Thermoelectric Diagnostic Instrument

1. Field of the Invention

This invention relates to diagnostic instruments and more particularly to a thermoelectric instrument for applying heat and cold to small selected portions of the patient's body. The device finds particular application as a dental pulp tester.

2. Description of the Prior Art

A diagnostic procedure often employed in dentistry is that of thermal pulp testing wherein the temperature of a tooth is either raised or lowered by the application of heat or cold. Conventionally used pulp testing procudures, such as those described in an article entitled "Thermal Pulp Testing" commencing on page 58 of the May/June, 1978 issue of General Dentistry magazine, are often inconvenient, time consuming, messy and potentially harmful to the patient. As a consequence, several attempts have been made in the past to design instruments specifically adapted for applying heat or cold to a localized area of the body such as a tooth surface. Examples of such instruments are shown in the following patents: Eidus U.S. Pat. No. 3,274,995 issued Sept. 27, 1966; Scher U.S. Pat. No. 3,533,397 issued Oct. 13, 1970; Crump et al U.S. Pat. No. 3,575,176 issued Apr. 20, 1971; Frank et al U..S. Pat. No. 3,618,590 issued Nov. 9, 1971; and Foti U.S. Pat. No. 4,143,649 issued Mar. 13, 1979.

A major difficulty in the prior art, especially with respect to those devices employing mechanisms utilizing the Peltier effect, has been the efficient dissipation of excess heat build-up. The complex and voluminous heat exchange systems and heat sinks thus far employed in an attempt to solve this problem has limited acceptance of such devices.

The purpose of the present invention is, therefore, to provide a compact, self contained diagnostic instrument for applying both heat and cold to localized areas which incorporates an efficient system for dissipating excess heat generated by a Peltier module employed therein. Several components of the device contribute to the attainment of this objective; in particular, the employment of insulated thermoconductor elements in operative association with the hot and cold junction plates of a Peltier device to deliver heat and cold to contact elements positioned externally of a housing accommodating said Peltier device, heat sink means operatively associated with the hot junction plate of said Peltier device, and a motor driven fan for drawing ambient air into the interior of said housing into contact with the heat sink means and out of the housing.

Other features, advantages and objects of the present invention will become apparent with reference to the following detailed description and accompanying drawings in which:

FIG. 1 is a side elevational sectional view of an instrument constructed according to the teachings of the present invention;

FIG. 2 is a sectional view taken along line 2--2 of FIG. 1;

FIG. 3 is an enlarged sectional view taken along line 3--3 of FIG. 1 with portions thereof broken away;

FIG. 4 is an isometric view illustrating details of the thermoconductor elements and contact elements employed in the embodiment of FIG. 1; and

FIGS. 5 and 6 are side elevational views of alternative embodiments of apparatus constructed in accordance with the teachings of the present invention.

A preferred form of apparatus constructed in accordance with the teachings of the present invention is shown in FIGS. 1-4, and includes a housing 10 incorporating a cap member 12. Housing 10 additionally comprises two threadedly engaged housing sections 14 and 16. The housing is preferably formed of plastic or other suitable insulating material. Cooperating flanges 18 and 20 at the ends of cap member 12 and section 14, respectively, serve to secure the cap member to the rest of the housing. The cap member may be readily removed from the rest of the housing for cleaning, replacement, etc.

Disposed within the interior of the cap member of housing 10 is thermocouple device 22 utilizing the Peltier effect, said device 22 being hereinafter referred to as the Peltier module. Peltier module 22 includes opposed junction plates 24 and 26. When electrical current is passed through the Peltier module the temperature of one of the plates is lowered and the temperature of the other is raised in a well known manner. In the disclosed arrangement, application of electrical energy to the Peltier module will result in plate 24 being heated and plate 26 being cooled.

Disposed in face to face engagement with plates 24 and 26 are thermoconductor means in the form of thin, elongated strips 30 and 32 of copper or other suitable thermoconductive material which are preferably embedded as shown in the insulating plastic material of cap member 12 so that they are maintained in generally parallel relationship. At the outermost extent of cap member 12, strips 30 and 32 are bent as shown to form curved contact elements 34 and 36 which extend outwardly from the cap member 12 in different directions whereby the contact elements are spaced from one another on opposite sides of the cap member. Contact elements 34 and 36 are preferably gold plated. It will be appreciated that upon actuation of Peltier module 22 heat will be transmitted to contact element 34 by strip 30 and cold will be transmitted to contact element 36 by strip 32. In FIG. 1 contact element 36 is shown in contact with a tooth to impart cold thereto. With a simple twist of the wrist the hot contact element 34 alternatively may be placed in engagement with a tooth. Suitable indicia is preferably provided on the contact elements themselves, or on the cap member, to indicate to the user which contact element is hot and which is cold. For example, red and blue dots 40 and 42 could be applied to the cap member as shown to indicate the hot contact element and cold contact element, respectively.

Disposed adjacent to Peltier module 22 within the interior of housing 10 is a heat sink 44 formed of aluminum or other suitable material. Strip 30 extends beyond junction plate 24 and is positioned in engagement with the heat sink 44 within a slot 46 formed therein as shown whereby excess heat generated by the Peltier module will be absorbed by the heat sink and dissipated thereby. It should be noted that the cap member cannot be properly affixed to the remainder of the housing unless strip 30 is in slot 46, thus insuring that the contact element 34 is always the heated contact element in conformance with the indication provided by indicia 40.

Positioned adjacent to heat sink 44 is a thermostat 50, the function of which will be described below. Adjacent to the thermostat 50 is another component of the heat dissipating mechanism of the present invention, namely, rotary fan 52 driven by electric motor 54. Upon actuation of motor 54 the fan 52 will serve to draw ambient air into the interior of the housing through air ingress apertures 60 formed in the housing about the periphery thereof. The air will flow along a flow path indicated by the arrows in FIG. 3. It will be noted that the flow path is partially defined by the heat sink and in particular by a groove 62 formed in the heat sink which provides communication between apertures 60 and spaced air flow passageways 64 formed in the heat sink. After passing through the heat sink the heated air passes fan 52 and proceeds along the interior of housing 10 until it leaves the housing through air egress apertures 66 formed therein.

The Peltier module 22 and electric motor 54 are powered by batteries 70 positioned within the housing interior. The batteries 70 are preferably of a rechargeable type, such as nickel cadmium batteries, and charger connector pins 72 are provided to permit recharging of the device when it is not in use. Suitable switch means 74 is provided to simultaneously establish electrical communication between the batteries, motor 54 and Peltier module 22 through wiring 76. Thermostat 50 is positioned in the electrical circuit so as to temporarily shut off power to the Peltier module when the heat of heat sink 44 passes a predetermined temperature. The motor 54 will continue to operate as long as switch means 74 is closed however, if it is in parallel with the thermostat as is preferred. FIG. 5 shows an alternative embodiment of the invention, differing from that previously described in that the Peltier module 22a is not removable with cap member 12a when the cap member is disconnected from the rest of housing 10a. Such an arrangement is particularly desirable for autoclaving. To assure correct alignment when the cap member is replaced with strips 30a and 32a in engagement with junction plates 24a and 26a, respectively, suitable alignment means such as a key and slot arrangement 82 and 84 are preferably employed.

FIG. 6 shows yet another alternative embodiment of the invention wherein the instrument 90 has a socket accommodating a removable plug 92 which is in turn connected by cord 94 to a transformer 96 adapted to be plugged into a conventional electrical socket.