Patent Application
20170151767
This application claims priority to Great Britain Patent Application No. 1521052.9 filed on Nov. 30, 2015, the entire contents of which are incorporated by reference herein
The invention relates to flatbed laminators in which a workpiece to be laminated or on which a vinyl coating or other similar coating is to be adhered is placed on a flatbed and a roller is rolled over the workpiece. The workpiece may comprise a sheet to be laminated together with laminating film to be applied to a surface of the sheet or it may comprise a mounting, such as a foam board, and a coating to be adhered to the mounting, such as a vinyl layer. The gap between the roller and the workpiece needs to be adjusted according to the thickness of the workpiece in order that the desired pressure may be applied during the laminating process.
The roller of a flatbed laminator is mounted such that it can be moved towards or away from the flatbed in order to adjust the size of the gap between them it is also mounted such that it can be rolled along the flatbed. The roller is normally arranged above the flatbed so that a workpiece can be positioned on the flatbed. Means are provided for lowering the roller until it comes into contact with a workpiece positioned on the flatbed and presses the workpiece against the flatbed and then rolling the roller along the flatbed such that the entire of the workpiece is laminated. As the roller rolls off the end of workpiece it may impact the flatbed due to a downward pressure acting on the roller. This may act to crush the end of the workpiece and is generally undesirable.
The means to adjust the gap between the roller and the flatbed is generally separate from the means that rolls the roller along the flatbed. In particular, the means for rolling the roller along the flatbed are generally separate from and not dependent on the means for adjusting the gap between the roller and the flatbed. The means for rolling the roller along the flatbed will roll the roller along the flatbed without adjusting the gap between the roller and the flatbed: a constant gap will be maintained between the roller and the flatbed, as determined by the means for adjusting the gap between the roller and the flatbed.
It is known to adjust the gap between the roller and the flatbed by purely mechanical means, typically controlled by a wheel on one end of a shaft that extends across the laminator. The wheel is turned manually to rotate the shaft, which then acts through gearing to raise or lower a mounting at each end of the roller. Such means allow the height of the roller to be adjustable through a continuous range and at any height a desired pressure can be applied by turning the wheel to a suitable position. However, mechanical means have the disadvantage that, owing to manufacturing tolerances or wear, it might not move the two ends of the roller by exactly equal amounts. If this occurs uneven pressure can be applied across the width of the workpiece.
As an alternative, it is known to adjust the gap between the roller and the flatbed by pneumatic means. Each end of the roller is supported on a pneumatic cylinder. By applying pressurised air to the pneumatic cylinders the roller can be moved towards the flatbed. The pneumatic system has the advantages that it can be actuated by the push of a button and that if both cylinders are supplied from a common source of pressurised air, they are guaranteed to apply equal pressure to the roller so pressure should be applied evenly across the width of the workpiece to the laminated.
A disadvantage of the pneumatic system is that the pressure applied to move the roller into position and maintain it there may be greater than the material of some workpieces can resist, for example if the workpiece is formed of foamed board. Thus the roller may crush the workpiece as the roller is brought into contact with the workpiece.
The problem that pneumatically operated rollers may crush delicate workpieces has been recognized and a known solution is to provide an insert that can be moved below the roller mountings to prevent the roller approaching the flatbed more closely than a fixed, minimum distance. Such inserts are generally separate from the laminator and are simply inserted below the roller mountings when required and removed when no longer required. As insert will have a stepped profile and the minimum distance is determined by the height of the selected step. Typically a few steps of different heights are provided to match standard thicknesses of workpiece but workpieces formed from the sheets and laminating materials of different manufacturers might not be exactly the same and non-standard thicknesses cannot be accommodated at all.
In light of the above there is a need for an improved flatbed laminator that can better control the distance between the roller and a workpiece positioned on the flatbed.
The invention provides a flatbed laminator as defined in claim 1.
The invention further provides a method of configuring a flatbed laminator as defined in claim 8.
Features of the invention that are preferred but not essential are defined in the dependent claims.
The flatbed laminator according to the invention combines the advantages of the mechanical and pneumatic systems known in the prior art. The pneumatic cylinders are easily operated and can be supplied from a common source to balance the pressure at each end of the roller. Unlike the prior art, the flatbed laminator of the present invention comprises an integral locking assembly that can be operated to prevent the gap between the roller and the flatbed reducing below a minimum size. Unlike the inserts known in the prior art, this minimum size can take any value within a continuous range (or alternatively any of a large number of closely spaced discrete values). The value does not have to be chosen in advance but can be determined by the thickness of an actual workpiece.
The locks of the locking assembly act on the cylinders, for example engaging with the piston shaft of each cylinder. They may be integrated in the cylinder housings.
The method according to the invention permits the roller to be brought into engagement with the workpiece at a relatively low pressure that will avoid crushing it. The locking assembly can then be operated and, if desired, the pressure can then be made higher during the laminating process, while the workpiece remains protected against crushing.
As shown in
The flatbed laminator operates in a conventional manner by pressure, and optionally heat, to the workpiece as the roller 2 is rolled over an upper side of the worksheet.
In order to accommodate workpieces of different thicknesses, the size of a gap 6 between the roller 2 and the flatbed 4 needs to be adjustable. The flatbed 4 is fixed in position. A mounting 10 of the roller 2 in the frame is adjustable relative to flatbed 4 so that the roller can be moved towards or away from the flatbed 4 to change the size of the gap 6, while an axis of the roller 2 is maintained parallel to the flatbed 4.
The respective ends of the roller 2 are supported on a pair of pneumatic cylinders 12. Each cylinder 12 comprises a tube 14 that is fixed to a mounting of the roller 2 and a piston 16 that slides within the tube and projects from it. The mounting 10 of the roller 2 is supported on the projecting part of the piston 16. The head of the piston 16 divides the tube 14 into two sealed chambers, each of which is coupled to a respective line 18, 20 of a drive air supply 22. The drive air supply 22 can direct pressurised air via a first line 18 into one of the chambers of the cylinder 12 to drive the piston 16 forwards and move the roller 2 towards the flatbed 4. At different times, the drive air supply 22 can direct pressurised air via a second line 20 into the other of the chambers of the cylinder 12 to drive the piston 16 back and move the roller 2 away from the flatbed 4.
In an alternative arrangement (not illustrated), the backward movement of the piston 16 can be effected by a return spring when the pressure to the first chamber is reduced. In this case, the supply line 20 to the second chamber is not required. Pneumatic control of the roller position in this way is known in the prior art and will not be described in detail here.
Preferably the pressurised air is delivered to the pair of pneumatic cylinders 12 from a common supply so that the two cylinders always operate at the same pressure and move the two pistons 16 through the same distance, whereby the roller 2 remains parallel to the flatbed 4. To further ensure balance between the cylinders 12, the length of each branch of the supply line 18 from the common source to its respective cylinder should preferably be equal.
In accordance with a first embodiment of the present invention, each cylinder 12 is provided with an integral pneumatically-operated lock 24. The two locks 24 are coupled via supply lines 26 to a common locking air supply 28. When pressurised air from the supply 28 is applied to a lock 24, it clamps onto the piston 16 to prevent further movement of the piston out of the tube 14 and thus prevent further movement of the roller 2 toward the flatbed 4. Preferably the lock 24 acts on the piston 16 in only one direction so that the roller 2 remains able to move away from the flatbed 4, while being cushioned by the pressurised air of the drive supply 22. Each lock 24 in this embodiment comprises a pair of jaws that can be pivoted into engagement with the piston shaft to clamp the shaft between them. A range of pneumatic cylinders with locks of this kind is available from suppliers of pneumatic apparatus. It is preferred that the locks 24 should be able to engage the cylinders 12 at any position within a continuous range of movement of the roller 2 so that workpieces of any thickness within that range can be accommodated by the flatbed laminator. However, it would be an acceptable alternative to employ locks that engage the cylinders via a series of teeth, for example in the manner of a ratchet, which would allow the roller position to be set at any of a large number of closely spaced discrete values.
A flatbed laminator according to this first embodiment of the invention may be configured in the following way. A sample workpiece is placed on the flatbed 4. The drive air supply 22 is then operated to send pressurised air through the first supply line 18 to the two cylinders 12. This drives the roller 2 towards the flatbed 4 until its further movement is resisted by contact with the workpiece. The drive air pressure should be selected so that the roller does not crush the workpiece: for delicate workpiece materials such as foam board a relatively low pressure may be used. The locking assembly is then operated by applying pressurised air from the locking supply 28 to engage the locks 24 with the pistons 16 and provide mechanical resistance to further reduction of the gap 6 between the roller 2 and the flatbed 4. The laminating process can then be carried out by rotating the roller 2 and moving it across the flatbed 4 by means of the frame on which the roller 2 is mounted. When the roller 2 is moved beyond the end of the workpiece it does not crush the edge of the workpiece nor will it impact the flatbed 4 of the laminator. This is prevented by the locking assembly acting to prevent the roller 2 moving towards the flatbed 4.
After the position of the roller 2 has been set in the manner just described, it may be desirable to change the pressure of the drive air supply 22 during operation of the flatbed laminator. For example, the pressure can be increased to ensure that the roller 2 does not lift away from the workpiece during lamination, while the operation of the locking assembly protects the workpiece against crushing. The setup procedure may be carried out using just the sheet that is to be laminated, without the additional film of laminating material. When a laminating material is added during a laminating process or a mounting material is added during a mounting process, the workpiece will be slightly thicker than it was during the setup procedure so that roller 2 is forced slightly further apart than the minimum gap 6 set by the locking assembly. The pressure applied to the laminating material can therefore still be controlled through the drive air supply 22, despite the action of the locks 24.
When lamination of a workpiece is complete, or if it is desired to increase the gap 6, the locking air supply 28 can be cut off to disengage the locks 24. The drive air supply 22 is then switched from line 18 to line 20 to drive the pistons 16 in the opposite direction and move the roller 2 away from the flatbed 4.
Because a pneumatic system is required for the drive air supply 22, it is generally convenient also to operate the locking assembly pneumatically, as shown in
Operation of the locks 24 by purely mechanical means is also envisaged as a further alternative.
A supply line 46 delivers pressurised air from a locking supply 48 to a chamber within the tube 44 to drive the piston 42 into a locking position. A first locking member 50 on the piston 42 engages the main piston 16 to prevent further movement towards the second flatbed 4 by the piston 16 and the roller 2 that it supports. The main piston 16 may carry a second locking member (not illustrated) for better engagement with the first locking member. The mutual engagement may act as a clutch and may include engagement surfaces that are inclined relative to the direction of movement of the piston 16 in order to effect a wedging action that mechanically resists that movement in the direction towards the flatbed 4 but not in the opposite direction.
To deactivate the locking assembly in this embodiment, air pressure on the supply line 46 is cut and the piston 42 is driven back into the tube 44 by the action of a return spring 54. Alternatively, a second supply line could be provided to deliver air into the tube on the opposite side of the piston 42 from the first supply line 46 so that the piston 42 is moved pneumatically in both directions.
In a further embodiment of the invention, illustrated in
Locks similar to those shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 1521052.9 | Nov 2015 | GB | national |
