CA1166998A - Load skidding vehicle - Google Patents

Abstract

Grapple System for Log Skidder Abstract Load skidding vehicles commonly include a grapple assembly which under load conditions can pivot rearwardly about its support point resulting in disproportionate loading of the rear wheels and consequently instability of the vehicle. A connecting member is pivotally attached between the grapple and a hydraulic cylinder which is attached to the skidder.
Operation of the hydraulic cylinder causes the grapple to rotate about its support pivot. The hydraulic cylinder may be locked causing the grapple to be locked in relation to the boom assembly. During load hauling operations this mechanism is used to lock the load in a position near the vehicle resulting in increased stability. The mechanism is also of use in positioning the grapple assembly with respect to the load prior to grasping it.

Description

Grapple System for Loq Skiclder I'echnical Field This invention relates to a load skidding vehicle of the type having a load enyaging grapple, and more particularly to a mechanism for controllably positioning and releasably locking the grapple with respect to the vehicle in a number of operating positions.

Background Art In certain classes of hauling operations, such as moving harvested trees from their felling point to a collection point, there is often no feasible means of transpor~ing a load other than by dragging it behind a vehicle. This is generally accomplished either by attaching the load to ~ load skidding vehicle with a cable or by grasping the load with a grapple suspended from an elevated support boom borne by the vehicle.
Basic examples of grapple assemblies for use in load skidding applications are set forth in U.S. Patent 3,620,394 which issued to Symons et al. on November 16r 25 1971 and U.S. Patent 3,513,998 which issued to Stone et al. on May 26, 1970.
I~he prime disadvantage of existing grapple skidders as opposed to cable skidders is that design strictures of the former necessitate that the grapple be pivotally connected to its support boom at a pivot point substantially above and behind the rear axle of the skidder. This results in the load being borne by the vehicle at this pivot point, this being the first point through which the load passes which is also rigidly connected to the skidding vehicle. This loading imposed upon the skiddiny vehicle may be described by a load vector having essentially two components both of which pass through the support boom-grapple pivot point. The first, rearwardly directed from and parallel to the longitudinal axis oE
the skiddiny vehicle, is the force required to overcome friction between the load and the ground across which it is skidded. The second, vertical and downwardly directed, is that portion of the weight of the load borne by the grapple.
As this load vector passes through a rearwardly extended elevated position, a substantial overturning moment exists about the rearmost ground contacting point of a loaded skidding vehicle.
Conse~uently, current grapple skidders lose maneuverability when skidding a load. For those grapple skidders including a plurality of axles, the rearmost axle will suffer disproportionately great loading. Moreover, aside from the reduction in maneuverability there is a relatively low limit on the size of the load that can be carried with a grapple skidder. In some instances a load easily handled by a cable skidder will, if attempted with a grapple skidder of equivalent power, lift the front of the grapple skidder from the ground.
Efforts have previously been made toward the solution of these problems. One scheme involves the use of a force applying arm attached to the vehicle for applying a downward force on the loacl at a point rearwardly located from the yrapple. Activating the arm provides a reactive force tending to equalize the weight distribution on the axles of the vehicle. This development is disclosed in U.S. Patent 4,140,233 which issued to Muntjanoff et al. on February 20, 1979.
Another manner of mitigating the problems detaile~ above involves fastening a cable from the boom supported grapple to the vehicle such that the cable may be placed in tension under load con~itions and made slack under no load conditions. This results in the load being primarily carried by the cable thereby lowering the load vector and consequently decreasing the distance or moment arm from the rearmost point of skidder-ground contact to the load vector. Decreasing the moment arm decreases -the overturning momen-t resulting in increased stability. This scheme is described in U.S. Patent 3,746,193 which issued to Eaves on July 17, 1973. Among the disadvantages of this advance are the need to include a winch on the skidding vehicle and the difficulties presented in achieving free rotation of the grapple about its vertical axis owing to the at-tached cable.
~ nother problem that is common in conventional grapple type load skidding vehicles is that they permit free swinging movement of the grapple when the vehicle is travelling without a load. This movement of the grapple about its pivot point is often severe enough that the grapple comes in contact with some portion of the vehicle, occasionally resulting in damage. A means of preventing -this involves snubbing the grapple to the back of the skidding vehicle by means of a cab]e and winch assembly. Such a scheme is set forth in U.S.
Patent 3,907,137 issued to Korbel et al. on September 23, 1975. The significant disadvantages of this development are the necessity for a winch and a potentially obstructing cable.

The present invention is directed to overcoming one or more of the problems as set forth above.

Disclosure of the Invention In one aspect of -the present invention a load skidding vehicle is provided with a boom pivotally mounted thereon and a load yrasping device rotatably and pivotally connected to the boom. There is also provided a mechanism for releasably locking and controllably positioning the grasping device with respect to the boom such that the grasping device may be controllably rotated or locked against movement in a direction aligned with the longitudinal axis of the vehicle.

Brief Description of the Drawings Fig. l is a side view of a load skidding vehicle showing a load control mechanism embodying the present invention mounted on a parallelogram type grapple support assembly;
Fig. 2 is a partial top view of the load skidding vehicle and load control mechanism corresponding to Fig. l;
Fig. 3 is a partial side view of a load skidding vehicle with a load control mechanism showing forward rotation of a grapple owing to extension of the control cylinder;
Fig. 4 is a partial side view of a load skidding vehicle with a load control mechanism showing rearward rotation of the grapple owing to retraction of the control cylinder;
Fig. 5 is a partial side view of the load skidding vehicle of Fig. 4 showing downward movement of the grapple due to the extension of boom cylinder 46;

Fig. 6 is a partial side view of the load skidding vehicle of Fig. 5 showing rearward movement of the grapple due to the extension of arch cylinder 30;
and Fig. 7 is a side view of a load skidding vehicle having a load control mechanism embodying the present invention mounted on an A-frame type grapple support assembly.
Fig. 8 is a side ~iew of an additional embodiment of the present in~ention shown mounted on an A-frame type ~rapple support assembly.

Best Mode for Carrying ~ut the Invention Referring to Fig. 7, a load control mechanism is generally indicated by the reference numeral 1 and is mounted on a load skidding vehicle 2 commonly known as a "log skidder". The skidder 2 is articulated, having a ~ront end 4 and a rear end 6 joined by a multiple a~is pivotal connection 8. The front end 4 has a chassis 10 and mounted thereon are a wheel assembly 12 power providing means (not shown) and an operator's station 14 containing controls (not shown) for operating the skidding vehicle 2.
The rear end 6 has a ~hassis 16 on which are mounted a wheel assembly 18 and a mounting frame 20.
~ounted on the mounting frame 20 is a support assembly such as grapple support assembly 29 which is preferably of the "A-rame" type as shown in Flg. 7.
Alternatively, as shown in Figs. 1-6, a "parallelogram"
type grapple support assembly 29 may be used. These differ from one another in a manner well known by those skilled in the art. Vehicles 2 incorporating each of these typ~s of yrapple support 21 will be discussed concurrently, as they are very similar. Where there are differences, these differences will be noted.

The grapple support assembly 29 is attached by twin pivotal connections 22 to the rear of mounting frame 20. This support assembly 29 includes a U-shaped arch 24 having two arch legs 26 and a crossmember 28 (not shown on Fig. 7) connecting these legs 26. ~rhe arch 24 is the main support for a boom assembly 84.
Each arch leg 26 ends at its respective pivotal connection 22. An arch cylinder 30 is pivotally attached at a first end 32 to an intermediate point 34 of each arch leg 26. A second end 36 of each arch cylinder 30 is pivotally connected to one of two forward points 38 on the mounting frame 20, so located that the arch cylinders 30 are substantially parallel.
The extension of the arch cylinders 30 may be controllably increased or decreased by means well known in the art so as to cause the arch 24 to pivot about its twin pivotal connections 22.
In the "parallelogram"-type grapple support 21, a boom 40 is pivotally connected along a pivotal axis 41 to the crossmember 28 of the arch 24. In the "A-frame" type grapple support 21, the boom 40 is rigidly attached to the crossmember 28. The boom 40 extends rearwardly from the arch 24 for supporting a grasping device such as grapple assembly 42 and includes two boom arms 44 which extend rearwardly from the arch 2~.
In the parallelogram type grapple support ~1, a pair of boom cylinders 46, each having a first end 48 and a second end 50, are pivotally connected by their first ends 48 to the boom 40 and by their second ends 50 to the mounting frame 20 such that the two boom cylinders 46 are substantially parallel. The length of:
the boom cylinders 46 may be controllably increased or decreased by means well known in the art so as to cause the boom ~0 to pivot about its connection on the crossmember 28.

Pivotally attached a-t a rear pivot point 52 on -the aftmost portion of the boom 40 is the grapple assembly 42. The grapple assembly 42 includes a rotator 54 Lor rotatably positioning the grapple assembly ~2, grapple arms 56 dependiny from the rotator 54 for grasping loads, a vertical extender 58 attached to the rotator 54, and means (not shown) for controllably opening and closing the grapple arms 56.
rrhe rear pivot point 52 passes through the vertical extender 58.
The vertical extender 58 is pivotally attached to the uppermost portion of the grapple assembly 42 so as to allow the grapple assembly 42 to rotate with respect to the vertical extender 58 along an axis parallel to the longitudinal axis of the load skidding vehicle 2. A pivot point 60 for a connecting member 62 is located on the vertical extender 58 a distance above the rear pivot point 52. This distance must be sufficiently great as to allow the force appliecl through the connecting member 62 to create a moment about the rear pivot point 52 sufficient to counter the opposite moment induced by a skidded load without allowing appreciable pivotal movement of the grapple 42 about the rear pivot point 52.
The connecting member 62 is connected at a first end 64 to pivot point 60 and at a second end 66 to a pivot point 68. Connecting member 62 must be of sufficient rigidity to withstand the compressive loading necessary to counter the moment of the load vector. It is additionally beneficial to orient pivot points 60 and 68 with respect to the rear pivot point 52 and the arch 24-boom 40 connection such that these four points approximately define the corners of a parallelogram.

.

At pivot point 68 the connecting me:mber 62 is attached to an upper aft portion of an equalizing link 70. The equalizing link 70 has a lower central point 73 at which it is connected to an upper central point 72 of the crossmember 28. A hydraulic control cylinder 74, having a first end 76 and a second end 78, is pivotally connected by its first end 76 to a central forward point 80 on the equalizing link 70. The equalizing link 70 has the function of rigidly lQ maintaining the distances bet~een the pivots at 68,72 and 80 such tha,t wikh the arch 24 locked in position (and consequently point 72 is locked since point 72 is fixedly attached to arch 24) a force may be transmitted from the control cylinder 74 to the connecting member 62.
The control cylinder 74 is pivotally attached at its second end 78 to the mounting frame 20 so that it lies in a ~ertical plane passing through the longitudinal axis of the load skidding vehicle 2.
Means (not shown) well known in the art is provided for operating the control cylinder 74 such that the distance from the first end 76 of the control cylinder 74 to the second end 78 may be increased, decreased, maintained at a set length or permitted -to float (that is, to vary with~minimal resistance). Like means is included for controlling the boom cylinders 46 and the arch cylinders 30.
It is apparent from the above described embodiments that a fluid jack 86 could be connected immediately intermediate the vertical extender 56 and the grapple support 21. Such an embodiment is shown in Fig. 8~ The ~luid jack 82 has first and second ends 88j90, and is connected by the first end 88 to the vertical extender 56 and by the second end 90 to the upper central point 72 of the crossmember 28.

g Industrial Applicability The present invention provides a solution to the difficulties inherent to load skidding vehicles with freely pivotable load engaging means. The present embodiment provides means for permitting the grasping device-boom 40 combination, for the purposes of skidding operations r to be made e~uivalent to a single rigid member. The load vector will then pass through a point lower khan the rear pivot point 52 resulting in a smaller moment about the rear wheel assembly 18 consequently yielding a more even distribution of the load between the axles of the load skidding ~ehicle 2.
In the preferred embodiment of this invention selective immobilization of the grapple 42 with respect to the boom 40 is achieved by fixing in relation to the work vehicle 2 two separated points 52,60 on the grapple assembly 42. While fixing the location of but a single pivot will not prevent rotation about that pivot, fixing the locations of two non-colinear pivots will prevent rotation about either pivot.
The means 62,70,74 for immobilizing the grapple assembly 42 can assume embodiments other than that considered the best mode. For example, the grapple-boom connection 52 could be a pin-type pivot (as shown in Figs. 1 and 2) wi~h means added for selectively increasing the friction between the pin and the two members connected to it to the point where no rotation is possible under the loadings anticipated.
Operation o~ the load control mechanism 1 that constitutes the advance of this load skidding vehicle 2 over existin~ designs is achieved through operation of the control cylinder 74. Contxollable rotation of the grapple assembly 42 about its rear pivot point 52 is obtained by increasing or decreasing the length of the control cylinder 74. This causes the central forward pivot point 80, direc-tly attached to the control cylinder 74, to move, respectively, away from or toward the mounting frame 20. This serves to rotate the equalizing link 70 about the pivot point 68 respectively toward or away from the grapple assembly 42. This forces the connecting member 62 to move rearwardly or forwardly, respectively, resulting in rotation of the grapple assembly 42 about the rear pivot 52 toward or away from t~e skidder 2, respecti~ely. Fig. 3 illustrates the grapple assembly 42 in a forwardly rotated position resulting from extendi~ the control cylinder 74. ~lg. 4 illustrates the grapple 42 in a rearwardly rotated position resulting from retracting the control cylinder 74.
Once the grapple assembly 42 has been rotated to the desixed angle it may be locked in position.
With the boom assembly 26 locked (achieved by locking the arch cylinders 30 and also, for the parallelogram-type grapple support 21, the boom cylinders 46), locking the control cylinder 74 results in fixing the position of the equalizing link 70 with respect to the load skidding vehicle 2~ This immobllizes the position of the pivot point 68 thereby locking the position of the connecting member 62. Once this is done, ~he locations with reference to the load skidding vehicle 2 of the pivot points 60 and 52 are fixed and consequently the ~rapple assembly 42 is not free to rotate.
The broad positional flexibility of the grapple assembly 42 is a major feature o~ the present embodiment. This is achieved through the combination of the controllable rotation of the grapple assembly 42 about the rear pi~ot point 52, detailed above, with the up and down fore and aft positioning capabilities of the parallelogram-type grapple support assembly 29, the lat-ter being well known in the art. Fore and aft movement o~ the grapple assembly 42 is achieved through control of the arch cylinders 30; extending the arch cylinders 30 causes movernent of the grapple assembly away from the vehicle 2, while retracting the arch cylinder 30 will result in movement toward the vehicle

2. ~n the parallelogram-type grapple support assembly 29, the elevation oE the grapple assembly 42 is altered through control of the boom cylinders 46. Retraction of the boom cylinders 46 will raise the grapple assembly 42 while extension of the boom cylinders 46 will lower it.
A description of the use of the grapple assembly 42 and grapple support assembly 29 to free the vehicle 2 when mired in mud will serve to illustrate the positional capabilities of the present invention.
The following description is applicable to the parallelogram-type grapple support assembly 29.
Consider the initial grapple assembly 42-work vehicle 2 orientation shown in Fig. 3, a forwardly rotated upper forward position. This is achieved by retracting both the arch cylinder 30 and the boom cylinders 46 while extending the control cylinder 74. From this position, the grapple assembly 42 is rotated away from the vehicle 2 by retracting the control cylinder 74 as illustrated in Fig. 4. Next, the boom cylinders 46 are extended until the grapple assembly 42 is pressed firmly into the mud as shown in Fig. 5. Lastly, using the locked grapple assembly 42 as an anchored point the arch cylinders 30 are extended forcing the grapple assembly 42 to move rearwards with respect to the worlc vehicle 2, or, as is reality, the work vehicle 2 to move forward in relation to the anchored grapple assembly 42. The result is shown in E'ig. 60 A prime advantage is the improvement imparted to the load handling characteristics of a load skiddiny vehicle. This improvement is achieved by grasping the load with the grapple assembly 42, positioning it as near the rear of the vehicle as possible, and locking the grapple assembly 42 in this position. This positioning may be achieved in one of two ways: if the load is suf~iciently light the control cylinder 74 and connecting member assembly 62,58,70 may be used to rotate the grapple and its load toward the rear of the vehicle; or, with heavier loads, the load control mechanism 1 may be placed in float and the vehicle 2 then backed toward the load until the position of the grapple assembly 42 is as desired at which point the grapple assembly 42 is locked.
A summary of the advantages detailed in this application over conventional skidders are as follows-1) For gi~en loading there is improved maneuverability.
2) The skidder is capa]ble o handling a greater total load.

3) When travelling in a no load situation the grapple can be locked to prevent it from swinging along the direction of the longitudinal axis of the skidder.

4) When the skidder becomes stuck in swampy or muddy areas the grapple assembly can be locked, lowered to the ~round and used to push the vehicle forward.

5) In the preferred embodiment o this invention the vertical axis of the grapple can be controllably rotated about the grapple~boom pivot point in the vertical plane passing through the longitudinal axis of the vehicle thereby providing for greater positional 1exibility.

6) The load control rnechanism 1 when embodied as the parallelogram linkage described previously maintains an essentially constant grapple orientation so long as the control cylinder 74 is of constant extension.
The invention herein described is not limited to use with parallelogram type and A-frame type boom assemblies such as those illustrated, but is equally applicable to other types of boom assemblies.
It should be understood that the load skidding vehicle can assume many other configurations without departing from the claims. Other aspects, objects and advantages of this invention can be obtained from a study of the drawings, the disclosure and the appended claims.

Claims

Claims 1. In a vehicle having a chassis, a support assembly mounted on and extending rearwardly from said chassis and log engaging means for lifting one portion of a log with another portion of the log remaining in contact with the ground while said chassis is moved in a forwardly direction, said log engaging means being pivotably connected to said support assembly, the improvement comprising:
means for hydraulically releasably locking said log engaging means with respect to said support assembly and for controllably maintaining said log engaging means against movement relative to the chassis in both a direction toward said chassis and an opposed direction away from said chassis.

2. The vehicle, as set forth in claim 1 wherein the locking means controllably locks and maintains said log engaging means at any desired position relative to the chassis, said position being selected in response to the magnitude of the load and forces expected to be exerted on the log during movement of the log by the vehicle.

3. The vehicle, as set forth in claim 1, wherein said locking means includes a hydraulic cylinder.

4. The vehicle, as set forth in claim 3, wherein said locking means is effective to controllably position said log engaging means about an axis substantially horizontal and perpendicular to the longitudinal axis of said vehicle.

5. The vehicle, as set forth in claim 4, wherein said log engaging means includes a grapple.

6. The vehicle, as set forth in claim 1, wherein said locking means further includes a connecting member having opposite ends pivotally attached at a first end to said log engaging means, and means for releasably locking a second end of said connecting member with respect to said chassis.

7. A log skidding vehicle, comprising:
a chassis;
a support assembly mounted on said chassis;
log engaging means for lifting one portion of an article and moving said article with another portion of the article being in contact with the ground, said load engaging means being pivotally connected to said support assembly about a substantially horizontal axis;
and, means for releasably locking against pivotability about said substantially horizontal axis said load engaging means.

8. The log skidding vehicle, as set forth in claim 7, wherein said locking means is adapted to controllably position said log engaging means about said substantially horizontal axis.

9. The log skidding vehicle, as set forth in claim 7, wherein said locking means comprises:
a connecting member having opposite ends pivotally attached at a first end to said log engaging means; and means for releasably locking a second end of said connecting member with respect to said log skidding vehicle.

10. The log skidding vehicle, as set forth in claim 9, wherein said means for releasably locking said connecting member includes a fluid motor having a first end and a second end pivotally attached to said chassis.

11. The log skidding vehicle, as set forth in claim 10, including an equalizing link pivotally attached to said connecting member and separately pivotally attached both to said first end of said fluid motor and to said support assembly.

12. The log skidding vehicle, as set forth in claim 11, wherein said fluid motor is a hydraulic cylinder.

13. The log skidding vehicle, as set forth in claim 12, including a vertical extender for pivotally connecting at a pivot point said connecting member to said log engaging means, said extender being laterally pivotably attached to said log engaging means such that it provides a location for said pivot point spaced a vertical distance above a rear pivot point where said log engaging means and said support assembly connect.

14. The log skidding vehicle, as set forth in claim 13, wherein said log engaging means is a grapple assembly.

15. The log skidding vehicle, as set forth in claim 17, wherein said locking means includes a controllable fluid cylinder having a first end and a second end, said first end being connected to said log engaging means and said second end being connected to said support assembly.

16. A log skidding vehicle comprising:
a chassis;
an arch pivotally joined at a connection to said chassis;
at least one arch cylinder pivotally mounted by a first end to said arch and by a second end to said chassis;
a boom, with at least one forwardly projecting boom arm, pivotally attached at a pivotal connection to said arch;
a boom cylinder pivotally mounted by a first end to said boom arm and by a second end to said chassis;
a grapple assembly pivotally connected at a rear pivot point to an aft position on said boom;
means for rotatably positioning in a controlled manner said grapple assembly about said rear pivot point; and means for locking said grapple assembly in any rotated position about said rear pivot point.

17. A method for transporting a log with log engaging means which is pivotally connected about a pivot axis to a support assembly extending rearwardly from and being mounted to a vehicle, said method comprising;
grasping a log lying on the ground with said log engaging means;
elevating one end of said log above the ground with said log engaging means while permitting the other end of the log to rest on the ground;
pivoting the log engaging means and the grasped log in either desired direction toward or away from the vehicle about the pivot axis through a desired arcuate distance; and moving said vehicle in a forwardly direction.

18. The method of claim 17 wherein said vehicle has an extendable fluid jack one end of which is connected to the log engaging means, said pivoting comprising:
supplying pressurized fluid to the fluid jack to pivot the log engaging means in the desired direction.

19. The method of claim 18 wherein said vehicle has a rear and a front ground engaging member respectively disposed adjacent and remote from said log engaging means, said log engaging means being pivoted in the direction for maintaining engagement between the ground and all the ground engaging members.