Viewing window for circular saw guard

Abstract: A viewing window (31) for covering an aperture (46) in a hand-held circular saw includes an optically transmissive member (32) adapted to be coupled with the guard. The member is movable between a closed position, wherein the member substantially covers the aperture, and the open position, wherein the member at least partially uncovers the aperture, to allow the cleaning of the member. A structure may be provided for biasing the member to the closed position.

Description: This invention relates to the field of hand-held power saws and, more particularly, to a guard for a circular saw blade. Hand-held power circular saws have been popular woodworking tools for many years. In a typical sawing operation, the user begins by marking or otherwise identifying a desired line along which to saw the material to be cut. The user then guides the saw during cutting, manually aligning the blade with the desired line of cut. Maintaining this alignment manually can be difficult because the typical circular saw has a blade guard that obscures the user's view of the blade at the point of cutting and thus impedes the user's ability to accurately align the blade with the desired cutting line. To overcome this difficulty, one alternative has been to provide the circular saw with a guide slot. Typically located on the base of the saw, the guide slot is so aligned ahead of the blade in the forward cutting direction to provide a visual indication of the anticipated blade path through the workpiece. During operation, the user typically positions the saw so that the guide slot, and thus the blade, are aligned with the line of cut. This approach can provide a satisfactory cut, unless the saw blade is improperly aligned with the guide slot. A blade is typically oriented at a predesignated location on an arbor driven by the saw motor. Deviations from this orientation can occur causing misalignment between the blade and the guide slot. The guide slot will then incorrectly indicate the blade path, and the user relying on the guide slot will less likely cut the material as desired. Furthermore, since the blade is covered by the saw guard, the user cannot directly monitor the blade travel and, therefore, may not detect the misalignment until substantial cutting has occurred. As a result, the workpiece may be ruined. To overcome these limitations, another alternative has been to supply the saw guard with a transparent viewing window covering an aperture in the saw guard. Such a window allows direct observation of the saw blade as it enters the workpiece, which in turn enables the user to better maintain a desired cutting path. For example, United States Patent No. 1,830,579 provides an observation opening in the side wall of a hand-held circular saw guard. However, the use of a side wall viewing port did not permit the user to saw from a comfortable position behind the saw and at the same time monitor the progress of the blade. Furthermore, to the extent the air currents directed towards the inside surface of the viewing pane were not sufficient to clear the pane of dust, manual clearing of the pane would be required which could more directly expose the saw blade. A viewing window covering an aperture on the outside circumference of a circular saw blade guard is disclosed in United States Patent No. 4,450,627. This viewing window is coupled with the saw guard in a variety of ways, including by means of a press fit, a sliding fit or a side hinge. When the viewing window requires cleaning, however, it must either be removed or substantially opened, thereby exposing the saw blade area. After cleaning, if the user neglects to install or close the viewing window, sawing operation without the viewing window in place could occur. The user may not notice the missing viewing window until sawing operations have begun, and cut material could be ejected through the uncovered aperture. The side hinge structure disclosed in this patent allows complete exposure of the aperture in the saw guard. US 4875398 discloses a retractable dust control hood 42 for a rotary table saw. The hood 42 comprises a generally triangular shaped hollow box having sloping front wall 64, a generally vertical back wall 66, opposed side walls 68 and 70 and an open bottom side. A major portion of the front wall of the hood 42 takes the form of a transparent window 74. DE 3104340 discloses a guard 9 for a rotary saw having a projection 20 which includes viewing windows 21, 22. A lens 24 positioned inside the guard enables an operator to view the blade 3 and work surface through the windows. To overcome these and other limitations in the prior art, an improved viewing window is desirable for a circular saw guard that is easily cleanable without requiring full exposure of the saw guard aperture. Accordingly, it is an object of the present invention to provide a clear viewing window in a circular saw guard to cover an aperture in the guard so as to minimise exposure of the aperture during cleaning. A related object is to provide such a window that is easy to operate and inexpensive to manufacture and assemble. It is a further object of the present invention to provide a clear viewing window for a circular saw guard so biased as to better ensure that the window returns to the closed position after cleaning. It is a further object of this invention to provide a means for biasing a viewing window in a circular saw guard to the closed position on the outside of the saw guard and in a manner less likely to be affected by material generated during saw operation. It is a further object of this invention to allow easy cleaning of a viewing window for a circular saw guard while greatly reducing any necessary exposure of the aperture. A related object is to provide a viewing window that is not easily removed from the saw guard and thus less likely to be misplaced. According to the present invention, there is provided a a guard assembly for a hand-held circular saw, the assembly comprising a guard having an aperture, and an at least partially optically transmissive member adapted to be coupled with the guard and to be movable between a closed position, wherein the member substantially covers the aperture, and a cleaning position, wherein at least part of the member is available for cleaning, characterised in that the member at least partially obstructs access to the aperture in the cleaning position. In one embodiment, the viewing window is hingedly coupled with the guard to rotate outwardly from the periphery of the guard about an axis parallel to the rotational axis of the blade. In this embodiment, the window is supplied with a means for biasing it to a closed position during use. The window may also be carried in a frame and supplied with a means for limiting its travel to minimise exposure of the aperture during cleaning. In another embodiment of the invention, the viewing window may be larger than the aperture in the saw guard. Tabs forming slots may be provided in the saw guard proximal the aperture to receive a rectangular, planar window that can slide laterally between the use position and the cleaning position. Alternatively, the oversize window may be triangular in shape and pivot about a single point in the periphery of the saw guard. In another embodiment, the window may be approximately the same size as the aperture and be adapted to rotate along its longitudinal axis within the aperture between a use position and a cleaning position. In a further embodiment, the window may be fixedly mounted to the saw guard proximate a second aperture oriented to permit convenient cleaning of the inside surface of the window with a cleaning tool or compressed air introduced through the second aperture. During sawing operations, the second aperture may be covered with a removable plug retained in the second aperture by a press fit. Preferred embodiments of a viewing window will now be described with reference to the accompanying drawings, in which: Figure 1 is a front perspective view showing a viewing window of the present invention in the closed position; Figure 2 is a partial side elevation view taken along line 2-2 of Figure 1 showing the viewing window in the closed position; Figure 3 is a partial side elevation similar to Figure 2 except showing the viewing window in the open position; Figure 4 is a partial top plan view taken along line 4-4 of Figure 2 with part of the viewing window being broken away to show particular details of construction; Figure 5 is a partial side elevation view taken along line 5-5 of Figure 2 with part of the viewing window assembly being broken away to show particular details of construction; Figure 6 is a partial side elevation view taken along line 6-6 of Figure 1 showing the viewing window in the closed position and the saw assembly broken away to show particular details of construction; Figure 7 is a front perspective view of a second embodiment of the present invention showing the viewing window in the closed position and, in phantom lines, in an open position; Figure 8 is a front perspective view of a third embodiment of the present invention showing a viewing window slidably coupled with the circular saw guard; Figure 9 is a front perspective view showing a fourth embodiment of the present invention wherein the viewing window pivots about a single point as shown by the indicating directional arrow; Figure 10 is a front perspective view of a fifth embodiment of the present invention showing a viewing window coupled with the circular saw guard and a plug removable from a second aperture to access the window for cleaning purposes; Figure 11 is a front perspective view of a sixth embodiment of the present invention wherein the viewing window rotates about its longitudinal axis lying on the periphery of the circular saw guard; Figure 12 is a partial side elevation view taken along line 12-12 of Figure 11 showing the viewing window in the closed position; Figure 13(a) is a front perspective view of a seventh embodiment of a viewing window in the closed position; and Figure 13(b) is a similar view, with the viewing window in the open position. Referring to the drawings in greater detail, a power circular saw is shown designated generally by 20. Saw 20 has a motor 22 operably attached to a circular saw blade 21. A power cord 24 supplies electrical power to motor 22. The upper portion of blade 21 is surrounded by a saw guard 26 secured to motor 22. Saw 20 further has a base 28 with a guide notch 30. Provided in saw guard 26 is an aperture 46 for viewing blade 21 as it travels through a workpiece 102. A window assembly 31 for covering aperture 46 and embodying the principles of the present invention is shown in Figure 1. Window assembly 31 is comprised of a frame 34 and an optically transmissive window 32 coupled therewith. Although window 32 is depicted as a generally planar rectangular structure in the drawings, window 32 can be of any suitable shape and curvature. Window assembly 31 is coupled with saw guard 26 by a fastener 36, such as a pin or rivet, that passes through an aperture in frame 34 and through a corresponding aperture in saw guard 26. In this configuration, window assembly 31 is rotatable outwardly from saw guard 26 about an axis parallel to the rotational axis of saw blade 21. A second fastener 48 may be provided that passes through an aperture on the opposite side, and along the rotational axis, of frame 34. Fastener 36 is often sufficient to pivotally support frame 34 and it may not be necessary to have fastener 48. Frame 34 has a flange 39 extending generally downwardly from one side. Flange 39 extends from the side of frame 34 that is opposite fastener 36. Flange 39 is generally perpendicular to window 32 and has an elongated arcuate slot 40 through which a stop pin 38 passes and frictionally couples with an aperture in saw guard 26. Disposed longitudinally between stop pin 38 and the opposite end of slot 40 is a compression spring 42. Slot 40 serves to contain spring 42 and to limit the travel of window assembly 31. As will be understood by those skilled in the art, additional means for retaining spring 42 may be provided, such as a retaining pin 41 protruding from frame 34 into slot 40 and into one end of spring 42. Saw guard 26 is preferably provided with a recessed area 44 about the edge of aperture 46 adapted to complementally receive window assembly 31 when in the closed position. In operation, the viewing window of the present invention is movable between a closed position, as shown in Figure 2, and an open position, as shown in Figure 3. In the closed position, spring 42 is slightly compressed, biasing window assembly 31 to the closed position sufficiently to generally maintain that position. Window assembly 31 can be moved to the open position by applying an external force outwardly from saw guard 26. The window assembly 31 then rotates about its axis to partially expose aperture 46. Opening window assembly 31 causes spring 42 to compress and thereby to exert an increased bias on window assembly 31 to the closed position. Further opening of window assembly 31 is prevented when pin 41 contacts stop pin 38. If pin 41 deflects downwardly due to increased pressure, fully compressed spring 42 will also prevent further opening of the window. In the open position, the inside portion of window 32 may be cleared of dust by a brush or other cleaning instrument. After cleaning operations are complete, window assembly 31 is released and thereupon returns to the closed position through the force exerted by spring 42. Alternatively, window assembly 50, comprised of a frame 52 and a window 54, may be biased to the closed portion using a torsion spring 56 as shown in Figure 7. As is apparent, window assembly 31 provides easily manufactured and efficient structure to allow easy cleaning of a viewing window. Figure 8 shows another window assembly embodying the principles of the present invention. In this embodiment, saw guard 26 is provided with an aperture 59. Located in saw guard 26 proximate the aperture are the tabs 60, 62, 64 and 66 forming a lateral slot. A window 58 is slidably coupled with saw guard 26 by insertion into the slot formed by tabs 60, 62, 64 and 66. Window 58 is sufficiently larger than the aperture to enable the window to slide a sufficient distance for cleaning. In operation, window 58 slides laterally in the direction of the arrow shown in Figure 8 to substantially expose the portion of the window 58 that had previously covered aperture 59 as shown in broken lines. This portion of the window may be cleaned with a brush or other appropriate material. Figure 9 shows another window assembly embodying the principles of the present invention. In this embodiment, saw guard 26 is provided with an aperture 72 covered by a window 68. A pivot pin 70 or other suitable fastener passes through window 68 and through an aperture in the periphery of saw guard 26. For reasons of mechanical geometry arising from placement of pivot pin 70, both window 68 and aperture 72 are preferably triangular shaped. Window 68 is furthermore larger than aperture 72 and is able to move from side to side. In operation, an external force is applied to window 68 causing it to pivot a desired distance in the direction of the force. Because window 68 is larger in size than aperture 72, the portion of window 68 previously covering the aperture can be exposed for cleaning as shown by the broken lines in Figure 9. Figure 10 shows another window assembly embodying the principles of the present invention. In this embodiment, a first aperture 76 in saw guard 26 is covered by a window 74. Saw guard 26 is further provided with a second aperture 78 proximate and generally perpendicular to aperture 76. Aperture 78 can be covered by a removable plug 80. In operation, plug 80 is removed to enable a cleaning tool or compressed air to be introduced through aperture 78 to dislodge dust from the underside of window 74. Figure 11 shows another window assembly embodying the principles of the present invention. In this embodiment, saw guard 26 is provided with an aperture 82. A window assembly 83 is adapted to be coupled with saw guard 26. Window assembly 83 is comprised of a transparent elongated, planar element 84 having planar ribs 86, 88, 90 and 92 disposed longitudinally on, and perpendicular to, planar element 84. Pivot pins 94 and 96 are located on opposite ends of element 84 along its, longitudinal centre axis. Pin guides 98 and 100 are provided in saw guard 26 to complementally receive pins 94 and 96. A pin retainer 102 is placed over pivot pin 94 to retain its position in pin guide 98. Pin retainer 102 is held in place by fasteners 104 and 106. Similarly, a pin retainer 108 is placed over pivot pin 96 to retain its position in pin guide 100. Pin retainer 108 is held in place by fasteners 110 and 112. In operation, window assembly 83 is shown in a closed position in Figure 12, whereby element 84 covers aperture 82. Window assembly 83 can be rotated about its longitudinal axis defined by pins 94 and 96 to permit cleaning. During rotation, planar ribs 86, 88, 90 and 92 serve to minimise exposure of aperture 82. Figures 13(a) and 13(b) show another window assembly embodying the principles of the present invention. In this embodiment, saw guard 26 is provided with a housing 113 with an aperture 114 formed therein and arranged to be substantially flush with the contour of the saw guard 26. A further aperture 116 is formed proximate and generally perpendicular to aperture 114. It can be seen from Figures 13(a) and 13(b) that the aperture 114 is formed so as to be standing slightly proud of the general periphery of saw guard 26. This is so that a cover member 118 can be held within the aperture 114. The cover member 118 extends in a direction generally orthogonal to the axis of rotation of the saw 21 and is at least twice the length of the aperture 114 itself in this direction. Furthermore, the cover member 118 is able to move along this direction within the aperture 114. As can be seen from the Figure, the end 120 of the cover member 118 adjacent the aperture 116 is formed with a downwardly facing ramp 122. This ramp 122 is formed to ensure that when the cover member 118 is fully retracted within the aperture 114, it sits flush with the outer surface of the guard 26. Movement of the cover member 118 within the aperture is controlled by a manually operable switch 124. The switch 124 couples directly to an edge of the cover member 118 and so movement of the switch 124 in a direction as shown by the arrows in the Figure causes the cover member 118 to move. The switch is confined to move along a recess 126 (not shown) also formed within the guard 26. Moving the switch 124 so as to cause it to travel to its extreme limit along recess 126 causes the cover member 118 to project as far as possible out of the aperture 116, as shown in Figure 13 (b). This then allows the user to clean the underside of the cover member 118. It will be appreciated that, due to the length of the cover member 118 being at least twice that of the aperture 114, then even with the cover member at its full projection out of aperture 116 (as shown in Figure 13(b)), the cover member still fills aperture 114. In this manner the aperture 114 is never without at least a portion of the cover member 118 filling it, i.e. the cover member 118 always covers the aperture 114. This provides an enhanced safety feature in the event that the saw 21 is operated whilst the user is cleaning the cover member 118. It is advantageous to have the rearward portion 128 of the viewing cover member 118 formed in a semi or totally opaque material. This could even be achieved by simply frosting of the rearward portion of the cover member 118 itself. This feature offers the advantage of reminding the user that the cover member 118 is in its "cleaning" position because the opacity prevents the blade 21 from being seen, until the cover member is returned to its "rest" position.

Claims: A guard assembly for a hand-held circular saw, the assembly comprising a guard (26) having an aperture (46), and an at least partially optically transmissive member (32) adapted to be coupled with the guard and to be movable between a closed position, wherein the member substantially covers the aperture, and a cleaning position, wherein at least part of the member is available for cleaning, characterised in that the member at least partially obstructs access to the aperture in the cleaning position. An assembly according to claim 1, further comprising means for biasing the member to the closed position. An assembly according to claim 2, characterised in that the biasing means includes a spring (42, 56). An assembly according to claim 3, characterised in that the biasing means includes a torsion spring (56). An assembly according to claim 3 or 4, characterised in that the biasing means includes a compression spring (42). An assembly according to any one of the preceding claims, characterised in that the member is further adapted to rotate about an axis substantially parallel to the rotational axis of the saw blade. An assembly according to claim 6, further comprising means for limiting the rotation of the member to less than 90 degrees to prevent the aperture from being fully uncovered. An assembly according to claim 7, further comprising a frame (34) carrying the member and wherein the rotation limiting means includes an elongated slot (40) formed in the frame and a stop pin (38) extending from the guard into said slot and the biasing means includes a compression spring (42) disposed longitudinally in the slot between the stop pin and one end of the slot. An assembly according to any one of the preceding claims, further comprising means for positioning the member between a use position and a cleaning position to allow the cleaning of said member without substantially uncovering the aperture during movement. An assembly according to claim 9, characterised in that the member (68) is larger in size than the aperture (72) and the positioning means includes a pivot arrangement (70) coupling the member with the guard to allow the member to pivot over the aperture between the use position, wherein one section of said member covers the aperture, and the cleaning position, wherein said one section may be cleaned. An assembly according to claim 10, characterised in that the member is triangular in shape. An assembly according to claim 9, characterised in that the member (58) is further adapted to slide between the use position and the cleaning position. An assembly according to claim 12, characterised in that the member (58) is larger in size than the aperture and wherein the positioning means includes tabs (60, 62, 64, 66) secured to the guard forming a slot that receives said member and through which the member can slide between the use position and the cleaning position. An assembly according to claim 13, characterised in that the member (58) is rectangular in shape. An assembly according to claim 9, characterised in that the member (68) is further adapted to rotate about an axis substantially lying in the plane of the saw blade and extending radially from the centre of the saw blade (21). An assembly according to claim 9, characterised in that the member (83) is further adapted to rotate about an axis substantially lying in the plane of the saw blade and perpendicular to the radius of the saw blade. An assembly according to claim 16, characterised in that the member (83) further comprises an elongated, planar element (83) having at least two planar ribs (86, 88) substantially disposed longitudinally on, and perpendicular to, the element and wherein the positioning means includes a pivot pin (94, 96) extending from each end of the member along its centre longitudinal axis, each said pin being received in pin guides (98, 100) on the guard so that the member can rotate in the aperture between the use position, wherein one section of the member covers the aperture, and the cleaning position, wherein the one section may be cleaned. An assembly according to any one of the preceding claims, wherein the guard comprises a housing (113) having a first aperture (114) and a second aperture (116) proximate the first aperture; and wherein said member comprises a cover member (118) coupled with the housing (113) to cover the first aperture (114), wherein the cover member (118) is moveable between a first position in which substantially all of the cover member is within the housing (113) and a second position wherein at least a portion of the cover member (118) protrudes out of the housing (113) via the second aperture (116), and wherein the cover member (118) always covers the first aperture (114). An assembly according to claim 18, further comprising a switch (124) coupled with the cover member (118) to permit manual movement of the cover member (118). An assembly according to claim 19, characterised in that the second aperture (116) is disposed substantially perpendicular to the first aperture (114). An assembly according to claim 18, characterised in that the housing (113) is formed integrally with the guard (26). An assembly according to any of claims 18 to 21, characterised in that a portion of the cover member (118) is generally opaque and covers the first aperture (114) when the cover member 118 is in the second position. An assembly according to any one of claims 1 to 17, wherein the guard comprises: a housing having a first aperture (76) and a second aperture (78) proximate said first aperture; and a removable plug (80) covering said second aperture to allow cleaning of a window (74). An assembly according to claim 23, characterised in that the second aperture (78) is disposed substantially perpendicular to said first aperture. An assembly according to claim 24, characterised in that the plug is press fittable into said second aperture.

Inventors: CAMPBELL DAVID C, HESLOP GALE A, LENTINO LYNN E, SELL MICHAEL R, WATSON BRIAN, CAMPBELL, DAVID C, HESLOP, GALE A, LENTINO, LYNN E, SELL, MICHAEL R, WATSON, BRIAN
Applicants: BLACK & DECKER INC, BLACK & DECKER INC.
Application year: 1997
Main classification: B27G19
IPC codes: B27G19, B23D59