Coupled pneumatic cylinder arrangement

Abstract

A sequence of pneumatic cylinders arranged in tandem relation upon a common stationary shaft and coupled for movement in concert. The cylinders comprise cylinder portions in the form of shell-shaped-housings with closed opposite ends containing central openings through which the shaft passes, and annular piston heads slidably arranged upon the shaft within the housings and having tubular piston stems that slide upon the shaft and project from one of the end walls of the housings. Each housing, but the first in the sequence of cylinders, is firmly mounted upon the projecting end portion of the tubular piston stem of the directly preceeding cylinder in juxtaposition with the housing of said preceeding cylinder. Means are provided to positively and yet adjustably limit the extent to which the piston stem of each cylinder may penetrate its housing which in turn limits positively the maximum contraction of which the cylinder is capable; these means have the form of an externally threaded bushing that is slidably mounted upon the tubular piston stem and threadably engages the cylinder housing along the opening of the end wall through which the piston stem protrudes. By adjusting the position of the bushing within said end wall relative to the cylinder housing, and by providing an abutment at the outer end of the piston stem, the extent to which the stem may penetrate the housing and hence the minimum axial length to which the cylinder can be contracted, may be predetermined very precisely.

Description

BACKGROUND OF THE INVENTION

The present invention relates to pneumatic cylinders. More particularly the present invention relates to arrangements wherein a sequence of such cylinders is arranged in tandem relation for operation in concert. In such arrangements each of the cylinders is individually controllable to expand And contract, and whatever elongation or contraction anyone in the sequence of cylinders undergoes, evidences itself at one or the other end of the column of cylinders. Sequences of coupled cylinders of this type may be used as actuators to move objects over precisely predeterminable distances to sought points of operation where they may be fitted into, and connected in proper position to, existing structures such as in the construction industry, or to sought points of contact wuch as in the electric and electronic industry where terminals are to be connected or electric or electronic components are to be fitted into particular sockets.

OBJECTS OF THE INVENTION

An object of the invention is to provide an arrangement of coupled cylinders wherein each cylinder imparts its changes in axial length dependably and positively to the cylinder to which it is coupled and in fact to the total column of cylinders of which it may form a part; or to put it differently, it is an object of the invention to provide a column of tendem related cylinders of the type referred to, wherein the column of coupled cylinders evidences dependably at one of its ends any changes in axial length which any one or all of the individual cylinders undergo.

Another object of the invention is to provide a cylinder construction for operation in coupled cylinder columns or sequences of the type referred to, whose throw or stroke, i.e. the distance between maximum axial expansion and the contraction to minimum axial length may easily and precisely be adjusted to exact desired limits.

In this connection it is still another object of the invention to provide a high precision pneumatic cylinder construction that may be assembled from loose tolerance components and is, therefore, inexpensive to manufacture and assemble.

BRIEF DESCRIPTION OF THE DRAWING

The present invention will best be understood by reference to the accompanying schematic drawing which shows in section a side elevation of a sequence of pneumatic cylinders constructed and coupled for movement in concert in accordance with the invention.

SUMMARY OF THE INVENTION

In accordance with the invention the piston stems of the coupled cylinders are of tubular conformation and are slidably mounted upon a common shaft, and the annular shell portion or housing of each succeeding cylinder is firmly supported upon the projecting piston stem portion of the directly preceeding cylinder. The degree to which each cylinder may expand is positively limited by a shoulder or boss on the underside of the annular piston of each cylinder, which is arranged to strike against an inner surface of the housing portion of the cylinder; and the degree to which a cylinder may contract is positively and adjustably limited by an abutment means that is secured to the projecting piston stem portion, and an annular bushing which is slidably supported upon the tubular piston stem and is threadably engaged within the central opening of the end wall of the cylinder housing from which the stem protrudes. Hence, its position relative to the shell portion of the cylinder may be adjusted at will axially of the tubular piston stem. When the outer end surface of said bushing strikes against the abutment means on the stem of the piston or against the end wall of the housing of the directly succeeding cylinder, the cylinder has reached its limit of maximum contraction.

DETAILED DESCRIPTION OF AN EXAMPLARY EMBODIMENT OF THE INVENTION

In the drawing the numeral 10 designates a cylindrical shaft upon which are supported in tandem relation four pneumatic cylinders of different axial length collectively identified by the letters A, B, C and D. Each of these cylinders has a cylinder portion in the form of a shell-shaped housing 12 whose opposite end walls are provided with circular openings for the shaft 10 to pass through. Slidably disposed within the shells or housings 12 are the disk-shaped piston heads 14, of the pneumatic cylinders, which are mounted at the ends of tubular stems 16 that slide upon shaft 10 and project from their respective housings through openings in the right end walls thereof.

The housings 12 of the cylinders B, C, and D are firmly mounted on the outer ends of the tubular piston stems 16, of the directly preceeding cylinders in the sequence of cylinders supported upon shaft 10. Provided in the right end wall of each of the housings 12 of the cylinders is an air inlet channel 18, respectively, through which atmospheric air may enter into the space between the right end wall of the housing and behind the underface of the piston head 14; and near the opposite end wall of each cylinder housing another passage 20 is provided in the shell portion of the housing 12 through which atmospheric air may enter into or may be evacuated from the space between the front face of the piston head 14 and the left end wall of the cylinder housing.

A spring 22 is suitably connected through a cord 23 to a disk 26 that is firmly mounted upon the projecting end portion of the tubular stem 16 of the last or rightmost of the hydraulic cylinders, i.e. cylinder D and pulls the pistons 14 of all the cylinders comprised in the actuator arrangement, into the rightmost position as viewed in the drawing when air is allowed to leave the interior of the cylinder housings A, B, C and D through the passage ways 18 while passages 20 are open to the atmosphere. These rightmost positions are determined by a boss 28 provided on the undersurface of the piston heads 14 which strikes against the inner surface of the right end wall of the cylinder housings 12, such a position being illustrated by cylinders A and B in the drawing. This is the position of maximum expansion for the cylinders, i.e. the axial length of the cylinders when measured between their left end walls and the outer ends of their outwardly projected cylinder stems 16 is at a maximum. On the other hand when the interior of the cylinder housings 12, i.e. the space between the left end walls of the housings 12 and the front face of the piston heads 14 is evaccuated through passage ways 20 by connecting them to an evaccuation pump 30 via a valve 31 as schematically indicated in the drawing, the air under atmospheric pressure rushing through passage ways 18 into the space behind the piston heads 14 forces the pistons forwardly within the piston housings i.e. to the left as viewed in the drawing, against the urgency of spring 22 and thus effects a contraction or shortening of the axial length of the particular cylinders. The extent to which each cylinder may contract, i.e. is minimum axial length is adjustably determined by a tubular bushing 32 that slides on the tubular stems 16 of the pistons and which is threadably engaged within the openings in the right end walls of the cylinder housings. As soon as the outer end face of the bushing 32 strikes against the outer retaining ring 34 of the structure that secures the housing of the next of the cylinders to the piston stem of the directly preceeding cylinder the cylinder reaches its position of maximum contraction, or expressed differently of minimum axial length, such a position being illustrated in the drawing by cylinders C and D. In the case of the last of the cylinders on shaft 10 which is the rightmost cylinder D in the drawing, the aforementioned disk 26 on the right end of the projecting end portion of tubular piston stem 16 of piston 14 serves as a movement-limiting abutment against which the outer end face of bushing 32 will strike. As pointed out before, the exact axial length to which each cylinder may be contracted, may be precisely predetermined for each cylinder by manipulation of its bushing 32. As a result the cylinders may be manufactured and assembled from low tolerance components and may yet be depended upon to produce very precisely predetermined contractions of the total axial length of each of the sequence of pneumatic cylinders supported upon shaft 10. In practice the housing of the cylinder at one of the ends of the sequence of cylinders must be secured in place relative to the shaft 10 so that the sum total of changes in the axial length of all the cylinders in the sequence of coupled cylinders will evidence itself fully on the opposite end of the column of cylinders. In the drawing this is indicated schematically by the spike 35 that secures the left side of cylinder housing 12 to the shaft 10, and by the arrow 36 that descends from the repeatedly mentioned abutment disk 26 on the protruding end of piston stem 16d of the rightmost cylinder D. In practice this arrow may represent an indicator or a tool or component-holder depending upon what use the actuator mechanism of the invention is put. It remains to point out that in embodiments of the invention which use the pressure of the atmosphere in combination with selective evaccuation of the interior of the cylinders, I have obtained best results with springs 22 of a strength about equal to half the pressure of the atmosphere.

While I have explained my invention in connection with power cylinders of the pneumatic type, it will be understood that the invention is applicable to hydraulic power cylinders.

Claims

I claim:

1. An actuator arrangement comprising a shaft, supported upon said shaft separate first and second power cylinders in tandem relation, each of said cylinders having an individual housing and within said housing an annular piston head having a tubular stem slidably mounted upon said shaft and arranged to project from said housing, the housing of said second cylinder being firmly supported upon the protruding end of the tubular piston stem of said first cylinder in juxtaposition with the housing of said first cylinder.

2. Arrangement according to claim 1 including tubular bushings slidably mounted upon said piston stems and threadably engaged with their respective cylinder housings to act as adjustable limit stops.

3. Arrangement according to claim 2 including abutment means mounted upon the projecting end portions of said tubular piston stems for engagement by the outer end faces of said tubular bushings.