Abstract:
A blow gun with an extensible wand includes a barrel for receiving and storing the wand. The wand passes through an inner collar and an outer collar, the inner collar mounted to the barrel and the outer collar eccentrically rotatable upon the inner collar. Rotation of the outer collar affects alignment of the bore of the outer collar with the bore of the inner collar. When the misalignment of the bores is increased, the wand is locked in a selected extension from the barrel.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from copending provisional patent application entitled “BLOW GUN WITH EXTENSIBLE WAND”, Ser. No. 60/443,055 filed Jan. 28, 2003. The disclosure of provisional patent application Ser. No. 60/443,055 is hereby incorporated in its entirety. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable 
     BACKGROUND OF THE INVENTION 
     The present invention pertains to compressed air blow guns. A blow gun to direct compressed air is a common tool used in factories, workshops and around trucks and other vehicles. Blow guns are frequently used around large truck tractors for the occasional need to use compressed air to expel debris and dust from a truck trailer or truck cab or sleeper and for other uses, as well as to inflate tires when the blow gun is equipped with an inflation chuck. The blow gun is coupled to an air hose coupled to a supply of compressed air which may be connected to the compressed air system of the truck tractor. 
     Adjustability of the length of the wand is a desirable feature in order to make the blow gun more versatile. An improvement for the standard fixed wand blow gun is shown in U.S. Pat. No. 5,832,974 to Jou which shows a blow gun with an adjustable wand. The prior art blow gun allows the wand to be adjusted by use of a threaded sleeve which urges clamping fingers into abutment with the outside of the wand of the blow gun. Adjustment of the extension of the wand requires the loosening of the threaded sleeve to a point which releases the clamping fingers and the retightening of the sleeve when the desired wand extension is made. 
     SUMMARY OF THE INVENTION 
     The present invention provides a blow gun with an extensible wand. Extension or retraction of the wand of the blow gun is accomplished by releasing the wand by rotation of a collar less than one half turn in either direction. The invention includes a handle having a trigger lever which opens a valve to permit compressed air from a source hose coupled to the handle to pass through the handle into an elongate wand on the end of which a nozzle may be mounted or alternatively a tire inflation chuck member may be mounted. The handle includes a barrel which serves as a storage housing for the wand when it is retracted. The wand through which compressed air may pass is adjustable in length by sliding it inwardly or outwardly longitudinally from the barrel of the handle. The wand may be extended to a desired length and locked into the particular extension position by use of an outer collar which is eccentrically rotatable upon an inner collar. The inner collar has a first section and an externally threaded extension which extends longitudinally from the first section. The extension is not coaxial with the first section but a longitudinal bore through the inner collar is coaxial with the first section and therefore is offset from the axis of the extension. The bore through the first section is internally threaded and sized to mount to the threads on the end of the barrel while the bore through the extension is smooth and is sized to permit the wand to be slid through it. The outer collar includes a threaded bore to receive the external threads of the extension of the inner collar. The threaded bore does not extend through the outer collar but rather longitudinally joins a smaller bore which is sized larger than the outer diameter of the wand. The axis of the smaller bore is slightly displaced from but parallel to the axis of the threaded bore of the outer collar. A ridge is formed longitudinally on the exterior of the outer collar to provide a lever to easily rotate the outer collar on the inner collar and to provide an indexing means. 
     Rotation of the outer collar less than one half of a turn will cause the bore of the outer collar to move such that the bore of the inner collar is no longer in registry with the small bore of the outer collar. Hence the outer collar forces the wand against the bore in the extension of the inner collar and thereby locks the wand in its then longitudinal position. 
     It is an object of the invention to provide a versatile blow gun which includes a wand which can quickly and simply be extended or retracted when released by less than a half turn of a collar surrounding the wand. 
     It is a further object of the invention to provide a blow gun with a variable length wand which may be extended or retracted without removing the wand from the handle of the blowgun. 
     It is also an object of the invention to provide an improved blow gun which allows for extension or retraction of the wand thereof without the use of numerous clamping parts mounted to the handle of the blow gun. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
     FIG. 1 is a front elevation of the invention with the wand in a retracted position. 
     FIG. 2 is an exploded view in perspective of the barrel and wand assembly of the blow gun invention. 
     FIG. 3 is a cross section of the barrel assembly of the invention taken along its longitudinal axis. 
     FIG. 4 is a cross section of the inner collar of the barrel assembly of the invention. 
     FIG. 5 is a top plan view of the inner collar of FIG.  3 . 
     FIG. 6 is a cross section of the outer collar of the barrel assembly of FIG.  1 . 
     FIG. 7 is a top plan view of the outer collar of the barrel assembly of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The assembled blow gun invention is illustrated in FIG. 1 with wand  18  in a retracted, released position so that wand  18  may be extended. Blow gun  8  comprises a handle  14  which includes intake port  50  and contains an internal actuable valve to selectively allow compressed air to pass through handle  14  and through barrel  12  and wand  18  and to be expressed from nozzle  58 . The internal valve of the handle is opened by movement of trigger  52  towards handle  14  in a conventional manner. A hook  54  is formed on handle  14  to provide a structure for suspending handle  14 . Barrel  12  has inner collar  16  mounted thereto with outer collar  20  mounted to inner collar  16 . The ridge  84  of outer collar  20  is aligned with protrusion  72  of inner collar  16  indicating that outer collar  20  is positioned such that wand  18  is free to be adjusted. 
     Now referring also to FIG. 2, barrel assembly  10  is shown in exploded view. Elongate hollow barrel  12  is mountable at its first end  22  to the handle  14  by conventional screw thread means or by other means such as bayonet mounting. Opposing second end  24  of barrel  12  includes external screw threads  26  for receiving inner collar  16 . Wand  18  is selectively slidably receivable within barrel  12  in a longitudinal fashion. Outer collar  20  is receivable upon externally threaded distal end  30  of inner collar  16 . Inner collar  16  is receivable at its proximal end  32  upon threads  26  of barrel  12 . Inner collar  16  is securely mounted to barrel  12  while outer collar  20  is manually rotatable over a limited range relative to inner collar  16 . 
     Large O-ring  34  is receivable within bore  36  of inner collar  16  to provide a seal between barrel  12  and inner collar  16 . Ring seals  40 ,  42  are slidably received around wand  18  to provide a seal around it. Wand  18  is provided with enlarged shoulder  44  at its proximal end  38 . Shoulder  44  functions as a stop against ring seals  40 ,  42  when wand  18  is maximally extended from barrel  12 . Wand  18  is provided with longitudinal bore  56  therethrough terminating with nozzle  58 . 
     Referring now additionally to FIG. 3, the assembled barrel assembly  10  is shown in longitudinal cross section with wand  18  at an intermediate extension from barrel  12 . Barrel  12  comprises longitudinal bore  47  which includes enlarged counter bore  48  adjacent second end  24  thereof. Large elastomeric O-ring  34  is positioned at the proximal end  28  of threads  26  such that inner collar  16  is sealed to barrel  12 . Semi-rigid ring seal  40  and elastomeric ring seal  42  surround wand  18  and are retained in a gap  46  formed by enlarged counter bore  48  of barrel  12 . Semi-rigid ring seal  40  is preferably made from nylon. Inner collar  16  is mounted securely upon screw threads of barrel  12  and outer collar  20  is in place on extension  60  of inner collar  16 . 
     Referring now also to FIGS. 4 and 5, it can be observed that inner collar  16  comprises first section  60  and includes extension  62  joined integrally to first section  60 . Preferably inner collar  16  will be formed from nylon or another rigid polymer or of metal. Inner collar  16  comprises internal threaded bore  64  in first section  60  thereof which is communicative with tapered passageway  68  which interconnects smooth bore  70  of extension  62  to threaded bore  64 . Smooth bore  70  is sized to allow wand  18  to slide snugly yet easily therealong and is coaxial with threaded bore  64  which is sized to receive second end  24  of barrel  12 . It can be seen in FIGS. 4 and 5 that smooth bore  70  is coaxial with first section  60  of inner collar  16  while extension  62  is offset on first section  60  such that it is not centered on first section  60 . In the preferred embodiment, the offset of axis A—A of extension  62  from the centerline D—D of first section  60  is approximately 0.040 inches. 
     Extension  62  is provided with external screw threads  66  therealong. A protrusion  72  is formed on the periphery of first section  60  of inner collar  16  to allow indexing of the outer collar  20  therewith. First section  60  is preferably textured on its outer surfaces. 
     Referring now to FIGS. 6 and 7, details of outer collar  20  may be visualized. Outer collar  20  is preferably constructed of nylon of another rigid polymer or of metal, and comprises internal threaded bore  78  opening at proximal end  74  of outer collar  20 , and smooth bore  80  opening at distal end  76  of outer collar  20 . The exterior of outer collar  20  is multi-sided, comprising segments  82  which facilitate manual rotation of outer collar  20  relative to inner collar  16 . The periphery of outer collar  20  also includes longitudinal ridge  84  which is formed on outer collar  20  to provide indexing means and is oriented on outer collar  20  such that when ridge  84  is aligned with protrusion  72  of inner collar  16 , the smooth bore  80  of outer collar is in registry with smooth bore  70  of inner collar  16 . Specifically, the entire area of smooth bore  70  of inner collar  16  is within, but not centered in, the area of smooth bore  80  when ridge  84  is aligned with protrusion  72 . When outer collar  20  is rotated such that ridge  84  is not aligned with protrusion  72 , at least some portion of smooth bore  70  is not in registry with smooth bore  80  of outer collar  20 . It should be understood that the centerline B—B of smooth bore  80  of outer collar  20  is parallel to but slightly offset from the centerline C—C of outer collar  20 . In the preferred embodiment, the offset is in the approximate range of 0.012 to 0.016 inches, preferably about 0.014 inches. Therefore, when outer collar  20  is rotated such that ridge  84  is out of longitudinal alignment with protrusion  72  of inner collar  16 , smooth bore  80  of outer collar  20  is offset by an increasing distance from smooth bore  70  of inner collar  16 . As outer collar  20  is rotated, smooth bore  80  thereof applies side force to wand  18  and forces it against a side of smooth bore  70  of inner collar  16 . 
     In the preferred embodiment, the smooth bore  80  of outer collar  20  is slightly larger than the smooth bore  70  of the inner collar  16 . Preferably, the diameter of smooth bore  80  is 0.290±0.002 inches and the diameter of smooth bore  70  is 0.243±0.002 inches. The diameter of the wand  18  is preferably approximately 0.236 inches and wand  18  therefore slides snugly but without interference within inner collar  16 . 
     When outer collar  20  is rotated to a position where ridge  84  thereof is aligned with protrusion  72  of inner collar  16 , smooth bore  70  is in registry with but not centered on smooth bore  80  of outer collar  20 . When outer collar  20  is rotated away from the position in which ridge  84  is aligned with protrusion  72 , shear force is applied to wand  18  from misalignment of smooth bore  70  with smooth bore  80 . 
     The amount of rotation of outer collar  20  needed to sufficiently offset smooth bore  80  from smooth bore  70  is approximately one quarter turn, in order for adequate shear force to be applied along wand  18  to bind it and thereby to restrain longitudinal movement of wand  18  in relation to barrel  12 . By rotating outer collar  20  into alignment of ridge  84  thereof with protrusion  72  of inner collar  16 , the axis of smooth bore  80  of outer collar  20  is oriented such that its axis B—B is in closest proximity with the axis of smooth bore  70  of inner collar  16  and smooth bore  70  is in registry with smooth bore  80  of outer collar  20 . In that disposition, wand  18  may be moved longitudinally into a desired position, whereupon outer collar  20  may then be rotated to sufficiently bind wand  18  into a temporarily fixed extended position.