BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention generally relates to modular fixturing systems used in the machine industry to accurately position workpieces relative to machine tools. It is particularly concerned with modular fixturing systems which can be adapted for use in the context of robotic workstations. 2. Description of the Prior Art

In any fixturing operation there are four essential considerations which must be addressed: locating, supporting, clamping and referencing a machine tool relative to a workpiece. Those skilled in this art will appreciate that the method used to reference a machine tool to a workpiece also is the principle means used to distinguish a jig from a fixture. Essentially, a jig guides the cutting tool while a fixture references the tool to the workpiece. While these definitions may seem similar,, different concepts are involved. In effect, a jig guides the cutting tool by containing the tool within a hardened bushing. A fixture, on the other hand, references the cutting tool with a set block or similar cutter tool setting device.

An ideal fixturing system would be one having a

single workholder, much like a vise, that could be used to hold any part. However, in practice this goal is impossible to achieve. The next best thing is to have as few workholders as possible while maintaining the capability- of holding virtually any part. This goal can be achieved by using a system of interchangeable and reusable parts. This general idea is often referred to as "modular fixturing". It has as its underlying concept the use of standardized parts to build specialized fixtures. Generally speaking such standardized parts comprise stacking elements each of which has an array of like holes (e.g. , an array of threaded holes or an array of dowel holes) . Such modular fixturing parts are, in principle, totally reusable; hence the cost per part or lot is significantly reduced. Additionally, since a modular fixture is not a permanent tool, the various components used to assemble the system can be disassembled at the end of the production run and used to make other fixtures.

Such modular fixturing systems have been the subject of several patents and technical publications. For example, United States Patent No. 3,537,697 (the 697 patent) teaches a modular fixturing arrangement for supporting workpieces for machining operations; it is comprised of a baseplate or pallet having tapped fixing holes arranged at the junctions of a square grid and support devices which can be secured to the baseplate or pallet by use of selected fixing holes. Different positional arrangements for various support devices relative to the baseplate can be achieved by using different selections of fixing holes. The holes also are arranged so that the plate member can be placed on a pallet in a number of different

relationships.

Reference works such as Modular Fixturing, by E.G. Hoffman, Manufacturing Technology Press, Lake Geneva, Wisconsin (1987) , disclose a wide variety of modular fixturing systems. The elements used in the therein disclosed fixture systems generally include baseplates or mounting bases, locating and supporting elements, mounting blocks and clamping elements. Most prior art systems are characterized by having either threaded holes or smooth bored holes which are specifically adapted to receive respectively a threaded bolt or a dowel pin. Hence stacking is typically done by aligning threaded holes of the stacking elements or aligning smooth bored holes of stacking elements. That is to say that, taken as a whole, the prior art teaches "stacking" by means of threaded bolts passing through aligned threaded holes or by means of dowel pins passing through aligned smooth bore holes in two or more stacking elements. Such prior art fixturing systems are ^' typically capable of achieving tolerances of approximately ± 0.030 to 0.040 inches, or roughly a "true position" tolerance of 0.070 inches diameter with respect to those coordinate dimensioning systems known to this art. Obviously, any fixturing systems capable of greater design and/or construction flexibility which can be achieved in conjunction with equal or improved tolerance capabilities would represent welcome additions to the modular fixturing art.

SUMMARY OF THE INVENTION

The modular fixturing system of this patent disclosure is based upon three stacking components, the use of counterbored holes in two of the three stacking components and as many as four types of fasteners (i.e., a threaded bolt, a shoulder bolt, a dowel pin and optionally, two types of threaded dowel pins) . More specifically, the components of the herein disclosed modular fixturing system are: a baseplate (B) , a middle stacking element (M) , a top stacking element (T) , a fastener means and means for preventing lateral movement of the stacking elements with respect to baseplate (B) . Any number of stacking elements (M) and/or (T) may be stacked in any combination. Standard fasteners (e.g., bolts, dowel pins, etc.) and conventional means (e.g., key and keyway locking systems, etc.) for preventing lateral movement of the system may be used in conjunction with the stacking elements of this system. Stated in still more detail, the herein disclosed modular fixturing system will comprise: (a) a baseplate (B) having a basing surface, an upper mounting face surface and a plurality of holes in an array or matrix which includes at least two holes which each have a counter bored, unthreaded, upper portion having a top end which opens to the top face surface of (B) and a bottom end which terminates in a concentric, threaded lower portion; (b) at least two stacking elements selected from the group -consisting of (1) a middle stacking element (M) having at least one threaded hole which extends through said middle stacking element (M) and, (2) a top stacking element (T) having at least one unthreaded hole which extends

through said top stacking element (T) and which further comprises a larger, counter bored, upper hole portion which terminates in a concentric ledge surface which leads to a smaller, concentric unthreaded lower hole which extends from the ledge to the lower surface of top element (T) ; (c) at least one fastener selected from the group consisting of: (1) a bolt whose shaft is essentially fully threaded such that it is capable of threadedly engaging the threaded hole of the middle stacking element (M) , (2) a shoulder bolt having a shoulder portion which is capable of passing through both the smaller concentric hole of the top stacking element (T) and through the threaded hole of middle stacking element (M) and which terminates in a threaded head (this threaded head can be of two general types: the first is capable of threadedly engaging the_ threaded lower portion of the baseplate (B) and the second is capable of threadedly engaging the threaded hole in the middle stacking element (M) ) ; and (3) a dowel pin capable of passing through the smaller concentric hole of the top stacking element (T) , the threaded hole of the middle stacking element (M) , and the upper unthreaded portion of the baseplate (B) ; and (d) means for preventing lateral movement of the middle and/or top stacking elements with respect to the baseplate (B) . Such means for preventing lateral movement can be separately affixed or tied down to the baseplate (B) or to some stationary object completely outside the modular fixturing system. This modular fixturing system also may further comprise: (1) a bushing having a hole capable of passing the shoulder portion of the shoulder bolt, an upper flange portion capable of resting upon the ledge surface created in the top stacking element (T) by the

larger, counter bored hole in the top of the top stacking element (T) and a tube-like body whose outer diameter is capable of fitting inside the smaller concentric hole of the top stacking element (T) ; (2) a washer having a hole capable of passing the shoulder portion of the shoulder bolt and an outside diameter which will fit inside the larger, counter bored, upper hole portion of the top stacking element (T) , but which will not fit inside the smaller, concentric lower hole of said top stacking element (T) and thereby be rendered capable of seating on the ledge surface of the top stacking element; (3) means for preventing lateral movement of the system which is preferably comprised of a key slot in the top stacking element (T) and/or a key slot in the middle stacking element (M) which are capable of being engaged by a key insert piece which is independently affixed to the baseplate (B) ; (4) a shoulder bolt having a necked down region capable of passing through the hole of the baseplate (B) (and hence through large holes of the top stacking element (T) and middle stacking element (M) ) , (5) an anchor stud which threadedly engages the hole in baseplate B, (6) an anchor stud which threadedly engages the threaded hole of stacking element M and (7) a threaded set screw which threadedly engages a lateral, threaded hole in the side of a top stacking element (T) or a lateral, threaded hole in the side of the middle stacking element (M) and thereby affixing a fastener associated with said top or said middle stacking element. Finally, a number of attachment pieces which are known to this art, but which are not a part of applicant's basic modular fixturing system, also may be attached to applicant's M or T elements.

One particularly preferred stacking arrangement is comprised of a baseplate (B) upon which is stacked a middle stacking element (M) upon which, in turn, is stacked a top stacking element (T) and fastened into a modular fixturing system by means of a shoulder bolt held in place in the top stacking element (T) by means of the herein described bushing. Another preferred stacking arrangement will be comprised of a baseplate (B) upon which are stacked at least two middle stacking elements (M) stacked upon each other and upon which, in turn, is stacked a top stacking element (T) and fastened into a modular fixturing system by means of a shoulder bolt.

Modular fixture systems based upon use of the elements of this system are faster and easier to design and to build. Their assembly time is only a fraction of the time required to set up prior art modular fixture systems based upon stacking elements having either an array of threaded holes or an array of smooth-bore, dowel receiving holes. The modular fixtures of this patent disclosure also can be assembled right on the machine tool if necessary. Overall, the total time required to design and assemble a modular fixture can be reduced by as much as 50 percent of the time required to design and assemble prior art modular fixturing systems and up to 95% of the time required to design and build conventionally constructed fixtures (i.e. , non-modular fixtures) . Moreover, these modular fixtures generally require less maintenance than those of the prior art, and since each tool is disassembled when a production run is complete, neither tool storage or fixture obsolescence are large factors in a decision to use

the . Hence, rather than storing a complete fixture, a list of parts and a few photographs are the only permanent record maintained for the tool. Should a tool be required for additional production runs, the parts list and photographs are simply retrieved and the tool is reassembled. The usual time to accomplish this is much less than even that required to re- qualify a dedicated workholder. Those skilled in this art also will appreciate that the resulting modular fixturing system of this patent disclosure can be used in quality control, automated assembly and inspection, as well as in machining operations. Thus for the purposes of this patent disclosure, including the language used to construct the patent claims, the expression "machining" and/or "machining operations" should be taken to include the term and concepts of automated _assembly operations, quality control operations and inspection operations. They are of course especially useful as fully automated tooling packages. Moreover, by storing the specifications for the various components in the memory of a computer aided drafting (CAD) system, each part required for a given fixture can be called up and placed on a drawing where needed. Again, it should be noted that this system is capable of achieving tolerances which are significantly greater than those achieved by many prior modular fixturing systems; depending on conditions, location accuracies approaching true position of .006 diameter may be achieved. That is to say that applicant's modular fixture system provides tolerance capabilities of approximately ± 0.003, or a "true position" of 0.006 "diameter" with respect to a coordinate dimensioning systems.

With respect to such coordinate dimensioning systems perhaps a few additional words about the concepts of "position" and "position tolerance" would be in order. Position is a term used to describe the perfect (exact) location of a point, line, or plane (normally the center) of a feature in relationship with a datum reference or other feature.. Position tolerance is the term used to designate the total permissible variation in the location of a feature about its exact position. For cylindrical features (holes and bosses) the position tolerance is the diameter (cylinder) of the tolerance zone within which the axis of the feature must lie, the center of the tolerance zone being at the exact position. For other features (slots, tabs, etc.) the position tolerance is the total width of the tolerance zone within which the center plane of the feature must lie, the center plane of the zone being at the exact position. Position tolerance calculations are based on the sizes of the holes and the screws and assuming the shaft is equal to the maximum of the size limit and assuming the hole to be the minimum of the size limit. A maximum material condition ("MMC") then sets the stage for maximum producibility, interchangeability, functional gaging (if desired) , etc. at production. Thus, part acceptance tolerances will increase as the hole sizes in the parts are actually produced and they will vary in size as a departure from MMC. By way of example, if a .016 diameter tolerance is calculated, the tolerance may increase to as much as .022 depending upon the actually produced hole size. It also should be noted that clearance between mating features is the criterion for establishing the position tolerances.

It should also be noted that standard materials can be used to construct all the components of this system, but anodized aluminum with hardened tool steel are generally preferred in constructing the B, M and T stacking elements. Moreover, for more extreme X-Y- Z axis positional accuracies, additional fine positioning components may also be made a part of the system in ways well known to this art.

With respect to the subject of accuracy, it should also be noted that, by using a number of standard parts, such as the standard fasteners, and by eliminating the use of special parts as much as possible, the time required to design any given fixture can be substantially reduced. Depending on the specific system, the individual stacking elements are generally made to tolerances of approximately -

0.0003 to 0.0005 inches per inch in flatness, parallelism and size. These close tolerances also serve to ensure accurate alignment and referencing of all elements in the workholder. Most preferably, the elements in these systems which actually contact the workpiece will be hardened or case hardened to resist wear and to maintain their accuracy. The specific tolerances on subplates and components are determined by the grade and size of the unit, but are usually within a 0.0005 to 0.001 inch range.

DESCRIPTION OF THE DRAWINGS

Figure 1 is an exploded perspective view of the basic elements which can be employed to create the overall modular fixturing system of this patent disclosure.

Figures 1-A, 1-B and 1-C show, respectively, side cut-away views of stacking elements T, M and B. By way of illustration a 0.375-0.376" ø (ø indicates diameter) hole system is indicated throughout the system of holes depicted in these figures.

Figures 2, 3 , and 4 show the three most common methods (i.e., capscrew, dowel and shoulder ^' bolt) used to affix prior art stacking elements A, B and C.

Figure 5 shows a "branched" system using a version (a B ₁ M ₁ , M ₂ system) of applicant's system which is given for purposes of comparison with the prior art system depicted in Figure 4.

Figures 6 and 6A depict representative "branched" systems which can be constructed with applicant's modular tooling system.

Figure 7 is a matrix indicating some of the simpler representative combinations of the B, M and T components of applicant's fixturing system.

Figures 8 through 17 depict a representative example of the matrix of component combinations generated in Figure 2.

Figure 18 depicts a version of applicant's modular fixture system comprised of, from bottom to top, a baseplate (B) , a first middle stacking element M ₁ , a second middle stacking element M ₂ (of the same dimensions as the first middle stacking element M.,) and a top stacking element T.

Figure 19 depicts a system comprised of a B element, a M element (which is different of different configuration than the M elements of Figure 18) and a T element, held together by various fastener elements and fastener element holders such as set screws.

Figure 20 details an "offset" system comprised of a baseplate (B) , a first middle stacking element M ₁ a second middle stacking element M ₂ which has a different configuration from the first middle stacking element M ₁ , a third middle stacking element M3 which is similar to the first middle stacking element and to which a generalized workpiece requiring loading clearance is attached. Figure 21 is an exploded, composite of several possible versions of the herein disclosed modular fixture system which depicts the use of various optional components in conjunction with the basic system. Figures 22, 23 and 24 depict various concepts and means to prevent lateral movement of B, M, T stacking elements.

Figure 25 depicts several alternative hole/fastener arrangements for baseplate B. Figure 26 illustrates several alternative hole/fastener arrangements for middle stacking element M.

Figure 27 illustrates alternative hole/fastener arrangements for top the stacking element T. Figure 28 illustrates two anchor studs which can be employed in connection with stacking elements M or B.

DESCRIPTION OF PREFERRED EMBODIMENTS

Figure 1 is an exploded perspective view of the basic elements which make up the modular ^' fixturing system 10 of this patent disclosure. The system is based upon a baseplate (B) 12 in the general configuration of a rectangular block having a plurality of holes such as hole 14. At least two, but preferably many more holes make up the plurality and they are fashioned in a specific matrix or array which is necessary in order for the baseplate to function in this modular fixture system. Such holes 14 are most preferably presented in an evenly spaced rectangular matrix of holes in at least two, but preferably all the holes 14 of the baseplate (B) 12 will have a counter bored, unthreaded (smooth-bored) upper portion 15 having a top end 16 which opens into the top surface 18 of the baseplate (B) 12 and a bottom end 20 which terminates in a concentric, threaded lower portion 22. Preferably the threaded lower portion 22 of hole 14 extends from the bottom end 20 of the unthreaded portion of hole 14 through the remainder of baseplate (B) 12 to the bottom surface 24 of said baseplate (B) 12. In a preferred embodiment the threaded lower portion of hole 14 and the unthreaded, upper portion will meet near the center of the thickness of the baseplate (B) 12 generally in the location shown in Figure 1.

The middle stacking element (M) 26 is also shown as having a generally rectangular, block-like configuration. It will have at least one (but preferably more than one) threaded hole 28 extending through its entire width W. as shown in Figure 1. As is better indicated later, in Figure 20, such middle

stacking elements (M) may be of differing width W. A lateral threaded hole 29 is shown extending from an outside surface of (M) to the vertically threaded hole 28; it is so located in order to receive a similarly threaded set screw 29' which can be used to further lock a fastener located in hole 28 of element (M) into position. Such a set screw 29' may also serve to prevent lateral movement of a loose fitting fastener and hence serve to prevent relative lateral movement of elements (M) or (T) with respect to element (B) .

The top stacking element (T) 30 has an upper surface 32 and a lower surface 34. The top stacking element (T) 30 has at least one unthreaded hole 36

(but preferably more than one) comprised of a larger, counter bored, upper portion 38 and a smaller, concentric, counter bored, unthreaded lower portion 40 which extends to the lower surface 34 of top stacking element (T) 30. The difference in the diameters of the upper portion 38 and lower portion 40 produces a ledge 42 which preferably will be located near the middle of the width of top stacking element (T) 30.

Means for tying down or fixing the resulting B/M/T system such as, for example, a slotted keyway 44 are shown in opposing sides 46 and 48 of top stacking element (T) 30. Thus for example keyway 44 can receive a key 50 which is attached to affixing elements 52 and 54 which are mounted to some stationary object such as for example baseplate (B) 12. The affixing elements 52 and 54 could also be affixed to some stationary object (not shown) located outside of the B/M/T system. Those skilled in this art will appreciate that such means for tying down or affixing the system could vary considerably. By way

of example only, the top stacking element 46 could be provided with a key and the affixing element 52 could be provided with a keyway. It should also be appreciated that middle stacking element (M) also could also be provided with means for fixing or tying down the entire system. Such means for fixing the system are primarily intended to prevent lateral movement along the X and/or Y axes, but they may also, to some degree, serve to provide fixing capabilities in the Z (vertical) axis.

The modular fixturing system 10 further comprises at least one fastener selected from the group consisting of: (1) a bolt 56 whose shaft 58 is essentially fully threaded and capable of threadedly engaging hole 28 of the middle stacking element (M) 26; (2) a shoulder bolt 60 whose shoulder portion 62 is capable_ of passing through both the smaller concentric hole 40 of top stacking element (T) 30, the threaded hole 28 of middle stacking element (M) 26 and the upper unthreaded portion 15 of hole 14 the baseplate (B) 12 and which further comprises a threaded nosepiece end 64 capable of threadedly engaging the threaded lower portion 22 of hole 14 in baseplate (B) 12; and (3) a dowel pin means 65 which is capable of passing through the smaller concentric hole 40 of the top stacking element (T) 46, the threaded hole 28 of the middle stacking element (M) 26 and into the unthreaded portion 15 of baseplate (B) . Again, this basic system may also be provided (their use is optional) with anchor studs such as the anchor stud 31 which can reside in and engage lower hole 14 of the baseplate (B) 12.

This modular fixturing system 10 may, optionally, also comprise an adapter bushing 66 having a larger

upper flange 68 whose lower surface 70 seats on ledge 42 of top stacking element (T) 34. A tube-like portion 72 of bushing 66 is capable of fitting inside (preferably with a snug fitting engagement) the unthreaded, lower portion 40 of the top stacking element (T) 34. A hole 74 in bushing 66 should be of a size which is capable of passing the diameter of the dowel pin 65 as well . as the shoulder region 62 of shoulder bolt 60. Figures 1-A (showing an adapter bushing 66 in position) , 1-B and 1-C illustrate a representative hole system in elements T, M and B respectively. The threaded hole 28 of middle stacking element is most preferably of the truncated thread form or type. This assures that the nosepiece of a threaded bolt sill engage a next similarly threaded stacking element, e.g. , engaging while traversing the threaded hole of an element M, to the threaded hole of an element M ₂ without causing the second element M ₁ to rotate with respect to element M ₂ in order to accept the threaded nosepiece of the incoming bolt. Figure 1-C depicts a B element having an accurately bored counter bore hole.

For the sake of illustration only, the appropriate portions of the holes of Figures 1-A, 1-B and 1-C are shown provided with a 0.375 - 0.376" ø hole system. Obviously any other hole size could also be employed to create such a system. In this case a B, M, T stack would have a 0.375 - 0.376" ø common hole that passes through the B, M and T stack to allow a shoulder and head type threaded fastener of 0.364-0.375 ø to accurately position said stack to within a true position theoretical limit of ø 0.002" , i.e., to a true centerline shift of 0.001". This degree of

accuracy compares very favorably to the accuracies achieved by prior art doweling and bolting tooling structures. Thus the modular fixturing system of this patent disclosure is capable of providing a reconfigurable (and hence reusable) system which provides accuracy comparable to most prior art, single purpose, nonreusable tooling structures.

Figures 2, 3 and 4 illustrate the three most common prior art modular fixturing practices for stacking and interconnecting three common prior art tool elements (A, B and C) . Note that a smooth-bore hole is common for at least 2 of the 3 stacking elements A, B and C. These prior art configurations are given to illustrate in a qualitative, orthogonal, sense (i.e., relative to the X-Y-Z planar system depicted in conjunction with Figure 2) , the relative orthogonal accuracies which can be obtained by each of these three prior art modular fixturing practices. The ensuing discussion of these prior art systems enables one to compare the modular fixturing system of this patent disclosure to those of the prior art. For example, the representative version of applicant's modular fixturing system given in Figure 5 can be compared, from the orthogonal accuracy point of view, with each of the prior art systems depicted by Figures 2, 3 and 4. Such a comparison will impress upon those skilled in this art that the overall modular fixture tooling system of this patent disclosure results in an extremely favorable trade- off between . the attributes of accuracy, flexibility and cost efficiency.

With respect to the subject of accuracy, for example, Figures 2, 3 and 4 will serve to illustrate how these prior art systems produce positional

accuracy in 2 planes but not all three. With respect to the subject of "flexibility", those skilled in the art will appreciate that through the use of, for example, multiple M elements provided with truncated threaded holes, any number of stacking components may be stacked and/or branched out from such a basic modular structure. Thus a "tree" of modular fixturing stacking elements can be constructed from levels of branches which move out in any radial direction at any desired vertical height, for example, in the manner illustrated by Figures 5, 6 and 6A.

The third favorable trade-off feature of applicant's system concerns costs efficiency. Those skilled in this art will appreciate that such cost efficiency is related to the simple equation:

Cost Efficiency (magnitude) = accuracy + flexibility. That is to say that the cost of this system is lowered by use of the herein disclosed "standard" elements (e.g., standard, bolts, dowels, etc.) and by how many such components standard or otherwise can be reused in new tooling structures.

For the sake of a more detailed comparison, Figure 2 depicts prior art modular fixturing elements A, B and C held together by a standard capscrew. Note that the shaft 65 of the capscrew extends "loosely" through both the lower portions 67 of the hole of the top element A and through the entire hole 69 of middle element B. That is to say the diameter of the shaft 65 of the capscrew is significantly less than the diameter of the holes in elements A and B and hence shaft 65 fits loosely in these elements. The threaded lower end of the capscrew does however "tightly" engage the threaded hole of the bottom element C. Consequently, the resulting A, B, C stack system is

securely held in place in the z plane only. The loose fit of the capscrew in the holes of elements A and B permits the A and B elements to shift relative to the C element, and relative to each other, in the x and/or y planes. Thus this system produces positional accuracy in the Z plane only.

Figure 3 depicts three prior art modular fixturing elements A, B and C fitted together by a press fitting standard dowel rod 71. That is to say the dowel rod press fits into the respective holes of elements A, B and C. Consequently, this dowel arrangement accurately locates elements A, B and C in the X and Y planes. It does not however, affix and/or locate these stacking elements in the Z plane. Figure 4 depicts three prior art modular fixturing elements, A, B and C held together by a standard shoulder bolt. Note that element B has an offset hole, D whose center line C ₁ is not aligned with the center line C ₂ of hole E of element C. Thus, in this smooth-bore hole array, the standard shoulder bolt accurately holds elements A, B and C in the X, Y and Z planes. However, hole D can only receive a dowel rod; hence any attachment (such as the one shown in Figure 5) affixed to element B cannot permanently be fixed to this system in the Z plane. In other words any attachment affixed to element B by a dowel rod will have the same possibility for Z plane movement as the system depicted in Figure 3. The system of Figure 4 now should be closely compared with the version of applicant's stacking system shown in Figure 5.

Figure 5 depicts a version of applicant's modular fixturing system wherein its three elements, B, M and T are affixed to each other with a shoulder bolt which

extends from the top element T, through the threaded hole of the middle element M to threadedly engage a threaded hole in baseplate B. Note that middle element M also, as in the case of the prior art B element shown in Figure 4, has an offset hole whose center line 28' is not aligned with the center line 14 ' of hole 14 in baseplate B ala the absence of alignment between the center lines of holes D and E in the prior art system depicted in Figure 4. However, threaded hole 28 of Figure 5 is capable of receiving a threaded bolt 62 ' in order to affix attachment piece AP in the Z plane as well as in the X and Y planes. This Z plane affixation is to be contrasted with the lack of such Z plane affixation inherent in the use of dowel hole D of the prior art stacking system shown in Figure 4. Thus .the result of the stacking system depicted in Figure 5 is that an unlimited number of attachment pieces (AP) can be accurately fixed in the X, Y and Z planes. Thus this feature provides for far greater accuracy and versatility with respect to the branching off of various attachment pieces AP relative to applicant's T, M, B system.

Figure 6 depicts a stacking arrangement wherein two separate attachment pieces AP., and AP ₂ are affixed to a reference T, M, B stacking system constructed according to this patent disclosure in order to go on to form, respectively, Branch 1 and Branch 2 to which various tooling elements (not shown) can be affixed. As in the case of the system shown in Figure 5, attachment pieces AP ₁ and AP ₂ are affixed- to middle element M respectively by means of threaded bolts 62 ' and 62". Thus not only are attachment pieces AP ₁ and AP, accurately affixed to middle element M in the Z

plane, they are fixed as well in the X and Y planes. The two branches, i.e., Branch 1 and Branch 2 are accurately located in the Z plane with respect to each other. Thus this system provides for greater versatility than the prior art systems depicted in Figures 2, 3 and 4. This feature follows from the ability of applicant's system to produce Z plane accuracy as well as X and Y plane accuracy.

Figure 6A another representative "branching" using another group of common, representative fastener elements.

Those skilled in this art also will appreciate that similar orthogonal accuracy comparisons could be made for each version of applicant's modular fixturing system and that similar advantages will be produced by each such version of applicant's overall system, in general, as well as by the specific examples of applicant's modular tooling system shown in Figures 1 and 5 through 21. Figure 7 represents a matrix of possibilities of a modular fixture system comprised of a baseplate element (B) , a middle stacking element (M) and a top stacking element (T) . It should be noted that the respective diagrammatic renditions of each member of this matrix shown in Figures 8 through 17 are given by way of example only. Other examples could be generated through the use of fastener elements other than those depicted in these particular illustrations. Similarly, other examples could be generated through the use multiple M elements, multiple T elements (e.g., such as those systems shown in Figures 18 through 20) and/or through the use of auxiliary elements such the threaded stud fasteners shown in Figure 28.

Figure 8 depicts a representative version of a T/T combination of the overall B, M, T matrix given in Figure 7. A baseplate (B) element is assumed to be below the T/T combination even though it is not 5 _. specifically shown in Figure 3. The T/T combination of the matrix can be thought of as being "representative" because other fastener elements (e.g., a shoulder bolt) could be employed in place of the dowel pin 65 depicted in Figure 3. Be that as it 0 may, top stacking element (T.,) is shown provided with a bushing 66A and top stacking element (T ₂ ) is shown provided with bushing 66B which each respectively receive dowel pin 65.

Figure 9 depicts a representative version of a 5 M/T combination of the overall B, M, T matrix. Here again a baseplate (B) element is assumed to be below the (M) element even though it is not shown. This M/T combination is held together by a shoulder bolt 68 which seats against a washer 71 which in turn seats 0 upon ledge 42 of top stacking element 46. The shoulder bolt 68 has a threaded shaft portion 75 which extends through the hole 28 of the middle stacking element (M) 26.

Figure 10 depicts a B/T combination of the B, M, 5 T matrix of Figure 2. It also employs a washer 71. The fastener 77 has a necked down shoulder portion 79 which extends through elements B and T.

Figure 11 depicts a T/M combination of the B, M, T matrix. A dowel pin 65 is shown positioned in the 0 top stacking element (T) 46 by use of bushing 66.

Figure 12 depicts an M/M combination of the matrix of possibilities generated by Figure 2. A dowel pin fastener 65 is shown in hole 28 ₁ of middle stacking element M ₁ and in hole 28 ₂ of middle stacking element

M ₂ . Middle stacking elements M ₁ and M ₂ are shown respectively provided with means 78 ₁ and 78 ₂ (such as set screws 79 ₁ and 79 ₂ for holding dowel pin 65 in place. Figure 13 depicts a M/B combination using a threaded anchor stud means 82 having a smooth head 84 which is capable of residing in threaded hole 28 of middle stacking element (M) 26. The threaded anchor stud 82 has a threaded nosepiece 86 which is capable of threadedly engaging the threaded lower portion 22 of hole 14 in baseplate (B) 12. A set screw 80 helps to hold threaded stud fastener 82 in place. A different version of this anchor stud means is also depicted in Figure 28. Figure 14 depicts a B/T combination of the matrix of possibilities of Figure 2. The fastener 60 is a shoulder bolt having a shaft 62 which extends through element T and a threaded nose 64 which does not extend completely through threaded hole 22 of baseplate (B) 12. The fastener action is augmented by use of washer

71 which is seated on ledge 42 of top stacking element (T) 46.

Figure 15 depicts a M/B combination using a washer 71 seated over threaded hole 28 of stacking element (M) 26.

Figure 16 depicts an alternative M/B combination using an anchor stud 88 and stud fastener (a set screw) 80. Further details regarding such an anchor stud are shown in Figure 28. Figure 17 depicts a B/B combination of the matrix of Figure 2 wherein baseplate B ₁ is attached to baseplate B ₂ by means of a shoulder bolt having a necked down portion 79 which freely passes through threaded hole 22 of B ₁ and a threaded portion 90 which

engages hole 22 of baseplate B ₂ .

Figure 18 depicts a combination of stacking elements which is not found in the matrix of combinations suggested by Figure 2. The most distinctive departure from the matrix of combinations suggested in Figure 2 is the fact that the system depicted by Figure 18 has two middle stacking elements M, and M ₂ . As a matter of fact any number of M or T elements are possible with applicant's modular fixturing system. However, in particular this rendition, a shoulder bolt 60 is shown resting on washer 71 which rests upon busing 66 which, in turn, is seated upon ledge 42 of top stacking element (T) 46. Figure 19 depicts a B/M/T stacking combination wherein the middle stacking element (M) , designated as 26A, has a width W ₁ greater than the width W of the middle stacking elements (M) shown in the other figures. Bolt 60, shown provided with washer 71, has a threaded end 64 which engages the threaded hole 28 of middle stacking element (M) 26A. Dowel pins 65 are shown provided with bushings 66 and anchor stud bolts 81 having a cylindrical head 83. The anchor studs 88 which help affix middle stacking element 26A to baseplate 12 are also positioned and affixed by the action of socket set screws 80 having conical nosepieces 85 which engage a beveled out region 87 of anchor studs 88.

Figure 20 depicts a representative system (i.e., a B/M/M/M system) which creates an offset configuration of stacking elements which provides a loading clearance for a workpiece 92 as indicated.

Figure 21 depicts an exploded, composite view of a preferred embodiment of an overall modular fixturing

system made according to this patent disclosure wherein standard fasteners are employed throughout. Thus a highly preferred version of a "kit" or "tool package" of applicant's overall system would comprise at least one (and preferably several) of each of the pieces depicted in Figure 21.

Figures 22, 23 and 24 are given to generally illustrate various attachment and/or tie down methods and concepts which may be applied in utilizing applicant's modular fixturing system. For example, Figure 22 illustrates "top attachment" wherein a standard bolt is used to affix elements T, M and B by means of pressure created on top surface of element T by means of pressure applied to the underside of the bolt's head and by means of threading engagement of the bolt's threaded nose with a suitable hole in element B.

Figure 23 illustrates "bottom attachment" wherein beveled anchor studs 88 are used to affix elements B, M ₁ , and M ₂ . The affixing function of the anchor studs 88 is shown supplemented by use of set screws 80 which engage a screw receiver means such as the beveled out region 85 shown in the anchor studs - 88 shown positioned in elements M ₁ , and M ₂ . Figure 24 illustrates a means for achieving "side attachment" or preventing lateral movement of the system. The side attachment means employed in this example is a tie down block 52 having a tie down key 50 which engages a keyway in an M or T element of this system. As was noted in the previous discussion of Figure 1, those skilled in this art will also appreciate that the sense of this key and keyway system could ^' be reversed. That is to say the tie down block could contain the keyway and stacking elements

M or T could contain the key portion of the system. Those skilled in this art will also appreciate that such side attachment means could also engage a stationery element (not shown) which is completely independent of the B, M, T system shown.

Figure 25 depicts some representative fastening options which can be used with the hole of baseplate (B) .

Figure 26 depicts some representative fastening options which can be used with the threaded hole of middle stacking element (M) .

Figure 27 depicts some representative fastening options which might be used with the hole of top stacking element (T) . Figure 28 depicts a representative anchor stud (B) suited for engagement with the threaded portion of the hole in a baseplate (B) (not shown) and anchor stud (M) suited for engagement with the threaded hole of middle stacking element M (not shown) . While the principles of this invention have now been made clear in the illustrated embodiments, there will be immediately obvious to those skilled in the art, many modifications of structure, arrangements, proportions, the elements, materials, components and attachments used in the practice of the invention, and otherwise, which are particularly adapted for specific work environments and operation requirements, without departing from the herein disclosed principles. The appended claims are therefore intended to cover and embrace any such modifications within the limits only of the true spirit and scope of this invention.