CHAMBER SHRINK WRAPPING MACHINE
A chamber shrink wrapping machine having a longitudinal body defining a lower portion of a chamber, a hood with an integral L-sealer transversely hinged to the body to define an upper portion of the chamber when lowered, an air heater to supply heated air to the chamber, a roller conveyor mounted to the body to initially support a product to be wrapped in the chamber longitudinally and transversely closely adjacent the L-sealer during sealing and cutting of heat-shrinkable film around the product when the hood is lowered, wherein the body defines longitudinal and transverse horizontal air ducts in the lower portion of the chamber to direct heated air toward the L-sealer and around the product.
The present invention relates to chamber shrink wrapping machines.
BACKGROUND OF THE INVENTIONSemi-automatic, hand-fed chamber shrink wrapping machines are capable of sealing and shrinking heat-shrinkable film in a single operation. Such machines have a chamber defined by a machine body and a hinged hood having an integral L-sealer. A product to be wrapped is placed by an operator into longitudinally centre-folded heat-shrinkable film on a product tray. The product in the film is then manually moved into the chamber where it is statically supported on an exit conveyor adjacent the L-sealer. The hood is then automatically lowered by a servo-mechanism to activate the L-sealer to seal and cut the film around the product, and heated air is supplied to the chamber to shrink the film onto the product. After a predetermined shrinking time, the hood is automatically raised, and the exit conveyor conveys the shrink-wrapped product out of the chamber for the wrapping cycle to start again.
Conventionally PVC film has been used in shrink wrap machines, though Polyolefin film has recently been used. Polyolefin film requires higher temperatures to effectively shrink wrap a product, thus increasing the importance of optimising a shrink wrap machine to efficiently use heat. The ability of a shrink wrap machine to generate, distribute and retain heat efficiently is an important performance characteristic that can influence energy use and process cycle times.
One disadvantage of conventional chamber shrink wrapping machines is that an L-shaped gap must be left between the edge of the product and the bars of L-sealer to ensure that heated air can flow around and over the product. Typically, the gap varies from 20 to 80 mm depending on the size and height of the product to be wrapped. The gap increases heated air flow, but also increases the amount of film used, which in turn increases the shrinking time and decreases energy efficiency.
Another disadvantage is that the automatic lowering and raising of the hood can allow an undesirable amount of heat to escape if an operator is not attentive to the machine. For automatic operation of the hood to provide sufficient force to positively seal the chamber and prevent excessive heat loss creates a safety risk to operators whose hands can be caught between the machine body and the hood during closing of the chamber. Electronic cut-out switches have been proposed to stop the hood lowering after a predetermined time when the hood encounters an obstacle. Such electronic safety switches are complicated and expensive and are thought to be less reliable than a mechanical failsafe.
What is needed is a chamber shrink wrapping machine which addresses the above difficulties.
SUMMARY OF THE INVENTIONAccording to the present invention, there is provided a chamber shrink wrapping machine having a longitudinal body defining a lower portion of a chamber, a hood with an integral L-sealer transversely hinged to the body to define an upper portion of the chamber when lowered, an air heater to supply heated air to the chamber, a roller conveyor mounted to the body to initially support a product to be wrapped in the chamber longitudinally and transversely closely adjacent the L-sealer during sealing and cutting of heat-shrinkable film around the product when the hood is lowered, wherein the body defines longitudinal and transverse horizontal air ducts in the lower portion of the chamber to direct heated air toward the L-sealer and around the product.
The ducts can peripherally surround the roller conveyor to allow heated air to flow therearound. The ducts can be formed as horizontal elongate slots. According to the present invention, there is also provided a chamber shrink wrapping machine having a longitudinal body defining a lower portion of a chamber, a hood with an integral L-sealer transversely hinged to the body to define an upper portion of the chamber when lowered, an air heater to supply heated air to the chamber, a roller conveyor mounted to the body to initially support a product to be wrapped in the chamber longitudinally and transversely closely adjacent the L-sealer during sealing and cutting of heat-shrinkable film around the product when the hood is lowered, wherein the roller conveyor has a plurality of parallel rollers that are transversely skewable and rotatable to subsequently convey the product longitudinally and transversely away from the L-sealer towards the centre of the chamber to allow heated air to circulate around the product to shrink the film thereon, and wherein the plurality of rollers are transversely unskewable and rotatable to finally convey the shrink-wrapped product longitudinally out of the chamber when the hood is raised.
The plurality of rollers can be rotatably and transversely skewably supported between two parallel side rails, one of which is fixed to the body and the other of which is longitudinally movable relative thereto to thereby collectively transversely skew the plurality of rollers.
One end of each roller can be rotatably and transversely skewably mounted to the fixed side rail by a spring, and the other end of each roller can be rotatably and longitudinally slidably mounted in an elliptical seat in the movable side rail.
According to the present invention, there is further provided a chamber shrink wrapping machine having a longitudinal body defining a lower portion of a chamber, a hood with an integral L-sealer transversely hinged to the body to define an upper portion of the chamber when lowered, an air heater to supply heated air to the chamber, a roller conveyor mounted to the body to initially support a product to be wrapped in the chamber longitudinally and transversely closely adjacent the L-sealer during sealing and cutting of heat-shrinkable film around the product when the hood is lowered, and a hood actuator, wherein the hood actuator is arranged to support the weight of the hood whilst it is lowered and then clamp the hood in a closed position.
The hood actuator can include a strut to support the hood, the strut being coupled to a spring loaded over-centre lever arranged to resist movement of the strut, and thereby support the weight of the hood, as the hood is lowered and then draw the strut downwards to clamp the hood closed. The over-centre lever can be loaded by a tension spring fixed to the body of the machine.
The hood actuator can be driven to lower the hood, the hood actuator having a one-way clutch that allows the hood to be idly raised.
The machine can further include a drive gear fixed to a motor, a free gear fixed to the one way clutch and an engagement device to rotationally fix the fixed gear to the free gear to transmit drive from the motor to lower the hood. The engagement device can be a gear which can be brought into contact with fixed gear and the free gear. The engagement gear can be arranged to be brought into engagement by moving the hood from an initial upright position to a closed position.
The hood actuator can be driven by a reduction drive electric motor. The motor can be pivotably mounted on a sprung base so that the motor moves against the action of the springs when the hood is closed to clamp the hood in a closed position.
The machine can further include a controller to control the hood actuator and can include a controller to control the air heater and the roller conveyor.
The invention will be further described by way of example only with reference to the accompanying drawings, in which:
Referring to
The body 12 of the machine 10 defines longitudinal and transverse horizontal air ducts 13 in the lower portion of the chamber below the sealing bar in mutually orthogonal sides of the body 12 to peripherally surround sides of the roller conveyor 20 adjacent where the L-sealer 18 contacts the body 12 to allow heated air to flow around a product (not shown) to be wrapped. For example, the chamber 14 is defined by longitudinal and transverse vertical panels 15a, 15b, as shown in
A hood actuator 35 is mounted in the body 12 to guide movement of the hood 16. In the example shown, the hood actuator 35 includes a strut 36 driven by a motor 38 via a one-way clutch 40 to automatically reciprocally lower and raise the hood 16. In one example, the hood actuator 35 is arranged to allow the hood 16 to be drivingly raised but idly lowered under its own weight so that an operator's hands can be easily withdrawn if caught under the hood 16 during closing of the chamber 14. The hood actuator 35, the roller conveyor 20, and the air heater 30 are controlled by the controller 26 which is programmed with different operating programs for products of different sizes and heights.
Referring to
In use, the rollers 42 are initially oriented in an unskewed position to statically support a product (not shown) to be wrapped in the chamber 14 longitudinally and transversely closely adjacent the L-sealer 18 during sealing and cutting of heat-shrinkable film around the product when the hood 16 is lowered. The rollers 42 are subsequently automatically transversely skewed and rotated to convey the product longitudinally and transversely away from the L-sealer 18 towards the centre of the chamber 14 to allow heated air to circulate around the product to shrink the film thereon. Finally, the rollers 42 are transversely unskewed and rotated to convey the shrink-wrapped product longitudinally out of the chamber 14 when the hood 16 is raised.
As illustrated in
The spring 68 is fixed to the machine 10 by an elongate washer 65 and a screw 69. The screw 69 can be received by the machine 10 in different locations so as to be vertically adjustable to change the point at which the weight of the hood is no longer supported and the hood becomes clamped, thereby providing fine tuning of the closing operation of the hood. The elongate washer 65 is provided to allow the tension of the spring 68 to be adjusted to increase the clamping force on the closed hood or to accommodate for hoods of different weight.
As illustrated in
As illustrated in
The strut 36 is drawn downward by the action of the motor 72 but can be stopped at any point prior to being closed as the one-way clutch allows the drive disc 74 to be rotated against the action of the motor 72.
As illustrated in
As illustrated in
After a predetermined amount of time has elapsed for the film to be shrunk, for example 0.7 to 1.0 sec, the motor 72 will reverse to open the hood 16. Once the spring loaded lever 82 moves a sufficient distance, the engagement gear 80 disengages from the first and second gears 76 and 78 to free the drive plate 74 so that it can rotate, via the one-way clutch, to allow the strut 36 to be lifted, thus releasing the hood 16.
It will be appreciated that the semi-automatic hood actuator 70 incorporates a number of components describe in relation to hood actuator 60, as shown in
It will be appreciated that embodiments of the invention provide a semi-automatic, hand-fed chamber shrink wrapping machine capable of automatically positioning a product centrally in a shrink wrap chamber after sealing and cutting of shrink film by an L-sealer.
The diverging exit roller conveyor of embodiments of the invention reduces shrink film consumption, as well as shrink time and energy consumption. In addition, the hood actuator of embodiments of the invention provides a simple mechanical solution which improves operator safety during automatic hood raising and lowering and may be suitable for use in other applications.
The embodiments have been described by way of example only and modifications are possible within the scope of the claims which follow.
Claims
1. A chamber shrink wrapping machine having a longitudinal body defining a lower portion of a chamber, a hood with an integral L-sealer transversely hinged to the body to define an upper portion of the chamber when lowered, an air heater to supply heated air to the chamber, a roller conveyor mounted to the body to initially support a product to be wrapped in the chamber longitudinally and transversely closely adjacent the L-sealer during sealing and cutting of heat-shrinkable film around the product when the hood is lowered, wherein the body defines longitudinal and transverse horizontal air ducts in the lower portion of the chamber to direct heated air toward the L-sealer and around the product.
2. A machine according to claim 1, wherein the ducts peripherally surround the roller conveyor to allow heated air to flow therearound.
3. A machine according to claim 1, wherein the ducts are formed as horizontal elongate slots.
4. A chamber shrink wrapping machine having a longitudinal body defining a lower portion of a chamber, a hood with an integral L-sealer transversely hinged to the body to define an upper portion of the chamber when lowered, an air heater to supply heated air to the chamber, a roller conveyor mounted to the body to initially support a product to be wrapped in the chamber longitudinally and transversely closely adjacent the L-sealer during sealing and cutting of heat-shrinkable film around the product when the hood is lowered, wherein the roller conveyor has a plurality of parallel rollers that are transversely skewable and rotatable to subsequently convey the product longitudinally and transversely away from the L-sealer towards the centre of the chamber to allow heated air to circulate around the product to shrink the film thereon, and wherein the plurality of rollers are transversely unskewable and rotatable to finally convey the shrink-wrapped product longitudinally out of the chamber when the hood is raised.
5. A machine according to claim 4, wherein the plurality of rollers are rotatably and transversely skewably supported between two parallel side rails, one of which is fixed to the body and the other of which is longitudinally movable relative thereto to thereby collectively transversely skew the plurality of rollers.
6. A machine according to claim 5, wherein one end of each roller is rotatably and transversely skewably mounted to the fixed side rail by a spring, and the other end of each roller is rotatably and longitudinally slidably mounted in an elliptical seat in the movable side rail.
7. A chamber shrink wrapping machine having a longitudinal body defining a lower portion of a chamber, a hood with an integral L-sealer transversely hinged to the body to define an upper portion of the chamber when lowered, an air heater to supply heated air to the chamber, a roller conveyor mounted to the body to initially support a product to be wrapped in the chamber longitudinally and transversely closely adjacent the L-sealer during sealing and cutting of heat-shrinkable film around the product when the hood is lowered, and a hood actuator, wherein the hood actuator is arranged to support the weight of the hood whilst it is lowered and then clamp the hood in a closed position.
8. A machine according to claim 7, wherein the hood actuator includes a strut to support the hood, the strut being coupled to a spring loaded over-centre lever arranged to resist movement of the strut, and thereby support the weight of the hood, as the hood is lowered and then draw the strut downwards to clamp the hood closed.
9. A machine according to claim 8, wherein the over-centre lever is loaded by a tension spring fixed to the body of the machine.
10. A machine according to claim 7, wherein the hood actuator is driven to lower the hood, the hood actuator having a one-way clutch that allows the hood to be idly raised.
11. A machine according to claim 10, further including a drive gear fixed to a motor, a free gear fixed to the one way clutch and an engagement device to rotationally fix the fixed gear to the free gear to transmit drive from the motor to lower the hood.
12. A machine according to claim 11, wherein the engagement device is a gear which can be brought into contact with fixed gear and the free gear.
13. A machine according to claim 12, wherein the engagement gear is arranged to be brought into engagement by moving the hood from an initial upright position to a closed position.
14. A machine according to claim 10, wherein the hood actuator is driven by a reduction drive electric motor.
15. A machine according to claim 14, wherein the motor is pivotably mounted on a sprung base so that the motor moves against the action of the springs when the hood is closed to clamp the hood in a closed position.
16. A machine according to claim 10, further including a controller to control the hood actuator.
17. A machine according to claim 1, further including a controller to control the air heater and the roller conveyor.
Type: Application
Filed: Aug 11, 2010
Publication Date: Jun 7, 2012
Inventor: Diego Barbaro (Coburg)
Application Number: 13/390,511