Abstract:
A bathtub providing safe egress from a slippery bathtub floor has a limited rectangular footprint and an optimized floor space is formed with a substantially planar base with a length and width that define the limited rectangular footprint and a front wall, a back wall, a first side wall and a second side wall integral with and extending substantially vertically upwards from the substantially planar base. Each of the front, back, first side wall and second side wall have minimal wall thicknesses to define the optimized floor space and the front wall has a substantially planar upper apron deck that extends inwardly from an outer substantially vertical front wall surface for a fixed amount in a substantially parallel relation to the substantially planar base.

Description:
RELATED APPLICATIONS 
     This application is a continuation-in-part of application Ser. No. 14/688,413 (the “413 application”), filed Apr. 16, 2015, which &#39;413 application is incorporated by reference herein, and claims priority in part under 35 USC§120 therefrom. This application also claims the benefit of provisional patent application No. 62/111,453 filed Feb. 3, 2015 (“the &#39;453 application”) under 35 USC§119(e). The &#39;453 application is incorporated by reference herein. This application also claims priority under 35 USC§120 from design patent application No. 29/521,732 (the &#39;732 application), filed Mar. 26, 2015. The &#39;732 application is incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to providing safe egress from wet bathtub floors and to maximizing internal bathtub/shower stall space within predetermined confines of typical residential bathroom space dimensions. 
     BACKGROUND OF THE INVENTION 
     Safety studies indicate over 234,000 bathroom injuries each year, of which 81 percent occurred because of falls in the bathroom. See Bakalar, “Watch Your Step While Washing Up”, New York Times, Aug. 15, 2011, citing CDC Centers for Disease Control and Prevention, “Nonfatal Bathroom Injuries Among Persons Aged &gt;15 Years, United States, 2008”, Morbidity and Mortality Weekly Report (MMWR), 60 (22); 729-733, Jun. 10, 2011. Of these injuries, more than one third happen while bathing or showing. The Center for Disease Controls (CDC) estimates that 9.8 percent of all bathroom injuries specifically occur when getting out of a bathtub, which equals at least 22,932 injuries. 
     Applicants believe that injuries while getting out of a bathtub occur because of the wide straddling of the bather&#39;s legs when exiting a bathtub. The horizontal component force Fs that arises from this arrangement is 0.306 W or almost 31% of the weight of the person. This horizontal component must be resisted by the frictional force between the ball of the anchor foot and the tub (or a tub mat). Several items affect the local coefficient of friction between foot and tub, or foot and mat and mat to tub. Water, and especially soapy water, is a good lubricant and dramatically reduces the coefficient of friction. If the widely straddled anchor foot slips, the bather&#39;s weight is subject to horizontal sideways force and prone to dangerous falls while attempting to exit the bathtub. 
     In addition to the aforementioned safety issues, when viewed in crossection from an end, conventional prior art bathtubs have limited interior bathing space by virtue of the fact that the upper apron deck provided for sliding glass doors is usually three or more inches in top width, which narrows considerably the interior bathing or showering space or volume within the conventional bathtub. Additionally, for symmetry purposes, a similar opposite wall abutting top edge is also typically three or more inches in top width, thereby further limiting the space or volume within the bathtub. Typical residential bathrooms generally have a limited rectangular footprint area of 60 inches by 30 or 32 inches within which to locate a bathtub and shower installation. So losing 1, 2, 3 or 4 inches in width results in a significant reduction in the overall internal space or volume within a typical bathtub. 
     Among known prior art patents includes U.S. Pat. No. 2,431,475 of Gruen, which discloses the elimination of a front bathtub apron wall and the creation of an apron effect, by providing a front wall having an upper edge wall fanning outward, both inside the tub and outwards from the front of the tub, to prevent water from splashing out of the bathtub. 
     US Patent Application 2011/0167728 of Alelov discloses an “Expandable Side Enclosure for Bathtubs/Showers”, to provide a solution to prevent arm movement restrictions caused to bathers in bathtubs and/or showers due to the lack of free body and limb movement in baths with standard enclosures. While Alelov provides outwardly extended bay-type windows in the sliding glass doors, which are at standing arm height, to provide more movement of the arms during a shower. However, Alelov does not increase the internal volume of the bathtub itself. 
     U.S. Pat. No. 1,811,896 of Ross discloses a circular topped truncated conical water basin/bowl/tub with an inwardly inverted anti-splash lip/flange. However, Ross cannot be installed in a typical rectangular bathtub footprint in a residential bathroom. 
     U.S. Design Pat. D619,685 of Hoernig discloses a shower and tub with a “flip up out of the way” apron deck, to expand the interior space of the bathtub. However, Hoernig requires moving parts and hinges, which are complicated and detrimental in a high humidity bathtub environment. 
     U.S. Design Pat. Des. 335,701 of Zaccui discloses a bathtub which increases interior space by having bulging outwardly extending side walls. However, the bulging sides of Zaccui &#39;701 prevents its installation within a standard bathtub area. 
     These known prior art devices do not maximize internal bathtub/shower stall space within the predetermined confines of typical residential bathroom space dimensions. The use of the an inwardly extending only cantilevered top apron edge in the present invention for an expanded space bathtub, where the rear wall has no apron edge, would be discouraged, if not clearly taught away from the prior art patents. 
     Therefore, the use of a bathtub with both an inwardly extending apron deck and an expanded footprint and volume for the bathtub, as in Applicants&#39; present invention, in conjunction with the spatial confines of a rectangular bathtub installation area of a residential bathroom, is not only not suggested, but would be discouraged or taught away by the designs known from the conventional arts. 
     OBJECTS OF THE INVENTION 
     An object of the present invention is to provide a bathtub which provides safe egress for the bather. 
     It is also an object of the present invention to minimize falls from bathtubs by providing a structural front wall which minimizes wide straddling of the bathtub front wall by a bather exiting from the wet bathtub. 
     Another object is to provide a bathtub that fits within standard tub dimensions but has a larger internal floor area and larger volume within. Most bathtubs are used for taking showers but are dimensioned for tub use. The inventive bathtub better accommodates its shower use while still affording the choice of use as a soaking tub. The larger interior floor area of the bathtub simulates the feel of a larger shower by being less confining. 
     These objects are achieved in the inventive bathtub design by use of thin front, back and side walls. The front deck width still is maintained to accommodate sliding door tracks thereon, however, to support sliding glass doors. The side decks and back deck are just the thickness of the tub material. The front deck is maintained with a width of up to a maximum of 3.5 inches, according to a width required to accommodate siding door tracks, but it is cantilevered from the front vertical surface of the front wall inward and then rejoins the thin front wall at near the top of the rear vertical surface of the front wall thereby realizing a tub that does not suffer a reduction in the interior floor space by the front deck width. The floor area covered by a projection of the front deck is usable space for visual appearance as well as actual space for feet while standing and taking a shower 
     SUMMARY OF THE INVENTION 
     The substantially vertical walls and thinness of the front wall of the bathtub of the present invention minimize injuries from falls by providing safe egress from the bathtub, by virtue of the fact that the user has a very small straddling angle measured by the angle of the anchor foot planted in the bathtub, as compared to an imaginary vertical line, when lifting the leading foot over the edge of the bathtub. 
     As a result, only a small percentage, such as ten percent, of the bather&#39;s weight, is subject to slippery horizontal sliding forces. This compares to a much larger percentage of weight, such as thirty percent, of the weight of a bather straddling the front wall of the bathtub when the anchor foot planted in the bathtub is far away from the front wall, resulting in a much larger straddling angle, causing substantial horizontal sliding forces of the bather&#39;s feet on the slippery bathtub floor, and/or slippery floor outside the bathtub. 
     The safety egress bathtub encompasses a method of providing and using a safe egress bathtub including the steps of: 
     a) providing the bathtub with substantially vertical back and front walls, first and second end walls, and a bottom wall, all of these walls being of rigid material, wherein the entry and egress of a bather user is accomplished by stepping over the front wall; 
     b) providing the front wall with a cantilevered top horizontal apron deck extending from an outer surface of the front wall toward the back wall, wherein the top horizontal apron deck has sufficient width to support sliding shower wall tracks thereon; 
     c) the bottom floor wall extends to a rear, vertical surface of the front wall with the cantilevered top apron deck overhanging an area of the bottom floor wall adjacent the rear, vertical surface of the front wall; 
     d) the user places a first leg on the bottom wall of the bathtub adjacent the vertical front wall of the bathtub, the foot of the leg being generally pointed toward the front wall, a front portion of the user&#39;s foot extending under the cantilevered top apron deck; and 
     e) the user places a second leg over the front wall for stepping out of the bathtub, wherein the first leg makes with the vertical front wall an angle sufficiently small so as to reduce a horizontal component of force on the foot of the user&#39;s first leg, for reducing the incidence of slippage on a wet surface of the bathtub bottom floor. 
     Additionally, the bathtub of the present invention has with a limited rectangular footprint and an optimized floor space, including: 
     a substantially planar base with a length and width that define the limited rectangular footprint; 
     a front wall, a back wall, a first side wall and a second side wall integral with and extending substantially vertically upwards from the substantially planar base; 
     wherein each of the front, back, first side wall and second side wall have minimal wall thicknesses to define the optimized floor space, and 
     wherein the front wall has a substantially planar upper apron deck that extends inwardly from an outer substantially vertical front wall surface for a fixed amount in a substantially parallel relation to the substantially planar base. 
     The substantially planar upper apron deck is preferably cantilevered inwardly from the top horizontal surface of the front wall of the bathtub. 
     The bathtub&#39;s front wall is arranged in opposing relation to the back wall and the first side wall is arranged in opposing relation to the second side wall such that all of the walls are integrally joined to define the inner bathtub volume therebetween. 
     The bathtub&#39;s minimal wall thickness is a minimum thickness to which the walls can be manufactured and maintain structural integrity, wherein the minimal thickness to which the wall can be manufactured is dependent on a material composition of the walls. 
     The bathtub&#39;s substantially planar upper apron deck extends inwardly between and integrally connected to upper portions of the first side wall and the second side wall, in a substantially parallel relation to substantially planar base. 
     While dimensions may vary, preferably the limited rectangular footprint of the base of the bathtub is approximately 1419 square inches. 
     The bathtub has a distance between an inner surface of the front and back walls and a distance between an inner surface of the first and second side walls, measured at an upper surface of the substantially planar base and a lower inner surface of the substantially planar upper apron deck, respectively, and a minimal distance between the upper surface of the substantially planar base and the lower inner surface of the substantially planar upper apron deck, define an inner air volume of the bathtub. 
     While dimensions may vary, preferably the Interior air volume is approximately 20,845 cubic inches. 
     Preferably the bathtub&#39;s thickness of the substantially planar upper apron deck is less than or equal to the thickness of the front wall, and wherein the thickness of the substantially planar upper apron deck is a minimum thickness to which the upper apron deck can be manufactured and maintain structural integrity. 
     One wall of the first side wall and the second side wall extends vertically at an angle that is greater than 90° between a plane of the base and a plane of the one of the first side wall and the second side wall. 
     Preferably, the inner corners formed by vertical ends of the first and second side walls of the bathtub, with vertical ends of the front and back walls, are substantially rounded. 
     Also preferably, the inner corners between lower ends of the first and second side walls and the front and back walls and, an inner surface of the substantially planar base are substantially rounded. 
     The bathtub&#39;s one or more first and second side walls extend inwardly from an outer substantially vertical wall surface of the one or more first and second side walls for a fixed amount, in a substantially parallel relation to the substantially planar base. 
     Also preferably, the bathtub&#39;s front wall and rear wall each have a thickness of about one inch. 
     Preferably, the bathtub&#39;s front wall and rear wall are tapered, with a top thickness of about one inch and with a bottom thickness of about one and one quarter inch in thickness. 
     The bathtub also may optionally have hollow interiors, wherein the front wall is hollow, with an outer front wall of about one quarter inch in thickness and an inner front wall of about one quarter inch in thickness, further with a hollow air space therebetween. 
     The bathtub&#39;s rear wall may also optionally have a front rear wall of about one quarter inch in thickness, and a hollow air space of about three quarter inches extending behind the front rear wall up to the surface of the bathroom wall, to accommodate tile and tile grout therebetween. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention can best be understood in connection with the accompanying drawings. It is noted that the invention is not limited to the precise embodiments shown in the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a portion of a bathroom enclosing a prior art bathtub; 
         FIG. 1A  is a cross-sectional view of a prior art bathtub with a limited space interior; 
         FIG. 2  is a perspective detail in partial crossection of a front corner of the prior art tub showing the front deck width; 
         FIG. 3  is perspective view of a portion of a bathroom enclosing the bathtub of this invention; 
         FIG. 4  is a perspective view of the bathtub of this invention; 
         FIG. 5  is an end view crossection showing the profile of the cantilevered front deck; 
         FIG. 5A  is an end view crossection of an alternate embodiment, showing the profile of the cantilevered front deck; 
         FIG. 6  is an enlarged cross-section detail of the cantilevered front deck; 
         FIG. 7  is a side cross-section view of the bathtub of this invention; 
         FIG. 8  is an end view profile of a prior art tub with rounded edges at bottom. An outline of the anchor leg of a person in unsupported egress is shown at a particular instant. Also shown is a vector force diagram at the same instant; and, 
         FIG. 9  is an end view profile of the tub of this invention with an outline of the anchor leg of a person in unsupported egress at a comparable instant to that shown in  FIG. 8 . Also shown is a vector force diagram at the same instant. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in Prior Art drawing  FIGS. 1 and 2 , the prior art tub  2  in bathroom  1  as shown in  FIG. 1  is meant to represent any commonly available design. Front deck  3 , back deck  4  and side decks  5  are shown.  FIG. 2  is a close-up showing the typical wide dimension  8  of front deck  3  as well as the narrower side decks  5  dimension  7 . 
       FIGS. 3-7  pertain to the bathtub of this invention.  FIG. 3  shows tub  15  in bathroom  10  which is of the same dimensions as bathroom  1  in  FIG. 1 .  FIG. 4  shows tub  15  in a perspective view with back deck  17  in the forefront and front deck  16  at the far side. It is noted that side decks  18  as well as back deck  17  have wall widths that are equivalent to the thickness or width of the material comprising the side walls, the back wall and the front wall below the front deck. The crossectional views of  FIGS. 5, 5A and 6  show the cantilevered shape of front deck  16  in detail, highlighting that the front deck width does not encumber the interior width of the tub floor. It is further noted that the width dimension  19  is the same as dimension  8  in prior art  FIG. 2 .  FIG. 7  is a length wise crossection showing sloping backrest  20  and slight drain slope  21 , which is preferred. In these figures, large sections are shown as being solid material just for interior dimensional clarity, however they may in fact have enclosed air spaces. This would be especially true of the large wedge shape under back rest  20  and the cantilevered front deck as in  FIG. 6 ; it would depend on the material used and method of construction. 
     An expanded space bathtub  15  fits in standard tub dimensions of bathroom  10  having footprint floor area  10   a  and vertically extending bathroom wall surfaces  10   b ,  10   c  and  10   d , and has a larger internal floor area  15   e  of bottom base wall  15   f , and larger air volume  30  within. The bathtub  15  includes thin walls, including four vertically extending walls, including front wall  15   a , rear wall  15   b , left side wall  15   c  with sloping backrest  20  adjacent thereto and separated from left side wall  15   c  by hollow interior area  21   a ′, and right side wall  15   d  having trip lever hole  23 . Vertical walls  15   a ,  15   b ,  15   c  and  15   d  extend vertically upward from rectangular bottom base wall  15   f  having an exterior footprint to fit within the pre-determined rectangular bathtub insertion floor footprint area  10   a  of bathroom  10 . Bottom base wall  15   f  has an interior footprint  15   e , which, with the inside surfaces of vertically extending walls  15   a ,  15   b    15   c  and sloping backrest wall  20  of left side wall  15   c , define the enlarged air volume  30  extending therebetween. 
     The thickness of the vertical walls  15   a ,  15   b ,  15   c ,  15   d  and sloping side backrest  20  is preferably one inch in thickness near the top, up to about one and one quarter inches on the bottom, to provide a slightly sloped surface for easy removal of the tub from a mold. The one inch and one and one quarter inch dimensions need not be solid, so that a wall (not shown) having a thickness of one quarter inch on each side can have a hollow interior of one half inch. A similar hollow area can be provided at the slightly wider bottom width of one and one quarter inches total, combined with the walls and hollow interior. Moreover, for the rear, wall facing wall  15   b , the wall  15   b  can be just one layer of one quarter inch in thickness, with a three quarter inch hollow area behind the one quarter inch wall, up to the bathroom wall surface  25  itself. The one inch thickness at the top  17  of rear wall  15   b  is required to accommodate tiles of up to ⅝ inch in thickness and accompanying grout against the bathroom wall surface  25 . As shown in  FIG. 5A , an optional attachment flange  24  can be attached to rear wall  15   b  for attachment to bathroom wall surface  25 . 
     As shown in the crossectional view of  FIG. 7 , the inside bottom footprint  15   e  of bottom base wall  15   f  preferably has a slope  21 , sloping downward from the corner  21   a  defined by sloping backrest  20  and an adjacent edge of interior footprint  15   e  of bottom base wall  15   f , downwards towards water drain hole  22 . 
     The front apron deck  16 &#39;s width of up to a maximum of 3.5 inches is maintained within normal construction requirements to support the sliding glass door tracks, but without the need for limiting interior bathtub volume with thick walls. The side decks  18  and back deck  17  are limited to the thickness of the tub material. The front apron deck  16  has a width which is maintained to industry standards to support sliding shower wall tracks thereon, but it is cantilevered from the front surface of front wall  15   a  inward and then rejoins the thin inner wall of the front wall  15   a  where its inwardly preferably curved backwards undersurface wall  16   a  meets near the top of the inner surface of front wall  15   a  of bathtub  15 , thereby not reducing the interior floor space  15   e  or the interior air volume  30  by the front deck  16 &#39;s width. The bathtub  15  therefore maximizes internal bathtub/shower stall space within the predetermined confines of typical residential bathroom bathtub and shower space dimensions. 
     The bathtub  15  of this invention can be made of steel or plastic resin materials and finished as is common in the industry. 
     A comparison of the interior floor space and enclosed air volume (to the top edge of all four vertical walls the tub) has been made to compare a prior art tub and a tub of this invention of the same external dimensions. A prior art front deck of 4″ and a back deck of 3″ with side decks of 2″ in a 60 inch external length by 30 inch tub of 15″ average internal depth was assumed for comparison. The wall thickness of the tub of this invention is assumed to be 1″. Both tubs have the angled backrest and straight vertical walls. The increased floor area and air volume in the tub of this invention is due to the 1″ wall thickness and decks (on 3 edges) vs. the decks of the prior art tub which reduce the internal dimensions. 
     The results of the comparison are as follows: 
     Interior Floor Area
         prior art 1120 sq. in.   this tub 1419 sq. in., a 27% increase.       

     Interior Air Volume
         prior art 16790 cubic in.   this tub 20845 cubic in., a 24% increase       

     Additionally, the above calculations were based upon a prior art bathtub with a front deck of 4″ and a back deck of 3″ with side decks of 2″ in a 60 inch external length by 30 inch tub of 15″ average internal depth for comparison. However, since most prior art tubs have sloping and bottom rounded sides, the numbers of this estimate represent the minimum percentage increases in interior floor area and interior volume. It is estimated that in comparison with other prior art bathtubs, with increased sloping and bottom rounded sides, the savings can be up to approximately 35% increase in interior floor area and interior air volume. 
     Bathtub  15  of this invention also offers safety improvement over that of the prior art. Safety studies indicate over 250,000 bathroom falls each year, the majority being of bathers exiting a bathtub.  FIG. 8  shows a profile of a person  42  exiting a prior art bathtub  40  with rounded walls at the bottom. The “average person”  42  is a composite 50 th  percentile man or woman with a hip joint to floor dimension L of 35″. Although the results of the analysis to follow are somewhat dependent on this selected number, let it be said that a taller person would experience slightly less difference in egress from either a prior art tub or the tub  15  of this invention, and vice versa for a shorter person. Note that the rounded side bottom edge forces the anchor foot farther away from the front edge of the tub (toward the middle) to be supported by the flat portion; this is also true of prior art profile shown in  FIG. 1A  with the sloping sides. 
     The instant for the static analysis of  FIG. 8  is that corresponding to the hip joint being directly above the front edge of the tub with the ball of the anchor foot carrying the entire weight of the person before the forward foot (not shown) touches the ground. For the purpose of analysis, the anchor leg can be represented by a rigid rod from the hip joint  44  to the ball of the anchor foot. By measuring the angle in  FIG. 8 , it is found that this rod makes a 17 degree angle with the vertical as shown in the vector force diagram to the right. The weight of person  42 , W, is shown vertically. The horizontal component force Fs that arises from this arrangement is 0.306 W or almost 31% of the weight of the person. This horizontal component must be resisted by the frictional force between the ball of the anchor foot and the tub (or a tub mat). Several items affect the local coefficient of friction between foot and tub, or foot and mat and mat to tub. Water, and especially soapy water, is a good lubricant and dramatically reduces the coefficient of friction. If the anchor foot slips, the bather is in trouble! 
     If a similar analysis of Applicants&#39; expanded space tub  15  is performed as depicted in  FIG. 9 , the angle of rigid rod and the vertical is only 5.5 degrees because now the anchor foot is so close to the front edge. The horizontal component force Fs that results in this analysis is 0.096 W or only less than 10% of the weight of the person. Thus with the same bather exiting either a prior art tub or a tub  15 , slippage can be avoided in a tub  15  of this invention even if the friction coefficient were ⅓ of that which minimally prevented a spill in a conventional tub. Common sense reinforces the numeric example; the tub  15  side walls are substantially vertical; the bather can have the planted leg being substantially vertical and stable, and this requires only lifting the leading leg up and over the thin apron of 3.5 inches or less. 
     In the foregoing description, certain terms and visual depictions are used to illustrate the preferred embodiment. However, no unnecessary limitations are to be construed by the terms used or illustrations depicted, beyond what is shown in the prior art, since the terms and illustrations are exemplary only, and are not meant to limit the scope of the present invention. 
     It is further known that other modifications may be made to the present invention, without departing the scope of the invention, as noted in the appended Claims.