DEPTH OF CUT ADJUSTMENT MECHANISM FOR A POWER PLANER

Abstract: A depth of cut adjustment mechanism for a portable power planer (20) having an adjustable front shoe (30) whose elevational position controls the depth of cut of the tool. An S-shaped rod (40) is fastened at one end to the adjustable front shoe (30) and is threadedly engaged at its other end to an adjustment nut (42) rotatably mounted in a race (44) formed in the housing (22). A control knob (46) having disposed thereon a scale (64) referenced to a mark (62) on the housing (22) is secured to the nut (42) so that rotation of the control knob (46) causes a corresponding adjustment in the elevational position of the front shoe (30). A tension spring (70) is connected between the front show (30) and the housing (22) to cancel out inherent tolerance play between the front shoe (30) and the housing (22).

Description: DEPTH OF CUT ADJUSTMENT MECHANISM FOR A POWER PLANER BACKGROUND AND SU{MARY OF THE INVENTION The present invention relates to portable power planers and in particular to an improved depth of cut adjustment mechanism for a power planer. In general, portable power planers comprise a motor driven rotary cutter head having one or more cutting blade assemblies disposed thereon for performing a planing operation on the surface of a workpiece as the cutter head rotates. The bottom surface of the tool consists of a fixed shoe located rearwardly of the cutter head and an adjustable shoe disposed forwardly of the cutter head. As the front shoe is adjusted upwardly or downwardly, the cutting depth of the cutting blade of the planer is adjusted accordingly. The adjustable front shoe of a portable power planer typically includes an integral stem or sleeve that is threaded either directly to an adjustment cap disposed atop the front end of the housing or to a threaded shaft or bolt that is in turn fastened at its other end to the adjustment cap for rotation therewith. In either arrangement, however, a powerful compression spring is interposed about the sleeve between the shoe and the housing to maintain the elevation of the adjustable shoe in the position set by the operator. The compression spring is held in compression between the adjustable shoe and the housing and must be of sufficient strength to resist the natural tendency of the operator to bear down upon the planer when performing a planing operation, and yet be sufficiently compressible to permit convenient upward adjustment of the adjustable front shoe. As a consequence, in some planers having conventional depth of cut adjustment mechanisms, the operator can overcome the thrust force of the compression spring and dislodge the adjustable shoe from its preset position, thereby causing an undesired variation in the depth of cut. Accordingly, it is the primary object of the present invention to provide an improved depth of cut adjustment mechanism for a portable power planer which accurately maintains the preset position of the adjustable shoe when the operator bears down upon the tool. Additionally, it is an object of the present invention to provide such a depth of cut adjustment mechanism for a power planer which utilizes a tension spring which works with the operator to take up the tolerance play at the interface between the adjustable shoe and the tool housing. Furthermore, it is an object of the present invention to provide such a depth of cut adjustment mechanism for a power planer that substantially reduces the space required within the tool housing, as well as the manufacturing cost of the tool, as compared to conventional prior art constructions. In general, the elevation adjustment arrangement according to the present invention includes an adjustable shoe having fixedly attached thereto a rod extending upwardly therefrom which is threadedly engaged at its upper end to an elevation positioning nut rotatably mounted in the housing and fxed against elevational movement relative thereto. An adjustment cap disposed atop the housing is affixed to the positioning nut so that rotation of the adjustent cap results in elevational movement of the adjustable front shoe. A tension spring is connected between the front end of the adjustable shoe and the housing to cancel out tolerance play between the adjustable shoe and the housing. Because the tension spring works with the operator as he bears down upon the tool, no unwanted movement or wobble of the adjustable front shoe results. In addition, the preferred embodiment of the present invention includes means for calibrating the elevation adjustment mechanism so that when the scale provided on the adjustment cap reads zero, the adjustable shoe is set for zero cutting depth. A positive park position is also provided which when engaged sets the adjustable shoe below zero elevation so that the cutting blades will not mar the surface upon which the tool is placed. Additional objects and advantages of the present invention will become apparent from a reading of the detailed description of the preferred embodiment which makes reference to the following set of drawings in which: BRIEF.DESCRIPTION OF THE DRAWINGS Figure 1 is a side elevational view of a power planer incorporating the depth of cut adjustment mechanism according to the present invention; Figure 2 is an enlarged detailed cutaway view exposing the depth of cut mechanism according to the present invention; Figure 3 is a side elevational view of tre front end of the left-hand portion of the housing; Figure 4 is an enlarged sectional view o- a portion of the housing half shown in Figure 3 taken along line 4-4; Figure 5 is a top plan view of the adjustable front shoe according to the present invention; ; Figure 6 is a sectional view of the elevation adjustment nut according to the present invention: Figure 7 is an enlarged sectional view ot a portion of the elevation adjustment nut shown in Figure 6 taken along line 7-7; Figure 8 is a sectional view of the adjustment cap of the present invention; Figure 9 is a bottom plan view of the adjustment cap shown in Figure 8; Figure 10 is an enlarged sectional view of a portion of the adjustment cap shown in Figure 8 taken along line 10-10; Figure 11 is a top plan view of the adjustment cap shown in Figure 8; and Figure 12 is an exploded perspective view of the depth of ct adjustment mechanism of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to Figures 1 and 2, a portable power planer 20 of t:ae type to which the present invention relates, is conentional in overall layout comprising a clamshell-type housing 22 incorporating a motor-driven cutter head 24 having mounted thereon a pair of cutting blade assemblies 26 for performing a planing operation of the surface of a workpiece as the cutter head 24 rotates. The Bottom surface of the tool 20 comprises a fixed shoe 2 located rearwardly of the cutter head 24 and an adjustable front shoe 30 disposed forwardly of the cutter :-.ead 24. Elevational adjustment or the front shoe 30 causes a corresponding adjustment cf the depth of cut o- the cutting blades 26. With additional reference to Figure 5, the adjustable frct shoe 30 includes an integral socketlike projection 32 extending upwardly from the base thereof. Projection 32 also contains diametrically opposed, radially outwardly extending integral flanges 34 which are adapted to be received within a pair of slots 36 (Figure 3) formed by boss members 38 in housing 22. The left-hand housing member shown in Figure 3 is illustrative oZ the complementary-shaped right-hand housing member. The flanges 34 serve to laterally stabilize the adjustable front shoe 30 as well as prevent the front shoe 30 from rotating relative to the housing 22. An S-shaped rod 40 is fixedly mounted at one end in the socket-like projection 32 of adjustable front shoe 30. An elevation positioning nut 42 is threadedly engaged to the upper end of rod 40. Elevation positioning nut 42 is rotatably mounted within a race 44 formed in housing 22 by the joinder of the right-hand and left-hand halves. The race 44 permits rotation of elevation positioning nut 42 relative to the housing 22 but prevents elevational movement with respect thereto. Thus, it will be appreciated that when elevational positioning nut 42 is rotated, rod 40 and hence adjustable front shoe 30 are moved in elevation, thereby resulting in a variation in the depth of cut. With particular reference to Figures 2 and 5, it will be noted that adjustable front shoe 30 has a ridge 50 formed along its rearward end which extends upwardly at an acute angle from the base of the shoe 30. Ridge 50 together with the rearward most tangential surface of socket-like projection 32 form a slot 52 adjacent the back portion of projection 32 which is adapted to engage a downwardly projecting wall 54 formed in the housing 22. Ride 50 coacts with downwardly projecting wall 54 to prevent rotation of adjustable front shoe 30 with respect to housing 22 and also to guide the elevational movement of front shoe 30. As best shown in Figure 2, sufficient clearance is provided between downwardly projecting wall 54 and the base of front shoe 30 to permit adequate elevational adjustment in the position of front shoe 30. Referring now additionally to Figures 8 and 9, a control knob 46 is fastened to elevation adjustment nut 42 so as to be exposed atop the forward end of housing 22. Control knob 46 is secured to adjustment nut 42 by means of a plurality of flexible fingers 48 which are adapted to grasp the undersurface of a circular ridge 56 formed around the nut 42. Control knob 46 is keyed to elevation adjustment nut 42 so as to rotate therewith by the mutual engagement of corresponding sets of fine teeth 58 and 60 formed on the inside surfaces of flexible fingers 48 of control knob 46 and the outer radial surrace of ridge 56 of nut 42, respectively. The tooth configuration, shown in detail in Figures 7 and 10, is fine enough to permit precise angular positioning of control knob 46 relative to elevational adjustment nut 2 while at the same time providing a tight connection therebetween. As best shown in Figure 11, a scale 64 is provided on the top surface of control knob 46 which is referenced to an arrow 62 (Figure 12) located on the outer surface o housing 22. The scale 64 on control knob 46 is calibrated in the following manner. Initially, with the control knob 46 removed, the elevation adjustment nut 42 is rotated until the adjustable front shoe 30 is located ir the zero depth of cut position. The control knob 46 is then properly oriented and fastened onto elevation adjustment nut 42 in the manner described so that the reference arrow 62 on housing 22 is aligned with the zero indication on the scale. Thereafter, manual rotation of control knob 46 will cause rotation of elevation adjustment nut 42 and a corresponding variation in the elevational position of front shoe 30, which will be reflected in the reading on the control knob scale 64. In addition, it will be noted that control knob 46 is provided with a downwardly projecting tab 66 which is adapted to abut a stop 68 located on the left-hand portion of housing 22, Engagement of the stop 68 by control knob 46 in the counterclockwise direction of rotation provides a positive "park" position wherein the adjustable front shoe is positioned below the zero depth of cut position to prevent the cutting blades 26 from marring the surface upon which the tool is placed. In the preferred embodiment herein, engagement of the stop 68 by the control knob 46 in the clockwise direction of rotation corresponds to the maximum cutting depth of 0.5 millimeters. Returning to Figure 2, a tension spring 70 is connected between the socket portion 32 of adjustable front shoe 30 and the front of housing 22. The spring 70 is maintained under tension and serves to cancel out any tolerance play which may exist between the adjustable front shoe 30 and the housing 22, thus avoiding a disconcerting wobble movement in the front shoe. In addition, it will be noted that tension spring 70 is disposed so that its axis is substantially parallel with the axes of S-shaped rod 40 at its upper and lower ends to prevent binding of adjustment nut 42. It is also preferred that spring 70 be mounted to the socket portion 32 of adjustable shoe 30 closely adjacent rod 40 to minimize the moment created by the slightly offset tension force of the spring 70 relative to the axes of rod 40. Significantly, it will be appreciated that, unlike conventional prior art mechanism which utilize strong compression springs, the present tension spring 70 works with the operator as he bears down upon the tool during operation. Thus, at no point does the adjustable front shoe 30 appear to "float" as in the case of a compression spring when the force of the spring is balanced by the downward force exerted by the operator. In other words, because the present tension spring 70 works with the natural tendencies of the operator, the adjustable front shoe 30 is always maintained in the desired elevational position. In addition, as will readily be appreciated by those skilled in the art, the use of the substantially smaller tension spring 70 in combination with the S-shaped rod 40 significantly reduces the space required within the tool housing 22 when compared to conventional compression spring designs. Moreover, by eliminating the heavy compression spring of prior art designs, a significant reduction in manufacturing cost is also realized. While the above description constitutes the preferred embodiment 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 accompanying claims.

Claims: WHAT IS CLAIMED IS: 1. A depth of cut adjustment mechanism for a portable power planer including an adjustable shoe (30) and positioning means (40, 42, 44, 46) interfacing said shoe with the housing (22) of the planer for controlling the elew-ational position of said shoe (30) to set the depth of cut of the planer, the depth of cut adjustment mechanism being characterized by: a resilient member (70) connected between said shoe (30) and said housing () for exerting a tension force therebetween to tae up the inherent tolerance play at the interface of said shoe (30) and said housing (22) to firmly hold said shoe (30) in the elevational position set by said positioning means (40, 42, 44, 46). 2. The depth of cut adjustment mechanism of Claim 1 wherein said positioning means includes a substantially S-shaped rod (40) affixed at one end to said shoe (30) and threadedly engaged at its other end to a positioning nut (42) rotatably mounted in said housing (22). 3. The depth of cut adjustment mechanism of Claim 2 wherein said positioning nut (42) is mounted in a race (44) formed in said housing (22) so as to be rotatable relative to said housing but fixed in elevation with respect thereto. 4. The depth of cut adjustment mechanism of Claim 3 wherein said resilient member comprises a tension spring (70) that is connected at one end to said shoe adjacent said rod (40) and at its other end to said housing (22) so that the axis of said spring (70) is substantially parallel to the axes of said S-shaped rod (40) at its ends thereof. 5. The depth of cut adjustment mechanism of Claim 3 wherein said positioning means further includes a control knob (46) secured to said positioning nut (42) for rotation therewith and having disposed thereon scale means (64) referenced to a fixed reference (62) on said housing (22) for providing an indication of the depth of cut of the cutting blade (26). 6. In a portable Fawner planer comprising a housing (22) incorporating â motor driven cutting blade (26), an adjustable shoe (30), and elevation adjustment means (4.0, 42, 4E, 70) for controlling the depth of cut of the cutting blade (26) by controlling the elevational position of said adjustable shoe (30); the improvement ;herein said elevation adjustment means is characterized by: position control means (42, 46) rotatably mounted in said housing (22) so as to be fixed against elevational movement with respect thereto; a substantially S-shaped rod (40) fastened at its lower end to said shoe (30) and threadedly engaged at its upper end to said position control means (42, 46) such that rotation of said position control means (42, 46) results in elevational adjustment in the position of said shoe (30); and a tension spring (-0) connected between said shoe (30) adjacent said rod (40) and said housing (22) for firmly holding sai shoe (30) in the elevational position set by said position control means (42, 46). 7. The portable power planer of Claim 6 wherein said position control means includes an adjustment nut (42) and a control knob (46) affixed to said adjustment nut (42) for rotation therewith and having disposed thereon scale means (64) referenced to a fixed reference (62) on said housing (22) for providing an indication of the depth of cut of the cutting blade (26). 8. The portable power planer of Claim 7 wherein said position control means further includes means (58, 60) disposed at the interface between said control knob (46) and said adjustment nut (42) for positively affixing said control knob (46) to said adjustment nut (42) in a preselect able angular position relative thereto for permitting calibration of said scale means (64). 9. The portable power planer of Claim wherein said position control means further includes means (66, 68) for positively locating said control knob (46) and adjustment nut (42) in a predeterrined angular position corresponding to the elevational position of said adjustable shoe (30) being below the lowermost point of travel of said cutting blade (26). 10. The portable power planer of Claim 10 wherein said tension spring (70) is disposed so that its axis is substantially parallel with the axes of said S-shaped rod (40) at its upper and lower ends.

Inventors: BACHMANN, RAINER
Applicants: BLACK & DECKER INC.
Application year: 1980
Main classification: B27C1
IPC codes: B27C1