FIXTURE SYSTEM

Abstract: In a fixture system for setting and fixing on a worktable an essentially parallelepipedic workpiece which is to be machined by cutting tools on two of the parallel faces, first on one face and then on a second face, with extremely precise coordination of machining on both faces, recesses (10, 11, 12) have been provided with vertical attachment faces (16, 17, 18) in three of the vertical faces (4, 5, 6) of the workpiece. Furthermore there are three shoulders or the like (31, 32, 33A/33B) so arranged that they can be introduced into recesses in the workpiece having stop faces (35, 36, 37A/37B) facing the respective attachment faces in the recesses, the said shoulders or the like being so arranged that they can be clamped on the worktable so that the stop faces on the first and third shoulders which are assigned to corresponding first and third grooves in the workpiece are orientated in parallel with a groove, projection, a number of recesses, projections or the like in the worktable, in addition to which means (41, 43, 48A, 50A/48B, 50B) are provided for pressing the attachment surfaces in the recesses of the workpiece against the stop faces of the shoulders.

Description: FIXTURE SYSTEM TECHNICAL SCOPE The invention relates to a fixture system for setting and fixing an essentielly parallelepipedic workpiece on a worktable. More particularly the invention relates to a fixture system for setting and fixing a workpiece which is to be machined by cutting tools on two of the parallel sides of the workpiece - first of all on one side and then on the other side - with very precise coordination of the machining on both sides. STATE OF THE ART When machining workpieces for the production of for example forming tools it is extraordinarily important that the workpiece be adjusted and clamped with extreme accuracy on the worktable so that machining can be carried out in the desired manner. Usually both sides of the workpiece are machined. If for example one side has been provided with an impression for a plastic mould, the pouring hole is normally drilled from the other side down to the mould impression. To ensure that the pouring hole will be in the absolutely correct location in the impression it is an indispensible requirement that the workpiece, after this has been turned, be adjusted with extreme accuracy so that machining on the other face of the workpiece can be precisely co¬ ordinated with the impression already produced on the opposite side. These operations require great skill and, in spite of modern align¬ ment instruments, are very time-consuming. Particular problems also arise if the vertical faces of the workpiece are not precisely at right angles. Fixture systems and other aids for setting and clamping of work- pieces on worktables have been proposed previously. Examples of such earlier aids are illustrated for example in US 3 554 530, US 3 622 145. and DE 28 51 700. However common to these earlier designs is the_ * fact that they insist that the workpiece have abso- lutely square angles and extremely straight sides. The systems do ot provide any zero point which can be easily defined with high Y?. accuracy to provide a basis during the machining of the two sides which are to be machined on the workpiece. KEVIEW OF THE INVENTION The object of the invention is to solve the problems outlined above. More particularly, one aim is to provide a fixture system with the aid of which it is possible to set and clamp the workpiece on a worktable rapidly and with very high accuracy. A further aim is to be able to provide a fixture system with the aid of which a zero point (reference point) can be obtained rapidly, from which it is possible to proceed into an assumed system of co¬ ordinates for carrying out machining. -A further aim is to provide a fixture system designed for machining workpieces of varying size. The normal shape of the workpiece is parallelepipedic, but precisely square angles and precisely square edge surfaces are not essential. The system also permits other deviations from the parallelepipedic main form. For example all edge faces can be designed in an arbitrary manner starting from a plane surface. These and other objectives can be achieved in that the fixture system comprises in combination certain recesses in the edge faces of the workpiece, i.e. the vertical faces when the workpiece is placed on the worktable, and devices on the worktable arranged so that they can interact with the recesses in the workpiece. To achieve the objectives in accordance with the invention three recesses are required in the vertical faces of the workpiece, namely an initial recess in a first side close to a first corner with an attachment surface in the said first recess facing the said first corner, a second recess in a second face which meets the first face at the said first corner, the said second recess having an attachment surface which also faces towards the first corner, and a third recess in the third side which is opposite to the first side close to a second corner near the said second and third faces, with an attachment surface at a distance from the said second cor¬ ner which is equal to the distance between the first corner and the attachment surface in the first recess. Furthermore the devi¬ ces on the worktable include three shoulders arranged so that they can be introduced into the recesses in the workpiece with stop faces directed towards the respective attachment surface, the said shoulders being so arranged that they can be clamped on the worktable so that the stop faces on the first and third shoulders which are assigned to the said first and third grooves in the workpiece are orientated in line parallel with a groove, projection, a number of recesses, projections or corresponding guide devices in the worktable, besides which means are provided for pressing the attachment surfaces in the projections in the workpiece against the stop faces of the shoulders. Further characteristics and advantages of the invention will be outlined in the following patent claims and by the following de¬ scription of a preferred embodiment. BRIEF DESCRIPTION OF DIAGRAMS In the following the invention will be described in greater de¬ tail with reference to the appended drawings in which: Fig. 1 illustrates a plan view of the fixture system in accor- dance with the invention, Fig. 2 shows a section II-II in Fig. 1, Fig. 3 shows a section III-III in Fig. 1, Fig. 4A illustrates in more schematic form the setting and clamping of a workpiece with the aid of the fixture system in accordance with the invention for machining one face of the workpiece and -βUREΛt Fig. 4B shows how the fixture system is rearranged for adjustment and clamping of the workpiece when this is to be machined on the opposite face and Fig. 5 shows a modified embodiment of the fixture system in accordance with the invention. DESCRIPTION OF PREFER_£ED EMBODIMENTS With reference to Fig. 1-4, a worktable is generally deisgnated as 1. In accordance with the chosen embodiment this is provided in the conventional manner with T-shaped grooves 2a, 2b etc. If a worktable with T-grooves of suitable design is not available it is possible, in combination with the fixture system and in accordance with the chosen embodiment of the invention, also ,to employ a spacer plate with suitably designed grooves which is placed on a worktable. Instead of T-grooves or other grooves the worktable or spacer plate can be provided with projections or re¬ cesses, e.g. cylindrical recesses. These are preferably arranged in rows with a pitch between the recesses which corresponds to the step variations in the standard sizes for tool steel plates, which are normally 5 cm. Here the fixture in accordance with the invention is provided with corresponding recesses, guide pins, shoulders or the like which correspond with the projections or recesses in the worktable or spacer plate. The workpiece is designated as 3. This has a general parallele¬ pipedic form. The object is that two of the sides will be machined by cutting tools, i.e. by drilling, milling, grinding etc. in order to produce a moulding die, e.g. a plastic moulding die. One of these faces, which can be called the impression face, iέ designated as A and faces upwards in Fig. 1 and Fig. A. The opposite face has been designated as B, Fig. 4B. The four vertical faces are designated as the first, second, third and fourth faces 4, 5, 6 and 7 respectively. The corner between the first and the second face 4 and 5 is designated as the first corner 8, and the corner between the second and the third face is designated as second corner 9. At a distance D1 from corner 8 the first face 4 is provided with a first recess 10. At a-idistance D2 from corner 8 the second face has a recess 11, and in the same way as with the first face 4, the third face 6 also exhibits a recess 12 at a distance D3 from the second corner 9. In accordance with the embodiment all three recesses 10, 11 and 12 have the same rectangular shape in a horizontal section. The grooves are produced by milling out from the top face A to the bottom face B of the workpiece and are provided with bottom sur- faces which are parallel with the vertical side faces of the work- piece and with ends which are at right angles to the bottoms and towards the said side faces. The bottoms are designated as 13, 14 and 15 respectively. The ends which face the corner 8 and 9 respec¬ tively are designated as attachment surfaces 16, 17 and 18 respec- tively. In accordance with the preferred embodiment D1 =• D2 = D3. The said distance can appropriately be between 1.5 and 6 cm, pre¬ ferably between 2 and 4 cm. Other .spacings and also differing spacings are feasible within the framework of the invention. How¬ ever the choice of spacings other than those recommended, or differing spacings, represents an unnecessary complication and is not recommended. One advantage of a spacing D1 = D2 is inter alia that it is possible to use a single holder, designated as 19, for interaction with the recesses 10 and 11 and the corner section adjacent to corner 8. A second holder assigned to the recess 12 and the corner section adjacent to corner 9 is designated as 20. The holder 19 will now be described in greater detail by refer- ence to Fig. 1, Fig. 2 and Fig. 3. It should be mentioned at the outset that the worktable 1 has not been shown in Fig. 3. The holder 19 consists of two .main portions, a lower portion 21 and an upper portion 22, The lower portion 21 is attached to the worktable 1 in a known manner by means of a bolted connection 23a which interacts with the T-groove 2a and two bolted connec¬ tions 23b interacting with the T-groove 2b. In addition the v bottom portion 21 is provided with an elongated guide 24. The guide 24 has the same width as the T-grooves 2a, 2b and is re¬ cessed in a groove 25 in the lower face of the bottom portion 21 and a portion of it extends downwards into the T-groove 2b, Fig. 1. The guide 24 is screwed into the bottom portion 21 by means of a screw 26. A second groove in the lower face of the bottom portion 21 has been designated as 27, Fig. 1. This has the same depth and width as groove 25 and is arranged at right angles to the groove 25. Both grooves 25 and 27 extend across the entire length of the lower face. A screw hole for alterna- - tive positioning of the guide 24 in groove 27 is designated as 28, Fig. 1. The purpose of the groove 27 which is arranged at right angles and of the screw hole 28 for alternative positio¬ ning of the guide 24 will be discussed in greater detail sub- sequently by reference to Fig. 4b. The upper portion 22 is screwed firmly in position from underneath by means of a number of screws 29. The upper portion 22 covers most of the bottom portion 21. The only part which is not covered, i.e. the area 30 which as shown in Fig. 1 is covered essentially by the workpiece 3, provides support for the said workpiece. The upper portion 22 has two shoulders orientated at right angles to each other, a first shoulder 31 and a second shoulder 32. The shoulders 31 and 32 have a width which is somewhat less than the width of grooves 10 and 11. In addition between shoulders 31 and 32 there is a recess 34, the size of which is sufficient to accommodate the corner section of the workpiece adjacent to corner 8, i.e. the corner section between the attachment surfaces 16, 17 and the corner 8. The shoulders 31 and 32 furthermore have stop faces 35 and 36 which are parallel with the corresponding attachment surfaces 16 and 17 on recesses 10 and 11. The stop face 35 is also parallel with the groove 25 and is in line with one forward and one rear centring hole 38a and 38b. The straight line which connects 38b and 38a and which coin- TREAIT cides with the stop face 35 is designated as 38. In a correspon¬ ding manner centring holes 39a and 39b are arranged in a straight line 39 which coincides with the stop face 36, arranged at right angles, on the second shoulder 32. The point of intersection bet- ween the straight lines 38 and 39 forms a reference point or zero point 40 for the fixture system in accordance with the invention. The holder 19 also comprises a slide 41 orientated diagonally in the holder 19 towards the recess 34. The slide 41 can be dis- placed in a diagonally arranged groove 42 which is accommodated in the upper portion 22 and the lower portion 21, Fig. 3. Further¬ more the side 41 is so arranged that it can be displaced in groove 42 by means of a screw 43 using generally known princip¬ les. The forward portion of slide 41 has a notch 44 arranged so that it can accept the corner 8 on the workpiece 3. The holder 20 greatly resembles holder 19. Thus it is provided with a bottom portion and an upper pσrtion 42 which are joined ^ to each other by screws 43. The unit, screwed together in this way, is in turn screwed to the worktable 1 by means of bolted connections 44a and 44b which interact with T-grooves 2a and 2b respectively. A groove 45 in the lower face of the bottom por¬ tion runs across groove 2b. A guide 46 of the same type as the guide 24 in holder 19 is recessed inside this groove 45. The guide 46 is fastened in groove 45 by means of a screw 47. The holder 20 is symmetrical around a line of symmetry which extends through the centre of screws 43, 47 and the bolted connec¬ tion 44a. On the left-hand half there is a left-hand slide 48A in a slide groove 49A. A screw for moving the left-hand slide 48A in the slide groove 49A is designated as 50A. The corresponding sections on the right-hand half are designated 48B, 49B and 50B respectively. On the left-hand half of holder 20 in the bottom corner there is a recess 51A in the upper portion 42 of the holder for a corner section on the workpiece 3 adjacent to its corner 9. The corresponding section of the lower portion has been designated 52A and provides support for the said corner section of work- piece 3. A shoulder 33A which has the same shape as the shoulder 31 which projects outwards from holder 19 towards the face 4 of workpiece 3, projects into the recess 51A which is almost square. " Hence the shoulder 33A projects out towards the face 6 on work- piece 3. Its front face is designated as 53A and a stop face which is directed towards the corner 9 is designated as 37A. In the ex¬ tension to the stop face 37A there is a centring hole 54A, the centre of which coincides with the straight line 38. The right-hand face of the holder 20 is shaped in a similar manner and hence does not require any further detailed explanation. For corresponding components the same reference notation has been em¬ ployed as for the left-hand half, but using the letter B instead of A. The mode of operation of the fixture system described will now be explained. The starting position is assumed to be that the bottom portions of the holders 19 and 20 have been joined to the upper portions 22 and 42 respectively, that the guides 24 and 46 respectively have been screwed home into the grooves 25 and 45 respectively, and that the units thus assembled have been fixed onto the worktable 1 by means of bolted connections 23a and 23b, and by 44a and 44b in the T-grooves 2a and 2b. The slides 41 and 48A are screwed back to their rear extreme posi¬ tions. Before the holders 19 and 20 are screwed firmly into the T-grooves, a check has been made, or measurements have been made, to ensure that the workpiece 3 can be located by its corner sec¬ tions so that the shoulders 31, 32 and 33a can engage in recesses 10, 11 and 12. If this is the case, holders 19 and 20 are fixed onto the table 1, after which the workpiece 3 is located in the manner described so that the corner sections illustrated in Fig. 1 rest on the bottom portions (sections 30 and 52A respectively) of the holders 19 and 20, which then function as distance pieces between - the workpiece 3 and the worktable 1. A further pair of distance- pieces 53 having the same height is also arranged underneath the workpiece 3, Fig. 4a. The screws 43 and 50a are then tightened. Start with screw'43, the slide 41 being pressed against the corner 8 on workpiece 3. The workpiece 3 is thus moved towards screw 43, i.e. diagonally, so that the attachment surfaces 16 and 17 or re¬ cesses 10 and 11 are pressed against the attachment surfaces 35 and 36 respectively of the shoulders 31 and 32. Then the screw 50a in the right-hand holder 20 is tightened. The slide 48a then presses the workpiece 3 downwards, with reference to Fig. 1, so that the attachment surface 18a of groove 12 is pressed against the stop face 37a on the shoulder 33a. When the workpiece 3 has been clamped in this way the only contacts between the workpiece and the shoulders 31, 32 and 33A are the contacts between firstly the attachment sur- faces 16, 17 and 18 and secondly the stop faces 35, 36 and 37A re¬ spectively. As such these contact surfaces represent the only points of contact between the workpiece 3 and the upper portions 22 and 42 respectively of holders 19 and 20. As the attachment surface 35 of shoulder 31 is parallel with and, in accordance with the embodiment, actually in line with the attachment surface 37A on the opposite shoulder 33a, the workpiece has now been set up parallel with reference to the T-grooves 2 in the worktable 1 , and the guides 24 and 46 respectively guarantee the parallelism re- quired during the mounting of holders 19 and 20. At the same time the workpiece 3 has also been fixed in the longitudinal direction by being pressed against the attachment surface 36 on the shoulder 32. By this means an assumed reference point on the workpiece 3, the said reference point being the point of intersection between the connecting line between the attachment surfaces 16 and 18 and the extension of the attachment surface 17 on shoulder 32, has been made to coincide exactly with.the reference point 40 of holder 19. This reference point 40 can now easily be localised by means of the centring holes 38a, 39a and 33a or, if the workpiece 3 is very thick so that the said holes are not easily accessible, instead by means of the rear centring holes 38b, 39b and 54b. It should be evident that the fixing of the workpiece 3 on table 1 is supplemented by con¬ ventional fixing devices-.- When the face A on workpiece 3 has been completely machined and a changeover is to be made to face B, the procedure is as follows. First of all release the workpiece 3 by releasing the supplementary fixing devices, the slides 41 and 48a being screwed to the rear. The work- piece 3 is removed and the holders 19 and 20 are released from the worktable 1 by releasing the bolted connections which interact with the T-grooves 2a and 2b. Concerning holder 19, this is removed com¬ pletely from the worktable, whilst in the case of holder 20 it suffi¬ ces to merely release the clamp slightly, so that holder 20 can be moved over to the left-hand portion of the worktable 1, see Fig. 4B. It is then re-clamped. In holder 1 however the bolted connection is released completely, this also applying to the guide 24. The latter is moved to groove 27 and screwed firmly home from underneath in screw hole 28. The holder 19 is then moved to the right-hand portion of the worktable, is rotated 90 clockwise in relation to its pre¬ vious orientation and is placed on the worktable so that the guide 24 once again drops down into the groove 2b. The workpiece 3 is turned so that face B is upwards and placed on the portions 30 and 52B respectively of the exposed bottom portions of holders 19 and 20, and if required the holder 19 is adjusted laterally relative to holder 20 so that shoulders 32 and 31 can now snap into the grooves 10 and 11 respectively, whilst at the same time shoulder 33b on holder 20 rests in groove 12. The two holders 19 and 20 are reclamped against the table 1, after which the workpiece, in the same manner as previously, is sla ped by means of screws 43 and 50B. Hence it should be noted that in this case the right-hand portion of holder 20 is employed. When the workpiece 3 has been clamped in this way the reference points 40 of holder 19 and of the workpiece 3 have again been made to -coincide. In other words it is now quite easy on face B to locate a point, namely the reference point 40, which corre¬ sponds to a known point on the first face A. Starting from this re- ference point it is then possible to carry out machining on face B so that this is coordinated precisely with the previous machining operation on face A. The invention can be varied within the framework of the inventive concept as defined by the patent claims which follow. Thus it is possible for"example, instead of a single holder 19 to employ two separate holders with a shoulder for the grooves 10 or 12, or 11 respectively. Furthermore, as stated in the preamble, instead of guides -24, 46 which are parallelepipedic in shape and interacting with a straight groove in the worktable it is possible for example to employ cylindrical guides interacting with cylindrical drilled holes in the worktable or in a spacer plate. This embodiment is illustrated schematically in Fig. 5. In Fig. 5 components corresponding to those in the preceding dia- grams have been ' given the same notation as in these diagrams but with the suffix '. The workpiece has not been illustrated in this * diagram. The worktable is designated 1 ' and a pair of holders as 19' and 20". These have the same general design as holders 19 and 20, so that not all the details have been illustrated in Fig. 5. The essential difference is that the grooves 25, 27 and 45 respec¬ tively and the guide devices 24 and 46 respectively in the lower faces of holders 19 and 20 have cylindrical drilled holes 25' and 27' and 45' respectively and cylindrical fixing pins 24' and 46' respectively which can be arranged in the said drilled holes. Corre- spondingly, a large number of drilled holes 2' are provided in the worktable 1' in a network pattern with a pitch of 50 on. In this way the holders 19' and 20' can be quickly fixed at the desired spacing from each other, dependent on the length of the workpiece, which corresponds to a multiple of the pitch of the network pattern. According to a conceivable modification it is also possible to pro¬ vide the slides 41 and 48A, 48B as well as the screws 43 and 50A, 50B slightly inclined downwards in the direction of the workpiece. Herethrough the additional effect is achieved that the workpiece is powerfully pressed down against the worktable as the screws 43 and 50A/50B are tightened up. Further in order to compensate for variations in the width of the grooves 2a, 2b etc. in the worktable the guides 24 and 46 of the holders 19 and 20, respectively, according to a preferred develop¬ ment are suitably expansible. Other modifications to the invention are also feasible. The descrip¬ tion provided of a couple of preferred embodiments hence does not impose any limitation on the present concept of the invention.

Claims: PATENT CLAIMS 1. Fixture system for setting and fixing on a worktable an essential¬ ly parallelepipedic workpiece which is to be machined by cutting tools on two of the parallel faces, first of all on one face and then on another face, with very precise coordination of the machining operations on both faces, c h a r a c t e r i s e d by a combination of firstly recesses (10, 11, 12) with vertical attachment surfaces (16, 17, 18) in three of the vertical faces (4, 5, 6) of the work- piece, namely a first recess (10) in a first face (4) close to a first corner (8) with an attachment face (16) in the said first recess facing the said first corner, a second recess (11) in a se¬ cond face (5) which meets the first face at the said first corner, the said second recess having an attachment face (17) which also faces towards the same first corner, and a third recess (12) in the third face (6) which is opposite to the first face close to a se¬ cond corner (9) between the said second and third face, with an attachment face (18) facing towards .the said second corner, also three shoulders or the like (31, 32, 33A/33B) arranged so that they can be introduced into recesses in the workpiece with stop faces (35, 36, 37A/37B) facing the respective attachment surfaces, the said shoulders or the like being arranged so that they can be clamped onto the worktable so that the stop faces on the first and third shoulders which are assigned to the said first and third recesses in the workpiece are orientated in parallel with a groove, projection, a number of recesses, projections or the like in the worktable, in addition to which means (41, 43, 48A, 50A/48B, 50B) are provided for pressing the attachment faces of the recesses in the workpiece against the stop faces of the shoulders. 2. Fixture system as in claim 1 , c h a r a c t e r i s e d by at least two holders (19, 20) of which one or two holders (19) support the two shoulders (31, 32) which are assigned to recesses (10, 11) close to the said first corner on the worktable and one holder (20) supports the shoulder (33A, 33B) which is assigned to the third recess (12) in the workpiece. vri 3. Fixture system as in claim 2, c h a r a c t e r i s e d in that the holder or holders which support the above-mentioned two shoulders (31, 32) is/are provided with at least one centring hole related to each shoulder, so that the point of intersection between a first straight line (38) through one centring hole (38a, b) related to the shoulder (31) of the first face, which straight line (38) is parallel with the said groove (25), row of recesses or the like in the worktable (1), and a second straight line (39) through a cen¬ tring hole (39a, b) related to the shoulder (32) of the second face, which second straight line is at right angles to the first straight line, provides a zero — or reference - point (40) for the fixture system, the said reference point being the same regardless of which side of the workpiece faces upwards at any time. 4. Fixture system as in claim 2 or 3, c h a r a c t e r i s e d in that each of said holders (19, 20) is provided with at least one slide (41 , 48A, 48B) provided displaceable in the holder relative to said shoulders, and means (43, 50A, 5DB) for displacing said slide against the workpiece in order that the attachment faces of the re- cesses in the workpiece are pressed against the stop faces of the shoulders. 5. Fixture system as in claim 4, c h a r a c t e r i s e d in that said slides are provided to be displaced in said holders in parallel with the surface of the worktable. 6. Fixture system as in claim 4, ch a r a c t e r,i s e d in that said slides..are provided to be displaced in said holder slightly downwards forwards against the workpiece" in order that the workpiece also will be pressed down against the worktable. 7. Fixture system as in. claim 5 or 6, c h a r a c t e r i s e d in that the slide (41) in that holder (19) which is provided with said first mentioned two shoulders (31 , 32) is provided to be displaced diagonatety .in the holder towards said first corner (8) of the work- piece. 15 8. Fixture system as in any of claims 1 - 7, c h a r a c t e r i ¬ s e d in that at least one of said holders in its lower surface is provided with at least one projecting member (24, 46) having a width corresponding to the width of a T-groove (2a, 2b) in the 5 worktable. 9. Fixture system as in claim 8, c h a r a c t e r i s e d in that said projecting member is a guide cooperating with a groove in the worktable. 10 10. Fixture system as in claim 8 or 9, c h a r a c t e r i s e d in that said projecting member is expansible in order to compensate for variations in the width of said groove in the worktable. 15

Inventors: LUNDGREN SIXTEN ALFRED LENNART
Applicants: LUNDGREN SIXTEN ALFRED LENNART, LUNDGRENS FORMVERKTYG AB
Application year: 1982
Main classification: B23Q3
IPC codes: B23Q3