Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24B—DOMESTIC STOVES OR RANGES FOR SOLID FUELS; IMPLEMENTS FOR USE IN CONNECTION WITH STOVES OR RANGES
  • F24B1/00—Stoves or ranges
  • F24B1/18—Stoves with open fires, e.g. fireplaces
  • F24B1/185—Stoves with open fires, e.g. fireplaces with air-handling means, heat exchange means, or additional provisions for convection heating ; Controlling combustion
  • F24B1/188—Stoves with open fires, e.g. fireplaces with air-handling means, heat exchange means, or additional provisions for convection heating ; Controlling combustion characterised by use of heat exchange means , e.g. using a particular heat exchange medium, e.g. oil, gas  
  • F24B1/1885—Stoves with open fires, e.g. fireplaces with air-handling means, heat exchange means, or additional provisions for convection heating ; Controlling combustion characterised by use of heat exchange means , e.g. using a particular heat exchange medium, e.g. oil, gas   the heat exchange medium being air only
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24B—DOMESTIC STOVES OR RANGES FOR SOLID FUELS; IMPLEMENTS FOR USE IN CONNECTION WITH STOVES OR RANGES
  • F24B7/00—Stoves, ranges or flue-gas ducts, with additional provisions for convection heating 
  • F24B7/02—Stoves, ranges or flue-gas ducts, with additional provisions for convection heating  with external air ducts
  • F24B7/025—Stoves, ranges or flue-gas ducts, with additional provisions for convection heating  with external air ducts with forced circulation
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24C—DOMESTIC STOVES OR RANGES ; DETAILS OF DOMESTIC STOVES OR RANGES, OF GENERAL APPLICATION
  • F24C1/00—Stoves or ranges in which the fuel or energy supply is not restricted to solid fuel or to a type covered by a single one of the following groups F24C3/00 - F24C9/00; Stoves or ranges in which the type of fuel or energy supply is not specified
  • F24C1/14—Radiation heating stoves and ranges, with additional provision for convection heating

Definitions

• the present invention relates generally to heating units and more specifi ⁇ cally to a free standing heater using forced air.
• Patents 1,490,135 and 3,094,980 make use of the flue heat in a stove and fireplace respectively to heat a second column of forced air which is introduced into the room in which the stove or fireplace is located.
• Heating units of the prior art have either used the natural upward flow of heating air by drawing cold air in at the bottom of a heating unit to exit heated from the top.
• forced air systems have been used to augment the natural upward flow by moving more air past the exterior of the fire box. Although the forced air systems have increased the capture of available heat, the prior art devices have not optimized the heat transfer from the burning material in the fire box to the air circulated about the exterior of the fire box.
• the present invention is a forced air heating unit having double walled sides, back, and bottom, and a single walled front and top.
• a forced air channel defined by the double sides, back and bottom wall, includes a system of baffles to direct forced air over substantially all of the surface area of the side, back, and bottom fire box walls.
• the baffles in the back portion of the forced air channel direct forced air between the back portion and the two side and bottom portions.
• the baffles in the bottom portion direct forced air between the bottom portion and the back and two side portions.
• the baffles in the side direct forced air between the side portions and the back and bottom portions.
• a blower is thermostatically controlled to introduce forced air into the air- channel for maintaining the back, side and bottom fire box walls in a minimum temperature range to heat the forced air while maximizing the transfer of heat from the burning material to the forced air channel instead of up the flue.
• the front wall of the heating unit includes an access opening and a pair of doors for covering the access opening.
• An adjustable draft valve in each door includes a positive screw lock.
• a gas baffle for directing rising gas to an area of the fire box where the gases are ignited.
• the gas baffle directs some of the gas downward to the burning material to be ignited and maintains some of the gases adjacent the top of the fire box in front of the gas baffle.
• the top of the doors are spaced from the top edge of the access opening to allow air to circulate into the firebox adjacent the top wall for aiding ignition of the gases collected adjacent the top wall.
• the major source of air is the space between the doors which is covered by a vertical strip mounted to one of the doors.
• a hood is mounted adjacent the top edge of the access opening for directing gases exiting the top edge of the access opening back into the fire box.
• a draft system including two vertical forced air channel exit vents adjacent the side edges of the access opening for creating hot air drafts which converge at a select eed distance in front of the access opening, limits the draft of air into the access opening.
• the converging hot air is effected by vertical deflection surfaces including vertical baffles in the side portion of the forced air channel or pneumatic surfaces produced by a lip extending across the vent opening or by the vent opening being offset from the exterior edge of the forced air channel.
• the less than ninety degree angle that the side walls form with the front of the forced air channel also aids the deflection.
• a mesh having inclined horizontal surfaces covers the vertical vents and directs the exiting air downward to be combined with heated forced air exiting horizontal vent in the front of the bottom portion of the forced air channel.
• the heated forced air from the two vertical vents and the horizontal vent pneumatically create a finite cool air pocket in front of the access opening to limit the amount of cool air available for the fire box.
• the forced air heating unit uniformly heats a room by introducing forced hot air adjacent the floor of the room by the horizontal vent and the downward directing vertical vents.
• the forced air device mounted to the rear of the free ⁇ standing unit draws air from above and around the sides of the unit and around the space defined by the exiting forced hot air.
• the width of the side portion of the forced air channel tapers from the wider rear portion to the front to increase the air intake.
• Gravity lock door handles are provided on the access doors.
• Figure 1 is a front perspective view of a forced air heating unit employing the principles of the present invention.
• Figure 2 is a partial cross-sectional view of the draft valve taken along lines ⁇ - ⁇ of Figure 1.
• Figure 3 is an exploded, partial perspective view of the relationship of the top of the doors to the fire box opening.
• Figure 4 is a partial side view illustrating the function of the hood according to the present invention.
• Figure 5 is a rear cutaway perspective of the forced air heating unit illus ⁇ trating the baffle system.
• Figure 6 is a front partial perspective of the bottom, back, and side walls of the forced air heating unit illustrating the baffle system.
• Figure 7 is a perspective schematic of the heat flow in the fire box.
• Figure 8 is a side cross-sectional view illustrating gas circulation in the fire box.
• Figure 9 is a front perspective of a fireplace employing the principles of the present invention.
• Figure 10 is a side view illustrating the forced air pattern according to the principles of the present invention.
• Figure 11 is a plan view illustrating the forced air pattern according to the principles of the present invention.
• Figure 12 is an enlarged plan view of a vertical vent illustrating the deflect ⁇ ing principle of the present invention.
• Figures 13 and 14 are enlarged plan cross-sectional view of alternative embodiments of vertical deflectors.
• Figure 15 is a front view of the mesh used in the vents.
• Figure 16 is a cross-sectional view taken along lines XVI-XVI of Figure 15.
• Figure 17 is a schematic of the air circulation produced by the present invention.
• Figure 18 is a front view of another embodiment of the principles of the present invention.
• Figure 19 is a perspective of another embodiment of the present invention.
• Figure 1 which illustrates a preferred embodiment of the forced air heating unit 10, shows a housing having top, front, bottom, two sides, and back walls, 12, 14,
• Top wall 12 which is a single walled portion of the housing, extends past the front, back, and side walls, and includes a collar 24 sur ⁇ rounding an orifice or flue port 26.
• a flue (not shown) to remove the fumes from a source of heat or combustible material is connected to flue port 26 through the collar 24.
• the heating unit 10 is supported by four legs 28 providing space betweeen the floor and the bottom wall 16.
• Front wall 14 has a pair of elongated vertical vents 30 and 32, each covered by a screen 31 which is secured to the front wall 14 by a bracket or lip 33.
• An access opening 34 in front wall 14 is covered by a closure including a pair of doors 36 and 38.
• the vertical vents 30, 32 extend substantially the height of the opening 34 and are spaced from the bottom and top of the opening 34.
• the door 38 has a strip 40 which overlaps door 36 and holds door 36 closed and covers the space between the adjacent edges of the doors.
• ' Handle 42 on door 38 is connected to a latch 43 which engages the top interior portion above the opening 34 so as to lock the doors closed.
• the handle 42 rotates down to close, thus providing a gravity lock of the doors.
• a pair of posts 41 and 45 on the interior of the doors 38 provides tops for latch 43.
• Post 41 may be mounted to the interior of front wall 14 if desired.
• a pair of draft valves 44 and 46 are also provided on doors 36 and 38.
• the sliding portions 50 and 52 of draft valves 44 and 46 slide within guide members 54 and 56 to adjust the size of a plurality of elongated openings 48 in doors 36 and 38.
• the slides 50 and 52 adjustably vary the draft valves 44 and 46 to regulate the amount of air or draft introduced into the chamber and are locked in the adjusted position by threaded knobs 51 and 53 respectively engaging the face of doors 36 and 38 respectively as illustrated in Figure 2.
• threaded knobs 51 and 53 respectively engaging the face of doors 36 and 38 respectively as illustrated in Figure 2.
• these valves are used in conjunction with an adjustable flue port 26.
• the draft valves 44, 46 are shown in the doors 36, 38, they may also be used on a front wall of the fire box below the doors if such a surface is made available.
• the doors 36 and 38 are mounted to the housing by upper hinges 58 and 60 and lower hinges 62 and 64, re ⁇ spectively.
• the doors and hinges are dimensional so that the bottom of doors 36, 38 rest flush against the front wall 14 and the top of doors 36, 38 are spaced from the front wall 14 at the top edge of opening 34 as illustrated in Figures 5 and 19. The importance of this separation will be discussed below in reference to Figures 3 and 8.
• a hood 66 and a platform 68 are mounted to the front wall 14 .
• the hood 66 traps any smoke pulled from the fire box at the upper edge of access opening 34 when the doors 36, 38 are rapidly opened and directs it back into the fire box as illustrated in Figure 4.
• the hood 66 includes a center portion 65 and a pair of side portions 67 for capturing the escaping gases and directing them back into the opening 34.
• the platform 68 provides a surface for supporting a fireplace screen when the heating unit 10 is used as a fireplace without doors.
• the forced air system includes a source of forced air, a channel, a baffle system, and deflectors.
• the source of foreed air including a housing 70, is mounted to the back wall 22 and includes an opening 72.
• a blower 71 or any other system which will receive air through opening 72 and provides a forced air flow within the channels to be described.
• a thermostatic control 73 is mounted in rear wall 22 ( Figure 6) and controls the operation of' fan 71 based on the temperature of the air in the forced air channel.
• Housing 70 may also contain a source of moisture which is illustrated in Figure 5, for example, as a pan 74 having water therein. The pan of water is merely one example of a source of moisture.
• Forced air housing 70 communicates with the forced air channels via an inlet 76 in the back wall 22.
• inlet 76 and blower 71 may be located any place which provides them access to the forced air channel.
• inlet 76 and blower 71 could be on either side wall 18, 20 or on top 12 over the back or either side portion of the foreed air
• OMPI ,fa W1PO channel may be on the front wall 14 with access to the two side o bottom portion of the forced air channel.
• the air channel of the present device includes the exterior sides, back, an bottom walls 18, 20, 22, and 16 respectively and interior sides, back, and botto walls 78, 80, 82, and 84 respectively.
• the sides and back walls of the housing an the sides and back interior walls form a generally U-shaped forced air channel wit the side walls at an angle other than ninety degrees relative to the back where th forced air from opening 76 is transmitted towards front vents 30 and 32.
• Th separation of the side walls 18 and 78 and 20 and 80 or the width of the side force air channel tapers or diminishes from the rear to the front.
• the increased width o the back air channel and the rear of the side air channel allows blower 71 to pum more air per minute into the foreed air channel.
• the forced air from opening 76 i also provided from the rear forced air channel through an opening 86 into th forced air channel formed by the housing and the interior bottom walls to exi through horizontal vent 88, illustrated in Figure 6, in the front portion of th bottom air channel.
• the air in the bottom foreed air channel also exits into th side forced air channels.
• baffle systems to create specific ai patterns which diverge from the forced air source at opening 76 and converge o the respective vents in the front of the air channels.
• the rear wall portions of th baffle system includes a horizontal baffle 90 substantially bisecting opening 7 from the forced air system.
• two upper baffles 9 and 94 and two lower baffles 96 and 98 which diverge from the foreed air openin 76.
• Baffles 94 and 96 direct divergent air flow towards one side wall channel whil baffle 92 and 96 in combination direct diverging air flow toward the other side wal channel.
• Upper baffles 92 and 94 direct an upward flow towards the respective sid wall channel portions and baffles 96 and 98 provide a flow towards opening 86 int the bottom foreed air channel as well as providing a small flow to the respective side forced air channel.
• baffles 102, 104, 106, and 108 Located in each side forced air channel are baffles 102, 104, 106, and 108, and in bottom forced air channel are baffles 112, 114, 116, 118, 120, 122, and 124.
• the inner ends of bottom baffles 114, 116, 118, and 120, 122, 124 are offset relative to the center bottom baffle 112 so as to divert varying portions of the air flowing towards bottom vent 88 and to direct it towards side wall baffles 102 and 104.
• baffles 114, 116, 118, 120, 122 and 124 are such that the air between baffles 114-116 and 120-122 is directed toward the lower face of side baffle 102j and the air between baffles 116 and 122 and the rear of the bottom is bisected by baffles 118 and 124 respectively and directed between baffles 102 and 104. Since the source of the temperature modification is generally placed adjacent interior bottom wall 84, the communication of the air flow from the bottom forced air channel to the side forced air channel increases the efficiency of the temperature transfer.
• baffles assures that the air traverses substantially all the interior walls and thereby allows a greater heat transfer from the interior or fire box to the forced air without sacrificing the head of the air emitting from the vents 30, 32, and 88 since it cools a greater surface area.
• Prior art devices generally substantially increase the length of the air path while sacrificing the head of the air at the vents and thereby reducing the heat transferability of the interior walls.
• the baffle system in the walls produce streams of air which are not troubled by eddy currents, dead air pockets, localized hot spots, and other disadvantageous features of the prior art systems.
• Blower 71 is chosen to have sufficient capacity to force air in the air channel at a sufficiently high velocity to lower the temperature of the interior walls and thereby increase the transfer of heat from the fire box to the interior walls to be removed by the forced air. Thus less heat from the fire box is available for transmission up the flue.
• thermodynamics of the heating unit 10 will substantiate the efficiency or maximization of heat transfer or capture of the unit.
• the formula for representing the heat transferred from the heated air in the fire box through the interior walls to the forced air in the forced air channel is:
• the overall heat transfer coefficient Q is a function of the resistance to the flow of heat of (a) the air in the fire box, (b) the firebox wall, (c) the forced air, and (d) the fouling on each side-of the fire box wall.
• the blower 71 in combination with thermostat control 73 maintain the back, two sides, and bottom wall of the fire box in a range of temperature to maximize the heat transfer through the fire box walls while heating the forced air to a sufficiently warm temperature.
• thermostat 73 could turn blower 71 on once the temperature in the forced air channel is 115° F. and turn the blower 71 off when the forced air temperature is reduced below 100° F.
• the thermostat control 73 could vary the speed of blower 71.
• the preferred range is 95° F. to 150° F.
• heating unit 10 substantially maximizes the effective surface area A at the
• This area could be further increased by extending the forced air channel over the top wall 12 of the fire box, if desired, but is not preferred.
• the heat flow within the fire box is also based on the above equation except that the temperature differential A T should be expressed as a temperature gradient or the change in temperature per unit distance.
• the amount of heat flow is illustrated in Figure 7 by the length of the vector. Since the bottom forced air channel, being the closest cool surface, has the largest gradient or vector D.
• the front wall being a non-forced air wall, can only cool by heat dissipation. Thus, the temperature gradient toward the front wall, and consequently the heat flow F, is substantially less than those toward the forced air cooled walls.
• the top wall is not forced air coof and thus has a small heat flow U. Since gas ignition occurs adjacent the top (as will be discussed for Figure 8), the surface of the top wall is even hotter than the front wall and consequently vector U is smaller than vector F. With a limited air flow up the flue, there is very little heat left to exit the flue port as illustrated by vector O.
• thermostatically controlled blower maximizes the surface area of maximum temperature differential to effectively capture or draw eighty percent of the heat available from the fire box into the forced air channel. This is comparable to the heat efficiency of a residential furnace.
• a device is provided to reduce the build-up of deposits on the fire box wall by igniting the rising gases from a wood fire. This ignition also increases the amount of heat available from the wood.
• This device includes a gas baffle 126 extending down from the top wall 126 adjacent the flue port 26 as illustrated in Figure 8.
• the slide drafts 44, 46 on the doors allow a controlled, even flow of air across the fire.
• the unburned gases rise from the fire up and slightly forward, to the top wall 12.
• they circulate to the rear of the fire box, toward the flue port 26 and contact baffle 120 which deflects the gases downward.
• baffle 120 which deflects the gases downward.
• a rolling cushion of smoke (partially burned gases) will build up under the top wall 12. This cushion acts to hold the resins and gases in the fire to burn longer and holds the gases in the fire box until they are recirculated and burned as completely as possible.
• the air space is provided by the tops of the doors being offset from the plane of the front wall 14, this space may also be provided by making the top of the doors shorter than the access opening 34.
• the forced air heating unit 10, as illustrated in Figure 9 may be used as a free standing fireplace.
• the doors 36 and 38 are removed and a screen 128 is provided underneath hood 66 and resting on platform 68.
• the screen may be a typical fireplace screen to prevent sparks and ashes from emitting from the fireplace and causing a fire hazard within the room.
• Adjacent to and surrounding openings 34 is a rim 130.
• Four pins 132 of hinges 58, 60, 62, 64 are provided on the rim 130 as well as four openings 134 in the rim.
• the matching hinge element of the closures 36, 38 move in and out of the openings 134 in the rim 130.
• the rim 130 provides a guide and retainer for the screen 128 which fits within the rim 130. Though not shown, the rim 130 extends above and across the top of the opening 34. A pair of andirons 136 are provided in the interior chamber to support the source of temperature modification. It should be noted that grating or other supports may be used instead of andirons 136.
• the forced air heating device 10 includes a system of deflectors at the vertical vents 30 and 32 to define a unique air flow pattern in front of the fire box opening 34.
• the heated forced air dashed lines
• the heated forced air are directed towards each other to converge in front of the fire box opening 34 a preselected distance.
• This creates an air pocket 140 in front of the fire box opening 34 in combination with the heated forced air exiting the bottom horizontal vent 88 which is illustrated in Figure 10 but deleted from the pattern of Figure U for. sake of clarity.
• the pneumatically created barrier for air pocket 140 limits the amount of air from which the fire can draw and thereby reduces the rate of combustion in the fire box.
• the outward moving heated air reduces cold air drafts toward the access opening 34.
• the U-shaped pneumatic barrier is a critical substitute for the open or removed doors 36 and 38.
• the major source of cool air (solid lines) for the pocket 140 in front of the fire box is the triangular aerodynamic openings 142 between the bottom of the vertical vents 30, 32 and the forced air from the horizontal vent 88.
• the forced air solid lines
• OMPI hot air from vertical vents 30, 32 also is directed downward, as well as inward converge, allowing air to flow into the pocket 140 over the top edge of the fre hot air V.
• the two vertical air streams converge preferably at about five feet front of the access opening. To converge much closer would draw smoke from t fire box.
• Blower 71 on the back wall draws air as indicated by the solid lines arou the sides of the unit and over the top.
• the cool or return air flow is outsi the air pattern defined by vents 30, 32 and 88 which pneumatically block cool a flow into the fire box.
• a preferred device for directing the air exiting the vertical vents 30 and to converge is illustrated in the enlarged view of Figure 12.
• the side walls 18 a 78 are mounted to the front wall 14 at an opening 144 in the front wall. While si wall 78 lies at the edge of the opening 144, side wall 18 is slightly offset. Th offset may be eliminated.
• the side walls 18, 78 form an angle less than nine degrees with the front wall 14 to aid the deflection of forced air inward.
• T bracket 33 is generally L-shaped having a portion extending across the opening 14 The bracket 33 forms an air pocket along the outside edge of opening 144 which is pneumatically produced deflection surface 146.
• the pneumatic deflection surfa exterior the forced air channel is sufficient to direct the heated forced air converge in-front of the fire box access opening 34.
• FIGs 13 and 14 Two alternative embodiments are illustrated in Figures 13 and 14.
• an internal pneumatic deflector could be used.
• the exterior side wall 18 is substantially offset fro the edge of opening 144 providing a pneumatically produced deflection surface 14
• Figure 14 shows a vertical deflection plate or baffle 150 mounted between t exterior side wall 18 and front wall 14.
• the side forced air channels form a nine degree angle with the front wall, although the non-ninety degree angle alignment preferred.
• Each embodiment may also include the pneumatical deflection surfa 136 produced by the L-shaped bracket 33.
• the downward air flow is produced by the mesh 31 secured to the L-shaped bracket 33 across vent opening 144.
• the mesh 31 includes a plurality of horizontal surfaces 152, at the intersection of adjacent openings, inclined downward from the back to the front to deflect air downward without retarding the air flow through the mesh 31. If the downward deflection is not required, mesh 31 may be mounted with the surfaces 152 vertical to provide the converging air flow. Basically, the mesh 31 may be mounted with any desired orientation of the surfaces 152 to produce a correspondingly directed air flow (e.g. 45° angle relative to the horizontal).
• the forced hot air patterns converging just off the floor in front of the unit push the cool air across the floor.
• the forced air strikes a wall it is deflected to either side and up.
• the blower 71 is pulling return air to either side and down over the top of the unit.
• Thfc push-pull action results in a high volume of air movement as the blower system forces hot air across the floor and returns cool air around either side and overhead. This is exactly the opposite of normal air movement within a house and results in a more uniform temperature from floor to ceiling.
• the air patterns are illustrated in Figure 17 where the solid lines represent cool air and the dashed lines represent warm air.
• thermostat 154 may be provided in the room to be heated. Whereas thermostat control 73 preferably turns the blower on and off as a function of the air temperature in the forced air channel, thermostat 154 varies the speed of the blower as a function of the air temperature in the room to be heated. The use of a room thermostat increases the comfort in the room, but reduces the efficiency of the unit 10 since the fire box walls may not be kept at the lowest possible temperature.
• the heating unit 10 could also be used as a furnace.
• top vents 160 and 162 may be connected to the plentum or duct system to be transmitted throughout a house.
• the baffle system is modified so as to direct air over the substantially all the surfaces and towards the vents without orming dead air pockets in the forced air channel.
• the heating unit 10 is effective for use with coal, oil, gas, or any other heat source in the fire box.
• Preferred method of assembly of the forced air heating unit 10 is to form the exterior side and back walls 18, 20, and 22, out of a single piece of material and the interior side- and back walls 78, 80, and 82 also out of a single piece of material.
• the baffles are mounted to the exterior side and back walls and the interior side and back walls are mounted to the baffles preferably by welding.
• the bottom exterior wall 16 is welded to the exterior side and back walls 18, 20, 22, and the baffles of the bottom forced air chamber are mounted to the bottom exterior wall.
• the bottom interior wall 84 is then joined to interior side and back walls 78, 80, 82.
• the top and front walls are then mounted to the structure by welding.
• the welding bead formed'between the top and the side and back walls provides a thermal barrier or guard such that the portion of the top 12 which extends beyond the side and back walls is cooler than a portion of the top which is directly over the fire box.
• the remaining elements are attached or mounted to the front wall and the forced air unit mounted to the rear wall.
• interior side and back walls 78, 80, and 82 be made of 3 ⁇ 6 inch thick steel and the exterior side and back walls as well as the top and front walls be made of 1/8 inch thick steel.
• the bottom exterior and interior walls may be made of 3 ⁇ 6 inch steel.
• a forced air heating unit is provided which maximizes the use of available heat from a fire box by a unique thermostatically controlled forced air system including pneumatically produced surfaces and barriers.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
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• 1978
  • 1978-06-05 CH CH401879A patent/CH625329A5/de not_active IP Right Cessation
  • 1978-06-05 WO PCT/US1978/000005 patent/WO1979000113A1/en unknown
  • 1978-06-05 GB GB7912773A patent/GB2036943B/en not_active Expired
  • 1978-06-05 CA CA304,805A patent/CA1115611A/en not_active Expired
• 1979
  • 1979-03-13 EP EP78900095A patent/EP0006897B1/de not_active Expired
  • 1979-04-26 SE SE7903684A patent/SE7903684L/xx unknown

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