Abstract:
Ion mobility spectrometer. The spectrometer includes an enclosure for receiving a sample therewithin and an electron beam window admits an electron beam into the enclosure to ionize the sample in an ionization region. A shutter grid is spaced apart from the ionization region and means are provided for sample ion preconcentration upstream of the shutter grid. The ion preconcentration is effective to reduce space charge resulting in a lowered threshold detection level.

Description:
REFERENCE TO RELATED APPLICATIONS  
       [0001]    The present application claims priority to and the benefit of U.S. Provisional Application No. 60/549,408, filed Mar. 1, 2004 and entitled A Single Main Beam Bicycle and A Separable Joint, the content of which is hereby incorporated by reference. 
     
     TECHNICAL FIELD 
       [0002]    The invention relates generally to separable joints and more particularly to a joint capable of joining ends of two beams. 
       BACKGROUND 
       [0003]    In the design and assembly of structures, joints are typically used to secure beams to one another. There is often a desire to join beams axially so as to form a longer, overall beam. Several methods for joining beams have been used, such as the use of plates on each side of the ends of the beam, or locating a rod or dowel axially within the ends of the beams. 
         [0004]    However, beam joints frequently require significant amounts of additional material, increasing the weight or dimensions of the beam joint. Beam joints requiring assembly of multiple, separate components for aligning the beams may be difficult to assemble. Examples include beam joints using plates with numerous bolts. Such conventional beam joints may also be difficult to disassemble. 
       SUMMARY 
       [0005]    The present invention seeks to address various needs in the art to provide a beam joint that can be readily assembled and disassembled, while providing a rigid joint. Various embodiments of the present invention are also directed to avoid a need for substantial amounts of additional, bulky parts, such as side plates bolted along the sides of the beams being joined. In some applications, the present invention can be located within the outer contours of the beams being joined, allowing for a consistent external diameter or cross-sectional dimensions. 
         [0006]    In one illustrative embodiment, a beam joint is provided having a first portion with a first protruding element and a second portion having a second protruding element configured to mate with the first protruding element. A transverse stabilizer is provided on the first portion, with a transverse stabilizer receptor for receiving the transverse stabilizer, provided on the second portion. The first protruding element can have a first beveled face and the second protruding element can have a second beveled face, the first beveled face is configured for mating with the second beveled face. Also, the beveled faces can extend across a full cross-section of their respective portion. A fastener may also be provided transversally in the first and second portion to retain the portions in a mating configuration. 
         [0007]    In one embodiment, the beam joint is used in a main beam of a bicycle, although the invention is not so limited. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0008]    The invention will be apparent from the description herein and the accompanying drawings, in which like reference characters refer to the same parts throughout the different views. 
           [0009]      FIG. 1  is an exploded view of a separable joint according to an embodiment of the invention; 
           [0010]      FIG. 2  is a reverse view of a second portion of the separable joint of  FIG. 2 ; 
           [0011]      FIG. 3  is an exploded view of a separable joint according to an embodiment of the invention; 
           [0012]      FIG. 4  is a reverse view of a second portion of the separable joint of  FIG. 4 ; 
           [0013]      FIG. 5  is an exploded view of a separable joint according to an embodiment of the invention; 
           [0014]      FIG. 6  is a reverse view of a second portion of the separable joint of  FIG. 6 ; and 
           [0015]      FIG. 7  is a side view of a separable joint used in a bicycle according to an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION  
       [0016]    The present invention provides a separable joint for use in joining beams. As used herein, the term “beam” is used to represent a wide variety of structural members. Examples include, but are not limited to, I-beams, tubes, poles, shafts, T-beams and rods. Applications can also vary widely and can include, but are not limited to, bicycles, structural members for buildings, bridges, towers, tents or any other application involving the coupling of ends of two members to form a longer overall member. 
         [0017]    Examples of separable joints according to illustrative embodiments of the invention are provided in  FIGS. 1-6 . With reference to  FIG. 1 , a separable joint  100 A is illustrated in exploded form. By way of example, the separable joint  100 A is implemented in a six-sided beam or post. According to the illustrative embodiment of  FIGS. 1 and 2 , the separable joint  100 A is provided with a first portion  120  that is separable from a second portion  160 .  FIG. 2  provides a reverse view of the second portion  160 . Each of the first and second portions  120 ,  160  has a protruding element that mates, interacts, or interlocks, with the protruding element of the other portion. The first portion  120  has a first protruding element  130 , and the second portion  160  has a second protruding element  170 . 
         [0018]    The first and second protruding elements  130 ,  160  are provided with first and second end faces  126 ,  166 , first and second bevel faces  132 ,  172  and optionally with first and second protruding element tip faces  131 ,  171 . As illustrated by way of example, the first and second bevel faces  132 ,  172  may extend across a full cross section of their respective first and second portions  120 ,  160 . Optional first and second side faces  124 ,  164  extend to first and second inner faces  127 ,  167 . The protruding element tip faces  131 ,  171  and/or the first and second inner faces  127 ,  167  may optionally be of a very small width or be omitted altogether. 
         [0019]    The first inner face  127  is provided with a transverse stabilizer  125  and the second end face  166  is provided with a transverse stabilizer receptor  165 . The location of the transverse stabilizer  125  and transverse stabilizer receptor  165  are illustrated by way of example only, as they can be located in a wide variety of positions in order to maintain the transverse alignment of the beam joint. An optional fastener hole  168  is provided in the second portion  160  in which to locate a fastener that can extend into or through the first portion  120  to further secure the first portion  120  to the second portion  160 . The fastener hole  168  may also be located in a wide variety of positions. If the fastener extends into the first portion  120 , the hole (not shown) in the first portion  120  to receive the fastener may be configured to retain the fastener in the hole, coupled to the first portion  120 . In one example, threads are provided in a hole in the first portion  120  such that a bolt provided through the fastener hole  168  in the second portion  160  may be secured to the first portion  120  by the use of the threads. 
         [0020]    In another example, a quick-release cam assembly can be used on an end of a rod. For example, one end of the rod could have a ball or other enlarged cross-section that can be secured to a suitable structure at or near one end of the fastener hole  168 . The opposing end of the rod could have a cam with a handle to enable the cam to be rotated to axially tighten against the ends of the fastener hole  168 , thereby securing the first portion  130  to the second portion  160 . Other examples of structures to secure the first portion  130  to the second portion  160  can include an outer sleeve or clamp assembly. 
         [0021]    In operation, the separable joint  100 A is configured to receive tensile, compression and shear loads, individually and in combination. The first portion  120  and second portion  160  are joined by a lateral or transverse motion to bring the first and second bevel faces  132 ,  172  into contact with each other and locate the transverse stabilizer  125  in the transverse stabilizer receptor  165 . The first and second bevel faces  132 ,  172  contact each other to inhibit separation of the first and second inner faces  127 ,  167  from the first and second end faces  126 ,  166 . By inhibiting separation of the first inner face  127  from the second end face  166 , the transverse stabilizer  125  remains coupled to the transverse stabilizer receptor  165 . The transverse stabilizer  125  and the transverse stabilizer receptor  165  maintain transverse alignment of the first and second portions  120 ,  160  by preventing the first and second portions  120 ,  160  from sliding past each other. In one embodiment, the first protruding element  130  and second protruding element  160  are configured to release from one another by movement that is opposite to the direction of movement for joining the first and second portions  120 ,  160  and is perpendicular to a direction of movement inhibited by the transverse stabilizer. The release movement may also be perpendicular to a longitudinal axis of a beam structure formed by the beam joint, e.g. the axis of the beam formed by the joining of an end of one beam to the end of another beam. 
         [0022]    The optional fastener is configured to inhibit separation of the first and second bevel faces  132 ,  172 . The fastener, if used, may, in some applications, not be subjected to substantial forces, as the fastener may be configured to not receive axial forces, but simply prevent a transverse or lateral force from separating the first and second bevel faces  132 ,  172 . The majority of the forces applied to the beam joint are translated from one beam to the other by the protruding portions and the various mating bevel faces and mating inner and outer faces. Even in cases in which a fastener is not used, the transverse stabilizer  125  and the transverse stabilizer receptor  165  maintain transverse alignment of the beam joint. 
         [0023]    To separate the separable joint  100 A, any fastener used may be removed from the fastener hole  168  and is at least removed from engagement of the first portion  120 . The separable joint  100 A may then be separated by laterally separating the first and second portions  120 ,  160 , sliding the transverse stabilizer  125  out from within the transverse stabilizer receptor  165 . 
         [0024]    The beam and/or separable joint may be formed of a wide variety of materials. Examples include metals, such as, for example, aluminum, magnesium, titanium, steel and others, plastics or wood. The first and second portions  120 ,  160  of the beam joint may be integrally formed from, with or on to, welded to, or otherwise secured to their respective beams. A wide variety of manufacturing methods for making the beam joint of the present invention will be apparent to one of skill in the art upon review of this description and are intended to be within the scope of the invention. In one example, the first and/or second portions may be hollowed out or formed with internal strengthening members to maintain the desired structural configuration. Such configurations can reduce overall weight and materials while maintaining the desired strength of the joint. 
         [0025]    In one application, the transverse stabilizer  125  is formed of aluminum and welded at the first inner face  127 . Optionally, the transverse stabilizer  125  may be formed of a high friction material to aid in retaining the transverse stabilizer  125  within the transverse stabilizer receptor  165 . Examples of such high friction material can include rubber or plastics. Surface treatments may also be used to aid in retaining the transverse stabilizer  125  within the transverse stabilizer receptor  165 . In such a case, the transverse stabilizer  125  and/or the transverse stabilizer receptor  165  may be provided with a high-friction surface treatment, such as, for example, a roughened surface, to seek to maintain the transverse stabilizer  125  within the transverse stabilizer receptor  165 . 
         [0026]      FIGS. 3 and 5  provide additional examples of separable joints  100 B,  100 C in tubes or beams of other cross-sections. The separable joints  100 B,  100 C have analogous components to those discussed above in relation to the separable joint  100 A of  FIG. 1 .  FIGS. 4 and 6  provide reverse views of the second portions  160  of the separable joints  100 B,  100 C of  FIGS. 3 and 5 , respectively. 
         [0027]      FIG. 7  illustrates a bicycle  200  including a separable joint  100  according to an example embodiment of the invention. The bicycle  200  includes a single main tube  210  having a portion  212  extending beyond a head tube  240 . Optionally, the main tube  210  may form a storage compartment in the portion  212  extending beyond the head tube  240 . A support tube  230  may be provided between a seat tube  220  and the main tube  210 . The support tube  230  may provide additional support to the seat tube  220  and may be used as a handle to lift the bicycle  200 . Optionally, a contoured hand grip (not shown) may be provided on the support tube  230  to aid in gripping the support tube  230 . Optionally, the seat tube  220  may be oversized in thickness. Examples of ranges of external diameters of the seat tube  220  include at least 45 millimeters and/or a range of 45 to 65 millimeters. In one embodiment, the seat tube  220  has an external diameter of 54 millimeters. 
         [0028]    The bicycle  200  may optionally use the separable joint  100  along the main tube  210 . The separable joint  100  may be located as illustrated in  FIG. 7 , or may be located anywhere along the main tube  210 . The separable joint  100  can allow the bicycle to be separated into two pieces to aid in transport or storage of the bicycle  200 . By providing an ability to separate the bicycle  200  into two pieces, the bicycle  200  may be more easily stored in a trunk of a car, a closet or an office, than a bicycle that merely provides a folding capability. 
         [0029]    The present invention has been described by way of example, and modifications and variations of the described embodiments will suggest themselves to skilled artisans in this field without departing from the spirit of the invention. Aspects and characteristics of the above-described embodiments may be used in combination. 
         [0030]    The described embodiments are merely illustrative and should not be considered restrictive in any way. The scope of the invention is to be measured by the appended claims, rather than the preceding description, and all variations and equivalents that fall within the range of the claims are intended to be embraced therein.