Abstract:
A vacuum lifter mountable on a fork lift has a low vertical profile particularly useful in the warehousing of sheet materials, minimizing the needed clearance thereabove to access the sheet materials. The lifter includes a low vertical profile frame having a protective wall to minimize damage to the vacuum cups mounted on the frame. The vacuum cups may be raised to a position within the protective wall and lowered to a position therebelow to facilitate vacuum attachment to sheet materials or other objects to be lifted. The vacuum cups may be mounted on the frame via pivot arms cantilevered from the frame. The pivot arms may be positioned in opposed pairs and raised by camming action such as by a cam bar extending between the pivot arms and slidably mounted on the frame.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Technical Field 
         [0002]    The present invention relates generally to a vacuum lifting mechanism. More particularly, the invention relates to a vacuum lifter which is mountable on a forklift and has a low profile. Specifically, the invention relates to such a vacuum lifter which has a protective wall for protecting the vacuum cups of the lifter. 
         [0003]    2. Background Information 
         [0004]    Vacuum lifters are commonly used to pick up a wide variety of materials, including flat sheet materials such as steel, plastic or wood. Vacuum lift devices are commonly mounted on heavy equipment such as an arm on an excavator, suspended from overhead hoists or mounted on the forks of a fork lift. Depending on the specific configuration and degree of suction from a vacuum source, vacuum lifters may lift relatively light objects or objects that weigh hundreds or thousands of pounds. 
         [0005]    In the warehousing of flat sheet materials and the like, vacuum lifters are commonly used with forklifts for stacking and removing the sheet materials from shelving at various heights. These vacuum lifters include a frame having mounted thereon vacuum cups which contact the sheet materials so that a vacuum subsequently applied via the vacuum cups to the sheet material allows the material to be lifted. The known prior art lifters are relatively bulky and have a rather large vertical profile which is commonly twelve inches or even more. As a result, there must be at least twelve inches of free space or clearance above the sheet material on a given shelf in order for the known vacuum lifters to be inserted therein for lifting the sheet material. Thus, for every shelf of sheet material, there must be twelve inches between the top sheet and the bottom of the shelf thereabove. This adds substantially to the amount of warehouse space required for the stacking of sheet materials. In addition, the known prior art vacuum lifters have vacuum cups which hang below the frame so that they are exposed to inadvertent damage during movement of the lifter into warehouse shelving and the like. Thus, there is a need in the art for a low profile vacuum lifter which is also capable of protecting the vacuum cups. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    The present invention provides an apparatus for lifting flat material comprising: a frame; a pair of fork lift arm receivers on the frame; and at least one vacuum cup mounted on and movable relative to the frame between raised and lowered positions. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0007]      FIG. 1  is a perspective view of the vacuum lifter of the present invention with the vacuum cups in the lowered position and the vacuum source shown diagrammatically in dashed lines. 
           [0008]      FIG. 2  is a rear elevational view of the lifter with the vacuum cups in the lowered position showing the fork receiving tubes. 
           [0009]      FIG. 3  is a top plan view of the vacuum lifter with the vacuum cups in the lowered position. 
           [0010]      FIG. 4  is a sectional view taken on lines  4 - 4  of  FIG. 3 . 
           [0011]      FIG. 5  is a top plan view of the lifter with the vacuum cups in the raised position. 
           [0012]      FIG. 6  is a sectional view taken on lines  6 - 6  of  FIG. 5 . 
           [0013]      FIG. 7  is a perspective view of the vacuum lifter with the central frame member removed to show the cam bar and the vacuum cups in the lowered position. 
           [0014]      FIG. 8  is similar to  FIG. 7  and shows the vacuum cups moved to the raised position in response to movement of the cam bar. 
       
    
    
       [0015]    Similar numbers refer to similar parts throughout the drawings. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    The vacuum lifter of the present invention is shown generally at  10  in  FIGS. 1-3 . Lifter  10  includes a rigid frame  12  and a plurality of vacuum cups  14  which are used to contact and apply a vacuum to sheet materials or other objects in order to lift said objects. Vacuum cups  14  are movable between a lowered position shown in  FIGS. 1-4  and  7  and a raised position shown in  FIGS. 5 ,  6  and  8 . 
         [0017]    Frame  12  has a front  16  and a rear  18  defining therebetween an axial direction, and first and second sides  20  and  22  defining therebetween a longitudinal direction. Frame  12  also has a top  17  and a bottom  19  defining uppermost and lowermost surfaces of frame  12 . Top  17  and bottom  19  define therebetween a height H 1  ( FIG. 2 ) of frame  12  which is substantially less than that of the known prior art lifters. Typically, the height H 1  is on the order of three to five inches. Frame  12  includes a perimeter wall  24  having an outer surface  26  defining an outer perimeter of wall  24  and frame  12 , and an inner surface  28  defining an inner perimeter of wall  24 . Perimeter wall  24  includes a longitudinally extending front wall  30  which extends nearly the entire length of frame  12 . Wall  24  further includes a rear wall divided into first and second segments  32  and  34  which extend longitudinally and are spaced from one another and are aligned along a common vertical longitudinal plane. Each of segments  32  and  34  are roughly one third the length of frame  12  in the exemplary embodiment. Perimeter wall  24  also include four beveled corner walls  40 A-D which connect the various other walls of wall  24  and are typically angled at approximately 45° relative to the other walls to eliminate a sharp 90° corner which may enhance the likelihood of property damage or personal injury. 
         [0018]    A longitudinally extending central frame member includes first and second central walls  42  and  44  each of which extends between and is connected to side walls  36  and  38  respectively at the central axial positions thereof. Five axially elongated slots  45 A-E are formed in each of central walls  42  and  44  although they are shown only in wall  42  in  FIG. 1 . Slots  45  are spaced longitudinally from one another so that the distance between each adjacent pair of slots  45  is roughly the same. First and second cross bars  46  and  48  extend axially between and are connected to first central wall  42  and front wall  30 . First cross bar  46  is positioned about one third the longitudinal distance of frame  12  from first side  36 . Likewise, second cross bar  48  is positioned about one third the longitudinal distance of frame  12  from second side  38 . Thus, first and second cross bars  46  and  48  define therebetween approximately one third of the length of frame  12 . All of the aforementioned walls and cross bars are preferably substantially flat and vertically oriented to provide a strong, yet relatively light weight frame although various configurations of frame  12  will be evident to one skilled in the art. In addition, rigid connections are formed at the intersections of the various walls of frame  12 . 
         [0019]    Lifter  10  further includes a forklift fork receiver assembly which is disposed partially within the perimeter of perimeter wall  24  and partially outside of perimeter wall in a rearward direction. More particularly, this assembly includes first and second axially extending fork arm receivers in the form of tubes  50  and  52 . Each of tubes  50  and  52  is connected at the respective front end thereof to second central wall  44  and extends rearwardly therefrom. Tube  50  is connected adjacent its midpoint to a terminal end of first segment  32 . Likewise, tube  52  is connected adjacent its midpoint to a terminal end of second segment  34 . Each of tubes  50  and  52  extend rearwardly from segments  32  and  34  to rear ends in which are formed rearwardly opening entrance openings  54  of respective interior chambers  56  which extend the entire axial length of tubes  50  and  52 . Interior chambers  56  are configured to receive respective fork lift arms via entrance openings  54  so that lifter  10  may be supported by a fork lift for the raising and lowering thereof. A tubular cross bar  58  extends axially between and is connected to each of tubes  50  and  52  rearwardly of segments  32  and  34 . Each of tubes  50  and  52  and cross bar  58  has a top  60  and a bottom  62  defining therebetween a height H 2  which is less than height H 1 . Thus, the receiver assembly including tubes  50  and  52  and cross bar  58  have a vertical profile which is completely within the vertical profile of frame  12 . More particularly, top  60  of the fork lift receiver assembly is below top  17  of frame  12  and bottom  62  of the assembly is above bottom  19  of frame  12  so that no portion of the fork lift receiver assembly is disposed above or below frame  12 . 
         [0020]    Lifter  10  includes a vacuum system which includes vacuum cups  14  and a vacuum source  64  which is preferably battery powered by an onboard battery to provide a vacuum or suction to cups  14  via vacuum conduits  66 A and B. More particularly, vacuum conduit  66 A is connected to source  64  and communicates with conduits  66 B connected to each of vacuum cups  14  (only one conduit  66 B being shown for clarity). Each vacuum cup  14  includes a rigid upper member  68  having formed in an upper wall thereof a port  70  to which a respective conduit  66 B is connected. Each vacuum cup  14  also includes a lower flexible suction cup  72  typically formed of rubber or a polymeric material. Each suction cup  72  has an annular lower attachment surface  74  which is substantially horizontal and configured to contact and attach to sheet material or other object which is to be picked up via the vacuum of lifter  10 . 
         [0021]    As previously noted, each vacuum cup is movable between raised and lowered positions. More particularly, each of vacuum cups  14  is mounted adjacent a free end  76  of an arm  78  which is cantilevered from one of central walls  42  and  44 . A plurality of mounting brackets  80  are mounted on walls  42  and  44  with each arm  78  pivotally mounted thereon via a pivot  82 . Each mounting bracket  80  includes a pair of axially spaced flat plates which define a space therebetween for receiving the inner end of each arm  78 . Each arm  78  has an inner end  84  which at a point below pivot  82  serves as a cam follower. As shown in  FIG. 5 , each vacuum cup  14  and arm  78  is circumscribed by various walls of frame  12  and/or by portions of the forklift receiving assembly. For instance, a pair of arms  78  and the vacuum cups  14  attached thereto are circumscribed by cross bar  46 , a portion of first central wall  42 , a forward portion of side wall  36  and a portion of front wall  30 . Another of arms  78  and the vacuum cup  14  mounted thereon is circumscribed by cross bars  46  and  48 , a central segment of first central wall  42  and a central segment of front wall  30 . Yet another arm  78  and vacuum cup  14  are circumscribed by a central segment of second central wall  44 , forward portions of forklift tubes  50  and  52 , and cross bar  58 . The remainder of arms  78  and vacuum cups  14  are likewise surrounded by various walls of frame  12  and/or portions of the forklift receiver assembly which will be evident upon review of the figures. 
         [0022]    A plurality of cams in the form of wings or ramps  86  extend from between walls  42  and  44  respectively through slots  45  and include tapered cam surfaces  88  which provide a camming engagement with cam followers  84  when ramps  86  move longitudinally. More particularly, ramps  86  are carried by and extend outwardly from a longitudinally elongated cam bar  90  ( FIG. 7 ) which extends nearly the entire length of frame  12  between central walls  42  and  44 . Preferably, cam bar  90  and ramps  86  are formed as an integral one-piece member. As shown in  FIG. 7 , each pair of ramps  86  which are opposite one another and the portion of cam bar  90  to the right thereof forms an arrow shaped configuration. 
         [0023]    An actuator  92  is pivotally mounted on a mounting bracket  94  which is rigidly attached to second central wall  44 . Actuator  92  includes an actuating arm  96  such as the piston of a piston cylinder combination which is pivotally mounted on a mounting plate  98  which extends rearwardly from cam bar  90  and extends through slot  45 A and central wall  44  along with one of ramps  86 . Actuator  92  may be powered by any suitable source including vacuum source  64 . Cam bar  90  is thus slidably mounted between walls  42  and  44  with ramps  86  slidably received within respective slots  45  and axially moveable in response to movement of actuating arm  96 . 
         [0024]    In keeping with maintaining a minimal vertical profile and with reference to  FIGS. 4 and 6 , pivot arms  78  are configured to stay within the vertical profile of perimeter wall  24  in the lowered position of  FIG. 4  and the raised position of  FIG. 6 . Pivot arms  78  have a triangular configuration which allow arms  78  to stay within this vertical profile. More particularly, each pivot arm  78  has a height adjacent inner end  84  which is greater than that of pivot arm  78  adjacent outer or free end  76 . Each pivot arm  78  has a top surface  100  and a bottom surface  102  each of which are straight and axially elongated. As shown in  FIG. 4 , bottom surface  102  in the lowered position is substantially horizontal and disposed closely adjacent bottom  19  of perimeter wall  24 , and top surface  100  angles downwardly and axially away from central walls  42  and  44 . Thus, in the lowered position, top surface  100  adjacent inner end  84  is closely adjacent top  17  of perimeter wall  24  and top surface  100  adjacent free end  76  is spaced downwardly from top  17  and is closer to bottom  19  of wall  24 . In the lowered position, each inner end  84  adjacent bottom surface  102  abuts either central wall  42  or  44 , which serves as a stop to prevent arm  78  from pivoting further downwardly about pivot  82 .  FIG. 4  shows that in the lowered position that each cup  14  is positioned mostly below bottom  19  of perimeter wall  24  with only a small portion of upper member  68  disposed thereabove. 
         [0025]    In the raised view shown in  FIG. 6 , top surface  100  of each arm  78  is closely adjacent top  17  of perimeter wall  24  and is substantially horizontal. Bottom surface  102  angles upwardly and away from central wall  42  and  44  so that bottom surface  102  adjacent inner end  84  is closely adjacent bottom  19  of perimeter wall  24  and bottom surface  102  adjacent free end  76  is positioned upwardly of bottom  19  and closer to top  17  of wall  24 . Preferably, inner end  84  of arm  78  adjacent top surface  102  abuts either central wall  42  or  44  to limit upward movement of arm  78  so that arm  78  remains within the vertical profile of perimeter wall  24 . As  FIG. 6  shows, most of each vacuum cup  14  is within the vertical profile of perimeter wall  24  and within the interior space defined within wall  24 . More particularly, upper member  68  is disposed entirely within said vertical profile and only a portion of suction cup  72  extends downwardly of bottom  19  of wall  24 . 
         [0026]    The operation of cam bar  90  in moving pivot arms  78  and vacuum cups  18  from the lowered position to the raised position is best seen with reference to  FIGS. 3 ,  5 ,  7  and  8 .  FIGS. 3 and 7  show ramps  86  of cam bar  90  positioned generally to the right of pivot arms  78  so that cam surfaces  88  are out of contact with cam followers  84  or so that a leading edge of cam surfaces  88  are barely in contact with cam followers  84  such that cam followers  84  rest on central walls  42  or  44  in the lowered position. In order to raise pivot arms  78  and vacuum cups  14 , actuator  92  is operated to extend arm  96  which drives cam bar  90  longitudinally to the left as shown in the drawings so that ramps  86  slide within slots  45  ( FIG. 1 ) and cam surfaces  88  slideably engage cam followers  84  so that the camming engagement therebetween causes pivot arms  78  to pivot about respective pivots  82  upwardly to the raised position ( FIGS. 5 ,  8 ). The retraction of arm  96  of actuator  92  causes the reverse movement of cam bar  90  to allow pivot arms  78  to return to the lowered position. The force of gravity thus brings pivot arms  78  and vacuum cups  14  back to the lowered position although in a different orientation of lifter  10 , pivot arms  78  may be spring biased to the lowered position if necessary. 
         [0027]    Lifter  10  thus provides for a vacuum lifter which is mountable on the fork arms of a fork lift so that lifter  10  may be utilized in spaces for which its minimal profile offers significant advantage. Lifter  10  thus substantially reduces the amount of space or clearance above an object for insertion of lifter  10  to lift the object, which is particularly useful for the more efficient storage of sheet materials in a warehouse. More particularly, the fork lift driver will operate vacuum source  64  and actuator  92  in order to position vacuum cups  14  in a raised position to minimize the vertical profile of lifter  10  for insertion thereof into the space above an object such as sheet material. A remote control may be provided for this purpose if desired. Depending on the configuration of vacuum source  64  and its position, lifter  10  in its entirety may be inserted into relatively small clearance spaces above sheet material and the like. Even if vacuum source  64  is, for instance, seated atop of tubes  50  and  52  and extends upwardly beyond top  17  of perimeter wall  24 , at least perimeter wall  24  in its entirety may be inserted into such a space. Once lifter  10  is positioned so that vacuum cups  14  are above the objects to be lifted, the operator then controls actuator  92  to lower vacuum cups  14  into contact with the upper surface of the object to be lifted, applies a vacuum via source  64  and conduits  66  to vacuum cups  14 , and lifts the objects via the suction of cups  14  onto the object. As previously noted, perimeter wall  24  further provides protection to vacuum cups  14  particularly in the raised position and especially during movement of lifter  10  having a horizontal or lateral component. 
         [0028]    In the foregoing description, certain terms have been used for brevity, clearness, and understanding. No unnecessary limitations are to be implied therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed. 
         [0029]    Moreover, the description and illustration of the invention is an example and the invention is not limited to the exact details shown or described.