Patent Application
20060159890
The present invention relates to a plastic deck plank or board which has a very high load bearing capacity and a high quality surface finish yet is of relatively low cost.
Conventional wooden deck planks or boards are often being replaced with plastic deck planks. These plastic deck planks have the benefit that they not only have an attractive appearance but they are not subject to the usual problems encountered with wood, such as rotting, splintering, warping or destruction by insect infestations, and they require essentially no maintenance.
Many of the prior art plastic planks such as the plank shown in U.S. Pat. No. 5,009,045 are of a one piece construction formed usually of polyvinyl chloride (PVC). Such planks have a load bearing platform spanning between rigid depending legs with the platform having a thickness sufficient to support the deck load on the spans between the depending legs.
Some prior art plastic deck planks use separate mounting bases and covers fitted to the tops of the bases as shown in U.S. Pat. Nos. 5,613,339 and 5,758,456. These bases and covers are formed of PVC which is a relatively high cost material.
More particularly, the bases of such two piece planks have bottom webs or walls which sit on the supporting beams and the bases are secured to the beams by screws driven through the bottom walls. At the top, the bases have spaced cover supporting platforms supported by legs extending up from the bottom walls. The covers, which provide the exposed walking surfaces, bridge gaps between adjoining supporting platforms and have to have sufficient rigidity or thickness to take the walking load across the spaces or gaps between the platforms.
It is the object of the present invention to provide a plastic deck plank which will be significantly less expensive than those presently available yet will have superior load bearing properties while presenting a high quality top surface.
In one particular aspect, the invention involves the provision of a load bearing plank support base or plank member formed of low cost plastic material. This load bearing plank member base has a top portion free of any gaps therethrough and presents a substantially continuous upper cover supporting surface. In contrast, the cover is formed of a higher cost PVC and, because of the substantially continuous supporting surface of the base member, the cover is made very thin.
In another aspect of the invention, the top portion of the load bearing plank member is formed with at least one very narrow longitudinal groove and preferably one such groove adjacent each edge. The grooves have a mouth with a width only sufficient to accept the head of a screw. Below the mouth of these grooves is a narrow channel having a width sufficient only to accept the shanks of the screws with the channels having bottom walls overlying open spaces therebeneath. This arrangement is such that, with screws introduced into the grooves and threaded through the bottom walls of the channels and into an underlying support beam on which the deck plank rests, the screws not only form the means of attaching the plank member to the support beams but also form steel columns spanning between the channel bottoms and the support beams which aid in supporting the deck loads.
With reference to
As hereinafter more fully described, each deck plank comprises a main load bearing plank member and a thin cover therefor.
In the embodiment of the invention shown in FIGS. 2 to 5, the plank member comprises a plastic extruded member 4 which has an upper cover supporting wall formation comprising a central wall 5 and edge walls 6a and 6b separated from the central wall 5 by grooves 7. The upper walls 5, 6a and 6b are supported by upright columns 9, 10, 11, 12 and 13 extending upwardly from a bottom wall or bearing 14.
Each of the grooves 7 has a mouth portion 15 adapted to receive the head of a screw Sc and a narrower channel portion 16 of a size to receive the shank of the screw with the channel portion 16 having a bottom wall 17 overlying a generally rectangular open longitudinal passageway or bore 18 extending down to the bottom wall 14.
The bore 18 in each of the columns 9 and 11 provides a space or void underneath the channel bottom walls 17 so that when the plank member 4 is being secured to an underlying support member or beam 3 the screw needs only to penetrate the channel bottom wall 17 of the groove 7, the bottom wall 14 and then bite into the support beam 3 until the head 19 of the screw seats at the bottom of the mouth 15 of the groove 7 at which time it becomes a reinforcing steel support column spanning between the top of the groove channel 16 and the support beam 3, all as shown in
To complete the deck plank, the load bearing plank member 4 is covered by a thin plastic cover 19 which is illustrated in
On the other hand, the thin cover 19 which is required to give a quality surface finish to the deck plank is extruded of higher cost material, preferably virgin, that is unprocessed, PVC with the conventional weathering, protective and colouring additives as desired or required.
Referring particularly to
Preferably the top edge walls 6a and 6b are slightly curved and have a depending edge ledge 21 terminating in an undercut hook formation 22.
In turn, the cover 19 is slightly curved at the edges 23 and is provided with downwardly curved hooked edge portions 24 adapted to interlock with the hook formations 22 of the plank member 4. By providing this slightly curved arrangement, the cover can be snap locked on to the top of the plank member 4 and drawn into tight contact with the generally planar central wall 5 of the plank member. This arrangement renders the cover readily removeable so that it can be replaced if desired or necessary.
In this connection, because the PVC of the cover 19 can include a colouring agent, the surface of the plank can have any selected colour as desired. Because the cover is substantially continuously supported and is made very thin, it will be appreciated that the cost of changing or replacing the cover for whatever reason is minimized.
FIGS. 6 to 10 illustrate an alternative form of the invention in which the main deck plank member 25 is formed of molded relatively low cost plastic material such as those used for the extrusion of the main deck plank member 4 discussed above.
Plank member 25 is molded with a top wall generally designated at 26 which is free of any openings or slots therethrough so that the plastic is continuous throughout both the width and the length thereof. Top wall 26 has a central generally planar cover supporting or bearing surface 27 and slightly curved edge cover supporting or bearing surfaces 28a and 28b separated from the central surface 27 by screw receiving grooves 29.
Plank member 25 further has a depending circumscribing border wall formation generally designated at 30 and a bracing network of webbing generally designated at 31 comprising twin webbing 32a and 32b connected to the surrounding wall formation 30 and extending from end to end of the plank member and transverse webbing 33 extending between and connected to the surrounding wall 30.
Added diagonal webbing 33 provides additional reinforcing strength.
On one longitudinal side of the depending wall formation 30, there is provided one or more spacer projecting blocks 34 to abut the next adjacent plank member to give accurate spacing between the deck planks. A viewing notch 35 enables the installer to determine the side of the plank member carrying the spacer block or blocks 34.
As in the case of plank member 4, plank member 25 has at each longitudinal edge a downwardly projecting ledge 36 ending in an undercut hook formation 37 on to which the hooked edge portions 24 of the cover 19 will interengage with a snap locking action.
As illustrated in
As before, the screws form reinforcing steel columns spanning between the bottom of the mouths of the grooves 29 and the support beam 3.
With the cover 19 snapped into place, any blemishes, discoloration or other mars of the lower cost plank member 25 are hidden by the higher cost better grade material of the cover 19.
While several embodiments of the invention have been described, it will be understood that other variations may be made without departing from the scope of the appended claims.
