Plant husbandry – Ornamental beds
Reexamination Certificate
1998-12-29
2001-07-03
Poon, Peter M. (Department: 3644)
Plant husbandry
Ornamental beds
Reexamination Certificate
active
06253486
ABSTRACT:
TECHNICAL FIELD
This invention relates to a lawn barrier and more particularly this invention relates to an improved synthetic composite lawn edging which acts as a divider between lawn areas containing different types of plants or ground cover.
1. Background of the Invention
Many lawns are landscaped to contain discrete areas or beds of ground cover such as grass, plants or non-growing materials such as stone or bark. In order to prevent growth across the common border; it is quite common to install a physical barrier at the border such as strips of wood, metal, brick or cement walls, or lawn edging formed of synthetic resin.
2. Description of the Prior Art
A popular form of synthetic resin lawn edging is in the form of a flange having an enlarged tube and a pair of anchoring means such as upwardly facing lips are provided between the lips and bottom of the flange as disclosed in U.S. Pat. No. 4,281,473.
This lawn edging is formed from polyethylene. It is very rigid and inflexible. The edging is marketed in twenty foot sections wound into a coil. The edging retains the memory of the bends in the coil. It is hard to install in a straight line and the edging also contains vertical ribs intended to aid in securing the edging in the ground. The edging kinks when bent into a narrow radius. The memory combined with a very smooth surface causes the edging to work its way out of the ground even though it contains the upwardly facing lips on the flange which are backfilled with dirt or stone and the alternating vertical rib structure.
Polyethylene is an expensive material and is manufactured by polymerizing ethylene, a material formed from petroleum, a dwindling resource.
STATEMENT OF THE INVENTION
The lawn edging of the invention is formed from a dispersion of ground-up, recycled rubber particles in a matrix resin. Millions of used tires are generated every year. They are fairly inert and do not decay when buried in land fills. They are a fire hazard when stored in sites above the ground. It is difficult to separate the steel and fabric cord from the rubber. Since the rubber is revulcanized to a cross-linked form, the rubber cannot be recovered by solution in solvent. It is not economical to degrade the long chain rubber molecules to smaller hydrocarbons by thermal or catalytic methods.
The rubber particles utilized in the lawn edging invention can be recovered from used tire carcasses by mechanical comminution of tires and separation of the fiber or metal cord from the rubber. Ground rubber particles can be sized between screens generally to particles retained by 10 mesh screens, preferably 30-40 mesh screens. The amount of rubber used in the composite lawn edging of the invention is generally from 20 to 80 percent by weight. The continuous phase binder resin is a thermoplastic polymer capable of melting to disperse the rubber particles into an extrudable mixture. The thermoplastic polymers can be a polymer of an alkylene containing 2 to 8 carbon atoms such as ethylene, propylene, butylene, hexylene and ethyl hexylene or mixtures thereof. Other suitable thermo-plastics polymers are vinyl polymers.
The mixture is extruded to form a lawn edging having a rough surface. The rough surface intensifies the frictional resistance of the buried edging reducing the tendency of the edging to creep out of the ground. The composite rubber-polymer lawn edging is much more flexible, pliable and bendable than an equivalent polyethylene edging. It can be bent into tighter radii to follow contours of garden beds without cracking or kinking. It can also be wound into tighter spirals to make smaller packages requiring less shelf space.
The invention also relates to a unique process for extruding the lawn edging. The lawn edging preferably contains an anchoring means provided at the mid section of the vertical flange of the edging. Prior devices used inverted V-shaped lips for this purpose. In the invention, wave-like protrusions are formed on the flange protruding normal to the axis of the flange. By controlling the pressure of the extrudate entering the central section of the die, pressure on the extruded material in this section is found to periodically build up and release to form wave-like structure corresponding to the die opening and which forms alternating protrusions and dimples in the wall of the flange. The other side has a horizontal edge and may run across the top edge of the wave structure.
The lawn edging of the invention contributes to the environment by using a recycled product that otherwise would accumulate and degrade the environment. The lawn edging of the invention is more flexible than prior products, can be installed with less force, can be bent into tighter radii and has less tendency to come out of the ground after installation.
These and many other features and attendant advantages of the invention will become apparent as the invention becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings.
REFERENCES:
patent: 3933311 (1976-01-01), Lemelson
patent: 4281473 (1981-08-01), Emalfarb et al.
patent: 5201154 (1993-04-01), Thomas
patent: 5242644 (1993-09-01), Thompson et al.
patent: 5252644 (1993-10-01), Edwards
patent: 5447671 (1995-09-01), Kato et al.
patent: 5456045 (1995-10-01), Bradley et al.
patent: 5519970 (1996-05-01), Reum et al.
Bard Shannon
Prassas Thomas N.
Aquapore Moisture Systems
Jacobs Marvin E.
Poon Peter M.
Shaw Elizabeth
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