Mechanical hydraulic counting and memory device
This invention relates generally to counting devices and more particularly to a device responding to a certain number of mechanical displacements of an input member received within a certain time and having a certain total amplitude to produce an output displacement of a predetermined amount. 
     There are many instances in the useful arts where it is desirable to perform a function after a certain number of inputs having a certain total magnitude and received within a certain period of time. It is frequently desirable to have such devices reset to their original condition in the event that there is a failure of the required number, amplitude, or frequency of inputs. In certain applications it is desirable that the inputs be in the form of mechanical displacements of an input member and that the output be in the form of a mechanical displacement of an output member which will perform a certain function upon reaching a certain magnitude. An example of a use of such a device is in an anti-tank mine fuze where a pressure or force sensing input member responds to external impulses and upon receipt of a certain number within a certain time will activate a mine. 
     It is, therefore, a general object of the present invention to provide a device for counting mechanical displacements and performing a function following a number of displacements. 
     A further object is to provide a device achieving the foregoing objects and which will reset if the pulsing sequence is initiated but not completed within a certain period of time. 
     A further object is to provide a device achieving the foregoing objects and characterized by simplicity and reliability of construction. 
     Described briefly, in a typical embodiment of the present invention, an input member is provided in a body, the input member being in the form of a plunger having a ball clutch engageable with a first hydraulic piston. The output member is connected to a second hydraulic piston and is disposed to perform a function when it is displaced a certain amount. 
     Depression of the input plunger causes the clutch to engage the first piston and displace it which causes hydraulic fluid in the device to displace the second piston and thereby the output member is displaced. When the input pulse is removed from the plunger, the clutch disengages and a spring load on the output member tends to return it to initial position, which action is delayed by a valve and orifice in the hydraulic return path. Thus the next impulse on the input member can cause the clutch to engage the first piston at a different point whereby the displacement of both pistons from their initial position will be greater at the end of the second impulse than it was at the end of the first. In the event there is failure of additional impulses within a predetermined time, the orifice will allow the output member to return to initial position. 
    
    
     The full nature of the invention will be understood from the accompanying drawings and the following description and claims. 
     FIG. 1 is a section through a typical embodiment of the device, with the section being taken on a vertical plane containing an axis of symmetry of the device. 
     FIG. 2 is a section taken along the line 2--2 in FIG. 1 and viewed in the direction of the arrows. 
    
    
     Referring now to the drawings in detail, the device is illustrated by the solid outlines in its initial equilibrium condition. Most of the parts are generally cylindrical in nature and therefore symmetrical with respect to a vertical axis 9. The parts include a plunger bias coil spring 11 acting upwardly on the plunger 12 and downwardly on the input piston 13. Three balls 14 are equally spaced in a circle by the ball retainer 15 and a ball retainer bias spring 16 is provided between the retainer 15 and the input piston 13. The upstanding stem of input piston 13 and in which the plunger bias spring 11 is disposed, is slidingly received in the plunger bore 17 and the plunger is slidingly received in the bore 18 of the input cap 19. 
     The input cap 19 is secured in the body 21 and an output cap 22 is also secured in the body. Hydraulic fluid 23 is confined in the body by an upper rolling diaphragm 24 and a lower rolling diaphragm 26. A valve seat member 27 is secured to said body and has an aperture 28 in the bottom thereof. 
     The valve seat member has a radially extending annular flange 45 sandwiched between an upwardly facing annular shelf 40 of said body and the outer marginal portion of said upper diaphragm, this marginal portion being sandwiched between the flange and the annular lower marginal edge 35 of said upper cap. In this way the body, upper cap, valve seat member, and rolling diaphragm are sealingly affixed together in a circle at the flange 45. Similarly the outer marginal portion of the lower rolling diaphragm is sandwiched between the annular upper marginal edge 50 of the lower cap and the annular shelf 55 of the body 21. 
     Check valve 29 is disposed in the chamber 31 below the valve seat member 27 and has an aperture 32 therein. Aperture 32 is actually an orifice for obtaining the desired time delay as will be described hereinafter. Coil spring 33 disposed between the check valve and the lower face 34 of chamber 31 normally biases the check valve closed as shown whereupon the only communication between the chamber 31 below the valve seat member 27 and chamber 36 above the valve seat member 27 is through the orifice 32. 
     Output piston 37 supports the central portion of the lower rolling diaphragm 26 by means of the coil spring 38 which is the output piston return spring. The lower end of this spring engages the inside face 39 of the bottom of the output cap 22, and the stem 41 of the output piston extends through a guiding aperture 42 in the output cap. 
     As will be described hereinafter, it is a certain amount of displacement of the output piston which is required to perform some function in response to a sequence of depressions of the plunger 12. One way of performing a function is by providing an electric switch below the lower end 43 of the output piston stem. This switch includes upper and lower spring leaf contactors 44 and 46, respectively, mounted by means of an insulated block 47 to the body 21. The contact points 48 and 49 are normally open but can be closed when the lower end 43 engages the ball 51 mounted to the upper leaf to depress it. Closure of the contacts completes a circuit through the battery 53 and a load 52 which could be the initiator for a mine fuze, for example. 
     OPERATION 
     In the operation, when the plunger is forced down in the direction of the arrow 54 by some external force, the inner conical surface 56 of the axially extending flange 70 thereof engages the balls 14, which are circularly spaced by retainer fingers 25 and disposed to project into the downwardly opening recess 30 of the plunger. The surface 56 thereupon urges the balls inwardly against the outer cylindrical surface 57 of the upper piston stem 20. As the downward force applied by the plunger on the balls reaches the opposing force transmitted by the ball retainer bias spring 16 through the retainer to the balls, the balls jam against the piston stem and the piston is forced downward displacing the rolling diaphragm 24, which displaces the hydraulic fluid 23. Rapid displacement of the hydraulic fluid is enabled by opening of the check valve 29 as the hydraulic pressure in chamber 36 forces the valve away from its seat. The hydraulic fluid displaces the output piston 37 by means of the rolling diaphragm 26. The output piston moves downwardly a distance determined by the length of the input stroke and the relative areas of the output piston and the input piston. For example, if the input piston is displaced to the position shown by the dotted outline 58, the output piston may be displaced to the position shown by the dotted outline 59. Note that this amount of displacement of the output piston is not sufficient to engage the ball 51 and close the switch contacts 48 and 49. 
     When the plunger is released, downward displacement of the hydraulic fluid ceases and the spring 33 closes check valve 29. Plunger bias spring 11 forces the plunger 12 up against the stop provided by abutment between the faces 61 and 62 of the plunger and the upper cap, respectively. The ball retainer spring 16 forces the ball retainer 15 and the balls 14 to follow the plunger 12 upwardly until the retainer is stopped by the ledge 63 on the input cap 19. The stopping of the ball retainer by the ledge on the input cap prevents the balls from remaining tightly engaged with the piston and plunger and therefore allows relative vertical motion between the plunger 12 and upper piston 13. 
     The output piston spring 38 forces the piston 37 upwardly, which forces hydraulic fluid in the chamber 31 upward through the orifice 32 in the check valve. The orifice restricts the hydraulic flow and controls the rate of return of the output piston toward its initial position. The slowly moving hydraulic fluid forces the input piston 13 upwardly slowly toward its initial position. 
     When the plunger 12 is again depressed downwardly, the balls again engage the stem and the action is repeated as described above. However, if the plunger is depressed downwardly before the upper piston 13 has returned to its initial position, the balls grip the stem at points above the points of first contact and cause the upper and lower pistons to move downwardly to points at greater downward displacements from their original positions than occurred during the first depression of the plunger. If this occurs one or two more times, the lower end 43 of the lower piston will close the switch contacts. On the other hand, if the input pulses on the plunger are of such small magnitude or are spaced sufficiently apart in time, both the upper and lower pistons will return to their initial rest positions and closure of the switch contacts 48 and 49 will not occur. 
     It can be seen that by employing a switch or other sensor for actuation by the output piston upon a certain predetermined displacement, and if the input pulses are of a certain displacement, the position of the output piston is representative of the number of input pulses. The device is, in effect, a counter. 
     It is believed that from the foregoing description the novelty and utility of the present invention are apparent. While the invention has been disclosed and described in some detail in the drawings and foregoing description, they are to be considered as illustrative and not restrictive in character, as other modifications may readily suggest themselves to persons skilled in this art and within the broad scope of the invention, reference being had to the appended claims.