Abstract:
In the mechanism for supplying waste metal cuttings from machine operations to a centrifuge having air suction means for separation and recovery of the cutting oils, a driven paddle-wheel type feed gate is provided in an inclined, gravity operated feed conduit for both maintaining a generally uniform rate of feed to the centrifuge and for serving as a barrier against the entry of air through the infeed end of the conduit. An air aspiration port is provided adjacent to and on the centrifuge side of the paddle wheel through which large metal chunks are discharged by gravity while smaller cuttings are entrained by the incoming air stream and transported past the port to the centrifuge. The bottom of the conduit at the feed gate is movably mounted to permit the passage of large, chunky material and means are provided to assure discharge of long pieces of material.

Description:
BACKGROUND OF THE INVENTION 
     In machine tool operations it is economically advantageous to recover cutting oil which is mixed with metal chips, turnings and large chunks of metal and the like generated by these operations. Means for separating the metal chips from oils are well known in the machine tool operations industry. Centrifuge separators are typically used. See, for example, U.S. Pat. Nos. 4,310,417, 4,137,176 and 3,850,814. 
     A well recognized problem with centrifuge separators is that they are easily and quickly damaged by the large chunks of metal, for instance, scrap parts and bar ends, which often are included in a stream of metal chips from such operations. Large pieces of metal will severely damage centrifuge rotors. In the past, this possibility required either that the mixture of metal chips, turnings, chunks and cutting oils be visually inspected before being fed into the centrifuge, or that frequent shutdowns and repairs to the centrifuge be tolerated. Either alternative increases the cost of operating such a system. 
     Several systems have been devised to separate the damaging large chunks of metal from the stream of oily metal chips before the stream is introduced into the centrifuge. These systems include the use of a means of air classification of the material in a metal chip stream prior to crushing. These earlier systems are very complicated and expensive which has discouraged their use. 
     U.S. Pat. No. 4,310,417 discloses a chute for feeding chips into a centrifuge or other separating equipment where an opening is provided on the bottom of said chute through which large pieces of metal can drop before such pieces are introduced into the centrifuge. In the chute of U.S. Pat. No. 4,310,417, small chips are prevented from falling through the opening by a strong current of air drawn through the opening by an appropriately equipped centrifuge or by another blower-like device attached to the downstream end of the chute. A pivotal gate in the chute upstream of the opening provides a partial restriction against air being drawn into the chute upstream of the opening while periodically permitting metal chips and metal chunks to be introduced into the chute separator. 
     While the invention of U.S. Pat. No. 4,310,417 was a significant improvement over prior separator systems, it was not entirely reliable as a chunk separator and was subject to surging or pulsing due to non-uniform feed rates to the classifier. 
     When the movement of the chips is by gravity, the rate of flow can become irregular resulting in a pulse type of flow with chips moving through the chute in large masses. Under such circumstances some large pieces of metal can &#34;wash over&#34; the opening and be fed into the centrifuge. In addition, when large amounts of metal chips are fed through the pivotal gate, the gate is opened sufficiently to allow significant quantities of air into the conduit, causing the air velocity through the opening in the bottom of the chute to decrease. This results in small metal chips falling through said opening. 
     Even when the device of U.S. Pat. No. 4,310,417 is fed by appropriate means to prevent the wash over described above, the separation is only partial and not efficient. A significant fraction of the small chips falls through the opening because of problems created when the pivotal gate opens i.e. the air velocity of the air entering through the chunk discharge opening decreases temporarily, creating a pulsing effect. 
     SUMMARY OF THE INVENTION 
     The present invention comprises a conduit with an opening in the bottom wall of the conduit intermediate the ends of the conduit. A paddle wheel type rotary metering element is provided between the opening and the intake end of the conduit. The paddle wheel regulates the flow of metal chips, chunks and the like into the chute. It also provides a damper controlling the entry of air and makes the air flow entering at this end substantially uniform. Attached to the conduit, typically at the outlet end, is means for generating air flow demand, frequently a centrifuge. The air is drawn through the opening, and, as the metal chips are fed into the conduit by the paddle wheel gate, the small metal chips are entrained in the air stream flowing through the opening and are carried down the chute into the centrifuge. By contrast, large chunks of metal fall through the opening for they are too heavy to be entrained in the air current. To protect the paddle wheel metering element and to accommodate extremely large chunks of metal a hinged segment of the bottom wall of said conduit is provided underneath the paddle wheel and resiliently biased into closed position. This segment extends from the intake end of the conduit to the opening in the bottom wall of the conduit and is hinged at the intake end. A modification of the invention combines a helix with the paddle wheel for separating long pieces of material. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevation of the invention as used in conjunction with the centrifuge connected to the outlet end of the separator; means for feeding the separator are also illustrated; 
     FIG. 2 is an enlarged side elevation view of the invention; 
     FIG. 3 is a sectional view taken on the line III--III of FIG. 4 showing in phantom the hinged section of the bottom wall of the conduit in the open position; 
     FIG. 4 is a partially broken top elevation view of the separator illustrating the paddle wheel gate which controls the feed to the separator; and 
     FIG. 5 is a fragmentary sectional view taken along the same plane as FIG. 3 illustrating a modified construction for the paddle wheel gate; 
     FIG. 6 is a sectional view taken along the plane VI--VI of FIG. 5; 
     FIG. 7 is an elevation view of the helix used in the paddle wheel gate of FIGS. 5 and 6; 
     FIG. 8 is a fragmentary sectional view taken along the plane VIII--VIII of FIG. 7; 
     FIG. 9 is a fragmentary side elevation view of a further modification of the invention; 
     FIG. 10 is a fragmentary plan view of the gate biasing device of FIG. 9; 
     FIG. 11 is a fragmentary view of the side opposite from that of FIG. 9 illustrating a further modification of the invention; and 
     FIG. 12 is a fragmentary sectional view taken along the line XII--XII of FIG. 11. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, conduit 10 is connected at its intake end to feed means 50 which can be either a gravity or a mechanical feeding device. The outlet end 13 of conduit 10 is attached to and discharges into a centrifuge 45 which is appropriately designed to create a suction through opening 11 in said conduit 10. Centrifuges of such design are well known in the prior art; see, for example, U.S. Pat. No. 4,310,417. Located intermediate opening 11 and intake end 12 is paddle wheel 30 shown in FIGS. 3 and 4 which is rotated clockwise to feed oily metal chips and chunks into said conduit 10. 
     The paddle wheel 30 has a plurality of blades 31 attached to shaft 33 and driven by pulleys 34 and 35 and motor means 37 and gear reducing means 37&#39; (FIG. 2). Circular flanges 36 are employed to reinforce the blades. Blades 31 can also be divided radially into inner blades 31a and outer blades 31b which are removably attached by fastener means 32. Thus, the outer blades of this design can easily be replaced as they wear out. 
     The bottom wall 23 of the conduit beneath the gate 30 has a hinged section 14. The hinged section 14 is pivotally attached to the intake end 12 of conduit 10 by means of hinge 15. However, it should be apparent that hinged section 14 can be hinged at various points between intake end 12 and paddle wheel 30. 
     The hinged section 14 extends beneath the paddle wheel 30 and forms the upstream end of the opening 11. The hinged section has upturned sides 26 which telescope over the outside of the conduit positively to confine the conduit&#39;s contents. To further assure positive sealing of the hinged section as it closes by eliminating interference from material in the conduit, the sides of the conduit are relieved at 27 from the hinge 15 to the upstream end of the opening 11. A baffle 20 is slidably secured to the hinged section at the opening 11. By means of the fastener 28, the position of the slide can be set to adjust the size of the throat of the opening 11 to provide the required air velocity for efficient classification and separation. 
     Preferably, the point of tangency between the paddle wheel 30 and the section 14 is closely adjacent the opening 11 and substantially spaced from the hinge 15. A pair of springs 16, one on each side of the conduit, are secured at 17 to the hinged section 14 intermediate the hinge 15 and the gate 30 (FIG. 2). The springs 16 bias the hinged section into closed position. 
     The conduit 10 should be dimensioned near said paddle wheel gate such that the distance between the top wall 24 of said conduit and the bottom wall 23 of said conduit is equal to the diameter of paddle wheel 30; the distance between side walls 25 should equal the width of paddle wheel gate 30. If dimensioned in this manner, the paddle wheel can form an effective barrier to the flow of air through the intake end as the paddle wheel gate rotates to meter the flow of metal chips into said conduit 10. 
     Preferably, the paddle wheel 30 is so designed that at least one paddle is always in contact with both the top of the conduit and with a layer of chips covering the bottom of the conduit. This is accomplished at the top of the paddle wheel by providing the arcuate segment 40 in top wall 24. This arcuate segment permits constant contact between the paddle wheel and the conduit, forming a continuous air flow seal. The ends of the paddle are designed to provide minimum clearance with the sides of the conduit. Practical minimum is that which will not cause a bind when a chip becomes wedged between the end of the paddle and the conduit side walls. 
     Vertical baffle 19, shown in FIGS. 2 and 3, is provided at the downstream end of opening 11 to create a surface against which a large piece of metal will impact and be caused to lose sufficient momentum to fall through opening 11. Smaller pieces of metal may also impact baffle 19. However, these smaller pieces will be entrained in the air current flowing upwardly through opening 11 and be carried through the outlet end 13 of conduit 10 into centrifuge 45. 
     The operation of the apparatus will now be explained in detail. From various metal machining operations a stream of metal wastes coated with cutting oil and including chunks of metal and small fine pieces of metal is fed by feed means 50 into intake end 12 of conduit 10. Paddle wheel 30 rotated in a clockwise direction, as illustrated in FIG. 1, feeds the metal chips into the conduit 10. Typically the paddle wheel is operated at a speed ranging from 10 to 50 revolutions per minute. However, there is no critical rotation speed; in fact, rotation speeds outside this range can be used to achieve desired results. 
     Centrifuge 45 or other blower means generates a suction through outlet 13 which in turn generates high velocity air current through opening 11. As paddle wheel 30 is metering the flow of chips and the like into the conduit, the velocity of the air current entrains the chips and carries them airborne across the opening 11 and then into the centrifuge while permitting the large chunks to hit baffle 19 and fall through opening 11. The position of the baffle 20 is adjusted to increase or decrease the velocity of the air flowing through opening 11. The adjustment will be varied to entrain all of the metal chips except those of greater than a preselected size. Baffle 19 can be raised or lowered to control the classification of the particles by varying the minimum size of chunks which will be separated from the material at opening 11. Raising baffle 19 will cause a smaller piece of metal to fall through opening 11. Lowering baffle 19 results in an increase in the size of particles which will be separated from the air stream. Means to provide such adjustments to baffles 19 and 20 are obvious and well known in the prior art, and will not specifically be discussed herein. Chute 22 is provided to direct into receptacle 60 the chunks falling through opening 11. 
     To protect the paddle wheel from damage and prevent it from being stalled by particularly large or odd shaped chunks of metal becoming caught between a blade and the bottom wall, the hinged section 14 of bottom wall 23 is provided to effect a safety release. When the gate 30 attempts to pass a large chunk of metal, hinge section 14 is forced downwardly against springs 16. Springs 16 restore hinged section 14 to the closed position against gate 30 after the large chunk has discharged. Since the end of the hinged section is within the chute 22 the chunk will discharge into the chute, particularly since the downward pivoting of the section enlarges the throat and decreases the air velocity. 
     FIGS. 1 and 2 illustrate a coil spring 16 attached to eyelets 17. The tension exerted by the springs is adjusted by the nuts 17a. The tension on the springs should be adjusted such that the hinged section will remain closed at all times unless forced open by a large chunk being forcibly carried under the rotating gate. 
     FIGS. 9 and 10 illustrate the use of weights 65 to bias the hinged section 14 into closed position. The weights, one on each side, are connected to the hinged section by a rope or chain passing over a pulley 66. The weights have the advantage over springs in that they maintain a uniform degree of bias at all times rather than a bias value which increases the further the hinged section is forced open. 
     FIG. 9 also illustrates a modified drive for the paddle wheel gate with the prime mover 37a mounted on the side of the conduit 10 connected to the gear reducer 67 mounted on the end of the paddle wheel shaft. 
     In the preferred embodiment of this invention, conduit 10 is positioned at approximately a 45 degree angle to the horizontal. Forty-five degrees is not a critical angle. Any angle between about 20 degrees and 50 degrees can normally be used, depending upon the sizes of the material to be moved through it and the viscosity of the oils coating the metal chips. While the preferred embodiment of this invention employs gravity to feed the material through the chute; it is possible to use a substantially horizontal chute with material movement down the chute assisted by vibration. 
     To increase the air seal efficiency and extend the life of the paddle wheel gate, the outer blade portions 31b are fabricated of a flexible material such as a medium durometer rubber or a reinforced material such as conveyor belting. When the outer blade portions are of a flexible material, no clearance need be maintained with the side walls since the blades will deflect to prevent any jamming of the mechanism. 
     FIGS. 5-8 illustrate a further modification designed to handle long objects. It has been discovered that some long objects such as lengths of bar or rod may not be effectively discharged by the paddle wheel gate 30 of FIGS. 3 and 4 because the gate and gravity combine to push the long pieces across the opening 11. To overcome this, the paddle wheel 30a has been modified by making its basic structure a helix 80 (FIG. 7). Within the helix 80 a plurality of paddles 81 are provided which extend to the periphery of the helix. A tapered guide plate 82 is secured to the inside face of the end of the hinge section 14. 
     Preferably, the guide plate 82 is not only tapered transversely of the conduit but also tapered in the direction of material movement so its thicker end will not act as a stop (FIG. 5). This plate is immediately downstream of the paddle wheel gate 30a and its downward taper is in the direction in which material is pushed by the helix as when the helix is rotated in the direction of arrow A in FIG. 6. The combination of the helix 80, paddles 81 and the guide plate 82 progressively pivot a long item into an angular position extending diagonally across the conduit. In this position it cannot bridge the opening 11 and its discharge through the chute 22 into the receptacle is assured. An adjustable baffle 20a can be provided below the guide plate 82 since the two serve different and non-conflicting purposes. 
     The paddle sections 81 are preferably of metal and secured to the helix 80 by suitable means such as welding. However, they could also be fabricated of other material such as reinforced rubber. A preferred construction for the paddle wheel gate 30a is to provide a plurality of radial slits 83 in the helix 80 and seat the paddles 81 in the slits with each paddle being a rectangular plate extending the full length of the paddle wheel. While FIG. 6 illustrates the plates extending to the root of the helix, this is not necessary since they are duly needed at the outer radial portion of the paddle as suggested by the short radial slots 84 illustrated in FIG. 7. 
     FIGS. 11 and 12 illustrate a further modification designed to accommodate particularly long chucks such as bars or rods. Occasionally the scrap will include pieces of such length that when turned sideways to the conduit 10 they may wedge between the sides of the conduit. When this happens, not only is the operation of the equipment stopped, significant damage to the equipment may also occur. 
     To eliminate this problem, a relief opening 70 is provided in the side of the conduit opposite from the end of the helix 80 of the gate 30a. The opening is located downstream of the paddle wheel gate and provides a means whereby the end of the long chunk can temporarily project out of the conduit. The opening 70 is normally closed by a panel or door 71 pivotally mounted along its upper edge by hinges 72. The hinges 72 incorporate means to bias the door closed unless forcibly caused to open. Such hinges have long been used for various purposes such as closing screen doors and the like. 
     In view of the foregoing, it is apparent that the present invention provides an effective means for separating large or oversize metal chunks from a stream of metal chips and cutting oil under a wide range of operating conditions. The invention provides an accurate and dependable means of classification through a wide range of conditions. Thus, the cutting oil laden metal chip stream can safely be introduced into a centrifuge. The machine can be adjusted as needed as the character of the chip stream varies from time to time. 
     Of course, it is understood that the above is merely a preferred embodiment of the invention and that various changes and alterations may be made without departing from the spirit and broader aspects of the invention. Such are to be considered as included in the hereinafter appended claims unless the claims by their language expressly state otherwise.