Abstract:
A measuring device for measuring the thread start distance of a thread formed on an outer surface of a container finish is provided. The measuring device includes a base having a first surface for receiving a rim of a container finish, a support member, a gauge, and a counterweight to balance the measuring device on the finish. The support member is movably attached to the base and adjacent the first surface. A side surface of the support element is in contact with the container finish. The gauge is attached to the base and a gauge actuator having a roller contact member is operatively associated with the gauge. The gauge actuator measures the distance between the rim of the container finish and a thread start point of the thread of the container finish, S-dimension, as the gauge actuator moves along an upper base line of the thread.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to measuring devices and, more particularly, to a device for measuring an S-dimension of container finishes. 
     2. Description of the Related Art 
     In the manufacture of containers, certain dimensions are required to be within predetermined tolerance limits in order for the containers to function properly. In particular, the upper surface of the container, commonly known as the finish, must be maintained within certain manufacturing tolerances in order to provide adequate cap retention for a liquid tight seal to be formed between the container finish and the container cap. 
     Variations in the dimensions of containers, particularly plastic containers, may occur during molding or trimming operations due to many factors, including differences in the molds used to form the containers, shrinkage of the containers after molding, materials used, curing temperatures, and trimming operations. 
     In order to determine whether produced containers, such as bottles, are within predetermined dimensional tolerances, generally a sampling of the bottles being produced is measured to determine actual dimensions. This is especially true for the finish (i.e., neck portion) of the bottles. For bottles which will hold fluids, including consumer products such as detergents and bleaches, it is important that the S-dimension (i.e., start of thread dimension) is within predetermined dimensional tolerances so that a bottle cap will be retained properly on the finish and leaks will be prevented. The S-dimension is defined as the distance between the top of the sealing surface and the top of the thread or the uppermost location where a thread can extend as it is extended around the finish. The S-dimension is measured from the minor diameter of the thread or the base of the thread where the thread adjoins the outer wall of the finish. 
     The S-dimension of a container finish can be determined by manual measurement with a caliper. However, such measurements will include inaccuracies which vary depending on the expertise of a particular user. The inaccuracies occur due to the manual placement of the caliper, variations in the manual force applied to the caliper, and the caliper blades cutting into the soft material of the bottle finish, such as when the bottle is made of a blown thermoplastic. If the calipers are tilted just a slight amount, the reading will fluctuate. Therefore, the measurements are very difficult to repeat. 
     As an alternative to manual measurement with a caliper, container finishes may also be measured by an optical comparator. The optical comparator takes an enlarged shadow-graph of the bottle finish to provide a highly accurate measurement of the finish diameter. However, optical comparators are quite expensive and are generally not available at the location where the bottles are made. Therefore, when using an optical comparator, bottles often must be shipped to a laboratory for measurement, providing a very delayed determination of dimensional tolerances. As a result, a large number of reject bottles may be made before the error is corrected by adjustments to the blow molding and/or trimming processes. 
     In view of the above drawbacks of the known methods for measuring S-dimension of a container finish, it would be desirable to provide a measuring device for accurately measuring the S-dimension of a container finish rapidly and with minimal user error. 
     SUMMARY OF THE INVENTION 
     In one aspect of the present invention, a measuring device for measuring the thread start distance of a thread formed on an outer surface of a first container finish includes a base comprising a first surface for receiving a rim of the first container finish, a support member movably attached to the base and adjacent the first surface such that a side surface of the support member is in contact with the first container finish, a gauge attached to the base, and a gauge actuator operatively associated with the gauge. The gauge actuator measures a distance between the rim of the first container finish and a thread start point of the thread of the container finish as the gauge actuator moves along an upper base line of the thread. Specifically, the distance between the rim of the first container finish and a thread start point is the thread start distance of the first container finish. The measuring device further includes a counterweight attached to the base to balance the measuring device on the first container finish. 
     In another aspect of the present invention, a process for measuring the thread start distance of a thread formed on an outer surface of a container finish includes the steps of positioning a first surface of a measuring device on an upper end of the container finish, moving a support member of the measuring device in contact with a side wall of the container finish, contacting a gauge actuator with an upper base line of the thread wherein the gauge actuator is operatively connected to a gauge having a display; and moving the gauge actuator along the upper base line of the thread so as to measure a vertical distance between a thread start point and the rim of the container finish. 
     These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic view of a fluid container having a finish portion; 
     FIG. 2A is a detailed schematic view of the finish portion shown in FIG. 1; 
     FIG. 2B is a top view of the finish portion shown in FIG. 2A; 
     FIG. 3A is a side view of the gauge system of the present invention that is mounted on a bottle finish for measuring the S-distance; 
     FIG. 3B is a detailed schematic view of the gauge actuator of the present invention; 
     FIG. 3C is a cross-sectional view of the gauge system shown in FIG. 3A; 
     FIG. 4 is a bottom view of the gauge system of the present invention shown in FIG. 3A; and 
     FIG. 5 is a perspective view of the gauge system of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made to the drawings wherein like numerals refer to like parts throughout. FIG. 1 illustrates an exemplary plastic container  100 , such as a bottle, to hold fluids such as detergent or bleach, or the like. The bottle may be manufactured by combining a first half  102  and a second half  104  through a molding part line  106  using well-known processes in the art of container manufacturing. In the preferred embodiment, the bottle may be made of high-density polyethylene. The bottle  100  may comprise a top portion  108  with a bottom portion  110 , and a body  112  of the bottle  100  is configured to retain fluids. A finish portion  114  is formed as an opening shaped as a neck or a short tube where the fluids are filled into or dispensed out of the bottle  100 . 
     As shown in FIG. 2A, the finish portion  114  of the bottle  100  may be integrally connected to the body  112  through a shoulder portion  116  or shelf at a lower end  118  of the finish  114 . An outer circumferential side wall  120  extends between the lower end  118  and an upper end  122  of the finish  114 . On the outer circumferential side wall  120 , the bottle finish  114  may have threads  124  for retaining a cap (not shown). In this embodiment, the threads  124  are defined by an upper surface  126  and a lower surface  128 . The threads  124  project outwardly and extend along a spiral path around the finish  114 . Further, the threads  124  extend generally, but not necessarily, between the upper and lower end  118  and  122  of the finish  114 . The upper surface  126  of the threads  124  may adjoin the side wall  120  under an obtuse angle and along an upper base line  130 . Similarly, the lower surface  128  may adjoin the side wall  120  along a lower base line  132 . The upper base line  130  terminates at a thread start point  134  which forms the uppermost end of the thread  124  as in the manner shown in FIG.  2 A. In this embodiment, the thread start point  134  is the first reference feature of an S-dimension  135 . 
     As illustrated in FIG. 2B, in a top view of the bottle  100 , the finish  114  may comprise an upper surface  136  or rim and inner circumferential side wall  138  defining a finish opening  140 . In this embodiment, the upper surface  136  forms a second reference feature of the S-dimension  135 . Accordingly, in this embodiment the S-dimension is the vertical distance between the thread start point  134  and the upper surface  136  of the finish  114 . As previously mentioned, for containers which will hold fluids, including consumer products such as detergents and bleaches, it is important that the S-dimension of the container be within predetermined dimensional tolerances so that a cap will be retained properly on the finish and leaks will be prevented. Therefore, the S-dimension of the bottles must be routinely measured to determine whether the distance  135  between the upper surface  136  and the thread start point  134  is in predetermined manufacturing limits. A gauge system  200  of the present invention provides an effective tool to facilitate this measurement process. 
     FIGS. 3A and 3B show the gauge system  200  of the present invention which is placed on the finish portion  114  of the bottle  100  during the measurement process. The gauge system  200  of the present invention may comprise a base  202 , a gauge  204 , and a counterweight  206 . The counterweight  206  comprises a cylindrical weight member that allows the system  200  to be balanced on the finish portion  114 . The base  202  comprises a first side  208 , a second side  210 , a top surface  212  and a bottom surface  214 . The counterweight  206  is attached to and extends from the second side  210  on which the gauge  204  is positioned. In this embodiment, the second side  210  of the base  202  is comprised of an L-bracket having a first arm member  216  perpendicularly attached to a second arm member  218 . The L-bracket  210  is secured to the upper surface  212  of the base  202  through the second arm member  218  such that an upper surface  220  of the first arm member  216  is substantially parallel to the upper surface  212  of the base  202 . 
     The gauge system  200  of the present invention can conveniently be custom manufactured for measuring the S-dimensions of various bottle sizes with differing finish opening diameters. In this embodiment, the gauge system  200  is adapted to operate on bottles having 33 and 38 millimeter finish diameters (FIG.  5 ). The gauge system may weight about 900 grams. Exemplary dimensions may be 7″ length and 2.75″ width. The base  202  may have a 1″ height, and the overall height of the gauge (including top of gauge  204 ) may be 6″. All machined pieces made from anodized aluminum except support member  242  made from delrin plastic, and the thumb screw is made of brass. 
     Referring to FIGS. 3A and 3B, during the measuring process, a first region  222  of the bottom surface  214  is placed on the finish surface  136  of the finish  114 . A gauge actuator  224  of the gauge  204  is then extended to contact the upper base line  130  of the threads  124 , and next the gauge system  200  is rotated towards the thread start point  134  to record the S-dimension. As the gauge system  200  is rotated, the gauge  204  records the distance between the upper base line  130  and the finish surface  136  based on the vertical displacement of the gauge actuator  224 . 
     As illustrated in FIG. 3A, the gauge  204  is placed on the upper surface  220  of the first arm member  216  and comprises a front side  226  having a digital display  228 , and control buttons  230  and  232  to control the gauge  204 . The control buttons  230  and  232  may serve to perform a variety of functions to control the gauge  204 , such as turning on and turning off the gauge  204 , setting the zero readout, as well as changing the measurement mode between different units, for example between millimeters and inches. The gauge  204  may have a memory to hold the height measurements as it is rotated. However, measurements may be read off the digital display  228  by a user as well. The gauge  204  may be available from the Fred V Fowler Co, Newton, Mass. and sold under the brand name Ultra Digit Mark V. 
     As shown in FIG. 2B in detail and in FIG. 3B in cross-section, the gauge actuator  224  may comprise a gauge rod  236  extending through a hole  238  formed in the body of the first arm member  216  of the L-bracket  210 , and a contact member  240 , preferably a roller member, having a roller surface  242  to engage or contact the upper base line  130  of the bottle  100 , as in the manner shown in FIGS. 3A-3C. The roller member  240  is movably attached to a first end of the gauge rod  236  using any one of the well known attachment methods in the art. The rotation axis of the roller member  240  is preferably perpendicular to the gauge rod  236 . The second end of the gauge rod  236  has a tip  244  for manually controlling the vertical position of the gauge rod  236 . As an example, the roller may be sized to have diameter of approximately ⅜″ and a width of {fraction (5/32)}″. The rod  236  may have a diameter of {fraction (5/32)}″. The rod and the roller may be made of hardened and ground stainless steel. 
     Referring now to FIGS. 3A,  3 B, and  3 C, the first side  208  of the base  202  comprises an inner cavity  246  to movably retain a support member  248  on a cavity floor  250 . The cavity floor  250  is a lateral extension of the bottom surface  214  and is in the plane of the bottom surface  214 . During the calibration of the gauge system  200 , the support member  248  is contacted with the threads  124  on the finish  114  thereby confining the finish  114  between the roller member  240  and the support member  248 . This, in turn, prevents lateral movement of the gauge system  200  but allows rotational movement of the gauge system  200  during the measurements. As will be described in detail below, the support member  248  may be moved into a first position to permit the gauge system  200  to operate on a 38 millimeter finish or it may be moved into a second position to permit the gauge system  200  to operate on a 33 millimeter finish. 
     As it is moved in the cavity  246  and on the cavity floor  250 , the support member  248  moves along a button  252  or a thumb nut which is placed on the top surface  212  of the base  202 . The thumb nut  252  holds the support member  248  at the predetermined positions by tightening the thumb nut  252 . The thumb nut  252  is connected to the support member  248  by a pin  254 . The pin  254  is placed through a second hole  256  formed through the body of the base  204 . The second hole  256  may be a rectangular hole allowing the button  252  to switch between the two predetermined positions. As will be described below, the support member  248  can be moved between the predetermined positions by rotating an adjustment screw  258  and hence moving the support member  248  between these predetermined positions. As mentioned, once the position is selected, the thumb nut  252  may be temporarily locked at that position by tightening the thumb nut  252 . 
     As shown in FIG. 4 in a bottom view, the base  202  is surrounded by a rectangular-U shaped side wall  260  or lip projecting perpendicularly from the bottom surface  214  and extending along an outer wall  262  of the first side  208  of the base  202 . The support member  248  is generally rectangular in shape and in engagement with the correspondingly shaped side wall  260 . Depending on the diameter of the finish being tested, the support member  248  may be laterally moved in the cavity  246  in a first direction  264  and in a second direction  266  by moving the adjustment screw  258  (FIGS. 3A,  3 C and  4 ). The adjustment screw  258  may comprise a threaded shaft  268  and a knob section  272 . The threaded shaft  268  is placed through a hole  270  formed in a rear wall portion  274  of the side wall  260  and engages with a threaded hole  276  formed in a rear end  278  of the support member  248 . Depending on the direction of the rotation, the support member  248  moves in the first direction  264  and the second direction  266 . When the support member  248  moves in the first direction  264  and into the first position as shown with dashed lines, it contacts the rear wall portion  274  of the side wall. The thread pitch on the threaded shaft is finer than most adjustment screws, which makes the positioning of the support member  248  more precise. 
     A front end  280  of the support member  248  comprises a V-shaped recess  282  having side walls  284  to contact the finish  114  when the first area  222  of the gauge  200  is placed on top of the finish  114 . In this respect, when the larger diameter finish is measured (i.e., the finish diameter of 38 millimeters), the support member  248  is moved in the first direction  264  to provide sufficient space on the first region  222 . Accordingly, when the smaller diameter finish is measured (i.e., finish diameter of 33 millimeters), the support member  248  is moved in the second direction  266  to provide enough space on the first region  222  for the finish. In addition, through the side walls  284  the support member establishes two-point contact with the finish which also improves stability of the gauge system  200 . 
     The calibration and measurement of the S-dimension with the gauge system  200  may be exemplified with reference to FIG.  5 . As shown, a user may grasp the entire gauge system  200  and place it on the bottle finish  114  as in the manner described above. Then, the calibration of the gauge  204  is initiated by turning it on by the on/off button  230 . Next, the gauge  204  is placed on a substantially flat reference surface (not shown) and the roller surface  242  is contacted with the reference surface. The gauge  204  is zeroed using the zeroing button  230  while holding the roller  240  against the flat reference surface. After the calibration step, the measurement process is initiated. During the measurements, the base  202  can be gripped between the thumb and the middle finger while the ring finger is used to rotate the knob  270  permitting one handed operation. Referring back to FIGS. 2A and 2B, accordingly, the knob  270  of the adjustment screw  258  is rotated and the support member is positioned for the desired finish diameter, in this example, 33 millimeters. The gauge system  200  is then placed on top of the finish  114  as in the manner described above and aligned such that the roller  240  rests at the edge of the upper surface  236  of the finish  114 . Then, the knob  270  is slowly rotated until the roller  240  slides on the side wall down to the upper base line  130 . In order to obtain accurate S-distance measurements, it is important that the roller be placed on the upper base line  130 . The finer thread pitch of the adjustment screw  258  advantageously facilitates this adjustment. At this point, the gauge system  200  is rotated so that the roller  140  rolls up to the thread start point  134 . The lowest reading displayed on the digital display  228  is recorded as the S-dimension  135 . Upon completing the measurements, the on/off button  230  is pressed and the gauge system  200  is turned off. The gauge system may have a measurement range of 0-1″ with 0.00005″ resolution, 0.0002″ accuracy and 0.0001″ repeatability. 
     It should be understood, of course, that the foregoing relates to preferred embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims.