The present invention relates generally to material handling equipment and relates more particularly to pneumatic pop-up units adapted for use in material handling equipment.
The manufacture and/or packaging of many types of commercial articles often involves the use of material handling equipment. One example of material handling equipment is a bench or workstation at which certain assembly or packaging steps for an article are performed. Another example of material handling equipment is a conveyor system for transporting an article from one workstation to another.
As can readily be appreciated, an article that is seated on top of a bench or workstation often must be re-positioned or rotated thereon so that certain assembly or packaging steps can be performed. Similarly, it is often the case that the direction in which an article is traveling along a conveyor system must be altered or its movement altogether stopped. For these reasons, various omni-directional devices and stopping devices have been devised that are adapted for use in material handling equipment.
For example, in U.S. Pat. No. 4,627,526, inventor Masciarelli, which issued Dec. 9, 1986, and which is incorporated herein by reference, there is disclosed a conveyor system which includes a number of driven rollers mounted in a spaced, parallel relationship. A conveyor element is located between adjacent driven rollers, the conveyor element consisting of a main body having a series of passages in which plungers are slidably carried. An inflatable bladder moves each of the plungers from a retracted position to an operative position. More specifically, each passage is a bore in the main body, and each plunger consists of a sphere rotatably carried in a sheath whose outer surface is formed to slide smoothly in the bore. In this manner, when the bladder is inflated, the spheres are moved from their retracted positions to their operative positions, where they engage the article and lift the article above the top level of the driven rollers, thereby enabling the article to be re-positioned relative to the rollers (or pushed off of the driven rollers, for example, onto a lateral conveyor). When the bladder is then deflated, the spheres retract and an article situated thereon is lowered back onto the driven rollers. Alternatively, instead of including a sphere, the plunger may include a stop pin for use in stopping the movement of the article across the series of driven rollers.
As another example of an omni-directional device adapted for material handling equipment, in U.S. Pat. No. 4,660,994, inventor Masciarelli, which issued Apr. 28, 1987, and which is incorporated herein by reference, there is disclosed an anti-friction (i.e., omni-directional) assembly adapted for use in material handling equipment. More specifically, the aforementioned assembly comprises a main body having a first bore entering one surface and a second bore concentric with but non-coextensive with the first bore. A piston is slidable in the second bore and has a stem whose free end is slidable in the first bore. The stem carries a ball which is rotatable on a nest of secondary balls in a cavity in the free end of the stem. The piston and the stem are movable from a first position in which the ball lies substantially within the first bore below a friction element (e.g., the workstation, driven rollers, etc.) to a second position in which the ball protrudes from the first bore above the friction element. Means are provided for introducing fluid under pressure to the second bore to move the piston and to carry the ball from the first position to the second position. In addition, means are provided in the second bore to bias the piston to normally maintain the piston and the ball in the first position.
As still another such example., in U.S. Pat. No. 6,019,211, inventor Masciarelli, Jr., which issued Feb. 1, 2000, and which is incorporated herein by reference, there is disclosed a conveyor having a plurality of spaced rollers mounted between a pair of elongated horizontal frame members for supporting an article and enabling the article to be conveyed longitudinally of the frame members. The conveyor has a workstation formed by a plurality of interrupter strips extending in the spaces between rollers. Each interrupter strip has a plurality of lifting pads which are selectively movable between a lower position in which the upper surface of the pads are below the tops of the rollers and an upper position in which the upper surface of the pads are above the tops of the rollers for supporting the article and frictionally engaging the article to maintain the article in a stable position above the strips. The interrupter strips also have a plurality of balls mounted for omnidirectional rotation on the interrupter strips. Each ball is selectively movable between a lower position in which the top of the ball is below the top of the rollers and an upper position in which the top of the ball is above the top of the rollers. The balls are selectively moved independently of the lifting pads so that the article can be supported solely by the balls or by the lifting pads.
Referring now to FIGS. 1 through 4, there are shown various views of still yet another example of a conventional pneumatic pop-up unit, said unit being of the omni-directional variety and being represented generally by reference numeral 11. Unit 11 comprises a housing 13, housing 13 being a generally cylindrical, cup-shaped member having a circular side wall 15, a bottom wall 17 and an open top. A nipple 19 is mounted in bottom wall 17, nipple 19 being adapted for connection to a pressurized gas (or other fluid) supply. Housing 13 is typically made of machined metal (e.g., aluminum, steel).
Unit 11 also comprises a cap 21, cap 21 also being made of machined metal (e.g., aluminum, steel). Cap 21 comprises a top wall 23 and a side wall 25. Top wall 23 is flat and annular in shape. Side wall 25, which extends downwardly from the inside diameter of top wall 23, is circular in cross-section. Side wall 25 is dimensioned to fit closely inside side wall 15 of housing 13, with top wall 23 extending radially outwardly across side wall 15 and defining a circumferential flange 27 used to mount unit 11 in a hole H formed in a workbench W or the like. A pair of spaced apart circumferential lips 29 and 31 are formed on the outside surface of side wall 25 of cap 21, lips 29 and 31 defining a groove 33 therebetween. The outside surface of side wall 25 tapers slightly inwardly in diameter from lip 31 to the bottom surface thereof. Housing 13 and cap 21 are secured to one another by staking (i.e., mechanically deforming) housing 13 into groove 33 at approximately four points 34 equidistantly spaced around the circumference of housing 13.
Unit 11 further comprises a piston 41, piston 41 being slidably mounted within housing 13. Piston 41, which is made by stamping and rolling a suitable sheet of metal, is a generally cylindrical, hollow member and includes a bottom wall 43, a circular side wall 45 and an open top. A ring 47 is fixedly secured by a press-fit to the outside surface of side wall 45, ring 47 being disposed a short distance from bottom wall 43. The top surface of ring 47 is used to engage the bottom end of a spring 49, the top end of spring 49 being engaged by lip 31 of cap 21. Spring 49 serves to bias piston 41 downwardly towards bottom wall 17 of housing 13. A rubber seal 51 is snugly fitted around side wall 45 of piston 41 and is engaged at its top surface by the bottom surface of ring 47 in such a way that ring 47 keeps seal 51 from sliding up on piston 41. Seal 51 serves to create an air-tight chamber between the bottom end of piston 41 and housing 13, seal 51 typically being of the split design variety (e.g., U-cup, block-V) so that, when seal 51 is subjected to upward fluid pressure, its outer leg is urged against the inside surface of wall 15 of housing 13 and its inner leg is urged against the outside surface of wall 45 of piston 41.
Unit 11 further comprises a bowl-shaped race 55, race 55 being disposed inside of piston 41. Race 55 is seated on top of a race support 57, race support 57 being seated directly on top of the inside surface of wall 43 of piston 41. Race 55, which is made by stamping, has an outer diameter slightly smaller than the inner diameter of piston 41 and is adapted to hold a plurality of ball bearings 59. Race support 57 is shaped to include a circular side wall 61, on which race 55 is seated, and an annular bottom wall 63, which extends radially outwardly from side wall 61 to slightly less than the inner diameter of piston 41. A primary ball 65 is seated on ball bearings 59 and extends partially through the open top of piston 41, the top of side wall 45 being, rolled around ball 65 to retain ball 65 within piston 41. Ball 65 is aligned with the central opening in cap 21 and is appropriately sized relative thereto to partially extend therethrough.
Although unit 11 has been found to be generally satisfactory for its intended purpose, the present inventor has observed the following shortcomings in connection therewith: First, as noted above, housing 13 and cap 21 are made by metal machining processes (either by screw machining or by powdered metal technology). Unfortunately, however, these metal machining processes often result in tolerances that are greater than optimally desired to enable housing 13 and cap 21 to fit together properly on a consistent basis when both are mass-produced. In addition, the aforementioned machining processes can be time-intensive and labor-intensive and, therefore, costly.
Second, as explained above, housing 13 and cap 21 are secured to one another by staking housing 13 into groove 33 of cap 21 at four equally spaced points 34 around the perimeter of housing 13. Unfortunately, however, said staking technique is, on occasion, not secure enough for cap 21 and housing 13 to withstand becoming separated by the force of the pressurized gas admitted into housing 13 to raise piston 41 therewithin and/or by the force of articles dropped or loaded on top of unit 11 during routine material handling steps.
Third, once cap 21 has been staked to housing 13 in the above-described manner, cap 21 cannot be removed from housing 13 and thereafter re-attached without causing damage to cap 21 and/or to housing 13 (see, for example, breaks 36 in lip 31 of cap 21, as shown in FIG. 4). This is unfortunate since the internal components of a unit can become worn and/or dirty over time. Consequently, at present, the only viable option is to replace the entire unit.
Fourth, as described above, the upper end of spring 49 wraps around side wall 25 of cap 21 and is abutted at its top surface by lower lip 31. Consequently, when piston 41 is elevated to its uppermost position within housing 13, spring 49 becomes completely compressedxe2x80x94an undesirable condition since it may result in spring 49 weakening or locking in its compressed state. Moreover, because the outside surface of side wall 25 tapers inwardly from lip 31 to the bottom of side wall 25, the diameter of the wire used to make spring 49 must be small enough to allow spring 49 at its top end to fit between the rather small space left between side wall 25 of cap 21 and housing 13. Typically, this amounts to a wire diameter of about seventy-thousandths of an inch for spring 49.
Fifth, the manner in which piston 41 is finished, with race 55, race support 57, bearings 59 and ball 65 all arranged therewithin is as follows: First, piston 41 is stamped into the shape of a hollow cylindrical can having an open top. Race support 57, race 55, bearings 59 and ball 65 are then positioned within piston 41 in the manner described above. Finally, the top edges of side wall 45 of piston 41 are rolled or coined inwardly around ball 65 so as to entrap ball 65 and the other contents of piston 41 therewithin. Unfortunately, the metal used to form piston 41 has a tendency to xe2x80x9cspring-backxe2x80x9d to its original shape after having been stamped or rolled/coined; consequently, it is necessary to xe2x80x9coverbendxe2x80x9d the metal to compensate for anticipated spring-back. Such overbending, however, can create its own problems. For example, the overbending of the top edges of piston 41 around ball 65 can create nicks or cuts in ball 65 or can otherwise damage ball 65, particularly if ball 65 is made of a soft material, such as a soft plastic. In addition, the overbending of the top edges of piston 41 against ball 65 results in a considerable force being applied by race support 57 to the bottom of piston 41, thereby occasionally resulting in the bottom of piston 41 becoming deformed (i.e., spreading radially outwardly and/or buckling downwardly towards the middle). Furthermore, the overbending of the top edges of piston 41 against ball 65 can cause bearings 59 to be driven into and to deform race 55.
It is an object of the present invention to provide a novel pneumatic pop-up unit adapted for use in material handling equipment.
It is another object of the present invention to provide a pneumatic pop-unit as described above that overcomes at least some of the disadvantages associated with existing pneumatic pop-up units.
It is still another object of the present invention to provide a pneumatic pop-up unit that can be mass-produced readily and relatively inexpensively.
Additional objects, features, aspects and advantages of the present invention will be set forth, in part, in the description which follows and, in part, will be obvious from the description or may be learned by practice of the invention. In the description, reference is made to the accompanying drawings which form a part thereof and in which is shown by way of illustration specific embodiments for practicing the invention. These embodiments will be described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural changes may be made without departing from the scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is best defined by the appended claims.