CA2181782A1 - Blow pin assembly for blow moulding machine - Google Patents
Blow pin assembly for blow moulding machineInfo
- Publication number
- CA2181782A1 CA2181782A1 CA 2181782 CA2181782A CA2181782A1 CA 2181782 A1 CA2181782 A1 CA 2181782A1 CA 2181782 CA2181782 CA 2181782 CA 2181782 A CA2181782 A CA 2181782A CA 2181782 A1 CA2181782 A1 CA 2181782A1
- Authority
- CA
- Canada
- Prior art keywords
- blow
- holder
- blow pin
- fluid
- centering
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
- B29C49/42—Component parts, details or accessories; Auxiliary operations
- B29C49/58—Blowing means
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
- B29C49/02—Combined blow-moulding and manufacture of the preform or the parison
- B29C49/04—Extrusion blow-moulding
Landscapes
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Mechanical Engineering (AREA)
- Blow-Moulding Or Thermoforming Of Plastics Or The Like (AREA)
Abstract
An automatic blow pin levelling apparatus for a blow moulding machine in which each of the blow pins in the apparatus are attached to pistons which are each slidably engaged to a cylinder. Each cylinder includes a fluid filled space between a closed end of the cylinder and the piston, and all the fluid filled spaces are interconnected such that the fluid within each of the spaces can be displaced to the other spaces in order to achieve an equilibrium state in which the pressure of the fluid in all of the spaces is the same. Also, a centering holder for a blow pin comprises a first holder, a second holder, means for fixing a blow pin to the second holder, and a clamp for fixing the second holder to the first holder, the clamp having a first position and a second position relative to the first holder, wherein in the first position the second holder is rigidly fixed to the first holder, and in the second position the second holder is permitted limited movement relative to the first holder such that a blow pin fixed to said second holder can be aligned with respect to an opening in a blow mould.
Description
BLOW PIN ~~ .v FOR 8LOW MOULDING MACHINE
This invention relates to blow moulding r-~h;n~s and in particular to a blow pin assembly for a blow moulding machine.
Blow moulding is commonly employed for the mass production of hollow bodies such as bottles, containers and tanks from thermoplastic materials. It involves trapping a tubular portion of molten thermoplastic material in a suitable blow mould and shaping the thermoplastic by injecting a pressurized gas into it through a blow pin.
Frequently, a calibrated opening must be formed in each of the hollow bodies which are mass produced by a blow moulding machine. The standard process employed to manufacture a calibrated opening is to include a cutting ring (or sleeve) of hardened steel on the blow pin shaft near its blowing nozzle. As the blowing nozzle is introduced to thermoplastic contained in the blow mould, the nozzle passes through an opening in the blow mould which is surrounded by a steel striking plate. The cutting ring presses against the striking surface, thereby cutting and compressing the thermoplastic and forming an opening.
In order to ensure that a proper opening is formed, the blowing nozzle of the blow pin must be symmetrically aligned in all directions with the opening provided in the blow mould. Proper ~ t will allow the cutting ring to be applied with uniform force to the striking plate the entire distance around the opening. If the blow pin is not correctly aligned or centred, then the cutting ring will not be applied with uniform pressure, and the opening that is formed in the hollow body may have a rough finish or a chamfer.
In addition to centering the blow pins, in a multi-pin blow station it is necessary to ensure that the cutting rings on all of the blow pins all contact their respective striking plates simultaneously and with the same force.
Failure to do so can result in uneven forces being applied across the blow pin assembly, which can cause the assembly to operate on a angle, and can adversely affect the ~ t of the blow pins. Additionally, if the blow pins are not introduced to the mould simultaneously, some cutting rings on some blow pins may not contact the striking surface with enough force to cleanly cut the thermoplastic material.
Therefore, in order to ensure that properly calibrated openings are formed in the hollow bodies being formed at a blow station, it is necessary to ensure that the blow pins in a blow station are aligned horizontally 80 that they will all contact the blow mould at the same time and with the same pressure, and it is also necessary to ensure that each of the blow pins is aligned or centred over its corresponding opening on the blow mould. In the blow pin assemblies provided by the prior art, operators typically have to level and centre the blow pins during the set-up of the blow station and during routine maintenance and repairs of the blow station, including each time the cutting rings on one or more of the blow pins is replaced or reground.
The prior art systems for levelling the blow pins in a blow station are somewhat tedious and time consuming to use.
_ 3 _ 2 1 8 1 782 Generally, an operator must level each of the blow pins at the blow station manually by using one or more tools. In one method commonly known in the art, a locking ring must be released by an operator who then must screw the blow pin upwards or downwards within a blow pin holder and then re-engage the locking ring. The time required for the levelling process increases substantially as the number of pins included at a particular blow station increases.
It is therefore desirable to provide a blow pin assembly which includes an automatic levelling system which ensures that all of the blow pins in a blow station are introduced to the blow mould openings simultaneously and with equal pressure.
Various prior art systems have been developed to permit a blow pin to be centred over a blow mould opening but they are also quite tedious and time consuming to use. one commonly used system employs a blow pin holder assembly which includes two adjacent rings which encircle a receptacle that supports a blow pin. The rings can be adjusted by means of set screws with respect to each other, thereby permitting the blow pin to be centred with the use of tools. Another commonly used centering method employs four screws which are provided radially around the circumference of a blow pin holder assembly. The blow pin can be centred by adjusting the screws.
It is therefore desirable to provide an improved centering system for the blow pins of a blow moulding machine which allows a blow pin to be centred quickly and without the use of any additional tools.
According to one aspect of the present invention, there is provided an automatic blow pin levelling apparatus for a blow moulding machine that comprises aplurality of cylinders, the cylinders all having a closed end and an open end, the open ends all opening in the same direction; a number of pistons corresponding to the number of said cylinders, each of said pistons being slidably engaged to one of said cylinders; means for fixing a blow pin to each of said pistons; and a space filled with a fluid between the closed end of each of said cylinders and the piston within said cylinder, wherein each of said fluid filled spaces are interconnected such that the fluid within each of said spaces can be displaced to other said spaces in order to achieve an equilibrium state in which the pressure of the fluid in all of said spaces is the same. Preferably, the fluid is a viscous liquid.
According to another aspect of the invention, there is provided a holder for a blow pin comprising a first holder; a second holder; means for fixing a blow pin to said second holder; and a clamp for fixing said second holder to said first holder, said clamp having a first position and a second position relative to said first holder, wherein in said first position said second holder is rigidly fixed to said first holder, and in said second position said second holder is permitted limited movement in at least 2 dimensions with respect to said first holder such that a blow pin fixed to said second holder can be aligned with respect to an opening in a blow mould.
_ 5 _ 2 1 8 1 782 In the drawings:
Figure 1 is a front view of a blow station of a blow moulding machine according to the present invention;
Figure 2 is a bottom view of a moving plate according to the present invention;
Figure 3 is an exploded cross-sectional view along the lines 3-3 of Figure 1 showing the blow pin assembly of the blow pin station;
Figure 4 is a side view of an adjustment bolt according to the present invention;
Figure 5 i8 a bottom view of a piston cover according to the present invention;
Figure 6 is a bottom view of a centering holder according to the present invention; and Figure 7 is a bottom view of a centering clamp according to the present invention.
A blow station of the invention is shown in Figure 1.
The blow station is intended for use with blow moulding r-~hin~s in which a plurality of hollow bodies with calibrated openings are formed simultaneously.
A typical blow mould 30 contains a plurality of cavities 32A, 32B and 32C into which molten thermoplastic parisons have been introduced. Each of the cavities 32A, 32B
and 32C includes an opening 34A, 34B and 34C into which the blowing nozzles 26A, 26B and 26C of the blowing pins 23A, 23B
and 23C are introduced 80 that a pressurized gas can be injected ~ 21 81 782 into the thermoplastic parisons, thus causing the parisons to form hollow bodies that conform to the shape of the cavities.
The walls of the openings 34A, 34B and 34C conform to the shape of the blowing nozzles 26A, 26B and 26C. The blow mould 30 includes an annular striking surface 28A, 28B and 28C around each of the openings 34A, 34B and 34C. A cutting ring 24A, 24B
and 24C is provided around the lower portion of each blowing pin 23A, 23B and 23C, such that when the blowing pins are introduced into their corresponding op_n;ngq 34A, 34B and 34C in the blow mould 30, the cutting rings 24A, 24B and 24C contact the striking surfaces 28A, 28B and 28C, thereby cutting and compressing the thermoplastic material at the openings 34A, 34B
and 34C and forming calibrated openings in the hollow bodies contained the cavities 32A, 32B and 32C. The blow pins are each attached to a blow pin assembly 10. The blow pin assembly 10 is attached to a support plate 40 which in turn is connected to a hydraulically or pneumatically activated piston 36. The piston 36 causes the blow pins to be raised or lowered during the operation of the blow station illustrated in figure 1. Guide bars 38 may be provided to st~hili7e ~. ~ of the blow pin assembly 10 in the horizontal plane. Apart from the blow pin assembly 10, the ~~ts and the process described above are all well known in the art.
Turning now to the blow pin assembly 10 of the invention, an exploded cross-sectional view thereof can be seen in Figure 3. The blow pin assembly 10 includes a moving plate ~ 2 1 8 1 782 12, a bottom view of which is shown in Figure 2. The moving plate 12 has a plurality of cylindrical bores 42A, 42B and 42C
arranged within it. The number of cylindrical bores in the moving plate 12 uuLLeD~ol-ds to the total number of blow pins contained in the blow station. Although three cylindrical bores 42A, 42B and 42C are illustrated, the number could vary as permitted by the capacity of the blow moulding machine to which the blow pin assembly 10 is attached.
A flow hole 50A, 50B and 50C is provided near the top of each of the bores 42A, 42B and 42C. The flow holes each communicate with a passageway 51A, 51B and 51C respectively.
Each of the passageways 51A, 51B and 51C is connected through connecting element 52A, 52B, 52C to a common passageway 48. The common passageway 48 and the connecting elements are preferably made of copper or steel tubing and corresponding copper or steel fasteners and c~nnPctors. Preferably, a portion of each of the pARsageways 51A, 51B and 52C is tapped 80 as to permit a threaded end of the connecting elements 52A, 52B, and 52C to be screwed into the pAc~a~ _yD 51A, 5ls and 51C.
Referring now to cylinder 42A, a cross-section of which can be seen in Figure 3, a portion of the flow hole 50A preferably extends above the upper surface 57 of the cylindrical bore 42, and a concave flow directing groove 54 extends towards the centre of the surface 57 away from the flow hole 50A. The cylinders 42B and 42C are identical to the cylinder 42A and the same description applies to them as well.
The passa-~ _y~ 51A, 51B and 51C of the cylinders 42A, 42B and 42C, together with the common passageway 48, form a closed system which provides a fluid flow path between all of the cylinders 42A, 42B and 42C in the moving plate 12. Four upwardly extending tapped bores 44 are located around the opening of each cylinder 42A, 42B and 42 C of the moving plate 12.
Referring again to Figure 3, a cross-section of the blow pin assembly for supporting the blow pin 23A iB
illustrated. Although the following description refers to the support assembly for blow pin 23A, the assemblies for blow pins 23B and 23C are identical and the same description applies to those assemblies as well. The cylinder 42A in the moving plate 12 is ~ir Rioned to slidably receive a circular piston 16A.
The piston 16A of the present invention has a planar upper surface 59. In order to ensure that the piston 16A does not rotate about a vertical axis, a vertical bore 60 extends downwards from the top 59 of the piston 16A. One end of an elongate circular guide pin 56 is slidably received in the vertical bore 60, and the other end of the guide pin 58 screws into a tapped bore 46 that is located in the top surface 57 of the cylinder 42A.
The piston 16A preferably includes an upper annular flange 62, a middle annular flange 66 and a lower annular flange 70 extending outwards from the upper half of the piston 16A.
The outer diameter of the piston 16A at the points where the 2 ~ 8 i 782 g middle flange 66 and the lower flange 70 extend therefrom is slightly less than the inner diameter of the cylinder 42A.
Preferably the upper flange 62 does not extend as far out from the centre of the piston 16A as the middle flange 66 and the lower flange 70.
An upper annular channel 64 is formed between the upper flange 62 and the middle flange 66 and a lower annular channel 68 is formed between the middle flange 66 and the lower flange 70 of the piston 16A.
Crucial to the blow pin levelling system of the present invention is a fluid medium (not shown) which is placed in the cylinder 42A between the upper surface 57 of the cylinder and the top 59 of the piston 16A. Similar fluid filled reservoirs are also provided in the other cylinders 42B and 42C
between the upper surfaces of those cylinders and the tops of the pistons 16B and 16C. These fluid filled reservoirs all communicate with each other via the passageways 51A, 51B, 51C
and the common passageway 48, which are also fluid filled. The passageways and the reservoirs form a closed system.
Preferably, the fluid which is contained in the closed system is of a relatively high viscosity. In the blow pin assembly of the present invention, common gear-box oil is used.
In order to ensure that the piston 16A is properly centred in the cylinder 42A and also to ensure that the fluid which is contained in the reservoir above the piston 16A does not blow by the piston 16A along walls of the cylinder 42A, guide/seal rings (not shown) are placed around the piston 16A in the upper channel 64 and the lower channel 68. In the preferred -';- L of the invention, a U-ring such as a MERKEL NOVAT~AN
(trade-mark) T18 U-ring is placed around the piston 16A in the upper groove 64 and a piston seal ring such as a MERKEL OMEGAT
(trade-mark) OM~ Piston Seal Ring is seated in the lower groove 68.
The piston 16A is slidably fastened within the cylinder 42A by means of a piston cover 14, a bottom view of which is illustrated in Figure 5. The piston cover 14 includes an annular hole 74 and four fastening holes 102. It is fastened to the bottom of the moving plate 12 by four bolts which pass through the holes 102 into the tapped bores 44. The holes 102 are each countersunk so that the heads of the bolts used to secure the piston cover do not protrude below the bottom surface of the piston cover 14.
The hole 74 in the piston cover 14 has an inside diameter which is slightly larger than the ~;i ter of the lower portion of the piston 16A, however the diameter of the hole 74 is less than the ~ r of the lower flange 70. Thus, the extent of the downward stroke of the piston 16 is defined by the point at which the underside of the lower flange 70 comes into contact with the top of the piston cover 14. Preferably, the piston cover 14 includes a centering rim 76 which extends around the hole 74 and which is received within the opening of the cylinder 42A.
~ 2 1 8 1 782 The blow pin assembly 10 includes a centering holder 18 which includes a circular upper portion 78 which is received in a counter bore 72 which iB provided in the base of the piston 16A. The centering holder 18 is secured to the piston 16A by a bolt which extends through a countersunk bore 81 in the upper portion 78 of the centering holder 18 and into a tapped bore 73 at the top of the counter bore 72 in the piston 16A.
Referring to Figure 6, which shows a bottom view of the centering holder 18, five tapped bores 104, 106 and 84 are provided in the bottom of the centering holder. The tapped bore 84 is preferably located near the front of the centering holder 18. Additionally, an annular cavity 80 extends upwardly from the bottom of the centering holder 18 for a portion of its height. A channel 82 extends from the back of the cavity 80 to the outside of the centering holder 18 for the purpose of allowing a source of compressed air to be connected to the blow pin 23A.
The cavity 80 receives the head portion 86 of a blow pin holder 22. The diameter of the cavity 80 is somewhat larger than the outer diameter of the head 86 of the blow pin holder 22 in order to permit the blow pin holder 22 to have some horizontal movement. In the preferred embodiment of the invention, the diameter of the cavity 80 is in the range of 0.2 to 0.3 inches larger than the diameter of the blow pin holder head 86.
The height of the head 86 of the blow pin holder 18 ~ 2181782 (as indicated by H in Figure 3) i8 of a magnitude slightly higher than the height C of the centering holder cavity 80. In the preferred ~ t, the height of the blow pin holder head 86 is in the range of 0.008 to 0.012 inches greater than the height C of the centering holder cavity 80. The reason for thi6 . difference in height i8 to allow the blow pin holder 22 to be firmly secured to the centering holder 18 by a centering clamp 20.
The blow pin holder 22 includes a tapped opening 90 into which a threaded end lO0 of the blow pin 23A can be screwed. The blow pin holder 22 includes a rearward facing tapped opening 92 to which a source of pressurized gas (such as a hose leading to a compressed gas source) can be connected.
The opening 92 communicates with the upper end of the blow pin 23 which is screwed into the lower opening 90, thus providing a path for pressurized gas to flow to the nozzle 26A. The hose which is connected to the opening 92 passes through the channel 82 which is provided in the centering holder 18.
Preferably, a guide pin 79, which is received in a bore 83 in the piston 16A and a bore 77 in the centering holder 18, ensures that the centering holder 18 is properly oriented when attached to the piston 16A so that the channel 82 faces towards the back of the blow pin assembly. As mentioned above, another guide pin 56 keeps the piston 16A from rotating about a vertical axis.
The blow pin holder 22 is attached to the centering holder 18 by means of the centering clamp 20, a bottom view of which can be seen in Figure 7. The centering clamp 20 includes a hole 96 through its centre which is large enough to pass over the outer diameter of the lower portion 88 of the blow pin 5 holder 22, but small enough to catch the lower supporting surface 94 of the head 86 of the blow pin holder 18.
Four identical countersunk fastening holes 108 and 110 are provided in the centering clamp 20. The holes 108 line up with the two tapped bores 104 in the centering holder 18, and the two holes 110 line up with the tapped bores 106 in the centering holder 18. A fifth fastening hole 98 is also provided in the centering clamp 20 which lines up with the tapped bore 84 in the centering holder 18. The centering clamp 20 is fastened to the centering holder 18 by means of four shoulder bolts (not shown) which are inserted through the four countersunk holes 108 and 110 and screwed into the corresponding tapped bores 104 and 106, and a centering adjustment bolt 21 (shown in Figure 4), which is inserted through the hole 98 and screwed into the tapped bore 84.
Although all of the shoulder bolts used to install the centering clamp 20 are of equal length, the tapped bores 104 and 106 are not identical in depth. Rather, they are precision tapped so that when the four shoulder bolts are fully inserted into the bores, the shoulder bolts which are screwed into the front bores 106 are in a slightly lower plane that the shoulder bolts which have been screwed into the rear bores 104. In other words, the two front tapped bores 106 are shorter in length than the two back tapped bores 104. In the preferred : 'o~ir-nt, the total difference in the tapped length between the front bores 106 and the rear bores 104 i6 in the range of 0.004 to 0.008 inches. Provided the adjustment screw 21 is not fully screwed in, the centering clamp 20 rests on the four shoulder bolts and the front portion of the clamp 20 is in a slightly lower plane than its back portion. When the clamp 20 is in such a position, it is possible to move the blow pin holder 22 in a horizontal plane within the confines of the cavity 80 in the centering holder 22.
When the adjustment bolt 21 is tightened, it causes the front of the centering clamp 20 to rise and apply pressure on the lower support surface 94 of the head 86 of the blow pin holder 22. It will thus be appreciated that the centering clamp 20 has two positions, a closed position in which the blow pin holder 22 is firmly clamped to the centering holder 18, and an "adjustment" position in which the blow pin holder 22 is permitted horizontal v. --t within the conf; n~5 of the cavity 80 of the centering holder 18. The clamp 20 can be placed in the adjustment position by loosening the adjustment bolt 21, and in closed position by tightening the adjustment bolt 21.
In the closed position of the clamp 20, the head 86 of the blow pin holder 22 is firmly clamped between the upper surface of the cavity 80 and the upper surface 97 of the centering clamp 20. The vertical range of motion of the front 2 1 8 ~ 782 of the clamp 20 between the closed and adjustment positions is a function of the difference between the lengths of the front bores 106 and the rear bores 104 in the centering holder 18.
The range should be sufficient to allow the blow pin holder 22 to be moved horizontally within the cavity 80 when the adjustment bolt 21 has been loosened, but not 80 large as to permit the blow pin holder 22 to become noticeably m;~ gnpd along its vertical axis.
The adjustment bolt 21 (see Figure 4) includes a handle portion 114 80 that no additional tools are required by an operator to turn the bolt 21 in order to move the centering clamp 20 between its closed position and its adjustment position. One suitable adjustment bolt is the JERGENS (trade-mark) Metric Button Head Adjustable Handle part number 34157I.
It will be appreciated that the figures do not illustrate all of the ~ ~~ts typically included in a blow station. For example, a blow pin locking ring could be threaded onto the upper portion of the blow pin 23A to rest against the underside of the lower portion 88 of the blow pin holder 22.
Additionally, as well known in the art, a float stripper plate could be supported from the moving plate 12 to remove the plastic residue from the blowing nozzles when they are withdrawn from the blow mould 30. However, such additional ~nts do not affect the scope of the present invention.
As discussed above, in a conventional multi blow pin station one of the most tedious and time consuming procedures - 16 _ 21 81 782 that mu6t be performed by a blow machine operator i8 levelling all the blow pins so that each cutting ring or sleeve will be introduced to its respective striking surface on the blow mould at the same time and with the same pressure.
However, the closed system of interconnected fluid filled reservoirs in the cylinders 42A, 42B and 42C of the blow pin assembly 10 of the invention eliminates the need for manual levelling. It will be understood that because each of the reservoirs are interconnected by means of the connectors 52A, 52B and 52C and the common passageway 48, the pressure applied by the viscous fluid on each of the pistons 16A, 16B and 16C
will be equal in an equilibrium state. ~f the fluid pressure is not equal in each of the cylinders 42A, 42B and 42C, then fluid will be displaced amongst the cylinders to achieve a new equilibrium. Thus, for example, if an upwards force is applied on the blow pin 23A and a simultaneous equal force is not applied to the other two blow pins 23B and 23C, then the pressure of the fluid contained in the cylinder 42A will be greater than the fluid pressure in the other two cylinders 42s and 42C. This unequalized pressure will cause an amount of fluid to be displaced from the cylinder 42A, via the common passageway 48, to the other cylinders 42B and 42C, until either a new equilibrium is reached, or the piston 16A reaches its highest stroke limit or the other pistons 42B and 42C reach their lowest stroke limit. Preferably, the stroke length of each of the pistons 16A, 16B and 16C is such that a fluid 2 1 8 ~ 782 pressure equilibrium will generally be achieved before any of the active pistons reach their upper or lower stroke limits.
Therefore, the application of upwards pressure on the blow pin 23A at a point in time when equal pressure is not being 5 applied to the other blow pins 23B and 23C will cause fluid to be displaced from the cylinder 42A to the other cylinders 42B
and 42C, thereby causing the piston 16A to rise, and the pistons 16B and 16C to lower. This in turn causes the blow nozzle 26A
of the blow pin 23A to be raised in height with respect to the blow nozzles 26B and 26C which will each be lowered in height.
It will thus be appreciated that each time the blow pins are introduced to the blow mould 30, any discrepancies between their respective introduction times and, correspnn~;ngly, any discrep~nci~s in the force with which each cutting ring 24A, 24B
and 24C meets its colL~onding striking surface 28A, 28B and 28C results in a pressure imbalance within the fluid contained in the cylinders 42A, 42B and 42C. If an i -l~nce occurs, the closed fluid flow system will cause fluid to be re-distributed amongst the cylinders in order to achieve a new equilibrium, and 20 thus any such discrep~nriee in force will be~ -nflated for and corrected.
Preferably, the fluid provided in the top of the cylinders 42A, 42B and 42C is of a viscosity such that the blow pins will generally not move with respect to each other during 25 normal operation of the blow station, unless a levelling correction is required. Therefore, the blow station is ~ 2 1 8 1 782 automatically levelled during its first blowing cycle, and it remains levelled throughout its continued operation.
It will be appreciated that the interconnected reservoir system of the invention provides an automatic S levelling system which ensures that all of the active blow pins at a blow station are introduced into their respective blow mould openings at the same time and with the same pressure.
This self-levelling feature of the blow pin assembly avoids twisting or skewing of the blow pin assembly and the application of uneven pressures on the mould 3S by the different blow pins, thereby helping to ensure that clean, level calibrated openings are formed in the hollow plastic bodies which are being blow moulded.
Although a three pin blow station is illustrated, the lS self-levelling system disclosed herein can be employed to level any number of blow pins at a multiple pin blow station.
Furthermore, it is not necessary that each of the cavities 32A, 32B and 32C in the blow mould 30 be in the same horizontal plane in order for the blow pin assembly 10 of the present invention to operate correctly. The mould opPn;~g~ 34A, 34B and 34C could be staggered in the horizontal plane and the stroke length of each of the pistons 16A, 16B and 16C could be such that the system would level each blow pin with respect to its corresponding mould opening.
Preferably, the stroke length of the pistons and the amount of fluid provided in the system is such that the station can function even if one blow pin (in a three or more blow pin machine) i8 removed. For example, if the hollow bodies being formed in cavities 32A and 32C are 50 large that there is not room for the cavity 32B, the centre blow pin 23B can be removed by removing the centering clamp. In the absence of any upward pressure, the piston 16B would be pushed to its lower stroke limit. However, enough fluid would be in the system to permit the 1~ -;ninrJ two pistons 16A and 16C to function without reaching their highest stroke limits. Alternatively, a valve means could be provided in each of the connectors 52A, 52B and 52C 80 that the fluid reservoirs of unused pistons could be isolated from the active reservoirs.
Although in the preferred : ~;r t illustrated in Figure l the moving plate 12 is bolted to the support plate 40, it is possible that these two Ants could be formed together from a single piece of steel. Having a separate moving plate 12 offers the advantage that the blow pin assembly 10 can easily be removed from the blow station and replaced with a different blow pin assembly that may contain a different number of blow pins.
In the ~ of the invention illustrated in the drawings, the common passageway 48 is provided externally to the moving plate 12 in order to interconnect the cylinders 42A, 42B
and 42c. However, it is possible that the external common passageway 48 could be replaced by an internal passageway or bore formed directly in the moving plate 12. Alternatively, each cylinder could be directly ported to the cylinder or cylinders adjacent to it by bores provided in the moving plate 12. It will thus be appreciated that there are a number of ways in which the cylinders 42A, 42B and 42C can be interconnected with each other in order to ensure that the fluid pressure in all of the cylinders is the same in an equilibrium state.
In another alternative ~ of the invention, the interconnected cylinders 42A, 42B and 42C could be formed in separate blocks of steel which could .then be attached to the moving plate 12 using a fastening means that permitted the blocks to be varied in position relative to each other during set-up of the blow station. Such means could includes a series of tapped bores in the moving block 12 that corresponded with the fastening holes in each of the blocks. Alternatively, a more elaborate fastening means in which the blocks were slidably clamped to a rail provided in the moving plate 12 could be used.
In an : 'ir-rt where the cylinders were formed in separate blocks, the common passageway 48 may include reinforced flexible tubing.
It is possible that the blow pins could be fixed directly to the piston 16A without the intervening centering ~ ts 18 and 22. However, the intervening ~ ~ts permit easier centering and alignment of the blow pins (as further described below), and additionally, the use of an int~ 'iAte blow pin holder 22 permits blow pins with a wide variety of threading and connection assemblies to be used with 2 1 8 ~ 782 the self-levelling system of the present invention. Thus, the present invention provides a versatile self-levelling system which can greatly reduce the set up and adjustment times required for a blow station.
In addition to providing a self-levelling system, the invention also provides an improved centering system for ~1 igning a blow pin over itg corregponding opening in a blow mould. As discussed above, the centering clamp 20 includes an adjustment position and a closed position. In its closed position, the front of the clamp 18 is firmly supported by the adjustment bolt 21 which passes through the hole 98, and the back portion of the clamp 18 is firmly supported by the two shoulder bolts which pass through the holes 108, such that the blow pin holder 22 is firmly clamped to the centering holder 18.
In order to move the clamp 18 into its adjustment state, an operator loosens the adjustment bolt 21 by rotating its handle 114. As the adjustment bolt 21 is loosened, the front of the clamp 20 pivots downwards about the two shoulder bolts which pass through the holes 108. The downward rotation of the front of the clamp 20 is stopped when the clamp 20 comes to rest on the shoulder bolts which pass through the holes 110, at which point the clamp 20 is in its adjustment position. Preferably, the operator has to turn the adjustment bolt 21 less than one rotation in order to place the clamp 20 in its adjustment position. In the adjustment position, the blow pin holder 22 is permitted a degree of horizontal ~ ~ within the confines of the cavity 80 of the centering holder 18.
In order to center the blow pins in a blow station, an operator places all the centering clamps into their adjustment positions, and then, by grasping each blow pin with his or her hand, the operator aligns the blow pins over their respective op~n; ngc in the blow mould. In order to ensure the pins are accurately centered, while each of the centering clamps are still in the adjustment position, the blow pin assembly is then slowly lowered so that the blowing nozzles are introduced into the op~n;ngc in the blow mould. If a blow pin is not exactly aligned, uneven forces will be applied around the circumference of its nozzle by the walls of the opening in the blow mould.
These forces will cause the blow pin to shift in the horizontal plane, thus ~lign;ng itself.
Once a blow pin i5 aligned, the operator can, without using any special tools, close the clamp 20 by rotating the adjustment bolt 21 so that it screws upwards into the bore 84.
When the clamp 20 is in a closed position, the blow pin is not permitted any horizontal v~ ~ in relation to the centering holder 18.
The total vertical v~ : of the front of the clamp 18 between the adjustment position and the closed position is small enough that the degree by which the blow pin varies from a vertical axis as the clamp is moved between the two positions is negligible. Thus, if the nozzle of the blow pin is aligned when the clamp is in the adjustment position, the alignment will not be noticeably affected by the tightening of the adjustment bolt 21.
Thus, it will be appreciated that the blow pin assembly 10 of the invention provides an ; uved blow pin centering system which allows an operator to easily centre a blow pin without the aid of any additional tools.
The centering system of the blow pin assembly 10 could vary from the preferred -';r--t disclosed herein. For example, the tapped bores 104 and 106 and the centering holder 18 could all be the same depth and the shoulder bolts could vary in length. Alternatively, a second adjustment bolt could be provided, together with a corresponding hole in the back portion of the centering clamp 20 and a corresponding tapped bore in the centering holder 18. As a further alternative, the adjustment bolt 21 could be replaced with some other sort of hand activated fastening means or could also include a bolt which does require an additional tool such as a hexhead or allen head bolt.
It is possible that the centering ~ nts 18, 22 and 20 of the blow pin assembly 10 could be used in a blow station in~p~nd~nt of the self-levelling system, including a blow station in which only one blow pin is present.
It will be appreciated that the self-levelling and i ~v~d centering systems of the blow pin assembly 10 of the invention could be used in a blow station that was oriented in a different direction than that shown in the drawings and described herein.
While various ~ s of this invention have been illustrated in the AC ~~nying drawings and described above, it will be evident to those skilled in the art that changes and modifications may be made therein without departing from the essence of this invention. All such modifications or variations are believed to be within the sphere and scope of the invention as defined by the claims appended hereto.
This invention relates to blow moulding r-~h;n~s and in particular to a blow pin assembly for a blow moulding machine.
Blow moulding is commonly employed for the mass production of hollow bodies such as bottles, containers and tanks from thermoplastic materials. It involves trapping a tubular portion of molten thermoplastic material in a suitable blow mould and shaping the thermoplastic by injecting a pressurized gas into it through a blow pin.
Frequently, a calibrated opening must be formed in each of the hollow bodies which are mass produced by a blow moulding machine. The standard process employed to manufacture a calibrated opening is to include a cutting ring (or sleeve) of hardened steel on the blow pin shaft near its blowing nozzle. As the blowing nozzle is introduced to thermoplastic contained in the blow mould, the nozzle passes through an opening in the blow mould which is surrounded by a steel striking plate. The cutting ring presses against the striking surface, thereby cutting and compressing the thermoplastic and forming an opening.
In order to ensure that a proper opening is formed, the blowing nozzle of the blow pin must be symmetrically aligned in all directions with the opening provided in the blow mould. Proper ~ t will allow the cutting ring to be applied with uniform force to the striking plate the entire distance around the opening. If the blow pin is not correctly aligned or centred, then the cutting ring will not be applied with uniform pressure, and the opening that is formed in the hollow body may have a rough finish or a chamfer.
In addition to centering the blow pins, in a multi-pin blow station it is necessary to ensure that the cutting rings on all of the blow pins all contact their respective striking plates simultaneously and with the same force.
Failure to do so can result in uneven forces being applied across the blow pin assembly, which can cause the assembly to operate on a angle, and can adversely affect the ~ t of the blow pins. Additionally, if the blow pins are not introduced to the mould simultaneously, some cutting rings on some blow pins may not contact the striking surface with enough force to cleanly cut the thermoplastic material.
Therefore, in order to ensure that properly calibrated openings are formed in the hollow bodies being formed at a blow station, it is necessary to ensure that the blow pins in a blow station are aligned horizontally 80 that they will all contact the blow mould at the same time and with the same pressure, and it is also necessary to ensure that each of the blow pins is aligned or centred over its corresponding opening on the blow mould. In the blow pin assemblies provided by the prior art, operators typically have to level and centre the blow pins during the set-up of the blow station and during routine maintenance and repairs of the blow station, including each time the cutting rings on one or more of the blow pins is replaced or reground.
The prior art systems for levelling the blow pins in a blow station are somewhat tedious and time consuming to use.
_ 3 _ 2 1 8 1 782 Generally, an operator must level each of the blow pins at the blow station manually by using one or more tools. In one method commonly known in the art, a locking ring must be released by an operator who then must screw the blow pin upwards or downwards within a blow pin holder and then re-engage the locking ring. The time required for the levelling process increases substantially as the number of pins included at a particular blow station increases.
It is therefore desirable to provide a blow pin assembly which includes an automatic levelling system which ensures that all of the blow pins in a blow station are introduced to the blow mould openings simultaneously and with equal pressure.
Various prior art systems have been developed to permit a blow pin to be centred over a blow mould opening but they are also quite tedious and time consuming to use. one commonly used system employs a blow pin holder assembly which includes two adjacent rings which encircle a receptacle that supports a blow pin. The rings can be adjusted by means of set screws with respect to each other, thereby permitting the blow pin to be centred with the use of tools. Another commonly used centering method employs four screws which are provided radially around the circumference of a blow pin holder assembly. The blow pin can be centred by adjusting the screws.
It is therefore desirable to provide an improved centering system for the blow pins of a blow moulding machine which allows a blow pin to be centred quickly and without the use of any additional tools.
According to one aspect of the present invention, there is provided an automatic blow pin levelling apparatus for a blow moulding machine that comprises aplurality of cylinders, the cylinders all having a closed end and an open end, the open ends all opening in the same direction; a number of pistons corresponding to the number of said cylinders, each of said pistons being slidably engaged to one of said cylinders; means for fixing a blow pin to each of said pistons; and a space filled with a fluid between the closed end of each of said cylinders and the piston within said cylinder, wherein each of said fluid filled spaces are interconnected such that the fluid within each of said spaces can be displaced to other said spaces in order to achieve an equilibrium state in which the pressure of the fluid in all of said spaces is the same. Preferably, the fluid is a viscous liquid.
According to another aspect of the invention, there is provided a holder for a blow pin comprising a first holder; a second holder; means for fixing a blow pin to said second holder; and a clamp for fixing said second holder to said first holder, said clamp having a first position and a second position relative to said first holder, wherein in said first position said second holder is rigidly fixed to said first holder, and in said second position said second holder is permitted limited movement in at least 2 dimensions with respect to said first holder such that a blow pin fixed to said second holder can be aligned with respect to an opening in a blow mould.
_ 5 _ 2 1 8 1 782 In the drawings:
Figure 1 is a front view of a blow station of a blow moulding machine according to the present invention;
Figure 2 is a bottom view of a moving plate according to the present invention;
Figure 3 is an exploded cross-sectional view along the lines 3-3 of Figure 1 showing the blow pin assembly of the blow pin station;
Figure 4 is a side view of an adjustment bolt according to the present invention;
Figure 5 i8 a bottom view of a piston cover according to the present invention;
Figure 6 is a bottom view of a centering holder according to the present invention; and Figure 7 is a bottom view of a centering clamp according to the present invention.
A blow station of the invention is shown in Figure 1.
The blow station is intended for use with blow moulding r-~hin~s in which a plurality of hollow bodies with calibrated openings are formed simultaneously.
A typical blow mould 30 contains a plurality of cavities 32A, 32B and 32C into which molten thermoplastic parisons have been introduced. Each of the cavities 32A, 32B
and 32C includes an opening 34A, 34B and 34C into which the blowing nozzles 26A, 26B and 26C of the blowing pins 23A, 23B
and 23C are introduced 80 that a pressurized gas can be injected ~ 21 81 782 into the thermoplastic parisons, thus causing the parisons to form hollow bodies that conform to the shape of the cavities.
The walls of the openings 34A, 34B and 34C conform to the shape of the blowing nozzles 26A, 26B and 26C. The blow mould 30 includes an annular striking surface 28A, 28B and 28C around each of the openings 34A, 34B and 34C. A cutting ring 24A, 24B
and 24C is provided around the lower portion of each blowing pin 23A, 23B and 23C, such that when the blowing pins are introduced into their corresponding op_n;ngq 34A, 34B and 34C in the blow mould 30, the cutting rings 24A, 24B and 24C contact the striking surfaces 28A, 28B and 28C, thereby cutting and compressing the thermoplastic material at the openings 34A, 34B
and 34C and forming calibrated openings in the hollow bodies contained the cavities 32A, 32B and 32C. The blow pins are each attached to a blow pin assembly 10. The blow pin assembly 10 is attached to a support plate 40 which in turn is connected to a hydraulically or pneumatically activated piston 36. The piston 36 causes the blow pins to be raised or lowered during the operation of the blow station illustrated in figure 1. Guide bars 38 may be provided to st~hili7e ~. ~ of the blow pin assembly 10 in the horizontal plane. Apart from the blow pin assembly 10, the ~~ts and the process described above are all well known in the art.
Turning now to the blow pin assembly 10 of the invention, an exploded cross-sectional view thereof can be seen in Figure 3. The blow pin assembly 10 includes a moving plate ~ 2 1 8 1 782 12, a bottom view of which is shown in Figure 2. The moving plate 12 has a plurality of cylindrical bores 42A, 42B and 42C
arranged within it. The number of cylindrical bores in the moving plate 12 uuLLeD~ol-ds to the total number of blow pins contained in the blow station. Although three cylindrical bores 42A, 42B and 42C are illustrated, the number could vary as permitted by the capacity of the blow moulding machine to which the blow pin assembly 10 is attached.
A flow hole 50A, 50B and 50C is provided near the top of each of the bores 42A, 42B and 42C. The flow holes each communicate with a passageway 51A, 51B and 51C respectively.
Each of the passageways 51A, 51B and 51C is connected through connecting element 52A, 52B, 52C to a common passageway 48. The common passageway 48 and the connecting elements are preferably made of copper or steel tubing and corresponding copper or steel fasteners and c~nnPctors. Preferably, a portion of each of the pARsageways 51A, 51B and 52C is tapped 80 as to permit a threaded end of the connecting elements 52A, 52B, and 52C to be screwed into the pAc~a~ _yD 51A, 5ls and 51C.
Referring now to cylinder 42A, a cross-section of which can be seen in Figure 3, a portion of the flow hole 50A preferably extends above the upper surface 57 of the cylindrical bore 42, and a concave flow directing groove 54 extends towards the centre of the surface 57 away from the flow hole 50A. The cylinders 42B and 42C are identical to the cylinder 42A and the same description applies to them as well.
The passa-~ _y~ 51A, 51B and 51C of the cylinders 42A, 42B and 42C, together with the common passageway 48, form a closed system which provides a fluid flow path between all of the cylinders 42A, 42B and 42C in the moving plate 12. Four upwardly extending tapped bores 44 are located around the opening of each cylinder 42A, 42B and 42 C of the moving plate 12.
Referring again to Figure 3, a cross-section of the blow pin assembly for supporting the blow pin 23A iB
illustrated. Although the following description refers to the support assembly for blow pin 23A, the assemblies for blow pins 23B and 23C are identical and the same description applies to those assemblies as well. The cylinder 42A in the moving plate 12 is ~ir Rioned to slidably receive a circular piston 16A.
The piston 16A of the present invention has a planar upper surface 59. In order to ensure that the piston 16A does not rotate about a vertical axis, a vertical bore 60 extends downwards from the top 59 of the piston 16A. One end of an elongate circular guide pin 56 is slidably received in the vertical bore 60, and the other end of the guide pin 58 screws into a tapped bore 46 that is located in the top surface 57 of the cylinder 42A.
The piston 16A preferably includes an upper annular flange 62, a middle annular flange 66 and a lower annular flange 70 extending outwards from the upper half of the piston 16A.
The outer diameter of the piston 16A at the points where the 2 ~ 8 i 782 g middle flange 66 and the lower flange 70 extend therefrom is slightly less than the inner diameter of the cylinder 42A.
Preferably the upper flange 62 does not extend as far out from the centre of the piston 16A as the middle flange 66 and the lower flange 70.
An upper annular channel 64 is formed between the upper flange 62 and the middle flange 66 and a lower annular channel 68 is formed between the middle flange 66 and the lower flange 70 of the piston 16A.
Crucial to the blow pin levelling system of the present invention is a fluid medium (not shown) which is placed in the cylinder 42A between the upper surface 57 of the cylinder and the top 59 of the piston 16A. Similar fluid filled reservoirs are also provided in the other cylinders 42B and 42C
between the upper surfaces of those cylinders and the tops of the pistons 16B and 16C. These fluid filled reservoirs all communicate with each other via the passageways 51A, 51B, 51C
and the common passageway 48, which are also fluid filled. The passageways and the reservoirs form a closed system.
Preferably, the fluid which is contained in the closed system is of a relatively high viscosity. In the blow pin assembly of the present invention, common gear-box oil is used.
In order to ensure that the piston 16A is properly centred in the cylinder 42A and also to ensure that the fluid which is contained in the reservoir above the piston 16A does not blow by the piston 16A along walls of the cylinder 42A, guide/seal rings (not shown) are placed around the piston 16A in the upper channel 64 and the lower channel 68. In the preferred -';- L of the invention, a U-ring such as a MERKEL NOVAT~AN
(trade-mark) T18 U-ring is placed around the piston 16A in the upper groove 64 and a piston seal ring such as a MERKEL OMEGAT
(trade-mark) OM~ Piston Seal Ring is seated in the lower groove 68.
The piston 16A is slidably fastened within the cylinder 42A by means of a piston cover 14, a bottom view of which is illustrated in Figure 5. The piston cover 14 includes an annular hole 74 and four fastening holes 102. It is fastened to the bottom of the moving plate 12 by four bolts which pass through the holes 102 into the tapped bores 44. The holes 102 are each countersunk so that the heads of the bolts used to secure the piston cover do not protrude below the bottom surface of the piston cover 14.
The hole 74 in the piston cover 14 has an inside diameter which is slightly larger than the ~;i ter of the lower portion of the piston 16A, however the diameter of the hole 74 is less than the ~ r of the lower flange 70. Thus, the extent of the downward stroke of the piston 16 is defined by the point at which the underside of the lower flange 70 comes into contact with the top of the piston cover 14. Preferably, the piston cover 14 includes a centering rim 76 which extends around the hole 74 and which is received within the opening of the cylinder 42A.
~ 2 1 8 1 782 The blow pin assembly 10 includes a centering holder 18 which includes a circular upper portion 78 which is received in a counter bore 72 which iB provided in the base of the piston 16A. The centering holder 18 is secured to the piston 16A by a bolt which extends through a countersunk bore 81 in the upper portion 78 of the centering holder 18 and into a tapped bore 73 at the top of the counter bore 72 in the piston 16A.
Referring to Figure 6, which shows a bottom view of the centering holder 18, five tapped bores 104, 106 and 84 are provided in the bottom of the centering holder. The tapped bore 84 is preferably located near the front of the centering holder 18. Additionally, an annular cavity 80 extends upwardly from the bottom of the centering holder 18 for a portion of its height. A channel 82 extends from the back of the cavity 80 to the outside of the centering holder 18 for the purpose of allowing a source of compressed air to be connected to the blow pin 23A.
The cavity 80 receives the head portion 86 of a blow pin holder 22. The diameter of the cavity 80 is somewhat larger than the outer diameter of the head 86 of the blow pin holder 22 in order to permit the blow pin holder 22 to have some horizontal movement. In the preferred embodiment of the invention, the diameter of the cavity 80 is in the range of 0.2 to 0.3 inches larger than the diameter of the blow pin holder head 86.
The height of the head 86 of the blow pin holder 18 ~ 2181782 (as indicated by H in Figure 3) i8 of a magnitude slightly higher than the height C of the centering holder cavity 80. In the preferred ~ t, the height of the blow pin holder head 86 is in the range of 0.008 to 0.012 inches greater than the height C of the centering holder cavity 80. The reason for thi6 . difference in height i8 to allow the blow pin holder 22 to be firmly secured to the centering holder 18 by a centering clamp 20.
The blow pin holder 22 includes a tapped opening 90 into which a threaded end lO0 of the blow pin 23A can be screwed. The blow pin holder 22 includes a rearward facing tapped opening 92 to which a source of pressurized gas (such as a hose leading to a compressed gas source) can be connected.
The opening 92 communicates with the upper end of the blow pin 23 which is screwed into the lower opening 90, thus providing a path for pressurized gas to flow to the nozzle 26A. The hose which is connected to the opening 92 passes through the channel 82 which is provided in the centering holder 18.
Preferably, a guide pin 79, which is received in a bore 83 in the piston 16A and a bore 77 in the centering holder 18, ensures that the centering holder 18 is properly oriented when attached to the piston 16A so that the channel 82 faces towards the back of the blow pin assembly. As mentioned above, another guide pin 56 keeps the piston 16A from rotating about a vertical axis.
The blow pin holder 22 is attached to the centering holder 18 by means of the centering clamp 20, a bottom view of which can be seen in Figure 7. The centering clamp 20 includes a hole 96 through its centre which is large enough to pass over the outer diameter of the lower portion 88 of the blow pin 5 holder 22, but small enough to catch the lower supporting surface 94 of the head 86 of the blow pin holder 18.
Four identical countersunk fastening holes 108 and 110 are provided in the centering clamp 20. The holes 108 line up with the two tapped bores 104 in the centering holder 18, and the two holes 110 line up with the tapped bores 106 in the centering holder 18. A fifth fastening hole 98 is also provided in the centering clamp 20 which lines up with the tapped bore 84 in the centering holder 18. The centering clamp 20 is fastened to the centering holder 18 by means of four shoulder bolts (not shown) which are inserted through the four countersunk holes 108 and 110 and screwed into the corresponding tapped bores 104 and 106, and a centering adjustment bolt 21 (shown in Figure 4), which is inserted through the hole 98 and screwed into the tapped bore 84.
Although all of the shoulder bolts used to install the centering clamp 20 are of equal length, the tapped bores 104 and 106 are not identical in depth. Rather, they are precision tapped so that when the four shoulder bolts are fully inserted into the bores, the shoulder bolts which are screwed into the front bores 106 are in a slightly lower plane that the shoulder bolts which have been screwed into the rear bores 104. In other words, the two front tapped bores 106 are shorter in length than the two back tapped bores 104. In the preferred : 'o~ir-nt, the total difference in the tapped length between the front bores 106 and the rear bores 104 i6 in the range of 0.004 to 0.008 inches. Provided the adjustment screw 21 is not fully screwed in, the centering clamp 20 rests on the four shoulder bolts and the front portion of the clamp 20 is in a slightly lower plane than its back portion. When the clamp 20 is in such a position, it is possible to move the blow pin holder 22 in a horizontal plane within the confines of the cavity 80 in the centering holder 22.
When the adjustment bolt 21 is tightened, it causes the front of the centering clamp 20 to rise and apply pressure on the lower support surface 94 of the head 86 of the blow pin holder 22. It will thus be appreciated that the centering clamp 20 has two positions, a closed position in which the blow pin holder 22 is firmly clamped to the centering holder 18, and an "adjustment" position in which the blow pin holder 22 is permitted horizontal v. --t within the conf; n~5 of the cavity 80 of the centering holder 18. The clamp 20 can be placed in the adjustment position by loosening the adjustment bolt 21, and in closed position by tightening the adjustment bolt 21.
In the closed position of the clamp 20, the head 86 of the blow pin holder 22 is firmly clamped between the upper surface of the cavity 80 and the upper surface 97 of the centering clamp 20. The vertical range of motion of the front 2 1 8 ~ 782 of the clamp 20 between the closed and adjustment positions is a function of the difference between the lengths of the front bores 106 and the rear bores 104 in the centering holder 18.
The range should be sufficient to allow the blow pin holder 22 to be moved horizontally within the cavity 80 when the adjustment bolt 21 has been loosened, but not 80 large as to permit the blow pin holder 22 to become noticeably m;~ gnpd along its vertical axis.
The adjustment bolt 21 (see Figure 4) includes a handle portion 114 80 that no additional tools are required by an operator to turn the bolt 21 in order to move the centering clamp 20 between its closed position and its adjustment position. One suitable adjustment bolt is the JERGENS (trade-mark) Metric Button Head Adjustable Handle part number 34157I.
It will be appreciated that the figures do not illustrate all of the ~ ~~ts typically included in a blow station. For example, a blow pin locking ring could be threaded onto the upper portion of the blow pin 23A to rest against the underside of the lower portion 88 of the blow pin holder 22.
Additionally, as well known in the art, a float stripper plate could be supported from the moving plate 12 to remove the plastic residue from the blowing nozzles when they are withdrawn from the blow mould 30. However, such additional ~nts do not affect the scope of the present invention.
As discussed above, in a conventional multi blow pin station one of the most tedious and time consuming procedures - 16 _ 21 81 782 that mu6t be performed by a blow machine operator i8 levelling all the blow pins so that each cutting ring or sleeve will be introduced to its respective striking surface on the blow mould at the same time and with the same pressure.
However, the closed system of interconnected fluid filled reservoirs in the cylinders 42A, 42B and 42C of the blow pin assembly 10 of the invention eliminates the need for manual levelling. It will be understood that because each of the reservoirs are interconnected by means of the connectors 52A, 52B and 52C and the common passageway 48, the pressure applied by the viscous fluid on each of the pistons 16A, 16B and 16C
will be equal in an equilibrium state. ~f the fluid pressure is not equal in each of the cylinders 42A, 42B and 42C, then fluid will be displaced amongst the cylinders to achieve a new equilibrium. Thus, for example, if an upwards force is applied on the blow pin 23A and a simultaneous equal force is not applied to the other two blow pins 23B and 23C, then the pressure of the fluid contained in the cylinder 42A will be greater than the fluid pressure in the other two cylinders 42s and 42C. This unequalized pressure will cause an amount of fluid to be displaced from the cylinder 42A, via the common passageway 48, to the other cylinders 42B and 42C, until either a new equilibrium is reached, or the piston 16A reaches its highest stroke limit or the other pistons 42B and 42C reach their lowest stroke limit. Preferably, the stroke length of each of the pistons 16A, 16B and 16C is such that a fluid 2 1 8 ~ 782 pressure equilibrium will generally be achieved before any of the active pistons reach their upper or lower stroke limits.
Therefore, the application of upwards pressure on the blow pin 23A at a point in time when equal pressure is not being 5 applied to the other blow pins 23B and 23C will cause fluid to be displaced from the cylinder 42A to the other cylinders 42B
and 42C, thereby causing the piston 16A to rise, and the pistons 16B and 16C to lower. This in turn causes the blow nozzle 26A
of the blow pin 23A to be raised in height with respect to the blow nozzles 26B and 26C which will each be lowered in height.
It will thus be appreciated that each time the blow pins are introduced to the blow mould 30, any discrepancies between their respective introduction times and, correspnn~;ngly, any discrep~nci~s in the force with which each cutting ring 24A, 24B
and 24C meets its colL~onding striking surface 28A, 28B and 28C results in a pressure imbalance within the fluid contained in the cylinders 42A, 42B and 42C. If an i -l~nce occurs, the closed fluid flow system will cause fluid to be re-distributed amongst the cylinders in order to achieve a new equilibrium, and 20 thus any such discrep~nriee in force will be~ -nflated for and corrected.
Preferably, the fluid provided in the top of the cylinders 42A, 42B and 42C is of a viscosity such that the blow pins will generally not move with respect to each other during 25 normal operation of the blow station, unless a levelling correction is required. Therefore, the blow station is ~ 2 1 8 1 782 automatically levelled during its first blowing cycle, and it remains levelled throughout its continued operation.
It will be appreciated that the interconnected reservoir system of the invention provides an automatic S levelling system which ensures that all of the active blow pins at a blow station are introduced into their respective blow mould openings at the same time and with the same pressure.
This self-levelling feature of the blow pin assembly avoids twisting or skewing of the blow pin assembly and the application of uneven pressures on the mould 3S by the different blow pins, thereby helping to ensure that clean, level calibrated openings are formed in the hollow plastic bodies which are being blow moulded.
Although a three pin blow station is illustrated, the lS self-levelling system disclosed herein can be employed to level any number of blow pins at a multiple pin blow station.
Furthermore, it is not necessary that each of the cavities 32A, 32B and 32C in the blow mould 30 be in the same horizontal plane in order for the blow pin assembly 10 of the present invention to operate correctly. The mould opPn;~g~ 34A, 34B and 34C could be staggered in the horizontal plane and the stroke length of each of the pistons 16A, 16B and 16C could be such that the system would level each blow pin with respect to its corresponding mould opening.
Preferably, the stroke length of the pistons and the amount of fluid provided in the system is such that the station can function even if one blow pin (in a three or more blow pin machine) i8 removed. For example, if the hollow bodies being formed in cavities 32A and 32C are 50 large that there is not room for the cavity 32B, the centre blow pin 23B can be removed by removing the centering clamp. In the absence of any upward pressure, the piston 16B would be pushed to its lower stroke limit. However, enough fluid would be in the system to permit the 1~ -;ninrJ two pistons 16A and 16C to function without reaching their highest stroke limits. Alternatively, a valve means could be provided in each of the connectors 52A, 52B and 52C 80 that the fluid reservoirs of unused pistons could be isolated from the active reservoirs.
Although in the preferred : ~;r t illustrated in Figure l the moving plate 12 is bolted to the support plate 40, it is possible that these two Ants could be formed together from a single piece of steel. Having a separate moving plate 12 offers the advantage that the blow pin assembly 10 can easily be removed from the blow station and replaced with a different blow pin assembly that may contain a different number of blow pins.
In the ~ of the invention illustrated in the drawings, the common passageway 48 is provided externally to the moving plate 12 in order to interconnect the cylinders 42A, 42B
and 42c. However, it is possible that the external common passageway 48 could be replaced by an internal passageway or bore formed directly in the moving plate 12. Alternatively, each cylinder could be directly ported to the cylinder or cylinders adjacent to it by bores provided in the moving plate 12. It will thus be appreciated that there are a number of ways in which the cylinders 42A, 42B and 42C can be interconnected with each other in order to ensure that the fluid pressure in all of the cylinders is the same in an equilibrium state.
In another alternative ~ of the invention, the interconnected cylinders 42A, 42B and 42C could be formed in separate blocks of steel which could .then be attached to the moving plate 12 using a fastening means that permitted the blocks to be varied in position relative to each other during set-up of the blow station. Such means could includes a series of tapped bores in the moving block 12 that corresponded with the fastening holes in each of the blocks. Alternatively, a more elaborate fastening means in which the blocks were slidably clamped to a rail provided in the moving plate 12 could be used.
In an : 'ir-rt where the cylinders were formed in separate blocks, the common passageway 48 may include reinforced flexible tubing.
It is possible that the blow pins could be fixed directly to the piston 16A without the intervening centering ~ ts 18 and 22. However, the intervening ~ ~ts permit easier centering and alignment of the blow pins (as further described below), and additionally, the use of an int~ 'iAte blow pin holder 22 permits blow pins with a wide variety of threading and connection assemblies to be used with 2 1 8 ~ 782 the self-levelling system of the present invention. Thus, the present invention provides a versatile self-levelling system which can greatly reduce the set up and adjustment times required for a blow station.
In addition to providing a self-levelling system, the invention also provides an improved centering system for ~1 igning a blow pin over itg corregponding opening in a blow mould. As discussed above, the centering clamp 20 includes an adjustment position and a closed position. In its closed position, the front of the clamp 18 is firmly supported by the adjustment bolt 21 which passes through the hole 98, and the back portion of the clamp 18 is firmly supported by the two shoulder bolts which pass through the holes 108, such that the blow pin holder 22 is firmly clamped to the centering holder 18.
In order to move the clamp 18 into its adjustment state, an operator loosens the adjustment bolt 21 by rotating its handle 114. As the adjustment bolt 21 is loosened, the front of the clamp 20 pivots downwards about the two shoulder bolts which pass through the holes 108. The downward rotation of the front of the clamp 20 is stopped when the clamp 20 comes to rest on the shoulder bolts which pass through the holes 110, at which point the clamp 20 is in its adjustment position. Preferably, the operator has to turn the adjustment bolt 21 less than one rotation in order to place the clamp 20 in its adjustment position. In the adjustment position, the blow pin holder 22 is permitted a degree of horizontal ~ ~ within the confines of the cavity 80 of the centering holder 18.
In order to center the blow pins in a blow station, an operator places all the centering clamps into their adjustment positions, and then, by grasping each blow pin with his or her hand, the operator aligns the blow pins over their respective op~n; ngc in the blow mould. In order to ensure the pins are accurately centered, while each of the centering clamps are still in the adjustment position, the blow pin assembly is then slowly lowered so that the blowing nozzles are introduced into the op~n;ngc in the blow mould. If a blow pin is not exactly aligned, uneven forces will be applied around the circumference of its nozzle by the walls of the opening in the blow mould.
These forces will cause the blow pin to shift in the horizontal plane, thus ~lign;ng itself.
Once a blow pin i5 aligned, the operator can, without using any special tools, close the clamp 20 by rotating the adjustment bolt 21 so that it screws upwards into the bore 84.
When the clamp 20 is in a closed position, the blow pin is not permitted any horizontal v~ ~ in relation to the centering holder 18.
The total vertical v~ : of the front of the clamp 18 between the adjustment position and the closed position is small enough that the degree by which the blow pin varies from a vertical axis as the clamp is moved between the two positions is negligible. Thus, if the nozzle of the blow pin is aligned when the clamp is in the adjustment position, the alignment will not be noticeably affected by the tightening of the adjustment bolt 21.
Thus, it will be appreciated that the blow pin assembly 10 of the invention provides an ; uved blow pin centering system which allows an operator to easily centre a blow pin without the aid of any additional tools.
The centering system of the blow pin assembly 10 could vary from the preferred -';r--t disclosed herein. For example, the tapped bores 104 and 106 and the centering holder 18 could all be the same depth and the shoulder bolts could vary in length. Alternatively, a second adjustment bolt could be provided, together with a corresponding hole in the back portion of the centering clamp 20 and a corresponding tapped bore in the centering holder 18. As a further alternative, the adjustment bolt 21 could be replaced with some other sort of hand activated fastening means or could also include a bolt which does require an additional tool such as a hexhead or allen head bolt.
It is possible that the centering ~ nts 18, 22 and 20 of the blow pin assembly 10 could be used in a blow station in~p~nd~nt of the self-levelling system, including a blow station in which only one blow pin is present.
It will be appreciated that the self-levelling and i ~v~d centering systems of the blow pin assembly 10 of the invention could be used in a blow station that was oriented in a different direction than that shown in the drawings and described herein.
While various ~ s of this invention have been illustrated in the AC ~~nying drawings and described above, it will be evident to those skilled in the art that changes and modifications may be made therein without departing from the essence of this invention. All such modifications or variations are believed to be within the sphere and scope of the invention as defined by the claims appended hereto.
Claims (3)
1. A blow pin apparatus for a blow moulding machine comprising:
a plurality of cylinders, said cylinders all having a closed end and an open end, said open ends opening in the same direction;
a number of pistons corresponding to the number of said cylinders, each of said pistons being slibably engaged to one of said cylinders;
means for fixing a blow pin to each of said pistons;
a space filled with a fluid between the closed end of each of said cylinders and the piston within said cylinder, wherein each of said fluid filled spaces are interconnected such that the fluid within each of said spaces can be displaced to other said spaces in order to achieve an equilibrium state in which the fluid pressure in all of said spaces is the same.
a plurality of cylinders, said cylinders all having a closed end and an open end, said open ends opening in the same direction;
a number of pistons corresponding to the number of said cylinders, each of said pistons being slibably engaged to one of said cylinders;
means for fixing a blow pin to each of said pistons;
a space filled with a fluid between the closed end of each of said cylinders and the piston within said cylinder, wherein each of said fluid filled spaces are interconnected such that the fluid within each of said spaces can be displaced to other said spaces in order to achieve an equilibrium state in which the fluid pressure in all of said spaces is the same.
2. A blow pin apparatus according to claim 1 wherein the fluid is a viscous liquid.
3. A holder for a blow pin comprising:
a first holder;
a second holder;
means for fixing a blow pin to said second holder;
a clamp for fixing said second holder to said first holder, said clamp having a first position and a second position relative to said first holder, wherein in said first position said second holder is rigidly fixed to said first holder, and in said second position said second holder is permitted limited movement in at least 2 dimensions with respect to said first holder such that a blow pin fixed to said second holder can be aligned with respect to a blow mould.
a first holder;
a second holder;
means for fixing a blow pin to said second holder;
a clamp for fixing said second holder to said first holder, said clamp having a first position and a second position relative to said first holder, wherein in said first position said second holder is rigidly fixed to said first holder, and in said second position said second holder is permitted limited movement in at least 2 dimensions with respect to said first holder such that a blow pin fixed to said second holder can be aligned with respect to a blow mould.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2181782 CA2181782A1 (en) | 1996-07-22 | 1996-07-22 | Blow pin assembly for blow moulding machine |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2181782 CA2181782A1 (en) | 1996-07-22 | 1996-07-22 | Blow pin assembly for blow moulding machine |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2181782A1 true CA2181782A1 (en) | 1998-01-23 |
Family
ID=4158645
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2181782 Abandoned CA2181782A1 (en) | 1996-07-22 | 1996-07-22 | Blow pin assembly for blow moulding machine |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2181782A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7150620B2 (en) * | 2002-03-04 | 2006-12-19 | Soplar Sa | Mounting for the blowing mandrel on a blow-molding device |
-
1996
- 1996-07-22 CA CA 2181782 patent/CA2181782A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7150620B2 (en) * | 2002-03-04 | 2006-12-19 | Soplar Sa | Mounting for the blowing mandrel on a blow-molding device |
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