One-size-fits-nearly-all, bendable, plastic lift arm for toilet flushers
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A toilet flusher in which the plastic lift arm normally hidden from view inside a toilet tank comprises a bi-concave segment readily bent by hand, allowing the toilet flusher to integrate well with a wide variety of flush mechanisms already found installed inside toilet tanks. Bending forces are concentrated along a line rather than at a point, so that the inadvertent cracking of the lift arm during on-site modification that sometimes occurs in lift arms having cruciform cross sections is much less likely to occur.

Olshausen, Michael Cohnitz (Washington, DC, US)
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Primary Examiner:
Attorney, Agent or Firm:
I claim:

1. A toilet flusher comprising a flush handle and a lift arm, said toilet flusher being adapted to transmit motion to said lift arm when said toilet flusher is attached to the water tank of a toilet and said flush handle is actuated by a person, said lift arm being made of plastic and comprising a bi-concave segment, and said lift arm being bendable by a force applied to said bi-concave segment.

2. A toilet flusher as in claim 1 wherein said force is applied by hand.

3. A toilet flusher as in claim 1 wherein said bi-concave segment has a least cross section, and wherein any other cross section of said bi-concave segment parallel to said least cross section has an area larger than the area of said least cross section.

4. A toilet flusher as in claim 1 wherein said bi-concave segment has two cylindrical surfaces.

5. A toilet flusher as in claim 4 wherein said two cylindrical surfaces have equal radii of curvature.

6. A toilet flusher as in claim 4 wherein one of the cylindrical surfaces is visually indistinguishable from a flat surface.

7. A toilet flusher as in claim 4 wherein said bi-concave segment has a thickness and said two cylindrical surfaces have parallel axes, and said thickness is equal to the perpendicular distance between said axes minus the sum of the radii of said two cylindrical surfaces.

8. A toilet flusher comprising a flush handle and a lift arm, said toilet flusher being adapted to transmit motion to said lift arm when said toilet flusher is attached to the water tank of a toilet and said flush handle is actuated by a person, said lift arm being made of plastic and comprising a segment adapted for bending, and wherein said segment adapted for bending comprises a visual cue directing the application of a bending force.

9. A toilet flusher as in claim 8 in which said visual cue is a cupped region of said lift arm.

10. A toilet flusher comprising a flush handle and a lift arm, said toilet flusher being adapted to transmit motion to said lift arm when said toilet flusher is attached to the water tank of a toilet and said flush handle is actuated by a person, said lift arm being made of plastic and comprising a segment adapted for bending, and wherein said segment adapted for bending comprises a tactile cue directing the application of a bending force.

11. A toilet flusher as in claim 10 in which said tactile cue is a cupped region of said lift arm.



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This invention relates to the plastic lift arms found inside conventional, North American toilet tanks, in particular to an improvement in their stress-strain architecture. These lift arms help to trigger the sudden release of water into a toilet's bowl that occurs when a person actuates the toilet's external flush handle, typically by rotating it counterclockwise. The lift arm rigidly transmits the rotary movement to a slack chain that connects the lift arm to a water valve within the tank, at the tank's juncture with the toilet's porcelain bowl. The lift arm lifts the chain. The chain tenses. An instant later, the chain lifts the water valve, opening it, and flushing starts.

Although lift arms have been generally made out of either metal or plastic, in recent decades the newer plastic arms have captured an ever enlarging share of the refit/repair market. Plastic lift arms first became commonplace only after an injection moldable architecture capable of holding both beaded and link chains was disclosed in U.S. Pat. No. 3,518,703 to Haldopoulos, et at. (1970). All rather similar, lift arms, both metal and plastic, nevertheless show a sufficient variety among them that no single, replacement toilet flusher, that is, a flush handle that a person can actuate together with a permanently attached lift arm, or alternatively together with a removably but securely attached lift arm (such as disclosed in U.S. patent application Ser. No. 10/967,227), can integrate well with all existing installations absent some on-site modification. Idiosyncratic differences among the flush mechanisms that have been sold over the decades by dozens of different manufacturers as original equipment, some dating back into the 1940s and earlier, have militated against a universal fixture.

Clearly, it has been desirable as a marketing matter to offer a plastic lift arm that could be readily adapted to work well in most, if not absolutely all, existing installations. Such one-size-fits-nearly-all lift arms have been available attached to conventional, plastic flush handles for several years, but they have been observed to crack at times when bent during their on-site modification. Not to crack in half, or even to crack so as to render the lift arms useless, but just enough to make an installer, possibly a first-time, do-it-yourself apartment dweller, wonder whether he/she has just compromised or else, worse, just ruined the thing. The experience is not confidence-inspiring. The available plastic lift arms furthermore do not appear to have been designed ergonomically, at least not from the perspective of novice fingers wishing to bend one in order to conform it to an existing lift arm slated for the dumpster. The present invention offers an improvement over these deficiencies.


The applicant knows of only a single U.S. patent that deals directly with the bendability of plastic, toilet-flusher lift arms: U.S. Pat. No. 6,092,245 to Jones (2000). Jones (who uses “lever” or “lever arm” for what is here called a “lift arm”) recommends using ABS, in particular the brand known as Cycolac (misspelled in Jones' patent as Cyclolac) GSM 450, for the lift arm, noting that the lift arm must retain its new form after it is bent (Jones, column 5, lines 4-8). Whether the manufacturers who currently market toilet flushers having bendable plastic lift arms actually use Jones' recommended ABS is not known. What is apparent, however, is that Jones' cruciform architecture for plastic lift arms is both widely employed and is the source of the cracking phenomenon herein addressed.

Many U.S. Patents have been granted on toilet flushers having lift arms that, conceivably, might easily be bent. An example is U.S. Pat. No. 2,529,844 to Keller (1950), with brass lift arm 13 (Keller calls it “lever 13”) having flat, presumably stamped segments along its length, each such segment pierced by a hole 45. Keller's lift arm 13 has a round cross section and thus should bend preferentially and comparatively easily near the midpoint of any of its flattened segments. The reason is that each of Keller's holes 45 discontinuously weakens the flat segment wherein it is centrally located, thus inviting easy bending. Keller himself, however, never addresses bending.

Canadian Design Patent 88158 to Elka Industries, Inc. (1999) shows a lift arm having a perfectly flat (Elka, FIG. 3), long member pieced at intervals by holes. In one commercial embodiment of the Elka design, the flat strip is made of brass. Such a flat brass strip can be bent rather easily, especially at one of its holes, and for the same reason—discontinuous, cross sectional weakening—that Keller's lift arm will bend easily.

In neither Keller, however, nor Jones nor Elka are cross sections shaped to distribute bending forces in an advantageous manner without discontinuities.


The present invention rejects the cruciform cross section of Jone's “lever arm shaft 311 at its “bend point” (Jones, FIGS. 1 and 4), and instead combines a finger-friendly, flat cross section with a bi-concave architecture that concentrates bending stress non-destructively.

The present invention non-destructively concentrates bending stress by introducing a cylindrically bi-concave segment between the lift arm's pivot portion and the lift arm's free end. The radii of this cylindrical bi-concavity are long relative to the bi-concave segment's thickness, and extend from parallel center lines on opposite sides of the segment's medial plane. The segment's thickness is thus the distance between the center lines minus the sum of the cylindrical radii. The respective sagittae of the curvatures from one end to the other of the bi-concave segment are small relative to the segment's thickness, but are visually evident. Thus, the bi-concave segment is gently but also noticeably curved.

Given such an architecture, even a novice installer can confidently bend the lift arm to match some outgoing lift arm, be the outgoing lift arm made of brass and/or plastic, because there is now a visual cue that locates the point of easiest bending. Clearly the point of easiest bending is in the middle of the bi-concave segment, in a region that also feels slightly cupped (preview FIGS. 6, 10, and 11).

Furthermore, because the new architecture does not have a narrow, arched member just opposite to the point of the application of bending force, that member's arched top is not available to give way and crack as the plastic immediately adjacent to and beneath the arch stretches. Bending forces in the plastic are concentrated at most along a line parallel to the cylindrical axes rather that at a point as bending occurs, so that strain beyond the elastic limit of the plastic is less likely to occur. Thus, the disconcerting unease of observing a crack develop also becomes less likely.

In all, the customer is supplied with a lift arm that is both easier to bend to match an existing installation and that is also less likely to crack in actual fact or, worse, appear to break, than a plastic lift arm made of the same plastic but having the conventional cruciform architecture.

Important objects of the present invention are thus

  • 1) To minimize product returns based on perceived or real part failure;
  • 2) To reduce real part failure;
  • 3) To provide a comfortable-to-modify, ergonomic product for novice installers;
  • 4) To stimulate customer satisfaction by providing built-in visual cues to supplement quickly-discarded, printed directions; and
  • 5) To stimulate customer satisfaction by providing built-in tactile cues that likewise supplement printed directions.

These and still-further objects and advantages of the present invention will become apparent from a consideration of the following drawing, detailed description, and appended claims.


Referring to the drawing, wherein like reference characters indicate like parts or elements throughout the several views, and wherein arrowheads indicate physically-composite objects whose numbered resolution into constituent parts occurs only when it is germane to the discussion:

FIG. 1 is a top, plan, partial breakaway view of a toilet having a tank with conventional, internal fittings.

FIG. 2 is a top, plan, partial breakaway view of a corner of a toilet tank with the present invention attached.

FIG. 3 is a top plan view of a conventional lift arm gripped by a phantom human hand.

FIG. 4 is a cross section along lines 4-4 of FIG. 3.

FIG. 5 is an enlarged, detailed view of the contents of box 5 in FIG. 3 after a bending stress has been applied.

FIG. 6 is a top plan view of the present invention.

FIG. 7 is a side plan view taken along lines 7-7 of FIG. 6.

FIG. 8 is a cross section taken along lines 8-8 of FIG. 7.

FIG. 9 is a cross section taken along lines 9-9 of FIG. 7.

FIG. 10 is an enlarged, detail view of the contents of box 10 in FIG. 6.

FIG. 11 is a top plan view of the present invention reduced in scale from FIG. 6.


FIG. 1 shows typical American toilet 100 having tank 11, tank lid 120, bowl 130, and seat 140. Attached to tank wall 111 by means of spud 40 and nut 30 is Flush Light™ 20, based on U.S. Pat. No. 6,231,203 to Olshausen (2001), comprising LED 28 and tact switch 29. Extending into tank 110 from spud 40 is conventional metal lift arm 50 to which Flush Light™ 20 is attached. Lift arm 50 is bent slightly at angle α relative to front wall 111 of tank 110. Within tank 110 and attached to lift arm 50 by slack chain 107 is water valve flapper 104 which rests on valve seat 105 and is movably attached to overflow pipe 103. When Flush Light™ 20 is rotated counterclockwise in the usual fashion, it causes lift arm 50 to lift up on chain 107, which lifts flapper 104 causing toilet 100 to flush. Water inflow mechanism 101 then quickly refills tank 110 while allowing water to continue to flow into bowl 130 via tube 102 attached to overflow pipe 103 by clip 106. The arrangement depicted in FIG. 1 is extremely common. As shown, α=6°, but it could be made equal to some other small angle with no practical effect.

FIG. 2 shows tank 210 having different internal tank fittings than tank 110, perhaps supplied by a vanished, mid-20th century manufacturer, in fact so different that lift arm 400, in order to work properly with these particular fittings, must be bent at angle θ>>α. As shown, θ=31°. Lift arm 400 has pivot half 410 comprising weight socket 411, and clip half 420 comprising break off notches 426 and weight socket 421. Halves 410 and 420 are chemically sealed at junction 450, and are themselves the subject of a separate patent application, filed simultaneously with the present application but unrelated in its proximate subject matter. Lift arm 400 is attached to Flush Light™ 20, and the resulting assembly is attached to wall 211 of tank 210 by spud 41 and nut 30.

Relative to their respective front tank walls the angles of the lift arms in common use appear to cluster. There is a cluster of small angles, typified by FIG. 1, then another cluster of intermediate angles, typified by FIG. 2, and finally a cluster around 42°. A one-size-fits-nearly-all lift arm will therefore have to accommodate all angles between 0° and about 45°.

FIG. 3 shows conventional plastic lift arm 600, very similar to the bendable lift arm shown in FIG. 4 of Jones, op cit., and comprising pivot portion 640, by means of which arm 600 is glued to its flush handle (not shown), extremity 620, typically having a plurality of apertures (not shown) for the attachment of various chain clips, square aperture 610 with transverse slot 611 for holding beaded chains and yet other clips in the manner of Jones, op cit., and long segment 630 comprising long arched (preview FIG. 4) members 631, 632, and 633. Hand 70 encompasses lift arm 600 preparatory to bending it, with thumb 71 and forefinger 72 tightly gripping long segment 630, thumb 71 pressing down just above point 635 of long arched member 633. Long arched member 633 changes shape at point 635 from a narrowly tapered linear to a circularly curved shape, as seen in this top plan view. Implied by FIG. 3, but not depicted, is a second hand gripping the unseen flush handle to which arm 600 is securely attached in order to supply the needed resistence to effect the desired bending.

FIG. 4 shows in cross section what happens to thumb 71 when it presses down forcibly on member 631. Thumb 71 flattens uncomfortably against the arched top of long arched member 631. The hatched cross section of long segment 630 has a clearly cruciform shape.

FIG. 5 shows what occasionally happens—in our experience, one out of four times—when force is exerted to bend lift arm 600 with fingers positioned as shown in FIGS. 3 and 4. A small crack 650 can develop right at point 635. The plastic constituting member 633 simply gets stretched either too far or too fast or perhaps with a bit too much gusto, beyond the elastic limit at point 635. Although crack 650 may not render lift arm 600 inoperable, the visual impression is obviously not a good one. A novice installer may well conclude that his/her new toilet lift arm 600 “is broken” and get, so to speak, pissed off.

FIG. 6 shows the present invention applied to weight-encapsulating lift arm 400, but before arm 400 was bent on site to form angle θ, as it was in FIG. 2. Pivot half 410 of arm 400 comprises weight socket 411 and pivot portion 440. Pivot portion 440 is used to attach lift arm 400 either permanently or removably, possibly by means of an intermediate connector, to an external flush handle, such as Flush Light™ 20 shown in FIG. 2 (cf. U.S. Pat. No. 6,231,203, op. Cit., and application Ser. No. 10/967,227 filed Oct. 19, 2004). Between pivot portion 440 and weight socket 411, pivot half 410 has substantially rectangular cross sections of substantially equal area, except in the bi-concave region between à and Ä. Here, in this bi-concave region, pivot half 410 has substantially rectangular cross sections that, however, change continuously in width, reaching their point of least width, and hence of least cross sectional area at B. B lies halfway between à and Ä in this preferred embodiment of the present invention.

FIG. 7 shows that, apart from weight socket 411 and pivot portion 440 (which may, like pivot portion 640 in FIG. 3, have a relatively complicated geometry), pivot half 410 has a substantially uniform height. The height at Ã, Ä, or at B or anywhere in between à and Ä is substantially the same. Also seen in FIG. 7 are the several holes 427 by means of which, typically in conjunction with a small, fish-hook or safety-pin style clip, chain 107 (review FIG. 1) may be easily attached to arm 400.

FIGS. 8 and 9 show cross sections taken respectively at Ä, Ã, and B in FIG. 7. Although their heights h are equal, the widths ÃW and BW of their cross sections are clearly unequal, BW being noticeably less than ÃWW. For cosmetic and comfort purposes it may be desirable to chamfer or to fillet slightly the corners of all the rectangular cross sections of 410, and in fact the cross sections shown in FIGS. 8 and 9 are so chamfered.

FIG. 10 shows in detail bi-concave region 430 of pivot half 410 of lift arm 400 extending between à and Ä and becoming thinnest at point B, where thumb 71 is shown to press. Point B marks the closest approach of oppositely curved, cylindrical surfaces 412 and 413. Between weight socket 411 and pivot portion 440 and except for region 430, that is from Å to à or from Ä to Â, all cross sections A of pivot half 410 are substantially identical. To the right of  in FIG. 10 is a short transitional region comprising fillets 414 and 415 supporting weight socket 411. Weight socket 411 has circumferential chamfers 416 and 417.

FIG. 11 locates the parallel axes of cylindrical surfaces 412 and 413, these axes being depicted in this top plan view as centers of curvature C1 and C2 having radii R1 and R2. The thickness at point B of arm 400 is just the distance D between the parallel cylindrical axes minus the sum of the cylindrical radii, R1 and R2. In the invention's preferred embodiment, R1≦R2. Arm 400 pivots about center line CLp during flushing of the toilet. Arm 400 has long center line CLL that passes centrally through clip half 420 of arm 400 in this top plan view. Arm 400 is easiest to package if center lines CLp and CLL are orthogonal. However, angle γ between them might be made less than 90°. If γ were about 5°, then arm 400, if installed without modification, would resemble arm 50 in FIG. 1.

A close variant of the present invention arises when R1 is as shown in FIG. 11, but R2>>R1. For very large R2 the bi-concave region appears to be a mono-concave region having a visibly concave surface opening up, as in FIG. 11, in the direction of the applied bending force, and an opposite surface visually indistinguishable from a flat surface. For example, if R1=9 inches and R2=12 feet, then the sagitta of surface 413 will be less than 0.001″. Surface 413 will appear to be flat, indeed will be measurably indistinguishable from a flat surface with ordinary tool room caliper.

Inasmuch as modifications and alterations apparent to one skilled in the art may be made to the herein described embodiments of the present invention without departing from the scope and spirit thereof, it is intended that all matter contained herein be interpreted in an illustrative, and not in a limiting, sense with respect to the invention claimed in the following claims and equivalents thereto.