EP2803425A1

EP2803425A1 - Dosage apparatus and operating method for a dosage apparatus

Info

Publication number: EP2803425A1
Application number: EP20130382178
Authority: EP
Inventors: Iñaki Miguel Perez; Pablo Valencia Marco; José Ramón Rodriguez Menendez; Angel Alegre Cortes; Ekaitz Barrasa Artamendi; Alesander Olea Abarrategi
Original assignee: Loramendi S Coop
Current assignee: Loramendi S Coop
Priority date: 2013-05-13
Filing date: 2013-05-13
Publication date: 2014-11-19
Also published as: WO2014184124A1

Abstract

Dosage apparatus for a machine adapted for manufacturing sand cores, comprising an inlet (1) for receiving bonding agent, a vessel (2) where the received bonding agent is stored, a conveying unit (3) for conveying the bonding agent from one site to another within the apparatus (100), control means for controlling the conveying unit (3) and an evacuation region (5) through which the bonding agent coming from the vessel (2) is evacuated towards its final destination. The conveying unit (3) comprises a variable-frequency drive, and the apparatus (100) comprises a scale (6) that is adapted for detecting the mass of the bonding agent that is supplied and is communicated with the control means, the control means being adapted for controlling the evacuation of the bonding agent from the vessel (2) depending on the detections obtained with the scale (6).

Description

TECHNICAL FIELD

The present invention is related to dosage apparatuses for machines adapted for manufacturing sand cores, and to operating methods for a dosage apparatus.

PRIOR ART

Sand cores are manufactured by mixing sand with a bonding agent, such as a type of resin for example, to harden it, and the process is performed in machines adapted for manufacturing sand cores. As a general rule, the amount of bonding agent to be used is predetermined, and a dosage apparatus for metering the bonding agent is used to control the amount of bonding agent that is supplied to the machine.
A dosage apparatus comprising a cylinder that receives bonding agent from a specific source and ejects it in a controlled manner towards the machine where the core will be manufactured is known. The ejection is performed in a controlled manner, so the ejected bonding agent is supplied in a controlled manner for manufacturing the core. The cylinder comprises a piston the movement of which causes the bonding agent to be ejected from cylinder, and said ejection, and therefore the supplied amount of bonding agent for manufacturing the core, is controlled by means of a controlled movement of the piston, the volume of bonding agent that is ejected when the piston moves being detected. Due to the accuracy requisites required in some cases, this dosage apparatus is not always the most appropriate. Such dosage apparatuses need leak-tight closures for their correct operation, and the elements providing the leak-tight closure can gradually deteriorate with use due to the chemical components of the bonding agent, for example, affecting the accuracy of the added bonding agent. This drawback also affects the quality of the added bonding agent, because with the deterioration of said elements air can be introduced, for example, contacting the bonding agent to be supplied. For example, in order to maintain high levels of accuracy in the supplied amount and a high quality of the supplied bonding agent, such dosage apparatuses require continuous maintenance and often times the replacement of the elements providing the closure, which is not always sustainable in economic terms. Furthermore, the wrong measurements of the supplied volume of bonding agent with the piston can occur with temperature changes due to the change in the density of the bonding agent, which directly affects the supply of bonding agent to the core, which can imply a core that does not comply with the necessary requirements for having received less bonding agent than that necessary, or it can otherwise imply a bonding agent excess in the core and therefore an increase in the cost of manufacturing the core.
Document US 4828461 discloses a dosage apparatus for machines adapted for manufacturing sand cores different from that discussed above. The apparatus disclosed in this document comprises a tubular vessel where the bonding agent to be supplied is introduced, and a plurality of sensors adjacent to the vessel. The vessel comprises a float in the bonding agent that acts as a moving indicator of the amount of bonding agent present in the vessel. The float comprises a permanent magnet and the sensors can comprise an electromagnet, such that they cooperate with the float and are able to emit a signal denoting the level (amount) of bonding agent in the vessel. The apparatus further comprises a conveying unit for conveying the bonding agent from the vessel to its final destination where it will be mixed with the sand, and as a result of the float and the sensors the amount of bonding agent that is supplied can be determined without the bonding agent coming into contact with elements that it could damage.

DISCLOSURE OF THE INVENTION

An object of the invention is to provide a dosage apparatus for machines adapted for manufacturing sand cores, as described in the claims.
The dosage apparatus of the invention is designed to be used in machines adapted for manufacturing sand cores, and more specifically for supplying a bonding agent in a controlled manner for manufacturing sand cores in machines used for such purpose.
The apparatus comprises an inlet for receiving the bonding agent coming from a supply source which is preferably external to the apparatus but which could also be part of the apparatus itself, a vessel where the bonding agent coming from the supply source is stored, a conveying unit for conveying the bonding agent from one site to another within the apparatus, control means adapted for controlling the conveying unit, and an evacuation region through which the bonding agent coming from the vessel is evacuated towards its final destination. The conveying unit comprises a motor, a pump operated by the rotation of the motor for loading the vessel with the bonding agent coming from the supply source and for discharging the bonding agent from the vessel towards the evacuation region, and a variable-frequency drive associated with the motor, which controls the rotation of the motor. Both the loading and unloading of the vessel can therefore be carried out in a simple manner.
The apparatus further comprises a scale which allows detecting the mass of the bonding agent being discharged from the vessel towards the evacuation region and which is communicated with the control means, the control means being adapted for acting on the variable-frequency drive depending on the information received from the scale so that the variable-frequency drive controls the rotation of the motor, the evacuation or discharge of the bonding agent from the vessel therefore being controlled depending on the measurements received from the scale. Thus the supply of the bonding agent is controlled taking into account the mass of the bonding agent and not its volume or its movement within a vessel, for example.
The bonding agent can therefore be supplied in a precise manner in order to obtain a sand core without the bonding agent coming into contact with sensitive elements that can deteriorate due to said contact. High precision in the supply of the bonding agent can be obtained by using high-precision scales for determining the mass of the vessel and its content, as required by the user. Furthermore, the temperature change does not affect precision because the mass, not the volume, is detected.
Another object of the invention is to provide a machine for manufacturing sand cores as described in the claims. The machine comprises a dosage apparatus such as the one discussed above, so the advantages discussed for the apparatus also serve for the machine.
Another object of the invention is to provide an operating method for a dosage apparatus for machines adapted for manufacturing sand cores, as described in the claims.
The method comprises a loading step in which bonding agent is loaded in a vessel of a dosage apparatus such as the one discussed above, and a supply step in which at least part of the bonding agent present in the vessel is discharged towards a machine adapted for manufacturing sand cores. In the supply step the mass of the vessel and its content is determined continuously, and the discharge is stopped depending on said measurement. A supply of bonding agent can be obtained with the method of the invention in an easy, simple and precise manner.
These and other advantages and features of the invention will become evident in view of the drawings and the detailed description of the invention.

DESCRIPTION OF THE DRAWINGS

Figure 1 schematically shows a first embodiment of the dosage apparatus according to the invention.
Figure 2 schematically shows a second embodiment of the dosage apparatus according to the invention.
Figure 3 schematically shows a third embodiment of the dosage apparatus according to the invention.

DETAILED DISCLOSURE OF THE INVENTION

One aspect of the invention is related to a dosage apparatus for a machine adapted for manufacturing sand cores. With reference to Figure 1, which schematically shows a first embodiment of the apparatus 100 of the invention, the apparatus 100 comprises an inlet 1 for receiving the bonding agent preferably coming from an external supply source 200, a vessel 2 where the bonding agent coming from the supply source 200 is stored, a conveying unit 3 for conveying the bonding agent from one site to another within the apparatus 100, control means (not depicted in the drawings) adapted for controlling the conveying unit 3, and an evacuation region 5 through which the bonding agent coming from the vessel 2 is evacuated towards the machine. The control means can comprise a controller, a microcontroller, a microprocessor, an FPGA or an equivalent device able to perform the required functions.
The conveying unit 3 comprises a motor M and a pump 30 operated by the rotation of the motor M for loading the vessel 2 with the bonding agent coming from the supply source 200 and for discharging the bonding agent from the vessel 2 towards the evacuation region 5, depending on the rotation direction of the motor M. Therefore, the conduit through which the bonding agent enters the vessel 2 and the conduit through which the bonding agent exits the vessel 2 correspond to one and the same conduit 7, the number of elements used in the apparatus 100 being reduced, resulting in a simpler, more compact and more economical apparatus 100.
The apparatus 100 further comprises a scale 6 which allows detecting the mass of the bonding agent being discharged from the vessel 2 towards the evacuation region 5 and which is communicated with the control means, the control means being adapted for acting on the variable-frequency drive of the conveying unit 3 depending on the information received from the scale 6, so that the variable-frequency drive controls the rotation of the motor M. The bonding agent can therefore be supplied in a precise manner to the evacuation region 5, and therefore to a machine adapted for manufacturing sand cores, without the bonding agent coming into contact with sensitive elements that can deteriorate due to said contact. Ample precision in the supply of bonding agent can further be obtained using high-precision scales for determining the mass of the vessel 2 and its content, as required by the user.
In the first embodiment, the scale 6 is arranged below the vessel 2 and is adapted for measuring or detecting the mass of the vessel 2 and of the bonding agent inside the vessel 2, the control means being adapted for receiving the measurement obtained on the scale 6 continuously and for determining the amount of bonding agent supplied towards the evacuation region 5 depending on the measurements received from the scale 6. The control means can have the mass of the vessel 2 stored therein, so the mass of the bonding agent that is being ejected or that is ejected from the vessel 2 can easily be obtained taking into account the stored mass of the vessel 2: the mass of the vessel is subtracted from the received measurements and the result will yield the mass of the bonding agent. So by knowing the initial mass of the bonding agent which corresponds to the amount of bonding agent present in the vessel 2 right before starting the supply thereof, the control means are able to identify the mass of the bonding agent that is supplied or that is being supplied by subtracting the value of the measurement that it receives from this initial value. The amount of bonding agent that is being supplied is therefore controlled in real time based on the mass thereof, and a very precise supply measurement is obtained.
Another simple way of being able to know the mass of the bonding agent that is supplied does not require knowing the mass of the vessel 2 beforehand; it is enough to compare both masses detected by the scale 6 (the initial mass and the mass detected at the current time during the supply). To that end, it is necessary to know the combined mass of the vessel 2 / bonding agent before starting the supply, and this can be known either by means of an initial weighing and/or by knowing the amount of bonding agent that is being loaded in the vessel 2 in the loading step beforehand, such as pre-establishing a maximum load of the bonding agent in the vessel 2 (maximum filling of the vessel 2 with bonding agent), for example. For safety's sake, even though an initial mass can be pre-established, it is preferable to perform an initial weighing to obtain this information.
Figure 2 schematically shows a second embodiment of the apparatus 100, which is analog to the first embodiment but further comprising an absorption valve 8 arranged between the conveying unit 3 and the inlet 1 and an ejection valve 9 arranged between the conveying unit 3 and the evacuation region 5. The absorption valve 8 preferably allows the flow-through passage of bonding agent in a single direction, specifically from the inlet 1 towards the conveying unit 3. The absorption valve 8 is communicated with the control means and, as it is controlled by the control means, it is adapted for allowing the flow-through passage of bonding agent only when the conveying unit 3 is acting for loading the vessel 2 with bonding agent. In another embodiment, the absorption valve 8 can correspond to a passive check valve or an equivalent element.
The ejection valve 9 preferably allows the flow-through passage of bonding agent in a single direction, specifically from the conveying unit 3 towards the evacuation region 5. The absorption valve 8 is communicated with the control means and, as it is controlled by the control means, it is adapted for allowing the flow-through passage of bonding agent only when the conveying unit 3 is acting to discharge or evacuate bonding agent from the vessel 2. In another embodiment, the ejection valve 9 can correspond to a passive check valve or an equivalent element.
In a third embodiment of the apparatus 100 shown by way of example in Figure 3, the apparatus 100 is analog to the apparatus of the second embodiment and further comprises safety means for the purpose of anticipating possible problems derived from excess pressure inside the vessel 2, which are associated with the vessel 2 and are adapted for detecting the pressure inside the vessel 2. An upper limit pressure value, which can be two bars, for example, is previously established, and the safety means are adapted for reducing the pressure inside the vessel 2 if it has been detected that this pressure is equal to or exceeds the upper limit value.
The safety means comprise a pressure controller 101 which is adapted for responding when the pressure detected inside the vessel 2 is equal to or greater than the upper limit value. Exceeding the upper limit pressure value can lead the vessel 2 breaking, so this breaking can be anticipated and prevented as a result of the pressure controller 101. The pressure controller 101 corresponds to a valve that is tared to approximately the previously established upper limit pressure value, such that when the pressure inside the vessel 2 is equal to or greater than this upper limit value, the valve opens and allows at least part of the air, bonding agent and/or mixture of air and bonding agent present inside the vessel 2 to be evacuated from the vessel 2 there through, the pressure inside the vessel 2 therefore being reduced. The pressure controller 101 can correspond, instead of to a valve, to any element or device that performs the same function as the valve. The container 2 comprises a hole for allowing the evacuation of air, bonding agent and/or mixture of air and bonding agent present in the vessel 2, and the pressure controller 101 is communicated with the hole directly or, preferably, through a conduit 21.
It has been mentioned that the supply source 200 is outside the apparatus 100, but in any of its embodiments said apparatus 100 can comprise an internal supply source instead of being connected to an external supply source.
A second aspect of the invention is related to a machine adapted for manufacturing sand cores and comprises a dosage apparatus 100 such as the one discussed for the first aspect of the invention in any of its embodiments.
A third aspect of the invention is related to an operating method adapted for being implemented in an apparatus according to the first aspect of the invention in any of its embodiments.
The method comprises a loading step in which bonding agent is loaded in the vessel 2 of the apparatus 100 through the conveying unit 3, and a supply step in which at least part of the bonding agent present in the vessel 2 is discharged towards the evacuation region 5 of the apparatus 100 so that it can be supplied through the conveying unit 3 to a machine adapted for manufacturing the sand core. The amount of bonding agent that is supplied during the discharge of said agent from the vessel 2 is determined in the supply step based on the mass thereof, and the discharge is stopped depending on said determination. The determination is performed continuously in real time, the amount of bonding agent that is being supplied being controlled at all times.
As discussed above, the apparatus 100 comprises at least one scale 6 which allows obtaining the mass of the bonding agent that is supplied, and one scale 6 or another can be selected depending on the precision needs of the supply, for example. Therefore, in order to obtain a sand core the bonding agent can be supplied in a simple and easy manner, and in the most precise manner required.
The scale 6 continuously detects the sum of the masses of the vessel 2 and of the bonding agent present inside the vessel 2 in real time, and this information reaches the control means which determine the supplied amount of bonding agent depending on said information. The explanation given in relation to the first aspect of the invention concerning different ways of obtaining the mass of the bonding agent depending on this information is also valid for the third aspect of the invention, so it is not repeated.
The supply step ends when the difference between the initial mass of the bonding agent in the vessel 2 at the beginning of the discharge (of the supply) and the mass of the bonding agent in the vessel 2 that is being detected at that time is substantially equal to the required amount of bonding agent. As discussed, the initial mass corresponds to the combined mass of the vessel 2 - bonding agent initially present in the vessel 2 or to the difference between the mass of the vessel 2 and the combined mass of the vessel 2 - bonding agent initially present in the vessel 2, and the current mass corresponds to the detected combined mass of the vessel 2 - bonding agent present at that time in the vessel 2 or to the difference between the mass of the vessel 2 and the combined mass of the vessel 2 - bonding agent present at that time in the vessel 2.
The supply step is preferably divided into at least two phases. In a first phase, the bonding agent is evacuated from the vessel 2 at a first speed, and in a second phase the bonding agent is evacuated from the vessel 2 at a second speed less than the first speed. The supply is performed through the conveying unit 3 of the apparatus 100, and the control of the control means allows performing same at two different speeds. The bonding agent is evacuated from the vessel 2 at the first speed until a predetermined amount of bonding agent less than the total required amount of bonding agent has been discharged, and at a second speed less than the first speed for discharging the remaining amount of bonding agent until the total required amount of bonding agent is reached. The predetermined amount preferably corresponds to approximately between 85% and 95% of the total required amount. A quick supply step is therefore obtained while at the same time precision of the supplied amount is maintained by ending with a lower speed. The amount of bonding agent that is supplied at the second speed is established as a function of a balance between the desired quickness of the supply step and the required precision in the supplied amount, so it is normal for the smallest possible amount of bonding agent which allows precisely controlling the total supplied amount to be supplied at that speed. The first speed will be the maximum speed at which it can be supplied, taking into account the elements present responsible for the supply and the control which is performed.
The method is also adapted for being implemented in a machine according to the second aspect of the invention in any of its embodiments.

Claims

Dosage apparatus for a machine adapted for manufacturing sand cores, comprising an inlet (1) for receiving a bonding agent from a supply source (200), a vessel (2) for storing in the apparatus (100) the bonding agent coming from the inlet (1), a conveying unit (3) for conveying the bonding agent between two separate points of the apparatus (100), control means adapted for controlling the conveying unit (3), and an evacuation region (5) through which the bonding agent is ejected or supplied in a controlled manner towards the machine adapted for manufacturing sand cores, characterized in that the conveying unit (3) comprises a motor (M), a pump (30) operated by the rotation of the motor (M) for loading the vessel (2) with the bonding agent coming from the supply source (200) and for discharging the bonding agent from the vessel (2) towards the evacuation region (5), and a variable-frequency drive associated with the motor (M), which controls the rotation of the motor (M), and in that the apparatus (100) comprises a scale (6) which allows detecting the mass of the bonding agent being discharged from the vessel (2) towards the evacuation region (5) and which is communicated with the control means, the control means being adapted for acting on the variable-frequency drive depending on the mass detected by the scale (6) so that the variable-frequency drive controls the rotation of the motor (M).
Dosage apparatus according to claim 1, wherein the scale (6) is arranged below the vessel (2) and is adapted for measuring or detecting the mass of the vessel (2) and of the bonding agent inside the vessel (2), the control means being adapted for receiving the measurement obtained on the scale (6) continuously and for determining the amount of bonding agent supplied towards the evacuation region (5) depending on the measurements received from the scale (6).
Dosage apparatus according to claim 1 or 2, comprising an absorption valve (8) which is arranged between the conveying unit (3) and the inlet (1) and which is adapted for allowing the flow-through passage of bonding agent coming from the inlet (1) towards the conveying unit (3) when the conveying unit (3) is cooperating in loading the vessel (2) with bonding agent.
Dosage apparatus according to any of the preceding claims, comprising an ejection valve (9) which is arranged between the conveying unit (3) and the evacuation region (5) and which is adapted for allowing the flow-through passage of bonding agent coming from the vessel (2) towards the evacuation region (5) when the conveying unit (3) is cooperating in ejecting the bonding agent from the vessel (2) and supplying it towards the evacuation region (5) for the machine adapted for manufacturing sand cores.
Dosage apparatus according to any of the preceding claims, comprising safety means for the purpose of anticipating possible problems derived from excess pressure inside the vessel (2), which are associated with the vessel (2) and are adapted for detecting the pressure inside the vessel (2).
Dosage apparatus according to claim 5, wherein the safety means comprise a pressure controller (101) which is adapted for responding when the detected pressure inside the vessel (2) is equal to or greater than a pre-established upper limit value, allowing the flow-through passage of air, bonding agent and/or a mixture of air and bonding agent present in the vessel (2) towards the outside of the vessel (2) in response to that situation.
Dosage apparatus according to claim 6, wherein the pressure controller (101) corresponds to a pressure valve that opens after reaching a pressure approximately equal to the upper limit pressure value.
Machine adapted for manufacturing sand cores, characterized in that it comprises at least one dosage apparatus (100) according to any of the preceding claims.
Operating method for a dosage apparatus according to any of claims 1 to 7, comprising a loading step in which bonding agent is loaded in a vessel (2) of the apparatus (100), and a supply step in which at least part of the bonding agent present in the vessel (2) is discharged towards an evacuation region (5) of the apparatus (100) so that it can be supplied, characterized in that the mass of the bonding agent is detected in the supply step during the discharge of said agent from the vessel (2), and the discharge is stopped depending on said detection.
Method according to claim 9, wherein during the supply step the mass of the bonding agent is being detected continuously in real time.
Method according to claim 10, wherein the supply step ends when the difference between the initial mass of the bonding agent in the vessel (2) at the beginning of the discharge and the mass of the bonding agent in the vessel (2) that is being detected at that time is substantially equal to the required amount of bonding agent.
Method according to claim 11, wherein the initial mass corresponds to the combined mass of the vessel (2) - bonding agent initially present in the vessel (2) or to the difference between the mass of the vessel (2) and the combined mass of the vessel (2) - bonding agent initially present in the vessel (2), and wherein the current mass corresponds to the detected combined mass of the vessel (2) - bonding agent present at that time in the vessel (2) or to the difference between the mass of the vessel (2) and the combined mass of the vessel (2) - bonding agent present at that time in the vessel (2).
Method according to claims 11 or 12, wherein during the supply step, the conveying unit (3) causes the evacuation of the bonding agent from the vessel (2) at a first speed until a predetermined amount of bonding agent less than the total required amount of bonding agent has been discharged, and at a second speed less than the first speed for discharging the remaining amount of bonding agent until the total required amount of bonding agent is reached.
Method according to claim 13, wherein the predetermined amount corresponds to approximately between 85% and 95% of the total required amount.
Method according to any of claims 9 to 14, wherein the vessel (2) is filled to its maximum capacity with bonding agent in the loading step.