Abstract:
An automatically retractable stop mechanism is provided for machine tools. The stop apparatus includes a base that is releasably fixed to the machine tool table. A stop bar is retractably mounted to the base. A spring urges the bar into a retracted condition disengaging the metal part being machined. The spring permits the bar to be selectively actuated to engage the part being machined and properly position that part on the machining table. After positioning is complete, the stop bar is released and the springs automatically retracted so that the machining operation can be performed without interference from the stop apparatus.

Description:
RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/233,184 filed Sep. 15, 2000. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to an automatically retractable stop apparatus that is used to position metal parts on the table of a conventional machine tool. More particularly, this invention relates to a spring loaded positioning stop that automatically retracts after the part is positioned so that the required machining operation can be successfully performed without damaging or disrupting the machine. 
     BACKGROUND OF THE INVENTION 
     CNC milling machines and other widely available machine tools are currently used to perform various operations (e.g. cutting, shaping, drilling, and routing) upon a virtually endless assortment of metal parts or components. Before the machining operation is performed, the part to be machined must be properly positioned and held in place on the machining table. Standard table-top vises are used to hold the part in place; however, before the vise is locked, the part must be accurately positioned within the jaws of the vise. A number of conventional positioning stops are currently used to accomplish this task. 
     Typically, the positioning stops that are currently available are relatively simple, manually operated devices. The machinist installs the stop at a desired location on the table, sets a plate, arm or other stop component and engages the metal part to be machined against the stop component. The stop must then be disassembled and removed so that the desired machining operation may be completed. 
     Unfortunately, the known positioning stop devices present serious problems. The machine operator must remember to remove the stop before the machine tool is operated. Otherwise, there is a serious risk that the cutting head or other part performing the machining operation will strike the stop. This is likely to cause serious and expensive damage to the drill, cutter or other machine tool. Valuable time and manpower must then be expended to repair the machine. In many cases, the tool is subjected to extended and very expensive down time. Replacing damaged tools can cost hundreds if not thousands of dollars. 
     It is not at all uncommon for the machine tool operator to forget to remove the positioning stop. Oftentimes, the machining operation is being performed repetitiously in a tedious manner. Moreover, in CNC applications the machine must be properly programmed by the operator. This can distract the operator&#39;s attention from the important task of removing the positioning stop before the cutter or other component is operated. Even when the machinist does remember to remove the positioning stop, this task must be performed manually. In situations were numerous parts must be machined, the positioning stop must be installed and removed for each and every part. This is tends to be an inefficient, time consuming, labor intensive and extremely tedious operation. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of this invention to provide a positioning stop for machine tools which is automatically retractable so that the machining operation may be completed quickly and effectively without having to manually remove the positioning stop prior to each such operation. 
     It is a further object of this invention to provide an automatically retractable positioning stop for machining tables which virtually eliminates the expensive, time consuming and disruptive damage often caused when the positioning stop is inadvertently left in place during the machining operation. 
     It is a further object of this invention to provide an automatically retractable positioning stop for machining tables which permits metal parts to be positioned on a machining table quickly, conveniently and accurately without requiring the manual assembly and disassembly of the stop between each machining operation. 
     It is a further object of this invention to provide a positioning stop for machine tools which automatically retracts after a part is positioned on the machining table so that the machining operation may be completed quickly and conveniently without risking potentially expensive damage to the machine tool and resulting repairs, wasted worker time and machine down time. 
     This invention results from a realization that an automatically retractable positioning stop would enable a machine tool operator to perform his job much quicker and more efficiently because he would no longer be required to disassemble the stop prior to each separate machining operation. 
     This invention features an automatically retractable positioning stop for machining tables. The stop includes a base that is secured to the machining table at a predetermined position. A retractable stop component is mounted to the base for alternating between retracted and extended positions. Spring means are engaged with the stop component for urging the stop component into the retracted condition and for permitting the stop component to be manually urged into the extended condition. In the extended condition, the part to be machined may be engaged with the stop component and thereby positioned properly on the machining table. In the retracted condition, the stop component is held sufficiently clear of the part to be machined such that the machining operation may be performed without interference from the stop component. After the part to be machined is properly positioned in this manner, that part is locked in a standard table-top vise and the stop component is manually released so that the spring returns the stop component to the retracted condition. 
     In a preferred embodiment, the stop component includes an elongate stop arm or bar that is pivotably mounted to the base. More particularly, a pivot axle may be rotatably interengaged with a cylindrical bearing in the base. The stop bar may be secured to one end of the pivot axle on a first side of the base and a collar may be secured proximate the second end of the pivot axle on an opposite second side of the base. The base may include an interior annular race or recess that interengages the collar. The race may be disposed about the interior bearing of the base. A first spring retaining element may be mounted to the base within the race and a second spring retaining element may be mounted to the collar and extend within the race. The spring means may comprise a helical compression spring that is formed between the first and second spring retaining elements within the race. Alternatively, the spring may be received in an interior race or chamber within the collar. 
     An annular groove may be formed within the side of the base opposite the side that includes the spring retaining race. A first limit pin may be mounted within the base and positioned within the annular groove. The pivot axle may include on the first side of the base a drum that is interconnected to the stop bar. Second and third limit pins may be mounted within to the drum and extend within the annular groove. In the retracted condition, the spring urges the pivot axle to rotate within the central bearing of the base such that the stop bar is pivoted away from the part to be machined. In this position, a first one of the limit pins carried by the drum interengages the limit pin mounted to the base. Alternatively, when the pivot arm is rotated into the extended condition, the spring is compressed between these spring retaining elements in the race. At the same time, the second limit pin carried by the drum engages the limit pin fixed to the base. This limits pivoting of the stop arm into the extended condition. The stop bar is then held in this position until the part to be machined is properly positioned against the stop bar. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Other objects, features and advantages will occur from the following description of a preferred embodiment and the accompanying drawings, in which: 
     FIG. 1 is a perspective view of a preferred automatically retractable stop apparatus according to this invention mounted on a machine tool table and interengaged with a part to be machined. 
     FIG. 2 is an exploded perspective view of the stop apparatus; 
     FIG. 3 is an elevational end view of the stop apparatus with the stop bar in an extended operational position; 
     FIG. 4 is an elevational side view of the stop apparatus in its retracted condition; the collar is removed to illustrate the retracting spring used by the apparatus; 
     FIG. 5 is a view similar to FIG. 4 of the stop apparatus with the stop bar in its extended, operational condition; 
     FIG. 6 is an elevational view of the opposite side of the stop apparatus with the cap of the pivot axle removed to illustrate the interengagement between the movement limiting dowel pins; the apparatus is illustrated in the retracted condition; 
     FIG. 7 is a view similar to FIG. 6 but illustrating the apparatus with the stop bar in the extended, operational condition; and 
     FIG. 8 is a plan view of a pair of opposing stop mechanisms positioned on a machine table-top on respective sides of a clamp vise. 
    
    
     There is shown in FIG. 1 an automatically retractable stop apparatus that is operably mounted to the platform or table-top  12  of a conventional machine tool  14 . The machine tool may comprise any one of a variety of tools for milling, cutting, stamping, drilling or routing metal parts. Apparatus  10  is particularly effective for use with CNC machines and similar types of machine tools. 
     In the embodiment shown in FIG. 1, table-top  12  includes a plurality of elongate slots, channels or grooves  16  that are formed into the table-top. The grooves permit a standard machine tool vise assembly  18  to be mounted to the table-top. Vise assembly  18  comprises a pair of jaws  20  and  22  and a vise table  23  that are positioned on the machining table in a conventional manner designed to hold a metal part P, which is to be machined. The slots  16  are interengaged by bolts  24 , two of which are shown, in order to secure the vise assembly  18  to table-top  12 . An elongate screw element  26  is turned axially rotatably by a vise handle  28  so that the jaws  20  and  22  may be selectively opened and closed relative to one another, as required. The construction of the vise assembly is conventional and does not comprise a part of this invention. Various known techniques and structure may be employed. 
     According to the prior art, the metal part P to be machined is conventionally placed on table-top  12  (and more particularly onto vise table  23 ) beneath the drilling, milling or cutting tool T. Until now, a variety of known stop mechanisms have been employed to properly position part P between the jaws  20  and  22  of vise  18 . The part is properly positioned by abutting the part against the stop. The jaws of the device are then closed by turning the handle  28 . The machinist or tool operator then removes the stop so that it does not interfere with the cutting tool during operation of the machine. If the tool is a CNC machine, it is properly programmed and then operated to mill, cut, drill, rout or otherwise perform a desired operation on the metal part. 
     Unfortunately, as previously described, the machine tool operator often forgets to retract or otherwise remove the stop element from the vicinity of the metal part and the component T. As a result, during the operation of the machine tool, the cutter or other element performing the operation may inadvertently strike the stop and cause serious damage to the cutting tool. 
     Apparatus  10  replaces the stop mechanisms used to date and provides significantly improved results. The stop apparatus, which is shown in exploded condition in FIG. 2, includes a base  30  that is composed of aluminum or some other high strength but relatively lightweight metal or metal alloy. The base includes a generally rectilinear foot or extension  32  that has a slot  34  extending generally longitudinally therein. Slot  34  extends from the bottom to the top of foot  32 . Base  30  also includes a bearing portion  36  that is attached integrally to and proximate one end of foot  32 . As best shown in FIG. 2 and 3, bearing portion  36  includes a central bore  34  that is surrounded at one end by an annular race or recess  37  formed in one side of base  30 . A second annular recess or groove  38 , obscured in FIG. 2 but shown in FIG. 3, is formed about the opposite end of central bore  34  in the opposite side of base  30 . 
     Bearing portion  36  of base  30  carries a pair of dowel pins  40  and  42  that are permanently fixed within respective annular recesses of the base. Specifically, a first dowel pin  40  is mounted to the base such that the pin extends across recess  37  at a position located at approximately 12 o&#39;clock within the recess. See FIGS. 3-5. A second dowel pin  42  is fixed to base  30  and extends outwardly into annular recess  38 , as best shown in FIGS. 3,  6  and  7 . These dowel pins define the limits of operation of the stop apparatus as is described more fully below. 
     As shown in FIG. 1, a pivot axle  50  is axially rotatably mounted to bearing portion  36  of base  30 . An elongate stop bar  52  having a convex outer surface  47 , FIG. 3, is secured proximate one end of pivot axle  50 . Bar  52  has a longitudinal axis that extends radially relative to pivot axle  50 . Cap  62  includes a radial notch  63 , FIGS. 1 and 2, that receives stop bar  52 . A locking bolt  65  is inserted through a corresponding hole  67  in bar  52  and is threadably engaged with a corresponding central hole  69  formed in cap  62 . As shown in FIG. 3, the distal end of bolt  65  is received in a threaded opening  71  in the end of the shaft  54  received by cap  62 . This interconnection fastens the stop bar  52  to pivot axle  50  and fixedly interconnects cap  62  and shaft  54  so that they rotate axially in unison. The stop bar is preferably composed of stainless steel or a similar material. 
     A stop bar actuating handle  49  is attached to and extends transversely from the stop bar. As shown in FIGS. 1-3, handle  49  comprises a generally tubular component  51  that is aligned with a hole  53  in stop bar  52 . The tubular component is preferably composed of aluminum of a similar material. A cap screw or bolt  55  is received through the axial opening of tubular component  51  and is threadably engaged with opening  53  in stop bar  52 . The threaded cap screw  55  is tightened to form the completed handle, best shown in FIGS. 1 and 3. 
     As illustrated shown in FIG. 2, pivot axle  50  comprises an elongate shaft  54  that includes a pair of flat surfaces  56  and  58  interconnected to one another at an angle of approximately 90°. A rounded comer surface  60  extends between the flat surfaces  56  and  58 . A generally annular cap  62  is attached to a first end of shaft  56 . More specifically, as shown in FIGS. 2 and 3, cap  62  includes a central opening  64  that receives shaft  54 . Cap  62  may be seated flush with the outer surface of bearing portion  36  or, alternatively, may be received in an annular notch  70  formed in the base generally surrounding recess  38  (see FIG.  3 ). 
     Shaft  54  extends through the central opening  34  of bearing portion  36 . The distal end of shaft  54  is received by an annular collar  72 , FIGS. 1-3, which is itself engaged with a notch  74  formed in the side of body  30  surrounding annular recess  37 . The distal end of shaft  54  is received by central opening  78  of collar  72 . A set screw  80  is received through a complimentary opening  82  in collar  72 . The set screw may be tightened to bear against flat surface  56  of shaft  54 . This locks the shaft within collar  72 . Because collar  72  is locked onto shaft  54 , the collar is rotatable in unison with the pivot axle  30  and attached stop bar  52 . 
     Several additional dowel pins are carried by cap  62  and collar  72 . Specifically, dowel pins  89  and  91 , FIGS. 2,  6  and  7 , are secured to cap  62  such that they extend transversely into annular recess  38  of base  30 . Likewise, a dowel pin  92 , FIGS. 2-5, is mounted to collar  72  such that when the stop apparatus is fully assembled, dowel pin  92  extends transversely across annular recess  37 . 
     A helical compression spring  90  is mounted within annular recess  37  such that it extends between the dowel pin  40  fixed to body  30  and the dowel pin  92  attached to collar  72 . See FIGS. 3-5. In its relaxed, expanded condition, spring  90  urges pin  92  into the position shown in FIG. 4 such that the spring extends through an angle of approximately 270° within recess  36 . Alternatively, in the compressed condition shown in FIG. 5, spring  90  extends through an angle of approximately 180° within recess  36 . 
     The foregoing structure permits stop bar  52  to be pivoted between the extreme positions shown in FIGS. 4,  6  and FIGS. 5,  7 , respectively. Specifically, when apparatus  10  is not being used, stop bar  52  is retracted and held as shown in FIGS. 4 and 6. Spring  90  biases dowel pin  92  and attached collar  72  (FIG. 2) into the retracted position shown in FIG. 4 so that pivot axle  50  is rotated to hold stop bar  52  in a generally horizontal position. 
     Alternatively, the operator may grasp stop bar handle  49  and rotate the stop bar about pivot axle  50  and into the vertical condition shown in FIGS. 5 and 7. In this condition, spring  90  is compressed between fixed dowel pin  40  and movable dowel pin  92  attached to the rotating collar  72 . 
     In operation, one or more stops  10  are mounted to table-top  12  in the manner shown in FIG.  1 . Each stop apparatus is secured to the table by inserting a mounting bolt or bracket  100  through slot  34  in foot  32  and interengaging that bolt or mounting component with a corresponding slot  16  in table-top  12 . Each stop apparatus is positioned as required on the table-top. Initially, before the metal part P is placed on the table, the stop apparatus is maintained in a retracted condition. The natural bias of spring  90  urges the pivot axle  50  to rotate stop bar  52  into a horizontal position as shown and as previously described in connection with FIG.  4 . In this position the bar is slightly below the upper surface of vise table  23  (see FIG.  1 ). 
     To position part P on table top  14 , the machinist or other machine tool operator operates apparatus  10  by grasping handle  49  and pivoting stop bar  52  about pivot axle  50  in the manner indicated by arrow  102  in FIGS. 1,  4  and  5 . The pivot axle and attached collar  72  rotate as indicated by arrows  104  in FIG.  1 . This causes the spring  90  to be compressed as shown in FIG.  5 . 
     Rotation of the pivot axle and pivoting of the stop bar are limited to a 90° range of movement by the dowel pins  42 ,  89  and  91  located on the opposite sides of base  30 . The operation of these pins is best shown in FIGS. 6 and 7. When the stop apparatus is in its retracted condition, FIG. 6, stop bar  52  maintains a generally horizontal orientation. As previously described, spring  90  on the opposite side of the apparatus extends through an angle of 270° within its respective recess. At that this position, dowel pin  89  engages fixed dowel pin  42  whereas dowel pin  91  is spaced approximately 90° from dowel pin  42 . The interengaged pins  89  and  42  effectively hold bar  52  horizontally and prevent the bar from rotating downwardly any farther in the direction of arrow  110 . 
     When bar  52  is pivoted upwardly into its extended, generally vertical position, FIG. 7, the pivot axle  50 , FIG.  2  and attached dowel pins  89  and  91  are rotated into the position shown therein. Dowel pin  91  engages and is stopped by fixed dowel pin  42 ; and dowel pin  89  is spaced approximately 90° apart from pin  42 . As a result, rotation of pivot axle  50  and pivoting of bar  52  in the direction of arrow  102  are limited by the interengaged pins  42  and  91 . 
     With bar  52  in the vertical position, metal part P is manipulated on the vise table  23  until it interengages the concave surface  47  of raised stop bar  52 . After the metal part P is properly positioned against stop bar  52 , as shown in FIG. 1, the operator releases handle  49  and permits the stop bar to retract automatically into its initial, generally horizontal position. When the operator releases handle  49 , spring  90  urges pivot axle  50  and attached bar  52  to rotate downwardly in the direction indicated by arrow  110  in FIG.  1 . The stop bar thereby disengages part P and returns automatically to a horizontal position. The machinist then tightens the metal parts between the jaws  20  and  22  of vise assembly  18 . The machine tool is programmed and operated as required so that tool T performs the desired operation (e.g. cutting, milling, drilling, routing, etc.) upon part P. While this operation is being performed, stop bar  52  is positioned safely out of the way so that it does not interfere with or potentially damage tool T. The stop bar retracts automatically when the operator releases handle  49 . The operator does not have to remember to manually retract or remove the stop bar. This not only saves time, but avoids the possibility of expensive and disruptive damage being caused to the machine if the machinists inadvertently forgets to retract or remove the stop bar. A desired machining operation may be performed on any surface of the part, including the surface previously engaged by the stop bar, without interference from the bar. 
     The concave outer surface  47  of stop bar  52  effectively engages metal parts having various configurations and permits the stop bar to drop conveniently away from the part when the user releases handle  49 . A flat, flush or square face on the stop bar would tend to cause the stop bar to jam against certain metal components being machined, especially components having angled surfaces abutting the stop apparatus. 
     Although stop bar  52  is depicted on the right-hand side of apparatus  10  in the versions previously described, in alternative embodiments, the stop bar may be switched to the left-hand side of base  30 . This is accomplished by loosening set screw  82  (FIG. 2) and removing collar  72  from annular recess  37 . Pivot axle  50  is removed from bearing  34 . Spring  90  is removed from recess  37 . Pivot axle  50  is reversed and shaft  52  is inserted through bearing  34  on the opposite side of body  30  such that cap  62  engages recess  37 . Spring  90  is inserted into groove  38  on the opposite side of body  30 . Collar  72  is then engaged with recess  38  such that central opening  78  receives shaft  54 . Set screw  80  is replaced in collar opening  82  and the set screw is tightened. As a result, the stop bar  52  is located on the opposite side of the body from that which is shown in the previous drawings. It should be noted that the previously described dowel pin arrangement is reversed in this version. In particular, three dowel pins  89 ,  91  and  40  are located in recess  37 ; whereas, two dowel pins  42  and  92  are located in groove  38  at opposite ends of spring  90 . 
     In FIG. 8 a pair of opposing stop devices  10  are mounted on a machine table  14  on opposite sides of a vise table  23 . In this embodiment, each apparatus is oriented such that the stop bar  52  extends at an angle of 5°-10° degrees relative to the axis of the vise. Each apparatus  10  is constructed and operates in a manner analogous to the apparatus previously described. 
     To properly position a part on table  14  using devices  10 , the arm  52  of a selected one of the devices is raised by grasping appropriate handle  49  and pivoting the stop bar upwardly. The machine operator then slides part P 1  along jaw  20  until the part engages the raised stop bar. This indicates that the proper position is obtained. The operator then releases the stop bar and it returns to its horizontal position below and disengaged from part P 1 . While releasing the stop bar, the operator holds part P 1  steady. Finally, with the stop bar in its retracted condition, the operator clamps the vise closed on part P 1 . The machine operation is then performed on the part. 
     The stop bar of this invention is extremely simply and convenient to operate. The apparatus may be adjusted and positioned on a wide variety of machine tool tables. The invention helps the user to avoid expensive and extremely inconvenient machine down time and significantly reduces machine tool repair costs. 
     It should be understood that the automatically retractable stop of this invention may employ a wide variety of alternative spring loaded retracting devices. For example, the stop arm may operate other than rotatably. In certain versions, a telescopically retractable stop arm may be used. It should also be understood that various types of spring mechanisms may be employed within the scope of this invention. For example, spiral or “watch spring” type springs may be utilized. 
     From the foregoing it may be seen that the apparatus of this invention provides for an automatically retractable stop apparatus that is used to quickly and effectively position metal parts on the table of a conventional machine tool. While this detailed description as set forth particularly preferred embodiments of the apparatus of this invention, numerous modifications and variations of the structure of this invention, all within the scope of the invention, will readily occur to those skilled in the art. Accordingly, it is understood that this description is illustrative only of the principles of the invention and is not limitative thereof. 
     Although specific features of the invention are shown in some of the drawings and not others, this is for convenience only, as each feature may be combined with any and all of the other features in accordance with this invention. 
     Other embodiments will occur to those skilled in the art and are within the following claims.