US2667667A

US2667667A - Acoustic ceiling construction

Info

Publication number: US2667667A
Application number: US58439A
Authority: US
Inventors: Jacobson Victor
Original assignee: LEVEL LINE CEILINGS Inc
Current assignee: LEVEL LINE CEILINGS Inc; LEVEL-LINE CEILINGS Inc
Priority date: 1948-11-05
Filing date: 1948-11-05
Publication date: 1954-02-02
Anticipated expiration: 1971-02-02

Description

1954 v. JACOBSON 2,667,667

ACOUSTIC CEILING CONSTRUCTION Filed Nov. 5, 1948 5 Sheets-Sheet l VJacobsan fin afar A 01mg v. JACOBSON 2,667,667 ACOUSTIC CEILING CONSTRUCTION 5 Sheets-Sheet 2 Feb. 2, 1954 Filed Nov. 5, 1948 1954 v. JACOBSON 2,667,667

ACOUSTIC CEILING CONSTRUCTION iled Nov. 5, 1948 5 Sheets-Sheet 3 V zfz 0 2265012 enfor Q, y I W ,iiorney Feb. 2, 1954 v JACQBSON 2,667,667

ACOUSTIC CEILING CONSTRUCTION iled Nov. 5, 1948 5 Sheets-Sheet 4 7: Jacobson orney Feb. 2, 1954 v. JACOBSON ACOUSTIC CEILING CONSTRUCTION 5 Sheets-Sheet 5 iled Nov. 5, 1948 Patented Feb. 2, 1954 ACOUSTIC CEILING CONSTRUCTION Victor Jacobson, New York, N. Y., assignor, by mesne assignments, to Level-Line Ceilings, -Inc.,

New York, N.

FL, a corporation ofNew York Application November 5, 1948, Serial No. 58,439

3 Claims.

This inventionrelates to ceiling constructions and more particularlyito. those of acoustic'corr'e'ctive nature,.the invention having for its principal object to provide a ceilingconstruction' which can be readily and quickly erected at a cost which is less than heretofore possible.

Another object of .the' invention is to provide a suspendedceiling wherein the total of the exposed-surfacearea-of the sound absorptive material is considerably less'than the areas heretofore tho'ught necessary to accomplish the same degree of acoustic correction.

Another object of the invention resides inan acoustical ceiling comprising primary and secondary supporting members, the secondary members having portions extending'through to and forming a part of the exposed surface of ceiling.

A further object of the invention is to provide for the installation of acoustical tile, mechanically suspended, as distinguished from heretofore known and usual types of ceilings depending for their securernent upon nailing, cementing, screwing and the like.

A still further object of the invention is to provide a ceiling the total of the exposed surface area of which comprises a combination of different sound dissipating materials, one material functioning by friction of the sound waves received, andthe other material functioning by diaphragmatic action caused by the impingement of the sound waves thereon, these materials hereinafter referred to generally as being sound absorptive and sound reflective.

Other objects and-advantages'of the invention will become apparent from a study of the following description and-the'drawings of a preferred embodiment of the invention.

With these and" other objects in View the invention resides in the novel details of construction and combinations of parts as will be disclosed more fully hereinafter and particularly covered by'the claims.

Referring to the accompanying drawings forming a part of this specification and in which ilke numerals designate like parts in all the views- Fig. 1 is a diagrammatic representation of the appearance of a ceiling made in accordance with this invention and showing alternate strips of sound-absorptive and sound reflective material;

Fig. 2 is a partial perspective view of a ceiling suspension incorporating the elements comprising'this invention;

Fig 3 is-a vertical sectionalview taken transverselyof th'e'alternated stripslof absorptive and reflective materials, and illustrating their suspension from a primary ceiling structural member;

Fig. 4 is a perspective View of a splicer utilized to align two abutting pans constituting thesound reflective medium employed in the ceiling; construction;

Fig. 5 is a detail view partly in section illustrating the securement of the sound absorptivema'terial by a clip bar with respect to the pans of sound reiiective material;

Fig. 5 is a perspective view of a modified form of hanger for suspending thev pans of soundireflective material from aprimary ceilingstructural member;

Fig. 7 is a partial perspectiveview of a reinforcing strip for the butt joint between adjacent blocks of sound absorptive material;

Fig. 8 is a detail sectionalview of a butt joint illustrating the application thereto of the reinforcing strip shown in Fig. 7

Fig. 9 is a perspective view'of a suspension clip for use with a clip bar at a butt joint between adjacent blocks of sound absorptive'material;

Fig. 10 is a vertical sectionalview of a butt joint with the suspension. clip of Fig. 9 applied thereto;

Fig. 11 is a partial perspective View of' a strip of finish mouldingto be applied at the joint between the ceiling and a vertical wall surface of a room;

Fig. 12 is a vertical sectional view through the finish moulding and illustrating its coaction with a block of. sound absorptive material;

Fig. 13 is a view similar to Fig. 12 but illustratzing the coaction between the finish moulding. and a pan of sound reflectivematerial.

Fig. is is a partial perspective viewof a ceiling suspension generally similar to that shown in Fig. 2, but incorporating a combined spreader bar and reinforcing strip which performs the. functions of the structures shown in Figs. 2, 5, 7 and 8;

Figs. 15 and 16 are respectively. a foreshortened top plan view, and a foreshortened side elevationa1 view, of the combined spreader bar and reim forcing strip; and

Fig. 17 is a verticalv transverse sectional view of the strip, said View being taken as onv thev line il -ll of Fig. 16 and looking in the direction of the arrows.

Acoustical correction material has been proposed heretofore for ceilings and walls, said material for best advantages being cheaply and satisfactorily formed in sheets or blocks: of morexor less. loosely compacted'fibers. of vegetable and/or cellulosic material, resulting in myriada of irregular cells, interstices, or openings communicating with the exterior surfaces, into which cells or openings sound waves may enter and be substantially completely absorbed through friction so that said waves will become dissipated, thereby rendering a room extremely quiet as compared to a room the ceilings and walls of which are not so treated for acoustical correction. In some instances the exposed surface portion of the locks of acoustical material has been purposely provided with mechanically drilled relatively large openings or cells for better penetration and entrapment of the sound waves within the block. It is to be understood that according to this invention there may be employed any satisfactory acoustical material which has the characteristic of frictionally absorbing sound waves, though preferably such acoustical material should be formed in sheets or blocks of relative rigidity for ease in handling and application to the wall or ceiling.

Also, in acoustical treatment of a room, there has been proposed the utilization of material which is sound reflective rather than absorptive, the benefit and advantage of the sound reflective material being due to the fact that the impingement of the sound waves thereon sets up diaphragmatic action or vibrations in the material chiefly due to the relative thinness of said material. These said vibrations change, modify, damp and/or otherwise affect the amplitude and/or rhythmic pulse of the original sound waves whereby the reflected sound waves are not harmonious therewith and hence counteract if not nullify the original sound waves to render the treated room more quiet. Here again latitude is desired in the selection of the sound refiective material though metal of extreme thinness, bent into the shape of a pan, has been found extremely practical and hence is preferred for its fire resistance and strength.

Heretofore, acoustical correction has comprised the application of material of the same kind to substantially the entire room surface, and chief of the acoustical materials is a product identified and sold in the building construction market under the trade-mark Acousti-Celotex which is made as a fibrous deposition in blocks, of the order of 12" x 12" dimensions and/or multiples thereof, in various thicknesses even up to approximately 1 These blocks, however, have required nailing to studs or furring strips, requiring considerable time and labor expense in their application, and it is an object of this invention to do away with this costly construction of a ceiling, for example, by making possible the sliding of such blocks into position with their sole support upon flanges of secondary supporting members of the ceiling, which secondary members are in turn suspended or hung on the primary members of the ceiling, thereby doing away entirely with nailing operations. Obviously this improvement in ceiling construction is also advantageous when repairs are necessary. The secondary ceiling members comprise the metallic pans or channels having sound reflective but vibratory characteristics, and these members have portions which extend through to and are exposed to the room area for receiving the sound waves thereon, said portions lying substantially in the plane of the exposed ceiling area and having the appearance of strips interposed between and separating the parallel rows of abutting blocks of sound absorbing material, such as Acousti-Celotex.

In Fig. 1 is depicted diagrammatically the appearance of a ceiling made in accordance with this invention, wherein the side walls of the room are indicated by the numeral 2, the strips 3 representing the exposed surfaces of the pans of sound reflective material, the numeral representing the ceiling area composed of rows of abutting blocks of sound absorptive material. The widths of the pan strips 3 may be made as desired, even up to the order of 7%" where the width of the exposed area of the rows of sound absorptive material is of the order of 11 this pan width having been found by experiment to be substantially the maximum in this combination of acoustical materials for practical results. In cases where exceptional noise is to be corrected, the total of the exposed pan siu'faces may be lessened to thereby relatively increase the total of the exposed area of the sound absorptive material in the ceiling as a whole. This may be done in several ways for example, as by providing pans of lesser Width while retaining the same width of fibrous block, or by utilizing the same 7% inch width of pan with blocks of greater multiple Width (24" width for example). A generally true statement is that the relationship of the width of the fibrous blocks to the width of the pans may be changed or made to vary by virtue of the fact that the centering of the pans can be so located as to provide for an acoustical tile or block 12 in width, or 24 in Width, and so forth, depending upon whatever performance may be required to meet the existing condition of noise. Per unit of exposed surface, the cost of the sound absorptive material is greater than the cost of the sound reflective material, and therefore by this invention the cost of a complete ceiling may be materially reduced by the use of the less expensive sound reflective material.

In Fig. 2 there is indicated at 5 a primary ceiling structural member (of which there may be many in the complete ceiling), which member as shown comprises a metallic channel having its web 6 disposed vertically and the parallel flanges 1 and 8 disposed horizontally. At spaced intervals, hangers indicated generally at 9 and iii are fitted over the uppermost flange 1, each hanger having an inverted U-shaped portion H at its middle which closely fits the width of said flange, the opposite end portions of the hanger comprising angularly disposed legs such as I2 with upwardly directed hook-like bends 13 at their extremities for engaging a metallic sound reflective pan generally identified by the numeral 14, so that said pan substantially contacts the outer surface of the lowermost flange 8 of the structural member 5 (see Fig. 3).

Each pan is bent or pressed out of thin metallic sheet material in substantially channel shaped formation as clearly shown in Fig. 2, the bottom or web portion thereof being indicated at 15 and adapted to lie in the plane of the exposed surface of the ceiling, the opposite parallel flange portions it and il extending vertically upward and connected to the web portion l5 by the oppositely and outwardly extending bends l8 and 15 respectively, which bends constitute shelves or shoulders upon which may be seated the side edges of the blocks such as 2i! of the sound absorptive material. The broken line 2| indicates that the width of the pan may be made as desired, though preferably all pans will be made of a uniform or standard width, and variations in ceiling performance will be accomplished by altering the centering of the pan rows, i, e.

To'correctlyposition or space a pansuch as M" from thenext adjacent pan such as wand thus in'sure theretentioni of the interposed blocks 2%! of "sound absorptive material; there isprovideda plurality ofspaced clipbars such as 25. Each clipbar is of'she'et material and maybe suitably reinforced as bya" central impressed rib' the opposite ends of saidb'ar being downwardly and inwardly bentv as clearlyshown' at 21- in Fig.5" to form a hook-like edge" to engage under the complement'ally formed'hookdike edge 22 of the flange such'as lB'of a pan such as M, this snap engagement being permitted by the yi'eldable springiness'of saidbar; sound absorptivematerial down on the shelf or shoulder portion such'as IQ of said pan, an edge portion of the clip bar adjacent one endthereof has a tongue 28 struck downwardly from the general plan of said bar, the extremity of said tongue preferably being curled or rounded as indicated at 29 to smoothly engage the upper surface of the fiber" block 29', and adjacent the oppositeend ofsaid bar but preferably in the opposite-edgeportion thereof, a similar tongue tifmay be formed;

The pans will be made in appropriate lengths wherefore it maybe possible that a plurality of pans'will be required, with their ends in abutment with eachoth'er; to make up one of the strips or rows shown at 3 in Fig; l separating two adjacent r'owsof fiber blocks of sound absorbing materiall In such case, and for the pleasing appearance of the finished ceiling it willbe advisable to insure the abutting pans be- 4 inginplanarregistry with each other, and to this end a splicer, generally identified by the numeral and'such as-illustrated in Fig. 4, is employed. This splicer ispreferably though not necessarily made of" the same thin gauge of sheet metal'as the pans, and is'formed'of channel-shaped transversesection providing the web portion 35and two parallelupwardlyext'ending flange portions 31 and 38; the transverse dimension of the splicer being such asto closely fit within the flanges of the pans; as indicated in Fig. 3;

To facilitate the correct positioning of the splicer, the upper edge portionsof the flanges thereof-are provided at their median points with outwardlyextendihg tabs such as 39 and is which preferably may be formed'by vertical cuts and deflection of the material (on one side of the out) out'of the plane of the flange, all as clearly illustrated; Thus it is only necessary to slide the splioerinto one end of a-pan-section until said tabs strike the end edge of the pan, and thenslide the next pan section over the protruding end oi": the splicer and tap itup into abutting relation with the first pan section, said tabs-yielding in an inward direction to permit the abutment of the two pans; due to the relative thinness of the sheet metal from which the splioer is-made.

Two modifications ofthe pan hangers are illustratediniFigs. 3' and 6, in the latter the hanger comprising a wire formation the middle portion of'which is'formed' of inverted U- shape-providing

thetwo'parallel portions

46 and 47 and the-oppositely inclined downwardly di- To hold the block 29 of vergent' leg portions 48' and 49 respectively, all" of which are in-a commonvertical plane The end portions of the'legs are bent upwardlylat'erally and angularly as indicated at 50 to com-- pleinentally engage the'angularly' bent edge p'or-- tion such as'22 of a flange of a pan. This con-- struction is common in both modifications or the hanger. The difference in-the modificationslies in the extreme end formationof the hangers, the hanger of Fig. 6 having theext-reme ends additionally bent as indicated at 5| to provide coaxial portions which-will smoothly fit andb'ein surface contact with the inner surface of the' hook-like bend of the edge portion of thepan flange, whereas in the other modification shown in-Fig. 3 the extreme ends do not have this additional coaxial end formation and'thus said ex' treme ends terminate with the angular bend such as 50, and hence are sharply capable of biting into the surface of the pan flange.

The dimension of a block 20 in a direction parallel to the adjacent supporting pans, may be variable, and it is contemplated havingaplurality of blocks filling the space between two such adjacent pans, said plurality of blocks being in end abutting relation with each other. Any suitable formation may be givento these abutting ends; in Figs. 8 and 10 there is indicated complemental rabbeted or ship-lap formations as between the abutting blocks 20 andil. Since a standard l2'- x 24" fibrous block or tile could be employed with either of its dimensions spanning the space between the two adjacent supporting pans, it is possible. that one of such blocks might sag Withrespect to its ad jacent block and thus provide an unsightly appearance to the finished ceiling. Therefore. it is contemplated providing a metallic reinforcing strip is such as indicated in Figs. '7 and 8, and/or a suspension clip SI such as illustratedin Figs. 9 and 10, to insure planar registration of the abutting blocks at all times.

The reinforcing strip be is formed of thin sheet metal to provide a vertically disposed web-portion 62 the edge portions of which are bent two parallel horizontally disposed flange portions 83 and er, the spacing between said flanges being substantially equal to thethickness of the tongue portion 65 of the rabbeted edge of the block 29. In other words, said tongue is adapted to fit closely between said flanges as clearly shown in Fig. 8, and the vertical web portion 62 of the strip and the lower flange 64 thereof are adapted to fit closely within the rabbet of the next ad- J'acent block. A tab 66, preferably'of triangular shape, is struck out of either the web 82 or the flange E4 and bent laterally of the strip toassume a position substantially in the planexof said flange, wherefore the point ofsaid tab may readily enter the material of block 2! at its approximate center and constitutes, means for insuring planar registration'of the abutting ends of blocks 26 and El. Thestrip 60 may be made of a length to fit between the flanges of two adjacent pans and may be provided with a suitable number of tabs for accomplishing" the dcsired result, only one tab being illustratedv in Fig. 7 in the interest of simplicity of drawing.

The suspension clip 5! has a vertical web por tion with a horizontal lower flange H, and two oppositely extending

upper flanges

72 and 73 whose outer end portions are bent upwardly and inwardly to terminate in hook-like edges "14 and 75 respectively, adapted to springoverand engage the oppositeedge portions of a cl-ip bar 25, wherefore this suspension clip is intended for use where the ship-lap joint between adjacent blocks 2i] and 2: underlies a clip bar. Out of the web it any suitable number of tabs such as iii are struck and bent to lie substantially in the plane of the lower flange TI. This clip may be of any suitable length, and one or more may be provided in the row of blocks between two adjacent pans, the clip being applied to the shiplap joint between the blocks as clearly illustrated in Fig. 10 with the tabs it pressed into the body of the block 2! and the flange "H supporting the tongue portion of the other block 28.

Where the ceiling joins a vertical wall, there may be provided a strip of finishing moulding generally identified by the numeral til in order to support the pans and/or the fiber blocks in the area of the wall, a foreshortened perspective view of such a finishing strip being shown in Fig. 11. This strip is formed of sheet metal bent to provide the vertical wall-engaging flange 8| and the horizontal ceiling-supporting flange 82, the edge of the latter being turned over or rolled to form a smooth bearing surface 83 for the supported block or pan. These strips may be of any suitable length and each is provided in the flange portion 8i thereof with a plurality of apertures 8 which preferably are elongated vertically as shown in order to provide adjustability when securing said strip to the wall 85 as by the nails 86 shown in Figs. 12 and 13. To hold the pan or fiber block in contacting engagement with the supporting flange 8'2, said strip is provided with a tongue secured at its upper end to the wall flange 31 in any con- 1 venient manner, the lower end of said tongue preferably being rounded as shown at St to provide a smooth bearing surface against the pan or block with which it is adapted to engage. Thus the tongue may be pressed out of the wail flange 8| or may be secured thereto by soldering or spot welding, the latter being indicated in Fig. 11 by the numeral 39. As shown in Figs. 12 and 13 it may be necessary to break or cut a block or pan in order to provide symmetry of design at the wall areas of the ceiling, but the construction of the strip of finish moulding takes care of this necessity and hides any broken or cut edges.

In Figs. 14 to 17 there is illustrated a modiflca tion of the ceiling suspension where there is incorporated a combined spreader bar and reinforcing strip which performs the functions of the structures shown in Figs. 2, 5, '7 and 8. This suspension comprises a plurality of spaced rigid structural members such as the member 5 here tofore described, and to which the sound reflective secondary members are attached by the hangers 45 particularly illustrated in Fig. 6, the subsidiary members of this ceiling suspension comprising a plurality of blocks of sound absorbing material mainly supported by underlying portions of the secondary members.

The secondary members comprise a plurality of pans such as 95 and 95 parallelly spaced from each other and. substantially of the general formation of the pans heretofore described in that each has the bottom or web portion l5 and the opposite upwardly extending or vertical and parallel flange portions 96 and I! joined to the web portion to form the outwardly extending bends l3 and I9, which bends constitute shelves or shoulders upon which may be seated the side edge portions of the blocks of sound absorptive material. However, in this modified construction the uppermost edge portion of the flanges is formed with an ogee or S-shaped bend as shown, in order to provide a rounded extreme edge portion 9? (see Figs. 14 and 16) for additional longitudinal reinforcing, and for smoothly engaging the combined spreader bar and reinforcing strip, the ends of a hanger 45 engaging said bend.

The combined spreader bar and reinforcing strip is shown in detail in Figs. 15, 16 and and is generally of an inverted T shape. In a practical and economically produced form, it comprises a strip of sheet metal bent to provide a longitudinally extending central vertical web 98 (of double thickness as shown) and two oppositely extending horizontal flanges 99 and Hit. The web is of a length substantially equal to the distance between a vertical flange of one pan and the vertical flange of the next adjacent pan, but each horizontal flange of this combined spreader bar and reinforcing strip is extended beyond said web and bent upwardly and outwardly to form a hook by means of which said strip is suspended from the upper edge portion of a pan flange.

That is to say, the horizontal flange 99 of said strip is extended and bent upwardly at one of its ends to form a vertical hanger plate IEII, the end portion of said plate being outwardly and downwardly bent to form the hook H32 adapted to overlie the upper edge portion of the vertical flange such as H of a pan (see Fig. 16) and springingly engage the rounded extreme edge 9'! of said flange. The other horizontal flange we of said strip is similarly extended, bent and formed to provide the hanger plate I03 and the hook I64, but the hooks Hi2 and its as shown are formed at opposite ends of said strip. Hence, when such a formed strip or bar is in place (see Fig. 14) it serves to tie two adjacent pans (55 and 96) together and thus prevents a spreading apart thereof such as might cause a dislodgement of their supported blocks of sound absorptive material. The hooks may be provided at one end only or at both ends of each flange, and the hanger plates may be suitably secured as by welding to the web 98 to give added rigidity if desired or found necessary.

When using this combined spreader bar and reinforcing strip, the blocks of sound absorptive material preferably are provided on all edges with horizontal kerfs such as Hi5 to positioned as to register with and snugly receive therein the flanges 59 and H38 of said strip, whereby said blocks are reinforced by the strips, as well as additionally supported by the flanges of the strips at the butting joint between two adjacent blocks, thereby insuring the blocks against such sagging movement as might result in an uneven planar registration which would be unsightly. The peripheral kerf described above permits the blocks of sound absorptive material to be placed in either direction relative the supporting pans. Furthermore, said strip serves to seal the joint between two adjacent blocks both as to ventilation and dirt (commonly known as breathing), and makes unnecessary the wasteful rabbeted edge formation of the blocks as shown in Fig. 8.

From the foregoing disclosure it will thus be seen that by this invention there is provided an acoustic ceiling construction comprising rigid primary supporting members such as 5, secondary members such as the pans it suspended therefrom and having portions such as I5 lying in the exposed surface area of the ceiling, and subsidiary members such as the blocks 20 suspended by the underlying portions I 8, 19 of said secondary members, said subsidiary members having their lowermost surface lying in the exposed surface area of the ceiling, said secondary and subsidiary members being of material susceptible of acoustic correction in that they are capable of disand demountable in the ceiling construction by virtue of such suspension. Said ceiling comprises alternate rows such as 3 of sound reflective elements and such as 4 of sound absorptive elements, the total of the exposed surface areas of the sound reflective elements being less than the total of the exposed surface areas of the sound absorptive elements, and the ratio of these totals is limited substantially to no greater than 1 to 12 respectively. The clip bars 25, hanger springs such as 9, the splicer such as 35, the reinforcing strips such as 69, the suspension clips such as El, and the finishing moulding such as 80 are provided as hereinabove set forth to make a unitary whole in the ceiling.

It is obvious that those skilled in the art may vary the details of construction and arrangements of parts without departing from the spirit of this invention wherefore it is desired not to be limited to the exact foregoing disclosure except as may be required by the claims.

What is claimed is:

1. An acoustic ceiling construction comprising alternate rows of sound absorptive and sound reflective elements, the sound absorptive elements comprising blocks of cellular material, the sound reflective elements comprising vibratory metallic sheets formed into substantially channel shape to provide a web portion lying in the plane of the exposed surface area of the ceiling, and upwardly extending flange portions having hooklike formations constituting means for suspending the sound reflective elements from a primary ceiling member, said flange portions joined to said web portion by bends providing laterally disposed shelves for supporting said blocks, and clipbars disposed over said blocks at spaced intervals. said bars having end formations complemental to and engageable with the hook-like formations of the flanges of said sound reflective elements to tie together two laterally adjacent rows of said sound reflective elements.

2. An acoustic alterna posed surface area of the ceiling, and upwardly extending flange portions having hook-like format-ions constituting means for suspending the sound reflective elements from a primary ceiling member, said flange portions joined to said web portion by bends providing laterally disposed shelves for supporting said blocks, and clip-bars disposed over said blocks at spaced intervals, said bars having end formations complemental to and engageable with the hook-like formations of the flanges of said sound reflective elements to tie together two laterally adjacent rows of said sound reflective elements, each clip bar having pressure means to force a block on said shelves.

3. An acoustic ceiling construction comprising alternate rows of sound absorptive and sound reflective elements, the sound absorptive elements comprising blocks of cellular material, the sound reflective elements comprising Vibratory metallic sheets formed into substantially channel shape to provide a web portion lying in the plane of the exposed surface area of the ceiling, and upwardly extending flange portions having hook-like formations constituting means for suspending the sound reflective elements from a blocks, and clip-bars disposed over said blocks at spaced intervals, said bars having end formations complemental to and engageable with the hook-like formations of the flanges of said sound reflective elements to tie together two laterally VICTOR J ACOBSON References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,931,713 Walper Oct. 24, 1933 1,974,819 Koerner Sept. 25, 1934 1,998,423 Stubbs Apr. 16, 1935 2,090,043 Heerwagen Aug. 17, 1937 2,099,211 Lucius Nov. 16, 1937 2,101,952 Olsen Dec. 14, 1937 2,121,213 Small June 21, 1938 2,270,268 Chambers Jan. 20, 1942 2,307,653 Wright Jan. 5, 1943 2,357,560 Taforo, Jr. Sept. 5, 1944 FOREIGN PATENTS Number Country Date 577,402 Great Britain May 16, 1946