BACKGROUND

The present invention relates to x-ray targets. X-ray devices of all types employ a cathode and an x-ray target, which serves as an anode. A voltage is connected across the cathode and the x-ray target to create a potential difference between the cathode and the x-ray target. Electrons emitted by the cathode are accelerated across the potential and collide with the x-ray target so as to produce x-rays.

The x-ray target must withstand high temperature operating conditions. The x-ray generation process causes the x-ray target to reach operating temperatures as high as several thousand degrees Celsius. The higher an x-ray device's radiation requirement, or x-ray power, the higher the operating temperature of the x-ray target. Thus, the x-ray target must be constructed from materials that can withstand x-ray generation operating temperatures.

Although all x-ray target materials experience high operating temperatures, the target track experiences the highest operating temperatures because it is the focal point of the x-ray generating process. In some high powered x-ray applications, the operating temperatures surpass the thermo-mechanical limitations of typical target track materials, and thus the target track fails. Past attempts to overcome thermo-mechanical limitations of the target track include increasing the overall x-ray target size, or rotating the x-ray target at higher rates. These actions focus on spreading the generated heat over a larger surface area to increase heat dissipation.

Larger x-ray target designs and higher rotation rates lead to several undesirable x- ray device characteristics, including: heavier x-ray targets, bigger x-ray tube housings, larger gantries, and slower access time. Moreover, these characteristics pose reliability problems associated with material strength limitations and significantly increase the cost of high powered x-ray devices.

BRIEF SUMMARY OF AN EXAMPLE EMBODIMENT OF THE INVENTION

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential characteristics of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. In one example, an x-ray target comprises a target track, a substrate, and a backing. The target track includes a base material and a grain growth inhibitor to reduce or prevent microstructure grain growth in the base material.

BRIEF DESCRIPTION OF THE DRAWINGS

To clarify certain aspects of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which are illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail through the use of the accompanying drawings.

Figure 1 illustrates a cross-sectional view of an example x-ray device;

Figure 2 illustrates a cross-sectional view of an example x-ray target; and

Figure 3 illustrates a flow diagram of an example method of making an x-ray target.

DETAILED DESCRIPTION OF SOME EXAMPLE EMBODIMENTS

Reference will now be made to the drawings to describe various aspects of some example embodiments of the invention. The drawings are only diagrammatic and schematic representations of such example embodiments and, accordingly, are not limiting of the scope of the present invention, nor are the drawings necessarily drawn to scale. Embodiments of the invention relate to x-ray devices, x-ray targets, and methods for making x-ray targets.

1. Example X-ray Device

Directing attention to Figure 1, aspects of one example of an x-ray device 100 are disclosed. The x-ray device 100 has a housing 102 within which various components are disposed. The components within the housing 102 include a cathode 104 that is spaced apart from an x-ray target 106. A window 108 is located in the housing 102. The x-ray target 106 may be connected to a shaft 110.

In operation, a voltage is applied across the cathode 104 and the x-ray target 106 to create a potential difference between the cathode 104 and the x-ray target 106. Electrons emitted by the cathode 104 are accelerated by the potential and collide with the x-ray target 106 so as to produce x-rays. The x-rays pass through the window 108 and into an x-ray subject (not shown).

In a rotating x-ray target 106 configuration, the x-ray target 106 is connected to the shaft 110. The shaft 110 is connected to a drive mechanism (not shown) that rotates the shaft 110 and imparts a rotational motion to the x-ray target 106 during the x-ray generation process. In this way, the heat created by the x-ray generation process is distributed more evenly throughout the x-ray target 106. In other embodiments, the x-ray target 106 may be stationary.

The x-ray device 100 may be configured for use in a variety of x-ray applications. Some example x-ray applications, in connection with embodiments of the invention, include, but are not limited to, medical, dental, industrial, and security or inspection. Of course, embodiments of the x-ray device 100 may be used in almost any x-ray application.

Different x-ray applications require varying amounts of x-ray power. In high power applications, e.g., CT applications, the x-ray power of the x-ray device 100 can be as high as about 150 kW or higher. Other embodiments of the x-ray device 100 may have more or less power as required by the specific application for which the x-ray device 100 is configured. Although embodiments of the x-ray device 100 may be used with various levels of x-ray power, the x-ray device 100 is particularly adept to handling high x-ray power requirements.

Generally, the higher the x-ray power, the higher the operating temperature of the x-ray device 100. As discussed above, higher operating temperatures may result in a larger x-ray target or faster rotational rates of the x-ray target. Embodiments of the x-ray device 100, however, incorporate the x-ray target 106 having a configuration that may withstand higher operational temperatures relative to typical x-ray targets. Thus, the x- ray target 106 may have a smaller overall size and a slower rotational rate compared to that of typical x-ray targets. For example, in the case of a high powered CT x-ray application, a typical x-ray device may have about a 240mm diameter x-ray target that is rotated at a rate of about 9,000 rpm in order to withstand the operating temperature. In comparison, for the same amount of x-ray power, the x-ray device 100 incorporating the x-ray target 106, having a configuration that may withstand higher operation temperatures, as described more fully below, may have about a 100mm diameter x-ray target 106 that is rotated at a rate of about 6,000 rpm. Other examples of the x-ray device 100 may have varying x-ray target 106 sizes and rotation rates depending on the requirements of the specific x-ray device.

2. Example X-ray Target and X-ray Target Track

Figure 2 illustrates one example x-ray target 106 that includes a substrate 202. A target track 204 is disposed on one side of the substrate 202 and a backing 206 is disposed on the opposite side of the substrate 202. The backing 206 may be attached to the substrate 202 by way of a bond layer 208.

In operation, for example, the x-ray target 106 includes a target track 204 made from a material or combination of materials that can reliably operate at higher temperatures during the x-ray generation process relative to a target track not made from the same material(s). Although the target track 204 can reliably operate at higher temperatures (e.g., about 1500 degrees Celsius or above), the target track 204 can still meet the x-ray generation requirements of various types of x-ray devices 100.

The target track 204 material may vary from one embodiment to the next, however, generally the target track 204 may be made from a base material in combination with a grain growth inhibitor. The introduction of a grain growth inhibitor to the base material affects the microstructure of the base material by preventing excess grain growth during the various processes that the target track 204 may undergo when manufacturing or producing the x-ray target 106. Reducing excess grain growth in the base material makes the target track 204 material able to better withstand high or operating temperatures relative to a target track material that lacks a grain growth inhibitor.

One way in which the target track 204 material may vary is the composition of the base material. For example, in one embodiment, the base material may be a tungsten- rhenium alloy. The base material may have various amounts of tungsten with respect to rhenium. In particular, in one embodiment the base material may be made of about 90% tungsten and about 10% rhenium, by weight. In other embodiments, however, the amounts of tungsten and rhenium may vary. For example, other base materials may be made from between about 85% to about 100% tungsten and about 15% to about 0% rhenium, by weight, respectively.

In addition to the various composition percentages, the elements that make up the base material may also vary. As discussed above, the target track 204 may be made from tungsten or various tungsten-rhenium alloys. However, any of a variety of high Z (atomic number) materials that produce x-rays when struck by electrons may be used, and any other suitable material(s) can likewise be employed in the construction of the target track 204.

Just as the base material of the target track 204 may vary, so too may the grain growth inhibitor vary. In one embodiment, the grain growth inhibitor may be a carbide material. The addition of the carbide material as a means for preventing excess grain growth is only one embodiment. Other types of materials may be used for the grain growth inhibitor and the scope of the invention is not limited to this example implementation.

In example embodiments that employ a carbide material as the grain growth inhibitor, one or more of a variety of carbides may be employed. For example, in one embodiment the grain growth inhibitor may be hafnium carbide. Hafnium carbide may be used as the sole additive, or in combination with other additives such as tantalum carbide, vanadium carbide, niobium carbide, zirconium carbide, and titanium carbide. The additional examples of carbides may also be used alone or in combination.

Depending on the type of grain growth inhibitor used, the amount of the grain growth inhibitor combined with the base material may vary from one embodiment to the next. For example, in one embodiment hafnium carbide is combined with tungsten- rhenium alloy in an amount such that the hafnium carbide is about 0.15% to about 0.5% of the total weight of the target track material. The amount of hafnium carbide used may be more or less than the above range, depending on, for example, the composition of the base material. Depending on the type of grain growth inhibitor or combination of grain growth inhibitors used, the amounts of grain growth inhibitor may vary.

The target track 204 material is not the only portion of the x-ray target 106 that can employ various materials. For example, the substrate 202 may be made from various materials that can withstand the high operating temperatures of the x-ray generation process. Some examples of substrate materials include tungsten alloys and molybdenum alloys. In particular, some specific examples of substrate materials include, but are not limited to, TZM, Mo-HfC, Mo-W, Mo-Re, and Mo-Nb. Furthermore, the substrate may be made from Mo-Lanthana, Mo-Ceria, Mo-Yttria, Mo-Thoria, or other combinations of the alloying elements. Any other suitable material(s) may likewise be employed for the substrate.

As with the substrate material, the backing 206 can be made from a variety of different materials. One purpose of the backing 206 material is to draw heat away from the substrate 202 and subsequently from the target track 204. Thus, the backing 206 material may be made from a material that has good heat absorption characteristics or high heat capacity. For example, the backing 206 can be made from various carbon bearing materials, including graphite and graphite based composites. However, any other suitable material(s) may additionally or alternatively be employed in the construction of the backing 206. In some example embodiments, positioned between the backing 206 and the substrate 202 may be a bond layer 208 that attaches the backing 206 to the substrate 202. The bond layer 208 may be made from a variety of materials that can chemically interact with both the backing 206 and substrate 202 materials. Some examples of bond layer 208 materials include zirconium, platinum, and titanium. Other examples of bond layer 208 materials include alloys of zirconium, platinum and titanium. Furthermore, a combination of one or more of zirconium, platinum and titanium, and/or a combination of their respective alloys, may be used in the bond layer 208. Any other suitable material(s) may likewise be employed for the bond layer 208.

Because at least some embodiments of the backing 206 comprise carbon, other example embodiments of the bond layer 208 may include a carbon management layer that may serve to retard, if not prevent, carbon diffusion out of the backing 206 and into one or more other layers of the substrate 202. In some embodiments, this carbon management layer takes the form of a carbide layer attached to the backing 206 surface to be attached to the substrate 202. The carbide layer may be made from a variety of carbide-based materials. Some examples of such materials include vanadium carbide, tantalum carbide, tungsten carbide, niobium carbide, hafnium carbide, and titanium carbide. Moreover, the carbide layer does not necessarily have to be a single material. Rather, multiple carbide materials may be used to make the carbide layer. For example, the carbide layer may be a combination of vanadium carbide and titanium carbide, or a combination of any of the other disclosed carbide-based materials. The foregoing is not an exhaustive list however, and any other suitable material(s) may be employed to form the carbon management layer.

Although the example embodiment of the x-ray target 106 shown in Figure 2 includes four layers (i.e., the target track 204, the substrate 202, the bond layer 208, and the backing 206), the x-ray target 106 may include more or less than four layers. For example, the x-ray target may have additional bond layers. In another example, there may be additional layers for various other purposes such as heat dissipation, weight distribution, and/or mechanical connection to the x-ray device 100 (e.g., connecting to the shaft 110.)

The materials used to construct the various layers of an example x-ray target 106 are only one example of how the x-ray target 106 may vary. For example, the x-ray target 106 may be designed with a variety of possible geometries. The thickness of each example layer of the x-ray target 106 is one example of how the geometric attributes of the x-ray target 106 may vary. Generally, Figure 2 illustrates an example of the thickness of each portion of the x-ray target 106 relative to other portions. However, there is no requirement that the relative thickness be configured in this way. The relative thickness for each portion may differ from one embodiment to another, and within a single embodiment. For example, the backing 206, shown in Figure 2, is relatively thicker than the substrate 202. In one alternative design, however, the backing 206 may be made thinner than the substrate 202 if less heat capacity were required for a particular x-ray application.

In addition to the relative thickness from one layer to then next, Figure 2 illustrates an example x-ray target 106 with each portion having a substantially constant thickness throughout the particular layer, except for the substrate 202. These example layers shown with substantially constant thickness, including the backing 206, bond layer 208, and target track 204, may alternatively have varying thickness throughout the portion.

Considering the thickness of the target track 204, the thickness of the target track 204 may vary from one embodiment to the next depending on requirements of the x-ray device 100, such as x-ray power. In one embodiment, the target track thickness is about one millimeter. Other target track thicknesses may be thicker or thinner as required by a particular x-ray application.

As with the target track thickness, the backing 206 and substrate 202 thicknesses may vary depending, for example, on the requirements of the x-ray device 100. In some embodiments, the thickness of the backing 206 is a function of required heat capacity and/or weight requirements so that the more heat capacity required, the thicker the backing 206, but the lower the weight requirement, the thinner the backing 206. The thickness of the substrate 202 may likewise be determined based on design requirements. For example, the thickness of the substrate 202 may be based on the required x-ray power and/or application of the x-ray device 100.

As in the case of the substrate 202 and backing 206, the bond layer 208 thickness may vary from one embodiment to the next, and within a single embodiment. The particular thickness employed can depend, for example, on the thickness required to create a suitable bond between the backing 206 and the substrate 202 that will withstand the heat and forces produced by the x-ray generation process. Some example thicknesses of the bond layer 208 range from about 5 microns to about 50 microns. The bond layer 208 thickness may be thinner or thicker than the ranges described above depending, for example, on the thickness and diameters of the backing 206 and substrate 202, and/or other variables.

Not only can the thickness of the example x-ray target 106 components vary, but various other geometric attributes of the example x-ray target 106 may likewise vary. By way of example, the respective cross-sectional dimensions of each component may vary from one embodiment to another, and within a single embodiment. In one embodiment, where the x-ray target 106 has a substantially cylindrical configuration, the backing 206 and substrate 202 may have a variety of diameters depending, for example, on the x-ray generation power requirements and/or application of the x-ray device 100. Some examples of outside diameters of the backing 206 and substrate 202 range from about one inch to about ten inches, but can be bigger or smaller depending on the x-ray generation power required and/or the application of the x-ray device 100 where the x-ray target 106 is used.

The cross-sectional dimension for each example layer may vary from one embodiment to another such that any given layer may have a cross-sectional dimension different from that of any other layer. Figure 2 illustrates one example of an x-ray target 106 where the cross-sectional dimension of the substrate 202, bond layer 208 and backing 206 are substantially equal. Alternatively, for example, the backing 206 may have a different diameter than the bond layer 208 and/or the substrate 202.

Just as the cross-sectional dimension of the various layers of the x-ray target 106 may vary, the extent to which each layer contacts or otherwise interfaces with adjacent layer(s) is another example of how the geometric configuration of the x-ray target 106 may vary. Figure 2 illustrates, for example, one embodiment of an x-ray target where layers of the example x-ray target 106 are substantially coextensive with the respective surfaces of one or more adjacent layers. In contrast, however, the example target track 204 extends over only a portion of the surface of the substrate 202. In an alternative example, the bond layer 208 may cover only a portion of the surface of the backing 206, while being substantially co-extensive with the substrate 202. Also, the target track 204 may substantially cover the upper surface 202A of the substrate 202.

The overall geometric configuration is yet another example of a geometric attribute of the x-ray target 106 that may vary. In particular, the shape of the each layer of the x-ray target 106 may vary from one embodiment to the next or from one layer to the next within the same embodiment. For example, Figure 2 illustrates one embodiment where the target track 204 has a substantially annular configuration. The inside and outside diameters of the target track 204 may vary depending, for example, on the design of the x-ray device 100 and placement of the cathode 104 within the x-ray device 100 with respect to the target track 204. As a further example, the backing 206 and the substrate 202 may each have a substantially cylindrical shape, while the bond layer 208 may have a substantially annular shape.

Varying geometric attributes such as the thickness, diameter, size and shape of one or more of the example layers of the example x-ray target 106 may be employed to desirably achieve a particular geometric configuration for the overall x-ray target 106. One example of an overall geometric configuration of the example x-ray target 106 is illustrated in Figure 2. As illustrated in Figure 2, the x-ray target 106 has a substrate 202, which is cylindrical with a trapezoidal cross-section, attached to a cylindrical backing 206. However, the overall shape of the x-ray target 106 may take any other suitable form as well, and the scope of the invention is not limited to past x-ray target geometries.

Geometric attributes, such as the examples discussed above, may also be varied as necessary to suit the particular way in which an x-ray target 106 is employed. As briefly mentioned above, example embodiments of the x-ray target 106 may be configured to be attached or coupled to the shaft 110 such that a rotational motion can be imparted to the x-ray target 106. For example, a rotating x-ray target 106 may include forming or creating a substantially circular hole in the backing 206 where the shaft 110 may be inserted. The shaft 110 may be attached to the backing 206 in a variety of ways including, but not limited to, welding, slip tolerance fit, or through the use of mechanical fasteners such as bolts or screws. Furthermore, the hole created in the backing 206 may extend through any layer, or all layers of the x-ray target 106.

3. Example Method of Making an X-ray Target

Figure 3 illustrates aspects of an example method 300 for creating an x-ray target. Briefly, in one example method, a target track is disposed 302 on a substrate, the target track material including a base material and a grain growth inhibitor. The target track may then be processed 304 such that the density of the target track is increased. The grain growth inhibitor prevents excess microstructure grain growth during processing 304. A backing may then be attached 306 to the substrate. The disposing 302, processing 304, and attaching 306 can each be performed using a variety of techniques, examples of which will be discussed.

In more detail, the disposing 302 of the target track on the substrate may be performed using a variety of methods. For example, in one embodiment, the target track is disposed 302 on the substrate using a Vacuum Plasma Spray ("VPS") process. In this example process, feedstock powder of the base material(s) and the grain growth inhibitor are combined and prepared to contain the desired amount of each material component. For example, the VPS combined feedstock powder may contain about 90% tungsten, about 10% rhenium, and about 0.15% hafnium carbide, by weight. In other embodiments, the VPS combined feedstock powder may contain various amounts of each of the components that will make up the target track material, as discussed above. Generally, if the base material is a tungsten alloy and the additive is hafnium carbide, the amount of hafnium carbide added may range from about 0.15% to about 0.5% by total weight. The additive weight percentage may be higher or lower in other embodiments.

Prior to VPS forming, the combined feedstock powder may be processed using a

Plasma Alloying and Spherodization technique, and may also be sieved to obtain a specific particle size. Example particle sizes may be about 0.5 μιη or smaller, however, larger size particles may be used as well. The prepared feedstock powder is then VPS formed onto the substrate by way of a plasma spray system to form the target track.

VPS is only one of many methods that may be used to dispose 302 the target track on the substrate. Other example methods include, but are not limited to, powder metallurgy (PM), electroplating, a hydride coating process or any other method where the target track material chemically interacts with the substrate and provides a way to include the grain growth inhibitor to prevent microstructure grain growth in the base material.

After disposing 302 the target track on the substrate, the target track may be processed 304 in order to increase the density of the target track material. One example of processing 304 is to heat treat the target track. In one implementation of this example process, the target track is placed in a high vacuum furnace at a temperature of about 1,700 degrees Celsius to about 1,800 degrees Celsius for a period of about twelve hours. The time, temperature and pressure may vary and be any combination that allows for the desired target track densification.

Other example methods of processing include, but are not limited to, placing the target track under high pressure, such as using a hydrostatic press with argon gas, or any other method that allows for the densification of the target track.

Processing 304 the target track may lead to varied densities of the target track. In one example embodiment, the target track may have a density of about 98% or more. However, in other embodiments the density may be higher or lower. As the density of the target track material increases during processing, the grain growth inhibitor may prevent excess grain growth in the microstructure of the base material(s). With the prevention of excess grain growth in the microstructure, the target track material may be stronger at high operating temperatures, relative to other target track materials that do not include a similarly functioning grain growth inhibitor.

After processing 304 the target track, a backing is attached 306 to the substrate.

There are a variety of methods that may be used to attach 306 the backing to the substrate. In one embodiment, the backing is attached 306 with a bond layer that is formed between the backing and the substrate, the bond layer configured to chemically interact with both the backing and substrate in a way that couples the backing and substrate together. In particular, for example, the bond layer may be formed by performing a braze process using a braze material that is secured between the backing and the substrate. During the brazing process, the braze material becomes molten and chemically interacts with the backing and substrate to form a bond.

There are several aspects of the brazing process that may vary from one embodiment to the next. For example, the time, temperature and pressure of the braze process may vary. In one specific example, the backing and substrate are brazed at a temperature in the range of about 1,560 degrees Celsius to about 1,590 degrees Celsius for about five to ten minutes in a vacuum furnace. Of course, various other times, pressures and/or temperatures may alternatively be employed.

The times, pressures and/or temperatures of the braze process often depend on the type of braze material used. Some example braze materials include zirconium, titanium, platinum, or any combination of zirconium, titanium or platinum. In one example braze process, the braze material comprises a zirconium washer that is secured between the substrate and backing. In another embodiment, several washers may be employed, with each washer being made from a different material, and used in combination with the above braze process to form the bond layer.

The use of a washer is not the only method to arrange the braze material between the substrate and backing. In another example, a hydride paste containing the braze material may be placed between the substrate and backing. For example, zirconium hydride paste may be placed between the backing and the substrate. Moreover, any other method that arranges the braze material between the backing and the substrate may also be used. The above brazing process, or any other suitable braze process, is then performed to form the bond layer and attach or couple the substrate to the backing. The bond layer may also be formed by employing the above brazing process in combination with a carbon management layer. For example, because the backing may be made from a graphite composite material, it may be desirable to form a carbon management layer on the backing that retards the diffusion of carbon from the backing into the braze material. After the carbon management layer is formed, the above brazing process, or any other suitable process, is then performed to form a multiple layer bond that may have a reduced interface stress between the backing and substrate relative to bond layer without a carbon management layer.

One way to form the carbon management layer is to coat the backing with a carbide forming metal and then process the carbide forming metal coat to form the carbon management layer. There are various carbide forming metals that may be used to coat the backing, such as vanadium, tantalum, tungsten, niobium, hafnium, and titanium. These example carbide forming metals may be used alone or in combination with one another. In one embodiment, the carbide forming metal coating deposited on the backing is pure or substantially pure metal.

There are a variety of ways to coat the backing with a carbide forming metal. For example, a chemical vapor deposition process may be used to coat the backing. In this example process, a metal hydride of a carbide forming metal is first deposited on the substrate. The metal hydride decomposes to form a carbide forming metal coat on the substrate. Other example coating methods may also be used, such as electrodeposition, electroplating, vacuum sputtering, melt evaporation, or any combination of the above processes.

The above coating processes may coat the backing with various thicknesses of carbide forming metal. One example embodiment of the carbide forming metal coat has a thickness in a range of about five to fifty microns. However, the thickness of the carbide forming metal coat may be any thickness that allows for the creation of the carbon management layer sufficient to retard carbon diffusion from the backing while attaching 306 the backing to the substrate. The carbide forming metal coat thickness may be deposited as a single coat or alternatively, may be formed by deposition of multiple coats of various materials on the backing.

Subsequent to coating the backing with the carbide forming metal, the coating is processed to form the carbon management layer. One example of processing is a vacuum outgassing process. In one specific implementation of this example process, the carbide forming metal coated substrate is placed in a high vacuum furnace with a temperature greater than about 1,600 degrees Celsius. The carbide forming metal coated substrate is outgassed for a period necessary for the carbide forming metal coat on the substrate to form the carbon management layer. An example outgas period for the carbide forming metal coat to form the carbide layer can range from about one-half hour to about four hours for the temperature noted above. Time and temperature of the outgassing process may vary.

During the outgassing process, the carbide forming metal coat on the substrate forms a carbon diffusion layer on the substrate that retards carbon diffusion from the substrate during the attaching 306 process, which effectively reduces the interface stress between the substrate and the target core. After the carbide diffusion layer is formed, the above brazing process, or any other suitable process, is then performed to form a multiple layer bond.

In contrast to the above described bonding processes, the attaching 306 process does not necessarily have to implement the use of a bond layer. Instead, other attaching methods may be used such as mechanical fasteners, structural retaining devices that hold the backing and substrate together, or any other suitable methods that may be used to attach the backing to the substrate.

The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.