Disc brake

A disc brake which allows immediate visual checking of the wear of the pad includes a caliper body straddling a disc, a pad supported in the caliper body by a metal plate in a position facing the disc, an indicator rod attached to the plate and extending outside the caliper body, and a visible reference associated with the caliper body and facing the indicator rod.

FIELD OF THE INVENTION 
The present invention concerns a disc brake of the type comprising a 
caliper body straddling a disc of predetermined axis, and a pad supported 
in the caliper body by a metal plate in a position facing the disc. 
In the field of disc brakes of the specified type, particularly when used 
in motor vehicles and the like, the wear of the pad needs to be checked. 
BACKGROUND OF THE INVENTION 
Electrical wear-indicating devices are known which indicate that the pad is 
practically worn out by switching on a warning light on the dashboard of 
the motor vehicle. 
Such warning devices are advantageous in many ways but do not, however, 
give any indication of the progressive state of wear of the pad, 
indicating the wear only when the pad is virtually worn out. 
They are, therefore, useless during regular servicing when it is advisable 
to replace the pads as a preventative measure even if they are not 
completely worn out so as to guarantee the efficiency of the motor vehicle 
during the interval between the current service and the next planned 
service. 
Sliding gauge tools are currently used to determine the wear of the pads 
but these, being universal instruments, cannot indicate the wear of the 
pad in situ, with the disc brake assembled and the wheel fitted. 
The problem upon which the present invention is based is that of devising a 
disc brake of the specified type having structural and functional 
characteristics which satisfy the aforesaid requirement while, at the same 
time, overcoming the disadvantages cited with respect to the prior art. 
SUMMARY OF THE INVENTION 
This problem is solved by a disc brake of the specified type characterised 
in that it comprises a device mounted on the disc brake for indicating 
visually the wear of the pad. 
According to the invention the device comprises an indicator rod attached 
to the plate by fixing means and extending parallel to the axis of the 
disc towards the outside, and a visible reference associated with the 
caliper body and facing the indicator rod.

DETAILED DESCRIPTION OF THE INVENTION 
With reference to the appended drawings, a disc brake according to the 
invention is generally indicated at 1. 
The disc brake 1 includes a caliper body 2 straddling a disc 3 having a 
predetermined axis X--X and an outer face 4. A pad 5 is supported in the 
caliper body 2 by a metal plate 6, of steel in this example, so that it 
faces the outer face 4 of the disc 3. The disc brake 1 according to the 
invention includes a device 7 mounted permanently on the disc brake for 
indicating visually the wear of the pad 5. 
In particular, the device 7 includes a small indicator rod 8 which extends 
parallel to the axis X--X and has a flat free end 9 towards the outside 
and an opposite end 10 attached to the plate 6 by releasable fixing means 
11. The releasable fixing means 11 are in the form of an arm 12 which 
projects at right angles from the end 10 of the indicator rod 8 and a head 
13 at the end of the arm 12 which is releasably snap-engaged in a seat 14 
formed in the plate 6. 
A U-shaped groove 13a formed in the head 13 is engaged by a cooperating 
U-shaped rib 14a which projects into the seat 14. 
The head 13 is snap-engageable in the seat 14 by means of a substantially 
U-shaped spring clip 15 housed in the groove 13a in the head 13 and which 
contacts the rib 14a. More particularly, the spring clip 15 almost 
surrounds the head 13 and is-retained on it by end portions 16 which are 
bent towards the-inside of the U-shape. The spring clip 15 is 
snap-retained in the seat 14 by the engagement of projections 17 which 
project outwardly from the sides of the U-shape in cooperating recesses 18 
in the rib 14a. 
The device 7 also includes a visible reference 19 associated with the 
caliper body 2 and facing the indicator rod 8. 
The indicator rod 8 preferably has a circular section and the caliper body 
2 includes an axially-extending channel 20 of substantially semi-circular 
section. The indicator rod 8 slides freely in the channel 20 in which it 
is partially housed. 
The visible reference 19 is on the outer surface of the caliper body 2 at 
the outer end of the channel 20; and, as can be seen in FIGS. 1 and 3, the 
visible reference 19 is formed by the intersection of the outer end of the 
channel 20 with the outer surface of the caliper body 2. 
The indicator rod 8 includes marks 21 and 22 which are located in 
correspondence with the visible reference 19 when the wear of the pad 
reaches 25% and 50% respectively. More particularly, the marks 21 and 22 
comprise two opposing shoulders 23 and 24 defined by a groove 25 formed in 
the indicator rod 8. 
It should be noted that the length of the indicator rod 8 is selected such 
that, when its flat free end 9 is in correspondence with the visible 
reference 19, the wear of the pad is virtually 100%. 
It should be noted that the seat 14 is preferably shaped such that it mates 
with a conventional terminal (FIG. 5) of a cable 27 of an electrical 
wear-indicating warning light 38. 
The indicator rod 8, the arm 12 and the head 13 are preferably formed as a 
single unit from an appropriate plastics material. 
In use, or rather as the result of use, the pad 5 gets thinner as a result 
of wear and the plate 6 consequently gets gradually closer to the outer 
face 4 of the disc 3 and the indicator rod 8 moves axially inwards, also 
getting gradually closer to the outer face 4 of the disc 3 in such a way 
that first the mark 21, then the mark 22, and finally the flat free end 9 
are brought successively into correspondence with the visible reference 
19. 
Whenever there is any intervention in the form of regular servicing, the 
wear on the pad 5 is seen immediately by the positioning of the marks 21, 
22 on the indicator rod 8 in relation to the visible reference 19. 
The main advantage of the disc brake according to the present invention is 
that the wear of the pads can be seen at any time. A further advantage of 
the disc brake according to the present invention lies in the exceptional 
structural simplicity of the wear-indicator, which is such that it would 
be expected to last almost indefinitely. 
It should also be noted that the device for indicating the wear of the disc 
brake according to the invention can be retrofitted on existing disc 
brakes. 
Obviously, an expert in the field may introduce numerous modifications and 
variants to the disc brake according to the invention in order to satisfy 
specific, contingent requirements, all however falling within the scope of 
protection of the invention as defined by the following claims.