GB2346336A - Apparatus for separating solids from oil - Google Patents

Abstract

Apparatus 10 for separating solids from oil comprises a housing 12 having a housing inlet 24 and a housing outlet 150. A rotatable drum spinner 50 has an inlet 116 and an outlet 57 at the opposite end thereof. A motor drives the spinner. A first pump 74 delivers oil to an inlet 112 of a second, disc, pump 120 concentric and rotatable with the spinner 50. The disc pump accelerates oil rotationally to the speed of rotation of the spinner and delivers the accelerated oil to the inlet of the spinner. Oil rotated by the spinner experiences centripetal acceleration so that denser particulate impurities 59 in the oil settle against the wall 58 of the spinner. Clean oil exits the spinner outlet and is directed therefrom to said housing outlet.

Description

APPARATS FOR SEPARTING SOLIDS FROM OIL The present'invention relates to an apparatus for separating solids from oil, and relates particularly, but not exclusively, to an apparatus for separating solid impurities from cooking oil.

It is known to separate splid impurities from cooking oil by passing the cooking oil through filtering apparatus.

Because of the tendency of cooking oil containing impurities to thicken at or near room temperature, especially if the oil contains animal fats, the oil needs to be filtered at elevated temperatures (typically 180 C), and often also needs to be passed through filtering apparatus at elevated pressure.

Prior art apparatus of this type suffers from the disadvantage that in order to, minimise the risk of hazardous escape of hot cooking oil at high pressure, specialist apparatus needs to be used. The use of such specialised equipment places a significant cost burden on users such as restaurants and fast foot outlets, with the result that the useful lifetime of cooking oil, is often significantly shorter than would be the case if filtering could be provided at lower cost. In addition, such specialised filtering apparatus cannot normally be operated without removing the oil from the fryer, which makes the process more time consuming and inconvenient.

US-A-3971508 discloses a wall-mounted oil clarification system comprising an open-topped drum rotated by a motor.

Oil, drawn by a pump also driyen by the motor, is delivered through the open top into the drum. The rotation of the drum causes higher density particulate material to settle to the outside of the drum under the action of centrifugal acceleration. Oil over-spills the drum and is returned to the source.

There are various issues with the arrangement and which casts doubt as to its general functionality. For example, the agitation of the oil by paddles in the drum, as well as spraying of the oil as it exits the drum, will exacerbate undesirable oxidation of the oil. Moreover, there would appear to be opportunity for oil, should it thicken on cooling, to block an exit from the device, so that there would be the subsequent danger that, on restarting, hot oil could flood the device. Moreover, there would seem to be the opportunity for oil entering the device to exit it immediately and without experiencing any great cleaning effect.

It is therefore an object of the present invention to provide apparatus for cleaning oil which does not suffer from the aforementioned, and other, problems, or at least mitigates their effects.

According to the present invention, there is provided an apparatus for separating solids from oil, the apparatus comprising: an apparatus housing having a housing inlet and a housing outlet and mounting a rotatable drum spinner having an inlet and an outlet at opposite ends thereof; a motor to drive the spinner; a first pump delivering oil from said housing inlet to an inlet of a second, disc, pump concentric and rotatable with the spinner, which disc pump is arranged to accelerate oil rotationally to the speed of rotation of the spinner and to deliver said accelerated oil to the inlet of the spinner by frictional engagement of the disc pump with the oil; whereby: oil rotated by the spinner experiences centripetal acceleration so that denser particulate impurities in the oil settle against the wall of the spinner and clean oil exits the spinner outlet and is directed therefrom to said housing outlet.

By means of the disc pump, no paddles are required in the drum spinner to accelerate the oil rotationally, and, as a result, there is reduced disturbance or agitation of the oil.

This has two effects: the first is that there is less encouragement to dissolve in the oil oxygen from the air which would promote oxidation, and thus deterioration, of the oil; and secondly, the settling out of solids in the oil is not prevented because of swirling of the oil. Instead there is only a smooth acceleration.

In another aspect, the present invention provides portable hand-held oil cleaning apparatus, comprising a spinner for centrifugal separation of dense particulate material from said oil, a motor to drive the spinner, and means delivering oil to the spinner on a continuous basis, wherein : the volume of the spinner is between 500 and 1000 ml, preferably between 700 and 800 ; ml, ideally about 750 ml; the speed of rotation of, the spinner is, in use of the apparatus, between 6,000 and 10,000 rpm, preferably between 7,000 and 9,000 rpm, ideally about 8,000 rpm; the diameter of the spinner is between 120 and 170 mm, preferably between 130 and 150 mm, ideally about 140 mm; the oil delivery rate is, in use of the apparatus, between 3 and 12 litres per minute, preferably between 4 and 8 litres per minute, ideally about 5 litres per minute; whereby: the spinner, in use of te apparatus, develops at least 4, OOOG, preferably in excesp of 5, OOOG, of centripetal acceleration and there is a'residence time of at least 3 seconds, preferably at least 4 seconds, of oil in the spinner.

By selection of these, parameters of the device, particularly in association with the design of cleaning apparatus defined in the first aspect of the present invention, a tool can be constructed which meets numerous criteria. The basic one of whjjch is that the tool (apparatus) should be portable and handheld, so that it can be employed to clean more than just one vat of oil. Thus the volume of liquid to be contained (bearing in mind the weight of the overall apparatus) should not be more than about 750 ml.

Furthermore, cleaning should not take longer than ten minutes or so because otherwise the job becomes too tedious and timeconsuming for an operator controlled task. Since oil is returned immediately it has been cleaned, it cannot be guaranteed that only unfiltered oil will enter the apparatus.

Thus, in this time, at least twice the normal volume of oil to be cleaned should be processed. An average vat volume is about twenty litres.

Therefore the resultant residence time, R, for oil in the apparatus will be: Vd x t R = Vt where Vd is the volume processed at a time, and Vt is the total volume to be processed in time t. This gives: 750x300 R = seconds, ie R = 5.625 seconds.

2 x 20 x 1000 The actual residence time is determined, of course, by the flow rate through the container, which, if that is set at 5 litres per minute, provides a residence time of 6.67 seconds and a total processing time of 8 minutes. With a residence time between 5 and 7 seconds, the required acceleration to achieve the requisite degree of cleaning is about 5000G. This acceleration for a period of 6 seconds is equivalent to 30,000 seconds at normal gravity, which time is found adequate to settle out most particulate contaminants of cooking oil to render the oil sufficiently clean and acceptable for reuse. A motor is, of course, required to drive a drum spinner. Most electrical motors can drive rotary apparatus at about 8,000rpm without introducing excessive vibration, at least not in a machine built to normal design tolerances. At 8000rpm, 5000G can be achieved with a spinner of diameter 140mm. Also, with this speed of rotation, a direct drive gear pump is capable of delivering the required flow, rate of 5 litres per minute.

With this weight of oil being spun at that speed, as well as driving a gear pump delivering that rate of flow with only a small head, about 350W of output power in an electric motor is found to be adequate, and not unduly heavy. This, together with the remaining apparatus, permits a liquid volume of 750 ml without infringing the basin desideratum.

Of course, the greater the residence time at any given speed, the finer will be the particles that are spun out of suspension in the oil. Since. this residence time is in direct conflict with the speed of processing of an entire vat of oil, it has been found that the be$t compromise is achieved when a vat is allowed to settle of ts own accord for two or three minutes prior to processing, po that larger particles can be swept up from the base of the vat. This effectively reduces the total volume of oil tho requires filtering (down to perhaps just 1.5 times the total volume).

In a yet further aspect, the present invention provides apparatus for separating solids from oil, the apparatus comprising an apparatus housing which mounts a rotatable drum spinner having an inlet and an outlet at opposite ends thereof, the inlet being radially outward of the outlet, and a motor to drive the spinner.

By arranging for the spinner outlet and inlet to be at opposite ends of the spinner, nd for the inlet of the spinner to be radially outward of tht inlet, the oil cannot shortcircuit the path of maximum acceleration or maximum residence time. Therefore, the most effective cleaning of the oil is assured.

Preferably, said disc puihp comprises two facing discs, which has the effect of increasing the surface area in contact with the oil. Indeed, facing discs may define an annular passage from the inlet of the second pump. The passage is preferably arranged substantially radially until it is adjacent the spinner inlet where it turns in a substantially axial direction. This has the effect of guiding the oil first radially and then axially as it enters the spinner. Ideally, the discs flare apart near the spinner inlet so that the cross section in the flow direction of the annular passage increases towards the spinner inlet. This has the effect of slowing the passage of the oil in both a radial and axial direction so that its entry into the spinner is quite smooth.

Preferably, the outlet of the first pump opens into a riser tube extending through the spinner. The riser tube may also flare outwardly at the inlet of the second pump so that the axial component of flow is converted into radial flow, in a smooth and non-turbulent manner.

Preferably, the motor rotates the first and second pumps at the same speed through a shared drive. Indeed, a shaft driving the first pump may extend along the riser tube from a drive flange driving the second pump. The drive flange may be mounted in the housing and comprise drive dogs which positively engage the first and second pumps whilst they are pressed against the drive flange.

Said first pump is preferably mounted in a pump housing received in said housing of the apparatus. Then, the shaft may be spring biassed between said pump housing and drive flange to accommodate thermal expansion of said shaft.

Moreover, the spinner may be rotationally mounted on said pump housing.

Preferably, said spinner is integral with said disc pump and one of said facing discs is an end wall of said spinner.

The spinner may also be spring biased between said pump housing and said drive flange. This again is to accommodate thermal expansion of the spinner. The spinner may comprise a substantially cylindrical side wall between its end walls, and may further comprise means to counter unbalancing effects of thermal expansion and contraction of the spinner by operation of the device in cleaning hot oil. Indeed, the spinner may comprise a pressing from sheet metal and said means may then comprise a circumferential convolution being formed in at least one end wall. Preferably, said convolution is radially outside the exit of said second pump. Alternatively, (or as well) said means may comprise at least one end wall being coned.

The outlet of the spinner may conveniently be through the pump housing around the outlet of the first pump. Indeed, said outlet of the spinner mgy be in the form of a sleeve received in the spinner which is a close sliding fit on a collar of the pump housing.

The spring bias for the spinner may be provided by a wave spring disposed between said sleeve and collar. A thrust washer can be disposed betweqn said spring and sleeve, the washer being rotationally fixed and axially limited by tabs on said collar which engage said washer.

Preferably, said first pump is a positive displacement pump, especially a gear pump. Said pump housing may include a pump plate and a pump body defining between them a pump inlet chamber in communication with the apparatus housing inlet through a port in the pump plate.

A further port in the pump plate can be in communication with both a pump outlet chamber and a passage in said pump body, which passage leads to said pump outlet. In which event, the further port might be closed to communication with said apparatus housing inlet by a pressure relief valve. This ensures that if there is a blocage inside the apparatus, hot oil will simply be short-circuited back to the housing inlet.

Said apparatus housing inlet may comprise a cone chamber, which preferably is cone-shaped, in communication with said first pump inlet, a suction tube depending from the end of said cone for immersion in a vat of oil to be cleaned.

In this way, oil may be drawn into the device at various angles of inclination of the suction tube with respect to the surface of the oil, and basically between about 10 and 90 degrees.

Said apparatus housing outlet may comprise an annular chamber surrounding said cone inlet chamber and having an annular orifice defined by a lip of said annular chamber and the wall of said cone chamber, whereby oil drawn into the apparatus through said suction tube and ejected through the apparatus housing outlet runs down the outsides of said cone chamber and suction tube. This ensures that at whatever angle the suction tube is disposed with respect to the oil surface while oil is drawn into the device, oil exiting simply flows down the outside of the cone chamber and suction tube in the safest possible manner, and so as to avoid splashing of oil which may pose a risk of scalding to an operator of the apparatus.

The apparatus preferably has a substantially vertical orientation, where the apparatus housing includes a top-most motor chamber, a spinner chamber disposed below the motor chamber and having an open bottom, and a base releasably connected to the open bottom of the spinner chamber and on which base the apparatus can be mounted on a support for vertical disassembly of the apparatus.

Thus, said drive flange may be mounted at the top of the spinner chamber and is driven by a shaft from the motor, and wherein release of the base from the spinner chamber automatically releases the connection between said drive flange and the first and second pumps and so that the first and second pumps and the spinner remain on the base when the motor and spinner chamber is disconnected from the base. This has several advantages. Firstly, the separation is between the"clean"motor and spinner chamber, on the one hand, and the"dirty"base, internal cpmponents and inlet and outlet chambers, on the other, which is left on the support.

Secondly, while the motor could still be switched on after separation, the only moving part exposed is now the drive flange deep within the spinner chamber, so that separation of the apparatus is an intrinsically safe procedure. Thirdly, no part in contact with the oil being cleaned requires any lubrication which the oil itself does not provide. This means that the opportunity for contamination of the oil by lubricant is minimised or even eradicated entirely with the design of the present invention. Of course, the motor and its support shafts require lubrication, but these are far removed from contact with the oil.

The invention is further described hereinafter, by way of example, with reference to the accompanying drawings, in which : Figure 1 is a cross-sectipn elevational view of apparatus embodying the present invention, Figure la being a detail rotated through 90 and showing flow directions and centripetal acceleration forces; Figure 2 is a view in the direction of the Arrow A in Figure 1, with a bottom part of the apparatus removed so that the pump body is visible; Figure 3 is a view in the same direction as Figure 2, except most removable contents of the apparatus housing have been removed; Figure 4 is a side view of the apparatus, with the apparatus housing removed; Figure 5 is a side view of the entire apparatus of the present invention; Figure 6 is a section through a lower part of the apparatus, shown seated on a mounting tray for the apparatus; and Figure 7 is an illustration of the design decision loops involved in reaching a practical design of apparatus in accordance with the present invention.

With reference first to Figure 5, apparatus 10 for cleaning oil comprises an apparatus housing 12 which, at an upper part, has an upper handle 14. Beneath the handle 14 is a casing or chamber 16 in which is received a motor (not shown), and beneath the motor chamber is a lower handle 18 which also receives a drive shaft from the motor. A spinner chamber 19 is part of the apparatus housing 12 and is located beneath the handle 18.

A lower part 20 of the housing 12 is connected to the chamber 19 by a band clamp 22. Out of the lower part 20 extends a suction tube 24 connected to an inlet chamber 26.

The base of the suction tube 24 is provided with a series of holes 28 to prevent the tube 24 from being blocked by the base of a vat of oil in which the apparatus is inserted. The suction tube 24 is long enough for most deep fat fryers such that the normal level of the oil would not rise above the base of the inlet chamber 26.

Turning to Figure 1, the apparatus housing 12 in the spinner chamber 19 rotationally mounts, through a bearing 30, a drive flange 32. The drive flange 32 is bolted by bolt 34 to the end of drive shaft 36 which extends through the intermediate handle 18.

Referring also to Figure 3, drive flange 32 has two outer dogs 36, and a central bore 38 formed in a sleeve 40 which has two sectors removed to define inner drive dogs 42.

Sleeve 40 also has an outer cylindrical surface 44 which centres a drum spinner 50 which has a central opening 52 in an end wall 54. Spot welded to the end wall 54 are two drive cups 56 adapted to be engaged by the dogs 36 in order to transmit rotary drive from the drive flange 32 to the spinner 50.

The spinner 50 has a cylindrical side wall 58 and bottom end wall 60. The spinner 50 ilp constructed from pressed steel components, the end wall 54 and side wall 58 being one component and the end wall 60 being connected thereto by a rolled edge 62. It may be desirable to have a similar rolled edge at the junction between te end wall 54 and side wall 58.

The end wall 54 is provided with a convolution 64. The end wall 60 has a short cylindrical flange 61 connecting it to the rolled edge 62. Both these features provide flexibility to the spinner 50 so that, when hQt oil first enters the spinner, as described further below, and the material of the spinner expands (or indeed as it contracts on cooling of the spinner) the convolution 64 and the hinge formed by flange 61 and rolled edge 62 enable the expansion/contraction to be accommodated without deformation or warping of the spinner which may cause imbalances in the spinner 50 and, more particularly, undesirable overlstresses of the material which could lead to cracking.

The lower end 20 of the housing 12, as mentioned above, comprises a cone inlet chamber'26, which is coned shaped, out of which suction tube 24 depeds. The chamber 26 is screw threaded to a base part 13 whiph also comprises a pump plate, as described further below. A, connection mechanism other than screw threading could, of course, be employed.

Between the chamber 26 and the pump plate 13 is retained a course filter 70 which prevents large particles from being drawn into the mechanism inside apparatus 10. In the pump I plate 13 is defined an inlet port 72 of a first pump 74. Pump 74 is formed in a pump body 76 (which is best seen also in Figure 2) and which is connected to the pump plate 13 by a number of screws 156 (see Figure 4) passing through bores 78 in the body 76. Two gears 80,82 are rotationally received in the body 76, a central one 82 being visible in Figure 1 and being journalled in the body 76 through a bearing 84. Gear 80 is likewise journalled in the body 76. However, central gear 82 receives a drive shaft 86 which is also received in, and centred by, the bore 38 of the drive flange 32. The shaft 86 has two drive pins 86a, 86b, 86a of which is engaged by the dogs 42 of the drive flange 32, while pin 86b engages a corresponding slot (not shown) in gear 82 to transmit drive from the flange 32 to the gear 82. A spring 88 biases the drive shaft into the bore 38 and prevents movement of the shaft 86 in an axial direction given its design tolerance in that respect in order to accommodate any thermal expansion/contraction thereof when hot oil is cleaned.

Gear 82 meshes with gear 80 and drives that gear so that both rotate in the direction shown by arrows in Figure 2.

Thus the suction chamber 90 of the pump 74, which is in communication with the port 72, becomes partially evacuated as the gears 80,82 rotate, such that oil at the bottom of the suction tube 24 can be drawn up the tube 24 and into the pump 74. There is thus no requirement for priming of that pump, as long as there is a reasonable seal between the gear 80,82 and the pump body 76 and pump plate 13, as well as the inlet duct being sealed above the oil surface. This latter feature may be ensured by an 0-ring seal 77. A pressure chamber 92 of the pump is in communication with a further port 94 of the pump plate 13. However, this port 94 is normally closed by a pressure relief valve 96 which is held in the closed position by a spring 98 bearing against a bridge 100 secured to the base of the pump plate 13. Thus, in the event that there is a blockage upstream of the port 94, oil pumped by the pump 74 is simply returned to the inlet chamber 26 from which it has just been drawn. It will be immediately apparent to the user, should this occur, because no oil will emanate from the proper exit 150 of the apparatus 10 a ; s described further below.

An arcuate passage 101 is formed in the body 76 in communication with the port 9. The passage 101 intersects a further passage 102 in the body 76. This passage is plugged by stopper 104, which is secured in place by grub screw 106.

Passage 102 opens into central axial bore 108 of the body 76 surrounding shaft 86. Received in bore 108 is a riser tube 110 which carries oil pumped by the pump 74 up to an inlet 112 of a second pump 120 which is 4 disc pump.

Disc pump 120 comprises qnd wall 54 of the spinner 50 and an annular disk 122 spot welded to the end wall 54 through a series of mating indentations 124 of the end wall 54 and disc 122 around the central axis of the apparatus 10. Thus the inlet 112 is formed by the edge of bore 52 of the wall 54, and a lip 114 of the disk 122. The lip 114 is designed to be close to, but not touching, the riser tube 110. The riser tube 110 is flared at its uppqr end so that its cross section increases very rapidly at its opening. This has the effect of reducing axial velocity of the oil rising in the tube 110, and instead translates that movement into radial outward flow.

The disc pump 120 is rotating with the spinner 50 being driven by the drive flange 32. Consequently, oil entering the inlet 112 immediately contacts the surfaces of the wall 54 and disc 122 and is accelerated rotationRlly.

Although, when fully primjed, disc pump 120 can pump oil, in fact, the only function of. disc pump 120 is to accelerate the oil rotationally. The capacity of the pump 120 to pump is entirely controlled by the positive displacement pump 74, and pump 120 can transport neither more nor less than the amount of oil metered by the pump 74.

Nevertheless, in the annular passage formed between the disc 122 and end wall 54, a Significant radial component of oil flow exists. The wall 54 and disk 122 is shaped to turn that flow from a radial direction into an axial direction.

Moreover, the cross section of that passage increases at an exit 116 of the pump 120, so that, once again, the rate of flow of the oil is slowed. The exit 116 of the pump 120 also constitutes the inlet of the spinner 50.

Thus oil pumped by the pump 74 enters the spinner 50 in a particularly smooth way having been accelerated rotationally to the same speed of rotation as the spinner 50 so that turbulence inside the spinner is kept to an absolute minimum.

Inside the spinner the oil 101 is retained for a period of time during which it is subject to an intense centripetal force G (see Figure la) so that denser, particulate matter in the oil tends to settle out against cylindrical wall 58 of the spinner 50, as shown at 59.

To the end wall 60 is connected a sleeve 118 which is a close sliding fit on a collar 126 of the pump body 76. A bushing 138 provides a seal therebetween. Axially through the collar 126 are formed three bores 128 which connect with further bores 130 inclined through the body 76. The bores 130 open opposite exit ports 132 in the pump plate 13. Beyond the ports 132 is an annular chamber 134 defined between a ring 136 screw threaded to the pump plate 13, and the cone chamber 26.

Thus an annular exit port 150 is defined through which the oil pumped by the pump 74 ultimately returns to its source. The orifice 150 is arranged so that the oil exits at low pressure and, by virtue of the coanda effect, sticks to the surface of the zone 26 and suction tube 24 and thus there is very little splashing of the oil. This both minimises danger to the user and oxidation and deterioration of the oil. Referring also to Figure 4, the sleeve 118 has a heel-flange 140 which abuts a thrust washer 142. Beneath the thrust washer is a wave spring 144 seated on a shoulder 146 of the body 76. A series of tabs 148 are secured to the body 76, and these engage ears 152 of the thrust washer 142 and prevent it from rotating with the spinner 150. Although preventing the thrust washer 142 from rotating, the tabs 148 also limit, but do not altogether prevent, axial movement of thq thrust washer 142. Thus the wave spring 144 presses the'thrust washer 142 against the heel-flange 140 of the sleeve 118 and thus the spinner 150 against the drive flange 32.

Returning to Figure 2, gear 82 is central, which implies that gear 80 is eccentric in the pump body 76. Pressure chamber 92 is offset between the two gears. Passages 130 are evenly spaced around the body 76. Therefore gear 80 is between two of the passages 130. This means that one passage 130 (x in Figure 2) is going to be substantially in line with pressure chamber 92. It is for this reason that passage 101 is partly arcuate, so that passage 102 can be angularly offset from that passage 130x.

As mentioned above, the pump 74, its bearings 84, thrust surfaces 140,142 and the bearing bush 126 are all lubricated by the oil being cleaned. therefore there is no risk of contamination of the oil by a separate lubricant. Bearing 30, supporting the motor drive shaft 36, does have independent lubrication, but the path to cpntaminate oil being cleaned in the apparatus 10 is so converted that the opportunity for contamination is practically eliminated.

By careful consideration of the various requirements of the apparatus 10, it has been concluded that the following parameters provide the optimut performance for the reasons expressed above. Thus the volume of the spinner is about 750ml. Its diameter is about 1, 40ml and its speed of rotation, in use, is about 8000rpm. In this way, about 5000G is developed. With this speed of rotation, the direct drive gear pump is capable of delivering 5'litres per minute, so that the average 20 litre vat of oil car be effectively cleaned in less than about ten minutes. To spin the spinner 50 and drive the pump 74, a 350 watt (of output power) motor is found to be adequate, with the end result that the overall apparatus 10 is manageable by a person of average build.

Figure 7 illustrates the numerous desiderata involved in reaching an appropriate specification for a practical design.

The various desiderata have impacts on each other so that selection of suitable parameters is not straightforward.

Thus in a first loop 200, the spinner diameter 202, spinner length 204, oil flow path 206 and bearing span 208 and overall product shape 209 all depend on one another. In loop 210, spinner diameter 202, motor speed 214 and centrifugal force available 216 are linked. On the other hand, in loop 220, residence time 222, bench settling time 224 (that is to say the time required of an equivalent device relying purely on gravity to settle out impurities) and centrifugal force required 226 are also linked. However, the centrifugal force available 216 and required 226 determine the effectiveness 228 of the device, which impacts then the number of passes 232 required through the device in loop 230. In loop 230, the number of passes 232 is dependent on the fryer capacity 234, the total job time limit 236 and the flow rate 238 through the device.

In loop 240, spinner length 204 and diameter 202 link with the spinner volume 242, which, in turn affects the question of residence time 222 and flow rate 238 in loop 250.

In loop 260, motor power 262 is linked with flow rate 238, oil viscosity 264, weight 266 and motor speed 214. Oil viscosity is, in turn, influenced by oil temperature 268 which also impacts oil density 270, oil viscosity 264 and density 270, as well as impurity particle density 272, determine the bench settling time 224.

Finally, in loop 280, weight 266, motor speed 214 and spinner volume 242 all influence each other.

Of all these criteria and parameters, only weight 266 (manageable by an individual of"normal"build), job time limit 236 (about ten minutes), fryer capacity 234 (about 20 litres), oil temperature 268 (hot, so that users do not need to wait for fryers to cool), and impurity particle density are inputs to the design. The remWinder are designer selected to optimise the performance of the apparatus.

Turning back to Figure 4, one each of two eye pairs 158, 160 are visible in the ring 136 and cone chamber 26 (the other of each pair being disposed'diametrically opposite those visible in Figure 4. These eyes 158,160 enable a tool (not shown) to be inserted and applied to unscrew the ring 136 and cone 26 (with its suction tube 24 connected thereto) respectively from the pump plat 13.

Turning to Figure 6, a support tray is shown which can be seated in a bucket and which comprises a support surface 172 on which the ring 136 may be seated. A depending orifice 174 receives the suction tube 24, and prevents the apparatus 10 from tilting when received on the tray.

Not only can the support tray 170 be employed to store the apparatus 10 when not in ue, it can also be employed for dismantling the apparatus 10 when parts of it are to be cleaned.

In this respect, the entire device is placed on the tray 170 with the suction tube 24 extending through the orifice 174. At this point, band clamp 22 is released so that housing 12 can be lifted off the pmp plate 13 leaving all the components below the drive flange 32 behind. Since all of those components are in contact with oil, and none of the components above the drive flange 32 are in contact with the oil, this is a very convenient split of the components. The casing 12 can then be placed anywhere without fear of dripping oil. On the other hand the spinner can be lifted off the collar 126 and over the riser tube 110. Any oil still contained therein can simply fall onto the body 76 and thereafter drain onto the tray 170.

Further dismantling of the pump 74 can also be effected, given that the screws 156 are easily accessible. However, on the whole, it will merely be a matter of washing out the spinner 50 to remove debris 59 that may be contained therein.

However, in normal use, it is intended that a user will maintain motor power while withdrawing the suction tube 24 from the vat of oil being cleaned. After a moment, no further significant amount oil will emanate from the exit 150, and indeed, the spinner (and to a certain extent its contained oil) will accelerate given that neither pump 74,120 is doing any further work. The apparatus is then transferred to the tray 170, whereupon the motor is switched off. The motor and spinner will quite rapidly come to a halt, so that oil still in the spinner 50 will continue to rotate and thereby swirl up the debris 59 hitherto firmly held lying against wall 58. As the oil slows spinning itself, it will drain from the spinner, and this is one reason why the end wall 60 is coned, so that run-off is facilitated. (The other reason it is coned is to give the spinner axial rigidity, which it needs to transmit the bias of the wave spring 144 against drive flange 32).

Thus the oil finally draining from the spinner 50 will be loaded with the debris 59, and mostly to such an extent that further cleaning of the spinner will not be required in normal use; the apparatus will be ready immediately for further cleaning operations.

As will be appreciated by persons skilled in the art, the parts removed from the apparatus can in most cases be cleaned in a conventional dishwasher, and the simple construction of the apparatus means that specialist personnel are not required to assemble and dismantle the apparatus. Finally, it is to be noted that the two pumps 74,120, are driven off a common drive, so that there is no requirement for any reduction gear.

Claims (1)

1. CLAIMS 1. Apparatus for separating solids from oil, the apparatus comprising: an apparatus housing having a housing inlet and a housing outlet and mounting a rotatable drum spinner having an inlet and an outlet at opposite ends thereof; a motor to drive the spinner ; a first pump delivering oil from said housing inlet to an inlet of a second, disc, pump concentric and rotatable with the spinner, which disc pump is arranged to accelerate oil rotationally to the speed of rotation of the spinner and to deliver said accelerated oil to the inlet of the spinner by frictional engagement of the dsc pump with the oil; whereby: oil rotated by the spinner experiences centripetal acceleration so that denser paxticulate impurities in the oil settle against the wall of the spinner and clean oil exits the spinner outlet and is directe therefrom to said housing outlet.

   2. Apparatus as claimed in Claim 1, in which said spinner inlet is radially outward of said spinner outlet and said second pump also transfers oil radially outwardly.

   3. Apparatus as claimed in claim 2, in which said disc pump comprises two facing discs.

   4. Apparatus as claimed in claim 3, in which said facing discs define an annular passage from the inlet of the second pump.

   5. Apparatus as claimed in claim 4, in which said passage is substantially radially arranged until it is adjacent the spinner inlet where it furies in a substantially axial direction.

   6. Apparatus according claim 4 or 5, in which the discs flare apart near the spinner itlet so that the cross section in the flow direction of the annular passage increases towards the spinner inlet.

   7. Apparatus as claimed in any preceding claim, in which the outlet of the first pump opens into a riser tube extending through the spinner.

   8. Apparatus as claimed in claim 7 in which the riser tube flares outwardly at the inlet of the second pump so that the axial component of flow is converted into radial flow.

   9. Apparatus as claimed in any preceding claim, in which the motor rotates the first and second pumps at the same speed through a shared drive.

   10. Apparatus as claimed in claim 9 when dependent on one of claims 7 or 8, in which a shaft driving the first pump extends inside said riser tube from a drive flange driving said second pump.

   11. Apparatus as claimed in claim 10, in which said drive flange is mounted in the housing and comprises drive dogs which positively engage the first and second pumps whilst pressed against the drive flange.

   12. Apparatus as claimed in any preceding claim, in which said first pump is mounted in a pump housing received in said housing of the apparatus.

   13. Apparatus as claimed in claims 11 and 12, in which the shaft is spring biassed between said pump housing and drive flange to accommodate thermal expansion of said shaft.

   14. Apparatus as claimed in claim 12 in which said spinner is rotationally mounted on said pump housing.

   15. Apparatus as claimed in any preceding claim, in which said spinner is integral with said disc pump and one of said facing discs is an end wall of said spinner.

   16. Apparatus as claimed in cilaim 15 when dependent on claim 14, in which said spinner is string biassed between said pump housing and said drive flange.

   17. Apparatus as claimed in any preceding claim, in which said spinner comprises a substantially cylindrical side wall between its end walls, and further comprises means to counter effects of thermal expansion and contraction of the spinner by operation of the device in cleaning hot oil18. Apparatus as claimed in claim 17, in which the spinner comprises a pressing from sheet. metal and said means comprises a circumferential convolution being formed in at least one end wall.

   19. Apparatus as claimed in, claim 18, when dependent on claim 15, in which said convolution is radially outside the exit of said second pump.

   20. Apparatus as claimed in claim 17, in which the spinner comprises a pressing from sheet metal and said means comprises at least one end wall having a cylindrical flange whose edge is rolled into connection with the side wall.

   21. Apparatus as claimed in claim 14 when dependent on claim 7, or as claimed in any of claims 15 to 20 when dependent on both claims 7 and 14, in which the outlet of the spinner is through the pump housing around the outlet of the first pump.

   22. Apparatus as claimed in claim 21, in which said outlet of the spinner is a sleeve received in the spinner which is a close sliding fit on a collar of the pump housing.

   23. Apparatus as claimed in claim 22 when dependent on claim 16, in which said spring bias is provided by a wave spring disposed between said sleeve and collar, and in which a thrust washer is disposed between said, spring and sleeve, the washer being rotationally fixed, and aially limited, by tabs on said collar.

   24. Apparatus as claimed in claim 23, in which said thrust washer is shaped so as also to form a bushing between the spinner and said collar.

   25. Apparatus as claimed in any preceding claim, in which said first pump is a positive displacement pump, preferably a gear pump.

   26. Apparatus as claimed in claim 25 when dependent on claim 12, in which said pump housing includes a pump plate and a pump body defining between them a pump inlet chamber in communication with the apparatus housing inlet through a port in the pump plate.

   27. Apparatus as claimed in claim 26, in which a further port in the pump plate is in communication with both a pump outlet chamber and a passage in said pump body, which passage leads to said pump outlet, said further port being closed to communication with said apparatus housing inlet by a pressure relief valve.

   28. Apparatus as claimed in claim 26 or 27, when dependent on claim 21, in which the outlet of the spinner is through an outlet passage in the pump body which communicates with an outlet port through the pump plate.

   29. Apparatus as claimed in any preceding claim, in which said apparatus housing inlet comprises a cone chamber in communication with said first pump inlet, a suction tube depending from the end of said cone chamber for immersion in a vat of oil to be cleaned.

   30. Apparatus as claimed in claim 29 when dependent on claim 26, in which the apparatus housing comprises a casing which is closed by connection thereto of said pump plate.

   31. Apparatus as claimed in claim 30 when dependent on claim 13 or 16, in which said connection biases said spring.

   32. Apparatus as claimed in claim 29 or 30, in which said apparatus housing outlet comprises an annular chamber surrounding said cone chamber, which cone chamber is coned shaped, said annular chamber having an annular orifice defined by a lip of said annular chamber and the wall of said cone chamber, whereby oil drawn ito the apparatus through said suction tube and ejected through the apparatus housing outlet runs down the outsides of said cone chamber and suction tube.

   33. Apparatus as claimed in claims 30 and 28, in which said outlet port opens directly into said annular chamber.

   34. Apparatus as claimed in any preceding claim, in which the volume of the spinner is between 500 and 1000 ml, preferably between 700 and 800, ml, ideally about 750 ml.

   35. Apparatus as claimed in any preceding claim, in which the speed of rotation of the spinner is, in use of the apparatus, between 6,000 and'10,000 rpm, preferably between 7,000 and 9,000 rpm, ideally about 8,000 rpm.

   36. Apparatus as claimed in any preceding claim, in which the diameter of the spinner'is between 120 and 170 mm, preferably between 130 and 150 mm, ideally about 140 mm.

   37. Apparatus as claimed in any preceding claim, in which the pump rate of the first puntp is, in use of the apparatus, between 3 and 12 litres per minute, preferably between 4 and 8 litres per minute, ideally about 5 litres per minute.

   38. Apparatus as claimed in any preceding claim, in which the spinner, in use of the apparatus, develops at least 4, OOOG, preferably in exces of 5, 000G, of centripetal acceleration and there is a'residence time of at least 3 seconds, preferably at least 4 seconds, of oil in the spinner.

   39. Apparatus as claimed in any preceding claim which, in use, has a substantially vertical orientation where the apparatus housing includes a top-most motor chamber, a spinner chamber below the motor chamber and having an open bottom, and a base releasably connected to the open bottom of the spinner chamber and on which base the apparatus can be mounted on a support for vertical disassembly of the apparatus.

   40. Apparatus as claimed in claim 39 when dependant on claim 11, in which said drive flange is mounted at the top of the spinner chamber and is driven by a shaft from the motor, and wherein release of the base from the spinner chamber automatically releases the connection between said drive flange and the first and second pumps and so that the first and second pumps and the spinner remain on the base when the spinner chamber is disconnected from the base.

   41. Apparatus as claimed in claim 39 or 40, in which the spinner has an outwardly coned bottom end so that, when not rotating, drainage of oil from the spinner is facilitated.

   42. Apparatus as claimed in claim 40, when dependent on claim 26, in which said pump plate comprises said base.

   43. Apparatus as claimed in claim 29 when dependent on claim 26, or any of claims 30 to 42 when dependent on both claim 25 and 28, in which said cone chamber is screw-threaded on a flange of said pump plate.

   44. Apparatus as claimed in claim 32 when dependent on claim 26, or any of claims 33 to 42 when dependent on both claim 26 and 32, in which said annular chamber is formed from a ring element screw threaded on a flange of said pump plate.

   45. Portable hand-held oil cleaning apparatus, comprising a spinner for centrifugal separation of dense particulate material from said oil, a motor to drive the spinner, and means delivering oil to the spinner on a continuous basis, wherein: the volume of the spinner is between 500 and 1000 ml, preferably between 700 and 800 ml, ideally about 750 ml; the speed of rotation of the spinner is, in use of the apparatus, between 6,000 and 10,000 rpm, preferably between 7,000 and 9,000 rpm, ideally about 8,000 rpm; the diameter of the spinner is between 120 and 170 mm, preferably between 130 and 150 mm, ideally about 140 mm; the delivery rate is, in'use of the apparatus, between 3 and 12 litres per minute, preferably between 4 and 8 litres per minute, ideally about 5 litres per minute; whereby: the spinner, in use of the apparatus develops at least 4, OOOG, preferably in exces of 5, OOOG, of centripetal acceleration and there is a residence time of at least 3 seconds, preferably at least 4 seconds, of oil in the spinner.

   46. Apparatus for separating solids from oil, the apparatus comprising an apparatus housing mounting a rotatable drum spinner having an inlet and an outlet at opposite ends thereof, the inlet being radially outward of the outlet, and a motor to drive the spinner.

   47. Apparatus as claimed in plaim 46, in which said spinner comprises a substantially cylindrical side wall between its end walls, and further comprises means to counter effects of thermal expansion and contraction of the spinner by operation of the device in cleaning hot oil.

   48. Apparatus as claimed in claim 47, in which the spinner comprises a pressing from sheet metal and said means comprises a circumferential convolution being formed in at least one end wall.

   49. Apparatus as claimed in claim 48, in which said convolution is in the wall including the spinner inlet and is radially outside said inlet.

   50. Apparatus as claimed in claim 47, in which the spinner comprises a pressing from sheet metal and said means comprises at least one end wall having a cylindrical flange whose edge is rolled into connection with the side wall.

   51. Apparatus as claimed in claims 49 and 50, in which the flanged end is in the wall including the spinner outlet, said end also being coned outwardly.

   52. Apparatus as claimed in claim 45, further comprising any of the features identified in any of claims 1 to 33, or 39 to 44.

   53. Apparatus as claimed in claim 46, further comprising any of the features identified in any of claims 1 to 16, or 21 to 45.

   54. Apparatus for cleaning cooking oil, substantially as hereinbefore described with reference to, and/or as illustrated in, the accompanying drawings.