WO2004013421A1

WO2004013421A1 - Method for producing a plastic pit-floor element

Info

Publication number: WO2004013421A1
Application number: PCT/NL2003/000558
Authority: WO
Inventors: Wilfried Spekhorst; Ole Heidemann Jensen
Original assignee: Wavin B.V.
Priority date: 2002-08-06
Filing date: 2003-08-04
Publication date: 2004-02-12
Also published as: AU2003254971A1; NL1021221C2; EP1552070A1

Abstract

A method for producing a plastic pit-floor element for a pit, in particular an inspection pit. The pit-floor element has one or more connection features for one or more lines. The method comprises the steps of : -(a)- providing a plastic shell part having a top surface which comprises at least one channel which is open at the top and the top surfaces which adjoin the top edge of the channel, :-(b)- providing a plastic shaft part having an annular wall, :-(c)- positioning the shell part in the shaft part, :-(d)- fixing the shell part to the annular wall of the shaft part, :-(e)- forming at least one opening in the shaft part and, aligned with this, an opening in the shell part, and :-(f)- positioning a pipe part, and connecting it in a watertight manner, in the aligned openings, in such a manner that the inwardly directed end of the pipe part adjoins the shell part in a watertight manner and the other end of the pipe part extends at least as far as the shaft part, where it forms a connection feature for a line which is to be connected

Description

Method for producing a plastic pit-floor element

The present invention relates to a method for producing a plastic pit-floor element for a pit, in particular an inspection pit, which pit-floor element has a connection feature, or in particular a plurality of connection features, for one or more lines.

In particular, the invention relates to a floor element for a pit which is provided at the top side with a manhole which can be closed off by an associated cover or grate and which also has a substantially vertical shaft between the said manhole and the floor element.

It is generally known that the connection features of a plastic pit-floor element in particular have to be matched to the diameter (s) and the position and orientation of the line(s) to be connected to the floor element. In view of the relatively large number of standard line diameters which are available and the large number of possible arrangements of lines which are to be connected, the producers of pit-floor elements of this type are required to be able to supply tailor-made pit-floor elements. In practice, products offer some 150 different versions.

The previously known methods for producing plastic pit-floor elements of this type are inefficient.

For example, in particular in the case of pit-floor elements of relatively large diameters, for example more than 700 millimetres, a known method involves assembling the pit-floor element mainly by means of manual work by forming a channel in a shaft element with an integral bottom wall with the aid of semicircular pipe sections and fitting the adjoining conical top surfaces by means of a large number of panel pieces made from plastic. The panel pieces in question are tailor made by hand and then secured in place by means of welded j oints . In practice, this means that the production of a single pit-floor element may require as much as 10 man hours .

It is an obj ect of the present invention to propose a more efficient method for the production of a plastic pit-floor element .

The invention achieves this object by means of a method which comprises at least the steps of : providing a plastic shell part having a top surface which comprises at lea st one channel which is open at the top and top surfaces which adj oin the top edge of the channel, - providing a plastic shaft part having an annular wall, positioning the shell part in the shaft part, fixing the shell part to the annular wall of the shaft part , - forming at least one opening in the shaft part and, aligned with this , an opening in the shell

, part, and positioning a pipe part, and connecting it in a watertight manner, in the aligned openings, in such a manner that the inwardly directed end of each pipe part adjoins the shell part in a watertight manner and the other end of each pipe part extends at least as far as the shaft part, where it forms a connection feature for a line which is to be connected.

The invention therefore provides for the production of a shell part and, separately, a shaft part, after which the shell part is positioned and fixed in the shaft part.

After the customer ordering the pit-floor element has indicated the locations at which hie wishes to be able to connect lines, in the method according to the 03 000558

- 3 - invention openings are formed at these locations both in the shaft part and in the shell part, preferably witϊi the aid of a drill, for example a tubular hole borer with cutting means at the end.

In an embodiment which is suitable in particular for large pit-floor elements, the assembly comprising shell part and pit-floor element is placed onto a turntable and oriented with respect to a drilling installation arranged alongside the turntable, with a drill which can move to and fro in a rectilinear guide.

After the openings have been formed, a pipe part is positioned in each pair of aligned openings, this pipe part then being matched, at the inwardly facing end, to the shell part and being fixed in a watertight manner thereto, while each pipe part is also joined in a watertight manner to the shaft part.

The free end of each pipe part may project outside the shaft part in order for a line to be connected to this projecting end. In a variant, a pipe part ends in the vicinity of the annular wall of the shaft part, where it is provided with an insertion socket or other coupling means for the line which is to be connected.

The method according to the invention enables the producer of the pit-floor element to produce a large number of different pit-floor elements using a relatively small number of different shell parts, shaft parts and operations.

By way of example, the producer can on demand produce different shell parts having a channel in which the diameter of the channel is matched to the particular requirements and corresponds to standard line diameters, for example 110, 160, 200, 250 or even 500 millimetres . In an advantageous embodiment, a shell part is provided having a channel which extends from the centre of the shell part to the outer periphery thereof, and the method also comprises the step of forming an opening in the shaft part at the level of the end of the channel which adjoins the outer periphery.

An embodiment of the shell part of this nature has the advantage that the channel which is open at the top continues all the way to the annular wall of the shaft part, which is advantageous in particular if the channel is used to discharge liquid via a line which is to be connected to the channel at that location, since the drainage capacity is then high and the risk of blockage low.

Particularly if a (rotational) moulding process is used for the production of the plastic shell part, it is preferable for the shell part, at the end of the channel which adjoins the outer periphery of the shell part, to form an end wall which extends substantially transversely with respect to the channel, in which case the method also comprises the step of forming an opening in each end wall or of removing the end wall, preferably prior to the positioning of the shell part in the shaft part.

In a variant, the shell part forms an open end of the channel at that end of the channel which adjoins the outer periphery.

In one specific embodiment, a shell part which forms a channel with two ends adjoining the outer periphery of the shell part is produced. The channel is then used in particular as a through-passage (drainage) channel. If appropriate, liquid which flows in from one or more other lines which are to be connected to the pit and/or via a grate in the top side of the pit can also enter this channel via the shell part. It is preferable for the top surfaces of the shell part which adjoin the channel to be substantially conical and for these top surfaces to slope downwards towards the channel.

In a variant, the shell part forms one or more substantially horizontal surface parts which can be walked on, for example along the outer periphery. In another variant, during the production of the pit, floor- parts which can be walked on are arranged above the shell part.

Particularly if a line which is to be connected to the channel is intended to drain liquid out of the pit, it is preferable for the opening for the pipe part which has been formed in the shell part to be such that the pipe part is a continuation of the channel.

If a shell part without an integrally formed channel is used, the opening which has been formed for the pipe part is arranged in such a manner that the lowermost point of the pipe part is located at a lower level than the lowermost point of the shell part, and it is desirable for the pipe part to be provided, at the inwardly projecting end, with a closure wall which adjoins the shell part and thereby closes off the corresponding end of the pipe part. By way of example, the closure wall is in the form of a part of a hemisphere.

In an advantageous embodiment of the method according to the invention, there is provision for the shell part to be provided using a moulding process by means of a suitable mould.

It is preferable for the shell part to be provided using a rotational moulding process. It is preferable to use a rotational mould by means of which two shell parts whose outer peripheries adjoin one another are produced simultaneously, which shell parts are then separated from one another. The mould then has a single mould cavity into which the plastic is introduced.

In an advantageous embodiment, this mould is designed in such a way that by positioning inserts it is possible to make shell parts with different channels, so that the producer only needs a small number of moulds .

In one possible embodiment, the shaft part has an integral bottom wall and the shell part is positioned and fixed in the shaft part which is open at the top.

In another embodiment, the shaft part of the floor element includes only the annular wall, and a separately produced bottom wall, preferably made from plastic, is secured to the annular wall beneath the shell part.

In one robust embodiment, plastic support elements are provided between the shell part and the bottom wall, which support elements are preferably formed integrally on the bottom wall.

As is known per se, it is preferable for the shaft part to be designed at its top side for a subsequent shaft part to be positioned on top of it, so that the pit can reach the desired height.

In an embodiment as a through-flow pit, there is provision for the channel to adjoin the outer periphery of the shell part at all ends and for the opening for one pipe part to be arranged in such a manner that the lowermost point thereof is at a higher level than the lowermost point of the channel. In this case, the line which is to be connected is then used as a feed line and the channel as a through-flow channel.

The invention will be explained in more detail below on the basis of the drawing, in which:

Fig. 1 shows a vertical section through a floor element during production using the method according to the invention, Fig. 2 shows a plan view of the floor element shown in Figure 1,

Figs. 3a-c respectively show a plan view of, a vertical section through and a further vertical section through the shell part of the pit-floor element shown in Figures 1 and 2,

Fig. 4 shows a vertical section through another floor element during its production using the method according to the invention, Fig. 5 shows the floor element from Figure 4 in plan view, and

Figs. 6a-c respectively show a plan view of, a vertical section through and a further vertical section through the shell part of the pit-floor element shown in Figures 4 and 5.

Figure 1 shows a vertical section through a plastic pit-floor element 1 for a pit, in particular an inspection pit, which pit-floor element ultimately is to receive two connection features for two lines.

The pit-floor element 1 is shown in an intermediate state which occurs during production using the method according to the invention. Figure 2 shows the floor element 1 from Figure 1 in plan view.

In the case of the method described here by way of example, a shell part 2, which is shown in detail in Figures 3a-c in the state prior to assembly of the floor element, has been produced in a suitable mould using a rotational moulding process.

The shell part 2 has a top surface which forms a channel 3 which is open at the top, as well as top surfaces 4 which adjoin the top edge of the channel 3. These top surfaces 4 are substantially conical, so that liquid from these top surfaces 4 enters the channel 3. The shell part 2 is in fact a dimensionally stable plastic panel with a specific shape with a wall thickness which makes the shell part 2 at least self-supporting, and preferably suitable for walking on.

The shell part 2 has a circular outer circumference 5 with, in this example, a raised circumferential edge 6.

The channel 3 lies substantially radially in the circular shell part 2 and at one end adjoins the outer circumference 5 of the shell part 2. The other end of the channel 3 is located in the central region of the shell part 2.

At the end of the channel 3 which adjoins the outer circumference of the shell part, the shell part 2 forms an end wall 7 which extends substantially transversely with respect to the channel 3 and the upper edge of which forms a part of the circular circumferential edge 6.

The above-described shell part 2 is positioned in a substantially cylindrical plastic shaft part 10 with an annular wall 11 and in this example an integral bottom wall 12.

The annular wall 11 is provided with ribs 13 on its outer circumference for reinforcement purposes . The shell part 2 is positioned in the shaft part 10 from above and is then fixed in place, in this example along the circumferential edge 6 which adjoins the inner circumference of the shaft part. It is preferably fixed in place using a welding process.

Now that the shell part 2 and shaft part 10 have been assembled to form a single unit, aligned openings are then formed in the shaft part 10 and the shell part 2. These openings are used to receive a pipe part 20 which is pushed into the openings. The pipe part 20, at the inwardly projecting end, adjoins the shell part 2, is fixedly welded to it all the way around and has been given an appropriate contour for this operation. Furthermore, the tubular part 20 has been welded into the opening in the shaft part and in this example projects slightly outside the shaft part 10. A line can then be connected to the projecting part 21, for example using a socket connection or fusion-welded joint.

The openings are advantageously formed using an elongate hole borer in the form of a tube with a cutting edge or toothing at the end side. By way of example, in this case the assembly of shaft part and shell part is arranged on a turntable, so that the desired positioning of the assembly with respect to the drill can be adjusted, the drill then being held in such a manner that it can move to and fro in a guide .

In the case of the floor element 1, provision is made for a line with a diameter of 200 millimetres to be connected at an angle with respect to the straight channel 3, as shown in Figure 2. The channel 3 likewise has this same diameter of 200 mm.

The opening for the pipe part 20 which has been formed in the shaft part 10 and shell part 2 is arranged in such a manner that the lowermost point of the pipe part 20 is located at the same level as the lowermost point of the channel 3. This prevents disturbance to the flow of liquid.

Furthermore, to complete the pit-floor element 1, an opening (not shown) is drilled at the height of the end wall 7 of the shell part 2, preferably with a diameter matched to the diameter of the channel 3. This opening is drilled through both the shaft part 10 and the end wall 7. Then, a pipe part is positioned and fixed to the shell part and the shaft part, and if appropriate this pipe part may be designed with an insertion socket or similar coupling for another line which is to be connected to the pit-floor element 1. In this way, the channel 3 can serve as a through-flow channel.

It is conceivable for it to be possible for one or more further lines to be connected to the pit-floor element 1. To this end, aligned openings can be formed in the shaft part and the shell part 2 in the manner described above, after which a pipe part is fitted. If it is intended for liquid to flow into the pit via the line which is to be connected to the said pipe part, it is preferable for the lowermost point of the pipe part in question to be located above the lowermost point of the channel.

Obviously, it is conceivable for any lines to be connected to the pit above the level of the shell part.

In a variant of the method described above, an opening is formed in the end wall 7 or the end wall is removed prior to the positioning of the shell part in the shaft part.

In another variant, there is provision for the end wall to be absent and for the shell part at the end of the channel which adjoins the outer periphery to form an open end of the channel. - li lt is also possible for the shell part not to be provided with a channel, in which case the opening formed for the pipe part is arranged in such a manner that the lowermost point of the pipe part is at a lower level than the lowermost point of the shell part. In this case, the pipe part is provided at the inwardly projecting end with a closure wall which adjoins the shell part and thereby closes off the corresponding end of the pipe part. By way of example, this closure wall is part of a hemispherical surface.

Figures 4-6 show a pit-floor element during its production and the associated shell part, largely corresponding to the pit-floor element shown in Figures 1-3.

In particular, the external diameter of the shell part 30 is identical to that of the shell part 2. A difference is that the channel 33 has a diameter of 250 millimetres.

As soon as the shell part 30 has been mounted in the shaft part 10, openings can be formed in the manner described above and one or more pipe parts can be positioned therein, all this as a function of the intended connection options for the pit-floor element.

It is advantageously provided for a rotational mould to be used, by means of which two shell parts 2, 30, whose outer peripheries adjoin one another, are produced simultaneously, which shell parts are then separated from one another. In this way, it is possible to efficiently produce shell parts with different channels .

It will be clear that the channel in the shell part may also be of completely different design, for example, in the form of a straight channel which at both ends extends as far as the outer periphery of the shell part. However, the embodiment shown offers a suitable universal starting point for a wide range of different pit-floor elements with different connection options.

The method described is very efficient and leads to a considerable time saving in conjunction with relatively low tool investment costs.

As an alternative, the shell part could also be produced using a vacuum-moulding process or even by means of injection moulding. A further alternative is the lay-up method for glass fibre-reinforced shell parts .

In an alternative embodiment, there is provision for the shaft part to include only the annular wall and for a bottom wall, preferably made from plastic, to be secured to the annular wall beneath the shell part.

If appropriate, plastic support elements, for example ribs, are provided between the shell part and the bottom wall, which support elements are preferably formed integrally on the bottom wall.

At their top side, the shell parts 2, 30 shown are designed for a subsequent shaft part to be positioned on top of them, so that it is possible to produce a pit of the desired height.

Claims

1. Method for producing a plastic pit-floor element for a pit, in particular an inspection pit, which pit-floor element has one or more connection features for one or more lines, the method comprising the steps of: providing a plastic shell part having a top surface which comprises at least one channel which is open at the top and top surfaces which adjoin the top edge of the channel, providing a plastic shaft part having an annular wall,

- positioning the shell part in the shaft part, - fixing the shell part to the annular wall of the shaft part,

- forming at least one opening in the shaft part and, aligned with this, an opening in the shell part, and - positioning a pipe part, and connecting it in a watertight manner, in the aligned openings, in such a manner that the inwardly directed end of the pipe part adjoins the shell part in a watertight manner and the other end of the pipe part extends at least as far as the shaft part, where it forms a connection feature for a line which is to be connected.

2. Method according to claim 1, in which a shell part is provided having a channel which, at at least one of its ends, extends as far as the outer periphery of the shell part, and in which the method also comprises the step of forming an opening in the shaft part at the level of each end of the channel which adjoins the outer periphery, a pipe part which forms the extension of the channel being secured at least in one opening.

3. Method according to claim 2, in which the shell part, at each end of the channel which adjoins the outer periphery of the shell part, has an end wall which in each case extends substantially transversely with respect to the channel, and in which the method also comprises the steps of forming an opening in each end wall after the shell part has been positioned in the shaft part, or of removing the end wall, preferably prior to positioning of the shell part in the shaft part.

4. Method according to one or more of the preceding claims, in which the shell part, at the end of the channel which adjoins the outer periphery, is formed as an open end of the channel.

5. Method according to one or more of the preceding claims, in which a shell part is formed with a channel with one end which adjoins the outer periphery of the shell part and another end located in a central region of the shell part.

6. Pit-floor element obtained using the method according to one or more of the preceding claims, in which the top surfaces of the shell part are substantially conical in shape and slope downwards towards the channel.

7. Pit-floor element obtained using the method according to one or more of the preceding claims 1-5, in which the opening for the pipe part which has been formed in the shell part is arranged in such a manner that the lowermost point of the pipe part is located at the same level as the lowermost point of the channel.

8. Pit-floor element obtained using the method according to one or more of the preceding claims 1-5, in which the opening for the pipe part which has been formed in the shell part is arranged in such a manner that the lowermost point of the pipe part is located at a lower level than the lowermost point of the shell part, and in which the pipe part is provided, at the inwardly projecting end, with a closure wall which adjoins the shell part and thereby closes off the corresponding end of the pipe part.

9. Method for making a pit-floor element according to one or more of the preceding claims, in which the shell part is provided using a moulding process by means of a suitable mould.

10. Method according to claim 9, in which the shell part is provided using a rotational moulding process.

11. Method according to claim 10, in which a rotational mould is used, by means of which two shell parts whose outer peripheries adjoin one another are produced simultaneously, which shell parts are then separated from one another.

12. Method according to claim 11, in which two shell parts with different channels are produced in one mould.

13. Method according to one or more of the preceding claims, in which the shaft part has an integral bottom wall and the shell part is positioned in the shaft part, which is open at the top.

14. Method according to one or more of claims 1-13, in which the shaft part includes only the annular wall and in which a bottom wall, preferably made from plastic, is secured to the annular wall beneath the shell part.

15. Method according to claim 13 or 14, in which plastic support elements are provided between the shell part and the bottom wall, which support elements are preferably formed integrally on the bottom wall.

16. Method according to one or more of the preceding claims, in which the shaft part is designed at its top side for a subsequent shaft part to be placed on top of it.

17. Method according to one or more of the preceding claims, in which the channel adjoins the outer periphery of the shell part at all ends and in which an opening for the pipe part is arranged in such a manner that the lowermost point of the pipe part is at a higher level than the lowermost point of the channel.