阅读说明：本技术 用于浆干燥机的设备和方法 (Apparatus and method for a pulp dryer ) 是由 理查德·索林 于 2020-04-26 设计创作，主要内容包括：本发明涉及一种用于浆干燥机的设备和方法,其包括在干燥机的第一端中的入口开口和在干燥机的第二端中的出口开口。干燥机还包括：多个水平叠置的干燥台,其中每个干燥台包括多个干燥组,这些干燥组包括用于干燥和支撑待干燥浆幅材的干燥装置；风扇塔,包括若干叠置风扇；以及在浆干燥机的第一端和第二端的辊塔。装置包括：至少一个压力传感器,其被布置在与多个干燥装置中的一个相连接的固定位置；可选的至少一个温度传感器,其被布置在与多个风扇中的一个相连接的固定位置；以及控制单元,其被布置为与一个或多个传感器在功能上联系并从一个或多个传感器接收测量值。控制单元包括用于基于测量值计算瞬时吹风速度值的装置。(The present invention relates to an apparatus and a method for a pulp dryer, comprising an inlet opening in a first end of the dryer and an outlet opening in a second end of the dryer. The dryer further includes: a plurality of horizontally stacked drying decks, wherein each drying deck comprises a plurality of drying groups comprising drying means for drying and supporting the pulp web to be dried; a fan tower comprising a plurality of stacked fans; and roll towers at the first and second ends of the pulp dryer. The device comprises: at least one pressure sensor disposed in a fixed position in connection with one of the plurality of drying devices; optionally at least one temperature sensor disposed in a fixed position in connection with one of the plurality of fans; and a control unit arranged to be in functional communication with and to receive measurements from the one or more sensors. The control unit comprises means for calculating an instantaneous blowing speed value on the basis of the measured values.)

1. An apparatus for a pulp dryer, the pulp dryer comprising:

-an inlet opening for a web of pulp in a first end of the dryer and an outlet opening for the web in a second end of the dryer;

-a plurality of horizontally superimposed drying decks, wherein each drying deck comprises a plurality of drying groups comprising a plurality of drying devices for drying and supporting the web of pulp to be dried;

-a fan tower comprising a plurality of stacked fans arranged to supply heated air to the drying group;

-a roll tower comprising, in a first end and a second end of the pulp dryer, a number of stacked parallel turn rolls for turning the pulp web from one drying station to a subsequent drying station;

it is characterized in that the preparation method is characterized in that,

the apparatus comprises:

-at least one pressure sensor arranged in a fixed position in connection with one of said plurality of drying means;

-optionally, at least one temperature sensor arranged in a fixed position in connection with one of said fans supplying air to said plurality of drying means;

-a control unit arranged in functional communication with and receiving measurement values from one or more of said sensors, and comprising means for calculating an instantaneous blowing speed value based on said measurement values.

2. The device according to claim 1, characterized in that one or more of the sensors are arranged to be wirelessly connected with the control unit.

3. An arrangement according to claim 1 or 2, characterized in that the arrangement comprises at least one pressure sensor and at least one temperature sensor, and that the control unit further comprises mathematical means for calculating the instantaneous evaporating capacity of the pulp dryer on the basis of said measurements.

4. The apparatus according to claim 1, 2 or 3, characterized in that the apparatus comprises at least one pressure sensor and at least one temperature sensor, which are arranged in connection with the same drying group.

5. The apparatus according to any of the preceding claims 1 to 4, characterized in that the apparatus comprises 2 to 15, preferably 3 to 12, more preferably 3 to 10 pressure sensors and/or 2 to 15, preferably 3 to 12, more preferably 3 to 10 temperature sensors.

6. The apparatus according to any of the preceding claims 1-5, characterized in that the apparatus comprises at least two pressure sensors and/or at least two temperature sensors arranged at different drying stations.

7. The apparatus according to any of the preceding claims 1-6, characterized in that at least one pressure sensor and optionally at least one temperature sensor is arranged near the inlet opening and/or the outlet opening.

8. An apparatus according to any one of the preceding claims 1-7, characterized in that the apparatus comprises at least two pressure sensors arranged at least in one of the fan towers closest to the roll tower.

9. An apparatus according to any one of the preceding claims 1-8, characterized in that the apparatus comprises an additional temperature device for measuring the temperature of the web before the inlet opening of the dryer.

10. The apparatus according to any of the preceding claims 1-9, characterized in that at least one pressure sensor and/or at least one temperature sensor is arranged in connection with between 1 and 5 drying decks, seen from the inlet opening.

11. The apparatus according to any of the preceding claims 1-10, characterized in that the control unit comprises a storage unit for storing measured measurement values, calculated blowing air speed values and/or calculated evaporation capacity values.

12. The apparatus according to claim 11, characterized in that the control unit comprises mathematical prediction means for calculating a drying capacity prediction value.

13. A method for monitoring a pulp dryer, wherein,

-drying the pulp web in the pulp dryer by blowing air from a drying device;

-supplying heated air to the drying means by means of a fan;

-measuring a pressure value from at least one drying device and optionally a temperature value of at least one air blast;

-transmitting said measurement value to a control unit;

-calculating an instantaneous blowing speed value based on said measurement values.

14. Method according to claim 13, characterized in that the interval and/or the position of the cleaning operation in the pulp dryer is determined on the basis of measured values and/or calculated blowing speed values.

15. Method according to claim 13 or 14, characterized in that pressure and temperature values are measured and the instantaneous evaporation capacity value of the pulp dryer is calculated.

Technical Field

The present invention relates to an apparatus and a method for a pulp dryer.

Background

The pulp is dried in a pulp dryer, which is formed by a drying device comprising blow nozzles, wherein a web of pulp is transported along a multi-layer path by floating the web on an air cushion. The drying means are arranged in a plurality of superimposed horizontal drying decks (drying decks). The pulp web is usually brought into the pulp dryer through a first end, the so-called wet end, of the pulp dryer. The web of pulp is then transported to the second end of the dryer on the uppermost drying deck of the pulp dryer. The end of the dryer comprises a turn roll which turns the pulp web to the next drying station. After the last drying station, the web of pulp is brought to a cooling station below the drying station and removed from the pulp dryer, typically from the second end of the pulp dryer. Pulp dryers typically have 10 to 30 drying decks. The gas blown out of the drying device is usually hot air and has a temperature of 120 to 170 ℃. The pulp web typically has a dry solids content of 48% to 54% when entering the pulp dryer. The dry solids content of the pulp web exiting the pulp dryer is typically in the range of 85% to 95%, most commonly about 90%.

Pulp dryers typically comprise a number of fans (fan) for removing humid air from inside the pulp dryer and also for supplying hot air to the drying means. A plurality of fans are usually arranged on top of each other forming a so-called fan tower, and a suitable number of fan towers are arranged adjacent to each other at a distance from each other. A heating device, such as a heat exchanger or a steam radiator, is arranged to heat the humid air before supplying it as drying air to the drying device. The heating device is arranged beside or in front of the suction opening of the fan, so that air is conveyed to the fan by the heating device. In front of the heating devices, i.e. on their inlet side, a filter screen or the like is usually arranged to prevent dust and debris such as pulp, paper, fibres or the like from entering the heating devices and further into the fan.

The pulp dryer has a theoretical evaporation capacity (evaporation capacity) which is determined in the design stage of the pulp dryer by using, in particular, the theoretical blowing speed and blowing temperature of the drying device. During operation of the pulp dryer, the evaporation capacity of the dryer decreases. One reason for the reduced evaporation capacity is the accumulation of dust and other debris on the filter screen of the heating device. This increases the pressure drop across the filter and reduces the volume and velocity of the air supplied to the drying apparatus. The filter screen is periodically cleaned to maintain the filter screen clean and reduce the degradation of evaporation capacity. However, no real-time information about the real instantaneous evaporation capacity is available and the operator does not receive any reliable feedback about the effectiveness of the cleaning operation performed. Therefore, there is a need for an apparatus that will provide real-time information about changes in the evaporation capacity and changes in the blowing conditions of a pulp dryer.

Disclosure of Invention

It is an object of the present invention to reduce or even completely eliminate the problems occurring in the prior art.

It is an object of the present invention to provide a solution enabling real-time monitoring of the evaporation capacity of a pulp dryer.

It is a further object of the present invention to provide an apparatus and method that provides information about the need and/or effectiveness of a cleaning operation.

Another object of the invention is to provide an apparatus and a method which provide new opportunities to promote and control the cleaning process (routine process) and to increase the productivity of the pulp dryer.

To the accomplishment of the foregoing and related ends, the features of the invention are presented and described herein.

The embodiments and advantages mentioned herein always relate to the device and method according to the invention, where applicable and even if not explicitly stated.

An exemplary apparatus for a pulp dryer according to the present invention comprises:

-an inlet opening for a pulp web in a first end of the pulp dryer, and an outlet opening for a pulp web in a second end of the pulp dryer;

-a plurality of horizontally superimposed drying decks, wherein each drying deck comprises a plurality of drying groups comprising a plurality of drying devices for drying and supporting the web of pulp to be dried;

-a fan tower comprising a plurality of stacked fans arranged to supply heated air to the drying group;

-a roll tower in the first and second ends of the pulp dryer, the roll tower comprising a number of stacked parallel turn rolls for turning the pulp web from one drying station to a subsequent drying station;

wherein, this equipment includes:

-at least one pressure sensor arranged in a fixed position in connection with one of the drying means;

-optionally, at least one temperature sensor arranged in a fixed position in connection with one of said plurality of fans supplying air to a plurality of drying means;

-a control unit arranged in functional connection with the one or more sensors and receiving measured values from the one or more sensors, and comprising means for calculating an instantaneous blowing speed value based on the measured values.

A typical method for monitoring a pulp dryer according to the invention comprises:

-drying the pulp web in the pulp dryer by blowing air from the drying means;

-supplying heated air to the drying means by means of a fan;

-measuring a pressure value from at least one drying device and optionally a temperature value of at least one air blast;

-transmitting the measurement values to a control unit;

-calculating an instantaneous blow speed value based on the measurement values.

It has now surprisingly been found that by arranging at least one pressure sensor in a fixed position in connection with one of a plurality of drying devices, it is possible to obtain instantaneous and relevant information about the value of the blowing speed in a pulp dryer. The measured pressure values may be used to calculate an instantaneous blow speed value, which may be used to estimate, for example, the condition of the filter screen, the appropriate cleaning interval and/or the effect of the cleaning operation performed. Further, optionally, at least one temperature sensor may be arranged at a fixed position in connection with one of the plurality of fans supplying air to the plurality of drying devices, which further improves the accuracy and versatility (versatility) of the calculated value. The calculated blow speed values can be used to further calculate the instantaneous evaporating capacity of the pulp dryer, which provides new possibilities for optimizing the production capacity and/or the production plan. By arranging the sensors in fixed positions, it is possible to collect and store measurements over a longer (period) of time and under actual process conditions and to compare the collected and stored measurements with observed changes in cleanliness and performance of the dryer. This provides a new and improved way of correlating the measured values with the actual changes.

In this context, the term "in a fixed position" means that the sensor is permanently arranged to the pulp dryer. The sensor is usually fastened to the pulp dryer, e.g. fixedly mounted inside the drying apparatus. The position of the sensor is fixed.

The apparatus of the invention may be arranged or incorporated in any pulp dryer, for example, as described in the background section of the present application. Typically, a pulp dryer comprises an inlet opening for a web of pulp at a first end of the dryer and an outlet opening for the web of pulp at a second end of the dryer. The pulp dryer comprises a plurality of horizontally stacked drying decks and at least one cooling deck. The inlet opening is arranged at the level of the first drying deck and the outlet opening is arranged at the level of the cooling deck below the drying deck. The roll towers are arranged at a first end and a second end of the dryer and comprise a number of stacked parallel turn rolls for turning the pulp web from a drying station to a subsequent drying station. Each drying station comprises a plurality of drying groups comprising a plurality of drying means for drying and supporting the web of pulp to be dried. The drying means is typically an elongated drying nozzle structure extending across the width of the web. The blowing surface of the drying means comprises nozzle openings, nozzle slots or the like, through which drying air is directed towards the web of pulp to be dried. The drying air also acts as a support medium for the web. The drying device has a first end and a second end, the first end comprising an air supply connection through which the fan supplies heated air to the drying device. The height of the drying means generally decreases from the first end towards the second end of the drying means, i.e. the drying means is thus wedge-shaped in its longitudinal direction. The pulp dryer further comprises fan towers, each comprising a plurality of stacked axial fans arranged to supply heated air to the drying group. A fan may supply hot air to one or more drying groups.

The apparatus according to the invention comprises at least one pressure sensor which is arranged in a fixed position in connection with one of the plurality of drying means. This means that the pressure sensor is able to measure and provide information about the blow pressure in real time during operation of the pulp dryer. The pressure measurements are transmitted to a control unit where they can be used to calculate the blowing speed value at which the fan supplies air to the drying appliance. If a significant reduction in the blowing speed value is observed, this may indicate that the filter screen associated with the fan is clogged or becomes clogged. This information about the instantaneous blowing speed and/or its variation over time can be used to monitor and/or adjust the cleaning program of the filter sieve. The blow speed value can further be used to calculate the instantaneous evaporating capacity of the pulp dryer.

The pressure sensor may be fixedly arranged at any suitable position within the drying apparatus. The dynamic pressure generally decreases along the length of the drying apparatus. The pressure sensor may thus preferably be fixedly arranged in the vicinity of the closed second end of the drying apparatus opposite the air supply connection. In this way, a measurement value can be obtained which describes relatively accurately the pressure at which the fan supplies air to the drying appliance. Preferably, the pressure sensor is arranged in connection with a drying apparatus belonging to the lower drying group of the drying deck. The lower drying group provides drying air to the pulp web located above the drying group.

The apparatus may comprise 2-15, preferably 3-12, more preferably 3-10 pressure sensors located at different parts or portions of the pulp dryer. Preferably, the apparatus may comprise at least two pressure sensors arranged in at least one fan tower, preferably in two axial fan towers closest to the first end and/or the second end of the pulp dryer. According to a preferred embodiment, the apparatus may comprise at least 5 pressure sensors, preferably located at different drying decks. The use of a plurality of pressure sensors ensures a more accurate knowledge of the pulp dryer condition, which may differ in different parts of the dryer. For example, dusting problems are generally more pronounced in the upper part of the pulp dryer and reduced towards the lower part, because the pulp web becomes dry and stiff during drying, and less fibres are shed from the web. Furthermore, dust laden air is removed from the upper part of the dryer. By carefully arranging pressure sensors at different heights of the pulp dryer, a new insight (insight) of the pulp dryer's condition can be obtained, which can be used to adapt the cleaning procedure and/or to predict changes in evaporation capacity.

At least two pressure sensors can also be arranged on the same drying deck. When at least two sensors are fixedly arranged on the same drying deck, any possible sensor errors can be effectively observed. On the same drying deck, the measurements from different sensors are usually close to each other. If a significant change in the measured values is observed, it may indicate a sensor error or an abnormal change in the pulp dryer condition.

The apparatus also preferably comprises at least one temperature sensor arranged in a fixed position in connection with one of the plurality of fans supplying air to the drying means. The temperature sensor provides a temperature measurement value related to the actual temperature of the drying air supplied to the drying arrangement and used for drying the pulp web. The temperature measurement can be used to calculate a more accurate value for the blowing speed, since the temperature influences the pressure measurement, so that it can be taken into account in a correct manner. Temperature measurements also provide the possibility to calculate the instantaneous evaporating capacity of the pulp dryer.

Preferably, the temperature sensor is located in the pressure chamber of the fan tower, close to the air supply connection of the drying device. Thus, the obtained temperature measurement describes well the temperature of the air supplied by the fan. In particular, when this temperature information is combined with pressure information, a completely new perspective (viewpoint) of the conditions inside the pulp dryer is provided.

The temperature sensor may be, for example, a resistance temperature Probe (PRT), a Platinum Resistance Thermometer (PRT), a thermocouple, or the like.

According to one embodiment of the invention, the device may comprise 2 to 15, preferably 3 to 12, more preferably 3 to 10 temperature sensors. Preferably, the device comprises the same number of temperature sensors and pressure sensors.

Preferably, the temperature sensor and the pressure sensor may be arranged close to each other in the same part or section of the pulp dryer. When the pressure sensor and the temperature sensor are disposed close to each other, they provide measurement values that are more closely related to each other, and provide improved calculation results and estimation values. According to a preferred embodiment, the apparatus comprises at least one pressure sensor and at least one temperature sensor, preferably arranged in connection with the same drying group. The pressure sensor need not be arranged in the same drying apparatus, i.e. in the same drying nozzle, but the pressure sensor is preferably arranged inside the drying apparatus, preferably at the closed second end of the drying apparatus, and the temperature sensor is arranged in connection with a fan supplying said drying apparatus.

According to a preferred embodiment, the pressure sensor and the temperature sensor are arranged in connection with the same drying apparatus. The temperature sensor may be fixedly arranged in connection with a first end of the drying means, for example in a pressure chamber of a fan, in connection with an air supply next to the drying means, and the pressure sensor may be fixedly arranged in connection with a second end of the same drying means.

The device may preferably comprise at least two pressure sensors and/or at least two temperature sensors, which are fixedly arranged at different drying decks. This provides relevant information from different parts of the pulp dryer and may help to locate the part where the filter screen needs to be cleaned. The position of the sensor may be chosen such that the sensor is arranged in a part or section of the dryer where traditional problems have occurred. According to one embodiment, at least two pressure sensors and/or temperature sensors are arranged in the vicinity of one fan tower, but at different drying decks. According to another embodiment, at least one pressure sensor and/or at least one temperature sensor is arranged in connection with between 1 and 5 drying decks, seen from the level of the inlet opening. In particular, the apparatus may comprise at least one pressure sensor and optionally at least one temperature sensor, which may be arranged near the inlet opening and/or the cooling deck and/or the outlet opening of the pulp dryer. Preferably, one pressure sensor is arranged near the inlet opening and one pressure sensor is arranged near the outlet opening or the cooling table.

The device further comprises a control unit arranged in functional communication with the pressure sensor and optionally the temperature sensor. The control unit is arranged or configured to receive measurement values from one or more sensors. The control unit may be arranged in wired connection with one or more pressure sensors and one or more optional temperature sensors. Alternatively, at least some of the sensors may be arranged to be in wireless connection with the control unit. According to a preferred embodiment, the pressure sensor and/or the optional temperature sensor is arranged in a wireless connection with the control unit. In case one or more pressure sensors and one or more optional temperature sensors are arranged in wireless connection with the control unit, the sensors comprise transmission means for transmitting measurement values from the sensors to the control unit.

For example, the control unit may be a separate or inseparable component of the control and monitoring system of the pulp dryer.

According to one embodiment, a pressure measurement and a temperature measurement are measured and an instantaneous evaporation capacity value of the pulp dryer is calculated. The control unit may comprise mathematical means for calculating the instantaneous blowing speed value based on measurements received from one or more pressure sensors and/or optional temperature sensors. The control unit may also comprise mathematical means for calculating the instantaneous evaporating capacity of the pulp dryer on the basis of the pressure measurement and optionally the temperature measurement. The on-line calculation of instantaneous blow-air speed values and evaporation capacity values provides in particular a new problem solving tool and production planning tool, which guarantees new possibilities for production optimization. The control unit may further comprise means for providing an alarm when the blowing speed value and/or the evaporation capacity value is below a predetermined limit value. The alarm guides the operator to initiate the cleaning program and/or targets the cleaning program to certain specific parts of the pulp dryer.

The control unit may include a storage unit for storing the measured value, the calculated blowing speed value, and/or the drying capability value. Various mathematical functions as well as known calculation constants and reference values may also be stored in the memory unit.

The control unit may also comprise mathematical prediction means for calculating a prediction (value) of the evaporation capacity. The prediction means may use the measured and calculated values stored in the memory unit, as well as various mathematical and statistical functions and/or models to calculate the evaporation capacity prediction (value). According to a preferred embodiment, the measured value and the calculated blowing speed value and/or evaporation capacity value are stored in a storage unit of the control unit, and a prediction of the drying capacity value is calculated based on the stored values.

Furthermore, the control unit may comprise a transmission device for transmitting the measured and/or calculated values to a central control system of the pulp mill. The control unit may form part of a central control system of the pulp mill. Alternatively, or in addition, the control unit may transmit the measured and/or calculated values to a remote external control system (e.g., at an external service provider). In this way, the service provider may suggest a schedule for future service operations, and the operations may be timed accurately.

The arrangement may also comprise any additional sensor providing relevant information about the condition of the pulp dryer. The measured values from the additional sensors can be used to fine-tune the calculated blowing speed and/or evaporation capacity value and/or evaporation capacity prediction. The apparatus may for example comprise one or more steam pressure sensors which measure the pressure of the steam used in the heating device. The apparatus further comprises additional temperature measuring means for measuring the temperature and/or moisture of the web before the inlet opening of the dryer. The temperature measuring means may be, for example, an IR sensor.

Drawings

Some embodiments of the invention are described in more detail in the accompanying schematic non-limiting drawings, in which:

fig. 1 schematically shows a side view of a pulp dryer comprising an apparatus according to an embodiment of the invention; and

fig. 2 schematically shows a longitudinal side view of two drying groups and an apparatus according to another embodiment of the invention.

Detailed Description

Fig. 1 schematically shows a side view of a pulp dryer comprising an arrangement according to an embodiment of the invention. The pulp dryer 1 comprises an inlet opening 11 and an outlet opening 11' for the pulp web 2. The pulp dryer 1 comprises a number of horizontally superposed drying decks as well as turning rolls 3, 3', 3 "which turn the pulp web 2 from a first drying deck to a subsequent drying deck.

Each drying deck comprises a plurality of drying groups 4 comprising a plurality of drying means 5, 5'. For the sake of clarity, only the upper left corner of the pulp dryer 1 in fig. 1 depicts some drying groups and drying means. It is understood, however, that the entire interior of the pulp dryer 1 is filled with drying means arranged in drying groups located on both sides of the pulp web 2 when the pulp web 2 passes through the pulp dryer 1.

The fan 6 supplies hot air to the drying group 4. Only one tower of the fan 6 is shown in the figure, but it is understood that the pulp dryer comprises a plurality of such towers, which towers are arranged on both sides of the pulp dryer 1. It can be seen that the airflow (shown by arrow A, A) to the fan 6 is directed through the filter 7, which filter 7 removes debris and dust from the airflow A, A 'before the airflow A, A' enters the fan. The air flows a, a ' originate from the area around the second ends of the drying means of the adjacent drying group 4', the fans (not shown) of which are located at the other side of the pulp dryer 1, at the other end of the drying group 4 '.

The pulp dryer 1 comprises an arrangement of a plurality of pressure sensors 100. The pressure sensors 100 are arranged near the first end 1' and the second end 1 "of the pulp dryer 1, some of which are also arranged in the middle of the pulp dryer 1. Furthermore, the pressure sensor 100 is arranged in the drying means of the drying group below the pulp web 2. The reduction of the blowing speed and volume in the drying group below the web is particularly harmful, since it may lead to insufficient support and contact between the web and the surface of the drying means. This contact increases dust and fibers coming loose from the web and exacerbates the loss of evaporation capacity.

Fig. 2 schematically shows a longitudinal side view of two drying groups and an apparatus according to another embodiment of the invention. The gas flow is indicated by arrows a in fig. 2. The fan 26 supplies air to the two drying groups 24, 24 'comprising drying means 25, 25'. The direction of movement of the pulp web 2 comes out of the figure towards the viewer. The air blow for drying and supporting the pulp web is schematically depicted by black small arrows. The dashed rectangles 27, 27' in fig. 2 show the conceptual position of the heating means at one fan 26, even though in practice the heating means extends over an area of 2-3 fans. The air flows around the drying group 24, 24' and its drying means 25, 25', through a filter screen (not shown) and a heating means 27' to another fan (not shown).

The temperature sensor 101 is fixedly arranged in the supply chamber 20 of the fan 26 close to the air supply connection to the drying means 25. In this way, an accurate temperature measurement of the air to be supplied can be obtained. The pressure sensor 100 is fixedly arranged in the closed second end 21 of the drying means 25. The pressure sensor 100 measures a pressure measurement of the drying air in the drying device 25. Due to the location of the pressure sensor 100, pressure measurements may be made in a relatively static environment, as there is no airflow out of the second end of the drying apparatus.

The stationary temperature sensor 101 and the stationary pressure sensor 100 are arranged in functional communication with the control unit 22, which control unit 22 comprises calculation means for calculating an instantaneous blowing speed value based on the measured values. The device comprises a transmitter 23 arranged in wireless or wired communication with both the sensors 100, 101 and the control unit 22 for transmitting measurement values from the sensors 100, 101 to the control unit 22.

Even though the invention has been described with reference to what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.