electronic circuit disrupts the electric power supply to the driving means. 
         [0057]    Therefore, in general, the proposed solution is effective and assures the clamping of the male portion in the respective seat with no electric power waste, since the driving means are supplied only for the time necessary to rotate the blocking disk. In other words, when the male portion is blocked in the respective seat, the device does not absorb current. 
         [0058]    In view of what above, it is clear that the device supports effectively the male portion and the load applied thereto also in case of electrical black-out. 
         [0059]    Preferably, the box-shaped body is liquid tight, or almost liquid tight, so that the device can be subjected to frequent washes with detergents or disinfectant agents with no damages. This aspect, at first seeming irrelevant for a device use in industrial environments, becomes important in medical fields in order to prevent accumulation of dirt in the device that favors the accumulation of bacterial load and, therefore, potential infection sources for patients using the medical devices handled by the device itself. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0060]    Further characteristics and advantages of the invention will be more evident from a review of the following specification of a preferred, but not exclusive, embodiment, shown for illustration purposes only and without limitation, with the aid of the attached drawings, in which: 
           [0061]      FIG. 1  is a rear elevation view of a part of the tool changing device according to the present invention; 
           [0062]      FIG. 2  is a side elevation view of the device shown in  FIG. 1 ; 
           [0063]      FIG. 3  is a top view of the device shown in  FIG. 1 ; 
           [0064]      FIG. 4  is an exploded view of the device shown in  FIG. 1 , assembled in all its parts; 
           [0065]      FIG. 5  is a vertical section view of the device shown in  FIG. 1 ; 
           [0066]      FIG. 6  is a front view of a component of the device shown in  FIG. 1 ; 
           [0067]      FIG. 7  is a side view of the device shown in  FIG. 4 ; 
           [0068]      FIG. 8  is an elevation view of a part of the device shown in  FIG. 4 , partially disassembled; 
           [0069]      FIG. 9  is an axially symmetrical section view of the device shown in  FIG. 4 ; 
           [0070]      FIG. 10  is an exploded view of a second embodiment of the device according to the present invention, without the male portion; 
           [0071]      FIG. 11  is a vertical section view of the device shown in  FIG. 10 ; 
           [0072]      FIG. 12  is an enlargement of a part of  FIG. 11 ; and 
           [0073]      FIG. 13  is a quality chart relating to the device shown in  FIG. 10 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0074]      FIGS. 1-9  show a device  100  according to the present invention, comprising a first assembly  200  and a second separated assembly  300 . The assembly  200  is intended to be fastened to a manipulator or similar handling system and the assembly  300  is intended to be fastened to the tool or the object or instrument to be taken and handled. 
         [0075]    In practice, the assembly  300 —and with it the tool or the corresponding instrument—is caught and raised by the assembly  200  and the respective manipulator. 
         [0076]    Particularly referring to  FIGS. 1-3 , the first assembly  200  comprises a main box-shaped body  201 , which defines an inner space in which some components of the device are housed. 
         [0077]    In particular, the main body  201  is defined by two covers  201 ′ and  201 ″ screwed one to another by means of the screws  202 . 
         [0078]    An electric connector  203  is present on a side of the main body  201 . 
         [0079]    Three aligning and centering pins  205  projects from the front face  204  of the main body  201 . The rear face  205  is intended to be fastened to a manipulator or equivalent handling system. 
         [0080]    Through the main body  201  a housing seat  207  is defined, in practice a through hole conveniently shaped for accommodating a complementary shaped element. 
         [0081]      FIG. 4  is an exploded view of the complete device  100 . In the main body  201  a blocking disk  208 , a reversible electric motor M and a worm  209  supported by corresponding bearings  210  are housed. 
         [0082]    The circular blocking disk  208  is housed in the main body  201  so that to rotate on the rotation axis X-X. In particular, the blocking disk  208  moves on corresponding tracks  211  obtained inside the covers  201 ′ and  201 ″. On the perimetrical edge of the blocking disk  208  there is the toothing  212 . 
         [0083]    The motor M and the worm  209  are housed in a corresponding seat  213  so that to be aligned and substantially tangential to the blocking disk  208 . The worm  209  is keyed to the shaft of the electric motor M, so that the clockwise and anticlockwise rotations of the motor are transmitted directly to the worm  209 . 
         [0084]    Between the motor M and the worm  209  there is not a speed reducer. In alternative, if necessary according to the features of the electric motor, a speed reducer can be interposed between the motor and the worm. 
         [0085]    In its turn the worm  209  meshes directly the perimetrical toothing  212  of the blocking disk  208  in order to make it rotate clockwise and counterclockwise on the axis X-X. 
         [0086]    As clearly evident from  FIG. 4 , the housing seat  207  is defined by corresponding through holes obtained across the covers  201 ′ and  201 ″ and the blocking disk  208 . 
         [0087]    In the example shown in figures la, the housing seat  207  is a trilobate circular through hole, i.e. it is provided with three lobes  207 ′ oriented so that to form corresponding angles of 120° at the center. 
         [0088]    The function of the housing seat  207  is to accommodate the assembly  300  at least in part. 
         [0089]    The assembly  300  comprises a male portion  301  and a corresponding flange  302  for coupling to the tool/instrument to be handled. In the example shown in figures, the male portion  301  is substantially cylindrical and has a diameter corresponding to the diameter of the housing seat  207 . Three pins  303  are inserted radially in corresponding holes obtained in the male portion  301 , along directions forming a center angle of 120°. 
         [0090]    In practice, the male portion  301 , with the properly assembled pins  303 , can be inserted perfectly in the housing seat  207  through a translatory movement along the axis X-X, taking care of aligning the pins  303  with the lobes  207 ′, meaning that the pins  303  must cross the corresponding lobes  208 ′ obtained through the blocking disk  208 . 
         [0091]      FIG. 5  shows a vertical section of the assembly  200 . It is evident that the worm  209  is keyed to the shaft M′ of the electric motor M and meshes directly the toothing  212  of the blocking disk. A limit stop  214  comprising a slot and a pin limits the clockwise and the counterclockwise rotations of the blocking disk in a predefined angle. 
         [0092]    In  FIG. 5 , the blocking disk  208  is shown in the releasing position in which it does not intercept the lobes  207 ′ of the housing seat, de facto allowing the male portion  301  to be inserted. 
         [0093]    The operation of the device  100  is simple: once the male portion  301  has been inserted in the housing seat  207 , the motor M is activated and drives the blocking disk  208  into rotation through the worm  209 . By rotating, the blocking disk  208  moves to the blocking position shown in  FIG. 8 : the disk now intercepts the lobes  207 ′ and prevents the male portion  301  from being drawn out from the seat  207 . 
         [0094]      FIG. 7  corresponds to  FIG. 2  but, differently from the latter, shows the assembly  300  operatively inserted in the assembly  200 . 
         [0095]      FIG. 8  is an elevation view of the device  100  with the male portion  301  inserted in the housing seat  207  and the pins  303  tightened to the blocking disk  208 . 
         [0096]    By comparing  FIGS. 5 and 8  it is more simple to understand that the rotation (counterclockwise when looking the sheet) of the blocking disk  208  allows intercepting the lobes  207 ′ of the housing seat  207 , so that the pins  303  of the male portion  301  cannot escape from the housing seat  207 . 
         [0097]    By considering the relative movement between the blocking disk  208  and the male portion  301  with the pins  303  thereof, the afore-described coupling can be named bayonet coupling. 
         [0098]    In a variation of the present invention, particularly effective because minimizing the starting power of the motor M, it is provided that the pins  303  can rotate on themselves in the respective seats of the flange  302 . This feature allows having a rolling friction and not a sliding friction between the pins  302  and the blocking disk  208 . A “smooth” operation of the device  100  is achieved and the wear between parts is reduced to minimum. In order to prevent the pins  302  from escaping from the seats of the flange  302 , it is possible to use retaining rings of Seager type, or other equivalent retaining systems. 
         [0099]      FIGS. 4 and 8  show another detail: at the through lobes  208 ′ obtained in the blocking disk  208 , there are some tapers  215  that can also be defined inclined planes. In practice, the inclined planes  215  are arranged as ramps for the pins  301  when the blocking disk  208  rotates for moving to the blocking position. De facto, the rotation involves the compensation of possible clearances among the pins  301  and the corresponding inclined planes  215 . In addition, the inclined planes  215  apply on the corresponding pins  301  a substantially axial thrust serving for holding firmly the assembly  300  on the assembly  200 , i.e. it serves for making the coupling stable to handle effectively the tool or instrument combined with the assembly  300 . 
         [0100]    Preferably, as shown in figures, the inclined planes  215  extend along a circle arc starting from the corresponding lobe  208 ′. 
         [0101]      FIG. 9  is a section view showing clearly the action of the inclined planes  215  onto the pins  301 . As can be noted, the blocking disk  208  interposes among the pins  303  of the male portion  301  and the exit from the housing seat  207 . Preferably, the blocking disk  208  is positioned on a median plane with respect to the depth of the housing seat  207 . 
         [0102]    In  FIGS. 4 ,  5  and  8 , with the numeral reference  216  is denoted a magnetic, capacitive or inductive encoder, etc., arranged to generate an electric signal indicative of the number of teeth passing in front of the same encoder when the blocking disk  208  rotates. A little printed circuit CB, visible in  FIG. 4  at the connector  203 , is configured to perform the processing of the electric signal generated by the encoder—in order to calculate the amplitude of the rotation the blocking disk  208  effectively made—and of the value of current absorbed by the motor M at a given moment. The circuit CB is preferably programmed to compare the amplitude of the just described rotation (i.e. the angle run by the disk  208 ) with the value of the current instantly absorbed by the motor M. In presence of an absorption peak, it disrupts the supply to the motor M in order to prevent malfunctions, overheating and failures thereof. 
         [0103]    In its turn, electric signals generated by the circuit CB are sent to an outside control unit connected to the connector  203 . 
         [0104]    In every case, the blocking disk  208  cannot counter-rotate autonomously to the releasing position. This circumstance can happen only when the motor M reverses the rotation of the shaft M′, for the coupling safety benefit. 
         [0105]      FIGS. 1-9  show evidently that the device  100  according to the present invention has an extremely simple structure and, therefore, can be made compact. This leads to a great versatility and the possibility of uses in several application fields, the handling of fragile diagnostic instruments not being the last. 
         [0106]    In alternative to the activation with the motor M inserted in the main body  201 , the device  100  can be implemented with the motor M on the outside, for example positioned on a robotic arm to which the device  100  itself is combined with. In this case the rotary movement of the shaft M′ is transmitted to the worm by means of a transmission cable (not shown). 
         [0107]    Still alternatively, in place of the electric motor M the device  100  can be pneumatically driven (not shown), for example compressed air, and in this case a cylinder and piston assembly is arranged in the seat  213 , where the piston is connected to the blocking disk  208 . This solution can be preferred when high powers are necessary. 
         [0108]    Even if not shown in figures, preferably the device  100  comprises a proximity sensor, for example of magnetic or capacitive type, positioned in the main body  201  to detect when the male portion  301  is correctly inserted in the housing seat  207  and generate a corresponding electric signal processed by the control unit. 
         [0109]      FIG. 10  is an exploded view of a second embodiment similar to the first one (numeral references, which are the same of those used in the preceding figures, identify equivalent elements) but, with respect to that one, is different because the sensor  216 ′ assembled on the printed circuit CB is not intended to count the number of the teeth of blocking disk  208 . A magnet assembly  217  is assembled on the blocking disk. In substance, the magnet assembly  217  lies at the edge of the blocking disk  208  and moves integrally therewith. The sensor  216 ′ and the magnet assembly  217  define a magnetic encoder. 
         [0110]    The magnet assembly comprises a casing  218  inside which two permanent magnets  219  are housed and aligned along a geometrical axis almost tangential with respect to the circumferential edge of the blocking disk  208 . 
         [0111]      FIGS. 11 and 12  show this aspect in a better way. In practice, at the perimetrical edge of the blocking disk  208 , a part of the respective teeth is removed to make a nick in which the magnet assembly  217  can be housed. The casing  218  remains substantially flush with the blocking disk  208  in order to not modify the bulk thereof. 
         [0112]    The two magnets  219  are aligned so that to form a single magnetic field. Obviously, a single magnet can be alternatively used with a length equal to two magnets  219 . Magnetic North pole and South pole are shown with letters N and S, respectively. 
         [0113]    The sensor  216 ′, which can be defined rotation sensor, detects the strength of the magnetic field B generated by the magnet assembly  217 . The detected strength B depends on the reciprocal distance between the sensor  216 ′ itself and the magnet assembly  217 , and such a distance varies with the rotation of the blocking disk  208 . 
         [0114]      FIG. 13  is a qualitative chart of the strength of the magnetic field B the sensor  216 ′ detects, for example measurable in Tesla or Wb/m2, with respect to the angular position, measured in sexagesimal or radiant degrees, the blocking disk  208  assumes with respect to zero. 
         [0115]    With the described arrangement the trend of the strength of the magnetic field B initially has an increase (area 1st) followed by an increase having a lower slope (area 2nd), in its turn followed by another slope increase similar to the first increase. 
         [0116]    This allows the control unit connected to the printed circuit CB to distinguish at least three angular positions of the blocking disk  208  corresponding to:
       assembly  300  released;   assembly  300  blocked;   the blocking disk  208  in the intermediate position.       
 
         [0120]    If the blocking disk  208  remains in the intermediate position despite the device  100  has been ordered to release or block the assembly  300 , this does mean that the disk  208  got jammed or the motor M does not work properly. The control unit generates an alarm signal with an assistance request, or it activates a self-diagnosis procedure. 
         [0121]    In conclusion, the magnetic field B the sensor  216  can detect is a known function of the angular position of the blocking disk  208 . 
         [0122]    The invention can be implemented also by providing a discretized stepped B/rad diagram. It is sufficient to arrange more magnets  219  in series and spaced out from one another. 
         [0123]    Preferably, in both the variations above described, the main body  201  is hermetic or almost hermetic, so that to withstand washing agents. For example, a gasket can be inserted between the two covers  201 ′ and  201 ″ screwed one to another. The device  100  can therefore undergo frequent washes with disinfectant and aggressive fluids, such those commonly used in medical field. 
         [0124]    This feature takes a great importance if considered that the device  100  can be used to handle laboratory and diagnostic instruments automatically, but anyway in environments that must undergo frequent sanitizations in order to prevent patient infections. 
         [0125]    Another important feature of the afore described devices  100  is the lightness. As can be deduced from the description above and by observing the enclosed figures, bulks of the device  100  are reduced to minimum. For example, the depth is a little greater than the outside diameter of motor M; length and width are a little greater than the diameter of the blocking disk  208 . This is possible since the structure of the device  100  is strongly simple if compared to solutions according to known art. 
         [0126]    For example, in device  100  according to the present invention, the blocking disk  208  is not necessarily supported by special bearings. As a matter of fact, as shown in figures, the blocking disk  208  can be simply supported along the respective circumference by the seat defined in the housing  201  by joined parts  201 ′ and  201 ″. Sacrificing the bearings also allows minimizing weight and simplifying the structure. 
         [0127]    It follows that the weight is held down in values extremely lower than solutions of the known art, and this is an advantage for the dynamic behavior of the robot that will use the device  100  for object handling.