Abstract:
An improved apparatus and/or method for safely lifting a load along a lift axis are provided, through utilization of an automatic lockout arrangement operatively connected between the point of application of a lifting force and a motorized clamping arrangement for grasping the load. The automatic lockout arrangement precludes electrical power from being applied to open the system when the lifting force being applied to the automatic lockout arrangement has reached a predetermined lockout value.

Description:
FIELD OF THE INVENTION 
     This patent application claims the benefit of U.S. Provisional Patent Application No. 61/580,958, filed Dec. 28, 2011, the entire teachings and disclosure of which are incorporated herein by reference thereto. 
     BACKGROUND OF THE INVENTION 
     During material handling processes, it is sometimes necessary to employ an apparatus having a clamping arrangement to grasp a load that is to be lifted by an overhead crane. For example, where the load to be lifted is a slab of material, or perhaps a stack of sheets of material, it may be necessary to use a clamping arrangement having fingers or flanges which extend under the load, to grasp or clamp the load in such a manner that it can be safely lifted with a crane. 
     In some instances, such a clamping arrangement may include moveable clamping arms or legs driven by a motor. Such a motor may be electric, pneumatic or hydraulic. 
     It is desirable when a motor-driven clamping arrangement is utilized to provide some form of lockout protection for operation of the motor while the load is being lifted. It is desirable that such a lockout arrangement preclude having the clamping arrangement release the load while lifting force is being applied. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention provides an improved apparatus and/or method for safely lifting a load along a lift axis through utilization of an automatic lockout arrangement connected between the point of application of a lifting force and a motorized clamping arrangement for grasping the load. 
     One form of the invention includes an electrically operable clamping arrangement, and an electrical lockout arrangement. The electrically operable clamping arrangement has clamping elements moveable between an open and a closed position of the clamping arrangement for selectively grasping and releasing the load. The electrical lockout arrangement is connected at a lower end thereof to the clamping arrangement and has an upper end thereof adapted for application of a lifting force along the lifting axis. 
     The electrically operable clamping arrangement and the electrical lockout arrangement are cooperatively configured such that the electrical lockout arrangement precludes electrical power from being applied to open the clamping arrangement when the lifting force being applied to the upper end of the electrical lockout arrangement has reached a predetermined lockout value while the clamping arrangement is grasping the load. The electrically operable clamping arrangement and the electrical lockout arrangement are also cooperatively configured such that the electrical lockout arrangement allows electrical power to be applied to the clamping arrangement for opening the clamping arrangement when the lifting force being applied to the upper end of the electrical lockout arrangement is below the predetermined lockout value. 
     In various forms of the invention, the clamping arrangement and lockout arrangement may be of any appropriate type, including configurations being mechanically, pneumatically or hydraulically driven, or various combinations of electrically, mechanically, pneumatically or hydraulically driven arrangements. 
     In some forms of the invention, the predetermined lockout value of the lifting force is adjustable. 
     In some forms of an apparatus/method according to the invention, the lockout arrangement may include an upper member adapted for connection to the lifting force, a lower member adapted for connection to the clamping arrangement, a spring arrangement disposed between the upper and lower members for urging the upper and lower members toward a non-lockout position of the lockout arrangement, and a switch arrangement operatively connected between the upper and lower members for detecting relative movement of the upper and lower members between the non-lockout position of the lockout arrangement and a lockout position of the lockout arrangement. The switch may take any appropriate form, including: electrical, pneumatic and hydraulic, or a mechanical switching arrangement. 
     In some forms of the invention, the switch arrangement is configured and operatively connected to an electrically operated clamping arrangement in such a manner that the switch arrangement conducts electrical current when the upper and lower members are disposed with respect to one another in the non-lockout position. The switch may be further configured and operatively connected in such a manner that the switch arrangement does not conduct electrical current when the upper and lower members are disposed with respect to one another in the lockout position. In some forms of the invention, the lockout switch arrangement directly cuts off, or reconnects, electric power to a motor driving the clamping arrangement. In other embodiments of the invention, the switch may be connected to a controller and supply only a control signal to the controller, with the controller then being operatively connected to the motor driving the clamping arrangement for controlling the application of electrical power to the motor. 
     In some forms of the invention, the spring arrangement defines upper and lower ends thereof. The upper member includes an opening extending generally perpendicularly to the lifting axis through the lifting member with the opening having an upward-facing surface thereof engaging the lower end of the spring arrangement. The lower member includes a downward-facing surface thereof engaging the upper end of the spring arrangement. 
     The upper member may extend entirely around the opening, and the lower member may form an inverted U-shape having two legs extending downward from a shelf element connecting the proximal ends of the two legs. At least one distal end of at least one of the legs may be configured for attachment to the clamping arrangement. The shelf of the U-shaped lower member may have a lower surface thereof forming the downward-facing surface of the lower member. 
     In some forms of the invention, the upper and lower members of the lockout arrangement are cooperatively configured for contacting one another to limit travel of the lower member with respect to the upper member when a load is applied to the lifting arrangement along the lifting axis. The upper member may define an upward-facing travel limit surface thereof disposed to contact a corresponding downward-facing travel limit surface of the lower member. The travel limit surface of the lower member may include a portion of a downward-facing surface on the shelf of the lower member. 
     The spring arrangement in a lockout arrangement, according to the invention, may include at least one compression spring element defining a central bore thereof extending substantially parallel to the lifting axis. The upper and lower members may each have stop elements thereof extending into lower and upper ends respectfully of the central bore in the spring element. Juxtaposed surfaces of the stop elements within the central bore of the compression spring element may be cooperatively configured for engaging one another to limit travel of the lower member with respect to the upper member when a load is applied to the lifting arrangement along the lifting axis. The compression spring arrangement may include two or more spring elements disposed in a parallel force arrangement, with at least one of the springs being removable and/or replaceable to adjust the force required to move the upper and lower members with respect to one another during an application of the lifting force. 
     The invention may take the form of a lifting apparatus/method, according to the invention, having a lockout arrangement according to any claim herein, and a clamping arrangement having clamping elements moveable between an open and a closed position of the clamping arrangement for selectively grasping and releasing the load. In some forms of the invention, the lockout arrangement is electrical, and the clamping arrangement is electrically operable. 
     A lifting apparatus/method, according to the invention, may also include a controller operatively connected between the lockout arrangement and the clamping arrangement, for selectively controlling the clamping arrangement in accordance with inputs received from the lockout arrangement. 
     Other aspects, objects and advantages of the invention will be apparent from the following detailed description and accompanying drawings of exemplary embodiments of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings: 
         FIG. 1  is a perspective illustration of a lifting apparatus, according to the invention; 
         FIG. 2  is a perspective illustration of an enlarged portion of  FIG. 1 , taken along the circular line “ 2 ”; 
         FIG. 3  is an exploded perspective illustration of a lockout arrangement of the apparatus of  FIG. 1 ; 
         FIG. 5  is an assembled perspective illustration of the exemplary embodiment of the lockout apparatus shown in  FIG. 4 ; 
       FIGS.  4  and  6 - 9  are orthographic illustrations of the exemplary embodiment of the lockout arrangement shown in  FIGS. 4 and 5 , with  FIGS. 4-9  illustrating various structural and functional elements and aspects of the lockout arrangement; 
         FIG. 10  is a schematic illustration of one possible control arrangement for connecting a limit switch of the lockout arrangement in a manner for controlling operation of a drive motor in a clamping arrangement according to the invention; 
         FIG. 11  is perspective view of an exemplary alternate embodiment of a lockout apparatus; and 
         FIG. 12  is a side cross sectional view of the embodiment of  FIG. 11 . 
     
    
    
     While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention. 
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows an exemplary embodiment of an electrically operable and electrically driven lifting apparatus  100 , according to the invention for application of a lifting load along a lifting axis  101 . The lifting apparatus  100  includes an electrically operable clamping arrangement  102 , and an electrical lockout arrangement  150 . 
     As shown in  FIG. 2 , the electrical lockout arrangement  150  is connected at a lower end  152  to the clamping arrangement  102 . The electrical lockout arrangement  150  is connected at an upper end  154  thereof to a lifting clevis  156  for application of a lifting load along the lifting axis  101 . 
     As will be described in more detail below, the electrically operable clamping arrangement  102  and the electrical lockout arrangement  150  are cooperatively configured such that the electrical lockout arrangement  150  precludes electrical power from being applied to open the clamping arrangement  102  when a lifting force being applied to the upper end  154  of the electrical lockout arrangement  150  has reached a predetermined lockout value while the clamping arrangement  102  is grasping the load  103 . The clamping arrangement  102  and the lockout arrangement  150  are also cooperatively configured such that the electrical lockout arrangement  150  allows electrical power to be applied to the clamping arrangement  102  for opening the clamping arrangement  102  when the lifting force being applied to the upper end  154  of the electrical lockout arrangement  150  is below the predetermined lockout value. 
     As shown in  FIG. 1 , the clamping arrangement  102  and the exemplary embodiment of the lifting apparatus  100  includes first and second moveable clamping arms  104 ,  106  which are operatively connected through a rack-and-pinion drive system to a central frame  108 , including a drive mechanism operatively connected to an electric motor  110 . The electric motor  110  may be operated in one direction to move the clamping arms  104 ,  106  outwardly to release the load  103 , or conversely be driven in an opposite direction to move the clamping arms  104 ,  106  inward to grasp the load  103 . The lifting apparatus  100  also includes an electrical controller  112  mounted on the central frame  108  of the clamping arrangement  102 . 
       FIG. 3  shows an exploded view of the electrical lockout arrangement  150  of the exemplary embodiment of the lifting apparatus  100 . The lockout apparatus  150  includes an upper member  158  (also referred to as a first member herein) formed by a top bail assembly  158 A and a bottom spring support  158 B, a lower member  160  (also referred to as a second member herein), a spring arrangement  162  and a limit switch arrangement  164 . 
     As will be understood from an examination of  FIGS. 3-9 , in the exemplary embodiment of the lifting apparatus  100 , the upper member  158  extends entirely around an opening  166  extending through the upper member  158  in a direction generally perpendicularly to the lifting axis  101 . The lower member  160  has a generally U-shaped form including first and second legs  168 ,  170  extending downward from a shelf element  172 , with the upper ends of the first and second legs  168 ,  170  being fixedly attached to the shelf element  172 . The lower ends of both the first and second legs  168 ,  170  are configured to form an attachment to the clamping arrangement  102 . 
     The spring arrangement  162  in the exemplary embodiment of the apparatus  100  includes a plurality of compression springs  174  (only one of which is labeled in  FIG. 3 ). The top ends of the compression springs  174  bear against a lower surface of the shelf element  172 , and the lower ends of the compression springs  174  bear against an upward-facing surface  176  of the upper member  158 . The compression springs  174  also define a central bore  178  into which guide pins  180 ,  182  extend from the upper and lower members  158 ,  160  respectively. 
     As will be understood from an examination of annotated  FIGS. 6-9 , when the lockout arrangement  150  is not exposed to a lifting load applied across the upper and lower ends  154 ,  152  of the lockout arrangement  150 , the springs  174  of the spring arrangement  162  urge the upper and lower members  158 ,  160  toward an un-locked position as shown in  FIGS. 6 and 7 . Conversely, when a sufficient lifting load is applied across the lockout arrangement  150 , the springs  174  of the spring arrangement  162  are compressed as the upper and lower elements  158 ,  160  move to the lockout position shown in  FIGS. 8 and 9 . 
     As will be understood from an examination of  FIGS. 3-9 , the limit switch  164  is mounted to the upper member  158 , in the exemplary embodiment of the apparatus  100 , and includes a limit switch arm  184  which pivotably contacts a limit switch bracket  186  attached to the lower member  160 . Relative movement of the upper and lower members  158 ,  160  with respect to one another as load is applied across the lockout arrangement  150  causes the limit switch arm  184  to move and close, or open, the limit switch  164 . 
     As shown in  FIG. 10 , the limit switch  164  of the exemplary embodiment  100  is operatively connected to the controller  112  in such a manner that operation of the limit switch  164  causes the controller to preclude movement of the clamping arrangement  102  toward an unclamped position thereof, whenever a preselected lifting load is applied across the lockout arrangement  150 . 
     As will be understood from an examination of  FIGS. 3-9 , the upper and lower members  158 ,  160  and the locating pins  180 ,  182 , of the lockout arrangement  150 , are configured and to have juxtaposed surfaces which contact each other when the upper and lower members  158 ,  160  have moved a predetermined maximum travel distance with respect to one another as the lifting force is applied. The spring arrangement  162  in the exemplary embodiment  100  is also configured so that the force required to move the upper and lower members  158 ,  160  the maximum travel distance with respect to one another can be adjusted for loads of different weights. This adjustment can be accomplished by removing some of the multiple compression springs  174 , or interchanging one or more of the compression springs  174  with compression springs having a different spring rate. 
     Turning now to  FIGS. 11 and 12 , an alternate embodiment of a lockout arrangement  250  is illustrated. This embodiment provides the same functionality and advantages as the lockout arrangement  150  described above, with some structural distinctions which will be discussed below. This embodiment is equally usable with the clamping arrangement  102  illustrated above, or other similar or dissimilar clamping arrangements. 
     With particular reference to  FIG. 11 , the lockout arrangement  250  includes a first member  258 , and a second member  260 . At least one spring  274  is positioned between the first and second members  258 ,  260 . As illustrated, a plurality of springs  274  are utilized. The springs  274  function in the same manner as described above relative to  FIGS. 1-10  in that they bias the first and second members  258 ,  260  to a non-lockout position. However, as a load is applied to a clevis  256  which is connected to the first member  258 , the first member  258  will move upwardly against the resistance of the springs  274  and towards a lockout position in the same manner as described above. 
     A sensor  264  in the form of an edge detector is positioned on the second member  260 . The sensor  264  detects the location of an edge of a tab  286  fixedly connected to the first member  258 . As the first member  258  moves, so too does the tab  286 , and the sensor  264  detects this motion. Those skilled in the art will recognize that other types of sensors may be utilized to detect the relative movement between the first and second members  258 ,  260 , e.g. proximity, light, hall effect, etc. 
     Turning now to  FIG. 12 , the first member  258  includes a pin  202  which extends through the second member  260 , as well as opposed spring retaining blocks  204 A of the first member  258 . A pair of opposed spring retaining blocks  204 B are also mounted on the second member  260 , such that the ends of springs  274  are held respectively by the spring retaining blocks  204 A,  204 B. 
     The second member  260  also includes a pair of opposed sidewalls  268 ,  270 . Each of the sidewalls  268 ,  270  includes a slotted opening  206  through which the pin  202  of the first member extends through. A pair of transverse members  208  extend between the sidewalls  268 ,  270  of the second member  260 , and maintain the spacing thereof. Additionally, a pair of opposed spacer elements  210  that also include slotted openings are mounted to interior sides of the sidewalls  268 ,  270  to maintain the centered position of clevis  256 . 
     As will be understood from inspection of  FIG. 12 , as the first member  258 , and more specifically the pin  202  thereof, moves upwardly within slots  206 , springs  274  will compress. The sensor  264  will detect this motion by detecting the movement of the tab  286  connected to the first member  258 . As will also be understood from inspection of  FIG. 12 , the slots  206  in the second member  260  define the maximum limit of upward travel of the first member  258  relative to the second member  260 . Once a predetermined amount of travel of the first member  258  relative to the second member  260 , the lock-out functionality described relative to the schematic at  FIG. 10  will ensue. 
     All references, including publications, patent applications, and patents cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein. 
     The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
     Preferred embodiments of this invention are described herein, including the best mode known to the inventor for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventor expects skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.