BACKGROUND OF INVENTION The art is replete with various types and sizes of pneumatic and other powered, positive displacement fluid-dispensing apparatus for a wide variety of industrial, specialized, and home applications, including, for example, viscous fluid cartridge dispensers of the type disclosed in the earlier US Patent No. of the present inventor herein and of common assignee Where hand-held application guns are desirable, moreover, it is tedious and tiring to operate successive manually or pneumatic-triggered"shots"in jolts.

It has also been proposed to provide microprocessor-controlled and smoother electrically driven pumps, as described; for example, on p. 1025-6 of the Cole-Parmer Instrument Company instruments catalog of 1993-1994, for single or multiple-component fluid dispensing ; and, where hand-held operation is desired, for providing electric motor driven rods for expelling fluids from cartridges or syringes, with a hand-held apparatus, as, for example, in US patents 5,630,527 and 5,765,722.

In dispensers of the prior art using electric motor drives, however, the motor has generally been mounted in-line with the drive rod (s) or screw, that actuates ptungers to dispense fluid from cartridges or syringes or the like, with the rod or screw often passing axially through the motor structure itself, as for example, in the last-named references.

For hand-held operation with such electric motor-drive rod in-line structures, the hand holds the apparatus longitudinally like a pencil or soldering iron. There are important applications, however, as in use by a dentist within a patient's mouth, and in other applications, as well, where such in-line holding of the apparatus blocks the view required to apply and control the dispensed fluid by the operator, such as the dentist.

Similarly, where the operator must have an unobstructed view of the dispensing within an enclosure or the like, such hand-held operation again blocks satisfactory viewing.

It is to the solution of these and other problems more particularly with hand-held fluid dispensing guns and the like, accordingly that the present invention is primarily directe.

The invention is also an improvement over pneumatic systems that require an air line. Because the invention provides for cordless operation via a battery pack, the system is portable and therefore useful in environments where running an air line or power cord is prohibitive.

OBJECTS OF THE INVENTION It is an object of the present invention, therefore, to provide a new and improved method of and apparatus for fluid dispensing, and more particularly, though not exclusively, for hand-held operation, and with smooth and easy electric motor powering, that shall not be subject to the above and other disadvantages of prior devices, but, to the contrary, shall provide a vastly improved electrically powered user-friendly small multiple or single fluid dispenser, with instantaneously responsive dispensing and cut-ofy.

A further object is to provide a novel hand-held dispensing gun that is particularly useful for dental and other confined area usage, and the like, with open view for the operator tosee and control the dispensing.

Another object is to lower the center-of-gravity of the gun for more facile hand use by incorporating the electric motor in the handle, transversely depending from the barrel.

Other and further objects will be explained hereinafter and are more particularly delineated in the appended claims.

SUMMARY In summary, however, from one of its important aspects, the invention embraces an electrically powered gun for dispensing fluid materials having, in combination, a fluid- containing longitudinally extending cartridge chamber having an inlet sealed by a piston plug and an orificed outlet ; a longitudinally extending and moveable rack mounted in-line with the cartridge chamber and provided with a terminal push pad surface adjacent the cartridge chamber piston plug ; an electric drive motor mounted transversely of the rack with its drive shaft extending orthogonal to the rack and coupled by beveled gears and a pinion to drive the rack, longitudinally forward towards the cartridge chamber upon energizing the motor in order to engage the push pad surface with the piston plug and push the piston plug into the cartridge chamber to dispense the fluid through the cartridge chamber outlet.

Preferred and best mode designs and construction and method of operation are later described in detail.

DRAWINGS The. invention will now be described in connection with the accompanying drawings, Fig. I of which is an isometric view, partly sectionalized, illustrating a hand gun dispenser designed in accordance with a preferred embodiment of the invention, Fig. 2 is a similar view of the external housing containing the apparatus of Fig. I ; and Fig. 3 is a fragmentary isometric of the gear drive section of the gun of Figs. l and 2, illustrating the release button mechanism.

PREFERRED EMBODIMENTS OF INVENTION As shown in Figs. 1 and 2, a longitudinally extending cartridge chamber I contains the material to be dispensed (as in a pair of side-by-side cartridges for multiple materials) and receives at its inlet, a piston plug or plunger 2, Fig. 1, which seals the cartridge or barrel chamber, and, when pushed longitudinally to the left in Fig. 1, forces the material in the cartridge to an orificed outiet 3 at the end (left hand, in Fig. 1, and right hand in Fig. 2). This pushing is effected in response to the operation of a longitudinally extending in-line rack and pinion type pusher assembly 4-5-6. The cartridge chamber 1 serves as the forward part of the dispensing gun barrel 13, Fig. 2, with the rack and pinion assembly occupying the rearward part of the gun barrez té cartridge chamber is provided with an inlet collar 1'that is traversely locked into a mounting slot 16 at the front of the barrel housing 13, Fig. 2.

In preferred form, the pinion 5 is provided with a beveled gear portion 6 (shown disposed in a vertical plane), driven by another beveled gear 7 (disposed in a horizontal plane) attached to the shaft 8 of a high torque electric motor 9, Fig. I. The shaft is an integral parl of the motor and extends vertically transversely orthogonally to the barrel 1 within the handle 14 therebelow, Fig. 2. As the motor shaft turns, the bevel gear 7 turns with it and through the action of the pinion 5, turns the bevel gear 6 attached to the longitudinal pinion 5, thus driving the pusher assembly rack 4 longitudinally. This causes terminal push pad (s) 2'at the end of the rack (s), to engage against the piston plug (s) 2 for expelling material out of the orificed end 3 of the cartridge system 1. The beveled gear 6 is pressed into engagement with the beveled gear 7 by a spring washer 11, Fig. 3. During the forward pushing of the assembly 4 under the control of the high torque motor 9, a spring 10, Fig.. 1, connected at one end to the pusher assembly and, at its other end, to the gun housing 13, is stretched, attempting to pull the pusher assembly back to its original position.

Once the cartridge chamber is emptied to a desired degree, the user, by pushing retract button 12, Figs. 2 and 3, disengages gears 6 and 7, freeing the pinion assembly and enabling the tensioned or stretched spring 10 to retract or spring-return the pusher assembly back to such original starting position The cartridge chamber I can then be then detachably transversely removed from its mounting slot 16 in the forward part of the barrel housing 13, and is replaced by another fluid-filled cartridge chamber.

One of the novel features of the invention resides in locating the motor and its shaft and drive gear in the handle 14, depending transversely at right angles below the longitudinally extending gun barrel portion 13 that encases the pinion, rack and cartridge chamber assembly, and not in-line as in prior art devices, such as, for example, those of the earlier cited patents. This allows the user, such as a dentist or other user, in gripping and operating the handle 14, to have a clear unobstructed view of the area of dispensing, as distinguihed from the blocking of the line-of-sight by the user's hand, as in prior in- line constructions. The design of the invention, moreover, through enabling a pinion system to drive the pusher rack assembly instead of straight-forward pistons, greatly facilitates disengagement from the motor to allow the rack system to snap back to its starting position, thereby speeding up the change of cartridge chambers. Such rapid change of cartridge chambers is particularly critical where fast-setting materials are dispensed. If, for example, enough material has not been dispensed when a cartridge chamber is emptied, the very rapid exchange of the empty cartridge chamber for a new fluid-filled cartridge chamber before the dispensed materials has set or hardened (in seconds), is essential. The right angle or orthogonal depending handle location for the motor, moreover, permits a lower center of gravity, making it easier for the operator to hold the handle and orient the gun, and enabling a smaller and more compact unit.

In preferred form, the rack and pinion combination with its pair of parallel rack arms and pusher pads 2', is injection molded in a single U-shaped piece. And, particularly where multiple materials are to be dispensed (resins, catalysts, etc.), there can be several versions for different ratios of material dispensing. The use of different-sized piston heads and/or different diameter cartridges, including different pre-manufactured combinations thereof, can achieve various desired ratios (1: 1,2 : 1, 4 : 1,10: 1, etc.).

In order to operate the gun, the user inserts cartridge chamber I into the housing ; 13 at the forward slot 16. The cartridge chamber aligns when it is dropped into the slot, seating the collar 1'therein. At the end 3 of the cartridge chamber, a static mixer 15 is provided, Fig. 2, for mixing the materials dispensed through small orifices O (shown dotted in Fi, S3.2) at the outlet end 3 of the cartridge chamber 1. In order to dispense, the user operates the trigger T in the handle 14 which then activates a switch (not shown) to turn on the motor 9. The motor then drives the mechanism as previously described to cause the cartridge material to be expelled into the static mixer 15 which mixes the compounds in the two sides of the cartridge container and ejects the mixed materials through the terminal nozzle N. At the bottom of the handle 14, furthermore, a compartment C may be provided that may contain batteries, if desired, and a connector C'is provided on the back of the battery compartment C otherwise enabling a wall mount to a transformer to bring power into the unit. The power may be varied in conventional manner, as by a speed control dial on the gun (not shown), to control the motor speed, enabling slow down when dispensing over more complex patterns, and speed up when fast performance is required.

The hand-held gun of the invention, (or optionally counter top or wall mount use and with optional battery or external powering), for the dispensing of two-component materials and the like, thus provides for easy finger trigger operation of electrically powered, motor-driven positive-displacement material dispensing, and with the release of the trigger immediately cutting off the force applied to the dispensing pistons--all as contrasted from pneumatic systems of less accuracy, having variability caused by waiting for air pressure to build up or evacuate from a pneumatic cylinder. With the rack and pinion construction of the invention, moreover, when the operator releases the trigger (switch), the unit automatically inherently retracts the push pads just slightly--causing a pressure release and fluid"suck-back"that eliminates dripping and enables sharp dispensing cut-off The high torque electric motor of the invention, indeed, enables working with some of the highest viscosity material components, even up to 2+ million cps. This provides for operation over a wide range of choices of materials.

Further modifications will also occur to those skilled in this art, and such are considered to fall within the spirit and scope of the invention as defined in the appended claims.