EP0110263B1

EP0110263B1 - Chamfering method for a curved slot corner

Info

Publication number: EP0110263B1
Application number: EP19830111557
Authority: EP
Inventors: Masaru Hamada; Mitsutoshi Tsutsumi
Original assignee: Toyota Motor Corp
Current assignee: Toyota Motor Corp
Priority date: 1982-11-20
Filing date: 1983-11-18
Publication date: 1988-03-09
Also published as: EP0110263A3; EP0110263A2; DE3375884D1; JPS5997833A

Description

Background of the invention

1. Field of the invention

The present invention relates to a method for chamfering a curved edge portion of a workpiece according to the preamble of claim 1.

2. Description of the prior art

The US―A―1 771 417 shows a method where the lower edge of workpieces having a curved shape is chamfered by a grinding belt travelling along a curved surface of a back-up plate. The workpiece is held relatively loosely here between an upper holder gripping around its upper edge and a lower holder gripping around the lower portions of its lateral edges.
In this method the pressure required for the chamfering operation is provided by the workpiece's own weight or by the upper holder's own weight, respectively. In cases where high pressures are required, the upper holder can be provided with an additional weight, or the back- up plate can be provided with a device pressing it against the workpiece.
The object of the invention is to so develop the method according to the preamble of claim 1 that it can be used in simple manner for workpieces with open slots.
According to the application, this object is achieved by the features in the characterizing portion of the claim 1.
In this method the pressure required for the chamfering operation is obtained by exploiting the geometry of the workpiece in connection with a change in the positional relationship of the two holders. It can be carried out without additional weights or pressing devices even in cases where high pressures are required.

Summary of the invention

An object of the present invention is to provide a method for chamfering a longitudinally curved slot corner formed by a front surface of a slotted member and a longitudinally curved surface of said slotted member defining a slot. The chamfering method for a curved slot corner according to the present invention comprises the following steps. The first step is to hold the upper end and the lower end of the slotted member with an upper holder and a lower holder respectively. The second step is to place in a slot of the slotted member a backup plate whose upper surface is curved in a plane normal to the- longitudinal direction of the backup plate. The third step is to apply a flexible grinding belt to the upper surface of the backup plate so as to let the grinding belt travel in the slot. The fourth step is to make said upper holder and lower holder shift relative to each other, thereby tilting the slotted member, and push said backup plate toward a longitudinally curved slot corner to be chamfered by a longitudinally straight slot corner diagonally opposed to said longitudinally curved slot corner, and then press the grinding belt which is running against the longitudinally curved slot corner to be chamfered by said backup plate, thereby executing the chamfering of said longitudinally curved slot corner.
In this method, since the upper surface of the backup plate is curved, the grinding belt, following the curvature of said backup plate, can grind the longitudinally curved slot corner of the slotted member. Thus it is made possible to chamfer a longitudinally curved slot corner, which has been impossible in the conventional method executed by using a flat backup plate.
In this method, by varying the thickness of the backup plate and the curvature of its upper surface, the chamfer angle and the width of the chamfer in the longitudinal direction of the slot can be arbitrarily selected.

Brief description of the drawings

The above and other objects, features and advantages of the present invention will be apparent and readily understood from the following detailed description of a preferred embodiment of the invention, taken in conjunction with the accompanying drawings, of which:

Figure 1 is a front view of a slotted workpiece before chamfering is executed;
Figure 2 is a sectional view of the slotted workpiece along to line II-II in Fig. 1;
Figure 3 is a front view of the slotted workpiece after chamfering is executed;
Figure 4 is a sectional view of the slotted workpiece along line IV-IV in Fig. 3;
Figure 5 is a partial sectional view of the chamfering device with slotted workpieces held between an upper holder and a lower holder;
Figure 6 is a partial sectional view of the chamfering device in which a backup plate is partly placed in the slots of the slotted workpieces;
Figure 7 is a partial sectional view of the chamfering device in which a grinding belt is applied to the upper surface of the backup plate;
Figure 8 is a whole sectional view of the chamfering device in which the slotted workpieces are being chamfered;
Figure 9 is a sectional view of the slotted workpiece along line IX-IX in Fig. 8;
Figure 10 is an oblique view of the backup plate;
Figure 11 is an oblique view showing a projection of a longitudinally curved corner portion onto a plane normal to the longitudinal direction of the grinding belt; and
Figure 12 is a partial sectional diagram illustrating the relationship among the thickness t of the backup plate, the thickness T of the slotted workpiece, the thickness t' of the grinding belt and the width W of the slot.

Detailed description of the preferred embodiment

Figures 1 and 2 illustrate a slotted workpiece before chamfered by the method of the present invention. Figures 3 and 4 illustrate the same slotted workpiece after chamfered by the method of the present invention. As seen from the figures, the slotted workpiece 1 constitutes of a plate with a slot 2. The slot 2 extends from one side 1 a of the slotted workpiece 1 toward the other side 1 b of the workpiece 1 and it is open at said one side 1 a. The slot 2 penetrates from the front surface 1c to the back surface 1d of the slotted workpiece 1 in the thickness direction of the member 1.
Of the two longitudinal side surfaces of the slot 2, one side surface 2a is curved in the longitudinal direction of the slot, while the other side surface 2b is flat and longitudinally straight. The side surface 2a is continuous to the bottom surface 2c of the slot 2 and the bottom surface 2c is continuous to the side surface 2b.
In the illustrated example, the side surface 2a consists of a cylindrical surface with a radius R which is convex toward the side surface 2b. The longitudinally curved corner portion 3 which is formed by the longitudinally curved side surface 2a of the slot 2 and the front surface 1a of the slotted member 1 is a corner to be chamfered.
Figures 5 to 9 illustrate the process of chamfering according to the present invention.
As indicated in Fig. 5, first a plurality of slotted workpieces 1 with slots 2 are held between the upper holder 5 and the lower holder 6. The upper holder 5 has a plurality of grooves 5a which are open downward, while the lower holder 6 has a plurality of grooves 6a which are open upward. The slotted workpieces 1 have their top ends held in the grooves 5a of the upper holder 5 and their bottom ends held in the grooves 6a of the lower holder 6.
The upper holder 5 and the lower holder 6 can be shifted in position relative to each other with parallelness maintained. By this positional shifting, the slotted workpieces 1 are tilted from vertical position.
Next, as indicated in Fig. 6, a backup plate 8 is placed so that it may partly be placed in every slot 2 of the slotted members 1. The upper surface 8a of the backup plate 8a, that is, the belt-contacting surface 8a of the backup plate 8 is curved within every plane normal to the longitudinal direction of the backup plate 8, while the back surface 8b of the backup plate 8 is flat and straight within every plane normal to the longitudinal direction of the backup plate 8.
Next, as indicated in Fig. 7, a grinding belt 7 is applied to the upper surface of the backup plate 8 so as to travel in every slot 2 of the slotted workpieces 1. The grinding belt 7 is flexible and it is made of, e.g., a non-woven textile with one side coated with abrasive grains. The grinding belt 7, as seen from Fig. 8, is an endless belt.
Then, as indicated in Fig. 8, the positions of the upper holder 5 and the lower holder 6 are relatively shifted, thereby causing the slotted workpieces 1 to tilt by a chamfering angle.
In this condition, the backup plate 8 is pushed toward the longitudinally curved corner portion 3 to be chamfered at the back surface 8b thereof by a longitudinally straight corner portion 3' diagonally opposed, in the slot cross section, to said longitudinally curved corner portion 3 to be chamfered. Since the side surface 2b of the slot 2 is longitudinally straight and the back surface 8b of the backup plate 8 is also straight in every plane normal to the longitudinal direction of said backup plate 8, in the process of chamfering, the back surface 8b of the backup plate 8 is brought into contact with the whole length of the longitudinally straight corner portion 3' diagonally opposed to the longitudinally curved corner portion 3. In consequence, the backup plate 8 presses the grinding belt 7, with which it is in contact, against the longitudinally curved corner portion 3 to be chamfered. Thus, the longitudinally curved corner portion 3 can be chamfered by the running grinding belt 7. In this instance, the grinding belt 7 travels in the direction from the front surfaces 1c of the slotted workpieces 1 toward the back surfaces 1d of the members 1.
In the above process of chamfering, since the grinding belt 7 is flexible, it can curve itself following the profile of the curved upper surface 8a of the backup plate 8 and thus well fitting the longitudinally curved corner portion 3 to be chamfered, the grinding belt 7 can form a successful chamfer 4 at the corner portion 3. In this manner, chamfering of a longitudinally curved corner portion which has been impossible by the conventional chamfering method is rendered possible.
The upper surface 8a of the backup plate 8 contacting with the grinding belt 7 is designed such that its profile within every plane normal to the longitudinal direction of the backup plate 8 is the same as the profile of the projection 9 (see Fig. 11) of the longitudinally curved corner portion 3 onto a plane A normal to the longitudinal direction of the grinding belt 7 when the slotted workpieces 1 are tilted by a chamfer angle 8, that is, the angle of the surface of the chamfer 4 against the longitudinally curved slot surface 2a.
Such a profile of the upper surface 8a of the backup plate 8 makes the width of the chamfer 4 uniform over the entire longitudinal length of the longitudinally curved corner portion 3. The profile of the upper surface 8a of the backup plate 8 may differ from that of said projection 9, but in such a case, the width of the chamfer 4 will vary in the longitudinal direction of the longitudinally curved corner portion 3.
Meanwhile, as indicated in Fig. 12, the thickness t of the backup plate 8 is in the following relationship with the desired chamfer angle 8, the width W of the slot 2, the thickness t' of the grinding belt 7 and the thickness T of the member 1:
Therefore, the chamfer angle 8 is variable through adjusting the thickness of the backup plate 8. Accordingly the width of the chamfer 4 and the chamfer angle can be controlled.
In a chamfering work, one slotted workpiece 1 or a plurality of slotted workpieces 1 may be held between the upper holder 5 and the lower holder 6. When a plurality of slotted workpieces 1 are held between the upper holder 5 and the lower holder 6 as shown in Fig. 8, the chamfering efficiency can be increased, because a plurality of workpieces 1 can be chamfered in a single chamfering work.
Although only a preferred embodiment of the present invention has been described in detail, it will be appreciated by those skilled in the art that various modifications and alterations can be made to the particular embodiment shown without materially departing from the novel teachings and advantages of this invention. Accordingly, it is to be understood that all such modifications and alterations are included within the scope of the invention as defined by the following claims.

Claims

1. Method for chamfering curved edge portions of a workpiece (1), said workpiece (1) being inserted between an upper holder (5) and a lower holder (6), a backup plate (8), a first surface (8a) of which is curved perpendicularly to its longitudinal direction, being disposed in opposed relationship to said edge portions to be chamfered, a grinding belt (7) travelling along said longitudinal direction of said backup plate (8) between said curved surface (8a) and said edge portions to be chamfered, said grinding belt (7) being sufficiently flexible to conform to the curvature of said curved surface (8a) when travelling along said backup plate (8), characterized in that said backup plate (8) is at least partially inserted into a slot (2) formed in said workpiece (1) with the longitudinal direction of said backup plate (8) being oriented perpendicular to a curved corner portion (3) to be chamfered of said slot (2), and in that said backup plate (8) is moved toward and said grinding belt (7) is pressed against said curved corner portion (3) to chamfered by changing the positional relationship of said upper and lower holders (5, 6) thereby tilting said workpiece (1) and pushing said backup plate (8) by contact between a diagonally opposed corner portion (3') of said slot (2) and a second surface of said backup plate (8).

2. A chamfering method of claim 1 characterized in that the upper surface profile of said backup plate (8) within every plane normal to the longitudinal direction of said backup plate (8) is the same as a profile of a projection (9) of said longitudinally curved corner portion (3) to be chamfered onto a plane normal to the longitudinal direction of said grinding belt (7).

3. A chamfering method of claim 1 characterized in that the thickness t of said backup plate (8) is in the following relationship with the desired chamfer angle 8, the width W of said slot (2), the thickness t' of said grinding belt (7) and the thickness T of said slotted member (1):

4. A chamfering method of claim 1 characterized in that surface (2b) of said slot (2) opposed to said longitudinally curved surface (2a) defining the slot (2) is longitudinally straight and the back surface (8b) of said backup plate (8) is also straight in every plane normal to the longitudinal direction of said backup plate (8) so that, in the process of chamfering, said back surface (8b) of the backup plate (8) is brought into contact with the whole length of said corner (3') diagonally opposed to said longitudinally curved corner portion (3).

5. A chamfering method of claim 1 characterized in that said slot (2) extends from one side (1a) of said workpiece (1) toward the other side (1 b) of said workpiece (1) and it is open at said one side (1a).

6. A chamfering method of claim 1 characterized in that a plurality of workpieces (1) are held by said upper holder (5) and said lower holder (6) so that all the longitudinally curved corner portions (3) of said workpieces (1) can be chamfered in a single chamfering work.

7. A chamfering method of claim 1 characterized in that said grinding belt (7) is an endless one.

8. A chamfering method of claim 1 characterized in that said grinding belt (7) consists of a flexible non-woven textile coated with abrasive grains on one side.