referring first to fig1 and 11 , an agricultural implement such as a harrow comprises a main or central frame mf and two wing frames ff of which only one of the latter is illustrated in fig1 . ( they are , left and right , otherwise alike .) the main or central frame mf ( fig1 ) has , adjacent the ends of each of its side bars 1 , main frame hinge brackets 3 , 3 the hinge or pivot pins 2b of which pivotally support the upper ends of wing hinge levers 3a , 3a ( fig2 and 8 ) at each end of the main frame , and auxiliary hinge brackets 2a , 2a on the longitudinally extending main frame side bar 1 and cooperating diagonal bracket arms 4 ( fig1 , 3 ). the wing hinge levers 3a , which are constituted initially as third class levers for the purpose of initially raising the wing frame from support by the ground , are adapted to have force applied to them by the plunger rods 8 at pivot pins 13 located intermediate the ends of said wing hinge levers 3a . the force applying means on each side of the frame comprises a double acting cylinder 6 disposed -- one at each side , front and back , of the main frame mf -- with pistons 7 and piston rods 8 , which rods 8 , with connecting thrust bars or links 11 , are each guided in a horizontal track or guide 10 ( see fig3 and 9 ), said cylinders 6 being mounted on pivots 5 on the lower side of the main frame side bar 1 . the hinge or crosshead pin 9 of each piston 7 is connected to its thrust bar or link 11 which is guided in a horizontal track 10 ( fig9 ) fixed to the lower side of the main frame bar 1 ( see fig3 and 9 ). the lever 3a assumes whatever position is required by the position of its pivot pins 2b , 12d and 13 . its function is to transmit thrust of the hydraulic piston 7 in one direction and tension or pull of the hydraulic plunger operating in the opposite direction . the piston 7 , through the aforementioned intermediate flat , plate like link 11 , is connected to the wing hinge arm 3a at pin 13 and guide - mounted in guideway 10 ( fig9 ). the piston 7 , through its extension 8 , 9 , 11 , is pivotally connected at 13 intermediate the ends of the wing hinge lever 3a , and during operation of the harrow said lever 3a is disposed in a generally vertical position , the wing 12 being then in substantially the normal operating , horizontal position illustrated in fig2 and 3 . the wing frame 12 at that time assumes the position shown in fig3 with the wing frame 12 moving endwise , that is , to the plane of the paper in fig3 in substantially the same plane as that in which the main frame mf in fig1 lies . the linkage is so proportioned as to allow tilting of the wings sidewise relative to the main frame above and below the line position shown in fig3 to the extent permitted by the pin 14 in the slot of link 15 . if , with the parts in the position shown in fig1 and 3 , it should be desired to fold the wing frame ff of fig1 over upon the main frame mf , the following operations are effected . the operator has in the cab of the pulling tractor hydraulic equipment providing a fluid pressure supply and a manual control valve . admission of pressure fluid to the left hand end of cylinder 6 in fig2 - 8 initiates a folding operation . referring particularly to fig2 and 3 , the parts are in normal unfolded position with the wing frame 12 supported on level ground by the depth control wheels 18m , 18m ( fig1 ). the main frame mf is supported partly upon its discs 19m which are held at a predetermined depth by the downward weight of the machine and held to a predetermined depth value by the ground engaging wheels 18m , 18m , the position of which is controlled by the cylinder 17 ( fig1 ). the operating position of the unfolded discs 19w with respect to the ground line , is such as to provide the desired depth of penetration , and the hydraulic depth control cylinders 17 ( fig1 ) are set accordingly . when the desired depth of penetration of the discs is duly adjusted , the harrow is moved by the tractor in a soil working or plowing operation . with the wing disc harrow moving over level ground with the discs set to penetrate the soil to a predetermined depth , the main frame of the machine will be substantially level at a depth of penetration of the discs controlled by the wheels 18m . adjustment of the wheels under the wing frame and the wheels under the adjacent side of the main frame is effected by the hydraulic piston and cylinder 17 as shown in fig1 . the other half of the main frame and its adjacent wing frame , which are not shown in fig1 will however have a similar arrangement for controlling the depth of penetration of the discs for the wing and for the adjacent main frame portion of the machine . in normal operation , which is above briefly described in connection with fig1 the position of the folding and unfolding mechanism of the individual wings maintains substantially the position of the parts illustrated in fig2 and 9 . in this condition the main frame 1 shown in fig2 and 3 is substantially level and the wing frame 12 likewise is in a level position in line with the main frame . the opposite side of the main frame and its connected wing frame is the same as that shown in fig2 and 3 for the right hand side of the machine -- that is to say , the right hand side and the left hand side are mirror images of each other . the main frame mf as shown in fig1 and 11 and the wing frame 12 ( see fig1 and 3 ) are horizontally in alignment being connected through the lever 3a hinged at its upper end at the pin 2b of the upwardly extending hinge bracket or lug 3 . at this time the plunger 7 of the hydraulic cylinder 6 is retracted -- that is , moved to the left in fig3 -- holding the link 3a against movement through the thrust link or bar 11 which is hinged at 13 to the link 3a . the wing frame 12 , however , is to some degree independent of the main frame in that the connection between the two is through the bracket arm 12a and pin 12d at the lower end of lever 3a . the slotted link 15 which is pin hinged at 12c to the wing frame bracket 12a carries the slot 15a and the pin 14 in the said slot approximately midway of the length of the slot . thereby the wing frame may rise and fall to the extent determined by the aforesaid pin and slot connection . the position of the wing hinge lever 3a is maintained by the hydraulic cylinder and plunger which operates with a liquid which is comressible . reference is now had to fig4 - 8 . the first step in folding the wing frame over the main frame comprises an elevation of the main frame mf by way of the ground engaging wheels so that the wing frame ff may rock on the pin 12d , as shown in fig4 to cause the pin 14 which is carried on the thrust bar or link 11 , connected to the hydraulic cylinder 6 , to move to the end of the slot 15a so that there is a solid connection between the wing frame and the link 3a to prevent further clockwise movement of bracket arm 12a around the pin 12d to hold the wing frame ff in a predetermined position as illustrated in fig4 . then operation of the hydraulic cylinder 6 thrusts bar 11 to the right as shown in fig4 . the wing frame and the main hinge lever 3a , being held together by the link 15 and pin 14 , can be rotated together by movement of the piston rod 8 of the cylinder 6 to the right in fig4 . this movement , transmitted through the pin 13 to the wing hinge lever 3a , swings the wing frame 12 in a counterclockwise direction to the position shown in fig5 . thus by extension of the piston rod , the main lever 3a and the wing hinge bracket 12a with the connected wing frame 12 will be moved counterclockwise around the pin 2b as a pivot . as movement of the piston 7 of the hydraulic cylinder 6 proceeds , the connected parts above referred to will continue to swing around the pin 2b on the main frame as shown in fig6 . as the rotary movement of the wing frame around the pivot pin 2b continues , a point will shortly be reached , as illustrated in fig7 where the center of gravity of the wing frame and its connected parts will swing the wing counterclockwise back over the hinge pin 2b of the main frame , and the wing frame 12 will tend to fall prematurely counterclockwise on its face since its center of gravity is at that stage on the left hand side of the pivot 2b on the main frame , as shown in fig8 . this , however , is prevented by the two point hold which the thrust bar or link 11 has on the wing frame 12 through the slotted link 15 and arcuate shoulder 16 to prevent counterclockwise motion of the wing about the hinge pin 12b and the restraint against backward angular motion prevented by the resistance of the arcuate shoulder 16 on the thrust bar 11 which can be unlocked only by movement of the slotted link 15 swinging away from the arcuate shoulder 16 . fig4 -- 8 illustrate the face that throughout the entire operation of swinging from normal horizontal position illustrated in fig3 to inverted horizontal position illustrated in fig8 the wing frame 12 is under the control of the hydraulic cylinder , no free fall being permitted . the unfolding operation is equally under control and it begins with reverse operation of the cylinder plunger 7 to the left as shown in fig8 to unwind , as it were , the wing frame controls around the main frame hinge pivot 2b in successive reverse positions illustrated in fig7 , 5 , 4 and 3 . in the above outline of the folding operation , the essential locking function of the slotted link 15 and the arcuate shoulder 16 have been stated briefly . it is essential to the folding operation that the hinge 12d between the wing frame and the main lever 3a be rigidified when the center of gravity of the wing frame moves counterclockwise toward a position vertically above the supporting pin 12d . this requirement is met by the cooperation of the slotted link 15 hinged at its upper end at 12c to the wing frame and the arcuate shoulder 16 on the thrust bar 11 which connects the plunger of the cylinder with the main operating link 3a through the pin hinge 13 . when the parts are in the position shown in fig3 the wing frame 12 is being supported by the ground wheels and is free to move up and down within the limits of the slot 15 and pin 14 shown in fig3 . in the operation of swinging the wing frame to its idle or rest inverted position ( fig8 ) from its working position ( fig3 ) with the plunger of the cylinder in maximum retracted position , the linkage between the main frame and the wing frame initially occupies the position shown in fig3 . admitting fluid to the left hand end of a cylinder , as shown in fig3 swings the main lever 3a counterclockwise and this tends to push the wing hinge arm 12a and the frame 12 diagonally upwardly to the right as viewed in fig5 . this results in decreasing the angle between the main operating lever 3a and the wing frame strut 12a as shown in fig4 . this action is limited by the pin 14 engaging the end of the slot 15a as shown in fig4 . further movement of the link 11 to the right in fig4 begins to swing the main lever 3a and wing frame bracket 12a together since the pin 14 on the plunger bar or link 11 has reached the end of the slot , as shown in fig4 and 5 , and the further movement of the plunger begins to swing the main lever 3a and the wing frame 12 as a unit in a counterclockwise direction , as shown in fig5 . further movement of the parts illustrated in fig6 shows the thrust bar or link 11 further advanced to the right which swings the wing hinge 3a and the wing frame 12 together as a unit in a counterclockwise direction . the wing frame 12 tends , under its own weight , to swing about the pivot 12d in a clockwise direction but is restrained from independent movement in that direction by the slotted link 15 engaging the pin 14 on the thrust bar 11 . however , if this motion is continued to the point where the wing frame center of gravity would tend to pass over the hinge pin 12d , the wing frame would then flop over counterclockwise . the pin 14 and slot 15a would not be able to prevent this . however , in the present construction , the arcuate shoulder or lug 16 which is affixed to the thrust bar or first link 11 now engages the arcuate end of the second link 15 as shown in fig6 . thereby the wing frame and its bracket arm 12a are held against counterclockwise movement with respect to the main lever 3a which is connected at the hinge pin 13 to the thrust bar or first link 11 and connected to the wing frame bracket 12b of the wing frame . thereby further movement of the thrust bar or link 11 to the right in fig6 results in moving these three elements -- namely , the wing hinge lever 3a , the bracket arm 12a and the slotted link 15a , together in unison . angular advance of the thrust bar or link 11 is continued and it moves the linkage and the wing frame 12 into the position shown in fig7 . continuing movement of the thrust bar or link 11 brings the parts through the position shown in fig7 to the position shown in fig8 where the folding motion of the wing frame has been completed . when both wings have thus been folded over on top of the main frame , the implement is in condition to travel . in this operation , the first link or thrust bar 11 performs simultaneously a number of important functions . first , it transmits the actuating thrust of the hydraulic plunger rod 8 tending to swing the wing frame counterclockwise around the stationary main pivot 2b , then through the pin 14 and slot 15a of the link 15 , it holds the wing frame at a predetermined angle relative to the main lever 3a . then for the final fold it acts as a strut through the arcuate shoulder lug and link 15 to swing the wing frame the last 90 ° to bring it face down on top of the main frame . for unfolding of the wings , the hydraulic pressure is applied on the right hand side of the piston 7 in fig8 and the unfolding operations proceed in reverse through the stages illustrated in fig8 , 6 , 5 , 4 and 3 .
the invention provides a folding wing disc harrow wherein a hydraulic operating mechanism is provided for folding and unfolding the wings through an arc of more than 180 ° through the positive bidirectional linear movement of the plunger of a double acting hydraulic cylinder cooperating with the wing to which it is connected , for said folding and unfolding operations , and which mechanism allows a limited angular free floating motion of the wing above and below the horizontal &# 34 ; unfolded &# 34 ; or &# 34 ; working &# 34 ; position when the hydraulic control valve is set accordingly . the connection of the hydraulic piston rod with the wing is so organized that the straight line motion of the piston rod is enabled to fold and unfold the wing through an arc well in excess of 180 ° and is organized to allow a limited free floating action of the wing for following the soil surface variations . the ability of the present invention to swing the wing through 180 ° of angular motion for folding and unfolding the wings about a horizontal longitudinal hinge axis by a simple straight line hydraulic cylinder motor operation allows a uniquely compact and stable folded condition of the implement which is advantageous and highly desirable . dispensing with the necessity for balancing springs , which is an undesirable feature common in the prior art , marks the present invention as a distinct advance in the art .