The present invention relates generally to a magnetic locking system, and more particularly to a magnetic locking system for selectively locking a first component into a desired position with respect to a second component.

DISCLOSURE OF INVENTION Preferred embodiments of the present magnetic locking system can be used for releasably locking a first component to a second component. In one embodiment, the locking system includes a ferro-magnetic member associated with the first component, where the ferro-magnetic member is made of a ferro-magnetic material, and a housing attached to the second component and positioned adjacent to the ferro-magnetic member. Preferably, the housing includes first and second blocks that sandwich an intermediate block. Further, the first and second blocks are each preferably made of a ferro-magnetic material and the intermediate block is made of a non-ferro-magnetic material. Additionally, there is also an aperture formed within the housing, with a permanent magnet rotatably seated within the aperture. The magnetic locking system preferably includes a switch mechanism that is operatively connected to one of the permanent magnet and the housing, wherein the switch mechanism is configured and arranged to rotate the housing and the permanent magnet relative to each other between an "on" position and an "off position, where the "on" position enables the housing to significantly attract the magnetic ferro- material because, when the magnetic field is considered outside of the magnetic housing, the magnetic field defined during the "on" position is much greater than that defined during the "off position, which "off position only permits a negligible magnetic field to pass outside of the housing. In one alternative embodiment, an electromagnet is used in place of the housing and permanent magnet assembly of the other embodiment. In this alternative embodiment, the electromagnet, which is associated with the second component, is wired to a power supply and is activated by a switch. Once activated, the electromagnet exerts a magnetic force on the ferro- magnetic member, which his associated with the first component.

BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the present invention are described herein with reference to the drawings wherein: Figure 1 is a schematic representation of an embodiment of the magnetic lock of the present invention; Figure 2 shows a representation of the magnetic field lines of the magnetic lock of Figure 1 in the "on" position; Figure 3 shows a representation of the magnetic field lines of the magnetic lock of Figure 1 in the "off position; Figure 4 shows an example embodiment of a compound miter saw, which is one type of device within which the present magnetic lock may be employed; Figure 5 is a top view of the table and base of a compound miter saw similar to that shown in Figure 4; Figure 6 is a top view of the base portion of the compound saw shown with the table removed; and Figure 7 is a bottom view of the table portion of the compound saw shown without the base.

BEST MODE OF CARRYING OUT THE INVENTION Turning now to the drawings, embodiments of the present invention will be described, where Figure 1 shows one embodiment of a housing 10 of a magnetic lock, which is configured and arranged to have its magnetic force modified between an "on" position, where the housing 10 is attracted to a ferro-magnetic member, such as a steel plate (not shown), and an "off position, in which the housing 10 is not significantly attracted to the ferro-magnetic member. The ferro-magnetic member may be made of any ferro-material (which is a material that is attracted to a magnet), such as iron, steel, another alloy containing iron, etc. The housing 10 is preferably made of three blocks 12, 14, and 16, where the first block 12 and the second block 14 sandwich an intermediate block 16. The first block 12 and the second block 14 are made of a ferro- magnetic material, such as iron, and the intermediate block is made of a non- ferro-magnetic material, such as brass or aluminum. Preferably, the same ferro-magnetic material is used for both the first block 12 and the second block 14. Formed within the housing 10 is an aperture 18, which is preferably round in shape, and which is configured and arranged to accept a permanent magnet 20 therein. As can be seen in Figure 1, aperture 18 is preferably defined by a portion of the first block 12, a portion of the second block 14 and a portion of the intermediate block 16. Permanent magnet 20, which includes North and South poles as indicated in Figure 1 by the letters "N" and "S," and housing 10 are configured and arranged such that permanent magnet 20 can be rotatably seated within the aperture 18. A magnetic direction, represented by arrow 23, of the permanent magnet 20 will be defined as extending from the South pole (S) to the North pole (N) inside the magnet and extending from the North pole (N) to the South pole (S) outside the magnet. The permanent magnet 20 and the housing 10 can be rotated with respect to each other between an "on" position, in which the North and South poles of permanent magnet 20 are positioned with respect to the housing 10 as shown in Figure 2 (such that the magnetic direction is transverse to the blocks 12, 14 and 16), and an "off position, in which the North and South poles of permanent magnet 20 are positioned with respect to housing 10 as shown in Figure 3 (such that the magnetic direction is aligned with blocks 12, 14 and 16, i.e., generally perpendicular to the magnetic direction of the "on" position"). Rotation of one of the permanent magnet 20 and the housing 10 with respect to the other between the "on" position and the "off position is accomplished through the use of a switch mechanism, an example of which will be described hereinbelow. In the preferred embodiment, the permanent magnet 20 is preferably formed of a generally cylindrical shape, and the aperture 18 is of a corresponding generally circular shape in cross-section, such as shown in Figure 1, which permits relative rotation between these two components. Permanent magnet 20 creates a magnetic field, which is represented by the various field lines shown in Figures 2 and 3. In the "on" position of Figure 2, the magnetic field extends generally transverse to the first block 12, the second block 14 and the intermediate block 16. In the "off position of Figure 3, the magnetic field extends generally perpendicular to the magnetic field of the "on" position of Figure 2, and the magnetic field is confined within blocks 12 and 14. Thus, when the magnetic field is considered outside of the housing 10, the magnetic field defined during the "on" position is strong, but the magnetic field defined during the "off position almost nothing. More specifically, the permanent magnet 20 is preferably of a generally cylindrical shape, and it is magnetized along its diameter such that it includes a semi-cylindrical North pole section 22 and a semi-cylindrical South pole section 24, as shown in Figure 1. As also shown in Figure 1, in this embodiment, the first block 12 and the second block 14 each include an upper surface (26, 28, respectively), a lower surface (30, 32, respectively), a front surface (34, 36, respectively), an inner side surface (38, 40, respectively) facing the intermediate block 16 and an outer side surface (42, 44, respectively) facing away from the intermediate block 16. Additionally, in this embodiment, the intermediate block 16 also includes an upper surface 46, a lower surface 48, a front surface 50, a first side surface 52 facing the first block 12 and a second side surface 54 facing the second block 14. In this embodiment, the "off position of Figure 3 results when the permanent magnet 20 is aligned within the aperture 18 such that the North pole faces towards either the upper surface 46 of the intermediate block 16 or towards the lower surface 48 of the intermediate block 16 and the South pole faces toward the other of the upper surface 46 and the lower surface 48 of the intermediate block 16. In contrast, in this embodiment, the "on" position of Figure 2 occurs when the permanent magnet 20 is rotated relative to the aperture 18 by approximately 90 degrees with respect to the "off position of Figure 3. As can be seen from a review of the magnetic field lines of Figure 2, when switched to the "on" position, the magnetic field lines show how the magnetic field is essentially passing across and outside of the blocks 12, 14 and 16. Thus, the entire housing 10 acts like a single magnet that can attract a piece of iron or steel or other ferro-magnetic material placed within the magnetic field. In contrast, when the magnetic locking system is switched to the "off position of Figure 3, such as by rotating permanent magnet 20 by approximately 90 degrees with respect to the "on" position shown in Figure 3, the magnetic field lines show how the magnetic field is essentially maintained within the blocks 12 and 14, with the blocks acting like a magnetic keeper that absorb the majority of the magnetic flux. As a result, there is only a negligible amount of magnetic force acting outside of housing 10. Additionally, such force is not strong enough to noticeably attract a piece of iron or steel or other ferro-magnetic material placed in the vicinity of housing 10. The magnetic locking system of the present invention can be employed in a variety of different devices to releasably lock a first component to a second component, where the two components are free to move with respect to each other when the system is in the "off state, but where relative movement between the two components is prevented, or at least severely hindered, when the system is in the "on" state. The magnetic locking system of the present invention can be used to allow either relative rotation or relative linear movement between two components, and then releasably lock the two components into a desired position with respect to each other. In use, a plate made of steel (or other ferro-magnetic material) can be attached to the first component, and the housing 10 can be attached to the second component. Alternatively, if the first component is made of iron, steel or other ferro- magnetic material, there is no need for a separate steel plate because the housing 10 will be magnetically attracted to the material of the first component when the system is in the "on" state. The housing 10 and permanent magnet 20 can be replaced by an electro-magnet with an appropriate circuit (power source, wiring, and switch) if desired. Examples of the types of devices in which the present magnetic locking system can be employed include household and commercial power tools, furniture (such as swivel chairs), toys, kitchen devices (such as lazy susans), etc. As one example, the present magnetic locking system can be used in a compound miter saw (such as saw 70 of Figure 4), as either a means for locking the table into position or for locking the saw at the desired bevel angle. More specifically, when used as a bevel locking device, a ferro-magnetic member could be attached to an arm (such as arm 78 of Figure 4) that is rigidly attached to a table of a miter saw and the housing 10 could be affixed to a bevel post (such as post 80 of Figure 4) of a saw assembly of the miter saw, where rotation of the bevel post with respect to the arm angles the saw assembly with respect to the table to enable the saw to be used for making bevel cuts. Alternatively, the components of the magnetic locking system could be reversed, such that the housing could be attached to the arm and the ferro- magnetic member attached to the bevel post. Additionally, another example of an embodiment of the present magnetic locking device employed for use as a miter locking system in a miter saw will be described next, while referring to Figures 4-7. Figure 4 shows one example of a miter saw 70 that includes a saw assembly 72, a base 74, a table 76, an arm 78 attached to the table 76 and a bevel post 80 that allows the saw assembly 72 to be angled with respect to the table and base to perform bevel cuts. In miter saw 70, table 76 is configured to be able to rotate with respect to base 74, and the magnetic locking system is utilized to lock the table 76 into a locked position with respect to the base 74. Turning now to Figures 5-7, the base 74 and the table 76 of the miter saw 70 are shown in Figure 5 without the saw assembly; Figure 6 shows a view of the upper side of the base 74 without the other components of the miter saw; and Figure 7 shows an underside view of the table 76 without any other components. In this embodiment, a pair of magnetic locking systems are used, with each system including a housings 110 (Figure 7) on the table 76, a ferro- magnetic material in the form of a steel plate 90 on the underside of base 74 (Figure 6). This embodiment also includes a linkage assembly 96 (Figure 7) that is configured to switch the magnetic locking systems between the "on" and "off positions via manipulation of handle 82. It should be noted that two or more housings may be used together to increase the magnetic locking force, such as demonstrated by the use of two housings 110 in this embodiment. Turning now to Figure 7, the details of this embodiment will be explained. The housings 110 are each configured in the same manner as housing 10 of Figure 1. More specifically, each housing 110 includes a first block 112, a second block 114 and an intermediate block 116 positioned between the first and second blocks. Additionally, each housing 110 also includes a permanent magnet 120 that is seated for rotation within an aperture defined within all three blocks 112, 114, 116. As described above with respect to Figures 1-3, when the permanent magnet (20, 120) is rotated within housing (10, 110) to be at the "on" position of Figure 2, the magnetic flux extends in the transverse direction to create a larger magnet formed by the combination of the three blocks (12/112, 14/114, and 16/116). Accordingly, housings 110 will be attracted to steel plate 90 (Figure 6), and will lock the table 76 into a desired position with respect to the base 74. In contrast, when permanent magnet (20, 120) is rotated within housing (10, 110) to be at the "off position of Figure 3, the magnetic flux is essentially maintained within the housing (10, 110), and the housings 110 are not attracted to steel plate 90 (Figure 6). Accordingly, the table 76 is free to be rotated with respect to base 74. Next, a description will be provided of some details of linkage assembly 96, which is one method of rotating the permanent magnets 120 within the housings 110. As can be seen in Figure 7, the linkage assembly 96 includes a handle 82 that is operatively attached to a cam 84, which converts the rotary motion of handle 82 into linear motion that moves actuation beam 86 linearly along its longitudinal axis. The other end of actuation beam 86 is attached to a pair of eccentric disks 88, and each eccentric disks 88 is attached to an axial extension 92 of permanent magnet 120. Each axial extension 92 passes through an aperture in yoke 94, where the apertures provide enough clearance to allow the extensions 92 to rotate within the apertures. This combination of eccentric disk 88, axial extensions 92 and yoke 94 converts the linear motion of actuation beam 86 back into rotary motion to rotate the permanent magnets 120 within housings 110 between the "on" and "off positions when handle 82 is manipulated. Of course, other configurations for switching between the "on" and "off positions besides the example just described are also contemplated as being within the scope of the invention. Additionally, while this embodiment included means for rotating the permanent magnetic within the housing, it is also contemplated that the housing can be rotated while the permanent magnet remains stationary, or that both the magnet and housing could both be rotated by about 45 degrees, as long as there is relative rotation between the magnet and the housing, and the rotation changes the direction of the magnetic flux between the "on" and "off positions as described above. However, if an electromagnet is used in place of housing/permanent magnet combination, there is no need for a mechanism to rotate a magnet within a housing. Instead, the electromagnet is merely connected to a power source via a switch. When the electromagnet is activated by the switch, the magnetic force attracts the ferro-magnetic member (such as steel plate 90, of Figure 6). On the other hand, when the electromagnet is turned off, there is no magnetic attraction between it and the ferromagnetic member (such as plate 90), and the first and second components (such as base 74 and table 76) are free to rotate relative to each other. While various embodiments of the present invention have been shown and described, it should be understood that other modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art. Such modifications, substitutions and alternatives can be made without departing from the spirit and scope of the invention, which should be determined from the appended claims. Various features of the invention are set forth in the appended example claims.