US2869060A - Ice maker and timer - Google Patents

Description

T. B. CHACE ICE MAKER AND TIMER Jan. 13, 1959 4 Sheets-Sheet 1 Filed April 2, 1956 Jan. 13, 1959 T. B. CHACE 2,869,060

ICEZ MAKER AND TIMER Filed April 2, 1956 4 Sheets-Sheet 2 hazzizzr Zia/v43 .5 (14,405

1959 T. B. CHACE 2,869,060

3 ICE MAKER AND TIMER Filed April 2, 1956 4 Sheets-Sheet 3 Jan. 13, 1959 Filed April 2, 1956 T. B. CHACE ICE MAKER AND TIMER 4 Sheets-Sheet 4 hazzfar M43 6540C ICE MAKER AND TIMER Thomas B. Chace, Winnetka, IlL, assignor to T Valve tlompany, Chicago, Ill a corporation of hi Application A ril 2, 1956, saint No. 575,623 7 Ciaims. c1. 318--37) This invention relates to improvements in ice makers and timers therefor.

Anobject of the invention is to provide a simplified form of ice maker in which the motive power for timing the ice making operation and ejecting the ice cubes from the molds comprises a simplified form crating heat motor.

' Another object of the invention is to provide a simple and improved form of heat motor operated timer particularly adapted for ice makers and the like.

Still another object of the invention is to provide continuously operating timer in which a plurality of sequentially operating heat motors provide the motive power for operating the timer and time the operation thereof.

Still another object of the invention is to provide a new and improved form of two speed timer operating at one speed to time certain operations, and at a lower speed to time certain other operations, in which a heat motor provides the motive power for the timer and the speed change is attained by varying the voltage supplied to heat the motor.

A further and more detailed object of the invention is to provide a simplified form of ice maker in which ice cubes are removed from ice cube molds by rotating the ice cubes therefrom in a continuous rotary operation and in which the motive power for rotating the ice cubes from the molds is generated by a plurality of alternately operating power type thermal elements successively heated by electrically energizable heating means.

Still another object of the invention is to provide an ice maker in which the ice cubes are rotated from their molds by operation of a rotatably movable ejector shaft, and in which the means for rotating the shaft also times the ice cube making operation and consist in a plurality of alternately energizable heat motors energized at one voltage during a part of the operation of freeing the ice cubes from their molds and at a lower voltage during the freezing operation to give the ice cubes time to freeze while the ejector shaft positions itself for a next succeeding ejecting operation.

These and other objects of the invention will appear from time to time as the following specification proceeds and with reference to the accompanying drawings wherein:

Figure 1 is a fragmentary plan view of an ice maker constructed in accordance with the invention;

Figure 2 is a fragmentary view in side elevation of one end of the ice maker shown in Figure 1 with certain parts of the ice molds shown in longitudinal section;

Figure 3 is a partial sectional view taken substantially along line III-III of Figure 1;

Figure 4 is a sectional view taken substantially along line IV-IV of Figure 1;

Figure 5 is a sectional view taken substantially along line V-V of Figure 1;

of positively op- Patent: W

" are inverted as shown Patented Jan. 13,

Figure 6 is an end view of the ice maker looking at the ice maker substantially along line VI-VI of Figure 1;

Figure 7 is an end view of the ice maker looking at the ice maker along line VllVll of Figure 1; and

Figure 8 is a diagrammatic view showing the circuit diagram for efiecting operation of the ice maker and carrying the ice maker through its ice making cycles.

in the embodiment of the invention illustrated in the drawings, the ice making apparatus includes generally a tray 1% which may be located in heat exchange relation with respect to the evaporator or freezing chamber of a refrigerator (not shown). The tray 10 has a plurality of cavities 11 therein opening to the top thereof and forming molds for freezing water in the form of individual cubes or blocks of ice 12, when the mold is conained within a refrigerator. The tray 10 may be made from a material havinga relatively high heat transfer such as copper, aluminum or any other suitable material. The cavities iii are shown in Figures 2 and 3 as having concave arcuate bottoms and outwardly flaring side walls and may be formed from a stainless steel clad copper, with the stainless steel in contact with the ice cubes and having a highly polished surface in contact with the ice, and the copper in contact with the body of the tray.

The walls of the cavities may also be coated with a silicone preparation to further facilitate the freeing of the ice cubes or blocks from their molds.

As herein shown, the tray 10 has a marginal recessed portion 15 extending along its bottom surface having an electric heating unit 16, such as a Cal-rod unit for heating the tray and individual cavities 11 to thaw the ice cubes 12 along their contacting surfaces with the cavities or molds 11 to facilitate the freeing of the ice cubes from their cavities. Where the outer surfaces of the cavities in contact with the ice are a highly polished stainless steel, the electric heating unit need not be provided. The heating unit, however, may be used to advantage where the cavities are lined with a material having a higher heat transfer than stainless steel clad copper, such as a copper clad stainless steel, in which case the cubes may tend to stick to the copper.

The means for removing the ice blocks from their cavities 11 comprises an ejector shaft 17 extending along the tray I'll above the cavities 11 and journaled in the end valls of the tray on bearings 19, retained in position by hearing caps 20 (see Figure 1). The ejector shaft 17 has ejector paddles 21 extending therefrom to one side of the axis of said shaft and herein shown as being formed integrally with said shaft. The ejector paddles 21 engage the ice blocks at one end thereof and pivot or sweep the ice blocks from the cavities 11 upon pivotal movement of the paddles 21 within and across said cavities. Upon further movement of said paddles the ice blocks in Figure 3 and then ejected along an inciined deflector 22 to one side of the tray. The deflector 22 is secured to a side wall of the tray 10 and extends therealong and inwardly therefrom over the cavities 11 at an acute angle with respect to the top A guard 24 is shown as being secured to the opposite side wall of the tray it from the deflector 22 and as having an arcuate wall 25 forming a continuation of the bottom wall of the cavities 11 and as extending over said path of travel e ector paddles 21 to provide clearance forthe ice blocks and to retain the ice blocks in inverted positions on the paddles 21 to be deposited on the deaseaoee u flector 2 2 and be moved therealong to one side of the ice tray upon rotational movement of the paddles 21 from the discharge to the entering ends of the cavities lit.

The means for operating the ejector shaft 17 and timing the ice making operation comprises two alternately operable heat motors 26 and Z7, herein shown as being electrically heated thermal elements, alternately operable to drive one-way drive mechanisms 29 and 3t) respectively, to eifect continuous rotation of the shaft 17 through 360 degrees.

The one-way drive mechanisms 29 and Fill and the thermal elements as and 27 are each of a similar construction so the thermal element 26 and the drive therefrom need only herein be described in detail.

The thermal element 26 is shown as being a well known form of power type of thermal element having an outer shield 31 encircling a resistor heater 32 diagrammatically illustrated in Figure 8. The resistor heater encircles a casing (not shown) for a fusible thermally responsive material, to etfect the extension of a piston 33 with respect to a heat conductor ring The thermal element operates on principles similar to those shown and described in the Vernet Patent No. 2,368,1Sl, dated January 30, 194-5, and is of a so-called power or highmotion solid fill type of thermal element. The wax or solid till type of thermal element shown has been selected for its compactness and simplicity, as well as its extreme power and relatively long range of travel of its power member or piston 33.

As herein shown, the thermal element 26 has a stud 3% extending from its end opposite the power member 33, which slidably extends through a guide lug 36, secured to a bracket 37 extending outwardly from an end wall 39 of the ice cube tray iii. A compression spring ill encircles the stud and is interposed between the thermal element and the bracket 37 to maintain the thermal element 26 in extended relation with respect to the bracket 37 during normal operating conditions, but to accommodate retractible movement of the thermal element with respect to its one-way drive mechanism 29 in cases where the ejector paddles may become jammed, allowing the thermal element-to move away from its power member 33.

Lock nuts 2-1 are provided to load the compression spring 4b and to locate the thermal element in the proper relation with respect to its associated one-way drive mechanism 2).

The one-way drive mechanism 29 is shown as being a pawl and ratchet type of drive mechanism and includes a ratchet Wheel 43 suitably secured to a collar 44 on the ejector shaft 17. A pin 45 extending through the collar 44 and ejector shaft 17 is provided to secure said collar 44 and ratchet wheel 43 to said ejector shaft 5.7. A pawl arm 46 is freely mounted on the ejector shaft 17 inwardly of the ratchet wheel 43 between the end wall 3% and. said ratchet wheel.

The pawl arm 46 has an arm 47 extending therefrom intermediate its ends having a bearing face 49 e: Ing inwardly toward thewall 39 and engaged by the end of the power member 33, for pivoting said pawl arm upon extensible movement of said power member with respect to the thermal element 26.

The pawl arm has an arm St), to which is connected a tension spring 51. The outer end of the tension spring 51 is connected to a stud 5% extending outwardly from the end wall 3% of the ice cube tray 10, for biasing the engaging face 4% of the arm 47 into engagement with the power member 33 and for returning the power member 33 with respect to the thermal element 26, upon dc energization of the heater 32 and cooling of the thermal element.

The pawl lever 46 also has a pawl arm 55 extending oppositely from the arm 5d and having a pawl 56 pivotally mounted thereon, on a pivot pin 5'7. A torsion spring 59 on the pin 57 engages the arm 4! at one end and v 4 the pawl 56 at its opposite end, to bias said pawl into engagement with the teeth of the ratchet wheel 43.

Thus, upon energization of the heater 32 and heating of the thermal element as the power member 33 extensibiy moving from the thermal element will pivot the pawl arm 36 in a direction, shown in Figure 4 as being a clockwise direction to engage the pawl 56 with a tooth of the ratchet wheel 4-3, and to move said ratchet wheel a distance equal to the length of one tooth of said ratchet wheel.

Upon deenergization of the heater 32 the tension spring 51 will return the power member 33 with respect to the thermal element 26 and also retractibly move the pawl 56 into position to engage a next succeeding tooth of the ratchet wheel A means is provided to cyclically energize the heater 32 alternately of energization of a heater 60 for the thermal element or heat motor 27. This means includes a switch 61 which may be a limit switch and which is operated by a cam wheel 63 suitably secured to the opposite end of the collar M from the ratchet wheel 43 and rotatably driven by said collar. The switch 61 may be a well known form of limit switch and is mounted on a bracket 64- secured to a side wall of the ice tray ill and extending from the end wall 39 over the ratchet wheel 43 to position a roller 65 on an operating arm 66 for the switch into position to be engaged by the cam wheel The switch 61 has a depressible button 67 depressed by the arm as as the roller 65' rides over a lobe 71 of the cam wheel 63. The switch arm 66 is shown as being pivotally mounted on the bracket 64 on a pivot pin 70, and as extending along said bracket into position to engage the button 67 to depress said button and close the switch til as the roller rides along a lobe 71 of the cam 63. This will effect energization of the heating element 3'2. for the thermal element 26, as will hereinafter more clearly appear as the specification proceeds.

The thermal element 27 at the opposite end of the ice cube tray ill from the thermal element 26 is supported On the ice cube tray to move along a power member '75 of said thermal element in cases where the ejector paddles may jam, and to operate a pawl lever '76 like the pawl lever 36 by engagement of its power member therewith. The power member 75 is returned by a return spring 77 connected between the ice cube tray and the pawl lever 76. A pawl 79 is engaged with the teeth of a ratchet wheel fill for rotating said ratchet wheel for a distance equal to the length of one tooth, each time the member 75 extensibly moves from its thermal element upon heating thereof, by energization of the heater 6!).

A cam wheel Sit is mounted on the shaft 17 outside of the ratchet wheel 8% for rotation with said ratchet Wheel. The cam till has a plurality of spaced lobes 83 along which rides a roller 34 on an arm 85, for periodically depressing a button 86 of a switch 37.

The cam wheel 31 like the cam wheel 63 is cut with the same number of lobes as there are teeth on the ratchet wheel The lobes of the cam wheel 81, however, are positioned one-half pitch from the lobes 71 of the cam wheel 63, to close the switch 37 as the switch 61 opens and vice versa.

Thus as the thermal element 26 is being heated, the thermal element 27 will cool and vice versa to cause the heat motors to operate with a self-contained oscillation in succession at a substantially constant period, causing step by step rotation of the ejector shaft 17 at a substantially average constant speed.

in driving the ejector shaft and the ejector paddles, I rotate said shaft and paddles at a relatively high rate of speed for degrees of rotation for removing the ice blocks from the cavities ill. I then rotate the ejector shaft 17 at a slower rate of speed for the next 180 degrees of rotation of said shaft in order to provide sufiicient time for the ice blocks turned from the molds to dry by t freezing the surfaces thereof, and to provide SlliTlClBIlt time to fill the mold with water and freeze the water as the ice cubes are dried and ejected without stopping travel of the ejector shaft 17 and paddles 21, and to bring the paddles 21 into engagement with a neXt succeeding batch of ice cubes as they are frozen.

This is attained by a cam 9t? on a right end of the shaft 17 and suitably secured to said shaft to be rotated therewith. The cam 9b is shown as having a lobe 91 extending thereabout for 186 degrees and engaging a roller 93 intermediate the ends of an arm 94-, pivoted on the bracket 64 for the switch or. on the pivot pin '76). The arm 94 operates a switch 96 on the bracket or, and engages an operating button W for said switch.

The switch 96 may be a double throw switch connecting the energizing circuit to the heaters and d9 directly to the main line circuit to energize said heaters at line voltage when the roller 93 is engaged by the lobe 91. As the roller 93 comes into engagement with the low part of the cam 9th, the switch 96 will connect a resistance 99 in series with the heaters 32 and ed and the control switches 61 and 87 therefor to reduce the voltage supplied to the heaters and tit and thus increase the time period required to heat the thermal elements and 27 to effect operation thereof. The paddle shaft 17 and ejector paddles 12 will thus rotate at a slower rate of speed during the second 180 degrees of rotation of said paddle shaft, during which time the paddles rotate over the tops of the cavities 11 to discharge the ice cubes to one side of the ice cube tray and move into position to turn a next succeeding batch of ice cubes from the ice cube tray, giving the ice cubes turned from their trays time to freeze dry on their outer surfaces and giving time to fill the tray and freeze a next succeeding batch of ice cubes as the paddles 21 turn over the top of the ice cube tray.

In the diagrammatic control circuit illustrated in Figure 8 of the drawings, 1 have shown an energizing circuit for the heaters 32 and on under the control of the switches 61 and 87 respectively, through main line conductors It)? and lt'ld. Parallel conductors 1 95 and as are c011- nected from the conductor to stationary contacts 107 and M9 and are engaged by a movable switch arm 11h operated by the cam The movable switch arm 11% has electrical connection with the switches 61 and 87 through conductors Ml. 15.2. The conductor 106 is shown as having the resistor connected therein, to provide a voltage at the stationary contact 199 which is substantially reduced from the voltage at the stationary contact 1W7.

When the lobe M is in engagement with the roller 93, the push button 97 will be depressed to complete a circuit from the stationary contact through the movable switch arm to the switches 61 and 537.

As a lobe 71 of the cam 63 engages the roller 65 to depress the lever arm as and the switch button 67, a circuit will be completed through the conductor Hi5, movable switch arm lltl, conductor H2, and switch 61 through the resistor heater 32 to the conductor to energize said resistor and heat the heat motor 46 to effect extensible movement of the plunger and the advance of the ratchet wheel 43 a distance equal to the length of one tooth of said ratchet wheel. At this point the roller 65 on the movable switch arm will have ridden off a lobe 71 into a recessed portion between said lobes. This will open the circuit to the heater 32 and the thermal element 26 will cool. The roller 84 on the switch arm 85, however, will have ridden on to a lobe 83 of the cam wheel 31 to depress the switch button 86 and close the switch 37 to energize the resistor heater 60 and effect pivotal movement of the cam wheel 80 and rotation of the shaft 17 a distance equal to the length of one tooth of said cam wheel.

As the ejector paddles 21 rotate 180 degrees and upwardly out of the cavities 11, the roller 93 will ride on to the low part of the earn 9%. This will cause engagement of the movable switch arm with the stationary contact 109 and place the resistor 99 in the circuit for the heaters 32 and 60. A low voltage will then be supplied to the heat motors 26 and 27, with a resultant slow speed rotation of the paddle shaft 17. The ice cubes removed from the cavities 11 will then rest on the ejector paddles 21.

During this time a measured volume of water may be supplied to the cavities 11 to fill the same for freezing. A valve operated by a solenoid 116 under the control of a switch 117 connecting the solenoid 116 to the conductors 103 and 104 is diagrammatically shown in Figure 8 as being provided to fill the ice cube tray 1G with a measured volume of water. The valve 115 may have flow control means therein to assure the delivery of a uniform volume of water over a predetermined time interval regardless of variations in pressure of the water at the source. The switch 117 may be cam operated by rotation of the shaft 17, the operating cam and switch not herein shown or described since they form no part of the present invention.

The resistor 99 is of such capacity that tl e time required for the paddles to move the ice cubes from the broken line position A in Figure 3 showing the ice cubes resting on the paddles, to the broken lines position shown in this figure showing the ice cubes being ejected along the deflector 22 to one side of the ice cube tray it is such as to completely dry the ice cubes by freezing the moisture on the surfaces thereof where the cubes have been loosened from their trays by heat. As the paddles rotate degrees from the time they leave the c..-.'.ies ll to the solid line position shown in Figure 3, sul'nc ent time will have elapsed to allow the water in the cavities ll to freeze solid.

When the ejector paddles 21 are in the solid line position shown in Figure 3, the lobe it of the cam 9:) will come into engagement with the roller 93 to depress the switch arm 9 and push button 97 and move the movable switch arm into engagement with the stationary contact 1637, to cut the resistor 9) out of the circuit to the heat motors 26 and 27 and to again successively energize the heaters 32 and on of said heat motors at a relatively high voltage to rotate the paddles at a relatively high speed of rotation in comparison with the speed of rotation when the heat motors 2d and 27 are energized through the resistor 9. A next succeeding ejecting operation may then commence.

fter the freezing operation and prior to the start of the eiecting operation, the heater 16 may be energized to thaw the surfaces of the ice cubes along the walls of the cavities ii to facilitate the removal of the ice cubes from said cavities. The heater 16 is shown in Figure 8 being energized through a switch 117 connecting said heater with the conductors 103 and lbs. The switch 119 may he cam operated in a well known manner so need not herein be shown or described further.

It should here be understood that whether the heater is used to loosen the ice cubes from their cavities depends upon the surface of the cavities. A. copper clad with stainless steel provides a good heat conductivity and also provides a surface from which the ice cubes may readily be removed from their trays without the use of heat. Stainless steel, however, clad with copper provides a surface having better heat conductivity than stainless steel clad copper, but with such a surface it is desirable to use heat to free the ice cubes from their cavities.

it will be understood that various modifications and variations of the present invention may be effected without departing from the spirit and scope of the novel concepts thereof.

I claim as my invention:

1. In a timer, at least two alternately operable thermal elements, a shaft for performing a work operation, spaced ratchets on said shaft for rotating the same, a separate pawl lever for each ratchet freely mounted on said shaft, each pawl lever having a pawl thereon engageable with said ratchet for driving the same in one direction, said thermal elements each having a casing containing a fusible thermally expansible material and a power member extensible with respect to said casing upon predetermined rises in tel iperature and having engagement w h said pawl lever for pivoting the same to effect engag ment of said pawl with said ratchet, an individual spring connected with each pawl lever and biasing levers into engagement with said power members, returning said members upon cooling of said thermal elements, electrically energizable heating means for said thermal elements for heating the same to effect the extensible movement of said power members, and n -c 1r; actuated by rotational. movement of said shaft for nately energizing said heating means to effect extensible movement of one power member and retractable moverent of the other power member and to thereby effect rotation of said shaft at a substantially average constant speed.

2. In two speed timer, at least two alternately operable ther if elements, each having a casing containing a fusible thermally expansible material and a power member extensible with respect to said casing upon predetermined rises in temperature, a separate heater for each of said thermal elements electrically energizable to heat said thermal elements, a shaft for performing a work operation, individual one-way drive mechanisms on said shaft and operated by said power members upon extensible movement thereof for driving said shaft in one direction, parallel energizing circuits to said heating elements, one energizing circuit having a resistor therein, means actuated by said one-way drive mechanisms to alternately energize said heating elements through either of said parallel circuits to effect alternate extension of said power members, a two-way switch operable when in one position to connect one circuit of said parallel energizing circuits to said heating element to energize the same at one voltage and when in another position to connect another circuit of said parallel energizing circuits to said heating elements to energize said heating elements at a lower voltage, and means operated by said one-way drive connection for opening and closing said switch during different cycles of rotation of said shaft, rotation of said shaft at different speeds.

3. In a two speed timer, atleast two alternately operable thermal elements, each having a casing containing a fusible thermally expansible material and a power member extensible with respect thereto upon predetermined rises in temperature, an individual electrically energizable heater for each thermal element, a one-way drive mechanism associated with each thermal element and operated by extensible movement of the power member thereof, a shaft rotatably driven by said one-way drive mechanism, means actuated by said one-way drive mechanisms to alternately energize said heaters to effect the operation of said thermal el ments, and other means actuated by operation of said one-way drive mechanisms to supply power to said thermal elements at different voltages upon different phases of rotation of said shaft, to vary the speed of rotation thereof.

4. In a two speed timer, at least two alternately operable thermal elements, each having a casing containing a fusible thermally expansible material and a power member extensibly movable with respect thereto upon predetermined increases in temperature, an individual electrically energizable heater for each thermal element, a one-way drive mechanism associated with each thermal element and operated by extensible movement of the power member thereof, a shaft driven by said one-way drive mechanisms, means actuated by said one-way drive mechanisms to alternately energize said heaters to effect the operation of said thermal elements, and other means actuated by operation of said one-way drive mechanisms to effect to supply power to said thermal elements at different voltages upon different phases of rotation of said shaft, to reduce the speed of rotation thereof, comprising a cam on said shaft, a two-way switch operated thereby, a resistor connected in an energizing circuit to said thermal elements, said cam moving said switch into one position to cut said resistor out of the circuit to said thermal elements and into another position to cut said resistor into the circuit to said thermal elements, to increase the heating time of said heaters and thermal elements and reduce the speed of rotation of said one-way drive mechanisms and shaft.

5. In a two speed timer, at least two alternately operable thermal elements, each having a casing containing a fusible thermally cxpansible material and a power member extensible with respect to said casing upon predetermined increases in temperature, an electrically energizable heater for each thermal element, a one-way drive mechanism for each thermal element, an individual operative connection between each power member and an associated one-way drive mechanism for operating the same upon extensible movement of said power members, an individual switch for energizing each heating element, individual cams operated by said one-way drive mechanisms for alternately operating said switches to alternately energize said heating elements, two energizing circuits to said switches, one circuit energizing said switches at line voltage and the other circuit having a resistor therein for supplying power to said switches at a lower voltage, a cam operated by one of said one-way drive mechanisms and a two-way switch operated thereby for connecting said switches in the energizing circuit to supply power to said heater at line voltage in one position of said cam, and through said resistor at a lower voltage than line voltage in another position of said cam.

6. In a combination heat motor and timer, a shaft for performing a work operation, spaced ratchets on said shaft, a separate pawl lever for each ratchet freely mounted on said shaft, each pawl lever having a pawl thereon engageable with said ratchet for driving the same in one direction, said thermal elements each having a casing containing a fusible thermally expansible material and a power member extensible with respect to said casing upon predetermined rises in temperature, an operative connection bet cen said power members and said pawl levers for pivoting said pawl levers to effect engagement of said pawls with said ratchets upon exensible movement of said power members, individual springs connected with the associated pawl levers and biasing said pawl levers into engagement with said power said power members upon cooling :iiilS, electrically energizable heatclements, means actuated by ing means for said ther rotational movement of said shaft for alternately energizing said heating means to effect extensible movement of said power rnerners alternately of each other and to thereby effect rota. on cf said shaft at a substantially average constant. 5 e mounting means for said thermal elements arcom lating axial movement of said thermal element with to said mounting means, and spring means normally rc "'ning said thermal elements from axial movement wit respect to said mounting means and accommodating axi" movement of said mounting means upon overload conditions to thereby discontinue rotat able movement id shaft.

7. in a two-"' o. con'ibinati n heat motor and timer, at least two .iatcly o erable thermal elements, an electrically c this b or for each thermal element, a one-way drive mechanism associated with each thermal element and ope ed thereby upon heating thereof, a shaft rotatably driven by said oncway drive mechanism, means actuated by said one-way drive mechanism to alternately ener e said heaters to effect the operation of said thermal elements, and other means actuated by operation of said one-way drive mechanisms to supply flower to said thermai elements at diiferen't vo1tages upon different phases of rotation of said shaft, to vary the speed of the rotation thereof.

Noble Oct. 11, 1932 Henninger Mar. 9, 1937 10 10 Vernet Jan. 30, 1945 Koonz Oct. 23, 1951 Knerr Sept. 13, 1955 Culbertson Nov. 1, 1955 Euler Jan. 3, 1956 FOREIGN PATENTS France Apr. 2, 1927

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