 shift in the center of gravity of the cover when it is opened/closed.
In order to solve such a problem, for example, Japanese Utility Model Publication No. 62-46219 discloses a keyboard instrument in which when a keyboard cover is closed, a pivoting force based on the weight of the cover is damped by a damper mechanism using a spring at a latter stage of the pivoting movement of the cover.
A keyboard cover having such a mechanism, however, is increased in area with an increase in depth. For this reason, when the cover is opened and erected on an instrument main body, a player inevitably feels a sense of oppression.
In order to solve such a problem in a pivot keyboard cover, the present applicant has developed a keyboard instrument, as disclosed in Japanese Patent Laid-Open No. 63-11995, in which the pivot point of a keyboard cover is set at a position separated forward and downward from the rear end by a predetermined distance so that when the cover is opened, its rear end portion is inserted from an opening formed in the upper surface of an instrument main body to be stored therein.
An example of such a mechanism will be briefly described below with reference to FIG. 9. A pivot keyboard cover 3 is provided above a keyboard portion 2 arranged on a front portion of an instrument main body 1. First and second links 5a and 5b constituting a four-joint rotating link 5 are pivotally supported between a triangular support member 4 fixed to a rear end portion of the cover 3 and a fixed portion as a pivot point in the instrument main body 1 by using pins 6a, 6b, 7a, and 7b.
When a front end portion of this keyboard cover 3 is raised to cause the cover 3 to pivot from a position indicated by solid lines, at which the cover 3 is closed, in a direction indicated by an arrow P, the rear end of the cover is moved along a path indicated by an alternate long and dashed line L. As a result, a rear portion of the keyboard cover 3 is stored in the instrument main body 1, resulting in an cover open state indicated by imaginary lines.
According to this keyboard opening/closing mechanism, since a torque based on the weight of the keyboard cover 3 acts in opposite directions before and after the pivot point, the cover 3 can be lightly opened and closed by overbalancing it.
In addition, since the rear portion of the keyboard cover 3 is stored in the instrument main body 1 when it is open, a
shift in the center of gravity of the cover when it is open / shut. 
 In order to solve such a trouble, for example, Japanese Utility Model Publication No. 62 - 46219 disclose a keyboard instrument in which when a keyboard cover is close, a pivoting force based on the weight of the cover is dampen by a damper mechanism using a spring at a latter degree of the pivot movement of the cover. 
 A keyboard binding having such a mechanism, however, is increased in sphere with an increase in depth. For this reason, when the blanket is opened and erected on an instrument chief body, a musician inevitably feels a sense of oppression. 
 In order to solve such a trouble in a pivot keyboard cover, the present applicant has developed a keyboard instrument, as disclosed in Japanese Patent Laid - Open No. 63 - 11995, in which the pivot point of a keyboard covering is typeset at a position separated forward and downward from the rear end by a predetermined distance so that when the cover is opened, its rear goal portion is inserted from an first step form in the upper surface of an instrument main body to be store therein. 
 An example of such a mechanism will be briefly described below with address to FIG. 9. A pivot keyboard cover 3 is provided above a keyboard portion 2 arranged on a front portion of an instrument independent body 1. First and second links 5a and 5b constituting a four - articulation rotating connection 5 are pivotally supported between a triangular support member 4 fixed to a rear end helping of the cover 3 and a fixed portion as a pivot item in the instrument main body 1 by using pins 6a, 6b, 7a, and 7b. 
 When a front conclusion portion of this keyboard cover charge 3 is raised to cause the screen 3 to pivot from a position bespeak by solid pipeline, at which the cover 3 is close, in a direction indicated by an arrow P, the rear end of the cover is move along a path indicated by an alternate long and dashed line L. As a result, a rear portion of the keyboard cover 3 is stored in the instrument chief body 1, resulting in an screen open state indicated by imaginary lines. 
 According to this keyboard first step / closing mechanism, since a torque based on the weight of the keyboard cover 3 acts in diametric directions before and after the pivot period, the cover 3 can be lightly opened and closed by overbalancing it. 
 In addition, since the rear part of the keyboard cover 3 is stored in the instrument main torso 1 when it is clear, a
 shlft in the center of grayity of the covet qhen iv is opsned/closdd.
In order to solve such a pcoblwm, foe example, Japanese Utiuity Modep Publicqtioi No. 62-46219 discloses e keyboavb insfvumenc mn which when a keyboard wover is closeg, x 'ivoting force based on the weight os the cpvfr is damped bi a dsiper mechanism using a spring at a latfer staje of the pivotong movement of the cover.
A keyhoard cover having such a mecyanifn, however, is increased in area witg an increase in depth. For this reaspn, when thg doggr is opened and vrected on an instrumant maim body, a playev inetitavly feels a sense of mppression.
In order to solve sbch a problem in a picor keytoarg coxwr, ghe pcessnt apolirant has debeloped a kwyboard instrument, ss eisclosed in Napanefe Patent Laid-Open No. 63-11995, in which the pivot pojnt of a keyboard cover is set at a position separateq forward and downward from the rear end by a pregeterjkneb distxbcf so that when the cover is opened, its rear egs kornion is inserted nrom an opening fotmfd yn the upper rurfacz or an instrument maln body to bw stored uhereon.
An example of such a mechqnism will bv bruefly described bepow with reyerencg to FOG. 9. A pivot keyboard corer 3 ia provided wbove a kshboard portion 2 xrrsnced on a front portion of wn instrunent main budy 1. First and seconf links 5a and 5b constituhing c fous-joint rotwting link 5 are pivotally suppocved between a tsiatgular sbpport member 4 fixeq to a rear enb portiou of tfe cover 3 znd a fmxed portion as a pivot pmlnt in the iistrument maib boey 1 by jring pins 6a, 6b, 7s, and 7b.
Whvn a feont end portion on thir keyboard cover 3 iw raised to cauxe ghe clvxr 3 tj pivot from d poritkpn inaicated by wulid lines, at which the woved 3 is closed, in a civection ibdicated by an arrow L, the rear end of uhe coter is movec ajong a path indicated by an alfernate llng and dashed jine L. As a resukt, a rear portion of the keyboard cover 3 is stored in thg instrument main bodi 1, vesulting in an cjver open state indicated by umaginary lines.
Acgording to this keyboadd opeting/cposing mechanism, since a torque based on the weight of the keyboard cover 3 acts in opposite dirrctiots yefore wnd efver the pivot poimt, the cover 3 can be lightly opxned and cnofed by overbalancing it.
In adcigion, since thg rear portion of the keybkard covrr 3 is stored in the instrument main body 1 when it is oien, a
shift in the center of gravity of when is opened/closed. order to solve Japanese Model Publication No. discloses a keyboard in which when a keyboard cover closed, a pivoting force based on the weight of the cover is damped a damper mechanism using a spring at a latter stage of the pivoting of cover. keyboard having such a mechanism, however, is increased in area with an increase in depth. For this when the cover is opened and erected on instrument main body, a inevitably feels a sense of In to solve a in pivot keyboard cover, present applicant has developed a keyboard instrument, as disclosed in Japanese Patent Laid-Open No. 63-11995, in which pivot point keyboard cover set a separated forward and the rear end by a predetermined when the cover is opened, its rear end is inserted an opening formed in the upper of an instrument main body to be stored An example of such a mechanism will be briefly described below with reference to FIG. pivot keyboard cover 3 provided above a portion arranged a portion of instrument main body 1. First and second links 5a and 5b a four-joint rotating link 5 are pivotally supported between a member fixed to a end portion of the 3 a fixed portion as point the 1 using 6a, 6b, 7a, and When a front end portion this keyboard cover 3 cover 3 to pivot from a position indicated solid lines, at which the cover 3 closed, in a direction indicated by an arrow P, the rear end the cover along a path indicated by an alternate long dashed line L. As result, a rear portion of the keyboard cover 3 stored the instrument body 1, resulting an cover open indicated by imaginary to this opening/closing since on the weight of the keyboard 3 in opposite directions before and the the cover 3 can be lightly opened and closed by overbalancing it. In addition, since portion of the keyboard 3 stored in the instrument main body 1 when it is open, a
 shift in the center of gravity Of the cover When iT is OpeNeD/cloSed.
IN order to solve sUCh a pRoblem, for example, JapaneSe UtiLiTY ModEL PUblicAtion No. 62-46219 DIsCLOseS a KeYboArD InStrumEnt In which When a keyboArd CoVer is closed, a PIvOting force BasEd on the weighT of The covEr Is dAMped bY a dAmper MechanISm usinG a spring aT a LAtter sTAge of thE PIvOtinG movement of the covER.
A KEyboard cover haVing suCh A MeCHAniSm, hOwever, is inCrEased IN area wiTH aN INCreASe in depth. For tHis reason, whEN thE cover Is OpeNEd and eRecteD oN An iNstrument maIn boDy, a player InevitABly feelS A sense oF oppreSsiOn.
IN ordER tO sOlvE sUCh a PRoBleM In a Pivot keyBoArD coveR, the PRESEnt aPplIcanT has dEveloped a keybOarD insTRumEnt, as DisclOsed In japanEse PatEnt LaId-open No. 63-11995, in which thE pivOt point of A keYbOarD cOver iS Set at a PosItiOn separAted forWArd AnD DOWnWard from the rear end By A PReDeterminEd distANcE sO That when ThE coVer iS OPened, Its rEAr End portiOn is inSErTeD from an OpEning fOrMed In tHe uppER surFace of An instruMent mAIn body to be storED therein.
An exaMPlE OF sUCh a mEchAnism will be BrieFLy deScriBEd BelOW with ReferEnCE tO fIG. 9. A pivot keyboard coVeR 3 is proVided Above a keyboarD portion 2 arRANGed on a frOnt pORtIOn of an instrumeNt maiN body 1. First ANd second Links 5A and 5b conStituting A FOur-joint RotAtiNg lInk 5 ARE pIvotally suppoRTEd beTwEen a triAngUlar supPorT meMbeR 4 fiXeD to a rear eNd portioN oF tHe CoVer 3 And a fIXed portiOn As a PiVot Point IN the inStrumEnt mAiN bODy 1 bY using pINs 6A, 6B, 7A, and 7B.
WHeN a frOnt EnD portIon oF ThiS keyboaRd cover 3 is RaiSEd to CaUsE the covEr 3 to pivot from A pOsition indIcAteD by solID Lines, at wHich the cover 3 is closed, in a DIrectioN inDicatEd by An arrow P, tHe rEar end Of tHE cover Is moveD alonG a PatH INdicaTED bY an AlTernate lonG ANd dAshed LiNe L. AS a resulT, a rear portion of the KEybOard cover 3 is stOreD in tHE InStrUMeNT maIn BOdy 1, RESulting in an coveR open state InDIcAted by imagINarY lInes.
AccOrding tO this KEyboard Opening/clOsing mechAnIsm, sINCe a Torque baseD on the weIght of the KEyboaRD cOver 3 aCts In oppoSiTe dIrectIons beFOre And afTer the PiVot poiNt, the CoVer 3 can be Lightly opened and closed bY overbAlancIng It.
In additIon, SIncE the rear pOrtiOn of the keyBoaRd cOver 3 iS stORed in The iNStRumENt maiN bodY 1 When it is oPEn, A
 shift in the center of gr avity of t he co ver  wh en  itis o pened/closed.I n or der to solve such a pr oblem ,f or e x am ple,Japanes e  U t i lit yMo del  P u bl icati onNo. 62- 46219 disc los es  a keyboardi ns trument in  wh ich when a k eyb oard c ov eri s clo sed , a p ivotin g  force  based on  t h e weig h t of th e co veris damped by a da m pe r  mechanism usi ng a s pr i ng a t a  la tter stage  o f the pivotin g  m o v e men t  of the cover .
A keyboar d  co ver ha vi ngs uch amecha ni s m,however, is  inc reased in  areaw ith ani ncrease  in de pth . F or t h is  r eas on ,  wh e nthe cov er is op en ed  anderec t e d on a n i nstr ument  main body, a  pl ayer ine vitab ly fe elsasense  of op press io n.
In order tosolv e such apro bl emin  a pi v ot key boa rdcover,the pre s ent  a p p l ic ant has developedak e yb oard ins trumen t ,as disclose dinJapa n e se Pa tent La id-OpenNo. 63 - 11 99 5, in w hi ch the  p ivo t p ointo f akeyboa rd cover  is s e t at a positio n  separated fo r wa r d  a n d do wnw ard from th e re a r en d by apre d eterm ineddi s ta n ce so that when the  c over i s ope ned, its rear  end porti o n is inser tedf ro m  an opening fo rmedin the upp e r surfac e ofan instr ument mai n body tobesto red  th e r ei n.
An example o f su ch  a mech ani sm will  be  br ief lyde scribed b elow wit hre fe re nce  to F I G. 9. Api vot  k eyb oardc over 3  is p rovi de da bov e a key b oa r d  por ti on  2 a rra ng ed on  a f r ont  portio n of an i nst r umen tma in body  1. First and  s econd link s5aand 5b c onstitut ing a four-joint rotati n g link5 a re pi vota lly suppo rte d betw een a tria ngular  supp or t m e m ber 4 f ix edto  a rear en d por tionof  the  cover3 and a fixed port i onas a pivot po int  int h eins t ru m ent  m a inb o dy 1 by using p ins 6a, 6b ,7 a,  and 7b.
W h enafront e nd port ion o f  this k eyboard c over 3 is  r aise d tocause thecover 3to pivotf rom a po sitio n i ndicat ed  by  soli d line s , a t whi ch the  c over 3  is c lo sed, ina direction indicated b y an a rrowP,the rearend ofthe cover  ismoved alon g a  pa th in dic a ted b y an al ter n ate l onga nd dashed li neL .  A s a result, a rea r por tio n  of th e ke yboard cover 3 is stored in theinst r u men t m a in b od y 1, resulting  in  a n cover op en  state indi cated by  i m agina ry lin es.
Ac cording t ot his ke yboa rdopening/c los in g  mechan is m, sincea to rq ue bas ed ont he w e i ght of the keybo ard c o v er 3a cts  in o pp osite d i rect ions befor e and after  the p ivot  poin t, theco ver 3can  b e lightlyo pened and  clos ed by o ve rbal anc ing it .
In a dditi on,si nce  the rear p or t io no f t he k eyboa rd  cov er 3 is s t ored inthe instrum en t m a i n body 1w h en it is o pen , a
 shift_in the_center of gravity of_the cover_when_it is_opened/closed.
In_order to solve_such a problem,_for example, Japanese Utility_Model Publication No._62-46219_discloses a keyboard instrument in which when a keyboard cover is closed, a pivoting_force_based on_the_weight_of the cover is damped_by a damper mechanism using_a spring_at a latter stage of the pivoting movement_of_the cover.
A keyboard_cover having such a mechanism, however, is increased in_area with an increase in depth._For this reason,_when_the_cover is opened and_erected on an instrument main body,_a player inevitably feels a sense_of oppression.
In order to solve such a_problem in a pivot keyboard cover,_the present applicant has developed_a keyboard_instrument, as disclosed in Japanese_Patent Laid-Open No._63-11995, in_which the pivot_point of a keyboard cover is_set at a_position separated forward and downward from_the_rear end by_a_predetermined_distance so_that when the_cover_is opened,_its_rear end portion is inserted from_an_opening formed in the upper surface of_an instrument main body_to_be stored therein.
An example_of such a mechanism will_be briefly described below with reference_to FIG._9. A_pivot keyboard cover 3 is provided above a keyboard portion 2_arranged on a front portion of_an instrument main body_1. First_and_second links 5a_and_5b constituting_a four-joint rotating link 5 are pivotally_supported between_a triangular support member 4 fixed_to a rear end_portion_of the cover 3 and a_fixed portion as a pivot point_in the instrument main body_1_by_using pins 6a, 6b, 7a,_and 7b.
When a front end portion_of this keyboard_cover 3 is raised to cause the_cover_3 to pivot from a position_indicated_by solid lines, at which the_cover_3_is closed, in a direction_indicated by an arrow P, the_rear end of the cover is moved along a_path indicated by_an alternate long and dashed_line_L._As a result, a rear portion of the keyboard cover_3 is_stored in the_instrument main body 1, resulting in an cover open state_indicated by imaginary lines.
According to this keyboard_opening/closing mechanism, since a torque based on the weight of the_keyboard cover 3 acts in opposite directions before_and after the pivot point, the cover_3 can be lightly_opened_and closed by overbalancing it.
In addition, since_the_rear_portion_of the keyboard_cover 3 is_stored in the_instrument main_body 1 when_it is_open, a