GB2196405A - Crown wheel cam gearbox - Google Patents
Crown wheel cam gearbox Download PDFInfo
- Publication number
- GB2196405A GB2196405A GB08723046A GB8723046A GB2196405A GB 2196405 A GB2196405 A GB 2196405A GB 08723046 A GB08723046 A GB 08723046A GB 8723046 A GB8723046 A GB 8723046A GB 2196405 A GB2196405 A GB 2196405A
- Authority
- GB
- United Kingdom
- Prior art keywords
- cam
- crown wheel
- shaft
- cam profiles
- gearbox
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16H—GEARING
- F16H1/00—Toothed gearings for conveying rotary motion
- F16H1/28—Toothed gearings for conveying rotary motion with gears having orbital motion
- F16H1/32—Toothed gearings for conveying rotary motion with gears having orbital motion in which the central axis of the gearing lies inside the periphery of an orbital gear
- F16H1/321—Toothed gearings for conveying rotary motion with gears having orbital motion in which the central axis of the gearing lies inside the periphery of an orbital gear the orbital gear being nutating
Landscapes
- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Transmission Devices (AREA)
Abstract
A gearbox comprises a casing 1, a first rotatable shaft 2, a second rotatable shaft 3, a crown wheel swash plate 4 mounted on the first shaft 2 for rotation about an axis 7 angled with respect to the axis of rotation of the first shaft 2 and operatively connected to the second shaft 3. The crown wheel 4 is provided with a plurality of cam profiles 5 on one face with a first set of cam followers 13 located on the inner wall of the gearbox casing 1 and positioned to engage respective cam profiles 5 on the crown wheel. A plurality of second cam profiles 6 is provided on the second face of the crown wheel 4, and a second set of cam followers 14 is circumferentially arranged about the second shaft 3 and positioned to engage respective second cam profiles 14 on the crown 24 wheel. The numbers of first and second cam profiles is made equal in one arrangement and in another the number of cam followers on one side of the crown wheel is made one more than the number of cam profiles and the number of cam followers on the other side of the crown wheel is made one less than the number of cam profiles. <IMAGE>
Description
SPECIFICATION
A crown wheel cam gearbox
The invention relates to cam wheel reduction
gearboxes and in particular to a crown wheel
cam gearbox wherein the gearing is deter
mined by cam followers engaging cam surfaces.
UK Patent GB21 17474A describes a crown wheel cam gearbox having a crown wheel eccentrically mounted on an input drive shaft. A first set of cam profiles on one side of the cam wheel is engaged by a set of roller cam followers located in the gearbox housing and a second set of cam profiles on the other side of the crown wheel is engaged by a second set of roller cam followers located around the periphery of the output shaft of the gearbox.
The reduction gearing of this gearbox is determined by the numbers of cam profiles on the two sides of the crown wheel and the numbers of cam followers. Replacement of roller bearings or rollers requires this gearbox to be stripped down. The crown wheel of this gearbox rotates and also executes a swashplate motion. The forces exerted on the cam profiles of the crown wheel by the cam followers of the gear box influence the strength and weight requirement for the crown wheel.
The object of the present invention is to provide a crown wheel cam gearbox of improved efficiency within a particular range of gearing.
The invention provides a gearbox comprising: a gearbox casing; a first rotatable shaft; a second rotatable shaft; a crown wheel mounted on the first for rotation about an axis angled with respect to the axis of rotation of the first shaft and operatively connected to the second shaft; the crown wheel being provided with a plurality of first cam profiles on one first face thereof; a first set of cam followers circumferentially spaced and located on the inner wall of the gearbox casing and positioned to engage respective first cam profiles onrthe crown wheel; a plurality of second cam profiles provided on the second face of the crown wheel; and a second set of cam followers circumferentially arranged about the second shaft and positioned to engage respective second cam profiles on the crown wheel;
the arrangement being such that the numbers of first and second cam profiles are equal.
By this arrangement the cam profiles on the two sides of the crown wheel can be interwoven thereby minimising the weight of the crown wheel. The number of cam followers on one side of the crown wheel is made one more than the number of cam profiles and the number of cam followers on the other side of the crown wheel is made one less than the number of cam profiles. The practical of gearing is from about 3:1 up to 25:1.
The invention will now be described by way of example only with reference to the accompanying Drawings of which:
Figure 1 shows a perspective view of a prior art crown wheel cam gearbox, partly cut away;
Figure 2 is a diagrammatic exploded axial view showing a known crown wheel cam with input and output sets of cam followers; and
Figure 3 is a view of the crown wheel cam according to the present invention.
Fig. 1 shows a known reduction gearbox described in UK patent number GB21 1747A connecting an input drive shaft 2 to an output shaft 3. A crown wheel 4 is mounted on bearings on the input shaft 2 such that its axis 7 is at an angle to the rotational axis of the input shaft 2. Saw tooth cam profiles 5 and 6 are provided respectively on the input and output sides of the crown wheel 4. The cam profiles 5 are engaged by a set of tapered input rollers 13 located in the casing 18 of the gearbox and the cam profiles 6 are engaged by an output set of tapered rollers 14 located at an end 24 of the output shaft 3. As the input shaft 2 is rotated the cam wheel rotates relative to the input shaft and executes a swash plate motion.Movement of the cam wheel through the interaction of cam profiles and rollers causes the output shaft 3 to rotate with a reduction gearing dependent on the numbers of rollers 13, 14 and cam profiles 5, 6.
Fig. 2 illustrates the arrangement of the crown wheel cam 21 which rotates between the fixed set of cam followers, preferably rollers, 22 located circumferentially around the gearbox casing and the moveable set of cam followers, again preferably rollers, 23 located around an end-face of one of the drive shafts.
Where the rollers 23 are on the output shaft they may be referred to as output rollers.
Let: Nd=No. of input rollers Nr=No. of input cam profiles
Ns=No. of output cam profiles Nc=N0. of output rollers
The gear ratio (R) is given by:
For successful transmission of power there must be adequate strength in the crown wheel 21 between the input cam profiles 24 and the output cam profiles. By selecting the numbers of the input cam profiles 24 and output cam profiles 25 to be equal (i.e. Nr=Ns=N(say)) the cam profiles may be interwoven as shown in
Fig. 3. By this means the weight of the crown wheel can be reduced to a minimum. For this arrangement the number of input rollers (Nd) is one more than N and the number of output rollers (Nc) is one less than N or conversely
Nd=(N-1) and NC=(N+1).
The practical limits for Nd and Nc lead to a gear ratio between about 3 or 4:1 and 25:1.
This assumes there is at one extreme a minimum number of rollers such that at least two are in driving contact with the cam wheel at any time, and at the other extreme the maximum practicable number of rollers which can be accommodated sensibly within the gearbox, assumed to be 50. This range is to be compared with a practical gearing ratio range of 10:1 to upwards of 1175:1 for the optimised case of NC=Ns+1, Nd=Nr+1 and NC#Nd as described in GB21 17474A. Thus with the number of rollers one more than the number of adjacent cams, the number of contacting rollers and cams is maximised. In certain applications, however, where minimum crown wheel weight is important and where relatively low reduction gearing is required, the present invention is useful.
At the highest gearing limit where space does not permit 50 rollers to be used and where a lower load capacity can be tolerated then some rollers can be omitted while retaining the the same design number of cam profiles. Thus, for example, when the design number of rollers is 50 every other roller can be omitted, or if the number is divisible by 3 then one roller in every 3 can be retained and the rest discarded.
Claims (3)
1. A gearbox comprising: a gearbox casing; a first rotatable shaft; a second rotatable shaft; a crown wheel mounted on the first shaft for rotation about an axis angled with respect to the axis of rotation of the first shaft and operatively connected to the second shaft; the crown wheel being provided with a plurality of first cam profiles on one first face thereof; a first set of cam followers circumferentially spaced and located on the inner wall of the gearbox casing and positioned to engage respective first cam profiles on the crown wheel; a plurality of second cam profiles provided on the second face of the crown wheel; and a second set of cam followers circumferentially arranged about the second shaft and positioned to engage respective second cam profiles on the crown wheel;
the arrangement being such that the numbers of first and second cam profiles are equal.
2. A gearbox as claimed in claim 1 wherein the number of cam followers on one side of the crown wheel is made one more than the number of cam profiles and the number of cam followers on the other side of the crown wheel is made one less than the number of cam profiles.
3. A gearbox substantially as described and with reference to Figs. 1 to 3 of the
Drawings.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB868625045A GB8625045D0 (en) | 1986-10-20 | 1986-10-20 | Crown wheel cam gearbox |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8723046D0 GB8723046D0 (en) | 1987-11-04 |
| GB2196405A true GB2196405A (en) | 1988-04-27 |
Family
ID=10606003
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB868625045A Pending GB8625045D0 (en) | 1986-10-20 | 1986-10-20 | Crown wheel cam gearbox |
| GB08723046A Withdrawn GB2196405A (en) | 1986-10-20 | 1987-10-01 | Crown wheel cam gearbox |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB868625045A Pending GB8625045D0 (en) | 1986-10-20 | 1986-10-20 | Crown wheel cam gearbox |
Country Status (1)
| Country | Link |
|---|---|
| GB (2) | GB8625045D0 (en) |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB656683A (en) * | 1947-10-02 | 1951-08-29 | Alois Tscherne | Improvements in or relating to reduction gears |
| GB1462850A (en) * | 1972-12-27 | 1977-01-26 | Davidson R | Speed change means |
| GB2117474A (en) * | 1982-04-01 | 1983-10-12 | Secr Defence | Improvements in or relating to gear boxes |
-
1986
- 1986-10-20 GB GB868625045A patent/GB8625045D0/en active Pending
-
1987
- 1987-10-01 GB GB08723046A patent/GB2196405A/en not_active Withdrawn
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB656683A (en) * | 1947-10-02 | 1951-08-29 | Alois Tscherne | Improvements in or relating to reduction gears |
| GB1462850A (en) * | 1972-12-27 | 1977-01-26 | Davidson R | Speed change means |
| GB2117474A (en) * | 1982-04-01 | 1983-10-12 | Secr Defence | Improvements in or relating to gear boxes |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8723046D0 (en) | 1987-11-04 |
| GB8625045D0 (en) | 1986-11-26 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US10670130B2 (en) | Harmonic drive apparatus | |
| US6824495B1 (en) | Planetary gear for mounting on an electromotor | |
| EP0556587B1 (en) | Series of speed increasing and reduction gear employing an inscribed meshing type planetary gear construction | |
| US10520062B2 (en) | Cycloid speed reducer | |
| US4429595A (en) | Motion transmitting device | |
| EP0305535A1 (en) | Epicyclic reduction gear | |
| EP2381130A2 (en) | Speed change gear | |
| US6093126A (en) | Transmission device | |
| US11788606B2 (en) | Transmission mechanism | |
| EP0447866B1 (en) | High ratio planetary type traction roller transmission | |
| US5443428A (en) | Gearless mechanical transmission | |
| JP2005517139A (en) | Transmission device with groove for lubricant | |
| JP2021517222A (en) | Planetary gear transmission mechanism with one-tooth planetary gear with evolut teeth | |
| US4103513A (en) | Constant velocity universal joint | |
| US5546822A (en) | Variable speed torque multiplying transmission | |
| GB2196405A (en) | Crown wheel cam gearbox | |
| KR100505017B1 (en) | Reduction gear with high reduction ratio | |
| KR19990033596U (en) | Use deceleration machine for bearing | |
| KR100294461B1 (en) | Reduction gear consisting of planetary gear and differential gear set | |
| JPS59121238A (en) | Transmission gear for motion | |
| KR20230155234A (en) | Double teeth mating cycloid reducer | |
| JP3166057B2 (en) | Coaxial speed reducer | |
| JP2007028883A (en) | Geared motor and shaft member for the same | |
| SU1587271A1 (en) | Planetary gearing | |
| KR102373668B1 (en) | Planetary gear system for electric motor |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |