BACKGROUND OF THE INVENTION

Field of the Invention This invention relates to visual cut line indicators for power cutting equipment, for example circular saws. More particularly, the invention relates to improved power cutting equipment of the type where a visual indication of the cut line is projected into a work place to be cut by the cutting equipment.

Description of Related Art

Cut line indicators allow an operator to more accurately relatively position a workpiece and a cutting element, such as a saw blade, to cut the workpiece. However, with conventional cut line indicators great skill and care must be exercised by the operator to cut only at the desired location on the workpiece. Time and training is required to develop this necessary skill. When cutting using such equipment, even a skilled operator must take the time to carefully align the workpiece for an accurate cut using conventional equipment, and even then a skilled operator may miscut a workpiece due to incorrect estimation of the alignment of the saw blade and the workpiece.

Using conventional power cutting equipment, for example a miter saw, an operator wishing to make a cut in a workpiece must visually line up a place desired to be cut on the workpiece with a plane of motion of a saw blade. Various means are used to assist the operator in this alignment. For example, conventional miter saws have a channel in a fence and a table that supports a workpiece. The channel receives the saw blade when the workpiece is being cut through, and there¬ fore can be used as a cut line indicator in determining where the cut in the workpiece will be made.

Since the channel necessarily is larger than the width of the saw blade, the exact position of the cut to be made is difficult to determine with precision. Moreover, a place desired to be cut on a convoluted surface (for example a molding) may be difficult to reference to the channel, as it may be interior to the edges of the workpiece.

The difficulties of making accurate cuts with conventional equipment are more stridently borne out in the situation where a workpiece is to be cut on an angle, as opposed to orthogonally. In this situation the point where the blade begins to cut the workpiece may appear to an operator to be displaced from the channel in a transverse direction due to the plane of cutting blade motion being disposed angularly to the operator. Lining up the place desired to be cut and the plane of blade motion is difficult even for an experienced user.

Furthermore, certain cutting equipment, for example radial aim saws and compound miter saws, allow adjustments of the saw blade for angular arts by rotation in two axes. This may further increase the difficulty of alignment, and increase the time required to perform the cutting operation may be increased.

In practice, experienced operators usually bring the blade into close proximity with the work piece to better estimate the position of the cut to be made. Many operators will actually bring the blade into contact with the work piece so that a very small portion of the work piece is removed, to determine where the cut line will begin on the work piece. This practice, sometimes referred to as "nibbling", as well as bringing the blade into close proximity, takes time and therefore detracts from productivity. Nibbling gives a precise indication of the beginning of the cut line through the work piece, but does not provide an indication of the direction of the cut through the work piece, which direction must still be estimated by the operator. This estimation can, of course, be done by the operator by visually aligning the operators eye

with the saw blade and mentally noting a projected path for the blade across the work piece. However, these procedures require additional time for the operator to carry out.

Analogous difficulties of alignment inherent in other types of cutting equipment have lead to various attempts to more accurately predict the cutting path of the cutting element of the cutting equipment. In particular, attempts have been made to solve this problem by projecting a shadow using a light source positioned behind the saw blade, or behind an object such as a wire or bar aligned with the blade, to provide the necessary reference for a cut line indicator.

Prior art devices using this method have a number of deficiencies, including the difficulty of aligning the light source, the wire or bar etc. (if such is used) and the cutting element, to give an accurate indication of the path of the cutting element. Elaborate provisions for this alignment have been provided in prior devices, requiring precise adjustment.

In prior art devices where the shadow of the cutting element is used as a cut line indicator, only one side of the cut to be made is indicated. This may require the operator to take the time to adjust the cut line indicator to the proper side of the cutting element, or to align the workpiece such that the waste side of the cut is properly aligned. In certain circumstances one or both of these options may be difficult, due, for example, to constraints of the work site, the size or dimensions of the workpiece, or immobility of the workpiece. These adjustments therefore may be difficult and time consuming.

Other arrangements, including projecting a laser beam aligned with the saw blade path have been used. These devices employing a laser beam are costly, and also have the same inherent difficulty of alignment with the cutting element path discussed above.

Also, changing the cutting element, such as a saw

blade, to one of another type may affect the alignment of the cut line indicator as saw blades vary in width. This change of alignment, or any other adjustment of the relative position of the saw blade requires the cut line indicator alignment to be adjusted.

Furthermore, prior art cut line indicators may require periodic adjustment due to misalignment caused by vibration of the equipment causing the elements to creep out of alignment, bending of mountings or brackets, etc. due to accidental contact with other objects or the operator, and thermal effects. Again, the requirement of adjustment reduces productivity due to the time involved, and is inconvenient for the operator.

Lastly, certain prior art cut line indicators of the type where a shadow line is projected do not take into consideration varying light conditions wherein the cutting equipment may be operated. Such prior art equipment may work as intended in subdued or indoor lighting but would be ineffective in bright sun light. Since various types of cutting equipment are used outdoors this can be a serious drawback.

Those concerned with the development and use of cut line indicators of this type have long recognized the need for an improved cut line indicator that retains the inherent advantages of prior art configurations, while reducing or eliminating the problems with prior art indicators discussed above. The present invention fulfills these needs.

SUMMARY OF THE INVENTION

Briefly, and in general terms, the present invention provides an improved visual cut line indicator for cutting equipment, having a collimated light source positioned and directed such that a shadow of the cutting element of a cutting apparatus is projected onto a workpiece, which coincides with the path of the cut about to be made, giving a user an accurate

indication of both edges of the cut. This allows the user to accurately position a workpiece for cutting on either side of a saw blade or other cutting element.

A colli ator is placed between a source of light and the cutting element to collimate the light emanating from the source of light, at least in one direction. A source of light capable of producing light of sufficient intensity to project a shadow, even in bright sun light, is provided. The intensity of the light is adjustable, to provide for use in different ambient light conditions, such as indoors or outdoors. Reflective and non-reflective surfaces adjacent the collimated light source and the cutting element are provided to further enhance the intensity and/or collimation of projected light. These improvements result in a shadow line indication which has improved characteristics. The edges of the shadow can be made quite sharp, and by adjusting the distance from the source of light to the blade and/or the collimation of the light, the edges of the shadow can be made to correspond exactly with the cut.

The cut line indicator is fixedly attached to the cutting apparatus and requires no adjustments. Collimation of the light minimizes the difficulty of aligning the light source with the cutting element, as the cutting element blade may be moved laterally within the light beam a small distance (such as may occur in changing to a different kind or thickness of blade) without effecting the operation of the cut line indicator.

The light may be collimated in one direction only, so that the light beam giving rise to the shadow line is projected in wide arc in one direction, and confined to a narrow band in the transverse direction. This gives rise to a shadow line longer in length, and allows the shadow line to be continuously projected on the workpiece through relatively large rotation and translation movements of the cut line indicator mounted adjacent the cutting element.

Additionally, the collimated light source may be turned on and off independently of the cutting apparatus, to improve bulb life and decrease heat build up. The intensity of the light may also be varied by a user to compensate for differing ambient light conditions, for example indoor versus outdoor use.

Other features and advantages the present invention will become apparent from the following detailed description, with the accompanying drawings, which illustrate, by way of example, the features of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a prospective view of cutting equipment embodying a cut line indicator according to the invention configured for cutting; FIG. 2 is a prospective view, partially in section, of a cut line indicator according to the invention, illustrating a portion of the cutting equipment illustrated in FIG. 1;

FIG. 3 is a side elevational view, partially in section, of another embodiment of the cut line indicator according to the invention;

FIG. 4 is a sectional view of a cut line indicator according to the invention taken along lines 4-4 in FIG. 3;

FIG. 5 is a side elevational view, partially in section, of another embodiment of a cut-line indicator according to the invention;

FIG. 6 is a sectional view of a cut line indicator according to the invention taken along lines 6-6 in FIG. 5;

FIG. 7 is a side elevational view, partially in section, of another embodiment of a cut line indicator according to the invention; and

FIG. 8 is a sectional view of a cut line indicator according to the invention taken along lines 8-8 in FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in the drawings, which are provided for purpose of illustration and not by way of limitation, the invention is embodied in a saw 10 of the type having a saw blade 11 as a cutting element for cutting a workpiece 12. The saw described herein is a miter saw; however it will be apparent to one skilled in the art that the invention could be embodied in any of a number of saw types, for example: radial arm saws; chop saws; and hand held circular saws.

Referring to figure 1, in accordance with the present invention a light source comprising a light bulb 13, is carried by a housing 14 fixedly mated or otherwise integral with a shroud 15 partially enclosing a saw blade 11. The light source projects light rays 20 through a slotted portion of the shroud defining a slot opening 30 and onto the workpiece 12 which is placed upon a table 21, and made to abut a fence 22. The workpiece is thus positioned relative to the saw blade 11 in a conventional manner. The light rays 20 are interrupted by the saw blade 11, which casts a shadow line 23 onto the workpiece.

An operator (not shown) perceives the location of the cut to be made in the workpiece 12 by means of the shadow line 23, and can easily adjust the relative position of the workpiece 12 to obtain an accurately located cut. Movement of the blade 11 is confined to a plane containing the blade and the shadow line 23, and is in an arc. The operator grasps a handle 24 and rotates a portion of the miter saw 10 (including a motor 25 as well as the blade 11 and shroud 15 carried on an arm 27 rotatably connected to a base 26) downward toward the workpiece, as is conventional in saws of this type. As the blade 11 travels in a plane that contains the saw blade 11 as well as the shadow line, the cut to be made is indicated by the shadow line 23 regardless of the position of the blade.

That the shadow line 23 comprises a narrow strip indicating the path of the blade 11, which can be made to correspond exactly to the width of the cut to be made and

therefore shows precisely the material to be removed in cutting. This is done by collimating the light 20 projected from the light source 13 in a direction orthagonal to the plane containing the blade 11, to provide a collimated light projection that contains light rays 20 that are directed substantially parallel to the plane of the blade 11. This is done by placing a collimation means between the light source 13 and the blade. A slot 30 in the shroud 15 is provided for this purpose in the illustrated device.

The relative distances between the light source 13, the slot 30, and the blade 11 are fixed at values which result in a shadow line 23 of the desired width. Once these distances are determined for a particular saw 10, it has been found that changing the blade 11 to one of slightly different thickness produces a shadow line of corresponding larger or smaller thickness so that the accuracy of the cut line indication is not effected by changing the saw blade. Also, the blade may be slightly displaced within the projected light by a small amount, such as may occur in changing the blade, without affecting accuracy. Thus adjustments necessary in prior art devices are not required.

Electrical power is conveyed to the light source 13 by means of a power cord 31 in a conventional manner. A switch 32 is employed in the illustrated embodiment to turn the light source 13 on and off independently of the saw 10. This allows a user to investigate the location of a cut to be made on a workpiece even before turning on the power to the saw, for example by means of a second switch 33. Turning on the light source only when needed may lengthen the service life of the bulb 13 and will decrease heat build up in the housing 14 in which the light source is mounted.

In another embodiment, the intensity of the light projected from the light source 13 may be varied by a further switch or dial (not shown) conventionally controlling power to the light source for that purpose. This may be convenient in using the saw 10 in differing ambient light conditions, for

example indoors vs. outdoors.

Referring now to FIG. 2, the housing 14 is fixedly attached to the shroud 15 by means of a mounting flange 34 on each of two opposite sides of the housing, and fasteners 35 such as bolts or screws. The light source 13 is carried by a cap portion 36 which is releasably attached to the rest of the housing 14. This allows the light source to be easily accessed for cleaning and to change the light bulb. Ventilation holes 37 are provided to decrease heat build up within the housing. The housing may be tipped somewhat in relation to the shroud 15 so that light rays 20 are directed so as to miss a shaft (not shown) which carries the blade 11.

The light bulb 13 is chosen on the basis of the intensity of the light projected, and preferably will cast a shadow 23 in bright sunlight when incorporated in the cut line indicator of the invention. Moreover, it has been found that certain light bulbs which somewhat collimate the light projected from the bulb work well for this application. For example, model 7 RM 19/25° Spotline™, or models 75 PAR 30/H/NSP, or 50 PAR 20/H/NSP halogen bulbs, all manufactured by the Phillips corporation may be employed. The halogen types are better suited to outdoor use. These types of bulbs come in varying arc measurements of projected light, for example 20, 25, and 30 degrees of divergence of light rays 20. As will be appreciated, the particular amount of collimation achieved by the light bulb 13 is chosen according to application, and can determine the length of the shadow line projected.

Collimation of the light 20 from the light source 13 is performed by the slot 30 which has an elongated configuration and is relatively narrow in width. While precise dimensions are not critical, and the general configuration of the slot varies with each type of saw 10 used, a generally long narrow opening is required. A slot having a width of about 5/32 inch (.4 centimeters) has been found to work well. The length of the slot determines the length of the shadow line 23 projected by the cut line indicator, which for a miter saw 10,

for example, is preferably quite long. A long shadow line 23 is provided so as to fall on a workpiece 12 throughout the travel of the saw blade 11 through the arc of its motion on arm 27 during cutting. It has been found that a length of about 2 inches (5 centimeters) at a minimum for the slot 30 is desirable.

The slot 30 is aligned with the plane of the blade 11, and its elongated direction is parallel to the plane of the blade. Thus light is collimated in a direction perpendicular to the blade, as predominantly only light rays 20 having directions roughly parallel to the blade 11 escape through the slot to project upon the blade and workpiece 12. The light is not collimated in the direction of the long dimension of the slot, or is collimated to a much lesser extent, which gives the elongated shadow 23 projection mentioned above. In certain saw types, for example radial arm saws, a shorter shadow line 23 projection would be adequate, as the light rays 20 may be directed more in line with the inherent linear translational movement of the blade in a cutting operation. In such saw types a relatively shorter elongated dimension for the slot may be used.

In addition to the slotted collimation means, or in place thereof, other means of collimation of the light 20 may be used. For example there is shown in FIG. 2 an optical element 40 interposed between the light source 13 and the saw blade 11 to collimate the light 20 projected onto the blade and workpiece 12. The optical element is a lens, and is preferably a lens having only one direction of curvature, or optical axis, which type is commonly known as a cylindrical lens. The lens of this type collimates light in one direction only, thus allowing for a long shadow line 23 projection in an analogous way to the collimation provided by the slot 30 discussed above.

It will be apparent that the lens is configured so that the

• direction of collimation is perpendicular to the plane of the blade 11 and the direction in which the lens provides no collimation effect is parallel- to the plane of the blade.

If an optical element 40 is used, the relative distances between the light source, optical element 40, and the blade 11 would be determined a conventional manner in conjunction with the curvature of the lens to provide the desired collimation effect. Additionally, it will be apparent that an optical system, comprising two or more optical elements may be substituted for the single optical element 40 shown.

The optical element 40 may also serve to protect the light bulb 17 from flying debris. A non-collimating sheet of clear material may alternately be provided solely for this purpose. Provision for periodic disassembly and cleaning must be made so that accumulations, for example from sappy or wet sawdust, can be removed. For this reason releasable connections between elements is provided.

The optical element 40 is fixedly mounted in the housing 14 in any of the well known ways of mounting lenses. This may be done by use of adhesive for example. Particularly if the optical element is used alone to provide collimation, the slotted opening 30 can be enlarged. The optical element may be sealingly mounted within the housing, and this has the advantage of keeping the light source 13 free from sawdust etc. The housing may be removed from the shroud 15 to allow periodic cleaning of the optical element.

It will be apparent that other conventional means of collimation could also be employed to achieve the desired collimation effect. However, the use of a slot 30 to collimate the light 20 projected has the advantage of less cost. Also, the provision of relatively reflective and non-reflective surfaces, for example by smooth or rough surface treatments, within the housing in appropriate areas may further enhance the operation of the cut line indicator of the invention. For example, it has been found that roughening the surfaces within the shroud 15 which are parallel to the plane of the blade, for example plastic guards (not shown) , improves the sharpness of the shadow line 23 projected.

The particular embodiment illustrated in FIG. 2 demonstrates the capability to adapt a cut line indicator according to principles of the present invention to an existing saw 10. By making a slotted opening 30 in the shroud 13 of an existing cutting apparatus 10 and attaching the housing having mounting flanges 34 with fasteners 35, the cut line indicator of the invention is thus adapted. A template (not shown) may be provided for assisting a user in correctly locating the slot 30 and correct locations for fasteners to attach the housing 14 to the shroud 15. After attachment of the housing 14 of a pre- assembled cut line indicator to the shroud, a power cord 31 is connected to an electrical power source, enabling operation.

Referring now to FIGS. 3 and 4, another embodiment is illustrated. A light source 13 is mounted within a containment 41 carried within a housing 14. The housing is fixedly mated to the shroud 15 by two mounting flanges 34 and fasteners 35 in the manner before described. The housing is tilted slightly to avoid projecting the light from the light source 13 directly onto the shaft (not shown) which carries the blade 11 and is centrally located on the blade. The housing 14 is open between the two mounting flanges to allow light from the light source 13 to pass through the housing to the slot 30 in the shroud. The housing is provided with numerous ventilation holes to allow heat to escape and also serves to protect the user from contact with the containment 41 which may become hot.

The containment 41 protects the light source 13 from flying debris and is carried by a cap member 42 which releasably mates with the housing 14. The containment is attached to the cap by means of fasteners 43 through flange members 44 and 47. The containment is formed of aluminum in the illustrated embodiment. The containment embodies a window portion 45 which is covered with a glass sheet 46 which is releaseably attached to the containment by means of clips 48 rotatably connected to the containment 41. This allows access to the bulb 13 for cleaning and replacement of the bulb 13. The glass sheet incorporated in the containment window 45 is preferably formed of etched glass, thereby having a roughened

surface. It has been found that providing a roughened surface enhances the clarity of the projected shadow line 23.

The light source 13 in this embodiment is a tubular halogen bulb. This type of bulb provides an intense light projection 20 and hence a visible shadow projection 23 even in bright sunlight. The bulb is conventional and is available commercially from a number of manufacturers. It has been found that a 150 watt halogen bulb, model number 150T21/2/Q/CL/CO manufactured by ABCO, Inc, works well. Other lamps of this type, manufactured for example by Reliant, and Angelo Bros. Co. of Philadelphia Pennsylvania, work well also. The light source can be mounted in the containment 41 in any number of conventional ways. As illustrated in FIG. 3, sockets 50 and 51 defining the electrical connections for the light bulb 13 and releasably holding the bulb in place, are attached to the containment 41. Socket 50 is attached at an end of the containment opposite the cap member 42, and the second socket 51 is attached within the containment to an annular inwardly projecting flange member 52 of the containment. The sockets allow the bulb 13 to be removed in a lateral direction through window portion 45 of the containment, when etched glass 46 is removed. Power is provided to the light source 13 in a conventional manner by a power cord 31 which is threaded through an opening 56 in the cap 42.

Referring now to FIGS. 5 and 6, another embodiment of the invention is illustrated. Here the containment 41 carrying the light source 13 is provided with a fan 57 for propelling cooling air through the containment. This keeps the bulb 13 and the containment 41 cool during operation. Air vent holes 58 are provided in the containment and in a cap member 59 incorporating the fan, to allow flow of air. Cap member 59 is removable to access the fan and interior of the containment.

In this embodiment the containment 41 is attached to the shroud 15 by attachment member 60 which surrounds containment 41 and incorporates flanges 34 for attachment as in the other embodiments. Access to the bulb 13 is gained by

removing the attachment member 60 and the containment 41 from the shroud 15 and opening the window portion 45 of the containment, which is removable as before described.

Referring now to FIGS. 7 and 8, a further embodiment is illustrated wherein a different ventilation means is employed. In this embodiment the containment 41, similar to that described in conjunction with FIGS. 3 and 4, is carried by a housing 61 which has ventilation holes 58 only at a first end where the fan 57 is mounted. The housing 61 is open to the slot 30 in the shroud 15 and air exits the housing through the slot 30 in the shroud. This configuration results in less accumulation of debris within the housing 61 due to air currents exiting the slot 30 and a pressure surcharge within the housing tending to keep air-borne matter from entering the housing 61.

While several particular forms of the invention have been illustrated and described, it will also be apparent that various modifications and improvements can be made without departing from the spirit and scope thereof. Accordingly, it is not intended that the invention be limited, except by the appended claims.