Abstract:
A single-cylinder pneumatic press has a ram member spaced apart from lower head die, and a work area being defined therebetween. The cylinder and the piston rod enable reciprocating movement of the ram member relative to the lower head die. A return spring biases the ram member away from the surface. A linkage mechanism enables cooperative engagement between the piston rod and the ram member. The linkage mechanism provides rolling contact with the ram member along four distinct linear locations. The linkage mechanism includes four pivot brackets, enabling pivotal rotation of the bell cranks relative thereto, and a lever pin pivotably connecting the bell cranks together. Sandwiched between the bell cranks are two cam followers, which are driven upwardly and downwardly by the piston rod, the bell cranks each including a pair of rollers which engage with the ram member and provide &#34;four point&#34; contact therewith.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a pneumatic press, and more specifically, to a pneumatic press actuated by a cylinder and piston rod whereby a linkage mechanism applies force to a ram member through a plurality of roller members. 
     Pneumatic presses are widely used in numerous applications. Pressure is defined as force acting per unit area. Presses conventionally include a ram member mounted on a plurality of upright guide posts, a ram plate sliding in a horizontal plane relative to the guide posts and a stationary bed. 
     U.S. Pat. No. 4,579,031 (Lash et al.) discloses a two-cycle pneumatic cut-off press with an improved power mechanism for reciprocally operating a ram plate relative to a bed plate. The press includes a single bell crank. The die set area is between the ram plate and the bed plate, and includes opposed upper and lower track members for mounting upper and lower die sets, respectively. 
     U.S. Pat. No. 4,685,367 (Lash et al.) discloses another two-cycle pneumatic cut-off press with an improved power mechanism for reciprocally operating a ram plate relative to a bed plate. An upper movable die set is cooperatively engaged with the ram plate, and a lower stationary die set is secured to the bed plate. The press has two bell cranks, and introduces roller contact between the top plate and the linkage mechanism, and roller contact between the linkage mechanism and the ram plate. 
     U.S. Pat. No. 5,062,357 (Senior et al.) discloses a pneumatic press having a single cylinder and piston, and the disclosure of which is incorporated herein by reference, as illustrative of the general operation of such a press. 
     The use of rollers have been shown to eliminate lateral forces on the guide posts, and reduce the normal wear on internal press surfaces. However, the use of a single roller on a surface provides linear roller contact with the surface, and while the position of the linear contact changes as the position of the linkage mechanism varies, such presses are somewhat unstable and tend to wobble during operation. 
     What is needed is a lever-type pneumatic press, that takes advantage of roller contact on the ram member, while minimizing the above disadvantages. 
     A low profile pneumatic press is needed that reduces noise, vibration, and wear caused by larger masses moving longer distances. 
     While roller contact is a major advance in improving press durability, a new type of roller contact is needed that will provide a uniform force across the surface of the ram member, and enable stable vertical movement of the ram member during the power stroke. 
     SUMMARY OF THE INVENTION 
     The press generally comprises a movable ram member or upper die head spaced vertically above a stationary lower die head secured relative to the base. A die set area is defined by and between the undersurface of the ram member or movable upper die head and the upper surface of the stationary lower die head. 
     A single cylinder is mounted upon a cylinder head or top plate. The cylinder includes a piston rod. The cylinder head includes a bore therein enabling the piston rod to pass therethrough and engages a linkage mechanism. The single cylinder and the piston rod enable reciprocating movement of the ram member relative to the lower die head. 
     The linkage mechanism is mounted upon the ram member or movable upper die head, and enables cooperative engagement between the piston and the ram member. 
     In the preferred embodiment, the linkage mechanism includes a pair of pivot brackets, each bracket having a pair of bracket elements which are mounted symmetrically about a corner of the cylinder head. Two bell cranks or levers are pivotally connected between opposing pivot brackets. The inner ends of the bell cranks are provided with cam followers which are spaced apart along a traverse axis. The cam followers are cooperatively engageable with the piston rod. 
     The linkage mechanism enables cooperative linear engagement between the piston rod along four distinct locations of the upper surface of the ram member. Each of the bell cranks cooperatively engages a pair of rollers for rolling engagement with the upper surface of the ram member, enabling &#34;four-point&#34; contact. 
     The ram member or movable upper die head is urged toward stationary the lower die head when the piston rod is extended, and the ram member is withdrawn when the piston rod is retracted. The press also preferably includes spring return means for biasing the ram member away from the lower die head. 
     The mechanical advantage of the linkage mechanism may be adjusted by varying the size of the lever arms of the bell cranks. 
     For a more complete understanding of the pneumatic press of the present invention, reference is made to the following detailed description and accompanying drawings in which the presently preferred embodiment of the invention is shown by way of example. As the invention may be embodied in many forms without departing from spirit of essential characteristics thereof, it is expressly understood that the drawings are for purposes of illustration and description only, and are not intended as a definition of the limits of the invention. Throughout the description, like reference numbers refer to the same component throughout the several views. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front elevational view of the preferred embodiment embodying the pneumatic press of the present invention, the piston rod and linkage mechanism being in the retracted position; 
     FIG. 2 is a side elevational view of the pneumatic press of FIG. 1, with the piston rod and the linkage mechanism in the retracted position; 
     FIG. 3 is a cross-sectional view of the linkage mechanism of the pneumatic press of the present invention in the retracted position taken along lines 3--3 of FIG. 1; 
     FIG. 4A is an enlarged front elevational view of the linkage mechanism of the pneumatic press of FIG. 1, with the piston rod in the retracted position; 
     FIG. 4B is an enlarged front elevational view of the linkage mechanism of the pneumatic press of FIG. 1, with the piston rod in the extended position; and 
     FIG. 5 is an enlarged isometric view of the linkage mechanism of the pneumatic press of FIG. 1, with the piston rod in the retracted position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Turning now to the drawings, FIGS. 1 and 2 disclose front and side elevational views, respectively, of the preferred embodiment of the pneumatic press  10! constructed according to the principles of the present invention. 
     The press  10! has a vertically extending longitudinal axis 11 and generally includes a pneumatic cylinder assembly  20!, a linkage mechanism  30!, a ram member or movable upper die head  70! spaced vertically above a stationary lower die head  80! disposed on the press base  90!. A die set area  78! is defined between the undersurface  72! of the ram member  70! and the upper surface  82! of the lower die head  80!. 
     The pneumatic cylinder assembly  20! includes a single, upright, high-pressure, air cylinder  21! mounted upon a stationary cylinder top plate or head  22! of the press  10!. The cylinder  21! has a reciprocating cylinder rod or piston  23! and an axially connected piston or cylinder rod extension  26! for upward and downward engagement. The cylinder head  22! includes a bore  25! that is centrally disposed therewithin and is cylindrical in shape, enabling the cylinder rod 23 and the cylinder or piston rod extension  26! to pass therethrough. 
     The cylinder head  22! also includes a pair of pivot brackets  28! for mounting the linkage mechanism  30! therebetween. Each bracket has a pair of bracket members 100 connected by welding to a cross member 102 as shown in FIG. 2. The cylinder  21! and the piston rod extension  26! enable reciprocating movement of the ram member  70! relative to the stationary lower die head  80!. The pivot brackets  28! are spaced-apart opposing each other as shown in FIGS. 2 and 3. Each bracket 28 is mounted symmetrically onto the cylinder head or top plate  22!, and extends downwardly therefrom into the space between the top plate 22 and the movable upper die head or ram member 70. Each pair of pivot bracket members 100 include opposing apertures  29! for mounting and retaining a bracket pin  43! therewithin. Each bracket pin  43! enables pivotal engagement with the novel linkage mechanism  30!. The two bracket pins  43! oppose each other when mounted relative to each pair of pivot brackets  28!. 
     The pneumatic cylinder  21! also includes spring return means  14! for biasing the ram member or movable upper die head  70! away from the lower die head  80! during reciprocating movement of the ram member  70! away from the lower die head  80!. 
     The linkage mechanism  30! is mounted between the pivot brackets  28!, and enables cooperative rolling engagement between the piston  23! and four distinct locations on the upper surface  71! of the ram member  70!. The linkage mechanism  30! includes two levers or bell cranks  40!, cam followers  45!with mounting pins  42! , two roller pins  44!, and four cylindrical rollers  60!. FIG. 5 discloses an isometric perspective of the linkage mechanism  30!, with the outermost bell crank or lever  40! cutaway. 
     As used herein, the top, front, and end planes relative to linkage mechanism  30! are normal to each other and are defined as follows: 
     a front plane is normal to the axis of mounting pin  42! of the cam followers 45, the axes of the bracket pin  43!, and the axes of the roller pin (FIG. 1 is the front view of the linkage mechanism  30!); 
     an end plane is parallel to the plane defined by the intersection of the longitudinal axis of the upward-downward motion of the piston rod  26! with the intersection of the axis of the mounting pin  42! (FIG. 2 is the end view of the linkage mechanism  30!); and 
     a top plane is parallel to the roller surface contact area on the ram member  70! (FIG. 3 is the top view of the linkage mechanism  30!). 
     As viewed from the front plane, the levers or bell cranks  40! have a generally triangular shape with rounded angles. The two smallest angles, the lever pin angle  32! and the bracket pin angle  33! are thickened and extend around the adjoining legs of the triangular shape. The front and rear surfaces of the levers or bell cranks  40! are parallel to the front plane. 
     A portion of each bell crank or lever  40! nearest the upper surface thereof is truncated to enable clearance for the centrally disposed cam followers  45!. The cam truncation  36! is formed by the intersection of one plane parallel to the nearest tangential surface of the cam follower  45! and a second plane parallel to the front plane. 
     A portion of each bell crank  40! nearest the surface that engages the mounting pin  42! is truncated to enable clearance for a pivot bracket  28!. The bracket truncation  37! is formed by the intersection of one plane parallel to the front surface, and a second plane parallel to and aligned with the nearest tangential surface of the cam follower  45! of the cam truncation  36!. 
     The two identical bell cranks or levers  40! oppose each other as mounted on the bracket pins  43! of the pivot brackets  28! (see FIGS. 4A or 4B). Each leg of the lever or bell crank  40! is of different length. Each bell crank  40! includes a cylindrically-shaped angular bore disposed near the intersection of each pair of legs of the triangular-shaped bell crank  40! enabling pivotal connection of the linkage mechanism  30!; 
     a bracket angular bore  46! enabling engagement of the bell crank  40! with the bracket pins  43! and the pivot bracket  28!, 
     a mounting angular bore  47! enabling engagement with the lever pin  42! of each cam follower 45 and the other bell crank  40!, and 
     a roller angular bore  48! enabling engagement with the roller pins  44! and the rollers  60!. 
     The cam follower mounting pin  42! is inserted into the laterally spaced apart bores  47 ! provided in the outer ends of the levers 40 as shown in FIG. 3,  47!. The lever pin angle  32! represents the smallest angle of each bell crank  40!. The cam follower mounting pins  42! join the two bell cranks  40! together. Sandwiched between the lever angular bores  47! of the two bell cranks  40! are the pair of cylindrical-shaped cam followers  45! for cooperative engagement with the reciprocating piston rod  26! as the piston rod  26! moves upward and downward. 
     The lever leg  41! is the longest of the three legs of the bell crank  40!. The lever leg  41! may be lengthened or shortened to vary the mechanical advantage of each bell crank  40!. Since the bell cranks  40! are identical to each other, the mechanical advantages of the two bell cranks  40! are the same. The roller angular bore  48! opposes the lever leg  41!, and the bracket angular bore  46! is nearest the roller angular bore  48!. 
     Each bell crank  40! pivots about its respective bracket pin  43!, and the bracket angular bore  46! is essentially stationary relative to the cylinder head  22! during the power stroke. The relative distance between the lever angular bore  47! and the piston rod  26! is unchanged during the power stroke. When the piston rod  26! is in the retracted position as shown in FIG. 4A, the ram member  70! is raised from the lower die head  80!, and when the piston rod  26! is in the extended position as shown in FIG. 4B, the ram member  70! is in its lowermost position relative to the lower die head  80!. As the power stroke begins, the piston rod  26! moves downwardly relative to the cylinder head  22!, repositioning the cam followers and their mounting pins  42! downwardly, and repositioning the respective rollers  60! both in an outward direction and in a downward direction, from the position of FIG. 4A to the position of FIG. 4B. 
     Force is transmitted from the piston rod  26! to the upper surface  71! of the ram member  70! by means of four rollers  60!. A pair of rollers  60! are disposed about opposing ends of each roller pin  44!, as positioned within the roller angular bore  48! of each bell crank  40!, providing &#34;four-point&#34; roller contact on the upper surface  71! of the ram member  70!. The rollers  60! are made by McGill Corp., and are CFH-25 having a two inch diameter. A pair of wear plates  49! are mounted by fasteners  73! onto the upper surface  71! of the ram member  70! to reduce roller wear, one wear plate  49! per a pair of rollers  60!. The wear plates  49! are cold rolled steel and are hardened and ground. The movement of the rollers  60! downward forces the ram member  70! downward toward the lower die head  80!. All four rollers  60! move the same distance during the power stroke outwardly and downwardly, moving away from the piston rod  26! when the piston rod  26! is moving downwardly, and toward the piston rod  26! when the piston rod  26! is moving upwardly. The two pair of rollers  60! are symmetrically balanced as positioned about the upper surface  71! of ram member  70!. 
     The linkage mechanism  30! has a low profile, with a vertical height of up to seven inches, but preferably only about six inches. The capacity of the pneumatic press  10! is from 10 to 50 tons. 
     The four upright drawbars  68! extend from the press base  90! through the cylinder head  22!. The ram member  70! has corresponding bores  73! disposed at each comer thereof. The ram member  70! slidably receives the four upright drawbars  68! through four bushings  69! disposed at the undersurface  72! of the ram member  70!, respectively, enabling movement of the ram member  70! relative to the drawbars  68!. Fastener means  15! secure each drawbar  68! to the cylinder head  22! and fasteners  91! secure each drawbar to the lower die head  80!. 
     The ram member  70! is horizontal throughout the power stroke. The ram member  70! is urged toward the lower die head  80! when the piston rod  26! is extended, and the ram member  70! is withdrawn from the lower die head  80! when the piston rod  26! is retracted. 
     A pair of die tracks  83 and 84! are provided on the undersurface  72! of the ram member  70!, and another pair of dies  85 and 86! are disposed on the upper surface  82! of the base plate or lower die head  80! to secure a die set (not shown) thereto in a conventional manner. 
     The press base  90! is positioned upon a foundation  92! and secured thereto by fastener means  93! (see FIG. 1). 
     A pair of horizontal set screws  96! disposed at opposing ends of the support angles  94! secure the support angles  94! to the press base  90!. Also, a pair of fasteners  99! extend through apertures (not shown) in the press base  90! and the support angles  94!, and similarly, another pair of fasteners  98! secure the vertical leg of the support angles  94! to the lower die head  80!. Leveling screws  95! are carried by the lower die head  80! for engagement with the press base  90! as illustrated in FIG. 1. 
     Furthermore, it is evident that many alternatives, modifications, and variations of the pneumatic press  10! of the present invention will be apparent to those skilled in the art in light of the disclosure herein. It is intended that the metes and bounds of the present invention be determined by the appended claims rather than by the language of the above specification, and that all such alternatives, modifications, and variations which form a conjointly cooperative equivalent are intended to be included within the spirit and scope of these claims.