WO1984000911A1

WO1984000911A1 - Computer controlled engraving table

Info

Publication number: WO1984000911A1
Application number: PCT/US1982/001199
Authority: WO
Inventors: Edward W Claire; Rodney Albin
Original assignee: Dahlgren Engraving Systems Inc
Priority date: 1982-09-07
Filing date: 1982-09-07
Publication date: 1984-03-15
Also published as: AU8955782A; EP0118429A1

Abstract

A computer controlled engraving table having a base (36) with an opened interior space (38) and a platform (40) for supporting the workpiece (42) to be engraved which can be quickly coupled or decoupled from the base. Also provided is a unique motor mount (34) similar to a ball and socket joint which facilitates the alignment of the stepper motor and lead screw component during the assembly of the engraving table.

Description

Description Computer Controlled Engraving Table

Technical Field

The present invention relates to computer con- trolled engraving and, more particularly, to a computer controlled engraving table.

Background Art

In recent years, with the increased availability of personal computers, there have been developed com- puter controlled engraving systems which are affordable to a substantial segment of the engraving trade, which offer sophisticated and precise engraving features, and which are of small physical size. In one such system, a central processing unit receives font and copy infor- mation from the user and converts this information into instructions which are then supplied to a control unit. The control unit then converts these instructions into a series of command signals which are supplied to an engraving table. Stepper motors on the engraving table receive these control signals and, in response thereto, cause the movement of an engraving tool with respect to a workpiece which is supported on an engrav¬ ing platform.

Reference is made to two previously filed patent applications entitled Tool Manipulating Method And Apparatus, Serial No. 257,581, filed April 27, 1981 and Mechanical Tool Manipulating Method And Apparatus, Serial No. 281,602, filed July 9, 1981, the disclosure of which is incorporated herein by reference, in which such a system is described in greater detail.

With respect to the engraving table described in the above-referenced applications, a two axis system is utilized in which the engraving tool is moved along one axis while the platform, supporting the workpiece, is moved along an independent axis, perpendicular to the axis of the engraving tool. With such a configuration, there are several disadvantages. Among these disadvan- tages is the requirement that the total mass of the engraving platform and workpiece be moved in order to implement the engraving action. Another disadvantage is that the configuration and location of the engrav¬ ing platform on one of the axes of movement dictates the types of workpieces upon which engraving can be performed.

During the engraving process, because the engrav¬ ing platform is an integral part of one of the axes of movement, it is also required that a just-completed workpiece be removed from the platform and a new workpiece be substituted on the platform before the actual engraving can be resumed. Thus, valuable engraving time is wasted while the operator aligns and positions the workpiece on the platform. In applica- tions where it is required that the starting point of the engraving occur consistently at a specific point on the workpiece, such positioning and alignment of the workpiece on the platform is potentially highly time- consuming. A further disadvantage of such a configuration is the limitation on the vertical dimension of a work¬ piece which can be engraved by the machine, due to the positioning of the platform on a moving axis of the machine. As such, workpieces of a substantial vertical dimension cannot be engraved with such a configuration. Neither can the configuration be used to engrave on small portions of a workpiece which is much larger than the platform.

In the engraving table, as described in the above-identified patent applications, the engraving

C^{' '}.P V . ^"vVii- tool and the platform are manipulated by way of lead screws which are driven by stepper motors. Thus, the precise alignment of each lead screw is critical to the "squareness" of the resulting engraving. In the assembly of the above described table, much effort is spent on the precise mounting of the stepper motors, and hence the precise alignment of the lead screws. Typically, this alignment effort takes the form of "shimming" a motor mount until the desired alignment is achieved. Because such a process involves trial and error, it is apparent that a large amount of time is required to achieve the alignment desired.

Disclosure of Invention

The foregoing and other problems of prior art computer controlled engraving tables are overcome by the present invention of an engraving^"table in which an engraving tool is manipulated with respect to a work¬ piece in response to computer generated control signals, wherein carriage means support the engraving tool and are driven along a first axis of alignment by first drive means and wherein second drive means drive the first drive means and carriage means along a second axis of alignment, which is perpendicular to the first axis of alignment. The first and second drive means are support by base means having an opened interior. Platform means are provided which are adapted to rapidly engage with and disengage from the base means. The platform means are positioned within the opened interior of the base means so that the engraving tool can be manipulated with respect to a workpiece positioned on the platform means. Also provided are means for the mounting and simplified positioning of the first and second drive means along their respective axes of alignment including a mounting -4-

body having a spherically-shaped head, wherein an axial bore extends through the head and body, and socket clamp means for receiving the head portion of the mounting body, such that a the motor and the lead screw being joined within the body and extending axially through the body, and so that in one position, the socket clamp means permit the axis of alignment of the lead screw and stepper motor to be pivotted with respect to the base means and in the second position the clamp means fixes the axis of alignment of the lead screw and stepper motor in its current position.

In a further embodiment of the present invention, rack means are provided for supporting the base means so that the vertical height of the platform can be varied by positioning the platform on pairs of ledges corresponding to different vertical heights with respect to the engraving tool.

Thus, it can be seen that the present invention provides a stationary platform which can be quickly engaged or disengaged from the base of the engraving table. As such, a palletizing operation can be instituted wherein a number of platforms are utilized, such that the next workpiece to be engraved can be mounted on one platform while the engraving operation is conducted on a workpiece mounted on another platform which is already engaged to the base of the engraving table. When the current engraving operation is com¬ pleted, the platform can be quickly removed from the base means and the next platform with the next work- piece can be rapidly substituted. Thus, valuable engraving time is saved.

By providing a base means having an opened interior space, the engraving machine can be positioned on top of larger objects to engrave a small area of the larger object. Thus, for example, where a small portion of a large sheet of material is desired to be engraved, the whole machine, without a platform, would be positioned on top of the sheet and over the area sought to be engraved. The engraving operation would then be conducted through the opened interior space of the base means.

Moreover, with an opened interior space in the base means, rack means can be added which permit the positioning of the platform at differing vertical heights with respect to the engraving tool. Thus, where tall objects are sought to be engraved, the platform can simply be positioned on the appropriate level of the rack such that th region of the workpiece which is sought to be engraved extends through the opened interior space and is positioned at the appro- priate height with respect to the engraving tool.

It is, therefore, an object of the present inven¬ tion to provide a computer controlled^" engraving appa¬ ratus, wherein the workpiece is held stationary with respect to the engraving tool and wherein a base having an opened interior space is provided.

It is another object of the present invention to provide a computer controlled engraving table, wherein the machine base has an opened interior space and a stationary platform for supporting the workpiece with respect to the engraving tool which can be quickly engaged or disengaged from the opened interior space of the base.

It is a further object of the pre.sent invention to provide a computer controlled engraving table wherein the base has an opened interior space so that the engraving machine can be positioned over a workpiece having substantially larger dimensions than the engrav¬ ing table and so that engraving can be performed upon a small portion of the workpiece. It is still another object of the present inven¬ tion to provide a computer controlled engraving table

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wherein the base of the machine has an opened interior space and, furtherwherein, rack means and a platform are provided such that the engraving machine is sup¬ ported by the rack means and so that the platform can be positioned at different levels of the rack means so that workpieces of different vertical heights can be accommodated thereby.

It is a still further object of the present invention to provide a computer controlled engraving table wherein means are provided for mounting the stepper motor and lead screws to the base of the table which utilize a mounting body having a spherical head and a clamp, such that in one position, the clamp permits the axis of alignment of the lead screw and stepper motor to be pivotted to the correct angle required for parallel alignment, and in the second position clamps the axis of alignment of the stepper motor and lead screw in its current angular position. The foregoing and other objectives, features and advantages of the invention will be more readily understood upon consideration of the following detailed description of certain preferred embodiments of the invention, taken in conjunction with the accompanying drawings.

Brief Description of the Drawings

Figure 1 is a perspective view of a simplified depiction of the present invention.

Figure 2 is a front, cut-away view of the present invention along lines 2-2 of Figure 1, also illustrat- ing the positioning of the platform and rack means.

Figure 3 is a break-away view of the motor mount for mounting the stepper motor and lead screw to the base of the engraving machine.

Figure 4 is a cut-away view, taken along the axis of the alignment of the motor mount.

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Figure 5 is a bottom view of an alternate platform configuration.

Figure 6 is a perspective view of a dovetail-shaped foot used in the alternate platform con iguration. Figure 7 is a cut-away view of an alternate means for quickly securing the free end of the platform to the base.

Modes For Carrying Out The Invention

Referring to Figure 1 , it can be seen that a "T" drive system is utilized in manipulating the engraving tool 10 with respect to the workpiece 42. The engrav¬ ing tool 10 is positioned on a carriage 12. The car¬ riage 12 is moved back and forth along a first axis which is defined by lead screw 14 and rail 16. Carriage 12 engages lead screw 14 via lead screw nut 18. Lead screw nut 18 is threaded to accommodate the threads of lead screw 14 such that, as lead screw 14 is rotated, lead screw nut 18 is urged along lead screw 14 which, in turn, urges carriage 12 in the same direction. Carriage 12 engages rail 16 by way of a conventional sliding bearing. Lead screw 14 is driven by drive means including stepper motor 20. Stepper motor 20 and lead screw 14 are coupled to one another in motor mount 22. Moveable base 24 supports rail 16, the free end of lead screw 14, and motor mount 22.

From Figure 1 , it can be seen that moveable base 24, and hence stepper motor 20, lead screw 14, and rail 16 are collectively driven by drive means including stepper motor 26 and lead screw 28 along a second axis perpendicular to the first axis. This second axis of motion is defined by rails 30 and lead screw 28 to be perpendicular to the axis defined by rail 16. As in the case of carriage 12, moveable base 24 is coupled to lead screw 28 by way of a lead screw nut 32. The lead screw nut 32 is threaded to accept the threads of lead screw 28 such that rotation of lead screw 28 causes lead screw nut 32, and hence moveable base 24, to move along lead screw 28. As is the case with carriage 12, moveable base 24 is coupled to rails 30 by way of conventional sliding bearings.

Stepper motor 26 is coupled to lead screw 28 in motor mount 34 and is supported by motor-mount 34. Motor mount 34, in turn, mounts the stepper motor and lead screw to table base 36. Rails 30 are also positioned on table base 36.

As can be seen from Figure 1 , table base 36 comprises an outer frame which surrounds an opened interior space 38. Thus, engraving tool 10 is manipu¬ lated over and above the workpiece 42 which is positioned on a platform 40, which in turn is located within the opened interior space 38.

Referring to Figure 2, a frontal, cut-away view of the engraving table is shown taken along lines 2-2 of Figure 1. Figure 2 illustrates the positioning of the platform 40, with respect to the table base 36 within the opened interior space 38. The workpiece 42 is shown positioned on platform 40 with respect to engraving tool 10. Also illustrated in Figure 2 is a vertical rack 44 which is designed to support the engraving table and to provide different levels upon which platform 40 can be positioned to provide a variety of vertical distances between the top of platform 40 and the engraving tool 10.

In Figure 2, it can be seen that table base 36 provides an edge portion 46 along the periphery of the interior space 38. This edge portion 46 includes a horizontal ledges 48A and 48B and an inclined face 50. In the preferred embodiment of the present invention, the angle of inclination of face 50 is approximately 30 degrees from vertical. Additionally, in the preferred embodiment of the present invention, the width of the horizontal ledges 48A and 48B are approximately three quarters of an inch.

As can be seen from Figures 1 and 2, one of the edges of platform 40 has a beveled face 52 which is inclined downward and at an angle substantially equal to that of face 50. Beveled face 52 extends to the bottom plane of platform 40, such that when platform 40 is inserted into opened inner space 38, beveled face 52 and face 50 are juxtaposed and a portion of the bottom plane of table 40 rests upon ledges 48A and 48B. This juxtapositioning of faces secures one edge of platform 40 to table base 36. The other edge of platform 40 is secured to ledge 48B by way of thumb screws 54 which are shown positioned adjacent the edge of platfrom 40 opposite that containing beveled face 52. These thumb screws screw into tapped holes 56 located within ledge portion 48B.

To engage or disengage platform 40 from table base 36, stepper motor 26 is energized to cause moveable base 24 to move to the rear of the table. This clears the opened interior space 38. Platform 40 is then positioned on ledge 48A so that inclined face 52 meets beveled face 50. The opposite end of platform 40 is then lowered to rest upon the opposite ledge 48B.

Thumb screws 54 are then screwed into tapped holes 56 to secure that end of the platform to the table base. The juxtapositioning of beveled face 52 and face 50 secure the beveled edge portion of platform 40 to the base. For removal of the table 40, the procedure is reversed.

The platform 40 can thus be quickly inserted or removed from table base 36. In turn, the pallettiz- ing operation, as discussed above, can be implemented. As one platform and workpiece are being worked upon on

_ OMFI the engraving table, a second platform can be concur¬ rently set up with the next workpiece to be engraved. When the current engraving operation is finished, thumb screws 54 are quickly disconnected from table base 36 and the platform 40 with finished workpiece can be easily lifted out. The next platform with new workpiece can then be quickly inserted into and secured to the table base for the next engraving operation. Valuable engraving time is thus saved. As can be seen from Figure 2, in the preferred embodiment of the present invention, table base 36 is formed from channel-like members. These members provide ribs 58 which support rails 30. These rails 30 are typically screwed into or bonded to the ridges 58. The channel-like members have an inverted "ϋ" shape to provide high strength with minimum weight. As can be seen from Figure 2, edge portion 46 of table base 36 are formed as an integral part of these channels, utilization of inverted "ϋ" shaped channels for table base 36 also provides for a "nest" within which platform 40 and workpiece 42 can be positioned. With such a "nest" configuration, the debris from the engraving operation can be confined within the nest and away from the moving parts of the engraving table, such as lead screws 14 and 28, and from rails 30 and 24.

In the preferred embodiment, the opened interior space 38 of table base 36 has the shape of a parallelogram. The dimensions of the parallelogram are selected to correspond to the range of movement of engraving tool 10. It is to be understood that the opened interior space 38 can take other shapes, such as a circle or an ellipse.

Figure 2 also illustrates another embodiment of the present invention in which a rack 44 supports table base 36 so that opened interior space 38 is disposed over the interior of rack 44. Disposed on sidewalls 60 and 62 of rack 44 are pairs of ledges 64 substantially similar in shape to ledges 48A and 48B and inclined face 50. These pairs of ledges 64 are each positioned in a different horizontal plane such that platform 40 can be supported on a pair of ledges 64 in the corresponding horizontal plane.

Rack 44 preferably has at least one opened side so that the platform 40 can be inserted into the interior of the rack. Additionally, the spacing between pairs of ledges 64 should be selected to be less than the maximum possible vertical movement of the engraving tool 10. In this manner, it can be assured that, for a workpiece of a given height, there will be one pair of ledges 64 upon which the platform 40 can be positioned to place the workpiece within the range of vertical movement of tool 10.

It is to be understood that means for varying the vertical height of engraving tool 10 over a small range is well-known in the engraving art. For example, the engraving tool could be mounted upon a threaded member, the position of which can be varied by rotating the member into or out of carriage 12. While these previously known methods for varying the vertical height of the engraving tool 10 permit the tool to be used with workpieces having a small range of vertical heights, the rack 44 permits workpieces having widely varying vertical heights to be accommodated by the engraving table. Referring to Figure 3, motor mount 22 will now be described in greater detail. Motor mount 34 is substantially similar to motor mount 22, so that the following description is equally applicable to motor mount 34. Figure 3 is a perspective, exploded, cut-away view of one embodiment of motor mount 22. Figure 4 provides a cross-sectional view of motor mount 22 taken along the axis of the shaft of the stepper motor and the lead screw 14. From Figure 3, it can be seen that the motor mount includes a clamp portion 64 and a mounting body portion 66.

Clamp 64 includes a fixed portion 68 which is screwed to table base 36 (in the case of motor mount 34) and to moveable base 24 (in the case of motor mount 22). A removable cap 70 is provided which screws onto fixed piece 68.

Mounting body 66 has a head portion 72 which is substantially spherical in shape, and which has a bore 74, see Figure 4, which permits the lead screw 14 to pass therethrough. Head 72 is fastened to one end of a cylindrical member 76. Mounting block 80 is attached to the other end of cylindrical member 76. Cylindrical member 76 contains a chamber 78. As can be seen from Figure 4, bore 74 of head portion 72 is extended hrough cylindrical member 76, by way of opening 82, where head portion 72 is attached to cylindrical member 76, by chamber 78, and by bore 84 through mounting block 80. As can be seen from Figure 4, shaft 86 of the stepper motor extends through bore 84 of mounting block 80 into chamber 78. Similarly, lead screw 14 extends through bore 74 of head portion 72, through opening 82, and into chamber 78. Within chamber 78, shaft 86 and lead screw 14 are coupled together by coupling body 88. Coupling body 88 is constructed of a resilient, flexible material which permits the shaft 86 and lead screw 14 to rotate together, even when there is a slight misalignment between the two. Note that chamber 78 is shaped to permit rotation of coupling body 88 with shaft 86 and lead screw 4. Note also that stepper motor 20 is fastened to mounting block 80 by way of screws 90. Referring to Figure 4, it can be seen that lead screw 14 is supported within head portion 72 and within the opening 82 of cylindrical body 76 by way of b or roller bearings 92. These bearings 92 are positioned within bearing seats formed within the head portion 72 and the cylindrical body 76. In the preferred embodiment, these bearing seats take the form of a cylindrical cavity 94 which is formed in the head portion 72 and the cylindrical member 76. The diameter of the cavity 94 is selected to be slightly larger than the outer diameter of the roller bearings 92 for a snug fit.

It can be seen from Figure 4 that, in assemb¬ ling the roller bearings 92 into the mounting body 66, the bearings 92 are first positioned in cylindrical cavity 94 of cylindrical member 76 to be coaxial with opening 82. Head portion 72 is then fastened to cylindrical member 76 with screws 73 so that the cylindrical cavity 94 in the head portion 72 completes the enclosure of the bearings 92. Bearings 92 are thereby snugly encased within mounting body 66 and disposed coaxially with bore 74. Lead screw 14 can then be inserted into bore 74, through bearings 92 and into chamber 78. In the preferred embodiment, lead screw 14 has a screw portion of one diameter and a threaded portion, at one end, of a smaller diameter. The thread portion is inserted through the bore 74 and bearings 92 and thence into the chamber 78. A nut 83 is threaded onto the threaded portion so that the screw portion of the lead screw abuts against. the bearings 92. The lead screw is thus secured for rotation in the mounting body 66. Thus, it can be seen that lead screw 14 rotates within bore 74 and opening 82. As discussed above, head portion 72 is substantially spherical in shape. Fixed portion 68 and cap portion 70 of clamp 64 each contains a half spherical concave cavity 69 such that when cap 70 is fastened to fixed portion 68, a substantially spherical chamber is defined which has substantially the same radius of curvature as that of the exterior surface of head portion 72. In other words, the contour of the chamber is a substantial compliment of the contour of the head portion 72 so that the area of contact between the internal surface of clamp 64 and the external surface of head portion 72 is maximized. It follows that when head portion 72 is disposed within the substantially spherical chamber, these spherical cavities 69 closely conform to the external surface of head portion 72, forming what can be loosely termed a ball and socket joint. When cap portion 70 is fastened with light pressure to fixed portion 68, head portion 72 is free to pivot within the spherical chamber. On the other hand, when cap 70 is tightly bolted to fixed portion 68, head portion 72 is clamped firmly in its present position. The close conformance of the inner surface of the cavities 69 of clamp 64 with the external surface of head portion 72 provides a tight and solid clamping action with a substantial amount of grip area. As such, the motor mount of the present invention is utilized as the major structural support for each stepper motor and lead screw. As can be seen from Figures 1 and 2, the free end of the lead screw is supported by adjustable end pieces 96, which are provided to prevent undue movement of the free ends and to provide some structural support.

In assembling the engraving table, a stepper motor is bolted to mounting block 80 of mounting body 66. The lead screw is inserted into bore 74 through bearings 92 and into chamber 78, where it is coupled to the stepper motor shaft 86 via coupling body 88. Coupling body 88 is resilient and flexible to permit rotation of the lead screw 14 by the stepper motor shaft 84, even when the two are slightly misaligned. One such commercially available coupling body is manufactured by Helical Products of Santa Maria, California.

Head portion 72 is then encased or nested within the spherical chamber defined by the cavities 69 of cap 70 and of fixed portion 68 of clamp 64. The free end of the lead screw is then coupled to end block 96. Cap portion 70 is first fastened to fixed portion 68 with light pressure so that head portion 72 is permitted to pivot within the chamber, and so that proper alignment is obtained along the particular drive axis. Once this alignment is obtained, cap 70 is tightly fastened to fixed portion 68 of clamp 64 thereby fixing the motor mount body 66 and hence the axis of alignment in the proper, aligned position. In this manner, no additional adjustments are needed. There is no requirement for "shimming" or any other fine tuning of the position of the lead screw and stepper motor.

From another point of view, the motor mount 22 provides a ball and socket joint which permits articulation of the stepper motor and lead screw axis of alignment, in one configuration, and which rigidly secures the stepper motor and lead screw to the base when proper alignment is obtained, in a second configura- tion.

In the preferred embodiment of the present invention, the "U" shaped channels which form base 26 are extruded of 6063-T5 aluminum material. The head portion of the motor mount is constructed from brass which has been nickel-plated.

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In the preferred embodiment of the present inven¬ tion, the head portion 72 is further modified so that an annular section 75 of the external surface, which is coaxial with bore 74, is flattened. See Figure 3. Preferably, this annular portion 75 is located at the mid-point of the spherical arc. By providing this flattened annular surface 75, an enhanced clamping of the head portion 72 by the clamp 62 can be obtained.

Figure 5 illustrates an alternative embodiment of platform 40. In this embodiment, the beveled face 52 required for juxtapositioning against face 50 of table base 36 is provided by dovetail footings 98. In the preferred embodiment, the angle of this beveled face is 60 degrees. See Figure 6. These footings 98 are secured to a platform portion 100 by screws, not shown. In order to compensate for the added height of the platform portion 100 due to footings 98 positioned at one end 99 thereof, spacers 102 are secured by screws, not shown, at the other end 101 of platform portion 100. These spacers 102 can be the footings 98 themselves which are aligned with end 101 of the platform portion 100, or any other spacers of appropriate height.

Also illustrated in Figure 5 is a alternative means for securing end 101 of platform portion 100 against ledge 48B. A cam 104 is shown rotatably mounted to platform portion 100 for movement between a first position, dotted line 103, and a second position, shown in solid line 105. Cam 104 is a disk having a beveled periphery 106. See Figure 7. Preferably the cam 104 has an axial thickness which is less than the thickness of spacers 102 so that cam 104 is free to rotate between platform portion 100 and ledge 48B.

When cam 104 is in the second position, beveled periphery 106 is caused to engage with face 50 adjacent ledge 48B. In this position beveled periphery 106 acts -17-

much like beveled edge 52 of platform 40, in Figure 2, in that it is juxtaposed against face 50.

When cam 104 is in its first position, beveled periphery 106 is disengaged from contact with face 50 and the platform portion 100 can then be quickly and easily lifted from base 36.

From Figures 5 and 7, it can be seen that cam 104 pivots about a point which is away from its center. Thus, as cam 104 is moved from its first position to its second position, an increasing portion of cam 104 is caused to extend beyond end 101 of the platform portion 100. The greater the extension of cam 104, the greater the amount of lateral force which is produced by the engagement of beveled periphery 106 with face 50, adjacent ledge 48B. This "camming" action causes platform portion 100 to be urged toward face 50, adjacent ledge 48A. As cam 104 is further rotated toward its second position, dovetail footings 98 are urged with increasing force against face 50. Because the periphery of cam 104 is beveled for juxtapositioning with face 50 adjacent ledge 48B, cam 104 is wedged against face 50 in its second position to hold end 101 against the base 36. In this manner, cam 104 simultaneously urges the dovetail footings 98 against face 50 adjacent ledge 48A to secure end 99 of platform portion 100 to base 36, while itself being wedged against face 50 adjacent ledge 48B to secure end 101 of the platform portion 100 to the base 36.

Figure 7 illustrates the manner in which cam 104 is mounted to platform portion 100. A cam shaft 108 extends through the platform portion 100 with a square head 110 provided at each end. The top end of cam shaft 108 is supported with respect to platform portion 100 by a snap ring 112 and a spring washer 114, both of which are mounted coaxially with the cam shaft 108.

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The spring washer 114 is positioned below the snap ring 112. The snap ring 112 acts to retain spring washer 114 on the cam shaft 108 when spring washer 114 is compressed by a downward force applied on the cam shaft 108. This downward force arises upon the engagement of beveled periphery 106 with face 50.

The bottom end of cam shaft 108 is coupled to cam 104 through a square hole ^ 16 positioned away from the center of cam 104. A screw 118 secures cam 104 to cam shaft 108.

In operation, a key having a square socket adapted for engagement with the square head 110 at the top of cam shaft 108 is used to rotate cam shaft 108 and hence to rotate cam 104 between its first and second posi- tions. As beveled periphery 106 begins to engage face 50, cam 104 is urged in a downward direction by such engagement. Spring washer 114 is compressed to a corresponding degree. As cam 104 is further engaged with face 50, spring washer 114 is further compressed. This compression of spring washer 114 acts to supply tension to cam shaft 108 so as to retain the beveled periphery 106 against face 50 when cam 104 is in its second position. The platform portion 100 is thus held in a locked position until cam 104 is rotated out of its second position. When cam 104 is rotated to its first position, platform portion 100 is disengaged from base 36.

It is to be understood that while the alternate platform configuration has been described in conjunc- ^' tion with a planar table portion, any work-holding fixture upon which the dovetail footings 98, the spacers 102 and the cam shaft 108 - cam 104 configu¬ ration are positioned for engagement with base 36 is contemplated to be embraced by the present invention. PCT/US82/01199

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The terms and expressions which have been employed here are used as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions of excluding equivalents of the features shown and described or portions thereof, it being recognized that various modifications are possible within the scope of the invention claimed.

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Claims

1. A computer controlled engraving table of the type in which an engraving tool is manipulated with respect to a workpiece in response to computer-generated control signals, comprising carriage means for supporting the engraving tool; first drive means responsive to the control signals for urging the carriage means along a first axis, wherein the carriage means are coupled for movement to the first drive means; moveable base means for supporting the first drive means; second drive means responsive to the control signals for urging the moveable base means along a second axis perpendicular to the first axis, wherein the moveable base means are coupled for movement to the second drive means, so that by movement of the moveable base means along the second axis, the carriage means is urged along an axis parallel to the second axis; table base means, for fixedly supporting the second drive means and for supporting the moveable base means for movement along the second axis, the table base means having an opened interior space; platform means adapted for engagement with the base means in the opened interior space for supporting the workpiece in relation to the engraving tool; and means for mounting the second drive means to the table base means and for mounting the first drive means to the moveable base means.

2. The apparatus of claim 1 wherein the first and second drive means each comprise a stepper motor which drives a lead screw, and furtherwherein the mounting means include a mounting body for supporting the stepper motor, the mounting body having an axial bore which is shaped to receive the lead screw for axial rotation therein, the mounting body having a head portion which contains a portion of the axial bore, the head portion having a substantially spherical shape; bearing means for rotatably supporting the lead screw, the bearing means being positioned within the mounting body and coaxially with the axial bore; clamp means fixedly mounted to the table base means for supporting the head portion of the mounting body, the clamp means having a spherical chamber in which the head portion is positioned and which has an interior surface which is complimentary to the exterior surface of the head portion, the chamber being configurable with a first radius of curvature and a second radius of curvature, so that the head portion is free to pivot about the chamber when the chamber is of the first radius of curvature, and the head portion is firmly grasped by the interior surface of the chamber when the chamber is of the second radius of curvature to secure the head in its current position.

3. The apparatus of claim 2 wherein the bearing means comprise a plurality of roller bearings and furtherwherein the mounting body includes a shell portion having one end adapted for fastening to the stepper motor and a second end which has a first bearing seat for supporting one of the plurality of roller bearings to be coaxial with the axial bore; and a separate spherical member forming the head portion and having a predetermined radius of curvature, the separate spherical member having a second bearing seat which is coaxial with the axial bore for supporting a different one of the plurality of roller bearings, the head portion being fastened to the shell portion so that the roller bearing which is positioned in the first bearing seat is coaxial with and abuts against the roller bearing which is positioned in the second bearing seat.

4. The apparatus of claim 3 wherein the stepper motor has a shaft which is coupled to the lead screw by way of a coupling body one end of which accepts the stepper motor shaft and the other end of which accepts the lead screw so that the stepper motor shaft and the lead screw are substantially coaxial with one another, and so that the rotation of the shaft is transferred to the lead screw, and furtherwherein the shell portion has a chamber which is concentric with the bore and which opens to the exterior of the shell portion so that the coupling body can be positioned for rotation therein.

5. The aparatus of claim 3 wherein the clamp means include a fixed member which is secured to the table base means, the fixed member having a spherically concave cavity, the concave cavity having a radius of curvature which corresponds to the radius of curvature of the head portion; a moveable member which can be fastened to the fixed member in a first and a second position, the moveable member having a concave cavity which is substantially similar to the concave cavity of the fixed member such that when the moveable member is fastened to the fixed member in the second position, the concave cavities of the fixed and moveable members are substantially aligned with one another to define a substantially spherical chamber which is opened at opposite ends and which has substantially the same radius of curvature as the head portion, and such that when the moveable member is in the first position the concave cavities collectively define an approximately spherical chamber having a radius of curvature which is greater than the radius of curvature of the head portion whereby the head portion is free to pivot within the chamber when the moveable member is fastened in the first position and is prevented from pivoting when the moveable member is fastened in the second position; and means for securing the moveable member in the first and second positions.

6. The apparatus of claim 4 wherein the coupling body is resiliently flexible to permit rotation of the stepper motor shaft in conjunction with the lead screw when there is a small amount misalignment between

5 the stepper motor shaft and the lead screw.

7. The apparatus of claim 5 wherein the securing means include a plurality of screws for fastening the moveable member of the clamp means to the fixed member of the clamp means

10 8. The apparatus of Claim 1 wherein the first and second drive means each include a stepper motor having a shaft which drives a lead screw and furtherwherein the mounting means include ball and socket joint means comprising T5 a first member which is fixedly mounted to the table base means and which has a socket portion; and a second member shaped for mounting to the stepper motor and having a ball portion which is 20 adapted for coupling with the socket portion and for pivoting within the socket portion, the combination of the ball and socket forming a ball and socket joint, wherein the the second member has a chamber which extends through one end of the 25 second member through the ball portion and through the opposite end of the second member so that the stepper motor shaft of the stepper motor shaft and the lead screw can be axially coupled within the chamber; and furtherwherein the socket portion 30 of the first member is open at opposite ends so that the ball portion can be encased in the socket portion with the remainder of the second member protruding from one open end of the socket portion and so that the lead screw can exit through the other open end, the socket portion being adjustable between a first and a second radius so that in the first radius, the ball portion is free to pivot and in the second radius, the ball portion is secured in a fixed position.

9. The apparatus of claim 8 wherein the ball portion has a substantially spherical shape and furtherwherein the socket portion has an internal surface which defines a substantially spherical region which is substantially complimentary to the shape of the ball portion so that the contact between the internal surface of the socket portion and the ball portion is maximized when the socket portion is adjusted to its second radius.

10. The apparatus of claim 8 further including a coupling body for coupling the stepper motor shaft to the lead screw; wherein the coupling body is flexibly resilient to permit rotation of the stepper motor shaft with the lead screw when there is a small axial misalignment between the lead screw and the shaft; and furtherwherein the chamber of the first member is shaped so that the coupling body can be disposed for axial rotation, therein.

11. The apparatus of claim 8 wherein the lead screw is supported within the chamber of the first member by bearing means positioned within the chamber.

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12. The apparatus of claim 11 wherein the second member comprises a separate head portion having an axial bore open to opposite ends of the head portion and having a bearing seat for supporting the bearing means; and a body portion which defines the chamber of the first member and which has one end adapted for mounting to the stepper motor and which has an opposite end in which is positioned a bearing seat for supporting the bearing means wherein the head portion is fastened to the body portion so that the axial bore of the head portion is substantially concentric with the chamber and so that the bearing seat of the body portion faces the bearing seat of the head portion such that the bearing means are supported within and by the juxtaposed bearing seats.

13. The apparatus of claim 1 wherein the platform means and the table base means include interlocking edge means for rapid coupling and decoupl¬ ing of the platform means to 'the table base means in an horizontal plane comprising

(a) a first edge member disposed on the table base means along the periphery of the opened interior space of the table base means including (i) a ledge portion which extends outwardly from the table base means into the opened interior space and having a top surface which is parallel to the horizontal plane; and

(ii) an inclined face section which is positioned above the the ledge portion and along the portion of the table base member from which the ledge portion extends; (b) a second edge member disposed along the outer periphery of one end of the platform means including

(i) a beveled face section, positioned along a predetermined portion of the platform means, which is shaped for juxtapositioning against the inclined face of the first edge member; and

(ii) a horizontal face which extends along the bottom of the platform means at the periphery of the second edge member for positioning on the ledge portion of the first edge member; and

(c) means for securing the end of the platform means, which is opposite the end upon which is disposed the beveled face section, to the corresponding ledge of the first member so that the platform means can be coupled to the table base means by juxtaposing the inclined face portion of the first edge member with the beveled face of the second edge member, by supporting the horizontal face of the second edge member on the ledge of the first edge member, and by securing the portion of the platform means, which is disposed opposite the beveled face section, to the ledge portion of the first edge member.

14. The apparatus of claim 1 further including vertical rack means adapted for supporting the base means, the vertical rack means comprising a bottom member; a top member having an interior open area of substantially the same dimensions as the opened interior space of the table base means and shaped . for supporting the table base means; a first side member; and a second side member which is spaced apart but parallel to the first side member, the side members joining the top member to the base member, each side member having a plurality of horizontal ledges wherein each one of the plurality of ledges on the first side member corresponds to one of the plurality of lips on the first side member corresponds to one of the plurality of lips on the second side member to form a plurality of pairs of lips such that each of the pairs of lips is disposed in a hypothetical horizontal plane, so that the table means can be slideably positioned on a pair of lips in the vertical rack means so that the vertical distance between the table means and the engraving tool can be varied to accomodate work pieces of varying vertical heights.

15. The apparatus of Claim 1, wherein the table base means is a rectangular frame including a first support arm which slideably supports one end of the moveable base means; a second support arm which slideably supports the other end of the moveable base means and which fixedly supports the second drive means; and first and second connecting arms for rigidly connecting corresponding ends of the first and second support arms to form the rectangular frame, so that the rectangular frame defines the area of the opened interior space, and so that the apparatus can be placed on top of a workpiece having substan¬ tially larger dimensions than the opened interior space,and so that the engraving tool can be manipulated with respect to the portion of the workpiece enclosed by the opened interior space.

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16. Apparatus for manipulating an. engraving tool with respect to a workpiece in response to control signals, comprising fixed base means for defining a work space, wherein the work space is framed by the fixed base means so that the perimeter of the work space is enclosed and so that the top and bottom of the work space are open; platform means for supporting the workpiece in the work space, the platform means being adapted for rapid engagement to and disengagement from the fixed base means; moveable drive means for urging the engraving tool along a first axis within the work space; moveable base means for supporting the moveable drive means and the engraving tool; fixed drive menas for urging the moveable base means along a second axis which is perpendi¬ cular to the first axis; and means for mounting the fixed drive means to the fixed base means and for mounting the moveable drive means to the moveable base means.

17. The apparatus of Claim 16 further including rack means for increasing the vertical dimension of the work space, wherein the rack means include a top platform for supporting the fixed base means, the top platform having an aperture which opens into the work space which is framed by the fixed base means; and

OMPI a plurality of side members for supporting the top platform and the platform means, wherein the side members include a plurality of ledges shaped for slideably supporting the platform means, and furtherwherein one of the plurality of ledges are positioned at predetermined vertical points along the side members so that the platform means can be positioned at differen distances from the engraving tool.

18. The apparatus of Claim 16, wherein the platform means are supported by the fixed base means along a horizontal ledge which extends from the inner periphery of the fixed base means, the fixed base means further including an inclined face which is positioned along a first portion of the fixed base means and which is inclined over a portion of the horizontal ledge, and the platform means further including a beveled edge shaped for juxtapositioning with the inclined face when the platform means is supported along the horizontal ledge, and further including screw means for removeably fastening the platform means to the horizontal ledge, which is disposed along a second portion of the platform means and which is located opposite the first portion of the platform means,so that one end of the platform means is held against the horizontal ledge by the juxtapositioning of the inclined face and the beveled face, and the other end of the platform means is fastened to the horizontal ledge by the screw means when the platform means is in engagement with the fixed base means.

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19. The apparatus of Claim 13, wherein the second edge member comprises a dovetail footing positioned along the end of the platform means, the dovetail footing including the beveled face section and having a predetermined height and furtherwherein the means for securing the oppo¬ site end of the platform means includes spacers positioned along the opposite end of the platform means, the spacers having height substantially equal to the predetermined height of the dovetail footing, and cam means mounted for movement between a first position, in which the cam means is disengaged from the inclined face of the first edge member and a second position in which the cam means is engaged with the inclined face of the first edge member.

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20. The apparatus of Claim 19, wherein the cam means comprises a cam shaft mounted for rotation at one end of the platform means and extending through the platform means; spring means positioned at the top of the cam shaft for resiliently supporting the cam shaft with respect to the top of the platform means; and a disk-shaped body fixedly connected to the bottom of the cam shaft and below the platform means, wherein the disked-shaped body has a beveled periphery shaped for engagement with the inclined face of the first edge member, and furtherwherein the cam shaft is connected to the disk-shaped body at a point away from the center of the body so that the disk-shaped body extends outwardly beyond the platform means when the cam means is in its second position and so that the disk-shaped body is positioned substantially beneath the platform means when the cam means is in its first position.