GB2281597A

GB2281597A - Drain rod connections

Info

Publication number: GB2281597A
Application number: GB9318316A
Authority: GB
Inventors: Richard Sanders
Original assignee: HOROBIN Ltd
Current assignee: HOROBIN Ltd
Priority date: 1993-09-03
Filing date: 1993-09-03
Publication date: 1995-03-08
Also published as: GB9318316D0

Abstract

A plastic drain rod is manufactured in one piece in a single moulding operation and is formed with an integral male connector (1) and an integral female connector (2). The rod has four limbs (11) providing a cruciform cross-section and has radially aligned discs (12) spaced at intervals therealong to provide stiffening. The male connector (1) is formed with a screw threaded portion (3) and a plain cylindrical portion (5) of the same peak diameter. The male connector is not provided with a shoulder or other formation which could limit its entry into the female connector. <IMAGE>

Description

DRAIN RODS The invention relates to plastic drain rods suitable for connection in series to similar rods and to various tools such as plunger heads.

Prior art plastic drain rods are formed from an extruded tube. Separate connectors are traditionally fitted, such as by rivetting, to the ends of lengths of the tube, or are or formed in the material of the tube by a separate forging operation such as described in GB 2075625.

The present invention provides a drain rod which is manufactured in one piece in a single moulding operation and is formed with an integral male connection at one end and an integral female connector at the other end.

A disadvantage of extruded tube drain rods lies in the fact that the tubes have a low resistance to bending unless made relatively thick, and are subject to kinking when bent.

In an embodiment of the present invention, the rod has a cross-section comprising at least three limbs extending radially from and equally spaced around the longitudinal axis of the rod. Preferably the rod has four limbs providing a cruciform cross-section. Stiffening means may be provided and are preferably in the form of radially aligned discs centred on the longitudinal axis of the rod and spaced at intervals therealong.

In known plastic drain rods, a shoulder formed on the male connector abuts against the free end of the female connector when the connection is fully made. The existence of the shoulder may prevent the male connector to be fully screwed into the female connector. Indeed, in order to ensure that the shoulder of the male connector does abut the free end of the female connector, it is necessary to ensure that the screw threaded portion of the male connector will always be slightly shorter than the internal screw threaded portion of the female connector.

Also, the opposing faces of the shoulder and the female connector form a fulcrum for forces bending the rod and tend to concentrate such forces at the root of the threaded portion of the male connector which is the weakest part of the rod and thus liable to failure.

In a preferred embodiment of the present invention, the male connector comprises an externally screw threaded portion which terminates at the free end of the rod and, at its other end, has a plain cylindrical portion of the same diameter as the peak diameter of the screw threaded portion, and the female connector comprises a cylindrical housing having an open end and a blind end, and having an internal profile conforming to substantially the external profile of the male connector; wherein the male connector is not provided with a shoulder or any other formation which could limit its entry into the female connector and in particular is not formed with a shoulder which bears against the free end of the female connector. Preferably the free end face of the male connector and the face of the blind end of the female connector are both flat so that they can engage over their whole surfaces. This provides added strength to the connection.

In a more preferred embodiment the radial outer ends of the ribs lie on the same imaginary cylindrical surface as the plain cylindrical portion and screw threaded portions of the male connector. This means there is no effective change of section between the rod and the male connector. The female connector must have a larger diameter than the male connector and in the preferred embodiment, the ribs are enlarged at their junction with the female connector to avoid a change of section at which stress concentration would occur.

An embodiment of the invention is described below with reference to the accompanying drawings, in which: Figure 1 is a side view of a drain rod; Figure 2 is a view of the connection between two drain rods with the male and female connectors in crosssection; and Figure 3 is a cross-section taken along lines III-III of Figure 1.

The drain rod of Figure 1 may be of any length to suit market requirements and is moulded from suitable plastic material. The rod has a male connector 1 and a female connector 2. The male connector comprises an externally screw threaded portion 3 terminating in a flat end face 4 at its free end and has a plain cylindrical portion 5 at its other end. The diameter of the cylindrical portion 5 is the same as the peak diameter of the threaded portion 3. The female connector 2 comprises a cylindrical housing 6 having an open end 7 and a blind end which has a flat end face 8. The housing 6 has an internal profile conforming to the external profile of the male connector as seen best in Figure 2. When male and female connectors are connected together as shown in Figure 2, the flat end face 4 of the male connector engages the flat end face 8 of the female connector and the plain cylindrical portion 5 of the male connector is received as a fit within the housing 6 of the female connector. Since there is no shoulder formed on the male connector, entry of the male connector into the female connector is not limited and bending forces are not concentrated at the root of the screw threaded portion.

The rod section 10 of the drain rod has a cruciform cross-section provided by four limbs 11 extending radially from and equally spaced around the longitudinal axis of the rod. In other embodiments (not shown) the rod may have 3, 5 or more limbs. Stiffening means are provided in the embodiment shown by radially aligned discs 12 centred on the longitudinal axis of the rod and spaced at intervals therealong. The outer ends of the limbs 11 lie on the same cylindrical surface as the outer edges of the discs 12, the plain cylindrical portion 5 of the male connector, and the peaks of the screw threaded portion 3. The ribs are slightly enlarged, however, at their junction with the female connector.

Although the internal profile of the female connector is shown as having a plain cylindrical section at its mouth, the screw thread may continue through this section. In this case the male connector will be a force fit with the last part of the thread of the female connector being distorted.

In another embodiment (not shown) the stiffening means may be provided by further ribs running along the radial ribs at right angles thereto. These may be in addition to the discs or in place of them. In a yet further embodiment (not shown), the rod may have a tubular form, with or without radial or other stiffening means.

Claims

1. A drain rod manufactured in a single moulding operation and formed with an integral male connector at one end and an integral female connector at the other.

2. A drain rod as claimed in Claim 1, wherein the rod has a transverse cross-section comprising at least three limbs extending radially from and spaced around the longitudinal axis of the rod.

3. A drain rod as claimed in Claim 2, wherein the rod has four limbs providing a cruciform cross-section.

4. A drain rod as claimed in any preceding claim, wherein stiffening means are provided in the form of radially aligned discs centred on the longitudinal axis of the rod and spaced therealong.

5. A drain rod as claimed in any preceding claim, wherein the male connector comprises an externally screw threaded portion which terminates at the free end of the rod and, at its other end, has a plain cylindrical portion of the same diameter as the peak diameter of the screw threaded portion, and the female connector comprises a cylindrical housing having an open end and a blind end, and having an internal profile conforming to substantially the external profile of the male connector; wherein the male connector is not provided with a shoulder or any other formation which could limit its entry into the female connector and in particular is not formed with a shoulder which bears against the free end of the female connector.

6. A drain rod as claimed in Claim 5, wherein the free end face of the male connector and the face of the blind end of the female connector are both flat so that they can engage over their whole surfaces.

7. A drain rod as claimed in Claim 5 or Claim 6, wherein the radial outer ends of the ribs lie on the same imaginary cylindrical surface as the plain cylindrical portion and screw threaded portions of the male connector.

8. A drain rod as claimed in Claim 7, wherein the ribs are enlarged at their junction with the female connector

9. A drain rod substantially as described herein with reference to the accompanying drawings.