AU606533B2 - Shearing handpiece - Google Patents

Description

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.25 I14 0 P/o/i Form I'AIENIS ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

['OR OFFICE USE Short Title: lit. CI: Application Number: Lodged: Complete S Heteted Art 3S008979 Narrie of A ;pecificatlon-Lodged: Accepted: Lapsed: Published:

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5.5, 0 /7 E39 TO BE COMPLETED BY APPLICANT ppllcant THE UNIVERSIETY OF MELBOURNE Address of Applicant: Grattan Street, Parkville, Victoria, Australia Actual Inventor: BRUCE WILLIAM FIELD Address for Service: SMITH SHELSTON BEADLE Suite 7, 207 Great North Road FIVE DOCK SYDNEY NSW 2046 Complete Specification for the Invention entitled: "SHEARING HANDPIECEI" The following statement is a full doscrip:~on of this Invention, including the best method of performing it known Note: Theo description is to be typed in douhirr spilcng. Ikec type fncc, In an [iron not exceeding 250 mm In depth and 160 mmin width, onl tough white paper of good quality and It Is to be Inserted Inside this form.

11d51910 -L )S Printed byC I 1tnwn, (nnmmrnnwearih Gorvernmnent Printer, Canberra 2 This invention relates to oscillatory shearing handpieces. Very briefly stated such handpieces comprise a generally cylindrical outer body adapted to be held in one hand, a fixed multi-toothed comb projecting beyond one end of the body and a multi-toothed oscillating cutter blade sliding upon and co-operating with the comb to constitute a cutter adapted to shear the fleece from a sheep or other animal.

For descriptive convenience terms such as "front", "rear", "behind", "forwardly", "vertical", "above", "below" and others of like positional or attitudinal intent are used hereinafter consistently with the assumptions that the cutter is at the lower front of the handpiece and that the handpiece is disposed as in use with the cutting plane horizontal.

Figure 8 of the accompanying drawings illustrates some of the internal parts of a conventional handpiece of the kind to which the invention relates.

Only a small part of the floor of the handpiece's outer body 7 is shown in figure 8. The handpiece further I C comprises a main spindle 8 mounted for rotation about a substantially horizontal axis extending longitudinally of the body 7. The spindle 8 projects through the rear end of the body 7 and is caused to rotate by drive means attached to or remote from the body 7.

I ,The front end of the spindle 8 is furnished with a forwardly projectirg crank pin on which a roller 9 is mounted. Thus when the spindle 8 rotates the roller 9 moves bodily along an orbital path and may at the same time rotate about the axis of the crank pin.

The roller 9 engages within a neat fitting upright slot in the back end of a first order lever 10, the socalled fork, fulcrummed intermediate its ends for I L ll_ 3 oscillation about a substantially vertical axis, as a result of the orbital motion of the roller 9.

The front end of the fork 10 carries two so-called chicken feet 11 drivingly connected to the oscillating cutter blade (not shown).

Pressure between the cutter blade and the comb is provided by an inclined oscillating strut 12, the so-called tension pin. The pin 12 is loaded downwardly by a force indicated by arrow A in figure 8 to cause the cutter to bear against the comb and the reaction force indicated by arrow B also acts on the fork 10. It follows that an equilibrant force exists between the fork 10 and the fulcrum pin on which it oscillates. To enable the force A C CCto be transmitted through the fork 10 to the cutter blade the fulcrum arrangements for the fork permit it to rock slightly about each of two intersecting horizontal axes, one extending laterally of, and the other extending longitudinally of, the handpiece and both intersecting the vertical axis about which the fork oscillates. The oscillating motion is the only substantial motion of the fork, the rocking referred to is merely positional adjustment effected from time to time to accommodate wear between the cutter blade and comb or the substitution of one cutter for another.

Thus the fork fulcrum has conventionally comprised a z centre post 12 extending upwardly from the floor of the body 7 with a part-spherical boss 13 at its top located in a part-spherical recess in the under side of the fork Unfortunately, because of the impracticability of precisely forming part-spherical surfaces on or in non-spherical articles, the contact between the boss 13 and the fork recess has been in actuality at best a line contact, more usually point contact at only a few points. This of course means high pressure between the parts which combined with i the rapid oscillatory movement has lead to rapid wear of i'he parts.

Therefore conventional handpieces as described above suffer from the disability that the fork fulcrum components have only a short working life, and an object of the present invention is to provide handpieces in which that disability is at least alleviated.

The invention consists in a shearing handpiece of the kind comprising a fork connected to a cutter blade at one end and to a drive means at its other end, fulcrum means supporting the fork intermediate its ends, and loading means acting downwardly on the fork intermediate said one end and said fulcrum means, said fulcrum means permitting oscillation of the fork about a substantially vertical axis and positional adjustment about two substantially horizontal axes intersecting each other and the said vertical axis, characterised in that said fulcrum means comprise a head piece comprising a part spherical head engaging a part spherical recess in the fork, a stationary base, and bearing means whereby said base supports said head piece in a manner permitting it to oscillate about a I substantially vertical axis, and in that the surface conditioning of the head and recess are such that there is gretir frictional restraint on relative movement between the haad piece and the fork than there is between the head i piece and the base.

Thus according to the invention the prior one piece fulcrum post is replaced by at least two components one of which permits rocking adjustment of the fork about the relevant horizontal axes but nevertheless oscillates with the fork about the vertical axis in bearing means suitable for that duty.

The bearing means may comprise separate items interposed between the head piece and the base, for example, ball or other rolling elements, oil retaining sleeves or hardened washers. Alternatively the bearing means may comprise no more than smooth cylindrical or planar bearing surfaces in rubbing contact on the head piece and base respectively.

The requisite surface conditioning of the head and recess may arise merely by leaving those surfaces in an as machined unpolished state, alternatively they may be deliberately roughened after being shaped.

described invention are described in more detail hereinafter with reference to figures 1 to 7 of the accompanying drawings.

0* Figure 1 is a view similar to figure 8 but of an embodiment of the invention. It is a partly sectioned side elevation of a handpiece fork and its co-acting components including the fulcrum means characteristic of the invention.

o, Figure 2 is a view similar to figure 1 but limited primarily to the fulcrum means of a second embodiment of the invention.

Figures 3, 4 and 5 are views similar to figure 2 of other embodiments of the invention.

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Figure 6 is a sectional side elevation of a handpiece including fulcrum means according to the figure 1 embodiment of the invention.

Figure 7 is a sectional view taken on line 7-7 of figure 6.

In figures 1 to 7, those parts which are conventional and correspond to parts described above with reference to figure 8 have been given reference numerals corresponding to those in figure 8 and are not further described below.

Similarly those components of the fulcrum means appearing in figure 6 bear reference numerals corresponding to those of figure 1 and are not further described with reference to figure 6.

The fulcrum means of figure 1 comprise a base comprising an externally threaded stem 13 and a spindle 14 integral therewith and a head piece consisting solely, in this instance, of a part spherical head 16.

The stem 13 extends through a threaded hole in the floor of the handpiece's outer body 7 and is fixed in place by a lock nut 15. The illustrated spindle 14 extends into a bore in the roof of the body 7 coaxial with the threaded hole in the floor, but in other similar embodiments the spindle may be truncated so as not to extend substantially above the head 16.

CC The head 16 may be regarded as a full sphere which has had a flat formed on it and has been pierced by a smooth diametral bore perpendicular to the flat, to leave a flat annular face surrounding one end of the bore. As flat faces and parallel sided bores and spindles may all be readily made to a high degree of accuracy and with smooth surface finishes by, for example, grinding, drilling and turning respectively, there is no great difficulty in manufacturing the two parts of the fulcrum means of figure 1 to provide full area contact between their respective contiguous surfaces, namely the annular end face of the stem 13 surrounding the spindle 14 and the annular face of the flat on the head 16 on the one hand, and the surface of the bore in the head 16 and the outer surface of the spindle 14 within it on the other hand. That is to say those contiguous surfaces may be readily manufactured to function satisfactorily as long lived co-acting bearing surfaces.

The spherical surface of the head 16 and/or the surface of the recess in the fork 10 in which it is homed may be deliberately roughened to ensure that the head 16 oscillates as one with the fork 10. This ensures that it is only the bearing surfaces referred to which rub together to accommodate the oscillation of the fork 10. However such roughness does not preclude the enforced re-alignment of the fork 10 as may be needed from time to time.

If desired, a washer may be positioned between the two annular surfaces.

Also if desired the one piece base of this embodiment may be replaced by two pieces, namely an externally a0 threaded bush correponding to the stem 13 and a separate o spindle fixed within the bore of the bush. The spindle may be so fixed by bonding or by virtue of the tightness of its fit within the bush. Alternatively the bush may be internally threaded to receive an externally threaded end of the spindle.

In the figure 2 embodiment the base is reduced to a cylindrical cup 17, which is externally threaded for securement by a lock nut in the same way as is the stem 13 of the figure 1 embodiment. In this instance the head piece comprises a spindle 18 and a part spherical head 19 integral with it. The difficulty of making the head 19 truly spherical is of no concern as its surface is not Ccalled upon to function as a bearing surface, indeed it is preferably deliberately roughened, whereas the cylindrical Scontiguous surfaces of the spindle 18 and cup 17 may be readily adapted to that duty.

In this figure 2 embodiment the bearing means may include a ball 20 interposed between the end of the spindle 18 and the floor of the cup 17 to take axial loading on the fulcrum means, in lieu of the annular bearing surfaces of the figure 1 embodiment.

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8 According to the figure 3 embodiment the base is a smooth bored externally threaded sleeve 21 and the head piece comprises a roughened part spherical head 22 with a downwardly extending smooth surfaced integral pin 23. For preference a thrust washer 24 is positioned between the end of the sleeve 21 and the annular under face of the head 22.

This embodiment achieves the major advantage of the invention in that the bearing surfaces are cylindrical or planar but the annular planar bearing surfaces are of limited extent. It is intended primarily as a replacement for worn fulcrum means in existing handpieces.

The figure 4 embodiment is very like the figure 1 CJ C embodiment except that the spindle 25 does not project beyond the head and an oil hole 26 is provided in the roof of the body 10 for lubricating the bearing surfaces.

The figure 5 embodiment is virtually the same as the figure 1 embodiment except that a rough surfaced insertable cup 27 is provided as an alternative to the part spherical recess formed directly in the fork 10 of that embodiment.

20 The handpiece illustrated by figures 6 and 7 includes many conventional components, including those bearing the same refernce numerals as the corresponding components in figure 8, a plain half joint 28 in which the main spindle 8 rotates, a screwed half joint 29 pivotted to the plain half joint and in which an input drive shaft or gut 30 rotates, bGvel cog wheels 31 and 32 transmitting drive to the main spindle 8 throughout the range of articulation of the two half joints, a dust cover 33 and a screw adjustable cap 34 providing an upper pivot housing for the tension pin 12 and whereby the loading by that pin upon the fork 10 may be adjusted as desired.

A novel feature of the figure 6 handpiece is the presence of a dynamic balancer to alleviate distressing I r j 9 vibrations experienced by shearers using conventional handpieces.

The dynamic balancer may best be appreciated by reference to figure 7. A cylinder 35 is formed integrally with the body wall extending transversely of the body 7 and positioned forwardly of the fulcrum means below the front arm of the fork 10. That front arm may be arched upwardly (see figure 6) to provide clearance for the cylinder The ends of the cylinder 35 may be closed by screw-in end caps 36 and 37 having skirts defining end portions of K the cylinder's curved wall. To provide adequate length in the cylinder space one or other of the end caps (in this instance cap 36) may project beyond the side of the body 7, that is to say one end cap may be longer than the other.

In that event the end caps are preferably interchangeable to enable the projecting end to be changed to suit the convenience of right or left handed shearers.

A cylindrical balance weight 38 having reduced diameter portions at each eid i slideable within the cylinder 35. It is axially shorter than the cylinder space to define two variable volume chambers 39 and 40 at the ends thereof. An axial passage 41 extends from one end of the balance weight 38 to the other to enable air within the cylinder to be pumped from one chamber to the other as the i 2 5 weight moves to and fro in the cylinder.

Two balanc3 springs, being helical compression springs 42, are respectively sleeved upon the balance weight end portions. The ends of the springs 42 abut the respective end caps 36 and 37 and the shoulders at the ends of the centre portion of the weight 38. The springs 42 may be designed to provide a resonant frequency of or about 3250 cycles/min. If need be that frequency may be altered by altering the diameter of the passage through the weight.

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The presence of this simple spring-mass dynamic balancer may reduce vibration of the handpiece by at least Another novel feature of the handpiece now being described is a safety clutch intended to reduce the potential danger should the handpiece escape from the shearer's hand accidentally. To this end the generally tubular stem of the plain half joint 28 is axially slideable within a bush 43 screwed into or otherwise fixed in the rear of the body 7. The stem is urged rearwardly out of the body 7 by a helical loading spring 44 sleeved upon the spindle and compressed between the inner end of the stem and a fixed spring abutment encircling the spindle 8, for example, a seating washer 45 lying against the front bearing 46 for the spindle.

The half joint 28 is normally retained in place against the effect of the loading spring 44 by a plurality of latch weights 47 disposed equiangularly about the stem and loading spring in cavities defined by the body 7. Each latch weight 47 has a radially inwardly directed projection engageable in a corresponding recess in the outer surface of the stem. The latch weights 47 are normally held in engagement with the stem as aforesaid by a light retaining spring or springs, for example a garter spring 48 encircling all of the weights 47.

4 If the cutter becomes jammed and the handpiece is wrenched from the shearer's hand, the entire handpiece is caused to spin as one with the spindle 8. This causes the latch weights 47 to retract centrifugally into the cavities in which they lie and withdraw their projections from the recesses in the stem of the plain half joint 28. The loading spring 44 then moves the plain half joint 28, and the screwed half joint 29 pivotted to it, rearwardly relative to the spindle 8, so separating the cog wheels 31 I 11 and 32 respectively to interrupt the drive to the handpiece.

Another novel feature of the illustrated handpiece is the fact that the cup accommodating the lower end of the tension pin 12 is mounted in a laterally extending recess or bore in the fork 10 enabling the cup to move laterally relative to the fork to some extent. This enables the pin to align itself within the slot of a conventional "nonrock" buttress 50 on the fork. This in turn allows a lower level of precision in the machining of the buttress slot without thereby incurring an undesirable increase in stress or operating noise.

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Claims (9)

1. A shearing handpiece of the kind comprising a fork connected to a cutter blade at one end and to a drive means at its other end, fulcrum means supporting the fork intermediate its ends, and loading means acting downwardly on the fork intermediate said one end and the fulcrum means, said fulcrum means permitting oscillation of the fork about a substantially vertical axis and positional adjustment about two substantially horizontal axes intersecting each other and the said vertical axis, characterised in that said fulcrum means comprise a head piece comprising a part spherical head engaging 9. part spherical recess in the fork, a stationary base, and bearing means whereby said base supports said head piece in a manner permitting it to oscillate about a substantially vertical axis, and in that the surface conditioning of the head and recess are such that there is greater frictional restraint on relative movement between the head piece and Sthe fork than there is between the head piece and the base.

2. A handpiece according to claim 1 wherein said bearing means comprise co-acting cylindrical bearing surfaces with vertical axes on said head piece and base respectively.

3. A handpiece according to claim 2 wherein said bearing means further comprise co-acting, flat, horizontal, annular I o bearing surfaces on said head piece and base respectively.

4. handpiece according to claim 3 wherein said annular bearing surfaces are separated by an anti-friction washer.

A handpiece according to claim 2 wherein said bearing means further comprise a ball interposed between said head piece and base whereby axial loading on said head piece is transferred to said base. 13

6. A handpiece according to any one of the preceding claims wherein said fork comprises an insert in which said part spherical recess is formed.

7. A handpiece according to any one of the preceding claims incorporating a dynamic balancer.

8. A handpiece according to any one of claims 1 to 6 incorporating a safety clutch operating automatically to render said cutter blade inoperative if and when the driven handpiece is released from the hand of the shearer.

9. A "non-rock" handpiece incorporating a slotted buttress according to any one of claims 1 to 6 wherein said loading means comprise a tension pin further characterised in that the fork end of the tension pin resides in an inserted cup accommodated in a recess in the fork which leaves the cup free to move laterally to enable the tension pin to align itself with the slot in the buttress. A shearing handpiece substantially as described herein with reference to figure 1, figure 2, figure 3, figure 4, figure 5 or figures 6 and 7 of the accompanying drawings. Dated this twenty-first day of July 1989. THE UNIVERSITY OF MELBOURNE Attorney: ROBERT G. SHELSTON Fellow Institute of Patent Attorneys of Australia of SMITH SHELSTON BEADLE K#.'I