GB2114375A - Antenna apparatus - Google Patents

Abstract

An antenna apparatus has a mounting device (12) to be fixed on a given installing plane (Z), a parabolic reflector (11) for receiving incoming waves, and a joint device (13) for mechanically coupling said reflector (11) with said mounting device (12). One of the surfaces (13A, 13B) formed between the mounting device (12) and joint device (13) and between the reflector (11) and joint device (13) is inclined from a plane which is normal to a central axis (CA) of the paraboloid of said reflector (11). Relative rotation of the surfaces 13A, 13B permits the parabolic reflector to be moved so as to receive signals from different directions. <IMAGE>

Description

SPECIFICATION Antenna apparatus The present invention relates to an antenna apparatus and, more particularly, to an antenna apparatus which allows easy setting or changing of the directivity of a parabolic antenna or the angle of tilt of the parabolic antenna.

In addition to television broadcasting services utilizing the VHF and UHF bands, attempts are being made to realize television broadcasting in the SHF (Super High Frequency) band of 3 to 30 GHz, which is higher than the UHF band. Conventional reception antennas such as Yagi antennas or loop antennas may not be used for reception of SHF waves. A parabolic antenna is used for this purpose: UHF broadcasting is used for local service areas, whereas VHF broadcasting is used forwide service areas. With an increase in the number of high buildings, the problem of broadcasting interference is becoming more pronounced. A community reception system has been proposed to solve this problem, which is useful for a service area of great population density.However, in the case of a service area wherein the population is sparse, cost factors prevent the actual adoption of the community reception system. Another problem of radio interference, such as ghosting which is caused bywaves reflected by a mountain, a building or the like, is also becoming more pronounced. A good solution to this problem has not yet been proposed. Although studies are being made on the use of CATV (community antenna television) and on the incorporation of a ghost canceller circuit in each TV set with a view to solving this problem, no successful practical measure has yet been reported.

According to the SHF broadcasting system, TV waves are radiated toward a geostationary satellite orbiting the equator, and the satellite retransmits the waves to the service area. The wave frequency in the SHF band is over 100 times that in the VHF band, so that the wavelength becomes as short as 25 cm and the waves propagate in the same manner as light rays, that is, in accordance with the line-of-sight theory. However, since a geostationary satellite is used for a relay station, the waves are not subject to the influence of mountains or buildings, and uniform transmission of the TV waves in a wide or even national area is thereby achieved. For reception of such SHF waves, the current type of TV set should be modified so as to be adapted to the new frequency.

The reception antenna of the set must first be considered; use of a parabolic antenna is feasible.

SHF waves received by the parabolic antenna are supplied to an SHF-UHF converter (hereinafter referred to as an S/U converter for brevity's sake) and are further supplied, if necessary, to a UHF-VHF converter before they are applied to the TV set. The S/U converter is often directly mounted on the parabolic antenna which is generally installed in the outdoors.

SHF waves may be received by a current type of TV set without any modification thereto if the S/U converter or S/U and UN converters are independently prepared as external adapters. A parabolic antenna for receiving SHF waves may be installed on a roof top or in the yard around the house, and the parabolic antenna is coupled via a cable to the TV set. In addition to the requirement of compactness, the parabolic antenna must satisfy the requirements of easy installation, light weight, and easy directional adjustment due to the fact that parabolic antennas are sold over a wide area and installed on various places. Since parabolic antennas are not currently generally used in general households, development of simple parabolic antennas is desired.

Various structures have been proposed to allow directionai adjustment of the conventional parabolic antennas as per Japanese Utility Model Publication Application No. 55-28004. According to the prior art technique in this publication (Figure 1), an antenna is mounted on a frame through a pivot mechanism.

The frame is supported on a reference plane such as the ground surface by a plurality of jacks. Individual jacks are adjusted so as to adjust the direction and angle of tilt of the antenna. In this prior art device, in order to support the total weight of the antenna and the frame with the jacks, the ruggedness or hardness of the jacks must be increased, resulting in a heavy structure and a high operating force forthe jack. An improvement to the aforesaid prior art device is proposed in the same publication (Figures 2 and 3) wherein a frame is mounted on a reference plane such as the ground surface and an antenna is mounted on the frame through a level adjustment mechanism. A support column is fixed to the frame, and a cylinder fixed to the antenna is fitted around the support column.The cylinder and the support column engage with each other th rough a spherical body and a bearing. Therefore, the cylinder is rotatable to a desired angle relative to the support column, so that the antenna may freely rotate relative to the frame. However, when the antenna is left unsupported in this state, it is inclined due to its own weight. In order to prevent this, tapping holes are formed on the cylinder at angular intervals of about 120% Screws are screwed into these tapping holes such that the distal ends of the screws may contact the support column. Therefore, individual adjustment of the three screws assures desired inclination of the cylinder (and hence the inclination of antenna) with respect to the support column, and allows fixing of the antenna.Thus, the antenna may be kept at a selected angle of tilt by appropriate tightening of the screws.

In the antenna apparatus of the aforementioned publication, the angle of tilt is adjusted through the spherical body and the bearing disposed between the cylinder and the support column. Therefore, although such an antenna apparatus may be conveniently used for radar, it is too complex in structure for a home TV set. Furthermore, this antenna apparatus only allows adjustment of the angle of tilt within a narrow angular range. In homeinstallations, an antenna apparatus may not be installed in a flat location; it may be installed in a yard, indoors, or on a roof top. Conventional apparatuses do not allow such wide selection of installation locations and therefore prevent actual home use.

It is accordingly an object of the present invention to provide an antenna apparatus which is easy to install at home, which allows easy adjustment of the direction and angle of tilt of the reflector, which is relatively simple in construction, and which allows a wide selection of installation locations.

The above object of the present invention is accomplished by an offset parabolic antenna apparatus having a mounting device fixed on an installing plane, a joint device joined to the mounting device, a reflector mounted on the joint device, and a primary feed mounted at a position deviated from the central axis of the reflector. According to this apparatus, at least one plane of the joint device which contacts with the reflector or with the mounting device is inclined with respect to the central axis of the paraboloid of the reflector. Utilizing this inclined or oblique plane, the direction and the angle of tilt of the reflector, or the direction of the antenna for maximum sensitivity, may be changed by changing the position of the reflector (or that of the primary feed) relative to the joint device.Accordingly, directional adjustment may be suitably performed without any limitation being imposed by the installation location.

This invention can be more fully understood from the following detailed description when taken in conjunction with the accompanying drawings, in which: Figure 1 is a side view of an antenna apparatus according to the present invention; Figure 2 is a rear view of a reflector and a joint device of the antenna apparatus shown in Figure 1; Figure 2A is a perspective view showing a joint device installed on the reflector of an antenna and a mounting device separated from the joint device; Figure 2B is a perspective view showing a joint device being formed of a framework; Figure 3 is a side view of the antenna apparatus shown in Figure 1; Figure 4 is a side view showing another fixing method of the joint device to a mounting device; Figures 5through 9 are views shwoing the adjustment range of the angle of tilt of the antenna apparatus according to the present invention;; Figure 70 is a schematic view showing installation states of the antenna apparatus shown in Figure 1; Figure 11 shows a figure having an elongated aperture for a fine angle adjustment; and Figure 12 is a side view of an antenna apparatus in which scales for the angle adjustment are provided.

The preferred embodiment of the present invention will now be described with reference to the accompanying drawings.

Figure 1 shows an antenna apparatus according to the present invention. A reflector 11 of a parabolic antenna is fixed through a joint device 13 onto a mounting device 12 fixed on an installing plane Z.

Reflector 11 is a parabolic reflector having a concave paraboloid front surface as a receiving surface.

Incident or incoming waves are received by reflector 11 and are focused on a predetermined focal point.

The direction of such incoming waves is the maximum sensitivity direction of the parabolic antenna.

A primary feed 14 is located at the focal point of the paraboloid and waves received thereby are supplied to an S/U converter (not shown) via a coaxial cable, wave guide or the like. One end of each of the suspension arms 15 is fixed to the reflector 11, while each of their other ends is mechanically fixed to the primary feed 14. The concave surface of reflector 11 is set such that primary feed 14 is deviated from the central axis CA of the paraboloid of reflector 11. This is to prevent deterioration in reception sensitivity due to a shadow formed by primary feed 14 if it is aligned with the central axis CA of reflector 11.

The relationship between reflector 11 and joint device 13 will now be described with reference to Figures 2 and 2A. Figure 2 shows reflector 11 from the rear surface side, and Figure 2A shows a perspective view of reflector 11, joint device 13 and mounting device 12. As may be seen from Figures 2 and 2A, joint device 13 is mounted on the rear surface of reflector 11. Joint device 13 comprises a tapered tubular member 16 having a bottom 13A, and an upper brim portion 17 which is formed integrally with tubular member 16 to extend radially outward from its edge. A plurality of apertures 18 are formed at equal intervals in the brim portion 17. A plurality of apertures 19 are similarly formed in the bottom 13A of tubular member 16.The two end planes of the tubular member 16, that is, the top end plane 13B containing brim portion 17 and the bottom end plane 13A are not perpendicular to the central axis AX of tubular member 16 but are oblique. Brim portion 17 of the end plane 13B is brought into contact with the rear surface of reflector 11, and fastening members 20 such as screws or nuts and bolts are inserted through the apertures 18 and are tightened, thereby fixing joint device 13 and reflector 11 to each other. When screws are used, they are inserted from the side of brim portion 17 and are screwed into tapping holes (not shown) formed in the reflector 11 or in a metal fixture integrally formed therewith. Reflector 11 and joint device 13 may be fixed to each other in a similar manner when nuts and bolts are used.In this case, the bolts may be embedded in reflector 11 or in brim portion 17 in advance. Other fixing methods such as a snap lock may alternatively be adopted. Although joint device 13 and reflector 11 are fixed in this manner, either of them may be rotated relative to each other after loosening the fastening members 20, so as to move or slide the reflector 11 at the positions of apertures 18. The position of primary feed 14 may be changed in this manner. The fixation by fastening members 20 also serve to reinforce the joint device 13 and the reflector 11.

The relationship between the joint device 13 and the mounting device 12 will now be described.

Mounting device 12 comprises, for example, a cylinder 21 with an upper surface 21A (Figure 1).

Upper surface 21A of cylinder 21 defines a mounting plane which is substantially identical in shape to the bottom 13A of tubular member 16 (Figure 2). A plurality of tapping holes or bolts (not shown), corresponding to the number of apertures 19, are circularly formed or arranged at equal intervals in the upper surface 21A of cylinder 21. With this arrangement, the tapping holes or the bolts of mounting device 12 coincide with apertures 19 of the joint device 13. Screws are inserted in the tapping holes of upper surface 21A, or the bolts are tightened with nuts (not shown) so as to fix joint device 13 to mounting device 12.For example, when tapping holes 32 are formed in the mounting device 12 (Figure 2A), screws 31 are inserted from the interior of the tubular member 16 of the joint device 13 through apertures 19 and are engaged with tapping holes 32 of the mounting device 12. In this case, the tubular member 16 must be fixed with screws 31 to the mounting device 12 before the reflector 11 is mounted on the joint device 13.

Openings 22 as indicated by broken lines in Figure 2 or 2A may be formed on the side wall of tubular member 16. When such openings are formed, a hand or a proper instrument may be inserted therethrough to allow easy attachment of the mounting device 12 to the tubular member 16 irrespective of whether or not reflector 11 is fixed to the joint device 13. As shown in Figure 2B, it is also possible to provide the tubular member 16 in the form of framework 16A and to form a brim portion 17 or mounting plane at each of the top and bottom ends of framework 16A. When nuts and bolts are used, they may be embedded in either the mounting device 12 or the joint device 13. In either case, the mounting device 12 and the joint device 13 may be fixed to each other by tightening the nuts and bolts.

Instead of using a cylindrical mounting device 12 which has an upper surface 21A (Figure 1), the mounting device 12 may have an upper brim portion similar to brim portion 17 of the joint device 13, and tapping holes, bolts or through holes may be formed in this brim portion in correspondence with apertures 19 of joint device 13.

Mounting device 12 may have a jack-like configuration as shown in Figure 2A. This device 12 comprises an inclination board 30. Board 30 is provided with eight tapping holes 32 arranged at 45Q angular intervals. The four apertures 19 of joint device 13 have 90 angular intervals which coincide with four holes 32 of the inclination board 30. With this arangement the relative angular position of reflector 11 with respect to board 30 can be changed every 45 . One side of the inclination board 30 is coupled to a base member 34 by means of a hinge member 36.

The other side of board 30 is coupled to a link member 40. Member 40 is U-shaped and the center position of the yoke 40A of member 40 is provided with a nut 42. Link member 40 is coupled at the nut 42 portion to a hinge member 44 via a screw 46.

An angle formed between inclination board 30 and base member 34 (or installing plane Z) can be change by ++. When the head 46A of screw 46 turns in a clockwise direction, the yoke 40A is pulled toward hinge member 44 (arrow a), the side yokes of link member 40 turn in a counterclockwise direction (arrow b), and the board 30 turns in clockwise direction (arrow c). Then the angle a is decreased by -. When the head 46A of screw 46 turns in a counterclockwise direction, the angle a is increased by +4).

Figure 3 shows a view in which the mounting device 12 does not show oblique end planes (a = 0); the same reference numerals as in Figures 1 and 2 denote the same parts and a detailed description thereof is omitted. Figure 3 illustrates the side view of the antenna apparatus seen from the downward side of Figure 1.

Joint device 13 and mounting device 12 may be fixed in the manner as shown in Figure 4. Referring to Figure 4, brim portions 23 and 24 are formed for the joint device 13 and the mounting device 12, respectively. Brim portions 23 and 24 are fixed to each other by nuts 26 and bolts 25 or by any other suitable fixing means. According to this arrangement, disassembly is easy. It is noted that the joint device 13 and the mounting device 12 may be fixed by any other suitable method. Another brim portion 27 is formed at the end plane of mounting device 12 which faces the installing plane Z. Using fastening members 28 such as dog nails or bolts, brim portion 27 of the mounting device 12 is fixed onto the installing plane Z of a stationary object.

With the arrangement as described above, when the joint position between the reflector 11 and the joint device 13 is changed or when the joint position between the joint device 13 and the mounting device 12 is changed, the angle of tilt of the reflector 11 or the position of primary feed 14 relative to the direction of incoming waves may be freely changed by means of the oblique end of the joint device 13 or that of the mounting device 12 with respect to the axial direction of reflector 11. The procedures for changing the angle of tilt of reflector 11 or the position of primaryfeed 14 will now be described with reference to Figures 5 through 9.

Figure 5 shows a case wherein the primary feed 14 is set at an upper position in the figure. The angle being defined by installing plane Z and the slidable positioning plane between devices 12 and 13 is represented by a, and the maximum variation of angle a is represented by + (cf. Figure 1). The angle of central axis CA of reflector 11 with respect to the direction of incoming waves is represented bye (cf.

Figure 1), while the angle of central axis CB of mounting device 12 with respect to central axis CA of reflector 11 is represented by ss (cf. Figure 3). In Figure 5, the angle of central axis CA of reflector 11 with respect to installing plane Z is presented by A which is equal to a/2 - (a + P + 4)). The angle of the direction of incoming waves with respect to installing plane Z is presented by B which is equal to a/2 (a++4))-(3.

Figure 6 shows a state wherein reflector 11 is rotated relative to joint device 13 by 1800 (half turn) from the state shown in Figure 5. In this case, the angle of central axis CA of reflector 11 with respect to installing plane Z remains A, while the angle of the direction of incoming waves with respect to installing plane Z changes from B to C which is equal to s/2 - (a + P + +) + e. Thus, the sign of the angle e has been inverted (- to +). From this, it is seen that the maximum angular range of 20 may be obtained by rotating the reflector 11 relative to the joint device 13.

A case wherein the joint device 13 is rotated relative to the reflector 11 and the mounting device 12 will now be described with reference to Figure 7.

Referring to Figure 7, the angle D of the central axis CB of the mounting device 12 with respect to the installing plane Z is represented by ::/2 - (a j 4)).

When the angle of the central axis CB of the mounting device 12 with respect to the central axis CA of the reflector 11 is represented by P and the angle of the central axis CA of the reflector 11 with respect to the direction of incoming waves is represented by 6, the angle C of the direction of incoming waves with respect to the installing plane Z is equal to jug/2 - (a + P i +) + 6, as in the case of Figure 6.

Figure 8 shows a state wherein the joint device 13 is rotated by 180 (half turn) relative to the reflector 11 and the mounting device 12 so as to invertthe relationship between the reflector 11 and the mounting device 12. In Figure 8, the angle D remains the same as it is in Figure 7, while the angle of the direction of incoming waves with respect to the installing plane Z changes from C to E which is equal to a/2 - (a - ss + zp) + 0. When the angles C and E are compared, the sign for P has been inverted from (+) to (-).Therefore, the joint device 13 maybe rotated for obtaining a maximum angular range of 2p. It is seen from the above description that the angles P and 6 may be adjusted within the ranges of 2P and 26, respectively. The unit of adjustment within these ranges may be freely changed by means of the number of apertures 18 and 19 formed in the joint device 13 and the angular intervals therebetween.

Figure 9 shows the adjustment of the angle of tilt of the reflector 11 with respect to Figures 5 through 8. In Figure 9, the adjustment ranges of angles a, P, 8 and f are shown, and the total adjustable range is represented by the angle F. Within the range of this total adjustment angle F, the angle of tilt of the reflector 11 may be freely adjusted.

With an antenna apparatus in which the range of adjustment for the angle of tilt is variable, the central axis CA of the reflector 11 may be set to the desired direction even if installing plane Z is at various angles as shown in Figure 10. For example, even if the installing plane Z extends vertically or horizontally, the angle of the reflector 11 with respect to the joint device 13 and the angle of the joint device 13 with respect to the mounting device 12 may be adjusted so as to allow appropriate setting of the angle of tilt of the antenna apparatus for any installing plane.

In the above description, the reflector 11, the joint device 13 and the mounting device 12 are fixed to each other by means of the apparatus 18 and 19. As shown in Figure 11, apertures 18 and/or 19 may alternatively comprise arcuated elongate holes to allow fine and smooth angular adjustment instead of stepped adjustment. However, in this case, a reinforcing member must be incorporated or thicker material must be used for the brim portion 17 or for the plate in which the apertures 19 are formed in view of mechanical strength, although convenient adjustment is obtained. Other fixing methods may also be adopted; adjustment is facilitated if scales Sa and/or Sû for an angle display is provided as shown in Figure 12 (a scale for the angle P is not shown).In such a case, the angles 6 and/or P should be set to be below 2 (cf. Figure 9). Also, the adjustment range ~ may be set to be smaller if 6 76 ss. If the mounting direction of reflector 11 is other than horizontal or vertical, both the direction and the angle of tilt of reflector 11 must be adjusted. If the direction and the angle of tilt are suitably selected in accordance with the latitude and longitude of an installation location, the amount of displacement or movement of the mounting device may be directly translated into changes in latitude and longitude. In this case, however, the value of the angle Q should be slightly larger than that in the cases described above.In the above description, the end planes of both the joint device 13 and the mounting device 12 are oblique.

However, the end planes of the mounting device 12 need not be oblique, while both end planes of the joint device 13 may be oblique. Alternatively, both end planes ofthe mounting device 12 may be oblique, while the end plane of the joint device 13 which faces the mounting device 12 may be parallel thereto. Various other changes and modifications may be made within the scope of the present invention.

According to the present invention, the antenna apparatus may be suitably mounted in accordance with the selected installation location and weather conditions, by suitably setting the angles a, ss, 6 and 4). Therefore, the installation location of the antenna apparatus is not limited to a specific one and the installation procedure is fast and easy. The adjustment range of the mounting device 12 may be reduced to 1/3 to 1/6 of the conventional range, resulting in a simple and inexpensive apparatus. The antenna apparatus of the present invention is mechanically strong and withstands bad weather conditions such as wind.

Claims (28)

1. An antenna apparatus comprising: a mounting device to be fixed to a given installing plane; a parabolic reflector for receiving incoming waves; a joint device for mechanically coupling said reflector with said mounting device, and having a first coupling plane formed between said mounting device and said joint device and a second coupling plane formed between said reflector and said joint device, at least one of said first and second coupling planes being inclined from a plane which is normal to the central axis of the paraboloid of said reflector, and at least one of said first and second coupling planes being slidable so that the direction of the antenna for maximum sensitivity or the direction of incoming waves is changed according to the relative sliding movement of at least one of said first and second coupling planes.

2. The antenna apparatus of claim 1, wherein said first coupling plane is defined between said mounting device and said joint device, and said mounting device and said joint device are coupled with each other by at least two first fastening means.

3. The antenna apparatus of claim 2, wherein said first fastening means are circularly and equidis tantly arranged on said joint device.

4. The antenna apparatusofclaim 1,wherein said second coupling plane is defined between said reflector and said joint device, and said reflector and said joint device are coupled with each other by at least two second fastening means.

5. The antenna apparatus of claim 4, wherein said second fastening means are circularly and equidistantly arranged on said joint device.

6. The antenna apparatus of claim 1, wherein said first and second coupling planes are inclined from the plane being normal to the central axis of said joint device, and said mounting device and said joint device are coupled with each other by a plurality of first fastening means, and said reflector and joint device are coupled with each other by a plurality of second fastening means.

7. The antenna apparatus of claim'6, wherein each of said first and second fastening means has a circular arrangement.

8. The antenna apparatus of claim 1, wherein said given installing plane is inclined from the plane being normal to the central axis of said reflector, and said mounting device is slided on said given installing plane so that the maximum sensitivity direction of the antenna is changed according to the relative sliding movement of said mounting device.

9. The antenna apparatus of claim 2, wherein said given installing plane is inclined from the plane being normal to the central axis of said reflector, and said mounting device is slidable on said given installing plane so that the maximum sensitivity direction of the antenna is changed according to the relative sliding movement of said mounting device.

10. The antenna apparatus of claim 4, wherein said given installing plane is inclined from the plane being normal to the centra axis of said reflector, and said mounting device is slidable on said given installing plane so that the maximum sensitivity direction of the antenna is changed according to the relative sliding movement of said mounting device.

11. The antenna apparatus of claim 6, wherein said given installing plane is inclined from the plane being normal to the central axis of said reflector, and said mounting device is slidable on said given installing plane so that the maximum sensitivity direction of the antenna is changed according to the relative sliding movement of said mounting device.

12. The antenna apparatus of claim 1,wherein said mounting device includes means for adjusting the angle formed between said given installing plane and the first coupling plane which is defined by said mounting device and said joint device.

13. The antenna apparatus of claim 2, wherein said mounting device includes means for adjusting the angle formed between said given installing plane and the first coupling plane which is defined by said mounting device and said joint device.

14. The antenna apparatus of claim 4, wherein said mounting device includes means for adjusting the angle formed between said given installing plane and the first coupling plane which is defined by said mounting device and said joint device.

15. The antenna apparatus of claim 6, wherein said mounting device includes means for adjusting the angle formed between said given installing plane and the first coupling plane which is defined by said mounting device and said joint device.

16. The antenna apparatus of claim 8, wherein said mounting device includes means for adjusting the angle formed between said given installing plane and the first coupling plane which is defined by said mounting device and said joint device.

17. The antenna apparatus of claim 9, wherein said mounting device includes means for adjusting the angle formed between said given installing plane and the first coupling plane which is defined by said mounting device and said joint device.

18. The antenna apparatus of claim 10, wherein said mounting device includes means for adjusting the angle formed between said given installing plane and the first coupling plane which is defined by said mounting device and said joint device.

19. The antenna apparatus of claim 11, wherein said mounting device includes means for adjusting the angle formed between said given installing plane and the first coupling plane which is defined by said mounting device and said joint device.

20. The antenna apparatus of claim 1, wherein said reflector is provided with a primary feed which is offset from the central axis of said reflector.

21. The antenna apparatus of claim 2, wherein a scale for indicating the relative sliding movement of at least one of said first and second coupling planes is provided on said mounting device.

22. The antenna apparatus of claim 4, wherein a scale for indicating the relative sliding movement of at least one of said first and second coupling means is provided on said reflector.

23. The antenna apparatus of claim 6, wherein scales for indicating the relative sliding movement of said first coupling means and said second coupling means are provided, respectively, on said joint device and reflector.

24. The antenna apparatus of claim 2, wherein a scale four indicating the relative sliding movement of at least one of said first and second coupling planes is provided on said joint device.

25. The antenna apparatus of claim 4, wherein a scale for indicating the relative sliding movement of at least one of said first and second coupling means is provided on said joint device.

26. The antenna apparatus of claim 6, wherein scales for indicating the relative sliding movement of said first coupling means and said second coupling means are provided, respectively, on said mounting device and reflector.

27. The antenna apparatus of claim 12, wherein said mounting device includes a scale for indicating the amount of said angle.

28. An antenna apparatus, substantially as hereinbefore described with reference to the accompanying drawings.