Composite material platen for portable wood working machine

A platen for supporting a wooden workpiece relative to cutting heads of a planing machine, said platen having an upper surface and a lower surface and said platen being integrally composed of a fiber reinforced composite material.

DETAILED DESCRIPTION As required, detailed embodiments of the present invention are disclosed herein. However, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific functional and structural details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. The present invention provides an improved base or platen or table or shoe along which a wood workpiece may move relative to a power tool or vice versa. One embodiment of the present invention provides a fiber reinforced composite material base or platen for a portable wood planing machine for the surface planing of a workpiece such as a wooden board or plank. A second embodiment of the present invention provides a fiber reinforced composite material shoe for a hand portable circular saw for gliding over and cutting a workpiece such as a wooden board or plank. The various features of such a base or platen or shoe, which are described in detail below, are shown cooperatively arranged within a the exemplary planing machine and circular saw. However, it will be appreciated that the scope of the present invention is not so limited. In other words, while the exemplary embodiments of a planing machine and circular saw with a composite material platen or shoe are shown and described, it will be understood that a similar composite material base, platen or shoe may be used in other power tool applications. Turning generally to the drawings in which identical or equivalent elements have been denoted with like reference numerals and specifically to FIGS. 1 through 3 thereof, an exemplary wood planing machine constructed in accordance with the teachings of the present invention is illustrated and identified generally at reference numeral 10 . The planing machine 10 is shown to generally include a frame 12 having a pair of opposing sides 14 and 16 , a top 18 and a base 20 . The base 20 includes a plurality of support feet 22 and a workpiece support surface or platen 23 . The planing machine 10 is also shown to include a carriage assembly 24 having an integrally formed casting 26 . The carriage assembly 24 and the base 20 cooperate to define a workpiece opening 28 for receiving a workpiece 30 . In one application, the workpiece opening 28 of the portable wood planing machine 10 is sized to accommodate a workpiece having a nominal width of twelve and one-half inches or less. The planing machine 10 also includes forwardly extending and rearwardly extending feed tables 32 and 34 for further supporting the workpiece 30 . The forwardly and rearwardly extending feed tables 32 and 34 are upwardly foldable from their positions shown in FIG. 1 to storage positions substantially adjacent the front and rear of the planing machine 10 , respectively. Transfer of the portable planing machine 10 is facilitated through a pair of carry handles 19 extending from opposing sides of the top 18 . In FIG. 1 , the workpiece 30 is shown in broken lines partially extending within the workpiece opening 28 . As shown in the exploded view of FIG. 2, a cutter head 36 is carried by the carriage assembly 24 such that it is exposed adjacent to the underside of the carriage assembly 24 which is adjacent the workpiece opening 28 . The carriage assembly 24 also carries a pair of feed rollers (not shown). Rotational attachment of the cutter head 36 and the feed rollers to the carriage assembly 24 is accomplished in a substantially conventional manner. The cutter head 36 includes a replaceable cutting blade 38 removably secured by a retention plate 40 and driven by a motor (not shown) located within the carriage assembly 24 . An on/off switch 42 extending from the front face 44 of the carriage assembly 24 controls the supply of electric power to the motor from a power cord (not shown). With specific reference to the exploded views of FIGS. 2 and 3 , the carriage assembly 24 is shown to be slidably mounted to a plurality of support columns or support posts for bi-directional vertical movement. FIG. 3 illustrates one of the support columns which has been identified with reference numeral 46 . Each of the plurality of support columns 46 is generally cylindrical and includes a lower end 48 which engages a circular recess 50 formed in the base 20 of the frame 12 . The support columns 46 also include upper ends 52 which engage similar recesses (not show) formed in the underside of the top 18 . Threaded fasteners 54 pass through the apertures 56 in the top 18 and base 20 and engage tapped holes (not shown) in the upper and lower ends 48 and 52 of the support columns 46 . In the embodiment illustrated, four support columns 46 support the carriage assembly 24 . The carriage assembly 24 may selectively be translated upward or downward along a path of travel and is guided by integrally formed apertures 58 located in the four comers of the casting 26 of the carriage assembly 24 . With means that are not the subject of the present invention, the carriage assembly 24 may be vertically adjusted relative to the support platen 23 . The vertical adjustment of the of the carriage assembly 24 relative to the support platen 23 serves to select the depth of cut of the workpiece 30 by selectively moving the cutting blade vertically relative to the workpiece 30 . An arrangement for translating the carriage assembly 24 is described in further detail in U.S. patent application Ser. No. 08/659,685, filed Jun. 5, 1996 and entitled “Apparatus for Adjusting the Relative Positions of Two Components of a Power Tool”. U.S. patent application Ser. No. 08/659,685 is incorporated by reference as if fully set forth herein. According to the present invention, base 20 and support platen 23 , as well as feed tables 36 and 38 , are constructed of a light weight fiber reinforced composite material. A fiber reinforced composite material is that constructed of a matrix material reinforced by a fibrous material. For example, the subject platen may be manufactured using a glass fiber reinforced vinyl ester thermoset sheet molding compound (SMC). Alternative base resins include epoxy, polyester, phenolic, polyurethane and polybutadiene resins. Alternative fiber reinforcements include aramid and carbon fibers. With specific reference to FIGS. 4 and 5 , the base 20 and support platen 23 are shown formed according to the present invention as an integral piece. The top of the platen 23 may be formed with integral ribs 23 a for supporting the workpiece 30 while reducing the total friction contact area. Similarly, the bottom of platen 23 may be formed with a lattice of stiffeners 23 b . The use of fiber reinforced composite materials according to the present invention, and the processes for manufacturing with such materials, are particularly suited to the production of complex forms like that of the integral base 20 and platen 23 with their incorporated elements. The inventors have found that a fiber reinforced composite material platen manufactured according to the present invention has substantial weight savings as compared to a conventional metal platen. The significant weight savings achieved in the platen improve the mobility, ease of use and accuracy of the tool. Furthermore, the structural toughness and rigidity of a fiber reinforced composite platen improves the service life and reduces maintenance/repair costs of a tool incorporating the present invention relative to a tool incorporating a heavier metal platen or shoe. Another embodiment of a fiber reinforced composite material platen according to the present invention is embodied in a circular saw. As shown in FIGS. 6 and 7 , a circular saw is designated generally by 70 . Saw 70 comprises a housing 72 , an arbor 74 and a circular saw blade 75 detachably secured to the arbor 74 in the known manner. The operational components of the circular saw are contained in a housing 72 , which also includes upper blade guard 76 and lower blade guard 77 . FIG. 6 shows the lower blade guard 77 in the fully extended position. FIG. 7 shows the lower blade guard 77 in the fully retracted position. For illustrative purposes, in FIG. 7 , the right half of the upper guard 76 has been removed and a portion of shoe 80 has been broken away. The housing 72 is formed with a rear handle 73 from which extends an electric cable (not shown). An on/off trigger switch 78 is provided in the upper part of the closed handle 73 which is shaped to enable the handle 73 to be conveniently and securely gripped by an operator's hand. Mounted below the housing 72 is a platen or shoe 80 for supporting the saw in sliding engagement with workpiece 100 . Shoe 80 is attached to the housing 72 and has an upper surface 82 , a lower surface 84 and defines an opening 86 through which the saw blade 75 can extend. Preferably, shoe 80 is pivotably attached to the housing 72 for movement about an axis parallel to the arbor 74 by a pivot (not shown) located at the rear of housing 72 and attached to the shoe by a pivot foundation 91 . The rear pivot permits the blade 75 to be adjusted for depth of cut through opening 86 and relative to the lower shoe surface 84 in accordance with well known principles which form no part of the present invention and will not be described in detail. Also, for bevel angle adjustment, shoe 80 is pivotally attached for movement about an axis perpendicular to the arbor 74 by a pivot 88 located at the front of the housing. The bevel angle adjustment mechanism 89 includes a quadrant 90 that projects in a plane perpendicular to that of the shoe 80 . Further details of the rear pivot and bevel angle adjustment mechanisms, which do not form a part of the present invention, are fully disclosed elsewhere, e.g. in U.S. Pat. No. 4,982,501. With specific reference to FIGS. 8, 9 and 10 , the saw shoe 80 is shown formed according to the present invention as an integral piece of fiber reinforced composite material. The shoe 80 may be formed with an integral bevel angle adjustment quadrant 90 , pivot 88 , and pivot foundation 91 for movement relative to the housing 72 and blade 75 . The use of composite materials according to the present invention, and the processes for manufacturing with such materials, are particularly suited to the production of complex forms like that of the saw shoe 80 with integrally incorporated elements. The inventors have found that a composite material shoe manufactured according to the present invention has particular advantages for hand portable power tools, like the circular saw. The shoes of such saws are subject to frequent drops and shocks. When made of metal they are prone to bend under heavy impact, and if made of plastic they may crack. A bent or cracked shoe adversely effects the accuracy and therefore utility of the saw. In contrast, a shoe made of fiber reinforced composite material may crumble at the point of impact, but it will not bend in a way that interferes with smooth even sliding over the workpiece. Additionally, such crumbling deformation as may occur can be quickly cleaned up with a rasp or file. Moreover, the weight saving of a composite shoe, as compared to a conventional metal shoe, reduces operator fatigue and enhances operator accuracy. While the above description constitutes alternative embodiments of the present invention, it will be appreciated that the invention is susceptible to modification, variation, and change without departing from the proper scope or fair meaning of the present invention. In this regard, while the various features of the present invention have been shown and described in connection with a portable wood planer and a circular saw, it will be appreciated by those skilled in that art that platens made of fiber reinforced composite materials are suitable in connection with other woodworking power tools. For example, many of the features may be readily modified for use with a jig saw or scroll saw.