GB2175869A - Rotary indexing apparatus - Google Patents

Abstract

Indexing apparatus 10 has surfaces 56, 60 relative, to which articles 32, for example containers for powders or liquid, are to be moved in sliding contact and input 24, work 26, 28 and output 30 stations. A rotary member 14 has walls 66 which, during rotation of the member 14, engage articles 32 at the stations 24, 26 and 28 and move the articles 32 relative to the surfaces 56, 60. Movement of the member 14 is controlled to locate the member 14 in a first position relative to the work stations whereby the walls 66 locate the articles within the boundaries of work areas and then to locate the member 14 in a second position relative to the work stations to locate the walls 66 outside of the boundaries. The work stations may be for determining sample volumes and densities. <IMAGE>

Description

SPECIFICATION Indexing apparatus The invention relates to indexing apparatus.

According to the invention, indexing apparatus comprises a surface relative to which articles are to be moved in sliding contact therewith, an input station, an output station, at least one work station intermediate said input and output stations, a member for moving articles successively from said input station to subsequent stations, said member comprising at least one wall engageable with an article to move the article relative to said surface, drive means for driving said member and said surface relatively to one another and control means for controlling said drive means to locate said member in a first position relative to said work station to locate the article within a boundary of a work area and then to locate said member in a second position relative to said work station to locate said wall outside said boundary.

Preferably, said wall is curvilinear in shape.

Preferably, said drive means is a rotary drive means, said stations being equiangularly located about a circular path swept by said wall.

Indexing apparatus will now be described to illustrate the invention by way of example only with reference to the accompanying drawings, in which: Figure 1 is a schematic plan view of the apparatus; Figure 2 is a schematic elevation, partly in section, on arrow II in Figure 1; Figures 3 to 5 show schematically the forces acting on an article being indexed; and Figures 6 and 7 are similar to Figure 5 but for modified wall shapes.

Referring to Figures 1 and 2, the indexing apparatus 10 has a stationary member 12 supported by legs 13; a rotary member 14 mounted on a bearing 15 in a central aperture in the stationary member 12; drive means for the rotary member 14 in the form of a stepper motor 16 and a gearbox 18 mounted underneath the stationary member 12; a power supply 20 for the motor 16; and a controller 22 which is any suitable microprocessor-based system.

The apparatus 10 has an input station 24, two work stations 26, 28 and an output station 30 equiangularly disposed relatively to the axis of rotation of the member 14.

Articles 32 can be fed to the input station 24 by any suitable feed mechanism. In this instance, the mechanism is a vibratory bowl feeder 34 having a chute 36 access to which is controlled by an escapement device 38.

The device 38 is controlled by the controller 22 in synchronism with the rotary member 14.

Any required mechanisms for performing operations on articles may be located at the work stations 26, 28. In this instance, the apparatus 10 is being used to index material samples to apparatus 40 for determining the volume of the sample, at station 26, and to weighing equipment 42, at station 28, whereby the densities of successive samples can be determined.

The apparatus 40 for determining the volume of a sample is particularly described and claimed in copending UK Patent Application No. 8611877 (Priority GB 85 13586, filed May 30, 1985 -Applicants' ref. IRD 1373).

Briefly, however, the sample is located in a variable volume chamber, volume of the chamber is decreased by a fixed volume and the resultant pressure differential between the between the chamber and a second identical chamber is used to derive the volume of the sample chamber. The first chamber can consist in part of a cylinder 44 (Figure 2) which engages an annular seal 46 (Figure 1) in a lower block 48 of the apparatus 40. The article 32 has to be located within the boundary of the seal 46 when the cylinder 44 is raised from the block 48. The second chamber has a second cylinder 50 which similarly engages with a second annular seal 52 in the block 48.

The weighing equipment 42 consists of a load celi having a cantilever oeam incorporating a strain gauge element, for example. The pan 54 of the cell is located within an aperture in the stationary member 12 of the apparatus 10, the upper surface of the pan 54 being substantially coplanar with the upper surface 56 of the member 12.

Output signals from the apparatus 40 and the weighing equipment 42 are fed to the controller 22 which calculates the volume and the density of successive articles 32.

The output station 30 can take any suitable form and in this instance consists of an aperture in the stationary member 12 of the apparatus 10 through which articles 32 fall onto a chute 58 for sorting, for example, on the basis of their densities, under the control of the controller 22.

The upper surface 56 of the stationary member 12 of the apparatus 10 together with the upper surface 60 of the block 48 of the apparatus 40 together form a surface relative to which the articles 32 are to be moved in sliding contact therewith. In some applications, the surfaces 56, 60 are coated with a material having a relatively low coefficient of friction, e.g. polytetrafluoroethylene, polyetheretherketone or polethersulphone.

The rotary member 14 of the apparatus 10 has a central hub from which extend four arms 62 each terminating in a ring 64. The inner walls 66 of the rings 64, during rotational movement of the member 14, sweep a circular path on which the stations are located and engage respective articles 32 at the sta tions 24, 26 and 28 and move the respective articles 32 relatively to the surfaces 56, 60.

Preferably, the inner walls 66 of the rings 64 are coated with a relatively low friction material similar to that used to coat the surfaces 56, 60.

The controller 22 is used to control the acceleration, steady speed and deceleration of the rotary member 14 so that an article 32 moved thereby is in a particular position relative to the wall 66 with which it is engaged when the member 14 is stopped at a first position relative to the work station. In the first position, assuming the article 32 has moved from station 24 to station 26, the article 32 is within the boundary of the annular seal 46 in the block 48. However, the ring 64 of the member 14 would interfere with the cylinder 44 when it is lowered to engage the seal 46. Consequently, the controller 22 then indexes the member 14 to a second position in which the rings 64, and the walls 66, are centralised relatively to the respective stations.

The actual instantaneous position of the article 32 relative to the wall 66 depends in a complex fashion upon the coefficients of friction between the article 32 and the wall 66 and the surfaces 56, 60 and the acceleration and deceleration rates of the member 14.

The situation may be understood more readily by reference to Figures 3 to 5, in which Figure 3 indicates the situation when the rotating member 14 is accelerating from rest, thereby imparting angular acceleration to the article 32 through contact with the wall 66 of the ring 64; Figure 4 indicates the situation when the member 14 is running at a steady speed; and Figure 5 indicates the situation when the member 14 is decelerating, as when approaching the station 26.

Referring to Figure 3, the forces on the article 32 are seen to be: R: the inertial force radially outwards along a line linking the centre of mass of the article 32 and the centre of rotation 0; N: the normal component of the force applied to the article 32 by the wail 66 along a line passing through the geometric centre P of the ring 64; F: the tangential component of the force applied to the article 32 by the wall 66, the magnitude of which depends, inter alia, upon the coefficient of friction at the region of contact between the article 32 and the wall 66; and F,: the retarding force opposing the instantaneous direction of motion of the article 32 arising from contact between the article 32 and the underlying surfaces 56, 60 (not shown), the magnitude of which depends upon the weight of the article 32 and the coefficient of friction at said contact and having a direction which depends upon the relative magnitude of the angular acceleration Wa.

The combined effect of these forces is to produce, at any given time, discrete angular accelerations of the article 32 about the main axis of rotation 0.

Referring to Figure 4, which depicts the situation in which there is no angular acceleration, the article 32 will tend to adopt a position as far as possible from the centre of rotation 0 but will be prevented from achieving this position by the frictional interactions F and F,.

Referring to Figure 5, which depicts the situation in which the angular acceleration Wa is large and in the opposite sense to the angular velocity Wv, the article 32 will assume a position towards the leading region of the wall, where the combined effect of the forces F,, F, and N is just sufficient to give the necessary retardation to the article 32.

It will thus be understood that by varying the rotational speed and rate of angular acceleration of the member 14 in response to signals from the controller 22, the position of the article within the ring 64 may be influenced to a substantial extent, subject to variations in uncontrolled parameters, principally the coefficients of friction between the article 32 and the wall 66 of the ring 64, and between the article 32 and the stationary surfaces 56, 60.

This is particularly apparent when the coefficients of friction are small and when the rates of angular acceleration are high, causing the inertial forces on the article 32 to predominate over the frictional forces.

Thus, the controller 22 can be programmed to ensure that the articles 32 follow trajectories similar to that depicted in Figures 3 to 5.

Once the member 14 has been stopped at the first position relative to the stations, the article 32 having consequently come to rest within the boundary of the seal 46, the controller 22 then indexes the member 14 through a small angle in the direction of arrow 68 (Figure 1) thereby ensuring that the rings 64 are centralised relative to the respective stations.

Improved location of the article 32 is possible during the decelerating phase of its movement by adopting a non-circular form of wall 66 in place of the circular form shown for the ring 64. Once such form is shown in Figure 6, in which the wall 66 is made up of two curves of different radii. The region 70 having the larger radius of curvature is designed to fit around the cylinder 44 when the latter is in the lowered position, whereas the region 72 having the smaller radius of curvature is designed to locate the article 32 within the boundary of the seal 46. Sufficiently rapid deceleration of member 14 causes the article 32 to adopt a position within the region 72, in a similar way to that described previously with reference to Figure 5. The controller 22 then causes the member 14 to stop with region 72 in a position overlying the area within the boundary of the seal 46. Further rotation of member 14 through the angle 0, being the angle subtended at the rotational axis 0 by the geometric centres P and Q of the curvilinear regions 70, 72 respectively, leaves the article 32 within the said boundary whilst allowing cylinder 14 to be lowered without mechanical interference from any part of rotating member 14.

In cases requiring a less rapid transfer of articles 32, the controller 22 may be programmed to accelerate and decelerate the member 14 at rates which allow the friction forces to predominate. In such cases, the articles 32 would remain in substantially the same position relative to the walls 66 of the rings 64 throughout the whole of the period of movement of the member 14. Once the member 14 has been stopped in a first position relative to the stations, the controller 22 indexes the member 14 in a reverse sense of motion to the second position relative to the stations.

Again, it is preferred that the wall 66 is of non-circular form (see Figure 7). In this instance, the region 74 of larger radius of curvature is leading, with respect to the direction of motion of the member 14, and the region 76 of smaller radius of curvature is trailing.

The reverse rotation of the member 14 from the first to the second position relative to the station is through an angle 6.

Modifications are possible within the scope of the invention. For example, when low acceleration and deceleration rates are used, the wall 66 could be open-ended instead of a closed loop; the number of stations and arms 62 can be varied, although usually the number of arms 62 will equal the number of stations; drives other than a stepper motor could be used; the apparatus could index articles in a linear direction instead of in a circular path, the surface could be moved whilst the member is held stationary. In the latter instance, different forces will act on the article 32, the article 32 remaining in substantially the same position throughout the indexing cycle and moving only within the boundary described by the now stationary wall 66 under the influences of forces F, and F,.

It will be appreciated, the apparatus according to the invention can index articles having any shape or size within the maximum volume envelope for which the apparatus has been designed. Additionally, the articles can be containers for powders or liquids.

Claims (7)

1. Indexing apparatus comprising a surface relative to which articles are to be moved in sliding contact therewith, an input station, an output station, at least one work station intermediate said input and output stations, a member for moving articles successively from said input station to subsequent stations, said member comprising at least one wall engageable with an article to move the article relative to said surface, drive means for driving said member and said said surface relatively to one another and control means for controlling said drive means to locate said member in a first position relative to said work station to locate the article within a boundary of a work area and then to locate said member in a second position relative to said work station to locate said wall outside said boundary.

2. Apparatus according to claim 1, in which said surface is stationary and said drive means is in driving engagement with said member.

3. Apparatus according to claim 1 or claim 2, in which said drive means is a rotary drive means, said stations being equiangularly located about a circular path swept by said wall.

4. Apparatus according to any one of the preceding claims, in which said wall is curvilinear in shape.

5. Apparatus according to claim 4, in which said wall is circular.

6. Apparatus according to claim 4, in which said wall has two regions of different radii of curvature, the centres of said regions lying substantially in a line parallel to the direction of said relative movement.

7. Apparatus according to claim 1 substantially as hereinbefore described with reference to the accompanying drawings.