阅读说明：本技术 一种用于冰箱压缩机的减振消音排气盘管 (Vibration-damping and silencing exhaust coil pipe for refrigerator compressor ) 是由 陈刚 李菁瑞 黄强胜 孟碧光 梁满仓 罗凯亮 于 2021-08-25 设计创作，主要内容包括：本发明公开一种用于冰箱压缩机的减振消音排气盘管,所述排气盘管的两端分别密封连接有进气管、出气管,所述排气盘管的内部设有排气缓冲腔,所述排气缓冲腔内设有隔板,所述隔板将所述排气缓冲腔分隔为一级缓冲室、二级缓冲室；所述进气管设有若干个贯通的条形狭缝,所述进气管的位于所述一级缓冲室内的端部为封闭的盲端；所述隔板设有至少一个贯穿其两个端面的孔洞和/或设有至少一个用于一级缓冲室与二级缓冲室之间气体流通的连通管；通过设置多级缓冲室,并且在进气管的管壁设置条形狭缝,利用多级降压原理改善导气缓冲效果,降低压缩机气流脉动。(The invention discloses a vibration-damping and noise-reducing exhaust coil pipe for a refrigerator compressor, wherein an air inlet pipe and an air outlet pipe are respectively connected to two ends of the exhaust coil pipe in a sealing manner, an exhaust buffer cavity is arranged in the exhaust coil pipe, a partition plate is arranged in the exhaust buffer cavity, and the exhaust buffer cavity is divided into a primary buffer chamber and a secondary buffer chamber by the partition plate; the air inlet pipe is provided with a plurality of through strip-shaped slits, and the end part of the air inlet pipe, which is positioned in the primary buffer chamber, is a closed blind end; the baffle is provided with at least one hole penetrating through two end faces of the baffle and/or at least one communicating pipe for gas circulation between the primary buffer chamber and the secondary buffer chamber; through setting up multistage buffer chamber to set up the bar slit at the pipe wall of intake pipe, utilize multistage step-down principle to improve the air guide buffering effect, reduce compressor air current pulsation.)

1. The vibration-damping, noise-reducing and exhaust coil pipe for the refrigerator compressor is characterized in that an air inlet pipe and an air outlet pipe are respectively connected to two ends of the exhaust coil pipe in a sealing mode, an exhaust buffer cavity is arranged inside the exhaust coil pipe, a partition plate is arranged in the exhaust buffer cavity and divides the exhaust buffer cavity into a primary buffer chamber and a secondary buffer chamber, the end portion of the air inlet pipe is arranged in the primary buffer chamber in an extending mode, and the end portion of the air outlet pipe is arranged in the secondary buffer chamber in an extending mode; the pipe wall of the air inlet pipe, which is positioned in the primary buffer chamber, is provided with a plurality of through strip-shaped slits, the extending direction of the strip-shaped slits is the same as that of the pipe wall of the air inlet pipe, and the end part of the air inlet pipe, which is positioned in the primary buffer chamber, is a closed blind end; the baffle is provided with at least one hole penetrating through two end faces of the baffle and/or at least one communicating pipe for gas circulation between the primary buffer chamber and the secondary buffer chamber.

2. The vibration-damping, noise-reducing and exhaust coil pipe for the refrigerator compressor as claimed in claim 1, wherein an included angle between a central axis of the communicating pipe and the partition plate is 90 ° to 180 °; the baffle plate comprises a plurality of communicating pipes, and included angles with different angles between each communicating pipe and the corresponding baffle plate.

3. The coil pipe of claim 1, wherein the end of the inlet pipe located in the exhaust buffer chamber is provided with a spiral structure portion, the strip-shaped slit is located in the spiral structure portion, and the strip-shaped slit has the same precession direction as the spiral structure portion.

4. The coil of claim 1, wherein the communicating tube extends through the partition plate, or the communicating tube is located on only one side of the partition plate.

5. The coil of claim 1, wherein the communicating tube has a multi-stage expansion and contraction chamber.

6. The coil of claim 1, wherein the discharge buffer chamber is a cylindrical structure, and the ratio of the inner diameter of the inlet pipe to the inner diameter of the discharge buffer chamber is less than 0.27 and greater than 0.1.

7. The coil pipe of claim 1, wherein the coil pipe comprises two slits symmetrically disposed at two sides of the inlet pipe.

8. The coil pipe for the compressor of the refrigerator, according to claim 1, is characterized in that the number of the strip-shaped slits is 1-6, and the ratio of the total ventilation area of the strip-shaped slits to the total area of the pipe wall of the air inlet pipe in the exhaust buffer cavity is 0.029-0.178.

9. The coil of claim 1, wherein the total ventilation area of the communicating tube is S1, the total ventilation area of the holes is S2, the area of the profile of the end face of the partition is S3, and S1+ S2 is not more than 0.4S 3.

10. The coil of claim 1, wherein the partition is perpendicular to the central axis of the discharge buffer chamber, the central axis of the inlet pipe coincides with the central axis of the discharge buffer chamber, and the central axis of the outlet pipe and the central axis of the discharge buffer chamber form an angle of 30 ° to 150 °.

Technical Field

The invention relates to the field of compressor equipment, in particular to a vibration-damping and silencing exhaust coil pipe for a refrigerator compressor.

Background

Nowadays, the noise quality of a refrigerator is gradually becoming one of the evaluation standards purchased by people. The compressor is a key component of the refrigerator system, and the noise level of the compressor seriously affects the noise quality of the refrigerator noise. The exhaust coil is one of the key parts generating pulsation noise and pipeline vibration in the compressor, and the optimization and improvement of the exhaust coil become the key points of research of various compressor manufacturers and scientific research institutions. Currently, a common exhaust coil is a single bundy tube of equal diameter. The refrigerant is compressed by the reciprocating motion of the piston to form high-temperature and high-pressure gas, and the high-temperature and high-pressure gas enters a refrigeration cycle system of the refrigerator through the exhaust coil. The refrigerant gas with high flow speed has obvious airflow pulsation characteristic due to intermittent exhaust action, and airflow noise and system pipeline vibration can be generated.

In order to reduce the noise vibration effect caused by the airflow pulsation, many engineers in the industry take various measures to continuously optimize and improve. Common optimization methods such as increasing the length of the exhaust pipe appropriately; selecting a coil pipe with a proper inner diameter; designing a pipeline structure with certain rigidity and elasticity; a damping spring is sleeved on the exhaust coil pipe; an exhaust buffer cavity and the like are added on the pipeline. Conventional exhaust coils are prone to the following drawbacks:

1) the common exhaust coil pipe is mostly a metal bundy pipe matched with the structure of the exhaust buffer cavity with the larger inner diameter. The high-temperature and high-pressure gas obtained by piston compression can realize secondary expansion in the exhaust buffer cavity, so that the aim of reducing exhaust pulsation is fulfilled. However, the exhaust coil pipe has a simple structure and limited vibration and noise reduction effects, and particularly has a weakening effect on pulsation in a specific frequency band.

2) When the air flow enters the exhaust buffer cavity, violent jet air flow and pulsating air flow are generally generated, which causes air flow noise, pipeline vibration and the like.

For example, a chinese patent of invention with application number CN201620361230.5 in 2016, 12, and 07 discloses a novel internal exhaust coil, which comprises an internal exhaust coil body, an exhaust buffer chamber is arranged on the exhaust coil body, the exhaust buffer chamber comprises a sealed shell, a silencing partition is arranged in the sealed shell, and the silencing partition divides the inner cavity of the shell into an upper cavity and a lower cavity; the silencing partition plate is provided with a silencing hole for communicating the upper cavity with the lower cavity; the top of the upper cavity is provided with an air inlet, the bottom of the lower cavity is provided with an air outlet, and the air inlet and the air outlet are respectively connected with the inner exhaust disc pipe body. The exhaust buffer cavity is arranged on the inner exhaust coil pipe, the silencing partition plate is arranged in the cavity, and the upper pipe body and the lower pipe body are arranged in different apertures, so that the noise generated when the compressor exhausts air is greatly reduced; although the scheme of this patent has adopted the baffle to divide into the multistage scheme with the surge-chamber, has certain noise cancelling effect, but the structure is comparatively simple, therefore noise cancelling effect is limited.

Disclosure of Invention

The invention aims to solve the problems in the prior art and provides a vibration-damping and silencing exhaust coil pipe for a refrigerator compressor.

In order to achieve the purpose, the invention adopts the technical scheme that:

a vibration-damping and noise-reducing exhaust coil pipe for a refrigerator compressor is characterized in that an air inlet pipe and an air outlet pipe are respectively connected to two ends of the exhaust coil pipe in a sealing mode, an exhaust buffer cavity is arranged inside the exhaust coil pipe, a partition plate is arranged in the exhaust buffer cavity and divides the exhaust buffer cavity into a primary buffer chamber and a secondary buffer chamber, the end portion of the air inlet pipe is arranged in the primary buffer chamber in an extending mode, and the end portion of the air outlet pipe is arranged in the secondary buffer chamber in an extending mode; the pipe wall of the air inlet pipe, which is positioned in the primary buffer chamber, is provided with a plurality of through strip-shaped slits, the extending direction of the strip-shaped slits is the same as that of the pipe wall of the air inlet pipe, and the end part of the air inlet pipe, which is positioned in the primary buffer chamber, is a closed blind end; the baffle is provided with at least one hole penetrating through two end faces of the baffle and/or at least one communicating pipe for gas circulation between the primary buffer chamber and the secondary buffer chamber.

The exhaust coil is used in a refrigerator compressor and is used for smoothing pulsating airflow formed after the piston reciprocates and is compressed, so that exhaust noise and pipeline vibration are reduced.

The exhaust coil pipe in the prior art only has a simple exhaust buffer cavity structure, pulse airflow is expanded for the second time in the exhaust buffer cavity, and the purpose of reducing exhaust pulsation is achieved.

Compared with the prior art, the improved structure has the key points that firstly, the partition plate is arranged in the exhaust buffer cavity, the exhaust buffer cavity is divided into the multistage buffer chambers through the partition plate, the flowing path of the refrigerating gas in the exhaust buffer cavity is prolonged through the multistage buffer chambers, the gas guide buffer effect is improved by utilizing the multistage pressure reduction principle, and the airflow pulsation of the compressor is reduced;

secondly, a strip-shaped slit is arranged on the pipe wall of the air inlet pipe, and the end part of the air inlet pipe is a closed blind end, so that the phenomenon that the flow speed of inlet air flow is too high and the inlet air flow is directly sprayed onto a partition plate to cause resonance of an exhaust coil and generate vibration noise is avoided, and the larger diameter ratio between the exhaust coil and the air inlet pipe is fully utilized, so that the pulse air flow obtains a better buffering effect;

and thirdly, at least one hole penetrating through two end faces of the partition board and/or at least one communicating pipe are arranged on the partition board, the hole and the communicating pipe have the throttling effect, and the first-stage buffer chamber and the second-stage buffer chamber are communicated, so that pulsating airflow is expanded and buffered for many times, the flow speed of the airflow is reduced, and the silencing performance of the exhaust coil pipe can be effectively improved.

Furthermore, the included angle between the central axis of the communicating pipe and the partition plate is limited to 90-180 degrees, and the communicating pipe is provided with a plurality of communicating pipes, and the included angle between each communicating pipe and the partition plate is different in angle. Therefore, the air flow entering the secondary buffer chamber from the primary buffer chamber has different jet directions, and collides with each other to interfere with each other to offset a part of sound energy, and simultaneously reduces the vibration noise of the exhaust coil.

Further, the communicating pipe penetrates through the partition plate, or the communicating pipe is only positioned on one side of the partition plate. When the communicating pipe penetrates through the partition plate, two ends of the communicating pipe are respectively located in the first-stage buffer chamber and the second-stage buffer chamber, when the air flow enters the second-stage buffer chamber from the first-stage buffer chamber, the air flow needs to pass through a longer distance, the air flow rubs with the pipe wall in the communicating pipe, partial sound energy is converted into heat energy to be released, and noise is further reduced.

Furthermore, the communicating pipe is provided with a multi-stage expansion and contraction inner cavity. Through set up multistage expansion shrink inner chamber in communicating pipe, take place violent friction when further making the air current contact with the inner wall of communicating pipe to make the acoustic energy consume or convert into heat energy.

Further, the exhaust buffer cavity is of a cylindrical structure, and the ratio of the inner diameter of the air inlet pipe to the inner diameter of the exhaust buffer cavity is smaller than 0.27 and larger than 0.1. Through improving the internal diameter difference between intake pipe and the exhaust cushion chamber, can reduce the velocity of flow of air current, but too big internal diameter difference can reduce the effect of offsetting the noise through the reflection, consequently need set up in reasonable scope.

Furthermore, the air inlet pipe comprises two strip-shaped slits, and the two strip-shaped slits are symmetrically arranged on two sides of the air inlet pipe. Through setting up two bar slit symmetries, the tip shake of intake pipe when avoiding jet-propelled reduces vibration noise.

Furthermore, the number of the strip-shaped slits is 1-6, and the ratio of the total ventilation area of the strip-shaped slits to the total area of the pipe wall of the air inlet pipe, which is located in the exhaust buffer cavity, is 0.029-0.178. Improve the bar slit number or increase bar slit flow area, can reduce the jet velocity of air current, reduce the air current and spout the vibration noise of exhaust cushion intracavity wall, but too big flow area can reduce the reflection effect of air current, reduces the noise cancelling effect of specific frequency noise, consequently need set up in reasonable scope.

Further, the total ventilation area of the communicating pipe is S1, the total ventilation area of the holes is S2, the area of the end surface profile of the partition board is S3, and S1+ S2 is not more than 0.4S 3. The total ventilating area of the communicating pipe and the holes is too large, which affects the reflection and noise reduction effect of the clapboard, so the range is limited in a reasonable range,

furthermore, the baffle is perpendicular to the axis of exhaust cushion chamber, the axis of intake pipe with the axis coincidence of exhaust cushion chamber, the angle range between the axis of outlet duct and the axis of exhaust cushion chamber is 30 ~ 150. Through setting up the slope with the outlet duct, avoid flowing through the air current from the baffle and directly get into the outlet duct, increase the diffusivity of air current, improve buffering effect.

Furthermore, the end portion, located in the exhaust buffer cavity, of the air inlet pipe is provided with a spiral structure portion, the strip-shaped slit is located in the spiral structure portion, and the strip-shaped slit has the same precession direction as the spiral structure portion. Through setting up helical structure portion at the intake pipe, make the air current that erupts have the angular velocity of slope, avoid spouting the air current perpendicular striking exhaust cushion chamber and arouse the vibration noise, simultaneously, convert the perpendicular application of force of jet air current to the intake pipe into torsion to avoid the shake of intake pipe tip, reduce the vibration noise, on the other hand makes the sound energy of stranded air current offset each other at spiral collision in-process, noise abatement.

Compared with the prior art, the invention has the beneficial effects that:

1. the exhaust buffer cavity is divided into a plurality of stages of buffer chambers by the partition plates, the flow path of the refrigerating gas in the exhaust buffer cavity is prolonged by the arrangement of the plurality of stages of buffer chambers, the gas guide buffer effect is improved by utilizing a multi-stage pressure reduction principle, and the airflow pulsation of the compressor is reduced;

2. the pipe wall of the air inlet pipe is provided with the strip-shaped slit, and the end part of the air inlet pipe is a closed blind end, so that the phenomenon that the flow speed of the air inlet flow is too high and the air inlet flow is directly sprayed onto the partition plate to cause resonance of the exhaust coil pipe and generate vibration noise is avoided, and the larger diameter ratio between the exhaust coil pipe and the air inlet pipe is fully utilized, so that the pulse air flow is better buffered;

3. the baffle is provided with at least one hole penetrating through two end faces of the baffle and/or at least one communicating pipe, the hole and the communicating pipe have the throttling function and are communicated with the primary buffer chamber and the secondary buffer chamber, so that pulsating airflow is expanded and buffered for many times, the flow rate of the airflow is reduced, and the silencing performance of the exhaust coil pipe can be effectively improved.

Drawings

FIG. 1 is a schematic view of a vibration damping and noise reducing exhaust coil for a compressor of a refrigerator according to the present invention;

FIG. 2 is a cross-sectional view of one embodiment of the present invention;

FIG. 3 is a cross-sectional view of one embodiment of the present invention;

FIG. 4 is a cross-sectional view of one embodiment of the present invention;

FIG. 5 is a cross-sectional view of one embodiment of the present invention;

in the figure: 1. an exhaust coil; 2. an air inlet pipe; 3. an air outlet pipe; 4. a primary buffer chamber; 5. a secondary buffer chamber; 6. a strip-shaped slit; 7. a partition plate; 8. a hole; 9. a communicating pipe; 10. expanding and contracting the inner cavity in multiple stages; 11. a helical structure portion.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. 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.

In the description of the present invention, it should be noted that the terms "upper", "lower", "left", "right", "top", "bottom", "inner", "outer", "horizontal", "vertical", and the like indicate orientations or positional relationships that are based on the orientations or positional relationships shown in the drawings, and are only used for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the device or element referred to must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present invention.

As shown in fig. 1 to 2, a vibration-damping and noise-reducing exhaust coil pipe for a refrigerator compressor, wherein an air inlet pipe 2 and an air outlet pipe 3 are respectively connected to two ends of the exhaust coil pipe 1 in a sealing manner, an exhaust buffer cavity is arranged inside the exhaust coil pipe 1, a partition plate 7 is arranged in the exhaust buffer cavity, the exhaust buffer cavity is divided into a primary buffer chamber 4 and a secondary buffer chamber 5 by the partition plate 7, the end of the air inlet pipe 2 is extended into the primary buffer chamber 4, and the end of the air outlet pipe 3 is extended into the secondary buffer chamber 5; the pipe wall of the air inlet pipe 2, which is positioned in the primary buffer chamber 4, is provided with a plurality of through strip-shaped slits 6, the extending direction of the strip-shaped slits 6 is the same as that of the pipe wall of the air inlet pipe 2, and the end part of the air inlet pipe 2, which is positioned in the primary buffer chamber 4, is a closed blind end; the partition plate 7 is provided with at least one hole 8 penetrating through two end faces of the partition plate and/or at least one communicating pipe 9 for gas communication between the primary buffer chamber 4 and the secondary buffer chamber 5.

The exhaust coil 1 is used in a refrigerator compressor and is used for smoothing pulsating airflow formed after the piston reciprocates and is compressed, so that exhaust noise and pipeline vibration are reduced.

The exhaust coil 1 in the prior art only has a simple exhaust buffer cavity structure, pulse airflow is expanded for the second time in the exhaust buffer cavity, and the purpose of reducing exhaust pulsation is achieved, but the structure has limited noise reduction effect, and pulsation of certain specific frequency bands is difficult to weaken.

Compared with the prior art, the improvement key point of the air guide compressor is that a partition plate 7 is arranged in an exhaust buffer cavity, the exhaust buffer cavity is divided into a multi-stage buffer cavity through the partition plate 7, the flow path of refrigerating gas in the exhaust buffer cavity is prolonged through the arrangement of the multi-stage buffer cavity, the air guide buffer effect is improved by utilizing a multi-stage pressure reduction principle, and the airflow pulsation of the compressor is reduced;

secondly, a strip-shaped slit 6 is arranged on the pipe wall of the air inlet pipe 2, and the end part of the air inlet pipe 2 is a closed blind end, so that the phenomenon that the flow speed of inlet air flow is too high and the inlet air flow is directly sprayed onto a partition plate 7 to cause resonance of the exhaust coil pipe 1 and generate vibration noise is avoided, and the larger pipe diameter ratio between the exhaust coil pipe 1 and the air inlet pipe 2 is fully utilized, so that the pulse air flow obtains a better buffering effect;

thirdly, at least one hole 8 penetrating through two end faces of the partition board 7 and/or at least one communicating pipe 9 are/is arranged, the hole 8 and the communicating pipe 9 have the throttling effect and are communicated with the primary buffer chamber 4 and the secondary buffer chamber 5, so that pulsating airflow is expanded and buffered for many times, the flow speed of the airflow is reduced, and the silencing performance of the exhaust coil 1 can be effectively improved.

In some embodiments, as shown in fig. 3, an included angle between the central axis of the communication pipe 9 and the partition 7 is defined as 90 ° to 180 °, and there are a plurality of communication pipes 9, each communication pipe 9 having a different included angle with the partition 7. Therefore, the air flows entering the secondary buffer chamber 5 from the primary buffer chamber 4 have different jet directions, collide with each other and interfere with each other to offset a part of sound energy, and reduce vibration noise of the exhaust coil 1.

In some embodiments, as shown in fig. 2 and 3, the communication pipe 9 penetrates the partition 7, while in other embodiments, the communication pipe 9 is located on only one side of the partition 7. When the communicating pipe 9 penetrates through the partition plate 7, two ends of the communicating pipe 9 are respectively located in the first-stage buffer chamber 4 and the second-stage buffer chamber 5, when airflow enters the second-stage buffer chamber 5 from the first-stage buffer chamber 4, the airflow needs to pass through a longer distance, the airflow rubs with the pipe wall in the communicating pipe 9, partial sound energy is converted into heat energy to be released, and noise is further reduced.

In some embodiments, as shown in fig. 4, the communicating tube 9 is provided with a multi-stage expansion and contraction cavity 10. By providing the multistage expansion and contraction cavity 10 in the communication pipe 9, the airflow is further subjected to intense friction when contacting the inner wall of the communication pipe 9, and thus the sound energy is consumed or converted into heat energy.

In some embodiments, the exhaust buffer chamber has a cylindrical structure, and the ratio of the inner diameter of the inlet pipe 2 to the inner diameter of the exhaust buffer chamber is less than 0.27 and greater than 0.1. The flow velocity of the air flow can be reduced by increasing the inner diameter difference between the air inlet pipe 2 and the exhaust buffer cavity, but the excessive inner diameter difference can reduce the effect of offsetting noise through reflection, and therefore, the air flow needs to be set in a reasonable range.

In some embodiments, two of the strip-shaped slits 6 are included, and the two strip-shaped slits 6 are symmetrically arranged on two sides of the air inlet pipe 2. Through setting up two bar slits 6 symmetries, the tip shake of intake pipe 2 when avoiding jet-propelled reduces vibration noise.

In some embodiments, the number of the strip-shaped slits 6 is 1-6, and the ratio of the total ventilation area of the strip-shaped slits 6 to the total area of the pipe wall of the air inlet pipe 2 in the exhaust buffer cavity is 0.029-0.178. Improve 6 numbers of bar slit or increase 6 flow area of bar slit, can reduce the jet velocity of air current, reduce the air current and spout the vibration noise of exhaust cushion chamber inner wall, but too big flow area can reduce the reflection effect of air current, reduces the noise cancelling effect of specific frequency noise, consequently needs to set up in reasonable scope.

In some embodiments, the total ventilation area of the communication pipe 2 is S1, the total ventilation area of the holes 8 is S2, the area of the end surface profile of the partition plate 7 is S3, and S1+ S2 is not more than 0.4S 3. The total ventilating area of the communicating pipe 9 and the hole 8 is too large, which affects the reflection and noise reduction effect of the baffle plate 7, so that the range is limited to a reasonable range,

in some embodiments, as shown in fig. 3, the partition 7 is perpendicular to the central axis of the exhaust buffer cavity, the central axis of the inlet pipe 2 coincides with the central axis of the exhaust buffer cavity, and an angle between the central axis of the outlet pipe 3 and the central axis of the exhaust buffer cavity ranges from 30 ° to 150 °. Through setting up the slope with outlet duct 3, avoid flowing through the air current from baffle 7 and directly get into outlet duct 3, increase the diffusivity of air current, improve buffering effect.

Further, as shown in fig. 5, a spiral structure portion 11 is disposed at an end portion of the intake pipe 2 located in the exhaust buffer cavity, the strip-shaped slit 6 is located in the spiral structure portion 11, and the strip-shaped slit 6 has a same screwing direction as the spiral structure portion 11. Through set up helical structure portion 11 at intake pipe 2, make the air current that erupts have the angular velocity of slope, avoid spouting the air current and strike the exhaust cushion chamber perpendicularly and arouse the vibration noise, simultaneously, convert the perpendicular application of force of jet air current to intake pipe 2 into torsion to avoid the shake of intake pipe 2 tip, reduce the vibration noise, on the other hand, make the acoustic energy of stranded air current offset each other at spiral collision in-process, noise abatement.

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.