Abstract:
Springs having various configurations include upper and lower connecting members and spring elements extending therebetween. The configurations of the springs may enable them to be formed of polymeric material such as by injection molding. Pumps for pumping fluid or adapted for other uses may include such springs and may include interfacing arrangements with the springs.

Description:
FIELD OF THE INVENTION 
       [0001]    The present disclosure generally relates to springs and more particularly compression springs. The present disclosure also generally relates to pumps and more particularly pumps for dispensing fluid. 
       BACKGROUND OF THE INVENTION 
       [0002]    Compression springs are used in countless applications to bias various components away from each other. For example, compression springs may be used in pumps for dispensers such as fluid dispensers. Some such fluid dispensers include lotion or soap dispensers (e.g., countertop hand lotion dispensers), cleanser dispensers (e.g., hand-held glass cleaner dispensers), and dispensers for liquid detergents, cosmetics, perfumes, medicine, and food. In general, the pumps include an actuator having unactuated and actuated positions. The springs bias the actuators toward the unactuated position, and when the actuator is moved from the unactuated position to the actuated position, fluid is dispensed from an outlet of the dispenser. Compression springs may be used in other applications such as in biasing valve members toward open or closed positions. One type of a conventional compression spring is an upright helical spring which includes a piece of wire configured to define a helix having several turns or coils along a height of the helix rising at a constant upward angle. The end coils may be closed to form substantially circular closed end coils which lie in parallel spaced-apart planes and are perpendicular to the longitudinal axis of the spring. Other types of conventional springs may also be used, such as bellows springs. 
       SUMMARY 
       [0003]    In a first aspect a spring includes first and second spring elements. The first spring element extends between first and second ends of the spring on a first side of the spring. The first spring element defines a first concave segment opening in a first direction. The second spring element extends between the first and second ends of the spring on a second side of the spring. The second spring element defines a first concave segment opening in a second direction generally opposite the first direction. 
         [0004]    In another aspect, a spring includes upper and lower support members defining respective upper and lower bearing surfaces and at least first and second spring elements extending between the upper and lower support members. The spring further comprises at least one brace connecting the first spring element to the second spring element. 
         [0005]    In yet another aspect, a pump for dispensing fluid comprises a spring and structure which houses the spring. The spring includes spring elements having side engagement surfaces. The structure has corresponding engagement surfaces for engaging respective engagement surfaces of the spring elements for substantially preventing the spring elements from bulging radially outward when the spring elements are compressed. 
         [0006]    In yet another aspect, a method of forming a spring such as those claimed above uses a single close-and-open injection molding step. 
         [0007]    In yet another aspect, a pump for dispensing fluid comprises a spring and a lost motion connection which compensates for reduction of length or reduction of resiliency of the spring. 
         [0008]    In yet another aspect, a pump for dispensing fluid comprises a spring and components which define corresponding structure for locking and unlocking the pump, wherein the corresponding structure includes a camming surface. 
         [0009]    In yet another aspect, a spring includes a generally cylindrical hollow body having hinges about which opposite vertical sections of the body are pivotable toward each other to form the generally cylindrical shape of the body. 
         [0010]    Other features and aspects of the present invention will in part be apparent and in part be pointed out hereinafter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a left front perspective of a pump showing an actuator of the pump in a locked position; 
           [0012]      FIG. 2  is an exploded view of the pump of  FIG. 1 ; 
           [0013]      FIG. 3  is a perspective of the pump similar to the view of  FIG. 1  but showing the actuator rotated to an unlocked position; 
           [0014]      FIG. 4  is a left side elevation of the pump; 
           [0015]      FIG. 5  is a right bottom perspective of the actuator; 
           [0016]      FIG. 6  is a front perspective of a piston and chaplet of the pump; 
           [0017]      FIG. 7  is a horizontal section of the pump taken in the plane including line  7 - 7  in  FIG. 3 , the valve being shown in the unlocked position; 
           [0018]      FIG. 8  is a top view of the section of  FIG. 7 ; 
           [0019]      FIG. 9  is a horizontal section of the pump taken in the plane including line  9 - 9  in  FIG. 1 , the valve being shown in the locked position; 
           [0020]      FIG. 10  a top view of the section of  FIG. 9 ; 
           [0021]      FIG. 11  is a vertical section of the pump taken in the plane including line  11 - 11  in  FIG. 3 , the valve being shown in the unlocked position and the actuator being shown in an unactuated position; 
           [0022]      FIG. 12  is a horizontal section of the pump taken in the plane including line  12 - 12  in  FIG. 4 ; 
           [0023]      FIG. 13  is a bottom perspective of the actuator with the spring on the actuator; 
           [0024]      FIG. 14  is a bottom view of the actuator and spring of  FIG. 13 ; 
           [0025]      FIG. 15  is a vertical section similar to the view of  FIG. 11  but having the actuator shown in an actuated position; 
           [0026]      FIG. 16  is a vertical section of the pump taken in the plane including line  16 - 16  in  FIG. 3 , the actuator being shown in the actuated position; 
           [0027]      FIGS. 17A-17E  illustrate various views of the spring of  FIG. 2  in a relaxed position; 
           [0028]      FIGS. 18A-18D  illustrate various views of the spring in a compressed position, the spring being shown schematically; 
           [0029]      FIGS. 19A-19C  illustrate enlarged views of a housing, piston shaft, and piston member, the piston shaft and piston member being shown in different positions which result from actuation of the actuator; 
           [0030]      FIGS. 20A-20E  illustrate a second embodiment of a spring of the present invention; 
           [0031]      FIGS. 21A-21E  illustrate a third embodiment of a spring of the present invention; 
           [0032]      FIGS. 22A-22E  illustrate a fourth embodiment of a spring of the present invention; 
           [0033]      FIGS. 23A-23E  illustrate a fifth embodiment of a spring of the present invention; 
           [0034]      FIGS. 24A-24E  illustrate a sixth embodiment of a spring of the present invention; 
           [0035]      FIGS. 25A-25E  illustrate a seventh embodiment of a spring of the present invention; 
           [0036]      FIGS. 26A-26E  illustrate an eighth embodiment of a spring of the present invention; 
           [0037]      FIGS. 27A-27E  illustrate a ninth embodiment of a spring of the present invention; 
           [0038]      FIGS. 28A-28F  illustrate a tenth embodiment of a spring of the present invention; 
           [0039]      FIGS. 29A-29F  illustrate an eleventh embodiment of a spring of the present invention; 
           [0040]      FIG. 30  illustrates a second embodiment of a pump according to the present invention; 
           [0041]      FIG. 31  is an exploded view of the pump of  FIG. 30 ; 
           [0042]      FIG. 32  is a bottom perspective of an actuator of the pump; 
           [0043]      FIG. 33  is a perspective of a piston and chaplet of the pump; 
           [0044]      FIG. 34A  is an elevation of the actuator on the chaplet showing the actuator in a locked position; 
           [0045]      FIG. 34B  is an elevation of the actuator and chaplet similar to  FIG. 34A  but showing the actuator in an unlocked, unactuated position; 
           [0046]      FIG. 34C  is an elevation of the actuator and chaplet similar to  FIG. 34B  but showing the actuator in an unlocked, actuated position; 
           [0047]      FIG. 34D  is an elevation of the actuator and chaplet similar to  FIG. 34B  but simulating the spring of the pump having a decreased length such that the actuator is supported by the spring in a lower position than in  FIG. 34B ; 
           [0048]      FIG. 35  is a perspective of a third embodiment of a pump of the present invention; 
           [0049]      FIG. 36  is an exploded view of the pump of  FIG. 35 ; 
           [0050]      FIG. 37  is a bottom perspective of an actuator of the pump; 
           [0051]      FIG. 38  is a vertical section of a housing of the pump showing a contoured surface of the housing; 
           [0052]      FIG. 39A  is an elevation of the actuator and housing, portions of the housing being broken away to expose the contoured surface of the housing, the actuator being shown in a locked position; 
           [0053]      FIG. 39B  is an elevation similar to  FIG. 39A  but showing the actuator in an unlocked, unactuated position; 
           [0054]      FIG. 40  is a perspective of a fourth embodiment of a pump of the present invention; 
           [0055]      FIG. 41  is an exploded view of the pump of  FIG. 40 ; 
           [0056]      FIG. 42  is a bottom perspective of an actuator of the pump; 
           [0057]      FIG. 43  is a perspective of a reservoir cap of the pump; 
           [0058]      FIG. 44  is a plan view of the pump; 
           [0059]      FIG. 45A  is a section taken in the plane including line  45 - 45  shown in  FIG. 44 , the actuator being shown in a locked position, a portion of the actuator being broken away to expose a slot of a contoured surface in the actuator; 
           [0060]      FIG. 45B  is a section similar to  FIG. 45A  but showing the actuator in an unlocked, unactuated position; and 
           [0061]      FIGS. 46A-46E  illustrate a twelfth embodiment of a spring of the present invention. 
       
    
    
       [0062]    Corresponding reference characters indicate corresponding parts throughout the drawings. 
       DETAILED DESCRIPTION 
       [0063]    Referring to  FIGS. 1-16 , a pump constructed according to principles of the present invention is designated generally by the reference number  10 . The pump may be adapted for mounting on a reservoir for forming a dispenser. Numerous types of such reservoirs are known in the art and are not illustrated herein. In general, a fluid to be dispensed is stored in the reservoir, and the pump  10  is configured for pumping the fluid out of the reservoir for dispensing the fluid as desired. For example, the illustrated pump  10  may be mounted on a suitable reservoir for forming a lotion or soap dispenser. The pump  10  may be used for dispensing other types of fluids without departing from the scope of the present invention. 
         [0064]    As shown in  FIG. 2 , the pump  10  includes several different parts. More specifically, the pump  10  includes, as shown from top to bottom, an actuator  12 , a piston shaft  14 , a chaplet  16 , a piston member  18 , a compression spring  20 , a reservoir cap  22 , a check valve  24 , a piston housing  26 , a dip tube  28 , and a gasket  30 . As shown in  FIG. 11 , the pump  10  has an inlet  32  positioned at a distal end of the dip tube and an outlet  34  positioned on a nozzle on the actuator. The actuator  12  and reservoir cap  22  at least partially define a housing which houses the spring  20  and conceals the spring from view. The pump  10  has a vertical axis indicated by the line A-A in  FIG. 1 . As will be explained in further detail below, the actuator  12  may be selectively actuated against a biasing force of the spring  20  to dispense fluid. 
         [0065]    The pump  10  of the present invention includes features which permit more efficient construction of the pump, reduce cost associated with construction of the pump, and enhance recyclability of the pump. The spring  20  may be formed substantially entirely of a non-metal material. For example, the spring  20  may be formed of a plastic material or thermoplastic polymer such as acetel or polypropylene. Desirably, the spring  20  has a construction which permits formation of the spring in a single close-and-open injection molding step (i.e., not requiring slides for additional injection molding steps). Use of such materials and relatively simple injection-molding techniques enhances efficiency of construction and manufacturing and decreases construction costs. The other components which make up the pump  10  may also be made of similar material to facilitate recycling of the pump. Springs formed of plastic material may not provide desired biasing force or have the necessary operating life unless suitably structured. The springs of the present invention include structure designed specifically for permitting use of plastic material in forming a spring which has sufficient biasing force for use in a pump of the type contemplated. Moreover, the pump  10  may include other features, which will become apparent, which cooperate with the spring  20  for assisting the spring in providing the desired biasing force. The components of the pump  10 , including the spring  20 , may be made of other materials and formed in other ways (e.g., using multiple-step injection molding operations) without departing from the scope of the present invention. 
         [0066]    The illustrated pump  10  may be unlocked and locked by rotating the actuator  12  between unlocked and locked rotational positions, and when the actuator is in the unlocked position, the actuator may be moved vertically between an upper, unactuated position and a lower, actuated position to dispense liquid.  FIG. 1  illustrates a left front perspective of the pump  10  in which the actuator  12  is in the locked position.  FIG. 3  also illustrates a left front perspective of the pump  10  but the actuator  12  has been rotated about 90 degrees counter-clockwise to the unlocked position. Other degrees of rotation may be used for moving the actuator  12  between the locked and unlocked positions without departing from the scope of the present invention. As will be explained in further detail below, the spring  20  and actuator  12  include mating structure which causes the spring to rotate about the vertical axis A-A of the pump conjointly with the actuator. 
         [0067]    Components of the pump may include cooperating structure which “locks” the pump when the actuator is in the locked position and “unlocks” the pump when the actuator is in the unlocked position. For example, in the illustrated embodiment, the actuator  12  and the chaplet  16  include cooperating structure which “locks” the pump when the actuator is in the locked position and “unlocks” the pump when the actuator is in the unlocked position. As shown in  FIG. 5 , a bottom perspective of the actuator  12 , the actuator includes ribs  40  extending radially outward from a vertical axis of the actuator. As shown in  FIG. 6 , a perspective of the chaplet  16 , piston shaft  14 , and piston member  18 , the chaplet includes opposite contoured upward facing surfaces  42 , for engaging the ribs of the actuator. Each contoured surface includes a first portion or notch  42 A in which a respective rib  40  is received when the actuator is in the locked position, a second portion or slot  42 B in which the rib is received when the actuator is in the unlocked position, and respective first and second detents  42 C,  42 D adjacent the notch and slot.  FIGS. 7 and 8  illustrate a horizontal section of the pump  10  in which the actuator  12  is in the unlocked position.  FIGS. 9 and 10  illustrate a horizontal section of the pump  10  in which the actuator  12  is in the closed position. The slots  42 B in the chaplet  16  have a height for receiving the ribs  40  of the actuator  12  so that the actuator may be moved from an unactuated position (e.g.,  FIGS. 3 and 11 ) downward to an actuated position (e.g.,  FIGS. 15 and 16 ) to cause the piston to move fluid through the pump. As illustrated in later embodiments, components of the pump  10  other than the actuator  12  and the chaplet  16  may include cooperating structure for “locking” and “unlocking” the pump without departing from the scope of the present invention. 
         [0068]    Referring now to  FIGS. 17A-17E , the spring  20  is generally cylindrical. The spring includes upper and lower support members  50 A,  50 B, first and second spring elements  52 A,  52 B, upper and lower braces  54 A,  54 B, and upper and lower intermediate braces  56 A,  56 B. The upper support member  50 A has an upper support surface, and the lower support member  50 B has a lower support surface. The upper support surface faces upward for engaging a downward facing surface of the actuator  12 , as shown in  FIGS. 11 ,  15 , and  16 . The lower support surface faces downward for engaging an upward facing surface of the cap  22 , as shown in  FIG. 11 . In the illustrated embodiment, the upper and lower support members  50 A,  50 B and the upper and lower support surfaces are generally U-shaped. Other spring shapes can be used without departing from the scope of the present invention. For example, the shape may be modified to further enhance the engagement of the spring  20  with the actuator  12  for conjoint rotation with the actuator or for permitting the spring to be used in other pumps. 
         [0069]      FIGS. 18A-18D  illustrate various schematic views of the spring  20  in a compressed state. The spring  20  is shown schematically in the sense that it is not shown exactly as the spring of  FIGS. 17A-17E  would appear when compressed. The spring  20  shown in  FIGS. 18A-18D  includes structural differences compared to the spring shown in  FIGS. 17A-17E  and is provided as an example of how components of the spring might look when the spring is compressed. As will be explained in further detail below, the spring elements  52 A,  52 B provide maximum biasing force when compressed if they can be prevented from bulging radially outward. The spring elements  52 A,  52 B as shown throughout the Figures are not bulging radially outward. 
         [0070]    Referring again to  FIGS. 17A-17E , the spring elements  52 A,  52 B extend along the height of the spring between the upper and lower support members  50 A,  50 B. The spring elements  52 A,  52 B connect the upper and lower support members  50 A,  50 B to each other. The spring elements  52 A,  52 B are constructed to be resiliently vertically compressible to provide a force biasing the actuator  12  toward its unactuated position. The spring elements  52 A,  52 B include multiple segments of curvature which bend when the spring is compressed. In the illustrated embodiment, the spring elements each include first (upper) and second (lower) segments  60 A,  60 B of curvature. The first and second segments  60 A,  60 B of curvature have opposite concavity. More specifically, the first segment  60 A has a concave surface which opens toward the rear of the spring, and the second segment  60 B has a concave surface which opens toward the front of the spring. The segments  60 A,  60 B are connected to each other at a region  62  positioned generally midway along the height of the spring. In the illustrated embodiment, the segments  60 A,  60 B of curvature are configured to provide the spring elements  52 A,  52 B with a generally S-shape. The spring elements  52 A,  52 B may include degrees of curvature other than shown without departing from the scope of the present invention. Moreover, other numbers of segments of curvature may be used without departing from the scope of the present invention. For example, three segments of curvature may be used, which may provide the spring elements with a curved generally M-shape (not shown). Still further, the spring segments may be all straight and have shapes such as “M”, “W” and “Z” with sharper corners (not shown). Moreover, the spring may include segments which include a mixture of straight and curved sections (not shown). 
         [0071]    In the illustrated embodiment, the spring elements  52 A,  52 B are provided on opposite left and right sides of the spring. More specifically, a vertical plane including the axis A-A indicated in  FIG. 1  divides the spring into opposite left and right sides. The plane would extend from left to right within the page in the views shown in  FIGS. 17B and 17C  and out of the page in the views shown in  FIGS. 17D and 17E . Substantially the entire height of each spring element  52 A,  52 B is positioned on the respective left or right side of the spring. In other words, the spring elements  52 A,  52 B do not intersect the plane which divides the spring into opposite left and right sides. Stated another way, the spring elements  52 A,  52 B make less than a 360 degree turn, and more particularly less than a 180 degree turn, around a circumference of the spring as they rise from the lower support member to the upper support member. Accordingly, the spring elements  52 A,  52 B are non-helical. The illustrated spring elements  52 A,  52 B are symmetrical about the plane which divides the spring into opposite left and right sides, but asymmetrical spring elements may be used without departing from the scope of the present invention. 
         [0072]    In the illustrated embodiment, the spring elements  52 A,  52 B extend upward in separate, spaced and generally parallel vertical planes. The planes would extend from left to right within the page in the views shown in  FIGS. 17B and 17C  and out of the page in the views shown in  FIGS. 17D and 17E . The spring elements  52 A,  52 B having such a vertical orientation provides the spring  20  with a leaf-spring type loading when compressed. The spring elements  52 A,  52 B each include an outer engagement surface extending along the height of the spring elements which may interface with the actuator  12 , as explained further below. As shown in  FIG. 17E , the outer engagement surfaces are minimally curved around the circumference of the spring. The engagement surfaces may be substantially flat. Such minimal curvature or substantial flatness may be referred to as “generally flat.” The engagement surfaces may have other shapes or profiles (e.g., more dramatic curvature) without departing from the scope of the present invention. 
         [0073]    The braces  54 A,  54 B,  56 A,  56 B extend along the width of the spring between the first and second spring elements  52 A,  52 B. The braces connect the first and second spring elements  52 A,  52 B to each other to prevent the spring elements from bulging radially outward when the spring  20  is compressed. Such radial bulging might decrease the biasing force which the spring is capable of exerting on the actuator. The illustrated braces  54 A,  54 B,  56 A,  56 B are substantially horizontal. In other words, the braces extend generally perpendicular to the vertical axis of the spring. As illustrated in  FIGS. 17B-17D , the braces  54 A,  54 B,  56 A,  56 B are positioned on the spring relative to the upper and lower support members  50 A,  50 B such that the braces are below the upper support member and above the lower support member. More specifically, the upper brace  54 A is positioned immediately below the upper support member  50 A, and the lower brace  54 B is positioned immediately above the lower support member  50 B. The upper intermediate brace  56 A is positioned immediately above the vertical midpoint (i.e., regions  62 ) of the spring elements  52 A,  52 B, and the lower intermediate brace  56 B is positioned immediately below the vertical midpoint of the spring elements. The braces  54 A,  54 B,  56 A,  56 B extend in horizontal planes which are generally parallel to and inboard heightwise from the horizontal planes in which the upper and lower support members  50 A,  50 B extend. It may be desirable to provide the upper and lower braces  54 A,  54 B as close to the respective vertical positions of the upper and lower support members  50 A,  50 B as possible. The upper and lower braces  54 A,  54 B of this embodiment are offset vertically with respect to the support members  50 A,  50 B (and the upper and lower intermediate braces  56 A,  56 B are vertically offset with respect to each other) so the spring may be formed in one close-and-open injection molding process. Braces having other configurations may be used without departing from the scope of the present invention. Moreover, in some embodiments, additional braces may be provided or braces may be omitted without departing from the scope of the present invention. 
         [0074]    The spring housing, and more particularly the actuator  12 , includes engagement structure configured for engaging the outer engagement surfaces of the spring elements to assist in preventing the spring elements from bulging radially outward when the spring is compressed. As mentioned above, such radial bulging might decrease the biasing force the spring  20  is capable of providing against the actuator  12 . Referring to  FIGS. 5 ,  13 ,  14 , and  16 , the actuator  12  includes opposite left and right inner walls  70 A,  70 B positioned for engaging the outer engagement surfaces of the spring elements  52 A,  52 B. In the illustrated embodiment, the inner walls  70 A,  70 B are generally flat to generally correspond to the generally flat left and right engagement surfaces of the spring elements  52 A,  52 B for engaging the outer engagement surfaces of the spring elements in generally flatwise engagement. The engagement structure may be modified to include curved walls (not shown) for more closely conforming to the minimally curved spring element engagement surfaces without departing from the scope of the present invention. As illustrated in  FIG. 16 , as the actuator  12  is moved downward toward the actuated position, the left and right inner walls  70 A,  70 B move downward along the outer engagement surfaces of the compressing spring elements  52 A,  52 B to a vertical position about mid-height of the spring elements (i.e., adjacent the regions  62  of the spring elements). Accordingly, the inner walls  70 A,  70 B engage and prevent the spring elements  52 A,  52 B from bulging outward away from the vertical axis of the spring  20 . 
         [0075]    Referring to  FIG. 17A , the spring  20  includes mating structure in the form of protrusions  78 A,  78 B provided on the upper support member  50 A and upper brace  54 A and protrusions  78 C,  78 D provided on the lower support member  50 B and lower brace  54 B. In the illustrated embodiment, the protrusions  78 A- 78 D have a generally rounded triangle profile, with the apex of the triangle facing away from the respective supports and braces. The mating structure on the spring  20  is provided for forming mating connections, generally indicated by  80 A,  80 B ( FIGS. 11 and 14 ), with mating structure on the actuator. As shown in  FIGS. 11 and 14 , the mating structure on the actuator includes recesses  82 A,  82 B positioned for receiving respective protrusions  78 A,  78 B when the spring  20  is operatively engaged with the actuator  12 .  FIG. 13  is a bottom perspective of the spring  20  engaged with the actuator  12 . The protrusions  78 A- 78 D are provided on the upper and lower ends of the spring so the spring can form mating connections with the actuator  12  regardless of whether the upper or lower end of the spring is engaged with the actuator.  FIG. 14  is a bottom view of the spring  20  and actuator  12  of  FIG. 13 . As shown, the reception of the protrusions  78 A,  78 B in the recesses  82 A,  82 B form the mating connections  80 A,  80 B which cause the spring  20  to rotate conjointly with the actuator  12  about the vertical axis of the pump  10  when the actuator is moved between the on and off positions. The mating structure at the lower end of the spring  20  does not mate with the cap  22  so the spring rotates independently from the cap. Accordingly, the mating connections  80 A,  80 B assist in maintaining the outer engagement surfaces of the spring elements  52 A,  52 B in register with the inner walls  70 A,  70 B of the actuator  12  for promoting maximum assistance of the inner walls in preventing the spring elements from bulging radially outward when compressed. Other types of mating connections may be used or the mating connections may be omitted without departing from the scope of the present invention. For example, the protrusions  78 A- 78 D may have other configurations or shapes without departing from the scope of the present invention. 
         [0076]      FIGS. 19A-19B  illustrate a shifting seal or lost motion connection of the piston shaft  14  with the piston member  18 . The piston shaft  14  is connected to the piston member  18  by reception of the piston shaft through a central opening in the piston member. The connection of the piston shaft  14  and piston member  18  acts as a valve to prevent fluid from flowing from the housing  26  into the piston shaft  14  when the pump  10  is not in the actuated position. Moreover, the shifting seal or lost motion connection assists in compensating for reduction of length of the compression spring  20  as the spring undergoes repeated compression cycles over time. 
         [0077]    As shown in  FIG. 19A , the piston shaft  14  includes a circumferential recess  14 A which receives an inner circumferential shoulder  18 A of the piston member  18 . The piston shaft  14  has a reduced external diameter at the circumferential recess  14 A. The circumferential shoulder  18 A of the piston member  18  has an inner diameter which is about the same as the outer diameter of the circumferential recess  14 A. The circumferential recess  14 A has an external diameter and a length extending along the length of the piston shaft  14  which are sized to permit the shoulder  18 A of the piston member to slide along the piston shaft  14  within the circumferential recess  14 A between lower and upper ends of the circumferential recess. The piston shaft  14  has inlet openings  14 B spaced around the circumference of the piston shaft adjacent the shifting seal or lost motion connection (e.g., within the circumferential recess  14 A). The piston member  18  blocks fluid from flowing from the housing  26  through the inlet openings  14 B when the shoulder  18 A of the piston member  18  is below the inlet openings  14 B. The piston member  18  permits flow of fluid from the housing  26  through the inlet openings  14 B when the shoulder  18 A of the piston member is above the inlet openings. 
         [0078]    As shown in  FIG. 19A , when the pump  10  is in an unactuated position, the piston member  20  is in a lowered position relative to the piston shaft  14 . The piston member  18  is seated in a lower end of the chaplet  16 . The compression spring  20  biases the actuator  12  away from the housing  26 , and the piston shaft  14  is connected to the actuator such that the spring maintains the piston shaft in a raised (unactuated) position within the housing such as illustrated in  FIG. 19A . In the raised position, the piston member  18  acts as a valve for preventing fluid from flowing from the housing  26  into the inlet openings  14 B. The shoulder  18 A of the piston member  18  is below the inlet openings  14 B of the piston shaft  14  and thus blocks flow of fluid from entering the piston shaft through the inlet openings. 
         [0079]    An actuation of the actuator  12  generally includes a downward stroke and an upward stroke. The downward stroke is caused by the user forcing the actuator downward against the bias of the spring from the unactuated position to the actuated position. The upward stroke is caused by the spring forcing the actuator upward to the unactuated position. As shown in  FIG. 19B , when a user begins the downward stroke by overcoming the bias of the spring  20 , initially the piston shaft  14  but not the piston member  18  moves downward within the housing  26 . The reduced external diameter of the circumferential recess  14 A of the piston shaft  14  permits the piston shaft to slide downward through the central opening of the piston member  18 . When the upper end of the circumferential recess  14 A reaches the shoulder  18 A of the piston member  18 , the piston member begins to move downward in the housing  26 , forcing fluid from in the housing through the inlet openings  14 B. For example, the circumferential recess  14 A may have a length of about 0.079 inches (2.0 mm) such that the piston shaft  14  moves downward about that length before positively engaging the piston member  18 . The connection is referred to as a shifting seal connection because the engagement of the piston shaft  14  with the piston member  18  creates a seal to prevent fluid from passing between the circumferential recess  14 A and the piston member shoulder  18 A but permits the piston shaft to move with respect to the piston member  18 . As shown by comparison of  FIGS. 19A and 19B , the seal formed adjacent the piston member shoulder  18 A “shifts” from below the piston shaft inlet openings  14 B to above the openings as the actuator  12  is moved downward to permit flow through the inlet openings from the housing  26 . For example, the actuator  12  may be moved to dispense fluid such that the piston member  18  is pushed downward at the bottom of the downward stroke to a position such as shown in  FIG. 19C . 
         [0080]    When the user releases pressure on the actuator  12 , the bias of the compression spring  20  causes the actuator  12  and the piston shaft  14  to move upward in the upward stroke. The piston member  18  moves upward together with the piston shaft  14 . Near the upper portion of the upper stroke, the piston member  18  seats in the bottom of the chaplet  16  and thus stops moving upward, as shown in  FIG. 19B . The spring  20  continues to move the piston shaft  14  upward. As the piston shaft  14  moves upward relative to the piston member  18 , the seal between the piston member and the piston shaft shifts to below the inlet openings  14 B, thus blocking flow through the inlet openings. The spring  20  continues to move the piston shaft  14  upward until the shoulder  18 A of the piston member  18  engages the bottom of the circumferential recess  14 A in the piston shaft, as shown in  FIG. 19A . The pump  20  is then ready for a subsequent downward stroke to dispense additional fluid. 
         [0081]    The shifting seal or lost motion connection between the piston shaft  14  and piston member  18  assists in compensating for reduction of length of the spring  20  which may occur over time (i.e., after numerous actuations of the actuator  12 ). For example, if the spring  20  is made of a plastic material, it may become less resilient or reduce in length after numerous compression cycles. To an extent, even if the spring  20  loses strength to move the piston shaft to its fully unactuated position (e.g.,  FIG. 19A ), the spring may still be able to move the piston member  18  to its fully unactuated position (e.g., seated in the bottom of the chaplet  16  as shown in  FIGS. 19A and 19B ). Thus, even if the spring  20  loses resiliency or length, to an extent the spring will still move the piston member  18  sufficiently upward on the upward stroke so on the downward stroke the piston member will displace the desired amount of fluid. For example, when the spring  20  shortens, the unactuated position of the pump may be as shown in  FIG. 19B . When the spring  20  shortens, the valve function of the shifting seal connection may be compromised because the spring is not strong enough to sufficiently raise the piston shaft to shift the seal between the shaft and the piston member above the inlet openings  14 B. However, as long as the spring  20  is strong enough to raise the piston member  18  into its seated position in the bottom of the chaplet  16 , as shown in  FIG. 19B , the piston will dispense the desired amount of fluid in the downward stroke. Accordingly, the shifting seal provides compensation for reduction of length of the spring  20 . It will be appreciated that the shifting seal connection could be modified (e.g., by increasing the length of the circumferential recess  14 A and appropriately positioning the inlet openings  14 B) such that the connection can compensate for reduction of spring length while still maintaining the valve function of the connection. 
         [0082]    The pump  10  may be designed to have an output which is slightly more than the desired output to compensate for reduction of length of the compression spring  20  over time. For example, the pump  10  may be designed to have an output (e.g., about 1.78 cc) which is about 20 percent higher than the desired output (e.g., about 1.5 cc). If the compression spring  20  is made of a material such as plastic, the spring may decrease in length after numerous compression cycles. As a result, the stroke length of the piston shaft  14  and the piston member  18  may be reduced. In other words, because the spring  20  does not raise the piston member  18  as high in the housing  26  as when the spring was new, not as much fluid will be moved through the pump  10  in a full stroke of the actuator  12 . Such reduction in length of the spring  20  may be anticipated and accounted for by providing the pump  10  with a greater initial output. 
         [0083]      FIGS. 20-29  illustrate additional embodiments of springs of the present invention. Although the springs are not illustrated as part of a pump, it will be understood the springs may be combined with the pump components illustrated in  FIGS. 1-16  (or suitably modified pump components) for forming a pump according to the present invention. 
         [0084]      FIGS. 20A-20E  illustrate various views of a second embodiment of a spring  220  of the present invention. The spring is similar to the spring described above, and corresponding reference numbers are provided, plus 200. For example, the spring is generally cylindrical and includes upper and lower connecting or support members  250 A,  250 B, spring elements  252 A,  252 B extending between the support members, and upper and lower braces  254 A,  254 B (broadly “connecting members”) extending between the spring elements. In this embodiment, the upper and lower intermediate braces are omitted. 
         [0085]      FIGS. 21A-21E  illustrate various views of a third embodiment of a spring  320  of the present invention. The spring is similar to the spring  20  described above, and corresponding reference numbers are provided, plus 300. For example, the spring is generally cylindrical and includes upper and lower support members  350 A,  350 B, spring elements  352 A,  352 B extending between the support members, upper and lower braces  354 A,  354 B, and upper and lower intermediate braces  356 A,  356 B. In this embodiment, the upper and lower support members  350 A,  350 B include feet  351 A,  351 B which provide the generally U-shapes of the support members and the bearing surfaces with extended bearing surfaces. In other words, the bearing surfaces are extended to assist in preventing the spring  320  from tipping forward or rearward inside the pump housing. 
         [0086]      FIGS. 22A-22E  illustrate various views of a fourth embodiment of a spring  420  of the present invention. The spring is similar to the spring  320  described above, and corresponding reference numbers are provided, plus 100. For example, the spring is generally cylindrical and includes upper and lower support members  450 A,  450 B, spring elements  452 A,  452 B, upper and lower braces  454 A,  454 B, and feet  451 A,  451 B. In this embodiment, the upper and lower intermediate braces are omitted. 
         [0087]      FIGS. 23A-23E  illustrate various views of a fifth embodiment of a spring  520  of the present invention. The spring is similar to the spring  420  described above, and corresponding reference numbers are provided, plus 100. For example, the spring is generally cylindrical and includes upper and lower support members  550 A,  550 B, spring elements  552 A,  552 B, upper and lower braces  554 A,  554 B, and feet  551 A,  551 B. In this embodiment, a greater vertical offset or spacing is provided between the upper and lower support members  550 A,  550 B and respective upper and lower braces  554 A,  554 B. Moreover, the protrusions on the upper and lower braces  554 A,  554 B are omitted. 
         [0088]      FIGS. 24A-24E  illustrate various views of a sixth embodiment of a spring  620  of the present invention. The spring is similar to the spring  420  described above, and corresponding reference numbers are provided, plus 200. For example, the spring is generally cylindrical and includes upper and lower support members  650 A,  650 B, spring elements  652 A,  652 B, upper and lower braces  654 A,  654 B, and feet  651 A,  651 B. In this embodiment, the spring elements  652 A,  652 B are positioned in opposite orientations on the left and right sides of the spring, instead of being positioned symmetrically with respect to the plane which divides the spring into the left and right sides. As shown in  FIG. 24B , the spring elements  652 A,  652 B form a  FIG. 8  shape when viewed from the side. It is believed such an asymmetrical orientation of the spring elements  652 A,  652 B may provide greater biasing force when the spring  620  is compressed because the opposite orientations cause torsion to be applied to the spring elements when loaded. In addition, in this embodiment, the spring elements  652 A,  652 B have a different side profile compared to prior embodiments. More specifically, as shown in  FIG. 24B , the segments  660 A,  660 B of curvature are curved more sharply, the first and second segments  660 A,  660 B of curvature are curved to different degrees with respect to each other, and a generally straight portion  661  is provided between the segments of curvature. Moreover, in this embodiment, the feet  651 A,  651 B are offset slightly inboard heightwise with respect to the upper and lower support members  650 A,  650 B. 
         [0089]      FIGS. 25A-25E  illustrate various views of a seventh embodiment of a spring  720  of the present invention. The spring is similar to the spring  620  described above, and corresponding reference numbers are provided, plus 100. For example, the spring is generally cylindrical and includes upper and lower support members  750 A,  750 B, spring elements  752 A,  752 B, upper and lower braces  754 A,  754 B, and feet  751 A,  751 B. In this embodiment, the spring elements  752 A,  752 B have a different side profile compared to prior embodiments. The spring elements  752 A,  752 B are similar to the spring elements  652 A,  652 B in that the spring elements are provided in opposite orientations and the first and second segments  760 A,  760 B of curvature of each spring element are curved to different degrees with respect to each other. In this embodiment, the segments  760 A,  760 B of curvature are curved more sharply, and the generally straight portion  761  between the segments of curvature is longer. 
         [0090]      FIGS. 26A-26E  illustrate various views of an eighth embodiment of a spring  820  of the present invention. The spring is similar to the spring  220  described above, and corresponding reference numbers are provided, plus 600. For example, the spring is generally cylindrical and includes upper and lower support members  850 A,  850 B, spring elements  852 A,  852 B, and upper and lower braces  854 A,  854 B. In this embodiment, the support members  850 A,  850 B and braces  854 A,  854 B are provided in the form of upper and lower rings. In other words, the braces  854 A,  854 B are not vertically offset from the support members  850 A,  850 B. In addition, the spring elements  852 A,  852 B have varying thickness along their height, and, as shown in  FIG. 26E , the outer engagement surfaces of the spring elements curve more dramatically around the circumference of the spring. In this embodiment, the spring has a more truly cylindrical outer profile. Structure provided on an actuator used with this spring  820  for limiting bulging of the spring elements  852 A,  852 B radially outward may be suitably curved to conform to the more dramatically curved outer engagment surfaces of the spring elements. The design of this spring  820  requires the spring to be formed in a two-step injection molding process using a slide. 
         [0091]      FIGS. 27A-27E  illustrate various views of a ninth embodiment of a spring  920  of the present invention. The spring is similar to the spring  820  described above, and corresponding reference numbers are provided, plus 100. For example, the spring has support members  950 A,  950 B and braces  954 A,  954 B provided in the form of upper and lower rings and the spring has spring elements  952 A,  952 B having varying thickness along their height. In this embodiment, the spring elements  952 A,  952 B are provided in opposite orientations instead of symmetrical orientations. The design of this spring  920  requires the spring to be formed in a two-step injection molding process using a slide. 
         [0092]      FIGS. 28A-28F  illustrate various views of a tenth embodiment of a spring  1020  of the present invention. The spring is particularly similar to the spring  820  described above, and corresponding reference numbers are provided, plus 200. For example, the spring has upper and lower rings and spring elements  1052 A,  1052 B having varying thickness. In this embodiment, the spring  1020  is designed such that it may be formed in one close-and-open injection molding process not requiring a slide. More specifically, as shown in  FIG. 28B , the spring  1020  is molded as two halves  1020 A,  1020 B which are pivoted toward each other about upper and lower hinges  1020 C and then locked in engagement with each other by corresponding mating male and female connection structure  1020 D,  1020 E on respective halves. 
         [0093]      FIGS. 29A-29F  illustrate various views of an eleventh embodiment of a spring  1120  of the present invention. The spring is particularly similar to the spring  920  described above, and corresponding reference numbers are provided, plus 200. For example, the spring has upper and lower rings and spring elements  1152 A,  1152 B having varying thickness. In addition, the spring  1120  has spring elements  1152 A,  1152 B having opposite orientations. In this embodiment, the spring  1120  is designed such that it may be formed in one close-and-open injection molding process not requiring a slide. More specifically, as shown in  FIG. 29B , the spring  1120  is molded as two halves  1120 A,  1120 B which are pivoted toward each other about upper and lower hinges  1120 C and then locked in engagement with each other by corresponding mating male and female connection structure  1120 D,  1120 E on respective halves. 
         [0094]      FIGS. 30-34  illustrate various views of a second embodiment of a pump of the present invention. The pump is similar to the pump  10  described above, and corresponding reference numbers are provided, plus 1200. For example, as shown in  FIG. 31 , the pump  1210  includes an actuator  1212 , a piston shaft  1214 , a chaplet  1216 , a piston member  1218 , a compression spring  1220 , a reservoir cap  1222 , and a housing  1226 . As in the first embodiment, the actuator  1212  and the chaplet  1216  include cooperating structure which “locks” the pump  1210  when the actuator is in the locked position and “unlocks” the pump when the actuator is in the unlocked position. As shown in  FIG. 32 , the actuator  1212  includes ribs  1240  extending radially outward from a vertical axis of the actuator. As shown in  FIG. 33 , the chaplet  1216  includes opposite contoured upward facing surfaces  1242 , for engaging the ribs  1240  of the actuator  1212 . Each contoured surface  1242  includes a first portion or notch  1242 A in which a respective rib  1240  is received when the actuator  1212  is in the locked position, a second portion or slot  1242 B in which the rib is received when the actuator is in the unlocked position, and a detent  1242 C adjacent the notch. In this embodiment, the contoured surfaces  1242  each include a ramp or camming surface  1242 E between the slot  1242 B and the notch  1242 A. The camming surface  1242 E includes an upper end adjacent the notch  1242 A and a lower end adjacent the slot  1242 B. The camming surface  1242 E ramps upward from the lower end to the upper end, and the lower end is lower than the notch  1242 A. As explained in further detail below, the camming surfaces  1242 E assist in preventing the spring  1220  from reducing in length after repeated compression cycles. 
         [0095]      FIG. 34A  shows the actuator  1212  on the chaplet  1216  and the actuator being in the locked position. A rib  1240  of the actuator  1212  is shown received the notch  1242 A of the chaplet  1216 . A portion of the lower part of the actuator  1212  is broken away to expose the rib  1240 .  FIG. 34B  shows the actuator  1212  rotated to the unlocked position in which the rib  1240  is in register with the slot  1242 B. The rib  1240  is shown at a height relative to the chaplet  1216  about the same as  FIG. 34A  when the actuator was in the locked position. The rib  1240  is supported in this vertical position by the bias of the compression spring  1220 . 
         [0096]      FIG. 34C  shows the actuator  1212  moved to the actuated position. The rib  1240  is received in the slot  1242 B at a vertical position lower than in the unactuated position. As the actuator  1212  is moved downward to this position, fluid is moved through the pump  1210 . When the user releases pressure on the actuator  1212 , the spring  1220  desirably raises the actuator back to its unactuated position such as shown in  FIG. 34B . Over time, multiple compression cycles may cause the compression spring  1220  to become less resilient or reduce in length. This may result in the spring  1220  supporting the rib  1240  of the actuator  1212  at a lower position with respect to the chaplet  1216  than when the spring  1220  was in a new condition. For example, the spring  1220  after numerous compression cycles may support the actuator  1212  at a height such as shown in  FIG. 34D  in which the rib  1240  is lower than shown in  FIG. 34B . 
         [0097]    The camming surfaces  1242 E facilitate locking of the pump  1210  after the spring  1220  has become less resilient and/or decreased in length. Moreover, the camming surfaces  1242 E assist in preventing the spring  1220  from losing resiliency or reducing in length and may actually restore some resiliency or length to the spring. When the spring  1220  has decreased in length or resiliency such that it supports the actuator  1212  in a lower position than the spring was originally capable, the camming surface  1242 E permits the user to rotate the actuator to the locked position by applying a rotational force to the actuator. Without the camming surface  1242 E, pure rotational movement of the actuator may be blocked by engagement of the rib  1240  with the side of the slot  1242 B. In other words, if the spring  1220  is not strong enough to support the rib  1240  at a position above the slot  1242 B instead of in the slot  1242 B, the user would need to raise the actuator  1212  (to lift the rib  1240  upward out of the slot  1242 B) before rotating the actuator to the locked position. The camming surface  1242 E compensates for reduction in length of the spring by raising the rib  1240  as the actuator  1212  is rotated toward the locked position. As long as the spring  1220  is strong enough to support the actuator at a height at which the rib  1240  is above the lower end of the camming surface  1242 E, a user may rotate the actuator to the locked position without lifting the actuator to raise the rib out of the slot  1242 B. Desirably, when the actuator  1212  is in the locked position, compression is relieved from the spring  1220 . This reduction in load on the spring  1220  assists in preventing length reduction of the spring. If the bottom end of the spring  1220  is prevented from moving upward (e.g., connected to a component of the pump  1210 ), the spring  1220  may even be tensioned when the actuator  1212  is in the locked position, which may restore length and/or resiliency to the spring. 
         [0098]      FIGS. 35-39  illustrate various views of a third embodiment of a pump  1310  of the present invention. The pump is similar to the pump  10  described above, and corresponding reference numbers are provided, plus 1300. For example, as shown in  FIG. 36 , the pump  1310  includes an actuator  1312 , a piston shaft  1314 , a chaplet  1316 , a piston member  1318 , a compression spring  1320 , a reservoir cap  1322 , and a housing  1326 . In this embodiment, the actuator  1312  and housing  1326  include cooperating structure which “locks” the pump  1310  when the actuator is in the locked position and “unlocks” the pump when the actuator is in the unlocked position. The cooperating structure is substantially similar to the cooperating structure on the pump  1210  but is provided on different components of the pump  1310 . As shown in  FIG. 37 , the actuator  1312  includes ribs  1340  extending along the height of the actuator, generally parallel the vertical axis of the actuator. As shown in  FIG. 38 , the housing  1326  includes inner contoured surfaces  1342  on opposite sides of the housing corresponding to each of the ribs  1340 . The bottom ends of the ribs  1340  engage the contoured surfaces  1342  as the actuator  1312  is rotated between the locked and unlocked positions. Each contoured surface  1342  includes a notch  1342 A, a slot  1342 B, a detent  1342 C adjacent the notch, and a camming surface  1342 E between the notch and slot. The interaction between the ribs  1340  and the contoured surfaces  1342  is functionally identical to the interaction of the ribs  1240  and contoured surfaces  1242  in the second embodiment of the pump  1210  for locking and unlocking the actuator  1212 . The actuator  1312  is shown in the locked position in  FIG. 39A  with a rib  1340  received in a notch  1342 A. The housing  1326  is shown with portions broken away to expose the contoured surface  1342 . The actuator  1312  is shown in the unlocked, unactuated position in  FIG. 39B , with the rib  1340  in register with the slot  1342 B. If the spring  1320  were to decrease in resiliency and/or reduce in length, the camming surface  1342 E would facilitate rotation of the actuator  1312  from the unlocked position to the locked position by ramping the rib  1340  upward as described with respect to the pump  1210 . 
         [0099]      FIGS. 40-45  illustrate various views of a fourth embodiment of a pump  1410  of the present invention. The pump is similar to the pump  10  described above, and corresponding reference numbers are provided, plus 1400. For example, as shown in  FIG. 41 , the pump  1410  includes an actuator  1412 , a piston shaft  1414 , a chaplet  1416 , a piston member  1418 , a compression spring  1420 , a reservoir cap  1422 , and a housing  1426 . In this embodiment, the actuator  1412  and reservoir cap  1422  include cooperating structure which “locks’ the pump  1410  when the actuator is in the locked position and “unlocks” the pump when the actuator is in the locked position. The cooperating structure is substantially similar to the cooperating structure on the pump  1210  but is provided on different components of the pump  1410 . As shown in  FIG. 43 , the reservoir cap  1422  includes ribs  1440  extending along the height of the reservoir cap, generally parallel the vertical axis of the reservoir cap. As shown in  FIG. 42 , the actuator  1412  includes inner contoured surfaces  1442  on opposite sides of the actuator  1412  corresponding to each of the ribs  1440 . The top ends of the ribs  1440  engage the contoured surfaces  1442  as the actuator  1412  is rotated between the locked and unlocked positions. Each contoured surface  1442  includes a notch  1442 A, a slot  1442 B, a detent  1442 C adjacent the notch, and a camming surface  1442 E between the notch and slot. The interaction between the ribs  1440  and the contoured surfaces  1442  is functionally identical to the interaction of the ribs  1240  and contoured surfaces  1242  in the second embodiment of the pump  1210  for locking and unlocking the actuator  1212 . The actuator  1412  is shown in the locked position in  FIG. 45A  with a rib  1440  received in a notch  1442 A. The actuator  1412  is shown in the unlocked, unactuated position in  FIG. 45B , with the rib  1440  in register with the slot  1442 B and a portion of the actuator broken away to expose the slot. If the spring  1420  were to decrease in resiliency and/or reduce in length, the camming surface  1442 E would facilitate rotation of the actuator  1412  from the unlocked position to the locked position as described with respect to the pump  1210 . 
         [0100]      FIGS. 46A-46D  illustrate another embodiment of a spring  1520  of the present invention. Although the spring  1520  is not illustrated as part of a pump, it will be understood the spring may be combined with pump components such as those disclosed herein for forming a pump according to the present invention. The spring  1520  is similar to the spring  220  described above, and corresponding reference numbers are provided, plus 1300. For example, the spring  1520  is generally cylindrical and includes upper and lower support members  1550 A,  1550 B, (first and second) spring elements  1552 A,  1552 B extending between the support members at first and second ends of the spring  1520 . Upper and lower braces  1554 A,  1554 B extend between the spring elements  1552 A,  1552 B′ and  1552 B,  1552 A′. The support members  1550 A,  1550 B and braces  1554 A,  1554 B may be broadly considered “connecting members.” In this embodiment, the spring  1520  also includes secondary (third and fourth) spring elements  1552 A′,  1552 B′ extending between the support members inboard of the spring elements  1552 A,  1552 B to form respective pairs of spring elements on each side of the spring. The spring elements  1552 A,  1552 B,  1552 A′,  1552 B′ are shown as generally S-shaped, but may have other shapes, such as a “Z” shape. As shown in  FIGS. 46A and 46C , the spring elements  1552 A,  1552 A′ and  1552 B,  1552 B′ are connected to each other at spaced apart locations adjacent the top and bottom of the spring. However, as shown in  FIG. 46B , the spring elements  1552 A,  1552 A′ and  1552 B,  1552 B′ are free from connection from each other along intermediate portions of the spring elements. The spring elements  1552 A,  1552 A′ and  1552 B,  1552 B′ each have similar configurations but are positioned in opposite orientations. The first and second concave segments of curvature  1560 A,  1560 B, of the spring elements  1552 A,  1552 B face in generally opposite first and second directions of the segments of curvature  1560 A′,  1560 B′ of the secondary spring elements  1552 A′,  1552 W. In other words, the spring elements  1552 A,  1552 B,  1552 A′,  1552 B′ of each pair are substantially mirror images of each other. As shown in  FIG. 46B , the spring elements  1552 A,  1552 A′ and  1552 B,  1552 B′ each form a  FIG. 8  shape when viewed from the side. The pairs of spring elements  1552 A,  1552 A′,  1552 B,  1552 B′ may provide the spring  1520  with greater balance (e.g., the spring does not tend to tilt off of its longitudinal axis) in response to compression forces and may increase the force required for compressing the spring  1520 . 
         [0101]    As viewed from the top ( FIG. 46D ), it may be seen that the spring elements  1552 A,  1552 B,  1552 A′,  1552 B′ are positioned closer to the vertical centerline of the spring  1520  to improve strength of the spring. Preferably, the spring elements  1552 A,  1552 B,  1552 A′,  1552 B′ are brought as close to the vertical centerline as possible while maintaining clearance for structure received through the center of the spring  1520 . As viewed from the top, the perimeter of the spring is non-circular. The spring elements  1552 A′,  1552 B′ are located within the smallest circle that contains the perimeter of the spring  1520  (as viewed from the top). 
         [0102]    Having described the invention in detail, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims. 
         [0103]    As various changes could be made in the above constructions and methods without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.