Patent Publication Number: US-9404236-B2

Title: Thumb assembly having a stop

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     The invention relates to material handling equipment such as excavators and backhoes and clamping and grappling equipment used with material handling equipment and, more particularly, to a thumb assembly for use with such equipment. 
     The use of a thumb on material handling machinery is well known. While a thumb may be used with other implements, such as a rake, a thumb is commonly used in conjunction with a bucket on an excavator to make the bucket more effective in picking up material. For example, at demolition sites a thumb in conjunction with a bucket is a particularly useful means of handling material, such as concrete, lumber or pipe, which would be too large or otherwise difficult to be picked up solely by the bucket. 
     A thumb typically comprises a thumb frame which is pivotally attached to the underside of an excavator&#39;s stick and a link extending between the thumb frame and the stick to secure the thumb frame in position. The thumb frame is commonly of modular construction comprising a thumb body which is arranged for pivotal connection to the underside of the machine&#39;s stick and a tooth bar which is attached to the thumb body. The tooth bar is commonly configured to suit a particular bucket with which it will be used and typically comprises a number of teeth arranged to intermesh with teeth arrayed on the lower edge of the bucket. 
     When not in use, the thumb frame is typically pivoted to a stored position somewhat parallel and adjacent to the underside of the excavator&#39;s stick. From this position, the thumb frame can be pivoted relative to the stick to a working position where material can be clamped between the thumb frame and the implement. A link between the stick and the thumb frame secures the thumb frame in the stored position and in one or more working positions. Manual thumbs include a rigid or manually telescoped link between an anchor secured to the underside of the stick and the thumb frame enabling the thumb frame to be secured in the stored position and one or more working positions where material may be grasped by curling the bucket toward the thumb frame projecting from the underside of the stick. Connecting the stick and the thumb frame with a linear hydraulic actuator enables pivoting of the thumb frame from the stored position to an infinite number of working positions enabling material to be grasped by pivoting the thumb frame as well as by curling the bucket. In addition, the thumb frame can be pivoted throughout at least a portion of the bucket&#39;s movement to continue grasping material as the bucket is uncurled toward the unloading position. 
     However, the hydraulic thumb actuator on the underside of the stick is exposed to damage as a result of overtravel of the thumb frame in the stored and extended positions. To minimize interference with the use of the excavator it is desirable that the thumb frame be stored close to the stick which places the thumb frame in close proximity to the thumb actuator. Movement of the bucket and/or contact between the thumb frame and the surroundings can cause damaging contact between the thumb frame and the thumb actuator. On the other hand, as the thumb frame is pivoted toward the bucket by extension of the thumb actuator the rod of the actuator approaches the underside of the stick and overtravel of the thumb frame, for example, as a result of contact with the surroundings, can cause damaging contact between the actuator&#39;s rod and the stick. One or more, mechanical stops may be attached to the underside of the stick to prevent contact between the thumb frame and the thumb actuator but the additional welding and weld preparation which may include removing parts attached the stick, and the need to precisely locate the stop on the stick complicates the installation of a stop to protect the thumb actuator. What is desired, therefore, is a hydraulic thumb incorporating a mechanical stop to protect the thumb actuator which does not require welding or precise positioning on the stick. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an elevation view of an exemplary materials handling machine equipped with a hydraulic thumb. 
         FIG. 2  is a plan view of a stick assembly for the materials handling machine of  FIG. 1 . 
         FIG. 3  is a side elevation view of the stick assembly of  FIG. 2  with the hydraulic thumb in the stored position. 
         FIG. 4  is a side elevation view of the stick assembly of  FIG. 2  with the hydraulic thumb in an extended position. 
         FIG. 4A  is a side elevation view of a portion of the stick assembly of  FIG. 2 , with the hydraulic thumb in an extended position. 
         FIG. 5  is an orthogonal view of a thumb body. 
         FIG. 6  is an orthogonal view of a tooth bar. 
         FIG. 7  is a first elevation view of a thumb control link. 
         FIG. 8  is a second elevation view of the thumb control link of  FIG. 7 . 
         FIG. 9  is a third elevation view of the thumb control link of  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring in detail to the drawings where similar parts are identified by like reference numerals, and, more particularly to  FIG. 1 , an exemplary material handling machine, an excavator  20 , includes a thumb assembly  22 . The excavator  20  comprises generally an undercarriage  24  which includes a drive system for propelling the machine; a platform or house  26  rotatably supported by the undercarriage and an implement system  28 . The house  26  commonly includes an operator station  30  and a power source  32  which may comprise a combustion power source, such as a diesel engine, or a non-combustion power source, such as an electric motor(s). The power source  32  commonly drives one or more hydraulic pumps which supply pressurized fluid to various actuators of the implement system, a rotator system for rotating the house relative to the undercarriage on a center pin and the drive system. The drive system commonly comprises hydraulic motors supplied with fluid through the center pin which power gearing and ground engaging elements, such as tracks  34  which are movable on track frames  36  supporting the undercarriage. 
     The implement system  28  typically comprises a boom  38 , fixedly or movably attached to the house  26 , a stick  40  pivotally attached proximate the end of the boom distal of its attachment to the house and an implement  42  pivotally attached to the end of the stick distal of its attachment to the boom. While the boom  38  may be immovably attached to the rotatable house  26 , the boom is commonly pivotally attached and tiltable fore-and aft with respect to the house by one or more hydraulic boom actuators  44 . However, the boom may also be mounted to be movable axially and/or to be pivoted horizontally with respect to a fore and aft axis of the house. The stick  40  is typically pivoted relative to the boom by a hydraulic stick actuator  46 . 
     The implement  42  may be, by way of example and without limitation one of a large number of different sizes and types of buckets, such as the exemplary bucket, a ripper, a clamshell, a grapple, a rake, a compaction wheel, a vibratory compactor or a vibratory breaker. The implement is pivotally mounted at the end of the stick  40  distal of the stick&#39;s attachment to the boom  38 . While the implement  42  may be attached directly to the stick, the excavator  20  may be equipped with a quick coupler  50 , such as the coupler illustrated in U.S. Pat. No. 7,828,070, which is pivotally attached to the stick  40  by a first pin  52  and pivotally attached to a curl link  54  by a second pin  56 . To attach an implement to the excavator  20 , coupling elements of the quick coupler are arranged to engage and secure transverse front  58  and rear  60  pins affixed to the implement. Release of the pins enables detachment of the implement in preparation for attachment of a different implement. 
     The operator of the exemplary excavator  20  may control the operation of the implement system by operating a pair of joysticks located in the operator station  30 . The exemplary implement system  28  can be extended or retracted by actuating the hydraulic boom actuator  44  to pivot the boom fore and aft relative to the house  26  and by actuating the stick actuator  46  to pivot the stick  40  relative to the boom. In addition, the implement, bucket  42 , can be pivoted toward the stick  40  (curled) to fill the bucket or away from the stick (uncurled) to empty the bucket by extension and retraction of a hydraulic curl actuator  62  which is connected to the quick coupler  50  by the curl link  54  and the curl control link  64  which are pivotally connected to the curl actuator  62 , the coupler  50 , and the stick  40 . 
     The exemplary excavator  20  is also equipped with a hydraulic thumb  22 . Referring also to  FIGS. 2, 3, 4, 5 and 6 , the thumb  22  comprises, generally, a modular thumb frame  80  including a tooth bar  82  which is affixed to a thumb body  84 . The exemplary tooth bar  82  comprises plural tooth plates  86 , a web plate  88  which stabilizes the tooth plates horizontally and limits the penetration and retention of material between the tooth plates and a mounting plate  90  to which the tooth plates and the web plate are affixed. Typically, the teeth of the tooth bar are arranged to pass between pairs of teeth arrayed along the front edge of the bucket and the number and spacing of teeth on the tooth bar are typically determined by the number and spacing of teeth on the bucket that is most likely to be used with the thumb. 
     The tooth bar  82  is attached to the thumb body  84  usually by welding or bolting the mounting plate  90  to plural elongate side plates  92 ,  94  defining the sides of the thumb body and to a separator plate  96  which is secured between the side plates and aids in maintaining a spaced relationship of the side plates. Proximate the ends of the side plates  92 ,  94  distal of the tooth bar attachment, the side plates may also define apertures  98  arranged to receive a pin which pivotally joins the thumb frame and the stick. Preferably, the thumb frame  80  is pivotally coupled to the stick  40  by the same pin  52  that joins the coupler to the stick or, if connected directly to the stick, the same pin that joins the implement  42  to the stick. Connecting the thumb frame  80  to the stick with the pin  52  that pivotally couples the implement  42  to the stick ensures that the thumb frame and the implement, the bucket, pivot about the same axis and that corresponding points on the edges of side plates of the thumb and side plates of the bucket will follow the same arc as the bucket is curled or uncurled aiding in retaining material  43  clamped between the bucket and the thumb frame. Serrations  100  along the edges of the side plates  92 ,  94  nearest the bucket aid in retaining material grasped between the side plates and the bucket. 
     The separator plate  96  may also support plural anchor plates  102 ,  104  which are reinforced by gusset plates  106 ,  108 ,  110  connecting the anchor plates to each other and to the side plates. Apertures  112 ,  114  in the side plates  92 ,  94  aligned with apertures  116  defined by the anchor plates facilitate the installation of a pin  140  to connect a first end of plural thumb frame links  142  to the thumb frame. The second ends of the thumb frame links  142  are connected by a pin  144  to the rod  152  of the linear, hydraulic thumb actuator  150  and to a thumb control link  160  on each side of the stick  40 . Second ends of the thumb control links  160  may be pivotally connected to the stick  40  by the curl control link pin  162  which pivotally connects the curl control link  64  to the stick. Extension and retraction of the thumb actuator  150  rotates the thumb control links  160  about the curl control link pin  162  moving the thumb links  142  to pivot the thumb frame  80  from a stored position proximate the underside  41  of the stick  40  to a range of working positions where material can be grasped between the thumb frame and the bucket  42 . 
     It is desirable the thumb frame  80  be in close proximity to the underside  41  of the stick  40  when the thumb frame is in the stored position so that, when not in use, the thumb frame does not interfere with access to the implement  42 . However, in the stored position the thumb frame  80  is also in close proximity to the thumb actuator  150  and a force applied to the thumb frame by, for examples, striking something in the surroundings with the thumb frame or the implement  42  or by something projecting from the implement, the bucket, when it is curled, can push the thumb frame into contact with and damage the shell  154  of the thumb actuator  150 . Mechanical stops can be welded to the underside to the stick  40  to block movement of the thumb frame and protect the thumb actuator when the thumb frame is in the stored position but installation is difficult because the location of the stop must be closely controlled and may interfere with other elements secured to the stick. 
     On the other hand, as the thumb actuator  150  is extended to pivot the thumb frame  80  into proximity with the edge of the bucket  42 , the distal end of the actuator&#39;s rod  152  moves away from the stick  40  and then toward the stick as the thumb control link  160  pivots about the curl control link pin  162 . When fully extended the actuator&#39;s rod  152  is in close proximity to the underside of the stick. A force applied to the back of the thumb frame  80  can cause overtravel of the thumb mechanism resulting in damage the actuator&#39;s rod, the seals and bushing in the actuator&#39;s head  156  and/or the piston attached to the end of the rod. 
     The inventor reasoned that integrating mechanical stops with the thumb linkage would enable mechanical stops at both limits of the thumb frame&#39;s movement; precise location of the stops could be achieved in a manufacturing environment; and a reduction weld preparation and welding on the stick during installation. Referring also to  FIGS. 7, 8 and 9 , the thumb control link  160  defines a first aperture  180  proximate one end for receiving the pin  162  on which the curl control link  64  pivots. Distal of the first aperture, the thumb control link  160  defines a second aperture  182  to receive the pin  144  that connects the rod  152  of the thumb actuator  150  and the thumb link  142 . A primary stop  184  projecting from the thumb control link and in a direction substantially normal to longitudinal axis of the stick  40  may be affixed to the thumb control link  160  between the first  180  and second  182  apertures. As the thumb actuator  150  is retracted, as illustrated in  FIG. 3 , the thumb control link  162  rotates around the curl control link pin  162  until the primary stop  184  contacts the underside  41  of the stick  40  limiting further retraction of the thumb actuator and movement of the thumb frame toward the thumb actuator. When the rod  152  of the thumb actuator  150  is extended to pivot the thumb frame  80  toward the bucket  42 , as illustrated in  FIG. 4 , the thumb control link  160  pivots toward the end of the stick until the primary stop  184  makes contact with the underside  41  of the stick  40  (as shown if  FIG. 4A ), thereby limiting movement of the thumb frame and preventing contact between the thumb actuator rod  152  and the stick. 
     While the primary mechanical stop  184  prevents overtravel of the mechanism at both limits of the thumb&#39;s movement, the inventor also realized that a force applied to the thumb frame, particularly at or near the tips of the teeth, could deflect the mechanism sufficiently so that the stored thumb frame might make contact with the thumb actuator  150 . The thumb assembly  22  may include a secondary stop for the thumb frame  80  when in the stored position. The ends  186  of the thumb control links  160  distal of the aperture  180  for pivotal connection to the curl control link pin  162  extend beyond the primary stops  184  and are arranged to contact the separator plate  90  of the thumb body  84  in the event that the stored thumb frame is displaced toward the underside  41  of the stick  40 . With one end of the thumb control link  160  secured by the curl control link pin  162  and with the primary stop  184  in contact with the underside of the stick  40 , potentially damaging overtravel of the thumb frame is avoided. 
     Potential damage to the thumb actuator is avoided and installation complexity is reduced by mechanical primary and secondary thumb frame stops incorporated in the thumb actuation linkage. 
     The detailed description, above, sets forth numerous specific details to provide a thorough understanding of the present invention. However, those skilled in the art will appreciate that the present invention may be practiced without these specific details. In other instances, well known methods, procedures, components, and circuitry have not been described in detail to avoid obscuring the present invention. 
     The terms and expressions that have been employed in the foregoing specification are used as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims that follow.