the braking quickly as an exceptional measure in an emergency when the standard drum-type oil brake is broken or goes out of order.

PRIOR ARTS

The conventional braking systems of prior arts are to stop cars, while running, generally through conversion of the kinetic energy of the running car into heat energy by a mechanic frictional device and having the heat diffuse in the air; the braking operation consisting generally in the conversion of the pressure applied on the brake pedal into oil pressure through the master cylinder, conveyance of the oil pressure to the wheel cylinder, and in sending the brake shoe covered with its lining to the inner circumferential surface of the brake drum or to both sides of the brake disc in tight pressure.

In the conventional car braking device outlined above, the device and medium for conveyance of the braking force are, as a general rule, the oil-pressure cylinder and brake oil, and therefore in case the brake oil hose or wheel cylinder breaks while the car is running it is impossible to bring the brake shoe to the brake drum or brake disc in tight pressure because of the fall of oil pressure, resulting in a fatal accident.

With a view to the prevention of such accidents or in order to secure an emergency braking force, various remedies have been developed, including

installation of an extra master cylinder or an extra wheel cylinder for emergency braking, besides the main master cylinder in addition to the oil cylinder itself

or a separate safety device for prevention of its breakage, and others, but most of these remedies, have a disadvantage in that their construction is extremely complicated, the production costly, and the installation difficult.

SUMMARY OF INVENTION

- ^*• The objective of the present invention is, in view of all this, to provide a new mechanical braking device of simple construction and yet with excellent braking force to instantly brake the speeding car to a stop in an emergency, even if the oil pressure devices of the brake, like the wheel cylinder, are broken; Said new mechanical braking device comprising; 0 a brake drum 2 whose outer circumferential surface very slightly tapers off internally towards the inside of the car and has a screw 01 shaped on the outer circumferential surface; an annular block 4, which has cogs 3 in the shape of a ratchet formed on one side along the cricumference, and has a smaller inner circumferential surface and 5 a larger inner circumferential surface which define a shoulder there between, and has a screw IE formed on said smaller inner circumferential surface for screwing it up tight with the outer circumferential surface of said brake drum 2; a foolproof antidisengagemnt ring which is so secured to the end surface of said drum by bolts as to have its outer circumference stop up said shoulder; and 0 a pawl 6, which is formed, as it moves forward and backward at the operation of a solenoyd 5, to engage with said ratchet-shaped cogs 3 of said annular block 4.

Construction and interrelations of these components each will be given in greater detail by reference to the attached drawings, Figs. 1 to 3, as follows:

BRIEF DESCRIPTION OF DRAWINGS Fig. 1 is a vertical section of the automobile wheel fitted with the brake drum of the present invention.

Fig. 2 is a plane view of it, seen along the A-A line of Fig. 1 Eig. 3 is a blown-up vertical section of the brake drum and the annular block of the present invention.

DETAILED DESCRIPTION OF INVENTION

The mechanical style brake drum of the present invention is connected by bolts to the axle 11 of the automobile and the tire rim 13, as is the conventional brake drum, but, characteristically, its circumference is shorter on its inside end and longer on its outside end, said drum totally very slightly tapering off inwardly, and a screw is cut in the outer circumferential surface.

Said tapering is intended to make the catch and attachment of the annular block 4

(described later), whose inner circumferential surface is to screw up with the outer circumferential surface of said drum 2, even tighter, in gradation, accordingly as the latter advances forward(to the left, in the drawing), and thus the degree of this tapering and the pitch and height of the screw shaped on the outer circumferential surface of said drum 2 must be decided according to the

magnitude of the braking force desired. The inner circumferential surface of said annular block 4 is divided in the part of the smaller inner circumference and the part of the larger inner cicmference, and in the part of the smaller inner circumference a screw IT is cut for said annular block 4 to be inserted in and screwed up with the outer

circumference surface of said brake drum 2, and on one side surface of said

annular block 4 is a set of ratchet-shaped cogs 3 along the circumference.

During the normal running of the car said annular block 4, joined to said drum 2 with said screw IE on the smaller inner circumference and said screw 01 on the outer circumference of said drum 2, rotates together with said drum 2 as the latter rotates; said annular block is not allowed to fall apart from said drum towards the inner sideCto the right in the drawing) because a foolproof antidisengagement ring 15 is so screwed to the end surface of said drum by bolts 14as to have its outer circumference stop up the shoulder(16) formed between the smaller inner circumferential surface and the larger inner circumferential surf ce of the annular block. As is illustrated in Fig. 3, the screw-cut part of the outer cricumferential surface of said drum 2 to the left of said annular block 4 may be filled with some packing materiial 7 of soft metal like, for example, lead or copper, in the bottom up to the middle or so of the height of the screw and this is, as is to be described later on, in order to bestow upon the device in general a means of securing stronger yet more smooth braking, besides the role as a wedge on the tapering surface, by making said annular block 4 advance biting up said packing material of soft metal with the ridge of the screw cut in its the inner circumferencial surface when it is set in motion in an emergency.

And as is illustrated in Eigs.1 and 2, a pawl 6, mounted on the upper part of the body of a car, works at the pull of a wire by a solenoid 5 of oil-pressure or electrical type, or else, manually, and said pawl 6 is designed to move forward and backward in the direction at a right angle to said annular block 4. Said pawl 6 has its free end shaped to exactly match with the ratchet-shape cogs 3 formed on one side of said annular block 4 along the circumference, and because said pawl 6 is set up in the direction of said solenoid 5 by a spring 9 it is not

in contact with said ratchetshape cogs 3 at normal times. The end surface of said cogs 3 is desired to be of a regular triangle and it is so in order to secure the maximum shearing stress applied laterally, at a right angle, on said

cogs 3 at the time of engaging with said pawl 6. Said pawl 6 is ushered in by a guide 10, which latter has a groove slightly bigger than the end surface of said pawl 6, and so a possible transformation of the end surface of said pawl 6 can be

prevented, even if a huge force is applied on it laterally, when said pawl 6 comes into contact with said cogs 3 on the side surface of said annular block 4.

As for said pawl 6, one may be enough but as many as three can be set up along the circumference, for example, one each at an interval of 120 degrees, if it is desirable, in order to distribute the load evenly among them.

The functions of the emergency braking device of the present invention, constructed as above, are given below:

When the oil-brake drum operates normally said pawl 6 remains in retreat, and said annular block 4, with its screw IT in occlusion with the screw OT on the outer circumferential surface of the drum, rotates in one with the drum. Thus if the wheel cylinder should break and the brake does not work while the car is running, the driver can yet, at this dire emergency, press the switch(not illustrated) installed at a convenient position within easy reach of his hand to start the emergency braking system of the present invention, and then said

solenoid 5 instantly functions to drive said pawl 6 forward to have its free end catch said cogs 3 of said annular block 4. By this occlusion of the free end of said pawl 6 and said cogs 3 of said annular block 4 the rotation of said annular

block 4, which has been rotating in one with said drum 2 at the rotation of the

tire 12, suffers braking. To elaborate, while said brake drum 2 is still

rotating, said annular block 4 rapidly advances following said brake drum 2 outwardly(toward the left side in the drawing) and said annular block 4, as it advances along the spiral grooves of the screw on the surface of the slightly tapering drum 2, said grooves getting ever tighter because of the tapering of the drum 2, immediately encounters the packing material 7 of such soft metal as lead or copper, the force of rotation of said annular block 4 being distributed evenly along the circumference for absorption, thus resulting in a speedy emergency braking of the running of the car to a halt.

The emergency braking device 1 of the present invention constructed in the manner given above is a mechanical car-braking device providing a mighty, effective braking force at a dire emergency, like a breakdown of the oil brake, and is one which can attain the purpose far better than does any other supplementary braking device or safety device.

In said emergency car-braking device 1 of the present invention, said annular block 4 and said brake drum 2 with which the former is fitted can both be standardized for production altogether in one at factories, and when they have been used once, achieving the intended purpose, they will be replaced with new ones, wherefore they are made easy for fitting and maintenance, thus the present invention is, in one word, a very useful invention that is expected to make a great contribu- tion to the safe driving of cars.