Tail set crupper

09688526 ยท 2017-06-27

    Inventors

    Cpc classification

    International classification

    Abstract

    A tailset crupper for an animal, such as a horse, may be made from a solid casting without lightening features, such as to produce a heavier, less easily dislodged object, such as may have a lower center of gravity, and a center of gravity located closer to the surface of the animal. The trough of the crupper may be predominantly open from below. The distal end of the crupper may have a large curl the bends on a large angle partially back toward the horse. The crupper may be substantially spoonless. That is, the protrusion at the front end of the crupper may be small, and may by shy of the cushioning on either side.

    Claims

    1. A tail set crupper comprising: a base portion and a trough portion; said base portion having left and right hand wings, each wing having a first surface for placement next to the hindquarters of an animal; said trough portion being immovably joined to said base portion between said wings, said trough portion, in use, extending outwardly away from the animal; said trough portion having a first end adjoining said base portion, a second end distant from said base portion and a medial portion between said first and second ends; said second end of said trough portion having a rounded mouth; said medial portion being predominantly downwardly open; said crupper having a centerline; each of said wings having a main post, a lower lobe, and a flange portion; said flange portion being located sideways outboard of said main post and upward of said lower lobe; and said flange portion being thinned relative to said main post and said lower lobe.

    2. The tail set crupper of claim 1 wherein said medial portion of said trough portion has a spine extending therealong, and apertures are formed in said trough portion adjacent to said spine, said spine being narrower than said apertures.

    3. The tail set crupper of claim 1 wherein said medial portion of said trough portion has a central spine and a cross-rib extending between said first end and said second end, and is otherwise downwardly open.

    4. The tail set crupper of claim 1 wherein said rounded mouth defines a continuous imperforate rounded surface.

    5. The tail set crupper of claim 1 wherein said lower lobe has a rebate defined therein, said rebate being sized to receive a recessed attachment hinge fitting.

    6. The tail set crupper of claim 1 wherein said thinned flange is less than half as thick as each of said main post and said lower lobe.

    7. The tail set crupper of claim 1 wherein said main post tapers into said lower lobe, said main post having an upper end, said upper end of said main post being thinner in through-thickness than said lower lobe.

    8. The tail set crupper of claim 1 wherein said flange portion meets said main post and said lower lobe at a step change in thickness.

    9. The tail set crupper of claim 8 wherein said crupper has a central longitudinal plane, and said rounded mouth presents a continuous rounded surface over a sweep in said central longitudinal plane of more than 2(Pi)/3 radians.

    10. The tail set crupper of claim 9 wherein said crupper has an outlet tangent portion extending away from said continuous rounded surface.

    11. The tail set crupper of claim 8 wherein said crupper is substantially spoonless.

    12. The tail set crupper of claim 8 wherein said first end of said trough is free of upward slope deviation.

    13. The tail set crupper of claim 1 wherein said medial portion of said trough portion has a spine extending therealong, and apertures are formed in said trough portion adjacent to said spine, said spine being narrower than said apertures; and a cross-rib extends between said first end and said second end, and said medial portion of said trough portion is otherwise downwardly open.

    14. The tail set crupper of claim 1 wherein said rounded mouth defines a continuous imperforate rounded surface; said crupper has a central longitudinal plane; and said rounded mouth presents a continuous rounded surface over a sweep in said central longitudinal plane of more than 2(Pi)/3 radians; and said crupper has an outlet tangent portion extending away from said continuous rounded surface.

    15. The tail set crupper of claim 1 wherein said crupper is substantially spoonless.

    16. The tail set crupper of claim 1 wherein said first end of said trough portion is free of upward slope deviation.

    Description

    BRIEF DESCRIPTION OF THE DRAWINGS

    (1) These aspects and other features of the invention can be understood with the aid of the following illustrations of a number of exemplary, and non-limiting, embodiments of the principles of the invention in which:

    (2) FIG. 1 shows the general arrangement of a harness on a horse, in side view, including the general positioning of a crupper according to the principles of the present invention;

    (3) FIG. 2 shows a perspective view of a crupper, with padding, ready for mounting on the horse of FIG. 1;

    (4) FIG. 3a shows a perspective view of the crupper of FIG. 2a, without padding or leather cover taken from above, behind, and to the right;

    (5) FIG. 3b shows a top perspective view of the crupper of FIG. 3a without padding;

    (6) FIG. 3c shows a bottom perspective view of the crupper of FIG. 3a with padding;

    (7) FIG. 3d shows a front perspective view of the crupper of FIG. 3a without padding;

    (8) FIG. 3e shows a rear perspective view of the crupper of FIG. 3a without padding;

    (9) FIG. 4a shows a side perspective view of the crupper of FIG. 3a;

    (10) FIG. 4b shows a cross-sectional view taken along the longitudinal centerline of the crupper of FIG. 3a, indicated by section 4b-4b of FIG. 3b.

    (11) FIG. 5a shows a top view of a detail of an embodiment of crupper casting such as that of the crupper of FIG. 2;

    (12) FIG. 5b shows a side view of the crupper casting of FIG. 5a; and

    (13) FIG. 5c is a rear view of the crupper casting of FIG. 5b on section 5c-5c.

    DETAILED DESCRIPTION OF THE INVENTION

    (14) The description that follows, and the embodiments described therein, are provided by way of illustration of an example, or examples of particular embodiments of the principles of the present invention. These examples are provided for the purposes of explanation, and not of limitation, of those principles and of the invention. In the description, like parts are marked throughout the specification and the drawings with the same respective reference numerals. The drawings are not necessarily to scale and in some instances proportions may have been exaggerated in order more clearly to depict certain features of the invention.

    (15) By way of a general overview, FIG. 1 shows a harness 10 for an animal, such as a horse 12. Harness 10 may include a breast collar 14 that extends about the fore quarters of the horse beneath the base of the neck, a sursingle 16 and crupper assembly 20. Sursingle 16 extends about the girth of horse 12, and includes a sursingle belly band 18 that extends beneath the horse's belly and a sursingle back 22 that extends over the horse's back. Breast collar 14 is maintained in position relative to sursingle 16 by upper and lower breast collar straps indicated respectively as 24 and 26. Crupper 20 is mounted to the rear end of horse 12, and may be maintained in position by a pair of turnback straps 28 that extend from the top of the sursingle, over the hindquarters of the horse, and which connect to the top or upper portion of crupper assembly 20, as is more fully described below. Turnback straps 28 are adjustable in length, and so govern the longitudinal distance along the back of horse 12 between the top of sursingle 16 and crupper 20. Lateral position of crupper assembly 20 may tend to be maintained by the use, and suitable adjustment, of upper, lower, and rearward spider straps 30, 32, and 34. Upper spider strap 30 runs from the top of sursingle back 22 generally rearwardly and diagonally to a node, or ring, 36. Lower spider strap 32 runs from a D-ring at one end of the center portion of the bottom of sursingle belly hand 18, generally diagonally upwardly and rearwardly to ring 36. Rear spider strap 34 runs rearwardly about the contours of the flank of horse 12 to attach to crupper assembly 20, described below. While right hand straps are visible in the figure, corresponding left hand spiders straps extend on the opposite side of horse 12 such that the forces in the straps relative to the lateral positioning of crupper assembly 20 may tend to the more or less symmetrically balanced and crupper assembly 20 may tend to be maintained in a central position to support the horse's tail in general longitudinal alignment with the spine of the horse (which, for the purposes of this description lies ideally in a fore-and-aft longitudinal vertical plane).

    (16) Crupper assembly 20 may include a crupper frame, referred to hereinafter simply as crupper 40, discussed in greater detail below, padding 42, and a leather cover 44. Crupper 40 has a compound concave surface that is fabricated to conform to the compound curvature of a horse's hindquarters adjacent to the root of the spine. Padding 42 is mounted to sit between the curvature of crupper 40 and the skin of horse 12. For other animals, a different curvature may be used, such as may correspond to the customary shape of that animal. Leather cover 44 is sewn to padding, the whole assembly of cover and padding fitting over the greater part of crupper 40. The terminology crupper may, depending on context, refer to either the entire assembly, i.e., crupper assembly 20, or more specifically, to the rigid crupper frame, i.e., designated as crupper 40, alone.

    (17) The illustrations provided herein are based on photographic views of an example of a crupper 40. Crupper 40 may be fabricated from a metal, such as aluminium, but may also be fabricated from other suitable materials. In general, crupper 40 may have a vertical-longitudinal plane of symmetry, allowing for the asymmetries and imperfections in production of castings, and, in particular, of sand castings.

    (18) Although crupper 40 may be formed as an integral, monolithic casting, crupper 40 can be thought of as having a base, or base portion, or base, 46, and a trough portion, or trough 48. In general terms, base portion 46 has a pair of left and right hand pad portions, 50, 52 joined by a U-shaped web portion 54.

    (19) Pad portions 50 and 52 may each have a contoured inward surface 56, 58 that may be formed on a compound concave curvature, that is generally symmetrical about a vertical longitudinal central plane bi-secting trough portion 48, the two compound curved surfaces tending to lie on the same geometric surface, the curvature being intended to permit crupper 40 to conform, in a general sense to the curvature of the hindquarters of the animal, such as horse 12, or as the case may be. The compound curvature may be formed according to a geometric polynominal function, or may be formed on radii of curvature about respective vertical and transverse axes, the resultant compound curvature being formed generally to conform to the shape of a horse's hind quarters. To that end, the transverse radius of curvature may be of the order of 80 to 100 inches, and may be about 90 inches (+/5); the vertical radius of curvature may be of the order of 10 to 15 inches, and may be approximately 11 inches (+/1 inch). The resultant surface may tend to be an ellipsoid, or a reasonably close approximation of an ellipsoid given the possible imprecision of a sand casting, if such is employed. That is, the surfaces of the two pad portions 50, 52 would then be portions lying on the same ellipsoidal surface. Put alternately, the two surfaces may tend to lie on a common torus (i.e., doughnut) surface, where, converting the radii above, the main radius of the torus may be about 75 to 80 inches in the horizontal plane, and the minor radius of the torus may be about 10 to 15 inches. While it is desirable for this curvature to conform closely to the size of the hindquarters of horse 12, a layer of padding 42 may generally be placed between the surface of the crupper frame pad portions 50, 52, and may tend to take up a reasonable degree of imprecision.

    (20) In one embodiment, the U-shaped web portion 54 may tend to have quite a square-cornered, or three-sides-of-the-rectangle appearance, with slightly splayed legs. The splay may be about .+0.2 inch in width over about a 4 inch rise in height, giving a splay angle of about 3 to 4 degrees from either side of vertical for the respective sides, if the back portion is taken as being substantially horizontal in terms of the view shown in FIG. 3d. The back of this web portion 54 is sometimes referred to as the bridge between the left and right hand pad portions 50, 52.

    (21) Each of the pad portions 50, 52 may have a lower, rather wider region 68, that may be smoothly radiused along the laterally outboard portions at its tipper end to give onto an upper, narrowing region or tail, or toe 60 (left or right hand, respectively). At the distal or upper extremity of each tail, or toe 60, is a strap attachment fitting 62, such as a rectangular ring, or eye, 64, whose hinge fitting 66 may be riveted in place. Given that the general use environment may tend to be acidic, mechanical fasteners in the nature of galvanically suitable rivets may be used, such as copper rivets being used in an aluminum casting with stainless steel hinge fittings, for example. The lower lobate regions 68 of pads 50, 52 also have mounting fittings 67, such as may be in the nature of hingedly mounted ring fittings 69 that may be mounted to the laterally outermost extremities of the outer surface 57, 59 of the wings (namely lobate regions 68) of crupper 40. Fittings 67 may be employed as connection points for rearward spider straps 34, whereby the lateral positioning of crupper 40 may be adjusted. In the embodiment shown, and in contrast to the crupper shown in FIG. 4a of U.S. Pat. No. 6,993,892, toe 60 is formed into a less sharp or pointed form, but rather retains a broader, more gently curved form to a relatively higher location such as may tend to increase the upper surface area, and spread, of the crupper, such as may be more comfortable for the animal. In the embodiment shown, the tangent of the uppermost slope portion of the outside edge of the crupper is shown, as alpha.sub.60. The maximum inward slope angle (taken at the tangent of the point of inflection of the transition, as indicated at alpha.sub.68 forms an intersection angle identified as beta. In the embodiment of U.S. Pat. No. 6,993,892, the corresponding angle is quite pronounced, being less than (Pi) radians, such that toe 60 is relatively long and thin. If the inside edge 71 of toe 60 is taken as a first datum, In U.S. Pat. No. 6,993,892 the intersection at angle beta is located less than halfway from the trough transition (i.e., the height h.sub.71 at which tangent 102 intersects pad portion 50, 52, as may be) to the uppermost tip h.sub.60 toe 60. By contrast, in the embodiment described herein, that point of intersection lies more than halfway toward datum toe 60, and may be more than of the way. Further, the angle of intersection is well more than (Pi) radians and may be more than (Pi) radians. Expressed differently, toe 60 in U.S. Pat. No. 6,993,892 has a significantly higher aspect-ratio of length to width from the inflexion point to the tip, being roughly 3:1, whereas toe 60 herein has an aspect ratio of less than 3:1, and which may be less than 2:1. As can be seen, the slope at the point of inflexion is also correspondingly shallower. Each of these measures is a proxy for the qualitative difference of the pads being fatter further upward to spread load.

    (22) The outer surfaces 57, 59 of pad portions 50, 52 may also be curved, but in such a way that the through thickness t.sub.1 at the extremity of toes 60 may be substantially less than the through thickness t.sub.2 at the lowest extremity of lobate regions 68. For example, the upper thickness may taper to thickness t.sub.1 of about half an inch, or less. The lower thickness may broaden to thickness t.sub.2 of roughly about an inch (+/), and the variation in thickness may be a smoothly continuous increase as a function of position along the arc. This may tend to result in a disproportionate biasing of the weight distribution of the pads toward the lower extremity.

    (23) Trough portion 48 may include an outboard, or rearward portion 70 that, in use, extends outwardly and upwardly away from the hind quarters of the animal, and an inward portion, 72 that extends inwardly of the surface of the body of revolution on which surfaces 56 and 58 of pad portions 50 and 52 are formed. Rearward portion 70 has the form of a nozzle or chute. Rearward portion may taper from its base (next to the animal) to its distal end. At its broad, proximal end adjacent pad portions 50, 52 rearward portion forms a smooth transition into the web, or bridge portion 54 of base portion 46. At the distal end of rearward portion 70, the tapered chute region gives onto a third region of trough 48, the outboard curl or mouth 74 with a downwardly opening arcuate lip 76. The outboard curl may be considered to commence at the outboard end or margin of apertures 84 noted below.

    (24) The chute of trough portion 48 has a base, or bottom portion, 78 and side portions 80, and may include respective inward and outward reliefs 82, and 84 in the nature of apertures. Apertures 82 and 84 are shown as being generally rectangular or square. Although apertures were provided in the embodiment shown and described in U.S. Pat. No. 6,993,892, for the purpose of making the section lighter, the inventor has observed that the horse's tail may tend to become warm, and may after time, be a source of discomfort. As horsehair is relatively insulating in a thermal sense, apertures relatively close to the top edge or margin of the trough, as in U.S. Pat. No. 6,993,892, did not apparently tend to promote cooling very well, if at all. To address this issue, trough portion 48 herein is more open than previously, the openings are larger than previously, and the openings are intended to be placed more predominantly below the tail rather than in the former, high up locations that were predominantly beside the tail. It is thought that this arrangement may tend to give better access for cooling air from below to cool the horse's tail. Trough portion 48 may include a centrally positioned, longitudinally extending external reinforcement rib, or spine, 88, and may include a transversely oriented, integrally formed rib 90 that may emanate from spine 88 and extend peripherally about thereabout from side to side of trough 48 in a U-shape. Rib 90 may be located at a longitudinal station roughly mid-way intermediate base portion 46 and the point of tangency where the downward curvature 92 of mouth 74 of trough 48 that leads to lip 76. Rib 90 may be located between inward relief 82, and outward relief 84. In the embodiment shown, rib 90 is the only laterally extending structural member between inward portion 72 and mouth portion 74. The longitudinal width or thickness W.sub.90 of rib 90 is less than either the longitudinal length L.sub.82 of relief 82 or length L.sub.84 of relief 84. When viewed in bottom view projection, width W.sub.82 of relief 82 may be wider than spine 88, and may extend lengthwise a distance L.sub.82 more than double W.sub.90. Similarly, and again as viewed in bottom view projection, as in FIG. 3c the longitudinal extent L.sub.82 of relief 84 is comparable to, or larger than, the longitudinal extent of rib 90, and the cross-wise projected width W.sub.84 of relief 84 is comparable to or greater than the projected width of spine 88. As such, more than of the projected underside area in trough 48 between inward portion 72 and mouth portion 74 is downwardly open for ventilation, and in the embodiment shown that proportion is greater than of the downwardly projected area in that region, i.e., roughly the total projected area of the region between the left and right hand side portions of trough 48 less the projected area of spine 88 and rib 90. Expressed differently, the solid portion of spine 88 defines less than of the total projected width of section in the region of either of apertures 82 and 84.

    (25) The upper edges or margins of the side portions 80 of the trough portion 48 are indicated as 94 and 96, and have a profile indicated as 98. Profile 98 includes an outward end portion 100 and an inward portion 102. Outward portion 100 is downwardly concave, with local radii of curvature having local centers of curvature lying below trough portion 48. Inward portion 102 is substantially straight and runs along, and defines the upper edge of, each respective side of trough 48. In contrast to the previous crupper of U.S. Pat. No. 6,993,892, the inventor has found that a larger curl 110 at mouth 74 may be helpful, such that the horse's tail may be less likely to rub on a relatively abrupt end edge and thereby irritate the horse. To that end, the outward facing or upper surface 112 of mouth 74 is formed on a large-radius curve alpha.sub.112 extending over more than 120 degrees of arc (i.e., more than (pi) radians), and having a generally downwardly and forwardly (i.e., with a component of direction toward the horse) extending cuff 114, which may extend away from curl 110 on a tangent portion 116 at its distal end. In one embodiment alpha 112 may be about 150 degrees. That is, the outer end portion of crupper 40 has a cross-sectional profile that merges into, or is substantially the same as, that of the intermediate portion of trough 48 more generally. However the outer end of the channel or trough is bent around and somewhat back upon itself on a return angle oriented partially back toward the horse. The end of the tail may then be supported on a well radiused large curve, and in the normal condition the tail may tend to hang vertically under gravity somewhat away from cuff 114 rather than swinging against a sharp edge. In the embodiment shown, there are no apertures in curl 110, such that a continuous, relatively smooth curved surface is presented to the horse's tail, the curve being both in the lengthwise orientation of crupper 40 (and or the horse's tail) and in the cross-wise orientation. Furthermore, trough 48 is wide and deep, with an inside depth that is greater than of the width, and the width at mouth 74 being more than the width of trough 48 at the junction with base portion 46. Thus mouth 74 presents a continuous surface of compound curvature around curl 110, and provides an out-feed or chute or collar, or cuff on the tangent at its outlet. The lip of curl 110, at the end of cuff 114, is also well radiused to be free of sharp edges.

    (26) The bottom or forward portion or region 78 of the trough portion 48 and 72 may sometimes be referred to as the spoon of the crupper. In the earlier apparatus of U.S. Pat. No. 6,993,892 the inner region of the spoon protruded significantly beyond, or inwardly proud of the surface of the body of revolution of the inner surfaces of pad portions 50, 52. The spoon was also angled upwardly and inwardly relative to the slope of the trough taken along the upper, or inside, surface at the trough centerline. This geometry may not have been as comfortable for the horse as might have been desired. In the embodiment shown herein, trough 48 is substantially spoonless. That is, inner portion 78 extends inwardly proud of pad portions 50, 52 described herein, but less far than the inward surface of the undeflected cushioning or padding 47, 49 on surfaces 56, 58. Expressed differently, the extension distance d.sub.78 inwardly proud of surfaces 56, 58 is less than the through thickness t.sub.50 of pad portions 59, 52. Expressed differently again, as a proportion of the width of trough 48 at its inward end, indicated as W.sub.48, d.sub.78 may be less than about of W.sub.48, may be in the range of to of W.sub.48, and in one embodiment may be about of W.sub.48. Moreover, in the embodiment the upper surface of inner portion 78 continues on the same, or substantially the same, slope or curvature as trough 48, rather than having a marked change in curvature, or other distinct deviation upward. That is, in the direction toward the horse it is free up upward slope deviation relative to the inside surface of trough 48 generally, such that no spoon shape is formed.

    (27) Certain geometric relationships between the forgoing elements may be observed. First, as compared to existing cruppers, the center of gravity CG, of crupper 40, as viewed from the side may tend (a) to be relatively low; and (b) may tend to lie relatively close to the bottom of trough portion 48, and may tend to lie relatively close to the surface of the body of revolution corresponding to the curvature of pad portions 50 and 52.

    (28) FIGS. 5a, 5b, and 5c are intended to show an alternate form of crupper casting to that described above. Casting 120 is a reduced weight casting, with the same front or rear facing profile, but with generally thinner wall sections. As before, casting 120 may be an aluminum casting. The form and curvature of the trough 122, and the trough geometry relative to the tail of the horse, as discussed above, is retained, although the wall thickness may be reduced. Casting 120 has a lateral base having two wings 124, being of left and right hand. As above, casting 120 may be taken as being symmetrical about the longitudinal vertical center-line plane of trough 122, such that a description of one half also describes the other half, allowing for handedness.

    (29) In FIG. 5c, the root of the central spine is shown in section as 126, and the root of the sidewall of the trough is shown in section as 128. The main vertical post portion is shown as 130 and the lateral outward and downwardly diagonal lobe is shown as 132. Main vertical post 130 has a rebate, or cut-out, or accommodation 134 of depth corresponding to, or somewhat deeper than, the through thickness of the land of the generally rectangular stainless steel harness mounting hardware, or hinge, to which attachment ring 64 is secured. Similarly, lobe 132 has a rebate, or cut-out, or accommodation 136 for the land of ring 69. In each case it is intended that the mounting hardware will sit flush with, or shy of, the adjacent surface of casting 120. The double-dashed lines R.sub.1 and R.sub.2 in FIG. 5c are intended to show the location of radii in casting 120. Vertical post 130 and lobe 132 are of full thickness, that full thickness tapering from a bottom end that is somewhat thicker, to a top end that is somewhat thinner. For example, the bottom edge of lobe 132 may be to thicker than the top end of post 130, and in one embodiment may be about thicker. For example, the top through thickness may be about 14 mm, ( 9/16) whereas the bottom edge may be about 21 mm (). The taper in thickness may be smooth, i.e., without a step discontinuity. The front face of wing 124 (i.e., the surface facing the horse) may be somewhat hollowed out, or concave, generally to follow the shape of the animal. In the rearward face, there is a portion between the substantially vertically running radius R.sub.1, to the radius R.sub.2 that runs at about a 4 o'clock angle (or 120 degrees) as seen in FIG. 5c. That portion may be termed flange 140, and it may be considered to be stepped at the radii from the greater thickness to the lesser flange thickness. The front face of flange 140 forms a smooth continuous surface with lobe 132 and post 130. The rearward face is stepped to a thinner section at radii R.sub.1 and R.sub.2, that thickness being of the order of between and of the overall thickness of the adjacent vertical post 130 or lobe 132, and in one embodiment is about of the thickness. For example, whereas the bottom edge of lobe 132 may be 21 mm thick, flange 140 may be 7 mm thick. The projected surface area of flange 140 may be about - of the total projected surface area of wing 124, and in one embodiment may be about of that projected area as seen in the view of FIG. 5c, for example.

    (30) In the example of FIGS. 5a, 5b and 5c, wing 124 is partially relieved by being thinned at flange 140, and the relieved portion lies generally upwardly of the lower lobe 132. Lower lobe 132 retains full thickness, and is correspondingly the region of greatest weight concentration of wing 124. Also in the embodiment of FIGS. 5a, 5b, and 5c, and unlike the embodiment of FIG. 2, the through-thickness of the trough portion is substantially uniform, and roughly the same as the through-thickness of the thinned flange portion of wing 124, allowing for the local variations of thickness in the casting generally. This can be seen in the section of items 126 and 128 in FIG. 5c where the through thickness is comparable to the through-thickness of flange 140, and substantially less than, and in one embodiment less than half as thick as, the average or mid-height, thickness of main vertical post 130, and much less than the thickness of pad 132 at its bottom edge. The casting thickness is, of course, greater in the radiused corner portions where the trough and base portions meet. As seen in FIGS. 5a and 5b, neither the longitudinal spine nor the lateral mid-trough cross-piece has enhanced thickness, and may be contrasted with the heavier, increased, thickness of spine 88 or rib 90 noted above.

    (31) Although the embodiments illustrated and described above are preferred, the principles of the present invention are not limited to this specific example which is given by way of illustration. It is possible to make other embodiments that employ the principles of the invention and that fall within its spirit and scope as defined by the following claims.