Locking system

Abstract: A compound miter saw has a unique locking system for locking the bevel angle support housing (32) to the table assembly (14) once the desired bevel angle has been set. The locking system includes a cam (52) and a handle (54) each with an angular cam surface (64,66). When the two cam surfaces (64,66) are aligned, the support housing (32) is free to pivot around a supporting shaft (40). When the handle (54) is rotated on the shaft (40), the two cam surfaces (64,66) are moved to a non-aligned position. This non-alignment of cam surfaces (64,66) causes axial movement of the cam (52) along the shaft (40) which in turn forces the support housing (32) against the table assembly (14) to lock the support housing (32) in the desired bevel angle.

Description: The present invention relates to a device for performing operations on a workpiece according to the preamble of claim 1 and as known for example from US-A-5.235.889. Devices of this kind include compound miter saws or other power operated equipment or machinery utilising a cutter for performing working operations on a workpiece. More particularly, the present invention relates to improvements in the locking mechanism for the bevel adjustment for such power operated equipment, with the locking mechanism having an adjustable cam lock arrangement for locking the bevel pivot/support housing to the table at any desired bevel angle. Saws and other apparatus designed for cutting or performing other working operations on a workpiece typically require adjustment mechanisms for moving the saw blade or cutting tool into an angular relationship to the workpiece. Examples of such equipment include cross-cut compound miter saws which are adapted to allow the user selectively to move the saw blade into any of a number of positions or modes for square cutting, miter cutting, bevel cutting, or compound miter cutting where a combination miter angle and bevel angle are cut. In addition, some operations, such as dado cutting or shaping operations, for example, require the use of saw blades or other cutting or working devices of different shapes or sizes to be substituted for one another in order to perform the desired operation on the workpiece, depending on whether the workpiece is composed of wood, plastic, metal or other materials. In order to allow for the adjustment in the miter and the bevel angle, the saw blade, cutter or other working device is angularly adjustable with respect to a horizontal base and a vertical fence against which the workpiece is positioned. The miter adjustment allows the saw blade, cutter or other working device to move angularly with respect to the vertical fence while maintaining perpendicularity with the horizontal base. The bevel adjustment allows the saw blade , cutter or other working device to move angularly with respect to the horizontal base while maintaining perpendicularity with the vertical fence. At times it may be desirable to cut a combination miter angle and bevel angle by simultaneously adjusting the angularity of the blade with respect to both the horizontal base and the vertical fence. Once the saw blade, cutter or other working device has been adjusted to the desired position with respect to the horizontal base and the vertical fence, locking mechanisms for the miter and bevel adjustment must be activated in order to prohibit movement of the saw blade, cutter or other working device with respect to the base and fence while the cutting operation is performed. These locking mechanisms need to be easily activated, adjustable and quick acting in order to optimise the efficiency of the cutting apparatus and provide convenience to the operator of the apparatus. US patent no 5,235,889 discloses a locking mechanism for bevel adjustment in which the support housing for the saw comprises a conically tapered recess within which a conically tapered extension of the saw table can be received, so that the support housing can rotate about a pivot axis which is also the common axis of the conically tapered recess and extension. A shaft is provided with a handle at its first end and a screw threaded portion at its second opposite end which screw threaded portion threadedly engages a screw threaded recess in the extension of the saw table. The shaft is located co-axially with the conically tapered recess and extension and a part of the support housing is mounted on the shaft in such a way that it cannot move axially on the shaft. Thus, when the shaft is rotated by the rotation of the handle, the screw threaded portion moves further into or out of the extension of the saw table (depending on the direction of rotation) to clamp together or release the conically tapered recess in the support housing and the conically tapered extension of the saw table. However, a drawback of this type of locking mechanism is that it can be difficult to actuate, because several rotations of the handle are required to lock or unlock the support housing. The present invention, provides a device for performing working operations on a workpiece, characterised in that the device comprises a table having a shaft fixedly secured to the table; a support housing supporting a motor and a working tool driven by the motor, the support housing being disposed on the shaft adjacent to the table, the support housing being axially movable along the pivotable around the shaft; a cam disposed on the shaft adjacent to the support housing, the cam being axially movable along but not rotatable with respect to the shaft, and a handle disposed on the shaft adjacent to the cam, the handle being rotatable with respect to the shaft but not axially movable with respect to the shaft in a direction away from the cam such that rotation of the handle on the shaft urges the support housing into contact with the table. The locking mechanism includes a base or table assembly having an axially extending locking rod and a bevel support housing disposed on the locking rod such that the housing can move axially along the rod as well as pivot on the rod. The axial movement permits the locking of the housing to the base and the pivoting movement permits the desired adjustment to the bevel angle. A cam is positioned on the rod adjacent to the housing such that it can move axially on the rod but it is not allowed to rotate with respect to the rod. The double cam includes an angular cam surface which abuts a second angular cam surface located on a locking handle. The locking handle is positioned on the rod adjacent the cam such that it cannot move axially on the rod in a direction away from the cam but it is free to rotate with respect to the rod. When the two cam surfaces are aligned, the support housing can be pivoted on the rod in order to adjust the bevel angle. Once the desired bevel angle has been attained, the locking handle is rotated on the rod mis-aligning the two camming surfaces resulting in the axial movement of the support housing into engagement with the base or table assembly, locking the support housing to the base. The adjustment to the locking mechanism is achieved by rotating a locknut which axially locates and secures the various components on the locking rod. An embodiment of a device according to the invention will now be described with reference to the accompanying drawings in which; In the drawings which illustrate the best mode presently contemplated for carrying out the present invention: Figure 1 is a front perspective view of a sliding compound miter saw in accordance with the present invention; Figure 2 is a front elevational view of the sliding compound miter saw shown in Figure 1; Figure 3 is a rear elevational view of the sliding compound miter saw shown in Figures 1 and 2; Figure 4 is a side elevational view of the sliding compound miter saw shown in Figures 1 to 3; Figure 5 is an exploded perspective view of the bevel cam locking mechanism in accordance with the present invention; Figure 6 is an assembled perspective view, partially in cross-section of the bevel cam locking mechanism shown in Figure 5; Figure 7 is a cross-sectional side view of the locking mechanism shown in Figure 5; and Figure 8 is a end view of the base or table assembly illustrating the adjustment feature provided for the positive stop. Referring now to the drawings in which like reference numerals designate like or corresponding parts throughout the several views, there is shown in Figures 1 to 4 a sliding compound miter saw incorporating a cam locking mechanism according to the present invention, shown for the purposes of illustration, and designated generally by the reference numeral 10. The principles of the present invention are equally applicable to sliding compound miter saws, compound miter saws, chop saws, radial arm saws, table saws or other saws of types other than that shown for purposes of illustration in the drawings. Similarly, the principles of the cam locking mechanism according to the present invention are also applicable to other types of powered or unpowered equipment for performing an operation on a workpiece. Such equipment includes, but is not limited to, dado saws, spindle shapers or sanders, or other types of powered or unpowered devices that would benefit from the cam locking mechanism of the present invention. Referring primarily to Figures 1 to 4, sliding compound miter saw 10 comprises a base assembly 12, a table assembly 14, a unique housing assembly 16, a saw blade 18, a blade guard 20, a motor 22 drivingly connected to saw blade 18, a handle 24 and a fence assembly 26. Table assembly 14 is secured to base assembly 12 such that it can be rotated in order to provide adjustment for miter cutting. The rotation of table assembly 14 changes the angle of saw blade 18 relative to fence assembly 26 but maintains the perpendicularity of saw blade 18 with table assembly 14. A locking mechanism 28 can be activated in order to lock table assembly 14 to base assembly 12. Housing assembly 16 is secured to table assembly 14 such that it can be pivoted with respect to table assembly 14 in order to provide adjustment for bevel cutting. As can be appreciated by one skilled in the art, the adjustments for mitering and beveling can be separate or they can be adjusted simultaneously in order to provide a compound miter and bevel cut. The pivoting of housing assembly 16 changes the angle of saw blade 18 relative to table assembly 14 but maintains the perpendicularity of saw blade 18 with respect fence assembly 26. A locking mechanism 30 can be activated in order to lock housing assembly 16 to table assembly 14. Referring to Figures 1 to 5, the present invention is directed towards housing assembly 16 and locking mechanism 30 which locks housing assembly 16 to table assembly 14 at any desired bevel angle. Housing assembly 16 includes support housing 32, which mounts a pair of support arms 34 for sliding movement with respect to housing 32. Saw blade 18, blade guard 20, motor 22 and handle 24 are all mounted to a drive housing 36 which is pivotably secured to support arms 34. The pivoting of drive housing 36 downward towards table assembly 14 operates to open blade guard 20 and cut a workpiece which is supported by table assembly 14 and fence assembly 26. The sliding movement of support arm 34 relative to housing 32 permits drive housing 36 and thus saw blade 18 to be pulled through the workpiece when the size of the workpiece exceeds the cutting width of saw blade 18. Referring now to Figures 5 to 8, support housing 32 is pivotably supported with respect to table assembly 14 on a steel shaft 40 which is secured to table assembly 14 and extends rearwardly from table assembly 14 to define a pivot axis 42 for support housing 32. Shaft 40 is inserted into a complimentary bore 44 located within table assembly 14 and is secured in place using a cross pin 46 which extends through a bore 47 extending through shaft 40 and a corresponding set of bores 48 located within table assembly 14 and being generally perpendicular to and extending into bore 44. The end of shaft 40 opposite to the end defining bore 46 includes a threaded stub 50 for retaining and adjusting locking mechanism 30 as will be described later herein. Locking mechanism 30 comprises a cam 52, a handle 54, a thrust bearing 55, a plurality of washers 56 and a locknut 58. Once support housing 32 is slidingly and pivotably received on shaft 40, cam 52 is slidingly positioned on shaft 40 adjacent support housing 32. Cam 52 includes a D-shaped through bore 60 which mates with a corresponding D-shaped portion 62 of shaft 40 such that cam 52 is allowed to move axially along portion 62 of shaft 40 but rotation of cam 52 with respect to shaft 40 is prohibited. Cam 52 further includes an angular camming surface 64 having a plurality of ramps which is located on the radial surface of cam 52 which is opposite to support housing 32. Camming surface 64 is designed to mate with handle 54 as will be described later herein. Handle 54 is slidingly and rotatably positioned on shaft 40 adjacent to and outboard of cam 52. Handle 54 includes an angular camming surface 66 having a plurality of ramps which mates with angular camming surface 64 on cam 52. Support housing 32, cam 52 and handle 54 are retained on shaft 40 by thrust washer 55, the plurality of washers 56 and locknut 58 which is threadingly received on stub 50 of shaft 40. When angular camming surface 64 and angular camming surface 66 are in full contact with each other as shown in Figure 7, support housing 32 is free to pivot on shaft 40 to change the bevel angle of saw blade 18. Once the desired bevel angle has been set, handle 54 is rotated with respect to shaft 40. Rotation of handle 54 mis-aligns camming surfaces 64 and 66 pushing support housing 32 and cam 52 axially along shaft 40. Support housing 32 contacts table assembly 14 and continued rotation of handle 54 forces support housing 32 into table assembly 14 locking the two components together. The locking of the two components together can be accomplished by rotating handle 54 in either a clockwise or a counter clockwise direction on order to mis-align camming surfaces 64 and 66. This bi-directional locking ability of handle 54 simplifies the adjustment of the bevel angle on opposite sides of centre. An indicator plate 68 is bolted to support housing 32 to allow the user to set a specific bevel angle. Indicator plate 68 is provided with a pair of slots which allow for the zero adjustment of plate 68 as is well known in the art. The present invention also incorporates two additional features within housing assembly 16. These two features are a detent system 70 and a positive stop system 72. Detent system 70 includes a biasing spring 74 and a ball 76. Biasing spring 74 and ball 76 are inserted into a blind aperture 78 located within support housing 32. The ends of aperture 78 are formed over ball 76 such that ball 76 is retained within aperture 78 while being biased by spring 74 against the formed ends of aperture 78. Table assembly 14 includes a pair of detents 80, Figure 8, which are formed into the face of table assembly 14. The position of detents 80 are selected such that ball 76 will drop into detent 80 when the bevel angle for support housing 32 reaches 31.62° either side of centre. A bevel angle of 31.62° is desired when miter saw 10 is being set to cut cove moulding. While the present invention is illustrated as having only one pair of detents 80, it is within the scope of the present invention to provide additional detents located at additional bevel angles which are commonly used if desired. Positive stop system 72 comprises a biasing spring 82, a stop rod 84, an override button 86 and a plurality of adjustable stops 88. Biasing spring 82 is inserted into a stepped aperture 90 extending through support housing 32 such that it abuts the step formed within aperture 90. Stop rod 84 is then inserted through spring 82 and through aperture 90 trapping spring 82 between rod 84 and stepped aperture 90. A reduced diameter portion 92 of rod 84 extends through housing 32 and is inserted into a slot 94 formed within override button 86. Override button 86 is pivotably secured to a pair of posts 96 formed as a part of housing 32 by a pair of bolts 98. Once secured to posts 96, pivoting movement of button 86 moves stop rod 84 axially within housing 32 between a stop position and a release position with spring 82 biasing stop rod 84 into its stopped position. When located in its stopped position, stop rod 84 extends out of housing 32 and into table assembly 14 such that it can engage one of the plurality of adjustable stops 88 shown in Figure 8. Table assembly 14 is shown, in the preferred embodiment, having an adjustable stop 88 located at a 0° bevel angle and at a bevel angle of 45° on both sides of centre. Each adjustable stop 88 includes a housing 98 and a threaded stop bolt 100. Each housing 98 is shown as an integral part of table assembly 14 but it is within the scope of the present invention to manufacture individual housings 98 and secure them to table assembly 14 if desired. Each housing 98 defines a threaded through bore 102 into which stop bolt 100 is threadably received. Threaded stop bolt 100 provides a surface for stop rod 84 to contact when the bevel angle of housing 32 is located at 0° or ±45° from the O° bevel angle as is shown in the preferred embodiment. The adjustability of each stop 88 is provided by the threaded connection between bolt 100 and housing 98 and this adjustability allows the operator to accurately set these specific bevel angles. When the bevel angle needs to be changed, handle 54 is rotated to release housing 32 from table assembly 14 and override button 86 is pivoted on posts 96 to withdraw stop rod 84 from within table assembly 14 to a position at which stop rod 84 does not contact bolt 100 or housing 98 when housing 32 is pivoted on shaft 40.

Claims: A device (10) for performing working operations on a workpiece comprising: a table (14) having a shaft (40); a handle (54) disposed on the shaft (40) a support housing (32) pivotable around the shaft (40) and supporting a motor (22) and a working tool (18) driven by the motor (22); characterized in that : the shaft (40) is fixedly secured to the table (14); the support housing (32) is disposed on the shaft (40) adjacent the table (14) and is axially moveable along the shaft (40); a cam (52) disposed on the shaft (40) adjacent to the support housing (32), the cam (52) being axially movable along but not rotatable with respect to the shaft (40), and the handle (54) is disposed adjacent to the cam (52). the handle (54) being rotatable with respect to the shaft (40) but not axially movable with respect to the shaft (40) in a direction away from the cam (52) such that rotation of the handle (54) on the shaft (40) urges the support housing (32) into contact with the table (14). A device according to Claim 1, characterised in that the cam (52) defines a first cam surface (64) and the handle defines a second cam surface (66), the handle (52) being rotatable between a first position where the first and second cam surfaces (64,66) are aligned thereby allowing movement of the support housing (32) and a second position where the first and second cam surfaces (64,66) are non-aligned thereby urging the support housing (32) into contact with the table (14) to prohibit movement of the support housing (32). A device according to Claim 1 characterised in that it further comprises a detent system (70) for releasably positioning the support housing (32) in at least one pivotable position with respect to the table (14). A device according to Claim 1 characterised in that it further comprises a locking system (72) for releasably locking the support housing (32) in at least one pivotable position with respect to the table (14). A device according to Claim 4 characterised in that the locking system (72) is capable of angularly adjusting the at least one position. A device according to Claim 1, characterised in that the device is a compound miter saw.

Inventors: BRUNSON MARK E, STUMPF WILLIAM R, BRUNSON, MARK E, STUMPF, WILLIAM R
Applicants: BLACK & DECKER INC, BLACK & DECKER INC.
Application year: 1996
Main classification: B23D45
IPC codes: B27B5, B23D47, B23D45, B23Q1