Source: http://www.docstoc.com/docs/57736989/Floor-Panels-With-Edge-Connectors---Patent-7644555
Timestamp: 2013-05-22 05:46:08
Document Index: 103885817

Matched Legal Cases: ['art. 13', 'arts 4', 'arts 4', 'arts 4', 'arts 4', 'arts 4', 'arts 4', 'arts 4', 'arts 4', 'art 5', 'arts 28', 'arts 28', 'arts 4', 'arts 4', 'arts 4', 'arts 4', 'arts 4', 'arts 28', 'arts 4', 'arts 22', 'arts 4']

Floor Panels With Edge Connectors - Patent 7644555 Abstract
Inventors:Stefan Simon Gustaaf Moriau; Mark Gaston Maurits Cappelle; Bernard Paul Joseph Thiers
Assignee:Unilin Beheer B.V., besloten vennootschap
Primary Examiner:Chilcot, Jr.; Richard E
Assistance Examiner:Gilbert; William V
Filed Date: 12/21/2006
US Patent Application: 11/642,778
Patent number: 7644555
Primary Class:Static Structures (E.G., Buildings) (52/588.1)
Other US Classes:Stock Material Or Miscellaneous Articles (428/50)Static Structures (E.G., Buildings) (52/390)Static Structures (E.G., Buildings) (52/539)Static Structures (E.G., Buildings) (52/592.2)
International Classes:E04B 2/0(20060101)
Tags:Floor panels with edge connectors, Moriau, et al., Stefan Simon Gustaaf Moriau, Mark Gaston Maurits Cappelle, Bernard Paul Joseph Thiers, Application number 11 642-778, Static Structures (E.G. Buildings), Stock Material Or Miscellaneous Articles, Floor panels, edge connectors, floor covering, Tongue and groove, patent search, lower lip, Patent Number, upper side, wall panel, Locking system
208036N/ARobley9/1/1878
213740N/AConner4/1/1879
308313N/AGerike11/1/1884
662458N/ANagel11/1/1900
713577N/AWickham11/1/1902
714987N/AWolfe12/1/1902
753791N/AFulghum3/1/1904
769355N/APlatow9/1/1904
832003N/ATorrenoe9/1/1906
877639N/AGalbraith1/1/1908
898381N/AMattison9/1/1908
956046N/ADavis4/1/1910
1078776N/ADunton11/1/1913
1097986N/AMoritz5/1/1914
1124228N/AHouston1/1/1915
1137197N/AEllis4/1/1915
1140958N/ACowan5/1/1915
1201285N/AGray10/1/1916
1319286N/AJohnson et al.10/1/1919
1371856N/ACade3/1/1921
1407679N/ARuthrauff2/1/1922
1411415N/ACooley4/1/1922
1454250N/AParsons5/1/1923
1468288N/AEen9/1/1923
1477813N/ADaniels et al.12/1/1923
1510924N/ADaniels et al.10/1/1924
1540128N/AHouston6/1/1925
1575821N/ADaniels3/1/1926
1602256N/ASellin10/1/1926
1602267N/AKarwisch10/1/1926
1615096N/AMeyers1/1/1927
1622103N/AFulton3/1/1927
1622104N/AFulton3/1/1927
1637634N/ACarter8/1/1927
1644710N/ACrooks10/1/1927
1660480N/ADaniels2/1/1928
1706924N/AKane3/1/1929
1714738N/ASmith5/1/1929
1718702N/APfeister6/1/1929
1734826N/APick11/1/1929
1764331N/AMoratz6/1/1930
1776188N/ALangbaum9/1/1930
1778069N/AFetz10/1/1930
1787027N/AWasleff12/1/1930
1823039N/AGruner9/1/1931
1838098N/AHolbrook12/1/1931
1854396N/ADavis4/1/1932
1859667N/AGruner5/1/1932
1864774N/AStorm6/1/1932
1898364N/AGynn2/1/1933
1906411N/APotvin5/1/1933
1913342N/ASchaffert6/1/1933
1923928N/AJacobs8/1/1933
1929871N/AJones10/1/1933
1940377N/AStorm12/1/1933
1953306N/AMoratz4/1/1934
1986739N/AMitte1/1/1935
1988201N/AHall1/1/1935
1991701N/ARoman2/1/1935
2004193N/ACherry6/1/1935
2027292N/ARockwell1/1/1936
2044216N/AKlages6/1/1936
2045067N/ABruce6/1/1936
2049571N/ASchuck8/1/1936
2141708N/AElmendorf12/1/1938
2142305N/ADavis1/1/1939
2199938N/AKloote5/1/1940
2222137N/ABruce11/1/1940
2226540N/ABoettcher12/1/1940
2245497N/APotchen6/1/1941
2261897N/AAdams11/1/1941
2263930N/APasquier11/1/1941
2266464N/AKraft12/1/1941
2276071N/AScull3/1/1942
2279670N/AFord et al.4/1/1942
2282559N/AByers5/1/1942
2306328N/ABiberthaler12/1/1942
2317223N/ARottman4/1/1943
2324628N/AKahr7/1/1943
2398632N/AFrost et al.4/1/1946
2430200N/AWilson11/1/1947
2441364N/AMaynard5/1/1948
2491498N/AKahr12/1/1949
2644552N/AMacDonald7/1/1953
2729584N/AFoster1/1/1956
2740167N/ARowley4/1/1956
2780253N/AJoa2/1/1957
2805852N/AMalm9/1/1957
2807401N/ASmith9/1/1957
2808624N/ASullivan10/1/1957
2858969N/AWilliams et al.11/1/1958
2875117N/APotchen et al.2/1/1959
2894292N/AGramelspacher7/1/1959
2914815N/AAlexander12/1/1959
2947040N/ASchultz8/1/1960
2952341N/AWeiler9/1/1960
2974692N/ABolenbach3/1/1961
3045294N/ALivezey, Jr.7/1/1962
3090082N/ABaumann5/1/1963
3098600N/AHagan et al.7/1/1963
3100556N/ADe Ridder8/1/1963
3125138N/ABolenbach3/1/1964
3128851N/ADeridder et al.4/1/1964
3178093N/AWasyluka4/1/1965
3182769N/ADe Ridder5/1/1965
3200553N/AFrashour et al.8/1/1965
3203149N/ASoddy8/1/1965
3204380N/ASmith et al.9/1/1965
3253377N/ASchakel5/1/1966
3267630N/AOmholt8/1/1966
3282010N/AKing, Jr.11/1/1966
3301147N/AClayton et al.1/1/1967
3310919N/ABue et al.3/1/1967
3313072N/ACue4/1/1967
3347048N/ABrown et al.10/1/1967
3373071N/AFuerst3/1/1968
3387422N/AWanzer6/1/1968
3425543N/AHarvey et al.2/1/1969
3460304N/ABraeuninger et al.8/1/1969
3469762N/ATorre9/1/1969
3481810N/AWaite12/1/1969
3526420N/ABrancaleone9/1/1970
3535844N/AGlaros10/1/1970
3538665N/AGall11/1/1970
3538819N/ABould, Jr. et al.11/1/1970
3548559N/ALevine12/1/1970
3553919N/AOmholt1/1/1971
3555762N/ACostanzo, Jr.1/1/1971
3559876N/AConescu2/1/1971
3579941N/ATibbals5/1/1971
3619964N/APassaro et al.11/1/1971
3640191N/AHendrich2/1/1972
3657852N/AWorthington et al.4/1/1972
3667153N/AChristiansen6/1/1972
3694983N/ACouquet10/1/1972
3698548N/AStenzel et al.10/1/1972
3714747N/ACurran2/1/1973
3731445N/AHoffmann et al.5/1/1973
3740914N/ADiez6/1/1973
3742672N/ASchaeufele7/1/1973
3759007N/AThiele9/1/1973
3760548N/ASauer et al.9/1/1973
3761338N/AUngar et al.9/1/1973
3768846N/AHensley et al.10/1/1973
3780469N/AHancovsky12/1/1973
3786608N/ABoettcher1/1/1974
3798111N/ALane et al.3/1/1974
3807113N/ATurner4/1/1974
3859000N/AWebster1/1/1975
3884328N/AWilliams5/1/1975
3902293N/AWitt et al.9/1/1975
3908053N/AHettich9/1/1975
3936551N/AElmendorf et al.2/1/1976
3964607N/AWagner6/1/1976
3987599N/AHines10/1/1976
3988187N/AWitt et al.10/1/1976
4021087 Multiple interlocking panel deskFegurson5/1/1977
4037377Foamed-in-place double-skin building panelHowell et al.7/1/1977
4074496Composite plateFischer2/1/1978
4090338 Parquet floor elements and parquet floor composed of such elementsBourgade5/1/1978
4095913 Tongue and groove jointPettersson et al.6/1/1978
4099358Interlocking panel sectionsCompaan7/1/1978
4100710Tongue-groove connectionKowallik7/1/1978
4156048 Soft floor covering protector for appliancesDavis5/1/1979
4164832Tongue and groove structure in preformed wall sectionsVan Zandt8/1/1979
4165305 Two-component binder for exterior fiberboardSundie et al.8/1/1979
4169688 Artificial skating-rink floorToshio10/1/1979
4182072 Toy construction kitMuch1/1/1980
4186539 Interlocking modular building panel with sealing stripHarmon et al.2/1/1980
4242390 Floor tileNemeth12/1/1980
4260442 Method for making an improved variable flute containerFord et al.4/1/1981
4299070Box formed building panel of extruded plasticOltmanns et al.11/1/1981
4316351Thermally insulated building construction panel and a wall formed from such panelsTing2/1/1982
4372899 Method of manufacturing particleboard and the likeWiemann et al.2/1/1983
4390580 High pressure laminate for access floor panelsDonovan et al.6/1/1983
4449346 Panel assemblyTremblay5/1/1984
4489115 Synthetic turf seam systemLayman et al.12/1/1984
4501102 Composite wood beam and method of making sameKnowles2/1/1985
4517147 Pressing process for composite wood panelsTaylor et al.5/1/1985
4538392Portable sectional flooring systemHamar et al.9/1/1985
4561233Wall panelHarter et al.12/1/1985
4599124 High impact resistant laminate surface for a bowling laneKelly et al.7/1/1986
4599841Panel structure comprising boards and for instance serving as a floor or a panelHaid7/1/1986
4612745 Board floorsHovde9/1/1986
4635815 Reinforced bulk material containerGrigsby1/1/1987
4640437 Insulated container and insulating element thereforWeingartner2/1/1987
4641469 Prefabricated insulating panelsWood2/1/1987
4643237 Method for fabricating molding or slotting boards such as shutter slats, molding for carpentry or for construction and apparatus for practicing this processRosa2/1/1987
4646494 Building panel and systemSaarinen et al.3/1/1987
4653242 Manufacture of wooden beamsEzard3/1/1987
4703597Arena floor and flooring elementEggemar11/1/1987
4715162 Wooden joist with web members having cut tapered edges and vent slotsBrightwell12/1/1987
4724187 Conductive laminate flooringUngar et al.2/1/1988
4738071Manufacture of wooden beamsEzard4/1/1988
4757658Panel structure with composite couplingKaempen7/1/1988
4769963Bonded panel interlock deviceMeyerson9/1/1988
4804138 Reinforced flange top lifting cartonMcFarland2/1/1989
4819932 Aerobic exercise floor systemTrotter4/1/1989
4831806 Free floating floor systemNiese et al.5/1/1989
4845907 Panel moduleMeek7/1/1989
4905442Latching joint couplingDaniels3/1/1990
5029425 Stone cladding system for wallsBogataj7/1/1991
5050362Constructional panelsTal et al.9/1/1991
5086599Building panel and methodMeyerson2/1/1992
5109898 Process for the manufacture of multi-ply panel boards preferably for floorsSchacht5/1/1992
5113632 Solid wood paneling systemHanson5/1/1992
5117603 Floorboards having patterned joint spacing and methodWeintraub6/1/1992
5148850Weatherproof continuous hinge connector for articulated vehicular overhead doorsUrbanick9/1/1992
5157890FlooringJines10/1/1992
5165816 Tongue and groove profileParasin11/1/1992
5179812Flooring productHill1/1/1993
5182892 Tongue and groove board productChase2/1/1993
5216861Building panel and methodMeyerson6/1/1993
5247773 Building structuresWeir9/1/1993
5253464 Resilient sports floorNilsen10/1/1993
5266384 Aesthetic surface layerO'Dell et al.11/1/1993
5274979 Insulating plate unitTsai1/1/1994
5283102 Laminated wood flooring product and wood floorSweet et al.2/1/1994
5295341 Snap-together flooring systemKajiwara3/1/1994
5348778 Sandwich elements in the form of slabs, shells and the likeKnipp et al.9/1/1994
5349796 Building panel and methodMeyerson9/1/1994
5390457 Mounting member for face tilesSjolander2/1/1995
5413840 Decorative laminated sheet having a feeling of coating and a process for producing sameMizuno5/1/1995
5433806 Procedure for the preparation of borders of chip-board panels to be covered subsequentlyPasquali et al.7/1/1995
5474831 Board for use in constructing a flooring surfaceNystrom12/1/1995
5475960 Wooden frame building constructionLindal12/1/1995
5495727 Container and expandable coolerStrong et al.3/1/1996
5497589 Structural insulated panels with metal edgesPorter3/1/1996
5502939Interlocking panels having flats for increased versatilityZadok et al.4/1/1996
5526857Method of manufacture of veneered door with raised panelForman6/1/1996
5540025Flooring material for buildingTakehara et al.7/1/1996
5545501Electrostatographic developer compositionTavernier et al.8/1/1996
5566519Prefabricated panel for buildings and constructions and system for its coupling and assemblyAlmaraz-Miera10/1/1996
5570554Interlocking stapled flooringSearer11/1/1996
5618602 Articles with tongue and groove joint and method of making such a jointNelson4/1/1997
5630304 Adjustable interlock floor tileAustin5/1/1997
5647181 Construction system and method for connecting rigid sheet-like panels together into doll houses, play houses, utility sheds and other structuresHunts7/1/1997
5706621 System for joining building boardsPervan1/1/1998
5736227 Laminated wood flooring product and wood floorSweet et al.4/1/1998
5755068 Veneer panels and method of makingOrmiston5/1/1998
5768850 Method for erecting floor boards and a board assembly using the methodChen6/1/1998
5797237 Flooring systemFinhell, Jr.8/1/1998
5860267 Method for joining building boardsPervan1/1/1999
0N/AFinkell, Jr.3/1/1999
5937612 Reversible decorative tile and method finishing same in situWiner et al.8/1/1999
6023907 Method for joining building boardsPervan2/1/2000
6029416 Jointing systemAndersson2/1/2000
6182410 System for joining building boardsPervan2/1/2001
6271156 Fire-resistant core for a combustible fire-rated panelGleason et al.8/1/2001
6588166 Flooring panel or wall panel and use thereofMartensson et al.7/1/2003
lmhstrumpet57
iknowgodaddy1216
ojp13483284
pengxuebo323
sushaifj88
liaoqinmei22
yaofenji668
leg38704479
absences76
sdfgsg2341161
Market Research for Connectors
cnr1720211
USB Connectors Tutorial
pengxuebo155
weloveike476
Claims The invention claimed is: 1. A floor panel for forming a floor covering, comprising a thickness dimension in the range of 5 to 15 mm; at least one pair of opposite side edges including upperside edges; a laminate construction including a core material made of medium density fiberboard or high density fiberboard; coupling parts made integrally in one piece with the panel core material on the opposite side edges respectively in the form ofa tongue part and a groove part; said groove part being bordered by an upper lip and a lower lip; said coupling parts including integrated mechanical locking elements and being configured so as to enable a pair of the panels to be coupled to each otherby placing a tongue pad of one panel in a groove part of the other panel, with the panel upper side edges adjoining each other; said tongue part, groove part and locking elements being formed in one piece with said core material; said locking elementsincluding a locking surface on the tongue part that is located on a protrusion extending from a lower side of the tongue part and a locking surface on the groove part that is located at one side of an upwardly facing recess in an upper surface of thelower lip, such that in coupled condition of two of such panels with the upper side edges adjoining each other and with a tongue part of one panel received in the groove part of the other panel, the protrusion of the tongue part of one panel cooperateswith the recess of the groove part of the other panel with the locking surfaces of the tongue part and the groove part contacting each other, said locking surfaces preventing unintentional separation between the upper side edges which would produceundesired gaps between the adjoined upper side edges in directions perpendicular to the related side edges and parallel to the underside of the coupled panels; said protrusion on the tongue part including a distally located lateral wall and a proximallylocated lateral wall, said distally located lateral wall extending obliquely downwardly from an upper distal area towards a lower proximal area and facing in a distal direction relative to the tongue part, said proximally located lateral wall facingproximally of the tongue part, and said locking surface on the protrusion being disposed on the proximally located lateral wall of the protrusion and facing in a proximal direction relative to the tongue part, said proximally located lateral wall of theprotrusion extending obliquely downwardly from an upper proximal area towards a lower distal area. 2. The floor panel of claim 1, wherein said distally located lateral wall is less obliquely inclined than said proximally located lateral wall. 3. The floor panel of claim 1, wherein said lower lip extends distally beyond said upper lip and the locking surface on the lower lip is located in a portion of said lower lip which lies distally beyond said upper lip. 4. The floor panel of claim 3, said upper side edges, coupling parts and locking elements being configured such that coupling of a pair of panels is achievable at least by a turning movement involving angling-in of one panel by its side edgeinto the side edge of the other panel until a tongue part is fully received in a groove part with the locking surfaces in contact with each other and said upper side edges adjoining each other. 5. The floor panel of claim 3, wherein the panel has a thickness and the difference between the length of the upper lip and the length of the lower lip, measured in a principal plane of the panel, is smaller than the thickness of the panel. 6. The floor panel of claim 1, wherein said core is a monolithic body. 7. A floor panel for forming a floor covering, comprising a thickness dimension in the range of 5 to 15 mm; at least one pair of opposite side edges including upper side edges; a laminate construction including a core material made of mediumdensity fiberboard or high density fiberboard; coupling parts made integrally in one piece with the panel core material on the opposite side edges respectively in the form of a tongue part and a groove part; said groove part being bordered by an upperlip and a lower lip; said coupling parts including integrated mechanical locking elements and being configured so as to enable a pair of the panels to be coupled to each other by placing a tongue part of one panel in a groove part of the other panel,with the panel upper side edges adjoining each other; said tongue part, groove part and locking elements being formed in one piece with said core material; said locking elements including a locking surface on the tongue part that is located on aprotrusion extending from a lower side of the tongue part and a locking surface on the groove part that is located at one side of an upwardly facing recess in an upper surface of the lower lip, such that in coupled condition of two of such panels withthe upper side edges adjoining each other and with a tongue part of one panel received in the groove part of the other panel, the protrusion of the tongue part of one panel cooperates with the recess of the groove part of the other panel with the lockingsurfaces of the tongue part and the groove part contacting each other, said locking surfaces preventing unintentional separation between the upper side edges which would produce undesired gaps between the adjoined upper side edges in directionsperpendicular to the related side edges and parallel to the underside of the coupled panels; said protrusion on the tongue part including a distally located lateral wall and a proximally located lateral wall, said distally located lateral wall extendingobliquely downwardly from an upper distal area towards a lower proximal area and facing in a distal direction relative to the tongue part, said proximally located lateral wall facing proximally of the tongue part, and said locking surface on theprotrusion being disposed on the proximally located lateral wall of the protrusion and facing in a proximal direction relative to the tongue part, wherein said proximally located wall and said locking surface on said proximally located lateral wall lieperpendicular in respect to a principal plane of the panel. 8. A floor panel for providing a floor covering, the panel having an elongated or square rectangular shape, first and second pairs of opposite linear side edges, a top side and an underside, said pairs of side edges including respective upperside edges adjacent the top side, and comprising: a first pair of coupling parts on said first pair of opposite side edges: said first pair of coupling pads made integrally in one piece with the panel respectively in the form of a tongue pad and a groovepart; said groove part being bordered by an upper lip and a lower lip; said first pair of coupling parts being configured so as to enable a pair of the panels to be coupled to each other by placing a tongue part of one panel in a groove part of theother panel, so that when coupled the panel upper side edges adjoin each other; said first pair of coupling pads further including integrated mechanical locking elements, said locking elements including respective locking surfaces on the respectivetongue pad and groove part of the first pair of coupling pads, the locking surface on the tongue part being located on a lower side of the respective tongue part, and the locking surface on the groove part being located on an upper side of the lower lipof the respective groove part; said locking surfaces of said first pair of coupling parts contacting each other when a pair of the panels are coupled by placement of the tongue part of a first pair of opposite side edges of one panel into the groovepart of a first pair of opposite side edges of the other panel with the respective upper side edges of the first pair of opposite side edges of the panels adjoining each other, to thereby secure the respective side edges of said coupled panels inadjoined relationship while preventing unintentional separation between the respective upper side edges which would produce undesired gaps between the upper side edges in directions perpendicular to the respective side edges and parallel to the undersideof the coupled panels; said upper side edges, first pair of coupling parts and locking elements of said first pair of opposite side edges being configured such that said coupling of a pair of panels along said first pair of opposite side edges isachievable by a turning movement involving angling-in of one panel by one of its side edges on said first pair of opposite side edges into a side edge of the first pair of opposite side edges of the other panel until a tongue part is fully received in agroove part with the locking surfaces in contact with each other and respective upper side edges of said first pair of opposite side edges adjoin each other; a second pair of coupling parts on said second pair of opposite side edges, said second pair ofcoupling parts in the form of a tongue part and a groove part; said groove part of the second pair of coupling parts being bordered by an upper lip and a lower lip; said second pair of coupling parts further including integrated mechanical lockingelements, said locking elements of the second pair of coupling parts including respective locking surfaces on the respective tongue part and the respective groove part, the locking surface on the tongue part being located on a lower side of the tonguepart, and the locking surface on the groove part being located on an upper side of the lower lip of the groove part; said locking surfaces of said locking elements of said second pair of coupling parts contacting each other when a pair of the panels arecoupled by placement of the tongue part of said second pair of opposite side edges of one panel into the groove part of the said second pair of opposite side edges of the other panel, with the respective upper side edges of the second pair of oppositeside edges of the panels adjoining each other, to thereby secure the upper side edges of the second pair of opposite side edges of said coupled panels in adjoined relationship while preventing unintentional separation between the upper side edges whichwould produce undesired gaps between the upper side edges in directions perpendicular to the second pair of opposite side edges and parallel to the underside of the coupled panels; said second pair of coupling pads, including the locking elements andlocking surfaces of said second pair of coupling parts, and said upper side edges of said second pair of opposite side edges being located and configured so that upon coupling of two panels along said second pair of opposite side edges with the tonguepart of the second pair of coupling parts received in the groove part of the second pair of coupling parts, the respective locking surfaces are brought into locking contact with each other by a snap action. 9. The floor panel of claim 8, wherein the panel is elongated with longer and shorter opposite side edges, and wherein said first pair of opposite side edges are the longer side edges and the second pair of opposite side edges are the shorterside edges. 10. The floor panel of claim 8, wherein the first pair of coupling parts and respective locking elements at the first pair of opposite side edges are configured such that said coupling of a pair of panels along said first pair of opposite sideedges is achievable by a turning movement including angling-in of one panel by one of its side edges on said first pair of opposite side edges into a side edge of the first pair of opposite side edges of the other panel until a tongue part is fullyreceived in a groove part with the locking surfaces in contact with each other and the respective upper side edges of said first pair of side edges adjoin each other. 11. The floor panel of claim 8, wherein the panel comprises a laminate having a core, and wherein the first pair of coupling parts and respective locking elements are made in one integral piece with said core. 12. The floor panel of claim 8, wherein the lower lip of the groove part of said first pair of coupling parts extends distally beyond the respective upper lip of the groove part. 13. The floor panel of claim 12, wherein the locking elements of the tongue and groove parts of the first pair of coupling parts comprise respectively a first locking element in the form of a downwardly extending protrusion provided at thelower side of the tongue part of said first pair of coupling parts, and a second locking element comprising an upwardly facing recess formed in an upper side of the lower lip of the groove part of the first pair of coupling parts, said protrusion andrecess cooperating with each other upon coupling of panels along said first pair of opposite side edges. 14. The floor panel of claim 13, wherein, upon said coupling of two panels along said first pair of opposite side edges, a lowermost point of cooperation between said locking elements is located in a portion of the lower lip which lies beyondthe upper lip. 15. The floor panel of claim 8, wherein at said first pair of opposite side edges, a lower side of the respective upper lip of the respective groove part includes a substantially planar lower lip contact surface and the upper side of therespective tongue part includes a substantially planar upper tongue contact surface, said contact surfaces extending substantially parallel to the top side of the panel. 16. The floor panel of claim 8, said locking surface on the tongue part of the first pair of coupling pads comprising an obliquely inclined locking surface extending downwardly in a distal direction relative to the tongue part and facing in aproximal direction of the tongue part; and said locking surface on the lower lip comprising an obliquely inclined locking surface extending downwardly in a proximal direction relative to the lower lip and facing in a proximal direction of the lower lip. 17. The floor panel of claim 8, wherein the respective lower lip of the groove part of the second pair of coupling parts extends distally beyond the upper lip of said groove part of the second pair of coupling parts. 18. The floor panel of claim 17, wherein the panel has a thickness and the distance by which the lower lip of the groove part of the second pair of coupling parts extends beyond the upper lip, measured in a principal plane of the panel, issmaller than the thickness of the panel. 19. The floor panel of claim 8, wherein the locking elements of the second pair of coupling parts comprise elements that are formed separately from the panel and which are fixedly secured to said second pair of opposite side edges of the panel. 20. The floor panel of claim 8, wherein the panel comprises a laminate having a core, and wherein the second pair of coupling pads and their respective locking elements are made in one integral piece with said core. 21. The floor panel of claim 8, said locking surface on the lower side of the tongue part of the second pair of coupling parts comprising a proximally facing surface of a downwardly extending protrusion on the lower side of the respectivetongue part, and the locking element of the lower lip of the groove part of the second pair of coupling parts comprising a proximally facing surface bordering an upwardly facing recess in the upper side of the lower lip, said protrusion and recesscooperating with each other such that the locking surfaces contact each other when a pair of the panels is coupled along said second pair of opposite side edges with the respective tongue part fully received in the respective groove part. Description BACKGROUND OF THE INVENTION1. Field of the InventionThis invention relates to a floor covering made of hard floor panels.2. Related TechnologyIn the first instance, the invention is intended for so-called laminated floors, but generally it can also be applied for other kinds of floor covering, consisting of hard floor panels, such as veneer parquet, prefabricated parquet, or otherfloor panels which can be compared to laminated flooring.It is known that such floor panels can be applied in various ways.According to a first possibility, the floor panels are attached at the underlying floor, either by glueing or by nailing them on. This technique has a disadvantage that is rather complicated and that subsequent changes can only be made bybreaking out the floor panels.According to a second possibility, the floor panels are installed loosely onto the subflooring, whereby the floor panels mutually match into each other by means of a tongue and groove coupling, whereby mostly they are glued together in the tongueand groove, too. The floor obtained in this manner, also called a floating parquet flooring, has as an advantage that it is easy to install and that the complete floor surface can move which often is convenient in order to receive possible expansion andshrinkage phenomena.A disadvantage with a floor covering of the above-mentioned type, above all, if the floor panels are installed loosely onto the subflooring, consists in that during the expansion of the floor and its subsequent shrinkage, the floor panelsthemselves can drift apart, as a result of which undesired gaps can be formed, for example, if the glue connection breaks.In order to remedy this disadvantage, techniques have already been through of whereby connection elements made of metal are provided between the single floor panels in order to keep them together. Such connection elements, however, are ratherexpensive to make and, furthermore, their provision or the installation thereof is a time-consuming occupation.Examples of embodiments which apply such metal connection elements are described, among others, in the documents WO 94/26999 and WO 93/13280.Furthermore, couplings are known which allow coupling parts to snap fit into each other, e.g., from the documents WO 94/1628, WO 96/27719 and WO 96/27721. The snapping-together effect obtained with these forms of embodiment, however, does notguarantee a 100-percent optimum counteraction against the development of gaps between the floor panels, more particularly, because in fact well-defined plays have to be provided in order to be sure that the snapping-together is possible.From GB 424.057, a coupling for parquetry parts is known which, in consideration of the nature of the coupling, only is appropriate for massive wooden parquetry.Furthermore, there are also couplings for panels known from the documents GB 2.117.813, GB 2,256.023 and DE 3.544.845. These couplings, however, are not appropriate for connecting floor panels.BRIEF SUMMARY OF THE INVENTIONThe invention aims at an improved floor covering of the aforementioned type, the floor panels of which can be coupled to each other in an optimum manner and/or the floor panels of which can be manufactured in a smooth manner, and wherebypreferably one or more of the aforementioned disadvantages are excluded.The invention also aims at a floor covering which has the advantage that no mistakes during installing, such as gaps and such, can be created.Furthermore, the invention also aims at a floor covering whereby the subsequent development of gaps is excluded or at least counteracted in an optimum manner, whereby also the possibility of the penetration of dirt and humidity is minimalized.To this aim, the invention relates to a floor covering, consisting of hard floor panels which, at least at the edges of the two opposite sides, are provided with coupling parts, cooperating which each other, substantially in the form of a tongueand a groove, wherein the coupling parts are provided with integrated mechanical locking elements which prevent the drifting apart of two coupled floor panels into a direction perpendicular to the related edges and parallel to the underside of thecoupled floor panels. Hereby, these coupling parts are optimalized in such a manner that they allow that any form of play is counteracted and preferably is excluded.By integrated mechanical locking elements is understood that these form a fixed part of the floor panels, either by being connected in a fixed manner to the floor panels, or by being formed in one piece therewith.In a first important preferred form of embodiment, the coupling parts are provided with locking elements which, in the engaged position of two or more of such floor panels, exert a tension force upon each other which force the floor panelstowards each other. As a result of this that not only the formation of gaps counteracted during installation, but also in a later stage the development of gaps, from any causes whatsoever, is counteracted.According to another characteristic of the intention, the coupling parts, hereby are formed in one piece with the core of the floor panels.According to a second important preferred embodiment, the aforementioned optimalization is achieved in that the floor covering panel possesses the following combination of characteristics: the coupling parts and locking elements are formed in onepiece with the core of the floor panels; the coupling parts have such a shape that two subsequent floor panels can be engaged into each other exclusively by snapping together and/or turning, whereby each subsequent floor panel can be inserted laterallyinto the previous; the coupling parts are interlocked free from play in all directions in a plane extending perpendicular to the aforementioned edges; the possible difference between the upper and lower lip of the lips which border the aforementionedgrooves, measured in the plane of the floor panel and perpendicular to the longitudinal direction of the groove, is smaller than one time the total of the thickness of the panel; the total thickness of each related floor panel is larger than or equal to5 mm; and that the basic material of the floor panels, of which the aforementioned core and locking elements are formed, consists of a ground product which, by means of a binding agent or by means of melting together, is made into a unitary composite,and/or of a product on the basis of synthetic material and/or of a chip board with fine chips.Due to the fact that the coupling parts provide for an interlocking free from play, as well as due to the fact that these coupling parts are manufactured in one piece, from the basic material of the floor panels, a perfect connection betweenadjacent floor panels can always be guaranteed, even with repeated expansion and shrinkage of the floor surface.This combination of characteristics can be combined or not with the aforementioned characteristic that the locking elements exert a tension force upon each other when panels are joined together.According to a third important preferred embodiment, the characteristics of which may or may not be combined with the characteristics of the embodiments described above, the floor covering is characterized in that the lower lip which limits ordefines the lower side of the groove, extends beyond the upper lip in the plane of the panel; the locking elements are formed at least of a contact portion which inwardly slopes downward; and that this portion, at least partially, is located in theportion of the lower lip which extends beyond the upper lip. The advantages of these features will appear from the further description.According to a preferred form of embodiment, the floor panels are configured as elongated panels and the coupling parts described above are applied along the longitudinal sides of these panels.According to a particular form of embodiment, coupling parts are provided at the other two sides, too, either of another construction than described above or not.In the most preferred form of embodiment, for the basic material use shall be made of the aforementioned product, which, as said, is ground and, by means of a binding agent, made into a unitary composite material. More particularly, for the coreuse shall be made of finely-ground wood which preferably is glued, more particularly, moisture resistant glued. Still more particularly, for the core use shall be made of so-called HDF board (High Density Fibreboard) or MDF board (Medium DensityFibreboard) which is highly compressed ground wood particles (fibers) and binder material. Hereinafter, the wood component of the core material shall be referred to as "wood product".The fact that the invention is applied to floor panels the basic material of which consists of the material described above, offers the advantage that with the processing of this material, very smooth surfaces are obtained whereby very precisecouplings can be realized, which, in first instance, is important in the case of a snap-together connection and/or turning connection free from play. Also, very special forms of coupling parts can be manufactured in a very simple manner because theaforementioned kinds of material can be processed particularly easy.The surfaces obtained with HDF and MDF also have the advantage that the floor panels mutually can be shifted readily alongside each other in interlocked condition, even when engaged with a tensioning force.The applicants also discovered that the aforementioned materials, in particular HDF and MDF, show ideal features in order to realize a connection, such as mentioned above, as these material show the right features in respect to elasticdeformation in order to, on the one hand, realize a snap-together effect, and, on the other hand, receive expansion and shrinkage forces in an elastic manner, whereby it is avoided that the floor panels come unlocked or are damaged in an irreparablemanner.In the case that for the core use is made of a material based on synthetic material, to this end solid synthetic material can be used as well as a mixture of synthetic materials, eventually composed of recycled materials.The floor covering preferably is formed by joining the floor panels into each other free of glue. Hereby, the connections are of such nature that the floor panels can be disassembled without being damaged, such that, for example, when movingfrom one residence or location to another, they can be taken along in order to be placed down again. It is, however, clear that a glueing between tongue and groove is not excluded.The invention, of course, also relates to floor panels which allow the realization of the aforementioned floor covering.The invention also relates to a method for the manufacturing of the aforementioned floor panels with which the advantage that the tongues and/or grooves, including the corresponding locking means, can be provided at the floor panels at highproduction speeds without problems. More particularly, it aims at a method which allows that the rather complicated forms of the tongue and the groove of the aforementioned floor panels can be formed completely by means of milling cutters, the diameterof which can be chosen independent of the form to be realized, such that the use of small milling cutters, for example finger cutters, with diameters smaller than the depth of the tongue or groove can be excluded.In accordance with this method the tongue and/or groove is formed by means of a milling process using at least two sequential milling cycles or passes by means of milling cutters which are positioned at different angles in respect to the relatedfloor panel. During each of the aforementioned milling cycles, preferably substantially the final form of one flank, either of the tongue or of the groove, is formed.For the aforementioned two milling cycles, thus, milling cutters are used which extend outside the groove, respectively the tongue. More particularly the diameters of these milling cutters shall at least be 5 times and even better 20 timeslarger than the thickness of the floor panels.The use of milling cutters having the aforementioned diameters has as an advantage that the normal production speeds can be maintained which are also applied during milling of a classical straight tongue and groove. There is also the advantageobtained that the installation of such milling cutters induce only minor or no additional costs because such milling cutters can be placed directly upon a motor shaft and/or the conventional machines can be used. BRIEF DESCRIPTION OF THE DRAWINGSWith the intention of better showing the characteristics according to the invention, in the following, as an example without any limitative character, several preferred forms of embodiment are described, with reference to the accompanyingdrawings, wherein:FIG. 1 represents a floor panel of a floor covering according to the invention;FIG. 2, on a larger scale, represents a cross-section according to line II-II in FIG. 1;FIGS. 3 and 4 represent how two floor panels with coupling parts according to FIG. 2 match into each other;FIG. 5, on a larger scale, represents a cross-section according to line V-V in FIG. 1;FIGS. 6 and 7 represent how two floor panels with coupling parts according to FIG. 5 match into each other;FIGS. 8 to 11 represent a number of variants of coupling parts of floor panels according to the invention;FIG. 12 schematically represents how the floor parts can be provided with coupling parts;FIG. 13 represents a cross-section according to line XIII-XIII in FIG. 12;FIGS. 14 to 21, on a larger scale and in cross-section, represent the penetration of the milling cutters which are indicated in FIG. 12 with arrows F14 to F21;FIG. 22 represents a floor panel according to the invention;FIG. 23, on a larger scale, represents the coupling of two floor panels of FIG. 22;FIGS. 24 and 25 represent two manners of coupling floor panels according to FIG. 22 to each other.DETAILED DESCRIPTIONThe invention relates to a floor covering which is composed of hard floor panels 1, for example, such as a laminated panel as shown in FIG. 1.These floor panels 1 can be of various shape, for example, elongated or square, or of any other shape having linear side edges intersecting at right angles (rectangular).In the most preferred form of embodiment, they shall be manufactured in an elongated form, such as shown in FIG. 1, for example, with a length of 1 to 2 meters. The thickness, however, can also vary, but is preferably 0.5 to 1.5 cm, and moreparticularly 0.8 cm.Each floor panel 1 is, at least at the edges of two opposite sides 2-3, provided with tongue and groove coupling parts 4-5 which permit two adjacent identical floor panels 1 to be coupled to each other.According to the invention, the coupling parts 4-5, as represented in the FIGS. 2 to 4, are provided with integrated mechanical locking parts or locking elements 6 which prevent the drifting or sliding apart of two coupled floor panels 1 in adirection D perpendicular to the respective sides 2-3 and parallel to the underside 7 of the coupled floor panels 1; the coupling parts 4-5 and the locking elements 6 are formed in one piece with the core 8 of the floor panels 1; the coupling parts 4-5have such a shape that two subsequent floor panels 1 can be engaged into each other solely by snapping-together and/or turning after the coupling parts are partially engaged, whereby each subsequent floor panel 1 can be laterally inserted into theprevious; and the coupling parts 4-5 preferably are interlocked free from play in all directions in a plane which is located perpendicular to the aforementioned edges.In the case of floor panels 1 with an elongated shape, as represented in FIG. 1, the respective coupling parts 4-5 are located at the longitudinal sides 2-3.The coupling parts 4-5 can be realized in various forms, although the basic forms thereof will always be formed by a tongue 9 and a groove 10.In the form of embodiment of FIGS. 2 to 4, the related floor panel 1 is provided with tongue and groove coupling parts 4-5 and locking means or locking elements 6 which allow the coupling parts of two floor panels 1 to be mutually engaged bymeans of a turning movement, without the occurrence of any snap-together effect.In the represented example, the locking elements 6 consist of a first locking element 11, formed by a protrusion with a bent round shape at the lower side 12 of the tongue 9, and a second locking element 13 (shown in FIG. 2), formed by a recesswith a bent hollow upwardly facing or downwardly concave shape in the upper side of lower wall 14 of the lower lip of the groove 10.The locking elements 11-13 ensure that two floor panels 1 which are coupled to each other can not move laterally in the horizontal plane with respect to each other.In order to enable two floor panels 1 to be inserted into each other by means of a turning movement, the curvatures preferably are circular. The bottom side 12 of locking means or locking elements 6 has a curvature with a radius R1, the centerof which coincides with the respective upper side edge 15 of the floor panel 1, whereas the upper side of the lower lip of the groove locking part 5 has a curvature with a radius R2 which is equal to the radius R1, but its center coincides with therespective upper edge 16. Radii R1 and R2 may also be applied which are larger or smaller than the distance to the upper side edges 15, 16 respectively, and/or which differ from each other in size.The upper side 17 of the tongue 9 (called an upper tongue contact surface) and the lower side of upper wall or side 18 of the upper lip of groove 10 are preferably flat and preferably are located in the horizontal plane.The inner side 20 of the groove 10 and the front side 19 of the tongue 9 of the two interlocked floor panels 1 preferably do not fit closely against each other, such that an intermediate space 21 is created between them into which possible dustremainders or such can be pushed away by means of the tongue 9.The tongue 9 and the groove 10 preferably have shapes which are complementary to each other, such that the upper side 17 of tongue 9 in the engaged condition of two identical floor panels 1 precisely sits against the upper lip lower side 18 andthe lower wall 14 of the lower lip of the groove 10, whereby a pressure P, exerted against the upper lip 22, is received or reacted not only by this lip 22, but by the complete structure, because this pressure can be transmitted through the tongue 9 andthe lower lip 23 to cause the panels to be urged towards each other.It is, however, clear that a number of minor deviations to these complementary forms can occur which, anyhow, have no or almost no effect upon the receipt and transmission of pressure forces. For example, a chamfer 24 on lip 22 and a recess 25can be provided, as represented in FIGS. 2 to 4, as a result of which the subsequent floor panels 1 can easily be pushed and guided into each other, such that no possible ridges in the subflooring or such render good insertion difficult.As represented in the FIGS. 5 to 7, the floor panels 1 according to the invention can also, along the sides 26-27 which are at a right angle to the sides 2-3, be provided with coupling parts 28-29 which have locking elements 30, too. Thecoupling parts 28-29 are preferably also realized in the shape of a tongue 31 and a groove 32. Hereby, the locking elements 30 do not have to be of the same nature as the locking elements 6.Preferably, at the sides 26-27 locking elements are provided which allow for an engagement and interlocking by means of a lateral translation movement in direction T only, as represented in FIGS. 6 and 7. To this aim, the locking elements 30consist of a snap-together connection with locking elements 33 and 34 which grip behind each other.As represented in FIGS. 5 to 7, the locking element 33 preferably consists of a downwardly extending protrusion of the lower side 35 of the tongue 31 which can be located in an upwardly facing recess 36 in a lower lip 43 extending distally fromthe inner side of the groove 32. The locking element 34 is formed by the upward directed part or protrusion which defines the distally outer end of recess 36.In this case, the locking elements 33-34 have contact or locking surfaces 38-39 which are parallel to each other and preferably extend in an obliquely inclined manner, according to a direction which simplifies the snapping-together of the panels,as illustrated. The common line or plane of tangency L which is determined by the common tangent at the meeting point or area of surfaces 38-39, hereby forms an angle A sloping inwardly and downwardly from an outer region to an inner region relative tothe underside 7 of the panel having the groove coupling part, which angle is smaller than 90.degree..The locking elements 33-34 preferably are provided with inclined portions 40 and 41 extending downwardly and proximally from a distal zone to a proximal zone on the tongue element and downwardly and distally from a proximal towards a distal zoneon the lower lip of the groove, which, when two floor panels 1 are engaged, cooperate with each other in such a manner that the locking elements 33-34 can easily be pushed over each other until they grip behind each other at their locking surfaces bymeans of a snap-together effect (FIGS. 6 and 7).The thickness W1 of the tongue 31 preferably is equal to the width W2 of the groove 32, such that compression pressure P applied to the upper lip 42 is reacted by the tongue 31 which, in its turn, then is reacted by the lower lip 43.Analogous to the chamfer 24 and recess 25, a recess 44 and a chamfer 45 are provided also at the edges 28-29.It is noted that such a snap-together coupling can also be applied at the edges 2-3. Hereby, this can be a snap-together coupling analogous to these of FIGS. 5 to 7, but this can also be a snap-together coupling using other forms of couplingconfigurations, for example, such as represented in FIGS. 8 and 9. Contrary to the locking elements 33-34 which consist of rather local protrusions, in the forms of embodiment of FIGS. 8 and 9 use is made of locking elements 46-47 which, in comparisonto the total width B of the coupling, extend over a rather large distance.In this case, the locking elements 46-47 are also provided at the lower side 12 of the tongue 9 and the upper side of the wall 14 of the lower lip of groove 10.According to FIG. 8, the locking elements 46-47 have locking surfaces 48-49 which are at an angle with the plane of the floor panel 1. In this manner, a coupling is obtained which is interlocked in a particularly fixed manner.As represented in FIG. 9, the locking elements 46-47 possibly can be configured in such a manner that substantially only a linear contact at the locking surfaces is obtained, for example, because the locking surfaces directed towards each otherare formed with different curvatures.The locking surfaces, directed towards each other, of the locking elements 45-47 according to FIG. 9 hereby consist of curved surfaces. The common line or plane of tangency L forms an angle A which is smaller than 90.degree., and more preferablyis smaller than 70.degree..In this manner, the locking element 46 preferably has two portions with a different curvature, on one hand, a portion 50 with a strong curvature and, on the other hand, a portion 51 with a weak curvature. The portion 50 with the strong curvatureprovides for the formation of a firm coupling. The portion 51 with the weak curvature facilitates the coupling parts 4-5 to be brought into each other easily. The intermediate space (shown at Z1 in FIG. 8) forms a chamber which offers space for dustand the like which, when engaging two floor panes 1, inevitably infiltrates there.In the case of a snap-together connection, for example, a connection such as represented in FIGS. 7 to 9, preferably the tongue 9-31 has a shape that thickens from below, which then can cooperate with a widened portion in the groove 10, the lowerlip of which likewise varies in thickness, as shown.In FIG. 10, a variant is represented whereby at least at the level of the upper side edges 15-16, a sealing material 52 is provided, as a result of which a watertight sealing can be assured. This sealing material 52 may consist of a strip orcovering which is provided previously at the floor panel 1, either at one or both upper side edges 15-16.In FIG. 11, a further variant is represented, whereby the locking element 6 is formed by an upward directed portion 53 at the tongue 9, which as a result of a turning movement of the panel, is brought behind a downward-directed portion 54 on theupper wall 18. More particularly, this is obtained by forming the upper side 17 and the upper wall 18 with a curvature R3, the center of which is situated at the upper side edges 15-16, and forming the tongue lower side 12 and the wall 14 of lower lip23 with a radius R4, the center of which is also situated at the upper side edges 15 and 16, respectively. These radii R3-R4 can be chosen otherwise, too.In general, according to the invention, the difference between, on one hand, the radius R1, R3 respectively, and, on the other hand, the radius R2, R4 respectively, preferably should not be larger than 2 mm.It is also preferred that the center of these radii be situated inside the circle C1, C2 (see FIG. 2) respectively, which extends with a radius R5 of 3 mm centered at upper side edge 15, 16 respectively.Finally is noted that, according to the invention, the lower lip 23-43, as represented in FIGS. 2 to 7, can be formed distally longer than the upper lip 22-42 possibly with the recesses of the locking elements extending partially under the upperlip and preferably, where the lower lip is longer than the upper lip, with the lower lip locking surface located beyond the upper lip. This has an advantage that the coupling parts 4-5-28-29 can be shaped in an easier manner by means of a milling cutteror the like. Furthermore, this simplifies the engagement of two floor panels 1, because each subsequent floor panel 1 during installation can be placed upon the protruding lower lip 23-43, as a result of which the tongue 9-31 and the groove 10-32automatically are positioned in front of each other.The embodiments wherein the lower lip 23 is equal to or distally shorter than the upper lip 22, in their turn, offer the advantage that no protruding lip 23 remains at the extreme edge of the floor which might cause problems in finishing thefloor installation.In order to allow for a smooth assembly, to guarantee the necessary stability and firmness and in order to limit the quantity of material to be cut away, the difference E between the distally outer edge of the upper lip 22-42 and the distallyouter edge of the lower lip 23-43, measured in the plane of the floor panel and perpendicular to the longitudinal direction of the groove 10, should preferably be kept smaller than one time the total thickness F of the floor panel 1. For stability'ssake, normally this total thickness F shall never be less than 5 mm.The small dimension of the difference E offers the advantage that the lower lip need not be strengthened by a reinforcement strip or the like.According to a particular form of embodiment, the central line M1 through the tongue 9 and the groove 10 is situated lower than the center line M2 of the floor panel 1, such, that the upper lip 22-42 is thicker than the lower lip 23-43. In firstinstance, this is essential in this kind of connection, because then it is the lower lip 23-43 which bends, whereby the upper side of the floor panel 1 is kept free of possible deformations.As explained in the introduction, for the core 8 a material is chosen from the following series: a ground product which, by means of a binding agent or by means of melting together is made into a unitary composite material; a product based onsynthetic material; chip board with fine chips.The invention shows its usefulness, in first instance, preferably with laminated flooring, due to the reasons explained in the introduction.As represented in the examples of the FIGS. 2 to 11, such laminated flooring preferably consists of a core 8 made of MDF medium density fiberboard board, HDF high density fiberboard board or similar, whereby at least at the upper side of thiscore 8 one or more layers of material are provided.More particularly, it is preferred that the laminated flooring is provided with a decorative layer 55 and a protective top layer 56. The decorative layer 55 is a layer, impregnated with resin, for example, made of paper, which can be imprintedwith a variety of patterns, such as a wood pattern, a pattern in the form of stone, cork, or similar or even with a fancy pattern. The protective top layer 56 preferably also consists of a layer saturated with resin, for example, melamine resin, whichin the final product is transparent.It is clear that still other layers can be applied, such as an intermediate layer 57 upon which the decorative layer 55 is provided.Preferably, also a backing layer 58 shall be applied at the underside 7, forming a counterbalancing element for the top layers and, thus, guaranteeing the stability of the form of the floor panel 1. This backing layer 58 may consist of amaterial, for example paper, impregnated with a resin, for example, a melamine resin.As represented schematically in FIG. 12, the tongue 9 and the groove 10, and preferably also the tongue 31 and the groove 32 are formed by means of a milling process. In the case that a profile has to be applied on all four sides, the floorpanels 1 preferably shall be displaced by means of two sequential perpendicular movements V1 and V2, whereby during the first movement profiles at two opposite edges are provided, in this case the longitudinal edges, by means of milling devices 59-60,whereas during the second movement profiles are provided at the other edges, in this case the small edges, by means of milling devices 61-62. During these processing, the floor panels 1 preferably are put with their decorative layer directed downward.According to an important characteristic of the invention, each respective tongue 9-31 and groove 10-32 are formed by means of a milling process with at least two sequential milling cycles or passes by means of milling cutters which arepositioned at different angles in reference to the related floor panel 1.This is illustrated in FIGS. 13, 14 and 15, wherein it is represented how a groove 10 is realized by means of two milling cycles by means of two milling cutters 63 and 64. FIGS. 16 and 17 represent how the tongue 9 is shaped by means of millingcutters 65 and 66.The FIGS. 18-19 and 20-21 represent similar views showing how the groove 32 and the tongue 31 are shaped by means of milling cutters 67-68 and 69-70, positioned at an angle.During each of the aforementioned milling passes, substantially the final shape of one flank is fully realized. For example, the milling cutter 63 of FIG. 14 determines the final shape of the lower flank 71 of the groove 10, whereas the millingcutter 64 determines the final shape of the upper flank 72.As mentioned in the introduction, preferably milling cutters 63 to 72 shall be used, having diameters G which are at least 5 times, and even better at least 20 times larger than the thickness F of the floor panels 1.Apart of the mentioned milling cutters, preferably still other milling cutters are applied, for example, in order to remove a part of the material to be removed during a first premachining cycle.In the FIGS. 22 to 25, a particularly preferred form of embodiment of a floor panel 1 according to the invention is represented. Hereby, the parts which correspond with the previous embodiments are indicated with corresponding references.An important characteristic herein consists in that the coupling parts 4-5 are provided with locking elements 6 which, in engaged condition with the panels in a common plane, exert a tension force upon each other, as a result of which the engagedfloor panels 1 are forced towards each other in compression. As represented, this is realized preferably by providing the coupling parts with an elastically yieldable or bendable portion, in this case the lower lip 43, which, in engaged condition, is atleast partially bent and in this way creates a tension force which results in the engaged floor panels 1 being forced towards each other. The resultant bending V, as well as the tension force K, are indicated in the enlargement view of FIG. 23.In order to obtain the tension force K pressing together the engaged floor panels 1, the bendable portion, in this case the lower lip 43, preferably is provided, as represented, with a proximally facing inwardly and downwardly inclined lockingsurface 73 which preferably can cooperate with a corresponding proximally facing (relative to the tongue) locking surface 74 on tongue 9. These locking surfaces 73-74 are similar to the aforementioned locking surfaces 39-38 and also similar to theinclined portions of the lower lip of FIGS. 2 to 4.In the FIGS. 2 and 5, the locking elements portions form complementary matching shapes; it is, however, clear that, by a modification, also a tension effect similar to that shown in FIG. 23 can be realized.Due to, on one hand, the contact between the locking surfaces along the angle A, and, on the other hand, the fact that a tension force K is created, a compression force component K1 is produced, as a result of which the floor panels 1 are drawnagainst each other in compression.Preferably, the angle A of the mutual line or plane of tangency of contact surfaces 73-74 relative to the principal horizontal plane of the panel is situated between 30 and 70 degrees. In the case that use is made of the embodiment whereby atension force K is realized, an angle A of 30 to 70 degrees is ideal in order, on one hand, to effect an optimum pressing-together of the floor panels 1 at their adjoining upper side edges and, on the other hand, to ensure that the floor panels 1 caneasily be engaged and respectively disassembled.Although the pressing or compression force component K1 preferably is delivered by the aforementioned lower lip 43, the invention does not exclude other forms of locking elements or structures whereby this force is delivered by other bendableportions.It is noted that the bending V is relatively small, for example, several hundredths up to several tenths of a millimeter, and does not have an influence upon the placement of the floor covering. Furthermore it should be noted that such floorcovering generally is placed upon an underlayer (not shown) which is elastically compressible, as a result of which the bending V of the lip 43 only produces local bending of the underlayer.Due to the fact that the lip 43 is bent apart and that it remains somewhat bent apart in engaged position, the additional advantage is obtained that, when exerting a pressure upon the floor covering, for example, when placing an object thereupon,the pressing-together compressive force is enhanced and, thus, the development of undesired gaps between adjoining upper side edges is counteracted even more.It is noted that the inventors have found that, contrary to all expectations, an ideal tension force can be realized by manufacturing the coupling parts 4-5, including the locking elements 33-34, and preferably the complete core 8, of HDF boardor MDF board, although these material normally only allow a minor elastic deformation.HDF and MDF also offer the advantage that smooth surfaces are obtained, as a result of which the locking elements can be moved easily over each other.According to a variant of the invention, the tension force can also be supplied by means of an elastic compression of the material of the coupling parts themselves, to which end these coupling parts, and preferably the complete core 8, would bemanufactured using an elastically compressible material.A further particular characteristic of the embodiment of FIGS. 22 to 25 consists in that the floor panels 1 can be selectively engaged by means of a turning or angling-in movement, as represented in FIG. 24, as well as by means of laterallyshifting them towards each other in substantially a common plane, as represented in FIG. 25, preferably in such a manner that, during the engagement by means of the turning movement with the coupling parts partially engaged, a maximum bending Vm resultsin the coupling parts, more particularly in the lip 43, which bending Vm is less pronounced, if not nonexistent, as in the FIGS. 2 to 4, in comparison to the bending Vm which results when the floor panels 1 are engaged by means of shifting them towardseach other, as in FIG. 15.The advantage of this consists in that the floor panels 1 can be engaged easily by means of a turning movement, without necessitating use of a tool therefore, whereas it still remains possible to engage the floor panels also by means of shiftingthem laterally. This latter is useful, in first instance, when the last panel has to be placed partially under a door frame or similar situation. In this case, the floor panel 1 can be pushed under the door frame with the side which does not have to beengaged and subsequently, possibly by means of tools, can be snapped into the adjacent floor panel by lateral sliding together.It is noted that the shapes of the coupling parts 4-5 shown in FIGS. 22 to 25 can also be used for the coupling parts 28-29 of the short sides of the panels.According to the invention, in the case that the four sides 2-3-26-27 are provided with coupling pars 4-5-28-29, these coupling parts can be formed in such a manner that in one direction a firmer engagement than in the other direction iseffected. In the case of elongated floor panels 1, for example, such as represented in FIG. 1, the locking at the small sides 26-27 preferably shall be more pronounced than at the longitudinal sides 2-3. The length of the parts at the small sides,namely, is smaller and, in principle, less firm. This is compensated for by providing a more pronounced locking.This difference in engagement can be obtained by shaping the contact surfaces 73-74 with different angles.Preferably, the aforementioned protrusion, more particularly the looking element 33, is bounded by at least two portions 75-76 (shown in FIG. 22), respectively a proximal portion 75 with a strong (steep) downward inclination from an upperproximal area to a lower distal area which provides for the locking, and a distal portion 76 with a weaker (less inclined) downward inclination from an upper distal area to a lower proximal area which renders the engagement or guidance of the couplingpads easier. In the embodiment of FIGS. 22 to 25, these portions 75-76 extend in straight planes, but, as already described with reference to FIG. 9, use can also be made of curved portions 50-51. In FIG. 5, these are the locking surface 38 and thedistal inclined portion 40.In the preferred form of the invention, the floor panels 1 comprise coupling parts 4-5 and/or 28-29 exhibiting one of the following or the combination of two or more of the following features: a curvature 77 (shown in FIG. 22) at the lower sideof the tongue 9 and/or a curvature 78 at the lower lip 43 which form a guidance when turning two floor panels 1 into each other, with the advantage that the floor panels 1 can be engaged into each other easily during installation; roundings 79-80 at theintersection of surfaces 74 and 75 on the tongue and on the upper edge of the locking, with the advantages that the locking elements 33-34 can easily shift over each other during their engagement, or during disassembly of the floor panels 1 and that thelocking elements will not be damaged, for example, crumble away at their edges, even if the floor panels are engaged and disassembled; dust chambers 81, or spaces 21 as in FIGS. 4 and 23, between all sides, directed laterally towards each other, of theengaged floor panels 1, with the advantage that inclusions which get between the floor panels 1 during the engagement do not exert an adverse influence upon good engagement; a shaping of the tongue 9 which is such, for example, by the presence of achamfer 82, that the upper side of the tongue 9 becomes situated from the first joining together or substantial contact of the panels, under the lower side of the upper lip 42 when the floor panels 1 are pushed towards each other in substantially thesame plane, as indicated in FIG. 25, with the advantage that the front or distal extremity or end of the tongue 9 does not press against the front side of the upper lip 42 or the front edge of the bottom lip 43 when the floor panels are pushed towardseach other in the same plane; a ramp surface 83, hereinbefore also called inclined portion 41, formed at the distally outer end of the lower lip 43, with the advantage that the locking elements 33-34 shift smoothly over each other and that the lower lip43 is bent uniformly; in the engagement direction only one important contact point which is formed by a section 84 at the location of the upper side edges of the floor panels 1, with the advantage that the aforementioned tension force is optimallytransferred to the upper side of the floor panels 1 and that the development of openings between the floor panels 1 is counteracted; contact surfaces 85-86, more particularly abutment surfaces, formed by the upper side of the tongue 9 and the upper sideof the groove 10 (or more precisely the lower side of the upper lip of the groove) which, over the largest portion of their length, are flat and run parallel to the plane which is defined by the floor panels 1, as well as lower tongue and groove contactsurfaces cooperating with each other, formed by curvatures 77-78, with the advantage that no mutual displacement in height between two engaged floor panels us possible, even if the insertion depth of the tongue 9 into the groove 10 should vary due tovarious causes; in other words, no height differences may occur between the adjacent floor panels.In the embodiment of FIGS. 22 to 25, all these characteristics are combined; it is, however, clear that, as becomes evident from FIGS. 2 to 11, these features can also be provided separately or in a limited combination with one another.As becomes evident from FIGS. 5 to 7 and 22 to 25, an important characteristic of the preferred embodiment of the invention consists in that the cooperative locking element 6, in other words, the portion providing for the snap-together andengagement effect, are situated in that portion of the lower lip 23-43 which lies beyond the distal edge of the upper lip 22-42, more particularly, the lowermost point 87 of the locking pad (i.e., protrusion) 33 is situated under the top layer of thefloor panel 1. For clarity's sake, this top layer is indicated in the FIGS. 22-25 only as a single layer.It should be noted that the combination of features, the lower lip 23-43 extending further than the upper lip 22-42; the lower lip locking elements 6 being formed at least by means of a locking surface which inwardly slopes downward relative tothe lower lip, and wherein this locking surface, at least partially, is located in the portion of the lower lip 23-43 which lies distally beyond the upper lip 22-42, is particularly advantageous, among others, in comparison with the couplings for floorpanels described in the documents WO 94/01628, WO 94/26999, WO 96/27719 and WO 96/27721. The sloping locking surfaces have the advantage that the floor panels 1 can be disassembled again. The fact that this sloping portion is situated in the extendedportion of the lower lip 23-43 adds the advantage that no deformations can occur during coupling which manifest themselves up to the top layer.According to a preferred characteristic of the invention, the aforementioned locking surfaces 39 or 73, preferably extend in such a manner that the distance between the upper edge 16 of the panel to the locking surface 39, 73 diminishes betweenthe proximal and distal ends of the sloping locking surface 39, 73, in other words, such that, as represented in FIG. 22, the distance X2 is smaller than the distance X1. This is also the case in FIG. 7.Still preferably, this portion only starts at a clear distance E1 (FIG. 22) from the outer edge of upper lip 42.It is obvious that the coupling parts 22 to 25 can also be shaped by means of said milling process.According to a particular characteristic of the invention, the floor panels 1 are treated at their sides 2-3 and/or 26-27 with a surface densifying agent, more particularly a surface hardening agent, which preferably is chosen from the followingseries of products: impregnation agents, pore-sealing agents, lacquers, resins, oils, paraffins and the like.In FIG. 22, such impregnation 88 is represented schematically. This treatment can be performed over the complete surface of the sides 2-3 and/or 26-27 or only over specific portions hereof, for example exclusively on the surfaces of the tongue 9and the groove 10.The treatment with a surface densifying agent offers, in combination with the snap-together effect, the advantage that in various aspects better coupling characteristics are obtained. As a result of this, the coupling parts 4-5 and/or 28-29better keep their shape and strength, even if the floor panels 1 are engaged and disassembled repeatedly. In particular, if the core 8 is made of HDF, MDF or similar materials, by means of this treatment a better quality of surface condition isobtained, such that no abrasion of material occurs during engaging, or during disassembling.This treatment also offers the advantage that, at least in the case of a surface hardening, the aforementioned elastic tensioning effect is enhanced.The present invention is in no way limited to the forms of embodiment described by way of example and represented in the figures, however, such floor covering and the pertaining floor panels 1 can be embodied in various forms and dimensionswithout departing from the scope of the invention.For example, the various characteristics which are described by means of the represented embodiments or examples may be selectively combined with each other.Furthermore, all embodiments of coupling elements described before can be applied at the longer side as well as at the shorter side of a panel.* * * * *