GB1572715A - Creación de Inventos y Patentes con Inteligencia Artificial

GB1572715A – Structures and structural members made wholly or partly of wood
– Google Patents

GB1572715A – Structures and structural members made wholly or partly of wood
– Google Patents
Structures and structural members made wholly or partly of wood

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Publication number
GB1572715A

GB1572715A
GB40380/76A
GB4038076A
GB1572715A
GB 1572715 A
GB1572715 A
GB 1572715A
GB 40380/76 A
GB40380/76 A
GB 40380/76A
GB 4038076 A
GB4038076 A
GB 4038076A
GB 1572715 A
GB1572715 A
GB 1572715A
Authority
GB
United Kingdom
Prior art keywords
structural member
fluid
wooden
wood preservative
exposed
Prior art date
1976-09-29
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

Application number
GB40380/76A
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)

Balfour Beatty Group Ltd

Original Assignee
Balfour Beatty Ltd
Priority date (The priority date 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 date listed.)
1976-09-29
Filing date
1976-09-29
Publication date
1980-07-30

1976-09-29
Application filed by Balfour Beatty Ltd
filed
Critical
Balfour Beatty Ltd

1976-09-29
Priority to GB40380/76A
priority
Critical
patent/GB1572715A/en

1977-09-28
Priority to IT51167/77A
priority
patent/IT1116116B/en

1977-09-28
Priority to FR7729219A
priority
patent/FR2366109A2/en

1977-09-28
Priority to DE19772743525
priority
patent/DE2743525A1/en

1977-09-28
Priority to US05/837,438
priority
patent/US4174412A/en

1977-09-28
Priority to CA287,659A
priority
patent/CA1103106A/en

1977-09-29
Priority to BE181303A
priority
patent/BE859194A/en

1977-10-25
Priority to FR7732150A
priority
patent/FR2407321A2/en

1977-10-29
Priority to BR7706512A
priority
patent/BR7706512A/en

1978-08-11
Priority to FR7823771A
priority
patent/FR2400097A2/en

1980-07-30
Publication of GB1572715A
publication
Critical
patent/GB1572715A/en

Status
Expired
legal-status
Critical
Current

Links

Espacenet

Global Dossier

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Classifications

E—FIXED CONSTRUCTIONS

E04—BUILDING

E04G—SCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS

E04G23/00—Working measures on existing buildings

E04G23/02—Repairing, e.g. filling cracks; Restoring; Altering; Enlarging

E04G23/0203—Arrangements for filling cracks or cavities in building constructions

B—PERFORMING OPERATIONS; TRANSPORTING

B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL

B27K—PROCESSES, APPARATUS OR SELECTION OF SUBSTANCES FOR IMPREGNATING, STAINING, DYEING, BLEACHING OF WOOD OR SIMILAR MATERIALS, OR TREATING OF WOOD OR SIMILAR MATERIALS WITH PERMEANT LIQUIDS, NOT OTHERWISE PROVIDED FOR; CHEMICAL OR PHYSICAL TREATMENT OF CORK, CANE, REED, STRAW OR SIMILAR MATERIALS

B27K3/00—Impregnating wood, e.g. impregnation pretreatment, for example puncturing; Wood impregnation aids not directly involved in the impregnation process

B27K3/02—Processes; Apparatus

B27K3/0235—Stationary devices on or in legs or poles

B—PERFORMING OPERATIONS; TRANSPORTING

B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL

B27K3/00—Impregnating wood, e.g. impregnation pretreatment, for example puncturing; Wood impregnation aids not directly involved in the impregnation process

B27K3/02—Processes; Apparatus

B27K3/08—Impregnating by pressure, e.g. vacuum impregnation

B—PERFORMING OPERATIONS; TRANSPORTING

B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL

B27K5/00—Treating of wood not provided for in groups B27K1/00, B27K3/00

B27K5/003—Treating of wood not provided for in groups B27K1/00, B27K3/00 by using electromagnetic radiation or mechanical waves

B27K5/006—Vibrations

Description

PATENT SPECIFICATION
( 11) 1 572 715 ( 21) Application No 40380/76 ( 22) Filed 29 Sep 1976 ( 19) ( 61) Patent of Addition to No 1399510 Dated 11 Oct 1973 ( 23) Complete Specification Filed 28 Sep 1977 ( 44) Complete Specification Published 30 Jul 1980 ( 51) INT CL 3 B 27 K 3/10 ( 52) Index at Acceptance DIP WDB ( 72) Inventors: R G TYRER J MILNE ( 54) IMPROVEMENTS IN OR RELATING TO STRUCTURES AND STRUCTURAL MEMBERS MADE WHOLLY OR PARTLY OF WOOD ( 71) We BALFOUR BEATTY LIMITED a British Company, of 7 Mayday Road Thornton Heath Surrey CR 4 7 XA.
do hereby declare the invention for which we pray that a patent may be granted to us.
and the method bv which it is to be performed to be particularly described in and by the following statement:
In the Complete Specification of our
Patent No 1399510 there is described and claimed a method of introducing a hardenable material in a liquid or semi-liquid state into cracks or other voids in an artificial or natural structure of the kind specified in the patent In this method the structure or a part of the structure containing the cracks or other voids that are to be filled is sorrounded by a closely-fitting, fluidimpermeable covering and boundary edges of the covering are sealed to the structure to form a substantially fluid-tight enclosure: air and any other fluid is evacuated from the cracks and other voids within the fluid-tight enclosure and when the cracks and other voids have been substantialv evacuated.
hardenable material in a liquid or semiliquid state is allowed to enter into the evacuated cracks or other voids until hardenable material appears at the openings of the cracks and voids in the surface or surfaces of the structure: and the hardenable material is permitted or caused to set.
Artificial or natural structures specified in the aforesaid patent include those built up of or comprising timber.
The present invention is concerned with a modification of or improvement in the method of the aforesaid patent hereinafter referred to as the main patent and relates to the preservation of structures and structural members made wholly or partly of wood.
The invention is particularly concerned with preservation in situ of at least that wooden part of a structure or structural member that is exposed to the atmosphere and may be subjected to extremes of weather conditions.
For many years it has been the general practice to preserve wooden poles from deterioration otherwise caused by damp by impregnating the pole with creosote or other suitable wood preservative Such impregnation with wood preservative can be effected before or after a pole is erected but.
for obvious reasons it is normal practice to impregnate thoroughly with wood preservaive the whole or a part of a pole before the pole is erected However thoroughly such impregnation is carried out in the course of time the effectiveness of the wood presrvative in a pole gradually diminishes and it is necessary to re-impregnate at least that part of the erected pole that is exposed to the amosphere.
It is an object of the present invention to provide a simple and inexpensive method of impregnating with non-hardenable wood preservative at least a wooden part of a structure or structural member that is exposed to the atmosphere.
According to the invention the method comprises surrounding said exposed wooden part of the structure or of the structural member by a closelv fitting fluidimpermeable covering and sealing boundary edges of the covering to the structure or structural member to form a substantially fluid-tieht enclosure: evacuating air and any other fluid from cracks and any other voids in said wooden part of the structure or structural member and from within the fluid-tight enclosure: and allowing nonhardenable wood perservative in a liquid or other flowable state to enter the enclosure and the cracks and other voids in said wooden part of the structure or structural member until said wooden part of the structure or structural member is fully impregnated with wood preservative.
Preferably wood preservative is not in 1 r CI tn 1 572 715 allowed to enter the fluid-tight enclosure until the enclosure and voids in said wooden part of the structure or structural member enclosed therein have been substantially evacuated.
The method of the present invention is especially suitable for impregnating with wood preservative that part of a telegraph pole, mast, post or similar upright wooden structural member that is exposed to the atmosphere but it can be employed in impregnating a wooden part of any other form of erected structure or structural member, for instance components of a wooden fence.
Where the wooden part of the structure or structural member is substantially higher than the head of wood preservative that the means for evacuating air can support or, in other circumstances, said wooden part may be treated in two or more section located one above the other.
The closely-fitting, fluid-impermeable covering may be formed wholly by a flexible shroud or, in some circumstances where the structure or structural member has a surface or surfaces of a shape or configuration that makes it difficult to envelop such surface or surfaces in a closely-fitting shroud, for instance where a surface of the structure or structural member has another structural member or other structural members upstanding from or projecting outwardly from the surface, the closely-fitting, fluidimpermeable covering may be formed in part by applying to an exposed surface or exposed surfaces of the structure or structural member a continuous layer of hardenable material in a liquid or semi-liquid state which, on setting forms a closely-fitting, fluid-impermeable coating.
Where the closely-fitting, fluidimpermeable covering consists of or comprises a flexible shroud, in order that progress of the impregnating operation can be observed at all times and that the supply of wood preservative can be cut off as soon as said wooden part of the structure or structural member has been fully impregnated the shroud is preferably formed of a transparent material.
Boundary edges of the flexible shroud may be sealed by means of a coating of resin or other hardenable material or by means of adhesive tape.
Evacuation of the substantially fluid-tight enclosure is preferably effected by at least one vacuum pump and/or a least one air compressor and associated venturi suction ejector Preferably the or each vacuum pump or air compressor and associated venturi suction ejector is connected to an outlet or outlets in an upper part of the closely-fitting, fluid-impermeable covering and at least one source of wood preservative in a liquid or other flowable state is connected to an inlet or inlets at a lower part of the covering so that the preservative flows upwardly within the enclosure.
Where the structure or structural member is erected with a lower part of the structure or structural member embedded in the ground, preferably the closely-fitting, fluidimpermeable covering is arranged to extend below ground level in order to ensure that that wooden part of the structure or structural member immediately adjacent the ground and immediately below ground level will be fully impregnated with preservative.
Where the structure or structural member consists of or includes a pole having a wooden part that is buried in the ground, the buried wooden part of the pole may be impregnated with wood preservative by the method described and claimed in the Complete Specification of our British Patent No.
1454917.
To ensure that the enclosed wooden part of the structure or structural member is substantially fully impregnated with wood preservaive throughout its thickness, the wood preservative may be forced into said wooden part at a pressure above atmospheric pressure Effective impregnation of said wooden part may be further enhanced by subjecting the or each stream of wood preservative being introduced under pressure into said wooden part to a hammer effect, for instance by means of a reciprocating piston working in a cylinder connected in a branch in the flow path between the source of wood preservative and the inlet.
To reduce the risk that small bubbles of air or other fluid may be trapped in the closed ends of cracks or other voids or may cling to the boundary surfaces of cracks or other voids in said wooden part of the structure or structural member, should the state or nature of the structure or structural member permit, the wooden part may be subjected to vibration effectively to shake out any such bubbles Such vibration may be either manually or mechanically applied.
The wood preservative is preferably creosote or other chemical preservative which soaks into and impregnates the material of which the structure or structural member is made.
The invention is further illustrated by a description, by way of example, of the preferred method of impregnating with wood preservative that part of an erected wooden telegraph pole that is exposed to the atmosphere, with reference to the accompanying drawing, which shows a fragmental cross-sectional side view of the pole.
Referring to the drawing, the erected wooden telegraph pole 1 that is to be impregnated with creosote is treated in two or more sections located one above the 1 572 715 other to limit the head of creosote that the vacuum pump or pumps has or have to support The lowermost section of the pole is first treated by wrapping a sheet 2 of transparent plastics material around said lowermost section and sealing the overlapping edges of the sheet with adhesive tape.
The bottom edge 3 of the sheet 1 extends below ground level and the sheet is sealed to the pole adjacent its bottom edge by adhesive tape 4; the sheet is sealed to the pole adjacent its top edge by adhesive tape 5.
Attached to and projecting from an upper part of the sheet 2 is an outlet fitting 6 to which can be connected a pipe for connection to a liquid trap (not shown) and vacuum pump (not shown) An inlet fitting 8 is attached to and projects outwardly from a lower part of the sheet 2 and this fitting is connected by a pipe 9 to a source of creosote (not shown) A tap 10 is provided in the pipe 9 connected to the creosote source.
In operation, the tap 10 connected in the pipe 9 is closed and air and any other fluid is evacuated from the substantially fluid-tight enclosure formed by the sealed sheet 2 and from the enveloped lowermost section of the wooden pole 1 When a satisfactory level of vacuum has been reached the tap 10 is opened and creosote is drawn upwardly into the enclosure to imprenate the enveloped section of the pole 1 until it appears at the outlet 6 At this juncture the tap 10 is closed and the vacuum pump is switched off.
After the enveloped section of the pole 1 has been allowed to soak in creosote remaining in the fluid-tight enclosure, a drain 11 at the lower end of the sheet 2 is opened to permit excess creosote in the fluid-tight enclosure to be drained off The sheet 2 is then removed and the next section of the pole 1 is treated in a similar manner until the entire length of the pole has been impregnated with creosote.

Claims (14)

WHAT WE CLAIM IS:-

1 A method of impregnating with wood preservative at least that wooden part of a structure or structural member that is exposed to the atmosphere which method comprises surrounding said exposed wooden part of the structure or of the structural member by a closely fitting, fluidimpermeable covering and sealing boundary edges of the covering to the structure or structural member to form a substantially fluid-tight enclosure; evacuating air and any other fluid from cracks and any other voids in the said wooden part of the structure or structural member and from within the fluid-tight enclosure: and allowing nonhardenable wood preservative in a liquid or other flowable state to enter the enclosure and the cracks and other voids in said wooden part of the structure or structural member until said wooden part of the structure or structural member is fully impregnated with wood preservative.

2 A method of impregnating with wood preservative that part of a wooden telegraph pole or other upright elongate wooden structural member that is exposed to the atmosphere, which method comprises surrounding said exposed part of the pole or member or a section of said exposed part by a closely fitting, fluid-impermeable flexible shroud and sealing boundary edges of the shroud to the strucutre or structural member to form a substantially fluid-tight enclosure; evacuating air and any other fluid from cracks and other voids in said part or section of said part of the pole or member and from within the fluid-tight enclosure; and allowing non-hardenable wood preservative in a liquid or other flowable state to enter the enclosure and the cracks and other voids in said part or section of said part of the pole or member until said part or section is fully impregnated with wood preservative.

3 A method as claimed in Claim 1 or 2, wherein said wooden part of the structure or structural member is treated in two or more sections located one above the other.

4 A method as claimed in any one of the preceding Claims, in which a lower section of the wooden part of the pole or other structure or structural member is embedded in the ground, wherein the closely fitting, fluid-impermeable flexible shroud or other covering is arranged to extend below ground level.

A method as claimed in any one of the preceding Claims, wherein air and any other fluid is evacuated through an outlet or outlets in an upper part of the flexible shroud or other covering and wood preservative enters the enclosure through an inlet or inlets in a lower part of the flexible shroud or other covering.

6 A method as claimed in claim 1, wherein the closely fitting, fluidimpermeable covering is formed wholly or in part by at least one flexible shroud.

7 A method as claimed in any one of Claims 2 to 6, wherein the flexible shroud is of transparent material.

8 A method as claimed in any one of Claims 2 to 7, wherein boundary edges of the flexible shroud are sealed to the pole or other structure or structural member by a coating of resin or other hardenable material or by means of adhesive tape.

9 A method as claimed in any one of the preceding Claims, wherein the closelyfitting, fluid-impermeable covering is formed in part by applying to an exposed surface or exposed surfaces of the structure or structural member a continuous layer of hardenable material in a liquid or semiliquid state which, on setting, forms a closely fitting, fluid-impermeable coating.

1 572 715 A method as claimed in any one of the preceding Claims, wherein wood preservative is not allowed to enter the fluid-tight enclosure until the enclosure and cracks and other voids in said wooden part of the structure or structural member enclosed therein have been substantially evacuated.

11 A method as claimed in any one of the preceding Claims, wherein wood preservative is forced into said wooden part of the structure or structural member at a pressure above atmospheric pressure.

12 A method as claimed in Claim 11, wherein the or each stream of wood preservative being introduced under pressure into said wooden part is subjected to a hammer effect.

13 A method as claimed in any one of the preceding Claims, wherein said wooden part of the structure or structural member is subjected to vibration effectively to shake out any bubbles of air or other fluid trapped in the closed ends of blind cracks and other blind voids or clinging to the boundary surfaces of cracks and other voids.

14 A method of impregnating with nonhardenable wood preservative the exposed part of a wooden telegraph pole substantially as hereinbefore described with reference to the accompanying drawing.
A structure or structural member having a wooden part that is exposed to the atmosphere and that has been impregnated with non-hardenable wood preservative by the method claimed in any one of the preceding Claims.
E L ROSS GOWER, Agents for the Applicants, 38 Wood Lane, London W 12 7 DX.
Printed for Her Majesty’s Stationery Office.
by Croydon Printing Company Limited Croydon, Surrey, 1980.
Published by The Patent Office 25 Southampton Buildings.
London WC 2 A l AY, from which copies may be obtained.

GB40380/76A
1972-11-01
1976-09-29
Structures and structural members made wholly or partly of wood

Expired

GB1572715A
(en)

Priority Applications (10)

Application Number
Priority Date
Filing Date
Title

GB40380/76A

GB1572715A
(en)

1976-09-29
1976-09-29
Structures and structural members made wholly or partly of wood

IT51167/77A

IT1116116B
(en)

1976-09-29
1977-09-28

METHOD FOR FORMING BUILDING WORK STRUCTURES AND STRUCTURES SO FORMED

FR7729219A

FR2366109A2
(en)

1972-11-01
1977-09-28
Impregnating wood with preserving fluid – by surrounding with flexible sealed jacket and pumping in fluid

DE19772743525

DE2743525A1
(en)

1976-09-29
1977-09-28

METHOD FOR IMPREGATING AT LEAST ONE WOODEN PART OF A STRUCTURE OR COMPONENT WITH A WOOD PRESERVATIVE

US05/837,438

US4174412A
(en)

1976-09-29
1977-09-28
Structures and structural members made wholly or partly of wood

CA287,659A

CA1103106A
(en)

1976-09-29
1977-09-28
Structures and structural members made wholly or partly of wood

BE181303A

BE859194A
(en)

1976-09-29
1977-09-29

WOOD IMPREGNATION PROCESS BY A PRESERVATIVE

FR7732150A

FR2407321A2
(en)

1972-11-01
1977-10-25
Grouting of fissured concrete or masonry faces – using sealed surface cover with tubular edge bead to apply vacuum and then inject grout

BR7706512A

BR7706512A
(en)

1976-09-29
1977-10-29

PROCESS TO IMPREGNATE WITH A WOOD PRESERVATION PRODUCT A PART OF WOOD EXPOSED TO THE ATMOSPHERE OF A STRUCTURAL STRUCTURE OR MEMBER

FR7823771A

FR2400097A2
(en)

1972-11-01
1978-08-11
Tunnel wall reinforcing and lining system – employs liq. or semi-liq. setting agent injected into porous base

Applications Claiming Priority (1)

Application Number
Priority Date
Filing Date
Title

GB40380/76A

GB1572715A
(en)

1976-09-29
1976-09-29
Structures and structural members made wholly or partly of wood

Publications (1)

Publication Number
Publication Date

GB1572715A
true

GB1572715A
(en)

1980-07-30

Family
ID=10414602
Family Applications (1)

Application Number
Title
Priority Date
Filing Date

GB40380/76A
Expired

GB1572715A
(en)

1972-11-01
1976-09-29
Structures and structural members made wholly or partly of wood

Country Status (7)

Country
Link

US
(1)

US4174412A
(en)

BE
(1)

BE859194A
(en)

BR
(1)

BR7706512A
(en)

CA
(1)

CA1103106A
(en)

DE
(1)

DE2743525A1
(en)

GB
(1)

GB1572715A
(en)

IT
(1)

IT1116116B
(en)

Cited By (2)

* Cited by examiner, † Cited by third party

Publication number
Priority date
Publication date
Assignee
Title

EP0213741A1
(en)

1985-07-29
1987-03-11
Dainippon Ink And Chemicals, Inc.
A method and an apparatus for injecting a treating liquid into a woody material

FR2631881A1
(en)

1988-05-25
1989-12-01
Ikeda Nobuo

Families Citing this family (11)

* Cited by examiner, † Cited by third party

Publication number
Priority date
Publication date
Assignee
Title

DE3245902A1
(en)

1982-12-11
1984-06-14
Dynamit Nobel Ag, 5210 Troisdorf
Method for impregnating porous bodies

US4719133A
(en)

1985-08-05
1988-01-12
Jacob Woudsma
Process for treating wood as well as product for treating wood

US4731267A
(en)

1986-07-28
1988-03-15
Makus Sharon J
Article and method for wood preservative treatment

US5591263A
(en)

1991-03-18
1997-01-07
Saneish Pty Ltd
Wood preservative applicator

US5770265A
(en)

1995-09-26
1998-06-23
Triangle Laboratories, Inc.
Environmentally friendly treatments to extend the functional life of wood structures and novel treated wood structures

US5783258A
(en)

1997-03-06
1998-07-21
Garapick; Ronald T.
Method for treating lumber

GB2327225B
(en)

1997-07-14
2001-06-27
Nigel Gary Frank Evans
Preserving wooden posts for fencing and the like

BR0112496A
(en)

2000-07-04
2003-12-02
Libere Nitunga

Wood preservation process, longitudinal injection device, safety device, radial injection device

AT411576B
(en)

2001-08-17
2004-03-25
Vujasin Nikola

METHOD FOR PRESERVING OBJECTS OF STONE, CERAMIC OR WOOD AND DEVICE FOR IMPLEMENTING THE METHOD

US20050274938A1
(en)

2004-06-12
2005-12-15
Nesbitt Daniel F
Wooden post with protective coating and method for making same

WO2017042742A1
(en)

2015-09-10
2017-03-16
Wood-Perfect Corporation
Self-treatment of wooden posts in use

Family Cites Families (7)

* Cited by examiner, † Cited by third party

Publication number
Priority date
Publication date
Assignee
Title

US2875020A
(en)

1956-11-05
1959-02-24
Chapman Chem Co
Wood preservation method and package

US3467546A
(en)

1966-06-23
1969-09-16
Robert Z Page
Method of impregnating wood

US3779797A
(en)

1968-09-20
1973-12-18
A Makinen
Method for the impregnation and surface treatment of porous board type products

US3595182A
(en)

1969-10-10
1971-07-27
Frank S Clapp
Apparatus for underground treatment of poles

US3834329A
(en)

1971-09-02
1974-09-10
J Suggitt
Apparatus for applying preservative material to erected poles and the like

CA994616A
(en)

1972-11-01
1976-08-10
Balfour, Beatty And Company Limited
Artificial and natural structures

US3987219A
(en)

1973-09-20
1976-10-19
Arvidsson E
Method for impregnation of wood by pressure surges during immersion

1976

1976-09-29
GB
GB40380/76A
patent/GB1572715A/en
not_active
Expired

1977

1977-09-28
DE
DE19772743525
patent/DE2743525A1/en
not_active
Ceased

1977-09-28
US
US05/837,438
patent/US4174412A/en
not_active
Expired – Lifetime

1977-09-28
CA
CA287,659A
patent/CA1103106A/en
not_active
Expired

1977-09-28
IT
IT51167/77A
patent/IT1116116B/en
active

1977-09-29
BE
BE181303A
patent/BE859194A/en
not_active
IP Right Cessation

1977-10-29
BR
BR7706512A
patent/BR7706512A/en
unknown

Cited By (2)

* Cited by examiner, † Cited by third party

Publication number
Priority date
Publication date
Assignee
Title

EP0213741A1
(en)

1985-07-29
1987-03-11
Dainippon Ink And Chemicals, Inc.
A method and an apparatus for injecting a treating liquid into a woody material

FR2631881A1
(en)

1988-05-25
1989-12-01
Ikeda Nobuo

Also Published As

Publication number
Publication date

DE2743525A1
(en)

1978-03-30

IT1116116B
(en)

1986-02-10

CA1103106A
(en)

1981-06-16

BR7706512A
(en)

1978-08-08

BE859194A
(en)

1978-01-16

US4174412A
(en)

1979-11-13

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