Blade collet

Abstract: A collet for attaching a blade 3 to a surgical saw is biased toward a closed position in which the blade 3 is securely clamped between a drive member 1 and a clamping member 6. A rotational movement of a knob 16 is converted into a translational movement of the clamp 6 to open the collet. A mechanism is provided for maintaining the collet in the open position for simplified operation and cleaning.

Description: BACKGROUND OF THE INVENTION The present invention relates to blade attachment mechanisms for surgical saws. Typical blade collets utilize a threaded stud extending from a drive mechanism and a nut engaging the stud to clamp the blade to the drive mechanism. These collets generally require the use of a separate wrench to turn the clamping nut. Other collets eliminate the need for a wrench by utilizing a nut, such as a wing nut that can be secured without tools. Yet another collet design utilizes a spring actuated clamping plate with extending locking pins for positive engagement with holes in the blade. The blade clamp is moved by finger pressure directed to compress the spring to an open position for receiving a blade. Such collets are limited in that the spring force must be low enough to allow the spring to be readily compressed using direct finger pressure, and low spring force results in a weak grip on the blade. They are also difficult to operate and clean due to the need for the spring to be manually held in a compressed position while a blade is inserted or removed or when the collet is cleaned. US 4,386,609 describes a collet assembly comprising a drive member having a portion with a slot adapted to receive an end portion of a blade with a larger portion of an aperture in the blade aligned with a socket in the head portion and a projection on the blade communicating with the slot. The blade is locked in position by a locking button mounted in the socket which is movable to a release position. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a blade collet that securely holds and transmits power from a saw to a blade. It is also an object of this invention to provide a blade collet that does not require a separate tool for its operation. It is another object of this invention to provide a blade collet that is easily operated and cleaned. These objects and others are achieved in a collet having a blade shaft for transmitting power to a blade and a blade clamp for holding the blade firmly against the blade shaft. The blade clamp is connected to a knob such that rotational movement of the knob is converted into translational movement to separate the blade shaft and the blade clamp. The blade clamp may be locked in an open position where it is separated from the blade shaft. BRIEF DESCRIPTION OF THE DRAWINGS The before mentioned features and advantages of the present invention are apparent from the following detailed description and the drawings wherein: FIG. 1 is an exploded perspective view of the preferred embodiment of the invention. FIG. 2 is a plan view of a component part of the preferred embodiment of the invention. FIG. 3 is a side view of another component part of the preferred embodiment of the invention. FIG. 4 is a section view taken along line 4-4 of FIG. 6. FIG. 5 is a section view of the assembled embodiment of FIG. 1. FIG. 6 is a section view similar to FIG. 4 but with the invention in another position of its operation. DETAILED DESCRIPTION OF THE INVENTION Referring to the drawings, FIGS. 1-6 depict a preferred embodiment of a collet for attaching a blade 3 to a surgical saw. A blade shaft 1, or first member, is mounted in a housing 2 in alignment with an axis. The blade shaft 1 transmits power from a source of power located in the saw to the blade. The blade shaft includes a first clamping surface 4, perpendicular to the axis, which has upstanding drive pins 5 for engaging the blade. The blade is held against the first clamping surface 4 and in engagement with the pins by a blade clamp 6, or second member, which includes a second clamping surface 7, perpendicular to the axis, with openings 8 in alignment with the pins. The blade clamp 6 further includes a blade clamp shaft 9 that is slidably mounted in a bore 10 through the blade shaft 1 so that the second clamping surface can translate axially away from the first clamping surface into an open, first, position in which the blade can be inserted for engagement with the blade shaft as shown in FIG. 5. The second clamping surface can move axially toward the first clamping surface into a closed, second, position in which the blade is securely clamped as shown in FIG. 6. A biasing means, such as a main spring 11, biases the blade clamp toward the closed position. The main spring is disposed around the blade clamp shaft and is constrained at one end by the blade shaft and at another end by a spring retainer 12 connected to the blade clamp shaft. The collet is opened via a mechanism that translates rotational input into the translational movement of the second clamping surface. This mechanism includes a hollow, cylindrical, grooved retainer 13 fixed to the housing 2. The grooved retainer has a helical groove 14 forming an opening along its wall. Cooperating with the grooved retainer are a plunger 15 and a knob 16. The plunger is disposed for axial movement within the grooved retainer and contains an annular groove 17 about its periphery. The plunger contacts the blade clamp. The knob forms a hollow cylinder open on one end and contains at least one vertical groove 18 formed in its inner wall parallel to the axis as shown in FIG. 2. A ball 19 is disposed in the vertical groove such that, with the plunger disposed in the grooved retainer and the knob rotatably attached to the housing so that its inner wall surrounds the grooved cylinder, the ball 19 protrudes from the vertical groove through the helical groove and into the annular groove as best shown in FIG. 5. Thus, rotational movement of the knob propels the ball, which is confined to move within the vertical groove, along the helical groove. The ball is also confined to move within the annular groove so that as the ball progresses around the helical groove the plunger moves along the axis. The blade clamp is pushed toward the open position by the plunger when the knob is rotated in one direction and the clamp is returned toward the closed position by the main spring when the knob is rotated in the opposite direction. The above described mechanism provides an operator with a mechanical advantage in opening the collet so that relatively high main spring forces may be employed for better blade retention. The collet is further provided with a means for locking the blade clamp in the open position for simplified operation and cleaning and the plunger can be locked in the closed position to reduce vibration. This locking action is provided by detents 20 and 21 formed in the helical groove at each of its ends. When the blade clamp is moved into the open position (FIG. 5), the ball may be disposed in a first detent 20 shown in FIG. 3 where it is stably held due to force exerted by the main spring 11. This first detent is such that, when the ball is so disposed, the collet will remain open without operator intervention. In order to return the collet to the closed position the operator need only apply a rotational force to the knob to move the ball from the first detent. When the blade clamp is in the closed position, the ball may be positioned in a second detent 20, shown in FIG. 1, where it is stably held due to force exerted by a conical spring 22 located so as to bias the plunger toward the open position. This reduces vibration in the plunger and knob. The conical spring exerts substantially less force than the main spring so as not to reduce the clamping load exerted on the blade. It will be understood by those skilled in the art that variations in design and construction of the preferred embodiment described above are possible without departing from the spirit and scope of the invention defined by the appended claims.

Claims: A collet for attaching a blade (3) to a surgical instrument having a source of power, the collet comprising; a housing (2) having an axis, a first member (1) mounted in the housing (2) for transmitting power from said source of power to said blade (3), the first member (1) including a first clamping surface perpendicular to the axis, a second member (6) mounted adjacent the first member (1), the second member (6) including a second clamping surface (7) perpendicular to the axis, characterised in that the second member (6) is movable along the axis between a closed position wherein the second clamping surface (7) is proximate the first clamping surface (4) to thereby hold said blade therebetween and an open position wherein the surfaces are separated, and the collet comprises a releasble holding means for selectively urging said first and second members toward each other, a third member (16) rotatably mounted to the housing (2), and a means (13) for moving the second member (6) between the open and closed positions in response to a rotation of the third member (16). The collet of claim 1 characterised in that it further comprises a spring biasing means (11) for biasing the second member (6) toward the closed position, The collet of claim 1 characterised in that the means for moving the second member comprises a grooved retainer (13) having a helical groove (14), the grooved retainer (13) being fixedly attached to the housing (2), and a fourth member (19) linking the second member (6) to the helical groove (14) such that as the forth member (19) moves along the helical groove (14) the second member (6) moves between the open and closed positions. The collet of claim 3 characterised in that the fourth member (19) comprises a ball. The collet of claim 4 characterised in that it further comprises a means (20) for locking the second member (6) in the open position. The collet of claim 5 characterised in that the means (20) for locking the second member in the open position includes a detent (20) formed in the helical groove (14) in which the ball (19) may be disposed. A collet as claimed in claim 1 for attaching a blade (3) to a surgical instrument having a source of power, characterised in that the collet comprises; a housing (2) having an axis; a blade shaft (1) mounted in the housing (2) for transmitting power from said source of power to said blade (3), the blade shaft (1) including a first clamping surface (4) perpendicular to the axis, a blade clamp (6) mounted in the housing for movement parallel to the axis, the blade clamp (6) including a second clamping surface (7) perpendicular to the axis, the blade clamp (6) being movable between a closed position wherein the second clamping surface (7) is adjacent the first clamping surface (4) and an open position in which the second clamping surface (7) is spaced from the first clamping surface (4), a spring (11) biasing the blade clamp (6) toward the open position, and a means (13) responsive to a rotational input for moving the blade clamp (6) between the open and closed positions. The collet of claim 7 characterised in that the means for moving the blade clamp comprises a grooved retainer (13) having a helical groove (14) and a ball (19) linking the blade clamp (6) to the helical groove (14) such that as the ball (19) moves along the helical groove (14) the blade clamp (6) moves between the open and closed positions. The collet of claim 8 characterised in that the grooved retainer (13) has a detent (20) formed at an end of the helical groove (14), the ball (19) being positionable in the detent (20) to maintain the blade clamp (6) in a fixed position. A collet as claimed in claim 1 for attaching a blade (3) to a surgical instrument having a source of power, the collet comprising a housing (2) having an axis and a blade shaft (1) mounted in the housing for transmitting power from said source of power to said blade, wherein the blade shaft is hollow and includes a first clamping surface (4) perpendicular to the axis for contacting said blade; a drive pin (5) connected to and extending from the first clamping surface (4) parallel to the axis, the pin being engageable with said blade (3); a blade clamp (6) including a blade clamp shaft (9) disposed for axial movement within the hollow blade shaft (1) between a first position and a second position and a second clamping surface (7) perpendicular to the axis, the second clamping surface (7) having an opening (8) aligned with the pin (5) to receive the pin when the blade shaft is in the second position; a main spring (11) disposed around the blade clamp shaft (9) for biasing the second clamping surface (7) toward the first clamping surface (4); a grooved retainer (13) fixedly attached to the housing (2), the grooved retainer defining a hollow cylinder parallel with the axis and with a wall, the grooved retainer having a helical groove (14) forming an opening along the wall with a first detent (20) at an end of the groove and a second detent (21) at another end of the groove; a plunger (15) disposed for axial movement within the grooved retainer (13), the plunger being adjacent an end of the blade clamp (6) opposite the second clamping surface, the plunger having an annular groove (17); a hollow knob (16) rotatably attached to the grooved retainer (13), the knob defining an inner wall adjacent the helical groove (14), the knob having a vertical groove (18) formed in the inner wall parallel to the axis; a conical spring (22) disposed within the knob for biasing the plunger away from the knob; and a ball (19) disposed within the vertical groove (18), the ball protruding from the vertical groove (18) into the helical groove (14) and also into the annular groove (17) such that rotational movement of the knob propels the ball along the helical groove thus causing the plunger (15) and likewise the blade clamp (6) to move along the axis, the ball being positionable in the first detent (20) wherein it is stably held due to force exerted by the main spring (11) and the ball being positionable in the second detent (21) wherein it is stably held due to force exerted by the conical spring (22).

Inventors: PASCALOFF JOHN HENRY, PASCALOFF, JOHN HENRY
Applicants: LINVATEC CORP, LINVATEC CORPORATION
Application year: 1993
Main classification: A61B17
IPC codes: A61B17, B23D51