US2338146A - Chalk trough - Google Patents

Description

Jaln.' 4, 1944.

original Filed oct. 1a, 1959 L. F. URBAIN CHLK THOUGH :s sheets-sheet 1 Q7/Mgg L. F. URBAIN CHALK TROUGH Jam. 4, 1944.

Original Filed Oct. 18. 1939 `3 Sheets-Sheet 2 I IN VEN TOR? @ra/20 I v 0 du. 7 l 1 Jan. 4, 1944.y

L. F. URBAIN GHALK THOUGH original Fil'ed oct, 18. 1939 3 Sheets-Sheet 3 Patented Jan. 4, 1944 CHALK THOUGH Leon F. Urbain, Chicago, Ill.

Original application October 18, 1939, Serial No. 299,925. Divided and this application June 29,

1942, Serial No. 448,970

24 Claims.

The present invention relates to a -chalk trough for blackboards. It is quite possible that the invention may have other uses, and, if so, they are within the contemplation of this invention.

This application is a division of my pending application Serial No. 299,925, led October 18, 1939, entitled Display board construction.

Among the objects of the present invention are to provide a chalk trough for a blackboard, or the like, having an eraser receiving surface, across which all chalk dust will normally gravitate to its chalk receiving groove positioned remotely with respect to the normal position of the eraser when supported on the trough.

Another object of the present invention is to 4provide a chalk trough arranged so as to present a knife edge against the lower portion of the blackboard or display board slab whereby to receive all gravitating dust, as a result of which construction the otherwise obnoxious particles are ultimately received within the specially disposed groove at the lower forward part of the tray, and are also prevented from passing downwardly beyond the chalk trough and dropping onto the floor.

Another object of the present invention is to provide a trough construction which is releasably secured in position relatively to a blackboard.

Further objects of the invention Will be apparent from a persusal of the following specification when taken in connection with the accom- -panying drawings, wherein- Figure 1 is a perspective view of ya blackboard showing the improved trough in relation thereto;

Figure 2 is a sectional view taken centrally and vertically through the blackboard on line 2-2 of Figure 1;

Figure 3 is a perspective view of a portion of a modified form of blackboard also showing the chalk trough in position with respect thereto;

Figure 4 is a detail sectional view taken on line 4-4 of Figure 3;

Figure 5 is a perspective view of a spring clip for retaining the trim or molding strip;

Figure 6 is a sectional detail view taken on line t--li vertically through the blackboard as shown in Figure 3;

Figure 7 is a front perspective view showing a portion of the blackboard construction with certain portions broken away todisclose the supporting and retaining members; y

Figure 8 is a detail sectional view taken horizontally on line 8--8 of Figure 6 to show the lll detail construction and arrangement of the yielding spring supports of the blackboard slab;

Figure 9 is a perspective view of a portion of a trough showing one end;

Figure 10 is a sectional view taken on line itl- I0 of Figure 9;

Figure 11 is a perspective view of one of the end plates;

Figure 12 is ya sectional view taken on line I2-l2 of Figure 9; and

Figure 13 is a perspective view of a trough showing the end plates removed and the trough in section.

Referring now to the drawings- Figures 1 and 2 disclose a preferred form of a display board or blackboard construction cornprising a ground or supporting frame l0 re-ceiving a blackboard slab l2, and also supporting a chalk trough which forms the subject matter of the present invention in association with its mounting, and also an appropriate trim or mold strip construction I6. The ground is mounted on suitable fastening means 20. As shown in Figure 2, the ground or supporting frame l0 is preferably mounted upon the surface of a subwall or partition just below the plaster surface 22, so that the outer surface of this ground or supporting frame is ultimately flush with the surface of this plaster 22. With such a construction the surface of the blackboard slab l2 falls into coplanar disposition with respect to the associated wall, thereby giving a more pleasing appearance and whereby the trim strip only projects outwardly of this plane.

Particular attention is directed to the construction of the so-called ground or supporting frame l0 and ko the structure of the strip material employed. Particular reference is made to Figure 7 of the drawings, which, while relating to an alternative embodiment of a 4blackboard construction nevertheless is formed from upper and lower ground strips of identical construction. It; will be noted that these ground members or supports l0 have a central channel section provided by a flat, vertical wall surface 24, and, likewise, including spaced, laterally extending walls 26 and 28 terminating in a vertical flange 39 parallel with the wall 24, and, therefore, parallel with the final wall surface and with the plane of the blackboard.

While the flange 39 may-be apertured to receive fasteners such, for instance, as 32 (see Figure 7) for engagement with the subwall or partition, the function of this flange 39 is primarily to support a plurality of yieldable spring members 36 disposed more or less regularly in spaced relation therealong. One of these spring members is composed of a resilient, yieldable leaf, gently and regularly curved at its central portions and ter minating at its oppositely curved contact surface 38. To receive the yieldable spring supports 36, the flange 3E) is struck out as at 40 to shift a predetermined tongue of metal laterally into parallel, spaced relation while remaining integrally connected with the flange along one side edge thereof.

Particular attention is directed to the fact that the formation of the struck-out portion results in an opposed recess or aperture 42 adapted to receive the central, curved portion of a spring leaf 36. It will be accordingly seen that when the spring leaf is yieldably urged behind the struckout portion 4U, its central part springs into the aperture 42 and positively retains the parts in the position shown, whereas the curved portions 38 project outwardly to receive the blackboard slate, n

as will hereinafter more fully appear.

The upper lateral flange 26 of the ground strip lll terminates in an inwardly disposed, vertical attachment flange 44 similarly apertured to receive wall attachment fasteners 20, which may be J nails. Here again, it is important to note that the ange 2t forms an acute angle with the wall surface 24 of the ground member which, in comn bination with the provision of a plurality of elongated apertures 48 at juncture with the inwardly bent flanges 26, provides for the interlocking reception of the final plaster surfa-ce 22.

Thus the present ground strip construction provides simple and improved means for the positive retention of the blackboard slab against the yieldable cushioning springs, in the form. of a plurality of spaced locking keys or plates 5f) (see Figure '7). Each of these keys or plates 50 in the present embodiment comprises a ilat sheet member beveled at its lower corners as at 52 to facilitate entry into an engaging sheath or keeper 5-/5 on the ground strip or frame, and has at its upper extremity, as viewed in the upper portion of Figure 7, laterally projecting ears E6.

The engaging sheath 54 is formed by striking out a portion of the area of the ground strip 2li to a parallel plane sufficiently spaced to receive the thickeness of the retaining plate 50. A struck out portion 54 remains integral with the Wall 24 at its longitudinal extremities 58. It should be particularly noted that each of the embracing straps 5t is disposed in longitudinal alignment with one of the foregoing yieldable spring units in such position that the extremity of the keeper or plate projects opposite the flange Sii, as is clearly shown in the drawings.

The foregoing elements confine, restrain and completely support the blackboard slab I2. Only the simplest of assembly operations are involved in arranging the periphery of the slab I2 against the regularly disposed yielding supports 38, shifting the blackboard rearwardly and then locking it in place by merely slipping the keeper fingers 5l) through their retaining sheaths and into engagement with the front surface of the board.

The foregoing strip construction which I provide in accordance with the present invention may be arranged in the form of a rectangular ground by cutting head, base and jamb pieces of the proper length and positioning these to the partition in the rectangular arrangement shown. Upon completion of plastering the ground thus formed provides a rectangular recess for the reception of the rectangular blackboard or display slab l2. There is provided, in accordance with the construction shown in Figure i, an insulating and preferably soundproof layer 6U, which, in accord ance with certain observations, eliminates cordensation and drumming. While any suitable in sulating and cushioning or soundproof board may be employed, I prefer any of the well-known insulating quilts, such as those made of wool shoddy 01' other layers known as Capots quilt. It is preferred that the quilt be so disposed as to exert on appreciable pressure against the surface of the blackboard.

The trim construction. Iii is formed with a plurality of strips having a channeled section with oppositely inturned edges as shown in Figure 2, embracing the opposite extremities of a retaining clip 64. The clip 64 shown in detail in Figure 5 of the drawings has a bowed central portion and opposite lateral margins formed with rounded, beaded sections 6%?. A central slot 63 permits attachment to the central wall or web 4 of the ground strip by means of any selfthreading fastener 1Q. It is important to note, as clearly shown in Figure 2, that trim strip, when pressed over the web 64, resiliently engages both of the beads Et. At all times, therefore, the beads exert an opposite, yieldable, internal pressure against the trim strip so that loosening or vibration is impossible.

The trim strip is cut into lengths corresponding to the jambs and head strip of the ground or supporting frame lil, and the corners may be mitered, as shown in Figure 1.

The foregoing details serve to present the background relative to and in combination with which the chalk trough is utilized in the present invention.

The chalk trough I4 of the present invention likewise functions as a lower trim. Details of construction of this chalk trough appear more particularly in Figures 9 to 13 of the drawings. With the exception of a pair of end stops 76, the trough is composed of a continuous length of extruded material having a uniform section, as indicated in Figures 9 and l2. This chalk trough I4 has an upper supporting surface 133, which is inclined downwardly at a substantial angle sufficient so that chalk dustwill gravitate downwardly or to the right, as viewed in Figure 2 of the drawings.

The surface is provided with a plurality of serrations or ridges ti), the lowermost serrations deiining a chalk groove 82, together with an upwardly extending looplike portion of the rail section designated at 84. This loop or abutment section 54 extends reversely with respect to the downward inclination of the upper supporting surface so as to provide a stop or abutment for the eraser, as illustrated in Figure l2. Hence, the working surface of the eraser, indicated by the letter A, normally rests on a surface clear of chalk dust, and which surface is spaced from the powder residue accumulating in the groove 82. A section of the trough curves downwardly and inwardly as at to to the horizontally extending portion 38. A vertically extending flange extremity 9d completes the lower portion. The upper extremity cf the trough similarly has a substantially vertical flanged portion 92 which, due to the inclination of the supporting surface forms a sharp acute angle therewith. Particular attention is directed to the fact that the rear surface of this flange B2 makes an angle with the vertical plane of the blackboard i2, as shown in Figure 12, this angle being illustrated by the dotted line indicated at B in Figure l2 of the drawings. A so-called feather edge 93 is thus provided for slabs are vspaced by horizontalv 'ground' strip 4| I4 making a line pressure contact against the lower surface of the front face of a. blackboard, as shown in Figures 12 and 13. Hence, this tight fitting pressure contact wilLprevent the passage of chalk dust from the blackboard downwardly past and hence into the hollow trough, or past the lower flange 90 thereof onto the floor.

Means is provided for releasably securing the trough in position. This means is preferably shown as comprising a plurality of clips 94, which are somewhat similar in construction to the clip til, except that they have an upper extremity 96 positively engageable behind the flange 92, as shown in Figure 12. The extremity 9B of the clip is yieldably tensioned in an inward direction to urge the feather edge 93 into pressure line contact with the surface of the blackboard l2, while the lower bead 66 of the clip engages behind the flange extremity 9U. For assembly purposes the flange 92 is merely engaged behind the spring 95 and the flange 90 clipped over the bead 66.

The end stops l of the chalk rail shown in Figure il comprise a vertical end wall 98 having laterally extending margins projecting into congruity with the walls of the chalk trough. The laterally extending upper surface portion of each of these end stops is continuous with the supporting surface o-f the trough and is recessed slightly as at mi! to provide a guideway or spout conguration for dust projected longitudinally across the extremity of the trough. The facility with which the dust in the trough may be removed is evidenced by the fact that the cleaning device may be moved longitudinally in the lower groove 82 vto direct the dust over the end stop into a suitable receptacle. The end stops are provided with a plurality of internal lugs |02 engageable interiorly with the walls of the trough and are adapted to receive the fastenings |04.

Where a lower trim or mold is desired in addition to the trough, as shown in Figure 4 of the drawings, a compound base ground construction is provided as therein shown, in which a second ground strip |06 is located above the ordinary base strip, and is provided with struck out lugs 40 mounting pressure clips 36 identical with those heretofore described. This ground strip |06 is otherwise provided with an outer, central wall 24a and a lateral wall 28a, the latter terminating in a vertical iiange 30a which mounts the tongue and clip spring construction. 'Ihe lower flange 26a denes the lateral margin of the strip to facilitate nesting with the lower ground strip |0. Vertical alignment of the compound base ground construction is positively maintained by a pin, which may be an ordinary nail or driven fastener |88 disposed in vertically aligned apertures in the flanges 26a and lateral wall 28a and extending into a longitudinal slot ||0 in the upper, lateral flange of the base ground strip. In accordance with this construction, the spring clip 94 supports the chalk trough upon the upper base ground |96, whereas the lower ground mounts the spaced clips 64 which retain the lower trim strip It. It will be seen that the lower horizontal surface portion 88 of the chalk trough thus cooperates with the upper flat surface of the trim strip so that these two reside in flatwise abutment.

In Figures 6 and 7 I have shown a modified form of work construction embodying a blackboard I2, and in combination therewith a bulletin board ||2 positioned above the blackboard for receivingy posted bulletins. The, boards or equivalent in configuration. to the foregoing strip l0, but having upper and lower inner vertical flanges 30a, mounting pressure clips 36 in struckfout tongues 40. The boards or slabs are retained against pressure clip foundation by angouterY display rail ||6 secured to the ground I4 by thread forming or tapping fasteners H8.k The rail .is of simple channel configuration having inturned marginal flanges |20 to retain a plurality of slidable display fixtures or blocks |22.

It is further important to note thatthe present chalk trough assembly positively accumulates chalk dust which normally might settle `'within internal crevices by directing these particlesonto the downwardly inclined receiving surface of the trough and to a receiving groove providedtherefor. The eraser in spaced relation to the receiving groove thus rests upon a supportingsurface relatively clean and free of dust. .Y

Of even greater importance, however, is -the fact that the chalk trough, because of its inclined position, presents the eraser at ally times facing the student who, being normally in front ofY the blackboard, directs his attention towardA 'the eraser trough at a downward angle. Thus the eraser is not only in plain view and more easily accessible but, at the same time, is spaced 'and located a substantial distance from the blackboard. It will' be realized that this is of great practical signicance in view ofthe objection-'- ability of contacting the fingers and particularly the linger nails with a slate or similar surface or with associated molding, as has hitherto vbeen the frequent case.' With the present construe'- tion, the eraser will always gravitate downwardly to the abutment rail 84 in a position where it is instantly accessible and free from inadvertent undesirable contact with the blackboard. l

It is further of great importance to note that the foregoing knife edge lip construction` 93 making a line contact with the blackboard provides an integral dust deflector whereby all falling and settling chalk dust is directed downwardly into the receiving groove 82 provided therefor. This provides a clean, sanitary construction as opposed to those prior constructions wherein the objectionable and pathologically harmful dust particles were normally permitted 'to collect within or adjacent the trim or other portions of the blackboard assembly, either internally or externally, wherein they could not be cleaned away and removed. Y

Another important new result flowing from the inclined supporting surface configuration of` the foregoing chalk trough resides in the facility with which this surface may be abuttingly associated with the trim and other strips. Thus it should be noted that the angle of the eraser supporting or dust deflecting surface is equal to 45 degrees. Therefore, when assembling blackboard constructions, such as shown in Figure 1, in which the side trim strips abut the chalk trough at their lower extremities, it is merely necessary to cut or miter the lower extremity of each of the side strips to 45 degrees, as shown in Figure 2, in order to secure a perfect fit Thus the side trim strips may be cut to size on any ordinary miter box equipment, having the conventional means for cutting a 45 degree angle.

It is thought that the invention and numerous of its attendant advantages will be understood from the foregoing description, and it is obvious thatA numerous changes may be made in the-form, construction and arrangement of the severalV parts without departing from the spirit or scope of the invention, or sacrificing any of its Hattendant advantages, the form herein described being a-preferred embodiment for the purpose of illustrating the invention.

I claim:

LA chalk trough construction for a display board having an upper abutment portion adapted Vto reside substantially in the plane of said display board, an eraser supporting surface inclined downwardly in a substantially acute inclination greater than the angle of response, and a dust receiving groove adjacent the lower extremity of said inclined surface and disposed `therebelow so as to maintain the collected dust out of con- -tact with the eraser.

2. A chalk trough construction for a display board'having an upper abutment portion adapted to reside substantially in the plane of said display board, and having a supporting surface inclined downwardly at a-substantially acute inclination, and a dust receiving groove adjacent the lower extremity of said inclined surface and disposed therebelow, said abutment portion having a relatively sharp upper marginal edge, and means for firmly pressing said relatively sharp marginal edge into line pressure contact with said display board when disposed thereagainst to deflect falling chalk dust into said receiving groove.

3. A chalk trough construction for a vertically disposed display board having an upper abutment portion adapted to reside substantially in the plane of said display board, a supporting sur- `face inclined downwardly in a substantially acute inclination, a dust receiving groove adjacent and belo-w the lower extremity of said inclined surface, and a marginal rail adjacent the lower portion of said supporting surface, said rail extending upwardly beyond the extremity of said downwardly inclined surface whereby an eraser disposed on said inclined surface is disposed outl of said chalk receiving groove.

LA chalk receiving trough adapted to be locatedadjacent the lower margin of a vertically disposed blackboard or the like, comprising, in section, a substantially, downwardly inclined upper eraser supporting surface, a lower section `extending below said inclined surfacey and terminating in a substantially vertical abutment portion, said inclined section having adjacent its upper margin an abutment surface disposed in general, verticalralignment to said blackboard, said last-named abutment portion being defined by a surface inclined inwardly with respect to the plane of said vertical blackboard and forming an acute angle with said inclined supporting surface to provide a relatively narrow marginal peripheral pressure Contact portion and means for resiliently maintaining said contact portion into firm pressing Contact with said blackboard.

5. An end stop construction for a chalk trough or tray having a sharply, downwardly inclined eraser supporting wall and a Chalk receiving groove at the lower extremity of said wall disposed below the lower `part of said inclined supporting wall, said end stop having a side wall for enclosing the end of said trough and having an upper marginal inwardly extending flange the outer surface of which is congruent with the profile of the outer face of said inclined supporting wall, the outer portion of said inwardly extending flange being curved outwardly and downwardly to provide aguide chute facilitating the projection and removal of dust from the end of said trough.

6. A chalk receiving trough for a vertical blackboard comprising a relatively narrow abutment surface adapted to contact with the vertical blackboard, said surface having an adjoining portion inclined out of the plane of said narrow abutment surface in a direction away from the plane of the blackboard, and said trough having an eraser supporting surface angularly adjoining said abutment surface and forming an acute angle therewith, said eraser supporting surface forming a trough at its lowest point, and an adjoining upstanding rail, said rail having an inwardly and downwardly extending wall contacting said blackboard, and means for resiliently clamping said abutment portion and said downwardly extending wall against said blackboard, abutment means for aligning said trough with respect to a vertical blackboard, said abutment means being adapted to locate said trough at a predetermined vertical plane parallel to the plane of said blackboard, said chalk trough having an eraser supporting surface extending outwardly and downwardly at a substantial angle of inclination from a point adjacent the top thereof.

7. In combination with a display board, a chalk trough therefor provided with an upper portion formed with a feather edge and an adjacent face disposed at an angle to the plane of said board, said trough having a lower portion extending inwardly in spaced relation to said upper portion to contact the display board and means for maintaining said feather edge portion and said inwardly extending portion in contact with said blackboard.

8. In combination with a display board, a chalk trough therefor having an upper portion provided with an edge formed by adjacent sides disposed at an acute angle with respect to each other, one of said sides contacting the board and being disposed at an acute angle diverging from the plane of the board in a direction away from i the edge, and means to maintain said trough in formed by adjacent sides converging at an acute angle with respect to each other, one of said sides contacting the board and having an adjacent portion disposed at an acute angle which diverges from the plane of the board in a direction away from the edge, said trough having a lower edge engaging the display board at a part remote from that portion of the horizontal edge that engages the board, and resilient means to hold the trough in position relatively to the board, including means to press said contacting side and said lower edge rmly against the front face of said board.

10. In combination with a dispiay board, a chalk trough therefor having an upper edge formed by adjacent sides converging at an acute angle with respect to each other, one of said sides contacting the board and having an adja cent portion disposed at an acute angle which diverges from the plane of the board in a direction away from the edge, and a spring clip for detachably pressing said trough into rm engagement with said board.

11. In combination with a display board, a chalktrough therefor having an upper edge formed by adjacent sides converging at an acute angle with respect to each other, one of said sides contacting the board and having an adjacent portion disposed at an acute angle which diverges from the plane of the board in a direction away from the edge, and a spring clip having a portion engaging the rear of said contacting side and engaging a spaced portion of said trough to hold said trough rmly assembled to said board.

12. In combination with a vertical support, a blackboard mounted vertically thereon, a chalk trough therefor having an upper portion provided with an edge overlying the bottom edge of said blackboard, the sides forming said upper edge of the trough being disposed at an acute angle with respect to each other, the inner side forming said acute angle overlying the lower horizontal edge portion of said board, a sheet metal ground attached to said support below the lower horizontal edge of said board, and a resilient fastening means carried by said ground and having a portion adapted to engage the rear wall of the upper portion of said trough and having a portion adapted to engage a lower spaced portion of said trough whereby detachably and resiliently to hold said trough in position with respect to the lower edge of said blackboard.

13. In combination with a vertical support, a horizontally disposed ground mounted thereon, a blackboard mounted on said vertical support, and having its lower edge overlying the upper portion of said ground, a hollow chalk trough, elongated horizontally and having an upper edge formed by walls converging at an acute angle, said upper portion extending horizontally and overlying the horizontal lower edge of said board, and the lower horizontal edge of said trough overlying said ground, a resilient clip, means for mounting said resilient clip on said ground, said clip having an upper portion adapted to engage in the rear of said upper horizontal edge portion of said trough and having a lower resilient portion adapted to engage the lower spaced portion of said trough whereby resiliently and firmly to maintain said trough assembled to said board and ground.

14. In combination with a vertical support, a horizontally disposed ground mounted thereon, a blackboard vertically mounted on said support with its horizontal lower edge adjacent said ground, a hollow chalk trough having spaced upper and lower edges, and an upper eraser and chalk supporting surface, the upper edge of said chalk trough extending horizontally and being formed by converging sides disposed at an acute angle with respect to each other, the inner side forming said acute angle having a portion thereof diverging away from the vertical wall of said blackboard at an acute angle, the lower edge of said trough having a iange portion extending substantially parallel to the vertical face of said blackboard, spring clip means mounted on said ground and having an upper portion resiliently and lockingly engaging a rear wall portion of said inner side of the upper edge portion of the trough, said clip having a lower resiliently formed lip engaging the inwardly extending iiange on the lower edge portion of said trough.

15. In combination with a substantially vertical display board, a chalk trough associated therewith. said trough having an upper chalk supporting surface disposed at an angle of substantially 45 to the vertical wall of said board,

said wall surface being formed with horizontally extending, substantially parallel, spaced apart grooves, there being an adjoining groove disposed horizontally and below the inclined grooves, the wall forming the lowermost groove terminating in an upstanding wall of suilicient height to engage the side of a chalk eraser to hold the eraser in inclined position on said board, said eraser in such position being supported above the adjoining groove.

16. In combination with a blackboard, a chalk trough comprising a hollow elongated member having spaced apart `legs interconnected by a body portion the intermediate portion of which is folded upon itself to provide an upstanding hollow elongated bottom rail for the chalk trough, and an adjacent upper surface inclined downwardly at an angle with respect to the vertical wall of the blackboard, said downwardly inclined' elongated wall being formed with alternate ridges and depressions which are disposed in parallel relationship extending longitudinally of the trough and means disposed within the hollow legs of said trough for mounting said trough in assembled relation with respect to the lower edge of said blackboard.

17. In combination with a vertical support and a blackboard vertically mounted thereon, a hollow chalk trough for said board comprising an elongated member having spaced legs and a body portion interconnecting the same, said body portion forming an upstanding rail extending horizontally and upwardly at the bottom portion of said trough, being inclined upwardly from said upstanding rail and terminating in a relatively sharp edge formed with converging wall portions meeting the blackboard at an acute angle, the upper face of said upper leg ,being formed with parallel horizontally extending alternate grooves and depressions, the lower leg underlying said upper leg in spaced relation therefrom, and attaching means disposed within the hollow chalk trough between said legs for iirmly attaching the same on said support with respect to an overlying lower horizontal edge of said blackboard.

18. In combination with a vertical support and a blackboard vertically mounted thereon, a hollow chalk trough for said board comprising an elongated member having spaced legs and a body portion interconnecting the same, said body portion forming an upstanding rail extending horizontally and upwardly at the bottom portion of said trough, being inclined upwardly from said upstanding rail and terminating in a relatively 'sharp edge formed with converging wall portions meeting the blackboard at an acute angle, the upper face of said upper leg being formed with parallel horizontally extending alternate grooves and depressions, the lower leg underlying said upper leg in spaced relation therefrom, and attaching means disposed within the hollow chalk trough between said legs for firmly attaching the same on said support with respect to an overlying lower horizontal edge of said blackboard, and detachable end caps for said trough whereby to close the ends of said trough.

19. In combination with a vertical support and a blackboard vertically mounted thereon, a hollow chalk trough for said board comprising an elongated member having upper and lower spaced legs and a body portion interconnecting the same, said body portion forming an upstanding rail extending horizontally and upwardly at the bottom portion of said trough, said upper leg being inclined upwardly from said upstanding rail and terminating in a relatively sharp edge formed by converging wall portions meetthe blackboard at acute angle, the upper face of said upper leg being formed with parallel horizontally extending alternate grooves and depressions, the lower leg underlying said upper leg in spaced relation therefrom, and attaching means disposed within the hollow chalk trough between said legs for firmly attaching the same on said support with respect to an overlying lower horizontal edge of said blackboard, and detachable end caps for said trough whereby to close the ends of said trough, said end caps having corresponding grooves and depressions adapted to register with the grooves and depresions in the upper surface of said upper leg of said tro-ugh, the said grooves and depressions forming chalk discharging spouts for the ends of said trough.

20. In combination with a vertical support, a

blackboard vertically mounted thereon, a chalk trough therefor comprising a sheet metal body formed to provide upper and lower spaced legs, the intermediate portion of said trough between said legs being double folded upon itself in spaced relationv to provide a hollow upstanding rail, the upper face of said upper leg adjacent said rail being bent downwardly to form a horizontal chalk trough adjacent and below said upper rail, and the adjacent wall oi said upper rail extending upwardly at an angle to the vertical, and terminating in an edge having wall portions converging at an acute angle, the inner wall thereof overlying the lower edge of said blackboard, the lower leg of said trough extending inwardly and provided with a foot or flange, fastening means disposed in said trough between said legs for attaching the trough to the support, and substantially triangular end caps for said trough, each cap including inwardly formed lugs adapted to lie within the trough and having fastening means passing through said trough and engaging said lugs.

21. In combination with a vertical support, a blackboard vertically mounted thereon, a chalk trough therefor comprising a sheet metal body formed to provide upper and lower spaced legs, the intermediate portion of said trough between said legs being double folded upon itself in spaced lll provided with a foot or flange, fastening means disposed in said trough between said legs for attaching the trough to the support, and substantially triangular end caps for said trough, each cap including inwardly formed lugs adapted to lie within the trough and having fastening means passing through said trough and engaging said lugs, each of said end caps having an upstanding substantially round rail portion, a horizontally disposed pin extending inwardly from said round portion adapted to register and lie within the hollow upstanding rail portion of said trough.

22. In combination with a supporting surface, a blackboard supported thereon, trim members forming a border-like frame for the blackboard and attached to said supporting surface, one of said tri'n members comprising a detachable chalk trough means detachably forming a pressure Contact between said chalk trough and the front wall of said black-board to prevent'l the dust downwardly therebetween,

2B. in combination with a vertical supporting surface, a blackboard supported vertically thereon, vertically spaced trim members and a horizontal upper trim member interconnected therewith and forming a border frame for the horizontai top and two vertical sides of board, a chalk trough disposed across and overlying a vertical face of the bottom of said boa-rd to form a trim member for the horizontal bottom edge of ti c and means detachably to support said trough on said vertical supporting surface with Si upper portion of the trough pressing firmly said board with suiicient force to prevent the passage of chalk dust between said trough and said board.

2d. In combination with a vertically disposed supporting wall surface, a lower trim member having a horizontally disposed upper face and mounted on said supporting wall surface, a blackboard vertically supported on said supporting wall surface above said trim member, and a chalk trough having upper and lower legs and an intermediate integral body portion providing upstanding rail and an adjacent, downwardly inclined eraser supporting surface, the lower leg of said chalk trough being disposed upon the horizontal upper surface of said trim member, and fastening means disposed within said chalk trough and adapted detachably to engage an inner wall portion of the upper leg and an inner wall portion of the lower leg, whereby to hold said chalk trough in position with respect to said trim member and said blackboard, the upper leg of said trough overlying the horizontal lower edge of said board.

LEON F. URBAIN.

v g CERTIFTLCATE ola-CORRECTION. Patent No. 2,538,1lp6. l afarlufnjyl LL, 19m.

4mom F. URBAIN.

It is hereby certified that error appears vinthe printed specification I o the above nmnbered patent requiring correction as follows: Page A2, second column, line lO, for the- WOI "on" before "appreciable'- read no; page LL, first column, line l2, `claim l, for response"' read repose-q page 6, second column, line )40, claim 2h, for"face" read --surace--g `and that thev said Letters Patent should be read with this correction therein that the-'same 'may conform tothe record ofthe case in the Patent Office.

' signed and sealed this 28th day of March, A. D. '19th.

Leslie Frazer (Seal), Acting, Commissioner of Patents

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