US2715275A - Mounting for gun sighting telescope - Google Patents

Description

OR 2 s 7 l 5 s 275 Aug- 16, 1955 H. B. KIPP MOUNTING FOR GUN SIGHTING TELESCOPE 2 Sheets-Sheet l Filed March 15. 1954 INVENTOR. HARRY e. K PP BYMJQQ ATTORNEY Flcl Aug. 16, 1955 H. B. KIPP MOUNTING FOR GUN SIGHTING TELESCOPE 2 Sheets-Sheet 2 Filed March l5, 1954 INVENTOR. HARRY B. KIPP QIJ fb AT TOBNEY United States' Patent O MOUNTING FOR GUN SIGHTING TELESCOPE Harry B. Kipp, Irondequoit, N. Y., assignor to Bausch &

Lomb Optical Company, Rochester, N. Y., a corporalion of New York Application March 15, 1954, Serial No. 416,031

9 Claims. (Cl. 33-50) This invention relates to mountings for gun sighting telescopes and more particularly relates to improvements in mechanism for adjusting the sighting position of a telescope held therein.

It is an object of this invention to provide a novel mounting for a gun sighting telescope which is economical to manufacture, is sturdily constructed for long wear and hard usage, and has the advantage of small size together with good streamlined appearance.

Other objects are to provide such a device in which the adjustments of the telescope for windage and elevation may easily and quickly be made repeatedly with a high degree of precision and to provide a telescope adjustment mechanism which is protected against entrance of dirt and foreign matter and is easy to clean and maintain in good operating condition.

Other objects and advantages reside in the features of construction and the arrangement and combination of its parts as described in the following specification and shown in the accompanying drawings in which:

Fig. 1 is a side elevation partly broken away of a gun on which a sighting telescope is mounted by means of mountings which are constructed according to my invention.

Fig. 2 is a plan view of the rear telescope mounting shown in Fig. 1.

Fig. 3 is a side view, partly in section and broken away, of the structure shown in Fig. 2.

Fig. 4 is a side view of the front telescope mounting shown in Fig. 1,.

Fig. 5 is a sectional view taken on the line 5-5 of Fig. 3.

Fig. 6 is a sectional view taken on the line 6-6 of Fig. 4.

Fig. 7 is a detailed perspective view, partly in section and with parts in separated relation, of the actuating ring shown in Fig. 3.

Fig. 8 is an exploded perspective view of a subassembly of certain operating parts shown in Fig. 3.

Fig. 9 is a sectional view taken substantially on the line 9-9 of Fig. 6.

Fig. 10 is a perspective View of an operating part shown in Fig. 4.

Fig. 11 is a perspective view of a detail, and

Fig. l2 is a fragmentary view, partly in section, showing the construction of the spring pressed plunger of Fig. 5.

A preferred form of my invention is shown generally in Fig. 1 of the drawings wherein a gun sighting telescope 10 is adjustably supported on a gun 11 by a front mounting bracket 12 and a rear mounting bracket 13. On the receiver part of the gun 11, the front and rear brackets 12 and 13, respectively, are secured by means of dovetail bases 14 and 15 which are closely tted individually to respective longitudinal dovetail keyways 16 and 17 that are formed in the bottom surfaces of brackets 12 and 13, respectively, as shown in Figs. 5 and 6. Attachment screws 18 and 19 extending through the bases 14 and 15, respectively, are threaded into the gun receiver to x said bases onto the barrel. To prevent longitudinal displacement, the brackets 12 and 13 are clamped onto their respective ice bases 14 and 15 by cup- pointed lock screws 20 and 21 which are laterally threaded through the lower part of said brackets so as to clamp against adjacent sides of said bases.

Said front bracket 12 has a central aperture within which is located the telescope 10 which has its upper side contacting a pair of angularly spaced support buttons 22 and 23 having reduced stems 24 and 25 that are held, respectively, in corresponding fitted bores 26 and 27 in the upper part of said bracket so as to project inwardly therefrom. For preventing the telescope 10 from rotating within its mounting, there is provided a parallel sided key 28 which is carried by bracket 12 and is slidably tted within an extended longitudinal keyway 29 formed in the underside of telescope 10. Key 28 forms the upper part of a pressure plug 30 which is slidably seated in a socket 31 and is pressed upwardly to hold the telescope in contact with the buttons 22 and 23 by a spring 32 nested in a recess 33 in the bottom of the plug 30.

Since it is necessary at times to incline the reticle of the telescope 12 with respect to its mounting to suit different users, novel means have been provided for this purpose by forming integrally at the upper end of the socket member 31 a laterally extended curved socket plate 34, as shown in Fig. 10. This plate is provided with opposite parallel sides 35 and 36 which operate in sliding contact with a conforming recessed guideway 37 formed laterally in the lower part of bracket 12 with a curvature to match that of said plate, as shown in Figs. 4, 6 and 9. Opening into the middle of guideway 37 is an elongated clearance space 38 wherein the socket 31 moves. In order to lock the socket plate 34 in any selected angular position on its guideway 37, two lock screws 39 and 40 having large diameter heads 41 are threaded into corresponding tapped holes 42 and 43 in bracket 12 which extend underneath said guideway as shown in Figs. 6 and 9 so that the heads 41 of the screws 39 and 40 overlap the edge 35 of plate 34. Clearance counterbores, one of which is shown at 44 cutting into the guideway 37, are provided in bracket 12 around the screw heads 41 so that the screws 39 and 40 may be clamped tightly against the side 35 of plate 34.

Longitudinal displacement or set-back of thel telescope 10 relative to its mounting at the moment of firing of the gun 11 is absorbed by a set-back spring 45 abutting at the forward end against bracket 12 and at the rear end against an adjustable abutment collar 46. A stop ring 47 is suitably xed to the telescope 10 at the other side of the bracket 12 to establish the normal longitudinal position of the telescope in its mounting.

The rear bracket 13 has a central aperture within which the telescope 10 is supported on three angularly spaced, radially extending plungers, namely, a vertical elevation adjusting plunger 48, a horizontal windage adjusting plunger 49, and an oblique pressure plunger 50 whose axis substantially bisects the angle between the other two plungers. Pressure plunger 50 which is preferably formed of a non-metallic plastic material, such as sold under the trade-name nylon, is slidably'mounted in a smooth bore 52 in bracket 13 which is covered at its outer end by a closure cap 53 xed to the bracket by suitable means such as threads S4. The outer end of plunger 50 is provided with a recess 51 in which a spring 55 is held under compression with its outer end abutting against the closure cap 53.

According to this invention, elevational and windage sighting adjustments to the telescope 10 are eifected, through the plungers 48 and 49, by two preferably duplicate actuating rings 56 and S7 which are rotatably fitted in spaced relation to each other within a cylindrical bearing surface 58 extending axially through bracket 13, as shown in Fig. 3. On the adjacent inner ends of the actuating rings 56 and 57, there are provided radial faces 59 and 60, respectively, in which are formed spiral cam surfaces or grooves 61 and 62, as shown in Figs. 3, 5 and 7. The vertical or elevation adjusting plunger 48 and the horizontal or windage adjusting plunger 49 are similarly constructed in cylindrical form and are, respectively, slidably mounted within corresponding radial bores 63 and 64 which extend through rear bracket 13 at about 90 angular separation into contiguity with the spiral cam grooves 61 and 62. Closure caps 65 and 66 having threaded connections 67 and 68 to the bracket 13 cover the outer ends of bores 63 and 64. Along one side of the horizontal windage plunger 49 there is formed a horizontal tooth-like projection or lug 69 of partial spiral form, as shown in Figs. and 8, which is tted to engage with the spiral cam surface or groove 62, for the purpose of moving plunger 49 horizontally by turning the actuating ring 57 in its bearing 58. On the side opposite to that in which said projection 69 is formed, the inner end of the plunger 49 is provided with a flat surface 70 which lies against the radial face 60 of the actuating -ring 56 to maintain the tooth-and-cam connection in operative position by preventing rotation of the plunger 49. Elevation adjusting plunger 48, shown in Fig. 3, is provided similarly to windage adjusting plunger 49, with a tooth-like projection or lug 71 for engagement with the spiral cam surface or groove 61 on actuating ring 56. A at surface 72 is provided on the plunger 48, on the opposite side from the lug 71, to lie against the radial face 60 of ring 57 so as to prevent rotation of plunger 48 and thereby hold the tooth-and-cam connection in operative position. The plunger 48 may thereby be moved vertically by rotation of its adjacent actuating ring 56.

In order that each of the vertical and horizontal aim adjusting motions per se shall be relatively truly rectilinear, both of the plungers 48 and 49 are provided, respectively, on their inner ends with contact pieces 73 and 75 which are preferably made of a plastic material such as that sold under the trademark nylon, and have tips which are formed with a slight cylindrical bulge or ridge extending normal to the axis of said plungers and crosswise to the axis of the telescope 10. The actual contacts between the telescope and the pieces 73 and 75 are therefore along straight narrow zones on the ridge portions of these contact pieces. Sterns 74 and 76 are formed on the contact pieces 73 and 75 of proper size to slidably t, respectively, in central holes 77 and 78 formed in the inner ends of plungers 48 and 49 and the stems are non-rotatably held in each plunger by a set screw 79 which snugly ts a longitudinal slot 80 provided in each of the stems 74 and 76, as shown in detail in Fig. 8.

A zeroing adjustment for presetting the line of sight of the telescope 10 to match individual gun characteristics is also provided by forming threads 81 and 82 in the outer ends of the central holes 77 and 78, respectively, and threading therein regulating plugs 83 and 84 against which the ends of the stems 74 and 76 rest to initially position said contact pieces 73 and 75 and consequently the telescope 10. It will be noticed that the flat surfaces 70 and 72, on plungers 49 and 48, respectively, not only serve to maintain alignment of the described lug-and-cam connection, but also serve to prevent the contact pieces 73 and 75 from rotating relative to the axis of the telescope 10.

Flat surfaces 85, shown in Figs. 5 and 12, are provided on opposite sides of the inner end of pressure plunger 50, the distance between said surfaces being slightly less than the distance between the radial faces 59 and 60 on the actuating rings S6 and 57, respectively, so that said end extends freely therebetween into supporting contact with the wall of telescope 10.

Rotation of the actuating rings 56 and 57 is effected by a pair of annular operating anges 86 and 87, each of which is secured to its respective actuating ring by attachment screws 88 extending through holes in said anges and threaded into tapped holes 94 which are formed in the outer radial faces 97 and 98 of the respective rings 56 and 57. The operating flanges 86 and 87 are made in the form of shallow cups having annular longitudinally extending lips 99 and 100, respectively, which cover the opposite ends of the bracket 13. On the outer surface of these lips 99 and 100, circular bands 101 of knurling are formed to provide a satisfactory linger grip for the operator, and appropriate elevation and windage scales 102 and 103 are formed, respectively, on said outer surfaces of lips 99 and 100 between the knurled bands. On the bracket 13, index marks 104 and 105 are provided adjacent to their respective scales 102 and 103 in substantially the same angular location so that both marks may be viewed from the same position by the user.

Since one of the purposes of this invention is to provide accuracy in adjusting the telescope to various scale settings, the knurling 101 is preferably manufactured in the form of straight longitudinal V-shaped teeth which are formed exactly the same distance apart by a precision method. A spring detent 106, shown in Figs. 3, 5, and 11, is held by screw 109, passing through hole 110, in a tted slot 107 extending longitudinally through the lower part of the bracket 13 so that the suitably shaped bosses 108 at the ends of detent 106 will resiliently engage between the knurled teeth 101 in both operating anges 86 and 87. The detent 106 in cooperation with said knurled teeth 101 thus serve as a click stop mechanism by which the aim of the gun may be adjusted in small precisely predetermined amounts without looking away from the target.

A further novel feature of this invention is provided in the demountable swivel connection located between each of the actuating rings 56 and 57 and the mounting bracket 13 wherein these rings are held. Since the swivel connections for both of said rings 56 and S7 are similar to each other, only one connection is here described in detail. With regard to the preferred form of swivel connection for the actuating ring 56 as shown in Figs. 3 and 7, it comprises a resilient circular coupling ring 111 which is made of spring material and is separated at 113 to allow expansion thereof during assembly. The coupling ring 111 is constructed with radial sides which are slidably fitted into a peripheral channel 114 formed in the actuating ring 56, the depth of the channel being at least as great as the radial thickness of the coupling ring 111 so as to entirely contain it. In longitudinal alignment with the coupling ring 111 there is formed, in the bearing surface 58 in bracket 13, an annular coupling groove 115 of shallow depth and having a width slightly greater than the coupling ring 111 so that it may easily enter therein.

The coupling ring 111 is expanded into groove 115 by means of the screws 88 which also hold the flange 86 to the actuating ring 56. The tapped holes 94 for said screws 88 are centered slightly below the bottom of channel 114 and are bored therethrough so that the holes intersect and cut across the channel 114. All of the screws 88 are formed with cone-pointed tips 116 which enter below and contact with the coupling ring 111 and raise it a definite predetermined distance into the groove 115 as the screws 88 are turned into the actuating ring 56. The radial location of the screws 88 with respect to the ring 56 is so chosen that said cone-pointed tips 116 cannot force the coupling ring 111 far enough into the groove 115 to cause binding and therefore the coupling is capable of free swiveling motion even though it is locked against longitudinal motion. The actuating ring 57 is similarly provided With a swivel coupling ring 112 for its retention in operative relation with the windage adjusting plunger 49 and screws 88 hold the operating flange 87 to the ring 57 and also serve to expand the coupling ring 112 in the same manner as heretofore described with respect to the actuating ring 56.

Both of the actuating rings 56 and 57 are provided with identical means for limiting turning thereof to substantially a single rotation. Such means, referring particularly to the ring 56 shown in Fig. 7, comprise a pair of rotation stop pins 119 and 120 which are secured in a corresponding pair of holes formed respectively in different convolutions of the spiral cam groove 61 so as to limit rotation of said ring by impingement of the plunger lug 71 against these pins. It is particularly important that the individual angular locations of these stop pins 119 and 120 relative to the screw holes 94 be so chosen that the zero mark on the elevation scale 102 of the operating ange 86 will match its index mark 104 when the telescope sight 10 has been adjusted for zero elevation of the gun 11.

With regard to the assembly of the parts of the rear mounting bracket 13, the actuating mechanisms for elevation plunger 48 and windage plunger 49 are of similar construction so that the assembly procedure is the same for both rings 56 and 57 so that only the assembly of the elevation adjusting mechanism is described in detail herebelow.

The elevation plunger 48 is set intoA the bore 63 and the actuating ring 56, together with its assembled coupling ring 111, is slid into the bearing surface 58 far enough to introduce the operating lug 71 of the plunger 48 into the cam groove 61 and simultaneously align the coupling ring 111 with its coupling groove 115. Then the ange 86 is placed over the front end of bracket 13 and it is fastened to the outer face 97 of the actuating ring 56 by the screws 88, care being taken to assure that the zero mark of the scale 102 on the flange is aligned with the index mark 104. As said screws are finally tightened, their cone points 116 expand the coupling ring 111 into the coupling groove 115 and lock the actuating ring swivelly to the bracket 13. In a similar manner, the windage actuating ring 57, plunger 49, operating flange 87 and coupling ring 112 are assembled at the other end of the bracket 13.

The assembly of the front mounting is believed to be obvious by reference to Figs. 4, 6 and 9.

The aforementioned zeroing operation, by which the telescope 10 is properly preset for zero elevation of the gun barrel, is performed in the following manner. After the completed front and rear mounting brackets 12 and 13 have been assembled on the bases 14 and 15, respectively, and locked thereon by the lock screws and 21, the telescope 10 is mounted therein, as shown in Fig. l, with the key 28 in engagement with the telescope keyway 29 to prevent relative rotation of the telescope. With the scales 102 and 103 set in their zero positions, the gun barrel is aligned with the center 0f a standard target and the reticle of the telescope 10 is centered on the target by turning the regulating screws 83 and 84 individually with a screw driver until the centers of the reticle and target are in coincidence. Finally, the closure caps 65 and 66 are screwed tightly onto their respective threads 67 and 68 and the telescopic sight is ready for use. Thereafter, only the operating flanges 86 and 87 are used to adjust the elevational and windage positions of the telescopic sight as long as it is used on the same gun.

It will be appreciated from the foregoing description that the arrangement of the two actuating rings 56 and 57 in contact with the opposite sides of the telescope supporting plungers 48 and 49 is extremely compact and is very effective in providing a close-coupled and j direct camming means for individually moving the plungers to effect elevation and windage adjustments. The secondary use of these actuating rings to prevent unwanted rotation of said plungers so as to correctly position the plunger contact pieces 73 and 75 crosswise to the telescope and at the same time align the camming connections 69 and 71 is also a feature. It is further pointed out that the swivel connections 111 and 112 for the actuating rings 56 and 57, respectively, together with their locking mechanism, is an effective mechanical combination. All of the operating parts are nested and concealed for their effective protection and ne streamlined appearance in addition to reducing the size of the bracket to a minimum. In a similar way, the angularly displaceable key socket 31 in bracket 12 permits the telescope 10 to be turned and locked with the reticle in any preferred position, this mechanism also being rugged, compact and concealed and, together with the other above-mentioned mechanism, fulfilling the stated objects of this invention.

Although but certain embodiments of my invention have been shown and described in detail, it is to be understood that other embodiments thereof are possible and changes may be made in the form and arrangement of the parts and substitutions may be made therein without departing from the spirit of the invention as claimed in the appended claims herebelow.

I claim:

l. A mounting for a gun sighting telescope comprising a bracket adapted to be attached to a gun, said bracket having a central circular aperture, a plurality of circumferentially spaced slidably mounted plungers carried by the bracket and radially positioned relative to the aperture for providing seating means for holding a sighting telescope therebetween, means for moving one of the plungers comprising an actuating ring rotatably carried by the bracket within the aperture and surrounding the telescope with the axis of rotation of the ring lying within and substantially longitudinally of the telescope, a. projection carried by a side of a plunger, said ring having on its radial inner face a spiral cam groove in which the projection is positioned whereby rotation of the actuating ring will move the plunger to eiect adjustments of the telescope.

2. A mounting for a gun sighting telescope comprising a front bracket in which said telescope is slidably and non-rotatably held and a rear bracket wherein said telescope is movably held for lateral windage and elevational adjustments, said brackets being adapted to be attached to a gun, means for effecting said adjustments including the combination of a vertical plunger and a horizontal plunger on which the telescope is seated, each said plunger being slidably mounted in individual radial bores which are located in the rear bracket in a common plane, a pair of coaxial actuating rings freely encircling the telescope and rotatably mounted on opposite ends of the rear bracket in a common axial bore in said rear bracket with their inner ends located contiguously to opposite sides of said plungers, each of said plungers having a lateral projection, and spiral cam means formed on the adjacent inner ends of said rings, the cam means on the rings being respectively in operative engagement with the projections on the plungers whereby rotation of one ring causes axial movement of the vertical plunger and rotation of the other ring causes axial movement of the p central aperture, a plurality of plungers horizontal plunger.

3. In a gun sighting telescope mounting, a bracket adapted to' be attached to a gun, said bracket having a slidably mounted on the bracket, said plungers extending radially into said aperture for adjustably supporting the telescope therebetween, means for moving two of said plungers for effecting elevation and windage adjustments of the telescope respectively, said means comprising a pair of actuating rings rotatably mounted on the bracket on spposite sides of the plungers, the inner faces of said rings being adjacent to the plungers and having spiral cam surfaces, each of said two plungers having a projection on one side and a at surface on the opposite side thereof, the projections on the plungers being in operative engagement with the respective cam surfaces on the adjacent rings whereby turning of the rings will produce movements of the respective plungers,

each flat surface on a plunger being in contact with the end face of a ring whereby the projections on the two plungers are held in operative engagement with the respective cam surfaces.

4. A mounting for a gun sighting telescope comprising a bracket wherein said telescope is movably held for lateral windage and elevational adjustments, means for effecting said adjustments including a vertical plunger and a horizontal plunger on which the telescope rests, said plungers being slidably mounted in radial cylindrical bores in said bracket, each plunger having a ridge shaped contact end resting transversely on said telescope and being provided with a longitudinal flat surface substantially parallel to the axis of the plunger and the ridge shaped contact end, a pair of coaxial actuating rings loosely surrounding the telescope and rotatably fitted to respective bearing surfaces on opposite sides of the bracket, said rings having adjacent inner radial faces in which spiral grooves are formed, laterally extending projections on said plungers engaging respectively with the grooves on the rings for moving the plungers radially upon rotation of said rings, the flat surface on each plunger being in contact with one of said radial faces to prevent rotation of the plunger and thereby maintain said ridge shaped contact ends crosswise to the telescope, and spring means for urging the telescope against the contact ends on said plungers whereby vertical and horizontal aiming adjustments of said telescope may be provided.

5. In a gun sighting telescope mount, a bracket adapted to be attached to a gun, said bracket having a central bearing aperture, a plurality of spaced plungers slidably carried by the bracket and extending radially into said aperture for supporting a telescope therebetween, means for moving one of the plungers comprising an actuating ring rotatably mounted on the surface of said aperture, a projection extending laterally from said one plunger, the inner radial face of said ring having a spiral cam surface which is engaged by said projection whereby turning of the ring will move the said one plunger to effect adjustments of the telescope, and means for swivelly mounting the ring in the bracket to prevent longitudinal movement thereof comprising a split spring coupling ring positioned in a circumferential groove formed on the outer surface of said ring, and a screw having a cam surface at its end, said screw being threaded into an opening in said ring which intersects said groove whereby the cam surface on the screw will expand said coupling ring to partially position it in a circumferential groove formed on the inner surface of said aperture and thereby hold the ring within the bracket while permitting rotation of the ring.

6. A mounting for a gun sighting telescope comprising a bracket wherein said telescope is movably held for lateral windage and elevational adjustments, means for attaching each said bracket to a gun barrel, means for effecting said adjustments including an actuating ring rotatably tted to a bearing surface on said bracket and loosely surrounding the telescope, an annular operating ange secured to said ring at its outer end, a plunger extending radially through said bracket contiguously to said ring and an operative connection between the plunger and the ring by which rotation of the ring produces radial motion of the plunger, a separable swivel connection between said ring and rear bracket including a resilient coupling ring seated substantially wholly within a channel in said actuating ring and expandable into an annular aligned groove in said bracket, and a combination expander and attachment screw which extends through a hole in said flange and is threaded into the actuating ring to secure it thereto, said screw having a cone shaped point, the tip of said point being located slightly below the underside of said coupling ring and free to move thereunder so that the nal movement of the screw into clamping position also expands the lock ring into said groove to form a swivel connection.

7. A mounting for a gun sighting telescope comprising a rear bracket wherein said telescope is movably held for lateral windage and elevational adjustments and a front bracket having an opening through which the telescope extends, said telescope having an extended longitudinal keyway therein which is slidably keyed to said front bracket to prevent relative rotation therewith but permit relative longitudinal motion therethrough, means for attaching each said bracket in mutual alignment to a gun, adjusting means in said front bracket for adjusting the angular position of the telescope relative to the front bracket, said adjusting means including a socket member formed integrally with a curved parallel-sided socket plate extending crosswise thereof, a curved guideway formed in the lower part of the front bracket along the periphery of said opening, said guideway being longer than and of like curvature to that of said plate and having a wide clearance recess extending thereinto to accommodate the socket member whereby said socket member may slide in its guideway, a spring-pressed key slidably fitted at one end into a radial bore in said socket member and having an end which slidably ts into said keyway so as to lock the member against rotation relative to the telescope, and means for locking the socket member in its guideway including a lock screw threaded into the front bracket through a hole which opens into the side of said guideway so as to permit the screw to be tightened against said side.

8. A mounting for a gun sighting telescope comprising a bracket adapted to be attached to a gun, said bracket having a central aperture, a plurality of plungers slidably mounted on said bracket and extending radially into said aperture to provide means for holding a telescope therebetween, means for moving one of said plungers comprising an actuating ring rotatably mounted on the bracket and in coaxial relation to the aperture,

a spiral cam surface formed on the inner radial face of the ring, a laterally extending projection on the plunger, said projection being in operative engagement with the cam surface whereby rotation of the ring will move the plunger to effect adjustment of the telescope, a contact piece which engages the telescope, said contact piece being slidably mounted in a bore in said plunger, and a screw in the bore for limiting the movement of the contact piece therein whereby zero adjustment of the telescope may be effected.

9. A mounting for a gun sighting telescope comprising a bracket adapted to be attached to a gun, said bracket having a central aperture, a plurality of plungers slidably mounted on the bracket and extending radially into the aperture to provide means for holding a telescope therebetween, means for moving two of said plungers for effecting windage and elevation adjustments of the telescope comprising a pair of actuating rings rotatably mounted on the respective opposite ends of the bracket and coaxially with the aperture, cam and tooth means operatively connecting the rings with the two respective plungers, a flange carried by each ring, a knurled portion on each flange, a resilient member positioned in a groove formed on the underside of the bracket, and detents formed at the two ends of said member, said detents being resiliently urged into engagement with the knurled portions of the respective flanges.

References Cited in the tile of this patent UNITED STATES PATENTS 870,272 Burton Nov. 5, 1907 1,391,908 Segler Sept. 27, 1921 2,161,051 Humeston June 6, 1939 2,208,913 Unertl July 23, 1940 2,539,256 Leupold Ian. 23, 1951 FOREIGN PATENTS 113,223 Sweden Feb. 13, 1945

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