JPH028274Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention is an overhead projector, more specifically, the base end is pivotally attached to a base having a Fresnel lens, and the projector is connected between a storage position and a use position. The present invention relates to an overhead projector having a projection lens support arm that is movable at a position such that the focus of the projection lens is adjusted at a use position.

[Conventional technology]

1 and 2 are a perspective view showing the appearance of a conventional overhead projector and a side view schematically showing the same.

The overhead projector 1 has a parallelogram-shaped link mechanism 6 built into the head support arm 2, and a head section 3 equipped with a projection lens, an illumination lamp, a reflector, etc. Using the arm rest 4 of the base as a fulcrum,
It is configured to open and close while always moving parallel to the Fresnel lens 5.

That is, as shown in FIG. 2, the link mechanism 6 has two links 9, built in the arm 2, and two support plates 7, 8 fixed to the head part 3 and arm holder 4, respectively. 10, each end of which is rotatably pivoted to form a parallelogram.

To adjust the focus, as shown in FIG.
This is done using the focus adjustment knob 13. When the focus adjustment knob 13 is rotated, a pinion provided on the focus adjustment knob 13 moves a rack integrated with the lens support up and down, thereby moving the projection lens 11 up and down.

[Problem that the invention attempts to solve]

In conventional overhead projectors,
After projection is complete, when the projection lens protrudes downward from the head and the head support arm 2 is placed in the retracted position as shown in FIG. 2, the projection lens collides with the Fresnel lens 5 and the Fresnel To avoid damaging the lens or the projection lens, there is a problem in that when the head support arm is placed in the retracted position, the focus adjustment knob must be rotated to retract the projection lens within the head. Ta.

[Means to solve the problem]

The present invention was made to solve the above-mentioned problems, and includes a base having a Fresnel lens on which a projection original is placed; It has a head part at its tip that supports a projection lens that is movable up and down, and has a storage position in which the projection lens lies down with respect to the base with the projection lens in contact with the Fresnel lens, and a storage position in which the projection lens is lowered relative to the base while being in contact with the Fresnel lens. An overhead projector having a head supporting arm that is erected around an end and is swingable between a use position in which the head is moved in parallel from the storage position and occupies a predetermined position above the Fresnel lens. The base ends of the two links are pivotally connected to the head part, and the free ends are pivotally connected to the support body to form a parallelogram, and the two links rotate about the base ends under the weight of the projection lens. a link mechanism that moves the projection lens vertically parallel to the head section, and one of the two links when the head section support arm is placed in the use position. A part of the link is provided on the focus adjustment cam and the focus adjustment cam, which are pressed against each other by the weight of the projection lens, and by rotating the focus adjustment cam, the link mechanism is centered around its base end. an operating knob for adjusting the focus of the projection lens; and a control knob for preventing the focus adjustment cam from rotating due to the pressing force of the one link against the focus adjustment cam. It is characterized by comprising a friction control means that acts on the adjustment cam.

[Effect]

According to the present invention, a part of the link that supports the projection lens is in pressure contact with the focus adjustment cam due to the weight of the projection lens, so that the head support arm is placed in the retracted position and the projection lens becomes a Fresnel lens. , the link moves in a direction away from the focus adjustment cam, so that no burden is placed on the projection lens.

〔Example〕

In FIG. 3, reference numeral 20 indicates a head portion;
indicate the lens parts.

The lens section 21 includes a lens barrel 23 that holds the projection lens 22, a mirror 24, a projection lens support 25 that pivotally supports the fixed mirror 24, and the like. The support 25 includes a horizontal plate 26 perpendicular to the optical axis of the projection lens 22, and standing pieces 2 bent in opposite directions from opposite side edges of the horizontal plate 26.
7. The hanging piece 28 etc. are integrally formed. One end of an upper link 30 is pivotally attached to the lower part of the standing piece 27 via a pin 29, and the other end of the upper link 30 is pivotally attached to the head portion 20 via a pin 31. Further, the upper part of the upright piece 27 is adapted to pivotally attach the mirror 24. One end of a lower link 33 is pivotally attached to the hanging piece 28 via a pin 32, and the other end of the lower link 33 is pivotally attached to the head portion 20 via a pin 34. The distances between the pins at both ends of the links 30 and 33 are the same, and the lens portion 21
Since the distance between the pins 29 and 32 of the head section 20 and the distance between the pins 31 and 34 of the head section 20 are set to be equal, a link mechanism that always forms a parallelogram is formed by these members. Therefore, the lens portion 21 can move up and down while always maintaining the same posture.
The optical axis of the projection lens 22 is kept perpendicular to the Fresnel lens (see FIG. 1).

An end portion 33a of one lower link 33, which is pivotally connected to the head portion 20, has an upwardly bent shape, and a pin 35 is implanted at the tip thereof.
It protrudes outward from the head portion 20 through a cutout portion 20a formed in the head portion 20. In this case end 3
Although 3a is bent upward, it is not limited to this shape.

A rotary shaft 36 is rotatably supported on the head portion 20, and a focus adjustment cam 37 is fixedly mounted on the rotary shaft 36 near the head portion 20, and an operating knob 38 is fixedly mounted on the outer end thereof. . A pin 35 is pressed against the focus adjustment cam 37 by the weight of the lens portion 21 .

The lens portion 21 is given the habit of always descending due to its own weight, and there is no need to provide a pressure means such as a spring even if the friction of the link mechanism is taken into account. Further, the rotating shaft 36 is configured not to rotate unless a certain amount of torque is applied to the knob 38 by a known friction control means (not shown). The torque above a certain level is sufficient as long as it is sufficient to prevent the adjustment cam 37 from rising the pin 35 due to the downward tendency of the lens portion 21. Preferably, the friction control means are adjustable.

The projection operation can be carried out by simply pulling up the head section to a predetermined projection position and then rotating the operation knob 38 to adjust the focus, as in the conventional manner. No matter which direction the operating knob 38 is rotated, the lens portion 21 always has a downward tendency, so the pin 35
is always in abutment with the focus adjustment cam 37.

When storing the lens unit 21 after projection is completed, the head unit may be gently pressed against the Fresnel lens without particularly changing the position of the focused lens unit 21. Even if the lens barrel 23 of the lens section 21 collides with the Fresnel lens, since the lens barrel 23 rises relative to the head section, the pin 35 separates from the focus adjustment cam 37 and the lens barrel 23 There is no burden on This does not interfere with head storage, and can prevent damage to components such as the lens barrel and Fresnel lens.

In this embodiment, one link brought into pressure contact with the focus adjustment cam is exemplified as the lower link, but the present invention is not limited to the lower link, and may of course be applied to the upper link.

[Effect of idea]

According to the present invention, even if the projection lens collides with the Fresnel lens when the head support arm is in the retracted position, the link supporting the projection lens separates from the focus adjustment cam, which places a large burden on the projection lens. The projection lens is housed in the head portion without any problems. Therefore, the Fresnel lens and the projection lens will not be damaged.

[Brief explanation of drawings]

1 and 2 are a perspective view and a side view showing an example of a conventional overhead projector, and FIG. 3 is a partial perspective view showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Overhead projector, 3... Head part, 5... Fresnel lens, 21... Lens part, 30... Upper link, 33... Lower link,
37... Focus adjustment cam, 38... Operation knob.

Claims (1)

[Scope of Claim for Utility Model Registration] A base having a Fresnel lens on which a projection manuscript is placed, and a base having a base end pivotally attached to the base and supporting a projection lens held by a support so as to be vertically movable. A storage position in which the projection lens has a head portion at its tip and lies down with respect to the base with the projection lens in contact with the Fresnel lens; An overhead projector having a head support arm that is swingable between a storage position and a use position that occupies a predetermined position above the Fresnel lens.
Each base end of the book link is pivotally connected to the head portion, and each free end is pivotally connected to the support body to form a parallelogram, and the habit of rotating around the base end due to the weight of the projection lens. a link mechanism for vertically moving the projection lens in parallel with the head; and one of the two links when the head support arm is placed in the use position. is provided on the focus adjustment cam and the focus adjustment cam, a part of which is pressed against the projection lens by its own weight, and by rotating the focus adjustment cam, the link mechanism is swung around its base end. an operation knob for adjusting the focus of the projection lens; and a focus adjustment knob for preventing the focus adjustment cam from rotating due to the pressing force of the one link against the focus adjustment cam. An overhead projector comprising: friction control means acting on a cam;