Low Noise Planing Machine, Particularly Hand Planer

The present invention relates to a planing machine, and more particularly to a hand-held planer, in which a rotary planing cutter is driven by an electric motor to rotate within a working or operating chamber and remove materials from the surface of a workpiece.

Customary planing machines, and particularly hand-held planers, use rotary cutters in which cutter blades are located on a cylindrical cutting element which is driven by an electric motor to rotate in a direction essentially transverse to the longitudinal extent of the machine. The cutter is operative within an operating or working chamber which is open at the planing surface to project slightly from the planing surface and thereby effect workpiece removal upon rotation. The opening at the planing surface is wider than the cutter to permit removal of workpiece material in chip form through a portion of the housing for ejection therefrom, usually in a lateral direction. The cutting edges of the planer, as they rotate, cause recurrent pressure wave to occur which arise at the edges of the respective housing portions defining the operating chamber. Since the cutter operates at high speed, the sharp, pulse-like pressure waves cause substantial operating noise which is highly disagreeable to the user and causes, overall, ambient noise pollution.

It is an object to provide a planing machine which has the operating efficiency and effectiveness of known planers but a substantially reduced operating noise level, and which is so constructed that it is not heavier than known planers and can be easily and simply made.

Briefly, at least one of the housing portions which define respective inlet, operating or chip transporting, and outlet portions of the operating chamber have edge zones terminating in edge or terminal lines which are inclined with respect to theoretical line parallel to the axis of rotation of the chip cutter and located in a plane parallel to a plane which is tangential to the chip cutter. In accordance with a preferred form, the inclination may extend in two directions, so that the edges present a roof-shaped, or shallow "V" appearance, diverging from a central apex.

Inclination of the edge of a wall portion defining the chamber has the result that incremental areas or portions o zones of the cutter blade on the cutter sequentially pass the edge of the wall portion, rather than at the same time as in an axially parallel edge of the wall portion.

The arrangement has the advantage that pressure waves which occur adjacent the rotary path of the cutting edges of the cutter are extended in time with respect to the impingement portion on the housing wall, so that impingement of the pressure waves on the housing wall is attenuated, thus preventing transfer of high-intensity pressure waves to the housing itself. The operating noise is substantially reduced. This is achieved without the addition of noise damping material, and only by shaping the respective walls defining the operating chambers or, rather, those portions which are subject to being impinged by pulse-type pressure waves. The weight of the machine and its handling characteristics are not changed.

In planing machines which have a common separating wall which separates both the chip removal duct and the cylindrical operating space of the rotary cutter from the remainder of the housing, it is particularly desirable to then form the end portion of this common separating wall in inclined direction with respect to the axis of rotation of the chip cutter, and especially in doubly-inclined direction, starting from a preferably central apex point. Other edge portions adjacent the working chamber within which the cutter operates likewise may be inclined. In a particularly preferred form, the forward edge of the cutting depth defining wedge and immediately adjacent the operating chamber is also formed with an inclined surface.

Forming the inclined surfaces in double-wedge form assists in ejecting chips from both sides of the housing, uniformly and without pile-up of chips within the operating chamber adjacent the ejection ports from the housing.

FIG. 1 is a side view, partly in section, of a hand planer, and showing only those portions of the planer material to an understanding of the present invention;

FIG. 2 is a section along line II--II of FIG. 1; and

FIG. 3 is a fragmentary bottom view, in the direction of arrow A of FIG. 1.

The planing machine has a housing 10, consisting of two longitudinal half shells, and defining plane flat bottom planing surfaces 11, 12, and further providing a unitary handle 14. Housing 10 retains an electric motor (not shown specifically and not visible in the figures) and drive gearing, as well known. The motor drives a cutter cylinder 16 which has axially extending, radially projecting cutter blades thereon. Cutter cylinder 16 is rotatably journaled in a cylindrical operating or working chamber 18 formed in housing 10. The cylindrical chamber 18 forms part of an internal chamber arrangement having various portions. Chamber 18 is open to the planing surface and forms an inlet portion 20. The chamber 18 is defined in part by an intermediate wall 22 to separate the chamber from the remaining inner space or chamber portion 24 of the housing 10. The subdividing wall 22 partly surrounds the cutter cylinder 16, and defines an edge 26 which starts adjacent the chip removal opening 28 of the working chamber 18 located in a plane parallel to a plane tangential to the cutter cylinder. The working chamber 18 then includes a chip removal duct portion 32 which terminates in lateral chip ejection openings 34 formed in the housing 10. The chip removal duct 32 is separated from the remainder of the interior space of the housing 10 by an intermediate wall 36. Wall 36 merges, in its lower portion, with wall 22 and thus has a common lower edge 26 therewith.

A planing depth control shoe 40, of wedge shape, is provided, tapering to an edge 42 which defines one end of the opening portion 28 of the operating chamber 18. The position of the shoe 40 with respect to the remainder of the machine can be adjusted by an adjustment screw 44 which determines the cutting depth of the machine. The wedge surface 46 (FIG. 1) of shoe 40 extends tangentially from the working chamber 18 and leads into the chip removal duct 32.

In accordance with the invention, and in order to reduce noise level in operation, the edge 26 of the end portion or edge zone of the separating wall 22, is defined by a terminal line which is inclined with respect to the axis of rotation of the cutter 16 or, rather, with respect to a theoretical line parallel thereto, as seen in FIG. 2. The edge 26 has an edge portion 48 extending at a positive angle with respect to line 46 to a central apex at center line 100, and then an edge portion 50 extending from the apex at center line 100 at a negative angle with an edge portion 50 with respect to line 46, to the other end of the housing. Thus, the edge 26 is roof shaped. The portions 48, 50 form an obtuse angle. Similarly, the edge 42 of shoe 40 also is roof shaped with edge portions 52, 54 (FIGS. 2 and 3). Forming the edges 26, 42 inclined, with respect to the axis of rotation of cutter 16, provides for impingement of pressure waves which cause noise at different times with respect to different incremental portions or zones of the respective edges of the outer blades, so that the intensity of generated noise is attenuated and, additionally, spread in time. Inclining these edges thus results in substantial decrease in the operating noise of the machine. Arranging the inclination to be peaked at the center, or roof shape results, additionally, in uniform distribution of the chips to oppositely located chip removal openings 34 formed in the housing 10.

In some machines it is sufficient to form only one of these edges in inclined form and, in the preferred form, the edge 26 of the common portion 38 of inner walls 22 and 36 is so shaped. In some tools it may additionally be desirable to form the edge 30 opposite edge 42 also at an inclination with respect to the axis of rotation, and preferably in roof shape form.

The angles of inclination are not critical, and may extend from between 10.degree. to about 30.degree. with respect to the theoretical line 46. As shown in FIG. 2, the edge 26 is inclined at an angle of about 17.degree.; as shown in FIG. 3, the edge 42 is inclined at an angle of about 12.degree. with respect to line 46, so that the included angle between surfaces 52, 54 (FIG. 3) will be about 156.degree..

Various changes and modifications may be made, and features described in connection with any one of the embodiments may be used with any of the others, within the scope of the inventive concept.

The edges which are inclined with respect to the axis of rotation of the rotary cutter 16 can be machined simply and easily, and no specific change in the overall design of the planing machine is necessary. The shapes shown in FIGS. 2 and 3 are particularly easy to produce. Of course, continuously curved edges, such as segments of circular openings, or the like, may also be used in which the reference to "angles of inclination" is deemed to tangential portions thereof.