BACKGROUND OF THE INVENTION 
     This invention relates to an air chuck for use in a capping or uncapping machine. More particularly, the invention relates to an improvement in an air chuck which holds a screw cap of a bottle in a capping or uncapping machine. 
     The capping or uncapping machine is provided with a rotary device which receives bottles from a conveyor and moves the bottles on a circular locus and air chucks which are disposed right above the received bottles. The air chucks revolve while holding bottle caps from the receiving to the releasing of bottles by the rotary device, thereby screwing caps onto bottles or unscrewing caps from bottles. 
     The cap holding portion of the conventional air chuck is composed of a holding member which is fitted in a chuck casing and is made of a soft elastic material and a compression disk which presses and deforms the holding member under the action of compressed air. Thus, when a bottle cap is led into the central bore of the holding member, the holding member is deformed by the pressure of the compression disk, thereby seizing the cap. 
     In such a prior art air chuck, however, since the holding member must be deformed by the pressure of the compression disk, the holding member must be made of a sufficiently soft elastic material so as to seize reliably a cap. As a result, wearing and deterioration of holding member occurs and the long term use of the member cannot be expected. 
     BRIEF SUMMARY OF THE INVENTION 
     It is, therefore, the primary object of the present invention to provide an air chuck for a capping or uncapping machine, which air chuck is free from the disadvantages that occur in the conventional devices. 
     Another object of the present invention is to provide an air chuck in which the wearing and deterioration of the holding members is minimal and, accordingly, to provide an air chuck which is durable in long term use. 
     In the present invention, the holding members are made of materials which are resistant to wearing or deterioration such as metals and synethetic resins. A plurality of hard members made of such material are disposed in a circle and a cap receiving recess is formed at the center of them. Further, the hard members are radially shifted by a driving member which receives the action of compressed air, thereby varying the inner diameter of the cap receiving recess and grasping or releasing a bottle cap. 
     A further object of the present invention is to provide an air chuck which is especially advantageous for an uncapping machine. The existence of a cap is detected by a detecting probe so as to prevent the air chuck from grasping the bottle neck without a cap. Therefore, the breaking of bottle necks and holding members can be avoided. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects and features of the present invention will become more apparent from the following description taken in connection with the accompanying drawings, in which: 
     FIG. 1 is a plan view of an uncapping machine; 
     FIG. 2 is a front view of the same; 
     FIG. 3 is a vertical cross-sectional view of an embodiment of the air chuck of the present invention; 
     FIG. 4 is a cross-sectional view of the same taken along the line IV--IV in FIG. 3; and 
     FIG. 5 is also a cross-sectional view of the same taken along the line V--V in FIG. 3. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
     Referring now to the accompanying drawings, the embodiment of the present invention will be described in more detail. 
     In FIGS. 1 and 2, there is shown an uncapping machine. Containers such as bottles are transferred in the direction of the arrow on a conveyor 1 and they are arranged one by one by timing screws 2. The bottles are then guided along a guide member 4 by an intake star wheel 3 and fed to a rotary table which is disposed right below a rotary device 5. Then, air chucks 6 are moved down toward the bottles on the rotary table from the rotary device 5 which rotates synchronously with the rotary table and the caps of bottles are grasped by the air chucks 6. By the revolutions of the air chucks 6, the bottle caps are unscrewed until the end of the rotation of the rotary device 5, and the unscrewed caps are then released from the air chucks 6 into a hopper 8 by way of a chute 7. Further, with the rise of the air chucks 6, the bottles are again delivered onto the conveyor 1 from the rotary table through the guide member 4 by means of the delivery star wheel 9 and are transferred to the next step. 
     Further, in FIGS. 3 and 4, the air chuck 6 has an outer casing 10, the upper inner wall of which is attached by screw threads to a supporting cylinder 11. The lowermost end of an attaching tube 12 is fixed to the supporting cylinder 11. The upper end of each air chuck 6 is carried by the above-mentioned rotary device 5 and the chucks are turned and moved vertically by means of gear mechanisms and cam mechanisms (not shown in drawings) in the rotary device 5. 
     A chuck casing 13 has a configuration of an inverted cup and is provided with a supporting cap 14 which is fixed to the casing 13 from below with screw threads. Vertically attached to the upper end of this chuck casing 13 is a chuck guide 15 which is composed of an upper small diameter portion 15a, an intermediate portion having vertical grooves 15b (see FIG. 4) and a lower portion having an annular support 15c. Under the weights of the cap holding portion including the chuck casing 13 and the chuck guide 15, the annular support 15c is held on a spherical or conical support face 16a of a casing cover 16 which is screwed to the lower end of the outer casing 10. The reference numeral 17 denotes a slip washer having inner lugs 17a which are received in the vertical grooves 15b of the intermediate portion of the chuck guide 15. This slip member 17 is interposed between slip rings 18, and the lugs 18a of these slip rings 18 are fitted into the vertical grooves 10a which are formed in the inside wall of the outer casing 10. A spring 19 is disposed between the upper slip ring 18 and the flange of an adjusting nut 20. The position of the adjusting nut 20 can be fixed by a set screw 22 which is in engagement with a threaded cylinder 21 that extends downwards from the supporting cylinder 11. Accordingly, the slip washer 17 interposed between the pair of slip rings 18 is pressed to against the upper surface of the case cover 16 by the adjusted spring force of the spring 19 and the rotation applied from the side of the outer casing 10 is transmitted to the chuck guide 15 until the rotational force overcomes the predetermined friction caused on the upper and lower surfaces of the slip washer 17. Therefore, when a screw cap is attached to a bottle, the cap can be screwed and tightened to a predetermined tightness. Further, in the case of cap removing, even when a cap sticks to the neck of a bottle by some cause, the excess force of the rotation of outer casing 10 is not transmitted to the cap holding portion due to the slipping of the slip washer 17. Therefore, the cap holding portion is prevented from damaging the bottle or cap. 
     The smaller diameter portion 15a in the upper portion of the chuck guide 15 is slidably inserted into the bore 23a of an air supply cylinder 23 which is connected to the air passage of the rotary device 5 by means of a rotary joint (not shown) through a flexible air tube 24. The compressed air that is supplied through the air tube 24 is led into the inner passage 25 of the air supply cylinder 23 and then into the annular space 26 formed around the smaller diameter portion 15a which communicates with the lower end of the inner passage 25. Further, through a passage 27 which communicates with the annular space 26 and is formed on the axis of the chuck guide 15, the compressed air is supplied into an air chamber 28 that is formed in the upper portion of the chuck casing 13, which will be further described later on. The tip end of a supporting pin 29 which is screwed into the supporting cylinder 11, is loosely fitted to the air supply cylinder 23 and thus, the air supply cylinder 23 can be moved about the fulcrum of the supporting pin 29. Accordingly, the chuck guide 15 and the cap holding portion such as the chuck casing 13 that are carried below the air supply cylinder 23 can be moved to some extent. For this purpose, the clearance e is previously left between the air supply cylinder 23 and the supporting cylinder 11. Since the cap holding portion can be moved in a horizontal plane due to the fulcrum of the supporting pin 29, even when the position of a receptacle such as a bottle is irregular, the cap holding portion can be adapted to the uneven condition and the capping or uncapping operation can be attained without trouble. 
     In this embodiment, the above-described chuck casing 13 is provided with the following holding mechanism. That is, as shown in FIGS. 3 and 5, the holding member 30 is provided with equally divided three sector hard members 31 which are arranged in a circle on a Teflon sheet 32 that is held on the supporting cap 14. In the middle portion of the circle of sector hard members 31, a cap receiving recess 33 is formed. Each hard member 31 is made of a material having excellent wear resistance such as a metal or a synthetic resin. In the middle portion of the bottom surface of the hard member 31, a guide groove 31a is formed in the radial direction. The guide portion 34a that is formed at the tip end of a bolt 34 is fitted into the guide groove 31a and a spring 35 is set in the space between the guide portion 34a and one end of the guide groove 31a. Thus, the sector hard members 31 can be slidably moved in the directions of the radii of the cap receiving recess 33. In the ordinary state, the sector hard members 31 are radially shifted outwards by the force of the springs 35 to enlarge the diameter of the cap receiving recess 33. Thus, a cap (not shown) can be freely inserted into the recess 33. The above-mentioned bolt 34 is fixed to the lower flange of a supporting member 36 which is screwed to the chuck casing 13. Further, a plate 37 is attached to the under surface of each sector hard member 31 and an aperture 38 is formed in the supporting cap 14 so as to allow bottle caps to pass through. As shown in the drawings, an elastic member 39 made of, for example, hard rubber is fixed to the inside wall of each hard member 31, so that when the hard members 31 are shifted toward the cap receiving recess 33, the cap can be grasped reliably. It is to be noted, however, that the elastic members 39 are not necessarily required and the inner wall of each hard member 31 may be provided with a projection which is integrally made of the same material or the inner wall may be simply a plane surface. 
     In the space between the chuck casing 13 and the supporting member 36 is disposed a cylindrical driving member 40 which is vertically slidably and air-tightly fitted to the chuck casing 13 with a sealing member. Between this driving member 40 and the flange of the supporting member 36, a spring 41 is interposed so as to urge the driving member 40 upward. The inner wall of the driving member 40 is brought into contact with the upper inclined surfaces 31b of the sector hard members 31 and the aforementioned air chamber 28 is formed between the driving member 40 and the under surface of the chuck casing 13. This air chamber 28 communicates with the foregoing passage 27 through a passage 42 is formed in the chuck casing 13 and with a valve 44 which is regulated by the action of a detecting probe 43 to detect the existence of a cap. The detecting probe 43 is slidably inserted through the axis of the supporting member 36 and the chuck casing 13 and, in the ordinary state, the detecting probe 43 is urged downward by a spring 46 which is disposed in the space between the upper end flange 45 and the inner wall of the bore of the chuck guide 15, thereby protruding the lowermost end of the probe 43 to the middle portion of the cap receiving recess 33. A through hole 47 is formed in the flange 45 at the position which does not coincide with the position of the passage 42 formed in the chuck casing 13. In the state of FIG. 3 in which the flange 45 is pressed to the upper surface of the chuck casing 13 by the force of the spring 46, the communication between the through hole 47 and the passage 42 is blocked, but when the flange 45 is separated from the upper surface of the chuck casing 13 against the force of the spring 46, the through hole 47 communicates with the passage 42, thereby constituting the above-mentioned valve 44. 
     The working of the air chuck having the above-described structure will be explained in the following example of uncapping. 
     When a capped bottle is fed on the rotary table from the conveyor 1 as shown in FIGS. 1 and 2, an air chuck 6 is lowered onto the bottle neck from the rotary device 5 which is rotating synchronously with the rotary table. The cap of the bottle is received in the cap receiving recess 33 of the holding mechanism 30 through the aperture 38 of the supporting cap 14. Simultaneously with this action, the detecting probe 43 is pushed up against the force of the spring 46, thereby opening the valve 44. In this state, the air tube 24 is connected to the source of compressed air by an ordinary detecting-controlling mechanism (not shown) and the compressed air is fed into the air chamber 28 from the air source through the air tube 24, inner passage 25, annular space 26, passage 27, and the through hole 47 and inner passage 42 of the valve 44. Thus, the driving member 40 is moved down by the pressure of the compressed air in the air chamber 28. Since the inclined surfaces 31b of the hard members 31 are in contact with the driving member 40, the hard members 31 are shifted in an inward direction to reduce the diameter of the cap receiving recess 33, against the force of the springs 35, whereby the cap in the cap receiving recess 33 can be grasped tightly. 
     Rotary motion is transmitted to the attaching tube 12 of the air chuck 6 from the gear mechanisms (not shown) of the rotary device 5 and it is further transmitted to the cap holding portion such as the chuck guide 15 through the supporting cylinder 11, outer casing 10, a pair of slip rings 18 rotating together with them, and the slip washer 17 that is interposed between the slip rings 18. Therefore, the cap caught by the holding mechanism 30 is unscrewed and raised up from the bottle. Thus, the cap holding portion is also raised and the upper smaller diameter portion 15a is raised into the bore 23a of the air supply cylinder 23. In this working, when the bottle has a problem, such as the sticking of cap, the rotary motion is not transmitted to the cap holding portion because the slip washer 17 slips as described above. Further, when a bottle having no cap is inserted into the cap receiving recess 33, the detecting probe 43 is not pushed up so that the valve 44 is not opened. Accordingly, the compressed air is not introduced into the air chamber 28 and, therefore, the bottle neck is prevented from being damaged by the contact with the hard members 31. 
     After the above uncapping operation, when the whole body of the air chuck 6 is moved up and the supply of compressed air is stopped, the compressed air in the air chamber 28 is released and the driving member 40 is returned to the original upper position by the force of the spring 41. Simultaneously with this action, the sector hard members 31 are returned to their rest positions by the force of springs 35. 
     Accordingly, the diameter of the cap receiving recess 33 becomes large and the cap is released from the holding mechanism and dropped into the hopper 8 through a chute 7. After that, the uncapped bottle is transferred onto the conveyor 1 through the delivery star wheel 9 and the air chuck 6 is moved down to the neck of the next bottle, and the above-described operation is repeated. In the above paragraphs, the uncapping operation of the air chuck has been described, however, it will be apparent that the device of the present invention can also be employed in the capping operation. 
     Although the present invention has been described in connection with a preferred embodiment thereof, many variation and modifications will now become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited not by the specific disclosure herein but only by the appended claims.
An air chuck for use in a capping or uncapping machine, in which air chuck a plurality of hard members are circularly disposed and a cap receiving recess is formed in the central portion of the hard members. The hard members are so arranged as to be slid in the directions of the radii of the cap receiving recess and the sliding movement of the hard members enlarges or reduces the inner diameter of the cap receiving recess, the air chuck thereby grasping or releasing a bottle cap which is introduced into the cap receiving recess. The hard members are made of materials which are excellent in wear resistance and deterioration resistance, such as metals and synthetic resins, so as to be usable for a long period of time. The sliding movement of the hard members is effected by a driving member which is driven by compressed air.