FR2474899A1 - Scraper blade for rotary heat exchanger drum - is endless strip or unwound from reel, driven by bobbin arrangement with sharpening wheel - Google Patents

Abstract

The scraper blade for a rotating drum, suitable for a rotary heat exchanger, is formed by a steel strip (3) which can be unrolled from a bobbin (5) at one end and rolled onto another bobbin (6) at the other end of the drum (1). Adjacent to the first bobbin is a drive unit (4) for advancing the strip, and which also includes a grinding wheel for sharpening the edge of the strip. Parallel with the face of the drum is a blade supporting assembly (2) with a backing plate for the strip retained by a housing supported by blocks spaced along it. Incorporated in the housing are pneumatic tubes which can be controlled to hold the strip in contact with the drum or free it. In one design, the strip can be joined at its end to form a continuous loop, instead of using bobbins. The design can be used for operation with a roller or drum rotating inside an enclosed vessel which may be under vacuum.

Description

 The present invention is in the field of apparatus for treating products with a scraped surface, the treatments possibly being, for example, concentration, drying, freezing treatments, said apparatus generally being of the type having a rotary drum with a horizontal axis; it relates more particularly to the scraping means generally designated by knife, used in these types of apparatus.

 In the current state of the art, a knife for a treatment device with a scraped surface generally consists of a blade-holding part, a single counter-blade part and, situated between them, a blade, each of these parts having substantially the length of a yénératrice of the drum, the knife thus constituted being supported by support means capable of maneuvering to apply said blade against the surface or to move it away. The blade is kept clamped between the blade-holding part and the counter-blade part by means of bolts bringing these two parts together, one against the other; when the edge of the blade is worn, which results in poor scraping of the surface and an increase in the consumption of energy for the rotary drive of the drum, it is advisable to remove the knife blade for sharpening; removing the blade requires stopping the drum.

 The stopping of the drum and the removal of the blade which, although this is a serious drawback when the treatment apparatus operates at atmospheric pressure, constitute operations which make the use of such treatment apparatus under vacuum. .

 The Applicant's initial inventive step was to design scraping means making it possible to avoid, if not stopping the drum, when the installation is operating under vacuum, putting it at atmospheric pressure. Following the testing of such scraping means allowing the treatment under vacuum, the Applicant has found that these same means, applied to devices operating at atmospheric pressure, brought considerable advantages in the latter operating case. scraping object of the present invention although having been initially designed to equip scraped surface devices operating under vacuum, were they, during a consecutive inventive step, generalized to all devices of surface treatment key.

 Thus and according to the present invention, a scraper device for a scraped surface treatment apparatus, such as a rotary drum heat exchanger, said device incorporating a scraper blade supported by support means for alternately either applying said blade against said scraped surface, ie moving said blade away from said surface, is mainly characterized in that said blade is at least twice as long as a generatrix of said surface, and in that said support means incorporate means for alternately either blocking said blade, or allow the movement of said blade along itself, said blade being blocked when the support means apply it against the surface and, alternatively, said blade being free to move along itself when the support means move said blade away from the scraped surface; where it follows that, while a part of the blade is performing its scraping function, another part can be sharpened by suitable sharpening means.

 Still according to the present invention, the scraper device is mainly characterized in that it also incorporates so-called drive means, for circulating said blade along itself, said drive means being essentially constituted by 'at least two rollers intended to put pressure on the sides of said blade, at least one of said rollers being a drive roller.

 Still according to the present invention, provision is made to associate with the scraper device as defined above, means for sharpening the blade; preferably these sharpening means comprise a rotary grinding wheel intended for the actual sharpening operation, a sharpening stone intended to remove the sharpening stone consecutive to the previous sharpening operation, and means for positioning the blade by relative to the grinding wheel, the latter positioning means being designed to compensate for the progressive wear of the blade.

Still according to the invention, the implementation of all of the aforementioned means is carried out according to an automatic cycle of operations which comprises the following phases - removal of the knife from the scraped surface, - release of the blade between the workpiece blade and counterblade - drive the blade along itself over a length of
less equal to that of the scraped surface, - reblocking of the blade, - simultaneously and consecutively sharpening of the blade, and - simultaneously and consecutively bringing the blade closer to the scraped surface.

 It will be noted that the aforementioned automatic cycle engagement signal may come either from a timer delivering the signal after periods of predetermined equal durations, or from a torque sensor developed between the knife and the drum, this torque being d 'The higher the blade is the less sharp. It will also be noted that since all the operations linked to sharpening are automatic, their cost will be lower than if they were done manually; consequently these operations can be carried out more frequently, therefore the blade will be in a better average state of sharpening and thereby very significant savings in energy will be made thanks to the increase in the efficiency of the blade, and consecutively, exchange across the surface.

 According to a first variant of the use of the sharpening means, these will be fixed on the path of the blade and advantage will be taken of the operation of driving and moving the blade to make its edge move against the grinding wheel.

 According to another variant, advantage will be taken of the immobility of the blade to move the sharpening means along a part of the cutting edge thereof; an advantage of this latter variant is that it allows very rapid drive of the blade, therefore a minimum duration of the scraping stop.

 According to a first variant of the embodiment of the blade itself, it is relatively rigid and it has a rectilinear conformation similar to that known in the current state of the art, except that it is substantially twice as much long. In this variant embodiment of the blade, the sharpening means will be arranged on either side of the blade support means, that is to say at each end of the drum; the drive of the blade will consist in moving it along itself, over half of its length, sometimes in one direction, sometimes in the opposite direction; alternatively it will sometimes be the sharpening means arranged at one end of the drum which will be used, sometimes the means arranged at the other end; preferably the sharpening means associated with this variant, will be movable along the blade.

 According to a second alternative embodiment of said blade, it consists of a sheet of elastic steel of high hardness, and it is wound on coils located on either side of the support means, that is to say at each end of the drum. According to this variant embodiment, the movement of the blade will, as in the previous variant, a back and forth movement with winding on the coils.

 According to a third alternative embodiment of the lamè, the latter is closed on itself by welding or brazing so as to form a circular loop. In this embodiment, the blade drive movement along itself will always take place in the same direction. Note that the loop formed by the blade can either surround the cylinder or be outside 8 thereof. In the latter case, the same blade can be used simultaneously in two distinct parts on two neighboring drums, while on third and fourth parts of this same blade, sharpening operations can be carried out, for example using mobile sharpening means.

 According to a preferred embodiment of the blade support means, these incorporating, as is known in the prior art, a blade-holding part, a counter-blade part, these two parts constituting with said blade situated between them a scraper knife extending over the entire length of the generator of the scraped surface, said blade-holder and counter-blade parts are made integral with one another by bolting, a space or corridor, for housing the blade being arranged between them its will be noted that in the prior art the tightening by bolts of the counter blade on the blade holder also had, contrary to what has just been said, the effect of also tightening and blocking the blade. Always according to the aforementioned embodiment at least one of said blade-holder and counter-blade parts is provided, opposite the other part, with an elastic pipe housed in a groove of said part at least, said pipe being intended , under the internal pressure of a fluid, to increase in diameter and to compress said blade against the other part.

 Preferably the above-mentioned blade support means further incorporate a so-called support plate situated against said blade in said passage, between said blade and said pipe, said support plate being intended to distribute over the side of the blade. the pressure of the hose and protect the hose against friction when moving the blade.

 The present invention also relates to the specific application of devices such as described above to vacuum-operated processing devices, in which the drum is contained in a sealed enclosure. Evaporators with a vacuum scraped surface are used in small numbers for very special uses and it seems that the reason for their low diffusion lies presisly in the need for frequent sharpening of the blades forcing the frequent breaking of the vacuum. described precisely allow the blade to be sharpened without having to break the vacuum.

 According to a first variant of such an application, the sharpening means can be arranged inside the enclosure.

 According to a second variant, the sharpening means are arranged outside the enclosure; in the latter case the blade passes through the wall of the enclosure at at least one sealed passage point.

 According to a preferred embodiment, said sealed passage at least incorporates a pair of flexible pipes arranged side by side, the blade being disposed between said pipes, said pipes being intended to receive a fluid under pressure so as to compress the blade between them; where it follows that the passage of the blade between the pipes is sealed, and that the pipes themselves being at least when they are under pressure, mounted in a sealed manner with respect to the enclosure, the passage of the blade through the enclosure is a sealed passage.

The present invention will be better understood and details will become apparent from the description which will be given of particular embodiments in relation to the figures of the appended plates, in which
Fig.l is a perspective schematic illustration of a rotary drum processing apparatus provided with a scraping device incorporating a strip blade wound on coils,
Fig.2 is a schematic sectional view of the blade support means,
Fig.3 is a schematic illustration of a member incorporating sharpening means and blade drive means,
Fig. 4 is a partial cutaway view of the same,
Fig. 5 is a schematic illustration of a drum seen from above equipped with a circular loop blade,
Fig.6 is a schematic sectional elevation of a vacuum treatment device equipped with a scraper device according to the invention,
Fig.7 is a schematic section of the same seen along the axis of the drum,
Fig.8 is an illustration of a sealed passage with which the apparatus of Fig.6 is provided, and
Fig.9 is a section along AA of the organ in Fig.8.

 In fig.1 a treatment device with a scraped surface which may for example be a rotary drum dryer 1 is provided with a scraping device according to the invention; the latter mainly consists of a blade or knife holder assembly 2, a blade 3 and means 4 for sharpening and driving the blade.

 The knife 2 is itself supported by means known in the prior art support and maneuverable for example pneumatically to alternately apply the blade against the drum or away from it. The knife itself, of which certain structural details fall within the scope of the invention, will be described in more detail in relation to FIG. 2.

 The blade 31 produced in accordance with the second variant described above is made of a strip wound on coils 5 and 6 located on either side of the blade support means, that is to say in the extension of each end of the knife 2, again on either side of the drum 1.

 In the embodiment of fig.1 the sharpening and driving means 4 which will be explained in relation to fig.3 and 4 are fixed relative to the knife.

 In fig.2 the knife 2 of the previous figure consists mainly of a blade-holder part 7, a counter-blade part 8, the parts 7 and 8 being made integral with each other by bolts such as 9 and spacer washers such as 10. The operating devices shown in the previous figure have not been shown in this figure. The spacer washers 10 provide between the blade holder and the counter blade a corridor extending over the entire length of the knife, this corridor serving to accommodate the blade 3 and a support plate 11.

 In the counter blade 8, and facing the blade holder 7, there is a first groove 12 of almost circular section extending over the entire length of the counter blade; this first groove serves as a housing for an elastic pipe 13; when the elastic pipe 13 is subjected to an internal fluid pressure, it presses on the support plate 11 which transmits this pressure to the blade 3 to block the latter against the blade holder 7; in the absence of pressure in the pipe 13 the blade can move freely along itself, that is to say in a direction perpendicular to the plane of the figure; it will be noted that the bolts 9 pass through the slots in the support plate 10 which is therefore wedged, with nevertheless a certain clearance, between the blade holder and the counterblade, and which therefore also does not accompany the blade when the latter is driven in displacement.

 A second groove 14 parallel to the groove 13 serves as a housing for a second pipe 15; this second groove is made in an overhanging part of the counterblade relative to the blade holder; this arrangement using the flexibility of the blade and the support plate makes it possible to standardize the pressure of the blade against the drum 1.

 The pressure, pneumatic for example, which is used to actuate the knife operating members to apply or move away (arrow 3 ') the blade of the drum, is applied to different values in the pipes 13 and 15.

 It will be noted that the arrangement of the support means of the blade as they have just been described in FIG. 2 is applicable not only to a strip blade wound at its ends, such as the blade 3 of the previous figure, but also to a circular loop blade such as that which will be described in relation to fig.5, as well as a rigid straight blade not shown in the figures.

 In fig.3 and 4 sharpening means mainly comprise a support 16, a support piece 17 between which is guided a blade 18 whose edge is subjected to the abrasive action of a grinding wheel 19; the blade 18 is positioned in height to be applied against the grinding wheel by a roller 20 adjustable in height; the blade is driven in displacement by drive means constituted by two rollers 21 and 22 pressing on the sides of said blade. In the example of the figures, the two rollers are motorized and made synchronous to each other by pinions 23 and 24 meshing one inside the other, the pinion 23 being driven by a motor shaft 25. Better visible on fig.4 a sharpening stone 26 is intended to remove the morfil consecutive to the sharpening operation.

 In fig.5 a rotary drum 30, seen from above, is provided with scraping means substantially similar to those of fig.1, except that a blade 31 is shaped in a circular loop; the loop is stretched between two drums 32 and 33 located on either side of the drum 30, at least one of which is a motor drum constituting the drive means of the blade.

 In the case of the figure in solid lines a sharpening means 34 is movable (arrow 35) along the part of the loop remote from the drum; in this embodiment, the blade is sharpened on part of the latter while another part performs the scraping function.

 There is shown in phantom a second drum 36 and a second sharpening means 37; the drum 36 rotates in the opposite direction to the drum 30 and it is scraped by a second part of the blade 31 which therefore scrapes the two drums 30 and 36 simultaneously. In the case of this double scraping action, the sharpening means 34 and 37 will be fixed relative to the drum and the blade 31 will be driven in scrolling in front of the grinding wheels with which the means 34 and 37 are provided, by the drive drums 32 and 33.

 In fig.6 and 7 a rotary drum 40 is contained in a sealed enclosure 41, as well as blade support means 42 similar for example to the support means shown in Figure 1. A blade 43 crosses the enclosure in sealed passages 44 and 45. Sharpening means and drive means for the blade1 similar for example to such means described above, are located outside the enclosure and are not shown in the figure.

 Recall that the blade 43 can be either a rigid rectilinear blade, or a flexible blade wound at each of its ends, or a flexible blade closed in a loop on itself.

 The passages 44 and 45 being sealed passages and the blade support means being included in.

the enclosure and operated from outside the latter, it is not necessary to break the vacuum of the enclosure to sharpen the blade. Such an arrangement makes it possible from a practical point of view the use under vacuum of dryers or scent concentrates with a scraped rotary drum.

 In Figs. 8 and 9, a sealed passage such as 44 or 45 consists of a solid piece 50, cylindrical for example, provided with two grooves of cylindrical section 51 and 52 opening into a slot 53 passing right through the piece 50 along its axis. The grooves 51 and 52 are intended to accommodate a pair of flexible pipes 54 and 55 respectively arranged side by side. The pipes 54 and 55 are each closed at one end by plugs 56 and 57 while their other end is connected by a conduit 58 to a source of compressed air. In the presence of a blade 43 in the slot 53 the pipes 54 and 55 subjected to an internal fluid pressure press against their respective housing 51 and 52 and against the blade 43; they thus close the gap between the slit and the blade almost perfectly. In the absence of pressure in the pipes, which occurs during the blade drive phase, the loss of vacuum due to the play existing between the blade and the slot is minimized.

 In the event that a greater passage seal is required, the couple of grooves and pipes can be doubled along the blade.

 Although we have described and shown examples of embodiment and application of a scraper device according to the invention, it should be understood that these are not limiting of the scope of the invention, which is defined by the claims which follow.

Claims (2)

1.- Scraping device for a surface treatment apparatus  key, such as a rotary drum heat exchanger, said  device incorporating a scraper blade supported by  support means for alternately either applying said la  me against said scraped surface, or move said blade away from  said surface, characterized  - in that said blade is at least twice as long  that a generator of said surface, and  - in that said support means incorporate means  to alternatively either block said blade or allow  moving said blade along itself, said la  being blocked when the support means apply it con  be the surface and, alternatively, said blade being free  to move along itself when the support means  move said blade away from the scraped surface,  where it follows that while part  of the blade performs its scraping function, another part  can be sharpened by appropriate sharpening means; 2.- Device according to claim 1, characterized  in that it further incorporates means  said to drive, to circulate said blade along  of itself, said drive means being essential  made up of at least two rollers intended to close  sion on the sides of said blade, at least one of said ga  lets being a drive roller 3.- Device according to claim 1, characterized:  in that it further incorporates  sharpening means comprising a grinding wheel and positioning means  height of the blade relative to the grinding wheel 4.- Device according to claim 1, characterized  in that said blade is flexible being  consisting of an elastic steel strip 5.- Device according to claim 4, characterized:  in that said flexible blade is wound  on either side of said support means on the coils 6.- Device according to claim 4, characterized  in that said blade is closed on  itself by welding or soldering, so as to form a bou  7. A circular key according to claim 1, in which said  support means further include a blade-holder part, a  counter blade piece, these two pieces constituting with said the  located between them a scraper knife extending over  the entire length of the generator from the scraped surface, ca characterized  - in that said blade holder and counter blade parts are  joined together by bolting, a space,  or corridor, housing the blade being formed between them,  and  - in that at least one of said blade-holder parts and con  tre-lame is provided, opposite the other piece of a pipe  elastic housed in a groove of said part at least, the  said pipe being intended, under the internal pressure of a  fluid, increase in diameter and compress said blade con  be the other part 8.- Device according to claim 7, characterized  by a so-called support plate located against  said blade in said corridor, between said blade and said  pipe, said support plate being intended to distribute over the  side of the blade the pressure of the pipe and to protect the latter  against friction when moving the blade  9.- Application of a device in accordance with any one of  previous claims to a scraped surface device  operating under vacuum in which the drum is contained  in a sealed enclosure,  where it follows that, said means  sharpening and said drive means being located either  inside the enclosure, or outside the enclosure  said blade crossing in the latter case said enclosure  thanks to watertight passages, the blade is sharpened  reads with a minimum loss of vacuum from said enclosure 10.- Device according to any one of claims 1 to 8  intended more particularly for an application in accordance with  claim 9, characterized  in that said watertight passages in  have at least a couple of flexible pipes arranged side by side,  the blade being disposed between said pipes, said pipes  being intended to receive a pressurized fluid so  to compress the blade between them,  from which it follows that the passage of the  blade between the pipes is waterproof, and that the pipes being  themselves at least when under pressure, mounted from  tightly relative to the enclosure, the passage of the  me through the enclosure is a sealed passage 11.- Device according to claim 1, characterized  in that said blade is a ri blade  straight guide.