Abstract:
A valve for an aerosol canister for containing medicaments is disclosed. The valve comprises a valve assembly, a ferrule for holding the valve assembly and a gasket for insertion into the ferrule. The ferrule has at least one ferrule interference surface and the gasket has at least one gasket interference surface, and the contact zone between the ferrule interference surface and the gasket interference surface comprises a plurality of relief portions. Preferably, the ferrule interference surface comprises a plurality of ferrule relief pockets and the gasket interference surface comprises a plurality of gasket relief pockets. Also disclosed is a method of manufacturing a valve for an aerosol canister.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to United Kingdom Application No. 1311034.1, filed Jun. 20, 2013, which is incorporated herein by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
       [0002]    The present specification relates to valves for aerosol containers, more particularly valves for aerosol containers for containing medicaments. The present specification also relates to aerosol containers having such valves fitted thereto and to methods for manufacturing such valves. 
         [0003]    Pressurized metered dose dispensers have been known for over 50 years, particularly inhalers for the treatment of asthma, but also for other diseases where the lung, throat or nasal passages are suitable sites for delivery of drugs. A formulation of drug in such a dispenser is typically either in the form of a suspension or a solution in a propellant system, depending on the solubility of the drug in the formulation. 
         [0004]    Medicinal aerosol formulations are often contained in a metal, plastic or glass vial or container equipped with a metered dose valve. The valve may be fitted to the body of the vial by crimping a ferrule, holding a valve assembly, against the body of the vial with an intermediate seal made of an elastomeric material compressed between the body and the ferrule. The intermediate seal can be in the form of a ferrule gasket placed and compressed between the top edge of the body of the vial and the opposing surface of the ferrule gasket, and/or it can be in the form of an O-ring placed around the body of the vial and compressed between the body of the vial and an annular flange of the valve ferrule. 
         [0005]    U.S. Pat. No. 3,556,357 relates to closures of aerosol containers of the kind having a valve with a tubular stem passed with clearance through an aperture in the container cap, the stem carrying at its outer end the conventional head and nozzle whereas its inner end is provided with a flange. Two further such designs are disclosed in United Kingdom Patent Nos. 1,336,379 and 2,077,229. 
       SUMMARY 
       [0006]    In some designs of valve, tolerance stack-up may occasionally lead to incorrectly seated or missing gaskets. Such a problem reduces efficiency and/or yield of production and can lead to higher costs and delays on the production line. There is therefore a need to provide for improved location and retention of gaskets in valves, especially during manufacture. 
         [0007]    In a first aspect the present invention accordingly provides a valve for an aerosol canister, the valve comprising a valve assembly, a ferrule for holding the valve assembly and a gasket for insertion in the ferrule, wherein the ferrule has at least one ferrule interference surface and the gasket has at least one gasket interference surface, and wherein the contact zone between the ferrule interference surface and the gasket interference surface comprises a plurality of relief portions. 
         [0008]    This is advantageous because the relief portions have surprisingly been found to maintain a good interference fit between the gasket and ferrule even with a reduction in average push-fit force, and to reduce the chances of gasket slippage or displacement or loss even when the dimensions of the gasket and/or ferrule are not exactly at their nominal values. 
         [0009]    Preferably, the ferrule interference surface comprises a plurality of ferrule relief pockets. 
         [0010]    Additionally or alternatively, preferably the gasket interference surface comprises a plurality of gasket relief pockets. 
         [0011]    Thus, in a second aspect the present invention provides a valve for an aerosol canister, the valve comprising a valve assembly, a ferrule for holding the valve assembly and a gasket for insertion into the ferrule, wherein the ferrule has at least one ferrule interference surface and the gasket has at least one gasket interference surface, and wherein the ferrule interference surface and/or the gasket interference surface comprise a plurality of relief pockets. 
         [0012]    The interference surface of the gasket may be either the inner interference surface (i.e. on the inside of an annular gasket), or the outer interference surface (i.e. on the outside of an annular gasket) or both. 
         [0013]    The interference surface of the ferrule may be either the inner interference surface (i.e. to contact the inside of an annular gasket), or the outer interference surface (i.e. to contact the outside of an annular gasket) or both. 
         [0014]    Usually, the gasket interference surface and/or the ferrule interference surface will be substantially cylindrical. 
         [0015]    Preferably, the relief portions will be distributed substantially evenly over the gasket interference surface. The number of relief pockets may be an even number (e.g. 6, 8, 10, 12, 14, 16, or 18) or an odd number (e.g. 5, 7, 9, 11, 13 or 15). It is preferred that there are five or more gasket relief pockets. 
         [0016]    It is preferred if the gasket relief pockets and/or the ferrule relief pockets, where applicable, are distributed substantially evenly on the gasket and/or ferrule interference surface. The number of gasket and/or ferrule relief pockets may be, independently of each other, an even number (e.g. 6, 8, 10, 12, 14 or 16) or an odd number (e.g. 5, 7, 9, 11, 13 or 15). It is preferred that there are five or more gasket and/or ferrule relief pockets. 
         [0017]    The profile of the relief pockets may be of generally any suitable shape, for example, (in plan view, and allowing for the curvature of the component) substantially square, substantially rectangular or shaped substantially as part of an oval or circle. From a side view the relief pockets may be of any suitable shape, but substantially square or substantially rectangular profiles are preferred. 
         [0018]    The invention is particularly advantageous where the valve is a metered dose aerosol valve. The valve is usually adapted for fitting to an aerosol container and the gasket is for sealing the valve ferrule to the aerosol container. 
         [0019]    The gasket may be made from any suitable elastomeric material. The gasket may therefore comprise a thermoset elastomer that may include one or more of thermoset ethylene-propylene-diene terpolymer (EPDM), acrylonitrile-butadiene copolymer (Nitrile rubber), isobutylene-isoprene copolymer (Butyl rubber), halogenated isobutylene-isoprene copolymer (e.g. Chlorobutyl rubber and Bromobutyl rubber), polychloroprene (Neoprene), and mixtures thereof, with EPDM, nitrile rubber and butyl rubber being more preferred, EPDM and nitrile rubber even more preferred and EPDM most preferred. Alternatively or additionally, the gasket may comprise one or more suitable thermoplastic elastomers including one or more of polyester rubbers, polyurethane rubbers, ethylene vinyl acetate rubber, styrene butadiene rubber, copolyester thermoplastic elastomers, copolyester ether thermoplastic elastomers, olefinic thermoplastic elastomers, mixture of inter-dispersed relative hard and relative soft domains of thermoplastics and elastomers (e.g. Santoprene), polyester amide thermoplastic elastomers, polyether amide thermoplastic elastomers, copolyamide thermoplastic elastomers and mixtures thereof. 
         [0020]    Generally, the valve assembly will comprise a helical spring, a seal and a valve stem, the valve stem and seal being in mutual sliding sealing engagement, the helical spring comprising a coil of elongate material for returning the valve stem to a rest position. 
         [0021]    The relief pockets will usually be recesses in the gasket interference surface or ferrule interference surface. 
         [0022]    Preferably, the ferrule relief pockets are recessed by between 0.01 and 5 mm from a substantially cylindrical ferrule interference surface, more preferably by between 0.02 and 2 mm, and most preferably by between 0.03 and 1.8 mm, or 0.1 mm to 1.5 mm. The most preferred ferrule recess is in the range 0.1 mm to 0.5 mm. 
         [0023]    Preferably, the gasket relief pockets are recessed by between 0.01 and 5 mm from a substantially cylindrical gasket interference surface, more preferably by between 0.02 and 2.5 mm, and most preferably by between 0.03 and 1.8 mm. 
         [0024]    The circumferential width of the ferrule and/or gasket relief pockets are independently selected to be in the range 0.5 mm to 7 mm, more preferably 1 mm to 5 mm and most preferably 1 mm to 4 mm. 
         [0025]    In a third aspect there is provided an aerosol container having fitted thereto a valve as in the first aspect. The aerosol canister may contain a medicament aerosol formulation. 
         [0026]    Medicinal aerosol formulations may comprise a medicament either in solution or as particles suspended in liquefied propellant(s), e.g. CFC propellant(s) or more usually non-CFC propellant(s) such as 1,1,1,2-tetrafluoroethane (HFA134a) and/or 1,1,1,2,3,3,3-heptafluoropropane (HFA227). If desired and/or deemed necessary, the formulation may comprise one or more other components, such as excipients, co-solvents, e.g. ethanol, and/or suspending aids (e.g. surfactants). Depending on the particular metered dose valve and/or filling system, medicament formulation may be filled into the pMDI either by cold-filling (in which chilled formulation is filled into the vial and subsequently the metered dose valve is fitted onto the vial) or by pressure filling (in which the metered dose valve is fitted onto the vial and then formulation is pressure filled through the valve into the vial). 
         [0027]    The medicament may be a drug, vaccine, DNA fragment, hormone or other treatment. The amount of medicament is typically determined by the required dose per puff (actuation) and by available valve sizes, which are typically around 25, 50 or 63 microlitres, but may be around 100 microlitres where particularly large doses are required. 
         [0028]    Suitable drugs include those for the treatment of respiratory disorders, e.g., bronchodilators, anti-inflammatories (e.g. corticosteroids), anti-allergies, anti-asthmatics, anti-histamines, and anti-cholinergic agents. Therapeutic proteins and peptides may be employed for delivery by inhalation. 
         [0029]    Exemplary drugs which may be employed for delivery by inhalation include but are not limited to: albuterol (salbutamol), terbutaline, ipratropium, oxitropium, tiotropium, aclidinium, glycopyrrolate, beclomethasone, flunisolide, budesonide, mometasone, ciclesonide, cromolyn sodium, nedocromil sodium, ketotifen, azelastine, ergotamine, cyclosporine, salmeterol, fluticasone, formoterol, procaterol, indacaterol, TA2005, vilanterol, olodaterol, milveterol, omalizumab, zileuton, insulin, pentamidine, calcitonin, leuprolide, alpha-1-antitrypsin, interferons, triamcinolone, and pharmaceutically acceptable salts and esters thereof for example albuterol sulfate, aclidinium bromide formoterol fumarate, salmeterol xinafoate, beclomethasone dipropionate, triamcinolone acetonide, fluticasone propionate, fluticasone furoate, vilanterol terfenetate, tiotropium bromide, leuprolide acetate and mometasone furoate. 
         [0030]    Medicinal aerosol formulations may comprise excipients other than surfactants or ethanol, such as a particulate bulking agent, which may be in micronized or submicron form. Examples of such excipients include lactose, sucrose, alanine and sodium sulphate. Other propellant components are possible, such as gases or liquids soluble in the HFAs, e.g. CO 2 . 
         [0031]    In a fourth aspect, the invention provides a method of manufacturing a valve for an aerosol canister, the valve comprising a valve assembly, a ferrule for holding the valve assembly and a gasket for insertion in the ferrule, the method comprising providing a ferrule, providing a gasket adapted to fit the ferrule, and inserting the gasket in the ferrule, wherein the ferrule has at least one ferrule interference surface and the gasket has at least one gasket interference surface, and wherein the contact zone between the ferrule interference surface and the gasket interference surface comprises a plurality of relief portions. Preferably, the ferrule interference surface and/or the gasket interference surface comprise a plurality of relief pockets. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0032]    So that the present specification may be more completely understood, reference is made to the accompanying drawings in which: 
           [0033]      FIG. 1  shows a cross-sectional view of a pressurised metered dose inhaler (pMDI). 
           [0034]      FIG. 2  shows an enlarged partial view of the inhaler shown in  FIG. 1 . 
           [0035]      FIG. 3 a    shows a side view of a ferrule for incorporation in valves of the invention. 
           [0036]      FIG. 3 b    shows a section on A-A of the ferrule of  FIG. 3   a.    
           [0037]      FIG. 3 c    shows a section on F-F of the ferrule of  FIG. 3   a.    
           [0038]      FIG. 4 a    shows a plan view of a first embodiment of a gasket for incorporation in valve assemblies of the invention. 
           [0039]      FIG. 4 b    shows a section on B-B of the gasket of  FIG. 4 a      
           [0040]      FIG. 5 a    shows a plan view of a second embodiment of a gasket for incorporation in valve assemblies of the invention. 
           [0041]      FIG. 5 b    shows a section on D-D of the gasket of  FIG. 5   a.    
           [0042]      FIG. 6  is a graph of the results of a load-extension test on a J. J. Lloyd function testing machine, showing the developed force as a function of distance traveled and also the corresponding reducing force upon retraction. 
       
    
    
     DETAILED DESCRIPTION 
       [0043]      FIG. 1  shows a pressurised metered dose inhaler (pMDI)  100  comprising a canister  10  including a metered dose-dispensing valve  2  mounted via a ferrule  11  onto an aerosol container or vial  1 .  FIG. 2  shows a detailed view of the lower part of the pMDI shown in  FIG. 1 . The container defines, in part, a formulation chamber  3  filled with medicinal inhalation formulation  4  and an actuator  5  including a mouthpiece  6  (in an alternative form, suitable for nasal drug delivery, the actuator may comprise a nosepiece rather than a mouthpiece). The canister  1  is placed within the actuator  5  by inserting the valve stem  14  of the valve  2 , which protrudes outside the ferrule  11 , into a support block  8  of the actuator  5 . The valve stem  14  has a dispensing passage  9  that allows for passage of substance from a metering chamber of the valve  2  out through the valve stem  14  and actuator mouthpiece  6  (or nosepiece) to the user. In operation, medicament formulation  4  can pass from the formulation chamber  3  into a pre-metering region  22  provided between the second valve body  20  housing and the first valve body  13  through an annular space  21  between a flange of the second valve body and the first valve body. To actuate (fire) the valve to deliver a dose of medicament formulation, the valve stem  14  is pushed inwardly relative to the aerosol container from its resting position shown in  FIGS. 1 and 2 , allowing formulation to pass from the metering chamber  12  through a side hole  23  in the valve stem  14  and through a stem outlet  24  out through an actuator nozzle  7  and then out to the patient. When the valve stem  14  is released, medicament formulation enters into the valve, in particular into the pre-metering chamber  22 , through the annular space  21  and thence from the pre-metering chamber  22  through a groove  25  in the valve stem  14  past the inner seal  16  into the metering chamber  12 . Because such valves retain the next dose of medication formulation in the metering chamber  12  between actuations, they are sometimes referred to as “retention valves”. 
         [0044]    A first valve body  13  defines in part a metering chamber  12 , a second valve body  20  defines in part a pre-metering region  22  and acts in this valve as a bottle emptier, a valve stem  14 , a biasing member in the form of a coil spring  15 , an inner seal  16 , an outer seal  17 , a ferrule  11  and a gasket  18 . A further seal may optionally be formed by an O-ring  19 . 
         [0045]      FIG. 3 a    shows a side view of a castellated ferrule  200  for incorporation into the valves of the invention. The ferrule  200  has a skirt  30  of cylindrical form. The skirt  30  is intended to be crimped on to the neck of a canister (not shown in  FIG. 3 ; see  FIG. 1 or 2 ). Above the skirt  30  (in the orientation shown in  FIG. 3 a   ), a valve portion  32  of smaller diameter is formed integrally with the skirt  30 . The valve portion  32  contains the valve stem opening  34  through which the valve stem of the valve is inserted when the valve is assembled. Between the skirt  30  and the valve portion  32 , the gasket portion  36  of the ferrule  200  has a number of recesses  38  stamped into the outer surface  37  of the gasket portion  36  and evenly spaced around the circumference of the ferrule  200 . 
         [0046]      FIGS. 3 b  and 3 c    show other perspectives of the castellated ferrule  200  shown in  FIG. 3 a   . The ferrule  200  is a hollow body with an outer seal volume  40  situated below the valve stem opening  34 . In the interior of the gasket portion  36 , there is a gasket volume  42  that is for holding and retaining a gasket. The gasket volume  42  is adapted to hold the gasket between the outer interference surface  44  and inner interference surface  46 . The recesses  38  stamped into the outer surface  37  of the gasket portion  36  form a castellated profile, giving relief pockets  48  on the outer interference surface  44 . When a gasket is inserted into the gasket volume  42  it is generally held in place by interference with the inner interference surface  46  and outer interference surface  44 . The relief pockets  48  reduce the push fit force to insert the gasket but improve retention of the gasket in the ferrule  200  thereby leading to important production advantages. The gaskets for insertion in the ferrule  200  will generally be annular and may be either standard or as illustrated in  FIG. 4 or 5 . 
         [0047]      FIGS. 4 a  and 4 b    illustrate a first embodiment of a castellated gasket  300  for use in a valve according to the invention. The gasket  300  is of generally annular form and the gasket material  50  is of ethylene propylene diene monomer (EPDM) although other elastomers with appropriate properties are also suitable. The inner surface of the gasket will form a gasket inner interference surface  57  and the outer surface of the gasket will form a gasket outer interference surface  55  when inserted into a ferrule. The ferrule (not shown in  FIGS. 4 a  and 4 b   ) may be either standard or may be shaped as a castellated ferrule  200  (e.g. as shown in  FIG. 3 ), in accordance with the present specification. The outer interference surface  55  has ten evenly spaced cut outs  53  of generally rectangular profile separated by protrusions  52  around its circumference. The cut outs  53  surprisingly improve retention of the gasket in the ferrule with important production advantages. 
         [0048]      FIGS. 5 a  and 5 b    illustrate a second embodiment of a pecked gasket  400  for use in a valve according to the invention. The gasket  400  is of generally annular form and the gasket material  150  is of ethylene propylene diene monomer (EPDM) although other elastomers with appropriate properties are also suitable. The inner surface of the gasket will form a gasket inner interference surface  157  and the outer surface of the gasket will form a gasket outer interference surface  155  when inserted into a ferrule. The ferrule (not shown in  FIGS. 5 a  and 5 b   ) may be either standard or may be shaped as a castellated ferrule  200  (e.g. as shown in  FIG. 3 ), in accordance with the present specification. The outer interference surface  155  has sixteen evenly spaced cut outs  153  of generally semi-circular profile separated by protrusions  152  around its circumference. The cut outs  153 , as in the castellated gasket embodiment of  FIG. 4 , surprisingly improve retention of the gasket in the ferrule with important production advantages. 
       EXAMPLES 
       [0049]    In the Examples, various ferrule/gasket sub-assemblies are assessed. The castellated ferrule as illustrated in  FIG. 3  was compared to a control ferrule, and pecked gaskets as illustrated in  FIG. 5  were compared with a control gasket without the cut-outs and hence with no relief pockets. 
       Assembly of the Valves 
       [0050]    Ferrule plus gasket subassemblies for valves of the type illustrated in  FIGS. 1 and 2  were assembled on a Haumiller production scale gasket insertion machine, which takes ferrules from a bowl feeder and in each one forces a gasket in place inside a groove designed to receive the gasket in the ferrule. The ferrule plus gasket subassemblies were inspected for gasket lifting immediately after assembly, i.e. for gaskets that were not properly located within ferrule grooves. 
         [0051]    Subsequently, assembled valves were circulated in a bowl feeder, normally used to supply components for valve assembly, for 1 hour±10 minutes. The circulation vibrates the valves and simulates the condition during aerosol filling when the valves are made ready for crimping onto aerosol vials. Valves were then inspected for gasket lifting. 
       Gasket Lifting Criteria 
       [0052]    In the ensuing tables, levels were used to characterise the gasket lifting as follows:
   Level 1 No lifting or creasing.   Level 1A No lifting or creasing, but the gasket inside diameter edge sits proud of the ferrule recess diameter.   Level 2 Creasing/slight lifting of the gasket, with the metal of the recess not visible underneath.   Level 3 Lifted gasket with the metal of the recess visible underneath.   Level 4 Missing gasket   
 
       Measurement of the Gasket Push Fit Force 
       [0058]    The force was measured on a Lloyd Instruments LRX Tensile/Compression Tester, fitted with a 1 kN load cell. A solid steel cylinder was manufactured to a diameter to just move freely within the outer interference surface of ferrules of valves to be tested. The cylinder was screwed into the load cell. A steel base was prepared with a central hole to accommodate the nose of the ferrule and valve stem, such that when a valve was inserted valve-down, the annular part of the ferrule that contains a gasket was directly supported by the base. 
         [0059]    A valve was placed valve stem down into the central hole of the base and a gasket placed lightly in the ferrule recess region. 
         [0060]    The Lloyd tester was operated by programme in compression mode directing the steel cylinder at the gasket at 20 mm per minute (333 μm per s), until a force of 200N developed, whereupon the steel cylinder was retracted at 20 mm per minute (333 μm per s). A trace was produced indicating the developed force as a function of distance traveled by the steel cylinder, and the corresponding reducing force upon retraction, as illustrated in  FIG. 6 . The force to push fit was determined by taking the intercept of the retraction trace with the axis of zero force, then looking up the developing force corresponding to the same extension. 
       Example 1 
     Ferrule Comparison 
       [0061]    Standard gaskets at different sizes within usual manufacturing tolerance were used, with the aim of investigating specific interference fit levels. The Mean Total Interference values were chosen to straddle the usual range of Mean Total Interference values of standard valves. 
         [0062]    The ‘Mean Total Interference’ is calculated as (Gasket Mean outer interference surface diameter (x)−Ferrule Mean outer interference surface diameter (y))+(Ferrule Mean inner interference surface diameter (w)−Gasket Mean inner interference surface diameter (v)). 
         [0063]    The recesses  38  in the Example ferrule were approximately 0.23 mm “deep” (radially) and approximately 3.00 mm “wide” (circumferentially). There were ten such recesses in each Example ferrule. 
         [0064]    Table 1 shows the individual mean measurements and the calculated total interference. Table 2A shows the results of visual inspection immediately upon assembly. Table 2B shows the results of visual inspection after bowl feeder trials. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
             
             
               
                   
                   
               
               
                   
                   
                   
                 Inter- 
               
               
                   
                   
                   
                 ference 
               
               
                   
                 Ferrule 
                 Gasket 
                 Mean 
               
             
          
           
               
                   
                   
                 w 
                 y 
                 x 
                 v 
                 Total 
               
               
                 Lot 
                 Description 
                 (mm) 
                 (mm) 
                 (mm) 
                 (mm) 
                 (mm) 
               
               
                   
               
             
          
           
               
                 1 
                 Control ferrule 
                 15.761 
                 19.677 
                 19.812 
                 15.621 
                 0.275 
               
               
                   
                 High interference 
               
               
                 2 
                 Control ferrule 
                 15.761 
                 19.677 
                 19.710 
                 15.723 
                 0.071 
               
               
                   
                 Low interference 
               
               
                 3 
                 Example ferrule 
                 15.748 
                 19.685 
                 19.812 
                 15.621 
                 0.254 
               
               
                   
                 High interference 
               
               
                 4 
                 Example ferrule 
                 15.756 
                 19.685 
                 19.710 
                 15.723 
                 0.058 
               
               
                   
                 Low interference 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 2A 
               
             
             
               
                   
                   
               
               
                   
                 Visual % (immediate post Haumiller) 
               
             
          
           
               
                 Lot 
                 Quantity 
                 Description 
                 Level 1 
                 Level 1A 
                 Level 2 
                 Level 3 
                 Level 4 
               
               
                   
               
             
          
           
               
                 1 
                 315 
                 Control ferrule High 
                 83.8 
                 15.9 
                 0.3 
                 0 
                 0 
               
               
                   
                   
                 interference 
               
               
                 2 
                 315 
                 Control ferrule Low 
                 83.8 
                 0 
                 14.6 
                 1.6 
                 0 
               
               
                   
                   
                 interference 
               
               
                 3 
                 315 
                 Example ferrule High 
                 100 
                 0 
                 0 
                 0 
                 0 
               
               
                   
                   
                 interference 
               
               
                 4 
                 315 
                 Example ferrule Low 
                 100 
                 0 
                 0 
                 0 
                 0 
               
               
                   
                   
                 interference 
               
               
                   
               
             
          
         
       
     
         [0000]                                                                                                TABLE 2B                           Visual % (post bowl feeder)            Lot   Quantity   Description   Level 1   Level 1A   Level 2   Level 3   Level 4                    1   315   Control ferrule High   73.3   26.4   0.3   0   0               interference       2   315   Control ferrule Low   78.4   1.6   16.8   3.2   0               interference       3   315   Example ferrule High   100   0   0   0   0               interference       4   315   Example ferrule Low   100   0   0   0   0               interference                    
Visual inspection results for the exemplary ferrules showed excellent gasket fit results compared with controls, both immediately after assembly and after bowl feeder trials. Push fit forces are shown in Table 3.
 
         [0000]                                                                                TABLE 3                           Lloyd Gasket Push Fit           Test: Force in Newtons            Lot   Description   Min   Max   Mean   Range                    1   Control ferrule High interference   70   80.1   75.7   10.1       2   Control ferrule Low interference   51.9   86.6   65.9   34.7       3   Example ferrule High interference   29.8   44.5   37.3   14.7       4   Example ferrule Low interference   29.3   52.5   43   23.2                    
The forces shown in Table 3 for the exemplary valves were lower than for the controls, independently of the extent of interference.
 
       Example 2 
     Gasket Comparison 
       [0065]    Standard ferrules at different sizes within usual manufacturing tolerance were used, with the aim of investigating specific interference fit levels. 
         [0066]    The Mean Total Interference values were chosen to straddle the usual range of Mean Total Interference values of standard valves. 
         [0067]    The Mean Total Interference was calculated as above. 
         [0068]    The cut outs  153  in the Example pecked gasket were approximately semi-cylindrical, with a “depth” (radially) of approximately 1.00 mm and hence an “opening width” (circumferentially) of approximately 2.00 mm. There were sixteen such cut outs in each Example pecked gasket. 
         [0069]    Table 4 shows the individual mean measurements and the calculated Mean Total Interference. Table 5A shows the results of visual inspection immediately upon assembly. 
         [0070]    Table 5B shows the results of visual inspection after bowl feeder trials. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 4 
               
             
             
               
                   
                   
               
               
                   
                   
                   
                 Interference 
               
               
                   
                 Ferrule 
                 Gasket 
                 Mean  
               
             
          
           
               
                   
                   
                 w 
                 y 
                 x 
                 v 
                 Total 
               
               
                 Lot 
                 Description 
                 (mm) 
                 (mm) 
                 (mm) 
                 (mm) 
                 (mm) 
               
               
                   
               
             
          
           
               
                 5 
                 Pecked 
                 15.718 
                 19.715 
                 19.685 
                 15.596 
                 0.092 
               
               
                   
                 gasket Low 
               
               
                   
                 interference 
               
               
                 6 
                 Pecked  
                 15.761 
                 19.677 
                 19.685 
                 15.596 
                 0.173 
               
               
                   
                 gasket High 
               
               
                   
                 interference 
               
               
                 7 
                 Control gasket 
                 15.672 
                 19.736 
                 19.812 
                 15.621 
                 0.127 
               
               
                   
                 Recommended 
               
               
                   
                 interference 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 5A 
               
             
             
               
                   
                   
               
               
                   
                 Visual % (immediate post Haumiller) 
               
             
          
           
               
                 Lot 
                 Quantity 
                 Description 
                 Level 1 
                 Level 1A 
                 Level 2 
                 Level 3 
                 Level 4 
               
               
                   
               
             
          
           
               
                 5 
                 112 
                 Pecked gasket Low 
                 99 
                 1 
                 0 
                 0 
                 0 
               
               
                   
                   
                 interference 
               
               
                 6 
                 115 
                 Pecked gasket High 
                 100 
                 0 
                 0 
                 0 
                 0 
               
               
                   
                   
                 interference 
               
               
                 7 
                 354 
                 Control gasket 
                 54.5 
                 0 
                 41.5 
                 4.0 
                 0 
               
               
                   
                   
                 Recommended interference 
               
               
                   
               
             
          
         
       
     
         [0000]                                                                                                TABLE 5B                           Visual % (post bowl feeder)            Lot   Quantity   Description    Level 1   Level 1A   Level 2   Level 3   Level 4                    5   112   Pecked gasket Low   99   1   0   0   0               interference       6   115   Pecked gasket High   100   0   0   0   0               interference       7   354   Control gasket   54.5   0   40.1   5.4   0               Recommended interference                    
Visual inspection results for the exemplary gaskets showed much improved gasket fit results compared with controls, both immediately after assembly and after bowl feeder trials. Push fit forces are shown in Table 6.
 
         [0000]    
       
         
               
               
             
               
               
               
               
               
               
             
           
               
                   
                 TABLE 6 
               
             
             
               
                   
                   
               
               
                   
                 Lloyd Gasket Push Fit 
               
               
                   
                 Test: Force in Newtons 
               
             
          
           
               
                 Lot 
                 Description 
                 Min 
                 Max 
                 Mean 
                 Range 
               
               
                   
               
               
                 5 
                 Pecked gasket Low interference 
                 48.9 
                 60.4 
                 55.7 
                 11.5 
               
               
                 6 
                 Pecked gasket High interference 
                 61.8 
                 90.2 
                 74.3 
                 28.4 
               
               
                 7 
                 Control gasket Recommended 
                 22.3 
                 64.2 
                 45.3 
                 41.9 
               
               
                   
                 interference