DE1051680B - Method and device for preprocessing three-dimensional curved surfaces - Google Patents

Description

GERMAN

The invention relates to a method and a device for preprocessing three-dimensional curved surfaces by cutting grooves corresponding to the surface shape. The invention aims at this ab, such a method and a device for the pre-machining of the drive surfaces on the blades of raw cast ship propellers. This should make the final edit the ship's propeller must be prepared or relieved.

In order to understand the subject matter of the invention, the definitions of terms for an It is assumed that there is a significant angle occurring in the propeller blade:

The shape of the driving surface of a ship prop eil is created by the angle of inclination and by determines the pitch angle. The pitch angle is the angle between one perpendicular to the propeller axis located plane and a line running on the center of the shovel from root to tip, d. H. from the blade part closest to the propeller hub to the blade part on the largest Diameter of the propeller. The lead angle is the angle between the blade surface and a plane perpendicular to the propeller axis, measured in a Plane that tangentially touches a cylinder that is coaxial with respect to the propeller axis at the measuring point. Of the The angle of inclination indicates the twist of the blades, while the angle of inclination indicates that of the stern of the ship represents backward blade inclination.

The angle of inclination remains constant from the foot to the tip of the shovel. But almost all of them Ship propellers of modern shape have blades, the pitch angle of which is in the range between The base and tip of the shovel vary. Therefore, it is only possible with great effort to remove the drift surfaces to process the blades according to manufacturing processes that were common at the time, as the Propeller blades usually have a pitch angle that is constant in the area between the root and the tip exhibited.

The invention aims to provide a relatively simple method and a corresponding one Machine that make it possible to achieve a high level of accuracy in the manufacture of a propeller achieve whose pitch angle changes in the area between the blade root and the blade tip, indifferent how big the change in the pitch angle is. There are already for processing such blades Machines have been proposed for cutting a series of grooves on the blade surface can be.

Method and device

for preprocessing
three-dimensional curved surfaces

Applicant:

Bull's Metal & Marine Limited,
Yoker, Glasgow (Great Britain)

Representative: Dipl.-Ing. B. Wehr, Dipl.-Ing. H. Seiler,

Berlin-Grunewald,

and Dipl.-Ing. H. Stehmann, Nuremberg 2,
Essenweinstrasse 4-6, patent attorneys

Claimed priority:
Great Britain 23 October 1952

Joseph Francis Tucker, Troon, Ayrshire,
and Peter Mathieson, Princess Crescent, Renfrewshire

(Great Britain),
have been named as inventors

In this case, the processing tool is synchronized with the sequence of an on by a follow-up gear controlled by a model or a sample piece guided copy roller.

A machine is also available for producing complex frustoconical surfaces with straight generatrices suggested. The tool can be pivoted about a vertical pivot pin Arm clamped, with the arm in a vertical plane around any point of its length or is pivotable in extension of its longitudinal direction. The arm is guided on two outline plates and by pivoting the arm about the vertical pivot along with the cutting tool can be a limited strip of the surface of the workpiece with the desired curve shape be provided. In this known embodiment, the tool is then clamped off, a Moved a short distance along the arm and clamped there again to make a new cut.

However, this machine is also generally used for machining ship propeller blades not applicable because these workpieces are very large, so that they can only be used under very difficult circumstances could be attached between contour plates.

8OJ 767/54

Claims (1)

The invention relates first of all to a method for pre-machining three-dimensional curved surfaces by cutting grooves corresponding to the surface shape. What is inventive here is that in the blades of ship propellers, first a radial groove is cut from the base to the tip and then circular sector grooves are cut at intervals with a corresponding pitch, the radial groove and the circular groove being the same depth. This process greatly simplifies setting or achieving the exact depth of cut of the grooves running in the circumferential direction. It is also of essential importance here that this method is readily applicable to ship propellers of very large dimensions. The invention also relates to a machine for pre-machining such three-dimensional curved surfaces with a grinding device sliding along a guide arm pivotable about a main axis of the device, the height and inclination of the guide arm being adjustable. According to the invention it is provided that the position of the guide arm is determined on the one hand by a joint near the main axis of the device and on the other hand at the free end by a circular rail whose inclination is adjustable. In the machine according to the invention, there is therefore no need for models or patterns that have to be scanned by a copying tool, nor is it necessary to provide the contour plates mentioned. The circular rail, which is used to guide the arm and whose inclination is adjustable, is of a much simpler construction than the known devices, and above all it can be used without further ado when machining large areas. The grooves cut by the grinding device serve as a means of precise control during the final manual finishing, in which they are ultimately made to disappear. An embodiment of the invention will now be described with reference to the drawings. 1 shows a view of the machine, partly in section, FIG. 2 a plan view, with certain parts being omitted for the sake of clarity, FIG. 3 an elevation of the guide and its fastening and FIG. 4 a partial view. In this embodiment, the propeller 1 is centered on a circular table 2 by means of claws or clamping screws 3 (FIG. 2). The table 2 is fastened on a piston 4 which is guided in a cylindrical cavity in the base plate 5. A tube 6 is connected to the bottom of the cylindrical cavity. It comes from a manually operated piston pump 7. When a propeller 1 is attached in this way, the table 2 cannot be easily rotated due to friction; if the oil pressure is increased sufficiently by the hand pump 7, on the other hand, the table 2 with the propeller 1 can easily be rotated into any desired position. The purpose of this arrangement, known per se, is to enable the propeller to be brought into the correct angular position, blade by blade, for machining with a minimum of labor and resources. A cylindrical shaft 8 is fixed in the table 2 and is held at its upper end by removable supports 9. A bracket 10 is arranged on the column 8 so as to be vertically displaceable and pivotable in the circumferential direction. On a downward extension 11 of the console 10, a tubular guide arm 12 is attached to a joint 11 a, which is supported at its outer end by an adjustable pull rod 13, the length of which is adjustable by means of a screwable end part 13 a and the other End with the upper part of the console 10 is hinged ίο. A slide 14, which is controlled by a lead screw 15, slides on the tubular guide arm 12. The slide 14 is secured on the guide arm 12 against rotation along the groove 16. A grinding machine 17 with a thin, preferably synthetic resin-bonded grinding wheel 18 is attached to the slide 14. In order to facilitate the work of the grinding machine 17 while the console 10 slides and is pivoted on the column 8, the latter is balanced by counterweights 19, 20 and provided with associated counter levers 21. At the outer end of the guide arm 12, a small carriage 22 is attached, which is provided with a roller 23 which rests on the surface of a rail 24. The length of the guide arm 12 can be adjusted by means of a slidable end part 12a and a clamping bolt 12b in order to keep the roller 23 in contact with the rail 24 when the angle of inclination of the guide arm 12 is changed by adjusting the pull rod 13. The rail 24 is supported by a number of adjustable supports 25 mounted on an arched bracket 26 of rigid but light construction which lie radially to the column S. The supports 25 are each engraved with numbers so that the rail 24 can easily be adjusted to any desired pitch angle. When the device is actuated, the propeller 1 is centered with respect to the column 8 after it has been fastened on the table 2 with the propulsion surface directed upwards. Then the table 2 is rotated after a slight lifting by means of the hand pump 7 so that a shovel is aligned with the center of the guide rail 24 Tip cut to the base of the propeller blade. By pivoting the guide arm 12 about the column 8, the circular sector grooves are then cut, the distances between which in the radial direction can be between 75 and 150 μm, depending on the circumstances. The angle of inclination belonging to the grooves running in the circumferential direction is set on the rail 24. The incised grooves with their bottom surface provide a guide for finishing. The finishing can be carried out in a manner known per se with manually operated machines. In order to remove the machined propeller, the supports 9 are to be swiveled sideways, and a crane can be used to remove the entire device including the workpiece via an eyelet attached to the top of the column S. Patent claims: 1. Method for pre-processing three-dimensional x-curve surfaces by cutting into the