Sealed tub

A stave for a tub has opposite elongate edges formed with formations each having a section transverse to the stave including an arcuate portion, and a rabbet for receiving a floor of the tub extending between the edges. The formations on each stave are desirably complementary, but need not be. Staves placed in edge-to-edge relation define a tub wall which can conform to an arbitrary shape and size. A tub is formed by a plurality of staves, an appropriately shaped floor, and bands extending around the outside of the tub wall.

This invention relates to a tub, such as a so-called hot tub or whirlpool 
spa, and to a method of and parts for making it. 
Coopers have, for a very long time, made tubs and barrels by cutting each 
edge of curved or straight staves, which make up the side of the tub or 
barrel, to a precise predetermined angle, placing a predetermined number 
of staves in edge-to-edge relation to form a cylindrical body, attaching 
thereto one or two circular wooden ends, and banding the body with iron 
bands. This method suffers from the disadvantage that the angle cut on 
each stave edge is dependent upon the diameter of the tub and the width of 
the stave. Accordingly tubs of particular diameters and/or stave widths 
must be designed and manufactured on an individual basis. This can be seen 
from the fact that, for example, a 3 foot diameter tub would require 4 
inch wide staves cut to a stave angle of 6.4 degrees but would require 6 
inch wide staves to be cut to a stave angle of 9.5 degrees, and a 4 foot 
diameter tub would require 6 inch wide staves cut to a stave angle of 7.2 
degrees. 
A further disadvantage of this known method is that it is not readily 
possibly to form tubs of non-circular cross-section. For example, to 
provide a tub of elliptical cross-section, it would be necessary to draw 
the elliptical cross-section, determine thereon the position of each 
stave, and to draw normals to the ellipse each cutting the ellipse at the 
junction between two staves to determine the stave angles for the 
individual staves. Each stave would then in general have different stave 
angles to the adjacent stave and different stave angles on its opposite 
edges. This same degree of complexity of design, and consequently also 
manufacture and stocking, of the staves applies to other curves, for 
example heart, kidney, and pear shapes. 
An object of the present invention is to provide an improved stave which 
can be used in different and arbitrarily shaped and sized tubs, and an 
improved tub including such staves. 
The invention also seeks to provide improved apparatus, including such 
staves, for forming a tub and a method of forming a tub using such 
apparatus. 
According to one aspect of the invention there is provided a stave 
comprising an elongate member having opposite elongate edges formed along 
their lengths with formations each of which, in a section transverse to 
the length of the member, includes a substantially arcuate portion which 
is engageable with a complementary portion of another stave when said 
staves are placed in edge-to-edge relation, said member further having a 
rabbet in an elongate face thereof extending between said elongate edges 
transversely of the length of the member and between the ends thereof. 
According to another aspect of the invention there is provided, for forming 
a tub, a plurality of staves each as recited above, said staves being able 
to be placed in edge-to-edge relation with the formations on the elongate 
edges of adjacent staves engaging one another to form a continuous wall of 
a tub with a continuous groove on the inner side of said wall formed by 
the rabbets in the staves; at least one member engageable within said 
groove to form a floor of the tub; and at least one band engageable around 
said staves on the outer side of said wall for retaining said staves in 
place. 
The invention extends to a method of forming a tub from the apparatus 
recited above, comprising the steps of disposing said staves in said 
edge-to-edge relation with said groove engaging said at least one member 
to form said continuous wall and floor of the tub, and engaging said at 
least one band around said staves on the outer side of said wall to retain 
said staves in place. 
According to a further aspect of the invention there is provided a tub 
comprising a continuous wall formed by a plurality of staves disposed in 
edge-to-edge relation, each stave comprising an elongate member having 
opposite elongate edges formed along their lengths with formations each of 
which, in a section transverse to the length of the member, includes a 
substantially arcuate portion which engages a corresponding portion of the 
adjacent stave, the member forming each stave further having a rabbet in 
that elongate face thereof which forms part of the inner side of said 
wall, said rabbet extending between said elongate edges of the member 
transversely of the length and between the ends thereof, the rabbets in 
said staves being aligned to form a continuous groove in said wall; a 
floor of the tub formed by at least one member engaged within said groove; 
and at least one band engaged around said staves on the outer side of said 
wall retaining said staves in place. 
The substantially arcuate form of the elongate edges of the staves enables 
the staves to be disposed in edge-to-edge relation at arbitrary angles to 
one another and thus avoids the need for the staves to be cut to precise 
predetermined stave angles. Thus the staves can be arranged to conform 
substantially to any desired curved or straight path, without the need for 
individual staves to be provided for individual positions along such path. 
In preferred embodiments of the invention, the substantially arcuate 
portions of the formations on the opposite elongate edges of the member 
are complementary to one another. This facilitates the disposition of the 
staves in edge-to-edge relation in that it enables a convex formation on 
one edge of each stave to be received in a complementary concave formation 
on the relevant edge of the adjacent stave. In contrast, known staves cut 
to precise stave angles are more difficult to position and retain in 
precise edge-to-edge relation during construction of the tub. 
The above advantage can also be provided in accordance with the invention 
by providing staves of two types, one of which has convex formations on 
both elongate edges and the other of which has concave formations, 
complementary to the convex formations, on both edges, the two types of 
staves being disposed alternately around the circumference of the tub. 
However, this involves the provision of the two types of staves, as 
opposed to merely one type being required according to the preferred 
embodiment recited above. 
Staves of only said one type, having convex formations on both elongate 
edges, can be used to form a tub within the broadest aspects of this 
invention, but the advantage that the disposition of the staves in 
edge-to-edge relation is facilitated is then lost. This advantage is 
particularly important when a tub is to be constructed by an individual 
not skilled in the art of tub-making. 
It is also conceivable, without departing from the present invention, to 
mix the three above-described types of staves otherwise in a single tub. 
It is also preferred that the diameter of a circle which is defined by the 
substantially arcuate portions of the formations is not greater than the 
thickness of the member between the opposite elongate faces thereof. This 
facilitates the provision of a relatively smooth surface provided by the 
staves, especially on the inner sides of curved paths followed by the 
staves. 
The staves are preferably of wood, which in use of the tub absorbs water 
and swells to provide a substantially water-tight seal between the staves 
without any separate sealant being required. For similar reasons, the 
floor of the tub is also preferably of wood. 
The bands around the tub are preferably metal straps, for example of 
stainless steel or some other material which has sufficient tensile 
strength and is corrosion-resistant or is protected against corrosion. The 
straps can be retained around the staves by any suitable means; for 
example each strap may have at one end a captive bolt and at the other end 
a nut secured thereto, in which case the bolt may be screwed into the nut 
to retain and tighten the strap around the staves. Naturally, it will be 
appreciated that it may be necessary to provide spacers between the bands 
and the staves in any region of the tub in which, as a result of the shape 
of the tub, the tightened bands do not provide a sufficient retaining 
force on the staves. This may particularly be the case in any generally 
concave region of the tub wall.

FIG. 1 illustrates a stave 1 in the form of a wooden member whose length 
corresponds to the overall height of a tub to be made from a plurality of 
such staves and is, for example, four feet. The stave has a 
cross-sectional size which is arbitrary, but for example conveniently 
about 51/2 inches by 15/8 inches so that the stave is readily formed from 
6 inch by 2 inch wood. These figures are given purely by way of example 
and it is clear that any practical width, thickness, and length of stave 
may be used in any particular circumstnces. 
The opposite elongate edges 2 and 3 of the stave 1 are formed along their 
lengths with formations each of which, in a section transverse to the 
length of the stave and hence as shown by the end view in FIG. 2, includes 
a substantially arcuate portion which is engageable with a complementary 
portion of another stave when said staves are placed in edge-to-edge 
relation. Thus the edge 2 is formed with a convex portion 4 which extends 
the entire length of the stave 1, and the edge 3 is formed with a 
complementary, concave, portion 5 which also extends the entire length of 
the stave 1. A plurality of such staves may be placed in edge-to-edge 
relation as shown in FIG. 2, with the convex portion 4 of one stave 
received in the concave portion 5 of the adjacent stave, to form a wall of 
a tub. The wall can substantially follow any desired curved or straight 
path by appropriate choice of the stave dimensions and the angles which 
adjacent staves make with respect to one another. FIG. 2 shows for example 
that the staves may be disposed to form an angle .alpha. therebetween 
which can be less than or greater than 180.degree.. 
FIG. 2 shows that the diameter of the circle defined by the substantially 
arcuate portion of the cross-sectional shape of the stave is, in this 
example, less than the thickness between the opposite faces of the stave. 
For example this diameter can be 11/4 inches when the stave thickness is 
15/8 inches. This enables the angle .alpha. between adjacent staves to 
vary within a large range, for example in the case illustrated in FIG. 2 
from about 90.degree. to about 270.degree.. 
FIG. 3 illustrates an end view of an alternative form of stave 7 which is 
identical to the stave 1 except that the diameter of the circle defined by 
the arcuate portions formed at the elongate edges of the stave is equal to 
the thickness of the stave. The stave 7 again has complementary convex and 
concave formations 4 and 5 respectively. However, the increased diameter 
of these formations reduces the range within which the angle .alpha. 
between adjacent staves placed in edge-to-edge relation may be varied. 
FIG. 4 illustrates similar staves 8 having complementary convex and concave 
edge formations 4 and 5 respectively the diameter of which is greater than 
the thickness of the staves 8. The further increased diameter has the 
disadvantage of further reducing the range within which the angle .alpha. 
between adjacent staves placed in edge-to-edge relation may be varied. In 
addition, in this case when the angle .alpha. is not 180.degree. the 
adjacent staves become offset relative to one another, the degree of 
offset being dependent upon the amount by which the angle .alpha. differs 
from 180.degree.. This offset results in undesirable projections 9 being 
formed on the internal angle side of the wall formed by the adjacent 
staves. 
The formations on the elongate edges of the individual staves of FIGS. 1 to 
4 are complementary to one another, but this need not necessarily be the 
case. For example, FIG. 5 shows staves 10 and 11 disposed in edge-to-edge 
relation and alternating with one another to form a wall which is shown as 
being straight but which could equally well be curved. The staves 10 have 
convex formations 4 on both elongate edges, and the staves 11 have concave 
formations, which are complementary to the convex formations 4, on both 
elongate edges. It will be appreciated that the same comments as are made 
above in relation to the staves of FIGS. 1 to 4 apply to the staves 10 and 
11, except that now two types of stave are required to be used alternately 
to form the wall. 
FIG. 6 shows that a wall may be formed by the staves 10 alone, placed in 
edge-to-edge relation so that the convex formations 4 on the elongate 
edges thereof abut one another. In this case only the one type of stave 10 
is required to form a wall, but the disposition and retention of the 
adjacent staves 10 in edge-to-edge relation is made considerably more 
difficult in that now convex formation abut one-another, rather than 
convex formations being received in complementary concave formations as is 
the case for the staves of FIGS. 1 to 5. 
From the above description it will be seen that the staves of FIGS. 1 to 6 
may be combined, in the same or different widths and the same or different 
types, to form a continuous wall of arbitrary shape and size. For the 
reasons already explained above, namely the large range within which the 
angle .alpha. can be varied, the ease of disposing and retaining staves in 
edge-to-edge relation by engaging convex formations with complementary 
concave formations on the stave edges, and the need for only a single type 
of stave, the form of the stave 1 of FIGS. 1 and 2 is preferred. 
Accordingly the remaining description relates only to this type of stave, 
but it should be appreciated that exactly the same applies to the other 
staves shown in FIGS. 3 to 6 as described above. 
Referring again to FIG. 1, each stave 1 is also provided between its ends, 
preferably spaced by only a short distance such as 11/2 from one end, with 
a rabbet 12 in one elongate face 13 of the stave. The rabbet 12 extends 
transversely of the stave from one elongate edge 2 and the associated 
formation 4 to the other edge 3 and its associated formation 5. The rabbet 
12 has a depth which is for example half the thickness of the stave, and a 
width which corresponds to the thickness of a base which is in use of the 
stave received therein. The rabbet width is for example 3/4 inch. FIG. 1 
shows the rabbet 12 as having a constant rectangular section, but it may 
alternatively have a nonrectangular and/or varying section. When a 
plurality of the staves are appropriately disposed in edge-to-edge 
relation to form a continuous wall, the rabbets 12 therein are aligned 
with one another to form a continuous groove on the inside of this wall, 
in which the edges of an appropriately shaped base are received to form 
the walls and a base of a tub. 
FIG. 7 illustrates by way of example a circular tub 14 formed by a 
plurality of staves 1 disposed in edge-to-edge relation to form a circular 
wall 15. For simplicity and clarity the details of the elongate edges of 
the staves are not shown. The circular shape of the tub 14 is defined by a 
circular base 16 which comprises, in this example, a plurality of pieces 
17 of medium density overlaid plywood in edge-to-edge relation which are 
for example joined together by dowels not shown. The base 16 is further 
supported and strengthened by one or more sub-floor cross members 18 to 
which the pieces 17 are joined or on which they rest. The edge of the 
circular base 16 is received within the continuous groove formed by the 
aligned rabbets 12 in the staves 1, the tub floor and wall being made up 
by disposing the individual staves 1 successively adjacent one another in 
edge-to-edge relation and at the same time engaging the edge of the base 
16 in the rabbet 12 in the respective stave. The positive engagement of 
convex and concave formations on the edges of the staves considerbly 
assists in the disposition and retention of the staves in place, as well 
as enabling the wall 15 to conform to the circular path. 
On completion of the wall 15, one or more bands 19, three of which are 
shown in FIG. 7, are disposed around the outside of the wall to retain the 
staves 1 in place. Each band 19 is for example in the form of a strap of 
stainless steel or other suitable corrosion-resistant or protected 
material the ends of which are secured together, and the band tightened, 
by suitable means of known form (not shown). For example one end of each 
strap may engage a captive bolt and the other end may engage a 
correspondingly threaded nut, the bolt being screwed into the nut to 
secure the strap around the wall 14 and tighten the band 19 formed 
thereby. The number of bands 19 which is provided will depend on the size 
of the tube 14 and the nature and size of the bands. For example a tub 6 
feet in diameter might have four bands 19 each of 11/2 inch wide 16 gauge 
stainless steel. 
One or more of the staves 1 is or are also provided with a hole 20 for the 
supply of heated water to the tub 14. One or more staves is or are also 
provided with an outlet, and/or the base 16 is provided with one or more 
drain holes, (not shown) for the removal of water from the tub. In use of 
the tub 14, the tub is filled and water is circulated therethrough via the 
hole(s) 20, which may be provided with appropriate valves, jets, and 
air-induction devices of known form, and the outlet(s) and/or drain 
hole(s). The circulation system can be of known form and conveniently 
includes a filter, chlorinator, heater, and pump. 
As has been explained above, the base or floor 16 of the tub 14 and the 
staves 1 are preferably of wood. Accordingly, when the tub 14 is filled 
with water, the wood swells by absorbing water. The abutting surfaces of 
adjacent staves therefore define a sealing zone to form a water-tight seal 
between the staves. 
As can best be seen in FIG. 8 the base 16 is engaged with the flanks of the 
rabbets 12. By utilizing a laminated material such as plywood in which the 
grain in adjacent layers is at right angles it has been found that 
improved sealing is achieved. The swelling of the base occurs in a 
direction normal to the plane of the base (i.e. the thickness increases) 
rather than in the plane of the base. Thus the base seals against the 
flanks of the rabbet over a large area and is not effected by small 
variations in the disposition of the staves. It will also be appreciated 
that the sealing forces act along the axis of the stave rather than normal 
thereto so that there is no tendency for adjacent staves to part due to 
swelling of the base. 
It is preferred to use a phenolic coated plywood for the base in which case 
it has been found that the sealing function may be improved by removing 
the upper laminate and coating at the periphery of the base to provide a 
shoulder 22. This encourages penetration of water and subsequent swelling. 
Materials other than wood may be used for the staves and/or the tub floor, 
but if such materials are not formed to provide a water-tight seal 
therebetween or do not swell by absorption of water it will be necessary 
to provide some separate means of ensuring an effective water-tight seal 
of the tub. 
The invention is not limited to the particular embodiments thereof 
described above, and many modifications, variations and equivalent 
arrangements thereof which may occur to those skilled in the art are 
within the scope of the invention as defined by the following claims.