FIELD OF THE INVENTION

The present invention relates to the field of sewage barriers, and more particularly to the field of non-return sewage barriers that prevent entrance of rodents, reptiles or frogs into a local sewage system and also serve as nonreturn valves to prevent back- flow of sewage into the local sewage system.

BACKGROUND OF THE INVENTION

Sewage barriers that are installed in a sewage system are known. These barriers vary in their function and construction.

EP 2 1 13 61 5 A l to Sorensen discloses a barrier for preventing rats or other vermin from entering a sewage pipe. The barrier comprises a support element (33) that is mountable within the pipe, and a first shutter (30) pivotally suspended within the support element (33) for rotation about a horizontal axis (32) and having a centre of gravity lying under the axis (32). The shutter (30) is pivotal between a first angular position (v) in which the first shutter is forming an acute angle with the direction of flow and at least substantially barring the aperture of the barrier. Preferably, a second shutter (3 1 ) is placed upstream of a first shutter (30) and is pivotally suspended about a second axis. The first shutter (30) can be suspended within the support element (33 ) in two different orientations.

A disadvantage of such a barrier is that its holding surfaces are located within the sewage pipe, depend on its internal surface condition, and may obstruct, at some cases, the downstream flow of the sewage. Also, manual force has to be applied in order to locate the contact surfaces of the barrier. WO 2007/079658 A l discloses a valve that can be mounted on a drainage pipe. The valve is provided with an automatic weight distribution system. The counterweight of the automatic weight distribution system can move according to the swing of the seal baffle to affect the opening and the closing between the seal baffle and the resistance portion.

The valve has the function of delaying the close of the valve, whereas the drainage of low discharge liquid can be carry out easily. A disadvantage of such a delay is the fact that rodents may enter the pipe during the period of the low discharge liquid while the valve is open.

US 1 ,018,569 to Kelty and Joralemon discloses a sewer trap that is provided with a mechanism enabling to install the sewer trap either vertically or horizontally. However, in order to locate the piv ot pin 12 for holding the finger 14, the arm 15 and the weight 16, and also the lugs 10 for holding the valve 9, a cup 1 8 has to be secured at the open side of the enlargement of the pipe. This structure encounters a relative large axial dimension of the sewer trap, and this may be a disadvantage when it is necessary to install the trap in relatively tight places.

US 3,955,596 to Diaz discloses a sewer pipe valve section comprising a removable one-way check valve and a separate removable screen provided to be interposed between the building sewer drain system and that of the city.

However, a disadvantage of the system of '596 is that pipe section (a) will function as part of the sewer pipe of the system into which it is installed. The size of the ends of pipe section (a) will be adapted to the size of existing sewer pipe specifications. This means that a part of the existing sewer pipe has to be cut away in order to install the present system, a task that is costly and time consuming. US 4,503,881 to Vecchio discloses an automatic valve for a sewer including a body having an upstream inlet and a downstream exit for liquid. A path joins the inlet and exit, and a closure gate is hingedly mounted to the body at a substantially horizontal axis located above the path, so that the gate can swing between a first position in which it blocks the path and a second position in which it unblocks the path. An arm is fixed with respect to the closure gate to swing with it in such a way that the arm is higher when the gate blocks the path then it is when the gate unblocks the path. The arm counterbalances the closure gate so that so that the latter normally seeks the second position. A cage surrounds the arm and communicates with the path. A float member in the cage under the arm means is free of connection to the arm means or any other part of the apparatus, whereby a rise in liquid level causes the float member to urge upwardly against the arm and close the closure gate.

Also this valve encounters a disadvantage since a part of the existing sewer pipe has to be cut away in order to install the present system.

Japanese publication number JP200 1 -348846 to Toshikazu discloses a gutter pipe valve that comprises a valve box 14 arranged in connection with a drain pipe 1 1 , a flap valve element 16 to be oscillated around a horizontal supporting axis for opening/closing a drain port of the valve box 14, a weight arm 19 to be oscillated integrally with the flap valve element 16, and a counter buoyancy weight 21 connected to one end of the weight arm 19 via a link 20. Water level setting means 25 is detachably provided in the link 20, where a joint pin 24 of the weight arm 19 is inserted in a slit 23 formed in the link 20 along the axial center and received by the slit 23 in position.

This device enables to quickly close the opening when a water level at the side of a drain end is increased. However, since the system is connected with a buoyancy weight under a lower portion thereof, it cannot be connected to a common sewer outlet where, typically, the outlet of the drain pipe is formed in the lowermost portion of the system. Japanese publication number JP2001 -349455 to Katsu discloses a flap valve which is normally slightly open by a small flow or opening moment by a weight, and quickly closable when the water level in a drain pit increases. As in the previous case of '846. since the system is connected with a buoyancy weight under a lower portion thereof, it cannot be connected to a common sewer outlet where, typically, the outlet of the drain pipe is formed in the lowermost portion of the system. Another disadvantage of the system of '455 is its mechanical complexity, a fact that leads to higher cost of the system, higher probability of a failure, and an infrastructure to be installed into. Furthermore, this system may be difficult for taken out for inspection or repairs.

Japanese publication number JP2002- 122255 to Toshikazu discloses a counterweight mechanism of a check valve that is capable of easily opening a valve element for fluid to be controlled in the forward direction and easily closing the valve element when a small amount of fluid flows in the reverse direction. The valve is seated within a valve casing 1 , a rail 7 with a down gradient is provided on one side of an arm 4 oscillating around a shaft core. A counterweight 9 is provided on the rail 7. and an air cylinder 13 receiving the counterweight 9.

This mechanism suffers from disadvantages similar to the ones described above, namely, a part of the sewer system has to be cut away in order to install the system, the installation requires extra infrastructure, it has relatively high mechanical complexity leading to high cost, and it is difficult taking the system out of a sewer for inspection and repairs.

Japanese publication number JP2006-283547 to Naoshi discloses a device for preventing backwardly flowed waste water from jetting out of a drain facility. The device comprises a substantially cylindrical backflow preventive device body 1 5 having an outer diameter substantially equal to an inner diameter of an inflow side connecting port 2 of a public basin body 1. The backflow preventive device body 15 is provided with a valve element 16 opening toward the inside of the public basin body 1 by the water flowing in from an inflow side connecting pipe 12. and an installation part 26 of an installation device for inserting and connecting the backflo preventive device body 15 into and to the inflow side connecting port 2 from the inside of the public basin body 1. A support bar 20 is connected to a support object part 21 formed in the backflow preventive device body 1 5. and the support bar 20 is provided with a bending part 23 for forming a support bar holding part 22 having the length substantially equal to an inner diameter of a cleaning port of the public basin body 1 from an upper end part.

A main disadvantage of the present device is that the outer diameter of the device is equal to the inner diameter of the inflow side connecting port 2. This means that the device is obstructing the flow within the pipe, a fact that may lead to accumulation of waste solids between the device and the incoming pipe and further negatively affecting the flo of wastes.

Further drawbacks of the device are the need to have an installation part

26 for inserting and connecting the backflow preventive device. Also, the support bar 20 provided with the bending part 23 further add additional components that complicate the system. DE 196 53 103 A 1 discloses a device 1 0 having a counterweight 36 for closing a damper 30. This device has a disadvantage that the mechanism for operating the damper is contained within the diameter of the device and therefore reduces the pipe's effective inner diameter for the passage of waste fluids and solids. Furthermore, the device may be limited to being installed horizontally since the stopper 38 will be obstructing the flow within the pipe, a fact that may lead to accumulation of waste solids and further negatively affect the flow in the pipe.

DE 200 17 636 U l discloses a damper 2 closed by a counterweight 3. Since the counterweight 3 is located beyond the diametrical dimensions of the damper, whether it is located inside a holding case or outwardly therefrom, this system cannot be installed within closed-space sewer system where the drainage pipe entering a drainage pit is closely confined by side walls of a discharge channel. It is the object of the present invention to provide a sewage barrier that significantly reduces or overcomes the aforementioned disadvantages.

It is a further object of the present invention to provide a sewage barrier that may prevent entrance of rodents, reptiles, frogs or insects into a local sewage system and also may serve as a non-return valve to prevent back-flow of sewage into the local sewage system.

It is still a further object of the present invention to provide a sewage barrier that has a simple construction, is relatively cheap, is very easy to install and very easy to maintain.

It is still yet a further object of the present invention to provide a compact sewage barrier that has diametrical dimensions similar to the diametrical dimensions of the drainage pipe of the sewage system.

It is another object of the present invention to provide a sewage barrier having extremely small axial dimensions thus being enabled to be installed in hard-to-reach and clustered group of drainage pipes.

SUMMARY OF THE INVENTION

In accordance with the present invention there is provided a sewage barrier having a longitudinal axis and comprising:

a body substantially symmetrical about the longitudinal axis and having an internal first diameter and a first length;

a shutter swingable between a closed position and an open position; wherein:

the first length is smaller than the first diameter.

In some embodiments, in a closed position of the shutter, the shutter is perpendicular to the longitudinal axis. Typically, a length to diameter ratio is defined as the ratio between the first length and the first diameter: and

the length to diameter ratio is in the range from 0.3 to 0.9.

Further typically, the length to diameter ratio is in the range from 0.5 to 0.6.

Generally, the shutter is connected to a counterweight through a connecting rod; and

the shutter is swingable about a swinging axis that is perpendicular to the longitudinal axis.

In some embodiments, the connecting rod has a first thickness dimension, as seen in a side view of the sewage barrier, and a second width dimension, as seen in a front view of the sewage barrier; and

the first thickness dimension is much smaller than the second width dimension.

Advantageously, the counterweight, the connecting rod and the shutter have a common center of gravity,

in the closed position of the shutter, the center of gravity is distanced from the longitudinal axis a second distance,

the swinging axis is distanced from the longitudinal axis a third distance; and

the second distance is equal to the third distance.

Typically, an inner end of the shutter defines a closing plane that is parallel to the swinging axis,

the center of gravity is distanced a fourth distance from the closing plane, the swinging axis is distanced a fifth distance from the closing plane; and the fourth distance is smaller than the fifth distance.

Further typically, the center of gravity is distanced a sixth distance from the swinging axis; and

the sixth distance is in the range from 0. 1 mm to 10 mm.

In some embodiments, the sixth distance is 1 mm. Typically, a holding structure is attached to an upper portion of the body,

the holding structure has a second width dimension as seen in a front view of the sewage barrier: and

the second w idth dimension is much smaller than the internal first diameter as seen in a front vie of the sewage barrier.

Further typically, the holding structure has a structure height; and the structure height is smaller than the internal first diameter.

Practically, the counterweight is provided with a sliding bore; and the sliding bore is rotatable around a sliding pin that is fixedly connected to the holding structure and directed in the direction of the swinging axis.

Advantageously, the body is provided w ith a body widening in a front portion thereof; and

in a closed position of the shutter, the shutter is located in its entirety within the body widening.

Further advantageously, the shutter is swingable from the closed position to an open position by a small amount of fluid flowing through the sewage barrier;

the shutter remains in the closed position through a range of inclination angles of the longitudinal axis with respect to level ground; and

the inclination angle is in the range from 0° to 10°.

Practically, the body and the shutter are made of stainless steel.

In some embodiments, the shutter is connected, through a connecting rod, to a resilient component having at least one portion thereof connected to a holding structure that is attached to an upper portion of the body.

Practically, the resilient component comprises a spring.

If desired, the spring comprises either a tension spring or a compression spring. BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding oi ^' the present invention and to show how the same may be carried out in practice, reference w ill now be made to the accompanying dra ings, in which :

Fig. 1 is a perspective view of a sew age barrier according to the present invention shown in a closed position of the shutter:

Fig. 2 is a perspective view of the sewage barrier of Fig. 1 with the shutter shown in an open position;

Fig. 3 is an enlarged side view of an upper portion of the sewage barrier of Fig. 1 ;

Fig. 4 is a cross-section of the sewage barrier of Fig. 3 taken along line IV-IV in Fig. 5;

Fig. 5 is a front view of the sewage barrier of Fig. 1 ;

Fig. 6 is an enlarged cross-section of the shutter opening and closing mechanism taken along line VI- VI in Fig. 5 :

Fig. 7 is an enlarged cross-sectional view of the body and the shutter in a closed position taken along line VII- VII in Fig. 5;

Fig. 8 is a side sectional view of the sewage barrier of Fig. 1 during its installation on an entrance pipe in a sewage pit;

Fig. 9 is a side sectional view of the sewage barrier of Fig. 8, shown in an installed position; and

Fig. 10 is a perspective view of an example of using of several sewage barriers in a household sewage pit. DESCRIPTION OF PREFERRED EMBODIMENTS

Attention is drawn to Figs. 1 to 10 that show a sewage barrier 10 or trap according to the present invention. As shown, the sewage barrier 10 comprises a body 12 in the form of a hollow cylinder having a longitudinal axis A. The body 12 has a very thin wall thickness WT. For example, according to some embodiments, the body 12 has an internal first diameter Dl of 1 1 1 mm and an external second diameter D2 of 1 12 mm. The body 12 has a first length LI as seen in a side view of the sewage barrier 10. The first length LI is relatively small, thus featuring advantages as will be later described. As clearly seen in a side view of the sewage barrier 10, the first length LI is much smaller than the internal first diameter Dl . A length to diameter ratio E is defined as the ratio between the first length LI and the first diameter Dl . Typically, the length to diameter ratio E is in the range from 0.3 to 0.9. Furthermore, according to specific embodiments of the present invention, the length to diameter ratio E is in the range from 0.5 to 0.6.

The body 12 is provided with a body widening 14 in a front portion thereof. The body widening 14 has a frusto-conical shape diverging forwardly and having a widening length WL measured parallel to the longitudinal axis A. A front portion of the body widening 14 has an internal third diameter D3, and is slanted at an acute body slant angle a with respect to the longitudinal axis A.

It should be noted that directional terms appearing throughout the specification and claims, e.g. "forward", "rear", "upper", "lower" etc., are used as terms of convenience to distinguish the location of various surfaces relative to each other. These terms are defined with reference to the figures, however, they are used for illustrative purposes only, and are not intended to limit the scope of the appended claims.

A holding structure 16 is attached to an upper portion of the body 12. If desired, the holding structure 16 may be releasably attached to the body 12. However, it is advantageous that the holding structure be fixedly attached to the body 12, for example, by point welding, and form therewith a unitary one-piece construction for reasons that will be later described. As seen in a side view of the sewage barrier 10. the holding structure has a structure length SL that is similar to the first length LI of the body 12. The holding structure has a first width dimension Wl as seen in a front view of the sewage barrier 10. The first width dimension Wl is much smaller than the internal first diameter Dl as seen in a front view of the sewage barrier 10. According to some embodiments, the holding structure 16 has a shape of a box having two opposite side walls 18 extending between a front wall 20 and a rear wall 22, and covered by an upper w all 24. The holding structure 16 has a structure height SH. Typically, the structure height SH is smaller than the internal first diameter Dl . The holding structure 16 may be enclosed from all sides except for an assembly aperture 26 in a lower portion of the front wall 20.

A pin bore 28 is provided in the holding structure 16 adjacent the assembly aperture 26. The pin bore 28 is preferably a through bore passing through the side walls 18 of the holding structure 16.

A counterweight 30 is located within the holding structure 16. The counterweight 30 has a shape of a box and having a front face 32, a rear face 34 opposite the front face 32, an upper face 36, a lower face 38 opposite the upper face 36, and two side faces 40 extending between the front, rear, upper and lower faces. It should be noted that the designation of the various surfaces of the counterweight 30 are taken when the counterweight is in an upright position as shown in Figs. 1. 3. 4 and 5.

The counterweight 30 has a sliding bore 42 which is a through bore that extends between the side faces 40 and is located close to the lower face 38 and between the front face 32 to the rear face 34. In order to assemble the counterweight 30 into the holding structure 16. the counterweight 30 is first inserted through the assembly aperture 26, with the counterweight 30 in the position shown in Fig. 6 and the upper face 36 is first inserted into the assembly aperture 26. Then, the sliding bore 42 is aligned with the pin bore 28. At the next step, a sliding pin 44. having a longitudinal axis, is inserted through one side wall 18, through the sliding bore 42. and eventually through the other side wall 18. The sliding pin 44 is then attached to the side walls 18 by methods known in the art.

The diameter of the sliding bore 42 (not specifically shown in the figures) is similar to the diameter of the sliding pin 44 and slightly larger therefrom. Thus, since the sliding pin 44 is fixedly attached to the holding - - structure 16 through the pin bores 28. the counterweight 30 can freely rotate around the sliding pin 44.

In some embodiments, it may be desired to separate between the sliding pin 44 and the sliding bore 42 in order to prevent any chemical reaction therebetween that may occur when two di ferent materials come in contact with each other. Hence, in such a case, a plastic sleeve (not shown in the figures) may be inserted betw een the sliding pin 44 and the sliding bore 42, and, accordingly, the diameter of the sliding bore is adapted to an external diameter of the sleeve, and the diameter of the sliding pin is adapted to an internal diameter of the sleeve.

The counterweight 30 may be made from any appropriate material. However, it is advantageous that the counterweight 30 be made from a non- rusting metal. According to some embodiments, the counterweight 30 is made of brass.

A connecting rod 46, having a rod upper end 48 and a rod lower end 50, is attached to the counterweight 30 at the rod upper end 48. The connecting rod 46 has a first thickness dimension Tl . as seen in a side view of the sewage barrier 10, and a second w idth dimension W2, as seen in a front view of the sewage barrier 10. According to some embodiments, the connecting rod 46 is relatively flat such that the first thickness dimension Tl is much smaller than the second width dimension W2.

The connecting rod 46 is provided with a rod step 52 in a general central portion thereof. The rod step 52 enables an upper portion 54 of the connecting rod 46 to be positioned within the holding structure 16, whilst a lower portion

56 of the connecting rod 46 is positioned out of the holding structure 16 and in front of the body 12.

The rod low er end 50 is connected to a shutter 58, preferably at a shutter center 60. The shutter 58 is typically made of a plate having a relatively thin shutter thickness ST. A forw ard end of the shutter 58 is provided with a shutter widening SW that diverges forwardly at an acute shutter slant angle β. The - - shutter slant angle β is similar to the body slant angle a and may be slightly larger therefrom. An external forwardmost portion of the shutter widening SW has an external fourth diameter D4 that is smaller than the internal third diameter D3 of the body widening 14.

When the shutter 58 is in a closed position, it rests within the body widening 14 and is perpendicular to the longitudinal axis A. Since the shutter slant angle β is similar to the body slant angle a or slightly larger therefrom, the shutter widening SW external surface mates with the body widening 14 and effectively sealing any gap therebetween. Furthermore, since the shutter external fourth diameter D4 is smaller than the internal third diameter D3, it guarantees that the shutter 58 in its entirety rests within the body widening 14. Hence, in a closed position of the shutter 58. it has no parts that protrude beyond the body widening 14 and therefore cannot be grabbed by a rodent or the like in order to forcibly open it while it is in a closed position. Thus, the closing of the shutter 58 is being done in a simple and effective manner.

Furthermore, such a construction limits, by a lower portion of the front wall 20 of the holding structure 16. the lifting of the lower portion 56 of the connecting rod 46, thus guaranteeing that the shutter 58 will always return to a closed position.

The shutter 58. being connected to the counterweight 30 through the connecting rod 46, is swingable between an opened position to a closed position around a swinging axis B that is perpendicular to the longitudinal axis A. The swinging axis B is also the longitudinal axis of the sliding pin 44.

The counterweight 30. the connecting rod 46 and the shutter 58 have a common center of gravity CG. In a closed position of the shutter 58, the center of gravity CG is distanced from the longitudinal axis A a second distance L2. Similarly, the swinging axis B is distanced from the longitudinal axis A a third distance L3, and the second distance L2 is equal to the third distance L3.

In a closed position of the shutter 58, an inner end 62 of the shutter 58 defines a closing plane PI that is parallel to the swinging axis B. In this position, the center of gravity CG is distanced a fourth distance L4 from the closing plane PI . The swinging axis B is distanced a fifth distance L5 from the closing plane PI . and the fourth distance L4 is smaller than the fifth distance L5.

The center of gravity CG is distanced a sixth distance L6 from the swinging axis B which is typically in the range from 0.1 mm to 10 mm. In the described embodiment of the present invention, the sixth distance L6 is 1 mm. Thus, by having the center of gravity CG in the same level of the swinging axis B and very close to it. two objectives are met. First, this guarantees that a constant moment is acting on the shutter 58 in a closing direction 64 (in a clockwise direction as seen in the drawings). Second, this guarantees that even a slight moment in an opening direction 66 (in an anticlockwise direction as seen in the drawings) will open the shutter 58 from the closed position. This is important during the operation of the sewage barrier 10 because the shutter 58 should be opened even with a slight amount of liquid that may pass through the sewage barrier 10 when installed in a sewage system.

The counterweight 30. the connecting rod 46 and the shutter 58 are designed such that their operation is not inclination sensitive, i.e., they operate in the same satisfactory manner regardless the inclination of the longitudinal axis A with respect to level ground LG. It is understood by a person skilled in the art that since sewage pipes may be instal led at different inclinations, it is necessary that the sew age barrier 10 will operate at those varying inclinations. Hence, the sewage barrier 10 according to the present invention is designed to operate satisfactorily at inclination angles γ of the longitudinal axis A with respect to level ground LG. of 0° to 10°. Typically, the range of inclinations of common sewage pipes is from 0° to 3°.

The sewage barrier 10 is installed into a sewage pit 68 of a common sewage system, being a domestic or a public system. Typically, the sewage pit 68 has one or more entrance or feeding pipes 70 and one drainage or exit pipe 72. Each of the entrance pipes has a longitudinal axis C. Since it is required, as already mentioned, to prevent any rodents or backflow to go into the entrance pipes 70. a sewage barrier 10 has to be installed on each of the entrance pipes 70. Each of the entrance pipes 70 enters the sewage pit 68 in a relatively tight fit. i.e.. w ith a small clearance betw een the entrance pipe 70 and the sewage pit 68. Alter the entrance into the sewage pit 68 the entrance pipe 70 ends in an open entrance channel 74 that joins other open entrance channels 74 into an open exit channel 76.

As is commonly known, there is a relatively very small clearance between the entrance pipe 70 and its associated channel 74. In order to install the sewage barrier 10. it is held by the holding structure 16 and assembled onto a free end 78 of the entrance pipe 70 by a simple axial movement 80 of the sewage barrier 10 with respect to the entrance pipe 70 when the longitudinal axis A of the body 12 is aligned with the longitudinal axis C of the entrance pipe 70. The axial movement 80 is carried out from a free end 78 of the entrance pipe 70 toward a rear wall 82 of the sewage pit 68 where the entrance pipe 70 enters into the sewage pit 68. Since the body 12 and the holding structure 16 have a one-piece construction, it becomes an easy task to accommodate the sew age barrier 10 on the free end 78 of the entrance pipe 70. Thus, the sewage barrier 10 is adjusted such that the holding structure 16 remains in an upper portion of the sewage barrier 10 and the shutter 58 effectively closing the sewage barrier 10 and. hence, also the free end 78 of the entrance pipe 70. Furthermore, since the sewage pit 68 has relatively small free space, it is advantageously that it will be enough to locate the sewage barrier 10 only a few centimeters on the entrance pipe 70 for ensuring tight grip therebetween and satisfactory functioning of the sewage barrier 10 (see Fig. 9). The internal first diameter D l of the body is designed to be in a close fit with an external diameter D5 of the entrance pipe 70. thus, the friction between the body 12 and the entrance pipe 70 w ill keep the sewage barrier 10 in its place. When installing the body 12 of the sew age barrier 10 on the entrance pipe 70, it is not necessary that the body w idening 14 reaches the free end 78 of the entrance pipe 70. and a small gap 84 may remain therebetween. Furthermore, since the axial dimension of the sewage barrier 10 is relatively small, as denoted by the lirst length LI . the installation of the sewage barrier 10 becomes an easy task, requiring no physical force or special training and being able to be conducted even in sewage pits having closed spaces.

An example of the installation of several sewage barriers 10 within a single sewage pit 68 is shown in Fig. 10. wherein the sewage pit 68 is shown with three entrance pipes 70 and with one exit pipe 72. In this example, the three open channels 74 of the entrance pipes 70 merge into one exit channel 76 that connects with the exit pipe 72.

It is appreciated that every sew age barrier 10 installed prevents rodents or the like from entering into the upstream piping. Therefore, when a household or public piping is provided with several sewage pits 68, the sewage barrier 10 that is installed downstream prevents rodents from entering into upstream sewage pits 68. thus preventing any damage to those pits by rodents, that, as is known, may damage sewage pits made from plastic materials.

Thus, as explained above, the objects of the present invention are met. As can be appreciated by a person skilled in the art, the sewage barrier 10 according to the present invention embodies several advantages:

1 - The construction of the sew age barrier 10 is relatively simple.

2- The simple construction leads to relatively low cost to produce and, therefore, relatively low cost to being purchased by a consumer.

3- It is very easy to install.

4- It is very quick to install.

5- It requires no special training for the installation.

6- It requires no tools for the installation.

7- It requires no physical force for the installation.

8- It is very easy and quickly to dismantle for inspection and repairs.

9- It is very easy to be thoroughly cleaned.

10-It may be installed in an existing sewage pit 68 without the necessity to dig into ground and cut into an existing sewage pipe. - -

1 1 - It may be installed into hard-to-reach places where the axial available space is limited.

12- It may be installed into shallow sewage pits where the height clearance is relatively small.

13- Since it has very small dimensions, several sewage barriers 10 may be installed within a single sewage pit 68.

14- When the shutter 58 is in a closed position, it is effectively concealed within the body widening 14. thus preventing the possibility to be opened by a rodent or the like.

15- The design ensures that even a small amount of exiting fluid will open the shutter 58.

16- The design ensures effective closing of the shutter 58 for a wide range of installation inclinations.

17- The sewage barrier 10 may effectively prevent back-flow into the household sewage system.

18- The sewage barrier 10 may be effectively made mainly from stainless steel, thus being resistant to rust and corrosion, and cannot being eaten or damaged by rodents or the like. Although the present invention has been described to a certain degree of particularity, it should be understood that various alterations and modifications could be made without departing from the spirit or scope of the invention as hereinafter claimed.

For example, the body and the shutter do not have to be formed from stainless steel and other construction materials may be equally applicable.

If an entrance pipe is not provided w ith a protruding free end and it is flush with an internal wall of a sewage pit. the body of the sewage barrier cannot be mounted on such a free end. In that case, the sewage barrier is not provided with a body, and the holding structure is fixed directly to the wall of the sewage pit above the opening of the entrance pipe. With such an - - installation, the orientation of the counterweight with respect to the shutter, as well as the position of the sliding pin should be accordingly modified.

The adaptation between the body and the shutter does not have to be as described with respect to some embodiments. Alternatively, the shutter may be flush with the body or have a gasket therebetw een. In some embodiments, the shutter is not provided with a frusto-conical w idening, instead, the shutter may be flat, at least along a rear portion thereof, and closing against a widening of the body that is perpendicular to the longitudinal axis A.

The connecting rod does not have to be provided with a step and other forms of the connecting rod may be applied, for example, straight. In that case, the front wall of the holding structure may be forwardly extended. Furthermore, the connecting rod may hav e other profile cross-sections rather than a flat one. Thus, for example, the cross-section of the connecting rod may comprise two flat sections that are angled with respect to each other.

The connecting rod may be connected to a front side of the shutter or it may be connected thereto by a connection that passes from a front side of the shutter to a rear side of the shutter.

The limiting of the opening of the shutter does not have to be carried out by a lower end of the front wall of the holding structure, and other limiting options may be chosen.

The holding structure may be connected to the body by welding or any other appropriate manner.

The sliding pin does not have to pass through both side walls of the holding structure.

The balancing of the shutter does not have to be made by a counterweight and other balancing means may be applied. For example, the connecting rod may be connected to the holding structure through springs or other resilient components (not shown in the figures). The connecting rod may be connected by a spring to the front wall of the holding structure or to the rear wall of the holding structure. Furthermore, in some embodiments, the connecting rod may be connected by a front spring to the front wall of the holding structure and by a rear spring to the rear wall of the holding structure. When springs are used, in a closed position of the shutter each one of the springs may be normally in a pressed position or in a tensioned position.

It should be appreciated that the use of springs, or other resilient components, may enable to increase the range of function of the sewage barrier. This is due to the fact that the use of a counter- weight, and the corresponding limitations of the geometrical dimensions, is avoided. Thus, a spring can be easily calibrated to different ranges, for example, when it is required to open the shutter by a much larger capacity than the normal sewage flow. Furthermore, a spring may be calibrated to function with different characteristics during opening or closing of the shutter.

The springs or the other resilient materials may be of a type known in the art. For example, each of the springs may be a tension spring, a compression spring, a torsion spring, a clock spring, a clip, or the like.