US3651876A

US3651876A - Quick acting drive cap assembly

Info

Publication number: US3651876A
Application number: US47736A
Authority: US
Inventors: William P Henson
Original assignee: Mobile Drilling Co Inc
Current assignee: Mobile Drilling Co Inc
Priority date: 1970-06-19
Filing date: 1970-06-19
Publication date: 1972-03-28
Anticipated expiration: 1989-03-28

Abstract

A drive cap assembly for quick attachment and detachment from the top end of an earth boring hollow auger. The assembly has an outer casing with a hexagonally shaped rod mounted to one end for receiving the auger driver. The opposite casing end slips over the top end of the auger. A latch key is mountable to the hexagonal rod with a plug attached to one end for passing through a casing opening and into a slot on the outside surface of the auger thereby securing the drive cap assembly and auger together. A lock ring fits over the casing and latch key. A center rod driver fits within and is rotated by the casing and is threaded on one end to a shaft passing through the hollow auger.

Description

United States Patent 1151 3,651,876

Henson 1451 Mar. 28, 1972 s41 QUICK ACTING DRIVE CAP 3,219,131 11/1965 Boyd ..175/323 ASSEMBLY 3,301,338 l/1967 Dickinson...

[72] Inventor: William P. Henson, Indianapolis, Ind. Primary Examiner james Leppink [73] Assignee: Mobile Drilling Company, Inc., lndi- Attorney-Woodard, Wikart, Emhardt & Naughton anapolis, Ind.

22 Filed: June 19,1970 [57] ABSTRACT A drive cap assembly for quick attachment and detachment [2]] Appl' from the top end of an earth boring hollow auger. The assembly has an outer casing with a 'hexagonally shaped rod [52] U.S. Cl ..l75/323, 285/82, 285/403 mounted to one end for receiving the auger drive The [5 hit. posite asing end slips over the top end of the auger A latch [58] Field of Search ..175/320, 323; 285/82, 403, key is mountable to the hexagonal rod with a plug attached to 285/404; 287/103 7 one end for passing through a casing opening and into a slot on the outside surface of the auger thereby securing the drive cap [56] References cued assembly and anger together. A lock ring fits over the casing and latch key. A center rod driver fits within and is rotated by UNITED STATES PATENTS v the casmg and is threaded on one end to a shaft passmg 3,190,377 6/1965 Rassieur ..l75/323 through the honow auger 2,304,038 12/1942 Thompson...

2,820,658 1/1958 Bender I. ..287/l03 l2Claims,l0DrawingFigures l0 //2 v v "I I f I 5 g l I Q 23 g 4 r a @5 4 "9, 2s 9 v gg a we PATENTl-Inmzamz 3,651,876

sum 2 OF 5 FigZ.

INVENTOR WILLIAM F? /-/N50/v Adm/ML MM,M rfiau ztrm ATTORNEYS PATENTEDHAH28 I972 3.651.876

SHEET 5 OF 5 i 5 x i ATTORNEYS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a drive cap assembly for a hollow auger.

2. Description of the Prior Art Certain types of hollow augers are used in various earth drilling applications wherein it is necessary or desirable to provide a smooth constant diameter passage through the auger to the bottom of the hole. Possibly the most important such application is that of earth sampling. In certain situations it is desirable to take samples at intervals for substantial distance down into the earth. The earth sampling does not occur while the auger is boring into the ground. In this latter case, it is desirable to have a second drill and rod positioned within the hollow auger for boring a pilot hole leading the auger drill. In order to eliminate the necessity for multiple drivers for rotating the two drills and shaft, it is desirable that they be connected at the top end in such a manner that a single driver will rotate both rods and drills.

It is present practice to manufacture hollow augers in sections of predetermined length which are connected together to make the auger longer as the drilling proceeds. The sections should be connected to one another in such a manner that they remain firmly coupled while in the earth so that the lower sections do not become disconnected while the auger is being rotated. The sections should also be easily disconnected after drilling has been completed. It is most desirable that the driver utilized to rotate the auger be easily and quickly connectable to the top of the auger. Likewise, it should be possible to easily and quickly detach the driver from the top of the auger. Various means have been provided to couple the sections of the hollow auger together. Four coupling devices are shown in the U.S. Pat. Nos. to Dickinson 3,301,338, Page 2,671,682, Blake 2,032,196 and Harper 2,407,983. All of these couplings will tighten under load preventing easy disassembly. The coupling employing threads will deteriorate as a result of sand and corrosive conditions.

From the above background it can be seen that there is a need for an apparatus for connecting the driver simultaneously with the hollow auger and the secondary drill shaft within the auger. The apparatus should be easily and quickly connectable to the auger and secondary drill shaft. Likewise, it should be possible to easily and quickly detach the apparatus from the auger and secondary drill shaft. It is desirable that the apparatus be operable in dirty and corrosive environments.

SUMMARY OF THE INVENTION The present invention involves a drive cap assembly for connecting a rotatable driver simultaneously with an earth boring hollow auger and a secondary drill shaft within the auger. The assembly has an outer hollow casing with a hexagonally shaped rod fixedly mounted to its top end for receiving the auger driver. The opposite casing end slips over the top end of the hollow auger. A latch key is slipped over the hexagonally shaped rod and has a plug at its opposite end for passing through an opening provided in the side of the casing and into a bayonet shaped slot on the outside surface of the top of the auger thereby securing the drive cap assembly and auger together. A lock ring slips over the casing and latch key. A center rod driver fits within the casing and is threaded on one end to the secondary drill shaft. The opposite end of the center rod driver has bosses integrally attached to its top which rest against bosses attached to the inside top casing wall.

It is one object of the present invention to provide a drive cap assembly which may be utilized to simultaneously drive a hollow auger and a secondary drill shaft within the auger.

It is another object of the present invention to provide a drive cap assembly which may be quickly and easily attached and detached from a hollow auger and secondary drill shaft within the auger.

Yet another object of the present invention is to provide a drive cap assembly for a hollow auger which is operable in dirty environments. I

Related objects and advantages will become apparent as the description proceeds.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an illustration of a drilling apparatus for drilling a hole into the ground incorporating the drive cap assembly of the present invention.

FIG. 2 is an enlarged fragmentary section of the device shown in FIG. 1 taken along the line 2-2 and viewed in the direction of the arrows.

FIG. 3 is a fragmentary enlarged side view of the top inner sleeve shown in FIG. 1.

FIG. 4 is an end view of the top inner sleeve shown in FIG. 3 looking in the direction of arrows 4-4.

FIG. 5 is an enlarged top view of the latch key shown in FIG. 1.

FIG. 6 is a side view of the latch key shown in FIG. 5 looking in the direction of arrows 6--6.

FIG. 7 is an enlarged top view of the lock ring shown in FIG. 1.

FIG. 8 is a side view of the device shown in FIG. 7 and viewed in the direction of arrows 8-8.

FIG. 9 is an enlarged perspective view of the center rod driver shown in FIG. 2.

FIG. 10 is a side view partially in section of shaft 30 shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT For the purposes and understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawing and specific language will be used to describe the same. It will-nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

Referring now more particularly to FIG. I, there is illustrated a drilling apparatus 11 for drilling a hole 12 in ground 10. Apparatus 11 comprises a cylindrical hollow auger l4 rotatable by a drive cap assembly 13. Auger 14 is made up of sections 23, each having a tube 31 with a helical flight 15 secured to the external periphery thereof by welding or the like. As hole 12 is advanced, sections 23 are added as required.

Fastened to the bottom of hollow auger 14 are drill teeth 16 for digging into the bottom 17 of hole 12. The dirt scraped and dug from the bottom 17 is conveyed upwardly along flight 15 being rotated in the direction of arrow 21. Each section 23 has an outer sleeve 24 fastened to one end of tube 31 by weld 25 extending around the circumference of the tube. The opposite end of each tube 31 has an inner sleeve 26 fastened by weld 27 also extending around the circumference of the tube. Inner sleeves 26 have outside diameters less than the inside diameters of outer sleeves 24 in order that the inner sleeve may be fitted within the outer sleeve thereby coupling each section together. A loose key 28 is slipped between the inner and outer sleeve to secure the sleeves together. A further explanation and description of

sleeves

24 and 26 and key 28 may be found in my copending U.S. Pat. Application, Ser. No. 36,279 entitled Coupling Incorporating a Welded Key and a Loose Key" filed on May 11, 1970. Sleeve 24 and key 28 will not be described since the subject of the present specification is the drive cap assembly 13.

The inner sleeve 26 of the uppermost section fits into drive cap assembly 13 and is locked therein in order that head 13 and auger 14 may rotate as a unit. Head 13 has a hexagonal drive rod 19 fixedly fastened to drive cap 20 which fits over inner sleeve 26. The power driver 22 fits over rod 19 driving head 13 and auger 14 in the direction of arrow 21 in order to advance hole 12 deeper into ground 10. To retract auger 14 from the ground, driver 22 is rotated in a direction opposite arrow 21 and the apparatus is lifted. Driver 22, head 13 and auger 14 are now shown connected together in FIG. 1 for illustrative purposes. Of course, in actual use the driver, head, and auger would be connected together rotating as a unit.

Auger 14 in conjunction with all outer sleeves 24 and inner sleeves 26 are hollow in order that a shaft may be extended therethrough to the bottom of the hole. In many cases, it is desirable to obtain a core sample from the bottom of the hole. Thus, a coring device, not shown in the drawing, is fastened to the end of a shaft and is extended down through the interior of auger 14 to bottom 17. During the core sampling process, auger 14 is not rotated and driving head 13 is removed from the auger providing an entrance for the coring device. Auger 14 acts like a casing preventing the material, such as dirt, from falling to bottom 17 thereby contaminating the core sample. During the periods of time when the core sample is not required, a rod 30 shown in break away sections 29 and 32 of FIG. I is extended through auger 14. The rod has mounted on its lower end a secondary drill 33 leading primary drill 34. Secondary drill 33 has teeth 35 fastened thereto for providing a pilot hole 36 for the primary drill 34. Shaft 30 (FIG. is composed of various sections similarly as auger 14 is composed of sections 23. Each section of shaft 30 is threaded on both ends to facilitate coupling of adjacent sections. That is, each section would have an externally threaded end 150 as well as an end having an internally threaded socket 151 for receiving the adjacent section. Many variations for coupling the sections are possible. Sections of shaft 30 allow easy assembly and disassembly of the shaft during the insertion and removal of the shaft from auger 14. In lieu of the secondary drill, a plug may be fastened at the lower end of the hollow interior of the primary drill.

FIG. 2 is an enlarged fragmentary section taken along the line 2-2 of FIG. I and viewed in the direction of the arrows particularly showing the drive cap assembly 13. Cap assembly 13 is shown connected to shaft 30; however, for illustrative purposes the cap assembly is not shown fastened to top inner I sleeve 26. In actual use, cap assembly 13 would be secured to sleeve 26. As may be seen from FIG. 2, cap assembly 13 has a drive cap 20 with a hexagonally shaped rod 19 fixedly fastened to its top wall 100 for receiving the power driver 22. Wall 100 is integrally joined to side wall 101 forming a cavity 102 for receiving sleeve 26. A latch key 110 has a hole for receiving rod 19 and a plug 111 for extending through opening 103 in cap 20 and into bayonet slot 43 of sleeve 26 thereby locking the cap and sleeve together. A lock ring 120 slips over drive cap 20 and locks latch key 110 to bayonet slot 43.

In order to achieve an understanding of cap assembly 13, the top inner sleeve 26 will now be described. Referring now to FIG. 3, sleeve 26 is welded to tube 31 by weld 27 extending around its periphery. Helical flight is attached to tube 31 and sleeve 26 in such a way so as to form a continuous uninterrupted flight. A large counterbore 54 is provided in the end of the sleeve body 46 for receiving the end of hollow tube 31. Sleeve 26 is hollow allowing the previously mentioned coring sample device or secondary drill to pass therethrough. Sleeve body 46 has a chamfer 47 extending around the outside edge of the open end to provide for easy insertion of the top inner sleeve into drive cap 20. Body 46 has a bayonet slot 43 partially through the wall of the body with a narrow rectangular shaped portion 48 located adjacent a smaller rectangular shaped portion 49. An end view of the top inner sleeve is shown in FIG. 4 illustrating that

slots

48 and 49 do not extend through the wall of body 46. Slot 43 receives plug 111 of latch key 110 (FIG. 2) as the drive cap is fitted and locked onto sleeve 26.

Referring to FIGS. 5 and 6, latch key 110 has a top member 112 integrally joined to a side member 113 at an angle slightly greater than 90. The best results appear to be achieved when the angle 114 between top member 112 and side member 113 is approximately 94. An elongated hole 115 is provided in top member 112 for receiving the hexagonally shaped rod 19. Hole has a

flat side

116 and 117 located on either side to preclude rotation of key 110 with respect to rod 19. Plug 111 is rectangular in shape as may be seen from the dashed line in FIG. 5 and is fastened to the lower portion of side member 113 by welding or other such suitable means. A through hole 103 (FIG. 2) is provided in side wall 101 of cap 20 for plug 111 to pass through. Of course, hole 103 must be positioned in such a way so as to receive plug 111 when top member 112 (FIG. 6) rests on the top surface 105 of shoulder 104 shown in FIG. 2. Surface 116 of plug 111 (FIG. 6) is concave so as to abut body 46 within slots 48 and 49 (FIG. 3).

Lock ring 120 is shown in FIG. 7 having a semicircular portion 121 defined by radius R integrally joined to two converging

side portions

122 and 123 which are in turn integrally joined to flat end portion 124 forming hole 125 for receiving cap 20 and latch key 110. With the ring installed in position over the cap and latch key, the inside surface 126 of the flat end portion 124 will abut against outside surface of member 113 (FIG. 6) at approximately point 106 thereby locking plug 111 in hole 103 and slot 43 (FIG. 2). At the same time, ring 120 will be held in place by the inside surface 127 (FIG. 7) abutting against the side 107 of drive cap 20 opposite hole 103 (FIG. 2).

Referring to FIG. 2, a chamfer 108 extends around the inside of the lower edge of cap 20 to facilitate insertion of sleeve 26 into cavity 102. Two equally

sized bosses

128 and 129 are fixedly fastened to top wall 100 of cap 20 by welding or other suitable means. The two bosses are located opposite each other and are positioned near side wall 101.

Bosses

128 and 129 abut against complementary bosses of center rod driver thereby allowing the drive cap 20, sleeve 26 and rod 30 to rotate as a unit. A perspective view of center rod driver 140 as shown in FIG. 9 with

bosses

141 and 142 fastened to the top disc-shaped portion 143. A shoulder 144 having a smaller outside diameter than portion 143 is integrally attached between disc 143 and cylinder-shaped member 145. Threaded end 146 is integrally attached to the bottom of member 145 having a smaller outside diameter than member 145. Referring now to FIG. 2, shaft 30 is threaded onto end 146 of driver 140. With drive cap 20 installed on sleeve 26 and plug 111 positioned through opening 103 and in slot 43, the bottom of disc portion 143 of driver 140 rests on the top edge 148 of sleeve 26. Of course, shoulder 144 and member 145 fit within sleeve 26. As the drive cap and auger rotate in the direction of arrow 21, boss 128 abuts against boss 142 and boss 129 abuts against boss 141 forcing driver 140 and shaft 30 to rotate in the direction of arrow 21. To install a new section 23 of auger 14 as hole 12 deepens, plug 111 should be disengaged from slot 43 and opening 103 thereby permitting removal of drive cap assembly 13 from outer sleeve 26. Driver 140 is then unthreaded from the top section of shaft 30 and new sections are added to shaft 30 and auger 14. Driver 140 and drive cap assembly 13 are then attached to the top end of the new section. To remove auger l4 and shaft 30 from the hole, drive cap assembly 13 and auger 14 should be rotated in a direction opposite to arrow 21. The drive cap assembly, auger and center shaft may then be lifted from the hole as a unit since the top of plug 111 will abut against edge 153 of rectangular portion 49. (FIG. 3) If it is desirable to rotate auger 14 without shaft 30 in place, then driver 140 may be removed and drive cap assembly 13 secured to the top sleeve 26 by placing plug 111 through opening 103 and into the bayonet slot 43.

It will be evident from the above description that the present invention provides a drive cap assembly which may be quickly and easily attached and detached from an auger and which is operable in dirty environments. In addition, it will be evident that the present drive cap assembly provides for the simultaneous driving of a first and second shaft wherein one of the shafts is positioned in the hollow center of the other shaft.

While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.

The invention claimed is:

l. A drive cap assembly for an earth-boring auger comprisa casing having a top and bottom end and a side wall, said top end having means for receiving rotating power, said bottom end being hollow for receiving the top portion of said auger, said side wall having a hole therethrough,

a latch key received upon said casing and having a plug passing through said hole and engaging said auger, said plug having a distal end lockingly abuttable against an outer wall of said auger;

a ring received over said casing and said key and maintaining said casing and said key together.

2. The assembly of claim 1 additionally comprising:

a center rod driver having a longitudinal driving axis and being coupled to a secondary drill shaft extending through said auger;

a first extension fixedly attached to said casing and projecting interiorly therein and being offset from said axis, said extension being spaced from said side wall of said casing;

a second extension fixedly attached to said center rod driver and positioned against said first extension to rotate about said axis with said auger and secondary drill shaft.

3. A drive cap assembly for an earth-boring auger comprisa casing having a top and bottom end and a side wall, said top end having means for receiving rotating power, said bottom end being hollow for receiving the top portion of said auger, said side wall having a hole therethrough,

a latch key received upon said casing and having a plug passing through said hole and engaging said auger;

a ring received over said casing and said key and maintaining said casing and said key together;

a center rod driver coupled to a secondary drill shaft extending through said auger;

a first extension fixedly attached to said casing;

a second extension fixedly attached to said center rod driver for side abutment against said first extension and therein:

said center rod driver is threadedly secured to said secondary drill shaft, said center rod driver has a disc-shaped member resting on said top portion of said auger, said top portion has a slot on its outer periphery for engaging said plug.

4. The assembly of claim 3 wherein:

said first extension includes a first pair of bosses each being positioned adjacent the outer periphery of said top end;

said second extension includes a second pair of bosses each positioned adjacent the outer periphery of said discshaped member adjacent said first pair of bosses.

5. The assembly of claim 4 wherein:

said ring has a semi-circular portion, a tapering portion and a straight portion all integrally joined, said circular portion slidingly abuts against said casing and said straight portion slidingly abuts against said latch key.

6. A drive cap assembly for connecting a rotatable driver with an earth-boring auger and a secondary drill comprising:

a hollow main body with a solid first end and a hollow second end;

a rod fixedly attached to said first end and extending thereabove for receiving said rotatable driver;

a plug separate from said body radially locking said main body to said auger, said plug projecting into said body and against said auger;

a ring fitted around said casing and said plug locking said casing and plug together.

7. The drive cap assembly of claim 6 additionally comprism a center rod driver removably positioned within said hollow main body and connected to said secondary drill, said center rod driver abuttingly engaging said hollow main body so as to rotate said secondary drill with said hollow main body, said driver having a first and second disc integrally connected together with said second disc being the smaller thereof fitting within said auger spacing said secondary drill therefrom, said first disc contacting said solid first end of said casing and resting atop said auger.

8. An apparatus for coupling a rotatable driver to an earthboring auger and a shaft extending through said auger comprising:

a casing into which said auger is telescoped, said casing having a top wall with a pair of depending members;

a loose plug freely mountable to said casing and removably extending therethrough; said auger having a slot into which said plug projects locking said auger and said casing together;

a headed bolt positioned entirely within said casing and having a pair of bosses fixedly fastened to its head, said bosses removable engaging said casing and abutting said members as said casing is rotated.

9. The apparatus of claim 8 wherein:

said means is a headed bolt with a pair of bosses fixedly fastened to its head, said pair of bosses removably engaging said casing.

10. The assembly of claim 1 wherein:

11. The assembly of claim 2 wherein:

said first extension includes a first pair of bosses each being positioned adjacent the outer periphery of said top end; and,

said second extension includes a second pair of bosses each positioned adjacent the outer periphery of said center rod driver adjacent said first pair of bosses.

12. The assembly of claim 1 wherein:

said ring has a semi-circular portion, a tapering portion and a straight portion all integrally joined, said circular portion slidingly abuts against said casing and said straight portion slidingly abuts against said latch key; and,

said latch key is removably mounted on said means of said casing.

Claims

1. A drive cap assembly for an earth-boring auger comprising: a casing having a top and bottom end and a side wall, said top end having means for receiving rotating power, said bottom end being hollow for receiving the top portion of said auger, said side wall having a hole therethrough, a latch key received upon said casing and having a plug passing through said hole and engaging said auger, said plug having a distal end lockingly abuttable against an outer wall of said auger; a ring received over said casing and said key and maintaining said casing and said key together.

2. The assembly of claim 1 additionally comprising: a center rod driver having a longitudinal driving axis and being coupled to a secondary drill shaft extending through said auger; a first extension fixedly attached to said casing and projecting interiorly therein and being offset from said axis, said extension being spaced from said side wall of said casing; a second extension fixedly attached to said center rod driver and positioned against said first extension to rotate about said axis with said auger and secondary drill shaft.

3. A drive cap assembly for an earth-boring auger comprising: a casing having a top and bottom end and a side wall, said top end having means for receiving rotating power, said bottom end being hollow for receiving the top portion of said auger, said side wall having a hole therethrough, a latch key received upon said casing and having a plug passing through said hole and engaging said auger; a ring received over said casing and said key and maintaining said casing and said key together; a center rod driver coupled to a secondary drill shaft extending througH said auger; a first extension fixedly attached to said casing; a second extension fixedly attached to said center rod driver for side abutment against said first extension and wherein: said center rod driver is threadedly secured to said secondary drill shaft, said center rod driver has a disc-shaped member resting on said top portion of said auger, said top portion has a slot on its outer periphery for engaging said plug.

4. The assembly of claim 3 wherein: said first extension includes a first pair of bosses each being positioned adjacent the outer periphery of said top end; said second extension includes a second pair of bosses each positioned adjacent the outer periphery of said disc-shaped member adjacent said first pair of bosses.

5. The assembly of claim 4 wherein: said ring has a semi-circular portion, a tapering portion and a straight portion all integrally joined, said circular portion slidingly abuts against said casing and said straight portion slidingly abuts against said latch key.

6. A drive cap assembly for connecting a rotatable driver with an earth-boring auger and a secondary drill comprising: a hollow main body with a solid first end and a hollow second end; a rod fixedly attached to said first end and extending thereabove for receiving said rotatable driver; a plug separate from said body radially locking said main body to said auger, said plug projecting into said body and against said auger; a ring fitted around said casing and said plug locking said casing and plug together.

7. The drive cap assembly of claim 6 additionally comprising: a center rod driver removably positioned within said hollow main body and connected to said secondary drill, said center rod driver abuttingly engaging said hollow main body so as to rotate said secondary drill with said hollow main body, said driver having a first and second disc integrally connected together with said second disc being the smaller thereof fitting within said auger spacing said secondary drill therefrom, said first disc contacting said solid first end of said casing and resting atop said auger.

8. An apparatus for coupling a rotatable driver to an earth-boring auger and a shaft extending through said auger comprising: a casing into which said auger is telescoped, said casing having a top wall with a pair of depending members; a loose plug freely mountable to said casing and removably extending therethrough; said auger having a slot into which said plug projects locking said auger and said casing together; a headed bolt positioned entirely within said casing and having a pair of bosses fixedly fastened to its head, said bosses removable engaging said casing and abutting said members as said casing is rotated.

9. The apparatus of claim 8 wherein: said means is a headed bolt with a pair of bosses fixedly fastened to its head, said pair of bosses removably engaging said casing.

10. The assembly of claim 1 wherein: said ring has a semi-circular portion, a tapering portion and a straight portion all integrally joined, said circular portion slidingly abuts against said casing and said straight portion slidingly abuts against said latch key.

11. The assembly of claim 2 wherein: said first extension includes a first pair of bosses each being positioned adjacent the outer periphery of said top end; and, said second extension includes a second pair of bosses each positioned adjacent the outer periphery of said center rod driver adjacent said first pair of bosses.

12. The assembly of claim 1 wherein: said ring has a semi-circular portion, a tapering portion and a straight portion all integrally joined, said circular portion slidingly abuts against said casing and said straight portion slidingly abuts against said latch key; and, said latch key is removably mounted on said means of said casing.