RELATED APPLICATIONS 
     This application is a C-I-P of U.S. patent application Ser. No. 09/137,649 filed on Aug. 20, 1998, now U.S. Pat. No. 6,095,533, which claimed the priority of U.S. Provisional Patent Application Ser. No. 60/082,531 filed on Apr. 20, 1998. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to mobile machine bases and, more specifically, to mobile machine bases that are adjustable to accommodate different machinery configurations. 
     BACKGROUND OF THE INVENTION 
     Machinery such as table saws, band saws, jointers, shapers, planers, sanders, and the like should be stationary during use. In many cases, this type of machinery is permanently installed at a predetermined location in a shop. Such machinery is thus commonly sold with a stationary base having feet that frictionally engage the floor to maintain the machinery at the predetermined location. 
     But in many situations it is desirable to move this type of machinery between uses. For example, a user may have limited shop space, and may want to store the machinery at a relatively inaccessible location when not in use and then, immediately prior to use, move the machinery to a more accessible location. Or the user may wish to use the machinery at a job site. In this case, movement of the machinery from one location to another at the job site may be desirable. 
     Accordingly, mobile machine bases are often sold as an accessory to fit under the stationary bases originally sold with shop machinery. Mobile bases further comprise a locking system that allows the machinery to be rolled from one location to another between uses yet immobilizes the machinery during use. 
     More specifically, conventional mobile machine bases comprise a relatively rigid frame assembly to which a plurality of wheel assemblies are attached. The stationary base is removed from the bottom of the machine, and the bottom of the machine is then bolted or otherwise rigidly attached to the frame assembly. Usually, the locking system employs a lock member that moves between a locked position and an unlocked position. When in the locked position, the lock member immobilizes the machinery by frictionally engaging either the wheels or the floor surface to substantially prevent relative movement between the frame assembly and the floor surface. When in the unlocked position, the lock member does not inhibit movement of the frame assembly relative to the floor surface. 
     Machinery of the type rendered movable by the mobile machine base of the present invention exists in a variety of shapes, sizes, and weights. Currently, manufacturers sell the mobile machine bases in a variety of configurations; the user selects one of these base configurations as appropriate for a given machine configuration. 
     What will be referred to herein as the “effective footprint” of the machine determines which base configuration should be selected. The effective footprint is normally defined as the outside width and depth dimensions of the bottom of the machinery. The configuration of the mobile base is defined by similar width and depth dimensions that should be just slightly larger than the width and depth dimensions of the effective footprint. 
     Requiring a base configuration for each effective footprint mandates a production and distribution system in which the manufacturer must design, build, and keep in inventory a plurality of base configurations. The retailers must similarly keep in stock at least the most popular, and preferably all, of these configurations. And the retailer&#39;s representative must have some expertise to advise the customer on the right base configuration for a required effective footprint. The result is an inefficient system that is labor and capital intensive. Even then, it would be difficult to provide machine bases for all machines on the market. The need thus exists for a single machine base configuration that can accommodate a number of effective footprints. 
     Another drawback of conventional machine bases is the locking system used. Some of these locking systems employ a lock member that, in the locked position, bears directly on the wheel to prevent rotation of the wheel. This causes excessive wear on the wheel. Other locking systems require tools to operate the locking system. The need thus exists for a machine base having improved locking systems that do not cause excessive wheel wear or require tools to operate. 
     Conventional machine bases further employ rigid frame assemblies that cause the machine base to occupy a relatively large volume during transportation and storage. The need thus exists for a machine base that occupies a smaller volume when not in use. 
     1. Prior Art 
     The Applicant is aware of a number of machine bases that are currently on the market. 
     The assignee of the present invention currently manufactures and sells a line of machine bases specially designed to fit the assignee&#39;s machinery but will also accommodate many machines manufactured by others. Each of the assignee&#39;s machine bases is specially constructed for a given effective footprint and thus a number of individual designs are required. The locking system bears directly on the wheel and thus can cause excessive wear over time. 
     HTC Products, Inc. and Delta each manufacture and sell a line of machine bases. The bases sold by each of these manufacturers are each designed for a specific effective footprint and thus suffer the problems described above associated with designing, building, keeping in inventory, distributing, and retailing a large number of separate base designs. 
     2. Objects of the Invention 
     From the foregoing, it should be clear that one object of the present invention is to provide an improved mobile base system for use on machinery such as table saws, band saws, jointers, shapers, planers, sanders, and the like. 
     SUMMARY OF THE INVENTION 
     These and other objects are obtained by the present invention, which is locking system for a mobile machine base. The exemplary locking system comprises at least one stop or lock member that may be fixed relative to the base such that the stop member frictionally engages the floor surface and prevents movement of the machinery. 
     In particular, a stop assembly of the present invention comprises a lock housing, a lock member, a drive member, and a magnetic portion. The lock housing defines a lock chamber and is rigidly attached to the frame of the base. 
     The lock member is slideably mounted within the lock chamber of the lock housing such that the lock member moves between an unlocked position in which the lock member does not engage the floor surface and a locked position in which the lock member frictionally engages the floor surface. 
     The drive member engages the lock housing such that rotation of the drive member causes the drive member to move towards or away from the floor surface. The drive member is at least partly located within the lock chamber above the lock member and is capable of rotating with respect to the lock member. 
     The magnetic portion is formed on one of the lock member and the drive member such that upward movement of the drive member causes upward movement of the lock member without inhibiting the ability of the drive member to rotate relative to the lock member. 
     The exemplary stop system disclosed herein comprises two such stop assemblies. 
     Other aspects of the present invention will be apparent from the following detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a mobile machine base of the present invention being used to support a planer at a desired location on a floor surface; 
     FIG. 2 is a top plan view of the mobile machine base shown in FIG. 1; 
     FIG. 3 is a side elevational view depicting the mobile machine base of FIG. 1; 
     FIG. 4 is a top plan view showing the mobile machine base of FIG. 1 in a different configuration from that shown in FIG. 1; 
     FIG. 5 is a section view taken along lines  5 — 5  in FIG. 2; 
     FIGS. 6-8 are section views taken along lines  6 — 6  in FIG. 2 that show the operation of one of the assemblies forming the lock system used by the mobile machine base of FIG. 1; 
     FIG. 9 is a side elevational view depicting the mobile machine base of a second embodiment of the present invention; 
     FIG. 10 is a top plan view of the mobile machine base shown in FIG. 9; 
     FIG. 11 is a section view taken along lines  11 — 11  in FIG. 10; 
     FIG. 12 is front elevation section view depicting a locking assembly that may be used in place of the lock systems depicted in FIGS. 6-8; and 
     FIG. 13 is an exploded front elevation view of the locking assembly of FIG.  12 . 
    
    
     DETAILED DESCRIPTION 
     Referring now to FIG. 1, depicted at  20  therein is a mobile machine base constructed in accordance with, and embodying the principles of the present invention. The mobile machine base  20  is shown supporting a machine  21 , which in this case is a planer. The machine  21  is relevant to the present invention only in that it defines an effective footprint having a width dimension W 1  and depth dimension D 1 . 
     FIG. 1 shows that the mobile machine base  20  comprises a frame assembly  22 , front and rear wheel assemblies  24  and  26 , and a locking system  28  comprising first and second locking assemblies  30  and  32 . 
     Referring now to FIG. 2, it can be seen that the frame assembly  22  comprises first, second, third, and fourth corner members  34 ,  36 ,  38 , and  40  and first, second, third, and fourth side members  42 ,  44 ,  46 , and  48 . The frame assembly further comprises a plurality of screw members  50  that join the corner members  34 - 40  to the side members  42 - 48 . 
     The corner members  34 - 40  are identical to each other; similarly, the side members  42 - 48  are identical to each other. Accordingly, only the first corner member  34  and first side member  42  will be described herein in detail. 
     The corner member  34  comprises first and second tube members  52  and  54 . The tube member  52  has a distal end  56  and a proximal end  58 ; the second tube member  54  similarly defines a distal end  60  and a proximal end  62 . The distal end  56  and  60  are cut at a 90° angle relative to the center axis of the tube members  52  and  54 . The proximal ends  58  and  62  are cut at a 45° angle relative to the longitudinal axes of the members  52  and  54 . The proximal ends  58  and  62  are welded along a seam  64  such that the tube members  52  and  54  extend from each other at a substantially right angle. 
     The corner member  34  further comprises a rectangular plate member  66  that is welded to one side of the tube members  52  and  54  to define a support surface  68  at the inside angle formed by the tube members  52  and  54 . The rectangular plate  66  thus braces and strengthens the corner formed by the tube members  52  and  54  and provides the surface  68  for supporting the machine  21 . In particular, as shown in FIG. 2, the machine  21  comprises first, second, third, and fourth corner portions  70 ,  72 ,  74 , and  76  that overlap the support surfaces  68  defined by the rectangular plates  66 . 
     The tube members  52  and  54  each have an inner length L 1  and an outer length L 2 . The significance of these lengths L 1  and L 2  will become apparent from the following discussion. 
     Referring now to the side member  42  of the frame assembly  22 , this is simply a rectangular bar having a length X 1  and first and second groups  78  and  80  of holes  82  formed therein. The first group of holes  78  is adjacent to a first end  84  of the member  42 , while a second group  80  is adjacent to a second end  86  thereof. 
     Referring now for a moment to FIG. 5, depicted therein is the tube member  52  of the corner member  38 , the side member  44 , and the screw  50   d.  FIG. 5 shows that an outer circumferential path  88  of the side member  44  is approximately the same (in practice slightly smaller) than an inner perimeter path  90  of the cross-sectional area of the tube member  52 . With the screw  50   d  removed, the tube member  52  and side member  44  may move relative to each other along a common axis A. FIG. 5 also shows that the screw  50   d  extends through an attachment hole  92  formed in the tube member  54  and one of the holes  82  formed in the side member  44 . 
     Comparing FIGS. 2 and 4, it can be seen that in FIG. 2 the mobile base  20  is in its largest configuration and in FIG. 4 is in its smallest configuration. In particular, the base assembly  20  defines a width dimension W 2  and a depth dimension D 2 . In FIG. 2, these dimensions are much longer than in FIG.  4 . 
     The largest dimensions of the assembly  20  are defined by the length X 1  of the side members  42 - 48  and the inner length L 1  of the corner members  52  and  54 . In this largest configuration, enough overlap is present between the side members  42  and the tube members  52  and  54  such that the weight of the machine  21  does not cause deflection of the tube members  52  and  54  relative to the side member  54 . In the exemplary embodiment  20 , this overlap is a distance Y 1  as shown in FIG.  3 . In this respect, it should be noted that the primary weight of the machine  21  is borne through the plate  66  and directly down to the wheels  24  and  26  and onto a floor surface  94  in which these wheels  24  and  26  are in contact. 
     The smallest configuration (FIG. 4) in which the assembly  20  may be placed is defined by the lengths of the side members  42 - 48  and the outer lengths L 2  of the bar members  52  and  54 . As shown in FIG. 4, almost all of the area within the corner members  34 - 40  is occupied in this configuration. 
     Referring now to FIGS. 6-8, the locking system  28  of the present invention will be described in further detail. As mentioned above, the locking system  28  comprises locking assemblies  30  and  32 . Each of these assemblies  30  and  32  are identical, and only the assembly  32  will be described herein in detail. 
     As shown in FIGS. 6-8, the lock assembly  32  comprises a stop member  120 , a lock housing  122 , and a drive member  124 . 
     The lock housing  122  defines a lock chamber  126  defined by an inner surface  128  of the housing  122 . The chamber  126  comprises a threaded portion  130  and a cylindrical portion  132 . 
     The stop member  120  has a cylindrical shaft  134  that is snugly received within the cylindrical portion  132  of the lock cavity  126 . The longitudinal axes of the shaft  134  and cylindrical portion  132  are aligned as shown at B in FIG.  6 . The tolerances between the shaft  134  and cylindrical portion  132  are such that the stop member  120  may move relative to the lock housing  122 . 
     A set screw  136  is threaded into the lock housing  122 . The set screw  136  selectively allows the user to prevent or allow relative movement between the stop member  120  and the lock housing  122 . 
     The drive member  124  has a shaft  138  with a threaded portion  140  and a cylindrical portion  142 . The threaded portion  140  of the drive member shaft  138  is threadably received by the threaded portion  130  of the lock chamber  126 . Rotation of the drive shaft  138  about the axis B allows the shaft to be displaced upward or downward along the axis B. 
     A resilient member  144  may be placed on the stop member  122  to prevent damage to the floor surface  94 . A handle  146  may be placed on the drive member  124  to facilitate rotation of the shaft  130  about the axis B. 
     The purpose and use of the lock system  28  is best understood in the context of the entire machine base assembly  20 . Accordingly, the operation of the lock system  28  will be described further below after an explanation of the use of the overall machine base assembly  20 . 
     Referring for a moment now to FIG. 3, it can be seen that the front and rear wheels  24  and  26  are different. The rear wheels are fixed such that they rotate only about a horizontal axis, while the front wheels  24  are swivel wheels that can rotate about both a horizontal axis and a vertical axis. Both types of wheel assemblies are widely available in the marketplace and will not be discussed herein in detail. This wheel configuration allows the base  20  to be steered as it rolls. 
     With the foregoing understanding of the construction of the present invention, the use of the present invention will now be described in detail. 
     Initially, the effective footprint of the machine  21  is determined. This is specifically accomplished by the measuring the width W 1  and depth D 1  of the particular machine  21  to be supported. Once the width W 1  and depth D 1  are known, the side members  42 - 48  are inserted into the corner members  34 - 40  such that the width W 2  and depth D 2  of the assembly  20  is slightly larger than the corresponding dimensions of the effective footprint. These dimensions W 2  and D 2  cannot be made too large, however, as enough of the corner portions  68 - 76  of the machine  21  must overlap the supports surfaces  68  to provide a stable platform for the machine  21 . 
     The bolts  50  are then inserted through the holes  92  in the bars  52  and  54  and threaded into the holes  82  in the side members  42 . This forms the rigid frame assembly  22  described above. 
     At this point, the machine  21  is placed onto the machine base assembly  20  such that the corner portions  68 - 76  thereof are supported on the support surfaces  68  of the rectangular plate  66 . 
     At this point, the machine  21  may be rolled on the wheels  24  and  26  to a desired location. At the desired location, the locking system  28  is used to prevent unwanted movement of the machine  21 . 
     In particular, the set screw  136  is backed off so that it does not engage the stop member  120 . The stop member  120  is thus free to fall until it contacts the floor surface  94  as shown in FIG.  7 . The handle  146  is then grasped and rotated as shown by arrow C 1  in FIG. 8 such that the cylindrical portion  142  of the drive member  24  engages an upper end  148  of the stop member  120 . Continued rotation of the handle  146  in the direction C 1  will cause the wheel  24  to lift off the ground a short distance Z as shown in FIG.  8 . At this point, the stop member  120  frictionally engages the floor surface  94  to prevent relative movement between the machine  21  and the floor  94 . The lock system thus securely locates the machine  21  at its desired location. Additionally, a certain amount of leveling can be obtained by altering the distances Z as necessary. 
     The set screw  136  can be used to further secure the stop member  120  relative to the lock housing  122  and maintain the distance Z as desired. 
     If the machine  20  is to be moved, the set screw  136  is disengaged from the stop member  120 . The handle  146  is then turned in the direction opposite the arrow C 1  until the wheel  24  again touches the ground. The handle  146  will be then moved further to a position as shown in FIG. 7 relative to the stop member  120 . At this point, the stop member  120  can be lifted by hand into the position shown in FIG. 6, at which point the set screw  136  is rotated to engage the stop member  120  and prevent it from dropping back down into contact with the floor surface  94 . 
     The locking system  28  thus provides a secure lock but can easily be engaged and disengaged as necessary to fix or change the location of the machine  21 . 
     Implicit in the discussion above is the fact that the machine base assembly  20  may be broken down into basically eight separate pieces for shipping and transportation. In particular, the screws  50  are simply removed and the side members  42 - 48  are removed from the corner members  34 - 40 . The broken-down mobile machine base assembly  20  may thus be stored in a much smaller configuration whenever desired. 
     Referring now to FIGS. 9-10, depicted therein is a mobile machine base  220  constructed in accordance with, and embodying, the principles of a second embodiment of the present invention. The mobile machine base  220  is constructed and operates in basically the same manner as the mobile machine base  20  described above. The mobile machine base  220  will thus be described herein only to the extent that it differs from the machine base  20  described above. 
     In particular, the machine base  220  comprises a frame assembly  222 , front and rear wheel assemblies  224  and  226 , and a locking system  228  comprising first and second locking assemblies  230  and  232 . And as shown in more detail in FIG. 10, the frame assembly  222  comprises first, second, third, and fourth corner members  234 ,  236 ,  238 , and  240  and first, second, third, and fourth side members  242 ,  244 ,  246 , and  248 . The frame assembly  222  further comprises a plurality of screw members that join the corner members  234 - 240  to the side members  242 - 248 . 
     The frame assembly  222  is similar to the frame assembly  22  described above, the primary difference being the cross sections of the corner members  234 - 240  and the side members  242 - 248 . 
     In particular, as shown in FIG. 11, the corner members and side members are provided with a generally rectangular cross-sectional area in contrast to the generally square rectangular area of the corner members and side members of the frame assembly  22  described above with reference to FIG.  5 . FIG. 11 depicts the corner member  238  and side member  244 ; the other corner members and side members have similar cross-sectional areas. 
     In use, the corner members and side members are joined together and assembled such that the longer surface of the rectangular cross-sectional area is generally vertically arranged. 
     FIG. 10 further shows that the front wheel assemblies  224  and rear wheel assemblies  226  are not mounted directly below the corner members as was the case in the exemplary mobile machine base  20  described above. To the contrary, as shown in FIG. 9, the wheel assemblies  224  and  226  are mounted on angle irons  252  and  254  that extend from front sides  256  and  258  of the frontmost corner members  238  and  240  and from the back sides  260  and  262  of the backmost corner members  234  and  236 . The connections between these wheel assemblies  224  and  226  and the front and back sides  256 - 262  are the same, and only the connection between the rear wheel assembly  226   b  and corner member  234  will be described in detail. 
     Referring initially to FIG. 9, it can be seen that the angle iron  254  has a generally L-shaped cross section comprising an upper portion  264  and a lower portion  266 . The lower portion  266  is welded to the back side  262  of the corner member  234  such that the lower portion  266  is generally vertically aligned and the upper portion  264  is generally horizontally aligned. These portions  264  and  266  extend at right angles from each other. 
     Referring now to FIG. 10, it can be seen that the angle iron  254   b  extends a short distance, approximately two to four inches, from a side surface  268  of the corner member  234  towards the adjacent corner member  236 . This upper portion  264  is sized and dimensioned to form a suitable mounting surface for the wheel assembly  226   b.  Again, the wheel assembly  226  is or may be conventional. 
     The angle irons perform two basic functions. First, they allow the frame assembly  222  to be slightly lower during use than the frame assembly  22  described above. This is because the surfaces on which the wheel assemblies  224  and  226  are attached are at or near the top of the corner members  234 - 240  rather than at the bottom of these members. In addition, they create a slightly larger footprint for the overall machine base  220 . 
     The benefits of the placement of the wheels  224  and  226  is that the level of the work surface of the machine  21  mounted thereon will not be significantly higher than the surface of the machine  21  when the base  220  is not in use. In addition, the slightly longer wheel base will slightly increase the stability of the system. 
     In all other respects, the mobile machine base  220  is constructed, operated, and used in the same manner as the mobile machine base  20  described above. 
     Referring now to FIGS. 12 and 13, depicted therein at  320  is a locking assembly that may be substituted for either or both of the locking assemblies  30  and  32  to form the locking system  28  discussed above. 
     As shown in FIG. 12 and 13, the lock assembly  320  comprises a stop member  322 , a lock housing  324 , a drive member  326 , and a magnetized portion  328 . The lock housing  324  defines a lock chamber  330  defined by an inner surface  332  of the housing  324 . The chamber  330  comprises a threaded portion  334  and a cylindrical portion  336 . 
     The stop member  322  has a cylindrical shaft  340  that is snugly received within the cylindrical portion  336  of the lock chamber  330 . The longitudinal axes of the shaft  340  and cylindrical chamber portion  336  are aligned along a lock axis  342 . The tolerances between the shaft  340  and cylindrical chamber portion  336  are such that the stop member  322  may move relative to the lock housing  324 . 
     The drive member  326  has a shaft  350  with a threaded portion  352  and a cylindrical portion  354 . The threaded portion  352  of the drive member shaft  350  is threadably received by the threaded portion  334  of the lock chamber  330 . Rotation of the drive shaft  350  about the lock axis  342  allows the shaft to be displaced upward or downward along the axis  342 . 
     A resilient member  360  may be placed on the stop member  322  to prevent damage to the floor surface  94 . A handle  362  may be placed or formed on the drive member  326  to facilitate rotation of the shaft  350  about the lock axis  342 . 
     The magnetized portion  328  is formed on an upper end  372  of the stop member  322  opposite the resilient member  360 . The exemplary magnetized portion  328  is a small magnet that is glued, threaded, or otherwise fixed in a magnet cavity  370  of the stop member upper end  372 . This arrangement causes the stop member  322  and drive member  326  to be attracted together. Of course, the parts may be reversed such that the magnetized portion  328  is formed on a lower end  374  of the drive member  326 , which causes the stop member  322  to be attracted to the drive member  326  instead of the other way around. 
     The purpose of the magnetized portion  328  is to allow the stop member  322  to travel along the lock axis  342  with the drive member  326  while also allowing axial rotation of the drive member  326  about the lock axis  342  relative to the drive member  326 . 
     The locking assembly  320  is similar in use and purpose to the locking assemblies  30  and  32  described above but differs in one significant detail. In particular, the locking assembly  320  may be substituted for one or preferably both of the locking assemblies  30  and  32 ; the locking assembly  320  will be attached to the base  20  in the same general fashion. The primary difference between the locking assembly  320  and the assemblies  30  and  32  is that the locking assembly  320  does not require a side mounted set screw such as the screw  136  described above. 
     Instead, the magnetic portion  328  is attracted to the drive member  326  and thus causes the stop member  322  to move up with the drive member  326  (e.g., from the configuration of FIG. 7 to the configuration of FIG. 6) when the wheel assembly  24  supports the weight of the base  20  (and anything thereon) and the drive member  326  is rotated counterclockwise. The magnetic portion  328  thus obviates the need for the user to lift the stop member by hand and tighten a set screw when the base  20  is to be moved. 
     However, because only magnetic attraction is used to cause the drive member  326  to lift the stop member  322 , the drive member  326  may freely axially rotate about the locking axis  342  when the locking system is used to lift the wheel assemblies  24  off of (e.g., from the configuration of FIG. 7 to the configuration of FIG. 8) or lower the wheel assemblies  24  onto (e.g., from the configuration of FIG. 8 to the configuration of FIG. 7) the floor surface  94 . 
     From the foregoing, it should be clear that the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive.
A mobile base for allowing machinery having an effective footprint within a predetermined range of effective footprints to be moved along and/or fixed relative to a floor surface. The base comprises a frame assembly having a width dimension and a depth dimension, first, second, third, and fourth wheels attached to the frame assembly such that the frame assembly may be moved, and a locking system. The locking system comprises a lock housing, a lock member, a drive member, and a magnetic portion. The lock housing defines a lock chamber. The lock member is slideably mounted within the lock chamber and moves between an unlocked position and a locked position in which the lock member frictionally engages the floor surface. Axial rotation of the drive member causes the drive member to move towards or away from the floor surface. The drive member is located above the lock member and is capable of rotating with respect to the lock member. The magnetic portion is arranged such that upward movement of the drive member causes upward movement of the lock member without inhibiting the ability of the drive member to rotate relative to the lock member.