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United States Patent Application	20060071001
Kind Code	A1
Chun; Victor L. ;   et al.	April 6, 2006

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Claims

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1. A removable closure for blocking an opening into a chamber capable of resisting high forces exerted thereon, comprising: a plug assembly including an elongated plug member having a threaded intermediate section engaging a threaded bore centrally located in a first oblong plate included in said plug assembly, a second oblong plate also included in said plug assembly affixed to an end of said plug member; a receptacle located at the entrance to a chamber to be closed, said receptacle including a bore of a diameter smaller than the length of said oblong plates at the entrance of said receptacle, and an adjacent inner bore of a larger diameter able to receive said second oblong plate, said bores together forming an inwardly extending rim adjacent the entrance to said receptacle and a groove adjacent said rim; said second oblong plate configured to be rotatable in said groove; a pair of opposite clearance spaces formed extending through said rim and into said groove, allowing said oblong plates to pass crosswise through said spaces and said inner bore within said rim when aligned therewith, said second oblong plate rotated therein into a crosswise orientation with respect to said first oblong plate which is configured to be fit to said spaces to be held against rotation, said rotation also tightening said threaded engagement of said first oblong plate on said threaded intermediate section on said plug member to create a frictional lock preventing rotation of said plug member relative said first oblong plate, thereby in turn preventing rotation of said second oblong plate into alignment with said spaces, said second oblong plate abutted against said rim to absorb said high forces.

2. The removable closure according to claim 1 further including a locking washer received over said plug adjacent said threaded section and section seated on a shoulder adjacent said locking washer, tightened into frictional locking engagement therewith by advance of said plug member into said threaded bore in said first oblong plate.

3. The removable closure according to claim 1 wherein said second oblong plate has rounded ends facilitating rotation thereof in said groove.

4. The removable closure according to claim 1 wherein said clearance spaces comprise slots each extending radially out in opposite directions from said first bore, said ends of both of said oblong plates able to be inserted therein.

5. The removable closure according to claim 1 wherein said plug member has one or more wrenching surfaces adjacent an end opposite said end affixed to said second oblong plate.

6. A method of blocking one end of a chamber in a structure with a plug assembly so as to resist high forces applied to said plug assembly while enabling ready removal of said plug assembly comprising: providing a receptacle at an entrance to said chamber formed with a smaller diameter bore and an adjacent larger diameter bore, said bores together form an inwardly extending rim at the beginning of said receptacle adjacent to a groove; forming one or more radial clearance openings extending through said rim; forming aid plug assembly by threading a first oblong plate onto an intermediate threaded section adjacent one end of a plug member included in said plug assembly tightly against an axially fixed surface adjacent thereto to create a frictional lock of said first oblong plate to said plug member; assembling a second oblong plate onto said one end of said plug member and fixing the same thereto in a crossing orientation with respect to said first oblong plate, both of said oblong plates being configured to pass crosswise through smaller diameter bore when aligned with said spaces, said second oblong plate rotatable in said groove; counterrotating said plug member and attached second oblong plate to align said oblong plates with each other and loosen said threaded engagement of said first oblong plate with said plug member; inserting said aligned oblong plates into said clearance openings to position said second oblong plate entirely within said groove with ends of said first oblong plate disposed within said clearance openings, interfitting the same therein so as to prevent rotation thereof; rotating said plug member to again position said second oblong plate crosswise to said first oblong plate and to retighten said threaded engagement, whereby said second oblong plate is positioned against one side of said rim to resist said high forces exerted thereagainst, and is prevented from rotating into alignment with said clearance opening by interfitting of the ends of said first oblong plate within said clearance openings and by said frictional locking of said first oblong plate to said plug member.

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Description

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BACKGROUND OF THE INVENTION

[0001] This invention concerns removable closures for use in closing an entrance into a chamber or other opening.

[0002] In certain forming press installations, very high spring forces are needed to return cam slides used to perform an operation on a part being formed. The high force levels required to return the cam slide have led to the development of "nitrogen springs", which are sealed cylinders containing pressurized nitrogen gas, which is compressed by a piston connected to a rod, in turn driven by movement of the cam slide. The nitrogen spring is received in a chamber in the cam slide.

[0003] While capable of generating high forces, nitrogen springs do require some occasional maintenance and replacement more often than mechanical springs.

[0004] Thus, chambers used to hold nitrogen springs have been closed by threaded plugs so as to allow convenient access to the nitrogen spring for maintenance or replacement of the nitrogen springs.

[0005] The plug is engaged by the nitrogen spring cylinder component such that the plug threads are loaded by the high forces generated during machine operation. Such presses are cycled over many thousands of cycles so that loosening of the threaded connection may result.

[0006] It is the object of the present invention to provide a readily removable closure capable of resisting very large forces repeated over large numbers of cycles without loosening.

SUMMARY OF THE INVENTION

[0007] The above recited object as well as other objects which will become apparent upon a reading of the specification and claims are achieved by a closure comprised of a plug assembly including a plug member having wrenching surfaces such as a hex shape formed on one end, the plug assembly also including a pair of oblong plates mounted on the other end of the plug member. The other end of the plug member has an intermediate threaded section adjacent thereto. A first one of the oblong plates has a threaded mounting hole and is threaded onto the threaded section of the plug member into tight abutment with a shoulder formed thereon, a locking washer also preferably installed abutting the shoulder.

[0008] The second oblong plate is fixed to the plug member other end, and is assembled so as to extend crosswise to the first oblong plate and is welded to the plug member end in that orientation.

[0009] The plug assembly is designed to mate with a specially shaped receptacle at the entrance of the chamber nitrogen spring receiving chamber. The receptacle comprises a stepped diameter opening including a smaller diameter outer bore and an adjacent larger diameter bore, together defining a rim and an adjacent groove. A pair of opposing slot openings are machined through the rim, sized to receive the ends of the oblong plates allowing the second oblong plate to pass into the groove which is configured to allow the second oblong plate to be rotated therein.

[0010] To install the plug assembly in the receptacle, the plug member is turned counterclockwise as with a wrench to rotate the second oblong plate into alignment with the first oblong plate. The plug assembly is then aligned with the receptacle slots and fully advanced therein, causing the second oblong plate to move completely into the groove while the first oblong plate remains within the rim openings to be prevented from rotating. The wrenching end of the plug member is rotated back to rotate the second oblong plate out of alignment with the slot openings and the first oblong plate, this also retightening the threads.

[0011] The nitrogen spring directly bears on the second oblong plate which transmits the thrust directly into the inside wall of the rim rather than loading the threaded connection between the plug member and the first oblong plate so that cycling of the load does not produce any tendency to loosen the threads.

[0012] The first oblong plate, disposed in the slot openings and frictionally locked to the second oblong plate prevents rotation of the second oblong plate to keep it from rotating into alignment with the slot openings and maintaining it abutting the rim. Thus, the closure may be readily removed from the receptacle by rotating the plug member to loosen the threads and bring the second oblong plate back into alignment with the slot openings, which allows the plug assembly to be pulled from the receptacle.

DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 is a pictorial fragmentary view of a cam slide partially broken away showing a receptacle formed therein into which the plug assembly shown displaced therefrom, is to be inserted.

[0014] FIG. 2 is an exploded view of the plug assembly shown in FIG. 1.

[0015] FIG. 3 is a pictorial view of a plug assembly in its initially assembled and locking condition.

[0016] FIG. 4 is a fragmentary pictorial view of a cam slide with the plug assembly inserted into the receptacle. FIG. 5 is a partially sectional fragmentary view of a housing for a nitrogen spring with a plug assembly inserted and locked therein.

[0017] FIG. 5A is a partially sectional fragmentary view of the installed plug assembly, the nitrogen spring partially shown in phantom lines in position against one of the oblong plates included in the plug assembly.

[0018] FIG. 6 is a sectional view of a receptacle for mating with the plug assembly.

[0019] FIG. 6A is an end view of the receptacle shown in FIG. 6.

DETAILED DESCRIPTION

[0020] In the following detailed description, certain specific terminology will be employed for the sake of clarity and a particular embodiment described in accordance with the requirements of 35 USC 112, but it is to be understood that the same is not intended to be limiting and should not be so construed inasmuch as the invention is capable of taking many forms and variations within the scope of the appended claims.

[0021] Referring to the drawings, FIG. 1 shows a cam slide 10 in a forming die of a type well known in the art, which has a chamber 12 for receiving a high force nitrogen spring (not shown in FIG. 1). The cam slide 10 is driven laterally by the action of a cam surface when a press lowers the cam slide into a mating driver (not shown) in the well known manner. The spring is used to return the cam slide as the press retracts the cam slide 10.

[0022] The entrance to the chamber 12 is configured as a receptacle 14 to receive and mate with a plug assembly 16 to form the closure according to the present invention.

[0023] The plug assembly 16 includes a plug member 18 formed with a hex shape 20 at one end to provide wrenching surfaces.

[0024] The opposite end of the plug member is formed as a smooth cylindrical pin 22 sized to be slidably received through a threaded bore 24 in a first oblong plate 26 and pressed into a centrally located bore 28 in a second oblong plate 30 (FIG. 2).

[0025] The plug member 18 is further formed with an intermediate external thread section 32 mating with the internal threads in a centrally located bore 24 in the first oblong plate 26.

[0026] A diameter 34 of the plug 18 has a locking washer 26 receiving thereover and abutting an adjacent 30 shoulder 35.

[0027] The components of the plug assembly 16 are assembled together by first placing the lock washer 36 onto the diameter 34 and against the shoulder 35, and then threading the section 32 into the threaded bore 24 in the first oblong plate 26 until firmly tightened against the washer 32 as by using the wrenching surfaces comprised of the hex shaped end 20.

[0028] The second oblong plate 30 is assembled onto the pin end 24 in the crosswise orientation with respect to the first oblong plate 26 as shown in FIGS. 2 and 3, and plug welded thereto to fix the same in that orientation.

[0029] To prepare for installation, the first oblong plate 26 is held while the plug member 18 is rotated counterclockwise a quarter turn so that the second oblong plate 30 is parallel and aligned with the first oblong plate 26 as seen in FIG. 1. This loosens the threaded connection with the first oblong plate 26.

[0030] The receptacle 14 comprises an outside smaller diameter bore substantially smaller than the length of the second oblong plate 30 and a larger diameter bore 40 axially adjacent thereto, slightly larger than the length of the second oblong plate 30, together forming an inwardly extending rim 38 at the entrance of the receptacle 14, defined on its inside by one side of a groove 48.

[0031] The rim 38 is formed with a pair of opposing slot openings 42 extending axially through the rim 38 and which extend radially outward a distance equal to the diameter of the groove 40.

[0032] The first oblong plate 26 and the second oblong plate 30 are of a length and width to just pass cross ways through the bore within the rim 30 when aligned with the slot openings 42 which the ends of the plates 26, 30 are fit. The second oblong plate 30 is of a similar length and is rotatable in the groove 40, the rounded ends thereof generally conforming to the curvature of groove 40 to facilitate rotation in the groove 40.

[0033] The slot openings 42 are configured to allow the ends of the second oblong plate 30 when aligned with the first oblong plate 26 to be inserted into the receptacle 14 to pass through the rim 38 and into the groove 40 which is deep enough to just accommodate the thickness of the second oblong plate 30 as seen in FIG. 5, with a slight axial clearance as shown to insure that it may be rotated in the groove 40.

[0034] The groove 40 is sufficient such that the first oblong plate 26 protrudes very slightly into the groove 40, to insure that the second oblong plate 30 completely enters groove 40.

[0035] The ends of the second oblong plate 30 are rounded to match the diameter of the slot 40 to allow rotation of the second oblong plate 26 within the groove 40.

[0036] The leading sides 44 of each end of the second oblong plate 30 is relieved to insure that the second oblong plate 30 may be easily rotated in the groove 40.

[0037] The hex end 20 of the plug member 18 is rotated a quarter turn, rotating the second oblong plate 30 out of alignment with the slot openings 42 and to be oriented crosswise to the first oblong plate 26.

[0038] This same rotation cause threads on the plug member 18 to again be fully tightened against the first oblong plate 42, this tightening creating a frictional lock preventing rotation of the first oblong plate 26 on the plug member 18. This lock in turn prevents the second oblong plate 30 from rotating back into alignment with the openings 42, since the plug member 18 cannot rotate because the first oblong plate 26 is prevented from rotating by its being fit into the slot openings 42. Thus, movement of the plug assembly 16 out of the receptacle 14 is prevented until the plug 18 member is loosened as with a wrench.

[0039] The threaded section 32 is not loaded when a nitrogen spring 46 abuts the second oblong plate 30, as this drives the second oblong plate 30 against one side of the groove 40 as seen in FIG. 5A, so that the rim 38 absorbs the axial load. Thus, cycling of the load does not impose any forces on the threads connecting the first oblong plate 26 and plug member 18, and this eliminates any tendency to loosen the connection. At the same time, the plug member 18 can be readily loosened when desired as with a wrench to rotate the second oblong plate 30 back into alignment with the slot openings 42 and allow removal of the plug assembly 16 and access to the nitrogen spring 46 for maintenance or replacement.

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