US3176408A

US3176408A - Freeze drying apparatus and method

Info

Publication number: US3176408A
Application number: US126234A
Authority: US
Inventors: Manuel E Fuentevilla
Original assignee: Pennsalt Chemical Corp
Current assignee: Pennwalt Corp
Priority date: 1961-07-24
Filing date: 1961-07-24
Publication date: 1965-04-06
Anticipated expiration: 1982-04-06

Description

April 6, 1965 M. E. FUENTEVILLA FREEZE DRYING APPARATUS AND METHOD Filed July 24, 1961 r I a 3 Sheets-Sheet l FIG.|

\LOAD CELL'S L ll:

INVENTOR. MANUEL E. FUENTEVILLA BY MAW ATTORNEY April 9 M. E. FUENTEVILLA 3,176,408

FREEZE DRYING APPARATUS AND METHOD Filed July 24, 1961 3 Sheets-Sheet 2 5 llNERT GAS INVENTOR. MANUEL E. FUENTEVILLA MHM ATTORNEY April 5 M. E. FUENTEVILLA 3,176,408

FREEZE DRYING APPARATUS AND METHOD Filed July 24, 1961 3 Sheets-Sheet 3 INVENTOR. MANUEL E. FUENTEVILLA By Mww ATTORNEY "United States Patent Ofiice 3,176,4h8 Patented Apr. 6, 1965 3,176,408 FREEZE DRYING APPARATUS AND METHOD Manuel E. Fuentevilla, Haddonfield, N..l., assignor, by mesne assignments, to Pennsalt Chemicals Corporation, Philadelphia, Pa., a corporation of Pennsylvania Filed July 24, 1961, Ser. No. 126,234 Claims. (Cl. 34-5) This invention relates to a freeze drying apparatus and method, and more particularly to a freeze drying apparatus and method wherein the freeze drying cycle is automatically controlled in response to the loss of weight of the articles undergoing freeze drying.

Numerous processes and apparatus for freeze drying specimens have been, proposed heretofore. In such devices and processes proposed heretofore, the length of the freeze drying cycle is based on empirical formulae. Accordingly, the cycle for the freeze drying process is nothing more than a calculated guess. Accordingly, it will be obvious that numerous inefficiencies are present in the apparatus and methods proposed heretofore.

The, present invention is directed to a method and apparatus wherein the freeze drying cycle is automatically controlled in response to the loss of weight of the articles being freeze dried. When using the apparatus or method of the present invention, it is not necessary for an operator to set any controls as to the timing of the cycle nor periodically inspect the articles being freeze dried so as to ascertain the status of the articles. In accordance with thepresent invention, the loss of weight of the articles being freeze dried is ascertained in accordance with any one of the embodiments of the present invention and means are provided for automatically stopping or varying the freeze drying cycle while at the same time activating an alarm so as to alert the operator.

In accordance with the present invention, the change in the loss of weight of the articles being freeze dried is ascertained in response to load cells which supportthe articles or in response to the electrical resistivity of the articles. As a result of the change in the weight of the articles being freeze dried, the heat being supplied to the articles may be, varied, or the pressure within the chamber enclosing the articles may be varied.

' It is an object of the present invention to provide a novel apparatus for freeze drying articles.

"It is another object of the present invention to provide a novel method for freeze drying articles.

It is still another object of the present invention to provide a novel apparatus for freeze drying articles wherein the freeze drying cycle is automatically controlled in response to the change in weight of the articles being freeze dried.

It is a still further object of the present invention to provide a novel method of freeze drying articles by varying the freeze drying cycle in response to the change of weight in the articles being freeze dried.

Other objects will appear hereinafter.

For the purpose of illustrating the invention there is shown in the drawings forms which are presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown.

FIGURE 1 is a schematic illustration of freeze drying apparatus in accordance with the present invention.

FIGURE 2 is a schematic illustration of another embodiment of the present invention.

FIGURE 3 is a schematic illustration of another embodiment of the present invention.

FIGURE 4 is a schematic illustration of another embodiment of the present invention.

FIGURE 5 is a schematic illustration of another embodiment of the present invention.

Referring to the drawing in detail, wherein like numerals indicate like elements, there is shown in FIGURE 1 a freeze drying apparatus designated generally as 10.

The freeze drying apparatus illustrated schematically as 10 comprises a housingv 12 having a plurality of hollow shelves 14 disposed one above the other and supported by said housing. Only one such shelf is illustrated in the drawing. The shelf 14 is hollow so that a heating medium may be circulated therethrough. The interior of the shelf 14 is connected to an inlet conduit 16 and an outlet conduit 18.

The

conduits

16 and 18 are connected to a pump 20 which continuously circulates the medium through the shelf 14. A heat exchanger 22 is disposed in the conduit 16 between the pump 20 and the shelf 14. The temperature of the heat exchanger 22 is regulated by a controlling fluid such as steam which is circulated therethrough by means of the inlet conduit 24 and the outlet conduit 26. The outlet conduit 26 is connected to a steam generator 28 having a pump 30. The outlet side of the pump 30 is connected to the inlet conduit 24. A valve 32 having a solenoid operator 34 is disposed within the conduit 24.

The shelf 14 is supported by

load cells

36 and 38.

Load cells

36 and 38 are commercially available devices which generate an electric current in response to pressure. Such load cells are extremely accurate and are not effected by the temperatures and pressures within the housing 12. The

load cells

36 and 38 are connected to the weight recorder and controller 44 by

wires

46 and 42. The weight recorder and controller 44 is a commercially available device which permanently records the electrical current generated by the load cells 36. and 38 on a graph which may be interpreted in terms of weight. In addition, the weight recorder and controller 44 relays the current received from the

load cells

36 and 38 to a controller 46.

The controller 46 regulates the flow of motive fluid to the diaphragm on a valve 48 in the conduit 50. The conduit 5%) is connected to the interior of the housing 12. The conduit 50 is provided with a vacuum pump 52 for evacuating the interior of the housing 12. An alarm 54 is connected to the weight controller and recorder 4,4 and is responsive to a minimal amount of current.

A tray is supported by the shelf 14 with legs on said tray spacing the same from the shelf 14. The tray 60 is filled with articles 62 which are to be freeze dried within the housing 12. The, condenser 66 is connected to the housing 12 by means of a conduit 64'.

The apparatus 10 operates as follows:

A tray 66 of articles 62; which are to be, freeze dried is disposed within the housing 12 On the shelf; 14;. The articles 62 are prefrozen. The door (not shown) providing access to the interior of the housing; 12 is provided with a seal means to that the housing 12 is hermetically sealed in the closed disposition of the door. A heating fluid is circulated through the shelf 14. by means of

conduits

16 and 18. The circulating fluid within the shelf 14 beats the articles 62 by radiation. All surfaces are colored black while the inner'gsurface on'the doorf is colored white.

As the articles 62 are heated by radiation, they are V 5 closes a plurality of'embodiments capable of controlling subject to a vacuum within the housing 12 effected by the pump 52. The combination of heat and the vacuum causes the ice within the frozen articles 62 to sublime with the resultant vapor being removed by therpurnp 52; As the ice Within the articles oz sublimes, the weight 1Q trated. For example, it is often'desirable to connect supported by the

load cells

36 and 38 decreases. 7

After a predetermined period of time,-the weight of the articles 62 will become stabilized thereby indicating" that substantially allroftheice is removed therefrom by sub-,

limation. a v

During the entire cycle, the controllen44ris recording the change in the current generated by the load cells 36' and 38 and relaying the same to alarm 54 and controller 45. a In response to a minimum current indicating that'- substantially all ice has been removed from thearticles '62, the alarm 54 is activated and controller46 is activated so as to close the valve 48. Thus, it will be seen that the freeze drying cycle is controlled so as to stop v V the cycle as soon as substantially allof theice has been removed from the'articles 62. v V n It has been determined that there is an optimum rate of change of weight of the articles 62 with respect to I time. It is possible to utilize a controller 46 which is of it the type which is capable .of receiving a signal" from the controller 44' so that the valve'48 is constantly varied durf ing the freeze drying process. Thus, the apparatus 1 may be operated with optimum efiiciency; I 1 An alternative embodiment of the present invention is illustrated schematically in FIGURE 2 and designated generally as 90. S Thetapparatus 9% is substantially identidal with the apparatus except as will be madeclear hereinaften' The controller 44 relays ja signalto a solef noid 7tl which operates the valve 63'in the conduitot). V In response to a minimalsignal, the solenoid '70 is .ac-

tuated to regulate the valve 68. The outlet side of the f condenser 66 is connected to manner side. of the vacuum" pump so that all condensate is removed fromthe air by g the condenserfdo beforebeing discharged toratmosphere by the pumpconnected thereto;

There is shown in FIGURE another embodiment of the present invention designated generally. as; 91. .The apparatus 91 is substantially identical with the apparatus 10 except as Willbe made clear hereinafter. In the lapfparatus 91, the signal received -,by theweightrecorder control is transmitted to the controller :46 Which'controls Y the how of motive fluid to the diaphragm actuated valve: 58 in the conduit 56. 1 The conduit 56' is'utilized to injecu .an inert atmo'sphere'into the housing 12. The injection;

of an inert atmosphere inthe housing lz' slowsidown' the freeze drying cycle .sinceit effects the vacuum therein.

As shown more clearly in FIGURE 4,-anotherfem bodiment of the present inventiom'designated generally as 92 is illustrated; In responseto an electrical signal from theload cells 36 and;38, the controller 44 aotuates' the alarm 54 and transmits'a signal to the controller72, 1 The controller 72,-inturn, actuates the solenoid 34 thereby closing the'valve 32. When'the valve 32- is closed,

the heat exchanger 22 ceases to be eifective- 7 Another. embodiment of the present invention designated generallyas 93 is illustrated in FIGURE 5. In

orderto ascertain the change in the weight of the articles 62- which are being freeze dried, an electrical resistor 74 is'dispos'ed within one or more ofthearticles' 62. The

resistor 72 is disposed ina11 electrical'circuit having a source 0f=power .76j'with the ehange in resistance being fed to thecontroller 44 through an amplifieri78,

As the ice inthe articles 62 sublimesgjthe 'resista nce of the articles. 62 is constantly changing. WhenHsubstari- ,tially .all of the ice has s'ublimed fromthe articles'62, the V resistance through the articles 62 will be substantially .35 tion of ice from the articles.

.59 V 4. A method of treating artlc signal; V r r g 1 5.- A rnethod inl accordance with claim 4 wherein said varying} step includes controlling the pressure'in said en- 60 closure in response to said'signal.

constant At'this point; the controller 44 will activate the alarm'54 and transmit a-signal to the controller 72 which causes the solenoid 34 to close the valve 32.

Then, it will betseen that the present invention disthe freeze drying process in response'to the change of Weight of the articles being freezedried. It will be apr preciated by those skilled in the art that it may be desirable to? combine orieor more of the embodiments illusvalve 32 at the same timethat the valve 63 is closed.

The present invention may be embodied in other specific formslwithout departing from the spirit or essential attributes thereof and, accordingly, reference should be i made to the appendedclaimg'rather than to the foregoing g0 specification as indicating the scope of the invention.

I claim; 7 v 5 1.. Apparatus for freeze dryingarticles of substantially I the same size andkind comprisinga housing having a chamber therein, a .shelf within said chamber, a tray for 2 5" frozen: articles to be-freeze dried within said housing, said tray being supported on said shelf, means forfreeze drying the articles on said tray by causing ice in the frozen specimens to sublime, and means responsive to the loss of weight of the articles for automaticallycontrolling said freeze dr in means, said last-mentionedmeans including at least one load cell supporting the Weight of said tray f and the articles to be freeze dried, whereby an electrical signal maybeg'enerat'ed which varies in accordance with the change of weight of the 'articles'due' to the sublima- 2. Apparatus in accordance withclaim lrwhereinfsaid 7 freeze drying means includesa valved -conduit through which the pressure 'in said'chamber'can be controlled, and the valve of saidvalved conduit being coupled to said 3. A method of freezedrying 'ar'ticles of substantially thes amesiz e and kind comprising the steps of freezing article s, disposing said frozenarticles in a hermetically ,sealedpnclosurje,evacuating said enclosure while subjecting said "articlesto heat so as to'cjause ice in said frozen 'L articles tosublime, and automatically continuously weighing the articles and generating asignalas a function there- 1 of, and controlling the amount of heat supplied to said articles inrepsonse to said signal. r

7 les of substantially the samefsize and kind comprising freeze dryingf'said-articles fin, a "he'rmetically sealed enclosure, automatically-icontinuously weighing the articles to ascertain the change in "loss-of Weight of the articles du'e'to sublimation of ice therefrom and generating a signalas a function thereof,

, and varying saidffreeze drying process in response to'said 6. A method inaccordance withclaim 4 wherein said weighing step includes supporting the articles by load cells,

and saidstep of generating a signal being accomplished by theload cells so thatthe signal generated will vary in accordance with the changeof weight of the articles due to the sublimation of ice from the articles; r

7.. Apparatus for freeze fdry'ng articles of substantially; thesame size and kind comprising a housing having a chambe'r'therein, a'shelf'within said chamber, said shelf being adapted to support frozen articles to befre'eze dried within s aidhousing means for freeze drying the articles I I on; said shelf byeausing ice in the frozen'articles', to sublime, and' wei'ghingfmeansfdirectlyjresponsive to the; loss f of weight jofthe articles for automatically controlling '75, saidfreezedrying-means; e r I 8. Apparatus in accordance with claim 7 wherein said means responsive to the loss of weight includes a device for varying the pressure in said chamber.

9. Apparatus in accordance with claim 8 wherein said device is a valved conduit for introducing a gas into the chamber.

10. Apparatus in accordance with claim 8 wherein said device is a valved conduit through which the chamber may be evacuated.

References Cited by the Examiner UNITED STATES PATENTS 2,994,132 8/61 Neumann 34-5 3,020,645 2/62 Copson 34-5 3,060,591 10/62 Lieberman 34-45 3,077,036 2/63 Neurnann 34--5 3,078,586 2/63 Rey 34-5 NORMAN YUDKOFF, Primary Examiner.

Claims

1. APPARATUS FOR FREEZE DRYING ARTICLES OF SUBSTANTIALLY THE SAME SIZE AND KIND COMPRISING A HOUSING HAVING A CHAMBER THEREIN, A SHELF WITHIN SAID CHAMBER, A TRAY FOR FROZEN ARTICLES TO BE FREEZE DRIED WITHIN SAID HOUSING, SAID TRAY BEING SUPPORTED ON SAID SHELF, MEANS FOR FREEZE DRYING THE ARTICLES IN SAID TRAY BY CAUSING ICE IN THE FROZEN SPECIMENS TO SUBLIME, AND MEANS RESPONSIVE TO THE LOSS OF WEIGHT OF THE ARTICLES FOR AUTOMATICALLY CONTROLLING SAID FREEZE DRYING MEANS, SAID LAST-MENTIONED MEANS INCLUDING AT LEAST ONE LOAD CELL SUPPORTING THE WEIGHT OF SAID TRAY AND THE ARTICLES TO BE FREEZE DRIED, WHEREBY AN ELECTRICAL SIGNAL MAY BE GENERATED WHICH VARIES IN ACCORDANCE WITH THE CHANGE OF WEIGHT OF THE ARTICLES DUE TO THE SUBLIMATION OF ICE FROM THE ARTICLES.