Vacuum chamber with double-propulsion material distributing device

Abstract

The utility model discloses a vacuum chamber with a double-propulsion material distribution device, which belongs to the technical field of vacuum pugging and comprises a pug feeding mechanism and a vacuum pugging chamber which are communicated with each other through a material distribution sieve plate, two pugging propulsion lines are arranged in the vacuum pugging chamber, and the two pugging propulsion lines respectively receive pug which is distributed by the material distribution sieve plate. And two pugging propelling lines are integrated in a vacuum cavity of the vacuum pugging chamber. The pug is distributed by the distribution sieve plate and then uniformly falls onto the corresponding pug propulsion lines, and is respectively and independently subjected to homogenization mixing and vacuum degassing treatment, and finally the pug is molded by the distribution lines and then pushed out. The capacity expansion of the vacuum pugging equipment is realized through double-line independent treatment, the production efficiency is improved, and the high integration degree of double lines ensures that the floor area expansion rate of the equipment is extremely low. Due to the fact that the pug of the double lines is processed in parallel after being distributed, the independent operation mode ensures the processing quality of the pug of each single line, and the homogenization and degassing effects are guaranteed.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the vacuum mud field, specifically a kind of vacuum chamber with double propulsion material distribution device. BACKGROUND

[0002] In the raw material processing field of ceramic, refractory material, building material and other industries, mud machine is used as core equipment to undertake the key process of homogenizing, degassing and extrusion molding of plastic raw materials. The traditional mud machine generally adopts single-line series structure design, that is, the raw materials are received through a single inlet, and the raw materials are pushed through the vacuum chamber, extrusion cavity and other processing units in turn by screw auger or hydraulic system, and finally the molded mud is output by a single outlet.

[0003] In the prior art, to meet the demand of large-scale production, enterprises usually adopt the following two solutions: one is to increase the equipment specifications (such as lengthening the auger shaft and expanding the cavity volume) on a single device to increase the processing capacity, but the production capacity improvement is obviously limited by the material strength, power system carrying capacity and equipment volume; the second is to configure multiple independent mud machines in parallel to form multiple production lines, which can realize the superposition of production capacity, but leads to the problems of doubled equipment procurement cost, significantly increased land occupation, significantly increased energy consumption and increased equipment maintenance complexity, which seriously restricts the production efficiency.

[0004] Some improved devices install a material distribution cylinder at the discharge port to automatically distribute the mud by mud thrust and mold distribution, realizing parallel production of two production lines on a single device. For example, the patent with publication number CN213107405U provides a double-outlet mud and mud strip cutting integrated device, which can extrude two mud strips at the same time through double discharge pipes and double discharge nozzles, and simultaneously perform operations such as adsorption, cutting, reversing, etc. on the two mud strips.

[0005] Although the above structure can realize double-line compatible parallel, it increases the load of screw auger and driving mechanism, and essentially realizes material distribution by increasing equipment specifications. The contradiction between the increase of single processing capacity of mud and the equipment load leads to the decrease of homogenization effect in the mud processing process, the significant increase of viscosity difference, feeding rate fluctuation, etc., which further leads to significant deviation of mud density, moisture content and homogenization degree of the two discharge ports, and it is difficult to meet the requirements of high-precision molding process on the consistency of mud, and repeated investment in mud machine is required for reprocessing, and the production efficiency is not significantly improved. UTILITY MODEL CONTENTS

[0006] The utility model aims to provide a vacuum chamber with double propulsion material distribution device to solve the problems in the prior art.

[0007] A vacuum chamber with double propulsion material distribution device is provided, comprising:

[0008] The mud feeding mechanism and the vacuum mud conditioning chamber are connected by the distribution sieve plate, and two mud conditioning advancing lines are arranged in the vacuum mud conditioning chamber.

[0009] As a further scheme of the present application, the mud conditioning advancing line comprises a feeding screw and a feeding cylinder, and the side of the feeding cylinder receiving the mud is recessed in the arc surface structure away from the distribution sieve plate.

[0010] The arc surface structure provides a space for the rotation of the feeding screw and matches the cross-sectional working area of the feeding screw and the spiral reamer, so that the dead zone of the mud treatment is avoided. In addition, the arc surface structures of the two mud conditioning advancing lines form independent working areas with both contact and space separation, so that the vacuum treatment of the vacuum mud conditioning chamber simultaneously acts on the mud on the two lines, and the cutting and crushing processes do not interfere with each other and are maximally integrated.

[0011] As a further scheme of the present application, the feeding cylinder of the two mud conditioning advancing lines has at least a parallel part close to the distribution sieve plate.

[0012] The shared part is formed by integral molding or welding molding to reduce the redundant space occupation, but still has a structure part separated from each other. The parallel part is to ensure that the mud distributed by the distribution sieve plate can smoothly fall into the respective mud conditioning advancing lines, to minimize the structural distance of the distribution sieve plate for the separation part and to reduce the probability of the mud falling and staying in the area between the two mud conditioning advancing lines.

[0013] As a further scheme of the present application, the feeding cylinder of the two mud conditioning advancing lines has at least a parallel part close to the distribution sieve plate.

[0014] The integral molding between the two feeding cylinders and the side wall of the vacuum mud conditioning chamber ensures that the area part will not have a weak structure, thereby reducing or even losing the vacuum effect due to the risk of damage and leakage.

[0015] As a further scheme of the present application, the feeding screw of the two mud conditioning advancing lines is opposite in the rotational linear velocity direction of the corresponding feeding cylinder bottom surface.

[0016] Through the arrangement, the advancing effect and the shearing direction of the feeding screw on the mud are biased towards the side wall of the vacuum mud conditioning chamber rather than the adjacent mud conditioning advancing line, so that the mud in the two mud conditioning advancing lines is not mixed and moved, and the uniformity of the final output of the double lines is ensured.

[0017] As a further scheme of the present application, the two side walls of the vacuum mud conditioning chamber are respectively provided with a distribution comb plate arranged opposite to the corresponding feeding cylinder.

[0018] The separating plate is used for cutting the mud into thin strips or small pieces, improving the degassing effect. On the basis that the feeding screw deviates the pushing direction of the mud to the side wall of the vacuum pug mill, the separating plate can better cut and recombine the mud, further disperses and homogenizes the water, additives or mineral particles in the raw material which are not fully mixed, eliminates local component differences, and ensures that the subsequent extrusion molded mud reaches high consistency in water content, viscosity and plasticity.

[0019] As a further scheme of the utility model, two discharge barrels are further included, and the two discharge barrels are respectively communicated with the corresponding feeding barrels.

[0020] The two discharge barrels can respectively and independently discharge, and since the discharging processes do not interfere with each other, the two discharge barrels can adjust the discharging angles thereof, provide larger operation space, and facilitate reprocessing or transportation.

[0021] As a further scheme of the utility model, the separating plate includes a partition plate and a plurality of through holes distributed on both sides of the partition plate and penetrating through the separating plate.

[0022] The separating plate forcibly divides the feeding mud flow into two independent substreams through the partition plate, blocks the cross mixing of the double-line mud, and ensures the process independence. The through hole area on both sides of the partition plate forms independent flow channels, and suppresses the non-uniform situation of the double-line mud discharge amount caused by the mutual conduction of the pressure fluctuation of the double-line mud.

[0023] As a further scheme of the utility model, the distribution rate of the through holes on the separating plate is 20% to 35%.

[0024] The through holes need to maintain a certain spacing to avoid pressure coupling effect, and appropriate through hole distribution rate balances the passing efficiency of the mud, the strength of the separating plate and the pressure coupling, and ensures that the separating plate always uniformly discharges and separates the mud.

[0025] As a further scheme of the utility model, the distribution rate of the through holes on the separating plate is 25% to 30%.

[0026] As a further scheme of the utility model, at least 95% of the through holes are rectangular round holes, and the width-length ratio of the rectangular round holes is 4 to 9:20.

[0027] As a further scheme of the utility model, the width-length ratio of the rectangular round holes is 5 to 6:20.

[0028] The bending resistance of the mud strip after extruding from the through hole is related to the section moment of inertia, and the risk of the mud strip buckling due to self weight or external disturbance can be reduced by limiting the width-length ratio. Properly reducing the width-length ratio can ensure that the mud strip does not immediately break and cause wall hanging when continuously extruding. If the width-length ratio is too small, the cross-sectional flow velocity distribution of the mud material passing through the through hole will be uneven, and instability will occur, which will aggravate the stress concentration and cause the mud material to break.

[0029] Compared with the prior art, the beneficial effects of the utility model are that:

[0030] Two mud mixing and advancing lines are integrated in the vacuum mud mixing chamber, and the two mud mixing and advancing lines share one vacuum chamber. The mud material pushed by the mud feeding mechanism is uniformly dropped on the corresponding mud mixing and advancing line after being separated by the separating sieve plate, and is independently subjected to homogenization mixing and vacuum degassing treatment in the two mud mixing and advancing lines, respectively, and is finally shaped and pushed out by the two lines. The expansion of the vacuum mud mixing equipment is realized by independent treatment of the two lines, the production efficiency is improved, and the high integration of the two lines ensures that the equipment occupies a very low expansion rate. Since the mud materials of the two lines are processed in parallel after being separated, the independent operation mode ensures the processing quality of the mud material of each single line, and the homogenization and degassing effect is guaranteed. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments or the prior art, the drawings needed to be used in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the drawings, and other drawings can be obtained by those skilled in the art without creative labor.

[0032] Figure 1 It is a top view of the vacuum chamber with a double advancing and separating device.

[0033] Figure 2 It is a top view of the internal structure of the vacuum mud mixing chamber.

[0034] Figure 3 It is a side view of the internal structure of the vacuum mud mixing chamber.

[0035] Figure 4 It is a structure schematic view of the separating sieve plate.

[0036] In the drawings: 1, mud feeding mechanism; 2, vacuum mud mixing chamber; 21, separating comb plate; 3, separating sieve plate; 31, separating plate; 32, through hole; 4, mud mixing and advancing line; 41, feeding screw; 42, feeding cylinder; 5, discharging cylinder. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical scheme and advantages of the utility model clearer and more understandable, the utility model is described and explained below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the utility model and not to limit the utility model. Based on the examples provided by the utility model, all other examples obtained by those of ordinary skill in the art without creative labor fall within the scope of the utility model.

[0038] Obviously, the drawings in the following description are only some examples or embodiments of the utility model, and for those of ordinary skill in the art, the utility model can be applied to other similar scenarios without creative labor on the basis of these drawings. In addition, it can also be understood that although the efforts made in this development process can be complex and lengthy, some design, manufacture or production changes based on the technical content disclosed by the utility model are only routine technical means for those of ordinary skill in the art related to the disclosed content of the utility model, and should not be understood as insufficient disclosure of the utility model.

[0039] However, there will be cases of omitting unnecessary detailed description. For example, there are cases of omitting detailed description of well-known matters, repeated description of practically identical structures. This is to avoid the following description from becoming unnecessarily lengthy, facilitating understanding by those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the utility model and are not intended to limit the subject matter recited in the claims.

[0040] Please refer to Figures 1-3 As shown in the drawings, in the utility model embodiment, a vacuum chamber with double propulsion material distribution devices comprises a mud feeding mechanism 1 and a vacuum mud conditioning chamber 2 which are in communication through a material distribution sieve plate 3, and two mud conditioning propulsion lines 4 are arranged in the vacuum mud conditioning chamber 2, and the two mud conditioning propulsion lines 4 respectively receive the mud material distributed by the material distribution sieve plate 3.

[0041] The mud feeding mechanism 1 rotates synchronously through double helical cutters or double screws to forcibly push the raw materials from the feeding port into the mixing cavity in front of the material distribution sieve plate 3. The material distribution sieve plate 3 uses the equal distribution structure to shunt, block and guide the mud material to be evenly distributed and flow out, and respectively falls onto the corresponding mud conditioning propulsion line 4. The two mud conditioning propulsion lines 4 are integrated in the same vacuum mud conditioning chamber 2, and the vacuum mud conditioning chamber 2 performs degassing treatment on the mud material through a vacuum pumping device. Each mud conditioning propulsion line 4 is driven by independent kinetic energy and is provided with a helical cutter to cut, crush, recombine and homogenize the mud material on the line. The mud material treated by the mud conditioning propulsion line 4 is finally shaped by the respective shaping outlet module at the extrusion end.

[0042] That is, the device divides the mud of the mud feeding mechanism 1 into two streams through the distribution sieve plate 3, and respectively sends them into two mud refining propulsion lines 4 in the vacuum mud refining chamber 2, each of which completes homogenization, vacuum degassing and extrusion. With a small increase in floor area, the production capacity is greatly improved, and the independent processing path ensures that the performance of the double-line mud is on par with that of the single-line equipment.

[0043] The mud refining propulsion line 4 includes a feeding screw 41 and a feeding cylinder 42. The mud falls into the feeding cylinder 42 from the distribution sieve plate 3, and the feeding screw 41 pushes the mud forward along the feeding cylinder 42, while the arc structure of the feeding cylinder 42 provides space for the screw and optimizes the mud flow path. Each feeding screw 41 is driven by an independent motor mechanism, avoiding the problem of excessive load caused by increasing the size of the traditional single machine.

[0044] The ends of the feeding cylinders 42 of the two mud refining propulsion lines 4 near the distribution sieve plate 3 have at least a section of the parallel part, so that the divided mud enters the respective feeding cylinders 42 more evenly, and the parallel part reduces the deviation of the mud flow, ensuring uniform feeding of the double lines. It should be noted that the parallel part does not mean that the two feeding cylinders 42 have a fusion part. In the parallel section, there is still a blocking structure protruding in the vertical direction between the two feeding cylinders 42 to prevent the mud from flowing between the two lines.

[0045] In one embodiment, the single feeding cylinder 42 has a semicircular arc plate structure, and the two arc-shaped feeding cylinders 42 are arranged in parallel and have a fitting part at the end near the distribution sieve plate 3. The fitting part can be formed by welding or one-piece molding.

[0046] Further, the contact side walls between the two feeding cylinders 42 and the feeding cylinder 42 and the vacuum mud refining chamber 2 are one-piece molded, that is, the feeding cylinder 42 and the vacuum mud refining chamber 2 are integrally cast. The one-piece structure can reduce the connection gap, increase the structural strength, avoid leakage or uneven pressure due to weak structure, improve the vacuum tightness, and ensure stable degassing.

[0047] In one embodiment, the one-piece structure formed by the two feeding cylinders 42 serves as the bottom wall part of the vacuum mud refining chamber 2, and the side wall bottom end of the vacuum mud refining chamber 2 extends out a rib plate to connect with the feeding cylinder 42, ensuring that the feeding cylinder 42 has sufficient load-bearing strength. This design avoids the need for the vacuum mud refining chamber 2 to have an additional bottom plate structure, reduces the steel plate feeding, and simplifies the equipment structure. The inner cavity has no additional joints except the detachable top cover, ensuring the sealing performance of the vacuum chamber.

[0048] At the operating level of the feeding screw 41, the two feeding screws 41 are respectively arranged in opposite directions of the rotational linear velocity of the bottom surface of the feeding cylinder 42. This feeding mode makes the clay advance along the inner wall of the feeding cylinder 42 close to the side of the vacuum clay refining chamber 2, rather than offset to the adjacent advancing line, thereby avoiding the mixing of the clay in the two lines in the process of shearing, crushing and recombination, improving the processing independence and the consistency of the final shaping.

[0049] The two side walls of the vacuum clay refining chamber 2 are respectively provided with a separate combing plate 21 arranged opposite to the corresponding feeding cylinder 42. The surface of the separate combing plate 21 is designed with densely arranged comb teeth or grid structures. When the clay pushed by the feeding screw 41 passes through the separate combing plate 21, the comb teeth or grid will cut the clay into strips or small pieces, forcibly destroying the original layered structure or agglomerates in the clay, thereby releasing the bubbles wrapped in the clay and creating a larger surface area for vacuum degassing.

[0050] It should be noted that the feeding screw 41 is not arranged in a continuous thread shape around the rotating rod, but is arranged by a plurality of spiral blades along the length direction of the rotating rod. The separate combing plate 21 is arranged on the side wall of the vacuum clay refining chamber 2, avoiding interference between the separate combing plate 21 and the feeding screw 41.

[0051] The vacuum chamber also includes two discharge cylinders 5, and the two independent discharge cylinders 5 are respectively corresponding to the two feeding cylinders 42. The clay is pushed by the feeding cylinder 42 and then discharged through the discharge cylinder 5. The discharge cylinder 5 can be replaced with a plastic body mold to discharge the clay in a certain shape.

[0052] In one embodiment, the connection part of the discharge cylinder 5 and the feeding cylinder 42 can be provided with a turning flange. The axis direction of the turning flange is shifted from coinciding with the axis of the feeding cylinder 42 to deviating from the axis of the feeding cylinder 42, so as to realize a certain deflection of the discharge cylinder 5, independently adjust the discharge angle, and improve the production flexibility.

[0053] Please refer to Figures 2-4 As shown in the figure, the separate distribution sieve plate 3 includes a partition plate 31 and a plurality of through holes 32 distributed on both sides of the partition plate 31 and penetrating the separate distribution sieve plate 3. The partition plate 31 plays a barrier role in the material channel, ensuring that the clay can be clearly distributed to the corresponding feeding cylinder 42 after being output from the clay feeding mechanism 1, and will not be mixed with each other. The partition plate 31 is arranged vertically on the separate distribution sieve plate 3 and can be used as the main skeleton of the separate distribution sieve plate 3 to bear the transportation pressure of the clay.

[0054] The shape, size and distribution of the through hole 32 determine the flow rate of the clay passing through the separate distribution sieve plate 3, thereby affecting the filling rate of the feeding cylinder 42. By reasonably designing the through hole 32, the two feeding cylinders 42 can synchronously obtain the clay, avoiding the problem of too fast or too slow feeding on one side. The stable feeding of each feeding line can avoid the uneven density of the clay caused by the flow fluctuation.

[0055] The clay passing through the through holes 32 will be subjected to shearing action on the surface of the distribution sieve plate 3, so that larger lumps are broken, which helps the subsequent vacuum degassing process, makes the clay more dense, and improves the molding quality.

[0056] The main part of the through hole 32 is a rectangular round hole. The rectangular structure provides a larger opening area, so that the clay can pass more smoothly and reduce the risk of blockage. The round corner part can reduce the stress concentration of the edge of the through hole 32, improve the overall fatigue resistance of the sieve plate, and reduce cracking or damage caused by long-term operation. The round design also helps the smooth passage of clay and reduces material residues, improving the continuity of equipment operation.

[0057] In one embodiment, the two round corners of the same end of the through hole 32 are combined and extended, forming a semicircular hole structure at both ends of the rectangle.

[0058] Further, the distribution rate of the rectangular round hole in the through hole 32 is at least 95%, and the remaining through holes 32 can use circular holes or elliptical holes as a supplement to fill the redundant solid area on the distribution sieve plate 3 due to insufficient distribution of through holes 32.

[0059] The distribution rate of the through hole 32 on the distribution sieve plate 3 is 20% to 35%. If the distribution rate of the through hole 32 is too low, it will form a larger clay resistance, causing a larger pressure difference when the clay enters the feeding cylinder 42, resulting in unstable flow rate, insufficient clay passing capacity, and affecting feeding efficiency. If the distribution rate of the through hole 32 is too high, the clay may pass in large quantities at a time, causing an imbalance in the feeding rate of the two advancing lines, making it difficult to ensure stable feeding of each clay advancing line, affecting the subsequent homogenization effect; in addition, the remaining solid part of the sieve plate is too small, and the overall structure will become fragile and prone to deformation or cracking under long-term stress, reducing the service life.

[0060] A reasonable distribution design of rectangular round holes, combined with a through hole 32 distribution rate of 20% to 35%, can ensure that the distribution sieve plate 3 is uniformly stressed, avoiding equipment vibration or structural deformation due to excessive local load. A moderate distribution rate of through holes 32 can avoid turbulent flow of clay, improve flow stability, allow the clay to fall gently into the double advancing lines, and improve the homogenization effect.

[0061] If the mud strip is immediately broken at the orifice during the extrusion process of the distribution sieve plate 3, part of the mud may be left on the hole wall, forming a "wall hanging" phenomenon, affecting the subsequent extrusion and equipment cleaning. The width-length ratio of the rectangular round hole is 4-9:20, which determines the cross-sectional shape of the mud strip and affects its mechanical strength after extrusion. Properly reducing the width-length ratio can increase the moment of inertia and improve the bending resistance, so that the mud strip is less likely to bend or break due to gravity or external disturbance. By reasonable design of the width-length ratio, the overall stability of the mud strip can be improved, and the bending deformation caused by gravity or external disturbance can be reduced, thereby reducing the wall hanging caused by too fast breaking of the mud strip.

[0062] Example 1

[0063] The mud with a moisture content of 21% was taken as the processing object, and the mud screening and distribution test was carried out on the distribution sieve plate 3 with different through hole 32 distribution rates.

[0064] Table 1 is a comparison table of test results caused by mud screening under different through hole distribution rates:

[0065]

[0066]

[0067] Example 2

[0068] The mud with a moisture content of 21% was taken as the processing object, and the mud screening and distribution test was carried out on the distribution sieve plate 3 with different through hole 32 distribution rates.

[0069] Table 2 is a comparison table of test results caused by mud screening under different rectangular round hole width-length ratios:

[0070]

[0071]

[0072] Example 3

[0073] The mud with a moisture content of 21% was taken as the processing object, and the mud screening and distribution test was carried out on the distribution sieve plate 3 with different through hole 32 distribution rates.

[0074] By comparing the output data of the left and right discharge cylinders 5, the effect of uniform discharge of the left and right is completely achieved, and the performance of the equipment is stable and mature.

[0075] Note that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and embodiments having the same configuration as the technical idea and achieving the same effects within the scope of the technical idea of the present application are included in the technical scope of the present application. Furthermore, various modifications that can be thought of by those skilled in the art, and other modes of embodiment constructed by combining part of the configuration elements of the embodiments within the scope of the gist of the present application are also included in the scope of the present application.

Claims

1. A vacuum chamber with a dual-propulsion dispensing device, characterized in that, include: The mud feeding mechanism (1) and the vacuum mud refining chamber (2) are interconnected by the material distribution screen plate (3). The vacuum mud refining chamber (2) is equipped with two mud refining propulsion lines (4), which respectively receive the mud after it is distributed by the material distribution screen plate (3).

2. A vacuum chamber with a dual-propulsion feeding device according to claim 1, characterized in that, The mud-refining propulsion line (4) includes a feeding screw (41) and a feeding cylinder (42). The side of the feeding cylinder (42) that receives the mud material has an arc-shaped structure that is concave away from the direction of the distributing screen plate (3).

3. A vacuum chamber with a dual-propulsion feeding device according to claim 2, characterized in that, The feed cylinders (42) of the two plowing feed lines (4) have at least one parallel section at the end near the distribution screen plate (3).

4. A vacuum chamber with a dual-propulsion feeding device according to claim 3, characterized in that, The two feeding cylinders (42) and the contact sidewall between the feeding cylinder (42) and the vacuum plowing chamber (2) are integrally formed.

5. A vacuum chamber with a dual-propulsion feeding device according to claim 2, characterized in that, The two feeding screws (41) have opposite rotational linear velocities on the bottom surface of the corresponding feeding cylinder (42).

6. A vacuum chamber with a dual-propulsion feeding device according to claim 5, characterized in that, The vacuum mixing chamber (2) has combing plates (21) arranged opposite to the corresponding feeding cylinders (42) on its two side walls.

7. A vacuum chamber with a dual-propulsion feeding device according to claim 1, characterized in that, It also includes two discharge cylinders (5), which are respectively connected to the corresponding feeding cylinders (42).

8. A vacuum chamber with a dual-propulsion feeding device according to claim 1, characterized in that, The material distribution screen plate (3) includes a partition plate (31) and a plurality of through holes (32) distributed on both sides of the partition plate (31) and penetrating the material distribution screen plate (3).

9. A vacuum chamber with a dual-propulsion feeding device according to claim 8, characterized in that, The distribution rate of through holes (32) on the material distribution screen plate (3) is 20% to 35%.

10. A vacuum chamber with a dual-propulsion feeding device according to claim 8, characterized in that, At least 95% of the through holes (32) are rectangular rounded corner holes, and the width-to-length ratio of the rectangular rounded corner holes is 4 to 9:20.

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