US 3688740 A
Apparatus for applying a non-slip coating to the bottom of an enameled bathtub or shower tray made of steel or cast iron, by atomizing or spraying on a refractory substance heated by means of a burner approximately to liquefaction, wherein the non-slip surface is subdivided into a plurality of individual areas spaced from each other by a mask having openings each separately defined by an open-ended cup-like element made of a thermally conductive metal resistant to heat and oxidation, said cup being adapted at one end to contact the surface to be coated along a line and being of increasing internal cross section and wall thickness at least for a part of the depth of the cup from said one end toward its other end and a cup support including a lost motion means effective upon registration with said bottom.
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Description (OCR text may contain errors)
United States Paten Gesche Sept. 5, 1972  Inventor:
Gunter Gesche, Budelsdorf, Germany  Assignee: Ahlmann-Carlshutte KG,
' sburg, Germany 22 Filed: Feb. 17,1971
21 Appl.No.: 116,076
Rend-  Foreign Application Priority Data Dec. 17, 1970 Germany ..P 20 62 101.6
 US. Cl ..118/504  Int. Cl. ..BOSb 15/04  Field of Search ..118/48-49.5, 301, 118/406, 47, 504, 505; 117/38, 48; 51/310, 268, 274
 References Cited UNITED STATES PATENTS 647,088 4/ 1900 Hammond, Jr ..1 18/504 1,692,920 11/1928 Baker ..118/504 1,813,390 7/1931 Dwyer ..117/38 A UX 2,395,743 2/1946 Kannenberg et al....1-17/38 X 3,226,245 12/1965 Dettling et a1. ..118/505 X 3,238,918 3/1966 Radke et al ..l l8/49.l 3,544,790 12/1970 Brown ..250/49.5 3,545,996 12/1970 Duncan ..118/301 X 3,577,325 5/1971 Fairchild ..1 18/504 X 3,608,518 9/1971 Poole ..118/48 FOREIGN PATENTS OR APPLICATIONS 520,800 l/l956 Canada ..1 18/49 Primary Examiner-Morris Kaplan Attorney-Beaman & Beaman ABSTRACT Apparatus for applying a non-slip coating to the bottom of an enameled bathtub or shower tray made of steel or cast iron, by atomizing or spraying on a refractory substance heated by means of a burner approxi mately to liquefaction, wherein the non-slip surface is subdivided into a plurality of individual areas spaced from each other by a mask having openings each separately defined by an opemended cup-like element made of a thermally conductive metal resistant to heat and oxidation, said cup being adapted at one end to contact the surface to be coated along a line and being of increasing internal cross section and wall thickness at least for a part of the depth of the cup from said one end toward its other end and a cup support including a lost motion means efi'ective upon registration with said bottom.
0 9 Claims, 10 Drawing Figures PATENTEDSEP 5:912 3.688. 740
PATENTEDSEP 5 m2 3.688.740
sum 2 OF 4 Fig.5
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BACKGROUND OF THE INVENTION There exist various known methods and apparatus for applying a non-slip coating to the bottom of an enameled bathtub or shower tray made of steel or cast iron, by atomizing and spraying-on a refractory substance heated by means of a burner approximately to the point of liquefaction.
In these known methods, the refractory substance, which is in a paste-like or liquid initial condition, is melted in a gas/oxygen combustion flame while being sprayed-on to the cold or hot bottom of the tub. The enamel of the tub bottom and the entire tub is in an already solidified condition while this process step is being carried out. Moreover, in order to avoid the formation of cracks during the spraying-on of the refractory substance it is well known to be preferable to carry out the spraying-on of the refractory substance while heating the bottom of the tub. However, the enamel of the tub floor is and remains solidified notwithstanding such heating.
In this known process, the refractory substance is melted in a hot gas/oxygen combustion flame emanating from the spraying apparatus; atomized by means of compressed air or an inert gas; and sprayed on to the enamel surface of the bottom of the tub while those regions of the tub inner wall and, in particular, the tub bottom, which it is not intended to make into a non-slip surface, are covered by a mask.
The fine particles of the paste-like or liquid refractory substance stick to the enamel layer of the tub bottom when impinging thereon and form a rough non-slip surface after solidification. As the refractory substance which has been heated to liquefaction in the gas/oxygen combustion flame is accompanied by a strong flow of relatively cold air or by a stream of inert gas, the enamel to which the coating is applied is insufficiently heated to cause melting of the enamel, and the smoothing. of the surface which would be connected therewith is thus avoided.
The refractory substance may be sprayed on to a base enamel as well as to a covering enamel, in the manner as described above, and it does not matter in this connection whether the covering enamel was applied by a wet or a dry process. The term refractory substance includes such substances as do not melt at a temperature of up to approximately 1,500C and which are resistant against slag formation, decomposition by gases, vapors, acid, and which are in addition resistant to abrasion and changes in temperature. For the purposes of the formation of a non-slip coating on the bottom of an enameled bathtub or shower tray, there is sprayed-on as a refractory substance at least one metal oxide and/or a ceramic material and pure clay, respectively, or enamel powder. It is convenient to select a substance which is also a component of the enamel, but other substances may be employed instead.
If the refractory substance is built-up like an enamel, it will include on the one hand glass-forming substances and, on the other hand, auxiliary substances. The glassforming substances include, in particular, quartz and feldspar. By adding boric acid, borax, Na O (in the form of soda or saltpetre), K (in the form of potassium nitrate or potash), lead oxide, or alumina, for example, the softening point of the substance is reduced to approximately 600 to 700C.
Auxiliary substances which may be used include adhesives, opacifiers, and colorants or pigments. These will often be metal oxides. The composition of the refractory substance, however, may vary within wide limits and has to be fixed more particularly in accordance with the well known basic concepts for an enamel mixture for enameling tubs of cast iron or steel.
When carrying out this known process, however, certain difficulties and shortcomings have to be faced, and it is the object of the invention as far as possible to overcome these difficulties and minimize these shortcomings. Of course, the non-slip surface of a bathtub or shower tray must be a certain size to be able to meet fundamental requirements. The minimum size overall is at least double the area covered by a foot. While on the one hand, it is an advantage of the known process that the non-slip coating may be applied with the aid of a gas/oxygen combustion flame when the enamel of the bathtub or shower tray has already solidified, this feature may also result in a shortcoming insofar as the gas/oxygen combustion flame can be made available only as one single flame and the application of the entire non-slip surface under these circumstances takes a relatively long time, thus leading to considerable labor costs. It is simply out of the question to overcome this shortcoming by the provision of a plurality ofgas/oxygen combustion flames in order to apply non-slip coatings to individual tubs. The shapes of individual tubs, even though they may be based on the same constructional drawing, differ from each other as a result of the preceding manufacturing process, so that the fitting of a plurality of gas/oxygen combustion flames meets with considerable difficulties. Added to this is the fact that the consumption of refractory substances to cause adherence of non-slip coatings is relatively high, which also adds to production costs. The result, too, namely the non-slip coating sprayed-on in the manner as described above, leaves much to be desired. Although the coating'as such is satisfactory when use is made of the usual masks which are applied directly to the inner wall of the tub, blurred edges or shadows forming at the edges of the coating spoil the good appearance of the enameled bathtub or shower tray. The perfect appearance of the inner wall of such an enameled tub, whether white or colored, is, however, of decisive importance for its selling value and thus also for the usefulness of such a tub.
In certain cases the edges of .the mask also stick to the surface of the enamel, which is a very severe shortcoming. Such tubs inevitably have had to be wasted.
BRIEF SUMMARY OF THE INVENTION In accordance with the invention, the non-slip surface is subdivided into a plurality of individual areas spaced from one another by a mask having openings each separately defined by an open-ended cuplike element made of a thermally conductive material resistant to heat and oxidation, said cup-like element being adapted to make line-contact with the surface to be coated at one open end and having an internal crosssectional area which defines the individual area to be coated, the internal cross section of said element increasing from said one end toward its other open end, at least over a part of the depth of the cup.
The practice of the invention commences when this mask is placed on the enameled bottom of a bathtub or shower tray made of steel or cast iron.
This subdivision of the non-slip surface by a plurality of cups designed in the manner above described substantially reduces the total area to be coated. In this manner labor costs are decisively reduced in that only the individual areas defined by the cups are sprayed with a non-slip coating, one after the other, with the aid of a gas/oxygen combustion flame to which the areas are exposed by the individual cups. The bottom area to be sprayed at one time is considerably reduced in this manner, so that uniformity of the non-slip coating is also improved within the area. Finally, the amount of refractory substance which has to be used for the provision of the entire non-slip coating is considerably reduced.
FURTHER FEATURES OF THE INVENTION In general, it will be preferred to design the cups according to the invention alike, but it is alternatively possible to design the shape and the free area of the cups in differing manners, in the one mask, so that the non-slip coating may appear as an ornament, a picture or even as an inscription.
The liquefaction of the non-slip coating may be achieved not only with the aid of a gas/oxygen combustion flame but also with the aid of the plasma flame spraying process in which the liquefaction of the refractory substance is achieved by means of an electric are. In these spraying processes it is easy to reach higher temperatures than with the gas/oxygen combustion flame, so that in performing the invention this spraying process also allows the use of refractory substances or mixtures of substances which liquefy only at relatively high temperatures or ranges of temperatures.
Owing to the fact that, independently of the respective shape of the inner wall of the tub which, owing to the preceding production steps, cannot be in strict conformity with the preconstructional dimensions, the individual cups designed in accordance with the invention lie perfectly against the inner wall of the tub bottom around the whole of their end peripheries; there is thus brought about a clear definition of the individual area that has been made into a non-slip surface, with no shadows appearing. It results from the wedge-shaped or cone-shaped design of the cup that heat is quickly dissipated from the line of abutment with the tub, so that no discolorations occur at the transition point from the individual non-slip areas to the enamel, as may be caused by chemical reactions in the form of an oxidation or reduction. The mask cups are wholly prevented from sticking because the heat supplied from a spray type burner and the hot particles of the refractory substance is quickly dissipated from the line of abutment along which each cup is in contact wit the bottom of the tub.
It has been found that the wedge or cone angle for the cup is preferably of the order of about 40. Here it must be taken into consideration that on the one hand the inside of the cup is to widen upwardly, that is from the line contacting the bottom of the tub, in order to facilitate the supply of particles of a more or less liquid refractory substance at the top of the cup. On the other hand, however, the outer surface of the cup must leave the line of abutment sharply enough to avoid discoloration or the formation of a shadow or even sticking phenomena in the region of this line.
Under consideration of these viewpoints, it has been found that the angle which is included between the lower end edge of the cup and the bottom of the tub advantageously should be about- 15. Taking into consideration the preferred wedge angle as stated above this will result in an inclination of about 35 of the internal cup surface with respect to the vertical.
As will be realized from the basic concept of the invention, the material of the cup is also of significance. Cups of brass with a copper content of about 60 percent, for example, and polished on the inside have proved to be very useful. Brass has a sufficient thermal conductivity and is sufficiently heat-resistant at the temperatures to be taken into consideration. At these temperatures, the usual brass alloys are not given to either oxidation or reduction, certainly in connection with particles of a refractory substance sprayed-on under high temperatures. Chromium-plated steel cups may'also be used instead of brass. Chromium-plating may be recommended in order on the one hand to prevent a chemical reaction between the steel and the refractory substance subjected to high temperatures and on the other hand to increase the heat resistance of the cup.
Apparatus to carry out the invention is characterized by a plurality of cups arranged in a mask which extends approximately over the entire region of the tub floor which it is intended to make into a non-slip area and has means for its detachable fastening at an approximately constant spacing from the bottom of the tub.
This device ensures at the same time a releasable positioning of all the cups which are provided for generation of the individual areas of non-slip coating.
The device in this manner considerably facilitates the coating process.
The entire non-slip coating is produced by successively spraying the inner surfaces of the individual cups,
Conveniently, all the cups are arranged in the mask in a manner to be loosely displaceable approximately normally, i.e. vertically, with respect to the bottom of the tub.
In this manner, the individual cups automatically fall into contacting engagement with the bottom of the tub under the influence of their own weights, in spite of the differences inspacing between the mask surface and the bottom of the tub which result from manufacturing inaccuracies. If desired or required, the individual cups may be slightly indented before starting to spray-on the non-slip coating, in order to ensure that their lowermost line is in sound contact with the bottom of the tub.
In a preferred embodiment of the invention, each cup is provided with a flange which is arranged to be loosely movable between two mask walls spaced from each other and which may be designated as outer and inner walls. These flanges do not have to be in the form of collars; the flanges only need to be provided in the form of projections arranged symmetrically with respect to the cup-like element. Three projections, for example, uniformly distributed about the circumference and offset from each other by will suffice.
In a corresponding manner, it is necessary to provide recesses corresponding to these projections in only one of the mask walls which are spaced from each other. The two mask walls may be spaced by a predetermined fixed distance, introduction of the cups into the corresponding mask openings being effected in the manner of a bayonet joint. The projections are at first introduced into the corresponding recesses of the one mask wall and thereupon the cup is rotated through an appropriate angle. It is, however, alternatively possible to provide the recesses in both mask walls.
In accordance with a further feature of the invention, the mask is supported in the tub .with the aid of a leg penetrating into the water outlet of the tub and guided therein, and two laterally projecting adjustable supports, said supports contacting the side wall of the tub. It is to be recommended to cover the leg and the supports or at least the leg or the supports with a resilient material, such as rubber, in particular.
DESCRIPTION OF EMBODIMENTS The invention will now be described by way of example with reference to the accompanying drawings which show two embodiments of the invention.
In the drawings:
FIG. 1 is a longitudinal sectional view of a mask designed in accordance with the invention for the production of a non-slip bottom surface of a built-in bathtub;
FIG. 2 is a top plan view taken on the mask of FIG. 1;
FIG. 3 is a sectional view taken on line IIIIII OF FIG. 1, on a slightly enlarged scale;
FIG. 4 is a partial sectional view taken on line IV- IV of FIG. 2, likewise on a slightly enlarged scale;
FIG. 5 is a longitudinal sectional view taken on a built-in bathtub with fitted mask according to FIGS. 1 to 4, on a slightly reduced scale;
FIG. 6 is a transverse sectional view of the tub according to FIG. 5, taken on line Vl--Vl of this Figure;
FIG. 7 is a longitudinal sectional view of a mask designed in accordance with the invention for the production of a non-slip coating on a shower tray of square base cross-sectional area, taken on line VIl VII of FIG. 8;
FIG. 8 is a top plan view taken on the mask of FIG. 7, with the outlines of the pertaining shower tray partly shown in dash-dotted lines; A
FIG. 9 is a sectional view of the shower tray and the pertaining mask in accordance with line X of FIG. 8, on a reduced scale; and
FIG. 10 is a sectional view of the shower tray and the pertaining mask taken on line XI-XI of FIG. 8.
The mask of FIGS. 1 to 6 is generally designated 1 and consists of an upper mask wall 2 and a lower mask wall 3, which are kept at a distance from each other by means of screw nuts 4 and spacers 5. As will be seen especially from FIG. 2, the mask walls 2 and 3 are both trapezoidal in plan form corresponding to the cross section of that portion of the built-in bathtub which faces towards the outlet opening. Both mask walls consist of sheet metal, preferably of steel sheet or brass sheet metal.
Both mask walls 2 and 3 are in addition slightly curved transversely of the built-in bathtub, i.e. in the direction of the cross-sectional area of FIG. 3. The
upper mask wall 2 is provided with a circumferentially extending outwardly inclined rim 6 while the lower mask wall 3 extends circumferentially, having no margin, and only covers below the corresponding surface of the upper mask wall 2. The mask walls serve to accommodate a plurality of masking cups 7. In the example of embodiment shown there are provided altogether seventeen cups generally uniformly distributed over the entire surface of the lower mask wall 3 and spaced from one another. These cups consist of brass, for example, and are conically shaped with a concentric axis 8 for the internal and external walls. To carry the invention into practice, however, a concen-. tric design of the cups is not essential. The cup 7 is provided with an inner cone 9 which in this example has a cone angle of Anouter cone 10, which in the example has a cone angle of intersects the inner cone 9 on a circular line 1 1. It is on this circular line 1 1 that each individual cup is supported on the bottom surface of the wall which is to be provided with a nonslip coating. The cup 7 is in addition provided with a cylindrical outer wall' 12 from which there extends a collar 13; this collar 13 locates each cup between the two mask walls, 2, 3, in that the mask walls are provided with openings axially aligned with respect to each other, said openings being of diameter slightly greater than the cylindrical outer diameter of the cup. In this manner, each cup may have its circular line 11 soundly contacting the bottom of the tub even through the entire mask may not be exactly adapted to the configuration of the bottom of the tub.
The two cone angles of 70 and 150 insure that the wedge cross-sectional areas which are formed by the two cones extend from the bottom wall of the tub at an angle of 15. Both cone angles may be varied. It is not necessary to generate both cones by a straight line, what is important, however, is that the individual cups are essentially adapted to make line contact with the bottom of the tub and that the cup wall comprises a wedge-shaped enlargement beginning at this line, in order to dissipate the heat concentration forming along this line as quickly as possible.
The mask 1 is provided with a leg 14 at one of its ends, namely its narrow end, said leg being provided with a conical extension 15 towards its lower end and fastened at the mask 1 by means of a screw 16, for example. This leg 14 consists of a plastically resilient but mechanically solid synthetic material. In the example of embodiment it consists of a synthetic material marketed under the trademark Pevolon. The leg 14, 15 is intended to penetrate to a considerable extent into the outlet 34 of the tub 17, thus fixing and centering the mask 1 on the drain side. On the other side of the mask there are provided two adjusting screws 18 disposed opposite each other, each screwed into a nut 19, said nuts being each fastened in a respective holder 20 extending above the rim 6 of the mask. The free end of the screw 18 is provided with a supporting head 21 which is designed as a cap of plastically elastic synthetic material such as rubber, for example. At the two lateral edges the mask handles 22 are provided on either side.
It will be seen from the drawings that the mask may be easily fitted and fixed in a tub the dimensions of which are generally adapted to the mask. As the side walls of the tub are diverging, the position of the mask may be easily adjusted also on the side of the adjusting screw 18 by adjustment of the caps 21. It is impossible to damage the tub by the leg 14 or the caps 21.
The adjusting screws 18 then determine the transverse position-of the mask. While in the vertical position the mask is exclusively retained due to the leg 14 being centered in the outlet of the tub. All the cups 7 are supported on the bottom of the tub. The operational step of spraying on the non-slip substance through the cups takes place with the tub in an approximately vertical position (70 to 80). The foot end of the bathtub is on top.
In accordance with P108. 7 to 10, a mask for a shower tray 35 designed in accordance with the invention has a square base surface. The masking cups 7 are designed completely in conformity with the cups described above. There is again provided an upper mask wall 23 and a lower mask wall 24 which are spaced from each other by means of screw nuts 25 and spacers 26. The upper mask wall 23 is again provided with a circumferentially extending rim 27. A leg 14 has its conical extension fastened by means of a screw 16 and engages within the outlet 28 of the shower tray, as will be seen from FIG. 10. Two sheet metal supporting members 29, 30 serve to fasten the leg 14, and may be adjustably fastened to each other using elongated holes 31 and screw nuts 32. The leg 14 is fastened to the one sheet metal carrier member 29, while the other sheet metal carrier member 30 is fastened at the upper mask wall 23. It is possible in this manner to use the mask for different shower trays and always to align the mask with the outlet. This is possible'with shower trays because as a rule they have an approximately plane base surface. The two lateral supports are again each provided with a rubber cap arranged on the free end of a screw 18. The screw 18 is threaded into a nut which is fastened at a holder 33 fastened in turn at a corner of the upper mask wall 23 and extending upwardly therefrom.
Here as well the distribution of the cups is freely selectable although care must be taken to distribute them sufficiently uniformly over the entire surface to be made into a non-slip area.
In these examples of embodiment, the circular line 11 which lies on the bottom of the tub and in which the two cone areas intersect with each other has a diameter of 30 mm, so that the entire non-slip area consists of a plurality of non-slip coatings each having a diameter of 30 mm. This size has proved to be especially suitable for carrying the invention into practice.
1. Apparatus for applying a non-slip coating to an enameled surface on a metal base by spraying a refractory substance heated to liquefaction on the enameled surface comprising, in combination, a mask adapted to be disposed over the surface to be coated, and comprising a bottom defined by spaced superposed walls and a plurality of tubular heat conductive means through which the coating substance is applied to the enameled surface, each said means having an outer peripheral flange disposed between said walls whereby to provide for a lost motion in the axial direction of said tubular means upon contact with said enameled surface and whereb eac said means i divi uall o ient themselves, zi relatiilely sharp annuiar edge of reduced crosssectional area defined on said heat conductive means defining that portion of said opening disposed adjacent the enameled surface and adapted to engage the enameled surface in substantially line contact, said heat conductive means having an increased cross-sectional area adjacent said annular edge defining a heat absorbing mass for drawing heat from said edge.
2. Apparatus for applying a non-slip coating to an enameled surface as in claim 1 wherein said heat conductive means openings are of a decreasing transverse cross-sectional area converging in the axial direction toward the enameled surface being coated.
3. Apparatus for applying a non-slip coating to an enameled surface as in claim 2 wherein said openings are of a conical configuration.
4. Apparatus for applying a non-slip coating to an enameled surface as in claim 1 wherein said heat conductive means comprises an annular cup formed of metal having an axis, inner and outer ends, an inner surface defining said opening and an annular outer surface intersecting said inner end, said inner and outer surfaces intersecting at said inner end defining said annular edge.
5. Apparatus for applying a non-slip coating to an enameled surface as in claim 4 wherein said inner and outer surfaces are of a conical configuration and define an included angle of approximately 40 at said annular edge.
6. Apparatus for applying a non-slip coating to an enameled surface as in claim 4 wherein said outer surface is conical and defines an included angle of approximately 15 with the surface to be coated.
7. Apparatus for applying a non-slip coating to an enameled surface as in claim 4 wherein said annular cup is formed of brass.
8. Apparatus for applying a non-slip coating to an enameled surface as in claim 4 wherein said annular cup is formed of chromium plated steel.
9. Apparatus for applying a non-slip coating to an enameled surface as in claim 1, mask positioning means defined on said mask for orienting said mask relative to the surface to be coated.