阅读说明：本技术 一种节能型高空作业车上下车互锁系统及其控制方法 (Energy-saving type high-altitude operation vehicle getting-on and getting-off interlocking system and control method thereof ) 是由 商晓恒 李根文 曹丹 满军 崔腾霞 张宇 于 2021-09-13 设计创作，主要内容包括：本发明公开了一种节能型高空作业车上下车互锁系统,包括泵组,泵组的出油口与上下车切换阀的进油口连接,上下车切换阀的上位出油口和下位出油口分布与上车控制多路阀组的进油口和支腿控制多路阀组的进油口连接,上车控制多路阀组的总油路上串联有上车电磁卸荷阀,上车控制多路阀组与上车执行元件连接,支腿控制多路阀组与下车执行元件连接；还包括上车控制器和下车控制器,下车控制器与四个垂直支腿压实检测开关连接,上车控制器连有臂体落回检测开关。本发明还公开一种节能型高空作业车上下车互锁系统的控制方法。本发明的一种节能型高空作业车上下车互锁系统及其控制方法,能够实现对阀组的节能控制和自动完成上下车互锁功能。(The invention discloses an energy-saving type upper and lower car interlocking system of an overhead working truck, which comprises a pump set, wherein an oil outlet of the pump set is connected with an oil inlet of an upper and lower car switching valve, an upper oil outlet and a lower oil outlet of the upper and lower car switching valve are respectively connected with an oil inlet of an upper car control multi-way valve bank and an oil inlet of a landing leg control multi-way valve bank, an upper car electromagnetic unloading valve is connected in series with a total oil path of the upper car control multi-way valve bank, the upper car control multi-way valve bank is connected with an upper car execution element, and the landing leg control multi-way valve bank is connected with a lower car execution element; the device is characterized by further comprising a vehicle loading controller and a vehicle unloading controller, wherein the vehicle unloading controller is connected with the four vertical supporting leg compaction detection switches, and the vehicle loading controller is connected with an arm body falling detection switch. The invention also discloses a control method of the energy-saving type high-altitude operation vehicle getting-on and getting-off interlocking system. The energy-saving type upper-altitude operation vehicle getting-on and getting-off interlocking system and the control method thereof can realize energy-saving control of the valve group and automatically complete the getting-on and getting-off interlocking function.)

1. The utility model provides an energy-saving high altitude construction car interlocking system that gets on or off bus which characterized in that: the hydraulic control system comprises a pump set (1), wherein an oil outlet of the pump set (1) is connected with an oil inlet of an upper vehicle switching valve (6) and a lower vehicle switching valve (6), a pressure switch (5) is installed at an oil inlet and an oil way of the upper vehicle switching valve (6) and the lower vehicle switching valve (6), an upper oil outlet and a lower oil outlet of the upper vehicle switching valve (6) are distributed and connected with an oil inlet of an upper vehicle control multi-way valve group (3) and an oil inlet of a landing leg control multi-way valve group (9), an upper vehicle electromagnetic unloading valve (2) is connected in series with a total oil way of the upper vehicle control multi-way valve group (3), a driving port of a rotary table rotary valve of the upper vehicle control multi-way valve group (3), a driving port of an arm body amplitude valve and a driving port of an arm body telescopic valve are respectively connected with a rotary table rotary motor, an amplitude oil cylinder and a telescopic oil cylinder of an upper vehicle execution element (4), driving ports of the landing leg telescopic control multi-way valve group (9) and driving ports of four groups of vertical/horizontal landing leg selection valves and four groups of a lower vehicle execution element (8) The telescopic oil cylinders are connected with four groups of horizontal supporting leg telescopic oil cylinders, and supporting leg locking valves (7) are connected in series on oil return paths of the supporting leg telescopic control valves; the hydraulic control system is characterized by further comprising a loading controller and a unloading controller which are connected through a CAN bus, wherein the unloading controller is connected with four vertical supporting leg compaction detection switches and the pressure switch (5) through DI points, the four vertical supporting leg compaction detection switches are respectively arranged above hydraulic locks of four vertical supporting leg oil cylinders, the loading controller is connected with an arm body falling-back detection switch, and the loading controller is respectively connected with a rotary table rotary valve, an arm body amplitude changing valve, an arm body telescopic valve, an loading electromagnetic unloading valve (2) and a supporting leg locking valve (7).

2. The energy-saving type interlocking system for getting on and off of high-altitude operation vehicle as claimed in claim 1, wherein: the upper electromagnetic unloading valve (2) is a normally closed two-position two-way electromagnetic valve.

3. The energy-saving type interlocking system for getting on and off of high-altitude operation vehicle as claimed in claim 1, wherein: the landing leg locking valve (7) is a normally open two-position two-way electromagnetic valve.

4. The energy-saving type interlocking system for getting on and off of high-altitude operation vehicle as claimed in claim 1, wherein: the getting-off controller is arranged on an auxiliary frame near the landing leg control multi-way valve group (9), and the getting-on controller is arranged on the part of the getting-on turntable.

5. A control method of the energy-saving type high-altitude operation vehicle getting on/off interlocking system as claimed in any one of claims 1 to 4, characterized in that: the method comprises the following steps:

s01, firstly, the getting-on electromagnetic unloading valve (2) and the supporting leg locking valve (7) are arranged in a power-off state;

s02, an operator drives the switching valve (6) for getting on and off the vehicle to the lower position, the landing leg controls the multi-way valve group (9) to obtain an oil source, and the landing leg valve rod is operated to enable the four horizontal landing legs and the four vertical landing legs to be in a fully extended state;

s03, the getting-off vehicle controller collects detection signals of the four vertical leg compaction detection switches through DI points and transmits the collected signals to the getting-on vehicle controller through a CAN bus;

s04, when the getting-on controller judges that the signal is not detected by the vertical supporting leg compaction detection switch, the getting-on controller controls the getting-on electromagnetic unloading valve (2) to continuously keep the power-off state, cuts off an oil way of the getting-on control multi-way clothing group (3), and locks the getting-on action; when the vehicle-mounted controller judges that the four vertical supporting leg compaction detection switches all detect signals, the vehicle-mounted controller controls the electromagnetic unloading valve (2) of the vehicle-mounted to be powered on, the switching valve (6) of the vehicle-mounted to the upper position at the moment, and the vehicle-mounted controller controls the multi-way valve group (3) to obtain an oil source, so that the vehicle-mounted action can be operated;

and S05, the vehicle-mounted controller receives a detection signal of the arm body fall-back detection switch, and when the arm body fall-back detection switch detects that the vehicle-mounted arm body leaves the arm support, the vehicle-mounted controller controls the supporting leg locking valve (7) to be powered on, cuts off an oil way at the supporting leg multi-way valve group (9), and locks the vehicle-mounting action.

6. The control method of the energy-saving type high-altitude operation vehicle getting-on and getting-off interlocking system according to claim 5, characterized in that: in S03, the vehicle control unit acquires a detection signal of a pressure switch (5) on the hydraulic system through a DI point, when the pressure switch (5) detects that the pressure value of the system exceeds the set pressure value of the system, the pressure switch (5) is judged to be conducted, otherwise, the pressure switch (5) is judged to be in a disconnected state.

7. The control method of the energy-saving type high-altitude operation vehicle getting-on and getting-off interlocking system according to claim 6, characterized in that: in S05, when the pressure switch (5) is on, the PWM port of the controller on board drives and outputs the leg lock valve (7) at a duty ratio of 100%, and when the pressure switch (5) is in an off state, the PWM port of the controller drives the leg lock valve (7) at a duty ratio of 40% to maintain the closed state of the valve body.

8. The control method of the energy-saving type high-altitude operation vehicle getting-on and getting-off interlocking system according to claim 6, characterized in that: in S04, when the vehicle control unit judges that all the four vertical leg compaction detection switches detect signals, if the pressure switch (5) is turned on, the PWM port of the vehicle control unit drives and outputs the upper electromagnetic unloading valve (2) at a duty ratio of 100%, and if the pressure switch (5) is in an off state, the PWM port of the vehicle control unit drives the upper electromagnetic unloading valve (2) at a duty ratio of 40% to keep the on state of the valve core.

Technical Field

The invention relates to an energy-saving type high-altitude operation vehicle getting-on and getting-off interlocking system and a control method thereof, belonging to the technical field of engineering machinery.

Background

As a typical overhead manned operation device, the safety and stability of operation of the overhead working truck are the most basic requirements, wherein the interlocking function of loading and unloading is almost the necessary function of each overhead working truck as an important safety measure. The overhead working truck getting-on refers to a rotary table and the devices, and comprises a rotary table structure, an arm body structure and a working bucket structure, and the getting-off refers to an auxiliary frame, supporting legs and a chassis part. The interlocking of the getting-on and getting-off legs means that after the arm body of the getting-on leg leaves the arm support, the control valve group of the landing leg of the getting-off leg is locked, and the operation of the landing leg of the getting-off leg is forbidden; when the lower landing leg is not completely supported in place, the upper arm body is forbidden to operate by locking the upper control valve group. The logic is generally completed by a controller arranged on a vehicle, and the controller controls the on-off of the support leg locking valve and the getting-on electromagnetic unloading valve. In a traditional control mode, after an upper arm body leaves an arm support, a controller drives a lower support leg locking valve to be electrified to lock the support leg actions, and simultaneously drives an upper unloading valve to be electrified to unlock the upper arm body to act. Because the electric control system of the overhead working truck generally directly gets electricity from a chassis storage battery, and an operator is used to stretch an upper arm body to an operation position and then flameout the operation for a long time. Therefore, the electric quantity of the chassis storage battery is greatly consumed due to long-time electrification of the supporting leg locking valve and the boarding unloading valve, and the timely power generation supplement cannot be obtained, so that the storage battery is in power shortage failure.

To get on or off the bus interlocking function, relevant technical personnel do a large amount of work: patent CN105288909A discloses an automatic interlocking device with dual protection for getting on and off a fire truck, in the scheme, the getting on part realizes the limitation of the action of an arm body by controlling a hydraulic pilot unloading valve group, and the getting off part realizes the limitation of the action of a leg part by adopting a mechanical interlocking limiting plate and a self-resetting cylinder. In addition, after the detection result of the position sensor and the logical operation of the controller are carried out, the upper hydraulic pilot unloading valve and the lower self-resetting cylinder are respectively driven to realize the interlocking function of the upper vehicle and the lower vehicle. This solution has the following problems: the technology is too complicated, the requirement on the processing precision of the structural member is high, the assembly is difficult, and after the upper arm body leaves the arm support, the lower cylinder needs to be continuously electrified to realize the locking of the action of the lower landing leg, so that the electric quantity of the storage battery is greatly consumed.

Patent CN110985464A discloses an automatic interlocking control system for getting on and off of an overhead working truck and a control method thereof. According to the scheme, the upper arm body action and the lower landing leg action are limited through two groups of normally closed two-position two-way electromagnetic valves, and the manual switching of the upper traffic flow and the lower traffic flow is realized through a group of upper traffic switching valves and lower traffic switching valves. This solution has the following problems: after the system is powered on, if the upper arm body is continuously maintained on the arm support, the supporting leg unloading valve can be continuously powered on, and the electric quantity consumption is large; in addition, when the supporting legs extend out, the arm body leaves the arm support, and if the power supply of the system is cut off due to faults, the supporting legs cannot be forcibly retracted, so that the vehicle can only occupy a field operation road for a long time, and great potential safety hazards exist.

Disclosure of Invention

The invention aims to solve the technical problem of providing an energy-saving type upper and lower car interlocking system of an overhead working truck and a control method thereof, which can avoid the phenomenon that a supporting leg locking valve and an upper car unloading valve are electrified for a long time to consume a large amount of electric quantity of a chassis storage battery, realize energy-saving control on a valve bank, have a simple structure and can automatically complete the upper and lower car interlocking function.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows:

an energy-saving type upper and lower car interlocking system of an overhead working truck comprises a pump unit, wherein an oil outlet of the pump unit is connected with an oil inlet of an upper and lower car switching valve, a pressure switch is arranged at an oil inlet passage of the upper and lower car switching valve, an upper oil outlet and a lower oil outlet of the upper and lower car switching valve are respectively connected with an oil inlet of an upper car control multi-way valve group and an oil inlet of a support leg control multi-way valve group, an upper car electromagnetic unloading valve is connected in series with a total oil passage of the upper car control multi-way valve group, driving ports of a rotary table rotary valve, a driving port of an arm body amplitude valve and a driving port of an arm body telescopic valve of the upper car control multi-way valve group are respectively connected with a rotary table rotary motor, an amplitude cylinder and a telescopic cylinder of an upper car executive component, driving ports of a support leg telescopic control valve and four groups of vertical/horizontal support leg selection valves of the support leg control multi-way valve group are respectively connected with four groups of vertical telescopic support leg cylinders and four groups of a horizontal telescopic cylinder of a lower car executive component, a supporting leg locking valve is connected in series on an oil return path of the supporting leg telescopic control valve; the hydraulic control system is characterized by further comprising a loading controller and a unloading controller which are connected through a CAN bus, wherein the unloading controller is connected with four vertical supporting leg compaction detection switches and the pressure switches through DI points, the four vertical supporting leg compaction detection switches are respectively arranged above hydraulic locks of the four vertical supporting leg oil cylinders, the loading controller is connected with an arm body fall-back detection switch, and the loading controller is respectively connected with the rotary table rotary valve, the arm body amplitude variation valve, the arm body expansion valve, the loading electromagnetic unloading valve and the supporting leg locking valve.

The upper electromagnetic unloading valve is a normally closed two-position two-way electromagnetic valve, and the supporting leg locking valve is a normally open two-position two-way electromagnetic valve.

The lower vehicle controller is arranged on an auxiliary frame near the landing leg control multi-way valve group, and the upper vehicle controller is arranged on the upper vehicle turntable part.

A control method of the energy-saving type high-altitude operation vehicle getting-on and getting-off interlocking system is characterized in that: the method comprises the following steps:

s01, firstly, the getting-on electromagnetic unloading valve and the supporting leg locking valve are arranged in a power-off state;

s02, an operator drives the switching valve for getting on and off the vehicle to the lower position, the landing leg controls the multi-way valve bank to obtain an oil source, and the landing leg valve rod is operated to enable the four horizontal landing legs and the four vertical landing legs to be in a fully extended state;

s03, the getting-off vehicle controller collects detection signals of the four vertical leg compaction detection switches through DI points and transmits the collected signals to the getting-on vehicle controller through a CAN bus;

s04, when the getting-on controller judges that the signal is not detected by the vertical leg compaction detection switch, the getting-on controller controls the getting-on electromagnetic unloading valve to continuously keep a power-off state, cuts off an oil way of the getting-on control multi-way clothing group and locks the getting-on action; when the vehicle-mounted controller judges that the four vertical supporting leg compaction detection switches all detect signals, the vehicle-mounted controller controls the electromagnetic unloading valve of the vehicle-mounted to be electrified, at the moment, the switching valve of the vehicle-mounted to the vehicle-mounted position is switched to the upper position, and the vehicle-mounted controller controls the multi-way valve bank to obtain an oil source, so that the vehicle-mounted action can be operated;

and S05, the vehicle-mounted controller receives a detection signal of the arm body fall-back detection switch, and when the arm body fall-back detection switch detects that the vehicle-mounted arm body leaves the arm support, the vehicle-mounted controller controls the landing leg locking valve to be powered on, cuts off an oil way at the landing leg multi-way valve group, and locks the vehicle-mounting action.

In S03, the vehicle controller acquires a detection signal of a pressure switch on the hydraulic system through the DI point, and when the pressure switch detects that the pressure value of the system exceeds the set pressure value of the system, the pressure switch is judged to be on, otherwise, the pressure switch is judged to be in an off state.

At S05, when the pressure switch is on, the PWM port of the controller on board drives and outputs the leg lock valve at a duty ratio of 100%, and when the pressure switch is off, the controller PWM port drives the leg lock valve at a duty ratio of 40% to maintain the closed state of the valve body.

In S04, when the controller of the upper vehicle determines that all of the four vertical leg compaction detection switches detect a signal, if the pressure switch is on, the PWM port of the controller of the upper vehicle drives the upper vehicle electromagnetic unloading valve at a duty ratio of 100%, and if the pressure switch is in an off state, the PWM port of the controller of the upper vehicle drives the upper vehicle electromagnetic unloading valve at a duty ratio of 40% to maintain the on state of the valve element.

The invention has the beneficial effects that: the invention provides an energy-saving type high-altitude operation vehicle getting-on and getting-off interlocking system and a control method thereof.A pressure switch is arranged at an oil inlet oil way of a switching valve for getting on and off the vehicle, the pressure switch is conducted, the hydraulic action output can be judged, if the pressure switch is disconnected below the value, the hydraulic action output is judged to be absent, when an arm body is separated from an arm support and a supporting leg locking valve needs to be locked, if the pressure switch is in a disconnected state, a PWM (pulse width modulation) port of a controller on the vehicle only needs to drive the supporting leg locking valve by 40% of duty ratio, and the closed state of a valve core can be maintained; when all the vertical supporting legs are compacted and the loading action is unlocked, if the pressure switch 5 is in a disconnected state, the PWM port of the controller can keep the on-state of the valve core only by driving the loading electromagnetic unloading valve 2 by 40% of duty ratio, the loading and unloading interlocking function of the overhead working truck can be realized, the electric energy consumption of the electromagnetic valve can be reduced, and the energy-saving control of the electromagnetic valve can be realized.

Drawings

FIG. 1 is a hydraulic schematic diagram of an energy-saving type overhead working truck getting on and off interlocking system of the present invention;

fig. 2 is an electrical schematic diagram of an energy-saving type overhead working truck getting-on and getting-off interlocking system of the invention.

The reference numbers in the figures are as follows: 1-a pump group; 2-getting on the bus electromagnetic unloading valve; 3-getting on the bus to control the multi-way valve bank; 4-a boarding actuator; 5-a pressure switch; 6-switching valve for getting on and off the train; 7-leg latch valve; 8-get-off actuator and 9-landing leg control multi-way valve set.

Detailed Description

The present invention is further described with reference to the accompanying drawings, and the following examples are only for clearly illustrating the technical solutions of the present invention, and should not be taken as limiting the scope of the present invention.

As shown in fig. 1, the invention discloses an energy-saving type upper and lower car interlocking system for an overhead working truck, which comprises a pump unit 1, an upper car electromagnetic unloading valve 2, an upper car control multi-way valve group 3, an upper car execution element 4, a pressure switch 5, an upper and lower car switching valve 6, a support leg locking valve 7, a lower car execution element 8 and a support leg control multi-way valve group 9.

Wherein, the oil outlet of the pump unit 1 is connected with the oil inlet of the switching valve 6 for getting on and off the train, and provides an oil source for the whole set of hydraulic system. An upper oil outlet of the get-on and get-off switching valve 6 is connected with an oil inlet of the get-on control multi-way valve group 3, and an oil source is provided for get-on motion. The lower oil outlet of the get-on and get-off switching valve 6 is connected with the oil inlet of the landing leg control multi-way valve group 9, and an oil source is provided for the landing leg action.

The pressure switch 5 is arranged at an oil path of an oil inlet of the loading and unloading switching valve 6 and used for measuring the pressure of a main oil path of the hydraulic system, comparing the pressure with a set pressure value, and converting a measurement result into an electric signal to be sent to a vehicle controller.

The oil inlet of the get-on control multi-way valve group 3 is connected with the upper oil outlet of the get-on and get-off switching valve 6, the get-on control multi-way valve group 3 is provided with three groups of driving ports which are respectively connected with corresponding get-on actuating elements 4, and the size of the valve core opening is controlled by a get-on controller. The upper vehicle executing element 4 comprises a rotary table rotary motor, a variable amplitude oil cylinder and a telescopic oil cylinder, and is directly connected with a driving port of the upper vehicle control multi-way valve group 3.

The upper electromagnetic unloading valve 2 is a normally closed two-position two-way electromagnetic valve, is connected in series on a main oil circuit of the upper control multi-way valve group 3, and cuts off an oil circuit of an upper part of the upper vehicle when power is lost, and is used for unloading control of the upper oil circuit. The support leg control multi-way valve group 9 comprises a support leg telescopic control valve and four groups of vertical/horizontal support leg selection valves. An oil inlet of the supporting leg telescopic control valve group 9 is connected with a lower oil outlet of the getting-on and getting-off switching valve 6, and a driving port of the supporting leg telescopic control valve group is directly connected with a getting-off actuating element 8. The lower vehicle executing element 8 comprises 4 groups of vertical supporting leg telescopic oil cylinders and 4 groups of horizontal supporting leg telescopic oil cylinders, and is directly connected with a driving port of the lower vehicle supporting leg multi-way valve group 9. The landing leg locking valve 7 is a normally open two-position two-way electromagnetic valve, is connected in series on an oil return path of the landing leg telescopic control valve, and cuts off an oil path of a landing leg part when power is supplied.

As shown in fig. 2, the electrical system of the present invention includes a lower car controller, 4 vertical leg compaction detection switches, an upper car controller, and an arm fall-back detection switch.

The lower vehicle controller is arranged on an auxiliary vehicle frame near the lower multi-way valve group, 4 vertical supporting leg compaction detection signals and detection signals of a pressure switch 5 on a hydraulic system are collected through DI points, the collected signals are transmitted to the upper vehicle controller through a CAN bus to carry out logic operation, and the on-off of a supporting leg locking valve 7 is driven according to an instruction transmitted by the upper vehicle controller.

The vertical supporting leg compaction detection switch is arranged above the hydraulic lock of the vertical supporting leg oil cylinder, and when the vertical supporting leg oil cylinder is in a compaction state, the trigger switch is switched on.

The upper vehicle controller is a main controller of the system, is arranged on the upper vehicle turntable part and is used for acquiring signals of the arm body fall-back detection switch and simultaneously carrying out logical operation according to information transmitted by the lower vehicle controller to drive the on-off of the upper vehicle electromagnetic unloading valve.

The working principle and the process of the invention are as follows: when the operation is started, the upper arm body falls on the arm support. The getting-on electromagnetic unloading valve 2 and the supporting leg locking valve 7 are in a power-off state. An operator drives the switching valve 6 for getting on and off the vehicle to the lower position, and the support leg controls the multi-way valve set 9 to obtain an oil source. The valve rod of the support leg is operated to ensure that the four horizontal support legs and the four vertical support legs are in a full-extension state. As long as 1 vertical supporting leg compaction detection switch does not detect a signal, the getting-on electromagnetic unloading valve 2 continuously keeps a power-off state, cuts off an oil way of the getting-on control multi-way suit group 3, and locks the getting-on action; after only four vertical supporting leg compaction detection switches detect signals completely, the getting-on electromagnetic unloading valve 2 is powered on, the getting-on and getting-off switching valve 6 is driven to the upper position at the moment, the getting-on multi-way valve group 3 obtains an oil source, and the getting-on action can be operated. When the arm fall-back detection switch detects that the upper arm body leaves the arm support, the support leg locking valve 7 is electrified, an oil way at the support leg multi-way valve group 9 is cut off, the lower-vehicle action is locked, and at the moment, even if the upper-vehicle switching valve 6 is switched to the lower position, the support leg cannot be operated, so that the automatic interlocking function of the upper-vehicle and the lower-vehicle of the high-altitude operation vehicle is realized.

The innovation points of the invention are as follows: 1) a pressure switch 5 is arranged on a hydraulic main oil path, the detection pressure value of the pressure switch is preset to 40bar, the system pressure exceeds 40bar, the pressure switch is conducted, hydraulic action output can be judged, and if the pressure switch is disconnected below the detection pressure value, no hydraulic action output is judged; 2) the upper vehicle electromagnetic unloading valve 2 and the supporting leg locking valve 7 are controlled by a PWM (pulse-width modulation) port of the controller, when the arm body is separated from the arm support and the supporting leg locking valve 7 needs to be locked, the on-off state of the pressure switch 5 is judged, if the pressure switch 5 is switched on, the PWM port of the controller drives the supporting leg locking valve 7 to output with a duty ratio of 100%, and if the pressure switch 5 is in the off state, the PWM port of the controller only needs to drive the supporting leg locking valve 7 with a duty ratio of 40% to maintain the closing state of the valve core; 3) when all the vertical supporting legs are compacted and the getting-on action is unlocked, the on-off state of the pressure switch 5 is judged, if the pressure switch 5 is switched on, the controller PWM port drives the getting-on electromagnetic unloading valve 2 to output with the duty ratio of 100%, and if the pressure switch 5 is in the off state, the controller PWM port only needs to drive the getting-on electromagnetic unloading valve 2 with the duty ratio of 40% to keep the on-state of the valve core. The scheme can not only realize the interlocking function of loading and unloading the high-altitude operation vehicle, but also reduce the power consumption of the electromagnetic valve and realize the energy-saving control of the electromagnetic valve.

The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention and these are intended to be within the scope of the invention.