Roller Tube

Abstract

The present invention is a roller tube for rolling up a fabric blind. The roller tube consists of an elongated tube having a length, an inner surface and an outer surface. An elongated lip is formed on the outer surface of the elongated tube and extends along the entire length of the elongated tube. The lip has a height substantially equal to the thickness of the fabric blind which is to be wound onto the roller tube. The outer surface of the elongated tube has a first cross sectional diameter at the lip and a second cross sectional diameter at an angle from the first cross sectional diameter, the first cross sectional diameter being larger than the second cross sectional diameter by the height. The inner surface of the elongated tube has a circular profile. A notch is formed on the inner surface of the elongated tube adjacent the lip, said notch extending along the length of the elongated tube. The notch and lip are parallel to the axis of the roller tube.

Description

FIELD OF THE INVENTION

The invention relates generally to roller tubes as used in roller blinds to roll up a fabric blind.

BACKGROUND OF THE INVENTION

Roller blinds generally consist of a fabric blind which is rolled onto an elongated cylindrical roller tube. The roller tube is coupled to some sort of clutch mechanism which operates to rotate the roller tube about its axis in order to roll up or roll down the fabric blind mounted to the roller tube. The fabric blind has one end affixed to the roller tube, usually by a length of adhesive tape. As the roller tube is rotated, the fabric blind is wound (i.e. rolled up) onto the roller tube. Since one end of the blind is attached to the roller tube by a length of adhesive tape, and since the roller tube has a circular cross sectional profile, the fabric does not maintain a circular cross sectional profile as it is wound onto the tube. Rather, it is more accurate to say that the fabric is oriented in a spiral fashion onto the roller tube, with one side of the wound fabric being slightly thicker than the other side.

Assembling a roller tube by attaching one end of the fabric blind to the tube is time consuming because the end of the fabric must be maintained perfectly parallel to the axis of the roller tube, otherwise the blind cannot be properly wound onto the roller tube. Therefore, assembling a roller blind takes a surprisingly long time. A guide line drawn on the tube may provide some assistance when aligning the end of the blind to the tube, but it is very easy to misalign the end of the fabric blind with a guide line during the securing process. An improved roller tube which permits the quick and accurate attachment of the fabric blind to the tube is therefore required.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, there is provided an improved roller tube for rolling up a fabric blind which overcomes the drawbacks of the prior art. In particular, a rolle tube made in accordance with the present invention includes an elongated tube having a length, an inner surface and an outer surface. An elongated lip is formed on the outer surface of the elongated roller tube and extends along the length of the elongated tube. The lip has a height substantially equal to the thickness of the fabric blind. The outer surface has a first cross sectional diameter at the lip and a second cross sectional diameter at an angle from the first cross sectional diameter, the first cross sectional diameter being larger than the second cross sectional diameter by the height. The inner surface of the elongated tube has a circular profile. A notch is formed on the inner surface of the elongated tube adjacent the lip, the notch extending along the length of the elongated tube.

With the foregoing in view, and other advantages as will become apparent to those skilled in the art to which this invention relates as this specification proceeds, the invention is herein described by reference to the accompanying drawings forming a part hereof, which includes a description of the preferred typical embodiment of the principles of the present invention.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a roller tube made in accordance with the present invention.

FIG. 2 is a close up of the lip portion of the roller tube shown in FIG. 1.

FIG. 3 is a perspective view of part of a blind rolled on a roller tube made in accordance with the present invention.

FIG. 4 is an exploded view of a roller blind made with the roller tube of the present invention.

In the drawings like characters of reference indicate corresponding parts in the different figures.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1 and 2, a roller tube made in accordance with the present invention is shown generally as item 10 and includes an elongated roughly cylindrical tube 12 having an outer surface 14 and an inner surface 16. Tube 12 preferably consists of an extruded aluminum tube. Lip 18 is formed on outer surface 14 of tube 12 and notch 20 is formed on inner surface 16 adjacent lip 18. Lip 18 has a wall 28 with an upper rim 26. Wall 28 has a height 30 which is selected to be substantially equal to the thickness of fabric blind 24. Lip 18 is exactly parallel to central axis 22 of roller tube 10.

Roller tube 10 has a cross sectional profile which is not perfectly circular. In particular, roller tube 10 has an external diameter which is different depending on where the diameter is measured, due to the height of wall 28 of lip 18. The external diameter of tube 10 taken at lip 18, which is indicated by dotted line 32 is slightly greater than the external diameter of tube 10 taken adjacent to lip 18 which is indicated by dotted line 34. Diameters 32 and 34 are separated by angle α. The internal diameter of tube 10, indicated by dotted line 36 is identical regardless of where the internal diameter is measured. The thickness of tube wall 13 very gradually changes relative to angle α, with the thickness of the wall being greatest at lip 18 (as indicated by dotted line 32) and thinnest at a point immediately counter clockwise (as viewed in FIG. 1) to lip 18 indicated by dotted line 34. Hence, difference in the thickness of wall 13 is equal to height 30. The structure of tube 10 can be made by machining a regular cylindrical aluminum tube, or more preferably, by creating a separate extrusion with the profile formed in the extrusion die. The desired effect is a blind/roller tube combination which, when end 25 of blind fabric 24 is attached at lip 18, will have an exactly circular combined cross section rather than a raised bump where the blind contacts the roller tube.

Notch 20 is positioned adjacent lip 18. Preferably, notch 20 is positioned away from notch 20 by a distance 38. Distance 38 is selected such that tube wall 13 will not be too thin immediately adjacent notch 20. Preferably, tube wall 13 should have a thickness of at least about 1.7 mm depending on the desired dimensions of the tube. Distance 38 should preferably be at least 1.7 mm to ensure that tube wall 13 is at least 1.7 mm thick between notch 20 and lip 18. Notch 20 acts as an attachment point for a clutch member and idle end (see FIG. 4).

Referring now to FIG. 4, roller tube 10 is used in conjunction with clutch motor 40, idler end 42, blind 24 and brackets 44 and 46 to form a roller blind. The internal notch in roller tube 10 provides an attachment point for clutch motor 40 and idle end 42. As shall be described below, the lip formed on the roller tube also ensures that blind 24 is properly aligned relative to roller tube 10.

Referring now to FIG. 3, lip 18 provides a very convenient means for properly aligning end 25 of blind 24 onto roller tube 10. In particular, lip 18, being the same thickness as fabric blind 24 acts as a wall which permits end 25 of the fabric blind to be butted against. Since lip 18 is exactly parallel to axis 22, lip 18 provides a physical alignment means for keeping end 25 of the fabric blind in alignment with axis 22. This makes the assembly of the blind quicker and easier. In addition, when blind 24 is attached as illustrated in FIG. 3, the blind will effectively maintain a circular cross section as the blind is wound onto the roller tube because the height of lip 18 is substantially equal to the thickness of the fabric forming blind 24.

A specific embodiment of the present invention has been disclosed; however, several variations of the disclosed embodiment could be envisioned as within the scope of this invention. It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.

Claims

1. A roller tube for rolling up a fabric blind, the roller tube comprising:

an elongated tube having a length, an inner surface and an outer surface;

an elongated lip formed on the outer surface of the elongated roller tube and extending along the length of the elongated tube, the lip having a height substantially equal to a thickness of the fabric blind;

the outer surface having a first cross sectional diameter at the lip and a second cross sectional diameter at an angle from the first cross sectional diameter, the first cross sectional diameter being larger than the second cross sectional diameter by the height;

the inner surface of the elongated tube having a circular profile;

a notch being formed on the inner surface of the elongated tube adjacent the lip, said notch extending along the length of the elongated tube.

2. The roller tube as defined in claim 1 wherein the notch and the lip are parallel.

3. The roller tube as defined in claim 1 wherein the tube has an axis and wherein the lip and groove are parallel to the axis.

4. The roller tube as defined in claim 1 wherein the notch is at least 1.7 mm from the lip.