US3877391A

US3877391A - Gantry loading bridge truck

Info

Publication number: US3877391A
Application number: US395247A
Authority: US
Inventors: Werner Gimperlein; Franz Sedlmayer
Original assignee: Fried Krupp AG
Current assignee: VULKAN HAFENTECHNIK GmbH
Priority date: 1972-09-14
Filing date: 1973-09-07
Publication date: 1975-04-15
Anticipated expiration: 1992-04-15
Also published as: JPS4992743A; FR2200182B3; FR2200182A1; DE2245031A1

Abstract

Implement, especially gantry and loading bridge, which comprises a frame structure including a polygonal support base and pivotally resting on compensating rockers of a rail carriage system, in which the frame structure and the compensating rockers are provided with pairs of abutments with the abutments of one and the same pair being located one above the other and offset in the travelling direction of the implement with regard to the pivotal connection of the frame structure with the compensating rockers, the abutment of each pair of abutments being so arranged or adjustable that they prevent a tilting of the frame structure in the pivotal connection of the frame structure with the compensating rockers or limit such tilting to a predetermined angle.

Description

United States Patent Gimperlein et al.

1 1 GANTRY LOADING BRIDGE TRUCK {75] Inventors: Werner Gimperlein; Franz Sedlmayer, both of Wilhelmshaven, Germany [73] Assignee: Fried. Krupp Gesellschaft mit beschrankter Haftung, Essen, Germany [22] Filed: Sept. 7, 1973 1211 Appl. No.: 395,247

[30] Foreign Application Priority Data Sept 14, 1972 Germany 2245031 [52] 0.5. CI 105/163 R; 105/26 A; 105/164; 105/183; 212/5; 212/15 [51] Int. Cl........ 861d 15/02; B6lf 1/08; B61f 3/10 [58] Field of Search 105/157 R, 163 R, 164, 105/199 R, 26 A, 183

[56] References Cited UNITED STATES PATENTS 572,195 12/1896 Crosby 105/163 R X 907.964 12/1908 Brown 105/163 R X 1,280,238 10/1918 King et a1 105/163 R X Primary E.raminer-Lloyd L. King Assistant Examiner-Howard Beltran Attorney. Agent, or FirmWalter Becker [57] ABSTRACT Implement, especially gantry and loading bridge, which comprises a frame structure including a polygonal support base and pivotally resting on compensating rockers of a rail carriage system. in which the frame structure and the compensating rockers are provided with pairs of abutments with the abutments of one and the same pair being located one above the other and offset in the travelling direction of the implement with regard to the pivotal connection of the frame structure with the compensating rockers, the abutment of each pair of abutments being so arranged or adjustable that they prevent a tilting of the frame structure in the pivotal connection of the frame structure with the compensating rockers or limit such tilting to a predetermined angle.

15 Claims, 3 Drawing Figures PATEHTEEAFRISm-s sz-zzu 3 m3 MGR GANTRY LOADING BRIDGE TRUCK The present invention relates to an upwardly extend ing implement or device. especially a gantry and a bridge crane. the framework of which rests in an articulated manner on compensating or balancing arms of carriages on rails. The framework has a rectangular or triangular supporting base the corner points of which are located in the centers of the joints by means of which the balancing arms are connected to the framework. Ordinarily. below each corner point of the supporting base there are provided a plurality of balancing arms in such a manner one above the other that each compensating or balancing arm rests at each end on two shorter compensating arms. and that the lowermost compensating arms have their ends respectively rest on two compensating bogies each having two wheels. Ac cordingly. the carriage has below each of the corner points of the supporting base a great number of serially arranged wheels and thereby a considerable length. Thus. on each side of the device the wheels running on a common rail go far beyond the corner points located above the rail. This results in a great clearance. which means that when one of the carriages with its buffers has reached one end of the crane travelling path. the center of the framework and consequently generally also the center ofthe load receiving means of the crane is still correspondingly far away from the end of the crane travelling path. Asa result thereof. the length of the crane travelling path is not fully made use of. It has therefore been endeavored to make the corner distance. which means the distance between two corner points of the supporting base of the framework which are located above one rail. as short as possible. This is particularly important with shipyards for making full use ofthe dock length. and is also important with load ing and unloading installations for making good use of the pier and storage place length. On the other hand. to the extent to which the corner distance becomes smaller. the ability of the device to resist tilting moments caused by wind forces is reduced in the longitudinal direction of the rails thereby decreasing the stability of the device. Such wind forces exert upon the framework tilting moments with a lever arm which corresponds to the height of the framework. These tilting moments are exerted with regard to those corner points ofthe supporting base which. when viewed in the direction of the wind. are located behind the center of the framework. These tilting moments are counteracted by the moment which results from the weight of the masses taking part in the tilting and. more specifically, this moment counteracts the tilting moments with a lever arm which equals the horizontal distance of the masses from these corner points. This lever arm is. however. the shorter the smaller the corner distance is selected for reducing the above referred to clearance.

It is. therefore. an object of the present invention, also with the design of a device or implement of the type set forth above having as small a corner distance as possible. to secure the necessary stability of the implement when the latter is not in operation.

This object and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawings. in which:

FIGS. I. 2 and 3 illustrate for three different embodi ments of the invention the side views of gantries with the carriage systems located below one or two corner points. and also illustrate those parts of the crane framework which are adjacent to these corner points.

The implement according to the present invention. the framework of which rests in an articulated manner in corner points of a supporting base on compensating arms of rail carriages. is characterized primarily in that on the framework and on the compensating arms there are provided abutments which are located in pairs opposite to each other and in the direction of the rails are relative to the corner points of the supporting base off set in such a way or adjustable in such a manner that they will prevent the tilting ofthe framework in the corner points or will limit such tilting to a predetermined extent.

Referring now to the drawings in detail. the gantry crane shown therein rests in all embodiments with its carriages on two rails 1 which are spaced from each other in conformity with the large span of the crane. Each of the supports of the crane framework located above one of the rails has a long travelling beam 2 the ends of which have arranged thereon upwardly converging legs 3 provided in sheet metal box manner. The beam 2 rests by means of downwardly directed extensions in joints 4 on main rockers. the axes of the joints 4 extending in a direction transverse to the travelling direction. The centers of the joints 4 form the corner points of the supporting base for the crane framework. In the specific embodiments shown. the supporting base forms a rectangle one side of which equals the corner distance e. which means the distance between the two corners E located above one and the same rail 1. One half of the corner distance Vac is shown in FIGS. l and 2 and extends from one corner point E to the vertical central plane M of the crane which central plane extends in a direction transverse to the rails 1.

With the embodiments of FIGS. 1 and 2. the main compensating rocker 5 forms a two-arm lever with equal lever arm lengths. The rocker 5 rests on its ends in joints 6 of further shorter compensating rockers 7 which likewise have lever arms of equal length. The rockers 7 rest at their ends on two further still shorter compensating rockers 8 having lever arms of equal length. Rockers 8 rest at their ends by means of supports or bearings 9 on the central portion of compensating bogies 10 each of which has two serially arranged wheels or wheel pairs ll. In this way the wheels or wheel pairs ll are in the carriage system located below each corner point E supported on the rail 1 or on two adjacent rails. At that end ofone compensating rocker 7 which faces away from the central plane M there is provided a buffer 12 which projects outwardly beyond the outermost wheel 11.

According to the embodiment of FIG. 1. at the end faces of the travelling beams 2 there are provided extensions 13. Below the extensions [3 supports or dogs [4 are mounted on the main rockers 5. To the bottom side of each extension 13 and to the top side of each dog 14 there are connected abutment plates 15. In the normal position of the main rockers 5. i.e.. when their planes passing through the centers of the joints 6 have not been moved out of their horizontal position due to an unevenness of the rail route. the abutment plates generally indicated by numeral 15 are separately identified by

reference designations

15a and 15b and at each corner point E these are vertically spaced from each other by the distance a. This distance is so selected that the main rocker will be able in conformity with the expected unevenness of the rail route to tilt or pivot about the joint 4 without the abutment plates l5 hitting each other. On the other hand. the distance a has been selected so as to be just large enough to permit such tilting of the main rocker 5 while pivoting movements of the framework in the joints 4 will be limited. When the crane is not in operation and is subjected to forces acting in a direction parallel to the rails l. for instance from the right-hand side to the left-hand side with regard to FIG. I. it will be appreciated that under the influence of a strong wind the crane framework will be tilted in the joints 4 located on the lefthand side of the central plane M. This will be the case when the moment due to the wind forces will exceed the moment resulting from the weight of the masses taking part in the tilting movement and the lever arm with regard to the respective corner points E which is somewhat shorter than /21. However, from the moment on at which the upper abutment plates abut the lower abutment plates. in other words when the framework 2. 3 can no longer tilt in the joints 4 relative to the main rockers 5. a tilting could now occur only in the joints 6 which when viewed in FIG. 1 are located on the left-hand side of the joints 4. As a result thereof the lever arm of the weight moment which acts counter to the tilting moment due to wind forces is increased by the distance It. i. e. by the horizontal distance between the centers of the joints 6 and the corner points E. Moreover. the weight moment which acts counter to the tilting moment is increased by the fact that also the masses of those elements of the carriage system which are located on the right-hand side (with regard to FIG. 1) of the corner points E would take part in a tilting movement about the centers of the joints 6. In this way the required safety against tilting of the crane due to wind forces will be realized.

The lever arm of the weight moment which acts counter to the tilting moment due to wind forces may. if necessary. be increased by the distances 1' or it when also the tilting movements of the main compensating rockers 5 are by corresponding abutments limited relative to those compensating rockers 7 which are facing away from the central plane M. and when the tilting movements of the rockers 7 are limited relative to the compensating rockers 8 facing away from the central plane M.

According to the embodiment of FIG. 2 and in contradistinction to the embodiment of FIG. l, the upper abutment plate 15. which in conformity with FlG. l is firmly mounted on the extension 13, has been replaced by a punch or plunger 16 which by means of a piston reciprocable in a cylinder 17 of a hydraulic power device is guided in vertical direction. The cylinder [7 of the hydraulic power device which is mounted in an extension 18 extending from the travelling beam 2 toward the left. has its upper end and its lower end connected to a control device 21 by conduits l9 and 20 respectively. The control device 21 is on the one hand in com munication with a pressure storage device 22 to which fluid under pressure is conveyed through a check valve 24. On the other hand. a discharge conduit 25 leads from the control device 21 to a liquid container 26.

In view of this hydraulic device. the piston is adapted in the cylinder 17 to be acted upon from above by pres sure fluid so that the punch will be moved downwardly until it engages the abutment plate 15 on the respective dog of the main compensating rocker 5. When thereupon the conduit 19 is shut off. the punch cannot escape in upward direction. Consequently. the framework will be prevented from tilting from the right toward the left under the influence of wind forces in the joints 4 shown on the left-hand side in FIG. 2 relative to the main compensating rocker 5. Thus. whereas according to the embodiment of FIG. 1 an initial tilting movement is permitted. until the upper abutment plate 15 abuts the lower abutment plate. according to the embodiment of FIG. 2 a tilting in the respective joints 4 is prevented from the start so that the lever arm for the weight moment which acts counter to the wind forces will immediately be increased by the distance h. Also in this instance. with a corresponding arrangement of further hydraulic power devices. increases in the lever arm by the distances 1 and k in conformity with FIG. 1 are possible.

Expediently. a common hydraulic device 2i 25 is employed for the two cylinders 17 at both ends of each travelling beam 2. Under certain circumstances. the punch 16 may also during the operation of the crane rest upon the abutment plate 15 if by corresponding adjustment of the control device 21 care is taken that the conduits l9 and 20 are connected to each other. in other words. when the chambers in cylinder 17 above and below the piston communicate with each other. The provision of the pressure storage device 22 has the advantage that also in case of a power failure the fluid pressure required for pressing the plunger 16 against the abutment plate 15 is available. By means of the pump 23 leakage losses will be avoided. By means of this pump it is also possible. if necessary. to increase the fluid pressure.

According to the embodiment of HO. 3 the main compensating rockers 26 have lever arms of different lengths. More specifically. the ratio of the length of the lever arm which faces away from the central plane M to the length of the other lever arm is l 2. The joints in which the corner points E are located have been designated with the reference numeral 27. By means of the short lever arm. each of the main rockers 26 rests in a joint 28 on a carriage system which is equipped with compensating

rockers

5, 7. 8, and with a compensating bogie 10 similar to the carriage system of FIGS. l and 2. and is consequently equipped with sixteen rollers or roller pairs ll.

By means of a long lever arm each main compensating rocker 26 rests in a joint 29 on a compensating rocker 30 which forms a lever with arms of equal length and the ends of which rest in joints on shorter rockers 31 with arms of equal length. The rockers 31 respectively rest on two compensating bogies 10. The entire travelling system which is located below a corner point E has twentyfour serially arranged rollers or roller pairs 1].

According to this embodiment. for preventing a tilting. there are provided pull rods 32 which engage the main rockers 26 at those ends thereof which face the central plane M. This is effected by means of oblong holes 33 in the lower ends of the pull rods 32. and by bolts 34 which are mounted on eyes 39 of the main compensating rockers 26 and engage the oblong holes 33. The pull rods 32 are passed through openings in the travelling beams 2. The upper ends of the pull rods 32 are pivotally connected to slide shoes 35 which are displaceably guided on the upper side of beam 2 in a direction parallel to the rail 1. The slide shoes 35 are engaged by threaded spindles 36 which extend in the direction toward the central plane M and are surrounded by nuts 37 which are mounted in supports 38 on the travelling beam 2. The nuts 37 are adapted to be ro tated by non-illustrated means so that the slide shoes 35 can be moved back and forth on the traveling beam 2. The arrangement is such that in all positions of the shoes 35. the pull rods 32 extend from the bolts 34 with a smaller or greater inclination toward the top in the direction toward the central plane M.

During the operation of the crane. the pull rods 32 occupy the central position which is illustrated on the right hand portion of FIG. 3 and in which the bolts 34 occupy a position in the central portion of the oblong holes 33. Accordingly, the main rockers 26 are permitted to tilt in the joints 27 in conformity with a corresponding unevenness in the rail route.

When the crane is stopped. the shoes 35 are by means of nuts 37 and the threaded spindles 36 displaced in the direction toward the central plane M in such a way that with the starting position of the main rockers. the bolts 34 will engage the lower ends of the oblong holes 33 as illustrated in the left-hand portion of FIG. 3.

If now wind forces tend to tilt the crane. for instance from the right to the left with regard to FIG. 3. the

framework

2, 3 cannot tilt relative to the main rockers 26 in the joints 27 located on the left hand side of FIG. 3 because the pull rods 32 on the left-hand side of FIG. 3 will prevent such tilting. Consequently. the tilting point is displaced to the centers of the joints 28 so that the lever arm of the weight forces acting counter to the tilting moment will be increased by the distance m. Also in this instance additional increases in the lever arm can be obtained when also tilting movements of the main rockers 26 relative to the compensating rockers 5 therebelow and. as the case may be. also tilting movements of additional compensating rockers relative to compensating rockers therebelow. are prevented by similar means.

The fact that the pull rods are subjected to pull and not to pressure and buckling forces and also the fact that the pull rods engage large lever arms of the main compensating rockers 26 results in favorable dimensions. The embodiments according to FIGS. 1 and 2 may be modified in a corresponding manner in such a way that the abutment plates 15 and the plungers 16 are provided on that side of the respective corner points E which face the central plane.

Instead of the embodiment illustrated in FIG. 3. it is also possible to pass the pull rods 32 from the bolts 34 in vertical direction through the beam 2 and that those ends of the pull rods which project beyond the beam 2 are by driving means. such as spindle-thread and nut or in a hydraulic manner. pulled in upward direction. The employment of pull rods for preventing tilting movements of the main compensating rockers. which tilting movements may be caused by wind forces. is feasible when the main compensating rockers have lever arms of equal length and when consequently the carriage systems are designed symmetrically with respect to the corner points.

As will be evident from the above. the foremost advantage ofthe present invention consists in that by simple structural means the necessary stability of the implement when not in operation will be assured while nevertheless a very satisfactory exploitation of the length of the crane path will be obtained.

It is. of course. to be understood that the present invention is. by no means. limited to the specific showing in the drawing but also comprises any modifications .within the scope of the appended claims.

What we claim is:

I. An implement. especially gantry and loading bridge. which includes: a rail carriage system comprising a plurality of rocker means. frame means including a supporting base having a plurality of supporting sections pivotally connected to the respective rocker means. and abutment means arranged in pairs on said frame means and the respective adjacent rocker means respectively and offset relative to said pivotal connections in the travelling direction of said carriage system so as to at least limit the angle of tilting of said frame means in said pivotal connections. the abutment means on said frame means being spaced from the pertaining abutment means on said rocker means by a distance permitting said rocker means to carry out oscillations relative to said frame means to compensate for unevenness caused by the rail route over which the implement is to be driven but limiting the angle oftilting ofthe implement for preventing jeopardizing the stability of the implement.

2. An implement according to claim 1. in which the abutment means cooperating with each other and per taining to one and the same pair are adjustable relative to each other.

3. An implement according to claim 1. in which at least one of the abutment means of the pairs of abutment means is so adjustable as in one position to permit the rocker means to oscillate relative to said frame means for compensating the oscillations caused by irregularities of the rail route and in another position to prevent a tilting of the frame means relative to said rocker means.

4. An implement according to claim 1. which includes hydraulic power operated means operatively connected to said pairs of abutment means and operable to move the abutment means pertaining to one and the same pair of abutment means into engagement with each other. and means associated with said hydraulic power operated means for blocking the flow of hydraulic power to thereby lock said abutment means in their respective position.

5. An implement according to claim 4, which includes pressure storage means hydraulically connected to said hydraulic power operated means.

6. An implement according to claim 4. in which each of the two oppositely located longitudinal sides of the implement is provided with the same number of hydraulic power operated means. and hydraulic pressure fluid supply means common to each two hydraulic power operated means on one and the same side of said implement.

7. An implement according to claim I. in which each pair of abutment means includes a first member con nected to a rocker means and a second member connected to said frame means. said second member having an oblong bore slidably engaged by a part of said first member. and adjusting means connected to one of said first and second members for selectively adjusting the same.

8. An implement according to claim 7. in which one of said first and second members is mounted on a rocker means. and which includes guiding means and also includes a guiding element movably guided on said guiding means. the other one of said first and second members being pivotally connected to said guiding element. and said guiding means forming a predetermined angle with the direction of the force acting upon said other member.

9. An implement according to claim I. in which said abutment means on each side of said implement are located on those end portions of said rocker means which face each other.

10. An implement according to claim I. which includes pairs of auxiliary rocker means arranged below and respectively supporting the end portions of each of said first mentioned rocker means. and auxiliary abut ment means respectively connected to said first mentioned rocker means and the respective auxiliary rocker means therebelow.

1]. An implement according to claim 1, which includes groups of superimposed auxiliary rocker means arranged below and supporting said first mentioned rocker means. and abutment means respectively arranged on said first mentioned rocker means and said auxiliary rocker means for cooperation with each other.

12. An implement. especially gantry and loading bridge. which includes:

a. a rail carriage system with a plurality of groups of wheels. the wheels of each group being connected to one another by compensating rocker means;

b. a frame means supported by main compensating rockers each of which pertaining to one of said groups of wheels in joints which form the corner points of the supporting base for said frame means;

c. pairs of abutment means one of which is arranged on said frame means and the other one of which is arranged on said compensating rocker means are offset relative to said joints in the travelling direction of said rail carriage system;

d. the abutment means of each said pair are in the normal position of said compensating rocker means spaced from each other by a distance permitting said compensating rocker means to carry out oscillations for unevenness caused by the rail route over which the implement is to be driven;

e. but limiting the angle of tilting of said frame means 8 in said joints relative to said compensating rocker means for preventing jeopardizing the stability of the implement.

l3. An implement. especially gantry and loading bridge. which includes:

f. at least one of abutment means of each said pair is so adjustable that g. in one position it permits said compensating rocker means to carry out oscillations relative to said frame means to compensate for unevenness caused by the rail route over which the implement is to be driven. and

h. in another position it prevents any tilting of said frame means in said joints relative to said compensating rocker means.

14. An implement according to claim 13, in which one abutment means of each said pair is formed by an oblong bore of a first member and the other abutment means of the same pair is a part of a second member and engages said oblong bore;

one of said first and second members being con nected to said frame means and the other one of said members being connected to the pertaining main compensating rocker.

adjusting means being connected to one of said first and second members for selectively adjusting the same.

15. An implement according to claim 14, in which said adjusting means comprises a guiding element to which is pivotally connected said first member and which is movably guided on a slide way of said frame means by means of a driving gear.

Claims

1. An implement, especially gantry and loading bridge, which includes: a rail carriage system comprising a plurality of rocker means, frame means including a supporting base having a plurality of supporting sections pivotally connected to the respective rocker means, and abutment means arranged in pairs on said frame means and the respective adjacent rocker means respectively and offset relative to said pivotal connections in the travelling direction of said carriage system so as to at least limit the angle of tilting of said frame means in said pivotal connections, the abutment means on said frame means being spaced from the pertaining abutment means on said rocker means by a distance permitting said rocker means to carry out oscillations relative to said frame means to compensate for unevenness caused by the rail route over which the implement is to be driven but limiting the angle of tilting of the implement for preventing jeopardizing the stability of the implement.

2. An implement according to claim 1, in which the abutment means cooperating with each other and pertaining to one and the same pair are adjustable relative to each other.

3. An implement according to claim 1, in which at least one of the abutment means of the pairs of abutment means is so adjustable as in one position to permit the rocker means to oscillate relative to said frame means for compensating the oscillations caused by irregularities of the rail route and in another position to prevent a tilting of the frame means relative to said rocker means.

4. An implement according to claim 1, which includes hydraulic power operated means operatively connected to said pairs of abutment means and operable to move the abutment means pertaining to one and the same pair of abutment means into engagement with each other, and means associated with said hydraulic power operated means for blocking the flow of hydraulic power to thereby lock said abutment means in their respective position.

6. An implement according to claim 4, in which each of the two oppositely located longitudinal sides of the implement is provided with the same number of hydraulic power operated means, and hydraulic pressure fluid supply means common to each two hydraulic power operated means on one and the same side of said implement.

7. An implement according to claim 1, in which each pair of abutment means includes a first member connected to a rocker means and a second member connected to said frame means, said second member having an oblong bore slidably engaged by a part of said first member, and adjusting means connected to one of said first and second members for selectively adjusting the same.

8. An implement according to claim 7, in which one of said first and second members is mounted on a rocker means, and which includes guiding means and also includes a guiding element movably guided on said guiding means, the other one of said first and second members being pivotally connected to said guiding element, and said guiding means forming a predetermined angle with the direction of the force acting upon said other member.

9. An implement according to claim 1, in which said abutment means on each side of said implement are located on those end portions of said rocker means which face each other.

10. An implement according to claim 1, which includes pairs of auxiliary rocker means arranged below and respectively supporting the end portions of each of said first mentioned rocker means, and auxiliary abutment means respectively connected to said first mentioned rocker means and the respective auxiliary rocker means therebelow.

11. An implement according to claim 1, which includes groups of superimposed auxiliary rocker means arranged below and supporting said first mentioned rocker means, and abutment means respectively arranged on said first mentioned rocker means and said auxiliary rocker means for cooperation with each other.

12. An implement, especially gantry and loading bridge, which includes: a. a rail carriage system with a plurality of groups of wheels, the wheels of each group being connected to one another by compensating rocker means; b. a frame means supported by main compensating rockers each of which pertaining to one of said groups of wheels in joints which form the corner points of the supporting base for said frame means; c. pairs of abutment means one of which is arraNged on said frame means and the other one of which is arranged on said compensating rocker means are offset relative to said joints in the travelling direction of said rail carriage system; d. the abutment means of each said pair are in the normal position of said compensating rocker means spaced from each other by a distance permitting said compensating rocker means to carry out oscillations for unevenness caused by the rail route over which the implement is to be driven; e. but limiting the angle of tilting of said frame means in said joints relative to said compensating rocker means for preventing jeopardizing the stability of the implement.

13. An implement, especially gantry and loading bridge, which includes: a. a rail carriage system with a plurality of groups of wheels, the wheels of each group being connected to one another by compensating rocker means; b. a frame means supported by main compensating rockers each of which pertaining to one of said groups of wheels in joints which form the corner points of the supporting base for said frame means; c. pairs of abutment means one of which is arranged on said frame means and the other one of which is arranged on said compensating rocker means are offset relative to said joints in the travelling direction of said rail carriage system; f. at least one of abutment means of each said pair is so adjustable that g. in one position it permits said compensating rocker means to carry out oscillations relative to said frame means to compensate for unevenness caused by the rail route over which the implement is to be driven, and h. in another position it prevents any tilting of said frame means in said joints relative to said compensating rocker means.

14. An implement according to claim 13, in which one abutment means of each said pair is formed by an oblong bore of a first member and the other abutment means of the same pair is a part of a second member and engages said oblong bore; one of said first and second members being connected to said frame means and the other one of said members being connected to the pertaining main compensating rocker; adjusting means being connected to one of said first and second members for selectively adjusting the same.