Device for checking linear dimensions of parts

Details Device for checking linear dimensions of parts Device for checking linear dimensions of parts

1990-03-15

1992-01-28

Cuchlinski, Jr., William A.

Geometrical instruments

Gauge

Internal

33783, 33832, G01B 712, G01B 512, G01B 346

Patent

active

050833847

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

1. Technical Field
The invention relates to a device for checking linear dimensions of parts, with support and protection means comprising a rigid support defining an open recess; a movable member housed within said recess; a feeler adapted to contact the part to be checked and to consequently cause displacements of the movable member; detecting means associated with the movable member for providing a signal depending on the feeler position; and closure and sealing means including at least two elements having relevant openings for the feeler passage, the first element being secured to the support and the second element being a resilient seal secured--in correspondence with the relevant opening--to the feeler, for sealingly closing said opening while permitting the displacements of the movable member and of the feeler.
The invention also relates to a plug gauge for checking internal diameters of parts, with a support structure; a protection structure secured to the support structure and having an opening recess; two movable arms arranged within the protection structure, substantially along a longitudinal direction, and having feelers protruding with respect to the openings of the protection structure, for contacting diametrically opposite points of the part to be checked; position transducer means associated with the movable arms; and sealing means coupled to the feelers for sealingly closing said open recess.
2. Background Art
For the devices for checking linear dimensions of parts--in particular for the electronic comparator guages with direct contact feelers for checking diameters, thickness and other linear dimensions--there is generally the need of preventing dust, coolants, swarf and other foreign matter from entering into the same devices so reaching delicate movable elements, transducers, etc. For this purpose there are used resilient sealing elements secured to the device casing and to the feeler, or to the movable arm carrying the feeler.
German patent application DE-Al-3303698 discloses a gauge including two movable arms carrying relevant feelers, and--for each movable arm--two seals, both secured to the gauge casing as well as to the movable arm and having openings for the passage of the movable arm. The outermost seal comprises a core made of metal cloth or textile fibre and a rubber coating, the inner seal is made of rubber.
European patent application EP-Al-0102744 discloses a measuring head comprising metal bellows, one of which performing several functions, among which that of sealing element between the head casing and the arm carrying the feeler.
Often there arises the need of manufacturing checking devices having very small dimensions, at least as far as the means for measurement detection and the relevant housings or casings are concerned. For example, if it is necessary to provide an electronic plug gauge for checking the diameter of small holes, such as holes having nominal diameter smaller than 8 mm, it is clearly difficult to find a compromise among the needs of protection and sealing and those of accuracy and repeatability. This problem considerably grows if the measurements must be performed at considerable depths, for example higher than 25 mm.
The devices described in the above mentioned patent applications, DE-Al-3303698 and EP-Al-0102744, have structures of the casings and of the sealing means unsuitable for solving the problem referred to above. In particular, the external casings are rather bulky.
The structure of the plug gauge described in U.S. Pat. No. 4447960 is bulky, too. In particular, this gauge has a protection nosepiece, substantially cylindrical, that takes considerable room in a radial direction, wherefore the gauge is not adapted for checking holes having small diameters.
Moreover, European patent application EP-Al-0129741 discloses a device having a measuring cell including a radially movable feeler adapted to cooperate at an end with the part and at the other end with a free end of a longitudinal flexible lamina whereto there is fixed a strain gau

REFERENCES:
patent: 3571934 (1971-03-01), Buck, Sr.
patent: 4386467 (1983-06-01), Possati et al.
patent: 4447960 (1984-05-01), Golinelli et al.
patent: 4493153 (1985-01-01), Esken
patent: 4679332 (1987-07-01), Lutite
patent: 4787149 (1988-11-01), Possati et al.
patent: 4907345 (1990-03-01), Dall'Aglio et al.
patent: 4910879 (1990-03-01), Golinelli et al.

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