Optical unit for image projection and tool incorporating same

Abstract: An optical unit (52) for projecting an image (54) including the first and second locating lines (72,74) for substantially eliminating the introduction of visual parallax error. In a preferred form, the optical unit (52) is incorporated into a machine (10) for performing a forming operation on a workpiece (30) and is operative to project an image (54) of a portion of a scale (50) to a position easily read by the user during machine operation. The optical unit (52) includes a prism portion (56) having a first side (64) disposed adjacent the scale (50), a second side (66) at an angle a to the first side (64) for reflecting the image (54) and a third side (68) through which the projected image (54) may be viewed. The first locating line (72) is disposed on the first side (64) and the second locating line (74) is disposed on the third side (68) such that visual alignment eliminates the introduction of visual parallax error associated with reading a scale (50).

Description: The present invention relates to an optical unit for projecting an image, in particular to a tool which includes an optical unit for projecting an image of a scale which permits the tool user to complete adjustments of the tool from a more ergonomically advantageous position without the introduction of visual parallax error. Various tools are used in woodworking and metal forming efficiently and accurately to shape workpieces to desired dimensions and surface qualities. Such tools often include a workpiece forming element such as a bit, cutting blade, or the like, which is adjustable relative to the workpiece. For example, the workpiece forming element is, in many instances, carried by a movable component which is adjustable relative to the workpiece or relative to a base plate or platen upon which the workpiece may be supported. The significant majority of workpiece forming applications require quick and accurate adjustment of the workpiece forming element relative to the workpiece in order to obtain results desired. A wood planing machine is an example of such a tool in which a workpiece forming element is adjustable relative to a workpiece. A conventional planing machine is used for the surface planing of boards and typically includes one or more rotatably mounted cutting blades attached to a vertically movable carriage assembly. In a typical wood surface planer, a selectively adjustable workpiece opening is defined between the carriage assembly and a workpiece support surface. The cutting blades are carried by the carriage assembly so as to be exposed adjacent to the workpiece opening. Generally, the carriage assembly is movably mounted to a plurality of support columns for movement with respect to the workpiece support surface, thereby permitting adjustment of the vertical dimension of the workpiece opening for selectively determining the amount of material to be removed from the workpiece and resultantly the ultimate thickness of the workpiece. Multiple passes of the workpiece through the workpiece opening are often necessary to obtain the desired thickness and surface quality. Through adjustment of the carriage assembly relative to the support surface, the amount of material removed during a single pass can be varied. A pointer is typically fixed for movement with the carriage assembly and co-operates with a scale carried by the frame for visually indicating the desired thickness of the workpiece. As with other woodworking and metal forming operations, it is highly desirable that a planing machine accomplish workpiece preparation within precise tolerances, high surface quality, and with a significant degree of reproducible results. While many commercially successful tools, including but not limited to known surface planers, are available which include an adjustable workpiece forming element adapted to be advanced relative to a workpiece and a scale and co-operating pointer for identifying the relative location of the workpiece forming element and the workpiece, all are subject to improvement. For example, such known tools require the user accurately to align his or her line of sight horizontally with the pointer in order to avoid the introduction of visual parallax error. This typically requires the user to bend or stoop to a position in which comfort is compromised and operation of the machine is hindered. This motion is particularly taxing on the user 5 where repetitive adjustment is required. As a result, the quality of the forming operation is often adversely affected. A known arrangement is shown in FR 1,417,228 which teaches the use of an optical unit attached to a translatable component of a tool, which optical unit is adapted to project an image of a scale at a projection angle in order to allow a user to read a measurement using the scale while remaining in the normal position for using the tool. It is an object of the present invention to provide an optical unit attached to a first element for projecting a substantially vertical image carried by a second element through an angle to the vertical for purposes of accurately adjusting the first element vertically with respect to the second element. It is a related object of the present invention to provide an optical unit which substantially eliminates visual parallax error associated with visual misalignment of a scale and co-operating pointing mechanism. It is another object of the present invention to provide an optical unit for projecting an image at an angle to the vertical without image is not inverted. A more specific object of the present invention is to provide an optical unit for a tool of the type adapted to carry out planing of the surface of a workpiece which is operative for enabling the user of the tool to quickly, easily and accurately read a scale mounted on a substantially vertical surface of the tool without requiring the user to horizontally align his or her line of sight with the scale. According to the present invention there is provided an optical unit for projecting an image of a scale of a tool at a projection angle, characterised in that the optical unit comprises: a first side disposed adjacent the scale; a second side disposed at a first angle α with respect to the first side; a third side disposed at a second angle β with respect to the first side; a first locating line extending transversely across the third side; and a second locating line extending transversely across the first side, the second locating line being positioned on the optical unit relative to the first locating line such that the first and second locating lines appear co-linear when viewed from the projection angle. The first side is preferably transparent. The second side is preferably internally reflective. When the image is viewed from the third angle, the image enters the first side substantially perpendicular thereto, thereby minimising visual parallax error. Furthermore, there is provided an apparatus for performing a forming operation on a workpiece, the apparatus comprising a frame; a translatable component including a workpiece forming element, said translatable component mounted within the apparatus for selective bi-directional movement along a path of travel; a workpiece support surface disposed relative to the translatable component so as to define a selectively adjustable workpiece opening therebetween and a scale carried by the frame adjacent to the translatable component, the scale being marked with indicia incrementally representing the position of the translatable component relative to the workpiece, characterised in that an optical unit according to the present invention is attached to the translatable component for projecting an image of the scale at the projection angle. Furthermore, there is provided a planing machine for planing a surface of a workpiece, the planing machine comprising: a frame; a plurality of vertical support columns mounted within the frame; a carriage assembly interconnected to the frame, the carriage assembly including a workpiece forming element, the carriage assembly mounted to the plurality of support columns for selective bi-directional movement along a path of travel; a workpiece support surface disposed relative to the carriage assembly so as to define a selectively adjustable workpiece opening therebetween and a scale carried by the frame adjacent to the carriage assembly, the scale being marked with indicia incrementally representing a desired thickness of the workpiece, characterised in that an optical unit according to the present invention attached to the carriage assembly, the optical unit adapted to project an image of the scale through at the projection angle. An embodiment of an apparatus for performing a forming operation on a workpiece will now be described with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a portable surface planing machine constructed to incorporate an optical unit; Figure 2 is an exploded perspective view of various elements of the planing machine associated with an upper portion thereof; Figure 3 is an enlarged perspective view of the optical unit of Figure 1; Figure 4 is an enlarged side view of a portion of the optical unit of Figure 3 in the direction of the line 4-4; Figure 5A is a schematic illustration of the optical unit of the present invention shown relative to a viewer positioned at a proper viewing angle; Figure 5B is a simplified illustration of the image of the scale as seen by the viewer in Figure 5A; Figure 6A is a schematic illustration of the optical unit of the present invention shown relative to a viewer positioned at an improper viewing angle; and Figure 6B is a simplified illustration of the image of the scale as seen by the viewer in Figure 6A. The present invention is broadly applicable to various tools and particularly applicable to workpiece forming tools of the type including an adjustable component which carries a workpiece forming element. With reference to the drawings in which identical or equivalent elements have been denoted with like reference numerals and specifically to Figures 1 and 2 thereof, an exemplary tool is illustrated as a portable surface planing machine adapted for planing the surface of a workpiece. The planing machine is generally identified in the drawings at reference numeral 10. In addition to the following detailed description, a further description of various features of the illustrated surface planing machine 10 not directly related to the present invention is provided in co-pending application US Patent No. 08/659,684, filed on June 5, 1996. The planing machine 10 is shown to include generally a frame 12 having a pair of opposing sides 14 and 16, a top 18 and a base 20. The base includes a pair of support feet 22 and a workpiece support surface or platen 24. The planing machine 10 is also shown to include a carriage assembly 26 having an integrally formed casting. The carriage assembly 26 and the platen 24 co-operate to define a workpiece opening 28 for receiving a workpiece 30. In one application, the workpiece opening 28 of the planing machine 10 is sized to accommodate a workpiece having a nominal width of 32cm (12.5 inches) or less. However, the present invention should not be considered to be limited thereto. In Figure 1, the workpiece 30 is shown in broken lines partially extending within the workpiece opening 28. As shown in the exploded view of Figure 2, a workpiece forming element in the form of a cutting blade 32 is attached to a cutter head 36. The cutter head 36 is carried by the carriage assembly 26 such that the blade 32 is exposed adjacent an underside of the carriage assembly 26 which is adjacent the workpiece opening 28. Rotational attachment of the cutter head 36 to the carriage assembly 26 is accomplished in a substantially conventional manner. The blade 32 is removably secured to the cutter head 36 by a retention plate 38 and is driven by a motor (not shown) located within the carriage assembly 26. The carriage assembly 26 is shown to be slidably mounted to a plurality of support columns or support posts for bi-directional vertical movement. One of the support columns is identified in Figure 1 with reference numeral 40. While not illustrated in detail, each of the plurality of support columns 40 is generally cylindrical and includes a lower end which engages a circular recesses formed in the base 20 of the frame 12. The support columns 40 also include upper ends which engage similar recesses (not shown) formed in the underside of the top 18. Threaded fasteners 42 pass through apertures 44 in the top 18 and base 20 and engage tapped holes (not shown) in the upper and lower ends of the support columns 40. In the embodiment illustrated, four support columns 40 support the carriage assembly 26. The carriage assembly 26 may selectively be translated upward or downward along a path of travel and is guided by integrally formed apertures 46 located in the four corners casting of the carriage assembly 26. Such translation is controlled by rotation of a handle assembly 48 which is interconnected to a threaded drive rod (not shown). As shown in the perspective view of Figure 1, a scale 50 is attached to a forward portion of the side 16 of the frame 12. The scale 50 is marked with indicia representing the desired thickness of the workpiece 30. In a conventional manner, a pointer would be carried by the carriage assembly 26 for indicating the relative position of the carriage assembly 26 with respect to the scale 50. With the appropriate indicia, the pointer and the scale 50 conventionally co-operate to identify the desired thickness of the workpiece 30 according to the vertical dimension of the workpiece opening 28. With such a conventional arrangement, however, the user of the machine 10 must align his or her line of sight horizontally with the pointer to avoid the introduction of visual parallax error. Such horizontal alignment is generally not desired, since the machine 10 is typically supported on a table or other surface such that bending or stooping would be required. As will be discussed below, the present invention is intended to overcome this inconvenience which may adversely effect the quality of machine operation. As illustrated, the surface planing machine 10 includes an optical unit 52 for projecting an image 54. In the application illustrated throughout the drawings, the image 54 to be projected by the optical unit 52 includes a variable portion of the scale 50. The optical unit 52 includes a prism portion 56 and a mounting portion 58. In the preferred embodiment, the optical unit 52 is unitarily constructed of plastic. One suitable plastic is acrylic. Alternatively, those skilled in the art will appreciated that the optical unit 52 can be constructed of glass or other suitable material capable of accurately reflecting the image 54. Furthermore, it will be understood that the mounting portion 58 can alternatively be formed independently from the prism portion 56. As shown most clearly in Figure 3, the mounting portion of the optical unit 52 is formed to include a pair of apertures 60 passing therethrough. The apertures 60 are adapted to receive threaded fasteners 62 (shown in Figure 1) which, in turn, engage threaded apertures (not shown) formed in the carriage assembly 26. The optical unit 52 can alternatively be adhesively or otherwise attached to the carriage assembly 26 for movement therewith. In the preferred embodiment, the prism portion 56 of the optical unit 52 is defined by a first side 64, a second side 66, and a third side 68. The first side 64 is oriented substantially vertically and is disposed adjacent to the scale 50. The second side 66 is disposed at a first angle α with respect to the first side 64. The third side 68 is disposed at a second angle β relative to the first side 64. The first side 64 of the prism portion 56 of the optical unit 52 is transparent while the second side 66 is internally reflective. The third side 68 includes a transparent window 70 through which the image 54 is visible. As will become more apparent below, proper viewing of the image 54 in the prism portion 56 requires the user to align his or her line of sight at a predetermined angle with respect to the third side 68 to ensure accuracy of reading (i.e. to avoid the introduction of visual parallax error). In the particular embodiment illustrated throughout the drawings, the first, second and third sides 64, 66, and 68 co-operate in end view (e.g. as shown in Figure 5A) to define a triangle. In one application, the triangle is a right triangle and the first angle α between the first side 64 and second side 66 is 30° and the second angle β between the first side 64 and third side 68 is 60°. In this particular application, the first side 64 is approximately 26 mm, the second side 66 is approximately 22.5 mm and the third side 68 is approximately 13.2 mm. The optical unit 52 additionally includes a pointer mechanism, or first locating line 72, for identifying a precise point on the portion of the scale 50 included in the reflected image 54. In the side views of Figures 4, 5A and 6A, the first locating line is shown as a point 72. The first locating line 72 is positioned to extend transversely across the first side 64. In the particular application discussed above, the first locating line 72 is spaced approximately 11 mm from the intersection of the first side 64 and the third side 68. In the preferred embodiment, the optical unit 52 further includes a hairline, or second locating line 74. As will become apparent below, the second locating line 74 co-operates with the first locating line 72 substantially to eliminate visual parallax error when viewing the scale 50 through the prism portion 56. In the application discussed above, the second locating line 74 is positioned approximately 5.5 mm from the intersection of the first side 64 and the third side 68. Figure 5A schematically illustrates a simplified view of the image 54 passing through the prism portion 56 of the optical unit 52 when the user's eye is aligned with the third side 68 at an angle  of approximately 90°. In this particular position, the first locating line 72 appears co-linear with the second locating line 74. The particular portion of the scale 50 which is aligned with the colinear first and second locating lines 72 and 74 enters the prism portion 56 along a horizontal line 76 at an angle substantially normal to the first side 64. The light rays continue horizontally through the prism portion 56 of the optical unit 52 until they contact the reflective second side 66. At this point, the light rays are reflected upwardly at an angle to the horizontal of approximately 60° until they contact the first side 64. This line of contact is coincident with the first locating line 72. Then, the light rays are reflected at an angle of approximately 30° within the vertical such that they pass through the aligned first and second locating lines 72 and 74. Since the light rays of the image 54 enter the first side 64 and exit the third side 68 substantially parallel thereto, diffraction of the light rays is minimal. Significantly, the image seen by the user is not inverted. With reference to Figure 5B, the image 54 seen by the user when viewed from the angle  with respect to the third side 68 is illustrated. Because the light rays enter the prism portion 56 of the optical unit 52 at an angle substantially normal to the first side 64, the introduction of visual parallax error is substantially avoided. It will now be appreciated that the image 54 visible with the window 70 of the prism portion 56 varies as the carriage assembly 26 is vertically translated relative to the remainder of the planing machine 10. Turning now to Figures 6A and 6B, the benefit of the first and second locating lines 72 and 74 will be apparent through discussion of the operation of the optical unit 52 when viewed from an improper angle. As shown in the simplified schematic view of Figure 6A, the line of sight is oriented at an angle σ from the third side 68. The angle is slightly greater than 90°. As shown in Figure 6B, in this incorrect position, the user sees both the first locating line 72 and the second locating line 74. Here, the light rays of the image 54 enter the first side 64 and exit the third side 68 at an angle that is not equal to 90°. In this example, the light rays enter the first side 64 along a line 76' displaced from the line 76 and exit the third side 68 along a line 74' spaced from the second locating line 74. For simplicity of illustration, the light rays in Figure 6A are not shown being diffracted as they pass through the first side 64 and the third side 68. However, those skilled in the art will recognise that an appreciable amount of diffraction will occur since the angles of entry and exit are not normal to the respective sides 64 and 68. As a result, visual parallax error is introduced and the precision with which the carriage assembly 26 is adjusted may be comprised. However, the user will readily recognise the potential for error since the first and second locating lines 72 and 74 do not appear colinear. With specific reference to Figures 3 and 4, the optical unit 52 is shown to further include a third locating line 78. The third locating line 78 is preferably in the form of a notch or groove which is horizontally located in the exterior of the second side 66. The third locating line 78 is horizontally aligned with the line 76. In certain applications, the user may desire to read the scale 50 without looking through the prism portion 56. In this regard, the third locating line 78 allows the user to read the scale 50 in a conventional manner along a horizontal line of sight.

Claims: An optical unit (52) for projecting an image (54) of a scale (50) on a tool at a projection angle, characterised in that the optical unit (52) comprises: a first side (64) disposed adjacent the scale (50); a second side (66) disposed at a first angle α with respect to the first side (64); a third side (68) disposed at a second angle β with respect to the first side (64); a first locating line (74) extending transversely across the third side (68); and a second locating line (72) extending transversely across the first side (64), the second locating line (72) being positioned on the optical unit (52) relative to the first locating line (74) such that the first and second locating lines (74,72) appear co-linear when viewed from the projection angle. An optical unit according to claim 1 characterised in that the optical unit (52) comprises a unitarily constructed prism (56). An optical unit according to claim 1 or claim 2 characterised in that the second angle β is complementary to the first angle α. An optical unit according to any of claims 1 to 3, characterised in that the projection angle is substantially equal to the first angle α. An optical unit according to any of claims 2 to 4, characterised in that the prism (56) is triangular and further characterised in that the first angle is approximately 30° and the second angle is approximately 60°. An optical unit according to any of claims 1 to 5 characterised in that it further comprises a third locating line (78) disposed adjacent to the second side (66), the third locating line (78) being visible from the exterior of the second side (66). An optical unit according to any of claims 1 to 6, characterised in that the second side (66) is internally reflective. An optical unit according to any one of the preceding claims characterised in that the first side (64) is substantially parallel to the scale (50). An optical unit according to any one of the preceding claims characterised in that the first side (64) is transparent. An optical unit according to any one of the preceding claims characterised in that the third side (68) is transparent. An apparatus for performing a forming operation on a workpiece (30), the apparatus (10) comprising: a frame (12); a translatable component (26) including a workpiece forming element (32), said translatable component (26) mounted within the apparatus (10) for selective bi-directional movement along a path of travel; a workpiece support surface (24) disposed relative to the translatable component (26) so as to define a selectively adjustable workpiece opening (28) therebetween and a scale (50) carried by the frame (12) adjacent to the translatable component (26), the scale (50) being marked with indicia incrementally representing the position of the translatable component (26) relative to the workpiece (30), characterised in that an optical unit (52) according to any one of the preceding claims is attached to the translatable component (26) for projecting an image (54) of the scale (50) at the projection angle. A planing machine (10) for planing a surface of a workpiece, the planing machine (10) comprising: a frame (12); a plurality of vertical support columns (40) mounted within the frame (12); a carriage assembly (26) interconnected to the frame, the carriage assembly (26) including a workpiece forming element (32), the carriage assembly (26) mounted to the plurality of support columns (40) for selective bi-directional movement along a path of travel; a workpiece support surface (24) disposed relative to the carriage assembly (26) so as to define a selectively adjustable workpiece opening (28) therebetween and a scale (50) carried by the frame (12) adjacent to the carriage assembly (26), the scale (50) being marked with indicia incrementally representing a desired thickness of the workpiece (30), characterised in that an optical unit (52) according to any one of claim 1 to 10 is attached to the carriage assembly (26), the optical unit (52) adapted to project an image (54) of the scale (50) through at the projection angle.

Inventors: WELSH ROBERT P, WIXEY BARRY D, WELSH, ROBERT P., WIXEY, BARRY D.
Applicants: BLACK & DECKER INC, BLACK & DECKER INC.
Application year: 1997
Main classification: B23Q17
IPC codes: G01B9, B23Q17, B27C1