1. An instrument for softening and extruding dental impression wax or compound and other thermoplastic materials which are normally in relatively solid, nonflowable state at room temperature, said instrument comprising:
2. An instrument in accordance with claim 1, wherein:
3. An instrument in accordance with claim 1, wherein:
4. An instrument in accordance with claim 1, wherein:
5. An instrument in accordance with claim 1, wherein:
6. An instrument in accordance with claim 1, wherein:
7. An instrument in accordance with claim 6, wherein:
8. An instrument in accordance with claim 7, wherein:
9. An instrument in accordance with claim 8, wherein:
10. An instrument for softening and extruding dental impression wax or compound and other thermoplastic materials which are normally in relatively solid, nonflowable state at room temperature, said instrument comprising:
11. An instrument in accordance with claim 10, wherein:
BACKGROUND OF THE INVENTION
1. Field of the Invention
Specifically, the dental procedure for making molding wax impressions in the mouth. Generally, metered dispensing of heat-softened thermoplastic materials in other procedures and fields.
2. Description of the Prior Art
The closest prior art known to applicant consists of the following U.S. patents:
1,751,129 Cocks 2,086,462 Bost 2,982,443 Ellis 3,228,566 Knox 3,439,839 Schumann 3,443,059 Spencer 3,522,654 Schoelz
Of these prior art patents, Bost U.S. Pat. No. 2,086,462, Knox U.S. Pat. No. 3,228,566 and Schoelz U.S. Pat. No. 3,522,654 deal with the specific procedure which is the primary concern of this patent application, to wit: the making of dental wax impressions. However, they make use of conventional sticks of dental impression wax, they apply direct heat to soften the wax, and they then apply a mechanical force directly to the softened wax to extrude it. These patents leave unanswered questions concerning methods of cleaning the instruments in which such sticks of dental wax are processed and dispensed, and concerning methods of assuring delivery of sterile or sterilized wax into the mouth.
There appear to be no substantial advantages in the use of the wax dispensing instruments disclosed in Bost, Knox and Schoelz over the time-honored method of softening a stick of dental wax over a flame and then manually applying the softened wax either directly into the mouth or into a molding form which is subsequently placed in the mouth. It does not appear that the Bost, Knox and Schoelz instruments have been widely adopted, if at all, by dental practitioners.
SUMMARY OF THE INVENTION
The present invention is of an instrument for heating and extruding dental impression wax and other thermoplastic materials, wherein the wax (or other materials) is packed in collapsible containers and is heated and extruded by applying heated and pressurized hydraulic fluid (preferably, in the case of dental wax, water) to the containers. The wax is not touched either to insert it into the instrument, or to process it in the instrument, or extrude it from the instrument. Indeed, even after it is discharged from the instrument it is worked by means of a tamping element on the instrument, so that manual handling or working of the material is entirely avoided.
More specifically, in the present invention the dental impression wax (or other material) is pre-packaged in the form of handy cartridges, that is, in collapsible containers such as conventional toothpaste tubes. These cartridges are inserted into an instrument which utilizes hydraulic fluid as the heating and pressurizing medium. An electric resistance element heats the hydraulic fluid and the heated fluid heats the cartridge. Manual force, exerted through a piston in a cylinder, pressurizes the heated fluid and thereby applies pressure to the cartridge. The heat-softened wax is thereby extruded from the cartridge and the instrument.
When one cartridge is exhausted, it may be removed and replaced by another cartridge. There is no direct handling of the wax per se and there is a minimum of wax residue left in the instrument. The procedure is clean and simple and contamination of the wax is avoided.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a longitudinal section through a Dental Wax Extruder made in accordance with the principles of this invention, said extruder being shown in the process of being used to extrude dental wax therefrom.
FIG. 2 is a view of said Dental Wax Extruder partly fragmentary and partly in longitudinal section, showing recharging or replenishing the hydraulic extruding system with additional hydraulic fluid.
DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION
Instrument 10 made in accordance with a preferred form of the invention is shown in the form of a pistol or gun, in a configuration and of a size convenient for holding in the hand and manipulating in relation to a locus operandi in the mouth. It includes a housing consisting of a hollow barrel 12, a forward end cap 14, a rear end cap 16 and a handle 18.
Within barrel 12 is hydraulic fluid chamber 20 containing water or other suitable liquid as the hydraulic fluid. An inlet opening 22 is provided in said barrel to introduce the hydraulic fluid and a plug 24 is provided for closing said opening. Adapted to be supported within said hydraulic fluid chamber is a collapsible cartridge 26 which, in the illustrated form of the invention, is a collapsible tube containing dental impression wax. At room temperature, such wax is a solid which would be difficult to extrude and mold. At known elevated temperatures the wax softens and flows. Preferably the barrel is made of transparent plastics (such as the polycarbonates which are sold by General Electric Company under the trademark LEXAN and by Mobay Chemical Co. under the trademark MERLON) so that the collapsible container may be observed without opening the barrel.
It will be observed that forward cap 14 is detachably secured to barrel 12 by means of a screw-threaded connection 30 or equivalent quick-locking and unlocking means. An O-ring 32 provides a liquid-tight seal between the forward cap and the barrel. Similarly, a screw-threaded connection 34 and O-ring 36 provide a liquid-tight lock between the barrel and rear cap 16.
A tapered discharge nozzle 40 is provided at the forward end of cap 14. Orifice 42 which extends through said nozzle is, at least in part, threaded to receive externally threaded neck 44 of collapsible tube 26. It is by this means, as an illustration, that the collapsible tube may be securely, but removably, supported in hydraulic fluid chamber 20. An O-ring 46 provides a liquid-tight seal between the collapsible tube and end cap 14.
Discharge nozzle 40 is longitudinally split at its forward end and externally threaded to receive a knurled nut 48. The discharge nozzle is thereby enabled to function as a chuck to hold a tubular tip 50 fitted into orifice 42. It is through nozzle 40, and more particularly tubular tip 50 extending into orifice 42, that the wax contents of collapsible tube 26 may be extruded, as will shortly appear. It will also be noted that a bead 52 is secured to the outlet end of tip 50. This bead serves as a tamping element to tamp the extruded wax into the dental molding form.
Supported in cap 16 and extending into hydraulic fluid chamber 20 is an electric resistance heater 54 whose function is to heat the hydraulic fluid in that chamber. A heat-sensitive control 56 (thermostat) is also supported in cap 16 and it too extends into the hydraulic fluid chamber. It is connected to resistance heater 54 to maintain the hydraulic fluid at a given, constant temperature.
The means for pressurizing the hydraulic fluid in chamber 20 will now be described. Mounted in handle 18 is a hydraulic cylinder 60 and mounted in said cylinder is an O-ring encircled piston 62. A plunger 64 (piston rod) is connected at one end to said piston, and it is connected at its opposite end to a link 66. The link is connected to trigger 68 by which the instrument is manually actuated. Pivotal connections 70 and 72 join the link to plunger 64 and trigger 68, respectively, and pivotal connection 74 mounts the trigger to the handle. Pivoted link 66 enables plunger 64 to move in a generally linear path coaxially with cylinder 60. It is supported for such linear movement by means of bushing 78 mounted in said cylinder. A bracket 76 is secured to plunger 64 adjacent pivotal connection 70, and it functions as a retaining cup or abutment to support one end of a compression spring 80. The opposite end of the compression spring bears against bushing 78. The function of the compression spring is to retract the piston and to return the trigger to its original position. The trigger is thereby cocked and the piston is poised for hydraulic action.
A hydraulic line 82 provides communication between cylinder 60 and chamber 20. A check valve 84 in said hydraulic line allows a flow of hydraulic fluid from the cylinder into the chamber, but blocks a return flow in the opposite direction. A second check valve 86 is connected to cylinder 60, and it functions to admit hydraulic fluid into said cylinder, while preventing an outward flow from said cylinder. Check valve 86 is also connected to a hydraulic fluid reservoir 88 which is formed within handle 18. Hydraulic fluid may be introduced into said reservoir through opening 90. A plug 92 closes the opening.
In the operation of this device, the trigger is pressed against the handle, thereby causing the piston to move toward the closed end 60a of the cylinder. Pressure is thereby applied to the hydraulic fluid in the cylinder and through hydraulic line 82 and hydraulic fluid chamber 20, to the collapsible container 26. This causes the softened wax in the collapsible container to extrude through nozzle 40 and tip 50. To the extent of the extrusion hydraulic fluid will be forced out of cylinder 60 and out of hydraulic line 82 and into hydraulic fluid chamber 20. The volume of fluid entering said chamber will balance the volume of wax extruded from the collapsible container.
When the trigger is released, spring 80 will cause it to retract to cocked position. This will also retract the piston and produce a negative or suction force in the cylinder. As a result, hydraulic fluid will be drawn out of the reservoir through check valve 86 to replace the hydraulic fluid which was forced out of said cylinder. An air vent 94 at the upper end of the reservoir enables air to enter the reservoir to replace the hydraulic fluid which was transferred from said reservoir to said cylinder.
The foregoing describes a preferred form of the invention, and it is understood that variations and refinements may be incorporated therein within the broad scope of the appended claims. For example, the invention is not limited to the precise form of collapsible container, discharge nozzle and nozzle tip shown in the drawing. All that is required is a suitable type of collapsible container, and convenient means for removably supporting it in the hydraulic fluid chamber in communication with the nozzle and its tip. For sanitary reasons the tip should be quickly detachable and replaceable, and either adapted to be sterilized by conventional dental means or disposable. Nor is the precise hydraulic system critical to the present invention. What is required is a convenient means for applying pressure to the hydraulic fluid and thereby to apply pressure to the collapsible container to extrude its contents.