GB2217403A

GB2217403A - Gear apparatus

Info

Publication number: GB2217403A
Application number: GB8823556A
Authority: GB
Inventors: Juan Lloveras
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-04-12
Filing date: 1988-10-07
Publication date: 1989-10-25
Anticipated expiration: 2008-10-07
Also published as: GB8808631D0; GB8823556D0; GB2217403B

Abstract

Gear apparatus (2) comprises a first gear member (4) and second and third gear members (6, 8) which engage with the first gear member (4) such that rotation of the first gear member (4) is transmitted to the second and third gear members (6, 8) or vice versa the first gear member (4) comprising circumferentially-spaced sets (10) of elongate gear teeth (12) which define part of a cone shape, the gear teeth (12) in each set (10) being parallel to each other with some of the gear teeth (12) in each set (10) being of different lengths, one of the second and third gear members (6, 8) always being in mesh with one of the sets (10) and the members (6, 8) being connected together (at 22, 24, 26) such that they rotate at the same speed and being movable along the gear teeth (12) in each set (10) to vary the gear ratio between the first gear member (4) and the second and third gear members (6, 8). <IMAGE>

Description

GEAR APPARATUS This invention relates to gear apparatus.

The gear apparatus may be used in road vehicles and other equipment where a gearing effect is required.

Some road vehicles have automatic gear boxes employing three, four or five different gears. The gear boxes are complex and the gearing jumps from one gear to another and the changes of gear can be felt by persons travelling in the road vehicles.

Attempts have been made to provide gear apparatus which is continuously variable so that the jumping from one gear to another is avoided and thus a smoother change of gearing can be effected. The known continuously variable gearing apparatus operates with pullies and belts, and belt sliding causes problems such for example as limiting the amount of power that the continuously variable gear apparatus can satisfactorily submit.

It is an aim of the present invention to provide gear apparatus which can operate in a continuously variable manner and which does not suffer from the disadvantages of known gear apparatus employing belt drive systems.

Accordingly, this invention provides gear apparatus comprising a first gear member and second and third gear members which engage with the first gear member such that rotation of the first gear member is transmitted to the second and third gear members or such that rotation of the second and third gear members is transmitted to the first gear member, the first gear member comprising sets of elongate gear teeth which define part of a cone shape, the gear teeth in each set being parallel to each other with some of the gear teeth in each set being of different lengths, the second and third gear members being connected together such that they rotate at the same speed during operation of the gear apparatus, and the second and third gear members being movable along the gear teeth in each set to vary the gear ratio between the first gear member and the second and third gear members.

The gear apparatus of the present invention is able to provide continuously variable gearing. Usually, motive power will be applied to the first gear member, in which case an appropriately geared power take-off would be obtainable from the second and third gear members. If desired however the reverse arrangement may be employed in which motive power is applied to the second and/or the third gear members, in which case a geared power take-off may be obtained from the first gear member. The gear apparatus of the present invention may also be of a simpler construction than known automatic gear boxes.

The gear teeth in each set are of varying lengths because the cone shape will narrow towards its narrower end, irrespective of whether the cone shape is a full cone or a frusto-cone. The provision of the varying lengths for the teeth in each set of teeth stop the teeth diverging as they would otherwise do at the narrower end of the cone shape, and the varying length of the teeth thus allows the teeth to be kept parallel to each other.

Preferably, the first gear member has three sets of the gear teeth with each set being equally spaced apart from the other set. With three sets of gear teeth, each set occupies one sixth of the circumference of the cone shape, with the spaces between the sets of teeth also being one sixth of the circumference of the cone shape.

Usually, the gear apparatus will be one in which the gear teeth in each set are such that the longest teeth are in the middle, and in which teeth of other lengths are symmetrically arranged on either side 6f the longest teeth in a descending order of length such that the shortest teeth are arranged at the outside of each set of teeth.

Preferably, there are nine teeth in each set.

More or less than nine teeth in each set may however be employed.

The length of the teeth in each set can be varied as may be desired depending upon required gear ratios.

Usually, the first gear member will be a frusto-conical gear member.

Also usually, the second and third gear members will be cogs.

The teeth on the second and the third gear members are preferably curved so that they engage with the gear teeth on the first gear member such that they only make contact at one point of their circumference to allow for different angles of gear teeth on the first gear member along the length of the gear teeth. The teeth on the second and third gear members are preferably cone shaped in cross section.

The gear apparatus may be one in which the first gear member is secured to a first shaft, in which the second gear member is secured to a second shaft, in which the third gear member is secured to a third shaft, and in which the second and third gear shafts are connected together such that rotation of the second shaft is transferred to the third shaft, and such that rotation of the third shaft is transferred to the second shaft.

Preferably, the second and third shafts are axially twisted to ensure that the second and third gear members are always substantially correctly aligned with the gear teeth on the first gear member.

Preferably, the gear apparatus is one in which the first shaft has an idler gear, in which the second shaft has a drive transfer gear, in which the third shaft has a drive transfer gear, and in which the idler gear and the two drive transfer gears are arranged to be in mesh such that rotation of the second shaft is transferred to the third shaft, and such that rotation of the third shaft is transferred to the second shaft.

The gear apparatus may include gear positioncontrol means for controlling the position of the second and third gears along the length of the gear teeth on the first gear member.

Any suitable and appropriate type of gear position-control means may be employed. By way of example, it is mentioned that the gear position-control means may include a lever operated member.

The gear apparatus may include more than two of the second and third gears for operation with the first gear.

If desired, two or more pieces of the gear apparatus may be arranged in sequence to increase the gearing effect.

The present invention also extends to a road vehicle when provided with the gear apparatus. As stated above, the gear apparatus may also be provided in equipment other than road vehicles.

An embodiment of the invention will now be described solely by way of example and with reference to the accompanying drawings in which: Figure 1 is a top plan view of gear apparatus; and Figure 2 is a section on the line II-II shown in Figure 1.

Referring to the drawings, there is shown gear apparatus 2 comprising a first gear member 4 and second and third gear members 6, 8 respectively. The second and third gear members 6, 8 engage with the first gear member 4 such that rotation of the first gear member 4 is transmitted to the second and third gear members 6, 8.

The first gear member 4 comprises three sets 10 of elongate gear teeth 12. The three sets 10 of elongate gear teeth 12 define part of a cone shape so that the first gear member 4 is in fact in the form of a frusto-cone.

The gear teeth 12 in each set 10 are parallel to each other. As can be seen from Figure 1, some of the gear teeth 12 in each set 10 are of different lengths.

The second and third gear members 6, 8 are connected together such that they rotate at the same speed during operation of the gear apparatus 2.

The second and third gear members 6, 8 are movable along the gear teeth 12 in each set 10 to vary the gear ratio between the first gear member 4 and the second and third gear members 6, 8.

The gear teeth 12 in each set 10 are of varying lengths to enable them to remain parallel to each other as shown in Figure 1. As can be seen from Figure 1, the gear teeth 12 in each set 10 are such that the longest teeth are in the middle, and the teeth of other lengths are symmetrically arranged on either side of the longest teeth in a descending order of length such that the shortest teeth are arranged at the outside of each set of teeth. If the teeth were not to be arranged to be of varying lengths, then they would all bunch up at the narrower end of the illustrated frusto-cone forming the first gear member 4 and thus they would not remain parallel to each other.

Figure 2 shows most clearly that the three sets 10 of gear teeth 12 are equally spaced apart from each other. Thus each set 10 of gear teeth 12 occupies one sixth of the circumference of the cone shape.

Spaces 14 between the sets 10 of gear teeth l2 also occupy one sixth of the circumference of the cone shape.

As can also be seen in Figure 2, there are nine gear teeth 12 in each set 10.

The second and third gear members 6, 8 are cogs as shown.

The first gear member 4 is secured to a first shaft 16, the second gear member 6 is secured to a second shaft 18, and the third gear member 8 is secured to a third shaft 20. The second and third shafts 18,20 are connected together such that rotation of the second shaft 18 is transferred to the first shaft 20, and such that rotation of the third shaft 20 is transferred to the second shaft 18. More specifically, the first and the second shafts 16, 18 are square in cross section and the second and third gears members 6, 8 thus rotate with the first and the second shafts 16, 18. The first shaft 16 has an idler gear 22, the second shaft 18 has a drive transfer gear 24, and the third shaft 20 has a drive transfer gear 26.The idler gear 22 and the two drive transfer gears 24, 26 are arranged in mesh as shown with the idler gear 22 positioned between the drive transfer gear 24 and the drive transfer gear 26. Thus rotation of the second shaft 18 is transferred to the third shaft 20, and rotation of the third shaft 20 is transferred to the second shaft 18. This ensures that during operation of the gear apparatus 2, the second and third gear members 6, 8 and therefore their respective second and third shafts 18,20 rotate at the same speed.

The gear apparatus 2 includes gear positioncontrol means 27 for controlling the position of the second and third gears 6, 8, along the length of the gear teeth 12 on the first gear. The gear positioncontrol means 27 comprises a control rod 28 which may be controlled by a lever operated member (not shown) The control rod 28 terminates in a flange 30. A control rod 32 extends from the flange 30 and connects via a connecting member 34 to the second gear member 6. A control rod 36 extends from the flange 30 and connects via a connecting member 38 to the third gear member 8.

Movement of the control rod 28 is thus effective to move the second and third gear members 6, 8 bachçards and forwards along the length of the gear teeth 12.

The arrangement is such that with the three sets 10 of gear teeth 12 and the second and third gear members 6,8, one of the gear members 6, 8 is always in drive engagement with the first gear member 4. As one of the gear members 6, 8 is about to disengage from the gear teeth 12, then the other gear member 6, 8 is about to engage with the gear teeth 12.

As can be seen from Figure 1, the second shaft 18 and the third shaft 20 are axially twisted.

As the second and third gear members 6, 8 are moved up and down along their respective second and third shafts 16, 18, they are kept continuously at the correct angle of engagement with the gear teeth 12 on the first gear member 4 due to this axial twisting of the second and third shafts 18, 20.

The first gear member 4 is mounted on an increased diameter portion 40 of the first shaft 16 and this increased diameter portion 40 is sandwiched between support plates 42,44. Appropriate bearings (not shown) may be employed between the ends of the increased diameter portion 40 and the support plates 42, 44 to facilitate rotation of the increased diameter portion 40 with respect to the support plates 42,44.

With such an arrangement, the first gear member 4 is axially held in position whilst being able to rotate as mentioned above. Motive power applied to the first shaft 16 causes the first gear member 4 to rotate since the first gear member 4 is secured on the first shaft 16. Rotation of the first gear member 4 is transferred to the second and third gear members 6, 8.

Since the second and third gear members 6, 8 are securely mounted on the second and third shafts 18, 20, these second and third shafts 18,20 are then caused to rotate. Rotation of the second and third shafts 18,20 will be in a geared ratio with respect to the rotation of the first shaft 16, the precise gear ratio depending upon the position of the second and third gear members 6, 8 along the length of the gear teeth 12. The gear apparatus 2 thus provides a continuously variable gearing facility without the problems of slipping belts as occurs in known continuously variable gear apparatus employing belt drive systems.

It is to be appreciated that the embodiment of the invention described above with reference to the accompanying drawings has been given by way of example only and that modifications may be effected. Thus, for example, the gear apparatus 2 could operate in the reverse way to that described above and, in this case, motive power applied to the second and third shafts 18,20 would be appropriately geared and then a geared power take-off would be available from the first shaft 16. More or less than the illustrated nine gear teeth 12 can be employed and the length of the teeth and therefore the length of the frusto- conical first gear member 4 be varied depending upon the gearing required. If desired, the first gear member 4 may have more than the illustrated three sets 10 of gear teeth 12. Further, different types of gear position-control means may be employed.

Claims

1, Gear apparatus comprising a first gear member and second and third gear members which engage with the first gear member such that rotation of the first gear member is transmitted to the second and third gear members or such that rotation of the second and third gear members is transmitted to the first gear member, the first gear member comprising sets of elongate gear teeth which define part of a cone shape, the gear teeth in each set being parallel to each other with some of the gear teeth in each set being of different lengths, the second and third gear members being connected together such that they rotate at the same speed during operation of the gear apparatus, and the second and third gear members being movable along the gear teeth in each set to vary the gear ratio between the first gear member and the second and third gear members.

2. Gear apparatus according to claim 1 in which the first gear member has three sets of the gear teeth with each set being equally spaced apart from the other sets.

3. Gear apparatus according to claim 1 or claim 2 in which the gear teeth in each set are such that the longest teeth are in the middle, and in which teeth of other lengths are symetrically arranged on either side of the longest teeth in a descending order of length such that the shortest teeth are arranged at the outside of each set of teeth.

4. Gear apparatus according to any one of the preceding claims in which there are nine teeth in each set.

5. Gear apparatus according to any one of the preceding claims in which the first gear member is a frusto-conical gear member.

6. Gear apparatus according to any one of the preceding claims in which the second and third gear members are cogs.

7. Gear apparatus according to any one of the preceding claims in which the first gear member is secured to a first shaft, in which the second gear member is secured to a second shaft, in which the third gear member is secured to a third shaft, and in which the second and third shafts are connected together such that rotation of the second shaft is transferred to the third shaft, and such that rotation of the third shaft is transferred to the second shaft.

8. Gear apparatus according to claim 7 in which the second and third shafts are axially twisted to ensure that the second and third gear members are always substantially directly aligned with the gear teeth on the first gear member.

9. Gear apparatus according to claim 7 or claim 8 in which the first shaft has an idler gear, in which the second shaft has a drive transfer gear, in which the third shaft has a drive transfer gear, and in which the idler gear and the two drive transfer gears are arranged to be in mesh such that the rotation of the second shaft is transferred to the third shaft, and such that the rotation of the third shaft is transferred to the second shaft.

10. Gear apparatus according to any one of the preceding claims and including gear position-control means for controlling the position of the second and third gears along the length of the gear teeth on the first gear member.

11. Gear apparatus substantially as herein described with reference to the accompanying drawings.

12. A road vehicle when provided with gear apparatus claimed in any one of the preceding claims.