CA1232951A - Microwave drying of pharmaceutical gelatin capsules - Google Patents
Microwave drying of pharmaceutical gelatin capsulesInfo
- Publication number
- CA1232951A CA1232951A CA000522067A CA522067A CA1232951A CA 1232951 A CA1232951 A CA 1232951A CA 000522067 A CA000522067 A CA 000522067A CA 522067 A CA522067 A CA 522067A CA 1232951 A CA1232951 A CA 1232951A
- Authority
- CA
- Canada
- Prior art keywords
- drying
- tunnel
- microwave
- tunnels
- recited
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B6/00—Heating by electric, magnetic or electromagnetic fields
- H05B6/64—Heating using microwaves
- H05B6/78—Arrangements for continuous movement of material
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B2206/00—Aspects relating to heating by electric, magnetic, or electromagnetic fields covered by group H05B6/00
- H05B2206/04—Heating using microwaves
- H05B2206/046—Microwave drying of wood, ink, food, ceramic, sintering of ceramic, clothes, hair
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- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Drying Of Solid Materials (AREA)
Abstract
ABSTRACT
A machine for the manufacture of gelatin pharmaceutical capsules is disclosed, in which microwave drying is used. The drying section of the machine has two upper tunnels and two corresponding return tunnels beneath them, through which pin bars carrying the hot moist gelatin capsule halves pass. microwave transmitters are positioned above the upper tunnels to transmit microwave energy towards the capsule halves for drying. Inlet ducts along the outer sides of the upper tunnels supply cool, dry air which flows through apertures in the tunnel side walls and across the tunnels to an exhaust duct. The return tunnels also have a conditioned air system, supplied through ducts above the return tunnels having apertured bottom plates, for fine tuning the temperature and moisture content of the capsules prior to final processing operations.
A machine for the manufacture of gelatin pharmaceutical capsules is disclosed, in which microwave drying is used. The drying section of the machine has two upper tunnels and two corresponding return tunnels beneath them, through which pin bars carrying the hot moist gelatin capsule halves pass. microwave transmitters are positioned above the upper tunnels to transmit microwave energy towards the capsule halves for drying. Inlet ducts along the outer sides of the upper tunnels supply cool, dry air which flows through apertures in the tunnel side walls and across the tunnels to an exhaust duct. The return tunnels also have a conditioned air system, supplied through ducts above the return tunnels having apertured bottom plates, for fine tuning the temperature and moisture content of the capsules prior to final processing operations.
Description
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This inven-tion relates to the manufact-lre of pharmace~ltica1 hard ge1atin capsules, and particularly to -the drying~ o-f' the capsules during t:he manufac-tur:irg process.
In conventional hard gelatin capsule manufacturing machines, the gela-tin solution is con-tinuously gravity-f'ed from holding tan~s into the dipping pans of a ~ipper sec-tion. The level :in the dipping pans is regulated and maintained at a constant level by automatic eloat valves.
These dipp:ing pans are hot-wa-ter jacketed and equipped with l0 thermostati.cally-controlled electric heaters. The gelatin in the dipp:ing pans i.s maintained at a pre-se1 -temperature by automatic temperature controls to ensure the proper gelatin distribu-t:ion. Automatic viscosity controls constan-tly moni-tor gelatin viscosity and add water to o.ffse-t evaporation.
The caps and bod:ies oF the capsules are formed on vertically oriented s-tainless steel mold pins, supported on what are commonly referred to as "pin bars". Each pin bar has stainless steel pins of the size of -the desired capsule.
The following is a simp].if'ied description of a full cycle through a conventional hard gelatin capsule manueac turing machine .
Two sets (one with the capsule bodies, one with the capsule caps) of pin bars are lowered into the gela-tin dipping pan to a level prede-tarmined by a cam (whose size and shape depends on the size of capsules being run on the machine). Once dipped, -the pin bars are slowly retracted erom the gelatin and elevated to the upper drying kiln.
This inven-tion relates to the manufact-lre of pharmace~ltica1 hard ge1atin capsules, and particularly to -the drying~ o-f' the capsules during t:he manufac-tur:irg process.
In conventional hard gelatin capsule manufacturing machines, the gela-tin solution is con-tinuously gravity-f'ed from holding tan~s into the dipping pans of a ~ipper sec-tion. The level :in the dipping pans is regulated and maintained at a constant level by automatic eloat valves.
These dipp:ing pans are hot-wa-ter jacketed and equipped with l0 thermostati.cally-controlled electric heaters. The gelatin in the dipp:ing pans i.s maintained at a pre-se1 -temperature by automatic temperature controls to ensure the proper gelatin distribu-t:ion. Automatic viscosity controls constan-tly moni-tor gelatin viscosity and add water to o.ffse-t evaporation.
The caps and bod:ies oF the capsules are formed on vertically oriented s-tainless steel mold pins, supported on what are commonly referred to as "pin bars". Each pin bar has stainless steel pins of the size of -the desired capsule.
The following is a simp].if'ied description of a full cycle through a conventional hard gelatin capsule manueac turing machine .
Two sets (one with the capsule bodies, one with the capsule caps) of pin bars are lowered into the gela-tin dipping pan to a level prede-tarmined by a cam (whose size and shape depends on the size of capsules being run on the machine). Once dipped, -the pin bars are slowly retracted erom the gelatin and elevated to the upper drying kiln.
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These -two se-t6 of pin bars are then ~sd into a pair o~ drying kiln systems eacll totalling some 50 to 52 ~eet in running leng-th. In these kilns, the pin bars are subjected -to very tightly controlled air conditions. Supply air i~ con-trolled -to wi-thin -~1% relative humidity and temperatures Or -~1 CeLsius. Likewise the volume rate of air in cubic -~eet per minute (cfm) or in cubic metres per hour (m /hr) is also tightly controlled. These close tolerances are essential so tha-t the capsules are not 10 subject to corruga-tion, brittleness, cracking and so on. If not enough moisture is removed from the capsules during the dryin~ -time dictated by the overall speed of the capsule machine, then the capsule halves enter the later operations o~ the machine in a -too we-t condition. In this case, ~urther processing (such as stripping the capsule halves from -the pin molds, cu-tting them to -the proper lengths, and assembling the two halves to make -finished capsules) is impossible. If too much moisture is removed, cracking will result.
The pin bars are -first *ed by a conveyor system through upper kilns with running lengths of about 26 to 28 feet (depending on the manufacturer of -the capsule machine).
When the pin bars reach -the rear end of the upper kiln, they are pushed onto an elevator. The eleva-tor lowers groups of pin bars into the lower kilns where further drying takes place. After passing -through the lower ~iln ~about 2~ feet in length), the drying cycle is complete and the capsules ~' ! ~ 3 :
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have a-t-tained the recluired moisture content. The pin bars llOW proceed to t~te T~ble section of the machille where they are properly pos-itioned and fecl one by one into -the ~u-tomatic or Finisher section for final operations. This entire drying cycle -takes about 36 -to 4~ minutes depending on the speed at which the capsule machine is being run.
When the pin bars are -fed into the Automatic or Finisher sec-tion from the ~able section, stripper jaws close over -the pins and remove the capsule halves. As -the capsule 10 halves are being stripped from the pins, collets Dtove forward and receive them. Rods ins;de the collets posi-tion the capsule halves and then the collets move back and lock.
The collets then rise and rota-tet while cut-ting knives precisely trim the capsules to the proper length and then withdraw. The trimmings are removed by vacuum in a cutting collector.
The collets containing bo-th caps and bodies move forward and ejector rods push the capsule halves into joiner blocks. A-t this poin-t the collets retract, leaving the 20 joined capsules in the joiner blocks. The joined capsules are pu~hed out of the joiner blocks onto a conveyor belt which carries them out of -the machine and into a container.
Meanwhile, the pin bars move through a ~reaser section, in which greaser heads polish the pins and apply a light film of special lubricant. This lubricant facilitates proper stripping of the capsules from the pins on the nex-t cycle.
The pin bars then enter the Dipper section to begin the cycle once more.
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The lengttly drying -time alld the unga:in:ly overall length of the machine has been necessary hereto-fore due to the ine:f-~icien-t nature o-~` conventional dry:ing wh:ich tends to form a skin on the surface of the capsule halves. This makes it very di~-~:icul-t :for the mois-ture within -the capsu:Le halves -to migrate to -the sur-~ace and subsequently evaporate as it absorbs hea-t ~rom -the air.
Because -the drying cycle is about 38 -to 40 minutes in -the conven-tiona:l capsule machine, the machine is about ~0 10 fee-t in length. A shorter drying cycle would permit the machiDe -to be shor-tened, which would have obvious cost and other advantages, but hitherto no satis-factory alternative drying means has been developecl.
It is an object of the present invention to reduce the drying -time involved in the production o-f hard gelatin capsules, thereby shortening the overall capsule processing t-ime.
It is a fur-ther objec-t o~ the invention -to reduce the amount of energy required to achieve the optimum 20 moisture con-ten-t in the capsule halves prior to the:ir final processing.
It is a :~urther object of the invention to reduce the overall length o-f the hard gelatin capsule manufacturing machinery.
It is a -further object o-f the invention to provide relatively lower cost and mechanical simplicity of the hard gelatin capsule machinery.
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It has been determined tha-t the mos-t ef-fect:ive way to address the objects of the invention is to use microwave power -to provicle energy clirec-tly to -the "bonded moisture"
within the capsule. This energy transmit-ted directly to the gelatin capsule ~without heat:ing the air) penetrates the gelatin and accelerates -the migration of moisture to the sur~ace of the capsu:les due to, among other reasons, the rise in -temperature. Moreover, with an adequate and con-t;ro:L:Led amoun-t Or absorbed energy, partial evaporation 10 takes place within the capsules. This generates sufficient pressure -to -further speed up the migra-tion o-~ mois-ture -to the surface of capsules. Thus, -the overall drying rate is signif:ican-tly increased. This a:Llows a large reduc-t:ion of the overall size of the drying chamber as well as drast:ically reducin~ -the amoun-t o-~ energy required to dry the capsules. It has been projected that for a typical capsule the drying -time can be reduced -to about ~ minutes and the overall length of the machine can be reduced to about 2~ feet.
Microwave technology has been used in -the past in, among other applications, the baking of bread, the drying of pasta, -the drying and curing of *oundry sand cores, and the curing of rubber.
This technology has not been employed in gelatin capsule manu~acturing in the past due to: (1) perceived problems in the use o~ stainless steel pin bars in a micro-wave field (The capsule industry regards stainless steel pin bars as standard, and this is not likely to change due to . . . ~ --,. .; .
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', ~3;29531 the huge quant:ities of pin bars prevalent in the field.);
(2) I;he percept-ion that when passing groups of pin bars through the microwave field tha-t they would be subjected to "hot æpots" where differen-t degrees of drying would exist on various areas of the capsules; and (3) the possibility o-f microwave leakage into the capsule production room.
In the invention, it is s-till necessary to provide a means -for conl;rolling the air -temperature and the relative humidity condi-tions in the kilns in a manner compatible with the simultaneous application of microwave energy. This is important because -the application of microwave energy alone does not achieve the proper characteris-tics in the capsules.
Further, such temperature and humidity control must be carried out in a manner which cloes not result in undesirable microwave attenuation.
The preferrecl embodiment of the inven-tion wi:Ll now be described, by way of example only, with reference to the accompanying drawings, in which:
Fig. 1 is a perspective of the preferred 20 embodiment of the appara-tus, cut open to show detai:Ls; and Fig. 2 is a side view, showing overlapping energy cones.
The machine of the present inven-tion is substantially as described above, but with a much shorter drying section than in conventional machines. The preferred embodiment of the drying section, as illus-trated in Fig. 1, comprises -two upper tunnels 1, 2 and two corresponding lower ; 7 :
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or return tunnels 3, 4 directly beneath the upper tunnels l, 2, a:L:I suppor-ted on a sui-table ~rame 5.
Each of the upper tunnels 1, 2 is de~ined by a solid bottom rack 6, apertured side walls 7, and a top plate 8, all made of shee-t metal or other suitable material.
~ ach of -the two bo-ttom racks 6 receives pin bars 9 ~rom the dipping section (no-t shown). The pin bars 9, carrying the hot moist gelatin capsule halves, pass through the upper tunnels 1,2 in approximately 3 to 4 minu-tes after 10 making a llu~ er of stops o-~ approximately ~0 to 5U seconds in duration. The pin bars are not continuously conveyed, but are pushed clown the tunnels stepwise by the introduction of subsequent pin bars.
Conventional microwa-ve -transmit-ters, comprising magnetrons 10 and downwardly opening horns 11, are pos-itioned above the upper tunnels 1, 2 -to transmit microwave energy towards the capsule halves passing -through the upper tunnels 1, 2. ~pér-tures 12 are provided in the top plates 8 of the upper tunnels 1, 2 in order to 20 accommodate these microwave transmit-ters. The magnetrons 10 are connected to a suitable conventional power supply (not shown).
~ pper -tunnel 1 receives pin bars 9 carry:ing^
capsule bodies, while upper tunnel 2 receives pin bars 9 carrying capsule caps.
Since the bodies o-f the capsules are roughly twice the length o~ the caps, different amounts of microwave ener~y are required to evaporate moisture in the cap and ., , . ~
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body sides of the machine. There-~ore, there are approximately twice as many microwave -tranc;mit-ters on the body side, i.e. above upper tunnel 1, as on the cap side, i.e. above uppe-r tunne] 2. I-t is however possible -to change either the configuration o-f the cap side or the body side by changing the nLImber, placement, and/or outpu-t o-~ the transmitters. The number and position of microwave -transmi-tters i:llus-trated in Fig. 1 is shown only as one example.
~s shown in Fig. 2, -the microwave transmit-ters preferably are arranged such that the emitted microwave energy over'laps by roughly 10 percen-t or more to avoid "cold spots." Their height above the pin bars 9 is approximately 2~ cent:imeters or 1() inches in order to achieve an even distribution over the capsule halves. ~i-fferent configura-tions are o-f course poss:ible, by employing dif-ferent numbers of microwave transmi-t-ters and a different design of dis-trib-ution of microwave power.
It should be clearly understood, however, that it 2n iS no-t s-tric-tly essen-tial to the inven-tion -that -the capsule halves pass through more than one microwave transmitter each, though i-t is cer-tainly pre~erable and more e~fective to have more -than one.
~ n airs-tream is still required, to carry away evaporated moisture. For this purpose, inlet ducts 13 along -the ou-ter sides o-f -the upper -tunnels 1, 2 supply cool, dry air ~rom a standard industrial type air conditioning and , . .~. . - -,.
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dehumidificat:ion system, typically a-t around 21 degrees Celo:ius ancl 40 percent relat:ive humiclity. ~ space between the upper tunIlels 1, 2 constitutes an exhaust duct 14. The a:ir enters the inlet duct~ 13 near the front end o:f the upper turlnels 1, 2, passes laterally through -the upper tunne.ls 1, 2 via the aper-tureæ in the side walls 7~ into -the exhaust duct 14, a~d out the exhaust 15 near the rear end oP
the upper tunne:ls 1, 2~ Passing -the air through laterally instead of longitudinally ensures that the air passing 10 around -the capsules in -the tunnel does not become saturated and thus unable to carry away moisture evaporated from the capsules.
The purpose oP -this air is -to carry away -the moisture evaporated Prom the capsules by the microwaves, rather than to carry ou-t dry:ing, though o-f course some limited drying action from the airstream is unavoidable, and there is no reason to avoid i-t. ~Iowever, since the drying is accomplished by the microwaves, there is no need for the .
expens:ive and wastePul energy input required to heat the 20 airstream, as is the case in conventional machines where the - drying action arises solely -Prom the airstream.
The pin bars 9 reach -the end of the upper tunnels 1, 2 in about 3 to 4 minutes. At -the end o-f -the upper -tunnels 1, 2, there is an elevator assembly, similar -to the assembly iD conventional machines and there-Pore not shown in ~ ~ detail, which is triggered automatically to lower the pin : bars 9 coming out oP the upper tunnels 1, 2 and push them _ .
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into the lower or return tunnels 3, 4. The capsules are essen-tially dry by the -t:ime they reach the return tunnels 3, ~, aDd thus there is no microwave drying in the return tunnels 3, 4. The return -tunnels 3, ~ do have a conditioned air system, supplied for example through ducts 20, 21 above return tunnels 3, ~ hav.ing aper-tured bo-t-tom plates 22. This conditioned air system, which may be o~ any other suitable s-tructure, is used ~or ~:ine tuning -to adjust the temperature o~ the pin bars, which are warm from the hot gelatin, and to 10 make any necessary m:inor adjus-tments in the mois-ture content o-~ the capsules prior to the final processing operations.
Since capsule clry:ing :is a cont:inuous process and the pin bars must enter and exit a microwave ~ield which is not turned on and o~, -the drying chambers must be constructed such that any microwave radiation leakage is attenuated, according to prevai:Ling sa-fety standards and governmen-t regulations. For this reason, and to prevent undesireable attenuation, the apertures in the side wallæ 7 preferably are small enough to prevent passage of the 2~ microwave. Similarly, at each end o-~ the chambers through ; which the pin bars pass, there is incorporated a comb shaped barrier 16 such that when the pin bar does pass through, the gap between the pins and the barrier will be o-~ the magnitude to stop propagation o-~ the microwave wavelength.
This comb shaped barrier 16 will be interchangeable such tha-t optimum attentuation o-~ microwave leakage is achieved when any size of pin bars are being run on the capsule machine. In both cases, the microwave energy will "see"
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these perforatio/ls or slits as solid walls, thus preven-ting their leakage into the capsule produc-tion room.
Tt must be appreciated that the area around where the pin bars 9 en-ter and exit -the upper tunnels 1, 2 is enclosed within the maehine as a whole, so -that any minor leakage out the ends o~ -the upper tunnels 1, 2 is largely contained within the machine as a whole. In any event, most o~ the energy is absorbed by the capsule halves on the pin bars 9.
~hatever shielding or labyrin-th arrangemen-t is used in any given installation is of course subject to considerab:Le designer discretion. I-t is the responsibility of anyone prac-tising the invention to ensure that adequate sa~ety precautions are employed, as is -the case wi-th any microwave facility. The specific precautions are not part o~ -this invention.
The microwave -rrequency employed is an ordinary design choice. Suitable microwave frequencies presently considered ~or this application are 915 MHz and 2~50 MHz, 20 although any o-ther suitable frequency could be employed.
As to the power level o~ the microwaves, this is readily calculated, with no need ~or special expertise, since the number of pins in the chamber at any given time, the moisture content of the capsule halves on the pins, and their speed through -the machine is known. Thus the rate at which the water must be evaporated can be calculated, as well as the total energy inpu-t required to do so. The ~ -_ .
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calculation determines the approximate power required, and -then the fina:l power inpu-t is determined empirically, by care~ul monitoring and sampling, and adjustment of the power level basecl on the moisture content of the samp:Les.
The power level o~ the microwaves may be constant along -the upper tunne:ls 1, 2, or may be se-t to gradually reduce along the length o~ the tunnels for more economical drying.
The advantages o~ -the inven-tion may be summarizeci 10 a~ ~ollows I-t is an-ticipated that signi-ficant energy savings can be reali~ed with the microwave drying system. The clima-te control energy requirements for a capsule producer's Pactory could po-tentially be reduced by as much as one hal~
in some cases. Not only is the capital cost o~ climate control equipment significantly reduced, but also the operating cos-ts are significantly reduced. For example, with the microwave system in a -~ac-tory currently requiring about 12~ tons o~ air conditioning, i-t is projected that 20 possibly only about 50 -tons may be required. This alone would represent enormous energy savings. In addition, -the haat added by the machine to dry the capsules may be reduced by as much as one -third. Currently about 22-2~ kw of heat typically are applied -to the capsules ~or each machine during -the drying cycle. During a 2~ hour prod-uc-tion process, on each o~ ~our machines in a typical capsule factory, this would represent approximately 210,000 kwh over a year only in added heat. With the microwave drying system ~ .
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this could conceivab:Ly be redllced -to possibly as :Li-ttle as about 140,000 kwh over a year. Thus with possibly only half the energy required for cl:imate control and poOEsibly only two--thirds the energy required -for added heat, a capsule mach:ine using the microwave dry:ing system is ex-tremely marketable on energy savings alone. In addition, roughly on:Ly ha]-f o:f the production room space is required in comparison with conventional machines. Thus the user's capital costs as well as operating costs for climate con-trol 10 will again be significan-tly reduced.
Other benefits may include an improved finished product as the drying process for the capsule may be more even, with the drying -taking place -from the inside of the capsule -to the outside. It is also expected that increased productivity in capsule production will be realized as experience with the microwave drying system grows.
Opera-ting costs wi:Ll also be signi-ficantly reduced -for the machine user, since -the microwave transmitters (megatrons) can be replaced at very nominal costs during routine 20 maintenance.
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These -two se-t6 of pin bars are then ~sd into a pair o~ drying kiln systems eacll totalling some 50 to 52 ~eet in running leng-th. In these kilns, the pin bars are subjected -to very tightly controlled air conditions. Supply air i~ con-trolled -to wi-thin -~1% relative humidity and temperatures Or -~1 CeLsius. Likewise the volume rate of air in cubic -~eet per minute (cfm) or in cubic metres per hour (m /hr) is also tightly controlled. These close tolerances are essential so tha-t the capsules are not 10 subject to corruga-tion, brittleness, cracking and so on. If not enough moisture is removed from the capsules during the dryin~ -time dictated by the overall speed of the capsule machine, then the capsule halves enter the later operations o~ the machine in a -too we-t condition. In this case, ~urther processing (such as stripping the capsule halves from -the pin molds, cu-tting them to -the proper lengths, and assembling the two halves to make -finished capsules) is impossible. If too much moisture is removed, cracking will result.
The pin bars are -first *ed by a conveyor system through upper kilns with running lengths of about 26 to 28 feet (depending on the manufacturer of -the capsule machine).
When the pin bars reach -the rear end of the upper kiln, they are pushed onto an elevator. The eleva-tor lowers groups of pin bars into the lower kilns where further drying takes place. After passing -through the lower ~iln ~about 2~ feet in length), the drying cycle is complete and the capsules ~' ! ~ 3 :
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have a-t-tained the recluired moisture content. The pin bars llOW proceed to t~te T~ble section of the machille where they are properly pos-itioned and fecl one by one into -the ~u-tomatic or Finisher section for final operations. This entire drying cycle -takes about 36 -to 4~ minutes depending on the speed at which the capsule machine is being run.
When the pin bars are -fed into the Automatic or Finisher sec-tion from the ~able section, stripper jaws close over -the pins and remove the capsule halves. As -the capsule 10 halves are being stripped from the pins, collets Dtove forward and receive them. Rods ins;de the collets posi-tion the capsule halves and then the collets move back and lock.
The collets then rise and rota-tet while cut-ting knives precisely trim the capsules to the proper length and then withdraw. The trimmings are removed by vacuum in a cutting collector.
The collets containing bo-th caps and bodies move forward and ejector rods push the capsule halves into joiner blocks. A-t this poin-t the collets retract, leaving the 20 joined capsules in the joiner blocks. The joined capsules are pu~hed out of the joiner blocks onto a conveyor belt which carries them out of -the machine and into a container.
Meanwhile, the pin bars move through a ~reaser section, in which greaser heads polish the pins and apply a light film of special lubricant. This lubricant facilitates proper stripping of the capsules from the pins on the nex-t cycle.
The pin bars then enter the Dipper section to begin the cycle once more.
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The lengttly drying -time alld the unga:in:ly overall length of the machine has been necessary hereto-fore due to the ine:f-~icien-t nature o-~` conventional dry:ing wh:ich tends to form a skin on the surface of the capsule halves. This makes it very di~-~:icul-t :for the mois-ture within -the capsu:Le halves -to migrate to -the sur-~ace and subsequently evaporate as it absorbs hea-t ~rom -the air.
Because -the drying cycle is about 38 -to 40 minutes in -the conven-tiona:l capsule machine, the machine is about ~0 10 fee-t in length. A shorter drying cycle would permit the machiDe -to be shor-tened, which would have obvious cost and other advantages, but hitherto no satis-factory alternative drying means has been developecl.
It is an object of the present invention to reduce the drying -time involved in the production o-f hard gelatin capsules, thereby shortening the overall capsule processing t-ime.
It is a fur-ther objec-t o~ the invention -to reduce the amount of energy required to achieve the optimum 20 moisture con-ten-t in the capsule halves prior to the:ir final processing.
It is a :~urther object of the invention to reduce the overall length o-f the hard gelatin capsule manufacturing machinery.
It is a -further object o-f the invention to provide relatively lower cost and mechanical simplicity of the hard gelatin capsule machinery.
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It has been determined tha-t the mos-t ef-fect:ive way to address the objects of the invention is to use microwave power -to provicle energy clirec-tly to -the "bonded moisture"
within the capsule. This energy transmit-ted directly to the gelatin capsule ~without heat:ing the air) penetrates the gelatin and accelerates -the migration of moisture to the sur~ace of the capsu:les due to, among other reasons, the rise in -temperature. Moreover, with an adequate and con-t;ro:L:Led amoun-t Or absorbed energy, partial evaporation 10 takes place within the capsules. This generates sufficient pressure -to -further speed up the migra-tion o-~ mois-ture -to the surface of capsules. Thus, -the overall drying rate is signif:ican-tly increased. This a:Llows a large reduc-t:ion of the overall size of the drying chamber as well as drast:ically reducin~ -the amoun-t o-~ energy required to dry the capsules. It has been projected that for a typical capsule the drying -time can be reduced -to about ~ minutes and the overall length of the machine can be reduced to about 2~ feet.
Microwave technology has been used in -the past in, among other applications, the baking of bread, the drying of pasta, -the drying and curing of *oundry sand cores, and the curing of rubber.
This technology has not been employed in gelatin capsule manu~acturing in the past due to: (1) perceived problems in the use o~ stainless steel pin bars in a micro-wave field (The capsule industry regards stainless steel pin bars as standard, and this is not likely to change due to . . . ~ --,. .; .
.. : ,. : : :
: :
', ~3;29531 the huge quant:ities of pin bars prevalent in the field.);
(2) I;he percept-ion that when passing groups of pin bars through the microwave field tha-t they would be subjected to "hot æpots" where differen-t degrees of drying would exist on various areas of the capsules; and (3) the possibility o-f microwave leakage into the capsule production room.
In the invention, it is s-till necessary to provide a means -for conl;rolling the air -temperature and the relative humidity condi-tions in the kilns in a manner compatible with the simultaneous application of microwave energy. This is important because -the application of microwave energy alone does not achieve the proper characteris-tics in the capsules.
Further, such temperature and humidity control must be carried out in a manner which cloes not result in undesirable microwave attenuation.
The preferrecl embodiment of the inven-tion wi:Ll now be described, by way of example only, with reference to the accompanying drawings, in which:
Fig. 1 is a perspective of the preferred 20 embodiment of the appara-tus, cut open to show detai:Ls; and Fig. 2 is a side view, showing overlapping energy cones.
The machine of the present inven-tion is substantially as described above, but with a much shorter drying section than in conventional machines. The preferred embodiment of the drying section, as illus-trated in Fig. 1, comprises -two upper tunnels 1, 2 and two corresponding lower ; 7 :
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. , ~23~95~
or return tunnels 3, 4 directly beneath the upper tunnels l, 2, a:L:I suppor-ted on a sui-table ~rame 5.
Each of the upper tunnels 1, 2 is de~ined by a solid bottom rack 6, apertured side walls 7, and a top plate 8, all made of shee-t metal or other suitable material.
~ ach of -the two bo-ttom racks 6 receives pin bars 9 ~rom the dipping section (no-t shown). The pin bars 9, carrying the hot moist gelatin capsule halves, pass through the upper tunnels 1,2 in approximately 3 to 4 minu-tes after 10 making a llu~ er of stops o-~ approximately ~0 to 5U seconds in duration. The pin bars are not continuously conveyed, but are pushed clown the tunnels stepwise by the introduction of subsequent pin bars.
Conventional microwa-ve -transmit-ters, comprising magnetrons 10 and downwardly opening horns 11, are pos-itioned above the upper tunnels 1, 2 -to transmit microwave energy towards the capsule halves passing -through the upper tunnels 1, 2. ~pér-tures 12 are provided in the top plates 8 of the upper tunnels 1, 2 in order to 20 accommodate these microwave transmit-ters. The magnetrons 10 are connected to a suitable conventional power supply (not shown).
~ pper -tunnel 1 receives pin bars 9 carry:ing^
capsule bodies, while upper tunnel 2 receives pin bars 9 carrying capsule caps.
Since the bodies o-f the capsules are roughly twice the length o~ the caps, different amounts of microwave ener~y are required to evaporate moisture in the cap and ., , . ~
~3~935~
body sides of the machine. There-~ore, there are approximately twice as many microwave -tranc;mit-ters on the body side, i.e. above upper tunnel 1, as on the cap side, i.e. above uppe-r tunne] 2. I-t is however possible -to change either the configuration o-f the cap side or the body side by changing the nLImber, placement, and/or outpu-t o-~ the transmitters. The number and position of microwave -transmi-tters i:llus-trated in Fig. 1 is shown only as one example.
~s shown in Fig. 2, -the microwave transmit-ters preferably are arranged such that the emitted microwave energy over'laps by roughly 10 percen-t or more to avoid "cold spots." Their height above the pin bars 9 is approximately 2~ cent:imeters or 1() inches in order to achieve an even distribution over the capsule halves. ~i-fferent configura-tions are o-f course poss:ible, by employing dif-ferent numbers of microwave transmi-t-ters and a different design of dis-trib-ution of microwave power.
It should be clearly understood, however, that it 2n iS no-t s-tric-tly essen-tial to the inven-tion -that -the capsule halves pass through more than one microwave transmitter each, though i-t is cer-tainly pre~erable and more e~fective to have more -than one.
~ n airs-tream is still required, to carry away evaporated moisture. For this purpose, inlet ducts 13 along -the ou-ter sides o-f -the upper -tunnels 1, 2 supply cool, dry air ~rom a standard industrial type air conditioning and , . .~. . - -,.
5~
dehumidificat:ion system, typically a-t around 21 degrees Celo:ius ancl 40 percent relat:ive humiclity. ~ space between the upper tunIlels 1, 2 constitutes an exhaust duct 14. The a:ir enters the inlet duct~ 13 near the front end o:f the upper turlnels 1, 2, passes laterally through -the upper tunne.ls 1, 2 via the aper-tureæ in the side walls 7~ into -the exhaust duct 14, a~d out the exhaust 15 near the rear end oP
the upper tunne:ls 1, 2~ Passing -the air through laterally instead of longitudinally ensures that the air passing 10 around -the capsules in -the tunnel does not become saturated and thus unable to carry away moisture evaporated from the capsules.
The purpose oP -this air is -to carry away -the moisture evaporated Prom the capsules by the microwaves, rather than to carry ou-t dry:ing, though o-f course some limited drying action from the airstream is unavoidable, and there is no reason to avoid i-t. ~Iowever, since the drying is accomplished by the microwaves, there is no need for the .
expens:ive and wastePul energy input required to heat the 20 airstream, as is the case in conventional machines where the - drying action arises solely -Prom the airstream.
The pin bars 9 reach -the end of the upper tunnels 1, 2 in about 3 to 4 minutes. At -the end o-f -the upper -tunnels 1, 2, there is an elevator assembly, similar -to the assembly iD conventional machines and there-Pore not shown in ~ ~ detail, which is triggered automatically to lower the pin : bars 9 coming out oP the upper tunnels 1, 2 and push them _ .
:
~Z3295~
into the lower or return tunnels 3, 4. The capsules are essen-tially dry by the -t:ime they reach the return tunnels 3, ~, aDd thus there is no microwave drying in the return tunnels 3, 4. The return -tunnels 3, ~ do have a conditioned air system, supplied for example through ducts 20, 21 above return tunnels 3, ~ hav.ing aper-tured bo-t-tom plates 22. This conditioned air system, which may be o~ any other suitable s-tructure, is used ~or ~:ine tuning -to adjust the temperature o~ the pin bars, which are warm from the hot gelatin, and to 10 make any necessary m:inor adjus-tments in the mois-ture content o-~ the capsules prior to the final processing operations.
Since capsule clry:ing :is a cont:inuous process and the pin bars must enter and exit a microwave ~ield which is not turned on and o~, -the drying chambers must be constructed such that any microwave radiation leakage is attenuated, according to prevai:Ling sa-fety standards and governmen-t regulations. For this reason, and to prevent undesireable attenuation, the apertures in the side wallæ 7 preferably are small enough to prevent passage of the 2~ microwave. Similarly, at each end o-~ the chambers through ; which the pin bars pass, there is incorporated a comb shaped barrier 16 such that when the pin bar does pass through, the gap between the pins and the barrier will be o-~ the magnitude to stop propagation o-~ the microwave wavelength.
This comb shaped barrier 16 will be interchangeable such tha-t optimum attentuation o-~ microwave leakage is achieved when any size of pin bars are being run on the capsule machine. In both cases, the microwave energy will "see"
ff~
' ~ ~ ' . ~ .
~Z32~5~L
these perforatio/ls or slits as solid walls, thus preven-ting their leakage into the capsule produc-tion room.
Tt must be appreciated that the area around where the pin bars 9 en-ter and exit -the upper tunnels 1, 2 is enclosed within the maehine as a whole, so -that any minor leakage out the ends o~ -the upper tunnels 1, 2 is largely contained within the machine as a whole. In any event, most o~ the energy is absorbed by the capsule halves on the pin bars 9.
~hatever shielding or labyrin-th arrangemen-t is used in any given installation is of course subject to considerab:Le designer discretion. I-t is the responsibility of anyone prac-tising the invention to ensure that adequate sa~ety precautions are employed, as is -the case wi-th any microwave facility. The specific precautions are not part o~ -this invention.
The microwave -rrequency employed is an ordinary design choice. Suitable microwave frequencies presently considered ~or this application are 915 MHz and 2~50 MHz, 20 although any o-ther suitable frequency could be employed.
As to the power level o~ the microwaves, this is readily calculated, with no need ~or special expertise, since the number of pins in the chamber at any given time, the moisture content of the capsule halves on the pins, and their speed through -the machine is known. Thus the rate at which the water must be evaporated can be calculated, as well as the total energy inpu-t required to do so. The ~ -_ .
..
.- ' ' ` :
:
:
~3~S~S~
calculation determines the approximate power required, and -then the fina:l power inpu-t is determined empirically, by care~ul monitoring and sampling, and adjustment of the power level basecl on the moisture content of the samp:Les.
The power level o~ the microwaves may be constant along -the upper tunne:ls 1, 2, or may be se-t to gradually reduce along the length o~ the tunnels for more economical drying.
The advantages o~ -the inven-tion may be summarizeci 10 a~ ~ollows I-t is an-ticipated that signi-ficant energy savings can be reali~ed with the microwave drying system. The clima-te control energy requirements for a capsule producer's Pactory could po-tentially be reduced by as much as one hal~
in some cases. Not only is the capital cost o~ climate control equipment significantly reduced, but also the operating cos-ts are significantly reduced. For example, with the microwave system in a -~ac-tory currently requiring about 12~ tons o~ air conditioning, i-t is projected that 20 possibly only about 50 -tons may be required. This alone would represent enormous energy savings. In addition, -the haat added by the machine to dry the capsules may be reduced by as much as one -third. Currently about 22-2~ kw of heat typically are applied -to the capsules ~or each machine during -the drying cycle. During a 2~ hour prod-uc-tion process, on each o~ ~our machines in a typical capsule factory, this would represent approximately 210,000 kwh over a year only in added heat. With the microwave drying system ~ .
.i.. . -, - .
' .
;~ ' 9~
this could conceivab:Ly be redllced -to possibly as :Li-ttle as about 140,000 kwh over a year. Thus with possibly only half the energy required for cl:imate control and poOEsibly only two--thirds the energy required -for added heat, a capsule mach:ine using the microwave dry:ing system is ex-tremely marketable on energy savings alone. In addition, roughly on:Ly ha]-f o:f the production room space is required in comparison with conventional machines. Thus the user's capital costs as well as operating costs for climate con-trol 10 will again be significan-tly reduced.
Other benefits may include an improved finished product as the drying process for the capsule may be more even, with the drying -taking place -from the inside of the capsule -to the outside. It is also expected that increased productivity in capsule production will be realized as experience with the microwave drying system grows.
Opera-ting costs wi:Ll also be signi-ficantly reduced -for the machine user, since -the microwave transmitters (megatrons) can be replaced at very nominal costs during routine 20 maintenance.
:
::
,, ~ .
::: ' :
Claims (12)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a capsule manufacturing machine in which pin bars carrying wet gelatin capsule halves on pins projecting from said pin bars pass through a drying tunnel, the improvement comprising at least one microwave transmitter disposed adjacent at least a portion of said drying tunnel for radiating said pin bars in said tunnel to dry said gelatin capsule halves.
2. A capsule manufacturing machine as recited in claim 1, further including air supply means communicating with said drying tunnel for passing relatively cool, dry air through said tunnel in the region of said portion of said drying tunnel adjacent to said at least one microwave transmitter.
3. A capsule manufacturing machine as recited in claim 2, in which said air supply means passes said relatively cool, dry air through said portion of said drying tunnel laterally.
4. A capsule manufacturing machine as recited in claim 1, in which said at least one microwave transmitter is disposed adjacent only a first portion of said tunnel, and in which a subsequent portion of said tunnel includes drying means other than microwave drying means.
5. A capsule manufacturing machine as recited in claim 4, further including air supply means communicating with said drying tunnel for passing relatively cool, dry air through said tunnel in the region of said portion of said drying tunnel adjacent to said at least one microwave transmitter.
6. A capsule manufacturing machine as recited in claim 5, in which said air supply means passes said relatively cool, dry air through said portion of said drying tunnel laterally.
7. A capsule manufacturing machine as recited in claim 1, comprising at least two said microwave transmitters, said microwave transmitters being arranged so as to have the cones of their radiated energy substantially overlapping each other in the region of said pin bars, thereby producing a more even energy distribution.
8. A capsule manufacturing machine as recited in claim 7, further including air supply means communicating with said drying tunnel for passing relatively cool, dry air through said tunnel in the region of said portion of said drying tunnel adjacent to said at least one microwave transmitter.
9. A capsule manufacturing machine as recited in claim 8, in which said air supply means passes said relatively cool, dry air through said portion of said drying tunnel laterally.
10. A capsule manufacturing machine as recited in claim 7, in which said at least one microwave transmitter is disposed adjacent only a first portion of said tunnel, and in which a subsequent portion of said tunnel includes drying means other than microwave drying means.
11. A capsule manufacturing machine as recited in claim 10, further including air supply means communicating with said drying tunnel for passing relatively cool, dry air through said tunnel in the region of said portion of said drying tunnel adjacent to said at least one microwave transmitter.
12. A capsule manufacturing machine as recited in claim 11, in which said air supply means passes said relatively cool, dry air through said portion of said drying tunnel laterally.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000522067A CA1232951A (en) | 1986-11-03 | 1986-11-03 | Microwave drying of pharmaceutical gelatin capsules |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000522067A CA1232951A (en) | 1986-11-03 | 1986-11-03 | Microwave drying of pharmaceutical gelatin capsules |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1232951A true CA1232951A (en) | 1988-02-16 |
Family
ID=4134284
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000522067A Expired CA1232951A (en) | 1986-11-03 | 1986-11-03 | Microwave drying of pharmaceutical gelatin capsules |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1232951A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2826338A4 (en) * | 2012-03-14 | 2015-12-02 | 915 Labs Llc | Multi-line microwave heating system with optimized launcher configuration |
| US9370052B2 (en) | 2012-03-14 | 2016-06-14 | Microwave Materials Technologies, Inc. | Optimized allocation of microwave power in multi-launcher systems |
-
1986
- 1986-11-03 CA CA000522067A patent/CA1232951A/en not_active Expired
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2826338A4 (en) * | 2012-03-14 | 2015-12-02 | 915 Labs Llc | Multi-line microwave heating system with optimized launcher configuration |
| US9370052B2 (en) | 2012-03-14 | 2016-06-14 | Microwave Materials Technologies, Inc. | Optimized allocation of microwave power in multi-launcher systems |
| US9380650B2 (en) | 2012-03-14 | 2016-06-28 | 915 Labs, LLC | Multi-line microwave heating system with optimized launcher configuration |
| US9622298B2 (en) | 2012-03-14 | 2017-04-11 | Microwave Materials Technologies, Inc. | Microwave launchers providing enhanced field uniformity |
| US9681500B2 (en) | 2012-03-14 | 2017-06-13 | Microwave Materials Technologies, Inc. | Enhanced microwave system employing inductive iris |
| US9980325B2 (en) | 2012-03-14 | 2018-05-22 | Microwave Materials Technologies, Inc. | Enhanced control of a microwave heating system |
| US10448465B2 (en) | 2012-03-14 | 2019-10-15 | 915 Labs, LLC | Multi-line microwave heating system with optimized launcher configuration |
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