Automatic blood smear device with vibration damping means

Abstract

A blood smear device which automatically prepares a slide for blood cell analysis. The device includes holding means for supporting a slide, spreading means provided in contact with the slide and translation means for causing relative linear movement between the slide and the spreading means to produce uniform blood smears for analysis. The translation means includes a motor and a rotatable shaft connected thereto for effecting the relative movement between the slide and the spreading means. Improved linkage means are provided for converting the rotation of the shaft to linear relative movement between the slide and the spreading means while eliminating vibrations or chatter produced in the translation means. The linkage assembly comprises a crank arm which is coupled, via a pivotable link, to the slide holding means and is freely rotatable on the drive shaft. Bracket means are fixedly secured to the shaft and are adapted for providing a force to the crank arm at a point thereon to cause the arm to rotate as the shaft rotates. A resilient shock absorbing member is located between the bracket and the arm and serves to dampen any vibrations or chatter resulting from the rotation of the shaft during operation of the device.

Description

This invention relates generally to blood cell analysis and more particularly to devices which automatically make ripple-free or chatter-free blood smears on glass slides for the purpose of blood cell analysis.

In order to analyze blood and specifically to make a white blood cell differential count, it is necessary to have a slide prepared with a specimen of blood smeared on the slide. The blood smear must be so made that a monolayer of blood is formed so that the cells can be examined under a microscope by a technician. The technician then counts the number of different types of white cells that are present in the sample in order to provide a white blood cell differential count. The most commonly used method of preparing a blood smear on a slide is the glass slide technique. This utilizes two 3 inches .times. 1 inch glass slides. A drop of blood is placed on the first slide and the second slide is used to smear the blood along the first slide. A Wright Stain is then applied to the blood smear in order to facilitate differentiation of the white cells from the red cells.

The problems with the manual techniques used is that there is a lack of uniformity in the appearance of the smear, even when the same person has prepared all of the slides. There is great difficulty in preparing the slide because the slides are difficult to hold, the angle between the first and second slide is critical, as well as the speed of the movement of one slide with respect to the other.

It has been estimated that over 50 percent of blood smears made in institutions are not good. A bad smear causes a skewed distribution of the white blood cells which makes it difficult to provide an accurate blood cell count since the choosing of the wrong area of the slide to examine will cause a distortion of the count. Moreover, the pressure provided from one slide to another in making the smears is also critical. If the pressure between the slides is released at the end of the smear, then the monolayer which is critical to examination of the smear will be lost.

With the advent of automatic blood cell differential analyzers, the need for a blood smearing device which provides uniform smears has become critical. That is, unless there is a uniform area of monolayer in the smear which is large enough, automatic blood smear differential analyzers do not adequately provide a good white blood cell differential count.

There have been various prior art attempts at making devices which will make it possible to provide uniform slides, however such devices have proved unsatisfactory for various reasons, e.g. lack of uniformity in the smear produced, distortion of the cells, amount of blood necessary to produce the slide, etc.

In copending application Ser. No. 413,004, filed on Nov. 5, 1973, assigned to the same assignee as this invention and whose disclosure is incorporated by reference herein, there is disclosed an automatic blood smearing device which overcomes the various disadvantages of the prior art by the making of uniform blood smear slides having a large monolayer area.

To that end the device comprises holding means for supporting the slide and spreading means provided in contact with the slide. The slide has a drop of blood on the top surface and located toward one end of the slide. Translation means are provided for causing relative movement between the slide and the spreading means. The translation means includes a motor, a shaft rotated by the motor, an arm rotated by the shaft and a linking member for connecting the arm to the slide supporting means. A vibration isolation member is provided in the linking member to isolate vibrations from the motor.

Prior to operation of the device, the spreading means is located adjacent to the end of the slide opposite the end at which the drop of blood is placed.

Control means are provided for causing the translation means to cause relative movement of the spreading means toward the drop of blood until the spreading means contacts the drop. The control means includes delay means for preventing further movement of the spreading device relative to the drop for a predetermined period of time to enable the blood to spread out across the spreading means. The control means initiates the translation means after a period of time to cause the spreading means to be moved relatively away from the drop, thereby effecting the smearing of the drop of blood and the concomitant creation of a monolayer. The control means causes the movement of the spreading means until the spreading means is disposed at its original position with respect to the slide.

While the device disclosed in the aforenoted copending application has proved extremely efficient, it has been discovered that, notwithstanding the presence of the vibration isolating member, motor vibrations or "chatter" are sometimes coupled through the translation means to the slide holder during the relative movement between the holding means and the spreading means. This action has the adverse effect of producing a blood smear having a non-uniform or "rippled" monolayer and in some cases even results in the crushing or destruction of cells.

Accordingly, it is a general object of this invention to provide in an automatic blood smearing device means for effecting the relative movement between the slide holder and the smearing means yet eliminating the effect of motor vibration.

It is a further object of this invention to provide in an automatic blood smearing device rotational motion-to-linear motion converting means which isolate rotationally produced vibrations.

These and other objects of this invention are achieved by providing in a blood smearing device including holding means for supporting a slide, spreading means in contact with the slide and translation means for causing the relative linear movement between the slide and the spreading means, with the translation means including a motor rotating a shaft, an improved linkage assembly for converting the rotation of the shaft to linear relative movement between the slide and the spreading means. The linkage assembly comprises a crank arm coupled to the slide holding means and freely rotatable on the shaft. Bracket means are provided fixedly secured to the shaft and adapted for applying a force to the arm at a point thereon to cause the arm to rotate as the shaft rotates. Shock absorbing resilient means are located between the bracket and the arm at the point at which the force is applied to the arm. The shock absorbing resilient means serve to isolate vibrations produced by said motor from appearing as said slide support.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a top plan view of a blood smearing device like that disclosed and claimed in the aforenoted patent application and with the cover portion removed to expose the linkage assembly of this invention;

FIG. 2 is an enlarged sectional view taken along line 2--2 of FIG. 1;

FIG. 3 is an enlarged fragmentary sectional view with portions shown in full for purposes of clarity taken within the area 3 in FIG. 2;

FIG. 4 is an enlarged perspective view of a portion of the linkage assembly of this invention;

FIG. 5 is a sectional view of a portion of the linkage assembly taken along line 5--5 of FIG. 2;

FIG. 6 is a sectional view taken along line 6--6 of FIG. 5;

FIG. 7 is an enlarged side elevational view of the spreader of the device shown in FIG. 1 in contact with a slide; and

FIG. 8 is a top plan view of a blood smear on a slide as produced by the device shown in FIG. 1.

Referring now in greater detail to the various figures of the drawings wherein like reference numerals refer to like parts, a blood smearing device embodying the present invention is shown generally at 20 in FIG. 1. The device 20 basically comprises a housing 22, a slide holder 24, a pair of spreading device holders 26 and 28 and a pair of glass slides 30. The housing has mounted in the front surface thereof a switch (not shown) which connects and disconnects the power and a control knob (not shown) which can be utilized to adjust the thickness of the smear. Also mounted in the front portion of the housing are a pair of buttons 36 and 38 for initiating a smearing cycle. Either one of the buttons 36 or 38 may be pressed. The buttons 36 and 38 are placed on the left and rights sides of the device, respectively, to enable either a left-handed or a right-handed operator of the device to have equal facility in initiating operation of the blood smearing device.

The slide holder 24 and the spreading device holders 26 and 28 are mounted within a U-shaped track 40 which acts to guide the linear movement of the slide holder 24 into and out of the housing. The slide holder 24 is linearly translatable in track 40 which includes a pair of ears or projections (see FIG. 2) which are planar and extend upward from the upstanding legs of the track 40. Each of the projections includes an opening in which is mounted a shaft 96 (FIG. 2) which pivotably supports the spreader holders 26 and 28.

An assembly 108, including a spring 114 is disposed below the track and is connected, via fastener 118, to the slide carrier 24 and serves to apply uniform pressure to the track so that the slide carrier slides smoothly. An extended slotted opening 100 is provided in the base wall of track 40. The slot serves to guide the linear movement of the slide holder 24 in the track.

The spreader holders 26 and 28 are each constructed in an identical manner and are supported by shaft 96, as best seen in FIG. 2. Each of the spreader holders include a pair of pinch members 122 and 124. The pinch member 122 is the planar end portion which extends at an angle from the main portion of an elongated planar lever member 126. The lever member 126 includes an integrally depending member 128. The pinch member 124 is integrally connected to the spreader holding member 132 of the holders 126 and 128 and extends parallel to the pinch member 122. At the rear of member 132 a recess with a cylindrical surface therein is provided which receives shaft 96 and enables member 132 to rotate about shaft 96. The cylindrical surface which journals shaft 96 extends over an arc of more than 180.degree. to maintain the shaft therein. The cylindrical portion of the surface about shaft 96 is slightly larger in diameter so that there can be a slight rocking about the horizontal axis extending from the front to rear of each of the holders 26 and 28. This enables the necessary tilting of the spreaders to cause self-alignment of the spreaders with the top surfaces of the slide.

As can be seen in FIG. 3 a vertically extending opening is also provided in member 132 through which a pin 134 extends. The pin extends through the entire member 132 from the top to bottom and extends out the bottom surface of member 132. A leaf spring 136 is secured to member 132 by a threaded fastener 138. The fastener 138 maintains the leaf spring against pin 134 which is urged against the bottom surface of lever member 126. A pad 140 (FIG. 2) is provided adjacent the transversely extending member 128 of the lever member 126 and on the opposite side of the member 128 from the pin 134. The pad 140 is preferably made of a cushioning material such as polyurethane foam and is adhesively secured between the lever member 126 and the member 132.

The spreader holding member 132 of each of the holders 26 and 28 also includes a slot in the forwardmost end of the member 132 which receives the spreader 142. As best seen in FIG. 3, spreader 142 has a chamfered lowermost edge 144. The spring 136 maintains the spreader within the slot in member 132 by pressing against the under surface 146 of the spreader, thereby pinching the spreader between the spring 136 and flange 147 of member 132. In order to remove or insert a spreader, the pinch members 122 and 124 are engaged by the fingers manually and squeezed together. This causes pin 134 to be pushed downwardly as seen in FIGS. 2 or 3 against the spring 136 thereby urging spring 136 away from surface 135 of the spreader 142. This action enables the insertion or removal of the spreader in the holding member 132.

As best seen in FIG. 3, each of the holding members 132 include a pair of depending projections 148. The projections are provided on each side of the holding members of each of the spreading device holders 126 and 128. The projections 148 co-act with the pair of projections 149 which extend upwardly from the top surface of the slide holder 24. Each of the projections 149 are aligned with one of the projections 148 to enable the spreaders to be lifted above the slides when the slide holder is moved to the outermost position of the blood smearing device 20. This action enables the spreader 142 to clear the leaf spring 84 as well as to enable the spreader to smoothly set upon the glass slide when the slide holder is moved inwardly of the blood smearing device.

Preferably, the spreader 142 is made of glass, because due to the wetability of glass a drop of blood will spread quickly and spread optimally as the spreader moves with respect to the slide. As best seen in FIG. 7 the chamfered edge of the spreader rests on the top surface of the slide. The rockability of the holder member with respect to the shaft 96 insures that there is alignment of and substantial contact along the entire surface of the chamfered edge of the spreader 142 with the top surface of the slide 30. The spreader 142 is so positioned with respect to the slide that the facing surface 170 of spreader 142 is at approximately a 35.degree. angle with respect to the horizontal top surface of the slide.

When the face surface 170 of the spreader contacts a spot of blood 90, the blood, because of the wetability of the glass spreader, starts to spread from the center towards the edges of the spreader. After the blood has had an opportunity to spread adjacent to the side edges of the spreader, the slide holder is moved in the direction of arrow 172 as shown in FIG. 7 and thereby causes the blood to be smeared across the top surface of the slide 30 to form a blood smear basically as shown in FIG. 8.

The blood drop 90 as shown in FIG. 8 was originally at the position shown at 174. The portion of the smear shown in shading at 176 represents the excess portion of the blood which is not used for a blood cell differential count. The unshaded portion 178 of the blood smear represents the feathered edge or monolayer within which the blood cells can be analyzed. Thus, in order to cause the blood smear shown in FIG. 8, it is necessary that the slide holder be moved in a first direction with respect to a blood drop, to be brought into contact with the drop of blood, a sufficient dwell time be allowed to enable the blood 90 to spread towards the lateral edges of the spreader 142, and then the slide holder be moved away in the reverse direction at a continuous and predetermined speed.

The translation means for moving the slide holder means linearly with respect to the blood on the slide 30 is best seen in FIGS. 1, 2, 4, 5 and 6. As can be seen therein, the translation means basically comprises a motor 42, a drive shaft 44 connected to the motor via a suitable gear train, only one gear of which, 46, is shown and a linkage assembly 500 connected between shaft 44 and slide holder 24.

The linkage assembly 500 is arranged to convert the rotational motion of shaft 44 into linear motion of the slide holder 24 while dampening vibrations produced by the motor to prevent such vibrations from being imparted to the slide holder. By isolating the motor-originated vibrations, the linear motion produced on the slide support is smooth and chatter-free such that the resulting blood smear is uniform with the cells therein undamaged.

As can be seen in FIGS. 2 and 6, drive shaft 44 is journalled in and is supported by bracket 48 which suitably houses the gear train. A crank or drive arm 502 is freely mounted for rotation at the top of the drive shaft 44. To that end, a resilient bearing 504 is disposed about shaft 44 and is disposed within an opening 506 in arm 502. The drive arm 502 and the bearing 504 form a portion of the linkage assembly 500. A cam 52 is disposed on shaft 44 below the arm 50 and is fixedly secured to the shaft, via set screw 53, so that the cam rotates with shaft 44. Also mounted on the bracket 48 is a microswitch 56 (FIG. 1). The cam coacts with the microswitch for controlling operation of the device, as will be described later.

The drive arm 502 is connected to the slide holder 24 via a linking member 508. The linking member 508 is connected at one end to the drive arm 502 by a threaded fastener 510. A plurality of washers 512 surround the fastener 510 and are interposed between the drive arm and the linking arm to insure the free pivoting of the arm and linking member with respect to each other. An opening is provided at the other end of the linking member 508 through which a threaded fastener 514 extends to connect the linking member to the slide holder 24. The slide holder 24 includes a recess 72 into which the end of the linking member is fastened so that the head of the threaded fastener will be below the top surface of the slide holder.

The end portion of the linking member adjacent the slide holder includes a central angled portion so that the force from the drive arm 52 is transmitted to the level of the slide holder 24. The linking member 508 is pivotable about the threaded fastener 70 and is also pivotable about the threaded fasteners 510 to enable the rotational movement of drive arm 52 to enable a linear motion of the slide holder 24 which is guided by track 40.

A bracket 516 is secured to an end wall 518 of cam 52 via plural threaded fasteners 520. Washers 522 are interposed between the wall 518 and the bracket 516 and are disposed about the threaded fasteners 520. The bracket includes two portions, one side portion, being denoted by the reference numeral 524 extends parallel to the longitudinal axis of the shaft, and the other portion being a free end portion, denoted by the reference number 526, extends normally to the side portion 524 and over the end of shaft 44. The normally directed portion 526 of the bracket serves to insure that the freely mounted arm 502 does not come off the shaft 44.

A resilient shock or vibration absorbing member 528 is adhesively secured within a recess 530 in the side wall of the arm which is immediately adjacent bracket 516. That side wall is denoted by the reference numeral 532. The member 528 is formed of a highly elastomeric material such as rubber in the interest of vibration dampening.

Operation of the translation means is as follows: Upon the rotation of shaft 44 and the concomitant rotation of cam 52 and bracket 516 secured thereto, a portion of the inside wall of bracket portion 524 contacts resilient member 528 to apply a force thereto and to arm 502 to effect the rotation thereof. Motor vibrations or other translation system generated vibrations are absorbed by the resilient member 528 interposed between the bracket 516 and the arm 502. In addition the resilient bearing 504 also serves to dampen vibrations.

As described heretofore, the rotary motion of arm 502 is converted into linear motion of the slide holder by the pivot mounted linkage arm 508.

Operation of the blood smear device 20 is as follows: The initial position of the slide holder 24 shown in FIG. 2 is in its outermost position with respect to the blood smearing device. After a drop of blood 90 is placed on the slide 30, the button 36 or 38 is depressed thereby effecting the energization of motor 42. As soon as the motor is energized, the slide holder 24 moves away from its initial position and starts moving inwardly of the blood smearing device. The movement of the slide holder is caused by the rotation of arm 502 in the counter clock-wise direction as shown in FIG. 1. When the arm 502 is moved approximately 180.degree. the cam 52 has been rotated to a point wherein it contacts an arm of microswitch 56 which results in the energization of the motor 42 via a resistor (not shown). The resistor has a high impedence to thereby cause an immediate slow down of the rotation of shaft 44 and thus the speed of rotation of arm 502 which rotates therewith. The slowing of movement of arm 502 causes a dwell time of at least one second at which time slide carrier 24 is at its innermost position with respect to the device. At this time, the facing surface 170 of the spreader 142 is in contact with the blood spot 90 on both slides. That is, the indicating spots 88 of slide carrier 24 move to a position directly below the face surface 170 of each of the spreaders 142. Thus, the drops of blood which have been aligned with the indicating spots on the top surface of the slide make contact with the face surface of the spreaders 142.

For approximately 90.degree. of movement of the arm 502 the cam maintains the energization of the motor via the high impedence resistor to thereby continue the lower speed of movement of the shaft 44 and arm 502 in the counter clockwise direction. As soon as the cam passes 90.degree. of movement the motor is energized via a smaller impedence resistor (not shown) to thereby cause the speed of movement of arm 502 in the counter clock-wise direction to increase, which in turn causes a swift movement of the slide holder to its original position outwardly of the blood smearing device, i.e., the position shown in FIG. 1.

As soon as the slide holder 24 has reached its original position, the motor 42 is de-energized.

Each of the slides 30 then have a blood smear similar to that shown in FIG. 8 provided thereon. The slides may then be removed by placement of one finger in notch 86 and then lifting the slide out of the recess of holder 24. New slides can then be inserted and drops of blood then placed on the slides in alignment with the indicating spots 88 and by pressing either button 36 or 38 a new smear cycle is initiated.

It should also be noted that the glass spreaders 142 are removable and replaceable. In order to remove the spreaders 142, the holders 26 and 28 may be pivoted upwardly. The pinch members 122 and 124 may then be squeezed towards each other manually and the spreader 142 removed and replaced by a similar spreader.

In view of the foregoing, it should be appreciated that a linkage assembly of the instant invention is effective for converting the rotation of a power shaft into linear relative movement between the slide support and the spreading means in a simple and expeditious manner, while successfully damping and thereby precluding the appearance of smear degrading vibrations on the slide holder.

Without further elaboration, the foregoing will so fully illustrate my invention that others may, by applying current or future knowledge, readily adapt the same for use under various conditions of service.

Claims

What is claimed as the invention is:

1. In a smearing device for slides including holding means for supporting a slide, spreading means in contact with the slide and translation means for causing relative linear movement between the slide and the spreading means, said translations means including a motor rotating a shaft, the improvement comprising a linkage assembly for converting the rotation of the shaft to linear relative movement between the slide and the spreading means, said linkage assembly comprising a crank arm coupled to said holding means and freely rotatable on said shaft, bracket means fixedly secured to said shaft and adapted for applying a force to the arm at a point thereon to cause the arm to rotate as the shaft rotates and shock absorbing, resilient means located between said bracket and said arm at said point.

2. The device of claim 1 wherein a bearing is provided between the shaft and the arm.

3. The device of claim 1 wherein the bracket includes a first portion disposed laterally of the shaft and parallel to the longitudinal axis thereof and wherein the crank arm extends radially from the shaft, with the first portion of the bracket means being disposed closely adjacent to the arm and with the resilient means being disposed between the first portion of the bracket means and the arm.

4. The device of claim 3 wherein the bracket includes a free end portion extending over the end of the shaft.

5. The device of claim 4 wherein cam means are fixedly secured to the shaft, with the first portion of the bracket means secured to the cam means.

6. The device of claim 1 wherein the shock absorbing, resilient means is formed of a highly elastomeric material.

7. The device of claim 2 wherein said bearing is formed of a resilient material.

8. The device of claim 6 wherein a bearing is provided between the shaft and the crank arm.

9. The device of claim 8 wherein said bearing is formed of a resilient material.