GB2091671A - Vacuum loader - Google Patents

Abstract

A vacuum loader (10) for pulverant, finely divided or granular material, comprising a material receiving hopper (12, 14) having a discharge valve (40) for controlling the application of a vacuum to the hopper 12, 14), which valve structure (40) is responsive solely to the discharge flow of material from the hopper or the blockage of such flow, said valve (40) having a magnet (42) for operating a switch (25) electrically connected to a control (60) for controlling operation of a vacuum pump (36) which creates a vacuum in the hopper (12, 14) to draw material into the hopper through a supply conduit (13), the material within the hopper acting on the valve (40) to move it to an open discharge position when a predetermined quantity of material is within the hopper and movement of the valve (40) causing the switch (25) to be operated to cut out the vacuum pump (36), said valve (40) being automatically returned to the closed position when the material has been discharged from the hopper and the switch (25) then being actuated to cause the vacuum pump (36) to be operated. <IMAGE>

Description

SPECIFICATION Vacuum loader This invention relates to granular or pulverant material vacuum loaders for initially receiving and subsequently delivering such material to the material receiving compartment of a machine for subsequent processing of the material.

As is known, granular or pulverant materials for use in the plastics moulding industry are suitably stored prior to use and techniques have been developed for transporting such materials through conduits by applying a vacuum to the receiving hopper of a vacuum loader. Once the loader has received a desired amount of such material, the material is discharged from the loader to the material receiving compartment of a moulding machine for subsequent use in the moulding machine. In sustained production of moulded plastics articles, the material in the material compartment is maintained at a level to provide sufficient material for each moulding cycle of the moulding machine.

It is also common practice to control the discharge of such materials from the receiving compartment of the moulding machine by providing a selectively operable valve between the hopper and the compartment such that when the vacuum in the hopper has been discontinued, the valve opens and material is discharged from the hopper by gravitational flow. Further, such valves are movable upon the application of a vacuum to the hopper to close the material discharge path from the hopper to permit the transported material to be deposited within the hopper. Such known valves are of various forms with one common form being a conic valve as shown in U.S. Patent No.

3,635,377. With such valve structure, the time period during which gravitational discharge of material occurs is determined by the time period the valve remains in the open position.

Accordingly, it is necessary to provide some control means, such as a timing control circuit, for actuating the actuating cylinder and establishing the time period the conic valve remains open.

Thus, the period of material discharge is determined solely by the control means regardless of any variations in the period required to entirely discharge the material from the hopper as may occur with various materials having different flow characteristics.

Another common for for such a valve is to form and support a flexible valve (see U.S. Patents 3,309,146 and 3,273,943) which is opened and closed in response to the applying and release of the vacuum in the hopper of the loader. Although such valves are satisfactory, they are not as efficient as a valve which is already in the closed position since closure of the valve is dependent upon the application of a vacuum in the hopper of the loader.

According to the present invention in one aspect there is provided a vacuum loader for granular or pulverant or the like material comprising; a material receiving hopper having a lowermost discharge opening for discharging material from said hopper, valve means supported for movement between a position in which said discharge opening is open and a position in which said discharge opening is at least substantially closed, biasing means co-operable with said valve means to bias said valve means into said at least substantially closed position, selectively energisable means for creating a vacuum within said hopper to hold said valve means in sealing engagement with said discharge opening and to convey material for deposit within said hopper, control means including co-operable portions carried by said valve means and fixed structure, respectively, for selectively controlling the energisation of said selectively energisable means for a period of time, said co-operable portions of said control means only being operable to permit energisation of said selectively energisable means when said valve means is initially in said at least substantially closed position and throughout said period of time, and said valve means having a surface thereof located in the material discharge flow path of said chamber such that material discharge flow from said chamber moves said valve means beyond said at least substantially closed position towards said open position.

According to the present invention in another aspect there is provided a vacuum loader for granular or pulverant material or the like in which such material is delivered via a vacuum line to the material receiving chamber of the loader for a period of time by a selectively energisable vacuum pump which creates a vacuum in the chamber and subsequently thereto the vacuum pump is deenergised and a valve member moves out of engagement with the discharge opening of the loader to permit the material in the chamber to be gravitationally discharged from the chamber and thereafter the valve member moves back into operative engagement with the discharge opening to permit a subsequent delivery of material to the chamber, said switch means having two portions, one portion of which is carried by such valve member and the other portion of which is stationary with respect to said on portion, said switch means being connected to means for controlling the energisation of such a vacuum pump, and said switch means being operable only to permit energisation of such a vacuum pump when such valve member is at least in close proximity to such a discharge opening.

In the present invention the movement of the valve for controlling the gravitational discharge of the material from the hopper of a vacuum loader is initiated by the flow of material over the valve after the vacuum in the hopper has been discontinued and the valve remains in its open position during the period of such material flow regardless of any variations in the time period required to obtain complete discharge of material from the hopper.In addition, control means having a portion thereof mounted with or movable by the valve structure co-operates with another portion of the control means to control the capability of energising the vacuum pump of the vacuum loader so that as soon as the material has been completely discharged from the hopper, the loader is again capable of receiving another load of material, provided the level of material in the hopper is such that the hopper can again receive another load of material from the hopper. In instances wherein the valve is restrained from movement by the material in the hopper the valve functions as a material level switch to prevent supplying additional material to the hopper.

Some embodiments of the invention will now be described, by way of examples, with reference to the accompanying drawings, in which: Figure 1 is a partial cross-section and partial side elevation view of a first embodiment of a vacuum loader according to the present invention; Figure 2 is an enlarged cross-sectional view of the valve structure portion in Figure 1; Figure 3 is an enlarged partial cross-sectional and partial side elevational view of a segment of an alternative form of valve structure; and Figure 4 is a partial side elevational view of an alternative embodiment of the invention.

A vacuum loader 10 (Figure 1) comprises an upper, vertically extending cylindrical body portion 12 having a frusto-conical lower body portion 14 extending coaxially downward therefrom which terminates in a lowermost downwardly extending circular flange portion 1 5. Cylindrical body portion 12 and lower body portion 14 define a hopper or chamber 1 8 of the loader 10. A suitable mounting plate 1 6 extends outwardly from and is suitably secured to the flange portion 1 5 to support the loader 10 on a material receiving bin (not shown) of a machine such as a plastics moulding machine.

The upper edge of the upper body section 12 is provided with an encompassing ring-shaped resilient seal or gasket 22 which resiliently engages a suitable cover 30. A suitable vacuum pump 36 is mounted externally on the cover 30 for selectively applying a vacuum to the hopper 18. Pump 36 is suitably driven by any suitable means such as an electric motor 38 (shown in part) supported by the housing of the pump 36.

Creation of a vacuum in the hopper 1 8 causes granular or pulverant material to be supplied to and deposited in hopper 1 8 through a suitable material feedline, such as a conduit or pipe 13, connected to an outwardly accessible end of a connector 20. Material is retained in and the discharge of material from the hopper 1 8 is controlled by the position of a movable material discharge control member which, in this embodiment, is a frusto-conical valve 40. In as much as the vacuum loader as heretofore described is well known to one skilled in the art, further description thereof is not necessary for the understanding of this invention; however, for additional details of such loaders and the controls therefor the disclosure of the previously mentioned U.S. patents can be referred to.

Flange portion 1 5 has a suitable encompassing resilient ring-shaped gasket 1 7 suitably secured thereto, which gasket 1 7 extends circumferentially around the interior surface of the flange portion 15 to define a discharge opening for the loader 1 0.

The lowermost portion of the gasket 17 extends around the lower free edge of the flange portion 1 5 and is engaged by the upwardly facing, outer conical surface of the valve 40 upwardly adjacent from the lower edge thereof when the valve 40 is in the illustrated closed position. An uppermost central portion 43 of the valve 40 extends horizontally to provide an uppermost flat area on the valve 40, which flat area is provided with a central clearance opening through which an elongated stationary support or rod 44 extends.

Rod 44 extends vertically and has a vertically extending central axis which is coextensive with the central axis (not shown) of the hopper 1 8. The central axis of the rod 44 is also perpendicular to the plane formed by the lower edge of flange portion 1 5. Rod 44 is suitably secured, as by welding, to a lowermost horizontal wall portion 49 of a bracket 48 spaced below the lower edge of the valve 40. Bracket 48 has a plurality of arms or wall portions extending upwardly from the ends of wall portion 49 with the upper ends thereof being suitably secured, such as by bolt and nut assemblies 52, to the mounting plate 1 6. A plurality of inverted L-shaped struts 50 are suitably rigidly secured to wall portion 49 such as by welding to encompass rod 44 such that their upper surfaces form a horizontal spring retaining platform 51.The struts 50 are also rigidly secured to the rod 44 in any suitable manner such as by welding. A circular spring retaining plate 56 is supported on the uppermost surfaces by struts 50 in any suitable manner. Plate 56 has a central opening therein to permit the rod 44 to extend therethrough. A biasing spring 54 concentrically encompasses the rod 44 and extends upwardly from the plate 56 with the upper and abuttingly engaging a ring magnet 42 for actuating a magnetic reed switch 25.

The ring magnet 42 is secured to the central portion 43 of the valve 40 in any suitable manner such as by bonding the upper surface of the magnet 42 to the lower surface of the central portion 43. Spring 54 is an open coil spring which, in its extended position, exerts a sufficient upward force on the undersur ce of the magnet 42 to place the upper conical surface of the valve 40 in engagement with the adjacent gasket 1 7 when no vacuum esists in the hopper 1 8. If desired, spring 54 in its extended position can support valve 40 so that the upper conical surface is spaced slightly downward from the gasket 1 7 to permit an air flow over the outer surface of valve 40 when a vacuum is applied to hopper 18 to remove any particles of the material being conveyed from the outer surface of the valve 40 which may have clung thereto from prior cycling operations.

Rod 44 has a central through bore 45 with the upper end thereof being closed in any suitable manner. The magnetic reed switch 25 is an elongated switch extending coaxially within the bore 45 and is secured to the rod 44 in any suitable manner such that when the valve 40 is in the closed position the magnet 42 surrounds the switch 25 and places the contacts of switch 25 in circuit making relationships. As is known, switch 25 comprises a pair of contacts with at least one of the contacts being biased out of circuit making relationship when the switch 25 is not in a magnetic flux field and which contacts are placed in circuit making relationship when the switch 25 is placed in a magnetic flux field. Suitable electrical conductors 62 are connected to the switch 25 and extend downwardly through the bore 45 to a known type of electrical control 60 externally of the vacuum loader.Control 60 is also electrically connected by suitable electrical conductors 63 to the motor 38 to control the energisation of the motor 38 as hereinafter described. The portion of conductors 62 external of the bore 45 may be located in a suitable wiring harness or channel to properly support the conductors 62.

As is known, in operation, material is selectively supplied to the hopper 18 of the loader 10 by energising the motor 38 and applying a vacuum to the hopper 18 by the pump 36. Upon applying the vacuum to the hopper 1 8 the valve 40 is moved upwardly by atmospheric air pressure existing on the underside of the valve 40 and effective thereon so that a proper air seal is obtained between the valve 40 and the gasket 1 7. Prior to energising the motor 38 and throughout the period of material conveying, switch 25 is in the flux field of the magnet 42 so that the contacts of the switch 25 are closed and the requisite control signal is provided to the control 60 to permit the energisation of the motor 38. Material is received in the hopper 1 8 until a predetermined amount of material is received therein such as at a level indicated at 27.It is to be realised that the applying and discontinuance of a vacuum in the hopper 18 is also controlled by other known control means (not shown) to provide the proper material conveying period. Once the hopper 1 8 has been filled to the desired level 27 the other control means de-energises the motor 38 and the vacuum being applied to the hopper 18 is discontinued.Upon discontinuance of the vacuum the material within the hopper 1 8 is effective upon the upward area of valve 40 to overcome the bias of the spring 54 to move the valve 40 to its lowermost position (shown in broken lines at 40') to permit the material to be gravitationally discharged from the hopper 1 8. Simultaneously with the downward movement of the valve 40, the magnet 42 is moved downwardly away from the switch 25 such that the flux field of the magnet 42 no longer retains the contacts of the switch 25 in circuit making relationship. Consequently after downward movement of the valve 40 the contacts of the switch 25 are in their open position and energisation of the motor 38 is prevented by the lack of signal through conductors 62 to control 60.

As the material from the hopper 18 is being discharged the force exerted on the valve 40 by the material will retain the valve 40 in its lowermost position until such time as the material is substantially completely discharged.

Accordingly, the bias of spring 54 is selected in conjunction with the weight of the valve 40 to provide for the longest period of material discharge consistent with the bias of the spring 54 which is needed to return spring 54 to the closed position. If desired, the spring 54 can be provided with a bias such that the upper surface of valve 40 is slightly spaced beiow the lower edge of gasket 1 7 in the normal upper position of valve 40 when no vacuum exists in hopper 1 8 to permit a slight discharge of material from hopper 18 until such time as a vacuum is reapplied to hopper 18.As an alternate construction a downwardly extending resilient sealing ring 55 (Figure 4) is suitably secured to the outer surface of the flange 1 5, which ring 55 slightly overlaps the outer surface of valve 40 to provide a wiping engagement therebetween when a vacuum is applied to hopper 18 and valve 40 moves upwardly. Although the bias of the spring 54 be sufficient to place the magnet 42 in encompassing relationship to the switch 25 when the material discharge from the hopper 1 8 is completed so that the contacts of the switch 25 are in circuit making relationship when the valve 40 is returned to its upper position by the bias of the spring 54. Also, when the valve 40 is moved downwardly by the material flow, the magnet 42 engages the upper surface of the plate 56 so that the total vertical movement of valve 40 is a specific dimension.Such limiting of the vertical movement of the valve 40 ensures that the valve 40 is returned to its proper upper position by the spring 54. If desired, the plate 56 can be selectively axially positioned with respect to the rod 44 to permit the bias of spring 54 to be selectively adjusted.

In as much as the rod 44 guides the magnet 42 through the relative axial movement described the central opening in the magnet 42 and the outer configuration of the rod 44 is selected as desired to ensure that the magnet 42 moves freely over the outer surface of the rod 44. As shown, the bore of the ring magnet 42 is slightly tapered in a downward direction to facilitate the free movement of the magnet 42 over the rod 44. If desired, suitable guide means, such as outwardly and axially extending circumferentially spaced projections, may be provided on the exterior of the rod 44 to guide the magnet 42 with a minimum of friction drag.

With the structure described the loader 10 is placed in condition for again receiving material as soon as the prior load of material has been discharged since the repositioning of the valve 40 in its upper position under the bias of the spring 54 occurs immediately after material discharge from the hopper 1 8 has been completed. Loader 10 is always in condition to receive material as soon as the material discharge from hopper 1 8 is completed. It should be noted, however, the repositioning of the valve 40 in its upper position does not mandate that a new material supply cycle be established as the other control means must be in a state to permit a subsequent material supply cycle.In instances where both control 60 and the other control means are in a state to permit material supply the supplying of material to the loader 10 can be controlled solely by the repositioning of the valve 40 in its upper position.

In instances where the material compartment of the machine receiving the material from the loader 10 is at a level that additional material is not desired, the valve 40 provides for discontinuing the material supply until the machine material compartment is in condition to receive additional material from hopper 1 8. For example, assuming a full load of material in hopper 18 and that the vacuum in the hopper 1 8 is discontinued, valve 40 will move to its lowermost position and material will be discharged from hopper 1 8 to the extent the machine compartment can receive material.If the full load of material in hopper 18 is in excess of that the machine compartment can receive, the material will stop flowing over the valve 40 and will rest above valve 40 in the lower portion of the hopper 1 8 and retain the valve 40 in its lowermost position at which the vacuum pump 36 cannot be re-energised due to the contacts of the switch 25 being out of circuit making relationship.

Eventually, as material is removed from the machine compartment, the material in the hdpper 18 will be fully discharged and the valve 40 returned to its upper position. In particular, there are no critical ratios with respect to the size of the hopper 18 and the size of the machine compartment as the valve 40 is restrained from upward movement as long as material remains in the lower portion of hopper 18. Nor will the valve 40 be restrained from its downward movement due to material levels in the machine compartment since the prior upward movement of the valve 40 only occurs after the weight of material restraining the upward movement of valve 40 has thus been removed by material flow within the machine compartment. Thus, the operation of valve 40 is responsive to the level of material in the machine compartment.

Figure 3 illustrates an alternative embodiment (in which like numbers identify like parts and like numbers primed identify parts of identical function) wherein the vacuum loader 10 is modified by having a flap or gate 82 to control and sense the flow of materials from the hopper 1 8. As shown, the loader 10 has a downwardly extending discharge throat 87 in the form of an inverted truncated cylinder such that the discharge opening extends at an upwardly extending angle. The discharge opening can be defined by essentially any geometric shape although circular is preferred.

A resilient gasket (not shown) like gasket 1 7 is suitably secured to the lowermost periphery of the discharge opening. Gate 82, shown in an open position as if material was flowing, is biased to a closed position (shown in broken lines at 82') by a counterweight 86 which is secured by an arm 88 extending outwardly and downwardly from the upper end of gate 82. Arm 88 is suitably fixed to the gate 82 and at the juncture point has an opening therein through which a pin 90 is inserted allowing the arm 88 and the gate 82 to rotate around the pin 90. Pin 90 extends through spaced brackets 92 (only one of which is shown) which are fixed to the mounting plate 1 6 as by welding and spaced part to allow the arm 88 and the gate 82 to rotate therebetween.A fixed support member 96 extends downwardly from the bracket 92 and has a magnetic reed switch 25' suitably supported thereby to be actuatad by a magnet 42'.

Magnet 42' is secured to the arm 88 in any suitable manner such that the magnet 42' is located adjacent the switch 25' with the gate 82 in the closed position (broken line outline) and is spaced from the switch 25' when the gate 82 is in the open position. Suitable electrical conductors (not shown) are connected to the switch 25' and to the control 60 such that the operation of this embodiment is the same as the operation of the previously described embodiment. Thus, with the gate 82 in the closed position the switch 25' is in the magnetic flux field of the magnetic 42' to permit material to be supplied to the hopper 1 8 for a selected time period.Once the hopper 1 8 is filled with the selected amount of material the vacuum is discontinued in the hopper 1 8 and the material in the hopper 1 8 weighs against the gate 82 to pivot the gate 82 to its open position. During such pivoting the magnet 42' is moved away from the switch 25' so that the contacts of the switch 25' are open. Once material discharge has been completed the material flow force.on the gate 82 ceases and the counterweight 86 returns the gate 82 to the closed position at which position the switch 25' is again in the magnetic flux field of magnet 42'.

Although the presentiy preferred embodiments have been described, it will be realised that various modifications can be made without departing from the scope of appended claims.

Thus, although a ring magnet 42 is preferred for the structure of Figures 1-3, any suitable form of magnet can be used which actuates the contacts of the switch 25 upon movement of the magnet into and out of operating proximity to the switch 25. Also, although a specific operation of the contacts of the switch 25 has been described, the control circuitry can be made to operate in response to either the opening or closing of the contacts of switches 25, 25'. Thus for example, the switches 25, 25' can be inverted as to their function. Also, if desired, the switches 25, 25' can be encapsulated in a suitable encapsulating medium to prevent the material from interfering with the function of the switches 25,25'. Also, although an individual motor 38 and pump 36 has been described in accordance with known practice, the valve 40 of this invention is equally applicable to a single vacuum line for a plurality of vacuum loaders such as a system as disclosed in U.S. Patent 3,431,026. Also, although a magnetic reed switch has been described, any switch which provides the operation as described can be employed, such as an electro-mechanical, fluid or electronic switch. Valve 40 may be made of a suitable resilient, deformable material and consequently gasket 1 7 need not be used. Further, bracket 48, struts 50, rod 44 and valve 40 and the pieces associated with that mechanism can be mounted on the receiving compartment of a plastics moulding machine rather than attached to the loader 10. Loader 10 would then be positioned on the receiving bin such that the valve 40 would engage the lower discharge opening in the same manner as heretofore described.

Claims (11)

1. A vacuum loader for granular or pulverant or the like material comprising; a material receiving hopper having a lowermost discharge opening for discharging material from said hopper, valve means supported for movement between a position in which said discharge opening is open and a position in which said discharge opening is at least substantially closed, biasing means cooperable with said valve means to bias said valve means into said at least substantially closed position, selectively energisable means for creating a vacuum within said hopper to hold said valve means in sealing engagement with said discharge opening and to convey material for deposit within said hopper, control means including co-operable portions carried by said valve means and fixed structure, respectively, for selectively controlling the energisation of said selectively energisable means for a period of time, and co-operable portions of said control means only being operable to permit energisation of said selectively energisable means when said valve means is initially in said at least substantially closed position and throughout said period of time, and said valve means having a surface thereof located in the material discharge flow path of said chamber such that material discharge flow from said chamber moves said valve means beyond said at least substantially closed position towards said open position.

2. A vacuum loader as claimed in claim 1, in which said co-operable portions of said control means comprises a magnet and a switch actuatable by said magnet.

3. A vacuum loader as claimed in claim 2, in which said magnet is carried by said valve means.

4. Vacuum loader as claimed in any preceding claim, in which the periphery of said lower discharge opening is annular and said control member has a cup-shaped upper surface which engages the periphery of said lower discharge opening when said control member is in said closed position.

5. A vacuum loader as claimed in any of claims 1 to 3, in which said co-operable portion of said control means comprises an arm movable into and out of juxtaposition with the other of said cooperable portions.

6. A vacuum loader for granular or pulverant material or the like in which such material is delivered via a vacuum line to the material receiving chamber of the loader for a period of time by a selectively energisable vacuum pump which creates a vacuum in the chamber and subsequently thereto the vacuum pump is deenergised and a valve member moves out of engagement with the discharge opening of the loader to permit the material in the chamber to be gravitationally discharged from the chamber and thereafter the valve member moves back into operative engagement with the discharge opening to permit a subsequent delivery of material to the chamber, said switch means having two portions, one portion of which is carried by such valve member and the other portion of which is stationary with respect to said one portion, said switch means being connected to means for controlling the energisation of such a vacuum pump, and said switch means being operable only to permit energisation of such a vacuum pump when such valve member is at least in close proximity to such a discharge opening.

7. A vacuum loader as claimed in claim 6, in which said two portions of said switch means comprise a magnet and a switch actuatable with respect to the presence or lack of the flux field of said magnet.

8. A vacuum loader as claimed in claim 6 or claim 7, in which one of said two portions is carried on a movable arm and is movable into and out of juxtaposition with the other of said portions,

9. A vacuum loader as claimed in any preceding claim, said valve member is restrained from movement by accumulation of such material thereabove.

10. A vacuum loader as claimed in claim 7, in which said magnet is carried by said valve member.

11. Avacuum loader for granular or the like material, substantially as hereinbefore described with reference to and as illustrated in Figures 1 and 2 or Figure 3 or Figure 4 of the accompanying drawings.