AU709899B2 - Declutching apparatus - Google Patents

Description

adapted to induce a bend in a belt run between driven and drive pulleys for tensioning purposes.

Frequently limitations in the travel of the idler or adjustment pulley determines the amount of stretch which may be tolerated in a belt drive assembly before it becomes inoperative as opposed to the state of the belt itself.

Furthermore, where the declutching means is associated with idler pulleys provided with a large adjustment travel to accommodate belt stretch, the movement of the declutching means is considerable when the belt is stretched. The resultant slackness of the belt which occurs in a stretched belt when in the declutched attitude may result in complete disengagement of the drive belt from a pulley or cause belt breakages or damage when the belt drive is rapidly engaged and/or disengaged. This may be compensated for to some .:oo.i **.extent by providing guards around pulleys and/or guides to maintain operative alignment of the belts and the pulleys for operative re-engagement. This adds to the complexity of the assembly.

20 A typical example of a long belt drive is illustrated in our co-pending Australian patent application No. 49087/93 wherein a declutching lever maintains an actuating rod in a rearwardly urged position to maintain a spring bias to a return pulley over the range of adjustment of the pulley to 25 accommodate stretch in the belt. In such arrangements the spring bias may be limited by travel considerations and the

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3 available mechanical advantage obtainable with a long travel actuating lever.

With the foregoing in view, this invention in one aspect resides broadly in a disengageable belt drive assembly having an adjustable pulley which may be adjusted for operatively disengaging the belt drive and declutching means for moving the adjustable pulley to a declutched attitude, wherein the declutching means includes a short stroke actuating link arranged when actuated to operatively lock with the adjustable pulley and move it from its operative position to the declutched attitude.

In order to facilitate replacement or removal of the drive belt the adjustable pulley may be provided with override means whereby it may be held in a fully or partly disengaged position independent of the short stroke actuating a..

*link. Suitably the override means is able to hold the pulley in successive disengaged positions corresponding to positions Sto which the pulley may be moved incrementally by the short stroke actuating link. The latter may then be used in 20 successive operations to move the pulley to its fully released position.

The short stroke actuating link may operatively lock with the adjustable pulley by being in the form of a telescopic link permanently connected to the adjustable 25 pulley and which operates as a solid link upon relatively fast axial movement thereof such as by operation of the ~1~1 declutching means. Thus for example, the telescopic link may be in the form of a fluid actuated telescopic ram having a slow bleed permitting the operative length of the telescopic ram to vary slowly, the bleed being sufficiently small so as to enable the telescopic ram to act as a fixed length ram for declutching the adjustable pulley.

Preferably however, the short stroke actuating link is in the form of a ratchet link which locks onto the adjustable pulley only when the declutching means is actuated and at other times is disengaged or disengageable from the adjustable pulley so as to permit the adjustable pulley to move as the drive belt stretches. For this purpose the ratchet means may be a rack which is maintained remote from the adjustable pulley while the declutching means is inoperative and engages the adjustable pulley only upon actuation of the declutching means.

Alternatively the declutching means may include an override means for overriding a ratchet mechanism associated with the adjustable pulley when the declutching means is inoperative. In a further variation the ratchet means is 15 selectively disengageable with the adjustable pulley, such as when the belt drive becomes inefficient, to enable the adjustable pulley to assume an operative position for the stretched belt whereafter the ratchet means is re-engaged with the adjustable oo. pulley.

In order that this invention may be more readily understood and put into practical effect, reference will now be made to the accompanying drawings which illustrate a typical embodiment of the invention adapted for transmitting drive from a motor drive pulley to the driven pulley of a cutter head assembly, and wherein:- FIG. 1 illustrates a portion of a belt drive assembly, including the return idler pulleys, in its drive attitude; FIG. 2 illustrates the belt drive assembly of Fig. 1 in a disengaged attitude, and FIGS. 3 and 4 illustrate a cutter head assembly according to the invention.

As shown in the drawings, a belt drive assembly 10 includes a return pulley 11 mounted on an axial slide assembly 12 generally of the type described in my earlier co-pending patent application No. 49087/93 whereby the pulley 11 may move in the direction of the runs of the belt 13 as it stretches, to maintain an operative driving tension, and in the reverse direction for operatively declutching the belt 13 from the pulley- 11. For this purpose the pulley 11 is mounted on a carrier bracket 14 supported on a shaft mounted slide assembly 15 which is urged by a compression spring 16 in a direction which maintains tension on the belt runs 13.

In this embodiment the slide assembly 15 is supported on spaced shafts 17 !•••••extending between opposed mounting brackets 18. One of the mounting brackets 18 provides an upper abutment surface 19 for the declutching mechanism as will be S: 15 hereinafter described.

The declutching mechanism 20 includes a declutching hand lever 21 which may be moved forwardly across a ramp face 22 to be retained in a declutched S position behind an abutment 23. This movement translates through cross-shaft 24 to the actuating lever or link 25 connected pivotly to a notched bar assembly 26 which extends across the abutment surface 19 and the carrier bracket 14 such that the series of notches 27 in the lower face thereof open towards a holding pin 28 associated with the carrier bracket 14. The notched bar assembly 26 carries a cam or eccentric member 30 intermediate its pivotal connection to the link 25 and the ,oOtches 27 which engages with the abutment surface 19 and holds the notches 27 above the holding pin 28 when the lever 21 is maintained in its clutch engaged position as shown in FIG. 1.

The notched bar assembly 26 is biased by tension spring 31 towards engagement with the holding pin 28 such that upon initial movement of the lever 21 to the disengaged position as shown in FIG. 2, the cam member or eccentric 30 will move away from the abutment surface 19 enabling the notched bar assembly 26 to move downwardly so that the nearest one of the notches 27 engages about the holding pin 28, as illustrated in Fig. 2. Further movement of the declutching lever 21 to the-disengaged position will translate through the cross-shaft 24 and linkage into forward movement of the notched bar assembly 26 and corresponding forward movement of the carrier bracket 14 and pulley 11 against the bias of the spring 16 to a belt declutched position. This will move the pulley 11 from the engaged position as illustrated in dotted outline at 29 to the declutched position shown spaced forwardly o 0 from the engaged position 29." It will be seen that the actuating lever 21 is :15 supported on an axially moveable lever portion 35 which is biased by compression 0.

0, spring 36 towards the side face 37 of the mounting bracket 40. A rear stop face 41 :0.

oo extends inwardly transversely from the face 37 as does the ramped face 22. Thus the lever 35 is constrained for movement between the engaged and disengaged position. This movement causes a relatively short forward movement or stroke of the notched bar assembly 26 which is just sufficient, in the order of 20mm 35mm to move the return pulley 11 to a disengaged position.

As the notched bar assembly 26 is disengaged from the holding pin 28 when the machine is operating, the pulley 11 is free to move fore and aft along the guide bars or shafts 17. Irrespective of the pulley location relative to the mounting brackets 18, which depends upon the stretch of the belt, initial movement of the declutching lever 21 will cause a notch 27 of the bar 26 to engage the holding pin 28. Further movement of the declutching lever 21 will cause the appropriate minimal movement of the return pulley 11, suitably 25mm and translating to 50mm of belt slackness, for declutching the belt from driving engagement with the belt 13. Thus the range of movement of the declutching means may be minimised so that the belt slackness induced by declutching is never sufficient to cause complete disconnection of the belt from any one of its associated pulleys. Furthermore the induced slackness will be insufficient to damage the belt when the drive is re-engaged or disengaged to the extent- possible where a belt is stretched and the declutching means has a long stroke, providing excess slack in the declutched attitude.

o As illustrated the pulley 11 is stabilised against rotation about the mounting :i shaft 42 by a slide tongue 43 fixed to the slide assembly 15 and slidably retained between spaced guide members 44. In this embodiment the guide members 44 are provided with corresponding apertures 45 to receive a holding pin 46 which may be 15 inserted, when the belt is removed, to hole the slide assembly 15 against sliding °oo movement resultant from the compression spring 16. Suitably the pin 46 is inserted after the lever 21 is moved forwards to the disengaged position and positioned adjacent and behind the tongue 43. The lever 21 can then be moved back to the engaged position without a corresponding movement of the slide assembly This action may be repeated if desired to move the slide assembly 15 all the way to the front of its travel so as to facilitate replacement of a new or used belt as required. After replacement, the lever 21 may be actuated to release the load on the pin 46 whereby it may be removed, the pulley 11 then, upon release of the lever 21, eturning to its adjusted position according to the belt length.

The belt drive assembly illustrated in Fig. 3 is a cutter drive assembly 50 for transferring drive from an engine pulley 51 to a cutter disc pulley 52 which transmits drive via the shaft 53 to a cutter disc or the like illustrated in dotted outline at 54.

The cutter drive assembly has a single drive belt 56 which extends from the pulley 51 around a fixed idler pulley 57 and an adjustable idler pulley 58 for return to the cutter disc pulley 52. As in the previous embodiment, the adjustable pulley 58 is supported for reciprocation along a shaft 59 through a stabilised slide assembly 60 of the type described in relation to the earlier embodiment.

The adjustable pulley 58 is biased by a tension spring 61 connected between a slide assembly 60 and an outrigger bracket 62 hung from the outer end of the shaft 59. This spring 61 resiliently biases the adjustable pulley 58 in the direction illustrated by arrow 63 in order to maintain operative tension in the belt 56 for effecting drive transfer from the engine pulley 51 to the pulley 52. In Fig. 3 the o adjustable pulley 59 is shown retracted against the biassing spring 61 and the drive 15 declutched, and engaged in Fig. 4.

0 0 0 •During normal operation, the rack 65 is held spaced above the lug 66 on the stabilised slide assembly 60 through engagement of the underside of the shaft 67 *0 with the lifting ramp 68. This action occurs as the shaft 67 moves downwardly and forwardly towards the disengaged attitude, engaging the underside of the shaft with the ramp 658 which pivots the rack end of the ratchet shaft 67 upwardly, freeing the rack 65 from the upstanding lug 66. Such disengagement is achieved by moving the clutch handle 71 inward and forwards past the abutment 72 behind which the clutch handle 71 may be engaged for maintaining it in the declutched attitude.

While the rack 65 is maintained in its elevated position when the clutch z handle is in its inoperative position, the rack 65 is biased downwardly by the light 9 spring 75 which connects between the outer end and the outrigger bracket 62 such that the initial upward lifting of the inner end 74 upon movement of the clutch handle towards the declutched attitude frees the underside of the bar 67 from the lifting ramp 68 enabling the spring 75 to pull the rack 65 downward into engagement with the lug 66 such that further pivoting of the clutch handle to the declutched attitude, which results in axial translation of the link 67 also results in axial translation of the lug 66 along the bar 59 and movement of the pulley 58 to its declutched attitude. The adjustable pulley 58 is retained declutched once the clutch handle 71 is moved behind the abutment 72.

A further lever 80 is fixed to the transfer shaft 81 on which the handle 71 is ooooo S mounted and connects via a linkage 82 through a biasing spring 83 to a friction brake e.*i assembly 84, biased by the spring 83 into engagement with the pulley 52 when the clutch handle is retained in its declutched attitude. The friction brake prevents :o .t, Saccidental rotation of the cutter disc 54 which may occur even though the drive belt 15 56 is declutched. Thus the one action of moving the short stroke lever 71 from its inoperative position to its declutched position behind the stop 72 urges the return pulley 58 against its spring bias to a declutched attitude and at the same time applies the friction brake 84 to hold the cutter assembly 54 stationery.

Should the belt stretch to an extent that the outermost tooth of the rack will not engage the lug 66, further adjustment may be achieved by adjusting the position of the fixed pulley 57 relative to the cutter housing by the slotted mounts or by mounting either pulley in a different one of the series of apertures 86 provided on the mounting plates 87.

It will of course be realised that the above has been given only by way of illustrative example of the invention and that all such modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of the invention as is defined in the appended claims.

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S 4 _I~L~II 11 THE CLAIMS DEFINING THIS INVENTION ARE AS FOLLOWS: 1. A disengageable belt drive assembly having an adjustable pulley assembly which may be moved from an engaged position to a declutched position for operatively disengaging the belt drive and declutching means for moving the adjustable pulley to a declutched position, wherein the declutching means includes a short stroke actuating link arranged when actuated to operatively lock with the adjustable pulley assembly and move the adjustable pulley assembly from its oooeo S operative position to its declutched position.

2. A disengageable belt drive assembly as claimed in claim 1, wherein the .i declutching means includes a hand lever assembly moveable from a disengaged attitude to an engaged attitude and a short stroke actuating link longitudinally moveable by said hand lever assembly and said short stroke actuating link being in the form of a ratchet link having a plurality of longitudinally spaced ratchet teeth individually engageable with the adjustable pulley assembly.

ooe°O 3. A disengageable belt drive assembly as claimed in claim 2, wherein said actuating link locks onto said adjustable pulley assembly only when said hand lever assembly is moved from said disengaged attitude towards said engaged attitude.

4. A disengageable belt drive assembly as claimed in claim 3, wherein said actuating link is pivotally connected to said hand lever assembly at one end only and pivots away from said adjustable pulley assembly when said declutching means is

Claims (1)

1. 7. A declutchable belt drive assembly substantially as hereinbefore described 9 with reference to the accompanying drawings. DATED THIS Fifteenth DAY OF July, 1999. BARTLEM PTY LTD BY PIZZEYS PATENT TRADE MARK ATTORNEYS I 13 ABSTRACT A disengageable belt drive assembly [10] is provided with an adjustable pulley assembly [11] which may be moved by declutching means [20] from an engaged position to a declutched position for operatively disengaging the belt drive. The declutching means [20] includes a short stroke actuating link [26] operated by a hand lever assembly [25] and arranged when actuated to operatively lock with the adjustable pulley assembly [11] and move it from its operative position to its declutched position. The stroke actuating link [26] may be in the form of a ratchet link having a plurality of longitudinally spaced ratchet teeth one of which will engage the adjustable pulley assembly [11] upon actuation of the declutching means S.. 4° *o• Document7