US 5,320,086 AGrant
Direct Vent Gas Appliance With Vertical and Horizontal Venting
Issue Date:1994-06-14
•16 Claims
•3 Drawing Sheets
Abstract
The invention relates to a direct vent gas fireplace adapted for attachment to a concentric flue pipe assembly having an exhaust pipe and fresh air pipe. A top wall, rear wall, bottom wall and side walls define a combustion chamber. A gas burner is disposed in the combustion chamber. A slanted flue attachment wall is attached to and extends between the top wall and rear wall. The slanted flue attachment wall is disposed at obtuse angles relative to the top wall and rear wall. A first pipe member is orthogonally attached to the flue attachment wall and is in fluid communication with the combustion chamber for conveying combustion products from the combustion chamber. A second pipe member having a diameter larger than the first pipe member is disposed concentrically around the first pipe member. The first and second pipe members define an annular space therebetween forming an air intake duct. A combustion air duct extends between and is in fluid communication with the air intake duct and the combustion chamber for supplying combustion air to the combustion chamber. The exhaust pipe and fresh air pipe are respectively attached to the first and second pipe members and can be selectively oriented to extend away from the fireplace in a substantially vertical or horizontal direction.
Metadata
Assignee
- Majco Building Specialties, L.P.
Inventors
- Thomas J. Beal
- Albert K. Teakell
- Robert E. Cabrera
Application Information
Application Number:US 0180513
Filing Date:1993-02-16
Priority Date:1993-02-16
Art Unit:346
Classifications
IPC:
F24C 300
Field of Search:
126512;515;516;517;518;85 B
Patent Drawings (3 sheets)
Description
Background of the Invention
1. Field of the Invention
The present invention relates to fireplaces and, in particular, to direct vent gas fireplaces.
2. Description of the Related Art
Gas fireplaces of conventional design typically utilize a source of combustion air from the room being heated. This lowers the efficiency of the gas fireplace because a portion of the heated air in the room is drawn into the combustion chamber and exhausted up the chimney. It is known to provide separate ducting from the outside ambient environment to the combustion chamber to increase the efficiency of the fireplace. The ducted air provides a source of oxygen for combustion in the combustion chamber and decreases the amount of air from the room being heated which is exhausted up the chimney. Such ducting, however, requires additional materials and labor to install.
It is also known in the art to utilize concentric flue pipes to exhaust combustion products to the outside environment and supply combustion air from the outside environment. Such fireplaces are termed "direct vent" fireplaces and are disclosed, e.g., in U.S. Pat. Nos. 4,793,322 (Shimek et al.) and 4,909,227 (Rieger). A direct vent fireplace has the advantage of utilizing a common concentric flue pipe assembly to both exhaust combustion products from and supply combustion air to the combustion chamber. Moreover, only a single opening need be cut through an exterior wall of a house to accommodate the concentric flue pipe assembly.
In general, a direct vent fireplace has a first pipe with a diameter larger than and disposed concentrically around a second pipe. The duct formed by the second pipe is used to convey exhaust products from the combustion chamber to the outside environment. The annular space formed between the first and second pipes defines a fresh air conduit through which combustion air flows from the outside ambient environment into the combustion chamber.
A problem with direct vent gas fireplaces is that the concentric flue pipe assembly cannot be easily vented in both a horizontal or vertical direction. Shimek et al. and Rieger disclose direct vent fireplaces which respectively connect the concentric flue to the back wall and top wall of the fireplace. A concentric flue attached to the back wall of the fireplace may be easily extended through an adjacent side wall of the house. However, if it is desirable to exhaust the concentric flue in a vertical direction, the fireplace must be moved forward a sufficient distance to allow coupling of a right angle concentric pipe elbow. Thus, additional floor space is required to accommodate the projected footprint of the fireplace and concentric flue pipe assembly.
A concentric flue pipe assembly attached to the top of a direct vent fireplace has a similar problem when it is desired to vent the concentric flue in a horizontal direction (see, e.g., Rieger at Col. 1, lines 23-32). That is, the fireplace must be moved forward a sufficient distance to allow coupling of a right angle concentric pipe elbow.
Because of two possible installation configurations, i.e., vertical or horizontal venting of the concentric flue pipe assembly, it is necessary with conventional direct vent fireplace designs to provide two totally different configurations. That is, for relatively close placement of the fireplace adjacent the outside wall of the house, it is necessary to provide one configuration allowing attachment of the concentric flue pipe assembly to the back of the fireplace for horizontal venting, and a second configuration allowing attachment of the concentric flue pipe assembly to the top of the fireplace for vertical venting. The necessity to provide two different configurations increases inventory requirements at the factory. An installer must order either a vertical or horizontal venting fireplace prior to installation. What is needed, therefore, is a direct vent fireplace which reduces the required inventory which must be kept on hand.
Moreover, an installer may not know whether a vertical or horizontal venting fireplace is needed prior to installation. Therefore, what is needed in the art is a direct vent gas fireplace allowing a concentric flue to be selectively vented in either a horizontal or vertical direction.
Summary of the Invention
The present invention provides a direct vent gas fireplace allowing a concentric flue to be selectively vented in either a vertical or horizontal direction.
The invention comprises, in one form thereof, a direct vent gas fireplace adapted for attachment to a concentric flue pipe assembly having an exhaust pipe and fresh air pipe. A top wall, rear wall, bottom wall and side walls define a combustion chamber. A gas burner is disposed in the combustion chamber. A slanted flue attachment wall is attached to and extends between the top wall and rear wall. The slanted flue attachment wall is disposed at obtuse angles relative to the top wall and rear wall. A first pipe member is orthogonally attached to the flue attachment wall and is in fluid communication with the combustion chamber for conveying combustion products from the combustion chamber. A second pipe member having a diameter larger than the first pipe member is disposed concentrically around the first pipe member. The first and second pipe members define an annular space therebetween forming an air intake duct. A combustion air duct extends between and is in fluid communication with the air intake duct and the combustion chamber for supplying combustion air to the combustion chamber. The exhaust pipe and fresh air pipe are respectively attached to the first and second pipe members and can be selectively oriented to extend away from the fireplace in a substantially vertical or horizontal direction.
An advantage of the present invention is that the concentric flue may be easily vented in either a horizontal or vertical direction.
A further advantage is that the concentric flue may be selectively vented in either a horizontal or vertical direction utilizing the same fireplace components.
Brief Description of the Drawings
The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:
FIG. 1 is a fragmentary perspective view of the direct vent gas fireplace according to one embodiment of the present invention;
FIG. 2 is a fragmentary sectional view taken along line 2--2 of FIG. 1;
FIG. 3 is a sectional view taken along line 3--3 of FIG. 1 illustrating vertical venting of the gas appliance; and
FIG. 4 is a sectional view similar to FIG. 3 illustrating horizontal venting of the gas appliance.
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates one preferred embodiment of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner.
Detailed Description of the Invention
Referring now to the drawings and particularly to FIGS. 1-3, there is shown a direct vent gas fireplace 10 having room air circulation channel 12 disposed between an exterior housing 14 and combustion chamber 16. Exterior housing 14 includes an exterior bottom wall 18, exterior top wall 20, exterior back wall 22, exterior side walls 24 and 26, and a front wall 28 defining an opening 30. In the embodiment shown, exterior top wall 20 defines a horizontal plane.
An interior housing defining combustion chamber 16 includes a top wall 32 rear wall 34 bottom wall 36, two sidewalls 38 and 40, and front wall 42 defining an opening 44. Disposed within combustion chamber 16 is a gas burner 46 disposed below a plurality of decorative logs 48. Decorative logs 48 are supported by a grate 50. Disposed at the upper portion of combustion chamber 16 are baffle plates 49 and 51 for directing the flow of combustion products from combustion chamber 16.
Disposed within room air circulation channel 12 is a blower 52 for circulating air. Ambient air from the living space in which direct vent gas fireplace 10 is located is drawn into room air circulation channel 12 at the bottom of direct vent gas fireplace 10 through openings 53 and is exhausted back into the ambient environment at the top of direct vent gas fireplace 10 through openings 55, as shown by air flow directional arrows 54. The ambient air drawn into room air circulation channel 12 is heated via convection heat transfer as it flows past bottom wall 36, rear wall 34 and top wall 32 and is exhausted back into the ambient environment at a higher temperature.
In accordance with the present invention, a slanted flue attachment wall 56 is attached to and extends between top wall 32 and rear wall 34 and forms obtuse angles with top wall 32 and rear wall 34. In the embodiment shown, slanted flue attachment wall 56 is disposed at obtuse angles of about 135.degree. with respect to each of top wall 32 and rear wall 34. That is, slanted flue attachment wall 56 is disposed at an angle of about 45.degree. with respect to a horizontal plane, which in the embodiment shown is defined by exterior top wall 20.
Disposed generally parallel to slanted flue attachment wall 56 is a slanted exterior flue attachment wall 58 attached to exterior top wall 20 and exterior back wall 22, and disposed at an angle of about 45.degree. with respect to the horizontal plane defined by exterior top wall 20.
Attached to slanted flue attachment wall 56 and extending orthogonally therefrom is a first pipe member 60 which is in fluid communication with the combustion chamber for conveying combustion products from the combustion chamber. First pipe member 60 extends through slanted exterior wall 58.
Disposed adjacent to slanted exterior wall 58 is a plenum 62. A second pipe member 64 is attached to and in fluid communication with plenum 62. Second pipe member 64 extends through slanted exterior wall 58 of exterior housing 14. Second pipe member 64 has a diameter larger than and is disposed concentrically around first pipe member 60. The annular space formed between first pipe member 60 and second pipe member 64 defines an air intake duct 65 through which combustion air flows into plenum 62.
A pair of air distribution conduits 68 and 70 are attached to plenum 62 at one end thereof, and respectively attached to a pair of second plenums 72 and 74 at the other ends thereof. Air distribution conduits 68 and 70 are respectively disclosed adjacent to sidewalls 38 and 40 of combustion chamber 16. First and second plenums 72 and 74 include a plurality of openings 76 through which combustion air is drawn into combustion chamber 16. Plenum 62, air distribution conduits 68 and 70, and second plenums 72 and 74 define a combustion air duct (not numbered) for supplying combustion air to combustion chamber 16.
A concentric flue pipe assembly 78 includes a fresh air pipe 80 and exhaust pipe 82. Fresh air pipe 80 and exhaust pipe 82 both include first and second tubular portions 84 and 86, and 88 and 90 respectively. First and second tubular portions 84 and 86 of fresh air pipe 80 have a diameter larger than and are concentrically disposed around first and second tubular portions 88 and 90 of exhaust pipe 82. Moreover, first and second tubular portions 84 and 86, and first and second tubular portions 88 and 90 are disposed relative to each other at an angle of about 135.degree. therebetween, indicated by the symbol .alpha. in FIGS. 2 and 4.
First tubular portions 88 and 84 of concentric flue pipe assembly 78 include mating flange portions 92 and 94 which respectively attach to first and second pipe members 60 and 64. Holes 95 formed in mating flange portion 94 align with holes formed in second pipe member 64. Fastening devices, such as screws 97, are threadingly engaged in holes 95 to fasten concentric flue pipe assembly 78 in place.
During operation, air flow through direct vent gas fireplace 10 is as follows: combustion air flows through the annular space defined between fresh air pipe 80 and exhaust pipe 82 from the ambient environment outside the house in which direct vent gas fireplace 10 is installed. The combustion air flows through air intake duct 65 and combustion air duct 66 (including plenum 62, air distribution conduits 68 and 70, and second plenums 72 and 74) into combustion chamber 16. The flow of combustion air into combustion chamber 16 is represented by air flow directional arrows 96 in FIGS. 1-3. The combustion air, drawn through openings 76, assists combustion within combustion chamber 16. Combustion products produced in combustion chamber 16 flow through the opening defined between baffle plates 49 and 51, first pipe member 60, and are exhausted to the outside environment through exhaust pipe 82. The flow of combustion products from combustion chamber 16 is represented in FIGS. 1 and 3 by directional arrows 98.
FIG. 4 illustrates attachment of concentric flue pipe assembly 78 to direct vent gas fireplace 10 whereby concentric flue pipe assembly 78 extends away from gas fireplace 10 in a generally horizontal direction. To select horizontal venting, concentric flue pipe assembly 78 is rotated 180.degree. from the position shown in FIGS. 1-3 prior to engagement of first tubular portions 88 and 84 with first and second pipe members 60 and 64. Holes 95 are located in mating flange portion 94 and second pipe member 64 such that screws 97 may be inserted in holes 95 and engage the aligned holes formed in second pipe member 64 regardless of whether concentric flue pipe assembly 78 is vented vertically (FIGS. 1-3) or horizontally (FIG. 4). When horizontal venting is selected, air flow through concentric flue pipe assembly 78 and direct vent gas fireplace 10 is the same as disclosed above. Thus, the embodiment of the present invention shown in the drawings allows selective venting of gas fireplace 10 whereby concentric flue pipe assembly 78 extends away from gas fireplace 10 in a substantially horizontal or vertical direction.
Thus, the embodiment of the present invention shown in the drawings allows second tubular portion 86 and 90 of eccentric flue pipe 78 to be selectively vented in either a vertical or horizontal direction. As shown in FIG. 3 (vertical venting) and FIG. 4 (horizontal venting), direct vent gas fireplace 10 may be disposed closely adjacent to an exterior wall 100 regardless of whether vertical or horizontal venting of concentric flue pipe assembly 78 is selected.
While this invention has been described a having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.
Claims
What is claimed is:
1. A direct vent gas fireplace adapted for attachment to a flue pipe assembly including an exhaust pipe and a surrounding fresh air pipe, said fireplace comprising: an interior housing forming a combustion chamber; a top wall, rear wall, bottom wall and side walls defining an exterior housing about said combustion chamber; a gas burner disposed in said combustion chamber; a slanted wall attached to and extending between said top and rear walls, said slanted wall disposed at obtuse angles relative to said top and rear walls; a first pipe member orthogonally extending to an opening in said slanted wall and in fluid communication with said combustion chamber for conveying combustion products from said combustion chamber; means forming a first plenum having a diameter larger than said first pipe and disposed around said first pipe member and in communication with said opening in said slanted wall, said first pipe member and said first plenum defining an annular space therebetween forming an air intake duct; and a combustion air duct extending between and in fluid communication with said first plenum and said combustion chamber for supplying combustion air to said combustion chamber; whereby the exhaust pipe and fresh air pipe of the flue pipe assembly are respectively adapted to be attached to said first pipe member and said first plenum and can be selectively oriented to extend away from said fireplace in either a substantially vertical or horizontal direction.
2. The fireplace of claim 1, wherein said combustion air duct comprises a second air collector plenum attached to said first plenum and at least one air distribution conduit extending between said second air collector plenum and said combustion chamber.
3. The fireplace of claim 2, comprising two said air distribution conduits respectively attached to said side walls.
4. The fireplace of claim 2, wherein said combustion air duct further comprises a third plenum having an opening in fluid communication with said combustion chamber.
5. The fireplace of claim 1, wherein said exterior housing and said interior housing define a space therebetween forming a room air circulation channel having a blower disposed therein, said blower receiving ambient air and circulating the air through said room air circulation channel, the air heated thereby and exhausted to the ambient environment.
6. The fireplace of claim 5, wherein said combustion air duct is disposed within said room air circulation channel.
7. The fireplace of claim 5, wherein said first plenum includes a flange extending through said slanted wall.
8. A direct vent gas fireplace, comprising: an interior housing forming a combustion chamber; a top wall, rear wall, bottom wall and side walls defining an exterior housing about said combustion chamber; a gas burner disposed in said combustion chamber; a slanted wall connected to and extending between said top and rear walls, said slanted wall disposed at obtuse angles relative to said top and rear walls; a first pipe member orthogonally extending to an opening in said slanted wall and in fluid communication with said combustion chamber for conveying combustion products from said combustion chamber; means forming a first plenum having a diameter larger than said first pipe and disposed around said first pipe member and in communication with said opening in said slanted wall, said first pipe member and said first plenum defining an annular space therebetween forming an air intake duct; and a combustion air duct extending between and in fluid communication with said plenum and said combustion chamber for supplying combustion air to said combustion chamber; whereby the exhaust pipe and fresh air pipe of the flue pipe assembly form a 135.degree. angle and are respectively attached to said first pipe member and said plenum and can be oriented to extend away from said fireplace selectively in either a substantially vertical or horizontal direction.
9. A direct vent fireplace adapted for attachment to a flue pipe assembly including an exhaust pipe and surrounding fresh air pipe, said fireplace comprising: an interior housing forming a combustion chamber; a top wall, rear wall, bottom wall, side walls and front opening defining an exterior housing about said combustion chamber; a slanted wall attached to and extending between said top wall and rear walls and forming obtuse angles relative to said top and rear walls; a first pipe member orthogonally extending to an opening in said slanted wall and in fluid communication with said combustion chamber for conveying combustion products from said combustion chamber; means forming a plenum having a diameter larger than said first pipe and disposed around said first pipe member and in communication with said opening in said slanted wall, said first pipe member and said plenum defining an annular space therebetween forming an air intake duct; and a combustion air duct extending between and in fluid communication with said plenum and said combustion chamber for supplying combustion air to said combustion chamber; whereby the exhaust pipe and fresh air pipe are adapted to be respectively adapted to be attached to said first pipe member and said plenum and can be oriented to extend away from said fireplace selectively in either a substantially vertical or horizontal direction.
10. A direct vent gas fireplace, comprising: a flue pipe assembly having an exhaust pipe and fresh air pipe, said fresh air pipe having a diameter larger than and disposed around said exhaust pipe, each of said exhaust pipe and fresh air pipe having first and second tubular portions disposed at about a 135.degree. angle relative to each other; an interior housing forming a combustion chamber; a top wall, rear wall, bottom wall and two side walls defining an exterior housing about said combustion chamber; a gas burner disposed within said combustion chamber; a slanted wall attached to and extending between said top wall and rear wall, said slanted wall disposed at an angle of about 45.degree. with respect to a horizontal plane; a first pipe member orthogonally extending to an opening in said slanted wall and in fluid communication with said combustion chamber for conveying combustion products from said combustion chamber; means forming a first plenum having a diameter larger than and disposed around said first pipe, said first pipe member and said first plenum defining an annular space therebetween forming an air intake duct; and a combustion air duct extending between and in fluid communication with said air intake duct and said combustion chamber for supplying combustion air to said combustion chamber; said first tubular portions of each said exhaust pipe and fresh air pipe respectively attachable to said first pipe member and said first plenum whereby said second tubular portions of each said exhaust pipe and fresh air pipe are selectively disposed in a substantially vertical or horizontal direction.
11. The fireplace of claim 10, wherein said combustion air duct further comprises at least one second plenum having a plurality of openings in fluid communication with said combustion chamber.
12. The fireplace of claim 10, wherein said exterior housing and said interior housing define a space therebetween forming a room air circulation channel having a blower disposed therein, said blower receiving ambient air and circulating the air through said room air circulation channel, the air heated thereby and exhausted to the ambient environment.
13. The fireplace of claim 12, wherein said combustion air duct comprises said first plenum comprising a flange extending through said slanted wall.
14. A direct vent fireplace, comprising: a flue pipe assembly including an exhaust pipe and a surrounding fresh air pipe; an interior housing forming a combustion chamber; a top wall, rear wall, bottom wall and side walls defining an exterior housing; a slanted exterior wall attached to and extending between said top and rear walls, said slanted outer wall disposed at obtuse angles relative to said top and rear walls; said combustion chamber including a slanted interior wall disposed in spaced apart parallel relationship from said slanted exterior wall; an intermediate wall disposed between said slanted inner wall and slanted exterior wall, said intermediate wall attached to said slanted exterior wall, said intermediate wall and slanted exterior wall forming a plenum in fluid communication with said combustion chamber for supplying combustion air to said combustion chamber; a first pipe member orthogonally attached to said slanted inner wall and extending through said slanted exterior wall and intermediate wall, said first pipe member in fluid communication with said combustion chamber for conveying combustion products from said combustion chamber; and a second pipe member orthogonally attached to said slanted exterior wall, said second pipe member having a diameter larger than said first pipe and disposed around said first pipe member, said first and second pipe members defining an annular space therebetween forming an air intake duct in fluid communication with said plenum.
15. The fireplace of claim 14, further comprising a combustion air duct extending between and in fluid communication with said plenum and said combustion chamber for supplying combustion air to said combustion chamber.
16. A direct vent fireplace adapted for attachment to a flue pipe assembly including an exhaust pipe and a surrounding fresh air pipe, said fireplace comprising: a top wall, rear wall, bottom wall and side walls defining combustion chamber, one of said walls defining said combustion chamber including an opening therein for admittance of combustion air; a slanted flue attachment wall attached to and extending between said top and rear walls, said slanted flue attachment wall disposed at obtuse angles relative to said top and rear walls; an exterior housing disposed in spaced apart relationship from said combustion chamber, said housing having an exterior bottom wall, exterior top wall, exterior back wall, two exterior side walls, an exterior front wall defining an opening, and a slanted exterior wall attached to and extending between said exterior top wall and exterior back wall, said slanted exterior wall disposed generally parallel to said slanted flue attachment wall; a first pipe member orthogonally attached to said flue attachment wall and in fluid communication with said combustion chamber for conveying combustion products from said combustion chamber; and means forming a plenum orthogonally attached to said slanted exterior wall, said plenum having a diameter larger than said first pipe and disposed around said first pipe member, a combustion air duct connected with said plenum and in fluid communication said combustion chamber; whereby the exhaust pipe and fresh air pipe are respectively adapted to be attached to said first pipe member and said plenum and can be selectively oriented to extend away from said fireplace in either a substantially vertical or horizontal direction.
Patent Citations (43)
| Patent | Date | Inventor | Cited By |
|---|---|---|---|
| US2582066 | 1952-01-01 | Resek | |
| US2998764 | 1961-09-01 | Bedell et al. | |
| US3168088 | 1965-02-01 | Martin et al. | |
| US3171402 | 1965-03-01 | Carlson | |
| US3395693 | 1968-08-01 | Cowan | |
| US3435816 | 1969-04-01 | De Werth | |
| US3614948 | 1971-10-01 | Jackson et al. | |
| US3741194 | 1973-06-01 | Herron | |
| US4112913 | 1978-09-01 | Shimek | |
| US4141336 | 1979-02-01 | Fitch | |
| US4184473 | 1980-01-01 | McIntire et al. | |
| US4204517 | 1980-05-01 | Rumsey | |
| US4224921 | 1980-09-01 | Petrescue | |
| US4271815 | 1981-06-01 | Johnson | |
| US4304215 | 1981-12-01 | Jarman | |
| US4347831 | 1982-09-01 | Graziano | |
| US4349009 | 1982-09-01 | Patterson et al. | |
| US4359040 | 1982-11-01 | Martenson | |
| US4377153 | 1983-03-01 | Flagg | |
| US4408594 | 1983-10-01 | Shimek | |
| US4412255 | 1983-11-01 | Aidla | |
| US4424792 | 1984-01-01 | Shimek et al. | |
| US4434783 | 1984-03-01 | O'Gorman | |
| US4465055 | 1984-08-01 | Bortz | |
| US4471755 | 1984-09-01 | Faehling et al. | |
| US4494525 | 1985-01-01 | Albertsen | |
| US4519376 | 1985-05-01 | Schoeff et al. | |
| US4545360 | 1985-10-01 | Smith et al. | |
| US4558688 | 1985-12-01 | Piazzetta | |
| US4574773 | 1986-03-01 | Moughamian | |
| US4611572 | 1986-09-01 | Martenson | |
| US4787365 | 1988-11-01 | Coleman | |
| US4793322 | 1988-12-01 | Shimek et al. | |
| US4852548 | 1989-08-01 | Shimek | |
| US4875464 | 1989-10-01 | Shimek | |
| US4886047 | 1989-12-01 | Bonin | |
| US4909227 | 1990-03-01 | Rieger | |
| US5000162 | 1991-03-01 | Shimek | |
| US5014684 | 1991-05-01 | Meeker | |
| US5016609 | 1991-05-01 | Shimek et al. | |
| US5076254 | 1991-12-01 | Shimek et al. | |
| US5191877 | 1993-03-01 | Shimek | |
| US5218953 | 1993-06-01 | Shimek |
Non-Patent Literature (1)
- European patent application 303559 Feb. 1989.