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Title:
HYPOCYCLOIDAL TRANSMISSION
Document Type and Number:
WIPO Patent Application WO/2008/046134
Kind Code:
A1
Abstract:
A hypocycloidal transmission (10) comprises a crank carrier (12) rotatable about a first axis (A1) and a crank assembly (14) supported in the crank carrier (12) and rotatable relative to the crank carrier (12) about a second axis (A2) that is parallel to and offset from the first axis (A1). The crank assembly (14) comprises a crank shaft (16) coaxial with the axis (A2), and a separate counter weight (18) releasably connected to the crank shaft (16). The counter weight (18) resides in a cavity (78) that is formed in the crank carrier (12) and opens onto an exterior surface (18) of the crank carrier (12). A chamber (162) is formed between a crank housing (146) and the crank carrier (12). A lubricating system provides lubricant to the chamber (162) that is able to subsequently pass through a passageway (200) formed in the crank shaft as well as bearing assemblies acting between the crank shaft (16), crank carrier (12) and crank housing (146).

Inventors:
CLARKE JOHN PATRICK (AU)
COCLIFF NIGEL DENE (AU)
Application Number:
PCT/AU2007/001565
Publication Date:
April 24, 2008
Filing Date:
October 16, 2007
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
WINTECH INTERNAT PTY LTD (AU)
CLARKE JOHN PATRICK (AU)
COCLIFF NIGEL DENE (AU)
International Classes:
F16H21/18; F01B9/02; F16H21/36
Domestic Patent References:
WO1995012076A11995-05-04
Foreign References:
US3744342A1973-07-10
US5158046A1992-10-27
US5067456A1991-11-26
US1056746A1913-03-18
US4237741A1980-12-09
US5943987A1999-08-31
US6012423A2000-01-11
DE3636873A11988-05-11
US3791227A1974-02-12
DE4142385A11993-06-24
Attorney, Agent or Firm:
GRIFFITH HACK (109 St Georges TcePerth, WA 6000, AU)
Download PDF:
Claims:

Claims

1. A hypocycloidal transmission comprising: a crank carrier rotatable about first axis; and, a crank assembly supported in the crank carrier and rotatable relative to the crank carrier about a second axis parallel to and laterally offset from the first axis, the crank assembly comprising a crank shaft through which the second axis co-axially passes and a separate counter weight releasably connectable to the crank shaft.

2. The hypocycloidal transmission according to claim 1 wherein the counter weight comprises a hole through which the crank shaft passes when the crank assembly is supported in the crank carrier.

3. The hypocycloidal transmission according to claim 2 wherein the crank carrier is provided with a cavity opening onto an exterior surface of the crank carrier and in which the counter weight is disposed, the cavity comprising first and second walls spaced along the second axis between which the counter weight passes when rotated about the second axis .

4. The hypocycloidal transmission according to claim 3 wherein the crank shaft comprises a tail portion coaxial with the second axis and located inside the crank carrier; and, a crank pin at an end distant the tail and laterally offset from the second axis.

5. The hypocycloidal transmission according to claim 4 wherein the crank assembly comprises a first bearing assembly fitted on the tail portion, the first bearing assembly being seated in a portion of the crank carrier that opens onto the cavity.

6. The hypocycloidal transmission according to claim 5 wherein the crank assembly comprises second bearing assembly fitted on the crank pin and located outside of the crank carrier.

7. The hypocycloidal transmission according to claim 6 wherein the crank assembly comprises a third bearing assembly fitted on the crank shaft intermediate the first and second bearing assemblies and seated in a bore formed in the crank carrier.

8. The hypocycloidal transmission according to claim 6 or 7 further comprising a con-rod rotatably coupled to the second bearing assembly.

9. The hypocycloidal transmission according to any one of claims 1 - 8 further comprising a crank housing that rotatably supports the crank carrier to rotate about the first axis, wherein a first chamber is formed between the crank housing and the crank carrier, and wherein one or more holes are formed in the crank housing that provide fluid communication with the first region.

10. The hypocycloidal transmission according to claim 9 further comprising a lubrication system that supplies lubricant to the first region through one or more of the holes formed in the crank housing.

11. The hypocycloidal transmission according to claim 10 wherein the lubrication system comprises a pump that delivers lubricant to the first chamber through the one or more holes formed in the crank housing.

12. The hypocycloidal transmission according to claim 10 or 11 wherein the lubrication system comprises a passage formed in the crank shaft, the passage having one end that

opens onto the tail portion and an opposite second end that opens onto the crank pin.

13. The hypocycloidal transmission according to claim 12 wherein the lubrication system further comprises a first flow path formed in the first bearing assembly through which lubricant can flow from the first chamber to first end of the page passage.

14. The hypocycloidal transmission according to claim 12 or 13 wherein the lubrication system further comprises a second flow path formed in the second bearing assembly through which lubricant can flow from the second end of the passage to the con-rod.

15. The hypocycloidal transmission according to any one of claims 11 - 14 wherein the lubrication system further comprises a third flow path formed in the third bearing assembly through which lubricant from the first chamber can flow.

16. The hypocycloidal transmission according to any one of claims 11 - 15 wherein the lubrication system further comprises one or more grooves formed along the con-rod.

17. The hypocycloidal transmission according to any one of claims 11 - 16 wherein the lubrication system further comprises one or more lubricant return galleries formed in the crank housing through which lubricant drains from the crank housing.

18. The hypocycloidal transmission according to any one of claims 11 - 17 further comprising a fourth bearing assembly seated in the crank housing and through which a portion of the crank carrier extends, the fourth bearing assembly separating the first chamber from the or each of the return galleries, and wherein the lubrication system

comprises a fourth flow path formed in the fourth bearing assembly through which lubricant can flow from the first chamber to the return galleries.

19. The hypocycloidal transmission according to any one of claims 11 - 18 further comprising one or more flow restrictors adjacent selected bearing assemblies to restrict flow of lubricant through the selected bearing assemblies whereby lubricant preferentially flows through the passage in the crank shaft.

20. The hypocycloidal transmission according to claim 19 wherein the one or more flow restrictors comprises a first flow restrictor on a side of the fourth bearing assembly adjacent the return galleries to restrict flow from the first chamber to the return galleries.

21. The hypocycloidal transmission according to claim 19 or 20 wherein the one or more flow restrictors comprises a second flow restrictor on a side of the third bearing assembly facing the first chamber to allow restricted flow of lubricant through the third bearing assembly.

22. The hypocycloidal transmission according to any one of claims 11 - 21 wherein the crank housing further comprises a second chamber in which the con-rod reciprocates, the second chamber provided with an opening through which con-rod or a device attached to the con-rod can reciprocate and wherein lubricant passing through the third bearing assembly can flow into the second chamber.

23. The hypocycloidal transmission according to any one of claims 11 - 22 further comprising the hypocycloidal transmission system further comprises a fifth bearing assembly mounted on an exterior surface of the crank carrier and seated inside the crank housing at a location in fluid communication with the first chamber wherein the

lubrication system comprises a fifth flow path formed in the fifth bearing assembly whereby lubricant can flow through the fifth bearing assembly from the first chamber into the second chamber.

24. The hypocycloidal transmission according to claim 23 wherein the lubrication system comprises a third flow restrictor on a side of the fifth bearing assembly facing the first chamber to restrict the flow of lubricant from the first chamber through the fifth bearing assembly into the second chamber.

25. The hypocycloidal transmission according to any one of claims 1 - 10 further comprising a lubrication system that generates a lubricant mist to facilitate lubrication of the crank carrier and the crank assembly.

26. The hypocycloidal transmission according to claim 25 wherein the lubrication system comprises a casing in which the crank carrier and crank assembly are located, a volume of liquid lubricant held within the casing, and a thrower attached to the crank carrier that cyclically passes through the volume of liquid lubricant as the crank carrier rotates to thereby generate the lubricant mist.

27. The hypocycloidal transmission according to any one of claims 1 - 24 wherein the crank assembly has a weight of 56Og ± 2Og.

28. The hypocycloidal transmission according to any one of claims 1 - 24 and 27 wherein the crank carrier has a weight of 933g ± 2Og.

29. A method of manufacturing a hypocycloidal transmission comprising: providing a crank carrier having a first axis that extends centrally and longitudinally through the carrier;

forming a bore in the crank carrier along a second axis parallel to and offset from the first axis; forming a cavity in the crank carrier that opens onto an exterior surface of the crank carrier and extends radially to the bore,- providing a crank assembly having a crank shaft and a counter weight where the counter weight is provided with an axial through hole; placing the counter weight in the cavity; and, coupling the crank shaft to the counter weight by inserting the crank shaft into the bore and through the axial through hole in the counter weight.

30. A method of operating a hypocycloidal transmission system having a crank carrier rotatable about a first axis, and a crank assembly supported in the crank carrier and rotatable relative to the crank carrier about a second axis parallel to and laterally offset from the first axis, the method comprising rotating the crank carrier about the first axis at a speed of between 60 - 100 revolutions per second.

31. A method of cutting a foam material comprising: providing an elongated flexible cutting blade having first and second ends; providing first and second hypocycloidal transmissions each transmission having a rotary power input and a reciprocating power take off; connecting the first and second ends of the blade to the reciprocating power take off of respective hypocycloidal transmissions; and, applying torque to the rotary power input of each hypocycloidal drive at a speed to cause the blade to reciprocate at a speed of between 60 - 100Hz.

32. The method according to claim 31 wherein each of the first and second hypocycloidal transmission is constructed in accordance with any one of claims 1 - 28.

Description:

HYPOCYCLOIDAL TRANSMISSION

Field of the Invention

The present invention relates to a hypocycloidal transmission, and in particular, but not exclusively, to a hypocycloidal transmission for reciprocating elongated blades in foam cutting machines .

Background of the Invention

It is known to cut foam materials such as, but not limited to, polyurethane, expanded polystyrene foam, PVC, EVA, rock wool, and phenolic using an oscillating or reciprocating blade. The blade may have a typical length of two to four metres and is held at opposite ends by respective reciprocating pistons. The pistons are driven by electric motors via a hypocycloidal transmission which converts the rotary drive of electric motors to a linear drive. An example of such an oscillating cutter is described in Applicant's international publication no. WO 94/02276.

In this except where the context requires otherwise due to express language or necessary implication, the words "comprise" or variations such as "comprises" or "comprising" are used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country.

Summary of the Invention

One aspect of the present invention provides a hypocycloidal transmission comprising: a crank carrier rotatable about first axis; and, a crank assembly supported in the crank carrier and rotatable relative to the crank carrier about a second axis parallel to and laterally offset from the first axis, the crank assembly comprising a crank shaft through which the second axis co-axially passes and a separate counter weight releasably connectable to the crank shaft.

The counter weight may comprise a hole through which the crank shaft passes when the crank assembly is supported in the crank carrier.

The crank carrier is provided with a cavity opening onto an exterior surface of the crank carrier and in which the counter weight is disposed, the cavity comprising first and second walls spaced along the second axis between which the counter weight passes when rotated about the second axis.

The crank shaft may comprise: a tail portion coaxial with the second axis and located inside the crank carrier; and, a crank pin at an end distant the tail and laterally offset from the second axis.

The crank assembly may further comprise a first bearing assembly fitted on the tail portion, the first bearing assembly being seated in a portion of the crank carrier that opens onto the cavity.

The crank assembly may further comprise a second bearing assembly fitted on the crank pin and located outside of

the crank carrier. The crank assembly may further comprise a third bearing assembly fitted on the crank shaft intermediate the first and second bearing assemblies and seated in a bore formed in the crank carrier.

The hypocycloidal transmission may further comprise a con- rod rotatably coupled to the second bearing assembly.

In one embodiment the crank carrier comprises an internal passageway providing fluid communication between first and second spaced apart holes that open onto the exterior surface of the crank carrier. A valve may be provided in the first hole to selectively open and close the first hole. In one embodiment the valve comprises a valve seat formed about a wall of the first hole and a stop that is displaced from the seat when the crank carrier is rotating about the first axis.

The crank carrier may also comprise a void or chamber that. is in fluid communication with the first hole and the passageway. The void or chamber is located eccentrically of the first axis.

In one embodiment the passageway extends generally diagonally relative to the first axis. Moreover the passageway has one end that opens onto the void and a distant second end, wherein the one end is radially spaced from the first axis by a distance greater than the second end. The second end may be coincident with the second hole. Further, the second end may lie on the first axis.

The hypocycloidal transmission system may further comprise a crank housing that rotatably supports the crank carrier to rotate about the first axis, wherein a first chamber is formed between the crank housing and the crank carrier, and wherein one or more holes are formed in the crank

housing that provide fluid communication with the first region. c

A lubrication system is provided that supplies lubricant to the first region through one or more of the holes formed in the crank housing.

In one embodiment the lubrication system comprises a pump that delivers lubricant to the first chamber through the one or more holes formed in the crank housing. In this embodiment the lubrication system comprises a passage formed in the crank shaft, the passage having one end that opens onto the tail portion and an opposite second end that opens onto the crank pin. The lubrication system further comprises a first flow path formed in the first bearing assembly through which lubricant can flow from the first chamber to first end of the page passage. The lubrication system further comprises a second flow path formed in the second bearing assembly through which lubricant can flow from the second end of the passage to the con-rod. The lubrication system further comprises a third flow path formed in the third bearing assembly through which lubricant from the first chamber can flow. The lubrication system further comprises one or more grooves formed along the con-rod. The lubrication system further comprises one or more lubricant return galleries formed in the crank housing through which lubricant drains from the crank housing. The hypocycloidal transmission system further comprises a fourth bearing assembly seated in the crank housing and through which a portion of the crank carrier extends, the fourth bearing assembly separating the first chamber from the or each of the return galleries, and wherein the lubrication system comprises a fourth flow path formed in the fourth bearing assembly through which lubricant can flow from the first chamber to the return galleries.

The lubrication system may further comprise a first flow restrictor on a side of the fourth bearing assembly adjacent the return galleries to restrict flow from the first chamber to the return galleries. The lubrication system may further comprise a second flow restrictor on a side of the third bearing assembly facing the first chamber to allow restricted flow of lubricant through the third bearing assembly.

The crank housing further comprises a second chamber in which the con-rod reciprocates, the second chamber provided with an opening through which con-rod or a device attached to the con-rod can reciprocate and wherein lubricant passing through the third bearing assembly can flow into the second chamber.

The hypocycloidal transmission system further comprises a fifth bearing assembly mounted on an exterior surface of the crank carrier and seated inside the crank housing at a location in fluid communication with the first chamber wherein the lubrication system comprises a fifth flow path formed in the fifth bearing assembly whereby lubricant can flow through the fifth bearing assembly from the first chamber into the second chamber.

The lubrication system may further comprise a third flow restrictor on a side of the fifth bearing assembly facing the first chamber to restrict the flow of lubricant from the first chamber through the fifth bearing assembly into the second chamber.

However in an alternate embodiment the hypocycloidal transmission system may comprise a lubrication system that generates a lubricant mist to facilitate lubrication of the crank carrier and the crank assembly. In this embodiment the lubrication system comprises a casing in which the crank carrier and crank assembly are located, a

volume of liquid lubricant held within the casing, and a thrower attached to the crank carrier that cyclically passes through the volume of liquid lubricant as the crank carrier rotates to thereby generate the lubricant mist. In this embodiment the first hole is located inside the casing and the second hole may be located outside the casing. Moreover in this embodiment the crank housing is coupled to the casing and the first chamber is located inside the casing. The crank housing further defines a second region outside the casing, wherein the first hole is inside the casing and the second hole opens into the second region. This enables the passageway and valve to act as a restricted breather allowing air to be vented from the casing while maintaining a positive pressure in the casing relative to atmospheric pressure. Further, the void acts as a centrifugal separator separating any lubricant mist within the void into an air fraction and a liquid lubricant fraction.

The crank housing may comprise one or more lubricant collection regions on its outer surface on which lubricant mist collects and agglomerates to reconstitute the liquid lubricant, wherein the one or more holes in the crank housing extend from each collection region to the first region whereby agglomerated liquid lubricant can flow into the crank housing.

In one embodiment, the crank assembly may have a weight of between 50Og to 55Og. In a further embodiment the crank assembly may have a weight of between 525g and 53Og.

Further, the crank carrier may have a weight in the order of 86Og to 88Og and more preferably a weight of between 872g and 874g.

A further aspect of the invention provides a method of manufacturing a hypocycloidal transmission comprising:

providing a crank carrier having a first axis that extends centrally and longitudinally through the carrier; forming a bore in the crank carrier along a second axis parallel to and offset from the first axis; forming a cavity in the crank carrier that opens onto an exterior surface of the crank carrier and extends radially to the bore; providing a crank assembly having a crank shaft and a counter weight where the counter weight is provided with an axial through hole; placing the counter weight in the cavity; and, coupling the crank shaft to the counter weight by inserting the crank shaft into the bore and through the axial through hole in the counter weight.

A further aspect of the invention provides a method of operating a hypocycloidal transmission system having a crank carrier rotatable about a first axis, and a crank assembly supported in the crank carrier and rotatable relative to the crank carrier about a second axis parallel to and laterally offset from the first axis, the method comprising rotating the crank carrier about the first axis at a speed of between 60 - 100 revolutions per second. There a 1:1 relationship between motor R. P.M. and piston speed, i.e. 60 rev/sec = 60 Hz.

According to a further aspect of the invention there is provided a method of cutting a foam material comprising: providing an elongated flexible cutting blade having first and second ends,- providing first and second hypocycloidal transmissions each transmission having a rotary power input and a reciprocating power take off; connecting the first and second ends of the blade to the reciprocating power take off of respective hypocycloidal transmissions; and,

applying torque to the rotary power input of each hypocycloidal drive at a speed to cause the blade to reciprocate at a speed of between 60 - 100Hz.

Brief Description of the Drawings

A embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings in which:

Figure 1 is an exploded view of a crank assembly incorporated in an embodiment of the hypocycloidal transmission; Figure 2 is a perspective view of a crank carrier incorporated in the hypocycloidal transmission; Figure 3 is an exploded assembly diagram of the crank assembly and crank carrier shown in Figures 1 and 2; Figure 4 is a partially exploded assembly diagram of a crank housing incorporated in the hypocycloidal transmission together with the crank assembly and crank carrier;

Figure 5 is a section view of the crank carrier; Figure 6 is a section view of a fully assembled hypocycloidal transmission system;

Figure 7 is a section view of a second embodiment of the hypocycloidal transmission;

Figure 8 is a isometric view of a crank carrier incorporated in the second embodiment of the hypocycloidal drive shown in Figure 7;

Figure 9 is a front elevation view of the crank carrier shown in Figure 8 ;

Figure 10 is a view of section AA of the crank carrier depicted in Figure 9; Figure 11 is a perspective view of the second embodiment of the transmission installed in a corresponding crank housing with a cover plate to the housing removed and a

- S - con-rod of the transmission reciprocating in a vertical plane;

Figure 12 is a plan view of the ensemble shown in Figure 11 but with the transmission orientated so that the con- rod reciprocates in a horizontal plane and extends to the left of the crank housing;

Figure 13 is a plan view of the ensemble shown in Figure 11 but with the transmission orientated so that the con- rod reciprocates in a horizontal plane and extends to the right of the crank housing;

Figure 14 is a top elevation of a fully assembled hypocycloidal transmission system incorporating the second embodiment of the transmission depicted in Figures 7 - 13; Figure 15 is a view of section X-X of the system shown in Figure 14 with a cover plate of the crank housing removed; and,

Figure 16 is a view of section X-X of the system shown in Figure 14 with a cover plate of the crank housing attached.

Detailed Description of Preferred Embodiments

Referring to the accompanying drawings, and in particular to Figure 3, an embodiment of the hypocycloidal transmission 10 comprises a crank carrier 12 rotatable about a first axis Al and a crank assembly 14 supported in the crank carrier 12 and rotatable relative to the crank carrier 12 about a second axis A2 that is parallel to and laterally offset from the first axis Al. The crank assembly 14 comprises a crank shaft 16, through which the axis A2 co-axially passes, and a separate counter weight 18 releasably connectable to the crank shaft 16. The counter weight 18 is formed with a hole 20 through which the crank shaft 16 passes when the crank assembly 14 is supported in the crank carrier 12. The hole 20 is further formed with a axially extending key way 22. A lobe 24 in

the general shape of a half annulus is formed to one side of the counter weight 18. A grub screw 26 passes through a radial hole 28 formed in the lobe 24 for engaging the crank shaft 16.

With particular reference to Figure 1, the crank assembly 14 further comprises a crank pin 30 that extends parallel with the crank shaft 16 but is off set from the axis A2. Mounted on the crank pin 30 is an inner washer 32, an inner race 34, an outer washer 38 and a circlip 40. As will be explained in greater detail below, in the fully assembled transmission, a con-rod is mounted on the crank pin 30. The circlip 40 seats in a groove 42 (shown in Figure 4) formed circumferentially about, and near a free end of, the crank pin 30.

The crank pin 30 extends from an integrated balance weight 44 which is in the general configuration of a semicircular disc. The crank shaft 16 extends from a side of the balance weight 44 opposite the crank pin 30 and is formed as three contiguous sections 46, 48 and 50 which are mutually coaxial and have a stepped reduction in outer diameter, with the section 46 having the largest outer diameter and section 50 having the smallest outer diameter. A longitudinal slot 52 is formed in the middle section 48 for seating a corresponding key 54. A roller bearing 56 and a single row ball bearing 58 are press fit onto the section 46 of the crank shaft 16.

A pinion gear 60 having a longitudinal key way 62 cut in its inner circumferential surface is press fit onto the section 48 with the key 54 in alignment with the key way 62. An inner race 64 is subsequently pressed onto the section 50 of the crank shaft 16.

With particular reference to Figures 2 and 5, the crank carrier 12 has a body comprising contiguous first, second

and third portions 66, 68 and 70, each coaxial with the axis Al. The first portion 66 has the greatest outer diameter with the third portion 70 having the smallest outer diameter. The second portion 68 includes a transition zone 72 of progressively decreasing diameter which adjoins the third portion 70.

A bore 74 is formed in the crank carrier 12 along the axis A2 extending from a front face 76 and into the second portion 68. A cavity 78 is formed in the crank carrier 12 and more particularly in the second portion 68. The cavity 78 opens onto an exterior surface 80 of the crank carrier 12. The cavity 78 comprises first and second walls 82 and 84 that are spaced apart along and extend transversely to the second axis A2. The cavity 78 divides the bore 74 into a first part 86 which is in the first portion 66, and a second part 88 that is in the second portion 68.

As shown in Figure 5, the crank carrier 12 also comprises an internal passageway 90 that provides fluid communication between first and second spaced apart holes 92 and 94 that open onto the exterior surface 80 of the crank carrier 12. The hole 92 extends in a radial direction through the first portion 66 while the second hole 94 is formed on a radial face of the third portion 70 and coaxial with the axis Al.

A void or chamber 96 is also formed in the first portion 66 of the crank carrier 12 from the front face 76. The void or chamber 96 is located eccentrically of the axis Al and is in fluid communication with both the first hole 92 and the passageway 90.

It will be seen that the passageway 90 extends in a generally diagonal manner relative to the axis Al, with one end 98 of the passageway 90 opening into the void 96

and an opposite second end 99 of the passageway 90 being coincident with the second hole 94. The end 98 is radially spaced from axis Al by a distance greater than the second end 99. In order to meet dimensional constraints the passageway 90 is formed as two contiguous straight sections but of different slope.

The first hole 92 is selectively opened and closed by a valve which comprises a valve seat 102 and a stop in the form of a ball 104. The seat 102 is formed about a wall of the first hole 92. When the crank carrier 12 is rotated about its axis A2, centrifugal force forces the ball 104 radially outward and off of the seat 102 thereby opening the valve. The ball 104 is retained by a pin 106 (see Figure 3) that is press fit into a hole 108 formed in a crank carrier balance weight 110 at a location in radial alignment with and spaced a small distance from the ball 104. Thus when the crank carrier 12 is rotated about its axis Al, the centrifugal force forces the ball 104 off the seat 102 and into abutment with the pin 106.

A first lubricant hole 112 is formed in the first portion 66 and leads into the first part 86 of the bore 74. A second lubricant hole 114 is formed through the transition section 72 of the second portion 68 leading into the second part 88 of the bore 74. Formed circumferentially about the first portion 66 is a bearing seat 116. The seat 116 is bound at a forward end by a circumferential ridge 118 and at a rear end by a circumferential groove 120.

A lower portion of the front face 76 which includes the void 96 is rebated and formed with two axially extending threaded blind holes 122 equally spaced on opposite sides of the void 96.

Referred to Figure 3, when assembling the transmission 10 the counter weight 18 is first dropped into the cavity 68 between the walls 82 and 84 with its lobe 24 and keyway 22 lower most. The crank shaft 16 with the fitted bearings 56 and 58 and pinion gear 60 is inserted into the bore 74 and through the hole 20 in the counter weight 18 with the key 54 mating with the keyway 22. By rotating the crank shaft 16 about axis A2 the counter weight 18 is rotated so that the hole 28 is now accessible and the grub screw 26 can be screwed into the hole 28 to lock the counter weight 18 onto the crank shaft 16.

A bearing outer race 124 in which is located a plurality of rollers 126 is press fit into the second part 88 of bore 74. When the crank assembly 12 is inserted into the bore 74, the inner race 64 is located inside the outer race 124 and rollers 126 to create a roller bearing assembly. Staying with Figure 3, single row ball bearing 128 assembly is pushed onto the seat 116 against the ridge 118. The ball bearing 128 is held in place by a circlip 130 that is seated in the groove 120. A dynamic weight 132 is fixed to the third portion 70 of the crank carrier 12 by three bolts 134. The dynamic weight 132 is formed with a central hole 136 that is in registration with the hole 94. Three pins 138 extend rearwardly of the dynamic weight 132 and form part of a limited slip clutch 133 (see Figure 6) through which torque from an electric motor 135 is transmitted about axis Al to the crank carrier 12.

At the opposite end of the carrier 12 the crank carrier balance weight 110 is attached to the front face 76 by bolts 140 that threadingly engage the holes 122. A thrower arm 142 is press fit into a hole 144 from a back face of the balance weight 110 and, as described in greater detail below, acts to provide lubricant to the moving parts of the transmission 10.

Referring to Figures 4 and 6, the transmission system 10 further comprises a crank housing 146 and a casing 148. The crank housing 146 comprises a tubular portion 150 and a outer radially extending flange 152. The tubular portion 150 has an internal circumferential seat 154 in which is located a ring gear 156. The ring gear 156 is retained within the crank housing 146 by a plurality of grub screws (not shown) that are screwed into radially extending holes 158 formed about the tubular portion 150 and have an inner end that can seat in a circumferential groove 160 formed about an outer surface of the ring gear 156. The use of the grub screws allows for fine adjustment of the alignment of the ring gear 156 with the axis Al .

Two lubricant collection regions or lands 157 (only one shown) are formed on the outer surface of the tubular portion 150. The regions 157 are spaced by 90° about the - portion 150 to facilitate different gear box configurations or orientations. A lubricant feed hole 159 passes from the region 157 to the interior of the portion 150.

The crank housing 146 is attached to the casing 148 by a plurality of bolts or screws (not shown) that pass through holes formed in the flange 152 and engage corresponding threaded holes formed in the casing 148. As shown in Figure 6, the crank housing 146 is orientated so that the tubular portion 150 is located in the interior of the casing 148. It will be further apparent from Figure 6 that the crank housing 146 defines a first chamber 162 that is located within the casing 148 and a region 164 located on the outside of the casing 148. The chamber and region 162 and 164 are separated by a radial wall 166 that seats a bearing assembly 168 which supports the crank carrier 12 and in particular the third portion 70 of the crank carrier 12.

During the assembly process, the crank assembly 14 is first loaded into the crank carrier 12 and then the crank carrier 12 without the dynamic weight 132 is inserted into the crank housing 146 so that the pinion gear 60 meshes with the ring gear 156 and the third portion 70 of the crank carrier 12 is received in the inner race of the bearing assembly 168. The dynamic weight 132 is then attached with an intervening lip seal 170 (see Figure 4) to the radial face of the third portion 70 on a side of the radial wall 166 interior of the second region 164.

The circlip 40 is removed from the crank pin 30 along with the outer washer 38. A con-rod 172 (see Figures 4 and 6) is coupled to the crank pin 30. The con-rod 172 is provided with a bearing 174 at one end that is seated on the inner race 34. The outer washer 38 is then placed on the crank pin 30 and finally the circlip 40 reseated in the groove 42 thereby retaining the con-rod 172 on the crank pin 30.

The hypocycloidal transmission 10 includes a lubrication system which generates a lubricant mist for lubricating the crank assembly 14 and crank carrier 12. The lubrication system comprises the casing 148, a volume of lubricant liquid such as oil held within the casing 148, and the thrower 142. As the crank carrier 12 is rotated by the electric motor 135 the thrower 142 cyclically passes through the oil within the casing 148 throwing or splashing lubricant within the casing 148 and also generating a lubricant mist.

The generation of the lubricant mist is due in part to the pressurising of the interior of the casing 148. Typically the interior of the casing 148 is at a pressure of approximately 6 atmospheres . Splashed lubricant landing on the region or land 157 is able to flow into the first

chamber 162 of the crank housing to lubricate the crank assembly 14 and crank carrier 12. Lubricant holes 112 and 114 on the crank carrier 12 further assist in allowing passage of lubricant and lubricant mist through the main parts of the transmission 10.

It will be noted that the hole 94 of the passage 90 opens into the region 164 of the crank housing and is therefore outside of the casing 148. This region is not pressurised but rather is at atmospheric pressure. When the transmission 10 is in use, and the crank carrier 12 rotating about axis Al, centrifugal force causes the ball 104 to move in a radial outward direction and thus off the valve seat 102 thereby allowing fluid communication between the interior of the casing 148 and the exterior of the casing via the hole 92, void 96, passageway 90 and hole 94. This entire path acts as a restricted breather which while allowing fluid communication between the interior and exterior of the casing 148 substantially maintains a pressure differential of 6 atmospheres.

Lubricant that enters through the hole 92 into the void 96 is separated by centrifugal forces. That is, the void 92 acts as a centrifugal separator separating the contents of the void into an air fraction and liquid fraction. The air fraction is able to pass through the passage 90 and out of hole 94. The liquid fraction which comprises lubricant is held on the radial outer side of the walls forming the void 96 and the passageway 90 and drips back into the casing 148 when the motor 135 is turned OFF.

The third portion 70 of the crank carrier 12 acts as a rotary power input, receiving torque from the electric motor 135. The crank pin 30 to which the con-rod 172 is coupled acts a linear power take off. In this regard the crank pin 30 reciprocates in a plane containing the axes

Al and A2. The con-rod 172 reciprocates a piston 180 held within a cylinder 182. Attached to the piston 180 is an

elongated blade 184 of a foam cutting machine. The construction of the piston 180, cylinder 182 and blade 184 are of no significance to the embodiments of the present invention. Further details of these aspects of a foam cutting machine may be derived from the above referenced publication no. WO 94/02276 the contents of which are incorporated herein by way of reference.

A transmission 10 constructed in accordance with the above described embodiment is able to reliably operate at a frequency of between 60 - 100 Hz (i.e. the crank pin 30 is reciprocated between 60 - 100 times/second) . This provides a significant speed advantage over prior art, hypocycloidal transmission which typically operate at speeds of up to 50Hz.

During construction of the transmission 10 the crank shaft assembly 14 and the crank carrier 12 are "balanced by design". That is, each of the components of the crank carrier 12 and the crank assembly 14 are designed and manufactured to have a specific weight and during the construction phase, each of the components are weighed to ensure they lie within a designated weight range. For example, with reference to the crank assembly 14, the crank shaft 16 is designed to have a weight of 298g -

302g, the outer washer 38 8.0g - 8.2g, the counter weight 18 40.5g - 41.2g, the pinion gear 60 46.5g - 46.9g, and the washer 32 3.5g - 3.8g with the weight of the overall assembly 14 shown in Figure 1 being between 525g - 53Og. The crank carrier 12 is to have a weight of between 872g - 875g but more preferably 873.5g - 874.Og. Further, the overall crank carrier assembly shown in Figure 3 is to have a weight of between 2,08Og - 2,10Og, and more preferably between 2,086g - 2,103g.

A second embodiment of the hypocycloidal transmission 1OA is depicted in Figures 7 - 16. In order to avoid

repetition and for ease of reference, components and features of the transmission 1OA have similar functionality of those identified in Figures 1 - 6 directed to the first embodiment of the hypocycloidal transmission 10 are designated with the same reference number but with the addition of the letter "A" , for example crank carrier 12A and crank housing 146A.

In broad terms, the construction and operation of the transmission 1OA are the same as the transmission 10 with the exception of the lubrication system, although there are several other differences which are explained later in this specification. In the transmission 1OA, lubrication is achieved by the use of an additional oil pump (not shown) and the provision of lubricant paths and galleries throughout the transmission 1OA to allow oil pumped from the oil pump by lubricate all moving parts.

Looking at the modifications required to each of the main components individually, the transmission 1OA does not require the thrower arm 142 of the transmission 10. Further, the crank carrier 12A does not include the passageway 90, hole 92, hole 94, chamber 96, and lubrication holes 112 and 114 of the crank carrier 12 depicted in Figure 5. In most other respects, the structure and operation of the crank carrier 12A is the same as crank carrier 12. In particular, the crank carrier 12A includes: a bore 74A, having the first part 86A and the second part 88A; and, a cavity 78A formed between walls 82A and 84A and defining a space for receiving counter weight 18A.

The crank shaft 16A (see Figure 7) differs from the crank shaft 16 by the inclusion of a passageway 200 which extends from the tail portion 5OA of the crank shaft 16A through to the crank pin 3OA. The passage 200 comprises a first length 202 that extends along the axis A2 and opens

at one end onto the tail portion 5OA. A second length 204 of the passage 200 extends diagonally from the length 202 opening onto a circumferential surface of the crank pin 3OA. A circumferential groove 206 is formed on an inner circumferential surface of the inner race 34A seated on the crank pin 3OA. The groove 206 is located above and in fluid communication with the end of the passageway 200 opening onto the crank pin 3OA. One or more flow paths such as radial holes (not shown) are formed through the bearing assembly 34A/174A which communicate with the groove 206.

The crank housing 146A differs from the housing 146 by the inclusion of lubricant inlet galleries 208 (only one shown) and a plurality of return galleries 210. The inlet galleries 208 are drilled diagonally through the crank housing 146A to supply lubricant such as oil pumped by a pump to the first chamber region 162A within the housing 146A. A further point of differentiation in the housing 146A reside in the reconfiguration of the tubular portion 150 to include an increased diameter circumferentially extending wall or collar 222 (see Figure 11) which is discussed in greater detail later.

The con-rod 172A of the transmission 1OA differs from the con-rod 172 by the inclusion of longitudinal channels 212 on opposite sides that are in fluid communication with the bearing 174A seated on the race 3OA.

Finally, the transmission 1OA differs from the transmission 10 by the inclusion of a plurality of restrictor plates adjacent various bearing assemblies. In particular, a restrictor plate 214 is placed adjacent the bearing assembly 168A on a side outside of the chamber 162A; a restrictor plate 216 is placed adjacent bearing assembly 128A inside the region 162A; and a restrictor

plate 218 is placed adjacent the bearing assembly 58A inside the region 162A.

Typically the restrictor plates 214, 216 and 218 are formed of spring steel of a thickness of between 0.3 - 0.5mm. The purpose of the restrictor plates is to restrict the flow of oil through the bearings so that oil is preferentially forced through the crank shaft 16A and into the crank pin bearing 174A. The restrictor plates do not prohibit oil from passing through the bearings 168A, 128A and 58A but simply provide increased flow resistance so that oil preferentially flows through the passageway 200.

In order to lubricate the transmission 1OA, oil is initially pumped through the inlet gallery 208 into the first chamber 162A. A portion of the oil flows through the bearing assembly 168A past the restrictor plate 214 and through the return galleries 210 to a lubricant sump, typically formed by the crank casing 148A. Seal 170A prevents oil from flowing past the portion of the crank carrier 12A to which the dynamic weight 132A is attached. Oil also flows through the bearing assembly 124A, the passage 200 and into the crank pin bearing assembly 174A. A volume of the oil flowing through the bearing assembly 174A also flows along the grooves 212 on the con-rod 172A. In addition, oil within the region 162A flows past the restrictor plates 216 and 218 through the bearing assemblies 128A, and 58A respectively. Oil passing through bearing assembly 58A is subsequently able to flow through adjacent bearing assembly 56A. In this regard each of the bearing assemblies 34A/174A; 56A; 58A; 128A; 124A; and 168A is unsealed and comprise, by virtue of their ordinary construction flow paths through which lubricant can flow. The flow of lubricant through these bearing assemblies is aided by pressurisation of the chamber 162A.

A cover plate 219 (see Figure 16) seals end 220 of the crank housing 146A forming a second chamber 221 to prevent uncontrolled leakage of oil. Oil that collects in chamber 221 is returned to casing 148A that acts as a sump.

The tubular portion 150A of crank housing 146A is configured to include an increased diameter circumferential wall or collar 222 that extends almost completely about the con-rod 172A, leaving a gap 224 through which the con-rod 172A reciprocates. Three oil return holes 226A, 226B and 226C are formed in the wall 222. One hole 226A is diametrically opposite the gap 224 and the other two holes 226B and 226C are angularly spaced by 90° on each side of the hole 226A. A raised lip 228 is formed along each edge of the gap 224 to collect lubricant when the transmission is arranged so that the con-rod 172A reciprocates in a vertical plane, shown in Figure 11. Rectangular holes 230 are formed in the wall 222 to drain lubricant collected on the lips 228 and drain the lubricant onto plates 232 attached to an outside of the wall 222. From here lubricant drips into the casing 148A which may act as a sump for the pump delivering lubricant to the inlet galleries 208. When the con-rod 172A is in the vertical plane (Figure 11) the holes 226A, 226B and 226C may be closed by plugging with grub screws (not shown) . The cover plate 219 is attached to the wall 222, the radial end of which constitutes the end 220 of the crank housing 146A.

However when the transmission 1OA is orientated so that the con-rod 172A reciprocates in a horizontal plane, shown in Figures 12 and 13, lubricant may flow into the casing 148A through one of the holes 226A, 226B or 226C.

A further point of differentiation between the transmission 10 and the transmission 1OA is in the weight

of the crank assembly and the crank carrier. In one embodiment of the transmission 1OA the crank assembly 14A has a weight of 56Og + 2Og, while the crank carrier 12A has a weight of 933g ± 2Og.

All modifications and variations of the above described embodiment that would be obvious to a person of ordinary skill in the art are deemed to be within the scope of the present invention the nature of which is to be determined from the above description. One example of such modifications is the placement of the restrictor plates 214, 216 and 218. While these are depicted on one side of their respective bearing they may alternately be located on the opposite side of their bearings. The net effect of restricting lubricant flow and having preferential flow through the passageway 200 to the crank pin and its bearing assembly 34A/174A will still be achieved.