AU600762B2 - Scale balancing device in drawing machine - Google Patents

Description

AUSTRALIA

Patents Act COMPLETE SPECIFICATION

(ORIGINAL)

Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority 600762 Int. Class Related Art: This document contains the amendmertis made unde-r Section 49 and is correct for printing___ 0 44, o ~4 4 APPLICANT'S REFERENCE: 87-Au-56 0 p 9 p 4 Namne(s) of Applicant(s): ASAHI SEIMITU KABUSHIKI KAISHA Address(es) of Applicant(s): 5-2 Higashi Ooizuii, 2-chomre, Nerima-kuf Tokyo,

JAPAN.

Address for Service is: PHILLIPS ORMONDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA 4 Complete Specification for the invention entitled: SCALE BALAN~CING DEVICE IN DRAWING MACHINE our Ref 71252 POF Code., 8569/76093 LQC)DGL, M~ :su3-rFcm 2 3 OCT 1987 Melbourne The following statement is a full description of this invention, including the best method of performing it known to applicant(s): 6003q/1 1 1 -la- BACKGROUND OF THE INVENTION The present invention relates to an improved scale balancing device incorporated into a scale manipulating head of the universal parallel ruler (drawing machine).

In the scale manipulating head of the drawing machine, an arrangement is generally provided such that the scale rotating shaft is rotatably supported in the bearing of the scale supporting base plate. The scale rotating shaft has the scale manipulating handle and the scale mounting plate both formed integrally therewith at the upper end and the lower end, respectively, so that said scale manipulating handle may be used to rotate the scale. In such an arrangement, due to the fact that the scale extends in one direction from its rotating shaft in a cantilever fashion, an empty weight or dead load of the scale produces an unbalanced load which is disedvantageously applied to the S scale rotating shaft so far as the scale is free to be S° rotated, when the drawing board is installed at an angle. A rotating moment due to such empty weight of the scale is o zero when the centre of gravity of the scale is vertically S2 just above the manipulating handle and when said centre of gravity is vertically just below said manipulating handle while said rotating moment gradually increases as the centre of gravity of the scale is rotated from said position just above the manipulating handle to the horizontal and at this moment said rotating moment reaches its maximum value. As i said center of gravity is further rotated from the hzirizontal to said position vertically just below the manipulating handle, said rotating moment due to the empty weight gradually decreases down to zero. Accordingly, the scale would be unintentionally rotated downwardly due to said empty weight of the scale Unless the scale is positively supported by the scale manipulating handle. It is an essential object of the present invention to balance such rotating moment produced due to the empty weight of the A LVF

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r scale so that the scale may be held at any desired angular position and the rotational manipulation of the scale may be smoothly achieved, by providing an improved scale balancing device.

A prior art device is disclosed by publications such as U.S. Patent 4,587,742 or U.S. Patent 4,601,107.

In this device of well known art, in order to avoid the inconvenience that, when the rotating moment developed by the empty weight of the scale is balanced by a balancing mechanism concentrically mounted on the scale rotating shaft, an unbalanced load is exerted on the scale rotating shaft to produce an error in the scale rotation angle, the first rotatable member adapted to be rotated concentrically with the scale rotating shaft is coupled through the interlocking mechanism to the second rotatable member separately provided on the non-rotatable member of the scale manipulating head so that the first and second rotatable members may be rotated synchronously with each other and thereby a tensile force against the rotating moment due to l the empty weight of the scale is exerted on said second 0,4 9 rotatable member in order to maintain the scale well balanced.

i With this prior art device, however, the design of the non-rotatable member included in the head of the conventional universal parallel ruler must be substantially modified, since the second rotatable member of the same size as the first rotatable member must be incorporated into the :j non-rotatable member. This prior art device is accompanied j! with further problems in that the non-rotatable member inevitably becomes bulky, it is impractical to completely remove the unbalanced load in order to balance the rotating J moment due to the dead weight of the scale, and finally the in' erlocking mechanism serving to achieve a synchronous rotation of the first and second rotatable members causes an error in the rotational angle of the scale rotating shaft,

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'4w r -3- SUMMARY OF THE INVENTION A primary object of the present invention is, in view of various drawbacks of the conventional device as mentioned above, to provide an improved scale balancing device in the drawing machine, said scale balancing device being constructed with a rotatable membe.r being rotatable concentrically and integrally with a scale rotating shaft in a scale manipulating head and being provided with an engaging member which is position-adjustable in a direction of the radius of said rotatable member, a tension member having a tensile elasticity i, connected at one end with said engaging member aind at the other end to one end of a biasing mechanism mounted of a non--rotatable member, and the other end of the biasing mechanism is held in contact with the rotatable member against the tensile elasticity of the tension member.

It is another object of the present invention to provide said scale balancing device in the universal oo, parallel ruler wherein the engaging member is positionadjustable in the direction of the radius of the rotatable ,2Q member with respect to its rotational center.

It is a further object of the present invention to provide the scale balancing device in the universal parallel Sruler characterized in that a locking force provided by a il combination of grooves formed in an indexing plate included Si in an indexing mechanism and an indexing detent adapted to Sbe received in said grooved to lock the scale at predetermined angular intervals can be mentioned under action of the scale balancing force.

Ar/ It is still another object of the present invention to provide the scale balancing device in the universal parallel ruler characterized in that a lever of the indexing mechanism provided along the scale rotating shaft in order to lock the scale at predetermined angular intervals is bent so that said lever may operate withuth any mechanical

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S Al L w -4interference of said engaging member.

According to the present invention there is provided a scale balancing device incorporated into a scale manipulating head of a drawing machine comprising: a bearing base plate provided in the scale manipulating head; a scale rotating shaft rotatably supported in said bearing base plate; a rotatable member having a rotational radius and being rotatable concentrically and integrally with said scale rotating shaft; an engaging member positioned on the rotatable member, with its position being adjustable in a direction of the rotational radius of said rotatable member; Sa tension member having two ends, one end of said i tension member being connected to said engaging member and having a tensile elasticity; i a biasing mechanism provided on said bearing base plate and having two ends, one end of said biasing mechanism being connected to the other end of said tension member; and i the other end of said biasing mechanism bearing against said rotatable member under the tensile elasticity of said tension member; wherein rotation of the rotatable member, causes elongation or contraction of the tension member such that the tension member applies an angular amount to the rotatable member balancing the angular moment applied to the I rotatable member by a load.

S The present invention further provides a scale balancing device incorporated into a scale manipulating head i of a drawing machine comprising; a bearing base plate provided in the scale manipulating head; a scale rotating shaft rotatably supported in said bearing base plate; a rotatable member having a rotational radius and A being rotatable concentrically and integrally with said

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-4ascale rotating shaft; an engaging member positioned on the rotatable member, with its position being adjustable in a direction of the rotational radius of said rotatable member; a tension member having two ends, one end of said tension member being connected to said engaging member and having a tensile elasticity; a biasing mechanism provided on said bearing base plate and having two ends, onie end of said biasing mechanism being connected to the other end of said tension member; the other end of said biasing mechanism bearing against said rotatable member under the tensile eLasticity of said tension member; and S a scale rotational angle indexing mechanism consisting of an indexing plate having grooves therein and an indexing 1 detent adapted to be received in any one of paid grooves to .r lock the scale at predetermined angular intervals, in which locking force provided by engagement of said grooves and said detent can be maintained by the scale balancing force; '20 wherein rotation of the rotatable member, causes elongation or contraction of the tension member such that the tension member applies an angular amount to the rotatable member balancing the angular moment applied to the rotatable member by a load.

1 The present invention further provides a scale balancing device incorporated mrito a scale manipulating head of a drawing machine comprising: a bearing base plate provided in the scale i manipulating head; a scale rotating shaft rotatably supported in said bearing base plate; Ai a rotatable member having a rotational radius and being rotatable concentrically and integrally with said scale rotating shaft; an engaging member positioned on the rotatable member, with its position being adjustable in a direction of the rotational radius of said rotatable member; a tension member having two ends, one end of said

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tension member being connected to said engaging member and having a tensile elasticity; a biasing mechanism provided on said bearing base plate and having two ends, one end of said biasing mechanism being connected to the other end of said tension member; the other end of said biasing mechanism bearing against said rotatable member under the tensile elasticity of said tension member; and a scale rotational angle indexing mechanism for locking the scale at predetermined angular intervals, in which a lever provided along the scale rotating shaft is bent for operation of said lever without any mechanical interference with said engaging member; wherein rotation of the rotatable member, causes elongation or contraction of the tension member such that the tension member applies an angular amount to the rotatable member balancing the angular moment applied to the rotatable member by a load.

a biasing mechanism provided on said bearing base plate and having two ends, one end of said biasing mechanism being connected to the other end of said tension member; the other end of said biasing mechanism bearing against said rotatable member under the tensile elasticity of said tension member; and a scale rotational angle indexing mechanism for locking the scale at predetermined angular intervals, S i10 in which a lever provided along the scale rotating shaf t is bent for operation of said lever without any echanical interference with said engaging member.

As has previously been mentioned, with a slanted drawing board, the rotating moment developed by the empty weight of the scale becomes zero when the scale is vertically oriented, and gradually increases as the scale is rotated from this vertical upper position to the horizontal S" position at which said rotating moment ireaches the maximum.

This rotating moment gradually decreases as the scale is rotated from the horizontal position to the vertical lower I position. In the scale balancing device constructed in accordance with the present invention, a rotating moment 4o" balancing such rotating moment developed by the dead load of the scale is exerted by the tension member having a tensile elasticity upon the rotatable member adapted to be

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rotated conoentrically and integrally wi th the scale ro tating shaf t wlii le the tensi le elanstici ty of said tonsion member is appi lud through the biasingw mochani nm to the some ro La table member and thoreby to ba lance said tensile elastici ty of the tension member ,o tha the unbalanced load developing in the s;cale r o La i rig sha t as a rus u 1t of the scale bal anc'i ng miay hK balanced or reduced. Furthermore, by pos i Li on adj ustmient of the engaging member in/direction of the radius; of the rotatable member Ni th respectI to i In rotational ceonter a scale balancing force is oasi lx adi unted to accommodate the incli nation of the drawing board from th hor i z'n ta 1 to the vertival or exchange of Phu scalos of different w eighItt For exaruplEn when thpe ngaging member i ned at the renter of the sc ale rnta Lin agTa ft, the wsunon npr ing can not prevent the nval e from being rota Led and, an the engagingj memberrr in moved iay from the scale rotating shaft, tht" e last icityv of the ten;ion npring acting upon the rota table member corres;pondi ogly increases, Conveniently, the( s;cale balancing device oif the invention has another important fea Lure( that the, f orce provi1ded f rom the conino Li on of the, gorioe formed in the indexing pla te nf the indexing iechani sin with thu indexing detunt of said mechan isin adopted Lo he rece ived i n a so I ec ted one of solid grooves i i order to lock the scale at the prude term! tied anigular in torva is iIs 1 i -7so adjusted as to be maintained by the scale balancing force. This feature allows the width and the depth of iaid grooves as well as the engaging force of said detent to be minimized. For example, it is easily achieved to reduce the indexing angular interval which has usually been 150 to and also to reduce the thickness of the indexing plate as well as the engaging strength of the deten'c As still another feature of the scale balancing device constructed in accordance with the present invention, the lever of the indexing mechanism provided along the scale rotating shaft in order to lock the scale at the predetermined angular intervals may be so bent that said lever may operate without any mechanical interference of said engaging member. This feature allows the universal parallel ruler to be provided in which the lever of the indexing mechanism and the engaging member of the scale balancing device mounted around the scale rotating shaft can S effectively operate without any mechanical interference with each other, Further scope of applicability of the preaent S invention will become apparent from the detailed description given hereinafter, However; it should be understood that the detailed desoripbion and specific examples, while inidicating preferred embodiments of the invention, are given by way of illustration only, since various ehang within the tabit of the invention will become apparent to those skilled in the art from this detailed descriptio,

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BRIEF DECRIPTION OF DRAWINGS Fig. 1 is a schematic plan view illustrating an important part in an embodiment of the device constructed according to the present invention; Fig. 2 is a front sectional view of said important part; Figs. 3 through 5 are schematic diagrams sequentially illustrating a manner in which said important part operates; Fig. 6 is a schematic plan view illustrating an important part in another embodiment of the device constructed according to the present invention; Fig. 7 is a front sectional view of the important part shown by Fig. 6; and Figs. 8 through 10 are schematic diagrams sequentially illustrating a manner in which the important part shown by Fig. 7 operates.

*r e P0 DESCRIPTION OF EMBODIMENTS d 4 a tf 6 A scale balancing device of the present invention will be described in more detail, by way of example, with reference with the accompanying drawings. Referring to Fig.

I and 2, reference numeral 1 designates a non-rotatable member of this invention serving as a bearing base plate f r a scale manipulating head connected to a '*uUI 9 member such as a cursor or a pully-carriage which is movable parallel to the top surface of the drawing board. A bearing I f of this bearing base plate 1 rotatable supports a hollow shaft 2. A rotatable member 3 of this invention is integrally secured to an upper portion of the shaft 2 by screws and a scale supporting base plate 4 is integrally secured to a lower portion of shaft 2 also by screws. The rotatable member 3 has a scale manipulating handle 5 integrally secured thereto at its upper portion and the scale supporting base plate 4 has a scale mounting plate 6 secured to a front end thereof so that said handle 5 may rotate the scale carried by the scale mounting plate 6. A protractor 7 adapted to be clamped to the bepring base plate 1 by use of a clamping lever 8 when necessary is rotatably mounted to the bearing in alignment with a vernier 9 secured to the scale supporting base plate 4. The protractor 7 further includes a scale clamping plate and an index plate 11 both integrally secured thereto.

The scale clamping plate 10 can be clamped to the scale supporting base plate 4 by use of the scale clamping lever whenever necessary in a manner not shown. The index plate 11 includes grooves formed at equiangular intervals therein so that an index/de-t. 12 is engaged into any one of said grooves and thereby said index plate 11 is fixed with respect to the scale ,spporting

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4 -*14 r a -11biasing mechanism 23 according to the present invention projects upwardly from the bearing base plate 1 at a point on an extension of the threaded shaft 20 and there is provided a tension member 25 having a tensile elasticity between said end 24 and said engaging member 22. In an embodiment as shown, the tension member 25 comprises a tension spring 26 and a wire 27 which is anchored by a wire anchoring member 28 projecting from the rotatable member 3 at a point adjacent the rotational center thereof so that the pin-like projection of the engaging member 22 adapted to be rotated as the rotatable member 3 is rotated comes into engagement with an intermediate portion of the wire 27 and thereby pulls the tension member 25 with a tensile force corresponding to a rotation radius of said projection.

While the biasing mechanism 5:3 may be of a simple structure, namely, a rod-like one-piece member Ling controllably movable along the longitudinal direction of the threaded o shaft 20, which bears against a side of the rotatable member j 3 at one end and is engaged with the tension member 25 at °0 the other end, the biasing mechanism 23 according to the CO present embodiment comprises a linkage mechanism. The linkage mechanism includes a pair of interlocking levers 31, S 32 actuated by a link lever 30 to be pivotally moved in parallel withi each other around pivots 28, 29 respectively, a biasing lever 33 mounted on an end of the interlocking

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4, I -12lever 32 so as to be movable along the threaded shaft 20, a roller 34 provided on a front end of said biasing lever 33 so as to be maintained bearing against the periphery of the rotatable member 3, and the tension member 25 anchored at an end of the interlocking lever 31 so that the tensile elasticity of the tension member 25 may be exerted on the rotatable member 3.

The engaging member 22 of the rotatable member 3 which is rotated in unison with said scale (or the scale mounting plate the tension member 25, and the biasing lever 33 of the biasing mechanism 23 are relatively positioned to one another as sequentially illustrated by Figs. 3 thorugh Specifically, when the center of gravity of the scale is vertically just above the rotatable member, the engaging member 22 occupies a position on the radius of the rotatable member 3 nearest the tension member 25 as shown in Fig. 3.

The tension member 25 and the biasing lever 33 are positioned along a straight line passing through the rotational center of the rotatable member 3, the tensile elasticity of the tension member 25 exerts no rotating moment on the rotatable member 3 and thus, in this situation, the scale is balanced with zero rotating moment due to the dead weight of the scale 6. As the scale is rotated together with the engaging member 22 from said vertical position to the horizontal position as shown in Fig. 4 by an angle of 90*, the tension member 25 gradually increases a tension angle around a pivot at which the tension member 25 is connected to the biasing mechanism 23 from the previous position as shown in Fig. 3, exerting upon jO the rotatable member 3 a rotating moment against the n.ment due to the dead weight of the scale. Both the tension angle and the rotating moment exerted on the rotatable member 3 reach their maximum values in the situation shown by Fig. 4 in which the centre of -13gravity of the scale is on the horizontal, balancing the rotating moment due to the empty weight of the scale. In this situation, the biasing lever 33 radially applies the tensile elasticity of the tension member 25 on the periphery of the rotatable member 3 so that any unbalanced load possibly exerted on the rotatable member 3 may be effectively reduced. As the scale is subsequently rotated from the horizontal position to the vertical position just below the rotatable member, the tension angle of the tension member 25 gradually decreases. At the position of Fig. 5 in which the gravity center of the scale has reached said position just below the rotatable member, the engaging member 22 is in the remotest position but the tension member and the biasing lever 33 are on a line along the diameter of the rotatable member 3 so that the tensile elasticity of the tension member 25 is balanced. No rotating moment is exerted upon the rotatable member 3 and this condition is balanced with the condition of zero rotating moment due to the dead weight of the scale 6.

Now another embodiment of the scale balancing device constructed in accordance with the present invention will be described in detail with reference to Figs. 6 through Reference numeral 1 designates a non-rotatable member of this invention serving as a bearing base plate for a scale manipulating head connected to a member such as a cursor or a pulley-carriage which is movable parallel to the top surface of the drawing board. A bearing la of this bearing

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-14base plate 1 rotatably supports a hollow shaft 2. A rotatable member 3 of this invention is integrally secured to an upper portion of the shaft 2 by screws 3a and a scale supporting base pl.ate 4 is integrally secured to a lower portion of the shaft 2 by screws 4a. It should be noted here that the shaft 2 and the rotatable member 3 are integral with each other so far as their rotary functions are concerned. Accordingly, it is unnecessary to distinguish the shaft 2 from the rotatable member 3 and the term "rotatable member" should be considered to be a member including said shaft 2. The rotatable member 3 has a scale manipulating handle 5 integrally secured thereto at its upper portion and the scale supporting base plate 4 has a scale mounting plate 6 secured to a front end thereof so that said handle 5 may rotate the scale carried by the scale mounting plate 6. A protractor 7 adapted to be clamped to Sthe bearing base plate 1 by use of a clamping lever 8 is rotatably mounted around the lower portion of the bearing la so that protractor graduations provided on the periphery of said protractor may correspond to vernier graduations on a vernier 9 mounted by screws 9c on the scale supporting base plate 4 with interposition of spacers 9a, 9b. Reference numeral 7a designates a protractor base line index plate 4 with interposition of spacer 9a, 9b. Reference numeral 7a designates a protractor base line index plate integrally mounted on the supporting base plate 1 in opposition to the inner periphery of the protractor graduations on the protractor 7 so that a rotational angle of the protractor 7 relative to the supporl:ting base plate 1 may be recognized by this protractor base line index plate 7a. The protractor 7 further includes a scale clamping plate 10 and an index plate 11 both integrally secured thereto. The scale

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I I 1 clamping plate 10 can be clamped to the scale supporting base plate 4 by use of a scale clamping lever 10a whenever necessary. The index plate 11 includes grooves lla formed therein at equiangular intervals so that an index detent 12 is engaged into any one of said grooves and thereby said index plate 11 is fixed with respect to the scale supporting base plate 4. A width of each groove lla formed in the index plate 11 and a groove interval e# 99 f r may be reduced aproximately to the minimum thickness of the index plate 11 for effective punching Tor example, the conventional angular interval of these grooves which is typically 15 may be reduced to 5 or less. fTrhe" engaging strength of the grooves lla and the index detent 12 may be set to a level such that a disengagement occurs when a load due to the /e -y weight of the scale reaches the maximum. The index it- 12 is operatively associated with an interlocking piece 13 being movable along a bottom surface of the scale supporting base plate 4, a lever 14 extending through the interiors of the shaft 2 and the rotatable member 3, respectively, and a lever 15 provided laterally of the handle 5 so as to be selectively engaged with and disengaged from the index plate 11. The lever 14 is engaged at its lower end 14a with the interlocking piece 13 and at its upper end 14b with the lever 15. Reference numeral 13a designates a spring member always exerting a tensile elasticity upon the interlocking piece 13 so as to urge said index detent 12 into engagement with any one of said I;rooves 11a. Said lever 14 has a bent portion 14c adjacent its upper end, being pivotally movable on a diamoetr reduced portion 2a provided inside the upper portion of the shaft 2, and is engaged with the lever Reference numerals 16, 17 designate covers adapted to be rotatable integrally with the scale mounting plate 6 an'l %AN

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17 a portion of the cover 16 which overlies the vernier 9 is provided with a loupe 18. Reference numeral 19 designates a scale mounting screw.

The rotatable member 3 according to the present invention includes a thr-.aded shaft 20 with a radially extending axis which can be rotated by a manipulating knob 21, and an engaging member 22 adapted to be engaged with said threaded shaft 20 in a radially movable fashion. In the embodiment as shown, the tbreaded shaft 20 is provided Nithin a guide frame 3b inside the rotatable member 3 and adapted to be engaged with the 4 engaging member 22. Thus, the engaging member 22 is free to reciprocate radially between a position adjacent the rotational center of the rotatable member 3 and a remote position as the threaded shaft 20 is rotated, A front end of a link member 27 extending through a lateral opening 3c of the rotatable member 3 is connected to the lower end of the engaging member 22 and a spring anchoring means 28 is provided on a rear end of said linv' member 27. An end 24 of a biasing mechanism 23 according to the present invention projects from the bearing base plate I at a point along a line extending transversely of the threaded shaft 20 and there is connected between said end 24 and the spring anchoring means 28 of said link member 27 a tension member having a tensile elasticity.

18 In this embodiment, the tension member 25 comprises a coil spring adapted to be tensiloned by the engaging member 22 through the l ink member 27 so tha t a tensi 1le force thereof depend ing on a rotational rad ius of the engaging member 22 whicht is ro La ted as the ro ta tablo member 3 may he appliled to the hi as i ng rfochan ism 231.

The biasi, mechanism 23 comprises an one pioece member in the form of a bent rod extending, longi tudinally oif the tension member 25 and having, i movomont Iimit WI by guide pins 23a, 23b. An end of tluo bias ing mechanism 2 is &mm1 bent/\anti terminates in a rotiAtable ceontact member 26 such as a bearing which is, in turn, radliallv' biased against a contact ring 3d forming a lower side portion of the rotatable member 3.

The engaging membor 22 of the rotatable member 3 being rota table in unison w ith sadscale (t he (scale mounting Plate 6) and the ten i on member relatLively positioned to each otiher ar, nequentially illustrated by Fig. 8 throuvh 10, or specifically, w heon L et- of t ho sc (ale S is vertical ly just above the rotatabhie member and no rotatLing moment dlue to the P w vig h t o f theo s cal Is1 a pp Ii ed t o th o r ota ta blIe meom bePr 3 the engaging, member 9.2 oce'upier a position on the rad ius of the rotLatable membver 3 nevarest the tension membeir 25 as seen in 1i, in which, the tens ion member 25 and the contact member 26 are r I -19positioned along a straight line passing through the rotational center 0 of the rotatable member 3, the tensile elasticity of the tension member 25 exerts no rotating moment on the rotatable member 3 and in such a situation, the scale is balanced with zero rotating moment due to the dead weight of the scale S. As the scale is rotated together with the engaging member 22 from said vertical position to the horizontal position as seen in Fig. 9 by an angle of 900, the tension member 25 gradually increases a tension angle around a joint 24 at which the tension member is connected to the biasing mechanism 23 from the previous position as shown by Fig. 8, exerting upon the rotatable member 3 a rotating moment against the moment due to the dead weight of the scale. Both the tension angle and the rotating moment exerted on the rotatable member 3 reach their maximum values in the situation shown by Fig. 9 in which the centre of gravity of the scale is on the horizontal, balancing the rotating moment due to the dead weight of the scale. In this situation, the contact member 0 26 applies in the direction of a radius of the rotatable member 3 the tensile elasticity of the tension member 25 to the periphery of the rotatable member 3 so that any I unbalanced load possibly exerted on the rotatable member 3 may be effectively reduced. As the scale is subsequently rotated from the horizontal position to the vertical position just below the rotatable member, the tension angle of the tension member 25 gradually decreases. At the position shown in Fig. 10 in which the centre of gravity of the scale has reached said position just below the rotatable member, the engaging member 22 is in the remotest position Awl but the tension member 25 and the contact member 26 are on a line along the diameter of the rotatable member 3 as in the situation of Fig. 8 so that the tensile elasticity of the tension member 25 is balanced. No rotating moment is exerted upon the rotatable member 3 and this condition is balanced with the condition of zero rotating moment due to the dead weight of the scale S.

i-ii ii 1 The tensile elasticity of the tension member increases as the engaging member 22 is moved radially away from the center of the rotatable member 3 and thus the engaging member 22 may be controllably moved radially away from the center of the rotatable member 3 in order to maintain the scale well balanced regardless of the drawing board's orientation which may vary between the horizontal orientation and the vertical orientation.

ji The invention being thus described, it will be obvious S i10 that the same may be varied in many ways. Such variations I ar. not to be regarded as a departure from the ambit of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.

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Claims (14)

1. A scale balancing device incorporated into a scale manipulating head of a drawing machine comprising: a bearing base plate provided in the scale manipulating head; a scale rotating shaft rotatably supported in said bearing base plate; a rotatable member having a rotational radius and being rotatable concentrically and integrally with said scale rotating shaft; an engaging member positioned on the rotatable member, with its position being adjustable in a direction of the rotational radius of said rotatable member; a tension member having two ends, one end of said tension member being connected to said engaging member and having a tensile elasticity; a biasing mechanism provided on said bearing base plate and having two ends, one end of said biasing mechanism being connected to the other end of said tension member; and the other end of said biasing mechanism bearing against said rotatable member under the tensile elasticity of said tension member; wherein rotation of the rotatable member, causes elongation or contraction of the tension member such that the tension member applies an angular moment to the rotatable member balancing the angular moment applied to the rotatable member by the seale and its mountings. L- XY ili.l. i_~ii._li tilii~i_(l~L li ijil* i;ii_;iiii(lYlii li-II. ;iiii. -23.- THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. A scale balancing device incorporated into a scale 7 manipulating head of a drawing machine comprising: a bearing base place provided in the scale manipulating head; a scale rotating shaft rotatably supported in said bearing base plate; a rotatable member having a rotational radius and being rotatable concentrically and integrally with said scale iotating shaft; an engaging member provided position-adjustably in a direction of the rotational radius of said rotatable member; a tension member having two ends, one end of said tension member being connected to said engaging member and having a tensile elasticity; a biasing mechanism provided on said bearing base plate and having two ends, one end of said biasing mechanism being connected to the other end of said tension member; and the other end of said biasing mechanism bearing against said rotatable member under the tensile elasticity of said tension member. S2. The scale balancing device incorporated into a scale manipulating head of a drawing machine as recited by claim i, wherein the engaging member is provided position-adjustably in a direction of the rotational radius of the rotatable member from the center of said rotatable member, S3. The scale balancing device incorporated into a scale manipulating head of a drawing machine as recited by claim 1 or 2, wherein the engaging member is position-adjustably movable as a threaded shaft provided on the rotatable member is rotated. VF ItUS .i- -22-

4. The scale balancing device incorporated into a scale manipulating head of a drawing machine as recited by any one of claims 1 to 3, wherein the rotatable member includes a guide frame within which there is the engaging member adapted to be position-adjustably guided as the threaded shaft is rotated. The scale balancing device incorporated into a scale manipulating head of a drawing machine as recited by any one of claims 1 to 4, wherein the tension member comprises a tension spring wire secured at one end to a wire anchoring meant 'ovided, adjacent the center of the rotatable memb ind adapted to be engaged at its intermediate portion .±th the engaging member.

6. The scale balancing device incorporated into a scale manipulating head of a drawing machine as recited by any one of claims 1 to 4, wherein biasing mechanism comprises an one-piece member having one end subjected to the tensile elasticity of the tension member and the other end bearing against the periphery of the rotatable member.

7. A scale balancing device incorporated into a scale S manipulating head of a drawing machine comprising: a bearing base plate provided in the scale manipulating head; a scale rotating shaft rotatably supported in said bearing base plate; a rotatable member having a rotational radius and being rotatable concentrically and integrally with said scale rotating shaft; an engaging member provided position-adjustably in direction of the rotational radius of rotatable member; a tension member ng two ends, one end of said tension e being connected to said engaging member a.n6ihving a tensile elasticity; rL1~*n., ur-*- -22a- an engaging member positioned on the rotatable member, with ics position being adjustable in a direction of the rotational radius of said rotatable member; a tension member having two ends, one end of said tension member being connected to said engaging member and having a tensile elasticity; a biasing mechanism provided on said bearing base plate aod having two ends, one end of said biasing mechanism being connected to the other end of said tension member; the ether end of said biasing mechanism bearing against said rotatable member under the tensile elasticity of said tension member; and a scale rotational angle indexing tiechanism consisting of an indexing plate having grooves therein and an indexing detent adapted to be received in any one of said grooves to lock the scale at predetermined angular intervals, in which locking force provided by engagement of said grooves and said detent can be maintained by the scale balancing force; wherein rotation of the rotatable member, causes elongation or contraction of the tension member such that the tension member applies an angular moment to the rotatable member balancing the angular moment applied to the rotatable member by the scale and its mountings. 7 AR -23- a biasing mechanism provided on said bearing base" plate and having two ends, one end of said biasing mechanism being connected to the other nd of said tension member; the other end of said bia s-g mechanism bearing against said rotatable /member under the tensile elasticity of said t ion member; and a scale rota 'i-nal angle indexing mechanism for locking t scale at predetermined angular intervals, in w h locking force provided by engagement of said ooves and said detent can be maintained by the scale balancing force.

8. The scale balancing device incorporated into a scale manipulating head of a drawing machine as recited by claim 7, wherein the engaging member is provided position- adjustably in a direction of the rotational radius of the rotatable member from the center of the rotatable member.

9. The scale balancing device incorporated into a scale manipulating head of a drawing machine as recited by claim 7 or 8, wherein the engaging member is position-adjustably movable as the threaded shaft provided on the rotatable member is rotated. S The scale balancing device incorporated int6 a scale manipulating head of a drawing machine as recited by any one of claims 7 to 9, wherein the rotatable member includes a guide frame within which the engaging member is position- adjustably guided as the threaded shaft is rotated.

11. The scale balancing device incorporated into a scale manipulating head of a drawing machine as recited hy any one of claims 7 to 10, wherein the tension member comprises a tension spring and wire secured at one end to a wire anchoring means provided adjacent the center of the rotatable member and adapted to be engaged at its intermediate portion with the engaging member. -24-

12. The scale balancing device incorporated into a scale manipulating head of a drawing machine as recited by any one of claims 7 to 10, wherein the biasing mechanism comprises an one-piece member having one eind subjected to the tensile elasticity of the tension member and the other end bearing against the periphery of the rotatable member.

13. A scale balancing device incorporated into a scale manipulating head of a drawing machine comprising: a bearing base plate provided in the scale manipulating head; a scale rotating shaft rotatably supported in said bearing base plate; a rotatable member having a rotational radius and being rotatable concentrically and integrally with said scale rotating shaft; an engaging member provided position-adjustably in a direction of the rotational r, of said rotatable member; a tension member having t, ,nd of said tension member being conne co -d engaging member and having a tensile elar .cy; a biasing mechanism ,'ided on s fd bearing base plate and having t ends, one of said biasing mechanism being connected to e other end of said tension member; the other end of sai biasing mechanism bearing against said rotata e member under the tensile elasticity of said ension member; and a scale rotatio angle indexing mechanism for locking the scale at predetermined angular intervals, in which lever provided along the scale rotating shaft /i bent for operation of said lever without any mecanical interference with said engaging member.

14. e scale balancing device incorporated into a scale ma i ulating head of a drawing machine as recited by claim 13, wherein the lever provided along the scale rotating VF hL -24a- an engaging member positioned on the rotatable member, with its position being adjustable in a direction of the rotational radius of said rotatable member; a tension member having two ends, one end of said tension member being connected to said engaging member and having a tensile elasticity; a biasing mechanism provided on said bearing base plate and having two ends', one end of said biasing mechanism being connected to the other end of said tension member; the other end of said biasing mechanism bearing against said rotatable member under the tensile elasticity of said tension member; and a scale rotational angle indexing mechanism for locking the scale at predetermined angular intervals, in which a lever provided along the scale rotating shaft is bent for operation of said lever without any mechanical interference with said engaging member; wherein rotation of the rotatable member, causes elongation or contraction of the tension member such that the tension member applies an angular moment to the rotatable member balancing the angular moment applied to the rotatable member by the scale and its mountings. 14. The scale balancing device incorporated into a scale manipulating head of a drawing machine as recited by claim 13, wherein the lever provided along the scale rotating -1- 9-i l- *i -l-rar*~ shaft is pivotally supported by a diameter-reduced portion inside the hollow scale rotating shaft and bent at a point above said diameter-reducted portion of the rotatable shaft serving as the pivot so that said lever may operate without any mechanical interference with said engaging member. The scale balancing device incorporated into a scale manipulating head of a drawing machine as recited by claim 13 or 14, wherein the engaging member is provided position- adjustably in a direction of the rotational radius of the rotatable member from the center of said rotatable member.

16. The scale balancing device incorporated into a scale manipulating head of a drawing machine as recited by any one of claims 13 to 15, wherein the engaging member is position- adjustably movable as the threaded shaft is rotated.

17. The scale balancing device incorporated into a scale manipulating head of a drawing machine as recited by any one of claims 13 to 16, wherein the rotatable member includes the guide frame within which the engaging member is position-adjustably guided as the threaded shaft is rotated,

18. The scale balancing device incorporated into a scale manipulating head of a drawing machine as recited by any one of claims 13 to 17, wherein the tension member comprises a tension spring and wire secured at one end to a wire anchoring means provided adjacent the center of the rotatable member and adapted to be engaged at its intermediate portion with the engaging member.

19. The scale balancing device incorporated into a scale manipulating head of a drawing machine as recited by any one of claims 13 to 17, wherein the biasing mechanism comprises an one-piece member having one end subjected to the tensile elasticity of the tension member and the other end bearing against the periphery of the rotatable member. A scale balancing device incorporated into a scale manipulating head of a drawing machine substantially as herein described with reference to the drawings. DATED: 1 December 1989 PHILLIPS ORMONDE FITZPATRICK k Attorneys for: ASAHI SEIMITU KABUSHIKI KAISHA