GB2067261A - Vibratory finishing machine - Google Patents

Abstract

A vibratory finishing machine comprises a receptacle 13 for workpieces to be finished, a rocker element 7, a first pivot means 6 about which the rocker element 7 is adapted to pivot, second pivot means 15 mounted on the rocker element about which the receptacle 13 is adapted to pivot and drive means 9, 10, 11, 12 adapted to oscillate the rocker element 7 about the first pivot means 6. The oscillation of the rocker element sets up a vibratory motion within the receptacle. Preferably, the machine comprises two receptacles, one disposed to either side of the pivot on which the rocker element is mounted. Preferably, means are provided to tilt the receptacle on its pivot mounting in order to alter the median position of the oscillatory motion of the receptacle. <IMAGE>

Description

SPECIFICATION Vibratory finishing machine Field of the Invention The present invention relates to vibratory finishing machines.

In general, vibratory finishing machines comprise a vibration-generating means, such as a rotary motor provided with an eccentric member, for imparting energy to a finishing chamber or receptacle in order to move a mass of workpieces therein. Finishing operations commonly effected in such machines include polishing, de-burring, descaling, roughening, grinding, mixing and drying; with the use of appropriate foraminous members or weirs, operations such as separating or sieving may also be accomplished.

The finishing chamber, depending on the nature of the finishing operation, may contain, in addition to the workpieces, such materials as a particulate abrasive, sawdust, plastic cones, steel balls and ceramic chips; such materials are commonly referred to as the "media". Chemical treating agents, e.g. in aqueous solution, may also be added.

Background to the Invention Vibratory finishing machines are known which comprise a finishing chamber or receptacle in the form of an annular tub or bowl to which is attached a vibration-generating unit comprising an electric motor driving a vertical shaft carrying weights that are out of balance. The tub is mounted on a base frame by means of resilient members, for example coil springs (see U.K.

Patent Specification 1,183,822) or air bags (see U.K. Patent Specification 1,543,721). During operation of the machine, the workpieces and media are caused to move along a helical path around the tub.

A disadvantage of this type of machine is that the bearings for the shaft carrying the unbalanced weights have to be extremely robust in order to withstand the vibration forces generated. A further disadvantage is that the annular bowl must be comparatively shallow if the effect of gravity on the motion of theworkpieces is to be minimised.

To compensate for the shallowness of the bowl by increasing the other dimensions of the bowl results in the occupation of a comparatively large floor area by the machine.

Another type of vibratory finishing machine is known which comprises a tub having bearings for a horizontally disposed, motor-driven shaft bearing out-of-balance weights. Again, the tub is supported on resilient members, such as coil springs. During operation of a machine of this type, workpieces and media within the tub are given an orbital motion in a vertical plane.

A disadvantage of this second type of machine is that the tub sides, which are provided with bearings for the shaft, must be sufficiently robust to withstand the forces generated; accordingly, the use of thick-gauge metal sheet or of reinforcing elements is necessary. Another feature is that a considerable proportion of the impetus given to the workpieces and media is derived from the reaction of the resilient supporting members.

This fact, together with the need for a heavy-duty tub, requires that the energy input be comparatively high, if satisfactory operation of the machine is to be obtained.

A further disadvantage of both types of prior-art machines is that a considerable level of noise is generated during operation.

An apparatus for polishing stones for lapidary purposes is disclosed in U.K. Patent Specification No. 1,447,022, which machine comprises a container for the stones and an abrasive medium, the container being supported by two support members on opposed sides of the container. One support member permits reciprocal movement of the container in a substantially horizontal direction whereas the second support means permits reciprocal movement of the container in a direction inclined between the vertical and horizontal directions. The second support means is attached to a resiliently mounted bar of magnetisable material, the bar having a reciprocal motion imparted thereto by an electromagnetic coil energised by an AC power source through an on-off switch and a suitable half-wave rectifying diode and rheostat.

This prior-art apparatus seems suitable only for small-scale operations, rather than the finishing of workpieces of any great mass. Moreover, there is no provision for varying the attitude or inclination of the container and thereby altering the position of the centre of gravity of the loaded container.

Summary of the Present Invention According to the present invention, a vibratory finishing machine comprises a receptacle for workpieces to be finished, a rocker element, first pivot means defining a first axis, about which first axis the rocker element is adapted to pivot, and drive means adapted to impart an oscillatory motion to the rocker element about the said first axis, characterised by second pivot means mounted on the rocker element at a distance from the first pivot means and defining a second axis, about which second axis the receptacle is adapted to pivot.

When the drive means is operated, the oscillatory motion of the rocker element about the first axis imparts an oscillatory motion to the receptacle about the said second axis. As will be explained hereinafter, the two oscillatory motions result in a vibration of the receptacle which imparts an orbital motion to any workpieces and media contained therein.

It is preferred that the receptacle should be so mounted as to permit it to oscillate about the said second axis, even when the rocker element is static.

Generally, the said first axis and second axis are substantially parallel, whereby the oscillatory motion of the rocker element and that of the receptacle will be in the same plane. In particular, it is preferred that the said axes be horizontal, whereby the oscillatory motions will be in the vertical plane.

In general, the vibratory finishing machine will comprise a support frame; the first pivot means may then serve to mount said rocker element on the support frame.

It is particularly preferred that the machine be provided with two receptacles that are each adapted to pivot about a respective pivot means mounted on the rocker element, one mounted to either side of the first pivot means. It is preferred that the two receptacles and their mountings be substantially identical and that the receptacles be equidistant from the first pivot means.

Resilient members, for example coil springs, may be provided to support the or each receptacle. Similarly, resilient members, such as coil springs, may be provided to counterbalance the rocker element.

It has been found that by means of the present invention, a vibratory finishing machine can be constructed that generates, in operation, significantly less noise that known vibratory machines. Furthermore, machines can be constructed having lower power consumption than known machines of equivalent capacity; this advantage is particularly pronounced in machines having two receptacles, owing to the possibility of counterposing the receptacles. Alternatively expressed, the machine can cope with a bigger load than prior-art machines for an equivalent power consumption. Furthermore, particularly in the case of twin-receptacle machines, the vibratory finishing machines of the present invention are amenable to multi-purpose usage and give rise to the possibility of a modular system.A further advantage is that the machines of the present invention can be used with widely differing loads; thus, for example, a twinreceptacle machine of the present invention has been used successfully with a charge of tabletennis balls in one receptacle (the balls being selftumbled to produce a desired degree of roughening of the surface) and a charge of metal parts and abrasive media in the other receptacle.

A further advantage is that the receptacles do not contain the bearings for the motor and thus can be made of lighter gauge material than would otherwise be necessary.

Brief Description of the Drawings FIGURE 1 is a schematic, perspective view of an exemplary vibratory finishing machine according to the present invention; FIGURE 2 is a vertical mid-section of a vibratory finishing machine similar to that of Figure 1, except for the arrangement of the drive means; FIGURE 3 is a diagram indicating the components of the movements of parts in the machine of Figure 2; FIGURE 4 is an end view of a device for varying the position of the centre of gravity of a receptacle similar to that employed in the machine of Figure 1 or2; FIGURE 5 is a side view of the device of Figure 4; and FIGURE 6 is a top view of the device of Figure 4.

Description of Preferred Embodiments In the accompanying drawings, like parts are indicated by like numerals.

The machine illustrated in Figure 1 comprises a frame 1 comprising main beams 2 connected by transverse beams 3, the beams 2 being supported by optionally adjustable feet 4.

The frame 1 also comprises support pillars 5, each support pillar being located substantially at the mid-point of a respective main beam 2. Each of the vertical support pillars 5 is surmounted by a pivot assembly 6 in which is mounted, for pivotal motion, a rocker arm 7. The rocker arms 7 are connected by transverse struts 8, the rocker arms and struts constituting the rocker assembly.

As shown in Figure 1, one of the transverse beams of the support frame constitutes a platform 3A on which is mounted a drive motor 9. This motor drives a shaft 10 supported in bearings 22 and attached to an eccentric member 11. The eccentric member 11 is connected to a transverse strut 8 of the rocker assembly by means of a drive arm 12.

The vibratory finishing machine, as illustrated, includes two similar receptacles 13, each being in the form of a substantially cylindrical work tub disposed with its longitudinal axis substantially horizontal. Each work tub 13 has a longitudinal aperture 14 through which the work load, e.g.

workpieces and media, can be charged and discharged.

Each work tub 13 is connected by a series of pivot members 15 to the rocker assembly. In the embodiment shown in Figure 1, three aligned pivot members 15 are located on a respective transverse strut 8. The pivot members 15 are attached to the work tub 13 along the lowermost part of its periphery. The axis defined by the pivots 15 is substantially parallel to the longitudinal axis of the worktub 13. The two transverse struts bearing the pivot members 15 are substantially equidistant from the pivot assembly 6.

At each end of the work tub 1 3, there are provided two generally opposed flanges 16 extending substantially parallel to the adjacent rocker arm 7. Between each flange 16 and the adjacent end of a rocker arm 7, there is secured a resilient support member, generally in the form of a coil spring 17.

Depending from each end of each rocker arm 7 is a rod 18, the end of which abuts a counterbalance spring 19. Each counterbalance spring 19 is supported by a stanchion 20 extending from a respective end of a main beam 2 of the support frame 1.

The vibratory finishing machine illustrated in Figure 2 is substantially identical to that shown in Figure 1, except for the arrangement of the drive means. As indicated, the drive arm 12 is in the form of a triangular plate, which depends from the rocker assembly, one edge of the triangle being secured to the transverse struts 8. The substantially triangular drive arm 12 is attached, at its lowermost apex, to the eccentric 11 by means of a link rod 21.

The modes of operation of the two illustrated machines are substantially similar. Actuation of the drive motor 11, which is conveniently an electric motor, will cause an oscillatory movement of each rocker arm 7 about its respective pivot assembly 6. The rocker arm will oscillate through a small amplitude in the vertical plane, the median position of the rocker arm being substantially horizontal. The counterbalance springs 19 serve to reduce the stress on the motor 9 as the motion of the rocker arm 7 reverses.

Owing to the rigid construction of the rocker assembly, namely the rocker arms 7 and the transverse struts 8, the pivot members 15 associated with each work tub 13 will oscillate in concert with the rocker assembly about the pivots 6. This motion, in turn, sets up an oscillatory motion of each work tub 13 about the associated pivot members 15. In other words, each receptacle undergoes an oscillatory motion about a single axis through pivots 15 which itself undergoes an oscillatory motion about an axis through pivots 6.

As indicated in Figure 3, the oscillation of the drive arm 12, which oscillation is indicated by a, results in each receptacle 13 being subjected to two oscillatory motions, the one indicated by ss being about the pivot members 15 and the other, indicated by y, being about the pivot assembly 6.

As indicated each pivot 1 5 may be located on the same horizontal axis of pivot 6 or offset both horizontally and vertically from pivot 6. The resultant vibration of the receptacle causes any charge therein that is capable of flow to move in a vertical, orbital path as indicated by the arrows A in Figure 2.

Displacement of the median position of the oscillation of the work tub 13 about pivot points 15 results in a change in the amplitude of the motion of the workpieces or the like within the receptacle. In other words, it is possible to fix points 15 and vary the attitude or inclination of the work tub in relation to the fixed points 15 to compensate for variations in work-load and as a means fo adjusting the amplitude to the said work load.

A device for altering the attitude or inclination of the receptacle with respect to the rocker arm, i.e. for altering the position of the centre of gravity of the receptacle, is illustrated in Figures 4, 5 and 6. As shown in these Figures, a transverse strut 8 extends beyond an end face 13A of a work tub 13.

The extension 8A of the transverse strut 8 supports a bracket 23 on which a cross-piece 24 is pivotally mounted at 25.

The work tub 13 is modified in that the flanges 16 extend from the end face 13A of the work tub 13, rather than laterally as shown in Figures 1 and 2.

Between each flange 16 and the opposite top surface of the cross piece 24, there is secured a coil spring 17. The springs 17 serve to support the work tub 13, which work tub is mounted on pivot members 15 (not shown in Figures 4, 5 and 6) in the manner indicated in Figures 1 and 2. The axis defined by the pivot members 15 is coincident with the axis defined by the pivot 25. The pivot 25 is provided with locking means (not shown).

The cross piece 24 supports a quadrant member 26 having therein an arcuate slot 27 which defines a series of notches 28.

Conveniently, the notches are provided with index numbers (-2 to +3 in Figure 4).

An index lever 29 is pivotally mounted at 30 within the transverse strut 8, 8A and extends through the arcuate slot 27. The index lever 29 can be received by any of the notches 28.

To alter the attitude of the work tub 13, the procedure is as follows. Firstly, the locking means for the pivot 25 is released and the index lever 29 is raised out of the notch in which it has been accommodated. The cross piece 24 is then pivoted about the pivot 25 until the desired tilt has been achieved; this is indicated by the appropriate notch 28 coming into the lowermost position. The index lever is then lowered into the lowermost notch 28 and the pivot 25 is then locked.

The tilting of the cross piece 24 will tend to tilt the work tub on its pivots 15, owing to the biassing action of the springs 17 acting on the flanges 16.

The extreme tilted position, indicated by the index +3, brings the receptacle into a position for discharging its load.

It will be appreciated that the machines illustrated can readily be modified to suit various needs. For example, the coil springs 17 and 19 could be replaced by other resilient members, for example pressurized air bags.

The receptacles or work tubs 13 may be provided with hinged covers to close the apertures 14 when the machine is in operation.

It will often be found advantageous to provide the motor 9 with a fly wheel.

Furthermore, the internal volume of the work tubs may be sub-divided by appropriate walls when the machine is to be used for more than one operation. The work tubs can, of course, be provided with appropriate outlets for the removal of liquids, when such are used in the finishing operation.

It is possible to provide at least one of the work tubs with a dryer, e.g. a turbo-dryer, the nozzle of which can conveniently be inserted through the aperture 14.

In some operations, it is desirable that the workpieces do not come into contact with each other. To meet this requirement, a spiral or helical member may be inserted into the tub. It is preferred that the spiral be permitted to move loosely within the tub, thereby avoiding the generation of undesirable pressure waves in the media. As the tub vibrates, the spiral or helical member will rotate: workpieces can then be placed at intervals of time into the work tub at one end and they will be guided along the tub by the spiral or helical member and can be removed at the other end of the tub.

It should be mentioned that the amplitude of the oscillation of the rocker arm need only be small. In a prototype machine occupying a floor space approximately 4 foot 6 inches square (140 centimetres square) the movement of the end of each rocker arm was only +1 inch (+0.32 cm). This same prototype operated satisfactorily with a motor rated at 9 horsepower on a load which required, in the case of a prior-art machine, a motor rated at 5 horsepower. This is because the motor in the present machine is required only to move the rocker assembly "off centre" (i.e. from the position of balance). The noise level was also considerably reduced.

The distance of the pivot to which the tub is attached from the pivot point of the rocker arm could be varied (as could other parameters) in order to obtain optimum vibration characteristics.

It is possible to construct the machine having adjustment means for altering the distance between the two said pivots.

In the illustrated embodiments, the work tub has been pivotally mounted at the lowermost point of its periphery. However, it will be appreciated that the work tub may be pivoted about any axis, in particular an axis that is not coincident with the axis through the centre of gravity of the work tub. It is greatly preferred that the axis of oscillation of the work tub be at a distance from the centre of gravity of the loaded work tub. Thus the line about which the work tub oscillates is preferably below the centre of gravity of the tub and is more preferably below the centre of gravity of the loaded tub. Since the mass of the load may vary from finishing operation to finishing operation, the line about which the tub may oscillate will normally be at a distance from the longitudinal axis of the work tub of at least twothirds of the radius of the work-tub cross-section.

Claims (14)

1. A vibratory finishing machine comprising a receptacle for workpieces to be finished, a rocker element, first pivot means defining a first axis, about which first axis the rocker element is adapted to pivot, and drive means adapted to impart an oscillatory motion to the rocker element about the said first axis, characterised by second pivot means mounted on the rocker element at a distance from the first pivot means and defining a second axis, about which second axis the receptacle is adapted to pivot.

2. A finishing machine according to claim 1, characterised in that the receptacle is so mounted as to permit it to oscillate about the said second axis even when the rocker element is static.

3. A finishing machine according to claim 1 or 2, characterised in that the said first axis and the said second axis are substantially parallel and substantially horizontal.

4. A machine according to claim 1,2 or 3, characterised in that two receptacles are each mounted on the rocker element by respective pivot means, one to either side of the first pivot means.

5. A machine according to claim 4, characterised in that the receptacles are equidistant from the said first pivot means.

6. A machine according to any of claims 1 to 5, characterised in that the median position of the rocker element during oscillation is substantially horizontal.

7. A machine according to any of claims 1 to 6, characterised in that the second pivot means is attached to the periphery of the receptacle at the lowermost point of said receptacle.

8. A machine according to any of claims 1 to 7, characterised in that resilient means are provided to support the or each receptacle.

9. A machine according to any of claims 1 to 8, characterised in that the rocker element is connected via a drive arm to an eccentric member driven by a motor.

10. A machine according to any of claims 1 to 9, characterised in that the or each receptacle is in the form of a cylindrical work tub arranged with its longitudinal axis horizontal.

11. A machine according to any of claims 1 to 10, characterised in that the attitude of the or each receptacle relative to the rocker element is adjustable.

12. A machine according to claim 11, characterised in that for the or each receptacle a pivotally mounted platform is provided, which platform can be fixed in any of a number of positions about its pivotal mounting, the platform supporting resilient means for biassing the receptacle into a required position.

13. A vibratory finishing machine substantially as herebefore described and as illustrated in Figure 1 or Figure 2 or Figures 4-6.

14. Workpieces whenever finished in a machine according to any of claims 1 to 13.