GB2096730A - Friction gear - Google Patents

Abstract

A low-power transmission has drive wheels 1 and 2 the contacting curved faces of which are provided with an upstanding plurality of fibrous hooks at 8, such as the material known as "Velcro" (RTM). Alternatively, using such a surface covering, the curved face of one wheel can drive the flat face of the other, e.g. as a change-speed gearing. <IMAGE>

Description

SPECIFICATION Friction gear This invention relates to a friction gear having a first and second faced drive wheel pressed into rolling contact with each other, the gear having a low power rating. The invention is suitable for incorporation into machines which have a low power consumption, such as mechanised toys, agitators, developing tanks and the like.

According to a first aspect of the invention, a friction gear suitable for low powers has a first and second faced drive wheel pressed into rolling contact with each other, the first drive wheel having a surface faced with a material having a pile of upstanding fibres or elements which can engage similar piled material on a surface on the second faced drive wheel.

According to a second aspect of the invention, a friction gear suitable for low powers has a first and second faced drive wheel pressed into rolling contact with each other, the first drive wheel having a surface faced with a material with a high coefficient of friction which can engage similar material on a surface on the second faced drive wheel.

The material is hereinafter referred to as friction material for the sake of convenience.

Preferably, the pile of upstanding fibres or elements comprises a plurality of small hooks on one side of the friction material.

The friction material is preferably a layer or strip made of a synthetic polymeric material, in particular nylon. The layer or strip is secured to the first and second faced drive wheel by, for example, adhesive. The layer or strip may be secured to the circumferential edge or a face of the faced drive wheel.

Preferably, the friction material having a high coefficient of friction on the surface of the first and second faced drive wheel comprises an abrading material attached to the friction material.

The friction material is preferably a layer or strip of cloth, which is secured to the first and second faced drive wheel by, for example, adhesive. The abrading material is preferably a thin coating of fine sand glued on to one side of the layer or strip of cloth.

The first and second faced drive wheel may be located in the same vertical plane, and may be arranged so that the circumferential edge of the first faced drive wheel engages the circumferential edge of the second faced drive wheel.

The first and second faced drive wheel may also be located in two planes at right angles to each other, and may be arranged so that the circumferential edge of the first faced drive wheel engages the peripheral edge portion of one face of the second faced drive wheel.

The first and second faced drive wheel may also be located in the same vertical plane but spaced apart from each other, and may be arranged so that a continuous flexible elongate element engages the circumferential edge of the first and second faced drive wheel. The continuous flexible elongate has a surface faced with a similar piled material or material with a high coefficient of friction to the friction material on the first and second faced drive wheel.

The continuous flexible elongate element is preferably a strip of a synthetic polymeric material, in particular nylon. The material has a pile of upstanding fibres or elements, in particular a plurality of small hooks on one side of the strip.

The continuous flexible elongate element may also be an elasticated strip of a synthetic polymeric material.

The invention will now be described by way of example with reference to the accompanying drawings, in which Figure 1 shows a schematic elevational view of first embodiment of a friction gear according to the invention; Figure 2 shows a schematic plan view of a second embodiment of a friction gear according to the invention; and Figure 3 is a schematic side view of a third embodiment of a friction gear according to the invention.

Figure 1 shows two faced drive wheels 1 and 2 pressed into rolling contact with each other. It is not necessary for the description of this invention to describe the further elements to which the faced drive wheels 1 and 2 are connected.

However, as the invention relates to a friction gear, one of the faced drive wheels, for example the faced drive wheel 1, is connected to and driven by a small motor, for example a 6 volt motor. The small motor can be of any suitable conventional construction and is therefore not described or shown in the accompanying drawings in any detail.

The second faced drive wheel 2 can be connected to a variety of elements, but in particular can be connected to or integral with an apparatus for developing undeveloped photographic film as claimed and described in our copending British Patent Application No.

8038025. The friction gear of the present invention can be used as the drive means for rotating the film carrier of the apparatus for developing undeveloped photographic film as claimed and described in our above mentioned copending British Patent Application.

For the sake of clarity, the arrangement of the first and second faced drive wheel 1 and 2 are only shown in the accompanying drawings.

The first faced drive wheel 1 is mounted on a suitable rotatable shaft 3, and the second faced drive wheel 2 is likewise mounted on a suitable rotatable shaft 4.

Figure 1 shows the circumferential edge 5 of the first faced drive wheel 1 contacting the circumferential edge 6 of the second faced drive wheel 2. The circumferential edges 5 and 6 of the first and second faced drive wheel 1 and 2 are covered with a material 7 having a pile of upstanding fibres or elements 8. The upstanding fibres or elements 8 extend around the entire circumferential edge of the two faced drive wheels. The accompanying drawings show the upstanding fibres or elements extending only partly around the circumferential edge or sides of the two faced drive wheels for the sake of clarity.

The preferred material is "Velcro" (Registered Trade Mark), and the pile of upstanding fibres or elements comprises a plurality of tiny hooks which are usually found on "Velcro" strips for use in touch and close fasteners.

The "Velcro" strip is attached to the circumferential edge of each faced drive wheel by, for example, adhesive. The plurality of tiny hooks on the material attached to the first drive wheel 1 engages the plurality of tiny hooks on the material attached to the circumferential edge of the second drive wheel. Thus, power is transmitted from, for example, the shaft 3 which is driven by a motor (not shown) to the second shaft 4 by "interengagement friction" set up between the first and second faced drive wheels pressed into rolling contact. By "interengagement friction" we mean the contacting and interengaging of the tiny hooks on the piled material on the two faced drive wheels. The relative size of the faced drive wheels can be varied in order to accommodate different power transmissions.

Figure 2 shows a second embodiment of the friction gear according to the invention. The first faced drive wheel 1 is the same as described above with reference to Figure 1 and uses the same reference numerals as used in Figure 1. The second faced drive wheel 2 also uses the same reference numerals as used in Figure 1, unless otherwise specified. The second faced drive wheel 2 has a material 9 having a pile of upstanding fibres or elements 10 attached to one face 11 of the second faced drive wheel 2. Figure 2 shows the material 9 extending across the entire face of the second face drive wheel 2, but of course it is possible that the material be arranged in an angular strip around the periphery of the second faced drive wheel 2.Figure 2 only shows for the sake of clarity the pair of faced drive wheels interengaging each other and does not show anything which is connected to the two shafts 3 and 4. The first faced drive wheel 1 is connected to and driven by a small motor, for example a 6 volt motor, which can be of any suitable conventional construction and is therefore not described.

If the material extends across the entire face of the second faced drive wheel, it is possible to have a continuously variable step-down or step-up gearing arrangement by varying the point of contact of the circumferential edge of the first faced drive wheel and the face of the second faced drive wheel. It is also possible to have a number of faced drive wheels, in particular the circumferential edges thereof, contacting the face of another faced drive wheel.

Figure 3 shows the first faced drive wheel 1 and second faced drive wheel 2 arranged in a common vertical plane, but spaced apart from each other. The same reference numerals are used as in Figures 1 and 2, unless otherwise specified.

The first and second faced drive wheel 1 and 2 are mounted on the respective shafts 3 and 4. A continuous flexible elongate element 12 engages the circumferential edge 5 of the first faced drive wheel 1 and the circumferential edge of the second faced drive wheel 2. As with the embodiment described with reference to Figure 1, the circumferential edges of the two faced drive wheels are covered by a material having a pile of upstanding fibres or elements, in particular "Velcro" material. The upstanding fibres or elements are preferably a plurality of tiny hooks 1 3. For the sake of clarity, only a portion of each circumferential edge of the first and second faced drive wheel is shown with the upstanding fibres or elements.The continuous flexible elongate element is covered on one side with a material or similar pile to that on the circumferential edge of the first and second faced drive wheel. The material has upstanding fibres or elements 14, which are preferably the tiny hooks as found on a "Velcro" strip. The tiny hooks 14 on the continuous flexible elongate element 12 engage the plurality of tiny hooks on the material on the circumferential edge of the first and second faced drive wheel, and thus power can be transmitted from the shaft 3 via'the first faced drive wheel 1 and the continuous flexible elongate element 12 to the second faced drive wheel 2 and finally to the shaft 4.

The continuous flexible elongate element can be made of a synthetic polymeric material, in particular nylon. However, it can also be made elasticated, in order to provide a certain degree of flexibility within the belt in order to ensure that the piled material on the one side of the continuous elongate element can closely engage the piled material on the circumferential edge of the first and second faced drive wheel.

Instead of using a piled material, it is possible to use a friction material having a high coefficient of friction. In this case, the material comprises a layer or strip of cloth having an abrading material attached thereto. The abrading material is preferably a thin coating of fine sand glued on to one side of the layer or strip of cloth. If the friction used is one having a high coefficient of friction, the embodiment shown in Figure 3 will use a continuous flexible elongate element having a suitable surface for engaging the material of high coefficient of friction on each of the faced drive wheels.

The present invention can be used for a variety of purposes, as long as it is desired to transmit low powers from one shaft to another shaft. An advantage of the present invention is that it is not necessary to align the drive wheel exactly, since the use of the "Velcro" strip ensures a sufficient interengagement between the faced drive wheels.

Another advantage is that lash-back which can occur with cogged drive wheels is eliminated, because of the interengagement of the piled material on the first and second faced drive wheels. Unlike conventional cogged drive wheels, it is not necessary with the present invention to exactly align the drive wheels. A further advantage of the friction gear according to the invention is that it is cheap and simple to use, and it is not necessary to get involved with complicated gearing devices.

It is of course possible that the strip of material on the circumferential edges of the first and the second faced drive wheels can be varied in width, typical widths ranging from 1 5-50 mm.

depending on the power transmission required.

When the friction gear of the present invention is used with an apparatus for developing undeveloped photographic film as claimed and described in our copending British Patent Application No. 8038025, it is necessary that the material having a pile of upstanding fibres or elements is inert to the processing solutions contained within such an apparatus.

Claims (5)

1. A drive suitable for low-power transmission having a first and second drive wheel with contacting faces each having a pile of upstanding fibres or like elements for interengagement.

2. A drive as claimed in Claim 1 in which the upstanding fibres are a plurality of small hooks.

3. A drive as claimed in Claim 1 or 2 in which both contacting faces are curved circumferential faces.

4. A drive as claimed in Claim 1 or 2 in which one face is a curved circumferential face and one is a flat side face.

5. A drive as claimed in Claim 1 and substantially as herein described with reference to the accompanying drawings.