Abstract:
A spring bias safety trip mechanism for holding a ground working tool in a fixed position with respect to a support frame is disclosed herein. The spring bias safety trip mechanism consists of a plurality of links that are interconnected in such a manner that the links act as a rigid bar between the frame and standard and collapse when excessive forces are encountered by the standard. The spring biased linkage system is designed to eliminate the need for large springs that must produce sufficient forces equal to the normal forces encountered during the normal earthworking operation.

Description:
BACKGROUND OF THE INVENTION 
     Tillage implements having safety trip mechanisms for protecting an earthworking tool against damage when an obstruction is encountered have been well known in the past. These units can normally be placed in two general categories. The first category consists of safety trip mechanisms which will automatically reset the earthworking tool with respect to the frame after the earthworking tool has cleared the obstruction. The other type of safety trip mechanism may be referred to as a manual reset type of unit which is operated when an obstruction is encountered and the operator must then perform some operation to return the ground or earthworking tool to its operative position. 
     Both of these types of units again may be categorized into two general categories. The first of these categories may be referred to as a pneumatic safety trip mechanism while the second category consists of spring biased safety trip mechanisms. 
     Examples of spring type trip mechanisms are shown in U.S. Pat. No. 3,662,839, issued May 16, 1972; U.S. Pat. No. 2,860,564, issued Nov. 18, 1958; and U.S. Pat. No. 2,756,659, issued July 31, 1956. 
     The known type of spring biased trip mechanisms require either an extremely large spring that produces a force greater than the forces acting on the tool or an extremely complicated camming mechanism or both. Both types of spring trip mechanisms, as well as the pneumatic system discussed above, are fairly expensive and, thus, manufacturers of earthworking tools are constantly striving toward producing a better mechanism which is capable of being produced at a reduced cost without sacrificing any benefits gained from the unit during operation. 
     SUMMARY OF THE INVENTION 
     The trip mechanism of the present invention may be referred to as a spring biased mechanism in which a plurality of simple links are interconnected in such a manner that they will act as a rigid unit during normal operation and will automatically collapse when a predetermined force is applied thereto. The links are arranged in such a manner that only a small spring force is required for holding the links in a normal operative position. Stated another way, the trip mechanism of the present invention consists of a plurality of links that are interconnected and spring biased to produce an overcenter toggle linkage incorporating a small spring which need only be compressed a small amount to allow the earthworking tool associated therewith to move to a tripped position. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     FIG. 1 is a side view of an earthworking tool having the present invention incorporated therein; 
     FIG. 2 is a fragmentary enlarged view of a portion of the earthworking tool; 
     FIG. 3 is a plan view of the trip mechanism as viewed along line 3--3 of FIG. 2; 
     FIG. 4 is an enlarged section of the trip mechanism as viewed along line 4--4 of FIG. 2; 
     FIG. 5 is a sectional view, as viewed along line 5--5 of FIG. 3 showing the first movement of the linkage; and 
     FIG. 6 is a side elevation view of the trip mechanism in a tripped position, with certain parts broken away for clarity. 
    
    
     DETAILED DESCRIPTION 
     While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail a preferred embodiment of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiment illustrated. 
     Referring now to FIG. 1 of the drawings, the trip mechanism of the present invention is illustrated in use with a moldboard plow type of earthworking implement 10. It is to be understood that the trip mechanism could also be used with other types of earthworking implements or tools, such as cultivators. 
     Earthworking tool 10 includes a main frame 12 that has a hitch structure 16 at the forward end thereof for attachment to a vehicle. A rear wheel (not shown) of the earthworking tool or plow is preferably connected by a linkage 18 to the frame 12 and is movable relative thereto by a fluid ram 20. 
     Main frame 12 also has a plurality of depending beams 22 rigidly secured thereto and forming a part thereof. A standard 24 is pivotally supported on each of the beams 22 by a pivot pin 26. Each standard 24 has a moldboard plow bottom 25 secured thereto and a coulter blade 27 associated therewith. 
     Standard 24 and moldboard bottom 25 are held in an earthworking position illustrated in FIGS. 1, 2 and 5 by a trip mechanism 28 that is constructed in accordance with the teachings of the present invention and is illustrated in FIGS. 2 and 3. Trip mechanism 28 consists of a first link 30 having an opening 32 at one end for receiving a pin 34 to pivotally support link 30 on frame 12. Trip mechanism or spring biased linkage means 28 also includes a second link 36 having an opening 38 at one end which receives a pin 40 to pivotally support second link 36 on standard 24. Thus, pin 34 defines a first pivot for first rigid link 30 on frame 12 while pin 40 defines a second pivot for second rigid link 36 on standard 24. 
     Trip mechanism 28 also includes a spring biased linkage mechanism 44 that defines a first position for first and second links 30 and 36, which is illustrated in FIG. 2. Spring biased mechanism 44 includes a third rigid link 46 that has one end connected to first link 30 by a pin 48 which defines a first pivotal connection of third link 46 to the free end of link 30. The opposite end of rigid link 46 is connected by a pin 50 to the free end of second link 36 and defines a second pivotal connection. 
     Before describing the remainder of the structure, it should be noted that in the specific embodiment illustrated, first link 30 (FIGS. 3 and 4) consists of a single member that is located between a pair of spaced parallel plates 54 which are rigidly secured to frame 12, as by welding, to form a part of frame 12. Preferably, suitable washers 56 are interposed between link 30 and plates 54. Third link 46 consists of a pair of short members 60 that are respectively located on opposite sides of link 30 and extend parallel thereto. Likewise, second link 36 consists of a pair of members 62 which again extend parallel to each other and are located on opposite sides of members 60 defining third link 46. While second and third link 36 and 46 each consist of a pair of members, they will subsequently be referred to as individual links. 
     According to the present invention, pin 50 defining the pivotal connection between second and third links 36 and 46 extends through an enlarged opening 70 located intermediate opposite ends of first link 30. Opening 70 is substantially larger than the size of pin 50, for a purpose that will be described later. 
     Also, spring biased linkage mechanism 44 includes a stop member 72 that is adapted to be biased into engagement with link 36 by spring means 74. As most clearly shown in FIG. 5, spring means 74 consists of a bolt 76 that extends through an opening in stop member 72 and through an enlarged opening 78 in a cup shaped member 80 that is rigidly secured to first link 30, as by welding. A coil spring 82 is positioned over bolt 76 and a washer 84 and nuts 86 are received on the free end of bolt 76. Thus, coil spring 82 engages cup 80 at one end and washer 84 at the opposite end and the compression of coil spring 82 can readily be varied by the use of nuts 86. 
     Spring means 74 will normally urge the three links to the position illustrated in FIG. 2 wherein stop means 72 engages second link 36 and the three links all extend generally parallel to each other. In this position, the center of pin 50 is located on one side of a plane P extending through the centers of pins 34 and 40 while pin 48 is located on the opposite side. The position of the three links 30, 36 and 46 illustrated in FIG. 2 is the first position for trip mechanism 28 which maintains standard 24 in an earthworking position with respect to frame 12. In this first position for links 30, 36 and 46, it will be noted that all three links extend generally parallel to each other and third link 46 is located between the overlapping portions of links 30 and 36. 
     In this position, the center of pivot pin 48, defining the first pivotal connection between links 30 and 46, is in very close proximity to plane P, and in certain instances, may in fact be located directly on plane P, but can never be located on the same side of plane P as pivot pin 50. In the position of spring biased linkage means 28 shown in FIG. 2, only a small force is necessary to maintain the linkage in the position illustrated while the linkage system is capable of resisting large forces developed on standard 24. The ability of utilizing a very small force as the spring force for the linkage system results for the fact that pivot pin 48 is located in close proximity to plane P. 
     When excessive forces are developed on standard 24 resulting from an obstruction for bottom 25, the spring force of coil spring 82 will be overcome and the initial movement of the linkage system will result in a small amount of pivotal movement of link 36 about pivot pin 40. During this initial movement, pivotal connection 50 will be moved from the position illustrated in FIG. 2 to that illustrated in FIG. 5 where it is clearly shown that both pivot pins 48 and 50 are now located on the same side of plane P. When pivotal connection 50 reaches the opposite side of enlarged opening 70, it will subsequently define the primary pivot between first and second links 30 and 36 during subsequent pivotal movement of the links about their respective pivots ultimately to the position illustrated in FIG. 6 wherein the standard 24 has been pivoted upwardly a sufficient amount to allow moldboard bottom 25 to pass over the obstruction. 
     After passing over the obstruction, it is only necessary for the operator to raise the main frame 12 to the position where all of the bottoms 25 are located above the ground during which time the weight of standard 24 and bottom 25 will cause the linkage to return to the first position illustrated in FIG. 2. 
     As can be appreciated from the above description, the spring biased linkage means or trip mechanism is extremely simple in construction and allows for the use of a small coil spring 82 which is never compressed any substantial amount. Since there is only limited relative movement between cup 80 and stop member 72, the amount of movement being illustrated by the respective positions of these elements in FIGS. 2 and 5, the service life of the coil spring is extended substantially. 
     By way of example and not of limitation, the coil spring incorporated into the trip mechanism of the present invention need only develop forces in the neighborhood of 400 pounds in order to provide sufficient resistance for holding a standard size moldboard bottom in an earthworking position and resisting forces on the bottom of at least 4,000 pounds.