Propeller comprising a counterweight system provided with an air discharge channel

Abstract

The main aim of the invention is a propeller (32) for a turboengine (1) comprising a plurality of blades (48) and a blade support ring (47) provided with housings (50), each receiving a pivot (52) bearing the foot (58) of one of said blades (48), characterized in that at least one of the pivots (52) is equipped with at least one counterweight system (90, 91) provided with at least one inner channel (93, 96) for airflow ventilation discharge (F.sub.1, F.sub.3) for capturing and guiding said airflow directly in contact with the blade foot (58) borne by said at least one of the pivots (52).

Claims

1. A propeller for a turboengine comprising: a blade; and a blade support ring provided with a housing, the housing receiving a pivot supporting a foot of the blade, wherein the pivot is equipped with a counterweight system provided with an inner ventilation discharge channel for airflow to capture and guide said airflow directly in contact with the foot of the blade supported by the pivot, wherein the pivot includes an inner communicating channel in fluid communication with the inner ventilation discharge channel, and wherein the counterweight system includes a counterweight arm in which the inner ventilation discharge channel is provided.

2. The propeller as claimed in claim 1, wherein said inner ventilation discharge channel has an inner end which terminates on said pivot and at least one of an airflow introduction end and an ejection end.

3. The propeller as claimed in claim 2, wherein said at least one of the introduction end and the ejection end includes at least one of an airflow introduction means and an ejection means including an orifice.

4. The propeller as claimed in claim 1, wherein a first end of the inner communicating channel terminates at a level of the blade foot and a second end of the inner communicating channel terminates at a level of said inner ventilation discharge channel of said counterweight system.

5. The propeller as claimed in claim 1, wherein said counterweight system further comprises a counterweight.

6. The propeller as claimed in claim 5, wherein the counterweight arm is made of two parts, said inner ventilation discharge channel being formed partially in each of the two parts.

7. The propeller as claimed in claim 1, wherein said pivot is equipped with a first counterweight system, provided with a first inner channel fitted with an airflow introduction end and an inner end, and a second counterweight system, provided with a second inner channel fitted with an airflow ejection end and an inner end, and wherein said pivot comprises a first inner communicating channel, whereof a first end terminates at a level of the blade foot and a second end terminates at a level of the inner end of the first inner channel, and a second inner communicating channel, whereof a first end terminates at the level of the blade foot and a second end terminates at a level of the inner end of the second inner channel.

8. The propeller as claimed in claim 1, wherein said pivot enables pitching of the blade by controlling rotation of said pivot within the housing of the blade support ring.

9. The propeller as claimed in claim 1, wherein said pivot comprises at least one of airflow introduction means and ejection means including an orifice to ventilate the foot of the blade.

10. The propeller as claimed in claim 9, wherein the at least one of the airflow introduction means and ejection means is integrated in a blade profile, at a level of at least one of a leading edge and trailing edge of the blade.

11. The propeller as claimed in claim 9, wherein said pivot is provided with an upright of aerodynamic form capable of engaging in a corresponding upright housing of the blade, said upright of aerodynamic form comprising the at least one of airflow introduction means and ejection means.

12. The propeller as claimed in claim 11, wherein the upright of aerodynamic form and the corresponding upright housing of the blade are formed at a level of a leading edge of the blade.

13. The propeller as claimed in claim 9, wherein the at least one of the airflow introduction means and ejection means is formed in a thickness of said pivot, on a lateral surface of said pivot at a level of a leading edge of the blade.

14. The propeller as claimed in claim 9, wherein said pivot is provided with a first upright of aerodynamic form at a level of a leading edge of the blade, capable of engaging in a first corresponding upright housing of the blade, and a second upright of aerodynamic form at a level of an edge opposite the blade, capable of engaging in a corresponding second upright housing of the blade, the first and second upright housings comprising respectively the airflow introduction means and ejection means.

15. The propeller as claimed in claim 9, wherein the at least one of the airflow introduction means and ejection means of said pivot allows cables through for operation of the turboengine.

16. The propeller as claimed in claim 1, wherein said pivot comprises cooling means of the blade foot by interaction with the ventilation airflow, the cooling means comprising cooling fins located inside the pivot.

17. The propeller as claimed in claim 16, wherein the cooling fins are distributed symmetrically inside the pivot.

18. The propeller as claimed in claim 16, wherein the pivot comprises a substantially cylindrical and hollow lower part having a general U-shaped cross-section, and an upper part having a groove for holding the blade foot, the cooling means being located inside the lower part.

19. The propeller as claimed in claim 16, wherein at least one of the blade, the pivot, the counterweight system, and the cooling means is made of composite material.

20. The propeller as claimed in claim 1, wherein said pivot comprises coolant.

21. The propeller as claimed in claim 20, wherein the coolant comprises sodium.

22. The propeller as claimed in claim 20, wherein the coolant is contained in a hermetically sealed container.

23. The propeller as claimed in claim 20, wherein the pivot comprises a substantially cylindrical and hollow lower part having a general U-shaped cross-section, and an upper part having a groove to hold the blade foot, the coolant being located inside the lower part.

24. The propeller as claimed in claim 1, wherein said pivot comprises a Peltier cell.

25. The propeller as claimed in claim 24, wherein the Peltier cell comprises fins.

26. The propeller as claimed in claim 24, further comprising electrical means, including an electric cable, for supplying the Peltier cell with electric current.

27. The propeller as claimed in claim 24, wherein a cold source of the Peltier cell comprises the ventilation airflow, and wherein a warm source of the Peltier cell comprises a zone located under the blade foot at a level of hot gas stream.

28. The propeller as claimed in claim 27, wherein said pivot comprises at least one of airflow introduction means and ejection means of the ventilation airflow including an orifice.

29. The propeller as claimed in claim 27, wherein said pivot comprises a circulation channel of the ventilation airflow.

30. The propeller as claimed in claim 29, wherein the circulation channel is formed at least partially around the blade foot.

31. A turboengine comprising a propeller as claimed in claim 1.

32. A turboengine comprising a pair of propellers, contrarotating with respect to each other, each propeller of the pair being according to the propeller of claim 1, said pair of propellers being located downstream of a combustion chamber of said turboengine.

Description

BRIEF DESCRIPTION OF FIGURES

(1) The invention will be better understood from the following detailed description of non-limiting examples of the latter, as well as from examination of the figures, schematic and partial, of the attached diagram, in which:

(2) FIG. 1 illustrates a schematic view in longitudinal half section of a turboengine for aircraft comprising a receiver with a pair of contrarotating propellers, according to a classic design of the prior art,

(3) FIG. 2 illustrates a partial view in perspective of one of the contrarotating propellers of the turboengine shown in FIG. 1,

(4) FIG. 3 illustrates a partial view in section showing in more detail the blade support ring of the propeller, and the surrounding elements,

(5) FIG. 4 illustrates an exploded view in perspective of a blade and its associated pivot,

(6) FIG. 5 illustrates a view in perspective of a propeller of the prior art, equipped with several blade feet cavities,

(7) FIG. 6 illustrates, in section and partially, an embodiment of a propeller according to a first aspect of the invention,

(8) FIG. 7 illustrates, in perspective, a variant embodiment of the example of FIG. 6,

(9) FIG. 8 illustrates, in perspective, another embodiment of a propeller according to a second aspect of the invention,

(10) FIG. 9 illustrates a frontal view of the embodiment of FIG. 8, and

(11) FIG. 10 illustrates, in section, another embodiment according to the second aspect of the invention,

(12) FIG. 11 illustrates, in perspective, an example of a pivot for a propeller according to a third aspect of the invention,

(13) FIG. 12 illustrates, in section and partially, another example of a pivot for a propeller according to the third aspect of the invention, comprising counterweight systems,

(14) FIG. 13 illustrates, in perspective, an example of a pivot for a propeller according to a fourth aspect of the invention,

(15) FIG. 14 illustrates partially, in perspective and in partial section, an example of a platform of a pivot fitted with a blade equipping a propeller according to a fifth aspect of the invention, and

(16) FIG. 15 is a plan view, schematic and partial, of the embodiment of FIG. 14.

(17) In all these figures, identical reference numerals can designate identical or similar elements.

(18) In addition, the different parts illustrated in the figures are not necessarily according to uniform scale, in the interest of making the figures more legible.

DETAILED EXPLANATION OF PARTICULAR EMBODIMENTS

(19) In reference to FIGS. 6 and 7, two embodiments of a first aspect of the invention relating to an aircraft turboengine with a pair of open contrarotating propellers will be described hereinbelow, though these examples are not limiting.

(20) FIGS. 6 and 7 are schematic and partial, and reference should be made to FIGS. 1 to 5 previously described for viewing those elements not illustrated in FIGS. 6 and 7. In FIG. 6 in particular, the cylindrical part of the pivot especially has been omitted.

(21) In reference to FIG. 6, this illustrates a pivot 52 fitted with a groove 56 for affixing a blade foot 58 (not illustrated), according to what has been described previously.

(22) The pivot 52 is equipped with a first counterweight system 90 and a second counterweight system 91. Each of the counterweight systems 90 and 91 is provided with an inner airflow discharge channel 93 and 96.

(23) The first counterweight system 90 comprises a counterweight arm 90a and a counterweight 90b at the end of the arm 90a opposite the pivot 52. Similarly, the second counterweight system 91 comprises a counterweight arm 91a and a counterweight 91b at the end of the arm 91a opposite the pivot 52. The counterweight arm 90a and 91a comprise respectively the inner channels 93 and 96.

(24) The inner channel 93 has an inner end 97a which terminates on the pivot 52 and an airflow introduction end 97b.

(25) Also, the inner channel 96 has an inner end 98a which terminates on the pivot 52 and an airflow ejection end 98b.

(26) The introduction end 97b and the ejection end 98b each comprise a detachable dynamic bailer for passage of the airflow.

(27) Also, the pivot 52 comprises a first inner communicating channel 99a whereof one end terminates at the level of the blade foot 58 and the other end terminates at the level of the inner channel 93 of the first counterweight system 90. Similarly, the pivot 52 comprises a second inner communicating channel 99b whereof one end terminates at the level of the blade foot 58 and the other end terminates at the level of the inner channel 96 of the second counterweight system 91.

(28) Therefore, the airflow is capable of being captured by the dynamic bailer at the level of the introduction end 97b of the first counterweight arm 90a according to arrow F.sub.1, then being discharged inside the inner channel 93 and the inner communicating channel 99a to cool the blade foot 58 according to arrow F.sub.2. Next, the resulting hot flow can discharge into the inner communicating channel 99b and into the inner channel 96 to be ejected at the level of the ejection end 98b of the second counterweight arm 91b according to arrow F.sub.3, to the outside or towards the nacelle of the engine.

(29) Making the inner channels 93 and 96 in the counterweight arm 90 and 91 and the presence of bailers at the ends 97b and 98b for introduction and ejection of airflow can produce optimal cooling of the blade foot 58 since fresh airflow comes into direct contact with the latter. The counterweight arms 90 and 91 can steer the dynamic bailers and channel airflow to send it directly towards the blade foot 58. The invention can directly and mechanically link the need for ventilation to the blade pitching, and then to the different flight points.

(30) The embodiment of the invention illustrated in FIG. 7 illustrates a variant embodiment of the counterweight arms 90a and 90b.

(31) In this example, each counterweight arm 90a and 90b is respectively made in two parts 90a′, 90a″ and 91a′, 91a″.

(32) The two parts 90a′, 90a″ and 91a′, 91a″ are preferably symmetrical relative to their parting line and are made of metallic material. They are joined together to be fixed in corresponding housings of the pivot 52 and counterweight 90a and 90b.

(33) The inner channel 93 is half formed, especially by machining, in the first part 90a′ of the counterweight arm 90a and half in the second part 90a″ of the arm 90a. Thus, joining the first 90a′ and second 90a″ parts of the arm 90a forms the inner channel 93.

(34) Similarly, the inner channel 96 is half formed, especially by machining, in the first part 91a′ of the counterweight arm 91a and half in the second part 91a″ of the arm 91a. Joining the first 91a′ and second 91a″ parts of the arm 91a forms the inner channel 96.

(35) As a variant, the inner channels 93 and 96 can be integrated directly in the counterweight arm 90a and 91a from manufacture onwards, especially when the latter are made of composite material, for example woven or laminated.

(36) Embodiments of a second aspect of the invention relating to an aircraft turboengine with a pair of open contrarotating propellers will now be described hereinbelow, in reference to FIGS. 8, 9 and 10, though these examples are limiting.

(37) FIGS. 8, 9 and 10 are schematic and partial, and reference should be made to FIGS. 1 to 5 previously described for viewing those elements not illustrated in FIGS. 8, 9 and 10.

(38) In reference to FIGS. 8 and 9, these illustrate a first embodiment of a propeller according to the invention.

(39) The pivot 52 comprises a part whereof the contour P is based on the external propeller cowling 46, such that this part is located above the nacelle, in contact with the air. It is said to be located above the nacelle line.

(40) The blade foot 58, illustrated in dotted lines in FIG. 8, is located under the external propeller cowling 46, otherwise known as under the nacelle line, as can be seen especially in FIG. 9.

(41) In keeping with the invention, the pivot 52, and especially the platform 59 of the pivot 52, comprises airflow introduction and/or ejection means intended to ventilate the blade foot 58.

(42) In particular, the pivot 52, and especially the platform 59 of the pivot 52, comprises a first upright of aerodynamic form 52e located on the front of the pivot 52, at the level of the leading edge of the blade 48, and a second upright of aerodynamic form 52f, located to the rear of the blade 48.

(43) The first 52e and second 52f uprights of aerodynamic form are capable of engaging in first 48a and second 48b housings of the blade 48.

(44) The first upright of aerodynamic form 52e can comprise airflow introduction means, especially a dynamic bailer 97a, and the second upright of aerodynamic form 52f can comprise airflow ejection means, especially a dynamic bailer 97b. The bailers 97a and 97b can respectively capture and evacuate the ventilation airflow.

(45) Also, the pivot 52, especially the platform 59, comprises in the thickness of its lateral surface 52l other introduction means of the airflow, specifically bailers 98a, 98b and 98c, arranged on the front of the pivot 52 at the level of the leading edge of the blade 48.

(46) These bailers 98a to 98c can for example be seen when the pivot 52 turns with the blade 48 and the step between the nacelle and the pivot 52 appears.

(47) As can be seen in FIGS. 8 and 9, the uprights of aerodynamic form 52e and 52f comprising the introduction and/or ejection means 97a and 97b in the form of dynamic bailers, as well as the introduction means 98a to 98c also in the form of dynamic bailers, are located beyond the nacelle line such that they enable introduction and/or ejection of ventilation airflow to the exterior of the nacelle.

(48) The fact of providing the bailer 97a in a profiled part of the pivot 52, at the level of the leading edge of the blade 48, can mean having a bailer always oriented in the same way as the blade 48, in other words with a slight angle of incidence relative to the discharge of airflow allowing good capacity for capturing air.

(49) In a frontal view, FIG. 9 illustrates more precisely the discharge of airflow in the bailers 97a and 98a to 98c arranged in the pivot 52.

(50) More particularly, the airflow comes from the front of the blade 48 and is then directed towards the blade foot 58, under the nacelle line, in the form for example of two discharge channels F.sub.1 and F.sub.2 passant on each side of the blade foot 58.

(51) More specifically, as illustrated, the first discharge channel F.sub.1 can essentially comprise for example airflow passing via the bailers 97a, 98b and 98a, and the discharge channel F.sub.2 can essentially comprise airflow passing via the bailers 97a, 98c and 98a.

(52) After passing on either side of the blade foot 58, the discharge channels F.sub.1 and F.sub.2, can be joined and directed towards the edge of the blade 48 and/or the surface of the pivot 52 to be evacuated, especially by means of the bailer 97b located to the rear of the blade 48.

(53) FIG. 10 illustrates another embodiment of a propeller according to the invention.

(54) In this example, bailers 97a and 97b can be arranged in the pivot 52 similarly to what has been described in reference to FIGS. 8 and 9, to allow passage of discharge channels F.sub.1 and F.sub.2.

(55) FIG. 10 illustrates more specifically that the introduction and/or ejection means, especially in the form of bailers 97a and 97b, can also allow passage of cables involved in operating the turboengine 1, for example electric supply cables for defrosting the blade 48 and/or instrumentation cables of the blade 48.

(56) In this example in particular, a defrosting device 106 can be provided on the front of the blade 48 to which electric supply cables 99 are connected, capable of being placed in the airflow introduction and/or ejection means provided in the pivot 52 under the blade foot 58.

(57) By providing airflow introduction and/or ejection means, especially in the form of dynamic bailers, on the pivot 52 provided especially with uprights 97a, 97b of aerodynamic form, the invention can ventilate, and in particular cool, the blade feet 58 by channeling the airflow directly to their contact for optimal ventilation.

(58) In reference to FIGS. 11 and 12, two embodiments of a third aspect of the invention relating to an aircraft turboengine with a pair of open contrarotating propellers will be described hereinbelow, though these examples are limiting.

(59) FIGS. 11 and 12 are schematic and partial, and reference should be made to aux FIGS. 1 to 5 previously described for viewing the elements not illustrated in FIGS. 11 and 12.

(60) In reference to FIG. 11, this illustrates a first example of a pivot 52 according to the invention.

(61) The pivot 52 comprises a substantially cylindrical and hollow lower part 52a having a general U-shaped cross-section, as well as an upper part 52b having a groove 56 for holding the blade foot 58.

(62) In keeping with the invention, the pivot 52 comprises cooling means 100.

(63) More specifically, the cooling means 100 comprise cooling fins 101 distributed symmetrically inside the pivot 52 (in the bore of the pivot 52), in particular inside the lower part 52a. The pivot 52 comprises for example at least six cooling fins 101.

(64) Advantageously, the cooling fins 101 can interact with ventilation airflow for cooling the blade foot 58. The airflow, in contact with the cooling fins 101, allows the latter to augment the air/metal thermal exchange surface by improving thermal exchanges between the airflow and the pivot 52.

(65) FIG. 12 illustrates another example of a pivot 52 according to the invention associated with counterweight systems 90 and 91 for conveying external airflow in contact with the blade foot 58 and cooling fins 101.

(66) More particularly, the pivot 52 is equipped with a first counterweight system 90 and a second counterweight system 91. Each of the counterweight systems 90 and 91 is provided with an inner airflow discharge channel 93 and 96.

(67) The first counterweight system 90 comprises a counterweight arm 90a and a counterweight 90b at the end of the arm 90a opposite the pivot 52. Similarly, the second counterweight system 91 comprises a counterweight arm 91a and a counterweight 91b at the end of the arm 91a opposite the pivot 52. The counterweight arm 90a and 91a comprise respectively the inner channels 93 and 96.

(68) The inner channel 93 has an inner end 97a which terminates on the pivot 52 and an airflow introduction end 97b.

(69) Also, the inner channel 96 has an inner end 98a which terminates on the pivot 52 and an airflow ejection end 98b.

(70) The introduction end 97b and the ejection end 98b each comprise a dynamic bailer detachable for the passage of airflow.

(71) Also, the pivot 52 comprises a first inner communicating channel 99a whereof one end terminates at the level of the blade foot 58 and the other end terminates at the level of the inner channel 93 of the first counterweight system 90. Similarly, the pivot 52 comprises a second inner communicating channel 99b whereof one end terminates at the level of the blade foot 58 and the other end terminates at the level of the inner channel 96 of the second counterweight system 91.

(72) Therefore, the airflow is capable of being captured by the dynamic bailer at the level of the introduction end 97b of the first counterweight arm 90a according to arrow F.sub.1, then discharging inside the inner channel 93 and the inner communicating channel 99a to cool the blade foot 58 according to arrow F.sub.2. At this level, the airflow also communicates with the cooling fins 101 of the pivot 52 according to arrow F.sub.4, which increases ventilation around the pivot 52 and the passage of fresh air on virtually the entire blade foot 58 to cool it. Next, the resulting hot flow can discharge into the inner communicating channel 99b and in the inner channel 96 to be ejected at the level of the ejection end 98b of the second counterweight arm 91b according to arrow F.sub.3, to the outside or towards the nacelle of the engine.

(73) In reference to FIG. 13, an embodiment of a fourth aspect of the invention relating to an aircraft turboengine with a pair of open contrarotating propellers will now be described hereinbelow, though this example is not limiting.

(74) FIG. 13 is schematic and partial, and reference should be made to FIGS. 1 to 5 previously described for viewing those elements not illustrated in FIG. 13.

(75) In reference to FIG. 13, this illustrates an example of a pivot 52 according to the invention.

(76) The pivot 52 comprises a substantially cylindrical and hollow lower part 52a having a general U-shaped cross-section, as well as an upper part 52b having a groove 56 for holding the blade foot 58.

(77) According to the invention, the pivot 52 comprises coolant 103, the latter especially comprising sodium.

(78) The coolant 103 is for example contained in a container 102, housed inside the pivot 52, in the lower part 52a.

(79) The presence of sodium 103 in the container 102 improves the thermal conductivity of the pivot 52 and augments possible thermal exchanges with ventilation airflow for cooling the blade foot 58.

(80) In particular, it can be possible to guide heat from the base of the pivot 52, that is, from the base of the lower part 52a near the hot vein, towards the top of the pivot 52, that is, at the level of the upper part 52b near the blade foot 58 in contact with the fresh ventilation air.

(81) The container 102 can be made by machining.

(82) The container 102 must preferably be made so as not to limit the mechanical performance of the pivot 52. In particular, the container 102 must be hermetically sealed once the sodium 103 or any other coolant is injected inside the latter.

(83) It is especially important to ensure that no air bubble is trapped inside the container 102 once the latter is filled with sodium, to prevent any risk of divergent chemical reaction between the sodium 103 and the water contained in the air in the form of humidity.

(84) In addition, the presence of air bubbles in the container 102 could cause reheating of the air due to thermal transfers, which would cause a rise in pressure in the container 102 and an unwanted rise in mechanical stresses on the pivot 52.

(85) In reference to FIGS. 14 and 15, an embodiment of a fifth aspect of the invention relating to an aircraft turboengine with a pair of open contrarotating propellers will finally be described hereinbelow, though these examples are not limiting.

(86) FIGS. 14 and 15 are schematic and partial, and reference should be made to FIGS. 1 to 5 previously described for viewing those elements not illustrated in FIGS. 14 and 15.

(87) In reference to FIGS. 14 and 15, these illustrate a pivot 52, especially the platform of the pivot 52, for affixing a blade foot 58, in accordance with what has been described previously.

(88) According to the invention, the pivot 52 comprises a Peltier cell in the form of fins 104 to enable cooling of the blade foot 58.

(89) More particularly, the fins 104 can connect a warm source to be cooled, and especially the interior of a turning nacelle of the turboengine 1 around the blade foot 58, to a cold source via which calories can be evacuated, for example by means of an electrical path.

(90) The cold source for example comprises ventilation airflow F, captured from the exterior because of the dynamic bailers 97, then is guided in a circulation channel 105 formed in the pivot 52, and especially in the platform 59, and intended to bring the ventilation airflow F into contact with the fins 104.

(91) The fins 104 also receive hot air originating from the warm source located under the blade foot 58.

(92) Electrical means, and especially an electric cable (not illustrated), are also provided for supplying continuous current from the fins 104 and the appearance of the Peltier effect.

(93) The Peltier effect can at least partially evacuate heat from the warm source by way of ventilation airflow F and therefore cool the zone located under the blade foot 58.

(94) Some of the dynamic bailers 97 can enable introduction of the ventilation airflow F but also evacuation of the heated airflow. Also, at least one part of the bailers 97 can be located at the level of the leading edge of the blade 48 so as to always be oriented in the same way as the blade 48 for best capturing external air.

(95) In all the examples previously described, the blades 48 and/or the pivots 52 and/or the counterweight systems 90 and 91 and/or the cooling fins 101 can be made of composite material.

(96) Of course, the invention is not limited to the embodiments which have just been described. Various modifications can be made by the person skilled in the art.

(97) In particular, the examples described hereinabove in reference to the first, second, third, fourth and fifth aspects of the invention can be combined together, according to all possible technical combinations.

(98) By way of examples, the propeller 32 of the example of FIG. 6 according to the first aspect of the invention can comprise cooling means 100 formed by cooling fins 101 such as according to the third aspect of the invention, and as illustrated in FIG. 12. Similarly, this same propeller 32 can also comprise coolant 103 contained in a hermetically sealed container 102 such as according to the fourth aspect of the invention, and as illustrated in FIG. 11. Thus, it is possible to favour and further improve the thermal transfer capacities of the pivot 52.

(99) Also, in variants, not shown, embodiments according to the second and fifth aspects of the invention, such as for example respectively according to FIGS. 8 and 14, can also be combined into embodiments according to the first, third and fourth aspects of the invention, such as for example respectively according to FIGS. 6, 11 and 13.

(100) The expression <<comprising a>> must be understood as being synonymous with <<comprising at least one>>, unless otherwise specified.