LOCKING MECHANISM FOR SAFETY GUARDS OF HANDHELD METALWORKING MACHINES

Scope of application

The preferred embodiment relates to a locking mechanism for the safety guards of handheld metal-working machines, especially angle grinders and straight grinding machines.

Background of the invention

A locking mechanism for the safety guards of angle grinders, which is described in (1), is known.

The concept of that mechanism is that a locking disk, on the surface of which riffles are cut to point towards one direction, is concentrically fixed to the safety guard. On the locking disk there is a catch disk on the periphery of which locking teeth are cut symmetrically in relation to one another. The teeth can go into riffles. A clamping ring, on which attachment holes are drilled, is mounted on the locking disk. The attachment holes are coaxial in relation to the fastening holes drilled on the catch disk. Through the attachment and fastening hole pass clamping bolts which are screwed into the case of the grinder.

One disadvantage of the construction described above is that the number of riffles is large thus they are of low height. This results in a small common contact surface between the locking disk and the catch disk and insufficient strength when considerable forces are applied in the blocked direction. This can be very dangerous in the event of accidental damage of the tool inside the safety guard.

Another disadvantage is the possibility of placing the safety guard in any position in relation to the machine. When a worker is operating the metal-working machine not every position of the safety guard can guarantee his safety.

Furthermore, the fact that the safety guard is retained in the desired position by means of a limited number of locking teeth makes it possible for that position to be changed during operation by the accidental application of a force onto the safety guard which might move into a position that does not guarantee the worker's safety.

A design described in (2) is known. Its concept is that a metal band, which goes partly round the case of the grinder, is attached in sectors to the safety guard of the grinder. An elastic band goes round the other part of the case. One of its ends is hinged by means of an eye ring to a pin which is attached to the safety guard. The other end of the elastic band is a screw joint with the screw in the form of a tightening handle.

One disadvantage of said design is poor reliability of mounting and possibility of turning the safety guard in the process of operation as a result of the use of an elastic band.

Another disadvantage is that due to the hinged type of attachment of the metal band and the fact that the band goes partly round the case of the grinder it is possible for the safety guard to tilt in one direction and get into contact with the tool during the process of operation.

Technical description of invention

The purpose of the preferred embodiment is to create a locking mechanism for the safety guards of handheld metal-working machines, which has to ensure the fixed position and stable attachment of the safety guard in specified limits that guarantee safe operation of the tool, and prevent the safety guard from coming off, tilting and turning into a position that does not guarantee the worker's safety in the event of accidental loosening of the joint between the machine and the safety guard as well as in the event of damaging of the tool during operation.

The purpose is achieved by means of a locking mechanism for the safety guards of handheld metal-working machines, which includes a safety guard with a metal band which is tightly fixed to the internal end of the guard and goes round the case of the grinder. The two ends of the band are connected by means of an adjustable screw joint. According to the invention, locking teeth are cut and located in sectors on the outer edge of the metal band above the level of the case of the grinder. The metal band of the safety guard is pressed towards the case of the grinder by means of a fixing plate. Along its periphery there is a locking sector and an angle catch which are located opposite each other. Their diameter is larger than the diameter of the metal band. The fixing plate is mounted to the case of the grinder by means of fastening screws.

On the fixing plate there is a locking hole in which there is a locking pin which is made on the case of the grinder.

The height of the locking teeth exceeds the thickness of the fixing plate.

One advantage of the locking mechanism for safety guards of handheld metal-working machines is that it ensures very good attachment of the safety guard to the case of the grinder due to the possibility of turning the guard within optimum limits.

Another advantage is that in the event of accidental damage of the tool during operation unwarranted turning of the safety guard and getting the worker hurt by pieces of the tool are impossible.

Yet another advantage is that the fixing plate prevents one-sided slipping and tilting of the safety guard during operation and its getting into contact with the tool.

Description of the enclosed drawings

Figure 1 gives a front view of the locking mechanism for the safety guards of handheld metal-working machines. The view is in the direction of the axis of the tool. Figure 2 is a section along A-A of Figure 1. Figure 3 is a view of the safety guard. Figure 4 is a section along B-B of Figure 3.

An example of the preferred embodiment

The locking mechanism for the safety guards of handheld metal-working machines comprises a safety guard 1 with a metal band 2 which is tightly fixed to the internal end of the guard and goes round the case 3 of the grinder. The two ends of

the metal band 2 are connected by means of an adjustable screw joint 4. The locking teeth 6 are cut and located in sectors on the outer edge 5 of the metal band 2 above the level of the case 3 of the grinder. The metal band 2 of the safety guard 1 is pressed by the fixing plate 7. Along its periphery there is a locking sector 8 and an angle catch 9 which are located opposite each other. Their diameter is larger than the diameter of the metal band 2. The fixing plate 7 is mounted to the case 3 of the grinder by means of the fastening screws 10. On the fixing plate 7 there is a locking hole 11 in which there is a locking pin 12 which is made on the case 3 of the grinder. The height of the locking teeth 6 exceeds the thickness of the fixing plate 7.

Application of preferred embodiment

The locking mechanism for the safety guards of handheld metal-working machines is used in the following way. By means of screw joint 4 the safety guard 1 is mounted in desired operation position. The fixing plate 7 is mounted to the case 3 of the grinder by means of fastening screws 10. The locking sector 8 and the angle catch 9 press the metal band 2 and the whole safety guard 1 to the case 3 of the grinder. The angle catch 9 is located between the locking teeth 6 of the metal band 2. The locking pin 12 of the case 3 of the grinder goes into the locking hole 11 of the fixing plate 7 and then the fastening screws 10 are tightened. The design ensures minimum turning of the safety guard only the locking teeth 6 and complete safety of the worker.

List of positions

1. Safety guard

2. Metal band

3. Case

4. Screw joint

5. Outer edge of the metal band

6. Locking teeth

7. Fixing plate

8. Locking sector

9. Angle catch

10. Fastening screws

11. Locking hole

12. Locking pin