Title of Invention

AN APPARATUS FOR HOLDING A WORKPIECE

Abstract

ABSTRACT OF THE DISCLOSURE A workpiece holding apparatus includes a swingable mount angularly movably supported on a support base by a pair of pivot shafts at respective ends of the swingable mount. The pivot shafts are positioned slightly above the specific gravity of the swingable mount with a workpiece held thereon. A plurality of holder jigs for holding re- spective parts of the workpiece are mounted on the swingable mount and positioned in respective locations spaced along The swingable mount.

Full Text

Field of the Invention; The present invention relates to an apparatus for holding a workpiece such as a motorcycle frame or the like while components are being welded to the workpiece, and a method of holding and welding a workpiece using such a work-piece holding apparatus. Description of the Prior Art: One known auxiliary apparatus used in a process of assembling motorcycles is disclosed in Japanese laid-open utility model publication No. 57-132790. The disclosed ap¬paratus includes a holder composed of a pair of laterally spaced hands for grippiny a motorcycle frame therebetween. The hands are angularly movable by rotating units to turn the motorcycle frame about transverse and longitudinal axes thereof for thereby changing the attitude of the motorcycle frame through successive angular positions. While the mo¬torcycle frame is held in each of desired angular positions by the hands, various components are welded to the motorcy¬cle frame. When the motorcycle frame is supported by the hands, the center of gravity of the motorcycle frame is po¬sitioned above the transverse and longitudinal axes about which the motorcycle frame is swingable by the hands. While components are being welded to the motorcycle frame, the motorcycle frame is subjected to moments about the trans¬verse and longitudinal axes thereof, and hence tends to be¬come unstable. Consequently, it has been difficult to keep the motorcycle frame at an accurate attitude in each of the desired positions, posing certain limitations on the degree of precision with which components are welded to the motor¬cycle frame. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an apparatus for holding a workpiece highly accu¬rately and stably in any of desired positions. Another object of the present invention is to pro¬vide a method of holding and welding a workpiece with a high degree of precision. According to the present invention, there is pro¬vided an apparatus for holding a workpiece, comprising a support base, and a swingable mount for holding a workpiece thereon, the swingable mount being supported on the support i base for angular movement aboujt an axis with respect to the support base, the swingable mount with the workpiece held i thereon having a specific gravity positioned slightly lower j than the vertical position of the axis. The apparatus further comprises clamping means for fixing the swingable mount in a selected angular position to the support base, and a pair of pivot shafts, the support base and the swingable mount being horizontally elonaate. the swingable mount being supported on the support base by the pivot shafts at longitudinal ends thereof for angular movement about the axis with respect to the support base. The apparatus further comprises a plurality of holder jigs mounted on the swingable mount for holding respective parts of the workpiece. The holder jigs are positioned in respec¬tive locations spaced along the swingable mount. According to the present invention, there is also provided an apparatus for holding a workpiece, comprising a support base, a swingable mount angularly movably supported on the support base by a pair of pivot shafts at respective ends of the swingable mount, the pivot shafts being posi¬tioned slightly above the specific gravity of the swingable mount with a workpiece held thereon, and holding means mounted on the swingable mount for holding the workpiece. The apparatuo further comprises clamping means for fixing the swingable mount in a selected position to the support base. The clamping means may comprise a pair of disks fixedly mounted on the pivot shafts, respectively, and a pair of calipers mounted on the ends of the swingable mount for selectively gripping and releasing the disks, re¬spectively. The holding means may comprise a plurality of holder jigs mounted on the swingable mount for holding re¬spective parts of the workpiece. According to the present invention, there is fur¬ther provided a method of welding components to a workpiece held by a swingable mount which is angularly movably supported on a support base, comprising the steps of holding the workpiece with holder jigs on tlie swingable mount which is supported on the support base for angular movement about an axis that is positioned slightly above the specific gravity of the swingable mount with the workpiece held thereon, fixing the swingable mount in a selected angular position to the support base, and welding the components to the workpiece held on the swingable mount fixed in the selected angular position to the support base. Accordingly the present invention provides an qjparatus for holding a workpiece, comprising a support base, a swingable mount supported on said support base for holding a workpiece thereon, and holding means mounted on said swingable mount for holding the workpiece; characterized in that said support base and said swingable mount are horizontally elongate in the same direction, said swingable mount being supported on said support base by a pair of pivot shafts at longitudinal ends thereof for angular movement about an axis extending between said pair of pivot shafts, said support base having clamping means for fixing said swingable mount in a selected angular position to said support base, and said swingable mount with the workpiece held thereon having a specific gravity positioned slightly lower than the vertical position of said axis. The above and fiirther objects, details and advantages of the present invention will become apparent from the following detailed description of a preterred embodiment thereof, when read in conjunction with the accompanying drawings. FIG 1 is a side elevational view of a workpiece holding apparatus according to the present invention; FIG. 2 is a front elevation view of the workpiece holding apparatus; FIG 3A is a side elevational view of a holder jig for holding a head pipe: FIG 3B is a plan view of the holder jig for holding a head pipe; FIG 4A is a side elevational view of a holder jig for holding a down tube pipe; FIG. 4B is a cross-sectional view taken along line IVB - IVB; FIG. 4C is a cross-sectional view taken along line IVC - IVC; FIG. 5A is a side elevational view of a holder jig for holding a steering head plate; FIG. 5B is a view of the holder jig for holding a steering head plate, as viewed in the direction of the arrow VB in FIG. 5A; FIG. 6 is a side elevational view of a holder jig for holding a rear tank cross member; FIG. 7A is a side elevational view of a holder jig for holding an auxiliary tube; FIG. 7B is a plan view of one of bearing members of the holder jig shown in FIG. 7A; - FIG. 0 is a aide elevational view of a holder jig for holding a pair of upper pipes; FIG. 9A is a plan view of a holder jig for holding an upper pipe end; FIG. 9B is a side elevational view of the holder jig for holding an upper pipe end; FIG. 10 is a side elevational view of a pair of holder jigs for holding a bottom plate and a main stand bracket, respectively; and FIG. 11 is a view of the holder jigs for holding a bottom plate and a main stand bracket, respectively, as viewed in the direction of the arrow XI in FIG. 10. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIGS. 1 and 2, a workpiece holding apparatus according to the present invention has a horizon¬tally elongate channel-shaped support base 1 and a horizon¬tally elongate swingable mount 2 positioned in and angularly movably supported by the support base 1. The support base 1 has a pair of horizontally spaced front and rear vertical plates la, lb and a horizontal bottom plate Ic interconnect¬ing the lower ends of the vertical plates la, lb. The swin¬gable mount 2 has a front pivot shaft 3 mounted on a front end thereof and rotatably supported by the front vertical plate la of the support base 1, and a rear pivot shaft 4 mounted on a rear end thereof and rotatably supported by the rear vertical plate lb of the support base 1. Disks 5, 6 are fixed to the front and rear pivot shafts 3, 4, r£spe position with respect to the support base 1 by the calipers ! 7, 8 which grip the respective (jlisks 5, 6. More specifi- I cally, the swingable mount 2 may be turned clockwise or counterclockwise about the pivot shafts 3, 4, and when the swingable mount 2 reaches a desired angular position with respect to the support base 1, the disks 5, 6 may be clamped by the respective calipers 7, 8 for thereby securely holding the swingable mounl: 2 in the angular position. The swin-gable mount 2 can be angularly moved about the pivot shafts 3, 4 through 45° in each of clockwise and counterclockwise directions from the lowermost position. Stated otherwise, the swingable mount 2 can be angularly moved about the pivot shafts 3, 4 from the lowermost position to a horizontal po¬sition either clockwise or counterclockwise. Casters 10 are mounted on the four corners of the lower surface of the bottom plate Ic, so that the workpiece holding apparatus is freely movable to any desired location. The workpiece holding apparatus also includes a plurality of holder jigs 11a, lib, •••, Ilk, 11m for jointly holding a workpiece, typically, a motorcycle frame F. After the motorcycle frame F has been held by the holder jigs 11a, lib, •••, Ilk, 11m, the swingable mount 2 is angularly moved to change the attitude or angular position of the mctoicycle frame F with respect to the support base 1, and components are welded to the motorcycle frame F while the swingable mount 2 is being held in one of desired angular positions. The holder jigs 11a, lib, •••, Ilk, 11m will suc¬cessively be described below in detail. FIGS. 3A and 3B show a holder jig 11a for holding a head pipe Fa of the motorcycle frame F. The holder jig 11a comprises an upper presser 12 for pressing an upper por¬tion of the head pipe Fa and a lower presser 13 for pressing a lower portion of the head pipe Fa. The upper presser 12 has a portion extending downwardly obliquely to the longitu- dinal direction of the swingable mount 2, and is pivotally supported at an intermediate position on a pivot pin 15 on an upper end of a support arm 14 which is fixed to the swin¬gable mount 2. The upper presser 12 has a presser member 12a on its lower end which is spaced upwardly from and aligned with the lower presser 13. The upper presser 12 has an upper end 12b connected to an upwardly extending rod 16a of an upper cylinder unit 16 which is connected to the swin¬gable mount 2. The lower presser 13 is mounted on an up¬wardly extending rod 17a of a lower cylinder unit 17 which is housed in and fixed to the swingable mount 2. When the upper and lower cylinder units 16, 17 are actuated to extend their rods 16a, 17a, the presser member 12a and the lower presser 13 are fitted in respective opposite ends of the head pipe Fa and grip the head ipipe Fa along its longitudi¬nal axis. FIGS. 4A, 4B, and 4C show a holder jig lib for holding a down tube pipe Fb of the motorcycle frame F. The holder jig lib comprises a presser 21 pivotally supported by 1 a hinge pin 20 on a hollow support arm 21a which is fixed to i the swingable mount 2 and a cylinder unit 19 supported in j the swingable mount 2 and having a rod 19a extending through i the hollow support arm 21a and coupled to the presser 21. When the cylinder unit 19 is actuated to extend the rod 19a, the presser 21 is turned about the hinge pin 20 to engage and press the down tube pipe Fb as shown in FIG. 4B. The holder jig lib also includes a pair of bearing members 22, 23 mounted on the swingable mount 2 upwardly and dovmwardly, respectively, of the presser 21 for supporting the down tube pipe Fb as it is pressed by the presser 21. As shown in FIG. 4C, the bearing member 23 has a recess 23a defined in its distal end for receiving the down tube pipe Fb therein. As shown in FIG. 1, a positioning pin 25 is mounted on the swingable mount 2 upwardly of the holder jig lib. The positioning pin 25 can be moved into and out of a hole (not shown) defined in a front path of the motorcycle frame F by a cylinder unit 24 disposed in the swingable mount 2. Similarly, a positioning pin 27 is mounted on the swingable mount 2 downwardly of the holder jig lib. The positioning pin 27 can be moved into and out of a hole (not shown) defined in an engine guard bracket of the motorcycle frame F by a cylinder unit 26 disposed in the swingable mount 2. FIGS. 5A and 5B illustrate a holder jig lie for holding a steering head plate Fc of the motorcycle frame F. The holder jig lie comprises a front presser 30 pivotally supported by a hinge pin 29 on a hollow support arm 30a and a front cylinder unit 28 supported on the swingable mount 2 and having a rod 28a extending through the hollow support arm 30a and coupled to the presser 30. When the front cyl¬inder unit 28 is actuated to pull the rod 28a, the front presser 30 is turned about the hinge pin 29 to engage and press the steering head plate Fc. The holder jig lie also comprises a rear presser 32 angularly movable into pressing engagement with the steering head plate Fc by a rear cylin¬der unit 31 supported on the swingable mount 2, and a bear¬ing member 33 positioned forwardly of the front cylinder unit 28 for supporting a lower surface of the steering head plate Fc. The bearing member 33 has a recess defined in an upper distal end thereof for receiving a lower portion of the steering head plate Fc. The pressers 30, 32 have press¬ing surfaces made of hard urethane. FIG. 6 shows a holder jig lid for holding a rear tank cross member Fd of the motorcycle frame F. The holder jig lid comprises a pin 35 which can be inserted in a hole defined in the rear tank cross member Fd and a presser 36 which can be pressed against the rear tank cross member Fd by a cylinder unit 34 mounted on the swingable mount 2. The cylinder unit 34 has a rod 34a connected to the pin 35 and the presser 36. When tho cylinder ur.it 34 is actuated to retract the rod 34a, the pin 35 is inserted in the hole de¬fined in the rear tank cross member Fd and the presser 36 is pressed against the rear tank cross member Fd. FIGS. 7A and 7B illustrate a holder jig lie for holding an auxiliary tube Fe 6± the motorcycle frame F. The holder jig lie comprises a pair of spaced bearing members 40, 41 mounted on the swingablie mount 2 for supporting and pressing the auxiliary tube Fe by respective cylinder units 37, 38 mounted on the swingable mount 2. The cylinder units 37, 38 have respective rods 37a, 38a connected to the bear¬ing members 40, 41, respectively. When the cylinder units f 17, 38 are actuated to extend the rods 37a, 38a, the bearing lembers 40, 41 are pressed against and support the auxiliary ;ube Fe. Each of the bearing members 40, 41 has a recess iOa defined in its distal end for receiving the auxiliary ;ube Fe therein. Actually, there is a pair of laterally spaced, identical holder jigs lie for holder respective aux--liary tubes Fe of the motorcycle frame F. FIG. 8 shows a holder jig llf for holding a pair )f laterally spaced upper pipes Ff of the motorcycle frame i". The holder jig llf comprises a pair of pressers 43 op-jratively coupled to a rod 42a of a cylinder unit 42 mounted )n the swingable mount 2 and a pair of laterally spaced rearing members 44 mounted on the swingable mount 2 for sup¬porting lower surfaces of the upper pipes Ff received in respective recesses 44a thereof. When the cylinder unit 42 Ls actuatfcu to extend the rod 42a, the pressers 43 press the respective upper pipes Ff down against the bfearing members 14. As shown in FIG. 1, a holder jig llg is mounted on :he swingable mount 2 forwardly of the holder jig llf for lolding a cushion cross plate and bar of the motorcycle Erame F, and a holder jig llh is mounted on the swingable nount 2 rearwardly of the holder jig llf for holding a tail ::ross plate of the motorcycle frame F. FIGS. 9A and 9B show a holder jig Hi for holding an upper pipe end Fi of the motorcycle frame F. The holder jig Hi con^rises a presser 46 coupled to a rod 45a of a horizontal cylinder unit 45 mounted on the swingable mount 2, and a bearing member 47 mounted on the swingable mount 2 and having a guide hole 47a defined therein. A pin 48 is mounted on a distal end of the presser 46 in alignment with the guide hole 47a. A bushing 50 is mounted in the guide hole 47a. When the cylinder unit 45 is actuated to project the rod 45a, the presser 46 is pressed against the upper pipe end Fi, and the pin 48 is inserted through a hole in the upper pipe end Fi into the bushing 50 in the guide hole 47a. Actually, there is a pair of laterally spaced, identi¬cal holder jigs Hi for holding respective upper pipe ends Fi of the upper pipes Ff of the motorcycle frame F. FIGS. 10 and 11 shows a pair of holder jigs 11j, Ilk for holding a bottom plate Fj and a main stand bracket Fk, respectively, of the motorcycle frame F. The holder jigallj, lik comprise respective upper and iower horizontal cylinder units 52, 53 vertically spaced from each other and having respective rods 52a, 53a with respective pins 54, 55 mounted on their distal ends. When the cylinder units 52, 53 are actuated to extend their rods 52a, 53a, the pins 54, 55 are inserted into respective holes defined in the bottom plate Fj and the main stand bracket Fk, with the lower pin 55 being also inserted in a hole 56a defined in a bearing member 56 that is mounted on the swingable mount 2 for sup¬porting the lower end of the main stand bracket Fk. Actu¬ally, there are two laterally spaced pairs of holder jigs 11j. Ilk for holding respective bottom plates Fj and respec¬tive main stand brackets Fk of the motorcycle frame F. As shown in FIG. 1, a holder jig 11m is mounted on the swingable mount 2 for holding a down tube collar of the motorcycle frame F. A plurality of ejector cylinder units 57, 58, 59 are mounted on the swingable mount 2 near the holder jigs 11j, Ilk, 11m for engaging a down tube assembly of the motorcycle frame F and ejecting the motorcycle frame F off the swingable mount 2 after desired components have been welded to the motorcycle frame F. The cylinder units of the holder jigs 11a - 11m described above are pneumatically operated, for example. The workpiece holding apparatus is arranged such that the specific gravity of the assembly composed of the swingable mount 2 and the holder jigs 11a ~ 11m with the motorcycle frame r-installad thereon is positioned slightly below the vertical position of the front and rear pivot shafts" 3, 4. Since the front and rear pivot shafts 3, 4 are vertically positioned very closely to the specific gravity of the as¬sembly composed of the swingable mount 2 and the holder jigs 11a - 11m with the motorcycle frame F installed thereon, the assembly can be angularly moved about the front and rear pivot shafts 3, 4 with highly light forces. The assembly and hence the supported motorcycle frame F are stabilized in attitude because they are always subject to recovering forces as the front and rear pivot shafts 3, 4 are verti¬cally positioned slightly above the specific gravity of the assembly. The attitude of the motorcycle frame F held on the swingable mount 2 by the holder jigs 11a ~ 11m is also made stable in any of selected angular positions because of a relatively long distance between the front and rear pivot shafts 3, 4 that are positioned at the longitudinally oppo¬site ends of the motorcycle frame F. After the assembly has been turned to a desired angular position with respect the support base 1, the assem¬bly is fixed to the desired angular position by the calipers 1, 8, and desired components are welded to the motorcycle frame F. While the components are welded to the motorcycle frame F, the motorcycle frame F is held stably in the se¬lected angular position by the fixed swingable mount 2 with no undesirable moment imposed thereon. Inasmuch as the holder jigs 11a - 11m are positioned in locations spaced "'.ongitudir^lly along the swingable mount 2-fcr holding vari¬ous parts of the motorcycle frame F, the holder jigs 11a -11m can hold various parts of the motorcycle frame F even if the parts of the motorcycle frame F are not yet coupled to¬gether. Although there has been described what is at pre¬sent considered to be the preferred embodiment of the in¬vention, it will be understood that the invention may be embodied in other specific forms without departing from the essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustra¬tive, and not restrictive. The scope of the invention is indicated by the appended claims rather than by the forego¬ing description. WE CLAIM : 1. An apparatus for holding a workpiece, comprising a support base, a swingable mount supported on said support base for holding a workpiece thereon, and holding means mounted on said swingable mount for holding the workpiece; characterized in that said support base and said swingable mount are horizontally elongate in the same direction, said swingable mount being supported on said support base by a pair of pivot shafts at longitudinal ends thereof for angular movement about an axis extending between said pair of pivot shafts, said support base having clamping means for fixing said swingable mount in a selected angular position to said support base, and said swingable mount with the workpiece held thereon having a specific gravity positioned slightly lower than the vertical position of said axis. 2. The apparatus according to claim 1, wherein the workpiece comprises a motorcycle frame, said axis extending in the longitudinal direction of said motorcycle frame between said pair of pivot shafts, one of said pair of pivot shafts being positioned in front of the front end of said motorcycle frame and the other of the pivot shafts being positioned in the rear end of said motorcycle frame. 3. The apparatus according to claim 1, wherein said holding means comprises a plurality of holder jigs mounted on said swingable mount for holding respective parts of the workpiece. 4. The apparatus according to claim 3, wherein said holder jigs are positioned in respective locations spaced along said swingable mount. 5. The apparatus according to claim 1, wherein said clamping means comprises a pair of disks fixedly mounted on said pivot shafts, respectively, and a pair of calipers mounted on said ends of the swingable mount for selectively gripping and releasing said disks, respectively. 6. An apparatus for holding a workpiece substantially as herein described with reference to the accompanying drawings.

Documents:

1141-mas-1995 abstract.pdf

1141-mas-1995 claims.pdf

1141-mas-1995 correspondence-others.pdf

1141-mas-1995 correspondence-po.pdf

1141-mas-1995 description(complete).pdf

1141-mas-1995 drawings.pdf

1141-mas-1995 form-1.pdf

1141-mas-1995 form-26.pdf

1141-mas-1995 form-4.pdf