GB1573277A

GB1573277A - Method and apparatus for mewtering portions ofr a substance

Info

Publication number: GB1573277A
Application number: GB1829177A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1976-05-07
Filing date: 1977-05-02
Publication date: 1980-08-20
Also published as: IT1086182B; NL7604941A; BE854026A; FR2350586A1; DE2719709A1; ES458581A1; JPS52145983A

Description

(54) METHOD AND APPARATUS FOR METERING PORTIONS OF A SUBSTANCE (71) I, ANTONIUS HURKMANS, a Netherlands subject of 71, Prof. Buyslaan, Baarn, the Netherlands, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed to be particularly described in and by the following statement-: The invention relates to a method for metering portions of a plastically deformable and at the same time somewhat resilient (i.e. compressible) substance, for which purpose a pressure chamber is provided with a reciprocating displacer, which chamber can, during the forward stroke of the displacer, be connected with at least one metering chamber, and during the return stroke with a supply of substance to be metered. Such a method for delivering portions of spongy dough is generally known.The reciprocating stroke of the displacer is obtained through a system of rods with a cam mechanism or a crank gear. In said system of rods an elastic link embodied as a spring is incorporated, in order to be able to assimilate smoothly the difference in the stroke of the displacer (depending on the size of the dough portions to be delivered) and the stroke of the cam- or crank gear. Said link, however, is the cause of some important disadvantages.

During the last phase of the forward stroke of the displacer, a standstill of the displacer will occur, in dependence on the size of the portion of dough to be delivered, during which standstill the energy produced by the cam- or crank mechanism, is accumulated in said spring.

When presently the pressure chamber is connected again with the dough supply, the force of the stressed spring will press back the dough from the pressure chamber, through the then still narrow passage to the supply, so that the energy, accumulated in the spring, is annihilated by the dough.

During the fast passage of the dough through the opening between the pressure chamber and the supply, the dough undergoes a sudden pressure drop, that is to say the pressure drops from a relatively high value in the pressure chamber, to the atmospheric pressure that prevails in the supply.

A second sudden pressure drop takes place in the dough, still present in the pressure chamber, at the moment that the expanding spring has reached its end phase and the displacer is coupled again suddenly, via an abutment, to the driving rod, which, however, at that moment has already started the suction stroke through the crank- or cam mechanism.

The result is an abrupt reverse motion of the displacer. Right before the reversal the dough is still influenced by the still high pressure of the spring. Right after the reversal the dough has to flow from the supply through the still narrow opening towards the pressure chamber, where a sub-atmospheric pressure arises. During reversal of the motion of the displacer, the dough in the pressure chamber undergoes a sudden pressure drop, i.e. from a rather high overpressure caused by the spring to a rather low sub-atmospheric pressure, that enables the dough to flow through the still narrow passage.

A sudden and considerable pressure drop in the dough is a very great disadvantage, since especially in pre-risen dough, gas bubbles occur, surrounded by a viscous layer of dough. When the pressure on the dough suddenly drops, the gas bubbles suddenly expand, so that the viscous cell membrane thins too fast and cracks. The escaped gas accumulates into larger gas bubbles and flows to the area with the lowest sub-atmospheric pressure. Consequently the homogenity of the dough gets lost and the quality decreases.

Moreover, these larger gas bubbles arrive, following a subsequent pressure stroke of the displacer, in the metering chambers and affect the volume of the dough confined in the metering chambers, so that the weight of the dough is then no longer constant. It is obvious that considerable sub-atmospheric pressures and sudden pressure drops should be prevented, in order to maintain the quality of the dough and for obtaining a constant weight of the produced pieces of dough.

Up to now one has tried to prevent the fast expansion of the spring by applying an oil buffer. A great part of the energy, accumulated in the spring, is then annihilated in the oil buffer. Presently, however, the resiliency of the dough itself, causes part of the dough to flow back to the supply, so that again, although to a smaller extent, a sudden pressure drop occurs.

According to the invention, there is provided a method of metering portions of a plastically deformable and resiliently compressible substance, wherein a pressure chamber is provided with a reciprocating displacer, the chamber being connected with at least one metering chamber during the forward stroke of the displacer, and with a supply of substance to be metered during the return stroke, the reciprocating movement of the displacer being generated by a pressure fluid in such a manner that on reaching a predetermined hydraulic pressure during the forward stroke of the displacer, pressure fluid is discharged to limit the pressure exerted, thus annihilating hydraulic energy and maintaining the pressure of the substance in the pressure chamber below a predetermined value.

Owing to the limitation of the pressure, the pressure on the dough only increases to a pre-adjusted, constant value, whereupon the displacer is stopped by the dough in the pressure and metering chambers.

The return stroke of the displacer preferably only starts when first the connection with the metering chamber(s) is closed, subsequently the displacer is discharged from the pressure fluid and finally the pressure chamber and the supply are interconnected. Dough will not then flow back to the supply, nor will energy be annihilated via the dough, and sudden pressure drops in the dough, extending down to considerable sub-atmospheric pressures, will not take place. The homogeneity and quality of the dough remain unchanged and the uniformity of the metered portions of dough is ensured.

The invention also provides an apparatus for metering portions of a plastically deformable and resiliently compressible substance, the apparatus comprising a hopper for the substance to be metered, a pressure chamber with a displacer for drawing substance from said hopper and discharging it into at least one metering chamber situated opposite the displacer, and motion means for connecting and disconnecting said metering chamber(s) with respect to the pressure chamber, wherein the displacer is connected with a double acting piston performing a metering stroke and a suction stroke, which piston is mounted in a cylinder having connections near both ends for the supply and the discharge of pressure fluid, the connection relating to the metering stroke also being in communication with a pressureless fluid container through a pressure limiting overflow valve and a mechanically operated valve.

The pressure fluid source is preferably formed by a cylinder having a double acting piston, actuated by a lever with an adjustable pivot, the lever being operated by mechanical means. By displacing the pivot, an adjustment is obtained of the reciprocating stroke of the displacer with respect to the volume/weight of the metered portions.

A further decrease of the subatmospheric pressure arising in the dough may be obtained by having the duration of the suction time relatively long with respect to the total cycle time. An important advantage of this is the fact that now the suction stroke need not be deferred until the time that an expanding spring has pressed the displacer to its outermost position, but that said suction stroke can be immediately put into operation, which means a further prolongation of the suction time. The fact, that the displacer is now no longer spring-biased when opening the connection between the supply and the pressure chamber, but that said'member is already displaced by the expanding dough in the direction of the suction motion before said opening operation, means a shortening of the suction stroke and consequently a further decrease of the suction speed.

The lever preferably has a slot in which a roller engages which is affixed to an arm, of which the position is determined by a double acting adjusting piston, the cylinder of which is linked in parallel with the cylinder of the source of pressure fluid.

Due to this arrangement an automatic adjustment is produced of the stroke of the double-acting piston of the pressure fluid source with respect to the length of the reciprocating stroke of the displacer, connected with the desired metering.

The preceding and further characteristics will be explained with the help of the drawing, which shows an exemplary embodiment of the apparatus according to the invention embodied in a dough metering machine.

Figure 1 is a schematic, partly sectional view of this apparatus; and Figure 2 is a diagram of the displacement of a number of elements of the apparatus of Figure 1.

The apparatus consists of a pressure chamber 1 having a reciprocating displacer 2. This chamber 1 is confined at its top by a movable slide 3, which simultaneously constitutes the bottom of a supply hopper 4. The slide 3 is connected to a rod 5, that forms part of a hydraulic operating piston 6. Opposite the displacer 2 is positioned at least one metering chamber 7, connected with the pressure chamber 1, and incorporated into a slidable head 8. The metering chamber is confined by a freely moving piston 9. The movability of the piston 9 is on one side confined by an adjustable abutment 11 and on the other side by an abutment edge 12.

In order to open and close the metering chamber(s) 7 with respect to the pressure chamber 1, motion means 13 are present, which consist of a hydraulic operating piston, by means of which the head 8 can be displaced between an uppermost position (shown in the drawing), in which the metering chamber(s) 7 is (are) fully connected with the pressure chamber 1, and a lowermost position, in which the pressure chamber is fully closed and the metering chamber(s) face(s) a discharge belt 44. The lowermost position of the head 8 causes the dog 10 to press the piston(s) 9 back, so that the dough pieces land onto a discharge belt 44, which further conveys said dough pieces.

The displacer 2 is affixed to a double acting piston 14, movable in a hydraulic cylinder 15. The forward (and in the drawing left-hand directed) stroke of the displacer 2 is generated by pressure fluid, from a source formed by a double acting operating piston 16 in a cylinder 17. This piston is displaced by a lever 18, which cooperates with a cam mechanism 19. The lever 18 has an adjustable pivot, being a roller 20. This roller is affixed to an arm 21, the position of which is determined by a double acting adjusting piston 22, of which the cylinder 23 is linked in parallel with the cylinder 17 from the source of pressure fluid. The roller 20 of the adjustable pivot of the lever 18 co-operates with a slot 24 in this lever.

Both extreme ends of the hydraulic cylinder 15 are connected at 25, 26 with the source of pressure medium, that is to say with the cylinder 17. Connection 25 is a conduit which connects slides of the covers of two cylinders 15 and 17. Connection 26 too is a conduit which interconnects the rod sides of said cylinders 15 and 17. The connection conduits 25 and 26 each have a branch 27, 28, which lead to the cover side, and the rod side respectively of the adjusting cylinder 12. In branch 27 a throttle 29 is accommodated and in branch 28 a nonreturn valve 30.

The connection conduit 25 moreover has a second branch 31, which is connected with a container 45 with pressureless fluid through a closing valve 32, which is operated by a cam disc 35, mounted on a central shaft 46. A third branch 33 of the connection conduit 31 is connected with the fluid container 45 through an overflow 34. The connection conduit 26 also has a second branch 36 communicating with the fluid container through a valve 37, operated by a cam disc 38, which is also mounted on the shaft 46.

In the part of branch 27 situated between the throttle 29 and the cylinder 23 there is another branch 39, that through an overflow valve 40 leads to the fluid container 45. In the part of branch 28 between the nonreturn valve 30 and the cylinder 23 a branch 41 is arranged, which also leads to the fluid container mentioned through a throttle 42.

The motions of the displacer 2, the head 8 and the slide 3, and the moments of opening and closing the valves 32 and 37 are shown schematically in a diagram in Figure 2. The positions of the front of the displacer 2 and the slide 3 are plotted horizontally against the angular displacement in degrees of the shaft 46 according to the scale on the left-hand side of the diagram.

The motion of the front side of the displacer 2 is represented by: line 50 during the pressure motion; line 51 during a standstill after completion of the pressure motion; line 52 during a suction motion; and line 53 during an inactive pressure motion.

The motion of the front side of slide 3 is represented by: line 54 during the closing motion; line 55 during completion of the closing motion; the pressure chamber 1 is then closed; line 56 during opening of the slide; and line 57 a standstill before the closing motion.

The positions of the upper side of the metering chamber 7 are plotted vertically, the angular displacement in degrees of the shaft 46 according to the lowermost scale in the diagram.

The positions with respect to the rotation of the shaft 46 of the upper side of the metering chamber 7 are represented by: line 58 during a standstill in the uppermost position; as is also shown in Figure 1; line 59 during descent of the head 8; line 60 during a standstill in the lowermost position of the head 8.

During this standstill dough is pushed by the carrier 10 out of the metering chamber(s); line 61 during ascent of the head 8.

Opening and closing the valves 32 and 37 takes place at the following points: points 62: valve 32 opens; points 63: valve 37 closes; points 64: valve 37 opens; points 65: valve 32 closes.

The dotted line shows the positions of the front side of the displacer when a short stroke is applied. It is clear that, during a short stroke, the speed of the displacer is lower than during a maximal stroke.

The apparatus as described hereinbefore operates as follows: We propose, that the situation, shown in the drawing, corresponds to an already partial forward stroke of the displacer 2, so that the piston 9 in the metering chamber 7 and the carrier 10 are gradually pushed back. The slide 3 is in the closed position. The motion of the displacer 2 is achieved by a supply of pressure fluid from cylinder 17 through the connection conduit 25 to cylinder 15. The piston 16 (the booster), is moved upwards by the cam disc 19, mounted on the shaft 46. Simultaneously the fluid, present at the rod side of said cylinder 15, is returned to the rod side of said cylinder 17 through a connection conduit 26.

During this phase of the motion of the displacer 2, shown in the motion diagram by line 50, the valve 32 is closed, for it only opens at point 62. The valve 37 is still open (from point 64), so that no subatmospheric pressure can arise in the connection conduit 26.

During the forward stroke of the displacer 2, the piston 9 will be moved so that it abuts against the adjustable abutment 11. From that moment the pressure in the substance (the dough), in the pressure chamber 1 and the metering chamber(s) 7 increases. The pressure of the pressure fluid in the connection conduit 25 and at the cover side of the pistons 14 and 16 also increased rapidly, until the adjusted pressure in the overflow valve 34 is exceeded. At a continuing motion of the booster 16 and a standstill of the piston 14, the pressure fluid will flow to the fluid container through branch 31 and 33, and the overflow 34. The pressure in the dough, in the pressure chamber 1 and the metering chamber(s) 7, remains constant, while in the mean time, via the motion means 13, the slidable head 8 is displaced downwards until the pressure chamber is fully closed.

At that moment (point 62 in the diagram) the cam 35 reaches a position by which the valve 32 is opened while the fluid pressure in the chamber between the pistons 14 and 16 is cut off and the dough under pressure in the pressure chamber 7 will expand, so that the displacer 2 is moved over some distance to the right. The motion (that is to say the rotation) of the cam 35 is, like all other motions, generated by the shaft 46, so that an exact coordination between the displacements of the elements is maintained. After the valve 32 is opened so that the pressure decreases, the slide 3 is opened (line 56 in the diagram). As a consequence of the pressureless state of the dough in the pressure chamber 1 a backflowing of the dough to the supply 4 will not occur so that the already mentioned disadvantage of a sudden pressure drop is effectively prevented.

At point 63 of the motion diagram the valve 37 is closed by the cam 38. At that moment the booster 16 has reached its uppermost position and starts its downward motion, caused by the cam gear 19.

During this downward motion the operating fluid will be moved, through the connection conduit 26, to the rod side of the piston 14, so that the displacer 2 immediately starts the return stroke. The fluid, present at the cover side of the piston 14, will be displaced through conduit 25 to the cover side of the cylinder 17, while missing fluid is supplied or excess fluid is removed through the branch 31 and the still open valve 32.

During the pressure motion, the displacer 2 has been stationary against the dough, enclosed in the pressure chamber 1, for some time while the booster piston 16 continued ascending. Piston 14 has consequently covered less than the full forward stroke. During the downward motion of the booster piston 16, the piston 14 will therefore accordingly complete the end phase of the stroke sooner than the booster 16. This completion time will get shorter when the standstill period has been prolonged, when the volume of the metering chamber was adjusted to a smaller extent or when the metered portions were smaller, respectively.

This offers the possibility of regulating the stroke of the piston 16 in such a way, that with larger portion weights a long stroke and with small dough weights a short stroke will arise. Consequently the suction speed of the displacer 2 will decrease, which drastically reduces the presence of any undesired sub-atmospheric pressures in the dough during the suction operation. Moreover less energy is annihilated through overflow 34, so that power is preserved. When piston 14 has reached the end phase of the suction stroke, the booster piston 16 will normally still have to descend a certain distance. The valve 37 is at that moment still closed.The operating fluid at the rod side of the cylinder 17 is displaced through the nonreturn valve 30 and the conduit 28 to the rod side of the adjusting cylinder 23, the piston 22 of which then moves to the right, together with the pivot (the roller 20) of the lever 18. The operating fluid at the cover side of the cylinder 23 will for the greater part flow back through the branch 39 and the overflow valve 40 to the container, so that in a subsequent cycle an identical motion of the cam mechanism 19 causes a shorter stroke of the booster 16.

In order to be able to increase the stroke of the displacer 2, a permanent provision constantly displaces the pivot over a small distance to the left. This provision is constituted by the branch 27 with the throttle 29 and the branch 41 with the throttle 42.

Said provision acts as soon as the metering piston 9 abuts against the abutment 11, while the stroke of the displacer 2 is blocked against the dough, enclosed in the pressure chamber 1 and thereby keeps the dough under pressure. Under these circumstances the operating fluid flows through the overflow valve 34 to the container, while part of the pressure fluid flows through the branch 27 and the throttle 29 to the cover side of the adjusting cylinder 23. The pressure fluid at the rod side of the piston 22 then flows through the branch 28 and 41 and the throttle 42 to the container 45.

Should during a single upward and downward motion of the booster piston 16 the full forward stroke of the piston 14 and consequently the stroke of the displacer 2 equal the return stroke, then the described method for adjusting the stroke of the displacer 2 tends to determine the position of the adjusting piston 22 and consequently the position of arm 21 and roller 20 thus, that the final pressure in the dough is just attained so that little or no operating fluid passes through the overflow valve 34.

In order to be sure that the final pressure, determined by the overflow valve 34 is attained in the dough in the pressure chamber 1 and the metering chambers 7 the amount of fluid displaced by the booster during the return stroke of the displacer 2 is smaller than required, in order to have the displacer perform the total stroke. The upward stroke of piston 16 (the pressure stroke) exceeds the downward stroke, so that during a part of said stroke the overflow valve 34 is constantly put into operation and the final pressure of the dough is always attained.

It should finally be noted that the invention is especially important in its application to a so-called dough distributing machine. Spongy dough is a vulnerable substance, which should not be submitted to a sudden pressure drop unnecessarily.

An effective prevention of said pressure drop is achieved to a great extent in the method and the apparatus according to the invention, this contrary to the prior art, which only includes insufficient means for satisfactorily correcting the use of an accumulation spring, required in a system, comprising rods.

WHAT I CLAIM IS: 1. A method of metering portions of a plastically deformable and resiliently compressible substance, wherein a pressure chamber is provided with a reciprocating displacer, the chamber being connected with at least one metering chamber during the forward stroke of the displacer, and with a supply of substance to be metered during the return stroke, the reciprocating movement of the displacer being generated by a pressure fluid in such a manner that on reaching a predetermined hydraulic pressure during the forward stroke of the displacer, pressure fluid is discharged to limit the pressure exerted, thus annihilating hydraulic energy and maintaining the pressure of the substance in the pressure chamber below a predetermined value.

2. A method as claimed in claim 1, wherein the return stroke of the displacer only starts when the connection with the metering chamber is closed.

3. A method as claimed in claim 2, wherein the return stroke of the displacer only starts when subsequently said displacer is discharged from the pressure fluid.

4. A method as claimed in claim 2 or claim 3, wherein the return stroke of the displacer only starts when the pressure chamber and the supply of substance are connected.

5. An apparatus for metering portions of a plastically deformable and resiliently compressible substance, the apparatus comprising a hopper for the substance to be metered, a pressure chamber with a displacer for drawing substance from said hopper and discharging it into at least one metering chamber situated opposite the displacer, and motion means for connecting and disconnecting said metering chamber(s) with respect to the pressure chamber, wherein the displacer is connected with a double acting piston performing a metering stroke and a suction stroke, which piston is mounted in a cylinder having connections

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. operation. Moreover less energy is annihilated through overflow 34, so that power is preserved. When piston 14 has reached the end phase of the suction stroke, the booster piston 16 will normally still have to descend a certain distance. The valve 37 is at that moment still closed. The operating fluid at the rod side of the cylinder 17 is displaced through the nonreturn valve 30 and the conduit 28 to the rod side of the adjusting cylinder 23, the piston 22 of which then moves to the right, together with the pivot (the roller 20) of the lever 18.The operating fluid at the cover side of the cylinder 23 will for the greater part flow back through the branch 39 and the overflow valve 40 to the container, so that in a subsequent cycle an identical motion of the cam mechanism 19 causes a shorter stroke of the booster 16. In order to be able to increase the stroke of the displacer 2, a permanent provision constantly displaces the pivot over a small distance to the left. This provision is constituted by the branch 27 with the throttle 29 and the branch 41 with the throttle 42. Said provision acts as soon as the metering piston 9 abuts against the abutment 11, while the stroke of the displacer 2 is blocked against the dough, enclosed in the pressure chamber 1 and thereby keeps the dough under pressure. Under these circumstances the operating fluid flows through the overflow valve 34 to the container, while part of the pressure fluid flows through the branch 27 and the throttle 29 to the cover side of the adjusting cylinder 23. The pressure fluid at the rod side of the piston 22 then flows through the branch 28 and 41 and the throttle 42 to the container 45. Should during a single upward and downward motion of the booster piston 16 the full forward stroke of the piston 14 and consequently the stroke of the displacer 2 equal the return stroke, then the described method for adjusting the stroke of the displacer 2 tends to determine the position of the adjusting piston 22 and consequently the position of arm 21 and roller 20 thus, that the final pressure in the dough is just attained so that little or no operating fluid passes through the overflow valve 34. In order to be sure that the final pressure, determined by the overflow valve 34 is attained in the dough in the pressure chamber 1 and the metering chambers 7 the amount of fluid displaced by the booster during the return stroke of the displacer 2 is smaller than required, in order to have the displacer perform the total stroke. The upward stroke of piston 16 (the pressure stroke) exceeds the downward stroke, so that during a part of said stroke the overflow valve 34 is constantly put into operation and the final pressure of the dough is always attained. It should finally be noted that the invention is especially important in its application to a so-called dough distributing machine. Spongy dough is a vulnerable substance, which should not be submitted to a sudden pressure drop unnecessarily. An effective prevention of said pressure drop is achieved to a great extent in the method and the apparatus according to the invention, this contrary to the prior art, which only includes insufficient means for satisfactorily correcting the use of an accumulation spring, required in a system, comprising rods. WHAT I CLAIM IS:

1. A method of metering portions of a plastically deformable and resiliently compressible substance, wherein a pressure chamber is provided with a reciprocating displacer, the chamber being connected with at least one metering chamber during the forward stroke of the displacer, and with a supply of substance to be metered during the return stroke, the reciprocating movement of the displacer being generated by a pressure fluid in such a manner that on reaching a predetermined hydraulic pressure during the forward stroke of the displacer, pressure fluid is discharged to limit the pressure exerted, thus annihilating hydraulic energy and maintaining the pressure of the substance in the pressure chamber below a predetermined value.

near both ends for the supply and the discharge of pressure fluid, the connection relating to the metering stroke also being in communication with a pressureless fluid container through a pressure limiting overflow valve and a mechanically operated valve.

6. An apparatus as claimed in claim 5, wherein the source of pressure fluid is formed by a cylinder having a double acting piston, actuated by a lever with an adjustable pivot, said lever being operated by mechanical means.

7. An apparatus as claimed in claim 6, wherein said lever has a slot in which a roller engages.

8. An apparatus as claimed in claim 7, wherein said roller is affixed to an arm, the position of which is determined by a double acting adjustable piston.

9. An apparatus as claimed in claim 8, wherein the cylinder of said double acting piston is linked in parallel with the cylinder of the pressure fluid source.

10. An apparatus as claimed in any one of claims 5 to 9, wherein the volume displaced by the piston of the pressure fluid source during the forward stroke of the displacer exceeds the volume of the return stroke.

11. A method of metering portions of a plastically deformable, compressible substance substantially as hereinbefore described with reference to the accompanying drawings.

12. Apparatus for metering portions of a plastically deformable, compressible substance substantially as hereinbefore described, with reference to the accompanying drawings.