The present invention relates to dispensing devices and, more particularly, to dispensing devices of the type often employing dual component cartridges and dual actuating ejector rams for dispensing dual component materials which cannot be mixed until immediately prior to use. Typical examples of such materials are epoxy resin compositions which are mixed when used with a hardener component which causes subsequent curing of the resin. Viscous materials such as caulks and adhesives are also commonly dispensed from disposable cartridges of standard configuration and standard sizes used in conjunction with dual component dispensing devices which are designed to accept such cartridges.
The cartridges comprise a tubular cylindrical body containing material to be dispensed, a movable plunger at the rearward end of the body retaining the material within the body and providing the means for a dispensing device to apply dispensing pressure to the contents of the cartridges, and an integral or detachable dispensing nozzle at the other end of the body. Some of these materials are of different viscosities which create uneven ejection pressures on the ejection rams. Some of the materials are very thick and difficult to eject and require considerable ejection ram pressure, e.g., 1100 pounds or 2500 pounds of thrust. Alternatively, one or both of the dual component cartridges may contain a low viscosity material. Often the overall diameter of dual component cartridges differ.
The dual component dispensing devices available in the prior art suffer from drawbacks as will be described with reference to FIGS. 1 and 1A. Referring now to FIG. 1A, a prior art dual component dispensing gun is loaded with two cartridge assemblies A and B, each containing one component of a dual component material, each component having a different viscosity. In operation, the trigger C (FIG. 1) is pulled toward the hand grip D (FIG. 1) which causes a drive shaft E which is disposed through the drive mechanism to be incrementally advanced in a forward direction. Likewise, push rods F and G, connected to the drive shaft E, are incrementally advanced in a forward direction within the cartridge assemblies. The push rods F and G engage cup-shaped plungers Axe2x80x2 and Bxe2x80x2 forming a portion of the cartridges A and B and located within the cartridges at the rear portions thereof. Pressure exerted by the push rods F and G upon the plungers Axe2x80x2 and Bxe2x80x2 forces the components outwardly through a nozzle H. Although both push rods F and G apply equal force upon the plungers Axe2x80x2 and Bxe2x80x2, respectively, the push rod F actually travels at a slower rate of speed than the push rod G (and thus, travels less distance in the same amount of time as indicated by vertical line I) due to the fact that the component contained by cartridge A has a greater viscosity than the component contained by cartridge B. Likewise, the push rod G travels at a greater rate of speed than push rod F due to the lower viscosity of component contained by cartridge B (as indicated by vertical line J). Because the two push rods F and G travel at different rates of speed, they apply uneven forces on the dispensing device which results in a lateral flexing of the push rods F and G as indicated by lines K and L. Ultimately, the component of cartridge B will be completely dispensed before the dispensing of the component of cartridge A has been completed. In many cases, this lateral flexing is visually perceptible and usually adversely affects operation of the dispensing device which can result in improper mixing of the components. This drawback only worsens as greater dispensing pressure is required.
Further, as illustrated in FIG. 1, due to the fact that the push rods F and G are located above the drive shaft E and connected to the drive shaft at the rear portion thereof, pressure applied to the push rods F and G during dispensing results in an undesirable downward bending of the push rods F and G which adversely affects operation of the dispensing device. The downward bending, illustrated by line M in FIG. 1, only increases where increased dispensing pressures are required.
In addition, in the event dispensing material contained within the cartridges A and/or B should flow back behind either of the plungers Axe2x80x2 and Bxe2x80x2, the push rods F and G will become contaminated with dispensing material thus requiring replacement of these push rods. The foregoing problems of conventional prior art dispensing devices are addressed in the dispensing device of the present invention which substantially reduces any lateral or vertical flexing of push rods and also eliminates the other drawbacks mentioned above.
These and other objects of this invention are achieved by providing a device and method for dispensing flowable materials from a plurality of cartridge assemblies. Under the preferred embodiment, the device comprises a receptacle for carrying a plurality of cartridge assemblies therein. The cartridge assemblies each have a longitudinal axis and include a dispensing nozzle and an elongated tubular wall portion for containing a flowable material therein for dispensing. The wall portion of the cartridge assemblies is formed of a material that can be cut by a cutting surface. A drive mechanism is provided for moving an elongate drive rod in a direction parallel to the longitudinal axis. A web assembly is secured to the drive rod, the web assembly including a plurality of ejectors extending therefrom. Each ejector is arranged for reciprocal movement along the longitudinal axis within one of the cartridge assemblies between a forward ejecting direction to dispense the flowable material from within the cartridge assembly and a return direction. There is disposed on the web assembly at least one cutting surface for slicing the tubular side wall of the cartridge assembly as the ejector moves in the forward ejecting direction. In a variation of the preferred embodiment, the ejectors are circular and have substantially the same outer diameter.
In another variation of the preferred embodiment, the ejectors have differing overall diameters.
In another variation of the preferred embodiment, the dispensing device includes at least one cutting surface that is oriented at an angle relative to the wall portion of the cartridge assembly.
In another variation of the preferred embodiment, the web assembly is V-shaped and comprises two flanges, each flange comprising a pair of plates oriented parallel to each other and being spaced apart. Under this variation, a cutting surface is affixed between each pair of plates.
In another variation of the preferred embodiment, the cutting surface is affixed between the plates by welding.
In a second embodiment of the present invention, the cutting surface is affixed to the web assembly by means of a screw.
In a variation of the second embodiment, the ejectors have differing outer diameters and may be centrally mounted or mounted in an offset manner to the web assembly.
In a third embodiment of the present invention, the web assembly comprises a forward edge that has been formed into a cutting surface.
In a variation of the third embodiment, the ejectors have different outer diameters.
In another variation of the third embodiment, two cartridge assemblies are carried by the dispensing device and the single cutting surface is arranged for slicing the tubular side wall of both cartridge assemblies.
In a fourth embodiment of the present invention, the cutting surface is circular in shape and rotatably mounted to the flange assembly.