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(11) Patent Number: KE 46

(45) Date of grant: 22/04/1998

(12) PATENT
 
(51) Int.CI.7: E 03B 5/00

(21) Application Number: 1996/000195

(22) Filing Date: 10/12/1996
 
(73) Owner: Kentainers Limited of, P.O. Box 42168, Nairobi, Kenya

(72) Inventor: NAKHIL SHAH
 
(54) Title: AN APPARATUS CALLED PIT LATRINE SLAB FOR USE AS A SLAB FOR PIT LATRINES OR TRENCHES AND METHOD OF MANUFACTURE OF THIS PIT LATRINE SLAB

(57) Abstract:
A Pit Latrine slab of any design with a substantially rectangular shape and with a relatively flat shape and of any dimensions, designed to incorporate as integral parts of the slab, or alternatively to make provision for , moulded-in through holes for affixing to the slab a vent pipe of any dimensions and/or moulded-in through holes of any dimensions for affixing tubes to form a frame and/or moulded-in through holes for affixing the Slab to the ground, and also designed to incorporate a central key hole for drainage and two slightly raised food rests adjacent to the central key hole and designed to incorporate a slightly downward slope from the four corners towards the central key hole for drainage and to incorporate also the desired number of kiss-off points of the desired dimensions to provide strength to the slab, the said slab being made of polyethylene and/or foamed polyethylene or other suitable polymer and/or foamed polymer by rotational moulding process or other suitable plastic moulding process.
 
AN APPARATUS CALLED PIT LATRINE SLAB FOR USE AS A SLAB FOR PIT LATRINES OR TRENCHES AND METHOD OF MANUFACTURE OF THIS PIT LATRINE SLAB
This invention relates to an apparatus called Pit Latrine Slab for use as a slab or cover over pit latrines or trenches used as latrines and the method of manufacture of such Pit Latrine Slab.

Population in most urban and rural areas in Africa and other less developed areas of the world use Pit Latrines or trenches. These latrines or trenches are dug by hand. The pits or trenches are then covered by slabs made of various materials. Currently the most commonly used slabs are made of timber or concrete. Timber slabs may rot and fall in and cause an accident. Concrete slabs have several disadvantages. Firstly, a skilled artisan is required to mix and set the concrete. Secondly, concrete slabs are heavy and difficult to load, transport and offload, and, therefore, costly and cumbersome to transport. They may crack when mishandled or during transportation. Thirdly, the concrete slabs absorb water and waste and are, therefore, difficult to clean and less hygienic.

Patents have been obtained in the United States of America and elsewhere for different types of latrines including portable latrines, chemicals latrines and composting latrines.

These latrines are better suited to the needs of the Armed Forces, country cottages, picnic sites, camping sites and other outdoor uses in affluent societies. The disadvantage of these types of latrines is that they are costly and need space while being stored or transported and their transportation is cumbersome and expensive. These latrines are not, therefore, suitable or appropriate products for use when relatively large numbers of Pit Latrines or trenches are required to be erected in remote areas which have been affected by civil strife, wars, floods, or famine and corresponding large numbers of Pit Latrine Slabs to cover such latrines or trenches are also required to be transported to such remote areas. All such events cause displacement of large numbers of human beings in a very short time span and require their temporary, but speedy, resettlement in large numbers in make shift camps set up with haste. These camps require speedy erection of Pit Latrines and expeditious supply of large quantity of Pit Latrine Slabs to cover such latrines. Often the locations of such camps are extremely remote and roads may not exist or may be impossible due to poor terrain or due to the danger of armed conflict along such roads. In such cases, air transport would be the only mode of transport. This necessitates that the pit latrine slab to be used in such situations is light in weight and yet relatively rigid and strong while maintaining a degree of flexibility and shock resistance so that it will not break or collapse under the weight of the user of the Pit Latrine, that it is durable and long lasting and it is easy to stack, occupies minimal space during its transportation and when stored and will not break or collapse during its loading, transportation and off-loading and that it is easy for unskilled persons to install when it arrives at the site and it is capable of being removed either when the pit is filled or when the camp is moved to another site and then re-stalled on a new Pit Latrine in the new site. In addition, such a Pit Latrine Slab must be easy to clean and hygienic especially when vast numbers of people are put so closely together and the sanitary conditions are generally poor in these camps and the danger of spread of diseases is ever present. Besides all these attributes, it must be inexpensive, affordable and economical.

Similarly, to-day in many large and small towns in Africa and other less developed areas of the world, large shanty towns have mushroomed. The inhabitants of these shanty towns also require Pit Latrine Slabs with all these features for their Pit Latrines. Their numbers throughout the world are growing rapidly and their requirements of the Pit Latrines and the Pit Latrine Slabs are also growing correspondingly as are concerns for the constant threat of spread of diseases due to poor state of sanitation in these slum areas.

The present invention relates to a Pit Latrine Slab indicated as (A) in Figure 1 containing an integrally moulded-in central key hole of desired dimensions indicated as (B). It is made by rotational moulding process which is a very versatile process and which allows for the use of several different polymer raw materials including, but not limited to, polyethylene, nylon and polycarbonate. In rotational moulding process, a metal mould containing suitable polymer raw material is rotated on one or more axes in a heated environment. The raw material adheres to the inner surface of the mould, forming its shape through heating and subsequent cooling.

The rotational moulding process is a low pressure process which imparts high impact strength and low stress properties to products made by that process and thus the Slabs made by this process using polyethylene, or other suitable polymer raw material, retain a high degree of flexibility and shock resistance making them suitable for long distance transport with no damage. Because of their relatively flat shapes, they can be stacked on each other for storage and transportation.

The polyethylene or other suitable polymer used to manufacture our pit latrine slabs is stabilised against ultra violet rays of the sun and, therefore, our Slabs are suitable for outdoor use. These polymers and the Pit Latrine Slabs remain stable even in extreme weather conditions, temperatures ranging front -40 to +60 degree Celsius.

In our present invention, polyethylene is used in the manufacture of our slab but it can be also made from a number of other suitable polymers. It has an outer skin of normal polyethylene indicated as (F) in Figure 2 and the inner core of foamed polyethylene indicated as (G) in Figure 2. Foamed polyethylene incorporates an active agent which, once all the polyethylene has melted, decomposes and releases inert gases. These gases create small bubbles in the inner polyethylene layer thereby increasing its thickness. This is the foaming process. The foamed polyethylene gives added rigidity and strength to this product making it more suitable for use as a Pit Latrine Slab. The design of our slab incorporates a number of kiss-offs of different dimensions, their numbers and dimensions being dependant on the dimensions of the Pit Latrine Slab itself. A cross section, indicated as (H-1) and (H-2) in Figure 2, show one of the kiss-offs incorporated in the design of the product.
 
Our Slab also incorporates, as an integral part of its design, a moulded-in hole of desired dimension indicated as (C) in Figure 1 for affixing to it a standard vent tube made of ordinary plastic and readily available in the market. The vent tube is used for emission through it of gases and other smells from the Pit Latrine or trench for release into the atmosphere above the roof of the Pit Latrine. Our Slab also incorporates, as an integral part of its design, two moulded-in foot rests indicated as (E) on Figure 1 symmetrically arranged adjacent to the central key hole and for considerations of hygiene and such foot rests are raised slightly to be a little higher than the central key hole. The Slab can also be manufactured with a number of moulded-in holes indicated as (D) in Figure 1 for affixing thereto plastic vertical tubes near the four corners of the slab for the purpose of forming a frame for making an enclosed Pit Latrine to provide privacy. Such enclosure can be made with hesian cloth or sisal cloth or woven matting or polythene sheeting or canvas all of which are standard items and readily available.

An optional key hole cover, indicated as (J) in Figure 3, made of polymer by similar rotational moulding process or other suitable plastic process, is also made by us and provided for covering the central key hole (B) to prevent flies and insects from coming up from the pit. However, such key hole cover (J) can also be made of other material such as metal.

Our invention of Pit Latrine Slab has following important characteristic and properties which distinguishes it from the prior art in that:-
 

              1. Our Slab is light in weight, yet relatively rigid, very strong, retains a high degree of flexibility and shock resistance and will not break or collapse during storage or transportation or under the weight of its user.

2. It is durable, stabilised against the ultra violet rays of the sun and long lasting even in the most extreme weather conditions. It is suitable for outdoor use.

3. It is easy to clean and hygienic and it does not absorb water or waste.

4. It is relatively flat, thin and easy to load, stack, transport and off-load and will not break during loading, transportation and off-loading. Because it is light in weight and capable of being stacked and occupies very little space, it is easy and inexpensive to transport, even by aeroplane, to remote areas.

5. It is very simple and easy to install, remove and re-install. An unskilled worker can carry out such installation, removal and re-installation.

6. It requires no maintenance. It does not rust nor rot nor chip off, making it very safe for use.

7. It is relatively inexpensive and economic bearing in mind that it can be removed and re-installed time and again.

8. Our slab is designed with following features, benefits or characteristics:-
(a) molded -in central key hole for drainage
(b) two raised foot rests
( c) moulded-in through hole for vent tube for emission of gases and smells from the Pit
 (d) slight downward slope from its four corners to allow for drainage of urine, water and other substances into the pit through the central key hole
(e) optional moulded-in additional through hole, or pre-marked locations for making such through holes, for affixing tubes to form a frame for attaching to them standard hesian cloth, sisal cloth, woven matting, polythene sheeting canvas or any other material which is readily available.
f) Optional moulded-in additional through holes, or pre-marked locations for making through holes, for affixing metal rods or pegs or wooden pegs or other suitable holding devices to affix the slab to the ground, or to the walling, of the pit latrine or the trench.
g) a number of moulded-in and integral kiss-off points from the underneath part of the slab reaching to its top surface to provide it with the strength and rigidity.
h) the ability, with the frame mentioned in subparagraph (e) of this paragraph, to create an inexpensive enclosure to provide privacy to the user of the pit latrine.

In many areas where our Pit Latrine Slab is to be used, flushing water toilets are not practical because water is a scarce commodity and may not be available for use in toilets. In any case Chemical toilets are also not practical in these areas because chemicals needed for the operation of these toilets may not be available or readily available and in any case both these chemical toilets and the chemicals are expensive and unaffordable by the needy persons. Similarly, composting toilets are also unsuitable because of their very high cost and they require, in many cases, an active agent to be used for composting. In any case, chemicals toilets, composting a toilets and portable toilets occupy too much space for transportation and would require inordinate number of lorry trips or aeroplanes trips to bring in the required quantity to the sites of such emergency relief situations or slum development and would cost a disproportionately vast sum only for their transportation apart from the impracticality and difficulty of transporting such vast numbers of them to such sites. Many of them would have to be brought from the developed industrial world, thousands of miles away, whereas our present invention makes it possible to transport them with ease and minimal time and cost. Its various distinguishing benefits including its compactness, stackability, light weight in addition to its other benefits such as rigidity and yet retaining a substantial degree of flexibility and shock resistance, strength, maintenance-free nature, long life and easy installability, removal and re-installability, all constitute a vast improvement, over all the alternatives, for use in various places mentioned above including locations where emergency relief situations arise and slums in urban and rural areas, generally for use by rural institutions such as schools, clinics, hospitals, armed forces, police, farms and other rural enterprises, camping safaris and other similar situations where it is impossible or impracticable or vastly uneconomic to use portable or chemical or composting toilets, water flushing toilets or any other forms of Pit Latrine Slabs.

The present invention, the Pit Latrine Slab, is characterized in that:-
1. Our Slab, of a substantially rectangular shape, comparatively thin and light in weight and yet relatively rigid and strong, retaining a substantial degree of flexibility and shock resistance, made from polyethylene or other suitable polymer raw material by rotational moulding process or other suitable plastic process and containing a central key hole of the desired dimensions for drainage and a set of two foot rests symmetrically arranged adjacent to the central key hole constitutes an improved slab to cover the hole of a pit latrine or a trench, both dug in the ground, mostly although not necessarily always, by hand.

2. Our Slab is designed so that the height of its side walls is minimal; the thickness of all its walls is also minimal to minimize its weight and thereby making it possible to stack them for transportation and to transport vast numbers of them by any available means of transport including transportation by air.

3. Although the surface of the Slab is substantially plain, it incorporates a slight downward slope from its four corners towards the central key hole to allow for drainage of urine, water and any other substances.

4. Our Slab also incorporated, as an integral part of its design, a number of kiss-off points of different dimensions starting from bottom surface of the slab and joining up with the top surface of the slab and an example of such liss-offs is shown indicated as (H-1) and IS    (H-2).

5. A cover for the central key hole which can also be made from the polyethylene or other suitable polymer by rotational moulding process or other suitable plastic moulding process is also provided along with the Slab as an option. Presence of flies and other insects and smells will be reduced and improved hygiene will be achieved by keeping the central key hole closed with such cover after the use of the Pit Latrine.

6. The Slab is also be manufactured with a moulded-in through hole (as an integral part of its design), in a pre-determined position, for placement of a vent tube in it leading from the pit upwards through the roof of the latrine for the emission of gases and smells. Any standard plastic pipe of the required dimension can be used as a vent pipe. Such pipes are readily available in the market. Alternatively, the slab is manufactured without such moulded-in through hole but a through hole can be cut into the slab for this purpose and its location can be pre-determined and marked out on the slab.

7. The Slab can also be manufactured with four (or, more if so desired,) through holes of desired dimensions at pm-determined locations for fixing additional tubes near the four corners to create a frame and for attaching to them inexpensive and readily available material such as hesian cloth, sisal cloth, any woven matting, polythene sheeting or canvas to make an enclosure for the pit latrine and provide privacy to its user. Similarly, a roof can also be provided by use of similar material thrown over and supported by a few standard wires or ropes in a cross-wise linking of these tubes. Standard plastic pipes readily available can be used as such tubes. If a vent pipe is installed in the latrine, an opening would be made in such roofing material at the top to allow the vent pipe to go through it to allow the gases from pit to escape into the air. The top exit point of the vent pipe is covered by a wire gauge to prevent entry into it by birds and insects.

8. The Slab can also be manufactured with four (or, if desired, more) locations or provisions for making through holes of desired dimensions in the slab or alternatively  with four (or, if desired, more) moulded-in through holes, in both cases, at or near the four corners for affixing the Slab to the ground or to the pit latrine walling using any readily available material such as a metal rods or pegs or wooden pegs.

9. The installation of our Pit Latrine Slab and, if desired, the vent tube and the enclosure made by such hesian cloth, sisal cloth, woven matting or polythene sheeting or canvas, all being standard, inexpensive items and readily available, is very simple and can all be carried out expeditiously by unskilled workers and with minimal expense. Large numbers of such slabs can be installed over pits or trenches and even complete latrines with such enclosures can be erected in a very short span of time which is a distinct advantage in emergency relief situations or when undertaking large slum development projects.

10. Our Slabs, and the tubes, pipes, pegs, wires, ropes and the enclosure materials can be stacked and transported with ease and minimal costs compared to the high costs and logistical problems of transporting complete toilets or slabs of any other kind and the costs of our toilet slab and the cost of such tubes and enclosing material is a fraction of such other types of water flushing toilets, portable, composting or chemical toilets.

11. A number of our Pit Latrine Slabs can also be installed side by side over a series of pits or alternatively over a long trench dug to serve as a Pit Latrine and thereby the needs of a large population in such emergency situations can be accommodated. By using the same idea, and several pits or trenches, in a numbers of rows, a very large number of Pit Latrines can be erected in a matter of days to meet such emergencies. It is the object dare present invention to provide a Pit Latrine Slab which is light in weight yet relatively rigid and strong and retaining a high degree of flexibility and shock resistance, and which is easy to clean and hygienic, easy to install, remove and re-install, safe to use, long lasting, maintenance-free, non-rusting, non-rotting, non-chipping, which wit/ not break or collapse during even long distance transportation or use and with capability to transport, by any means of transport, including air transport, large numbers of such slabs to meet the needs of large communities and, even more importantly, the needs of emergency relief situations, armed forces and the like in remote areas and large and small projects for improvement of  sanitation in poor urban and rural locations everywhere, such Pit Latrine slab being made by rotational moulding process using polyethylene or other suitable polymer as raw material and which is a better and more efficient and economic alternate to all other alternate forms of Pit Latrine Slabs for Pit Latrine Toilets, or of flushing toilets, chemical toilets and composting toilets.
 
CLAIMS

1. A Pit Latrine Slab Device, for use as a slab to be placed over a pit latrine hole or a trench dug in the ground and suitable for use in emergency relief situations, in slums in urban and also rural areas, characterized in comprising of a substantially rectangular shape and of any dimensions, comparatively thin and light in weight, yet relatively rigid  and strong while retaining a high degree of flexibility and shock resistance, made by rotational moulding process using two layers of polyethylene, the outer layer being made of normal (non-foamed) polyethylene and the inner core or layer being made of foamed polyethylene with an integrally formed, moulded-in, central key hole for drainage and slightly raised foot rests symmetrically arranged adjacent to the central
key hole.

2. A Pit Latrine Slab Device according to Claim 1, characterized in that the Device is manufactured with a series of Kiss-off points of different dimensions starting from the underneath surface of the Device and joining up the top surface of the Device at predetermined locations to provide rigidity and strength to the Device.

3. A Pit Latrine Slab Device according to Claims 1 and 2 characterized in that its top surface slopes inwardly from its four corners towards the central key hole for drainage.

4. A Pit Latrine Slab Device according to Claims 1 and/or 2 and/or 3 characterized in that it comprises a moulded-in hole for affixing to it a vent tube of standard plastic material for emission of gases from the Pit Latrine through the roof of the latrine to the atmosphere 
 
5. A Pit Latrine Slab Device according to all or any of the Claims 1, 2, 3 and 4
characterized in comprising a key hole lid for covering the central key hole when not in use

6. A Pit Latrine Slab Device according to Claims 1, 2, 3, 4 and/or 5 characterized in that it has a desired number of moulded-in holes near the four corners at pre-determined locations to affix the slab to the ground or to affix vertical tubes or pipes to form a supporting frame for attaching standard hesian cloth, sisal cloth, woven matting or polythene sheeting or canvas to form an enclosed latrine.

7. A Pit Latrine Slab Device according to Claims 1, 2, 3, 4, 5 and/or 6 characterized in that the device is made by rotational moulding process using any other suitable polymer or polymers for the outer layer and the inner layer or core of the device.

8. A Pit Latrine Slab device according to Claims 1, 2, 3, 4, 5, 6 and/or 7, characterized in that the Device is made by any other suitable plastic moulding process.

9. A method of manufacturing a Pit Latrine Slab of any design or dimensions according to each and/or any of the Claims 1 to 8 by rotational moulding process and using two layers of polyethylene, the outer layer of normal (non-foamed) polyethylene and the inner layer or core of foamed polyethylene.

10. A method of manufacturing a Pit Latrine Slab of any design or dimensions according to each and/or any of the Claims 1 to 8 by rotational moulding process and using two layers of any other polymer, the outer layer being made of non-foamed polymer and the inner layer or core of a foamed polymer.

11. A design in accordance with each of the Claims 1 to 8 above and any designs or
designs derived there from to allow for a Pit Latrine Slab of any dimension and shape suitable for use in rotational moulding process.
 
ABSTRACT

A Pit Latrine slab of any design with a substantially rectangular shape and with a relatively flat shape and of any dimensions, designed to incorporate as integral parts of the slab, or alternatively to make provision for, moulded-in through holes for affixing to the slab a vent pipe of any dimensions and/or moulded-in through holes of any dimensions for affixing tubes to form a frame and/or moulded-in through holes for affixing the Slab to the ground, and also designed to incorporate a central key hole for drainage and two slightly raised food rests adjacent to the central key hole and a designed to incorporate a slightly downward slope from the four corners towards the central key hole for drainage and to incorporate also the desired number of kiss-off points of the desired dimensions to provide strength to the slab, the said slab being made of polyethylene and/or foamed polyethylene or other suitable polymer and/or foamed polymer by roational moulding process or other suitable plastic moulding process.

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