CA2312299A1 - Golf green cover - Google Patents

Abstract

The golf green cover is made of three layers; a water-impermeable top layer and intermediate and bottom layers made of semi-rigid insulating foam. The bottom layer has perforations therein. Transversal air passages are formed between the intermediate and the bottom layers and communicate with the perforations. Each transversal air passage has a cord segment and an arc segment whereby it is non-collapsible under snow loads. Longitudinal air passages are formed under the seams between adjacent cover panels and communicate with the transversal air passages.
A gas collection pipe is mounted in one of the longitudinal air passages and communicates with an air valve and a rotary ventilator. The perforations, the air passages, the air valve and the ventilator are usable to evacuate gases accumulating under the cover and to periodically aerate the covered grass. A thermocouple is bonded to the underside surface of the bottom layer and is usable as a learning tool to develop knowledge of the conditions of a covered golf green.

Description

TITLE: GOLF GREEN COVER
FIELD OF THE INVENTION
The present invention relates to flexible ground covers, and more particularly, the present invention pertains to a water-impermeable, heat-insulating golf green cover having breathing abilities to aerate and to evacuate noxious gases from the covered grass.
BACKGROUND OF THE INVENTION
It is generally well known that golf greens have very short and dense turf that is susceptible to freezing and wind burn during the winter months, especially in regions where there is insufficient snow or belated snow fall to protect the root systems of the grass. It is also known that too much water absorption by the grass of a golf green that is later subject to freezing temperatures, is often detrimental to the plants for expanding and bursting the roots of the plants. It is therefore preferable to protect a golf green with a water-impermeable cover during winter, to prevent excessive water absorption by the grass and to shield the grass from winter conditions.
A water-impermeable cover, however, is often airtight. It deprives the soil of oxygen and tends to accumulate carbon dioxide, nitrous oxide and methane. The lack of aeration together with a prolonged moisture stress predispose the grass to rotting fungi and other plant diseases. It is therefore also preferable to protect a golf green with a water-impermeable cover which has breathing abilities to periodically aerate and evacuate noxious gases.

It is also believed that it is preferable to install a heat-insulating cover over a golf green to protect the grass from freeze-and-thaw cycles in case of an absence or a scarcity of snow.
A number of ground covers have been developed in the past to protect the grass of recreational grounds. Examples of these covers are illustrated and described in the following documents:
US Patent 974,091 issued on Oct. 25, 1910 to J.L. O'Donnell;
US Patent 1,576,888 issued on Mar. 16, 1926 to J.H. Woodward;
US Patent 1,580,396 issued on Apr. 13, 1926 to J.H. Woodward;
US Patent 1,966,687 issued on July 17, 1934 to J.A. Scott et al.;
US Patent 2,578,135 issued on Dec. 11, 1951 to C.J. Hoigaard et al.;
US Patent 2,540,380 issued on Feb. 6, 1951 to L.J. Schultheis;
US Patent 2,848,233 issued on Aug. 19, 1958 to H.D. Wynn;
US Patent 3,005,461 issued on Oct. 24, 1961 to R. Arganbright;
US Patent 3,099,444 issued on July 30, 1963 to F.E. Burt;
US Patent 3,108,804 issued on Oct. 29, 1963 to A.W. Wagner;
US Patent 4,050,972 issued on Sept. 27, 1977 to D.E. Cardinal, Jr.;
US Patent 4,590,714 issued on May 27, 1986 to S.F. Walker;
US Patent 4,632,329 issued on Dec. 30, 1986 to W.G. Burley;
CA Patent 1,272,027 issued on July 31, 1990 to C.A. Hinsperger.
Although the prior art ground covers deserve undeniable merits, there is no known prior art cover which combines the advantages of preserving a golf green from all the aforesaid winterkill conditions. As such it may be appreciated that there continues to be a need for a golf green cover which is water-impermeable, which has heat-insulating properties, and which has means to periodically ventilate the covered grass.

SUMMARY OF THE INVENTION
The present invention provides for a heat-insulating, water impermeable golf green cover which has water-resistant seams and non collapsible air passages to evacuate offensive gases accumulating under the cover.
Broadly, in a first aspect of the present invention, there is provided a golf green cover comprising at least one flexible panel having first and second layers bonded to each other. The second layer has heat-insulation properties and perforations therein. There are also provided a plurality of air passages between the first and second layers communicating with the perforations. When this flexible panel is laid on a grass, the grass is protected from winter conditions and the air passages and the perforations are usable for aerating and removing harmful gases from the covered grass.
In accordance with another aspect of the present invention, the golf green cover further comprises a ventilator connected to the air passages.
The ventilator is a wind-actuated-type rotary ventilator. A major advantage of this installation is that noxious gases accumulating under the cover are automatically evacuated by the action of the wind on the ventilator.
In accordance with yet another aspect of the present invention, the second layer is bonded to the first layer along bond lines extending across each panel. The air passages mentioned before comprise transversal air passages extending between the bond lines. Each of the transversal air passages has a cross-section comprising a cord segment and an arc segment being longer than the cord segment. When the cover is compressed under a substantial amount of snow, the arc segments tend to buckle and form ripples without completely obstructing the transversal air passages, whereby ventilation of the grass is still maintainable.
In yet another aspect of the present invention, there is provided a golf green cover comprising at least one flexible panel laid on a grass and having a water-impermeable top layer and a heat-insulating bottom layer attached to the top layer. There is also provided a thermocouple bonded to an underside surface of the bottom layer. This thermocouple is usable to develop a history of the conditions of the covered golf green and to develop knowledge of the best installation and removal time, the ideal heat-insulating properties and so forth for a covered golf green. The thermocouple is also usable to control ventilation equipment connected to the aforesaid air passages, to automatically ventilate the grass and evacuate noxious gases under preferred temperature conditions.
In still another aspect of the present invention, there is provided a golf green cover comprising a pair of juxtaposed flexible panels each having a central region, a water-impermeable top layer and marginal strips bordering the central region and having spaced-apart grommets there-along. The adjacent marginal strips in the juxtaposed panels are lashed to each other and are set in an elevated mode relative to the central region.
This installation is advantageous for preventing water and melting snow accumulating on the central region of the cover from seeping between the juxtaposed panels.
In accordance with a further aspect of the present invention, the adj acent marginal strips are lashed to each other by a string laced through the grommets. The string has a series of spaced apart loops. A stitch is formed with one loop extending through a pair of juxtaposed grommets and into an adj acent loop. The stitch is easily undone in the spring for example, by pulling of the string such as on a broken thread in a garment.
Still another feature of the invention is that it is susceptible of a low cost of manufacture with regard to materials, equipment and labour, and which accordingly is then susceptible of low price of sale to the industry, thereby making such golf green cover economically available to the golf course owners.
Other advantages and novel features of the invention will become apparent from the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
A preferred embodiment of the present invention selected by way of examples will now be described with reference to the accompanying drawings in which:
FIG. 1 illustrates an installed golf green cover according to the preferred embodiment of the present invention;
FIG. 2 is a top view of the golf green cover;
FIG. 3 is a side view of the golf green cover;
FIG. 4 is a cross-section view of a raised seam or j oint between the panels of the golf green cover and of the gas collection pipe, as seen along line 4-4 in FIG. 2;

FIG. 5 is a cross-section view of an upright seam or joint between the panels of the golf green cover, as seen along line 5-5 in FIG. 2;
FIG. 6 is a cross-section view through the thickness of the golf green cover as seen along line 6-6 in FIG. 2 and illustrating cross-sections of the transversal air passages in the cover;
FIG. 7 is also a cross-section view through the thickness of the golf green cover as seen along line 6-6 in FIG. 2 illustrating the longitudinal air passages in a compressed mode, under a snow load for example;
FIG. 8 is a cross-section view through the thickness of the golf green cover as seen along line 8 in FIG. 4 showing the transversal air passages near the slits across the transversal air passages along the gas collection pipe;
FIG. 9 is a cross-section view through the thickness of a golf green cover illustrating a first alternate arrangement forming transversal air passages;
FIG. 10 is a cross-section view through the thickness of a golf green cover illustrating a second alternate arrangement forming transversal air passages;
FIG. 11 illustrates a top view of the upright joint between adjacent panels of the golf green cover and a preferred lashing thereof;

FIG. 12 is a side view of the lashed upright joint as seen along line 12-12 in FIG. 5;
FIG. 13 is a cross-section view through an edge of the cover showing a preferred placement of the temperature probe under the cover;
FIG. 14 is a first perspective view of a preferred peg usable to retain the golf green cover to the ground;
FIG. 15 is another perspective view of the preferred peg with a protective liner installed over the crossbar thereof.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
While this invention is susceptible of embodiments in many various forms, there is shown in the drawings and will be described in details herein a specific embodiment and alternate arrangements of some feature of this specific embodiment, with the understanding that the present disclosure is to be considered as an example of the principles of the invention and is not intended to limit the invention to the embodiment illustrated.
The golf green cover 20 according to the preferred embodiment is illustrated in its entirety in FIGS. 1 and 2. The golf green cover 20 is made of two or more flexible panels 22, 24, 26 that are laid side by side and have combined deployed dimensions in excess of the area to be protected. In common applications, the golf green cover 20 is manufactured in panels having widths'A' of between about 30-40 feet (9-12 m) and lengths'B' of 80-100 feet (24-30 m) or more.

In use, the juxtaposed panels 22, 24, 26 are lashed to each other as will be described later, and are pegged to the ground through grommets 28 in the marginal strips 30 along the outside edges of each panel. The grommets 28 are spaced at about 12-14 inches (30-35 cm) intervals.
As will be understood from the following disclosure, the golf green cover 20 has air passages 32 that are integrally formed in the structure of each panel. The ventilation of the covered turf is effected through these air passages and through one or more gas collection pipes installed under one or more seams of the cover.
Refernng to FIGS. 2, 3, 4 and 5, there are two types of marginal strips around each panel; the first type is a same thickness as the panel itself and is referenced by numeral 30, and the second type is thinner than the panel and is referenced by numeral 36. Both types are usable to make different joints or seams between the panels. The marginal strips of the first type 30 are attachable to each other and to the gas collection pipe 34, as shown in FIG. 4 to make a first type of seam or joint, referred to herein as a raised seam or joint 38. The marginal strips of the second type 36 are usable to make a second type of seam or joint as illustrated in FIG. 5 and referred to herein as an upright seam 40. Both types of seams 38, 40 have distinct features and advantages and are usable together, or solely, in a same cover depending on the conditions at the installation site.
In the raised joint 38, both marginal strips 30 of the first type are set over each other and retained to the gas collection pipe 34 to prevent water from seeping between the panels. Similarly, in an upright seam 40, adjacent strips 36 ofthe second type are set in an upright mode flat against each other, and retained in this manner by a string 42 or a light rope laced through the grommets 28 in these strips. This upright joint 40 also prevents water or melting snow which may accumulate over the cover from seeping between the panels.
When an outside edge of the cover 20 is laid over a depression 44 in the soil, a flat bar 46 made of malleable material is preferably laid over the section of the marginal strip 30 or 36 immediately over the soil depression, and is pegged down to retain the outside edge of the cover down against the contour of the ground at that location. The preferred malleable material of the flat bar is mild steel or low-yield-strength aluminium. The use of such flat bars 46 along the outside edges prevents the infiltration of cold air under the cover.
Referring specifically to FIGS. 4 and 5, the golf green cover 20 according to the preferred embodiment, comprises a top layer 50 made of light-reflecting and water-impermeable material; an intermediate layer 52 made of a semi-rigid, closed cell, water-impermeable and insulating foam, such as a closed cell polyethylene foam for example, and a bottom layer 54 also made of semi-rigid low density insulating foam. The intermediate and bottom layers 52, 54 are made of juxtaposed strips of foam sheeting and have seams at right angle to each other. The top layer 50 is bonded to the intermediate layer 52 along the marginal strips 30 or 36. The marginal strip 30 or 36 comprises a double thickness of the light-reflecting, water-impermeable top layer material. The second thickness or flap 56 of the top layer 50 extends under and is bonded to the bottom layer 54. This flap 56, together with the top layer 50 contribute to securing both insulating layers 52, 54 to the marginal strips 30 or 36.

The top layer 50 is preferably made with an ultraviolet-light resistant, reinforced plastic fabric tarpaulin, being white in color and having strength, stiffness and scratch-resistance to resist limited foot traffic and limited movements of small wheeled-vehicles.
Both insulating layers 52, 54 have thicknesses and heat-insulating properties selected according to the location of the golf green to be protected and the winter conditions at that location. The thickness of each layer and the total insulating properties of the cover is preferably determined to maintain a temperature under the cover of between about minus 10 and minus 5 degree Celsius in cold weather, and of between minus 5 and 0-degree Celsius during warm thaw periods.
As mentioned, the material of the intermediate layer is preferably a closed cell water-impermeable foam. This material constitutes an additional protection against infiltration of water through the cover, whereas the top layer may be susceptible to damage from rough traffic, from improper handling or from improper installation.
Referring now to FIGS.1, 2, 6 and 8, the bottom layer 54 is bonded to the intermediate layer 52 along transversal bond lines 58 across each panel. The width 'C' of each bond line 58 may vary according to the adhesive or welding method utilized during the fabrication of the cover, and according to physical properties and dimensions of the panels. Prior to bonding the bottom layer 54 to the intermediate layer 52, the bottom layer 54 is formed into a series of juxtaposed elongated valleys extending across the panel. During the bonding of the layers, the intermediate layer 52 is maintained in a flat alignment. When the intermediate layer 52 is bonded to the bottom layer 54, the intermediate layer 52 and the valleys formed in the bottom layer 54 define the transversal air passages 32 across each panel. The forming of these transversal air passages 32 and the bonding of the layers are not explained in details herein because various methods are available to those skilled in the art of foam structure fabrication.
The configuration of the transversal air passages 32 is advantageous because the air passages do not completely collapse under heavy snow loads. Each curved wall 62 of the bottom layer 54 has an arc length which is longer than the width or the cord length of the straight segment 64 of the intermediate layer 52. When the golf green cover is under pressure, such as under a thick snow cover, the curved wall 62 of bottom layer tends to buckle and form ripples as illustrated in FIG. 7. These ripples allow the passage of air there-along such that the ventilation of the cover is nevertheless maintainable.
It will be appreciated that the valleys formed in the bottom layer 54 also form air passages 68 between the bottom layer 54 and the covered turf. These air passages 68 also contribute to aerating the covered turf.
The bottom layer 54 has perforations 70 therein to allow the passage of gases from the covered grass to the transversal air passages 32. These perforations 70 are also advantageous for selectively aerating the covered grass as will be explained later.
Referring back to FIGS. 4 and 5, the extremities of the transversal air passages 32 and 68 are in communication with each other across longitudinal air passages 72, 74 extending under the raised seam 38 and the upright seam 40 respectively. The gas collection pipe 34 is installed in the longitudinal air passage 72. The gas collection pipe 34 is preferably a ribbed plastic pipe with perforations 76 therein. The gas present in the covered turf, as represented by arrows 78, is therefore free to flow through the perforations 70; along the transversal air passages 32, 68; across the longitudinal air passages 74; along the longitudinal air passages 72 and into the gas collection pipe 34. For this purpose, the bottom layer 54 has slits 80 across the transversal air passages, at each end of each transversal air passage 32, to allow gas to move under an upright seam 40, from one panel to an adjacent one and into the longitudinal air passages 72. The arced walls 62 of the bottom layer 54 contributes to opening the slits 80 between each panels across an upright seam 40. The arced walls 62 of the bottom layer 54 as well as gravity contribute to opening the slits 80 near the gas collection pipe 34, as illustrated in FIG. 4.
It will be appreciated that other arrangements are also possible to form air passages under a golf green cover without departing from the true spirit and scope of the present invention. Examples of alternate arrangements are illustrated in FIGS. 9 and 10. In the first alternate arrangement, the bottom layer 82 is made of spaced-apart sections. The spaces 84 between the sections constitute transversal air passages under the cover. In the second alternate arrangement the bottom layer 86 is pressed, heated and bonded to the top layer along transversal bond lines 88. The deformations 90 constitute transversal air passages under the cover.
Referring back to FIG. 1, 2 and 3 in particular, the gas collection pipe 34 has one end thereof connected to a flexible hose 94 and to an air valve 96. The air valve 96 is mounted to the inlet of a rotary ventilator 98.
The air valve 96 comprises control equipment, either manual or automatic, to regulate the amount of air entering the rotary ventilator 98. This control equipment is preferably time and temperature sensitive and is not described further herein for being known to those skilled in the art of ventilation.
The rotary ventilator 98 is a wind-actuated type, which function is to periodically generate a negative pressure in the air passages 32, 68, 72 and 74, and in the perforations 70, to extract and vent out offensive gases from the covered grass. The rotary ventilator 98 is also advantageous for drawing fresh air inside the air passages for aerating the covered grass.
The frequency and duration of the venting periods are determined according to the ambient temperature and the time left until spring time.
The air valve 96 and ventilator 98 are also useful to ventilate the covered grass during warm fall periods or mid-winter thawing spells. The ventilation system is also usable as a spring chiller for drawing dry cold air at night from along the perimeter of the cover and for circulating this cold air under the cover for preventing premature thawing of the covered soil.
At least one thermocouple 110 is permanently affixed to the bottom layer 54 of the cover. The thermocouple 110 has leads extending out of the cover and a connector mounted on a stake 112 for example above the cover. The thermocouple 110 can be read from time to time to monitor the temperature under the cover 20. This thermocouple is preferably used as a learning tool to establish a history of the temperature variations under the cover and of the conditions of the golf green protected by the cover. These temperature measurements can be used to determine an ideal ventilation schedule and a best time to remove the cover in the spring.

Referring to FIG. 13, the thermocouple 110 is preferably bonded to the underside surface of the bottom layer 54. Lead wire 114 extends from the thermocouple 110 to the upper surface of the cover. The preferred installation also comprises a connector 116 on the lead wire 114, and an extension wire 118 having an extremity tied to the stake 112 at a height above an anticipated snow accumulation. It will be appreciated that the thermocouple 110 may also be permanently connected to the air valve 96 for automatic operation of the air valve 96 by a programmable controller for example.
FIGS. 5, 11 and 12 are now referred to for describing a preferred method for lashing an upright seam 40. In the preferred method, the string 42 is arranged in loops 120 at spaced intervals, which intervals correspond in lengths to the spacings between the grommets 28 along the marginal strips 36 of each panel. The length of each loop 120 is also about the same, or slightly longer than the spacing between the grommets 28. Each loop 120 is defined by a clip 122. In use, each loop 120 extends through juxtaposed grommets 28 in the marginal strips 36 and around the strands of an adj acent loop as illustrated in FIGS.11 and 12 in particular. The last loop 120 of a stitch is pegged to the ground as illustrated in FIG. 2.
The width 'D' or height of the marginal strip 36 is preferably between about 2 inches (5 cm) and about 6 inches (15 cm). It will be appreciated that when a pair of adj acent panels, 24 and 26 for example are laid side by side, with the adjacent marginal strips 36 set upward, it is relatively easy for someone to lash both panels together. One does not have to reach under a panel or to otherwise manipulate one of the panels.
As previously explained, the arrangement of both strips 36 provides for a sealed joint whereby water or melting snow which may accumulate on the cover cannot get in between the panels. The thickness of the string 42 threaded through the grommets 28, prevents the juxtaposed strips 36 from laying flat over the panel such that the effectiveness of the sealing joint is maintained.
While the string 42 has been described as a continuous length of string or a light rope formed into a plurality of spaced-apart loops 120, it will be appreciated that a lacing string or rope may be supplied to a user of the cover 20 in a plain form without knot nor clip, but with markings 124 at intervals, for assisting a user in finding the location where each loop 120 should be formed. In this case, the spacing on the rope between each mark 124 is proportional to the spacing between the grommets 28 in a particular cover 20. This variant of the string 42 is particularly easy and inexpensive to manufacture.
As illustrated in FIG.11, when the string 42 is a continuous length of string or light rope with or without clip, the lashing described herein is advantageous for being easily removable from the grommets 28 when uncovering a golf green. The undoing of a stitch is effected by releasing the first loop 120 from its peg and pulling on the string 42 at substantially a right angle from the alignment of the juxtaposed strips 36 to cause a first loop 120 to disengage from the first grommets 28 and from a second loop.
A further pulling on the string in a direction generally represented by arrow 126 in FIG. 11, causes the second and subsequent loops to successively disengage from the strips 36 in a manner which is similar to the pulling of a broken thread in a garment.

As to the raised joint 38, the marginal strips 30 are laid over each other and over the rigid gas collection pipe 34. A series of individual loops 130 are affixed to the gas collection pipe 34 and are lashed together through the grommets 28 in a similar manner as just described, to retain the marginal strips 30 to the gas collection pipe 34.
Referring now to FIGS. 14 and 15, there is illustrated therein a preferred peg 140 for use in retaining the cover 20 according to the preferred embodiment to the ground. The peg 140 is preferably made of welded metal rod or stiff plastic. It has a threaded shank 142, a crossbar 144 near an upper end of the shank and a hook member 146 above the cross bar 144. The cross bar 144 on each peg is advantageous for preventing any concentration of stresses on the cover. The hook member 146 is advantageous for installing or removing the peg with a socket-type tool.
The cross bar 144 is preferably concealed into a padding member 148 that is made of soft material such as closed cell polyethylene foam.
The padding member 148 is preferably tinted with a bright color. The foam padding member 148 further protects the cover against excessive pressure from the peg's cross bar 144, as well as from rust staining from the peg being in contact with the cover for several months. The tinting of the padding member 148 with a bright color is advantageous for providing a visual indication of the contour of an installed cover 20, especially when the top layer 50 is white for example, and for preventing excessive traffic over a golf green.

Although it is preferable to limit the traffic over an installed cover 20 to a minimum, the structure of the foam layers 52, 54 bonded to the top reinforced fabric layer 50 described above has been found to be sufficiently resistant to support a walk-behind type snowblower and few people with plastic shovels, for the purpose of removing snow from an installed cover 20. Upon removal of the golf green cover, the panels are preferably rolled up along their lengths and stored away.
As to additional details related to the manufacturing, installation and use of the golf green cover of the present invention, the same should be apparent from the above description, and accordingly further discussion relative to the manner of making and using the cover would be considered redundant and is not provided.
It will also be appreciated by those skilled in the art that various modifications, alternate constructions and equivalents may be employed without departing from the true spirit and scope of the invention. For example, one may appreciate that a ventilated cover as described without the gas collection pipe and without a rotary ventilator may still provide to some degrees, the advantageous results recited herein by venting gases through a loosely tied upright joint for example, which partial results may be sufficient to protect a golf green in certain conditions. Similarly the air valve may be installed away from the ventilator at the far end of the gas collection pipe or at the far end of another gas collection pipe under an adjacent seam, to still provide to some degrees the advantageous ventilation effects described herein. Therefore, the above description and the illustrations should not be construed as limiting the scope of the invention which is defined by the appended claims.

Claims (20)

1. A golf green cover comprising:
a flexible panel having a length, a width, and first and second layers bonded to each other; said second layer having perforations therein;
air passages between said first and second layers communicating with said perforations and with a region outside said flexible panel;
such that when said flexible panel is laid on a grass, with said second layer against said grass, said air passages and said perforations are usable for aerating said grass.

2. The golf green cover as claimed in claim 1, further comprising an air valve and a ventilator connected to said air passages.

3. The golf green cover as claimed in claim 1, wherein said second layer is bonded to said first layer along bond lines extending across said panel, and said air passages comprise transversal air passages extending between said bond lines.

4. The golf green cover as claimed in claim 3, wherein each of said transversal air passages has a cross-section comprising a cord segment and an arc segment being longer than said cord segment.

5. The golf green cover as claimed in claim 3, wherein said air passages also comprise longitudinal air passages communicating with said transversal air passages at each end of said transversal air passages.

6. A golf green cover comprising:
a flexible panel laid on a grass and having a water-impermeable top layer and an insulating bottom layer attached to said top layer; and a thermocouple bonded to an underside surface of said bottom layer and having a wire extending above said top layer;
such that said thermocouple is usable to develop a history of conditions of said grass.

7. The golf green cover as claimed in claim 6, further comprising air passages between said top layer and said bottom layer, perforations through said bottom layer, air circulation equipment connected to said air passages, and said thermocouple being connected to said air circulation equipment for operation of said air circulation equipment.

8. A golf green cover comprising:
a pair of juxtaposed flexible panels laid on a grass, each having a width, a length, a central region, a water-impermeable top layer, marginal strips bordering said central region and spaced-apart grommets along said marginal strips;
said marginal strips adjacent each other in said juxtaposed flexible panels being attached to each other in a raised mode relative to said central region thereby defining a seam between said juxtaposed flexible panels;

such that water and melting snow accumulating on said central region is prevented from entering between said juxtaposed flexible panels.

9. The golf green cover as claimed in claim 8, wherein said marginal strips adjacent each other are attached flat against each other by a string laced through said grommets.

10. The golf green cover as claimed in claim 9, wherein said string comprised a series of spaced apart loops with one of said loops extending into a pair of said grommets and into an adjacent one of said loops.

11. The golf green cover as claimed in claim 10, wherein each of said loops is defined by a clip attached to said string.

12. The golf green cover as claimed in claim 8, wherein each of said juxtaposed flexible panels comprises:
a water-impermeable top layer, an insulating intermediate layer and an insulating bottom layer having perforations therein;
transversal air passages between said intermediate layer and said bottom layer communicating with said perforations;
a longitudinal air passage under said seam and communicating with said transversal air passages, and further comprising a gas collection pipe mounted in said longitudinal air passage and a ventilator mounted above said flexible panels and being connected to said gas collection pipe for drawing gases from said longitudinal air passage, from said transversal air passages and from said perforations.

13. The golf green cover as claimed in claim 12, wherein said top layer is a light-reflecting, reinforced-plastic tarpaulin, white in color.

14. The golf green cover as claimed in claim 13, wherein said intermediate layer is made of a semi-rigid closed-cell heat-insulating polyethylene foam, and said bottom layer is made of a semi-rigid low density heat-insulating foam.

15. The golf green cover as claimed in claim 14, wherein said bottom layer is bonded to said intermediate layer along spaced-apart bond lines extending across said flexible panel.

16. The golf green cover as claimed in claim 15, wherein each of said transversal air passages has a cross-section defined by a cord segment and an arc segment.

17. The golf green cover as claimed in claim 16, wherein each of said transversal air passages has a slit at each end thereof for opening said transversal air passages to air circulation with said longitudinal air passage.

18. The golf green cover as claimed in claim 12, wherein said gas collection pipe is affixed to said marginal strips under said seam.

19. The golf green cover as claimed in claim 12, further comprising an air valve mounted on said gas collection pipe for controlling a volume of air drawn by said ventilator.

20. The golf green cover as claimed in claim 12, further comprising a thermocouple bonded to an underside surface of said bottom layer and having a wire extending above said top layer.