Automatic balancing structure of medical balancing stand

An automatic balancing structure of a medical balancing stand has stoppers arranged on a turn plate. In a normal state, the stoppers are in contact with and hold a contact part of a lever so that the lever and turn plate follow a rotative motion of a lateral arm. If the lateral arm causes an imbalance, a strain occurs on the lever to which a strain sensor is attached. The strain sensor detects the strain and outputs a signal to an adjustment unit so as to cancel the imbalance of the lateral arm. The strain sensor helps downsizing the automatic balancing structure and making the balance adjustment easier.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an automatic balancing structure of a medical balancing stand.

2. Description of Related Art

The medical balancing stand is used to support and suspend a medical device such as a surgical microscope at an optional position in midair. The medical balancing stand includes a vertical arm and a lateral arm. A first end of the lateral arm supports a relatively heavy load such as a surgical microscope and a second end of the lateral arm supports a counterweight to balance the load. An intermediate part of the lateral arm is provided with a turn shaft that is horizontally supported with the vertical arm so that the lateral arm is able to turn relative to the vertical arm.

The turn shaft has a clutch unit that is locked in a normal state to prevent the lateral arm from turning relative to the vertical arm. When moving the load (for example, a surgical microscope) supported at the first end of the lateral arm to an optional height position, an operator who may be a doctor releases the clutch unit and turns the surgical microscope together with the lateral arm. The lateral arm having the surgical microscope is balanced on the turn shaft due to the counterweight, and therefore, stops at an optional turned position in midair as if in a gravity-free state even if the operator removes his or her hands from the surgical microscope. Accordingly, the operator is able to freely change the position of the surgical microscope in midair. Once the position and orientation of the surgical microscope are optimized as required, the operator locks the clutch unit to fix the lateral arm at the position.

Balance of the lateral arm on the turn shaft is detected and adjusted with the use of an encoder that detects a turn angle of the turn shaft and a computer that adjusts the counterweight according to a signal from the encoder. In connection with this, a related art is disclosed in, for example, Japanese Unexamined Patent Application Publication No. 2005-52679.

SUMMARY OF THE INVENTION

The related art that employs the encoder and computer to balance the lateral arm is large and needs a complicated adjusting operation. If the lateral arm is a multi-joint arm having a plurality of horizontal turn shafts, the related art must conduct further complicated operations because it must detect a turn angle of each turn shaft and balance the multi-joint arm according to the detected turn angles.

In consideration of the problems of the related art, the present invention provides an automatic balancing structure of a medical balancing stand, capable of independently establishing a balance on each horizontal turn shaft without using an encoder or a computer.

According to an aspect of the present invention, the medical balancing stand includes a first arm and a second arm, the second arm having a turn shaft which is horizontally fitted into a predetermined position of the first arm and with which the second arm is turnable relative to the first arm, a first end of the second arm supporting a load, a second end of the second arm having an adjustment unit to balance the second arm on the turn shaft. The automatic balancing structure of the medical balancing stand includes a lever that is attached to the turn shaft, is positionally fixed to the second arm, and has a contact part at a front end thereof, a turn plate that is attached to the turn shaft so as to freely turn around the turn shaft and has a pair of stoppers that are in contact with the contact part and hold the contact part, a clutch unit that is fixed to the first arm and engages with a part of the turn plate to lock the turn plate, and a strain sensor that is arranged on the lever, detects a strain occurring on the lever, and according to the detected strain, outputs a signal to the adjustment unit to balance the second arm. In a normal state, the turn plate turns with the lever. In a balance adjusting state to cancel an imbalance, the clutch unit locks the turn plate and the strain sensor detects a strain occurring on the lever due to torque generated by the imbalance.

DESCRIPTION OF PREFERRED EMBODIMENTS

An automatic balancing structure of a medial balancing stand according to an embodiment of the present invention will be explained with reference to the drawings.

InFIG. 1, the medical balancing stand includes a vertical arm1(corresponding to the “first arm” in the claims) that is fixed relative to, for example, a floor that has a predetermined positional relationship with respect to a gravitational direction. An upper end of the vertical arm1rotatably supports an intermediate part of a lateral arm2(corresponding to the “second arm” in the claims). The lateral arm2integrally has a turn shaft3that horizontally passes through the upper part of the vertical arm1, supported with a bearing4, and defines a virtual rotational axis of the lateral arm2. Namely, a main axis of the turn shaft3is horizontally fixed with respect to the vertical arm1and the lateral arm2is turnable around the main axis of the turn shaft3.

A first end of the lateral arm2supports a relatively heavy load such as a surgical microscope5, a side microscope6, and a camera7. The side microscope6and camera7are detachably attached to the surgical microscope5. When these items are detached from the surgical microscope5, the weight of the load changes.

A second end of the lateral arm2has a counterweight9that is moved by a motor8. The motor8and counterweight9form the “adjustment unit” stipulated in the claims.

The upper end of the vertical arm1where the turn shaft3of the lateral arm2horizontally passes through is covered with a cover10(FIG. 4). Inside the cover10, a turn plate11is supported with a bearing4so that the turn plate11is turnable relative to the turn shaft3.

A front end of the turn shaft3is passed through the turn plate11and is fixed to a lever12that turns together with the turn shaft3. Namely, the lever12is fixed through the turn shaft3relative to the lateral arm2, and therefore, a position (angle) of the lever12reflects a position of the lateral arm2.

The lever12integrally has a contact part13that downwardly extends when the lateral arm2is horizontal. On each side of the contact part13, the turn plate11has a stopper14that is in contact with and holds the contact part13.

A strain sensor15such as a strain gauge is adhered to a side face of the lever12. The strain sensor15is connected through a controller18to the motor8that moves the counterweight9. According to a signal from the strain sensor15, the controller18determines the magnitude of a strain occurring on the lever12and drives the motor8accordingly.

The back of the turn plate11is provided with a circular flange19around the turn shaft3. The vertical arm1is fixedly provided with a clutch20. When instructed, the clutch20holds and locks the flange19so that the turn plate11becomes immovable around the turn shaft3. The flange19and clutch20form the “clutch unit” stipulated in the claims.

Operation of the automatic balancing structure according to the embodiment will be explained.

When the clutch20is released, the turn plate11is turnable. In this state, the contact part13and stoppers14are in contact with each other, and therefore, the turn plate11and lever12turn together to follow a movement of the turn shaft3of the lateral arm2. When the turn plate11is freely turnable, the lever12causes no strain.

When a doctor or an operator who manipulates the surgical microscope5wants to change a vertical position of the surgical microscope5, the doctor turns the lateral arm2. To achieve this, the doctor pushes a button (not illustrated) on the surgical microscope5to release the clutch20and turns the lateral arm2by holding and moving the surgical microscope5. Since the surgical microscope5is balanced with the counterweight9, the doctor can easily and lightly turn the lateral arm2.

At a required position, the doctor removes his or her hands from the surgical microscope5, which stops at the position because the lateral arm2having the surgical microscope5is balanced. When the doctor releases his or her finger from the button (not illustrated) on the surgical microscope5, the clutch20locks the flange19of the turn plate11to fix the lateral arm2at the position.

When the clutch20is locked, the lateral arm2is almost unable to turn because the contact part13of the lever12is in face-to-face contact with the stoppers14of the turn plate11.

If the side microscope6or the camera7is attached to or detached from the surgical microscope5, the balanced state breaks into an imbalanced state that must be corrected.

To attach or detach, for example, the camera7, the clutch20is first locked. When the camera7is attached to or detached from the surgical microscope5, the balance of the lateral arm2on the turn shaft3breaks to cause torque about the rotational axis3to turn the lateral arm2.

The torque of the lateral arm2in the imbalanced state acts through the stopper14of the turn plate11onto the contact part13to generate torque on the lever12around the rotational axis3. This torque generates stress on the lever12and contact part13extending from the turn shaft3to the stopper14. This stress causes a strain on the lever12in a compression or tension direction. The strain is detected by the strain sensor15, which outputs a signal indicating the magnitude and direction of the strain. According to the direction of the strain, it is possible to detect a direction of the torque. According to this embodiment, the strain sensor15, i.e., a dynamic sensor arranged on the lever12detects a strain caused by torque, converts the detected strain into an electrical signal, and sends the signal through a preamplifier to the controller18.

Namely, when the strain sensor15detects a strain ε, the strain sensor15outputs a signal representing the strain to the controller18. According to the signal, the controller18controls and drives the motor8to move the counterweight9in a direction to remove the strain and correct an imbalance. When the imbalance is corrected to a balanced state, no strain exists on the lever12. Accordingly, the counterweight9is stopped at the position and the lateral arm2is balanced on the turn shaft3.

After the camera7or the like is attached to or detached from the surgical microscope5and the balanced state is reestablished, the clutch20may be released to vertically adjust the surgical microscope5.

In this way, the embodiment employs no encoder or computer. Only with the strain sensor15, the embodiment adjusts the balance of the lateral arm2on the turn shaft3. Accordingly, the embodiment is capable of downsizing the medical balancing stand. The balancing operation according to the embodiment is easy to carry out at high speed and is stable and reliable.

If the lateral arm2is a multi-joint arm having a plurality of horizontal turn shafts, the embodiment is capable of independently achieving the balancing operation on each of the turn shafts and thereby totally balancing the multi-joint arm.

In this way, the present invention employs no encoder or computer. Instead, the present invention employs a strain sensor to easily establish a balanced state and downsize the automatic balancing structure of the medical balancing stand. Even if the medical balancing stand employs a multi-joint lateral arm having a plurality of horizontal turn shafts, the present invention is able to separately adjust the turn shafts to balance the multi-joint lateral arm on the turn shafts.

According to the present invention, the stoppers hold the contact part of the lever, and therefore, the lever and turn plate turn together to follow a movement of the second arm (lateral arm) without bothering the movement of the second arm. In a balanced state, the second arm having the turn shaft turns with light force relative to the first arm (vertical arm), and when an operator removes his or her hands from the second arm, stops at the position. The stopped state of the second arm may be locked with the clutch unit. In the locked state, the second arm causes no play, and in this state, the medical balancing stand can safely be moved for storage or transportation.

If the second arm is put into an imbalanced state, the clutch unit is used to lock the turn plate. As a result, the turn plate becomes immovable and the lever tries to turn due to torque generated by the imbalanced state, thereby creating a strain on the lever. The strain is detected by the strain sensor, which outputs a signal to the adjustment unit. According to the signal, the adjustment unit acts to solve the imbalanced state and restore the balanced state.

The adjustment unit according to the present invention employs the movable counterweight that simplifies the adjustment unit.

This patent application claims the benefit of priority under 35 U.S.C. 119(a) to Japanese Patent Application No. 2012-268091 filed on Dec. 7, 2012 whose disclosed contents are incorporated by reference herein.