Abstract:
An apparatus for measuring the alignment of a valve sealed onto a canister comprises hollow lower and upper sections, a mounting platform, and a transducer. The upper and lower interior regions cooperatively define an inner chamber in which the mounting platform is disposed. The transducer is mounted to the upper section and includes a probe extending through the upper section and into the inner chamber. The apparatus is adapted for relative rotational movement between the mounting platform and the upper section. The transducer is responsive to linear translation of the probe and displays a human-readable indication of the alignment of a valve sealed in a canister as the probe moves around the circumference of the top surface of the valve.

Description:
TECHNICAL FIELD 
     The present invention is generally directed to the manufacturing of sealed canisters containing an operative substance such as a medicine and a propellant. More particularly, the present invention is directed to testing the integrity of the seal of such canisters, especially canisters utilized in metered dose inhaler systems. 
     BACKGROUND ART 
     Many types of medicines are provided in fluid form, such as a solution or suspension of particles in a propellant or emulsion, and are adapted for oral inhalation by a patient. As one example, a canister might contain asthma medicine such as fluticasone propionate. During a typical manufacturing process, the canister is sealed with a cap that includes a metering valve. The seal is effected by crimping the valve cap onto the neck of the canister. The canister is then, many times, charged through the valve stem with an aerosol or other propellant. 
     In order to deliver medicine to the patient, the canister operates in conjunction with an actuator as a system commonly known as a metered dose inhaler (MDI) system. The actuator includes a housing having an open canister-loading end and an open mouthpiece. A nozzle element is disposed within the housing and includes a valve stem-receiving bore communicating with a nozzle orifice. The orifice is aimed toward the mouthpiece. In order to receive a properly metered dosage of medicine from the canister, the patient installs the canister into the actuator through the canister-loading end until the valve stem is fitted into the receiving bore of the nozzle element. With the canister so installed, the opposite end of the canister typically extends to some degree outside the actuator housing. The patient then places the mouthpiece into his or her mouth and pushes downwardly on the exposed canister end. This action causes the canister to displace downwardly with respect to the valve stem, which in turn unseats the valve. Owing to the design of the valve, the design of the nozzle element, and the pressure differential between the interior of the canister and the ambient air, a short burst of precisely metered, atomized medicine is thereby delivered to the patient. 
     As known to those skilled in the art, the quality of the crimping process by which the valve cap is sealed onto the canister is of utmost criticality. Even a slight defect in the resulting crimp will constitute an improperly sealed valve cap. That is, because of the significant pressure differential between the interior of the canister and the ambient air, the slightest leak will render the canister commercially valueless. By the time the defective canister has been distributed to the patient, most or all of the propellant will have escaped the confines of the canister. As a result, the pressure differential has been eliminated and the canister rendered inoperative. 
     It would therefore be advantageous to provide a feasible method for identifying and diagnosing problems associated with the canister crimping assemblies employed in MDI production lines. The present invention is provided to address these and other problems associated with the assembly of ends, tops or caps onto open-ended canisters, as well as problems associated with the measurement of height or the determination of levelness for the ends of other types of objects. 
     DISCLOSURE OF THE INVENTION 
     The present invention disclosed herein results from an acknowledgment that in order for the valve cap to be crimped onto the canister properly, thus ensuring the integrity of the seal, the valve cap must be accurately aligned onto the canister during the crimping process. It is further acknowledged that accurate alignment, and thus a seal of acceptable quality, can be indicated by measuring the height or the distance of a top surface of the valve cap of an assembled canister with respect to a reference point. By taking several such measurements around a circular line on a flat portion of the top surface of the valve cap, and by comparing those measurements with a predetermined value or range of acceptable values, the levelness of the valve cap can be determined and the integrity of the seal adjudged from the resulting data. The measurements can be taken either by axially rotating the canister and its valve cap with respect to the probing element of a transducer, or by axially rotating the probing element with respect to the valve cap. 
     The present invention generally provides two approaches to determining the alignment and levelness of the valve cap. In the first approach, a portable, hand-held measuring apparatus is provided for analyzing assembled canisters off-line with regard to the manufacturing process. The first approach is most practicably implemented by employing a micrometer or other transducer that includes a mechanical probe to physically contact the valve cap. In the second approach, a measurement system that includes a measurement station is adapted for integration with the in-line canister assembly process. The second approach is most practicable implemented be employing a non-contacting type of micrometer or transducer. In both approaches, a plurality of standard-sized canisters can be analyzed without changing the set-up or configuration of the apparatus. 
     In accordance with a first embodiment of the present invention, a measuring apparatus comprises a housing defining an inner chamber therein and a transducer mounted to the housing. The transducer includes a probe that extends into the inner chamber. A mounting platform is disposed within the inner chamber of the housing and is adapted for mounting an object thereon having opposing first and second end surfaces. The measuring apparatus is adapted for relative rotational movement between the mounting platform in the transducer probe so that the probe is caused to contact a portion of the first end surface of the object. 
     In accordance with another embodiment of the present invention, measuring device comprises a lower section defining a lower interior region, an upper section defining an upper interior region, a mounting platform, and a transducer. The lower section includes a first end surface having an aperture communicating with the lower interior region. The upper section includes first and second end surfaces. The upper section second end surface has an aperture communicating with the upper interior region and extends into the lower interior region of the lower section. The aperture of the upper section second end surface communicates with the lower interior region, and the upper and lower interior regions cooperatively define an inner chamber. The mounting platform is disposed within the inner chamber and is adapted for mounting an object thereon having opposing first and second end surfaces. The transducer is mounted to the upper section and includes a linearly movable probe. The probe extends through the upper interior region and into the inner chamber. The transducer is responsive to a translation of the probe. The apparatus is structurally adapted for relative rotational movement between the mounting platform and the transducer probe so that the probe is caused to contact a portion of the first end surface of the object. 
     In one of the preferred embodiments according to the present invention, a hollow insert is disposed within the lower section of the measuring device. The insert has an outer lateral surface and an inner lateral surface. When the insert is disposed within the lower section, the outer lateral surface of the insert is adjacent to an inner lateral surface of the lower section. The insert includes a longitudinal slot disposed in parallel with the longitudinal axis and is exposed to the lower interior region of the lower section. A transverse member is attached to an outside lateral surface of the upper section, and extends radially outwardly with respect to the longitudinal axis. The transverse member is slidably disposed in the longitudinal slot. 
     In another method for determining the levelness of an end surface of an object, a measuring device is provided which comprises a housing defining an inner chamber, a transducer mounted to the housing, and a mounting platform disposed within the inner chamber. The transducer includes a probe extending into the inner chamber. An object including opposed first and second inner surfaces is placed into the inner chamber, and the second end surface of the object is secured onto the mounting platform. The probe is brought into contact with the first end surface of the object. Relative rotational movement is then carried out between the mounting platform and the probe such that the probe travels along a portion of the first end surface of the object. 
     In another method for determining the levelness of an end surface of an object, a measuring device is provided which comprises a housing including a hollow upper section and a hollow lower section cooperatively defining an inner chamber, a transducer mounted to the housing and including a probe extending into the inner chamber, and a mounting platform disposed within the inner chamber. An object having opposed first and second end surfaces is placed into the inner chamber. The second end surface of the object is secured onto the mounting platform by sliding the upper section into the lower section. The sliding causes a downward displacement of the upper section with respect to the lower section along a central longitudinal axis common to both the upper and lower sections. A distal end of the probe is brought into contact with the first end surface of the object at a point disposed along a circumference of the first end surface. An indication of the levelness of the first end surface of the object is produced by comparing a zero reference point of the probe to a change in displacement of the probe, which displacement change is effected by the contacting of the distal end with the first end surface. The distal end of the probe is then brought into contact with the first end surface at another point disposed along the circumference of the first end surface, and another indication of levelness is produced. This process can be repeated a number of times in order to produce a plurality of indications. 
     In a further embodiment according to the present invention, a system is provided for detecting an improperly sealed valve of a canister during a canister assembly or filling process. The system comprises a detection station, a conveying device, and a non-contacting measuring device. The conveying device extends through the detection station and includes a movable element. A canister is disposed on the movable element and can be advanced by the movable element through the detection station. The canister includes an open upper canister end sealed by a valve cap having a top surface. The non-contacting measuring device is mounted to the detection station such that it can measure the height of the top surface of the valve cap. 
     It is therefore an object of the present invention to provide a method and apparatus for measuring the alignment of an end of an object, such as a valve assembled onto a canister. 
     It is another object of the present invention to provide a method and apparatus for measuring the alignment of a valve assembled onto a plurality of differently sized canisters without having to change the configuration of setup of such apparatus. 
     It is a further object of the present invention to provide a portable, hand-held apparatus for measuring the alignment of a valve assembled onto a canister. 
     It is a still further object of the present invention to provide a method and apparatus for measuring the alignment of a valve assembled onto a canister while either axially rotating the canister with respect to a transducer or axially rotating the transducer with respect to the canister. 
     It is yet another object of the present invention to provide an apparatus for measuring the alignment of a valve assembled onto a canister, wherein the apparatus is integrated with the in-line manufacturing or filling process of the canister. 
     Some of the objects of the invention having been stated hereinabove, other objects will be evident as the description proceeds, when taken in connection with the accompanying drawings as best described hereinbelow. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevation view of a canister to be measured by a measuring apparatus provided in accordance with the present invention; 
     FIG. 1A is a top plan view of the canister of FIG. 1; 
     FIG. 2 is a perspective view of a portable measuring apparatus according to one embodiment of the present invention; 
     FIG. 3 is an exploded perspective view of upper components included with the measuring apparatus of FIG. 2; 
     FIG. 4 is an exploded perspective view of lower components included with the measuring apparatus of FIG. 2; 
     FIG. 5 is a perspective view of an insert provided with the measuring apparatus of FIG. 2; 
     FIG. 6 is a perspective cut-away view of the measuring apparatus of FIG. 2 illustrated with a canister loaded therein; 
     FIG. 7A is a perspective view of the measuring apparatus of FIG. 2 illustrated in its open position with a canister loaded therein; 
     FIG. 7B is a perspective view of the measuring apparatus of FIG. 2 illustrated in its closed position with a canister loaded therein; 
     FIG. 8 is a partially cut-away view of an upper portion of the measuring apparatus of FIG. 2 illustrated with a canister loaded therein; 
     FIGS. 9A,  9 B and  9 C are partially cut-away views of the measuring apparatus of FIG. 2 respectively showing sequential positions taken by the measuring apparatus while a canister is being secured into a locked position therein; 
     FIG. 10A is a front elevation view of an in-line measuring apparatus according to another embodiment of the present invention; and 
     FIG. 10B is a front elevation view of an in-line measuring apparatus according to a further embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1 and 1A illustrate a typical MDI canister generally designated  10 . Canister  10  includes a canister body  12  having a typical diameter of 0.87 inches. Canister body  12  is bounded by a closed bottom canister end  12 A, which usually has a concave profile  12 B (shown in phantom), and an open upper canister end concealed by a valve cap  14 . A canister shoulder  12 C provides a regional transition from canister body  12  to the upper canister end. Valve cap  14  is sealed over the upper canister end at a crimped section  14 A. Valve cap  14  includes a valve stem  14 B extending outwardly therefrom. As shown in FIG. 1A, a top surface  14 C of valve cap  14  is flat in at least an annular region  14 D of valve cap  14 . There are three standard sizes for canister  10 , which may be referred to as short, medium, and tall. Short, medium and tall canisters  10  have respective heights of 1.54, 1.93, and 2.37 inches. Short canister  10  typically delivers 60 metered doses, medium canister  10  typically delivers 120 doses, and tall canister  10  typically delivers 200 doses. 
     Referring to FIG. 2, a preferred embodiment of an off-line MDI valve alignment measuring device generally designated  20  is illustrated in assembled form according to the present invention. Measuring device  20  is shown in its open position. Measuring device  20  includes a lower body generally designated  30 , an upper body generally designated  60 , a transducer generally designated  80 , a mounting platform  90 , a rotatable dial or handle  110 , and a cylindrical sleeve or insert  120 . Lower body  30  and upper body  60  have respective outer lateral surfaces  32  and  62 . Each outer lateral surface  32 ,  62  is shown to be cylindrical, but this is not a requirement. Lower body  30  and upper body  60  also have respective inner lateral surfaces  34  and  64  and hence hollow interiors. Lower body  30  and upper body  60  are disposed coaxially with respect to a central longitudinal axis L common to both lower and upper bodies  30  and  60 . Lower body  30  further includes a main section  36  and a reduced-diameter section  38 . As described in more detail below, upper body  60  is slidably mounted within the interior of lower body  30  along longitudinal axis L. 
     Platform  90  for mounting canister  10  within measuring device  20  is disposed within the interior of lower body  30 , and is accessible through a side port formed by the combination of a cut-out section  42  of lower body  30  and a cut-out section  72  of upper body  60 . As described in more detail below, platform  90  rotates with handle  110  disposed below reduced-diameter section  38  of lower body  30 . The rotation of platform  90  and handle  110  is about longitudinal axis L, and is generally indicated by arrow A. Insert  120 , also described below, is disposed within lower body  30  and is secured therein by means of an annular cap ring  145 , holes  145 A, and appropriate fastening means in holes  145 A such as screws (not shown). 
     Referring to FIG. 3, transducer  80  includes a housing  82  and a spring-loaded probe  84  depending downwardly therefrom. The distal end of probe  84  includes a roller-ball tip  84 A. Transducer  80  is preferably a micrometer equipped with a digital readout such as a liquid crystal display  82 A. A suitable, off-the-shelf micrometer is available from MITUTOYO and designated as Model No. 543-253. Transducer  80  is designed to measure the magnitude and direction of the linear movement of probe  84 , and to convert that measurement into a representative digital value for display at readout  82 A. Transducer  80  is situated above upper body  60  such that probe  84  can extend through an opening  61  at the top of upper body  60  into the interior thereof. For this purpose, transducer  80  is preferably secured to a flanged portion  63  of upper body  60  by employing a combination of devises  86 A and  86 B, screws  88 A,  88 B and  88 C, and an extension rod  89 . In this manner, one or more screws  88 A- 88 C can be loosened and extension rod  89  manipulated in order to adjust the position of transducer  80  over upper body  60  and consequently the position of probe  84  within measuring device  20 . In addition, transducer  80  can be removed from measuring device  20  in order to replace batteries, to service transducer  80 , or to perform calibrations if necessary. 
     A pair of roller-type cam followers  65 A and  65 B with rollers  65 A′ and  65 B′ are mounted in countersunk holes  67  of upper body  60  by known means. Cam followers  65 A and  65 B interact with insert  120  in a manner described below. Also shown in FIG. 3 is a three-tiered disk spring  150  and C-clip  158 , which are disposed coaxially within the interior of upper body  60 . Referring to the cut-away view of FIG. 6, an annular collar  66  extends from inner lateral surface  64  of upper body  60  radially inwardly toward longitudinal axis L. Collar  66  has an upper shoulder  66 A on which disk spring  150  rests. Disk spring  150  is secured within the interior of upper body  60  between upper shoulder  66 A and C-clip  158 . C-clip  158  is disposed in a fixed position through its expansion into a circumferential groove  68  located on inner lateral surface  64  of upper body  60 . The function of disk spring  150  is described below. 
     Referring to FIGS. 4 and 6, insert  120  is secured within lower body  30  between cap ring  145  and an annular shoulder  44  located at the transition between main section  36  and reduced-diameter section  38 . Insert  120  can be secured by aligning a cut-out section  122 A thereof with cut-out section of lower body  30 , disposing a dowel or shim  162  in a recess  120 A of insert  120  and a recess  46  of reduced-diameter section  38 , and aligning countersunk holes  145 A of cap ring  145  with corresponding threaded bores  48  of main section  36  and threading screws (not shown) into bores  48 . In order to provide structural reinforcement for insert  120 , side holes  52  of lower body  30  can be aligned with side holes  120 B of insert  120  (see FIG.  5 ), and screws (not shown) threaded through side holes  52  and into side holes  120 B. Although only one pair of side holes  120 B are shown in FIG.  5  and only one pair of side holes  52  are shown in FIGS. 2 and 4, additional pairs of corresponding side holes  120 B and side holes  52  (not shown) could be provided around the periphery of insert  120  and lower body  30 , respectively. 
     Handle  110  shown in FIGS. 4 and 6 includes a cap portion  112  and a hollow cylindrical portion  114  centrally disposed within reduced-diameter section  38  of lower body  30 . Cap portion  112  can include a plurality of hash marks  112 A, which are either embossed or grooved. As shown in FIG. 2, handle  110  can be rotated to align hash marks  112 A with a reference mark  54  provided on outside lateral surface  32  of lower body  30  at reduced-diameter section  38 . 
     Platform  90  is preferably cup-shaped with an outer wall  92  and a base  92 A. Base  92 A has a convex profile  92 B (see FIG. 6) to conform with concave profile  12 B of bottom canister end  12 A of canister  10 . Platform  90  includes a lower plug portion  94  having a blind threaded bore  94 A. Platform  90  is seated on a ball bearing  96  fitted into reduced-diameter section  38  of lower body  30 . Platform  90  is installed into measuring device  20  by extending lower plug portion  94  through the bore of ball bearing  96 , extending a mounting stud such as an axial bolt  98  through hollow cylindrical portion  114  of handle  110 , and threading axial bolt  98  into blind bore  94 A of lower plug portion  94 . As a result, platform  90  is secured to handle  110  and rotates with handle  110  about longitudinal axis L. 
     Referring to FIG. 5, insert  120  includes a cylindrical wall  122  having cut-out section  122 A which cooperates with cut-out section  42  of lower body  30  to form the side port of measuring device  20 . Insert  120  is preferably constructed of glass-filled nylon, although such a choice of materials is not a limitation of the present invention. Insert  120  also includes a pair of diametrically opposed, parallel longitudinal tracks or slots  124 A and  124 B cut out of cylindrical wall  122  of insert  120 . A plurality of transitional slots branch off each corresponding longitudinal slot  124 A and  124 B. There are preferably three transitional slots for each longitudinal slot  124 A and  124 B. Thus, longitudinal slot  124 A is associated with an upper transitional slot  126 A, a medial transitional slot  128 A, and a lower transitional slot  132 A. Each transitional slot  126 A,  128 A and  132 A is oriented at a downward angle, which orientation could take a helical path if desired. There also exist corresponding upper, medial and lower transitional slots which branch off longitudinal slot  124 B, although these transitional slots are not shown in FIG.  5 . For clarity, the corresponding pairs of upper, medial and lower transitional slots of longitudinal slots  124 A and  124 B are collectively referenced hereinafter as upper transitional slots  126 , medial transitional slots  128 , and lower transitional slots  132 . Insert  120  further includes a plurality of terminal slots such as an upper terminal slot  134 A, a medial terminal slot  136 A, and a lower terminal slot  138 A. Each terminal slot  134 A,  136 A and  138 A branches off the lower end of its corresponding transitional slot  126 A,  128 A and  132 A at an upward angle. Although not shown, upper, medial and lower terminal slots are similarly associated with the transitional slots of longitudinal slot  124 B. The corresponding pairs of upper, medial and lower terminal slots associated with longitudinal slots  124 A and  124 B are collectively referenced hereinafter as upper terminal slots  134 , medial terminal slots  136 , are lower terminal slots  138 . 
     Accordingly, when insert  120  is installed into lower body  30 , longitudinal slots  124 A and  124 B, transitional slots  126 ,  128  and  132  and terminal slots  134 ,  136  and  138  cooperate with inner lateral surface  34  of lower body  30  to form grooved paths in which cam followers  65 A and  65 B of upper body  60  respectively travel during movement of measuring device  20  from an open position to a closed position. It should be noted that measuring device  20  according to the present invention is particularly adapted to measure canisters  10  of either the standard short, medium or tall size. Thus, in the exemplary embodiment described herein, three paths through which cam followers  65 A and  65 B can travel are provided. The particular path taken depends upon the size of canister  10  to be analyzed. Each path includes longitudinal slots  124 A and  124 B. When a tall canister  10  is loaded into measuring device  20 , a first path is characterized as following longitudinal slots  124 A and  124 B downwardly, branching off longitudinal slots  124 A and  124 B to progress along upper transitional slots  126 , and terminating in upper terminal slots  134 . When a medium canister  10  is loaded, a second path is characterized as following longitudinal slots  124 A and  124 B downwardly, branching off longitudinal slots  124 A and  124 B to progress along medial transitional slots  128 , and terminating in medial terminal slots  136 . When a short canister  10  is loaded, a third path is characterized as following longitudinal slots  124 A and  124 B downwardly, branching off longitudinal slots  124 A and  124 B to progress along lower transitional slots  132 , and terminating in lower terminal slots  138 . As described in more detail below, it will be seen that insert  120  with its slotted configuration serves as a cam cylinder for cam followers  65 A and  65 B. 
     It will be understood that the number of slots provided by insert  120  could be varied without departing from the scope of the present invention. For example, measuring device  20  could be adapted to measure canister  10  of only a single height, in which case insert  120  would provide a single path defined by longitudinal slots  124 A and  124 B, one pair of transitional slots  126 ,  128  or  132 , and one pair of terminal slots  134 ,  136  or  138 . In another example, measuring device  20  could be adapted to measure more than three sizes of canisters  10 , in which case insert  120  would provide more than three paths. 
     As an alternative to providing insert  120 , lower body  30  could itself serve as the cam cylinder for cam followers  65 A and  65 B. In such a case, longitudinal slots  124 A and  124 B, transitional slots  126 ,  128  and  132 , and terminal slots  134 ,  136  and  138  would be respectively be replaced by similarly configured longitudinal grooves, transitional grooves and terminal grooves located on inner lateral surface  34  of lower body  30 . 
     As a further alternative, insert  120  could be provided with longitudinal slots  124 A and  124 B but without transitional slots  126 ,  128 , and  132  and terminal slots  134 ,  136 , and  138 . Or, where insert  120  is not utilized, lower body  30  could be provided with longitudinal grooves but without transitional and terminal grooves. In such cases, some type of releasable latch or catch arrangement could be substituted such that upper body  60  would slide downwardly into lower body  60  and lock onto canister  10  at a vertical position dependent on the height of canister  10 . 
     The operation of measuring device  20  will now generally be described with particular reference to FIGS. 6-8. Referring to FIG. 7A, measuring device  20  is shown in its open position. Canister  10  has been loaded into an inner chamber  165  of measuring device  20  defined by the respective interiors of upper body  60  and lower body  30 . In the open position, the side port defined by respective cut-out sections  42 ,  72  and  122 A preferably has a large enough area to enable canister  10  to be loaded onto platform  90  in inner chamber  165 , although some degree of tilting of canister  10  is acceptable in order for valve stem  14 B to clear cut-out section  72  of upper body  60  and outer wall  92  of platform  90 . Once canister  10  has been loaded, upper body  60  is slid axially downwardly into lower body  30  and onto canister  10 . Upper body  60  is then rotated in the direction of transitional slots  126 A,  128 A or  132 A, of insert  120 , until measuring device  20  assumes the closed, locked position illustrated in FIG.  7 B. 
     Referring to FIG. 6, after measuring device  20  reaches its closed position, canister  10  is locked in place and the compressive forces imparted by disk spring  150  act to secure canister  10  in frictional contact with base  92 A and profile  92 B of platform  90 . Hence, in the closed position, rotation of handle  110  (and thus platform  90 ) causes canister  10  to rotate as well. 
     Referring to the detailed view of FIG. 8, an annular, chamfered section  74  of upper body  60  rests on canister shoulder  12 C when canister  10  is in its locked position. In addition, roller-ball tip  84 A of probe  84  is spring-biased into contact with annular region  14 D of top surface  14 C of valve cap  14 . Canister  10  is then measured by rotating handle  110  about longitudinal axis L. Rotation of handle  110  in turn rotates canister  10  with respect to probe  84 . If at any point during rotation top surface  14 C of valve cap  14  is not level, probe  84  will displace upwardly or downwardly. Transducer  80  registers changes in displacement of probe  84  as indications of deviations in the height of top surface  14 C of valve cap  14 . Excessive out-of-level measurements indicate problems with the crimping process employed during assembly of canister  10 . 
     It should be noted that before measuring device  20  is employed to take measurements of actual production-run canisters  10 , a similarly sized “calibration canister” can first be loaded into measuring device  20  in order to properly obtain a zero reference position for probe  84  of transducer  80 . Moreover, at some point before measurements of canister  10  are taken, handle  110  can initially be rotated to align hash marks  112 A with reference mark  54  to define a starting datum point for analysis. 
     As an alternative to taking measurements of canister  10  by rotating canister  10  with respect to probe  84 , probe  84  could be adapted to rotate with respect to canister  10 . In this alternative embodiment, mounting platform  90  would be fixedly disposed within lower body  30  and flanged portion  63  of upper body  60  would be rotatably mounted to upper body  60 . Thus, flanged portion  63  would take the form of a rotary member and serve as a substitute for handle  110 . Extension rod  89  could then be used as a handle to rotate transducer and thus probe  84 . This alternative, however, is less preferred as it renders display  82 A of transducer  80  more difficult to read since display  82 A would be moving while transducer  80  takes measurements. 
     Referring to FIGS. 9A-9C, the sequence for locking short-sized canister  10  into measuring device  20  is illustrated. For short canisters  10 , cam followers  65 A and  65 B take the first path described hereinabove. Accordingly, in FIG. 9A upper body  60  has begun its descent into lower body  30  in the general direction indicated by arrow B, and cam followers  65 A and  65 B are traveling in the portion of longitudinal slots  124 A and  124 B above transitional slots  126 ,  128  or  132 . In FIG. 9B, upper body  60  has been pushed further downwardly into lower body  30  to a point where chamfered section  74  has almost made contact with canister shoulder  12 C, a bottom end surface  76  of upper body  60  has almost made contact with a corresponding shoulder base  56  of lower body  30 , cam followers  65 A and  65 B are almost fully adjacent to their corresponding lower transitional slots  132 , and roller-ball tip  84 A of probe  84  has contacted or is about to contact top surface  14 C of valve cap  14 . 
     Referring to FIG. 9C, as upper body  60  is rotated or twisted, cam followers  65 A and  65 B travel along their corresponding lower transitional slots  132 , thereby forcing upper body  60  further downwardly onto canister  10 . A lower portion of upper body  60  has been removed in FIG. 9C in order to best show the position of cam follower  65 A. The twisting direction taken by cam followers  65 A and  65 B is generally indicated by arrow C. Disk spring  150  simultaneously begins to be compressed, thus pushing canister  10  downwardly and ensuring that canister  10  is properly seated on platform  90 . Cam followers  65 A and  65 B then enter their corresponding lower terminal slots  138  (not specifically shown in FIG.  9 C). Because lower terminal slots  138 A are angled slightly upwardly with respect to lower transitional slots  132  (see FIG. 5) and disk spring  150  maintains its compressive force on canister  10 , cam followers  65 A and  65 B (and accordingly canister  10  and measuring device  20 ) are locked in place in the closed position of measuring device  20 . 
     Referring to FIGS. 10A and 10B, a preferred embodiment of an in-line MDI valve alignment measuring system or station generally designated  150  is illustrated. Canister  10  travels along its assembly line by means of a movable member  152  of a conveying device in accordance with known technology. Measuring system  150  includes a transducer head  160  operatively situated by conventional means above movable member  152 . Transducer head  160  can be lowered toward canister  10  to be measured through the use of guide rods  162 . 
     In FIG. 10A, transducer head  160  includes a non-contacting transducer in the form of a laser micrometer generally designated  165 , which includes an emitter element  167  and a receiver element  169 . Laser micrometer  165  takes measurements of the distance from a reference point to top surface  14 C of valve cap  14  by directing a light beam from emitter element  167  toward top surface  14 C and receiving at receiver element  169  the resultant light beam reflected off top surface  14 C. It will be understood that an infrared transducer could be substituted for laser micrometer  165 . 
     In FIG. 10B, transducer head  160  includes an inductive-type distance transducer  170 . Inductive transducer  170  is threaded through a nut  172  into a blind counterbored opening  160 A in transducer head  160 , and includes electrical leads  174  to output a voltage signal proportional to the distance between inductive transducer  170  and top surface  14 C of valve cap  14 . 
     Referring to both FIGS. 10A and 10B, a plurality of measurements can be taken by axially rotating transducer head  160  with respect to canister  10 . This can be accomplished by mechanically linking transducer head  160  to a turntable  164  attached to a rotating shaft  166 . Alternatively, movable member  152  of the conveying device in FIGS. 10A or  10 B could take the form of a platform  152  rotatable about a shaft  154 . In this case, canister  10  could be loaded into the platform from the conveying device and held in place by a vacuum line  156 . Transducer  165  or  170  could remain stationary and take measurements while platform  152  rotates. 
     It will be understood that various details of the invention may be changed without departing from the scope of the invention. Furthermore, the foregoing description is for the purpose of illustration only, and not for the purpose of limitation--the invention being defined by the claims.