Articulating log loading boom

Abstract

 A relatively small range of relative movement between the inner boom 10 and the outer boom 12 of an articulated log loader and the problems associated therewith may be avoided through the use of links (32) having spaced pivot pins (34,35) respectively connected to adjacent ends of an inner boom (10) and an outer boom (12) along with meshed sector gears (39,40) which act to synchronize relative movement between the inner boom (10') and the outer boom (12') upon operation of a hydraulic cylinder (20') inter-connecting the two.

Description

[0001] This invention relates to articulating booms and more particularly to an articulating boom for loading logs.

[0002] Articulating booms usually consist of an inner and an outer boom. These booms are connected by a hydraulic cylinder which causes the outer boom to rotate with respect to the inner boom. The inner boom is conventionally connected by a hydraulic cylinder to a base and is allowed to pivot with respect to the base by action of the hydraulic cylinder. A grapple is typically located on the remote end of the outer boom. This allows the articulating boom to pick up and move heavy objects, such as logs, from one position to another. In a typical application, the articulating boom is used to load logs onto a truck for transportation and later to take the logs off the truck for delivery at a mill.

[0003] A typical prior art construction has a couple of problems. The rotation between the upper boom and lower boom is limited to approximately 161° for a variety of reasons. To obtain this amount of rotation, the pivot point of the two booms must be placed substantially below the centerline of the boom structure. This creates a more complex design. Another problem of note is that the moment arm which can be applied to the outer boom is considerably less when the outer boom is fully retracted than when it is fully extended. This effectively limits the lifting capacity of the loader in certain configurations.

[0004] The limited relative motion between the inner and outer booms results in an inability to properly position logs close to the mast of the loader. Boom operators have developed a variety of techniques for getting around this limitation. One is the practice of swinging the grapple while loaded with wood toward the mast and the operator while simultaneously opening the grapple to release the wood. Rather than simply dropping the load in the desired location, this method literally "flings" the load in the desired direction, which can result in the load undesirably scattering when it impacts the truck bed, mast or the like.

[0005] Another problem occurs when trying to lift logs close to the mast of the loader. The relatively small moment arm effectively limits the lifting capability which makes it difficult to unload logs near the mast.

[0006] Several designs have been developed to overcome these shortcomings. These designs are capable of relative motion to 175° and even greater while retaining acceptable moment arms. However, these designs have not been well received because they require multiple additional links, an additional number of pins and other added parts. The additional parts result in increased maintenance cost. A further drawback is that these designs require additional space which reduces the potential payload capacity.

[0007] It is an object of the invention to provide an improved articulated log boom. More specifically, it is an object of the invention to provide an articulated log boom with inner and outer booms that may be rotated relative to one another over an increased arc while maintaining an acceptable moment arm in connection with a motor or the like for moving the booms so as to maximize lifting capacity and which is simple in construction to provide for economic manufacture and long life.

[0008] An exemplary embodiment of the invention achieves the foregoing object in a construction for an articulating boom that includes an inner boom, an outer boom near an end of the inner boom and a short link extending between the adjacent ends of the inner and outer booms. A first pivot connects the link to an end of the inner boom and a second pivot spaced from the first pivot connects the link to the end of the outer boom. A motor is located to interconnect the booms and is operable to effect relative movement between the booms. The structure is completed by a synchronizing mechanism interconnecting the adjacent ends of the boom so that when the motor effects relative movement between the booms, the outer boom will swing about the adjacent end of the inner boom about the first and second pivots and the link will swing about the inner boom about the first pivot. This construction increases the arc of relative movement between the inner and outer booms while maintaining an acceptable moment arm that provides good lifting capacity without requiring an overly large motor. The structure is simple and therefore economically manufactured and maintained to promote long life.

[0009] In a preferred embodiment, the synchronizing mechanism is a set of mating gears. In a highly preferred embodiment, the gears have equal pitches.

[0010] In one embodiment, one of the gears is centered on the first pivot and the other of the gears is centered on the second pivot.

[0011] In a highly preferred embodiment of the invention, the first and second pivots are on the centerlines of respective ones of the booms.

[0012] Preferably, the outer boom has a grapple connected to a remote end thereof.

[0013] According to the invention, the motor is preferably a hydraulic cylinder.

[0014] In one embodiment of the invention, an upright mast is provided which has a post and a base. The base is rotatable about the post in a horizontal plane through 360° so that the boom can be rotated through 360°.

[0015] Preferably, the upright mast is located on a movable platform.

[0016] Other objects and advantages will become apparent from the following specification taken in connection with the accompanying drawings, in which:

Fig. 1 is a somewhat schematic, fragmentary elevation of a prior art boom;

Fig. 2 is a side elevation of a vehicle mounted boom made according to the prior art which illustrates certain of the problems encountered with the use of the same;

Fig. 3 is a view similar to Fig. 1 but illustrating an articulated boom construction made according to the invention with the boom fully extended;

Fig. 4 is a view similar to Fig. 3 but illustrating the outer boom fully retracted; and

Fig. 5 is a view similar to Fig. 2, illustrating how the problems of the prior art construction are overcome through use of the invention.

[0017] Figure 1 shows one prior art design of an articulating log loader boom. The inner boom 10 is connected to the outer boom 12 by side-by-side flanges 14 (only one of which is shown). Each flange 14 mounts a pair of pivot pins 16,18. The outer boom 12 and the inner boom 10 pivot relative to each other about the pin 16 while the pivot pin 18 is connected to the rod end 19 of a hydraulic cylinder 20. When the rod end 19 of the hydraulic cylinder 20 is extended or retracted, the outer boom 12 pivots with respect to the inner boom 10 about the pivot 16. The cylinder end 21 of the hydraulic cylinder 20 is pivotally connected to a pivot collar 22 on the inner boom 10 via a pivot pin 24. Another hydraulic cylinder 27 (Fig. 2) is connected to the pivot pin 26 and to a base, generally designated 30, as seen in Figure 2. This cylinder pivots the inner boom 10 with respect to the base 30 around a pivot 28. The articulating boom also includes a grapple 31 at the end of outer boom 12. Returning to Fig. 1, dimension D1 shows the moment arm generated between the inner and outer booms 10 and 12 by the hydraulic cylinder 20 when the outer boom 12 is fully extended. Dimension D2 shows the rather minuscule moment arm over which the hydraulic cylinder 20 operates when the outer boom 12 is fully retracted.

[0018] Fig. 2 illustrates one of the difficulties that arises from the limited relative motion attainable between the inner boom 10 and the outer boom 12 as mentioned previously. Because of the limited relative motion, the grapple 31 cannot be moved any closer to the base 30 than illustrated in Fig. 2, even when the outer boom 12 is fully retracted. Consequently, loading logs adjacent the base 30 is difficult.

[0019] Furthermore, when one considers the relatively small moment arm D2 (Fig. 1) over which the cylinder 20 operates when the outer boom 12 is fully retracted, it will be readily appreciated that the load lifting capacity of the grapple 31 is at a minimum when the grapple 31 is in a position illustrated in Fig. 2, thereby making it extremely difficult to unload the logs.

[0020] One embodiment of the invention is illustrated in Figs. 3 and 4 and in the interest of brevity, identical, but primed, reference numerals are used on their counterparts heretofore described in connection with the description of the prior art. Thus, in the description that follows, the inner boom is 10' while the outer boom is 12', etc.

[0021] The inner boom 10' is connected to the outer boom 12' by a single link 32 on the centerlines of the boom. The link has two spaced pivot pins 34 and 35. The pivot pin 34 connects the link 32 to the outer boom 12 while the pivot pin 35 connects the link 32 to the inner boom 10'.

[0022] Alternatively, a pair of the links 32 can be employed, one on each side of the booms, with the pivot pins 34,35 extending through the two booms 10',12' and the two links 32.

[0023] As can be appreciated by a comparison of Figs. 3 and 4, the use of the links 32 allow movement of the outer boom from a position such as shown in Fig. 3 wherein the centerlines 36 and 37 of the inner and outer booms 10',12', respectively are geometrically congruent to one wherein they are almost parallel but spaced a distance approximately equal to the distance between the centerlines of the pivot pins 34,35.

[0024] In order to assure proper folding of the outer boom 12' upon the inner boom 10' when the former is moved to its fully retracted position, a synchronizing means, generally designated 38, interconnects the adjacent end of the booms 10' and 12'. In the preferred embodiment, the synchronizing mechanism is in the form of a pair of mating sector gears 39,40. The sector gear 39 is a affixed to the outer end of the inner boom 10' while the sector gear 40 is affixed to the inner end of the outer boom 12'. That is to say, the sector gears 39 and 40 are affixed to adjacent ends of the inner and outer booms 10',12' and with their centers on the pivot pins 35 and 34 respectively.

[0025] In addition, the sector gear 40 includes a depending tongue 42 which captures a pivot pin 44. The pivot pin 44 is connected to the rod end 19' of the hydraulic cylinder 20'. The cylinder end 21' of the hydraulic cylinder 20' is connected to a pivot collar 22' by a pivot pin 24'.

[0026] When the hydraulic cylinder 20' is extended or retracted, the outer boom 12' pivots about the pivot axis defined by the pivot pin 34. At the same time, by reason of the mating sector gears 39,40, the pivot axis defined by the pivot pin 34 translates in an arc about the pivot axis defined by the pivot pin 35. In a preferred embodiment, the sector gears 39 and 40 are of equal pitch diameter. As a consequence, for each 2° of rotation from the position shown in Fig. 3 undergone by the outer boom 12', the links 32 will pivot 1° in the same direction. In some instances, however, it may be desirable to increase or decrease the rates of relative pivotal movement of the outer boom 12 and links 32 in which case, different pitch diameters for the sector gears 39,40 will be selected.f

[0027] As seen in Fig. 5, the inner boom 10' is pivoted by a pivot pin 28' to an upright boom mast, generally designated 50. The mast 50 includes a base 46 mounted on the upper end of a post 48. Preferably, the base 46 is journaled on the post 48 for rotation about a horizontal axis and in a horizontal plane through a full 360°. A hydraulic motor (not shown) is typically employed to drive the base 46 about the aforementioned vertical axis.

[0028] The pivot collar 22' also mounts a pivot pin 26' which is connected to the rod end of a hydraulic cylinder 45. The opposite end of the cylinder 45 is connected via a pivot pin 49 to the base 46. Consequently, the inner boom 10' may be elevated or lowered about the pivot pin 28' by appropriate operation of the cylinder 45.

[0029] Typically, but not always, the entire boom assembly, including the post 48 is mounted to the bed of a truck 52.

[0030] It will be observed that the spacing between the booms 10',12' provided by the links 32 between the pivot points 34 and 36 provide for greater rotation of the outer boom 12' relative to the inner boom 10', in the preferred embodiment 175° or more, than the prior art structure shown in Fig. 1. Moreover, the use of the links 32 allow the pivot pins 34 and 36, and the pivot axes defined thereby, to be located on the centerline of the inner boom 10, and 12, respectively. This provides a simpler design than in the prior art, allowing elimination of the flanges 14.

[0031] It will also be appreciated from a comparison of Fig. 1 on the one hand and Figs. 3 and 4 on the other hand that the use of the links according to the invention provide a greater, and more uniform moment arm throughout the range of movement of the outer boom 12' relative to the inner boom 10'. By way of example, when the outer boom 12' is fully extended, the motor arm is illustrated as D7 in Fig. 3 whereas, when the outer boom 10' is fully retracted, relatively large moment arms D8 and D9 will be present. This in turn allows the boom of the present invention to be constructed with a smaller cylinder 20' than the cylinder 20 (Fig. 1) that would be required in the prior art construction to have the same lifting capacity.

[0032] Viewing Fig. 5, it will be readily appreciated that with the increased range of movement provided by the invention, the grapple 31' can be brought into much closer proximity to the mast 50 to facilitate full loading of the truck 52 in the area of the mast 50, something that is not easily accomplished with the prior art structure. And, as mentioned previously, unloading at this location is efficiently accomplished because of the greater moment arm D8,D9 in an embodiment of the invention than the moment arm D2 of the prior art structure.

[0033] Finally, the boom of the invention is not limited to log loading users but may find utility in other material handling operations.

Claims

1. An articulating boom comprising:
   an inner boom;
   an outer boom near an end of said inner boom;
   a short link extending between the adjacent ends of said inner and outer boom;
   a first pivot connecting said link to the end of said inner boom;
   a second pivot spaced from said first pivot and connecting said link to the end of said outer boom;
   a motor interconnecting said booms and operable to effect relative movement between the booms; and
   a synchronizing mechanism interconnecting said ends so that when said motor effects said relative movement, said outer boom will swing about said adjacent end of said inner boom about said first and said second pivots and said link will swing about said inner boom about said first pivot.

2. An articulating boom comprising:
   an upright mast;
   an inner boom pivoted at one end to said mast;
   an outer boom near the end of said inner boom remote from said mast;
   a short link extending between said remote end and an adjacent end of said outer boom;
   a first pivot connecting said link to said remote end;
   a second pivot spaced from said first pivot and connecting said link to said adjacent end;
   a motor interconnecting said booms and operable to effect relative movement between the booms; and
   a synchronizing mechanism interconnecting said remote end and said adjacent end so that when said motor effects said relative movement, said outer boom will swing about said remote end about first and said second pivot and said link will swing about said inner boom about said first pivot.

3. The articulating boom of Claim 1 or Claim 2, wherein the synchronizing mechanism is a set of mating gears.

4. The articulating boom of Claim 3, wherein said gears have equal pitches so that there is equal angular movement about the pivots.

5. The articulating boom of Claim 3 or Claim 4, wherein one of said gears is centered on said first pivot and the other of said gears is centered on said second pivot.

6. The articulating boom of any preceding claim, wherein said pivots are on the centerline of the booms.

7. The articulating boom of any preceding claim, wherein the outer boom has a grapple connected to a remote end of said outer boom.

8. The articulating boom of any preceding claim, wherein the motor is a hydraulic cylinder.

9. The articulating boom of Claim 2, wherein the upright mast has a post and a base, the base being rotatable about the post in a horizontal plan so that the articulating boom can be rotated through 360°.

10. The articulating boom of Claim 2, wherein the upright mast is located on a movable platform.

11. An articulating boom comprising:
   a base mounted on an upright mast and rotatable thereabout, having upper and lower pivots;
   a long lower boom pivoted at one end to said upper pivot of said base;
   a short link consisting of two connecting members each having two pivot points spaced from each other, one member pivoting from a front side of the remote end of said lower boom and the other member pivoting from a back side of the remote end of said lower boom;
   a long outer boom pivoting about the remote ends of said members, so that the inner boom and outer boom are in the same plane, said outer boom having a grapple at the remote end of said outer boom;
   a set of mating gears, one mating gear affixed to the remote end of said lower boom, the second mating gear affixed to an adjacent end of said outer boom;
   a pair of hydraulic cylinders, one cylinder connected at one end to said lower pivot of said base the other end pivoting about a flange affixed to said inner boom, a second hydraulic cylinder pivoting about said pivot flange and at the other end pivoting about a flange on said second mating gear affixed to said outer boom.

Drawing