US2685931A - Scratcher for well bores - Google Patents

Description

g- 1954 R. c. BAKER ET AL 2,685,931

SCRATCHER FOR WELL BORES Filed Feb. 7, 1950 5 Sheets-Sheet l INVENTORS. JPEUBEN C. BAKER,

ZZ/OMAS M BA 6AM Wad MM A77- TOE/V575 Aug. 10, 1954 R. c, BAKER ET AL 2,685,931

SCRATCHER FOR WELL BORES Filed Feb. 7, 1950 5 Sheets-Sheet 2 JPEUBEN C. BAKER,

711044.45 M. EA GAIV,

INVENTORS.

,QrraEA/EYS Aug. 10, 1954 R. c. BAKER ET AL SCRATCHER FOR WELL BORES 3 Sheets-Sheet Filed Feb. 7, 1950 iii, 5 I: iviNi It!!! iiihu W!!! 5155 iii! 7!!! iii! PEI/BEN C. BAKER,

INVEN TORS.

Arraaws Y5 Patented Aug. 10, 1954 SCRATCHER FOR WELL BORES Reuben C. Baker, Coalinga, and Thomas M. Ragan, Downey, Calif., assignors to Baker Oil Tools, Inc., Vernon, Calif., a corporation of California Application February 7, 1950, Serial No. 142,748

21 Claims. (Cl. 166173) The present invention relates to subsurface well tools, and more particularly to devices for scratching or scraping the walls of open well bores, pipe disposed in well bores, and the like.

An object of the present invention is to provide improved scratcher devices for more effectively removing mud cakes and other sheaths of undesired materialsfrom the walls of bore holes, well conduits and the like.

Another object of the invention is to provide wall scratchers having outwardly extending fingers that can engage and scrape a greater surface around the hole or pipe than in prior devices.

A further object of the invention is to provide wall scratchers that are of strong and sturdy construction, and which are economical to manufacture and easy to assemble. 7

Yet another object of the invention is to provide wall scratchers than can be assembled easily on a casing or similar string to be disposed in a well bore.

Still a further object of the invention is to provide wall scratchers in which each spring scratching element supports and supplements the other, thereby providing a greater spring force for scratcher purposes than the individual scratching elements can f urnish.

Another object of the invention is to provide wall scratcher devices possessing zero or light wall scratching force when the devices are moved through the well bore in one direction, as downwardly, and a maximum wall scratcher force when the devices are moved in the opposite direction, as upwardly.

Still another object of the invention is to provide wall scratchers that not only are effective in scratching the wall of the hole, but which are also capable of centering the well conduit,,on which one or more of the scratchers are mounted, in the hole.

This invention possesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of several forms in which it may be embodied. Such forms are shown in the drawings accompanying and forming part of the present speci- 'fication. These forms will now be described in detail, illustrating the general principles of the invention; but it is to be understood that such detailed description is not to be taken in a limiting sense, since the scope of the inventionis best defined by the appended claims.

Referring to the drawings:

Figure 1 is a side elevation of one form of wall scratcher mounted on a cas ng Section;

Fig. 2 is a cross-section taken along the line 2-2 on Fig. 1;

Fig. 3 is a somewhat diagrammatic view of a Wall scratcher mounted on a casing string during lowering of the latter in a well bore;

Fig. 4 is a view similar to Fig. 3, disclosing elevation of the casing string and scratcher in a the Well bore;

Fig. 5 is a fragmentary cross-section, on an enlarged scale, through part of the scratcher device disclosed in Figs. 1 and 2;

Fig. 6 is a section taken along the line- 6-E on Fig. 5;

Fig. 7 is a fragmentary interior elevation taken as indicated by the line '!'I on Fig. 6;

Fig. 8 is a view similar to Fig. 6 of a modified form of wall scratcher;

Fig. 9 is a view similar to Fig. 5 of still another form of wall scratcher;

Fig. 10 is a plan view of one of the scratcher elements employed in the embodiment of invention disclosed in Figs. 1 to 7, inclusive;

Fig. 11 is a side elevation of the scrateher element shown in Fig. 10;

Fig. 12 is a fragmentary longitudinal section through a hinge element used in the scratcher devices;

Fig. 13 is a view similar to Fig. 6 of another embodiment of wall scratcher.

As disclosed in the drawings, a wall scratcher A is mounted on a casing or well conduit section B for the purpose of removing the mud cake from a portion of the well bore C in which the casing string is to be disposed, and also to center the casing string in the Well bore. It is de-- sired to remove the mud cake or sheath D from a particular portion of the well bore, in order to insure a proper bond between the formation wall and cement slurry, or other cementitious ma terial, pumped down the casing string for up Ward passage through the annulus around the latter. However, it is preferred not to disturb the mud cake to any substantial extent, except along that portion of the formation wall at which cement is to be disposed. For that reason, the Wall scratcher A should scratch the mud cake D lightly, if at all, during descent of the casing string through the well bore. However, the scratching effectiveness should be at a maximum during the upward movement of the casing scratcher in the well bore.

The wall scratcher A could be firmly secured to the casing string, but it is preferred to provide for its slidable mounting thereon. Thus, the Wall scratcher includes a collar or sleeve it slidable on a casing section B, and adapted to engages stop elements ll, [2, such as ring mem bers, welded to the casing section on opposite sides of the scratcher A. These stop elements I I, H may be disposed a few feet apart. During downward movement of the casing string in the well bore, the upper stop elementl I will engage the collar 43 and force the scratcher device downwardly through the well casing. However, during upward movement of the casing string B to a slight extent, such as occurs'in lifting the casing string out of the rotary table slips at the top of the well bore, the scratcher device need not move in an upward direction, inasmuch as the lower stop element" i'zwillnot en gage the lower end of the collar It during such slight upward movements of-the casing string. Greater upward movements, however, will. engage the lower ring with-the collar and'mcve' the scratcher device upwardly with the casing string.

The collar has an outwardly directed bead portion it formed in it provided with a rowof circumferentially spaced apertures or holes Hi, that are preferably equi-distantf-rom one another. A retainer fulcrum or assembly ring 15, which may be made of steel wire, is disposed Within the head 13 and extends substantially entirely around the interior of the collar Ill. Scratcher elements it are mounted on-"the ring Ii-which serves as af-ulcrum'about which the elements l'fi'inay-pivot.

Each scratcher element it includes a heel or base portion i'l extending along the ring 15 and merging into coil portions 8 at its opposite ends. Each coil portion iflmayconsist of one or a plurality of turns, asdesired-and is disposed opposite one or" the bead apertures i l on opposite sides of the heel or base ll. From each c'oilpo'rtion H3, a comparatively long-wire finger til or 28 ex tends through the aperture or hole it. Thus, one elongate finger I9 extends through onehole it at one side of the" base l1,andanother wire finger 2!! extends through an adjacent'h'ole'i at the other side of the base.

It is evident that the "coils l8 serve'to mount "each'scratcherelement on the ring 5. The parts are so arran ed that the heel portion i"! of the element it is disposed above the ring I 5 and will engage the upper inner'portion of the head it (see Fig. 6) to limit the extent of outward swinging of the fingers i9, about the ring t5. When 'the heel portion I l engages thebea'd l3, the fingers i9, 26 are preferably inclined in an up ward and outwarddirectionas disclosed most clearly in Fig. 6. Thespring fingers 19, 2'0 can swing in a downward direction about'the ring [5 to a still further extentf'but such action is resisted by the coil portions it, which are wound or unwound (depending upon "the direction of their coiling) to provide the spring force resisting outward swinging of thefingers. During such winding or unwinding of'the coils I'8,the'heel portions il engagelthe inner wall of the bead l3, and offer resistance to the winding action of the coils with respect to the retainer ring i5.

Upward and inward movement of the spring fingers 5'9, 29 about the retainer ring cantake place to an extent limited by engagement of the innerportions 2! of the fingers with the sides of the collar apertures l4. Such engagement will insure the upward and outward inclination of the fingers I9, 2 tea minimum extent, which may be sufficient tobear against the wall of the well here C relatively lightly. Any further inward force of the wallof the well core on the, springs 19, as will bend them inwardly about the wall defining the aperture 14.

The scratcher elements it are mounted on the ring with their finger portions is, as extending through the apertures i4 and projecting outwardly beyond the collar iii to a substantial extent. The assembled scratcher device A is mounted on a casing section B,'-with the upper and lower stop elements 5 Llz'weldecl to the latter appropriate distance apart on opposite sides of the scratcher device. Th casing string -islowered through the well here, the upper stop element H engaging the collar i6 moving the'scratcher downwardly through the well casing. During-such downward movement, the spring fingers While can merely ride along the mud cake D or wall of the well here C, exerting alight or zeroforce against the casing wall. The extent of inward movement of the fingers i9, 29 is determined by engagement of their inner portions 2i with the upper walls of the apertures M. As indicated above, small'elevation of thesesing string will not move the 'scratcher in' an upward direction, inasmuch as the lower stop'el'ement 12 will not brought into'engagement with the lower end i thecollar H3.

-When the portion in the ell loore C has been reached in which the scratching operation isto take place, the casing string is elevated the proper distance, the lower stop element 2?. engaging'the collar It 'and moving'it-in an upward direction. Duringsuch upward movement, the ends of-t'ne fingers 19, engage the mud cake D, such engagement causing the fingers to tendto swing downwardly and outwardly, shifting the fingers to a position in which they penetra-tethe mud cake and possibly lie-"riding them downwardly through the transverse plane of the bead as indicated. in the-lowermost broken line position. Shown in Fig. 6. Continued upward movement causes the fingers -19, "25 to scratch along the mud cake D, breaking it intorelativeiy small pieces, which can be flushed from the well core by the circulating fluid pumped downwardly through the well-casing, Such downward and outward swinging of fingers i3, is resisted :by the engagement of the heels ii of the scratcher elements with the collar l3, and by the winding or unwinding of the coils l8 about the retainer ring i 5.

Most of the spring force resisting pivoting or" the fingers it, about the retainer ring it is supplied by the spring coils it, a small amount being furnished by the bending of the fingers themselves.

The casing string B may be reciprocated the 'desirednumber of times to insure removal of the mud cake from the wall or" the well here along thedesired'length. The removal of the mud cake is evidenced by the mud particles appearing in' the circulating fluid. as it leaves the top of the well bore.

'In' the scratcher assembly disclosed in Figs. 1 to 7, inclusive, each scratcher element is is mounts on the ring 65, "with its fingers i9, 29 passing through adjacent holes id, M on opposite sides of the heel portion H" or" he element. The next adjacent scrateher' element It is mounted on the retainer or assembly l5, with one of its fingers 59 extending through the same hole it a-s-a finger 29 of an adjoining element. That is, the scratcher elements are so arranged that two fingers i9, '29 of different elements pass through each bead hole or aperture it, one finger from one element and another finger from the adjacent element. Because of this arrangement, a gr ater number of scratcher elements it can be disposed around the collar I0, multiplying the number of fingers I9, 20 available for scratching purposes on the formation wall C or on the wall of a pipe (when the device is used for scratching or scraping the wall of the pipe).

In the arrangement disclosed in Figs. 1 to 7, the scratcher elements It are caused to support or supplement one another. This is accomplished by bending the major portion 25 or 25 ofeach finger with respect to its inner portion 21 or 28 adjacent the collar bead I3. As disclosed in the drawings, the fingers I9, 28 of each element are bent away from one another so as to overlie one or more fingers of adjacent elements. Thus, an inner portion 26a of a finger 2:! of one scratcher element is caused to overlie and will cross the inner portion 25a of an adjacent finger I 9 of another element. In addition, the same finger 29 of a scratcher element will overlie and cross an intermediate portion 25b of a finger is of a third scratcher element. Because of this engagement of a scratcher finger 21' with one or a plurality of fingers I9 of other scratcher elements, the latter two support the first-mentioned finger 2B. As a result, during upward movement of the casing string to scratch the mud cake D from the wall of the formation, the first finger it will engage the wall of the hole and its downward pivoting about the retainer ring I5 will be resisted not only by its own coil spring portion I8, but also by engaging and tending to move downwardly the fingers I 9 of the other two scratcher elements, the downward movement of these fingers being resisted by their respective coil spring portions :6.

It is to be noted that one finger 26 of each scratcher element It is supported by two fingers I9 on two other scratcher elements and that the other finger I9 of the first-mentioned scratcher element It furnishes the supplemental force and resistance for two other fingers 28 of two other scratcher elements.

The crossing arrangement of fingers 29, It not only supplements the scratcher force available for removing the mud cake from the formation Wall, but also insures engagement of all of the fingers with the Wall of the hole. As one finger 29'is swung downwardly and outwardly about the retainer ring I5, it moves the overlapped fingers i9 downwardly; so as to insure their engagement with and digging into the mud cake I) and formation wall C. V The scratcher device can be easily assembled, each spring element I6 being placed within the collar and its opposite fingers I 8, is disposed through a pair of bead apertures or holes I4, with the fingers appropriately overlapping one another. The wire retainer ring 15 can then be threaded through all of the coils I8, and the ring itself appropriately secured, as by welding, to the bead I3 to insure that it will remain in place.

In order to obtain a greater number of scratch ing elements It for action upon the mud cake and to insure that a much greater wall surface will be scratched, a plurality of sets 3B, 3! of scratcher elements may be mounted on the collar It. As shown in Fig. 1, an upper and a lower bead 53, I30. is formed in the collar, the apertures I ia in the lower bead I34: being offset with respect to the apertures I 4 in the upper bead I3. The spring elements It extend through the upper and lower beads I3, I 3a and are assembled in essentially the same manner, the lower scratcher elements I6 being offset slightly with respect to the upper scratcher elements, in order that the ends of the v 6 fingers I9, 20 of the lower set 3! will engage different circumferential portions of the formation wall than the ends of the fingers of the upper set 30. I

The action of the multiple set arrangement of scratcher elements disclosed in Fig. l is essentially the same as the single set, the multiple set ofiering assurance of effective removal of the mud cake from the desired region where the cement bond is to be achieved with the formation wall.

In order to facilitate mounting of the scratcher device on the casing section, it can be made of split or hinged construction. As disclosed in the drawings, the collar or sleeve 19 is made in two parts 59a, Iiib, which is also true of the retainer or fulcrum ring I501, I522. Each retainer or fulcrum ring portion is suitably secured, as by welding, to the bead portion 13 of the collar, each ring section i504, I52) terminating at the ends of the collar section Illa, Ifib. The collar sections Illa, Illb are hinged together at one side of the device by welding or otherwise securing opposed hinge plates 35at the ends of opposite sections, and by inserting a suitable hinge pin 36 through the interleaved hinge knuckles 3's". Preferably, a hinge 35, 35, 3? is placed on the upper and lower portions of the collar sections laid, it?) above and below the collar heads is (see Fig. 1). Such pair of hinges have a common axis about which they may pivot.

On the opposite side of the collar a like pair of hinges 38 is provided. However, the hinge pins 36 are omitted from such hinges, in order that the collar Ill may be opened, swinging its half sections Ifia, lob about the axis of the other hinge pins 36, the device then being moved transversely and placed around a casing section between the stop elements I I, I 2 that may already be provided thereon. As a matter of fact, one of the stop elements may be constituted by the usual coupling (not shown) that may be employed to connect adjacent casing sections together. The collar is then closed about the casing section and pins 39 placed through the knuckle portions 3'1 of the opposite hinge parts. As disclosed in the drawings, such pin elements may take the form of drive screw nails which are driven through the interleaved knuckles 3?, the helical threads or ribs 3 0 on the shank portions of the nails forming or cutting their own threads in the interior of the knuckles 3?, and securely fastening the two halves of each hinge it together. The drive screw nails form a rapid and eifective mannor of closing the scratcher device A around the casing and of holding them properly mounted in position thereon, inasmuch as pivoting action of the hinges 35, (it, 37 is no longer necessary once the device has been assembled on the casing section.

In the form of invention disclosed in Figs. 1 to 7, inclusive, upward movement of the spring fingers I9, 29 is limited by engagement of their inner portions 21, 28 with the side walls of the apertures Id. In the form disclosed in Fig. 8, the spring elements 55a are inverted with respect to the positions they occupied in the other form of the invention, with the heel portions Ila disposed downwardly and exteriorly of the head 53. With this arrangement, the heel portion lla will engage the lower external surface of the head i3 to limit the extent of free downward swinging of the fingers I9a or 2%. However, the inverting of the elements allows them to swing upwardly about the retainer ring it to a greater extent before the finger 19a or 20a will engage the sides of the aperture Id, thefingers, in fact, being able to be collapsed to a comparatively small effective diameter and completely out of engagement with the wall of the well bore. As a result, during downward movement of the casing string in the well bore, the fingers tea, tea will offer no scratching force upon the formation wall or mud cake D, but upon upward movement of the casing string with the lower stop element l2 in engagement with the collar id, the outer ends of the spring elements will engage the formation wall or mud cake and perform a scratching action in the same manner as in the other form of the invention.

In the form disclosed in Fig. 9, the fingers Isl), 20b of each scratoher element do not overlap one another, but extend substantially radially outward; so as to engage the mud cake D and scratch it from the formation wall, without the spring force of one element ltb being supplemented by the resisting spring force of adjacent elements lfib.

The scratcher element illustrated in Fi 13 has its end portions-50 turned upwardly at an angle to the main portions of the fingers IS, 29. With this arrangement, the terminals of the portions 56 can function like claws or teeth in di ging away the mud cake D during upward move ment of the scratcher device, as is evident from the broken line position shown in Fig. 13.

It is apparent that scratcher elements have been devised which can effectively remove the mud cake and other sheaths from the walls of bore holes and well conduits, and in which a maximum scratcher force is available for resisting deflection of the spring fingers and for insuring removal of the toughest mud sheaths from the wall of the well bore. The provision of a plurality of rows of scratcher elements onset with respect to each other insures the coverage of a greater circumferential extent by the scratcher fingers along the wall of the well bore, and the removal of all of the mud cake from the desired. region in the hole. Each scratcher finger may operate individually or may have its scratching action supplemented by the resisting force of adjacent spring fingers, which increases the strength and sturdiness oi" the device considerably. During downward movement of the casing string in the well casing, a small or non-existent scratching force is applied against the wall of the well bore, but during upward movement, a substantial and great force for scratching the hole wall is present. The wall scratchers can be readily assembled and can be easily mounted on a casing or similar conduit string. In addition totheir scratching action, they serve to center the conduit string in the well bore, in order to insure a more uniform deposition of cement slurry around the casing string and thereby prevent channeling.

The inventors claim:

1. In a wall scratcher: a collar having a pin rality of apertures extending through its side wall and adapted to'be mounted on exterior of a well conduit; a plurality of spring elements disposed adjacent each other substantially in a common plane and extending laterally outward through said collar apertures, each element havinga coil portion disposed in the in'erior of said collar; and means inside of said collar extending through said coil portions for. mounting. said elements on said collar.

2. In a wall scratcher: a. collar having a plurality of apertures extending through its side wall and adapted to be mounted on the exterior of a well conduit; a plurality of sping elements disposed adjacent each other substantially in a common plane and arranged around said collar; each element including an outwardly projecting finger extending laterally outward through an aperture and merging into a spring coil disposed inside of said collar, said coil merging into a heel contactable with said collar; and means in the interior of said collar extending through said coils for mounting said elements on said collar.

8. In a wall scratcher: a tubular collar adapted to be mounted on the exterior of a well conduit and having an inner generally cylindrical wall, said collar having a plurality of apertures extending through said wall; a plurality of spring elements disposed adjacent each other substantially a common plane and arranged around said collar; each element including an outwardly projecting finger extending laterally outward through an aperture and merging into a spring coil disposed in the interior of said collar, said coil merging into a heel oontactahle with the inner wall of said collar; and means inside of and secured to said collar extending through said coils for mounting said elements on said collar.

i. In a wall scratcher: a collar having an apertured, outwardly directed circumferential head formed therein; a plurality of spring elements arranged around said collar, each element including a finger extending through a bead aperture and a spring coil disposed in the interior of said collar and within said head; and means within said head extending through said coils for mounting said elements on said collar.

5. In a wall scratcher: a collar havingan apertured, outwardly directed circumferential bead formed therein; a plurality of spring elements arranged around said. collar, each element including a finger extending through a bead aperture, a spring coil disposed in the interior of said collar and within said bead, and a heel secured to said coil and contactable with said collar; and means within said head extending through said coils for mounting said elements on said collar.

6. In a wall scratcher: a tubular collar adapted to be mounted on the exterior of a well conduit and having a plurality of apertures extending through its side wall; a plurality of spring elements disposed adjacent each other substantially in a comrnonplane and arranged around and extending laterally through said collar apertures; each element including a pair of outward ly projecting fingers separate from each other, spring coils in the interior of said collar and secured to said pair of fingers, and a heel secured to said coils and contactable withsaid collar; and

cans extending through said coils for mounting said elements on said collar.

7. In a wall scratcher: a tubular collar adapted to be mounted on the exterior of a well conduit and having an inner generally cylindrical wall, said collar having a plurality of apertures extending through its side wall; a plurality spring elements arranged around and extending laterally through said collar. apertures; each element including a pair of outwardly projecting separate fingers, spring coils in the interior of said collar and secured to said pair of fingers and disposed within said collar, andaheel secured to said coil and contactable with the inner wall or said collar; and means withinandsecured to said collar extending through said coils for mounting said elements on said. collar.

8. In a wall scratcher: a collar having an apertured, outwardly directed circumferential bead formed therein; a plurality of spring elements arranged around said collar, each element including a pair of outwardly projecting fingers extending through said bead apertures, spring coils secured to said pair of fingers and disposed in the interior of said collar and within said bead, and a heel secured to said coils and contactable with the inner wall of said collar; and means within said bead extending through said coils for mounting said elements on said collar.

9. In a wall scratcher: a collar having a plurality of apertures extending through its side wall; a plurality of spring elements disposed circumierentially around said collar substantially in a common plane and extending laterally through said collar apertures, said elements having fingers separate from each other and overlapping and contacting fingers of adjacent elements in a direction circumferentially around said collar, said fingers extending laterally outward of said collar to a substantial extent; and means mounting said elements on said collar.

10. In a wall scratcher: a collar having a plurality of apertures extending through its side wall; a plurality of spring elements arranged circumferentially around and extending laterally through said collar apertures; each element including a lateral and outwardly projecting finger merging into a spring coil disposed in the interior of said collar, said coil merging into a heel contactable with said collarythe finger of one element overlapping and contacting finger of an adjacent element in a direction circumferentially around said collar; and means within said collar extending through said coils for mounting said elements on said collar.

11. In a wall scratcher: a collar having a plurality of apertures extending through its side wall; ,a plurality of spring elements arranged circumferentially around and extending laterally through said collar; each element including a pair of lateral outwardly projecting fingers, spring coils secured to said pair of fingers and disposed in the interior of said collar, and a heel secured to said coils and contactable with said collar; a finger of each element overlapping and contact- .ing one or more fingers of other elements in a direction circuinferentially around said collar; and means extending through said coils for mounting said elements on said collar.

12. In a wall scratcher: a collar having an apertured, outwardly directed circumferential bead formed therein; a plurality of spring elements arranged around said collar, each element including a pair of outwardly projecting fingers extending through adjacent bead apertures, spring coils secured to said pair or fingers, and a heel secured to said coils and contactable with said collar between the apertures through which the fingers project; the fingers of each element diverging in an outward direction with respect to each other so as to overlap and contact the fingers of adjacent spring elements; and means within said bead extending through said coils for mounting said elements on said collar.

13. In a scratcher: a collar having an apertured, outwardly directed circumferential bead formed therein, said collar comprising a plurality of sections longitudinally spaced hinge means on opposite sides of said head securing said sections together at one side of said collar; longitudinally spaced detachable means on opposite sides of said bead securing said sections together at the opposite side of said collar; a plurality of spring elements arranged around said collar, each element including a finger extending through a bead aperture anda spring coil disposed within said bear; and an annular member secured to said collar andextending through said coils to mount said elements on said collar, said annular member comprising a plurality of sections conforming to the collar sections.

14. In a wall scratcher: a collar having an apertured, outwardly directed circumferential bead formed therein; a plurality of spring elements arranged around said collar, each element including a pair of outwardly projecting fingers extending through different bead apertures, spring coils secured to said pair of fingers, and a heel secured to said coils and contactable with said collar between the apertures through which the fingers project; the fingers of each element diverging in an outward direction with respect to each other so as to overlap and contact the fingers of adjacent spring elements in a direction circumferentially of said collar.

15. In a wall scratcher: a collar having an apertured, outwardly directed circumferential bead formed therein; a plurality of spring ele-. ments arranged around said collar, each element including a pair of outwardly projecting fingers extending through difierent bead apertures, spring coils disposed within said bead and secured to said pair of fingers, and a heel secured to said coils and contactable with said collar between the apertures through which the fingers project, the fingers of each element diverging in an outward direction with respect to each other so as to overlap and contact the fingers of adjacent spring elements in a direction circumferentially of said collar.

16. In a Wall scratcher: a collar having a plurality of apertures disposed circumferentially therearound; a plurality of spring elements arranged around said collar, each element including a pair of outwardly projecting fingers extending through different collar apertures, spring coils on the inside of said collar and secured to said pair of fingers, and a, heel secured to said coils and contactable with said collar between the apertures through which the fingers project; the fingers or each element diverging in an outward direction with respect to each other so as to overlap and contact the fingers of adjacent spring elements in a direction circumferentially of said collar.

17. In a wall scratcher: a member having an apertured, outwardly directed bead formed therein; a plurality of spring elements disposed along said bead, each element including a pair of outwardly projecting fingers extending through different bead apertures, spring coils disposed within said bead and secured to said pair of fingers, the axes of said coils extending generally along the length of said bead, and a heel secured to said coils and contactable with said member between the apertures through which the fingers project; the fingers of each element diverging in an outward direction with respect to each other so as to overlap and contact the fingers of adjacent spring elements.

18. In a wall scratcher: a member havin an apertured, outwardly directed bead formed therein; a plurality of spring elements disposed along said bead, each element including a pair of outwardly projecting fingers extending through different bead apertures, spring coils disposed within said bead and secured to said pair of fingers, the axes of said coils extending generally alon the 11 length of said bead, and a heel secured to said coils and contactable with saidmember between the apertures through which the fingers project.

19. In a wall scratcher: a member having an apertured and outwardly directed bead formed therein; a plurality of spring elements disposed along said head, each element including an outwardly projecting finger extending through a bead aperture, a sprin coil disposed within said bead and secured to said fingers, and a heel secured to said coil and contac'table with said member; the axes of said coils extending generally along the length of said bead.

20. In a wall scratcher: a member having an internal groove therein and a plurality of spaced apertures; a plurality of spring elements disposed alon said groove, each element including a pair of outwardly projecting fingers extending through different apertures, spring coils disposed within said groove and secured to said pair of fingers, and a heel secured directly to said coils and contactable with said member; the axes of the coils of said spring elements extending generally lengthwise of said groove.

21. In a wall scratcher: a collar having an apertured, outwardly directed bead formed therein; a plurality of spring elements arranged circumferentially around said collar, each element including a pair of lateral and outwardly projectin fingers extending through difierent bead apertures and also including an intermediate portion disposed within said bead; said apertures being of a greater area thanthe area of said fingers to permit rotation of said spring elements in said head; meansadapted to abut each spring element to prevent rotation of said element on the collar beyond a predetermined point, said means comprising a portion of the collar adjacent said aperture which is engaged by a portion of each spring element, the fingers of each element diverging in an outward direction with respect to each other so as to overlap and contact the fingers of adjacent elements in a direction circumferentially around said collar; and means engageable with said elements to prevent substantial movement of said elements inwardly of said collar.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 181,416 Davis Aug. 22, 1876 574,972 Wiens Jan. 12, 1897 1,040,118 Batt Oct, 1, 1912 1,371,425 Jones Mar. 15, 1921 1,557,166 Horn Oct. 13, 1925 2,298,985 Still et al Oct. 13, 1942 2,315,069 McKean et al Mar. 30, 1943 ,36 ,198 Gibson Nov. 7, 1944 2,412,876 Edwards Dec. 17, 1946 2,421,434 Reistle et a1 June 3, 1947 2,427,632 Stephens Sept. 16,1947 2,506,405

Wright May 2, 1950

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