FR2531636A1 - SCREENING DEVICE HAVING A SCREENING PANEL COMPRISING TWO SCREENING FRAMES - Google Patents

Abstract

THE SCREENING DEVICE HAS A SCREENING PANEL COMPOSED OF TWO SCREENING CHASSIS 11, 27 HAVING PARALLEL ELONGATED SCREENING ELEMENTS 20, 28, THE ELEMENTS 20 OF THE FIRST CHASSIS PROVIDED BETWEEN ELEMENTS 28 OF THE SECOND CHASSIS. THE SECOND CHASSIS 27 IS BASED ON THE FIRST CHASSIS 11. THE CHASSIS ARE PROVIDED WITH GUIDANCE AND CONTACT ELEMENTS 22-26, 32 TO GUIDE AND RETAIN THE SECOND CHASSIS IN A PREDETERMINED POSITION ON THE FIRST CHASSIS. THE SECOND CHASSIS 27 MAY, TO CLEAR THE PARTICLES OF MATERIAL WHICH HAVE CORNERED BETWEEN THE SCREENING ELEMENTS 20, 28, BEEN LIFT FREELY IN RELATION TO THE FIRST SCREENING CHASSIS UNTIL A PREDETERMINED HEIGHT, THE CHASSIS AND THEIR SHEETS REMAINING PARALLEL TO EACH OTHER. THE CHASSIS MAY BE ELASTICALLY SUPPORTED TO ACCOMPLISH OSCILLATION MOVEMENTS IN RELATION TO A SUPPORT CHASSIS 5 AND IN RELATION TO ONE ANOTHER.

Description

The present invention relates to a screening device according to the

  preamble of claim 1 More

  specifically, the invention relates to sieves and available

  similar screening devices which consist of a support frame provided with feet in which a screening panel

  has oblong screening openings.

  tures are formed between oblong screening elements such as, for example, steel bars O In general, the

  panel is tilted down from its receiving end

  trice at its end of discharge of the material which does not

  do not pass through openings o

  wiring of this kind exists both with and without an auxiliary device in the form of a vibrator to communicate to the panel a vibration movement in screening panels of this kind, and

  in particular in the case of relative orifice opening

  tivemen-t grades (above about 30 mm) closing the panel as a result of a material of critical size wedging between the screening elements always poses a problem C St why we have proposed for this type of panel different kinds of cleaning meanso For example, it is known to arrange one on two of the bars so that it pivots with respect to the other bars around a horizontal shaft provided at one end of the panel. Thus, one bar on two can pivot towards at the top, which increases its spacing from neighboring fixed bars so that the particles of accumulated material can slide along the panel to its discharge end or fall through the openings thus widened. One drawback of this arrangement is, however, that the movement which widens the openings is very reduced near the pivot axis o It will happen that stones of critical size are not released but sink only a little more

  deep into the openingso This results in an obstruction

  Even worse, which prevents the bars from pivoting back and can cause deformation and deterioration of the panel when an attempt is made to carry out this operation. An object of the present invention is to provide a screening panel composed of two sets of elements of

  screening, each set being supported by a screening frame

  blocking so as to allow one game to be moved away from the other without giving rise to the drawback mentioned above. An additional aim is to arrange the screening frames in such a way that for example with the aid of a vibrator entered 2 born by motor attached to l 2 one of them movements

  of oscillation can be advised to the chassis of cri-

  blocking with respect to a supporting frame, although with one of the screening frames with respect to the other, this will oppose the lob Iruction of the panel and, consequently, will require cleaning of the pa Lnneau less frequently by spacing

  panel bars These goals have been achieved with the-

  device according to the present invention defined by

claims.

  The device will be described below in more detail with reference to the annlexed drawing, in which: FIG. 1 shows a side view of the screening device installed in the working position; Figure 2 is an end view, the left half shows the screen panel 1 according to the invention in its working position while the right half shows the cleaning position with the screen bars spaced from each other; and Figures 3 and 4 show side views with

  sections, the screening panel being shown respectively-

  in the working position and in the cleaning position.

  The screening device in general is indicated in 1 in the drawing, 2 being the bucket of a loading machine indicated in broken lines and 3 denoting the material of lower dimension which has passed through the screen while 4 denotes the material of larger dimension passed on the screening panel The screening device includes

  a support frame 5 having four feet 6 which are available

  for sliding (not shown) in tubular elements 7 fixed to the support frame Thus the inclination and the height of the support frame above the ground can be modified by changing the fixing height of one of the pairs of feet or both in their receiving tubes On the pair of feet located at the discharge end, a plate or the like 8 is suitably mounted to form a partition between the material of large dimension and the material of small dimension that has

  passed through the screening panel.

  The support frame 5 comprises two longitudinal chassis beams 9 and two dech beams Transverse seats 10 These beams support a first

  screening frame 11 by means of elastic elements

  ques 12 such as helical springs At the four corners of the support frame and with a certain clearance against the screening frame 11, buffers 13 are arranged by having a coating 14 insulating against vibrations and

  shock absorbing, these pads used to limit the movement

  ment of the screening frame in the longitudinal and transverse directions Above the buffers, stops 15 are provided to limit the upward movement of the screening frame 11 by preventing it from being carried by lifting or tilting away from its support springs 12 Between the springs and the screening frame 11 and the beams 9 of the support frame respectively, spring guides are obviously provided in the usual way, these guides

having not been represented.

  The first screening frame 11 comprises two lanyards

  rons 16, a rear cross member 17 and a number of others: reduced height cross members indicated at 18 On the cross members 18, short vertical support bars 19 are mounted to support screening members 20 in the form of bars At their rear ends, these bars are also fixed to the cross member 170 The side members 16 of the screening frame are used for mounting two inclined side plates 21 Two of the cross members 18 are each equipped with a pair of supports each comprising a support 22 mounted under the crosspieces by means of two support irons 23 stanting down below the crosspieces

  supports is provided with a lining 24 made of elastic material

  or rubber or similar pads.

  In addition, the two crosspieces 18 in question are each equipped with two short contact plates 25 extending in the longitudinal direction of the crosspieces and forming a downward extension on one side of these crosspieces A

  right angles to the plates 25 and in conjunction with a.

  side of these, vertical lateral guide plates

  the 26 are mounted on the sleepers and extend from the upper edge thereof to a distance beyond

below their bottom edge.

  The second screening frame 27 is made up of screening elements 28 in the form of bars mounted on support irons 29 which are in turn mounted on a certain number

  1 o of sleepers 30 which maintain the structure of the chassis.

  At their rear ends, the screening elements in the form of bars are further maintained by means of a transverse flat bar 31 fixed to them. The screening frame 27 rests, by means of two of its crosspieces 30, on the support 22 by through the elastic coating of the support or the rubber pad (see Figure-2, left-hand side and Figure 3) In addition, the second screening frame 27 rests elastically, via pads 32, against the contact plates 25 which form a downward extension of one side of the crosspieces 18 of the first screening frame The buffers 32 are further guided laterally by lateral guide plates 26 of said crosspieces 18 The buffers 32 can be made in the form rollers coated with elastic material which circulate on the

side guide plates 26.

  By means of support irons 33, a lifting support

  34 is mounted on two crosspieces 30 of the second screen chassis.

  this support can also carry a vibrator 35 indicated diagrammatically which must be suitably covered to protect it from the material falling through

the screening panel.

  The installation of the second screening frame 27 is carried out in such a way that the complete frame is placed in its place inside the first screening frame 11 against the support and guide members 22-26 before the elements of screening 20 of the first screening frame have been connected to its crosspieces 17, 18 After their assembly, the screening elements 20 will serve as stops in an upward direction for the transverse parts 30 of the second

screening frame.

  The screening device operates in the manner set out below. The material to be screened is, by means of a loading bucket or a comparable member, supplied to the screening panel composed of the two screening frames 11, 27 which are then in the working position according to FIG. 2, half on the left, and FIG. 3 The material of reduced size falls through the openings between the screening elements 20, 28 and forms a heap below the screening device. reduced dimension and that of large dimension are kept separate by means of the plate 8 e The material is suitably supplied to the screening device near the highest end thereof If the screening panel receives a sufficient inclination, the screening device can operate without a vibrator 35 The device however requires less

  height and works more efficiently with a vibra-

  tor which will allow a reduced inclination of the screening panel and will ensure an improved transport of material and a reduced obstruction of the screening openings. The vibrator can, for example, be of the type which, by means of off-center rotating masses, produces a practically circular movement. movement is transmitted by the lifting support 349 to the second screening frame 27 which is connected to the first ch Screening seat 11 via the elastic elements 249 32 The first screening frame in turn is resiliently supported on the elements

elastic 12.

  The screening frames form a two-mass system with the first frame and the second which oscillate with respect to each other The second frame 27, which can be lighter than the first frame and which is driven directly by the vibrator 35, can receive the oscillation movement of greater amplitude As only one of the chassis is driven and a relative movement is established 3; 5 between the screening elements of the chassis, a particularly favorable transport and cleaning effect is thus obtained. It is therefore possible to use a weak vibrator effect than if, in the traditional way, the screening chassis assembly was vibrated

  with a common movement of all the screening elements.

  The continuous effective cleaning which is obtained by the relative movements of the screening elements 20 and 28 gives the result that only the particles of critical dimension, that is to say the particles of material which have their largest dimension not exceeding that slightly opening width of the screening panel and which have a shape which

  gives them a pronounced tendency to get stuck, will be immo-

  twisted between the screening elements Thus, the screening device, as a rule, performs a significant amount of work before the openings are closed to a degree which disrupts the operation. The speed or slowness at which the shutter is established depends in a large measure of the screen opening size chosen

  and the quantity of particles having a critical dimension

  disturbing tick in the mass of material to be screened.

  When it is necessary to clean the screening panel to rid it of trapped material particles, the loading bucket 2 is placed against the underside of the lifting support 34 and the second screening frame 27 is lifted until its sleepers 30 come into contact with the underside of the screening elements of the first screening frame It is obviously also possible to have stops between the lifting support 34 and the support frame 5 so as not to load the first screening frame 11 by the lifting forces, The screening elements 20 and 28 are then separated from each other according to FIG. 2, right half, and FIG. 4 During the lifting, the vibrator 35 can operate, which promotes the cleaning effect. The jammed particles of critical size then slide along the screening elements 20, 28 and fall from the discharge end of the screening device.

  screening or else fall between the screening elements.

  As for screening devices of the type

  dere, a very precise separation limit between the fractions of material is not generally imposed and since, mainly, only the particles of critical dimensions will get caught between the screening elements, it is acceptable

  in most cases leave the particles of dimen-

  critical ions falling through the panel when the cleaning operation is carried out mixing with the reduced size material 3 If, in some cases, this becomes unacceptable, it is possible to remove the reduced size material before start the lifting and cleaning operation and, after the end of this operation, remove

  the critical size particles that have fallen.

  The buffers 13 coated with elastic material 14 are suitably placed at a distance from the screening frames 11, 27 such that parts of these frames do not

  do not come into contact with the pads during oscillations

  Normal chassis conditions On the other hand, the buffers will come into operation when the oscillating movements have increased, for example as a result of heavy loads during the supply of material coming from the loader bucket 2 or during the passage of the so-called critical speed when the

  vibrator 35 is activated or put to rest.

  Relative movements between screeners

  11 and 27 result in only part of the ampli

  total study of the two-mass system carries out the suspension

  spring 12 Thus, the transmission of vibrations to the chassis

if support 5 is insignificant.

  When the screening panel is cleaned by lifting

  of the second screening frame 27, the frame is guided sideways -

  mentally by the cooperation between the pads 32 and the lateral guide plates 26 and in the forward direction by the cooperation between the pads 32 and the

  contact plates 25 or the side of two cross sections

  dirty 18 during the stage where the pads pass over the plates In the drawing, no guide means has been shown in the rearward direction The length of the support 22 however gives room for a movement backwards if the lifting is carried out obliquely O As soon as the second chassis is lowered again on the support 22, it will move forward due to the inclination and vibrations until the buffers 32 come into contact with the plates 25 In addition, it is simple to have stops which limit the rearward movement of the second

  screening frame 27 when it is raised.

8 2531636

  The lateral guidance of the second screening frame 27 can obviously be done otherwise than by means of vertical guide plates 26 and buffers 32 established in the form of rollers. The embodiment shown, in which the outer ends of the sleepers 30 are arranged with clearance against the side members 16 of the first screening frame and in which the lateral guiding function is accomplished by means of the buffers 32 which act as rollers is however advantageous This design prevents 1 o that the second screening frame gets stuck is raised or lowered obliquely and reduces the stress on the

guiding elements.

  To carry out the lifting operation, the bucket 2 is applied suitably from a position of the loader which is behind the screening device, that is to say according to FIG. 10 Thus, the upward movement will describe an arc in an upward and rearward direction The buffers 32 will then pass away from the contact plates 25 and will not resume contact with these plates until the last stage of a downward movement following the same stroke The buffers do not are not stressed this way

  by a strong friction against the guide surfaces.

  Above the pads 32 are suitably arranged protective screens (not shown), for example in the form of rubber bands or plates protruding from

  neighboring sleepers to prevent abrasive particles

  sives come between the pads and the side plates of

guide 26.

  The slightly elastic lateral guidance of the second screening frame 27 by means of the buffers 32 also allows a certain degree of relative lateral movement of the screening elements 20, 28 during the screening operation, which

  improves continuous cleaning of screening openings.

  The elastic guidance of the screening frames 11, 27 relative to each other with the spring suspension 12 and the pads 13 coated with elastic material ensures the operation of the screening device without rattling or

  metal-against-metal hammering, which has a strong lowering effect

  additionally, the screening elements and other parts are protected by the damping effect of the elastic elements, especially when heavy pieces of material fall on the screening device.

from the loader bucket.

  The solution chosen to obtain the separation of

  screening elements has no negative effect on the stability

  lity of the screening panel as is the case for known screening panels which are provided with screening elements which can pivot with respect to one another or deviate otherwise, but it is possible to have, at

  any necessary degree, lateral reinforcements between the elements

  screening elements 20, 28 at their ends as well as

various points between them.

  It is advantageous to arrange, as shown in FIG. 2, the outermost screening element on each side of the screening device on the second screening frame 27 which can be raised and lowered. This ensures that the particles which have become trapped between the elements of

  external screening and side plates 21 or lanyards

  lines 16 are released when the chassis is lifted.

  The drawings show an embodiment of the invention.

  tion by way of example and it is obvious that we could envisage various modifications without leaving

  scope of the invention defined by the claims.

Claims (4)

R E V E N D I C A T I O N S.   1 screening device having a screening panel   wiring consisting of two screening frames (11, 27) equipped with screening elements (20, 28) elongated practically parallel, the elements (20) of the first chassis being arranged practically centrally between the elements (28) of the second chassis, characterized in that the second chassis (27) is supported on the first chassis (11), that the chassis are provided with guide and contact elements (22-26, 32) for guiding and retaining the second chassis in a predetermined position on the first frame and that the second frame (27) can be lifted freely relative to the first frame (11) Up to a predetermined maximum height, the screening elements (20, 28) of the first frame and the second remaining   parallel or practically parallel to each other.   2 screening device according to claim 1, characterized in that the two screening frames (11, 27) are arranged to perform oscillating movements relative to a support frame (5) in which they are supported and the relative to each other by means of elastic elements (24, 32) forming part of the guide elements and contact (22-26, 32).   3 screening device according to claim 2, characterized in that elastic buffer elements (13,14) are provided on the support frame (5) with a clearance against the screening frames (11, 27) in order to limit the range movements in the longitudinal direction as well as in transverse directions.   4 Screening device according to any one of   previous claims, characterized in that the   guide and contact elements (22-26, 32) comprise buffers (32) provided on the second screening frame (27), these buffers being able, on the one hand, to bear against contact surfaces (25, 30) effective in the longitudinal direction of the screening device and, on the other hand, against contact surfaces (26) effective in the   transverse direction of the device.   Screening device according to Claim 4, characterized in that the buffers (32) are in the form of rollers: the path of the rollers is carried out along the contact surfaces (26) effective in the direction transverse of the device.   Screening device according to any one of   previous claims, characterized by a support for   lifting (34) rigidly fixed to the second screening frame (27) projecting from this frame down to a position below the support frame (5) while, against the underside of this support, a loader bucket or a comparable element (2) can be applied to lift the second screening frame, said lifting support being at the same time capable of acting as support for a vibrator (35) intended to communicate a vibration movement to the second screening frame.