阅读说明：本技术 一种燃料电池系统的启动准备方法 (Start preparation method of fuel cell system ) 是由 徐云飞 张国强 周鹏飞 曲观书 胥巍巍 于 2019-10-29 设计创作，主要内容包括：本发明提供了一种燃料电池系统的启动准备方法包括开启旁通阀；启动供气组件的空压机；启动供氢组件；开启供气组件中的进气节气门和出气节气门；关闭尾排阀。这种方法的优点在于:燃料电池空气供给系统的开启不受到电堆关闭状态的约束,可先于阳极氢气吹扫开启,或者与阳极空气吹扫同步开；实现了燃料电池空气供给系统在电堆关闭状态下的灵活开启；满足了阳极氢气吹扫产生的混和气稀释及燃料电池箱体通风的空气需求；燃料电池空压机的开启时间更灵活；可避免减缓因空压机的瞬态响应滞后效果,缩短燃料电池开关机时间。(The invention provides a start preparation method of a fuel cell system, comprising the steps of opening a bypass valve; starting an air compressor of the air supply assembly; starting the hydrogen supply assembly; opening an air inlet throttle valve and an air outlet throttle valve in the air supply assembly; and closing the tail discharge valve. The method has the advantages that the opening of the fuel cell air supply system is not restricted by the closing state of the electric pile, and can be started before the anode hydrogen purging, or synchronously started with the anode air purging; the fuel cell air supply system is flexibly started in the shutdown state of the electric pile; the air requirements of mixed gas dilution generated by anode hydrogen purging and fuel cell box ventilation are met; the starting time of the fuel cell air compressor is more flexible; the transient response hysteresis effect of the air compressor can be avoided, and the startup and shutdown time of the fuel cell is shortened.)

1. A start preparation method of a fuel cell system, characterized by comprising a plurality of steps of:

step 1: opening a bypass valve;

step 2: starting an air compressor of the air supply assembly;

and step 3: starting the hydrogen supply assembly;

and 4, step 4: opening an air inlet throttle valve and an air outlet throttle valve in the air supply assembly;

and 5: and closing the tail discharge valve.

2. A start-up preparation method of a fuel cell system according to claim 1, wherein the step 3: the start-up hydrogen supply assembly includes:

step 301: detecting the air flow and the air pressure of an air inlet of a cathode of the pile;

step 302: judging whether the air entering the cathode of the pile meets the conditions that the flow is more than 27g/s and the pressure is more than 120kpa, if so, starting an air pump of the hydrogen supply assembly and opening a pressure regulator and a tail exhaust valve of the hydrogen supply assembly; if not, step 301 is executed again.

3. A start-up preparation method of a fuel cell system according to claim 1, characterized in that the step 4: opening an intake throttle valve and an outlet throttle valve in an air supply assembly includes:

step 401: detecting the hydrogen pressure of a hydrogen inlet of the anode of the galvanic pile and the rotating speed of an air pump in the hydrogen supply assembly;

step 402: judging whether the hydrogen pressure of the hydrogen inlet of the anode of the galvanic pile is more than 120kpa and the rotation speed of an air pump in the hydrogen supply assembly is more than 1000rpm, if so, executing a step 403; if not, executing step 401 again;

step 403: and opening an air inlet throttle valve and an air outlet throttle valve in the air supply assembly.

4. A start-up preparation method of a fuel cell system according to claim 3, characterized in that the step 5: closing the tail gate valve comprises:

step 501: judging whether the opening degrees of an air inlet throttle valve and an air outlet throttle valve in the air supply assembly reach a preset target opening degree or not, and if so, closing a tail exhaust valve; if not, step 403 is performed again.

5. The start-up preparation method of a fuel cell system according to claim 1, wherein the fuel cell system includes a stack assembly, a hydrogen supply assembly, a gas supply assembly, and a bypass assembly, the stack assembly communicates with the hydrogen supply assembly, the gas supply assembly, and the bypass assembly, respectively, and the bypass assembly communicates with the hydrogen supply assembly and the gas supply assembly, respectively.

6. The start-up preparation method of a fuel cell system according to claim 5, wherein the stack assembly includes a stack and a case, the anode of the stack is provided with a hydrogen inlet and a hydrogen outlet, the cathode of the stack is provided with an air inlet and an air outlet, the case is provided with a ventilation inlet and a ventilation outlet, the stack is mounted in the case, the anode of the stack is communicated with the hydrogen supply assembly through the hydrogen inlet and the hydrogen outlet, the cathode of the stack is communicated with the air supply assembly through the air inlet and the air outlet, the ventilation inlet of the case is communicated with the air supply assembly, and the ventilation outlet of the case is communicated with the bypass assembly.

7. The start-up preparation method of the fuel cell system according to claim 6, wherein the stack assembly includes a stack and a tank, the hydrogen supply assembly includes a hydrogen bottle, a first pipeline, a pressure regulator, a second pipeline, a third pipeline, an air pump, a fourth pipeline, and a tail exhaust valve, the hydrogen bottle is communicated with the pressure regulator through the first pipeline, the pressure regulator is communicated with a hydrogen inlet of the stack through the second pipeline, the air pump is communicated with the pressure regulator through the third pipeline, a first end of the fourth pipeline is communicated with a hydrogen outlet of the stack, a second end of the fourth pipeline is communicated with the air pump, and a third end of the fourth pipeline is communicated with the tail exhaust valve.

8. The start-up preparation method of a fuel cell system according to claim 7, wherein the air supply module includes an air inlet, a fifth pipeline, an air compressor, a sixth pipeline, a throttle valve, a seventh pipeline, a first throttle valve, an eighth pipeline, a second throttle valve, and a ninth pipeline, the air inlet communicates with the air compressor through the fifth pipeline, a first end of the sixth pipeline communicates with the air compressor, a second end of the sixth pipeline communicates with the throttle valve, a third end of the sixth pipeline communicates with the first throttle valve, a fourth end of the sixth pipeline communicates with the bypass module, the throttle valve communicates with the ventilation air inlet through the seventh pipeline, the first throttle valve communicates with the air inlet of the cell stack through the eighth pipeline, and the second throttle valve communicates with the air outlet of the cell stack through the ninth pipeline.

9. The fuel cell system start-up preparation method of claim 8, wherein the bypass assembly includes a bypass valve, a tenth line and a tail discharge port, the bypass valve being in communication with a fourth end of the sixth line, a first end of the tenth line being in communication with the bypass valve, a second end of the tenth line being in communication with the second throttle valve, a third end of the tenth line being in communication with the vent outlet port, a fourth end of the tenth line being in communication with the tail discharge valve, and a fifth end of the tenth line being in communication with the tail discharge port.

10. The start-up preparation method of a fuel cell system according to claim 9, wherein the fuel cell system further includes a control unit that is electrically connected to the air compressor, the bypass valve, the first throttle valve, the second throttle valve, the pressure regulator, and the tail gate valve, respectively.

Technical Field

The present invention relates to a control method, and more particularly, to a start preparation method of a fuel cell system.

Background

The hydrogen fuel cell automobile technology is gradually developed and matured, and as a new energy automobile with zero pollution and zero emission, the hydrogen fuel cell automobile has increasingly entered a traffic system and is widely accepted by the public. The fuel cell vehicle takes hydrogen as fuel, chemical energy is efficiently converted into electric energy through a fuel engine so as to drive the vehicle, and pure water is only discharged in the whole process, so that the fuel cell vehicle is an ideal energy-saving environment-friendly zero-emission vehicle for replacing the traditional fossil fuel vehicle in the near future.

In an air supply system of a fuel cell, an air compressor is a power source for air flow, air is sucked from the environment, enters the cathode side of a galvanic pile through an air filter, an intercooler, a humidifier and the like, and residual air after reaction is discharged through a tail discharge port such as an exhaust throttle valve and the like and flows into the environment. The air compressor for the fuel cell usually adopts a centrifugal structure, and the air compressor with the structure can normally work in a range above the flow corresponding to a surge line and below a blocking line; the air flow required by the fuel cell stack under idle speed and low load conditions is low, and the excessive air flowing into the stack can influence the normal operation of the fuel cell. In order to avoid the instantaneous air compressor flow supply and the small flow demand of the pile, the prior patents CN108172866A and CN108278218A set an air bypass valve in the fuel cell system. When the fuel cell needs small flow, the air bypass valve is opened, and partial air is bypassed under the action of pressure difference, so that the surge of the air compressor is avoided.

In the prior art, the fuel cell stack has strict requirements on air supply in different states, and an air supply system needs to work together with the fuel cell stack. Aiming at the starting process of the fuel cell, in order to prevent the service life attenuation of the stack caused by the hydrogen-oxygen interface, the anode hydrogen purging is performed before the air supply of the stack is performed in an open state, and at the moment, the air supply of the fuel cell cannot be applied to the dilution of the hydrogen concentration of the mixed gas in the hydrogen cavity blown by the anode hydrogen. The fuel cell air compressor needs to be started sequentially after hydrogen side purging is completed and the stack air inlet throttle valve and the stack air exhaust throttle valve are opened, the transient response of the air compressor is delayed, and the total startup accumulated time is prolonged.

In view of the foregoing, it would be desirable to provide a method for preparing a start-up of a fuel cell system that overcomes the deficiencies of the prior art.

Disclosure of Invention

The present invention is directed to a start-up preparation method of a fuel cell system that overcomes the disadvantages of the prior art. The object of the present invention is achieved by the following technical means.

One embodiment of the present invention provides a start preparation method of a fuel cell system, the start preparation method including a plurality of steps of:

step 1: opening a bypass valve;

step 2: starting an air compressor of the air supply assembly;

and step 3: starting the hydrogen supply assembly;

and 4, step 4: opening an air inlet throttle valve and an air outlet throttle valve in the air supply assembly;

and 5: and closing the tail discharge valve.

According to the startup preparation method provided by the above one embodiment of the present invention, the step 3: the start-up hydrogen supply assembly includes:

step 301: detecting the air flow and the air pressure of an air inlet of a cathode of the pile;

step 302: judging whether the air entering the cathode of the pile meets the conditions that the flow is more than 27g/s and the pressure is more than 120kpa, if so, starting an air pump of the hydrogen supply assembly and opening a pressure regulator and a tail exhaust valve of the hydrogen supply assembly; if not, step 301 is executed again.

According to the start preparation method provided by the above one embodiment of the present invention, the step 4: opening an intake throttle valve and an outlet throttle valve in an air supply assembly includes:

step 401: detecting the hydrogen pressure of a hydrogen inlet of the anode of the galvanic pile and the rotating speed of an air pump in the hydrogen supply assembly;

step 402: judging whether the hydrogen pressure of the hydrogen inlet of the anode of the galvanic pile is more than 120kpa and the rotation speed of an air pump in the hydrogen supply assembly is more than 1000rpm, if so, executing a step 403; if not, executing step 401 again;

step 403: and opening an air inlet throttle valve and an air outlet throttle valve in the air supply assembly.

According to the start preparation method provided by the above one embodiment of the present invention, the step 5: closing the tail gate valve comprises:

step 501: judging whether the opening degrees of an air inlet throttle valve and an air outlet throttle valve in the air supply assembly reach a preset target opening degree or not, and if so, closing a tail exhaust valve; if not, step 403 is performed again.

According to the start-up preparation method provided by the above-mentioned one embodiment of the present invention, the fuel cell system includes a stack assembly, a hydrogen supply assembly, a gas supply assembly, and a bypass assembly, the stack assembly communicates with the hydrogen supply assembly, the gas supply assembly, and the bypass assembly, respectively, and the bypass assembly communicates with the hydrogen supply assembly and the gas supply assembly, respectively.

According to the start-up preparation method provided by the above embodiment of the present invention, the stack assembly includes a stack and a box, a hydrogen inlet and a hydrogen outlet are provided on an anode of the stack, an air inlet and an air outlet are provided on a cathode of the stack, a ventilation inlet and a ventilation outlet are provided on the box, the stack is installed in the box, the anode of the stack is communicated with the hydrogen supply assembly through the hydrogen inlet and the hydrogen outlet, the cathode of the stack is communicated with the air supply assembly through the air inlet and the air outlet, the ventilation inlet of the box is communicated with the air supply assembly, and the ventilation outlet of the box is communicated with the bypass assembly.

According to the start-up preparation method provided by the above one embodiment of the present invention, the stack assembly includes a stack and a tank, the hydrogen supply assembly includes a hydrogen bottle, a first pipeline, a pressure regulator, a second pipeline, a third pipeline, an air pump, a fourth pipeline and a tail exhaust valve, the hydrogen bottle is communicated with the pressure regulator through the first pipeline, the pressure regulator is communicated with a hydrogen inlet of the stack through the second pipeline, the air pump is communicated with the pressure regulator through the third pipeline, a first end of the fourth pipeline is communicated with a hydrogen outlet of the stack, a second end of the fourth pipeline is communicated with the air pump, and a third end of the fourth pipeline is communicated with the tail exhaust valve.

According to the start preparation method provided by the above one embodiment of the present invention, the air supply assembly includes an air inlet, a fifth pipeline, an air compressor, a sixth pipeline, a throttle valve, a seventh pipeline, a first throttle valve, an eighth pipeline, a second throttle valve, and a ninth pipeline, the air inlet is communicated with the air compressor through the fifth pipeline, a first end of the sixth pipeline is communicated with the air compressor, a second end of the sixth pipeline is communicated with the throttle valve, a third end of the sixth pipeline is communicated with the first throttle valve, a fourth end of the sixth pipeline is communicated with the bypass assembly, the throttle valve is communicated with the ventilation air inlet through the seventh pipeline, the first throttle valve is communicated with the air inlet of the stack through the eighth pipeline, and the second throttle valve is communicated with the air outlet of the stack through the ninth pipeline.

According to the start preparation method provided by the above one embodiment of the present invention, the bypass assembly includes a bypass valve, a tenth pipeline and a tail discharge port, the bypass valve is communicated with the fourth end of the sixth pipeline, the first end of the tenth pipeline is communicated with the bypass valve, the second end of the tenth pipeline is communicated with the second throttle valve, the third end of the tenth pipeline is communicated with the ventilation air outlet, the fourth end of the tenth pipeline is communicated with the tail discharge valve, and the fifth end of the tenth pipeline is communicated with the tail discharge port.

According to the start preparation method provided by the above-mentioned one embodiment of the present invention, the fuel cell system further includes a control unit electrically connected to the air compressor, the bypass valve, the first throttle valve, the second throttle valve, the pressure regulator, and the tail gate valve, respectively.

The advantages of the start preparation method are that: the opening of the fuel cell air supply system is not restricted by the closing state of the electric pile, and can be started before the anode hydrogen purging, or synchronously started with the anode air purging; the fuel cell air supply system is flexibly started in the shutdown state of the electric pile; the air requirements of mixed gas dilution generated by anode hydrogen purging and fuel cell box ventilation are met; the starting time of the fuel cell air compressor is more flexible; the transient response hysteresis effect of the air compressor can be avoided, and the startup and shutdown time of the fuel cell is shortened.

Drawings

The disclosure of the present invention will become more readily understood with reference to the accompanying drawings. As is readily understood by those skilled in the art: these drawings are only for illustrating the technical solutions of the present invention and are not intended to limit the scope of the present invention. In the figure:

fig. 1 shows a schematic view of a fuel cell system according to an embodiment of the invention;

fig. 2 shows a flowchart of a start-up preparation method of a fuel cell system according to an embodiment of the invention.

Detailed Description

Fig. 1-2 and the following description depict alternative embodiments of the invention to teach those skilled in the art how to make and reproduce the invention. Some conventional aspects have been simplified or omitted for the purpose of teaching the present invention. Those skilled in the art will appreciate that variations or substitutions from these embodiments will fall within the scope of the invention. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple variations of the invention. Thus, the present invention is not limited to the following alternative embodiments, but is only limited by the claims and their equivalents.

Fig. 1 shows a schematic view of a fuel cell system according to an embodiment of the present invention. As shown in fig. 1, the fuel cell system includes a stack assembly 1, a hydrogen supply assembly 2, a gas supply assembly 3, and a bypass assembly 4, the stack assembly 1 is respectively communicated with the hydrogen supply assembly 2, the gas supply assembly 3, and the bypass assembly 4 is respectively communicated with the hydrogen supply assembly 2 and the gas supply assembly 3.

According to the start-up preparation method provided by the above embodiment of the present invention, the stack assembly 1 includes a stack 11 and a case 12, the anode of the stack 11 is provided with a hydrogen inlet 111 and a hydrogen outlet 112, the cathode of the stack 11 is provided with an air inlet 113 and an air outlet 114, the case 12 is provided with a ventilation inlet 121 and a ventilation outlet 122, the stack 11 is installed in the case 12, the anode of the stack 11 is communicated with the hydrogen supply assembly 2 through the hydrogen inlet 111 and the hydrogen outlet 112, the cathode of the stack 11 is communicated with the air supply assembly 3 through the air inlet 113 and the air outlet 114, the ventilation inlet 121 of the case 12 is communicated with the air supply assembly 3, and the ventilation outlet 122 of the case is communicated with the bypass assembly 4.

According to the start-up preparation method provided by the above one embodiment of the present invention, the hydrogen supply assembly 2 includes a hydrogen bottle 21, a first pipeline 22, a pressure regulator 23, a second pipeline 24, a third pipeline 25, an air pump 26, a fourth pipeline 27 and a tail valve 28, the hydrogen bottle 21 is communicated with the pressure regulator 23 through the first pipeline 22, the pressure regulator 23 is communicated with the hydrogen inlet 111 of the stack 11 through the second pipeline 24, the air pump 26 is communicated with the pressure regulator 23 through the third pipeline 25, a first end of the fourth pipeline 27 is communicated with the hydrogen outlet 112 of the stack 11, a second end of the fourth pipeline 27 is communicated with the air pump 26, and a third end of the fourth pipeline 27 is communicated with the tail valve 28.

According to the start preparation method provided by the above-mentioned one embodiment of the present invention, the air supply assembly 3 includes the air inlet 31, the fifth pipeline 32, the air compressor 33, the sixth pipeline 34, the throttle valve 35, the seventh pipeline 36, the first throttle valve 37, the eighth pipeline 38, the second throttle valve 39 and the ninth pipeline 310, the air inlet 31 communicates with the air compressor 33 through the fifth pipeline 32, the first end of the sixth pipeline 34 communicates with the air compressor 33, the second end of the sixth pipeline 34 communicates with the throttle valve 35, the third end of the sixth pipeline 34 communicates with the first throttle valve 37, the fourth end of the sixth pipeline 34 communicates with the bypass assembly 4, the throttle valve 35 communicates with the ventilation air inlet 121 through the seventh pipeline 36, the first throttle valve 37 communicates with the air inlet 113 of the cell stack 11 through the eighth pipeline 38, the second throttle valve 39 communicates with the air outlet 114 of the cell stack 11 through the ninth pipeline 310,

according to the start preparation method provided by the above-mentioned embodiment of the present invention, the bypass assembly 4 includes a bypass valve 41, a tenth pipeline 42 and a tail discharge port 43, the bypass valve 41 is communicated with the fourth end of the sixth pipeline 34, the first end of the tenth pipeline 42 is communicated with the bypass valve 41, the second end of the tenth pipeline 42 is communicated with the second throttle valve 39, the third end of the tenth pipeline 42 is communicated with the ventilation air outlet, the fourth end of the tenth pipeline 42 is communicated with the tail discharge valve 28, and the fifth end of the tenth pipeline 42 is communicated with the tail discharge port 43.

According to the start preparation method provided by the above-described one embodiment of the present invention, the first throttle valve 37 is an intake throttle valve, and the second throttle valve 39 is an outlet throttle valve.

According to the start-up preparation method provided by the above-described one embodiment of the present invention, when the fuel cell system is operating, air enters the cathode of the electric pile 11 through an air inlet 31, a fifth pipeline 32, an air compressor 33, a sixth pipeline 34 and a first throttle valve 37 through an eighth pipeline 38, hydrogen enters the anode of the electric pile 11 from a hydrogen bottle 21 through a first pipeline 22, a pressure regulator 23 and a second pipeline 24, the hydrogen and the oxygen generate catalytic combustion reaction in the electric pile 11, the reacted oxygen leaves the cathode of the electric pile 11 and is discharged out of the fuel cell system through a ninth pipeline 310, a second throttle valve 39, a tenth pipeline 42 and a tail discharge port 43, the reacted hydrogen leaves the anode of the electric pile 11 and returns to the pressure regulator 23 through a fourth pipeline 27, an air pump 26 and a third pipeline 25 for recycling, and a tail discharge valve 28 is used for discharging water and waste gas generated by catalytic combustion in the electric pile 11 out of the fuel cell system through the tenth pipeline 42 and the tail discharge port 43.

According to the start preparation method provided by the above-described one embodiment of the present invention, the fuel cell system further includes the control unit 5, and the control unit 5 is electrically connected to the air compressor 33, the bypass valve 41, the first throttle valve 37, the second throttle valve 39, the pressure regulator 23, and the tail valve 28, respectively.

According to the start preparation method provided by the embodiment of the invention, the bypass assembly 4 is used for preventing the air compressor 33 from surging and diluting the tail gas mixture of the fuel cell system. The valve body size of the bypass valve 41 and the flow capacity of the tenth conduit 42 are determined according to the flow demand of the fuel cell system, and the opening degree of the bypass valve 41 is controlled by the control unit 5.

According to the start preparation method provided in the above-described one embodiment of the present invention, the first throttle valve 37 and the second throttle valve 39 are controlled by the control unit 5; when the electric pile 11 works, different pressure requirements of air supply are realized through controlling the opening degree of the first throttle valve 37 and the second throttle valve 39; when the stack 11 is closed, the first and second shutters 37 and 39 are closed, and the air supply assembly 3 is isolated from the cathode of the stack 11. At this time, the air compressor 33 and the bypass valve 41 work in a matching manner, and the control unit adjusts the rotation speed of the air compressor 33 and the opening degree of the bypass valve 41.

Fig. 2 shows a flowchart of a start-up preparation method of a fuel cell system according to an embodiment of the invention. As shown in fig. 2, the start preparation method includes a plurality of steps:

step 101: opening a bypass valve;

step 102: starting an air compressor of the air supply assembly;

step 103: starting the hydrogen supply assembly;

step 104: opening an air inlet throttle valve and an air outlet throttle valve in the air supply assembly;

step 105: and closing the tail discharge valve.

The start preparation method according to the above one embodiment of the present invention, wherein the step 103: the start-up hydrogen supply assembly includes:

step 103 a: detecting the air flow and the air pressure of an air inlet of a cathode of the pile;

step 103 b: judging whether the air entering the cathode of the pile meets the conditions that the flow is more than 27g/s and the pressure is more than 120kpa, if so, executing a step 103 c; if not, executing step 103a again;

step 103 c: starting the air pump of the hydrogen supply assembly and opening the pressure regulator and the tail exhaust valve of the hydrogen supply assembly.

The start preparation method according to the above one embodiment of the present invention, wherein the step 104: opening an intake throttle valve and an outlet throttle valve in an air supply assembly includes:

step 104 a: detecting the hydrogen pressure of a hydrogen inlet of the anode of the galvanic pile and the rotating speed of an air pump in the hydrogen supply assembly;

step 104 b: judging whether the hydrogen pressure of the hydrogen inlet of the anode of the galvanic pile is more than 120kpa and the rotation speed of an air pump in the hydrogen supply assembly is more than 1000rpm, if so, executing a step 104 c; if not, executing step 104a again;

step 104 c: and opening an air inlet throttle valve and an air outlet throttle valve in the air supply assembly.

According to the start preparation method provided by the above one embodiment of the present invention, the step 105: closing the tail gate valve comprises:

step 105 a: judging whether the opening degrees of an air inlet throttle valve and an air outlet throttle valve in the air supply assembly reach preset target opening degrees or not, and if so, executing a step 105 b; if not, executing step 104c again;

step 105 b: and closing the tail discharge valve.

According to the start preparation method provided by the above-described embodiment of the present invention, after the start preparation operation of the fuel cell is completed, the fuel cell starts the normal operation and outputs the power.

The advantages of the start preparation method are that: the opening of the fuel cell air supply system is not restricted by the closing state of the electric pile, and can be started before the anode hydrogen purging, or synchronously started with the anode air purging; the fuel cell air supply system is flexibly started in the shutdown state of the electric pile; the air requirements of mixed gas dilution generated by anode hydrogen purging and fuel cell box ventilation are met; the starting time of the fuel cell air compressor is more flexible; the transient response hysteresis effect of the air compressor can be avoided, and the startup and shutdown time of the fuel cell is shortened.

It will of course be realised that whilst the foregoing has been given by way of illustrative example of this invention, all such and other modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of this invention as is herein set forth. Therefore, while this invention has been described with reference to preferred embodiments, it is not intended that the novel apparatus be limited thereby, but on the contrary, it is intended to cover various modifications and equivalent arrangements included within the broad scope of the above disclosure and the appended claims.