阅读说明：本技术 航空发动机非全环风扇叶片的旋转冲击试验装置 (Rotary impact test device for non-full-ring fan blade of aero-engine ) 是由 唐振南 王祯鑫 杨坤 侯乃先 于 2020-04-03 设计创作，主要内容包括：本发明提供了一种航空发动机非全环风扇叶片的旋转冲击试验装置,其包括转子试验台和气炮系统,转子试验台包括防护机匣,承力框架、转轴、风扇组件和阻通盘,承力框架固定在防护机匣内,转轴通过多个轴承装置水平地固定在承力框架上,转轴的一端连接电机,风扇组件安装在转轴的另一端,且阻通盘安装在转轴的另一端的端部,阻通盘上开设有至少一通口,阻通盘和风扇组件同步转动；当气炮系统向转子试验台发射外物时,阻通盘阻挡住非预期冲击工况下的外物。本发明对于常规的外物冲击损伤,只需安装3个叶片,节省叶片个数,从而节省试验成本,对于价格高昂的风扇叶片如复合材料风扇叶片,能极大地节省试验成本。(The invention provides a rotary impact test device for non-full-ring fan blades of an aircraft engine, which comprises a rotor test bed and an air gun system, wherein the rotor test bed comprises a protective casing, a force-bearing frame, a rotating shaft, a fan assembly and a blocking disc, the force-bearing frame is fixed in the protective casing, the rotating shaft is horizontally fixed on the force-bearing frame through a plurality of bearing devices, one end of the rotating shaft is connected with a motor, the fan assembly is arranged at the other end of the rotating shaft, the blocking disc is arranged at the end part of the other end of the rotating shaft, at least one through hole is formed in the blocking disc, and the blocking disc and the fan assembly synchronously rotate; when the air gun system launches a foreign object to the rotor test bed, the blocking disc blocks the foreign object under an unexpected impact working condition. For the impact damage of the conventional foreign objects, only 3 blades are needed to be installed, the number of the blades is saved, the test cost is saved, and the test cost can be greatly saved for the high-price fan blades such as composite material fan blades.)

1. A rotary impact test device for non-full-ring fan blades of an aircraft engine is characterized by comprising a rotor test bed and an air gun system, wherein the rotor test bed comprises a protective casing, a bearing frame, a rotating shaft, a fan assembly and a blocking disc, the bearing frame is fixed in the protective casing, the rotating shaft is horizontally fixed on the bearing frame through a plurality of bearing devices, one end of the rotating shaft is connected with a motor, the fan assembly is installed at the other end of the rotating shaft, the blocking disc is installed at the end part of the other end of the rotating shaft, at least one through hole is formed in the blocking disc, and the blocking disc and the fan assembly rotate synchronously;

when the air gun system launches a foreign object to the rotor test bed, the blocking disc blocks the foreign object under an unexpected impact working condition.

2. The rotary impact testing apparatus for an aircraft engine non-full ring fan blade as defined in claim 1, wherein said fan assembly comprises a fan disc, a plurality of fan blades and fan blade weights, said fan blades and said fan blade weights being mounted on said fan disc, said fan disc being mounted on said shaft.

3. The rotary impact testing apparatus for an aircraft engine non-full ring fan blade as defined in claim 2, wherein said fan blade comprises 2 blades or 3 blades.

4. The rotary impact testing device for the non-full-circle fan blade of the aircraft engine as claimed in claim 1, wherein the bearing device comprises a bearing seat and a bearing, and the bearing seat is connected with the bearing frame.

5. The rotary impact testing apparatus for an aero-engine non-full ring fan blade as claimed in claim 2 wherein the setting angle of said port with respect to a first of said fan blades satisfies the formula 6 x ω x L/v;

wherein omega is the rotating speed of the blade, L is the axial distance between the blocking disc and the impact position of the blade, and v is the impact speed of the foreign object.

6. The device for testing the rotational impact of a non-full-circle fan blade of an aircraft engine according to claim 5, wherein the angle corresponding to the circumferential arc length of the through opening satisfies the formula 6 x ω x Z/v- θ;

wherein omega is the rotating speed of the blades, v is the impact speed of the foreign object, Z is the length of the foreign object, and theta is the included angle between the adjacent blades.

7. The rotary impact testing apparatus for an aircraft engine non-full ring fan blade as defined in claim 5, wherein a radial width of said port is greater than an outer diameter of said foreign body.

8. The rotary impact testing apparatus for an aircraft engine non-full-circle fan blade as defined in claim 5, wherein a radius of a center of the port is equal to a radius of a point of impact of the fan blade.

9. The rotary impact testing apparatus for an aircraft engine non-full ring fan blade as defined in claim 5, wherein said port is a scalloped hole.

10. The rotary impact testing apparatus for an aero-engine non-all-ring fan blade according to claim 1, wherein the gas gun system comprises a high pressure gas tank, a valve, a gun barrel, a tachometer sensor, and a hulling device, the gun barrel is connected to the high pressure gas tank, the valve is installed at an inlet of the gun barrel, the tachometer sensor is installed on the gun barrel, and the hulling device is installed outside an outlet of the gun barrel.

Technical Field

The invention relates to the field of a rotary impact test of an aero-engine blade, in particular to a rotary impact test device of a non-full-ring fan blade of an aero-engine.

Background

In the field of aero-engines, with the increasing requirements of people on low energy consumption and high efficiency of aero-engines, the adoption of larger and lighter fan blades has become the mainstream development trend of aero-turbofan engine fan blades at present. Composite materials are increasingly used for fan blades of turbofan engines due to their advantages of low density, high specific strength and high specific stiffness.

The fan blades of the civil aviation turbofan engine are used as a rotating mechanism with high suction force and large cross section area, and are very easy to be impacted by foreign objects (such as birds, ice flakes, tire fragments, runway redundant objects and the like), so that the impact damage of the foreign objects is caused. Because the rotating speed of the fan blades is high, the impact action time is short, and the impact energy is very concentrated in time and space, the fan blades can be damaged, deformed, broken, quickly dropped and the like, the blade tip clearance is changed, the pneumatic performance and the rotor balance of an engine are influenced, and secondary damage and even a casing breakdown are caused. These effects make the engine unable to work normally, threaten the reliability of engine work directly, and the light person leads to engine impact area mechanical damage and vibration, and the heavy person leads to the catastrophic consequence of machine destruction people's death.

Therefore, the aircraft engine usually needs to perform foreign matter suction tests such as bird sucking, ice sucking and the like to verify the safety of the engine. Common test methods are static single blade impact test, single blade rotary impact test, and full ring blade rotary impact test.

Firstly, a rotor table is not needed in a static single blade impact test, only one blade is needed, the cost is the lowest, the influence of centrifugal force on the rigidity/strength/shape/size of the blade is not considered in the test, the test result needs to be corrected, the most dangerous position of impact damage of foreign objects of a fan blade is close to the blade tip, the speed of the blade at the blade tip is close to or even exceeds the sound velocity, so the linear speed of the blade tip needs to be superposed on the impact speed of the foreign objects in the static blade impact test, and the requirement on a launching device of the foreign objects is high.

Therefore, the influence of centrifugal force on the blade is not considered in the static single blade impact test, the test result needs to be corrected, the linear speed of the blade at the impact position needs to be superposed on the speed of the foreign object, the impact speed of the foreign object is close to or even exceeds the sound speed, and the difficulty of launching the foreign object is increased.

Secondly, in the single-blade rotating impact test, a single rotating blade is adopted to simulate the influence of centrifugal force on the blade under the real condition, and a foreign object is usually driven in a free-falling mode, but the influence of the change of the geometric shape/surface state/kinetic energy and the like of the foreign object on the impact damage of the subsequent blade after the adjacent blade cuts the foreign object is not considered, and the influence of the damaged and fallen blade on the subsequent blade is not considered.

Therefore, the single blade rotation impact test does not consider the complex influence between adjacent blades and between the blades and foreign objects under the real condition, for example, the impact damage caused by impact of the damaged and fallen blades of the preceding blades and the cut foreign objects on the blades is not considered.

In addition, the full-ring blade rotation impact test needs a rotor test bed, the influence of centrifugal force on the blades can be really considered, the shooting time of foreign objects does not need to be considered, and the influence of the preorder blades on the cutting of the foreign objects and the impact damage of damaged blades on the subsequent blades after the damaged blades fall quickly can be really considered. However, for high cost fan blades such as composite fan blades, the full-ring blade greatly increases the test cost, and at the initial stage of blade design, the full-ring blade manufactured without test and check has the risks of test failure, structural design failure and even scrapping of a whole circle of blade.

It can be seen that the spin-impact test of a full-circle blade requires the manufacture of a full-circle blade, which is costly for expensive fan blades such as composite fan blades, and that the full-circle blade is wasted if the blade fails the spin-impact test at the early design stage.

In view of the above, those skilled in the art have devised a device for testing the rotational impact of a non-full-circle fan blade of an aircraft engine in order to overcome the above technical problems.

Disclosure of Invention

The invention aims to overcome the defects that a rotary impact test device in the prior art is high in structural requirement and cost, and easily damages blades, and the like, and provides a rotary impact test device for non-full-ring fan blades of an aero-engine.

The invention solves the technical problems through the following technical scheme:

a rotary impact test device for non-full-ring fan blades of an aircraft engine is characterized by comprising a rotor test bed and an air gun system, wherein the rotor test bed comprises a protective casing, a bearing frame, a rotating shaft, a fan assembly and a blocking disc, the bearing frame is fixed in the protective casing, the rotating shaft is horizontally fixed on the bearing frame through a plurality of bearing devices, one end of the rotating shaft is connected with a motor, the fan assembly is installed at the other end of the rotating shaft, the blocking disc is installed at the end part of the other end of the rotating shaft, at least one through hole is formed in the blocking disc, and the blocking disc and the fan assembly rotate synchronously;

when the air gun system launches a foreign object to the rotor test bed, the blocking disc blocks the foreign object body under an unexpected impact working condition.

According to one embodiment of the invention, the fan assembly includes a fan disc, a plurality of fan blades and fan blade weights mounted on the fan disc, the fan disc being mounted on the shaft.

According to one embodiment of the invention, the fan blade comprises 2 blades or 3 blades.

According to one embodiment of the invention, the bearing device comprises a bearing seat and a bearing, wherein the bearing seat is connected with the bearing frame.

According to one embodiment of the invention, the mounting angle of the through opening relative to the first fan blade satisfies the formula 6 x ω x L/v;

wherein omega is the rotating speed of the blade, L is the axial distance between the blocking disc and the impact position of the blade, and v is the impact speed of the foreign object.

According to one embodiment of the invention, the angle corresponding to the circumferential arc length of the through opening meets the formula of 6 multiplied by omega multiplied by Z/v-theta;

wherein omega is the rotating speed of the blades, v is the impact speed of the foreign object, Z is the length of the foreign object, and theta is the included angle between the adjacent blades. .

According to an embodiment of the invention, the radial width of the through opening is larger than the outer diameter of the foreign body.

According to one embodiment of the invention, the radius of the center of the through opening is equal to the radius of the point of impact of the fan blade.

According to one embodiment of the invention, the through openings are scallops.

According to one embodiment of the invention, the gas gun system comprises a high-pressure gas tank, a valve, a gun barrel, a speed sensor and a shelling device, wherein the gun barrel is connected with the high-pressure gas tank, the valve is installed at the inlet of the gun barrel, the speed sensor is installed on the gun barrel, and the shelling device is installed outside the outlet of the gun barrel.

The positive progress effects of the invention are as follows:

the rotary impact test device for the non-full-ring fan blade of the aero-engine has the following advantages:

for the impact damage of the conventional foreign objects, only 3 blades are needed to be installed, the number of the blades is saved, the test cost is saved, and the test cost can be greatly saved for the high-price fan blades such as composite fan blades.

And secondly, unexpected impact damage caused by foreign objects to the rotation test platform is avoided, and the cost for replacing the structural part of the test platform is avoided.

And thirdly, the blade is prevented from being damaged or even destroyed by unexpected impact, and is prevented from being damaged by secondary impact, and the cost of replacing the blade is avoided.

And fourthly, when the rotating blade is impacted by a foreign object, the expected impact working condition is ensured, and a real impact damage result is obtained.

Drawings

The above and other features, properties and advantages of the present invention will become more apparent from the following description of the embodiments with reference to the accompanying drawings in which like reference numerals denote like features throughout the several views, wherein:

FIG. 1 is a schematic structural diagram of a rotary impact test device for a non-full-circle fan blade of an aircraft engine.

FIG. 2 is a schematic view of a blocking disk in a rotating shaft direction in the device for testing the rotating impact of the non-full-ring fan blade of the aero-engine according to the invention.

FIG. 3 is a schematic diagram of a foreign object body passing through a blocking disc in the rotary impact test device for the non-full-circle fan blade of the aero-engine of the present invention. The fan blade rotation direction is counterclockwise.

FIG. 4 is a schematic view of an external object body blocked by a blocking disk in the rotary impact testing device for the non-full-circle fan blade of the aero-engine according to the present invention. The fan blade rotation direction is counterclockwise.

[ reference numerals ]

Rotor test stand 10

Gas gun system 20

Protective casing 11

Bearing frame 12

Rotating shaft 13

Fan assembly 14

Blocking disk 15

Electric machine 16

Blocking disk port 151

Block plate counterweight 152

Fan disk 141

Fan blade 142

Fan blade counterweight 143

Bearing block 17

Bearing 18

Blade speed omega

Axial distance L between blocking disc and impact point of blade

Center radius of through opening A

Radial width B of the through opening

Included angle C between opening and impact point

Circumferential angle D of the through opening

Angle theta between adjacent blades

High pressure gas tank 21

Valve 22

Gun barrel 23

Velocity measuring sensor 24

Hulling apparatus 25

Foreign object projectile 30

Foreign body 40

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

Further, although the terms used in the present invention are selected from publicly known and used terms, some of the terms mentioned in the description of the present invention may be selected by the applicant at his or her discretion, the detailed meanings of which are described in relevant parts of the description herein.

Furthermore, it is required that the present invention is understood, not simply by the actual terms used but by the meaning of each term lying within.

FIG. 1 is a schematic structural diagram of a rotary impact test device for a non-full-circle fan blade of an aircraft engine. FIG. 2 is a schematic view of a blocking disk in a rotating shaft direction in the device for testing the rotating impact of the non-full-ring fan blade of the aero-engine according to the invention. FIG. 3 is a schematic diagram of a foreign object body passing through a blocking disc in the rotary impact test device for the non-full-circle fan blade of the aero-engine of the present invention. FIG. 4 is a schematic view of an external object body blocked by a blocking disk in the rotary impact testing device for the non-full-circle fan blade of the aero-engine according to the present invention.

The non-full-ring fan blade is adopted for carrying out the rotating impact test, the rotating impact test of the non-full-ring fan blade has high requirement on the time for launching foreign objects, and for the fan blade with the rotating speed of 4000RPM, the time for one circle of rotation of the rotor is 0.015 second. Assuming that the actual number of fan blades is 20, the time interval between two blades is only 0.75 milliseconds, and the response time of the air cannon has uncertainty in the order of milliseconds or even tens of milliseconds, so that the target position of the target blade in one hit is difficult to achieve in actual operation, and repeated attempts are needed.

If the opportunity is not right, the space is left, and foreign objects of the rotor test bed structure can be damaged. If the firing timing is slightly advanced, foreign objects (such as birds and ice flakes) can be caused to impact the first mounting blade without cutting the preceding blade, causing unintended and secondary damage (the first blade breaks and then impacts the subsequent blade). If the firing timing is delayed, a small portion of the soft foreign object (e.g., bird) is cut by the last blade and the remaining foreign object impacts the structural members of the rotor test stand causing an unintended level of damage to the last blade and damage to the test stand structure.

After trying the experiment at every turn, all will change the blade and the experimental structure of damage, increase test cost, based on this, this application has set up on the rotatory impact test device of non-full ring blade and has blocked the logical dish, can avoid unexpected impact condition to cause unexpected impact damage for blade and test bench structure.

As shown in FIGS. 1 to 4, the invention discloses a rotary impact test device for a non-full-circle fan blade of an aircraft engine, which comprises a rotor test bed 10 and an air gun system 20. Wherein, rotor test bench 10 is including protection machine casket 11, bearing frame 12, pivot 13, fan assembly 14 and logical dish 15 of hindering, bearing frame 12 is fixed in protection machine casket 11, pivot 13 is fixed on bearing frame 12 through a plurality of bearing device levels, motor 16 is connected to the one end of pivot 13, the other end of fan assembly 14 installation pivot 13, and the tip at the other end of pivot 13 is installed to logical dish 15 of hindering, hinder and lead to having seted up an at least opening 151 on the dish 15, for avoiding hindering to lead to the vibration problem that dish 15 rotates the back unbalance and lead to, increase on hindering logical dish 15 and hinder and lead to a dish balancing weight 152, hinder logical dish 15 and fan assembly 14 synchronous revolution. When the gas cannon system 20 fires a foreign object cannonball 30 onto the rotor test stand 10, the blocking disc 15 blocks the foreign object body 40 under unexpected impact conditions.

Typically the fan blade rotation direction is counter clockwise. The through holes are formed in the blocking disc 15, so that the axial symmetry of the blocking disc is damaged, the vibration problem caused by unbalance can occur when the blocking disc 15 is installed on a rotor, and the blocking disc 15 needs to be trimmed on a dynamic balancing machine. According to the result of dynamic balance, a blocking disc balancing weight 152 is added to the corresponding position of the blocking disc 15, so that the final blocking disc 15 can have good dynamic balance performance in the rotating speed range of the blade.

Preferably, the fan assembly 14 of the present embodiment includes a fan plate 141, a plurality of fan blades 142 and a fan blade weight 143, the fan blades 142 and the fan blade weight 143 are mounted on the fan plate 141, and the fan plate 141 is mounted on the rotating shaft 13.

The fan blades 142 here may preferably comprise 2 blades or 3 blades.

The bearing device can comprise a bearing seat 17 and a bearing 18, and the bearing seat 17 is connected with the bearing frame 12. The bearing 18 is installed in the bearing seat 17, the rotating shaft 13 is arranged in the bearing 18 in a penetrating mode, and the bearing 18 supports the rotating shaft 13.

It is further preferred that the distance between the center of port 151 to the center of the block disk 15 (i.e., radius a of port 151) is consistent with the radius of the critical impact location. The radial width B of the through opening 151 is greater than the outer diameter of the foreign body 40. The mounting angle C between the through opening 151 and the first blade of the fan blades 142 is 6 x ω x L/v, wherein ω is the rotating speed of the fan blades 142, L is the axial distance between the blocking disc 15 and the impact position of the fan blades 142, v is the impact speed of the foreign object cannonball 30, and θ is the included angle between the adjacent fan blades 142.

When the blocking disc 15 is mounted on the rotating shaft 13, the relative angle C is fixed, and the blocking disc 15 and the fan blades 142 rotate synchronously. This ensures that foreign objects are first cut by the first blade, and then the remaining foreign objects after cutting strike the second blade and are cut by the second blade, ensuring that foreign objects passing through the barrier disc strike the second fan blade in a true state.

The through opening 151 may here preferably be a fan-shaped hole. Sector angle D of port 151 satisfies the formula: 6X ω XZ/v- θ. Wherein omega is the rotating speed of the blades, v is the impact speed of the foreign object, Z is the length of the foreign object, and theta is the included angle between the adjacent blades.

For example, in one embodiment, the axial distance L between the blocking disc and the impact point of the fan blade is 0.05m, the included angle theta between the adjacent fan blades is 15 degrees, the rotating speed omega of the fan blade is 4000RPM, the impact speed v of a foreign object is 200m/s, the outer diameter d of the foreign object is 0.1m, the length Z of the foreign object is 0.2m, and the radius r of the impact position of the fan blade is 0.8 m. The radius at the centre of the opening of the blocking disk is 0.8m and the width of the opening should be greater than 0.1m, here 0.12m, the opening sector angle is 9 ° and the mounting angle between the opening and the point of impact of the fan blade is 6 °.

Preferably, the air gun system 20 in this embodiment includes a high pressure air tank 21, a valve 22, a gun barrel 23, a tacho sensor 24, and a hulling device 25, the gun barrel 23 is connected to the high pressure air tank 21, the valve 22 is installed at an inlet of the gun barrel 23, the tacho sensor 24 is installed on the gun barrel 23, and the hulling device 25 is installed outside an outlet of the gun barrel 23.

According to the structural description, the use mode of the rotary impact test device for the non-full-ring fan blade of the aero-engine is as follows:

as shown in FIG. 1, the right part is the rotor test stand 10, the fan blades 142 and the fan blade balancing weights 143 are installed on the fan disk 141, wherein the number of the blades is only used as reference. For example, the number of blades of fan blade 142 may be only 2 when considering only the cutting effect of the preceding blades on the foreign object. The number of blades of fan blade 142 is at least 3 when further consideration is given to the effect of chipping off of an impinging blade on a subsequent blade. The fan disk 141 is connected to the rotary shaft 13 and is rotated by the motor 16, and the rotary shaft 13 is supported by the bearing support base 17 through the bearing 18. In the figure 1, the number of the bearings 18 is only used as reference, the supporting seat 17 is connected with the bearing frame 12, the bearing frame 12 is connected with a foundation, the rotating shaft 13 which is at a distance L from the front end of the fan blade 142 is provided with the blocking disc 15, the blocking disc 15 and the rotating shaft 13 rotate at the same rotating speed, and the periphery of the fan blade 142 is connected with the bearing frame 12 to form the protective casing 11.

The foreign object shells 30 are fired through the gas gun system 20, the gas gun system 20 is shown in the left side of fig. 1, the gas pressure in the high pressure gas tank 21 is adjusted according to the velocity required by the foreign object, when the valve 22 is opened, the foreign object shells 30 loaded in the barrel 23 are fired through the velocity measuring sensor 24 along the barrel 23 by the high pressure gas, and the shells 30 are shelled by the shelling means 25.

The blocking disk 15 may adopt any structure form to block the foreign object under the unexpected impact condition, so as to ensure that the impact between the foreign object passing through the blocking disk 15 and the fan blades 142 is expected to obtain the expected impact response result of the rotating blades.

As shown in fig. 3, when the firing timing of the foreign object shell 30 falls within the impact window of the fan blades 142, the shelled foreign object body 40 (shown in fig. 3) of the foreign object shell 30 passes through the baffle plate 15 and makes an expected impact with the fan blades 142.

As shown in fig. 4, when the firing opportunity of the foreign object cannonball 30 is not within the impact window period of the fan blade 142, the foreign object body 40 is blocked by the blocking disc 15 (as shown in fig. 4), so that the unexpected impact damage of the foreign object body 40 to the fan blade 142 and the test bed structural component is avoided, and the replacement cost of the blade/test bed structural component is saved.

The invention is based on the fact that the influence of centrifugal force on the blades cannot be ignored, and a rotating test bed is adopted to apply normal rotating speed to the blades so as to consider the centrifugal force. In the aspect of determining the number of the blades, if the impact damage caused by the change of parameters such as shape/kinetic energy after foreign objects are cut is considered, 2 blades are needed, and if the impact damage caused by the falling blocks of the impact damaged blades to the subsequent blades is further considered, at least 3 blades are needed.

In addition, the blades are adjacently installed on a fan disc, balancing weights are installed in the other mortises of the fan disc, the fan disc is installed on a rotating shaft, the rotating shaft is supported through a bearing, the bearing is connected to a bearing casing through a bearing seat, the bearing casing is connected with a foundation through a connecting piece, and a protective casing is arranged on the periphery of the fan to perform safety protection.

The front end of the fan disc adopts a blocking disc to block foreign objects in unexpected impact states. The blocking disk is provided with through holes, and foreign objects which meet the expected impact state can pass through the through holes on the blocking disk so as to impact on the fan blades. The size of the through hole of the blocking disc and the installation angle of the through hole are obtained through the conversion of the position of the group through disc and the impact parameters.

Therefore, the rotary impact test device for the non-full-ring fan blade can be obtained, and can ensure that foreign objects cannot impact the blade or the rotary table at unexpected impact time, avoid causing unnecessary structural damage and avoid increasing test cost. Ensuring that the foreign objects impact on the blade at the expected impact time to obtain the expected dynamic response result.

While specific embodiments of the invention have been described above, it will be appreciated by those skilled in the art that these are by way of example only, and that the scope of the invention is defined by the appended claims. Various changes and modifications to these embodiments may be made by those skilled in the art without departing from the spirit and scope of the invention, and these changes and modifications are within the scope of the invention.