Dryer-cooler apparatus

Abstract: An improved dryer-cooler apparatus (10) cures or dries a heat sensitive coating (9) on a moving subtrate (5) in a manner to minimize problems related to heating. The apparatus comprises a cooling plate (20), and end block 30, 31) at each end (25, 26) of the cooling plate and a plurality of heating lamps (50) extending between the end blocks, above a reflective face (21) of the cooling plate. The cooling plate has a plurality of cooling passages (27) which extend from the top of bottom ends thereof, and each end block has a plurality of lamp openings (38) and has a plurality of coolant passage openings (39) that each aligns with a coolant passage of the cooling plate. The ends (52, 54) of each heating lamp are supported in an unencumbered manner in the lamp openings (38) of the end blocks. Thus, the heating lamps (50) and the cooling plate (20) and end blocks (30, 31) can expand and contract without damage when cyclically heated and cooled during periodic operation of the dryer-cooler apparatus. Coolant from a refrigeration system is circulated in a serpentine manner through the cooling plate while the heat generat­ ed by the adjacent heating lamps is reflected down­ wardly from the cooling plate reflective surface. Thus, the cooling plate acts as a heat-sink to absorb unused energy from the lamps and to cool the space on the opposite side of the cooling plate from the heating lamps.

Description: Field of the Invention. This invention relates to improved dryer-cooler apparatus and is particularly directed to apparatus using infra-red heating for curing or drying a heat sensitive coating on a moving substrate so as to minimize problems related to heating. Background of the Invention Recent advances in printing press drying applications using infra-red equipment have led to higher powered systems. In many drying applications, for both ink and other heat sensitive coatings, press operations have increased to the extent that substrate speeds of 152 m (500 feet) per minute are common. As a consequence, the surfaces of such substrates are irradiated or exposed to heat for only a very limited time. There has been a trend toward the used of higher specific output heating units. Lamps capable of up to 200 watts per 25,4 mm (inch) of infra-red power are currently in use. Due to the physical limitations on space within most printing press housings, the drying apparatus must accomplish its purposes more rapidly than in the past and within the restricted available space. With the higher operating temperatures of the high powered lamps the resultant heat behind conventional heating units is easily 10 to 37,8 °C (50 to 100 degrees Fahrenheit) above ambient temperatures, which initiates a detrimental increase in heat in the vicinity of the drying units. As the heat accumulates around the dryers, the temperature rises in the final housing in which the drying equipment is located and backs up into the adjacent printing unit creating further problems. It is well known that changes of as little as -12,2 °C to -9,4 °C (10° F. to 15° F). can significantly alter ink and coating viscosities, as well as affect water balance and alcohol content. The expansion and contraction of the dryer equipment leads to equipment failures. For example, many printing presses utilize chain driven continuous belts with grippers to feed the sheets by the dryers, and the spring loaded elements associated with such parts soften under the increasingly higher temperatures, creating further problems. Of course, when presses using infra-red drying apparatus are operated for long periods, e.g. three shifts per day, or during hot, high humidity conditions during the summer months the heating problems are compounded. Currently presses with infra-red drying systems operate with higher powered lamps in one of several ways. Some presses are operated in the old manner without adequate cooling, and the equipment is shut down when higher temperatures create problems. More efficient presses have associated cooling systems that utilize either air or water cooling apparatus. There has been a variety of prior art systems for dealing with the heat problems created by drying equipment. U. S. Patent No. 3,825,407 to Y. Fujite et al. describes a reflector for reducing heat in a copying machine by the use of a reflector plate adjacent the heating elements. While the system employs no direct cooling of the reflector, loosely mounted brackets for the reflector permit thermal distortion to take place without damage to the reflector. U. S. Patent No. 4,135,098 to H. Troue describes the use of a mercury vapor lamp with a reflector module to direct ultra-violet light to a coating on a moving substrate. The temperature of each reflector, which partially surrounds each lamp, is controlled by means of a water cooled heat sink spaced above the reflector so that only radiation heat transfer takes place between the reflector module surface and the heat sink. U. S. Patent No. 4,143,278 to R. L. Koch, II, describes the use of a cooling pipe arrangement positioned between a substrate and downwardly open lamp assemblies, which have ultra-violet lamps for heating the substrate. In addition to the cooling provided by the pipe arrangement, ambient air is circulated to the dryer housing and is exhausted from the lower portion thereof. U.S. Patent No. 4,408,400 to F. Colapinto, describes the use of a radiation type of heat exchanger which is positioned beneath the guide path of moving sheets to cool the unprinted underside of the passing sheets for the purpose of preventing any overheating. The above mentioned prior art inventions have helped reduce some heating problems associated with specific drying apparatus. However, modern, multi-stage high speed presses which utilize infra-red heating lamps to dry coatings on moving substrates continue to be plagued with problems created by excessive detrimental heat build-up in the immediate vicinity of the heating lamps, in the housings where they are located, and in the adjacent press components. From U.S. Patent No. 4 101 759 a dryer-cooler apparatus is known which is used for the purpose of batch heating and drying of semiconductor wavers by heating and drying of a number of wavers during a cycle. The wavers are not moving but are in a static condition and supported on refractory pins spaced below lamps which are used to cause a temperature gradient across the semiconductor wavers. Between the lamps and the semiconductor wavers there is a diffusion plate and a convection surpressor plate. Thus, the lamps are not adjacent the coated substrate. Accordingly, the lamps are not acting directly on the semiconductor wavers when drying. The parallel arranged lamps are mounting in a planar array. The end of each lamp shows a metal seal and it is fixed to engage in a position and slots at the lower edge of a terminal plate. A cooling reflector is mounted at a certain distance above the lamps. This reflector shows a cooling passage around the periphery thereof for liquid cooling means and a gas coolant passage extending through the center of the reflector. The cooling of the reflector by liquid coolant and by air requires two independent cooling systems which are expensive to realize. Each lamp is individually removeable, however, only downward through the open end of the respective slot. Further, as the terminal plate abuts the diffuser plate it is necessary to remove the diffuser plate before a lamp can be removed from its position through the open end of the slot. The semiconductor body heater according to U.S. Patent No. 4 101 759 is totally designed in a way to heat semiconductor wavers in a static condition in a batch where it is essential to have a uniform properly directed temperature gradient at the edge of the array of the semiconductor body. Object of the Invention Drying systems that make use of forced air circulation to cool both dryers and the environment within the housing of the final stage of a multi-unit press are favored by many manufacturers. The fans and blowers for such systems are not restricted in size as they are mounted outside the housing and they are easy to maintain and operate. However, forced air systems must operate at a restricted flow rate since an excess volume of air disturbs the flow current for which the equipment is designed for optimum coating drying conditions and also disrupts the smooth flat passage of the substrate as it passes the dryer. On the other hand, present water cooled systems generally are restricted in size and structure by virtue of the limited space available within the final housing of multi-stage presses. As a consequence, many such systems are fabricated of lightweight welded cooling panels that sometimes rupture due to the thermocycling. This causes both physical damage to the equipment and water damage to the coated substrates. Also, the panels fail to provide adequate cooling for different operating conditions. The object of the present invention is to provide an apparatus to be used with infra-red lamps which effectively reflects the radiant energy from the lamps to the coating on the passing substrate, while acting as a heat sink to reduce temperatures behind the apparatus to a reasonable level. This object is achieved in accordance with the invention by a dryer-cooler apparatus according to claim 1. Further, advantageous developments are given by the subclaims. Summary of the Invention The present invention overcomes the problems and disadvantages of the prior art apparatus by providing a compact, structurally sound, water-cooled apparatus for curing or drying heat sensitive coatings on substrates moving rapidly past the apparatus. More specifically, the apparatus comprises a cooling plate having a flat top-reflective surface and a plurality of internal passages for the circulation of liquid coolant. Mounted at opposite sides of the cooling plate are refractory insulating blocks which have a plurality of openings to support lamp ends and to permit the passage of coolant tubing to the plate. A plurality of high-powered lamps is mounted in parallel arrangement above the plate-reflective surface with the opposite ends of each lamp loosely supported in openings in the insulating end blocks. Leads from the ends of each lamp pass through the end block openings in which the lamp is supported and are interconnected to the leads of the ends of other lamps and to an appropriate source of power. In somewhat similar fashion, the coolant passages in the plate are interconnected by tubing for the circulation of coolant through the plate. The inlet tubing to the plate and discharge tubing from the plate are part of a closed circuit system joined to a refrigerating unit that controls the temperature of the dryer-cooler apparatus, regardless of the ambient temperature and the time of dryer operation. By employing the apparatus of the present invention, the temperature within the housing in which the dryer is located is maintained at a reasonable level such that an associated printing press may be continuously operated, despite relatively high ambient temperatures, to effectively dry the coatings on substrates rapidly passing adjacent such apparatus without contributing to problems with the associated equipment. The apparatus according to the invention functions well with high powered lamps, permits thermal extension and contraction, especially of the lamps without structural problems and is easy to maintain, particularly with respect to the replacement of the infra-red lamps. Such replacement can be done in an apparatus according to the invention within a few minutes through the lamp openings. Brief Description of the Drawings The nature of the invention will be more clearly understood by reference to the following description, the appended claims and the several views illustrated in the accompanying drawings. FIG. 1 is a schematic cross sectional view of the last stand of a multi-stand, multi-color sheet fed printing press through which a rapidly moving coated substrate is passed for the purpose of drying the substrate coating by means of the apparatus of this invention. FIG. 2 is an isometric view of an embodiment of the dryer-cooler assembly of this invention. FIG. 3 is a partial plan sectional view illustrating details of the dryer invention. FIG. 4 is an end view of the arrangement shown in Fig. 3. FIG. 5 is an enlarged sectional view taken along the line 5-5 of Fig. 3. Detailed Description of the Preferred Embodiments For purposes of this invention, it will be described for use with a multi-color, multi-stand printing press capable of handling individual printed sheets having a width of approximately 1,0 m (40 inches) and traveling at a speed of approximately 90 m/min (300 feet per minute). Referring to Fig. 1, there is shown a final housing 1 of such press in which is located feed chain 2 traveling in the direction of arrow A and driven by sprocket 3. A plurality of releasable clamps 4 connected to chain 2 engages the leading edges of sheets 5, which have on their upper surfaces a thin ink coating 9 and convey the sheets along a fixed feed path controlled by the feed chain 2. Adjacent the end of housing 1 the clamps 4 release and the individual sheets 5 drop through housing opening 6 onto the top of a stack of sheets 7 from where they are subsequently moved to a desired location. As sheets 5 travel along the feed path they pass dryer-cooler assembly 10. Exhaust blower 8 continually removes hot moist air from the interior of housing 1. As best shown in Figs. 2 and 3, dryer-cooler assembly 10 comprises cooling plate 20, top end block 30 and bottom end block 31, tubular lamps 50 and support arms 60 that connect with appropriate structural members, not shown, within housing 1. As shown in Figs. 3 and 5, cooling plate 20 has a length L, a width W, and a thickness T. Cooling plate 20 has a front reflective surface 21, back surface 22, sides 23 and 24, top end 25 and bottom end 26. Extending through plate 21 from top end 25 to bottom end 26 is a plurality of coolant passages 27. As shown in Fig. 3, top end block 30 and bottom end block 31 are fastened to cooling plate 20 by means of countersunk machine screws 61, in a manner well known to those skilled in the art. As shown in Figs. 3, 4 and 5, blocks 30 and 31 have inside faces 32, outside faces 33, tops 34, bottoms 35 and ends 36 and 37. Block 30 has a length l, width w and thickness t. A plurality of openings, including lamp openings 38, water conduit openings 39 and connector stud openings 40, extends through blocks 30 and 31 from inside face 32 to outside face 33. A plurality of spaced lamp openings 38 is spaced from top 34 of blocks 30 and 31 and has a diameter D. A plurality of spaced water conduit openings 39, each which has a diameter d and aligns with water conduit passages 27 of cooling plate 20, is spaced intermediate top 34 and bottom 35 of top end blocks 30 and 31. A plurality of connector stud openings 40 is spaced from the bottom 35 of blocks 30 and 31, and countersunk connector studs 62 extend through openings 40. Connector stud nuts 63 are threaded on studs 62. The number of connector stud openings 40 and studs 62 are equal to the number of lamp openings 38. As best shown in Figs. 4 and 5, a plurality of lamps 50 is loosely mounted in dryer-cooler assembly 10, spaced above cooler reflector surface 21. Each lamp 50 has a tubular body portion 51, flattened metal top end portion 52 from which lead wire 53 extends, and flattened metal bottom end portion 54 from which lead wire 55 extends. Lamp end portions 52 and 54 each have a height h, as shown in Fig. 4, slightly less than diameter D of lamp openings 38 of end blocks 30 and 31. Each lamp 50, including end portions 52 and 54, has a length x somewhat longer than the width W of cooling plate 20. Thus, the metal end portions 52 and 54 of each lamp 50 extend into lamp openings 38 of end blocks 30 and 31, respectively, and body 51 of each lamp 50 is positioned above reflector surface 21 of cooling plate 20. Fig. 4 illustrates the manner in which dryer assembly 10 is wired. Top lead wire 53 from each lamp top metal end portion 52 is connected to the adjacent connector stud 62 associated with each such lamp, and a jumper wire 64 extends from each connector stud 62 to the next such adjacent stud and so on for the number of lamps 50 and associated studs 62 for top end block 30 and bottom end block 31 of dryer assembly 10. A main lead wire 65 is also connected to one of several connector studs, and similar main lead wires are connected to other such studs in a manner known to those skilled in the art. The lead wires 65 for top end block 30 are formed into a top cable 66, as shown in Fig. 2, which connects with a central control panel and power source, not shown. The wires joining each connector stud 62 are held in place by stud nut 63. The bottom lead wire 55 from each lamp bottom metal end portion 54 is connected to a connector stud 62 associated therewith in bottom end block 31, and is wired, not shown, in a manner similar to that of end block 30, including comparable bottom main lead wires 65′ to bottom cable 66′. As shown in Figs. 3 and 5, extending outwardly from the top and bottom ends of each coolant passage 27 of cooling plate 20 are a series of connector fittings 28. Inlet tube 71 at one end thereof connects with a refrigeration system 80, shown in Fig. 1, and at the other end thereof with the first connecting fitting 28, which is at the top end 25 of cooling plate 20 and connects with the first coolant passage 27. At the bottom end of the first coolant passage 27, connection fitting 28 connects with one end of bottom cross-over tube 72, the other end of which connects with connector fitting 28 of the next adjacent or second coolant passage 27. At the top end of second coolant passage 27, connector fitting 28 connects with one end of the top cross-over tube 73 the other end of which connects with a connector fitting 28, not shown, of the next adjacent or third coolant passage 27, etc., for the length of cooling plate 20. As shown in Fig. 2, the last coolant passage 27 of cooling plate 20 connects with coolant discharge tube 74 and thence to refrigeration system 80. In a second embodiment of this invention, dryer-cooler assembly 10 includes a second cooling plate 20′, as shown in Fig. 1. Cooling plate 20′ is positioned in housing 1 on the underside of feed chain 2, spaced therefrom and opposite dryer-cooler assembly 10. Cooling plate 20′ is identical to cooling plate 20 of dryer-cooler assembly 10, except that its reflector surface 21′ faces toward dryer-cooler assembly 10. Coolant discharge tube 74 from cooler plate 20 connects with the coolant inlet end of cooling plate 20′, and the discharge end of cooling plate 20′ connects through coolant discharge tube 74′ to refrigeration system 80. In the preferred embodiments of the invention described above and used on a multi-stand printing press capable of handling individual sheets having a width of approximately 1,0 m (40 inches), cooling plates 20 and 20' are made of machined aluminum plate approximately 1,0 m (40 inches) long, 0,27 m (10.5 inches) wide and 19 mm (0.75 inches) thick. Reflector surfaces 21 and 21' are highly polished to reflect about 90% of short wave energy, have a flat smooth surface and may be coated with a reflective coating, such as lithium oxide or gold. A plurality of spaced passages 27 having a diameter of approximately 8,1 mm (0.32 inches) is drilled through cooler plates 20 and 20' for the passage of coolant. The passages are spaced to provide for reasonably uniform cooling throughout the plates and in the 1,016 m (40 inches) long plate there are 10 transverse passages 27. End blocks 30 and 31 are fired ceramic for insulating purposes and are approximately 1,0 m (40 inches) long, 5,7 cm (2.25 inches) wide and 19 mm (0.75 inches) thick. Lamp openings 38, of which there are 30, are approximately 16 mm (0.625 inches) in diameter and equally spaced along the block length, except for half spaces at either ends of the blocks. Coolant passage openings 39, of which there are 10, equal to the number of coolant passages in the cooling plate, are approximately 17,5 mm (0.688 inches) in diameter, and align with the coolant passages 27 in cooling plate 20. However, openings 39 are larger in diameter than the diameter of passage 27 to permit clearance for easy manipulation of coolant passage connection fittings 28. Lamps 50 are of the T-3 short wave type, such as manufactured by Sylvania. These types of lamps are preferred for an in-press situation for the following reasons: (a) They provide greater percentage absorption/power input to the substrate. In addition, the total heat obtainable is significantly greater since a short wave filament reaches approximately 2200° C., while a medium or long wave device cannot exceed 800° C. (b) They have low thermal inertia. A T-3 lamp reaches full output in less than 2 seconds and more importantly dissipates heat within 2 seconds when power is removed. (c) They have a power to size advantage. With an average length of approximately 0,29 m (11-1/2 inches), width of approximately 9,5 mm (3/8 inches) and power of approximately 1000 watts, the short wave lamp provides superior power to size ratio, which allows a smaller dryer to be used in a given installation. Although the preferred embodiments were described with reference to a press capable of handling individual printed sheets having a width of approximately 1,0 m (40 inches), the apparatus of this invention may be designed for installation in presses handling narrower or wider sheets. Furthermore, while dryer-cooler assembly 10 was described as having component lengths of the approximate width of such printed sheets, it should be recognized that the dryer-cooler assembly 10 can be made in modular form such that the block ends 30 and 31 and/or cooling plate 20 may be made of different lengths and widths described above, assembled in abutting relationship and fastened to support arms 60. The wiring and cooling tubes are connected in a manner similar to that described above. The preferred embodiments of cooling plates 20 and 20', is described, are made of aluminum with a thickness T of approximately 19 mm (0.75 inches). Other superior heat-sink materials, such as copper, may be used for such cooling plates and the thickness may be varied, depending upon the heat generated by lamps 50 and the degree of cooling to be accomplished. In similar fashion, the number of plate coolant passages, their diameter and the coolant flow rate may also be varied to accomplish the desired degree of cooling. The use of the term "plate" as used herein includes, for the purposes of this invention, a plate, solid casting or extrusion. The coolant passes through cooling plates 20 and 20' in a serpentine manner. That is, it passes downwardly through the first coolant passage 27 and out the bottom thereof, continues through first bottom crossover tube 72 and passes upwardly through the second coolant passage 27, continues through the first top coolant passage 73, as shown by arrow B in Fig 3., etc. for the length of the cooling plates 20 and 20' and then passes from the plates through discharge tubes 74 and 74' respectively. The preferred cooling described for the cooling plates 20 and 20', as used in conjunction with refrigeration system 80, is a closed circuit system that is designed with thermostatically controlled valves, well known to those skilled in the art, to maintain the temperature of coolant passing through the plates at any desired level. The width w and thickness t of the end blocks 30 and 31 may also be varied. The simple means, i.e. machine screw 61, by which end blocks 30 and 31 are fastened to the cooling plate 20 enables the plate to expand and contract freely without setting up damaging stresses in either the cooling plate or the end blocks. In similar fashion the lamps 50 may also expand and contract freely since each lamp top and bottom metal end portions 52 and 54, respectively, has a height h less than the diameter D of the block lamp openings 38 in which such end portions are supported. The only restraint on a lamp is that provided by top and bottom end portion lead wires 53 and 55, respectively, which are flexible and loose, except where they are connected to studs 62. The manner in which the ends of lamps 50 are mounted permits their easy replacement. A lamp may be changed by merely disconnecting top and bottom lead wires 53 and 55 from their adjacent connector studs 62 and withdrawing the lamp through one of its lamp openings 38 in either end block 30 or 31. A new lamp is installed in the reverse manner. The improved dryer-cooler apparatus of this invention permits expansion and contraction, without damage of lamps 50, end blocks 30 and 31 and cooling plate 20, when cyclically heated and cooled during use of the lamps in day-to-day press operations. Cooling plate 21 acts as a heat sink to absorb from lamps 50 as much unused energy generated as possible and to lower the operating temperature in the vicinity of the cooling plate, particularly on the back or opposite side thereof from the lamps. The invention described above is particularly applicable for retrofitting in existing presses where severe space limitations exist. The invention is a compact, highly effective dryer-cooler apparatus which employs a heat-sink reflector intrinsically more substantial than prior art-conventional aluminum or stainless sheet reflectors. Furthermore, the directed cooling circuit significantly reduces temperature zones across the length and width of the reflector, thus reducing any chance for thermally induced physical shifts in the panel and expansion-contraction stresses that lead to damage to the apparatus. The use of the dryer-cooler apparatus of the invention in high-speed presses permits press operation at lower housing temperatures than is experienced with use of other dryer-cooler apparatus.

Claims: Dryer-cooler apparatus mounted within the final stage housing of a printing press for infra-red curing of a heat sensitive coating on a moving substrate conveyed along a fixed feed path adjacent such apparatus by feed chain (2) comprising: (A) a plurality of spaced infrared lamps (50) each having: a tubular body portion (51), a flattened end portion (52 and 54) at each end of the body portion, and lead wire (53 and 55) extending from each end portion; (B) cooled reflector (20) having a reflective surface adjacent said lamps and also adjacent to the feed path of the feed chain (2); whereby (1) said cooled reflector (20) is a cooling plate having: (a) four sides, (b) a first plate surface (21) adjacent the infrared lamps (50) and the fixed feed path of feed chain (2) conveying the coated substrate, and (c) a plurality of internal coolant passages (27) extending through said reflector plate (20) spaced to provide reasonably uniform cooling throughout the plate; (2) a first end block (30) abuts one of said reflector sides (25) and has a plurality of spaced lamp openings (38) larger than the height of lamp end portions (52) and extends through the end block for support of the lamp end portions in an unencumbered manner, restrained only by lead wires (53) extending from the ends of the lamp; (3) a second end block (31) abuts another one of said reflector sides (26) and has a plurality of spaced lamp openings (38) larger than the height of lamp end portions (54) and extends through the end block for support of lamp end portions in an unencumbered manner restrained only by lead wires (55) extending from the end of the lamp end portions 54. The apparatus of claim 1 wherein infra-red lamps (50) are short-wave, high powered lamps. The apparatus of claim 2 wherein the infrared lamps (50) have low thermal inertia. The apparatus of claim 1 wherein cooling plate (20) is flat. The apparatus of claim 4 wherein flat cooling plate (20) has a thickness of about 19mm (0.75 inches). The apparatus of claim 1 wherein end blocks (30 and 31) are of insulating refractory material. The apparatus of claim 6 wherein end blocks (30 and 31) are about 19mm (0.75 inches) thick. The apparatus of claim 1 wherein lead wires (53 and 55) connect with studs (62) mounted on end blocks (30 and 31). Dryer-cooler apparatus of claim 1 wherein said coolant passages comprise: (A) a first coolant passage and a last coolant passage, a plurality of intermediate coolant passages (27) extending through said cooling plate (20) from said one side (25) to said other side (26); (B) a first cross-over conduit (72) connecting said first coolant passage with one of said intermediate coolant passages; and (C) a second cross-over conduit (73) connecting one of said intermediate coolant passages with said last coolant passage. The dryer-cooler apparatus of claim 1 wherein said first end block (30) has a plurality of connecting means (62,63) and said lead wire (53) from said first end portion (52) of each said lamp means (50) connects with an adjacent connecting stud (62) of said first end block (30) and said second end block (31) has a plurality of connecting means and said lead wire (55) from said second end portion (54) of each said lamp means connects with an adjacent connecting means (62) of said second end block, and the adjacent connecting means of said first and said second end blocks are connected by jumper means (64). The dryer-cooler apparatus of claim 1 wherein said first end block (30) is fastened to said cooling plate first end (25) by connecting means (61) and said second end block (31) is fastened to said cooling plate second end (26) by connecting means (61) whereby said cooling plate and said first and second end blocks may expand without damage when cyclically heated and cooled during periodic operations of said lamp means (50) of said apparatus. The dryer-cooler apparatus of claim 3 where said apparatus (10) further comprises a second flat cooling plate (20') spaced from said first cooling plate (20) on the opposite side of the feed path of the feed chain (2) conveying the coated substrate.

Inventors: BURGIO JOSEPH THOMAS JR, BURGIO, JOSEPH THOMAS, JR.
Applicants: BURGIO JOSEPH THOMAS, BURGIO, JOSEPH THOMAS, JR.
Application year: 1988
Main classification: F26B3
IPC codes: F26B3, F26B13, B41F23