Abstract:
The invention concerns a device for operating gripping or movement tools provided at least with a movable member ( 16, 17 ) movable alternatively between a first and a second position distanced between them by a cursor ( 18 ) susceptible to controlled alter native linear movements starting from an electric actuator. The device comprises a transmission means ( 27 ) of the movement connected to the actuator, one towing slide ( 26 ) associated with the cursor ( 18 ) and susceptible to alternative movements caused by said actuator by means of said transmission means, and at least an elastic member ( 28 ) positioned preloaded between said towing slide ( 26 ) and said cursor ( 18 ) parallel both to their movement direction and to the movement direction of at least a mobile member. The cursor and the towing slide can both move rigidly together as long as the preload of the elastic means remains unchanged, both independently one with the other in reply to the variation of the preload of the elastic means deriving from a resistance against the movement of at least said mobile member.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a device for operating gripping or movement tools, such as a gripper, a slide and the like, by means of an actuator, such as an electric control motor. 
       STATE OF THE TECHNIQUE 
       [0002]    In the tools field for gripping items, objects or various bodies during their production and/or manipulation and/or assembly steps, well known are the grippers with two functional members in the form of gripping means provided with jaws and movable in opposite directions between two extreme positions, respectively active and inactive, that is to say closed and open. Movement systems are also well known as they have a member, for example of the slide type, provided with alternative forward and backward movements. 
         [0003]    In particular, said tools or gripper or movement systems can be of the pneumatic control or of the electric control type. In the case of pneumatic control grippers, the jaws are properly connected to and operated alternatively by a piston which is movable in a relative chamber by means of a fluid under pressure. The electric control grippers on the other hand comprise, as an actuator, an electric or a solenoid motor that moves the gripper jaws between the active and inactive positions by means of a translating member. 
         [0004]    Nevertheless, keeping to the well known realizations, the electric control grippers have an actuator and a kinematic transmission able to transmit a set stroke both towards the inactive position and towards the active position to the gripper jaws. The drawback that derives from it is not to be able to adapt to at least the active stroke and the gripper force in relation to the difference in the nominal dimensions of the items or objects that the tool is designed to grip. It may however happen that said items or objects have for various reasons, at least because of the tolerance of processing, different dimensions one from the other, in which case the smallest can be gripped with insufficient force and the largest with excessive force. The result is that in a case an item or object does not get correctly gripped and in the other case induces unwanted solicitations in the actuator and in the kinematic transmission of the motion. 
         [0005]    In order to avoid the inconvenience, at present mechanical or electronic management is applied to the electric actuator, that is to say of the control motor group of the gripper, by means of a sophisticated, complex and expensive programming and control system so as to be able to finely set up the operation depending on the trend of the or those controlled mobile members. In other words, the strokes of the gripper jaws depend directly on the rotation of the motor and if this is not chosen, adjusted and controlled with precision, the correct gripping action of the to of becomes incorrect. Furthermore to maintain the gripper in an active position, that is gripping an item or the like, the motor must remain continuously active with a relative absorption of energy. 
         [0006]    On the other hand should the feed current lack the gripper can be deactivated, releasing the item. 
         [0007]    Similar problems can be verified also in slide movement systems with a single member movable between two extreme positions defined by the stop. 
       OBJECTIVE AND SUMMARY OF THE INVENTION 
       [0008]    An objective of the present invention is to improve the conditions and the precision of impulse of a gripper tool or electric control movement devices of the type mentioned above and to effectively resolve the above complained about problems regarding the known technique, simplifying furthermore the kinematic transmission of the motion by the electric actuator to the moveable member or members between two extreme positions and ensuring, where required, an item and objects gripping with an appropriate force also when they have different nominal dimensions. 
         [0009]    This objective is reached with a device for operating a gripping or of movement system that comprises a body, at least a mobile member associated with said body and moveable alternately between a first position and a second position at a distance between each to other, a slide susceptible to alternative linear movements in said body and connected to said at least a mobile member for the movements of the latter from one to the other of said positions, and an actuator, preferably electric, designed to control the alternating movements of said cursor and through the latter said at least a mobile device. 
         [0010]    According to the invention said device basically comprises a means of transmission of the movement actuated by the actuator, a towing slide associated with said cursor and subject to alternative movements caused by said actuator through said transmission means, and at least an elastic means positioned preloaded between said towing slide and said cursor in parallel both to their movement direction and to the movement direction of at least a mobile member, so that cursor and towing slide can move both together as one as long as the preload of the elastic means remains unchanged, and independently one from the other in answer to the variation of the preload of the elastic means deriving from a resistance against the movement of said movable member. 
         [0011]    The device to be operated can be a slide provided with a single alternative movable member between two limit stop. 
         [0012]    Otherwise, the device to be operated can be made up of a gripper provided with, as mobile members, two gripping jaws moveable in opposite directions to grip or release from time to time an item or object. 
         [0013]    Basically, the towing slide driven by the actuator by means of the transmission is always subject to a set stroke, whereas the cursor can move in line also relatively to the towing slide and carry out variable strokes within certain limits depending on the resistance to the movement that the mobile member or members can meet. 
         [0014]    By this, the device according to the invention has at least the advantages: 
         [0015]    of eliminating the necessity of having to resort to a sophisticated electronic and mechanical management of the electric actuator; 
         [0016]    of removing the electric actuator from the function of carrying out and maintaining exactly the member or members controlled in each of the two extreme positions that they can assume; 
         [0017]    of exercising at least in one movement direction of each mobile member a positive force supplied by the elastic means and not a lot by the actuator; 
         [0018]    of providing the controller device of the elastic stroke compensator that consents to control, at least in the case of the gripper, an appropriate gripping force on the part of the jaws even on items with different dimensions; 
         [0019]    of being able to adjust, by means of a choice of the preload of the elastic means, the force exercised on a level with the or each of the controlled mobile members in at least one direction; 
         [0020]    of allowing the rotation of the electric actuator and with it the transmission means always in the same direction. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    Further details of the invention will become evident from the continuation of the description carried out in reference to the enclosed drawings and explanatory of an example of an application oft he impulse device to a gripping means in the form of a linear gripper with two opposed members movable in the opposite directions, remaining however understood that a similar application device may be suitable and used also in connection with tools to control as they have a single alternating movable member motion, such as slides and the like. Therefore, in said drawings: 
           [0022]      FIG. 1  shows an exploded view of the components of a linear gripper incorporating the device of the invention; 
           [0023]      FIG. 2  shows a perspective view of the assembled gripper with relative approached jaws; 
           [0024]      FIG. 3  shows a front view of the gripper in  FIG. 1  and by dotted lines and the relative jaws at a distance one from the other; 
           [0025]      FIGS. 4 and 5  show two views, respectively, from the top and side of the assembled gripper; 
           [0026]      FIG. 6  shows an enlarged section of the gripper according to arrows A-A in  FIG. 4 ; and 
           [0027]      FIG. 7  shows a section of the gripper according to the arrows B-B in  FIG. 6 , also enlarged. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0028]    In the drawings is indicatively represented a gripper that basically comprises a gripper body  10  made up of a profile element  11  basically in an upside-down form U, to which a base plate  12  and two heads  13  at its opposite ends are fixed by screws  12 ′ respectively  13 ′ so as to delimit a chamber  14 . On one of its sides, the one opposite the base plate  12 , the body of the gripper  10  is provided with a guide groove  15  in which two mobile members in the shape of gripping jaws  16 ,  17  are guided and susceptible to movements in opposite directions, alternatively between a position in which they are approached and a position in which they are spread apart one from the other. 
         [0029]    In particular, the guide groove  15  can have a an upside-down shape T, and the gripping jaws  16 ,  17  will be configured correspondingly to slide in said guide and result with the it top side facing the longitudinal opening of said guide groove  15 . 
         [0030]    The gripping jaws  16 ,  17  can be fixed from time to time to fasteners—not shown—configured depending on the shapes of the items or objects to grip. For example, the gripper can be equipped so as to be active, that is to say so that it can grip an item or an object with said fasteners, when the two gripping jaws are approached between them and inactive when the jaws are moved away from each other, or on the contrary to be inactive when the jaws are approached and active when they are separated. 
         [0031]    On the top side of the gripper body  10  a protection plate  18  is attached, located above and facing in a transversal direction to an intermediate part of the guide groove  15 . At their facing ends, the jaws gripping  16 ,  17  each have a portion that extends and always remains protected under the said protection plate  17   a —FIG.  6 —so as to prevent the penetration of dirt and extraneous elements between the jaws during alternating movements from one of their positions to another. 
         [0032]    For their movements, the two gripping jaws  16 ,  17  are connected to a cursor  18  which is placed in the chamber  14  delimited by the gripper body  10  and is susceptible to alternative linear movements controlled by an electric actuator  19 , preferably an electric motor, as will be described further on. 
         [0033]    The connection of the gripping jaws  16 ,  17  to the cursor  18  can be carried out in any appropriate way, as long as they move at the same time in opposite directions in reply to the movements of said cursor. 
         [0034]    For example and how it is represented, a first gripping jaw  16  can be rigidly connected radically to the cursor  18  to follow by mutual consent the movements, by means of a pin  20  that is inserted in a hole  20 ′ and that passes and moves in a slot  21  made in the gripper body  10  between the chamber  14  and the guide groove  15 . The second gripping jaw  17  can be connected to the cursor  18  by means of an oscillating transmission lever  22  so that the movement of said cursor in one direction corresponds to a movement of the second gripping jaw  17  in the opposite direction and however in an opposite direction to that of the first moveable gripping jaw  16 , and vice versa in the opposite direction. The transmission lever  22  oscillates on an intermediate fulcrum  22 ′ inserted transversely in the gripper body  10  and extends between the cursor  18  and the second jaw  17  crosses a hole  23  also made in the gripper body between the chamber  14  and the guide groove  15 . 
         [0035]    Furthermore, the ends of the oscillating lever  22  each presents a rolling surface, preferably cylindrical or spherical, and engage in corresponding seats  25 ,  25 ′ respectively obtained in a lower part of the second jaw  17  and respectively in a higher part of the cursor  18 . 
         [0036]    The cursor  18  on the other hand, is associated with a towing slide  26  that is housed in the chamber  14  of the gripper body  10  and is susceptible to alternative movements controlled by the electric actuator  19  by means of a transmission of the motion which preferably is made up of a rotating cam  27  as shown in the drawings. The towing slide  26  is guided in said chamber  14  in parallel to its movement direction and that of the cursor  18  and interacts with the rotating cam  27  through of mechanical contact means. Obviously, to allow the movements, the towing slide  26  has a shorter length than that of the chamber  14  in which it is guided. 
         [0037]    More precisely, the cursor  18  and the towing slide  26  are not rigidly paired, but with the interposition of at least an elastic member  28  positioned and working on the movement directrix of these two associated components  18 ,  26 . 
         [0038]    The towing slide  26  has two shoulders  29  in the movement direction at a given distance one from the other; the cursor  18  has a shorter length than the distance between said shoulders  29  and is positioned movably between the latter; and at least an elastic member  28 , is interposed with a preload and compressible between one shoulder  29  of the towing slide  26  and an end of the cursor  18  as shown in  FIG. 6 . 
         [0039]    In the example illustrated, the elastic member  28  is made up of one or more helical springs  28   a , parallel or coaxial, and is positioned at only one end of the cursor  18 . However it could also be of another type and furthermore an elastic means could be positioned at each of the ends of the cursor  18 , between the latter and each shoulder  29  of the towing slide  26 . 
         [0040]    The rotating cam  27  is positioned adjacent to the base plate  12  of the gripper body, therein supported by a bearing  30  and turning on an X axis, it being connected to the output shaft  19   a  of the electric actuator  19 . Peripherally, the cam  27  has a profile defined by a first portion of the cam  27 ′ which is roughly semicircular, with the function of a dead angle, having a first R radius, and by a second cam portion  27 ″ diametraly opposite, having a second r minor radius of the radius of said first portion. 
         [0041]    The two cam portions connect one to the other through intermediate planes  27   a  and the difference in measure between their R and r radius corresponds to the maximum length of the strokes of the gripping jaws between their extreme positions. 
         [0042]    The mechanical contact means between the towing slide  26  and the transmission cam  27  are set up by two contact rollers  31   a ,  31   b , attached to said slide  26  by means of respective pins  32   a ,  32   b  and resting against the profile of said cam, on opposite parts to this one. As shown in  FIG. 7 , the contact rollers  31   a ,  31   b  can be placed in line with corresponding recesses  33  provided in the base plate  12  of the gripper body  10  and translated in said recesses by following the movements of the towing slide  26  consequent to the rotation of said cam. 
         [0043]    On the whole, however, both the presence of a single elastic means and the presence of two elastic means on opposite parts, cursor  18  and towing slide  26  can move both together as a rigid whole until the load of the elastic means  28 / 28   a  remain unchanged, both independently one from the other due to a compression and successive expansion which the elastic means can become subject to. 
         [0044]    With the gripper in a rest position, the action of the or each elastic means  28 / 28   a  is directed to maintain the cursor  18  in a certain static position relatively on the towing slide  26  or better still, agreed that the latter, tends to move the gripping jaws  16 ,  17  normally in the direction of the grip of the item by means of the jaws they are equipped with. 
         [0045]    When the electric actuator is active, it causes the rotation of the transmission cam  27  the profile of which, by interacting with the contact rollers  31   a ,  31   b , determines the translation of the towing slide  26  and with it the cursor for an operation of the jaws  16 ,  17  by nearing or distancing it alternately. So, assuming that the gripper is preset, as for example is shown in the drawings, to grip an item or object when the jaws are approached, when the first portion of the profile  27 ′—with greater radius R—of the transmission cam  27  it finds itself having to engage with the contact roller  31   a —the one o n the right in FIG.  7 —the slide  26  and the cursor  18  are moved in the approach direction of the jaws. On the contrary, when the first portion  27 ′ of said cam has to engage with the other contact roller  31   b —the one on the left in FIG.  7 —the slide and the cursor are moved in the opposite direction and the jaws are spread open. 
         [0046]    It is therefore sufficient for the first portion  27 ′ of the profile of the cam  27  to be rotated towards and engage with one or the other contact roller  31   a ,  31   b  to provoke the closing and opening movements, that is to say the active and inactive strokes of the jaws. Until any loss of resistance contrary to their movement and to the movement of the jaws, the towing slide  26  and the cursor  18  move solidly together thanks the elastic means  28 / 28   a  interposed between them. 
         [0047]    Given its angular extension or dead angle, which as said beforehand is semicircular, it is sufficient should any part of said portion of the cam  27 ′ engage with one of the contact rollers  31   a ,  31   b  to determine a stroke of the gripping jaws in one direction or in the other even if the rotation of the electric actuator is not exactly equal to the stroke of the slides. Then, as soon as the jaws meet the item or object to grip and therefore find a resistance to their movement, enter into action the elastic means which on one hand allow a relative movement of the cursor compared to the slide and on the other hand they define the gripper force of the item notwithstanding the force of the actuator. 
         [0048]    The same happens when the driven member is single, such as the sliding element provided with an alternative motion of a slide, and said member reaches the means that delimit the strokes. 
         [0049]    Note that the devices described above can undergo modifications without however departing from the aim of the invention. So, instead of a cam, as a transmission system for the control of the towing slide and, by means of this, of the cursor and device or devices to control a connecting-rod assembly or the like can be adopted. Furthermore, on one side of the body  10 , in necessary grooves, sensors, for example of the magnetic type, can be applied, which are suitable for detecting the positions of the cursor and correspondingly the active and inactive positions of the controlled fixture, through at least a magnetic device  35 —FIG.  1 —directly or indirectly associated with the cursor itself.