WO1999007486A1

WO1999007486A1 - Vibratory screening apparatus

Info

Publication number: WO1999007486A1
Application number: PCT/GB1998/002182
Authority: WO
Inventors: Patrick Joseph Douglas
Original assignee: Douglas Patrick J
Priority date: 1997-08-08
Filing date: 1998-08-03
Publication date: 1999-02-18
Also published as: DE19881311T1; JP2001501870A

Abstract

A vibratory screening apparatus comprises a frame having a pair of opposed screen frame sides (101), at least one screen (12a) mounted on the frame sides, and a shaft-driven vibrating mechanism (102) mounted on the frame and which comprises: a shaft (103, 104) which extend throughout the width of the apparatus between the screen frame sides (101), and has shaft ends (104) projecting outwardly of the screen frame sides (101); each shaft end (104) is mounted on a respective frame side (101) via mounting means including a respective bearing assembly (105); and each shaft end (104) carries, and/or embodies a rotatable mass which has a centre of rotation which is radially spaced from the axis (108) of the shaft (103) in order to transmit vibrational energy to the screen frame sides (101): characterised in that the shaft (103) is hollow, and each shaft end (104) comprises a stubshaft which is solid and which is secured to a respective end of the hollow shaft; and each bearing assembly (105) is mounted inboard of the respective frame side (101).

Description

VIBRATORY SCREENING APPARATUS

This invention relates to a vibratory screening apparatus comprising a frame, at least one screen deck mounted on the frame, and a shaft-driven vibrating mechanism coupled with the screen deck in order to impart vibration thereto so as to assist the screening action.

A vibratory screening apparatus can be used in a quarry installation, in order to separate crushed stone, aggregate and the like into portions of different sizes, and usually will be provided with more than one screen deck, in order to separate- out different sized portions of the material to be screened.

A vibratory screening apparatus can also be used to carry out site clearance work, in which soil, stones, rubble, tree roots etc can be loaded onto the screening apparatus, and then separated out into useful fractions or portions e.g. to separate out usable "top soil" from the bulk material supplied to the apparatus .

One known construction of vibratory screening apparatus is disclosed in International publication No W093/24245, to which reference is made, for a general description of typical types of vibratory screening apparatus to which the present invention may be applied.

A shaft driven vibrating mechanism provided in a vibratory screening apparatus usually comprises a single shaft which extends horizontally through the screen frame between opposed frame sides in the space between two screen decks, and each end region of the shaft is mounted on the respective screen side by any suitable mounting means. A counterweight can be mounted on each free end of the shaft, which projects outwardly of the frame side, and upon rotation of the shaft, the counterweight, comprising an eccentric mass, applies vibration energy to the shaft which is transmitted via the mounting means to the respective screen frame side, and then to the screen deck or decks provided on the apparatus.

In publication No W093/24245, the free ends of a long shaft project outwardly of the respective frame sides by a sufficient distance to allow each shaft end to be supported by a respective pair of axially spaced bearing housings, and with the counterweight being arranged on the shaft end at a location between the spaced bearing housings. This provides efficient transfer of vibration energy to the components of the screen, but in a way which does not apply unduly large bending loads to the shaft, by virtue of the support of each projecting shaft end by a pair of spaced bearing housings, and with the counterweight arranged therebetween.

The present invention is concerned with a shaft-mounted vibratory mechanism for a vibratory screening apparatus in which the shaft extends throughout the width of the apparatus i.e. between each pair of opposed screen frame sides, and the shaft has short ends projecting outwardly of each frame side, but without need for bearing housings to be provided externally of the screen frame sides to support the shaft ends.

According to the invention there is provided a vibratory screening apparatus which comprises a frame having a pair of opposed screen frame sides, at least one screen mounted on said frame sides, and a shaft-driven vibrating mechanism mounted on the frame and operative to impart vibration energy to the screen so a to assist the screening operation, in which the vibrating mechanism comprises:

(a) a shaft when extends throughout the width of the apparatus between said screen frame sides, and has shaft ends projecting outwardly of said screen frame sides;

(b) each shaft end is mounted on a respective frame side via mounting means which includes a respective bearing housing; and,

(c) each shaft end carries, and / or embodies a rotatable mass which has a centre of rotation which is radially spaced from the axis of the shaft whereby, upon rotation of the shaft, vibrational energy is transmissible to the respective screen frame side: characterised in that the shaft is hollow, and each shaft end comprises a stubshaft which is solid and which is secured to a respective end of said hollow shaft.

Therefore, the weight of the shaft (which is hollow) can be kept small, but being tubular has substantial strength to withstand applied bending and other loads. However, the shaft ends (which are solid stubshafts of relatively short length) have substantial strength to transmit vibrational energy direct to the screen frame sides.

The stubshafts can be secured to the ends of the hollow -shaft by any suitable securement means, and which can include; (a) press-fitting into the hollow shaft ends; (b) presentation of each stubshaft to the respective hollow shaft end with an instantaneous temperature differential between them in the sense of the shaft end being at a higher temperature than the stubshaft so that, upon both components reaching ambient temperature, a tight fit is obtained; (c) welding together; and, (d) bolt or other means of securement.

Each stubshaft carries and / or embodies an eccentric mass (counterweight) , with respect to the hollow shaft, and this may be achieved in a number of ways.

In one arrangement, each stubshaft axis is coincident with the axis of the hollow shaft, and an eccentric mass (counterweight) is mounted on the stubshaft.

In a further arrangement, each stubshaft axis is radially spaced from the axis of the hollow shaft, and a circular mass can be mounted on the stubshaft with its axis of rotation coinciding with the axis of the stubshaft.

In another arrangement, no counterweight is provided, but the mass of the stubshaft itself is utilised to generate vibrational energy upon rotation, in which case the weight distribution of the stubshaft (relative to the axis of the hollow shaft) will be such that the stubshaft is dynamically out of balance, so as to apply repeated cycles of vibrational energy to the screen frame sides upon rotation. The "out of balance" weight distribution may be achieved by having: i. a circular cross section of stubshaft with uniform weight distribution, but with the stubshaft axis radially spaced from the axis of the hollow shaft; ii. a stubshaft axis coinciding with the axis of the hollow shaft, but with non-uniform distribution of mass about this axis; or iii. non-uniform distribution of weight about the axis of the stubshaft, and radial spacing of the stubshaft axis from the hollow shaft axis.

Preferably, the assembly of components making-up the shaft-driven vibrating mechanism, which extend between the screen frame sides, (namely the hollow shaft, the bearing housings, and portions of the stubshafts) , are shielded by being housed within a stationary protective tube which extends between the screen frame sides, and such protective tube also serving to provide lateral rigidity to the frame of the screen, by being secured at each end to the screen frame sides.

The bearing housings also can be securely secured internally to the wall of the protective tube.

A preferred embodiment of vibratory screening apparatus according to the invention will now be described in detail, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a front elevation of one known type of vibratory screening apparatus, which will be described in order to set out the background to the invention;

Figure 2 is a general assembly view of a shaft-driven vibratory mechanism for use in a vibratory screening apparatus according to the invention, and to replace the vibratory mechanism shown in the known apparatus of Figure 1;

Figure 3 is a side view of a central hollow drive shaft tube, forr.ing part of the drive to operate the vibratory mechanism shown in Figure 2;

Figure 4 is a side view of one of a pair of stubshafts, each adapted to be mounted in a respective end of the hollow drive tube shown in Figure 3;

Figure 5 is a side view of a stationary outer protective tube, extending between opposed screen frame sides, and shielding the internally mounted shaft drive train components; and

Figure 6 shows side and end view of one of a pair of press-in bearing housings, to be mounted internally of the outer protective tube shown in Figure 5, (and also to mount respective ones of the solid projecting shaft ends shown in Figure 4) .

The general type of vibratory screening apparatus to which the invention may be applied will now be described first with reference to Figure 1.

A vibratory screening apparatus 10a comprises a frame having a pair of opposed screen frame sides 11a, and at least one screen is mounted on the frame sides 11a. In the illustrated arrangement, a multi-deck of screens is mounted on frame sides 11a, and this is designated generally by reference 12a, with individual screen decks or meshes thereof being designated by reference 13a.

A shaft-driven vibratory mechanism is coupled indirectly with the screen deck 12a, via its mounting on the screen frame sides 11a, in order to impart vibration energy to the screen so as to assist the screening operation. The mechanism comprises a single shaft 14a extending between the two frame sides 11a, and having end portions 14b projecting outwardly of each frame side 11a. Each shaft end 14b is supported by a respective pair of bearing housings, comprising an inboard housing 15a and an outboard housing 16a.

The housings 15a and 16a of each pair are spaced apart from each other, and a respective counterweight 17a is mounted on each shaft end portion 14b in the space between housings 15a and 16a, and is keyed to the shaft 14a to be rotatable therewith. Therefore, upon application of drive to the shaft 14a, the counterweights 17a are driven in rotation, and by virtue of being off-set masses, this applies centrifugal force to the shaft 14a. This applies vibration energy to the shaft, which is transmitted to the screen 12a via the bearing housings 15a and 16a and the frame sides 11a.

Each of the housings 15a and 16a is rigidly secured to a short length of box-shaped support beam 19a which extends between upright support beams (not shown) which form part of a rigid side frame support frame structure.

Drive means is coupled with the shaft 14a to apply rotation thereto, and may comprise a hydraulic or electric motor 20a coupled with one of the free projecting ends of the shaft 14a. This can drive the shaft 14a at a high speed of rotation to apply vibration energy to the screen deck 12a. Resilient dampers may be arranged to absorb the vibration imparted to the components of the screen under the action of the shaft driven vibratory mechanism.

Referring now to the further figures of drawings, a preferred embodiment of shaft-driven vibratory mechanism will now be described, which is suitable to be incorporated in a vibratory screening apparatus of the general type described herein, and referred to by way of example with reference to the known construction shown in Figure 1.

A preferred embodiment of shaft-driven vibratory mechanism, for use in a general type of vibratory screening apparatus of the general type shown in Figure 1, will now be described in detail with reference to Figures 2 to 6.

The vibratory screening apparatus in which the shaft- driven vibrating mechanism is mounted is not shown in detail, but may be generally similar to the apparatus shown in Figure 1. The screening apparatus has a pair of opposed screen frame sides formed by side plates 101, and at least one screen deck (not shown) is mounted on the side plates 101, and arranged to be caused to vibrate, by operation of the shaft driven vibrating mechanism which will be described below.

The shaft-driven vibrating mechanism is designated generally by reference 102, and upon application of drive rotation thereto (by means not shown) , vibration energy is imparted to the screen via the side plates 101, to assist the screening operation.

The mechanism 102 comprises a hollow drive shaft 103 which extends substantially throughout the major part of the width of the apparatus between the screen side plates 101, and has shaft ends 104 projecting outwardly of the ends of the shaft 103, and outwardly through the side plates 101. Each shaft end 104 is mounted on a respective side plate 101 via mounting means which includes a respective bearing housing, shown by reference 105.

Each shaft end 104 carries a rotatable mass which has a centre of rotation which is radially spaced from the axis of the hollow drive shaft 103 whereby, upon rotation of the shaft, vibrational energy is transmissible to the respective screen side plate 101. In the illustrated embodiment, the rotatable mass carried by each shaft end 104 comprises an eccentric mass in the form of counterweight 106.

However, as an alternative arrangement to that shown in Figure 2, each shaft end may itself embody a rotatable mass having a centre of rotation which is radially spaced from the axis of the hollow drive shaft 103, and this will have the same effect upon rotation.

As can be seen in Figure 2, and also in Figure 3 which shows the drive shaft 103, this is hollow throughout its length, and this therefore contributes to low rotating mass, but being tubular, has substantial resistance to applied loads. However, each shaft end 104 comprises a stubshaft which is solid, and which is secured to a respective end of the hollow shaft 103, as can be seen in Figure 2, and with the construction of the stubshaft being shown in more detail in Figure . Being solid stubshafts of relatively short length, they have substantial strength, in order to transmit vibrational energy direct to the screen side plates 101. The stubshafts can be secured to the ends of the hollow shaft 103 by any suitable securement means, and which can include;

(a) press-fitting into the hollow shaft ends;

(b) presentation of each stubshaft to the respective hollow shaft end with an instantaneous temperature differential between them whereby the shaft end is at a higher temperature than the stubshaft so that, upon both components reaching ambient temperature, a tight fit is obtained;

(c) welding together; and

(d) bolt or other means of securement.

In the case of use of a temperature differential, this may be achieved by heating the hollow shaft ends and introducing the stubshafts at a lower temperature; alternatively, the stub shafts could be chilled temporarily to a temperature lower than that prevailing in the hollow shaft end.

In the illustrated embodiment, the axis 107 of each shaft end 104 is non-coincident with the axis 108 of the drive shaft 103, i.e. there is radial spacing between them, so as to generate cyclic vibrational energy, upon rotation of the shaft assembly, to be applied to the screen side plates 101.

Evidently, there are many other ways in which cyclic vibration can be applied, such as arrangement of the stubshaft axis 107 to be coincident with the axis 108 of the hollow shaft 103, but with an eccentrically mounted mass or counterweight mounted on the stubshaft.

In another arrangement, each stubshaft axis 107 can be radially spaced from the axis 108, and a circular mass can be mounted on the stubshaft 104.

Finally, a separate counterweight or eccentric mass may be omitted, and the mass of the stubshaft itself can be utilised to generate vibrational energy upon rotation. In this case, the weight distribution of the stubshaft, relative to the axis of the hollow shaft, will be such that the stubshaft is dynamically out of balance, so as to apply repeated cycles of vibrational energy to the screen side plates upon rotation. The "out of balance" weight distribution may be achieved by having: i. A circular cross-section of stubshaft with uniform weight distribution, but with the stubshaft axis 107 radially spaced from the axis 108 of the hollow shaft; ii. A stubshaft axis 107 coinciding with the axis 108 of the hollow shaft, but with non-uniform distribution of mass about this axis; or iii. Non-uniform distribution of weight of the constituent parts of the stubshaft about its axis, and radial spacing of the stubshaft axis from the hollow shaft axis.

The assembly of components making up the shaft-driven vibrating mechanism, which extend between the screen side plates 101 i.e. the hollow shaft 103, bearing housings 105, and portions of the stubshaft 104, are shielded by being housed within a stationary protective tube 109 (see Figures 2 and 5) which extends between the side plates 101, and which is rigidly secured thereto e.g. by threaded fasteners 110 as shown in Figure 2. The protective tube 109 therefore serves to provide lateral rigidity to the frame of the screen, and also shields the rotating components of the shaft drive train.

The stubshafts 104 are of stepped construction, as shown in Figure 4, and the inner race (111) and rotary bearings (112) of each bearing housing 105 are mounted on the reduced diameter portion of each stub shaft 104, as shown in Figure 2. The housings 105 are also press-fitted into suitably formed seatings fo'_*- the housings formed in the inner wall of the protective outer tube 109.

Although the central shaft portion (103) has been described and shown in the drawings as being of hollow construction, it is within the scope of another aspect of the invention for the shaft portion (103), and each of the stubshaft ends (104) to be of solid construction. According to a further aspect of the invention, the bearing assemblies which mount the shaft ends (104) on the screen frame sides (101) are characterised by being mounted in board of the respective frame sides.

This is achieved by fixing the bearing assembly in position by any suitable means, and which includes:

(a) fixing^'of flanges of a bearing housing to an inner face of the screen frame side (101);

(b) fixedly mounting an outer housing part of the bearing assembly within an end portion o'f the outer protective tube (109); and,

(c) a combination of features (a) and (b) .

Claims

1. A vibratory screening apparatus which comprises a frame having a pair of opposed screen frame sides (101), at least one screen (12a) mounted on said frame sides, and a shaft-driven vibrating mechanism (102) mounted on the frame and operative to impart vibration energy to the screen so as to assist the screening operation, in which the vibrating mechanism comprises:

(a) a shaft (103,104) which extends throughout the width of the apparatus between said screen frame sides (101), and has shaft ends (104) projecting outwardly of said screen frame sides (101)

(b) each shaft end (104) is mounted on a respective frame side (101) via mounting means which includes a respective bearing assembly (105); and,

(c) each shaft end (104) carries, and / or embodies a rotatable mass which has a centre of rotation which is radially spaced from the axis (108) of the shaft (103) whereby, upon rotation of the shaft, vibrational energy is transmissible to the respective screen frame side (101): characterised in that the shaft (103) is hollow, and each shaft end (104) comprises a stubshaft which is solid and which is secured to a respective end of said hollow shaft.

2. A vibratory screening apparatus which comprises a frame having a pair of opposed screen frame sides (101), at least one screen (12a) mounted on said frame sides, and a shaft-driven vibrating mechanism (102) mounted on the frame and operative to impart vibration energy to the screen so as to assist the screening operation, in which the vibrating mechanism comprises:

(a) a shaft (103,104) which extends throughout the width of the apparatus between said screen frame sides (101), and has shaft ends (104) projecting outwardly of said screen frame sides (101) (b) each shaft end (104) is mounted on a respective frame side (101) via mounting means which includes a respective bearing assembly (105) ; and,

(c) each shaft end (104) carries, and / or embodies a rotatable mass which has a centre of rotation which is radially spaced from the axis (108) of the shaft (103) whereby, upon rotation of the shaft, vibrational energy is transmissible to the respective screen frame side (101) : characterised in that each bearing assembly is mounted inboard of the respective frame sides. ^ΓÇó

3. Apparatus according to claim 2, in which a stationary protective tube (109) extends between the screen frame sides (101), and is rigidly secured thereto in order to provide lateral rigidity to the frame of the screen, and also houses internally the shaft-driven vibrating mechanism.

4. Apparatus according to claim 2, in which each bearing assembly includes a housing which is fixed to an inner face of the respective frame side.

5. Apparatus according to claim 3, in which each bearing assembly is fixed within one end portion of said stationary protective tube (109).

6. Apparatus according to claim 5, in which each bearing assembly includes a flanged housing which is fixed to an inner face of the respective frame side (101), and which is also fixedly secured within said end portion of the protective tube .

7. Apparatus according to any one of claims 2 to 6, in which said shaft (103) is hollow, and each shaft end (104) comprises a stubshaft which is solid and which is secured to a respective end of said hollow shaft.

8. Apparatus according to any one of claims 2 to 6, in which the shaft (103) and the two shaft ends (104) are solid.

9. Apparatus according to claim 1, in which each stubshaft (104) is secured to a respective end of the hollow shaft (103) by; (a) press-fitting into the respective hollow shaft ends ;

(b) presentation of the stubshaft to the respective hollow shaft end with a temperature differential whereby the shaft end is at a higher temperature than the stubshaft so that, upon both components reaching ambient temperature, a tight fit is obtained;

(c) welding together; and

(d) bolt or other means of securement.

10. Apparatus according to claim" 1 or 9, in which each stubshaft (104) carries an eccentric mass (106) .

11. Apparatus according to any one of claims 1 to 3, in which each stubshaft axis (107) is coincident with the axis

(108) of the hollow shaft (103), and has an eccentrically mounted counterweight (106) on the outer projecting end of the stubshaft.

12. Apparatus according to claim 1, in which each stubshaft axis (107) is radially spaced from the axis (108) of the hollow shaft (103), and a circular mass is mounted on the stubshaft with its axis of rotation coinciding with the axis of the stubshaft.

13. Apparatus according to claim i, in which the mass of the stubshaft itself is utilised to generate vibrational energy upon rotation.

14. Apparatus according to claim 6, in which an out of balance weight distribution of the constituents of the stubshaft is achieved by having: i. a circular cross-section with uniform weight distribution, but with the stubshaft axis radially spaced from the axis of the hollow shaft; ii. a stubshaft axis coinciding with the axis of the hollow shaft, but with non-uniform distribution of mass about this axis; or iii. non-uniform distribution of weight about the axis of the stubshaft and radial spacing of the stubshaft axis from the hollow shaft axis.

15. Apparatus according to claim 2, in which the bearing housings (105) are secured internally of the wall of the protective tube (109) via seatings provided in the tube, and each bearing housing is mounted externally on a reduced diameter portion of each stubshaft.