US3345497A

US3345497A - Electric water bath heater for conditioning hydrocolloids

Info

Publication number: US3345497A
Application number: US332712A
Authority: US
Inventors: Don D Porteous
Original assignee: Van R Dental Products Inc
Current assignee: Van R Dental Products Inc
Priority date: 1963-12-23
Filing date: 1963-12-23
Publication date: 1967-10-03
Anticipated expiration: 1984-10-03

Description

Qct. 3,1967 D, D PORTEOUS 3,345,497

ELECTRIC WATER BATH HEATER FORCONDITIONING HYDRQCOLLOIDS Filed Dec. 25, 1963 2 Sheets-Sheet 1 Uni/Z 10 OM ,3 1 091150 12 I? 9 4 9 F5 40 In/VEMrag D Z ,2 8 (J (D 53 =2 Oct. 3, 1967 D. D. PORTEOUS ELECTRIC WATER BATH HEATER FOR CONDITION ING HYDROCOLLOIDS I 2 Sheets-Sheet 2 Filed Dec. 23, 1963 United States Patent Ofiice Filed Dec. 23, 1963, Ser. No. 332,712 16 Claims. (Cl. 219-417) The present invention relates generally to heating equipment of the water bath type, and is more particularly concerned with equipment of this general character which is especially designed for use by dentists for heating thermoplastic materials employed by them in preparing material for dental impressions and the like in connection with making inlays, castings, and similar articles when repairing damaged teeth or manufacturing dentures.

In this work, it is necessary to soften or render more or less liquid the thermoplastic materials used for taking an impression, including particularly the class of impression materials known as hydrocolloids, then store them for a time at a suitable lower temperature, and finally to temper them at a still lower temperature for immediate use in a patients mouth. These functions require different temperatures to meet different conditions and the requirements of different materials, such temperatures normally being in the range from the boiling point of water downward to perhaps 100 F.

It is very important to the dentist that he always have available in his office or laboratory heating apparatus which is ready and in operating condition to do the work required. However, as sometimes, happens, the equi ment breaks down and fails to work properly, in which event it must be sent out of the office for repairs. It has been a characteristic of known types of heaters that they are of such unitary character in their construction that when a portion of the heater malfunctions, the entire heater must be sent out for repair, thus totally depriving the dentist of services of the entire piece of equipment. As a consequence of this, the dentist must make use of unsatisfactory substitutes, postpone his work, or obtain a replacement of the entire apparatus if he is denied the use of his own equipment as a result of mechanical failure.

Thus, it is a general object of the present invention to provide an electrical heater or hydrocolloid conditioner of the water bath type, adequate to meet the particular needs of dentists and dental laboratories, which is constructed in a plurality of removable units, any one of which may be withdrawn from the heater in the event of failure without impairing the serviceability of the remaining units.

It is also an object of the present invention to provide a heater of this character having a plurality of substantially duplicate units which can be interchanged within the heater at any one of a plurality of locations and still perform all of the functions required of the unit at any one of the locations, thereby permitting withdrawal of one or more of such units for repairs while retaining the remaining units in service.

Another object of the invention is to provide a conditioner of this character adapted to maintain different temperatures in different units of the apparatus in accordance with essential requirements of different materials, functions, or stages of work to be performed.

Another object of the present invention is to provide a conditioner having a plurality of interchangeable heating units with a corresponding plurality of removable, substantially duplicate cans for receiving the heat-transfer medium, typically water, providing a plurality of baths for immersing the dental materials to 'be used, and maintaining such materials at predetermined temperatures.

3,345,497 Patented Oct. 3, 1967 A further object is to provide in an electrically heated colloid conditioner of the character mentioned, a plurality of interchangeable units each of which is provided with a means of assuring individual temperature control, with at least one station for the units having means permitting the water bath to be brought to the boiling point for heating the dental impression material.

In a preferred embodiment of the present invention the above objects and advantages are achieved by providing a plurality, for example, three, of substantially duplicate, interchangeable carrier units with electrical heaters and an equal number of water cans, the water cans also being substantially duplicates and interchangeable with each other in each of the carrier units. These carrier units are selectively introduceable into any one of a corresponding plurality of compartments provided in a housing or cabinet, an electrical socket or receptacle means being provided in the cabinet at each of the compartments to receive the prongs of an electrical plug carried by the unit and inserted into the socket as the unit is inserted into the cabinet compartment. Each of the carrier units is provided with a thermostatically controlled switch to the electrical heater of that carrier unit. In addition, at least one socket in the cabinet is connected with a second electric circuit which includes a clock controlled switch for supplying current independently of the thermostatically controlled switch in order to bring about a higher temperature of the water bath in the unit located at said one socket than is permitted by the thermostat.

Other objects and features of the present invention will become apparent to those skilled in the art by reference to the accompanying drawings and to the following specification wherein there is disclosed an embodiment of the present invention deemed presently as best representing the invention.

In the drawing:

FIG. 1 is a top, front, and side perspective view of the conditioner containing a plurality of interchangeable heater units, embodying the present invention.

FIG. 2 is an exploded perspective view of the cabinet of FIG. 1 with various removable parts shown in positions aligned for assembly and hinged covers in alternate positions, broken lines indicating the relative movement of the parts for assembly.

FIG. 3 is an enlarged vertical transverse section taken approximately on line 33 of FIG. 1, some portions being indicated as broken away to facilitate illustration.

FIG. 4 is a rear elevation of the housing as indicated by arrow 4 in FIG. 1, the carrier unit at the right hand end of FIG. 4 being removed.

FIG. 5 is a fragmentary plan view of a basket handle alone, as indicated by line 5-5 of FIG. 3.

FIG. 6 is a wiring diagram of the heater.

FIG. 7 is a fragmentary section on line 77 of FIG. 2.

Referring now to the drawings, and particularly to FIG. 2, it will be seen that the principal relatively separable parts of the apparatus include a cabinet or housing A, three interchangeable units B, each comprising a heating element, thermostat and supply circuit, three interchangeable and reversible water cans or receptacles C for water or other fluid constituting the liquid bath, and one or more baskets D.

The cabinet A comprises a housing generally indicated at 10 which preferably is of sheet metal and includes end walls 12, a lower front panel 14, a rearwardly offset indicator panel 15 integral with or otherwise connected to the lower panel 14 in such a manner as to form a horizontal shelf 16, an apertured top panel 18 which may be integral with panel 15, a main bottom wall 20 (FIG. 3) and a forward bottom wall portion 21 which may be integral with the lower front panel 14, all supported upon feet 22 which are preferably of rubber or the like. The lower edges of the side walls 12 have inwardly turned marginal flanges 12a beneath and rigidly secured to the bottom wall 20 by screws, bolts, or the like. A swinging, sloping cover 24 is mounted on the cabinet at the top of panel 14 by a spring hinge 25 which tends to close the cover against the forward sloping edges of the end walls 12 and against an upper sloping portion 15a of the upper panel 15. The cover conceals and protects indicators and dials on the panel 15 or any tools or the like lying on the shelf 16.

Also provided to overlie the carriers B in their water cans C are three lids 26 individually hinged at 27 to a downwardly turned rear flange 18a of the top panel 18. These lids 26 desirably are formed from heat-resistant, relatively non-conductive plastic material and have integral downwardly directed flanges 28 which fit within the open tops of the cans C to return to the cans any condensate which collects on the lids within the area bounded by flanges 28. The rearward portion 28a of each annular flange 28 is considerably enlarged so that it forms a pocket or trap 28b, as shown in FIG. 3, when the lid is opened and tilted rearwardly to the open position shown in the figure. Condensate on the lid runs down into the trap and collects there, being returned to the associated can C when the lid is moved forwardly and downwardly into the closed position.

There is also an area on lid 26 around the flange 28 on which water vapor condenses. When the lid is raised, as in FIG. 3, this condensate runs down the lid and collects above the lip 29 and is deposited on top wall 18 when the lid is closed. For this reason top wall is formed with a depressed marginal area 18s (FIG. 7) to form a sump or gutter to hold this water and prevent is from running down the sides of the cabinet. The rim of each can C conveniently overhangs this sump to direct into the sump water falling from the edges of the can. The quantity of water deposited into the sump at any time is normally small and is evaporated in a short time by heat from the cabinet.

Cabinet or housing is open at its rear end as shown in FIGS. 3 and 4. The interior of the cabinet is divided into a plurality, typically and preferably, three, although a larger or smaller number may be used, of similar compartments 30. Each compartment receives snugly a selected one of the three duplicate carriers B. This division of the interior of the cabinet into separate carrier-receiving compartments is effected by two intermediate upwardly extending dividers 32 and two similar end posts 33', all of channel shape in cross-section. The compartments are also separated by horizontally extending bottom guides 34 rigidly secured to the bottom cabinet wall 20 in any suitable manner, as by spot welding or by bolts or sheet metal screws. These bottom guides are conveniently and typically integral with the respective dividers 32 and posts 33 and are accordingly also of similar channel shape in cross-section. The guides extend forwardly from and in vertical alignment with posts 33 and dividers 32 to engage the sides of the carriers and guide them as they are moved from rear to front into compartments 30. Thus, the upright divider bars 32 and posts 33 may be considered as initially positioning the heater carriers B laterally while the lower horizontal guides 34 guide the carriers B during sliding movement over bottom wall 20 as they are individually inserted into a compartment 30 and moved into their operative position.

When inserting a carrier B, its forward movement within a compartment 30 is limited by the position of an upstanding stub wall 40 which may be an integral forward portion of the main cabinet bottom wall 20' and is located in the space beneath shelf 16 and a short distance behind front panel 14. This stub wall 40 serves as a support at the end of each compartment 30 for a three element electric socket or receptacle 42 for receiving a three-prong electric plug 43 mounted on the opposing .4 forward wall of the carrier B. As will be more fully explained, when the prongs of plug 43 are inserted in socket 42, an electrical connection is established with the heating element of the carrier B to warm the water bath in the associated can C. The range of movement of the carrier unit allows the prongs to become fully seated in the receptacle, at which time engagement of the plug with the receptacle limits inward travel of the carrier.

Each heater carrier B is in the form of a rectangular box having generally planar exterior walls at the four upwardly extending side walls but open at the top, as shown in FIG. 2. The interior space of the carrier B is divided vertically into a relatively larger rearward chamber 45 and a smaller forward chamber 46 separated from each other by vertically extending wall 48. Wall 48 becomes the forward wall of the larger chamber 45 while the rearward wall is indicated at 49 and the two side walls thereof at 47. The larger compartment is sized to receive with a sliding fit through its open upper end any one of the three cans C which serve as receptacles for the fluid heat transfer medium. Thus, each carrier B is also a carrier for a can C as well as the electrical heating element 52, which is disposed immediately beneath the bottom wall of the can, as shown in FIG. 3, and the associated electrical elements. The heating element is rigidly fixed in place by attachment to side walls 47 by brackets 50. Electrical heating element 52 is of the resistance type and is preferably in heat transferring contact with the can above it. Heating element 52 is approximately coextensive in size with the area of the bottom wall of the can, in order to obtain a favorable amount of heat transferring area.

It is contemplated that the heater will normally be operated with all three carriers B in place within the cabinet and that there will be no occasion to remove them except for repair, replacement or interchange. Consequently, it is preferable that these carriers be held in their operative position forwardly in compartments 30 by some suitable means, such as bracket 53 which is attached to each carrier B at the rear face of back wall 49. A sheet metal screw 54 passes through the bracket into bottom wall 20 of the cabinet to anchor the carrier in place. Bracket 53 preferably has a rear upturned flange, giving to the bracket a channel shape in cross section as'may be seen in FIG. 3, since this rearward flange of the bracket provides agrip by which the carrier'may be pulled rearwardly out of the cabinet when occasion demands.

Wall 48 of the carrierd provides a convenient member to which may be attached the wall means forming the smaller forward compartment 46. Such wall means comprises a front wall 56 of the carrier which is joined to partition wall 48 by narrow side walls 55. Compartment 46 may conveniently be left openat both the top and bottom. Adjacent the bottom edge of wall 56 there is rigidly attached tothis wall the three-prong electrical plug 43, as previously mentioned. The prongs of this plug are mounted on the carrier in such a position that they are aligned with the receiving openings in socket 42 when the carrier slides over cabinet wall 20 and is confined laterally between horizontal guides 34.

Each wall 56- preferably also carries a pilot light 58 which isconnected to one prong of plug and also connected to thermostatically controlled electrical switch 60; as will be explained in greater detail later. Thermostat 60 is mounted for horizontal movement relative to wall 48 so that the thermostat can move through an opening 61 in the wall and 'into engagement with the vertical front face ofa can C. This arrangement is such that the rear flat face of the thermostat is in sliding contact with the opposing flat wall of the associated can C when the can is inserted into the carrier as in FIG. 3, and the location of the contact between the thermostat and the can is such that the normal water level in the can is above the lower end of the thermostat and preferably near the upper end of it. Thus, the temperature of the water in the can C is accurately transmitted to the thermostat so that the thermostat is responsivev to the water temperature, heat from the water being transmitted through the can wall to the thermostat.

To insure good contact between the can and the thermostat, since such contact is desirable in order to effect a good heat transmitting relation between the can wall and the thermostat, a compression spring 62 bears against the rear or inner face of front cabinet wall 56 and also against the thermostat to normally urge the thermostat rearwardly against the can. Spring 62 is mounted upon and is held in place by shaft 63 which extends forwardly from the thermostat and through openings in wall 56 and panel 15 to receive knob 64 by which shaft 63 can be turned manually to adjust the setting of the thermostat at which it opens and closes the electrical switch, as will be understood. Suitable markings or indicia are applied to the front face of panel 15 to form a dial 65 (FIG. 2) associated with knob 64 whereby the setting of shaft 63 can be determined by visual inspection and the shaft can be changed in position by a known amount. Dial 65 may be graduated in an arbitrary manner or it may be designed to indicate directly the temperature to be reached by the water in can C at the time that the thermostat opens the electric switch. Although optional, an access opening 66 is preferably cut in wall 56 at a position below thermostat shaft 63 in order to provide access to the electrical connections located within compartment 46.

Each of the three cans C serves as a receptacle for a body of water, which is the most convenient and most commonly employed fluid heat-transfer medium, for obvious reasons. Each can has a heat-conductive metal body 68 formed by vertically extending side walls 70, vertically extending front and rear walls 72, and a bottom wall 74. As will be seen in FIG. 2, all of these walls have large, substantially flat areas and are connected by rounded corners. The can is preferably symmetrical about each of two median vertical intersecting planes and consequently each can is reversible front to rear. All three cans are the same size, for reasons set forth above, and consequently they are fully interchangeable and any one of the cans fits equally well into any one of the carriers B with the flat bottom '74 of the can in heat-receiving contact with the heating element 52 of the associated carrier B. As also shown in FIG. 2 and FIG. 3, each can C has an overhanging peripheral flange 75 at the top which has downturned edges 76. The panel 18 is preferably recessed at 18s, as may be seen in FIGS. 3 and 7, to receive the water dropping off edges 76.

When any carrier unit B is disposed within a compartment 30 of the cabinet in the operative position illustrated in FIG. 2 with the prongs of the plug 43 engaged in the prong-receiving openings in socket 42, the open top of carrier chamber 45 is located directly beneath the respective opening in top wall 18. In this position, a can C can be readily inserted from above the cabinet through the top wall 18 thereof into the carrier B. The curved lower corner of the can serves as a cam engaging and moving thermostat 60 from the broken line position of FIG. 3 to the solid line position of the figure which is the normal operative position of the thermostat. Good heat conducting contact is made between the outer face of the can and the opposing wall of the thermostat by having the two engaging surfaces conform to each other, and for this reason the opposing faces of the can and thermostat are preferably made flat. For the same reason, the bottom wall 74 of the can is preferably also made flat where it engages the heating element 52.

Electric power is supplied to the heater by two conductors 90 and 91 contained in an insulated cable 80 which is also preferably provided with a ground connection for safety reasons, as is well known with electrical appliances. Cable 80 conveniently enters the base of housing at one rear lower corner thereof as shown in FIG.

4 and extends forwardly in the cabinet through the space forwardly of an end post 33 to the space 82 beneath the shelf 16. Here the two conductors 90 and 91 are connected to the two blades of a double pole main switch 84. This switch is opened and closed manually by means of an element which extends through an opening in lower panel 14,as may be seen in FIG. 1. One of the two power supply conductors, here shown as conductor 90, includes a fuse 84a. The fuse is contained in a capsule indicated at 84b and located on shelf 16, as shown in FIG. 2.

A circuit diagram of the heater is shown in FIG. 6 from which it will be seen that two conductors 90 and 91 are connected between main switch 84 and sockets 42 in such a way as to supply corresponding elements of each of the sockets, and therefore the corresponding prongs of plugs 43 therein, with electric power. As shown in FIG. 6, the sockets 42 are wired in parallel with elements 92 of the sockets all connected to conductor 91 while elements 93 of the sockets are all connected to conductor 90. For convenience of analysis, the conductor 90 may be considered as the hot lead, while the other conductor 91 is the return lead.

The wiring carried by the cabinet is completed by a clock controlled switch which is serially connected between lead and the third element of the socket 42 at one of the locations for a carrier B. Although such a switch may be supplied for any one, or more than one, of the carrier units B, it is here shown that a clock driven switch 85 (FIG. 3) is supplied only for the unit at the left-hand end of the heater, when viewed from the front as in FIG. 2. In this way the third or center receptacle 94 of the one socket and the corresponding prong on plug 42 therein is supplied with current when the movable element 95 of switch 85 is closed. Typically, the clock mechanism is of any suitable type but conveniently may be a spring operated timing mechanism which is manually wound and set in operation by means of knob 86 on the front of the heater at lower panel 14. Such spring driven timing mechanisms are well known in the art and need no further disclosure here except to say that they are the type in which the switch element 95' is of normally open type and is closed by manual manipulation of knob 86, the knob being returned to the initial, normally open position by action of the spring. The length of time that the switch is closed is controlled by the degree of rotation imparted to knob 86 as this in turn determines the length of time the clock runs. This rotation can be determined by visual observation from reference to dial 88 behind the knob, dial 88 conveniently being graduated in minutes. Thus, it will be seen that element 94 of receptacle 42 is energized by the user by manipulating the knob closing switch contacts 95, and that the element remains energized for a predetermined length of time according to the setting of knob 86 which determines the time required for the clock mechanism to return the switch to open position.

Each of the three carriers B is provided with an electrical circuit which is an exact duplicate of the circuits in the other carriers. Obviously, this is done in order that the carriers may be entirely interchangeable and can function fully as well as any one of the three stations or locations in which the carriers may be placed within the cabinet. Only one of the complete circuits is indicated in FIG. 6. The circuits for the other carriers are duplicates of the one shown and are merely indicated diagrammatically as being contained within the rectangle B.

Each plug 43 of the carriers B is provided with three

prongs

96, 97 and 98 which are positioned to enter respectively the

socket elements

92, 93 and 94. Each prong 96 directly supplies the thermostatically controlled switch 60 by way of a line 100 leading to the movable contact 101 of the switch which supplies electrical power to the respective heater 52 through conductor 192. By means of this latter conductor the circuit is completed through heater 52 and conductor 104 to the respective prong 97 in socket element 93. Pilot light 58, previously mentioned, is connected to conductor 102 and conductor 104 in parallel with heater 52 by conductor 105. Thus, the pilot light is energized at all times that the heating unit is energized, giving a visual indication that the resistance heating element is energized and that the temperature of the water in the associated can C is being raised by the heater element. As long as power is supplied to the heating element through prong 96 and the closed, thermostatically controlled switch 101, the heater is energized and the temperature of the water is being raised. This, of course, ceases when the temperature of the water in the associated can reaches a predetermined temperature at which .point the thermostat causes switch 101 to open, interrupting the circuit to the heater element and preventing any further rise in temperature of the water.

The operation of the thermostat 60, heater 52, and pilot light 58 as so far described is the same for all three carrier units B regardless of their location in the cabinet. That is, the power supplied to sockets 42 is the same in all cases to enable the operation as just recited. However, when it is desired to operate the heater 52 of the first unit to a higher temperature than is permitted by the setting of its thermostat 60, the thermostat is by-passed by setting the switch element 95 of the clock-controlled switch in circuit closing position. This energizes the line 107 connected to the third socket element 94 and this in turn energizes the respective prong 98 of the three-prong plug 43 on the carrier unit B. Prong 98 is connected by conductor 108 to resistance element 52 in such a manner as to by-pass thermostat 60 and supply electrical current directly to the heater 52 and pilot light 58. This condition of energizing the heater continues as long as normally open contact 95 is held closed by the clock-controlled mechanism 85.

Another feature of the present invention resides in the optional provision of basket D which is insertible into any one of the water cans C to receive a package of impression material to be softened or conditioned, or for the purpose of receiving instruments which are to be retained in hot water or are to be sterilized, as will be explained. This basket D, of which there may be one for each water can C or a total of three, includes a peripheral vertical wall 110 and a perforated bottom 112. The corners of the basket are beveled; providing angular fiat walls at 114 to facilitate escape of steam and free water movement during boiling of the water in the can. The vertical side walls 110 engage the flat walls 70 of the can C whereby the curved lower corners of the can C hold the basket spaced from the bottom of the can. A vertical partition 115 is mounted at an intermediate position in the basket and is provided with an overhanging, horizontal flange 116. Flange 116 has notches 118 open to one edge of the flange to receive and hold syringes or other instruments in the basket. A vertical tube 120 is secured to the flange 116, as by clamp nut 122, to receive a thermometer stem 124. The top of the tube is provided with a recess 125 to receive the circular indicator dial 126 of the thermometer. Vertical tube 120 is a handle by which the basket may be raised out of or lowered into the water can C, and the diameter of the button 'on the top of the tube is larger than the diameter of thermometer dial 126 in order that the basket may be lowered into or removed from the can with the thermometer in place and without in any away disturbing the thermometer. The height of tube 120 is such that the top of thermometer dial 126 normally lies below the top of the can C in which it is located.

With a conditioner for hydrocolloid materials as described above, the dentist has a variety of temperatures for the several water baths available to him. Thus, the left hand unit, as viewed in FIG. 2, can provide him on demand with liquifying and sterilizing conditions by boiling water in the can C, conditions which can be brought about through the use of the clock controlled switch 25.

It will be recalled that this switch by-passes or over-rides the thermostat and, consequently, applies heat to the heating unit 52 in this particular heater-carrier as long as the clock controlled switch is in the closed position. This may be set for any suitable period of time which is long enough to raise the water in the can C to the boiling temperature and cause it to boil for a desired length of time. The temperature of 212 F. or thereabouts is commonly used to liquify the impression material as the first step in preparing a hydrocolloid for use.

When the clock opens the switch after the set time has elapsed, or the dentist manually opens the switch by actuating knob 86, the respective thermostat 60 takes over control of supplying electricity to the heating unit 52. This, of course, results in the temperature of the water in the can dropping to that temperature at which the thermostat is set, after which any further drop in temperature causes the thermostat to close the switch element 101 providing energizing current to heater 52. This initial higher temperature operation is possible only with the single unit at the left hand end of the cabinet, because of the extra circuit energizing receptacle element 94 which is unique with this particular station for a carrier B. Such a circuit could be applied to other receptacles 42, if desired. However, one unit with maximum tem perature ranges is normally adequate.

When the temperature in the first or left-hand unit is under control of the thermostat, it drops ordinarily to a temperature suitable for storage of the impression material. Of course, this temperature diifers for different materials but is usually within the range of 140 F. to 165 F., a typical storage temperature for hydrocolloid material being about 150 F. The impression material, once liquified, remains ready for use at this storage temperature.

The circuit of FIG. 6 is designed to supply the dentist with storing and/0r tempering conditions in the other two carrier units below the boiling point of water. In each unit the temperature may be determined by the setting given to the associated thermostat 60, the temperatures being controlled through the settings given to knobs 64.

In ordinary usage it is contemplated that the center unit operates at a storage temperature in the range given above. The third or right hand unit (as viewed in FIG. 2) is set to temper the impression material, i.e. reduce its temperature, immediately prior to use, sufficiently that it does not burn or injure the patient. This usually requires a temperature of about F. to F'., but for some materials the range may be as high as F. At this temperature the impression material may begin to harden so it should be used as soon as practical; but just the same the mass of material may remain in the temporary bath for an appreciable length of time.

Should the heater 52 in any carrier B of the conditioner fail, this entire carrier may be removed from the cabinet and may be replaced by either one of the two remaining units. In any location within the cabinet, any of the carrier units B is enabled to work in the same manner as any other carrier, as previously described. The unit in which the failure occurred can be Withdrawn from the heater and sent to the factory for repair or replacement, leaving the entire heater capable of operating with only two of the units B but at the same time capable of carrying on the full range of operations and giving the dentist the full range of liquifying, storage, and tempering temperatures that would be possible with all three of the heater carriers B present in the cabinet. It will be clear that this arrangement enables the dentist to continue to obtain full service out of the heater in spite of the failure of one heating element, since the carrier units are duplicates of each other, are interchangeable, and are capable of independent operation, and are independently removable from the cabinets without altering the operation of the other unit.

From the foregoing description, it will be apparent that various changes in the detailed construction and arrangement of parts of the heater constituting the present invention may occur to persons skilled in the art without departing from the spirit and scope of the present invention. Accordingly, it is to be understood that the foregoing description is considered as being illustrative of, rather than limitative upon, the invention as defined by the appended claims.

I claim:

1. A hydrocoll-oid conditioner comprising:

a cabinet;

first electrical circuit means in the cabinet providing a plurality of similar electrical outlets each having a plurality of contacts and located one at each of a plurality of stations, said circuit means including means connecting a pair of contacts of each outlet to a source of electrical energy and a time-controlled switch at one station serially connecting a third contact of the outlet at said station to said source of electrical energy;

a plurality of substantially duplicate carriers located one at each station, each carrier being removable individually from the cabinet and interchangeable with the other carriers at any other station;

and second electrical circuit means on each carrier comprising;

a plug having a plurality of prongs engageable with the contacts of an outlet;

an electrical heating element and thermally responsive switch means connected in series with each other and with a pair of prongs on said plug engageable with said pair of contacts on a selected outlet to energize the heating element at any station;

and a conductor connected to said heating element in parallel with the thermally responsive switch means and to a third prong on said plug engageable with the third contact on said outlet to connect the heating element to the tin1econtrolled switch means to bypass the thermally responsive switch means and energize the heating element independently thereof when the carrier is at the station having said time-controlled switch means;

each outlet not having a time-controlled switch means having a contact engageable by the third prong of a carrier plug.

2. Heating apparatus as in claim 1 in which the thermostat controlled electric switch means is adjustable to a selected temperature and that also includes:

a pilot light on each carrier connected across the respective heating element and illuminated when the connected heating element is energized;

and temperature indicating means on each carrier indicating temperature of the Water in the respective can;

whereby the thermally responsive switch means on the respective carrier can be adjusted to a desired setting by reference to the pilot light and the temperature indicating means.

3. In heating apparatus, the combination comprising:

a housing providing a plurality of chambers of similar size and shape said housing having an upstanding transverse wall extending across said chambers at one end thereof;

multiple-element electric socket members mounted in on said transverse wall said housing respectively adjacent one side of each of said chambers;

a plurality of removable interchangeable carriers respectively insertable into said chambers by movement in a common direction, each carrier having an electric heater element and having a multiple-prong electric plug electrically connected to the heater element and insertable into a respective socket member in the housing by said movement;

a plurality of removable cans insertable interchangeably into said heater carriers through a wall of the housing for heating heat-transfer medium therein;

and a thermostat controlled electric switch mounted on a side wall of each carrier in position for slidable heat-transmitting engagement with a respective can upon insertion thereof into the carrier, the switch being at a position adjacent a normal level of heattransfer medium in the respective can for controlling the supply of heating current to the heating element in response to temperature of the medium to regulate the temperature of the medium in the associated can.

4. Apparatus as in claim 3, including resilient means connected with each thermostat for pressing the latter into heating-conducting contact with the respective can.

5. Apparatus as in claim 3 having a shelf overlying said socket members, an indicator panel rearward of said shelf and forward of said plural chambers and forming a closable space, and a sloping swinging cover enclosing said space.

6. In heating apparatus, the combination comprising:

a housing providing a chamber open at the top and back;

a multiple-element electric socket member disposed in said housing adjacent the front of said chamber;

a removable carrier container insertable into said chamber and having an electrical heater on the bottom wall thereof, and also having a multiple-prong electric plug insertable into said socket member by movement of the carrier from rear to front in said chamber;

said carrier having an opening at the top thereof in registration with the open top of the housing when the prongs of said plug are seated in the socket member;

a can insertable downwardly into said carrier container through the open top of the housing and carrier int-o heating contact with said heater, for reception of heat-transfer medium to be heated;

thermostat means provided in a side Wall of said carrier container in position for sliding heat-transmitting contact with a wall of said can for controlling electric current supply to the heater to regulate the temperature of said medium in the can;

and electric circuit means connected to elements of said socket member to supply said heater by way of said plug.

7. Apparatus as in claim 6, including resilient means pressing said thermostat into contact with a side wall of said can.

8. Apparatus as in claim 6 in which a pair of prongs and an associated pair of elements of the socket member are connected to the electric circuit means and to the thermostat and heater and that also includes an auxiliary circuit comprising a clock-controlled switch connected to said circuit means in series with an additional element of said socket member receiving a corresponding additional prong of said plug, said corresponding prong being connected to the heater in parallel with the thermostat means, said auxiliary circuit thereby connecting the electric circuit means to said heater to by-pass said thermostat I when the clock-controlled switch is closed.

9. Apparatus as in claim 6, wherein said housing has a lid swingingly mounted at the back thereof to cover said container and can, said lid having a depending flange adjacent its periphery to enter said can and return condensate, the rearward portion of such flange being enlarged to form a condensate trap When the lid is raised.

10. Apparatus as in claim 6 that also comprises a perforated basket removably supported in said can receiving articles for heating.

11. Apparatus as in claim 10 wherein said basket carries an upstanding hollow handle with a vertical post receiving the stern of a thermometer.

12. Apparatus as in claim 10 wherein said basket carries an upstanding thermometer holder adapted to receive a thermometer having a stern and a head and the holder carries at its top an enlargement engaging the head of a thermometer.

13. Heating apparatus as in claim 6 in which the thermostat means is adjustable to a selected temperature and that also includes a pilot light connected across the heating element and illuminated when the element is energized and temperature indicating means indicating temperature of the water can, whereby the thermostat means can be adjusted to a desired temperature by reference to said pilot light.

14. Heating apparatus comprising:

a housing having a generally horizontal top Wall with an. opening therein, said wall having a depressed gutter extending around the opening and located in part adjacent one edge of the wall;

av removable water container inserted in said opening and having an open upper end;

heating means within the housing adjacent the container to heat water in said container;

a lid hinged to the cabinet adjacent said one edge of the wall and swingable between a lowered position covering the open end of the water container and a raised position in which the lid extends upwardly and away from the cabinet wall;

and condensate retaining means on the underside of the lid adjacent the hinged end thereof comprising an angular member extending outwardly from the underside of the lid and adapted to catch condensate when the lid is in raised position and to return said condensate to the gutter on the cabinet when the lid is lowered.

15, In heating apparatus, the combination comprising:

a housing providing a plurality of chambers;

a first circuit means including electric socket members having at least three contact elements and mounted in said housing respectively adjacent each of said chambers and all socket members having two contact elements connectible with a source of electrical energy and one socket member having the third contact element connected in parallel with one of said two contact elements;

a plurality of removable interchangeable. carriers respectively insertable into said chambers, each carrier having an electric heater element and a multipleprong electric plug connected to the heater elements, the plug being insertable into a respective socket member in the housing and each plug having at least three prongs engageable with the contact elements of a socket member;

a plurality of cans insertable interchangeably into said heater carriers for heating heat-transfer medium therein;

a second circuit means on each. carrier connected to said three prongs of the plug associated with the carrier and including a thermostat controlledelectric switch provided in a Wall of each carrier in position for heat-transmitting engagement with. a respectivev can at a position adjacent a normal level of heattransfer medium in the respective can, the switch being connected to the heater element to control the supply of heating current to the heating element toregulate the temperature of the medium in the ass'ociated can; the second circuit means oneach carrier also including a shunt circuit across the thermostat controlled switch from one of said prongs energizingsaid third contact element;

and clock-controlled switch means in said first circuit means serially connected to said third contact element of one of the socket members and in parallel with another contact element of said one socket member to by-pass the respective thermostat-controlled switch to supply energy to the respective heater through the clock-controlled switch and said one contact element, at least one other socket member being without a clock-controlled switch.

16. In heating apparatus, the combination comprising:

a housing providing a plurality of chambers of similar size and shape;

multiple-element electric socket members mounted in said housing respectively adjacent one side ofeach of said chambers;

a plurality of removable interchangeable carriers respectively insertable into said chambers by movement in a common direction, each carrier having an electric heater element and having a multiple-prong electric plug electrically connected to the heater element and insertable into a respective socket memher in the housing by said movement;

a plurality of removable cans insertable interchangeable into said heater carriers through openings in the top wall of the housing for heating heat-transfer medium therein; said top wall being provided with a depressed gutter extending around each of said openings;

a plurality of lids hinged to the housing adjacent one edge of the top wall of the housing and individually swingable between a lowered position covering the open end of one of said removable cans and a raised position in which the lid extends upwardly and away from the top wall of the housing and provides access to the open end of the uncovered can;

and condensate retaining means on the underside of each lid adjacent the hinged end thereof comprising an angular member extending outwardly from the underside of the lid and adapted to catch condensate when the lid is in raised position and to return said condensate to the gutter on the housing when the lid is lowered.

References Cited UNITED STATES PATENTS 1,336,728 4/ 1920 Christensen 219-282 1,368,152 2/1921 Huff 219417 1,767,034 6/1930 Andersen 21'-100 2,066,476 1/1937 Lacy 219441 2,182,682 12/1939 Shroyer 219417 2,264,611 12/1941 Bemis 99333 2,371,975 3/1945 Parsons 219433 2,379,504 7/1945 Thompson 219417 X 2,463,329 3/ 1949 Stansbury 219422 2,528,579 11/1950 Clark 219416 X 2,735,356 2/1956 Sacks 219415 X FOREIGN PATENTS 444,124 3/ 1936 Great Britain.

ANTHONY BARTIS, Primary Examiner.

Claims

1. A HYDROCOLLOID CONDITIONER COMPRISING: A CABINET; FIRST ELECTRICAL CIRCUIT MEANS IN THE CABINET PROVIDING A PLURALITY OF SIMILAR ELECTRICAL OUTLETS EACH HAVING A PLURALITY OF CONTACTS AND LOCATED ONE AT EACH OF A PLURALITY OF STATIONS, SAID CIRCUIT MEANS INCLUDING MEANS CONNECTING A PAIR OF CONTACTS OF EACH OUTLET TO A SOURCE OF ELECTRICAL ENERGY AND A TIME-CONTROLLED SWITCH AT ONE STATION SERIALLY CONNECTING A THIRD CONTACT OF THE OUTLET AT SAID STATION TO SAID SOURCE OF ELECTRICAL ENERGY; A PLURALITY OF SUBSTANTIALLY DUPLICATE CARRIERS LOCATED ONE AT EACH STATION, EACH CARRIER BEING REMOVABLE INDIVIDUALLY FROM THE CABINET AND INTERCHANGEABLE WITH THE OTHER CARRIERS AT ANY OTHER STATION; AND SECOND ELECTRICAL CIRCUIT MEANS ON EACH CARRIER COMPRISING; A PLUG HAVING A PLURALITY OF PRONGS ENGAGEABLE WITH THE CONTACTS OF AN OUTLET; AN ELECTRICAL HEATING ELEMENT AND THERMALLY RESPONSIVE SWITCH MEANS CONNECTED IN SERIES WITH EACH OTHER AND WITH A PAIR OF PRONGS ON SAID PLUG ENGAGEABLE WITH SAID PAIR OF CONTACTS ON A SELECTED OUTLET TO ENERGIZE THE HEATING ELEMENT AT ANY STATION; AND A CONDUCTOR CONNECTED TO SAID HEATING ELEMENT IN PARALLEL WITH THE THERMALLY RESPONSIVE SWITCH MEANS AND TO A THIRD PRONG ON SAID PLUG ENGAGEABLE WITH THE THIRD CONTACT ON SAID OUTLET TO CONNECTED THE HEATING ELEMENT TO THE TIME-CONTROLLED SWITCH MEANS AND ENERPASS THE THERMALLY RESPONSIVE SWITCH MEANS TO BYGIZE THE HEATING ELEMENT INDEPENDENTLY THEREOF WHEN THE CARRIER IS AT THE STATION HAVING SAID TIME-CONTROLLED SWITCH MEANS; EACH OUTLET NOT HAVING A TIME-CONTROLLED SWITCH MEANS HAVING A CONTACT ENGAGEABLE BY THE THIRD PRONG OF A CARRIER PLUG.