Seal load inspection apparatus

A metal cap 12 is fitted over a vessel (vial 2), into which a rubber plug 4 is driven, and using a pressure block 10, a load is applied to the cap 12 through the top surface 12b thereof to maintain the rubber plug 4 compressed. Under this condition, a tightening roller 14 folds a skirt (lower end 12c of a cylindrical portion 12a) of the cap 12 inwardly to perform a tightening operation. Subsequently, the load applied to the top surface 12b of the cap is once released, and then a load is applied again starting from a value FB which is less than the load FA applied during the tightening operation, gradually increasing to a higher value. In the course of increasing the load, a load FC at the instant when a displacement in the elevation of the top surface of the cap is detected, and this load FC is determined to be a seal load upon completion of the tightening operation. By detecting the load FC upon completion of the tightening operation, a seal capacity of the rubber plug 14 can be confirmed.

BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT

The present invention relates to a seal load inspection apparatus which is installed in or separately provided from a capping unit which drives a rubber plug into a vessel such as vial and then applies a metal cap over the rubber plug and tightens it around the full perimeter while applying a load to the metal cap, and in particular, to such apparatus which allows a seal capacity of the rubber plug to be confirmed by detecting a load acting on the metal cap upon completion of the tightening operation.

A vial which is filled with a medication is sealed, for example, by driving a rubber plug into an opening thereof after it is filled with a content, fitting a cap formed of a metal such as aluminum over the rubber plug and tightening the cap by folding the skirt (lower end) of the cap inwardly.

A sealing load of such a vial depends on the seal capacity of the rubber plug. To achieve a sufficient sealing performance with the rubber plug, the latter must be maintained in an adequately compressed condition. If the tightening operation were performed without a compression of the rubber plug, a failure of obtaining a satisfactory seal capacity results.

Accordingly, it is a general practice that a tightening around the metal cap takes place while a vessel fitted with the metal cap over the driven rubber plug is loaded as by a pressure block. However, the metal cap having its skirt (lower end) folded inwardly in conformity to the outer profile of the vessel may spring back or the folded portion may tend to be restored to its original configuration upon completion of the tightening operation, creating a clearance with respect to the outer surface of the vessel. As a consequence, the rubber plug may be restored due to its own resilience by an amount corresponding to such clearance when the load which has been applied from over the metal cap is released, and the load of the cap which prevails subsequent to the completion of the tightening operation may be diminished from the load applied during the tightening operation. In such an instance, the seal capacity of the rubber plug is likely to be insufficient. Thus, there is a need to detect a load acting on the cap subsequent to the completion of the tightening operation in order to confirm that the rubber plug provides a sufficient seal capacity.

A capping unit which detects a load during a tightening operation which takes place by applying a load from over a cap fitted over a vessel opening or a capping unit which detects a load applied when a cap is driven into a vessel opening is known in the art (see Japanese Laid-Open Patent Publications No. 61-189 and No. 8-58889, for example). In the capping unit disclosed in the first citation (which is referred to therein as a lid clamping device), a load cell is mounted on a cam which elevates a capping head (clamping head), and a load on a roll-on cap as it is tightened is detected in an in-line manner. In the capping unit disclosed in the second citation (which is referred to therein as a capper), a load cell is mounted on a bottle receptacle to detect a load as a cap is driven.

Capping units described in the above patent literature are not constructed in a manner to provide a seal capacity by a rubber plug as it is driven into a vessel, and are therefore not subject to any significant variation in the load at the end of a capping operation. A desired load can be obtained after the end of a capping operation by applying a preset load during the capping operation, and hence, there is no detection of a variation in the load upon releasing the load at the end of the capping step such as a tightening operation.

OBJECT AND SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a seal load inspection apparatus for use with a capping unit in which a tightening of a metal cap tales place by folding a lower end of the cap which is fitted over a driven rubber plug while applying a load thereon, the apparatus being capable of detecting a load acting on the cap not only during, but also subsequent to the completion of a tightening operation.

Above object is accomplished by providing a seal load inspection apparatus installed in a capping unit in which a metal cap fitted over a vessel having a rubber plug driven into it is tightened, the apparatus comprising a pressure block for applying a load to a rubber plug through a cap to cause it to be compressed, an air cylinder for elevating the pressure block, a tightening member for folding a skirt of the cap inwardly, rotating means for rotating at least one of the tightening member and a table on which a vessel is placed, moving means for moving the tightening member to a position where it abuts against the cap and to a position where it does not abut, load detecting means for detecting a load applied to the cap, displacement detecting means for detecting a displacement of an elevation of a top surface of the cap, air pressure control means for controlling the air pressure of the air cylinder, and load value memory means for storing a load detected by the load detecting means, an arrangement being such that a load is initially applied to the metal cap to cause the rubber plug to be compressed and the tightening member performs a tightening operation under this condition by folding the skirt of the cap inwardly, the load is once released, and the air pressure control means is controlled so that the load increases gradually beginning from a low value which does not cause the rubber plug to be compressed to a higher value, and a load which is detected at an instant in the course of increasing the load when the elevation of the top surface of the cap is displaced is determined to be a seal load which prevails subsequent to the end of the tightening operation.

Above object is also accomplished by a seal load inspection apparatus which detects a seal load of a metal cap fitted over a vessel into which a rubber plug is driven when the cap has been subjected to a tightening operation, the apparatus comprising a pressure block for applying a load on a rubber plug through a cap to cause the rubber plug to be compressed, an air cylinder for elevating the pressure block, load detecting means for detecting a load applied to the cap, displacement detecting means for detecting a displacement of the elevation of a top surface of the cap, air pressure control means for controlling an air pressure of the air cylinder, and load value memory means for storing a load value detected by the load detecting means, an arrangement being such that the air pressure control means is controlled so that a load applied to the cap is gradually increased from a low value which does not cause the rubber plug to be compressed to a higher value, and a load detected at an instant in the course of increasing the load when a displacement occurs in the elevation of the top surface of the cap is determined to be a seal load which prevails subsequent to the tightening operation.

In addition, above object is accomplished by a seal load inspection apparatus which detects a seal load of a metal cap fitted over a vessel into which a rubber plug is driven subsequent to a tightening operation, the apparatus comprising a pressure block disposed to be capable of abutment against the top surface of the cap, a table on which the vessel is placed, an air cylinder for elevating the table, load detecting means for detecting a load applied to the cap, displacement detecting means for detecting a displacement in the elevation of the table, air pressure control means for controlling the air pressure of the air cylinder, and load value memory means for storing a load value detected by the load detecting means, an arrangement being such that the table is elevated upward under a low load which does not cause the rubber plug to be compressed to bring the top surface of the cap into abutment against the pressure block, whereupon the load applied to the table is increased, and a load detected at an instant in the course of increasing the load when a displacement occurs in the elevation of the table is determined to be a seal load which prevails after the completion of the tightening operation.

In the seal load inspection apparatus according to the present invention, a metal cap is fitted over a vessel into which a rubber plug is driven, a tightening operation takes place by applying a load to the top surface of the cap to cause the rubber plug to be compressed while folding the skirt of the metal cap inwardly, and subsequently, the load applied to the cap is once released, and thereafter the load is gradually increased beginning with a low load which is insufficient to cause a completion of the rubber plug to a higher value. In this manner, it is possible to confirm a seal capacity of the rubber plug upon completion of the tightening operation exactly, allowing defective products to be detected reliably.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Several embodiments of the present invention shown in the drawings will now be described. A capping unit (generally indicated by a denotation1) provided with a seal load inspection apparatus according to one embodiment of the present invention comprises a table6on which a vessel2(which is a vial into which a rubber plug4is driven in this embodiment) is supplied, a pressure block10which is elevated up and down by an air cylinder8, and a tightening roller14which tightens a cap12which is formed of a metal such as aluminum and which is fitted over the rubber plug4driven into the vial2.

A number of vials2which are conveyed in succession by a vessel conveying conveyor L are separated from each other into a giving spacing by an in-feed screw M, and are introduced into the capping unit1through an inlet star wheel N. These vials2are subject to a tightening of metal caps12and an inspection of a seal load within the capping unit1, and are delivered onto the vessel conveying conveyor L through an outlet star wheel P to be fed to a succeeding step.

The vial2includes an opening2a, into which the rubber plug4is a press fit, a portion2bof a reduced diameter which is less than the external diameter of the opening2a, and the outer surface of the opening2aand the portion2bare connected together by a tapered surface2c. The vial2also includes a portion2eof an increased diameter which is located below the portion2bof a reduced diameter and which continues to a bottom2d.

The rubber plug4which is disposed as a press fit in the opening2aof the vial2includes a press fit region4ahaving an external diameter which is substantially equal to or slightly greater than the internal diameter of the opening2a, and a head4bof an increased diameter having an external diameter which substantially matches the external diameter of the opening2a. A metal cap12which is fitted over the rubber plug4includes a cylindrical portion12awhich surrounds the head4bof an increased diameter of the rubber plug4and the external surface of the opening2ain the vial2, and a top surface12bwhich is located on top of the head4bof an increased diameter. The metal cap12has a length such that when it is fitted over the rubber plug4, the lower end (skirt) of the cylindrical portion12ais located outside of the tapered portion2cof the vial2or slightly below it. It is to be noted that a resin cap16including a cylindrical portion16awhich is shorter than the cylindrical portion12aand a top surface16bis integrally bonded to the metal cap12at a location around the outer periphery of the upper portion of the cylindrical portion12aand over the top surface12badhesively.

The table6is mounted on a vertical rotary shaft20which is connected to a drive shaft of a motor (rotating means)18, and is adapted to be rotated with the vial2thereon when the motor18is driven. The rotation of the motor18is controlled by a controller22which will be described later.

A pressure block10disposed above the table6is connected to the lower end of a rod8aof the air cylinder8fixedly mounted to depend downwardly, and is adapted to be elevated up and down by an actuation of the air cylinder8. The pressure block10has a shank10awhich extends upwardly from the center of the block and which is connected to the inside of the rod8aof the air cylinder8by means of a lock ring24. A ball bearing26is interposed between the bottom surface of the rod8aof the air cylinder8and the pressure block10, which is thus elevatable by an actuation of the air cylinder8and is also rotatable with respect to the air cylinder8. The lower surface of the pressure block10is formed with a circular recess10b, which is urged against the top surface12bof the metal cap12awhich is fitted over the vial2(in the present embodiment, the metal cap12and the resin cap16are formed to be integral, and therefore, is urged against the top surface16bof the resin cap16).

The elevating air cylinder8is provided with a load cell28acting as load detecting means, which is adapted to detect a load acting on the cap12when the air cylinder8is actuated to urge the pressure block10against the metal cap12.

The pressure block10which is elevated up and down by the actuation of the air cylinder8is connected with a potentiometer30acting as elevetion detecting means which detects a change in the direction of the elevation, and the elevation of the pressure block10which is elevated by the air cylinder8is detected by the potentiometer30.

As mentioned previously, the vial2is formed with the tapered portion2cat a location below the opening2a, into which the rubber plug4is disposed as a press fit, and continuing to the portion2bof a reduced diameter, thereby allowing the lower end12cof the cylindrical portion12aof the metal cap12to be folded toward the tapered portion2c. To perform a folding of the lower end12cof the metal cap12a, a tightening roller14is disposed at a location adjacent to the pressure block10and the table6which are disposed one above another. The tightening roller14is formed with a pusher14awhich abuts against the lower end12cof the cylindrical portion12aof the metal cap12to fold it inwardly, the pusher14abeing sloped in substantial the same manner as the tapered portion2cof the vial2. The tightening roller14is movable horizontally by means of an air cylinder32, and is moved between a position (refer toFIG. 4Awhich will be described later) where it is urged against the metal cap12to fold the lower end12cof the cylindrical portion12ainwardly and a position (seeFIG. 2) where it does not abut against the metal cap12.

A controller22which controls the operations of various parts of the capping unit1comprises a load detector34which detects a load applied to the metal cap12from the pressure block10in response to a signal fed from the load cell28, and an elevation detector36which detects a position in the direction of the elevation of the pressure block10in response to a signal fed from the potentiometer30. In addition, it comprises a load memory38for storing a load detected by the load detector34in response to a signal fed from the load cell28and for storing a preset proper load, and an elevation memory40which stores an elevation detected by the elevation detector36in response to a signal fed from the potentiometer30. In addition, it comprises a comparator/decision unit42which compares values detected by the load detector34and the elevation detector36against values stored by the load memory38and the elevation memory40and determines whether or not they are in a proper range, and a control unit46which controls the operations of an auto-regulator44controlling an air pressure supplied to the elevating air cylinder which drives the pressure block10and the motor (rotating means)18which rotates the table6.

The air cylinder8which elevates the pressure block10up and down has an upper and a lower pressure chamber (not shown) formed in its interior, and these pressure chambers are connected to a source of air supply52through solenoid operated valves48and50. The pressure block10is elevated up and down by supplying the air to each of these pressure chambers from the source of air supply52or by opening the pressure chambers to the atmosphere. When tightening the lower end12cof the metal cap12, the air from the source of air supply52having a pressure which is controlled by the auto-regulator44is supplied to the upper pressure chamber while the lower pressure chamber is opened to the atmosphere to lower the pressure blocking10to urge against the metal cap12which is fitted over the vial2under a given load.

The operation of the capping unit1constructed in the manner mentioned above will now be described. Vessels (vials)2, each having the rubber plug4driven into it and fitted with the metal cap12and its integral resin cap16over the rubber plug at a preceding step, are conveyed in succession by the conveyor L, separated from each other into a given spacing by the in-feed screw M and introduced into the capping unit1through the inlet star wheel N to be supplied to each of the tables6. At the time the vial2is supplied to the table6, the upper pressure chamber in the elevating air cylinder8is open to the atmosphere while an air pressure is supplied to the lower pressured chamber, whereby the pressure block10assumes a raised position.

The press fit region4aof the rubber plug4which has an external diameter equal to or slightly greater than the internal diameter of the opening2aof the vial2is disposed as a press fit in the opening2aof the vial2, and the head4bof an increased diameter which is located above the press fit region4ais disposed on the peripheral edge of the opening2aof the vial2. The external diameter of the head4bof the rubber plug4is substantially equal to the external diameter of the opening2aof the vial2, and the cylindrical portion12bof the metal cap12is fitted so as to be in contact with the outer peripheral surfaces of the head4bof the rubber plug4and the opening2aof the vial2. The lower end12cof the cylindrical portion12aof the metal cap12which is fitted over the rubber plug4and the vial2in this manner extends to a point which is located below the opening2aof the vial2, and is spaced from the tapered surface2cof the vial2.

When the vial2is supplied to the table6, the air from the source52is supplied through the auto-regulator44to the upper pressure chamber of the elevating air cylinder8which is disposed above the table6, whereby the pressure block10is lowered. The pressure block10is urged against the top surface12bof the metal cap12which is fitted over the vial2(or directly, against the top surface16bof the resin cap16), thus applying a load to the rubber plug4through the top surface12bof the metal cap12. An interval A shown inFIG. 1represents an interval in which the pressure block10is lowered.

During the operation of the capping unit1, the load cell28and the potentiometer30detect the load applied to the metal cap12(resin cap16) and the elevation of the pressure block10at a given time interval, and the controller22recognizes signals fed from the load cell28and the potentiometer30. Upper graph ofFIG. 5graphically shows a change in the elevation of the pressure block10as detected by the potentiometer30while the lower graph ofFIG. 5graphically shows a change in the magnitude of the load acting on the metal cap12as detected by the load cell28. The capping step will be described below with reference to this Figure.

The magnitude of a load applied to the metal cap12is set up by the pressure block10(this commanded load is indicated by a denotation FO in the lower portion ofFIG. 5). An air pressure which is required to apply the commanded load FO is previously determined experimentally so that this air pressure can be supplied to the elevating air cylinder8.FIG. 6graphically shows a relationship between the air pressure and the load acting on the metal cap12. A preset air pressure is supplied through the auto-regulator44which is controlled by the control unit46within the controller22to the upper pressure chamber of the elevating air cylinder8, whereby the commanded load FO is applied. Specifically, the auto-regulator44may be set up to provide an air pressure which can apply a load of 20 kg, for example, and this air pressure is supplied to the elevating air cylinder8to apply a corresponding load to the rubber plug4.

As the elevating air cylinder8is actuated, the pressure block10is lowered in a gradual manner as indicated in the upper portion ofFIG. 5, and when it moves into contact with the resin cap16which is integral with the metal cap12(position T1inFIG. 5), a high load is detected momentarily. Subsequently, when the pressure block10is lowered to a minimum elevation (position T2inFIG. 5), a cap load FA which substantially matches the commanded load FO is detected by the load cell28.

After the pressure load10has reached the lower limit of movement, a tightening operation is initiated (position T3inFIG. 5). When performing a tightening operation, the air cylinder32which is used for horizontal movement is actuated to move the tightening roller14toward the vial2to urge the pusher14aof the tightening roller14against the lower end12cof the cylindrical portion12aof the metal cap12while rotating the table6by driving the motor18.

The tightening operation takes place for a given time interval (which corresponds to an interval from position T3to position T4in this embodiment) by urging the tightening roller against the lower end12cof the metal cap12and rotating the table6. The pusher14aof the tightening roller14has a slope which substantially matches the slope of the tapered surface2cformed around the outer peripheral surface of the vial2, whereby the lower end12cof the metal cap12is folded inwardly in conformity to the profile of the tapered surface2cof the vial (seeFIG. 4A). In the tightening interval (T3to T4and corresponding to an interval B shown inFIG. 1), the air pressure supplied to the elevating air cylinder8which lowers the pressure block10remains constant, but the load applied to the cap12varies as shown in the lower portion ofFIG. 5.

Upon completion of the tightening operation, the air cylinder32which is used for horizontal movement is actuated to retract the tightening roller14to a position where it cannot contact the metal cap12. The tightening roller14which has been urging the lower end12cof the metal cap12against the tapered surface2cof the vial is retracted while maintaining the load applied by the pressure block10(the load which is detected by the load cell at this time is indicated by FA). The lower end of the metal cap12slightly moves away from the tapered surface2cof the vial2by spring-back (seeFIG. 4B).

Upon completion of the tightening operation, the load which is applied by the pressure block10is removed. During the tightening operation, the air pressure is supplied to the upper pressure chamber of the elevating air cylinder8while opening the lower pressure chamber to the atmosphere, but to remove the load, the solenoid operated valve48is switched to open the upper pressure chamber to the atmosphere in a similar manner as for the lower pressure chamber. When the upper and lower pressure chambers are open to the atmosphere, the load acting on the cap12is removed while the pressure block10remains lowered. When the load from the pressure block10is removed, the rubber plug4which has been compressed up to this point is allowed to expand, pushing up the pressure block10through the metal cap12(seeFIG. 4C). Even though the pressure block10is pushed up by the rubber plug4, upon abutment of the folded lower end12cof the cylindrical portion12aof the metal cap12against the tapered surface2cof the vial2, the metal cap12can no longer be pushed up by the resilience of the rubber plug4, and the metal cap12and the pressure block10cease to rise thereafter (position T5in the upper portion ofFIG. 5).

The load is removed while maintaining the pressure block10in its lowered condition in the present embodiment, but the load may be removed by allowing the pressure block10to rise. In this instance, the upper pressure chamber of the air cylinder8to which the air pressure has been supplied during the tightening operation is made open to the atmosphere while the air pressure is supplied to the lower pressure chamber to cause the pressure block10to be raised. However, if the pressure block10is raised in order to remove the load on the metal cap12, it is necessary that the lower pressure chamber be made open to the atmosphere to bring the pressure block10into abutment against the top surface12bof the metal cap12subsequently.

FIG. 4Cshows a condition where the metal cap12and the pressure block10have ceased to be raised by the expansion of the rubber plug4. A displacement of the metal cap12and the pressure block10in the upward direction which has occurred at this time is indicated by denotation S1betweenFIGS. 4B and 4CandFIG. 5in the upper portion thereof. After the load is once released in this manner, a load is applied again through the top surface12bof the metal cap12. While maintaining the lower pressure chamber of the elevating air cylinder8open to the atmosphere, the compressed air is supplied from the source52to the upper pressure chamber through the auto-regulator44. The auto-regulator44which is disposed in the path through which the air pressure is supplied to the upper pressure chamber is controlled so as to increase the supplied pressure in a gradual manner, as indicated in the lower portion ofFIG. 5from position T6to position T8.

It is to be noted that when the load is applied again subsequent to the completion of the tightening operation, the load is gradually increased starting with a load value FB (see the lower portion ofFIG. 5) which is less than the load FA which is used during the tightening operation. There is no displacement of the metal cap12as long as the load applied remains low, but as the applied load increases, the metal cap12begins to be displaced downwardly. As mentioned previously, a change in the elevation of the pressure block10is detected by the potentiometer30, and a change in the cap load is detected by the load cell18. The instant where a downward displacement of the metal cap12occurs (see T7inFIG. 5) is detected by the potentiometer30, and the load FC at this instant is detected by the load cell28. The load FC at the instant where the potentiometer30has detected a displacement of the metal cap12is determined to be a load acting upon the metal cap12subsequent to the completion of the tightening operation or the seal capacity of the compressed rubber plug4.FIG. 4Dshows a compressed condition of the rubber plug4as a result of applying the load again from the pressure block10. An interval C inFIG. 1represents an inspection interval of the cap load. It should be understood that the load FB which is applied again after completion of the tightening operation at the moment the load begins to be applied again has a low value which is insufficient to cause a compression of the rubber plug4.

Subsequently, the upper pressure chamber of the elevating air cylinder8is made open to the atmosphere while the air pressure is supplied to the lower pressure chamber to raise the pressure block10, thus completely removing the load on the metal cap12(see T9inFIG. 5). An interval D inFIG. 1represents an interval during which the pressure block10rises.

The load memory38of the controller22has a proper load which is required to secure the seal capacity of the rubber plug4in storage and the comparator/decision unit42compares the seal load FC upon completion of the tightening operation against the proper load, and in the event there is a departure from the proper load, it determines it to be a defective product, which is rejected. In this manner, the seal capacity of the rubber plug4subsequent to the tightening operation can be exactly confirmed from product to product, allowing any defective product which has an insufficient seal capacity by the rubber plug4to be detected.

The capping unit1according to this embodiment is arranged to provide a feedback control. Specifically, the comparator/decision unit42compares the load FC which is obtained upon completion of the tightening operation and the proper load, and whenever there is a difference therebetween which exceeds a predetermined value, the magnitude of a load applied to the top surface12bof the metal cap12by the pressure block10is corrected during the next cap load operation in accordance with the load FC which is obtained upon completion of the tightening operation. The auto-regulator44is disposed in an air piping supplying the air to the air cylinder8which elevates the pressure block10, and when it is necessary to correct the load to be applied to the metal cap12, the air pressure which is supplied to the upper pressure chamber of the air cylinder8is automatically regulated in accordance with a signal delivered from the control unit46which depends on the detected load FC. By introducing the detected load into the feedback control, it is possible to control the seal capacity of the rubber plug4to a proper value. In addition, a load acting on the cap is normally monitored in this embodiment, and this allows the occurrence of any abnormality in the capping unit1to be detected.

In the present embodiment, the table6is rotated by the motor18, but the tightening roller may be arranged to be rotatable so as to turn around the vial2over which the metal cap12is fitted.

FIGS. 7 and 8are a plan view schematically illustrating an overall arrangement of a capping line including a seal load inspection apparatus101according to a second embodiment, and a schematic view showing the arrangement of the seal load inspection apparatus101. In this embodiment, the seal load inspection apparatus101is provided separately from a capping unit1which performs a tightening of a metal cap12. Vessels (vials which are already fitted with rubber plugs4) which have been conveyed by the vessel conveying conveyor L are separated from each other in to a given spacing by an in-feed screw N, supplied to the capping unit1through an inlet star wheel M, and are discharged onto the conveyor L through an outlet star wheel P after a capping (a tightening of the metal cap) has been performed to be fed to the seal load inspection apparatus101.

Since the seal load inspection apparatus101of this embodiment is provided independently from the capping unit1which performs a tightening of the metal cap12, the tightening roller14, the air cylinder32for horizontal movement which moves the tightening roller14to a position where it abuts against the metal cap12and a position where it does not abut and rotating means which rotates the table6which are used in the first embodiment are omitted, but in other respects, the arrangement is identical with the first embodiment, and accordingly, corresponding parts are designated by like denotations as used before to omit their description, and only what is required will be described below.

The seal load inspection apparatus101is of a type having a fixed table106, and a vial2which has completed a tightening operation of the metal cap12in the capping unit is conveyed on the conveyor L to be supplied onto the fixed table106. Accordingly, the vial2supplied to the table106has the lower end12cof the metal cap12already folded to extend along the outer profile of the tapered portion2cof the vial2. Disposed above the fixed table106are a pressure block10which applies a load to the metal cap12, an air cylinder8which elevates the pressure block10up and down, a load cell28which detects a load acting on the metal cap12, and a potentiometer30which detects the elevation of the top surface12bof the metal cap12. The elevating air cylinder8has upper and lower pressure chambers, which are connected to a source of air supply52through solenoid operated valves48and50and an auto-regulator44in order to supply the air to or displace the air from these pressure chambers. When the air is supplied to the upper pressure chamber through the auto-regulator44, the pressure block10is lowered to apply a preset load on the metal cap12while when the air is supplied to the lower pressure chamber, the pressure block10is raised.

In this embodiment, before the vial2is supplied to the table106, the upper pressure chamber of the elevating air cylinder8is open to the atmosphere while the air is supplied to the lower pressure chamber to maintain the pressure block10in its raised position (a condition shown inFIG. 9A). Under this condition, when the vial2conveyed by the conveyor L is supplied onto the table106, the solenoid operated valve50is operated to interrupt the air supply to the lower pressure chamber and to make it open to the atmosphere. The pressure block10then descends by its own gravity (see the upper portion ofFIG. 10from T10to T11). As the pressure block10descends, a value detected by the potentiometer goes up. When the pressure block10which descends by its own gravity abuts against the top surface12bof the metal cap12(or directly against the top surface16bof the resin cap16), the pressure block10ceases to descend (a condition shown inFIG. 9B), and a value detected by the potentiometer30also ceases to change (a position shown in the upper portion ofFIG. 10at T11).

The solenoid operated valve48connected to the upper pressure chamber of the elevating air cylinder8is then switched from its condition where the upper pressure chamber is open to the atmosphere in order to supply an air pressure which is set up by the auto-regulator44from the source52to the upper pressure chamber, thus urging the pressure block10to be lowered to apply a load on the metal cap12. In this embodiment, the auto-regulator44is controlled to increase the supplied air pressure so that the load acting on the cap top surface12bincreases gradually from zero until a preset value FD is reached (see an interval from T12to T14in the lower portion ofFIG. 10). The controller22has a relationship between the air pressure and the load acting on the metal cap12in storage, and accordingly, a load is applied in accordance with the air pressure, and the magnitude of the load is recognized by the controller22.

When the load applied to the metal cap12exceeds the seal load, the rubber plug4is compressed, whereby the metal cap12begins to descend (seeFIG. 9Cand the upper portion ofFIG. 10at T13). Signals from the load cell28and the potentiometer30are transmitted to the controller22(seeFIG. 3) at a given time interval (such as 0.2 msec, for example), and such signals are stored in a load memory38and an elevation memory40. The controller22detects the instant (T13) when the rubber plug4shrinks and the value from the potentiometer begins to rise, and reads out a prevailing load from the load memory38and determines it to be a seal load FE. Also with this embodiment, the seal capacity of the rubber plug4subsequent to the tightening operation can be exactly confirmed, allowing any defective product having an insufficient seal capacity of the rubber seal4to be detected in a reliable manner. In this embodiment, a plurality of sets each including the pressure block10, the elevating air cylinder8and the table106as shown inFIG. 8are provided to permit a plurality of vials2to be processed simultaneously, but only one set may be used as well. It is also possible to utilize the vessel conveying conveyor L which conveys vessels from the capping unit1to the seal load inspection apparatus101directly as tables. In addition, the load cell28may be disposed on the table106.

FIG. 11is a longitudinal section showing an arrangement of a seal load inspectional apparatus201according to a third embodiment. In this embodiment, in the similar manner as in the second embodiment, the seal load inspectional apparatus201is provided separately from the capping unit1at a location downstream thereof (seeFIG. 7).

In the arrangement of the second embodiment, the table106is fixedly mounted and has a constant height. However, in the present embodiment, a table206is mounted on a piston rod208aof an elevating air cylinder208, and can be elevated up and down by supplying the air to or displacing the air from the upper and lower pressure chambers (not shown) of the elevating air cylinder208. In order to detect the elevation of the table206, a potentiometer230is mounted on the table206. On the other hand, a pressure block210is secured at a location above the table206so as to be capable of abutment against the top surface12bof the metal cap12(or more exactly, the top surface16bof the resin cap16) which is capped over the vessel (vial)2when it is raised by the table206.

The elevating air cylinder208of this embodiment has upper and lower pressure chambers (not shown) which are connected through solenoid operated valves248and250, respectively, to a source of air supply252. An auto-regulator244is disposed in an air supply passage to a lower pressure chamber. By supplying the air pressure which is regulated by the auto-regulator44which is in turn controlled by the control means22(seeFIG. 3) to the lower pressure chamber, the table206is raised to urge the metal cap12against the pressure block210to produce a given load thereon. Accordingly, in this embodiment, the load cell228which detects the load is provided on the side of the air cylinder208which elevates the table206.

With the seal load inspection apparatus201constructed in the manner mentioned above, when the vial2to which a tightening operation of the metal cap12has been performed by the capping unit1is conveyed by the conveyor L to be supplied onto the table206, the air is supplied to the lower pressure chamber of the elevating air cylinder208to raise the table206. In this embodiment, the load is increased in two stages as shown in the lower portion ofFIG. 13. The air pressure is controlled by the auto-regulator44so that the initial load FF applied in the first stage (see the lower portion ofFIG. 13from T20to T21) is less than the seal load FG. At this load FF, the top surface12bof the metal cap12is urged against the circular recess210bin the lower surface of the pressure block210, but the rubber plug4cannot be compressed since the load FF is less than the seal load FG, and the table206ceases to rise. The abutment of the top surface12bof the metal cap12against the pressure block210to stop its movement is determined from a value of the potentiometer230which ceases to change (see T22inFIG. 13).

To apply the load in the second stage, the air pressure supplied to the lower pressure chamber of the elevating air cylinder208is increased gradually (see the lower portion ofFIG. 13form T23to T25). The load detected by the load cell228increases from time to time, and when it reaches a given value (see the lower portion ofFIG. 13at T24), the rubber plug4is compressed, allowing the table206to begin rising. The load FG detected by the load cell228at the instant when the table begins to rise as detected by a signal from the potentiometer230is determined to be a seal load.FIG. 12shows a condition in which the rubber plug4is compressed to allow the table206to rise.

The load which is applied at the first stage is determined as follows:when a load of 20 kg is applied as a tightening operation is performed by the upstream capping unit1, the seal load subsequent to the tightening operation will be smaller than 20 kg on account of factors such as spring-back mentioned above. Assuming that this value were on the order of 15 kg, the air pressure supplied will be chosen so that the load in the first stage be lower than 15 kg while still allowing the table206carrying the vial2thereon to be raised, which may be on the order 10 kg. When so chosen, rubber plug4cannot be compressed if the air pressure continues to be supplied after the cap top surface12babuts against the pressure block210as a result of a rising movement of the vessel2.

With the third embodiment, a seal load which can be obtained with the compressed rubber plug4as a result of a tightening of the metal cap12under load in the capping unit1can be exactly confirmed for each instance in the similar manner as in the described embodiments, allowing a defective product having a insufficient seal capacity to be detected in an reliable manner.