阅读说明：本技术 一种结冰风洞试验冰形切割装置及切割方法 (Icing wind tunnel test ice-shaped cutting device and cutting method ) 是由 张平涛 胡站伟 易贤 柳庆林 郭向东 熊建军 冉林 于 2021-09-07 设计创作，主要内容包括：本发明适用于风洞试验技术领域,提供了一种结冰风洞试验冰形切割装置及切割方法。本发明的切割装置包括支撑架、Y轴滑动装置和切割刀具；Y轴滑动装置固定在所述支撑架上,所述Y轴滑动装置包括至少两根Y轴光轴和Y轴滑块,所述Y轴滑块在所述Y轴光轴上滑动；所述Y轴滑块上固定安装所述切割刀具,所述切割刀具包括加热器和热管刀,所述热管刀可拆卸连接在所述加热器上。本发明采用热管刀作为切割用的热刀,其尺寸小,传热效率高,切割时对切割位置相邻区域的积冰影响小；由于切割时只存在1个切割点位,冷却介质吹扫角度与热刀始终保持同步,可以很好的保护切割相邻区域积冰处于低温状态而不融化,最大程度的保证了冰形获取的保真度。(The invention is suitable for the technical field of wind tunnel tests and provides an icing wind tunnel test ice-shaped cutting device and a cutting method. The cutting device comprises a support frame, a Y-axis sliding device and a cutting tool; the Y-axis sliding device is fixed on the supporting frame and comprises at least two Y-axis optical axes and Y-axis sliding blocks, and the Y-axis sliding blocks slide on the Y-axis optical axes; the Y-axis sliding block is fixedly provided with the cutting tool, the cutting tool comprises a heater and a heat pipe cutter, and the heat pipe cutter is detachably connected to the heater. The invention adopts the heat pipe cutter as the heat cutter for cutting, has small size and high heat transfer efficiency, and has little influence on the ice accretion in the adjacent area of the cutting position during cutting; because only 1 cutting point position exists during cutting, the cooling medium purging angle and the hot knife are always kept synchronous, accumulated ice in the adjacent cutting area can be well protected from being melted under the low-temperature state, and the fidelity of ice shape acquisition is guaranteed to the maximum extent.)

1. An icing wind tunnel test ice-shaped cutting device is characterized by comprising a support frame, a Y-axis sliding device (30) and a cutting tool (40);

the Y-axis sliding device (30) is fixed on the supporting frame, the Y-axis sliding device (30) comprises at least two Y-axis optical axes (31) and a Y-axis sliding block (32), and the Y-axis sliding block (32) slides on the Y-axis optical axes (31);

the Y-axis sliding block (32) is fixedly provided with the cutting tool (40), the cutting tool (40) comprises a heater (41) and a heat pipe knife (42), and the heat pipe knife (42) is detachably connected to the heater (41).

2. An icing wind tunnel test ice-shaped cutting device according to claim 1, further comprising a cooling device (50), wherein said cooling device (50) is arranged around said cutting tool (40), said cooling device (50) comprises a hose and a nozzle, said nozzle is connected to a front end of said hose, and a rear end of said hose is connectable to a cooling medium storage device.

3. The icing wind tunnel test ice-shaped cutting device according to claim 2, wherein the supporting frame comprises two symmetrically arranged sub-supports and a horizontal connecting rod (03), and each sub-support comprises a base (01) and an upright post (02);

the upright columns (02) are vertically fixed on the base (01), and the horizontal connecting rod (03) is transversely and fixedly arranged between the two upright columns (02).

4. The icing wind tunnel test ice-shaped cutting device according to claim 3, further comprising a Z-axis sliding device, wherein the Z-axis sliding device comprises a linear rail (13) and a Z-axis sliding block (14) which are arranged on each sub-bracket, the linear rail (13) is fixed on the upright post (02), and the Z-axis sliding block (14) slides on the linear rail (13);

a horizontal connecting plate is arranged between the two Z-axis sliding blocks (14), and threaded holes are formed in the horizontal connecting plate;

still include screw rod (11), screw rod pulley holder (12) and hand wheel (15), the one end screwed connection of screw rod (11) screw rod pulley holder (12), the other end with screw hole screwed connection, hand wheel (15) with screw rod pulley holder (12) are connected for hand wheel (15) rotate and drive screw rod (11) and rotate.

5. The icing wind tunnel test ice-shaped cutting device according to claim 4, further comprising an X-axis sliding device (20), wherein the X-axis sliding device (20) comprises an X-axis optical axis (21), an X-axis sliding block (22), a stop block and a pre-tightening force spring (23); one end of the X-axis optical axis (21) is perpendicular to the upright column (02) and is fixed on the Z-axis sliding block (14), and the other end of the X-axis optical axis is fixedly connected with the stop block; the X-axis sliding block (22) slides on the X-axis optical axis (21), and the pre-tightening force spring (23) is sleeved on the X-axis optical axis (21) and is arranged between the Z-axis sliding block (14) and the X-axis sliding block (22).

6. Icing wind tunnel test ice-shaped cutting device according to claim 5, characterized in that the heat pipe cutter (42) is parallel to the X-axis optical axis (21).

7. Icing wind tunnel test ice-shaped cutting device according to any one of claims 1 to 6, characterised in that the heater (41) is an eddy current heater.

8. The icing wind tunnel test ice-shaped cutting device according to any one of claims 3-6, wherein the base (01) is a magnetic base.

9. An icing wind tunnel test ice-shaped cutting method is characterized in that the icing wind tunnel test ice-shaped cutting device as claimed in claim 6 is used for cutting, and the method specifically comprises the following steps:

s10, fixing the icing wind tunnel test ice-shaped cutting device on the front edge of a model, moving the Y-axis slide block (32), and moving the heat pipe cutter (42) to one side of the Y-axis optical axis (31);

s20, rotating the hand wheel (15), adjusting the vertical height of the cutting knife (40), and enabling the hot tube knife (42) to be located at the same horizontal height of the ice shape acquisition position and locked;

s30, turning on the heater (41) to heat the hot pipe cutter (42) so that the hot pipe cutter (42) reaches a set temperature;

s40, starting the cooling device (50), and manually adjusting the purging angle and flow of the cooling medium to a proper angle and a proper flow;

s50, slowly moving the heat pipe cutter (42) to enable the heat pipe cutter (42) to move along the Y-axis direction, and enabling the top end of the heat pipe cutter (42) to abut against the surface of the model; meanwhile, the cooling medium synchronously blows and cools the accumulated ice at the adjacent cutting positions;

s60, the hot tube cutter (42) and the cooling device (50) are continuously moved until the ice on the ice accumulation sectional area is completely cut, and 1 ice-shaped cut is completed.

10. The icing wind tunnel test ice-shaped cutting method according to claim 9, wherein in step S60, the temperature of the heat pipe cutter (42) is adjusted according to the thickness of the accumulated ice at the cutting part and the cutting speed.

Technical Field

The invention relates to the technical field of wind tunnel tests, in particular to an icing wind tunnel test ice-shaped cutting device and a cutting method.

Background

When the aircraft passes through the low-temperature cloud layer rich in the supercooled liquid drops at low speed, the icing phenomenon is easily generated on the windward side of the aircraft, and the flight safety of the aircraft is seriously threatened by the icing. The development of an aircraft model icing test in an icing wind tunnel becomes an important link for the design and verification of an aircraft anti-icing and deicing system.

In an aircraft model icing test, the 2-dimensional cross-sectional shape (called ice shape for short) of ice accumulated on the surface of a model needs to be accurately obtained, and the accuracy and speed of obtaining the ice shape directly influence the quality and efficiency of the test. Currently, the ice shape acquisition of the icing wind tunnel mainly adopts a hot knife cutting device, and a hot knife of the hot knife cutting device is generally made by cutting a copper sheet with the same profile as the section of a model on the front edge. When in use, a copper sheet is heated to a high temperature, then a hot knife is horizontally inserted into accumulated ice at the front edge of a model needing to obtain an ice shape, the accumulated ice at the contact part is melted by utilizing the temperature of the copper sheet, the hot knife is drawn out after cutting is finished, and then prefabricated checkerboard paper is inserted for ice shape drawing, as disclosed in patent 201810768271. The method has the advantages of easy hot knife processing and simple operation. However, there are some disadvantages in obtaining accurate fidelity of ice shape, which are mainly expressed as follows:

1. when the ice shape is obtained by the method, the temperature of the hot knife is not controlled during cutting, and the initial temperature of the hot knife is high, so that the ice in the region with less accumulated ice is easily melted excessively to damage the ice shape. The low initial temperature of the hot knife causes the cutting difficulty of the region with much accumulated ice, and the hot knife needs to be heated for many times for repeated cutting, so that the ice shape of the region with less accumulated ice is further damaged, the fidelity obtained by the ice shape is not high, and the quality of test data is influenced.

2. The front edge molded line of the copper sheet hot knife in the mode needs to be customized according to the model, when the copper sheet hot knife is applied to a complex molded surface, if the space positioning precision of the hot knife is insufficient, a local ice accretion cutting blind area is easily caused, the existence of residual ice accretion causes that the front edge molded line of the checkered paper cannot be well attached to the model, and the drawn ice shape is distorted. Meanwhile, after the hot knife is machined, only the ice shape of the specific position of the model can be obtained, the ice shape obtaining point position sometimes needs to be increased according to the model icing condition in the test, and the hot knife needs to be machined again at the moment, so that the test efficiency is influenced.

3. When the ice shape is cut by the method, a plurality of persons are needed to work cooperatively, one person is responsible for the hot knife, and 2-3 persons use the quick-freezing agent to cool the accumulated ice on the upper surface of the ice knife, so that the ice shape is prevented from being damaged by excessive melting of the ice on the upper surface, and the efficiency is low.

4. When this mode cutting ice shape, often use the flame heating hot sword copper sheet of gas burning, this mode can not realize the accurate control to hot sword temperature, and the copper sheet is heated for a long time and the temperature and is relied on operating personnel's experience and to the color judgement after the copper sheet is heated. The copper sheet is heated by adopting an oven mode, although the temperature control of the copper sheet can be improved to a certain degree, the heated hot knife needs to be transferred to a wind tunnel model from a heating environment, the wind tunnel airflow is in a low-temperature condition during operation, and the copper sheet is easy to dissipate heat and cool to influence the cutting effect. The hot knife is dangerous to scald by operators in the transfer process, and the safety is poor.

Disclosure of Invention

In order to solve the technical problems, the invention provides an icing wind tunnel test ice-shaped cutting device and a cutting method. The invention is realized by the following steps:

an icing wind tunnel test ice-shaped cutting device comprises a support frame, a Y-axis sliding device and a cutting tool;

the Y-axis sliding device is fixed on the supporting frame and comprises at least two Y-axis optical axes and Y-axis sliding blocks, and the Y-axis sliding blocks slide on the Y-axis optical axes;

the Y-axis sliding block is fixedly provided with the cutting tool, the cutting tool comprises a heater and a heat pipe cutter, and the heat pipe cutter is detachably connected to the heater.

Further, the cutting tool further comprises a cooling device, the cooling device is arranged around the cutting tool and comprises a hose and a spray head, the spray head is connected to the front end of the hose, and the rear end of the hose can be connected to a cooling medium storage device.

Furthermore, the support frame comprises two symmetrically arranged sub-supports and a horizontal connecting rod, and each sub-support comprises a base and an upright post;

the stand vertical fixation is in on the base, two transversely fixed setting between the stand horizontal connecting rod.

Further, the device comprises a Z-axis sliding device, wherein the Z-axis sliding device comprises a linear rail and a Z-axis sliding block, the linear rail is arranged on each sub-bracket, and the Z-axis sliding block slides on the linear rail;

a horizontal connecting plate is arranged between the two Z-axis sliding blocks, and threaded holes are formed in the horizontal connecting plate;

the screw rod, screw rod pulley seat and hand wheel, the one end screwed connection of screw rod the screw rod pulley seat, the other end with screw hole screwed connection, the hand wheel with the screw rod pulley seat is connected for the hand wheel rotates and drives the screw rod and rotate.

The X-axis sliding device comprises an X-axis optical axis, an X-axis sliding block, a stop block and a pretightening force spring; one end of the X-axis optical axis is perpendicular to the upright column and is fixed on the Z-axis sliding block, and the other end of the X-axis optical axis is fixedly connected with the stop block; the X-axis sliding block slides on the X-axis optical axis, and the pre-tightening force spring is sleeved on the X-axis optical axis and is arranged between the Z-axis sliding block and the X-axis sliding block.

Further, the hot pipe cutter is parallel to the X-axis optical axis.

Further, the heater is an eddy current heater.

Further, the base is a magnetic base.

The icing wind tunnel test ice-shaped cutting method adopts the icing wind tunnel test ice-shaped cutting device for cutting, and specifically comprises the following steps:

s10, fixing the icing wind tunnel test ice-shaped cutting device on the front edge of a model, moving the Y-axis slide block, and moving the heat pipe cutter to one side of the Y-axis optical axis;

s20, rotating a hand wheel, adjusting the vertical height of the cutting knife, and enabling the heat pipe knife to be located at the same horizontal height of the ice-shaped acquisition position and locked;

s30, starting the heater to heat the hot tube cutter so that the hot tube cutter reaches a set temperature;

s40, starting a cooling device, and manually adjusting the purging angle and flow of the cooling medium to a proper angle and a proper flow;

s50, slowly moving the heat pipe cutter to enable the heat pipe cutter to move along the Y-axis direction, wherein the top end of the heat pipe cutter abuts against the surface of the model; meanwhile, the cooling medium synchronously blows and cools the accumulated ice at the adjacent cutting positions;

s60, the hot tube cutter and the cooling device are continuously moved until the ice on the ice-accretion cross section is completely cut, and 1 ice-shaped cut is completed.

Further, in step S60, the temperature of the hot pipe cutter is adjusted according to the thickness of the ice accumulated at the cutting portion and the cutting speed.

Compared with the prior art, the icing wind tunnel test ice-shaped cutting device and the cutting method have the following beneficial effects:

(1) the invention adopts the heat pipe cutter as the heat cutter for cutting, has small size and high heat transfer efficiency, and has little influence on the ice accretion in the adjacent area of the cutting position during cutting; because only 1 cutting point position exists during cutting, the nitrogen purging angle and the hot knife are always kept synchronous, accumulated ice in the adjacent cutting area can be well protected from being melted under the low-temperature state, and the fidelity of ice shape acquisition is guaranteed to the maximum extent;

(2) the heat pipe cutter adopts an eddy current heating mode, and has the advantages of high power density, high heating speed and flexible temperature control. The temperature of the hot knife can be adjusted in real time according to the ice accumulation condition of the cutting part during cutting by controlling the power of the eddy current heater, so that the optimal cutting effect is ensured.

(3) Because the rear end of the heat pipe cutter is provided with the spring action mechanism, the front edge of the heat pipe cutter is always tightly attached to the surface of the model in the cutting process, and no blind area and residue are generated in cutting;

(4) the support frame of the cutting device enables the cutting tool to move in the XYZ three directions, so that the ice-shaped cutting device can realize ice-shaped cutting at any horizontal position, is more flexible in selecting the ice-shaped acquisition position on the surface of the model, and can meet the multi-ice-shaped acquisition requirement in the test.

(5) Because this device degree of automation is high, easy operation, and cutting work 1 people just can accomplish, and efficiency is higher, low in labor strength.

(6) By adopting the cutting device, the hot knife which is consistent with the molded surface of the model to be tested is not required to be prepared before the ice shape is measured each time like the prior art, the test flow is simple, and the cutting device can be repeatedly used.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments of the present invention or in the description of the prior art will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic structural diagram of an icing wind tunnel test ice-shaped cutting device according to an embodiment of the invention.

In the figure, 01-base, 02-upright post, 03-horizontal connecting rod; 11-screw, 12-screw pulley seat, 13-linear rail, 14-Z-axis slider and 15-hand wheel; 20-X-axis sliding device, 21-X-axis optical axis, 22-X-axis sliding block and 23-pretightening force spring; 30-Y axis sliding device, 31-Y axis optical axis, 32-Y axis sliding block; 40-cutting knife, 41-heater, 42-hot tube knife, 50-cooling device.

Detailed Description

The following description provides many different embodiments, or examples, for implementing different features of the invention. The particular examples set forth below are illustrative only and are not intended to be limiting.

Example one

An icing wind tunnel test ice-shaped cutting device is shown in figure 1 and comprises a support frame, a Y-axis sliding device 30 and a cutting tool 40;

a Y-axis sliding device 30 is fixed on the support frame, the Y-axis sliding device 30 comprises at least two Y-axis optical axes 31 and Y-axis sliders 32, and the Y-axis sliders 32 slide on the Y-axis optical axes 31;

the cutting tool 40 is fixedly mounted on the Y-axis slider 32, the cutting tool 40 includes a heater 41 and a heat pipe knife 42, and the heat pipe knife 42 is detachably connected to the heater 41. Wherein, can dismantle the connection and insert this heat pipe sword on the heater when needing to use the heat pipe sword promptly, can dismantle the heat pipe sword when not using.

It is worth to be noted that the Y-axis sliding device and the Y-axis sliding block are both arranged along the Y axis and are mutually vertical to the X axis and the Z axis which are described below; the two Y-axis optical axes 31 penetrating through the Y-axis slider are adopted in the embodiment to fix the Y-axis slider in the XY plane, so as to ensure that the heat pipe cutter 42 fixed thereon can also be located in the XY plane, and preferably, the heat pipe cutter 42 is parallel to the X-axis optical axis 21.

The heat pipe cutter of the embodiment can be realized by adopting a conventional heat pipe cutter; because the heat pipe cutter is of a heat pipe structure, the heat pipe cutter is small in size and high in heat transfer efficiency, and the influence on ice accretion in the adjacent area of a cutting position is small during cutting.

Preferably, the heater 41 is an eddy current heater, and the eddy current heating method has high power density, high heating speed, and flexible temperature control. The temperature of the hot knife can be adjusted in real time according to the ice accumulation condition of the cutting part during cutting by controlling the power of the eddy current heater, so that the optimal cutting effect is ensured.

The ice-shaped cutting device of the present embodiment further includes a cooling device 50, the cooling device 50 is disposed around the cutting tool 40, the cooling device 50 includes a hose and a nozzle, the nozzle is connected to the front end of the hose, the rear end of the hose is connectable to a cooling medium storage device, as shown in fig. 1, the hose is fixed below the Y-axis slider in the drawing, the position and angle of the jet flow of the hose can be manually changed, and it can be understood by those skilled in the art that the hose can also be fixed at other positions of the Y-axis slider, such as the left and right sides, or above, even another slider fixing hose is separately provided, as long as the nozzle at the front end of the hose can be placed near the position where the hot pipe cutter cuts accumulated ice.

The cooling medium is preferably nitrogen, which can cool the ice accretion adjacent to the cutting and blow away a small amount of melted water.

Further, as shown in fig. 1, the support frame includes a left sub-support and a right sub-support, which are symmetrically disposed, and a horizontal connecting rod 03, wherein the two vertical columns 02 are vertically fixed on the base 01, and the horizontal connecting rod 03 is transversely fixed between the two vertical columns 02. In order to fix the support frame in the test position, the base 01 is preferably a magnetic base which is fixed to the wind tunnel lower wall plate at the front edge of the model by magnetic attraction.

Meanwhile, in order to enable the cutting device of the invention to cut the accumulated ice at different height positions, the embodiment is further provided with a Z-axis sliding device, the Z-axis sliding device comprises a linear rail 13 and a Z-axis sliding block 14, the linear rail 13 is fixed on the upright column 02, and the Z-axis sliding block 14 slides on the linear rail 13; that is, each sub-mount is provided with a wire rail 13 and a Z-axis slider 14; a horizontal connecting plate is arranged between the two Z-axis sliding blocks 14, and threaded holes are formed in the horizontal connecting plate; the screw rod 11, the screw rod pulley seat 12 and the hand wheel 15 are further included, one end of the screw rod 11 is in threaded connection with the screw rod pulley seat 12, the other end of the screw rod 11 is in threaded connection with the threaded hole, and the hand wheel 15 is connected with the screw rod pulley seat 12, so that the hand wheel 15 rotates to drive the screw rod 11 to rotate.

When the hand wheel 15 rotates, the screw rod 11 is driven to rotate through the transmission of the screw rod pulley seat, the screw rod 11 rotates to enable the connecting plate which is in threaded connection with the screw rod to vertically move, so that the Z-axis sliding block is driven to vertically move, and finally the function of driving the cutting tool and the cooling device which are fixed on the Z-axis sliding block to vertically move is achieved.

When the heat pipe cutter 42 is used, one end of the heat pipe cutter needs to be abutted against the surface of the model when moving along the Y-axis direction to cut accumulated ice, so that the accumulated ice is completely cut through during cutting. In order to ensure that the heat pipe cutter abuts against the surface of the model, the cutting device provided by the embodiment of the invention is further provided with an X-axis sliding device 20, wherein the X-axis sliding device 20 comprises a left X-axis optical axis 21, a left X-axis sliding block 22, a left stop block, a right stop block and a left pre-tightening spring 23; one end of the X-axis optical axis 21 is perpendicular to the upright column 02 and is fixed on the Z-axis sliding block 14, and the other end of the X-axis optical axis is fixedly connected with a stop block; the X-axis sliding block 22 slides on the X-axis optical axis 21, and the pre-tightening force spring 23 is sleeved on the X-axis optical axis 21 and is arranged between the Z-axis sliding block 14 and the X-axis sliding block 22; the Y-axis optical axis 31 is fixedly connected between the left and right X-axis sliders 22. In this embodiment, two X-axis sliders 22 are respectively disposed on the left and right sides, and each slider is fixedly connected to one end of one X-axis optical axis, but this way is not intended to limit the present invention.

From this, pretightning force spring 23 is through applying the mode of thrust with heat pipe sword 42 butt on the model surface to the X axle slider all the time for the cutting does not have the blind area, does not have the residue, thereby provides the guarantee for ice shape measuring accuracy.

Meanwhile, in order to ensure the stability of the support frame, some reinforcing members are further provided in the embodiment of the present invention, as shown in fig. 1, which is not described herein again.

Example two

The embodiment relates to a method for performing ice shape cutting by adopting an icing wind tunnel test ice shape cutting device in the first embodiment, which specifically comprises the following steps:

s10, fixing the icing wind tunnel test ice-shaped cutting device on the front edge of a model, moving the Y-axis slide block 32, and moving the heat pipe cutter 42 to one side of the Y-axis optical axis 31;

at the moment, the magnetic base is fixed on a wall plate under the wind tunnel at the front edge of the model through magnetic attraction;

s20, rotating the hand wheel 15, adjusting the vertical height of the cutting knife 40, and enabling the heat pipe knife 42 to be located at the same horizontal height of the ice shape acquisition position and locked;

s30, turning on the heater 41 to heat the hot pipe cutter 42, so that the hot pipe cutter 42 reaches a set temperature;

s40, starting the cooling device 50, and manually adjusting the purging angle and flow rate of the cooling medium to a proper angle and a proper flow rate;

in steps S30 and S40, the set temperature of the hot pipe cutter, the purge angle and the flow rate of the cooling medium (such as nitrogen gas) are set according to the experience of those skilled in the art;

s50, moving the heat pipe cutter 42 slowly, so that the heat pipe cutter 42 moves along the Y-axis direction, and the top end of the heat pipe cutter 42 abuts against the surface of the model; meanwhile, the cooling medium synchronously blows and cools the accumulated ice at the adjacent cutting positions;

s60, the hot tube cutter 42 and the cooling device 50 are continuously moved until the ice on the ice-accreted section area is completely cut, and 1 ice-shaped cut is completed.

During the continuous movement of the heat pipe cutter 42, the technician may adjust the temperature of the heat pipe cutter empirically, for example, according to the thickness of the ice accretion at the cutting site and the cutting speed; in general, the thickness of the accumulated ice is thickened, the temperature is increased by a proper amount, or the cutting speed is slowed down; the cutting speed is increased and the temperature is increased in a proper amount.

The cutting device adopts the heat pipe cutter as the cutting tool, has small size and high heat transfer efficiency, and has small influence on the ice accumulation of the adjacent area of the cutting position during cutting. Because only 1 cutting point position exists during cutting, the cooling medium blowing angle and the heat pipe cutter are always kept synchronous, accumulated ice in the adjacent cutting area can be well protected from being melted under the low-temperature state, and the fidelity of ice shape acquisition is guaranteed to the maximum extent.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.