AU603687B2 - Dog clutch - Google Patents

Description

i COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 Form COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE Short Title: Int. Cl: Application 009* o 4 44 44 or o Number: PI 2956 Lodged: 7 July 1987 Complete Specification-Lodged: Accepted: Lapsed: Published: Priority: Relatrd Art: TO BE COMPLETED t3Y APPLICANT Name of Applicant: Address of Applicant: Actual Inventor: Address for Service: FORMARK PTY. LIMITED 3-5 Seville Street, Villawood, New South Wales, 2163, Australia COLIN HICKEY GRiFFITH HACK CO.

71 YORK STREET SYDNEY NSW 2000

AUSTRALIA

Complete Specification for the invention entitled: "DOG CLUTCH" The following statement is a full description of this invention, including the best method of performing it known to me/us:- 6354A/MS SOOO 20 06/07/88 7 The present invention relates to a dog clutch which is substantially self-locking and is capable of carrying higher loads than conventional friction clutches of the same size.

By "self-locking" is meant that the clutch, once engaged, requires no applied force to keep the dogs in engagement.

The present inventioni provides a dog clutch of particularly compact dimensions, and which is self-locking by virtue of the shape of the dog teeth.

o"o' In particular- the present invention provides a dog clutch which comprises a drive input means having operaiively connected 00 .se thereto a drive dog plate; *e 0 1a5 a driven output means having operatively connected 0 0 qo q thereto a driven dog plate; disengagement means for engaging and disengaging the dog plates; 10 to o the dog plates having a series of intermeshing teeth and sockets respectiviely, each tooth having a pair of circumferentially opposed end faces which incline at an angle OL towards each other in a direction away from the root of the tooth and which each subtend an angle ,6 in the range 0.5 to 10" to a radius glancing each respective radially-inner tooth corner, and defining therebetween a pair of parallel radially-inner and radially-outer sides, and each socket being of generally complementary shape thereto; such that when the drive plate drives the driven plate each tooth bears against a respective socket and exerts substantially no net force tending to draw the dog plates towards or away from each other.

The drive input means and driven output means can be of any conventional type, such as a shaft or a toothed wheel. Generally the clutch includes one central shaft on which two dog plates are mounted concentrically.

5073S/MS -2- ,i The configuration of the clutch may be a conventional one in which the drive and driven means are disposed on either side of the dog plates. However, a particularly compact arrangement results when the driven output means is arranged around a drive input shaft and on the same side of the dog plates, the drive shaft and the drive dog plate being operatively connected via a sleeve capable of sliding axially relative to the drive shaft. In a particularly preferred embodiment the sliding sleeve slides in one direction to engage one driven output means and in the opposite direction to engage a further driven 0 output means; thereby allowing drive to be sei^-tive.y transferred to either of the outputs.

The teeth and corresponding sockets are of generally complementary shape (though not necessarily identical).

The circumferentially opposed end faces of each tooth incline upwardly from the root at an angle 0, to enable the teeth and sockets to be led into engagement. The angle may be any suitable angle which achieves this but is conveniently in the range to 2-10°, preferably 3-80 According to the invention, it has been found that if the teeth have an end face that angles outwards from the radial axis at an angle 8 then the resultant forces in the clutch system are brought in almost zero therefore balancing the system thus allowing very minimal forces to engage/disengage the clutch. The angle 3 is any suitable angle which achieves the self-locking effect in the range to 100, preferably 1 to In order to allow the clutch to be disengaged, disengagement means "re provided, such as a mechanical lever, air cylinder or hydraulic cylinder, to pull the dog plates out of engagement. It has been found that only relatively small forces are required to disengage the clutch.

Although in principle any number of dovg teeth can be provided, it has been found that three teeth are usually sufficient.

5073S/MS -3- Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings, wherein: Figure 1 is a part sectional elevation of a first embodiment; Figure 2 is a part sectional view along lines II-II; Figure 3 is a section along lines III-III; Figure 4 is a section along part of the line IV-IV; and Figure 5 is a iectional elevation of a second embodiment h<uing two outputs.

Figure 1 shows a dog clutch drive input shaft 1 keyed to an inner splined sleeve 2 on which slides an outer splined sleeve 3 welded at its forward end to a drive dog plate 4, which is engagable with a driven dog plate provided on a driven output toothed wheel 6 mounted by means of bearings 7 on the input shaft. The input shaft comes from a housing 8 (for example of an engine). An air cylinder 9 is provided for axially sliding outer sleeve 3 to (ngage and disengage the dog clutch.

Inner splined sleeve 2 is located on drive shaft 1 by means of a grub screw 10 threaded thereto and turned by passing a tool through aperture 11 in the outer splined sleeve 3. Inner sleeve 2 carries splines 12 which are in sliding engagement with splines 13 provided on outer sleeve 3.

At one end outer sleeve 3 carries drive dog plate 4, whilst at the other end it is connected by means of a circlip 14 and interference fit to outer end plate which in turn is connected by means of bearings 16 to inner end plate 17. The inner end plate is connected to ram 18 of air cylinder 9.

The output of the dog clutch is taken from a double chain drivj 19 which engages pairs of teeth 20, 21 provided on toothed wheel 6.

The configuration of the dog teeth provided on driven dog 5 can be seen more clearly from Figures 2 to 4. The 5073S/MS ,i driven plate 6 carries driven dog plate 5, which has three dog teeth 30, 31, 32 protruding therefrom. Tooth 32 is shown in more detail in Figures 3 and 4 and has circumferentially opposed end faces 40, 41 and a top face 42. As shown in Figure 2, end faces 40, 41 lie at angles B to radii from the centre of the shaft 1, and B is typically As shown in Figure 3, the end faces 40, 41 are inclined to the vertical a plane pposing through the axis of shaft 1) at an angle O which is typically degrees. Top face 42 is flat. Inner and outer sides 43, 44 are parallel to each other.

The corresponding sockets (not shown) on drive dog plate 4 are of complementary configuration and angles o<, B. As shown in Figure 2, the teeth 30, 31, 32 are of different size to the recesses cherebetween, but may be the same size if desired.

The dog clutch may be operated as follows. The dog clutch is keyed on the input shaft 1 from engine housing 8 and located by grub screw 10. The free end of air cylinder 9 is mounted on a housing (not shown). When the clutch is to be engaged, air cylinder 9 is pressurised with a light air pressure to move end plates 15, 17, outer splined sleeve 3 and to bring drive dog plate 4 into engagement with driven dog plate 5. The purpose of bearings 16 is to allow outer sleeve 3 to rotate whilst air cylinder 9 remains stationery. Engagement may take place at relatively low speeds 15 to 20 RPM) in view i of the lead-in taper Once engaged, taper B keeps thp Sdog plates into engagement. To disengage the clutch, air cylinder 9 is activated again to retract ram 18 and I disengage the dog plates.

A 3 inch clutch of the type described has been found capable of handling 7,000 Nm torque (about 670 horsepower), which is 15 to 20 times conventional loadings on a friction clutch of the same size. (To handle such loadings, a friction clutch about 26 feet in diameter would be requred.) The clutch of the present invention is thus capable of engaging and disengaging very high loads 5073S/MS whilst at the same time being extremely compact.

Typically, it finds application for mounting on trucks where it may be desirable to switch drives from a hydraulic to a diesel engine without taking up too much space. Operation is simply by means of the low pressure air cylinder.

Figure 5 shows a second embodiment wherein drive can be selectively transfered to either of two alternative i output means. The first output means is of the type shown in Figctre 1, whilst the second output means is a coaxially arranged shaft. Input shaft 51 is mounted in a housing by bearings 71 and fixed to one end thereof is an inner splined sleeve 52. An outer splined sleeve 53 is engaged therewith and may be slid to left or right by means of a yolk 72.

On one side of the outer splined sleeve 53 is provided a first drive dog plate 54 engageable with a first driven dog plate 55 provided on a toothed wheel 56 mounted in bearings 57 around the input shaft 51.

On the other side, the outer splined sleeve 53 carries a second drive dog plate 64 engageable with a second driven dog plate 65 provided on a bos 66 fixed to one end of a first output shaft 73. The first output shaft 73 is mounted in housing 70 by bearings 74 and is rotatably connected with input shaft 51 by means of jbearings 75 and 76.

K $Drive from tooth to wheel 56 is transferred via chain I 77 to cog 78 mounted on a second output shaft 79 rotatably mounted in housing 70 by means of bearings 80 and 81.

S 3C The construction of the dog plates 54, 55 and 64, is analogous to that shown in Figures 2 to 4.

The dog clutch is shown in the neutral position in Figure 5 with neither of the pairs of dogs engaged.

Operation of the yolk 72 manually or by means of an air cylinder to the right causes dog plates 54 and 55 to engage 'hereby transferring drive to the second output shaft 79. Movement to the lett engages dog plates 64 and thereby transferring drive to the first output shaft 73.

5073S/MS -6- 1 ~1

Claims (8)

1. A dog clutch which comprises a drive input means having operatively connected thereto a drive dog plate; a driven output means having operatively connected thereto a driven dog plate; disengagement means for engaging and disengaging the dog plates; the dog plates having a series of intermeshing teeth and sockets respectively, each tooth having a pair of circumferentially opposed end faces which incline at an angle d. towards each other in a direction away from the root of the tooth and which each subtend an angle B in the range 0.5 to 100 to a radius glancing each respective radially-inner tooth corner, and defining therebetween a pair of parallel radially-inner and radially-outer sides, and i each socket being of generally complementary shape 2 thereto; such that when the drive plate drives the driven plate each tooth bears against a respective socket and exerts substantially no net force tending to draw the dog plates towards or away from each other.

2. A dog clutch according to the preceding claim wherein the angle P is 1 to 8.

3. A dog clutch according to either preceding claim wherein the angle c. is 2 to 100.

4. A dog clutch according to any preceding claim having three teeth and corresponding sockets.

5. A dog clutch according to any preceding claim wherein the drive input means is a shaft and the driven output means is a wheel rotatably mounted in bearings around the 5073S/MS -7- shaft, the driven dog plate being mounted directly on the wheel, and the drive dog plate being in splined engagement with the shaft and moveable therealong to engage and disengage the dog plates.

6. A dog clutch according to claim 5 which further comprises a further drive output means in the form of a further shaft coaxial with said shaft, a further driven dog plate being mounted directly on an end of said further shaft and engageable with a further drive dog plate, the drive dog plate and said further drive dog plate being mounted on either side of a carrier, the carrier being in splined engagement with the shaft and moveable therealong by a yolk in one direction to engage the drive dog plate with the driven dog plate and in an opposite direction to engage said further drive dog plate with said further driven dog plate.

7. A dog clutch according to any preceding claim wherein the disengagement means is an air cylinder or a hydraulic cylinder.

8. A dog clutch substantially according to either embodiment described in conjunction with the drawings. DATED 24th day of May, 1988 FORMARK PTY. LIMITED By their Patent Attorneys GRIFFITH HASSEL FRAZER 5073S/MS -8-