Two-part epoxy adhesive resins are well-known and consist of a fluid resin and a fluid hardener that are maintained separately prior to use and then are joined and mixed to create an adhesive material. The mixed material is initially in a fluid state and then cures or hardens.
Commercially available delivery systems for relatively small projects needing adhesion typically utilize an applicator comprising (1) a hand-held, two-chamber tube with one chamber containing the resin and the other chamber containing the hardener, and (2) a bifurcated, two-section, manually operated plunger that, when depressed, causes both the resin and the hardener to move within and from the associated chamber and to be dispensed from an associated nozzle at a depending end of each chamber such that the two fluids are moved outside the chambers and are adjacent to each other. When the resin and the hardener are thus dispensed, one mixes the two fluids, which become tacky and function as an adhesive. By placing objects in contact with the mixed fluids, the objects will adhere, and will permanently adhere once the mixed fluids cure or harden.
Commercially available delivery systems for relatively large projects operate in a similar manner; however, relatively large quantities of fluids are employed and electrically actuated, mechanical pumps are used to move the resin and the hardener from associated tanks or reservoirs. The two fluids are moved by the pumps through hoses and to a nozzle for dispensing onto a surface for adhesion. A drawback of these larger systems is that the fluids tend to gum up within the impellers or rotors of one or more of the pumps, especially when the system is unused for several hours, often to such a degree that the pumps fail to operate. Such pump failures cause wasteful down time on projects and usually result in the pump being discarded rather than repaired. Also, pump components such as clutches may fail. A further drawback of such systems is that the electrical systems may also fail, such as a blown fuse or a complete loss of electric power due to lightning strikes in the area, which may interrupt a project while the problem is being assessed and solved. Another drawback of such systems is that they typically operate at relatively high pressures (such as 350 psi), which place severe stress on system components, and present safety issues, or which require relatively heavy-duty, expensive components.