Conveyance system

Abstract: A non-water cooled conveyance vehicle for the transportation of a wholly or partially evacuated vessel, the vessel including: a vacuum pumping system gripper means for receiving a neck of the vessel and sealingly connecting the interior of the vessel to the pumping system via the neck an on-board refrigeration system for providing circulating refrigerant fluid to and from heat exchange means associated with the gripper means.

Description: This invention relates to improved conveyance systems for use in the processing of evacuated picture tube vessels and, more particularly to individual vehicles for use in such systems. In the production of television picture tubes or other forms of similar tubes, it is generally necessary in a final process stage to evacuate the tube to a residual pressure of less than about 10 -6 mbar whilst allowing for the tube to be heated during at least some of the process stages. In a typical production line, each tube is mounted on to an individual conveyance vehicle (sometimes referred to as a "cart") with a plurality of such vehicles forming part of a conveyance system in which the vehicles are in slow but continuous motion along straight or circular/oval production lines. Each conveyance system can typically comprise up to two hundred and fifty vehicles with a production line time of, for example, seventy to one hundred minutes (or more depending on the article being processed.) Each vehicle generally incorporates equipment required to carry out the various finishing process stages for the picture tubes. The known vehicles generally possess a vacuum system in the form, for example, of a diffusion pump or turbomolecular pump backed by a rotary pump. The known vehicles generally also possess a gripper assembly for receiving the "neck" of the television tube and sealingly connecting the interior of the tube to the vacuum system for maintaining a vacuum therein. However, vehicles incorporating such equipment generally require the supply of water thereto to effect cooling of the equipment. Firstly, the gripper assembly is commonly water cooled in order to maintain it at the required temperature whilst in contact with a heated tube. It is known from the introduction to US-A-4071058 that cooling water from a simple water pumping system may be employed for such purposes and that cooling of a gripper assembly may be effected by urging cooled air in the direction of the gripper as part of the inventive concept. Equally, it is generally necessary to supply cooling water to diffusion vacuum pumps for their overall operation in a manner well known in the art. In addition, in order to prevent what is known as "back-streaming" of the diffusion pump working fluid from the pump nozzle towards the mouth of the pump and hence the chamber to which the pump is attached, it is well known for such pumps to incorporate a water cooled "guard ring" or "baffle" on which the back- streaming vapour can be intercepted by causing it to condense on the guard ring or baffle. However, the disadvantages associated with the use of water cooling of such moving vehicles are obvious. The vehicles usually require out-rigged cooling water pick-up and discharge lines together with an on-board water circulation pump; the water pick-up and discharge lines are liable to damage and dislocation due to their out-rigged location, thereby giving rise to considerable maintenance and low reliability. Furthermore, the conveyance system for the vehicles must be equipped with water in-take and discharge troughs, which also require considerable maintenance due to trough obstructions caused by imploding tube parts which in turn cause the pick-up and discharge tubes to bend and/or lift out of this water leading to pump and gripper overheating and cart switch-off. There are also difficulties in maintaining the high levels of cleanliness necessarily required in the production of high quality electronic devices. The present invention is concerned with the provision of conveyance vehicles of the type described above in which the above noted difficulties are overcome. In accordance with the invention, there is provided a non-water cooled conveyance vehicle for the transportation of a wholly or partially evacuated picture tube vessel, the vehicle including a vacuum pumping system; gripper means for receiving a neck of the vessel and sealingly connecting the interior of the vessel to the pumping system via the neck characterised in that an on-board refrigeration system is present for providing circulating refrigerant fluid to and from heat exchange means of the gripper means in which cooling of the gripper means is caused by expansion of the fluid Preferably, the vehicle refrigeration system also includes further heat exchange means associated with the mouth of a vacuum pump of the vacuum pumping system. Such further heat exchange means can thereby provide a "guard ring" or "baffle" in the case of diffusion vacuum pumps in particular. The use of an on-board refrigeration unit obviates the need for water cooling to the gripper means and also, if present, to the guard ring or baffle associated with a diffusion vacuum pump. The refrigeration unit can comprise any known form but preferably incorporates a compressor to urge refrigerant fluid around a closed circuit and, in particular, urging compressed fluid to a heat exchanger associated with the gripper means where the fluid is allowed to expand and cool the gripper means. Preferably the expanded refrigerant fluid is also caused to pass through further heat exchange means incorporated in to the circuit and being associated with a diffusion pump (if present) as part of the pumping system. All the conveyance vehicle components must necessarily be mounted on a suitable vehicle body which is appropriately adapted for use within a conveyance system so that the vehicle can generally be caused to move slowly along its production line. For a better understanding of the invention, reference will now be made, by way of exemplification only, to the accompanying drawing, which shows schematically the major features of a vehicle in accordance with the invention. With reference to the drawing, there is shown, incorporated on to a vehicle chassis (not itself shown), a pump porting arrangement comprising a number of different components sealingly connected to each other, notably cylindrical main manifold 1, smaller generally cylindrical components 2, 3 and 4 and a hollow support head 5. The support head 5 has a flange 6 to which a diffusion pump or turbomolecular pump (not shown) of standard design may be attached; the diffusion pump may if desired be backed with an oil-sealed rotary pump. In accordance with preferred embodiments, the diffusion pump is of air-cooled design. Component 3 has a horizontally-directed extension 7 ending in a flange 8 to which a vacuum gauge of known design may be attached. The component 3 also has a vertically-directed extension "cup" 8 which acts as a glass trap to receive any physical debris which might be present. Cup 8 is sealingly connected to the component 3 in use but may be disconnected to remove debris after use of the vehicle. The main manifold component 1 has attached at its upper end a gripper means 9 having a gripper head 10 made of thermal conducting material and having a triple vertical bore passing vertically therethrough, the broadest two 11,12 of which are designed to receive the sealing ring (not shown) and the open neck contours of a tube to be conveyed along a production line and the third 13 of which allows a connection between the interior of the tube and the pumping system of the vehicle. The gripper means 9 also includes in close physical contact with the head 10, a heat exchanger arrangement 14 comprising a number of metal discs with a variety of internal spaces/passageways defined therebetween. The vehicles also possesses an on-board refrigeration system comprising a refrigeration unit 15 in the form of an air-cooled compressor system. The refrigeration system also defines a closed circuit for the circulation of refrigerant fluid from the compressor system in the form of a capillary tube connection 16 to an inlet 17 of the heat exchanger arrangement 14 of the gripper head 10, thence via the internal passageways of the arrangement 14 and thence via the tubular system 18 back to the refrigeration unit 15. In preferred embodiments shown in the drawing, the tubular system 18 passes through the walls of the support head 5; at the centre of the head 5, a further heat exchanger arrangement is provided in the form of a "chevron" baffle 19. This baffle 19 provides a "guard ring" or "baffle" associated with the mouth of the diffusion pump which, in use, is secured to the flange 6. The guard ring or cold cap can thereby function in the manner described above. In use of the vehicle, an air-cooled diffusion pump (or turbomolecular pump) is attached to the flange 6 and preferably backed with an oil sealed pump and a tube to be processed in the production line is sealingly received in the gripper 9 with a vacuum gauge sealingly attached to flange 6. Refrigerant fluid is urged around the refrigeration system from the air-cooled compression system of unit 15 via the tube 16, ie. in the direction of the arrows, and thereafter is allowed to expand in the heat exchanger arrangement 14 and thereby cool the gripper 9; expanded, cooled refrigerant fluid thereafter is urged via the tubular system 18 to the chevron baffle 19, thereby cooling the baffle, and thence returning to the unit 15.

Claims: A non-water cooled conveyance vehicle for the transportation of a wholly or partially evacuated picture tube vessel, the vehicle including: a vacuum pumping system gripper means (9) for receiving a neck of the vessel and sealingly connecting the interior of the vessel to the pumping system via the neck characterised in that an on-board refrigeration system (15) is present for providing circulating refrigerant fluid to and from heat exchange means (14) of the gripper means (9) in which cooling of the gripper means (9) is caused by expansion of the fluid. A conveyance vehicle according to Claim 1 which also includes further heat exchange means (19) at the mouth of a vacuum pump of the vacuum pumping system. A conveyance vehicle according to Claim 2 in which the further heat exchange means (19) provides a guard ring or baffle. A conveyance vehicle according to any preceding claim in which the refrigeration system (15) incorporates a compressor to urge the refrigerant fluid around a closed circuit. A conveyance vehicle according to Claim 4 in which the expanded refrigerant fluid is caused to pass through further heat exchange means (19)incorporated in to the circuit. A conveyance vehicle according to Claim 5 in which the further heat exchange fluid is associated with a diffusion pump as part of the pumping system. A conveyance vehicle according to any preceding claim comprising a vehicle body on which the vehicle components are mounted and which is appropriately adapted for use within a conveyance system so that the vehicle can be caused to move slowly along a production line.

Inventors: BENDALL COLIN WILLIAM, FOOTE WILLIAM JAMES DR, KUSAY ROLAND GREGOR PAUL, BENDALL, COLIN WILLIAM, FOOTE, WILLIAM JAMES, DR., KUSAY, ROLAND GREGOR PAUL
Applicants: BOC GROUP PLC, THE BOC GROUP PLC
Application year: 1995
Main classification: H01J9
IPC codes: F25D7, H01J9