Patent Publication Number: US-6712245-B2

Title: Venting plunger for caulk cartridges

Description:
RELATED APPLICATION 
     Reference is made to my provisional application, Serial No.: 60/395,565 filed Jul. 15, 2002, now abandoned, to which a claim of priority is made. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to the field of caulking cartridges used for ejecting a caulking composition from a nozzle at a free end thereof, and more particularly to an improved plunger which is mechanically advanced by a lever on a caulking device to propel the caulking material. Devices of this general type are known in the art, and the invention relates to details of structure which provide improved operation. 
     Devices known in the art include a caulking cartridge which comprises a metallic tube having an ejecting nozzle at one end thereof. The tube is charged at an opposite end of caulking material following which the cartridge is closed by a movable plunger which is incrementally advanced by means on the caulking gun to eject a required amount of material through the nozzle. The initial insertion of the plunger entraps a quantity of air within the tube which must be compressed to transmit motion to the mass of caulking material. However, the air, if not released, tends to cause the upper surface of the caulking material in some areas to harden, making the advancement of the plunger difficult. 
     This problem has been recognized in the art. One attempted solution is the provision of small longitudinally-oriented grooves on the inner surface of the tube. This will allow atmospheric pressure to enter the tube from the free nozzle end of the cartridge, an undesirable result. 
     SUMMARY OF THE INVENTION 
     Briefly stated, the invention contemplates the provision of an improved plunger for use with a caulking tube having air venting means about the periphery thereof which is sufficiently small to permit the passage of air, but prevent the passage of caulking material therepast. This is accomplished by providing small longitudinally-oriented ribs spaced along the periphery having a width of approximately 0.020 inch, and a height of approximately 0.004 inch. Preferably the ribs are in spaced pairs providing a passage therebetween. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings, to which reference will be made in the specification, similar reference characters have been employed to designate corresponding parts throughout the several views. 
     FIG. 1 is a longitudinal section view of an embodiment of the invention. 
     FIG. 2 is a fragmentary enlarged sectional view corresponding to the right hand portion of FIG.  1 . 
     FIG. 3 is a side elevational view thereof. 
    
    
     DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENT 
     In accordance with the invention, the device generally indicated by reference character  10 , comprises a single molding of synthetic resinous material bounded by a peripheral edge  11 , having an upper edge  12  and a lower edge  13 . A cylindrical outer surface  14  mounts a plurality of pairs of longitudinal projections  16 - 17 , most conveniently spaced at 120 degree arcuate intervals. 
     An end wall  20  is of slightly arcuate configuration, including a frusto-conical vertical portion  21  and a horizontal portion  23  having arcuate reinforcing projections  24  and  25 . A centrally-disposed sleeve  26  selectively engages with the plunger advancing means on a caulking gun (not shown). An inner surface  27  engages the exposed end surface of caulking material disposed within the caulking tube. 
     Operation of the plunger will be apparent from a consideration of the drawings. Once inserted within the caulk holding tube (not shown), the end wall, which is of slightly bowed cross section, will tend to move to generally planar condition, thus exerting a radially-outward pressure which is transmitted to the peripheral wall. As the plunger is depressed, any air trapped within the tube will be vented under compression through the interstices formed between each pair of projections  16 - 17  to the atmosphere. This space is sufficiently narrow that the passage of caulking material will not occur. 
     Since the end wall is of slightly smaller diameter than that of peripheral wall  11 , insertion of the plunger is facilitated, and the entrapped air will be completely vented prior to initial use. 
     I wish it to be understood that it is not considered that the invention is limited to the practice details illustrated and described, for obvious modifications will occur to those skilled in the art to which the invention pertains.