CA1237377A - Accumulating transfer unit - Google Patents

Abstract

ACCUMULATING TRANSFER UNIT

Abstract In a walking beam type accumulating conveyor there is provided a transfer bar which moves in a rectangular motion, first upward, then longitudinally a distance corresponding to the distance between station, then down and then back longitudinally to the initial position. On the transfer bar are pivoted carriers, one for each station. The decision to lift a workpiece and transferred, is made during the elevation step of the cycle of movement based upon whether an empty station exits ahead of the workpiece. The decision is communicated between stations by rope or chain.

Description

~7~7 The present inven-tion relates to an automatic conveyor system, particularly of the reciprocating walking beam accumula-ting type.
Accumulatiny conveyors used in industry generally fall in two types. The firs-t are generally pneumatic -type accumula-tors making use oE a switch at each station which controls ac-tu-ators for moving carriers into -their proper position for the accumulation. The second type are normally called mechanical, and do not make use of elec-trical or pneumatics in con-trolling the accumulation. This inven-tion deals with an improved mech-anical type accumulator. In the past mechanical accumulators have employed complicated designs for transferring informa-tion that a station is empty to the carrier behind that s-tation so that they may move more pieces up to fill the empty station.
The most common types of mechanical accumula-tor have made use of circui-t bars for insuring the accumulation. The need for numerous linkages in most mechanical accumulators make them expensive, although generally cheaper than pneumatics.
Also in the prior ar-t attempts have been made to get away from the need of a circuit bar -through use of purely tension means such as chains which connect the sta-tions. An example of this type of art is shown in U.S. Patent No. 3,747, 741, yet this design requires relatively complicated controls to activate the carriers behind the empty station.
According to the present invention there is provided in an accumulating transfer unit including an elongate fixed frame having an upstream end and a downs-tream end, means de-fining a plurality of workpiece support stations uniformly longitudinally spaced from each other along said fixed frame, an elongate transfer frame, drive means for driving said transfer frame in repea-ted cycles of movement relative to said fixed frame, each cycle of movement commencing at a rest posi-tion from ~a~

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which said transfer frame is firs-t elevated, then moved longi-tudinally downs-tream relative to said fixed frame, -then lowered and tilen returned to said rest posi-tion, a plurali-ty of work-piece carrier members mounted at uniformly spaced positions longitudinally along said transfer frame for movement relatlve to said -transfer frame between an opera-tive position and an inoperative position, each carrier member being operable when in its operative position to lift a workpiece from one station and carry said workpiece downstream to the nex-t station during a cycle of movemen-t of said -transfer frame and each carrier member being inoperable to lift or carry workpieces when in its inoper a-tive position, a sensing means mounted on said fixed frame adjacent each station to be located in a first position in response to the presence of a workpiece a-t the associa-ted sta-tion and gravitationally biased to a second position in the absence of a workpiece at the associated station, a plurality of actuating members mounted at uniformly spaced positions along said transfer frame between said carrier members, e~ch actuating member being associated with one of said sensing means and movable thereby when the associated sensing means is in its second position from an inoperative position -to an operative position, and connector means coupling said carrier members to each o-ther for transmitting movement of one carrier member from its inoperative to its operative position to all carrier members upstream from said one carrier member to cause said carrier mem-bers upstream from said one carrier member -to move from their inoperative to t.heir operative positions simultaneously with said one carrier member; the improvement wherein each of said carrier members and each of said actuating members comprise a pivotal support mounting the member for pivotal movement on said transfer frame and an ar~ portion extending radially from said pivotal support, said arm portions being of uniform radial ~3~73~7 length, said connecting means comprising a flexible cord or chain connected to each of said arm portions -to extend between adjacent arm portions in a taut condition when said adjacent arm portions are in parallel rela-tionship with each other, each of said sensing means having an abutmen-t thereon engagable when the sensing means is in its second position with its associated actuating means when said transfer frame is elevated to pivot the arm portion of -the engaged actuating member from its inoper-ative to its operative position by swinging -the arm portion in a direction tensioning the cord or chain coupled thereto in a downstream direction to thereby cause a corresponding pivoting movement of all mermbers upstream thereof, and reset means operable during return movement of said transfer frame for restoring all members located in -their operative position to their inoperative position.
Thus the invention provides an automatic transfer unit which has a plurality of work sta-tions each capable of support-ing a workpiece thereat and associa-ted with a sensing element which assumes a work sta-tion empty or a work station full posi-tion. When the sensing element is in a work s-tation empty posi-tion, as the transfer bar is faced vertically an element pivoted to that bar engages the sensor ele~ent thereby elevating the carriers upstream from an idle position to a feed position through the pulling of chain or rope or other tension only transmitting means. When -the carrier is in its eleva-ted posi-tion, the transfer bars continue to move vertically until all carriers in a feed position lift the workpieces from -the res-pective work stations. The transfer bars move laterally posi-tioning the carriers at the next succeeding sta-tion, whereupon the carriers deposit the workpieces a-t the succeeding station.
Whell the transfer bar is~vertically lowered -the transfer bar is moved vertically towards the initiating position said carriers - 2a -3~
being lowered to their idle position by a stop positively engaging the end carrier.
In one embodiment of the presen-t invention said reset means comprises an abutment member mounted on said fixed frame to be engaged by the endmost carrier member adjacen-t the up-stream end of said transfer frame during i-ts ups-tream movement with said transfer frame to pivot said endmost carrier member to its passive position as said transfer frame re-turns to its rest position, the arm portion of said endmost carrier member thereby tensioning the cord or chain coupled -thereto in the upstream direction to pivot all arm members downstream thereof which are in their active position simultaneously with said endmost carrier. Preferably said carrier members are gravitationally maintained in either of -their operative and inoperative posi-tions.
The present invention will be fur-ther illus-trated by way of the accompanying drawings, in which:-Fig. 1 is a side elevation of a portion of an accu-mulating transfer unit embodying the invention;
Fig. 2 is a top view of the uni-t portion; and Fig.s 3 and 4 are similar to Fig. 1 showing parts in sequentially different operating posi-tions.
Referring now -to the Figures, there is illustrated a portion of an accumulating walking beam conveyor embodying the invention wherein the transfer decision is made on the verti-cal stroke of a transfer bar. The conveyor comprises a sup-porting por-tion comprising a pair of stationary side bars or work supporting rails 34,36. A series of spaced apart notches - 2b -~37~
In the ralls 34 and 36 deflne work statlons For supportlng work-pleces W. Posltloned between ralls 34 and 36 are a palr of lon-gltudlnally e~tendlng transfer bars 56 and 58 supported for rec-t-angular movement between the ralls. The basic relatlonshlp between the slde bars and the transfer bars Is well known In the prlor art. Llkewlse, It Is known In the art how to move the transfer bar rectangularly. In thls partlcular embodlment means are provlded for longltudinally movlng the transfer bars 56 and 58 a dlstance correspondlng to the dlstance between statlons.
SpeclfIcally, Jolned to the transfer bars Is a bracket 72 for connectlon wlth a plston rod 74 whlch Is In turn connected to a plston (not shown) located wlthln a cyllnder 76, -the cyllnder belng plvoted for swlnglng movement In a vertlcal plane to accom-modate vertlcal movement of -the sllde, as wlll subsequently be descrlbed. Alternatlvely, a system may be used whlcl1 Includes a Scotch Yoke mechanlsm. Means are also provlded for ralslng and lowerlng the transfer bars. In thls embodlment these take -the form of a pluralIty of transversely extendlng rollers 78 carrled by an arm 80 of a lever 82, the other arm 84, of whlch Is con-nected to a plston rod 86 extendlng from a plston located wlthlna second cylInder 88. A plurallty of supportlng rollers 78 are provlded and the arms 80 supportlng these rollers are connected by sultable llnkage (not shown) so that the transfer bars may be elevated vertlcally whlle malntalned In a str-lctly horlzontal relatlonshlp. The Wlknlch appllcatlon teaches an alternatlve arrangement for attalnlng vertlcal movement.

The parts travel along the transfer unlt from the left to the rlght wlth the dlrectlon to the left belng referred to as "upstream", whlle the dlrectlon to the rlght Is referred to as "downstream".

Carrled by statlonary rall 34 are sens I ng means for determlnlng the presence of a workplece W In a partlcular work statlon. As best seen In Flg.s 1 and 2, each work statlon com-prlses a palr of recesses 37 on respectlve work statlon 3~

rails 34, 36 for receiving a workpiece therein, and the rece~-ses have been primed to distingui~h individual station~. A
sensing element 98 i6 provided at each station, the reference numeral-for which ha~ been primed to distingui~h individual sensing element~. Each element i5 supported on a shaft 100 mounted in rail 34 a~ shown in Fig. 2. The sensing element includes a dog 102 of sufficient mass to maintain it against a fixed stop 106 when no part rests in the as~ociated work sta-tion. The do~ 102 carries a tripping element 104 as shown in Figs. 1 and 2.
When a workpiece W' i5 resting on a particular work station, a~ ln worX ~tation 37', lt engages the sen6ing ele-ment 98' rotating the ~haft lV0' in a clocXwi~e direction and thu~ elevating tripping element 104 ' on dog 102 ' to the poHi-tion shown in Fig. 1. However, if no worXpiec~ i~ present at the 3tation, a condition illu6trated by work station 37'' of FigO 1, the ~ensing element 98'' will be in the position shown with dog 102'' abutting a ~top 106'' ~ecured to rail 34~ In thi~ po~ition the tripping element 104'' is in the p~th o~
roller 108'' mounted on roller support 110'', which i6 one of a number of ~upport~, one for each ~tation, which are di6tin gui~hed by primung reference numeral~. The support i~ pivote~
to tran6fer bar 56 at 112'' and ha~ a depending portion 114''.
Pivotally m~unted in pair~d relation on the transfer bar6 56 and 5~, one pair for eac~ workpiece 6upporting sta-tion, are workpiece carriers generally de~ignated 116, but having primed reference numeral~ to individually di~tingui~h them. Each pair i0 connected by a ~lee~e 118 (~ee Fig. 2) mounted on shaft 120. The top of ~top 122 limits the clocX-wise rotation of the carrier while a lower portion of the stop limit~ the counterclockwi~e rotation of ~aid carriers on the ~haft. The carrier~ are counterweigh~ed ~o they have ~table rest positions when abutting either portion of the stop. rhe position corre6ponding to the clockwi~e position (as ~hown in Fig. 1~ iB their inoperative po~ition, while the co~lntercloc~-wi~e positio~ as 6hown by carrier pair 116i'' in ~i9o 4~ ~hi~
latt~r po~ition iB referred to a~ th~ operative position~

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Extending rom one of the carriers of the carrier pair mo6t upstream to the depending portion 114 of the roller BUp-port most downstre~m, there iB ~ingle flexible means 124 join-ing each depending segment to adjacent downstream carrier de-pending arms 126 so to transmit forces in tension only, 6uch as by a rope or chain. The depen~ing portion i5 also joined by the tension mean~ to the adjacent upstream carri~r depen-ding arm 126. ~he length of chain 124 i~ joined 80 t~at when the carrier moet up~tream i~ in ~t8 inoperative po~ition, the chain ifi taut and all of th~ depending segments and depending carrier arm6 are aligned in the up~tream direction a~ 6hown in Fig. 1 the weight of each of said carriers i8 BUf ficient not only to maintain the carrier6 in their clockwise inoperative position but to al~o counteract the weight of the downstream roller and roller ~upport ~o to maintain it in the position shown in Fig. lo In operation the transfer unit works as follows~ From an initial position with all the carrier~ in inoperative posi-tion as shown in Fig. 1, the tran6fer bars are moved upward.
If all the work st~tions are filled with workpiece6, the sen-sor~ will be pivoted in a cl~ckwise position so that ~ripping element 104 is out of the path of travel of roller 108 as it i6 elevated. Thi~ is ~hown by sensor 98'~ No element on the transfer bar~ i6 effected therefor~ by the upward movem~nt ~o that the carrier~ remain in their inoperative position.
If, however, a vacant ~tation occurs, as in worX ~ta-tion 37~ a Ben~Or element 9B'' rotate~ on shaft 00'' in a counterclockwi~e direction to the position ~ho~n in FigO lo Xn thi~ position the tripping ~lement will lie in the path of roller 108'' during the elevation of the transfer bar~. AB
the transfer ~ax~ are elevated, roller 108'' will abut-trip-ping element 104'' and roll along its lower ~ide cau~ing rol-ler support 110'' to pivot in a countercl~ckwise direction pulling the chain upstream fr~m thak roller 6upport to the right, which in turn will pull all carriers roller support~
upstream from thi~ vacant ~tation in a counterclockwi~e 7~
~6--direction and ~au6e the carrier~ upstream to take ~heir opera-tive position. Since the chain only transfers force~ in ten-~ion, the length of chain between the roller support and t~e next downstream carrier 116'' will not carry any forceR but merely become slack, therefore all the carriers downst~eam from the foremost empty station will remain in their inopera-tive position.
The elevation of the transfer bars is controlled BO
that it will stop while above the ~urface of the carrier~ in their inoper~tiv~ poH$tion would pa~Q under any worXpieces when moved horizontally a6 ~hown in Fig. 4. The carriers in their operative position on the other hand lift t~e workpi~ce~
above the support ~B ~hown by carrier 116''' in Fig. 4.
After completing elevation of the transfer bars, the transfer bar is moved downstream a distance equal to the spac-ing between 6tation~ and the~ i8 lowered a distance corre~-ponding to the elevation which previously occurred. ~hU6, the workpiece~ formerly up6tream of the empty station are transferred to the next station located downstre~m from ~here the workpi~ce originally sat. The tran~fer bar iB then moved hori~ontally in the upstream direction a distance correspon-ding to the di~tance between 6tations, at which time it is in po~ition corre~ponding to the initial position.
During the lowering or return stroXe, the upstreammost carrier is pivoted bacX to its inoperative position by re~et mechani~m 130. The reset mechanism is mounted in the path of the most up~tream carrier i it i~ in operative position. If in inoperative position as shown in Fig. 1, the carrier will pas6 beneath the reset mechani~m. When the m~t up6tre~m car-rier 118' ' ' i~ in its operative position, on the return ~troke it will abut the ~orwar~ surface of re~et dog 132. Iq~e dog }B
prevented ~rom pivoting in the upstrea~ dire~tion becau6e of ledge 134 and thu~ cause~ the carrier instead to pivot back to it~ inoperative position. A~ the upstreammost carrier ~o pi-vots, it pull~ ch~in 124 to the left ~nd the ten~ion tran6mit-t~d pulls all the chain~ ups~ream which are in their operative po~ition down to their inoperative position, thu~ returning ~:3~37~
the carrlers to the posltlo,n shown In Flg. 1. To prevent Inad-vertent knockdown of the carrlers durlng thelr forward movement, the reset dog Is plvotally mounted to allow movement In the down-stream dlrectlon as shown In Flg. 2 In phantom outlIne. Thls wlll allow the carrler to pass dur~lng downstream movement wlthout belng affected. Sprlng means 136 are pr-ovlded on the dog to return the dog to Its solld llne posltlon as shown In Flg. 2.
The reset mechanlsm Is Jolned by sultable means 138 to a slde bar.

Claims (3)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In an accumulating transfer unit including an elongate fixed frame having an upstream end and a downstream end, means defining a plurality of workpiece support stations uniformly longitudinally spaced from each other along said fixed frame, an elongate transfer frame, drive means for driving said transfer frame in repeated cycles of movement relative to said fixed frame, each cycle of movement commencing at a rest posi-tion from which said transfer frame is first elevated, then moved longitudinally downstream relative to said fixed frame, then lowered and then returned to said rest position, a plura-lity of workpiece carrier members mounted at uniformly spaced positions longitudinally along said transfer frame for movement relative to said transfer frame between an operative position and an inoperative position, each carrier member being operable when in its operative position to lift a workpiece from one station and carry said workpiece downstream to the next station during a cycle of movement of said transfer frame and each car-rier member being inoperable to lift or carry workpieces when in its inoperative position, a sensing means mounted on said fixed frame adjacent each station to be located in a first position in response to the presence of a workpiece at the associated sta-tion and gravitationally biased to a second position in the absence of a workpiece at the associated station, a plurality of actuating members mounted at uniformly spaced positions along said transfer frame between said carrier members, each actuating member being associated with one of said sensing means and mov-able thereby when the associated sensing means is in its second position from an inoperative position to an operative position, and connector means coupling said carrier members to each other for transmitting movement of one carrier member from its inoper-ative to its operative position to all carrier members upstream from said one carrier member to cause said carrier members up-stream from said one carrier member to move from their inopera-tive to their operative positions simultaneously with said one carrier member; the improvement wherein each of said carrier members and each of said actuating members comprise a pivotal support mounting the member for pivotal movement on said transfer frame and an arm portion extending radially from said pivotal support, said arm portions being of uniform radial length, said connecting means comprising a flexible cord or chain connected to each of said arm portions to extend between adjacent arm portions in a taut condition when said adjacent arm portions are in parallel relationship with each other, each of said sensing means having an abutment thereon engageable when the sensing means is in its second position with its associated actuating means when said transfer frame is elevated to pivot the arm portion of the engaged actuating member from its ino-perative to its operative position by swinging the arm portion in a direction tensioning the cord or chain coupled thereto in a downstream direction to therby cause a corresponding pivoting movement of all members upstream thereof, and reset means operable during return movement of said transfer frame for restoring all members located in their operative position to their inoperative position.

2. The invention defined in claim 1 wherein said reset means comprises an abutment member mounted on said fixed frame to be engaged by the endmost carrier member adjacent the upstream end of said transfer frame during its upstream movement with said transfer frame to pivot said endmost carrier member to its passive position as said transfer frame returns to its rest position, the arm portion of said endmost carrier member thereby tensioning the cord or chain coupled thereto in the upstream direction to pivot all arm members downstream thereof which are in their active position simultaneously with said endmost carrier.

3. The invention defined in claim 1 or 2 wherein said carrier members are gravitationally maintained in either of their operative and inoperative positions.