now , an embodiment of the present invention will be described with reference to the drawings . referring to fig1 to 3 , reference numeral 1 denotes a bobbin tray feeding path which extends , for example , along spindles 3 of a spinning frame 2 . the bobbin tray feeding path 1 is composed of a pair of tray receiving plates 4a , 4b defining a cut away portion therebetween , and a pair of guide plates 5a , 5b for controlling the feeding direction of trays on the tray receiving plates 4a , 4b . the trays t include a base member 6 in the form of , for example , a disk , and a peg 7 formed on the base member 6 for receiving a bobbin thereon . each of the trays t has a concave engaging portion 8 formed in a lower face thereof and adapted for a tray feeding device described below . a tray feeding device 9 is composed of sliding bars 10 , 10 each formed of one or a plurality of divided parts and located along the spindles of the spinning frame 2 , and engaging members 11 located in an equal pitch with the spindles on the sliding bars 10 , 10 . the sliding bars 10 , 10 are securely supported on a reciprocal rod 14 connected to a piston rod 13 of a hydraulic cylinder 12 . in particular , each of the engaging members 11 is composed of one or a plurality of leaf springs which has or have one end or ends thereof secured to the corresponding bar 10 by means of a screw 15 and the other ends thereof positioned adjacent the engaging portion 8 of a tray . the pitch between ends of the engaging members 11 is equal to the pitch p1 of the spindles . accordingly , if the piston rod 13 is moved a fixed stroke s in a direction of an arrow mark 16 in fig1 then each of the leaf springs 11 is a little deformed in the counterclockwise direction around a fulcrum of the fixed position 15 by a lower face of a tray t and thus passes below the lower face of the tray t until it comes to a position below the lower face of another tray located rightwardly of the former tray by a distance equal to one pitch with the end thereof positioned in the engaging portion 8 of the latter tray . subsequently , as the piston rod 13 is moved by the stroke s in a direction of an arrow mark 17 , all the trays which engage with the engaging members 11 are fed at a time by a distance equal to one pitch p1 in a direction of the arrow mark 16 . it is to be noted that the stroke s of the piston rod 13 by the hydraulic cylinder 12 is a little greater than the spindle pitch p1 so that when the engaging members are returned to their initial positions , they may be located assuredly in the engaging portions 8 on the lower faces of the trays . it is to be noted that adjacent trays do not contact with each other in the embodiment described above . accordingly , if a tray is only pushed by an engaging member 11 , there is the possibility that it may overrun without stopping at a predetermined position due to its own inertia or that it may turn back when a leaf spring is deformed and pass below the lower face of the tray upon returning of an engaging member 11 . accordingly , in the embodiment described above , a positioning plate 18 for preventing overrunning and turning back of a tray is securely located at each of positions adjacent the spindles . in particular , referring to fig4 and 5 , the positioning plate 18 is secured for adjustment in a tray feeding direction on one 5a of guide plates 5a , 5b of the feeding path by means of an elongated hole 19 and a screw 20 . the positioning plate 18 is formed by bending a single plate and has a contacting portion 21 for contacting with part of the base of a tray t , and a turning back preventing stopper 22 for preventing turning back of a preceding tray . the contacting portion 21 is an inclined edge which is inclined in a direction opposite to the tray feeding direction and is contacted and pushed by an upper circumferential edge 6a of the base member 6 of a tray t thereby to prevent overrunning of the tray . meanwhile , when a tray t of fig5 is fed by a distance equal to one pitch in a leftward direction by the engaging member 11 , the plate 18 is pushed by the tray and is thus displaced in the clockwise direction around a fulcrum of the fixed position 20 whereafter it is returned to its initial position after the tray has passed thereby . thus , the plate 18 is composed of a leaf spring member having an urging force . the sliding bars 10 are divided into a plurality of parts as shown in fig6 in order to reduce the cumulative error of the mounted positions of the engaging members , and each of the sliding bars 10 is secured to and moved in an integral relationship with a plurality of rods 14 . it is to be noted that because the number of the spindles of the spinning frame reaches up to several hundreds and accordingly a great driving force is required for simultaneous feeding of trays , a plurality of hydraulic cylinders are used , but it is possible to provide a single cylinder having a high power at an end portion of the spinning frame . further , it is also possible to employ a motor as a driving source for a reciprocal motion of the sliding bars 10 and employ a transmission mechanism involving a rack and a pinion . while fig1 and 2 illustrate an example wherein trays t are fed in a spaced relationship by a distance equal to the pitch p1 , fig6 illustrates another example wherein the same trays t are arranged in a row in accordance with another spindle pitch p2 . in this instance , the pitch of the mounted positions of the engaging members 10 on the sliding bars 10 is also equal to the spindle pitch p2 , and naturally it is necessary to adjust the positions of the tray position plates 18 of fig2 in accordance with the spindle pitch . however , if the spindle pitches p1 , p2 of the spinning spindles are greater than the diameter d of the trays , the trays t can be applied to any of the spinning frames . further , it is possible to employ , in a single spinning frame , various trays of different sizes as lot changing is to be effected . in this case , only if the engaging portions of the various trays do not vary in size but have a fixed size , there is no necessity of adjustment of the positions of the engaging members . another embodiment of the present invention is shown in fig7 . in particular , engaging pieces 23 are secured to each of liftable frames 24 in a spaced relationship by a distance equal to a pitch p1 of spinning spindles . each of the frames 24 is in turn secured to a piston rod 27 of a vertical cylinder 26 on a sliding frame 25 . reference numerals 28 , 28 denote guide tubes secured to the frame 25 , and the guide tubes 28 , 28 guide rods 29 , 29 on a lower face of the liftable frame 24 . the sliding frame 25 is secured to a piston rod 31 of a horizontal cylinder 30 by way of a leg 32 . in particular , when a tray t on the feeding face 4 is to be fed by one pitch in a direction of an arrow mark 33 , at first the piston rod 27 of the cylinder 26 is lifted 35 to advance an engaging piece 23 in a position retracted below the feeding path into the engaging portion of the tray t , and then the cylinder 20 is rendered operative so that the piston rod 31 is advanced by a fixed stroke , that is , by a distance equal to the pitch p1 in a direction of an arrow mark 34 to move the members on the sliding frame 25 by a fixed pitch at a time in the direction of the arrow mark 33 to feed the tray by a distance equal to the pitch p1 . then , the piston rod 31 is moved down 36 so that the engaging pieces 23 is moved away from the tray t and retracted below the feeding face whereafter the sliding frame 25 is moved by a distance equal to the fixed pitch p1 in a direction of an arrow mark 37 back to its initial position by the cylinder 30 . in this manner , trays on the feeding face 4 are fed at a time in a spaced relationship by a distance equal to the pitch p1 . as apparent from the foregoing description , according to the present invention , an engaging piece for engaging with a tray is located at each of locations spaced by a distance equal to the spindle pitch , and by reciprocating the engaging pieces , trays of even different types can be arranged in a row and fed in a spaced relationship by a distance equal to the spindle pitch . besides , trays of a single type can be used for another spinning frame which has a different spindle pitch . thus , a tray feeding device of the present invention is effective particularly in a production system for production of a large number of kinds of articles in small lots .