CA1066859A - Windshield wiper transmission - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A longitudinally adjustable lever in the form of a two piece housing mounted for oscillatory motion adjacent one end to the oscillating output of a wiper motor carries at its other end a pivot shaft adapted to receive a wiper arm. A crank arm is mounted on said lever for pivotal motion on an axis coaxial with the axis of the pivot shaft. Adjacent its free end the crank arm is adapted to have a drag link pivotally secured there-to. The free ends of the wiper arm and drag link are pivotally secured to opposite ends by a link element to form a parallelo-gram linkage. Enclosed within the housing which forms the lever is a rotatably adjustable stationary chain anchor, a sprocket fixed to the pivot shaft for rotation therewith and a drive chain looped around the sprocket extending between the chain anchor and the sprocket for effecting oscillatory movement of the arm pivot shaft relative to the lever when the lever is oscillating about an axis coaxial with the chain anchor. A gear train driven by the sprocket causes rotation of the crank arm relative to the pivot shaft so as to maintain substantially constant angular orientation of the crank arm relative to a fixed line. The lon-gitudinal axis of the drag link and the longitudinal axis of the wiper arm are maintained in parallel relationship so that a wiper blade secured to the end of the wiper arm will produce a sub-stantially rectangular wiping pattern. This is desirable for wi-ping a windshield which is extremely wide relative to its height.

Description

The present invention relates to improvements in a wind-shield wiper transmission mechanism and more particularly to a windshield wiper having an oscillating pivot shaft for producing a substantiall~ rectangular wiping pattern. W:indshield wipers for achieving similar results are disclose~ in U.S. Patent 3,590~415 issued July 6, 1971; U. S. Paten~ 3,688,334 issued August 5, 1972; U. S. Patent 3,831,219 issued ~ugust 27, 1974 and British Patent 1,304,469 published Jamlary 24, 1973.' All of these patents disclose a chain driven transmission mechanism for effecting oscillation of the pivot shaft. Other prior art dis- -....:.: . . .
closes a gear drive ~or achieving the results. With the excep-tion of British Patent 1,304,469 all of the above-mentioned ' - -prior art utilizes a pair of chains disposed in paralleIism, one for driving the wiper arm and the other for controlling movement ~
of a crank arm to which a dra~ link is secured or the dra~ link ;~ ' in turn controlling the orientation of the wiper blade. British ~ -Patent specification 1,304,469 discloses a single'chain mechan- - ' ,-.. .. .
ism disposed at the'free end of the wiper arm.
In chain drive mechanisms, because of manufacturing toler-ances and the fixed length of the chain links, it is essential "~
to provide mean~ for adjusting tha tension on the'chain for proper operation. It also bec`omes neces~sary from tim to time to adjust the tension on the chain because of wear on the ~' mechanism. In certain of the above-mentioned dual chain drive ~- ' :
~mechanisms of the`prior art resilient belts are used, and in others no means are dis~losed for chain adjustments. 'i'`'` '' ' ~ : :
An adjus~ment for rotating the windshield wiper axm and .
;~ ~blade to the'desired park position is desirable.' An accumula-tion of ~oleran~e differences can cause a minimal displacement fr~m the proper arm position.

An efficient method for properly tensioning the chain i~

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to provide a longitudina:Lly adjustable support for the elements which engage the chain at its extremities; however, wi.th t~o chains and two chain drives in parallel on a single lever such.
an adjustment i5 not feasible as each chai~l in most cases will require indivi.dual adjustment.
Provisions of a chain drive and ~earing at the free end of the arm as $hown in the ahove-mentioned British Pat~nt 1,3Q4,469 increases: the momentum to ~uch an extent that inter-ference with reversal and damage to the motor could occu:r at the end of the arm stroke upon reversal o~ direction.
The pre~ent invention comprises a lever oscillated by the output of a wiper motor in the form of a t~o part housing in ~hich the parts are longitudinally adjustable relative to each other. A ch.ain anchor coaxial with tha oscilla~ing axis of the lever i~ independently and rigidly secured to a support and is enclosed hy the upper portion of the lever casing. The lower portion o~ the lever casing rotatably carries a pivo-t shaft ha~-in~ a chain sprocket fixed thereto for rotation therewith.
Gearing i~ provided for transmitting torque from the pivot shaft 2Q to the crank arm. The crank arm is osci-llatable about an axis coaxial ~ith the pivot shaft relative to the pivot shaft and independent thereo~. The crank arm is adapted to pivotally carry a dra~. link at its free end. A sin~le:chain anchored at its ends i$ looped around the sprocket which~drive~ the pivot sh.aft. The.spr.ocket through an idler gear dr;ves a gear secured to the crank arm. A wiper arm may bP:secured to the output o~
the pi.vot shaft, The ~i~er arm and drag link are each pivotal-ly connected at their free end~ to a link on an axis spaced a-part a distance equal to the:distance bet~een the pivot shaft and tha pivotal cQnnection between the crank arm and the drag link. With:the arm and drag link so attached a substantially 1C1~6~

rectangular wip.ing pattern is achieved. The result of the ar-rangement described is to generate a wiping pattern equivalent to that produced by a wiper arm having an effective wiper arm : length which is a multiple of the actual arm length. This re-sults in a pa-ttern having a relatively large radius and thus a small curvature at the windshieldt The chain anchor is arcuate and is attached to a supporting bracket in a manner tha-t permits adjustment of the.chain anchor which in turn adjusts. the park position of the wiper arm.
Because only a single:chain is employed in combination with g~aring it is:possible to: adjust the:tension of the:chain by longitudinal adjustment of the lever and.to utilize a rigid link chain rather than a resilient chain for positi.ve and ac-.` curate:operation. :
The principal obj:ect of the p~esent inventi:on is to:pro~
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vide.an improved oscillating pivot shaft.which:is reIatively . light in weight.and economical to manu~acture.and which is cap- . .
; ahle of producing a su~stantially quadrilateral wiping pattern.
Another ohj:ect of.the invention is to provide an improved `~ 20~ ~indshield wiper transmission mechanism employing an oscillat- iu able p.ivot shaft for producing a substanti:ally rectangular .~ pattern whîch i~:readily adjustahIe:to compensate::for manufactur- :
ing toler.ances: and wear.
A further obj.e~t of the: invention is to provide:an im-

2~ proved windshiel.d wiper transmisslon mechanism which can be adjusted for accurate positioning of the wiper pattern.
.~ Other objects and ad~antages of.the invention wi:ll be ap-parent:from the.following.detaile:d des:cription taken in connec-, ~ , .
t~ion with.the accompanying dra~ing~.
~ Fi;gure l is a partial perspective ViQW.of a motor. vehicle employing the improved windshield wiper transmission;

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Figure 2 is a perspecti.ve view enlarged of the wiper transmission shown in Figure l;
Figure 3 is a side eIevation vie~ of the transmission partly in sectioll and partly broken away;
Figure 4 is a ~ront el.ev~tion view of a windshield wiper transmission mechanism, partly broken away; and Figure S is an exploded perspective:view of a windshieId wiper transmission mechanism.
In Flgure'l there'is shown a portion o~ a motor vehicle lO: having a windshield 12:with:a wiper set 14~mounted on the firewall (not shown) of the vehicle ~elo~.the ~indshi:eld. The wiper set includes a wiper blade:16, a main wiper arm 18, a drag link or auxiliary a:rm 2Q and a wiper.:tr.ansmission mechanism 22 including a support assemhly 24.driven by a fluid operated re-ciprocat.ing motor 25 (best shown in ~igure 5~ which may be of the air or vacuum type. It will o~ cour~e be.:unders~ood.that in accordance with~:the~roader aspects of th.e:invention any suit-able~type'of prime mover havin~ an oscillating outp.ut may be em- -.ployed.
: The wi.p~r transmission mechanism 22 includes a lever arm -~
:26 in.the~orm of a housing which:includes: an upper body 26a and' .-a lower body 26b... The upper and.lower.hodies.26a and 26.b :in-clude ~asa plates.2ga and:28b, respectiveI.y, havi.ng peripheral flanges 30a and 30~,: re~pectively, and rear covers-32a and 32b, .' res'pe~tiveIy:O The.'upper and lower bodies'.26a and 26b are secured ~.
to.gether for longitudinal adjustment relati~e:to: each.other by a pair;of~clampin~ screws 34.which:are recei.ved in threaded aper- :
.tures 3~6 in.the base plate.28b of~the lower body. The cl~amping ~.
s~crews. 34. extend~through axially~ extending elongated aper.~ures .~
30: 38 ln~t~e~base pla~te~28a of the upper bod~:26a, ~he'slots 38 be . ':' .
: ing ~n alignment with.the.threaded apertures 36. A lug'40. having '~
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a threaded aperture protrudes outwardly from the base plate 28a and threadably receives an adjusting screw or ti.ghtening screw 42. ~ shoulder 44 is formed on the base plate 28b of -the lower body 26b in opposition to the l~lg 40 and is positioned to engage the end of the tightening screw 42. When the clampi.ng screws 34 axe loosened the upper and lower housing bodies 26a and 26b can be adjusted longi.tudinally rela~ive to each other and maintained .
: in longitudinal adjustment by movement.of the'adjusti,ng or tightening sare~ 42. As it is moved down~ardly it engages the :' , 10. shoulder 44.on the:lower body 26b .and drives:the:lo~er body 26b downward relative:to the:upper housing body 26a. ~ jam nut:.46 is prov.ided to retain the adjusting screw 42.in adjusted posi- , tion. Tightening of the;clamping.screws 34.retain~ the:upper and: lo~er bodies 26a and 26b in adju~ted position relati~e:to ~... --. each other.
As best seen in Figure.:5, a mounting bracke`t:assembly 24 :-' includes a mounting plate:.48 and an adjustment pla-t~ 5aO .Tha:
: mounting plate.:48 has~an opening.S2.therethrough in alignment ;~ with;an OpenLng.54:in the adj.u~tment plate.'50.. Openings 52 and :~ :20. 54:are dî~posed in ~alignment ~ith'an opening.56 in.the rear cover plate:3Za of the.:upper. hQusin~ body 26a, .A chain anchox element..58 having an arcuate.periphery interrupted by a pxotrud~
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:ing flattened chain anchoring l~g portion 59 includes a con-'~: centric hub~'60.which extends through:the:openings S6 and 5~ and ,~ 25 : is ~ixedly .secured to.the:adjustment plate'50.in any suitable '~ ,,.

. or desirable~mannex as,,for e~ample,.,by rive-ts 62 as shown. An ..' ~: axially ;.extending journal 64 is provide~ centrally in chain .~

' anchor~58 and rotatably received the:outpNt shaft 70 o~ motvr '. ,'. :' : ~ .25. The output shaft:70.extends through aperture 54.in adjust- : .. -ment plate.'50.and aper.ture;5~ in suppork plate::48. The motor ., 25 i~ rigidly mounted on su~port plate:48. on the ~ide:opposite : ', ~""
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the chain anchor 58. The adjustmQnt plate.50 includes an arcu-ate slot 66 adjacent the end opposite the aperture 54 and is in alignment with an opening 68 through support plate 48. A screw 71 extends thr.ough aperture 68, lock washer 72, apertuxe 66, washer 74 and a threadably engaging nut 76. When the nut 76 is loosened the adjustment plate 50 can be rotated on an axis through opening 54 to vary the position of lug 59 ~or a purpose to.be explained hereinafter~
In order to oscillate:the:lever.26 the motor shaft extends la into a splined aperture':80 adjacent the:end of upper body 26a and is rigidly se:cured thereto. The:upper body 26a engages rear ff closure plate:32a and encloses. chain anchor 58 therein. Adja-: cent the lower end o~ lower bod~.26b~a bearing boss 82:is formedthereon and protrudes: from.the base plate'28b. Similarly a ~earing boss 84.is formed and protrudes: rearwardly ~rom the:rear cover 32b of lower body 26b .and is coaxial wi.th:the bearing boss 82. The,bearing boss 82.has a j.ournal bearing 86 press fitted therein and the bearing boss'84 has a jouxnal bearing'88 press ~' fitted.therein. A hollow shaft 90.having an internal press fitted hearing 9~.is journaled in bearing''86 and extends ~rom the :internal portion of.the:lower. body.26b :adjacent.the ba~e .
plate.'28b through.the:boss'82 and projects: externally.thereof. .: :
A crank:arm 94 is pres~- fitted to the:outer end of the hollow shaft sa .and.rotates therewith.: At its: inner. end within the~ .
~25 lower housing 26b~a driven geàr 96 is pres.s fitted to the hollow sha~t 90 for rotation .therewi~h.:. Thus ~hen ~he gear 96 is ro- ' tated the hollow.sha~t 90 and crank arm 94.rotate with.it. ' Jo,urnalled ~ithin the int2rnal ~earing 92 of hollow.~haft 90. and :~
coaxial.therPwith.:is a pivot sha~t 98 which:extends through bearing ~8 in boss 84 of rear cover'plate.. 32~ o~ lower body 26b. ~ :
.The:end of pivot ~ha~t 98 is 'journallea in bearing 88.
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A co-ordinating gear assembly 104 is splined to pivot shaft 98 within the lower housing 26b and is enclosed by the rear cover mem~er 32b. The co-ordinating gear assembly 104 in-cludes a driving gear lOS spaced from a chain sprocket lOQ by a hub 102 which serves as a spacer. The sprocket 100 is rivited ~ .
to the driving gear 105. ~ pivot shaft lever. 106 is splined to ~ ..... ' pivot shaft 98 externally of the boss'82. An axially extending drive burr 108 i5 rigidly secured thereto for fixedly mounting ' ' '- ' .the wiper arm for movement with.the'shàft lever 106. An auxil-iary pivot shaft 109 extends from the:free'end of crank arm 94 - ' and caxries a drag link lever 110. A drag link drive burr 112 ~( '.
extends radially and is pivotally moun~ed on the free end of drag link lever:llO. An auxi:lliary link:ll4 connects:the drag . link le~er llO.and the'pivot shaft le~er 106. The:connections bet~een the:link 114 and the:levers: 110 and 106 are pivotal con-nections. , ' A link.chain :116 has an end.connected to the'lug.59 of chain anchor 58. The:chàin: 116 i5 :then looped around and en-gages the teeth o~ chain sprocket:100, its other end being also ~ ~:
~con~ec,ted to the:lug 59. An idler shaft 118 is splined to a r ' .
~ . boss ll9-in.the:lower body base plate:2gb at one'end and is se~
:~ cured wi:thin an internally extending bos~- 121 formed in the' ' ,' '.
lower housing cover member 32b providing a fixea po6ition ~ '. ' haft~ An idler gear assembly~ comprising first and second .25 idler gears 120.and .122:are-fixed to:gethe'r either as a: unitary t~uoture'as shown:or~y riveting or in any :suitabIe'or desir-: .:
~ ' able manner,.and rotatabl:y mounted on idlex shaft 118. Idler ~:':,.:
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: ~gears 120:and 122 mesh with co-ordinating gear 105 and gear 96, ,':

~; ;respecti~ely. Idler gears 120 and 122:kransmit ~or~.ue from the 30' pivot shaft 98 ~hich'oscillatea::the'wiper arm drive:lever; 106 , to hollow shaft gO which oscilIates the crank arm 94. The:gear '' ~
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ratios are so selected as to cause the crank arm to oscillate at a speed different from but relative to th.e lever arm 26 and the pivot shaEt 98 so that its angular orientation i5 maintained fixed relative to a fixed line.: In the'example sho~n it i,s mai,n-tained horizontal to provide a substantially rectangular wipingpattern.
In the example:shown the distance betweèn the pivotal axis of the:drag link and shaft or auxilliary pivot shaft 109 and the pivot shaft 98 are maintained e~ual to..the distance ~etween the axis of the:drag link drive burr 112 and.the wiper~ arm clrive:
burr 108. The arm and drag link:shown includes a link 1`24 piv- e otally connected at each'end to.the~f.ree:end of the drag link 20 and.the free end of the wi,per arm 180 .The'distance between the axes of the link 124 at:their pivotal connection with.the:drag ' 15 link and arm respectively is e~ual to. the distance between the :
pivo,tal axes of the pivot:shaft 98 and the.auxilliary pivot shaft 109,. so that.the'wiper arm and drag link remain parallel to: each other.throughout the wiping pattern; be~ause,this forms :: :
a parallelogram linkage:the wiper arm moves in a path wi:th its longitudiNal axis par:allel to itself at all times. By varying . -:
the'ratios of.the:distance bet~een.the'pivotal connections of ."::
link 124~and the distance between pivot:shaft 38 and 109 the wi-piny pattern can be varied from a substantially rectangular pat- ':
, tern to a:trapazoidal pattern or to a regular parallelogram. As sho,wn,,a rectangular pattern is provide~ but it will be'under- .
atood,,of course,' that the'dra~ link and wiper arm may be so oriented as to provide'diverse .substantially quadrilateral~.~on~ ' figuration~. -In operation the w~per,transmission mechanism o:E this '~
inventi~n ~ipes a pattern that ~o:uld requ.ire~a:7 foot ~iper' arm ., .
~ut a~complishes:this with'a l~ inch wiper arm because of its :. :
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unique construction. The leve.r arm 26 oscillates about the axis of the motor shaft 70 while:the pivot shaft 98 to whi.ch, the wiper '' arm is connected oscillates~ relative.to the crank. arm 94 and the lever arm 26 to thereby maintain a fixed angular orientation of the cxank arm 94 re,lative to. a hor.i~ontal or other fixed line.
Mainta.ining the:angular orientation of.the crank arm constant causes the blade:to maintain a position paralleI to it~elf thxough-out the ~ipin~ pattern. The lon~ radius of the wiping path is effected by the o~cillation of the pivot.shaft 98 relative.to the lever arm 26.
In the example:shown the:le~er arm 26 oscillate:s':through an angle :of 13~~. As:the.lever arm 26 oscillates::thQ co-ordinating gear assembly 104:.rotates ~ith the.shaft 98 because thé'chain is held stationary at.the:chain anchor 58 and the: ..
~procket 100. eff.ects rotation of the.shaft 98. Rotation of.the - ., driving gear 104 meshing with:the:idler gear 120:causes.:the~
idler gear 122:fixed to the i:dler gear 120.. to rotate:about.the ~ ' fixed po~ition idler shaft 118o The:idler gear 122 in.turn : :
meshes with:the gear 96 which drive~::the'crank:arm 94 because .
: 2Q of its ri~id attachment to.the hollow.shaft 90. At.the:same.time., the:sprocket.to which:the pivot shaft.98 is ri~ialy secured ' ~
causes rotation of the pivot.shaft g8 and in turn rotation of .~.: -the:wi,per. arm drive:lever 106, which:rotation is tr.ansferred to ': :
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a ~ipex. arm which'ma~ be.secured.thereto. ..Thè:ratio o~ the~v~r- ,'..
~: .25 .ious gears to. one'another.is:selected so that the crank arm 94 ': ' maintains a cQnstant.angular orientation rel.ative:to a fixea line, .The~crank arm 94 contrals.the:drag link:20 which in turn ~ :
contxols.the:angula~ orien'!tation of.the:wiper blade.I6 relative '."~
; to.the main wiper. arm 18~ In the'instant example:the wiper arm 18 maintains a moti.on wherein each,positi.on of.the wi.per blade . 16 is paral.lel.throughout.the wiping p~th.so as to.provide a .. , ~ ; : ~ - , : . ~

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substantially rectancJular pattern.
The chain anchor 58 is fixed b~-t all of the remaining transmission parts including the sprocket 100 are movable with the lower housing 26b of the lever arm 26~ Therefore, the lower housing 26b can be adjusted longitudinally relative to th~ upper housing 26a and the chain anchor 58 to lengthen the di.~tance be-tween the pivot shaft 98 and the axes: of t:he.chain anchor 58.
This properly tensions the:chain 116 and thereby eliminates backlash. If looseness deveIops in the mechanism in service dur-ing the lifetime:of the wiper set the transmissi.on: can be re-adju~ted to the'pre-load condition and zero backlash by merely loosening the:clamping 'screws 34 and driving th:e tighte.ning screw 42:ag~inst the shoulder 44. Adju~tment of the posi-tion ~ -of the lug 59 by rotation of the~adjustment plate 50 ahout its -~.
~xi~ and along the~arcuate.opening 66 provides~ a means for set- :
ting the ~iper. arm and blade'pre~is:ely at its desired parked position.
It is now apparent that a uni~ue wind~hieId wiper trans-mission mechanism has been provided for multiplying the'effective length of the wiper arm with:respect to its true:length. The uni~ue combination of a single.chain .~or driving the wi~er arm pivot shaft in combination with a ~eared tor~ue:transmitting ar- -rangement for controlling a drag link crank arm provides. a : l~ght.~eight, e~ficient transmis~i:on ~ith:simplified adjustment :
maan~for el'iminatin~ backlash:and loosenes's due to wear~
Means are'also p~.ovided for a~justin~:the'~eometry of the wiping pattern to park the wiper arm at precisel~ the~desired position.
This precludes unneces~sary inte~ference with the dri~er's visio~.
Although a certain specific embodiment of the:invention has been sho~n and de~cribed for.the purposa of illustration it ~L~66~S5~
will be apparent that various other moclifications and embodi-ments are possible within the scope.of the invention~ For ex~
ample, other and different specific lon~itudinal adjustment means may be employed for varying the:len~th of the lever arm in ac-S cordance with the broader as~ects of the invention. Other and diffexent types of motors and oscillatin~ motor output mechanism may be employed~ The'drive burrs may be positioned directly on the crank arm and on the PiYot shaft, for example. It is to be understood, therefore, that.the invention is not limited to the -specific arrangement shown but in its broades't aspects i.t in- ' ' ' cludes all e~uivalent embodiments and'modifications which.come ~ithin.the scope of the'invention.

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Claims (7)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A windshield wiper transmission assembly comprising a support assembly, an arcuate chain anchor fixed to said support, a prime mover having an oscillating output, a lever operatively connected adjacent its one end to said output for oscillatory movement about an axis coaxial with said arcuate chain anchor, a pivot shaft rotatably mounted on said lever adjacent its other end, chain drive means secured to said chain anchor and operative-ly connected to said pivot shaft for causing oscillation of said pivot shaft relative to said lever when said lever is oscillating, means for securing a radially extending wiper arm at its: inner end to said pivot shaft for movement therewith, a radially extending crank arm rotatably mounted on said lever for rotation about an axis coaxial with the axis of rotation of said pivot shaft, means fox pivotally securing a drag link adjacent inner end to said crank arm, means for maintaining a fixed angular relationship be-tween the wiper arm and the drag link, torque transmitting gear means operatively connecting said pivot shaft to said crank arm for effecting oscillation of said crank relative to said lever and said pivot shaft when said pivot shaft is oscillating rela-tive to said lever to thereby maintain a constant angular orienta-tion of said crank arm throughout its 3path relative to a fixed line whereby the effective length of the wiper arm is a multiple of its true lenght to thereby increase the radius of the wiping path to produce a substantially quadrilaterial wiping pettern.

2. A windsheild wiper transmisson assembly according to claim 1 wherein said chain drive means comprises a single loop of chain anchored at each end to said chain anchor, a chain sprocket fixed to said pivot shaft for rotation therewith, said single loop of said chain engages said sprocket.

3. A windshield wiper transmission assembly according to claim 2 wherein said torque transmitting gear means comprises a gear train having a driving gear fixed to said pivot shaft for rota-tion therewith, a driven. gear operatively connected to said crank arm and idler gearing intermediate and meshing with said driven gear and said driving gear.

4. A windshield wiper transmission assembly according to claim 2 wherein said lever comprises a casing having an upper and lower body secured together, first external means for effect ing longitudinal adjustment of the upper and lower blades rela-tive to each other, and externally operated clamping means for retaining said bodies in adjusted position to thereby effect correct tensioning of said chain drive means.

5. A windsheild wiper transmission assembly according to claim 4 wherein one of said upper and lower bodies. includes a base plate having a threaded lug protruding therefrom, a tighten-ing screw threadably received in said threaded lug, a shoulder protruding from the other of said upper and lower bodies in alignment with said threaded lug, said tightening screw being positioned to engage said shoulder whereby longitudinal movement of said tightening screw increases the length of said lever to effect increasing of the tension on said chain.

6. A windsheild wiper transmission assembly according to claim 1 wherein said support assembly includes a support plate and adjustment means secured thereto for rotatably displacing said chain anchor about its axis for positioning the wiper arm relative to the parked position thereof.

7. A windshield wiper transmission assembly according to claim 6 wherein said adjustment means comprises an adjustment plate pivotally mounted about the axis of the chain anchor, means for securing the chain anchor to the adjustment plate for movement therewith and means for retaining the adjustment plate in adjusted position relative to said support plate.