MULTI-COMPARTMENT TEMPERATURE-CONTROLLED ROAD VEHICLES

Abstract: A multicompartmented road vehicle e.g. a six-lane delivery truck 16 has a separate refrigerator system 18 or 19 for each lane 17, governed by a separate theremostat 24 in each case. The corresponding condensers 20 are conveniently arranged in a bank or accumulation. A common generator 21, preferably supplied with a sequencing arrangement to prevent start-up overload or casual overload generates the electrical power to drive the refrigeration systems. The cost of initial installation is an acceptable proportion of the cost of a heavy truck, the cost of maintenance is less than for maintenance of complex valving, ducting and internal prioritizing logic systems as in interconnected refrigeration systems of the prior art, and the mass and size of the installation is again compatible with the truck size and shape. Thus the normally counterindicated provision of separate rather than shared systems has unexpected advantage. Also, the single on-board generator would be powerful enough to operate loading and unloading equipment when desired.

Description: THIS INVENTION relates to temperature-controlled road vehicles, and more especially to multi-compartmented temperature-controlled road vehicles. It has been well known for many years to provide an essentially closed delivery vehicle with an on-board refrigeration circuit. Initially, only a singly storage chamber was present, and air was cooled over the evaporator coils of the refrigeration unit, pumped into the chamber, recycled for further passage over the cooling coils of the evaporator, and so on. The heat absorbed by these coils was dissipated by passing the refrigerator fluid through an external condenser before recycling and expansion. Subsequently, the need arose to provide the vehicle with two compartments, for holding goods at different temperatures e.g. frozen and chilled, or chilled and "controlled ambient" temperatures. This could be accommodated by generally maintaining the circuit of cold air as before in the colder compartment, but occasionally, e.g. as required by a thermostat, diverting a supply of such air to the less cold compartment. Alternative systems, e.g. involving a permanent bleed of colder air were also possible. REVUE PRACTIQUE DU FROIDS, No.249, December 1966, pages 46-52, figure 14, discloses such a road vehicle having two compartments. More recently, three-compartment vehicles have been utilised.Various expedients have been adopted to ensure supplies of cool air, as needed, without cross-flavouring the compartment contents. Moreover, in recognition of the problem that there may be a warming equirement (e.g. because external temperature is below the "controlled ambient" requirement, or because of loss of heat through internal bulkheads to a deep-frozen compartment, with the same consequence), elaborate systems of sensing, and valving, and ducting, and reversal of evaporator action by passage of hot refrigerant, and application of extraneous heat supplies such as electrical fan heaters, have been proposed. In practice, with vehicles sold as suitable for operation in very hot or very cold climates, with different loadings of goods needing different conditions and with varying frequency of loading of compartments the various temperature sensors in these vehicles can sometimes send conflicting operating signals to the compressor and to the valving of the ducted air supply, so that a prioritising logic circuit is required for practical operation to deal with the compartments for optimum results. There is nowadays a requirement for highly compartmented vehicles e.g. six-compartment vehicles, and rapid changeover of storage conditions within each compartment. The present invention is based upon the realisation that existing technology, based on sensor-controlled selective valving of supply ducting and ability to supply hot or cold air, is too complex to use in these multicompartment vehicles because of the possible interactions of the pressure and temperature conditions in the various compartments during the transient phases of operation. Six-compartment vehicles are nowadays typically designed with six separate and thermally insulated longitudinal lanes of storage, three at a lower level and three at a higher. The need for such vehicles does not exclusively reside in the ability to convey goods at six different temperatures, but has its origins in traffic congestion conditions at supermarkets or the like. Nowadays, to economise on stock and on holding space at their retail outlets (with high land values) it is typical for supermarkets to require frequent and smaller deliveries. Thus, a number of large specialist trucks will accumulate for unloading causing congestion, and must each moreover service say up to ten deliveries a day.Multicompartment and multi-temperature trucks, however, can each carry a range of delivery items, and consequently lead to less congestion and fewer deliveries each per day. Such trucks, with elongate lanes, typically have movable floors which convey goods sequentially to the open rearward ends of the lanes and have also a relatively elaborate goods-handling loading/unloading mechanism which can operate between the floor, lower lane level! and upper lane level in any one of three lane positions. Because they are used to convey a multi-product load they are typically loaded to a pre-existing program given to the driver for operation (or even fed in to the equipment at the depot) thus minimising delivery error, theft or pressures on the driver for a larger or smaller delivery. Their complexity makes then an expensive prime cost, even though a fleet of such vehicles can be more cheaply operated, so that they are most economic if manufactured to the limit of legal sizes and weights. The above combination of characteristics, problems and opportunities has led to the present invention which consists in a multicompartmented road vehicle, the compartments of which are thermally insulated, having a generally separate electrically driven refrigeration circuit for each compartment, characterised in that there is provided at least one temperature sensor in each compartment to govern switching on and off of the electrical supply, and a common generator for the electrical supply. By "generally separate" is meant that the condenser unit of each refrigeration circuit can be totally separate from the others, or be made up as separate ducting portions of one mechanical condenser structure or can possibly be subsumed in a shared condenser system. Totally separate condesers, located in an accessible accumulation or bank , are however preferred. The system as described above, with its high prime cost, multitude of working refrigerator units to maintain; and weight and bulk is completely counterindicated in prior art vehicular refrigeration techniques, but we have realised that for a multi-compartment e.g. six-lane vehicle (a) the high prime cost is an acceptable proportion of the cost of the whole vehicle (b) the cost of maintenance is outweighed by the avoidance of complex ducting, shutter-valves, and prioritising logic and safety circuits,and also by the attractively flexible working characteristics of such vehicles and (c) weight and bulk are again commensurate with the large size and high weight of the vehicle. Moreover, the presence of an on-board diesel generator powerful enough to operate all six refrigeration systems gives the facility of providing power for hydraulic or pneumatic loading and unloading equipment i.e. the moving lane floors and complex handling equipment as discussed above. A particularly preferred feature of the invention is the provision of a mechanical, hydraulic or electronic sequencing means governing the switch-on of each refrigeration system for its electrically driven operation. Once again, a man skilled in the art would not be led to drive six systems of such equipment froma common generator. The load characteristics of each system are such that, after switch-on, the load rises to a peak and then falls away to a maintenance level. Six coinciding peaks would burn out most feasible generator systems, but the interposition of a single sequencing means whereby the systems never come on together (or whereby not more than, say, two systems come on together) can avoid damage and facilitate use of a practically-sized generator. For instance, a sequence of six operating cams on a common rotary shift can control the switching in of the refrigeration system load. it is also within the scope of the invention to route working signals received from compartment thermostats through the same system so that whenever instruction is given can only take its priority within the sequence, even if earlier instructions on other systems are merely confirmed by the sequencing means. Other features of the invention include mounting of the diesel generator beneath the vehicle if desired, and the presence of a control cubicle, if desired, at the forward part of the vehicle, e.g. to switch from generator operation to mains electricity while loading, or to connect in ancillary equipment. The refrigeration systems will normally each be of the recirculated cold-air type so that all parts of the elongate lanes can be effectively reached. The invention will be further described with reference to the accompanying drawings, in which:- Figure 1 shows a refrigeration circuit which can be used one for each compartment of a multicompartment vehicle; Figure 2 shows diagrammatically from above a temperature-controlled six-lane trailer unit; Figure 3 shows diagrammatically from one side the unit of Figure 2; and. Figure 4 shows diagrammatically equipment for providing sequential start-up for the separate refrigeration units. Figure 1 shows a compressor 1, a discharge valve location 2 and a vibration-absorbing run of ducting 3. Pumped gas passes via valve 4 into the coils of condensor 5, where a fan draws cold external air past the coils to condense the gas to liquid. This liquid passes through check valve 6 to receiver tank 7. It then passes still at high pressure past valve 8 and dehydrator 9, where mixture and impurities are removed, into sight glass 10 which remains clear when the refrigerant charge is sufficient. Liquid then passes in heat exchange at 11, to cool against the cold refrigerant returning from the evaporator 13. Cool liquid enters evaporator 13 via expansion valve 12,and loses pressure and hence temperature to cool the coils of evaporator 13, over which air feed to the compartment passes. The cooled refrigerant passes back (usually as a vapour/liquid mixture via heat-exchanger 11) to warm slightly and liberate any refrigerant present in lubricating oil droplets. The refrigerant, by now in gas form, then passes again through reverse cycle valve 4, a vibration-absorbing ducting 14 and, via suction valve location 15, into compressor 1. Figures 2 and 3 show from the top and side respectively a six-lane temperature controlled trailer 16 with lanes as at 17, three at the top and three at the bottom. Each top lane is provided with a separate evaporator/fan unit 18 for cold air, and each bottom lane with a similar evaporator/fan unit 19, in each case as integer 13 in Figure 1. Each such unit 18 or 19 has a separate circuit as shown in Figure 1, with a separate condenser 20 (cf. condenser 5), the condensers being mutually arranged as a bank of condensers as and where shown. The electrical drive for each system is provided by a diesel generator 21 within cubicle 22 or beneath the floor of the vehicle. Preferably a sequencing means to prevent electrical overload e.g. a logic controller system or a mechanically cammed sequence controlling switch-on, is present in the system. The cubicle 22 further comprises electrical control panels 23, and can include hydraulic or pneumatic units connected to the generator 21 to operate moving-floor or tailgate lift systems as and when desired, possibly only on switch-off of refrigeration. Thermostats 24, one in each lane, are operatively connected to each electrical drive for each separate refrigeration system; preferably their action is, however, sequenced or prioritized in the event of excess or conflicting demand on the equipment. Although Figures 2 and 3 show longitudinal lanes the system illustrated will operate in other numbers, combinations and shapes of compartment. Figure 4 shows diagrammatically equipment for providing sequential start-up for the separate refrigeration units. For clarity of illustration, the diagram illustrates sequencing for three units only but the man skilled in the art will appreciate that the same principles will apply to a six-unit installation as shown in Figures 2 and 3. Sequential start-up is valuable (a) to avoid the initial overload of the combined starting torque of the motors in all units simultaneously, and (b) to avoid casual overload when several unit motors switch on simultneously during operation of the installation, by coincidental, operation of two or more of thermostats 24. The equipment shown essentially comprises a cam timer, the mechanism of which includes four switching cams 402, 403, 404, 405 mounted at 90° intervals on a common shaft driven by motor 401, and three refrigeration units, only one of which (UNIT III) is shown in its control and circuitry details, the other two being essentially identical. The equipment operates as follows:- A signal from thermostat 24 feeds via cam timer switch 404 to cam timer control relay CTR1. This closes contact CTR1/1, and motor 401 starts to rotate its shaft and cams 402 - 405. Cam switch 402 closes and will stay closed for the whole revolution of the shaft. After for example 15 seconds (or whatever time is equivalent to one quarter turn) switch 403 normally either (a) closes, finds the relevant thermostat not calling for supply, and opens again or (b) is found to be closed because unit I is already operative. After 30 seconds, the same situation applies to switch 404 and Unit II. After 45 seconds, switch 405 closes and opens again. As it closes, relay CR2 is energised. Contact CR2/1 locks the relay CR2 on. Contact CR2/2 closes and energises the main unit contactor UC, thereby starting the refrigeration system of unit III. The auxiliary unit contractor UC AUX opens to ensure that no feed is given to the timer 401 - 405 while the unit III is running. After 60 seconds, the shaft has returned to its starting position, changing back cam switch 402, and thus switches. Unit III will continue to operate until its thermostat 24 is satisfied, at which point the thermostat contacts open to de-energise CR2 and UC, and thus also restore UC AUX to its oririginal position. The man skilled in the art will appreciate that if say 20 seconds after unit III thermostat calls for cooling unit II thermostat also opens and interposes a signal, the rotation of the cam will actuate equivalent circuitry for unit II and, fifteen seconds later, for unit III as above. Thus, rotation of the cam leads each switch in turn to a confirmatory, non-operative or operative situation, but the sequencing is always present however simultaneous the calls on the generator. If desired, the sequencing can also be effected electronically.

Claims: A multicompartmented road vehicle, the compartments of which are thermally insulated, having a generally separate electrically driven refrigeration circuit (18,19) for each compartment, characterised in that there is provided at least one temperature sensor (24) in each compartment to govern switching on and off of the electrical supply to the said circuit, and a common generator (21) for the electrical supply. A multicompartmented road vehicle as claimed in claim 1 characterised in that the respective condenser units (18, 19) of each refrigeration circuit are totally separate fabrications. A multicompartmented road vehicle as claimed in claim 2 characterised in that the condenser units are located adjacent each other as an accessible accumulation or bank of such condenser units. A multicompartmented road vehicle as claimed in claim 1 characterised in that the respective condenser units (18, 19) are separately ducted portions of one overall mechanical structure. A multicompartmented road vehicle as claimed in any one preceding claim characterised by further comprising sequencing means governing switch-on of the respective circuits for drive from the common generator. A multicompartmented road vehicle as claimed in claim 5, characterised in that the said sequencing means are in operative connection with each of said thermostats (24). A multicompartmented vehicle as claimed in claim 5 or 6, characterised in that the sequencing means are mechanical sequencing means utilising a sequence of operating cams (402, 403, 404, 405) on a rotary shaft. A multicompartmented road vehicle as claimed in any one preceding claim characterised in that the common generator (21) is located beneath the vehicle. A multicompartmented road vehicle as claimed in any one preceding claim characterised by further comprising an operator control cubicle (22) in the forward part of said vehicle. A multicompartmented road vehicle as claimed in any one preceding claim characterised in that the refrigeration systems are each of the recirculated cold-air type.

Inventors: RYDE, MICHAEL JOHN, WARWICK, PETER JOSEPH
Applicants: PETTER REFRIGERATION LIMITED
Application year: 1989
Main classification: B60H1
IPC codes: B60P3, B60H1