阅读说明：本技术 一种柴油机冷却控制试验装置及方法 (Diesel engine cooling control test device and method ) 是由 牛晓晓 王志磊 宋杨 张祥臣 胡玮 于 2021-07-15 设计创作，主要内容包括：本发明公开了一种柴油机冷却控制试验装置及方法,包括柴油机本体、传动齿轮、热交换器、气缸套、气缸盖和外部柴油机ECU,所述气缸套设置在柴油机本体的外侧面,所述气缸盖设置在柴油机本体的上端,所述热交换器设置在柴油机本体的一侧,热交换器上分别设置有冷却水进水口和冷却水出水口,所述传动齿轮上的曲轴与离心淡水泵的输入端连接,所述气缸套内设置有气缸套上水腔和气缸套下水腔,气缸套上水腔和气缸套下水腔之间设置有水腔隔板,本柴油机冷却控制试验装置及方法可以根据柴油机在不同的工况下,调整各区域达到最佳的冷却效果,大大的提高了柴油机的工作效率,延长柴油机的使用寿命。(The invention discloses a diesel engine cooling control test device and a method, which comprises a diesel engine body, a transmission gear, a heat exchanger, a cylinder sleeve, a cylinder cover and an external diesel engine ECU, wherein the cylinder sleeve is arranged on the outer side surface of the diesel engine body, the cylinder cover is arranged at the upper end of the diesel engine body, the heat exchanger is arranged on one side of the diesel engine body, the heat exchanger is respectively provided with a cooling water inlet and a cooling water outlet, a crankshaft on the transmission gear is connected with the input end of a centrifugal fresh water pump, an upper cylinder sleeve water cavity and a lower cylinder sleeve water cavity are arranged in the cylinder sleeve, and a water cavity clapboard is arranged between the upper cylinder sleeve water cavity and the lower cylinder sleeve water cavity. The service life of the diesel engine is prolonged.)

1. The utility model provides a diesel engine cooling control test device, includes diesel engine body, drive gear (2), heat exchanger (14), cylinder jacket, cylinder head and outside diesel engine ECU, the cylinder jacket sets up the lateral surface at the diesel engine body, the cylinder head sets up the upper end at the diesel engine body, heat exchanger (14) set up one side at the diesel engine body, are provided with cooling water inlet (13) and cooling water delivery port (15) on heat exchanger (14) respectively, its characterized in that: the crankshaft on the transmission gear (2) is connected with the input end of the centrifugal fresh water pump (1), an air cylinder upper water feeding cavity (21) and an air cylinder sleeve lower water cavity (22) are arranged in the air cylinder sleeve, a water cavity partition plate (23) is arranged between the air cylinder upper water feeding cavity (21) and the air cylinder sleeve lower water cavity (22), a cylinder cover is arranged in the air cylinder cover and longitudinally penetrates through the water cavity (20), the centrifugal fresh water pump (1) is connected with a water outlet of the heat exchanger (14) through a fresh water pump inlet pipe (16), a water outlet of the centrifugal fresh water pump (1) is respectively connected with the air cylinder upper water feeding cavity (21), the air cylinder sleeve lower water cavity (22) and the cylinder cover water cavity inlet pipe (5) and the air cylinder upper water feeding cavity (21), the air cylinder sleeve lower water cavity (22) and the cylinder cover water cavity (20) through the air outlet of the air cylinder upper water feeding cavity (21), the air cylinder sleeve lower water cavity (22) and the cylinder cover longitudinally penetrates through the water cavity (20) respectively, The water outlet pipe (10) of the water cavity of the cylinder sleeve and the water outlet pipe (12) of the water cavity of the cylinder cover are connected with a water inlet of a heat exchanger (14), and a temperature sensor (6), an electromagnetic pressure regulating valve (7) and a flowmeter (8) are arranged on the outer side surfaces of the water outlet pipe (11) of the water cavity of the cylinder sleeve, the water outlet pipe (10) of the water cavity of the cylinder sleeve and the water outlet pipe (12) of the water cavity of the cylinder cover.

2. The diesel engine cooling control test device according to claim 1, characterized in that: one side of the cylinder upper water cavity (21) is provided with a cylinder upper water cavity water inlet hole (18), one side of the cylinder sleeve lower water cavity (22) is provided with a cylinder sleeve lower water cavity water inlet hole (17), and the cylinder upper water cavity water inlet pipe (4) and the cylinder sleeve lower water cavity water inlet pipe (3) are respectively fixed in the cylinder upper water cavity water inlet hole (18) and the cylinder sleeve lower water cavity water inlet hole (17).

3. The diesel engine cooling control test device according to claim 1, characterized in that: and arc-shaped guide plates (19) are respectively arranged in the cylinder sleeve upper water cavity (21) and the cylinder sleeve lower water cavity (22).

4. The diesel engine cooling control test device according to claim 1, characterized in that: and the outer side surfaces of the cylinder sleeve upper water cavity water outlet pipe (11), the cylinder sleeve lower water cavity water outlet pipe (10) and the cylinder cover water cavity water outlet pipe (12) are respectively provided with a check valve (9).

5. The diesel engine cooling control test device according to claim 1, characterized in that: the output ends of the temperature sensor (6) and the flowmeter (8) are respectively and electrically connected with the input end of an external diesel engine ECU through a CAN bus, and the output end of the external diesel engine ECU is electrically connected with the electromagnetic pressure regulating valve (7) and the input end.

6. The control method of the diesel engine cooling control test device according to claim 1, characterized in that: according to cooling modes required by the diesel engine under different working conditions, an external diesel engine ECU respectively collects temperature signals and flow signals of a water outlet pipe (11) of an upper water cavity of the air cylinder sleeve, a water outlet pipe (10) of a lower water cavity of the air cylinder sleeve and a water outlet pipe (12) of a water cavity of the air cylinder cover, further judges the running condition of the engine, further sends corresponding instructions to the electromagnetic pressure regulating valve (7), adjusts the opening degree of the electromagnetic pressure regulating valve (7), and keeps the optimal cooling effect of a required area.

Technical Field

The invention relates to the technical field of diesel engines, in particular to a diesel engine cooling control test device and a diesel engine cooling control test method.

Background

The diesel engine cooling system takes away excessive heat generated by combustion, and needs to prevent the cylinder sleeve, the cylinder cover, the air valve and the like from losing effectiveness due to overheating and prevent the reduction of the thermal efficiency of the diesel engine caused by excessive cooling.

Because the thermal load of each area of the diesel engine is different, most cooling systems consider meeting the requirement of a certain section of power or rotating speed, other power sections are either over-cooled or under-cooled, and further the diesel engine can not achieve the best cooling effect under different working conditions, and the working efficiency and the service life of the diesel engine are influenced.

Disclosure of Invention

The invention aims to overcome the defects in the prior art, and provides a cooling control test device and method for a diesel engine, which can adjust each area to achieve the optimal cooling effect according to different working conditions of the diesel engine, improve the working efficiency of the diesel engine and effectively solve the problems in the background art.

In order to achieve the purpose, the invention provides the following technical scheme: the utility model provides a diesel engine cooling control test device, includes diesel engine body, drive gear, heat exchanger, cylinder jacket, cylinder head and outside diesel engine ECU, the cylinder jacket sets up the lateral surface at the diesel engine body, the cylinder head sets up the upper end at the diesel engine body, heat exchanger sets up the one side at the diesel engine body, is provided with cooling water inlet and cooling water delivery port on the heat exchanger respectively, the bent axle on the drive gear is connected with centrifugal fresh-water pump's input, be provided with cylinder jacket upper water cavity and cylinder jacket lower water cavity in the cylinder jacket, be provided with the water cavity baffle between cylinder jacket upper water cavity and the cylinder jacket lower water cavity, be provided with the cylinder head in the cylinder head and vertically run through the water cavity, centrifugal fresh-water pump passes through the fresh-water pump inlet tube and is connected with heat exchanger's delivery port, centrifugal fresh-water pump's delivery port is respectively through cylinder jacket upper water cavity inlet tube, cylinder jacket upper water cavity, The water cavity is gone up to cylinder jacket under water chamber inlet tube and cylinder cap water cavity inlet tube and cylinder, the water cavity is vertically run through to cylinder jacket under water chamber and cylinder cap and is connected, the water cavity is gone up to the cylinder jacket, the water cavity outlet pipe is gone up through the cylinder jacket respectively to the delivery port that water cavity and cylinder cap vertically run through the water cavity under water chamber and cylinder cap, water cavity outlet pipe and cylinder cap water cavity outlet pipe are connected with heat exchanger's water inlet under the cylinder jacket, the lateral surface that water cavity outlet pipe and cylinder cap water cavity outlet pipe were gone up to the cylinder jacket all is provided with temperature sensor, electromagnetic pressure regulating valve and flowmeter.

According to the preferable technical scheme, a water inlet hole of the cylinder upper water cavity is formed in one side of the cylinder upper water cavity, a water inlet hole of the cylinder lower water cavity is formed in one side of the cylinder lower water cavity, and the cylinder upper water cavity water inlet pipe and the cylinder lower water cavity water inlet pipe are respectively fixed in the cylinder upper water cavity water inlet hole and the cylinder lower water cavity water inlet hole.

As a preferred technical scheme of the invention, arc-shaped guide plates are arranged in the cylinder sleeve upper water cavity and the cylinder sleeve lower water cavity.

As a preferred technical scheme of the invention, the outer side surfaces of the water outlet pipe of the water cavity on the cylinder sleeve, the water outlet pipe of the water cavity under the cylinder sleeve and the water outlet pipe of the water cavity of the cylinder cover are respectively provided with a one-way valve.

As a preferable technical scheme of the invention, the output ends of the temperature sensor and the flowmeter are respectively and electrically connected with the input end of an external diesel engine ECU through a CAN bus, and the output end of the external diesel engine ECU is electrically connected with the electromagnetic pressure regulating valve and the input end.

As a preferred technical scheme of the invention, according to cooling modes required by the diesel engine under different working conditions, an external diesel engine ECU respectively collects temperature signals and flow signals of a water outlet pipe of a water cavity of a cylinder sleeve, a water outlet pipe of a water cavity of the cylinder sleeve and a water outlet pipe of a water cavity of a cylinder cover, further judges the running condition of the engine, further sends corresponding instructions to an electromagnetic pressure regulating valve, adjusts the opening degree of the electromagnetic pressure regulating valve and keeps the optimal cooling effect of a required area.

Compared with the prior art, the invention has the beneficial effects that: the cooling control test device and the cooling control test method for the diesel engine are compact in structure, reasonable in design and ingenious in conception, as the upper half part of a water cavity in a machine body and a cylinder sleeve region is positioned in a combustion chamber region, the heat load of the water cavity is large, the heat load of the lower half part of the water cavity is small, and the whole water cavity is divided into a cylinder upper water cavity and a cylinder sleeve lower water cavity; compared with the traditional cooling mode, the cooling water cavity is divided into three water cavity areas, namely an upper water cavity of the air cylinder, a lower water cavity of the air cylinder sleeve and a longitudinal water cavity penetrating through the air cylinder cover, according to the heat load characteristic, each water cavity area is respectively provided with a temperature sensor, an electromagnetic pressure regulating valve and a flowmeter, and the opening of the electromagnetic pressure regulating valve is regulated according to the measured value of the temperature sensor and the optimal temperature deviation: if the measured value of the temperature sensor is greater than the optimal temperature, the opening degree of the electromagnetic pressure regulating valve is increased, the cooling water flow is increased, if the measured value of the temperature sensor is less than the optimal temperature, the opening degree of the electromagnetic pressure regulating valve is reduced, the cooling water flow is reduced, the optimal flow of each area is recorded by each water cavity area flowmeter, and different control strategies are selected according to the heat load characteristics of different areas so as to achieve the purpose of optimal cooling effect.

Drawings

FIG. 1 is a schematic structural view of the present invention;

FIG. 2 is a schematic front cross-sectional view of the present invention;

fig. 3 is a schematic diagram of the system connection of the present invention.

In the figure: 1 centrifugal fresh water pump, 2 transmission gear, 3 cylinder sleeve water cavity inlet pipe, 4 cylinder sleeve water cavity inlet pipe, 5 cylinder cover water cavity inlet pipe, 6 temperature sensor (6a cylinder cover water cavity temperature sensor, 6b cylinder sleeve water cavity temperature sensor, 6c cylinder sleeve water cavity temperature sensor), 7 electromagnetic pressure regulating valve (7a cylinder cover water cavity electromagnetic pressure regulating valve, 7b cylinder sleeve water cavity electromagnetic pressure regulating valve, 7c cylinder sleeve water cavity electromagnetic pressure regulating valve), 8 flowmeter (8a cylinder cover water cavity flowmeter, 8b cylinder sleeve water cavity electromagnetic flowmeter, 8c cylinder sleeve water cavity flowmeter), 9 check valve (9a cylinder cover water cavity check valve, 9b cylinder sleeve water cavity check valve, 9c cylinder sleeve water cavity check valve), 10 cylinder sleeve water cavity outlet pipe, 11 cylinder sleeve water cavity outlet pipe, 12 cylinder cover water cavity outlet pipe, 13 cooling water inlet, 14 heat exchanger, 15 cooling water delivery ports, 16 fresh water pump inlet pipes, 17 cylinder jacket launching cavity inlet holes, 18 cylinder jacket launching cavity inlet ports, 19 guide plates, 20 cylinder cover longitudinal penetration water cavity, 21 cylinder jacket launching cavity, 22 cylinder jacket launching cavity and 23 water cavity partition plates.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments (for convenience of description and understanding, the upper side of fig. 1 is described as the upper side below). All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1: referring to fig. 1-3, the present invention provides a technical solution: a diesel engine cooling control test device comprises a diesel engine body, a transmission gear 2, a heat exchanger 14, a cylinder sleeve, a cylinder cover and an external diesel engine ECU, wherein the cylinder sleeve is arranged on the outer side surface of the diesel engine body, the cylinder cover is arranged at the upper end of the diesel engine body, the heat exchanger 14 is arranged on one side of the diesel engine body, the heat exchanger 14 is respectively provided with a cooling water inlet 13 and a cooling water outlet 15, a crankshaft on the transmission gear 2 is connected with the input end of a centrifugal fresh water pump 1, a cylinder sleeve upper water cavity 21 and a cylinder sleeve lower water cavity 22 are arranged in the cylinder sleeve, a water cavity clapboard 23 is arranged between the cylinder sleeve upper water cavity 21 and the cylinder sleeve lower water cavity 22, the cylinder sleeve upper water cavity 21 and the cylinder sleeve lower water cavity 22 are completely separated through the water cavity clapboard 23, arc-shaped guide plates 19 are respectively arranged in the cylinder sleeve upper water cavity 21 and the cylinder sleeve lower water cavity 22, and the guide plates 19 can prevent cooling water from flowing, a cylinder cover longitudinal through water cavity 20 is arranged in the cylinder cover, a centrifugal fresh water pump 1 is connected with a water outlet of a heat exchanger 14 through a fresh water pump inlet pipe 16, the water outlet of the centrifugal fresh water pump 1 is respectively connected with a cylinder upper water cavity 21, a cylinder sleeve lower water cavity 22 and the cylinder cover longitudinal through water cavity 20 through a cylinder upper water cavity inlet pipe 4, a cylinder sleeve lower water cavity inlet pipe 3 and a cylinder cover water cavity inlet pipe 5, one side of the cylinder upper water cavity 21 is provided with a cylinder upper water cavity inlet hole 18, one side of the cylinder sleeve lower water cavity 22 is provided with a cylinder sleeve lower water cavity inlet hole 17, the cylinder upper water cavity inlet pipe 4 and the cylinder sleeve lower water cavity inlet pipe 3 are respectively fixed in the cylinder upper water cavity inlet hole 18 and the cylinder sleeve lower water cavity inlet hole 17, the cylinder upper water cavity 21, the cylinder sleeve lower water cavity 22 and the water outlet of the cylinder cover longitudinal through water cavity 20 are respectively through the cylinder upper water cavity upper water outlet pipe 11, The water outlet pipe 10 of the cylinder sleeve water cavity and the water outlet pipe 12 of the cylinder cover water cavity are connected with a water inlet of a heat exchanger 14, the outer side surfaces of the water outlet pipe 11 of the cylinder sleeve water cavity, the water outlet pipe 10 of the cylinder sleeve water cavity and the water outlet pipe 12 of the cylinder cover water cavity are respectively provided with a temperature sensor 6, an electromagnetic pressure regulating valve 7 and a flowmeter 8, the output ends of the temperature sensor 6 and the flowmeter 8 are respectively electrically connected with the input end of an external diesel engine ECU through a CAN bus, and the output end of the external diesel engine ECU is electrically connected with the electromagnetic pressure regulating valve 7 and the input end.

Wherein, the temperature sensors 6 arranged on the outer side surfaces of the water outlet pipe 11 of the cylinder jacket water cavity, the water outlet pipe 10 of the cylinder jacket water cavity and the water outlet pipe 12 of the cylinder cover water cavity are respectively a temperature sensor 6b of the cylinder jacket water cavity, a temperature sensor 6c of the cylinder jacket water cavity and a temperature sensor 6a of the cylinder cover water cavity, the electromagnetic pressure regulating valves 7 arranged on the outer side surfaces of the water outlet pipe 11 of the cylinder jacket water cavity, the water outlet pipe 10 of the cylinder jacket water cavity and the water outlet pipe 12 of the cylinder cover water cavity are respectively an electromagnetic pressure regulating valve 7b of the cylinder jacket water cavity, an electromagnetic pressure regulating valve 7c of the cylinder jacket water cavity and an electromagnetic pressure regulating valve 7a of the cylinder cover water cavity, the flowmeters 8 arranged on the outer side surfaces of the water outlet pipe 11 of the upper water cavity of the air cylinder sleeve, the water outlet pipe 10 of the lower water cavity of the air cylinder sleeve and the water outlet pipe 12 of the water cavity of the air cylinder cover are respectively an electromagnetic flowmeter 8b of the upper water cavity of the air cylinder sleeve, a flowmeter 8c of the lower water cavity of the air cylinder sleeve and a flowmeter 8a of the water cavity of the air cylinder cover.

A control method of a diesel engine cooling control test device is characterized in that according to cooling modes required by a diesel engine under different working conditions, signals of temperature sensors (6a, 6b and 6c) and flow meters (8a, 8b and 8c) are respectively collected by an external diesel engine ECU, the running condition of the engine is further judged, an instruction is sent to electromagnetic pressure regulating valves (7a, 7b and 7c), and the cooling mode of the diesel engine is controlled, wherein the operation arrangement is as follows:

(1) selection of engine cooling mode when the engine is in start-up condition:

when the diesel engine is in a starting state, the temperature of cooling water is low, at the moment, the optimal control strategy increases the temperature of the cooling water as soon as possible, firstly, all three electromagnetic pressure regulating valves (7a, 7b and 7c) are closed, after a period of time, the temperature of the cooling water in the water cavity rises quickly due to the fact that the temperature of a nose bridge area between exhaust valves is high, the electromagnetic pressure regulating valve 7a of the cylinder cover longitudinally penetrating through the water cavity 20 is slightly opened, the temperature collected by the temperature sensor 6a reaches the optimal temperature, and the electromagnetic pressure regulating valve 7a is kept still.

(2) When the engine is in a low-load working condition, selecting an engine cooling mode:

firstly, respectively opening an electromagnetic pressure regulating valve 7a and an electromagnetic pressure regulating valve 7b corresponding to a cylinder cover longitudinal through water cavity 20 and a cylinder sleeve water feeding cavity 21, wherein the optimal temperatures of the cylinder cover longitudinal through water cavity 20 and the cylinder sleeve water feeding cavity 21 are respectively T_haAnd T_ca1If the temperature of the thermometer sensor 6a longitudinally penetrating the water chamber 20 of the cylinder head is T_hIf T is_h>T_haIncreasing the opening of the electromagnetic pressure regulating valve 7a if T_h.<T_haThe opening degree of the electromagnetic pressure regulating valve 7a is reduced, and the optimal cooling effect in the region is maintained.

(3) When the engine is in a high-load working condition, selecting an engine cooling mode:

firstly, respectively opening an electromagnetic pressure regulating valve 7a, an electromagnetic pressure regulating valve 7b and an electromagnetic pressure regulating valve 7c corresponding to a cylinder head longitudinal through water cavity 20, a cylinder sleeve upper water cavity 21 and a cylinder sleeve lower water cavity 22, wherein the optimal temperatures of the cylinder head longitudinal through water cavity 20, the cylinder sleeve upper water cavity 21 and the cylinder sleeve lower water cavity 22 are respectively T_ha、T_ca1And T_ca2If the cylinder head has a thermometer temperature T running longitudinally through the water chamber 20_hIf T is_h>T_haIncreasing the opening of the electromagnetic pressure regulating valve 7a if T_h.<T_haThe opening degree of the electromagnetic pressure regulating valve 7a is reduced, the optimal cooling effect of the area is kept,the control strategy of the cylinder sleeve water cavity 21, the control strategy of the cylinder sleeve water cavity 22 and the strategy of the cylinder head longitudinal penetrating water cavity 20 are similar.

(4) Engine degradation test, selection of engine cooling mode:

when the operation parameters of the diesel engine under the worst environment are measured, the electromagnetic pressure regulating valve 7a of the cylinder cover longitudinally penetrating through the water cavity 20 is closed, and the electromagnetic pressure regulating valves (7b and 7c) of the cylinder sleeve water cavity 21 and the cylinder sleeve water cavity 22 are normally opened, so that the operation parameters of the cylinder cover under the worst working conditions can be measured. If the operation parameters of the cylinder sleeve under severe conditions are measured, the electromagnetic pressure regulating valves (7b and 7c) of the water cavity 21 on the cylinder sleeve and the water cavity 22 under the cylinder sleeve need to be closed, and the electromagnetic pressure regulating valve 7a of the cylinder cover longitudinally penetrating through the water cavity 20 is normally opened.

The invention determines the optimal flow rate of each cooling water cavity area: the invention divides the cooling water cavity into three areas: the cylinder head longitudinally penetrates through a water cavity 20, a cylinder jacket water cavity 21 and a cylinder liner water cavity 22, a temperature sensor (6a, 6b and 6c), an electromagnetic pressure regulating valve (7a, 7b and 7c) and a flowmeter (8a, 8b and 8c) are respectively arranged in each water cavity region, and the opening degree of the electromagnetic pressure regulating valve is regulated according to the measured value of the temperature sensor and the optimal temperature deviation because the optimal cooling temperature of each cooling water cavity region is different: if the measured values of the temperature sensors (6a, 6b and 6c) are greater than the optimum temperature, the opening degrees of the electromagnetic pressure regulating valves (7a, 7b and 7c) are increased, the flow rate of the cooling water is increased, if the measured values of the temperature sensors (6a, 6b and 6c) are less than the optimum temperature, the opening degrees of the electromagnetic pressure regulating valves (7a, 7b and 7c) are decreased, the flow rate of the cooling water is decreased, and each water chamber area flow meter (8a, 8b and 8c) records the optimum flow rate of each area.

The invention determines a control strategy of a cooling water cavity area: according to the invention, the cooling water cavities in each area are determined to be closed and opened according to different loads of the diesel engine, in a warm-up state, when the engine is started, the electromagnetic pressure regulating valves 7 of the three water cavities are completely closed, and after a period of time, because the temperature of the fire surface of the cylinder cover is high, particularly in a nose bridge area, only the electromagnetic pressure regulating valves 7a of the cylinder cover longitudinally penetrating through the water cavities 20 are opened; when the engine is in a low load state, the upper half part of the water cavity of the engine body and the cylinder sleeve region is positioned in the combustion chamber region, so that the thermal load is large, and then the electromagnetic pressure regulating valve 7b of the water cavity 21 of the cylinder sleeve is opened; when the diesel engine is in a high load region, three regional electromagnetic pressure regulating valves (7a, 7b, and 7c) are opened to perform the whole regional cooling.

Example 2: the difference with embodiment 1 lies in that the outer side surfaces of the cylinder upper water cavity water outlet pipe 11, the cylinder liner lower water cavity water outlet pipe 10 and the cylinder cover water cavity water outlet pipe 12 are respectively provided with a check valve 9, and the check valves 9 can respectively and manually control the original water passing amount of the cylinder upper water cavity water outlet pipe 11, the cylinder liner lower water cavity water outlet pipe 10 and the cylinder cover water cavity water outlet pipe 12, so that the measurement and recording are further facilitated.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.